Science.gov

Sample records for stellar cusp formation

  1. Beach-cusp formation

    USGS Publications Warehouse

    Sallenger, A.H.

    1979-01-01

    Field experiments on beach-cusp formation were undertaken to document how the cuspate form develops and to test the edge-wave hypothesis on the uniform spacing of cusps. These involved observations of cusps forming from an initially plane foreshore. The cuspate form was observed to be a product of swash modification of an intertidal beach ridge as follows. A ridge, cut by a series of channels quasi-equally spaced along its length, was deposited onto the lower foreshore. The ridge migrated shoreward with flood tide, while the longshore positions of the channels remained fixed. On ebb tide, changes in swash circulation over the ridge allowed the upwash to flow shoreward through the channels and the channel mouths were eroded progressively wider until adjacent mouths met, effecting a cuspate shape. Measured spacings of cusps, ranging in size from less than 1 m to more than 12 m, agree well with computed spacings due to either zero-mode subharmonic or zero-mode synchronous edge waves. Edge-wave-induced longshore variations in run up will cause water ponded behind a ridge to converge at points of low swash and flow seaward as relatively narrow currents eroding channels spaced at one edge-wave wavelength for synchronous edge waves or one half wavelength for subharmonic edge waves. The channels are subsequently modified into cusp troughs as described above.

  2. Analytical galactic models with mild stellar cusps

    NASA Astrophysics Data System (ADS)

    Rindler-Daller, T.

    2009-06-01

    In the past two decades, it has been established by high-resolution observations of early-type galaxies that their nuclear surface brightness and corresponding stellar mass densities are characterized by cusps. In this paper, we present a new spherical analytical model family describing mild cuspy centres. We study isotropic and anisotropic models of Osipkov-Merritt type. It is shown that the associated distribution functions and intrinsic velocity dispersions can be represented analytically in a unified way in terms of hypergeometric series, allowing thus a straightforward comparison of these important global quantities for galaxies having underlying mass densities which may differ significantly in their degree of central cuspiness or radial falloff.

  3. The stellar cusp around the Milky Way's central black hole

    NASA Astrophysics Data System (ADS)

    Schodel, R.; Gallego Cano, E.; Nogueras Lara, F.; Dong, H.; Gallego Calvente, T.

    2017-03-01

    The existence of stellar cusps in dense clusters around massive black holes is a fundamental, decades-old prediction of theoretical stellar dynamics. Yet, observational evidence has been elusive so far. With a new, improved analysis of high-angular resolution images of the central parsecs of the Galactic Center, we are finally able to provide the first solid evidence for the existence of a stellar cusp around the Milky Way's massive black hole. The existence of stellar cusps is not only of theoretical importance, but has a significant impact on predicted event rates of phenomena like tidal disruptions of stars and extreme mass ratio inspiral events, which are expected to be strong sources of gravitational wave emission.

  4. Cusp Formation for a Nonlocal Evolution Equation

    NASA Astrophysics Data System (ADS)

    Hoang, Vu; Radosz, Maria

    2017-02-01

    Córdoba et al. (Ann Math 162(3):1377-1389, 2005) introduced a nonlocal active scalar equation as a one-dimensional analogue of the surface-quasigeostrophic equation. It has been conjectured, based on numerical evidence, that the solution forms a cusp-like singularity in finite time. Up until now, no active scalar with nonlocal flux is known for which cusp formation has been rigorously shown. In this paper, we introduce and study a nonlocal active scalar, inspired by the Córdoba-Córdoba-Fontelos equation, and prove that either a cusp- or needle-like singularity forms in finite time.

  5. Cusp formation in drops inside Taylor cones

    NASA Astrophysics Data System (ADS)

    Marin, Alvaro G.; Loscertales, Ignacio G.; Barrero, Antonio

    2005-11-01

    Here, we report the formation of cusp in insulating drops inside compound Taylor cones. The action of the electrical shear stress acting on the outer interface, which is transmitted by viscous forces inside the Taylor cone, tends to deform the drop of insulating liquid placed inside. For appropriate values of the capillary number, the insulating drop develops a steady cusp angle which depends on both the capillary number and the conducting to insulating viscosity ratio. A self-similar analysis has been developed to qualitatively describe the flow inside these compounds Taylor cones. Any perturbation of the cusp gives rise to an intermittent emission of tiny droplets; this effect may recall the tip-streaming observed by G.I. Taylor in his four-roll mill device. This emission can be stabilized by an appropriate control of the injected flow rate of the insulating liquid. When the capillary number increases, the cusped interface turns into a spout which flows coated by the conducting liquid forming the electrified coaxial jet which has been successfully employed for the production of nanocapsules, coaxial nanofibers and nanotubes (Science 295, n. 5560, 1695, 2002; JACS 126, 5376, 2004).

  6. The stellar cusp around the Milky Way’s central black hole

    NASA Astrophysics Data System (ADS)

    Schödel, R.; Gallego-Cano, E.; Amaro-Seoane, P.

    2017-05-01

    The existence of stellar cusps in dense clusters around massive black holes is a fundamental, decades-old prediction of theoretical stellar dynamics. Yet, observational evidence has been difficult to obtain. With a new, improved analysis of high-angular resolution images of the central parsecs of the Galactic Center, we are finally able to provide the first solid evidence for the existence of a stellar cusp around the Milky Way’s massive black hole. The existence of stellar cusps has a significant impact on predicted event rates of phenomena like tidal disruptions of stars and extreme mass ratio inspirals.

  7. The Stellar Cusp in the Galactic Center: Three-Dimensional Orbits of Stars

    NASA Astrophysics Data System (ADS)

    Chappell, Samantha; Ghez, Andrea M.; Boehle, Anna; Yelda, Sylvana; Sitarski, Breann; Witzel, Gunther; Do, Tuan; Lu, Jessica R.; Morris, Mark; Becklin, Eric E.

    2015-01-01

    We present new findings from our long term study of the nuclear star cluster around the Galaxy's central supermassive blackhole (SMBH). Measurements where made using speckle and laser guided adaptive optics imaging and integral field spectroscopy on the Keck telescopes. We report 13 new measurable accelerating sources around the SMBH, down to ~17 mag in K band, only 4 of which are known to be young stars, the rest are either known to be old stars or have yet to be spectral typed. Thus we more than double the number of measured accelerations for the known old stars and unknown spectral type population (increasing the number from 6 to 15). Previous observations suggest a flat density profile of late-type stars, contrary to the theorized Bahcall-Wolf cusp (Bahcall & Wolf 1976, 1977; Buchholz et al. 2009; Do et al. 2009; Bartko et al. 2010). With three-dimensional orbits of significantly accelerating sources, we will be able to better characterize the stellar cusp in the Galactic center, including the slope of the stellar density profile.

  8. The removal of cusps from galaxy centres by stellar feedback in the early Universe.

    PubMed

    Mashchenko, Sergey; Couchman, H M P; Wadsley, James

    2006-08-03

    The standard cosmological model, now strongly constrained by direct observations of the Universe at early epochs, is very successful in describing the evolution of structure on large and intermediate scales. Unfortunately, serious contradictions remain on smaller, galactic scales. Among the main small-scale problems is a significant and persistent discrepancy between observations of nearby galaxies, which imply that galactic dark matter haloes have a density profile with a flat core, and the cosmological model, which predicts that the haloes should have divergent density (a cusp) at the centre. Here we report numerical simulations that show that random bulk motions of gas in small primordial galaxies, of the magnitude expected in these systems, will result in a flattening of the central dark matter cusp on relatively short timescales (approximately 10(8) years). Gas bulk motions in early galaxies are driven by supernova explosions that result from ongoing star formation. Our mechanism is general, and would have operated in all star-forming galaxies at redshifts z > or = 10. Once removed, the cusp cannot be reintroduced during the subsequent mergers involved in the build-up of larger galaxies. As a consequence, in the present Universe both small and large galaxies would have flat dark matter core density profiles, in agreement with observations.

  9. A field data assessment of contemporary models of beach cusp formation

    USGS Publications Warehouse

    Allen, J.R.; Psuty, N.P.; Bauer, B.O.; Carter, R.W.G.

    1996-01-01

    Cusp formation was observed during an instrumented, daily profiled, time series of a reflective beach in Canaveral National Seashore, Florida on January 5, 1988. The monitored cusp embayment formed by erosion of the foreshore and the cusp series had a mean spacing of approximately 28 m. During this time, inshore fluid flows were dominated by two standing edge waves at frequencies of 0.06 Hz (primary) and 0.035 Hz (secondary) whereas incident waves were broadbanded at 0.12-0.16 Hz. Directly measured flows (and indirectly estimated swash excursion) data support both the standing wave subharmonic model and the self-organization model of cusp formation in this study.

  10. Beach cusp destruction, formation, and evolution during and subsequent to an extratropical storm, Duck, North Carolina

    SciTech Connect

    Miller, J.R.; Miller, S.M.O.; Torzynski, C.A.; Kochel, R.C. )

    1989-11-01

    Many studies have debated whether beach cusps are erosional or depositional features. The April 12-14, 1988, extratropical storm provided an opportunity to view the direct effects of one of the largest storms of the past decade upon beach sedimentology and morphology on barrier islands near Duck, North Carolina. Prior to the storm, the beach at Duck was characterized by a well-defined pattern of beach cusps with horn-to-horn spacings averaging 35 m. Storm-induced alterations were dominated by an initial period of beach erosion that remobilized the upper 30 to 50 cm of beach sediment, followed by aggradation. Net aggradation was most prominent along the middle beachface and within the pre-storm cusp bays. These morphologic adjustments resulted in the destruction of cusps, which were replaced with a post-storm planar beachface composed of horizontally bedded fine- to coarse-grained sediments. Within 24 hrs of storm subsidence, new beach cusps formed sequentially along the coast in the direction of longshore transport. Initial cusp formation resulted from beach erosion and the creation of bays in the planar storm-beach surface at positions of preferential post-storm runup. The initial cusp horns were composed of truncated horizontal beds of the planar beach accreted during the storm. After their formation, the cusps sequentially migrated downdrift. Migrating horns were composed of a coarse-grained sediment wedge that thickened toward horn crests, suggesting formation by deposition. It is concluded from these observations that beach cusps are both erosional and depositional in nature.

  11. First records of talon cusps on baboon maxillary incisors argue for standardizing terminology and prompt a hypothesis of their formation.

    PubMed

    Heaton, Jason L; Pickering, Travis Rayne

    2013-12-01

    Dental characters can provide vital clues for understanding intra- and intertaxonomic morphological variation and its underlying genetic and environmental components. However, the unambiguous identification of particular traits and their comparative study is often confounded by lack of consistent terminology in the relevant literature. This difficulty is exacerbated when the etiologies are not completely understood, as is the case with talon cusps. To date, research on talon cusps has focused on modern humans. In many instances, descriptions of talon cusps appear in clinical case studies focusing on their treatment and removal. What is lacking in those discussions, though, is a comparative framework, in which the occurrence of talon cusps in nonhuman primates, and possibly other mammals, is established and understood. Here, we report on a taloned upper central incisor of a wild baboon (Papio hamadryas ursinus) from South Africa. The anomalous incisor of this individual includes an exaggerated accessory cusp diagnosed as a Type II talon. Microcomputed tomographic and radiographic analyses show that the taloned cusp possesses enamel, dentin, and pulp. In addition, we identified an unclassifiable talon cusp on a central maxillary incisor of a baboon skull housed in the Smithsonian Institution's Natural History Museum collection. Our observations of talon cusps on baboon incisors demonstrate that, with regard to this phenomenon, systematic study of nonhuman primates is much needed, along with a consistent use of terminology in the anatomical and anthropological literature. Finally, we present a hypothesis of the formation of talon cusps on mammalian incisors. Copyright © 2013 Wiley Periodicals, Inc.

  12. Study of the electric field formation in a multi-cusped magnetic field

    SciTech Connect

    Liu, Hui Yu, Daren; Wu, Huan; Zhao, Yinjian; Ma, Chengyu; Wang, Di; Wei, Haoyu

    2014-09-15

    The multi-cusped field thruster is a kind of electric thruster adopting a cusped magnetic field to achieve a potentially longer lifetime. It is observed in some experiments that the main electric potential drop forms near the exhaust plane, but the formation mechanism of the electric field in this kind of thrusters is not fully clear yet. Based on the analysis of the electron movement, a 2D Particle-in-Cell plus Monte Carlo model is built to reveal the difference of the constraint to electrons between the central leak path and the lateral region of the thruster. Electron trajectories from cathode are analyzed furthermore. It is found that the central leak path inside the discharge channel may play a significant role in the formation of the main electric potential drop near the exhaust plane.

  13. Simulating Stellar Cluster Formation and Early Evolution

    NASA Astrophysics Data System (ADS)

    Wall, Joshua; McMillan, Stephen L. W.; Mac Low, Mordecai-Mark; Ibañez-Mejia, Juan; Portegies Zwart, Simon; Pellegrino, Andrew

    2017-01-01

    We present our current development of a model of stellar cluster formation and evolution in the presence of stellar feedback. We have integrated the MHD code Flash into the Astrophysical Multi-Use Software Environment (AMUSE) and coupled the gas dynamics to an N-body code using a Fujii gravity bridge. Further we have integrated feedback from radiation using the FERVENT module for Flash, supernovae by thermal and kinetic energy injection, and winds by kinetic energy injection. Finally we have developed a method of implementing star formation using the Jeans criterion of the gas. We present initial results from our cluster formation model in a cloud using self-consistent boundary conditions drawn from a model of supernova-driven interstellar turbulence.

  14. The formation of stellar black holes

    NASA Astrophysics Data System (ADS)

    Mirabel, Félix

    2017-08-01

    It is believed that stellar black holes (BHs) can be formed in two different ways: Either a massive star collapses directly into a BH without a supernova (SN) explosion, or an explosion occurs in a proto-neutron star, but the energy is too low to completely unbind the stellar envelope, and a large fraction of it falls back onto the short-lived neutron star (NS), leading to the delayed formation of a BH. Theoretical models set progenitor masses for BH formation by implosion, namely, by complete or almost complete collapse, but observational evidences have been elusive. Here are reviewed the observational insights on BHs formed by implosion without large natal kicks from: (1) the kinematics in three dimensions of space of five Galactic BH X-ray binaries (BH-XRBs), (2) the diversity of optical and infrared observations of massive stars that collapse in the dark, with no luminous SN explosions, possibly leading to the formation of BHs, and (3) the sources of gravitational waves (GWs) produced by mergers of stellar BHs so far detected with LIGO. Multiple indications of BH formation without ejection of a significant amount of matter and with no natal kicks obtained from these different areas of observational astrophysics, and the recent observational confirmation of the expected dependence of BH formation on metallicity and redshift, are qualitatively consistent with the high merger rates of binary black holes (BBHs) inferred from the first detections with LIGO.

  15. On the formation mechanisms of kinetic Alfven waves in the mid-altitude cusp region: Cluster observations

    NASA Astrophysics Data System (ADS)

    Duan, S. P.; Liu, Z. X.; Cao, J. B.; Reme, H.; Balogh, A.; Fazakerley, A. N.

    According to the observation data by the Cluster spacecraft encountering the mid-altitude cusp region and the theory research work of the formation mechanism of kinetic Alfven waves it can be concluded that kinetic Alfven waves can be come into being in the mid-altitude polar cusp Using the observation data detected by the Cluster CIS FGM and PEACE crossing through the mid-altitude cusp region on 4 July 2001 we find that ion and electron number densities are obviously disturbed and protons are always in the down-going direction We obtain that the values of plasma beta are in the range between 0 002 and 0 01 from 13 24 00 to 13 39 00 They are larger than the mass ratio value of electron and proton That implies the mid-altitude polar cusp is a kinetic region Ion and electron density inhomogeneity and the ion beam with down-going direction are the main factors for the formation of kinetic Alfven waves The observational results are consonant with the results obtained from the theory research that the plasma density inhomogeneity and ions motion play important roles in the formation process of kinetic Alfven waves The observational properties of kinetic Alfven waves will be investigated in our following research work

  16. Mineral formation in stellar winds. V. Formation of calcium carbonate

    NASA Astrophysics Data System (ADS)

    Ferrarotti, A. S.; Gail, H.-P.

    2005-02-01

    An emission band around 92 μm found in a few IR spectra from highly evolved stars was proposed to be due to the presence of carbonate dust grains in the circumstellar material (Kemper et al. \\cite{Kem02a}, Nature, 415, 295). This contribution presents the results of a model calculation for the condensation of calcite (CaCO_3) in the stellar wind of AGB stars. It is shown that the quantities of carbonate dust formed relative to the quantities of silicate dust are negligibly small. This results from the fact that carbonates form at a much lower temperature than the silicate dust components. Carbonate dust formation then is suppressed by the strong acceleration of the wind material by radiation pressure on the silicate dust and the subsequent rapid dilution of the wind material. This makes it highly improbable that carbonate dust can be formed in stellar outflows.

  17. Stellar halos: a rosetta stone for galaxy formation and cosmology

    NASA Astrophysics Data System (ADS)

    Inglis Read, Justin

    2015-08-01

    Stellar halos make up about a percent of the total stellar mass in galaxies. Yet their old age and long phase mixing times make them living fossil records of galactic history. In this talk, I review the latest simulations of structure formation in our standard Lambda Cold Dark Matter cosmology. I discuss the latest predictions for stellar halos and the relationship between the stellar halo light and the underlying dark matter. Finally, I discuss how these simulations compare to observations of the Milky Way and Andromeda and, ultimately, what this means for our cosmological model and the formation history of the Galaxy.

  18. Short- and long-term evolution of a stellar disc around a massive black hole: the role of the cusp, stellar evolution and binaries

    NASA Astrophysics Data System (ADS)

    Mikhaloff, Diego N.; Perets, Hagai B.

    2017-02-01

    We study the dynamical evolution of a stellar disc orbiting a massive black hole. We explore the role of two-body relaxation, mass segregation, stellar evolution and binary-heating in affecting the disc evolution and consider the impact of the nuclear cluster properties and the stellar-disc mass-function. We use analytic arguments and apply them to study the evolution of a the velocity dispersion of stars in a Galatic Centre (GC) - like stellar disc on both short (few million years) and longer (100 Myr) evolutionary time-scales. The dominant processes affecting the disc evolution are two-body relaxation and mass-stratification, where the massive stars play a key role in kinematically heating lower mass stars; binary-heating has only a little contribution. In particular, models with realistic mass-functions show the disc structure to be mass-stratified. The number of massive stars in the disc decrease due to stellar evolution, consequently leading to slower relaxation. At these later evolutionary stages, dynamical heating by the nuclear cluster plays a progressively more important role. Given these findings, it is likely that two-body relaxation alone could not produce the observed configuration of the stellar disc in the GC and other collective processes might have played an important role. Such processes are less likely to produce mass-stratification in the disc and therefore a detailed study of the mass-stratification of the GC disc may provide a handle on the processes that dominate its evolution. Finally, two-body relaxation would leave a stellar disc in a relatively thin configuration even after 100 Myr and therefore earlier discs, now containing only older, lower mass stars, might still be observed in the GC, unless destroyed/smeared by other processes.

  19. Stellar feedback in dwarf galaxy formation.

    PubMed

    Mashchenko, Sergey; Wadsley, James; Couchman, H M P

    2008-01-11

    Dwarf galaxies pose substantial challenges for cosmological models. In particular, current models predict a dark-matter density that is divergent at the center, which is in sharp contrast with observations that indicate a core of roughly constant density. Energy feedback, from supernova explosions and stellar winds, has been proposed as a major factor shaping the evolution of dwarf galaxies. We present detailed cosmological simulations with sufficient resolution both to model the relevant physical processes and to directly assess the impact of stellar feedback on observable properties of dwarf galaxies. We show that feedback drives large-scale, bulk motions of the interstellar gas, resulting in substantial gravitational potential fluctuations and a consequent reduction in the central matter density, bringing the theoretical predictions in agreement with observations.

  20. How Stellar Feedback Simultaneously Regulates Star Formation and Drives Outflows

    NASA Astrophysics Data System (ADS)

    Hayward, Christopher C.

    2017-07-01

    Stellar-feedback-driven outflows are thought to be a crucial process in galaxy formation, but our physical understanding of them is still rudimentary. I will present an analytical model for how stellar feedback simultaneously regulates star formation and drives outflows. One interesting prediction of the model is that although stellar feedback can efficiently generate outflows in all galaxies at high redshift, it is unable to drive outflows in massive galaxies below z 1. This prediction agrees with the results of state-of-the-art cosmological zoom simulations that include explicit stellar feedback. This model, combined with the aforementioned simulations, suggests that high-redshift galaxies are highly turbulent, disordered and characterized by strong starbursts and subsequent violent outflows, and the suppression of outflows in massive galaxies at z 1 is crucial for the emergence of well-ordered, steadily star-forming disk galaxies.

  1. Feedback and the formation of dwarf galaxy stellar haloes

    NASA Astrophysics Data System (ADS)

    Stinson, G. S.; Dalcanton, J. J.; Quinn, T.; Gogarten, S. M.; Kaufmann, T.; Wadsley, J.

    2009-05-01

    Stellar population studies show that low-mass galaxies in all environments exhibit stellar haloes that are older and more spherically distributed than the main body of the galaxy. In some cases, there is a significant intermediate age component that extends beyond the young disc. We examine a suite of Smoothed Particle Hydrodynamic simulations and find that elevated early star formation activity combined with supernova feedback can produce an extended stellar distribution that resembles these haloes for model galaxies ranging from v200 = 15 to 35 km s-1, without the need for accretion of subhaloes.

  2. Stellar signatures of AGN-jet-triggered star formation

    SciTech Connect

    Dugan, Zachary; Silk, Joseph; Bryan, Sarah; Gaibler, Volker; Haas, Marcel

    2014-12-01

    To investigate feedback between relativistic jets emanating from active galactic nuclei and the stellar population of the host galaxy, we analyze the long-term evolution of the orbits of the stars formed in the galaxy-scale simulations by Gaibler et al. of jets in massive, gas-rich galaxies at z ∼ 2-3. We find strong, jet-induced differences in the resulting stellar populations of galaxies that host relativistic jets and galaxies that do not, including correlations in stellar locations, velocities, and ages. Jets are found to generate distributions of increased radial and vertical velocities that persist long enough to effectively augment the stellar structure of the host. The jets cause the formation of bow shocks that move out through the disk, generating rings of star formation within the disk. The bow shock often accelerates pockets of gas in which stars form, yielding populations of stars with significant radial and vertical velocities, some of which have large enough velocities to escape the galaxy. These stellar population signatures can serve to identify past jet activity as well as jet-induced star formation.

  3. Evidences for Black Hole Formation by Complete Stellar Collapse

    NASA Astrophysics Data System (ADS)

    Mirabel, Igor Felix

    2016-07-01

    One of the most critical parameters that determines the formation of binary black holes is the range of masses of black holes that may form by direct collapse, namely, with no energetic supernova kicks that would unbound the stellar binary. Theoretical models set mass ranges and limits for black hole formation through the complete collapse of the stellar progenitor. However, observational constraints for those mass limits have been elusive. Since the velocity of a stellar black hole encodes the history of its formation and evolution, it may provide observational constraints on the strength of kicks by natal supernova explosions in the formation of the black hole. Based on the motion in three dimensions of five black hole binaries in our Galaxy it is found that the three black holes with < 10 solar masses are runaway black hole binaries due to kicks from natal supernovae, whereas the two black holes with 10 to 15 solar masses remained in their birth place and must have been form by complete or almost complete collapse of the progenitor star. These observations show that there may be binary black holes with components having masses as low as 10 solar masses, which suggests that a significant fraction of massive stellar binaries would end as black hole binaries that would produce a large stochastic gravitational-wave background.

  4. Testing galaxy formation models with galaxy stellar mass functions

    NASA Astrophysics Data System (ADS)

    Lim, S. H.; Mo, H. J.; Lan, T.-W.; Ménard, B.

    2017-01-01

    We compare predictions of a number of empirical models and numerical simulations of galaxy formation to the conditional stellar mass functions of galaxies in groups of different masses obtained recently by Lan et al. to test how well different models accommodate the data. The observational data clearly prefer a model in which star formation in low-mass haloes changes behaviour at a characteristic redshift zc ˜ 2. There is also tentative evidence that this characteristic redshift depends on environment, becoming zc ˜ 4 in regions that eventually evolve into rich clusters of galaxies. The constrained model is used to understand how galaxies form and evolve in dark matter haloes, and to make predictions for other statistical properties of the galaxy population, such as the stellar mass functions of galaxies at high z, the star formation, and stellar mass assembly histories in dark matter haloes. A comparison of our model predictions with those of other empirical models shows that different models can make vastly different predictions, even though all of them are tuned to match the observed stellar mass functions of galaxies.

  5. Cusp Cap

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    A brightening at one or other of the tips—cusps—of the crescent phase of Venus, as seen from Earth. Cusp caps were first reported by the German amateur astronomer Baron Franz Paula von Gruithuisen in 1813, and have been recorded by telescopic observers ever since. They were named by analogy with the Earth's polar caps; early observers fancied they were seeing glimpses of a possibly Earth-like sur...

  6. Lack of nuclear clusters in dwarf spheroidal galaxies: implications for massive black holes formation and the cusp/core problem

    NASA Astrophysics Data System (ADS)

    Arca-Sedda, Manuel; Capuzzo-Dolcetta, Roberto

    2017-01-01

    One of the leading scenarios for the formation of nuclear star clusters in galaxies is related to the orbital decay of globular clusters (GCs) and their subsequent merging, though alternative theories are currently debated. The availability of high-quality data for structural and orbital parameters of GCs allows us to test different nuclear star cluster formation scenarios. The Fornax dwarf spheroidal (dSph) galaxy is the heaviest satellite of the Milky Way and it is the only known dSph hosting five GCs, whereas there are no clear signatures for the presence of a central massive black hole. For this reason, it represents a suited place to study the orbital decay process in dwarf galaxies. In this paper, we model the future evolution of the Fornax GCs simulating them and the host galaxy by means of direct N-body simulations. Our simulations also take into account the gravitational field generated by the Milky Way. We found that if the Fornax galaxy is embedded in a standard cold dark matter halo, the nuclear cluster formation would be significantly hampered by the high central galactic mass density. In this context, we discuss the possibility that infalling GCs drive the flattening of the galactic density profile, giving a possible alternative explanation to the so-called cusp/core problem. Moreover, we briefly discuss the link between GC infall process and the absence of massive black holes in the centre of dSphs.

  7. Long-term Variability of Beach Cusps

    NASA Astrophysics Data System (ADS)

    Pianca, C.; Holman, R. A.; Siegle, E.

    2016-02-01

    The most curious morphological features observed on beaches are the cusps. Due to their rhythmic spacing, beach cusps have attracted many observers and many, often contradictory, theories as to their form. Moreover, most of the research about beach cusps has focused on their formation. Few had available long time series to study such things as the variability of alongshore and cross-shore position and spacing on the cusp field, the presence, longevity and interactions between higher and lower sets of cusps, and the processes by which cusp fields extend, shrink or change length scale. The purpose of this work is to use long-term data sets of video images from two study sites, an intermediate (Duck, USA, 26 years) and a reflective beach (Massaguaçu, Brazil, 3 years), to investigate the temporal and spatial changes of cusps conditions. Time-evolving shoreline data were first extracted using an algorithm called ASLIM (Pianca et al 2015). Cusps were then identified based on the band-passed variability of time exposure image data about this shoreline as a function of elevation relative to MSL. The identified beaches cusps will be analyzed for cusp spacing, positions (upper or lower cusps), alongshore variability, merging events, percentage of cusp events, patterns of the events and time scales of variability. Finally, the relationship of these characteristics to environmental conditions (wave, tides, beach conditions) will be studied.

  8. Formation of the Galactic Stellar Halo. I. Structure and Kinematics

    NASA Astrophysics Data System (ADS)

    Bekki, Kenji; Chiba, Masashi

    2001-09-01

    We perform numerical simulations for the formation of the Galactic stellar halo, based on the currently favored cold dark matter theory of galaxy formation. Our numerical models, taking into account both dynamical and chemical evolution processes in a consistent manner, are aimed at explaining the observed structure and kinematics of the stellar halo in the context of hierarchical galaxy formation. The main results of the present simulations are summarized as follows: (1) Basic physical processes involved in the formation of the stellar halo, composed of metal-deficient stars with [Fe/H]<=-1.0, are described by both dissipative and dissipationless merging of subgalactic clumps and their resultant tidal disruption in the course of gravitational contraction of the Galaxy at high redshift (z>1). (2) The simulated halo has a density profile similar to the observed power-law form of ρ(r)~r-3.5 and also has a metallicity distribution similar to the observations. The halo shows virtually no radial gradient for stellar ages and only a small gradient for metallicities. (3) The dual nature of the halo, i.e., its inner flattened and outer spherical density distribution, is reproduced, at least qualitatively, by the present model. The outer spherical halo is formed via essentially dissipationless merging of small subgalactic clumps, whereas the inner flattened one is formed via three different mechanisms, i.e., dissipative merging between larger, more massive clumps, adiabatic contraction due to the growing Galactic disk, and gaseous accretion onto the equatorial plane. (4) For the simulated metal-poor stars with [Fe/H]<=-1.0, there is no strong correlation between metal abundances and orbital eccentricities, in good agreement with the recent observations. Moreover, the observed fraction of the low-eccentricity stars is reproduced correctly for [Fe/H]<=-1.6 and approximately for the intermediate-abundance range of -1.6<[Fe/H]<=-1.0. (5) The mean rotational velocity of the

  9. Stellar velocity dispersion in dissipative galaxy mergers with star formation

    SciTech Connect

    Stickley, Nathaniel R.; Canalizo, Gabriela

    2014-05-01

    In order to better understand stellar dynamics in merging systems, such as NGC 6240, we examine the evolution of central stellar velocity dispersion (σ{sub *}) in dissipative galaxy mergers using a suite of binary disk merger simulations that include feedback from stellar formation and active galactic nuclei (AGNs). We find that σ{sub *} undergoes the same general stages of evolution that were observed in our previous dissipationless simulations: coherent oscillation, then phase mixing, followed by dynamical equilibrium. We also find that measurements of σ{sub *} that are based only upon the youngest stars in simulations consistently yield lower values than measurements based upon the total stellar population. This finding appears to be consistent with the so-called 'σ{sub *} discrepancy', observed in real galaxies. We note that quasar-level AGN activity is much more likely to occur when σ{sub *} is near its equilibrium value rather than during periods of extreme σ{sub *}. Finally, we provide estimates of the scatter inherent in measuring σ{sub *} in ongoing mergers.

  10. Formation Flying and the Stellar Imager Mission Concept

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth G.

    2003-01-01

    The Stellar Imager (SI) is envisioned as a space-based, W-optical interferometer composed of 10 or more one-meter class elements distributed with a maximum baseline of 0.5 km. image stars and binaries with sufficient resolution to enable long-term studies of stellar magnetic activity patterns, for comparison with those on the sun. It will also support asteroseismology (acoustic imaging) to probe stellar internal structure, differential rotation, and large-scale circulations. SI will enable us to understand the various effects of the magnetic fields of stars, the dynamos that generate these fields, and the internal structure and dynamics of the stars. The ultimate goal of the mission is to achieve the best-possible forecasting of solar activity as a driver of climate and space weather on time scales ranging from months up to decades, and an understanding of the impact of stellar magnetic activity on life in the Universe. In this paper we briefly describe the scientific goals of the mission, the performance requirements needed to address these goals, and the "enabling technology" development efforts required, with specific attention for this meeting to the formation-flying aspects. It is designed to

  11. Clump formation through colliding stellar winds in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Calderón, Diego

    2016-07-01

    The gas cloud G2 is currently being tidally disrupted by the Galactic Center super-massive black hole, Sgr A*. The region around the black hole is populated by ˜30 Wolf-Rayet stars, which produce strong outflows. Following an analytical approach, we explore the possibility that gas clumps, such as G2, originate from the collision of identical stellar winds via the Non-Linear Thin Shell Instability. We have found that the collision of relatively slow (<750 km s^{-1}) and strong (˜10^{-5} M_{⊙} yr^{-1}) stellar winds from stars at short separations (<2000 AU) is a process that indeed could produce clumps of G2's mass and above. Such short separation encounters of single stars along their orbits are not common in the Galactic Centre, however close binaries, such as IRS 16SW, are promising clump sources (see Calderón et al. 2016). We also present the first results of 2D models of colliding wind systems using the hydrodynamics adaptive mesh refinement code RAMSES, aiming to obtain a clump mass function, and the rate of clump formation and ejection to the ISM. We study the effect of parameters such as wind properties, stellar separation and orbital motion, in order to understand how likely the formation of G2 is in this context.

  12. Star formation histories from resolved stellar populations in nearby galaxies

    NASA Astrophysics Data System (ADS)

    Gogarten, Stephanie Morris

    We present the results of three applications of using resolved stellar populations to derive star formation histories (SFHs) of regions in the nearby spiral galaxies M81 and NGC 300. We use data from the Advanced Camera for Surveys (ACS) Nearby Galaxy Survey Treasury (ANGST) and compare observed color- magnitude diagrams (CMDs) with synthetic CMDs from stellar evolution models to find the best-fitting combination of stellar ages and metallicities. In the outer disk of M81, we probe the stellar populations of small regions which are UV-bright but Ha-faint as well as HII regions. We determine that the HII regions contain more massive stars than the other regions and are therefore consistent with being at least a few Myr younger; however, we cannot rule out a truncated initial mass function as an explanation for the differences between these regions. Our data for NGC 300 cover the location of an unusual optical transient, NGC 300 OT2008-1, which has been speculated to represent a new class of objects. Despite the lack of an optical precursor for this object, we infer the mass of the progenitor by deriving the SFH from the stars surrounding the transient location, under the assumption that since most stars form in clusters, the population should be coeval. We find a star formation event of age 8-13 Myr and determine that the progenitor should be a star which has recently turned off the main sequence, of mass 12-17 [Special characters omitted.] . Expanding our view of NGC 300 to a radial strip of the disk from the center to 5.4 kpc, we divide the galaxy into radial bins and derive the SFH at each location. We find that the percentage of young stars in the outer regions is considerably greater than in the inner regions, but the slope of the surface density of the disk increases only slightly with time.

  13. How stellar feedback simultaneously regulates star formation and drives outflows

    NASA Astrophysics Data System (ADS)

    Hayward, Christopher C.; Hopkins, Philip F.

    2017-02-01

    We present an analytic model for how momentum deposition from stellar feedback simultaneously regulates star formation and drives outflows in a turbulent interstellar medium (ISM). Because the ISM is turbulent, a given patch of ISM exhibits sub-patches with a range of surface densities. The high-density patches are 'pushed' by feedback, thereby driving turbulence and self-regulating local star formation. Sufficiently low-density patches, however, are accelerated to above the escape velocity before the region can self-adjust and are thus vented as outflows. When the gas fraction is ≳ 0.3, the ratio of the turbulent velocity dispersion to the circular velocity is sufficiently high that at any given time, of the order of half of the ISM has surface density less than the critical value and thus can be blown out on a dynamical time. The resulting outflows have a mass-loading factor (η ≡ dot{M}_{out}/M_{star }) that is inversely proportional to the gas fraction times the circular velocity. At low gas fractions, the star formation rate needed for local self-regulation, and corresponding turbulent Mach number, declines rapidly; the ISM is 'smoother', and it is actually more difficult to drive winds with large mass-loading factors. Crucially, our model predicts that stellar-feedback-driven outflows should be suppressed at z ≲ 1 in M⋆ ≳ 1010 M⊙ galaxies. This mechanism allows massive galaxies to exhibit violent outflows at high redshifts and then 'shut down' those outflows at late times, thereby enabling the formation of a smooth, extended thin stellar disc. We provide simple fitting functions for η that should be useful for sub-resolution and semi-analytic models.

  14. Clustered star formation and the origin of stellar masses.

    PubMed

    Pudritz, Ralph E

    2002-01-04

    Star clusters are ubiquitous in galaxies of all types and at all stages of their evolution. We also observe them to be forming in a wide variety of environments, ranging from nearby giant molecular clouds to the supergiant molecular clouds found in starburst and merging galaxies. The typical star in our galaxy and probably in others formed as a member of a star cluster, so star formation is an intrinsically clustered and not an isolated phenomenon. The greatest challenge regarding clustered star formation is to understand why stars have a mass spectrum that appears to be universal. This review examines the observations and models that have been proposed to explain these fundamental issues in stellar formation.

  15. Galaxy Evolution: Effects of Stellar Feedback on the Halo Formation

    NASA Astrophysics Data System (ADS)

    Myers, J. M.; Hartmann, D. H.; The, L.-S.

    2003-05-01

    Recent reviews of Milky Way globular cluster formation indicate three groups associated with the formation of the bulge, disk and halo, and one group associated with accretion processes (van den Bergh 2000). Malinie et al. (1991) showed that the metallicity distribution of the halo globular clusters can be reproduced in the ELS scenario if the initial density profile is nonuniform and kinetic feedback from supernovae is taken into account. Their simulations were performed in 1D and did not include dark matter. In this study, using an N-body/SPH simulation, we attempt to explain the effect of stellar feedback on the formation and distribution of the halo globular clusters. We present 3D simulations of a rotating homogeneous collapse including dark matter, cooling gas, and stars. Three formulations of supernova feedback are considered.

  16. DO MOST ACTIVE GALACTIC NUCLEI LIVE IN HIGH STAR FORMATION NUCLEAR CUSPS?

    SciTech Connect

    Mushotzky, Richard F.; Shimizu, T. Taro; Meléndez, Marcio; Koss, Michael

    2014-02-01

    We present early results of the Herschel PACS (70 and 160 μm) and SPIRE (250, 350, and 500 μm) survey of 313 low redshift (z < 0.05), ultra-hard X-ray (14-195 keV) selected active galactic nuclei (AGNs) from the 58 month Swift/Burst Alert Telescope catalog. Selection of AGNs from ultra-hard X-rays avoids bias from obscuration, providing a complete sample of AGNs to study the connection between nuclear activity and star formation in host galaxies. With the high angular resolution of PACS, we find that >35% and >20% of the sources are ''point-like'' at 70 and 160 μm respectively and many more have their flux dominated by a point source located at the nucleus. The inferred star formation rates (SFRs) of 0.1-100 M {sub ☉} yr{sup –1} using the 70 and 160 μm flux densities as SFR indicators are consistent with those inferred from Spitzer Ne II fluxes, but we find that 11.25 μm polycyclic aromatic hydrocarbon data give ∼3× lower SFR. Using GALFIT to measure the size of the far-infrared emitting regions, we determined the SFR surface density (M {sub ☉} yr{sup –1} kpc{sup –2}) for our sample, finding that a significant fraction of these sources exceed the threshold for star formation driven winds (0.1 M {sub ☉} yr{sup –1} kpc{sup –2})

  17. STELLAR ELEMENTAL ABUNDANCE PATTERNS: IMPLICATIONS FOR PLANET FORMATION

    SciTech Connect

    Chambers, J. E.

    2010-11-20

    The solar photosphere is depleted in refractory elements compared to most solar twins, with the degree of depletion increasing with an element's condensation temperature. Here, I show that adding 4 Earth masses of Earth-like and carbonaceous-chondrite-like material to the solar convection zone brings the Sun's composition into line with the mean value for the solar twins. The observed solar composition could have arisen if the Sun's convection zone accreted material from the solar nebula that was depleted in refractory elements due to the formation of the terrestrial planets and ejection of rocky protoplanets from the asteroid belt. Most solar analogs are missing 0-10 Earth masses of rocky material compared to the most refractory-rich stars, providing an upper limit to the mass of rocky terrestrial planets that they possess. The missing mass is correlated with stellar metallicity. This suggests that the efficiency of planetesimal formation increases with stellar metallicity. Stars with and without known giant planets show a similar distribution of abundance trends. If refractory depletion is a signature of the presence of terrestrial planets, this suggests that there is not a strong correlation between the presence of terrestrial and giant planets in the same system.

  18. Galactic flows and the formation of stellar clusters

    NASA Astrophysics Data System (ADS)

    Smilgys, Romas; Bonnell, Ian A.

    2017-03-01

    We investigate the formation of stellar clusters from a Galactic scale SPH simulation. The simulation traces star formation over a 5.6 Myr timescale, with local gravitational instabilities resulting in ~ 105 solar masses of star formation in the form of sink particles. We investigate the time evolution of the physical properties of the forming clusters including their half-mass radii, their energies and the depletion time of the gas. Star formation is driven by the large scale flows which compress the gas to higher densities where self gravity takes over and collapse occurs. We show that the more massive clusters (up to ~ 2 × 104 solar masses) gather their material from of order 10 pc due to these large scale motions associated with the spiral arm passage and shock. The bulk of the gas becomes gravitationally bound near 1-2 Myr before sink formation, and in the absence of feedback, significant accretion ongoing on longer timescales. We trace the hierarchical merging process of cluster formation which naturally results in age spreads of order the crossing time of the original region which provides the gas reservoir for the cluster.

  19. Herschel/HIFI reveals the first stages of stellar formation

    NASA Astrophysics Data System (ADS)

    Herpin, F.; Bontemps, S.; Chavarria, L.; van der Tak, F.; Wyrowski, F.; van Dishoeck, E.

    2010-12-01

    The understanding of the star formation is still on progress. Especially, the formation of high-mass stars is much less understood than the low-mass case: even the time order of observational phenomena is uncertain. Water, one of the most important molecules in the Universe, might elucidate key episodes in the process of stellar birth, and especially could be a major role in the formation of high-mass stars. For both types of stars, the source chemical composition is not well known and even less known is the chemical evolution of the interstellar matter throughout the various phases of star formation. This talk presents the first results of the various Herschel Space Observatory star formation key-programs. One of the instruments on-board HSO, HIFI, is the most powerful spectrometer never built, covering a huge frequency range, most of them unaccessible from ground. In particular, one of the KP, WISH, aims at following the process of star formation during the various stages and at using the water as a physical diagnostic throughout the evolution.

  20. The Formation of Brown Dwarfs as Ejected Stellar Embryos

    NASA Astrophysics Data System (ADS)

    Reipurth, Bo; Clarke, Cathie

    2001-07-01

    We conjecture that brown dwarfs are substellar objects because they have been ejected from small newborn multiple systems that have decayed in dynamical interactions. In this view, brown dwarfs are stellar embryos for which the star formation process was aborted before the hydrostatic cores could build up enough mass to eventually start hydrogen burning. The disintegration of a small multiple system is a stochastic process, which can be described only in terms of the half-life of the decay. A stellar embryo competes with its siblings in order to accrete infalling matter, and the one that grows slowest is most likely to be ejected. With better luck, a brown dwarf would therefore have become a normal star. This interpretation of brown dwarfs readily explains the rarity of brown dwarfs as close companions to normal stars, the absence of wide brown dwarf binaries, and the flattening of the low-mass end of the initial mass function. Possible observational tests of this scenario include statistics of brown dwarfs near Class 0 sources and the kinematics of brown dwarfs in star-forming regions, while they still retain a kinematic signature of their expulsion. Because the ejection process limits the amount of gas brought along in a disk, it is predicted that substellar equivalents to the classical T Tauri stars should be rather short-lived.

  1. Clump formation through colliding stellar winds in the Galactic Centre

    NASA Astrophysics Data System (ADS)

    Calderón, D.; Ballone, A.; Cuadra, J.; Schartmann, M.; Burkert, A.; Gillessen, S.

    2016-02-01

    The gas cloud G2 is currently being tidally disrupted by the Galactic Centre supermassive black hole, Sgr A*. The region around the black hole is populated by ˜30 Wolf-Rayet stars, which produce strong outflows. We explore the possibility that gas clumps, such as G2, originate from the collision of stellar winds via the non-linear thin shell instability. Following an analytical approach, we study the thermal evolution of slabs formed in the symmetric collision of winds, evaluating whether instabilities occur, and estimating possible clump masses. We find that the collision of relatively slow (≲750 km s-1) and strong (˜10-5 M⊙ yr-1) stellar winds from stars at short separations (<10 mpc) is a process that indeed could produce clumps of G2's mass and above. Such short separation encounters of single stars along their known orbits are not common in the Galactic Centre, making this process a possible but unlikely origin for G2. We also discuss clump formation in close binaries such as IRS 16SW and in asymmetric encounters as promising alternatives that deserve further numerical study.

  2. Formation and stellar spin-orbit misalignment of hot Jupiters from Lidov-Kozai oscillations in stellar binaries

    NASA Astrophysics Data System (ADS)

    Anderson, Kassandra R.; Storch, Natalia I.; Lai, Dong

    2016-03-01

    Observed hot Jupiter (HJ) systems exhibit a wide range of stellar spin-orbit misalignment angles. This paper investigates the inward migration of giant planets due to Lidov-Kozai (LK) oscillations induced by a distant stellar companion. We conduct a large population synthesis study, including the octupole gravitational potential from the stellar companion, mutual precession of the host stellar spin axis and planet orbital axis, tidal dissipation in the planet and stellar spin-down in the host star due to magnetic braking. We consider a range of planet masses (0.3-5 MJ) and initial semimajor axes (1-5 au), different properties for the host star, and varying tidal dissipation strengths. The fraction of systems that result in HJs depends on planet mass and stellar type, with fHJ = 1-4 per cent (depending on tidal dissipation strength) for Mp = 1 MJ, and larger (up to 8 per cent) for more massive planets. The production efficiency of `hot Saturns' (Mp = 0.3MJ) is much lower, because most migrating planets are tidally disrupted. We find that the fraction of systems that result in either HJ formation or tidal disruption, fmig ≃ 11-14 per cent is roughly constant, having little variation with planet mass, stellar type and tidal dissipation strength. The distribution of final HJ stellar obliquities exhibits a complex dependence on the planet mass and stellar type. For Mp = (1-3)MJ, the distribution is always bimodal, with peaks around 30° and 130°. The distribution for 5MJ planets depends on host stellar type, with a preference for low obliquities for solar-type stars, and higher obliquities for more massive (1.4 M⊙) stars.

  3. Stellarators

    SciTech Connect

    Hartmann, D.A.

    2004-03-15

    Stellarators are toroidal devices where the required rotational transform of the magnetic field lines is generated by external field coils and not via an induced net toroidal plasma current. This confinement scheme has the advantages that, in principle, steady-state plasma operation is possible and that it does not have to brace itself against disruptions of a toroidal plasma current. At the cost of having to give up toroidal symmetry the properties of the stellarator field can be tailored to suit reactor needs. Research focuses on the plasma confinement properties of different stellarator fields and investigates the problems arising when one extrapolates to reactor parameters.

  4. Why stellar feedback promotes disc formation in simulated galaxies

    NASA Astrophysics Data System (ADS)

    Übler, Hannah; Naab, Thorsten; Oser, Ludwig; Aumer, Michael; Sales, Laura V.; White, Simon D. M.

    2014-09-01

    We study how feedback influences baryon infall on to galaxies using cosmological, zoom-in simulations of haloes with present mass Mvir = 6.9 × 1011 to 1.7 × 1012 M⊙. Starting at z = 4 from identical initial conditions, implementations of weak and strong stellar feedback produce bulge- and disc-dominated galaxies, respectively. Strong feedback favours disc formation: (1) because conversion of gas into stars is suppressed at early times, as required by abundance matching arguments, resulting in flat star formation histories and higher gas fractions; (2) because 50 per cent of the stars form in situ from recycled disc gas with angular momentum only weakly related to that of the z = 0 dark halo; (3) because late-time gas accretion is typically an order of magnitude stronger and has higher specific angular momentum, with recycled gas dominating over primordial infall; (4) because 25-30 per cent of the total accreted gas is ejected entirely before z ˜ 1, removing primarily low angular momentum material which enriches the nearby intergalactic medium. Most recycled gas roughly conserves its angular momentum, but material ejected for long times and to large radii can gain significant angular momentum before re-accretion. These processes lower galaxy formation efficiency in addition to promoting disc formation.

  5. Laboratory simulation of graphite formation in stellar envelopes

    NASA Technical Reports Server (NTRS)

    Dorfeld, W. G.; Hudson, J. B.

    1973-01-01

    A technique has been developed which permits laboratory simulation of graphite condensation in the envelopes of cool, late sequence stars. Processes in the stellar envelope were simulated by allowing hydrogen-carbon mixtures of typical circumstellar composition and temperature to expand freely into vacuum, cooling and supersaturating the vapor. Expansion products were determined mass spectrometrically through the use of molecular beam techniques. The results of laboratory expansions were scaled to those occurring near M and N stars by comparing the number of collisional events in each case. Kinetic considerations indicate that the important rate process in rarefied envelopes will be C2 formation; consequently scaling by termolecular collisions was employed. Results of this study imply that envelope expansions near M giants contribute at most .01 of the observed interstellar grain density. In the case of pulsating N stars, on the other hand, the results are not inconsistent with previous predictions of essentially complete carbon condensation.

  6. Stellar contents and star formation in the NGC 7538 region

    NASA Astrophysics Data System (ADS)

    Sharma, Saurabh; Pandey, A. K.; Ojha, D. K.; Bhatt, Himali; Ogura, K.; Kobayashi, N.; Yadav, R.; Pandey, J. C.

    2017-05-01

    Deep optical photometric data on the NGC 7538 region were collected and combined with archival data sets from the Chandra, 2MASS and Spitzer surveys to generate a new catalogue of young stellar objects (YSOs) including those not showing infrared excess emission. This new catalogue is complete down to 0.8 M⊙. The nature of the YSOs associated with the NGC 7538 region and their spatial distribution are used to study the star-formation process and the resultant mass function (MF) in the region. Out of the 419 YSOs, ˜91 per cent have ages between 0.1 and 2.5 Myr and ˜86 per cent have masses between 0.5 and 3.5 M⊙, as derived by the spectral energy distribution fitting analysis. Around 24, 62 and 2 per cent of these YSOs are classified to be class I, class II and class III sources, respectively. The X-ray activities for the class I, class II and class III objects are not significantly different from each other. This result implies that the enhanced X-ray surface flux due to the increase in the rotation rate may be compensated for by the decrease in the stellar surface area during the pre-main-sequence evolution. Our analysis shows that the O3V type high-mass star IRS 6 may have triggered the formation of young low-mass stars up to a radial distance of 3 pc. The MF shows a turn-off at around 1.5 M⊙ and the value of its slope Γ in the mass range 1.5 < M/M⊙ < 6 is -1.76 ± 0.24, which is steeper than the Salpeter value.

  7. Complex molecule formation around massive young stellar objects.

    PubMed

    Oberg, Karin I; Fayolle, Edith C; Reiter, John B; Cyganowski, Claudia

    2014-01-01

    Interstellar complex organic molecules were first identified in the hot inner regions of massive young stellar objects (MYSOs), but have more recently been found in many colder sources, indicating that complex molecules can form at a range of temperatures. However, individually these observations provide limited constraints on how complex molecules form, and whether the same formation pathways dominate in cold, warm and hot environments. To address these questions, we use spatially resolved observations from the Submillimeter Array of three MYSOs together with mostly unresolved literature data to explore how molecular ratios depend on environmental parameters, especially temperature. Towards the three MYSOs, we find multiple complex organic emission peaks characterized by different molecular compositions and temperatures. In particular, CH3CCH and CH3CN seem to always trace a lukewarm (T = 60 K) and a hot (T > 100 K) complex chemistry, respectively. These spatial trends are consistent with abundance-temperature correlations of four representative complex organics--CH3CCH, CH3CN, CH3OCH3 and CH3CHO--in a large sample of complex molecule hosts mined from the literature. Together, these results indicate a general chemical evolution with temperature, i.e. that new complex molecule formation pathways are activated as a MYSO heats up. This is qualitatively consistent with model predictions. Furthermore, these results suggest that ratios of complex molecules may be developed into a powerful probe of the evolutionary stage of a MYSO, and may provide information about its formation history.

  8. Stellar Absorption Line Analysis of Local Star-forming Galaxies: The Relation between Stellar Mass, Metallicity, Dust Attenuation, and Star Formation Rate

    NASA Astrophysics Data System (ADS)

    Zahid, H. Jabran; Kudritzki, Rolf-Peter; Conroy, Charlie; Andrews, Brett; Ho, I.-Ting

    2017-09-01

    We analyze the optical continuum of star-forming galaxies in the Sloan Digital Sky Survey by fitting stacked spectra with stellar population synthesis models to investigate the relation between stellar mass, stellar metallicity, dust attenuation, and star formation rate. We fit models calculated with star formation and chemical evolution histories that are derived empirically from multi-epoch observations of the stellar mass–star formation rate and the stellar mass–gas-phase metallicity relations, respectively. We also fit linear combinations of single-burst models with a range of metallicities and ages. Star formation and chemical evolution histories are unconstrained for these models. The stellar mass–stellar metallicity relations obtained from the two methods agree with the relation measured from individual supergiant stars in nearby galaxies. These relations are also consistent with the relation obtained from emission-line analysis of gas-phase metallicity after accounting for systematic offsets in the gas-phase metallicity. We measure dust attenuation of the stellar continuum and show that its dependence on stellar mass and star formation rate is consistent with previously reported results derived from nebular emission lines. However, stellar continuum attenuation is smaller than nebular emission line attenuation. The continuum-to-nebular attenuation ratio depends on stellar mass and is smaller in more massive galaxies. Our consistent analysis of stellar continuum and nebular emission lines paves the way for a comprehensive investigation of stellar metallicities of star-forming and quiescent galaxies.

  9. Modeling for Stellar Feedback in Galaxy Formation Simulations

    NASA Astrophysics Data System (ADS)

    Núñez, Alejandro; Ostriker, Jeremiah P.; Naab, Thorsten; Oser, Ludwig; Hu, Chia-Yu; Choi, Ena

    2017-02-01

    Various heuristic approaches to model unresolved supernova (SN) feedback in galaxy formation simulations exist to reproduce the formation of spiral galaxies and the overall inefficient conversion of gas into stars. Some models, however, require resolution-dependent scalings. We present a subresolution model representing the three major phases of supernova blast wave evolution—free expansion, energy-conserving Sedov–Taylor, and momentum-conserving snowplow—with energy scalings adopted from high-resolution interstellar-medium simulations in both uniform and multiphase media. We allow for the effects of significantly enhanced SN remnant propagation in a multiphase medium with the cooling radius scaling with the hot volume fraction, {f}{hot}, as {(1-{f}{hot})}-4/5. We also include winds from young massive stars and AGB stars, Strömgren sphere gas heating by massive stars, and a mechanism that limits gas cooling that is driven by radiative recombination of dense H ii regions. We present initial tests for isolated Milky Way-like systems simulated with the Gadget-based code SPHgal with improved SPH prescription. Compared to pure thermal SN input, the model significantly suppresses star formation at early epochs, with star formation extended both in time and space in better accord with observations. Compared to models with pure thermal SN feedback, the age at which half the stellar mass is assembled increases by a factor of 2.4, and the mass-loading parameter and gas outflow rate from the galactic disk increase by a factor of 2. Simulation results are converged for a variation of two orders of magnitude in particle mass in the range (1.3–130) × 104 solar masses.

