Sample records for cluster forming clump

  1. Filamentary flow and magnetic geometry in evolving cluster-forming molecular cloud clumps

    NASA Astrophysics Data System (ADS)

    Klassen, Mikhail; Pudritz, Ralph E.; Kirk, Helen

    2017-02-01

    We present an analysis of the relationship between the orientation of magnetic fields and filaments that form in 3D magnetohydrodynamic simulations of cluster-forming, turbulent molecular cloud clumps. We examine simulated cloud clumps with size scales of L ˜ 2-4 pc and densities of n ˜ 400-1000 cm-3 with Alfvén Mach numbers near unity. We simulated two cloud clumps of different masses, one in virial equilibrium, the other strongly gravitationally bound, but with the same initial turbulent velocity field and similar mass-to-flux ratio. We apply various techniques to analyse the filamentary and magnetic structure of the resulting cloud, including the DISPERSE filament-finding algorithm in 3D. The largest structure that forms is a 1-2 parsec-long filament, with smaller connecting sub-filaments. We find that our simulated clouds, wherein magnetic forces and turbulence are comparable, coherent orientation of the magnetic field depends on the virial parameter. Sub-virial clumps undergo strong gravitational collapse and magnetic field lines are dragged with the accretion flow. We see evidence of filament-aligned flow and accretion flow on to the filament in the sub-virial cloud. Magnetic fields oriented more parallel in the sub-virial cloud and more perpendicular in the denser, marginally bound cloud. Radiative feedback from a 16 M⊙ star forming in a cluster in one of our simulation's ultimately results in the destruction of the main filament, the formation of an H II region, and the sweeping up of magnetic fields within an expanding shell at the edges of the H II region.

  2. Stellar age spreads in clusters as imprints of cluster-parent clump densities

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Parmentier, G.; Grebel, E. K.; Pfalzner, S.

    2014-08-20

    It has recently been suggested that high-density star clusters have stellar age distributions much narrower than that of the Orion Nebula Cluster, indicating a possible trend of narrower age distributions for denser clusters. We show this effect to likely arise from star formation being faster in gas with a higher density. We model the star formation history of molecular clumps in equilibrium by associating a star formation efficiency per free-fall time, ε{sub ff}, to their volume density profile. We focus on the case of isothermal spheres and we obtain the evolution with time of their star formation rate. Our modelmore » predicts a steady decline of the star formation rate, which we quantify with its half-life time, namely, the time needed for the star formation rate to drop to half its initial value. Given the uncertainties affecting the star formation efficiency per free-fall time, we consider two distinct values: ε{sub ff} = 0.1 and ε{sub ff} = 0.01. When ε{sub ff} = 0.1, the half-life time is of the order of the clump free-fall time, τ{sub ff}. As a result, the age distributions of stars formed in high-density clumps have smaller full-widths at half-maximum than those of stars formed in low-density clumps. When the star formation efficiency per free-fall time is 0.01, the half-life time is 10 times longer, i.e., 10 clump free-fall times. We explore what happens if the duration of star formation is shorter than 10τ{sub ff}, that is, if the half-life time of the star formation rate cannot be defined. There, we build on the invariance of the shape of the young cluster mass function to show that an anti-correlation between the clump density and the duration of star formation is expected. We therefore conclude that, regardless of whether the duration of star formation is longer than the star formation rate half-life time, denser molecular clumps yield narrower star age distributions in clusters. Published densities and stellar age spreads of young clusters

  3. A comparative study of high-mass cluster forming clumps

    NASA Astrophysics Data System (ADS)

    López-Sepulcre, A.; Cesaroni, R.; Walmsley, C. M.

    2010-07-01

    Aims: We have searched for star formation activity (mainly infall and outflow signatures) in a sample of high-mass molecular clumps (M > 100 M⊙) in different evolutionary stages and with a wide range of surface densities, with the aim of looking for evolutionary trends and testing observationally recent theoretical models which predict the need for a minimum surface density to form high-mass stars. Methods: Our sample has been selected from single-dish 1.2 mm continuum surveys and is composed of 48 massive molecular clumps, of which 29 are IR-loud and 19 are IR-dark. Each of these has been mapped in the HCO+(1-0), HCN(1-0) and C18O(2-1) transitions with the IRAM-30 m telescope on Pico Veleta (Spain). We derive basic parameters (mass, momentum, kinetic energy) for the clumps and their associated outflows and examine the HCO+(1-0) line profiles for evidence of infall or expansion. Results: Molecular outflows have been detected in 75% of our targets from the presence of high-velocity wings in the HCO+(1-0) spectra. These are equally frequent and massive (between ~1 and ~100 M⊙) in IR-dark and IR-loud clumps, implying similar levels of star formation activity in both kinds of objects. A surface density threshold at Σ = 0.3 g cm-2 has been found above which the outflow detection rate increases significantly and the outflows are on average more massive. The infall detection rate in our sample is low, but significantly higher in the IR-dark sub-sample. Our clump mass estimates using the mm dust emission and C18O(2-1) are sensitive to the temperature, but assuming a value of 15 K for the IR-dark sub-sample, we find evidence that C18O is depleted by a factor ~4.5. The HCO+(1-0) to HCN(1-0) integrated intensity ratios measured reveal a greater dispersion about the mean value in the IR-dark sub-sample than in the IR-loud by a factor of about 5. We find that a considerable number of IR-dark sources are self-absorbed in HCN(1-0) suggesting that radiative transport effects

  4. The NGC 281 west cluster. I. Star formation in photoevaporating clumps.

    NASA Astrophysics Data System (ADS)

    Megeath, S. T.; Wilson, T. L.

    1997-09-01

    spherical clumps. We discuss the possibility that the knots of \\cs emission may trace gas compressed by converging shock waves. The K'-band observations show a rich cluster of primarily low mass stars in the \\hii/molecular interface, which we argue is divided into two distinct sub-clusters. We associate one sub-cluster with the two clumps nearest the OB stars, and the second sub-cluster with the third clump. The two clumps nearest the OB stars contain an embedded population, suggesting that star formation is ongoing. We discuss the impact photoevaporation is having on star formation in these two clumps. We find that photoevaporation is dispersing the molecular gas from which the cluster is forming and estimate that the molecular gas will be completely evaporated in 5 Myr. Deep K'-band imaging of the two clumps show that the stars are detected primarily on the sides of the clumps facing the OB stars and in the adjoining \\hii region. We examine three explanations for this asymmetry: displacement of the clump centers from the cluster center by the acceleration of the molecular gas through photoevaporation (i.e. the rocket effect), unveiling of young, embedded stars by ionization-shock fronts, and the triggered formation of stars by shocks advancing into the clumps. If shock compression is indeed ongoing in the clumps, then we argue that there is a good case for shock triggered star formation.

  5. The sparkling Universe: clustering of voids and void clumps

    NASA Astrophysics Data System (ADS)

    Lares, Marcelo; Ruiz, Andrés N.; Luparello, Heliana E.; Ceccarelli, Laura; Garcia Lambas, Diego; Paz, Dante J.

    2017-07-01

    We analyse the clustering of cosmic voids using a numerical simulation and the main galaxy sample from the Sloan Digital Sky Survey. We take into account the classification of voids into two types that resemble different evolutionary modes: those with a rising integrated density profile (void-in-void mode or R-type) and voids with shells (void-in-cloud mode or S-type). The results show that voids of the same type have stronger clustering than the full sample. We use the correlation analysis to define void clumps, associations with at least two voids separated by a distance of at most the mean void separation. In order to study the spatial configuration of void clumps, we compute the minimal spanning tree and analyse their multiplicity, maximum length and elongation parameter. We further study the dynamics of the smaller sphere that enclose all the voids in each clump. Although the global densities of void clumps are different according to their member-void types, the bulk motions of these spheres are remarkably lower than those of randomly placed spheres with the same radius distribution. In addition, the coherence of pairwise void motions does not strongly depend on whether voids belong to the same clump. Void clumps are useful to analyse the large-scale flows around voids, since voids embedded in large underdense regions are mostly in the void-in-void regime, where the expansion of the larger region produces the separation of voids. Similarly, voids around overdense regions form clumps that are in collapse, as reflected in the relative velocities of voids that are mostly approaching.

  6. MAPS OF MASSIVE CLUMPS IN THE EARLY STAGE OF CLUSTER FORMATION: TWO MODES OF CLUSTER FORMATION, COEVAL OR NON-COEVAL?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Higuchi, Aya E.; Saito, Masao; Mauersberger, Rainer

    2013-03-10

    We present maps of seven young massive molecular clumps within five target regions in C{sup 18}O (J = 1-0) line emission, using the Nobeyama 45 m telescope. These clumps, which are not associated with clusters, lie at distances between 0.7 and 2.1 kpc. We find C{sup 18}O clumps with radii of 0.5-1.7 pc, masses of 470-4200 M{sub Sun }, and velocity widths of 1.4-3.3 km s{sup -1}. All of the clumps are massive and approximately in virial equilibrium, suggesting they will potentially form clusters. Three of our target regions are associated with H II regions (CWHRs), while the other twomore » are unassociated with H II regions (CWOHRs). The C{sup 18}O clumps can be classified into two morphological types: CWHRs with a filamentary or shell-like structure and spherical CWOHRs. The two CWOHRs have systematic velocity gradients. Using the publicly released WISE database, Class I and Class II protostellar candidates are identified within the C{sup 18}O clumps. The fraction of Class I candidates among all YSO candidates (Class I+Class II) is {>=}50% in CWHRs and {<=}50% in CWOHRs. We conclude that effects from the H II regions can be seen in (1) the spatial distributions of the clumps: filamentary or shell-like structure running along the H II regions; (2) the velocity structures of the clumps: large velocity dispersion along shells; and (3) the small age spreads of YSOs. The small spreads in age of the YSOs show that the presence of H II regions tends to trigger coeval cluster formation.« less

  7. An extremely young massive clump forming by gravitational collapse in a primordial galaxy.

    PubMed

    Zanella, A; Daddi, E; Le Floc'h, E; Bournaud, F; Gobat, R; Valentino, F; Strazzullo, V; Cibinel, A; Onodera, M; Perret, V; Renaud, F; Vignali, C

    2015-05-07

    When cosmic star formation history reaches a peak (at about redshift z ≈ 2), galaxies vigorously fed by cosmic reservoirs are dominated by gas and contain massive star-forming clumps, which are thought to form by violent gravitational instabilities in highly turbulent gas-rich disks. However, a clump formation event has not yet been observed, and it is debated whether clumps can survive energetic feedback from young stars, and afterwards migrate inwards to form galaxy bulges. Here we report the spatially resolved spectroscopy of a bright off-nuclear emission line region in a galaxy at z = 1.987. Although this region dominates star formation in the galaxy disk, its stellar continuum remains undetected in deep imaging, revealing an extremely young (less than ten million years old) massive clump, forming through the gravitational collapse of more than one billion solar masses of gas. Gas consumption in this young clump is more than tenfold faster than in the host galaxy, displaying high star-formation efficiency during this phase, in agreement with our hydrodynamic simulations. The frequency of older clumps with similar masses, coupled with our initial estimate of their formation rate (about 2.5 per billion years), supports long lifetimes (about 500 million years), favouring models in which clumps survive feedback and grow the bulges of present-day galaxies.

  8. ATLASGAL: Chemical evolution of star forming clumps

    NASA Astrophysics Data System (ADS)

    Figura, Charles C.; Urquhart, James S.; Wyrowski, Friedrich

    2017-01-01

    Although massive stars are few in number, they impact their host molecular clouds, clusters, and galaxies in profound ways, playing a vital role in regulating star formation in their host galaxy. Understanding the formation of these massive stars is critical to understanding this evolution, but their rapid early development causes them to reach the main sequence while still shrouded in their natal molecular cloud. Many studies have investigated these regions in a targeted manner, but a full understanding necessitates a broader view at all stages of formation across many star forming regions.We have used mid-infrared continuum surveys to guide selection of a statistically large sample of massive dust clumps from the 10,000 such clumps identified in the ATLASGAL Compact Source Catalogue (CSC), ensuring that all stages of the evolutionary process are included. A final sample of 600 fourth-quadrant sources within 1 degree of the Galactic plane were observed with the Mopra telescope with an 8 GHz bandwidth between 85.2 and 93.4 GHz.We present an overview of our results. We have identified over 30 molecular lines, seven of which with detected hyperfine structure, as well as several mm-radio recombination line transitions. Source velocities indicate that these regions trace the Crux-Scutum, Norma, and Carina Sagitarius arms. We have performed an analysis of linewidth and line intensity ratios, correlating these with star formation stages as identified by IR brightness at the 70 and 24 μm bands, and present several molecular pairs whose linewidth and intensity might serve as significant tracers of the evolutionary stage of star formation. We comment on the results of PCA analysis of the measured parameters for the overall population and the star formation stage subgroups with an eye toward characterising early stellar development through molecular line observations.

  9. ATLASGAL - towards a complete sample of massive star forming clumps

    NASA Astrophysics Data System (ADS)

    Urquhart, J. S.; Moore, T. J. T.; Csengeri, T.; Wyrowski, F.; Schuller, F.; Hoare, M. G.; Lumsden, S. L.; Mottram, J. C.; Thompson, M. A.; Menten, K. M.; Walmsley, C. M.; Bronfman, L.; Pfalzner, S.; König, C.; Wienen, M.

    2014-09-01

    By matching infrared-selected, massive young stellar objects (MYSOs) and compact H II regions in the Red MSX Source survey to massive clumps found in the submillimetre ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) survey, we have identified ˜1000 embedded young massive stars between 280° < ℓ < 350° and 10° < ℓ < 60° with | b | < 1.5°. Combined with an existing sample of radio-selected methanol masers and compact H II regions, the result is a catalogue of ˜1700 massive stars embedded within ˜1300 clumps located across the inner Galaxy, containing three observationally distinct subsamples, methanol-maser, MYSO and H II-region associations, covering the most important tracers of massive star formation, thought to represent key stages of evolution. We find that massive star formation is strongly correlated with the regions of highest column density in spherical, centrally condensed clumps. We find no significant differences between the three samples in clump structure or the relative location of the embedded stars, which suggests that the structure of a clump is set before the onset of star formation, and changes little as the embedded object evolves towards the main sequence. There is a strong linear correlation between clump mass and bolometric luminosity, with the most massive stars forming in the most massive clumps. We find that the MYSO and H II-region subsamples are likely to cover a similar range of evolutionary stages and that the majority are near the end of their main accretion phase. We find few infrared-bright MYSOs associated with the most massive clumps, probably due to very short pre-main-sequence lifetimes in the most luminous sources.

  10. Molecular clumps in the W51 giant molecular cloud

    NASA Astrophysics Data System (ADS)

    Parsons, H.; Thompson, M. A.; Clark, J. S.; Chrysostomou, A.

    2012-08-01

    In this paper, we present a catalogue of dense molecular clumps located within the W51 giant molecular cloud (GMC). This work is based on Heterodyne Array Receiver Programme 13CO J = 3-2 observations of the W51 GMC and uses the automated CLUMPFIND algorithm to decompose the region into a total of 1575 clumps of which 1130 are associated with the W51 GMC. We clearly see the distinct structures of the W51 complex and the high-velocity stream previously reported. We find the clumps have characteristic diameters of 1.4 pc, excitation temperatures of 12 K, densities of 5.6 × 1021 cm-2, surface densities 0.02 g cm-2 and masses of 90 M⊙. We find a total mass of dense clumps within the GMC of 1.5 × 105 M⊙, with only 1 per cent of the clumps detected by number and 4 per cent by mass found to be supercritical. We find a clump-forming efficiency of 14 ± 1 per cent for the W51 GMC and a supercritical clump-forming efficiency of 0.5-0.5+2.3 per cent. Looking at the clump mass distribution, we find it is described by a single power law with a slope of α=2.4-0.1+0.2 above ˜100 M⊙. By comparing locations of supercritical clumps and young clusters, we see that any future star formation is likely to be located away from the currently active W51A region.

  11. SHORT-LIVED STAR-FORMING GIANT CLUMPS IN COSMOLOGICAL SIMULATIONS OF z Almost-Equal-To 2 DISKS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Genel, Shy; Genzel, Reinhard; Foerster Schreiber, Natascha M.

    Many observed massive star-forming z Almost-Equal-To 2 galaxies are large disks that exhibit irregular morphologies, with Almost-Equal-To 1 kpc, Almost-Equal-To 10{sup 8}-10{sup 10}M{sub o-dot} clumps. We present the largest sample to date of high-resolution cosmological smoothed particle hydrodynamics simulations that zoom-in on the formation of individual M{sub *} Almost-Equal-To 10{sup 10.5}M{sub o-dot} galaxies in Almost-Equal-To 10{sup 12}M{sub o-dot} halos at z Almost-Equal-To 2. Our code includes strong stellar feedback parameterized as momentum-driven galactic winds. This model reproduces many characteristic features of this observed class of galaxies, such as their clumpy morphologies, smooth and monotonic velocity gradients, high gas fractions (f{submore » g} Almost-Equal-To 50%), and high specific star formation rates ({approx}>1 Gyr{sup -1}). In accord with recent models, giant clumps (M{sub clump} Almost-Equal-To (5 Multiplication-Sign 10{sup 8}-10{sup 9})M{sub o-dot}) form in situ via gravitational instabilities. However, the galactic winds are critical for their subsequent evolution. The giant clumps we obtain are short-lived and are disrupted by wind-driven mass loss. They do not virialize or migrate to the galaxy centers as suggested in recent work neglecting strong winds. By phenomenologically implementing the winds that are observed from high-redshift galaxies and in particular from individual clumps, our simulations reproduce well new observational constraints on clump kinematics and clump ages. In particular, the observation that older clumps appear closer to their galaxy centers is reproduced in our simulations, as a result of inside-out formation of the disks rather than inward clump migration.« less

  12. Cloud Structure of Galactic OB Cluster-forming Regions from Combining Ground- and Space-based Bolometric Observations

    NASA Astrophysics Data System (ADS)

    Lin, Yuxin; Liu, Hauyu Baobab; Li, Di; Zhang, Zhi-Yu; Ginsburg, Adam; Pineda, Jaime E.; Qian, Lei; Galván-Madrid, Roberto; McLeod, Anna Faye; Rosolowsky, Erik; Dale, James E.; Immer, Katharina; Koch, Eric; Longmore, Steve; Walker, Daniel; Testi, Leonardo

    2016-09-01

    We have developed an iterative procedure to systematically combine the millimeter and submillimeter images of OB cluster-forming molecular clouds, which were taken by ground-based (CSO, JCMT, APEX, and IRAM-30 m) and space telescopes (Herschel and Planck). For the seven luminous (L\\gt {10}6 L ⊙) Galactic OB cluster-forming molecular clouds selected for our analyses, namely W49A, W43-Main, W43-South, W33, G10.6-0.4, G10.2-0.3, and G10.3-0.1, we have performed single-component, modified blackbody fits to each pixel of the combined (sub)millimeter images, and the Herschel PACS and SPIRE images at shorter wavelengths. The ˜10″ resolution dust column density and temperature maps of these sources revealed dramatically different morphologies, indicating very different modes of OB cluster-formation, or parent molecular cloud structures in different evolutionary stages. The molecular clouds W49A, W33, and G10.6-0.4 show centrally concentrated massive molecular clumps that are connected with approximately radially orientated molecular gas filaments. The W43-Main and W43-South molecular cloud complexes, which are located at the intersection of the Galactic near 3 kpc (or Scutum) arm and the Galactic bar, show a widely scattered distribution of dense molecular clumps/cores over the observed ˜10 pc spatial scale. The relatively evolved sources G10.2-0.3 and G10.3-0.1 appear to be affected by stellar feedback, and show a complicated cloud morphology embedded with abundant dense molecular clumps/cores. We find that with the high angular resolution we achieved, our visual classification of cloud morphology can be linked to the systematically derived statistical quantities (I.e., the enclosed mass profile, the column density probability distribution function (N-PDF), the two-point correlation function of column density, and the probability distribution function of clump/core separations). In particular, the massive molecular gas clumps located at the center of G10.6-0.4 and

  13. Forming clusters within clusters: how 30 Doradus recollapsed and gave birth again

    NASA Astrophysics Data System (ADS)

    Rahner, Daniel; Pellegrini, Eric W.; Glover, Simon C. O.; Klessen, Ralf S.

    2018-01-01

    The 30 Doradus nebula in the Large Magellanic Cloud (LMC) contains the massive starburst cluster NGC 2070 with a massive and probably younger stellar sub clump at its centre: R136. It is not clear how such a massive inner cluster could form several million years after the older stars in NGC 2070, given that stellar feedback is usually thought to expel gas and inhibit further star formation. Using the recently developed 1D feedback scheme WARPFIELD to scan a large range of cloud and cluster properties, we show that an age offset of several million years between the stellar populations is in fact to be expected given the interplay between feedback and gravity in a giant molecular cloud with a density ≳500 cm-3 due to re-accretion of gas on to the older stellar population. Neither capture of field stars nor gas retention inside the cluster have to be invoked in order to explain the observed age offset in NGC 2070 as well as the structure of the interstellar medium around it.

  14. Physical Properties of UV-bright Clumps in Star-forming Galaxies at 0.5 ≤ z < 3

    NASA Astrophysics Data System (ADS)

    Guo, Yicheng; Rafelski, Marc; Bell, Eric F.; Dekel, Avishai; Mandelker, Nir; Primack, Joel R.; CANDELS

    2018-06-01

    Studying giant star-forming clumps in distant galaxies is important to understand galaxy formation and evolution. At present, however, observers and theorists have not reached a consensus on whether the observed “clumps” in distant galaxies are the same phenomenon that is seen in simulations. As a step to establish a benchmark of direct comparisons between observations and theories, we publish a sample of clumps constructed to represent the commonly observed “clumps” in the literature. This sample contains 3193 clumps detected from the rest-frame images of 1270 galaxies at 0.5≤z<3.0. The physical properties of clumps (e.g., rest-frame color, stellar mass, star formation rate, age, and dust extinction) are measured by fitting the spectral energy distribution (SED) to synthetic stellar population models. We carefully test the procedures of measuring clump properties, especially the method of subtracting background fluxes from the diffuse component of galaxies. With our fiducial background subtraction, we find a radial clump U-V color variation, where clumps close to galactic centers are redder than those in outskirts. The slope of the color gradient (clump color as a function of their galactocentric distance scaled by the semimajor axis of galaxies) changes with redshift and stellar mass of the host galaxies: at a fixed stellar mass, the slope becomes steeper toward low redshift, and at a fixed redshift, it becomes slightly steeper with stellar mass. Based on our SED fitting, this observed color gradient can be explained by a combination of a negative age gradient, a negative E(B-V) gradient, and a positive specific star formation rate gradient of the clumps. We also find that the color gradients of clumps are steeper than those of intra-clump regions. Correspondingly, the radial gradients of the derived physical properties of clumps are different from those of the diffuse component or intra-clump regions.

  15. THE JCMT GOULD BELT SURVEY: EVIDENCE FOR DUST GRAIN EVOLUTION IN PERSEUS STAR-FORMING CLUMPS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Michael Chun-Yuan; Francesco, J. Di; Johnstone, D.

    2016-07-20

    The dust emissivity spectral index, β , is a critical parameter for deriving the mass and temperature of star-forming structures and, consequently, their gravitational stability. The β value is dependent on various dust grain properties, such as size, porosity, and surface composition, and is expected to vary as dust grains evolve. Here we present β , dust temperature, and optical depth maps of the star-forming clumps in the Perseus Molecular Cloud determined from fitting spectral energy distributions to combined Herschel and JCMT observations in the 160, 250, 350, 500, and 850 μ m bands. Most of the derived β andmore » dust temperature values fall within the ranges of 1.0–2.7 and 8–20 K, respectively. In Perseus, we find the β distribution differs significantly from clump to clump, indicative of grain growth. Furthermore, we also see significant localized β variations within individual clumps and find low- β regions correlate with local temperature peaks, hinting at the possible origins of low- β grains. Throughout Perseus, we also see indications of heating from B stars and embedded protostars, as well evidence of outflows shaping the local landscape.« less

  16. Radiative Feedback of Forming Star Clusters on Their GMC Environments: Theory and Simulation

    NASA Astrophysics Data System (ADS)

    Howard, C. S.; Pudritz, R. E.; Harris, W. E.

    2013-07-01

    Star clusters form from dense clumps within a molecular cloud. Radiation from these newly formed clusters feeds back on their natal molecular cloud through heating and ionization which ultimately stops gas accretion into the cluster. Recent studies suggest that radiative feedback effects from a single cluster may be sufficient to disrupt an entire cloud over a short timescale. Simulating cluster formation on a large scale, however, is computationally demanding due to the high number of stars involved. For this reason, we present a model for representing the radiative output of an entire cluster which involves randomly sampling an initial mass function (IMF) as the cluster accretes mass. We show that this model is able to reproduce the star formation histories of observed clusters. To examine the degree to which radiative feedback shapes the evolution of a molecular cloud, we use the FLASH adaptive-mesh refinement hydrodynamics code to simulate cluster formation in a turbulent cloud. Unlike previous studies, sink particles are used to represent a forming cluster rather than individual stars. Our cluster model is then coupled with a raytracing scheme to treat radiative transfer as the clusters grow in mass. This poster will outline the details of our model and present preliminary results from our 3D hydrodynamical simulations.

  17. First constraints on the stellar mass function of star-forming clumps at the peak of cosmic star formation

    NASA Astrophysics Data System (ADS)

    Dessauges-Zavadsky, Miroslava; Adamo, Angela

    2018-06-01

    Star-forming clumps dominate the rest-frame ultraviolet morphology of galaxies at the peak of cosmic star formation. If turbulence driven fragmentation is the mechanism responsible for their formation, we expect their stellar mass function to follow a power-law of slope close to -2. We test this hypothesis performing the first analysis of the stellar mass function of clumps hosted in galaxies at z ˜ 1 - 3.5. The sample is gathered from the literature with similar detection thresholds and stellar masses determined in a homogeneous way. To overcome the small number statistics per galaxy (each galaxy hosts up to a few tens of clumps only), we combine all high-redshift clumps. The resulting clump mass function follows a power-law of slope ˜-1.7 and flattens at masses below 2 × 107 M⊙. By means of randomly sampled clump populations, drawn out of a power-law mass function of slope -2, we test the effect of combining small clump populations, detection limits of the surveys, and blending on the mass function. Our numerical exercise reproduces all the features observed in the real clump mass function confirming that it is consistent with a power-law of slope ≃ -2. This result supports the high-redshift clump formation through fragmentation in a similar fashion as in local galaxies, but under different gas conditions.

  18. ATLASGAL -- A molecular view of an unbiased sample of massive star forming clumps

    NASA Astrophysics Data System (ADS)

    Figura, Charles; Urquhart, James; Wyrowski, Friedrich; Giannetti, Andrea; Kim, Wonju

    2018-01-01

    Massive stars play an important role in many areas of astrophysics, from regulating star formation to driving the evolution of their host galaxy. Study of these stars is made difficult by their short evolutionary timescales, small populations and greater distances, and further complicated because they reach the main sequence while still shrouded in their natal clumps. As a result, many aspects of their formation are still poorly understood.We have assembled a large and statistically representative collection of massive star-forming environments that span all evolutionary stages of development by correlating mid-infrared and dust continnum surveys. We have conducted follow-up single-pointing observations toward a sample of approximately 600 of these clumps with the Mopra telescope using an 8 GHz bandwidth that spans some 27 molecular and mm-radio recombination line transitions. These lines trace a wide range of interstellar conditions with varying thermal, chemical, and kinematic properties. Many of these lines exhibit hyperfine structure allowing more detailed measurements of the clump environment (e.g. rotation temperatures and column densities).From these twenty-seven lines, we have identified thirteen line intensity ratios that strongly trace the evolutionary state of these clumps. We have investigated individual molecular and mm-radio recombination lines, contrasting these with radio and sub-mm continuum observations. We present a summary of the results of the statistical analysis of the sample, and compare them with previous similar studies to test their utility as chemical clocks of the evolutionary processes.

  19. Photoevaporation of Clumps in Photodissociation Regions

    NASA Technical Reports Server (NTRS)

    Gorti, Uma; Hollenbach, David; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    We present the results of an investigation of the effects of Far Ultraviolet (FUV) radiation (6.0eV < hv < 13.6eV) from hot early type OB stars on clumps in star-forming molecular clouds. Clumps in FUV-illuminated regions (or photodissociation regions or PDRs) undergo external heating and photodissociation as they are exposed to the FUV field, resulting in a loss of cold, molecular lump mass as it is converted to warm atomic gas. The heating, if rapid, creates strong photoevaporative mass flows off the clump surfaces, and drives shocks into the clumps, compressing them to high densities. The clumps lose mass on relatively short timescales. The evolution of an individual clump is found to be sensitive to three dimensionless parameters: Nc0, the ratio of the initial column density of the clump to the column N(0) approx. 10(exp 21) cm(exp -2) of a warm FUV-heated surface region; upsilon, the ratio of the sound speed in the heated surface to that in the cold clump material: and t(FUV)t(c), the ratio of the "turn-on time" t(FUV) of the heating flux on a clump to its initial sound crossing-time t(c). The evolution also depends on whether a confining interclump medium exists, or whether the interclump region has negligible pressure, as is the case for turbulence-generated clumps. In this paper, we use spherical 1-D numerical hydrodynamic models as well as approximate analytical models to study the dependence of clump photoevaporation on the physical parameters of the clump, and to derive the dynamical evolution, mass loss rates and photoevaporative timescales of a clump for a variety of astrophysical situations. Turbulent clumps evolve so that their column densities are equal to a critical value determined by the local FUV field, and typically have short photo evaporation timescales, approx. 10(exp 4-5) years for a 1 M(solar mass) clump in a typical star-forming region (Nc0 = 10, upsilon = 10). Clumps with insufficient magnetic pressure support, and in strong FUV fields

  20. Why the dark matter of galaxies is clumps of micro­ brown­dwarfs and not Cold Dark Matter

    NASA Astrophysics Data System (ADS)

    Gibson, Carl H.

    Observations of quasar microlensing by Schild 1996 show the baryonic dark matter BDM of galaxies is micro-brown-dwarfs, primordial hydrogen-helium planets formed at the plasma to gas transition 10^13 seconds, in trillion-planet clumps termed proto-globular-star-clusters PGCs. Large photon-viscosity {nu} of the plasma permits supercluster-mass gravitational fragmentation at 10^12 seconds when the horizon scale L_H = ct is matched by the Schwarz viscous scale L_SV of Gibson 1996. Voids begin expansion at sonic speeds c/ 3^1/2, where c is light speed and t is time, explaining 10^25 meter size regions observed to be devoid of all matter, either BDM or non-baryonic NBDM. Most of the NBDM is weakly-collisional, strongly-diffusive, neutrino-like particles. If cold NBDM (CDM) is assumed, it must soon become warm and diffuse because it is weakly-collisional. It cannot clump and its clumps cannot clump. CDM is ruled out with 99% confidence by local-group satellite observations of Kroupa et al. 2010. The satellites are clusters of PGCs. PGCs are recaptured by the Galaxy on an accretion disk as they freeze and diffuse from its core to form its BDM halo. Stars form by viscous mergers of primordial gas planets within PGCs. Stars die by overeating mBDs, making the first chemicals, oceans and life at 2-8 Myr.

  1. Stellar Population Synthesis of Star-forming Clumps in Galaxy Pairs and Non-interacting Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Zaragoza-Cardiel, Javier; Smith, Beverly J.; Rosado, Margarita; Beckman, John E.; Bitsakis, Theodoros; Camps-Fariña, Artemi; Font, Joan; Cox, Isaiah S.

    2018-02-01

    We have identified 1027 star-forming complexes in a sample of 46 galaxies from the Spirals, Bridges, and Tails (SB&T) sample of interacting galaxies, and 693 star-forming complexes in a sample of 38 non-interacting spiral (NIS) galaxies in 8 μm observations from the Spitzer Infrared Array Camera. We have used archival multi-wavelength UV-to IR observations to fit the observed spectral energy distribution of our clumps with the Code Investigating GALaxy Emission using a double exponentially declined star formation history. We derive the star formation rates (SFRs), stellar masses, ages and fractions of the most recent burst, dust attenuation, and fractional emission due to an active galactic nucleus for these clumps. The resolved star formation main sequence holds on 2.5 kpc scales, although it does not hold on 1 kpc scales. We analyzed the relation between SFR, stellar mass, and age of the recent burst in the SB&T and NIS samples, and we found that the SFR per stellar mass is higher in the SB&T galaxies, and the clumps are younger in the galaxy pairs. We analyzed the SFR radial profile and found that the SFR is enhanced through the disk and in the tidal features relative to normal spirals.

  2. Energy Budget of Forming Clumps in Numerical Simulations of Collapsing Clouds

    NASA Astrophysics Data System (ADS)

    Camacho, Vianey; Vázquez-Semadeni, Enrique; Ballesteros-Paredes, Javier; Gómez, Gilberto C.; Fall, S. Michael; Mata-Chávez, M. Dolores

    2016-12-01

    We analyze the physical properties and energy balance of density enhancements in two SPH simulations of the formation, evolution, and collapse of giant molecular clouds. In the simulations, no feedback is included, so all motions are due either to the initial decaying turbulence or to gravitational contraction. We define clumps as connected regions above a series of density thresholds. The resulting full set of clumps follows the generalized energy equipartition relation, {σ }v/{R}1/2\\propto {{{Σ }}}1/2, where {σ }v is the velocity dispersion, R is the “radius,” and Σ is the column density. We interpret this as a natural consequence of gravitational contraction at all scales rather than virial equilibrium. Nevertheless, clumps with low Σ tend to show a large scatter around equipartition. In more than half of the cases, this scatter is dominated by external turbulent compressions that assemble the clumps rather than by small-scale random motions that would disperse them. The other half does actually disperse. Moreover, clump sub-samples selected by means of different criteria exhibit different scalings. Sub-samples with narrow Σ ranges follow Larson-like relations, although characterized by their respective values of Σ. Finally, we find that (I) clumps lying in filaments tend to appear sub-virial, (II) high-density cores (n≥slant {10}5 cm3) that exhibit moderate kinetic energy excesses often contain sink (“stellar”) particles and the excess disappears when the stellar mass is taken into account in the energy balance, and (III) cores with kinetic energy excess but no stellar particles are truly in a state of dispersal.

  3. From gas to stars in energetic environments: dense gas clumps in the 30 Doradus region within the Large Magellanic Cloud

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Anderson, Crystal N.; Meier, David S.; Ott, Jürgen

    2014-09-20

    We present parsec-scale interferometric maps of HCN(1-0) and HCO{sup +}(1-0) emission from dense gas in the star-forming region 30 Doradus, obtained using the Australia Telescope Compact Array. This extreme star-forming region, located in the Large Magellanic Cloud (LMC), is characterized by a very intense ultraviolet ionizing radiation field and sub-solar metallicity, both of which are expected to impact molecular cloud structure. We detect 13 bright, dense clumps within the 30 Doradus-10 giant molecular cloud. Some of the clumps are aligned along a filamentary structure with a characteristic spacing that is consistent with formation via varicose fluid instability. Our analysis showsmore » that the filament is gravitationally unstable and collapsing to form stars. There is a good correlation between HCO{sup +} emission in the filament and signatures of recent star formation activity including H{sub 2}O masers and young stellar objects (YSOs). YSOs seem to continue along the same direction of the filament toward the massive compact star cluster R136 in the southwest. We present detailed comparisons of clump properties (masses, linewidths, and sizes) in 30Dor-10 to those in other star forming regions of the LMC (N159, N113, N105, and N44). Our analysis shows that the 30Dor-10 clumps have similar masses but wider linewidths and similar HCN/HCO{sup +} (1-0) line ratios as clumps detected in other LMC star-forming regions. Our results suggest that the dense molecular gas clumps in the interior of 30Dor-10 are well shielded against the intense ionizing field that is present in the 30 Doradus region.« less

  4. Massive star clusters in a z=1 star-forming galaxy seen at a 100 pc scale thanks to strong gravitational lensing

    NASA Astrophysics Data System (ADS)

    Dessauges-Zavadsky, Miroslava; Cava, Antonio; Richard, Johan; Schaerer, Daniel; Egami, Eiichi

    2015-08-01

    Deep and high-resolution imaging has revealed clumpy, rest-frame UV morphologies among z=1-3 galaxies. The majority of these galaxies has been shown to be dominated by ordered disk rotation, which led to the conclusion that the observed giant clumps, resolved on kpc-scales, are generated from disk fragmentation due to gravitational instability. State-of-the-art numerical simulations show that they may occupy a relevant role in galaxy evolution, contributing to the galactic bulge formation. Despite the high resolution attained by the most advanced ground- and space-based facilities, as well as in numerical simulations, the intrinsic typical masses and scale sizes of these star-forming clumps remain unconstrained, since they are barely resolved at z=1-3.Thanks to the amplification and stretching power provided by strong gravitational lensing, we are likely to reach the spatial resolving power for unveiling the physics of these star-forming regions. We report on the study of clumpy star formation observed in the Cosmic Snake, a strongly lensed galaxy at z=1, representative of the typical star-forming population close to the peak of Universe activity. About 20 clumps are identified in the HST images. Benefiting from extreme amplification factors up to 100, they are resolved down to an intrinsic scale of 100 pc, never reached before at z=1.The HST multi-wavelength analysis of these individual star clusters allows us to determine their intrinsic physical properties, showing stellar masses (Ms) from 106 to 108.3 Msun, sizes from 100 to 400 pc, and ages from 106 to 108.5 yr. The masses we find are in line with the new, very high resolution numerical simulations, which also suggest that the massive giant clumps previously observed at high redshift with Ms as high as 109-10 Msun may suffer from low resolution effects, being unresolved conglomerates of less massive star clusters. We also compare our results with those of massive young clusters in nearby galaxies. Our approved

  5. The ages and baryonic masses of clumps in turbulent, clumpy disk galaxies

    NASA Astrophysics Data System (ADS)

    Fisher, David

    2017-08-01

    We propose to measure the stellar populations and masses of massive star forming clumps at the resolution of the Jeans' length in a sample of massive, turbulent disk galaxies. Massive star-forming clumps are a critical component of the morphogical transformation of galaxies and the build-up of bulges. If, however, clumps dissipate quickly bulges may not form through clump phase, then clumps would build thick disks. Different feedback prescriptions have drastically different effects on clumps. Some feedback models (e.g. Hopkins et al 2012, FIRE simulations) completely destroy clumps whereas other feedback models allow clumps to persist (e.g. Bournaud et al. 2014). Therefore, to build accurate models of galaxy evolution we must know how long the lives of clumps are. The problem is that both due to resolution and available wavelength coverage it is impossible to precisely measure the ages and stellar masses of individual clumps in high-z galaxies. We have discovered a sample of extremely rare galaxies at z 0.1 that are extremely gas rich, turbulent and have a clumpy distribution of ionized gas. In all ways they are identical to those of the high-redshift Universe. We propose to employ UV-optical-near IR imaging with WFC3 to measure the stellar masses and mean ages of a set of 6 clumpy galaxies, containing 80 giant star forming clumps. This data complements our ALMA CO(1-0) maps of the same targets, and we will thus make the first maps of the full baryonic mass in turbulent disk galaxies. This work builds on our previous HST Halpha imaging program, and validates massive investments of HST time on high-z surveys of galaxies.

  6. Kinetic temperature of massive star forming molecular clumps measured with formaldehyde

    NASA Astrophysics Data System (ADS)

    Tang, X. D.; Henkel, C.; Menten, K. M.; Zheng, X. W.; Esimbek, J.; Zhou, J. J.; Yeh, C. C.; König, C.; Yuan, Y.; He, Y. X.; Li, D. L.

    2017-02-01

    Context. For a general understanding of the physics involved in the star formation process, measurements of physical parameters such as temperature and density are indispensable. The chemical and physical properties of dense clumps of molecular clouds are strongly affected by the kinetic temperature. Therefore, this parameter is essential for a better understanding of the interstellar medium. Formaldehyde, a molecule which traces the entire dense molecular gas, appears to be the most reliable tracer to directly measure the gas kinetic temperature. Aims: We aim to determine the kinetic temperature with spectral lines from formaldehyde and to compare the results with those obtained from ammonia lines for a large number of massive clumps. Methods: Three 218 GHz transitions (JKAKC = 303-202, 322-221, and 321-220) of para-H2CO were observed with the 15 m James Clerk Maxwell Telescope (JCMT) toward 30 massive clumps of the Galactic disk at various stages of high-mass star formation. Using the RADEX non-LTE model, we derive the gas kinetic temperature modeling the measured para-H2CO 322-221/303-202 and 321-220/303-202 ratios. Results: The gas kinetic temperatures derived from the para-H2CO (321-220/303-202) line ratios range from 30 to 61 K with an average of 46 ± 9 K. A comparison of kinetic temperature derived from para-H2CO, NH3, and the dust emission indicates that in many cases para-H2CO traces a similar kinetic temperature to the NH3 (2, 2)/(1, 1) transitions and the dust associated with the HII regions. Distinctly higher temperatures are probed by para-H2CO in the clumps associated with outflows/shocks. Kinetic temperatures obtained from para-H2CO trace turbulence to a higher degree than NH3 (2, 2)/(1, 1) in the massive clumps. The non-thermal velocity dispersions of para-H2CO lines are positively correlated with the gas kinetic temperature. The massive clumps are significantly influenced by supersonic non-thermal motions. The reduced spectra (FITS files) are only

  7. The Bolocam Galactic Plane Survey. XIV. Physical Properties of Massive Starless and Star-forming Clumps

    NASA Astrophysics Data System (ADS)

    Svoboda, Brian E.; Shirley, Yancy L.; Battersby, Cara; Rosolowsky, Erik W.; Ginsburg, Adam G.; Ellsworth-Bowers, Timothy P.; Pestalozzi, Michele R.; Dunham, Miranda K.; Evans, Neal J., II; Bally, John; Glenn, Jason

    2016-05-01

    We sort 4683 molecular clouds between 10° < ℓ < 65° from the Bolocam Galactic Plane Survey based on observational diagnostics of star formation activity: compact 70 μm sources, mid-IR color-selected YSOs, H2O and CH3OH masers, and UCH II regions. We also present a combined NH3-derived gas kinetic temperature and H2O maser catalog for 1788 clumps from our own GBT 100 m observations and from the literature. We identify a subsample of 2223 (47.5%) starless clump candidates (SCCs), the largest and most robust sample identified from a blind survey to date. Distributions of flux density, flux concentration, solid angle, kinetic temperature, column density, radius, and mass show strong (>1 dex) progressions when sorted by star formation indicator. The median SCC is marginally subvirial (α ˜ 0.7) with >75% of clumps with known distance being gravitationally bound (α < 2). These samples show a statistically significant increase in the median clump mass of ΔM ˜ 170-370 M ⊙ from the starless candidates to clumps associated with protostars. This trend could be due to (I) mass growth of the clumps at \\dot{M}˜ 200{--}440 M ⊙ Myr-1 for an average freefall 0.8 Myr timescale, (II) a systematic factor of two increase in dust opacity from starless to protostellar phases, and/or (III) a variation in the ratio of starless to protostellar clump lifetime that scales as ˜M -0.4. By comparing to the observed number of CH3OH maser containing clumps, we estimate the phase lifetime of massive (M > 103 M ⊙) starless clumps to be 0.37 ± 0.08 Myr (M/103 M ⊙)-1 the majority (M < 450 M ⊙) have phase lifetimes longer than their average freefall time.

  8. Physical properties of high-mass star-forming clumps in different evolutionary stages from the Bolocam Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    Svoboda, Brian; Shirley, Yancy; Rosolowsky, Erik; Dunham, Miranda; Ellsworth-Bowers, Timothy; Ginsburg, Adam

    2013-07-01

    High mass stars play a key role in the physical and chemical evolution of the interstellar medium, yet the evolutionary sequence for high mass star forming regions is poorly understood. Recent Galactic plane surveys are providing the first systematic view of high-mass star-forming regions in all evolutionary phases across the Milky Way. We present observations of the 22.23 GHz H2O maser transition J(Ka,Kc) = 6(1,6)→5(2,3) transition toward 1398 clumps identified in the Bolocam Galactic Plane Survey using the 100m Green Bank Telescope (GBT). We detect 392 H2O masers, 279 (71%) newly discovered. We show that H2O masers can identify the presence of protostars which were not previously identified by Spitzer/MSX Galactic plane IR surveys: 25% of IR-dark clumps have an H2O maser. We compare the physical properties of the clumps in the Bolocam Galactic Plane Survey (BGPS) with observations of diagnostics of star formation activity: 8 and 24 um YSO candidates, H2O and CH3OH masers, shocked H2, EGOs, and UCHII regions. We identify a sub-sample of 400 clumps with no star formation indicators representing the largest and most robust sample of pre-protocluster candidates from an unbiased survey to date. The different evolutionary stages show strong separations in HCO+ linewidth and integrated intensity, surface mass density, and kinetic temperature. Monte Carlo techniques are applied to distance probability distribution functions (DPDFs) in order to marginalize over the kinematic distance ambiguity and calculate the distribution of derived quantities for clumps in different evolutionary stages. Surface area and dust mass show weak separations above > 2 pc^2 and > 3x10^3 solar masses. An observed breakdown occurs in the size-linewidth relationship with no differentiation by evolutionary stage. Future work includes adding evolutionary indicators (MIPSGAL, HiGal, MMB) and expanding DPDF priors (HI self-absorption, Galactic structure) for more well-resolved KDAs.

  9. Star Formation in Massive Clusters via Bondi Accretion

    NASA Astrophysics Data System (ADS)

    Murray, Norman; Chang, Philip

    2012-02-01

    Essentially all stars form in giant molecular clouds (GMCs). However, inside GMCs, most of the gas does not participate in star formation; rather, denser gas accumulates in clumps in the GMC, with the bulk of the stars in a given GMC forming in a few of the most massive clumps. In the Milky Way, these clumps have masses M cl <~ 5 × 10-2 of the GMC, radii r cl ~ 1 pc, and free-fall times τcl ~ 2 × 105 yr. We show that clumps inside GMCs should accrete at a modified Bondi accretion rate, which depends on clump mass as \\dot{M}_{cl}\\sim M_{cl}^{5/4}. This rate is initially rather slow, usually slower than the initial star formation rate inside the clump (we adopt the common assumption that inside the clump, \\dot{M}_*=\\epsilon _ffM_{cl}/\\tau _{cl}, with epsilonff ≈ 0.017). However, after ~2 GMC free-fall times τGMC, the clump accretion rate accelerates rapidly; formally, the clump can accrete the entire GMC in ~3τGMC. At the same time, the star formation rate accelerates, tracking the Bondi accretion rate. If the GMC is disrupted by feedback from the largest clump, half the stars in that clump form in the final τGMC before the GMC is disrupted. The theory predicts that the distribution of effective star formation rates, measured per GMC free-fall time, is broad, ranging from ~0.001 up to 0.1 or larger and that the mass spectrum of star clusters is flatter than that of clumps, consistent with observations.

  10. Spatially associated clump populations in Rosette from CO and dust maps

    NASA Astrophysics Data System (ADS)

    Veltchev, Todor V.; Ossenkopf-Okada, Volker; Stanchev, Orlin; Schneider, Nicola; Donkov, Sava; Klessen, Ralf S.

    2018-04-01

    Spatial association of clumps from different tracers turns out to be a valuable tool to determine the physical properties of molecular clouds. It provides a reliable estimate for the X-factors, serves to trace the density of clumps seen in column densities only, and allows one to measure the velocity dispersion of clumps identified in dust emission. We study the spatial association between clump populations, extracted by use of the GAUSSCLUMPS technique from 12CO (1-0), 13CO (1-0) line maps and Herschel dust-emission maps of the star-forming region Rosette, and analyse their physical properties. All CO clumps that overlap with another CO or dust counterpart are found to be gravitationally bound and located in the massive star-forming filaments of the molecular cloud. They obey a single mass-size relation M_cl∝ R_cl^γ with γ ≃ 3 (implying constant mean density) and display virtually no velocity-size relation. We interpret their population as low-density structures formed through compression by converging flows and still not evolved under the influence of self-gravity. The high-mass parts of their clump mass functions are fitted by a power law dN_cl/d log M_cl∝ M_cl^{Γ } and display a nearly Salpeter slope Γ ˜ -1.3. On the other hand, clumps extracted from the dust-emission map exhibit a shallower mass-size relation with γ = 2.5 and mass functions with very steep slopes Γ ˜ -2.3 even if associated with CO clumps. They trace density peaks of the associated CO clumps at scales of a few tenths of pc where no single density scaling law should be expected.

  11. Early dynamical evolution of young substructured clusters

    NASA Astrophysics Data System (ADS)

    Dorval, Julien; Boily, Christian

    2017-03-01

    Stellar clusters form with a high level of substructure, inherited from the molecular cloud and the star formation process. Evidence from observations and simulations also indicate the stars in such young clusters form a subvirial system. The subsequent dynamical evolution can cause important mass loss, ejecting a large part of the birth population in the field. It can also imprint the stellar population and still be inferred from observations of evolved clusters. Nbody simulations allow a better understanding of these early twists and turns, given realistic initial conditions. Nowadays, substructured, clumpy young clusters are usually obtained through pseudo-fractal growth and velocity inheritance. We introduce a new way to create clumpy initial conditions through a ''Hubble expansion'' which naturally produces self consistent clumps, velocity-wise. In depth analysis of the resulting clumps shows consistency with hydrodynamical simulations of young star clusters. We use these initial conditions to investigate the dynamical evolution of young subvirial clusters. We find the collapse to be soft, with hierarchical merging leading to a high level of mass segregation. The subsequent evolution is less pronounced than the equilibrium achieved from a cold collapse formation scenario.

  12. PREDICTED SIZES OF PRESSURE-SUPPORTED HI CLOUDS IN THE OUTSKIRTS OF THE VIRGO CLUSTER

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Burkhart, Blakesley; Loeb, Abraham

    Using data from the ALFALFA AGES Arecibo HI survey of galaxies and the Virgo cluster X-ray pressure profiles from XMM-Newton , we investigate the possibility that starless dark HI clumps, also known as “dark galaxies,” are supported by external pressure in the surrounding intercluster medium. We find that the starless HI clump masses, velocity dispersions, and positions allow these clumps to be in pressure equilibrium with the X-ray gas near the virial radius of the Virgo cluster. We predict the sizes of these clumps to range from 1 to 10 kpc, in agreement with the range of sizes found formore » spatially resolved HI starless clumps outside of Virgo. Based on the predicted HI surface density of the Virgo sources, as well as a sample of other similar resolved ALFALFA HI dark clumps with follow-up optical/radio observations, we predict that most of the HI dark clumps are on the cusp of forming stars. These HI sources therefore mark the transition between starless HI clouds and dwarf galaxies with stars.« less

  13. [Foliage clumping index of main vegetation types in Daxing'an Mountains, Northeast China].

    PubMed

    Huang, Ting; Fan, Wen Yi; Mao, Xue Gang; Yu, Ying

    2017-03-18

    The foliage clumping index quantifies the cluster degree of the leaf spatial distribution under random canopy. It is of comparable importance for establishment of ecological models. MODIS BRDF model parameter products (MCD43A1 data) and land cover types (MCD12Q1 data) were used in this study to simulate the reflectivity of the hot spots and dark spots, and calculate the normalized difference between hotspot and darkspot (NDHD) based on the Ross-Li semi-empirical model. Least square method was then used to simulate the relationship between NDHD and the foliage clumping index and foliage clumping index products of 500-m resolution in August 2014 were retrieved. Measurements of the foliage clumping index in Daxing'an Mountains were conducted by using the TRAC (Tracing Radiation and Architecture of Canopies) sampling instrument for mo-del validation and analysis. Results showed that it was a feasible algorithm to retrieve clumping index from MCD43A1 product with the correlation of simulated data and the measured data of significance (R 2 =0.8879). The MODIS near infrared wave band was more sensitive than that on red band to foliage clumping index change. With the increase of the solar zenith angle, the clumping index retrieved by Ross-Li model had a linear increase (R 2 =0.9699), which indicated that the foliage clumping index related to the solar zenith angle.

  14. Statistical clumped isotope signatures

    PubMed Central

    Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

  15. Massive Outflows Associated with ATLASGAL Clumps

    NASA Astrophysics Data System (ADS)

    Yang, A. Y.; Thompson, M. A.; Urquhart, J. S.; Tian, W. W.

    2018-03-01

    We have undertaken the largest survey for outflows within the Galactic plane using simultaneously observed {}13{CO} and {{{C}}}18{{O}} data. Out of a total of 919 ATLASGAL clumps, 325 have data suitable to identify outflows, and 225 (69% ± 3%) show high-velocity outflows. The clumps with detected outflows show significantly higher clump masses ({M}clump}), bolometric luminosities ({L}bol}), luminosity-to-mass ratios ({L}bol}/{M}clump}), and peak H2 column densities ({N}{{{H}}2}) compared to those without outflows. Outflow activity has been detected within the youngest quiescent clump (i.e., 70 μ {{m}} weak) in this sample, and we find that the outflow detection rate increases with {M}clump}, {L}bol}, {L}bol}/{M}clump}, and {N}{{{H}}2}, approaching 90% in some cases (UC H II regions = 93% ± 3%; masers = 86% ± 4%; HC H II regions = 100%). This high detection rate suggests that outflows are ubiquitous phenomena of massive star formation (MSF). The mean outflow mass entrainment rate implies a mean accretion rate of ∼ {10}-4 {M}ȯ {yr}}-1, in full agreement with the accretion rate predicted by theoretical models of MSF. Outflow properties are tightly correlated with {M}clump}, {L}bol}, and {L}bol}/{M}clump} and show the strongest relation with the bolometric clump luminosity. This suggests that outflows might be driven by the most massive and luminous source within the clump. The correlations are similar for both low-mass and high-mass outflows over 7 orders of magnitude, indicating that they may share a similar outflow mechanism. Outflow energy is comparable to the turbulent energy within the clump; however, we find no evidence that outflows increase the level of clump turbulence as the clumps evolve. This implies that the origin of turbulence within clumps is fixed before the onset of star formation.

  16. The rate and latency of star formation in dense, massive clumps in the Milky Way

    NASA Astrophysics Data System (ADS)

    Heyer, M.; Gutermuth, R.; Urquhart, J. S.; Csengeri, T.; Wienen, M.; Leurini, S.; Menten, K.; Wyrowski, F.

    2016-04-01

    Context. Newborn stars form within the localized, high density regions of molecular clouds. The sequence and rate at which stars form in dense clumps and the dependence on local and global environments are key factors in developing descriptions of stellar production in galaxies. Aims: We seek to observationally constrain the rate and latency of star formation in dense massive clumps that are distributed throughout the Galaxy and to compare these results to proposed prescriptions for stellar production. Methods: A sample of 24 μm-based Class I protostars are linked to dust clumps that are embedded within molecular clouds selected from the APEX Telescope Large Area Survey of the Galaxy. We determine the fraction of star-forming clumps, f∗, that imposes a constraint on the latency of star formation in units of a clump's lifetime. Protostellar masses are estimated from models of circumstellar environments of young stellar objects from which star formation rates are derived. Physical properties of the clumps are calculated from 870 μm dust continuum emission and NH3 line emission. Results: Linear correlations are identified between the star formation rate surface density, ΣSFR, and the quantities ΣH2/τff and ΣH2/τcross, suggesting that star formation is regulated at the local scales of molecular clouds. The measured fraction of star forming clumps is 23%. Accounting for star formation within clumps that are excluded from our sample due to 24 μm saturation, this fraction can be as high as 31%, which is similar to previous results. Dense, massive clumps form primarily low mass (<1-2 M⊙) stars with emergent 24 μm fluxes below our sensitivity limit or are incapable of forming any stars for the initial 70% of their lifetimes. The low fraction of star forming clumps in the Galactic center relative to those located in the disk of the Milky Way is verified. Full Tables 2-4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130

  17. Methane clumped isotopes: Progress and potential for a new isotopic tracer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Douglas, Peter M. J.; Stolper, Daniel A.; Eiler, John M.

    The isotopic composition of methane is of longstanding geochemical interest, with important implications for understanding hydrocarbon systems, atmospheric greenhouse gas concentrations, the global carbon cycle, and life in extreme environments. Recent analytical developments focusing on multiply substituted isotopologues (‘clumped isotopes’) are opening a potentially valuable new window into methane geochemistry. When methane forms in internal isotopic equilibrium, clumped isotopes can provide a direct record of formation temperature, making this property particularly valuable for identifying different methane origins. However, it has also become clear that in certain settings methane clumped isotope measurements record kinetic rather than equilibrium isotope effects. Here wemore » present a substantially expanded dataset of methane clumped isotope analyses, and provide a synthesis of the current interpretive framework for this parameter. We review different processes affecting methane clumped isotope compositions, describe the relationships between conventional isotope and clumped isotope data, and summarize the types of information that this measurement can provide in different Earth and planetary environments.« less

  18. Young Stellar Variability of GM Cephei by Circumstellar Dust Clumps

    NASA Astrophysics Data System (ADS)

    Huang, Po-Chieh; Chen, Wen-Ping; Hu, Chia-Ling; Burkhonov, Otabek; Ehgamberdiev, Shuhrat; Liu, Jinzhong; Naito, Hiroyuki; Pakstiene, Erika; Qvam, Jan Kare Trandem; Rätz, Stefanie; Semkov, Evgeni

    2018-04-01

    UX Orionis stars are a sub-type of Herbig Ae/be or T Tauri stars exhibiting sporadic extinction of stellar light due to circumstellar dust obscuration. GM Cep is such an UX Orionis star in the young (∼ 4 Myr) open cluster Trumpler 37 at ∼ 900 pc, showing a prominent infrared access, H-alpha emission, and flare activity. Our multi-color photometric monitoring from 2009 to 2016 showed (i) sporadic brightening on a time scale of days due to young stellar accretion, (ii) cyclic, but not strictly periodical, occultation events, each lasting for a couple months, with a probable recurrence time of about two years, (iii) normal dust reddening as the star became redder when dimmer, (iv) the unusual "blueing" phenomena near the brightness minima, during which the star appeared bluer when dimmer, and (v) a noticeable polarization, from 3 to 9 percent in g', r', and i' -bands. The occultation events may be caused by dust clumps, signifying the density inhomogeneity in a young stellar disk from grain coagulation to planetesimal formation. The level of polarization was anti-correlated with the brightness in the bright state, when the dust clump backscattered stellar light. We discussed two potential hypotheses: orbiting dust clumps versus dust clumps along a spiral arm structure.

  19. Molecular clumps photoevaporation in ionized regions

    NASA Astrophysics Data System (ADS)

    Decataldo, D.; Ferrara, A.; Pallottini, A.; Gallerani, S.; Vallini, L.

    2017-11-01

    We study the photoevaporation of molecular clumps exposed to a UV radiation field including hydrogen-ionizing photons (hν > 13.6 eV) produced by massive stars or quasars. We follow the propagation and collision of shock waves inside clumps and take into account self-shielding effects, determining the evolution of clump size and density with time. The structure of the ionization-photodissociation region is obtained for different initial clump masses (M = 0.01-104 M⊙) and impinging fluxes (G0 = 102-105 in units of the Habing flux). The cases of molecular clumps engulfed in the H II region of an OB star and clumps carried within quasar outflows are treated separately. We find that the clump undergoes in both cases an initial shock-contraction phase and a following expansion phase, which lets the radiation penetrate in until the clump is completely evaporated. Typical evaporation time-scales are ≃0.01 Myr in the stellar case and 0.1 Myr in the quasar case, where the clump mass is 0.1 M⊙ and 103 M⊙, respectively. We find that clump lifetimes in quasar outflows are compatible with their observed extension, suggesting that photoevaporation is the main mechanism regulating the size of molecular outflows.

  20. A Massive Prestellar Clump Hosting No High-mass Cores

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sanhueza, Patricio; Lu, Xing; Tatematsu, Ken’ichi

    The infrared dark cloud (IRDC) G028.23-00.19 hosts a massive (1500 M {sub ⊙}), cold (12 K), and 3.6–70 μ m IR dark clump (MM1) that has the potential to form high-mass stars. We observed this prestellar clump candidate with the Submillimeter Array (∼3.″5 resolution) and Jansky Very Large Array (∼2.″1 resolution) in order to characterize the early stages of high-mass star formation and to constrain theoretical models. Dust emission at 1.3 mm wavelength reveals five cores with masses ≤15 M {sub ⊙}. None of the cores currently have the mass reservoir to form a high-mass star in the prestellar phase.more » If the MM1 clump will ultimately form high-mass stars, its embedded cores must gather a significant amount of additional mass over time. No molecular outflows are detected in the CO (2-1) and SiO (5-4) transitions, suggesting that the SMA cores are starless. By using the NH{sub 3} (1, 1) line, the velocity dispersion of the gas is determined to be transonic or mildly supersonic (Δ V {sub nt}/Δ V {sub th} ∼ 1.1–1.8). The cores are not highly supersonic as some theories of high-mass star formation predict. The embedded cores are four to seven times more massive than the clump thermal Jeans mass and the most massive core (SMA1) is nine times less massive than the clump turbulent Jeans mass. These values indicate that neither thermal pressure nor turbulent pressure dominates the fragmentation of MM1. The low virial parameters of the cores (0.1–0.5) suggest that they are not in virial equilibrium, unless strong magnetic fields of ∼1–2 mG are present. We discuss high-mass star formation scenarios in a context based on IRDC G028.23-00.19, a study case believed to represent the initial fragmentation of molecular clouds that will form high-mass stars.« less

  1. Connecting Clump Sizes in Turbulent Disk Galaxies to Instability Theory

    NASA Astrophysics Data System (ADS)

    Fisher, David B.; Glazebrook, Karl; Abraham, Roberto G.; Damjanov, Ivana; White, Heidi A.; Obreschkow, Danail; Basset, Robert; Bekiaris, Georgios; Wisnioski, Emily; Green, Andy; Bolatto, Alberto D.

    2017-04-01

    In this letter we study the mean sizes of Hα clumps in turbulent disk galaxies relative to kinematics, gas fractions, and Toomre Q. We use ˜100 pc resolution HST images, IFU kinematics, and gas fractions of a sample of rare, nearby turbulent disks with properties closely matched to z˜ 1.5{--}2 main-sequence galaxies (the DYNAMO sample). We find linear correlations of normalized mean clump sizes with both the gas fraction and the velocity dispersion-to-rotation velocity ratio of the host galaxy. We show that these correlations are consistent with predictions derived from a model of instabilities in a self-gravitating disk (the so-called “violent disk instability model”). We also observe, using a two-fluid model for Q, a correlation between the size of clumps and self-gravity-driven unstable regions. These results are most consistent with the hypothesis that massive star-forming clumps in turbulent disks are the result of instabilities in self-gravitating gas-rich disks, and therefore provide a direct connection between resolved clump sizes and this in situ mechanism.

  2. HOW TO FIND YOUNG MASSIVE CLUSTER PROGENITORS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bressert, E.; Longmore, S.; Testi, L.

    2012-10-20

    We propose that bound, young massive stellar clusters form from dense clouds that have escape speeds greater than the sound speed in photo-ionized gas. In these clumps, radiative feedback in the form of gas ionization is bottled up, enabling star formation to proceed to sufficiently high efficiency so that the resulting star cluster remains bound even after gas removal. We estimate the observable properties of the massive proto-clusters (MPCs) for existing Galactic plane surveys and suggest how they may be sought in recent and upcoming extragalactic observations. These surveys will potentially provide a significant sample of MPC candidates that willmore » allow us to better understand extreme star-formation and massive cluster formation in the Local Universe.« less

  3. Physical Properties of Sub-galactic Clumps at 0.5 ≤ Z ≤ 1.5 in the UVUDF

    NASA Astrophysics Data System (ADS)

    Soto, Emmaris; de Mello, Duilia F.; Rafelski, Marc; Gardner, Jonathan P.; Teplitz, Harry I.; Koekemoer, Anton M.; Ravindranath, Swara; Grogin, Norman A.; Scarlata, Claudia; Kurczynski, Peter; Gawiser, Eric

    2017-03-01

    We present an investigation of clumpy galaxies in the Hubble Ultra Deep Field at 0.5≤slant z≤slant 1.5 in the rest-frame far-ultraviolet (FUV) using Hubble Space Telescope Wide Field Camera 3 broadband imaging in F225W, F275W, and F336W. An analysis of 1404 galaxies yields 209 galaxies that host 403 kpc scale clumps. These host galaxies appear to be typical star-forming galaxies, with an average of 2 clumps per galaxy and reaching a maximum of 8 clumps. We measure the photometry of the clumps and determine the mass, age, and star formation rates (SFR) using the spectral energy distribution fitting code FAST. We find that clumps make an average contribution of 19% to the total rest-frame FUV flux of their host galaxy. Individually, clumps contribute a median of 5% to the host galaxy SFR and an average of ˜4% to the host galaxy mass, with total clump contributions to the host galaxy stellar mass ranging widely from lower than 1% up to 93%. Clumps in the outskirts of galaxies are typically younger, with higher SFRs, than clumps in the inner regions. The results are consistent with clump migration theories in which clumps form through violent gravitational instabilities in gas-rich turbulent disks, eventually migrate toward the center of the galaxies, and coalesce into the bulge.

  4. Dynamics of Clumps in Saturn's F Ring

    NASA Astrophysics Data System (ADS)

    Showalter, M. R.

    1997-07-01

    An exhaustive analysis of the Voyager image data sets reveals the F Ring to be the most dynamic ring in the solar system. Principal properties are as follows. (1) At any given time, the ring holds 2--3 extremely bright clumps (each several times brighter than the local average for the ring) and perhaps 20--40 identifiable smaller clumps. In practice, the closer one looks at the rings, the finer detail one finds. (2) No major clumps persist for the nine months between the Voyager encounters, but most survive for the ~ 6 weeks they can be detected during a single encounter. (3) A few major clumps are seen to appear or disappear very quickly, on time scales as brief as days. One clump appears to spread longitudinally after it first appears, but other clumps stay roughly fixed in longitudinal extend. The processes behind clump formation and destruction are unknown. (4) Clumps propagate at different mean motions; there is no evidence for a discrete set of rates that might correspond to the individual ``strands'' described in some models. Motions range from 581.81(deg) /day to 582.41(deg) /day, implying that the F Ring's clumps span a semimajor axis range of ~ 80 km. (5) Some sections of the ring show a distinct 3.2(deg) periodicity in clump spacing, as expected from the gravitational perturbations by Prometheus. Others do not. (6) In the Voyager 2 images, a single prominent clump seems to eject smaller clumps behind it on time scales of ~ 2 weeks. However, nothing analogous is observed in Voyager 1 data.

  5. Kinematics and dynamics of the MKW/AWM poor clusters

    NASA Technical Reports Server (NTRS)

    Beers, Timothy C.; Kriessler, Jeffrey R.; Bird, Christina M.; Huchra, John P.

    1995-01-01

    We report 472 new redshifts for 416 galaxies in the regions of the 23 poor clusters of galaxies originally identified by Morgan, Kayser, and White (MKW), and Albert, White, and Morgan (AWM). Eighteen of the poor clusters now have 10 or more available redshifts within 1.5/h Mpc of the central galaxy; 11 clusters have at least 20 available redshifts. Based on the 21 clusters for which we have sufficient velocity information, the median velocity scale is 336 km/s, a factor of 2 smaller than found for rich clusters. Several of the poor clusters exhibit complex velocity distributions due to the presence of nearby clumps of galaxies. We check on the velocity of the dominant galaxy in each poor cluster relative to the remaining cluster members. Significantly high relative velocities of the dominant galaxy are found in only 4 of 21 poor clusters, 3 of which we suspect are due to contamination of the parent velocity distribution. Several statistical tests indicate that the D/cD galaxies are at the kinematic centers of the parent poor cluster velocity distributions. Mass-to-light ratios for 13 of the 15 poor clusters for which we have the required data are in the range 50 less than or = M/L(sub B(0)) less than or = 200 solar mass/solar luminosity. The complex nature of the regions surrounding many of the poor clusters suggests that these groupings may represent an early epoch of cluster formation. For example, the poor clusters MKW7 and MKWS are shown to be gravitationally bound and likely to merge to form a richer cluster within the next several Gyrs. Eight of the nine other poor clusters for which simple two-body dynamical models can be carried out are consistent with being bound to other clumps in their vicinity. Additional complex systems with more than two gravitationally bound clumps are observed among the poor clusters.

  6. HIGH-RESOLUTION STUDY OF THE CLUSTER COMPLEXES IN A LENSED SPIRAL AT REDSHIFT 1.5: CONSTRAINTS ON THE BULGE FORMATION AND DISK EVOLUTION

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Adamo, Angela; Oestlin, G.; Zackrisson, E.

    2013-04-01

    We analyze the clump population of the spiral galaxy Sp 1149 at redshift 1.5. Located behind the galaxy cluster MACS J1149.5+2223, Sp 1149 has been significantly magnified allowing us to study the galaxy on physical scales down to {approx}100 pc. The galaxy cluster frame is among the targets of the Cluster Lensing And Supernova survey with Hubble (CLASH), an ongoing Hubble Space Telescope (HST) Multi-Cycle Treasury program. We have used the publicly available multi-band imaging data set to reconstruct the spectral energy distributions of the clumps in Sp 1149, and derive, by means of stellar evolutionary models, their physical properties.more » We found that 40% of the clumps observed in Sp 1149 are older than 30 Myr and can be as old as 300 Myr. These are also the more massive (luminous) clumps in the galaxy. Among the complexes in the local reference sample, the star-forming knots in luminous blue compact galaxies could be considered progenitor analogs of these long-lived clumps. The remaining 60% of clumps have colors comparable to local cluster complexes, suggesting a similar young age. We observe that the Sp 1149 clumps follow the M{proportional_to}R {sup 2} relation similar to local cluster complexes, suggesting similar formation mechanisms although they may have different initial conditions (e.g., higher gas surface densities). We suggest that the galaxy is experiencing a slow decline in star formation rate and a likely transitional phase toward a more quiescent star formation mode. The older clumps have survived between 6 and 20 dynamical times and are all located at projected distances smaller than 4 kpc from the center. Their current location suggests migration toward the center and the possibility of being the building blocks of the bulge. On the other hand, the dynamical timescale of the younger clumps is significantly shorter, meaning that they are quite close to their birthplace. We show that the clumps of Sp 1149 may account for the expected metal

  7. Radiation hydrodynamics of super star cluster formation

    NASA Astrophysics Data System (ADS)

    Tsang, Benny Tsz Ho; Milos Milosavljevic

    2018-01-01

    Throughout the history of the Universe, the nuclei of super star clusters represent the most active sites for star formation. The high densities of massive stars within the clusters produce intense radiation that imparts both energy and momentum on the surrounding star-forming gas. Theoretical claims based on idealized geometries have claimed the dominant role of radiation pressure in controlling the star formation activity within the clusters. In order for cluster formation simulations to be reliable, numerical schemes have to be able to model accurately the radiation flows through the gas clumps at the cluster nuclei with high density contrasts. With a hybrid Monte Carlo radiation transport module we developed, we performed 3D radiation hydrodynamical simulations of super star cluster formation in turbulent clouds. Furthermore, our Monte Carlo radiation treatment provides a native capability to produce synthetic observations, which allows us to predict observational indicators and to inform future observations. We found that radiation pressure has definite, but minor effects on limiting the gas supply for star formation, and the final mass of the most massive cluster is about one million solar masses. The ineffective forcing was due to the density variations inside the clusters, i.e. radiation takes the paths of low densities and avoids forcing on dense clumps. Compared to a radiation-free control run, we further found that the presence of radiation amplifies the density variations. The core of the resulting cluster has a high stellar density, about the threshold required for stellar collisions and merging. The very massive star that form from the stellar merging could continue to gain mass from the surrounding gas reservoir that is gravitationally confined by the deep potential of the cluster, seeding the potential formation of a massive black hole.

  8. ON HIGHLY CLUMPED MAGNETIC WIND MODELS FOR COOL EVOLVED STARS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Harper, G. M.

    2010-09-10

    Recently, it has been proposed that the winds of non-pulsating and non-dusty K and M giants and supergiants may be driven by some form of magnetic pressure acting on highly clumped wind material. While many researchers believe that magnetic processes are responsible for cool evolved stellar winds, existing MHD and Alfven wave-driven wind models have magnetic fields that are essentially radial and tied to the photosphere. The clumped magnetic wind scenario is quite different in that the magnetic flux is also being carried away from the star with the wind. We test this clumped wind hypothesis by computing continuum radiomore » fluxes from the {zeta} Aur semiempirical model of Baade et al., which is based on wind-scattered line profiles. The radio continuum opacity is proportional to the electron density squared, while the line scattering opacity is proportional to the gas density. This difference in proportionality provides a test for the presence of large clumping factors. We derive the radial distribution of clump factors (CFs) for {zeta} Aur by comparing the nonthermal pressures required to produce the semiempirical velocity distribution with the expected thermal pressures. The CFs are {approx}5 throughout the sub-sonic inner wind region and then decline outward. These implied clumping factors lead to excess radio emission at 2.0 cm, while at 6.2 cm it improves agreement with the smooth unclumped model. Smaller clumping factors of {approx}2 lead to better overall agreement but also increase the discrepancy at 2 cm. These results do not support the magnetic clumped wind hypothesis and instead suggest that inherent uncertainties in the underlying semiempirical model probably dominate uncertainties in predicted radio fluxes. However, new ultraviolet line and radio continuum observations are needed to test the new generations of inhomogeneous magnetohydrodynamic wind models.« less

  9. Distance biases in the estimation of the physical properties of Hi-GAL compact sources - I. Clump properties and the identification of high-mass star-forming candidates

    NASA Astrophysics Data System (ADS)

    Baldeschi, Adriano; Elia, D.; Molinari, S.; Pezzuto, S.; Schisano, E.; Gatti, M.; Serra, A.; Merello, M.; Benedettini, M.; Di Giorgio, A. M.; Liu, J. S.

    2017-04-01

    The degradation of spatial resolution in star-forming regions, observed at large distances (d ≳ 1 kpc) with Herschel, can lead to estimates of the physical parameters of the detected compact sources (clumps), which do not necessarily mirror the properties of the original population of cores. This paper aims at quantifying the bias introduced in the estimation of these parameters by the distance effect. To do so, we consider Herschel maps of nearby star-forming regions taken from the Herschel Gould Belt survey, and simulate the effect of increased distance to understand what amount of information is lost when a distant star-forming region is observed with Herschel resolution. In the maps displaced to different distances we extract compact sources, and we derive their physical parameters as if they were original Herschel infrared Galactic Plane Survey maps of the extracted source samples. In this way, we are able to discuss how the main physical properties change with distance. In particular, we discuss the ability of clumps to form massive stars: we estimate the fraction of distant sources that are classified as high-mass stars-forming objects due to their position in the mass versus radius diagram, that are only 'false positives'. We also give a threshold for high-mass star formation M>1282 (r/ [pc])^{1.42} M_{⊙}. In conclusion, this paper provides the astronomer dealing with Herschel maps of distant star-forming regions with a set of prescriptions to partially recover the character of the core population in unresolved clumps.

  10. Clumps in the F Ring

    NASA Image and Video Library

    2004-03-12

    Scientists have only a rough idea of the lifetime of clumps in Saturn's rings - a mystery that Cassini may help answer. The latest images taken by the Cassini-Huygens spacecraft show clumps seemingly embedded within Saturn's narrow, outermost F ring. The narrow angle camera took the images on Feb. 23, 2004, from a distance of 62.9 million kilometers (39 million miles). The two images taken nearly two hours apart show these clumps as they revolve about the planet. The small dot at center right in the second image is one of Saturn's small moons, Janus, which is 181 kilometers, (112 miles) across. Like all particles in Saturn's ring system, these clump features orbit the planet in the same direction in which the planet rotates. This direction is clockwise as seen from Cassini's southern vantage point below the ring plane. Two clumps in particular, one of them extended, is visible in the upper part of the F ring in the image on the left, and in the lower part of the ring in the image on the right. Other knot-like irregularities in the ring's brightness are visible in the image on the right. The core of the F ring is about 50 kilometers (31miles) wide, and from Cassini's current distance, is not fully visible. The imaging team enhanced the contrast of the images and magnified them to aid visibility of the F ring and the clump features. The camera took the images with the green filter, which is centered at 568 nanometers. The image scale is 377 kilometers (234 miles) per pixel. NASA's two Voyager spacecraft that flew past Saturn in 1980 and 1981 were the first to see these clumps. The Voyager data suggest that the clumps change very little and can be tracked as they orbit for 30 days or more. No clump survived from the time of the first Voyager flyby to the Voyager 2 flyby nine months later. Scientists are not certain of the cause of these features. Among the theories proposed are meteoroid bombardments and inter-particle collisions in the F ring. http

  11. CHEMICAL DIAGNOSTICS OF THE MASSIVE STAR CLUSTER-FORMING CLOUD G33.92+0.11. I. {sup 13}CS, CH{sub 3}OH, CH{sub 3}N, OCS, H{sub 2}S, SO{sub 2}, and SiO

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Minh, Young Chol; Liu, Hauyu Baobab; Galvań-Madrid, Roberto

    2016-06-20

    Large chemical diversity was found in the gas clumps associated with the massive star cluster-forming G33.92+0.11 region with sub-arcsecond angular resolution (0.″6–0.″8) observations with ALMA. The most prominent gas clumps are associated with the dust emission peaks A1, A2, and A5. The close correlation between CH{sub 3}OH and OCS in the emission distributions strongly suggests that these species share a common origin of hot core grain mantle evaporation. The latest generation of star clusters are forming in the A5 clump, as indicated by multiple SiO outflows and its rich hot core chemistry. We also found a narrow SiO emission associatedmore » with the outflows, which may trace a cooled component of the outflows. Part of the chemical complexity may have resulted from the accreting gas from the ambient clouds, especially in the northern part of A1 and the southern part of A2. The chemical diversity found in this region is believed to mainly result from the different chemical evolutionary timescales of massive star formation. In particular, the abundance ratio between CH{sub 3}OH and CH{sub 3}CN may be a good chemical clock for the early phase of star formation.« less

  12. Root-Knot Nematodes Exhibit Strain-Specific Clumping Behavior That Is Inherited as a Simple Genetic Trait

    PubMed Central

    Wang, Congli; Lower, Steven; Thomas, Varghese P.; Williamson, Valerie M.

    2010-01-01

    Root-knot nematodes are obligate parasites of a wide range of plant species and can feed only on the cytoplasm of living plant cells. In the absence of a suitable plant host, infective juveniles of strain VW9 of the Northern root-knot nematode, Meloidogyne hapla, when dispersed in Pluronic F-127 gel, aggregate into tight, spherical clumps containing thousands of worms. Aggregation or clumping behavior has been observed in diverse genera in the phylum Nematoda spanning free-living species such as Caenorhabditis elegans as well as both plant and animal parasites. Clumping behavior differs between strains of M. hapla and occurs with other species within this genus where strain-specific differences in clumping ability are also apparent. Exposure of M. hapla juveniles to a gradient formed using low levels of cyanide promotes formation of clumps at a preferred cyanide level. Analysis of F2 lines from a cross of M. hapla strains that differ in clump-forming behavior reveals that the behavior segregates as a single, major locus that can be positioned on the genetic map of this nematode. Clumping behavior may be a survival strategy whose importance and function depend on the niche of the nematode strain or species. PMID:21151553

  13. Probing the Building Blocks of Galactic Disks: An Analysis of Ultraviolet Clumps

    NASA Astrophysics Data System (ADS)

    Soto, Emmaris

    The universe is filled with a diversity of galaxies; however, despite these diversities we are able to group galaxies into morphological categories, such as Hubble types, that may indicate different paths of evolution. In order to understand the evolution of galaxies, such as our own Milk Way, it is necessary to study the underlying star formation over cosmic time. At high redshift (z>2) star-forming galaxies reveal asymmetric and clumpy morphologies. However, the evolutionary process which takes clumpy galaxies from z>2 to the smooth axially symmetric Hubble-type galaxies in place at z˜0.5 is still unknown. Therefore, it is vital to make a connection between the morphologies of galaxies at the peak epoch of cosmic star formation at z˜2 with the galaxies observed in the local universe to better understand the mechanisms that led to their evolution. To address this and chronicle the progression of galaxy evolution, deep high resolution multi-wavelength data is used to study galaxies across cosmic time. This dissertation provides a detailed study of clumpy star-forming galaxies at intermediate redshifts, 0.5 ≤ z ≤ 1.5, focusing on sub-galactic regions of star formation which provide a mechanism to explain the evolution of clumpy galaxies to the spiral galaxies we observe today. We developed a clump-finding algorithm to select a sample of clumpy galaxies from the Ultraviolet Ultra Deep Field (UVUDF). The UVUDF was the first deep image (˜28 AB mag) ever taken with the Hubble Space Telescope (HST) showing the rest-frame far-ultraviolet (FUV, 1500A) at intermediate-z. The rest-frame FUV probes the young star-forming regions which are often seen in clumpy galaxies at high redshift. We identified 209 clumpy galaxies (hereafter host galaxies) from 1,404 candidates at intermediate redshifts. We used the HST Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS) broadband images from the UVUDF with observed near-ultraviolet, optical, and near

  14. Testing the Larson relations in massive clumps

    NASA Astrophysics Data System (ADS)

    Traficante, A.; Duarte-Cabral, A.; Elia, D.; Fuller, G. A.; Merello, M.; Molinari, S.; Peretto, N.; Schisano, E.; Di Giorgio, A.

    2018-06-01

    We tested the validity of the three Larson relations in a sample of 213 massive clumps selected from the Herschel infrared Galactic Plane (Hi-GAL) survey, also using data from the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey of 3-mm emission lines. The clumps are divided into five evolutionary stages so that we can also discuss the Larson relations as a function of evolution. We show that this ensemble does not follow the three Larson relations, regardless of the clump's evolutionary phase. A consequence of this breakdown is that the dependence of the virial parameter αvir on mass (and radius) is only a function of the gravitational energy, independent of the kinetic energy of the system; thus, αvir is not a good descriptor of clump dynamics. Our results suggest that clumps with clear signatures of infall motions are statistically indistinguishable from clumps with no such signatures. The observed non-thermal motions are not necessarily ascribed to turbulence acting to sustain the gravity, but they might be a result of the gravitational collapse at the clump scales. This seems to be particularly true for the most massive (M ≥ 1000 M⊙) clumps in the sample, where exceptionally high magnetic fields might not be enough to stabilize the collapse.

  15. Spiral-arm instability: giant clump formation via fragmentation of a galactic spiral arm

    NASA Astrophysics Data System (ADS)

    Inoue, Shigeki; Yoshida, Naoki

    2018-03-01

    Fragmentation of a spiral arm is thought to drive the formation of giant clumps in galaxies. Using linear perturbation analysis for self-gravitating spiral arms, we derive an instability parameter and define the conditions for clump formation. We extend our analysis to multicomponent systems that consist of gas and stars in an external potential. We then perform numerical simulations of isolated disc galaxies with isothermal gas, and compare the results with the prediction of our analytic model. Our model describes accurately the evolution of the spiral arms in our simulations, even when spiral arms dynamically interact with one another. We show that most of the giant clumps formed in the simulated disc galaxies satisfy the instability condition. The clump masses predicted by our model are in agreement with the simulation results, but the growth time-scale of unstable perturbations is overestimated by a factor of a few. We also apply our instability analysis to derive scaling relations of clump properties. The expected scaling relation between the clump size, velocity dispersion, and circular velocity is slightly different from that given by the Toomre instability analyses, but neither is inconsistent with currently available observations. We argue that the spiral-arm instability is a viable formation mechanism of giant clumps in gas-rich disc galaxies.

  16. Steps toward identifying a biogeochemical signal in non-equilibrium methane clumped isotope measurements

    NASA Astrophysics Data System (ADS)

    Douglas, P. M.; Eiler, J. M.; Sessions, A. L.; Dawson, K.; Walter Anthony, K. M.; Smith, D. A.; Lloyd, M. K.; Yanay, E.

    2016-12-01

    Microbially produced methane is a globally important greenhouse gas, energy source, and biological substrate. Methane clumped isotope measurements have recently been developed as a new analytical tool for understanding the source of methane in different environments. When methane forms in isotopic equilibrium clumped isotope values are determined by formation temperature, but in many cases microbial methane clumped isotope values deviate strongly from expected equilibrium values. Indeed, we observe a very wide range of clumped isotope values in microbial methane, which are likely strongly influenced by kinetic isotope effects, but thus far the biological and environmental parameters controlling this variability are not understood. We will present data from both culture experiments and natural environments to explore patterns of variability in non-equilibrium clumped isotope values on temporal and spatial scales. In methanogen batch cultures sampled at different time points along a growth curve we observe significant variability in clumped isotope values, with values decreasing from early to late exponential growth. Clumped isotope values then increase during stationary growth. This result is consistent with previous work suggesting that differences in the reversibility of methanogenesis related to metabolic rates control non-equilibrium clumped isotope values. Within single lakes in Alaska and Sweden we observe substantial variability in clumped isotope values on the order of 5‰. Lower clumped isotope values are associated with larger 2H isotopic fractionation between water and methane, which is also consistent with a kinetic isotope effect determined by the reversibility of methanogenesis. Finally, we analyzed a time-series clumped isotope compositions of methane emitted from two seeps in an Alaskan lake over several months. Temporal variability in these seeps is on the order of 2‰, which is much less than the observed spatial variability within the lake

  17. Rotation in young massive star clusters

    NASA Astrophysics Data System (ADS)

    Mapelli, Michela

    2017-05-01

    Hydrodynamical simulations of turbulent molecular clouds show that star clusters form from the hierarchical merger of several sub-clumps. We run smoothed-particle hydrodynamics simulations of turbulence-supported molecular clouds with mass ranging from 1700 to 43 000 M⊙. We study the kinematic evolution of the main cluster that forms in each cloud. We find that the parent gas acquires significant rotation, because of large-scale torques during the process of hierarchical assembly. The stellar component of the embedded star cluster inherits the rotation signature from the parent gas. Only star clusters with final mass < few × 100 M⊙ do not show any clear indication of rotation. Our simulated star clusters have high ellipticity (˜0.4-0.5 at t = 4 Myr) and are subvirial (Qvir ≲ 0.4). The signature of rotation is stronger than radial motions due to subvirial collapse. Our results suggest that rotation is common in embedded massive (≳1000 M⊙) star clusters. This might provide a key observational test for the hierarchical assembly scenario.

  18. Interacting Star Clusters

    NASA Astrophysics Data System (ADS)

    Gieles, M.

    2013-06-01

    The early evolution of star cluster formation is a complicated phase in which several astrophysical processes with different time-scales operate simultaneously. From kinematical data of the young massive cluster R136 it was recently found that the cluster is in virial equilibrium; despite its young age it has already settled in a dynamical equilibrium. Somewhat surprisigly, about a quarter of the (kinetic) energy is in a rotational component. From HST observations of R136 a small clump of stars to the North-East of R136 was found, with indications that this clump is interacting/merging with R136. In this talk I will discuss whether these two observational results should be connected, i.e. whether the rotation signal is due to an ongoing "dry" interaction. The results are illustrated with a suite of N-body simulations of R136 like systems.

  19. Astrochemical Properties of Planck Cold Clumps

    NASA Astrophysics Data System (ADS)

    Tatematsu, Ken'ichi; Liu, Tie; Ohashi, Satoshi; Sanhueza, Patricio; Nguyen Lu'o'ng, Quang; Hirota, Tomoya; Liu, Sheng-Yuan; Hirano, Naomi; Choi, Minho; Kang, Miju; Thompson, Mark A.; Fuller, Gary; Wu, Yuefang; Li, Di; Di Francesco, James; Kim, Kee-Tae; Wang, Ke; Ristorcelli, Isabelle; Juvela, Mika; Shinnaga, Hiroko; Cunningham, Maria; Saito, Masao; Lee, Jeong-Eun; Tóth, L. Viktor; He, Jinhua; Sakai, Takeshi; Kim, Jungha; JCMT Large Program "SCOPE" Collaboration; TRAO Key Science Program "TOP" Collaboration

    2017-02-01

    We observed 13 Planck cold clumps with the James Clerk Maxwell Telescope/SCUBA-2 and with the Nobeyama 45 m radio telescope. The N2H+ distribution obtained with the Nobeyama telescope is quite similar to SCUBA-2 dust distribution. The 82 GHz HC3N, 82 GHz CCS, and 94 GHz CCS emission are often distributed differently with respect to the N2H+ emission. The CCS emission, which is known to be abundant in starless molecular cloud cores, is often very clumpy in the observed targets. We made deep single-pointing observations in DNC, HN13C, N2D+, and cyclic-C3H2 toward nine clumps. The detection rate of N2D+ is 50%. Furthermore, we observed the NH3 emission toward 15 Planck cold clumps to estimate the kinetic temperature, and confirmed that most targets are cold (≲20 K). In two of the starless clumps we observed, the CCS emission is distributed as it surrounds the N2H+ core (chemically evolved gas), which resembles the case of L1544, a prestellar core showing collapse. In addition, we detected both DNC and N2D+. These two clumps are most likely on the verge of star formation. We introduce the chemical evolution factor (CEF) for starless cores to describe the chemical evolutionary stage, and analyze the observed Planck cold clumps.

  20. Combinatorial effects on clumped isotopes and their significance in biogeochemistry

    NASA Astrophysics Data System (ADS)

    Yeung, Laurence Y.

    2016-01-01

    The arrangement of isotopes within a collection of molecules records their physical and chemical histories. Clumped-isotope analysis interrogates these arrangements, i.e., how often rare isotopes are bound together, which in many cases can be explained by equilibrium and/or kinetic isotope fractionation. However, purely combinatorial effects, rooted in the statistics of pairing atoms in a closed system, are also relevant, and not well understood. Here, I show that combinatorial isotope effects are most important when two identical atoms are neighbors on the same molecule (e.g., O2, N2, and D-D clumping in CH4). When the two halves of an atom pair are either assembled with different isotopic preferences or drawn from different reservoirs, combinatorial effects cause depletions in clumped-isotope abundance that are most likely between zero and -1‰, although they could potentially be -10‰ or larger for D-D pairs. These depletions are of similar magnitude, but of opposite sign, to low-temperature equilibrium clumped-isotope effects for many small molecules. Enzymatic isotope-pairing reactions, which can have site-specific isotopic fractionation factors and atom reservoirs, should express this class of combinatorial isotope effect, although it is not limited to biological reactions. Chemical-kinetic isotope effects, which are related to a bond-forming transition state, arise independently and express second-order combinatorial effects related to the abundance of the rare isotope. Heteronuclear moeties (e.g., Csbnd O and Csbnd H), are insensitive to direct combinatorial influences, but secondary combinatorial influences are evident. In general, both combinatorial and chemical-kinetic factors are important for calculating and interpreting clumped-isotope signatures of kinetically controlled reactions. I apply this analytical framework to isotope-pairing reactions relevant to geochemical oxygen, carbon, and nitrogen cycling that may be influenced by combinatorial

  1. A Deuteration Survey of Starless Clumps in GemOB1 and the First Quadrant

    NASA Astrophysics Data System (ADS)

    Henrici, Andrew; Shirley, Yancy L.; Svoboda, Brian

    2018-01-01

    One very strong chemical process in star-forming regions is the fractionation of deuterium in molecules, which results in an increase in the deuterium ratio many orders of magnitude over the ISM [D]/[H] ratio and provides a chemical probe of cold, dense regions. Recent maps of dust continuum emission at (sub)millimeter wavelengths have identified tens of thousands of dense clumps of gas and dust. By comparing these regions to infrared and radio surveys, we have identified starless clump candidates which have no evidence for embedded star formation. These objects represent the earliest phase of star formation throughout the Milky Way. One benefit of the Milky Way surveys is that it is also possible to study the chemistry of entire core and clump populations within a single cloud. We used the 10m Heinrich Hertz Submillimeter Telescope to survey starless clump candidates in the First Quadrant identified from the Bolocam Galactic Plane Survey 1.1 mm continuum in the deuterated molecular transitions of DCO+ 3-2 and N2D+ 3-2. We also survey the entire clump population of the Gemini OB1 molecular cloud. In both surveys, we compared detection statistics and compare deuteration fraction to physical properties of the clumps and their evolutionary stage. High resolution ALMA observations of 9 starless clump candidates of the same lines are used to analyze how the cold deuterated gas is spatially distributed in these clumps.

  2. An ALMA Archival Study of the Clump Mass Function in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Brunetti, Nathan

    2017-11-01

    This thesis presents 1.3 mm and 3.1 mm continuum maps of seven star forming regions within the Large Magellanic Cloud (LMC) as observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). The data were taken as part of six projects retrieved from the ALMA public archive plus one project observed specifically for this work. We developed a technique to combine Band 3 and Band 6 maps to estimate dust-only emission corrected for free-free emission contamination. We also present an automated clean masking script, with a listing of the code, which we adapted and used for all of the imaging in this thesis. From these observations we identify 32 molecular clumps in the LMC and estimate their total mass from their dust emission. We derive a cumulative clump mass function (N(≥M) ≈ M(α+1)) and fit it with a double power law to find α_low = -1.76+0.07-0.1, α_high = -3.3+0.3-0.6, and a break mass of 2500+700-300 M⊙. Comparing to the clump mass function derived by Indebetouw et al. (2013) from carbon monoxide spectral line emission for 30 Doradus-10 shows a consistent mass range of clumps between 205 M⊙ and 5740 M⊙ as well as consistency between their single power law fit and our low mass power law index. Also comparing to core and clump mass functions from several star forming regions in the Milky Way we find consistency between most of their high mass indices and our low mass index, which is where the clump mass ranges overlap.

  3. Astrochemical Properties of Planck Cold Clumps

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tatematsu, Ken’ichi; Sanhueza, Patricio; Nguyễn Lu’o’ng, Quang

    We observed 13 Planck cold clumps with the James Clerk Maxwell Telescope/SCUBA-2 and with the Nobeyama 45 m radio telescope. The N{sub 2}H{sup +} distribution obtained with the Nobeyama telescope is quite similar to SCUBA-2 dust distribution. The 82 GHz HC{sub 3}N, 82 GHz CCS, and 94 GHz CCS emission are often distributed differently with respect to the N{sub 2}H{sup +} emission. The CCS emission, which is known to be abundant in starless molecular cloud cores, is often very clumpy in the observed targets. We made deep single-pointing observations in DNC, HN{sup 13}C, N{sub 2}D{sup +}, and cyclic-C{sub 3}H{sub 2}more » toward nine clumps. The detection rate of N{sub 2}D{sup +} is 50%. Furthermore, we observed the NH{sub 3} emission toward 15 Planck cold clumps to estimate the kinetic temperature, and confirmed that most targets are cold (≲20 K). In two of the starless clumps we observed, the CCS emission is distributed as it surrounds the N{sub 2}H{sup +} core (chemically evolved gas), which resembles the case of L1544, a prestellar core showing collapse. In addition, we detected both DNC and N{sub 2}D{sup +}. These two clumps are most likely on the verge of star formation. We introduce the chemical evolution factor (CEF) for starless cores to describe the chemical evolutionary stage, and analyze the observed Planck cold clumps.« less

  4. CLUMPY GALAXIES IN CANDELS. I. THE DEFINITION OF UV CLUMPS AND THE FRACTION OF CLUMPY GALAXIES AT 0.5 < z < 3

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Guo, Yicheng; Koo, David C.; Barro, Guillermo

    Although giant clumps of stars are thought to be crucial to galaxy formation and evolution, the most basic demographics of clumps are still uncertain, mainly because the definition of clumps has not been thoroughly discussed. In this paper, we carry out a study of the basic demographics of clumps in star-forming galaxies at 0.5 < z < 3, using our proposed physical definition that UV-bright clumps are discrete star-forming regions that individually contribute more than 8% of the rest-frame UV light of their galaxies. Clumps defined this way are significantly brighter than the H II regions of nearby large spiral galaxies,more » either individually or blended, when physical spatial resolution and cosmological dimming are considered. Under this definition, we measure the fraction of star-forming galaxies that have at least one off-center clump (f {sub clumpy}) and the contributions of clumps to the rest-frame UV light and star formation rate (SFR) of star-forming galaxies in the CANDELS/GOODS-S and UDS fields, where our mass-complete sample consists of 3239 galaxies with axial ratio q > 0.5. The redshift evolution of f {sub clumpy} changes with the stellar mass (M {sub *}) of the galaxies. Low-mass (log (M {sub *}/M {sub ☉}) < 9.8) galaxies keep an almost constant f {sub clumpy} of ∼60% from z ∼ 3 to z ∼ 0.5. Intermediate-mass and massive galaxies drop their f {sub clumpy} from 55% at z ∼ 3 to 40% and 15%, respectively, at z ∼ 0.5. We find that (1) the trend of disk stabilization predicted by violent disk instability matches the f {sub clumpy} trend of massive galaxies; (2) minor mergers are a viable explanation of the f {sub clumpy} trend of intermediate-mass galaxies at z < 1.5, given a realistic observability timescale; and (3) major mergers are unlikely responsible for the f {sub clumpy} trend in all masses at z < 1.5. The clump contribution to the rest-frame UV light of star-forming galaxies shows a broad peak around galaxies with log (M {sub *}/M

  5. Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

    NASA Astrophysics Data System (ADS)

    Bekki, Kenji

    2017-05-01

    Most old globular clusters (GCs) in the Galaxy are observed to have internal chemical abundance spreads in light elements. We discuss a new GC formation scenario based on hierarchical star formation within fractal molecular clouds. In the new scenario, a cluster of bound and unbound star clusters ('star cluster complex', SCC) that have a power-law cluster mass function with a slope (β) of 2 is first formed from a massive gas clump developed in a dwarf galaxy. Such cluster complexes and β = 2 are observed and expected from hierarchical star formation. The most massive star cluster ('main cluster'), which is the progenitor of a GC, can accrete gas ejected from asymptotic giant branch (AGB) stars initially in the cluster and other low-mass clusters before the clusters are tidally stripped or destroyed to become field stars in the dwarf. The SCC is initially embedded in a giant gas hole created by numerous supernovae of the SCC so that cold gas outside the hole can be accreted on to the main cluster later. New stars formed from the accreted gas have chemical abundances that are different from those of the original SCC. Using hydrodynamical simulations of GC formation based on this scenario, we show that the main cluster with the initial mass as large as [2-5] × 105 M⊙ can accrete more than 105 M⊙ gas from AGB stars of the SCC. We suggest that merging of hierarchical SSCs can play key roles in stellar halo formation around GCs and self-enrichment processes in the early phase of GC formation.

  6. Factors influencing platelet clumping during peripheral blood hematopoietic stem cell collection

    PubMed Central

    Mathur, Gagan; Bell, Sarah L.; Collins, Laura; Nelson, Gail A.; Knudson, C. Michael; Schlueter, Annette J.

    2018-01-01

    BACKGROUND Platelet clumping is a common occurrence during peripheral blood hematopoietic stem cell (HSC) collection using the Spectra Optia mononuclear cell (MNC) protocol. If clumping persists, it may prevent continuation of the collection and interfere with proper MNC separation. This study is the first to report the incidence of clumping, identify precollection factors associated with platelet clumping, and describe the degree to which platelet clumping interferes with HSC product yield. STUDY DESIGN AND METHODS In total, 258 HSC collections performed on 116 patients using the Optia MNC protocol were reviewed. Collections utilized heparin in anticoagulant citrate dextrose to facilitate large-volume leukapheresis. Linear and logistic regression models were utilized to determine which precollection factors were predictive of platelet clumping and whether clumping was associated with product yield or collection efficiency. RESULTS Platelet clumping was observed in 63% of collections. Multivariable analysis revealed that a lower white blood cell count was an independent predictor of clumping occurrence. Chemotherapy mobilization and a lower peripheral blood CD34+ cell count were predictors of the degree of clumping. Procedures with clumping had higher collection efficiency but lower blood volume processed on average, resulting in no difference in collection yields. Citrate toxicity did not correlate with clumping. CONCLUSION Although platelet clumping is a common technical problem seen during HSC collection, the total CD34+ cell-collection yields were not affected by clumping. WBC count, mobilization approach, and peripheral blood CD34+ cell count can help predict clumping and potentially drive interventions to proactively manage clumping. PMID:28150319

  7. Metabolic Adaptations of Azospirillum brasilense to Oxygen Stress by Cell-to-Cell Clumping and Flocculation

    DOE PAGES

    Bible, Amber N.; Khalsa-Moyers, Gurusahai K.; Mukherjee, Tanmoy; ...

    2015-09-25

    The ability of bacteria to monitor their metabolism and adjust their behavior accordingly is critical to maintain competitiveness in the environment. The motile microaerophilic bacteriumAzospirillum brasilensenavigates oxygen gradients by aerotaxis in order to locate low oxygen concentrations that can support metabolism. When cells are exposed to elevated levels of oxygen in their surroundings, motileA. brasilensecells implement an alternative response to aerotaxis and form transient clumps by cell-to-cell interactions. Clumping was suggested to represent a behavior protecting motile cells from transiently elevated levels of aeration. Using the proteomics of wild-type and mutant strains affected in the extent of their clumping abilities,more » we show that cell-to-cell clumping represents a metabolic scavenging strategy that likely prepares the cells for further metabolic stresses. Analysis of mutants affected in carbon or nitrogen metabolism confirmed this assumption. The metabolic changes experienced as clumping progresses prime cells for flocculation, a morphological and metabolic shift of cells triggered under elevated-aeration conditions and nitrogen limitation. The analysis of various mutants during clumping and flocculation characterized an ordered set of changes in cell envelope properties accompanying the metabolic changes. These data also identify clumping and early flocculation to be behaviors compatible with the expression of nitrogen fixation genes, despite the elevated-aeration conditions. Finally, cell-to-cell clumping may thus license diazotrophy to microaerophilicA. brasilensecells under elevated oxygen conditions and prime them for long-term survival via flocculation if metabolic stress persists.« less

  8. Metabolic Adaptations of Azospirillum brasilense to Oxygen Stress by Cell-to-Cell Clumping and Flocculation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bible, Amber N.; Khalsa-Moyers, Gurusahai K.; Mukherjee, Tanmoy

    The ability of bacteria to monitor their metabolism and adjust their behavior accordingly is critical to maintain competitiveness in the environment. The motile microaerophilic bacteriumAzospirillum brasilensenavigates oxygen gradients by aerotaxis in order to locate low oxygen concentrations that can support metabolism. When cells are exposed to elevated levels of oxygen in their surroundings, motileA. brasilensecells implement an alternative response to aerotaxis and form transient clumps by cell-to-cell interactions. Clumping was suggested to represent a behavior protecting motile cells from transiently elevated levels of aeration. Using the proteomics of wild-type and mutant strains affected in the extent of their clumping abilities,more » we show that cell-to-cell clumping represents a metabolic scavenging strategy that likely prepares the cells for further metabolic stresses. Analysis of mutants affected in carbon or nitrogen metabolism confirmed this assumption. The metabolic changes experienced as clumping progresses prime cells for flocculation, a morphological and metabolic shift of cells triggered under elevated-aeration conditions and nitrogen limitation. The analysis of various mutants during clumping and flocculation characterized an ordered set of changes in cell envelope properties accompanying the metabolic changes. These data also identify clumping and early flocculation to be behaviors compatible with the expression of nitrogen fixation genes, despite the elevated-aeration conditions. Finally, cell-to-cell clumping may thus license diazotrophy to microaerophilicA. brasilensecells under elevated oxygen conditions and prime them for long-term survival via flocculation if metabolic stress persists.« less

  9. Metabolic Adaptations of Azospirillum brasilense to Oxygen Stress by Cell-to-Cell Clumping and Flocculation

    PubMed Central

    Bible, Amber N.; Khalsa-Moyers, Gurusahai K.; Mukherjee, Tanmoy; Green, Calvin S.; Mishra, Priyanka; Purcell, Alicia; Aksenova, Anastasia; Hurst, Gregory B.

    2015-01-01

    The ability of bacteria to monitor their metabolism and adjust their behavior accordingly is critical to maintain competitiveness in the environment. The motile microaerophilic bacterium Azospirillum brasilense navigates oxygen gradients by aerotaxis in order to locate low oxygen concentrations that can support metabolism. When cells are exposed to elevated levels of oxygen in their surroundings, motile A. brasilense cells implement an alternative response to aerotaxis and form transient clumps by cell-to-cell interactions. Clumping was suggested to represent a behavior protecting motile cells from transiently elevated levels of aeration. Using the proteomics of wild-type and mutant strains affected in the extent of their clumping abilities, we show that cell-to-cell clumping represents a metabolic scavenging strategy that likely prepares the cells for further metabolic stresses. Analysis of mutants affected in carbon or nitrogen metabolism confirmed this assumption. The metabolic changes experienced as clumping progresses prime cells for flocculation, a morphological and metabolic shift of cells triggered under elevated-aeration conditions and nitrogen limitation. The analysis of various mutants during clumping and flocculation characterized an ordered set of changes in cell envelope properties accompanying the metabolic changes. These data also identify clumping and early flocculation to be behaviors compatible with the expression of nitrogen fixation genes, despite the elevated-aeration conditions. Cell-to-cell clumping may thus license diazotrophy to microaerophilic A. brasilense cells under elevated oxygen conditions and prime them for long-term survival via flocculation if metabolic stress persists. PMID:26407887

  10. Simulations of galaxy cluster collisions with a dark plasma component

    NASA Astrophysics Data System (ADS)

    Spethmann, Christian; Veermäe, Hardi; Sepp, Tiit; Heikinheimo, Matti; Deshev, Boris; Hektor, Andi; Raidal, Martti

    2017-12-01

    Context. Dark plasma is an intriguing form of self-interacting dark matter with an effective fluid-like behavior, which is well motivated by various theoretical particle physics models. Aims: We aim to find an explanation for an isolated mass clump in the Abell 520 system, which cannot be explained by traditional models of dark matter, but has been detected in weak lensing observations. Methods: We performed N-body smoothed particle hydrodynamics simulations of galaxy cluster collisions with a two component model of dark matter, which is assumed to consist of a predominant non-interacting dark matter component and a 10-40% mass fraction of dark plasma. Results: The mass of a possible dark clump was calculated for each simulation in a parameter scan over the underlying model parameters. In two higher resolution simulations shock-waves and Mach cones were observed to form in the dark plasma halos. Conclusions: By choosing suitable simulation parameters, the observed distributions of dark matter in both the Bullet cluster (1E 0657-558) and Abell 520 (MS 0451.5+0250) can be qualitatively reproduced. Movies associated to Figs. A.1 and A.2 are available at http://www.aanda.org

  11. Hub-filament System in IRAS 05480+2545: Young Stellar Cluster and 6.7 GHz Methanol Maser

    NASA Astrophysics Data System (ADS)

    Dewangan, L. K.; Ojha, D. K.; Baug, T.

    2017-07-01

    To probe the star formation (SF) process, we present a multi-wavelength study of IRAS 05480+2545 (hereafter I05480+2545). Analysis of Herschel data reveals a massive clump (M clump ˜ 1875 {M}⊙ ; peak N(H2) ˜ 4.8 × 1022 cm-2 A V ˜ 51 mag) containing the 6.7 GHz methanol maser and I05480+2545, which is also depicted in a temperature range of 18-26 K. Several noticeable parsec-scale filaments are detected in the Herschel 250 μm image and seem to be radially directed to the massive clump. It resembles more of a “hub-filament” system. Deeply embedded young stellar objects (YSOs) have been identified using the 1-5 μm photometric data, and a significant fraction of YSOs and their clustering are spatially found toward the massive clump, revealing the intense SF activities. An infrared counterpart (IRc) of the maser is investigated in the Spitzer 3.6-4.5 μm images. The IRc does not appear as a point-like source and is most likely associated with the molecular outflow. Based on the 1.4 GHz and Hα continuum images, the ionized emission is absent toward the IRc, indicating that the massive clump harbors an early phase of a massive protostar before the onset of an ultracompact H II region. Together, the I05480+2545 is embedded in a very similar “hub-filament” system to those seen in the Rosette Molecular Cloud. The outcome of the present work indicates the role of filaments in the formation of the massive star-forming clump and cluster of YSOs, which might help channel material to the central hub configuration and the clump/core.

  12. X-RAY EMISSION LINE PROFILES FROM WIND CLUMP BOW SHOCKS IN MASSIVE STARS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ignace, R.; Waldron, W. L.; Cassinelli, J. P.

    2012-05-01

    The consequences of structured flows continue to be a pressing topic in relating spectral data to physical processes occurring in massive star winds. In a preceding paper, our group reported on hydrodynamic simulations of hypersonic flow past a rigid spherical clump to explore the structure of bow shocks that can form around wind clumps. Here we report on profiles of emission lines that arise from such bow shock morphologies. To compute emission line profiles, we adopt a two-component flow structure of wind and clumps using two 'beta' velocity laws. While individual bow shocks tend to generate double-horned emission line profiles,more » a group of bow shocks can lead to line profiles with a range of shapes with blueshifted peak emission that depends on the degree of X-ray photoabsorption by the interclump wind medium, the number of clump structures in the flow, and the radial distribution of the clumps. Using the two beta law prescription, the theoretical emission measure and temperature distribution throughout the wind can be derived. The emission measure tends to be power law, and the temperature distribution is broad in terms of wind velocity. Although restricted to the case of adiabatic cooling, our models highlight the influence of bow shock effects for hot plasma temperature and emission measure distributions in stellar winds and their impact on X-ray line profile shapes. Previous models have focused on geometrical considerations of the clumps and their distribution in the wind. Our results represent the first time that the temperature distribution of wind clump structures are explicitly and self-consistently accounted for in modeling X-ray line profile shapes for massive stars.« less

  13. On the benefits of living in clumps: a case study on Polytrichastrum formosum.

    PubMed

    Zajączkowska, U; Grabowska, K; Kokot, G; Kruk, M

    2017-03-01

    The study concerns the mechanics and water relationships of clumps of a species of endohydric moss, Polytrichastrum formosum. Anatomical and morphological studies were done using optical and scanning electron microscopy. Experiments on waterdrop capture and their distribution to adjacent shoots within a moss clump were performed with the experimental set-up for the droplet collision phenomena and ultra-high speed camera. The mechanical strength of the moss clump was tested on an electromechanical testing machine. During the process of moss clump wetting, the falling water drops were captured by the apical stem part or leaves, then flowed down while adhering to the gametophore and never lost their surface continuity. In places of contact with another leaf, the water drop stops there and joins the leaves, enabling their hydration. Mathematical analysis of anatomical images showed that moss stems have different zones with varying cell lumen and cell wall/cell radius ratios, suggesting the occurrence of a periodic component structure. Our study provides evidence that the reaction of mosses to mechanical forces depends on the size of the clump, and that small groups are clearly stronger than larger groups. The clump structure of mosses acts as a net for falling rain droplets. Clumps of Polytrichastrum having overlapping leaves, at the time of loading formed a structure similar to a lattice. The observed reaction of mosses to mechanical forces indicates that this phenomenon appears to be analogous to the 'size effect on structural strength' that is of great importance for various fields of engineering. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

  14. MALT90 Kinematic Distances to Dense Molecular Clumps

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Whitaker, J. Scott; Jackson, James M.; Sanhueza, Patricio

    Using molecular-line data from the Millimetre Astronomy Legacy Team 90 GHz Survey (MALT90), we have estimated kinematic distances to 1905 molecular clumps identified in the ATLASGAL 870 μ m continuum survey over the longitude range 295° <  l  < 350°. The clump velocities were determined using a flux-weighted average of the velocities obtained from Gaussian fits to the HCO{sup +}, HNC, and N{sub 2}H{sup +} (1–0) transitions. The near/far kinematic distance ambiguity was addressed by searching for the presence or absence of absorption or self-absorption features in 21 cm atomic hydrogen spectra from the Southern Galactic Plane Survey. Our algorithm provides anmore » estimation of the reliability of the ambiguity resolution. The Galactic distribution of the clumps indicates positions where the clumps are bunched together, and these locations probably trace the locations of spiral arms. Several clumps fall at the predicted location of the far side of the Scutum–Centaurus arm. Moreover, a number of clumps with positive radial velocities are unambiguously located on the far side of the Milky Way at galactocentric radii beyond the solar circle. The measurement of these kinematic distances, in combination with continuum or molecular-line data, now enables the determination of fundamental parameters such as mass, size, and luminosity for each clump.« less

  15. VizieR Online Data Catalog: ATLASGAL massive clumps H2CO data (Tang+,

    NASA Astrophysics Data System (ADS)

    Tang, X. D.; Henkel, C.; Wyrowski, F.; Giannetti, A.; Menten, K. M.; Csengeri, T.; Leurini, S.; Urquhart, J. S.; Koenig, C.; Guesten, R.; Lin, Y. X.; Zheng, X. W.; Esimbek, J.; Zhou, J. J.

    2017-11-01

    We selected the 110 brightest clumps from the ATLASGAL survey (the TOP100 sample) obeying simple IR criteria to cover a range in evolutionary stages as described in Giannetti et al. (2014, Cat. J/A+A/570/A65, Paper I) and Koenig et al. (2017, Cat. J/A+A/599/A139, Paper III). These clumps consist almost entirely of clumps that have the potential to form, or are forming, massive stars. Our observations were carried out on 2013 July and December, 2014 September and November, and 2015 April, June, July, and October with the Atacama Pathfinder EXperiment (APEX) 12m telescope located on Chajnantor (Chile). Five transitions of H2CO (J=3-2) were observed with the new MPIfR 1-mm receiver (PI230) with a beam size from 27.6" to 29.5" and integration times of 1 to 3 minutes. Five H2CO (J=4-3) transitions were observed with the FLASH receiver with a beam size ~21.4" and integration times of 2 to 4 minutes. (7 data files).

  16. Metabolic adaptations of Azospirillum brasilense to oxygen stress by cell-to-cell clumping and flocculation.

    PubMed

    Bible, Amber N; Khalsa-Moyers, Gurusahai K; Mukherjee, Tanmoy; Green, Calvin S; Mishra, Priyanka; Purcell, Alicia; Aksenova, Anastasia; Hurst, Gregory B; Alexandre, Gladys

    2015-12-01

    The ability of bacteria to monitor their metabolism and adjust their behavior accordingly is critical to maintain competitiveness in the environment. The motile microaerophilic bacterium Azospirillum brasilense navigates oxygen gradients by aerotaxis in order to locate low oxygen concentrations that can support metabolism. When cells are exposed to elevated levels of oxygen in their surroundings, motile A. brasilense cells implement an alternative response to aerotaxis and form transient clumps by cell-to-cell interactions. Clumping was suggested to represent a behavior protecting motile cells from transiently elevated levels of aeration. Using the proteomics of wild-type and mutant strains affected in the extent of their clumping abilities, we show that cell-to-cell clumping represents a metabolic scavenging strategy that likely prepares the cells for further metabolic stresses. Analysis of mutants affected in carbon or nitrogen metabolism confirmed this assumption. The metabolic changes experienced as clumping progresses prime cells for flocculation, a morphological and metabolic shift of cells triggered under elevated-aeration conditions and nitrogen limitation. The analysis of various mutants during clumping and flocculation characterized an ordered set of changes in cell envelope properties accompanying the metabolic changes. These data also identify clumping and early flocculation to be behaviors compatible with the expression of nitrogen fixation genes, despite the elevated-aeration conditions. Cell-to-cell clumping may thus license diazotrophy to microaerophilic A. brasilense cells under elevated oxygen conditions and prime them for long-term survival via flocculation if metabolic stress persists. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  17. The VIMOS Ultra-Deep Survey: A major merger origin for the high fraction of galaxies at 2 < z < 6 with two bright clumps

    NASA Astrophysics Data System (ADS)

    Ribeiro, B.; Le Fèvre, O.; Cassata, P.; Garilli, B.; Lemaux, B. C.; Maccagni, D.; Schaerer, D.; Tasca, L. A. M.; Zamorani, G.; Zucca, E.; Amorín, R.; Bardelli, S.; Hathi, N. P.; Koekemoer, A.; Pforr, J.

    2017-11-01

    The properties of stellar clumps in star-forming galaxies and their evolution over the redshift range 2 ≲ z ≲ 6 are presented and discussed in the context of the build-up of massive galaxies at early cosmic times. We focused on galaxies with spectroscopic redshifts from the VIMOS Ultra Deep Survey (VUDS) and stellar masses log 10(M⋆/M⊙) > -0.204 × (z-4.5) + 9.35. We analyzed HST-ACS images to identify clumps within a 20 kpc radius using a method taking into account differential surface brightness dimming and luminosity evolution with redshift. We find that the population of galaxies with more than one clump is dominated by galaxies with two clumps, representing 21-25% of the population, while the fraction of galaxies with three, or four and more, clumps is 8-11% and 7-9%, respectively. The fraction of clumpy galaxies is in the range 35-55% over 2 < z < 6, increasing at higher redshifts, indicating that the fraction of irregular galaxies remains high up to the highest redshifts. The large and bright clumps (M⋆ 109 up to 1010 M⊙) are found to reside predominantly in galaxies with two clumps. Smaller and lower luminosity clumps (M⋆ < 109 M⊙) are found in galaxies with three clumps or more. We interpret these results as evidence for two different modes of clump formation working in parallel. The small low luminosity clumps are likely the result of disk fragmentation, with violent disk instabilities (VDI) forming several long-lived clumps in-situ as suggested from simulations. A fraction of these clumps is also likely coming from minor mergers as confirmed from spectroscopy in several cases. The clumps in the dominating population of galaxies with two clumps are significantly more massive and have properties akin to those in galaxy pairs undergoing massive merging observed at similar redshifts; they appear as more massive than the most massive clumps observed in numerical simulations of disks with VDI. We infer from these properties that the bright and

  18. High-mass Starless Clumps in the Inner Galactic Plane: The Sample and Dust Properties

    NASA Astrophysics Data System (ADS)

    Yuan, Jinghua; Wu, Yuefang; Ellingsen, Simon P.; Evans, Neal J., II; Henkel, Christian; Wang, Ke; Liu, Hong-Li; Liu, Tie; Li, Jin-Zeng; Zavagno, Annie

    2017-07-01

    We report a sample of 463 high-mass starless clump (HMSC) candidates within -60^\\circ < l< 60^\\circ and -1^\\circ < b< 1^\\circ . This sample has been singled out from 10,861 ATLASGAL clumps. None of these sources are associated with any known star-forming activities collected in SIMBAD and young stellar objects identified using color-based criteria. We also make sure that the HMSC candidates have neither point sources at 24 and 70 μm nor strong extended emission at 24 μm. Most of the identified HMSCs are infrared dark, and some are even dark at 70 μm. Their distribution shows crowding in Galactic spiral arms and toward the Galactic center and some well-known star-forming complexes. Many HMSCs are associated with large-scale filaments. Some basic parameters were attained from column density and dust temperature maps constructed via fitting far-infrared and submillimeter continuum data to modified blackbodies. The HMSC candidates have sizes, masses, and densities similar to clumps associated with Class II methanol masers and H II regions, suggesting that they will evolve into star-forming clumps. More than 90% of the HMSC candidates have densities above some proposed thresholds for forming high-mass stars. With dust temperatures and luminosity-to-mass ratios significantly lower than that for star-forming sources, the HMSC candidates are externally heated and genuinely at very early stages of high-mass star formation. Twenty sources with equivalent radii {r}{eq}< 0.15 pc and mass surface densities {{Σ }}> 0.08 g cm-2 could be possible high-mass starless cores. Further investigations toward these HMSCs would undoubtedly shed light on comprehensively understanding the birth of high-mass stars.

  19. The Formation and Early Evolution of Embedded Massive Star Clusters

    NASA Astrophysics Data System (ADS)

    Barnes, Peter

    We propose to combine Spitzer, WISE, Herschel, and other archival spacecraft data with an existing ground- and space-based mm-wave to near-IR survey of molecular clouds over a large portion of the Milky Way, in order to systematically study the formation and early evolution of massive stars and star clusters, and provide new observational calibrations for a theoretical paradigm of this key astrophysical problem. Central Objectives: The Galactic Census of High- and Medium-mass Protostars (CHaMP) is a large, unbiased, uniform, and panchromatic survey of massive star and cluster formation and early evolution, covering 20°x6° of the Galactic Plane. Its uniqueness lies in the comprehensive molecular spectroscopy of 303 massive dense clumps, which have also been included in several archival spacecraft surveys. Our objective is a systematic demographic analysis of massive star and cluster formation, one which has not been possible without knowledge of our CHaMP cloud sample, including all clouds with embedded clusters as well as those that have not yet formed massive stars. For proto-clusters deeply embedded within dense molecular clouds, analysis of these space-based data will: 1. Yield a complete census of Young Stellar Objects in each cluster. 2. Allow systematic measurements of embedded cluster properties: spectral energy distributions, luminosity functions, protostellar and disk fractions, and how these vary with cluster mass, age, and density. Combined with other, similarly complete and unbiased infrared and mm data, CHaMP's goals include: 3. A detailed comparison of the embedded stellar populations with their natal dense gas to derive extinction maps, star formation efficiencies and feedback effects, and the kinematics, physics, and chemistry of the gas in and around the clusters. 4. Tying the demographics, age spreads, and timescales of the clusters, based on pre-Main Sequence evolution, to that of the dense gas clumps and Giant Molecular Clouds. 5. A

  20. Analysis of dark matter axion clumps with spherical symmetry

    NASA Astrophysics Data System (ADS)

    Schiappacasse, Enrico D.; Hertzberg, Mark P.

    2018-01-01

    Recently there has been much interest in the spatial distribution of light scalar dark matter, especially axions, throughout the universe. When the local gravitational interactions between the scalar modes are sufficiently rapid, it can cause the field to re-organize into a BEC of gravitationally bound clumps. While these clumps are stable when only gravitation is included, the picture is complicated by the presence of the axion's attractive self-interactions, which can potentially cause the clumps to collapse. Here we perform a detailed stability analysis to determine under what conditions the clumps are stable. In this paper we focus on spherical configurations, leaving aspherical configurations for future work. We identify branches of clump solutions of the axion-gravity-self-interacting system and study their stability properties. We find that clumps that are (spatially) large are stable, while clumps that are (spatially) small are unstable and may collapse. Furthermore, there is a maximum number of particles that can be in a clump. We map out the full space of solutions, which includes quasi-stable axitons, and clarify how a recent claim in the literature of a new ultra-dense branch of stable solutions rests on an invalid use of the non-relativistic approximation. We also consider repulsive self-interactions that may arise from a generic scalar dark matter candidate, finding a single stable branch that extends to arbitrary particle number.

  1. Massive 70 μm quiet clumps I: evidence of embedded low/intermediate-mass star formation activity

    NASA Astrophysics Data System (ADS)

    Traficante, A.; Fuller, G. A.; Billot, N.; Duarte-Cabral, A.; Merello, M.; Molinari, S.; Peretto, N.; Schisano, E.

    2017-10-01

    Massive clumps, prior to the formation of any visible protostars, are the best candidates to search for the elusive massive starless cores. In this work, we investigate the dust and gas properties of massive clumps selected to be 70 μm quiet, therefore good starless candidates. Our sample of 18 clumps has masses 300 ≲ M ≲ 3000 M⊙, radius 0.54 ≤ R ≤ 1.00 pc, surface densities Σ ≥ 0.05 g cm-2 and luminosity/mass ratio L/M ≤ 0.3. We show that half of these 70 μm quiet clumps embed faint 24 μm sources. Comparison with GLIMPSE counterparts shows that five clumps embed young stars of intermediate stellar mass up to ≃5.5 M⊙. We study the clump dynamics with observations of N2H+ (1-0), HNC (1-0) and HCO+ (1-0) made with the IRAM 30 m telescope. Seven clumps have blue-shifted spectra compatible with infall signatures, for which we estimate a mass accretion rate 0.04≲ \\dot{M}≲ 2.0× 10^{-3} M⊙ yr-1, comparable with values found in high-mass protostellar regions, and free-fall time of the order of tff ≃ 3 × 105 yr. The only appreciable difference we find between objects with and without embedded 24 μm sources is that the infall rate appears to increase from 24 μm dark to 24 μm bright objects. We conclude that all 70 μm quiet objects have similar properties on clump scales, independently of the presence of an embedded protostar. Based on our data, we speculate that the majority, if not all of these clumps, may already embed faint, low-mass protostellar cores. If these clumps are to form massive stars, this must occur after the formation of these lower mass stars.

  2. G30.79 FIR 10: a gravitationally bound infalling high-mass star-forming clump

    NASA Astrophysics Data System (ADS)

    Cortes, P. C.; Parra, R.; Cortes, J. R.; Hardy, E.

    2010-09-01

    Context. The process of high-mass star formation is still shrouded in controversy. Models are still tentative and current observations are just beginning to probe the densest inner regions of giant molecular clouds. Aims: The study of high-mass star formation requires the observation and analysis of high-density gas. This can be achieved by the detection of emission from higher rotational transitions of molecules in the sub-millimeter. Here, we studied the high-mass clump G30.79 FIR 10 by observing molecular emission in the 345 GHz band. The goal is to understand the gravitational state of this clump, considering turbulence and magnetic fields, and to study the kinematics of dense gas. Methods: We approached this region by mapping the spatial distribution of HCO+(J = 4 →) 3, H13CO+ (J = 4 → 3), CS(J = 7 → 6), 12CO(J = 3 → 2), and 13CO(J = 3 → 2) molecular emission by using the ASTE telescope and by observing the 12C18O(J = 3 → 2), HCN(J = 4 → 3), and H13CN(J = 4 → 3) molecular transitions with the APEX telescope. Results: Infalling motions were detected and modeled toward this source. A mean infall velocity of 0.5 km s-1 with an infall mass rate of 5 × 10-3 M⊙ yr-1 was obtained. Also, a previously estimated value for the magnetic field strength in the plane of the sky was refined to be 855 μG which we used to calculate a mass-to-magnetic flux ratio, λ = 1.9, or super-critical. The virial mass from turbulent motions was also calculated finding Mvir = 563 M⊙, which gives a ratio of Msubmm/Mvir = 5.9. Both values strongly suggest that this clump must be in a state of gravitational collapse. Additionally, we estimated the HCO+ abundance, obtaining X(HCO+) = 2.4 × 10-10.

  3. Preservation of carbonate clumped isotopes in sedimentary paleoclimate archives

    NASA Astrophysics Data System (ADS)

    Henkes, G. A.; Passey, B. H.; Grossman, E. L.; Shenton, B.; Perez-Huerta, A.

    2014-12-01

    Carbonate clumped isotope thermometry is increasingly used to reconstruct paleotemperatures of ancient terrestrial environments. One promising application is elucidating paleoelevation from carbonate archives such as paleosols, lacustrine marls, and fossil freshwater shells. Unlike conventional stable isotope approaches (e.g., mineral δ18O or δD), clumped isotope thermometry is independent of the isotopic composition of the precipitating waters and can therefore be used to reconstruct elevation by both the temperature-altitude relationship and the rainfall δ18O-altitude relationship. However, interpretation of clumped isotope data is not without its own complications. Like conventional stable isotopes, clumped isotope paleotemperatures can be effectively reset to warmer values by dissolution/reprecipitation-type diagenesis during sedimentary burial. It is also known that carbonate clumped isotope bonds (i.e., 13C-18O) are susceptible to 'reordering' in the solid mineral lattice at warmer burial temperatures, with laboratory studies of natural carbonates indicating activation of this phenomenon at temperatures as low as 100 °C over geologic timescales. A challenge in applying carbonate clumped isotope thermometry to natural samples is now evaluating terrestrial archives with respect to both types of alteration: 'open-system' alteration and 'closed-system' bond reordering. In this talk we will review our experimental efforts to constrain the kinetics of clumped isotope reordering, with relevance to low-temperature carbonates like fossil shells and early diagenetic minerals, and present new laboratory data that further inform our theoretical framework for the mechanism(s) of 13C-18O bond reordering. Together with traditional analytical and petrographic screening for recrystallization, empirical and laboratory studies of carbonate clumped isotope reordering represent the next steps in evaluating isotopic records of paleoclimate, paleobiology, and paleoelevation

  4. Physical and Chemical Properties of Protocluster Clumps and Massive Young Stellar Objects Associated to Infrared Dark Clouds

    NASA Astrophysics Data System (ADS)

    Gomez Gonzalez, Laura

    2012-01-01

    The study of high-mass stars is important not only because of the effects they produce in their environment through outflows, expanding HII regions, stellar winds, and eventually supernova shock waves, but also because they play a crucial role in estimating star formation rates in other galaxies. Although we have an accepted evolutionary scenario that explains (isolated) low-mass star formation, the processes that produce massive stars (M_star > 8 M_sol) and star clusters, especially their earliest stages, are not well understood. The newly discovered class of interstellar clouds now termed infrared dark clouds (IRDCs) represent excellent laboratories to study the earliest stages of high-mass star formation given that some of the clumps within them are known to have high masses (~100's M_sol), high densities (n > 10^5 cm^-3), and low temperatures (10-20K) as expected for the birthplaces of high-mass stars. Some questions remain unanswered: Do IRDCs harbor the very early stages of high-mass star formation, i.e., the pre-protocluster phase? If so, how do they compare with low-mass star formation sites? Is there chemical differentiation in IRDC clumps? What is the mass distribution of IRDCs? In this dissertation and for the first time, a catalog of 12529 IRDC candidates at 24 um has been created using archival data from the MIPSGAL/Spitzer survey, as a first step in searching for the massive pre-protocluster clumps. From this catalog, a sample of ~60 clumps has been selected in order to perform single-pointing observations with the IRAM 30m, Effelsberg 100m, and APEX 12m telescopes. One IRDC clump seems to be a promising candidate for being in the pre-protocluster phase. In addition, molecular line mapping observations have been performed on three clumps within IRDCs and a detailed chemical study of 10 molecular lines has been carried out. A larger difference in column densities and abundances has been found between these clumps and high-m! ass protostellar objects

  5. VizieR Online Data Catalog: ATLASGAL clumps with IRAS flux and MALT90 data (Stephens+, 2016)

    NASA Astrophysics Data System (ADS)

    Stephens, I. W.; Jackson, J. M.; Whitaker, J. S.; Contreras, Y.; Guzman, A. E.; Sanhueza, P.; Foster, J. B.; Rathborne, J. M.

    2016-08-01

    The Millimetre Astronomy Legacy Team 90GHz (MALT90) survey (Foster+ 2011, J/ApJS/197/25; 2013PASA...30...38F; Jackson+ 2013PASA...30...57J) mapped 16 lines for 3246 clumps, primarily high-mass star-forming clumps that are >200M⊙, as identified from the ATLASGAL 870um survey (Schuller et al. 2009A&A...504..415S). In order to compare luminosities derived from IRAS (LIR) to molecular line luminosities from MALT90 (Lmolecule), we first matched the MALT90 clumps to the IRAS Point Source Catalog v2.1 (PSC; see Cat. II/125). See section 2.1 for further explanations. (1 data file).

  6. Was the Milky Way Bulge Formed from the Buckling Disk Instability, Hierarchical Collapse, Accretion of Clumps, or All of the Above?

    NASA Astrophysics Data System (ADS)

    Nataf, David M.

    2017-09-01

    The assembly of the Milky Way bulge is an old topic in astronomy, one now in a period of renewed and rapid development. That is due to tremendous advances in observations of bulge stars, motivating observations of both local and high-redshift galaxies, and increasingly sophisticated simulations. The dominant scenario for bulge formation is that of the Milky Way as a nearly pure disk galaxy, with the inner disk having formed a bar and buckled. This can potentially explain virtually all bulge stars with [Fe/H] ≳ -1.0, which comprise 95% of the stellar population. The evidence is the incredible success in N-body models of this type in making non-trivial, non-generic predictions, such as the rotation curve and velocity dispersion measured from radial velocities, and the spatial morphologies of the peanut/X-shape and the long bar. The classical bulge scenario, whereby the bulge formed from early dissipative collapse and mergers, remains viable for stars with [Fe/H] ≲ -1.0 and potentially a minority of the other stars. A classical bulge is expected from Λ-CDM cosmological simulations, can accentuate the properties of an existing bar in a hybrid system, and is most consistent with the bulge abundance trends such as [Mg/Fe], which are elevated relative to both the thin and thick disks. Finally, the clumpy-galaxy scenario is considered, as it is the correct description of most Milky Way precursors given observations of high-redshift galaxies. Simulations predict that these star-forming clumps will sometimes migrate to the centres of galaxies where they may form a bulge, and galaxies often include a bulge clump as well. They will possibly form a bar with properties consistent with those of the Milky Way, such as the exponential profile and metallicity gradient. Given the relative successes of these scenarios, the Milky Way bulge is plausibly of composite origin, with a classical bulge and/or inner halo numerically dominant for stars with [Fe/H] ≲ -1.0, a buckling

  7. Impact of a star formation efficiency profile on the evolution of open clusters

    NASA Astrophysics Data System (ADS)

    Shukirgaliyev, B.; Parmentier, G.; Berczik, P.; Just, A.

    2017-09-01

    Aims: We study the effect of the instantaneous expulsion of residual star-forming gas on star clusters in which the residual gas has a density profile that is shallower than that of the embedded cluster. This configuration is expected if star formation proceeds with a given star-formation efficiency per free-fall time in a centrally concentrated molecular gas clump. Methods: We performed direct N-body simulations whose initial conditions were generated by the program "mkhalo" from the package "falcON", adapted for our models. Our model clusters initially had a Plummer profile and are in virial equilibrium with the gravitational potential of the cluster-forming clump. The residual gas contribution was computed based on a local-density driven clustered star formation model. Our simulations included mass loss by stellar evolution and the tidal field of a host galaxy. Results: We find that a star cluster with a minimum global star formation efficiency (SFE) of 15 percent is able to survive instantaneous gas expulsion and to produce a bound cluster. Its violent relaxation lasts no longer than 20 Myr, independently of its global SFE and initial stellar mass. At the end of violent relaxation, the bound fractions of the surviving clusters with the same global SFEs are similar, regardless of their initial stellar mass. Their subsequent lifetime in the gravitational field of the Galaxy depends on their bound stellar masses. Conclusions: We therefore conclude that the critical SFE needed to produce a bound cluster is 15 percent, which is roughly half the earlier estimates of 33 percent. Thus we have improved the survival likelihood of young clusters after instantaneous gas expulsion. Young clusters can now survive instantaneous gas expulsion with a global SFEs as low as the SFEs observed for embedded clusters in the solar neighborhood (15-30 percent). The reason is that the star cluster density profile is steeper than that of the residual gas. However, in terms of the

  8. The Cancer Cluster - An unbound collection of groups

    NASA Technical Reports Server (NTRS)

    Geller, M. J.; Beers, T. C.; Bothun, G. D.; Huchra, J. P.

    1983-01-01

    A surface density contour map of the Cancer Cluster derived from galaxy counts in the Zwicky catalog is presented. The contour map shows that the galaxy distribution is clumpy. When this spatial distribution is combined with nearly complete velocity information, the clumps stand out more clearly; there are significant differences in the mean velocities of the clumps which exceed their internal velocity dispersions. The Cancer Cluster is not a proper 'cluster' but is a collection of discrete groups, each with a velocity dispersion of approximately 300 km/s, separating from one another with the cosmological flow. The mass-to-light ratio for galaxies in the main concentration is approximately 320 solar masses/solar luminosities (H sub 0 = 100 km/s Mpc).

  9. High-mass Star Formation through Filamentary Collapse and Clump-fed Accretion in G22

    NASA Astrophysics Data System (ADS)

    Yuan, Jinghua; Li, Jin-Zeng; Wu, Yuefang; Ellingsen, Simon P.; Henkel, Christian; Wang, Ke; Liu, Tie; Liu, Hong-Li; Zavagno, Annie; Ren, Zhiyuan; Huang, Ya-Fang

    2018-01-01

    How mass is accumulated from cloud-scale down to individual stars is a key open question in understanding high-mass star formation. Here, we present the mass accumulation process in a hub-filament cloud G22 that is composed of four supercritical filaments. Velocity gradients detected along three filaments indicate that they are collapsing with a total mass infall rate of about 440 M ⊙ Myr‑1, suggesting the hub mass would be doubled in six free-fall times, adding up to ∼2 Myr. A fraction of the masses in the central clumps C1 and C2 can be accounted for through large-scale filamentary collapse. Ubiquitous blue profiles in HCO+ (3–2) and 13CO (3–2) spectra suggest a clump-scale collapse scenario in the most massive and densest clump C1. The estimated infall velocity and mass infall rate are 0.31 km s‑1 and 7.2 × 10‑4 M ⊙ yr‑1, respectively. In clump C1, a hot molecular core (SMA1) is revealed by the Submillimeter Array observations and an outflow-driving high-mass protostar is located at the center of SMA1. The mass of the protostar is estimated to be 11–15 M ⊙ and it is still growing with an accretion rate of 7 × 10‑5 M ⊙ yr‑1. The coexistent infall in filaments, clump C1, and the central hot core in G22 suggests that pre-assembled mass reservoirs (i.e., high-mass starless cores) may not be required to form high-mass stars. In the course of high-mass star formation, the central protostar, the core, and the clump can simultaneously grow in mass via core-fed/disk accretion, clump-fed accretion, and filamentary/cloud collapse.

  10. Black hole binaries dynamically formed in globular clusters

    NASA Astrophysics Data System (ADS)

    Park, Dawoo; Kim, Chunglee; Lee, Hyung Mok; Bae, Yeong-Bok; Belczynski, Krzysztof

    2017-08-01

    We investigate properties of black hole (BH) binaries formed in globular clusters via dynamical processes, using directN-body simulations. We pay attention to effects of BH mass function on the total mass and mass ratio distributions of BH binaries ejected from clusters. First, we consider BH populations with two different masses in order to learn basic differences from models with single-mass BHs only. Secondly, we consider continuous BH mass functions adapted from recent studies on massive star evolution in a low metallicity environment, where globular clusters are formed. In this work, we consider only binaries that are formed by three-body processes and ignore stellar evolution and primordial binaries for simplicity. Our results imply that most BH binary mergers take place after they get ejected from the cluster. Also, mass ratios of dynamically formed binaries should be close to 1 or likely to be less than 2:1. Since the binary formation efficiency is larger for higher-mass BHs, it is likely that a BH mass function sampled by gravitational-wave observations would be weighed towards higher masses than the mass function of single BHs for a dynamically formed population. Applying conservative assumptions regarding globular cluster populations such as small BH mass fraction and no primordial binaries, the merger rate of BH binaries originated from globular clusters is estimated to be at least 6.5 yr-1 Gpc-3. Actual rate can be up to more than several times of our conservative estimate.

  11. Gas clump formation via thermal instability in high-redshift dwarf galaxy mergers

    NASA Astrophysics Data System (ADS)

    Arata, Shohei; Yajima, Hidenobu; Nagamine, Kentaro

    2018-04-01

    Star formation in high-redshift dwarf galaxies is a key to understand early galaxy evolution in the early Universe. Using the three-dimensional hydrodynamics code GIZMO, we study the formation mechanism of cold, high-density gas clouds in interacting dwarf galaxies with halo masses of ˜3 × 107 M⊙, which are likely to be the formation sites of early star clusters. Our simulations can resolve both the structure of interstellar medium on small scales of ≲ 0.1 pc and the galactic disc simultaneously. We find that the cold gas clouds form in the post-shock region via thermal instability due to metal-line cooling, when the cooling time is shorter than the galactic dynamical time. The mass function of cold clouds shows almost a power-law initially with an upper limit of thermally unstable scale. We find that some clouds merge into more massive ones with ≳104 M⊙ within ˜ 2 Myr. Only the massive cold clouds with ≳ 103 M⊙ can keep collapsing due to gravitational instability, resulting in the formation of star clusters. We find that the clump formation is more efficient in the prograde-prograde merger than the prograde-retrograde case due to the difference in the degree of shear flow. In addition, we investigate the dependence of cloud mass function on metallicity and H2 abundance, and show that the cases with low metallicities (≲10-2 Z⊙) or high H2 abundance (≳10-3) cannot form massive cold clouds with ≳103 M⊙.

  12. ATCA survey of ammonia in the galactic center: The temperatures of dense gas clumps between Sgr A* and Sgr B2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ott, Jürgen; Weiß, Axel; Henkel, Christian

    We present a large-scale, interferometric survey of ammonia (1, 1) and (2, 2) toward the Galactic center observed with the Australia Telescope Compact Array. The survey covers Δℓ ∼ 1° (∼150 pc at an assumed distance of 8.5 kpc) and Δb ∼ 0.°2 (∼30 pc) which spans the region between the supermassive black hole Sgr A* and the massive star forming region Sgr B2. The resolution is ∼20'' (∼0.8 pc) and emission at scales ≳ 2' (≳ 3.2 pc) is filtered out due to missing interferometric short spacings. Consequently, the data represent the denser, compact clouds and disregards the large-scale,more » diffuse gas. Many of the clumps align with the 100 pc dust ring and mostly anti-correlate with 1.2 cm continuum emission. We present a kinetic temperature map of the dense gas. The temperature distribution peaks at ∼38 K with a width at half maximum between 18 K and 61 K (measurements sensitive within T {sub kin} ∼ 10-80 K). Larger clumps are on average warmer than smaller clumps which suggests internal heating sources. Our observations indicate that the circumnuclear disk ∼1.5 pc around Sgr A* is supplied with gas from the 20 km s{sup –1} molecular cloud. This gas is substantially cooler than gas ∼3-15 pc away from Sgr A*. We find a strong temperature gradient across Sgr B2. Ammonia column densities correlate well with SCUBA 850 μm fluxes, but the relation is shifted from the origin, which may indicate a requirement for a minimum amount of dust to form and shield ammonia. Around the Arches and Quintuplet clusters we find shell morphologies with UV-influenced gas in their centers, followed by ammonia and radio continuum layers.« less

  13. Chemistry of the High-mass Protostellar Molecular Clump IRAS 16562–3959

    NASA Astrophysics Data System (ADS)

    Guzmán, Andrés E.; Guzmán, Viviana V.; Garay, Guido; Bronfman, Leonardo; Hechenleitner, Federico

    2018-06-01

    We present molecular line observations of the high-mass molecular clump IRAS 16562‑3959 taken at 3 mm using the Atacama Large Millimeter/submillimeter Array at 1.″7 angular resolution (0.014 pc spatial resolution). This clump hosts the actively accreting high-mass young stellar object (HMYSO) G345.4938+01.4677, which is associated with a hypercompact H II region. We identify and analyze emission lines from 22 molecular species (encompassing 34 isomers) and classify them into two groups, depending on their spatial distribution within the clump. One of these groups gathers shock tracers (e.g., SiO, SO, HNCO) and species formed in dust grains like methanol (CH3OH), ethenone or ketene (H2CCO), and acetaldehyde (CH3CHO). The second group collects species closely resembling the dust continuum emission morphology and are formed mainly in the gas phase, like hydrocarbons (CCH, c-C3H2, CH3CCH), cyanopolyynes (HC3N and HC5N), and cyanides (HCN and CH3C3N). Emission from complex organic molecules (COMs) like CH3OH, propanenitrile (CH3CH2CN), and methoxymethane (CH3OCH3) arise from gas in the vicinity of a hot molecular core (T ≳ 100 K) associated with the HMYSO. Other COMs such as propyne (CH3CCH), acrylonitrile (CH2CHCN), and acetaldehyde seem to better trace warm (T ≲ 80 K) dense gas. In addition, deuterated ammonia (NH2D) is detected mostly in the outskirts of IRAS 16562‑3959 and associated with near-infrared dark globules, probably gaseous remnants of the clump’s prestellar phase. The spatial distribution of molecules in IRAS 16562‑3959 supports the view that in protostellar clumps, chemical tracers associated with different evolutionary stages—starless to hot cores/H II regions—exist coevally.

  14. Observational and Numerical Diagnostics of Galaxy Cluster Outer Regions

    NASA Technical Reports Server (NTRS)

    Eckert, D.; Vazza, F.; Ettori, S.; Molendi, S.; Nagai, D.; Lau, E.; Roncarelli, M.; Rossetti, M.; Snowden, S. L.; Gastaldello, F.

    2011-01-01

    Aims. We present the analysis of a local (z = 0.04 - 0.2) sample of 31 galaxy clusters with the aim of measuring the density of the X-ray emitting gas in cluster outskirts. We compare our results with numerical simulations to set constraints on the azimuthal symmetry and gas clumping in the outer regions of galaxy clusters. Methods. We exploit the large field-of-view and low instrumental background of ROSAT/PSPC to trace the density of the intracluster gas out to the virial radius. We perform a stacking of the density profiles to detect a signal beyond r(sub 200) and measure the typical density and scatter in cluster outskirts. We also compute the azimuthal scatter of the profiles with respect to the mean value to look for deviations from spherical symmetry. Finally, we compare our average density and scatter profiles with the results of numerical simulations. Results. As opposed to several recent results, we observe a steepening of the density profiles beyond approximately 0.3r(sub 500). Comparing our density profiles with simulations, we find that non-radiative runs predict too steep density profiles, whereas runs including additional physics and/or gas clumping are in better agreement with the observed gas distribution. We note a systematic difference between cool-core and non-cool core clusters beyond approximately 0.3r(sub 200), which we explain by a different distribution of the gas in the two classes. Beyond approximately r(sub 500), galaxy clusters deviate significantly from spherical symmetry, with only little differences between relaxed and disturbed systems. We find good agreement between the observed and predicted scatter profiles, but only when the 1% densest clumps are filtered out in the simulations. Conclusions. The general trend of steepening density around the virial radius indicates that the shallow density profiles found in several recent works were probably obtained along particular directions (e.g., filaments) and are not representative of the

  15. A mysterious dust clump in a disk around an evolved binary star system.

    PubMed

    Jura, M; Turner, J

    1998-09-10

    The discovery of planets in orbit around the pulsar PSR1257+12 shows that planets may form around post-main-sequence stars. Other evolved stars, such as HD44179 (an evolved star which is part of the binary system that has expelled the gas and dust that make the Red Rectangle nebula), possess gravitationally bound orbiting dust disks. It is possible that planets might form from gravitational collapse in such disks. Here we report high-angular-resolution observations at millimetre and submillimetre wavelengths of the dusk disk associated with the Red Rectangle. We find a dust clump with an estimated mass near that of Jupiter in the outer region of the disk. The clump is larger than our Solar System, and far beyond where planet formation would normally be expected, so its nature is at present unclear.

  16. CLUMP-3D: Testing ΛCDM with Galaxy Cluster Shapes

    NASA Astrophysics Data System (ADS)

    Sereno, Mauro; Umetsu, Keiichi; Ettori, Stefano; Sayers, Jack; Chiu, I.-Non; Meneghetti, Massimo; Vega-Ferrero, Jesús; Zitrin, Adi

    2018-06-01

    The ΛCDM model of structure formation makes strong predictions on the concentration and shape of dark matter (DM) halos, which are determined by mass accretion processes. Comparison between predicted shapes and observations provides a geometric test of the ΛCDM model. Accurate and precise measurements needs a full three-dimensional (3D) analysis of the cluster mass distribution. We accomplish this with a multi-probe 3D analysis of the X-ray regular Cluster Lensing and Supernova survey with Hubble (CLASH) clusters combining strong and weak lensing, X-ray photometry and spectroscopy, and the Sunyaev–Zel’dovich effect (SZe). The cluster shapes and concentrations are consistent with ΛCDM predictions. The CLASH clusters are randomly oriented, as expected given the sample selection criteria. Shapes agree with numerical results for DM-only halos, which hints at baryonic physics being less effective in making halos rounder.

  17. Dissociation and Re-Aggregation of Multicell-Ensheathed Fragments Responsible for Rapid Production of Massive Clumps of Leptothrix Sheaths

    PubMed Central

    Kunoh, Tatsuki; Nagaoka, Noriyuki; McFarlane, Ian R.; Tamura, Katsunori; El-Naggar, Mohamed Y.; Kunoh, Hitoshi; Takada, Jun

    2016-01-01

    Species of the Fe/Mn-oxidizing bacteria Leptothrix produce tremendous amounts of microtubular, Fe/Mn-encrusted sheaths within a few days in outwells of groundwater that can rapidly clog water systems. To understand this mode of rapid sheath production and define the timescales involved, behaviors of sheath-forming Leptothrix sp. strain OUMS1 were examined using time-lapse video at the initial stage of sheath formation. OUMS1 formed clumps of tangled sheaths. Electron microscopy confirmed the presence of a thin layer of bacterial exopolymer fibrils around catenulate cells (corresponding to the immature sheath). In time-lapse videos, numerous sheath filaments that extended from the periphery of sheath clumps repeatedly fragmented at the apex of the same fragment, the fragments then aggregated and again elongated, eventually forming a large sheath clump comprising tangled sheaths within two days. In this study, we found that fast microscopic fragmentation, dissociation, re-aggregation and re-elongation events are the basis of the rapid, massive production of Leptothrix sheaths typically observed at macroscopic scales. PMID:27490579

  18. The connection between the peaks in velocity dispersion and star-forming clumps of turbulent galaxies

    NASA Astrophysics Data System (ADS)

    Oliva-Altamirano, P.; Fisher, D. B.; Glazebrook, K.; Wisnioski, E.; Bekiaris, G.; Bassett, R.; Obreschkow, D.; Abraham, R.

    2018-02-01

    We present Keck/OSIRIS adaptive optics observations with 150-400 pc spatial sampling of 7 turbulent, clumpy disc galaxies from the DYNAMO sample ($0.07clump measured with HST H$\\alpha$ maps. This could suggest that the peaks in velocity dispersion in clumpy galaxies likely arise due to some interaction between the clump and the surrounding ISM of the galaxy, though our observations cannot distinguish between outflows, inflows or velocity shear. Observations covering a wider area of the galaxies will be needed to confirm this result.

  19. Benthic Foraminifera Clumped Isotope Calibration

    NASA Astrophysics Data System (ADS)

    Piasecki, A.; Marchitto, T. M., Jr.; Bernasconi, S. M.; Grauel, A. L.; Tisserand, A. A.; Meckler, N.

    2017-12-01

    Due to the widespread spatial and temporal distribution of benthic foraminifera within ocean sediments, they are a commonly used for reconstructing past ocean temperatures and environmental conditions. Many foraminifera-based proxies, however, require calibration schemes that are species specific, which becomes complicated in deep time due to extinct species. Furthermore, calibrations often depend on seawater chemistry being stable and/or constrained, which is not always the case over significant climate state changes like the Eocene Oligocene Transition. Here we study the effect of varying benthic foraminifera species using the clumped isotope proxy for temperature. The benefit of this proxy is that it is independent of seawater chemistry, whereas the downside is that it requires a relatively large sample amounts. Due to recent advancements in sample processing that reduce the sample weight by a factor of 10, clumped isotopes can now be applied to a range paleoceanographic questions. First however, we need to prove that, unlike for other proxies, there are no interspecies differences with clumped isotopes, as is predicted by first principles modeling. We used a range of surface sediment samples covering a temperature range of 1-20°C from the Pacific, Mediterranean, Bahamas, and the Atlantic, and measured the clumped isotope composition of 11 different species of benthic foraminifera. We find that there are indeed no discernible species-specific differences within the sample set. In addition, the samples have the same temperature response to the proxy as inorganic carbonate samples over the same temperature range. As a result, we can now apply this proxy to a wide range of samples and foraminifera species from different ocean basins with different ocean chemistry and be confident that observed signals reflect variations in temperature.

  20. Starless Clumps and the Earliest Phases of High-mass Star Formation in the Milky Way

    NASA Astrophysics Data System (ADS)

    Svoboda, Brian

    2018-01-01

    High-mass stars are key to regulating the interstellar medium, star formation activity, and overall evolution of galaxies, but their formation remains an open problem in astrophysics. In order to understand the physical conditions during the earliest phases of high-mass star formation, I report on observational studies of dense starless clump candidates (SCCs) that show no signatures of star formation activity. I identify 2223 SCCs from the 1.1 mm Bolocam Galactic Plane Survey, systematically analyze their physical properties, and show that the starless phase is not represented by a single timescale, but evolves more rapidly with increasing clump mass. To investigate the sub-structure in SCCs at high spatial resolution, I study the 12 most high-mass SCCs within 5 kpc using ALMA. I report previously undetected low-luminosity protostars in 11 out of 12 SCCs, fragmentation equal to the thermal Jeans length of the clump, and no starless cores exceeding 30 solar masses. While uncertainties remain concerning the star formation effeciency in this sample, these observational facts are consistent with models where high-mass stars form from intially low- to intermediate-mass protostars that accrete most of their mass from the surrounding clump.

  1. Equilibrium temperature in a clump of bacteria heated in fluid.

    PubMed Central

    Davey, K R

    1990-01-01

    A theoretical model was developed and used to estimate quantitatively the "worst case", i.e., the longest, time to reach equilibrium temperature in the center of a clump of bacteria heated in fluid. For clumps with 10 to 10(6) cells heated in vapor, such as dry and moist air, and liquid fluids such as purees and juices, predictions show that temperature equilibrium will occur with sterilization temperatures up to 130 degrees C in under 0.02 s. Model development highlighted that the controlling influence on time for heating up the clump is the surface convection thermal resistance and that the internal conduction resistance of the clump mass is negligible by comparison. The time for a clump to reach equilibrium sterilization temperature was therefore decreased with relative turbulence (velocity) of the heating fluid, such as occurs in many process operations. These results confirm widely held suppositions that the heat-up time of bacteria in vapor or liquid is not significant with usual sterilization times. PMID:2306095

  2. VizieR Online Data Catalog: Young clumps embedded in IRDC (Traficante+, 2015)

    NASA Astrophysics Data System (ADS)

    Traficante, A.; Fuller, G. A.; Peretto, N.; Pineda, J. E.; Molinari, S.

    2015-06-01

    Photometric parameters for 667 starless clumps (sources identified at 160um with a counterpart at 250 and 350um) and 1056 protostellar clumps (sources identified at 160um with a counterpart at 70, 250 and 350um). Photometric parameters obtained with Hyper photometry code (2015A&A...574A.119T). The photometry is corrected for aperture and colour corrections. The parameter list is the standard Hyper output (see description below). SED fit parameters for 650 starless clumps and 1034 protostellar clumps (all clumps with good SED fitting: Chi2<10, Temperature<40K. See the paper for details) (4 data files).

  3. The Application of Methane Clumped Isotope Measurements to Determine the Source of Large Methane Seeps in Alaskan Lakes

    NASA Astrophysics Data System (ADS)

    Douglas, P. M.; Stolper, D. A.; Eiler, J. M.; Sessions, A. L.; Walter Anthony, K. M.

    2014-12-01

    Natural methane emissions from the Arctic present an important potential feedback to global warming. Arctic methane emissions may come from either active microbial sources or from deep fossil reservoirs released by the thawing of permafrost and melting of glaciers. It is often difficult to distinguish between and quantify contributions from these methane sources based on stable isotope data. Analyses of methane clumped isotopes (isotopologues with two or more rare isotopes such as 13CH3D) can complement traditional stable isotope-based classifications of methane sources. This is because clumped isotope abundances (for isotopically equilibrated systems) are a function of temperature and can be used to identify pathways of methane generation. Additionally, distinctive effects of mixing on clumped isotope abundances make this analysis valuable for determining the origins of mixed gasses. We find large variability in clumped isotope compositions of methane from seeps in several lakes, including thermokarst lakes, across Alaska. At Lake Sukok in northern Alaska we observe the emission of dominantly thermogenic methane, with a formation temperature of at least 100° C. At several other lakes we find evidence for mixing between thermogenic methane and biogenic methane that forms in low-temperature isotopic equilibrium. For example, at Eyak Lake in southeastern Alaska, analysis of three methane samples results in a distinctive isotopic mixing line between a high-temperature end-member that formed between 100-170° C, and a biogenic end-member that formed in isotopic equilibrium between 0-20° C. In this respect, biogenic methane in these lakes resembles observations from marine gas seeps, oil degradation, and sub-surface aquifers. Interestingly, at Goldstream Lake in interior Alaska, methane with strongly depleted clumped-isotope abundances, indicative of disequilibrium gas formation, is found, similar to observations from methanogen culture experiments.

  4. The Gas Distribution in Galaxy Cluster Outer Regions

    NASA Technical Reports Server (NTRS)

    Eckert, D.; Vazza, F.; Ettori, S.; Molendi, S.; Nagai, D.; Laue, E. T.; Roncarelli, M.; Rossetti, M.; Snowden, S. L.; Gastaldello, F.

    2012-01-01

    Aims. We present the analysis of a local (z = 0.04 - 0.2) sample of 31 galaxy clusters with the aim of measuring the density of the X-ray emitting gas in cluster outskirts. We compare our results with numerical simulations to set constraints on the azimuthal symmetry and gas clumping in the outer regions of galaxy clusters. Methods. We exploit the large field-of-view and low instrumental background of ROSAT/PSPC to trace the density of the intracluster gas out to the virial radius. We perform a stacking of the density profiles to detect a signal beyond r200 and measure the typical density and scatter in cluster outskirts. We also compute the azimuthal scatter of the profiles with respect to the mean value to look for deviations from spherical symmetry. Finally, we compare our average density and scatter profiles with the results of numerical simulations. Results. As opposed to some recent Suzaku results, and confirming previous evidence from ROSAT and Chandra, we observe a steepening of the density profiles beyond approximately r(sub 500). Comparing our density profiles with simulations, we find that non-radiative runs predict too steep density profiles, whereas runs including additional physics and/or treating gas clumping are in better agreement with the observed gas distribution. We report for the first time the high-confidence detection of a systematic difference between cool-core and non-cool core clusters beyond 0.3r(sub 200), which we explain by a different distribution of the gas in the two classes. Beyond r(sub 500), galaxy clusters deviate significantly from spherical symmetry, with only little differences between relaxed and disturbed systems. We find good agreement between the observed and predicted scatter profiles, but only when the 1% densest clumps are filtered out in the simulations. Conclusions. Comparing our results with numerical simulations, we find that non-radiative simulations fail to reproduce the gas distribution, even well outside cluster

  5. Clumpy Galaxies in CANDELS. II. Physical Properties of UV-bright Clumps at 0.5 ≤ z < 3

    NASA Astrophysics Data System (ADS)

    Guo, Yicheng; Rafelski, Marc; Bell, Eric F.; Conselice, Christopher J.; Dekel, Avishai; Faber, S. M.; Giavalisco, Mauro; Koekemoer, Anton M.; Koo, David C.; Lu, Yu; Mandelker, Nir; Primack, Joel R.; Ceverino, Daniel; de Mello, Duilia F.; Ferguson, Henry C.; Hathi, Nimish; Kocevski, Dale; Lucas, Ray A.; Pérez-González, Pablo G.; Ravindranath, Swara; Soto, Emmaris; Straughn, Amber; Wang, Weichen

    2018-02-01

    Studying giant star-forming clumps in distant galaxies is important to understand galaxy formation and evolution. At present, however, observers and theorists have not reached a consensus on whether the observed “clumps” in distant galaxies are the same phenomenon that is seen in simulations. In this paper, as a step to establish a benchmark of direct comparisons between observations and theories, we publish a sample of clumps constructed to represent the commonly observed “clumps” in the literature. This sample contains 3193 clumps detected from 1270 galaxies at 0.5≤slant z< 3.0. The clumps are detected from rest-frame UV images, as described in our previous paper. Their physical properties (e.g., rest-frame color, stellar mass ({M}* ), star formation rate (SFR), age, and dust extinction) are measured by fitting the spectral energy distribution (SED) to synthetic stellar population models. We carefully test the procedures of measuring clump properties, especially the method of subtracting background fluxes from the diffuse component of galaxies. With our fiducial background subtraction, we find a radial clump U ‑ V color variation, where clumps close to galactic centers are redder than those in outskirts. The slope of the color gradient (clump color as a function of their galactocentric distance scaled by the semimajor axis of galaxies) changes with redshift and {M}* of the host galaxies: at a fixed {M}* , the slope becomes steeper toward low redshift, and at a fixed redshift, it becomes slightly steeper with {M}* . Based on our SED fitting, this observed color gradient can be explained by a combination of a negative age gradient, a negative E(B ‑ V) gradient, and a positive specific SFR gradient of the clumps. We also find that the color gradients of clumps are steeper than those of intra-clump regions. Correspondingly, the radial gradients of the derived physical properties of clumps are different from those of the diffuse component or intra-clump

  6. Clusters of Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Fort, Bernard

    For a long time, the small number of clusters at z > 0.3 in the Abell survey catalogue and simulations of the standard CDM formation of large scale structures provided a paradigm where clusters were considered as young merging structures. At earlier times, loose concentrations of galaxy clumps were mostly anticipated. Recent observations broke the taboo. Progressively we became convinced that compact and massive clusters at z = 1 or possibly beyond exist and should be searched for.

  7. Do All O Stars Form in Star Clusters?

    NASA Astrophysics Data System (ADS)

    Weidner, C.; Gvaramadze, V. V.; Kroupa, P.; Pflamm-Altenburg, J.

    The question whether or not massive stars can form in isolation or only in star clusters is of great importance for the theory of (massive) star formation as well as for the stellar initial mass function of whole galaxies (IGIMF-theory). While a seemingly easy question it is rather difficult to answer. Several physical processes (e.g. star-loss due to stellar dynamics or gas expulsion) and observational limitations (e.g. dust obscuration of young clusters, resolution) pose severe challenges to answer this question. In this contribution we will present the current arguments in favour and against the idea that all O stars form in clusters.

  8. Tidal disruption of open clusters in their parent molecular clouds

    NASA Technical Reports Server (NTRS)

    Long, Kevin

    1989-01-01

    A simple model of tidal encounters has been applied to the problem of an open cluster in a clumpy molecular cloud. The parameters of the clumps are taken from the Blitz, Stark, and Long (1988) catalog of clumps in the Rosette molecular cloud. Encounters are modeled as impulsive, rectilinear collisions between Plummer spheres, but the tidal approximation is not invoked. Mass and binding energy changes during an encounter are computed by considering the velocity impulses given to individual stars in a random realization of a Plummer sphere. Mean rates of mass and binding energy loss are then computed by integrating over many encounters. Self-similar evolutionary calculations using these rates indicate that the disruption process is most sensitive to the cluster radius and relatively insensitive to cluster mass. The calculations indicate that clusters which are born in a cloud similar to the Rosette with a cluster radius greater than about 2.5 pc will not survive long enough to leave the cloud. The majority of clusters, however, have smaller radii and will survive the passage through their parent cloud.

  9. Properties of Starless Clumps through Protoclusters from the Bolocam Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    Svoboda, Brian E.; Shirley, Yancy

    2014-07-01

    High mass stars play a key role in the physical and chemical evolution of the interstellar medium, yet the evolution of physical properties for high-mass star-forming regions remains unclear. We sort a sample of ~4668 molecular cloud clumps from the Bolocam Galactic Plane Survey (BGPS) into different evolutionary stages by combining the BGPS 1.1 mm continuum and observational diagnostics of star-formation activity from a variety of Galactic plane surveys: 70 um compact sources, mid-IR color-selected YSOs, H2O and CH3OH masers, EGOs, and UCHII regions. We apply Monte Carlo techniques to distance probability distribution functions (DPDFs) in order to marginalize over the kinematic distance ambiguity and calculate distributions for derived quantities of clumps in different evolutionary stages. We also present a combined NH3 and H2O maser catalog for ~1590 clumps from the literature and our own GBT 100m observations. We identify a sub-sample of 440 dense clumps with no star-formation indicators, representing the largest and most robust sample of pre-protocluster candidates from a blind survey to date. Distributions of I(HCO+), I(N2H+), dv(HCO+), dv(N2H+), mass surface density, and kinetic temperature show strong progressions when separated by evolutionary stage. No progressions are found in size or dust mass; however, weak progressions are observed in area > 2 pc^2 and dust mass > 3 10^3 Msun. An observed breakdown occurs in the size-linewidth relationship and we find no improvement when sampling by evolutionary stage.

  10. Merging Clusters, Cluster Outskirts, and Large Scale Filaments

    NASA Astrophysics Data System (ADS)

    Randall, Scott; Alvarez, Gabriella; Bulbul, Esra; Jones, Christine; Forman, William; Su, Yuanyuan; Miller, Eric D.; Bourdin, Herve; Scott Randall

    2018-01-01

    Recent X-ray observations of the outskirts of clusters show that entropy profiles of the intracluster medium (ICM) generally flatten and lie below what is expected from purely gravitational structure formation near the cluster's virial radius. Possible explanations include electron/ion non-equilibrium, accretion shocks that weaken during cluster formation, and the presence of unresolved cool gas clumps. Some of these mechanisms are expected to correlate with large scale structure (LSS), such that the entropy is lower in regions where the ICM interfaces with LSS filaments and, presumably, the warm-hot intergalactic medium (WHIM). Major, binary cluster mergers are expected to take place at the intersection of LSS filaments, with the merger axis initially oriented along a filament. We present results from deep X-ray observations of the virialization regions of binary, early-stage merging clusters, including a possible detection of the dense end of the WHIM along a LSS filament.

  11. Reconstruction of limnology and microbialite formation conditions from carbonate clumped isotope thermometry.

    PubMed

    Petryshyn, V A; Lim, D; Laval, B L; Brady, A; Slater, G; Tripati, A K

    2015-01-01

    Quantitative tools for deciphering the environment of microbialite formation are relatively limited. For example, the oxygen isotope carbonate-water geothermometer requires assumptions about the isotopic composition of the water of formation. We explored the utility of using 'clumped' isotope thermometry as a tool to study the temperatures of microbialite formation. We studied microbialites recovered from water depths of 10-55 m in Pavilion Lake, and 10-25 m in Kelly Lake, spanning the thermocline in both lakes. We determined the temperature of carbonate growth and the (18)O/(16)O ratio of the waters that microbialites grew in. Results were then compared to current limnological data from the lakes to reconstruct the history of microbialite formation. Modern microbialites collected at shallow depths (11.7 m) in both lakes yield clumped isotope-based temperatures of formation that are within error of summer water temperatures, suggesting that clumped isotope analyses may be used to reconstruct past climates and to probe the environments in which microbialites formed. The deepest microbialites (21.7-55 m) were recovered from below the present-day thermoclines in both lakes and yield radioisotope ages indicating they primarily formed earlier in the Holocene. During this time, pollen data and our reconstructed water (18)O/(16)O ratios indicate a period of aridity, with lower lake levels. At present, there is a close association between both photosynthetic and heterotrophic communities, and carbonate precipitation/microbialite formation, with biosignatures of photosynthetic influences on carbonate detected in microbialites from the photic zone and above the thermocline (i.e., depths of generally <20 m). Given the deeper microbialites are receiving <1% of photosynthetically active radiation (PAR), it is likely these microbialites primarily formed when lower lake levels resulted in microbialites being located higher in the photic zone, in warm surface waters. © 2014 John

  12. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ginsburg, A.; Bally, J.; Battersby, C.

    We search the {lambda} = 1.1 mm Bolocam Galactic Plane Survey for clumps containing sufficient mass to form {approx}10{sup 4} M{sub Sun} star clusters. Eighteen candidate massive proto-clusters are identified in the first Galactic quadrant outside of the central kiloparsec. This sample is complete to clumps with mass M{sub clump} > 10{sup 4} M{sub Sun} and radius r {approx}< 2.5 pc. The overall Galactic massive cluster formation rate is CFR(M{sub cluster} > 10{sup 4}) {approx}<5 Myr{sup -1}, which is in agreement with the rates inferred from Galactic open clusters and M31 massive clusters. We find that all massive proto-clusters inmore » the first quadrant are actively forming massive stars and place an upper limit of {tau}{sub starless} < 0.5 Myr on the lifetime of the starless phase of massive cluster formation. If massive clusters go through a starless phase with all of their mass in a single clump, the lifetime of this phase is very short.« less

  13. Clump detections and limits on moons in Jupiter's ring system.

    PubMed

    Showalter, Mark R; Cheng, Andrew F; Weaver, Harold A; Stern, S Alan; Spencer, John R; Throop, Henry B; Birath, Emma M; Rose, Debi; Moore, Jeffrey M

    2007-10-12

    The dusty jovian ring system must be replenished continuously from embedded source bodies. The New Horizons spacecraft has performed a comprehensive search for kilometer-sized moons within the system, which might have revealed the larger members of this population. No new moons were found, however, indicating a sharp cutoff in the population of jovian bodies smaller than 8-kilometer-radius Adrastea. However, the search revealed two families of clumps in the main ring: one close pair and one cluster of three to five. All orbit within a brighter ringlet just interior to Adrastea. Their properties are very different from those of the few other clumpy rings known; the origin and nonrandom distribution of these features remain unexplained, but resonant confinement by Metis may play a role.

  14. THE BOLOCAM GALACTIC PLANE SURVEY. XI. TEMPERATURES AND SUBSTRUCTURE OF GALACTIC CLUMPS BASED ON 350 μM OBSERVATIONS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Merello, Manuel; Evans II, Neal J.; Shirley, Yancy L.

    We present 107 maps of continuum emission at 350 μm from Galactic molecular clumps. Observed sources were mainly selected from the Bolocam Galactic Plane Survey (BGPS) catalog, with three additional maps covering star-forming regions in the outer Galaxy. The higher resolution of the SHARC-II images (8.″5 beam) compared with the 1.1 mm images from BGPS (33″ beam) allowed us to identify a large population of smaller substructures within the clumps. A catalog is presented for the 1386 sources extracted from the 350 μm maps. The color temperature distribution of clumps based on the two wavelengths has a median of 13.3more » K and mean of 16.3 ± 0.4 K, assuming an opacity law index of 1.7. For the structures with good determination of color temperatures, the mean ratio of gas temperature, determined from NH{sub 3} observations, to dust color temperature is 0.88 and the median ratio is 0.76. About half the clumps have more than 2 substructures and 22 clumps have more than 10. The fraction of the mass in dense substructures seen at 350 μm compared to the mass of their parental clump is ∼0.19, and the surface densities of these substructures are, on average, 2.2 times those seen in the clumps identified at 1.1 mm. For a well-characterized sample, 88 structures (31%) exceed a surface density of 0.2 g cm{sup −2}, and 18 (6%) exceed 1.0 g cm{sup −2}, thresholds for massive star formation suggested by theorists.« less

  15. Clumped isotope composition of cold-water corals: A role for vital effects?

    NASA Astrophysics Data System (ADS)

    Spooner, Peter T.; Guo, Weifu; Robinson, Laura F.; Thiagarajan, Nivedita; Hendry, Katharine R.; Rosenheim, Brad E.; Leng, Melanie J.

    2016-04-01

    The carbonate clumped isotope thermometer is a promising tool for determining past ocean temperatures. It is based on the temperature dependence of rare isotopes 'clumping' into the same carbonate ion group in the carbonate mineral lattice. The extent of this clumping effect is independent of the isotope composition of the water from which carbonate precipitates, providing unique advantages over many other paleotemperature proxies. Existing calibrations of this thermometer in cold-water and warm-water corals suggest clumped isotope 'vital effects' are negligible in cold-water corals but may be significant in warm-water corals. Here, we test the calibration of the carbonate clumped isotope thermometer in cold-water corals with a recently collected and well characterised sample set spanning a range of coral genera (Balanophyllia, Caryophyllia, Dasmosmilia, Desmophyllum, Enallopsammia and Javania). The clumped isotope compositions (Δ47) of these corals exhibit systematic dependences on their growth temperatures, confirming the basis of the carbonate clumped isotope thermometer. However, some cold-water coral genera show Δ47 values that are higher than the expected equilibrium values by up to 0.05‰ (equivalent to underestimating temperature by ∼9 °C) similar to previous findings for some warm-water corals. This finding suggests that the vital effects affecting corals Δ47 are common to both warm- and cold-water corals. By comparison with models of the coral calcification process we suggest that the clumped isotope offsets in these genera are related to the kinetic isotope effects associated with CO2 hydration/hydroxylation reactions in the corals' calcifying fluid. Our findings complicate the use of the carbonate clumped isotope thermometer in corals, but suggest that species- or genus-specific calibrations could be useful for the future application of this paleotemperature proxy.

  16. The Staphylococcus aureus Global Regulator MgrA Modulates Clumping and Virulence by Controlling Surface Protein Expression

    PubMed Central

    Crosby, Heidi A.; Schlievert, Patrick M.; Merriman, Joseph A.; King, Jessica M.; Salgado-Pabón, Wilmara; Horswill, Alexander R.

    2016-01-01

    Staphylococcus aureus is a human commensal and opportunistic pathogen that causes devastating infections in a wide range of locations within the body. One of the defining characteristics of S. aureus is its ability to form clumps in the presence of soluble fibrinogen, which likely has a protective benefit and facilitates adhesion to host tissue. We have previously shown that the ArlRS two-component regulatory system controls clumping, in part by repressing production of the large surface protein Ebh. In this work we show that ArlRS does not directly regulate Ebh, but instead ArlRS activates expression of the global regulator MgrA. Strains lacking mgrA fail to clump in the presence of fibrinogen, and clumping can be restored to an arlRS mutant by overexpressing either arlRS or mgrA, indicating that ArlRS and MgrA constitute a regulatory pathway. We used RNA-seq to show that MgrA represses ebh, as well as seven cell wall-associated proteins (SraP, Spa, FnbB, SasG, SasC, FmtB, and SdrD). EMSA analysis showed that MgrA directly represses expression of ebh and sraP. Clumping can be restored to an mgrA mutant by deleting the genes for Ebh, SraP and SasG, suggesting that increased expression of these proteins blocks clumping by steric hindrance. We show that mgrA mutants are less virulent in a rabbit model of endocarditis, and virulence can be partially restored by deleting the genes for the surface proteins ebh, sraP, and sasG. While mgrA mutants are unable to clump, they are known to have enhanced biofilm capacity. We demonstrate that this increase in biofilm formation is partially due to up-regulation of SasG, a surface protein known to promote intercellular interactions. These results confirm that ArlRS and MgrA constitute a regulatory cascade, and that they control expression of a number of genes important for virulence, including those for eight large surface proteins. PMID:27144398

  17. Inter- and intra-annual variations of clumping index derived from the MODIS BRDF product

    NASA Astrophysics Data System (ADS)

    He, Liming; Liu, Jane; Chen, Jing M.; Croft, Holly; Wang, Rong; Sprintsin, Michael; Zheng, Ting; Ryu, Youngryel; Pisek, Jan; Gonsamo, Alemu; Deng, Feng; Zhang, Yongqin

    2016-02-01

    Clumping index quantifies the level of foliage aggregation, relative to a random distribution, and is a key structural parameter of plant canopies and is widely used in ecological and meteorological models. In this study, the inter- and intra-annual variations in clumping index values, derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) BRDF product, are investigated at six forest sites, including conifer forests, a mixed deciduous forest and an oak-savanna system. We find that the clumping index displays large seasonal variation, particularly for the deciduous sites, with the magnitude in clumping index values at each site comparable on an intra-annual basis, and the seasonality of clumping index well captured after noise removal. For broadleaved and mixed forest sites, minimum clumping index values are usually found during the season when leaf area index is at its maximum. The magnitude of MODIS clumping index is validated by ground data collected from 17 sites. Validation shows that the MODIS clumping index can explain 75% of variance in measured values (bias = 0.03 and rmse = 0.08), although with a narrower amplitude in variation. This study suggests that the MODIS BRDF product has the potential to produce good seasonal trajectories of clumping index values, but with an improved estimation of background reflectance.

  18. F Ring Bright Core Clumps

    NASA Image and Video Library

    2010-07-20

    Bright clumps of ring material and a fan-like structure appear near the core of Saturn tenuous F ring in this mosaic of images from NASA Cassini spacecraft. Such features suggest the existence of additional objects in the F ring.

  19. The Gas Distribution in the Outer Regions of Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Eckert, D.; Vazza, F.; Ettori, S.; Molendi, S.; Nagai, D.; Lau, E. T.; Roncarelli, M.; Rossetti, M.; Snowden, L.; Gastaldello, F.

    2012-01-01

    Aims. We present our analysis of a local (z = 0.04 - 0.2) sample of 31 galaxy clusters with the aim of measuring the density of the X-ray emitting gas in cluster outskirts. We compare our results with numerical simulations to set constraints on the azimuthal symmetry and gas clumping in the outer regions of galaxy clusters. Methods. We have exploited the large field-of-view and low instrumental background of ROSAT/PSPC to trace the density of the intracluster gas out to the virial radius, We stacked the density profiles to detect a signal beyond T200 and measured the typical density and scatter in cluster outskirts. We also computed the azimuthal scatter of the profiles with respect to the mean value to look for deviations from spherical symmetry. Finally, we compared our average density and scatter profiles with the results of numerical simulations. Results. As opposed to some recent Suzaku results, and confirming previous evidence from ROSAT and Chandra, we observe a steepening of the density profiles beyond approximately r(sub 500). Comparing our density profiles with simulations, we find that non-radiative runs predict density profiles that are too steep, whereas runs including additional physics and/ or treating gas clumping agree better with the observed gas distribution. We report high-confidence detection of a systematic difference between cool-core and non cool-core clusters beyond approximately 0.3r(sub 200), which we explain by a different distribution of the gas in the two classes. Beyond approximately r(sub 500), galaxy clusters deviate significantly from spherical symmetry, with only small differences between relaxed and disturbed systems. We find good agreement between the observed and predicted scatter profiles, but only when the 1% densest clumps are filtered out in the ENZO simulations. Conclusions. Comparing our results with numerical simulations, we find that non-radiative simulations fail to reproduce the gas distribution, even well outside

  20. The star-forming history of the young cluster NGC 2264

    NASA Technical Reports Server (NTRS)

    Adams, M. T.; Strom, K. M.; Strom, S. E.

    1983-01-01

    UBVRI H-alpha photographic photometry was obtained for a sample of low-mass stars in the young open cluster NGC 2264 in order to investigate the star-forming history of this region. A theoretical H-R diagram was constructed for the sample of probable cluster members. Isochrones and evolutionary tracks were adopted from Cohen and Kuhi (1979). Evidence for a significant age spread in the cluster was found amounting to over ten million yr. In addition, the derived star formation rate as a function of stellar mass suggests that the principal star-forming mass range in NGC 2264 has proceeded sequentially in time from the lowest to the highest masses. The low-mass cluster stars were the first cluster members to form in significant numbers, although their present birth rate is much lower now than it was about ten million yr ago. The star-formation rate has risen to a peak at successively higher masses and then declined.

  1. Cosmic Reionization On Computers III. The Clumping Factor

    DOE PAGES

    Kaurov, Alexander A.; Gnedin, Nickolay Y.

    2015-09-09

    We use fully self-consistent numerical simulations of cosmic reionization, completed under the Cosmic Reionization On Computers project, to explore how well the recombinations in the ionized intergalactic medium (IGM) can be quantified by the effective "clumping factor." The density distribution in the simulations (and, presumably, in a real universe) is highly inhomogeneous and more-or-less smoothly varying in space. However, even in highly complex and dynamic environments, the concept of the IGM remains reasonably well-defined; the largest ambiguity comes from the unvirialized regions around galaxies that are over-ionized by the local enhancement in the radiation field ("proximity zones"). This ambiguity precludesmore » computing the IGM clumping factor to better than about 20%. Furthermore, we discuss a "local clumping factor," defined over a particular spatial scale, and quantify its scatter on a given scale and its variation as a function of scale.« less

  2. Cosmic Reionization On Computers III. The Clumping Factor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kaurov, Alexander A.; Gnedin, Nickolay Y.

    We use fully self-consistent numerical simulations of cosmic reionization, completed under the Cosmic Reionization On Computers project, to explore how well the recombinations in the ionized intergalactic medium (IGM) can be quantified by the effective "clumping factor." The density distribution in the simulations (and, presumably, in a real universe) is highly inhomogeneous and more-or-less smoothly varying in space. However, even in highly complex and dynamic environments, the concept of the IGM remains reasonably well-defined; the largest ambiguity comes from the unvirialized regions around galaxies that are over-ionized by the local enhancement in the radiation field ("proximity zones"). This ambiguity precludesmore » computing the IGM clumping factor to better than about 20%. Furthermore, we discuss a "local clumping factor," defined over a particular spatial scale, and quantify its scatter on a given scale and its variation as a function of scale.« less

  3. Eccentric black hole mergers forming in globular clusters

    NASA Astrophysics Data System (ADS)

    Samsing, Johan

    2018-05-01

    We derive the probability for a newly formed binary black hole (BBH) to undergo an eccentric gravitational wave (GW) merger during binary-single interactions inside a stellar cluster. By integrating over the hardening interactions such a BBH must undergo before ejection, we find that the observable rate of BBH mergers with eccentricity >0.1 at 10 Hz relative to the rate of circular mergers can be as high as ˜5 % for a typical globular cluster (GC). This further suggests that BBH mergers forming through GW captures in binary-single interactions, eccentric or not, are likely to constitute ˜10 % of the total BBH merger rate from GCs. Such GW capture mergers can only be probed with an N -body code that includes general relativistic corrections, which explains why recent Newtonian cluster studies have not been able to resolve this population. Finally, we show that the relative rate of eccentric BBH mergers depends on the compactness of their host cluster, suggesting that an observed eccentricity distribution can be used to probe the origin of BBH mergers.

  4. Star-forming brightest cluster galaxies at 0.25

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McDonald, M.; Stalder, B.; Bayliss, M.

    2016-01-22

    We present a multiwavelength study of the 90 brightest cluster galaxies (BCGs) in a sample of galaxy clusters selected via the Sunyaev Zel'dovich effect by the South Pole Telescope, utilizing data from various ground- and space-based facilities. We infer the star-formation rate (SFR) for the BCG in each cluster—based on the UV and IR continuum luminosity, as well as the [O ii]λλ3726,3729 emission line luminosity in cases where spectroscopy is available—and find seven systems with SFR > 100 M⊙ yr-1. We find that the BCG SFR exceeds 10 M⊙ yr-1 in 31 of 90 (34%) cases at 0.25 < z < 1.25, compared to ~1%–5% at z ~ 0 from the literature. At z gsim 1, this fraction increases tomore » $${92}_{-31}^{+6}$$%, implying a steady decrease in the BCG SFR over the past ~9 Gyr. At low-z, we find that the specific SFR in BCGs is declining more slowly with time than for field or cluster galaxies, which is most likely due to the replenishing fuel from the cooling ICM in relaxed, cool core clusters. At z gsim 0.6, the correlation between the cluster central entropy and BCG star formation—which is well established at z ~ 0—is not present. Instead, we find that the most star-forming BCGs at high-z are found in the cores of dynamically unrelaxed clusters. We use data from the Hubble Space Telescope to investigate the rest-frame near-UV morphology of a subsample of the most star-forming BCGs, and find complex, highly asymmetric UV morphologies on scales as large as ~50–60 kpc. The high fraction of star-forming BCGs hosted in unrelaxed, non-cool core clusters at early times suggests that the dominant mode of fueling star formation in BCGs may have recently transitioned from galaxy–galaxy interactions to ICM cooling.« less

  5. COSMIC REIONIZATION ON COMPUTERS. III. THE CLUMPING FACTOR

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kaurov, Alexander A.; Gnedin, Nickolay Y., E-mail: kaurov@uchicago.edu, E-mail: gnedin@fnal.gov

    We use fully self-consistent numerical simulations of cosmic reionization, completed under the Cosmic Reionization On Computers project, to explore how well the recombinations in the ionized intergalactic medium (IGM) can be quantified by the effective “clumping factor.” The density distribution in the simulations (and, presumably, in a real universe) is highly inhomogeneous and more-or-less smoothly varying in space. However, even in highly complex and dynamic environments, the concept of the IGM remains reasonably well-defined; the largest ambiguity comes from the unvirialized regions around galaxies that are over-ionized by the local enhancement in the radiation field (“proximity zones”). That ambiguity precludesmore » computing the IGM clumping factor to better than about 20%. We also discuss a “local clumping factor,” defined over a particular spatial scale, and quantify its scatter on a given scale and its variation as a function of scale.« less

  6. Cosmic void clumps

    NASA Astrophysics Data System (ADS)

    Lares, M.; Luparello, H. E.; Garcia Lambas, D.; Ruiz, A. N.; Ceccarelli, L.; Paz, D.

    2017-10-01

    Cosmic voids are of great interest given their relation to the large scale distribution of mass and the way they trace cosmic flows shaping the cosmic web. Here we show that the distribution of voids has, in consonance with the distribution of mass, a characteristic scale at which void pairs are preferentially located. We identify clumps of voids with similar environments and use them to define second order underdensities. Also, we characterize its properties and analyze its impact on the cosmic microwave background.