  10. Spiral Galaxies with HST/NICMOS. II. Isophotal Fits and Nuclear Cusp Slopes

    NASA Astrophysics Data System (ADS)

    Seigar, Marc; Carollo, C. Marcella; Stiavelli, Massimo; de Zeeuw, P. Tim; Dejonghe, Herwig

    2002-01-01

    We present surface brightness profiles for 56 of the 78 spiral galaxies observed in the HST/NICMOS2 F160W snapshot survey introduced in Paper I of this series, as well as surface brightness profiles for 23 objects out of the 41 that were also observed in the F110W filter. We fit these surface brightness profiles with the Nuker law of Lauer et al. and use the smooth analytical descriptions of the data to compute the average nuclear stellar cusp slopes <γ> in the 0.1"-0.5" radial range. Our main result is the startling similarity between the nuclear stellar cusp slopes <γ> in the near-infrared compared with those derived in the visual passband. This similarity has several implications: (1) Despite the significant local color variations that are found in the nuclear regions of spirals and that are documented in Paper I, there are typically little or no optical-NIR global color gradients, and thus no global stellar population variations, inside ~50-100 pc from the nucleus in nearby spirals. (2) The large observed range of the strength of the nuclear stellar cusps seen in the HST optical study of spiral galaxies reflects a physical difference between galaxies and is not an artifact caused by nuclear dust and/or recent star formation. (3) The dichotomy between R1/4 bulges, with steep nuclear stellar cusps <γ>~1, and exponential bulges, with shallow nuclear stellar cusps <γ><0.3, is also not an artifact of the effects of dust or recent star formation. (4) The presence of a surrounding massive disk appears to have no effect on the rise of the stellar density distribution within the innermost hundred parsecs of the R1/4 spheroids. These results imply a breakdown within the family of exponential bulges of the nuclear versus global relationships that have been found for the R1/4 spheroids. Such a breakdown is likely to have significant implications concerning the formation of exponential bulges and their connection with the R1/4 spheroids. Based on observations with the

  11. Initiating solar system formation through stellar shock waves

    NASA Technical Reports Server (NTRS)

    Boss, A. P.; Myhill, E. A.

    1993-01-01

    Isotopic anomalies in presolar grains and other meteoritical components require nucleosynthesis in stellar interiors, condensation into dust grains in stellar envelopes, transport of the grains through the interstellar medium by stellar outflows, and finally injection of the grains into the presolar nebula. The proximity of the presolar cloud to these energetic stellar events suggests that a shock wave from a stellar outflow might have initiated the collapse of an otherwise stable presolar cloud. We have begun to study the interactions of stellar shock waves with thermally supported, dense molecular cloud cores, using a three spatial dimension (3D) radiative hydrodynamics code. Supernova shock waves have been shown by others to destroy quiescent clouds, so we are trying to determine if the much smaller shock speeds found in, e.g., asymptotic giant branch (AGB) star winds, are strong enough to initiate collapse in an otherwise stable, rotating, solar-mass cloud core, without leading to destruction of the cloud.

  12. THE OBSERVED RELATION BETWEEN STELLAR MASS, DUST EXTINCTION, AND STAR FORMATION RATE IN LOCAL GALAXIES

    SciTech Connect

    Zahid, H. J.; Kewley, L. J.; Kudritzki, R. P.; Yates, R. M.

    2013-02-15

    In this study, we investigate the relation between stellar mass, dust extinction, and star formation rate (SFR) using {approx}150,000 star-forming galaxies from SDSS DR7. We show that the relation between dust extinction and SFR changes with stellar mass. For galaxies at the same stellar mass, dust extinction is anti-correlated with the SFR at stellar masses <10{sup 10} M {sub Sun }. There is a sharp transition in the relation at a stellar mass of 10{sup 10} M {sub Sun }. At larger stellar masses, dust extinction is positively correlated with the SFR for galaxies at the same stellar mass. The observed relation between stellar mass, dust extinction, and SFR presented in this study helps to confirm similar trends observed in the relation between stellar mass, metallicity, and SFR. The relation reported in this study provides important new constraints on the physical processes governing the chemical evolution of galaxies. The correlation between SFR and dust extinction for galaxies with stellar masses >10{sup 10} M {sub Sun} is shown to extend to the population of quiescent galaxies suggesting that the physical processes responsible for the observed relation between stellar mass, dust extinction, and SFR may be related to the processes leading to the shutdown of star formation in galaxies.

  13. The stellar mass function and star formation rate-stellar mass relation of galaxies at z ˜ 4-7

    NASA Astrophysics Data System (ADS)

    Katsianis, A.; Tescari, E.; Wyithe, J. S. B.

    2015-04-01

    We investigate the evolution of the star formation rate-stellar mass relation (SFR-M⋆) and galaxy stellar mass function (GSMF) of z ˜ 4-7 galaxies, using cosmological simulations run with the smoothed particle hydrodynamics code P-GADGET3(XXL). We explore the effects of different feedback prescriptions (supernova-driven galactic winds and AGN feedback), initial stellar mass functions and metal cooling. We show that our fiducial model, with strong energy-driven winds and early active galactic nuclei (AGN) feedback, is able to reproduce the observed stellar mass function obtained from Lyman-break selected samples of star-forming galaxies at redshift 6 ≤ z ≤ 7. At z ˜ 4, observed estimates of the GSMF vary according to how the sample was selected. Our simulations are more consistent with recent results from K-selected samples, which provide a better proxy of stellar masses and are more complete at the high-mass end of the distribution. We find that in some cases simulated and observed SFR-M⋆ relations are in tension, and this can lead to numerical predictions for the GSMF in excess of the GSMF observed. By combining the simulated SFR(M⋆) relationship with the observed star formation rate function at a given redshift, we argue that this disagreement may be the result of the uncertainty in the SFR-M⋆ (LUV-M⋆) conversion. Our simulations predict a population of faint galaxies not seen by current observations.

  14. GAS ACCRETION BY STAR CLUSTERS AND THE FORMATION OF ULTRALUMINOUS X-RAY SOURCES FROM CUSPS OF COMPACT REMNANTS

    SciTech Connect

    Naiman, J. P.; Ramirez-Ruiz, Enrico; Lin, Douglas N. C.

    2009-11-10

    Here, we show that the overabundance of ultraluminous, compact X-ray sources associated with moderately young clusters in interacting galaxies such as the Antennae and the Cartwheel can be given an alternative explanation that does not involve the presence of intermediate mass black holes (IMBHs). We argue that gas density within these systems is enhanced by the collective potential of the cluster prior to being accreted onto the individual cluster members and, as a result, the aggregate X-ray luminosity arising from the neutron star cluster members can exceed > 10{sup 39} erg s{sup -1}. Various observational tests to distinguish between IMBHs and accreting neutron star cusps are discussed.

  15. Formation and Assembly History of Stellar Components in Galaxies as a Function of Stellar and Halo Mass

    NASA Astrophysics Data System (ADS)

    Lee, Jaehyun; Yi, Sukyoung K.

    2017-02-01

    Galaxy mass assembly is an end product of structure formation in the ΛCDM cosmology. As an extension of Lee & Yi, we investigate the assembly history of stellar components in galaxies as a function of halo environments and stellar mass using semi-analytic approaches. In our fiducial model, halo mass intrinsically determines the formation and assembly of the stellar mass. Overall, the ex situ fraction slowly increases in central galaxies with increasing halo mass but sharply increases for {log}{M}* /{M}ȯ ≳ 11. A similar trend is also found in satellite galaxies, which implies that mergers are essential to build stellar masses above {log}{M}* /{M}ȯ ∼ 11. We also examine the time evolution of the contribution of mass growth channels. Mergers become the primary channel in the mass growth of central galaxies when their host halo mass begins to exceed {log}{M}200/{M}ȯ ∼ 13. However, satellite galaxies seldom reach the merger-dominant phase despite their reduced star-formation activities due to environmental effects.

  16. The stellar mass-halo mass relation of isolated field dwarfs: a critical test of ΛCDM at the edge of galaxy formation

    NASA Astrophysics Data System (ADS)

    Read, J. I.; Iorio, G.; Agertz, O.; Fraternali, F.

    2017-01-01

    We fit the rotation curves of isolated dwarf galaxies to directly measure the stellar mass-halo mass relation (M★ - M200) over the mass range 5 {×} 10^5 ≲ M_{*} / M_⊙ ≲ 108. By accounting for cusp-core transformations due to stellar feedback, we find a monotonic relation with little scatter. Such monotonicity implies that abundance matching should yield a similar M★ - M200 if the cosmological model is correct. Using the `field galaxy' stellar mass function from the Sloan Digital Sky Survey (SDSS) and the halo mass function from the Λ Cold Dark Matter Bolshoi simulation, we find remarkable agreement between the two. This holds down to M200 ˜ 5 × 109 M⊙, and to M200 ˜ 5 × 108 M⊙ if we assume a power law extrapolation of the SDSS stellar mass function below M★ ˜ 107 M⊙. However, if instead of SDSS we use the stellar mass function of nearby galaxy groups, then the agreement is poor. This occurs because the group stellar mass function is shallower than that of the field below M★ ˜ 109 M⊙, recovering the familiar `missing satellites' and `too big to fail' problems. Our result demonstrates that both problems are confined to group environments and must, therefore, owe to `galaxy formation physics' rather than exotic cosmology. Finally, we repeat our analysis for a Λ Warm Dark Matter cosmology, finding that it fails at 68% confidence for a thermal relic mass of mWDM < 1.25 keV, and mWDM < 2 keV if we use the power law extrapolation of SDSS. We conclude by making a number of predictions for future surveys based on these results.

  17. Prevalence and characteristics of talon cusps in Turkish population

    PubMed Central

    Guven, Yeliz; Kasimoglu, Yelda; Tuna, Elif Bahar; Gencay, Koray; Aktoren, Oya

    2016-01-01

    Background: Talon cusp is a rare dental anomaly characterized by a cusp-like projection, often including the palatal surface of the affected tooth. The aim of the present study was to investigate the prevalence and characteristics of talon cusps in a group of Turkish children. Materials and Methods: The study population consisted of 14,400 subjects who attended the clinics of the Department of Pediatric Dentistry at the Istanbul University, Istanbul, Turkey. Subjects ranged in age from 1 to 14 years with a mean age of 10.5 ± 2.55 years. Talon cusps were mainly categorized by visual examination according to the classification of Hattab et al. The distribution and frequency of talon cusps were calculated with respect to dentition type, tooth type, talon type, the affected surface, associated dental anomalies, and clinical complications. Statistical analysis included descriptive statistics, frequencies, and crosstabs with Chi-square analysis. Results: Talon cusps were detected in 49 subjects (26 males and 23 females) of 14,400 (0.34%). A total of 108 teeth showed talon cusps. Distribution of talon cusps according to gender showed no statistically significant differences. The incidence of talon cusps was found to be greater in maxillary lateral incisors (53.7%) than central incisors (29.62%). Regarding the type of talon cusp, 47.22% of teeth showed a Type III talon cusp, whereas 30.55% of teeth demonstrated a Type II talon and 22.22% of teeth demonstrated a Type I talon cusp. Nine patients (18.36%) with talon cups also exhibited other developmental dental anomalies. Clinical complications associated with talon cusps were detected as caries formation and occlusal interference. Conclusion: This is the most comprehensive study of the prevalence of talon cusps in Turkish population using the largest sample size to date. Also, taurodontism associated with a talon cusp has been reported here for the 1st time. Clinical complications associated with talon cusps need more

  18. Spatially Resolved Spectroscopic Star Formation Histories of nearby Disks: Hints of Stellar Migration

    NASA Astrophysics Data System (ADS)

    Yoachim, Peter; Roškar, Rok; Debattista, Victor P.

    2012-06-01

    We use the Mitchell Spectrograph (formerly VIRUS-P) to observe 12 nearby disk galaxies. We successfully measure ages in the outer disk in six systems. In three cases (NGC 2684, NGC 6155, and NGC 7437), we find that a downward break in the disk surface brightness profile corresponds with a change in the dominant stellar population with the interior being dominated by active star formation and the exterior having older stellar populations that are best fit with star formation histories that decline with time. The observed increase in average stellar ages beyond a profile break is similar to theoretical models that predict surface brightness breaks are caused by stellar migration, with the outer disk being populated from scattered old interior stars. In three more cases (IC 1132, NGC 4904, and NGC 6691), we find no significant change in the stellar population as one crosses the break radius. In these galaxies, both the inner and outer disks are dominated by active star formation and younger stellar populations. While radial migration can contribute to the stellar populations beyond the break, it appears that more than one mechanism is required to explain all of our observed stellar profile breaks. This paper includes data taken at The McDonald Observatory of The University of Texas at Austin.

  19. The Formation of Secondary Stellar Generations in Massive Young Star Clusters from Rapidly Cooling Shocked Stellar Winds

    NASA Astrophysics Data System (ADS)

    Wünsch, R.; Palouš, J.; Tenorio-Tagle, G.; Ehlerová, S.

    2017-01-01

    We study a model of rapidly cooling shocked stellar winds in young massive clusters and estimate the circumstances under which secondary star formation, out of the reinserted winds from a first stellar generation (1G), is possible. We have used two implementations of the model: a highly idealized, computationally inexpensive, spherically symmetric semi-analytic model, and a complex, three-dimensional radiation-hydrodynamic, simulation; they are in a good mutual agreement. The results confirm our previous findings that, in a cluster with 1G mass 107 M⊙ and half-mass-radius 2.38 pc, the shocked stellar winds become thermally unstable, collapse into dense gaseous structures that partially accumulate inside the cluster, self-shield against ionizing stellar radiation, and form the second generation (2G) of stars. We have used the semi-analytic model to explore a subset of the parameter space covering a wide range of the observationally poorly constrained parameters: the heating efficiency, ηhe, and the mass loading, ηml. The results show that the fraction of the 1G stellar winds accumulating inside the cluster can be larger than 50% if ηhe ≲ 10%, which is suggested by the observations. Furthermore, for low ηhe, the model provides a self-consistent mechanism predicting 2G stars forming only in the central zones of the cluster. Finally, we have calculated the accumulated warm gas emission in the H30α recombination line, analyzed its velocity profile, and estimated its intensity for super star clusters in interacting galaxies NGC4038/9 (Antennae) showing that the warm gas should be detectable with ALMA.

  20. Constraints on the Evolution of the Galaxy Stellar Mass Function I: Role of Star Formation, Mergers, and Stellar Stripping

    NASA Astrophysics Data System (ADS)

    Contini, E.; Kang, Xi; Romeo, A. D.; Xia, Q.

    2017-03-01

    We study the connection between the observed star formation rate-stellar mass (SFR-M *) relation and the evolution of the stellar mass function (SMF) by means of a subhalo abundance matching technique coupled to merger trees extracted from an N-body simulation. Our approach, which considers both galaxy mergers and stellar stripping, is to force the model to match the observed SMF at redshift z> 2, and let it evolve down to the present time according to the observed SFR-M * relation. In this study, we use two different sets of SMFs and two SFR-M * relations: a simple power law and a relation with a mass-dependent slope. Our analysis shows that the evolution of the SMF is more consistent with an SFR-M * relation with a mass-dependent slope, in agreement with predictions from other models of galaxy evolution and recent observations. In order to fully and realistically describe the evolution of the SMF, both mergers and stellar stripping must be considered, and we find that both have almost equal effects on the evolution of SMF at the massive end. Taking into account the systematic uncertainties in the observed data, the high-mass end of the SMF obtained by considering stellar stripping results in good agreement with recent observational data from the Sloan Digital Sky Survey. At {log} {M}* < 11.2, our prediction at z = 0.1 is close to Li & White data, but the high-mass end ({log} {M}* > 11.2) is in better agreement with D’Souza et al. data which account for more massive galaxies.

  1. Star Formation and Stellar Evolution: Future Surveys and Instrumentation

    NASA Astrophysics Data System (ADS)

    Evans, C. J.

    2016-10-01

    The next generation of multi-object spectrographs (MOS) will deliver comprehensive surveys of the Galaxy, Magellanic Clouds and nearby dwarfs. These will provide us with the vast samples, spanning the full extent of the Hertzsprung-Russell diagram, that are needed to explore the chemistry, history and dynamics of their host systems. Further ahead, the Extremely Large Telescopes (ELTs) will have sufficient sensitivity and angular resolution to extend stellar spectroscopy well beyond the Local Group, opening-up studies of the chemical evolution of galaxies across a broad range of galaxy types and environments. In this contribution I briefly reflect on current and future studies of stellar populations, and introduce plans for the MOSAIC instrument for the European ELT.

  2. The importance of stellar feedback for high-redshift galaxy populations in hierarchical formation models

    NASA Astrophysics Data System (ADS)

    Hirschmann, Michaela; De Lucia, Gabriella

    2015-08-01

    One major deficiency of most state-of-the-art galaxy formation models consists in their inability of capturing the observed galaxy downsizing trend as they significantly over-estimate the number density of low-mass galaxies at high redshifts. This points towards fundamental modifications in modeling the interplay between star formation and stellar feedback. Employing an enhanced galaxy formation model with a full chemical enrichment scheme, we present an improved model for stellar feedback (based on parametrizations extracted from cosmological zoom simulations), in which strong gas outflows happen due to bursty star formation at high redshift, while star formation is mainly "quiescent" not causing any significant outflows anymore at low redshift. Due to the stronger gas outflows at high z, early star formation is strongly delayed towards later times in good agreement with abundance matching predictions. As a consequence, also metal enrichment gets significantly delayed, resulting in a much more realistic redshift evolution of the gaseous metallicity. Overall, with our new stellar feedback model, we can successfully reproduce many observational constraints, such as the redshift evolution of the stellar mass function and of the SFR function, the gaseous and stellar metallicity content, the cold gas fractions and the fraction of quiescent/red galaxies at both low and high redshifts. The resulting new-generation galaxy catalogues based on that model are expected to significantly contribute to the interpretation of current and up-coming large-scale surveys (HST, JWST, Euclid) which in turn may also help to further constrain feedback models.

  3. Testing the Formation Mechanism of Sub-Stellar Objects in Lupus (A SOLA Team Study)

    NASA Astrophysics Data System (ADS)

    De Gregorio-Monsalvo, Itziar; Lopez, C.; Takahashi, S.; Santamaria-Miranda

    2017-06-01

    The international SOLA team (Soul of Lupus with ALMA) has identified a set of pre- and proto-stellar candidates in Lupus 1 and 3 of substellar nature using 1.1mm ASTE/AzTEC maps and our optical to submillimeter database. We have observed with ALMA the most promising pre- and proto-brown dwarfs candidates. Our aims are to provide insights on how substellar objects form and evolve, from the equivalent to the pre-stellar cores to the Class II stage in the low mass regime of star formation. Our sample comprises 33 pre-stellar objects, 7 Class 0 and I objects, and 22 Class II objects.

  4. The Stellar Population and Star Formation Properties of Blue Compact Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Zhao, Yinghe; Gu, Qiusheng; Gao, Yu

    2011-02-01

    We study stellar populations, star formation histories (SFHs), and star formation properties for a sample of blue compact dwarf galaxies (BCDs) selected by cross-correlating the Gil de Paz et al. sample with the Sloan Digital Sky Survey Data Release 6. The sample includes 31 BCDs, which span a large range of galactic parameters. Using a stellar population synthesis method, we derive stellar populations and reconstruct SFHs for these BCDs. Our studies confirm that BCDs are not young systems experiencing their first star formation, but old systems undergoing a starburst activity. The stellar mass-weighted ages can be up to 10 Gyr, while the luminosity-weighted ages might be up to approximately three orders of magnitude younger (~10 Myr) for most galaxies. Based on multiwavelength data, we also study the integrated star formation properties. The star formation rate (SFR) for our sample galaxies spans nearly three orders of magnitude, from a few 10-3 to ~1 M sun yr-1, with a median value of ~0.1 M sun yr-1. We find that about 90% of BCDs in our sample have their birthrate parameter (the ratio of the current SFR to the averaged past SFR) b>2-3. We further discuss correlations of the current SFR with the integrated galactic stellar mass and explore the connection between SFR and metallicity.

  5. On the Formation of Hot Jupiters in Stellar Binaries

    NASA Astrophysics Data System (ADS)

    Naoz, Smadar; Farr, Will M.; Rasio, Frederic A.

    2012-08-01

    We study the production of hot Jupiters (HJs) in stellar binaries. We show that the "eccentric Kozai-Lidov" (EKL) mechanism can play a key role in the dynamical evolution of a star-planet-star triple system. We run a large set of Monte Carlo simulations including the secular evolution of the orbits, general relativistic precession, and tides, and we determine the semimajor axis, eccentricity, inclination, and spin-orbit angle distributions of the HJs that are produced. We explore the effect of different tidal friction parameters on the results. We find that the efficiency of forming HJs when taking the EKL mechanism into account is higher then previously estimated. Accounting for the frequency of stellar binaries, we find that this production mechanism can account for about 30% of the observed HJ population. Current observations of spin-orbit angles are consistent with this mechanism producing ~30% of all HJs, and up to 100% of the misaligned systems. Based on the properties of binaries without an HJ in our simulations, we predict the existence of many Jupiter-like planets with moderately eccentric and inclined orbits and semimajor axes of several AU.

  6. ON THE FORMATION OF HOT JUPITERS IN STELLAR BINARIES

    SciTech Connect

    Naoz, Smadar; Farr, Will M.; Rasio, Frederic A.

    2012-08-01

    We study the production of hot Jupiters (HJs) in stellar binaries. We show that the 'eccentric Kozai-Lidov' (EKL) mechanism can play a key role in the dynamical evolution of a star-planet-star triple system. We run a large set of Monte Carlo simulations including the secular evolution of the orbits, general relativistic precession, and tides, and we determine the semimajor axis, eccentricity, inclination, and spin-orbit angle distributions of the HJs that are produced. We explore the effect of different tidal friction parameters on the results. We find that the efficiency of forming HJs when taking the EKL mechanism into account is higher then previously estimated. Accounting for the frequency of stellar binaries, we find that this production mechanism can account for about 30% of the observed HJ population. Current observations of spin-orbit angles are consistent with this mechanism producing {approx}30% of all HJs, and up to 100% of the misaligned systems. Based on the properties of binaries without an HJ in our simulations, we predict the existence of many Jupiter-like planets with moderately eccentric and inclined orbits and semimajor axes of several AU.

  7. Axion dark matter, solitons and the cusp-core problem

    NASA Astrophysics Data System (ADS)

    Marsh, David J. E.; Pop, Ana-Roxana

    2015-08-01

    Self-gravitating bosonic fields can support stable and localized (solitonic) field configurations. Such solitons should be ubiquitous in models of axion dark matter, with their characteristic mass and size depending on some inverse power of the axion mass, ma. Using a scaling symmetry and the uncertainty principle, the soliton core size can be related to the central density and axion mass in a universal way. Solitons have a constant central density due to pressure support, unlike the cuspy profile of cold dark matter (CDM). Consequently, solitons composed of ultralight axions (ULAs) may resolve the `cusp-core' problem of CDM. In dark matter (DM) haloes, thermodynamics will lead to a CDM-like Navarro-Frenk-White (NFW) profile at large radii, with a central soliton core at small radii. Using Monte Carlo techniques to explore the possible density profiles of this form, a fit to stellar kinematical data of dwarf spheroidal galaxies is performed. The data favour cores, and show no preference concerning the NFW part of the halo. In order for ULAs to resolve the cusp-core problem (without recourse to baryon feedback, or other astrophysical effects) the axion mass must satisfy ma < 1.1 × 10-22 eV at 95 per cent C.L. However, ULAs with ma ≲ 1 × 10-22 eV are in some tension with cosmological structure formation. An axion solution to the cusp-core problem thus makes novel predictions for future measurements of the epoch of reionization. On the other hand, improved measurements of structure formation could soon impose a Catch 22 on axion/scalar field DM, similar to the case of warm DM.

  8. The star-formation history of the Universe from the stellar populations of nearby galaxies.

    PubMed

    Heavens, Alan; Panter, Benjamin; Jimenez, Raul; Dunlop, James

    2004-04-08

    The determination of the star-formation history of the Universe is a key goal of modern cosmology, as it is crucial to our understanding of how galactic structures form and evolve. Observations of young stars in distant galaxies at different times in the past have indicated that the stellar birthrate peaked some eight billion years ago before declining by a factor of around ten to its present value. Here we report an analysis of the 'fossil record' of the current stellar populations of 96,545 nearby galaxies, from which we obtained a complete star-formation history. Our results broadly support those derived from high-redshift galaxies. We find, however, that the peak of star formation was more recent--around five billion years ago. We also show that the bigger the stellar mass of the galaxy, the earlier the stars were formed, which indicates that high- and low-mass galaxies have very different histories.

  9. The formation of stellar systems from interstellar molecular clouds.

    PubMed

    Gehrz, R D; Black, D C; Solomon, P M

    1984-05-25

    Star formation, a crucial link in the chain of events that led from the early expansion of the universe to the formation of the solar system, continues to play a major role in the evolution of many galaxies. Observational and theoretical studies of regions of ongoing star formation provide insight into the physical conditions and events that must have attended the formation of the solar system. Such investigations also elucidate the role played by star formation in the evolutionary cycle which appears to dominate the chemical processing of interstellar material by successive generations of stars in spiral galaxies like our own. New astronomical facilities planned for development during the 1980's could lead to significant advances in our understanding of the star formation process. Efforts to identify and examine both the elusive protostellar collapse phase of star formation and planetary systems around nearby stars will be especially significant.

  10. Mapping the star formation history of Mrk 86. II. Stellar populations and global interpretation

    NASA Astrophysics Data System (ADS)

    Gil de Paz, A.; Zamorano, J.; Gallego, J.

    2000-09-01

    In this paper, continuation of Gil de Paz et al. (Paper I), we derive the main properties of the stellar populations in the Blue Compact Dwarf galaxy Mrk 86. Ages, stellar masses, metallicites and burst strengths have been obtained using the combination of Monte Carlo simulations, a maximum likelihood estimator and Cluster and Principal Component Analysis. The three stellar populations detected show well defined properties. We have studied the underlying stellar population, which shows an age between 5-13 Gyr and no significant color gradients. The intermediate aged (30 Myr old) central starburst show a very low dust extinction with high burst strength and high stellar mass content ( ~ 9x106 Msun). Finally, the properties of 46 low-metallicity ( ~ 1/10 Zsun ) star-forming regions were also studied. The properties derived suggest that the most recent star-forming activity in Mrk 86 was triggered by the evolution of a superbubble originated at the central starburst by the energy deposition of stellar winds and supernova explosions. This superbubble produced the blowout of a fraction of the interstellar medium at distances of about 1 kpc with high gas surface densities, leading to the activation of the star formation. Finally, different mechanisms for the star formation triggering in this massive central starburst are studied, including the merging with a low mass companion and the interaction with UGC 4278. We have assumed a distance to Mrk 86 of 6.9 Mpc.

  11. Opening the cusp

    SciTech Connect

    Crooker, N.U. ); Toffoletto, F.R. ); Gussenhoven, M.S. )

    1991-03-01

    Defining the equatorward boundary of the cusp region in the ionosphere as the projection of the merging line from the magnetopause, the authors use a quantitative, geometrically realistic model to show how the local time span of the cusp increases with increasing merging rate for southward interplanetary magnetic field. Since the merging rate is fixed by the magnitude of the magnetic field component normal to the model magnetopause and then normalized to the cross-polar-cap potential, the result gives the variation of cusp local time span as a function of potential. From 0 kV up to 60 kV, the cusp expands from a point at noon to 2 hours on either side. Nearly tripling the voltage to 170 kV adds one more hour to each side, yielding a span from 0900 to 1500 LT. As an example of broad local time span during magnetically active periods, they present spacecraft observations of cusp particles during the grat storm of March 1989 that cover more than 8 hours of local time. An important aspect of the result is the demonstration that a merging line of fixed length on the magnetopause, as assumed in the model, maps to a projected length in the ionosphere that increases as the funnel-shaped cusp opens. This behavior contrasts with earlier models that have cleft rather than cusp geometry, where the projected merging line length is proportional only to its length on the magnetopause. The model results are used to construct the footprint of a flux transfer event by time variations of the merging rate, uniform along the length of the merging line. The cusp geometry distorts the field lines mapped from the magnetopause to yield footprints with dawn and dusk protrusions into the region of closed magnetic flux.

  12. A new methodology to test galaxy formation models using the dependence of clustering on stellar mass

    NASA Astrophysics Data System (ADS)

    Campbell, David J. R.; Baugh, Carlton M.; Mitchell, Peter D.; Helly, John C.; Gonzalez-Perez, Violeta; Lacey, Cedric G.; Lagos, Claudia del P.; Simha, Vimal; Farrow, Daniel J.

    2015-09-01

    We present predictions for the two-point correlation function of galaxy clustering as a function of stellar mass, computed using two new versions of the GALFORM semi-analytic galaxy formation model. These models make use of a high resolution, large volume N-body simulation, set in the 7-year Wilkinson Microwave Anisotropy Probe cosmology. One model uses a universal stellar initial mass function (IMF), while the other assumes different IMFs for quiescent star formation and bursts. Particular consideration is given to how the assumptions required to estimate the stellar masses of observed galaxies (such as the choice of IMF, stellar population synthesis model, and dust extinction) influence the perceived dependence of galaxy clustering on stellar mass. Broad-band spectral energy distribution fitting is carried out to estimate stellar masses for the model galaxies in the same manner as in observational studies. We show clear differences between the clustering signals computed using the true and estimated model stellar masses. As such, we highlight the importance of applying our methodology to compare theoretical models to observations. We introduce an alternative scheme for the calculation of the merger time-scales for satellite galaxies in GALFORM, which takes into account the dark matter subhalo information from the simulation. This reduces the amplitude of small-scale clustering. The new merger scheme offers improved or similar agreement with observational clustering measurements, over the redshift range 0 < z < 0.7. We find reasonable agreement with clustering measurements from the Galaxy and Mass Assembly Survey, but find larger discrepancies for some stellar mass ranges and separation scales with respect to measurements from the Sloan Digital Sky Survey and the VIMOS Public Extragalactic Redshift Survey, depending on the GALFORM model used.

  13. Galaxies on FIRE (Feedback In Realistic Environments): stellar feedback explains cosmologically inefficient star formation

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Kereš, Dušan; Oñorbe, José; Faucher-Giguère, Claude-André; Quataert, Eliot; Murray, Norman; Bullock, James S.

    2014-11-01

    We present a series of high-resolution cosmological simulations1 of galaxy formation to z = 0, spanning halo masses ˜108-1013 M⊙, and stellar masses ˜104-1011 M⊙. Our simulations include fully explicit treatment of the multiphase interstellar medium and stellar feedback. The stellar feedback inputs (energy, momentum, mass, and metal fluxes) are taken directly from stellar population models. These sources of feedback, with zero adjusted parameters, reproduce the observed relation between stellar and halo mass up to Mhalo ˜ 1012 M⊙. We predict weak redshift evolution in the M*-Mhalo relation, consistent with current constraints to z > 6. We find that the M*-Mhalo relation is insensitive to numerical details, but is sensitive to feedback physics. Simulations with only supernova feedback fail to reproduce observed stellar masses, particularly in dwarf and high-redshift galaxies: radiative feedback (photoheating and radiation pressure) is necessary to destroy giant molecular clouds and enable efficient coupling of later supernovae to the gas. Star formation rates (SFRs) agree well with the observed Kennicutt relation at all redshifts. The galaxy-averaged Kennicutt relation is very different from the numerically imposed law for converting gas into stars, and is determined by self-regulation via stellar feedback. Feedback reduces SFRs and produces reservoirs of gas that lead to rising late-time star formation histories, significantly different from halo accretion histories. Feedback also produces large short-time-scale variability in galactic SFRs, especially in dwarfs. These properties are not captured by common `sub-grid' wind models.

  14. The stellar masses and specific star-formation rates of submillimetre galaxies

    NASA Astrophysics Data System (ADS)

    Michałowski, M. J.; Dunlop, J. S.; Cirasuolo, M.; Hjorth, J.; Hayward, C. C.; Watson, D.

    2012-05-01

    Establishing the stellar masses, and hence specific star-formation rates of submillimetre galaxies is crucial for determining the role of such objects in the cosmic history of galaxy/star formation. However, there is as yet no consensus over the typical stellar masses of submillimetre galaxies, as illustrated by the widely differing results reported from recent optical-infrared studies of submillimetre galaxies with spectroscopic redshifts z ≃ 2-3. Specifically, even for the same set of submillimetre galaxies, the reported average stellar masses have ranged over an order of magnitude, from ≃5 × 1010 M⊙ to ≃5 × 1011 M⊙. Here we study how different methods of analysis can lead to such widely varying results. We find that, contrary to recent claims in the literature, potential contamination of IRAC 3-8 μm photometry from hot dust associated with an active nucleus is not the origin of the published discrepancies in derived stellar masses. Instead, we expose in detail how inferred stellar mass depends on assumptions made in the photometric fitting, and quantify the individual and cumulative effects of different choices of initial mass function, different "brands" of evolutionary synthesis models, and different forms of assumed star-formation history. We review current observational evidence for and against these alternatives as well as clues from the hydrodynamical simulations, and conclude that, for the most justifiable choices of these model inputs, the average stellar mass of luminous (S850 ≳ 5 mJy) submillimetre galaxies is ≃2 × 1011 M⊙ to within a factor ≃2. We also check and confirm that this number is perfectly reasonable in the light of the latest measurements of the dynamical masses of these objects (≃2-6 × 1011 M⊙ from CO (1-0) observations), and the evolving stellar mass function of the overall galaxy population. Galaxy stellar masses of this order imply that the average specific star-formation rate of submillimetre galaxies is

  15. Shock Dynamics in Stellar Outbursts. I. Shock Formation

    NASA Astrophysics Data System (ADS)

    Ro, Stephen; Matzner, Christopher D.

    2017-05-01

    Wave-driven outflows and non-disruptive explosions have been implicated in pre-supernova outbursts, supernova impostors, luminous blue variable eruptions, and some narrow-line and superluminous supernovae. To model these events, we investigate the dynamics of stars set in motion by strong acoustic pulses and wave trains, focusing on nonlinear wave propagation, shock formation, and an early phase of the development of a weak shock. We identify the shock formation radius, showing that a heuristic estimate based on crossing characteristics matches an exact expansion around the wave front and verifying both with numerical experiments. Our general analytical condition for shock formation applies to one-dimensional motions within any static environment, including both eruptions and implosions. We also consider the early phase of shock energy dissipation. We find that waves of super-Eddington acoustic luminosity always create shocks, rather than damping by radiative diffusion. Therefore, shock formation is integral to super-Eddington outbursts.

  16. Binary interactions as a possible scenario for the formation of multiple stellar populations in globular clusters

    SciTech Connect

    Jiang, Dengkai; Han, Zhanwen; Li, Lifang E-mail: zhanwenhan@ynao.ac.cn

    2014-07-01

    Observations have revealed the presence of multiple stellar populations in globular clusters (GCs) that exhibit wide abundance variations and multiple sequences in the Hertzsprung-Russell (HR) diagram. We present a scenario for the formation of multiple stellar populations in GCs. In this scenario, initial GCs are single-generation clusters, and our model predicts that the stars with anomalous abundances observed in GCs are merged stars and accretor stars produced by binary interactions—rapidly rotating stars at the moment of their formation—and that these stars are more massive than normal single stars in the same evolutionary stage. We find that, due to their own evolution, these rapidly rotating stars have surface abundances, effective temperatures, and luminosities that are different from normal single stars in the same evolutionary stage. This stellar population of binaries reproduces two important points of observational evidence of multiple stellar populations: a Na-O anticorrelation and multiple sequences in the HR diagram. This evidence suggests that binary interactions may be a possible scenario for the formation of multiple stellar populations in GCs.

  17. Effects of binary stellar populations on direct collapse black hole formation

    NASA Astrophysics Data System (ADS)

    Agarwal, Bhaskar; Cullen, Fergus; Khochfar, Sadegh; Klessen, Ralf S.; Glover, Simon C. O.; Johnson, Jarrett

    2017-06-01

    The critical Lyman-Werner (LW) flux required for direct collapse blackholes (DCBH) formation, or Jcrit, depends on the shape of the irradiating spectral energy distribution (SED). The SEDs employed thus far have been representative of realistic single stellar populations. We study the effect of binary stellar populations on the formation of DCBH, as a result of their contribution to the LW radiation field. Although binary populations with ages > 10 Myr yield a larger LW photon output, we find that the corresponding values of Jcrit can be up to 100 times higher than single stellar populations. We attribute this to the shape of the binary SEDs as they produce a sub-critical rate of H- photodetaching 0.76 eV photons as compared to single stellar populations, reaffirming the role that H- plays in DCBH formation. This further corroborates the idea that DCBH formation is better understood in terms of a critical region in the H2-H- photodestruction rate parameter space, rather than a single value of LW flux.

  18. Equatorial disk formation around rotating stars due to ram pressure confinement by the stellar wind

    NASA Technical Reports Server (NTRS)

    Bjorkman, J. E.; Cassinelli, J. P.

    1993-01-01

    The axisymmetric 2D supersonic solution of a rotating, radiation-driven stellar wind presently obtained by a simple approximation predicts the formation of a dense equatorial disk, when the star's rotation rate lies above a threshold value that depends on the ratio of the wind's terminal speed to the escape speed of the star. The disk is formed because the trajectories of the wind leaving the stellar surface at high latitudes carry it down to the equatorial plane; there, the material passes through a standing oblique shock atop the disk; it is therefore the ram pressure of the polar wind that compresses and confines the disk.

  19. TOWARD A COMPLETE ACCOUNTING OF ENERGY AND MOMENTUM FROM STELLAR FEEDBACK IN GALAXY FORMATION SIMULATIONS

    SciTech Connect

    Agertz, Oscar; Kravtsov, Andrey V.; Leitner, Samuel N.; Gnedin, Nickolay Y.

    2013-06-10

    We investigate the momentum and energy budget of stellar feedback during different stages of stellar evolution, and study its impact on the interstellar medium (ISM) using simulations of local star-forming regions and galactic disks at the resolution affordable in modern cosmological zoom-in simulations. In particular, we present a novel subgrid model for the momentum injection due to radiation pressure and stellar winds from massive stars during early, pre-supernova (pre-SN) evolutionary stages of young star clusters. Early injection of momentum acts to clear out dense gas in star-forming regions, hence limiting star formation. The reduced gas density mitigates radiative losses of thermal feedback energy from subsequent SN explosions. The detailed impact of stellar feedback depends sensitively on the implementation and choice of parameters. Somewhat encouragingly, we find that implementations in which feedback is efficient lead to approximate self-regulation of the global star formation efficiency. We compare simulation results using our feedback implementation to other phenomenological feedback methods, where thermal feedback energy is allowed to dissipate over timescales longer than the formal gas cooling time. We find that simulations with maximal momentum injection suppress star formation to a similar degree as is found in simulations adopting adiabatic thermal feedback. However, different feedback schemes are found to produce significant differences in the density and thermodynamic structure of the ISM, and are hence expected to have a qualitatively different impact on galaxy evolution.

  20. Stellar Dynamical Processes in Massive Star and Star Cluster Formation

    NASA Astrophysics Data System (ADS)

    Tan, Jonathan; Eyer, L.

    2009-01-01

    We study how high precision astrometric measurements by SIM and GAIA of stars involved in dynamical ejection events from star clusters can constrain theories of massive star and star cluster formation. We focus on the Orion Nebula Cluster (ONC). First, we investigate the scientific potential associated with an accurate measurement of the distance and proper motion of Theta 1 Ori C, which is the most massive star in the cluster and was recently involved (about 4000 years ago) in the ejection of a B star: the Becklin-Neugebauer (BN) star. The motion of the BN star has taken it close to a massive protostar, known as source I, where it appears to have influenced the accretion and outflow activity, most likely by a tidal interaction with the accretion disk. An accurate proper motion measurement of Theta 1 Ori C will constrain BN's initial motion, allowing us to search for deflections caused by the gravitational potential of the massive protostar. Second, we search the Hipparcos catalog for candidate runaway stars, i.e. that have been dynamically ejected from the cluster over the course of the last several Myr. SIM and GAIA observations of these stars will be needed to confirm their origin from the ONC. The results of this study will constrain the star cluster formation timescale and the statistics of the population of ejected stars. JCT acknowledges support from from NSF CAREER grant AST-0645412 and a grant from NASA for SIM Science Studies.

  1. Formation of new stellar populations from gas accreted by massive young star clusters.

    PubMed

    Li, Chengyuan; de Grijs, Richard; Deng, Licai; Geller, Aaron M; Xin, Yu; Hu, Yi; Faucher-Giguère, Claude-André

    2016-01-28

    Stars in clusters are thought to form in a single burst from a common progenitor cloud of molecular gas. However, massive, old 'globular' clusters--those with ages greater than ten billion years and masses several hundred thousand times that of the Sun--often harbour multiple stellar populations, indicating that more than one star-forming event occurred during their lifetimes. Colliding stellar winds from late-stage, asymptotic-giant-branch stars are often suggested to be triggers of second-generation star formation. For this to occur, the initial cluster masses need to be greater than a few million solar masses. Here we report observations of three massive relatively young star clusters (1-2 billion years old) in the Magellanic Clouds that show clear evidence of burst-like star formation that occurred a few hundred million years after their initial formation era. We show that such clusters could have accreted sufficient gas to form new stars if they had orbited in their host galaxies' gaseous disks throughout the period between their initial formation and the more recent bursts of star formation. This process may eventually give rise to the ubiquitous multiple stellar populations in globular clusters.

  2. STAR FORMATION IN DISK GALAXIES. III. DOES STELLAR FEEDBACK RESULT IN CLOUD DEATH?

    SciTech Connect

    Tasker, Elizabeth J.; Wadsley, James; Pudritz, Ralph

    2015-03-01

    Stellar feedback, star formation, and gravitational interactions are major controlling forces in the evolution of giant molecular clouds (GMCs). To explore their relative roles, we examine the properties and evolution of GMCs forming in an isolated galactic disk simulation that includes both localized thermal feedback and photoelectric heating. The results are compared with the three previous simulations in this series, which consists of a model with no star formation, star formation but no form of feedback, and star formation with photoelectric heating in a set with steadily increasing physical effects. We find that the addition of localized thermal feedback greatly suppresses star formation but does not destroy the surrounding GMC, giving cloud properties closely resembling the run in which no stellar physics is included. The outflows from the feedback reduce the mass of the cloud but do not destroy it, allowing the cloud to survive its stellar children. This suggests that weak thermal feedback such as the lower bound expected for a supernova may play a relatively minor role in the galactic structure of quiescent Milky-Way-type galaxies, compared to gravitational interactions and disk shear.

  3. Star Formation in Disk Galaxies. III. Does Stellar Feedback Result in Cloud Death?

    NASA Astrophysics Data System (ADS)

    Tasker, Elizabeth J.; Wadsley, James; Pudritz, Ralph

    2015-03-01

    Stellar feedback, star formation, and gravitational interactions are major controlling forces in the evolution of giant molecular clouds (GMCs). To explore their relative roles, we examine the properties and evolution of GMCs forming in an isolated galactic disk simulation that includes both localized thermal feedback and photoelectric heating. The results are compared with the three previous simulations in this series, which consists of a model with no star formation, star formation but no form of feedback, and star formation with photoelectric heating in a set with steadily increasing physical effects. We find that the addition of localized thermal feedback greatly suppresses star formation but does not destroy the surrounding GMC, giving cloud properties closely resembling the run in which no stellar physics is included. The outflows from the feedback reduce the mass of the cloud but do not destroy it, allowing the cloud to survive its stellar children. This suggests that weak thermal feedback such as the lower bound expected for a supernova may play a relatively minor role in the galactic structure of quiescent Milky-Way-type galaxies, compared to gravitational interactions and disk shear.

  4. Self-Consistent Magnetohydrodynamic Modeling of a Coronal Mass Ejection, Coronal Dimming, and a Giant Cusp-shaped Arcade Formation

    NASA Astrophysics Data System (ADS)

    Shiota, Daikou; Isobe, Hiroaki; Chen, P. F.; Yamamoto, Tetsuya T.; Sakajiri, Takuma; Shibata, Kazunari

    2005-11-01

    We performed magnetohydrodynamic simulations of coronal mass ejections (CMEs) and associated giant arcade formations, and the results suggest new interpretations of observations of CMEs. We performed two cases of the simulation: with and without heat conduction. Comparing between the results of the two cases, we found that the reconnection rate in the conductive case is a little higher than that in the adiabatic case and that the temperature of the loop top is consistent with the theoretical value predicted by the Yokoyama-Shibata scaling law. The dynamical properties such as velocity and magnetic field are similar in the two cases, whereas thermal properties such as temperature and density are very different. In both cases, slow shocks associated with magnetic reconnection propagate from the reconnection region along the magnetic field lines around the flux rope, and the shock fronts form spiral patterns. Just outside the slow shocks, the plasma density decreases greatly. The soft X-ray images synthesized from the numerical results are compared with the soft X-ray images of a giant arcade observed with the Soft X-Ray Telescope aboard Yohkoh; it is confirmed that the effect of heat conduction is significant for the detailed comparison between simulation and observation. The comparison between synthesized and observed soft X-ray images provides new interpretations of various features associated with CMEs and giant arcades. (1) It is likely that the Y-shaped ejecting structure, observed in the giant arcade on 1992 January 24, corresponds to slow and fast shocks associated with magnetic reconnection. (2) Soft X-ray twin dimming corresponds to the rarefaction induced by reconnection. (3) The inner boundary of the dimming region corresponds to the slow shocks. (4) The ``three-part structure'' of a CME can be explained by our numerical results. (5) The numerical results also suggest that a backbone feature of a flare/giant arcade may correspond to the fast shock formed

  5. Formation and survival of Population III stellar systems

    NASA Astrophysics Data System (ADS)

    Hirano, Shingo; Bromm, Volker

    2017-09-01

    The initial mass function of the first, Population III (Pop III), stars plays a vital role in shaping galaxy formation and evolution in the early Universe. One key remaining issue is the final fate of secondary protostars formed in the accretion disc, specifically whether they merge or survive. We perform a suite of hydrodynamic simulations of the complex interplay among fragmentation, protostellar accretion and merging inside dark matter minihaloes. Instead of the traditional sink particle method, we employ a stiff equation of state approach, so that we can more robustly ascertain the viscous transport inside the disc. The simulations show inside-out fragmentation because the gas collapses faster in the central region. Fragments migrate on the viscous time-scale, over which angular momentum is lost, enabling them to move towards the disc centre, where merging with the primary protostar can occur. This process depends on the fragmentation scale, such that there is a maximum scale of (1-5) × 104 au, inside which fragments can migrate to the primary protostar. Viscous transport is active until radiative feedback from the primary protostar destroys the accretion disc. The final mass spectrum and multiplicity thus crucially depends on the effect of viscosity in the disc. The entire disc is subjected to efficient viscous transport in the primordial case with viscous parameter α ≤ 1. An important aspect of this question is the survival probability of Pop III binary systems, possible gravitational wave sources to be probed with the Advanced LIGO detectors.

  6. Matching the Evolution of the Stellar Mass Function Using Log-Normal Star Formation Histories

    NASA Astrophysics Data System (ADS)

    Abramson, Louis E.; Gladders, Michael D.; Dressler, Alan; Oemler, Augustus, Jr.; Poggianti, Bianca; Vulcani, Benedetta

    2015-03-01

    We show that a model consisting of individual, log-normal star formation histories for a volume-limited sample of z ≈ 0 galaxies reproduces the evolution of the total and quiescent stellar mass functions at z ≲ 2.5 and stellar masses {{M}*}≥slant {{10}10} {{M}⊙ }. This model has previously been shown to reproduce the star formation rate/stellar mass relation (SFR-{{M}*}) over the same interval, is fully consistent with the observed evolution of the cosmic SFR density at z≤slant 8, and entails no explicit “quenching” prescription. We interpret these results/features in the context of other models demonstrating a similar ability to reproduce the evolution of (1) the cosmic SFR density, (2) the total/quiescent stellar mass functions, and (3) the SFR-{{M}*} relation, proposing that the key difference between modeling approaches is the extent to which they stress/address diversity in the (star-forming) galaxy population. Finally, we suggest that observations revealing the timescale associated with dispersion in SFR({{M}*}) will help establish which models are the most relevant to galaxy evolution.

  7. Bimodal regime in young massive clusters leading to formation of subsequent stellar generations

    NASA Astrophysics Data System (ADS)

    Wunsch, Richard; Palous, Jan; Tenorio-Tagle, Guillermo; Munoz-Tunon, Casiana; Ehlerova, Sona

    2015-08-01

    Massive stars in young massive clusters insert tremendous amounts of mass and energy into their surroundings in the form of stellar winds and supernova ejecta. Mutual shock-shock collisions lead to formation of hot gas, filling the volume of the cluster. The pressure of this gas then drives a powerful cluster wind. However, it has been shown that if the cluster is massive and dense enough, it can evolve in the so called bimodal regime, in which the hot gas inside the cluster becomes thermally unstable and forms dense clumps which are trapped inside the cluster by its gravity.We will review works on the bimodal regime and discuss the implications for the formation of subsequent stellar generations. The mass accumulates inside the cluster and as soon as a high enough column density is reached, the interior of the clumps becomes self-shielded against the ionising radiation of, stars and the clumps collapse and form new stars. The second stellar generation will be enriched by products of the stellar evolution of the first generation, and will be concentrated near the cluster center.

  8. The dynamic cusp

    SciTech Connect

    Potemra, T.A.; Erlandson, R.E.; Zanetti, L.J. ); Arnoldy, R.L. ); Woch, J. ); Friis-Christensen, E. )

    1992-03-01

    A unique alignment of the Viking satellite with respect to a network of magnetometers in Greenland has provided the opportunity to study the relationship of pulsations and plasma characteristics in the dayside cusp. The presence of Pc 1 bursts, Pc 4-5 pulsations, and a tailward traveling twin vortex pattern of ionospheric convection suggests that the magnetosphere may have been temporarily compressed. Magnetic field data acquired at synchrotrons altitude from GOES 5 and on the ground from Huancayo support this suggestion. Plasma with ion dispersion characteristics associated with a cusp during southward IMF was detected by Viking over a 3.5{degree} range of latitude. The presence of standing Alfven waves and ring current ions suggest that this cusplike plasma was observed on closed geomagnetic field lines. As Viking moved further poleward, it detected a different region of plasma with characteristics associated with a cusp during northward IMF. The presence of plasma on closed field lines with southward IMF ion dispersion characteristics can be explained with a poleward moving plasma source. The authors suggest that the magnetosphere, during a northward IMF, is temporarily compressed by a solar wind pressure enhancement that produces the Pc 1 bursts, Pc 4-5 pulsations, and ionospheric vortices. As the magnetosphere recovers to its precompressed shape, the source of cusp plasma will move poleward until it reaches an equilibrium position for northward IMF. The Viking satellite, following in the wake of this source, will detect plasma with southward IMF characteristics until it reaches the latitude of the actual northward IMF cusp.

  9. Galaxy formation in the Planck cosmology - I. Matching the observed evolution of star formation rates, colours and stellar masses

    NASA Astrophysics Data System (ADS)

    Henriques, Bruno M. B.; White, Simon D. M.; Thomas, Peter A.; Angulo, Raul; Guo, Qi; Lemson, Gerard; Springel, Volker; Overzier, Roderik

    2015-08-01

    We have updated the Munich galaxy formation model to the Planck first-year cosmology, while modifying the treatment of baryonic processes to reproduce recent data on the abundance and passive fractions of galaxies from z = 3 down to z = 0. Matching these more extensive and more precise observational results requires us to delay the reincorporation of wind ejecta, to lower the surface density threshold for turning cold gas into stars, to eliminate ram-pressure stripping in haloes less massive than {˜ }10^{14}{ M_{⊙}}, and to modify our model for radio mode feedback. These changes cure the most obvious failings of our previous models, namely the overly early formation of low-mass galaxies and the overly large fraction of them that are passive at late times. The new model is calibrated to reproduce the observed evolution both of the stellar mass function and of the distribution of star formation rate at each stellar mass. Massive galaxies (log M⋆/M⊙ ≥ 11.0) assemble most of their mass before z = 1 and are predominantly old and passive at z = 0, while lower mass galaxies assemble later and, for log M⋆/M⊙ ≤ 9.5, are still predominantly blue and star forming at z = 0. This phenomenological but physically based model allows the observations to be interpreted in terms of the efficiency of the various processes that control the formation and evolution of galaxies as a function of their stellar mass, gas content, environment and time.

  10. THE AGE, STELLAR CONTENT, AND STAR FORMATION TIMESCALE OF THE B59 DENSE CORE

    SciTech Connect

    Covey, K. R.; Lada, C. J.; Muench, A. A.; Forbrich, J.; Ascenso, J.; Roman-Zuniga, C.

    2010-10-20

    We have investigated the stellar content of Barnard 59 (B59), the most active star-forming core in the Pipe Nebula. Using the SpeX spectrograph on the NASA Infrared Telescope Facility, we obtained moderate resolution, near-infrared (NIR) spectra for 20 candidate young stellar objects (YSOs) in B59 and a representative sample of NIR and mid-IR bright sources distributed throughout the Pipe. Measuring luminosity and temperature sensitive features in these spectra, we identified likely background giant stars and measured each star's spectral type, extinction, and NIR continuum excess. To measure B59's age, we place its candidate YSOs in the Hertzsprung-Russell diagram and compare their location to YSOs in several well-studied star-forming regions, as well as predictions of pre-main-sequence (PMS) evolutionary models. We find that B59 is composed of late-type (K4-M6) low-mass (0.9-0.1 M{sub sun}) YSOs whose median stellar age is comparable to, if not slightly older than, that of YSOs within the {rho} Oph, Taurus, and Chameleon star-forming regions. Deriving absolute age estimates from PMS models computed by D'Antona et al., and accounting only for statistical uncertainties, we measure B59's median stellar age to be 2.6 {+-} 0.8 Myr. Including potential systematic effects increases the error budget for B59's median (DM98) stellar age to 2.6{sup +4.1}{sub -2.6} Myr. We also find that the relative age orderings implied by PMS evolutionary tracks depend on the range of stellar masses sampled, as model isochrones possess significantly different mass dependences. The maximum likelihood median stellar age we measure for B59, and the region's observed gas properties, suggests that the B59 dense core has been stable against global collapse for roughly six dynamical timescales and is actively forming stars with a star formation efficiency per dynamical time of {approx}6%. While the {approx}150% uncertainties associated with our age measurement propagate directly into these

  11. Star formation at low rates - the impact of lacking massive stars on stellar feedback

    NASA Astrophysics Data System (ADS)

    Hensler, Gerhard; Steyrleithner, Patrick; Recchi, Simone

    2017-03-01

    Due to their low masses dwarf galaxies experience low star-formation rates resulting in stellar cluster masses insufficient to fill the initial mass function (IMF) to the uppermost mass. Numerical simulations usually do not account for the completeness of the IMF, but treat a filed IMF by numbers, masses, and stellar feedback by fractions. To ensure that only entire stars are formed, we consider an IMF filled from the lower-mass regime and truncated where at least one entire massive star is formed. By 3D simulations we investigate the effects of two possible IMFs on the evolution of dwarf galaxies: filled vs. truncated IMF. For the truncated IMF the star-formation self-regulation is suppressed, while the energy release by typeII supernovae is larger, both compared to the filled IMF. Moreover, the abundance ratios of particular elements yielded from massive and intermediate-mass stars differ significantly between the two IMF distributions.

  12. The rise and fall of stellar across the peak of cosmic star formation history: effects of mergers versus diffuse stellar mass acquisition

    NASA Astrophysics Data System (ADS)

    Welker, C.; Dubois, Y.; Devriendt, J.; Pichon, C.; Kaviraj, S.; Peirani, S.

    2017-02-01

    Building galaxy merger trees from a state-of-the-art cosmological hydrodynamical simulation, Horizon-AGN, we perform a statistical study of how mergers and diffuse stellar mass acquisition processes drive galaxy morphologic properties above z > 1. By diffuse mass acquisition here, we mean both accretion of stars by unresolved mergers (relative stellar mass growth smaller than 4.5 per cent) as well as in situ star formation when no resolved mergers are detected along the main progenitor branch of a galaxy. We investigate how stellar densities, galaxy sizes and galaxy morphologies (defined via shape parameters derived from the inertia tensor of the stellar density) depend on mergers of different mass ratios. We investigate how stellar densities, effective radii and shape parameters derived from the inertia tensor depend on mergers of different mass ratios. We find strong evidence that diffuse stellar accretion and in situ formation tend to flatten small galaxies over cosmic time, leading to the formation of discs. On the other hand, mergers, and not only the major ones, exhibit a propensity to puff up and destroy stellar discs, confirming the origin of elliptical galaxies. We confirm that mergers grow galaxy sizes more efficiently than diffuse processes (r_{0.5}∝ M_s^{0.85} and r_{0.5}∝ M_s^{0.1} on average, respectively) and we also find that elliptical galaxies are more susceptible to grow in size through mergers than disc galaxies with a size-mass evolution r_{0.5}∝ M_s^{1.2} instead of r_{0.5}∝ M_s^{-0.5}-M^{0.5} for discs depending on the merger mass ratio. The gas content drives the size-mass evolution due to merger with a faster size growth for gas-poor galaxies r_{0.5}∝ M_s2 than for gas-rich galaxies r0.5 ∝ Ms.

  13. The SILCC project - III. Regulation of star formation and outflows by stellar winds and supernovae

    NASA Astrophysics Data System (ADS)

    Gatto, Andrea; Walch, Stefanie; Naab, Thorsten; Girichidis, Philipp; Wünsch, Richard; Glover, Simon C. O.; Klessen, Ralf S.; Clark, Paul C.; Peters, Thomas; Derigs, Dominik; Baczynski, Christian; Puls, Joachim

    2017-04-01

    We study the impact of stellar winds and supernovae on the multiphase interstellar medium using three-dimensional hydrodynamical simulations carried out with FLASH. The selected galactic disc region has a size of (500 pc)2 × ±5 kpc and a gas surface density of 10 M⊙ pc-2. The simulations include an external stellar potential and gas self-gravity, radiative cooling and diffuse heating, sink particles representing star clusters, stellar winds from these clusters that combine the winds from individual massive stars by following their evolution tracks, and subsequent supernova explosions. Dust and gas (self-) shielding is followed to compute the chemical state of the gas with a chemical network. We find that stellar winds can regulate star (cluster) formation. Since the winds suppress the accretion of fresh gas soon after the cluster has formed, they lead to clusters that have lower average masses (102-104.3 M⊙) and form on shorter time-scales (10-3-10 Myr). In particular, we find an anticorrelation of cluster mass and accretion time-scale. Without winds, the star clusters easily grow to larger masses for ∼5 Myr until the first supernova explodes. Overall, the most massive stars provide the most wind energy input, while objects beginning their evolution as B-type stars contribute most of the supernova energy input. A significant outflow from the disc (mass loading ≳1 at 1 kpc) can be launched by thermal gas pressure if more than 50 per cent of the volume near the disc mid-plane can be heated to T > 3 × 105 K. Stellar winds alone cannot create a hot volume-filling phase. The models that are in best agreement with observed star formation rates drive either no outflows or weak outflows.

  14. Structure and Formation of Massive Galaxies with Old Stellar Populations at z=1.5

    NASA Astrophysics Data System (ADS)

    McGrath, Elizabeth J.; Stockton, A.

    2006-12-01

    Observational evidence has been mounting over the past decade that at least some luminous ( 2 L*) galaxies at high redshift have formed nearly all of their stars within the first billion years after the big bang. These are examples of the first major episodes of star formation in the universe and provide insights into the formation of the earliest massive galaxies. We have examined in detail the morphologies and stellar populations of seven z=1.5 passively evolving galaxies using high resolution HST NICMOS and ACS imaging data as well as medium resolution Keck spectroscopy. Almost all of these galaxies appear to be relaxed systems, with smooth morphologies at both rest-frame UV and visible wavelengths. Furthermore, spectral synthesis modeling favors a single burst of star formation more than 2 Gyr before the observed epoch. We note, however, that the prevalence of old stellar populations does not necessarily correlate with early-type morphologies, as the light profiles for several of these galaxies appear to be dominated by massive exponential disks. This evidence for massive old disks, along with the uniformity of stellar age across the disk, suggests formation by a mechanism better described as a form of monolithic collapse than as a hierarchical merger. There is at least one case, however, that appears to be undergoing a "dry merger", which may be an example of the process that converts these unusual galaxies into the familiar spheroids that dominate galaxies comprising old stellar populations at the present epoch. We acknowledge our collaborators in the HST observations, Gabriela Canalizo, Masanori Iye, and Toshinori Maihara. This research was supported by NSF grant AST03-07335 and HST grant GO-10418.01-A.

  15. Ages, chemistry, and type 1A supernovae: Clues to the formation of the galactic stellar halo

    NASA Technical Reports Server (NTRS)

    Smecker-Hane, Tammy A.; Wyse, Rosemary F. G.

    1993-01-01

    We endeavor to resolve two conflicting constraints on the duration of the formation of the Galactic stellar halo - 2-3 Gyr age differences in halo stars, and the time scale inferred from the observed constant values of chemical element abundance ratios characteristic of enrichment by Type II supernovae - by investigating the time scale for the onset of Type Ia supernovae (SNIa) in the currently favored progenitor model - mergers of carbon and oxygen white dwarfs (CO WDs).

  16. STAR FORMATION AND YOUNG STELLAR CONTENT IN THE W3 GIANT MOLECULAR CLOUD

    SciTech Connect

    Rivera-Ingraham, Alana; Martin, Peter G.; Polychroni, Danae; Moore, Toby J. T.

    2011-12-10

    In this work, we have carried out an in-depth analysis of the young stellar content in the W3 giant molecular cloud (GMC). The young stellar object (YSO) population was identified and classified in the Infrared Array Camera/Multiband Imaging Photometer color-magnitude space according to the 'Class' scheme and compared to other classifications based on intrinsic properties. Class 0/I and II candidates were also compared to low-/intermediate-mass pre-main-sequence (PMS) stars selected through their colors and magnitudes in the Two Micron All Sky Survey. We find that a reliable color/magnitude selection of low-mass PMS stars in the infrared requires prior knowledge of the protostar population, while intermediate-mass objects can be more reliably identified. By means of the minimum spanning tree algorithm and our YSO spatial distribution and age maps, we investigated the YSO groups and the star formation history in W3. We find signatures of clustered and distributed star formation in both triggered and quiescent environments. The central/western parts of the GMC are dominated by large-scale turbulence likely powered by isolated bursts of star formation that triggered secondary star formation events. Star formation in the eastern high-density layer (HDL) also shows signs of quiescent and triggered stellar activity, as well as extended periods of star formation. While our findings support triggering as a key factor for inducing and enhancing some of the major star-forming activity in the HDL (e.g., W3 Main/W3(OH)), we argue that some degree of quiescent or spontaneous star formation is required to explain the observed YSO population. Our results also support previous studies claiming a spontaneous origin for the isolated massive star(s) powering KR 140.

  17. Star formation in early-type galaxies: the role of stellar winds and kinematics.

    NASA Astrophysics Data System (ADS)

    Pellegrini, Silvia; Negri, Andrea; Ciotti, Luca

    2015-08-01

    Early-Type galaxies (ETGs) host a hot ISM produced mainly by stellar winds, and heated by Type Ia supernovae (SNIa) and the thermalization of stellar motions. Recent high resolution 2D hydrodynamical simulations (Negri et al. 2014) showed that ordered rotation in the stellar component alters significantly the evolution of the hot ISM, and results in the formation of a centrifugally supported cold equatorial disc. This agrees well with the recent evidence that approximately 50% of massive ETGs host significant quantities of cold gas (Morganti et al. 2006; Young et al. 2014), often in settled configurations, sharing the same kinematics of the stars. In particular, in a systematic investigation of the ATLAS3D sample, the most massive fast-rotating ETGs always have kinematically aligned gas, which suggests an internal origin for it, and molecular gas is detected only in fast rotators (Davis et al. 2011). The observed cold gas seems also to provide material for low level star formation (SF) activity (Combes et al. 2007, Davis et al. 2014). Interestingly, in the ATLAS3D sample, SF and young stellar populations are detected only in fast rotators (Sarzi et al. 2013). In a recent work we investigated whether and how SF takes place in the cold gas disc typically produced in rotating ETGs by our previous 2D simulations, by adding to them the possibility for the gas to form stars (Negri et al. 2015). We also inserted the injection of mass, momentum and energy appropriate for the newly (and continuously) forming stellar population. We found that subsequent generations of stars are formed, and that most of the extended and massive cold disc is consumed by this process, leaving at the present epoch cold gas masses that compare well with those observed. The mass in secondary generations of stars resides mostly in a disc, and could be related to a younger, more metal rich disky stellar component indeed observed in fast rotator ETGs (Cappellari et al. 2013). Most of the mass in

  18. Brightest group galaxies: stellar mass and star formation rate (paper I)

    NASA Astrophysics Data System (ADS)

    Gozaliasl, Ghassem; Finoguenov, Alexis; Khosroshahi, Habib G.; Mirkazemi, Mohammad; Erfanianfar, Ghazaleh; Tanaka, Masayuki

    2016-05-01

    We study the distribution and evolution of the stellar mass and the star formation rate (SFR) of the brightest group galaxies (BGGs) over 0.04 < z < 1.3 using a large sample of 407 X-ray galaxy groups selected from the COSMOS, AEGIS, and XMM-LSS fields. We compare our results with predictions from the semi-analytic models based on the Millennium simulation. In contrast to model predictions, we find that, as the Universe evolves, the stellar mass distribution evolves towards a normal distribution. This distribution tends to skew to low-mass BGGs at all redshifts implying the presence of a star-forming population of the BGGs with MS ˜ 1010.5 M⊙ which results in the shape of the stellar mass distribution deviating from a normal distribution. In agreement with the models and previous studies, we find that the mean stellar mass of BGGs grows with time by a factor of ˜2 between z = 1.3 and z = 0.1, however, the significant growth occurs above z = 0.4. The BGGs are not entirely a dormant population of galaxies, as low-mass BGGs in low-mass haloes are more active in forming stars than the BGGs in more massive haloes, over the same redshift range. We find that the average SFR of the BGGs evolves steeply with redshift and fraction of the passive BGGs increases as a function of increasing stellar mass and halo mass. Finally, we show that the specific SFR of the BGGs within haloes with M200 ≤ 1013.4 M⊙ decreases with increasing halo mass at z < 0.4.

  19. STELLAR POPULATIONS AND THE STAR FORMATION HISTORIES OF LOW SURFACE BRIGHTNESS GALAXIES. II. H II REGIONS

    SciTech Connect

    Schombert, James; McGaugh, Stacy; Maciel, Tamela E-mail: stacy.mcgaugh@case.edu

    2013-08-01

    The luminosities, colors, and H{alpha} emission for 429 H II regions in 54 low surface brightness (LSB) galaxies are presented. While the number of H II regions per galaxy is lower in LSB galaxies compared to star-forming irregulars and spirals, there is no indication that the size or luminosity function of H II regions differs from other galaxy types. The lower number of H II regions per galaxy is consistent with their lower total star formation rates. The fraction of the total L{sub H{alpha}} contributed by H II regions varies from 10% to 90% in LSB galaxies (the rest of the H{alpha} emission being associated with a diffuse component) with no correlation with galaxy stellar or gas mass. Bright H II regions have bluer colors, similar to the trend in spirals; their number and luminosities are consistent with the hypothesis that they are produced by the same H II luminosity function as spirals. Comparison with stellar population models indicates that the brightest H II regions in LSB galaxies range in cluster mass from a few 10{sup 3} M{sub Sun} (e.g., {rho} Oph) to globular-cluster-sized systems (e.g., 30 Dor) and that their ages are consistent with clusters from 2 to 15 Myr old. The faintest H II regions are comparable to those in the LMC powered by a single O or B star. Thus, star formation in LSB galaxies covers the full range of stellar cluster mass.

  20. On the fraction of star formation occurring in bound stellar clusters

    NASA Astrophysics Data System (ADS)

    Kruijssen, J. M. Diederik

    2012-11-01

    We present a theoretical framework in which bound stellar clusters arise naturally at the high-density end of the hierarchy of the interstellar medium (ISM). Due to short free-fall times, these high-density regions achieve high local star formation efficiencies, enabling them to form bound clusters. Star-forming regions of lower density remain substructured and gas-rich, ending up unbound when the residual gas is expelled. Additionally, the tidal perturbation of star-forming regions by nearby, dense giant molecular clouds imposes a minimum density contrast required for the collapse to a bound cluster. The fraction of all star formation that occurs in bound stellar clusters (the cluster formation efficiency, hereafter CFE) follows by integration of these local clustering and survival properties over the full density spectrum of the ISM, and hence is set by galaxy-scale physics. We derive the CFE as a function of observable galaxy properties, and find that it increases with the gas surface density, from Γ ˜ 1 per cent in low-density galaxies to a peak value of Γ ˜ 70 per cent at densities of Σg ˜ 103 M⊙ pc-2. This explains the observation that the CFE increases with the star formation rate density in nearby dwarf, spiral and starburst galaxies. Indeed, comparing our model results with observed galaxies yields excellent agreement. The model is applied further by calculating the spatial variation of the CFE within single galaxies. We also consider the variation of the CFE with cosmic time and show that it increases with redshift, peaking in high-redshift, gas-rich disc galaxies. It is estimated that up to 30-35 per cent of all stars in the Universe once formed in bound stellar clusters. We discuss how our theory can be verified with Gaia and ALMA, and provide possible implementations for theoretical work and for simulations of galaxy formation and evolution.

  1. MASSIVE STARS IN THE LOCAL GROUP: Implications for Stellar Evolution and Star Formation

    NASA Astrophysics Data System (ADS)

    Massey, Philip

    The galaxies of the Local Group serve as important laboratories for understanding the physics of massive stars. Here I discuss what is involved in identifying various kinds of massive stars in nearby galaxies: the hydrogen-burning O-type stars and their evolved He-burning evolutionary descendants, the luminous blue variables, red supergiants, and Wolf-Rayet stars. Primarily I review what our knowledge of the massive star population in nearby galaxies has taught us about stellar evolution and star formation. I show that the current generation of stellar evolutionary models do well at matching some of the observed features and provide a look at the sort of new observational data that will provide a benchmark against which new models can be evaluated.

  2. Exploring Systematic Effects in the Relation Between Stellar Mass, Gas Phase Metallicity, and Star Formation Rate

    NASA Astrophysics Data System (ADS)

    Telford, O. Grace; Dalcanton, Julianne J.; Skillman, Evan D.; Conroy, Charlie

    2016-08-01

    There is evidence that the well-established mass-metallicity relation in galaxies is correlated with a third parameter: star formation rate (SFR). The strength of this correlation may be used to disentangle the relative importance of different physical processes (e.g., infall of pristine gas, metal-enriched outflows) in governing chemical evolution. However, all three parameters are susceptible to biases that might affect the observed strength of the relation between them. We analyze possible sources of systematic error, including sample bias, application of signal-to-noise ratio cuts on emission lines, choice of metallicity calibration, uncertainty in stellar mass determination, aperture effects, and dust. We present the first analysis of the relation between stellar mass, gas phase metallicity, and SFR using strong line abundance diagnostics from Dopita et al. for ˜130,000 star-forming galaxies in the Sloan Digital Sky Survey and provide a detailed comparison of these diagnostics in an appendix. Using these new abundance diagnostics yields a 30%-55% weaker anti-correlation between metallicity and SFR at fixed stellar mass than that reported by Mannucci et al. We find that, for all abundance diagnostics, the anti-correlation with SFR is stronger for the relatively few galaxies whose current SFRs are elevated above their past average SFRs. This is also true for the new abundance diagnostic of Dopita et al., which gives anti-correlation between Z and SFR only in the high specific star formation rate (sSFR) regime, in contrast to the recent results of Kashino et al. The poorly constrained strength of the relation between stellar mass, metallicity, and SFR must be carefully accounted for in theoretical studies of chemical evolution.

  3. Planet formation in a triple stellar system: implications of the third star's orbital inclination

    NASA Astrophysics Data System (ADS)

    Domingos, R. C.; Winter, O. C.; Izidoro, A.

    2015-04-01

    Planets have been revealed both in binary and triple stellar systems. Although there have been several studies of the late stages of planet formation in binary stars this process does not appear to have been studied in triple stellar systems. To understand how the late stage of planetary accretion is affected by a third companion, in this work we have numerically investigated the formation of planets in a hypothetical triple stellar system. The system is composed by an inner binary formed by two half-solar-mass components orbited by a solar-mass star. In our experiments, lunar and Mars-sized planetary embryos are distributed around the centre of mass of the inner binary system. Our main goal is to analyse how the formation of planets evolves depending on the orbital configuration of the massive distant companion. We have performed an extensive number of numerical simulations considering different orbital configurations for the third star. All simulations were numerically integrated for at least 107 years. The results show that when the protoplanetary disc and the stars are initially on coplanar orbits, one or two planets are quickly formed between 6 and 8 AU. In general such planets have also small eccentricities with values about 10-2. On the other hand, when the third star is considered initially on inclined orbits (even tiny values), there tends to occur a significant increase in the inclination of bodies of protoplanetary disc, which prevents the collisions between these objects and their growth. As a result, in this latter case we do not evidence the formation of planets during the timescale of our integrations but note the existence of several leftover objects that can survive for longer than 10 Myr, moving in orbits with semi-major axes ranging between ~6 and 8 AU. Thus, our results do not rule out the planet formation in this kind of stellar arrangements at all, but they indicate that, if planetary bodies keep stable orbits, the late stage of planet

  4. STAR CLUSTER FORMATION WITH STELLAR FEEDBACK AND LARGE-SCALE INFLOW

    SciTech Connect

    Matzner, Christopher D.; Jumper, Peter H.

    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 its 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.

  5. Mandibular facial talon cusp: case report.

    PubMed

    Oredugba, Folakemi A

    2005-12-08

    Talon cusp is a supernumerary structure projecting from the dento-enamel junction to a variable distance towards the incisal edge of an anterior tooth. Studies have shown that it consists of enamel, dentine and a variable amount of pulp tissue. Hyperactivity of the enamel organ during morphodifferentiation has been attributed to its formation. Most previous reports have been made concerning the occurrence of this structure on primary and permanent teeth and mostly on the palatal aspect. Only few have been reported on the facial aspect of the teeth. When it occurs, the effects are mainly aesthetic and functional and so early detection and treatment is essential in its management to avoid complications. An unusual case of talon cusp on the facial aspect of a mandibular central incisor is reported. Its presence resulted in attrition of the opposing tooth. Reduction of the cusp and topical application of fluoride gel was initiated. The management and treatment outcome of talon cusp depends on the size, presenting complications and patient cooperation.

  6. Bilateral talon cusp: case report.

    PubMed

    Soares, A B; de Araújo, J J; de Sousa, S M; Veronezi, M C

    2001-04-01

    Talon cusp is an uncommon condition often present in the maxillary incisors and mandibular premolars. Morphologically, this anomaly has a well-delineated cusp that extends at least half the distance from the cementoenamel junction or cingulum area to the incisal edge. The alteration can cause clinical problems such as caries or occlusal interference. Management of the talon cusp varies according to the circumstances of the individual case and should be as conservative as possible. Presented is a case of bilateral bifid talon cusp in maxillary central incisors that was successfully managed with conservative therapy.

  7. Properties and formation mechanism of the stellar counter-rotating components in NGC 4191

    NASA Astrophysics Data System (ADS)

    Coccato, L.; Fabricius, M.; Morelli, L.; Corsini, E. M.; Pizzella, A.; Erwin, P.; Dalla Bontà, E.; Saglia, R.; Bender, R.; Williams, M.

    2015-09-01

    Aims: We here distinguish two counter-rotating stellar components in NGC 4191 and characterize their physical properties such as kinematics, morphology, age, and metallicity. Methods: We obtained integral field spectroscopic observations with VIRUS-W and used a spectroscopic decomposition technique to separate the contribution of two stellar components to the observed galaxy spectrum. We also performed a photometric decomposition, modeling the galaxy with a Sérsic bulge and two exponential disks of different scale length, with the aim of associating these structural components with the kinematic components. We then measured the equivalent width of the absorption line indices on the best-fit models that represent the kinematic components and compared our measurements to the predictions of stellar population models that also account for the variable abundance ratio of α elements. Results: We have evidence that the line-of-sight velocity distributions (LOSVDs) are bimodal and asymmetric, consistent with the presence of two distinct kinematic components. The combined information of the intensity of the peaks of the LOSVDs and the photometric decomposition allows us to associate the Sérsic bulge and the outer disk with the main kinematic component and to associate the inner disk with the secondary kinematic component. We find that the two kinematic stellar components counter-rotate with respect to each other. The main component is the most luminous and massive; the secondary component rotates along the same direction as the ionized gas. The study of the stellar populations reveals that the two kinematic components have the same solar metallicity and subsolar abundance ratio, without significant radial gradients. On the other hand, their ages show negative gradients and the possible indication that the secondary component is the younger. We interpret our results in light of recent cosmological simulations and suggest gas accretion along two filaments as the formation

  8. SuperMassive Blackholes grow from stellar BHs of star formation history?

    NASA Astrophysics Data System (ADS)

    Rocca-Volmerange, Brigitte

    The origin of the supermassive black hole masses M SMBH discovered at the highest redshifts is still actively debated. Moreover the statistically significant relation of M SMBH with bulge luminosities L V , extended on several magnitude orders, confirms a common physical process linking small (<= 1pc) to large (kpcs) size scales. The Spectral Energy Distributions (SEDs) of two z=3.8 radio galaxies 4C41.17 and TN J2007-1316, best-fitted by evolved early type galaxy and starburst scenarios also imply masses of stellar remnants. Computed with the evolutionary code Pegase.3, the cumulated stellar black hole mass M sBH reach up to several 109M⊙, similar to M SMBH at same z. We propose the SMBH growth is due to the migration of the stellar dense residues (sBH) towards the galaxy core by dynamical friction. Discussed in terms of time-scales, this process which is linking AGN and star formation, also fully justifies the famous relation M SMBH -L V .

  9. Young stellar populations in type II quasars: timing the onset of star formation and nuclear activity

    NASA Astrophysics Data System (ADS)

    Bessiere, P. S.; Tadhunter, C. N.; Ramos Almeida, C.; Villar Martín, M.; Cabrera-Lavers, A.

    2017-04-01

    Despite the emerging morphological evidence that luminous quasar-like active galactic nuclei (AGN) are triggered in galaxy mergers, the natures of the triggering mergers and the order of events in the triggering sequence remain uncertain. In this work, we present a detailed study of the stellar populations of the host galaxies of 21 type II quasars, with the aim of understanding the sequence of events between the onset of the merger, the triggering of the associated starburst and the initiation of the quasar activity. To this end, we model high-quality, wide spectral coverage, intermediate-resolution optical spectra of the type II quasars. We find that of the 21 objects, the higher order Balmer absorption lines, characteristic of young stellar populations (YSPs), are directly detected in ˜62 per cent of the sample. We also fit these spectra using a number of combinations of stellar and/or power-law components, representative of viable formation histories, as well as including the possibility of scattered AGN light. We find that ˜90 per cent of the type II quasar host galaxies require the inclusion of a YSP to adequately model their spectra, whilst 71 per cent of the sample require the inclusion of a YSP with age <100 Myr. Since the ages of the YSP in most type II quasar host galaxies are comparable with the expected lifetimes of the AGN activity, these results provide strong evidence that the quasars are triggered close to the peaks of the merger-induced starbursts.

  10. A FORMATION SCENARIO OF YOUNG STELLAR GROUPS IN THE REGION OF THE SCORPIO CENTAURUS OB ASSOCIATION

    SciTech Connect

    Ortega, V. G.; Jilinski, E.; De la Reza, R.; Bazzanella, B.

    2009-04-15

    The main objective of this work is to investigate the role played by Lower Centaurus Crux (LCC) and Upper Centaurus Lupus (UCL), both subcomponents of the Scorpio Centaurus OB association (Sco-Cen), in the formation of the groups {beta} Pictoris, TW Hydrae, and the {eta} Chamaeleontis cluster. The dynamical evolution of all the stellar groups involved and of the bubbles and shells blown by LCC and UCL are calculated, and followed from the past to the present. This leads to a formation scenario in which (1) the groups {beta} Pictoris, TW Hydrae were formed in the wake of the shells created by LCC and UCL, (2) the young cluster {eta} Chamaeleontis was born as a consequence of the collision of the shells of LCC and UCL, and (3) the formation of Upper Scorpius (US), the other main subcomponent of the Sco-Cen association, may have been started by the same process that created {eta} Chamaeleontis.

  11. The anatomy of the NGC5044 group - II. Stellar populations and star formation histories

    NASA Astrophysics Data System (ADS)

    Mendel, J. Trevor; Proctor, Robert N.; Rasmussen, Jesper; Brough, Sarah; Forbes, Duncan A.

    2009-07-01

    The distribution of galaxy properties in groups and clusters holds important information on galaxy evolution and growth of structure in the Universe. While clusters have received appreciable attention in this regard, the role of groups as fundamental to formation of the present-day galaxy population has remained relatively unaddressed. Here, we present stellar ages, metallicities and α-element abundances derived using Lick indices for 67 spectroscopically confirmed members of the NGC5044 galaxy group with the aim of shedding light on galaxy evolution in the context of the group environment. We find that galaxies in the NGC5044 group show evidence for a strong relationship between stellar mass and metallicity, consistent with their counterparts in both higher and lower mass groups and clusters. Galaxies show no clear trend of age or α-element abundance with mass, but these data form a tight sequence when fitted simultaneously in age, metallicity and stellar mass. In the context of the group environment, our data support the tidal disruption of low-mass galaxies at small group-centric radii, as evident from an apparent lack of galaxies below ~109Msolar within ~100kpc of the brightest group galaxy. Using a joint analysis of absorption- and emission-line metallicities, we are able to show that the star-forming galaxy population in the NGC5044 group appears to require gas removal to explain the ~1.5dex offset between absorption- and emission-line metallicities observed in some cases. A comparison with other stellar population properties suggests that this gas removal is dominated by galaxy interactions with the hot intragroup medium.

  12. The gaseous proto-cluster: better characterizing the initial conditions of stellar cluster formation?

    NASA Astrophysics Data System (ADS)

    Lee, Y.-N.; Hennebelle, P.

    2016-12-01

    Cluster formation simulations have always been numerically challenging due to the large range of spatial and temporal scales that vary by orders of magnitudes and multiple physical mechanisms involved. The simulation box is typically of parsec (pc) scale while resolution down to a few astronomical units (AUs) is needed to well resolve individual stars. However, studies of this kind are important for the understanding of the interaction between gravity and turbulence that guides the star formation and the mechanisms through which the possibly self-regulated initial mass function (IMF) is shaped by stellar feedback. Most simulation works have initial conditions that correspond to molecular clouds (MCs), while the actual star formation occurs in a very small volume fraction of the whole simulation box. We present a series of simulations to characterise the early stage of cluster formation, of which a primary stage of gas concentration is noticed. We denote this stage as the gaseous proto-cluster, which forms from gravo-turbulent collapse of the MC. This high-density region is indeed the principle site of star formation. The existence of this primary stage implies that the cluster formation environment is somewhat universal and cluster formation studies could therefore set out from more local conditions, therefore reducing the computational demand.

  13. Constraints on galaxy formation models from the galaxy stellar mass function and its evolution

    NASA Astrophysics Data System (ADS)

    Rodrigues, Luiz Felippe S.; Vernon, Ian; Bower, Richard G.

    2017-04-01

    We explore the parameter space of the semi-analytic galaxy formation model GALFORM, studying the constraints imposed by measurements of the galaxy stellar mass function (GSMF) and its evolution. We use the Bayesian emulator method to quickly eliminate vast implausible volumes of the parameter space and zoom in on the most interesting regions, allowing us to identify a set of models that match the observational data within model uncertainties. We find that the GSMF strongly constrains parameters related to quiescent star formation in discs, stellar and active galactic nucleus feedback and threshold for disc instabilities, but weakly restricts other parameters. Constraining the model using local data alone does not usually select models that match the evolution of the GSMF well. Nevertheless, we show that a small subset of models provides acceptable match to GSMF data out to redshift 1.5. We explore the physical significance of the parameters of these models, in particular exploring whether the model provides a better description if the mass loading of the galactic winds generated by starbursts (β0,burst) and quiescent discs (β0,disc) is different. Performing a principal component analysis of the plausible volume of the parameter space, we write a set of relations between parameters obeyed by plausible models with respect to GSMF evolution. We find that while β0,disc is strongly constrained by GSMF evolution data, constraints on β0,burst are weak. Although it is possible to find plausible models for which β0,burst = β0,disc, most plausible models have β0,burst > β0,disc, implying - for these - larger stellar feedback efficiency at higher redshifts.

  14. WINGS-SPE II: A catalog of stellar ages and star formation histories, stellar masses and dust extinction values for local clusters galaxies

    NASA Astrophysics Data System (ADS)

    Fritz, J.; Poggianti, B. M.; Cava, A.; Valentinuzzi, T.; Moretti, A.; Bettoni, D.; Bressan, A.; Couch, W. J.; D'Onofrio, M.; Dressler, A.; Fasano, G.; Kjærgaard, P.; Moles, M.; Omizzolo, A.; Varela, J.

    2011-02-01

    Context. The WIde-field Nearby Galaxy clusters Survey (wings) is a project whose primary goal is to study the galaxy populations in clusters in the local universe (z < 0.07) and of the influence of environment on their stellar populations. This survey has provided the astronomical community with a high quality set of photometric and spectroscopic data for 77 and 48 nearby galaxy clusters, respectively. Aims: In this paper we present the catalog containing the properties of galaxies observed by the wings SPEctroscopic (wings-spe) survey, which were derived using stellar populations synthesis modelling approach. We also check the consistency of our results with other data in the literature. Methods: Using a spectrophotometric model that reproduces the main features of observed spectra by summing the theoretical spectra of simple stellar populations of different ages, we derive the stellar masses, star formation histories, average age and dust attenuation of galaxies in our sample. Results: ~ 5300 spectra were analyzed with spectrophotometric techniques, and this allowed us to derive the star formation history, stellar masses and ages, and extinction for the wings spectroscopic sample that we present in this paper. Conclusions: The comparison with the total mass values of the same galaxies derived by other authors based on sdss data, confirms the reliability of the adopted methods and data. Based on observations taken at the Anglo Australian Telescope (3.9 m- AAT), and at the William Herschel Telescope (4.2 m- WHT).Full Table 2 is available in electronic form both at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A45, and by querying the wings database at http://web.oapd.inaf.it/wings/new/index.html

  15. A multiwavelength investigation of the H II region S311: young stellar population and star formation

    NASA Astrophysics Data System (ADS)

    Yadav, Ram Kesh; Pandey, A. K.; Sharma, Saurabh; Ojha, D. K.; Samal, M. R.; Mallick, K. K.; Jose, J.; Ogura, K.; Richichi, Andrea; Irawati, Puji; Kobayashi, N.; Eswaraiah, C.

    2016-09-01

    We present a multiwavelength investigation of the young stellar population and star formation activities around the H II region Sharpless 311. Using our deep near-infrared observations and archival Spitzer-IRAC observations, we have detected a total of 125 young stellar objects (YSOs) in an area of ˜86 arcmin2. The YSO sample includes eight Class I and 117 Class II candidate YSOs. The mass completeness of the identified YSO sample is estimated to be 1.0 M⊙. The ages and masses of the majority of the candidate YSOs are estimated to be in the range ˜0.1-5 Myr and ˜0.3-6 M⊙, respectively. The 8-μm image of S311 displays an approximately spherical cavity around the ionizing source, which was possibly created by the expansion of the H II region. The spatial distribution of the candidate YSOs reveals that a significant number of them are distributed systematically along the 8-μm emission with a majority clustered around the eastern border of the H II region. Four clumps/compact H II regions are detected in the radio continuum observations at 1280 MHz, which may have been formed during the expansion of the H II region. The estimated dynamical age of the region, main-sequence lifetime of the ionizing source, the spatial distribution and ages of the candidate YSOs indicate triggered star formation in the complex.

  16. Constraining the Stellar Populations and Star Formation Histories of Blue Compact Dwarf Galaxies with SED Fits

    NASA Astrophysics Data System (ADS)

    Janowiecki, Steven; Salzer, John J.; van Zee, Liese; Rosenberg, Jessica L.; Skillman, Evan

    2017-02-01

    We discuss and test possible evolutionary connections between blue compact dwarf galaxies (BCDs) and other types of dwarf galaxies. BCDs provide ideal laboratories to study intense star formation episodes in low-mass dwarf galaxies, and have sometimes been considered a short-lived evolutionary stage between types of dwarf galaxies. To test these connections, we consider a sample of BCDs as well as a comparison sample of nearby galaxies from the Local Volume Legacy (LVL) survey for context. We fit the multi-wavelength spectral energy distributions (SED, far-ultra-violet to far-infrared) of each galaxy with a grid of theoretical models to determine their stellar masses and star formation properties. We compare our results for BCDs with the LVL galaxies to put BCDs in the context of normal galaxy evolution. The SED fits demonstrate that the star formation events currently underway in BCDs are at the extreme of the continuum of normal dwarf galaxies, both in terms of the relative mass involved and in the relative increase over previous star formation rates. Today’s BCDs are distinctive objects in a state of extreme star formation that is rapidly transforming them. This study also suggests ways to identify former BCDs whose star formation episodes have since faded.

  17. Star formation in the first galaxies - III. Formation, evolution, and characteristics of the first metal-enriched stellar cluster

    NASA Astrophysics Data System (ADS)

    Safranek-Shrader, Chalence; Montgomery, Michael H.; Milosavljević, Miloš; Bromm, Volker

    2016-01-01

    We simulate the formation of a low-metallicity (10-2 Z⊙) stellar cluster at redshift z ˜ 14. Beginning with cosmological initial conditions, the simulation utilizes adaptive mesh refinement and sink particles to follow the collapse and evolution of gas past the opacity limit for fragmentation, thus resolving the formation of individual protostellar cores. A time- and location-dependent protostellar radiation field, which heats the gas by absorption on dust, is computed by integration of protostellar evolutionary tracks. The simulation also includes a robust non-equilibrium chemical network that self-consistently treats gas thermodynamics and dust-gas coupling. The system is evolved for 18 kyr after the first protostellar source has formed. In this time span, 30 sink particles representing protostellar cores form with a total mass of 81 M⊙. Their masses range from ˜0.1 to 14.4 M⊙ with a median mass ˜0.5-1 M⊙. Massive protostars grow by competitive accretion while lower mass protostars are stunted in growth by close encounters and many-body ejections. In the regime explored here, the characteristic mass scale is determined by the cosmic microwave background temperature floor and the onset of efficient dust-gas coupling. It seems unlikely that host galaxies of the first bursts of metal-enriched star formation will be detectable with the James Webb Space Telescope or other next-generation infrared observatories. Instead, the most promising access route to the dawn of cosmic star formation may lie in the scrutiny of metal-poor, ancient stellar populations in the Galactic neighbourhood. The observable targets corresponding to the system simulated here are ultra-faint dwarf satellite galaxies such as Boötes II and Willman I.

  18. Recovering star formation histories: Integrated-light analyses vs. stellar colour-magnitude diagrams

    NASA Astrophysics Data System (ADS)

    Ruiz-Lara, T.; Pérez, I.; Gallart, C.; Alloin, D.; Monelli, M.; Koleva, M.; Pompei, E.; Beasley, M.; Sánchez-Blázquez, P.; Florido, E.; Aparicio, A.; Fleurence, E.; Hardy, E.; Hidalgo, S.; Raimann, D.

    2015-11-01

    Context. Accurate star formation histories (SFHs) of galaxies are fundamental for understanding the build-up of their stellar content. However, the most accurate SFHs - those obtained from colour-magnitude diagrams (CMDs) of resolved stars reaching the oldest main-sequence turnoffs (oMSTO) - are presently limited to a few systems in the Local Group. It is therefore crucial to determine the reliability and range of applicability of SFHs derived from integrated light spectroscopy, as this affects our understanding of unresolved galaxies from low to high redshift. Aims: We evaluate the reliability of current full spectral fitting techniques in deriving SFHs from integrated light spectroscopy by comparing SFHs from integrated spectra to those obtained from deep CMDs of resolved stars. Methods: We have obtained a high signal-to-noise (S/N ~ 36.3 per Å) integrated spectrum of a field in the bar of the Large Magellanic Cloud (LMC) using EFOSC2 at the 3.6-metre telescope at La Silla Observatory. For this same field, resolved stellar data reaching the oMSTO are available. We have compared the star formation rate (SFR) as a function of time and the age-metallicity relation (AMR) obtained from the integrated spectrum using STECKMAP, and the CMD using the IAC-star/MinnIAC/IAC-pop set of routines. For the sake of completeness we also use and discuss other synthesis codes (STARLIGHT and ULySS) to derive the SFR and AMR from the integrated LMC spectrum. Results: We find very good agreement (average differences ~4.1%) between the SFR (t) and the AMR obtained using STECKMAP on the integrated light spectrum, and the CMD analysis. STECKMAP minimizes the impact of the age-metallicity degeneracy and has the advantage of preferring smooth solutions to recover complex SFHs by means of a penalized χ2. We find that the use of single stellar populations (SSPs) to recover the stellar content, using for instance STARLIGHT or ULySS codes, hampers the reconstruction of the SFR (t) and AMR

  19. Syndontia with talon cusp

    PubMed Central

    Gupta, Shalini; Tandon, Ankita; Chandra, Anil; Gupta, Om Prakash

    2012-01-01

    Teeth are specialized structural components of the craniofacial skeleton. Developmental defects occur either alone or in combination with other birth defects. Macrodontia of anterior teeth may occur as an isolated condition or as a result of fusion or gemination and can occur in the primary or permanent dentition. Fusion is more commonly seen in the anterior maxillary region. This case presentation reports a case of fusion of a supplemental tooth to one in the normal series in conjunction with a talon cusp. This condition is extremely rare and has been reported at fourth occasion in the literature. The etiology, prevalence, clinical features, and management of the aforementioned anomalies have been reviewed in detail. Early diagnosis of this condition is important because it may cause clinical problems, such as esthetic concerns and tooth crowding. PMID:22923902

  20. The role of stellar relaxation in the formation and evolution of the first massive black holes

    NASA Astrophysics Data System (ADS)

    Yajima, Hidenobu; Khochfar, Sadegh

    2016-04-01

    We present calculations on the formation of massive black holes of 105 M⊙ at z > 6, which can be the seeds of supermassive black holes at z ≳ 6. Under the assumption of compact star cluster formation in merging galaxies, star clusters in haloes of ˜ 108-109 M⊙ can undergo rapid core collapse, leading to the formation of very massive stars (VMSs) of ˜ 1000 M⊙ that collapse directly into black holes with similar masses. Star clusters in haloes of ≳ 109 M⊙ experience Type II supernovae before the formation of VMSs, due to long core-collapse time-scales. We also model the subsequent growth of black holes via accretion of residual stars in clusters. Two-body relaxation refills the loss cones of stellar orbits efficiently at larger radii and resonant relaxation at small radii is the main driver for accretion of stars on to black holes. As a result, more than 90 percent of stars in the initial cluster are swallowed by the central black holes before z = 6. Using dark matter merger trees, we derive black hole mass functions at z = 6-20. The mass function ranges from 103-105 M⊙ at z ≲ 15. Major merging of galaxies of ≳ 4 × 108 M⊙ at z ˜ 20 leads successfully to the formation of ≳ 105 M⊙ black holes by z ≳ 10, which could be the potential seeds of supermassive black holes seen today.

  1. Analyzing the Formation of Ultra-compact Dwarfs through Stellar Populations

    NASA Astrophysics Data System (ADS)

    Seshadri, Anish; Wang, Carolyn; Romanowsky, Aaron J.; Martin-navarro, Ignacio

    2017-01-01

    Since their discovery in 1999, ultra-compact dwarfs (UCDs) have been the subjects of intense study. Their small size, yet tremendous mass, brings into question their place among celestial objects. Are they galaxies or globular clusters? The answer to this question could come from analyzing how they formed. Thus, the goal of this project is to test one of the theories for the formation of UCDs, the theory of tidal stripping.This project approaches the issue by looking at dwarf galaxies currently in the process of stripping to understand formation history. Over twenty such dwarf galaxies were identified and their stellar populations analyzed. Using modeling techniques on spectroscopic and photometric data, the age, metallicity, and color of each object was identified. By objectively categorizing each object into a stage of evolution in the process of tidal stripping, a virtual timeline was built for the formation of UCDs. Data for each object were plotted vs. stage of formation, with pristine dwarfs and UCDs signifying the endpoints. Trends in the data revealed a natural progression over all stages of evolution, showing that tidally stripped dwarfs likely represent an intermediate stage in the formation of UCDs.This research was supported by NSF Grant AST-1515084. Most of this work was carried out by high school students working under the auspices of the Science Internship Program at UC Santa Cruz.

  2. Properties of Cusp Diamagnetic Cavities

    NASA Technical Reports Server (NTRS)

    Sheldon, Robert B.

    2003-01-01

    Progress can be reported in two areas related to characterizing the properties of cusp diamagnetic cavities. Laboratory terrella experiments have been conducted for the purpose of using neutral gas excitation as a tracer of trapped electron populations in the presence of two dipoles that are used to develop a magnetic cusp topology. Figure 1 and 2 show top and side views of two configurations. Dipole trapped electron populations appear as the two luminous annular rings. Other populations are the most intense regions are shown. Interspersed between these regions are narrow regions that represent the topological cusps in these configurations. That they contain luminous gas is evidence for cusp trapping similar to what we believe exists in the terrestrial magnetosphere. The asymmetry of these cusp regions as seen in Figure 1 is the result of a relative tilt between the two dipoles suggestive of what would be expected in space. It is in these regions that particle observations were sought, so as to validate the realization of proposed and laboratory achieved trapping in a diamagnetic cusp. Figure 3 shows particle trajectories in a modeled cusp magnetic topology for three particle energies. Blue, green, and red traces correspond to increasing energies. Due to factors discussed outside of this final report, a thorough exploration of relevant satellite observations have not been achieved.

  3. On the formation of hot and warm Jupiters via secular high-eccentricity migration in stellar triples

    NASA Astrophysics Data System (ADS)

    Hamers, Adrian S.

    2017-04-01

    Hot Jupiters (HJs) are Jupiter-like planets orbiting their host star in tight orbits of a few days. They are commonly believed not to have formed in situ, requiring inwards migration towards the host star. One of the proposed migration scenarios is secular high-eccentricity or high-e migration, in which the orbit of the planet is perturbed to high eccentricity by secular processes, triggering strong tidal evolution and orbital migration. Previous theoretical studies have considered secular excitation in stellar binaries. Recently, a number of HJs have been observed in stellar triple systems. In the latter, the secular dynamics are much richer compared to stellar binaries, and HJs could potentially be formed more efficiently. Here, we investigate this possibility by modelling the secular dynamical and tidal evolution of planets in two hierarchical configurations in stellar triple systems. We find that the HJ formation efficiency is higher compared to stellar binaries, but only by at most a few tens of per cent. The orbital properties of the HJs formed in the simulations are very similar to HJs formed in stellar binaries, and similarly to studies of the latter we find no significant number of warm Jupiters. HJs are only formed in our simulations for triples with specific orbital configurations, and our constraints are approximately consistent with current observations. In future, this allows us to rule out high-e migration in stellar triples if a HJ is detected in a triple grossly violating these constraints.

  4. On the formation of hot and warm Jupiters via secular high-eccentricity migration in stellar triples

    NASA Astrophysics Data System (ADS)

    Hamers, Adrian S.

    2017-01-01

    Hot Jupiters (HJs) are Jupiter-like planets orbiting their host star in tight orbits of a few days. They are commonly believed not to have formed in situ, requiring inwards migration towards the host star. One of the proposed migration scenarios is secular high-eccentricity or high-e migration, in which the orbit of the planet is perturbed to high eccentricity by secular processes, triggering strong tidal evolution and orbital migration. Previous theoretical studies have considered secular excitation in stellar binaries. Recently, a number of HJs have been observed in stellar triple systems. In the latter, the secular dynamics are much richer compared to stellar binaries, and HJs could potentially be formed more efficiently. Here, we investigate this possibility by modeling the secular dynamical and tidal evolution of planets in two hierarchical configurations in stellar triple systems. We find that the HJ formation efficiency is higher compared to stellar binaries, but only by at most a few tens of per cent. The orbital properties of the HJs formed in the simulations are very similar to HJs formed in stellar binaries, and similarly to studies of the latter we find no significant number of warm Jupiters. HJs are only formed in our simulations for triples with specific orbital configurations, and our constraints are approximately consistent with current observations. In future, this allows to rule out high-e migration in stellar triples if a HJ is detected in a triple grossly violating these constraints.

  5. Ultraviolet to infrared emission of z > 1 galaxies: Can we derive reliable star formation rates and stellar masses?

    NASA Astrophysics Data System (ADS)

    Buat, V.; Heinis, S.; Boquien, M.; Burgarella, D.; Charmandaris, V.; Boissier, S.; Boselli, A.; Le Borgne, D.; Morrison, G.

    2014-01-01

    Aims: Our knowledge of the cosmic mass assembly relies on measurements of star formation rates (SFRs) and stellar masses (Mstar), of galaxies as a function of redshift. These parameters must be estimated in a consistent way with a good knowledge of systematics before studying their correlation and the variation of the specific SFR. Constraining these fundamental properties of galaxies across the Universe is of utmost importance if we want to understand galaxy formation and evolution. Methods: We seek to derive SFRs and stellar masses in distant galaxies and to quantify the main uncertainties affecting their measurement. We explore the impact of the assumptions made in their derivation with standard calibrations or through a fitting process, as well as the impact of the available data, focusing on the role of infrared emission originating from dust. Results: We build a sample of galaxies with z > 1, all observed from the ultraviolet to the infrared in their rest frame. The data are fitted with the code CIGALE, which is also used to build and analyse a catalogue of mock galaxies. Models with different star formation histories are introduced: an exponentially decreasing or increasing SFR and a more complex one coupling a decreasing SFR with a younger burst of constant star formation. We define different sets of data, with or without a good sampling of the ultraviolet range, near-infrared, and thermal infrared data. Variations of the metallicity are also investigated. The impact of these different cases on the determination of stellar mass and SFR are analysed. Conclusions: Exponentially decreasing models with a redshift formation of the stellar population zf ≃ 8 cannot fit the data correctly. All the other models fit the data correctly at the price of unrealistically young ages when the age of the single stellar population is taken to be a free parameter, especially for the exponentially decreasing models. The best fits are obtained with two stellar populations. As

  6. The formation and gravitational-wave detection of massive stellar black hole binaries

    SciTech Connect

    Belczynski, Krzysztof; Walczak, Marek; Buonanno, Alessandra; Cantiello, Matteo; Fryer, Chris L.; Holz, Daniel E.; Mandel, Ilya; Miller, M. Coleman

    2014-07-10

    If binaries consisting of two ∼100 M{sub ☉} black holes exist, they would serve as extraordinarily powerful gravitational-wave sources, detectable to redshifts of z ∼ 2 with the advanced LIGO/Virgo ground-based detectors. Large uncertainties about the evolution of massive stars preclude definitive rate predictions for mergers of these massive black holes. We show that rates as high as hundreds of detections per year, or as low as no detections whatsoever, are both possible. It was thought that the only way to produce these massive binaries was via dynamical interactions in dense stellar systems. This view has been challenged by the recent discovery of several ≳ 150 M{sub ☉} stars in the R136 region of the Large Magellanic Cloud. Current models predict that when stars of this mass leave the main sequence, their expansion is insufficient to allow common envelope evolution to efficiently reduce the orbital separation. The resulting black hole-black hole binary remains too wide to be able to coalesce within a Hubble time. If this assessment is correct, isolated very massive binaries do not evolve to be gravitational-wave sources. However, other formation channels exist. For example, the high multiplicity of massive stars, and their common formation in relatively dense stellar associations, opens up dynamical channels for massive black hole mergers (e.g., via Kozai cycles or repeated binary-single interactions). We identify key physical factors that shape the population of very massive black hole-black hole binaries. Advanced gravitational-wave detectors will provide important constraints on the formation and evolution of very massive stars.

  7. Young Stellar Objects in Lynds 1641: Disks, Accretion, and Star Formation History

    NASA Astrophysics Data System (ADS)

    Fang, Min; Kim, Jinyoung Serena; van Boekel, Roy; Sicilia-Aguilar, Aurora; Henning, Thomas; Flaherty, Kevin

    2013-07-01

    We investigate the young stellar objects (YSOs) in the Lynds 1641 (L1641) cloud using multi-wavelength data including Spitzer, WISE, the Two Micron All Sky Survey, and XMM covering ~1390 YSOs across a range of evolutionary stages. In addition, we targeted a sub-sample of YSOs for optical spectroscopy with the MMT/Hectospec and the MMT/Hectochelle. We use these data, along with archival photometric data, to derive spectral types, extinction values, masses, ages, and accretion rates. We obtain a disk fraction of ~50% in L1641. The disk frequency is almost constant as a function of stellar mass with a slight peak at log (M */M ⊙) ≈ -0.25. The analysis of multi-epoch spectroscopic data indicates that the accretion variability of YSOs cannot explain the two orders of magnitude of scatter for YSOs with similar masses. Forty-six new transition disk (TD) objects are confirmed in this work, and we find that the fraction of accreting TDs is lower than for optically thick disks (40%-45% versus 77%-79%, respectively). We confirm our previous result that the accreting TDs have a median accretion rate similar to normal optically thick disks. We confirm that two star formation modes (isolated versus clustered) exist in L1641. We find that the diskless YSOs are statistically older than the YSOs with optically thick disks and the TD objects have a median age that is intermediate between those of the other two populations. We tentatively study the star formation history in L1641 based on the age distribution and find that star formation started to be active 2-3 Myr ago.

  8. Characterizing Extragalactic Star Formation with GALEX Legacy Photometric Analysis of UV-Bright Stellar Complexes

    NASA Astrophysics Data System (ADS)

    Thilker, David

    At the close of nearly a decade of observing, GALEX has accumulated an unprecedented archive of ultraviolet (UV) images revealing both the scope and intricacy of star formation (SF) in many thousands of galaxies inhabiting the local universe. If the observed hierarchical SF morphology can be quantified systematically, and physically interpreted with multi-wavelength ancillary data and modeling, then the low redshift GALEX legacy will approach completion. However, the GALEX GR6 pipeline database contains a highly incomplete census of young stellar complexes even for very well-studied galaxies. We propose to apply a dedicated photometry algorithm that has been optimized for measuring the properties of irregularly shaped sources in crowded galaxy images containing spatially variant, diffuse intra-clump emission. Structures will be selected in the UV, but we will compile UV-visible-MIR SEDs for each detection utilizing Pan-STARRS1+SDSS and WISE data. These SEDs will then be fit using population-synthesis models to derive estimated stellar mass, age, and extinction. Processing will be completed for the entire diameter-limited GALEX Large Galaxy Atlas (GLGA) sample of 20,000+ galaxies, at a variety of standardized spatial resolutions. Although the precise categorization of the cataloged substructures will depend on galaxy distance, the outcome of our analysis will be a catalog similar to the stellar association surveys of past decades for very nearby galaxies based on resolved stars (e.g. van den Bergh 1964, Hodge 1986, Efremov et al. 1987), except that our investigation will probe a galaxy sample of dramatically larger size using the integrated UV light from such groupings of young stars. Our algorithm is multi-scale in nature and will thus preserve the hierarchical properties of the stellar distribution, by linking sub-clumps to their larger-scale parent feature(s). The resulting database will be a fundamental resource for follow-up multi-wavelength studies probing SF

  9. Observational Constraints on Low-Mass Stellar Evolution and Planet Formation

    NASA Astrophysics Data System (ADS)

    Birkby, Jayne Louise

    2011-07-01

    Low-mass stars (? < 1.0M⊙) account for more than 70% of the galactic stellar population yet models describing the evolution of their fundamental properties lack stringent observational constraints, especially at early ages. Furthermore, recent observations indicate a significant discrepancy between model predictions and the precise (2 - 3%) observed, dynamical masses and radii measured using low-mass eclipsing binary systems (EBs). Additionally, the theory of planet formation via core accretion predicts notably less hot-Jupiter formation around M-dwarfs (Mdot ? ≤ 0.6M⊙), but as yet, no large enough study exists to robustly test it. Further still, it is predicted that the dynamic environment of stellar clusters, in which most stars are believed to form, hampers planet formation, but again, current null detections of planets in stellar clusters are not statistically significant to test the theory. More observations are required to cement both the theory of low-mass stellar evolution and planet formation. This thesis aims to provide the necessary constraints by uncovering new low-mass EBs and transiting exoplanets in time-series photometry and follow-up spectroscopy from the Monitor project, a photometric monitoring campaign of low-mass stars in nine young open clusters, and in the WFCAM Transit Survey (WTS), a photometric monitoring campaign of ∼10,000 field M-dwarfs. Chapters 3 and 4 present my study of the young (130 Myr) cluster, M 50. I confirm three EB candidates as cluster members, including evidence that one of these is in a triple system with a wide-separation, low-mass tertiary component. The derived masses and radii for this system and one further double-lined, non-cluster member are presented, but these objects required dedicated, single-slit spectroscopic follow-up to yield the accuracy required to test pre-main sequence models. My non-detection of planets in this cluster is consistent with the results of all other cluster transit surveys. The

  10. Globular cluster formation with multiple stellar populations: self-enrichment in fractal massive molecular clouds

    NASA Astrophysics Data System (ADS)

    Bekki, Kenji

    2017-08-01

    Internal chemical abundance spreads are one of fundamental properties of globular clusters (GCs) in the Galaxy. In order to understand the origin of such abundance spreads, we numerically investigate GC formation from massive molecular clouds (MCs) with fractal structures using our new hydrodynamical simulations with star formation and feedback effects of core-collapse supernovae (SNe) and asymptotic giant branch (AGB) stars. We particularly investigate star formation from gas chemically contaminated by SNe and AGB stars ('self-enrichment') in forming GCs within MCs with different initial conditions and environments. The principal results are as follows. GCs with multiple generations of stars can be formed from merging of hierarchical star cluster complexes that are developed from high-density regions of fractal MCs. Feedback effects of SNe and AGB stars can control the formation efficiencies of stars formed from original gas of MCs and from gas ejected from AGB stars. The simulated GCs have strong radial gradients of helium abundances within the central 3 pc. The original MC masses need to be as large as 107 M⊙ for a canonical initial stellar mass function (IMF) so that the final masses of stars formed from AGB ejecta can be ∼105 M⊙. Since star formation from AGB ejecta is rather prolonged (∼108 yr), their formation can be strongly suppressed by SNe of the stars themselves. This result implies that the so-called mass budget problem is much more severe than ever thought in the self-enrichment scenario of GC formation and thus that IMF for the second generation of stars should be 'top-light'.