  7. INTER- AND INTRA-CLUSTER AGE GRADIENTS IN MASSIVE STAR FORMING REGIONS AND INDIVIDUAL NEARBY STELLAR CLUSTERS REVEALED BY MYStIX

    NASA Astrophysics Data System (ADS)

    Getman, Konstantin V.; Feigelson, Eric; Kuhn, Michael A.; Broos, Patrick S; Townsley, Leisa K.; Naylor, Tim; Povich, Matthew S.; Luhman, Kevin; Garmire, Gordon

    2014-08-01

    The MYStIX (Massive Young Star-Forming Complex Study in Infrared and X-ray) project seeks to characterize 20 OB-dominated young star forming regions (SFRs) at distances <4 kpc using photometric catalogs from the Chandra X-ray Observatory, Spitzer Space Telescope, UKIRT and 2MASS surveys. As part of the MYStIX project, we developed a new stellar chronometer that employs near-infrared and X-ray photometry data, AgeJX. Computing AgeJX averaged over MYStIX (sub)clusters reveals previously unknown age gradients across most of the MYStIX regions as well as within some individual rich clusters. Within the SFRs, the inferred AgeJX ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed stellar populations. Noticeable intra-cluster gradients are seen in the NGC 2024 (Flame Nebula) star cluster and the Orion Nebula Cluster (ONC): stars in cluster cores appear younger and thus were formed later than stars in cluster halos. The latter result has two important implications for the formation of young stellar clusters. Clusters likely form slowly: they do not arise from a single nearly-instantaneous burst of star formation. The simple models where clusters form inside-out are likely incorrect, and more complex models are needed. We provide several star formation scenarios that alone or in combination may lead to the observed core-halo age gradients.

  8. Formation and evolution of magnetised filaments in wind-swept turbulent clumps

    NASA Astrophysics Data System (ADS)

    Banda-Barragan, Wladimir Eduardo; Federrath, Christoph; Crocker, Roland M.; Bicknell, Geoffrey Vincent; Parkin, Elliot Ross

    2015-08-01

    Using high-resolution three-dimensional simulations, we examine the formation and evolution of filamentary structures arising from magnetohydrodynamic interactions between supersonic winds and turbulent clumps in the interstellar medium. Previous numerical studies assumed homogenous density profiles, null velocity fields, and uniformly distributed magnetic fields as the initial conditions for interstellar clumps. Here, we have, for the first time, incorporated fractal clumps with log-normal density distributions, random velocity fields and turbulent magnetic fields (superimposed on top of a uniform background field). Disruptive processes, instigated by dynamical instabilities and akin to those observed in simulations with uniform media, lead to stripping of clump material and the subsequent formation of filamentary tails. The evolution of filaments in uniform and turbulent models is, however, radically different as evidenced by comparisons of global quantities in both scenarios. We show, for example, that turbulent clumps produce tails with higher velocity dispersions, increased gas mixing, greater kinetic energy, and lower plasma beta than their uniform counterparts. We attribute the observed differences to: 1) the turbulence-driven enhanced growth of dynamical instabilities (e.g. Kelvin-Helmholtz and Rayleigh-Taylor instabilities) at fluid interfaces, and 2) the localised amplification of magnetic fields caused by the stretching of field lines trapped in the numerous surface deformations of fractal clumps. We briefly discuss the implications of this work to the physics of the optical filaments observed in the starburst galaxy M82.

  9. Clumped Isotope Composition of Cold-Water Corals: A Role for Vital Effects?

    NASA Astrophysics Data System (ADS)

    Spooner, P.; Guo, W.; Robinson, L. F.

    2014-12-01

    Measurements on a set of cold-water corals (mainly Desmophyllum dianthus) have suggested that their clumped isotope composition could serve as a promising proxy for reconstructing paleocean temperatures. Such measurements have also offered support for certain isotope models of coral calcification. However, there are differences in the clumped isotope compositions between warm-water and cold-water corals, suggesting that different kinds of corals could have differences in their biocalcification processes. In order to understand the systematics of clumped isotope variations in cold-water corals more fully, we present clumped isotope data from a range of cold-water coral species from the tropical Atlantic and the Southern Ocean.Our samples were either collected live or recently dead (14C ages < 1,000 yrs) with associated temperature data. They include a total of 11 solitary corals and 1 colonial coral from the Atlantic, and 8 solitary corals from the Southern Ocean. The data indicate that coral clumped isotope systematics may be more complicated than previously thought. For example, for the genus Caryophyllia we observe significant variations in clumped isotope compositions for corals which grew at the same temperature with an apparent negative correlation between Δ47 and δ18O, different to patterns previously observed in Desmophyllum. These results indicate that existing isotope models of biocalcification may not apply equally well to all corals. Clumped isotope vital effects may be present in certain cold-water corals as they are in warm-water corals, complicating the use of this paleoclimate proxy.

  10. Merger types forming the Virgo cluster in recent gigayears

    NASA Astrophysics Data System (ADS)

    Olchanski, M.; Sorce, J. G.

    2018-06-01

    Context. As our closest cluster-neighbor, the Virgo cluster of galaxies is intensely studied by observers to unravel the mysteries of galaxy evolution within clusters. At this stage, cosmological numerical simulations of the cluster are useful to efficiently test theories and calibrate models. However, it is not trivial to select the perfect simulacrum of the Virgo cluster to fairly compare in detail its observed and simulated galaxy populations that are affected by the type and history of the cluster. Aims: Determining precisely the properties of Virgo for a later selection of simulated clusters becomes essential. It is still not clear how to access some of these properties, such as the past history of the Virgo cluster from current observations. Therefore, directly producing effective simulacra of the Virgo cluster is inevitable. Methods: Efficient simulacra of the Virgo cluster can be obtained via simulations that resemble the local Universe down to the cluster scale. In such simulations, Virgo-like halos form in the proper local environment and permit assessing the most probable formation history of the cluster. Studies based on these simulations have already revealed that the Virgo cluster has had a quiet merging history over the last seven gigayears and that the cluster accretes matter along a preferential direction. Results: This paper reveals that in addition such Virgo halos have had on average only one merger larger than about a tenth of their mass at redshift zero within the last four gigayears. This second branch (by opposition to main branch) formed in a given sub-region and merged recently (within the last gigayear). These properties are not shared with a set of random halos within the same mass range. Conclusions: This study extends the validity of the scheme used to produce the Virgo simulacra down to the largest sub-halos of the Virgo cluster. It opens up great prospects for detailed comparisons with observations, including substructures and

  11. A large-scale structure traced by [O II] emitters hosting a distant cluster at z= 1.62

    NASA Astrophysics Data System (ADS)

    Tadaki, Ken-ichi; Kodama, Tadayuki; Ota, Kazuaki; Hayashi, Masao; Koyama, Yusei; Papovich, Casey; Brodwin, Mark; Tanaka, Masayuki; Iye, Masanori

    2012-07-01

    We present a panoramic narrow-band imaging survey of [O II] emitters in and around the ClG J0218.3-0510 cluster at z= 1.62 with Suprime-Cam on Subaru Telescope. 352 [O II] emitters were identified on the basis of narrow-band excesses and photometric redshifts. We discovered a huge filamentary structure with some clumps traced by [O II] emitters and found that the ClG J0218.3-0510 cluster is embedded in an even larger superstructure than the one reported previously. 31 [O II] emitters were spectroscopically confirmed with the detection of Hα and/or [O III] emission lines by Fibre Multi Object Spectrograph observations. In the high-density regions such as cluster core and clumps, star-forming [O II] emitters show a high overdensity by a factor of more than 10 compared to the field region. Interestingly, the relative fraction of [O II] emitters in photo-z selected sample does not depend significantly on the local density. Although the star formation activity is very high even in the cluster core, some massive quiescent galaxies also exist at the same time. Furthermore, the properties of the individual [O II] emitters, such as star formation rates (SFRs), stellar masses and specific SFRs, do not show a significant dependence on the local density, either. Such a lack of environmental dependence is consistent with our earlier result by Hayashi et al. on a z= 1.5 cluster and its surrounding region. The fact that the star-forming activity of galaxies in the cluster core is as high as that in the field at z˜ 1.6 may suggest that the star-forming galaxies are probably just in a transition phase from a starburst mode to a quiescent mode, and are thus showing comparable level of star formation rates to those in lower density environments. We may be witnessing the start of the reversal of the local SFR-density relation due to the 'biased' galaxy formation and evolution in high-density regions at this high redshift, beyond which massive galaxies would be forming vigorously in

  12. Chemistry of dense clumps near moving Herbig-Haro objects

    NASA Astrophysics Data System (ADS)

    Christie, H.; Viti, S.; Williams, D. A.; Girart, J. M.; Morata, O.

    2011-09-01

    Localized regions of enhanced emission from HCO+, NH3 and other species near Herbig-Haro objects (HHOs) have been interpreted as arising in a photochemistry stimulated by the HHO radiation on high-density quiescent clumps in molecular clouds. Static models of this process have been successful in accounting for the variety of molecular species arising ahead of the jet; however, recent observations show that the enhanced molecular emission is widespread along the jet as well as ahead. Hence, a realistic model must take into account the movement of the radiation field past the clump. It was previously unclear as to whether the short interaction time between the clump and the HHO in a moving source model would allow molecules such as HCO+ to reach high enough levels, and to survive for long enough to be observed. In this work we model a moving radiation source that approaches and passes a clump. The chemical picture is qualitatively unchanged by the addition of the moving source, strengthening the idea that enhancements are due to evaporation of molecules from dust grains. In addition, in the case of several molecules, the enhanced emission regions are longer lived. Some photochemically induced species, including methanol, are expected to maintain high abundances for ˜104 yr.

  13. Molecular Gas Clumps from the Destruction of Icy Bodies in the beta Pictoris Debris Disk

    NASA Technical Reports Server (NTRS)

    Dent, W. R. F.; Wyatt, M. C.; Roberge, A.; Augereau, J. -C.; Casassus, S.; Corder, S.; Greaves, J. S.; DeGregorio-Monsalvo, I.; Hales, A.; Jackson, A. P.; hide

    2014-01-01

    Many stars are surrounded by disks of dusty debris formed in the collisions of asteroids, comets and dwarf planets. But is gas also released in such events? Observations at sub-mm wavelengths of the archetypal debris disk around ß Pictoris show that 0.3% of a Moon mass of carbon monoxide orbits in its debris belt. The gas distribution is highly asymmetric, with 30% found in a single clump 85 AU from the star, in a plane closely aligned with the orbit of the inner planet, beta Pic b. This gas clump delineates a region of enhanced collisions, either from a mean motion resonance with an unseen giant planet, or from the remnants of a collision of Mars-mass planets.

  14. Clumps in the outer disk by disk instability: Why they are initially gas giants and the legacy of disruption

    NASA Astrophysics Data System (ADS)

    Boley, Aaron C.; Hayfield, Tristen; Mayer, Lucio; Durisen, Richard H.

    2010-06-01

    We explore the initial conditions for fragments in the extended regions (r≳50AU) of gravitationally unstable disks. We combine analytic estimates for the fragmentation of spiral arms with 3D SPH simulations to show that initial fragment masses are in the gas giant regime. These initial fragments will have substantial angular momentum, and should form disks with radii of a few AU. We show that clumps will survive for multiple orbits before they undergo a second, rapid collapse due to H 2 dissociation and that it is possible to destroy bound clumps by transporting them into the inner disk. The consequences of disrupted clumps for planet formation, dust processing, and disk evolution are discussed. We argue that it is possible to produce Earth-mass cores in the outer disk during the earliest phases of disk evolution.

  15. MYStIX: Dynamical evolution of young clusters

    NASA Astrophysics Data System (ADS)

    Kuhn, Michael A.

    2014-08-01

    The spatial structure of young stellar clusters in Galactic star-forming regions provides insight into these clusters’ dynamical evolution---a topic with implications for open questions in star-formation and cluster survival. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) provides a sample of >30,000 young stars in star-forming regions (d<3.6 kpc) that contain at least one O-type star. We use the finite mixture model analysis to identify subclusters of stars and determine their properties: including subcluster radii, intrinsic numbers of stars, central density, ellipticity, obscuration, and age. In 17 MYStIX regions we find 142 subclusters, with a diverse radii and densities and age spreads of up to ~1 Myr in a region. There is a strong negative correlation between subcluster radius and density, which indicates that embedded subclusters expand but also gain stars as they age. Subcluster expansion is also shown by a positive radius--age correlation, which indicates that subclusters are expanding at <1 km/s. The subcluster ellipticity distribution and number--density relation show signs of a hierarchical merger scenario, whereby young stellar clusters are built up through mergers of smaller clumps, causing evolution from a clumpy spatial distribution of stars (seen in some regions) to a simpler distribution of stars (seen in other regions). Many of the simple young stellar clusters show signs of dynamically relaxation, even though they are not old enough for this to have occurred through two-body interactions. However, this apparent contradiction might be explained if small subcluster, which have shorter dynamical relaxation times, can produce dynamically relaxed clusters through hierarchical mergers.

  16. Early dynamical evolution of substructured stellar clusters

    NASA Astrophysics Data System (ADS)

    Dorval, Julien; Boily, Christian

    2015-08-01

    It is now widely accepted that stellar clusters form with a high level of substructure (Kuhn et al. 2014, Bate 2009), inherited from the molecular cloud and the star formation process. Evidence from observations and simulations also indicate the stars in such young clusters form a subvirial system (Kirk et al. 2007, Maschberger et al. 2010). The subsequent dynamical evolution can cause important mass loss, ejecting a large part of the birth population in the field. It can also imprint the stellar population and still be inferred from observations of evolved clusters. Nbody simulations allow a better understanding of these early twists and turns, given realistic initial conditions. Nowadays, substructured, clumpy young clusters are usually obtained through pseudo-fractal growth (Goodwin et al. 2004) and velocity inheritance. Such models are visually realistics and are very useful, they are however somewhat artificial in their velocity distribution. I introduce a new way to create clumpy initial conditions through a "Hubble expansion" which naturally produces self consistent clumps, velocity-wise. A velocity distribution analysis shows the new method produces realistic models, consistent with the dynamical state of the newly created cores in hydrodynamic simulation of cluster formation (Klessen & Burkert 2000). I use these initial conditions to investigate the dynamical evolution of young subvirial clusters, up to 80000 stars. I find an overall soft evolution, with hierarchical merging leading to a high level of mass segregation. I investigate the influence of the mass function on the fate of the cluster, specifically on the amount of mass loss induced by the early violent relaxation. Using a new binary detection algorithm, I also find a strong processing of the native binary population.

  17. Methane cycling. Nonequilibrium clumped isotope signals in microbial methane.

    PubMed

    Wang, David T; Gruen, Danielle S; Lollar, Barbara Sherwood; Hinrichs, Kai-Uwe; Stewart, Lucy C; Holden, James F; Hristov, Alexander N; Pohlman, John W; Morrill, Penny L; Könneke, Martin; Delwiche, Kyle B; Reeves, Eoghan P; Sutcliffe, Chelsea N; Ritter, Daniel J; Seewald, Jeffrey S; McIntosh, Jennifer C; Hemond, Harold F; Kubo, Michael D; Cardace, Dawn; Hoehler, Tori M; Ono, Shuhei

    2015-04-24

    Methane is a key component in the global carbon cycle, with a wide range of anthropogenic and natural sources. Although isotopic compositions of methane have traditionally aided source identification, the abundance of its multiply substituted "clumped" isotopologues (for example, (13)CH3D) has recently emerged as a proxy for determining methane-formation temperatures. However, the effect of biological processes on methane's clumped isotopologue signature is poorly constrained. We show that methanogenesis proceeding at relatively high rates in cattle, surface environments, and laboratory cultures exerts kinetic control on (13)CH3D abundances and results in anomalously elevated formation-temperature estimates. We demonstrate quantitatively that H2 availability accounts for this effect. Clumped methane thermometry can therefore provide constraints on the generation of methane in diverse settings, including continental serpentinization sites and ancient, deep groundwaters. Copyright © 2015, American Association for the Advancement of Science.

  18. Calibration and characterisation of the Gaia Red Clump

    NASA Astrophysics Data System (ADS)

    Ruiz-Dern, L.; Babusiaux, C.; Arenou, F.; Danielski, C.; Turon, C.; Sartoretti, P.

    2018-04-01

    We present new empirical Colour-Colour and Effective Temperature-Colour Gaia Red Clump calibrations. The selected sample takes into account high photometric quality, good spectrometric metallicity, homogeneous effective temperatures and low interstellar extinctions. From those calibrations we developed a method to derive the absolute magnitude, temperature and extinction of the Gaia RC. We tested our colour and extinction estimates on stars with measured spectroscopic effective temperatures and Diffuse Interstellar Band (DIB) constraints. Within the Gaia Validation team these calibrations are also being used, together with asteroseismic constraints, to check the parallax zero-point with Red Clump stars.

  19. IONIZED GAS KINEMATICS AT HIGH RESOLUTION. V. [Ne ii], MULTIPLE CLUSTERS, HIGH EFFICIENCY STAR FORMATION, AND BLUE FLOWS IN HE 2–10

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Beck, Sara; Turner, Jean; Lacy, John

    2015-11-20

    We measured the 12.8 μm [Ne ii] line in the dwarf starburst galaxy He 2–10 with the high-resolution spectrometer TEXES on the NASA IRTF. The data cube has a diffraction-limited spatial resolution of ∼1″ and a total velocity resolution, including thermal broadening, of ∼5 km s{sup −1}. This makes it possible to compare the kinematics of individual star-forming clumps and molecular clouds in the three dimensions of space and velocity, and allows us to determine star formation efficiencies. The kinematics of the ionized gas confirm that the starburst contains multiple dense clusters. From the M/R of the clusters and themore » ≃30%–40% star formation efficiencies, the clusters are likely to be bound and long lived, like globulars. Non-gravitational features in the line profiles show how the ionized gas flows through the ambient molecular material, as well as a narrow velocity feature, which we identify with the interface of the H ii region and a cold dense clump. These data offer an unprecedented view of the interaction of embedded H ii regions with their environment.« less

  20. Does selection for gamete dispersal and capture lead to a sex difference in clump water-holding capacity?

    PubMed

    Moore, Jonathan D; Kollar, Leslie M; McLetchie, D Nicholas

    2016-08-01

    Differences in male and female reproductive function can lead to selection for sex-specific gamete dispersal and capture traits. These traits have been explored from shoot to whole plant levels in wind-pollinated species. While shoot traits have been explored in water-fertilized species, little is known about how whole plant morphology affects gamete dispersal and capture. We used the dioecious, water-fertilized plant Bryum argenteum to test for differences in clump morphology and water-holding characteristics consistent with divergent selection. We hypothesized that sex-specific clump morphology, arising at maturity, produces relatively low male water-holding capacity for gamete dispersal and high female capacity for gamete capture. We measured isolated young shoot and clump water-holding capacity and clump morphological characteristics on greenhouse-grown plants. Young shoot capacity was used to predict clump capacity, which was compared with actual clump capacity. Young male shoots held more water per unit length, and male clumps had higher shoot density, which extrapolated to higher clump water-holding capacity. However, female clumps held more water and were taller with more robust shoots. Actual clump capacity correlated positively with clump height and shoot cross-sectional area. The sex difference in actual clump capacity and its unpredictability from younger shoots are consistent with our hypothesis that males should hold less water than females to facilitate sexual reproduction. These results provide conceptual connections to other plant groups and implications for connecting divergent selection to female-biased sex ratios in B. argenteum and other bryophytes. © 2016 Botanical Society of America.

  1. RANDOMNESS of Numbers DEFINITION(QUERY:WHAT? V HOW?) ONLY Via MAXWELL-BOLTZMANN CLASSICAL-Statistics(MBCS) Hot-Plasma VS. Digits-Clumping Log-Law NON-Randomness Inversion ONLY BOSE-EINSTEIN QUANTUM-Statistics(BEQS) .

    NASA Astrophysics Data System (ADS)

    Siegel, Z.; Siegel, Edward Carl-Ludwig

    2011-03-01

    RANDOMNESS of Numbers cognitive-semantics DEFINITION VIA Cognition QUERY: WHAT???, NOT HOW?) VS. computer-``science" mindLESS number-crunching (Harrel-Sipser-...) algorithmics Goldreich "PSEUDO-randomness"[Not.AMS(02)] mea-culpa is ONLY via MAXWELL-BOLTZMANN CLASSICAL-STATISTICS(NOT FDQS!!!) "hot-plasma" REPULSION VERSUS Newcomb(1881)-Weyl(1914;1916)-Benford(1938) "NeWBe" logarithmic-law digit-CLUMPING/ CLUSTERING NON-Randomness simple Siegel[AMS Joint.Mtg.(02)-Abs. # 973-60-124] algebraic-inversion to THE QUANTUM and ONLY BEQS preferentially SEQUENTIALLY lower-DIGITS CLUMPING/CLUSTERING with d = 0 BEC, is ONLY VIA Siegel-Baez FUZZYICS=CATEGORYICS (SON OF TRIZ)/"Category-Semantics"(C-S), latter intersection/union of Lawvere(1964)-Siegel(1964)] category-theory (matrix: MORPHISMS V FUNCTORS) "+" cognitive-semantics'' (matrix: ANTONYMS V SYNONYMS) yields Siegel-Baez FUZZYICS=CATEGORYICS/C-S tabular list-format matrix truth-table analytics: MBCS RANDOMNESS TRUTH/EMET!!!

  2. ATLASGAL-selected massive clumps in the inner Galaxy. V. Temperature structure and evolution

    NASA Astrophysics Data System (ADS)

    Giannetti, A.; Leurini, S.; Wyrowski, F.; Urquhart, J.; Csengeri, T.; Menten, K. M.; König, C.; Güsten, R.

    2017-07-01

    Context. Observational identification of a solid evolutionary sequence for high-mass star-forming regions is still missing. Spectroscopic observations give the opportunity to test possible schemes and connect the phases identified to physical processes. Aims: We aim to use the progressive heating of the gas caused by the feedback of high-mass young stellar objects to prove the statistical validity of the most common schemes used to observationally define an evolutionary sequence for high-mass clumps, and characterise the sensitivity of different tracers to this process. Methods: From the spectroscopic follow-ups carried out towards submillimeter continuum (dust) emission-selected massive clumps (the ATLASGAL TOP100 sample) with the IRAM 30 m, Mopra, and APEX telescopes between 84 GHz and 365 GHz, we selected several multiplets of CH3CN, CH3CCH, and CH3OH emission lines to derive and compare the physical properties of the gas in the clumps along the evolutionary sequence, fitting simultaneously the large number of lines that these molecules have in the observed band. Our findings are compared with results obtained from optically thin CO isotopologues, dust, and ammonia from previous studies on the same sample. Results: The chemical properties of each species have a major role on the measured physical properties. Low temperatures are traced by ammonia, methanol, and CO (in the early phases), the warm and dense envelope can be probed with CH3CN, CH3CCH, and, in evolved sources where CO is abundant in the gas phase, via its optically thin isotopologues. CH3OH and CH3CN are also abundant in the hot cores, and we suggest that their high-excitation transitions are good tools to study the kinematics in the hot gas associated with the inner envelope surrounding the young stellar objects that these clumps are hosting. All tracers show, to different degrees according to their properties, progressive warming with evolution. The relation between gas temperature and the

  3. The Optical Gravitational Lensing Experiment: Red Clump Stars as a Distance Indicator.

    PubMed

    Udalski

    2000-03-01

    We present relation of the mean I-band brightness of red clump stars on metallicity. Red clump stars were proposed to be a very attractive standard candle for distance determination. The calibration is based on 284 nearby red giant stars whose high-quality spectra made it possible to determine accurate individual metal abundances. High-quality parallaxes (sigmapi&solm0;pi<10%) and photometry of these very bright stars come from Hipparcos measurements. Metallicity of the sample covers a large range: -0.6 dex<&sqbl0;Fe&solm0;H&sqbr0;<+0.2 dex. We find a weak dependence of the mean I-band brightness on metallicity ( approximately 0.13 mag dex-1). What is more important, the range of metallicity of the Hipparcos sample partially overlaps with metallicity of field giants in the LMC, thus making it possible to determine the distance to the LMC by almost direct comparison of brightness of the local Hipparcos red clump giants with that of LMC stars. Photometry of field red clump giants in nine low-extinction fields of the LMC halo collected during the OGLE II microlensing survey compared with the Hipparcos red clump stars data yields the distance modulus to the LMC: &parl0;m-M&parr0;LMC=18.24+/-0.08 mag.

  4. Dense clumps of ionized gas near Pi Scorpii, as revealed by the fine-structure excitation of N II

    NASA Technical Reports Server (NTRS)

    Bertoldi, Frank; Jenkins, Edward B.

    1992-01-01

    The column density and the emission of the ionized gas along the line of sight toward the B1 V + B2 V binary star Pi Sco are measured on the basis of the fine-structure absorption lines of the ground state N II. It is found that the bulk of this ionized gas must be clumped on a length scale of 0.025 pc, which is far smaller than the observed size of the diffuse H II region surrounding Pi Sco of about 6 pc. The observed column density of S III toward Pi Sco yields an upper limit on the distance of the absorbing, clumped gas from the star of less than about 0.02 pc, assuming that both the N II and S III absorption arise from the same gas. The possibility that the ionized gas originates from a photoevaporating circumstellar disk directly surrounding Pi Sco is excluded, since such a disk would have an unusual size of order 0.025 pc and would have had to survive for the estimated age of Pi Sco of 5-8 Myr. The derived mean density of the clumped gas is of order 40/cu cm, so that the gas is at a pressure that far exceeds the mean pressure in the H II region. It is concluded that the ionized gas could originate from evaporation flows off a cluster of compact neutral objects that evaporate due to the ionizing radiation of Pi Sco.

  5. Clumping in the Cassini Division and C Ring: Constraints from Stellar Occultations

    NASA Astrophysics Data System (ADS)

    Colwell, J. E.; Jerousek, R. G.; Esposito, L. W.

    2014-12-01

    Particles in Saturn's rings are engaged in a constant tug-of-war between interparticle gravitational and adhesive forces that lead to clumping, on the one hand, and Keplerian shear that inhibits accretion on the other. Depending on the surface mass density of the rings and the local orbital velocity, ephemeral clumps or self-gravity wakes can form, giving the rings granularity on the scale of the most-unstable length scale against gravitational collapse. The A ring and many regions of the B ring are dominated by self-gravity wakes with a typical radial wavelength of ~50-100 m. A characteristic of self-gravity wakes is that they can effectively shadow the relatively empty spaces in between them, depending on viewing geometry. This leads to geometry-dependent measurements of optical depth in occultations of the rings. The C ring and Cassini Division have significantly lower surface mass densities than the A and B ring such that in most of these regions the most-unstable wavelength is comparable to the size of the ring particles (~1 m) so that self-gravity wake formation is not expected nor have its characteristics in various measurements been observed. Here we present measurements of the optical depth of the C ring and Cassini Division with the Cassini Ultraviolet Imaging Spectrograph (UVIS) showing variations with viewing geometry in the "ramp" regions and the Cassini Division "triple band". These variations are characteristic of self-gravity wakes. We place limits on clumping in other regions of the C ring and Cassini Division.

  6. ATLASGAL-selected massive clumps in the inner Galaxy. II. Characterisation of different evolutionary stages and their SiO emission

    NASA Astrophysics Data System (ADS)

    Csengeri, T.; Leurini, S.; Wyrowski, F.; Urquhart, J. S.; Menten, K. M.; Walmsley, M.; Bontemps, S.; Wienen, M.; Beuther, H.; Motte, F.; Nguyen-Luong, Q.; Schilke, P.; Schuller, F.; Zavagno, A.; Sanna, C.

    2016-02-01

    Context. The processes leading to the birth of high-mass stars are poorly understood. The key first step to reveal their formation processes is characterising the clumps and cores from which they form. Aims: We define a representative sample of massive clumps in different evolutionary stages selected from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), from which we aim to establish a census of molecular tracers of their evolution. As a first step, we study the shock tracer, SiO, mainly associated with shocks from jets probing accretion processes. In low-mass young stellar objects (YSOs), outflow and jet activity decreases with time during the star formation processes. Recently, a similar scenario was suggested for massive clumps based on SiO observations. Here we analyse observations of the SiO (2-1) and (5-4) lines in a statistically significant sample to constrain the change of SiO abundance and the excitation conditions as a function of evolutionary stage of massive star-forming clumps. Methods: We performed an unbiased spectral line survey covering the 3-mm atmospheric window between 84-117 GHz with the IRAM 30 m telescope of a sample of 430 sources of the ATLASGAL survey, covering various evolutionary stages of massive clumps. A smaller sample of 128 clumps has been observed in the SiO (5-4) transition with the APEX telescope to complement the (2-1) line and probe the excitation conditions of the emitting gas. We derived detection rates to assess the star formation activity of the sample, and we estimated the column density and abundance using both an LTE approximation and non-LTE calculations for a smaller subsample, where both transitions have been observed. Results: We characterise the physical properties of the selected sources, which greatly supersedes the largest samples studied so far, and show that they are representative of different evolutionary stages. We report a high detection rate of >75% of the SiO (2-1) line and a >90% detection

  7. Physical conditions in star-forming regions around S235

    NASA Astrophysics Data System (ADS)

    Kirsanova, M. S.; Wiebe, D. S.; Sobolev, A. M.; Henkel, C.; Tsivilev, A. P.

    2014-01-01

    Gas density and temperature in star-forming regions around Sh2-235 are derived from ammonia line observations. This information is used to evaluate formation scenarios and to determine evolutionary stages of the young embedded clusters S235 East 1, S235 East 2 and S235 Central. We also estimate the gas mass in the embedded clusters and its ratio to the stellar mass. S235 East 1 appears to be less evolved than S235 East 2 and S235 Central. In S235 East 1 the molecular gas mass exceeds that in the other clusters. Also, this cluster is more embedded in the parent gas cloud than the other two. Comparison with a theoretical model shows that the formation of these three clusters could have been stimulated by the expansion of the Sh2-235 H II region (hereafter S235) via a collect-and-collapse process, provided the density in the surrounding gas exceeds 3 × 103 cm-3, or via collapse of pre-existing clumps. The expansion of S235 cannot be responsible for star formation in the southern S235 A-B region. However, formation of the massive stars in this region might have been triggered by a large-scale supernova shock. Thus, triggered star formation in the studied region may come in three varieties, namely collect-and-collapse and collapse of pre-existing clumps, both initiated by expansion of the local H II regions, and triggered by an external large-scale shock. We argue that the S235 A H II region expands into a highly non-uniform medium with increasing density. It is too young to trigger star formation in its vicinity by a collect-and-collapse process. There is an age spread inside the S235 A-B region. Massive stars in the S235 A-B region are considerably younger than lower mass stars in the same area. This follows from the estimates of their ages and the ages of associated H II regions.

  8. The effect of clumped population structure on the variability of spreading dynamics.

    PubMed

    Black, Andrew J; House, Thomas; Keeling, Matt J; Ross, Joshua V

    2014-10-21

    Processes that spread through local contact, including outbreaks of infectious diseases, are inherently noisy, and are frequently observed to be far noisier than predicted by standard stochastic models that assume homogeneous mixing. One way to reproduce the observed levels of noise is to introduce significant individual-level heterogeneity with respect to infection processes, such that some individuals are expected to generate more secondary cases than others. Here we consider a population where individuals can be naturally aggregated into clumps (subpopulations) with stronger interaction within clumps than between them. This clumped structure induces significant increases in the noisiness of a spreading process, such as the transmission of infection, despite complete homogeneity at the individual level. Given the ubiquity of such clumped aggregations (such as homes, schools and workplaces for humans or farms for livestock) we suggest this as a plausible explanation for noisiness of many epidemic time series. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Growth and Development of Thinned Versus Unthinned Yellow-Poplar Sprout Clumps

    Treesearch

    Donald E. Beck

    1977-01-01

    Yellow-poplar stump sprouts are capable of very rapid growth and often dominate stands on good sites following harvest cutting. Thinning to one stem per stump at 6 years of age did not affect either height or diameter growth over the succeeding 18 years. The untreated clumps thinned themselves to an average of two stems per clump during the same time period. Thinning...

  10. ATLASGAL-selected massive clumps in the inner Galaxy. III. Dust continuum characterization of an evolutionary sample

    NASA Astrophysics Data System (ADS)

    König, C.; Urquhart, J. S.; Csengeri, T.; Leurini, S.; Wyrowski, F.; Giannetti, A.; Wienen, M.; Pillai, T.; Kauffmann, J.; Menten, K. M.; Schuller, F.

    2017-03-01

    Context. Massive-star formation and the processes involved are still poorly understood. The ATLASGAL survey provides an ideal basis for detailed studies of large numbers of massive-star forming clumps covering the whole range of evolutionary stages. The ATLASGAL Top100 is a sample of clumps selected by their infrared and radio properties to be representative for the whole range of evolutionary stages. Aims: The ATLASGAL Top100 sources are the focus of a number of detailed follow-up studies that will be presented in a series of papers. In the present work we use the dust continuum emission to constrain the physical properties of this sample and identify trends as a function of source evolution. Methods: We determine flux densities from mid-infrared to submillimeter wavelength (8-870 μm) images and use these values to fit their spectral energy distributions and determine their dust temperature and flux. Combining these with recent distances from the literature including maser parallax measurements we determine clump masses, luminosities and column densities. Results: We define four distinct source classes from the available continuum data and arrange these into an evolutionary sequence. This begins with sources found to be dark at 70 μm, followed by 24 μm weak sources with an embedded 70 μm source, continues through mid-infrared bright sources and ends with infrared bright sources associated with radio emission (I.e., H II regions). We find trends for increasing temperature, luminosity, and column density with the proposed evolution sequence, confirming that this sample is representative of different evolutionary stages of massive star formation. Our sources span temperatures from approximately 11 to 41 K, with bolometric luminosities in the range 57 L⊙-3.8 × 106L⊙. The highest masses reach 4.3 × 104M⊙ and peak column densities up to 1.1 × 1024 cm-1, and therefore have the potential to form the most massive O-type stars. We show that at least 93 sources

  11. Empirical High-Temperature Calibration for the Carbonate Clumped Isotopes Paleothermometer

    NASA Astrophysics Data System (ADS)

    Kluge, T.; John, C. M.; Jourdan, A.; Davis, S.; Crawshaw, J.

    2013-12-01

    The clumped isotope paleothermometer is being used in a wide range of applications related to carbonate mineral formation, focusing on temperature and fluid δ18O reconstruction. Whereas the range of typical Earth surface temperatures has been the focus of several studies based on laboratory experiments and biogenic carbonates of known growth temperatures, the clumped isotope-temperature relationship above 70 °C has not been assessed by direct precipitation of carbonates. We investigated the clumped isotope-temperature relationship by precipitating carbonates between 20 and 200°C in the laboratory. The setup consists of a pressurized vessel in which carbonate minerals are precipitated from the mixture of two solutions (CaCl2, NaHCO3). Both solutions are thermally and isotopically equilibrated before injection in the pressure vessel. Minerals precipitated in this setup generally consist of calcite. Samples were reacted with 105% orthophosphoric acid for 10 min at 90°C. The evolved CO2 was continuously collected and subsequently purified with a Porapak trap held at -35°C. Measurements were performed on a MAT 253 using the protocol of Huntington et al. (2009) and Dennis et al. (2011). Clumped isotope values from 20-90°C are consistent with carbonates that were precipitated from a CaCO3 super-saturated solution using the method of McCrea (1950). This demonstrates that the experimental setup does not induce any kinetic fractionation, and can be used for high-temperature carbonate precipitation. The new clumped isotope calibration at high temperature follows the theoretical calculations of Schauble et al. (2006) adjusted for phosphoric acid digestion at 90°C. We gratefully acknowledge funding from Qatar Petroleum, Shell and the Qatar Science and Technology Park.

  12. Chemistry in Infrared Dark Cloud Clumps: A Molecular Line Survey at 3 mm

    NASA Astrophysics Data System (ADS)

    Sanhueza, Patricio; Jackson, James M.; Foster, Jonathan B.; Garay, Guido; Silva, Andrea; Finn, Susanna C.

    2012-09-01

    We have observed 37 Infrared Dark Clouds (IRDCs), containing a total of 159 clumps, in high-density molecular tracers at 3 mm using the 22 m ATNF Mopra Telescope located in Australia. After determining kinematic distances, we eliminated clumps that are not located in IRDCs and clumps with a separation between them of less than one Mopra beam. Our final sample consists of 92 IRDC clumps. The most commonly detected molecular lines are (detection rates higher than 8%) N2H+, HNC, HN13C, HCO+, H13CO+, HCN, C2H, HC3N, HNCO, and SiO. We investigate the behavior of the different molecular tracers and look for chemical variations as a function of an evolutionary sequence based on Spitzer IRAC and MIPS emission. We find that the molecular tracers behave differently through the evolutionary sequence and some of them can be used to yield useful relative age information. The presence of HNC and N2H+ lines does not depend on the star formation activity. On the other hand, HC3N, HNCO, and SiO are predominantly detected in later stages of evolution. Optical depth calculations show that in IRDC clumps the N2H+ line is optically thin, the C2H line is moderately optically thick, and HNC and HCO+ are optically thick. The HCN hyperfine transitions are blended, and, in addition, show self-absorbed line profiles and extended wing emission. These factors combined prevent the use of HCN hyperfine transitions for the calculation of physical parameters. Total column densities of the different molecules, except C2H, increase with the evolutionary stage of the clumps. Molecular abundances increase with the evolutionary stage for N2H+ and HCO+. The N2H+/HCO+ and N2H+/HNC abundance ratios act as chemical clocks, increasing with the evolution of the clumps.

  13. ALMA constraints on star-forming gas in a prototypical z = 1.5 clumpy galaxy: the dearth of CO(5-4) emission from UV-bright clumps

    NASA Astrophysics Data System (ADS)

    Cibinel, A.; Daddi, E.; Bournaud, F.; Sargent, M. T.; le Floc'h, E.; Magdis, G. E.; Pannella, M.; Rujopakarn, W.; Juneau, S.; Zanella, A.; Duc, P.-A.; Oesch, P. A.; Elbaz, D.; Jagannathan, P.; Nyland, K.; Wang, T.

    2017-08-01

    We present deep ALMA CO(5-4) observations of a main-sequence, clumpy galaxy at z = 1.5 in the HUDF. Thanks to the ˜0{^''.}5 resolution of the ALMA data, we can link stellar population properties to the CO(5-4) emission on scales of a few kiloparsec. We detect strong CO(5-4) emission from the nuclear region of the galaxy, consistent with the observed LIR-L^' }_CO(5-4) correlation and indicating ongoing nuclear star formation. The CO(5-4) gas component appears more concentrated than other star formation tracers or the dust distribution in this galaxy. We discuss possible implications of this difference in terms of star formation efficiency and mass build-up at the galaxy centre. Conversely, we do not detect any CO(5-4) emission from the UV-bright clumps. This might imply that clumps have a high star formation efficiency (although they do not display unusually high specific star formation rates) and are not entirely gas dominated, with gas fractions no larger than that of their host galaxy (˜50 per cent). Stellar feedback and disc instability torques funnelling gas towards the galaxy centre could contribute to the relatively low gas content. Alternatively, clumps could fall in a more standard star formation efficiency regime if their actual star formation rates are lower than generally assumed. We find that clump star formation rates derived with several different, plausible methods can vary by up to an order of magnitude. The lowest estimates would be compatible with a CO(5-4) non-detection even for main-sequence like values of star formation efficiency and gas content.

  14. Nonequilibrium clumped isotope signals in microbial methane

    USGS Publications Warehouse

    Wang, David T.; Gruen, Danielle S.; Lollar, Barbara Sherwood; Hinrichs, Kai-Uwe; Stewart, Lucy C.; Holden, James F.; Hristov, Alexander N.; Pohlman, John W.; Morrill, Penny L.; Könneke, Martin; Delwiche, Kyle B.; Reeves, Eoghan P.; Sutcliffe, Chelsea N.; Ritter, Daniel J.; Seewald, Jeffrey S.; McIntosh, Jennifer C.; Hemond, Harold F.; Kubo, Michael D.; Cardace, Dawn; Hoehler, Tori M.; Ono, Shuhei

    2015-01-01

    Methane is a key component in the global carbon cycle with a wide range of anthropogenic and natural sources. Although isotopic compositions of methane have traditionally aided source identification, the abundance of its multiply-substituted “clumped” isotopologues, e.g., 13CH3D, has recently emerged as a proxy for determining methane-formation temperatures; however, the impact of biological processes on methane’s clumped isotopologue signature is poorly constrained. We show that methanogenesis proceeding at relatively high rates in cattle, surface environments, and laboratory cultures exerts kinetic control on 13CH3D abundances and results in anomalously elevated formation temperature estimates. We demonstrate quantitatively that H2 availability accounts for this effect. Clumped methane thermometry can therefore provide constraints on the generation of methane in diverse settings, including continental serpentinization sites and ancient, deep groundwaters.

  15. Witnessing the growth of the nearest galaxy cluster: thermodynamics of the Virgo Cluster outskirts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Simionescu, A.; Werner, N.; Mantz, A.

    Here, we present results from Suzaku Key Project observations of the Virgo Cluster, the nearest galaxy cluster to us, mapping its X-ray properties along four long ‘arms’ extending beyond the virial radius. The entropy profiles along all four azimuths increase with radius, then level out beyond ~0.5r 200, while the average pressure at large radii exceeds Planck Sunyaev–Zel'dovich measurements. These results can be explained by enhanced gas density fluctuations (clumping) in the cluster's outskirts. Using a standard Navarro, Frenk and White model, we estimate a virial mass, radius and concentration parameter of M 200 = 1.05 ± 0.02 × 10more » 14 M⊙, r 200 = 974.1 ± 5.7 kpc and c = 8.8 ± 0.2, respectively. The inferred cumulative baryon fraction exceeds the cosmic mean at r ~r 200 along the major axis, suggesting enhanced gas clumping possibly sourced by a candidate large-scale structure filament along the north–south direction. The Suzaku data reveal a large-scale sloshing pattern, with two new cold fronts detected at radii of 233 and 280 kpc along the western and southern arms, respectively. Two high-temperature regions are also identified 1 Mpc towards the south and 605 kpc towards the west of M87, likely representing shocks associated with the ongoing cluster growth. Although systematic uncertainties in measuring the metallicity for low-temperature plasma remain, the data at large radii appear consistent with a uniform metal distribution on scales of ~90 × 180 kpc and larger, providing additional support for the early chemical enrichment scenario driven by galactic winds at redshifts of 2–3.« less

  16. Witnessing the growth of the nearest galaxy cluster: thermodynamics of the Virgo Cluster outskirts

    DOE PAGES

    Simionescu, A.; Werner, N.; Mantz, A.; ...

    2017-04-17

    Here, we present results from Suzaku Key Project observations of the Virgo Cluster, the nearest galaxy cluster to us, mapping its X-ray properties along four long ‘arms’ extending beyond the virial radius. The entropy profiles along all four azimuths increase with radius, then level out beyond ~0.5r 200, while the average pressure at large radii exceeds Planck Sunyaev–Zel'dovich measurements. These results can be explained by enhanced gas density fluctuations (clumping) in the cluster's outskirts. Using a standard Navarro, Frenk and White model, we estimate a virial mass, radius and concentration parameter of M 200 = 1.05 ± 0.02 × 10more » 14 M⊙, r 200 = 974.1 ± 5.7 kpc and c = 8.8 ± 0.2, respectively. The inferred cumulative baryon fraction exceeds the cosmic mean at r ~r 200 along the major axis, suggesting enhanced gas clumping possibly sourced by a candidate large-scale structure filament along the north–south direction. The Suzaku data reveal a large-scale sloshing pattern, with two new cold fronts detected at radii of 233 and 280 kpc along the western and southern arms, respectively. Two high-temperature regions are also identified 1 Mpc towards the south and 605 kpc towards the west of M87, likely representing shocks associated with the ongoing cluster growth. Although systematic uncertainties in measuring the metallicity for low-temperature plasma remain, the data at large radii appear consistent with a uniform metal distribution on scales of ~90 × 180 kpc and larger, providing additional support for the early chemical enrichment scenario driven by galactic winds at redshifts of 2–3.« less

  17. WIYN open cluster study. LIX. Radial velocity membership of the evolved population of the old open cluster NGC 6791

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tofflemire, Benjamin M.; Gosnell, Natalie M.; Mathieu, Robert D.

    2014-10-01

    The open cluster NGC 6791 has been the focus of much recent study due to its intriguing combination of old age and high metallicity (∼8 Gyr, [Fe/H] = +0.30), as well as its location within the Kepler field. As part of the WIYN Open Cluster Study, we present precise (σ = 0.38 km s{sup –1}) radial velocities for proper motion candidate members of NGC 6791 from Platais et al. Our survey, extending down to g' ∼ 16.8, is comprised of the evolved cluster population, including blue stragglers, giants, and horizontal branch stars. Of the 280 proper-motion-selected stars above our magnitudemore » limit, 93% have at least one radial velocity measurement and 79% have three measurements over the course of at least 200 days, sufficient for secure radial-velocity-determined membership of non-velocity-variable stars. The Platais et al. proper motion catalog includes 12 anomalous horizontal branch candidates blueward of the red clump, of which we find only 4 to be cluster members. Three fall slightly blueward of the red clump and the fourth is consistent with being a blue straggler. The cleaned color-magnitude diagram shows a richly populated red giant branch and a blue straggler population. Half of the blue stragglers are in binaries. From our radial velocity measurement distribution, we find the cluster's radial velocity dispersion to be σ {sub c} = 0.62 ± 0.10 km s{sup –1}. This corresponds to a dynamical mass of ∼4600 M {sub ☉}.« less

  18. Pressure of the hot gas in simulations of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Planelles, S.; Fabjan, D.; Borgani, S.; Murante, G.; Rasia, E.; Biffi, V.; Truong, N.; Ragone-Figueroa, C.; Granato, G. L.; Dolag, K.; Pierpaoli, E.; Beck, A. M.; Steinborn, Lisa K.; Gaspari, M.

    2017-06-01

    We analyse the radial pressure profiles, the intracluster medium (ICM) clumping factor and the Sunyaev-Zel'dovich (SZ) scaling relations of a sample of simulated galaxy clusters and groups identified in a set of hydrodynamical simulations based on an updated version of the treepm-SPH GADGET-3 code. Three different sets of simulations are performed: the first assumes non-radiative physics, the others include, among other processes, active galactic nucleus (AGN) and/or stellar feedback. Our results are analysed as a function of redshift, ICM physics, cluster mass and cluster cool-coreness or dynamical state. In general, the mean pressure profiles obtained for our sample of groups and clusters show a good agreement with X-ray and SZ observations. Simulated cool-core (CC) and non-cool-core (NCC) clusters also show a good match with real data. We obtain in all cases a small (if any) redshift evolution of the pressure profiles of massive clusters, at least back to z = 1. We find that the clumpiness of gas density and pressure increases with the distance from the cluster centre and with the dynamical activity. The inclusion of AGN feedback in our simulations generates values for the gas clumping (√{C}_{ρ }˜ 1.2 at R200) in good agreement with recent observational estimates. The simulated YSZ-M scaling relations are in good accordance with several observed samples, especially for massive clusters. As for the scatter of these relations, we obtain a clear dependence on the cluster dynamical state, whereas this distinction is not so evident when looking at the subsamples of CC and NCC clusters.

  19. The Azospirillum brasilense Che1 chemotaxis pathway controls swimming velocity, which affects transient cell-to-cell clumping.

    PubMed

    Bible, Amber; Russell, Matthew H; Alexandre, Gladys

    2012-07-01

    The Che1 chemotaxis-like pathway of Azospirillum brasilense contributes to chemotaxis and aerotaxis, and it has also been found to contribute to regulating changes in cell surface adhesive properties that affect the propensity of cells to clump and to flocculate. The exact contribution of Che1 to the control of chemotaxis and flocculation in A. brasilense remains poorly understood. Here, we show that Che1 affects reversible cell-to-cell clumping, a cellular behavior in which motile cells transiently interact by adhering to one another at their nonflagellated poles before swimming apart. Clumping precedes and is required for flocculation, and both processes appear to be independently regulated. The phenotypes of a ΔaerC receptor mutant and of mutant strains lacking cheA1, cheY1, cheB1, or cheR1 (alone or in combination) or with che1 deleted show that Che1 directly mediates changes in the flagellar swimming velocity and that this behavior directly modulates the transient nature of clumping. Our results also suggest that an additional receptor(s) and signaling pathway(s) are implicated in mediating other Che1-independent changes in clumping identified in the present study. Transient clumping precedes the transition to stable clump formation, which involves the production of specific extracellular polysaccharides (EPS); however, production of these clumping-specific EPS is not directly controlled by Che1 activity. Che1-dependent clumping may antagonize motility and prevent chemotaxis, thereby maintaining cells in a metabolically favorable niche.

  20. What Feeds the Beast in a Galaxy Cluster?

    NASA Image and Video Library

    2015-09-10

    A massive cluster of galaxies, called SpARCS1049+56, can be seen in this multi-wavelength view from NASA Hubble and Spitzer space telescopes. At the middle of the picture is the largest, central member of the family of galaxies (upper right red dot of central pair). Unlike other central galaxies in clusters, this one is bursting with the birth of new stars. Scientists say this star birth was triggered by a collision between a smaller galaxy and the giant, central galaxy. The smaller galaxy's wispy, shredded parts, called a tidal tail, can be seen coming out below the larger galaxy. Throughout this region are features called "beads on a string," which are areas where gas has clumped to form new stars. This type of "feeding" mechanism for galaxy clusters -- where gas from the merging of galaxies is converted to new stars -- is rare. The Hubble data in this image show infrared light with a wavelength of 1 micron in blue, and 1.6 microns in green. The Spitzer data show infrared light of 3.6 microns in red. http://photojournal.jpl.nasa.gov/catalog/PIA19837

  1. Graph analysis of cell clusters forming vascular networks

    NASA Astrophysics Data System (ADS)

    Alves, A. P.; Mesquita, O. N.; Gómez-Gardeñes, J.; Agero, U.

    2018-03-01

    This manuscript describes the experimental observation of vasculogenesis in chick embryos by means of network analysis. The formation of the vascular network was observed in the area opaca of embryos from 40 to 55 h of development. In the area opaca endothelial cell clusters self-organize as a primitive and approximately regular network of capillaries. The process was observed by bright-field microscopy in control embryos and in embryos treated with Bevacizumab (Avastin), an antibody that inhibits the signalling of the vascular endothelial growth factor (VEGF). The sequence of images of the vascular growth were thresholded, and used to quantify the forming network in control and Avastin-treated embryos. This characterization is made by measuring vessels density, number of cell clusters and the largest cluster density. From the original images, the topology of the vascular network was extracted and characterized by means of the usual network metrics such as: the degree distribution, average clustering coefficient, average short path length and assortativity, among others. This analysis allows to monitor how the largest connected cluster of the vascular network evolves in time and provides with quantitative evidence of the disruptive effects that Avastin has on the tree structure of vascular networks.

  2. STIRRED, NOT CLUMPED: EVOLUTION OF TEMPERATURE PROFILES IN THE OUTSKIRTS OF GALAXY CLUSTERS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Avestruz, Camille; Nagai, Daisuke; Lau, Erwin T., E-mail: avestruz@uchicago.edu

    Recent statistical X-ray measurements of the intracluster medium (ICM) indicate that gas temperature profiles in the outskirts of galaxy clusters deviate from self-similar evolution. Using a mass-limited sample of galaxy clusters from cosmological hydrodynamical simulations, we show that the departure from self-similarity can be explained by non-thermal gas motions driven by mergers and accretion. Contrary to previous claims, gaseous substructures only play a minor role in the temperature evolution in cluster outskirts. A careful choice of halo overdensity definition in self-similar scaling mitigates these departures. Our work highlights the importance of non-thermal gas motions in ICM evolution and the usemore » of galaxy clusters as cosmological probes.« less

  3. Stirred, Not Clumped: Evolution of Temperature Profiles in the Outskirts of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Avestruz, Camille; Nagai, Daisuke; Lau, Erwin T.

    2016-12-01

    Recent statistical X-ray measurements of the intracluster medium (ICM) indicate that gas temperature profiles in the outskirts of galaxy clusters deviate from self-similar evolution. Using a mass-limited sample of galaxy clusters from cosmological hydrodynamical simulations, we show that the departure from self-similarity can be explained by non-thermal gas motions driven by mergers and accretion. Contrary to previous claims, gaseous substructures only play a minor role in the temperature evolution in cluster outskirts. A careful choice of halo overdensity definition in self-similar scaling mitigates these departures. Our work highlights the importance of non-thermal gas motions in ICM evolution and the use of galaxy clusters as cosmological probes.

  4. Theoretical estimates of equilibrium 13C-18O clumping in carbonates and organic acids

    NASA Astrophysics Data System (ADS)

    Schauble, E. A.; Eiler, J. M.

    2004-12-01

    The development of techniques for measuring small gas-phase molecules containing more than one rare stable isotope (e.g., 13C18O16O) at natural, ppm-level abundances1,2 has made it possible to track sources and sinks of atmospheric gases from a new perspective. Similar measurements of 13C-18O clumping in ancient samples could improve our understanding of ancient climates, if the abundances of `clumped' rare stable isotopes in materials that retain isotopic signatures over geologic time can be measured with sufficient precision. This theoretical study estimates the abundances of such 13C-18O `clumps' in carbonates and organic acids and discusses their potential applications. Accompanying abstracts by Eiler et al. and Ghosh et al. will present the analytical methods and some initial data for carbonate minerals to examine the applicability of our theoretical models. Equilibrium isotopic speciations in carbonate minerals and organic acids are calculated from the reduced partition function ratios of isotopically substituted crystals and molecules. Vibrational frequencies used as input for these calculations come from ab initio force fields, determined using density functional theory. Our calculations indicate that carbonate minerals, including calcite, dolomite, and aragonite, when equilibrated at earth-surface temperatures, will have a slight overabundance of CO32- groups containing both 13C and 18O (i.e., 13C18O16O22-) relative to what would be expected if carbon and oxygen isotopes were distributed randomly in the crystal lattice. Calcite and dolomite crystals are predicted to have 0.4‰ excesses of 13C18O16O22- at 298 K; in aragonite the excess will be about 0.05‰ larger. The excesses are smaller for crystals formed or equilibrated at higher temperatures, decreasing by 0.003\\permil/oC at room temperature and essentially disappearing at temperatures of 1000 K or higher. Similarly, there is an excess of both 13C18O16OH and 13C16O18OH groups in organic acids like

  5. The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

    NASA Astrophysics Data System (ADS)

    Grasha, K.; Calzetti, D.; Adamo, A.; Kim, H.; Elmegreen, B. G.; Gouliermis, D. A.; Dale, D. A.; Fumagalli, M.; Grebel, E. K.; Johnson, K. E.; Kahre, L.; Kennicutt, R. C.; Messa, M.; Pellerin, A.; Ryon, J. E.; Smith, L. J.; Shabani, F.; Thilker, D.; Ubeda, L.

    2017-05-01

    We present a study of the hierarchical clustering of the young stellar clusters in six local (3-15 Mpc) star-forming galaxies using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey). We identified 3685 likely clusters and associations, each visually classified by their morphology, and we use the angular two-point correlation function to study the clustering of these stellar systems. We find that the spatial distribution of the young clusters and associations are clustered with respect to each other, forming large, unbound hierarchical star-forming complexes that are in general very young. The strength of the clustering decreases with increasing age of the star clusters and stellar associations, becoming more homogeneously distributed after ˜40-60 Myr and on scales larger than a few hundred parsecs. In all galaxies, the associations exhibit a global behavior that is distinct and more strongly correlated from compact clusters. Thus, populations of clusters are more evolved than associations in terms of their spatial distribution, traveling significantly from their birth site within a few tens of Myr, whereas associations show evidence of disruption occurring very quickly after their formation. The clustering of the stellar systems resembles that of a turbulent interstellar medium that drives the star formation process, correlating the components in unbound star-forming complexes in a hierarchical manner, dispersing shortly after formation, suggestive of a single, continuous mode of star formation across all galaxies.

  6. Form gene clustering method about pan-ethnic-group products based on emotional semantic

    NASA Astrophysics Data System (ADS)

    Chen, Dengkai; Ding, Jingjing; Gao, Minzhuo; Ma, Danping; Liu, Donghui

    2016-09-01

    The use of pan-ethnic-group products form knowledge primarily depends on a designer's subjective experience without user participation. The majority of studies primarily focus on the detection of the perceptual demands of consumers from the target product category. A pan-ethnic-group products form gene clustering method based on emotional semantic is constructed. Consumers' perceptual images of the pan-ethnic-group products are obtained by means of product form gene extraction and coding and computer aided product form clustering technology. A case of form gene clustering about the typical pan-ethnic-group products is investigated which indicates that the method is feasible. This paper opens up a new direction for the future development of product form design which improves the agility of product design process in the era of Industry 4.0.

  7. The Merging Galaxy Cluster A520 - A Broken-Up Cool Core, A Dark Subcluster, and an X-Ray Channel

    NASA Technical Reports Server (NTRS)

    Wang, Qian H.S.; Markevitch, Maxim; Giacintucci, Simona

    2016-01-01

    We present results from a deep Chandra X-ray observation of a merging galaxy cluster A520. A high-resolution gas temperature map reveals a long trail of dense, cool clumpsapparently the fragments of a cool core that has been stripped from the infalling subcluster by ram pressure. The clumps should still be connected by the stretched magnetic field lines. The observed temperature variations imply that thermal conductivity is suppressed by a factor greater than 100 across the presumed direction of the magnetic field (as found in other clusters), and is also suppressed along the field lines by a factor of several. Two massive clumps in the periphery of A520, visible in the weak-lensing mass map and the X-ray image, have apparently been completely stripped of gas during the merger, but then re-accreted the surrounding high-entropy gas upon exit from the cluster. The mass clump that hosted the stripped cool core is also re-accreting hotter gas. An X-ray hydrostatic mass estimate for the clump that has the simplest geometry agrees with the lensing mass. Its current gas mass to total mass ratio is very low, 1.5 percent to 3 percent, which makes it a "dark subcluster." We also found a curious low X-ray brightness channel (likely a low-density sheet in projection) going across the cluster along the direction of an apparent secondary merger. The channel may be caused by plasma depletion in a region of an amplified magnetic field (with plasma Beta approximately equal to 10-20). The shock in A520 will be studied in a separate paper.

  8. The Azospirillum brasilense Che1 Chemotaxis Pathway Controls Swimming Velocity, Which Affects Transient Cell-to-Cell Clumping

    PubMed Central

    Bible, Amber; Russell, Matthew H.

    2012-01-01

    The Che1 chemotaxis-like pathway of Azospirillum brasilense contributes to chemotaxis and aerotaxis, and it has also been found to contribute to regulating changes in cell surface adhesive properties that affect the propensity of cells to clump and to flocculate. The exact contribution of Che1 to the control of chemotaxis and flocculation in A. brasilense remains poorly understood. Here, we show that Che1 affects reversible cell-to-cell clumping, a cellular behavior in which motile cells transiently interact by adhering to one another at their nonflagellated poles before swimming apart. Clumping precedes and is required for flocculation, and both processes appear to be independently regulated. The phenotypes of a ΔaerC receptor mutant and of mutant strains lacking cheA1, cheY1, cheB1, or cheR1 (alone or in combination) or with che1 deleted show that Che1 directly mediates changes in the flagellar swimming velocity and that this behavior directly modulates the transient nature of clumping. Our results also suggest that an additional receptor(s) and signaling pathway(s) are implicated in mediating other Che1-independent changes in clumping identified in the present study. Transient clumping precedes the transition to stable clump formation, which involves the production of specific extracellular polysaccharides (EPS); however, production of these clumping-specific EPS is not directly controlled by Che1 activity. Che1-dependent clumping may antagonize motility and prevent chemotaxis, thereby maintaining cells in a metabolically favorable niche. PMID:22522896

  9. Epithelial stem cells are formed by small-particles released from particle-producing cells

    PubMed Central

    Kong, Wuyi; Zhu, Xiao Ping; Han, Xiu Juan; Nuo, Mu; Wang, Hong

    2017-01-01

    Recent spatiotemporal report demonstrated that epidermal stem cells have equal potential to divide or differentiate, with no asymmetric cell division observed. Therefore, how epithelial stem cells maintain lifelong stem-cell support still needs to be elucidated. In mouse blood and bone marrow, we found a group of large cells stained strongly for eosin and containing coiled-tubing-like structures. Many were tightly attached to each other to form large cellular clumps. After sectioning, these large cell-clumps were composed of not cells but numerous small particles, however with few small “naked” nuclei. The small particles were about 2 to 3 μm in diameter and stained dense red for eosin, so they may be rich in proteins. Besides the clumps composed of small particles, we identified clumps formed by fusion of the small particles and clumps of newly formed nucleated cells. These observations suggest that these small particles further fused and underwent cellularization. E-cadherin was expressed in particle-fusion areas, some “naked” nuclei and the newly formed nucleated cells, which suggests that these particles can form epithelial cells via fusion and nuclear remodeling. In addition, we observed similar-particle fusion before epithelial cellularization in mouse kidney ducts after kidney ischemia, which suggests that these particles can be released in the blood and carried to the target tissues for epithelial-cell regeneration. Oct4 and E-cadherin expressed in the cytoplasmic areas in cells that were rich in protein and mainly located in the center of the cellular clumps, suggesting that these newly formed cells have become tissue-specific epithelial stem cells. Our data provide evidence that these large particle-producing cells are the origin of epithelial stem cells. The epithelial stem cells are newly formed by particle fusion. PMID:28253358

  10. The clumped isotope geothermometer in soil and paleosol carbonate

    NASA Astrophysics Data System (ADS)

    Quade, J.; Eiler, J.; Daëron, M.; Achyuthan, H.

    2013-03-01

    We studied both modern soils and buried paleosols in order to understand the relationship of temperature (T°C(47)) estimated from clumped isotope compositions (Δ47) of soil carbonates to actual surface and burial temperatures. Carbonates from modern soils with differing rainfall seasonality were sampled from Arizona, Nevada, Tibet, Pakistan, and India. T°C(47) obtained from these soils shows that soil carbonate forms in the warmest months of the year, in the late morning to afternoon, and probably in response to intense soil dewatering. T°C(47) obtained from modern soil carbonate ranges from 10.8 to 39.5 °C. On average, T°C(47) exceeds mean annual temperature by 10-15 °C due to summertime bias in soil carbonate formation, and to summertime ground heating by incident solar radiation. Secondary controls on T°C(47) are soil depth and shading. Site mean annual air temperature (MAAT) across a broad range (0-30 °C) of site temperatures is highly correlated with T°C(47) from soils, following the equation: MAAT(°C)=1.20(T°C(47)0)-21.72(r2=0.92) where T°C(47)0 is the effective air temperature at the site estimated from T°C(47). The effective air temperature represents the air temperature required to account for the T°C(47) at each site, after consideration of variations in T°C(47) with soil depth and ground heating. The highly correlated relationship in this equation should now permit mean annual temperature in the past to be reconstructed from T°C(47) in paleosol carbonate, assuming one is studying paleosols that formed in environments generally similar in seasonality and ground cover to our calibration sites. T°C(47)0 decreases systematically with elevation gain in the Himalaya, following the equation: elevation(m)=-229(T°C(47)0)+9300(r2=0.95) Assuming that temperature varied similarly with elevation in the past, this equation can be used to reconstruct paleoelevation from clumped isotope analysis of ancient soil carbonates. We also measured T°C(47

  11. VizieR Online Data Catalog: Massive star forming molecular clumps Tkin (Tang+, 2017)

    NASA Astrophysics Data System (ADS)

    Tang, X. D.; Henkel, C.; Menten, K. M.; Zheng, X. W.; Esimbek, J.; Zhou, J. J.; Yeh, C. C.; Konig, C.; Yuan, Y.; He, Y. X.; Li, D. L.

    2016-10-01

    We have selected 30 massive clumps of the Galactic disk at various stages of high-mass star formation and with strong NH3 emission from the ATLASGAL survey (see Table 1). Our observations were carried out in 2015 April, July, and October with the 15m James Clerk Maxwell Telescope telescope (JCMT) on Mauna Kea. The beam size is ~23" and the main-beam efficiency is {eta}mb=Ta*/Tmb~=0.7 at 218GHz. The para-H2CO JKAKC =303-202, 322-221, and 321-220 transitions have rest frequencies of 218.222, 218.475, and 218.760GHz, respectively, which are measured simultaneously by employing the ACSIS digital autocorrelation spectrometer with the special backend configuration RxAH2CO250x3 allowing for three windows, each with a bandwidth of 250MHz. This provides a velocity resolution of 0.084km/s for para-H2CO (303-202 and 322-221) and 0.042km/s for para-H2CO (321-220); CH3OH (422-312) at 218.440GHz is also observed together with para-H2CO (322-221). (6 data files).

  12. The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Grasha, K.; Calzetti, D.; Adamo, A.

    We present a study of the hierarchical clustering of the young stellar clusters in six local (3–15 Mpc) star-forming galaxies using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey). We identified 3685 likely clusters and associations, each visually classified by their morphology, and we use the angular two-point correlation function to study the clustering of these stellar systems. We find that the spatial distribution of the young clusters and associations are clustered with respect to each other, forming large, unbound hierarchical star-forming complexes that are in general very young. Themore » strength of the clustering decreases with increasing age of the star clusters and stellar associations, becoming more homogeneously distributed after ∼40–60 Myr and on scales larger than a few hundred parsecs. In all galaxies, the associations exhibit a global behavior that is distinct and more strongly correlated from compact clusters. Thus, populations of clusters are more evolved than associations in terms of their spatial distribution, traveling significantly from their birth site within a few tens of Myr, whereas associations show evidence of disruption occurring very quickly after their formation. The clustering of the stellar systems resembles that of a turbulent interstellar medium that drives the star formation process, correlating the components in unbound star-forming complexes in a hierarchical manner, dispersing shortly after formation, suggestive of a single, continuous mode of star formation across all galaxies.« less

  13. STAR CLUSTERS IN A NUCLEAR STAR FORMING RING: THE DISAPPEARING STRING OF PEARLS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Väisänen, Petri; Barway, Sudhanshu; Randriamanakoto, Zara, E-mail: petri@saao.ac.za

    2014-12-20

    An analysis of the star cluster population in a low-luminosity early-type galaxy, NGC 2328, is presented. The clusters are found in a tight star forming nuclear spiral/ring pattern and we also identify a bar from structural two-dimensional decomposition. These massive clusters are forming very efficiently in the circumnuclear environment and they are young, possibly all less than 30 Myr of age. The clusters indicate an azimuthal age gradient, consistent with a ''pearls-on-a-string'' formation scenario, suggesting bar-driven gas inflow. The cluster mass function has a robust down turn at low masses at all age bins. Assuming clusters are born with a power-lawmore » distribution, this indicates extremely rapid disruption at timescales of just several million years. If found to be typical, it means that clusters born in dense circumnuclear rings do not survive to become old globular clusters in non-interacting systems.« less

  14. Influence of water on clumped-isotope bond reordering kinetics in calcite

    NASA Astrophysics Data System (ADS)

    Brenner, Dana C.; Passey, Benjamin H.; Stolper, Daniel A.

    2018-03-01

    Oxygen self-diffusion in calcite and many other minerals is considerably faster under wet conditions relative to dry conditions. Here we investigate whether this "water effect" also holds true for solid-state isotope exchange reactions that alter the abundance of carbonate groups with multiple rare isotopes ('clumped' isotope groups) via the process of solid-state bond reordering. We present clumped-isotope reordering rates for optical calcite heated under wet, high-pressure (100 MPa) conditions. We observe only modest increases in reordering rates under such conditions compared with rates for the same material reacted in dry CO2 under low-pressure conditions. Activation energies under wet, high-pressure conditions are indistinguishable from those for dry, low-pressure conditions, while rate constants are resolvably higher (up to ∼3 times) for wet, high-pressure relative to dry, low-pressure conditions in most of our interpretations of experimental results. This contrasts with the water effect for oxygen self-diffusion in calcite, which is associated with lower activation energies, and diffusion coefficients that are ≥103 times higher compared with dry (pure CO2) conditions in the temperature range of this study (385-450 °C). The water effect for clumped-isotopes leads to calculated apparent equilibrium temperatures ("blocking temperatures") for typical geological cooling rates that are only a few degrees higher than those for dry conditions, while O self-diffusion blocking temperatures in calcite grains are ∼150-200 °C lower in wet conditions compared with dry conditions. Since clumped-isotope reordering is a distributed process that occurs throughout the mineral volume, our clumped-isotope results support the suggestion of Labotka et al. (2011) that the water effect in calcite does not involve major changes in bulk (volume) diffusivity, but rather is primarily a surface phenomenon that facilitates oxygen exchange between the calcite surface and external

  15. Calibration of the clumped isotope thermometer for planktic foraminifers

    NASA Astrophysics Data System (ADS)

    Meinicke, N.; Ho, S. L.; Nürnberg, D.; Tripati, A. K.; Jansen, E.; Dokken, T.; Schiebel, R.; Meckler, A. N.

    2017-12-01

    Many proxies for past ocean temperature suffer from secondary influences or require species-specific calibrations that might not be applicable on longer time scales. Being thermodynamically based and thus independent of seawater composition, clumped isotopes in carbonates (Δ47) have the potential to circumvent such issues affecting other proxies and provide reliable temperature reconstructions far back in time and in unknown settings. Although foraminifers are commonly used for paleoclimate reconstructions, their use for clumped isotope thermometry has been hindered so far by large sample-size requirements. Existing calibration studies suggest that data from a variety of foraminifer species agree with synthetic carbonate calibrations (Tripati, et al., GCA, 2010; Grauel, et al., GCA, 2013). However, these studies did not include a sufficient number of samples to fully assess the existence of species-specific effects, and data coverage was especially sparse in the low temperature range (<10 °C). To expand the calibration database of clumped isotopes in planktic foraminifers, especially for colder temperatures (<10°C), we present new Δ47 data analysed on 14 species of planktic foraminifers from 13 sites, covering a temperature range of 1-29 °C. Our method allows for analysis of smaller sample sizes (3-5 mg), hence also the measurement of multiple species from the same samples. We analyzed surface-dwelling ( 0-50 m) species and deep-dwelling (habitat depth up to several hundred meters) planktic foraminifers from the same sites to evaluate species-specific effects and to assess the feasibility of temperature reconstructions for different water depths. We also assess the effects of different techniques in estimating foraminifer calcification temperature on the calibration. Finally, we compare our calibration to existing clumped isotope calibrations. Our results confirm previous findings that indicate no species-specific effects on the Δ47-temperature relationship

  16. How to form planetesimals from mm-sized chondrules and chondrule aggregates

    NASA Astrophysics Data System (ADS)

    Carrera, Daniel; Johansen, Anders; Davies, Melvyn B.

    2015-07-01

    The size distribution of asteroids and Kuiper belt objects in the solar system is difficult to reconcile with a bottom-up formation scenario due to the observed scarcity of objects smaller than ~100 km in size. Instead, planetesimals appear to form top-down, with large 100-1000 km bodies forming from the rapid gravitational collapse of dense clumps of small solid particles. In this paper we investigate the conditions under which solid particles can form dense clumps in a protoplanetary disk. We used a hydrodynamic code to model the interaction between solid particles and the gas inside a shearing box inside the disk, considering particle sizes from submillimeter-sized chondrules to meter-sized rocks. We found that particles down to millimeter sizes can form dense particle clouds through the run-away convergence of radial drift known as the streaming instability. We made a map of the range of conditions (strength of turbulence, particle mass-loading, disk mass, and distance to the star) that are prone to producing dense particle clumps. Finally, we estimate the distribution of collision speeds between mm-sized particles. We calculated the rate of sticking collisions and obtain a robust upper limit on the particle growth timescale of ~105 years. This means that mm-sized chondrule aggregates can grow on a timescale much smaller than the disk accretion timescale (~106-107 years). Our results suggest a pathway from the mm-sized grains found in primitive meteorites to fully formed asteroids. We speculate that asteroids may form from a positive feedback loop in which coagualation leads to particle clumping driven by the streaming instability. This clumping, in turn, reduces collision speeds and enhances coagulation. Future simulations should model coagulation and the streaming instability together to explore this feedback loop further. Appendices are available in electronic form at http://www.aanda.org

  17. Extreme Mergers from the Massive Cluster Survey

    NASA Astrophysics Data System (ADS)

    Morris, Roger

    2010-09-01

    We propose to observe two extraordinary, high-redshift galaxy clusters from the Massive Cluster Survey. Both targets are very rare, triple merger systems (one a nearly co-linear merger), and likely lie at the deepest nodes of the cosmic web. Both targets show multiple strong gravitational lensing arcs in the cluster cores. These targets only possess very short (10ks) Chandra observations, and are unobserved by XMM-Newton. The X-ray data will be used to probe the mass distribution of hot, baryonic gas, and to reveal the details of the merger physics and the process of cluster assembly. We will also search for hints of X-ray emission from filaments between the merging clumps. Subaru and Hubble Space Telescope imaging data are in hand; we request additional HST coverage for one object.

  18. Laser spectrometer for CO2 clumped isotope analysis

    NASA Astrophysics Data System (ADS)

    Prokhorov, Ivan; Kluge, Tobias; Janssen, Christof

    2017-04-01

    Carbon dioxide clumped isotope thermometry has proven to be a reliable method for biogeochemical and atmospheric research. We present a new laser spectroscopic instrument for doubly-substituted isotopologues analysis. In contrast to a conventional isotope ratio mass spectrometry (IRMS), tunable laser direct absorption spectroscopy (TLDAS) has the advantage of isotopologue-specific determination free of isobaric interferences. Tunable infrared laser based spectrometer for clumped isotope analysis is being developed in collaboration between Heidelberg University, Germany, and LERMA-IPSL, CNRS, France. The instrument employs two continuous intraband cascade lasers (ICL) tuned at 4439 and 4329 nm. The spectral windows covered by the lasers contain absorption lines of the six most abundant CO2 isotopologues, including the two doubly substituted species 16O13C18O and 16O13C17O, and all singly substituted isotopologues with 13C, 18O and 17O. A Herriott-type multi-pass cell provides two different absorption pathlengths to compensate the abundance difference between singly- and doubly-substituted isotopologues. We have reached the sub-permill precision required for clumped isotope measurements within the integration time of several seconds. The test version of the instrument demonstrates a performance comparable to state of the art IRMS. We highlight the following features of the instrument that are strong advantages compared to conventional mass spectrometry: measurement cycle in the minute range, simplified sample preparation routine, table-top layout with a potential for in-situ applications.

  19. Lithium Inventory of 2 Solar Mass Red Clump Stars in Open Clusters: A Test of the Helium Flash Mechanism

    NASA Technical Reports Server (NTRS)

    Carlberg, Joleen K.; Cunha, Katia; Smith, Verne V.

    2016-01-01

    The temperature distribution of field Li-rich red giants suggests the presence of a population of Li-rich red clump (RC) stars. One proposed explanation for this population is that all stars with masses near 2 solar mass experience a shortlived phase of Li-richness at the onset of core He-burning. Many of these stars have low C-12/C-13, a signature of deep mixing that is presumably associated with the Li regeneration. To test this purported mechanism of Li enrichment, we measured abundances in 38 RC stars and 6 red giant branch (RGB) stars in four open clusters selected to have RC masses near 2 solar mass. We find six Li-rich stars (A(Li) greater than or equal to 1.50 dex) of which only two may be RC stars. None of the RC stars have Li exceeding the levels observed in the RGB stars, but given the brevity of the suggested Li-rich phase and the modest sample size, it is probable that stars with larger Li-enrichments were missed simply by chance. However, we find very few stars in our sample with low C-12/C-13. Such low C-12/C-13, seen in many field Li-rich stars, should persist even after lithium has returned to normal low levels. Thus, if Li synthesis during the He flash occurs, it is a rare, but potentially long-lived occurrence rather than a short-lived phase for all stars. We estimate a conservative upper limit of the fraction of stars going through a Li-rich phase to be less than 47%, based on stars that have low C-12/C-13 for their observed A(Li).

  20. Stochastic effects on phase-space holes and clumps in kinetic systems near marginal stability

    DOE PAGES

    Woods, Benjamin J. Q.; Duarte, Vinicius N.; De-Gol, Anthony J.; ...

    2018-01-23

    The creation and subsequent evolution of marginally-unstable modes have been observed in a wide range of fusion devices. This behaviour has been successfully explained, for a single frequency shifting mode, in terms of phase-space structures known as a 'hole' and 'clump'. Here in this paper, we introduce stochasticity into a 1D kinetic model, affecting the formation and evolution of resonant modes in the system. We find that noise in the fast particle distribution or electric field leads to a shift in the asymptotic behaviour of a chirping resonant mode; this noise heuristically maps onto radial microturbulence via canonical toroidal momentummore » scattering, affecting hole and clump formation. While the mechanism allowing for the formation of the hole and clump is coherent, the lifetime of a hole and clump is shown to be highly sensitive to initial conditions, affecting the temporal profile of a single bursting event in mode amplitude.« less

  1. Stochastic effects on phase-space holes and clumps in kinetic systems near marginal stability

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Woods, Benjamin J. Q.; Duarte, Vinicius N.; De-Gol, Anthony J.

    The creation and subsequent evolution of marginally-unstable modes have been observed in a wide range of fusion devices. This behaviour has been successfully explained, for a single frequency shifting mode, in terms of phase-space structures known as a 'hole' and 'clump'. Here in this paper, we introduce stochasticity into a 1D kinetic model, affecting the formation and evolution of resonant modes in the system. We find that noise in the fast particle distribution or electric field leads to a shift in the asymptotic behaviour of a chirping resonant mode; this noise heuristically maps onto radial microturbulence via canonical toroidal momentummore » scattering, affecting hole and clump formation. While the mechanism allowing for the formation of the hole and clump is coherent, the lifetime of a hole and clump is shown to be highly sensitive to initial conditions, affecting the temporal profile of a single bursting event in mode amplitude.« less

  2. The nature of giant clumps in distant galaxies probed by the anatomy of the cosmic snake

    NASA Astrophysics Data System (ADS)

    Cava, Antonio; Schaerer, Daniel; Richard, Johan; Pérez-González, Pablo G.; Dessauges-Zavadsky, Miroslava; Mayer, Lucio; Tamburello, Valentina

    2018-01-01

    Giant stellar clumps are ubiquitous in high-redshift galaxies1,2. They are thought to play an important role in the build-up of galactic bulges3 and as diagnostics of star formation feedback in galactic discs4. Hubble Space Telescope (HST) blank field imaging surveys have estimated that these clumps have masses of up to 109.5 M⊙ and linear sizes of ≳1 kpc5,6. Recently, gravitational lensing has also been used to get higher spatial resolution7-9. However, both recent lensed observations10,11 and models12,13 suggest that the clumps' properties may be overestimated by the limited resolution of standard imaging techniques. A definitive proof of this observational bias is nevertheless still missing. Here we investigate directly the effect of resolution on clump properties by analysing multiple gravitationally lensed images of the same galaxy at different spatial resolutions, down to 30 pc. We show that the typical mass and size of giant clumps, generally observed at 1 kpc resolution in high-redshift galaxies, are systematically overestimated. The high spatial resolution data, only enabled by strong gravitational lensing using currently available facilities, support smaller scales of clump formation by fragmentation of the galactic gas disk via gravitational instabilities.

  3. Theoretical estimation of 13C-D clumped isotope effects in methyl of several organic compound

    NASA Astrophysics Data System (ADS)

    LIU, Q.; Yin, X.; Liu, Y.

    2015-12-01

    Recent developments in mass spectrometry and tunable infrared laser direct absorption spectroscopy make it possible to measure 13C-D clumped isotope effects of methane. These techniques can be further applied to determine 13C-D clumped isotope effects of methyl fragments, therefore need accurate equilirbium Δi values to calibrate experimental measurements. In this study, we calculate temperature depandences of 13C-D clumped isotope signatures in methyl of several organic compounds including ethane, propane, acetic acid, etc. Our calculation are performed at CCSD/6-311+G(3df,3pd) by using Gaussian 03 program with no scale treament. Our results show that the Δi values of 13C-D clumping in methyl fragments of different organic compounds yield similar signals (~5.5‰ at 25˚C, slightly lower than Δi value of 13C-D clumping in methane). For testing the calculated accuracy, theoretical treaments beyond the harmonic level by including several higher-order corrections to the Bigeleisen-Mayer equation are used. Contributions from higher-order corrections (e.g., AnZPE, AnEXC, VrZPE, VrEXC, QmCorr and CenDist) are estimated to repire the ignorings of the Bigeleisen-Mayer equation (the anharmonic effects of vibration, vibration-rotation coupling, quantum mechanics and centrifugal distortion for rotation, etc.) for the calculation of partition function ratios. The results show that the higher-order corrections contribute ~0.05‰ at 25˚C, which is similar to the contribution for calculating 13C-D clumped isotope signature of methane. By comparing our calculated frequencies to the measured ones, the uncertainty of our calculation of Δi values 13C-D clumping in methyl fragments is considered to be within ~0.05‰ at room temperature.

  4. Source clustering in the Hi-GAL survey determined using a minimum spanning tree method

    NASA Astrophysics Data System (ADS)

    Beuret, M.; Billot, N.; Cambrésy, L.; Eden, D. J.; Elia, D.; Molinari, S.; Pezzuto, S.; Schisano, E.

    2017-01-01

    Aims: The aims are to investigate the clustering of the far-infrared sources from the Herschel infrared Galactic Plane Survey (Hi-GAL) in the Galactic longitude range of -71 to 67 deg. These clumps, and their spatial distribution, are an imprint of the original conditions within a molecular cloud. This will produce a catalogue of over-densities. Methods: The minimum spanning tree (MST) method was used to identify the over-densities in two dimensions. The catalogue was further refined by folding in heliocentric distances, resulting in more reliable over-densities, which are cluster candidates. Results: We found 1633 over-densities with more than ten members. Of these, 496 are defined as cluster candidates because of the reliability of the distances, with a further 1137 potential cluster candidates. The spatial distributions of the cluster candidates are different in the first and fourth quadrants, with all clusters following the spiral structure of the Milky Way. The cluster candidates are fractal. The clump mass functions of the clustered and isolated are statistically indistinguishable from each other and are consistent with Kroupa's initial mass function. Hi-GAL is a key-project of the Herschel Space Observatory survey (Pilbratt et al. 2010) and uses the PACS (Poglitsch et al. 2010) and SPIRE (Griffin et al. 2010) cameras in parallel mode.The catalogues of cluster candidates and potential clusters are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/597/A114

  5. Not all stars form in clusters - measuring the kinematics of OB associations with Gaia

    NASA Astrophysics Data System (ADS)

    Ward, Jacob L.; Kruijssen, J. M. Diederik

    2018-04-01

    It is often stated that star clusters are the fundamental units of star formation and that most (if not all) stars form in dense stellar clusters. In this monolithic formation scenario, low-density OB associations are formed from the expansion of gravitationally bound clusters following gas expulsion due to stellar feedback. N-body simulations of this process show that OB associations formed this way retain signs of expansion and elevated radial anisotropy over tens of Myr. However, recent theoretical and observational studies suggest that star formation is a hierarchical process, following the fractal nature of natal molecular clouds and allowing the formation of large-scale associations in situ. We distinguish between these two scenarios by characterizing the kinematics of OB associations using the Tycho-Gaia Astrometric Solution catalogue. To this end, we quantify four key kinematic diagnostics: the number ratio of stars with positive radial velocities to those with negative radial velocities, the median radial velocity, the median radial velocity normalized by the tangential velocity, and the radial anisotropy parameter. Each quantity presents a useful diagnostic of whether the association was more compact in the past. We compare these diagnostics to models representing random motion and the expanding products of monolithic cluster formation. None of these diagnostics show evidence of expansion, either from a single cluster or multiple clusters, and the observed kinematics are better represented by a random velocity distribution. This result favours the hierarchical star formation model in which a minority of stars forms in bound clusters and large-scale, hierarchically structured associations are formed in situ.

  6. Effects of cutting time, stump height, parent tree characteristics, and harvest variables on development of bigleaf maple sprout clumps

    USGS Publications Warehouse

    Tappeiner, J. C.; Zasada, J.; Maxwell, B.

    1996-01-01

    In order to determine the effects of stump height, year of cutting, parent-tree size, logging damage, and deer browsing on bigleaf maple (Acer macrophyllum) sprout clump development, maple trees were cut to two stump heights at three different times. Stump height had the greatest impact on sprout clump size. Two years after clearcutting, the sprout clump volume for short stumps was significantly less than that for tall stumps. The sprout clump volume, area, and number of sprouts were significantly less for trees cut 1 and 2 yr before harvest than for trees cut at harvest. Sprout clump size was positively correlated with parent tree stem diameter and stump volume, and negatively correlated with the percentage of bark removed during logging. Browsing had no significant impact on average clump size. Uncut trees produced sprout clumps at their base and epicormic branches along the length of their stems; thus their crown volume averaged four to five times that of cut trees. Cutting maple in clearcuts to low stumps may reduce maple competition with Douglas-fir regeneration and still maintain maple in the next stand.

  7. A {sup 13}CO Detection in a Brightest Cluster Galaxy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vantyghem, A. N.; McNamara, B. R.; Hogan, M. T.

    We present ALMA Cycle 4 observations of CO(1-0), CO(3-2), and {sup 13}CO(3-2) line emission in the brightest cluster galaxy (BCG) of RXJ0821+0752. This is one of the first detections of {sup 13}CO line emission in a galaxy cluster. Half of the CO(3-2) line emission originates from two clumps of molecular gas that are spatially offset from the galactic center. These clumps are surrounded by diffuse emission that extends 8 kpc in length. The detected {sup 13}CO emission is confined entirely to the two bright clumps, with any emission outside of this region lying below our detection threshold. Two distinct velocitymore » components with similar integrated fluxes are detected in the {sup 12}CO spectra. The narrower component (60 km s{sup −1} FWHM) is consistent in both velocity centroid and linewidth with {sup 13}CO(3-2) emission, while the broader (130–160 km s{sup −1}), slightly blueshifted wing has no associated {sup 13}CO(3-2) emission. A simple local thermodynamic model indicates that the {sup 13}CO emission traces 2.1 × 10{sup 9} M {sub ⊙} of molecular gas. Isolating the {sup 12}CO velocity component that accompanies the {sup 13}CO emission yields a CO-to-H{sub 2} conversion factor of α {sub CO} = 2.3 M {sub ⊙} (K km s{sup −1}){sup −1}, which is a factor of two lower than the Galactic value. Adopting the Galactic CO-to-H{sub 2} conversion factor in BCGs may therefore overestimate their molecular gas masses by a factor of two. This is within the object-to-object scatter from extragalactic sources, so calibrations in a larger sample of clusters are necessary in order to confirm a sub-Galactic conversion factor.« less

  8. Young massive star clusters in the era of HST and integral field spectroscopy

    NASA Astrophysics Data System (ADS)

    Zeidler, Peter; Nota, Antonella; Sabbi, Elena; Grebel, Eva K.; Pasquali, Anna

    2018-01-01

    With an age of 1 – 2 Myr at a distance of 4 kpc and a total stellar mass of 3.7×104 M⊙, Westerlund 2 (Wd2) is one of the most massive young star clusters in the Milky Way. We present a detailed analysis of its prominent pre-main-sequence population using the data of a high-resolution multi-band survey in the optical and near-infrared with the Hubble Space Telescope (HST), in combination with our spectroscopic survey, observed with the VLT/MUSE integral field unit. With our derived high-resolution extinction map of the region, which is absolutely essential giving the dominating presences of the gas and dust, we derived the spatial dependence of the mass function and quantify the degree of mass segregation down to 0.65 M⊙ with a completeness level better than 50%. Studying the radial dependence of the mass function of Wd2 and quantifying the degree of mass segregation in this young massive star cluster showed that it consists of two sub-clumps, namely the main cluster and the northern clump. From the MUSE data, we can extract individual stellar spectra and spectral energy distributions of the stars, based on the astrometry, provided by our high-resolution HST photometric catalog. This data will provide us with an almost complete spectral classification of a young massive star cluster down to 1.0 M⊙. The combination of the MUSE data, together with 3 more years of approved HST data will allow us to obtain, for the first time, the 3D motions of the stars with an accuracy of 1-2 km s-2 to determine the stellar velocity dispersion in order to study the fate of Wd2. This information is of great importance to adjust the initial conditions in cluster evolution models in order to connect these young massive star clusters and the old globular cluster population. Additionally, the combination of the photometric and spectroscopic datasets allows us to study the stars and their feedback onto the surrounding HII region simultaneously, as well as peculiar objects such as

  9. Extreme Mergers from the Massive Cluster Survey

    NASA Astrophysics Data System (ADS)

    Morris, R.

    2010-09-01

    We will observe an extraordinary, high-redshift galaxy cluster from the Massive Cluster Survey. The target is a very rare, triple merger system, and likely lies at the one of deepest nodes of the cosmic web. The target shows multiple strong gravitational lensing arcs in the cluster core. This target only possesses a very short {10ks} Chandra observations, and is unobserved by XMM-Newton. The X-ray data from this joint Chandra/HST proposal will be used to probe the mass distribution of hot, baryonic gas, and to reveal the details of the merger physics and the process of cluster assembly. We will also search for hints of X-ray emission from filaments between the merging clumps. Subaru and some Hubble Space Telescope imaging data are in hand; we will gather additional HST coverage for a lensing analysis.

  10. Effects of foliage clumping on the estimation of global terrestrial gross primary productivity

    NASA Astrophysics Data System (ADS)

    Chen, Jing M.; Mo, Gang; Pisek, Jan; Liu, Jane; Deng, Feng; Ishizawa, Misa; Chan, Douglas

    2012-03-01

    Sunlit and shaded leaf separation proposed by Norman (1982) is an effective way to upscale from leaf to canopy in modeling vegetation photosynthesis. The Boreal Ecosystem Productivity Simulator (BEPS) makes use of this methodology, and has been shown to be reliable in modeling the gross primary productivity (GPP) derived from CO2flux and tree ring measurements. In this study, we use BEPS to investigate the effect of canopy architecture on the global distribution of GPP. For this purpose, we use not only leaf area index (LAI) but also the first ever global map of the foliage clumping index derived from the multiangle satellite sensor POLDER at 6 km resolution. The clumping index, which characterizes the degree of the deviation of 3-dimensional leaf spatial distributions from the random case, is used to separate sunlit and shaded LAI values for a given LAI. Our model results show that global GPP in 2003 was 132 ± 22 Pg C. Relative to this baseline case, our results also show: (1) global GPP is overestimated by 12% when accurate LAI is available but clumping is ignored, and (2) global GPP is underestimated by 9% when the effective LAI is available and clumping is ignored. The clumping effects in both cases are statistically significant (p < 0.001). The effective LAI is often derived from remote sensing by inverting the measured canopy gap fraction to LAI without considering the clumping. Global GPP would therefore be generally underestimated when remotely sensed LAI (actually effective LAI by our definition) is used. This is due to the underestimation of the shaded LAI and therefore the contribution of shaded leaves to GPP. We found that shaded leaves contribute 50%, 38%, 37%, 39%, 26%, 29% and 21% to the total GPP for broadleaf evergreen forest, broadleaf deciduous forest, evergreen conifer forest, deciduous conifer forest, shrub, C4 vegetation, and other vegetation, respectively. The global average of this ratio is 35%.

  11. Limitations of the clump-correlation theories of shear-induced turbulence suppression

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Z.; Mahajan, S. M.

    2017-05-01

    The clump theory, primarily constructed by Dupree [Phys. Fluids 15, 334 (1972)] based on the moment approach and then generalized to the correlation theory [Y. Z. Zhang and S. M. Mahajan, Phys. Fluids B 5, 2000 (1993)], has long served as a basis for constructing theories of turbulence suppression by shear flow. In order to reveal the "intrinsic approximation" invoked in the clump-correlation theory, we examine a model based on two dimensional magnetized drift waves. After a rigorous derivation of the exact response function—a key to average the Green function of the system—we show that the Dupree, Zhang-Mahajan approach is recovered as the lowest order approximation in a small dimensionless parameter ϒ which is a triple product of the correlation time, wave number, and fluctuating drift velocity. The clump-correlation theory, thus, constitutes the Gaussian and lowest order non-Markovian process for a homogeneous stationary turbulence. We also provide, especially for the tokamak community, a readily usable formula to evaluate the effectiveness of shear-flow suppression; this formula pertains regardless of the specific model of correlation time.

  12. "Anticlumping" and Other Combinatorial Effects on Clumped Isotopes: Implications for Tracing Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Yeung, L.