  11. Formation of standing shocks in stellar winds and related astrophysical flows

    NASA Technical Reports Server (NTRS)

    Tsinganos, K.; Habbal, S. R.; Rosner, R.

    1983-01-01

    Stellar winds and other analogous astrophysical flows can be described, to lowest order, by the familiar one dimensional hydrodynamic equations which, being nonlinear, admit in some instances discontinuous as well as continuous transonic solutions for identical inner boundary conditions. The characteristics of the time dependent differential equations of motion are described to show how a perturbation changes profile in time and, under well defined conditions, develops into a stationary shock discontinuity. The formation of standing shocks in wind type astrophysical flows depends on the fulfillment of appropriate necessary conditions, which are determined by the conservation of mass, momentum and energy across the discontinuity, and certain sufficient conditions, which are determined by the flow's history.

  12. Blast wave formation of the extended stellar shells surrounding elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Williams, R. E.; Christiansen, W. A.

    1985-01-01

    The existence of stellar shells at large distances from isolated elliptical galaxies is explained in terms of a blast wave associated with an active nucleus phase early in the history of the galaxy. The blast wave sweeps the initial interstellar medium out of the galaxy into an expanding shell which radiatively cools behind its leading shock front. Cooling of the shell following turnoff of the nucleus activity, which keeps the shell photoionized, leads to a brief epoch of star formation which is terminated by heating of the shell from supernovae and UV radiation from massive stars. The stars so formed follow similar, highly radial, bound orbits, moving in phase with each other and spending much of their time near apogalacteum, thus taking on the appearance of a shell. Multiple shells may be produced when conditions allow repeated episodes of shell cooling and supernovae heating to occur in the blast wave.

  13. SUPERMASSIVE BLACK HOLE FORMATION VIA GAS ACCRETION IN NUCLEAR STELLAR CLUSTERS

    SciTech Connect

    Davies, Melvyn B.; Coleman Miller, M.; Bellovary, Jillian M.

    2011-10-20

    Black holes exceeding a billion solar masses have been detected at redshifts greater than six. The rapid formation of these objects may suggest a massive early seed or a period of growth faster than Eddington. Here we suggest a new mechanism along these lines. We propose that in the process of hierarchical structure assembly, dense star clusters can be contracted on dynamical timescales due to the nearly free-fall inflow of self-gravitating gas with a mass comparable to or larger than that of the clusters. This process increases the velocity dispersion to the point where the few remaining hard binaries can no longer effectively heat the cluster, and the cluster goes into a period of homologous core collapse. The cluster core can then reach a central density high enough for fast mergers of stellar-mass black holes and hence the rapid production of a black hole seed that could be 10{sup 5} M{sub sun} or larger.

  14. Blast wave formation of the extended stellar shells surrounding elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Williams, R. E.; Christiansen, W. A.

    1985-01-01

    The existence of stellar shells at large distances from isolated elliptical galaxies is explained in terms of a blast wave associated with an active nucleus phase early in the history of the galaxy. The blast wave sweeps the initial interstellar medium out of the galaxy into an expanding shell which radiatively cools behind its leading shock front. Cooling of the shell following turnoff of the nucleus activity, which keeps the shell photoionized, leads to a brief epoch of star formation which is terminated by heating of the shell from supernovae and UV radiation from massive stars. The stars so formed follow similar, highly radial, bound orbits, moving in phase with each other and spending much of their time near apogalacteum, thus taking on the appearance of a shell. Multiple shells may be produced when conditions allow repeated episodes of shell cooling and supernovae heating to occur in the blast wave.

  15. Star Formation in W3—AFGL 333: Young Stellar Content, Properties, and Roles of External Feedback

    NASA Astrophysics Data System (ADS)

    Jose, Jessy; Kim, Jinyoung S.; Herczeg, Gregory J.; Samal, Manash R.; Bieging, John H.; Meyer, Michael R.; Sherry, William H.

    2016-05-01

    One of the key questions in the field of star formation is the role of stellar feedback on the subsequent star formation process. The W3 giant molecular cloud complex at the western border of the W4 super bubble is thought to be influenced by the massive stars in W4. This paper presents a study of the star formation activity within AFGL 333, a ˜104 M ⊙ cloud within W3, using deep JHK s photometry obtained from the NOAO Extremely Wide Field Infrared Imager combined with Spitzer IRAC and MIPS photometry. Based on the infrared excess, we identify 812 candidate young stellar objects (YSOs) in the complex, of which 99 are Class I and 713 are Class II sources. The stellar density analysis of YSOs reveals three major stellar aggregates within AFGL 333, namely AFGL 333 Main, AFGL 333 NW1 and AFGL 333 NW2. The disk fraction within AFGL 333 is estimated to be ˜50%-60%. We use the extinction map made from the H-{K}s colors of the background stars and CO data to understand the cloud structure and to estimate the cloud mass. From the stellar and cloud mass associated with AFGL 333, we infer that the region is currently forming stars with an efficiency of ˜4.5% and at a rate of ˜2-3 M ⊙ Myr-1 pc-2. In general, the star formation activity within AFGL 333 is comparable to that of nearby low mass star-forming regions. We do not find any strong evidence to suggest that the stellar feedback from the massive stars of nearby W4 super bubble has affected the global star formation properties of the AFGL 333 region.

  16. The ATLAS3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies

    NASA Astrophysics Data System (ADS)

    McDermid, Richard M.; Alatalo, Katherine; Blitz, Leo; Bournaud, Frédéric; Bureau, Martin; Cappellari, Michele; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

    2015-04-01

    We present the stellar population content of early-type galaxies from the ATLAS3D survey. Using spectra integrated within apertures covering up to one effective radius, we apply two methods: one based on measuring line-strength indices and applying single stellar population (SSP) models to derive SSP-equivalent values of stellar age, metallicity, and alpha enhancement; and one based on spectral fitting to derive non-parametric star formation histories, mass-weighted average values of age, metallicity, and half-mass formation time-scales. Using homogeneously derived effective radii and dynamically determined galaxy masses, we present the distribution of stellar population parameters on the Mass Plane (MJAM, σe, R^maj_e), showing that at fixed mass, compact early-type galaxies are on average older, more metal-rich, and more alpha-enhanced than their larger counterparts. From non-parametric star formation histories, we find that the duration of star formation is systematically more extended in lower mass objects. Assuming that our sample represents most of the stellar content of today's local Universe, approximately 50 per cent of all stars formed within the first 2 Gyr following the big bang. Most of these stars reside today in the most massive galaxies (>1010.5 M⊙), which themselves formed 90 per cent of their stars by z ˜ 2. The lower mass objects, in contrast, have formed barely half their stars in this time interval. Stellar population properties are independent of environment over two orders of magnitude in local density, varying only with galaxy mass. In the highest density regions of our volume (dominated by the Virgo cluster), galaxies are older, alpha-enhanced, and have shorter star formation histories with respect to lower density regions.

  17. Growth of First Galaxies: Impacts of Star Formation and Stellar Feedback

    NASA Astrophysics Data System (ADS)

    Yajima, Hidenobu; Nagamine, Kentaro; Zhu, Qirong; Khochfar, Sadegh; Dalla Vecchia, Claudio

    2017-09-01

    Recent observations have detected galaxies at high-redshift z∼ 6{--}11, and revealed the diversity of their physical properties, from normal star-forming galaxies to starburst galaxies. To understand the properties of these observed galaxies, it is crucial to understand the star formation (SF) history of high-redshift galaxies under the influence of stellar feedback. In this work, we present the results of cosmological hydrodynamic simulations with zoom-in initial conditions, and investigate the formation of the first galaxies and their evolution toward observable galaxies at z∼ 6. We focus on three different galaxies that end up in halos with masses {M}{{h}}=2.4× {10}10 {h}-1 {M}ȯ (Halo-10), 1.6× {10}11 {h}-1 {M}ȯ (Halo-11), and 0.7× {10}12 {h}-1 {M}ȯ (Halo-12) at z = 6. Our simulations also probe the impacts of different subgrid assumptions, i.e., SF efficiency and cosmic reionization, on SF histories in the first galaxies. We find that SF occurs intermittently due to supernova (SN) feedback at z≳ 10, and then it proceeds more smoothly as the halo mass grows at lower redshifts. Galactic disks are destroyed due to SN feedback, while galaxies in simulations with no feedback or lower SF efficiency models can sustain a galactic disk for long periods ≳ 10 {Myr}. The expulsion of gas at the galactic center also affects the inner dark matter density profile for a short period. Our simulated galaxies in Halo-11 and Halo-12 reproduce the SF rates and stellar masses of observed Lyα emitters at z∼ 7{--}8 fairly well given the observational uncertainties.

  18. Sex discrimination potential of permanent maxillary molar cusp diameters.

    PubMed

    Macaluso, P J

    2010-12-01

    The purpose of the present investigation was to assess the potential usefulness of permanent maxillary molar cusp diameters for sex discrimination of poorly preserved skeletal remains. Cusp diameters were measured from standardized occlusal view photographs in a sample of black South Africans consisting of 130 males and 105 females. Results demonstrated that all cusp dimensions for both first and second maxillary molars exhibited significant sexual dimorphism (p < 0.001). Univariate and multivariate discriminant function equations permitted low to moderate classification accuracy in discriminating sex (58.3%-73.6%). The allocation accuracies for cusp diameter measurements were as high as, and even surpassed, those observed for conventional crown length and breadth dimensions of the same teeth. The most accurate result (73.6%, with a sex bias of only 0.5%) was obtained when all cusp diameters from both maxillary molars were used concurrently. However, only slightly less accurate results (~70.0%) were achieved when selected dimensions from only one of the molars, or even a single cusp, were utilized. Although not as reliable at predicting sex as other skeletal elements in black South Africans, the derived odontometric standards can be used with highly fragmentary skeletal material, as well as immature remains in which crown formation of the maxillary molars is complete.

  19. Star-formation and stellar feedback recipes in galaxy evolution models

    NASA Astrophysics Data System (ADS)

    Hensler, Gerhard; Recchi, Simone; Ploeckinger, Sylvia; Kuehtreiber, Matthias; Steyrleithner, Patrick; Liu, Lei

    2015-08-01

    Modeling galaxy formation and evolution is critically depending on star formation (SF). Since cosmological and galaxy-scale simulations cannot resolve the spatial and density scales on which SF acts, a large variety of methods are developed and applied over the last decades. Nonetheless, we are still in the test phase how the choice of parameters affects the models and how they agree with observations.As a simple ansatz, recipes are based on power-law SF dependences on gas density as justified by gas cooling and collapse timescales. In order to prevent SF spread throughout the gas, temperature and density thresholds are also used, although gas dynamical effects, like e.g. gas infall, seem to trigger SF significantly.The formed stars influence their environment immediately by energetic and materialistic feedback. It has been experienced in numerical models that supernova typeII explosions act with a too long time delay to regulate the SF, but that winds and ionizing radiation by massive stars must be included. The implementation of feedback processes, their efficiencies and timescales, is still in an experimental state, because they depend also on the physical state of the surrounding interstellar medium (ISM).Combining a SF-gas density relation with stellar heating vs. gas cooling and taking the temperature dependence into account, we have derived an analytical expression of self-regulated SF which is free of arbitrary parameters. We have performed numerical models to study this recipe and different widely used SF criteria in both, particle and grid codes. Moreover, we compare the SF behavior between single-gas phase and multi-phase treatments of the ISM.Since dwarf galaxies (DGs) are most sensitive to environmental influences and contain only low SF rates, we explore two main affects on their models: 1. For external effects we compare SF rates of isolated and ram-pressure suffering DGs. Moreover, we find a SF enhancement in tidal-tail DGs by the compressive tidal

  20. Triggered Star Formation and Young Stellar Population in Bright-rimmed Cloud SFO 38

    NASA Astrophysics Data System (ADS)

    Choudhury, Rumpa; Mookerjea, Bhaswati; Bhatt, H. C.

    2010-07-01

    We have investigated the young stellar population in and around SFO 38, one of the massive globules located in the northern part of the Galactic H II region IC 1396, using the Spitzer IRAC and MIPS observations (3.6-24 μm), and followed up with ground-based optical photometric and spectroscopic observations. Based on the IRAC and MIPS colors and Hα emission, we identify ~45 young stellar objects (Classes 0/I/II) and 13 probable pre-main-sequence candidates. We derive the spectral types (mostly K- and M-type stars), effective temperatures, and individual extinction of the relatively bright and optically visible Class II objects. Most of the Class II objects show variable Hα emission as well as optical and near-infrared photometric variability, which confirm their "youth." Based on optical photometry and theoretical isochrones, we estimate the spread in stellar ages to be between 1 and 8 Myr with a median age of 3 Myr and a mass distribution of 0.3-2.2 M sun with a median value around 0.5 M sun. Using the width of the Hα emission line measured at 10% peak intensity, we derive the mass accretion rates of individual objects to be between 10-10 and 10-8 M sun yr-1. From the continuum-subtracted Hα line image, we find that the Hα emission of the globule is not spatially symmetric with respect to the O-type ionizing star HD 206267, and the interstellar extinction toward the globule is also anomalous. We clearly detect an enhanced concentration of YSOs closer to the southern rim of SFO 38 and identify an evolutionary sequence of YSOs from the rim to the dense core of the cloud, with most of the Class II objects located at the bright rim. The YSOs appear to be aligned along two different directions toward the O6.5V type star HD 206267 and the B0V type star HD 206773. This is consistent with the Radiation Driven Implosion (RDI) model for triggered star formation. Further, the apparent speed of sequential star formation is consistent with the speed of propagation of

  1. TRIGGERED STAR FORMATION AND YOUNG STELLAR POPULATION IN BRIGHT-RIMMED CLOUD SFO 38

    SciTech Connect

    Choudhury, Rumpa; Bhatt, H. C.; Mookerjea, Bhaswati E-mail: hcbhatt@iiap.res.i

    2010-07-10

    We have investigated the young stellar population in and around SFO 38, one of the massive globules located in the northern part of the Galactic H II region IC 1396, using the Spitzer IRAC and MIPS observations (3.6-24 {mu}m), and followed up with ground-based optical photometric and spectroscopic observations. Based on the IRAC and MIPS colors and H{alpha} emission, we identify {approx}45 young stellar objects (Classes 0/I/II) and 13 probable pre-main-sequence candidates. We derive the spectral types (mostly K- and M-type stars), effective temperatures, and individual extinction of the relatively bright and optically visible Class II objects. Most of the Class II objects show variable H{alpha} emission as well as optical and near-infrared photometric variability, which confirm their 'youth'. Based on optical photometry and theoretical isochrones, we estimate the spread in stellar ages to be between 1 and 8 Myr with a median age of 3 Myr and a mass distribution of 0.3-2.2 M{sub sun} with a median value around 0.5 M{sub sun}. Using the width of the H{alpha} emission line measured at 10% peak intensity, we derive the mass accretion rates of individual objects to be between 10{sup -10} and 10{sup -8} M{sub sun} yr{sup -1}. From the continuum-subtracted H{alpha} line image, we find that the H{alpha} emission of the globule is not spatially symmetric with respect to the O-type ionizing star HD 206267, and the interstellar extinction toward the globule is also anomalous. We clearly detect an enhanced concentration of YSOs closer to the southern rim of SFO 38 and identify an evolutionary sequence of YSOs from the rim to the dense core of the cloud, with most of the Class II objects located at the bright rim. The YSOs appear to be aligned along two different directions toward the O6.5V type star HD 206267 and the B0V type star HD 206773. This is consistent with the Radiation Driven Implosion (RDI) model for triggered star formation. Further, the apparent speed of

  2. 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.

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

    NASA Astrophysics Data System (ADS)

    Bekki, Kenji

    2017-01-01

    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 onto 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] × 105M⊙ can accrete more than 105M⊙ gas from AGB stars of the SCC. We suggest that merging of hierarchical star cluster complexes can play key roles in stellar halo formation around GCs and self-enrichment processes in the early phase of GC formation.

  4. Influence of stellar multiplicity on planet formation. I. Evidence of suppressed planet formation due to stellar companions within 20 au and validation of four planets from the Kepler multiple planet candidates

    SciTech Connect

    Wang, Ji; Fischer, Debra A.; Xie, Ji-Wei; Barclay, Thomas

    2014-03-01

    The planet occurrence rate for multiple stars is important in two aspects. First, almost half of stellar systems in the solar neighborhood are multiple systems. Second, the comparison of the planet occurrence rate for multiple stars to that for single stars sheds light on the influence of stellar multiplicity on planet formation and evolution. We developed a method of distinguishing planet occurrence rates for single and multiple stars. From a sample of 138 bright (K{sub P} < 13.5) Kepler multi-planet candidate systems, we compared the stellar multiplicity rate of these planet host stars to that of field stars. Using dynamical stability analyses and archival Doppler measurements, we find that the stellar multiplicity rate of planet host stars is significantly lower than field stars for semimajor axes less than 20 AU, suggesting that planet formation and evolution are suppressed by the presence of a close-in companion star at these separations. The influence of stellar multiplicity at larger separations is uncertain because of search incompleteness due to a limited Doppler observation time baseline and a lack of high-resolution imaging observation. We calculated the planet confidence for the sample of multi-planet candidates and find that the planet confidences for KOI 82.01, KOI 115.01, KOI 282.01, and KOI 1781.02 are higher than 99.7% and thus validate the planetary nature of these four planet candidates. This sample of bright Kepler multi-planet candidates with refined stellar and orbital parameters, planet confidence estimation, and nearby stellar companion identification offers a well-characterized sample for future theoretical and observational study.

  5. Star formation in the vicinity of nuclear black holes: young stellar objects close to Sgr A*

    NASA Astrophysics Data System (ADS)

    Jalali, B.; Pelupessy, F. I.; Eckart, A.; Portegies Zwart, S.; Sabha, N.; Borkar, A.; Moultaka, J.; Mužić, K.; Moser, L.

    2014-10-01

    It is often assumed that the strong gravitational field of a super-massive black hole disrupts an adjacent molecular cloud preventing classical star formation in the deep potential well of the black hole. Yet, young stars have been observed across the entire nuclear star cluster of the Milky Way including the region close (<0.5 pc) to the central black hole, Sgr A*. Here, we focus particularly on small groups of young stars, such as IRS 13N located 0.1 pc away from Sgr A*, which is suggested to contain about five embedded massive young stellar objects (<1 Myr). We perform three-dimensional hydrodynamical simulations to follow the evolution of molecular clumps orbiting about a 4 × 106 M⊙ black hole, to constrain the formation and the physical conditions of such groups. The molecular clumps in our models are assumed to be isothermal containing 100 M⊙ in <0.2 pc radius. Such molecular clumps exist in the circumnuclear disc of the Galaxy. In our highly eccentrically orbiting clump, the strong orbital compression of the clump along the orbital radius vector and perpendicular to the orbital plane causes the gas densities to increase to values higher than the tidal density of Sgr A*, which are required for star formation. Additionally, we speculate that the infrared excess source G2/DSO approaching Sgr A* on a highly eccentric orbit could be associated with a dust-enshrouded star that may have been formed recently through the mechanism supported by our models.

  6. Auto-consistent test of Galaxy star formation histories derived from resolved stellar population and integral spectroscopy

    NASA Astrophysics Data System (ADS)

    Rodrigues, M.; Patricio, V.; Rothberg, B.; Sanchez-Janssen, R.; Vale Asari, N.

    We present the first results of our observational project 'Starfish' (STellar Population From Integrated Spectrum). The goal of this project is to calibrate, for the first time, the properties of stellar populations derived from integrated spectra with the same properties derived from direct imaging of stellar populations in the same set of galaxies. These properties include the star-formation history (SFH), stellar mass, age, and metallicity. To date, such calibrations have been demonstrated only in star clusters, globular clusters with single stellar populations, not in complex and composite objects such as galaxies. We are currently constructing a library of integrated spectra obtained from a sample of 38 nearby dwarf galaxies obtained with GEMINI/GMOS-N&S (25h) and VLT/VIMOS-IFU (43h). These are to be compared with color magnitude diagrams (CMDs) of the same galaxies constructed from archival HST imaging sensitive to at least 1.5 magnitudes below the tip of the red giant branch. From this comparison we will assess the systematics and uncertainties from integrated spectral techniques. The spectra library will be made publicly available to the community via a dedicated web-page and Vizier database. This dataset will provide a unique benchmark for testing fitting procedures and stellar population models for both nearby and distant galaxies. http://www.sc.eso.org/˜marodrig/Starfish/

  7. Star formation in galaxy mergers with realistic models of stellar feedback and the interstellar medium

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Cox, Thomas J.; Hernquist, Lars; Narayanan, Desika; Hayward, Christopher C.; Murray, Norman

    2013-04-01

    We use hydrodynamic simulations with detailed, explicit models for stellar feedback to study galaxy mergers. These high-resolution (˜1 pc) simulations follow the formation and destruction of individual giant molecular clouds (GMC) and star clusters. We find that the final starburst is dominated by in situ star formation, fuelled by gas which flows inwards due to global torques. The resulting high gas density results in rapid star formation. The gas is self-gravitating, and forms massive (≲1010 M⊙) GMC and subsequently super star clusters (with masses up to 108 M⊙). However, in contrast to some recent simulations, the bulk of new stars which eventually form the central bulge are not born in super-clusters which then sink to the centre of the galaxy. This is because feedback efficiently disperses GMC after they turn several per cent of their mass into stars. In other words, most of the mass that reaches the nucleus does so in the form of gas. The Kennicutt-Schmidt law emerges naturally as a consequence of feedback balancing gravitational collapse, independent of the small-scale star formation microphysics. The same mechanisms that drive this relation in isolated galaxies, in particular radiation pressure from infrared photons, extend, with no fine-tuning, over seven decades in star formation rate (SFR) to regulate star formation in the most extreme starburst systems with densities ≳104 M⊙ pc-2. This feedback also drives super-winds with large mass-loss rates; however, a significant fraction of the wind material falls back on to the discs at later times, leading to higher post-starburst SFRs in the presence of stellar feedback. This suggests that strong active galactic nucleus feedback may be required to explain the sharp cut-offs in SFR that are observed in post-merger galaxies. We compare the results to those from simulations with no explicit resolution of GMC or feedback [`effective equation-of-state' (EOS) models]. We find that global galaxy properties

  8. Structure of the Outer Cusp and Sources of the Cusp Precipitation during Intervals of a Horizontal IMF

    NASA Technical Reports Server (NTRS)

    Nemecek, Z.; Safrankova, J.; Prech, L.; Simunek, J.; Sauvaud, J.-A.; Fedorov, A.; Stenuit, H.; Fuselier, S. A.; Savin, S.; Zelenyi, L.

    2003-01-01

    The cusp represents a place where the magnetosheath plasma can directly penetrate into the magnetosphere. Since the main transport processes are connected with merging of the interplanetary and magnetospheric field lines, the interplanetary magnetic field (IMF) Orientation plays a decisive role in the formation of the high-altitude cusp. The importance of the sign of the IMF Bz component for this process was suggested about 40 years ago and later it was documented by many experimental investigations. However, situations when IMF Bz is the major IMF component are rather rare. The structure of the cusp during periods of a small IMF BZ is generally unknown, probably due to the fully 3-D nature of the interaction. The present case study reveals the importance of horizontal IMF components on the global magnetospheric configuration as well as on small-scale processes at the cusp-magnetosheath interface. We have used simultaneous measurements of several spacecraft (ISTP program) operating in different regions of interplanetary space and two closely spaced satellites (INTERBALL-1/MAGION- 4) crossing the cusp-magnetosheath boundary to show the connection between the short- and large-scale phenomena. In the northern hemisphere, observations suggest a presence of two spots of cusp-like precipitation supplied by reconnection occurring simultaneously in both hemispheres. A source of this bifurcation is the positive IMF By component further enhanced by the field draping in the magnetosheath. This magnetic field component shifts the entry point far away from the local noon but in opposite sense in either hemisphere.

  9. Stellar mass to halo mass relation from galaxy clustering in VUDS: a high star formation efficiency at z ≃ 3

    NASA Astrophysics Data System (ADS)

    Durkalec, A.; Le Fèvre, O.; de la Torre, S.; Pollo, A.; Cassata, P.; Garilli, B.; Le Brun, V.; Lemaux, B. C.; Maccagni, D.; Pentericci, L.; Tasca, L. A. M.; Thomas, R.; Vanzella, E.; Zamorani, G.; Zucca, E.; Amorín, R.; Bardelli, S.; Cassarà, L. P.; Castellano, M.; Cimatti, A.; Cucciati, O.; Fontana, A.; Giavalisco, M.; Grazian, A.; Hathi, N. P.; Ilbert, O.; Paltani, S.; Ribeiro, B.; Schaerer, D.; Scodeggio, M.; Sommariva, V.; Talia, M.; Tresse, L.; Vergani, D.; Capak, P.; Charlot, S.; Contini, T.; Cuby, J. G.; Dunlop, J.; Fotopoulou, S.; Koekemoer, A.; López-Sanjuan, C.; Mellier, Y.; Pforr, J.; Salvato, M.; Scoville, N.; Taniguchi, Y.; Wang, P. W.

    2015-04-01

    The relation between the galaxy stellar mass M⋆ and the dark matter halo mass Mh gives important information on the efficiency in forming stars and assembling stellar mass in galaxies. We present measurements of the ratio of stellar mass to halo mass (SMHR) at redshifts 2 < z < 5, obtained from the VIMOS Ultra Deep Survey. We use halo occupation distribution (HOD) modelling of clustering measurements on ~3000 galaxies with spectroscopic redshifts to derive the dark matter halo mass Mh, and spectral energy density fitting over a large set of multi-wavelength data to derive the stellar mass M⋆ and compute the SMHR = M⋆/Mh. We find that the SMHR ranges from 1% to 2.5% for galaxies with M⋆ = 1.3 × 109 M⊙ to M⋆ = 7.4 × 109 M⊙ in DM halos with Mh = 1.3 × 1011 M⊙ to Mh = 3 × 1011 M⊙. We derive the integrated star formation efficiency (ISFE) of these galaxies and find that the star formation efficiency is a moderate 6-9% for lower mass galaxies, while it is relatively high at 16% for galaxies with the median stellar mass of the sample ~ 7 × 109 M⊙. The lower ISFE at lower masses may indicate that some efficient means of suppressing star formation is at work (like SNe feedback), while the high ISFE for the average galaxy at z ~ 3 indicates that these galaxies efficiently build up their stellar mass at a key epoch in the mass assembly process. Based on our results, we propose a possible scenario in which the average massive galaxy at z ~ 3 begins to experience truncation of its star formation within a few million years. Based on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, under Large Program 185.A-0791.

  10. The Ara OB1a association. Stellar population and star formation history

    NASA Astrophysics Data System (ADS)

    Baume, G.; Carraro, G.; Comeron, F.; de Elía, G. C.

    2011-07-01

    Context. The Ara OB1a association is a nearby complex in the fourth Galactic quadrant where a number of young/embedded star clusters are projected close to more evolved, intermediate age clusters. It is also rich in interstellar matter, and contains evidence of the interplay between massive stars and their surrounding medium, such as the rim HII region NGC 6188. Aims: We provide robust estimates of the fundamental parameters (age and distance) of the two most prominent stellar clusters, NGC 6167 and NGC 6193, that may be used as a basis for studing the star formation history of the region. Methods: The study is based on a photometric optical survey (UBVIHα) of NGC 6167 and NGC 6193 and their nearby field, complemented with data from 2MASS-VVV, UCAC3, and IRAC-Spitzer in this region. Results: We produce a uniform photometric catalogue and estimate more robustly the fundamental parameters of NGC 6167 and NGC 6193, in addition to the IRAS 16375-4854 source. As a consequence, all of them are located at approximately the same distance from the Sun in the Sagittarius-Carina Galactic arm. However, the ages we estimate differ widely: NGC 6167 is found to be an intermediate-age cluster (20-30 Myr), NGC 6193 a very young one (1-5 Myr) with PMS, Hα emitters and class II objects, and the IRAS 16375-4854 source is the youngest of the three containing several YSOs. Conclusions: These results support a picture in which Ara OB1a is a region where star formation has proceeded for several tens of Myr until the present. The difference in the ages of the different stellar groups can be interpreted as a consequence of a triggered star formation process. In the specific case of NGC 6193, we find evidence of possible non-coeval star formation. Two catalogs are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/531/A73

  11. Core-halo age gradients and star formation in the Orion Nebula and NGS 2024 young stellar clusters

    SciTech Connect

    Getman, Konstantin V.; Feigelson, Eric D.; Kuhn, Michael A.

    2014-06-01

    We analyze age distributions of two nearby rich stellar clusters, the NGC 2024 (Flame Nebula) and Orion Nebula cluster (ONC) in the Orion molecular cloud complex. Our analysis is based on samples from the MYStIX survey and a new estimator of pre-main sequence (PMS) stellar ages, Age{sub JX} , derived from X-ray and near-infrared photometric data. To overcome the problem of uncertain individual ages and large spreads of age distributions for entire clusters, we compute median ages and their confidence intervals of stellar samples within annular subregions of the clusters. We find core-halo age gradients in both the NGC 2024 cluster and ONC: PMS stars in cluster cores appear younger and thus were formed later than PMS stars in cluster peripheries. These findings are further supported by the spatial gradients in the disk fraction and K-band excess frequency. Our age analysis is based on Age{sub JX} estimates for PMS stars and is independent of any consideration of OB stars. The result has important implications for the formation of young stellar clusters. One basic implication is that clusters form slowly and the apparent age spreads in young stellar clusters, which are often controversial, are (at least in part) real. The result further implies that simple models where clusters form inside-out are 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.

  12. Mg line formation in late-type stellar atmospheres. I. The model atom

    NASA Astrophysics Data System (ADS)

    Osorio, Y.; Barklem, P. S.; Lind, K.; Belyaev, A. K.; Spielfiedel, A.; Guitou, M.; Feautrier, N.

    2015-07-01

    Context. Magnesium is an element of significant astrophysical importance, often traced in late-type stars using lines of neutral magnesium, which is expected to be subject to departures from local thermodynamic equilibrium (LTE). The importance of Mg , together with the unique range of spectral features in late-type stars probing different parts of the atom, as well as its relative simplicity from an atomic physics point of view, makes it a prime target and test bed for detailed ab initio non-LTE modelling in stellar atmospheres. Previous non-LTE modelling of spectral line formation has, however, been subject to uncertainties due to lack of accurate data for inelastic collisions with electrons and hydrogen atoms. Aims: In this paper we build and test a Mg model atom for spectral line formation in late-type stars with new or recent inelastic collision data and no associated free parameters. We aim to reduce these uncertainties and thereby improve the accuracy of Mg non-LTE modelling in late-type stars. Methods: For the low-lying states of Mg i, electron collision data were calculated using the R-matrix method. Hydrogen collision data, including charge transfer processes, were taken from recent calculations by some of us. Calculations for collisional broadening by neutral hydrogen were also performed where data were missing. These calculations, together with data from the literature, were used to build a model atom. This model was then employed in the context of standard non-LTE modelling in 1D (including average 3D) model atmospheres in a small set of stellar atmosphere models. First, the modelling was tested by comparisons with observed spectra of benchmark stars with well-known parameters. Second, the spectral line behaviour and uncertainties were explored by extensive experiments in which sets of collisional data were changed or removed. Results: The modelled spectra agree well with observed spectra from benchmark stars, showing much better agreement with line

  13. Initial conditions of formation of starburst clusters: constraints from stellar dynamics

    NASA Astrophysics Data System (ADS)

    Banerjee, Sambaran; Kroupa, Pavel

    2015-08-01

    Recent high resolution observations of dense regions of molecular clouds and massive gaseous clumps with instruments like Herschel and ALMA have revealed intricate and filamentary overdensity structures in them. Such progenitors of massive starburst clusters are in contrast with smooth, centrally-pronounced profiles of the latter. In this work, we intend to constrain massive, substructured stellar distributions that would evolve to cluster-like profiles at very young ages (~Myr), as seen in starburst clusters. Taking the well observed NGC3603 Young Cluster (NYC) as an example, we compute the infall and final merger of filament-like compact (0.1-0.3 pc) subclusters, totalling 10000 M_sun, from a range of spatial scales and modes of sub-clustering, using direct N-body calculations. These calculations infer an allowable span of approx. 2.5 pc from which the subclusters can fall in a gas potential and merge to form a single centrally-dense structure in near dynamical equilibrium, within the young age of NYC (1-2 Myr). However, these merged clusters are too compact and centrally overdense compared to typical young clusters. Our N-body calculations, beginning from such compact initial conditions, show that even stellar wind and supernova mass loss, dynamical heating from retaining black holes, external tidal field and heating due to tight O-star binaries together cannot expand these clusters to their observed sizes, even in 100 Myr. Hence an explosive gas dispersal phase seems essential for forming starburst and other young clusters observed in the Milky Way and in the Local Group which can expand the clusters to their observed sizes and concentrations; including that for NYC with approx. 30% clump star formation efficiency. However, some observed massive but highly extended (>10 pc) , >10 Myr old clusters better fit a slow (several Myr timescale) gas dispersal from parsec-scale initial profiles, which can be the future of embedded systems like W3 Main.

  14. The regulation of star formation in cool-core clusters: imprints on the stellar populations of brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Loubser, S. I.; Babul, A.; Hoekstra, H.; Mahdavi, A.; Donahue, M.; Bildfell, C.; Voit, G. M.

    2016-02-01

    A fraction of brightest cluster galaxies (BCGs) show bright emission in the ultraviolet and the blue part of the optical spectrum, which has been interpreted as evidence of recent star formation. Most of these results are based on the analysis of broad-band photometric data. Here, we study the optical spectra of a sample of 19 BCGs hosted by X-ray luminous galaxy clusters at 0.15 formation histories of the galaxies by fitting simple stellar populations as well as composite populations, consisting of a young stellar component superimposed on an intermediate/old stellar component, to accurately constrain their star formation histories. We detect prominent young (˜200 Myr) stellar populations in four of the 19 galaxies. Of the four, the BCG in Abell 1835 shows remarkable A-type stellar features indicating a relatively large population of young stars, which is extremely unusual even amongst star-forming BCGs. We constrain the mass contribution of these young components to the total stellar mass to be typically between 1 and 3 per cent, but rising to 7 per cent in Abell 1835. We find that the four of the BCGs with strong evidence for recent star formation (and only these four galaxies) are found within a projected distance of 5 kpc of their host cluster's X-ray peak, and the diffuse, X-ray gas surrounding the BCGs exhibits a ratio of the radiative cooling-to-free-fall time (tc/tff) of ≤10. These are also some of the clusters with the lowest central entropy. Our results are consistent with the predictions of the precipitation-driven star formation and active galactic nucleus feedback model, in which the radiatively cooling diffuse gas is subject to local thermal instabilities once the instability parameter tc/tff falls below ˜10, leading to the condensation and precipitation of cold gas. The number of galaxies in our sample where the host cluster satisfies all the

  15. Stellar Masses and Star Formation Rates for 1M Galaxies from SDSS+WISE

    NASA Astrophysics Data System (ADS)

    Chang, Yu-Yen; van der Wel, Arjen; da Cunha, Elisabete; Rix, Hans-Walter

    2015-07-01

    We combine Sloan Digitital Sky Survey (SDSS) and WISE photometry for the full SDSS spectroscopic galaxy sample, creating spectral energy distributions (SEDs) that cover λ = 0.4-22 μm for an unprecedentedly large and comprehensive sample of 858,365 present-epoch galaxies. Using MAGPHYS, we then simultaneously and consistently model both the attenuated stellar SED and the dust emission at 12 and 22 μm, producing robust new calibrations for monochromatic mid-IR star formation rate (SFR) proxies. These modeling results provide the first mid-IR-based view of the bimodality in star formation activity among galaxies, exhibiting the sequence of star-forming galaxies (“main sequence”) with a slope of d {log} {SFR}/d{log}{M}* = 0.80 and a scatter of 0.39 dex. We find that these new SFRs along the SF main sequence are systematically lower by a factor of 1.4 than those derived from optical spectroscopy. We show that for most present-day galaxies, the 0.4-22 μm SED fits can exquisitely predict the fluxes measured by Herschel at much longer wavelengths. Our analysis also illustrates that the majority of stars in the present-day universe are formed in luminous galaxies (˜ {L}*) in and around the “green valley” of the color-luminosity plane. We make publicly available the matched photometry catalog and SED modeling results.

  16. Formation of the Galactic Stellar Halo: Origin of the Metallicity-Eccentricity Relation.

    PubMed

    Bekki; Chiba

    2000-05-01

    Motivated by the recently improved knowledge on the kinematic and chemical properties of the Galactic metal-poor stars, we present the numerical simulation for the formation of the Galactic stellar halo to interpret the observational results. As a model for the Galaxy contraction, we adopt the currently standard theory of galaxy formation based on the hierarchical assembly of the cold dark matter fluctuations. We find, for the simulated stars with &sqbl0;Fe&solm0;H&sqbr0;

  17. CHARACTERIZING THE FORMATION HISTORY OF MILKY WAY LIKE STELLAR HALOS WITH MODEL EMULATORS

    SciTech Connect

    Gomez, Facundo A.; O'Shea, Brian W.; Coleman-Smith, Christopher E.; Tumlinson, Jason; Wolpert, Robert L.

    2012-12-01

    We use the semi-analytic model ChemTreeN, coupled to cosmological N-body simulations, to explore how different galaxy formation histories can affect observational properties of Milky Way like galaxies' stellar halos and their satellite populations. Gaussian processes are used to generate model emulators that allow one to statistically estimate a desired set of model outputs at any location of a p-dimensional input parameter space. This enables one to explore the full input parameter space orders of magnitude faster than could be done otherwise. Using mock observational data sets generated by ChemTreeN itself, we show that it is possible to successfully recover the input parameter vectors used to generate the mock observables if the merger history of the host halo is known. However, our results indicate that for a given observational data set, the determination of 'best-fit' parameters is highly susceptible to the particular merger history of the host. Very different halo merger histories can reproduce the same observational data set, if the 'best-fit' parameters are allowed to vary from history to history. Thus, attempts to characterize the formation history of the Milky Way using these kind of techniques must be performed statistically, analyzing large samples of high-resolution N-body simulations.

  18. Formation of the Galactic Stellar Halo: Origin of the Metallicity-Eccentricity Relation

    NASA Astrophysics Data System (ADS)

    Bekki, Kenji; Chiba, Masashi

    2000-05-01

    Motivated by the recently improved knowledge on the kinematic and chemical properties of the Galactic metal-poor stars, we present the numerical simulation for the formation of the Galactic stellar halo to interpret the observational results. As a model for the Galaxy contraction, we adopt the currently standard theory of galaxy formation based on the hierarchical assembly of the cold dark matter fluctuations. We find, for the simulated stars with [Fe/H]<=-1.0, that there is no strong correlation between metal abundances and orbital eccentricities, in good agreement with the observations. Moreover, the observed fraction of the low-eccentricity stars is reproduced correctly for [Fe/H]<=-1.6 and approximately for the intermediate abundance range of -1.6<[Fe/H]<=-1.0. We show that this successful reproduction of the kinematics of the Galactic halo is a natural consequence of the hierarchical evolution of the subgalactic clumps seeded from the cold dark matter density fluctuations.

  19. From cusps to cores: a stochastic model

    NASA Astrophysics Data System (ADS)

    El-Zant, Amr A.; Freundlich, Jonathan; Combes, Françoise

    2016-09-01

    The cold dark matter model of structure formation faces apparent problems on galactic scales. Several threads point to excessive halo concentration, including central densities that rise too steeply with decreasing radius. Yet, random fluctuations in the gaseous component can `heat' the centres of haloes, decreasing their densities. We present a theoretical model deriving this effect from first principles: stochastic variations in the gas density are converted into potential fluctuations that act on the dark matter; the associated force correlation function is calculated and the corresponding stochastic equation solved. Assuming a power-law spectrum of fluctuations with maximal and minimal cutoff scales, we derive the velocity dispersion imparted to the halo particles and the relevant relaxation time. We further perform numerical simulations, with fluctuations realized as a Gaussian random field, which confirm the formation of a core within a time-scale comparable to that derived analytically. Non-radial collective modes enhance the energy transport process that erases the cusp, though the parametrizations of the analytical model persist. In our model, the dominant contribution to the dynamical coupling driving the cusp-core transformation comes from the largest scale fluctuations. Yet, the efficiency of the transformation is independent of the value of the largest scale and depends weakly (linearly) on the power-law exponent; it effectively depends on two parameters: the gas mass fraction and the normalization of the power spectrum. This suggests that cusp-core transformations observed in hydrodynamic simulations of galaxy formation may be understood and parametrized in simple terms, the physical and numerical complexities of the various implementations notwithstanding.

  20. Connecting stellar mass and star-formation rate to dark matter halo mass out to z ˜ 2

    NASA Astrophysics Data System (ADS)

    Wang, L.; Farrah, D.; Oliver, S. J.; Amblard, A.; Béthermin, M.; Bock, J.; Conley, A.; Cooray, A.; Halpern, M.; Heinis, S.; Ibar, E.; Ilbert, O.; Ivison, R. J.; Marsden, G.; Roseboom, I. G.; Rowan-Robinson, M.; Schulz, B.; Smith, A. J.; Viero, M.; Zemcov, M.

    2013-05-01

    We have constructed an extended halo model (EHM) which relates the total stellar mass and star-formation rate (SFR) to halo mass (Mh). An empirical relation between the distribution functions of total stellar mass of galaxies and host halo mass, tuned to match the spatial density of galaxies over 0 < z < 2 and the clustering properties at z ˜ 0, is extended to include two different scenarios describing the variation of SFR on Mh. We also present new measurements of the redshift evolution of the average SFR for star-forming galaxies of different stellar masses up to z = 2, using data from the Herschel Multi-tiered Extragalactic Survey for infrared bright galaxies. Combining the EHM with the halo accretion histories from numerical simulations, we trace the stellar mass growth and star-formation history in haloes spanning a range of masses. We find that: (1) the intensity of the star-forming activity in haloes in the probed mass range has steadily decreased from z ˜ 2 to 0; (2) at a given epoch, haloes in the mass range between a few times 1011 M⊙ and a few times 1012 M⊙ are the most efficient at hosting star formation; (3) the peak of SFR density shifts to lower mass haloes over time; and (4) galaxies that are forming stars most actively at z ˜ 2 evolve into quiescent galaxies in today's group environments, strongly supporting previous claims that the most powerful starbursts at z ˜ 2 are progenitors of today's elliptical galaxies.

  1. Stellar populations and Star Formation Rates in NGC 6872, the Condor galaxy

    NASA Astrophysics Data System (ADS)

    Eufrasio, Rafael T.; De Mello, D. F.; Dwek, E.; Arendt, R. G.; Gadotti, D. A.

    2014-01-01

    We present a detailed analysis of the Spectral Energy Distributions (SEDs) of 10 kpc regions across the giant spiral galaxy NGC 6872, the Condor galaxy. We made use of archival data from the FUV (GALEX) to 22 μm (WISE). In order to find any signature of the recent interaction 130 Myr) with its companion, the S0 galaxy IC 4970, we inspected the SED of Condor's bar. One possibility is that is would have been formed by passage of the companion. We find that it is a particularly long bar (9 kpc semi-major axis), with a size almost twice as large as the average found in other barred galaxies (4.5 kpc median in the local universe, Gadotti 2011). A bulge/bar/disk 2D decomposition using the Spitzer 3.6 μm image and the budda package (de Souza et al. 2004; Gadotti 2008) reveals that the ratio of the bar semi-major axis to the disk scale-length is 1.4, which is a value typically found in other barred galaxies (see Fig. 1 in Gadotti 2011). The disk scale-length is ~ 7 kpc, which is extremely large (2.8 kpc median in local galaxies, Gadotti 2009). Our analysis also shows that there are no signs of recent star formation along the bar. We find no signs of a box-peanut structure near the central regions, which is also another signature of an evolved bar. Taken altogether, the evidence points to a bar formed at least a few billion years ago and the stars in the bar seem to be a fossil record of the stellar population in the galaxy before the interaction with its companion. Then, we modeled the SFH of each 10 kpc region as constant Star Formation Rate (SFR) for the past 100 Myr superposed on an exponentially decaying, longstanding SFR. We find a single exponential SFH to account for all the recent SFR of the galaxy, with no need for an additional SFR due to the interaction. Av is low all across the galaxy 0.25), but increases near 0.7) the point of collision. The SFH of the arms are asymmetric. The northeastern arm having older ages 5 Gyr) and SFH closer to constant, while the

  2. A robust sample of galaxies at redshifts 6.0stellar populations, star formation rates and stellar masses

    NASA Astrophysics Data System (ADS)

    McLure, R. J.; Dunlop, J. S.; de Ravel, L.; Cirasuolo, M.; Ellis, R. S.; Schenker, M.; Robertson, B. E.; Koekemoer, A. M.; Stark, D. P.; Bowler, R. A. A.

    2011-12-01

    We present the results of a photometric redshift analysis designed to identify z≥ 6 galaxies from the near-infrared Hubble Space Telescope imaging in three deep fields [Hubble Ultra Deep Field (HUDF), HUDF09-2 and Early Release Science] covering a total area of 45 square arcmin. By adopting a rigorous set of criteria for rejecting low-redshift interlopers, and by employing a deconfusion technique to allow the available ultradeep IRAC imaging to be included in the candidate-selection process, we have derived a robust sample of 70 Lyman break galaxies (LBGs) spanning the redshift range 6.0 < z < 8.7. Based on our final sample, we investigate the distribution of ultraviolet (UV) spectral slopes (fλ∝λβ), finding a variance-weighted mean value of <β>=-2.05 ± 0.09 which, contrary to some previous results, is not significantly bluer than displayed by lower redshift starburst galaxies. We confirm the correlation between UV luminosity and stellar mass reported elsewhere, but based on fitting galaxy templates featuring a range of star formation histories (SFHs), metallicities and reddening, we find that, at z≥ 6, the range in mass-to-light ratio (M★/LUV) at a given UV luminosity could span a factor of ≃50. Focusing on a subsample of 21 candidates with IRAC detections at ?m, we find that L★ LBGs at z≃ 6.5 have a median stellar mass of M★= (2.1 ± 1.1) × 109 M⊙ (Chabrier initial mass function) and a median specific star formation rate (sSFR) of 1.9 ± 0.8 Gyr-1. Using the same subsample, we have investigated the influence of nebular continuum and line emission, finding that for the majority of candidates (16 out of 21), the best-fitting stellar masses are reduced by less than a factor of 2.5. However, galaxy template fits exploring a plausible range of SFHs and metallicities provide no compelling evidence of a clear connection between SFR and stellar mass at these redshifts. Finally, a detailed comparison of our final sample with the results of previous

  3. The SLUGGS survey: using extended stellar kinematics to disentangle the formation histories of low-mass S0 galaxies

    NASA Astrophysics Data System (ADS)

    Bellstedt, Sabine; Forbes, Duncan A.; Foster, Caroline; Romanowsky, Aaron J.; Brodie, Jean P.; Pastorello, Nicola; Alabi, Adebusola; Villaume, Alexa

    2017-06-01

    We utilize the DEIMOS instrument on the Keck telescope to measure the wide-field stellar kinematics of early-type galaxies as part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey. In this paper, we focus on some of the lowest stellar mass lenticular galaxies within this survey, namely NGC 2549, NGC 4474, NGC 4459 and NGC 7457, performing detailed kinematic analyses out to large radial distances of ˜2-3 effective radii. For NGC 2549, we present the first analysis of data taken with the SuperSKiMS (Stellar Kinematics from Multiple Slits) technique. To better probe kinematic variations in the outskirts of the SLUGGS galaxies, we have defined a local measure of stellar spin. We use this parameter and identify a clear separation in the radial behaviour of stellar spin between lenticular and elliptical galaxies. We compare the kinematic properties of our galaxies with those from various simulated galaxies to extract plausible formation scenarios. By doing this for multiple simulations, we assess the consistency of the theoretical results. Comparisons to binary merger simulations show that low-mass lenticular galaxies generally resemble the spiral progenitors more than the merger remnants themselves, which is an indication that these galaxies are not formed through merger events. We find, however, that recent mergers cannot be ruled out for some lenticular galaxies.

  4. The growth of discs and bulges during hierarchical galaxy formation - II. Metallicity, stellar populations and dynamical evolution

    NASA Astrophysics Data System (ADS)

    Tonini, C.; Mutch, S. J.; Wyithe, J. S. B.; Croton, D. J.

    2017-03-01

    We investigate the properties of the stellar populations of model galaxies as a function of galaxy evolutionary history and angular momentum content. We use the new semi-analytic model presented in Tonini et al. This new model follows the angular momentum evolution of gas and stars, providing the base for a new star formation recipe, and treatment of the effects of mergers that depends on the central galaxy dynamical structure. We find that the new recipes have the effect of boosting the efficiency of the baryonic cycle in producing and recycling metals, as well as preventing minor mergers from diluting the metallicity of bulges and ellipticals. The model reproduces the stellar mass-stellar metallicity relation for galaxies above 1010 solar masses, including Brightest Cluster Galaxies. Model discs, galaxies dominated by instability-driven components, and merger-driven objects each stem from different evolutionary channels. These model galaxies therefore occupy different loci in the galaxy mass-size relation, which we find to be in accord with the ATLAS 3D classification of disc galaxies, fast rotators and slow rotators. We find that the stellar populations' properties depend on the galaxy evolutionary type, with more evolved stellar populations being part of systems that have lost or dissipated more angular momentum during their assembly history.

  5. The gaseous proto-cluster as a product of gravo-turbulent interaction: modified local environment for stellar cluster formation?

    NASA Astrophysics Data System (ADS)

    Lee, Y.-N.; Hennebelle, P.

    2016-12-01

    Stars are often observed to form in clusters, while the formation of the gaseous proto-cluster precedes that of the stellar cluster. We discuss the assembly of gas via gravo-turbulent reprocessing inside collapsing molecular clouds, and demonstrate that virial equilibrium is established for the gaseous proto-cluster, of which the higher density is favorable for clustered star formation, and that some physical characteristics of the stellar cluster are inherited from the gaseous proto-cluster. We introduce an analytical two-dimensional virial model to account for the quasi-stationary accreting gaseous proto-cluster which has non-negligible rotation. Results are compared to observations and simulations and the fact that gaseous proto-clusters lie on an equilibrium sequence may imply that star formation could be to some extent disentangled from larger scale physics, offering an encouraging explanation for the universality of IMF.

  6. Formation of Wide-orbit Gas Giants Near the Stability Limit in Multi-stellar Systems

    NASA Astrophysics Data System (ADS)

    Higuchi, A.; Ida, S.

    2017-09-01

    We have investigated the formation of a circumstellar wide-orbit gas giant planet in a multiple stellar system. We consider a model of orbital circularization for the core of a giant planet after it is scattered from an inner disk region by a more massive planet, which was proposed by Kikuchi et al. We extend their model for single star systems to binary (multiple) star systems, by taking into account tidal truncation of the protoplanetary gas disk by a binary companion. As an example, we consider a wide-orbit gas giant in a hierarchical triple system, HD131399Ab. The best-fit orbit of the planet is that with semimajor axis ˜80 au and eccentricity ˜0.35. As the binary separation is ˜350 au, it is very close to the stability limit, which is puzzling. With the original core location ˜20-30 au, the core (planet) mass ˜50 M E and the disk truncation radius ˜150 au, our model reproduces the best-fit orbit of HD131399Ab. We find that the orbit after the circularization is usually close to the stability limit against the perturbations from the binary companion, because the scattered core accretes gas from the truncated disk. Our conclusion can also be applied to wider or more compact binary systems if the separation is not too large and another planet with ≳20-30 Earth masses that scattered the core existed in inner region of the system.

  7. Formation of warped disks by galactic flyby encounters. I. Stellar disks

    SciTech Connect

    Kim, Jeonghwan H.; An, Sung-Ho; Yoon, Suk-Jin; Peirani, Sebastien; Kim, Sungsoo; Ann, Hong Bae

    2014-07-01

    Warped disks are almost ubiquitous among spiral galaxies. Here we revisit and test the 'flyby scenario' of warp formation, in which impulsive encounters between galaxies are responsible for warped disks. Based on N-body simulations, we investigate the morphological and kinematical evolution of the stellar component of disks when galaxies undergo flyby interactions with adjacent dark matter halos. We find that the so-called 'S'-shaped warps can be excited by flybys and sustained for even up to a few billion years, and that this scenario provides a cohesive explanation for several key observations. We show that disk warp properties are governed primarily by the following three parameters: (1) the impact parameter, i.e., the minimum distance between two halos; (2) the mass ratio between two halos; and (3) the incident angle of the flyby perturber. The warp angle is tied up with all three parameters, yet the warp lifetime is particularly sensitive to the incident angle of the perturber. Interestingly, the modeled S-shaped warps are often non-symmetric depending on the incident angle. We speculate that the puzzling U- and L-shaped warps are geometrically superimposed S-types produced by successive flybys with different incident angles, including multiple interactions with a satellite on a highly elongated orbit.

  8. Determining the mechanism of cusp proton aurora

    PubMed Central

    Xiao, Fuliang; Zong, Qiugang; Su, Zhenpeng; Yang, Chang; He, Zhaoguo; Wang, Yongfu; Gao, Zhonglei

    2013-01-01

    Earth's cusp proton aurora occurs near the prenoon and is primarily produced by the precipitation of solar energetic (2–10 keV) protons. Cusp auroral precipitation provides a direct source of energy for the high-latitude dayside upper atmosphere, contributing to chemical composition change and global climate variability. Previous studies have indicated that magnetic reconnection allows solar energetic protons to cross the magnetopause and enter the cusp region, producing cusp auroral precipitation. However, energetic protons are easily trapped in the cusp region due to a minimum magnetic field existing there. Hence, the mechanism of cusp proton aurora has remained a significant challenge for tens of years. Based on the satellite data and calculations of diffusion equation, we demonstrate that EMIC waves can yield the trapped proton scattering that causes cusp proton aurora. This moves forward a step toward identifying the generation mechanism of cusp proton aurora. PMID:23575366

  9. Determining the mechanism of cusp proton aurora.

    PubMed

    Xiao, Fuliang; Zong, Qiugang; Su, Zhenpeng; Yang, Chang; He, Zhaoguo; Wang, Yongfu; Gao, Zhonglei

    2013-01-01

    Earth's cusp proton aurora occurs near the prenoon and is primarily produced by the precipitation of solar energetic (2-10 keV) protons. Cusp auroral precipitation provides a direct source of energy for the high-latitude dayside upper atmosphere, contributing to chemical composition change and global climate variability. Previous studies have indicated that magnetic reconnection allows solar energetic protons to cross the magnetopause and enter the cusp region, producing cusp auroral precipitation. However, energetic protons are easily trapped in the cusp region due to a minimum magnetic field existing there. Hence, the mechanism of cusp proton aurora has remained a significant challenge for tens of years. Based on the satellite data and calculations of diffusion equation, we demonstrate that EMIC waves can yield the trapped proton scattering that causes cusp proton aurora. This moves forward a step toward identifying the generation mechanism of cusp proton aurora.

  10. Structure of the Outer Cusp and Sources of the Cusp Precipitation during Intervals of a Horizontal IMF

    NASA Technical Reports Server (NTRS)

    Berchem, Jean; Nemecek, Z.; Safrankova, J.; Prech, L.; Simunek, J.; Sauvaud, J.-A.; Fedorov, A.; Stenuit, H.; Fuselier, S. A.; Savin, S.; hide

    2003-01-01

    The cusp represents a place where the magnetosheath plasma can directly penetrate into the magnetosphere. Since the main transport processes are connected with merging of the interplanetary and magnetospheric field lines: the interplanetary magnetic field (IMF) Orientation plays a decisive role in the formation of the high-altitude cusp. The importance of the sign of the IMF B(sub Z) component for this process was suggested about 40 years ago and later it was documented by many experimental investigations. However, situations when IMF Bz is the major IMF component are rather rare. The structure of the cusp during periods of a small IMF B(sub Z) is generally unknown, probably due to the fully 3-D nature of the interaction. The present case study reveals the importance of horizontal IMF components on the global magnetospheric configuration as well as on small-scale processes at the cusp-magnetosheath interface. We have used simultaneous measurements of several spacecraft (ISTP program) operating in different regions of interplanetary space and two closely spaced satellites (INTERBALL-1/MAGION-4) crossing the cusp-magnetosheath boundary to show the connection between the short- and large-scale phenomena. In the northern hemisphere, observations suggest a presence of two spots of cusp-like precipitation supplied by reconnection occurring simultaneously in both hemispheres. A source of this bifurcation is the positive IMF B(sub y) component further enhanced by the field draping in the magnetosheath. This magnetic field component shifts the entry point far away from the local noon but in opposite sense in either hemisphere. The cusp represents a place where the magnetosheath plasma can directly

  11. The initial stellar masses for the formation of white dwarfs, neutron stars and black holes

    NASA Astrophysics Data System (ADS)

    Meynet, Georges

    As is well known a star may end its nuclear lifetime as a white dwarf, neutron star, black hole or may, in certain circumstances, leave no remnant at all. The main question to be addressed in this review is the following: what are the progenitors of these different final stages? After a brief review of the major physical principles governing stellar evolution, we present the different evolutionary scenarios resulting from numerical calculations. Particular attention will be paid to the effect of mass loss on theoretical determinations of the mass limits M WD and MBH which are respectively the maximum initial mass leading to the formation of a white dwarf and the minimum initial mass for the formation of a black hole. We terminate this review by the presentation of some relevant observational results. The bulk of this paper is devoted to the discussion of the evolution of single Population I stars. Les étoiles terminent leur évolution soit comme naines blanches, étoiles à neutrons, ou trous noirs, il peut également arriver qu'aucun résidu ne subsiste, l'étoile étant complètement détruite dans ses phases ultimes. La question à laquelle nous allons essayer de répondre dans cet article est la suivante : quels sont les progéniteurs de ces états finaux? Après un bref rappel de quelques principes importants gouvernant l'évolution stellaire, les différents scénarios évolutifs, tels qu'ils sont proposés par les modèles numériques, sont présentés. Les valeurs de la masse initiale maximale pour la formation des naines blanches ainsi que celles de la masse initiale minimale pour la formation des trous noirs sont discutées tant du point de vue théorique, qu'observationnel. La majeure partie de cet article concerne l'évolution d'étoiles simples et de composition chimique solaire.

  12. SIMULTANEOUS MODELING OF THE STELLAR AND DUST EMISSION IN DISTANT GALAXIES: IMPLICATIONS FOR STAR FORMATION RATE MEASUREMENTS

    SciTech Connect

    Utomo, Dyas; Kriek, Mariska; Labbé, Ivo; Fumagalli, Mattia; Conroy, Charlie

    2014-03-10

    We have used near-ultraviolet (NUV) to mid-infrared (MIR) composite spectral energy distributions (SEDs) to simultaneously model the attenuated stellar and dust emission of 0.5 ≲ z ≲ 2.0 galaxies. These composite SEDs were previously constructed from the photometric catalogs of the NEWFIRM Medium-Band Survey by stacking the observed photometry of galaxies that have similar rest-frame NUV-to-NIR SEDs. In this work, we include a stacked MIPS 24 μm measurement for each SED type to extend the SEDs to rest-frame MIR wavelengths. Consistent with previous studies, the observed MIR emission for most SED types is higher than expected from only the attenuated stellar emission. We fit the NUV-to-MIR composite SEDs with the Flexible Stellar Population Synthesis (FSPS) models, which include both stellar and dust emission. We compare the best-fit star formation rates (SFRs) to the SFRs based on simple UV+IR estimators. Interestingly, the UV and IR luminosities overestimate SFRs—compared to the model SFRs—by more than ∼1 dex for quiescent galaxies, while for the highest star-forming galaxies in our sample the two SFRs are broadly consistent. The difference in specific SFRs also shows a gradually increasing trend with declining specific SFR, implying that quiescent galaxies have even lower specific SFRs than previously found. Contributions from evolved stellar populations to both the UV and the MIR SEDs most likely explain the discrepancy. Based on this work, we conclude that SFRs should be determined from modeling the attenuated stellar and dust emission simultaneously, instead of employing simple UV+IR-based SFR estimators.

  13. From molecules to young stellar clusters: the star formation cycle across the disk of M 33

    NASA Astrophysics Data System (ADS)

    Corbelli, Edvige; Braine, Jonathan; Bandiera, Rino; Brouillet, Nathalie; Combes, Françoise; Druard, Clément; Gratier, Pierre; Mata, Jimmy; Schuster, Karl; Xilouris, Manolis; Palla, Francesco

    2017-05-01

    Aims: We study the association between giant molecular clouds (GMCs) and young stellar cluster candidates (YSCCs) to shed light on the time evolution of local star formation episodes in the nearby galaxy M 33. Methods: The CO (J = 2-1) IRAM all-disk survey was used to identify and classify 566 GMCs with masses between 2 × 104 and 2 × 106M⊙ across the whole star-forming disk of M 33. In the same area, there are 630 YSCCs that we identified using Spitzer-24 μm data. Some YSCCs are embedded star-forming sites, while the majority have GALEX-UV and Hα counterparts with estimated cluster masses and ages. Results: The GMC classes correspond to different cloud evolutionary stages: inactive clouds are 32% of the total and classified clouds with embedded and exposed star formation are 16% and 52% of the total, respectively. Across the regular southern spiral arm, inactive clouds are preferentially located in the inner part of the arm, possibly suggesting a triggering of star formation as the cloud crosses the arm. The spatial correlation between YSCCs and GMCs is extremely strong, with a typical separation of 17 pc. This is less than half the CO (2-1) beam size and illustrates the remarkable physical link between the two populations. GMCs and YSCCs follow the HI filaments, except in the outermost regions, where the survey finds fewer GMCs than YSCCs, which is most likely due to undetected clouds with low CO luminosity. The distribution of the non-embedded YSCC ages peaks around 5 Myr, with only a few being as old as 8-10 Myr. These age estimates together with the number of GMCs in the various evolutionary stages lead us to conclude that 14 Myr is the typical lifetime of a GMC in M 33 prior to cloud dispersal. The inactive and embedded phases are short, lasting about 4 and 2 Myr, respectively. This underlines that embedded YSCCs rapidly break out from the clouds and become partially visible in Hα or UV long before cloud dispersal. Full Tables 5 and 6 are only available

  14. Stellar Masses and Start Formation Rates of Lensed Dusty Star-Forming Galaxies from the SPT Survey

    NASA Astrophysics Data System (ADS)

    Ma, Jingzhe; Gonzalez, Anthony; SPT SMG Collaboration

    2016-01-01

    To understand cosmic mass assembly in the Universe at early epochs, we primarily rely on measurements of stellar mass and star formation rate of distant galaxies. In this paper, we present stellar masses and star formation rates of six high-redshift (2.8 ≤ z ≤ 5.7) dusty, star-forming galaxies (DSFGs) that are strongly gravitationally lensed by foreground galaxies. These sources were first discovered by the South Pole Telescope (SPT) at millimeter wavelengths and all have spectroscopic redshifts and robust lens models derived from ALMA observations. We have conducted follow-up observations, obtaining multi-wavelength imaging data, using HST, Spitzer, Herschel and the Atacama Pathfinder EXperiment (APEX). We use the high-resolution HST/WFC3 images to disentangle the background source from the foreground lens in Spitzer/IRAC data. The detections and upper limits provide important constraints on the spectral energy distributions (SEDs) for these DSFGs, yielding stellar masses, IR luminosities, and star formation rates (SFRs). The SED fits of six SPT sources show that the intrinsic stellar masses span a range more than one order of magnitude with a median value ˜ 5 ×1010M⊙. The intrinsic IR luminosities range from 4×1012L⊙ to 4×1013L⊙. They all have prodigious intrinsic star formation rates of 510 to 4800 M⊙yr-1. Compared to the star-forming main sequence (MS), these six DSFGs have specific SFRs that all lie above the MS, including two galaxies that are a factor of 10 higher than the MS. Our results suggest that we are witnessing the ongoing strong starburst events which may be driven by major mergers.

  15. A PANCHROMATIC STUDY OF BLAST COUNTERPARTS: TOTAL STAR FORMATION RATE, MORPHOLOGY, ACTIVE GALACTIC NUCLEUS FRACTION, AND STELLAR MASS

    SciTech Connect

    Moncelsi, Lorenzo; Ade, Peter A. R.; Cortese, Luca; Dye, Simon; Eales, Stephen; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Pascale, Enzo; Tucker, Carole; Chapin, Edward L.; Halpern, Mark; Marsden, Gaelen; Scott, Douglas; Wiebe, Donald V.; Devlin, Mark J.; Truch, Matthew D. P.; Netterfield, Calvin B.; Viero, Marco P.

    2011-02-01

    We carry out a multi-wavelength study of individual galaxies detected by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) and identified at other wavelengths, using data spanning the radio to the ultraviolet (UV). We develop a Monte Carlo method to account for flux boosting, source blending, and correlations among bands, which we use to derive deboosted far-infrared (FIR) luminosities for our sample. We estimate total star-formation rates (SFRs) for BLAST counterparts with z {<=} 0.9 by combining their FIR and UV luminosities. Star formation is heavily obscured at L{sub FIR} {approx}> 10{sup 11} L{sub sun}, z {approx}> 0.5, but the contribution from unobscured starlight cannot be neglected at L{sub FIR} {approx}< 10{sup 11} L{sub sun}, z {approx}< 0.25. We assess that about 20% of the galaxies in our sample show indication of a type 1 active galactic nucleus, but their submillimeter emission is mainly due to star formation in the host galaxy. We compute stellar masses for a subset of 92 BLAST counterparts; these are relatively massive objects, with a median mass of {approx}10{sup 11} M{sub sun}, which seem to link the 24 {mu}m and Submillimetre Common-User Bolometer Array (SCUBA) populations, in terms of both stellar mass and star formation activity. The bulk of the BLAST counterparts at z {approx}< 1 appears to be run-of-the-mill star-forming galaxies, typically spiral in shape, with intermediate stellar masses and practically constant specific SFRs. On the other hand, the high-z tail of the BLAST counterparts significantly overlaps with the SCUBA population, in terms of both SFRs and stellar masses, with observed trends of specific SFR that support strong evolution and downsizing.

  16. The role of Super Stellar Cluster in extreme stellar formation: which programme for the E-ELT ?

    NASA Astrophysics Data System (ADS)

    Rouan, D.; Gratadour, D.; Perrot, C.

    2013-11-01

    In ULIRGs, the intense star formation (up to 1000 Msol / year ) induced by the direct interaction of two galaxies is concretized as extremely compact and bright star clusters with no equivalent in the Galaxy. These super star cluster ( SSC ) which play a major role in the structural and chemical Evolution of galaxies are rare and distant (d ≈ 150 Mpc ) with a diameter lower than the resolution achieved with adaptive optics on a 8 -10m telescope. The resolution offered by MICADO on the EELT (10 mas , 8 pc at 150 Mpc ) will allow a major leap in three types of programs: 1) characterizing the starburst on five times more distant objects; 2) spatial resolution of the close SSC to address many questions: Schmidt law, filiation with globular clusters, proper spatial structure ( IMF, HII region clustering, dust clustering, etc.); 3) finding direct links between a starburst and the presence of a central super-massive black hole. Instrumental choices are analyzed against these objectives.

  17. Formation scenarios for the young stellar associations between galactic longitudes l = 280degr - 360degr

    NASA Astrophysics Data System (ADS)

    Sartori, M. J.; Lépine, J. R. D.; Dias, W. S.

    2003-06-01

    We investigate the spatial distribution, the space velocities and age distribution of the pre-main sequence (PMS) stars belonging to Ophiuchus, Lupus and Chamaeleon star-forming regions (SFRs), and of the young early-type star members of the Scorpius-Centaurus OB association. These young stellar associations extend over the galactic longitude range from 280degr to 360degr , and are at a distance interval of around 100 and 200 pc. This study is based on a compilation of distances, proper motions and radial velocities from the literature for the kinematic properties, and of basic stellar data for the construction of Hertzsprung-Russel diagrams. Although there was no well-known OB association in Chamaeleon, the distances and the proper motions of a group of 21 B- and A-type stars, taken from the Hipparcos Catalogue, lead us to propose that they form a young association. We show that the young early-type stars of the OB associations and the PMS stars of the SFRs follow a similar spatial distribution, i.e., there is no separation between the low and the high-mass young stars. We find no difference in the kinematics nor in the ages of these two populations studied. Considering not only the stars selected by kinematic criteria but the whole sample of young early-type stars, the scattering of their proper motions is similar to that of the PMS stars and all the young stars exhibit a common direction of motion. The space velocities of the Hipparcos PMS stars of each SFR are compatible with the mean values of the OB associations. The PMS stars in each SFR span a wide range of ages (from 1 to 20 Myr). The ages of the OB subgroups are 8-10 Myr for Upper Scorpius (US), and 16-20 Myr for Upper Centaurus Lupus (UCL) and for Lower Centaurus Crux (LCC). Thus, our results do not confirm that UCL is older than the LCC association. Based on these results and the uncertainties associated with the age determination, we cannot say that there is indeed a difference in the age of the two

  18. Testing galaxy formation models with the GHOSTS survey: The stellar halo of M81

    NASA Astrophysics Data System (ADS)

    Monachesi, A.; Bell, E.; Radburn-Smith, D.; Vlajić, M.; de Jong, R.; Bailin, J.; Dalcanton, J.; Holwerda, B.; Streich, D.

    2015-03-01

    The GHOSTS survey is the largest study to date of the resolved stellar populations in the outskirts of disk galaxies (Radburn-Smith et al. 2011). The sample currently consists of 16 nearby disk galaxies, whose outer disks and halos are imaged with the Hubble Space Telescope (HST). I will present new results obtained from the study of 19 GHOSTS fields in M81's outermost part. The observed fields probe the stellar halo of M81 out to projected distances of ~50 kpc, an unprecedented distance for halo studies outside the Local Group. The 50% completeness levels of the color magnitude diagrams are typically at 2.5 mag below the tip of the red giant branch. When considering only fields located at galactocentric radius R > 15 kpc, we detect no color gradient in the stellar halo of M81. We compare these results with model predictions for the colors of stellar halos formed purely via accretion of satellite galaxies (Bullock & Johnston 2005). When we analyze the cosmologically motivated models in the same way as the HST data, we find that they predict no color gradient for the stellar halos, in good agreement with the observations (see Fig. 1).

  19. Hippo pathway/Yap regulates primary enamel knot and dental cusp patterning in tooth morphogenesis.

    PubMed

    Kwon, Hyuk-Jae Edward; Li, Liwen; Jung, Han-Sung

    2015-11-01

    The shape of an individual tooth crown is primarily determined by the number and arrangement of its cusps, i.e., cusp patterning. Enamel knots that appear in the enamel organ during tooth morphogenesis have been suggested to play important roles in cusp patterning. Animal model studies have shown that the Hippo pathway effector Yap has a critical function in tooth morphogenesis. However, the role of the Hippo pathway/Yap in cusp patterning has not been well documented and its specific roles in tooth morphogenesis remain unclear. Here, we provide evidence that Yap is a key mediator in tooth cusp patterning. We demonstrate a correlation between Yap localization and cell proliferation in developing tooth germs. We also show that, between the cap stage and bell stage, Yap is crucial for the suppression of the primary enamel knot and for the patterning of secondary enamel knots, which are the future cusp regions. When Yap expression is stage-specifically knocked down during the cap stage, the activity of the primary enamel knot persists into the bell-stage tooth germ, leading to ectopic cusp formation. Our data reveal the importance of the Hippo pathway/Yap in enamel knots and in the proper patterning of tooth cusps.

  20. Redshift evolution of stellar mass versus gas fraction relation in 0 < z < 2 regime: observational constraint for galaxy formation models

    NASA Astrophysics Data System (ADS)

    Morokuma-Matsui, Kana; Baba, Junichi

    2015-12-01

    We investigate the redshift evolution of molecular gas mass fraction (f_mol = M_mol/M_star +M_mol, where Mmol is molecular gas mass and M⋆ is stellar mass) of galaxies in the redshift range of 0 < z < 2 as a function of the stellar mass by combining carbon monoxide (CO) literature data. We observe a stellar-mass dependence of the fmol evolution where massive galaxies have largely depleted their molecular gas at z = 1, whereas the fmol value of less massive galaxies drastically decreases from z = 1. We compare the observed M⋆ - fmol relation with theoretical predictions from cosmological hydrodynamic simulations and semi-analytical models for galaxy formation. Although the theoretical studies approximately reproduce the observed mass dependence of the fmol evolution, they tend to underestimate the fmol values, particularly of less massive (<1010 M⊙) and massive galaxies (>1011 M⊙) when compared with the observational values. Our result suggests the importance of the feedback models which suppress the star formation while simultaneously preserving the molecular gas in order to reproduce the observed M⋆ - fmol relation.

  1. Cusped-gaussian wave functions

    NASA Astrophysics Data System (ADS)

    Dyer, Sara; Steiner, Erich

    The single-excitation configuration interaction method is used to calculate the spin density at the nucleus in the Li atom and the LiH+ molecular ion. A variety of cusped-gaussian, all-gaussian and Slater function basis sets are compared. It is shown that whilst it is difficult to obtain reliable values for the spin density with conventional gaussian basis sets, the cusped-gaussian basis can give values of the properties at a nucleus that are very similar to those obtained with a Slater function basis. It is shown that it is essential for accurate work to ensure that the basis is highly flexible in the region close to a nucleus.

  2. Compact stellar systems in the polar ring galaxies NGC 4650A and NGC 3808B: Clues to polar disk formation

    NASA Astrophysics Data System (ADS)

    Ordenes-Briceño, Yasna; Georgiev, Iskren Y.; Puzia, Thomas H.; Goudfrooij, Paul; Arnaboldi, Magda

    2016-01-01

    Context. Polar ring galaxies (PRGs) are composed of two kinematically distinct and nearly orthogonal components, a host galaxy (HG) and a polar ring/disk (PR). The HG usually contains an older stellar population than the PR. The suggested formation channel of PRGs is still poorly constrained. Suggested options are merger, gas accretion, tidal interaction, or a combination of both. Aims: To constrain the formation scenario of PRGs, we study the compact stellar systems (CSSs) in two PRGs at different evolutionary stages: NGC 4650A with well-defined PR, and NGC 3808 B, which is in the process of PR formation. Methods: We use archival HST/WFPC2 imaging in the F450W, F555W, or F606W and F814W filters. Extensive completeness tests, PSF-fitting techniques, and color selection criteria are used to select cluster candidates. Photometric analysis of the CSSs was performed to determine their ages and masses using stellar population models at a fixed metallicity. Results: Both PRGs contain young CSSs (<1 Gyr) with masses of up to 5 × 106M⊙, mostly located in the PR and along the tidal debris. The most massive CSSs may be progenitors of metal-rich globular clusters or ultra compact dwarf (UCD) galaxies. We identify one such young UCD candidate, NGC 3808 B-8, and measure its size of reff = 25.23+1.43-2.01 pc. We reconstruct the star formation history of the two PRGs and find strong peaks in the star formation rate (SFR, ≃200 M⊙/yr) in NGC 3808 B, while NGC 4650 A shows milder (declining) star formation (SFR< 10 M⊙/yr). This difference may support different evolutionary paths between these PRGs. Conclusions: The spatial distribution, masses, and peak star formation epoch of the clusters in NGC 3808 suggest for a tidally triggered star formation. Incompleteness at old ages prevents us from probing the SFR at earlier epochs of NGC 4650 A, where we observe the fading tail of CSS formation. This also impedes us from testing the formation scenarios of this PRG.

  3. FORMATION OF LATE-TYPE SPIRAL GALAXIES: GAS RETURN FROM STELLAR POPULATIONS REGULATES DISK DESTRUCTION AND BULGE GROWTH

    SciTech Connect

    Martig, Marie; Bournaud, Frederic

    2010-05-10

    Spiral galaxies have most of their stellar mass in a large rotating disk, and only a modest fraction in a central spheroidal bulge. This challenges present models of galaxy formation: galaxies form at the center of dark matter halos through a combination of hierarchical merging and gas accretion along cold streams. Cosmological simulations thus predict that galaxies rapidly grow their bulge through mergers and instabilities and end up with most of their mass in the bulge and an angular momentum much below the observed level, except in dwarf galaxies. We propose that the continuous return of gas by stellar populations over cosmic times could help to solve this issue. A population of stars formed at a given instant typically returns half of its initial mass in the form of gas over 10 billion years, and the process is not dominated by supernovae explosions but by the long-term mass-loss from low- and intermediate-mass stars. Using simulations of galaxy formation, we show that this gas recycling can strongly affect the structural evolution of massive galaxies, potentially solving the bulge fraction issue, as the bulge-to-disk ratio of a massive galaxy can be divided by a factor of 3. The continuous recycling of baryons through star formation and stellar mass loss helps the growth of disks and their survival to interactions and mergers. Instead of forming only early-type, spheroid-dominated galaxies (S0 and ellipticals), the standard cosmological model can successfully account for massive late-type, disk-dominated spiral galaxies (Sb-Sc).

  4. STELLAR MASSES AND STAR FORMATION RATES OF LENSED, DUSTY, STAR-FORMING GALAXIES FROM THE SPT SURVEY

    SciTech Connect

    Ma, Jingzhe; Gonzalez, Anthony H.; Spilker, J. S.; Marrone, D. P.; Strandet, M.; Ashby, M. L. N.; Aravena, M.; Béthermin, M.; Breuck, C. de; Gullberg, B.; Bothwell, M. S.; Brodwin, M.; Chapman, S. C.; Fassnacht, C. D.; Greve, T. R.; Hezaveh, Y.; Malkan, M.; Saliwanchik, B. R.; and others

    2015-10-10

    To understand cosmic mass assembly in the universe at early epochs, we primarily rely on measurements of the stellar masses and star formation rates (SFRs) of distant galaxies. In this paper, we present stellar masses and SFRs of six high-redshift (2.8 ≤ z ≤ 5.7) dusty, star-forming galaxies (DSFGs) that are strongly gravitationally lensed by foreground galaxies. These sources were first discovered by the South Pole Telescope (SPT) at millimeter wavelengths and all have spectroscopic redshifts and robust lens models derived from Atacama Large Millimeter/submillimeter Array observations. We have conducted follow-up observations to obtain multi-wavelength imaging data using the Hubble Space Telescope (HST), Spitzer, Herschel, and the Atacama Pathfinder EXperiment. We use the high-resolution HST/Wide Field Camera 3 images to disentangle the background source from the foreground lens in Spitzer/IRAC data. The detections and upper limits provide important constraints on the spectral energy distributions (SEDs) for these DSFGs, yielding stellar masses, IR luminosities, and SFRs. The SED fits of six SPT sources show that the intrinsic stellar masses span a range more than one order of magnitude with a median value ∼5 ×10{sup 10} M{sub ⊙}. The intrinsic IR luminosities range from 4 × 10{sup 12} L{sub ⊙} to 4 × 10{sup 13} L{sub ⊙}. They all have prodigious intrinsic SFRs of 510–4800 M{sub ⊙} yr{sup −1}. Compared to the star-forming main sequence (MS), these six DSFGs have specific SFRs that all lie above the MS, including two galaxies that are a factor of 10 higher than the MS. Our results suggest that we are witnessing ongoing strong starburst events that may be driven by major mergers.

  5. Stellar Masses and Star Formation Rates of Lensed, Dusty, Star-forming Galaxies from the SPT Survey

    NASA Astrophysics Data System (ADS)

    Ma, Jingzhe; Gonzalez, Anthony. H.; Spilker, J. S.; Strandet, M.; Ashby, M. L. N.; Aravena, M.; Béthermin, M.; Bothwell, M. S.; de Breuck, C.; Brodwin, M.; Chapman, S. C.; Fassnacht, C. D.; Greve, T. R.; Gullberg, B.; Hezaveh, Y.; Malkan, M.; Marrone, D. P.; Saliwanchik, B. R.; Vieira, J. D.; Weiss, A.; Welikala, N.

    2015-10-01

    To understand cosmic mass assembly in the universe at early epochs, we primarily rely on measurements of the stellar masses and star formation rates (SFRs) of distant galaxies. In this paper, we present stellar masses and SFRs of six high-redshift (2.8 ≤ z ≤ 5.7) dusty, star-forming galaxies (DSFGs) that are strongly gravitationally lensed by foreground galaxies. These sources were first discovered by the South Pole Telescope (SPT) at millimeter wavelengths and all have spectroscopic redshifts and robust lens models derived from Atacama Large Millimeter/submillimeter Array observations. We have conducted follow-up observations to obtain multi-wavelength imaging data using the Hubble Space Telescope (HST), Spitzer, Herschel, and the Atacama Pathfinder EXperiment. We use the high-resolution HST/Wide Field Camera 3 images to disentangle the background source from the foreground lens in Spitzer/IRAC data. The detections and upper limits provide important constraints on the spectral energy distributions (SEDs) for these DSFGs, yielding stellar masses, IR luminosities, and SFRs. The SED fits of six SPT sources show that the intrinsic stellar masses span a range more than one order of magnitude with a median value ˜5 ×1010 M⊙. The intrinsic IR luminosities range from 4 × 1012 L⊙ to 4 × 1013 L⊙. They all have prodigious intrinsic SFRs of 510-4800 M⊙ yr-1. Compared to the star-forming main sequence (MS), these six DSFGs have specific SFRs that all lie above the MS, including two galaxies that are a factor of 10 higher than the MS. Our results suggest that we are witnessing ongoing strong starburst events that may be driven by major mergers.

  6. THE DEEP2 GALAXY REDSHIFT SURVEY: CLUSTERING DEPENDENCE ON GALAXY STELLAR MASS AND STAR FORMATION RATE AT z {approx} 1

    SciTech Connect

    Mostek, Nick; Coil, Alison L.; Cooper, Michael; Davis, Marc; Newman, Jeffrey A.; Weiner, Benjamin J.

    2013-04-10

    We present DEEP2 galaxy clustering measurements at z {approx} 1 as a function of stellar mass, star formation rate (SFR), and specific SFR (sSFR). We find a strong positive correlation between stellar mass and clustering amplitude on 1-10 h {sup -1} Mpc scales for blue, star-forming galaxies with 9.5 < log(M{sub *}/M{sub Sun }) < 11 and no dependence for red, quiescent galaxies with 10.5 < log(M{sub *}/M{sub Sun }) < 11.5. Using recently re-calibrated DEEP2 SFRs from restframe B-band magnitude and optical colors, we find that within the blue galaxy population at z {approx} 1 the clustering amplitude increases strongly with increasing SFR and decreasing sSFR. For red galaxies there is no significant correlation between clustering amplitude and either SFR or sSFR. Blue galaxies with high SFR or low sSFR are as clustered on large scales as red galaxies. We find that the clustering trend observed with SFR can be explained mostly, but not entirely, by the correlation between stellar mass and clustering amplitude for blue galaxies. We also show that galaxies above the star-forming 'main sequence' are less clustered than galaxies below the main sequence, at a given stellar mass. These results are not consistent with the high-sSFR population being dominated by major mergers. We also measure the clustering amplitude on small scales ({<=}0.3 h {sup -1} Mpc) and find an enhanced clustering signal relative to the best-fit large-scale power law for red galaxies with high stellar mass, blue galaxies with high SFR, and both red and blue galaxies with high sSFR. The increased small-scale clustering for galaxies with high sSFRs is likely linked to triggered star formation in interacting galaxies. These measurements provide strong constraints on galaxy evolution and halo occupation distribution models at z {approx} 1.

  7. Mapping a stellar disk into a boxy bulge: The outside-in part of the Milky Way bulge formation

    NASA Astrophysics Data System (ADS)

    Di Matteo, P.; Haywood, M.; Gómez, A.; van Damme, L.; Combes, F.; Hallé, A.; Semelin, B.; Lehnert, M. D.; Katz, D.

    2014-07-01

    By means of idealized, dissipationless N-body simulations that follow the formation and subsequent buckling of a stellar bar, we study the characteristics of boxy/peanut-shaped bulges and compare them with the properties of the stellar populations in the Milky Way (MW) bulge. The main results of our modeling, valid for the general family of boxy/peanut shaped bulges, are the following: (i) Because of the spatial redistribution in the disk initiated at the epoch of bar formation, stars from the innermost regions to the outer Lindblad resonance (OLR) of the stellar bar are mapped into a boxy bulge. (ii) The contribution of stars to the local bulge density depends on their birth radius: stars born in the innermost disk tend to dominate the innermost regions of the boxy bulge, while stars originating closer to the OLR are preferably found in the outer regions of the boxy/peanut structure. (iii) Stellar birth radii are imprinted in the bulge kinematics: the larger the birth radii of stars ending up in the bulge, the greater their rotational support and the higher their line-of-sight velocity dispersions (but note that this last trend depends on the bar viewing angle). (iv) The higher the classical bulge-over-disk ratio, the larger its fractional contribution of stars at large vertical distance from the galaxy midplane. Comparing these results with the properties of the stellar populations of the MW bulge recently revealed by the ARGOS survey, we conclude that (I) the two most metal-rich populations of the MW bulge, labeled A and B in the ARGOS survey, originate in the disk, with the population of A having formed on average closer to the Galaxy center than the population of component B; (II) a massive (B/D ~ 0.25) classical spheroid can be excluded for the MW, thus confirming previous findings that the MW bulge is composed of populations that mostly have a disk origin. On the basis of their chemical and kinematic characteristics, the results of our modeling suggest that

  8. The CUSP as a Source of Magnetospheric Particles

    NASA Technical Reports Server (NTRS)

    Fritz, Theodore A.; Chen, Jiasheng

    1999-01-01

    Observations made by the Polar satellite have shown that plasma of solar wind magnetosheath origin is rammed into the high altitude polar cusp creating a diamagnetic cavity of large dimensions. The Earth's dipole field can be excluded from this region in it turbulent manner with the magnitude of the field strength reaching close to zero nT at times. At such times energetic particles are produced in this region in intensities which exceed those measured in the trapping regions of the magnetosphere beyond L = 6.5. These particles can then flow back out of the cusp along field lines that form the magnetopause. A fraction of these particles can enter the magnetosphere along the magnetopause on the dusk and dawn flanks. Due to existing gradients in the geomagnetic field, cusp accelerated ions can enter the magnetosphere along the dawn flank and electrons along the dusk flank. For those particles entering near the geomagnetic equatorial plane with pitch angles close to ninety degrees they will drift along contours of constant magnetic field strength reaching deep into the nightside inner magnetosphere. From observations made by the Polar ATS-6, and ISEE satellites it is argued that this cusp source appears to be capable of providing energetic ions to the magnetosphere and possibly energetic electrons which form the source population of the Subsequent radial diffusion and formation of the radiation belts.

  9. Metallofullerene and fullerene formation from condensing carbon gas under conditions of stellar outflows and implication to stardust.

    PubMed

    Dunk, Paul W; Adjizian, Jean-Joseph; Kaiser, Nathan K; Quinn, John P; Blakney, Gregory T; Ewels, Christopher P; Marshall, Alan G; Kroto, Harold W

    2013-11-05

    Carbonaceous presolar grains of supernovae origin have long been isolated and are determined to be the carrier of anomalous (22)Ne in ancient meteorites. That exotic (22)Ne is, in fact, the decay isotope of relatively short-lived (22)Na formed by explosive nucleosynthesis, and therefore, a selective and rapid Na physical trapping mechanism must take place during carbon condensation in supernova ejecta. Elucidation of the processes that trap Na and produce large carbon molecules should yield insight into carbon stardust enrichment and formation. Herein, we demonstrate that Na effectively nucleates formation of Na@C60 and other metallofullerenes during carbon condensation under highly energetic conditions in oxygen- and hydrogen-rich environments. Thus, fundamental carbon chemistry that leads to trapping of Na is revealed, and should be directly applicable to gas-phase chemistry involving stellar environments, such as supernova ejecta. The results indicate that, in addition to empty fullerenes, metallofullerenes should be constituents of stellar/circumstellar and interstellar space. In addition, gas-phase reactions of fullerenes with polycyclic aromatic hydrocarbons are investigated to probe "build-up" and formation of carbon stardust, and provide insight into fullerene astrochemistry.

  10. Metallofullerene and fullerene formation from condensing carbon gas under conditions of stellar outflows and implication to stardust

    PubMed Central

    Dunk, Paul W.; Adjizian, Jean-Joseph; Kaiser, Nathan K.; Quinn, John P.; Blakney, Gregory T.; Ewels, Christopher P.; Marshall, Alan G.; Kroto, Harold W.

    2013-01-01

    Carbonaceous presolar grains of supernovae origin have long been isolated and are determined to be the carrier of anomalous 22Ne in ancient meteorites. That exotic 22Ne is, in fact, the decay isotope of relatively short-lived 22Na formed by explosive nucleosynthesis, and therefore, a selective and rapid Na physical trapping mechanism must take place during carbon condensation in supernova ejecta. Elucidation of the processes that trap Na and produce large carbon molecules should yield insight into carbon stardust enrichment and formation. Herein, we demonstrate that Na effectively nucleates formation of Na@C60 and other metallofullerenes during carbon condensation under highly energetic conditions in oxygen- and hydrogen-rich environments. Thus, fundamental carbon chemistry that leads to trapping of Na is revealed, and should be directly applicable to gas-phase chemistry involving stellar environments, such as supernova ejecta. The results indicate that, in addition to empty fullerenes, metallofullerenes should be constituents of stellar/circumstellar and interstellar space. In addition, gas-phase reactions of fullerenes with polycyclic aromatic hydrocarbons are investigated to probe “build-up” and formation of carbon stardust, and provide insight into fullerene astrochemistry. PMID:24145444

  11. Influence of stellar multiplicity on planet formation. II. Planets are less common in multiple-star systems with separations smaller than 1500 AU

    SciTech Connect

    Wang, Ji; Fischer, Debra A.; Xie, Ji-Wei; Ciardi, David R.

    2014-08-20

    Almost half of the stellar systems in the solar neighborhood are made up of multiple stars. In multiple-star systems, planet formation is under the dynamical influence of stellar companions, and the planet occurrence rate is expected to be different from that of single stars. There have been numerous studies on the planet occurrence rate of single star systems. However, to fully understand planet formation, the planet occurrence rate in multiple-star systems needs to be addressed. In this work, we infer the planet occurrence rate in multiple-star systems by measuring the stellar multiplicity rate for planet host stars. For a subsample of 56 Kepler planet host stars, we use adaptive optics (AO) imaging and the radial velocity (RV) technique to search for stellar companions. The combination of these two techniques results in high search completeness for stellar companions. We detect 59 visual stellar companions to 25 planet host stars with AO data. Three stellar companions are within 2'' and 27 within 6''. We also detect two possible stellar companions (KOI 5 and KOI 69) showing long-term RV acceleration. After correcting for a bias against planet detection in multiple-star systems due to flux contamination, we find that planet formation is suppressed in multiple-star systems with separations smaller than 1500 AU. Specifically, we find that compared to single star systems, planets in multiple-star systems occur 4.5 ± 3.2, 2.6 ± 1.0, and 1.7 ± 0.5 times less frequently when a stellar companion is present at a distance of 10, 100, and 1000 AU, respectively. This conclusion applies only to circumstellar planets; the planet occurrence rate for circumbinary planets requires further investigation.

  12. Electrostatic Plugging of Multidipole Cusps.

    DTIC Science & Technology

    1982-05-01

    IN, rtid’( rio~ s I REORTNUMER 2 GOVT ACCESSION No 3 RECIPtE%T’. CATALOG, # MtSF.P 4. TTLE wd Sbt,( ) TYPE OF REPDRT & PER,00 COvERED jElectrostatic...corresponding loss widths are W = 9 mm and W = 3 mm. This L ~ L2 analysis was performed for many ’PE, and a linear relationship was found between n and...VE)/Te (18)e t o reP Now V/rp = A the surface area of the plasma: A = SL , (19)c with S the distance between cusps ( 8 cm) and L the magnetic cuspc

  13. The Specific Star Formation Rate and Stellar Mass Fraction of Low-mass Central Galaxies in Cosmological Simulations

    NASA Astrophysics Data System (ADS)

    Avila-Reese, V.; Colín, P.; González-Samaniego, A.; Valenzuela, O.; Firmani, C.; Velázquez, H.; Ceverino, D.

    2011-08-01

    By means of cosmological N-body + hydrodynamics simulations of galaxies in the context of the Λ cold dark matter (ΛCDM) scenario we explore the specific star formation rates (SSFR = SFR/Ms , Ms is the stellar mass) and stellar mass fractions (Fs ≡ Ms /Mh , Mh is the halo mass) for sub-M* field galaxies at different redshifts (0 <~ z <~ 1.5). Distinct low-mass halos (2.5 <~ Mh /1010 M sun <~ 50 at z = 0) were selected for the high-resolution re-simulations. The Hydrodynamics Adaptive Refinement Tree (ART) code was used and some variations of the sub-grid parameters were explored. Most simulated galaxies, specially those with the highest resolutions, have significant disk components and their structural and dynamical properties are in reasonable agreement with observations of sub-M* field galaxies. However, the SSFRs are 5-10 times smaller than the averages of several (compiled and homogenized here) observational determinations for field blue/star-forming galaxies at z < 0.3 (at low masses, most observed field galaxies are actually blue/star forming). This inconsistency seems to remain even at z ~ 1-1.5, although it is less drastic. The Fs of simulated galaxies increases with Mh as semi-empirical inferences show. However, the values of Fs at z ≈ 0 are ~5-10 times larger in the simulations than in the inferences; these differences increases probably to larger factors at z ~ 1-1.5. The inconsistencies reported here imply that simulated low-mass galaxies (0.2 <~ Ms /109 M sun <~ 30 at z = 0) assembled their stellar masses much earlier than observations suggest. Our results confirm the predictions found by means of ΛCDM-based models of disk galaxy formation and evolution for isolated low-mass galaxies, and highlight that our understanding and implementation of astrophysics into simulations and models are still lacking vital ingredients.

  14. Stellar Population and Star Formation History of the Distant Galactic H II Regions NGC 2282 and Sh2-149

    NASA Astrophysics Data System (ADS)

    Dutta, S.; Mondal, S.; Jose, J.; Das, R. K.

    2017-06-01

    We present here the recent results on two distant Galactic H II regions, namely NGC 2282 and Sh2-149, obtained with multiwavelength observations. Our optical spectroscopic analysis of the bright sources have been used to identify the massive members, and to derive the fundamental parameters such as age and distance of these regions. Using IR color-color criteria and Hα-emission properties, we have identified and classified the candidate young stellar objects (YSOs) in these regions. The 12CO(1-0) continuum maps along with the K-band extinction maps, and spatial distribution of YSOs are used to investigate the structure and morphology of the molecular cloud associated with these H II regions. Overall analysis of these regions suggests that the star formation occurs at the locations of the denser gas, and we also find possible evidences of the induced star formation due to the feedback from massive stars to its surrounding molecular medium.

  15. Cassini observations of Saturn's southern polar cusp

    NASA Astrophysics Data System (ADS)

    Arridge, C. S.; Jasinski, J. M.; Achilleos, N.; Bogdanova, Y. V.; Bunce, E. J.; Cowley, S. W. H.; Fazakerley, A. N.; Khurana, K. K.; Lamy, L.; Leisner, J. S.; Roussos, E.; Russell, C. T.; Zarka, P.; Coates, A. J.; Dougherty, M. K.; Jones, G. H.; Krimigis, S. M.; Krupp, N.

    2016-04-01

    The magnetospheric cusps are important sites of the coupling of a magnetosphere with the solar wind. The combination of both ground- and space-based observations at Earth has enabled considerable progress to be made in understanding the terrestrial cusp and its role in the coupling of the magnetosphere to the solar wind via the polar magnetosphere. Voyager 2 fully explored Neptune's cusp in 1989, but highly inclined orbits of the Cassini spacecraft at Saturn present the most recent opportunity to repeatedly study the polar magnetosphere of a rapidly rotating planet. In this paper we discuss observations made by Cassini during two passes through Saturn's southern polar magnetosphere. Our main findings are that (i) Cassini directly encounters the southern polar cusp with evidence for the entry of magnetosheath plasma into the cusp via magnetopause reconnection, (ii) magnetopause reconnection and entry of plasma into the cusp can occur over a range of solar wind conditions, and (iii) double cusp morphologies are consistent with the position of the cusp oscillating in phase with Saturn's global magnetospheric periodicities.

  16. Cassini plasma observations of Saturn's magnetospheric cusp

    NASA Astrophysics Data System (ADS)

    Jasinski, Jamie M.; Arridge, Christopher S.; Coates, Andrew J.; Jones, Geraint H.; Sergis, Nick; Thomsen, Michelle F.; Reisenfeld, Daniel B.; Krupp, Norbert; Waite, J. Hunter

    2016-12-01

    The magnetospheric cusp is a funnel-shaped region where shocked solar wind plasma is able to enter the high-latitude magnetosphere via the process of magnetic reconnection. The plasma observations include various cusp signatures such as ion energy dispersions and diamagnetic effects. We present an overview analysis of cusp plasma observations at the Saturnian magnetosphere from the Cassini spacecraft era. A comparison of the observations is made as well as classification into groups due to varying characteristics. The locations of the reconnection site are calculated and shown to vary along the subsolar magnetopause. We show the first in situ evidence for lobe reconnection that occurred at nearly the same time as dayside reconnection for one of the cusp crossings. Evidence for "bursty" and more "continuous" reconnection signatures is observed at different cusp events. The events are compared to solar wind propagation models, and it is shown that magnetic reconnection and plasma injection into the cusp can occur for a variety of upstream conditions. These are important results because they show that Saturn's magnetospheric interaction with the solar wind and the resulting cusp signatures are dynamic and that plasma injection in the cusp occurs due to a variety of solar wind conditions. Furthermore, reconnection can proceed at a variety of locations along the magnetopause.

  17. Stellarator hybrids

    SciTech Connect

    Furth, H.P.; Ludescher, C.

    1984-08-01

    The present paper briefly reviews the subject of tokamak-stellarator and pinch-stellarator hybrids, and points to two interesting new possibilities: compact-torus-stellarators and mirror-stellarators.

  18. A LINK BETWEEN STAR FORMATION QUENCHING AND INNER STELLAR MASS DENSITY IN SLOAN DIGITAL SKY SURVEY CENTRAL GALAXIES

    SciTech Connect

    Fang, Jerome J.; Faber, S. M.; Koo, David C.

    2013-10-10

    We study the correlation between galaxy structure and the quenching of star formation using a sample of Sloan Digital Sky Survey central galaxies with stellar masses 9.75 < log M{sub *}/M{sub ☉} < 11.25 and redshifts z < 0.075. Galaxy Evolution Explorer UV data are used to cleanly divide the sample into star-forming and quenched galaxies and to identify galaxies in transition (the green valley). Despite a stark difference in visual appearance between blue and red galaxies, their average radial stellar mass density profiles are remarkably similar (especially in the outer regions) at fixed mass. The inner stellar mass surface density within a radius of 1 kpc, Σ{sub 1}, is used to quantify the growth of the bulge as galaxies evolve. When galaxies are divided into narrow mass bins, their distribution in the color-Σ{sub 1} plane at fixed mass forms plausible evolutionary tracks. Σ{sub 1} seems to grow as galaxies evolve through the blue cloud, and once it crosses a threshold value, galaxies are seen to quench at fixed Σ{sub 1}. The Σ{sub 1} threshold for quenching grows with stellar mass, Σ{sub 1}∝M{sub *}{sup 0.64}. However, the existence of some star-forming galaxies above the threshold Σ{sub 1} implies that a dense bulge is necessary but not sufficient to quench a galaxy fully. This would be consistent with a two-step quenching process in which gas within a galaxy is removed or stabilized against star formation by bulge-driven processes (such as a starburst, active galactic nucleus feedback, or morphological quenching), whereas external gas accretion is suppressed by separate halo-driven processes (such as halo gas shock heating). Quenching thus depends on an interplay between the inner structure of a galaxy and its surrounding dark matter halo, and lack of perfect synchrony between the two could produce the observed scatter in color versus Σ{sub 1}.

  19. Stellar Imager

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth

    2007-01-01

    The Stellar Imager (SI) is one of NASA's "Vision Missions" - concepts for future, space-based, strategic missions that could enormously increase our capabilities for observing the Cosmos. SI is designed as a UV/Optical Interferometer which will enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and, via asteroseismology, stellar interiors and of the Universe in general. The ultra-sharp images of the Stellar Imager will revolutionize our view of many dynamic astrophysical processes by transforming point sources into extended sources, and snapshots into evolving views. SI, with a characteristic angular resolution of 0.1 milli-arcseconds at 2000 Angstroms, represents an advance in image detail of several hundred times over that provided by the Hubble Space Telescope. The Stellar Imager will zoom in on what today-with few exceptions - we only know as point sources, revealing processes never before seen, thus providing a tool as fundamental to astrophysics as the microscope is to the study of life on Earth. SI's science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. It's prime goal is to enable long-term forecasting of solar activity and the space weather that it drives, in support of the Living With a Star program in the Exploration Era. SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes in the Universe. Stellar Imager is included as a "Flagship and Landmark Discovery Mission" in the 2005 Sun Solar System Connection (SSSC) Roadmap and as a candidate for a "Pathways to Life Observatory" in the Exploration of the Universe Division (EUD) Roadmap (May, 2005) and as such is a candidate mission for the 2025-2030 timeframe. An artist's drawing of the current "baseline" concept for SI is presented.

  20. Talon's cusp: report of four unusual cases.

    PubMed

    Tulunoglu, O; Cankala, D U; Ozdemir, R C

    2007-03-01

    Talon cusp is a developmental dental anomaly thought to arise as a result of evagination on the surface of a tooth crown before calcification has occurred. The etiology remains unknown. The incidence is 0.04-10%. Any tooth may have a talon cusp but most of the cases involve maxillary lateral incisors, with some instances of bilateral involvement. The anomaly has been reported to be rare in the mandible. This article reports four cases of talon cusp. The first and the second cases describe bilateral involvement of talon cusp on palatal surfaces of maxillary primary centrals; in the third case talon tubercle occurs on palatal surfaces of both maxillary permanent lateral incisors and the maxillary left central incisor and in the last case a talon cusp in the lingual surface of mandibular permanent lateral incisor.

  1. Cusps on cosmic superstrings with junctions

    SciTech Connect

    Davis, Anne-Christine; Rajamanoharan, Senthooran; Nelson, William; Sakellariadou, Mairi E-mail: william.nelson@kcl.ac.uk E-mail: mairi.sakellariadou@kcl.ac.uk

    2008-11-15

    The existence of cusps on non-periodic strings ending on D-branes is demonstrated and the conditions for which such cusps are generic are derived. The dynamics of F-strings, D-strings and FD-string junctions are investigated. It is shown that pairs of FD-string junctions, such as would form after intercommutations of F-strings and D-strings, generically contain cusps. This new feature of cosmic superstrings opens up the possibility of extra channels of energy loss from a string network. The phenomenology of cusps on such cosmic superstring networks is compared to that of cusps formed on networks of their field theory analogues, the standard cosmic strings.

  2. Line formation in Be star circumstellar disks Shear broadening, shell absorption, stellar obscuration and rotational parameter

    NASA Astrophysics Data System (ADS)

    Hummel, W.; Vrancken, M.

    2000-07-01

    We improve the theory of Horne & Marsh on shear broadening in accretion disks of CVs and adapt it to Be star circumstellar disks. Stellar obscuration and shell absorption are taken into account in detail. It is shown that shell absorption is already present in those emission lines where the central depression does not drop below the stellar continuum. The model profiles are fitted to observed symmetric Hα net emission lines with low equivalent width. The derived disk radii range from Rd = 5.3 R_* to Rd = 18 R_* and the surface emissivity varies as ~ R-m with 1.6 < m < 3.5. The comparison between model profiles of rotational parameter j>(1)/(2) with the optically thick Hα profile of HR 5440 rules out the range of j>(1)/(2). This can be understood by the lack of velocity shear in the outer disk regions. We conclude that Keplerian rotation (j=(1)/(2)) is a valid approximation. Based on observations collected at the German-Spanish Astronomical Center (DSAZ), Calar Alto, operated by the Max-Plank-Institut für Astronomie Heidelberg jointly with the Spanish National Commission for Astronomy. Based on observations collected at the Observatoire de Haute-Provence (OHP), CNRS, France.

  3. THE INTERSTELLAR BUBBLES OF G38.9-0.4 AND THE IMPACT OF STELLAR FEEDBACK ON STAR FORMATION

    SciTech Connect

    Alexander, Michael J.; Kobulnicky, Henry A.; Kerton, Charles R.; Arvidsson, Kim E-mail: chipk@uwyo.edu E-mail: karvidsson@adlerplanetarium.org

    2013-06-10

    We present a study of the star formation (SF) region G38.9-0.4 using publicly available multiwavelength Galactic plane surveys from ground- and space-based observatories. This region is composed of four bright mid-IR bubbles and numerous infrared dark clouds. Two bubbles, N 74 and N 75, each host a star cluster anchored by a single O9.5V star. We identified 162 young stellar objects (YSOs) and classify 54 as stage I, 7 as stage II, 6 as stage III, and 32 as ambiguous. We do not detect the classical signposts of triggered SF, i.e., star-forming pillars or YSOs embedded within bubble rims. We conclude that feedback-triggered SF has not occurred in G38.9-0.4. The YSOs are preferentially coincident with infrared dark clouds. This leads to a strong correlation between areal YSO mass surface density and gas mass surface density with a power law slope near 1.3, which closely matches the Schmidt-Kennicutt Law. The correlation is similar inside and outside the bubbles and may mean that the SF efficiency is neither enhanced nor suppressed in regions potentially influenced by stellar feedback. This suggests that gas density, regardless of how it is collected, is a more important driver of SF than stellar feedback. Larger studies should be able to quantify the fraction of all SF that is feedback-triggered by determining the fraction SF, feedback-compressed gas surrounding H II regions relative to that already present in molecular clouds.

  4. Stellar Winds

    NASA Astrophysics Data System (ADS)

    Owocki, Stan

    A "stellar wind" is the continuous, supersonic outflow of matter from the surface layers of a star. Our sun has a solar wind, driven by the gas-pressure expansion of the hot (T > 106 K) solar corona. It can be studied through direct in situ measurement by interplanetary spacecraft; but analogous coronal winds in more distant solar-type stars are so tenuous and transparent that that they are difficult to detect directly. Many more luminous stars have winds that are dense enough to be opaque at certain wavelengths of the star's radiation, making it possible to study their wind outflows remotely through careful interpretation of the observed stellar spectra. Red giant stars show slow, dense winds that may be driven by the pressure from magnetohydrodyanmic waves. As stars with initial mass up to 8 M ⊙ evolve toward the Asymptotic Giant Branch (AGB), a combination of stellar pulsations and radiative scattering off dust can culminate in "superwinds" that strip away the entire stellar envelope, leaving behind a hot white dwarf stellar core with less than the Chandrasekhar mass of ˜ ​​ 1. 4M ⊙. The winds of hot, luminous, massive stars are driven by line-scattering of stellar radiation, but such massive stars can also exhibit superwind episodes, either as Red Supergiants or Luminous Blue Variable stars. The combined wind and superwind mass loss can strip the star's hydrogen envelope, leaving behind a Wolf-Rayet star composed of the products of earlier nuclear burning via the CNO cycle. In addition to such direct effects on a star's own evolution, stellar winds can be a substantial source of mass, momentum, and energy to the interstellar medium, blowing open large cavities or "bubbles" in this ISM, seeding it with nuclear processed material, and even helping trigger the formation of new stars, and influencing their eventual fate as white dwarves or core-collapse supernovae. This chapter reviews the properties of such stellar winds, with an emphasis on the various

  5. Metal-Poor, Strongly Star-Forming Galaxies in the DEEP2 Survey: The Relationship Between Stellar Mass, Temperature-Based Metallicity, and Star Formation Rate

    NASA Technical Reports Server (NTRS)

    Ly, Chun; Rigby, Jane R.; Cooper, Michael; Yan, Renbin

    2015-01-01

    We report on the discovery of 28 redshift (z) approximately 0.8 metal-poor galaxies in DEEP2. These galaxies were selected for their detection of the weak [O (sub III)] lambda 4363 emission line, which provides a "direct" measure of the gas-phase metallicity. A primary goal for identifying these rare galaxies is to examine whether the fundamental metallicity relation (FMR) between stellar mass, gas metallicity, and star formation rate (SFR) extends to low stellar mass and high SFR. The FMR suggests that higher SFR galaxies have lower metallicity (at fixed stellar mass). To test this trend, we combine spectroscopic measurements of metallicity and dust-corrected SFRs, with stellar mass estimates from modeling the optical photometry. We find that these galaxies are 1.05 plus or minus 0.61 decimal exponent (dex) above the redshift (z) approximately equal to 1 stellar mass-SFR relation, and 0.23 plus or minus 0.23 decimal exponent (dex) below the local mass-metallicity relation. Relative to the FMR, the latter offset is reduced to 0.01 decimal exponent (dex), but significant dispersion remains (0.29 decimal exponent (dex) with 0.16 decimal exponent (dex) due to measurement uncertainties). This dispersion suggests that gas accretion, star formation and chemical enrichment have not reached equilibrium in these galaxies. This is evident by their short stellar mass doubling timescale of approximately 100 (sup plus 310) (sub minus 75) million years that suggests stochastic star formation. Combining our sample with other redshift (z) of approximately 1 metal-poor galaxies, we find a weak positive SFR-metallicity dependence (at fixed stellar mass) that is significant at 97.3 percent confidence. We interpret this positive correlation as recent star formation that has enriched the gas, but has not had time to drive the metal-enriched gas out with feedback mechanisms.