    2015-12-01

    I present a mode of isotopic ordering that has purely combinatorial origins. It can be important when identical rare isotopes are paired by coincidence (e.g., they are neighbors on the same molecule), or when extrinsic factors govern the isotopic composition of the two atoms that share a chemical bond. By itself, combinatorial isotope pairing yields products with isotopes either randomly distributed or with a deficit relative to a random distribution of isotopes. These systematics arise because of an unconventional coupling between the formation of singly- and multiply-substituted isotopic moieties. In a random distribution, rare isotopes are symmetrically distributed: Single isotopic substitutions (e.g., H‒D and D‒H in H2) occur with equal probability, and double isotopic substitutions (e.g., D2) occur according to random chance. The absence of symmetry in a bond-making complex can yield unequal numbers of singly-substituted molecules (e.g., more H‒D than D‒H in H2), which is recorded in the product molecule as a deficit in doubly-substituted moieties and an "anticlumped" isotope distribution (i.e., Δn < 0). Enzymatic isotope pairing reactions, which can have site-specific isotopic fractionation factors and atom reservoirs, should express this class of combinatorial isotope effect. Chemical-kinetic isotope effects, which are related to the bond-forming transition state, arise independently and express second-order combinatorial effects. In general, both combinatorial and chemical factors are important for calculating and interpreting clumped-isotope signatures of individual reactions. In many reactions relevant to geochemical oxygen, carbon, and nitrogen cycling, combinatorial isotope pairing likely plays a strong role in the clumped isotope distribution of the products. These isotopic signatures, manifest as either directly bound isotope clumps or as features of a molecule's isotopic anatomy, could be exploited as tracers of biogeochemistry that can

  13. MOLECULAR CLOUDS AND CLUMPS IN THE BOSTON UNIVERSITY-FIVE COLLEGE RADIO ASTRONOMY OBSERVATORY GALACTIC RING SURVEY

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rathborne, J. M.; Johnson, A. M.; Jackson, J. M.

    2009-05-15

    The Boston University-Five College Radio Astronomy Observatory (BU-FCRAO) Galactic Ring Survey (GRS) of {sup 13}CO J = 1 {yields} 0 emission covers Galactic longitudes 18{sup 0} < l < 55.{sup 0}7 and Galactic latitudes |b| {<=} 1{sup 0}. Using the SEQUOIA array on the FCRAO 14 m telescope, the GRS fully sampled the {sup 13}CO Galactic emission (46'' angular resolution on a 22'' grid) and achieved a spectral resolution of 0.21 km s{sup -1}. Because the GRS uses {sup 13}CO, an optically thin tracer, rather than {sup 12}CO, an optically thick tracer, the GRS allows a much better determination ofmore » column density and also a cleaner separation of velocity components along a line of sight. With this homogeneous, fully sampled survey of {sup 13}CO emission, we have identified 829 molecular clouds and 6124 clumps throughout the inner Galaxy using the CLUMPFIND algorithm. Here we present details of the catalog and a preliminary analysis of the properties of the molecular clouds and their clumps. Moreover, we compare clouds inside and outside of the 5 kpc ring and find that clouds within the ring typically have warmer temperatures, higher column densities, larger areas, and more clumps compared with clouds located outside the ring. This is expected if these clouds are actively forming stars. This catalog provides a useful tool for the study of molecular clouds and their embedded young stellar objects.« less

  14. Structural transitions and hysteresis in clump- and stripe-forming systems under dynamic compression.

    PubMed

    McDermott, Danielle; Olson Reichhardt, Cynthia J; Reichhardt, Charles

    2016-11-28

    Using numerical simulations, we study the dynamical evolution of particles interacting via competing long-range repulsion and short-range attraction in two dimensions. The particles are compressed using a time-dependent quasi-one dimensional trough potential that controls the local density, causing the system to undergo a series of structural phase transitions from a low density clump lattice to stripes, voids, and a high density uniform state. The compression proceeds via slow elastic motion that is interrupted with avalanche-like bursts of activity as the system collapses to progressively higher densities via plastic rearrangements. The plastic events vary in magnitude from small rearrangements of particles, including the formation of quadrupole-like defects, to large-scale vorticity and structural phase transitions. In the dense uniform phase, the system compresses through row reduction transitions mediated by a disorder-order process. We characterize the rearrangement events by measuring changes in the potential energy, the fraction of sixfold coordinated particles, the local density, and the velocity distribution. At high confinements, we find power law scaling of the velocity distribution during row reduction transitions. We observe hysteresis under a reversal of the compression when relatively few plastic rearrangements occur. The decompressing system exhibits distinct phase morphologies, and the phase transitions occur at lower compression forces as the system expands compared to when it is compressed.

  15. Structural transitions and hysteresis in clump- and stripe-forming systems under dynamic compression

    DOE PAGES

    McDermott, Danielle; Olson Reichhardt, Cynthia J.; Reichhardt, Charles

    2016-11-11

    In using numerical simulations, we study the dynamical evolution of particles interacting via competing long-range repulsion and short-range attraction in two dimensions. The particles are compressed using a time-dependent quasi-one dimensional trough potential that controls the local density, causing the system to undergo a series of structural phase transitions from a low density clump lattice to stripes, voids, and a high density uniform state. The compression proceeds via slow elastic motion that is interrupted with avalanche-like bursts of activity as the system collapses to progressively higher densities via plastic rearrangements. The plastic events vary in magnitude from small rearrangements ofmore » particles, including the formation of quadrupole-like defects, to large-scale vorticity and structural phase transitions. In the dense uniform phase, the system compresses through row reduction transitions mediated by a disorder-order process. We also characterize the rearrangement events by measuring changes in the potential energy, the fraction of sixfold coordinated particles, the local density, and the velocity distribution. At high confinements, we find power law scaling of the velocity distribution during row reduction transitions. We observe hysteresis under a reversal of the compression when relatively few plastic rearrangements occur. The decompressing system exhibits distinct phase morphologies, and the phase transitions occur at lower compression forces as the system expands compared to when it is compressed.« less

  16. Gemini spectroscopy of the outer disk star cluster BH176

    NASA Astrophysics Data System (ADS)

    Sharina, M. E.; Donzelli, C. J.; Davoust, E.; Shimansky, V. V.; Charbonnel, C.

    2014-10-01

    Context. BH176 is an old metal-rich star cluster. It is spatially and kinematically consistent with belonging to the Monoceros Ring. It is larger in size and more distant from the Galactic plane than typical open clusters, and it does not belong to the Galactic bulge. Aims: Our aim is to determine the origin of this unique object by accurately determining its distance, metallicity, and age. The best way to reach this goal is to combine spectroscopic and photometric methods. Methods: We present medium-resolution observations of red clump and red giant branch stars in BH176 obtained with the Gemini South Multi-Object Spectrograph. We derive radial velocities, metallicities, effective temperatures, and surface gravities of the observed stars and use these parameters to distinguish member stars from field objects. Results: We determine the following parameters for BH176: Vh = 0 ± 15 km s-1, [Fe/H] = -0.1 ± 0.1, age 7 ± 0.5 Gyr, E(V - I) = 0.79 ± 0.03, distance 15.2 ± 0.2 kpc, α-element abundance [α/Fe] ~ 0.25 dex (the mean of [Mg/Fe], and [Ca/Fe]). Conclusions: BH176 is a member of old Galactic open clusters that presumably belong to the thick disk. It may have originated as a massive star cluster after the encounter of the forming thin disk with a high-velocity gas cloud or as a satellite dwarf galaxy. Appendix A is available in electronic form at http://www.aanda.org

  17. Swimming motility plays a key role in the stochastic dynamics of cell clumping

    NASA Astrophysics Data System (ADS)

    Qi, Xianghong; Nellas, Ricky B.; Byrn, Matthew W.; Russell, Matthew H.; Bible, Amber N.; Alexandre, Gladys; Shen, Tongye

    2013-04-01

    Dynamic cell-to-cell interactions are a prerequisite to many biological processes, including development and biofilm formation. Flagellum induced motility has been shown to modulate the initial cell-cell or cell-surface interaction and to contribute to the emergence of macroscopic patterns. While the role of swimming motility in surface colonization has been analyzed in some detail, a quantitative physical analysis of transient interactions between motile cells is lacking. We examined the Brownian dynamics of swimming cells in a crowded environment using a model of motorized adhesive tandem particles. Focusing on the motility and geometry of an exemplary motile bacterium Azospirillum brasilense, which is capable of transient cell-cell association (clumping), we constructed a physical model with proper parameters for the computer simulation of the clumping dynamics. By modulating mechanical interaction (‘stickiness’) between cells and swimming speed, we investigated how equilibrium and active features affect the clumping dynamics. We found that the modulation of active motion is required for the initial aggregation of cells to occur at a realistic time scale. Slowing down the rotation of flagellar motors (and thus swimming speeds) is correlated to the degree of clumping, which is consistent with the experimental results obtained for A. brasilense.

  18. Intercomparison of clumping index estimates from POLDER, MODIS, and MISR satellite data over reference sites

    NASA Astrophysics Data System (ADS)

    Pisek, Jan; Govind, Ajit; Arndt, Stefan K.; Hocking, Darren; Wardlaw, Timothy J.; Fang, Hongliang; Matteucci, Giorgio; Longdoz, Bernard

    2015-03-01

    Clumping index is the measure of foliage grouping relative to a random distribution of leaves in space. It is a key structural parameter of plant canopies that influences canopy radiation regimes and controls canopy photosynthesis and other land-atmosphere interactions. The Normalized Difference between Hotspot and Darkspot (NDHD) index has been previously used to retrieve global clumping index maps from POLarization and Directionality of the Earth's Reflectances (POLDER) data at ˜6 km resolution and the Bidirectional Reflectance Distribution Function (BRDF) product from Moderate Resolution Imaging Spectroradiometer (MODIS) at 500 m resolution. Most recently the algorithm was also applied with Multi-angle Imaging SpectroRadiometer (MISR) data at 275 m resolution over selected areas. In this study for the first time we characterized and compared the three products over a set of sites representing diverse biomes and different canopy structures. The products were also directly validated with both in-situ vertical profiles and available seasonal trajectories of clumping index over several sites. We demonstrated that the vertical distribution of foliage and especially the effect of understory need to be taken into account while validating foliage clumping products from remote sensing products with values measured in the field. Satellite measurements responded to the structural effects near the top of canopies, while ground measurements may be biased by the lower vegetation layers. Additionally, caution should be taken regarding the misclassification in land cover maps as their errors can propagate into the foliage clumping maps. Our results indicate that MODIS data and MISR data, with 275 m in particular, can provide good quality clumping index estimates at spatial scales pertinent for modeling local carbon and energy fluxes.

  19. Diverse Nuclear Star-forming Activities in the Heart of NGC 253 Resolved with 10-pc-scale ALMA Images

    NASA Astrophysics Data System (ADS)

    Ando, Ryo; Nakanishi, Kouichiro; Kohno, Kotaro; Izumi, Takuma; Martín, Sergio; Harada, Nanase; Takano, Shuro; Kuno, Nario; Nakai, Naomasa; Sugai, Hajime; Sorai, Kazuo; Tosaki, Tomoka; Matsubayashi, Kazuya; Nakajima, Taku; Nishimura, Yuri; Tamura, Yoichi

    2017-11-01

    We present an 8 pc × 5 pc resolution view of the central ˜200 pc region of the nearby starburst galaxy NGC 253, based on ALMA Band 7 (λ ≃ 0.85 {mm} or ν ˜ 350 GHz) observations covering 11 GHz. We resolve the nuclear starburst of NGC 253 into eight dusty star-forming clumps, 10 pc in scale, for the first time. These clumps, each of which contains (4-10) × {10}4 {M}⊙ of dust (assuming that the dust temperature is 25 K) and up to 6× {10}2 massive (O5V) stars, appear to be aligned in two parallel ridges, while they have been blended in previous studies. Despite the similarities in sizes and dust masses of these clumps, their line spectra vary drastically from clump to clump, although they are separated by only ˜10 pc. Specifically, one of the clumps, Clump 1, exhibits line-confusion-limited spectra with at least 36 emission lines from 19 molecules (including CH3OH, HNCO, H2CO, CH3CCH, H2CS, and H3O+) and a hydrogen recombination line (H26α), while far fewer kinds of molecular lines are detected in some other clumps where fragile species, such as complex organic molecules and HNCO, completely disappear from their spectra. We demonstrate the existence of hot molecular gas ({T}{rot}({{SO}}2)=90+/- 11 K) in the former clump, which suggests that the hot and chemically rich environments are localized within a 10-pc-scale star-forming clump.

  20. The Isotopologue Record of Repeat Vital Effect Offenders: Tracking (Dis)equilibrium Effects in Sea Urchins and Nannofossil Using Clumped Isotopes

    NASA Astrophysics Data System (ADS)

    John, C. M.; Davies, A.; Drury, A. J.

    2016-12-01

    Vital effects vary between species and affect various isotopic systems in unequal proportion. The magnitude of the response of different isotopic systems might thus be key in understanding biologically-mediated disequilibrium, especially in groups that show a tendency to be "repeat offenders" with regards to vital effects. Here we present carbon, oxygen, and clumped isotope data from echinoderm calcite and nannofossil ooze, both of which exhibit strong vital effects in bulk isotopes. Our study is the first to investigate the clumped isotope (dis)equilibrium of echinoids. Results from two echinoids, three marine gastropods and a bivalve mollusk from modern beach deposits of Bali, Indonesia, highlight a significant offset in clumped isotopes of a regular echinoid test from expected values, interpreted as evidence of a similar "vital effect" as observed in surface corals. This is in contrast to the test of an irregular "sand dollar" echinoid, with clumped isotope values within error of expected sea surface temperature. Furthermore, data on the inter-skeletal variability in the clumped isotopic composition of two regular echinoid species shows that the spines of the echinoids are in equilibrium with seawater with respect to clumped isotopes, but the test is not. For the nannofossil material, no clumped isotope vital effects are observed, consistent with previously published studies but at odds with strong vital effects in carbon and oxygen isotopes, often correlated with cell-size. In addition, we reveal that the <63 micron fraction of deep-sea ooze could constitute useful material for clumped isotope studies. An intriguing result of our study is that vital effects are mostly absent in clumped isotopes, even in phylums known for important isotopic effects. It remains to be explained why some parts of the echinoids show clear vital effects, notably enrichment in clumped isotopes of urchin tests. Mechanisms that could explain this include pH effects during calcification

  1. Recessive NRL mutations in patients with clumped pigmentary retinal degeneration and relative preservation of blue cone function.

    PubMed

    Nishiguchi, Koji M; Friedman, James S; Sandberg, Michael A; Swaroop, Anand; Berson, Eliot L; Dryja, Thaddeus P

    2004-12-21

    Mice lacking the transcription factor Nrl have no rod photoreceptors and an increased number of short-wavelength-sensitive cones. Missense mutations in NRL are associated with autosomal dominant retinitis pigmentosa; however, the phenotype associated with the loss of NRL function in humans has not been reported. We identified two siblings who carried two allelic mutations: a predicted null allele (L75fs) and a missense mutation (L160P) altering a highly conserved residue in the domain involved in DNA-binding-site recognition. In vitro luciferase reporter assays demonstrated that the NRL-L160P mutant had severely reduced transcriptional activity compared with the WT NRL protein, consistent with a severe loss of function. The affected patients had night blindness since early childhood, consistent with a severe reduction in rod function. Color vision was normal, suggesting the presence of all cone color types; nevertheless, a comparison of central visual fields evaluated with white-on-white and blue-on-yellow light stimuli was consistent with a relatively enhanced function of short-wavelength-sensitive cones in the macula. The fundi had signs of retinal degeneration (such as vascular attenuation) and clusters of large, clumped, pigment deposits in the peripheral fundus at the level of the retinal pigment epithelium (clumped pigmentary retinal degeneration). Our report presents an unusual clinical phenotype in humans with loss-of-function mutations in NRL.

  2. The Evolution of the Globular Cluster System in a Triaxial Galaxy: Can a Galactic Nucleus Form by Globular Cluster Capture?

    NASA Astrophysics Data System (ADS)

    Capuzzo-Dolcetta, Roberto

    1993-10-01

    Among the possible phenomena inducing evolution of the globular cluster system in an elliptical galaxy, dynamical friction due to field stars and tidal disruption caused by a central nucleus is of crucial importance. The aim of this paper is the study of the evolution of the globular cluster system in a triaxial galaxy in the presence of these phenomena. In particular, the possibility is examined that some galactic nuclei have been formed by frictionally decayed globular clusters moving in a triaxial potential. We find that the initial rapid growth of the nucleus, due mainly to massive clusters on box orbits falling in a short time scale into the galactic center, is later slowed by tidal disruption induced by the nucleus itself on less massive clusters in the way described by Ostriker, Binney, and Saha. The efficiency of dynamical friction is such to carry to the center of the galaxy enough globular cluster mass available to form a compact nucleus, but the actual modes and results of cluster-cluster encounters in the central potential well are complicated phenomena which remains to be investigated. The mass of the resulting nucleus is determined by the mutual feedback of the described processes, together with the initial spatial, velocity, and mass distributions of the globular cluster family. The effect on the system mass function is studied, showing the development of a low- and high-mass turnover even with an initially flat mass function. Moreover, in this paper is discussed the possibility that the globular cluster fall to the galactic center has been a cause of primordial violent galactic activity. An application of the model to M31 is presented.

  3. ATLASGAL-selected massive clumps in the inner Galaxy. VI. Kinetic temperature and spatial density measured with formaldehyde

    NASA Astrophysics Data System (ADS)

    Tang, X. D.; Henkel, C.; Wyrowski, F.; Giannetti, A.; Menten, K. M.; Csengeri, T.; Leurini, S.; Urquhart, J. S.; König, C.; Güsten, R.; Lin, Y. X.; Zheng, X. W.; Esimbek, J.; Zhou, J. J.

    2018-03-01

    Context. Formaldehyde (H2CO) is a reliable tracer to accurately measure the physical parameters of dense gas in star-forming regions. Aim. We aim to determine directly the kinetic temperature and spatial density with formaldehyde for the 100 brightest ATLASGAL-selected clumps (the TOP100 sample) at 870 μm representing various evolutionary stages of high-mass star formation. Methods: Ten transitions (J = 3-2 and 4-3) of ortho- and para-H2CO near 211, 218, 225, and 291 GHz were observed with the Atacama Pathfinder EXperiment (APEX) 12 m telescope. Results: Using non-LTE models with RADEX, we derived the gas kinetic temperature and spatial density with the measured para-H2CO 321-220/303-202, 422-321/404-303, and 404-303/303-202 ratios. The gas kinetic temperatures derived from the para-H2CO 321-220/303-202 and 422-321/404-303 line ratios are high, ranging from 43 to >300 K with an unweighted average of 91 ± 4 K. Deduced Tkin values from the J = 3-2 and 4-3 transitions are similar. Spatial densities of the gas derived from the para-H2CO 404-303/303-202 line ratios yield 0.6-8.3 × 106 cm-3 with an unweighted average of 1.5 (±0.1) × 106 cm-3. A comparison of kinetic temperatures derived from para-H2CO, NH3, and dust emission indicates that para-H2CO traces a distinctly higher temperature than the NH3 (2, 2)/(1, 1) transitions and the dust, tracing heated gas more directly associated with the star formation process. The H2CO line widths are found to be correlated with bolometric luminosity and increase with the evolutionary stage of the clumps, which suggests that higher luminosities tend to be associated with a more turbulent molecular medium. It seems that the spatial densities measured with H2CO do not vary significantly with the evolutionary stage of the clumps. However, averaged gas kinetic temperatures derived from H2CO increase with time through the evolution of the clumps. The high temperature of the gas traced by H2CO may be mainly caused by radiation from

  4. Massive star-forming regions across the galaxy

    NASA Astrophysics Data System (ADS)

    Rygl, Kazi Lucie Jessica

    2010-04-01

    Star-forming regions trace the spiral structure of the Galaxy. They are regions of increased column density and therefore traced well by the extinction in the mid-infrared based on the Spitzer/GLIMPSE 3.6-4.5 micron color excess maps. A sample of 25 high extinction clouds (HECs) was studied in the 1.2 mm dust continuum emission, and followed up by observations of ammonia plus several other molecules using the Effelsberg 100m, IRAM 30m and APEX telescopes. With these data we want to investigate the most early stages of massive star formation, which are currently still largely unknown. Three cloud classes were defined from their morphology in the 1.2 mm continuum maps: the early diffuse HECs, with a low contrast between the clump and cloud emission; the peaked HECs, with an increased contrast; the late multiply peaked HECs, with more than one clump and a high contrast between the clump and the cloud emission. The clouds are cold (T 16 K) and massive (M 800 M_sun) and contain dense clumps (n 10^5 cm^{-3}) of 0.3 pc in size. These clumps were investigated for evidence of gravitational collapse or expansion, for high velocity outflows, and for the presence of young stellar objects. Based on these results we interpret the three cloud classes as an evolutionary sequence of star-forming clouds. Accurate distances are a crucial parameter for establishing the mass, size, and luminosity of an object. Also, for understanding the spiral structure of the Galaxy trustworthy distances are necessary. The most accurate method to measure these is the trigonometric parallax. Using the European Very Large Baseline Interferometry Network of radio antennas we measured, for the first time, parallaxes of 6.7 GHz methanol masers. This transition belongs to the strongest maser species in the Galaxy, it is stable and observed toward numerous massive star-forming regions. We measured distances and proper motions toward L 1287, L 1206, NGC 281-W, ON 1 and S 255, and obtained their 3-dimensional

  5. Characterization, validation and intercomparison of clumping index maps from POLDER, MODIS, and MISR satellite data over reference sites

    NASA Astrophysics Data System (ADS)

    Pisek, Jan; He, Liming; Chen, Jing; Govind, Ajit; Sprintsin, Michael; Ryu, Youngryel; Arndt, Stefan; Hocking, Darren; Wardlaw, Timothy; Kuusk, Joel; Oliphant, Andrew; Korhonen, Lauri; Fang, Hongliang; Matteucci, Giorgio; Longdoz, Bernard; Raabe, Kairi

    2015-04-01

    Vegetation foliage clumping significantly alters its radiation environment and therefore affects vegetation growth as well as water and carbon cycles. The clumping index is useful in ecological and meteorological models because it provides new structural information in addition to the effective leaf area index (LAI) retrieved from mono-angle remote sensing and allows accurate separation of sunlit and shaded leaves in the canopy. Not accounting for the foliage clumping in LAI retrieval algorithms leads to substantial underestimation of actual LAI, especially for needleleaf forests. Normalized Difference between Hotspot and Darkspot (NDHD) index has been previously used to retrieve global clumping index maps from POLarization and Directionality of the Earth's Reflectances (POLDER) data at ~6 km resolution, from Moderate Resolution Imaging Spectroradiometer (MODIS) Bidirectional Reflectance Distribution Function (BRDF) product at 500 m resolution. Most recently the algorithm was applied with Multi-angle Imaging SpectroRadiometer (MISR) data at 275 m resolution over selected areas. In this presentation we characterize and intercompare the three products over a set of sites representing diverse biomes and different canopy structures. The products are also directly validated with both in-situ vertical profiles and seasonal trajectories of clumping index. We illustrate that the vertical distribution of foliage and especially the effect of understory needs to be taken into account while validating foliage clumping products from remote sensing products with values measured in the field. Satellite measurements respond to the structural effects near the top of canopies, while ground measurements may be biased by the lower vegetation layers. Additionally, caution should be taken regarding the misclassification in land cover maps as their errors can be propagated into the foliage clumping maps. Our results indicate that MODIS data and MISR data with 275 m in particular can

  6. Characterization, Validation and Intercomparison of Clumping Index Maps from POLDER, MODIS, and MISR Satellite Data Over Reference Sites

    NASA Astrophysics Data System (ADS)

    Pisek, J.; He, L.; Chen, J. M.; Govind, A.; Sprintsin, M.; Ryu, Y.; Arndt, S. K.; Hocking, D.; Wardlaw, T.; Kuusk, J.; Oliphant, A. J.; Korhonen, L.; Fang, H.; Matteucci, G.; Longdoz, B.; Raabe, K.

    2015-12-01

    Vegetation foliage clumping significantly alters its radiation environment and therefore affects vegetation growth as well as water and carbon cycles. The clumping index is useful in ecological and meteorological models because it provides new structural information in addition to the effective leaf area index (LAI) retrieved from mono-angle remote sensing and allows accurate separation of sunlit and shaded leaves in the canopy. Not accounting for the foliage clumping in LAI retrieval algorithms leads to substantial underestimation of actual LAI, especially for needleleaf forests. Normalized Difference between Hotspot and Darkspot (NDHD) index has been previously used to retrieve global clumping index maps from POLarization and Directionality of the Earth's Reflectances (POLDER) data at ~6 km resolution, from Moderate Resolution Imaging Spectroradiometer (MODIS) Bidirectional Reflectance Distribution Function (BRDF) product at 500 m resolution. Most recently the algorithm was applied with Multi-angle Imaging SpectroRadiometer (MISR) data at 275 m resolution over selected areas. In this presentation we characterize and intercompare the three products over a set of sites representing diverse biomes and different canopy structures. The products are also directly validated with both in-situ vertical profiles and seasonal trajectories of clumping index. We illustrate that the vertical distribution of foliage and especially the effect of understory needs to be taken into account while validating foliage clumping products from remote sensing products with values measured in the field. Satellite measurements respond to the structural effects near the top of canopies, while ground measurements may be biased by the lower vegetation layers. Additionally, caution should be taken regarding the misclassification in land cover maps as their errors can be propagated into the foliage clumping maps. Our results indicate that MODIS data and MISR data with 275 m resolution in

  7. Properties of Merger Shocks in Merging Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Ha, Ji-Hoon; Ryu, Dongsu; Kang, Hyesung

    2018-04-01

    X-ray shocks and radio relics detected in the cluster outskirts are commonly interpreted as shocks induced by mergers of subclumps. We study the properties of merger shocks in merging galaxy clusters, using a set of cosmological simulations for the large-scale structure formation of the universe. As a representative case, we focus on the simulated clusters that undergo almost head-on collisions with mass ratio ∼2. Due to the turbulent nature of the intracluster medium, shock surfaces are not smooth, but composed of shocks with different Mach numbers. As the merger shocks expand outward from the core to the outskirts, the average Mach number, < {M}s> , increases in time. We suggest that the shocks propagating along the merger axis could be manifested as X-ray shocks and/or radio relics. The kinetic energy through the shocks, F ϕ , peaks at ∼1 Gyr after their initial launching, or at ∼1–2 Mpc from the core. Because of the Mach number dependent model adopted here for the cosmic-ray (CR) acceleration efficiency, their CR-energy-weighted Mach number is higher with < {M}s{> }CR}∼ 3{--}4, compared to the kinetic-energy-weighted Mach number, < {M}s{> }φ ∼ 2{--}3. Most energetic shocks are to be found ahead of the lighter dark matter (DM) clump, while the heavier DM clump is located on the opposite side of clusters. Although our study is limited to the merger case considered, the results such as the means and variations of shock properties and their time evolution could be compared with the observed characteristics of merger shocks, constraining interpretations of relevant observations.

  8. On the formation and evolution of clumps of galaxies in an expanding universe

    NASA Technical Reports Server (NTRS)

    Norman, C. A.; Silk, J.

    1978-01-01

    Results are derived for the development of phase-space clumps of mass points in a background spectrum of gravitational-potential fluctuations. The Vlasov equation and the pair correlation equation (in the weak coupling limit) are solved exactly in an Einstein-de Sitter cosmology, and the plasma-clumping theory is used to identify terms that yield important collective effects. Various astrophysical implications are discussed, including the formation of large-scale inhomogeneity and the enhanced generation of correlations in the distribution of galaxies.

  9. MOLECULAR OUTFLOWS FROM THE PROTOCLUSTER SERPENS SOUTH

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nakamura, Fumitaka; Higuchi, Aya; Sugitani, Kohji

    2011-08-20

    We present the results of CO (J = 3-2) and HCO{sup +} (J = 4-3) mapping observations toward a nearby embedded cluster, Serpens South, using the ASTE 10 m telescope. Our CO (J = 3-2) map reveals that many outflows are crowded in the dense cluster-forming clump that can be recognized as an HCO{sup +} clump with a size of {approx}0.2 pc and mass of {approx}80 M{sub sun}. The clump contains several subfragments with sizes of {approx}0.05 pc. By comparing the CO (J = 3-2) map with the 1.1 mm dust continuum image taken by AzTEC on ASTE, we findmore » that the spatial extents of the outflow lobes are sometimes anti-correlated with the distribution of the dense gas, and some of the outflow lobes apparently collide with the dense gas. The total outflow mass, momentum, and energy are estimated to be 0.6 M{sub sun}, 8 M{sub sun} km s{sup -1}, and 64 M{sub sun} km{sup 2} s{sup -2}, respectively. The energy injection rate due to the outflows is comparable to the turbulence dissipation rate in the clump, implying that the protostellar outflows can maintain the supersonic turbulence in this region. The total outflow energy seems only about 10% of the clump gravitational energy. We conclude that the current outflow activity is not enough to destroy the whole cluster-forming clump, and therefore star formation is likely to continue for several or many local dynamical times.« less

  10. Clumped isotope effects during OH and Cl oxidation of methane

    NASA Astrophysics Data System (ADS)

    Whitehill, Andrew R.; Joelsson, Lars Magnus T.; Schmidt, Johan A.; Wang, David T.; Johnson, Matthew S.; Ono, Shuhei

    2017-01-01

    A series of experiments were carried out to determine the clumped (13CH3D) methane kinetic isotope effects during oxidation of methane by OH and Cl radicals, the major sink reactions for atmospheric methane. Experiments were performed in a 100 L quartz photochemical reactor, in which OH was produced from the reaction of O(1D) (from O3 photolysis) with H2O, and Cl was from photolysis of Cl2. Samples were taken from the reaction cell and analyzed for methane (12CH4, 12CH3D, 13CH4, 13CH3D) isotopologue ratios using tunable infrared laser direct absorption spectroscopy. Measured kinetic isotope effects for singly substituted species were consistent with previous experimental studies. For doubly substituted methane, 13CH3D, the observed kinetic isotope effects closely follow the product of the kinetic isotope effects for the 13C and deuterium substituted species (i.e., 13,2KIE = 13KIE × 2KIE). The deviation from this relationship is 0.3‰ ± 1.2‰ and 3.5‰ ± 0.7‰ for OH and Cl oxidation, respectively. This is consistent with model calculations performed using quantum chemistry and transition state theory. The OH and Cl reactions enrich the residual methane in the clumped isotopologue in open system reactions. In a closed system, however, this effect is overtaken by the large D/H isotope effect, which causes the residual methane to become anti-clumped relative to the initial methane. Based on these results, we demonstrate that oxidation of methane by OH, the predominant oxidant for tropospheric methane, will only have a minor (∼0.3‰) impact on the clumped isotope signature (Δ13CH3D, measured as a deviation from a stochastic distribution of isotopes) of tropospheric methane. This paper shows that Δ13CH3D will provide constraints on methane source strengths, and predicts that Δ12CH2D2 can provide information on methane sink strengths.

  11. Clumped isotope thermometry in deeply buried sedimentary carbonates: The effects of C-O bond reordering and recrystallization

    NASA Astrophysics Data System (ADS)

    Passey, B. H.; Shenton, B.; Grossman, E. L.; Henkes, G. A.; Laya, J. C.; Perez-Huerta, A.

    2014-12-01

    Constraining the thermal histories of sedimentary basins is fundamental to a range of geologic applications including tectonics, petroleum system analysis, and the genesis of ore deposits. Carbonate rocks can serve as archives of basin thermal histories through solid-state reordering of their 13C-18O, or 'clumped isotope', bonds at elevated burial temperatures. Here we present one of the first applied studies of carbonate clumped isotope reordering to explore the diagenetic and thermal histories of exhumed brachiopods, crinoids, cements, and host rock in the Permian Palmarito Formation, Venezuela and the Carboniferous Bird Spring Formation, Nevada, USA. Carbonate components in the Palmarito Formation, buried to ~4 km depth, yield statistically indistinguishable clumped isotope temperatures (T(Δ47)) ranging from 86 to 122 °C. Clumped isotope temperatures of components in the more deeply buried Bird Spring Formation (>5 km), range from ~100 to 165 °C and differ by component type, with brachiopods and pore-filling cements yielding the highest T(Δ47) (mean = 153 and 141 °C, respectively) and crinoids and host rock yielding significantly cooler T(Δ47) (mean = 103 and 114 °C). New high-resolution thermal histories are coupled with kinetic models to predict the extent of solid-state C-O bond reordering during burial and exhumation for both sites. Application of these models suggests that brachiopods in the Palmarito Formation experienced partial bond reordering without complete equilibration of clumped isotopes at maximum burial temperature. In contrast, clumped isotope bonds of brachiopods from the Bird Spring Formation appear to have completely equilibrated at maximum burial temperature, and now reflect blocking temperatures 'locked-in' during cooling. The 40-50 °C cooler clumped isotope temperatures measured in Bird Spring Formation crinoids and host rock can be explained by both recrystallization and cementation during shallow burial and a greater inherent

  12. The Mysterious Sickle Object in the Carina Nebula: A Stellar Wind Induced Bow Shock Grazing a Clump?

    NASA Astrophysics Data System (ADS)

    Ngoumou, Judith; Preibisch, Thomas; Ratzka, Thorsten; Burkert, Andreas

    2013-06-01

    Optical and near-infrared images of the Carina Nebula show a peculiar arc-shaped feature, which we call the "Sickle," next to the B-type star Trumpler 14 MJ 218. We use multi-wavelength observations to explore and constrain the nature and origin of the nebulosity. Using submillimeter data from APEX/LABOCA as well as Herschel far-infrared maps, we discovered a dense, compact clump with a mass of ~40 M ⊙ located close to the apex of the Sickle. We investigate how the B star MJ 218, the Sickle, and the clump are related. Our numerical simulations show that, in principle, a B-type star located near the edge of a clump can produce a crescent-shaped wind shock front, similar to the observed morphology. However, the observed proper motion of MJ 218 suggests that the star moves with high velocity (~100 km s-1) through the ambient interstellar gas. We argue that the star is just about to graze along the surface of the clump, and the Sickle is a bow shock induced by the stellar wind, as the object moves supersonically through the density gradient in the envelope of the clump.

  13. Statistical properties of the polarized emission of Planck Galactic cold clumps

    NASA Astrophysics Data System (ADS)

    Ristorcelli, Isabelle; Planck Collaboration

    2015-08-01

    The Galactic magnetic fields are considered as one of the key components regulating star formation, but their actual role on the dense cores formation and evolution remains today an open question.Dust polarized continuum emission is particularly well suited to probe the dense and cold medium and study the magnetic field structure. Such observations also provide tight constraints to better understand the efficiency of the dust alignment along the magnetic field lines, which in turn relate on our grasp to properly interpret the B-field properties.With the Planck all-sky survey of dust submillimeter emission in intensity and polarization, we can investigate the intermediate scales, between that of molecular cloud and of prestellar cores, and perform a statistical analysis on the polarization properties of cold clumps.Combined with the IRAS map at 100microns, the Planck survey has allowed to build the first all-sky catalogue of Galactic Cold Clumps (PGCC, Planck 2015 results XXVIII 2015). The corresponding 13188 sources cover a broad range in physical properties, and correspond to different evolutionary stages, from cold and starless clumps, nearby cores, to young protostellar objects still embedded in their cold surrounding cloud.I will present the main results of our polarization analysis obtained on different samples of sources from the PGCC catalogue, based on the 353GHz polarized emission measured with Planck. The statistical properties are derived from a stacking method, using optimized estimators for the polarization fraction and angle parameters. These properties are determined and compared according to the nature of the sources (starless or YSOs), their size or density range. Finally, I will present a comparison of our results with predictions from MHD simulations of clumps including radiative transfer and the dust radiative torque alignment mechanism.

  14. Multivalent Cation-Bridged PI(4,5)P2 Clusters Form at Very Low Concentrations.

    PubMed

    Wen, Yi; Vogt, Volker M; Feigenson, Gerald W

    2018-06-05

    Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 or PIP2), is a key component of the inner leaflet of the plasma membrane in eukaryotic cells. In model membranes, PIP2 has been reported to form clusters, but whether these locally different conditions could give rise to distinct pools of unclustered and clustered PIP2 is unclear. By use of both fluorescence self-quenching and Förster resonance energy transfer assays, we have discovered that PIP2 self-associates at remarkably low concentrations starting below 0.05 mol% of total lipids. Formation of these clusters was dependent on physiological divalent metal ions, such as Ca 2+ , Mg 2+ , Zn 2+ , or trivalent ions Fe 3+ and Al 3+ . Formation of PIP2 clusters was also headgroup-specific, being largely independent of the type of acyl chain. The similarly labeled phospholipids phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol exhibited no such clustering. However, six phosphoinositide species coclustered with PIP2. The degree of PIP2 cation clustering was significantly influenced by the composition of the surrounding lipids, with cholesterol and phosphatidylinositol enhancing this behavior. We propose that PIP2 cation-bridged cluster formation, which might be similar to micelle formation, can be used as a physical model for what could be distinct pools of PIP2 in biological membranes. To our knowledge, this study provides the first evidence of PIP2 forming clusters at such low concentrations. The property of PIP2 to form such clusters at such extremely low concentrations in model membranes reveals, to our knowledge, a new behavior of PIP2 proposed to occur in cells, in which local multivalent metal ions, lipid compositions, and various binding proteins could greatly influence PIP2 properties. In turn, these different pools of PIP2 could further regulate cellular events. Copyright © 2018 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  15. ALMA Detects CO(3-2) within a Super Star Cluster in NGC 5253

    NASA Astrophysics Data System (ADS)

    Turner, Jean L.; Consiglio, S. Michelle; Beck, Sara C.; Goss, W. M.; Ho, Paul. T. P.; Meier, David S.; Silich, Sergiy; Zhao, Jun-Hui

    2017-09-01

    We present observations of CO(3-2) and 13CO(3-2) emission near the supernebula in the dwarf galaxy NGC 5253, which contains one of the best examples of a potential globular cluster in formation. The 0.″3 resolution images reveal an unusual molecular cloud, “Cloud D1,” that is coincident with the radio-infrared supernebula. The ˜6 pc diameter cloud has a linewidth, Δ v = 21.7 {km} {{{s}}}-1, that reflects only the gravitational potential of the star cluster residing within it. The corresponding virial mass is 2.5 × 105 {M}⊙ . The cluster appears to have a top-heavy initial mass function, with M * ≳ 1-2 {M}⊙ . Cloud D1 is optically thin in CO(3-2), probably because the gas is hot. Molecular gas mass is very uncertain but constitutes <35% of the dynamical mass within the cloud boundaries. In spite of the presence of an estimated ˜1500-2000 O stars within the small cloud, the CO appears relatively undisturbed. We propose that Cloud D1 consists of molecular clumps or cores, possibly star-forming, orbiting with more evolved stars in the core of the giant cluster.

  16. The SUNBIRD survey: characterizing the super star cluster populations of intensely star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Randriamanakoto, Zara; Väisänen, Petri

    2017-03-01

    Super star clusters (SSCs) represent the youngest and most massive form of known gravitationally bound star clusters in the Universe. They are born abundantly in environments that trigger strong and violent star formation. We investigate the properties of these massive SSCs in a sample of 42 nearby starbursts and luminous infrared galaxies. The targets form the sample of the SUperNovae and starBursts in the InfraReD (SUNBIRD) survey that were imaged using near-infrared (NIR) K-band adaptive optics mounted on the Gemini/NIRI and the VLT/NaCo instruments. Results from i) the fitted power-laws to the SSC K-band luminosity functions, ii) the NIR brightest star cluster magnitude - star formation rate (SFR) relation and iii) the star cluster age and mass distributions have shown the importance of studying SSC host galaxies with high SFR levels to determine the role of the galactic environments in the star cluster formation, evolution and disruption mechanisms.

  17. Beyond temperature: Clumped isotope signatures in dissolved inorganic carbon species and the influence of solution chemistry on carbonate mineral composition

    NASA Astrophysics Data System (ADS)

    Tripati, Aradhna K.; Hill, Pamela S.; Eagle, Robert A.; Mosenfelder, Jed L.; Tang, Jianwu; Schauble, Edwin A.; Eiler, John M.; Zeebe, Richard E.; Uchikawa, Joji; Coplen, Tyler B.; Ries, Justin B.; Henry, Drew

    2015-10-01

    ;Clumped-isotope; thermometry is an emerging tool to probe the temperature history of surface and subsurface environments based on measurements of the proportion of 13C and 18O isotopes bound to each other within carbonate minerals in 13C18O16O22- groups (heavy isotope ;clumps;). Although most clumped isotope geothermometry implicitly presumes carbonate crystals have attained lattice equilibrium (i.e., thermodynamic equilibrium for a mineral, which is independent of solution chemistry), several factors other than temperature, including dissolved inorganic carbon (DIC) speciation may influence mineral isotopic signatures. Therefore we used a combination of approaches to understand the potential influence of different variables on the clumped isotope (and oxygen isotope) composition of minerals. We conducted witherite precipitation experiments at a single temperature and at varied pH to empirically determine 13C-18O bond ordering (Δ47) and δ18O of CO32- and HCO3- molecules at a 25 °C equilibrium. Ab initio cluster models based on density functional theory were used to predict equilibrium 13C-18O bond abundances and δ18O of different DIC species and minerals as a function of temperature. Experiments and theory indicate Δ47 and δ18O compositions of CO32- and HCO3- ions are significantly different from each other. Experiments constrain the Δ47-δ18O slope for a pH effect (0.011 ± 0.001; 12 ⩾ pH ⩾ 7). Rapidly-growing temperate corals exhibit disequilibrium mineral isotopic signatures with a Δ47-δ18O slope of 0.011 ± 0.003, consistent with a pH effect. Our theoretical calculations for carbonate minerals indicate equilibrium lattice calcite values for Δ47 and δ18O are intermediate between HCO3- and CO32-. We analyzed synthetic calcites grown at temperatures ranging from 0.5 to 50 °C with and without the enzyme carbonic anhydrase present. This enzyme catalyzes oxygen isotopic exchange between DIC species and is present in many natural systems. The two

  18. THE MYSTERIOUS SICKLE OBJECT IN THE CARINA NEBULA: A STELLAR WIND INDUCED BOW SHOCK GRAZING A CLUMP?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ngoumou, Judith; Preibisch, Thomas; Ratzka, Thorsten

    2013-06-01

    Optical and near-infrared images of the Carina Nebula show a peculiar arc-shaped feature, which we call the ''Sickle'', next to the B-type star Trumpler 14 MJ 218. We use multi-wavelength observations to explore and constrain the nature and origin of the nebulosity. Using submillimeter data from APEX/LABOCA as well as Herschel far-infrared maps, we discovered a dense, compact clump with a mass of {approx}40 M{sub Sun} located close to the apex of the Sickle. We investigate how the B star MJ 218, the Sickle, and the clump are related. Our numerical simulations show that, in principle, a B-type star locatedmore » near the edge of a clump can produce a crescent-shaped wind shock front, similar to the observed morphology. However, the observed proper motion of MJ 218 suggests that the star moves with high velocity ({approx}100 km s{sup -1}) through the ambient interstellar gas. We argue that the star is just about to graze along the surface of the clump, and the Sickle is a bow shock induced by the stellar wind, as the object moves supersonically through the density gradient in the envelope of the clump.« less

  19. Synthesis and characterization of beta-Ga2O3 nanorod array clumps by chemical vapor deposition.

    PubMed

    Shi, Feng; Wei, Xiaofeng

    2012-11-01

    beta-Ga2O3 nanorod array clumps were successfully synthesized on Si (111) substrates by chemical vapor deposition. The composition, microstructure, morphology, and light-emitting property of these clumps were characterized by X-ray diffraction, Fourier transform infrared spectrophotometry, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and photoluminescence. The results demonstrate that the sample synthesized at 1050 degrees C for 15 min was composed of monoclinic beta-Ga2O3 nanorod array clumps, where each single nanorod was about 300 nm in diameter with some nano-droplets on its tip. These results reveal that the growth mechanism agrees with the vapor-liquid-solid (VLS) process. The photoluminescence spectrum shows that the Ga2O3 nanorods have a blue emission at 438 nm, which may be attributed to defects, such as oxygen vacancies and gallium-oxygen vacancy pairs. Defect-energy aggregation confinement growth theory was proposed to explain the growth mechanism of Ga2O3 nanorod array clumps collaborated with the VLS mechanism.

  20. Empirical photometric calibration of the Gaia red clump: Colours, effective temperature, and absolute magnitude

    NASA Astrophysics Data System (ADS)

    Ruiz-Dern, L.; Babusiaux, C.; Arenou, F.; Turon, C.; Lallement, R.

    2018-01-01

    Context. Gaia Data Release 1 allows the recalibration of standard candles such as the red clump stars. To use those stars, they first need to be accurately characterised. In particular, colours are needed to derive interstellar extinction. As no filter is available for the first Gaia data release and to avoid the atmosphere model mismatch, an empirical calibration is unavoidable. Aims: The purpose of this work is to provide the first complete and robust photometric empirical calibration of the Gaia red clump stars of the solar neighbourhood through colour-colour, effective temperature-colour, and absolute magnitude-colour relations from the Gaia, Johnson, 2MASS, HIPPARCOS, Tycho-2, APASS-SLOAN, and WISE photometric systems, and the APOGEE DR13 spectroscopic temperatures. Methods: We used a 3D extinction map to select low reddening red giants. To calibrate the colour-colour and the effective temperature-colour relations, we developed a MCMC method that accounts for all variable uncertainties and selects the best model for each photometric relation. We estimated the red clump absolute magnitude through the mode of a kernel-based distribution function. Results: We provide 20 colour versus G-Ks relations and the first Teff versus G-Ks calibration. We obtained the red clump absolute magnitudes for 15 photometric bands with, in particular, MKs = (-1.606 ± 0.009) and MG = (0.495 ± 0.009) + (1.121 ± 0.128)(G-Ks-2.1). We present a dereddened Gaia-TGAS HR diagram and use the calibrations to compare its red clump and its red giant branch bump with Padova isochrones. Full Table A.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A116

  1. Formation of the First Star Clusters and Massive Star Binaries by Fragmentation of Filamentary Primordial Gas Clouds

    NASA Astrophysics Data System (ADS)

    Hirano, Shingo; Yoshida, Naoki; Sakurai, Yuya; Fujii, Michiko S.

    2018-03-01

    We perform a set of cosmological simulations of early structure formation incorporating baryonic streaming motions. We present a case where a significantly elongated gas cloud with ∼104 solar mass (M ⊙) is formed in a pre-galactic (∼107 M ⊙) dark halo. The gas streaming into the halo compresses and heats the massive filamentary cloud to a temperature of ∼10,000 Kelvin. The gas cloud cools rapidly by atomic hydrogen cooling, and then by molecular hydrogen cooling down to ∼400 Kelvin. The rapid decrease of the temperature and hence of the Jeans mass triggers fragmentation of the filament to yield multiple gas clumps with a few hundred solar masses. We estimate the mass of the primordial star formed in each fragment by adopting an analytic model based on a large set of radiation hydrodynamics simulations of protostellar evolution. The resulting stellar masses are in the range of ∼50–120 M ⊙. The massive stars gravitationally attract each other and form a compact star cluster. We follow the dynamics of the star cluster using a hybrid N-body simulation. We show that massive star binaries are formed in a few million years through multi-body interactions at the cluster center. The eventual formation of the remnant black holes will leave a massive black hole binary, which can be a progenitor of strong gravitational wave sources similar to those recently detected by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO).

  2. Measuring Gap Fraction, Element Clumping Index and LAI in Sierra Forest Stands Using a Full-Waveform Ground-Based Lidar

    NASA Technical Reports Server (NTRS)

    Zhao, Feng; Strahler, Alan H.; Crystal L. Schaaf; Yao, Tian; Yang, Xiaoyuan; Wang, Zhuosen; Schull, Mitchell A.; Roman, Miguel O.; Woodcock, Curtis E.; Olofsson, Pontus; hide

    2012-01-01

    The Echidna Validation Instrument (EVI), a ground-based, near-infrared (1064 nm) scanning lidar, provides gap fraction measurements, element clumping index measurements, effective leaf area index (LAIe) and leaf area index (LAI) measurements that are statistically similar to those from hemispherical photos. In this research, a new method integrating the range dimension is presented for retrieving element clumping index using a unique series of images of gap probability (Pgap) with range from EVI. From these images, we identified connected gap components and found the approximate physical, rather than angular, size of connected gap component. We conducted trials at 30 plots within six conifer stands of varying height and stocking densities in the Sierra National Forest, CA, in August 2008. The element clumping index measurements retrieved from EVI Pgap image series for the hinge angle region are highly consistent (R2=0.866) with those of hemispherical photos. Furthermore, the information contained in connected gap component size profiles does account for the difference between our method and gap-size distribution theory based method, suggesting a new perspective to measure element clumping index with EVI Pgap image series and also a potential advantage of three dimensional Lidar data for element clumping index retrieval. Therefore further exploration is required for better characterization of clumped condition from EVI Pgap image series.

  3. A statistical study towards high-mass BGPS clumps with the MALT90 survey

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Lan; Xu, Jin-Long; Ning, Chang-Chun; Zhang, Chuan-Peng; Liu, Xiao-Tao

    2018-01-01

    In this work, we perform a statistical investigation towards 50 high-mass clumps using data from the Bolocam Galactic Plane Survey (BGPS) and Millimetre Astronomy Legacy Team 90-GHz survey (MALT90). Eleven dense molecular lines (N2H+(1–0), HNC(1–0), HCO+(1–0), HCN(1–0), HN13C(1–0), H13CO+(1–0), C2H(1–0), HC3N(10–9), SiO(2–1), 13CS(2–1)and HNCO(44,0 ‑ 30,3)) are detected. N2H+ and HNC are shown to be good tracers for clumps in various evolutionary stages since they are detected in all the fields. The detection rates of N-bearing molecules decrease as the clumps evolve, but those of O-bearing species increase with evolution. Furthermore, the abundance ratios [N2H+]/[HCO+] and log([HC3N]/[HCO+]) decline with log([HCO+]) as two linear functions, respectively. This suggests that N2H+ and HC3N transform to HCO+ as the clumps evolve. We also find that C2H is the most abundant molecule with an order of magnitude 10‑8. In addition, three new infall candidates, G010.214–00.324, G011.121–00.128 and G012.215–00.118(a), are discovered to have large-scale infall motions and infall rates with an order of magnitude 10‑3 M ⊙ yr‑1.

  4. VizieR Online Data Catalog: High-mass starless clump candidates from ATLASGAL (Yuan+, 2017)

    NASA Astrophysics Data System (ADS)

    Yuan, J.; Wu, Y.; Ellingsen, S. P.; Evans, N. J., II; Henkel, C.; Wang, K.; Liu, H.-L.; Liu, T.; Li, J.-Z.; Zavagno, A.

    2017-08-01

    This work is based on data from several Galactic plane surveys covering wavelengths from mid-IR to submillimeter. The sample of dense clumps from the ATLASGAL survey (Schuller+ 2009A&A...504..415S) provides the basis for our investigation. The ATLASGAL survey mapped 420 square degrees of the Galactic plane between -80°clumps. Far-IR data from the Hi-GAL survey (Herschel-PACS and -SPIRE) have been used to further constrain the starless clump candidates and investigate their dust properties. (2 data files).

  5. MLAOS: A Multi-Point Linear Array of Optical Sensors for Coniferous Foliage Clumping Index Measurement

    PubMed Central

    Qu, Yonghua; Fu, Lizhe; Han, Wenchao; Zhu, Yeqing; Wang, Jindi

    2014-01-01

    The canopy foliage clumping effect is primarily caused by the non-random distribution of canopy foliage. Currently, measurements of clumping index (CI) by handheld instruments is typically time- and labor-intensive. We propose a low-cost and low-power automatic measurement system called Multi-point Linear Array of Optical Sensors (MLAOS), which consists of three above-canopy and nine below-canopy optical sensors that capture plant transmittance at different times of the day. Data communication between the MLAOS node is facilitated by using a ZigBee network, and the data are transmitted from the field MLAOS to a remote data server using the Internet. The choice of the electronic element and design of the MLAOS software is aimed at reducing costs and power consumption. A power consumption test showed that, when a 4000 mAH Li-ion battery is used, a maximum of 8–10 months of work can be achieved. A field experiment on a coniferous forest revealed that the CI of MLAOS may reveal a clumping effect that occurs within the canopy. In further work, measurement of the multi-scale clumping effect can be achieved by utilizing a greater number of MLAOS devices to capture the heterogeneity of the plant canopy. PMID:24859029

  6. Estimation of leaf area index and foliage clumping in deciduous forests using digital photography

    NASA Astrophysics Data System (ADS)

    Chianucci, Francesco; Cutini, Andrea

    2013-04-01

    Rapid, reliable and meaningful estimates of leaf area index (LAI) are essential to the characterization of forest ecosystems. In this contribution the accuracy of both fisheye and non-fisheye digital photography for the estimation of forest leaf area in deciduous stands was evaluated. We compared digital hemispherical photography (DHP), the most widely used technique that measures the gap fraction at multiple zenith angles, with methods that measure the gap fraction at a single zenith angle, namely 57.5 degree photography and cover photography (DCP). Comparison with other different gap fraction methods used to calculate LAI such as canopy transmittance measurements from AccuPAR ceptometer and LAI- 2000 Plant Canopy Analyzer (PCA) were also performed. LAI estimated from all these indirect methods were compared with direct measurements obtained by litter traps (LAILT). We applied these methods in 10 deciduous stands of Quercus cerris, Castanea sativa and Fagus sylvatica, the most common deciduous species in Italy, where LAILT ranged from 3.9 to 7.3. DHP and DCP provided good indirect estimates of LAILT, and outperformed the other indirect methods. The DCP method provided estimates of crown porosity, crown cover, foliage cover and the clumping index at the zenith, but required assumptions about the light extinction coefficient at the zenith (k), to accurately estimate LAI. Cover photography provided good indirect estimates of LAI assuming a spherical leaf angle distribution, even though k appeared to decrease as LAI increased, thus affecting the accuracy of LAI estimates in DCP. In contrast, the accuracy of LAI estimates in DHP appeared insensitive to LAILT values, but the method was sensitive to photographic exposure, gamma-correction and was more time-consuming than DCP. Foliage clumping was estimated from all the photographic methods by analyzing either gap size distribution (DCP) or gap fraction distribution (DHP). Foliage clumping was also calculated from PCA and

  7. A Generalised Porosity Formalism for Isotropic and Anisotropic Effective Opacity and Its Effects on X-ray Line Attenuation in Clumped O Star Winds

    NASA Technical Reports Server (NTRS)

    Sundqvist, Jon O.; Owocki, Stanley P.; Cohen, David H.; Leutenegger, Maurice A.; Townsend, Richard H. D.

    2002-01-01

    We present a generalised formalism for treating the porosity-associated reduction in continuum opacity that occurs when individual clumps in a stochastic medium become optically thick. As in previous work, we concentrate on developing bridging laws between the limits of optically thin and thick clumps. We consider geometries resulting in either isotropic or anisotropic effective opacity, and, in addition to an idealised model in which all clumps have the same local overdensity and scale, we also treat an ensemble of clumps with optical depths set by Markovian statistics. This formalism is then applied to the specific case of bound-free absorption of X- rays in hot star winds, a process not directly affected by clumping in the optically thin limit. We find that the Markov model gives surprisingly similar results to those found previously for the single clump model, suggesting that porous opacity is not very sensitive to details of the assumed clump distribution function. Further, an anisotropic effective opacity favours escape of X-rays emitted in the tangential direction (the venetian blind effect), resulting in a bump of higher flux close to line centre as compared to profiles computed from isotropic porosity models. We demonstrate how this characteristic line shape may be used to diagnose the clump geometry, and we confirm previous results that for optically thick clumping to significantly influence X-ray line profiles, very large porosity lengths, defined as the mean free path between clumps, are required. Moreover, we present the first X-ray line profiles computed directly from line-driven instability simulations using a 3-D patch method, and find that porosity effects from such models also are very small. This further supports the view that porosity has, at most, a marginal effect on X-ray line diagnostics in O stars, and therefore that these diagnostics do indeed provide a good clumping insensitive method for deriving O star mass-loss rates.

  8. A Generalised Porosity Formalism for Isotropic and Anisotropic Effective Opacity and its Effects on X-ray Line Attenuation in Clumped O Star Winds

    NASA Technical Reports Server (NTRS)

    Sundqvist, Jon O.; Owocki, Stanley P.; Cohen, David H.; Leutenegger, Maurice A.

    2011-01-01

    We present a generalised formalism for treating the porosity-associated reduction in continuum opacity that occurs when individual clumps in a stochastic medium become optically thick. As in previous work, we concentrate on developing bridging laws between the limits of optically thin and thick clumps. We consider geometries resulting in either isotropic or anisotropic effective opacity, and, in addition to an idealised model in which all clumps have the same local overdensity and scale, we also treat an ensemble of clumps with optical depths set by Markovian statistics. This formalism is then applied to the specific case of bound-free absorption of X- rays in hot star winds, a process not directly affected by clumping in the optically thin limit. We find that the Markov model gives surprisingly similar results to those found previously for the single clump model, suggesting that porous opacity is not very sensitive to details of the assumed clump distribution function. Further, an anisotropic effective opacity favours escape of X-rays emitted in the tangential direction (the venetian blind effect), resulting in a bump of higher flux close to line centre as compared to profiles computed from isotropic porosity models. We demonstrate how this characteristic line shape may be used to diagnose the clump geometry, and we confirm previous results that for optically thick clumping to significantly influence X-ray line profiles, very large porosity lengths, defined as the mean free path between clumps, are required. Moreover, we present the first X-ray line profiles computed directly from line-driven instability simulations using a 3-D patch method, and find that porosity effects from such models also are very small. This further supports the view that porosity has, at most, a marginal effect on X-ray line diagnostics in O stars, and therefore that these diagnostics do indeed provide a good clumping insensitive method for deriving O star mass-loss rates.

  9. VizieR Online Data Catalog: Galactic CHaMP. II. Dense gas clumps. (Ma+, 2013)

    NASA Astrophysics Data System (ADS)

    Ma, B.; Tan, J. C.; Barnes, P. J.

    2015-04-01

    A total of 303 dense gas clumps have been detected using the HCO+(1-0) line in the CHaMP survey (Paper I, Barnes et al. 2011, J/ApJS/196/12). In this article we have derived the SED for these clumps using Spitzer, MSX, and IRAS data. The Midcourse Space Experiment (MSX) was launched in 1996 April. It conducted a Galactic plane survey (0clumps. The four MSX band wavelengths are centered at 8.28, 12.13, 14.65, and 21.3um. The best image resolution is ~18" in the 8.28um band, with positional accuracy of about 2". Calibrated images of the Galactic plane were obtained from the online MSX image server at the IPAC website. The IRAS performed an all-sky survey at 12, 25, 60, and 100um. The nominal resolution is about 4' at 60um. High Resolution Image Restoration (HIRES) uses the maximum correlation method to produce higher resolution images, better than 1' at 60um. Sources chosen for processing with HIRES were processed at all four IRAS bands with 20 iterations. The Spitzer InfraRed Array Camera (IRAC) is a four-channel camera that provides simultaneous 5.2"x5.2" images at 3.6, 4.5, 5.8, and 8um with an angular resolution of about 2" at 8um. We searched the Spitzer archive at IPAC. Most of these data are from two large survey programs: PID 189 (Churchwell, E., "The SIRTF Galactic Plane Survey") and PID 40791 (Majewski, S., "Galactic Structure and Star Formation in Vela-Carina"). Hill et al. (2005, J/MNRAS/363/405) carried out a 1.2mm continuum emission survey toward 131 star-forming complexes using the Swedish ESO Submillimetre Telescope (SEST) IMaging Bolometer Array (SIMBA). Hill et al. list the 1.2mm flux for 404 sources, 15 of which are in our sample. (2 data files).

  10. In-vitro morphogenesis of corn (Zea mays L.) : I. Differentiation of multiple shoot clumps and somatic embryos from shoot tips.

    PubMed

    Zhong, H; Srinivasan, C; Sticklen, M B

    1992-07-01

    In-vitro methods have been developed to regenerate clumps of multiple shoots and somatic embryos at high frequency from shoot tips of aseptically-grown seedlings as well as from shoot apices of precociously-germinated immature zygotic embryos of corn (Zea mays L.). About 500 shoots were produced from a shoot tip after eight weeks of culture (primary culture and one subculture of four weeks) in darkness on Murashige and Skoog basal medium (MS) supplemented with 500 mg/L casein hydrolysate (CH) and 9 μM N(6)-benzyladenine (BA). In this medium, shoots formed in shoot tips as tightly packed "multiple shoot clumps" (MSC), which were composed of some axillary shoots and many adventitious shoots. When the shoot tips were cultured on MS medium containing 500 mg/L CH, 9 μM BA and 2.25 μM 2,4-dichlorophenoxyacetic acid (2,4-D), most of the shoots in the clumps were adventitious in origin. Similar shoot tips cultured on MS medium containing 500 mg/L CH, 4.5 μM BA and 2.25 μM 2,4-D regenerated many somatic embryos within eight weeks of culture. Somatic embryos were produced either directly from the shoot apical meristems or from calli derived from the shoots apices. Both the MSC and the embryos produced normal shoots on MS medium containing 2.25 μM BA and 1.8 μM indole-3-butyric acid (IBA). These shoots were rooted on MS medium containing 3.6 μM IBA, and fertile corn plants were grown in the greenhouse. The sweet-corn genotype, Honey N Pearl, was used for the experiments described above, but shoot-tip cultures from all of 19 other corn genotypes tested also formed MSC on MS medium containing 500 mg/L CH and 9 μM BA.

  11. Spectroscopic constraints on the form of the stellar cluster mass function

    NASA Astrophysics Data System (ADS)

    Bastian, N.; Konstantopoulos, I. S.; Trancho, G.; Weisz, D. R.; Larsen, S. S.; Fouesneau, M.; Kaschinski, C. B.; Gieles, M.

    2012-05-01

    This contribution addresses the question of whether the initial cluster mass function (ICMF) has a fundamental limit (or truncation) at high masses. The shape of the ICMF at high masses can be studied using the most massive young (<10 Myr) clusters, however this has proven difficult due to low-number statistics. In this contribution we use an alternative method based on the luminosities of the brightest clusters, combined with their ages. The advantages are that more clusters can be used and that the ICMF leaves a distinct pattern on the global relation between the cluster luminosity and median age within a population. If a truncation is present, a generic prediction (nearly independent of the cluster disruption law adopted) is that the median age of bright clusters should be younger than that of fainter clusters. In the case of an non-truncated ICMF, the median age should be independent of cluster luminosity. Here, we present optical spectroscopy of twelve young stellar clusters in the face-on spiral galaxy NGC 2997. The spectra are used to estimate the age of each cluster, and the brightness of the clusters is taken from the literature. The observations are compared with the model expectations of Larsen (2009, A&A, 494, 539) for various ICMF forms and both mass dependent and mass independent cluster disruption. While there exists some degeneracy between the truncation mass and the amount of mass independent disruption, the observations favour a truncated ICMF. For low or modest amounts of mass independent disruption, a truncation mass of 5-6 × 105 M⊙ is estimated, consistent with previous determinations. Additionally, we investigate possible truncations in the ICMF in the spiral galaxy M 83, the interacting Antennae galaxies, and the collection of spiral and dwarf galaxies present in Larsen (2009, A&A, 494, 539) based on photometric catalogues taken from the literature, and find that all catalogues are consistent with having a truncation in the cluster mass

  12. Reentrant and Isostructural Transitions in the Cluster-Crystal Forming GEM-4

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Charbonneau, Patrick; Mladek, Bianca

    2011-03-01

    Systems governed by soft, bounded, purely repulsive interactions show two possible equilibrium behaviors under compression: reentrant melting, as in the Gaussian core model (GCM), or clustering, as in the penetrable sphere model (PSM). The generalized exponential model of power 4 (GEM-4), which is the intermedia of the GCM and PSM with a simple isotropic pair interaction u (r) ~e-r4 , is thought to belong to the second family and was indeed found to form clusters at sufficiently high densities at high temperatures. Here, we present the low-temperature behavior of GEM-4 through Monte Carlo simulations using a specially developed free energy integration scheme. We find the phase behavior to be hybrid between the GCM and the PSM limits, showing a surprisingly rich phase behavior in spite of the simplicity of the interaction form. For instance, S- shaped doubly reentrant phase sequences and evidence of a cascade of critical isostructural transitions between crystals of different average lattice site occupancy are observed. The possible annihilation of lattice sites and accompanying clustering moreover leads to an unusual softening upon compression, which suggest that these materials may have interesting mechanical properties. We discuss possible experimental realizations and challenges of this class of materials.

  13. Mapping Forest Structure From Tree Clump And Opening Patterns Across Landscapes With Airborne Lidar To Study Response To Disturbances And Map Habitat

    NASA Astrophysics Data System (ADS)

    Kane, V. R.; McGaughey, R. J.; Asner, G. P.; Kane, J. T.; Churchill, D.; Vaughn, N.

    2016-12-01

    Most natural forests are structured as mosaics of tree clumps and openings. These mosaics reflect both the underlying patterns of the biophysical environment and the finer scale patterns of disturbance and regrowth. We have developed methods to quantify and map patterns of tree clumps and openings at scales from within stands to landscapes using airborne LiDAR. While many studies have used LiDAR data to identify individual trees, we also identify clumps as adjacent trees with similar heights within a stand that likely established at a similar time following a disturbance. We characterize openings by both size class and shape complexity. Spatial statistics are used to identify patterns of tree clumps and openings at the local (0.81 ha) scale, and these patterns are then mapped across entire landscapes. We use LiDAR data acquired over Sequoia National Park, California, USA, to show how forest structure varies with patterns of productivity driven by the biophysical environment. We then show how clump and opening patterns vary with different fire histories and how recent drought mortality correlates with different tree clump and opening structural mosaics. We also demonstrate that nesting sites for the California spotted owl, a species of concern, are associated with clumps of large (>32 and especially >48 m) trees but that the surrounding foraging areas consist of a heterogeneous pattern of forest structure. These methods are especially useful for studying clumps of large trees, which dominate above ground forest biomass, and the effects of disturbance on the abundance and pattern of large trees as key forest structures.

  14. Thermodynamic stability and structural properties of cluster crystals formed by amphiphilic dendrimers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lenz, Dominic A.; Likos, Christos N.; Blaak, Ronald

    We pursue the goal of finding real-world examples of macromolecular aggregates that form cluster crystals, which have been predicted on the basis of coarse-grained, ultrasoft pair potentials belonging to a particular mathematical class [B. M. Mladek et al., Phys. Rev. Lett. 46, 045701 (2006)]. For this purpose, we examine in detail the phase behavior and structural properties of model amphiphilic dendrimers of the second generation by means of monomer-resolved computer simulations. On augmenting the density of these systems, a fluid comprised of clusters that contain several overlapping and penetrating macromolecules is spontaneously formed. Upon further compression of the system, amore » transition to multi-occupancy crystals takes place, the thermodynamic stability of which is demonstrated by means of free-energy calculations, and where the FCC is preferred over the BCC-phase. Contrary to predictions for coarse-grained theoretical models in which the particles interact exclusively by effective pair potentials, the internal degrees of freedom of these molecules cause the lattice constant to be density-dependent. Furthermore, the mechanical stability of monodisperse BCC and FCC cluster crystals is restricted to a bounded region in the plane of cluster occupation number versus density. The structural properties of the dendrimers in the dense crystals, including their overall sizes and the distribution of monomers are also thoroughly analyzed.« less

  15. Platelet-mediated clumping of Plasmodium falciparum infected erythrocytes is associated with high parasitemia but not severe clinical manifestations of malaria in African children

    PubMed Central

    Arman, Mònica; Raza, Ahmed; Tempest, Louisa J.; Lyke, Kirsten E.; Thera, Mahamadou A.; Koné, Abdoulaye; Plowe, Christopher V.; Doumbo, Ogobara K.; Rowe, J. Alexandra

    2009-01-01

    Platelet-mediated clumping of Plasmodium falciparum infected erythrocytes is an adhesive phenotype commonly found in field isolates that has previously been associated with severe malaria. Here, clumping was assessed in 131 isolates from Malian children. The clumping phenotype was seen in 6% (n=51) of uncomplicated malaria, 24% (n=51) of severe malaria, and 45% (n=29) of high parasitemia non-severe malaria isolates. Multivariate analysis indicated that clumping was strongly positively associated with parasitemia (F1,122=24.1, p<0.001) but not with disease category (F2,122=1.8, p=0.17). Therefore platelet-mediated clumping in Malian P. falciparum isolates is primarily associated with high parasitemia and not with severe clinical manifestations of malaria. PMID:17984358

  16. Impact of surface processes and climate variability on clumped isotope thermometry of soil carbonates, southern Central Andes, Argentina (Invited)

    NASA Astrophysics Data System (ADS)

    Huntington, K. W.; Peters, N.; Roe, G.; Hoke, G. D.; Eiler, J.

    2010-12-01

    Soil carbonates archive a potentially rich record of past climate, but rates of pedogenic carbonate formation, erosion, and deposition impact how the isotopic composition and formation temperature of carbonate-bearing paleosols reflect the local environmental conditions under which they form. We investigate these processes using conventional stable isotope (δ18O and δ13C) and clumped isotope thermometry data for Quaternary pedogenic carbonates from the southern Central Andes at ~33°S, Argentina. The study area spans over 2 km of relief in the Río Mendoza and Río de las Cuevas valleys, accessing a range of mean annual temperature conditions and vegetative cover and exhibiting large seasonal variations in temperature, precipitation, and soil moisture. Variations in soil conditions influence carbonate precipitation and dissolution reactions and the rate and depth of pedogenic carbonate formation. Because soil temperature varies predictably as a function of depth in the soil and seasonal and secular variations in air temperature, clumped isotope thermometry of samples collected in soil pits offers a direct way to estimate the seasonality of pedogenic carbonate formation and potential biases in the long-term climate record. We explore potential complications due to the effects of radiative solar heating on the relationship between air and soil temperatures by examining clumped isotope thermometry results in the context of site-to-site variations in vegetative cover. Temperature estimates from clumped isotope thermometry of pedogenic carbonate collected 5-110 cm below geomorphically stable soil surfaces from 1200-3400 m a.s.l. are compared to temperature profiles predicted by simple rule-based models of soil carbonate formation. The models use climate reanalysis daily diagnostic data (soil temperature, soil moisture, and latent heat flux as a proxy for evaporation) and weather station data as input to assess how varying rates of pedogenic carbonate formation

  17. Formation and internal structure of superdense dark matter clumps and ultracompact minihaloes

    NASA Astrophysics Data System (ADS)

    Berezinsky, V. S.; Dokuchaev, V. I.; Eroshenko, Yu. N.

    2013-11-01

    We discuss the formation mechanisms and structure of the superdense dark matter clumps (SDMC) and ultracompact minihaloes (UCMH), outlining the differences between these types of DM objects. We define as SDMC the gravitationally bounded DM objects which have come into virial equilibrium at the radiation-dominated (RD) stage of the universe evolution. Such objects can be formed from the isocurvature (entropy) density perturbations or from the peaks in the spectrum of curvature (adiabatic) perturbation. The axion miniclusters (Kolb and Tkachev 1994) are the example of the former model. The system of central compact mass (e.g. in the form of SDMC or primordial black hole (PBH)) with the outer DM envelope formed in the process of secondary accretion we refer to as UCMH. Therefore, the SDMC can serve as the seed for the UCMH in some scenarios. Recently, the SDMC and UCMH were considered in the many works, and we try to systematize them here. We consider also the effect of asphericity of the initial density perturbation in the gravitational evolution, which decreases the SDMC amount and, as the result, suppresses the gamma-ray signal from DM annihilation.

  18. BLUE STRAGGLERS IN GLOBULAR CLUSTER 47 TUCANAE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The core of globular cluster 47 Tucanae is home to many blue stragglers, rejuvenated stars that glow with the blue light of young stars. A ground-based telescope image (on the left) shows the entire crowded core of 47 Tucanae, located 15,000 light-years away in the constellation Tucana. Peering into the heart of the globular cluster's bright core, the Hubble Space Telescope's Wide Field and Planetary Camera 2 separated the dense clump of stars into many individual stars (image on right). Some of these stars shine with the light of old stars; others with the blue light of blue stragglers. The yellow circles in the Hubble telescope image highlight several of the cluster's blue stragglers. Analysis for this observation centered on one massive blue straggler. Astronomers theorize that blue stragglers are formed either by the slow merger of stars in a double-star system or by the collision of two unrelated stars. For the blue straggler in 47 Tucanae, astronomers favor the slow merger scenario. This image is a 3-color composite of archival Hubble Wide Field and Planetary Camera 2 images in the ultraviolet (blue), blue (green), and violet (red) filters. Color tables were assigned and scaled so that the red giant stars appear orange, main-sequence stars are white/green, and blue stragglers are appropriately blue. The ultraviolet images were taken on Oct. 25, 1995, and the blue and violet images were taken on Sept. 1, 1995. Credit: Rex Saffer (Villanova University) and Dave Zurek (STScI), and NASA

  19. Concurrent Effects of Sediment Accretion and Nutrient Availability on the Clonal Growth Strategy of Carex brevicuspis-A Wetland Sedge That Produces Both Spreading and Clumping Ramets

    PubMed Central

    Chen, Xinsheng; Liao, Yulin; Xie, Yonghong; Li, Feng; Deng, Zhengmiao; Hou, Zhiyong; Wu, Chao

    2017-01-01

    Clonal plants producing both clumping and spreading ramets can adjust their growth forms in response to resource heterogeneity or environmental stress. They might produce clumping ramets to retain favorable patches, or produce spreading ramets to escape from stress-affected patches. This study aimed to investigate the rarely reported concurrent effects of sediment accretion and nutrient enrichment, which often occur simultaneously in lacustrine wetlands, on the vegetative propagation and clonal growth forms of Carex brevicuspis C.B. Clarke by conducting a factorial experiment of sediment burial and nutrient addition. Biomass accumulation, new ramet and rhizome numbers, and ramet length of C. brevicuspis were not affected at moderate burial, but were significantly lower after deep burial. Similarly, nutrient enrichment increased the growth and vegetative propagation of C. brevicuspis up to moderate sediment burial, but not after deep burial. Sediment accretion increased the proportion of spreading ramets produced by C. brevicuspis, whereas nutrient addition had no effect on the clonal growth forms. Our results indicated that the plasticity of clonal growth forms is an effective strategy used by plants to acclimate to moderate sediment accretion. Nutrient enrichment did not influence the clonal growth forms of C. brevicuspis and could not facilitate its acclimation to heavy sedimentation condition. PMID:29021805

  20. Re-evaluation of temperature of replacement dolomitization in the Triassic Latemar platform with clumped isotope thermometry

    NASA Astrophysics Data System (ADS)

    Müller, Inigo Andreas; Rodriguez-Blanco, Juan D.; Storck, Julian-Christopher; Benning, Liane G.; Wilson, Edith N.; Brack, Peter; Bernasconi, Stefano M.

    2017-04-01

    The Triassic Latemar platform shows different types of dolomitization styles including features such as dolomitized zones around basaltic dykes and patchy reddish or greyish dolomitization features in the central part of the platform. The processes leading to this partial dolomitization are still debated. Different geochemical tools were applied to determine the formation temperature of the patchy dolomite phases, thereby microthermometry on fluid inclusions and clumped isotope thermometry revealed significantly different temperature ranges (100 to 200 °C vs. 40 to 80 °C, from Wilson et al., 1990 and Ferry et al., 2011, respectively). We re-evaluated the origin of these patchy dolomites at Latemar using a new dolomite-specific clumped isotope temperature calibration based on dolomites synthetized in the laboratory at different temperatures. We directly compare the clumped isotope temperatures of patchy dolomites from Latemar with those obtained on the same samples by fluid inclusion microthermometry. With the new dolomite specific clumped isotope temperature calibration it is possible to determine more precisely the dolomite formation temperature and the oxygen isotope composition of the fluid source. Both are critical parameters for better constraining the origin of different dolomite fabrics on the Earth's surface and in ancient sediments. E.N. Wilson, L.A. Hardie and O.M. Phillips, 1990. Dolomitization front geometry, fluid flow patterns, and the origin of massive dolomite: the Triassic Latemar buildup, northern Italy. American Journal of Science 290, 741-796. J.M. Ferry, B.H. Passey, C. Vasconcelos and J.M. Eiler, 2011. Formation of dolomite at 40-80 °C in the Latemar carbonate buildup, Dolomites, Italy, from clumped isotope thermometry. Geology 39, 571-574.

  1. Not-so-simple stellar populations in the intermediate-age Large Magellanic Cloud star clusters NGC 1831 and NGC 1868

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Chengyuan; De Grijs, Richard; Deng, Licai, E-mail: joshuali@pku.edu.cn, E-mail: grijs@pku.edu.cn

    2014-04-01

    Using a combination of high-resolution Hubble Space Telescope/Wide-Field and Planetary Camera-2 observations, we explore the physical properties of the stellar populations in two intermediate-age star clusters, NGC 1831 and NGC 1868, in the Large Magellanic Cloud based on their color-magnitude diagrams. We show that both clusters exhibit extended main-sequence turn offs. To explain the observations, we consider variations in helium abundance, binarity, age dispersions, and the fast rotation of the clusters' member stars. The observed narrow main sequence excludes significant variations in helium abundance in both clusters. We first establish the clusters' main-sequence binary fractions using the bulk of themore » clusters' main-sequence stellar populations ≳ 1 mag below their turn-offs. The extent of the turn-off regions in color-magnitude space, corrected for the effects of binarity, implies that age spreads of order 300 Myr may be inferred for both clusters if the stellar distributions in color-magnitude space were entirely due to the presence of multiple populations characterized by an age range. Invoking rapid rotation of the population of cluster members characterized by a single age also allows us to match the observed data in detail. However, when taking into account the extent of the red clump in color-magnitude space, we encounter an apparent conflict for NGC 1831 between the age dispersion derived from that based on the extent of the main-sequence turn off and that implied by the compact red clump. We therefore conclude that, for this cluster, variations in stellar rotation rate are preferred over an age dispersion. For NGC 1868, both models perform equally well.« less

  2. Diamond-like phases formed from fullerene-like clusters

    NASA Astrophysics Data System (ADS)

    Belenkov, E. A.; Greshnyakov, V. A.

    2015-11-01

    The geometrically optimized structure and properties of thirteen diamond-like carbon phases formed by linking or combining fullerene-like clusters (C4, C6, C8, C12, C16, C24, or C48) have been investigated. Atoms in the structures of these phases are located in crystallographically equivalent positions. The calculations have been performed using the density functional theory in the generalized gradient approximation. The calculated values of the structural characteristics and properties (sublimation energies, bulk moduli, band gaps, X-ray diffraction patterns) of the studied diamond-like phases differ significantly from the corresponding values for cubic diamond.

  3. The TOP-SCOPE Survey of Planck Galactic Cold Clumps: Survey Overview and Results of an Exemplar Source, PGCC G26.53+0.17

    NASA Astrophysics Data System (ADS)

    Liu, Tie; Kim, Kee-Tae; Juvela, Mika; Wang, Ke; Tatematsu, Ken’ichi; Di Francesco, James; Liu, Sheng-Yuan; Wu, Yuefang; Thompson, Mark; Fuller, Gary; Eden, David; Li, Di; Ristorcelli, I.; Kang, Sung-ju; Lin, Yuxin; Johnstone, D.; He, J. H.; Koch, P. M.; Sanhueza, Patricio; Qin, Sheng-Li; Zhang, Q.; Hirano, N.; Goldsmith, Paul F.; Evans, Neal J., II; White, Glenn J.; Choi, Minho; Lee, Chang Won; Toth, L. V.; Mairs, Steve; Yi, H.-W.; Tang, Mengyao; Soam, Archana; Peretto, N.; Samal, Manash R.; Fich, Michel; Parsons, Harriet; Yuan, Jinghua; Zhang, Chuan-Peng; Malinen, Johanna; Bendo, George J.; Rivera-Ingraham, A.; Liu, Hong-Li; Wouterloot, Jan; Li, Pak Shing; Qian, Lei; Rawlings, Jonathan; Rawlings, Mark G.; Feng, Siyi; Aikawa, Yuri; Akhter, S.; Alina, Dana; Bell, Graham; Bernard, J.-P.; Blain, Andrew; Bőgner, Rebeka; Bronfman, L.; Byun, D.-Y.; Chapman, Scott; Chen, Huei-Ru; Chen, M.; Chen, Wen-Ping; Chen, X.; Chen, Xuepeng; Chrysostomou, A.; Cosentino, Giuliana; Cunningham, M. R.; Demyk, K.; Drabek-Maunder, Emily; Doi, Yasuo; Eswaraiah, C.; Falgarone, Edith; Fehér, O.; Fraser, Helen; Friberg, Per; Garay, G.; Ge, J. X.; Gear, W. K.; Greaves, Jane; Guan, X.; Harvey-Smith, Lisa; HASEGAWA, Tetsuo; Hatchell, J.; He, Yuxin; Henkel, C.; Hirota, T.; Holland, W.; Hughes, A.; Jarken, E.; Ji, Tae-Geun; Jimenez-Serra, Izaskun; Kang, Miju; Kawabata, Koji S.; Kim, Gwanjeong; Kim, Jungha; Kim, Jongsoo; Kim, Shinyoung; Koo, B.-C.; Kwon, Woojin; Kuan, Yi-Jehng; Lacaille, K. M.; Lai, Shih-Ping; Lee, C. F.; Lee, J.-E.; Lee, Y.-U.; Li, Dalei; Li, Hua-bai; Lo, N.; Lopez, John A. P.; Lu, Xing; Lyo, A.-Ran; Mardones, D.; Marston, A.; McGehee, P.; Meng, F.; Montier, L.; Montillaud, Julien; Moore, T.; Morata, O.; Moriarty-Schieven, Gerald H.; Ohashi, S.; Pak, Soojong; Park, Geumsook; Paladini, R.; Pattle, Kate M.; Pech, Gerardo; Pelkonen, V.-M.; Qiu, K.; Ren, Zhi-Yuan; Richer, John; Saito, M.; Sakai, Takeshi; Shang, H.; Shinnaga, Hiroko; Stamatellos, Dimitris; Tang, Y.-W.; Traficante, Alessio; Vastel, Charlotte; Viti, S.; Walsh, Andrew; Wang, Bingru; Wang, Hongchi; Wang, Junzhi; Ward-Thompson, D.; Whitworth, Anthony; Xu, Ye; Yang, J.; Yang, Yao-Lun; Yuan, Lixia; Zavagno, A.; Zhang, Guoyin; Zhang, H.-W.; Zhou, Chenlin; Zhou, Jianjun; Zhu, Lei; Zuo, Pei; Zhang, Chao

    2018-02-01

    The low dust temperatures (<14 K) of Planck Galactic cold clumps (PGCCs) make them ideal targets to probe the initial conditions and very early phase of star formation. “TOP-SCOPE” is a joint survey program targeting ∼2000 PGCCs in J = 1–0 transitions of CO isotopologues and ∼1000 PGCCs in 850 μm continuum emission. The objective of the “TOP-SCOPE” survey and the joint surveys (SMT 10 m, KVN 21 m, and NRO 45 m) is to statistically study the initial conditions occurring during star formation and the evolution of molecular clouds, across a wide range of environments. The observations, data analysis, and example science cases for these surveys are introduced with an exemplar source, PGCC G26.53+0.17 (G26), which is a filamentary infrared dark cloud (IRDC). The total mass, length, and mean line mass (M/L) of the G26 filament are ∼6200 M ⊙, ∼12 pc, and ∼500 M ⊙ pc‑1, respectively. Ten massive clumps, including eight starless ones, are found along the filament. The most massive clump as a whole may still be in global collapse, while its denser part seems to be undergoing expansion owing to outflow feedback. The fragmentation in the G26 filament from cloud scale to clump scale is in agreement with gravitational fragmentation of an isothermal, nonmagnetized, and turbulent supported cylinder. A bimodal behavior in dust emissivity spectral index (β) distribution is found in G26, suggesting grain growth along the filament. The G26 filament may be formed owing to large-scale compression flows evidenced by the temperature and velocity gradients across its natal cloud.

  4. VizieR Online Data Catalog: Structure of young stellar clusters. II. (Kuhn+, 2015)

    NASA Astrophysics Data System (ADS)

    Kuhn, M. A.; Getman, K. V.; Feigelson, E. D.

    2015-07-01

    We investigate the intrinsic stellar populations (estimated total numbers of OB and pre-main-sequence stars down to 0.1Mȯ) that are present in 17 massive star-forming regions (MSFRs) surveyed by the MYStIX project. The study is based on the catalog of >31000 MYStIX Probable Complex Members with both disk-bearing and disk-free populations, compensating for extinction, nebulosity, and crowding effects. Correction for observational sensitivities is made using the X-ray luminosity function and the near-infrared initial mass function --a correction that is often not made by infrared surveys of young stars. The resulting maps of the projected structure of the young stellar populations, in units of intrinsic stellar surface density, allow direct comparison between different regions. Several regions have multiple dense clumps, similar in size and density to the Orion Nebula Cluster. The highest projected density of ~34000 stars/pc2 is found in the core of the RCW 38 cluster. Histograms of surface density show different ranges of values in different regions, supporting the conclusion of Bressert et al. (B10; 2010MNRAS.409L..54B) that no universal surface-density threshold can distinguish between clustered and distributed star formation. However, a large component of the young stellar population of MSFRs resides in dense environments of 200-10000 stars/pc2 (including within the nearby Orion molecular clouds), and we find that there is no evidence for the B10 conclusion that such dense regions form an extreme "tail" of the distribution. Tables of intrinsic populations for these regions are used in our companion study of young cluster properties and evolution. (3 data files).

  5. TWO-STAGE FRAGMENTATION FOR CLUSTER FORMATION: ANALYTICAL MODEL AND OBSERVATIONAL CONSIDERATIONS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bailey, Nicole D.; Basu, Shantanu, E-mail: nwityk@uwo.ca, E-mail: basu@uwo.ca

    2012-12-10

    Linear analysis of the formation of protostellar cores in planar magnetic interstellar clouds shows that molecular clouds exhibit a preferred length scale for collapse that depends on the mass-to-flux ratio and neutral-ion collision time within the cloud. We extend this linear analysis to the context of clustered star formation. By combining the results of the linear analysis with a realistic ionization profile for the cloud, we find that a molecular cloud may evolve through two fragmentation events in the evolution toward the formation of stars. Our model suggests that the initial fragmentation into clumps occurs for a transcritical cloud onmore » parsec scales while the second fragmentation can occur for transcritical and supercritical cores on subparsec scales. Comparison of our results with several star-forming regions (Perseus, Taurus, Pipe Nebula) shows support for a two-stage fragmentation model.« less

  6. Herschel and SCUBA-2 observations of dust emission in a sample of Planck cold clumps

    NASA Astrophysics Data System (ADS)

    Juvela, Mika; He, Jinhua; Pattle, Katherine; Liu, Tie; Bendo, George; Eden, David J.; Fehér, Orsolya; Michel, Fich; Fuller, Gary; Hirano, Naomi; Kim, Kee-Tae; Li, Di; Liu, Sheng-Yuan; Malinen, Johanna; Marshall, Douglas J.; Paradis, Deborah; Parsons, Harriet; Pelkonen, Veli-Matti; Rawlings, Mark G.; Ristorcelli, Isabelle; Samal, Manash R.; Tatematsu, Ken'ichi; Thompson, Mark; Traficante, Alessio; Wang, Ke; Ward-Thompson, Derek; Wu, Yuefang; Yi, Hee-Weon; Yoo, Hyunju

    2018-04-01

    Context. Analysis of all-sky Planck submillimetre observations and the IRAS 100 μm data has led to the detection of a population of Galactic cold clumps. The clumps can be used to study star formation and dust properties in a wide range of Galactic environments. Aims: Our aim is to measure dust spectral energy distribution (SED) variations as a function of the spatial scale and the wavelength. Methods: We examined the SEDs at large scales using IRAS, Planck, and Herschel data. At smaller scales, we compared JCMT/SCUBA-2 850 μm maps with Herschel data that were filtered using the SCUBA-2 pipeline. Clumps were extracted using the Fellwalker method, and their spectra were modelled as modified blackbody functions. Results: According to IRAS and Planck data, most fields have dust colour temperatures TC 14-18 K and opacity spectral index values of β = 1.5-1.9. The clumps and cores identified in SCUBA-2 maps have T 13 K and similar β values. There are some indications of the dust emission spectrum becoming flatter at wavelengths longer than 500 μm. In fits involving Planck data, the significance is limited by the uncertainty of the corrections for CO line contamination. The fits to the SPIRE data give a median β value that is slightly above 1.8. In the joint SPIRE and SCUBA-2 850 μm fits, the value decreases to β 1.6. Most of the observed T-β anticorrelation can be explained by noise. Conclusions: The typical submillimetre opacity spectral index β of cold clumps is found to be 1.7. This is above the values of diffuse clouds, but lower than in some previous studies of dense clumps. There is only tentative evidence of a T-β anticorrelation and β decreasing at millimetre wavelengths. Planck (http://www.esa.int/Planck) is a project of the European Space Agency - ESA - with instruments provided by two scientific consortia funded by ESA member states (in particular the lead countries: France and Italy) with contributions from NASA (USA), and telescope reflectors

  7. Equilibrium and non-equilibrium controls on the abundances of clumped isotopologues of methane during thermogenic formation in laboratory experiments: Implications for the chemistry of pyrolysis and the origins of natural gases

    NASA Astrophysics Data System (ADS)

    Shuai, Yanhua; Douglas, Peter M. J.; Zhang, Shuichang; Stolper, Daniel A.; Ellis, Geoffrey S.; Lawson, Michael; Lewan, Michael D.; Formolo, Michael; Mi, Jingkui; He, Kun; Hu, Guoyi; Eiler, John M.

    2018-02-01

    Multiply isotopically substituted molecules ('clumped' isotopologues) can be used as geothermometers because their proportions at isotopic equilibrium relative to a random distribution of isotopes amongst all isotopologues are functions of temperature. This has allowed measurements of clumped-isotope abundances to be used to constrain formation temperatures of several natural materials. However, kinetic processes during generation, modification, or transport of natural materials can also affect their clumped-isotope compositions. Herein, we show that methane generated experimentally by closed-system hydrous pyrolysis of shale or nonhydrous pyrolysis of coal yields clumped-isotope compositions consistent with an equilibrium distribution of isotopologues under some experimental conditions (temperature-time conditions corresponding to 'low,' 'mature,' and 'over-mature' stages of catagenesis), but can have non-equilibrium (i.e., kinetically controlled) distributions under other experimental conditions ('high' to 'over-mature' stages), particularly for pyrolysis of coal. Non-equilibrium compositions, when present, lead the measured proportions of clumped species to be lower than expected for equilibrium at the experimental temperature, and in some cases to be lower than a random distribution of isotopes (i.e., negative Δ18 values). We propose that the consistency with equilibrium for methane formed by relatively low temperature pyrolysis reflects local reversibility of isotope exchange reactions involving a reactant or transition state species during demethylation of one or more components of kerogen. Non-equilibrium clumped-isotope compositions occur under conditions where 'secondary' cracking of retained oil in shale or wet gas hydrocarbons (C2-5, especially ethane) in coal is prominent. We suggest these non-equilibrium isotopic compositions are the result of the expression of kinetic isotope effects during the irreversible generation of methane from an alkyl

  8. Beyond temperature: Clumped isotope signatures in dissolved inorganic carbon species and the influence of solution chemistry on carbonate mineral composition

    USGS Publications Warehouse

    Tripati, Aradhna K.; Hill, Pamela S.; Eagle, Robert A.; Mosenfelder, Jed L.; Tang, Jianwu; Schauble, Edwin A.; Eiler, John M.; Zeebe, Richard E.; Uchikawa, Joji; Coplen, Tyler B.; Ries, Justin B.; Henry, Drew

    2015-01-01

    Clumped-isotope” thermometry is an emerging tool to probe the temperature history of surface and subsurface environments based on measurements of the proportion of 13C and 18O isotopes bound to each other within carbonate minerals in 13C18O16O22- groups (heavy isotope “clumps”). Although most clumped isotope geothermometry implicitly presumes carbonate crystals have attained lattice equilibrium (i.e., thermodynamic equilibrium for a mineral, which is independent of solution chemistry), several factors other than temperature, including dissolved inorganic carbon (DIC) speciation may influence mineral isotopic signatures. Therefore we used a combination of approaches to understand the potential influence of different variables on the clumped isotope (and oxygen isotope) composition of minerals.We conducted witherite precipitation experiments at a single temperature and at varied pH to empirically determine 13C-18O bond ordering (Δ47) and δ18O of CO32- and HCO3- molecules at a 25 °C equilibrium. Ab initio cluster models based on density functional theory were used to predict equilibrium 13C-18O bond abundances and δ18O of different DIC species and minerals as a function of temperature. Experiments and theory indicate Δ47 and δ18O compositions of CO32- and HCO3- ions are significantly different from each other. Experiments constrain the Δ47-δ18O slope for a pH effect (0.011 ± 0.001; 12 ⩾ pH ⩾ 7). Rapidly-growing temperate corals exhibit disequilibrium mineral isotopic signatures with a Δ47-δ18O slope of 0.011 ± 0.003, consistent with a pH effect.Our theoretical calculations for carbonate minerals indicate equilibrium lattice calcite values for Δ47 and δ18O are intermediate between HCO3− and CO32−. We analyzed synthetic calcites grown at temperatures ranging from 0.5 to 50 °C with and without the enzyme carbonic anhydrase present. This enzyme catalyzes oxygen isotopic exchange between DIC species and is present in many

  9. Young stellar clumps in the interacting system Arp 305

    NASA Astrophysics Data System (ADS)

    Zasov, Anatoly V.; Saburova, Anna S.; Egorov, Oleg V.; Afanasiev, Viktor L.