  6. Metal-Poor, Strongly Star-Forming Galaxies in the DEEP2 Survey: The Relationship Between Stellar Mass, Temperature-Based Metallicity, and Star Formation Rate

    NASA Technical Reports Server (NTRS)

    Ly, Chun; Rigby, Jane R.; Cooper, Michael; Yan, Renbin

    2015-01-01

    We report on the discovery of 28 redshift (z) approximately equal to 0.8 metal-poor galaxies in DEEP2. These galaxies were selected for their detection of the weak [O (sub III)] lambda 4363 emission line, which provides a "direct" measure of the gas-phase metallicity. A primary goal for identifying these rare galaxies is to examine whether the fundamental metallicity relation (FMR) between stellar mass, gas metallicity, and star formation rate (SFR) holds for low stellar mass and high SFR galaxies. The FMR suggests that higher SFR galaxies have lower metallicity (at fixed stellar mass). To test this trend, we combine spectroscopic measurements of metallicity and dust-corrected SFR with stellar mass estimates from modeling the optical photometry. We find that these galaxies are 1.05 plus or minus 0.61 dex above the redshift (z) approximately 1 stellar mass-SFR relation and 0.23 plus or minus 0.23 dex below the local mass-metallicity relation. Relative to the FMR, the latter offset is reduced to 0.01 dex, but significant dispersion remains dex with 0.16 dex due to measurement uncertainties). This dispersion suggests that gas accretion, star formation, and chemical enrichment have not reached equilibrium in these galaxies. This is evident by their short stellar mass doubling timescale of approximately equal to 100 (sup plus 310) (sub minus 75) million years which suggests stochastic star formation. Combining our sample with other redshift (z) of approximately 1 metal-poor galaxies, we find a weak positive SFR-metallicity dependence (at fixed stellar mass) that is significant at 94.4 percent confidence. We interpret this positive correlation as recent star formation that has enriched the gas but has not had time to drive the metal-enriched gas out with feedback mechanisms.

  7. Metal-Poor, Strongly Star-Forming Galaxies in the DEEP2 Survey: The Relationship Between Stellar Mass, Temperature-Based Metallicity, and Star Formation Rate

    NASA Technical Reports Server (NTRS)

    Ly, Chun; Rigby, Jane R.; Cooper, Michael; Yan, Renbin

    2015-01-01

    We report on the discovery of 28 redshift (z) approximately equal to 0.8 metal-poor galaxies in DEEP2. These galaxies were selected for their detection of the weak [O (sub III)] lambda 4363 emission line, which provides a "direct" measure of the gas-phase metallicity. A primary goal for identifying these rare galaxies is to examine whether the fundamental metallicity relation (FMR) between stellar mass, gas metallicity, and star formation rate (SFR) holds for low stellar mass and high SFR galaxies. The FMR suggests that higher SFR galaxies have lower metallicity (at fixed stellar mass). To test this trend, we combine spectroscopic measurements of metallicity and dust-corrected SFR with stellar mass estimates from modeling the optical photometry. We find that these galaxies are 1.05 plus or minus 0.61 dex above the redshift (z) approximately 1 stellar mass-SFR relation and 0.23 plus or minus 0.23 dex below the local mass-metallicity relation. Relative to the FMR, the latter offset is reduced to 0.01 dex, but significant dispersion remains dex with 0.16 dex due to measurement uncertainties). This dispersion suggests that gas accretion, star formation, and chemical enrichment have not reached equilibrium in these galaxies. This is evident by their short stellar mass doubling timescale of approximately equal to 100 (sup plus 310) (sub minus 75) million years which suggests stochastic star formation. Combining our sample with other redshift (z) of approximately 1 metal-poor galaxies, we find a weak positive SFR-metallicity dependence (at fixed stellar mass) that is significant at 94.4 percent confidence. We interpret this positive correlation as recent star formation that has enriched the gas but has not had time to drive the metal-enriched gas out with feedback mechanisms.

  8. Solutions of the coagulation equation with time-dependent coagulation rates. [For stellar formation mass functions

    SciTech Connect

    Lejeune, C.; Bastien, P.

    1986-10-01

    In attempting to reproduce the initial stellar mass function, the authors solved analytically the coagulation equation with an explicit time dependence in the coagulation rate in order to simulate the gravitational collapse of the fragments upon themselves as they move within the progenitor cloud. Two separate cases have been studied, with and without a mass dependence in the coagulation rate. The solutions show that: (1) inclusion of self-gravitation can change the results to the point of preventing coalescence to work altogether, depending on the values of the two free parameters; (2) the precise form of the mass dependence of the coagulation rate is not of prime importance in most situations of astrophysical interest; (3) coagulation alone is not sufficient to yield a realistic mass spectrum, and fragmentation must also be taken into account. 30 references.

  9. FORMATION OF COMPACT STELLAR CLUSTERS BY HIGH-REDSHIFT GALAXY OUTFLOWS. III. OBSERVABILITY AND CONNECTION TO HALO GLOBULAR CLUSTERS

    SciTech Connect

    Gray, William J.; Scannapieco, Evan

    2011-12-01

    The early universe hosted a large population of low-mass virialized 'minihalos', that were not massive enough to form stars on their own. While most minihalos were photoevaporated by ionizing photons from star-forming galaxies, these galaxies also drove large outflows, which in some cases would have reached the minihalos in advance of ionization fronts. In the previous papers in this series, we carried out high-resolution, three-dimensional adaptive mesh refinement simulations of outflow-minihalo interactions that included non-equilibrium chemistry, radiative cooling, and turbulent mixing. We found that, for a fiducial set of parameters, minihalos were transformed into dense, chemically homogenous stellar clusters. Here we conduct a suite of simulations that follow these interactions over a wide range of parameters including minihalo mass, minihalo formation redshift, outflow energy, outflow redshift, distance, concentration, and spin. In almost all cases, the shocked minihalos form molecules through non-equilibrium reactions and then cool rapidly to become compact, chemically homogenous stellar clusters. Furthermore, we show that the unique properties of these clusters make them a prime target for direct study with the next generation of telescopes, and that there are many reasons to suspect that their low-redshift counterparts are the observed population of halo globular clusters.

  10. STAR FORMATION: STATISTICAL MEASURE OF THE CORRELATION BETWEEN THE PRESTELLAR CORE MASS FUNCTION AND THE STELLAR INITIAL MASS FUNCTION

    SciTech Connect

    Chabrier, Gilles; Hennebelle, Patrick

    2010-12-10

    We present a simple statistical analysis of recent numerical simulations exploring the correlation between the core mass function (CMF) obtained from the fragmentation of a molecular cloud and the stellar mass function which forms from these collapsing cores. Our analysis shows that the distributions of bound cores and sink particles obtained in the simulations are consistent with the sinks being formed predominantly from their parent core mass reservoir, with a statistical dispersion of the order of one-third of the core mass. Such a characteristic dispersion suggests that the stellar initial mass function (IMF) is relatively tightly correlated to the parent CMF, leading to two similar distributions, as observed. This in turn argues in favor of the IMF being essentially determined at the early stages of core formation and being only weakly affected by the various environmental factors beyond the initial core mass reservoir, at least in the mass range explored in the present study. Accordingly, the final IMF of a star-forming region should be determined reasonably accurately, statistically speaking, from the initial CMF, provided some uniform efficiency factor. The calculations also show that these statistical fluctuations, due to, e.g., variations among the core properties, broaden the low-mass tail of the IMF compared with the parent CMF, providing an explanation for the fact that the latter appears to underestimate the number of 'pre brown dwarf' cores compared with the observationally derived brown dwarf IMF.

  11. Friends of Hot Jupiters. IV. Stellar Companions Beyond 50 au Might Facilitate Giant Planet Formation, but Most are Unlikely to Cause Kozai-Lidov Migration

    NASA Astrophysics Data System (ADS)

    Ngo, Henry; Knutson, Heather A.; Hinkley, Sasha; Bryan, Marta; Crepp, Justin R.; Batygin, Konstantin; Crossfield, Ian; Hansen, Brad; Howard, Andrew W.; Johnson, John A.; Mawet, Dimitri; Morton, Timothy D.; Muirhead, Philip S.; Wang, Ji

    2016-08-01

    Stellar companions can influence the formation and evolution of planetary systems, but there are currently few observational constraints on the properties of planet-hosting binary star systems. We search for stellar companions around 77 transiting hot Jupiter systems to explore the statistical properties of this population of companions as compared to field stars of similar spectral type. After correcting for survey incompleteness, we find that 47 % +/- 7 % of hot Jupiter systems have stellar companions with semimajor axes between 50 and 2000 au. This is 2.9 times larger than the field star companion fraction in this separation range, with a significance of 4.4σ . In the 1-50 au range, only {3.9}-2.0+4.5 % of hot Jupiters host stellar companions, compared to the field star value of 16.4 % +/- 0.7 % , which is a 2.7σ difference. We find that the distribution of mass ratios for stellar companions to hot Jupiter systems peaks at small values and therefore differs from that of field star binaries which tend to be uniformly distributed across all mass ratios. We conclude that either wide separation stellar binaries are more favorable sites for gas giant planet formation at all separations, or that the presence of stellar companions preferentially causes the inward migration of gas giant planets that formed farther out in the disk via dynamical processes such as Kozai-Lidov oscillations. We determine that less than 20% of hot Jupiters have stellar companions capable of inducing Kozai-Lidov oscillations assuming initial semimajor axes between 1 and 5 au, implying that the enhanced companion occurrence is likely correlated with environments where gas giants can form efficiently.

  12. ON THE INCONSISTENCY BETWEEN COSMIC STELLAR MASS DENSITY AND STAR FORMATION RATE UP TO z ∼ 8

    SciTech Connect

    Yu, H.; Wang, F. Y.

    2016-04-01

    In this paper, we test the discrepancy between the stellar mass density (SMD) and instantaneous star formation rate in the redshift range 0 < z < 8 using a large observational data sample. We first compile the measurements of SMDs up to z ∼ 8. Comparing the observed SMDs with the time-integral of instantaneous star formation history (SFH), we find that the observed SMDs are lower than that implied from the SFH at z < 4. We also use the Markov chain Monte Carlo (MCMC) method to derive the best-fitting SFH from the observed SMD data. At 0.5 < z < 6, the observed star formation rate densities are larger than the best-fitting one, especially at z ∼ 2 where they are larger by a factor of about two. However, at lower (z < 0.5) and higher redshifts (z > 6), the derived SFH is consistent with the observations. This is the first time that the discrepancy between the observed SMD and instantaneous star formation rate has been tested up to very high redshift z ≈ 8 using the MCMC method and a varying recycling factor. Several possible reasons for this discrepancy are discussed, such as underestimation of SMD, initial mass function, and evolution of cosmic metallicity.

  13. On the Inconsistency between Cosmic Stellar Mass Density and Star Formation Rate up to z ∼ 8

    NASA Astrophysics Data System (ADS)

    Yu, H.; Wang, F. Y.

    2016-04-01

    In this paper, we test the discrepancy between the stellar mass density (SMD) and instantaneous star formation rate in the redshift range 0 < z < 8 using a large observational data sample. We first compile the measurements of SMDs up to z ∼ 8. Comparing the observed SMDs with the time-integral of instantaneous star formation history (SFH), we find that the observed SMDs are lower than that implied from the SFH at z < 4. We also use the Markov chain Monte Carlo (MCMC) method to derive the best-fitting SFH from the observed SMD data. At 0.5 < z < 6, the observed star formation rate densities are larger than the best-fitting one, especially at z ∼ 2 where they are larger by a factor of about two. However, at lower (z < 0.5) and higher redshifts (z > 6), the derived SFH is consistent with the observations. This is the first time that the discrepancy between the observed SMD and instantaneous star formation rate has been tested up to very high redshift z ≈ 8 using the MCMC method and a varying recycling factor. Several possible reasons for this discrepancy are discussed, such as underestimation of SMD, initial mass function, and evolution of cosmic metallicity.

  14. Stellar model chromospheres. IV - The formation of the H-epsilon feature in the sun /G2 V/ and Arcturus /K2 III/

    NASA Technical Reports Server (NTRS)

    Ayres, T. R.; Linsky, J. L.

    1975-01-01

    The formation of the Balmer-series member H-epsilon in the near-red wing of the Ca II H line is discussed for two cases: the sun (H-epsilon absorption profile) and Arcturus (H-epsilon emission profile). It is shown that although the H-epsilon source functions in both stars are dominated by the Balmer-continuum radiation field through photoionizations, the line-formation problems in the two stars are quantitatively different, owing to a substantial difference in the relative importance of the stellar chromosphere temperature inversion as compared with the stellar photosphere.

  15. Three loop cusp anomalous dimension in QCD.

    PubMed

    Grozin, Andrey; Henn, Johannes M; Korchemsky, Gregory P; Marquard, Peter

    2015-02-13

    We present the full analytic result for the three loop angle-dependent cusp anomalous dimension in QCD. With this result, infrared divergences of planar scattering processes with massive particles can be predicted to that order. Moreover, we define a closely related quantity in terms of an effective coupling defined by the lightlike cusp anomalous dimension. We find evidence that this quantity is universal for any gauge theory and use this observation to predict the nonplanar n(f)-dependent terms of the four loop cusp anomalous dimension.

  16. Nuclear cusps in the HSF electron density

    NASA Astrophysics Data System (ADS)

    Cioslowski, Jerzy; Challacombe, Matt

    1994-07-01

    The Hiller-Sucher-Feinberg (HSF) identity provides an alternative definition for the electron density. The behavior of the HSF electron density in the vicinity of nuclei is analyzed. It is shown that the HSF density possesses nuclear cusps at which its gradient is discontinuous. The discontinuities in the HSF density gradient satisfy a simple equation analogous to Kato's electron-nuclear cusp condition. However, in contrast to Kato's condition, the electron-nuclear cusp condition is satisfied by HSF densities originating from both exact and approximate electronic wavefunctions. Several numerical examples are presented to illustrate this property of the HSF electron density.

  17. Stellar scattering and the formation of hot Jupiters in binary systems

    NASA Astrophysics Data System (ADS)

    Martí, J. G.; Beaugé, C.

    2015-04-01

    Hot Jupiters (HJs) are usually defined as giant Jovian-size planets with orbital periods P<=10 days. Although they lie close to the star, several have finite eccentricities and significant misalignment angle with respect to the stellar equator, leading to ~20% of HJs in retrograde orbits. More than half, however, seem consistent with near-circular and planar orbits. In recent years, two mechanisms have been proposed to explain the excited and misaligned subpopulation of HJs: Lidov-Kozai migration and planet-planet scattering. Although both are based on completely different dynamical phenomena, at first hand they appear to be equally effective in generating hot planets. Nevertheless, there has been no detailed analysis comparing the predictions of both mechanisms, especially with respect to the final distribution of orbital characteristics. In this paper, we present a series of numerical simulations of Lidov-Kozai trapping of single planets in compact binary systems that suffered a close fly-by of a background star. Both the planet and the binary component are initially placed in coplanar orbits, although the inclination of the impactor is assumed random. After the passage of the third star, we follow the orbital and spin evolution of the planet using analytical models based on the octupole expansion of the secular Hamiltonian. We also include tidal effects, stellar oblateness and post-Newtonian perturbations. The present work aims at the comparison of the two mechanisms (Lidov-Kozai and planet-planet scattering) as an explanation for the excited and inclined HJs in binary systems. We compare the results obtained through this paper with results in Beaugé & Nesvorný (2012), where the authors analyse how the planet-planet scattering mechanisms works in order to form this hot Jovian-size planets. We find that several of the orbital characteristics of the simulated HJs are caused by tidal trapping from quasi-parabolic orbits, independent of the driving mechanism

  18. PLANET FORMATION IN STELLAR BINARIES. I. PLANETESIMAL DYNAMICS IN MASSIVE PROTOPLANETARY DISKS

    SciTech Connect

    Rafikov, Roman R.; Silsbee, Kedron

    2015-01-10

    About 20% of exoplanets discovered by radial velocity surveys reside in stellar binaries. To clarify their origin one has to understand the dynamics of planetesimals in protoplanetary disks within binaries. The standard description, accounting for only gas drag and gravity of the companion star, has been challenged recently, as the gravity of the protoplanetary disk was shown to play a crucial role in planetesimal dynamics. An added complication is the tendency of protoplanetary disks in binaries to become eccentric, giving rise to additional excitation of planetesimal eccentricity. Here, for the first time, we analytically explore the secular dynamics of planetesimals in binaries such as α Cen and γ Cep under the combined action of (1) gravity of the eccentric protoplanetary disk, (2) perturbations due to the (coplanar) eccentric companion, and (3) gas drag. We derive explicit solutions for the behavior of planetesimal eccentricity e {sub p} in non-precessing disks (and in precessing disks in certain limits). We obtain the analytical form of the distribution of the relative velocities of planetesimals, which is a key input for understanding their collisional evolution. Disk gravity strongly influences relative velocities and tends to push the sizes of planetesimals colliding with comparable objects at the highest speed to small values, ∼1 km. We also find that planetesimals in eccentric protoplanetary disks apsidally aligned with the binary orbit collide at lower relative velocities than in misaligned disks. Our results highlight the decisive role that disk gravity plays in planetesimal dynamics in binaries.

  19. Planet Formation in Stellar Binaries. I. Planetesimal Dynamics in Massive Protoplanetary Disks

    NASA Astrophysics Data System (ADS)

    Rafikov, Roman R.; Silsbee, Kedron

    2015-01-01

    About 20% of exoplanets discovered by radial velocity surveys reside in stellar binaries. To clarify their origin one has to understand the dynamics of planetesimals in protoplanetary disks within binaries. The standard description, accounting for only gas drag and gravity of the companion star, has been challenged recently, as the gravity of the protoplanetary disk was shown to play a crucial role in planetesimal dynamics. An added complication is the tendency of protoplanetary disks in binaries to become eccentric, giving rise to additional excitation of planetesimal eccentricity. Here, for the first time, we analytically explore the secular dynamics of planetesimals in binaries such as α Cen and γ Cep under the combined action of (1) gravity of the eccentric protoplanetary disk, (2) perturbations due to the (coplanar) eccentric companion, and (3) gas drag. We derive explicit solutions for the behavior of planetesimal eccentricity e p in non-precessing disks (and in precessing disks in certain limits). We obtain the analytical form of the distribution of the relative velocities of planetesimals, which is a key input for understanding their collisional evolution. Disk gravity strongly influences relative velocities and tends to push the sizes of planetesimals colliding with comparable objects at the highest speed to small values, ~1 km. We also find that planetesimals in eccentric protoplanetary disks apsidally aligned with the binary orbit collide at lower relative velocities than in misaligned disks. Our results highlight the decisive role that disk gravity plays in planetesimal dynamics in binaries.

  20. Do stellar winds prevent the formation of supermassive stars by accretion?

    NASA Astrophysics Data System (ADS)

    Nakauchi, Daisuke; Hosokawa, Takashi; Omukai, Kazuyuki; Saio, Hideyuki; Nomoto, Ken'ichi

    2017-03-01

    Supermassive stars (SMSs; ∼105 M⊙) formed from metal-free gas in the early Universe attract attention as progenitors of supermassive black holes observed at high redshifts. To form SMSs by accretion, central protostars must accrete at as high rates as ∼0.1-1 M⊙ yr-1. Such protostars have very extended structures with bloated envelopes, like supergiant stars, and are called supergiant protostars (SGPSs). Under the assumption of hydrostatic equilibrium, SGPSs have density-inverted layers, where the luminosity becomes locally super-Eddington, near the surface. If the envelope matter is allowed to flow out, however, a stellar wind could be launched and hinder the accretion growth of SGPSs before reaching the supermassive regime. We examine whether radiation-driven winds are launched from SGPSs by constructing steady and spherically symmetric wind solutions. We find that the wind velocity does not reach the escape velocity in any case considered. This is because once the temperature falls below ∼104 K, the opacity plummet drastically owing to the recombination of hydrogen and the acceleration ceases suddenly. This indicates that, in realistic non-steady cases, even if outflows are launched from the surface of SGPSs, they would fall back again. Such a 'wind' does not result in net mass-loss and does not prevent the growth of SGPSs. In conclusion, SGPSs will grow to SMSs and eventually collapse to massive black holes of ∼105 M⊙, as long as the rapid accretion is maintained.

  1. Modeling Massive Cluster Formation with Stellar Feedback using Flash and AMUSE

    NASA Astrophysics Data System (ADS)

    McMillan, Stephen; Wall, Joshua; Mac Low, Mordecai-Mark

    2015-08-01

    Star cluster formation is a complex astrophysical problem combining multiple competing physical processes in a challenging computational environment, placing stringent demands on both software and hardware. Current simulations still fall short of a realistic description of the physical processes at work in star-forming regions. We are developing a hybrid simulation code to explore the formation and assembly of massive star clusters by combining the magnetohydrodynamics code Flash and the AMUSE software environment. Flash handles gas dynamics and star formation through cloud collapse, while AMUSE manages the dynamics and evolution of stars and binary systems. The gravitational interaction between the gas and the stars is treated via a symplectic gravity bridge between the codes in AMUSE. Radiative, wind, and supernova feedback are followed in FLASH based on information provided by the AMUSE system. We present some early results of this work, focusing on cluster formation and assembly, and including simplified models of feedback to study gas expulsion and cluster survival.

  2. DARK MATTER HEATING AND EARLY CORE FORMATION IN DWARF GALAXIES

    SciTech Connect

    Madau, Piero; Shen, Sijing; Governato, Fabio

    2014-07-01

    We present more results from a fully cosmological ΛCDM simulation of a group of isolated dwarf galaxies that has been shown to reproduce the observed stellar mass and cold gas content, resolved star formation histories, and metallicities of dwarfs in the Local Volume. Here we investigate the energetics and timetable of the cusp-core transformation. As suggested by previous work, supernova-driven gas outflows remove dark matter (DM) cusps and create kiloparsec-size cores in all systems having a stellar mass M {sub *} > 10{sup 6} M {sub ☉}. The {sup D}M core mass removal efficiency{sup —}dark mass ejected per unit stellar mass—ranges today from a few to a dozen, and increases with decreasing host mass. Because dwarfs form the bulk of their stars prior to redshift 1 and the amount of work required for DM heating and core formation scales approximately as M{sub vir}{sup 5/3}, the unbinding of the DM cusp starts early and the formation of cored profiles is not as energetically onerous as previously claimed. DM particles in the cusp typically migrate to 2-3 core radii after absorbing a few percent of the energy released by supernovae. The present-day slopes of the inner DM mass profiles, Γ ≡ dlog M/dlog R ≅ 2.5-3, of the simulated ''Bashful'' and ''Doc'' dwarfs are similar to those measured in the luminous Fornax and Sculptor dwarf spheroidals. None of the simulated galaxies has a circular velocity profile exceeding 20 km s{sup –1} in the inner 1 kpc, implying that supernova feedback is key to solve the ''too-big-to-fail'' problem for Milky Way subhalos.

  3. 21 CFR 872.3360 - Preformed cusp.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... prefabricated device made of plastic or austenitic alloys or alloys containing 75 percent or greater gold and metals of the platinum group intended to be used as a temporary cusp (a projection on the chewing...

  4. 21 CFR 872.3360 - Preformed cusp.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... prefabricated device made of plastic or austenitic alloys or alloys containing 75 percent or greater gold and metals of the platinum group intended to be used as a temporary cusp (a projection on the chewing...

  5. 21 CFR 872.3360 - Preformed cusp.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... prefabricated device made of plastic or austenitic alloys or alloys containing 75 percent or greater gold and metals of the platinum group intended to be used as a temporary cusp (a projection on the chewing...

  6. 21 CFR 872.3360 - Preformed cusp.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... prefabricated device made of plastic or austenitic alloys or alloys containing 75 percent or greater gold and metals of the platinum group intended to be used as a temporary cusp (a projection on the chewing...

  7. ULF turbulence in the Neptunian polar cusp

    NASA Astrophysics Data System (ADS)

    Farrell, W. M.; Lepping, R. P.; Smith, C. W.

    1993-03-01

    Results of a spectral analysis of the ULF wave turbulence in the Neptunian polar cusp are presented. The activity is characterized as broadbanded, extending up to a maximum frequency of about 0.5 Hz, and having maximum wave amplitudes as large as 6 percent of the dc magnetic field. Activity in the cusp region was particularly intense at its frontside and backside, associated with the magnetopause and cusp/magnetosphere boundaries, respectively. The turbulence, particularly that above f(ci), is tentatively identified as whistler mode. It is argued that such whistler mode turbulence should resonate with electrons having energies in the tens of kiloelectron volts. Observations indicate a very strong correlation of the ULF turbulence with the energetic electrons between 22 and 35 keV measured by Voyager's low-energy charged particle experiment. A vigorous interaction between the two is inferred. ULF wave turbulence in the cusp may represent a significant but not complete power source for the magnetosphere.

  8. Constraining the dark cusp in the galactic center by long-period binaries

    SciTech Connect

    Alexander, Tal; Pfuhl, Oliver

    2014-01-10

    Massive black holes (MBHs) in galactic nuclei are believed to be surrounded by a high-density stellar cluster, whose mass is mostly in hard-to-detect faint stars and compact remnants. Such dark cusps dominate the dynamics near the MBH: a dark cusp in the Galactic center (GC) of the Milky Way would strongly affect orbital tests of general relativity there; on cosmic scales, dark cusps set the rates of gravitational wave emission events from compact remnants that spiral into MBHs, and they modify the rates of tidal disruption events, to list only some implications. A recently discovered long-period massive young binary (with period P {sub 12} ≲ 1 yr, total mass M{sub 12}∼O(100 M{sub ⊙}), and age T {sub 12} ∼ 6 × 10{sup 6} yr), only ∼0.1 pc from the Galactic MBH, sets a lower bound on the stellar two-body relaxation timescale there, min t {sub rlx}∝(P {sub 12}/M {sub 12}){sup 2/3} T {sub 12} ∼ 10{sup 7} yr, and, correspondingly, an upper bound on the stellar number density, maxn{sub ⋆}∼few×10{sup 8}/〈M{sub ⋆}{sup 2}〉 pc{sup −3} (〈M{sub ⋆}{sup 2}〉{sup 1/2} is the rms stellar mass), based on the binary's survival against evaporation by the dark cusp. However, a conservative dynamical estimate, the drain limit, implies t{sub rlx}>O(10{sup 8} yr). Such massive binaries are thus too short-lived and tightly bound to constrain a dense relaxed dark cusp. We explore here in detail the use of longer-period, less massive, and longer-lived binaries (P {sub 12} ∼ few yr, M {sub 12} ∼ 2-4 M {sub ☉}, T {sub 12} ∼ 10{sup 8}-10{sup 10} yr), presently just below the detection threshold, for probing the dark cusp and develop the framework for translating their future detections among the giants in the GC into dynamical constraints.

  9. Evidence of Multiple Reconnection Lines at the Magnetopause from Cusp Observations

    NASA Technical Reports Server (NTRS)

    Trattner, K. J.; Petrinec, S. M.; Fuselier, S. A.; Omidi, N.; Sibeck, David Gary

    2012-01-01

    Recent global hybrid simulations investigated the formation of flux transfer events (FTEs) and their convection and interaction with the cusp. Based on these simulations, we have analyzed several Polar cusp crossings in the Northern Hemisphere to search for the signature of such FTEs in the energy distribution of downward precipitating ions: precipitating ion beams at different energies parallel to the ambient magnetic field and overlapping in time. Overlapping ion distributions in the cusp are usually attributed to a combination of variable ion acceleration during the magnetopause crossing together with the time-of-flight effect from the entry point to the observing satellite. Most "step up" ion cusp structures (steps in the ion energy dispersions) only overlap for the populations with large pitch angles and not for the parallel streaming populations. Such cusp structures are the signatures predicted by the pulsed reconnection model, where the reconnection rate at the magnetopause decreased to zero, physically separating convecting flux tubes and their parallel streaming ions. However, several Polar cusp events discussed in this study also show an energy overlap for parallel-streaming precipitating ions. This condition might be caused by reopening an already reconnected field line, forming a magnetic island (flux rope) at the magnetopause similar to that reported in global MHD and Hybrid simulations

  10. Magnetic-cusp, cathodic-arc source

    DOEpatents

    Falabella, Steven

    1995-01-01

    A magnetic-cusp for a cathodic-arc source wherein the arc is confined to the desired cathode surface, provides a current path for electrons from the cathode to the anode, and utilizes electric and magnetic fields to guide ions from the cathode to a point of use, such as substrates to be coated. The magnetic-cusp insures arc stability by an easy magnetic path from anode to cathode, while the straight-through arrangement leads to high ion transmission.

  11. Constraining stellar binary black hole formation scenarios with eLISA eccentricity measurements

    NASA Astrophysics Data System (ADS)

    Nishizawa, Atsushi; Sesana, Alberto; Berti, Emanuele; Klein, Antoine

    2017-03-01

    A space-based interferometer such as the evolved Laser Interferometer Space Antenna (eLISA) could observe a few to a few thousands of progenitors of black hole binaries (BHBs) similar to those recently detected by Advanced LIGO. Gravitational radiation circularizes the orbit during inspiral, but some BHBs retain a measurable eccentricity at the low frequencies where eLISA is the most sensitive. The eccentricity of a BHB carries precious information about its formation channel: BHBs formed in the field, in globular clusters, or close to a massive black hole (MBH) have distinct eccentricity distributions in the eLISA band. We generate mock eLISA observations, folding in measurement errors, and using a Bayesian model selection, we study whether eLISA measurements can identify the BHB formation channel. We find that a handful of observations would suffice to tell whether BHBs were formed in the gravitational field of an MBH. Conversely, several tens of observations are needed to tell apart field formation from globular cluster formation. A 5-yr eLISA mission with the longest possible armlength is desirable to shed light on BHB formation scenarios.

  12. Constraining stellar binary black hole formation scenarios with LISA eccentricity measurements

    NASA Astrophysics Data System (ADS)

    Berti, Emanuele; Nishizawa, Atsushi; Sesana, Alberto; Klein, Antoine

    2017-01-01

    A space-based interferometer such as LISA could observe few to few thousands progenitors of black hole binaries (BHBs) similar to those recently detected by Advanced LIGO. Gravitational radiation circularizes the orbit during inspiral, but some BHBs retain a measurable eccentricity at the low frequencies where LISA is most sensitive. The eccentricity of a BHB carries precious information about its formation channel: BHBs formed in the field, in globular clusters, or close to a massive black hole (MBH) have distinct eccentricity distributions in the LISA band. We generate mock LISA observations, folding in measurement errors, and using Bayesian model selection we study whether LISA measurements can identify the BHB formation channel. We find that a handful of observations would suffice to tell whether BHBs were formed in the gravitational field of a MBH. Conversely, several tens of observations are needed to tell apart field formation from globular cluster formation. A five-year LISA mission with the longest possible armlength is desirable to shed light on BHB formation scenarios. NSF CAREER Grant No. PHY-1055103, NSF Grant No. PHY-1607130, FCT contract IF/00797/2014/CP1214/CT0012.

  13. Dayside and Cusp Plasma Dynamics at Mercury's Magnetosphere

    NASA Astrophysics Data System (ADS)

    Schriver, D.; Travnicek, P. M.; Hellinger, P.; Richard, R. L.; Perkins, D. J.; Berchem, J.; Raines, J. M.; Ho, G. C.

    2016-12-01

    When the solar wind with its interplanetary magnetic field (IMF) interacts with a planetary magnetosphere, a foreshock forms upstream of the bow shock, an upstream magnetosheath consisting of thermalized plasma is created between the bow shock and the magnetopause, and a funnel shaped magnetic cusp extending down to the planet forms at high northern and southern latitudes on the dayside. The foreshock location, thickness of the magnetosheath and location of the northern and southern cusps depends on the solar wind pressure, IMF orientation and properties of the planet's internal magnetic field. Global kinetic simulations of the solar wind interaction with Mercury's intrinsic magnetic field have been carried out in close coordination with data from the MESSENGER spacecraft during its 4 year orbital mission to examine the formation and dynamics of the various dayside structures for different solar wind conditions. Unique aspects of Mercury's magnetosphere that affect dayside dynamics include the intrinsic planetary magnetic dipole being shifted directly to the north by 450 km (with no tilt), the lack of an atmosphere or ionosphere, and the presence of heavy ions (primarily sodium ions) of planetary origin that mass load the plasma. Ion and electron transport, acceleration and loss will be examined in the dayside and cusp regions in Mercury's magnetosphere and broad comparisons will be made with the same features found at Earth's magnetosphere.

  14. A pilot study using deep infrared imaging to constrain the star formation history of the XUV stellar populations in NGC 4625

    SciTech Connect

    Bush, Stephanie J.; Ashby, M. L. N.; Fazio, Giovanni; Kennicutt, Robert C.; Johnson, Benjamin D.; Bresolin, Fabio

    2014-09-20

    In a ΛCDM universe, disk galaxies' outer regions are the last to form. Characterizing their contents is critical for understanding the ongoing process of disk formation, but observing outer disk stellar populations is challenging due to their low surface brightness. We present extremely deep 3.6 μm observations (Spitzer/Infrared Array Camera) of NGC 4625, a galaxy known for its radially extended ultraviolet-emitting stellar population. We combine the new imaging with archival UV imaging from the GALEX mission to derive multi-wavelength radial profiles for NGC 4625 and compare them to stellar populations models. The colors can be explained by the young stellar population that is responsible for the UV emission and indicate that the current star formation rates in the outermost disk are recent. Extended star formation in NGC 4625 may have been initiated by an interaction with neighboring galaxies NGC 4618 and NGC 4625a, supporting speculation that minor interactions are a common trigger for outer disk star formation and late stage disk growth.

  15. Thermospheric winds around the cusp region

    NASA Astrophysics Data System (ADS)

    Sheng, C.; Deng, Y.; Wu, Q.; Ridley, A. J.

    2013-12-01

    Due to the change of advection, the horizontal winds can be strongly influenced by the large vertical wind in the cusp. Indeed, the sunward wind has been observed by the balloon-borne Fabry-Perot interferometer (FPI) at the equatorward of the cusp on the dayside [Wu et al., 2012], which is caused by the heating added in the cusp and the corresponding changes of the horizontal pressure gradient. However, this phenomenon has not been reproduced by the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) under low resolution (5x5 degrees). The Global Ionosphere Thermosphere Model (GITM) has been run in different cases and different resolutions. First, we compare the simulations with and without the cusp energy inputs to identify the influence on the horizontal dynamics. Both runs are done under high resolution in order to better resolve the cusp region. Then we also compare the simulations with the same cusp energy inputs but different horizontal resolutions to identify the influence of the simulation resolution on the results. This work will significantly advance our understanding of the neutral dynamics and the relationship between winds and upper atmosphere storm time response.

  16. Density Variations in the Earth's Magnetospheric Cusps

    NASA Technical Reports Server (NTRS)

    Walsh, B. M.; Niehof, J.; Collier, M. R.; Welling, D. T.; Sibeck, D. G.; Mozer, F. S.; Fritz, T. A.; Kuntz, K. D.

    2016-01-01

    Seven years of measurements from the Polar spacecraft are surveyed to monitor the variations of plasma density within the magnetospheric cusps. The spacecraft's orbital precession from 1998 through 2005 allows for coverage of both the northern and southern cusps from low altitude out to the magnetopause. In the mid- and high- altitude cusps, plasma density scales well with the solar wind density (n(sub cusp)/n(sub sw) approximately 0.8). This trend is fairly steady for radial distances greater then 4 R(sub E). At low altitudes (r less than 4R(sub E)) the density increases with decreasing altitude and even exceeds the solar wind density due to contributions from the ionosphere. The density of high charge state oxygen (O(greater +2) also displays a positive trend with solar wind density within the cusp. A multifluid simulation with the Block-Adaptive-Tree Solar Wind Roe-Type Upwind Scheme MHD model was run to monitor the relative contributions of the ionosphere and solar wind plasma within the cusp. The simulation provides similar results to the statistical measurements from Polar and confirms the presence of ionospheric plasma at low altitudes.

  17. Density Variations in the Earth's Magnetospheric Cusps

    NASA Technical Reports Server (NTRS)

    Walsh, B. M.; Niehof, J.; Collier, M. R.; Welling, D. T.; Sibeck, D. G.; Mozer, F. S.; Fritz, T. A.; Kuntz, K. D.

    2016-01-01

    Seven years of measurements from the Polar spacecraft are surveyed to monitor the variations of plasma density within the magnetospheric cusps. The spacecraft's orbital precession from 1998 through 2005 allows for coverage of both the northern and southern cusps from low altitude out to the magnetopause. In the mid- and high- altitude cusps, plasma density scales well with the solar wind density (n(sub cusp)/n(sub sw) approximately 0.8). This trend is fairly steady for radial distances greater then 4 R(sub E). At low altitudes (r less than 4R(sub E)) the density increases with decreasing altitude and even exceeds the solar wind density due to contributions from the ionosphere. The density of high charge state oxygen (O(greater +2) also displays a positive trend with solar wind density within the cusp. A multifluid simulation with the Block-Adaptive-Tree Solar Wind Roe-Type Upwind Scheme MHD model was run to monitor the relative contributions of the ionosphere and solar wind plasma within the cusp. The simulation provides similar results to the statistical measurements from Polar and confirms the presence of ionospheric plasma at low altitudes.

  18. On star formation in stellar systems. II - Photoionization in protodwarf galaxies

    NASA Technical Reports Server (NTRS)

    Noriega-Crespo, A.; Bodenheimer, P.; Lin, D. N. C.; Tenorio-Tagle, G.

    1989-01-01

    Numerical hydrodynamical calculations are used to study the effects of the onset of star formation on the residual gas in a primordial low-mass Local-Group dwarf spheroidal galaxy in the size range 0.3-1.0 kpc. It is demonstrated that photoionization in the presence of a moderate gas-density gradient can be responsible for gas ejection on a time-scale of a few times 10 to the 7th yr. The results indicate that, given a normal initial mass function, many protodwarf galaxies may have been dispersed by the onset of star formation.

  19. The evolving relation between star formation rate and stellar mass in the VIDEO survey since z = 3

    NASA Astrophysics Data System (ADS)

    Johnston, Russell; Vaccari, Mattia; Jarvis, Matt; Smith, Mathew; Giovannoli, Elodie; Häußler, Boris; Prescott, Matthew

    2015-11-01

    We investigate the star formation rate (SFR) and stellar mass, M*, relation of a star-forming (SF) galaxy (SFG) sample in the XMM-LSS field to z ˜ 3.0 using the near-infrared data from the VISTA Deep Extragalactic Observations (VIDEO) survey. Combining VIDEO with broad-band photometry, we use the SED fitting algorithm CIGALE to derive SFRs and M* and have adapted it to account for the full photometric redshift probability-distribution-function uncertainty. Applying an SF selection using the D4000 index, we find evidence for strong evolution in the normalization of the SFR-M* relation out to z ˜ 3 and a roughly constant slope of (SFR ∝ M_*^{α }) α = 0.69 ± 0.02 to z ˜ 1.7. We find this increases close to unity towards z ˜ 2.65. Alternatively, if we apply a colour selection, we find a distinct turnover in the SFR-M* relation between 0.7 ≲ z ≲ 2.0 at the high-mass end, and suggest that this is due to an increased contamination from passive galaxies. We find evolution of the specific SFR ∝ (1 + z)2.60 at log10(M*/M⊙) ˜ 10.5, out to z ≲ 2.4 with an observed flattening beyond z ˜ 2 with increased stellar mass. Comparing to a range of simulations we find the analytical scaling relation approaches, that invoke an equilibrium model, a good fit to our data, suggesting that a continual smooth accretion regulated by continual outflows may be a key driver in the overall growth of SFGs.

  20. Ambiguities in the rate of oxygen formation during stellar helium burning in the 12C(α,γ) reaction

    NASA Astrophysics Data System (ADS)

    Gai, Moshe

    2013-12-01

    The rate of oxygen formation determines the C/O ratio during stellar helium burning. It is the single most important nuclear input in stellar evolution theory, including the evolution of type II and type Ia supernova. However, the low-energy cross section of the fusion of 4He +12C, denoted as the 12C(α,γ)16O reaction, still remains uncertain. I analyze and critically review the most recent measurements of complete angular distributions of the outgoing γ rays at very low energies (Ec.m.≥1.0 MeV). My analysis of the angular distributions measured with the EUROGAM/GANDI arrays leads to considerably larger error bars than have been published, which excludes them from the current sample of “world data.” I show that the current sample of “world data” of the measured E2 cross-section factors below 1.7 MeV cluster into two distinct groups that lead to two distinct extrapolations: SE2(300)≈60 or SE2(300)≈154 keVb. There is a discrepancy between the measured E1-E2 phase difference (ϕ12) and unitarity as required by the Watson theorem, which suggests systematic problem(s) in some of the measured γ-ray angular distributions. The ambiguity of the extrapolated SE2(300) together with the previously observed ambiguity of SE1(300) (approximately 80 or 10 keVb) must be resolved by future measurements of complete and detailed angular distributions of the 12C(α,γ) reaction at very low energies (Ec.m.≤1.0 MeV).

  1. The formation of eccentric compact binary inspirals and the role of gravitational wave emission in binary-single stellar encounters

    SciTech Connect

    Samsing, Johan; MacLeod, Morgan; Ramirez-Ruiz, Enrico

    2014-03-20

    The inspiral and merger of eccentric binaries leads to gravitational waveforms distinct from those generated by circularly merging binaries. Dynamical environments can assemble binaries with high eccentricity and peak frequencies within the LIGO band. In this paper, we study binary-single stellar scatterings occurring in dense stellar systems as a source of eccentrically inspiraling binaries. Many interactions between compact binaries and single objects are characterized by chaotic resonances in which the binary-single system undergoes many exchanges before reaching a final state. During these chaotic resonances, a pair of objects has a non-negligible probability of experiencing a very close passage. Significant orbital energy and angular momentum are carried away from the system by gravitational wave (GW) radiation in these close passages, and in some cases this implies an inspiral time shorter than the orbital period of the bound third body. We derive the cross section for such dynamical inspiral outcomes through analytical arguments and through numerical scattering experiments including GW losses. We show that the cross section for dynamical inspirals grows with increasing target binary semi-major axis a and that for equal-mass binaries it scales as a {sup 2/7}. Thus, we expect wide target binaries to predominantly contribute to the production of these relativistic outcomes. We estimate that eccentric inspirals account for approximately 1% of dynamically assembled non-eccentric merging binaries. While these events are rare, we show that binary-single scatterings are a more effective formation channel than single-single captures for the production of eccentrically inspiraling binaries, even given modest binary fractions.

  2. A compact dc cusp source

    SciTech Connect

    Yuan, D.H.; McDonald, M.; Schmor, P.W. ); Jayamanna, K. )

    1990-08-05

    This paper presents the results of an experimental investigation of the parameters effecting the quality of the {ital H}{sup {minus}} beam extracted from a small source employing multicusp confinement and the magnetic filter to enhance the {ital H}{sup {minus}} production. The source was designed to operate the d.c. mode, to have a long filament lifetime and to provide an intense {ital H}{sup {minus}} beam with low emittance. The {ital H}{sup {minus}} beam is initially transported about 2 m at 25 keV with a measured 95% space charge neutralization. The experimental results indicate that the small cusp source is {similar to}4 times brighter than the large one for arc current less than 25 A. A 7 mA {ital H}{sup {minus}} beam with a normalized emittance of 0.34 {pi}mm.mrad at an arc current of 27 A and the voltage of 127 V is obtained.

  3. PLANET FORMATION IN STELLAR BINARIES. II. OVERCOMING THE FRAGMENTATION BARRIER IN α CENTAURI AND γ CEPHEI-LIKE SYSTEMS

    SciTech Connect

    Rafikov, Roman R.; Silsbee, Kedron

    2015-01-10

    Planet formation in small-separation (∼20 AU) eccentric binaries such as γ Cephei or α Centauri is believed to be adversely affected by the presence of the stellar companion. Strong dynamical excitation of planetesimals by the eccentric companion can result in collisional destruction (rather than growth) of 1-100 km objects, giving rise to the ''fragmentation barrier'' for planet formation. We revise this issue using a novel description of secular dynamics of planetesimals in binaries, which accounts for the gravity of the eccentric, coplanar protoplanetary disk, as well as gas drag. By studying planetesimal collision outcomes, we show, in contrast to many previous studies, that planetesimal growth and subsequent formation of planets (including gas giants) in AU-scale orbits within ∼20 AU separation binaries may be possible, provided that the protoplanetary disks are massive (≳ 10{sup –2} M {sub ☉}) and only weakly eccentric (disk eccentricity ≲ 0.01). These requirements are compatible with both the existence of massive (several M{sub J} ) planets in γ Cep-like systems and the results of recent simulations of gaseous disks in eccentric binaries. Terrestrial and Neptune-like planets can also form in lower-mass disks at small (sub-AU) radii. We find that the fragmentation barrier is less of a problem in eccentric disks that are apsidally aligned with the binary orbit. Alignment gives rise to special locations, where (1) relative planetesimal velocities are low and (2) the timescale of their drag-induced radial drift is long. This causes planetesimal pileup at such locations in the disk and promotes their growth locally, helping to alleviate the timescale problem for core formation.

  4. On the formation of compact, massive subsystems in stellar clusters and its relation with intermediate-mass black holes

    NASA Astrophysics Data System (ADS)

    Arca-Sedda, M.

    2016-01-01

    During their evolution, star clusters undergo mass segregation, by which the orbits of the most massive stars shrink, while the lighter stars move outwards from the cluster centre. In this context, recent observations and dynamical modelling of several galactic and extragalactic globular clusters (GCs) suggest that most of them show, close to their centre, an overabundance of mass whose nature is still matter of debate. For instance, many works show that orbitally segregated stars may collide with each other in a runaway fashion, leading to the formation of a very massive star or an intermediate-mass black hole (IMBH) with a mass comparable to the observed mass excess. On the other hand, segregated stars can form a dense system if the IMBH formation fails. In this paper we study the early formation phase of a dense, massive subsystem (MSS) in several GCs models using a recently developed semi-analytical treatment of the mass segregation process. In order to investigate how the MSS properties depend on the host cluster properties, we varied initial mass function (IMF), total mass, spatial distribution and metallicity of our models. Our results show how the IMF contributes to determine the final mass of the MSS, while the metallicity and the spatial distribution play a minor role. The method presented in this paper allowed us to provide scaling relations that connect the MSS mass and the host cluster mass in agreement with the observed correlation. In order to follow the early formation stage of the MSSs and improve our statistical results, we performed several N-body simulations of stellar clusters with masses between 103 and 2 × 105 M⊙.

  5. The SAMI Galaxy Survey: asymmetry in gas kinematics and its links to stellar mass and star formation

    NASA Astrophysics Data System (ADS)

    Bloom, J. V.; Fogarty, L. M. R.; Croom, S. M.; Schaefer, A.; Bryant, J. J.; Cortese, L.; Richards, S.; Bland-Hawthorn, J.; Ho, I.-T.; Scott, N.; Goldstein, G.; Medling, A.; Brough, S.; Sweet, S. M.; Cecil, G.; López-Sánchez, A.; Glazebrook, K.; Parker, Q.; Allen, J. T.; Goodwin, M.; Green, A. W.; Konstantopoulos, I. S.; Lawrence, J. S.; Lorente, N.; Owers, M. S.; Sharp, R.

    2017-02-01

    We study the properties of kinematically disturbed galaxies in the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey using a quantitative criterion, based on kinemetry (Krajnović et al.). The approach, similar to the application of kinemetry by Shapiro et al., uses ionized gas kinematics, probed by H α emission. By this method, 23 ± 7 per cent of our 360-galaxy sub-sample of the SAMI Galaxy Survey are kinematically asymmetric. Visual classifications agree with our kinemetric results for 90 per cent of asymmetric and 95 per cent of normal galaxies. We find that stellar mass and kinematic asymmetry are inversely correlated and that kinematic asymmetry is both more frequent and stronger in low-mass galaxies. This builds on previous studies that found high fractions of kinematic asymmetry in low-mass galaxies using a variety of different methods. Concentration of star formation and kinematic disturbance are found to be correlated, confirming results found in previous work. This effect is stronger for high-mass galaxies (log(M*) > 10) and indicates that kinematic disturbance is linked to centrally concentrated star formation. Comparison of the inner (within 0.5Re) and outer H α equivalent widths of asymmetric and normal galaxies shows a small but significant increase in inner equivalent width for asymmetric galaxies.

  6. New open-source approaches to the modeling of stellar collapse and the formation of black holes

    NASA Astrophysics Data System (ADS)

    Ott, C. D.; O'Connor, E.; Peng, F.; Reisswig, C.; Sperhake, U.; Schnetter, E.; Abdikamalov, E.; Diener, P.; Löffler, F.; Hawke, I.; Meakin, C. A.; Burrows, A.

    2011-11-01

    We present new approaches to the simulation of stellar collapse, the formation of black holes, and explosive core-collapse supernova nucleosynthesis that build upon open-source codes and microphysics. We discuss the new spherically-symmetric general-relativistic (GR) collapse code GR1D that is endowed with an approximate 1.5D treatment of rotation, comes with multiple nuclear equations of state, and handles neutrinos with a multi-species leakage scheme. Results from a first set of spinning black hole formation simulations are presented. We go on to discuss the derivative code GR1D+ N which is tuned for calculations of explosive nucleosynthesis and includes a NSE/non-NSE equation of state treatment, and a nuclear reaction network. We present sample results showing GR1D+ N's performance in reproducing previous results with thermal-bomb-driven explosions. Finally, we introduce the 3 + 1 GR Zelmani core collapse simulation package and present first results obtained in its application to the 3D modeling of failing core-collapse supernovae.

  7. FORMATION OF COMPACT STELLAR CLUSTERS BY HIGH-REDSHIFT GALAXY OUTFLOWS. II. EFFECT OF TURBULENCE AND METAL-LINE COOLING

    SciTech Connect

    Gray, William J.; Scannapieco, Evan

    2011-06-01

    In the primordial universe, low-mass structures with virial temperatures less than 10{sup 4} K were unable to cool by atomic line transitions, leading to a strong suppression of star formation. On the other hand, these 'minihalos' were highly prone to triggered star formation by interactions from nearby galaxy outflows. In Gray and Scannapieco, we explored the impact of nonequilibrium chemistry on these interactions. Here we turn our attention to the role of metals, carrying out a series of high-resolution three-dimensional adaptive mesh refinement simulations that include both metal cooling and a subgrid turbulent mixing model. Despite the presence of an additional coolant, we again find that outflow-minihalo interactions produce a distribution of dense, massive stellar clusters. We also find that these clusters are evenly enriched with metals to a final abundance of Z {approx} 10{sup -2} Z{sub sun}. As in our previous simulations, all of these properties suggest that these interactions may have given rise to present-day halo globular clusters.

  8. Kiloparsec-scale Simulations of Star Formation in Disk Galaxies. IV. Regulation of Galactic Star Formation Rates by Stellar Feedback

    NASA Astrophysics Data System (ADS)

    Butler, Michael J.; Tan, Jonathan C.; Teyssier, Romain; Rosdahl, Joakim; Van Loo, Sven; Nickerson, Sarah

    2017-06-01

    Star formation from the interstellar medium of galactic disks is a basic process controlling the evolution of galaxies. Understanding the star formation rate (SFR) in a local patch of a disk with a given gas mass is thus an important challenge for theoretical models. Here we simulate a kiloparsec region of a disk, following the evolution of self-gravitating molecular clouds down to subparsec scales, as they form stars that then inject feedback energy by dissociating and ionizing UV photons and supernova explosions. We assess the relative importance of each feedback mechanism. We find that H2-dissociating feedback results in the largest absolute reduction in star formation compared to the run with no feedback. Subsequently adding photoionization feedback produces a more modest reduction. Our fiducial models that combine all three feedback mechanisms yield, without fine-tuning, SFRs that are in excellent agreement with observations, with H2-dissociating photons playing a crucial role. Models that only include supernova feedback—a common method in galaxy evolution simulations—settle to similar SFRs, but with very different temperatures and chemical states of the gas, and with very different spatial distributions of young stars.