    2018-07-01

    We present the results from optical long-slit spectral observations of the interacting system Arp 305 that were carried out at the 6-m Big Telescope Alt-azimuth (BTA) at the Special Astrophysical Observatory, Russian Academy of Sciences. We look at the radial variation of gas kinematics and oxygen abundance. This study continues the series of spectral observations of tidal debris in interacting galaxies. Here we pay special attention to the star-forming region between the interacting galaxies - a tidal dwarf galaxy (TDG) candidate. This star-forming system appears to be gravitationally bound, or close to this condition. We show that the TDG is metal-poor in comparison to the parental galaxy. This can indicate that either the origin of the TDG's star-forming gas was very far from the centre of the parent galaxy or its gas has been diluted by the accretion of metal-poor intergalactic gas. Nevertheless, the region of the brightest emission clump in the TDG, where current star formation takes place, reveals a noticeable colour excess, which might indicate a local gas concentration. We note that the TDG is situated in the region where two gas flows intersect and that it is in a process of formation probably caused by the collision of these flows. The small difference in the velocity of the TDG, NGC 4017 and the gaseous bridge between them indicates that the lifetime of the TDG is restricted by the time of its fall back on to the parent galaxy.

  10. Multi-wavelength Morphological Study Of Star Forming Regions In Nearby Cluster-rich Lirgs

    NASA Astrophysics Data System (ADS)

    Vavilkin, Tatjana; Evans, A.; Mazzarella, J.; Surace, J.; Kim, D.; Howell, J.; Armus, L.; GOALS Team

    2009-05-01

    Luminous Infrared Galaxies (LIRGs) are believed to play an important role in star formation history of the universe. Many LIRGs undergo intense bursts of star formation as a result of interaction/merger process. Given the dusty nature of LIRGs, it is necessary to probe Luminous Infrared Galaxies at multiple wavelengths. The Great Observatories All-sky LIRG Survey (GOALS) combines data from NASA's Spitzer, Hubble, Chandra and GALEX observatories and offers a unique opportunity to gain insights into the physical processes in these highly dust enshrouded systems. We examine a sample of 11 nearby (z < 0.03) cluster-rich (> 200 clusters as seen in HST ACS images) LIRG systems at various interaction stages. The combined HST ACS optical imaging, Spitzer IRAC 8 micron channel and GALEX near-UV imaging allows us to access the properties of visible and obscured star forming regions. We study the spatial distribution of star forming regions at these wavelengths, correlate locations of young stellar clusters with PAH and UV emission regions and trace changes with merger stage.

  11. Evaluating Bayesian spatial methods for modelling species distributions with clumped and restricted occurrence data.

    PubMed

    Redding, David W; Lucas, Tim C D; Blackburn, Tim M; Jones, Kate E

    2017-01-01

    Statistical approaches for inferring the spatial distribution of taxa (Species Distribution Models, SDMs) commonly rely on available occurrence data, which is often clumped and geographically restricted. Although available SDM methods address some of these factors, they could be more directly and accurately modelled using a spatially-explicit approach. Software to fit models with spatial autocorrelation parameters in SDMs are now widely available, but whether such approaches for inferring SDMs aid predictions compared to other methodologies is unknown. Here, within a simulated environment using 1000 generated species' ranges, we compared the performance of two commonly used non-spatial SDM methods (Maximum Entropy Modelling, MAXENT and boosted regression trees, BRT), to a spatial Bayesian SDM method (fitted using R-INLA), when the underlying data exhibit varying combinations of clumping and geographic restriction. Finally, we tested how any recommended methodological settings designed to account for spatially non-random patterns in the data impact inference. Spatial Bayesian SDM method was the most consistently accurate method, being in the top 2 most accurate methods in 7 out of 8 data sampling scenarios. Within high-coverage sample datasets, all methods performed fairly similarly. When sampling points were randomly spread, BRT had a 1-3% greater accuracy over the other methods and when samples were clumped, the spatial Bayesian SDM method had a 4%-8% better AUC score. Alternatively, when sampling points were restricted to a small section of the true range all methods were on average 10-12% less accurate, with greater variation among the methods. Model inference under the recommended settings to account for autocorrelation was not impacted by clumping or restriction of data, except for the complexity of the spatial regression term in the spatial Bayesian model. Methods, such as those made available by R-INLA, can be successfully used to account for spatial

  12. Evaporation-driven clustering of microscale pillars and lamellae

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kim, Tae-Hong; Kim, Jungchul; Kim, Ho-Young, E-mail: hyk@snu.ac.kr

    As a liquid film covering an array of micro- or nanoscale pillars or lamellae evaporates, its meniscus pulls the elastic patterns together because of capillary effects, leading to clustering of the slender microstructures. While this elastocapillary coalescence may imply various useful applications, it is detrimental to a semiconductor manufacturing process called the spin drying, where a liquid film rinses patterned wafers until drying. To understand the transient mechanism underlying such self-organization during and after liquid evaporation, we visualize the clustering dynamics of polymer micropatterns. Our visualization experiments reveal that the patterns clumped during liquid evaporation can be re-separated when completelymore » dried in some cases. This restoration behavior is explained by considering adhesion energy of the patterns as well as capillary forces, which leads to a regime map to predict whether permanent stiction would occur. This work does not only extend our understanding of micropattern stiction, but also suggests a novel path to control and prevent pattern clustering.« less

  13. Modeling the effects of diagenesis on carbonate clumped-isotope values in deep- and shallow-water settings

    NASA Astrophysics Data System (ADS)

    Stolper, Daniel A.; Eiler, John M.; Higgins, John A.

    2018-04-01

    The measurement of multiply isotopically substituted ('clumped isotope') carbonate groups provides a way to reconstruct past mineral formation temperatures. However, dissolution-reprecipitation (i.e., recrystallization) reactions, which commonly occur during sedimentary burial, can alter a sample's clumped-isotope composition such that it partially or wholly reflects deeper burial temperatures. Here we derive a quantitative model of diagenesis to explore how diagenesis alters carbonate clumped-isotope values. We apply the model to a new dataset from deep-sea sediments taken from Ocean Drilling Project site 807 in the equatorial Pacific. This dataset is used to ground truth the model. We demonstrate that the use of the model with accompanying carbonate clumped-isotope and carbonate δ18O values provides new constraints on both the diagenetic history of deep-sea settings as well as past equatorial sea-surface temperatures. Specifically, the combination of the diagenetic model and data support previous work that indicates equatorial sea-surface temperatures were warmer in the Paleogene as compared to today. We then explore whether the model is applicable to shallow-water settings commonly preserved in the rock record. Using a previously published dataset from the Bahamas, we demonstrate that the model captures the main trends of the data as a function of burial depth and thus appears applicable to a range of depositional settings.

  14. Spectroscopic and functional characterization of iron-sulfur cluster-bound forms of Azotobacter vinelandii (Nif)IscA.

    PubMed

    Mapolelo, Daphne T; Zhang, Bo; Naik, Sunil G; Huynh, Boi Hanh; Johnson, Michael K

    2012-10-16

    The mechanism of [4Fe-4S] cluster assembly on A-type Fe-S cluster assembly proteins, in general, and the specific role of (Nif)IscA in the maturation of nitrogen fixation proteins are currently unknown. To address these questions, in vitro spectroscopic studies (UV-visible absorption/CD, resonance Raman and Mössbauer) have been used to investigate the mechanism of [4Fe-4S] cluster assembly on Azotobacter vinelandii(Nif)IscA, and the ability of (Nif)IscA to accept clusters from NifU and to donate clusters to the apo form of the nitrogenase Fe-protein. The results show that (Nif)IscA can rapidly and reversibly cycle between forms containing one [2Fe-2S](2+) and one [4Fe-4S](2+) cluster per homodimer via DTT-induced two-electron reductive coupling of two [2Fe-2S](2+) clusters and O(2)-induced [4Fe-4S](2+) oxidative cleavage. This unique type of cluster interconversion in response to cellular redox status and oxygen levels is likely to be important for the specific role of A-type proteins in the maturation of [4Fe-4S] cluster-containing proteins under aerobic growth or oxidative stress conditions. Only the [4Fe-4S](2+)-(Nif)IscA was competent for rapid activation of apo-nitrogenase Fe protein under anaerobic conditions. Apo-(Nif)IscA was shown to accept clusters from [4Fe-4S] cluster-bound NifU via rapid intact cluster transfer, indicating a potential role as a cluster carrier for delivery of clusters assembled on NifU. Overall the results support the proposal that A-type proteins can function as carrier proteins for clusters assembled on U-type proteins and suggest that they are likely to supply [2Fe-2S] clusters rather than [4Fe-4S] for the maturation of [4Fe-4S] cluster-containing proteins under aerobic or oxidative stress growth conditions.

  15. Spectroscopic and Functional Characterization of Iron-Sulfur Cluster-Bound Forms of Azotobacter vinelandii NifIscA†

    PubMed Central

    Mapolelo, Daphne T.; Zhang, Bo; Naik, Sunil G.; Huynh, Boi Hanh; Johnson, Michael K.

    2012-01-01

    The mechanism of [4Fe-4S] cluster assembly on A-type Fe-S cluster assembly proteins, in general, and the specific role of NifIscA in the maturation of nitrogen fixation proteins are currently unknown. To address these questions, in vitro spectroscopic studies (UV–visible absorption/CD, resonance Raman and Mössbauer) have been used to investigate the mechanism of [4Fe-4S] cluster assembly on Azotobacter vinelandii NifIscA, and the ability of NifIscA to accept clusters from NifU and to donate clusters to the apo form of the nitrogenase Fe-protein. The results show that NifIscA can rapidly and reversibly cycle between forms containing one [2Fe-2S]2+ and one [4Fe-4S]2+ cluster per homodimer via DTT-induced two-electron reductive coupling of two [2Fe-2S]2+ clusters and O2-induced [4Fe-4S]2+ oxidative cleavage. This unique type of cluster interconversion in response to cellular redox status and oxygen levels is likely to be important for the specific role of A-type proteins in the maturation of [4Fe-4S] cluster-containing proteins under aerobic growth or oxidative stress conditions. Only the [4Fe-4S]2+-NifIscA was competent for rapid activation of apo-nitrogenase Fe protein under anaerobic conditions. Apo-NifIscA was shown to accept clusters from [4Fe-4S] cluster-bound NifU via rapid intact cluster transfer, indicating a potential role as a cluster carrier for delivery of clusters assembled on NifU. Overall the results support the proposal that A-type proteins can function as carrier proteins for clusters assembled on U-type proteins and suggest that they are likely to supply [2Fe-2S] clusters rather than [4Fe-4S] for the maturation of [4Fe-4S] cluster-containing proteins under aerobic or oxidative stress growth conditions. PMID:23003323

  16. Carbonate clumped-isotope constraints on the burial and exhumation history of the Colorado Plateau

    NASA Astrophysics Data System (ADS)

    Ryb, U.; Lloyd, M. K.; Eiler, J. M.

    2016-12-01

    Reconstruction of the thermal history of rocks is key to study the geodynamic evolution of sedimentary basins. Carbonate clumped-isotope measurements of minerals formed or re-equilibrated at elevated temperatures can constrain thermal histories of rocks. Experimental constraints on solid state isotopic reordering in carbonates let us translate clumped-isotope measurements into quantitative statements about the thermal history, and thus burial and exhumation. We use this approach to constrain peak burial temperatures of Paleozoic rocks across the Colorado Plateau, sampled carbonate rocks from the southwestern Plateau margin and from borehole cores in the Plateau interior. We sub-sampled specific fabrics (fossils, cements, etc.), determined their calcite and dolomite proportions using XRD, and analyzed clumped-isotope compositions (reported as apparent temperatures using Stolper and Eiler's (2015) calibration) for pure calcite or dolomite samples (>97 wt.%). At the Plateau margin, calcite and dolomite apparent temperatures are 49-79°C and 67-97°C, respectively. The maximum apparent temperature constrains the minimum peak burial temperature. The distribution of calcite apparent temperatures independently constrains the maximum burial temperature as follows: If the "coldest" sample had an initial apparent temperature of 20°C, then its observed value can be explained by isotopic reordering to a peak temperature of 105-120°C. We therefore hypothesize peak temperature at the base of the Paleozoic was 97-120°C. At the Plateau interior, apparent temperatures of Mississippian calcite samples are depth-dependent: Samples cored from <2km depth have apparent temperatures of 54-68°C; similar samples from 3km depth have apparent temperatures of 105-165°C and a smaller variability between sub-samples, interpreted to result from isotopic reordering at >150°C. Assuming a surface temperature of 20°C and a thermal gradient of 25°C km-1, we calculate total overburden (above

  17. Weak and Compact Radio Emission in Early High-Mass Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Rosero, Viviana; P. Hofner, M. Claussen, S. Kurtz, R. Cesaroni, E. D. Araya, C. Carrasco-González, L. F. Rodríguez, K. M. Menten, F. Wyrowski, L. Loinard, S. P. Ellingsen

    2018-01-01

    High-mass protostars are difficult to detect: they have short evolutionary timescales, they tend to be located at large distances, and they are usually embedded within complicated cluster environments. In this work, we aimed to identify and analyze candidates at the earliest stages of high-mass star formation, where only low-level (< 1 mJy) radio emission is expected. We used the Karl G. Jansky Very Large Array to achieve one of the most sensitive (image RMS < 3 -- 10 μJy/beam) centimeter continuum surveys towards high-mass star forming regions to date, with observations at 1.3 and 6 cm and an angular resolution < 0.5". The sample is composed of cold molecular clumps with and without infrared sources (CMC--IRs and CMCs, respectively) and hot molecular cores (HMCs), covering a wide range of parameters such as bolometric luminosity and distance. We detected 70 radio continuum sources that are associated with dust clumps, most of which are weak and compact. We detected centimeter wavelength sources in 100% of our HMCs, which is a higher fraction than previously expected and suggests that radio continuum may be detectable at weak levels in all HMCs. The lack of radio detections for some objects in the sample (including most CMCs) contributes strong evidence that these are prestellar clumps, providing interesting constraints and ideal follow up candidates for studies of the earliest stages of high-mass stars. Our results show further evidence for an evolutionary sequence in the formation of high-mass stars, from starless cores (i.e., CMCs) to relatively more evolved ones (i.e., HMCs). Many of our detections have morphologies and other observational parameters that resemble collimated ionized jets, which is highly relevant for recent theoretical models based on core accretion that predict that the first stages of ionization from high-mass stars are in the form of jets. Additionally, we found that properties of ionized jets from low and high-mass stars are extremely well

  18. Aggregated Clumps of Lithistid Sponges: A Singular, Reef-Like Bathyal Habitat with Relevant Paleontological Connections

    PubMed Central

    Maldonado, Manuel; Aguilar, Ricardo; Blanco, Jorge; García, Silvia; Serrano, Alberto; Punzón, Antonio

    2015-01-01

    The advent of deep-sea exploration using video cameras has uncovered extensive sponge aggregations in virtually all oceans. Yet, a distinct type is herein reported from the Mediterranean: a monospecific reef-like formation built by the lithistid demosponge Leiodermatium pfeifferae. Erect, plate-like individuals (up to 80 cm) form bulky clumps, making up to 1.8 m high mounds (1.14 m on average) on the bottom, at a 760 m-deep seamount named SSS. The siliceous skeletal frameworks of the lithistids persist after sponge death, serving as a complex 3D substratum where new lithistids recruit, along with a varied fauna of other sessile and vagile organisms. The intricate aggregation of lithistid mounds functions as a “reef” formation, architecturally different from the archetypal "demosponge gardens" with disaggregating siliceous skeletons. Leiodermatium pfeifferae also occurred at two additional, close seamounts (EBJ and EBS), but, unlike at SSS, the isolated individuals never formed accretive clumps. The general oceanographic variables (temperature, salinity, dissolved nutrients, chlorophyll, and oxygen) revealed only minimal between-seamount differences, which cannot explain why sponge abundance at SSS is about two orders of magnitude higher than at EBJ or EBS. Large areas of the dense SSS aggregation were damaged, with detached and broken sponges and a few tangled fishing lines. Satellite vessel monitoring revealed low fishing activity around these seamounts. In contrast, international plans for gas and oil extraction at those locations raise serious concerns over the need for protecting urgently this unique, vulnerable habitat to avoid further alteration. Modern lithistids are a relict fauna from Jurassic and Cretaceous reefs and the roots of the very genus Leiodermatium can be traced back to those fossil formations. Therefore, understanding the causes behind the discovered lithistid aggregation is critical not only to its preservation, but also to elucidate how

  19. Star-forming brightest cluster galaxies at 0.25 < z < 1.25: A transitioning fuel supply

    DOE PAGES

    McDonald, M.; Stalder, B.; Bayliss, M.; ...

    2016-01-22

    In this paper, we present a multiwavelength study of the 90 brightest cluster galaxies (BCGs) in a sample of galaxy clusters selected via the Sunyaev Zel'dovich effect by the South Pole Telescope, utilizing data from various ground- and space-based facilities. We infer the star-formation rate (SFR) for the BCG in each cluster—based on the UV and IR continuum luminosity, as well as the [O ii]λλ3726,3729 emission line luminosity in cases where spectroscopy is available—and find seven systems with SFR > 100 M ⊙ yr -1. We find that the BCG SFR exceeds 10 M ⊙ yr -1 in 31 of 90 (34%) cases at 0.25 < z < 1.25, compared to ~1%–5% at z ~ 0 from the literature. At z ≳ 1, this fraction increases tomore » $${92}_{-31}^{+6}$$%, implying a steady decrease in the BCG SFR over the past ~9 Gyr. At low-z, we find that the specific SFR in BCGs is declining more slowly with time than for field or cluster galaxies, which is most likely due to the replenishing fuel from the cooling ICM in relaxed, cool core clusters. At z ≳ 0.6, the correlation between the cluster central entropy and BCG star formation—which is well established at z ~ 0—is not present. Instead, we find that the most star-forming BCGs at high-z are found in the cores of dynamically unrelaxed clusters. We use data from the Hubble Space Telescope to investigate the rest-frame near-UV morphology of a subsample of the most star-forming BCGs, and find complex, highly asymmetric UV morphologies on scales as large as ~50–60 kpc. Finally, the high fraction of star-forming BCGs hosted in unrelaxed, non-cool core clusters at early times suggests that the dominant mode of fueling star formation in BCGs may have recently transitioned from galaxy–galaxy interactions to ICM cooling.« less

  20. Rotational and radial velocities of 1.3-2.2 M {sub ☉} red giants in open clusters

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Carlberg, Joleen K., E-mail: jcarlberg@dtm.ciw.edu

    2014-06-01

    This study presents the rotational distribution of red giant (RG) stars in 11 old to intermediate age open clusters. The masses of these stars are all above the Kraft break, so they lose negligible amounts of their birth angular momentum (AM) during the main-sequence (MS) evolution. However, they do span a mass range with quite different AM distributions imparted during formation, with the stars less massive than ∼1.6M {sub ☉} arriving on the MS with lower rotation rates than the more massive stars. The majority of RGs in this study are slow rotators across the entire red giant branch regardlessmore » of mass, supporting the picture that intermediate-mass stars rapidly spin down when they evolve off the MS and develop convection zones capable of driving a magnetic dynamo. Nevertheless, a small fraction of RGs in open clusters show some level of enhanced rotation, and faster rotators are as common in these clusters as in the field RG population. Most of these enhanced rotators appear to be red clump stars, which is also true of the underlying stellar sample, while others are clearly RGs that are above or below the clump. In addition to rotational velocities, the radial velocities (RVs) and membership probabilities of individual stars are also presented. Cluster heliocentric RVs for NGC 6005 and Pismis 18 are reported for the first time.« less

  1. Clumped isotope calibration data for lacustrine carbonates: A progress report

    NASA Astrophysics Data System (ADS)

    Tripati, A.

    2015-12-01

    Our capacity to understand Earth's environmental history is highly dependent on the accuracy of reconstructions of past climates. Lake sediments provide important archives of terrestrial climate change, and represent an important tool for reconstructing paleohydrology, paleoclimate, paleoenvironment, and paleoaltimetry. Unfortunately, while multiple methods for constraining marine temperature exist, quantitative terrestrial proxies are scarcer - tree rings, speleothems, and leaf margin analyses have all been used with varying degrees of accuracy. Clumped isotope thermometry has the potential to be a useful instrument for determining terrestrial climates: multiple studies have shown the fraction of 13C—18O bonds in carbonates is inversely related to the temperature at which the rocks formed. We have been measuring the abundance of 13C18O16O in the CO2 produced by the dissolution of carbonate minerals in phosphoric acid in modern lake samples and comparing results to independently known estimates of lake water temperature. Here we discuss an extensive calibration dataset comprised of 132 analyses of 97 samples from 44 localities, including microbialites, tufas, and micrites endogenic carbonates, freshwater gastropods, bivalves, microbialites, and ooids.

  2. Clumped Isotope Thermometry Reveals Variations in Soil Carbonate Seasonal Biases Over >4 km of Relief in the Semi-Arid Andes of Central Chile

    NASA Astrophysics Data System (ADS)

    Burgener, L. K.; Huntington, K. W.; Hoke, G. D.; Schauer, A. J.; Ringham, M. C.; Latorre Hidalgo, C.; Díaz, F.

    2015-12-01

    The application of carbonate clumped isotope thermometry to soil carbonates has the potential to shed new light on questions regarding terrestrial paleoclimate. In order to better utilize this paleoclimate tool, outstanding questions regarding seasonal biases in soil carbonate formation and the relationship between soil carbonate formation temperatures (T(Δ47)) and surface temperatures must be resolved. We address these questions by comparing C, O, and clumped isotope data from Holocene/modern soil carbonates to modern meteorological data. The data were collected along a 170 km transect with >4 km of relief in central Chile (~30°S). Previous studies have suggested that soil carbonates should record a warm season bias and form in isotopic equilibrium with soil water and soil CO2. We identify two discrete climate zones separated by the local winter snow line (~3200 m). Below this boundary, precipitation falls as rain and soil carbonate T(Δ47) values at depths >40 cm resemble summer soil temperatures; at higher elevations, precipitation falls as snow and T(Δ47) values resemble mean annual soil temperatures. Soil carbonates from the highest sample site (4700 m), which is devoid of vegetation and located near perennial snow fields, yield anomalous δ18O, δ13C, and T(Δ47) values, indicative of kinetic isotope effects that we attribute to cryogenic carbonate formation. Our results suggest that soil carbonates from depths <40 cm are affected by large, high frequency variations in temperature and precipitation, and should not be used as paleotemperature proxies. These findings (1) highlight the role of soil moisture in modulating soil carbonate formation and the resulting T(Δ47) values, (2) underscore the importance of understanding past soil moisture conditions when attempting to reconstruct paleotemperatures using carbonate clumped isotope thermometry, and (3) suggest that soil carbonates from high elevation or high latitude sites may form under non

  3. Constraining the Thermal History of the Midcontinent Rift System with Clumped Isotopes and Organic Thermal Maturity Indices

    NASA Astrophysics Data System (ADS)

    Gallagher, T. M.; Sheldon, N. D.; Mauk, J. L.; Gueneli, N.; Brocks, J. J.

    2015-12-01

    The Mesoproterozoic (~1.1 Ga) North American Midcontinent Rift System (MRS) has been of widespread interest to researchers studying its economic mineral deposits, continental rifting processes, and the evolution of early terrestrial life and environments. For their age, the MRS rocks are well preserved and have not been deeply buried, yet a thorough understanding of the regional thermal history is necessary to constrain the processes that emplaced the mineral deposits and how post-burial alteration may have affected various paleo-records. To understand the thermal history of the MRS better, this study presents carbonate clumped isotope (Δ47) temperatures from deposits on the north and south sides of the rift. Due to the age of these deposits and known post-depositional processes, uncertainties exist about whether the clumped isotope signature has been reset. To test this, three generations of calcite were analyzed from the Nonesuch Fm. from the White Pine mine in Michigan including: sedimentary limestone beds, early diagenetic carbonate nodules, and hydrothermal calcite veins associated with the emplacement of copper mineralization. Clumped isotope temperatures from the White Pine mine range from 84 to 131°C, with a hydrothermal vein producing the hottest temperature. The clumped isotope temperature range for samples throughout the rift expands to 41-134°C. The hottest temperatures are associated with areas of known copper mineralization, whereas the coolest temperatures are found on the northern arm of the rift in Minnesota, far from known basin-bounding faults. Our hottest temperatures are broadly consistent with preexisting maximum thermal temperature estimates based on clay mineralogy, fluid inclusions, and organic geochemistry data. Clumped isotope results will also be compared to new hydrocarbon maturity data from the Nonesuch Fm., which suggest that bitumen maturities consistently fall within the early oil window across Michigan and Wisconsin.

  4. Reconstruction of cluster masses using particle based lensing

    NASA Astrophysics Data System (ADS)

    Deb, Sanghamitra

    Clusters of galaxies are among the richest astrophysical data systems, but to truly understand these systems, we need a detailed study of the relationship between observables and the underlying cluster dark matter distribution. Gravitational lensing is the most direct probe of dark matter, but many mass reconstruction techniques assume that cluster light traces mass, or combine different lensing signals in an ad hoc way. In this talk, we will describe "Particle Based Lensing" (PBL), a new method for cluster mass reconstruction, that avoids many of the pitfalls of previous techniques. PBL optimally combines lensing information of varying signal-to-noise, and makes no assumptions about the relationship between mass and light. We will describe mass reconstructions in three very different, but very illuminating cluster systems: the "Bullet Cluster" (lE 0657-56), A901/902 and A1689. The "Bullet Cluster" is a system of merging clusters made famous by the first unambiguous lensing detection of dark matter. A901/902 is a multi-cluster system with four peaks, and provides an ideal laboratory for studying cluster interaction. We are particularly interested in measuring and correlating the dark matter clump ellipticities. A1689 is one of the richest clusters known, and has significant substructure at the core. It is also my first exercise in optimally combining weak and strong gravitational lensing in a cluster reconstruction. We find that the dark matter distribution is significantly clumpier than indicated by X-ray maps of the gas. We conclude by discussing various potential applications of PBL to existing and future data.

  5. Cluster Masses Derived from X-ray and Sunyaev-Zeldovich Effect Measurements

    NASA Technical Reports Server (NTRS)

    Laroque, S.; Joy, Marshall; Bonamente, M.; Carlstrom, J.; Dawson, K.

    2003-01-01

    We infer the gas mass and total gravitational mass of 11 clusters using two different methods; analysis of X-ray data from the Chandra X-ray Observatory and analysis of centimeter-wave Sunyaev-Zel'dovich Effect (SZE) data from the BIMA and OVRO interferometers. This flux-limited sample of clusters from the BCS cluster catalogue was chosen so as to be well above the surface brightness limit of the ROSAT All Sky Survey; this is therefore an orientation unbiased sample. The gas mass fraction, f_g, is calculated for each cluster using both X-ray and SZE data, and the results are compared at a fiducial radius of r_500. Comparison of the X-ray and SZE results for this orientation unbiased sample allows us to constrain cluster systematics, such as clumping of the intracluster medium. We derive an upper limit on Omega_M assuming that the mass composition of clusters within r_500 reflects the universal mass composition Omega_M h_100 is greater than Omega _B / f-g. We also demonstrate how the mean f_g derived from the sample can be used to estimate the masses of clusters discovered by upcoming deep SZE surveys.

  6. The clumped-isotope geochemistry of exhumed marbles from Naxos, Greece

    NASA Astrophysics Data System (ADS)

    Ryb, U.; Lloyd, M. K.; Stolper, D. A.; Eiler, J. M.

    2017-07-01

    Exhumation and accompanying retrograde metamorphism alter the compositions and textures of metamorphic rocks through deformation, mineral-mineral reactions, water-rock reactions, and diffusion-controlled intra- and inter-mineral atomic mobility. Here, we demonstrate that these processes are recorded in the clumped- and single-isotope (δ13 C and δ18 O) compositions of marbles, which can be used to constrain retrograde metamorphic histories. We collected 27 calcite and dolomite marbles along a transect from the rim to the center of the metamorphic core-complex of Naxos (Greece), and analyzed their carbonate single- and clumped-isotope compositions. The majority of Δ47 values of whole-rock samples are consistent with exhumation- controlled cooling of the metamorphic complex. However, the data also reveal that water-rock interaction, deformation driven recrystallization and thermal shock associated with hydrothermal alteration may considerably impact the overall distribution of Δ47 values. We analyzed specific carbonate fabrics influenced by deformation and fluid-rock reaction to study how these processes register in the carbonate clumped-isotope system. Δ47 values of domains drilled from a calcite marble show a bimodal distribution. Low Δ47 values correspond to an apparent temperature of 260 °C and are common in static fabrics; high Δ47 values correspond to an apparent temperature of 200 °C and are common in dynamically recrystallized fabrics. We suggest that the low Δ47 values reflect diffusion-controlled isotopic reordering during cooling, whereas high Δ47 values reflect isotopic reordering driven by dynamic recrystallization. We further studied the mechanism by which dynamic recrystallization may alter Δ47 values by controlled heating experiments. Results show no significant difference between laboratory reactions rates in the static and dynamic fabrics, consistent with a mineral-extrinsic mechanism, in which slip along crystal planes was associated

  7. Characterization of [4Fe-4S]-containing and cluster-free forms of Streptomyces WhiD

    PubMed Central

    Crack, Jason C.; den Hengst, Chris D.; Jakimowicz, Piotr; Subramanian, Sowmya; Johnson, Michael K.; Buttner, Mark J.; Thomson, Andrew J.; Le Brun, Nick E.

    2009-01-01

    WhiD, a member of the WhiB-like (Wbl) family of iron-sulfur proteins found exclusively within the actinomycetes, is required for the late stages of sporulation in Streptomyces coelicolor. Like all other Wbl proteins, WhiD has not so far been purified in a soluble form that contains a significant amount of cluster and characterization has relied on cluster-reconstituted protein. Thus, a major goal in Wbl research is to obtain and characterize native protein containing iron-sulfur clusters. Here we report the analysis of S. coelicolor WhiD purified anaerobically from E. coli as a soluble protein containing a single [4Fe-4S]2+ cluster ligated by four cysteines. Upon exposure to oxygen, spectral features associated with the [4Fe-4S] cluster were lost in a slow reaction that unusually yielded apo-WhiD directly without significant concentrations of cluster intermediates. This process was found to be highly pH dependent with an optimal stability observed between pH 7.0 and 8.0. Low molecular weight thiols, including a mycothiol analogue and thioredoxin, exerted a small but significant protective effect against WhiD cluster loss, an activity that could be of physiological importance. [4Fe-4S]2+ WhiD was found to react much more rapidly with superoxide than with either oxygen or hydrogen peroxide, which may also be of physiological significance. Loss of the [4Fe-4S] cluster to form apo-protein destabilized the protein fold significantly, but did not lead to complete unfolding. Finally, apo-WhiD exhibited negligible activity in an insulin-based disulfide reductase assay demonstrating that it does not function as a general protein disulfide reductase. PMID:19954209

  8. BARNARD 59: NO EVIDENCE FOR FURTHER FRAGMENTATION

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Roman-Zuniga, C. G.; Frau, P.; Girart, J. M.

    2012-03-10

    The dense molecular clump at the center of the Barnard 59 (B59) complex is the only region in the Pipe Nebula that has formed a small, stellar cluster. The previous analysis of a high-resolution near-IR dust extinction map revealed that the nuclear region in B59 is a massive, mostly quiescent clump of 18.9 M{sub Sun }. The clump shows a monolithic profile, possibly indicating that the clump is on the way to collapse, with no evident fragmentation that could lead to another group of star systems. In this paper, we present new analysis that compares the dust extinction map withmore » a new dust emission radio-continuum map of higher spatial resolution. We confirm that the clump does not show any significant evidence for prestellar fragmentation at scales smaller than those probed previously.« less

  9. The transiting dust clumps in the evolved disc of the Sun-like UXor RZ Psc

    PubMed Central

    Kenworthy, Matthew A.; Pepper, Joshua; Rodriguez, Joseph E.; Siverd, Robert J.; Stassun, Keivan G.; Wyatt, Mark C.

    2017-01-01

    RZ Psc is a young Sun-like star, long associated with the UXor class of variable stars, which is partially or wholly dimmed by dust clumps several times each year. The system has a bright and variable infrared excess, which has been interpreted as evidence that the dimming events are the passage of asteroidal fragments in front of the host star. Here, we present a decade of optical photometry of RZ Psc and take a critical look at the asteroid belt interpretation. We show that the distribution of light curve gradients is non-uniform for deep events, which we interpret as possible evidence for an asteroidal fragment-like clump structure. However, the clumps are very likely seen above a high optical depth midplane, so the disc’s bulk clumpiness is not revealed. While circumstantial evidence suggests an asteroid belt is more plausible than a gas-rich transition disc, the evolutionary status remains uncertain. We suggest that the rarity of Sun-like stars showing disc-related variability may arise because (i) any accretion streams are transparent and/or (ii) turbulence above the inner rim is normally shadowed by a flared outer disc. PMID:28280566

  10. The transiting dust clumps in the evolved disc of the Sun-like UXor RZ Psc

    NASA Astrophysics Data System (ADS)

    Kennedy, Grant M.; Kenworthy, Matthew A.; Pepper, Joshua; Rodriguez, Joseph E.; Siverd, Robert J.; Stassun, Keivan G.; Wyatt, Mark C.

    2017-01-01

    RZ Psc is a young Sun-like star, long associated with the UXor class of variable stars, which is partially or wholly dimmed by dust clumps several times each year. The system has a bright and variable infrared excess, which has been interpreted as evidence that the dimming events are the passage of asteroidal fragments in front of the host star. Here, we present a decade of optical photometry of RZ Psc and take a critical look at the asteroid belt interpretation. We show that the distribution of light curve gradients is non-uniform for deep events, which we interpret as possible evidence for an asteroidal fragment-like clump structure. However, the clumps are very likely seen above a high optical depth midplane, so the disc's bulk clumpiness is not revealed. While circumstantial evidence suggests an asteroid belt is more plausible than a gas-rich transition disc, the evolutionary status remains uncertain. We suggest that the rarity of Sun-like stars showing disc-related variability may arise because (i) any accretion streams are transparent and/or (ii) turbulence above the inner rim is normally shadowed by a flared outer disc.

  11. The transiting dust clumps in the evolved disc of the Sun-like UXor RZ Psc.

    PubMed

    Kennedy, Grant M; Kenworthy, Matthew A; Pepper, Joshua; Rodriguez, Joseph E; Siverd, Robert J; Stassun, Keivan G; Wyatt, Mark C

    2017-01-01

    RZ Psc is a young Sun-like star, long associated with the UXor class of variable stars, which is partially or wholly dimmed by dust clumps several times each year. The system has a bright and variable infrared excess, which has been interpreted as evidence that the dimming events are the passage of asteroidal fragments in front of the host star. Here, we present a decade of optical photometry of RZ Psc and take a critical look at the asteroid belt interpretation. We show that the distribution of light curve gradients is non-uniform for deep events, which we interpret as possible evidence for an asteroidal fragment-like clump structure. However, the clumps are very likely seen above a high optical depth midplane, so the disc's bulk clumpiness is not revealed. While circumstantial evidence suggests an asteroid belt is more plausible than a gas-rich transition disc, the evolutionary status remains uncertain. We suggest that the rarity of Sun-like stars showing disc-related variability may arise because (i) any accretion streams are transparent and/or (ii) turbulence above the inner rim is normally shadowed by a flared outer disc.

  12. The Spatial Distribution of the Young Stellar Clusters in the Star-forming Galaxy NGC 628

    NASA Astrophysics Data System (ADS)

    Grasha, K.; Calzetti, D.; Adamo, A.; Kim, H.; Elmegreen, B. G.; Gouliermis, D. A.; Aloisi, A.; Bright, S. N.; Christian, C.; Cignoni, M.; Dale, D. A.; Dobbs, C.; Elmegreen, D. M.; Fumagalli, M.; Gallagher, J. S., III; Grebel, E. K.; Johnson, K. E.; Lee, J. C.; Messa, M.; Smith, L. J.; Ryon, J. E.; Thilker, D.; Ubeda, L.; Wofford, A.

    2015-12-01

    We present a study of the spatial distribution of the stellar cluster populations in the star-forming galaxy NGC 628. Using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey), we have identified 1392 potential young (≲ 100 Myr) stellar clusters within the galaxy using a combination of visual inspection and automatic selection. We investigate the clustering of these young stellar clusters and quantify the strength and change of clustering strength with scale using the two-point correlation function. We also investigate how image boundary conditions and dust lanes affect the observed clustering. The distribution of the clusters is well fit by a broken power law with negative exponent α. We recover a weighted mean index of α ∼ -0.8 for all spatial scales below the break at 3.″3 (158 pc at a distance of 9.9 Mpc) and an index of α ∼ -0.18 above 158 pc for the accumulation of all cluster types. The strength of the clustering increases with decreasing age and clusters older than 40 Myr lose their clustered structure very rapidly and tend to be randomly distributed in this galaxy, whereas the mass of the star cluster has little effect on the clustering strength. This is consistent with results from other studies that the morphological hierarchy in stellar clustering resembles the same hierarchy as the turbulent interstellar medium.

  13. On the statistics of proto-cluster candidates detected in the Planck all-sky survey

    NASA Astrophysics Data System (ADS)

    Negrello, M.; Gonzalez-Nuevo, J.; De Zotti, G.; Bonato, M.; Cai, Z.-Y.; Clements, D.; Danese, L.; Dole, H.; Greenslade, J.; Lapi, A.; Montier, L.

    2017-09-01

    Observational investigations of the abundance of massive precursors of local galaxy clusters ('proto-clusters') allow us to test the growth of density perturbations, to constrain cosmological parameters that control it, to test the theory of non-linear collapse and how the galaxy formation takes place in dense environments. The Planck collaboration has recently published a catalogue of ≳2000 cold extragalactic sub-millimeter sources, I.e. with colours indicative of z ≳ 2, almost all of which appear to be overdensities of star-forming galaxies. They are thus considered as proto-cluster candidates. Their number densities (or their flux densities) are far in excess of expectations from the standard scenario for the evolution of large-scale structure. Simulations based on a physically motivated galaxy evolution model show that essentially all cold peaks brighter than S545GHz = 500 mJy found in Planck maps after having removed the Galactic dust emission can be interpreted as positive Poisson fluctuations of the number of high-z dusty proto-clusters within the same Planck beam, rather then being individual clumps of physically bound galaxies. This conclusion does not change if an empirical fit to the luminosity function of dusty galaxies is used instead of the physical model. The simulations accurately reproduce the statistic of the Planck detections and yield distributions of sizes and ellipticities in qualitative agreement with observations. The redshift distribution of the brightest proto-clusters contributing to the cold peaks has a broad maximum at 1.5 ≤ z ≤ 3. Therefore follow-up of Planck proto-cluster candidates will provide key information on the high-z evolution of large scale structure.

  14. Advances in Significance Testing for Cluster Detection

    NASA Astrophysics Data System (ADS)

    Coleman, Deidra Andrea

    Over the past two decades, much attention has been given to data driven project goals such as the Human Genome Project and the development of syndromic surveillance systems. A major component of these types of projects is analyzing the abundance of data. Detecting clusters within the data can be beneficial as it can lead to the identification of specified sequences of DNA nucleotides that are related to important biological functions or the locations of epidemics such as disease outbreaks or bioterrorism attacks. Cluster detection techniques require efficient and accurate hypothesis testing procedures. In this dissertation, we improve upon the hypothesis testing procedures for cluster detection by enhancing distributional theory and providing an alternative method for spatial cluster detection using syndromic surveillance data. In Chapter 2, we provide an efficient method to compute the exact distribution of the number and coverage of h-clumps of a collection of words. This method involves defining a Markov chain using a minimal deterministic automaton to reduce the number of states needed for computation. We allow words of the collection to contain other words of the collection making the method more general. We use our method to compute the distributions of the number and coverage of h-clumps in the Chi motif of H. influenza.. In Chapter 3, we provide an efficient algorithm to compute the exact distribution of multiple window discrete scan statistics for higher-order, multi-state Markovian sequences. This algorithm involves defining a Markov chain to efficiently keep track of probabilities needed to compute p-values of the statistic. We use our algorithm to identify cases where the available approximation does not perform well. We also use our algorithm to detect unusual clusters of made free throw shots by National Basketball Association players during the 2009-2010 regular season. In Chapter 4, we give a procedure to detect outbreaks using syndromic

  15. Properties of compact HII regions and their host clumps in the inner vs outer Galaxy - early results from SASSy

    NASA Astrophysics Data System (ADS)

    Djordjevic, Julie; Thompson, Mark; Urquhart, James S.

    2017-01-01

    We present a catalog of compact and ultracompact HII regions for all Galactocentric radii. Previous catalogs focus on the inner Galaxy (Rgal ≤ 8 kpc) but the recent SASSy 870 µm survey allows us to identify regions out to ~20 kpc. Early samples are also filled with false classifications leading to uncertainty when deriving star formation efficiencies in Galactic models. These objects have similar mid-IR colours to HII regions. Urquhart et al. (2013) found that they could use mid-IR, submm, and radio data to identify the genuine compact HII regions, avoiding confusion. They used this method on a small portion of the Galaxy (10 < l < 60), identifying 213 HII regions embedded in 170 clumps. We use ATLASGAL and SASSy, crossmatched with RMS, to sample the remaining galactic longitudes out to Rgal = 20 kpc. We derive the properties of the identified compact HII regions and their host clumps while addressing the implications for recent massive star formation in the outer Galaxy. Observations towards nearby galaxies are biased towards massive stars, affecting simulations and overestimating models for galactic evolution and star formation rates. The Milky Way provides the ideal template for studying factors affecting massive star formation rates and efficiencies at high resolution, thus fine-tuning those models. We find that there is no significant change in the rate of massive star formation in the outer vs inner Galaxy. Despite some peaks in known complexes and possible correlation with spiral arms, the outer Galaxy appears to produce massive stars as efficiently as the inner regions. However, many of the potential star forming SASSy clumps have no available radio counterpart to confirm the presence of an HII region or other star formation tracer. Follow-up observations will be required to verify this conclusion and are currently in progress.

  16. Cause and Effect of Feedback: Multiphase Gas in Cluster Cores Heated by AGN Jets

    NASA Astrophysics Data System (ADS)

    Gaspari, M.; Ruszkowski, M.; Sharma, P.

    2012-02-01

    Multiwavelength data indicate that the X-ray-emitting plasma in the cores of galaxy clusters is not cooling catastrophically. To a large extent, cooling is offset by heating due to active galactic nuclei (AGNs) via jets. The cool-core clusters, with cooler/denser plasmas, show multiphase gas and signs of some cooling in their cores. These observations suggest that the cool core is locally thermally unstable while maintaining global thermal equilibrium. Using high-resolution, three-dimensional simulations we study the formation of multiphase gas in cluster cores heated by collimated bipolar AGN jets. Our key conclusion is that spatially extended multiphase filaments form only when the instantaneous ratio of the thermal instability and free-fall timescales (t TI/t ff) falls below a critical threshold of ≈10. When this happens, dense cold gas decouples from the hot intracluster medium (ICM) phase and generates inhomogeneous and spatially extended Hα filaments. These cold gas clumps and filaments "rain" down onto the central regions of the core, forming a cold rotating torus and in part feeding the supermassive black hole. Consequently, the self-regulated feedback enhances AGN heating and the core returns to a higher entropy level with t TI/t ff > 10. Eventually, the core reaches quasi-stable global thermal equilibrium, and cold filaments condense out of the hot ICM whenever t TI/t ff <~ 10. This occurs despite the fact that the energy from AGN jets is supplied to the core in a highly anisotropic fashion. The effective spatial redistribution of heat is enabled in part by the turbulent motions in the wake of freely falling cold filaments. Increased AGN activity can locally reverse the cold gas flow, launching cold filamentary gas away from the cluster center. Our criterion for the condensation of spatially extended cold gas is in agreement with observations and previous idealized simulations.

  17. Linear and nonlinear evolution of azimuthal clumping instabilities in a Z-pinch wire array

    DOE PAGES

    Tang, Wilkin; Strickler, T. S.; Lau, Y. Y.; ...

    2007-01-31

    This study presents an analytic theory on the linear and nonlinear evolution of the most unstable azimuthal clumping mode, known as the pi-mode, in a discrete wire array. In the pi-mode, neighboring wires of the array pair-up as a result of the mutual attraction of the wires which carry current in the same direction. The analytic solution displays two regimes, where the collective interactions of all wires dominate, versus where the interaction of the neighboring, single wire dominates. This solution was corroborated by two vastly different numerical codes which were used to simulate arrays with both high wire numbers (upmore » to 600) and low wire number (8). All solutions show that azimuthal clumping of discrete wires occurs before appreciable radial motion of the wires. Thus, absence of azimuthal clumping of wires in comparison with the wires’ radial motion may imply substantial lack of wire currents. Finally, while the present theory and simulations have ignored the plasma corona and axial variations, it is argued that their effects, and the complete account of the three-dimensional feature of the pi-mode, together with a scaling study of the wire number, may be expediently simulated by using only one single wire in an annular wedge with a reflection condition imposed on the wedge’s boundary.« less

  18. A method for quantitative analysis of clump thickness in cervical cytology slides.

    PubMed

    Fan, Yilun; Bradley, Andrew P

    2016-01-01

    Knowledge of the spatial distribution and thickness of cytology specimens is critical to the development of digital slide acquisition techniques that minimise both scan times and image file size. In this paper, we evaluate a novel method to achieve this goal utilising an exhaustive high-resolution scan, an over-complete wavelet transform across multi-focal planes and a clump segmentation of all cellular materials on the slide. The method is demonstrated with a quantitative analysis of ten normal, but difficult to scan Pap stained, Thin-prep, cervical cytology slides. We show that with this method the top and bottom of the specimen can be estimated to an accuracy of 1 μm in 88% and 97% of the fields of view respectively. Overall, cellular material can be over 30 μm thick and the distribution of cells is skewed towards the cover-slip (top of the slide). However, the median clump thickness is 10 μm and only 31% of clumps contain more than three nuclei. Therefore, by finding a focal map of the specimen the number of 1 μm spaced focal planes that are required to be scanned to acquire 95% of the in-focus material can be reduced from 25.4 to 21.4 on average. In addition, we show that by considering the thickness of the specimen, an improved focal map can be produced which further reduces the required number of 1 μm spaced focal planes to 18.6. This has the potential to reduce scan times and raw image data by over 25%. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Chemical composition of the stellar cluster Gaia1: no surprise behind Sirius

    NASA Astrophysics Data System (ADS)

    Mucciarelli, A.; Monaco, L.; Bonifacio, P.; Saviane, I.

    2017-07-01

    We observed six He-clump stars of the intermediate-age stellar cluster Gaia1 with the MIKE/Magellan spectrograph. A possible extra-galactic origin of this cluster, recently discovered thanks to the first data release of the ESA Gaia mission, has been suggested, based on its orbital parameters. Abundances for Fe, α, proton- and neutron-capture elements have been obtained. We find no evidence of intrinsic abundance spreads. The iron abundance is solar ([FeI/H] = + 0.00 ± 0.01; σ = 0.03 dex). All the other abundance ratios are generally solar-scaled, similar to the Galactic thin disk and open cluster stars of similar metallicity. The chemical composition of Gaia1 does not support an extra-galactic origin for this stellar cluster, which can be considered as a standard Galactic open cluster. The full Table A.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/603/L7

  20. Clumped isotope thermometry of calcite and dolomite in a contact metamorphic environment

    NASA Astrophysics Data System (ADS)

    Lloyd, Max K.; Eiler, John M.; Nabelek, Peter I.

    2017-01-01

    Clumped isotope compositions of slowly-cooled calcite and dolomite marbles record apparent equilibrium temperatures of roughly 150-200 °C and 300-350 °C, respectively. Because clumped isotope compositions are sensitive to the details of T-t path within these intervals, measurements of the Δ47 values of coexisting calcite and dolomite can place new constraints on thermal history of low-grade metamorphic rocks over a large portion of the upper crust (from ∼5 to ∼15 km depth). We studied the clumped isotope geochemistry of coexisting calcite and dolomite in marbles from the Notch Peak contact metamorphic aureole, Utah. Here, flat-lying limestones were intruded by a pluton, producing a regular, zoned metamorphic aureole. Calcite Δ47 temperatures are uniform, 156 ± 12 °C (2σ s.e.), across rocks varying from high-grade marbles that exceeded 500 °C to nominally unmetamorphosed limestones >5 km from the intrusion. This result appears to require that the temperature far from the pluton was close to this value; an ambient temperature just 20 °C lower would not have permitted substantial re-equilibration, and should have preserved depositional or early diagenetic Δ47 values several km from the pluton. Combining this result with depth constraints from overlying strata suggests the country rock here had an average regional geotherm of 22.3-27.4 °C/km from the late Jurassic Period until at least the middle Paleogene Period. Dolomite Δ47 in all samples above the talc + tremolite-in isograd record apparent equilibrium temperatures of 328-12+13 °C (1σ s.e.), consistent with the apparent equilibrium blocking temperature we expect for cooling from peak metamorphic conditions. At greater distances, dolomite Δ47 records temperatures of peak (anchi)metamorphism or pre-metamorphic diagenetic conditions. The interface between these domains is the location of the 330 °C isotherm associated with intrusion. Multiple-phase clumped isotope measurements are complemented by

  1. The G305 star-forming complex: the central star clusters Danks 1 and Danks 2

    NASA Astrophysics Data System (ADS)

    Davies, Ben; Clark, J. S.; Trombley, Christine; Figer, Donald F.; Najarro, Francisco; Crowther, Paul A.; Kudritzki, Rolf-Peter; Thompson, Mark; Urquhart, James S.; Hindson, Luke

    2012-01-01

    The G305 H II complex (G305.4+0.1) is one of the most massive star-forming structures yet identified within the Galaxy. It is host to many massive stars at all stages of formation and evolution, from embedded molecular cores to post-main-sequence stars. Here, we present a detailed near-infrared analysis of the two central star clusters Danks 1 and Danks 2, using Hubble Space Telescope+NICMOS imaging and Very Large Telescope+ISAAC spectroscopy. We find that the spectrophotometric distance to the clusters is consistent with the kinematic distance to the G305 complex, an average of all measurements giving a distance of 3.8 ± 0.6 kpc. From analysis of the stellar populations and the pre-main-sequence stars, we find that Danks 2 is the elder of the two clusters, with an age of 3+3- 1 Myr. Danks 1 is clearly younger with an age of 1.5+1.5- 0.5 Myr, and is dominated by three very luminous H-rich Wolf-Rayet stars which may have masses ≳100 M⊙. The two clusters have mass functions consistent with the Salpeter slope, and total cluster masses of 8000 ± 1500 and 3000 ± 800 M⊙ for Danks 1 and Danks 2, respectively. Danks 1 is significantly the more compact cluster of the two, and is one of the densest clusters in the Galaxy with log (ρ/M⊙ pc-3) = 5.5+0.5- 0.4. In addition to the clusters, there is a population of apparently isolated Wolf-Rayet stars within the molecular cloud's cavity. Our results suggest that the star-forming history of G305 began with the formation of Danks 2, and subsequently Danks 1, with the origin of the diffuse evolved population currently uncertain. Together, the massive stars at the centre of the G305 region appear to be clearing away what is left of the natal cloud, triggering a further generation of star formation at the cloud's periphery.

  2. Constraining the thermal history of the North American Midcontinent Rift System using carbonate clumped isotopes and organic thermal maturity indices

    USGS Publications Warehouse

    Gallagher, Timothy M.; Sheldon, Nathan D.; Mauk, Jeffrey L.; Petersen, Sierra V.; Gueneli, Nur; Brocks, Jochen J.

    2017-01-01

    The Midcontinent Rift System (MRS) is a Late Mesoproterozoic (∼1.1 Ga) sequence of volcanic and sedimentary rocks exposed in the Lake Superior Region of North America. The MRS continues to be the focus of much research due to its economic mineral deposits as well as its archive of Precambrian life and tectonic processes. In order to constrain the post-depositional thermal history of the MRS, samples were analyzed for carbonate clumped isotope composition and organic thermal maturity. Clumped isotope values from sedimentary/early-diagenetic samples were partially reset during burial to temperatures between 68 and 75 °C. Solid-state reordering models indicate that maximum burial temperatures of 125–155 °C would reset the clumped isotope values to the observed temperature range prior to the onset of regional cooling and uplift. Clumped isotope results from late-stage veins in the White Pine Mine encompass a greater temperature range (49–116 °C), indicative of spatially variable hydrothermal activity and vein emplacement after burial temperatures fell below 100 °C during regional cooling and uplift. Clumped isotope and organic thermal maturity data do not indicate significant spatial differences in thermal history along the MRS. Observed variability in bulk organic matter composition and biomarker indices are therefore more likely a result of shifts in primary productivity or early-degradation processes. These results demonstrate that the MRS experienced a spatially consistent, relatively mild thermal history (125–155 °C) and is therefore a valuable archive for understanding the Late Mesoproterozoic environment.

  3. On the Diversity in Mass and Orbital Radius of Giant Planets Formed via Disk Instability

    NASA Astrophysics Data System (ADS)

    Müller, Simon; Helled, Ravit; Mayer, Lucio

    2018-02-01

    We present a semi-analytical population synthesis model of protoplanetary clumps formed by disk instability at radial distances of 80–120 au. Various clump density profiles, initial mass functions, protoplanetary disk models, stellar masses, and gap opening criteria are considered. When we use more realistic gap opening criteria, we find that gaps open only rarely, which strongly affects clump survival rates and their physical properties (mass, radius, and radial distance). The inferred surviving population is then shifted toward less massive clumps at smaller radial distances. We also find that populations of surviving clumps are very sensitive to the model assumptions and used parameters. Depending on the chosen parameters, the protoplanets occupy a mass range between 0.01 and 16 M J and may either orbit close to the central star or as far out as 75 au, with a sweet spot at 10–30 au for the massive ones. However, in all of the cases we consider, we find that massive giant planets at very large radial distances are rare, in qualitative agreement with current direct imaging surveys. We conclude that caution should be taken in deriving population synthesis models as well as when comparing the models’ results with observations.

  4. The Planck Catalogue of Galactic Cold Clumps : PGCC

    NASA Astrophysics Data System (ADS)

    Montier, L.

    The Planck satellite has provided an unprecedented view of the submm sky, allowing us to search for the dust emission of Galactic cold sources. Combining Planck-HFI all-sky maps in the high frequency channels with the IRAS map at 100um, we built the Planck catalogue of Galactic Cold Clumps (PGCC, Planck 2015 results. XXVIII), counting 13188 sources distributed over the whole sky, and following mainly the Galactic structures at low and intermediate latitudes. This is the first all-sky catalogue of Galactic cold sources obtained with a single instrument at this resolution and sensitivity, which opens a new window on star-formation processes in our Galaxy.

  5. Cytoarchitecture and Ultrastructure of Neural Stem Cell Niches and Neurogenic Complexes Maintaining Adult Neurogenesis in the Olfactory Midbrain of Spiny Lobsters, Panulirus argus

    PubMed Central

    Schmidt, Manfred; Derby, Charles D.

    2013-01-01

    New interneurons are continuously generated in small proliferation zones within neuronal somata clusters in the olfactory deutocerebrum of adult decapod crustaceans. Each proliferation zone is connected to a clump of cells containing one neural stem cell (i.e., adult neuroblast), thus forming a “neurogenic complex.” Here we provide a detailed analysis of the cytoarchitecture of neurogenic complexes in adult spiny lobsters, Panulirus argus, based on transmission electron microscopy and labeling with cell-type-selective markers. The clump of cells is composed of unique bipolar clump-forming cells that collectively completely envelop the adult neuroblast and are themselves ensheathed by a layer of processes of multipolar cell body glia. An arteriole is attached to the clump of cells, but dye perfusion experiments show that hemolymph has no access to the interior of the clump of cells. Thus, the clump of cells fulfills morphological criteria of a protective stem cell niche, with clump-forming cells constituting the adult neuroblast’s microenvironment together with the cell body glia processes separating it from other tissue components. Bromodeoxyuridine pulse-chase experiments with short survival times suggest that adult neuroblasts are not quiescent but rather cycle actively during daytime. We propose a cell lineage model in which an asymmetrically dividing adult neuroblast repopulates the pool of neuronal progenitor cells in the associated proliferation zone. In conclusion, as in mammalian brains, adult neurogenesis in crustacean brains is fueled by neural stem cells that are maintained by stem cell niches that preserve elements of the embryonic microenvironment and contain glial and vascular elements. PMID:21523781

  6. Cytoarchitecture and ultrastructure of neural stem cell niches and neurogenic complexes maintaining adult neurogenesis in the olfactory midbrain of spiny lobsters, Panulirus argus.

    PubMed

    Schmidt, Manfred; Derby, Charles D

    2011-08-15

    New interneurons are continuously generated in small proliferation zones within neuronal somata clusters in the olfactory deutocerebrum of adult decapod crustaceans. Each proliferation zone is connected to a clump of cells containing one neural stem cell (i.e., adult neuroblast), thus forming a "neurogenic complex." Here we provide a detailed analysis of the cytoarchitecture of neurogenic complexes in adult spiny lobsters, Panulirus argus, based on transmission electron microscopy and labeling with cell-type-selective markers. The clump of cells is composed of unique bipolar clump-forming cells that collectively completely envelop the adult neuroblast and are themselves ensheathed by a layer of processes of multipolar cell body glia. An arteriole is attached to the clump of cells, but dye perfusion experiments show that hemolymph has no access to the interior of the clump of cells. Thus, the clump of cells fulfills morphological criteria of a protective stem cell niche, with clump-forming cells constituting the adult neuroblast's microenvironment together with the cell body glia processes separating it from other tissue components. Bromodeoxyuridine pulse-chase experiments with short survival times suggest that adult neuroblasts are not quiescent but rather cycle actively during daytime. We propose a cell lineage model in which an asymmetrically dividing adult neuroblast repopulates the pool of neuronal progenitor cells in the associated proliferation zone. In conclusion, as in mammalian brains, adult neurogenesis in crustacean brains is fueled by neural stem cells that are maintained by stem cell niches that preserve elements of the embryonic microenvironment and contain glial and vascular elements. Copyright © 2011 Wiley-Liss, Inc.

  7. Methane seep carbonates yield clumped isotope signatures out of equilibrium with formation temperatures

    DOE PAGES

    Loyd, S. J.; Sample, J.; Tripati, R. E.; ...

    2016-07-22

    Here, methane cold seep systems typically exhibit extensive buildups of authigenic carbonate minerals, resulting from local increases in alkalinity driven by methane oxidation. Here, we demonstrate that modern seep authigenic carbonates exhibit anomalously low clumped isotope values (Δ47), as much as ~0.2‰ lower than expected values. In modern seeps, this range of disequilibrium translates into apparent temperatures that are always warmer than ambient temperatures, by up to 50 °C. We examine various mechanisms that may induce disequilibrium behaviour in modern seep carbonates, and suggest that the observed values result from several factors including kinetic isotopic effects during methane oxidation, mixingmore » of inorganic carbon pools, pH effects and rapid precipitation. Ancient seep carbonates studied here also exhibit potential disequilibrium signals. Ultimately, these findings indicate the predominance of disequilibrium clumped isotope behaviour in modern cold seep carbonates that must be considered when characterizing environmental conditions in both modern and ancient cold seep settings.« less

  8. Wide- and contact-binary formation in substructured young stellar clusters

    NASA Astrophysics Data System (ADS)

    Dorval, J.; Boily, C. M.; Moraux, E.; Roos, O.

    2017-02-01

    We explore with collisional gravitational N-body models the evolution of binary stars in initially fragmented and globally subvirial clusters of stars. Binaries are inserted in the (initially) clumpy configurations so as to match the observed distributions of the field-binary-stars' semimajor axes a and binary fraction versus primary mass. The dissolution rate of wide binaries is very high at the start of the simulations, and is much reduced once the clumps are eroded by the global infall. The transition between the two regimes is sharper as the number of stars N is increased, from N = 1.5 k up to 80 k. The fraction of dissolved binary stars increases only mildly with N, from ≈15 per cent to ≈25 per cent for the same range in N. We repeated the calculation for two initial system mean number densities of 6 per pc3 (low) and 400 per pc3 (high). We found that the longer free-fall time of the low-density runs allows for prolonged binary-binary interactions inside clumps and the formation of very tight (a ≈ 0.01 au) binaries by exchange collisions. This is an indication that the statistics of such compact binaries bear a direct link to their environment at birth. We also explore the formation of wide (a ≳ 5 × 104 au) binaries and find a low (≈0.01 per cent) fraction mildly bound to the central star cluster. The high-precision astrometric mission Gaia could identify them as outflowing shells or streams.

  9. The JCMT Gould Belt Survey: A First Look at IC 5146

    NASA Astrophysics Data System (ADS)

    Johnstone, D.; Ciccone, S.; Kirk, H.; Mairs, S.; Buckle, J.; Berry, D. S.; Broekhoven-Fiene, H.; Currie, M. J.; Hatchell, J.; Jenness, T.; Mottram, J. C.; Pattle, K.; Tisi, S.; Di Francesco, J.; Hogerheijde, M. R.; Ward-Thompson, D.; Bastien, P.; Bresnahan, D.; Butner, H.; Chen, M.; Chrysostomou, A.; Coudé, S.; Davis, C. J.; Drabek-Maunder, E.; Duarte-Cabral, A.; Fich, M.; Fiege, J.; Friberg, P.; Friesen, R.; Fuller, G. A.; Graves, S.; Greaves, J.; Gregson, J.; Holland, W.; Joncas, G.; Kirk, J. M.; Knee, L. B. G.; Marsh, K.; Matthews, B. C.; Moriarty-Schieven, G.; Mowat, C.; Nutter, D.; Pineda, J. E.; Salji, C.; Rawlings, J.; Richer, J.; Robertson, D.; Rosolowsky, E.; Rumble, D.; Sadavoy, S.; Thomas, H.; Tothill, N.; Viti, S.; White, G. J.; Wouterloot, J.; Yates, J.; Zhu, M.

    2017-02-01

    We present 450 and 850 μm submillimeter continuum observations of the IC 5146 star-forming region taken as part of the James Clerk Maxwell Telescope Gould Belt Survey. We investigate the location of bright submillimeter (clumped) emission with the larger-scale molecular cloud through comparison with extinction maps, and find that these denser structures correlate with higher cloud column density. Ninety-six individual submillimeter clumps are identified using FellWalker, and their physical properties are examined. These clumps are found to be relatively massive, ranging from 0.5 {M}⊙ to 116 {M}⊙ with a mean mass of 8 {M}⊙ and a median mass of 3.7 {M}⊙ . A stability analysis for the clumps suggests that the majority are (thermally) Jeans stable, with M/{M}J< 1. We further compare the locations of known protostars with the observed submillimeter emission, finding that younger protostars, I.e., Class 0 and I sources, are strongly correlated with submillimeter peaks and that the clumps with protostars are among the most Jeans unstable. Finally, we contrast the evolutionary conditions in the two major star-forming regions within IC 5146: the young cluster associated with the Cocoon Nebula and the more distributed star formation associated with the Northern Streamer filaments. The Cocoon Nebula appears to have converted a higher fraction of its mass into dense clumps and protostars, the clumps are more likely to be Jeans unstable, and a larger fraction of these remaining clumps contain embedded protostars. The Northern Streamer, however, has a larger number of clumps in total and a larger fraction of the known protostars are still embedded within these clumps.

  10. Two Key Parameters Controlling Particle Clumping Caused by Streaming Instability in the Dead-zone Dust Layer of a Protoplanetary Disk

    NASA Astrophysics Data System (ADS)

    Sekiya, Minoru; Onishi, Isamu K.

    2018-06-01

    The streaming instability and Kelvin–Helmholtz instability are considered the two major sources causing clumping of dust particles and turbulence in the dust layer of a protoplanetary disk as long as we consider the dead zone where the magnetorotational instability does not grow. Extensive numerical simulations have been carried out in order to elucidate the condition for the development of particle clumping caused by the streaming instability. In this paper, a set of two parameters suitable for classifying the numerical results is proposed. One is the Stokes number that has been employed in previous works and the other is the dust particle column density that is nondimensionalized using the gas density in the midplane, Keplerian angular velocity, and difference between the Keplerian and gaseous orbital velocities. The magnitude of dust clumping is a measure of the behavior of the dust layer. Using three-dimensional numerical simulations of dust particles and gas based on Athena code v. 4.2, it is confirmed that the magnitude of dust clumping for two disk models are similar if the corresponding sets of values of the two parameters are identical to each other, even if the values of the metallicity (i.e., the ratio of the columns density of the dust particles to that of the gas) are different.

  11. Equilibrium and non-equilibrium controls on the abundances of clumped isotopologues of methane during thermogenic formation in laboratory experiments: Implications for the chemistry of pyrolysis and the origins of natural gases

    USGS Publications Warehouse

    Shuai, Yanhua; Douglas, Peter M.J.; Zhang, Shuichang; Stolper, Daniel A.; Ellis, Geoffrey S.; Lawson, Michael; Lewan, Michael; Formolo, Michael; Mi, Jingkui; He, Kun; Hu, Guoyi; Eiler, John M.

    2018-01-01

    Multiply isotopically substituted molecules (‘clumped’ isotopologues) can be used as geothermometers because their proportions at isotopic equilibrium relative to a random distribution of isotopes amongst all isotopologues are functions of temperature. This has allowed measurements of clumped-isotope abundances to be used to constrain formation temperatures of several natural materials. However, kinetic processes during generation, modification, or transport of natural materials can also affect their clumped-isotope compositions. Herein, we show that methane generated experimentally by closed-system hydrous pyrolysis of shale or nonhydrous pyrolysis of coal yields clumped-isotope compositions consistent with an equilibrium distribution of isotopologues under some experimental conditions (temperature–time conditions corresponding to ‘low,’ ‘mature,’ and ‘over-mature’ stages of catagenesis), but can have non-equilibrium (i.e., kinetically controlled) distributions under other experimental conditions (‘high’ to ‘over-mature’ stages), particularly for pyrolysis of coal. Non-equilibrium compositions, when present, lead the measured proportions of clumped species to be lower than expected for equilibrium at the experimental temperature, and in some cases to be lower than a random distribution of isotopes (i.e., negative Δ18 values). We propose that the consistency with equilibrium for methane formed by relatively low temperature pyrolysis reflects local reversibility of isotope exchange reactions involving a reactant or transition state species during demethylation of one or more components of kerogen. Non-equilibrium clumped-isotope compositions occur under conditions where ‘secondary’ cracking of retained oil in shale or wet gas hydrocarbons (C2-5, especially ethane) in coal is prominent. We suggest these non-equilibrium isotopic compositions are the result of the expression of kinetic isotope effects during the irreversible generation

  12. Small scale clustering of late forming dark matter

    NASA Astrophysics Data System (ADS)

    Agarwal, S.; Corasaniti, P.-S.; Das, S.; Rasera, Y.

    2015-09-01

    We perform a study of the nonlinear clustering of matter in the late-forming dark matter (LFDM) scenario in which dark matter results from the transition of a nonminimally coupled scalar field from radiation to collisionless matter. A distinct feature of this model is the presence of a damped oscillatory cutoff in the linear matter power spectrum at small scales. We use a suite of high-resolution N-body simulations to study the imprints of LFDM on the nonlinear matter power spectrum, the halo mass and velocity functions and the halo density profiles. The model largely satisfies high-redshift matter power spectrum constraints from Lyman-α forest measurements, while it predicts suppressed abundance of low-mass halos (˜109- 1010 h-1 M⊙ ) at all redshifts compared to a vanilla Λ CDM model. The analysis of the LFDM halo velocity function shows a better agreement than the Λ CDM prediction with the observed abundance of low-velocity galaxies in the local volume. Halos with mass M ≳1011 h-1 M⊙ show minor departures of the density profiles from Λ CDM expectations, while smaller-mass halos are less dense, consistent with the fact that they form later than their Λ CDM counterparts.

  13. Clustered streamlined forms in Athabasca Valles, Mars: Evidence for sediment deposition during floodwater ponding

    USGS Publications Warehouse

    Burr, D.

    2005-01-01

    A unique clustering of layered streamlined forms in Athabasca Valles is hypothesized to reflect a significant hydraulic event. The forms, interpreted as sedimentary, are attributed to extensive sediment deposition during ponding and then streamlining of this sediment behind flow obstacles during ponded water outflow. These streamlined forms are analogous to those found in depositional basins and other loci of ponding in terrestrial catastrophic flood landscapes. These terrestrial streamlined forms can provide the best opportunity for reconstructing the history of the terrestrial flooding. Likewise, the streamlined forms in Athabasca Valles may provide the best opportunity to reconstruct the recent geologic history of this young Martian outflow channel. ?? 2005 Elsevier B.V. All rights reserved.

  14. Assessing Past Fracture Connectivity in Geothermal Reservoirs Using Clumped Isotopes: Proof of Concept in the Blue Mountain Geothermal Field, Nevada USA

    NASA Astrophysics Data System (ADS)

    Huntington, K. W.; Sumner, K. K.; Camp, E. R.; Cladouhos, T. T.; Uddenberg, M.; Swyer, M.; Garrison, G. H.

    2015-12-01

    Subsurface fluid flow is strongly influenced by faults and fractures, yet the transmissivity of faults and fractures changes through time due to deformation and cement precipitation, making flow paths difficult to predict. Here we assess past fracture connectivity in an active hydrothermal system in the Basin and Range, Nevada, USA, using clumped isotope geochemistry and cold cathodoluminescence (CL) analysis of fracture filling cements from the Blue Mountain geothermal field. Calcite cements were sampled from drill cuttings and two cores at varying distances from faults. CL microscopy of some of the cements shows banding parallel to the fracture walls as well as brecciation, indicating that the cements record variations in the composition and source of fluids that moved through the fractures as they opened episodically. CL microscopy, δ13C and δ18O values were used to screen homogeneous samples for clumped isotope analysis. Clumped isotope thermometry of most samples indicates paleofluid temperatures of around 150°C, with several wells peaking at above 200°C. We suggest that the consistency of these temperatures is related to upwelling of fluids in the convective hydrothermal system, and interpret the similarity of the clumped isotope temperatures to modern geothermal fluid temperatures of ~160-180°C as evidence that average reservoir temperatures have changed little since precipitation of the calcite cements. In contrast, two samples, one of which was associated with fault gauge observed in drill logs, record significantly cooler temperatures of 19 and 73°C and anomalous δ13C and δ18Owater values, which point to fault-controlled pathways for downwelling meteoric fluid. Finally, we interpret correspondence of paleofluid temperatures and δ18Owater values constrained by clumped isotope thermometry of calcite from different wells to suggest past connectivity of fractures among wells within the geothermal field. Results show the ability of clumped isotope

  15. 13C 18O clumping in speleothems: Observations from natural caves and precipitation experiments

    NASA Astrophysics Data System (ADS)

    Daëron, M.; Guo, W.; Eiler, J.; Genty, D.; Blamart, D.; Boch, R.; Drysdale, R.; Maire, R.; Wainer, K.; Zanchetta, G.

    2011-06-01

    The oxygen isotope composition of speleothems is an important proxy of continental paleoenvironments, because of its sensitivity to variations in cave temperature and drip water δ 18O. Interpreting speleothem δ 18O records in terms of absolute paleotemperatures and δ 18O values of paleo-precipitation requires quantitative separation of the effects of these two parameters, and correcting for possible kinetic isotope fractionation associated with precipitation of calcite out of thermodynamic equilibrium. Carbonate clumped-isotope thermometry, based on measurements of Δ47 (a geochemical variable reflecting the statistical overabundance of 13C 18O bonds in CO 2 evolved from phosphoric acid digestion of carbonate minerals), potentially provides a method for absolute speleothem paleotemperature reconstructions independent of drip water composition. Application of this new technique to karst records is currently limited by the scarcity of published clumped-isotope studies of modern speleothems. The only modern stalagmite reported so far in the literature yielded a lower Δ47 value than expected for equilibrium precipitation, possibly due to kinetic isotope fractionation. Here we report Δ47 values measured in natural speleothems from various cave settings, in carbonate produced by cave precipitation experiments, and in synthetic stalagmite analogs precipitated in controlled laboratory conditions designed to mimic natural cave processes. All samples yield lower Δ47 and heavier δ 18O values than predicted by experimental calibrations of thermodynamic equilibrium in inorganic calcite. The amplitudes of these isotopic disequilibria vary between samples, but there is clear correlation between the amount of Δ47 disequilibrium and that of δ 18O. Even pool carbonates believed to offer excellent conditions for equilibrium precipitation of calcite display out-of-equilibrium δ 18O and Δ47 values, probably inherited from prior degassing within the cave system. In addition

  16. Clustering Effect on the Dynamics in a Spatial Rock-Paper-Scissors System

    NASA Astrophysics Data System (ADS)

    Hashimoto, Tsuyoshi; Sato, Kazunori; Ichinose, Genki; Miyazaki, Rinko; Tainaka, Kei-ichi

    2018-01-01

    The lattice dynamics for rock-paper-scissors games is related to population theories in ecology. In most cases, simulations are performed by local and global interactions. It is known in the former case that the dynamics is usually stable. We find two types of non-random distributions in the stationary state. One is a cluster formation of endangered species: when the density of a species approaches zero, its clumping degree diverges to infinity. The other is the strong aggregations of high-density species. Such spatial pattern formations play important roles in population dynamics.

  17. HIGHLY VARIABLE YOUNG MASSIVE STARS IN ATLASGAL CLUMPS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kumar, M. S. N.; Contreras Peña, C.; Lucas, P. W.

    High-amplitude variability in young stellar objects (YSOs) is usually associated with episodic accretion events. It has not been observed so far in massive YSOs. Here, the high-amplitude variable star sample of Contreras Peña et al. has been used to search for highly variable (Δ K  ≥ 1 mag) sources coinciding with dense clumps mapped using the 850  μ m continuum emission by the ATLASGAL survey. A total of 18 variable sources are centered on the submillimeter clump peaks and coincide (<1″) with a 24  μ m point or compact (<10″) source. Of these 18 sources, 13 can be fit by YSOmore » models. The 13 variable YSOs (VYSOs) have luminosities of ∼10{sup 3} L {sub ⊙}, an average mass of 8  M {sub ⊙}, and a range of ages up to 10{sup 6} yr. A total of 11 of these 13 VYSOs are located in the midst of infrared dark clouds. Nine of the 13 sources have Δ K  > 2 mag, significantly higher compared to the mean variability of the entire VVV sample. The light curves of these objects sampled between 2010 and 2015 display rising, declining, or quasi-periodic behavior but no clear periodicity. Light-curve analysis using the Plavchan method shows that the most prominent phased signals have periods of a few hundred days. The nature and timescale of variations found in 6.7 Ghz methanol maser emission in massive stars are similar to that of the VYSO light curves. We argue that the origin of the observed variability is episodic accretion. We suggest that the timescale of a few hundred days may represent the frequency at which a spiraling disk feeds dense gas to the young massive star.« less

  18. Cytological Study of Grade 3 Endometrioid Adenocarcinoma of Endometrial Origin: Cytoarchitecture and Features of Cell Clusters Assessed With Endometrial Brushing Cytology--Focusing on a comparison with endometrioid adenocarcinoma Grade 1, 2.

    PubMed

    Matsui, Naruaki; Kajiwara, Hiroshi; Morishita, Akihiro; Tsukada, Hitomi; Nakazawa, Kazumi; Miyazawa, Masaki; Mikami, Mikio; Nakamura, Naoya; Sato, Shinkichi

    2015-06-20

    Aim of study was to clarify the cytological characteristics of grade 3 endometrioid adenocarcinoma of endometrial origin (G3 EA) by endometrial brushing cytology. The subjects were 11 patients in whom G3 EA was diagnosed by review of preoperative cytological specimens obtained at our hospital and related institutions between 2000 and 2010. These patients were investigated with respect to the preoperative cytological diagnosis, background changes, cell cluster patterns, and individual cellular findings. Background changes were classified as inflammatory or tumorous, while cell clusters were classified as overlapping cell cluster, sheet-like cell cluster, clump of high dense gland, papillary, or other cell cluster. Cellular findings were investigated by comparing the incidence of squamous and clear cell metaplasia, the nuclear rounding rate, and the nuclear area with the findings in a control group (35 patients with G1-2 EA). Background changes were classified as inflammatory in 63.6% and necrotic in 36.4%. The cell clusters were classified as overlapping cell cluster in 44.8%, cell cluster in 21.7%, clump of high dense gland in 10.0%, papillary in 4.0%, and other cell cluster in 19.5%. The incidence of squamous and clear cell metaplasia was 27.2% and 18.1%, respectively. The mean nuclear rounding rate was 0.97, and the mean nuclear area was 55.98 µm2. Investigation of the cytoarchitecture of G3 EA with endometrial brushing cytology revealed overlapping cell cluster and tumor cells of a relatively uniform size. These findings suggest that it is necessary to recognize that there are differences between the cytological findings of G3 EA and the usual features of G1-2 EA.

  19. MC 2: Mapping the dark matter distribution of the “Toothbrush” cluster RX J0603.3+4214 with Hubble Space Telescope and Subaru weak lensing

    DOE PAGES

    Jee, M. James; Dawson, William A.; Stroe, Andra; ...

    2016-02-01

    The galaxy cluster RX J0603.3+4214 at z = 0:225 is one of the rarest clusters boasting an extremely large ( 2 Mpc) radio relic. Because of the remarkable morphology of the relic, the cluster is nicknamed the \\Toothbrush Cluster". Although the cluster's underlying mass distribution is one of the critical pieces of information needed to reconstruct the merger scenario responsible for the puzzling radio relic morphology, its proximity to the Galactic plane b 10 has imposed signi cant observational challenges. We present a high-resolution weak-lensing study of the cluster with Subaru/Suprime Cam and Hubble Space Telescope imaging data. Our massmore » reconstruction reveals that the cluster is composed of complicated dark matter substructures closely tracing the galaxy distribution, in contrast, however, with the relatively simple binary X-ray morphology. Nevertheless, we nd that the cluster mass is still dominated by the two most massive clumps aligned north-south with a 3:1 mass ratio (M 200 = 6:29 +2:24 -1:62 X 10 14M⊙ and 1:98 +1:24 -0:74 X 10 14M⊙ for the northern and southern clumps, respectively). The southern mass peak is 20 o set toward the south with respect to the corresponding X-ray peak, which has a \\bullet"-like morphology pointing south. Comparison of the current weak- lensing result with the X-ray, galaxy, and radio relic suggests that perhaps the dominant mechanism responsible for the observed relic may be a high-speed collision of the two most massive subclusters, although the peculiarity of the morphology necessitates involvement of additional subclusters. Careful numerical simulations should follow in order to obtain more complete understanding of the merger scenario utilizing all existing observations.« less

  20. Star Formation Conditions in a Planck Galactic Cold Clump, G108.84–00.81

    NASA Astrophysics Data System (ADS)

    Kim, Jungha; Lee, Jeong-Eun; Liu, Tie; Kim, Kee-Tae; Wu, Yuefang; Tatematsu, Ken‧ichi; Liu, Sheng-Yuan; JCMT Large Program “SCOPE” Collaboration; TRAO Key Science Program “TOP” Collaboration

    2017-07-01

    We present the results from a series of ground-based radio observations toward a Planck Galactic Cold Clump (PGCC), PGCC G108.84–00.81, which is located in one curved filamentary cloud in the vicinity of an extended H II region Sh2-152 and SNR G109.1-1.0. PGCC G108.84–00.81 is mainly composed of two clumps, “G108–N” and “G108–S”. In the 850 μm dust continuum emission map, G108–N is shown as one component while G108–S is fragmented into four components. There is no infrared source associated with G108–N, while there are two infrared sources (IRS 1 and IRS 2) associated with G108–S. The total mass of G108–N is larger than the Jeans mass, suggesting that G108–N is gravitationally unstable and a potential place for a future star formation. The clump properties of G108–N and G108–S such as the gas temperature and the column density, are not distinctly different. However, G108–S is slightly more evolved than G108–N, if considering the CO depletion factor, molecular abundances, and association with infrared sources. G108–S seems to be affected by the compression from Sh2-152, while G108–N is relatively protected from the external effect.

  1. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Asahina, Yuta; Kawashima, Tomohisa; Furukawa, Naoko

    The formation mechanism of CO clouds observed with the NANTEN2 and Mopra telescopes toward the stellar cluster Westerlund 2 is studied by 3D magnetohydrodynamic simulations, taking into account the interstellar cooling. These molecular clouds show a peculiar shape composed of an arc-shaped cloud on one side of the TeV γ -ray source HESS J1023-575 and a linear distribution of clouds (jet clouds) on the other side. We propose that these clouds are formed by the interaction of a jet with clumps of interstellar neutral hydrogen (H i). By studying the dependence of the shape of dense cold clouds formed bymore » shock compression and cooling on the filling factor of H i clumps, we found that the density distribution of H i clumps determines the shape of molecular clouds formed by the jet–cloud interaction: arc clouds are formed when the filling factor is large. On the other hand, when the filling factor is small, molecular clouds align with the jet. The jet propagates faster in models with small filling factors.« less

  2. New VVV Survey Globular Cluster Candidates in the Milky Way Bulge

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Minniti, Dante; Gómez, Matías; Geisler, Douglas

    It is likely that a number of Galactic globular clusters remain to be discovered, especially toward the Galactic bulge. High stellar density combined with high and differential interstellar reddening are the two major problems for finding globular clusters located toward the bulge. We use the deep near-IR photometry of the VISTA Variables in the Vía Láctea (VVV) Survey to search for globular clusters projected toward the Galactic bulge, and hereby report the discovery of 22 new candidate globular clusters. These objects, detected as high density regions in our maps of bulge red giants, are confirmed as globular cluster candidates bymore » their color–magnitude diagrams. We provide their coordinates as well as their near-IR color–magnitude diagrams, from which some basic parameters are derived, such as reddenings and heliocentric distances. The color–magnitude diagrams reveal well defined red giant branches in all cases, often including a prominent red clump. The new globular cluster candidates exhibit a variety of extinctions (0.06 < A {sub Ks} < 2.77) and distances (5.3 < D < 9.5 kpc). We also classify the globular cluster candidates into 10 metal-poor and 12 metal-rich clusters, based on the comparison of their color–magnitude diagrams with those of known globular clusters also observed by the VVV Survey. Finally, we argue that the census for Galactic globular clusters still remains incomplete, and that many more candidate globular clusters (particularly the low luminosity ones) await to be found and studied in detail in the central regions of the Milky Way.« less

  3. An Observational Study of Blended Young Stellar Clusters in the Galactic Plane - Do Massive Stars form First?

    NASA Astrophysics Data System (ADS)

    Martínez-Galarza, Rafael; Protopapas, Pavlos; Smith, Howard A.; Morales, Esteban

    2018-01-01

    From an observational point of view, the early life of massive stars is difficult to understand partly because star formation occurs in crowded clusters where individual stars often appear blended together in the beams of infrared telescopes. This renders the characterization of the physical properties of young embedded clusters via spectral energy distribution (SED) fitting a challenging task. Of particular relevance for the testing of star formation models is the question of whether the claimed universality of the IMF (references) is reflected in an equally universal integrated galactic initial mass function (IGIMF) of stars. In other words, is the set of all stellar masses in the galaxy sampled from a single universal IMF, or does the distribution of masses depend on the environment, making the IGIMF different from the canonical IMF? If the latter is true, how different are the two? We present a infrared SED analysis of ~70 Spitzer-selected, low mass ($<100~\\rm{M}_{\\odot}$), galactic blended clusters. For all of the clusters we obtain the most probable individual SED of each member and derive their physical properties, effectively deblending the confused emission from individual YSOs. Our algorithm incorporates a combined probabilistic model of the blended SEDs and the unresolved images in the long-wavelength end. We find that our results are compatible with competitive accretion in the central regions of young clusters, with the most massive stars forming early on in the process and less massive stars forming about 1Myr later. We also find evidence for a relationship between the total stellar mass of the cluster and the mass of the most massive member that favors optimal sampling in the cluster and disfavors random sampling for the canonical IMF, implying that star formation is self-regulated, and that the mass of the most massive star in a cluster depends on the available resources. The method presented here is easily adapted to future observations of

  4. Astrophysics. Multiple images of a highly magnified supernova formed by an early-type cluster galaxy lens.

    PubMed

    Kelly, Patrick L; Rodney, Steven A; Treu, Tommaso; Foley, Ryan J; Brammer, Gabriel; Schmidt, Kasper B; Zitrin, Adi; Sonnenfeld, Alessandro; Strolger, Louis-Gregory; Graur, Or; Filippenko, Alexei V; Jha, Saurabh W; Riess, Adam G; Bradac, Marusa; Weiner, Benjamin J; Scolnic, Daniel; Malkan, Matthew A; von der Linden, Anja; Trenti, Michele; Hjorth, Jens; Gavazzi, Raphael; Fontana, Adriano; Merten, Julian C; McCully, Curtis; Jones, Tucker; Postman, Marc; Dressler, Alan; Patel, Brandon; Cenko, S Bradley; Graham, Melissa L; Tucker, Bradley E

    2015-03-06

    In 1964, Refsdal hypothesized that a supernova whose light traversed multiple paths around a strong gravitational lens could be used to measure the rate of cosmic expansion. We report the discovery of such a system. In Hubble Space Telescope imaging, we have found four images of a single supernova forming an Einstein cross configuration around a redshift z = 0.54 elliptical galaxy in the MACS J1149.6+2223 cluster. The cluster's gravitational potential also creates multiple images of the z = 1.49 spiral supernova host galaxy, and a future appearance of the supernova elsewhere in the cluster field is expected. The magnifications and staggered arrivals of the supernova images probe the cosmic expansion rate, as well as the distribution of matter in the galaxy and cluster lenses. Copyright © 2015, American Association for the Advancement of Science.

  5. SANTA BARBARA CLUSTER COMPARISON TEST WITH DISPH

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Saitoh, Takayuki R.; Makino, Junichiro, E-mail: saitoh@elsi.jp

    2016-06-01

    The Santa Barbara cluster comparison project revealed that there is a systematic difference between entropy profiles of clusters of galaxies obtained by Eulerian mesh and Lagrangian smoothed particle hydrodynamics (SPH) codes: mesh codes gave a core with a constant entropy, whereas SPH codes did not. One possible reason for this difference is that mesh codes are not Galilean invariant. Another possible reason is the problem of the SPH method, which might give too much “protection” to cold clumps because of the unphysical surface tension induced at contact discontinuities. In this paper, we apply the density-independent formulation of SPH (DISPH), whichmore » can handle contact discontinuities accurately, to simulations of a cluster of galaxies and compare the results with those with the standard SPH. We obtained the entropy core when we adopt DISPH. The size of the core is, however, significantly smaller than those obtained with mesh simulations and is comparable to those obtained with quasi-Lagrangian schemes such as “moving mesh” and “mesh free” schemes. We conclude that both the standard SPH without artificial conductivity and Eulerian mesh codes have serious problems even with such an idealized simulation, while DISPH, SPH with artificial conductivity, and quasi-Lagrangian schemes have sufficient capability to deal with it.« less

  6. Photothermolysis by laser-induced microbubbles generated around gold nanorod clusters selectively formed in leukemia cells

    NASA Astrophysics Data System (ADS)

    Lapotko, Dmitri; Lukianova-Hleb, Ekaterina; Zhdanok, Sergei; Rostro, Betty; Simonette, Rebecca; Hafner, Jason; Konopleva, Marina; Andreeff, Michael; Conjusteau, Andre; Oraevsky, Alexander

    2008-02-01

    In an effort of developing clinical LANTCET (laser-activated nano-thermolysis as cell elimination technology) we achieved selective destruction of individual tumor cells through laser generation of vapor microbubbles around clusters of light absorbing gold nanorods (GNR) selectively formed in target tumor cells. Among all gold nanoparticles, nanorods offer the highest optical absorption in the near-infrared. We applied covalent conjugates of gold nanorods with targeting vectors such as monoclonal antibodies CD33 (specific for Acute Myeloid Leukemia), while GNR conjugates with polyethylene-glycol (PEG) were used as nonspecific targeting control. GNR clusters were formed inside the tumor cells at 37 °C due to endocytosis of large concentration of nanorods accumulated on the surface of tumor cells targeted at 4 °C. Formation of GNR clusters significantly reduces the threshold of tumor cell damage making LANTCET safe for normal cells. Appearance of GNR clusters was verified directly with optical resonance scattering microscopy. LANTCET was performed in vitro with living cells of (1) model myeloid K562 cells (CD33 positive), (2) primary human bone marrow CD33-positive blast cells from patients diagnosed with acute myeloid leukemia. Laser-induced microbubbles were generated and detected with a photothermal microscope equipped with a tunable Ti-Sa pulsed laser. GNT cluster formation caused a 100-fold decrease in the threshold optical fluence for laser microbubble generation in tumor cells compared with that in normal cells under the same targeting and irradiation conditions. Combining imaging based on resonance optical scattering with photothermal imaging of microbubbles, we developed a method for detection, image-guided treatment and monitoring of LANTCET. Pilot experiments were performed in flow mode bringing LANTCET closer to reality of clinical procedure of purging tumor cells from bone marrow grafts.

  7. CLUMP-3D: Three-dimensional Shape and Structure of 20 CLASH Galaxy Clusters from Combined Weak and Strong Lensing

    NASA Astrophysics Data System (ADS)

    Chiu, I.-Non; Umetsu, Keiichi; Sereno, Mauro; Ettori, Stefano; Meneghetti, Massimo; Merten, Julian; Sayers, Jack; Zitrin, Adi

    2018-06-01

    We perform a three-dimensional triaxial analysis of 16 X-ray regular and 4 high-magnification galaxy clusters selected from the CLASH survey by combining two-dimensional weak-lensing and central strong-lensing constraints. In a Bayesian framework, we constrain the intrinsic structure and geometry of each individual cluster assuming a triaxial Navarro–Frenk–White halo with arbitrary orientations, characterized by the mass {M}200{{c}}, halo concentration {c}200{{c}}, and triaxial axis ratios ({q}{{a}}≤slant {q}{{b}}), and investigate scaling relations between these halo structural parameters. From triaxial modeling of the X-ray-selected subsample, we find that the halo concentration decreases with increasing cluster mass, with a mean concentration of {c}200{{c}}=4.82+/- 0.30 at the pivot mass {M}200{{c}}={10}15{M}ȯ {h}-1. This is consistent with the result from spherical modeling, {c}200{{c}}=4.51+/- 0.14. Independently of the priors, the minor-to-major axis ratio {q}{{a}} of our full sample exhibits a clear deviation from the spherical configuration ({q}{{a}}=0.52+/- 0.04 at {10}15{M}ȯ {h}-1 with uniform priors), with a weak dependence on the cluster mass. Combining all 20 clusters, we obtain a joint ensemble constraint on the minor-to-major axis ratio of {q}{{a}}={0.652}-0.078+0.162 and a lower bound on the intermediate-to-major axis ratio of {q}{{b}}> 0.63 at the 2σ level from an analysis with uniform priors. Assuming priors on the axis ratios derived from numerical simulations, we constrain the degree of triaxiality for the full sample to be { \\mathcal T }=0.79+/- 0.03 at {10}15{M}ȯ {h}-1, indicating a preference for a prolate geometry of cluster halos. We find no statistical evidence for an orientation bias ({f}geo}=0.93+/- 0.07), which is insensitive to the priors and in agreement with the theoretical expectation for the CLASH clusters.