  9. Solar wind controls on Mercury's magnetospheric cusp

    NASA Astrophysics Data System (ADS)

    He, Maosheng; Vogt, Joachim; Heyner, Daniel; Zhong, Jun

    2017-06-01

    This study assesses the response of the cusp to solar wind changes comprehensively, using 2848 orbits of MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) observation. The assessment entails four steps: (1) propose and validate an approach to estimate the solar wind magnetic field (interplanetary magnetic field (IMF)) for MESSENGER's cusp transit; (2) define an index σ measuring the intensity of the magnetic disturbance which significantly peaks within the cusp and serves as an indicator of the cusp activity level; (3) construct an empirical model of σ as a function of IMF and Mercury's heliocentric distance rsun, through linear regression; and (4) use the model to estimate and compare the polar distribution of the disturbance σ under different conditions for a systematic comparison. The comparison illustrates that the disturbance peak over the cusp is strongest and widest extending in local time for negative IMF Bx and negative IMF Bz, and when Mercury is around the perihelion. Azimuthal shifts are associated with both IMF By and rsun: the cusp moves toward dawn when IMF By or rsun decrease. These dependences are explained in terms of the IMF Bx-controlled dayside magnetospheric topology, the component reconnection model applied to IMF By and Bz, and the variability of solar wind ram pressure associated with heliocentric distance rsun. The applicability of the component reconnection model on IMF By indicates that at Mercury reconnection occurs at lower shear angles than at Earth.Plain Language SummaryMercury's magnetosphere was suggested to be particularly sensitive to solar wind conditions. This study investigates the response of the magnetospheric <span class="hlt">cusp</span> to solar wind conditions systematically. For this purpose, we analyze the statistical predictability of interplanetary magnetic field (IMF) at Mercury, develop an approach for estimating the solar wind magnetic field (IMF) for MErcury Surface</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000040062&hterms=fi&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dfi','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000040062&hterms=fi&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dfi"><span><span class="hlt">CUSP</span> Energetic Particles: Confinement, Acceleration and Implications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chen, Jiasheng</p> <p>1999-01-01</p> <p>The <span class="hlt">cusp</span> energetic particle (CEP) event is a new magnetospheric phenomenon. The events were detected in the dayside <span class="hlt">cusp</span> for hours, in which the measured helium ions had energies up to 8 MeV. All of these events were associated with a dramatic decrease and large fluctuations in the local magnetic field strength. During January 1999 - December 1999 covered by this report, I have studied the CEP events by analyzing the POLAR, GEOTAIL, and WIND particle and magnetic field data measured during the geomagnetic quiet periods in 1996 and one geomagnetic storm period in 1998. The simultaneous observations indicated that the ion fluxes in the CEP events were higher than that in both the upstream and the downstream from the bow shock. The pitch angle distribution of the helium ions in the CEP events was found to peak around 90 deg. It was found that the mirror parameter, defined as the ratio of the square root of the integration of the parallel turbulent power spectral component over the ultra-low frequency (ULF) ranges to the mean field in the <span class="hlt">cusp</span>, is correlated with the intensity of the <span class="hlt">cusp</span> MeV helium flux, which is a measure of the influence of mirroring interactions and an indication of local effect. It was also found that the turbulent power of the local magnetic field in the ultra-low frequency (ULF) ranges is correlated with the intensity of the <span class="hlt">cusp</span> energetic helium ions. Such ULF ranges correspond to periods of about 0.33-500 seconds that cover the gyroperiods, the bounce periods, and the drift periods of the tens keV to MeV charged particles when they are temporarily confined in the high-altitude dayside <span class="hlt">cusp</span>. These observations represent a discovery that the high-altitude dayside <span class="hlt">cusp</span> is a new acceleration and dynamic trapping region of the magnetosphere. The <span class="hlt">cusp</span> geometry is connected via gradient and curvature drift of these energized ions to the equatorial plasma sheet as close as the geostationary orbit at local midnight. It implies that the dayside <span class="hlt">cusp</span> is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000040062&hterms=acceleration+physics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dacceleration%2Bphysics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000040062&hterms=acceleration+physics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dacceleration%2Bphysics"><span><span class="hlt">CUSP</span> Energetic Particles: Confinement, Acceleration and Implications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chen, Jiasheng</p> <p>1999-01-01</p> <p>The <span class="hlt">cusp</span> energetic particle (CEP) event is a new magnetospheric phenomenon. The events were detected in the dayside <span class="hlt">cusp</span> for hours, in which the measured helium ions had energies up to 8 MeV. All of these events were associated with a dramatic decrease and large fluctuations in the local magnetic field strength. During January 1999 - December 1999 covered by this report, I have studied the CEP events by analyzing the POLAR, GEOTAIL, and WIND particle and magnetic field data measured during the geomagnetic quiet periods in 1996 and one geomagnetic storm period in 1998. The simultaneous observations indicated that the ion fluxes in the CEP events were higher than that in both the upstream and the downstream from the bow shock. The pitch angle distribution of the helium ions in the CEP events was found to peak around 90 deg. It was found that the mirror parameter, defined as the ratio of the square root of the integration of the parallel turbulent power spectral component over the ultra-low frequency (ULF) ranges to the mean field in the <span class="hlt">cusp</span>, is correlated with the intensity of the <span class="hlt">cusp</span> MeV helium flux, which is a measure of the influence of mirroring interactions and an indication of local effect. It was also found that the turbulent power of the local magnetic field in the ultra-low frequency (ULF) ranges is correlated with the intensity of the <span class="hlt">cusp</span> energetic helium ions. Such ULF ranges correspond to periods of about 0.33-500 seconds that cover the gyroperiods, the bounce periods, and the drift periods of the tens keV to MeV charged particles when they are temporarily confined in the high-altitude dayside <span class="hlt">cusp</span>. These observations represent a discovery that the high-altitude dayside <span class="hlt">cusp</span> is a new acceleration and dynamic trapping region of the magnetosphere. The <span class="hlt">cusp</span> geometry is connected via gradient and curvature drift of these energized ions to the equatorial plasma sheet as close as the geostationary orbit at local midnight. It implies that the dayside <span class="hlt">cusp</span> is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870024312&hterms=Noriega&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DNoriega','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870024312&hterms=Noriega&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DNoriega"><span>On star <span class="hlt">formation</span> in <span class="hlt">stellar</span> systems. I - Photoionization effects in protoglobular clusters</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tenorio-Tagle, G.; Bodenheimer, P.; Lin, D. N. C.; Noriega-Crespo, A.</p> <p>1986-01-01</p> <p>The progressive ionization and subsequent dynamical evolution of nonhomogeneously distributed low-metal-abundance diffuse gas after star <span class="hlt">formation</span> in globular clusters are investigated analytically, taking the gravitational acceleration due to the stars into account. The basic equations are derived; the underlying assumptions, input parameters, and solution methods are explained; and numerical results for three standard cases (ionization during star <span class="hlt">formation</span>, ionization during expansion, and evolution resulting in a stable H II region at its equilibrium Stromgren radius) are presented in graphs and characterized in detail. The time scale of residual-gas loss in typical clusters is found to be about the same as the lifetime of a massive star on the main sequence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25355359','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25355359"><span>Possible planet <span class="hlt">formation</span> in the young, low-mass, multiple <span class="hlt">stellar</span> system GG Tau A.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dutrey, Anne; Di Folco, Emmanuel; Guilloteau, Stéphane; Boehler, Yann; Bary, Jeff; Beck, Tracy; Beust, Hervé; Chapillon, Edwige; Gueth, Fredéric; Huré, Jean-Marc; Pierens, Arnaud; Piétu, Vincent; Simon, Michal; Tang, Ya-Wen</p> <p>2014-10-30</p> <p>The <span class="hlt">formation</span> of planets around binary stars may be more difficult than around single stars. In a close binary star (with a separation of less than a hundred astronomical units), theory predicts the presence of circumstellar disks around each star, and an outer circumbinary disk surrounding a gravitationally cleared inner cavity around the stars. Given that the inner disks are depleted by accretion onto the stars on timescales of a few thousand years, any replenishing material must be transferred from the outer reservoir to fuel planet <span class="hlt">formation</span> (which occurs on timescales of about one million years). Gas flowing through disk cavities has been detected in single star systems. A circumbinary disk was discovered around the young low-mass binary system GG Tau A (ref. 7), which has recently been shown to be a hierarchical triple system. It has one large inner disk around the single star, GG Tau Aa, and shows small amounts of shocked hydrogen gas residing within the central cavity, but other than a single weak detection, the distribution of cold gas in this cavity or in any other binary or multiple star system has not hitherto been determined. Here we report imaging of gas fragments emitting radiation characteristic of carbon monoxide within the GG Tau A cavity. From the kinematics we conclude that the flow appears capable of sustaining the inner disk (around GG Tau Aa) beyond the accretion lifetime, leaving time for planet <span class="hlt">formation</span> to occur there. These results show the complexity of planet <span class="hlt">formation</span> around multiple stars and confirm the general picture predicted by numerical simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AAS...22934615F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AAS...22934615F"><span>Star <span class="hlt">formation</span> quenching and <span class="hlt">stellar</span> mass in the cluster Abell 85</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fadda, Dario; Habas, Rebecca; Marleau, Francine; Biviano, Andrea; Durret, Florence</p> <p>2017-01-01</p> <p>We report the discovery of a group of galaxies falling into the cluster Abell 85 showing a decrease in star <span class="hlt">formation</span> limited to its dwarf galaxy population. We covered the cluster and its surroundings with a multi-wavelength survey from the UV to the far-IR using ground and space telescopes (including GALEX, Spitzer, and Herschel) and followed-up these observations with spectroscopic surveys with the WIYN/Hydra and VLT/VIMOS instruments. We were able to obtain spectra for 522 members down to r'=20, 30% of them showing H-alpha emission. We estimated the variation in star <span class="hlt">formation</span> rate by using two different estimators based on continuum (UV) and line (H-alpha) emission. While massive infalling galaxies continue to produce stars during the infall, the star <span class="hlt">formation</span> in dwarf galaxies appear to be quenched by the cluster environment. Considering the different time-scales of the two estimators, we can estimate that the quenching happens in a period of approximately 10 Myr.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22121788','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22121788"><span>GAS REGULATION OF GALAXIES: THE EVOLUTION OF THE COSMIC SPECIFIC STAR <span class="hlt">FORMATION</span> RATE, THE METALLICITY-MASS-STAR-<span class="hlt">FORMATION</span> RATE RELATION, AND THE <span class="hlt">STELLAR</span> CONTENT OF HALOS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lilly, Simon J.; Carollo, C. Marcella; Pipino, Antonio; Peng Yingjie; Renzini, Alvio</p> <p>2013-08-01</p> <p>A very simple physical model of galaxies is one in which the <span class="hlt">formation</span> of stars is instantaneously regulated by the mass of gas in a reservoir with mass loss scaling with the star-<span class="hlt">formation</span> rate (SFR). This model links together three different aspects of the evolving galaxy population: (1) the cosmic time evolution of the specific star-<span class="hlt">formation</span> rate (sSFR) relative to the growth of halos, (2) the gas-phase metallicities across the galaxy population and over cosmic time, and (3) the ratio of the <span class="hlt">stellar</span> to dark matter mass of halos. The gas regulator is defined by the gas consumption timescale ({epsilon}{sup -1}) and the mass loading {lambda} of the wind outflow {lambda}{center_dot}SFR. The simplest regulator, in which {epsilon} and {lambda} are constant, sets the sSFR equal to exactly the specific accretion rate of the galaxy; more realistic situations lead to an sSFR that is perturbed from this precise relation. Because the gas consumption timescale is shorter than the timescale on which the system evolves, the metallicity Z is set primarily by the instantaneous operation of the regulator system rather than by the past history of the system. The metallicity of the gas reservoir depends on {epsilon}, {lambda}, and sSFR, and the regulator system therefore naturally produces a Z(m{sub star}, SFR) relation if {epsilon} and {lambda} depend on the <span class="hlt">stellar</span> mass m{sub star}. Furthermore, this relation will be the same at all epochs unless the parameters {epsilon} and {lambda} themselves change with time. A so-called fundamental metallicity relation is naturally produced by these conditions. The overall mass-metallicity relation Z(m{sub star}) directly provides the fraction f{sub star}(m{sub star}) of incoming baryons that are being transformed into stars. The observed Z(m{sub star}) relation of Sloan Digital Sky Survey (SDSS) galaxies implies a strong dependence of <span class="hlt">stellar</span> mass on halo mass that reconciles the different faint-end slopes of the <span class="hlt">stellar</span> and halo mass</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22370426','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22370426"><span>On the distribution of <span class="hlt">stellar</span> remnants around massive black holes: slow mass segregation, star cluster inspirals, and correlated orbits</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Antonini, Fabio</p> <p>2014-10-20</p> <p>We use N-body simulations as well as analytical techniques to study the long-term dynamical evolution of <span class="hlt">stellar</span> black holes (BHs) at the Galactic center (GC) and to put constraints on their number and mass distribution. Starting from models that have not yet achieved a state of collisional equilibrium, we find that timescales associated with <span class="hlt">cusp</span> regrowth can be longer than the Hubble time. Our results cast doubts on standard models that postulate high densities of BHs near the GC and motivate studies that start from initial conditions that correspond to well-defined physical models. For the first time, we consider the distribution of BHs in a dissipationless model for the <span class="hlt">formation</span> of the Milky Way nuclear cluster (NC), in which massive <span class="hlt">stellar</span> clusters merge to form a compact nucleus. We simulate the consecutive merger of ∼10 clusters containing an inner dense sub-cluster of BHs. After the formed NC is evolved for ∼5 Gyr, the BHs do form a steep central <span class="hlt">cusp</span>, while the <span class="hlt">stellar</span> distribution maintains properties that resemble those of the GC NC. Finally, we investigate the effect of BH perturbations on the motion of the GC S-stars as a means of constraining the number of the perturbers. We find that reproducing the quasi-thermal character of the S-star orbital eccentricities requires ≳ 1000 BHs within 0.1 pc of Sgr A*. A dissipationless <span class="hlt">formation</span> scenario for the GC NC is consistent with this lower limit and therefore could reconcile the need for high central densities of BHs (to explain the S-stars orbits) with the 'missing-<span class="hlt">cusp</span>' problem of the GC giant star population.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.442L..51L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.442L..51L"><span>A high-precision chemical abundance analysis of the HAT-P-1 <span class="hlt">stellar</span> binary: constraints on planet <span class="hlt">formation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, F.; Asplund, M.; Ramírez, I.; Yong, D.; Meléndez, J.</p> <p>2014-07-01</p> <p>We present a high-precision, differential elemental abundance analysis of the HAT-P-1 <span class="hlt">stellar</span> binary based on high-resolution, high signal-to-noise ratio Keck/HIRES (High Resolution Echelle Spectrometer) spectra. The secondary star in this double system is known to host a transiting giant planet while no planets have yet been detected around the primary star. The derived metallicities ([Fe/H]) of the primary and secondary stars are identical within the errors: 0.146 ± 0.014 dex (σ = 0.033 dex) and 0.155 ± 0.007 dex (σ = 0.023 dex), respectively. Extremely precise differential abundance ratios of 23 elements have been measured (mean error of σ([X/Fe]) = 0.013 dex) and are found to be indistinguishable between the two stars: Δ[X/Fe] (secondary - primary) = +0.001 ± 0.006 dex (σ = 0.008 dex). The striking similarity in the chemical composition of the two <span class="hlt">stellar</span> components in HAT-P-1 is contrary to the possible 0.04 dex level difference seen in 16 Cyg A+B, which also hosts a giant planet, at least three times more massive than the one around HAT-P-1 secondary star. We conclude that the presence of giant planets does not necessarily imply differences in the chemical compositions of the host stars. The elemental abundances of each star in HAT-P-1 relative to the Sun show an identical, positive correlation with the condensation temperature of the elements; their abundance patterns are thus very similar to those observed in the majority of solar twins. In view of the Meléndez et al. interpretation of the peculiar solar abundance pattern, we conclude that HAT-P-1 experienced less efficient <span class="hlt">formation</span> of terrestrial planets than the Sun. This is in line with the expectation that the presence of close-in giant planets preventing the <span class="hlt">formation</span> or survival of terrestrial planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...830....3S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...830....3S"><span><span class="hlt">Stellar</span> Populations and Star <span class="hlt">Formation</span> History of the Metal-poor Dwarf Galaxy DDO 68</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sacchi, E.; Annibali, F.; Cignoni, M.; Aloisi, A.; Sohn, T.; Tosi, M.; van der Marel, R. P.; Grocholski, A. J.; James, B.</p> <p>2016-10-01</p> <p>We present the star <span class="hlt">formation</span> history (SFH) of the extremely metal-poor dwarf galaxy DDO 68, based on our photometry with the Advanced Camera for Surveys. With a metallicity of only 12+{log}({{O}}/{{H}})=7.15 and a very isolated location, DDO 68 is one of the most metal-poor galaxies known. It has been argued that DDO 68 is a young system that started forming stars only ˜0.15 Gyr ago. Our data provide a deep and uncontaminated optical color-magnitude diagram (CMD) that allows us to disprove this hypothesis since we find a population of at least ˜1 Gyr old stars. The star <span class="hlt">formation</span> activity has been fairly continuous over all the look-back time. The current rate is quite low, and the highest activity occurred between 10 and 100 Myr ago. The average star <span class="hlt">formation</span> rate over the whole Hubble time is ≃0.01 M ⊙ yr-1, corresponding to a total astrated mass of ≃1.3 × 108 M ⊙. Our photometry allows us to infer the distance from the tip of the red giant branch, D = 12.08 ± 0.67 Mpc; however, to let our synthetic CMD reproduce the observed ones, we need a slightly higher distance, D = 12.65 Mpc, or (m - M)0 = 30.51, still inside the errors of the previous determination, and we adopt the latter. DDO 68 shows a very interesting and complex history, with its quite disturbed shape and a long tail, probably due to tidal interactions. The SFH of the tail differs from that of the main body mainly for enhanced activity at recent epochs likely triggered by the interaction. Based on observations obtained with the NASA/ESA Hubble Space Telescope at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA Contract NAS5-26555.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMEP23A0947O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMEP23A0947O"><span>Observations of beach <span class="hlt">cusp</span> evolution using a stationary, shore-based lidar system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Dea, A.; Whitesides, E. T.; Brodie, K.; Spore, N.</p> <p>2016-12-01</p> <p>Although beach <span class="hlt">cusps</span> are common features on beaches around the world, questions still remain regarding the range of conditions in which they form, the initial forcing conditions under which they form, and the erosive or accretionary nature of <span class="hlt">cusp</span> events. While many prior studies have focused on the <span class="hlt">formation</span> and morphology of beach <span class="hlt">cusps</span>, many of these are limited in the spatial extent of observations, in their spatial or temporal resolution, or in the availability of accompanying hydrodynamic data. In this study, beach <span class="hlt">cusp</span> <span class="hlt">formation</span> and evolution is investigated using an automated lidar system that provides hourly three-dimensional scans of subaerial beach topography with high spatial resolution ([O(1 cm)]). The stationary lidar scanner is mounted on a 4-m tower located on the crest of a shore-backing dune on an Atlantic Ocean beach near Duck, North Carolina. The device measures a 237°-framescan of the nearshore region over a 15 minute period each hour. Individual scans are coregistered to a baseline scan using an iterative closest point (ICP) algorithm and then filtered to remove noise, dune vegetation, and water. To assess the accuracy of the coregistration algorithm, the 3-dimensional location of five permanent reflectors near the device are found for each scan and compared to their measured GPS location. Precisely coregistered scans allow for an assessment of elevation change across cuspate features in addition to traditional measurements of <span class="hlt">cusp</span> wavelength. Beach <span class="hlt">cusp</span> events are assessed over a three month period from September through November 2015. Wave and current data from a cross-shore array of sensors deployed continuously throughout the three month period as well as from two alongshore arrays of ADV sensors deployed from October 13 through November 1 are used to determine the forcing conditions under which the <span class="hlt">cusps</span> formed and evolved. Funded by the USACE Coastal Field Data Collection Program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011MNRAS.416.1284G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011MNRAS.416.1284G"><span>Shock <span class="hlt">formation</span> in <span class="hlt">stellar</span> perturbations and tidal shock waves in binaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gundlach, Carsten; Murphy, Jeremiah W.</p> <p>2011-09-01</p> <p>We investigate whether tidal forcing can result in sound waves steepening into shocks at the surface of a star. To model the sound waves and shocks, we consider adiabatic non-spherical perturbations of a Newtonian perfect fluid star. Because tidal forcing of sound waves is naturally treated with linear theory, but the <span class="hlt">formation</span> of shocks is necessarily non-linear, we consider the perturbations in two regimes. In most of the interior, where tidal forcing dominates, we treat the perturbations as linear, while in a thin layer near the surface we treat them in full non-linearity but in the approximation of plane symmetry, fixed gravitational field and a barotropic equation of state. Using a hodograph transformation, this non-linear regime is also described by a linear equation. We show that the two regimes can be matched to give rise to a single-mode equation which is linear but models non-linearity in the outer layers. This can then be used to obtain an estimate for the critical mode amplitude at which a shock forms near the surface. As an application, we consider the tidal waves raised by the companion in an irrotational binary system in circular orbit. We find that shocks form at the same orbital separation where Roche lobe overflow occurs, and so shock <span class="hlt">formation</span> is unlikely to occur.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MNRAS.465.2198D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MNRAS.465.2198D"><span>Wide- and contact-binary <span class="hlt">formation</span> in substructured young <span class="hlt">stellar</span> clusters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dorval, J.; Boily, C. M.; Moraux, E.; Roos, O.</p> <p>2017-02-01</p> <p>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 <span class="hlt">formation</span> 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 <span class="hlt">formation</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9699439','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9699439"><span><span class="hlt">Cusp</span> reinforcement by bonding of amalgam restorations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pilo, R; Brosh, T; Chweidan, H</p> <p>1998-01-01</p> <p>The purpose of the present study was to assess the effectivenes of several adhesives in bonding amalgam in order to recover tooth stiffness. A non-destructive experimental methodology was adopted, using strain gauges bonded to the midbuccal surfaces of 40 teeth, with sequential evaluation of loaded intact, prepared and restored stages of the same tooth. Continuous strain measurement as a function of the applied load was acquired by A/D equipment and a data acquisition programme. The strain-force behaviour of the sound teeth under non-axial force up to 97.5 N served as the baseline. The five experimental groups (8 x 5) consisted of control (no adhesive) and four different adhesives. One-way analysis of variance with repeated measures was calculated for the deformation ratio, relative stiffness and recovery values. Reductions in tooth structure by cutting a mesio-occlusal-distal preparation, width one-third intercuspal distance, resulted in 39-52% loss of buccal <span class="hlt">cusp</span> stiffness. Non-bonded amalgam produced negligible increase (5%) in the stiffness recovery values of the buccal <span class="hlt">cusps</span>. The adhesives splinted the <span class="hlt">cusps</span> together, thereby decreasing cuspal flexure and increasing relative stiffness values. Recovery values obtained ranged from 39% to 61%. Assuming that <span class="hlt">cusp</span> fracture occurs as a result of brittle tooth structure fatigue, amalgam adhesives may contribute to the strengthening of weakened <span class="hlt">cusps</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5265674','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5265674"><span>Hemispherical asymmetry in <span class="hlt">cusp</span> precipitation near solstices</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Newell, P.T.; Meng, C.</p> <p>1988-04-01</p> <p>A statistical comparison of the peak flux in electron and ion polar <span class="hlt">cusp</span> precipitation in the summer and winter hemispheres as observed by the low-altitude DMSP F7 satellite is performed. Data studied encompass four consecutive solstices from December 1983 to June 1985, comprising 77 days of data with a total of 292 individual <span class="hlt">cusp</span> passes. On each day, observations were restricted to those few hours UT in which the interhemispherical MLT variation of DMSP F7 was smallest. After the remaining local time effect was averaged out, the summer hemisphere ion (electron) precipitating energy flux was larger, on the average, by 61 +- 11% (51 +- 5%) than that in the winter hemisphere. However, the average particle energy was always lower for both species in the summer hemisphere. These effects generally hold true for northward as well as southward interplanetary magnetic fields (IMF). It is argued that the observed asymmetry is very hard to explain if the most intense part of the <span class="hlt">cusp</span> lies on closed field lines, but it is shown that the standard open field line model of the <span class="hlt">cusp</span> virtually requires the observed differences to occur. The present results thus suggest that the most intense portion of the <span class="hlt">cusp</span> lies on open field lines even for northward IMF. copyright American Geophysical Union 1988</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920046816&hterms=star+classification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dstar%2Bclassification','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920046816&hterms=star+classification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dstar%2Bclassification"><span>The <span class="hlt">stellar</span> content of LH 9 and 10 (N11) in the LMC - A case for sequential star <span class="hlt">formation</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parker, Joel WM.; Garmany, Catharine D.; Massey, Philip; Walborn, Nolan R.</p> <p>1992-01-01</p> <p>The young OB associations Lucke-Hodge 9 and 10 are studied with UBV photometry that is independent of reddening to determine the IMF directly from star counts. The temperature and reddening of the stars are determined which, in conjunction with the spectroscopic classification of the earliest stars, is employed to place the <span class="hlt">stellar</span> groups on the theoretical H-R diagram. Observations are also presented of the highly compact H II region/knot N11A and the multiple system HD 32228, and LH 9 and 10 are compared. The Lyman ionizing flux calculated at 4.9-7.2 x 10 exp 50/s agrees well with flux required to generate the H-alpha luminosity of the H II region. LH 10 has a much flatter slope, a higher ratio of higher-mass to lower-mass stars, and greater reddening than LH 9, and LH 10 contains all of the O stars earlier than O6. It is concluded that LH 9 is older than LH 10 and probably contributed to the initiation of star <span class="hlt">formation</span> in LH 10.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...586A.156K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...586A.156K"><span>Lithium spectral line <span class="hlt">formation</span> in <span class="hlt">stellar</span> atmospheres. The impact of convection and NLTE effects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klevas, J.; Kučinskas, A.; Steffen, M.; Caffau, E.; Ludwig, H.-G.</p> <p>2016-02-01</p> <p>Aims: Because of the complexities involved in treating spectral line <span class="hlt">formation</span> in full 3D and non-local thermodynamic equilibrium (NLTE), different simplified approaches are sometimes used to account for the NLTE effects with 3D hydrodynamical model atmospheres. In certain cases, chemical abundances are derived in 1D NLTE and then corrected for the 3D effects by adding 3D-1D LTE (Local Thermodynamic Equilibrium, LTE) abundance corrections (3D+NLTE approach). Alternatively, average ⟨3D⟩ model atmospheres are sometimes used to substitute for the full 3D hydrodynamical models. Methods: In this work we tested whether the results obtained using these simplified schemes (3D+NLTE, ⟨3D⟩ NLTE) may reproduce those derived using the full 3D NLTE computations. The tests were made using 3D hydrodynamical CO5BOLD model atmospheres of the main sequence (MS), main sequence turn-off (TO), subgiant (SGB), and red giant branch (RGB) stars, all at two metallicities, [ M / H ] = 0.0 and -2.0. Our goal was to investigate the role of 3D and NLTE effects on the <span class="hlt">formation</span> of the 670.8 nm lithium resonance line. This was done by assessing differences in the strengths of synthetic 670.8 nm line profiles, which were computed using 3D/1D NLTE/LTE approaches. Results: Our results show that Li 670.8 nm line strengths obtained using different methodologies differ only slightly in most of the models at solar metallicity studied here. However, the line strengths predicted with the 3D NLTE and 3D+NLTE approaches become significantly different at subsolar metallicities. At [ M / H ] = -2.0, this may lead to (3D NLTE) - (3D+NLTE) differences in the predicted lithium abundance of ~0.46 and ~0.31 dex in the TO and RGB stars respectively. On the other hand, NLTE line strengths computed with the average ⟨3D⟩ and 1D model atmospheres are similar to those obtained with the full 3D NLTE approach for MS, TO, SGB, and RGB stars, at all metallicities; 3D - ⟨3D⟩ and 3D - 1D differences in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22364344','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22364344"><span>THE RELATION BETWEEN STAR <span class="hlt">FORMATION</span> RATE AND <span class="hlt">STELLAR</span> MASS FOR GALAXIES AT 3.5 ≤ z ≤ 6.5 IN CANDELS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Salmon, Brett; Papovich, Casey; Tilvi, Vithal; Finkelstein, Steven L.; Finlator, Kristian; Behroozi, Peter; Lu, Yu; Wechsler, Risa H.; Dahlen, Tomas; Ferguson, Henry C.; Davé, Romeel; Dekel, Avishai; Dickinson, Mark; Giavalisco, Mauro; Long, James; Mobasher, Bahram; Reddy, Naveen; Somerville, Rachel S.</p> <p>2015-02-01</p> <p>Distant star-forming galaxies show a correlation between their star <span class="hlt">formation</span> rates (SFRs) and <span class="hlt">stellar</span> masses, and this has deep implications for galaxy <span class="hlt">formation</span>. Here, we present a study on the evolution of the slope and scatter of the SFR-<span class="hlt">stellar</span> mass relation for galaxies at 3.5 ≤ z ≤ 6.5 using multi-wavelength photometry in GOODS-S from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and Spitzer Extended Deep Survey. We describe an updated, Bayesian spectral-energy distribution fitting method that incorporates effects of nebular line emission, star <span class="hlt">formation</span> histories that are constant or rising with time, and different dust-attenuation prescriptions (starburst and Small Magellanic Cloud). From z = 6.5 to z = 3.5 star-forming galaxies in CANDELS follow a nearly unevolving correlation between <span class="hlt">stellar</span> mass and SFR that follows SFR ∼ M{sub ⋆}{sup a} with a =0.54 ± 0.16 at z ∼ 6 and 0.70 ± 0.21 at z ∼ 4. This evolution requires a star <span class="hlt">formation</span> history that increases with decreasing redshift (on average, the SFRs of individual galaxies rise with time). The observed scatter in the SFR-<span class="hlt">stellar</span> mass relation is tight, σ(log SFR/M {sub ☉} yr{sup –1}) < 0.3-0.4 dex, for galaxies with log M {sub *}/M {sub ☉} > 9 dex. Assuming that the SFR is tied to the net gas inflow rate (SFR ∼ M-dot {sub gas}), then the scatter in the gas inflow rate is also smaller than 0.3–0.4 dex for star-forming galaxies in these <span class="hlt">stellar</span> mass and redshift ranges, at least when averaged over the timescale of star <span class="hlt">formation</span>. We further show that the implied star <span class="hlt">formation</span> history of objects selected on the basis of their co-moving number densities is consistent with the evolution in the SFR-<span class="hlt">stellar</span> mass relation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AAS...21421002S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AAS...21421002S"><span>Young <span class="hlt">Stellar</span> Object Variability at IRAC Wavelengths: Clues to Star and Planet <span class="hlt">Formation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stauffer, John R.</p> <p>2009-05-01</p> <p>Spitzer/IRAC in the warm mission is the only facility, now existing or planned, capable of carrying out an extensive, accurate time series photometric monitoring survey of star-forming regions in the thermal infrared The demonstrated sensitivity and stability of IRAC allows measurement of the relative fluxes of YSO's down to the substellar mass limit to 1-2% accuracy in star-forming regions out to >500 pc. Our exploration science project - YSOVAR - will obtain synoptic data for the Orion Nebula Cluster and 11 very young, populous embedded star-forming cores. Each cluster will be observed at 80 or more epochs spread over 40+ days, with generally two observations per day. These data will allow us to: (a) provide otherwise unobtainable constraints on the structure of the inner disks in Class I and II YSOs - and hence, perhaps, provide clues to the <span class="hlt">formation</span> and migration of planets at young ages; (b) measure the short and long-term stability of hot spots on the surfaces of YSO's of all evolutionary stages; and (c) determine rotational periods for the largest sample to date of Class I YSO's and hence obtain the best measure of the initial angular momentum distribution of young stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22520158','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22520158"><span><span class="hlt">STELLAR</span> POPULATIONS AND THE STAR <span class="hlt">FORMATION</span> HISTORIES OF LSB GALAXIES. V. WFC3 COLOR–MAGNITUDE DIAGRAMS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schombert, James; McGaugh, Stacy E-mail: stacy.mcgaugh@case.edu</p> <p>2015-09-15</p> <p>We present WFC3 observations of three low surface brightness (LSB) galaxies from the Schombert et al. LSB catalog that are within 11 Mpc of the Milky Way. Deep imaging at F336W, F555W, and F814W allow the construction of the V − I color–magnitude diagrams (CMD) to M{sub I} = −2. Overall 1869, 465, and 501 <span class="hlt">stellar</span> sources are identified in the three LSB galaxies F415-3, F608-1, and F750-V1, respectively. The spatial distribution of young blue stars matches the Hα maps from ground-based imaging, indicating that star <span class="hlt">formation</span> in LSB galaxies follows the same style as in other irregular galaxies. Several star complexes are identified, matching regions of higher surface brightness as seen from ground-based imaging. The CMD for each LSB galaxy has a similar morphology to Local Volume (LV) dwarf galaxies (i.e., a blue main sequence, blue and red He burning branches, and asymptotic giant branch (AGB) stars). The LSB CMD’s distinguish themselves from nearby dwarf CMD’s by having a higher proportion of blue main sequence stars and fewer AGB stars than expected from their mean metallicities. Current [Fe/H] values below −0.6 are deduced from the position of the red helium-burning branch (rHeB) stars in the V − I diagram. The distribution of stars on the blue helium-burning branch (bHeB) and rHeB from the U − V and V − I CMD indicate a history of constant star <span class="hlt">formation</span> for the last 100 Myr.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AJ....150...72S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AJ....150...72S"><span><span class="hlt">Stellar</span> Populations and the Star <span class="hlt">Formation</span> Histories of LSB Galaxies. V. WFC3 Color-Magnitude Diagrams</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schombert, James; McGaugh, Stacy</p> <p>2015-09-01</p> <p>We present WFC3 observations of three low surface brightness (LSB) galaxies from the Schombert et al. LSB catalog that are within 11 Mpc of the Milky Way. Deep imaging at F336W, F555W, and F814W allow the construction of the V - I color-magnitude diagrams (CMD) to MI = -2. Overall 1869, 465, and 501 <span class="hlt">stellar</span> sources are identified in the three LSB galaxies F415-3, F608-1, and F750-V1, respectively. The spatial distribution of young blue stars matches the Hα maps from ground-based imaging, indicating that star <span class="hlt">formation</span> in LSB galaxies follows the same style as in other irregular galaxies. Several star complexes are identified, matching regions of higher surface brightness as seen from ground-based imaging. The CMD for each LSB galaxy has a similar morphology to Local Volume (LV) dwarf galaxies (i.e., a blue main sequence, blue and red He burning branches, and asymptotic giant branch (AGB) stars). The LSB CMD’s distinguish themselves from nearby dwarf CMD’s by having a higher proportion of blue main sequence stars and fewer AGB stars than expected from their mean metallicities. Current [Fe/H] values below -0.6 are deduced from the position of the red helium-burning branch (rHeB) stars in the V - I diagram. The distribution of stars on the blue helium-burning branch (bHeB) and rHeB from the U - V and V - I CMD indicate a history of constant star <span class="hlt">formation</span> for the last 100 Myr.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MNRAS.470.1570H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MNRAS.470.1570H"><span>Integral field spectroscopy of nearby quasi-<span class="hlt">stellar</span> objects - II. Molecular gas content and conditions for star <span class="hlt">formation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Husemann, B.; Davis, T. A.; Jahnke, K.; Dannerbauer, H.; Urrutia, T.; Hodge, J.</p> <p>2017-09-01</p> <p>We present single-dish 12CO(1-0) and 12CO(2-1) observations for 14 low-redshift quasi-<span class="hlt">stellar</span> objects (QSOs). In combination with optical integral field spectroscopy, we study how the cold gas content relates to the star <span class="hlt">formation</span> rate (SFR) and black hole accretion rate. 12CO(1-0) is detected in 8 of 14 targets and 12CO(2-1) is detected in 7 out of 11 cases. The majority of disc-dominated QSOs reveal gas fractions and depletion times matching normal star-forming systems. Two gas-rich major mergers show clear starburst signatures with higher than average gas fractions and shorter depletion times. Bulge-dominated QSO hosts are mainly undetected in 12CO(1-0), which corresponds, on average, to lower gas fractions than in disc-dominated counterparts. Their SFRs, however, imply shorter than average depletion times and higher star <span class="hlt">formation</span> efficiencies. Negative QSO feedback through removal of cold gas seems to play a negligible role in our sample. We find a trend between black hole accretion rate and total molecular gas content for disc-dominated QSOs when combined with literature samples. We interpret this as an upper envelope for the nuclear activity and it is well represented by a scaling relation between the total and circumnuclear gas reservoir accessible for accretion. Bulge-dominated QSOs significantly differ from that scaling relation and appear uncorrelated with the total molecular gas content. This could be explained either by a more compact gas reservoir, blown out of the gas envelope through outflows, or a different interstellar medium phase composition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...838..151T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...838..151T"><span>Apparent Disk-mass Reduction and Planetisimal <span class="hlt">Formation</span> in Gravitationally Unstable Disks in Class 0/I Young <span class="hlt">Stellar</span> Objects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsukamoto, Y.; Okuzumi, S.; Kataoka, A.</p> <p>2017-04-01</p> <p>We investigate the dust structure of gravitationally unstable disks undergoing mass accretion from the envelope, envisioning its application to Class 0/I young <span class="hlt">stellar</span> objects (YSOs). We find that the dust disk quickly settles into a steady state and that, compared to a disk with interstellar medium (ISM) dust-to-gas mass ratio and micron-sized dust, the dust mass in the steady state decreases by a factor of 1/2 to 1/3, and the dust thermal emission decreases by a factor of 1/3 to 1/5. The latter decrease is caused by dust depletion and opacity decrease owing to dust growth. Our results suggest that the masses of gravitationally unstable disks in Class 0/I YSOs are underestimated by a factor of 1/3 to 1/5 when calculated from the dust thermal emission assuming an ISM dust-to-gas mass ratio and micron-sized dust opacity, and that a larger fraction of disks in Class 0/I YSOs is gravitationally unstable than was previously believed. We also investigate the orbital radius {r}{{P}} within which planetesimals form via coagulation of porous dust aggregates and show that {r}{{P}} becomes ∼20 au for a gravitationally unstable disk around a solar mass star. Because {r}{{P}} increases as the gas surface density increases and a gravitationally unstable disk has maximum gas surface density, {r}{{P}}∼ 20 {au} is the theoretical maximum radius for planetesimal <span class="hlt">formation</span>. We suggest that planetesimal <span class="hlt">formation</span> in the Class 0/I phase is preferable to that in the Class II phase because a large amount of dust is supplied by envelope-to-disk accretion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...822...70L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...822...70L"><span>Dual <span class="hlt">Stellar</span> Halos in the Standard Elliptical Galaxy M105 and <span class="hlt">Formation</span> of Massive Early-type Galaxies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Myung Gyoon; Jang, In Sung</p> <p>2016-05-01</p> <p>M105 is a standard elliptical galaxy, located in the Leo I Group. We present photometry of the resolved stars in its inner region at R ≈ 4‧ ≈ 4R eff, obtained from F606W and F814W images in the Hubble Space Telescope archive. We combine this with photometry of the outer region at R ≈ 12‧ ≈ 12R eff from archival imaging data. Color-magnitude diagrams of the resolved stars in the inner region show a prominent red giant branch (RGB) with a large color range, while those for the outer region show better a narrow blue RGB. The metallicity distribution function (MDF) of the RGB stars shows the existence of two distinct subpopulations: a dominant metal-rich population (with a peak at [M/H] ≈ 0.0) and a much weaker metal-poor population (with a peak at [M/H] ≈ -1.1). The radial number density profiles of the metal-rich and metal-poor RGB stars are fit well by a Sérsic law with n = 2.75 ± 0.10 and n = 6.89 ± 0.94, and by a single power law (σ ∝ R -3.8 and σ ∝ R -2.6), respectively. The MDFs of the inner and outer regions can be described well by accretion gas models of chemical evolution with two components. These provide strong evidence that there are two distinct <span class="hlt">stellar</span> halos in this galaxy, blue metal-poor and red metal-rich halos, consistent with the results based on globular cluster systems in bright early-type galaxies (ETGs). We discuss the implications of these results with regard to the <span class="hlt">formation</span> of massive ETGs in the dual halo mode <span class="hlt">formation</span> scenario.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21378365','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21378365"><span>THE DEPENDENCE OF STAR <span class="hlt">FORMATION</span> RATES ON <span class="hlt">STELLAR</span> MASS AND ENVIRONMENT AT z approx 0.8</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Patel, Shannon G.; Holden, Bradford P.; Illingworth, Garth D.; Franx, Marijn</p> <p>2009-11-01</p> <p>We examine the star <span class="hlt">formation</span> rates (SFRs) of galaxies in a redshift slice encompassing the z = 0.834 cluster RX J0152.7 - 1357. We used a low-dispersion prism in the Inamori Magellan Areal Camera and Spectrograph to identify galaxies with z {sub AB} < 23.3 mag in diverse environments around the cluster out to projected distances of approx8 Mpc from the cluster center. We utilize a mass-limited sample (M > 2 x 10{sup 10} M{sub sun}) of 330 galaxies that were imaged by Spitzer MIPS at 24 mum to derive SFRs and study the dependence of specific SFR (SSFR) on <span class="hlt">stellar</span> mass and environment. We find that the SFR and SSFR show a strong decrease with increasing local density, similar to the relation at z approx 0. Our result contrasts with other work at z approx 1 that finds the SFR-density trend to reverse for luminosity-limited samples. These other results appear to be driven by star <span class="hlt">formation</span> (SF) in lower mass systems (M approx 10{sup 10} M{sub sun}). Our results imply that the processes that shut down SF are present in groups and other dense regions in the field. Our data also suggest that the lower SFRs of galaxies in higher density environments may reflect a change in the ratio of star-forming to non-star-forming galaxies, rather than a change in SFRs. As a consequence, the SFRs of star-forming galaxies, in environments ranging from small groups to clusters, appear to be similar and largely unaffected by the local processes that truncate SF at z approx 0.8.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19518401','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19518401"><span><span class="hlt">Cusps</span>, self-organization, and absorbing states.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bonachela, Juan A; Alava, Mikko; Muñoz, Miguel A</p> <p>2009-05-01</p> <p>Elastic interfaces embedded in (quenched) random media exhibit metastability and stick-slip dynamics. These nontrivial dynamical features have been shown to be associated with <span class="hlt">cusp</span> singularities of the coarse-grained disorder correlator. Here we show that annealed systems with many absorbing states and a conservation law but no quenched disorder exhibit identical <span class="hlt">cusps</span>. On the other hand, similar nonconserved systems in the directed percolation class are also shown to exhibit <span class="hlt">cusps</span> but of a different type. These results are obtained both by a recent method to explicitly measure disorder correlators and by defining an alternative new protocol inspired by self-organized criticality, which opens the door to easily accessible experimental realizations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990A%26A...230..238V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990A%26A...230..238V"><span><span class="hlt">Cusp</span>-points and current sheet dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vainshtein, S. I.</p> <p>1990-04-01</p> <p><span class="hlt">Cusp</span> points are produced in magnetic streamers of the solar corona. They may also be produced in the tail region of the earth's magnetosphere. This paper makes an analysis of such points in an equilibrium plasma. It is found that the very presence of a <span class="hlt">cusp</span> point is inevitably associated with current sheets; these are the site of magnetic-field line reconnection. Special attention is paid to two examples. One examines a current sheet in a very much rarefield plasma (a problem formulated by Syrovatskii, 1966). The other one investigates the rosette structure of two merging magnetic islands. Analysis of the plasma behavior in the vicinity of the <span class="hlt">cusp</span> points shows that, in the latter case, equilibrium cannot be realized. Therefore reconnection must proceed violently, at the high rates observed in numerical simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910043358&hterms=topology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dtopology','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910043358&hterms=topology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dtopology"><span>Opening the <span class="hlt">cusp</span>. [using magnetic field topology</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Crooker, N. U.; Toffoletto, F. R.; Gussenhoven, M. S.</p> <p>1991-01-01</p> <p>This paper discusses the magnetic field topology (determined by the superposition of dipole, image, and uniform fields) for mapping the <span class="hlt">cusp</span> to the ionosphere. The model results are compared to both new and published observations and are then used to map the footprint of a flux transfer event caused by a time variation in the merging rate. It is shown that the <span class="hlt">cusp</span> geometry distorts the field lines mapped from the magnetopause to yield footprints with dawn and dusk protrusions into the region of closed magnetic flux.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22486177','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22486177"><span>Self-bending symmetric <span class="hlt">cusp</span> beams</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gong, Lei; Liu, Wei-Wei; Lu, Yao; Li, Yin-Mei; Ren, Yu-Xuan</p> <p>2015-12-07</p> <p>A type of self-bending symmetric <span class="hlt">cusp</span> beams with four accelerating intensity maxima is theoretically and experimentally presented. Distinguished from the reported regular polygon beams, the symmetric <span class="hlt">cusp</span> beams simultaneously exhibit peculiar features of natural autofocusing and self-acceleration during propagation. Further, such beams take the shape of a fine longitudinal needle-like structure at the focal region and possess the strong ability of self-healing over obstacles. All these intriguing properties were verified experimentally. Particularly, the spatial profile of the reconstructed beam exhibits spatially sculpted optical structure with four siamesed curved arms. Thus, we anticipate that the structured beam will benefit optical guiding and optofluidics in surprising ways.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982PhDT........60R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982PhDT........60R"><span>Computer Simulations of the Toroidal <span class="hlt">Cusp</span> Experiment.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ratliff, Steven Theodore</p> <p>1982-03-01</p> <p>The Toroidal <span class="hlt">Cusp</span> Experiment (TCX) is a toroidal plasma device in which the external magnetic field is produced by permanent magnets arranged in 48 poloidal rings to form 48 magnetic <span class="hlt">cusps</span> (the maximum field strength is 1.3 kG). A transformer drives a toroidal current which produces a Hydrogen plasma with n(,e) = electron density = 1.2 x 10('13)cm(' -3), T(,i) = ion temperature = 40 - 100 eV, T(,e) = electron temperature = 10 - 20 eV, and (beta) = ratio of maximum plasma pressure to maximum magnetic field pressure = 20% to 30%. The purpose of this dissertation is to investigate some physical phenomena in TCX by using theory and computer simulations. The operation of TCX is simulated by using a 2 1/2 dimensional ((PAR-DIFF)/(PAR-DIFF)z = 0) electromagnetic particle code. The positions (x, y) and velocities (v(,x), v(,y), v(,z)) of ions and electrons are calculated using the Lorentz force law and the electric and magnetic fields are calculated from the full set of Maxwell's equations. The computer model is described and its relationship to the experiment is given. Simple explanations of the magnetic lens effect of the array of 48 magnetic <span class="hlt">cusps</span> and of the pinch effect are given. A simple theory is used to explain how the ratio of electron-to-ion toroidal current could be less than the mass ratio m(,i)/m(,e). Pressure balance results and a simple physical picture are explained. Electron and ion currents in the model are estimated from average velocities. The electrons are restrained by the <span class="hlt">cusp</span> fields and the ions are relatively unrestrained. The <span class="hlt">cusp</span> fields are stretched in the direction of the electron acceleration. The electrons execute E(' )x(' )B motion in the <span class="hlt">cusps</span>; the ions are relatively unaffected by the <span class="hlt">cusp</span> fields. For strong enough electric fields, an instability is observed in the computer model. We give evidence and theoretical arguments that this instability is a type of two-stream instability in which the streaming electrons in the center of the device</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/131941','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/131941"><span>Magnetic-<span class="hlt">cusp</span>, cathodic-arc source</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Falabella, S.</p> <p>1995-11-21</p> <p>A magnetic-<span class="hlt">cusp</span> for a cathodic-arc source wherein the arc is confined to the desired cathode surface, provides a current path for electrons from the cathode to the anode, and utilizes electric and magnetic fields to guide ions from the cathode to a point of use, such as substrates to be coated. The magnetic-<span class="hlt">cusp</span> insures arc stability by an easy magnetic path from anode to cathode, while the straight-through arrangement leads to high ion transmission. 3 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880043910&hterms=mass+density&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dmass%2Bdensity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880043910&hterms=mass+density&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dmass%2Bdensity"><span>Near-infrared mass-to-light ratios in galaxies - <span class="hlt">Stellar</span> mass and star <span class="hlt">formation</span> in the heart of the Whirlpool</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thronson, Harley A., Jr.; Greenhouse, Matthew A.</p> <p>1988-01-01</p> <p>The observed <span class="hlt">stellar</span> population in the solar neighborhood is used to derive a relationship between the local <span class="hlt">stellar</span> mass density and the visual and near-IR brightness, which is then extended to a wide range of galaxies. This technique is applied to near-IR (J, H, and K) images of the central 2.3 kpc (50 arcsec) of the Whirlpool Galaxy (M51, NGC 5194). It is estimated that the current high rate of star <span class="hlt">formation</span> can last no more than about another 10-million years, and that, if a large fraction of the stars in the nucleus of M51 was created in periods of enhanced <span class="hlt">formation</span>, the duty cycle for such events is about 5 percent.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AAS...21740303A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AAS...21740303A"><span>The Dark Matter Halo Profile Of NGC 2976 Via <span class="hlt">Stellar</span> Kinematics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adams, Joshua J.; Gebhardt, K.; Hill, G. J.; van den Bosch, R. C. E.; Blanc, G. A.</p> <p>2011-01-01</p> <p>The observations of kinematics in low surface brightness (LSB) and dwarf late type galaxies have stubbornly resisted giving clear evidence for the cuspy Navarro-Frenk-White (NFW) dark matter (DM) halo profiles that simulations with ΛCDM inputs predict. Instead, most LSBs and late type dwarfs suggest cored DM halos or the observations are not yet constraining enough to rule out <span class="hlt">cusps</span>. One viable theory to explain cored DM halos relies on the gravitational perturbation of a growing baryonic disk that is then rapidly removed causing the halo to expand to a cored equilibrium. Weakly self-interacting dark matter has also been invoked to explain cored DM halos. This problem may loom large over small galaxy <span class="hlt">formation</span> and growth. However, different measurements can be taken to further test the apparent problem. Most previous data have relied on HI or Hα as kinematic tracers. A small number of works have studied the problem with longslit <span class="hlt">stellar</span> kinematics. Ideally, the advantages of 2D spectroscopic coverage and a collisionless kinematic tracer would be combined. So far, NGC 2976 has made one of the cleanest cases for a cored DM halo via integral field spectroscopy in Hα. We here report on observations of NGC 2976 with the large field-of-view fiber-fed Visible Integral field Replicable Unit Spectrograph Prototype (VIRUS-P) at R=3200 to concurrently measure the gaseous and <span class="hlt">stellar</span> kinematics and probe the DM halo. We find that the gas and <span class="hlt">stellar</span> kinematics disagree both in the magnitude of their second velocity moments and their detailed profiles. We unexpectedly find emission features in one of NGC 2976's two large star-forming regions which may be indicative of carbon-rich Wolf-Rayet stars. A putative bar further complicates the use of gaseous tracers. We solve the Jeans equations with <span class="hlt">stellar</span> kinematics to reevaluate the DM profile in this exemplar galaxy of the core-<span class="hlt">cusp</span> problem.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19730044174&hterms=stellar+evolution&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dstellar%2Bevolution','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19730044174&hterms=stellar+evolution&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dstellar%2Bevolution"><span><span class="hlt">Stellar</span> evolution.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chiu, H.-Y. (Editor); Muriel, A.</p> <p>1972-01-01</p> <p>Aspects of normal <span class="hlt">stellar</span> evolution are discussed together with evolution near the main sequence, <span class="hlt">stellar</span> evolution from main sequence to white dwarf or carbon ignition, the structure of massive main-sequence stars, and problems of <span class="hlt">stellar</span> stability and <span class="hlt">stellar</span> pulsation. Other subjects considered include variable stars, white dwarfs, close binaries, novae, early supernova luminosity, neutron stars, the photometry of field horizontal-branch stars, and <span class="hlt">stellar</span> opacity. Transport mechanisms in stars are examined together with thermonuclear reactions and nucleosynthesis, the instability problem in nuclear burning shells, <span class="hlt">stellar</span> coalescence, and intense magnetic fields in astrophysics. Individual items are announced in this issue.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MNRAS.470..401R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MNRAS.470..401R"><span>The evolution of CNO isotopes: a new window on cosmic star <span class="hlt">formation</span> history and the <span class="hlt">stellar</span> IMF in the age of ALMA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Romano, D.; Matteucci, F.; Zhang, Z.-Y.; Papadopoulos, P. P.; Ivison, R. J.</p> <p>2017-09-01</p> <p>We use state-of-the-art chemical models to track the cosmic evolution of the CNO isotopes in the interstellar medium of galaxies, yielding powerful constraints on their <span class="hlt">stellar</span> initial mass function (IMF). We re-assess the relative roles of massive stars, asymptotic giant branch (AGB) stars and novae in the production of rare isotopes such as 13C, 15N, 17O and 18O, along with 12C, 14N and 16O. The CNO isotope yields of super-AGB stars, novae and fast-rotating massive stars are included. Having reproduced the available isotope enrichment data in the solar neighbourhood, and across the Galaxy, and having assessed the sensitivity of our models to the remaining uncertainties, e.g. nova yields and star <span class="hlt">formation</span> history, we show that we can meaningfully constrain the <span class="hlt">stellar</span> IMF in galaxies using C, O and N isotope abundance ratios. In starburst galaxies, where data for multiple isotopologue lines are available, we find compelling new evidence for a top-heavy <span class="hlt">stellar</span> IMF, with profound implications for their star <span class="hlt">formation</span> rates and efficiencies, perhaps also their <span class="hlt">stellar</span> masses. Neither chemical fractionation nor selective photodissociation can significantly perturb globally averaged isotopologue abundance ratios away from the corresponding isotope ones, as both these processes will typically affect only small mass fractions of molecular clouds in galaxies. Thus, the Atacama Large Millimeter Array now stands ready to probe the <span class="hlt">stellar</span> IMF, and even the ages of specific starburst events in star-forming galaxies across cosmic time unaffected by the dust obscuration effects that plague optical/near-infrared studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008Icar..193..158G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008Icar..193..158G"><span>Cycloid crack sequences on Europa: Relationship to stress history and constraints on growth mechanics based on <span class="hlt">cusp</span> angles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Groenleer, Julie M.; Kattenhorn, Simon A.</p> <p>2008-01-01</p> <p>The original model developed to explain cycloidal cracks on Europa interprets cycloids as tensile fractures that grow in a curved path in response to the constantly rotating diurnal tidal stress field. <span class="hlt">Cusps</span> form when a new cycloid crack segment propagates at an angle to the first in response to a rotation of the principal tidal stress orientation during a period of no crack growth. A recent revised model states that a cycloid <span class="hlt">cusp</span> forms through the creation of a secondary fracture called a tailcrack at the tip of an existing cycloid segment during shearing motion induced by the rotating tidal stress field. As the tailcrack propagates away from the <span class="hlt">cusp</span>, it becomes the next cycloid segment in the chain. The qualitative tailcrack model uniquely accounts for the normal and shear stresses that mechanically must resolve onto the tip of an existing cycloid segment at the instant of <span class="hlt">cusp</span> <span class="hlt">formation</span>. In this work, we provide a quantitative framework and test of the hitherto purely conceptual tailcrack model. We first present a relative age sequence inferred from geologic mapping of multiply cross-cutting cycloids in Europa's trailing hemisphere and place this into the context of the global stress history. The age sequence requires a cumulative minimum of 630° of shell reorientation due to nonsynchronous rotation to account for the observed range of orientations of cycloids of different ages. We determined the back-rotated longitudes of <span class="hlt">formation</span> of two cycloid chain examples and used mathematical modeling of europan tidal stresses to show that the tailcrack model for <span class="hlt">cusp</span> <span class="hlt">formation</span> is not only viable, but places constraints on the overall development of a cycloid chain by controlling the timing of <span class="hlt">cusp</span> development within Europa's orbit. For all <span class="hlt">cusps</span> analyzed, the exact ratio of resolved shear to normal stress required to form the <span class="hlt">cusp</span> angles by a process of tailcracking, as governed by the principles of linear elastic fracture mechanics, is produced at the tip of a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=Infrared+AND+radiation&pg=3&id=EJ187432','ERIC'); return false;" href="https://eric.ed.gov/?q=Infrared+AND+radiation&pg=3&id=EJ187432"><span><span class="hlt">Stellar</span> Ontogeny: From Dust...</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>MOSAIC, 1978</p> <p>1978-01-01</p> <p>Discusses the process of star <span class="hlt">formation</span>. Infrared and radio astronomy, particularly microwave astronomy is used to provide information on different stages of <span class="hlt">stellar</span> <span class="hlt">formation</span>. The role of dust and gas which swirl through the interstellar regions of a galaxy and the collapse of a cloud in star <span class="hlt">formation</span> are also presented. (HM)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=stellar+AND+evolution&pg=3&id=EJ187432','ERIC'); return false;" href="http://eric.ed.gov/?q=stellar+AND+evolution&pg=3&id=EJ187432"><span><span class="hlt">Stellar</span> Ontogeny: From Dust...