  8. New insights on multiplicity and clustering in Taurus.

    NASA Astrophysics Data System (ADS)

    Joncour, Isabelle; Duchene, Gaspard; Moraux, Estelle; Mundy, Lee

    2018-01-01

    Multiplicity and clustering of young stars are critical clues to constraint star formation process. The Taurus molecular complex is the archetype of a quiescent star forming region that may retain primeval signature of star formation.Using statistical and clustering tools such as nearest neighbor statistics, correlation functions and the density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm, this work reveals new spatial substructures in Taurus.We have identified unexpected ultra wide pairs (UWPs) candidates of high order multiplicity in Taurus in the 5-60 kAU separation range (Joncour et al 2017), beyond the separation assessed for wide pairs (Kraus & Hillenbrand 2009).Our work reveals 20 local stellar substructures, the Nested Elementary Structures (NESTs). These NESTs contain nearly half the stars of Taurus and 75% of the Class 0/I objects probing that they are the preferred sites of star formation (Joncour et al, sub.). The NESTs size ranges from few kAU up to 80 kAU making a length scale bridge between wide pairs and loose group (few hundreds kAU, Kirk & Myers, 2011). The NESTs mass ranges from 0.5-10 solar mass. The balance between Class I, II and III in NESTs suggests that they may be ordered as an evolutionary temporal scheme, some of them got infertile, while other shelter stars in infancy.The UWPs and the NESTs may be pristine imprints of their spatial configuration at birth. The UWPs population may result from a cascade fragmentation scenario of the natal molecular core. They could be the older counterparts, to the 0.5 Myr prestellar cores/Class 0 multiple objects observed at radio/millimeter wavelengths (Tobin et al 2010, 2016) and the precursors of the large number of UWPs (10–100 kAU) recently identified in older moving groups (Floriano-Alonso et al, 2015 ; Elliot et al 2016). The NESTs may result from the gravitational collapse of a gas clump that fragments to give a tight collection of stars within few millions years

  9. The Planck Catalogue of Galactic Cold Clumps : Looking at the early stages of star-formation

    NASA Astrophysics Data System (ADS)

    Montier, Ludovic

    2015-08-01

    The Planck satellite has provided an unprecedented view of the submm sky, allowing us to search for the dust emission of Galactic cold sources. Combining Planck-HFI all-sky maps in the high frequency channels with the IRAS map at 100um, we built the Planck catalogue of Galactic Cold Clumps (PGCC, Planck 2015 results XXVIII 2015), counting 13188 sources distributed over the whole sky, and following mainly the Galactic structures at low and intermediate latitudes. This is the first all-sky catalogue of Galactic cold sources obtained with a single instrument at this resolution and sensitivity, which opens a new window on star-formation processes in our Galaxy.I will briefly describe the colour detection method used to extract the Galactic cold sources, i.e., the Cold Core Colour Detection Tool (CoCoCoDeT, Montier et al. 2010), and its application to the Planck data. I will discuss the statistical distribution of the properties of the PGCC sources (in terms of dust temperature, distance, mass, density and luminosity), which illustrates that the PGCC catalogue spans a large variety of environments and objects, from molecular clouds to cold cores, and covers various stages of evolution. The Planck catalogue is a very powerful tool to study the formation and the evolution of prestellar objects and star-forming regions.I will finally present an overview of the Herschel Key Program Galactic Cold Cores (PI. M.Juvela), which allowed us to follow-up about 350 Planck Galactic Cold Clumps, in various stages of evolution and environments. With this program, the nature and the composition of the 5' Planck sources have been revealed at a sub-arcmin resolution, showing very different configurations, such as starless cold cores or multiple Young Stellar objects still embedded in their cold envelope.

  10. Integral field spectroscopy of local LCBGs: NGC 7673, a case study. Physical properties of star-forming regions

    NASA Astrophysics Data System (ADS)

    Castillo-Morales, A.; Gallego, J.; Pérez-Gallego, J.; Guzmán, R.; Muñoz-Mateos, J. C.; Zamorano, J.; Sánchez, S. F.

    2011-03-01

    Physical properties of the star-forming regions in the local Luminous Compact Blue Galaxy (LCBG) NGC 7673 are studied in detail using 3D spectroscopic data taken with the PMAS fibre pack (PPAK) integral field unit at the 3.5-m telescope in the Centro Astronómico Hispano Alemán (CAHA). We derive integrated and spatially resolved properties such as extinction, star formation rate (SFR) and metallicity for this galaxy. Our data show an extinction map with maximum values located at the position of the main clumps of star formation showing small spatial variations [E(B-V)t= 0.12-0.21 mag]. We derive an Hα-based SFR for this galaxy of 6.2 ± 0.8 M⊙ yr-1 in agreement with the SFR derived from infrared and radio continuum fluxes. The star formation is located mainly in clumps A, B, C and F. Different properties measured in clump B make this region peculiar. We find the highest Hα luminosity with an SFR surface density of 0.5 M⊙ yr-1 kpc-2 in this clump. In our previous work, the kinematic analysis for this galaxy shows an asymmetrical ionized gas velocity field with a kinematic decoupled component located at the position of clump B. This region shows the absence of strong absorption features and the presence of a Wolf-Rayet stellar population indicating that this is a young burst of massive stars. Furthermore, we estimate a gas metallicity of 12 + log(O/H) = 8.20 ± 0.15 (0.32 solar) for the integrated galaxy using the R23 index. The values derived for the different clumps with this method show small metallicity variations in this galaxy, with values in the range 8.12 (for clump A) to 8.23 (for clump B) for 12 + log(O/H). The analysis of the emission-line ratios discards the presence of any active galactic nuclei (AGN) activity or shocks as the ionization source in this galaxy. Between the possible mechanisms to explain the starburst activity in this galaxy, our 3D spectroscopic data support the scenario of an on-going interaction with the possibility for clump B

  11. Evolution of high-mass star-forming regions .

    NASA Astrophysics Data System (ADS)

    Giannetti, A.; Leurini, S.; Wyrowski, F.; Urquhart, J.; König, C.; Csengeri, T.; Güsten, R.; Menten, K. M.

    Observational identification of a coherent evolutionary sequence for high-mass star-forming regions is still missing. We use the progressive heating of the gas caused by the feedback of high-mass young stellar objects to prove the statistical validity of the most common schemes used to observationally define an evolutionary sequence for high-mass clumps, and identify which physical process dominates in the different phases. From the spectroscopic follow-ups carried out towards the TOP100 sample between 84 and 365 km s^-1 giga hertz, we selected several multiplets of CH3CN, CH3CCH, and CH3OH lines to derive the physical properties of the gas in the clumps along the evolutionary sequence. We demonstrate that the evolutionary sequence is statistically valid, and we define intervals in L/M separating the compression, collapse and accretion, and disruption phases. The first hot cores and ZAMS stars appear at L/M≈10usk {L_ȯ}msun-1

  12. ALMA view of the massive dense clump in the Galactic center 50 km s-1 molecular cloud .

    NASA Astrophysics Data System (ADS)

    Uehara, K.; Tsuboi, M.; Kitamura, Y.; Miyawaki, R.; Miyazaki, A.

    We observed the 50 km s-1 molecular cloud with a high angular resolution (˜1.5 arcsec) using ALMA in the H13CO+ J=1-0, C34S J=2-1, CS J=2-1 and SiO v=0 J=2-1 emission lines. This cloud is a candidate for the massive star forming region induced by cloud-cloud collision (CCC). We newly found a massive dense clump (DC1) with a size of ˜0.3 pc in the CCC region of the cloud in the H13CO+ J=1-0 map. The DC1 seems to be located on a line where the four HII regions line up. Furthermore, the DC1 has a broad velocity width covering ˜30 km s-1 and ˜60 km s-1 components in the CS J=2-1 map; the 30 km s-1 component has filamentary structures and the 60 km s-1 one a sheet-like structure. From the position-velocity diagrams of the H13CO+ J=1-0 and CS J=2-1 lines and the intensity ratio of T(SiO v=0 J=2-1)/T(H13CO+ J=1-0), i.e., a shock tracer, we consider that the DC1 has formed by the CCC between the filaments and the sheet-like gas. The LTE mass and virial parameter of the DC1 is estimated to be ˜1.3×104 M_ȯ and ˜5, respectively. These facts suggest that the DC1 is likely in a gravitationally bound state and may start massive star formation. We propose a scenario that the CCC induced the massive star formation in the HII region A ˜105 years ago and now causes the formation and collapse of the DC1; the clump would evolve to an HII region within ˜105 years.

  13. Gram-positive, motile, cluster-forming cocci as a cause of urinary infection

    PubMed Central

    Virtanen, S.

    1974-01-01

    One hundred and thirteen strains of motile, Gram-positive, catalase-positive, cluster-forming cocci were isolated from patients with urinary infection attending a private surgery. They constituted 1% of the total 11 302 positive cultures. The biochemical characteristics and the drug sensitivities of the strains are described. The significance of motility for organisms which cause urinary infections is pointed out. At the present time the organisms isolated are orphans in the controversial classification of staphylococci and micrococci. Images PMID:4852184

  14. The Luminosity Function of Star Clusters in 20 Star-Forming Galaxies Based on Hubble Legacy Archive Photometry

    NASA Astrophysics Data System (ADS)

    Bowers, Ariel; Whitmore, B. C.; Chandar, R.; Larsen, S. S.

    2014-01-01

    Luminosity functions have been determined for star cluster populations in 20 nearby (4 - 30 Mpc), star-forming galaxies based on ACS source lists generated by the Hubble Legacy Archive (http://hla.stsci.edu). These cluster catalogs provide one of the largest sets of uniform, automatically-generated cluster candidates available in the literature at present. Comparisons are made with other recently generated cluster catalogs demonstrating that the HLA-generated catalogs are of similar quality, but in general do not go as deep. A typical cluster luminosity function can be approximated by a power-law, dN/dL ∝ Lα, with an average value for α of -2.37 and rms scatter = 0.18. A comparison of fitting results based on methods which use binned and unbinned data shows good agreement, although there may be a systematic tendency for the unbinned (maximum-likelihood) method to give slightly more negative values of α for galaxies with steper luminosity functions. Our uniform database results in a small scatter (0.5 magnitude) in the correlation between the magnitude of the brightest cluster (Mbrightest) and Log of the number of clusters brighter than MI = -9 (Log N). We also examine the magnitude of the brightest cluster vs. Log SFR for a sample including LIRGS and ULIRGS.

  15. Extended main sequence turnoffs in intermediate-age star clusters: a correlation between turnoff width and early escape velocity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Goudfrooij, Paul; Kozhurina-Platais, Vera; Kalirai, Jason S.

    2014-12-10

    We present a color-magnitude diagram analysis of deep Hubble Space Telescope imaging of a mass-limited sample of 18 intermediate-age (1-2 Gyr old) star clusters in the Magellanic Clouds, including eight clusters for which new data were obtained. We find that all star clusters in our sample feature extended main-sequence turnoff (eMSTO) regions that are wider than can be accounted for by a simple stellar population (including unresolved binary stars). FWHM widths of the MSTOs indicate age spreads of 200-550 Myr. We evaluate the dynamical evolution of clusters with and without initial mass segregation. Our main results are (1) the fractionmore » of red clump (RC) stars in secondary RCs in eMSTO clusters scales with the fraction of MSTO stars having pseudo-ages of ≲1.35 Gyr; (2) the width of the pseudo-age distributions of eMSTO clusters is correlated with their central escape velocity v {sub esc}, both currently and at an age of 10 Myr. We find that these two results are unlikely to be reproduced by the effects of interactive binary stars or a range of stellar rotation velocities. We therefore argue that the eMSTO phenomenon is mainly caused by extended star formation within the clusters; and (3) we find that v {sub esc} ≥ 15 km s{sup –1} out to ages of at least 100 Myr for all clusters featuring eMSTOs, and v {sub esc} ≤ 12 km s{sup –1} at all ages for two lower-mass clusters in the same age range that do not show eMSTOs. We argue that eMSTOs only occur for clusters whose early escape velocities are higher than the wind velocities of stars that provide material from which second-generation stars can form. The threshold of 12-15 km s{sup –1} is consistent with wind velocities of intermediate-mass asymptotic giant branch stars and massive binary stars in the literature.« less

  16. New VVV Survey Globular Cluster Candidates in the Milky Way Bulge

    NASA Astrophysics Data System (ADS)

    Minniti, Dante; Geisler, Douglas; Alonso-García, Javier; Palma, Tali; Beamín, Juan Carlos; Borissova, Jura; Catelan, Marcio; Clariá, Juan J.; Cohen, Roger E.; Contreras Ramos, Rodrigo; Dias, Bruno; Fernández-Trincado, Jose G.; Gómez, Matías; Hempel, Maren; Ivanov, Valentin D.; Kurtev, Radostin; Lucas, Phillip W.; Moni-Bidin, Christian; Pullen, Joyce; Ramírez Alegría, Sebastian; Saito, Roberto K.; Valenti, Elena

    2017-11-01

    It is likely that a number of Galactic globular clusters remain to be discovered, especially toward the Galactic bulge. High stellar density combined with high and differential interstellar reddening are the two major problems for finding globular clusters located toward the bulge. We use the deep near-IR photometry of the VISTA Variables in the Vía Láctea (VVV) Survey to search for globular clusters projected toward the Galactic bulge, and hereby report the discovery of 22 new candidate globular clusters. These objects, detected as high density regions in our maps of bulge red giants, are confirmed as globular cluster candidates by their color-magnitude diagrams. We provide their coordinates as well as their near-IR color-magnitude diagrams, from which some basic parameters are derived, such as reddenings and heliocentric distances. The color-magnitude diagrams reveal well defined red giant branches in all cases, often including a prominent red clump. The new globular cluster candidates exhibit a variety of extinctions (0.06 < A Ks < 2.77) and distances (5.3 < D < 9.5 kpc). We also classify the globular cluster candidates into 10 metal-poor and 12 metal-rich clusters, based on the comparison of their color-magnitude diagrams with those of known globular clusters also observed by the VVV Survey. Finally, we argue that the census for Galactic globular clusters still remains incomplete, and that many more candidate globular clusters (particularly the low luminosity ones) await to be found and studied in detail in the central regions of the Milky Way. Based on observations taken within the ESO programs 179.B-2002 and 298.D-5048.

  17. Living on the Edge? Clumped Isotope and Oxygen Isotope Record of Early Cascade Topography (Eocene Chumstick Basin, WA, USA)

    NASA Astrophysics Data System (ADS)

    Methner, K.; Mulch, A.; Fiebig, J.; Wacker, U.; Umhoefer, P. J.; Chamberlain, C. P.

    2014-12-01

    The topographic evolution of the world's major orogens exerts a strong impact on atmospheric circulation and precipitation patterns and is a key element in reconstructing the interactions among tectonics, climate, and Earth surface processes. Using carbonate stable and clumped isotope data together with low-temperature thermochronology information from the terrestrial Eocene Chumstick Basin (Central Washington; USA), today located to the East of the Washington Cascades, we investigate the E-W extent of the western North American plateau region and the evolution of Cascade topography. Oxygen isotope measurements of Eocene (51 to 37 Ma) pedogenic carbonate concretions and calcic horizons yield low δ18Ocarbonate values of +9 to +13 ‰ (SMOW) despite the proximity of the Eocene Chumstick Basin to the Pacific moisture source and paleofloral data that indicate moderate elevations and montane rain forest conditions during a warm and rather wet, seasonal climate. This either suggests that 51-37 Ma ago Cascade-like topography characterized the western edge of the North American-Pacific plate margin to the West of the Chumstick Basin or that the δ18Ocarbonate data were variably reset or only formed during burial and diagenesis. Clumped isotope (Δ47) thermometry of pedogenic carbonate and carbonate concretions (n=11 samples) indicates spatially variable burial temperatures of 80 to 120 °C that correlate with vitrinite reflectance data in these sediments. In concordance with changes in depositional environment the youngest (<40 Ma) Chumstick sediments experienced a lesser degree of post-depositional burial and heating (ca. 70 - 80 °C) compared to the older Chumstick series (80 - 120 °C). Calculated δ18O values of the circulating fluids in the Chumstick basin sediments range from -6 ‰ (T ~100 °C at ca. 40-30 Ma) to -9 ‰ (T ~75 °C at ca. 25-15 Ma). These values suggest a low-altitude meteoric fluid source and as a consequence only moderate Cascade topography during

  18. Stellar Clusters in the NGC 6334 Star-Forming Complex

    NASA Astrophysics Data System (ADS)

    Feigelson, Eric D.; Martin, Amanda L.; McNeill, Collin J.; Broos, Patrick S.; Garmire, Gordon P.

    2009-07-01

    The full stellar population of NGC 6334, one of the most spectacular regions of massive star formation in the nearby Galaxy, has not been well sampled in past studies. We analyze here a mosaic of two Chandra X-ray Observatory images of the region using sensitive data analysis methods, giving a list of 1607 faint X-ray sources with arcsecond positions and approximate line-of-sight absorption. About 95% of these are expected to be cluster members, most lower mass pre-main-sequence stars. Extrapolating to low X-ray levels, the total stellar population is estimated to be 20,000-30,000 pre-main-sequence stars. The X-ray sources show a complicated spatial pattern with ~10 distinct star clusters. The heavily obscured clusters are mostly associated with previously known far-infrared sources and radio H II regions. The lightly obscured clusters are mostly newly identified in the X-ray images. Dozens of likely OB stars are found, both in clusters and dispersed throughout the region, suggesting that star formation in the complex has proceeded over millions of years. A number of extraordinarily heavily absorbed X-ray sources are associated with the active regions of star formation.

  19. Spitzer Imaging of Planck-Herschel Dusty Proto-Clusters at z=2-3

    NASA Astrophysics Data System (ADS)

    Cooray, Asantha; Ma, Jingzhe; Greenslade, Joshua; Kubo, Mariko; Nayyeri, Hooshang; Clements, David; Cheng, Tai-An

    2018-05-01

    We have recently introduced a new proto-cluster selection technique by combing Herschel/SPIRE imaging data and Planck/HFIk all-sky survey point source catalog. These sources are identified as Planck point sources with clumps of Herschel source over-densities with far-IR colors comparable to z=0 ULIRGS redshifted to z=2 to 3. The selection is sensitive to dusty starbursts and obscured QSOs and we have recovered couple of the known proto-clusters and close to 30 new proto-clusters. The candidate proto-clusters selected from this technique have far-IR flux densities several times higher than those that are optically selected, such as using LBG selection, implying that the member galaxies are in a special phase of heightened dusty starburst and dusty QSO activity. This far-IR luminous phase may be short but likely to be necessary piece to understand the whole stellar mass assembly history of clusters. Moreover, our photo-clusters are missed in optical selections, suggesting that optically selected proto-clusters alone do not provide adequate statistics and a comparison of the far-IR and optical selected clusters may reveal the importance of the dusty stellar mass assembly. Here, we propose IRAC observations of six of the highest priority new proto-clusters, to establish the validity of the technique and to determine the total stellar mass through SED models. For a modest observing time the science program will have a substantial impact on an upcoming science topic in cosmology with implications for observations with JWST and WFIRST to understand the mass assembly in the universe.

  20. Hubble tracks down a galaxy cluster's dark matter

    NASA Astrophysics Data System (ADS)

    2003-07-01

    Unique mass map hi-res Size hi-res: 495 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Unique mass map This is a mass map of galaxy cluster Cl0024+1654 derived from an extensive Hubble Space Telescope campaign. The colour image is made from two images: a dark-matter map (the blue part of the image) and a 'luminous-matter' map determined from the galaxies in the cluster (the red part of the image). They were constructed by feeding Hubble and ground-based observations into advanced mathematical mass-mapping models. The map shows that dark matter is present where the galaxies clump together. The mass of the galaxies is shown in red, the mass of the dark matter in blue. The dark matter behaves like a 'glue', holding the cluster together. The dark-matter distribution in the cluster is not spherical. A secondary concentration of dark-matter mass is shown in blue to the upper right of the main concentration. Sky around galaxy cluster Cl0024+1654 hi-res Size hi-res: 3742 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Sky around galaxy cluster Cl0024+1654 This is a 2.5-degree field around galaxy cluster Cl0024+1654. The cluster galaxies are visible in the centre of the image in yellow. The image is a colour composite constructed from three Digitized Sky Survey 2 images: Blue (shown in blue), Red (shown in green), and Infrared (shown in red). HST observes shapes of more than 7000 faint background galaxies hi-res Size hi-res: 5593 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Hubble observes shapes of more than 7000 faint background galaxies Five days of observations produced the altogether 39 Hubble Wide Field and Planetary Camera 2 (WFPC2) images required to map the mass of the galaxy cluster Cl0024+1654. Each WFPC2 image has a size of about 1/150 the diameter of the full Moon. In

  1. Interaction of clumpy dark matter with interstellar medium in astrophysical systems

    NASA Astrophysics Data System (ADS)

    Baushev, A. N.

    2012-02-01

    Contemporary cosmological conceptions suggest that the dark matter in haloes of galaxies and galaxy clusters has most likely a clumpy structure. If a stream of gas penetrates through it, a small-scale gravitational field created by the clumps disturbs the flow resulting in momentum exchange between the stream and the dark matter. In this article, we perform an analysis of this effect, based on the hierarchical halo model of the dark matter structure and Navarro-Frenk-White density profiles. We consider the clumps of various masses, from the smallest up to the highest ones M≥ 109 M⊙. It has been found that in any event the effect grows with the mass of the clump: not only the drag force ? acting on the clump but also its acceleration ? increases. We discuss various astrophysical systems. The mechanism proved to be ineffective in the case of galaxy or galaxy cluster collisions. On the other hand, it played an important role during the process of galaxy formation. As a result, the dark matter should have formed a more compact, oblate and faster rotating substructure in the halo of our Galaxy. We have shown that this thick disc should be more clumpy than the halo. This fact is very important for the indirect detection experiments since it is the clumps that give the main contribution to the annihilation signal. Our calculations show that the mechanism of momentum exchange between the dark and baryon matter is ineffective on the outskirts of the galactic halo. It means that the clumps from there were not transported to the thick disc, and this region should be more clumpy than the halo on the average.

  2. The Physical Environment around IRAS 17599-2148: Infrared Dark Cloud and Bipolar Nebula

    NASA Astrophysics Data System (ADS)

    Dewangan, L. K.; Ojha, D. K.; Zinchenko, I.; Janardhan, P.; Ghosh, S. K.; Luna, A.

    2016-12-01

    We present a multiscale and multiwavelength study to investigate the star formation process around IRAS 17599-2148, which is part of an elongated filamentary structure (EFS) (extension ˜21 pc) seen in the Herschel maps. Using the Herschel data analysis, at least six massive clumps (M clump ˜ 777-7024 M ⊙) are found in the EFS with a range of temperature and column density of ˜16-39 K and ˜(0.6-11) × 1022 cm-2 (A V ˜ 7-117 mag), respectively. The EFS hosts cold gas regions (I.e., infrared dark cloud) without any radio detection and a bipolar nebula (BN) linked with the H II region IRAS 17599-2148, tracing two distinct environments inferred through the temperature distribution and ionized emission. Based on virial analysis and higher values of self-gravitating pressure, the clumps are found unstable against gravitational collapse. We find 474 young stellar objects (YSOs) in the selected region, and ˜72% of these YSOs are found in the clusters distributed mainly toward the clumps in the EFS. These YSOs might have spontaneously formed due to processes not related to the expanding H II region. At the edges of BN, four additional clumps are also associated with YSO clusters, which appear to be influenced by the expanding H II region. The most massive clump in the EFS contains two compact radio sources traced in the Giant Metre-wave Radio Telescope 1.28 GHz map and a massive protostar candidate, IRS 1, prior to an ultracompact H II phase. Using the Very Large Telescope/NACO near-infrared images, IRS 1 is resolved with a jet-like feature within a 4200 au scale.

  3. A Reassessment of the Precision of Carbonate Clumped Isotope Measurements: Implications for Calibrations and Paleoclimate Reconstructions

    NASA Astrophysics Data System (ADS)

    Fernandez, Alvaro; Müller, Inigo A.; Rodríguez-Sanz, Laura; van Dijk, Joep; Looser, Nathan; Bernasconi, Stefano M.

    2017-12-01

    Carbonate clumped isotopes offer a potentially transformational tool to interpret Earth's history, but the proxy is still limited by poor interlaboratory reproducibility. Here, we focus on the uncertainties that result from the analysis of only a few replicate measurements to understand the extent to which unconstrained errors affect calibration relationships and paleoclimate reconstructions. We find that highly precise data can be routinely obtained with multiple replicate analyses, but this is not always done in many laboratories. For instance, using published estimates of external reproducibilities we find that typical clumped isotope measurements (three replicate analyses) have margins of error at the 95% confidence level (CL) that are too large for many applications. These errors, however, can be systematically reduced with more replicate measurements. Second, using a Monte Carlo-type simulation we demonstrate that the degree of disagreement on published calibration slopes is about what we should expect considering the precision of Δ47 data, the number of samples and replicate analyses, and the temperature range covered in published calibrations. Finally, we show that the way errors are typically reported in clumped isotope data can be problematic and lead to the impression that data are more precise than warranted. We recommend that uncertainties in Δ47 data should no longer be reported as the standard error of a few replicate measurements. Instead, uncertainties should be reported as margins of error at a specified confidence level (e.g., 68% or 95% CL). These error bars are a more realistic indication of the reliability of a measurement.

  4. Advancing Astronomical Instrumentation: an Adaptive Optics Kinematic Study of z 1 Star-Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Mieda, Etsuko

    This thesis has a dual focus on improving ground-based astronomical instruments and an observational study of distant star-forming galaxies to study galaxy formation and evolution. Of fundamental importance to this work are adaptive optics (AO) technology and integral field spectrographs (IFSs), both of which offer powerful means of studying high redshift galaxies. First, I describe the design and development of an instrument to characterize the vertical atmospheric turbulence using the SLODAR (SLOpe Detection and Ranging) method. This instrument was used in a campaign at Ellesmere island ( 80 degN) nd determined that the site has half of the total turbulence residing in the ground layer (< 1 km), and that the median seeing at Ellesmere is comparable to the best worldwide observing sites. Secondly, I present the design and implementation of an experimental setup to evaluate a new grating designed for OSIRIS (OH-Suppressing Infra-Red Imaging Spectrograph), an IFS at the Keck I telescope. I tested and installed a new grating in OSIRIS, and the improved sensitivity with the new grating is a factor of 1.83 between 1-2.4 um. Finally, taking direct advantage of the improved OSIRIS performance, I built-up the currently largest sample of z 1 star-forming galaxies taken with an IFS coupled with AO. I present the first results of IROCKS (Intermediate Redshift OSIRIS Chemo-Kinematic Survey), a spatially resolved Halpha survey containing sixteen z 1 and one z 1.5 star-forming galaxies. The Halpha kinematics and morphologies of these galaxies were investigated, including resolved star-forming clumps. These IROCKS results show that z 1 star-forming galaxies have elevated line-of-sight velocity dispersions (sigma_ave 60 km/s) compared to local galaxies yet have lower dispersions compared to their counterparts at higher redshift (z > 1.5). Four of the z 1 galaxies are well-fit to an inclined disk model, and the disk fraction is similar to high-z samples. The size

  5. Pseudothrombocytopenia or platelet clumping as a possible cause of low platelet count in patients with viral infection: a case series from single institution focusing on hepatitis A virus infection.

    PubMed

    Choe, W-H; Cho, Y-U; Chae, J-D; Kim, S-H

    2013-02-01

    Pseudothrombocytopenia (PTCP) is the phenomenon of ethylenediaminetetraacetic acid anticoagulant-activated platelet clumping, which results in artificially low platelet counts. Other investigators have reported a few cases of PTCP associated with viral infections. The objective of this study was to demonstrate the association of viral infection with PTCP. Medical records of patients with thrombocytopenia who were tested for peripheral blood smear examination between March 2009 and February 2011 were reviewed for platelet clumping and viral infection. Thrombocytopenic patients with viral infection had a higher frequency of platelet clumping than those with other diseases, which was statistically significant (13.8% vs. 6.5%, respectively: P = 0.003). Among the 18 cases where PTCP or platelet clumping was related to viral infection, hepatitis A virus infection (72.2%) was most common, followed by cytomegalovirus (11.1%) and influenza A H1N1 infections (5.6%). A third (33.3%) of the patients had platelet counts <100 × 10⁹/L. Pseudothrombocytopenia or platelet clumping should be considered in patients with acute viral infection, particularly if the platelet count is unexpectedly low, because failure to recognize PTCP may lead to unnecessary diagnostic tests and patient mismanagement. © 2012 Blackwell Publishing Ltd.

  6. The merging cluster Abell 1758: an optical and dynamical view

    NASA Astrophysics Data System (ADS)

    Monteiro-Oliveira, Rogerio; Serra Cypriano, Eduardo; Machado, Rubens; Lima Neto, Gastao B.

    2015-08-01

    The galaxy cluster Abell 1758-North (z=0.28) is a binary system composed by the sub-structures NW and NE. This is supposed to be a post-merging cluster due to observed detachment between the NE BCG and the respective X-ray emitting hot gas clump in a scenario very close to the famous Bullet Cluster. On the other hand, the projected position of the NW BCG coincides with the local hot gas peak. This system was been targeted previously by several studies, using multiple wavelengths and techniques, but there is still no clear picture of the scenario that could have caused this unusual configuration. To help solving this complex puzzle we added some pieces: firstly, we have used deep B, RC and z' Subaru images to perform both weak lensing shear and magnification analysis of A1758 (including here the South component that is not in interaction with A1758-North) modeling each sub-clump as an NFW profile in order to constrain masses and its center positions through MCMC methods; the second piece is the dynamical analysis using radial velocities available in the literature (143) plus new Gemini-GMOS/N measurements (68 new redshifts).From weak lensing we found that independent shear and magnification mass determinations are in excellent agreement between them and combining both we could reduce mass error bar by ~30% compared to shear alone. By combining this two weak-lensing probes we found that the position of both Northern BCGs are consistent with the masses centers within 2σ and and the NE hot gas peak to be offseted of the respective mass peak (M200=5.5 X 1014 M⊙) with very high significance. The most massive structure is NW (M200=7.95 X 1014 M⊙ ) where we observed no detachment between gas, DM and BCG.We have calculated a low line-of-sight velocity difference (<300 km/s) between A1758 NW and NE. We have combined it with the projected velocity of 1600 km/s which was estimated by previous X-ray analysis (David & Kempner 2004) and we have obtained a small angle between

  7. Sh2-138: physical environment around a small cluster of massive stars

    NASA Astrophysics Data System (ADS)

    Baug, T.; Ojha, D. K.; Dewangan, L. K.; Ninan, J. P.; Bhatt, B. C.; Ghosh, S. K.; Mallick, K. K.

    2015-12-01

    We present a multiwavelength study of the Sh2-138, a Galactic compact H II region. The data comprise of optical and near-infrared (NIR) photometric and spectroscopic observations from the 2-m Himalayan Chandra Telescope, radio observations from the Giant Metrewave Radio Telescope (GMRT), and archival data covering radio through NIR wavelengths. A total of 10 Class I and 54 Class II young stellar objects (YSOs) are identified in a 4.6 arcmin×4.6 arcmin area of the Sh2-138 region. Five compact ionized clumps, with four lacking of any optical or NIR counterparts, are identified using the 1280 MHz radio map, and correspond to sources with spectral type earlier than B0.5. Free-free emission spectral energy distribution fitting of the central compact H II region yields an electron density of ˜2250 ± 400 cm-3. With the aid of a wide range of spectra, from 0.5-15 μm, the central brightest source - previously hypothesized to be the main ionizing source - is characterized as a Herbig Be type star. At large scale (15 arcmin ×15 arcmin), the Herschel images (70-500 μm) and the nearest neighbour analysis of YSOs suggest the formation of an isolated cluster at the junction of filaments. Furthermore, using a greybody fit to the dust spectrum, the cluster is found to be associated with the highest column density (˜3 × 1022 cm-2) and high temperature (˜35 K) regime, as well as with the radio continuum emission. The mass of the central clump seen in the column density map is estimated to be ˜3770 M⊙.

  8. NASA Telescopes Help Identify Most Distant Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    2011-01-01

    WASHINGTON -- Astronomers have uncovered a burgeoning galactic metropolis, the most distant known in the early universe. This ancient collection of galaxies presumably grew into a modern galaxy cluster similar to the massive ones seen today. The developing cluster, named COSMOS-AzTEC3, was discovered and characterized by multi-wavelength telescopes, including NASA's Spitzer, Chandra and Hubble space telescopes, and the ground-based W.M. Keck Observatory and Japan's Subaru Telescope. "This exciting discovery showcases the exceptional science made possible through collaboration among NASA projects and our international partners," said Jon Morse, NASA's Astrophysics Division director at NASA Headquarters in Washington. Scientists refer to this growing lump of galaxies as a proto-cluster. COSMOS-AzTEC3 is the most distant massive proto-cluster known, and also one of the youngest, because it is being seen when the universe itself was young. The cluster is roughly 12.6 billion light-years away from Earth. Our universe is estimated to be 13.7 billion years old. Previously, more mature versions of these clusters had been spotted at 10 billion light-years away. The astronomers also found that this cluster is buzzing with extreme bursts of star formation and one enormous feeding black hole. "We think the starbursts and black holes are the seeds of the cluster," said Peter Capak of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena. "These seeds will eventually grow into a giant, central galaxy that will dominate the cluster -- a trait found in modern-day galaxy clusters." Capak is first author of a paper appearing in the Jan. 13 issue of the journal Nature. Most galaxies in our universe are bound together into clusters that dot the cosmic landscape like urban sprawls, usually centered around one old, monstrous galaxy containing a massive black hole. Astronomers thought that primitive versions of these clusters, still forming and clumping

  9. Watching the Birth of a Galaxy Cluster?

    NASA Astrophysics Data System (ADS)

    1999-07-01

    First Visiting Astronomers to VLT ANTU Observe the Early Universe When the first 8.2-m VLT Unit Telescope (ANTU) was "handed over" to the scientists on April 1, 1999, the first "visiting astronomers" at Paranal were George Miley and Huub Rottgering from the Leiden Observatory (The Netherlands) [1]. They obtained unique pictures of a distant exploding galaxy known as 1138 - 262 . These images provide new information about how massive galaxies and clusters of galaxies may have formed in the early Universe. Formation of clusters of galaxies An intriguing question in modern astronomy is how the first galaxies and groupings or clusters of galaxies emerged from the primeval gas produced in the Big Bang. Some theories predict that giant galaxies, often found at the centres of rich galaxy clusters, are built up through a step-wise process. Clumps develop in this gas and stars condense out of those clumps to form small galaxies. Finally these small galaxies merge together to form larger units. An enigmatic class of objects important for investigating such scenarios are galaxies which emit intense radio emission from explosions that occur deep in their nuclei. The explosions are believed to be triggered when material from the merging swarm of smaller galaxies is fed into a rotating black hole located in the central regions. There is strong evidence that these distant radio galaxies are amongst the oldest and most massive galaxies in the early Universe and are often located at the heart of rich clusters of galaxies. They can therefore help pinpoint regions of the Universe in which large galaxies and clusters of galaxies are being formed. The radio galaxy 1138-262 The first visiting astronomers pointed ANTU towards a particularly important radio galaxy named 1138-262 . It is located in the southern constellation Hydra (The Water Snake). This galaxy was discovered some years ago using ESO's 3.5-m New Technology Telescope (NTT) at La Silla. Because 1138-262 is at a distance of

  10. Spherical cluster ensembles with fractal structure in LaSrMnO: New form of self-organization in solids

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Okunev, V. D.; Samoilenko, Z. A.; Burkhovetski, V. V.

    The growth of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} films in magnetron plasma, in special conditions, leads to the appearance of ensembles of micron-sized spherical crystalline clusters with fractal structure, which we consider to be a new form of self-organization in solids. Each ensemble contains 10{sup 5}-10{sup 6} elementary clusters, 100-250 A in diameter. Interaction of the clusters in the ensemble is realized through the interatomic chemical bonds, intrinsic to the manganites. Integration of peripheral areas of interacting clusters results in the formation of common intercluster medium in the ensemble. We argue that the ensembles with fractal structure built into paramagnetic disorderedmore » matrix have ferromagnetic properties. Absence of sharp borders between elementary clusters and the presence of common intercluster medium inside each ensemble permits to rearrange magnetic order and to change the volume of the ferromagnetic phase, providing automatically a high sensitivity of the material to the external field.« less

  11. CLASH-VLT: DISSECTING THE FRONTIER FIELDS GALAXY CLUSTER MACS J0416.1-2403 WITH ∼800 SPECTRA OF MEMBER GALAXIES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Balestra, I.; Sartoris, B.; Girardi, M.

    2016-06-01

    We present VIMOS-Very Large Telescope (VLT) spectroscopy of the Frontier Fields cluster MACS J0416.1-2403 ( z  = 0.397). Taken as part of the CLASH-VLT survey, the large spectroscopic campaign provided more than 4000 reliable redshifts over ∼600 arcmin{sup 2}, including ∼800 cluster member galaxies. The unprecedented sample of cluster members at this redshift allows us to perform a highly detailed dynamical and structural analysis of the cluster out to ∼2.2 r {sub 200} (∼4 Mpc). Our analysis of substructures reveals a complex system composed of a main massive cluster ( M {sub 200} ∼ 0.9 × 10{sup 15} M {sub ⊙} and σ{sub V,r200} ∼ 1000 km s{supmore » −1}) presenting two major features: (i) a bimodal velocity distribution, showing two central peaks separated by Δ V {sub rf} ∼ 1100 km s{sup −1} with comparable galaxy content and velocity dispersion, and (ii) a projected elongation of the main substructures along the NE–SW direction, with a prominent sub-clump ∼600 kpc SW of the center and an isolated BCG approximately halfway between the center and the SW clump. We also detect a low-mass structure at z  ∼ 0.390, ∼10′ south of the cluster center, projected at ∼3 Mpc, with a relative line-of-sight velocity of Δ V{sub rf} ∼ −1700 km s{sup −1}. The cluster mass profile that we obtain through our dynamical analysis deviates significantly from the “universal” NFW, being best fit by a Softened Isothermal Sphere model instead. The mass profile measured from the galaxy dynamics is found to be in relatively good agreement with those obtained from strong and weak lensing, as well as with that from the X-rays, despite the clearly unrelaxed nature of the cluster. Our results reveal an overall complex dynamical state of this massive cluster and support the hypothesis that the two main subclusters are being observed in a pre-collisional phase, in agreement with recent findings from radio and deep X-ray data. In this

  12. The luminosity function of star clusters in 20 star-forming galaxies based on Hubble legacy archive photometry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Whitmore, Bradley C.; Bowers, Ariel S.; Lindsay, Kevin

    2014-04-01

    Luminosity functions (LFs) have been determined for star cluster populations in 20 nearby (4-30 Mpc), star-forming galaxies based on Advanced Camera for Surveys source lists generated by the Hubble Legacy Archive (HLA). These cluster catalogs provide one of the largest sets of uniform, automatically generated cluster candidates available in the literature at present. Comparisons are made with other recently generated cluster catalogs demonstrating that the HLA-generated catalogs are of similar quality, but in general do not go as deep. A typical cluster LF can be approximated by a power law, dN/dL∝L {sup α}, with an average value for α ofmore » –2.37 and rms scatter = 0.18 when using the F814W ('I') band. A comparison of fitting results based on methods that use binned and unbinned data shows good agreement, although there may be a systematic tendency for the unbinned (maximum likelihood) method to give slightly more negative values of α for galaxies with steeper LFs. We find that galaxies with high rates of star formation (or equivalently, with the brightest or largest numbers of clusters) have a slight tendency to have shallower values of α. In particular, the Antennae galaxy (NGC 4038/39), a merging system with a relatively high star formation rate (SFR), has the second flattest LF in the sample. A tentative correlation may also be present between Hubble type and values of α, in the sense that later type galaxies (i.e., Sd and Sm) appear to have flatter LFs. Hence, while there do appear to be some weak correlations, the relative similarity in the values of α for a large number of star-forming galaxies suggests that, to first order, the LFs are fairly universal. We examine the bright end of the LFs and find evidence for a downturn, although it only pertains to about 1% of the clusters. Our uniform database results in a small scatter (≈0.4 to 0.5 mag) in the correlation between the magnitude of the brightest cluster (M {sub brightest}) and log of the

  13. ALMA RESOLVES 30 DORADUS: SUB-PARSEC MOLECULAR CLOUD STRUCTURE NEAR THE CLOSEST SUPER STAR CLUSTER

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Indebetouw, Remy; Brogan, Crystal; Leroy, Adam

    2013-09-01

    We present Atacama Large (sub)Millimeter Array observations of 30 Doradus-the highest resolution view of molecular gas in an extragalactic star formation region to date ({approx}0.4 pc Multiplication-Sign 0.6 pc). The 30Dor-10 cloud north of R136 was mapped in {sup 12}CO 2-1, {sup 13}CO 2-1, C{sup 18}O 2-1, 1.3 mm continuum, the H30{alpha} recombination line, and two H{sub 2}CO 3-2 transitions. Most {sup 12}CO emission is associated with small filaments and clumps ({approx}<1 pc, {approx}10{sup 3} M{sub Sun} at the current resolution). Some clumps are associated with protostars, including ''pillars of creation'' photoablated by intense radiation from R136. Emission from molecularmore » clouds is often analyzed by decomposition into approximately beam-sized clumps. Such clumps in 30 Doradus follow similar trends in size, linewidth, and surface density to Milky Way clumps. The 30 Doradus clumps have somewhat larger linewidths for a given size than predicted by Larson's scaling relation, consistent with pressure confinement. They extend to a higher surface density at a given size and linewidth compared to clouds studied at 10 pc resolution. These trends are also true of clumps in Galactic infrared-dark clouds; higher resolution observations of both environments are required. Consistency of clump masses calculated from dust continuum, CO, and the virial theorem reveals that the CO abundance in 30 Doradus clumps is not significantly different from the Large Magellanic Cloud mean, but the dust abundance may be reduced by {approx}2. There are no strong trends in clump properties with distance from R136; dense clumps are not strongly affected by the external radiation field, but there is a modest trend toward lower dense clump filling fraction deeper in the cloud.« less

  14. Cold fronts and shocks formed by gas streams in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Zinger, E.; Dekel, A.; Birnboim, Y.; Nagai, D.; Lau, E.; Kravtsov, A. V.

    2018-05-01

    Cold fronts (CFs) and shocks are hallmarks of the complex intra-cluster medium (ICM) in galaxy clusters. They are thought to occur due to gas motions within the ICM and are often attributed to galaxy mergers within the cluster. Using hydro-cosmological simulations of clusters of galaxies, we show that collisions of inflowing gas streams, seen to penetrate to the very centre of about half the clusters, offer an additional mechanism for the formation of shocks and CFs in cluster cores. Unlike episodic merger events, a gas stream inflow persists over a period of several Gyr and it could generate a particular pattern of multiple CFs and shocks.

  15. SODIUM AND OXYGEN ABUNDANCES IN THE OPEN CLUSTER NGC 6791 FROM APOGEE H-BAND SPECTROSCOPY

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cunha, Katia; Souto, Diogo; Smith, Verne V.

    2015-01-10

    The open cluster NGC 6791 is among the oldest, most massive, and metal-rich open clusters in the Galaxy. High-resolution H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) of 11 red giants in NGC 6791 are analyzed for their chemical abundances of iron, oxygen, and sodium. The abundances of these three elements are found to be homogeneous (with abundance dispersions at the level of ∼0.05-0.07 dex) in these cluster red giants, which span much of the red-giant branch (T {sub eff} ∼ 3500-4600 K), and include two red clump giants. From the infrared spectra, this cluster is confirmed to be amongmore » the most metal-rich clusters in the Galaxy (([Fe/H]) = 0.34 ± 0.06) and is found to have a roughly solar value of [O/Fe] and slightly enhanced [Na/Fe]. Our non-LTE calculations for the studied Na I lines in the APOGEE spectral region (16373.86 Å and 16388.85 Å) indicate only small departures from LTE (≤0.04 dex) for the parameter range and metallicity of the studied stars. The previously reported double population of cluster members with different Na abundances is not found among the studied sample.« less

  16. Trehalose Polyphleates, External Cell Wall Lipids in Mycobacterium abscessus, Are Associated with the Formation of Clumps with Cording Morphology, Which Have Been Associated with Virulence

    PubMed Central

    Llorens-Fons, Marta; Pérez-Trujillo, Míriam; Julián, Esther; Brambilla, Cecilia; Alcaide, Fernando; Byrd, Thomas F.; Luquin, Marina

    2017-01-01

    Mycobacterium abscessus is a reemerging pathogen that causes pulmonary diseases similar to tuberculosis, which is caused by Mycobacterium tuberculosis. When grown in agar medium, M. abscessus strains generate rough (R) or smooth colonies (S). R morphotypes are more virulent than S morphotypes. In searching for the virulence factors responsible for this difference, R morphotypes have been found to form large aggregates (clumps) that, after being phagocytozed, result in macrophage death. Furthermore, the aggregates released to the extracellular space by damaged macrophages grow, forming unphagocytosable structures that resemble cords. In contrast, bacilli of the S morphotype, which do not form aggregates, do not damage macrophages after phagocytosis and do not form cords. Cording has also been related to the virulence of M. tuberculosis. In this species, the presence of mycolic acids and surface-exposed cell wall lipids has been correlated with the formation of cords. The objective of this work was to study the roles of the surface-exposed cell wall lipids and mycolic acids in the formation of cords in M. abscessus. A comparative study of the pattern and structure of mycolic acids was performed on R (cording) and S (non-cording) morphotypes derived from the same parent strains, and no differences were observed between morphotypes. Furthermore, cords formed by R morphotypes were disrupted with petroleum ether (PE), and the extracted lipids were analyzed by thin layer chromatography, nuclear magnetic resonance spectroscopy and mass spectrometry. Substantial amounts of trehalose polyphleates (TPP) were recovered as major lipids from PE extracts, and images obtained by transmission electron microscopy suggested that these lipids are localized to the external surfaces of cords and R bacilli. The structure of M. abscessus TPP was revealed to be similar to those previously described in Mycobacterium smegmatis. Although the exact role of TPP is unknown, our results

  17. Improvements in Ionized Cluster-Beam Deposition

    NASA Technical Reports Server (NTRS)

    Fitzgerald, D. J.; Compton, L. E.; Pawlik, E. V.

    1986-01-01

    Lower temperatures result in higher purity and fewer equipment problems. In cluster-beam deposition, clusters of atoms formed by adiabatic expansion nozzle and with proper nozzle design, expanding vapor cools sufficiently to become supersaturated and form clusters of material deposited. Clusters are ionized and accelerated in electric field and then impacted on substrate where films form. Improved cluster-beam technique useful for deposition of refractory metals.

  18. δ18O and Carbonate Clumped Isotopes as Proxies of Lake Level Change: Mono Lake Modern Sediments Inform Pleistocene Interpretations

    NASA Astrophysics Data System (ADS)

    Westacott, S.; Ingalls, M.; Meixnerova, J.; Betts, M.; Lloyd, M. K.; Miller, L. G.; Sessions, A. L.; Trower, L.; Geobiology Course, A.

    2017-12-01

    , suggesting that potentially more of Lake Russell carbonates formed at or near the surface. Clumped isotope analysis thus holds significant potential to improve our interpretation of sedimentary carbonates as proxies for lake level and other paleo-environmental conditions.

  19. The SCUBA-2 cosmology legacy survey: Ultraluminous star-forming galaxies in a z = 1.6 cluster

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Smail, Ian; Swinbank, A. M.; Danielson, A. L. R.

    2014-02-10

    We analyze new SCUBA-2 submillimeter and archival SPIRE far-infrared imaging of a z = 1.62 cluster, Cl 0218.3–0510, which lies in the UKIRT Infrared Deep Sky Survey/Ultra-Deep Survey field of the SCUBA-2 Cosmology Legacy Survey. Combining these tracers of obscured star-formation activity with the extensive photometric and spectroscopic information available for this field, we identify 31 far-infrared/submillimeter-detected probable cluster members with bolometric luminosities ≳10{sup 12} L {sub ☉} and show that by virtue of their dust content and activity, these represent some of the reddest and brightest galaxies in this structure. We exploit ALMA submillimeter continuum observations, which cover onemore » of these sources, to confirm the identification of a SCUBA-2-detected ultraluminous star-forming galaxy in this structure. Integrating the total star-formation activity in the central region of the structure, we estimate that it is an order of magnitude higher (in a mass-normalized sense) than clusters at z ∼ 0.5-1. However, we also find that the most active cluster members do not reside in the densest regions of the structure, which instead host a population of passive and massive, red galaxies. We suggest that while the passive and active populations have comparable near-infrared luminosities at z = 1.6, M{sub H} ∼ –23, the subsequent stronger fading of the more active galaxies means that they will evolve into passive systems at the present day that are less luminous than the descendants of those galaxies that were already passive at z ∼ 1.6 (M{sub H} ∼ –20.5 and M{sub H} ∼ –21.5, respectively, at z ∼ 0). We conclude that the massive galaxy population in the dense cores of present-day clusters were already in place at z = 1.6 and that in Cl 0218.3–0510 we are seeing continuing infall of less extreme, but still ultraluminous, star-forming galaxies onto a pre-existing structure.« less

  20. VizieR Online Data Catalog: Planck Catalogue of Galactic cold clumps (PGCC) (Planck+, 2016)

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit, A.; Benoit-Levy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Butler, R. C.; Calabrese, E.; Catalano, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; De Rosa, A.; de Zotti, G.; Delabrouille, J.; Desert, F.-X.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Dore, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Ensslin, T. A.; Eriksen, H. K.; Falgarone, E.; Fergusson, J.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Heraud, Y.; Gjerlow, E.; Gonzalez-Nuevo, J.; Gorsk, I. K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Helou, G.; Henrot-Versille, S.; Hernandez-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihanen, E.; Keskitalo, R.; Kisner, T. S.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vornle, M.; Lopez-Caniego, M.; Lubin, P. M.; Macias-Perez, J. F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Marshall, D. J.; Martin, P. G.; Martinez-Gonzalez, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; McGehee, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschenes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Norgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Pelkonen, V.-M.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Prezeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubino-Martin, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Stolyarov, V.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Valiviita, J.; van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

    2017-01-01

    The Planck Catalogue of Galactic Cold Clumps (PGCC) is a list of 13188 Galactic sources and 54 sources located in the Small and Large Magellanic Clouds. The sources have been identified in Planck data as sources colder than their environment. It has been built using the 48 months Planck data at 857, 545, and 353GHz combined with the 3THz IRAS data. (1 data file).

  1. Abundance differences among globular-cluster giants: Primordial versus evolutionary scenarios

    NASA Astrophysics Data System (ADS)

    Kraft, Robert P.

    1994-06-01

    Contrary to historical expectation, stars within a given globular cluster often exhibit wide variations in the abundance of C, N, and O as well as certain light metals, particularly Na and Al. Owing to flux limitations, studies have been confined to evolved stars, especially giants, but in few instances variations have been detected among main-sequence stars. Among giants, the variations are of two kinds. The abundances of C and N are often anticorrelated, and in the limited number of cases in which both have been measured, O and N abundances have also often proved to be anticorrelated (Pilachowski 1988; Sneden et al. 1991; Brown et al. 1991; Kraft et al. 1992). Following pioneering work by Cohen (1978) and Peterson (1980), strong evidence has recently emerged for the existence of a significant global anticorrelation between O and Na abundances (Drake et al. 1992, Kraft et al. 1993). The observations are discussed in terms of contrasting hypotheses: evolutionary versus primordial. In the former, the variations are attributed to the dredgeup of material that has been processed through the CNO cycle in the globular-cluster stars themselves. In the latter, the variations are attributed to primordial chemical inhomogeneities in the material out of which the cluster stars were formed, the composition of these 'clumps' having been determined by nuclear processing in a prior generation of more massive stars. Observational evidence supporting each of these scenarios is cited. Recent studies of stellar rotation among horizontal branch stars in certain clusters (Peterson et al. 1994) as well as new calculations of Na-23 and Al-27 production in the CNO processing regions of evolving low-mass giants (Langer et al. 1993) lend fresh support to the evolutionary hypothesis. However, such calculations do not explain the variation of C and N abundances found among cluster main-sequence stars (Suntzeff 1989; Briley et al. 1991) which therefore seem explicable only on the basis of a

  2. The flat density profiles of massive, and relaxed galaxy clusters

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Popolo, A. Del, E-mail: adelpopolo@oact.inaf.it

    2014-07-01

    The present paper is an extension and continuation of Del Popolo (2012a) which studied the role of baryon physics on clusters of galaxies formation. In the present paper, we studied by means of the SIM introduced in Del Popolo (2009), the total and DM density profiles, and the correlations among different quantities, observed by Newman et al. (2012a,b), in seven massive and relaxed clusters, namely MS2137, A963, A383, A611, A2537, A2667, A2390. As already found in Del Popolo 2012a, the density profiles depend on baryonic fraction, angular momentum, and the angular momentum transferred from baryons to DM through dynamical friction.more » Similarly to Newman et al. (2012a,b), the total density profile, in the radius range 0.003–0.03r{sub 200}, has a mean total density profile in agreement with dissipationless simulations. The slope of the DM profiles of all clusters is flatter than -1. The slope, α, has a maximum value (including errors) of α = −0.88 in the case of A2390, and minimum value α = −0.14 for A2537. The baryonic component dominates the mass distribution at radii < 5–10 kpc, while the outer distribution is dark matter dominated. We found an anti-correlation among the slope α, the effective radius, R{sub e}, and the BCG mass, and a correlation among the core radius r{sub core}, and R{sub e}. Moreover, the mass in 100 kpc (mainly dark matter) is correlated with the mass inside 5 kpc (mainly baryons). The behavior of the total mass density profile, the DM density profile, and the quoted correlations can be understood in a double phase scenario. In the first dissipative phase the proto-BCG forms, and in the second dissipationless phase, dynamical friction between baryonic clumps (collapsing to the center) and the DM halo flattens the inner slope of the density profile. In simple terms, the large scatter in the inner slope from cluster to cluster, and the anti-correlation among the slope, α and R{sub e} is due to the fact that in order to have a

  3. The Structure of the Star-forming Cluster RCW 38

    NASA Astrophysics Data System (ADS)

    Winston, E.; Wolk, S. J.; Bourke, T. L.; Megeath, S. T.; Gutermuth, R.; Spitzbart, B.

    2011-12-01

    We present a study of the structure of the high-mass star-forming region RCW 38 and the spatial distribution of its young stellar population. Spitzer Infrared Array Camera (IRAC) photometry (3-8 μm) is combined with Two Micron All Sky Survey near-IR data to identify young stellar objects (YSOs) by IR-excess emission from their circumstellar material. Chandra X-ray data are used to identify class III pre-main-sequence stars lacking circumstellar material. We identify 624 YSOs: 23 class 0/I and 90 flat spectrum protostars, 437 class II stars, and 74 class III stars. We also identify 29 (27 new) O star candidates over the IRAC field. Seventy-two stars exhibit IR-variability, including 7 class 0/I and 12 flat spectrum YSOs. A further 177 tentative candidates are identified by their location in the IRAC [3.6] versus [3.6]-[5.8] color-magnitude diagram. We find strong evidence of subclustering in the region. Three subclusters were identified surrounding the central cluster, with massive and variable stars in each subcluster. The central region shows evidence of distinct spatial distributions of the protostars and pre-main-sequence stars. A previously detected IR cluster, DB2001_Obj36, has been established as a subcluster of RCW 38. This suggests that star formation in RCW 38 occurs over a more extended area than previously thought. The gas-to-dust ratio is examined using the X-ray derived hydrogen column density, N H and the K-band extinction, and found to be consistent with the diffuse interstellar medium, in contrast with Serpens and NGC 1333. We posit that the high photoionizing flux of massive stars in RCW 38 affects the agglomeration of the dust grains.

  4. Enhanced water window x-ray emission from in situ formed carbon clusters irradiated by intense ultra-short laser pulses

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chakravarty, U.; Rao, B. S.; Arora, V.

    Enhanced water window x-ray emission (23–44 Å) from carbon clusters, formed in situ using a pre-pulse, irradiated by intense (I > 10{sup 17} W/cm{sup 2}) ultra-short laser pulse, is demonstrated. An order of magnitude x-ray enhancement over planar graphite target is observed in carbon clusters, formed by a sub-ns pre-pulse, interacting with intense main pulse after a delay. The effect of the delay and the duration of the main pulse is studied for optimizing the x-ray emission in the water window region. This x-ray source has added advantages of being an efficient, high repetition rate, and low debris x-ray source.

  5. Star-forming galaxies in intermediate-redshift clusters: stellar versus dynamical masses of luminous compact blue galaxies

    NASA Astrophysics Data System (ADS)

    Randriamampandry, S. M.; Crawford, S. M.; Bershady, M. A.; Wirth, G. D.; Cress, C. M.

    2017-10-01

    We investigate the stellar masses of the class of star-forming objects known as luminous compact blue galaxies (LCBGs) by studying a sample of galaxies in the distant cluster MS 0451.6-0305 at z ≈ 0.54 with ground-based multicolour imaging and spectroscopy. For a sample of 16 spectroscopically confirmed cluster LCBGs (colour B - V < 0.5, surface brightness μB < 21 mag arcsec-2 and magnitude MB < -18.5), we measure stellar masses by fitting spectral energy distribution (SED) models to multiband photometry, and compare with dynamical masses [determined from velocity dispersion in the range 10 < σv(km s- 1) < 80] we previously obtained from their emission-line spectra. We compare two different stellar population models that measure stellar mass in star-bursting galaxies, indicating correlations between the stellar age, extinction and stellar mass derived from the two different SED models. The stellar masses of cluster LCBGs are distributed similarly to those of field LCBGs, but the cluster LCBGs show lower dynamical-to-stellar mass ratios (Mdyn/M⋆ = 2.6) than their field LCBG counterparts (Mdyn/M⋆ = 4.8), echoing trends noted previously in low-redshift dwarf elliptical galaxies. Within this limited sample, the specific star formation rate declines steeply with increasing mass, suggesting that these cluster LCBGs have undergone vigorous star formation.

  6. Laboratory calibration of the calcium carbonate clumped isotope thermometer in the 25-250 °C temperature range

    NASA Astrophysics Data System (ADS)

    Kluge, Tobias; John, Cédric M.; Jourdan, Anne-Lise; Davis, Simon; Crawshaw, John

    2015-05-01

    Many fields of Earth sciences benefit from the knowledge of mineral formation temperatures. For example, carbonates are extensively used for reconstruction of the Earth's past climatic variations by determining ocean, lake, and soil paleotemperatures. Furthermore, diagenetic minerals and their formation or alteration temperature may provide information about the burial history of important geological units and can have practical applications, for instance, for reconstructing the geochemical and thermal histories of hydrocarbon reservoirs. Carbonate clumped isotope thermometry is a relatively new technique that can provide the formation temperature of carbonate minerals without requiring a priori knowledge of the isotopic composition of the initial solution. It is based on the temperature-dependent abundance of the rare 13C-18O bonds in carbonate minerals, specified as a Δ47 value. The clumped isotope thermometer has been calibrated experimentally from 1 °C to 70 °C. However, higher temperatures that are relevant to geological processes have so far not been directly calibrated in the laboratory. In order to close this calibration gap and to provide a robust basis for the application of clumped isotopes to high-temperature geological processes we precipitated CaCO3 (mainly calcite) in the laboratory between 23 and 250 °C. We used two different precipitation techniques: first, minerals were precipitated from a CaCO3 supersaturated solution at atmospheric pressure (23-91 °C), and, second, from a solution resulting from the mixing of CaCl2 and NaHCO3 in a pressurized reaction vessel at a pressure of up to 80 bar (25-250 °C).

  7. STAR-FORMING ACTIVITY IN THE H ii REGIONS ASSOCIATED WITH THE IRAS 17160–3707 COMPLEX

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nandakumar, G.; Veena, V. S.; Vig, S.

    2016-11-01

    We present a multiwavelength investigation of star formation activity toward the southern H ii regions associated with IRAS 17160–3707, located at a distance of 6.2 kpc with a bolometric luminosity of 8.3 × 10{sup 5} L {sub ⊙}. The ionized gas distribution and dust clumps in the parental molecular cloud are examined in detail using measurements at infrared, submillimeter and radio wavelengths. The radio continuum images at 1280 and 610 MHz obtained using the Giant Metrewave Radio Telescope reveal the presence of multiple compact sources as well as nebulous emission. At submillimeter wavelengths, we identify seven dust clumps and estimate their physical properties suchmore » as temperature: 24–30 K, mass: 300–4800 M {sub ⊙} and luminosity: 9–317 × 10{sup 2} L {sub ⊙} using modified blackbody fits to the spectral energy distributions (SEDs) between 70 and 870 μ m. We find 24 young stellar objects (YSOs) in the mid-infrared, with a few of them coincident with the compact radio sources. The SEDs of the YSOs have been fitted by the Robitaille models and the results indicate that those having radio compact sources as counterparts host massive objects in early evolutionary stages with best fit age ≤0.2 Myr. We compare the relative evolutionary stages of clumps using various signposts such as masers, ionized gas, presence of YSOs and infrared nebulosity, and find six massive star-forming clumps and one quiescent clump. Of the former, five are in a relatively advanced stage and one in an earlier stage.« less

  8. Star-Forming Galaxies in the Hercules Cluster: Hα Imaging of A2151

    NASA Astrophysics Data System (ADS)

    Cedrés, Bernabé; Iglesias-Páramo, Jorge; Vílchez, José Manuel; Reverte, Daniel; Petropoulou, Vasiliki; Hernández-Fernández, Jonathan

    2009-09-01

    This paper presents the first results of an Hα imaging survey of galaxies in the central regions of the A2151 cluster. A total of 50 sources were detected in Hα, from which 41 were classified as secure members of the cluster and 2 as likely members based on spectroscopic and photometric redshift considerations. The remaining seven galaxies were classified as background contaminants and thus excluded from our study on the Hα properties of the cluster. The morphologies of the 43 Hα selected galaxies range from grand design spirals and interacting galaxies to blue compacts and tidal dwarfs or isolated extragalactic H II regions, spanning a range of magnitudes of -21 <= MB <= -12.5 mag. From these 43 galaxies, 7 have been classified as active galactic nucleus (AGN) candidates. These AGN candidates follow the L(Hα) versus MB relationship of the normal galaxies, implying that the emission associated with the nuclear engine has a rather secondary impact on the total Hα emission of these galaxies. A comparison with the clusters Coma and A1367 and a sample of field galaxies has shown the presence of cluster galaxies with L(Hα) lower than expected for their MB , a consequence of the cluster environment. This fact results in differences in the L(Hα) versus EW(Hα) and L(Hα) distributions of the clusters with respect to the field, and in cluster-to-cluster variations of these quantities, which we propose are driven by a global cluster property as the total mass. In addition, the cluster Hα emitting galaxies tend to avoid the central regions of the clusters, again with different intensity depending on the cluster total mass. For the particular case of A2151, we find that most Hα emitting galaxies are located close to the regions with the higher galaxy density, offset from the main X-ray peak. Overall, we conclude that both the global cluster environment and the cluster merging history play a non-negligible role in the integral star formation properties of clusters of

  9. STAR FORMATION ACROSS THE W3 COMPLEX

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Román-Zúñiga, Carlos G.; Ybarra, Jason E.; Tapia, Mauricio

    We present a multi-wavelength analysis of the history of star formation in the W3 complex. Using deep, near-infrared ground-based images combined with images obtained with Spitzer and Chandra observatories, we identified and classified young embedded sources. We identified the principal clusters in the complex and determined their structure and extension. We constructed extinction-limited samples for five principal clusters and constructed K-band luminosity functions that we compare with those of artificial clusters with varying ages. This analysis provided mean ages and possible age spreads for the clusters. We found that IC 1795, the centermost cluster of the complex, still hosts amore » large fraction of young sources with circumstellar disks. This indicates that star formation was active in IC 1795 as recently as 2 Myr ago, simultaneous to the star-forming activity in the flanking embedded clusters, W3-Main and W3(OH). A comparison with carbon monoxide emission maps indicates strong velocity gradients in the gas clumps hosting W3-Main and W3(OH) and shows small receding clumps of gas at IC 1795, suggestive of rapid gas removal (faster than the T Tauri timescale) in the cluster-forming regions. We discuss one possible scenario for the progression of cluster formation in the W3 complex. We propose that early processes of gas collapse in the main structure of the complex could have defined the progression of cluster formation across the complex with relatively small age differences from one group to another. However, triggering effects could act as catalysts for enhanced efficiency of formation at a local level, in agreement with previous studies.« less

  10. THE PHYSICAL ENVIRONMENT AROUND IRAS 17599–2148: INFRARED DARK CLOUD AND BIPOLAR NEBULA

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dewangan, L. K.; Janardhan, P.; Ojha, D. K.

    We present a multiscale and multiwavelength study to investigate the star formation process around IRAS 17599–2148, which is part of an elongated filamentary structure (EFS) (extension ∼21 pc) seen in the Herschel maps. Using the Herschel data analysis, at least six massive clumps (M {sub clump} ∼ 777–7024 M {sub ⊙}) are found in the EFS with a range of temperature and column density of ∼16–39 K and ∼(0.6–11) × 10{sup 22} cm{sup −2} (A {sub V}  ∼ 7–117 mag), respectively. The EFS hosts cold gas regions (i.e., infrared dark cloud) without any radio detection and a bipolar nebula (BN) linked with the Hmore » ii region IRAS 17599–2148, tracing two distinct environments inferred through the temperature distribution and ionized emission. Based on virial analysis and higher values of self-gravitating pressure, the clumps are found unstable against gravitational collapse. We find 474 young stellar objects (YSOs) in the selected region, and ∼72% of these YSOs are found in the clusters distributed mainly toward the clumps in the EFS. These YSOs might have spontaneously formed due to processes not related to the expanding H ii region. At the edges of BN, four additional clumps are also associated with YSO clusters, which appear to be influenced by the expanding H ii region. The most massive clump in the EFS contains two compact radio sources traced in the Giant Metre-wave Radio Telescope 1.28 GHz map and a massive protostar candidate, IRS 1, prior to an ultracompact H ii phase. Using the Very Large Telescope/NACO near-infrared images, IRS 1 is resolved with a jet-like feature within a 4200 au scale.« less

  11. Structure of massive star forming clumps from the Red MSX Source Survey

    NASA Astrophysics Data System (ADS)

    Figura, Charles C.; Urquhart, J. S.; Morgan, L.

    2014-01-01

    We present ammonia (1,1) and (2,2) emission maps of 61 high-mass star forming regions drawn from the Red MSX Source (RMS) Survey and observed with the Green Bank Telescope's K-Band Focal Plane Array. We use these observations to investigate the spatial distribution of the environmental conditions associated with this sample of embedded massive young stellar objects (MYSOs). Ammonia is an excellent high-density tracer of star-forming regions as its hyperfine structure allows relatively simple characterisation of the molecular environment. These maps are used to measure the column density, kinetic gas temperature distributions and velocity structure across these regions. We compare the distribution of these properties to that of the associated dust and mid-infrared emission traced by the ATLASGAL 870 micron emission maps and the Spitzer GLIMPSE IRAC images. We present a summary of these results and highlight some of more interesting finds.

  12. DIRECT DETECTION OF PRECURSORS OF GAS GIANTS FORMED BY GRAVITATIONAL INSTABILITY WITH THE ATACAMA LARGE MILLIMETER/SUBMILLIMETER ARRAY

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mayer, Lucio; Peters, Thomas; Pineda, Jaime E.

    Phases of gravitational instability are expected in the early phases of disk evolution, when the disk mass is still a substantial fraction of the mass of the star. Disk fragmentation into sub-stellar objects could occur in the cold exterior part of the disk. Direct detection of massive gaseous clumps on their way to collapse into gas giant planets would offer an unprecedented test of the disk instability model. Here we use state-of-the-art 3D radiation-hydro simulations of disks undergoing fragmentation into massive gas giants, post-processed with RADMC-3D to produce dust continuum emission maps. These are then fed into the Common Astronomymore » Software Applications (CASA) ALMA simulator. The synthetic maps show that both overdense spiral arms and actual clumps at different stages of collapse can be detected with the Atacama Large Millimeter/submillimeter Array (ALMA) in the full configuration at the distance of the Ophiuchus star forming region (125 pc). The detection of clumps is particularly effective at shorter wavelengths (690 GHz) combining two resolutions with multi-scale clean. Furthermore, we show that a flux-based estimate of the mass of a protoplanetary clump can be comparable to a factor of three higher than the gravitationally bound clump mass. The estimated mass depends on the assumed opacity, and on the gas temperature, which should be set using the input of radiation-hydro simulations. We conclude that ALMA has the capability to detect “smoking gun” systems that are a signpost of the disk instability model for gas giant planet formation.« less

  13. Observational Signatures of Cloud-Cloud Collision in the Extended Star-forming Region S235

    NASA Astrophysics Data System (ADS)

    Dewangan, L. K.; Ojha, D. K.

    2017-11-01

    We present a multi-wavelength data analysis of the extended star-forming region S235 (hereafter E-S235), where two molecular clouds are present. In E-S235, using the 12CO (1-0) and 13CO (1-0) line data, a molecular cloud linked with the site “S235main” is traced in a velocity range [-24, -18] km s-1, while the other one containing the sites S235A, S235B, and S235C (hereafter “S235ABC”) is depicted in a velocity range [-18, -13] km s-1. In the velocity space, these two clouds are separated by ˜4 km s-1, and are interconnected by a lower-intensity intermediate velocity emission, tracing a broad bridge feature. In the velocity channel maps, a possible complementary molecular pair at [-21, -20] km s-1 and [-16, -15] km s-1 is also evident. The sites, “S235ABC,” east 1, and south-west, are spatially seen in the interface of two clouds. Together, these observed features are consistent with the predictions of numerical models of the cloud-cloud collision (CCC) process, favoring the onset of the CCC in E-S235 about 0.5 Myr ago. Deep UKIDSS near-infrared photometric analysis of point-like sources reveals significant clustering of young stellar populations toward the sites located at the junction, and the “S235main.” The sites “S235ABC” harbor young compact H II regions with dynamical ages of ˜0.06-0.22 Myr, and these sites (including south-west and east 1) also contain dust clumps (having M clump ˜ 40 to 635 {M}⊙ ). Our observational findings suggest that the star formation activities (including massive stars) appear to be influenced by the CCC mechanism at the junction.

  14. A molecular line study towards massive extended green object clumps in the southern sky: chemical properties

    NASA Astrophysics Data System (ADS)

    Yu, Naiping; Wang, Jun-Jie

    2015-08-01

    We present a molecular line study towards 31 extended green object (EGO) clumps in the southern sky using data from MALT90 (Millimetre Astronomy Legacy Team 90 GHz). According to previous multiwavelength observations, we divide our sample into two groups: massive young stellar objects (MYSOs) and H II regions. The most detected lines are N2H+ (J = 1 - 0), HCO+ (J = 1 - 0), HNC (J = 1 - 0), HCN (J = 1 - 0), HC3N (J = 10 - 9), H13CO+ (J = 1 - 0), C2H (N = 1 - 0) and SiO (J = 2 - 1), indicating that most EGOs are indeed associated with dense clumps and recent outflow activities. The velocity widths of the N2H+ (J = 1 - 0), H13CO+ (J = 1 - 0), C2H (N = 1 - 0) and HC3N (J = 10 - 9) lines are comparable to each other in MYSOs. However, in H II regions the velocity widths of the N2H+ (J = 1 - 0) and C2H (N = 1 - 0) lines tend to be narrower than those of H13CO+ (J = 1 - 0) and HC3N (J = 10 - 9). Our results seem to support that N2H+ and C2H emissions mainly come from the gas inside quiescent clumps. In addition, we also find that the [N2H+]/[H13CO+] and [C2H]/[H13CO+] relative abundance ratios decrease from MYSOs to H II regions. These results suggest depletion of N2H+ and C2H in the late stages of massive-star formation, probably caused by the formation of H II regions inside. N2H+ and C2H might be used as chemical clocks for massive-star formation by comparing with other molecules such as H13CO+ and HC3N.

  15. Probing the Dragonfish star-forming complex: the ionizing population of the young massive cluster Mercer 30

    NASA Astrophysics Data System (ADS)

    de la Fuente, D.; Najarro, F.; Borissova, J.; Ramírez Alegría, S.; Hanson, M. M.; Trombley, C.; Figer, D. F.; Davies, B.; Garcia, M.; Kurtev, R.; Urbaneja, M. A.; Smith, L. C.; Lucas, P. W.; Herrero, A.

    2016-05-01

    It has recently been claimed that the nebula, Dragonfish, is powered by a superluminous but elusive OB association. However, systematic searches in near-infrared photometric surveys have found many other cluster candidates in this region of the sky. Among these, the first confirmed young massive cluster was Mercer 30, where Wolf-Rayet stars were found.We perform a new characterization of Mercer 30 with unprecedented accuracy, combining NICMOS/HST and VVV photometric data with multi-epoch ISAAC/VLT H- and K-band spectra. Stellar parameters for most of spectroscopically observed cluster members are found through precise non-LTE atmosphere modeling with the CMFGEN code. Our spectrophotometric study for this cluster yields a new, revised distance of d = (12.4 ± 1.7) kpc and a total of QHMc30 ≈ 6.70 × 1050 s-1 Lyman ionizing photons. A cluster age of (4.0 ± 0.8) Myr is found through isochrone fitting, and a total mass of (1.6 ± 0.6) × 104M⊙ is estimated, thanks to our extensive knowledge of the post-main-sequence population. As a consequence, membership of Mercer 30 to the Dragonfish star-forming complex is confirmed, allowing us to use this cluster as a probe for the whole complex, which turns out to be extremely large (~400 pc across) and located at the outer edge of the Sagittarius-Carina spiral arm (~11 kpc from the Galactic center). The Dragonfish complex hosts 19 young clusters or cluster candidates (including Mercer 30 and a new candidate presented in this work) and an estimated minimum of nine field Wolf-Rayet stars. All these contributions account for, at least 73% of the ionization of the Dragonfish nebula and leaves little or no room for the alleged superluminous OB association; alternative explanations are discussed. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under programs IDs 179.B-2002, 081.D-0471, 083.D-0765, 087.D-0957, and 089.D-0989.

  16. The Spots and Activity of Stars in the Beehive Cluster Observed by the Kepler Space Telescope (K2)

    NASA Astrophysics Data System (ADS)

    Savanov, I. S.; Kalinicheva, E. S.; Dmitrienko, E. S.

    2018-05-01

    The spottedness parameters S (the fraction of the visible surface of the star occupied by spots) characterizing the activity of 674 stars in the Beehive Cluster (age 650 Myr) are estimated, together with variations of this parameter as a function of the rotation period, Rossby number Ro and other characteristics of the stars. The activity of the stars in this cluster is lower than the activity of stars in the younger Pleiades (125 Myr). The average S value for the Beehive Cluster stars is 0.014, while Pleiades stars have the much higher average value 0.052. The activity parameters of 61 solar-type stars in the Beehive Cluster, similar Hyades stars (of about the same age), and stars in the younger Pleiades are compared. The average S value of such objects in the Beehive Cluster is 0.014± 0.008, nearly coincident with the estimate obtained for solar-type Hyades stars. The rotation periods of these objects are 9.1 ± 3.4 day, on average, in agreement with the average rotation period of the Hyades stars (8.6 d ). Stars with periods exceeding 3-4 d are more numerous in the Beehive Cluster than in the Pleiades, and their periods have a larger range, 3-30 d . The characteristic dependence with a kink at Ro (saturation) = 0.13 is not observed in the S-Rossby number diagram for the Beehive and Hyades stars, only a clump of objects with Rossby numbers Ro > 0.7. The spottedness data for the Beehive Cluster and Hyades stars are in good agreement with the S values for dwarfs with ages of 600-700 Myr. This provides evidence for the reliability of the results of gyrochronological calibrations. The data for the Beehive and Pleiades stars are used to analyze variations in the spot-forming activity for a large number of stars of the same age that are members of a single cluster. A joint consideration of the data for two clusters can be used to draw conclusions about the time evolution of the activity of stars of different masses (over a time interval of the order of 500 Myr).

  17. The star-forming content of the W3 giant molecular cloud

    NASA Astrophysics Data System (ADS)

    Moore, T. J. T.; Bretherton, D. E.; Fujiyoshi, T.; Ridge, N. A.; Allsopp, J.; Hoare, M. G.; Lumsden, S. L.; Richer, J. S.

    2007-08-01

    We have surveyed a ˜0.9 square degree area of the W3 giant molecular cloud (GMC) and star-forming region in the 850-μm continuum, using the Submillimetre Common-User Bolometer Array on the James Clerk Maxwell Telescope. A complete sample of 316 dense clumps were detected with a mass range from around 13 to 2500 M⊙. Part of the W3 GMC is subject to an interaction with the H ii region and fast stellar winds generated by the nearby W4 OB association. We find that the fraction of total gas mass in dense, 850-μm traced structures is significantly altered by this interaction, being around 5-13 per cent in the undisturbed cloud but ˜25-37 per cent in the feedback-affected region. The mass distribution in the detected clump sample depends somewhat on assumptions of dust temperature and is not a simple, single power law but contains significant structure at intermediate masses. This structure is likely to be due to crowding of sources near or below the spatial resolution of the observations. There is little evidence of any difference between the index of the high-mass end of the clump mass function in the compressed region and in the unaffected cloud. The consequences of these results are discussed in terms of current models of triggered star formation.

  18. Clumped Isotope Values from the Doushantuo Formation of South China: Evaluation of Hydrothermal Influence, Disequilibria and Diagenetic Effects

    NASA Astrophysics Data System (ADS)

    Foster, I. S.; Zhu, M.; Lu, M.; Bristow, T.; Bonifacie, M.; Tripati, A.

    2015-12-01

    The Ediacaran Doushantuo Formation (635 - 551 Ma) of southern China is a phosphate-dolostone-black shale sequence following the Marinoan "Snowball Earth" episode that represents an important period in Earth history. It contains abundant phosphate-preserved microfossils, and extremely low carbon isotope values in the cap dolostone unit that have been interpreted to reflect formation in a methane seep environment [1]. Previous clumped isotope analysis of 13C-depleted carbonate veins from the basal Doushantuo samples have been interpreted to reflect hydrothermally-derived thermogenic methane oxidation [2], however recent work on modern and ancient cold seep samples suggests clumped isotope signatures in these environments are influenced by disequilibria effects [3] and are vulnerable to post-depositional diagenesis via internal reordering at temperatures exceeding ~ 100 - 120 ˚C [4]. Here we present initial data from the cap-carbonates overlying the Nantuo diamictite. Our analysis includes a variety of micro-facies from the cap-carbonate including pure calcite and micrite, with a range of carbonate carbon isotopic values. Data presented here will be used to attempt to determine if the samples exhibit disequilibria effects such as those observed in modern cold seep environments, as well as to evaluate the role of hydrothermal activity in the Doushantuo Formation. [1] Jiang, G., Kennedy, M.J., Christie-Blick, N., 2003. Stable isotope evidence for methane seeps in Neoproterozoic postglacial cap carbonates. Nature 426, 822-826. [2] Bristow, T.F., Bonifacie, M., Derkowski, A., Eiler, J.M., Grotzinger, J.P., 2011. A hydrothermal origin for isotopically anomalous cap dolostone cements from south China. Nature 474, 68-72. [3] Loyd, S., Sample, J.C., Orphan, V.J., Marlow, J., Eagle, R., Tripati, A.K., 2012. Clumped isotope analyses of cold seep carbonates: Insights into formation environment and mechanisms. Abstract B51G-0639 presented at 2012 Fall Meeting, AGU, San Francisco

  19. A paired apatite and calcite clumped isotope thermometry approach to estimating Cambro-Ordovician seawater temperatures and isotopic composition

    NASA Astrophysics Data System (ADS)

    Bergmann, Kristin D.; Finnegan, Seth; Creel, Roger; Eiler, John M.; Hughes, Nigel C.; Popov, Leonid E.; Fischer, Woodward W.

    2018-03-01

    The secular increase in δ18O values of both calcitic and phosphatic marine fossils through early Phanerozoic time suggests either that (1) early Paleozoic surface temperatures were high, in excess of 40 °C (tropical MAT), (2) the δ18O value of seawater has increased by 7-8‰ VSMOW through Paleozoic time, or (3) diagenesis has altered secular trends in early Paleozoic samples. Carbonate clumped isotope analysis, in combination with petrographic and elemental analysis, can deconvolve fluid composition from temperature effects and therefore determine which of these hypotheses best explain the secular δ18O increase. Clumped isotope measurements of a suite of calcitic and phosphatic marine fossils from late Cambrian- to Middle-late Ordovician-aged strata-the first paired fossil study of its kind-document tropical sea surface temperatures near modern temperatures (26-38 °C) and seawater oxygen isotope ratios similar to today's ratios.

  20. Driven and decaying turbulence simulations of low–mass star formation: From clumps to cores to protostars

    DOE PAGES

    Offner, Stella S. R.; Klein, Richard I.; McKee, Christopher F.

    2008-10-20

    Molecular clouds are observed to be turbulent, but the origin of this turbulence is not well understood. As a result, there are two different approaches to simulating molecular clouds, one in which the turbulence is allowed to decay after it is initialized, and one in which it is driven. We use the adaptive mesh refinement (AMR) code, Orion, to perform high-resolution simulations of molecular cloud cores and protostars in environments with both driven and decaying turbulence. We include self-gravity, use a barotropic equation of state, and represent regions exceeding the maximum grid resolution with sink particles. We analyze the propertiesmore » of bound cores such as size, shape, line width, and rotational energy, and we find reasonable agreement with observation. At high resolution the different rates of core accretion in the two cases have a significant effect on protostellar system development. Clumps forming in a decaying turbulence environment produce high-multiplicity protostellar systems with Toomre Q unstable disks that exhibit characteristics of the competitive accretion model for star formation. In contrast, cores forming in the context of continuously driven turbulence and virial equilibrium form smaller protostellar systems with fewer low-mass members. Furthermore, our simulations of driven and decaying turbulence show some statistically significant differences, particularly in the production of brown dwarfs and core rotation, but the uncertainties are large enough that we are not able to conclude whether observations favor one or the other.« less

  1. Flow over gravel beds with clusters

    NASA Astrophysics Data System (ADS)

    Little, M.; Venditti, J. G.

    2014-12-01

    The structure of a gravel bed has been shown to alter the entrainment threshold. Structures such as clusters, reticulate stone cells and other discrete structures lock grains together, making it more difficult for them to be mobilized. These structures also generate form drag, reducing the shear stress available for mobilization. Form drag over gravel beds is often assumed to be negligible, but this assumption is not well supported. Here, we explore how cluster density and arrangement affect flow resistance and the flow structure over a fixed gravel bed in a flume experiment. Cluster density was varied from 6 to 68.3 clusters per square meter which corresponds to areal bed coverages of 2 to 17%. We used regular, irregular and random arrangements of the clusters. Our results show that flow resistance over a planar gravel bed initially declines, then increases with flow depth. The addition of clusters increases flow resistance, but the effect is dependent on cluster density, flow depth and arrangement. At the highest density, clusters can increase flow resistance as by as much as 8 times when compared to flat planar bed with no grain-related form drag. Spatially resolved observations of flow over the clusters indicate that a well-defined wake forms in the lee of each cluster. At low cluster density, the wakes are isolated and weak. As cluster density increases, the wakes become stronger. At the highest density, the wakes interact and the within cluster flow field detaches from the overlying flow. This generates a distinct shear layer at the height of the clusters. In spite of this change in the flow field at high density, our results suggest that flow resistance simply increases with cluster density. Our results suggest that the form drag associated with a gravel bed can be substantial and that it depends on the arrangement of the grains on the bed.

  2. A reconnaissance study of 13C-13C clumping in ethane from natural gas

    NASA Astrophysics Data System (ADS)

    Clog, Matthieu; Lawson, Michael; Peterson, Brian; Ferreira, Alexandre A.; Santos Neto, Eugenio V.; Eiler, John M.

    2018-02-01

    Ethane is the second most abundant alkane in most natural gas reservoirs. Its bulk isotopic compositions (δ13C and δD) are used to understand conditions and progress of cracking reactions that lead to the accumulation of hydrocarbons. Bulk isotopic compositions are dominated by the concentrations of singly-substituted isotopologues (13CH3-12CH3 for δ13C and 12CDH2-12CH3 for δD). However, multiply-substituted isotopologues can bring additional independent constraints on the origins of natural ethane. The 13C2H6 isotopologue is particularly interesting as it can potentially inform the distribution of 13C atoms in the parent biomolecules whose thermal cracking lead to the production of natural gas. This work presents methods to purify ethane from natural gas samples and quantify the abundance of the rare isotopologue 13C2H6 in ethane at natural abundances to a precision of ±0.12 ‰ using a high-resolution gas source mass spectrometer. To investigate the natural variability in carbon-carbon clumping, we measured twenty-five samples of thermogenic ethane from a range of geological settings, supported by two hydrous pyrolysis of shales experiments and a dry pyrolysis of ethane experiment. The natural gas samples exhibit a range of 'clumped isotope' signatures (Δ13C2H6) at least 30 times larger than our analytical precision, and significantly larger than expected for thermodynamic equilibration of the carbon-carbon bonds during or after formation of ethane, inheritance from the distribution of isotopes in organic molecules or different extents of cracking of the source. However we show a relationship between the Δ13C2H6 and the proportion of alkanes in natural gas samples, which we believe can be associated to the extent of secondary ethane cracking. This scenario is consistent with the results of laboratory experiments, where breaking down ethane leaves the residue with a low Δ13C2H6 compared to the initial gas. Carbon-carbon clumping is therefore a new

  3. Al7CX (X=Li-Cs) clusters: Stability and the prospect for cluster materials

    NASA Astrophysics Data System (ADS)

    Ashman, C.; Khanna, S. N.; Pederson, M. R.; Kortus, J.

    2000-12-01

    Al7C clusters, recently found to have a high-electron affinity and exceptional stability, are shown to form ionic molecules when combined with alkali-metal atoms. Our studies, based on an ab initio gradient-corrected density-functional scheme, show that Al7CX (X=Li-Cs) clusters have a very low-electron affinity and a high-ionization potential. When combined, the two- and four-atom composite clusters of Al7CLi units leave the Al7C clusters almost intact. Preliminary studies indicate that Al7CLi may be suitable to form cluster-based materials.

  4. Star Formation at z = 2.481 in the Lensed Galaxy SDSS J1110 = 6459. I. Lens Modeling and Source Reconstruction

    NASA Astrophysics Data System (ADS)

    Johnson, Traci L.; Sharon, Keren; Gladders, Michael D.; Rigby, Jane R.; Bayliss, Matthew B.; Wuyts, Eva; Whitaker, Katherine E.; Florian, Michael; Murray, Katherine T.

    2017-07-01

    Using the combined resolving power of the Hubble Space Telescope and gravitational lensing, we resolve star-forming structures in a z˜ 2.5 galaxy on scales much smaller than the usual kiloparsec diffraction limit of HST. SGAS J111020.0+645950.8 is a clumpy, star-forming galaxy lensed by the galaxy cluster SDSS J1110+6459 at z=0.659, with a total magnification ˜ 30× across the entire arc. We use a hybrid parametric/non-parametric strong lensing mass model to compute the deflection and magnification of this giant arc, reconstruct the light distribution of the lensed galaxy in the source plane, and resolve the star formation into two dozen clumps. We develop a forward-modeling technique to model each clump in the source plane. We ray-trace the model to the image plane, convolve with the instrumental point-spread function (PSF), and compare with the GALFIT model of the clumps in the image plane, which decomposes clump structure from more extended emission. This technique has the advantage, over ray-tracing, of accounting for the asymmetric lensing shear of the galaxy in the image plane and the instrument PSF. At this resolution, we can begin to study star formation on a clump-by-clump basis, toward the goal of understanding feedback mechanisms and the buildup of exponential disks at high redshift. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program # 13003.

  5. ROSAT HRI images of Abell 85 and Abell 496: Evidence for inhomogeneities in cooling flows

    NASA Technical Reports Server (NTRS)

    Prestwich, Andrea H.; Guimond, Stephen J.; Luginbuhl, Christian B.; Joy, Marshall

    1995-01-01

    We present ROSAT high-resolution images of two clusters of galaxies with cooling flows, Abell 496 and Abell 85. In these clusters, X-ray emission on small scales above the general cluster emission is significant at the 3 sigma level. There is no evidence for optical counterparts. If real, the enhancements may be associated with clumps of gas at a lower temperature and higher density than the ambient medium, or hotter, denser gas perhaps compressed by magnetic fields. These observations can be used to test models of how thermal instabilities form and evolve in cooling flows.

  6. Clumped isotope paleothermometry of eggshells as an indicator of vertebrate endothermy

    NASA Astrophysics Data System (ADS)

    Canavan, R. R.; Field, D. J.; Therrien, F.; Zelenitsky, D.; Affek, H. P.

    2014-12-01

    Isotopic analyses of the calcite or aragonite shells of aquatic organisms are often used in the study of the environmental conditions in which they grow; however, this approach is less straightforward in the terrestrial realm, where environments may be more heterogeneous. In such terrestrial localities, the bioapatite of vertebrate teeth comprises the typical archival material for isotopic analyses. The calcitic eggshells of birds and other reptiles may provide suitable material for isotopic analyses that are aimed at studying their physiology and ecology. Here we apply a novel thermometer, carbonate clumped isotopes (Δ47), to test for endothermy in extinct non-avian dinosaurs in the context provided by eggs of modern reptiles and birds. These Δ47-derived temperatures should reflect the temperature of shell formation, which in endothermic animals such as birds should represent the mother's internal body temperature. In ectothermic animals, the same is true although their body temperatures are more affected by the external environment and thus Δ47 temperatures could more accurately describe local environmental temperatures during eggshell formation. Fossil eggshells represent appropriate material for reconstructing internal body temperatures of extinct non-avian dinosaurs since they mineralized within the mother's body, and fragments of eggshell are commonly recovered from dinosaur-bearing fossil deposits. The dimensions of these fragments provide sufficient material for the relatively large sample required for clumped isotope analysis (~20mg). Fossil eggshell samples from several taxa of Late Cretaceous non-avian dinosaurs were analyzed using Δ47 paleothermometry. Textural inspection was used as a first test for diagenetic alteration of the original calcite, and histological indicators were used for broad taxonomic identifications. Preliminary results of Δ47-derived body temperature estimates from eggshells are consistent with previous body temperatures

  7. Transformation of a Virgo Cluster dwarf irregular galaxy by ram pressure stripping: IC3418 and its fireballs

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kenney, Jeffrey D. P.; Geha, Marla; Jáchym, Pavel

    We present optical imaging and spectroscopy and H I imaging of the Virgo Cluster galaxy IC 3418, which is likely a 'smoking gun' example of the transformation of a dwarf irregular into a dwarf elliptical galaxy by ram pressure stripping. IC 3418 has a spectacular 17 kpc length UV-bright tail comprised of knots, head-tail, and linear stellar features. The only Hα emission arises from a few H II regions in the tail, the brightest of which are at the heads of head-tail UV sources whose tails point toward the galaxy ('fireballs'). Several of the elongated tail sources have Hα peaksmore » outwardly offset by ∼80-150 pc from the UV peaks, suggesting that gas clumps continue to accelerate through ram pressure, leaving behind streams of newly formed stars which have decoupled from the gas. Absorption line strengths, measured from Keck DEIMOS spectra, together with UV colors, show star formation stopped 300 ± 100 Myr ago in the main body, and a strong starburst occurred prior to quenching. While neither Hα nor H I emission are detected in the main body of the galaxy, we have detected 4 × 10{sup 7} M {sub ☉} of H I from the tail with the Very Large Array. The velocities of tail H II regions, measured from Keck LRIS spectra, extend only a small fraction of the way to the cluster velocity, suggesting that star formation does not happen in more distant parts of the tail. Stars in the outer tail have velocities exceeding the escape speed, but some in the inner tail should fall back into the galaxy, forming halo streams.« less

  8. NGC 6067: a young and massive open cluster with high metallicity

    NASA Astrophysics Data System (ADS)

    Alonso-Santiago, J.; Negueruela, I.; Marco, A.; Tabernero, H. M.; González-Fernández, C.; Castro, N.

    2017-08-01

    NGC 6067 is a young open cluster hosting the largest population of evolved stars among known Milky Way clusters in the 50-150 Ma age range. It thus represents the best laboratory in our Galaxy to constrain the evolutionary tracks of 5-7 M⊙ stars. We have used high-resolution spectra of a large sample of bright cluster members (45), combined with archival photometry, to obtain accurate parameters for the cluster as well as stellar atmospheric parameters. We derive a distance of 1.78 ± 0.12 kpc, an age of 90 ± 20 Ma and a tidal radius of 14.8^{+6.8}_{-3.2} arcmin. We estimate an initial mass above 5700 M⊙, for a present-day evolved population of two Cepheids, two A supergiants and 12 red giants with masses ≈6 M⊙. We also determine chemical abundances of Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y and Ba for the red clump stars. We find a supersolar metallicity, [Fe/H] = +0.19 ± 0.05, and a homogeneous chemical composition, consistent with the Galactic metallicity gradient. The presence of a Li-rich red giant, star 276 with A(Li) = 2.41, is also detected. An overabundance of Ba is found, supporting the enhanced s-process. The ratio of yellow to red giants is much smaller than 1, in agreement with models with moderate overshooting, but the properties of the cluster Cepheids do not seem consistent with current Padova models for supersolar metallicity.

  9. The Luminosity Function of Star Clusters in 20 Star-forming Galaxies Based on Hubble Legacy Archive Photometry

    NASA Astrophysics Data System (ADS)

    Whitmore, Bradley C.; Chandar, Rupali; Bowers, Ariel S.; Larsen, Soeren; Lindsay, Kevin; Ansari, Asna; Evans, Jessica

    2014-04-01

    Luminosity functions (LFs) have been determined for star cluster populations in 20 nearby (4-30 Mpc), star-forming galaxies based on Advanced Camera for Surveys source lists generated by the Hubble Legacy Archive (HLA). These cluster catalogs provide one of the largest sets of uniform, automatically generated cluster candidates available in the literature at present. Comparisons are made with other recently generated cluster catalogs demonstrating that the HLA-generated catalogs are of similar quality, but in general do not go as deep. A typical cluster LF can be approximated by a power law, dN/dLvpropL α, with an average value for α of -2.37 and rms scatter = 0.18 when using the F814W ("I") band. A comparison of fitting results based on methods that use binned and unbinned data shows good agreement, although there may be a systematic tendency for the unbinned (maximum likelihood) method to give slightly more negative values of α for galaxies with steeper LFs. We find that galaxies with high rates of star formation (or equivalently, with the brightest or largest numbers of clusters) have a slight tendency to have shallower values of α. In particular, the Antennae galaxy (NGC 4038/39), a merging system with a relatively high star formation rate (SFR), has the second flattest LF in the sample. A tentative correlation may also be present between Hubble type and values of α, in the sense that later type galaxies (i.e., Sd and Sm) appear to have flatter LFs. Hence, while there do appear to be some weak correlations, the relative similarity in the values of α for a large number of star-forming galaxies suggests that, to first order, the LFs are fairly universal. We examine the bright end of the LFs and find evidence for a downturn, although it only pertains to about 1% of the clusters. Our uniform database results in a small scatter (≈0.4 to 0.5 mag) in the correlation between the magnitude of the brightest cluster (M brightest) and log of the number of clusters

  10. Compact clumps of dark matter near the solar surface

    NASA Astrophysics Data System (ADS)

    Pokrovsky, Yu. E.

    2018-01-01

    The solar surface oscillations observed in the Crimean Astrophysical Observatory (CrAO) at the frequency 104.1890 μHz and in the Solar and Heliospheric Observatory (SoHO) at 220.72 μHz are considered as a result of existence of Compact Clumps of Dark Matter (CCDM) at orbits near the solar surface. These CCDM have to emit Gravitational Waves (GW) which are estimated to be the most intensive ones expected in the vicinity of the Earth and can be easily detected in the near future by means of the Evolved Laser Interferometer Space Antenna (eLISA). In addition to CCDMCrAO and CCDMSoHO some other CCDM may exist in the solar structure. It is shown that GW radiated by most of these CCDM could be detected by eLISA even if the respective solar surface oscillations are too small to be observed.

  11. Cluster Size Optimization in Sensor Networks with Decentralized Cluster-Based Protocols

    PubMed Central

    Amini, Navid; Vahdatpour, Alireza; Xu, Wenyao; Gerla, Mario; Sarrafzadeh, Majid

    2011-01-01

    Network lifetime and energy-efficiency are viewed as the dominating considerations in designing cluster-based communication protocols for wireless sensor networks. This paper analytically provides the optimal cluster size that minimizes the total energy expenditure in such networks, where all sensors communicate data through their elected cluster heads to the base station in a decentralized fashion. LEACH, LEACH-Coverage, and DBS comprise three cluster-based protocols investigated in this paper that do not require any centralized support from a certain node. The analytical outcomes are given in the form of closed-form expressions for various widely-used network configurations. Extensive simulations on different networks are used to confirm the expectations based on the analytical results. To obtain a thorough understanding of the results, cluster number variability problem is identified and inspected from the energy consumption point of view. PMID:22267882

  12. Chemical Abundances of Giants in Globular Clusters

    NASA Astrophysics Data System (ADS)

    Gratton, Raffaele G.; Bragaglia, Angela; Carretta, Eugenio; D'Orazi, Valentina; Lucatello, Sara

    A large fraction of stars form in clusters. According to a widespread paradigma, stellar clusters are prototypes of single stellar populations. According to this concept, they formed on a very short time scale, and all their stars share the same chemical composition. Recently it has been understood that massive stellar clusters (the globular clusters) rather host various stellar populations, characterized by different chemical composition: these stellar populations have also slightly different ages, stars of the second generations being formed from the ejecta of part of those of an earlier one. Furthermore, it is becoming clear that the efficiency of the process is quite low: many more stars formed within this process than currently present in the clusters. This implies that a significant, perhaps even dominant fraction of the ancient population of galaxies formed within the episodes that lead to formation the globular clusters.

  13. The Outer Limits of Galaxy Clusters: Observations to the Virial Radius with Suzaku, XMM,and Chandra

    NASA Technical Reports Server (NTRS)

    Miller, Eric D.; Bautz, Marshall; George, Jithin; Mushotzky, Richard; Davis, David; Henry, J. Patrick

    2012-01-01

    The outskirts of galaxy clusters, near the virial radius, remain relatively unexplored territory and yet are vital to our understanding of cluster growth, structure, and mass. In this presentation, we show the first results from a program to constrain the sate of the outer intra-cluster medium (ICM) in a large sample of galaxy clusters, exploiting the strengths of three complementary X-ray observatories: Suzaku (low, stable background), XMM-Newton (high sensitivity),and Chandra (good spatial resolution). By carefully combining observations from the cluster core to beyond r200, we are able to identify and reduce systematic uncertainties that would impede our spatial and spectral analysis using a single telescope. Our sample comprises nine clusters at z is approximately 0.1-0.2 fully covered in azimuth to beyond r200, and our analysis indicates that the ICM is not in hydrostatic equilibrium in the cluster outskirts, where we see clear azimuthal variations in temperature and surface brightness. In one of the clusters, we are able to measure the diffuse X-ray emission well beyond r200, and we find that the entropy profile and the gas fraction are consistent with expectations from theory and numerical simulations. These results stand in contrast to recent studies which point to gas clumping in the outskirts; the extent to which differences of cluster environment or instrumental effects factor in this difference remains unclear. From a broader perspective, this project will produce a sizeable fiducial data set for detailed comparison with high-resolution numerical simulations.

  14. Exploring the potential of clumped isotope thermometry on coccolith-rich sediments as a sea surface temperature proxy

    NASA Astrophysics Data System (ADS)

    Drury, Anna Joy; John, Cédric M.

    2016-10-01

    Understanding past changes in sea surface temperatures (SSTs) is crucial; however, existing proxies for reconstructing past SSTs are hindered by unknown ancient seawater composition (foraminiferal Mg/Ca and δ18O) or reflect subsurface temperatures (TEX86) or have a limited applicable temperature range (U37k'). We examine clumped isotope (Δ47) thermometry to fossil coccolith-rich material as an SST proxy, as clumped isotopes are independent of original seawater composition and applicable to a wide temperature range and coccolithophores are widespread and dissolution resistant. The Δ47-derived temperatures from <63, <20, <10, and 2-5 μm size fractions of two equatorial Pacific late Miocene-early Pliocene sediment samples (c1; c2) range between ˜18 and 29°C, with c1 temperatures consistently above c2. Removing the >63 μm fraction removes most nonmixed layer components; however, the Δ47-derived temperatures display an unexpected slight decreasing trend with decreasing size fraction. This unexpected trend could partly arise because larger coccoliths (5-12 μm) are removed during the size fraction separation process. The c1 and <63 μm c2 Δ47-derived temperatures are comparable to concurrent U37k' SSTs. The <20, <10, and 2-5 μm c2 Δ47-derived temperatures are consistently cooler than expected. The Δ47-U37k' temperature offset is probably caused by abiotic/diagenetic calcite present in the c2 2-5 μm fraction (˜53% by area), which potentially precipitated at bottom water temperatures of ˜6°C. Our results indicate that clumped isotopes on coccolith-rich sediment fractions have potential as an SST proxy, particularly in tropical regions, providing that careful investigation of the appropriate size fraction for the region and time scale is undertaken.

  15. WEAK AND COMPACT RADIO EMISSION IN EARLY HIGH-MASS STAR-FORMING REGIONS. I. VLA OBSERVATIONS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rosero, V.; Hofner, P.; Claussen, M.

    2016-12-01

    We present a high-sensitivity radio continuum survey at 6 and 1.3 cm using the Karl G. Jansky Very Large Array toward a sample of 58 high-mass star-forming regions. Our sample was chosen from dust clumps within infrared dark clouds with and without IR sources (CMC–IRs and CMCs, respectively), and hot molecular cores (HMCs), with no previous, or relatively weak radio continuum detection at the 1 mJy level. Due to the improvement in the continuum sensitivity of the Very Large Array, this survey achieved map rms levels of ∼3–10  μ Jy beam{sup −1} at sub-arcsecond angular resolution. We extracted 70 continuum sourcesmore » associated with 1.2 mm dust clumps. Most sources are weak, compact, and prime candidates for high-mass protostars. Detection rates of radio sources associated with the millimeter dust clumps for CMCs, CMC–IRs, and HMCs are 6%, 53%, and 100%, respectively. This result is consistent with increasing high-mass star formation activity from CMCs to HMCs. The radio sources located within HMCs and CMC–IRs occur close to the dust clump centers, with a median offset from it of 12,000 au and 4000 au, respectively. We calculated 5–25 GHz spectral indices using power-law fits and obtained a median value of 0.5 (i.e., flux increasing with frequency), suggestive of thermal emission from ionized jets. In this paper we describe the sample, observations, and detections. The analysis and discussion will be presented in Paper II.« less

  16. The Science of Inaccurate Temperatures: Explaining How the Bahamas Did Not Form in a Jacuzzi

    NASA Astrophysics Data System (ADS)

    Murray, S.; Swart, P. K.; McNeill, D. F.

    2016-12-01

    The Bahamas archipelago is a carbonate platform that formed in the warm waters of the Gulf Stream current. Using clumped isotope paleothermometry, it has been shown that carbonates extending back through the Miocene taken from cores throughout the Bahamas have all precipitated from fluids at temperatures similar to what is found in the Bahamas in the present day (15 to 35°C). However, in a single core, (Clino), collected off the western edge of Great Bahama Bank, Δ47 values have been measured which suggest formation at significantly warmer temperatures (42 to 53°C). These values are present in spite of the fact that the sediments have never been deeply buried. In a parallel study, these same cores were measured for their carbonate associated sulfate (CAS). The only core that presented evidence of elevated CAS, indicative of bacterial sulfate reduction (BSR), was the Clino core. In this core the clumped isotope temperatures are correlated with changes in the δ34S of the CAS. This finding suggests that BSR can have a significant effect on the Δ47 value producing erroneous temperatures. This is further supported by examining a carbonate concretion with extreme negative δ13C values (-30‰) taken as evidence of BSR. The clumped isotope temperatures in this nodule are elevated relative to its burial history with an increase of 15 °C from the outer edge of the concretion to the center. The increase in temperature correlates well with the decreasing δ13C suggesting increasing fractionation associated with BSR is directly impacting the clumped isotope measurements.

  17. Zinc and the iron donor frataxin regulate oligomerization of the scaffold protein to form new Fe-S cluster assembly centers.

    PubMed

    Galeano, B K; Ranatunga, W; Gakh, O; Smith, D Y; Thompson, J R; Isaya, G

    2017-06-21

    Early studies of the bacterial Fe-S cluster assembly system provided structural details for how the scaffold protein and the cysteine desulfurase interact. This work and additional work on the yeast and human systems elucidated a conserved mechanism for sulfur donation but did not provide any conclusive insights into the mechanism for iron delivery from the iron donor, frataxin, to the scaffold. We previously showed that oligomerization is a mechanism by which yeast frataxin (Yfh1) can promote assembly of the core machinery for Fe-S cluster synthesis both in vitro and in cells, in such a manner that the scaffold protein, Isu1, can bind to Yfh1 independent of the presence of the cysteine desulfurase, Nfs1. Here, in the absence of Yfh1, Isu1 was found to exist in two forms, one mostly monomeric with limited tendency to dimerize, and one with a strong propensity to oligomerize. Whereas the monomeric form is stabilized by zinc, the loss of zinc promotes formation of dimer and higher order oligomers. However, upon binding to oligomeric Yfh1, both forms take on a similar symmetrical trimeric configuration that places the Fe-S cluster coordinating residues of Isu1 in close proximity of iron-binding residues of Yfh1. This configuration is suitable for docking of Nfs1 in a manner that provides a structural context for coordinate iron and sulfur donation to the scaffold. Moreover, distinct structural features suggest that in physiological conditions the zinc-regulated abundance of monomeric vs. oligomeric Isu1 yields [Yfh1]·[Isu1] complexes with different Isu1 configurations that afford unique functional properties for Fe-S cluster assembly and delivery.

  18. Star formation in shells of colliding multi-SNe bubbles

    NASA Astrophysics Data System (ADS)

    Vasiliev, Evgenii O.; Shchekinov, Yuri A.

    2017-12-01

    It is believed that when bubbles formed by multiple supernovae explosions interact with one another, they stimulate star formation in overlapping shells. We consider the evolution of a shocked layer formed by the collision of two identical bubbles each of which originated from OB clusters of ˜ 50 members and ˜ 50 pc. The clusters are separated by 200-400 pc.We found that depending on evolutionary status of colliding bubbles the shocked layer can either be destroyed into diffuse lumps, or be fragmented into dense clumps: the former occurs in collisions of young bubbles with continuing supernovae explosions, and the latter occurs in older bubble interactions.We argue that fragmentation efficiency in shells depends on external heating: for a heating rate <˜ 1.7×10-24 erg s-1 the number of fragments formed in a collision of two old bubbles reaches several tens at t ˜ 4 Myr, while a heating rate >˜ 7 × 10-24 erg s-1 prevents fragmentation. The clumps formed in freely expanding parts of bubbles are gradually destroyed and disappear on t <˜ 1 Myr,whereas those formed in the overlapping shells survive much longer. Because of this the number of fragments in an isolated bubble begins to decrease after reaching a maximum, while in collision of two old bubbles it fluctuates around 60-70 until longer than t ˜ 5 Myr.

  19. Imprints of feedback in young gasless clusters?

    NASA Astrophysics Data System (ADS)

    Parker, Richard J.; Dale, James E.

    2013-06-01

    We present the results of N-body simulations in which we take the masses, positions and velocities of sink particles from five pairs of hydrodynamical simulations of star formation by Dale et al. and evolve them for further 10 Myr. We compare the dynamical evolution of star clusters that formed under the influence of mass-loss driven by photoionization feedback to the evolution of clusters that formed without feedback. We remove any remaining gas and follow the evolution of structure in the clusters (measured by the Q-parameter), half-mass radius, central density, surface density and the fraction of bound stars. There is little discernible difference in the evolution of clusters that formed with feedback compared to those that formed without. The only clear trend is that all clusters which form without feedback in the hydrodynamical simulations lose any initial structure over 10 Myr, whereas some of the clusters which form with feedback retain structure for the duration of the subsequent N-body simulation. This is due to lower initial densities (and hence longer relaxation times) in the clusters from Dale et al. which formed with feedback, which prevents dynamical mixing from erasing substructure. However, several other conditions (such as supervirial initial velocities) also preserve substructure, so at a given epoch one would require knowledge of the initial density and virial state of the cluster in order to determine whether star formation in a cluster has been strongly influenced by feedback.

  20. SUZAKU OBSERVATIONS OF SUBHALOS IN THE COMA CLUSTER

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sasaki, Toru; Matsushita, Kyoko; Sato, Kosuke

    2015-06-10

    We observed three massive subhalos in the Coma cluster with Suzaku. These subhalos, labeled “ID 1,” “ID 2,” and “ID 32,” were detected with a weak-lensing survey using Subaru/Suprime-Cam, and are located at the projected distances of 1.4 r{sub 500}, 1.2 r{sub 500}, and 1.6 r{sub 500} from the center of the Coma cluster, respectively. The subhalo “ID 1” has a compact X-ray excess emission close to the center of the weak-lensing mass contour, and the gas mass to weak-lensing mass ratio is about 0.001. The temperature of the emission is about 3 keV, which is slightly lower than thatmore » of the surrounding intracluster medium (ICM) and that expected for the temperature versus mass relation of clusters of galaxies. The subhalo “ID 32” shows an excess emission whose peak is shifted toward the opposite direction from the center of the Coma cluster. The gas mass to weak-lensing mass ratio is also about 0.001, which is significantly smaller than regular galaxy groups. The temperature of the excess is about 0.5 keV and significantly lower than that of the surrounding ICM and far from the temperature versus mass relation of clusters. However, there is no significant excess X-ray emission in the “ID 2” subhalo. Assuming an infall velocity of about 2000 km s{sup −1}, at the border of the excess X-ray emission, the ram pressures for “ID 1” and “ID 32” are comparable to the gravitational restoring force per area. We also studied the effect of the Kelvin–Helmholtz instability to strip the gas. Although we found X-ray clumps associated with the weak-lensing subhalos, their X-ray luminosities are much lower than the total ICM luminosity in the cluster outskirts.« less

  1. Structural evolutions and hereditary characteristics of icosahedral nano-clusters formed in Mg70Zn30 alloys during rapid solidification processes

    NASA Astrophysics Data System (ADS)

    Liang, Yong-Chao; Liu, Rang-Su; Xie, Quan; Tian, Ze-An; Mo, Yun-Fei; Zhang, Hai-Tao; Liu, Hai-Rong; Hou, Zhao-Yang; Zhou, Li-Li; Peng, Ping

    2017-02-01

    To investigate the structural evolution and hereditary mechanism of icosahedral nano-clusters formed during rapid solidification, a molecular dynamics (MD) simulation study has been performed for a system consisting of 107 atoms of liquid Mg70Zn30 alloy. Adopting Honeycutt-Anderson (HA) bond-type index method and cluster type index method (CTIM-3) to analyse the microstructures in the system it is found that for all the nano-clusters including 2~8 icosahedral clusters in the system, there are 62 kinds of geometrical structures, and those can be classified, by the configurations of the central atoms of basic clusters they contained, into four types: chain-like, triangle-tailed, quadrilateral-tailed and pyramidal-tailed. The evolution of icosahedral nano-clusters can be conducted by perfect heredity and replacement heredity, and the perfect heredity emerges when temperature is slightly less than Tm then increase rapidly and far exceeds the replacement heredity at Tg; while for the replacement heredity, there are three major modes: replaced by triangle (3-atoms), quadrangle (4-atoms) and pentagonal pyramid (6-atoms), rather than by single atom step by step during rapid solidification processes.

  2. Quantification of Spore-forming Bacteria Carried by Dust Particles

    NASA Technical Reports Server (NTRS)

    Lin, Ying; Cholakian, Tanya; Gao, Wenming; Osman, Shariff; Barengoltz, Jack

    2006-01-01

    In order to establish a biological contamination transport model for predicting the cross contamination risk during spacecraft assembly and upon landing on Mars, it is important to understand the relationship between spore-forming bacteria and their carrier particles. We conducted air and surface sampling in indoor, outdoor, and cleanroom environments to determine the ratio of spore forming bacteria to their dust particle carriers of different sizes. The number of spore forming bacteria was determined from various size groups of particles in a given environment. Our data also confirms the existence of multiple spores on a single particle and spore clumps. This study will help in developing a better bio-contamination transport model, which in turn will help in determining forward contamination risks for future missions.

  3. The quest for infall in star-forming regions

    NASA Astrophysics Data System (ADS)

    Wyrowski, Friedrich

    2018-06-01

    Observation of infall is key to our understanding of the accretion process in star formation. High-resolution spectroscopy allows us to resolve molecular lines originating from the dense molecular envelopes of the forming (proto-) stars to deduce the kinematics of the gas. In this contribution, I'll describe how SOFIA can significantly contribute to the quest for and characterisation of infall by providing unique access to molecular lines at THz frequencies that allow red-shifted absorption studies as direct probe of infall and that provide access to fine structure and high excitation lines that probe outflowing gas as indirect evidence for accretion. In particular, I will report on a recent study using the GREAT high-spectral resolution instrument on-board of SOFIA to observe ammonia at 1.8 THz. Eight out of eleven observed massive clumps have been found with red-shifted absorption that is indicative of infall motions. This fraction of 72% is substantially higher than that found in past searches for the blue-skewed profile signature. The observations show that infall on clump scales is ubiquitous through a wide range of evolutionary stages.

  4. STAR-FORMING GALAXIES IN THE HERCULES CLUSTER: H{alpha} IMAGING OF A2151

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cedres, Bernabe; Iglesias-Paramo, Jorge; VIlchez, Jose Manuel

    2009-09-15

    This paper presents the first results of an H{alpha} imaging survey of galaxies in the central regions of the A2151 cluster. A total of 50 sources were detected in H{alpha}, from which 41 were classified as secure members of the cluster and 2 as likely members based on spectroscopic and photometric redshift considerations. The remaining seven galaxies were classified as background contaminants and thus excluded from our study on the H{alpha} properties of the cluster. The morphologies of the 43 H{alpha} selected galaxies range from grand design spirals and interacting galaxies to blue compacts and tidal dwarfs or isolated extragalacticmore » H II regions, spanning a range of magnitudes of -21 {<=} M{sub B} {<=} -12.5 mag. From these 43 galaxies, 7 have been classified as active galactic nucleus (AGN) candidates. These AGN candidates follow the L(H{alpha}) versus M{sub B} relationship of the normal galaxies, implying that the emission associated with the nuclear engine has a rather secondary impact on the total H{alpha} emission of these galaxies. A comparison with the clusters Coma and A1367 and a sample of field galaxies has shown the presence of cluster galaxies with L(H{alpha}) lower than expected for their M{sub B} , a consequence of the cluster environment. This fact results in differences in the L(H{alpha}) versus EW(H{alpha}) and L(H{alpha}) distributions of the clusters with respect to the field, and in cluster-to-cluster variations of these quantities, which we propose are driven by a global cluster property as the total mass. In addition, the cluster H{alpha} emitting galaxies tend to avoid the central regions of the clusters, again with different intensity depending on the cluster total mass. For the particular case of A2151, we find that most H{alpha} emitting galaxies are located close to the regions with the higher galaxy density, offset from the main X-ray peak. Overall, we conclude that both the global cluster environment and the cluster merging

  5. Search for Stellar Streams Based on Data from the RAVE5 and Gaia TGAS Catalogues

    NASA Astrophysics Data System (ADS)

    Bajkova, A. T.; Bobylev, V. V.

    2018-03-01

    We have analyzed the space velocities of stars with the proper motions and trigonometric parallaxes from the Gaia TGAS catalogue in combination with the line-of-sight velocities from the RAVE5 catalogue. In the V, √ {{U^2} + 2{V^2}} velocity plane we have identified three clumps, BB17-1, BB17-2, and BB17-3, in the region of large velocities ( V<-150 km s-1). The stars of the BB17-1 and BB17-2 clumps are associated with the kinematic groups VelHel-6 and VelHel-7 detected previously by Helmi et al. We give the greatest attention to the BB17-3 clump. The latter is shown to be most closely linked with the debris of the globular cluster ω Cen. In the BB17-3 clump we have identified 28 stars with a low velocity dispersion with respect to the center of their distribution. All these stars have very close individual age estimates: log t ≈ 10. The distribution of metallicity indices in this sample is typical for the stars of the globular cluster ω Cen. In our opinion, the BB17-3 clump can be described as a homogeneous stream in the debris of the cluster ω Cen.

  6. SEEDisCs: How Clusters Form and Galaxies Transform in the Cosmic Web

    NASA Astrophysics Data System (ADS)

    Jablonka, P.

    2017-08-01

    This presentation introduces a new survey, the Spatial Extended EDisCS Survey (SEEDisCS), which aims at understanding how clusters assemble and the level at which galaxies are preprocessed before falling on the cluster cores. I focus on the changes in galaxy properties in the cluster large scale environments, and how we can get constraints on the timescale of star formation quenching. I also discuss new ALMA CO observations, which trace the fate of the galaxy cold gas content along the infalling paths towards the cluster cores.

  7. OBSERVATIONS OF MOLECULAR OUTFLOW IN CAR 291.6-01.9

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Saul, M.; Saul, L., E-mail: msaul@phys.unsw.edu.au, E-mail: luke.saul@space.unibe.ch

    We report the first observations of a dense molecular gas nebula and bipolar outflow in Car 291.6-01.9, showing characteristics of an embedded young stellar object (YSO). Using the Mopra radio telescope near Coonabarabaran, Australia, we image the kinematic structure of several emission features to examine physical properties within a molecular clump of mass {approx}3.2 {+-} 0.6 Multiplication-Sign 10{sup 3} M{sub Sun} in which a stellar cluster may be forming. Motivated by acquiring a more thorough understanding of star formation we ask what may have initiated collapse in the clump; observed outflow alignment is suggestive of {approx}1.0 pc distant massive starmore » HD 308280 radiative-driven compression as a formation trigger for the dense core. An outflow derived age of <10{sup 6} years, together with significant C{sup 18}O and SO core depletion, support the case for the core as the host of an extremely YSO cluster.« less

  8. Methane clumped isotopes in the Songliao Basin (China): New insights into abiotic vs. biotic hydrocarbon formation

    NASA Astrophysics Data System (ADS)

    Shuai, Yanhua; Etiope, Giuseppe; Zhang, Shuichang; Douglas, Peter M. J.; Huang, Ling; Eiler, John M.

    2018-01-01

    Abiotic hydrocarbon gas, typically generated in serpentinized ultramafic rocks and crystalline shields, has important implications for the deep biosphere, petroleum systems, the carbon cycle and astrobiology. Distinguishing abiotic gas (produced by chemical reactions like Sabatier synthesis) from biotic gas (produced from degradation of organic matter or microbial activity) is sometimes challenging because their isotopic and molecular composition may overlap. Abiotic gas has been recognized in numerous locations on the Earth, although there are no confirmed instances where it is the dominant source of commercially valuable quantities in reservoir rocks. The deep hydrocarbon reservoirs of the Xujiaweizi Depression in the Songliao Basin (China) have been considered to host significant amounts of abiotic methane. Here we report methane clumped-isotope values (Δ18) and the isotopic composition of C1-C3 alkanes, CO2 and helium of five gas samples collected from those Xujiaweizi deep reservoirs. Some geochemical features of these samples resemble previously suggested identifiers of abiotic gas (13C-enriched CH4; decrease in 13C/12C ratio with increasing carbon number for the C1-C4 alkanes; abundant, apparently non-biogenic CO2; and mantle-derived helium). However, combining these constraints with new measurements of the clumped-isotope composition of methane and careful consideration of the geological context, suggests that the Xujiaweizi depression gas is dominantly, if not exclusively, thermogenic and derived from over-mature source rocks, i.e., from catagenesis of buried organic matter at high temperatures. Methane formation temperatures suggested by clumped-isotopes (167-213 °C) are lower than magmatic gas generation processes and consistent with the maturity of local source rocks. Also, there are no geological conditions (e.g., serpentinized ultramafic rocks) that may lead to high production of H2 and thus abiotic production of CH4 via CO2 reduction. We propose

  9. Paleoaltimetry of the Oiyug Basin, southern Tibet using clumped-isotope paleothermometry

    NASA Astrophysics Data System (ADS)

    Abbot, M. I.; Rowley, D. B.; Currie, B. S.; Colman, A. S.; He, B.; Olack, G.

    2013-12-01

    We present new paleoelevation estimates of the Oiyug Basin of the southern Tibetan Plateau during the mid-Miocene to Pliocene using carbonate Δ47 clumped isotope and conventional δ18O paleoaltimetry. Δ47 reflects the statistical overabundance of 13C-18O bonds in multiply-substituted isotopologues of CO2 generated from phosphoric acid digestion of carbonate minerals (Eiler, 2007). Paleoelevation estimates inform geodynamic models of the earth's surface response to climate, tectonics, and erosion at high elevations (Clark, 2007). Commonly applied techniques for reconstructing paleoelevation histories are based on paleobotany (paleoenthalpy derived from floral physiognomy, e.g. Spicer et al., 2003) the oxygen isotope record of meteoric and pedogenic minerals (e.g. Chamberlain and Poage, 2000), and compound specific δD of organic matter (Polissar et al. 2009). The carbonate clumped isotope paleothermometer provides independent constraints on both the temperature and isotopic composition of ancient surface waters (Ghosh et al., 2006a), making it a potentially powerful paleoaltimeter (Ghosh et al., 2006b, Quade et al., 2007) when the original isotopic signature is preserved. A burial history reconstructed from lipid-δD measurements in the Oiyug Basin suggests that these carbonates have not been buried, and give us high confidence that the carbonates are unaltered and retain their primary isotopic signature. This study tests the use of multiply substituted CO2 isotopologues as a paleoaltimeter for the Tibetan Plateau. We will obtain independent paleoelevation estimates from Δ47 temperatures to test our hypothesis that the Oiyug Basin has remained high (~5300-4600 meters) for the past 15 million years. Chamberlain, C.P., and M. A. Poage, 2000, Reconstructing the paleotopography of mountain belts from the isotopic composition of authigenic minerals, Geology, 28, 115-118. Eiler, J.M., 2007, 'Clumped-isotope' geochemistry-The study of naturally occurring multiply

  10. Star Clusters within FIRE

    NASA Astrophysics Data System (ADS)

    Perez, Adrianna; Moreno, Jorge; Naiman, Jill; Ramirez-Ruiz, Enrico; Hopkins, Philip F.

    2017-01-01

    In this work, we analyze the environments surrounding star clusters of simulated merging galaxies. Our framework employs Feedback In Realistic Environments (FIRE) model (Hopkins et al., 2014). The FIRE project is a high resolution cosmological simulation that resolves star forming regions and incorporates stellar feedback in a physically realistic way. The project focuses on analyzing the properties of the star clusters formed in merging galaxies. The locations of these star clusters are identified with astrodendro.py, a publicly available dendrogram algorithm. Once star cluster properties are extracted, they will be used to create a sub-grid (smaller than the resolution scale of FIRE) of gas confinement in these clusters. Then, we can examine how the star clusters interact with these available gas reservoirs (either by accreting this mass or blowing it out via feedback), which will determine many properties of the cluster (star formation history, compact object accretion, etc). These simulations will further our understanding of star formation within stellar clusters during galaxy evolution. In the future, we aim to enhance sub-grid prescriptions for feedback specific to processes within star clusters; such as, interaction with stellar winds and gas accretion onto black holes and neutron stars.

  11. Optimising the Number of Replicate- Versus Standard Measurements for Carbonate Clumped Isotope Thermometry

    NASA Astrophysics Data System (ADS)

    Kocken, I.; Ziegler, M.

    2017-12-01

    Clumped isotope measurements on carbonates are a quickly developing and promising palaeothermometry proxy1-3. Developments in the field have brought down the necessary sample amount and improved the precision and accuracy of the measurements. The developments have included inter-laboratory comparison and the introduction of an absolute reference frame4, determination of acid fractionation effects5, correction for the pressure baseline6, as well as improved temperature calibrations2, and most recently new approaches to improve efficiency in terms of sample gas usage7. However, a large-scale application of clumped isotope thermometry is still hampered by required large sample amounts, but also the time-consuming analysis. In general, a lot of time is goes into the measurement of standards. Here we present a study on the optimal ratio between standard- and sample measurements using the Kiel Carbonate Device method. We also consider the optimal initial signal intensity. We analyse ETH-standard measurements from several months to determine the measurement regime with the highest precision and optimised measurement time management.References 1. Eiler, J. M. Earth Planet. Sci. Lett. 262, 309-327 (2007).2. Kelson, J. R., et al. Geochim. Cosmochim. Acta 197, 104-131 (2017).3. Kele, S. et al. Geochim. Cosmochim. Acta 168, 172-192 (2015).4. Dennis, K. J. et al. Geochim. Cosmochim. Acta 75, 7117-7131 (2011).5. Müller, I. A. et al. Chem. Geol. 449, 1-14 (2017).6. Meckler, A. N. et al. Rapid Commun. Mass Spectrom. 28, 1705-1715 (2014).7. Hu, B. et al. Rapid Commun. Mass Spectrom. 28, 1413-1425 (2014).

  12. Carbonate "Clumped" Isotope Determination of Seawater Temperature During the End-Triassic Extinction Event

    NASA Astrophysics Data System (ADS)

    Gammariello, R. T., Jr.; Petryshyn, V. A.; Ibarra, Y.; Greene, S. E.; Corsetti, F. A.; Bottjer, D. J.; Tripati, A.

    2014-12-01

    Stromatolites are laminated sedimentary structures that are commonly thought to be created by cyanobacteria, either through the trapping and binding of sediment, or through metabolically-induced precipitation. However, stromatolite formation is poorly understood. In general, stromatolite abundance was higher in the Proterozoic than the Phanerozoic, but notable increases in stromatolite abundance occur in association with Phanerozoic mass extinction events. Here, we focus on stromatolites from the latest Triassic Cotham Marble (United Kingdom) that are associated with the extinction interval. The end-Triassic mass extinction is coincident with large-scale volcanism in the Central Atlantic Magmatic Province (CAMP) and the associated breakup of Pangea. Some hypothesize that CAMP-associated increases in atmospheric CO2 led to a rise in global temperatures and ocean acidification that caused or enhanced the extinction. In order to quantify the role of climate change with respect to the end-Triassic mass extinction, we applied the carbonate "clumped" isotope paleothermometer to the well-preserved Cotham Marble stromatolites. The stromatolites were deposited in the shallow Tethys Sea, and today occur in several localities across the southwestern UK. The stromatolites alternate on the cm scale between laminated and dendrolitic microstructures and each was microdrilled for clumped isotope analysis. The two microstructures display different temperatures of formation, where the dendrolitic portions apparently grew under cooler conditions than laminated layers, and younger layers grew in cooler conditions than older layers. Our results suggest that temperature fluctuated and potentially trended towards amelioration of the warm temperatures during the deposition of the Cotham Marble.

  13. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bally, John; Ginsburg, Adam; Probst, Ron

    We present observations of near-infrared 2.12 μm molecular hydrogen outflows emerging from 1.1 mm dust continuum clumps in the North America and Pelican Nebula (NAP) complex selected from the Bolocam Galactic Plane Survey (BGPS). Hundreds of individual shocks powered by over 50 outflows from young stars are identified, indicating that the dusty molecular clumps surrounding the NGC 7000/IC 5070/W80 H II region are among the most active sites of ongoing star formation in the solar vicinity. A spectacular X-shaped outflow, MHO 3400, emerges from a young star system embedded in a dense clump more than a parsec from the ionizationmore » front associated with the Pelican Nebula (IC 5070). Suspected to be a binary, the source drives a pair of outflows with orientations differing by 80°. Each flow exhibits S-shaped symmetry and multiple shocks indicating a pulsed and precessing jet. The 'Gulf of Mexico', located south of the North America Nebula (NGC 7000), contains a dense cluster of molecular hydrogen objects (MHOs), Herbig-Haro (HH) objects, and over 300 young stellar objects (YSOs), indicating a recent burst of star formation. The largest outflow detected thus far in the North America and Pelican Nebula complex, the 1.6 parsec long MHO 3417 flow, emerges from a 500 M {sub ☉} BGPS clump and may be powered by a forming massive star. Several prominent outflows such as MHO 3427 appear to be powered by highly embedded YSOs only visible at λ > 70 μm. An 'activity index' formed by dividing the number of shocks by the mass of the cloud containing their source stars is used to estimate the relative evolutionary states of Bolocam clumps. Outflows can be used as indicators of the evolutionary state of clumps detected in millimeter and submillimeter dust continuum surveys.« less

  14. LBT/LUCIFER view of star-forming galaxies in the cluster 7C 1756+6520 at z ˜ 1.4

    NASA Astrophysics Data System (ADS)

    Magrini, Laura; Sommariva, Veronica; Cresci, Giovanni; Sani, Eleonora; Galametz, Audrey; Mannucci, Filippo; Petropoulou, Vasiliki; Fumana, Marco

    2012-10-01

    Galaxy clusters are key places to study the contribution of nature (i.e. mass and morphology) and nurture (i.e. environment) in the formation and evolution of galaxies. Recently, a number of clusters at z > 1, i.e. corresponding to the first epochs of the cluster formation, have been discovered and confirmed spectroscopically. We present new observations obtained with the LBT Near Infrared Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research (LUCIFER) spectrograph at Large Binocular Telescope (LBT) of a sample of star-forming galaxies associated with a large-scale structure around the radio galaxy 7C 1756+6520 at z = 1.42. Combining our spectroscopic data and the literature photometric data, we derived some of the properties of these galaxies: star formation rate, metallicity and stellar mass. With the aim of analysing the effect of the cluster environment on galaxy evolution, we have located the galaxies in the plane of the so-called fundamental metallicity relation (FMR), which is known not to evolve with redshift up to z = 2.5 for field galaxies, but it is still unexplored in rich environments at low and high redshifts. We found that the properties of the galaxies in the cluster 7C 1756+6520 are compatible with the FMR which suggests that the effect of the environment on galaxy metallicity at this early epoch of cluster formation is marginal. As a side study, we also report the spectroscopic analysis of a bright active galactic nucleus, belonging to the cluster, which shows a significant outflow of gas.

  15. The Formation of Cluster Populations Through Direct Galaxy Collisions

    NASA Astrophysics Data System (ADS)

    Peterson, Bradley W.; Smith, Beverly J.; Struck, Curtis

    2016-01-01

    Much progress has been made on the question of how globular clusters form. In particular, the study of extragalactic populations of young, high-mass clusters ("super star clusters") has revealed a class of objects can evolve into globular clusters. The process by which these clusters form, and how many survive long enough to become globular clusters, is not wholly understood. Here, we use new data on the colliding galaxy system Arp 261 to investigate the possibility that young, massive clusters form in greater numbers during direct galaxy collisions, compared to less direct tidal collisions.

  16. A clustered origin for isolated massive stars

    NASA Astrophysics Data System (ADS)

    Lucas, William E.; Rybak, Matus; Bonnell, Ian A.; Gieles, Mark

    2018-03-01

    High-mass stars are commonly found in stellar clusters promoting the idea that their formation occurs due to the physical processes linked with a young stellar cluster. It has recently been reported that isolated high-mass stars are present in the Large Magellanic Cloud. Due to their low velocities, it has been argued that these are high-mass stars which formed without a surrounding stellar cluster. In this paper, we present an alternative explanation for the origin of these stars in which they formed in a cluster environment but are subsequently dispersed into the field as their natal cluster is tidally disrupted in a merger with a higher mass cluster. They escape the merged cluster with relatively low velocities typical of the cluster interaction and thus of the larger scale velocity dispersion, similarly to the observed stars. N-body simulations of cluster mergers predict a sizeable population of low-velocity (≤20 km s-1), high-mass stars at distances of >20 pc from the cluster. High-mass clusters in which gas poor mergers are frequent would be expected to commonly have haloes of young stars, including high-mass stars, which were actually formed in a cluster environment.

  17. Clumped isotopes reveal the influence of deformation style on fluid flow and cementation along the Moab Fault, Paradox Basin, Utah

    NASA Astrophysics Data System (ADS)

    Huntington, K. W.; Bergman, S.; Crider, J. G.

    2012-12-01

    Brittle fault systems can serve as either conduits or barriers to fluid flow, impacting mass and heat transfer in the crust and influencing the potential storage and migration of hydrocarbons and geothermal fluids. For fault systems in porous sandstones, different classes of structures control both hydrological and mechanical behavior during fault evolution: while cataclastic deformation bands form zones of localized deformation and crushed grains that reduce permeability within and across fault zones, joints can act as significant conduits for fluid. We investigate the relationship between structures and fluid flow in porous sandstones by studying calcite cements along the Moab Fault, a large normal fault system in the Paradox Basin, Utah. We use clumped isotope thermometry of fault cements to independently determine both the temperature and δ18O of the water from which the cements grew, placing new constraints on the source and path of diagenetic fluids in the basin. Based on fluid inclusion micro-thermometry and stable isotopic analysis of calcite cements from the Moab Fault, previous workers have hypothesized that joints served as conduits for the ascension of warm (84-125 °C) basinal fluids and deeply circulating meteoric waters. At the minor joint-dominated fault segment from which these data were collected, clumped isotope temperatures range from 57±10 to 101±2°C (2 SE), consistent with this hypothesis. However, at the nearby intersection of two major fault segments - in a zone characterized by both deformation bands and abundant joints - we find a broad range of temperatures (12±4 to 78±4°C) that vary spatially with distance from the fault and correlate with variations in secondary deformation structures (joints and deformation bands). These data provide the first evidence for cement growth from Earth surface-temperature fluids along the Moab Fault and suggests that the Fault served as a conduit for both ascending and descending fluids. The spatial

  18. High Resolution Three-Color Imaging of Spirals With Nuclear Star-Forming Rings

    NASA Technical Reports Server (NTRS)

    Mazzuca, Lisa; Obenschain, Arthur (Technical Monitor)

    2001-01-01

    Nuclear rings in barred spirals offer an opportunity to study starburst properties in order to develop an understanding of the evolution of star formation in galaxies. To achieve this understanding, a large scale imaging survey in the H alpha line and in the B and I broad bands has been performed. Analysis of all galaxies that reveal nuclear rings in the H alpha line will be compared to numerical models so that the relative ages between the starforming clumps can be estimated. The luminosity function of the starforming regions will be related to the measured properties of the associated star-cluster and the required ionizing flux. Also B - I color index images will be performed to indicate the location of the dust lanes.

  19. Formation of Very Young Massive Clusters and Implications for Globular Clusters

    NASA Astrophysics Data System (ADS)

    Banerjee, Sambaran; Kroupa, Pavel

    How Very Young Massive star Clusters (VYMCs; also known as "starburst" clusters), which typically are of ≳ 104 M ⊙ and are a few Myr old, form out of Giant Molecular Clouds is still largely an open question. Increasingly detailed observations of young star clusters and star-forming molecular clouds and computational studies provide clues about their formation scenarios and the underlying physical processes involved. This chapter is focused on reviewing the decade-long studies that attempt to computationally reproduce the well-observed nearby VYMCs, such as the Orion Nebula Cluster, R136 and NGC 3603 young cluster, thereby shedding light on birth conditions of massive star clusters, in general. On this regard, focus is given on direct N-body modelling of real-sized massive star clusters, with a monolithic structure and undergoing residual gas expulsion, which have consistently reproduced the observed characteristics of several VYMCs and also of young star clusters, in general. The connection of these relatively simplified model calculations with the structural richness of dense molecular clouds and the complexity of hydrodynamic calculations of star cluster formation is presented in detail. Furthermore, the connections of such VYMCs with globular clusters, which are nearly as old as our Universe, is discussed. The chapter is concluded by addressing long-term deeply gas-embedded (at least apparently) and substructured systems like W3 Main. While most of the results are quoted from existing and up-to-date literature, in an integrated fashion, several new insights and discussions are provided.

  20. Planck 2015 results. XXVIII. The Planck Catalogue of Galactic cold clumps

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Butler, R. C.; Calabrese, E.; Catalano, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Helou, G.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; McGehee, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Pelkonen, V.-M.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Stolyarov, V.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

    2016-09-01

    We present the Planck Catalogue of Galactic Cold Clumps (PGCC), an all-sky catalogue of Galactic cold clump candidates detected by Planck. This catalogue is the full version of the Early Cold Core (ECC) catalogue, which was made available in 2011 with the Early Release Compact Source Catalogue (ERCSC) and which contained 915 high signal-to-noise sources. It is based on the Planck 48-month mission data that are currently being released to the astronomical community. The PGCC catalogue is an observational catalogue consisting exclusively of Galactic cold sources. The three highest Planck bands (857, 454, and 353 GHz) have been combined with IRAS data at 3 THz to perform a multi-frequency detection of sources colder than their local environment. After rejection of possible extragalactic contaminants, the PGCC catalogue contains 13188 Galactic sources spread across the whole sky, I.e., from the Galactic plane to high latitudes, following the spatial distribution of the main molecular cloud complexes. The median temperature of PGCC sources lies between 13 and 14.5 K, depending on the quality of the flux density measurements, with a temperature ranging from 5.8 to 20 K after removing the sources with the top 1% highest temperature estimates. Using seven independent methods, reliable distance estimates have been obtained for 5574 sources, which allows us to derive their physical properties such as their mass, physical size, mean density, and luminosity.The PGCC sources are located mainly in the solar neighbourhood, but also up to a distance of 10.5 kpc in the direction of the Galactic centre, and range from low-mass cores to large molecular clouds. Because of this diversity and because the PGCC catalogue contains sources in very different environments, the catalogue is useful for investigating the evolution from molecular clouds to cores. Finally, it also includes 54 additional sources located in the Small and Large Magellanic Clouds.

  1. Identification of Anthropogenic CO2 Using Triple Oxygen and Clumped Isotopes.

    PubMed

    Laskar, Amzad H; Mahata, Sasadhar; Liang, Mao-Chang

    2016-11-01

    Quantification of contributions from various sources of CO 2 is important for understanding the atmospheric CO 2 budget. Considering the number and diversity of sources and sinks, the widely used proxies such as concentration and conventional isotopic compositions (δ 13 C and δ 18 O) are not always sufficient to fully constrain the CO 2 budget. Additional constraints may help in understanding the mechanisms of CO 2 production and consumption. The anomaly in triple oxygen isotopes or 17 O excess (denoted by Δ 17 O) and molecules containing two rare isotopes, called clumped isotopes, are two recently developed tracers with potentials to independently constrain some important processes that regulate CO 2 in the atmosphere. The clumped isotope for CO 2 , denoted by Δ 47 , is the excess of 13 C 16 O 18 O over a random distribution of isotopes in a CO 2 molecule. We measured the concentrations of δ 13 C, δ 18 O, Δ 17 O, and Δ 47 in air CO 2 samples collected from the Hsuehshan tunnel (length: 12.9 km), and applied linear and polynomial regressions to obtain the fossil fuel end-members for all these isotope proxies. The other end-members, the values of all these proxies for background air CO 2 , are either assumed or taken as the values obtained over the tunnel and ocean. The fossil fuel (anthropogenic) CO 2 end-member values for δ 13 C, δ 18 O, Δ 17 O, and Δ 47 are estimated using the two component mixing approach: the derived values are -26.76 ± 0.25‰, 24.57 ± 0.33‰, -0.219 ± 0.021‰, and 0.267 ± 0.036‰, respectively. These four major CO 2 isotope tracers along with the concentration were used to estimate the anthropogenic contribution in the atmospheric CO 2 in urban and suburban locations. We demonstrate that Δ 17 O and Δ 47 have the potential to independently estimate anthropogenic contribution, and the advantages of these two over the conventional isotope proxies are discussed.

  2. Planck 2015 results: XXVIII. The Planck Catalogue of Galactic cold clumps

    DOE PAGES

    Ade, P. A. R.; Aghanim, N.; Arnaud, M.; ...

    2016-09-20

    Here, we present the Planck Catalogue of Galactic Cold Clumps (PGCC), an all-sky catalogue of Galactic cold clump candidates detected by Planck. This catalogue is the full version of the Early Cold Core (ECC) catalogue, which was made available in 2011 with the Early Release Compact Source Catalogue (ERCSC) and which contained 915 high signal-to-noise sources. It is based on the Planck 48-month mission data that are currently being released to the astronomical community. The PGCC catalogue is an observational catalogue consisting exclusively of Galactic cold sources. The three highest Planck bands (857, 454, and 353 GHz) have been combinedmore » with IRAS data at 3 THz to perform a multi-frequency detection of sources colder than their local environment. After rejection of possible extragalactic contaminants, the PGCC catalogue contains 13188 Galactic sources spread across the whole sky, i.e., from the Galactic plane to high latitudes, following the spatial distribution of the main molecular cloud complexes. The median temperature of PGCC sources lies between 13 and 14.5 K, depending on the quality of the flux density measurements, with a temperature ranging from 5.8 to 20 K after removing the sources with the top 1% highest temperature estimates. Using seven independent methods, reliable distance estimates have been obtained for 5574 sources, which allows us to derive their physical properties such as their mass, physical size, mean density, and luminosity.The PGCC sources are located mainly in the solar neighbourhood, but also up to a distance of 10.5 kpc in the direction of the Galactic centre, and range from low-mass cores to large molecular clouds. Because of this diversity and because the PGCC catalogue contains sources in very different environments, the catalogue is useful for investigating the evolution from molecular clouds to cores. Finally, it also includes 54 additional sources located in the Small and Large Magellanic Clouds.« less

  3. PREFACE: Nuclear Cluster Conference; Cluster'07

    NASA Astrophysics Data System (ADS)

    Freer, Martin

    2008-05-01

    The Cluster Conference is a long-running conference series dating back to the 1960's, the first being initiated by Wildermuth in Bochum, Germany, in 1969. The most recent meeting was held in Nara, Japan, in 2003, and in 2007 the 9th Cluster Conference was held in Stratford-upon-Avon, UK. As the name suggests the town of Stratford lies upon the River Avon, and shortly before the conference, due to unprecedented rainfall in the area (approximately 10 cm within half a day), lay in the River Avon! Stratford is the birthplace of the `Bard of Avon' William Shakespeare, and this formed an intriguing conference backdrop. The meeting was attended by some 90 delegates and the programme contained 65 70 oral presentations, and was opened by a historical perspective presented by Professor Brink (Oxford) and closed by Professor Horiuchi (RCNP) with an overview of the conference and future perspectives. In between, the conference covered aspects of clustering in exotic nuclei (both neutron and proton-rich), molecular structures in which valence neutrons are exchanged between cluster cores, condensates in nuclei, neutron-clusters, superheavy nuclei, clusters in nuclear astrophysical processes and exotic cluster decays such as 2p and ternary cluster decay. The field of nuclear clustering has become strongly influenced by the physics of radioactive beam facilities (reflected in the programme), and by the excitement that clustering may have an important impact on the structure of nuclei at the neutron drip-line. It was clear that since Nara the field had progressed substantially and that new themes had emerged and others had crystallized. Two particular topics resonated strongly condensates and nuclear molecules. These topics are thus likely to be central in the next cluster conference which will be held in 2011 in the Hungarian city of Debrechen. Martin Freer Participants and Cluster'07

  4. Centenarian scientists: an unusual cluster newly formed in the 20th century.

    PubMed

    Sri Kantha, S

    2001-12-01

    From biographical data sources on ranking scientists, I was able to identify 35 centenarians. Among these, only one (Michel Chevereul from France) lived before the 20th century. Since the remaining 34 individuals became centenarians only from 1965, I propose that centenarian scientists are an unusual cluster, first formed in the 20th century. Among these, all except one (Alice Hamilton) were men. Six centenarian scientists, including Hamilton, had received professional medical training. The nationality ranks of the 34 centenarian scientists identified in the 20th century show 26 Americans, 6 British, one German and one French. Four of the 26 Americans were immigrants from Europe. At least three centenarians, namely Michael Heidelberger, Nathaniel Kleitman and Victor Hamburger, belong to the 'Nobel class' category, being pioneers in the disciplines of immunochemistry, sleep physiology and neuroembryology respectively.

  5. The Split Red Clump of the Galactic Bulge from OGLE-III

    NASA Astrophysics Data System (ADS)

    Nataf, D. M.; Udalski, A.; Gould, A.; Fouqué, P.; Stanek, K. Z.

    2010-09-01

    The red clump (RC) is found to be split into two components along several sightlines toward the Galactic bulge. This split is detected with high significance toward the areas (-3.5 < l < 1, b < -5) and (l, b) = (0, + 5.2), i.e., along the bulge minor axis and at least 5 deg off the plane. The fainter (hereafter "main") component is the one that more closely follows the distance-longitude relation of the bulge RC. The main component is ~0.5 mag fainter than the secondary component and with an overall approximately equal population. For sightlines further from the plane, the difference in brightness increases, and more stars are found in the secondary component than in the main component. The two components have very nearly equal (V - I) color.

  6. Photon Recollision Probability: a Useful Concept for Cross Scale Consistency Check between Leaf Area Index and Foliage Clumping Products

    NASA Astrophysics Data System (ADS)

    Pisek, J.

    2017-12-01

    Clumping index (CI) is the measure of foliage aggregation relative to a random distribution of leaves in space. CI is an important factor for the correct quantification of true leaf area index (LAI). Global and regional scale CI maps have been generated from various multi-angle sensors based on an empirical relationship with the normalized difference between hotspot and darkspot (NDHD) index (Chen et al., 2005). Ryu et al. (2011) suggested that accurate calculation of radiative transfer in a canopy, important for controlling gross primary productivity (GPP) and evapotranspiration (ET) (Baldocchi and Harley, 1995), should be possible by integrating CI with incoming solar irradiance and LAI from MODIS land and atmosphere products. It should be noted that MODIS LAI/FPAR product uses internal non-empirical, stochastic equations for parameterization of foliage clumping. This raises a question if integration of the MODIS LAI product with empirically-based CI maps does not introduce any inconsistencies. Here, the consistency is examined independently through the `recollision probability theory' or `p-theory' (Knyazikhin et al., 1998) along with raw LAI-2000/2200 Plant Canopy Analyzer (PCA) data from > 30 sites, surveyed across a range of vegetation types. The theory predicts that the amount of radiation scattered by a canopy should depend only on the wavelength and the spectrally invariant canopy structural parameter p. The parameter p is linked to the foliage clumping (Stenberg et al., 2016). Results indicate that integration of the MODIS LAI product with empirically-based CI maps is feasible. Importantly, for the first time it is shown that it is possible to obtain p values for any location solely from Earth Observation data. This is very relevant for future applications of photon recollision probability concept for global and local monitoring of vegetation using Earth Observation data.

  7. Impacts of including forest understory brightness and foliage clumping information from multiangular measurements on leaf area index mapping over North America

    NASA Astrophysics Data System (ADS)

    Pisek, Jan; Chen, Jing M.; Alikas, Krista; Deng, Feng

    2010-09-01

    A new leaf area index (LAI) data set in 10 day intervals with consideration of the understory reflectance and foliage clumping effects over North America for 1 year is developed. The data set brings effectively together measurements from multiple sensors with complementary capabilities (SPOT-VEGETATION, Multiangle Imaging Spectroradiometer, POLDER). First, the temporal consistency analysis indicated the new product is on par with other available LAI data sets currently used by the community. Second, with the removal of the background (understory in forests, moss, litter, and soil) effect on the forest overstory LAI retrieval, slightly different LAI reductions were found between needleleaf and broadleaf forests. This is caused by the more clumped nature of needleleaf forests, especially at higher LAI values, which allows more light to penetrate through the overstory canopy, making the understory more visible for equal LAI as compared to broadleaf forests. This is found over a representative set of 105 CEOS Benchmark Land Multisite Analysis and Intercomparison of Products sites in North America used for indirect validation. Third, the data set was directly validated and compared with Moderate Resolution Imaging Spectroradiometer Collection 5 LAI product using results from the BigFoot project for available forest test sites. This study demonstrates that the fusion of data inputs between multiple sensors can indeed lead to improved products and that multiangle remote sensing can help us to address effectively the issues (separating the signal from the understory and overstory, foliage clumping) that could not be solved via the means of the conventional mono-angle remote sensing.

  8. A perfect starburst cluster made in one go: The NGC 3603 young cluster

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Banerjee, Sambaran; Kroupa, Pavel

    2014-06-01

    Understanding how distinct, near-spherical gas-free clusters of very young, massive stars shape out of vast, complex clouds of molecular hydrogen is one of the biggest challenges in astrophysics. A popular thought dictates that a single gas cloud fragments into many newborn stars which, in turn, energize and rapidly expel the residual gas to form a gas-free cluster. This study demonstrates that the above classical paradigm remarkably reproduces the well-observed central, young cluster (HD 97950) of the Galactic NGC 3603 star-forming region, in particular, its shape, internal motion, and mass distribution of stars naturally and consistently follow from a single modelmore » calculation. Remarkably, the same parameters (star formation efficiency, gas expulsion timescale, and delay) reproduce HD 97950, as were found to reproduce the Orion Nebula Cluster, Pleiades, and R136. The present results therefore provide intriguing evidence of formation of star clusters through single-starburst events followed by significant residual gas expulsion.« less

  9. Cluster compression algorithm: A joint clustering/data compression concept

    NASA Technical Reports Server (NTRS)

    Hilbert, E. E.

    1977-01-01

    The Cluster Compression Algorithm (CCA), which was developed to reduce costs associated with transmitting, storing, distributing, and interpreting LANDSAT multispectral image data is described. The CCA is a preprocessing algorithm that uses feature extraction and data compression to more efficiently represent the information in the image data. The format of the preprocessed data enables simply a look-up table decoding and direct use of the extracted features to reduce user computation for either image reconstruction, or computer interpretation of the image data. Basically, the CCA uses spatially local clustering to extract features from the image data to describe spectral characteristics of the data set. In addition, the features may be used to form a sequence of scalar numbers that define each picture element in terms of the cluster features. This sequence, called the feature map, is then efficiently represented by using source encoding concepts. Various forms of the CCA are defined and experimental results are presented to show trade-offs and characteristics of the various implementations. Examples are provided that demonstrate the application of the cluster compression concept to multi-spectral images from LANDSAT and other sources.

  10. Hubble Space Telescope Hx Imaging of Star-forming Galaxies at z approximately equal to 1-1.5: Evolution in the Size and Luminosity of Giant H II Regions

    NASA Technical Reports Server (NTRS)

    Livermore, R. C.; Jones, T.; Richard, J.; Bower, R. G.; Ellis, R. S.; Swinbank, A. M.; Rigby, J. R.; Smail, Ian; Arribas, S.; Rodriguez-Zaurin, J.; hide

    2013-01-01

    We present Hubble Space Telescope/Wide Field Camera 3 narrow-band imaging of the Ha emission in a sample of eight gravitationally lensed galaxies at z = 1-1.5. The magnification caused by the foreground clusters enables us to obtain a median source plane spatial resolution of 360 pc, as well as providing magnifications in flux ranging from approximately 10× to approximately 50×. This enables us to identify resolved star-forming HII regions at this epoch and therefore study their Ha luminosity distributions for comparisons with equivalent samples at z approximately 2 and in the local Universe. We find evolution in the both luminosity and surface brightness of HII regions with redshift. The distribution of clump properties can be quantified with an HII region luminosity function, which can be fit by a power law with an exponential break at some cut-off, and we find that the cut-off evolves with redshift. We therefore conclude that 'clumpy' galaxies are seen at high redshift because of the evolution of the cut-off mass; the galaxies themselves follow similar scaling relations to those at z = 0, but their HII regions are larger and brighter and thus appear as clumps which dominate the morphology of the galaxy. A simple theoretical argument based on gas collapsing on scales of the Jeans mass in a marginally unstable disc shows that the clumpy morphologies of high-z galaxies are driven by the competing effects of higher gas fractions causing perturbations on larger scales, partially compensated by higher epicyclic frequencies which stabilize the disc.

  11. Dolomite clumped isotope constraints on the oxygen isotope composition of the Phanerozoic Sea

    NASA Astrophysics Data System (ADS)

    Ryb, U.; Eiler, J. M.

    2017-12-01

    The δ18O value of the Phanerozoic Sea has been debated several decades, largely motivated by an 8‰ increase in δ18O of sedimentary carbonates between the Cambrian and the present. Some previous studies have interpreted this increase to be a primary depositional signal, resulting from an increase in the 18O content of ocean water over time, or from a decrease in ocean temperature increasing the oxygen isotope fractionation between seawater and carbonates. In contrast, other studies have interpreted lower δ18O compositions as the products of diagenetic alteration at elevated burial temperatures. Here, we show that the Phanerozoic dolomite δ18O record overlaps with that of well-preserved calcite fossils, and use carbonate clumped isotope measurements of Cambrian to Pleistocene dolomites to calculate their formation temperatures and the isotopic compositions of their parent-waters. The observed variation in dolomite δ18O is largely explained by dolomite formation at burial temperatures of up to 158°C. The δ18O values of dolomite parent-waters range -2 to +12‰ and are correlated with formation temperatures. Such correlation is consistent with the modification of seawater (0±2‰, VSMOW) toward isotopically heavier compositions through water-rock reactions at elevated burial temperatures. The similarity between the dolomite and calcite δ18O records, and published clumped isotope-based calculations of water compositions, suggests that like dolomite, temporal variations of the calcite δ18O record may also be largely driven by diagenetic alteration. Finally, the relationship we observe between temperature of dolomitization and d18O of dolomite suggests platform carbonates generally undergo dolomitization through reaction with modified marine waters, and that there is no evidence those waters were ever significantly lower in d18O than the modern ocean.

  12. Stellar black holes in globular clusters

    NASA Technical Reports Server (NTRS)

    Kulkarni, S. R.; Hut, Piet; Mcmillan, Steve

    1993-01-01

    The recent discovery of large populations of millisec pulsars associated with neutron stars in globular clusters indicates that several hundred stellar black holes of about 10 solar masses each can form within a typical cluster. While, in clusters of high central density, the rapid dynamical evolution of the black-hole population leads to an ejection of nearly all holes on a short timescale, systems of intermediate density may involve a normal star's capture by one of the surviving holes to form a low-mass X-ray binary. One or more such binaries may be found in the globular clusters surrounding our galaxy.

  13. A Deep-Sea Coral Clumped Isotope Record From Southern Ocean Intermediate Water Spanning the Most Recent Glacial Termination

    NASA Astrophysics Data System (ADS)

    Hines, S.; Eiler, J. M.; Adkins, J. F.

    2015-12-01

    Movement of intermediate waters plays an important role in global heat and carbon transport in the ocean and changes in their distribution are closely tied to glacial-interglacial climate change. Ocean temperature is necessarily linked to circulation because density is a function of temperature and salinity. In the modern ocean, stratification is dominated by differences in temperature, but this may not have been the case in the past. Coupled radiocarbon and U/Th dates on deep-sea Desmophyllum dianthus corals allow for the reconstruction of past intermediate water circulation rates. The addition of temperature measurements further aids in understanding of the mechanisms driving the observed signals, since there are different boundary conditions for resetting these two properties at the surface. In the modern Southern Ocean, temperature and radiocarbon are broadly correlated. At the surface there are meridional gradients of these properties, with colder, more radiocarbon-depleted water closer to the Antarctic continent. We present a high-resolution time series of clumped isotope temperature measurements on 30 corals spanning the Last Glacial Maximum through the end of the Antarctic Cold Reversal (ACR). These samples have previously been U/Th and radiocarbon dated. Corals were collected south of Tasmania from depths of between ~1450 - 1900 m, with 70% between 1500 and 1700 m. Uranium and thorium measurements were made by MC-ICP-MS on a ThermoFinnigan Neptune, radiocarbon was measured by AMS at the KCCAMS Laboratory at UC Irvine, and clumped isotope temperatures were measured on a MAT 253 attached to an automated carbonate preparation line. Preliminary results show constant temperature between ~20 - 18 ka, a gradual rise of ~6 ºC through Heinrich Stadial 1 (~18 - 15 ka), an abrupt drop of ~7 ºC directly preceeding the start of the Bølling at 14.7 ka, and another slight rise of ~4 ºC through the ACR (14.7 - 12.8 ka). The addition of clumped isotope temperatures to

  14. Star Formation in Nearby Clusters (SFiNCs)

    NASA Astrophysics Data System (ADS)

    Getman, Konstantin

    Most stars form in clusters that rapidly disperse, yet we have a poor understanding of the processes of cluster formation and early evolution. Do clusters form `top-down', rapidly in a dense molecular cloud core? Or, since clouds are turbulent, do clusters form `bottomup' by merging subclusters produced in small kinematically-distinct molecular structures? Do clusters principally form in elongated molecular structures such as Infrared Dark Clouds and Herschel filaments? One of the central reasons for slow progress in resolving these questions is the lack of homogeneous and reliable census of stellar members (both disk-bearing and disk-free) for a wide range of star forming environments. To address these issues we are now completing our major effort, called MYStIX (Massive Young Star-Forming Complex Study in Infrared and X-ray). It combines the Chandra archive with UKIRT+2MASS near-infrared and Spitzer mid-infrared surveys to identify young stellar objects in a wide range of evolutionary stages, from protostars to disk-free pre-main sequence stars, in 20 star forming regions at distances from 0.4 to 3.6 kpc. Each MYStIX region was chosen to have a rich OB-dominated cluster. Started in 2009 with NASA/ADAP and NSF funding, MYStIX has emerged with 8 technical/catalog and the first 4 of a series of science papers (http://astro.psu.edu/mystix). Early MYStIX results include: demonstration of diverse morphologies of young clusters from simple ellipsoids to elongated, clumpy substructures; demonstration of spatio-age gradients across star formation regions; the discovery of core-halo age gradients within two rich nearby MYStIX clusters; and the discovery of important astrophysically empirical correlations among different subcluster properties such as age, absorption, core radius, central stellar density, and total intrinsic population. The early MYStIX result provide new observational evidence for subcluster merging and cluster expansion following gas dissipation. We

  15. Homogeneous photometry and star counts in the field of 9 Galactic star clusters

    NASA Astrophysics Data System (ADS)

    Seleznev, A. F.; Carraro, G.; Costa, E.; Loktin, A. V.

    2010-01-01

    We present homogeneous V, I CCD photometry of nine stellar fields in the two inner quadrants of the Galactic plane. The lines-of-view to most of these fields aim in the direction of the very inner Galaxy, where the Galactic field is very dense, and extinction is high and patchy. Our nine fields are, according to several catalogs, centred on Galactic star clusters, namely Trumpler 13, Trumpler 20, Lynga 4, Hogg 19, Lynga 12, Trumpler 25, Trumpler 26, Ruprecht 128, and Trumpler 34. Apart from their coordinates, and in some cases additional basic data (mainly from the 2MASS archive), their properties are poorly known. By means of star count techniques and field star decontaminated Color Magnitude diagrams, the nature and size of these visual over-densities has been established; and, when possible, new cluster fundamental parameters have been derived. To strengthen our findings, we complement our data-set with JHKs photometry from the 2MASS archive, that we analyze using a suitably defined Q-parameter. Most clusters are projected towards the Carina-Sagittarium spiral arm. Because of that, we detect in the Color Magnitude diagrams of most of the other fields several distinctive sequences produced by young population within the arm. All the clusters are of intermediate or old age. The most interesting cases detected by our study are, perhaps, that of Trumpler 20, which seems to be much older than previously believed, as indicated by its prominent - and double - red clump; and that of Hogg 19, a previously overlooked old open cluster, whose existence in such regions of the Milky Way is puzzling.

  16. Clustering of low-valence particles: structure and kinetics.

    PubMed

    Markova, Olga; Alberts, Jonathan; Munro, Edwin; Lenne, Pierre-François

    2014-08-01

    We compute the structure and kinetics of two systems of low-valence particles with three or six freely oriented bonds in two dimensions. The structure of clusters formed by trivalent particles is complex with loops and holes, while hexavalent particles self-organize into regular and compact structures. We identify the elementary structures which compose the clusters of trivalent particles. At initial stages of clustering, the clusters of trivalent particles grow with a power-law time dependence. Yet at longer times fusion and fission of clusters equilibrates and clusters form a heterogeneous phase with polydispersed sizes. These results emphasize the role of valence in the kinetics and stability of finite-size clusters.

  17. Clumped isotopologue constraints on the origin of methane at seafloor hot springs

    NASA Astrophysics Data System (ADS)

    Wang, David T.; Reeves, Eoghan P.; McDermott, Jill M.; Seewald, Jeffrey S.; Ono, Shuhei

    2018-02-01

    Hot-spring fluids emanating from deep-sea vents hosted in unsedimented ultramafic and mafic rock commonly contain high concentrations of methane. Multiple hypotheses have been proposed for the origin(s) of this methane, ranging from synthesis via reduction of aqueous inorganic carbon (∑CO2) during active fluid circulation to leaching of methane-rich fluid inclusions from plutonic rocks of the oceanic crust. To further resolve the process(es) responsible for methane generation in these systems, we determined the relative abundances of several methane isotopologues (including 13CH3D, a "clumped" isotopologue containing two rare isotope substitutions) in hot-spring source fluids sampled from four geochemically-distinct hydrothermal vent fields (Rainbow, Von Damm, Lost City, and Lucky Strike). Apparent equilibrium temperatures retrieved from methane clumped isotopologue analyses average 310-42+53 °C, with no apparent relation to the wide range of fluid temperatures (96-370 °C) and chemical compositions (pH, [H2], [∑CO2], [CH4]) represented. Combined with very similar bulk stable isotope ratios (13C/12C and D/H) of methane across the suite of hydrothermal fluids, all available geochemical and isotopic data suggest a common mechanism of methane generation at depth that is disconnected from active fluid circulation. Attainment of equilibrium amongst methane isotopologues at temperatures of ca. 270-360 °C is compatible with the thermodynamically-favorable reduction of CO2 to CH4 at temperatures at or below ca. 400 °C under redox conditions characterizing intrusive rocks derived from sub-ridge melts. Collectively, the observations support a model where methane-rich aqueous fluids, known to be trapped in rocks of the oceanic lithosphere, are liberated from host rocks during hydrothermal circulation and perhaps represent the major source of methane venting with thermal waters at unsedimented hydrothermal fields. The results also provide further evidence that water

  18. Triple oxygen isotopes and clumped isotopes in modern vertebrate and dinosaur biominerals: Records of paleoecology, paleoaridity, and paleo-carbon-cycling

    NASA Astrophysics Data System (ADS)

    Hu, H.; Passey, B. H.; Lehmann, S. B.; Levin, N. E.; Montanari, S.; Chin, K.; Johnson, B. J.

    2015-12-01

    The parameter Δ17O describes the departure of δ17O from an expected equilibrium relationship with δ18O, which can be caused by factors such as evaporation of parent waters, and photochemical reactions among oxygen-bearing gases in stratosphere. Hence, the Δ17O of water records information about environmental aridity, and the Δ17O of atmospheric O2 is related to atmospheric concentrations of CO2 and O2, and gross primary productivity (GPP). Vertebrates incorporate Δ17O signals of input water (e.g. drinking water and free food water) and atmospheric O2 into body water through respiration, and biominerals forming in equilibrium with body water can preserve this signal over geological timescales. The preservation of fossil biominerals can be evaluated by clumped isotopes as they record the temperature of mineralization, be it primary mineralization in the living animal (at body temperature), or secondary mineralization during diagenesis. We can distinguish the alteration of samples from the deviation between observed clumped isotope temperatures and plausible body temperatures. Meanwhile, diagenesis tends to moderate Δ17O of biominerals towards Δ17O of meteoric waters, such that measured Δ17O values reflect the minimum anomaly in fossil samples. Thus, preservation of anomalous Δ17O indicates at least partial preservation of the original signal. We present Δ17O data from both modern vertebrate and fossil dinosaur biominerals. We use a 17O-enabled body water model to explore the influence of aridity and dietary ecology on animal Δ17O, and to predict the degree of dilution of the atmospheric O2 Δ17O signal by other sources of oxygen to the animal. We observe: 1) animals consuming more leaf water than drinking water are "evaporation sensitive" (ES) animals, and have lower Δ17O relative to "evaporation insensitive" animals in the same climates; 2) ES animals from arid climates have lower Δ17O values compared to ES animals from humid climates, which forms the

  19. Characterization of the effect of serum and chelating agents on Staphylococcus aureus biofilm formation; chelating agents augment biofilm formation through clumping factor B

    NASA Astrophysics Data System (ADS)

    Abraham, Nabil Mathew

    investigated the molecular basis of this phenomenon. Deletion and complementation analysis and thereafter antibody based inhibition assays confirmed a functional role for the surface adhesin clumping factor B as the causative determinant associated with the increased biofilm phenotype. Finally, we investigated the regulation of clumping factor B-mediated biofilm formation and the basis for the strain dependence. Regulation was determined to occur via two novel post-translational networks- one affecting ClfB activity, mediated by Ca2+ binding to the EF-Hand domain, and the other affecting protein stability, mediated by the enzymatic activity of the metalloprotease-aureolysin. Polymorphisms within the aureolysin gene sequence, between strains, was identified as the basis for some strains forming robust biofilms within chelated media versus other than do not exhibit this phenotype.

  20. Precision and long-term stability of clumped-isotope analysis of CO2 using a small-sector isotope ratio mass spectrometer.

    PubMed

    Yoshida, Naohiro; Vasilev, Mikhail; Ghosh, Prosenjit; Abe, Osamu; Yamada, Keita; Morimoto, Maki

    2013-01-15

    The ratio of the measured abundance of (13)C-(18)O bonding CO(2) to its stochastic abundance, prescribed by the δ(13)C and δ(18)O values from a carbonate mineral, is sensitive to its growth temperature. Recently, clumped-isotope thermometry, which uses this ratio, has been adopted as a new tool to elucidate paleotemperatures quantitatively. Clumped isotopes in CO(2) were measured with a small-sector isotope ratio mass spectrometer. CO(2) samples digested from several kinds of calcium carbonates by phosphoric acid at 25 °C were purified using both cryogenic and gas-chromatographic separations, and their isotopic composition (δ(13)C, δ(18)O, Δ(47), Δ(48) and Δ(49) values) were then determined using a dual-inlet Delta XP mass spectrometer. The internal precisions of the single gas Δ(47) measurements were 0.005 and 0.02‰ (1 SE) for the optimum and the routine analytical conditions, respectively, which are comparable with those obtained using a MAT 253 mass spectrometer. The long-term variations in the Δ(47) values for the in-house working standard and the heated CO(2) gases since 2007 were close to the routine, single gas uncertainty while showing seasonal-like periodicities with a decreasing trend. Unlike the MAT 253, the Delta XP did not show any significant relationship between the Δ(47) and δ(47) values. The Delta XP gave results that were approximately as precise as those of the MAT 253 for clumped-isotope analysis. The temporal stability of the Delta XP seemed to be lower, although an advantage of the Delta XP was that no dependency of δ(47) on Δ(47) was found. Copyright © 2012 John Wiley & Sons, Ltd.

  1. Diffuse Optical Light in Galaxy Clusters. II. Correlations with Cluster Properties

    NASA Astrophysics Data System (ADS)

    Krick, J. E.; Bernstein, R. A.

    2007-08-01

    We have measured the flux, profile, color, and substructure in the diffuse intracluster light (ICL) in a sample of 10 galaxy clusters with a range of mass, morphology, redshift, and density. Deep, wide-field observations for this project were made in two bands at the 1 m Swope and 2.5 m du Pont telescopes at Las Campanas Observatory. Careful attention in reduction and analysis was paid to the illumination correction, background subtraction, point-spread function determination, and galaxy subtraction. ICL flux is detected in both bands in all 10 clusters ranging from 7.6×1010 to 7.0×1011 h-170 Lsolar in r and 1.4×1010 to 1.2×1011 h-170 Lsolar in the B band. These fluxes account for 6%-22% of the total cluster light within one-quarter of the virial radius in r and 4%-21% in the B band. Average ICL B-r colors range from 1.5 to 2.8 mag when k- and evolution corrected to the present epoch. In several clusters we also detect ICL in group environments near the cluster center and up to 1 h-170 Mpc distant from the cluster center. Our sample, having been selected from the Abell sample, is incomplete in that it does not include high-redshift clusters with low density, low flux, or low mass, and it does not include low-redshift clusters with high flux, high mass, or high density. This bias makes it difficult to interpret correlations between ICL flux and cluster properties. Despite this selection bias, we do find that the presence of a cD galaxy corresponds to both centrally concentrated galaxy profiles and centrally concentrated ICL profiles. This is consistent with ICL either forming from galaxy interactions at the center or forming at earlier times in groups and later combining in the center.

  2. Infrared extinction in the inner Milky Way through red clump giants

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    González-Fernández, C.; Asensio Ramos, A.; Garzón, F.

    While the shape of the extinction curve in the infrared is considered to be set and the extinction ratios between infrared bands are usually taken to be approximately constant, a number of recent studies point to either a spatially variable behavior of the exponent of the power law or a different extinction law altogether. In this paper, we propose a method to analyze the overall behavior of the interstellar extinction by means of the red-clump population, and we apply it to those areas of the Milky Way where the presence of interstellar matter is heavily felt: areas located in 5°more » < l < 30° and b = 0°. We show that the extinction ratios traditionally used for the near infrared could be inappropriate for the inner Galaxy and we analyze the behavior of the extinction law from 1 μm to 8 μm.« less

  3. The origin of the Milky Way globular clusters

    NASA Astrophysics Data System (ADS)

    Renaud, Florent; Agertz, Oscar; Gieles, Mark

    2017-03-01

    We present a cosmological zoom-in simulation of a Milky Way-like galaxy used to explore the formation and evolution of star clusters. We investigate in particular the origin of the bimodality observed in the colour and metallicity of globular clusters, and the environmental evolution through cosmic times in the form of tidal tensors. Our results self-consistently confirm previous findings that the blue, metal-poor clusters form in satellite galaxies that are accreted on to the Milky Way, while the red, metal-rich clusters form mostly in situ, or, to a lower extent, in massive, self-enriched galaxies merging with the Milky Way. By monitoring the tidal fields these populations experience, we find that clusters formed in situ (generally centrally concentrated) feel significantly stronger tides than the accreted ones, both in the present day, and when averaged over their entire life. Furthermore, we note that the tidal field experienced by Milky Way clusters is significantly weaker in the past than at present day, confirming that it is unlikely that a power-law cluster initial mass function like that of young massive clusters, is transformed into the observed peaked distribution in the Milky Way with relaxation-driven evaporation in a tidal field.

  4. The Hi-GAL compact source catalogue - I. The physical properties of the clumps in the inner Galaxy (-71.0° < ℓ < 67.0°)

    NASA Astrophysics Data System (ADS)

    Elia, Davide; Molinari, S.; Schisano, E.; Pestalozzi, M.; Pezzuto, S.; Merello, M.; Noriega-Crespo, A.; Moore, T. J. T.; Russeil, D.; Mottram, J. C.; Paladini, R.; Strafella, F.; Benedettini, M.; Bernard, J. P.; Di Giorgio, A.; Eden, D. J.; Fukui, Y.; Plume, R.; Bally, J.; Martin, P. G.; Ragan, S. E.; Jaffa, S. E.; Motte, F.; Olmi, L.; Schneider, N.; Testi, L.; Wyrowski, F.; Zavagno, A.; Calzoletti, L.; Faustini, F.; Natoli, P.; Palmeirim, P.; Piacentini, F.; Piazzo, L.; Pilbratt, G. L.; Polychroni, D.; Baldeschi, A.; Beltrán, M. T.; Billot, N.; Cambrésy, L.; Cesaroni, R.; García-Lario, P.; Hoare, M. G.; Huang, M.; Joncas, G.; Liu, S. J.; Maiolo, B. M. T.; Marsh, K. A.; Maruccia, Y.; Mège, P.; Peretto, N.; Rygl, K. L. J.; Schilke, P.; Thompson, M. A.; Traficante, A.; Umana, G.; Veneziani, M.; Ward-Thompson, D.; Whitworth, A. P.; Arab, H.; Bandieramonte, M.; Becciani, U.; Brescia, M.; Buemi, C.; Bufano, F.; Butora, R.; Cavuoti, S.; Costa, A.; Fiorellino, E.; Hajnal, A.; Hayakawa, T.; Kacsuk, P.; Leto, P.; Li Causi, G.; Marchili, N.; Martinavarro-Armengol, S.; Mercurio, A.; Molinaro, M.; Riccio, G.; Sano, H.; Sciacca, E.; Tachihara, K.; Torii, K.; Trigilio, C.; Vitello, F.; Yamamoto, H.

    2017-10-01

    Hi-GAL (Herschel InfraRed Galactic Plane Survey) is a large-scale survey of the Galactic plane, performed with Herschel in five infrared continuum bands between 70 and 500 μm. We present a band-merged catalogue of spatially matched sources and their properties derived from fits to the spectral energy distributions (SEDs) and heliocentric distances, based on the photometric catalogues presented in Molinari et al., covering the portion of Galactic plane -71.0° < ℓ < 67.0°. The band-merged catalogue contains 100 922 sources with a regular SED, 24 584 of which show a 70-μm counterpart and are thus considered protostellar, while the remainder are considered starless. Thanks to this huge number of sources, we are able to carry out a preliminary analysis of early stages of star formation, identifying the conditions that characterize different evolutionary phases on a statistically significant basis. We calculate surface densities to investigate the gravitational stability of clumps and their potential to form massive stars. We also explore evolutionary status metrics such as the dust temperature, luminosity and bolometric temperature, finding that these are higher in protostellar sources compared to pre-stellar ones. The surface density of sources follows an increasing trend as they evolve from pre-stellar to protostellar, but then it is found to decrease again in the majority of the most evolved clumps. Finally, we study the physical parameters of sources with respect to Galactic longitude and the association with spiral arms, finding only minor or no differences between the average evolutionary status of sources in the fourth and first Galactic quadrants, or between 'on-arm' and 'interarm' positions.

  5. Collective thermoregulation in bee clusters

    PubMed Central

    Ocko, Samuel A.; Mahadevan, L.

    2014-01-01

    Swarming is an essential part of honeybee behaviour, wherein thousands of bees cling onto each other to form a dense cluster that may be exposed to the environment for several days. This cluster has the ability to maintain its core temperature actively without a central controller. We suggest that the swarm cluster is akin to an active porous structure whose functional requirement is to adjust to outside conditions by varying its porosity to control its core temperature. Using a continuum model that takes the form of a set of advection–diffusion equations for heat transfer in a mobile porous medium, we show that the equalization of an effective ‘behavioural pressure’, which propagates information about the ambient temperature through variations in density, leads to effective thermoregulation. Our model extends and generalizes previous models by focusing the question of mechanism on the form and role of the behavioural pressure, and allows us to explain the vertical asymmetry of the cluster (as a consequence of buoyancy-driven flows), the ability of the cluster to overpack at low ambient temperatures without breaking up at high ambient temperatures, and the relative insensitivity to large variations in the ambient temperature. Our theory also makes testable hypotheses for the response of the cluster to external temperature inhomogeneities and suggests strategies for biomimetic thermoregulation. PMID:24335563

  6. Search for OB stars running away from young star clusters. II. The NGC 6357 star-forming region

    NASA Astrophysics Data System (ADS)

    Gvaramadze, V. V.; Kniazev, A. Y.; Kroupa, P.; Oh, S.

    2011-11-01

    Dynamical few-body encounters in the dense cores of young massive star clusters are responsible for the loss of a significant fraction of their massive stellar content. Some of the escaping (runaway) stars move through the ambient medium supersonically and can be revealed via detection of their bow shocks (visible in the infrared, optical or radio). In this paper, which is the second of a series of papers devoted to the search for OB stars running away from young ( ≲ several Myr) Galactic clusters and OB associations, we present the results of the search for bow shocks around the star-forming region NGC 6357. Using the archival data of the Midcourse Space Experiment (MSX) satellite and the Spitzer Space Telescope, and the preliminary data release of the Wide-Field Infrared Survey Explorer (WISE), we discovered seven bow shocks, whose geometry is consistent with the possibility that they are generated by stars expelled from the young (~1-2 Myr) star clusters, Pismis 24 and AH03 J1725-34.4, associated with NGC 6357. Two of the seven bow shocks are driven by the already known OB stars, HD 319881 and [N78] 34. Follow-up spectroscopy of three other bow-shock-producing stars showed that they are massive (O-type) stars as well, while the 2MASS photometry of the remaining two stars suggests that they could be B0 V stars, provided that both are located at the same distance as NGC 6357. Detection of numerous massive stars ejected from the very young clusters is consistent with the theoretical expectation that star clusters can effectively lose massive stars at the very beginning of their dynamical evolution (long before the second mechanism for production of runaway stars, based on a supernova explosion in a massive tight binary system, begins to operate) and lends strong support to the idea that probably all field OB stars have been dynamically ejected from their birth clusters. A by-product of our search for bow shocks around NGC 6357 is the detection of three circular

  7. Shaping a high-mass star-forming cluster through stellar feedback. The case of the NGC 7538 IRS 1-3 complex

    NASA Astrophysics Data System (ADS)

    Frau, P.; Girart, J. M.; Zhang, Q.; Rao, R.

    2014-07-01

    Context. NGC 7538 IRS 1-3 is a high-mass star-forming cluster with several detected dust cores, infrared sources, (ultra)compact H II regions, molecular outflows, and masers. In such a complex environment, interactions and feedback among the embedded objects are expected to play a major role in the evolution of the region. Aims: We study the dust, kinematic, and polarimetric properties of the NGC 7538 IRS 1-3 region to investigate the role of the different forces in the formation and evolution of high-mass star-forming clusters. Methods: We performed SMA high angular resolution observations at 880 μm with the compact configuration. We developed the RATPACKS code to generate synthetic velocity cubes from models of choice to be compared to the observational data. To quantify the stability against gravitational collapse we developed the "mass balance" analysis that accounts for all the energetics on core scales. Results: We detect 14 dust cores from 3.5 M⊙ to 37 M⊙ arranged in two larger scale structures: a central bar and a filamentary spiral arm. The spiral arm presents large-scale velocity gradients in H13CO+ 4-3 and C17O 3-2, and magnetic field segments aligned well to the dust main axis. The velocity gradient is reproduced well by a spiral arm expanding at 9 km s-1 with respect to the central core MM1, which is known to power a large precessing outflow. The energy of the outflow is comparable to the spiral-arm kinetic energy, which dominates gravitational and magnetic energies. In addition, the dynamical ages of the outflow and spiral arm are comparable. On core scales, those embedded in the central bar seem to be unstable against gravitational collapse and prone to forming high-mass stars, while those in the spiral arm have lower masses that seem to be supported by non-thermal motions and magnetic fields. Conclusions: The NGC 7538 IRS 1-3 cluster seems to be dominated by protostellar feedback. The dusty spiral arm appears to be formed in a snowplow fashion

  8. Gas Dynamics in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    McCourt, Michael Kingsley, Jr.

    Galaxy clusters are the most massive structures in the universe and, in the hierarchical pattern of cosmological structure formation, the largest objects in the universe form last. Galaxy clusters are thus interesting objects for a number of reasons. Three examples relevant to this thesis are: 1. Constraining the properties of dark energy: Due to the hierarchical nature of structure formation, the largest objects in the universe form last. The cluster mass function is thus sensitive to the entire expansion history of the universe and can be used to constrain the properties of dark energy. This constraint complements others derived from the CMB or from Type Ia supernovae and provides an important, independent confirmation of such methods. In particular, clusters provide detailed information about the equation of state parameter w because they sample a large redshift range z ˜ 0 - 1. 2. Probing galaxy formation: Clusters contain the most massive galaxies in the uni- verse, and the most massive black holes; because clusters form so late, we can still witness the assembly of these objects in the nearby universe. Clusters thus provide a more detailed view of galaxy formation than is possible in studies of lower-mass ob- jects. An important example comes from x-ray studies of clusters, which unexpectedly found that star formation in massive galaxies in clusters is closely correlated with the properties of the hot, virialized gas in their halos. This correlation persists despite the enormous separation in temperature, in dynamical time-scales, and in length-scales between the virialized gas in the halo and the star-forming regions in the galaxy. This remains a challenge to interpret theoretically. 3. Developing our knowledge of dilute plasmas: The masses and sizes of galaxy clusters imply that the plasma which permeates them is both very hot (˜ 108 K) and very dilute (˜ 10 -2 cm-3). This plasma is collisional enough to be considered a fluid, but collisionless enough to

  9. Novel approaches to pin cluster synchronization on complex dynamical networks in Lur'e forms

    NASA Astrophysics Data System (ADS)

    Tang, Ze; Park, Ju H.; Feng, Jianwen

    2018-04-01

    This paper investigates the cluster synchronization of complex dynamical networks consisted of identical or nonidentical Lur'e systems. Due to the special topology structure of the complex networks and the existence of stochastic perturbations, a kind of randomly occurring pinning controller is designed which not only synchronizes all Lur'e systems in the same cluster but also decreases the negative influence among different clusters. Firstly, based on an extended integral inequality, the convex combination theorem and S-procedure, the conditions for cluster synchronization of identical Lur'e networks are derived in a convex domain. Secondly, randomly occurring adaptive pinning controllers with two independent Bernoulli stochastic variables are designed and then sufficient conditions are obtained for the cluster synchronization on complex networks consisted of nonidentical Lur'e systems. In addition, suitable control gains for successful cluster synchronization of nonidentical Lur'e networks are acquired by designing some adaptive updating laws. Finally, we present two numerical examples to demonstrate the validity of the control scheme and the theoretical analysis.

  10. Targeting Clusters, Achieving Excellence.

    ERIC Educational Resources Information Center

    Rosenfeld, Stuart; Jacobs, Jim; Liston, Cynthia

    2003-01-01

    Suggests that groups, or clusters, of industries form partnerships with community colleges in order to positively impact economic development. Asserts that a cluster-oriented community college system requires innovation, specialized resources and expertise, knowledge of trends, and links to industry. Offers suggestions for developing such a…

  11. Internal dynamics of the radio-halo cluster A2219: A multi-wavelength analysis

    NASA Astrophysics Data System (ADS)

    Boschin, W.; Girardi, M.; Barrena, R.; Biviano, A.; Feretti, L.; Ramella, M.

    2004-03-01

    We present the results of the dynamical analysis of the rich, hot, and X-ray very luminous galaxy cluster A2219, containing a powerful diffuse radio-halo. Our analysis is based on new redshift data for 27 galaxies in the cluster region, measured from spectra obtained at the TNG, with the addition of other 105 galaxies recovered from reduction of CFHT archive data in a cluster region of ˜5 arcmin radius (˜ 0.8 h-1 Mpc ; at the cluster distance) centered on the cD galaxy. The investigation of the dynamical status is also performed using X-ray data stored in the Chandra archive. Further, valuable information comes from other bands - optical photometric, infrared, and radio data - which are analyzed and/or discussed, too. We find that A2219 appears as a peak in the velocity space at z=0.225, and select 113 cluster members. We compute a high value for the line-of-sight velocity dispersion, σv= 1438+109-86 km s-1, consistent with the high average X-ray temperature of 10.3 keV. If dynamical equilibrium is assumed, the virial theorem leads to M˜2.8× 1015 M⊙ ;sun for the global mass within the virial region. However, further investigation based on both optical and X-ray data shows significant signs of a young dynamical status. In fact, we find strong evidence for the elongation of the cluster in the SE-NW direction coupled with a significant velocity gradient, as well as for the presence of substructure both in optical data and X-ray data. Moreover, we point out the presence of several active galaxies. We discuss the results of our multi-wavelength investigation suggesting a complex merging scenario where the main, original structure is subject to an ongoing merger with a few clumps aligned in a filament in the foreground oriented in an oblique direction with respect to the line-of-sight. Our conclusion supports the view of the connection between extended radio emission and merging phenomena in galaxy clusters. Based on observations made on the island of La Palma

  12. Dynamic stabilities of icosahedral-like clusters and their ability to form quasicrystals

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liang, Xiaogang; Hamid, Ilyar; Duan, Haiming, E-mail: dhm@xju.edu.cn

    2016-06-15

    The dynamic stabilities of the icosahedral-like clusters containing up to 2200 atoms are investigated for 15 metal elements. The clusters originate from five different initial structures (icosahedron, truncated decahedron, octahedron, closed-shell fragment of an HCP structure, and non-closed-shell fragment of an HCP structure). The obtained order of the dynamic stabilities of the icosahedral-like clusters can be assigned to three groups, from stronger to weaker, according to the size ranges involved: (Zr, Al, Ti) > (Cu, Fe, Co, Ni, Mg, Ag) > (Pb, Au, Pd, Pt, Rh, Ir), which correspond to the predicted formation ability of the quasicrystals. The differences ofmore » the sequences can be explained by analyzing the parameters of the Gupta-type many-body inter-atomic potentials.« less

  13. Star formation towards the southern cometary H II region IRAS 17256-3631

    NASA Astrophysics Data System (ADS)

    Veena, V. S.; Vig, S.; Tej, A.; Varricatt, W. P.; Ghosh, S. K.; Chandrasekhar, T.; Ashok, N. M.

    2016-03-01

    IRAS 17256-3631 is a southern Galactic massive star-forming region located at a distance of 2 kpc. In this paper, we present a multiwavelength investigation of the embedded cluster, the H II region, as well as the parent cloud. Radio images at 325, 610 and 1372 MHz were obtained using Giant Metrewave Radio Telescope, India while the near-infrared imaging and spectroscopy were carried out using United Kingdom Infrared Telescope and Mt. Abu Infrared Telescope, India. The near-infrared K-band image reveals the presence of a partially embedded infrared cluster. The spectral features of the brightest star in the cluster, IRS-1, spectroscopically agree with a late O or early B star and could be the driving source of this region. Filamentary H2 emission detected towards the outer envelope indicates the presence of highly excited gas. The parent cloud is investigated at far-infrared to millimetre wavelengths and 18 dust clumps have been identified. The spectral energy distributions of these clumps have been fitted as modified blackbodies and the best-fitting peak temperatures are found to range from 14 to 33 K, while the column densities vary from 0.7 to 8.5 × 1022 cm-2. The radio maps show a cometary morphology for the distribution of ionized gas that is density bounded towards the north-west and ionization bounded towards the south-east. This morphology is better explained with the champagne flow model as compared to the bow-shock model. Using observations at near-, mid- and far-infrared, submillimetre and radio wavelengths, we examine the evolutionary stages of various clumps.

  14. Spitzer Clusters

    NASA Astrophysics Data System (ADS)

    Krick, Kessica

    This proposal is a specific response to the strategic goal of NASA's research program to "discover how the universe works and explore how the universe evolved into its present form." Towards this goal, we propose to mine the Spitzer archive for all observations of galaxy groups and clusters for the purpose of studying galaxy evolution in clusters, contamination rates for Sunyaev Zeldovich cluster surveys, and to provide a database of Spitzer observed clusters to the broader community. Funding from this proposal will go towards two years of support for a Postdoc to do this work. After searching the Spitzer Heritage Archive, we have found 194 unique galaxy groups and clusters that have data from both the Infrared array camera (IRAC; Fazio et al. 2004) at 3.6 - 8 microns and the multiband imaging photometer for Spitzer (MIPS; Rieke et al. 2004) at 24microns. This large sample will add value beyond the individual datasets because it will be a larger sample of IR clusters than ever before and will have sufficient diversity in mass, redshift, and dynamical state to allow us to differentiate amongst the effects of these cluster properties. An infrared sample is important because it is unaffected by dust extinction while at the same time is an excellent measure of both stellar mass (IRAC wavelengths) and star formation rate (MIPS wavelengths). Additionally, IRAC can be used to differentiate star forming galaxies (SFG) from active galactic nuclei (AGN), due to their different spectral shapes in this wavelength regime. Specifically, we intend to identify SFG and AGN in galaxy groups and clusters. Groups and clusters differ from the field because the galaxy densities are higher, there is a large potential well due mainly to the mass of the dark matter, and there is hot X-ray gas (the intracluster medium; ICM). We will examine the impact of these differences in environment on galaxy formation by comparing cluster properties of AGN and SFG to those in the field. Also, we will

  15. Fuzzy Subspace Clustering

    NASA Astrophysics Data System (ADS)

    Borgelt, Christian

    In clustering we often face the situation that only a subset of the available attributes is relevant for forming clusters, even though this may not be known beforehand. In such cases it is desirable to have a clustering algorithm that automatically weights attributes or even selects a proper subset. In this paper I study such an approach for fuzzy clustering, which is based on the idea to transfer an alternative to the fuzzifier (Klawonn and Höppner, What is fuzzy about fuzzy clustering? Understanding and improving the concept of the fuzzifier, In: Proc. 5th Int. Symp. on Intelligent Data Analysis, 254-264, Springer, Berlin, 2003) to attribute weighting fuzzy clustering (Keller and Klawonn, Int J Uncertain Fuzziness Knowl Based Syst 8:735-746, 2000). In addition, by reformulating Gustafson-Kessel fuzzy clustering, a scheme for weighting and selecting principal axes can be obtained. While in Borgelt (Feature weighting and feature selection in fuzzy clustering, In: Proc. 17th IEEE Int. Conf. on Fuzzy Systems, IEEE Press, Piscataway, NJ, 2008) I already presented such an approach for a global selection of attributes and principal axes, this paper extends it to a cluster-specific selection, thus arriving at a fuzzy subspace clustering algorithm (Parsons, Haque, and Liu, 2004).

  16. Multi-wavelength characterisation of z ~ 2 clustered, dusty star-forming galaxies discovered by Planck

    NASA Astrophysics Data System (ADS)

    Flores-Cacho, I.; Pierini, D.; Soucail, G.; Montier, L.; Dole, H.; Pointecouteau, E.; Pelló, R.; Le Floc'h, E.; Nesvadba, N.; Lagache, G.; Guery, D.; Cañameras, R.

    2016-01-01

    that Planck data can be used to detect the emission from clustered, dusty star-forming galaxies at high z, and, thus, to pierce through the early growth of cluster-scale structures.

  17. The Coronae of Moderate-Mass Giants in the Hertzsprung Gap and the Clump

    NASA Technical Reports Server (NTRS)

    Ayres, Thomas R.; Simon, Theodore; Stern, Robert A.; Drake, Stephen A.; Wood, Brian E.; Brown, Alexander

    1998-01-01

    We have used the Roentgensatellit (ROSAT), the Extreme Ultraviolet Explorer (EUVE), and the Hubble Space Telescope (HST) to measure X-ray and ultraviolet emissions of moderate-mass (APPROX. 2-3 solar mass) giants in the Hertzsprung gap (spectral types early F to mid-G) and the post-helium flash "clump" (approx. G8-K0). Our motivation was to document the evolution of hot coronae (T greater than 10(exp 6)K) along the post-main-sequence trajectories traveled by such stars in order to gain insight concerning the "X-ray deficiency" of the F-GO giants and the strong braking of stellar rotation at the red edge of the Hertzsprung gap. With few exceptions, Hertzsprung gap and clump giants observed by ROSAT PSPC show hot (T approx. 10(exp 7)K) coronal energy distributions, regardless of any X-ray deficiency, EUVE spectra of gap star 31 Com (G0 111) indicate a broad coronal emission measure hump at approx. 10(exp 7.2)K, while the active clump giant beta Ceti (K0 III) displays a sharp peak at approx. 10(exp 6.8)K, as seen previously in the mixed clump/gap binary Capella (alpha Aur: G8 III + G0 III). The gap giants upsilon Peg (F8 III) and 24 UMa (G4 III) have EUV emissions of intermediate temperature (approx. 10(exp 7.0)K). The stars 31 Com, psi(sup 3) Psc (G0 III), and beta Cet exhibit redshifted transition zone (TZ: approx. 10(exp 5)K) lines in HST GHRS spectra, as reported earlier in Procyon (alpha CMi: F5 IV-V) and Capella G0. Such redshifts on the Sun are thought to signify flows in magnetic loops. beta Cas (F2 III)-a rare soft coronal source among the gap stars-displays blueshifts of C iv and 0 iv], although emissions at cooler and hotter temperatures are near the photospheric velocity. The remarkably broad line profiles of the fastest rotating gap giants suggest that the 10(exp 5) K "subcoronal " emission zones extend to h approx. R(sub *) above the photosphere, about 50 scale heights. In contrast to the TZ line redshifts, the upper chromospheric emissions (e.g., Mg II

  18. AMOEBA clustering revisited. [cluster analysis, classification, and image display program

    NASA Technical Reports Server (NTRS)

    Bryant, Jack

    1990-01-01

    A description of the clustering, classification, and image display program AMOEBA is presented. Using a difficult high resolution aircraft-acquired MSS image, the steps the program takes in forming clusters are traced. A number of new features are described here for the first time. Usage of the program is discussed. The theoretical foundation (the underlying mathematical model) is briefly presented. The program can handle images of any size and dimensionality.

  19. Large Magellanic Cloud Distance and Structure from Near-Infrared Red Clump Observations

    NASA Astrophysics Data System (ADS)

    Koerwer, Joel F.

    2009-07-01

    We have applied the Infrared Survey Facility Magellanic Clouds Point-Source Catalog to the mapping of the red clump (RC) distance modulus across the Large Magellanic Cloud (LMC). Using the J- (1.25 μm) and H- (1.63 μm) band data to derive a reddening free luminosity function and a theoretical RC absolute magnitude from stellar evolution libraries, we estimate a distance modulus to the LMC of μ = 18.54 ± 0.06. The best fitting plane inclination, i, and the position angle of the line of nodes, phi, have little dependence on the assumed RC absolute magnitude; we find i = 23fdg5 ± 0fdg4 and phi = 154fdg6 ± 1fdg2. It was also noted that many fields included a significant asymptotic giant branch bump population that must be accounted for.

  20. Clustering-based classification of road traffic accidents using hierarchical clustering and artificial neural networks.

    PubMed

    Taamneh, Madhar; Taamneh, Salah; Alkheder, Sharaf

    2017-09-01

    Artificial neural networks (ANNs) have been widely used in predicting the severity of road traffic crashes. All available information about previously occurred accidents is typically used for building a single prediction model (i.e., classifier). Too little attention has been paid to the differences between these accidents, leading, in most cases, to build less accurate predictors. Hierarchical clustering is a well-known clustering method that seeks to group data by creating a hierarchy of clusters. Using hierarchical clustering and ANNs, a clustering-based classification approach for predicting the injury severity of road traffic accidents was proposed. About 6000 road accidents occurred over a six-year period from 2008 to 2013 in Abu Dhabi were used throughout this study. In order to reduce the amount of variation in data, hierarchical clustering was applied on the data set to organize it into six different forms, each with different number of clusters (i.e., clusters from 1 to 6). Two ANN models were subsequently built for each cluster of accidents in each generated form. The first model was built and validated using all accidents (training set), whereas only 66% of the accidents were used to build the second model, and the remaining 34% were used to test it (percentage split). Finally, the weighted average accuracy was computed for each type of models in each from of data. The results show that when testing the models using the training set, clustering prior to classification achieves (11%-16%) more accuracy than without using clustering, while the percentage split achieves (2%-5%) more accuracy. The results also suggest that partitioning the accidents into six clusters achieves the best accuracy if both types of models are taken into account.

  1. Cluster of Genes That Encode Positive and Negative Elements Influencing Filament Length in a Heterocyst-Forming Cyanobacterium

    PubMed Central

    Merino-Puerto, Victoria; Herrero, Antonia

    2013-01-01

    The filamentous, heterocyst-forming cyanobacteria perform oxygenic photosynthesis in vegetative cells and nitrogen fixation in heterocysts, and their filaments can be hundreds of cells long. In the model heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120, the genes in the fraC-fraD-fraE operon are required for filament integrity mainly under conditions of nitrogen deprivation. The fraC operon transcript partially overlaps gene all2395, which lies in the opposite DNA strand and ends 1 bp beyond fraE. Gene all2395 produces transcripts of 1.35 kb (major transcript) and 2.2 kb (minor transcript) that overlap fraE and whose expression is dependent on the N-control transcription factor NtcA. Insertion of a gene cassette containing transcriptional terminators between fraE and all2395 prevented production of the antisense RNAs and resulted in an increased length of the cyanobacterial filaments. Deletion of all2395 resulted in a larger increase of filament length and in impaired growth, mainly under N2-fixing conditions and specifically on solid medium. We denote all2395 the fraF gene, which encodes a protein restricting filament length. A FraF-green fluorescent protein (GFP) fusion protein accumulated significantly in heterocysts. Similar to some heterocyst differentiation-related proteins such as HglK, HetL, and PatL, FraF is a pentapeptide repeat protein. We conclude that the fraC-fraD-fraE←fraF gene cluster (where the arrow indicates a change in orientation), in which cis antisense RNAs are produced, regulates morphology by encoding proteins that influence positively (FraC, FraD, FraE) or negatively (FraF) the length of the filament mainly under conditions of nitrogen deprivation. This gene cluster is often conserved in heterocyst-forming cyanobacteria. PMID:23813733

  2. Shear heating and solid state diffusion: Constraints from clumped isotope thermometry in carbonate faults

    NASA Astrophysics Data System (ADS)

    Siman-Tov, S.; Affek, H. P.; Matthews, A.; Aharonov, E.; Reches, Z.

    2015-12-01

    Natural faults are expected to heat rapidly during seismic slip and to cool quite quickly after the event. Here we examine clumped isotope thermometry for its ability to identify short duration elevated temperature events along frictionally heated carbonate faults. This method is based on measured Δ47 values that indicate the relative atomic order of oxygen and carbon stable isotopes in the calcite lattice, which is affected by heat and thus can serve as a thermometer. We examine three types of calcite rock samples: (1) samples that were rapidly heated and then cooled in static laboratory experiments, simulating the temperature cycle experienced by fault rock during earthquake slip; (2) limestone samples that were experimentally sheared to simulate earthquake slip events; and (3) samples taken from principle slip zones of natural carbonate faults that likely experienced earthquake slip. Experimental results show that Δ47 values decrease rapidly (in the course of seconds) and systematically both with increasing temperature and shear velocity. On the other hand, carbonate shear zone from natural faults do not show such Δ47 reduction. We propose that the experimental Δ47 response is controlled by the presence of high-stressed nano-grains within the fault zone that can reduce the activation energy for diffusion by up to 60%, and thus lead to an increased rate of solid-state diffusion in the experiments. However, the lowering of activation energy is a double-edged sword in terms of clumped isotopes: In laboratory experiments, it allows for rapid disordering so that isotopic signal appears after very short heating, but in natural faults it also leads to relatively fast isotopic re-ordering after the cessation of frictional heating, thus erasing the high temperature signature in Δ47 values within relatively short geological times (<1 Ma).

  3. Hydrodynamic simulations of mechanical stellar feedback in a molecular cloud formed by thermal instability

    NASA Astrophysics Data System (ADS)

    Wareing, C. J.; Pittard, J. M.; Falle, S. A. E. G.

    2017-09-01

    We have used the AMR hydrodynamic code, mg, to perform 3D hydrodynamic simulations with self-gravity of stellar feedback in a spherical clumpy molecular cloud formed through the action of thermal instability. We simulate the interaction of the mechanical energy input from 15, 40, 60 and 120 M⊙ stars into a 100 pc diameter 16 500 M⊙ cloud with a roughly spherical morphology with randomly distributed high-density condensations. The stellar winds are introduced using appropriate non-rotating Geneva stellar evolution models. In the 15 M⊙ star case, the wind has very little effect, spreading around a few neighbouring clumps before becoming overwhelmed by the cloud collapse. In contrast, in the 40, 60 and 120 M⊙ star cases, the more powerful stellar winds create large cavities and carve channels through the cloud, breaking out into the surrounding tenuous medium during the wind phase and considerably altering the cloud structure. After 4.97, 3.97 and 3.01 Myr, respectively, the massive stars explode as supernovae (SNe). The wind-sculpted surroundings considerably affect the evolution of these SN events as they both escape the cloud along wind-carved channels and sweep up remaining clumps of cloud/wind material. The 'cloud' as a coherent structure does not survive the SN from any of these stars, but only in the 120 M⊙ case is the cold molecular material completely destabilized and returned to the unstable thermal phase. In the 40 and 60 M⊙ cases, coherent clumps of cold material are ejected from the cloud by the SN, potentially capable of further star formation.

  4. Cluster generator

    DOEpatents

    Donchev, Todor I [Urbana, IL; Petrov, Ivan G [Champaign, IL

    2011-05-31

    Described herein is an apparatus and a method for producing atom clusters based on a gas discharge within a hollow cathode. The hollow cathode includes one or more walls. The one or more walls define a sputtering chamber within the hollow cathode and include a material to be sputtered. A hollow anode is positioned at an end of the sputtering chamber, and atom clusters are formed when a gas discharge is generated between the hollow anode and the hollow cathode.

  5. The different types of sperm morphology and behavior within a single species: Why do sperm of squid sneaker males form a cluster?

    PubMed

    Hirohashi, Noritaka; Iwata, Yoko

    2013-11-01

    Some coastal squids exhibit male dimorphism (large and small body size) that is linked to mating behaviors. Large "consort" males compete with other, rival males to copulate with a female, and thereby transfer their spermatophores to her internal site around the oviduct. Small "sneaker" males rush to a single female or copulating pair and transfer spermatophores to her external body surface around the seminal receptacle near the mouth. We previously found that in Loligo bleekeri, sneaker sperm are ~50% longer than consort sperm, and only the sneaker sperm, once ejaculated from the spermatophore (sperm mass), form a cluster because of chemoattraction toward their own respiratory CO2. Here, we report that sperm clusters are able to move en masse. Because a fraction of ejaculated sperm from a sneaker's spermatophore are eventually located in the female's seminal receptacle, we hypothesize that sperm clustering facilitates collective migration to the seminal receptacle or an egg micropyle. Sperm clustering is regarded as a cooperative behavior that may have evolved by sperm competition and/or physical and physiological constraints imposed by male mating tactics.

  6. Water clusters in amorphous pharmaceuticals.

    PubMed

    Authelin, Jean-Rene; MacKenzie, Alan P; Rasmussen, Don H; Shalaev, Evgenyi Y

    2014-09-01

    Amorphous materials, although lacking the long-range translational and rotational order of crystalline and liquid crystalline materials, possess certain local (short-range) structure. This paper reviews the distribution of one particular component present in all amorphous pharmaceuticals, that is, water. Based on the current understanding of the structure of water, water molecules can exist in either unclustered form or as aggregates (clusters) of different sizes and geometries. Water clusters are reported in a range of amorphous systems including carbohydrates and their aqueous solutions, synthetic polymers, and proteins. Evidence of water clustering is obtained by various methods that include neutron and X-ray scattering, molecular dynamics simulation, water sorption isotherm, concentration dependence of the calorimetric Tg , dielectric relaxation, and nuclear magnetic resonance. A review of the published data suggests that clustering depends on water concentration, with unclustered water molecules existing at low water contents, whereas clusters form at intermediate water contents. The transition from water clusters to unclustered water molecules can be expected to change water dependence of pharmaceutical properties, such as rates of degradation. We conclude that a mechanistic understanding of the impact of water on the stability of amorphous pharmaceuticals would require systematic studies of water distribution and clustering, while such investigations are lacking. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  7. CHEMICAL ABUNDANCES OF MEMBER STARS IN THE OPEN CLUSTER NGC 2632 (PRAESEPE)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang, X. L.; Chen, Y. Q.; Zhao, G.

    2015-11-15

    Based on high-resolution, high signal-to-noise ratio spectra, we present abundances of 17 elements (Fe, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Co, Ni, Y, Zr, Ba, La) for six stars (one Am star, one F dwarf star, and four GK giant stars) and radial velocities for 18 proper-motion selected member stars in the open cluster NGC 2632. In the Am star, s-process elements Y and Ba are clearly overabundant, which may be considered as an indicator of a peculiar Am star. The average [Fe/H] is 0.16 ± 0.06 from four GK giant member stars, which is similarmore » to that of solar-type stars in the literature. As compared with dwarf stars, significant overabundances are found for Na, Mg, and Ba elements in our giant stars, which can be explained by the evolutionary effect. We also detect a star-to-star scatter of [Na/Fe] ratios among four giants which locate approximately at the same position in the CMD. Finally, we perform an analysis on the possible connection between the abundance and spatial structure of NGC 2632, but we find no inhomogeneous abundance among different clumps of stars in this cluster based on our limited sample.« less

  8. HUBBLE SPIES HUGE CLUSTERS OF STARS FORMED BY ANCIENT ENCOUNTER

    NASA Technical Reports Server (NTRS)

    2002-01-01

    NASA's Hubble Space Telescope snapped these two views of the heart of the galaxy M82. The image at left was taken in visible light; the picture at right, in infrared light. In the infrared view, the telescope's Near Infrared Camera and Multi-Object Spectrometer peered through thick dust lanes to find some of the galaxy's more than 100 super star clusters. The clusters are the larger pink and yellow dots scattered throughout the picture. They were formed during a violent collision with the galaxy M81 about 600 million years ago. The galaxy is 12 million light-years from Earth in the constellation Ursa Major. The pictures were taken Sept. 15, 1997. Credits: NASA, ESA, R. de Grijs (Institute of Astronomy, Cambridge, UK) NOTE TO EDITORS: For additional information, please contact Richard de Grijs, Institute of Astronomy, Cambridge University, Madingley Road, Cambridge CB3 0HA, UK, +44(0)1223-337528 (phone), +44(0)1223-337523 (fax), grijs@ast.cam.ac.uk (e-mail). The Space Telescope Science Institute (STScI) is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), for NASA, under contract with the Goddard Space Flight Center, Greenbelt, MD. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA). This image is issued jointly by NASA and ESA. Electronic images, animation and additional information are available at: http://oposite.stsci.edu/pubinfo/pr/2001/08 and via links in http://oposite.stsci.edu/pubinfo/latest.html http://oposite.stsci.edu/pubinfo/pictures.html http://hubble.stsci.edu/go/news http://hubble.esa.int To receive STScI press releases electronically, send an Internet electronic mail message to public-request@stsci.edu. Leave the subject line blank, and type the word subscribe in the body of the message. The system will respond with a confirmation of the subscription, and you will receive new press releases as they are issued. Please subscribe using the email account

  9. A youthful cluster

    NASA Image and Video Library

    2015-08-24

    Shown here in a new image taken with the Advanced Camera for Surveys (ACS) on board the NASA/ESA Hubble Space Telescope, is the globular cluster NGC 1783. This is one of the biggest globular clusters in the Large Magellanic Cloud, a satellite galaxy of our own galaxy, the Milky Way, in the southern hemisphere constellation of Dorado. First observed by John Herschel in 1835, NGC 1783 is nearly 160 000 light-years from Earth, and has a mass around 170 000 times that of the Sun. Globular clusters are dense collections of stars held together by their own gravity, which orbit around galaxies like satellites. The image clearly shows the symmetrical shape of NGC 1783 and the concentration of stars towards the centre, both typical features of globular clusters. By measuring the colour and brightness of individual stars, astronomers can deduce an overall age for a cluster and a picture of its star formation history. NGC 1783 is thought to be under one and a half billion years old — which is very young for globular clusters, which are typically several billion years old. During that time, it is thought to have undergone at least two periods of star formation, separated by 50 to 100 million years. This ebb and flow of star-forming activity is an indicator of how much gas is available for star formation at any one time. When the most massive stars created in the first burst of formation explode as supernovae they blow away the gas needed to form further stars, but the gas reservoir can later be replenished by less massive stars which last longer and shed their gas less violently. After this gas flows to the dense central regions of the star cluster, a second phase of star formation can take place and once again the short-lived massive stars blow away any leftover gas. This cycle can continue a few times, at which time the remaining gas reservoir is thought to be too small to form any new stars. A version of this image was entered into the Hubble's Hidden Treasures image pr

  10. Internal gettering by metal alloy clusters

    DOEpatents

    Buonassisi, Anthony; Heuer, Matthias; Istratov, Andrei A.; Pickett, Matthew D.; Marcus, Mathew A.; Weber, Eicke R.

    2010-07-27

    The present invention relates to the internal gettering of impurities in semiconductors by metal alloy clusters. In particular, intermetallic clusters are formed within silicon, such clusters containing two or more transition metal species. Such clusters have melting temperatures below that of the host material and are shown to be particularly effective in gettering impurities within the silicon and collecting them into isolated, less harmful locations. Novel compositions for some of the metal alloy clusters are also described.

  11. Characterization and prediction of the backscattered form function of an immersed cylindrical shell using hybrid fuzzy clustering and bio-inspired algorithms.

    PubMed

    Agounad, Said; Aassif, El Houcein; Khandouch, Younes; Maze, Gérard; Décultot, Dominique

    2018-02-01

    The acoustic scattering of a plane wave by an elastic cylindrical shell is studied. A new approach is developed to predict the form function of an immersed cylindrical shell of the radius ratio b/a ('b' is the inner radius and 'a' is the outer radius). The prediction of the backscattered form function is investigated by a combined approach between fuzzy clustering algorithms and bio-inspired algorithms. Four famous fuzzy clustering algorithms: the fuzzy c-means (FCM), the Gustafson-Kessel algorithm (GK), the fuzzy c-regression model (FCRM) and the Gath-Geva algorithm (GG) are combined with particle swarm optimization and genetic algorithm. The symmetric and antisymmetric circumferential waves A, S 0 , A 1 , S 1 and S 2 are investigated in a reduced frequency (k 1 a) range extends over 0.1form functions. This representation is used as a comparison criterion between the calculated form function by the analytical method and that predicted by the proposed approach on the one hand and is used to extract the predicted cut-off frequencies on the other hand. Moreover, the transverse velocity of the material constituting the cylindrical shell is extracted. The computational results show that the proposed approach is very efficient to predict the form function and consequently, for acoustic characterization purposes. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Formation and Assembly of Massive Star Clusters

    NASA Astrophysics Data System (ADS)

    McMillan, Stephen

    The formation of stars and star clusters is a major unresolved problem in astrophysics. It is central to modeling stellar populations and understanding galaxy luminosity distributions in cosmological models. Young massive clusters are major components of starburst galaxies, while globular clusters are cornerstones of the cosmic distance scale and represent vital laboratories for studies of stellar dynamics and stellar evolution. Yet how these clusters form and how rapidly and efficiently they expel their natal gas remain unclear, as do the consequences of this gas expulsion for cluster structure and survival. Also unclear is how the properties of low-mass clusters, which form from small-scale instabilities in galactic disks and inform much of our understanding of cluster formation and star-formation efficiency, differ from those of more massive clusters, which probably formed in starburst events driven by fast accretion at high redshift, or colliding gas flows in merging galaxies. Modeling cluster formation requires simulating many simultaneous physical processes, placing stringent demands on both software and hardware. Simulations of galaxies evolving in cosmological contexts usually lack the numerical resolution to simulate star formation in detail. They do not include detailed treatments of important physical effects such as magnetic fields, radiation pressure, ionization, and supernova feedback. Simulations of smaller clusters include these effects, but fall far short of the mass of even single young globular clusters. With major advances in computing power and software, we can now directly address this problem. We propose to model the formation of massive star clusters by integrating the FLASH adaptive mesh refinement magnetohydrodynamics (MHD) code into the Astrophysical Multi-purpose Software Environment (AMUSE) framework, to work with existing stellar-dynamical and stellar evolution modules in AMUSE. All software will be freely distributed on-line, allowing

  13. Carbonate clumped isotopes and in situ temperature monitoring for Holocene soils in the San Luis Valley, USA indicate springtime carbonate formation

    NASA Astrophysics Data System (ADS)

    Hudson, A. M.; Paces, J. B.; Ruleman, C.

    2017-12-01

    Pedogenic carbonate horizons are abundant in semi-arid and arid regions worldwide and within the geologic record. They present a widely distributed archive of past environmental conditions, driven by global climate or tectonically-controlled elevation changes. Oxygen and carbon isotopes in calcite-rich nodules and clast rinds are widely-applied indicators of past soil water and CO2 composition linked to changing precipitation and plant communities. The temperature of carbonate formation, however, provides key constraint on past water/CO2 values and elucidate why they may have changed in the past. Clumped isotope thermometry can provide this constraint and additional climate information, given the carbonate forming system is well understood. We present preliminary clumped isotope (Δ47) temperatures for Holocene soil carbonates, constrained by 14C and U-Th disequilibrium dating, compared with two years of in situ soil temperature data to better understand the mechanism and seasonality of carbonate formation in the San Luis Valley region of the southern Rocky Mountains. Five temperature-monitoring sites ranging in elevation (1940-2450 m) and latitude (36.2-37.9°N) were installed in a variety of settings (range front, valley center, and canyon). The resulting records show indistinguishable seasonal temperature variations at >60 cm depth. This suggests Δ47 temperatures should be comparable at sites across the region. Temperatures based on Δ47 measurements of Holocene (>1.8 to 11.0 ka BP) carbonates at these sites yield consistent inter-site temperatures of 10±4°C, which are similar to modern springtime soil temperatures at depth. This seasonality matches previous results of isotopic modeling at sites further south along the Rio Grande corridor. Temperatures during March to May show multiple, abrupt warming and cooling cycles on weekly timescales caused by wetting and drying of the soil during spring precipitation events. This may drive carbonate precipitation

  14. Evaluation of clumped isotope paleotemperatures across carbon isotope excursions from lacustrine strata of the Aptian Xiagou Formation, China

    NASA Astrophysics Data System (ADS)

    Suarez, M. B.; Gonzalez, L. A.; Ludvigson, G. A.; You, H.

    2014-12-01

    Carbon cycle perturbations associated with Ocean Anoxic Event 1a have been implicated in global climate and environmental changes in the Early Aptian, in particular evidence for high sea surface temperatures (SST) and carbonate platform drowning. Records of environmental changes in the terrestrial realm remain sparse. This study provides additional data on clumped isotope derived temperatures (T(Δ47)) from lacustrine carbonates of the Xiagou Formation, Gansu Province, China. In addition, Vitrinite reflectance and the Rock-Eval parameter Tmax were used to evaluate the potential for 13C-18O bonds in the carbonates to have experienced reordering. Clumped isotope derived temperatures range from 28.8 °C to 45.9°C. Vitrinite reflectance values range from 0.67 to 0.72 and Tmax ranges from 429 °C to 443 °C. The warmest temperature, derived from a very fine-grained calcareous sandstone, is at the upper limit of known modern Earth surface temperatures, and prompts concern that the T(Δ47) may be shifted to warmer temperatures as a result of burial diagenesis. Vitrinite reflectance and Tmax values indicate the samples have reached early maturity for oil generation (oil window from 60 °C to 150°C), so may have reached the lower end of temperatures for bond reordering to have occurred (~100 °C for ~100 million years). Despite this, the T(Δ47) are consistent with summer temperatures in a warm Cretaceous. In addition, temperature variations are similar to TEX86 records, especially from SST of the tropical Pacific. Two temperature increases and decreases occur, with the first peak in temperature occurring at the negative carbon isotope excursion (C3) associated with the initiation of the Selli Event (OAE1a). This study provides evidence that climate variations occurring during the Selli Event were experienced in terrestrial environments, and provides maximum summer temperatures for this part of the Asian continent during the Cretaceous. While it was intended that thermal

  15. Temperature evolution and the oxygen isotope composition of Phanerozoic oceans from carbonate clumped isotope thermometry

    NASA Astrophysics Data System (ADS)

    Henkes, Gregory A.; Passey, Benjamin H.; Grossman, Ethan L.; Shenton, Brock J.; Yancey, Thomas E.; Pérez-Huerta, Alberto

    2018-05-01

    Surface temperature is among the most important parameters describing planetary climate and habitability, and yet there remains considerable debate about the temperature evolution of the Earth's oceans during the Phanerozoic Eon (541 million years ago to present), the time during which complex metazoan life radiated on Earth. Here we critically assess the emerging record of Phanerozoic ocean temperatures based on carbonate clumped isotope thermometry of fossil brachiopod and mollusk shells, and we present new data that fill important gaps in the Late Paleozoic record. We evaluate and reject the hypothesis that solid-state reordering of 13C-18O bonds has destroyed the primary clumped isotope temperature signal of most fossils during sedimentary burial at elevated temperatures. The resulting Phanerozoic record, which shows a general coupling between tropical seawater temperatures and atmospheric carbon dioxide (CO2) levels since the Paleozoic, indicates that tropical temperatures during the icehouse climate of the Carboniferous period were broadly similar to present (∼25-30 °C), and suggests that benthic metazoans were able to thrive at temperatures of 35-40 °C during intervals of the early and possibly the latest Paleozoic when CO2 levels were likely 5-10× higher than present-day values. Equally important, there is no resolvable trend in seawater oxygen isotope ratios (δ18 O) over the past ∼500 million years, indicating that the average temperature of oxygen exchange between seawater and the oceanic crust has been high (∼270 °C) since at least the early Paleozoic, which points to mid-ocean ridges as the dominant locus of water-rock interaction over the past half-billion years.

  16. Primordial binary populations in low-density star clusters as seen by Chandra: globular clusters versus old open clusters

    NASA Astrophysics Data System (ADS)

    van den Berg, Maureen C.

    2015-08-01

    The binaries in the core of a star cluster are the energy source that prevents the cluster from experiencing core collapse. To model the dynamical evolution of a cluster, it is important to have constraints on the primordial binary content. X-ray observations of old star clusters are very efficient in detecting the close interacting binaries among the cluster members. The X-ray sources in star clusters are a mix of binaries that were dynamically formed and primordial binaries. In massive, dense star clusters, dynamical encounters play an important role in shaping the properties and numbers of the binaries. In contrast, in the low-density clusters the impact of dynamical encounters is presumed to be very small, and the close binaries detected in X-rays represent a primordial population. The lowest density globular clusters have current masses and central densities similar to those of the oldest open clusters in our Milky Way. I will discuss the results of studies with the Chandra X-ray Observatory that have nevertheless revealed a clear dichotomy: far fewer (if any at all) X-ray sources are detected in the central regions of the low-density globular clusters compared to the number of secure cluster members that have been detected in old open clusters (above a limiting X-ray luminosity of typically 4e30 erg/s). The low stellar encounter rates imply that dynamical destruction of binaries can be ignored at present, therefore an explanation must be sought elsewhere. I will discuss several factors that can shed light on the implied differences between the primordial close binary populations in the two types of star clusters.

  17. Dynamic multifactor clustering of financial networks

    NASA Astrophysics Data System (ADS)

    Ross, Gordon J.

    2014-02-01

    We investigate the tendency for financial instruments to form clusters when there are multiple factors influencing the correlation structure. Specifically, we consider a stock portfolio which contains companies from different industrial sectors, located in several different countries. Both sector membership and geography combine to create a complex clustering structure where companies seem to first be divided based on sector, with geographical subclusters emerging within each industrial sector. We argue that standard techniques for detecting overlapping clusters and communities are not able to capture this type of structure and show how robust regression techniques can instead be used to remove the influence of both sector and geography from the correlation matrix separately. Our analysis reveals that prior to the 2008 financial crisis, companies did not tend to form clusters based on geography. This changed immediately following the crisis, with geography becoming a more important determinant of clustering structure.

  18. Major cluster mergers and the location of the brightest cluster galaxy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Martel, Hugo; Robichaud, Fidèle; Barai, Paramita, E-mail: Hugo.Martel@phy.ulaval.ca

    semi-major mergers in the past. These mergers leave each cluster in a non-equilibrium state, but eventually the cluster settles into an equilibrium configuration, unless it is disturbed by another major or semi-major merger. We found evidence that these mergers are responsible for the off-center positions and peculiar velocities of some BCGs. Our results thus support the merging-group scenario, in which some clusters form by the merging of smaller groups in which the galaxies have already formed, including the galaxy destined to become the BCG. Finally, we argue that f {sub BNC} is not a very robust statistics, as it is very sensitive to projection and selection effects, but that Δv/σ is more robust. Still, both statistics exhibit a signature of major mergers between clusters of galaxies.« less

  19. Ethane C-C clumping in natural gas : a proxy for cracking processes ?

    NASA Astrophysics Data System (ADS)

    Clog, M. D.; Ferreira, A. A.; Santos Neto, E. V.; Eiler, J. M.

    2014-12-01

    Ethane (C2H6) is the second-most abundant alkane in most natural gas reservoirs, and is used to produce ethylene for petrochemical industries. It is arguably the simplest molecule that can manifest multiple 13C substitutions. There are several plausible controls on Δ13C2H6in natural gas: thermodynamically controlled homogeneous isotope exchange reactions analogous to those behind carbonate clumped isotope thermometry; inheritance from larger biomolecules that undergo thermal degradation to produce natural gas; mixing of natural gases that differ markedly in bulk isotopic composition; diffusive fractionation; or combinations of these and/or other, less expected fractionations. There is little basis for predicting which of these will control isotopic variations among natural ethanes, but we think it likely that addition of this new isotopic proxy will reveal new insights into the natural chemistry of ethane. We have developed a method to measure the abundance of 13C2H6 in natural samples, using high-resolution mass spectrometry. We define Δ13C2H6 as 1000 . ((13C2H6/12C2H6)measured/(13C2H6/12C2H6)stochastic -1). We studied several suites of natural gas samples and experimentally produced or modified ethane. Natural ethanes, including closely related samples from a single natural gas field, exhibit surprisingly large ranges in Δ13C2H6 (4 ‰ overall; up to 3 ‰ in one gas field). Such ranges cannot be explained by thermodynamic equilibrium at a range of different temperatures, or by diffusive fractionation. Kinetic isotope effects associated with 'cracking' reactions, and/or inheritance of non-equilibrium carbon isotope structures from source organics are more likely causes. We observe a correlation between Δ13C2H6 and the concentration of alkanes other than methane in several suites of natural gases, suggesting the causes of clumped isotope variations are tied to the controls on gas wetness. An experiment examining ethane residual to high-temperature pyrolysis

  20. Interacting star clusters in the Large Magellanic Cloud. Overmerging problem solved by cluster group formation

    NASA Astrophysics Data System (ADS)

    Leon, Stéphane; Bergond, Gilles; Vallenari, Antonella

    1999-04-01

    We present the tidal tail distributions of a sample of candidate binary clusters located in the bar of the Large Magellanic Cloud (LMC). One isolated cluster, SL 268, is presented in order to study the effect of the LMC tidal field. All the candidate binary clusters show tidal tails, confirming that the pairs are formed by physically linked objects. The stellar mass in the tails covers a large range, from 1.8x 10(3) to 3x 10(4) \\msun. We derive a total mass estimate for SL 268 and SL 356. At large radii, the projected density profiles of SL 268 and SL 356 fall off as r(-gamma ) , with gamma = 2.27 and gamma =3.44, respectively. Out of 4 pairs or multiple systems, 2 are older than the theoretical survival time of binary clusters (going from a few 10(6) years to 10(8) years). A pair shows too large age difference between the components to be consistent with classical theoretical models of binary cluster formation (Fujimoto & Kumai \\cite{fujimoto97}). We refer to this as the ``overmerging'' problem. A different scenario is proposed: the formation proceeds in large molecular complexes giving birth to groups of clusters over a few 10(7) years. In these groups the expected cluster encounter rate is larger, and tidal capture has higher probability. Cluster pairs are not born together through the splitting of the parent cloud, but formed later by tidal capture. For 3 pairs, we tentatively identify the star cluster group (SCG) memberships. The SCG formation, through the recent cluster starburst triggered by the LMC-SMC encounter, in contrast with the quiescent open cluster formation in the Milky Way can be an explanation to the paucity of binary clusters observed in our Galaxy. Based on observations collected at the European Southern Observatory, La Silla, Chile}

  1. Primordial black holes in globular clusters

    NASA Technical Reports Server (NTRS)

    Sigurdsson, Steinn; Hernquist, Lars

    1993-01-01

    It has recently been recognized that significant numbers of medium-mass back holes (of order 10 solar masses) should form in globular clusters during the early stages of their evolution. Here we explore the dynamical and observational consequences of the presence of such a primordial black-hole population in a globular cluster. The holes initially segregate to the cluster cores, where they form binary and multiple black-hole systems. The subsequent dynamical evolution of the black-hole population ejects most of the holes on a relatively short timescale: a typical cluster will retain between zero and four black holes in its core, and possibly a few black holes in its halo. The presence of binary, triple, and quadruple black-hole systems in cluster cores will disrupt main-sequence and giant stellar binaries; this may account for the observed anomalies in the distribution of binaries in globular clusters. Furthermore, tidal interactions between a multiple black-hole system and a red giant star can remove much of the red giant's stellar envelope, which may explain the puzzling absence of larger red giants in the cores of some very dense clusters.

  2. RADIO AND DEEP CHANDRA OBSERVATIONS OF THE DISTURBED COOL CORE CLUSTER ABELL 133

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Randall, S. W.; Nulsen, P. E. J.; Forman, W. R.

    2010-10-10

    We present results based on new Chandra and multi-frequency radio observations of the disturbed cool core cluster Abell 133. The diffuse gas has a complex bird-like morphology, with a plume of emission extending from two symmetric wing-like features. The plume is capped with a filamentary radio structure that has been previously classified as a radio relic. X-ray spectral fits in the region of the relic indicate the presence of either high-temperature gas or non-thermal emission, although the measured photon index is flatter than would be expected if the non-thermal emission is from inverse Compton scattering of the cosmic microwave backgroundmore » by the radio-emitting particles. We find evidence for a weak elliptical X-ray surface brightness edge surrounding the core, which we show is consistent with a sloshing cold front. The plume is consistent with having formed due to uplift by a buoyantly rising radio bubble, now seen as the radio relic, and has properties consistent with buoyantly lifted plumes seen in other systems (e.g., M87). Alternatively, the plume may be a gas sloshing spiral viewed edge-on. Results from spectral analysis of the wing-like features are inconsistent with the previous suggestion that the wings formed due to the passage of a weak shock through the cool core. We instead conclude that the wings are due to X-ray cavities formed by displacement of X-ray gas by the radio relic. The central cD galaxy contains two small-scale cold gas clumps that are slightly offset from their optical and UV counterparts, suggestive of a galaxy-galaxy merger event. On larger scales, there is evidence for cluster substructure in both optical observations and the X-ray temperature map. We suggest that the Abell 133 cluster has recently undergone a merger event with an interloping subgroup, initialing gas sloshing in the core. The torus of sloshed gas is seen close to edge-on, leading to the somewhat ragged appearance of the elliptical surface brightness edge

  3. RESONANT CLUMPING AND SUBSTRUCTURE IN GALACTIC DISKS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Molloy, Matthew; Smith, Martin C.; Shen, Juntai

    2015-05-10

    We describe a method to extract resonant orbits from N-body simulations, exploiting the fact that they close in frames rotating with a constant pattern speed. Our method is applied to the N-body simulation of the Milky Way by Shen et al. This simulation hosts a massive bar, which drives strong resonances and persistent angular momentum exchange. Resonant orbits are found throughout the disk, both close to the bar and out to the very edges of the disk. Using Fourier spectrograms, we demonstrate that the bar is driving kinematic substructure even in the very outer parts of the disk. We identifymore » two major orbit families in the outskirts of the disk, one of which makes significant contributions to the kinematic landscape, namely, the m:l = 3:−2 family, resonating with the bar. A mechanism is described that produces bimodal distributions of Galactocentric radial velocities at selected azimuths in the outer disk. It occurs as a result of the temporal coherence of particles on the 3:−2 resonant orbits, which causes them to arrive simultaneously at pericenter or apocenter. This resonant clumping, due to the in-phase motion of the particles through their epicycle, leads to both inward and outward moving groups that belong to the same orbital family and consequently produce bimodal radial velocity distributions. This is a possible explanation of the bimodal velocity distributions observed toward the Galactic anticenter by Liu et al. Another consequence is that transient overdensities appear and dissipate (in a symmetric fashion), resulting in a periodic pulsing of the disk’s surface density.« less

  4. Multi-phase gas, clumping and non-thermal pressure in cluster outskirts via X-ray, SZ and lensing data

    NASA Astrophysics Data System (ADS)

    Morandi, Andrea

    2017-09-01

    We propose to study multitemperature structure, clumpy gas distribution and non-thermal pressure in the outskirts of a sample of galaxy clusters by means of Chandra X-ray, Sunyaev Zeldovich and lensing data. We propose to recover the X-ray spectroscopic temperatures close to the virial radius and compare them to the average (gas mass-weighted) temperature probed through SZ. Our preliminary analysis reveals compelling evidence of a substantial amounts of cold gas (T 0.8 keV) at subvirial temperature which coexists with the hot (>4 keV) thermal component of the intracluster medium (ICM). The proposed investigation has important implications for understanding the astrophysics of the ICM in the outer volumes and the CDM scenario, and it has crucial ramifications for the cosmology.

  5. Reactivity Control of Rhodium Cluster Ions by Alloying with Tantalum Atoms.

    PubMed

    Mafuné, Fumitaka; Tawaraya, Yuki; Kudoh, Satoshi

    2016-02-18

    Gas phase, bielement rhodium and tantalum clusters, RhnTam(+) (n + m = 6), were prepared by the double laser ablation of Rh and Ta rods in He carrier gas. The clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He and were subjected to collisions with NO and He at room temperature. The product species were observed by mass spectrometry, demonstrating that the NO molecules were sequentially adsorbed on the RhnTam(+) clusters to form RhnTam(+)NxOx (x = 1, 2, 3, ...) species. In addition, oxide clusters, RhnTam(+)O2, were also observed, suggesting that the NO molecules were dissociatively adsorbed on the cluster, the N atoms migrated on the surface to form N2, and the N2 molecules were released from RhnTam(+)N2O2. The reactivity, leading to oxide formation, was composition dependent: oxide clusters were dominantly formed for the bielement clusters containing both Rh and Ta atoms, whereas such clusters were hardly formed for the single-element Rhn(+) and Tam(+) clusters. DFT calculations indicated that the Ta atoms induce dissociation of NO on the clusters by lowering the dissociation energy, whereas the Rh atoms enable release of N2 by lowering the binding energy of the N atoms on the clusters.

  6. Ionized Gas Motions and the Structure of Feedback near a Forming Globular Cluster in NGC 5253

    NASA Astrophysics Data System (ADS)

    Cohen, Daniel P.; Turner, Jean L.; Consiglio, S. Michelle; Martin, Emily C.; Beck, Sara C.

    2018-06-01

    We observed Brackett α 4.05 μm emission toward the supernebula in NGC 5253 with NIRSPEC on Keck II in adaptive optics mode, NIRSPAO, to probe feedback from its exciting embedded super star cluster (SSC). NIRSPEC's Slit-viewing Camera was simultaneously used to image the K-band continuum at ∼0.″1 resolution. We register the IR continuum with HST imaging, and find that the visible clusters are offset from the K-band peak, which coincides with the Brα peak of the supernebula and its associated molecular cloud. The spectra of the supernebula exhibit Brα emission with a strong, narrow core. The linewidths are 65–76 km s‑1, FWHM, comparable to those around individual ultra-compact H II regions within our Galaxy. A weak, broad (FWHM ≃ 150–175 km s‑1) component is detected on the base of the line, which could trace a population of sources with high-velocity winds. The core velocity of Brα emission shifts by +13 km s‑1 from NE to SW across the supernebula, possibly indicating a bipolar outflow from an embedded object or a link to a foreground redshifted gas filament. The results can be explained if the supernebula comprises thousands of ionized wind regions around individual massive stars, stalled in their expansion due to critical radiative cooling and unable to merge to drive a coherent cluster wind. Based on the absence of an outflow with large mass loss, we conclude that feedback is currently ineffective at dispersing gas, and the SSC retains enriched material out of which it may continue to form stars.

  7. Stellar Snowflake Cluster

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1 Stellar Snowflake Cluster Combined Image [figure removed for brevity, see original site] Figure 2 Infrared Array CameraFigure 3 Multiband Imaging Photometer

    Newborn stars, hidden behind thick dust, are revealed in this image of a section of the Christmas Tree cluster from NASA's Spitzer Space Telescope, created in joint effort between Spitzer's infrared array camera and multiband imaging photometer instruments.

    The newly revealed infant stars appear as pink and red specks toward the center of the combined image (fig. 1). The stars appear to have formed in regularly spaced intervals along linear structures in a configuration that resembles the spokes of a wheel or the pattern of a snowflake. Hence, astronomers have nicknamed this the 'Snowflake' cluster.

    Star-forming clouds like this one are dynamic and evolving structures. Since the stars trace the straight line pattern of spokes of a wheel, scientists believe that these are newborn stars, or 'protostars.' At a mere 100,000 years old, these infant structures have yet to 'crawl' away from their location of birth. Over time, the natural drifting motions of each star will break this order, and the snowflake design will be no more.

    While most of the visible-light stars that give the Christmas Tree cluster its name and triangular shape do not shine brightly in Spitzer's infrared eyes, all of the stars forming from this dusty cloud are considered part of the cluster.

    Like a dusty cosmic finger pointing up to the newborn clusters, Spitzer also illuminates the optically dark and dense Cone nebula, the tip of which can be seen towards the bottom left corner of each image.

    This combined image shows the presence of organic molecules mixed with dust as wisps of green, which have been illuminated by nearby star formation. The larger yellowish dots neighboring the baby red stars in the Snowflake Cluster are massive stellar infants forming

  8. Optical signatures of high-redshift galaxy clusters

    NASA Technical Reports Server (NTRS)

    Evrard, August E.; Charlot, Stephane

    1994-01-01

    We combine an N-body and gasdynamic simulation of structure formation with an updated population synthesis code to explore the expected optical characteristics of a high-redshift cluster of galaxies. We examine a poor (2 keV) cluster formed in a biased, cold dark matter cosmology and employ simple, but plausible, threshold criteria to convert gas into stars. At z = 2, the forming cluster appears as a linear chain of very blue (g-r approximately equals 0) galaxies, with 15 objects brighter than r = 25 within a 1 square arcmin field of view. After 2 Gyr of evolution, the cluster viewed at z = 1 displays both freshly infalling blue galaxies and red galaxies robbed of recent accretion by interaction with the hot intracluster medium. The range in G-R colors is approximately 3 mag at z = 1, with the reddest objects lying at sites of highest galaxy density. We suggest that red, high-redshift galaxies lie in the cores of forming clusters and that their existence indicates the presence of a hot intracluster medium at redshifts z approximately equals 2. The simulated cluster viewed at z = 2 has several characteristics similar to the collection of faint, blue objects identified by Dressler et al. in a deep Hubble Space Telescope observation. The similarities provide some support for the interpretation of this collection as a high-redshift cluster of galaxies.

  9. Optical/Near-IR spatially resolved study of the H II galaxy Tol 02★

    NASA Astrophysics Data System (ADS)

    Torres-Campos, A.; Terlevich, E.; Rosa-González, D.; Terlevich, R.; Telles, E.; Díaz, A. I.

    2017-11-01

    The main goal of this study is to characterize the stellar populations in very low-metallicity galaxies. We have obtained broad U, B, R, I, J, H, K, intermediate Strömgren y and narrow H α and [O III] deep images of the Wolf-Rayet, blue compact dwarf, H II galaxy Tol 02. We have analysed the low surface brightness component, the stellar cluster complexes and the H II regions. The stellar populations in the galaxy have been characterized by comparing the observed broad-band colours with those of single stellar population models. The main results are consistent with Tol 02 being formed by a 1.5 Gyr old disc component at the centre of which a group of eight massive (>104 M⊙) stellar cluster clumps is located. Six of these clumps are 10 Myr old and their near-infrared colours suggest that their light is dominated by Red Supergiant (RSG) stars, the other two are young Wolf-Rayet cluster candidates of ages 3 and 5 Myr, respectively. 12 H II regions in the star-forming region of the galaxy are also identified. These are immersed in a diffuse H α and [O III] emission that spreads towards the north and south covering the old stellar disc. Our spatial-temporal analysis shows that star formation is more likely stochastic and simultaneous within short time-scales. The mismatch between observations and models cannot be attributed alone to a mistreat of the RSG phase and still needs to be further investigated.

  10. Application of clustering methods: Regularized Markov clustering (R-MCL) for analyzing dengue virus similarity

    NASA Astrophysics Data System (ADS)

    Lestari, D.; Raharjo, D.; Bustamam, A.; Abdillah, B.; Widhianto, W.

    2017-07-01

    Dengue virus consists of 10 different constituent proteins and are classified into 4 major serotypes (DEN 1 - DEN 4). This study was designed to perform clustering against 30 protein sequences of dengue virus taken from Virus Pathogen Database and Analysis Resource (VIPR) using Regularized Markov Clustering (R-MCL) algorithm and then we analyze the result. By using Python program 3.4, R-MCL algorithm produces 8 clusters with more than one centroid in several clusters. The number of centroid shows the density level of interaction. Protein interactions that are connected in a tissue, form a complex protein that serves as a specific biological process unit. The analysis of result shows the R-MCL clustering produces clusters of dengue virus family based on the similarity role of their constituent protein, regardless of serotypes.

  11. Chirally directed formation of nanometer-scale proline clusters.

    PubMed

    Myung, Sunnie; Fioroni, Marco; Julian, Ryan R; Koeniger, Stormy L; Baik, Mu-Hyun; Clemmer, David E

    2006-08-23

    Ion mobility measurements, combined with molecular mechanics simulations, are used to study enantiopure and racemic proline clusters formed by electrospray ionization. Broad distributions of cluster sizes and charge states are observed, ranging from clusters containing only a few proline units to clusters that contain more than 100 proline units (i.e., protonated clusters of the form [xPro + nH](n+) with x = 1 to >100 and n = 1-7). As the sizes of clusters increase, there is direct evidence for nanometer scale, chirally induced organization into specific structures. For n = 4 and 5, enantiopure clusters of approximately 50 to 100 prolines assemble into structures that are more elongated than the most compact structure that is observed from the racemic proline clusters. A molecular analogue, cis-4-hydroxy-proline, displays significantly different behavior, indicating that in addition to the rigidity of the side chain ring, intermolecular interactions are important in the formation of chirally directed clusters. This is the first case in which assemblies of chirally selective elongated structures are observed in this size range of amino acid clusters. Relationships between enantiopurity, cluster shape, and overall energetics are discussed.

  12. Photometric redshifts as a tool for studying the Coma cluster galaxy populations

    NASA Astrophysics Data System (ADS)

    Adami, C.; Ilbert, O.; Pelló, R.; Cuillandre, J. C.; Durret, F.; Mazure, A.; Picat, J. P.; Ulmer, M. P.

    2008-12-01

    Aims: We apply photometric redshift techniques to an investigation of the Coma cluster galaxy luminosity function (GLF) at faint magnitudes, in particular in the u* band where basically no studies are presently available at these magnitudes. Methods: Cluster members were selected based on probability distribution function from photometric redshift calculations applied to deep u^*, B, V, R, I images covering a region of almost 1 deg2 (completeness limit R ~ 24). In the area covered only by the u* image, the GLF was also derived after a statistical background subtraction. Results: Global and local GLFs in the B, V, R, and I bands obtained with photometric redshift selection are consistent with our previous results based on a statistical background subtraction. The GLF in the u* band shows an increase in the faint end slope towards the outer regions of the cluster. The analysis of the multicolor type spatial distribution reveals that late type galaxies are distributed in clumps in the cluster outskirts, where X-ray substructures are also detected and where the GLF in the u* band is steeper. Conclusions: We can reproduce the GLFs computed with classical statistical subtraction methods by applying a photometric redshift technique. The u* GLF slope is steeper in the cluster outskirts, varying from α ~ -1 in the cluster center to α ~ -2 in the cluster periphery. The concentrations of faint late type galaxies in the cluster outskirts could explain these very steep slopes, assuming a short burst of star formation in these galaxies when entering the cluster. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is also partly based on data products produced at

  13. Effective implementation of hierarchical clustering

    NASA Astrophysics Data System (ADS)

    Verma, Mudita; Vijayarajan, V.; Sivashanmugam, G.; Bessie Amali, D. Geraldine

    2017-11-01

    Hierarchical clustering is generally used for cluster analysis in which we build up a hierarchy of clusters. In order to find that which cluster should be split a large amount of observations are being carried out. Here the data set of US based personalities has been considered for clustering. After implementation of hierarchical clustering on the data set we group it in three different clusters one is of politician, sports person and musicians. Training set is the main parameter which decides the category which has to be assigned to the observations that are being collected. The category of these observations must be known. Recognition comes from the formulation of classification. Supervised learning has the main instance in the form of classification. While on the other hand Clustering is an instance of unsupervised procedure. Clustering consists of grouping of data that have similar properties which are either their own or are inherited from some other sources.

  14. HUBBLE SPIES HUGE CLUSTERS OF STARS FORMED

    NASA Technical Reports Server (NTRS)

    2002-01-01

    BY ANCIENT ENCOUNTER This stunningly beautiful image [right] taken with the NASA Hubble Space Telescope shows the heart of the prototypical starburst galaxy M82. The ongoing violent star formation due to an ancient encounter with its large galactic neighbor, M81, gives this galaxy its disturbed appearance. The smaller picture at upper left shows the entire galaxy. The image was taken in December 1994 by the Kitt Peak National Observatory's 0.9-meter telescope. Hubble's view is represented by the white outline in the center. In the Hubble image, taken by the Wide Field and Planetary Camera 2, the huge lanes of dust that crisscross M82's disk are another telltale sign of the flurry of star formation. Below the center and to the right, a strong galactic wind is spewing knotty filaments of hydrogen and nitrogen gas. More than 100 super star clusters -- very bright, compact groupings of about 100,000 stars -- are seen in this detailed Hubble picture as white dots sprinkled throughout M82's central region. The dark region just above the center of the picture is a huge dust cloud. A collaboration of European and American scientists used these clusters to date the ancient interaction between M82 and M81. About 600 million years ago, a region called 'M82 B' (the bright area just below and to the left of the central dust cloud) exploded with new stars. Scientists have discovered that this ancient starburst was triggered by the violent encounter with M81. M82 is a bright (eighth magnitude), nearby (12 million light-years from Earth) galaxy in the constellation Ursa Major (the Great Bear). The Hubble picture was taken Sept. 15, 1997. The natural-color composite was constructed from three Wide Field and Planetary Camera 2 exposures, which were combined in chromatic order: 4,250 seconds through a blue filter (428 nm); 2,800 seconds through a green filter (520 nm); and 2,200 seconds through a red (820 nm) filter. Credits for Hubble image: NASA, ESA, R. de Grijs (Institute of

  15. The nature, origin and evolution of embedded star clusters

    NASA Technical Reports Server (NTRS)

    Lada, Charles J.; Lada, Elizabeth A.

    1991-01-01

    The recent development of imaging infrared array cameras has enabled the first systematic studies of embedded protoclusters in the galaxy. Initial investigations suggest that rich embedded clusters are quite numerous and that a significant fraction of all stars formed in the galaxy may begin their lives in such stellar systems. These clusters contain extremely young stellar objects and are important laboratories for star formation research. However, observational and theoretical considerations suggest that most embedded clusters do not survive emergence from molecular clouds as bound clusters. Understanding the origin, nature, and evolution of embedded clusters requires understanding the intimate physical relation between embedded clusters and the dense molecular cloud cores from which they form.

  16. Electron attenuation in free, neutral ethane clusters.

    PubMed

    Winkler, M; Myrseth, V; Harnes, J; Børve, K J

    2014-10-28

    The electron effective attenuation length (EAL) in free, neutral ethane clusters has been determined at 40 eV kinetic energy by combining carbon 1s x-ray photoelectron spectroscopy and theoretical lineshape modeling. More specifically, theory is employed to form model spectra on a grid in cluster size (N) and EAL (λ), allowing N and λ to be determined by optimizing the goodness-of-fit χ(2)(N, λ) between model and observed spectra. Experimentally, the clusters were produced in an adiabatic-expansion setup using helium as the driving gas, spanning a range of 100-600 molecules in mean cluster size. The effective attenuation length was determined to be 8.4 ± 1.9 Å, in good agreement with an independent estimate of 10 Å formed on the basis of molecular electron-scattering data and Monte Carlo simulations. The aggregation state of the clusters as well as the cluster temperature and its importance to the derived EAL value are discussed in some depth.

  17. Studies of the Virgo cluster. VI - Morphological and kinematical structure of the Virgo cluster

    NASA Technical Reports Server (NTRS)

    Binggeli, Bruno; Tammann, G. A.; Sandage, Allan

    1987-01-01

    The structure of the Virgo cluster is analyzed on the basis of the positions, Hubble types, and radial velocities of 1277 Virgo cluster galaxies. The surface distribution of galaxies is considered according to type, and is discussed using maps, isopleths, strip counts, and radial-density distributions. It is found that the Virgo cluster shows pronounced double structure. The main concentration has a large velocity dispersion and is made up predominantly of early-type galaxies, while the secondary concentration has a much smaller velocity dispersion and contains late types. There is a strong spatial segregation of the Hubble types, the early-type galaxies being more concentrated toward the cluster center. There is significant substructure in the cluster core. The irregularity of the Virgo cluster in both configuration and velocity space shows that the core and the envelope are still forming, and hence that the cluster is young.

  18. Subcluster mergers and galaxy infall in A2151

    NASA Technical Reports Server (NTRS)

    Bird, Christina M.; Davis, David S.; Beers, Timothy C.

    1995-01-01

    We have obtained a 12.5 ks image of the Hercules Cluster, A2151, with the ROSAT PSPC. Comparison of the optical and X-ray emission coincides with the highest-density peak in the distribution, and is bimodal. The northern subclummp, distinct in position and velocity, has no detectable X-ray gas. The eastern subclump, apparent in the optical contour map, is indistinguishable from the clump in velocity space, but is clearly visible in the X-ray image. X-ray spectra derived from the central peak of emission yield a best-fit temperature of 1.6 keV. The emission coincident with the eastern clump of galaxies is cooler, 0.8 keV, and is outside the 90% confidence intervals of the central peak temperature. We suggest that the eastern and central subclusters have recently undergone a merger event. The lack of X-ray emission to the north suggests that those galaxies do not form a physically distinct structure (i.e., they are not located within a distinct gravitational potential), but rather that they are falling into the cluster core along the filament defined by the Hercules Supercluster.

  19. Large-scale clustering measurements with photometric redshifts: comparing the dark matter haloes of X-ray AGN, star-forming and passive galaxies at z ≈ 1

    NASA Astrophysics Data System (ADS)

    Georgakakis, A.; Mountrichas, G.; Salvato, M.; Rosario, D.; Pérez-González, P. G.; Lutz, D.; Nandra, K.; Coil, A.; Cooper, M. C.; Newman, J. A.; Berta, S.; Magnelli, B.; Popesso, P.; Pozzi, F.

    2014-10-01

    We combine multi-wavelength data in the AEGIS-XD and C-COSMOS surveys to measure the typical dark matter halo mass of X-ray selected active galactic nuclei (AGN) [LX(2-10 keV) > 1042 erg s- 1] in comparison with far-infrared selected star-forming galaxies detected in the Herschel/PEP survey (PACS Evolutionary Probe; LIR > 1011 L⊙) and quiescent systems at z ≈ 1. We develop a novel method to measure the clustering of extragalactic populations that uses photometric redshift probability distribution functions in addition to any spectroscopy. This is advantageous in that all sources in the sample are used in the clustering analysis, not just the subset with secure spectroscopy. The method works best for large samples. The loss of accuracy because of the lack of spectroscopy is balanced by increasing the number of sources used to measure the clustering. We find that X-ray AGN, far-infrared selected star-forming galaxies and passive systems in the redshift interval 0.6 < z < 1.4 are found in haloes of similar mass, log MDMH/(M⊙ h-1) ≈ 13.0. We argue that this is because the galaxies in all three samples (AGN, star-forming, passive) have similar stellar mass distributions, approximated by the J-band luminosity. Therefore, all galaxies that can potentially host X-ray AGN, because they have stellar masses in the appropriate range, live in dark matter haloes of log MDMH/(M⊙ h-1) ≈ 13.0 independent of their star formation rates. This suggests that the stellar mass of X-ray AGN hosts is driving the observed clustering properties of this population. We also speculate that trends between AGN properties (e.g. luminosity, level of obscuration) and large-scale environment may be related to differences in the stellar mass of the host galaxies.

  20. STAR CLUSTER FORMATION WITH STELLAR FEEDBACK AND LARGE-SCALE INFLOW

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Matzner, Christopher D.; Jumper, Peter H., E-mail: matzner@astro.utoronto.ca

    2015-12-10

    During star cluster formation, ongoing mass accretion is resisted by stellar feedback in the form of protostellar outflows from the low-mass stars and photo-ionization and radiation pressure feedback from the massive stars. We model the evolution of cluster-forming regions during a phase in which both accretion and feedback are present and use these models to investigate how star cluster formation might terminate. Protostellar outflows are the strongest form of feedback in low-mass regions, but these cannot stop cluster formation if matter continues to flow in. In more massive clusters, radiation pressure and photo-ionization rapidly clear the cluster-forming gas when itsmore » column density is too small. We assess the rates of dynamical mass ejection and of evaporation, while accounting for the important effect of dust opacity on photo-ionization. Our models are consistent with the census of protostellar outflows in NGC 1333 and Serpens South and with the dust temperatures observed in regions of massive star formation. Comparing observations of massive cluster-forming regions against our model parameter space, and against our expectations for accretion-driven evolution, we infer that massive-star feedback is a likely cause of gas disruption in regions with velocity dispersions less than a few kilometers per second, but that more massive and more turbulent regions are too strongly bound for stellar feedback to be disruptive.« less

  1. Probing Globular Cluster Formation in Low Metallicity Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Johnson, Kelsey E.; Hunt, Leslie K.; Reines, Amy E.

    2008-12-01

    The ubiquitous presence of globular clusters around massive galaxies today suggests that these extreme star clusters must have been formed prolifically in the earlier universe in low-metallicity galaxies. Numerous adolescent and massive star clusters are already known to be present in a variety of galaxies in the local universe; however most of these systems have metallicities of 12 + log(O/H) > 8, and are thus not representative of the galaxies in which today's ancient globular clusters were formed. In order to better understand the formation and evolution of these massive clusters in environments with few heavy elements, we have targeted several low-metallicity dwarf galaxies with radio observations, searching for newly-formed massive star clusters still embedded in their birth material. The galaxies in this initial study are HS 0822+3542, UGC 4483, Pox 186, and SBS 0335-052, all of which have metallicities of 12 + log(O/H) < 7.75. While no thermal radio sources, indicative of natal massive star clusters, are found in three of the four galaxies, SBS 0335-052 hosts two such objects, which are incredibly luminous. The radio spectral energy distributions of these intense star-forming regions in SBS 0335-052 suggest the presence of ~12,000 equivalent O-type stars, and the implied star formation rate is nearing the maximum starburst intensity limit.

  2. Cluster-cluster clustering

    NASA Technical Reports Server (NTRS)

    Barnes, J.; Dekel, A.; Efstathiou, G.; Frenk, C. S.

    1985-01-01

    The cluster correlation function xi sub c(r) is compared with the particle correlation function, xi(r) in cosmological N-body simulations with a wide range of initial conditions. The experiments include scale-free initial conditions, pancake models with a coherence length in the initial density field, and hybrid models. Three N-body techniques and two cluster-finding algorithms are used. In scale-free models with white noise initial conditions, xi sub c and xi are essentially identical. In scale-free models with more power on large scales, it is found that the amplitude of xi sub c increases with cluster richness; in this case the clusters give a biased estimate of the particle correlations. In the pancake and hybrid models (with n = 0 or 1), xi sub c is steeper than xi, but the cluster correlation length exceeds that of the points by less than a factor of 2, independent of cluster richness. Thus the high amplitude of xi sub c found in studies of rich clusters of galaxies is inconsistent with white noise and pancake models and may indicate a primordial fluctuation spectrum with substantial power on large scales.

  3. Record-breaking ancient galaxy clusters

    NASA Astrophysics Data System (ADS)

    2003-12-01

    A tale of two record-breaking clusters hi-res Size hi-res: 768 kb Credits: for RDCS1252: NASA, ESA, J.Blakeslee (Johns Hopkins Univ.), M.Postman (Space Telescope Science Inst.) and P.Rosati, Chris Lidman & Ricardo Demarco (European Southern Observ.) for TNJ1338: NASA, ESA, G.Miley (Leiden Observ.) and R.Overzier (Leiden Obs) A tale of two record-breaking clusters Looking back in time to when the universe was in its formative youth, the Advanced Camera for Surveys (ACS) aboard the NASA/ESA Hubble Space Telescope captured these revealing images of two galaxy clusters. The image at left, which is made with an additional infrared exposure taken with the European Southern Observatory’s Very Large Telescope, shows mature galaxies in a massive cluster that existed when the cosmos was 5000 million years old. The cluster, called RDCS1252.9-2927, is as massive as ‘300 trillion’ suns and is the most massive known cluster for its epoch. The image reveals the core of the cluster and is part of a much larger mosaic of the entire cluster. Dominating the core are a pair of large, reddish elliptical galaxies [near centre of image]. Their red colour indicates an older population of stars. Most of the stars are at least 1000 million years old. The two galaxies appear to be interacting and may eventually merge to form a larger galaxy that is comparable to the brightest galaxies seen in present-day clusters. The red galaxies surrounding the central pair are also cluster members. The cluster probably contains many thousands of galaxies, but only about 50 can be seen in this image. The full mosaic (heic0313d) reveals several hundred cluster members. Many of the other galaxies in the image, including several of the blue galaxies, are foreground or background galaxies. The colour-composite image was assembled from two observations (through i and z filters) taken between May and June 2002 by the ACS Wide Field Camera, and one image with the ISAAC instrument on the VLT taken in 2002

  4. Determining the Absolute Magnitudes of Galactic-Bulge Red Clump Giants in the Z and Y Filters of the Vista Sky Surveys and the IRAC Filters of the Spitzer Sky Surveys

    NASA Astrophysics Data System (ADS)

    Karasev, D. I.; Lutovinov, A. A.

    2018-04-01

    The properties of red clump giants in the central regions of the Galactic bulge are investigated in the photometric Z and Y bands of the infrared VVV (VISTA/ESO) survey and the [3.6], [4.5], [5.8], and [8.0] μm bands of the GLIMPSE (Spitzer/IRAC) Galactic plane survey. The absolute magnitudes for objects of this class have been determined in these bands for the first time: M Z = -0.20 ± 0.04, M Y = -0.470 ± 0.045, M [3.6] = -1.70 ± 0.03, M [4.5] = -1.60 ± 0.03, M [5.8] = -1.67 ± 0.03, and M [8.0] = -1.70 ± 0.03. A comparison of the measured magnitudes with the predictions of theoretical models for the spectra of the objects under study has demonstrated good mutual agreement and has allowed some important constraints to be obtained for the properties of bulge red clump giants. In particular, a comparison with evolutionary tracks has shown that we are dealing predominantly with the high-metallicity subgroup of bulge red clump giants. Their metallicity is slightly higher than has been thought previously, [ M/H] ≃ 0.40 ( Z ≃ 0.038) with an error of [ M/H] ≃ 0.1 dex, while the effective temperature is 4250± 150 K. Stars with an age of 9-10 Gyr are shown to dominate among the red clump giants, although some number of younger objects with an age of 8 Gyr can also be present. In addition, the distances to several Galactic bulge regions have been measured, as D = 8200-8500 pc, and the extinction law in these directions is shown to differ noticeably from the standard one.

  5. Properties of small Ar sub N-1 K/+/ ionic clusters

    NASA Technical Reports Server (NTRS)

    Etters, R. D.; Danilowicz, R.; Dugan, J.

    1977-01-01

    A self-consistent formalism is developed that, based upon a many-body potential, dynamically determines the thermodynamic properties of ionic clusters without an a priori designation of the equilibrium structures. Aggregates consisting of a single closed shell K(+) ion and N-1 isoelectronic argon atoms were studied. The clusters form crystallites at low temperatures, and melting transitions and spontaneous dissociations are indicated. The results confirm experimental evidence that shows that ionic clusters become less stable with increasing N. The crystallite structures formed by four different clusters are isosceles triangle, skewed form, octahedron with ion in the middle, and icosahedron with the ion in the middle.

  6. Monothiol glutaredoxins and A-type proteins: partners in Fe-S cluster trafficking.

    PubMed

    Mapolelo, Daphne T; Zhang, Bo; Randeniya, Sajini; Albetel, Angela-Nadia; Li, Haoran; Couturier, Jérémy; Outten, Caryn E; Rouhier, Nicolas; Johnson, Michael K

    2013-03-07

    Monothiol glutaredoxins (Grxs) are proposed to function in Fe-S cluster storage and delivery, based on their ability to exist as apo monomeric forms and dimeric forms containing a subunit-bridging [Fe(2)S(2)](2+) cluster, and to accept [Fe(2)S(2)](2+) clusters from primary scaffold proteins. In addition yeast cytosolic monothiol Grxs interact with Fra2 (Fe repressor of activation-2), to form a heterodimeric complex with a bound [Fe(2)S(2)](2+) cluster that plays a key role in iron sensing and regulation of iron homeostasis. In this work, we report on in vitro UV-visible CD studies of cluster transfer between homodimeric monothiol Grxs and members of the ubiquitous A-type class of Fe-S cluster carrier proteins ((Nif)IscA and SufA). The results reveal rapid, unidirectional, intact and quantitative cluster transfer from the [Fe(2)S(2)](2+) cluster-bound forms of A. thaliana GrxS14, S. cerevisiae Grx3, and A. vinelandii Grx-nif homodimers to A. vinelandii(Nif)IscA and from A. thaliana GrxS14 to A. thaliana SufA1. Coupled with in vivo evidence for interaction between monothiol Grxs and A-type Fe-S cluster carrier proteins, the results indicate that these two classes of proteins work together in cellular Fe-S cluster trafficking. However, cluster transfer is reversed in the presence of Fra2, since the [Fe(2)S(2)](2+) cluster-bound heterodimeric Grx3-Fra2 complex can be formed by intact [Fe(2)S(2)](2+) cluster transfer from (Nif)IscA. The significance of these results for Fe-S cluster biogenesis or repair and the cellular regulation of the Fe-S cluster status are discussed.

  7. Corepressive interaction and clustering of degrade-and-fire oscillators

    PubMed Central

    Fernandez, Bastien; Tsimring, Lev S.

    2016-01-01

    Strongly nonlinear degrade-and-fire (DF) oscillations may emerge in genetic circuits having a delayed negative feedback loop as their core element. Here we study the synchronization of DF oscillators coupled through a common repressor field. For weak coupling, initially distinct oscillators remain desynchronized. For stronger coupling, oscillators can be forced to wait in the repressed state until the global repressor field is sufficiently degraded, and then they fire simultaneously forming a synchronized cluster. Our analytical theory provides necessary and sufficient conditions for clustering and specifies the maximum number of clusters that can be formed in the asymptotic regime. We find that in the thermodynamic limit a phase transition occurs at a certain coupling strength from the weakly clustered regime with only microscopic clusters to a strongly clustered regime where at least one giant cluster has to be present. PMID:22181453

  8. The Cluster Environment of Two High-mass Protostars

    NASA Astrophysics Data System (ADS)

    Montes, Virginie; Hofner, Peter

    2017-06-01

    Characterizing the environment and stellar population in which high-mass stars form is an important step to decide between the main massive star formation theories. In the monolithic collapse model, the mass of the core will determine the final stellar mass (e.g., McKee & Tan 2003). In contrast, in the competitive accretion model (e.g., Bonnell & Bate 2006), the mass of the high-mass star is related to the properties of the cluster. As dynamical processes substantially affect the appearance of a cluster, we study early stages of high-mass star formation. These regions often show extended emission from hot dust at infrared wavelengths, which can cause difficulties to define the cluster. We use a multi-wavelength technique to study nearby high-mass star clusters, based on X-ray observations with the Chandra X-Ray Telescope, in conjunction with infrared data and VLA data. The technique relies on the fact that YSOs are particularly bright in X-ray and that contamination is relatively small. X-ray observations allow us to determine the cluster size. The cluster membership and YSOs classification is established using infrared identification of the X-ray sources, and color-color and color-magnitude diagrams.In this talk, I will present our findings on the cluster study of two high-mass star forming regions: IRAS 20126+4104 and IRAS 16562-3959. While most massive stars appear to be formed in rich a cluster environment, those two sources are candidates for the formation of massive stars in a relatively poor cluster. In contrast to what was found in previous studies (Qiu et al. 2008), the dominant B0-type protostar in IRAS 20126+4104 is associated with a small cluster of low-mass stars. I will also show our current work on IRAS 16562-3959, which contains one of the most luminous O-type protostars in the Galaxy. In the vicinity of this particularly interesting region there is a multitude of small clusters, for which I will present how their stellar population differ from the

  9. Cluster assembly in nitrogenase.

    PubMed

    Sickerman, Nathaniel S; Rettberg, Lee A; Lee, Chi Chung; Hu, Yilin; Ribbe, Markus W

    2017-05-09

    The versatile enzyme system nitrogenase accomplishes the challenging reduction of N 2 and other substrates through the use of two main metalloclusters. For molybdenum nitrogenase, the catalytic component NifDK contains the [Fe 8 S 7 ]-core P-cluster and a [MoFe 7 S 9 C-homocitrate] cofactor called the M-cluster. These chemically unprecedented metalloclusters play a critical role in the reduction of N 2 , and both originate from [Fe 4 S 4 ] clusters produced by the actions of NifS and NifU. Maturation of P-cluster begins with a pair of these [Fe 4 S 4 ] clusters on NifDK called the P*-cluster. An accessory protein NifZ aids in P-cluster fusion, and reductive coupling is facilitated by NifH in a stepwise manner to form P-cluster on each half of NifDK. For M-cluster biosynthesis, two [Fe 4 S 4 ] clusters on NifB are coupled with a carbon atom in a radical-SAM dependent process, and concomitant addition of a 'ninth' sulfur atom generates the [Fe 8 S 9 C]-core L-cluster. On the scaffold protein NifEN, L-cluster is matured to M-cluster by the addition of Mo and homocitrate provided by NifH. Finally, matured M-cluster in NifEN is directly transferred to NifDK, where a conformational change locks the cofactor in place. Mechanistic insights into these fascinating biosynthetic processes are detailed in this chapter. © 2017 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

  10. The rates and time-delay distribution of multiply imaged supernovae behind lensing clusters

    NASA Astrophysics Data System (ADS)

    Li, Xue; Hjorth, Jens; Richard, Johan

    2012-11-01

    Time delays of gravitationally lensed sources can be used to constrain the mass model of a deflector and determine cosmological parameters. We here present an analysis of the time-delay distribution of multiply imaged sources behind 17 strong lensing galaxy clusters with well-calibrated mass models. We find that for time delays less than 1000 days, at z = 3.0, their logarithmic probability distribution functions are well represented by P(log Δt) = 5.3 × 10-4Δttilde beta/M2502tilde beta, with tilde beta = 0.77, where M250 is the projected cluster mass inside 250 kpc (in 1014M⊙), and tilde beta is the power-law slope of the distribution. The resultant probability distribution function enables us to estimate the time-delay distribution in a lensing cluster of known mass. For a cluster with M250 = 2 × 1014M⊙, the fraction of time delays less than 1000 days is approximately 3%. Taking Abell 1689 as an example, its dark halo and brightest galaxies, with central velocity dispersions σ>=500kms-1, mainly produce large time delays, while galaxy-scale mass clumps are responsible for generating smaller time delays. We estimate the probability of observing multiple images of a supernova in the known images of Abell 1689. A two-component model of estimating the supernova rate is applied in this work. For a magnitude threshold of mAB = 26.5, the yearly rate of Type Ia (core-collapse) supernovae with time delays less than 1000 days is 0.004±0.002 (0.029±0.001). If the magnitude threshold is lowered to mAB ~ 27.0, the rate of core-collapse supernovae suitable for time delay observation is 0.044±0.015 per year.

  11. Where are Low Mass X-ray Binaries Formed?

    NASA Astrophysics Data System (ADS)

    Kundu, A.; Maccarone, T. J.; Zepf, S. E.

    2004-08-01

    Chandra images of nearby galaxies reveal large numbers of low mass X-ray binaries (LMXBs). As in the Galaxy, a significant fraction of these are associated with globular clusters. We exploit the LMXB-globular cluster link in order to probe both the physical properties of globular clusters that promote the formation of LMXBs within clusters with specific characteristics, and to study whether the non-cluster field LMXB population was originally formed in clusters and then released into the field. The large population of globular clusters around nearby galaxies and the range of properties such as age, metallicity and host galaxy environment spanned by these objects enables us to identify and probe the link between these characteristics and the formation of LMXBs. We present the results of our study of a large sample of elliptical and S0 galaxies which reveals among other things that bright LMXBs definitively prefer metal-rich cluster hosts and that this relationship is unlikely to be driven by age effects. The ancestry of the non-cluster field LMXBs is a matter of some debate with suggestions that they they might have formed in the field, or created in globular clusters and then subsequently released into the field either by being ejected from clusters by dynamical processes or as remnants of dynamically destroyed clusters. Each of these scenarios has a specific spatial signature that can be tested by our combined optical and X-ray study. Furthermore, these scenarios predict additional statistical variations that may be driven by the specific host galaxy environment. We present a detailed analysis of our sample galaxies and comment on the probability that the field sources were actually formed in clusters.

  12. Aggregation Number in Water/n-Hexanol Molecular Clusters Formed in Cyclohexane at Different Water/n-Hexanol/Cyclohexane Compositions Calculated by Titration 1H NMR.

    PubMed

    Flores, Mario E; Shibue, Toshimichi; Sugimura, Natsuhiko; Nishide, Hiroyuki; Moreno-Villoslada, Ignacio

    2017-11-09

    Upon titration of n-hexanol/cyclohexane mixtures of different molar compositions with water, water/n-hexanol clusters are formed in cyclohexane. Here, we develop a new method to estimate the water and n-hexanol aggregation numbers in the clusters that combines integration analysis in one-dimensional 1 H NMR spectra, diffusion coefficients calculated by diffusion-ordered NMR spectroscopy, and further application of the Stokes-Einstein equation to calculate the hydrodynamic volume of the clusters. Aggregation numbers of 5-15 molecules of n-hexanol per cluster in the absence of water were observed in the whole range of n-hexanol/cyclohexane molar fractions studied. After saturation with water, aggregation numbers of 6-13 n-hexanol and 0.5-5 water molecules per cluster were found. O-H and O-O atom distances related to hydrogen bonds between donor/acceptor molecules were theoretically calculated using density functional theory. The results show that at low n-hexanol molar fractions, where a robust hydrogen-bond network is held between n-hexanol molecules, addition of water makes the intermolecular O-O atom distance shorter, reinforcing molecular association in the clusters, whereas at high n-hexanol molar fractions, where dipole-dipole interactions dominate, addition of water makes the intermolecular O-O atom distance longer, weakening the cluster structure. This correlates with experimental NMR results, which show an increase in the size and aggregation number in the clusters upon addition of water at low n-hexanol molar fractions, and a decrease of these magnitudes at high n-hexanol molar fractions. In addition, water produces an increase in the proton exchange rate between donor/acceptor molecules at all n-hexanol molar fractions.

  13. UV-light-driven prebiotic synthesis of iron-sulfur clusters

    NASA Astrophysics Data System (ADS)

    Bonfio, Claudia; Valer, Luca; Scintilla, Simone; Shah, Sachin; Evans, David J.; Jin, Lin; Szostak, Jack W.; Sasselov, Dimitar D.; Sutherland, John D.; Mansy, Sheref S.

    2017-12-01

    Iron-sulfur clusters are ancient cofactors that play a fundamental role in metabolism and may have impacted the prebiotic chemistry that led to life. However, it is unclear whether iron-sulfur clusters could have been synthesized on prebiotic Earth. Dissolved iron on early Earth was predominantly in the reduced ferrous state, but ferrous ions alone cannot form polynuclear iron-sulfur clusters. Similarly, free sulfide may not have been readily available. Here we show that UV light drives the synthesis of [2Fe-2S] and [4Fe-4S] clusters through the photooxidation of ferrous ions and the photolysis of organic thiols. Iron-sulfur clusters coordinate to and are stabilized by a wide range of cysteine-containing peptides and the assembly of iron-sulfur cluster-peptide complexes can take place within model protocells in a process that parallels extant pathways. Our experiments suggest that iron-sulfur clusters may have formed easily on early Earth, facilitating the emergence of an iron-sulfur-cluster-dependent metabolism.

  14. TADPOLE GALAXIES IN THE HUBBLE ULTRA DEEP FIELD

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Elmegreen, Bruce G.; Elmegreen, Debra Meloy, E-mail: bge@watson.ibm.co, E-mail: elmegreen@vassar.ed

    2010-10-20

    Tadpole galaxies have a head-tail shape with a large clump of star formation at the head and a diffuse tail or streak of stars off to one side. We measured the head and tail masses, ages, surface brightnesses, and sizes for 66 tadpoles in the Hubble Ultra Deep Field (UDF) and looked at the distribution of neighbor densities and tadpole orientations with respect to neighbors. The heads have masses of 10{sup 7}-10{sup 8} M{sub sun} and photometric ages of {approx}0.1 Gyr for z {approx} 2. The tails have slightly larger masses than the heads and comparable or slightly older ages.more » The most obvious interpretation of tadpoles as young merger remnants is difficult to verify. They have no enhanced proximity to other resolved galaxies as a class, and the heads, typically <0.2 kpc in diameter, usually have no obvious double-core structure. Another possibility is ram pressure interaction between a gas-rich galaxy and a diffuse cosmological flow. Ram pressure can trigger star formation on one side of a galaxy disk, giving the tadpole shape when viewed edge-on. Ram pressure can also strip away gas from a galaxy and put it into a tail, which then forms new stars and gravitationally drags along old stars with it. Such an effect might have already been observed in the Virgo Cluster. Another possibility is that tadpoles are edge-on disks with large, off-center clumps. Analogous lop-sided star formation in UDF clump clusters is shown.« less

  15. Reversible cluster formation in concentrated monoclonal antibody solutions

    NASA Astrophysics Data System (ADS)

    Godfrin, P. Douglas; Porcar, Lionel; Falus, Peter; Zarraga, Isidro; Wagner, Norm; Liu, Yun

    2015-03-01

    Protein cluster formation in solution is of fundamental interest for both academic research and industrial applications. Recently, industrial scientists are also exploring the effect of reversible cluster formation on biopharmaceutical processing and delivery. However, despite of its importance, the understanding of protein clusters at concentrated solutions remains scientifically very challenging. Using the neutron spin echo technique to study the short time dynamics of proteins in solutions, we have recently systematically studied cluster formation in a few monoclonal antibody (mAb) solutions and their relation with solution viscosity. We show that the existence of anisotropic attraction can cause the formation of finite sized clusters, which increases the solution viscosity. Interestingly, once clusters form at relatively low concentrations, the average size of clusters in solutions remains almost constant over a wide range of concentrations similar to that of micelle formation. For a different mAb we have also investigated, the attraction is mostly induced by hydrophobic patches. As a result, these mAbs form large clusters with loosely linked proteins. In both cases, the formation of clusters all increases the solution viscosity substantially. However, due to different physics origins of cluster formation, solutions viscosities for these two different types of mAbs need to be controlled by different ways.

  16. VizieR Online Data Catalog: Star-forming potential in the Perseus complex (Mercimek+, 2017)

    NASA Astrophysics Data System (ADS)

    Mercimek, S.; Myers, P. C.; Lee, K. I.; Sadavoy, S. I.

    2018-05-01

    We used published catalogs of cores and YSOs at different wavelengths ranging from sub-millimeter (850 μm) to infrared (1.25 μm). We focus on seven clumps in Perseus, which Sadavoy et al. (2014ApJ...787L..18S) showed in their Figure 1. They defined these clumps and their boundaries using a fitted Herschel-derived column density map. The column density threshold of AV~7 mag is proposed as a star formation threshold by Andre et al. (2010A&A...518L.102A), Lada et al. (2010ApJ...724..687L), and Evans et al. (2014ApJ...782..114E) and is equal to N(H2)~5x1021/cm2 (see also, Kirk et al. 2006, J/ApJ/646/1009; Andre et al. 2010A&A...518L.102A). We considered a core or YSO to be associated with a clump if it is located within the AV=7 mag contour of that clump from Sadavoy et al. (2014ApJ...787L..18S). We define a "source" to be a starless core or a YSO. (7 data files).

  17. Clustering Module in OLAP for Horticultural Crops using SpagoBI

    NASA Astrophysics Data System (ADS)

    Putri, D.; Sitanggang, I. S.

    2017-03-01

    Horticultural crops data are organized by the Ministry of Agriculture, Republic of Indonesia. The data are presented annually in a tabular form and result a large data set. This situation makes users difficult to obtain summaries of horticultural crops data. This study aims to develop a clustering module in the SOLAP system for the distribution of horticultural crops in Indonesia and to visualize the results of clustering in a map using SpagoBI. The algorithm used for clustering is K-Means. Horticultural crops data include vegetables, ornamental plants, medicinal plants, and fruits from 2000 to 2013. The clustering module displays clustering results of horticultural crops in the form of text and table on SpagoBI. This module can also visualize the distribution of horticultural crops in the form of map on the HTML page. The application is expected to be useful for users in order to easily obtain summaries of the horticultural crops distribution data and its clusters. The summaries and clusters can be beneficial for the stakeholders to determine potential areas in Indonesia for horticultural crops.

  18. Preparing transition-metal clusters in known structural forms: the mass-analyzed threshold ionization spectrum of V3.

    PubMed

    Ford, Mark S; Mackenzie, Stuart R

    2005-08-22

    The first results are presented of a new experiment designed both to generate and characterize spectroscopically individual isomers of transition-metal cluster cations. As a proof of concept the one-photon mass-analyzed threshold ionization (MATI) spectrum of V3 has been recorded in the region of 44,000-45,000 cm-1. This study extends the range of a previous zero-kinetic-energy (ZEKE) photoelectron study of Yang et al. [Chem. Phys. Lett. 231, 177 (1994)] with which the current results are compared. The MATI spectra reported here exhibit surprisingly high resolution (0.2 cm-1) for this technique despite the use of large discrimination and extraction fields. Analysis of the rotational profile of the origin band allows assignment of the V3 ground state as and the V3+ ground state as , both with D3h geometry, in agreement with the density-functional theory study of the V3 ZEKE spectrum by Calaminici et al. [J. Chem. Phys. 114, 4036 (2001)]. There is also some evidence in the spectrum of transitions to the low-lying excited state of the ion. The vibrational structure observed in the MATI spectrum is, however, significantly different to and less extensive than that predicted in the density-functional theory study. Possible reasons for the discrepancies are discussed and an alternative assignment is proposed which results in revised values for the vibrational wave numbers of both the neutral and ionic states. These studies demonstrate the efficient generation of cluster ions in known structural (isomeric) forms and pave the way for the study of cluster reactivity as a function of geometrical structure.

  19. Bacteria form tellurium nanocrystals

    USGS Publications Warehouse

    Oremland, R.S.

    2007-01-01

    A team of researchers have found two bacterial species that produce tellurium oxyanions as respiratory electron acceptors for growth, leaving elemental tellurium in the form of nanoparticles. The crystals from the two organisms exhibit distinctively different structures. Bacillus selenitireducens initially forms nanorods that cluster together to form rosettes. Sulfurospirillum barnesii forms irregularly-shaped nanospheres that coalesce into larger composite aggregates.

  20. The extent of mixing in stellar interiors: the open clusters Collinder 261 and Melotte 66

    NASA Astrophysics Data System (ADS)

    Drazdauskas, Arnas; Tautvaišienė, Gražina; Randich, Sofia; Bragaglia, Angela; Mikolaitis, Šarūnas; Janulis, Rimvydas

    2016-05-01

    Context. Determining carbon and nitrogen abundances in red giants provides useful diagnostics to test mixing processes in stellar atmospheres. Aims: Our main aim is to determine carbon-to-nitrogen and carbon isotope ratios for evolved giants in the open clusters Collinder 261 and Melotte 66 and to compare the results with predictions of theoretical models. Methods: High-resolution spectra were analysed using a differential model atmosphere method. Abundances of carbon were derived using the C2 Swan (0, 1) band head at 5635.5 Å. The wavelength interval 7940-8130 Å, which contains CN features, was analysed to determine nitrogen abundances and carbon isotope ratios. The oxygen abundances were determined from the [O I] line at 6300 Å. Results: The mean values of the elemental abundances in Collinder 261, as determined from seven stars, are: [ C/Fe ] = -0.23 ± 0.02 (s.d.), [ N/Fe ] = 0.18 ± 0.09, [ O/Fe ] = -0.03 ± 0.07. The mean 12C /13C ratio is 11 ± 2, considering four red clump stars and 18 for one star above the clump. The mean C/N ratios are 1.60 ± 0.30 and 1.74, respectively. For the five stars in Melotte 66 we obtained: [ C/Fe ] = -0.21 ± 0.07 (s.d.), [ N/Fe ] = 0.17 ± 0.07, [ O/Fe ] = 0.16 ± 0.04. The 12C /13C and C/N ratios are 8 ± 2 and 1.67 ± 0.21, respectively. Conclusions: The 12C /13C and C/N ratios of stars in the investigated open clusters were compared with the ratios predicted by stellar evolution models. The mean values of 12C /13C ratios in Collinder 261 and Melotte 66 agree well with models of thermohaline-induced extra-mixing for the corresponding stellar turn-off masses of about 1.1-1.2 M⊙. The mean C/N ratios are not decreased as much as predicted by the model in which the thermohaline- and rotation-induced extra-mixing act together. Based on observations collected at ESO telescopes under Guaranteed Time Observation programmes 071.D-0065, 072.D-0019, and 076.D-0220.