</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>MOSAIC, 1978</p> <p>1978-01-01</p> <p>Discusses the process of star <span class="hlt">formation</span>. Infrared and radio astronomy, particularly microwave astronomy is used to provide information on different stages of <span class="hlt">stellar</span> <span class="hlt">formation</span>. The role of dust and gas which swirl through the interstellar regions of a galaxy and the collapse of a cloud in star <span class="hlt">formation</span> are also presented. (HM)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19107814','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19107814"><span>The chiton stylus canal: An element delivery pathway for tooth <span class="hlt">cusp</span> biomineralization.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shaw, Jeremy A; Macey, David J; Brooker, Lesley R; Stockdale, Edward J; Saunders, Martin; Clode, Peta L</p> <p>2009-05-01</p> <p>A detailed investigation of the stylus canal situated within the iron mineralized major lateral teeth of the chiton Acanthopleura hirtosa was undertaken in conjunction with a row-by-row examination of <span class="hlt">cusp</span> mineralization. The canal is shown to contain columnar epithelial tissue similar to that surrounding the mineralized <span class="hlt">cusps</span>, including the presence of iron rich particles characteristic of the iron storage protein ferritin. Within the tooth core, a previously undescribed internal pathway or plume is evident above the stylus canal, between the junction zone and mineralizing posterior face of the <span class="hlt">cusp</span>. Plume <span class="hlt">formation</span> coincides with the appearance of iron in the superior epithelium and the onset of mineralization at tooth row 13. The plume persists during the delivery of phosphorous and calcium into the tooth core, and is the final region of the <span class="hlt">cusp</span> to become mineralized. The presence of the stylus canal was confirmed in a further 18 chiton species, revealing that the canal is common to polyplacophoran molluscs. These new data strongly support the growing body of evidence highlighting the importance of the junction zone for tooth mineralization in chiton teeth, and indicate that the chemical and structural environment within the tooth <span class="hlt">cusp</span> is under far greater biological control than previously considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983EOSTr..64S.378.','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983EOSTr..64S.378."><span><span class="hlt">Stellar</span> cannibalism</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p></p> <p></p> <p>Astronomers have obtained evidence that stars can literally swallow other stars, leading to the ejection of <span class="hlt">stellar</span> material into space and the <span class="hlt">formation</span> of extremely close pairs of stars, according to the National Science Foundation (NSF). The discovery supports theoretical predictions of the evolution of double stars.While studying the central stars of planetary nebulae—disk-shaped gas clouds that vaguely resemble planets—Albert D. Grauer of the University of Arkansas at Little Rock and Howard E. Bond of Louisiana State University at Baton Rouge found that several of these central stars are actually very close <span class="hlt">stellar</span> pairs. Previously, it had been thought that the central star in a planetary nebula was a single star that expelled a gas cloud as it neared the end of its life. Their latest discovery, the central star of planetary nebula Abell 41, consists of a pair of stars that orbit each other in 2 hours and 43 minutes. The researchers also have found three other central star pairs that have orbital periods of between 11 and 16 hours.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21452825','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21452825"><span>WIDESPREAD PRESENCE OF SHALLOW <span class="hlt">CUSPS</span> IN THE SURFACE-BRIGHTNESS PROFILE OF GLOBULAR CLUSTERS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Vesperini, Enrico; Trenti, Michele E-mail: trenti@colorado.ed</p> <p>2010-09-10</p> <p>Surface-brightness profiles of globular clusters with shallow central <span class="hlt">cusps</span> ({Sigma} {approx} R {sup {nu}} with -0.3 {approx_lt} {nu} {approx_lt} -0.05) have been associated by several recent studies with the presence of a central intermediate-mass black hole (IMBH). Such shallow slopes are observed in several globular clusters thanks to the high angular resolution of Hubble Space Telescope (HST) imaging. In this Letter, we evaluate whether shallow <span class="hlt">cusps</span> are a unique signature of a central IMBH by analyzing a sample of direct N-body simulations of star clusters with and without a central IMBH. We 'observe' the simulations as if they were HST images. Shallow <span class="hlt">cusps</span> are common in our simulation sample: star clusters without an IMBH have {nu} {approx_gt} -0.3 in the pre-core-collapse and core-collapse phases. Post-core-collapse clusters without an IMBH transition to steeper <span class="hlt">cusps</span>, -0.7 {approx_lt} {nu} {approx_lt} -0.4, only if the primordial binary fraction is very small, f {sub bin} < 3%, and if there are few <span class="hlt">stellar</span>-mass BHs remaining. Otherwise {nu} values overlap the range usually ascribed to the presence of an IMBH throughout the entire duration of the simulations. In addition, measuring {nu} is intrinsically prone to significant uncertainty, therefore typical measurement errors may lead to {nu} {>=} -0.3 even when ({nu}) {approx_lt} -0.4. Overall our analysis shows that a shallow <span class="hlt">cusp</span> is not an unequivocal signature of a central IMBH and casts serious doubts on the usefulness of measuring {nu} in the context of the hunt for IMBHs in globular clusters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2013-title21-vol8/pdf/CFR-2013-title21-vol8-sec872-3350.pdf','CFR2013'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2013-title21-vol8/pdf/CFR-2013-title21-vol8-sec872-3350.pdf"><span>21 CFR 872.3350 - Gold or stainless steel <span class="hlt">cusp</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2013&page.go=Go">Code of Federal Regulations, 2013 CFR</a></p> <p></p> <p>2013-04-01</p> <p>... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Gold or stainless steel <span class="hlt">cusp</span>. 872.3350 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3350 Gold or stainless steel <span class="hlt">cusp</span>. (a) Identification. A gold or stainless steel <span class="hlt">cusp</span> is a prefabricated device made of austenitic alloys or...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2011-title21-vol8/pdf/CFR-2011-title21-vol8-sec872-3350.pdf','CFR2011'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2011-title21-vol8/pdf/CFR-2011-title21-vol8-sec872-3350.pdf"><span>21 CFR 872.3350 - Gold or stainless steel <span class="hlt">cusp</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2011&page.go=Go">Code of Federal Regulations, 2011 CFR</a></p> <p></p> <p>2011-04-01</p> <p>... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Gold or stainless steel <span class="hlt">cusp</span>. 872.3350 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3350 Gold or stainless steel <span class="hlt">cusp</span>. (a) Identification. A gold or stainless steel <span class="hlt">cusp</span> is a prefabricated device made of austenitic alloys or...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2010-title21-vol8/pdf/CFR-2010-title21-vol8-sec872-3350.pdf','CFR'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2010-title21-vol8/pdf/CFR-2010-title21-vol8-sec872-3350.pdf"><span>21 CFR 872.3350 - Gold or stainless steel <span class="hlt">cusp</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2010&page.go=Go">Code of Federal Regulations, 2010 CFR</a></p> <p></p> <p>2010-04-01</p> <p>... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Gold or stainless steel <span class="hlt">cusp</span>. 872.3350 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3350 Gold or stainless steel <span class="hlt">cusp</span>. (a) Identification. A gold or stainless steel <span class="hlt">cusp</span> is a prefabricated device made of austenitic alloys or...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2012-title21-vol8/pdf/CFR-2012-title21-vol8-sec872-3350.pdf','CFR2012'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2012-title21-vol8/pdf/CFR-2012-title21-vol8-sec872-3350.pdf"><span>21 CFR 872.3350 - Gold or stainless steel <span class="hlt">cusp</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2012&page.go=Go">Code of Federal Regulations, 2012 CFR</a></p> <p></p> <p>2012-04-01</p> <p>... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Gold or stainless steel <span class="hlt">cusp</span>. 872.3350 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3350 Gold or stainless steel <span class="hlt">cusp</span>. (a) Identification. A gold or stainless steel <span class="hlt">cusp</span> is a prefabricated device made of austenitic alloys or...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2014-title21-vol8/pdf/CFR-2014-title21-vol8-sec872-3350.pdf','CFR2014'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2014-title21-vol8/pdf/CFR-2014-title21-vol8-sec872-3350.pdf"><span>21 CFR 872.3350 - Gold or stainless steel <span class="hlt">cusp</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2014&page.go=Go">Code of Federal Regulations, 2014 CFR</a></p> <p></p> <p>2014-04-01</p> <p>... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Gold or stainless steel <span class="hlt">cusp</span>. 872.3350 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3350 Gold or stainless steel <span class="hlt">cusp</span>. (a) Identification. A gold or stainless steel <span class="hlt">cusp</span> is a prefabricated device made of austenitic alloys or...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5220459','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5220459"><span>Comprehensive and Conservative Management of Talon <span class="hlt">Cusp</span>: A New Technique</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lodha, Surendra</p> <p>2016-01-01</p> <p>Talon <span class="hlt">cusp</span> is a common dental anomaly affecting maxillary central incisors. Gradual grinding of this additional <span class="hlt">cusp</span> is commonly followed now. Advocated below is a new technique explaining the use of air abrasion and putty index during the stepwise reduction of the <span class="hlt">cusp</span>. The technique is advantageous in preventing patient discomfort and tracking the amount of reduction in a predictable way. PMID:28105377</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997PhDT........20S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997PhDT........20S"><span>Hubble Space Telescope Observations of Globular Clusters with Central Density <span class="hlt">Cusps</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sosin, Craig Anthony</p> <p>1997-07-01</p> <p>We use the Hubble Space Telescope to observe crowded fields in globular clusters with central density <span class="hlt">cusps</span>, and use the observed <span class="hlt">stellar</span> distributions to study the internal dynamics of clusters in advanced stages of evolution. We begin by discussing images of the <span class="hlt">cusp</span> of NGC 6624. From the positions of individual stars, we measure the logarithmic slope of the central density <span class="hlt">cusp</span>, but do not resolve the cluster core. We also detect a central population of blue stragglers, and compare the frequencies of such stars in several clusters. NGC 6397, as well as photometric techniques for use with diffraction-limited HST images. We measure logarithmic <span class="hlt">cusp</span> slopes for various groups of main-sequence stars in each cluster; we also set upper limits on the core radii of M15 and M30, and measure a radius of ~5' for the NGC 6397 core. We compare mass functions (MFs) measured at several radii in each cluster, and find substantial mass segregation. In M30, the observed segregation is well matched by the predictions of a King-Michie model, but similar models of M15 and NGC 6397 predict more mass segregation than we observe. We then use the Jeans equation and our MFs to investigate the degree of equipartition of energy between <span class="hlt">stellar</span> species in each cluster. We find that M30 is very close to equipartition over the observed radial range between the <span class="hlt">cusp</span> and the envelope, while M15 and NGC 6397 are not. The difference between M30 and M15 might be explained by the difference in relaxation times at the observed radii, but this scenario fails to explain the NGC 6397 data. We discuss the possibility that post-collapse clusters remain subject to the Spitzer instability, and the possibility that the tidal shocks suffered by NGC 6397 have affected its degree of mass segregation. We also propose that the observed differences between the central <span class="hlt">cusps</span> of the clusters could be due to gravothermal oscillations, to differences in binary populations, or to the presence of a ~103Msolar black hole</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/7826235','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/7826235"><span>[Mitral valve prolapse and <span class="hlt">cusp</span> elasticity].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Curti, H J; Ferreira, M C; Silveira, S A; Sanches, P C; Carvalhal, S</p> <p>1994-06-01</p> <p>To verify if systolic bulging of floppy mitral <span class="hlt">cusps</span> can to elastic behavior of their myxomatous collagen tissue. Five hearts with floppy mitral valves obtained from autopsies were distended with air (20 to 250 mmHg) through a catheter connected to the left ventricle. It was observed if some area of the atrial surface of the coapted <span class="hlt">cusps</span> showed variable bulging according to the variation of air injection pressures. Molding of those surfaces (gypsum) allowed the same kind of analysis by other four researches. It was analyzed the cut surfaces of these radially sectioned molds. Lately, isolated tendinae chords were submitted to repeated tractions and observed if they exhibited elastic behavior. Histological study defined the presence of collagen myxomatous degeneration and quantified the amount of elastic tissue. In no case it was detected elastic bulding of mitral <span class="hlt">cusps</span>. Cut surfaces of the molds confirmed that no increment of the prominent areas occurred, even in those regions with extensive, histologically confirmed, myxomatous substitution of the native collagen tissue. Increment of the degree of mitral bulging occurring during ventricular systole can not be ascertained to <span class="hlt">cusp</span> elasticity but probably to papilar muscle traction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2012-title21-vol8/pdf/CFR-2012-title21-vol8-sec872-3360.pdf','CFR2012'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2012-title21-vol8/pdf/CFR-2012-title21-vol8-sec872-3360.pdf"><span>21 CFR 872.3360 - Preformed <span class="hlt">cusp</span>.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2012&page.go=Go">Code of Federal Regulations, 2012 CFR</a></p> <p></p> <p>2012-04-01</p> <p>... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Preformed <span class="hlt">cusp</span>. 872.3360 Section 872.3360 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... of a tooth) to achieve occlusal harmony (a proper bite) before permanent restoration of a tooth....</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1914789H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1914789H"><span>Solar wind controls on Mercury's magnetospheric <span class="hlt">cusp</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, Maosheng; Vogt, Joachim; Heyner, Daniel; Zhong, Jun</p> <p>2017-04-01</p> <p>Mercury's magnetospheric <span class="hlt">cusp</span> results from the interaction between the planetary intrinsic magnetic field and the solar wind. In this study, we assemble 2848 orbits of MESSENGER data for a comprehensive assessment of solar wind control on Mercury's <span class="hlt">cusp</span>. We propose and validate an IMF estimation approach for the <span class="hlt">cusp</span> transit, and construct an index to measure the magnetic disturbance. The index maximizes within the <span class="hlt">cusp</span>, more intense than in the adjacent magnetosphere by several orders of magnitude. We develop an empirical model of the index as a function of IMFvector and Mercury's solar orbital phase. The model is used to study the <span class="hlt">cusp</span> activity under different conditions. Comparisons reveal the <span class="hlt">cusp</span> activity is more intense and extends further in local time, under antisunward IMF (IMFx<0) than sunward (IMFx>0), under southward IMF (IMFz<0) than northward (IMFz>0), and when Mercury orbits at its perihelion than at aphelion. Besides, the <span class="hlt">cusp</span> shifts azimuthally towards dawn when IMF reverses from westward (IMFy<0) to eastward (IMFy>0), and when Mercury approaches its perihelion. The IMFx dependence is consistent with existing observations and simulations which are ascribed to the asymmetry of dayside magnetospheric configuration between sunward and anti-sunward IMF conditions. We explain the IMFy and IMFz dependences in terms of component reconnection of the magnetospheric field merging with By-dominant and Bz-dominant IMF, respectively. The control of the Mercury solar orbit phase on the intensity and local time location of the disturbance peak are possibly arising from the modulations of the heliocentric distance on the solar wind ram pressure. The existence of significant IMF dependence suggests the IMF orientation plays a role in the convection configuration at Mercury. The IMFy-dependence at Mercury is opposite to that at Earth, suggesting that component reconnection at the dayside magnetopause is more important in the Hermean system than in the terrestrial</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AAS...22830405H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AAS...22830405H"><span>Failures no More: The Radical Consequences of Realistic <span class="hlt">Stellar</span> Feedback for Dwarf Galaxies, the Milky Way, and Reionization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hopkins, Philip F.</p> <p>2016-06-01</p> <p>Many of the most fundamental unsolved questions in star and galaxy <span class="hlt">formation</span> revolve around star <span class="hlt">formation</span> and "feedback" from massive stars, in-extricably linking galaxy <span class="hlt">formation</span> and <span class="hlt">stellar</span> evolution. I'll present simulations with un-precedented resolution of Milky-Way (MW) mass galaxies, followed cosmologically to redshift zero. For the first time, these simulations resolve the internal structure of small dwarf satellites around a MW-like host, with detailed models for <span class="hlt">stellar</span> evolution including radiation pressure, supernovae, <span class="hlt">stellar</span> winds, and photo-heating. I'll show that, without fine-tuning, these feedback processes naturally resolve the "missing satellites," "too big to fail," and "<span class="hlt">cusp</span>-core" problems, and produce realistic galaxy populations. At high redshifts however, the realistic ISM structure predicted, coupled to standard <span class="hlt">stellar</span> population models, naively leads to the prediction that only ~1-2% of ionizing photons can ever escape galaxies, insufficient to ionize the Universe. But these models assume all stars are single: if we account for binary evolution, the escape fraction increases dramatically to ~20% for the small, low-metallicity galaxies believed to ionize the Universe.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920069052&hterms=stellar+evolution&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dstellar%2Bevolution','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920069052&hterms=stellar+evolution&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dstellar%2Bevolution"><span>Frontiers of <span class="hlt">stellar</span> evolution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lambert, David L. (Editor)</p> <p>1991-01-01</p> <p>The present conference discusses theoretical and observational views of star <span class="hlt">formation</span>, spectroscopic constraints on the evolution of massive stars, very low mass stars and brown dwarfs, asteroseismology, globular clusters as tests of <span class="hlt">stellar</span> evolution, observational tests of <span class="hlt">stellar</span> evolution, and mass loss from cool evolved giant stars. Also discussed are white dwarfs and hot subdwarfs, neutron stars and black holes, supernovae from single stars, close binaries with evolved components, accretion disks in interacting binaries, supernovae in binary systems, <span class="hlt">stellar</span> evolution and galactic chemical evolution, and interacting binaries containing compact components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24227163','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24227163"><span>Tooth <span class="hlt">cusp</span> sharpness as a dietary correlate in great apes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Berthaume, Michael A</p> <p>2014-02-01</p> <p>Mammalian molars have undergone heavy scrutiny to determine correlates between morphology and diet. Here, the relationship between one aspect of occlusal morphology, tooth <span class="hlt">cusp</span> radius of curvature (RoC), and two broad dietary categories, folivory and frugivory, is analyzed in apes. The author hypothesizes that there is a relationship between tooth <span class="hlt">cusp</span> RoC and diet, and that folivores have sharper teeth than frugivores, and further test the correlation between tooth <span class="hlt">cusp</span> RoC and tooth <span class="hlt">cusp</span> size. Eight measures of tooth <span class="hlt">cusp</span> RoC (two RoCs per <span class="hlt">cusp</span>) were taken from 53 M(2) s from four species and subspecies of frugivorous apes (Pongo pygmaeus, Pan troglodytes troglodytes, Pan troglodytes schweinfurthii, and Gorilla gorilla gorilla) and two subspecies of folivorous apes (Gorilla beringei beringei, and Gorilla beringei graueri). Phylogenetically corrected ANOVAs were run on the full dataset and several subsets of the full dataset, revealing that, when buccolingual RoCs are taken into account, tooth <span class="hlt">cusp</span> RoCs can successfully differentiate folivores and frugivores. PCAs revealed that folivores consistently had duller teeth than frugivores. In addition, a weak, statistically significant positive correlation exists between tooth <span class="hlt">cusp</span> size and tooth <span class="hlt">cusp</span> RoC. The author hypothesizes differences in tooth <span class="hlt">cusp</span> RoC are correlated with wear rates, where, per vertical unit of wear, duller <span class="hlt">cusps</span> will have a longer length of exposed enamel ridge than sharper <span class="hlt">cusps</span>. More data need to be gathered to determine if the correlation between tooth <span class="hlt">cusp</span> RoC and tooth <span class="hlt">cusp</span> size holds true when small primates are considered. Copyright © 2013 Wiley Periodicals, Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...843..144T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...843..144T"><span>An Investigation of the <span class="hlt">Formation</span> and Line Properties of MgH in 3D Hydrodynamical Model <span class="hlt">Stellar</span> Atmospheres</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thygesen, Anders O.; Kirby, Evan N.; Gallagher, Andrew J.; Ludwig, Hans-G.; Caffau, Elisabetta; Bonifacio, Piercarlo; Sbordone, Luca</p> <p>2017-07-01</p> <p>Studies of the isotopic composition of magnesium in cool stars have so far relied upon the use of 1D model atmospheres. Since the isotopic ratios derived are based on asymmetries of optical MgH lines, it is important to test the impact from other effects affecting line asymmetries, like <span class="hlt">stellar</span> convection. Here, we present a theoretical investigation of the effects of including self-consistent modeling of convection. Using spectral syntheses based on 3D hydrodynamical CO5BOLD models of dwarfs (4000 K ≲ T eff ≲ 5160 K, 4.0 ≤ {log}g ≤ 4.5, -3.0≤slant [{Fe}/{{H}}]≤slant -1.0) and giants (T eff ˜ 4000 K, {log}g = 1.5, -3.0≤slant [{Fe}/{{H}}]≤slant -1.0), we perform a detailed analysis comparing 3D and 1D syntheses. We describe the impact on the <span class="hlt">formation</span> and behavior of MgH lines from using 3D models, and perform a qualitative assessment of the systematics introduced by the use of 1D syntheses. Using 3D model atmospheres significantly affect the strength of the MgH lines, especially in dwarfs, with 1D syntheses requiring an abundance correction of up to +0.69 dex, with the largest for our 5000 K models. The corrections are correlated with T eff and are also affected by the metallicity. The shape of the strong 24MgH component in the 3D syntheses is poorly reproduced in 1D. This results in 1D syntheses underestimating 25Mg by up to ˜5 percentage points and overestimating 24Mg by a similar amount for dwarfs. This discrepancy increases with decreasing metallicity. 26Mg is recovered relatively well, with the largest difference being ˜2 percentage points. The use of 3D for giants has less impact, due to smaller differences in the atmospheric structure and a better reproduction of the line shape in 1D.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008ApJ...689..936J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008ApJ...689..936J"><span>Tracing Galaxy <span class="hlt">Formation</span> with <span class="hlt">Stellar</span> Halos. II. Relating Substructure in Phase and Abundance Space to Accretion Histories</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Johnston, Kathryn V.; Bullock, James S.; Sharma, Sanjib; Font, Andreea; Robertson, Brant E.; Leitner, Samuel N.</p> <p>2008-12-01</p> <p>This paper explores the mapping between the observable properties of a <span class="hlt">stellar</span> halo in phase and abundance space and the parent galaxy's accretion history in terms of the characteristic epoch of accretion and mass and orbits of progenitor objects. The study utilizes a suite of 11 <span class="hlt">stellar</span> halo models constructed within the context of a standard ΛCDM cosmology. The results demonstrate that coordinate-space studies are sensitive to the recent (0-8 Gyr ago) merger histories of galaxies (this timescale corresponds to the last few percent to tens of percent of mass accretion for a Milky Way-type galaxy). Specifically, the frequency, sky coverage, and fraction of stars in substructures in the <span class="hlt">stellar</span> halo as a function of surface brightness are indicators of the importance of recent merging and of the luminosity function of infalling dwarfs. The morphology of features serves as a guide to the orbital distribution of those dwarfs. Constraints on the earlier merger history (>8 Gyr ago) can be gleaned from the abundance patterns in halo stars: within our models, dramatic differences in the dominant epoch of accretion or luminosity function of progenitor objects leave clear signatures in the [α/Fe] and [Fe/H] distributions of the <span class="hlt">stellar</span> halo; halos dominated by very early accretion have higher average [α/Fe], while those dominated by high-luminosity satellites have higher [Fe/H]. This insight can be applied to reconstruct much about the merger histories of nearby galaxies from current and future data sets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011MNRAS.417..216S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011MNRAS.417..216S"><span>The initial conditions of isolated star <span class="hlt">formation</span> - X. A suggested evolutionary diagram for pre-<span class="hlt">stellar</span> cores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Simpson, R. J.; Johnstone, D.; Nutter, D.; Ward-Thompson, D.; Whitworth, A. P.</p> <p>2011-10-01</p> <p>We propose an evolutionary path for pre-<span class="hlt">stellar</span> cores on the radius-mass diagram, which is analogous to <span class="hlt">stellar</span> evolutionary paths on the Hertzsprung-Russell diagram. Using James Clerk Maxwell Telescope (JCMT) observations of L1688 in the Ophiuchus star-forming complex, we analyse the HCO+ (J= 4 → 3) spectral line profiles of pre-<span class="hlt">stellar</span> cores. We find that of the 58 cores observed, 14 show signs of infall in the form of a blue-asymmetric double-peaked line profile. These 14 cores all lie beyond the Jeans mass line for the region on a radius-mass plot. Furthermore, another 10 cores showing tentative signs of infall, in their spectral line profile shapes, appear on or just over the Jeans mass line. We therefore propose the manner in which a pre-<span class="hlt">stellar</span> core evolves across this diagram. We hypothesize that a core is formed in the low-mass, low-radius region of the plot. It then accretes quasi-statically, increasing in both mass and radius. When it crosses the limit of gravitational instability, it begins to collapse, decreasing in radius, towards the region of the diagram where protostellar cores are seen.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...847...72B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...847...72B"><span><span class="hlt">Stellar</span> Dynamics and Star <span class="hlt">Formation</span> Histories of z ∼ 1 Radio-loud Galaxies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barišić, Ivana; van der Wel, Arjen; Bezanson, Rachel; Pacifici, Camilla; Noeske, Kai; Muñoz-Mateos, Juan C.; Franx, Marijn; Smolčić, Vernesa; Bell, Eric F.; Brammer, Gabriel; Calhau, João; Chauké, Priscilla; van Dokkum, Pieter G.; van Houdt, Josha; Gallazzi, Anna; Labbé, Ivo; Maseda, Michael V.; Muzzin, Adam; Sobral, David; Straatman, Caroline; Wu, Po-Feng</p> <p>2017-09-01</p> <p>We investigate the <span class="hlt">stellar</span> kinematics and <span class="hlt">stellar</span> populations of 58 radio-loud galaxies of intermediate luminosities (L 3 GHz > 1023 W Hz‑1) at 0.6 < z < 1. This sample is constructed by cross-matching galaxies from the deep VLT/VIMOS LEGA-C spectroscopic survey with the VLA 3 GHz data set. The LEGA-C continuum spectra reveal for the first time <span class="hlt">stellar</span> velocity dispersions and age indicators of z ∼ 1 radio galaxies. We find that z ∼ 1 radio-loud active galactic nucleus (AGN) occur exclusively in predominantly old galaxies with high velocity dispersions: σ * > 175 km s‑1, corresponding to black hole masses in excess of 108 M ⊙. Furthermore, we confirm that at a fixed <span class="hlt">stellar</span> mass the fraction of radio-loud AGN at z ∼ 1 is five to 10 times higher than in the local universe, suggesting that quiescent, massive galaxies at z ∼ 1 switch on as radio AGN on average once every Gyr. Our results strengthen the existing evidence for a link between high black hole masses, radio loudness, and quiescence at z ∼ 1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22167499','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22167499"><span>TESTING GALAXY <span class="hlt">FORMATION</span> MODELS WITH THE GHOSTS SURVEY: THE COLOR PROFILE OF M81's <span class="hlt">STELLAR</span> HALO</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Monachesi, Antonela; Bell, Eric F.; Bailin, Jeremy; Radburn-Smith, David J.; Dalcanton, Julianne J.; Vlajic, Marija; De Jong, Roelof S.; Streich, David; Holwerda, Benne W.</p> <p>2013-04-01</p> <p>We study the properties of the <span class="hlt">stellar</span> populations in M81's outermost part, which hereafter we will call the <span class="hlt">stellar</span> halo, using Hubble Space Telescope (HST) Advanced Camera for Surveys observations of 19 fields from the GHOSTS survey. The observed fields probe the <span class="hlt">stellar</span> halo out to a projected distance of {approx}50 kpc from the galactic center. Each field was observed in both F606W and F814W filters. The 50% completeness levels of the color-magnitude diagrams (CMDs) are typically at 2 mag below the tip of the red giant branch (TRGB). Fields at distances closer than 15 kpc show evidence of disk-dominated populations whereas fields at larger distances are mostly populated by halo stars. The red giant branch (RGB) of the M81's halo CMDs is well matched with isochrones of {approx}10 Gyr and metallicities [Fe/H] {approx} - 1.2 dex, suggesting that the dominant <span class="hlt">stellar</span> population of M81's halo has a similar age and metallicity. The halo of M81 is characterized by a color distribution of width {approx}0.4 mag and an approximately constant median value of (F606W - F814W) {approx}1 mag measured using stars within the magnitude range 23.7 {approx}< F814W {approx}< 25.5. When considering only fields located at galactocentric radius R > 15 kpc, we detect no color gradient in the <span class="hlt">stellar</span> halo of M81. We place a limit of 0.03 {+-} 0.11 mag difference between the median color of RGB M81 halo stars at {approx}15 and at 50 kpc, corresponding to a metallicity difference of 0.08 {+-} 0.35 dex over that radial range for an assumed constant age of 10 Gyr. We compare these results with model predictions for the colors of <span class="hlt">stellar</span> halos formed purely via accretion of satellite galaxies. When we analyze the cosmologically motivated models in the same way as the HST data, we find that they predict no color gradient for the <span class="hlt">stellar</span> halos, in good agreement with the observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810818J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810818J"><span>Ion observations at Mercury's Magnetospheric <span class="hlt">Cusp</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jasinski, Jamie; Raines, Jim; Slavin, James</p> <p>2016-04-01</p> <p>The magnetospheric <span class="hlt">cusp</span> is a region of direct entry for solar wind mass, energy and momentum into a planetary magnetosphere. Dayside magnetic reconnection between the interplanetary magnetic field and the planetary field allows shocked solar wind plasma to flow down open magnetospheric field lines. Whilst this is occurring these magnetic field lines convect poleward. For a spacecraft travelling through the high latitudes, this causes a velocity filter effect to be observed in the ion data, whereby higher energy ions are observed at lower latitudes. Here we present the ion observations from the MESSENGER spacecraft at Mercury's <span class="hlt">cusp</span>, specifically focusing on ions latitudinally dispersed in energy. From these dispersions, the distance to the reconnection site is calculated and used to better understand the process of reconnection at Mercury's dayside magnetopause.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JHEP...09..138D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JHEP...09..138D"><span>Resurgence of the <span class="hlt">cusp</span> anomalous dimension</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dorigoni, Daniele; Hatsuda, Yasuyuki</p> <p>2015-09-01</p> <p>We revisit the strong coupling limit of the <span class="hlt">cusp</span> anomalous dimension in planar N=4 super Yang-Mills theory. It is known that the strong coupling expansion is asymptotic and non-Borel summable. As a consequence, the <span class="hlt">cusp</span> anomalous dimension receives non-perturbative corrections, and the complete strong coupling expansion should be a resurgent transseries. We reveal that the perturbative and non-perturbative parts in the transseries are closely interrelated. Solving the Beisert-Eden-Staudacher equation systematically, we analyze in detail the large order behavior in the strong coupling pertur- bative expansion and show that the non-perturbative information is indeed encoded there. An ambiguity of (lateral) Borel resummations of the perturbative expansion is precisely canceled by the contributions from the non-perturbative sectors, and the final result is real and unambiguous.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhA...49f5403A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhA...49f5403A"><span>The resurgence of the <span class="hlt">cusp</span> anomalous dimension</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aniceto, Inês</p> <p>2016-02-01</p> <p>This work addresses the resurgent properties of the <span class="hlt">cusp</span> anomalous dimension’s strong coupling expansion, obtained from the integral Beisert-Eden-Staudacher (BES) equation. This expansion is factorially divergent, and its first non-perturbative corrections are related to the mass gap of the O(6)σ -model. The factorial divergence can also be analyzed from a resurgence perspective. Building on the work of Basso and Korchemsky, a transseries ansatz for the <span class="hlt">cusp</span> anomalous dimension is proposed and the corresponding expected large-order behaviour studied. One finds non-perturbative phenomena in both the positive and negative real coupling directions, which need to be included to address the analyticity conditions coming from the BES equation. After checking the resurgence structure of the proposed transseries, it is shown that it naturally leads to an unambiguous resummation procedure, furthermore allowing for a strong/weak coupling interpolation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27938526','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27938526"><span>A <span class="hlt">Cusp</span> Catastrophe Model of Tax Behavior.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Katerelos, Ioannis; Varotsis, Nikolaos</p> <p>2017-01-01</p> <p>The paper addresses the timeless failure of the tax system in Greece despite its constant reform, highlighting the study of tax evasion phenomenon with a different approach. This study aims to assess tax behavior with a model of <span class="hlt">cusp</span> catastrophe, where fear and peer pressure are control parameters. The survey involved 320 taxpayers from the entire Greek territory. Mathematical study using linear analysis and catastrophe modelling showed that a non-linear system is dramatically better in representing tax behavior than is any linear model. Specifically, the <span class="hlt">Cusp</span> catastrophe model is much more accurate (R2 = .911) bettering the corresponding linear model (R2 = .003). These results strongly infer the conclusion that tax behavior in Greece might involve systemic uncertainty.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985GeoRL..12..469B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985GeoRL..12..469B"><span>Quasi-neutrality in the polar <span class="hlt">cusp</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burch, J. L.</p> <p>1985-07-01</p> <p>Data from the High Altitude Plasma Instrument on Dynamics Explorer have shown a remarkably close correspondence between the densities of suprathermal electrons and positive ions at altitudes between 16,000 and 23,000 km in the polar <span class="hlt">cusp</span>. It is argued that this quasi-neutrality results from an ambipolar electric field at the magnetopause, which allows the entry of magnetosheath electrons only to the extent required to balance the charge carried by the positive ions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......185R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......185R"><span>Understanding the <span class="hlt">formation</span> and evolution of early-type galaxies based on newly developed single-burst <span class="hlt">stellar</span> population synthesis models in the infrared</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roeck, Benjamin</p> <p>2015-12-01</p> <p> whole optical and infrared wavelength range between 3500 and 50000Å which are almost completely based on spectra of observed stars (apart from two gaps which were fitted with theoretical <span class="hlt">stellar</span> spectra) . We analyze the behaviour of the near-infrared (J - K) and the Spitzer ([3.6]-[4.5]) colour calculated from our models. For ages older than 3 Gyr, both colours depend only slightly on age and metallicity. However, for younger ages, both colours become redder which is caused by the asymptotic giant branch stars contributing significantly to the light in the infrared at ages between 0.1 and 3 Gyr. Furthermore, we find a satisfactory agreement between the optical and near-infrared colours measured from our models and the colours observed from various samples of globular clusters and early-type x galaxies. However, our model predictions are only able to reproduce correctly the Spitzer ([3.6]-[4.5]) colours of older, more massive galaxies that resemble a single-burst population. Younger, less massive and more metal-poor galaxies show redder colours than our models. This mismatch can be explained by a more extended star <span class="hlt">formation</span> history of these galaxies which includes a metal-poor or/and young population. The Spitzer ([3.6]-[4.5]) colours derived from our models also agree very well with those from most other models available in this wavelength range as long as they also correctly take into account a strong CO absorption band situated at 4.5 μm. The model predictions for colours in the near-infrared, such as (J - K), differ more between the different sets of models, depending on the underlying prescriptions for the asymptotic giant branch <span class="hlt">stellar</span> evolutionary phase. Compared to other authors, we adopt only a moderate contribution of asymptotic giant branch stars to our models. Our <span class="hlt">stellar</span> population models allow us also to determine mass-to-light ratios in different infrared bands. Consequently, we can confirm that the massto- light ratio determined in the Spitzer [3</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...844...64A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...844...64A"><span>Deadly Dark Matter <span class="hlt">Cusps</span> versus Faint and Extended Star Clusters: Eridanus II and Andromeda XXV</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amorisco, Nicola C.</p> <p>2017-07-01</p> <p>The recent detection of two faint and extended star clusters in the central regions of two Local Group dwarf galaxies, Eridanus II and Andromeda XXV, raises the question of whether clusters with such low densities can survive the tidal field of cold dark matter halos with central density <span class="hlt">cusps</span>. Using both analytic arguments and a suite of collisionless N-body simulations, I show that these clusters are extremely fragile and quickly disrupted in the presence of central <span class="hlt">cusps</span> ρ ˜ {r}-α with α ≳ 0.2. Furthermore, the scenario in which the clusters were originally more massive and sank to the center of the halo requires extreme fine tuning and does not naturally reproduce the observed systems. In turn, these clusters are long lived in cored halos, whose central regions are safe shelters for α ≲ 0.2. The only viable scenario for hosts that have preserved their primordial <span class="hlt">cusp</span> to the present time is that the clusters formed at rest at the bottom of the potential, which is easily tested by measurement of the clusters proper velocity within the host. This offers means to readily probe the central density profile of two dwarf galaxies as faint as {L}V˜ 5× {10}5 {L}⊙ and {L}V˜ 6× {10}4 {L}⊙ , in which <span class="hlt">stellar</span> feedback is unlikely to be effective.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22364333','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22364333"><span><span class="hlt">STELLAR</span> KINEMATICS AND STRUCTURAL PROPERTIES OF VIRGO CLUSTER DWARF EARLY-TYPE GALAXIES FROM THE SMAKCED PROJECT. III. ANGULAR MOMENTUM AND CONSTRAINTS ON <span class="hlt">FORMATION</span> SCENARIOS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Toloba, E.; Guhathakurta, P.; Peletier, R. F.; Emsellem, E.; Lisker, T.; Van de Ven, G.; Simon, J. D.; Adams, J. J.; Benson, A. J.; Falcón-Barroso, J.; Ryś, A.; Gorgas, J.; Hensler, G.; Janz, J.; Laurikainen, E.; Salo, H.; Paudel, S.</p> <p>2015-02-01</p> <p>We analyze the <span class="hlt">stellar</span> kinematics of 39 dwarf early-type galaxies (dEs) in the Virgo Cluster. Based on the specific <span class="hlt">stellar</span> angular momentum λ{sub Re} and the ellipticity, we find 11 slow rotators and 28 fast rotators. The fast rotators in the outer parts of the Virgo Cluster rotate significantly faster than fast rotators in the inner parts of the cluster. Moreover, 10 out of the 11 slow rotators are located in the inner 3° (D < 1 Mpc) of the cluster. The fast rotators contain subtle disk-like structures that are visible in high-pass filtered optical images, while the slow rotators do not exhibit these structures. In addition, two of the dEs have kinematically decoupled cores and four more have emission partially filling in the Balmer absorption lines. These properties suggest that Virgo Cluster dEs may have originated from late-type star-forming galaxies that were transformed by the environment after their infall into the cluster. The correlation between λ{sub Re} and the clustercentric distance can be explained by a scenario where low luminosity star-forming galaxies fall into the cluster, their gas is rapidly removed by ram-pressure stripping, although some of it can be retained in their core, their star <span class="hlt">formation</span> is quenched but their <span class="hlt">stellar</span> kinematics are preserved. After a long time in the cluster and several passes through its center, the galaxies are heated up and transformed into slow rotating dEs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21560401','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21560401"><span>UV-TO-FIR ANALYSIS OF SPITZER/IRAC SOURCES IN THE EXTENDED GROTH STRIP. II. PHOTOMETRIC REDSHIFTS, <span class="hlt">STELLAR</span> MASSES, AND STAR <span class="hlt">FORMATION</span> RATES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Barro, G.; Perez-Gonzalez, P. G.; Gallego, J.; Villar, V.; Zamorano, J.; Ashby, M. L. N.; Kajisawa, M.; Yamada, T.; Miyazaki, S.</p> <p>2011-04-01</p> <p>Based on the ultraviolet to far-infrared photometry already compiled and presented in a companion paper (Paper I), we present a detailed spectral energy distribution (SED) analysis of nearly 80,000 IRAC 3.6 + 4.5 {mu}m selected galaxies in the Extended Groth Strip. We estimate photometric redshifts, <span class="hlt">stellar</span> masses, and star <span class="hlt">formation</span> rates (SFRs) separately for each galaxy in this large sample. The catalog includes 76,936 sources with [3.6] {<=} 23.75 (85% completeness level of the IRAC survey) over 0.48 deg{sup 2}. The typical photometric redshift accuracy is {Delta}z/(1 + z) = 0.034, with a catastrophic outlier fraction of just 2%. We quantify the systematics introduced by the use of different <span class="hlt">stellar</span> population synthesis libraries and initial mass functions in the calculation of <span class="hlt">stellar</span> masses. We find systematic offsets ranging from 0.1 to 0.4 dex, with a typical scatter of 0.3 dex. We also provide UV- and IR-based SFRs for all sample galaxies, based on several sets of dust emission templates and SFR indicators. We evaluate the systematic differences and goodness of the different SFR estimations using the deep FIDEL 70 {mu}m data available in the Extended Groth Strip. Typical random uncertainties of the IR-bases SFRs are a factor of two, with non-negligible systematic effects at z {approx}> 1.5 observed when only MIPS 24 {mu}m data are available. All data products (SEDs, postage stamps from imaging data, and different estimations of the photometric redshifts, <span class="hlt">stellar</span> masses, and SFRs of each galaxy) described in this and the companion paper are publicly available, and they can be accessed through our the Web interface utility Rainbow-navigator.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22518605','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22518605"><span>EVIDENCE FOR NON-<span class="hlt">STELLAR</span> REST-FRAME NEAR-IR EMISSION ASSOCIATED WITH INCREASED STAR <span class="hlt">FORMATION</span> IN GALAXIES AT z ∼ 1</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lange, Johannes U.; Van Dokkum, Pieter G.; Momcheva, Ivelina G.; Nelson, Erica J.; Leja, Joel; Brammer, Gabriel; Whitaker, Katherine E.; Franx, Marijn</p> <p>2016-03-01</p> <p>We explore the presence of non-<span class="hlt">stellar</span> rest-frame near-IR (2–5 μm) emission in galaxies at z ∼ 1. Previous studies identified this excess in relatively small samples and suggested that such non-<span class="hlt">stellar</span> emission, which could be linked to the 3.3 μm polycyclic aromatic hydrocarbons feature or hot dust emission, is associated with an increased star <span class="hlt">formation</span> rate (SFR). In this Letter, we confirm and quantify the presence of an IR excess in a significant fraction of galaxies in the 3D-HST GOODS catalogs. By constructing a matched sample of galaxies with and without strong non-<span class="hlt">stellar</span> near-IR emission, we find that galaxies with such emission are predominantly star-forming galaxies. Moreover, star-forming galaxies with an excess show increased mid- and far-IR and Hα emission compared to other star-forming galaxies without. While galaxies with a near-IR excess show a larger fraction of individually detected X-ray active galactic nuclei (AGNs), an X-ray stacking analysis, together with the IR-colors and Hα profiles, shows that AGNs are unlikely to be the dominant source of excess in the majority of galaxies. Our results suggest that non-<span class="hlt">stellar</span> near-IR emission is linked to increased SFRs and is ubiquitous among star-forming galaxies. As such, the near-IR emission might be a powerful tool to measure SFRs in the era of the James Webb Space Telescope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvD..96f3014I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvD..96f3014I"><span>Probing <span class="hlt">stellar</span> binary black hole <span class="hlt">formation</span> in galactic nuclei via the imprint of their center of mass acceleration on their gravitational wave signal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Inayoshi, Kohei; Tamanini, Nicola; Caprini, Chiara; Haiman, Zoltán</p> <p>2017-09-01</p> <p>Multifrequency gravitational wave (GW) observations are useful probes of the <span class="hlt">formation</span> processes of coalescing <span class="hlt">stellar</span>-mass binary black holes (BBHs). We discuss the phase drift in the GW inspiral waveform of the merging BBH caused by its center-of-mass acceleration. The acceleration strongly depends on the location where a BBH forms within a galaxy, allowing observations of the early inspiral phase of Laser Interferometer Gravitational Wave Observatory (LIGO)-like BBH mergers by the Laser Interferometer Space Antenna (LISA) to test the <span class="hlt">formation</span> mechanism. In particular, BBHs formed in dense nuclear star clusters or via compact accretion disks around a nuclear supermassive black hole in active galactic nuclei would suffer strong acceleration, and produce large phase drifts measurable by LISA. The host galaxies of the coalescing BBHs in these scenarios can also be uniquely identified in the LISA error volume, without electromagnetic counterparts. A nondetection of phase drifts would rule out or constrain the contribution of the nuclear <span class="hlt">formation</span> channels to the <span class="hlt">stellar</span>-mass BBH population.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...838...87C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...838...87C"><span>PRIMUS+DEEP2: The Dependence of Galaxy Clustering on <span class="hlt">Stellar</span> Mass and Specific Star <span class="hlt">Formation</span> Rate at 0.2 < z < 1.2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coil, Alison L.; Mendez, Alexander J.; Eisenstein, Daniel J.; Moustakas, John</p> <p>2017-04-01</p> <p>We present results on the clustering properties of galaxies as a function of both <span class="hlt">stellar</span> mass and specific star <span class="hlt">formation</span> rate (sSFR) using data from the PRIMUS and DEEP2 galaxy redshift surveys spanning 0.2< z< 1.2. We use spectroscopic redshifts of over 100,000 galaxies covering an area of 7.2 deg2 over five separate fields on the sky, from which we calculate cosmic variance errors. We find that the galaxy clustering amplitude is as strong of a function of sSFR as of <span class="hlt">stellar</span> mass, and that at a given sSFR, it does not significantly depend on <span class="hlt">stellar</span> mass within the range probed here. We further find that within the star-forming population and at a given <span class="hlt">stellar</span> mass, galaxies above the main sequence of star <span class="hlt">formation</span> with higher sSFR are less clustered than galaxies below the main sequence with lower sSFR. We also find that within the quiescent population, galaxies with higher sSFR are less clustered than galaxies with lower sSFR, at a given <span class="hlt">stellar</span> mass. We show that the galaxy clustering amplitude smoothly increases with both increasing <span class="hlt">stellar</span> mass and decreasing sSFR, implying that galaxies likely evolve across the main sequence, not only along it, before galaxies eventually become quiescent. These results imply that the relation of <span class="hlt">stellar</span> mass to halo mass, which connects galaxies to dark matter halos, likely depends on sSFR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1016568','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1016568"><span>Characterization of a Diverging <span class="hlt">Cusped</span> Field Thruster Operating on Krypton</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2014-11-04</p> <p>Charts 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Characterization of a Diverging <span class="hlt">Cusped</span> Field Thruster Operating on Krypton 5a. CONTRACT...Tuesday, November 4, 2014 Characterization of a  Diverging <span class="hlt">Cusped</span> Field Thruster  Operating on  Krypton DISTRIBUTION A: Approved for public release...distribution unlimited. AFTC/PA Clearance No. 14511 Outline • Motivation for using krypton • Diverging <span class="hlt">Cusped</span> Field Thruster (DCFT) – Operation on krypton</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...562A...1P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...562A...1P"><span>Evolution of the mass, size, and star <span class="hlt">formation</span> rate in high redshift merging galaxies. MIRAGE - A new sample of simulations with detailed <span class="hlt">stellar</span> feedback</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perret, V.; Renaud, F.; Epinat, B.; Amram, P.; Bournaud, F.; Contini, T.; Teyssier, R.; Lambert, J.-C.</p> <p>2014-02-01</p> <p>Context. In Λ-CDM models, galaxies are thought to grow both through continuous cold gas accretion coming from the cosmic web and episodic merger events. The relative importance of these different mechanisms at different cosmic epochs is nevertheless not yet understood well. Aims: We aim to address questions related to galaxy mass assembly through major and minor wet merging processes in the redshift range 1 < z < 2, an epoch that corresponds to the peak of cosmic star <span class="hlt">formation</span> history. A significant fraction of Milky Way-like galaxies are thought to have undergone an unstable clumpy phase at this early stage. We focus on the behavior of the young clumpy disks when galaxies are undergoing gas-rich galaxy mergers. Methods: Using the adaptive mesh-refinement code RAMSES, we build the Merging and Isolated high redshift Adaptive mesh refinement Galaxies (MIRAGE) sample. It is composed of 20 mergers and 3 isolated idealized disks simulations, which sample disk orientations and merger masses. Our simulations can reach a physical resolution of 7 parsecs, and include star <span class="hlt">formation</span>, metal line cooling, metallicity advection, and a recent physically-motivated implementation of <span class="hlt">stellar</span> feedback that encompasses OB-type stars radiative pressure, photo-ionization heating, and supernovae. Results: The star <span class="hlt">formation</span> history of isolated disks shows a stochastic star <span class="hlt">formation</span> rate, which proceeds from the complex behavior of the giant clumps. Our minor and major gas-rich merger simulations do not trigger starbursts, suggesting a saturation of the star <span class="hlt">formation</span> due to the detailed accounting of <span class="hlt">stellar</span> feedback processes in a turbulent and clumpy interstellar medium fed by substantial accretion from the circumgalactic medium. Our simulations are close to the normal regime of the disk-like star <span class="hlt">formation</span> on a Schmidt-Kennicutt diagram. The mass-size relation and its rate of evolution in the redshift range 1 < z < 2 matches observations, suggesting that the inside-out growth</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22167089','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22167089"><span>KECK SPECTROSCOPY OF 3 < z < 7 FAINT LYMAN BREAK GALAXIES: THE IMPORTANCE OF NEBULAR EMISSION IN UNDERSTANDING THE SPECIFIC STAR <span class="hlt">FORMATION</span> RATE AND <span class="hlt">STELLAR</span> MASS DENSITY</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Stark, Daniel P.; Robertson, Brant; Schenker, Matthew A.; Ellis, Richard; McLure, Ross; Dunlop, James</p> <p>2013-02-15</p> <p>The physical properties inferred from the spectral energy distributions (SEDs) of z > 3 galaxies have been influential in shaping our understanding of early galaxy <span class="hlt">formation</span> and the role galaxies may play in cosmic reionization. Of particular importance is the <span class="hlt">stellar</span> mass density at early times, which represents the integral of earlier star <span class="hlt">formation</span>. An important puzzle arising from the measurements so far reported is that the specific star <span class="hlt">formation</span> rates (sSFRs) evolve far less rapidly than expected in most theoretical models. Yet the observations underpinning these results remain very uncertain, owing in part to the possible contamination of rest-optical broadband light from strong nebular emission lines. To quantify the contribution of nebular emission to broadband fluxes, we investigate the SEDs of 92 spectroscopically confirmed galaxies in the redshift range 3.8 < z < 5.0 chosen because the H{alpha} line lies within the Spitzer/IRAC 3.6 {mu}m filter. We demonstrate that the 3.6 {mu}m flux is systematically in excess of that expected from <span class="hlt">stellar</span> continuum alone, which we derive by fitting the SED with population synthesis models. No such excess is seen in a control sample of spectroscopically confirmed galaxies with 3.1 < z < 3.6 in which there is no nebular contamination in the IRAC filters. From the distribution of our 3.6 {mu}m flux excesses, we derive an H{alpha} equivalent width distribution and consider the implications for both the derived <span class="hlt">stellar</span> masses and the sSFR evolution. The mean rest-frame H{alpha} equivalent width we infer at 3.8 < z < 5.0 (270 A) indicates that nebular emission contributes at least 30% of the 3.6 {mu}m flux and, by implication, nebular emission is likely to have a much greater impact for galaxies with z {approx_equal} 6-7 where both warm IRAC filters are contaminated. Via our empirically derived equivalent width distribution, we correct the available <span class="hlt">stellar</span> mass densities and show that the sSFR evolves more rapidly at z</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012MNRAS.426.1632P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012MNRAS.426.1632P"><span>The role of <span class="hlt">stellar</span> mass and environment for cluster blue fraction, AGN fraction and star <span class="hlt">formation</span> indicators from a targeted analysis of Abell 1691</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pimbblet, Kevin A.; Jensen, Peter C.</p> <p>2012-10-01</p> <p>We present an analysis of the galaxy population of the intermediate X-ray luminosity galaxy cluster, Abell 1691, from Sloan Digital Sky Survey (SDSS) and Galaxy Zoo data to elucidate the relationships between environment and galaxy <span class="hlt">stellar</span> mass for a variety of observationally important cluster populations that include the Butcher-Oemler blue fraction, the active galactic nucleus (AGN) fraction and other spectroscopic classifications of galaxies. From 342 cluster members, we determine a cluster recession velocity of 21257 ± 54 km s-1 and velocity dispersion of 1009-36+40 km s-1 and show that although the cluster is fed by multiple filaments of galaxies it does not possess significant sub-structure in its core. We identify the AGN population of the cluster from a Baldwin, Phillips & Terlevich diagram and show that there is a mild increase in the AGN fraction with radius from the cluster centre that appears mainly driven by high-mass galaxies [log(<span class="hlt">stellar</span> mass) > 10.8]. Although the cluster blue fraction follows the same radial trend, it is caused primarily by lower mass galaxies [log(<span class="hlt">stellar</span> mass) < 10.8]. Significantly, the galaxies that have undergone recent starbursts or are presently starbursting but dust-shrouded [spectroscopic e(a) class galaxies] are also nearly exclusively driven by low-mass galaxies. We therefore suggest that the Butcher-Oemler effect may be a mass-dependent effect. We also examine red and passive spiral galaxies and show that the majority are massive galaxies, much like the rest of the red and spectroscopically passive cluster population. We further demonstrate that the velocity dispersion profiles of low- and high-mass cluster galaxies are different. Taken together, we infer that the duty cycle of high- and low-mass cluster galaxies is markedly different, with a significant departure in star <span class="hlt">formation</span> and specific star <span class="hlt">formation</span> rates observed beyond r200 and we discuss these findings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EP%26S...64...93F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EP%26S...64...93F"><span>On wind-driven electrojets at magnetic <span class="hlt">cusps</span> in the nightside ionosphere of Mars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fillingim, M. O.; Lillis, R. J.; England, S. L.; Peticolas, L. M.; Brain, D. A.; Halekas, J. S.; Paty, C.; Lummerzheim, D.; Bougher, S. W.</p> <p>2012-02-01</p> <p>Mars has a complex magnetic topology where crustal magnetic fields can interact with the solar wind magnetic field to form magnetic <span class="hlt">cusps</span>. On the nightside, solar wind electron precipitation can produce enhanced ionization at <span class="hlt">cusps</span> while closed field regions adjacent to <span class="hlt">cusps</span> can be devoid of significant ionization. Using an electron transport model, we calculate the spatial structure of the nightside ionosphere of Mars using Mars Global Surveyor electron measurements as input. We find that localized regions of enhanced ionospheric density can occur at magnetic <span class="hlt">cusps</span> adjacent to low density regions. Under this configuration, thermospheric winds can drive ionospheric electrojets. Collisional ions move in the direction of the neutral winds while magnetized electrons move perpendicular to the wind direction. This difference in motion drives currents and can lead to charge accumulation at the edges of regions of enhanced ionization. Polarization fields drive secondary currents which can reinforce the primary currents leading to electrojet <span class="hlt">formation</span>. We estimate the magnitude of these electrojets and show that their magnetic perturbations can be detectable from both orbiting spacecraft and the surface. The magnitude of the electrojets can vary on diurnal and annual time scales as the strength and direction of the winds vary. These electrojets may lead to localized Joule heating, and closure of these currents may require field-aligned currents which may play a role in high altitude acceleration processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM31E4248M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM31E4248M"><span>Plasma Instability Growth Rates in the F-Region <span class="hlt">Cusp</span> Ionosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moen, J. I.; Daabakk, Y.; Oksavik, K.; Clausen, L.; Bekkeng, T. A.; Abe, T.; Saito, Y.; Baddeley, L. J.; Lorentzen, D. A.; Sigernes, F.; Yeoman, T. K.</p> <p>2014-12-01</p> <p>There are at least two different micro-instability processes that applies to the F-region <span class="hlt">cusp</span>/polar cap ionosphere. These are the Gradient Drift Instability (GDI) and the Kelvin Helmholtz Instability (KHI). Due to space weather effects on radio communication and satellite signals it is of practical interest to assess the relative importance of these two instability modes and to quantify their growth rates. The Investigation of <span class="hlt">Cusp</span> Irregularities (ICI) rocket program has been developed to investigate these plasma instabilities and <span class="hlt">formation</span> scintillation irregularities. High resolution measurements are critical to get realistic quantities on the growth rates. The results achieved so far demonstrates that <span class="hlt">cusp</span> ionosphere precipitation can give rise to km scale plasma structures on which grow rates are down to a few tens of seconds compared to earlier measures of ten minutes based on ground observations. This has to do with the spatial resolution required for these measurements. Growth rates for the KHI instability is found to be of the same order, which is consistent with growth rates calculated from the EISCAT Svalbard Radar. I.e. both instability modes can be highly efficient in the <span class="hlt">cusp</span> ionosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10815590','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10815590"><span>Mandibular talon <span class="hlt">cusp</span>: report of two rare cases.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hegde, S; Kumar, B R</p> <p>1999-12-01</p> <p>Two rare cases of talon <span class="hlt">cusps</span> in the mandibular incisors were observed during a prevalence study on talon <span class="hlt">cusp</span>. One of them was seen on a mandibular primary lateral incisor. The other one was observed on the mandibular left permanent central incisor, and the right mandibular permanent central incisor was congenitally missing. There were no associated developmental syndromes with either of the cases reported. Of the 4770 children examined, nine cases had talon <span class="hlt">cusp</span> with only two rare cases of mandibular talon <span class="hlt">cusp</span>, one in the primary dentition and the other in the permanent dentition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16215568','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16215568"><span>An unusual presentation of talon <span class="hlt">cusp</span>: a case report.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sumer, A P; Zengin, A Z</p> <p>2005-10-08</p> <p>The talon <span class="hlt">cusp</span> is a relatively rare dental developmental anomaly characterised by <span class="hlt">cusp</span>-like projections, usually observed on the lingual surface of the affected tooth. Normal enamel covers the <span class="hlt">cusp</span> and fuses with the lingual aspect of the tooth. The <span class="hlt">cusp</span> may or may not contain an extension of the pulp. This occurs in either maxillary or mandibular anterior teeth in both the primary and permanent dentition. This study reports the unusual case of a 47-year-old female with a taloned tooth on the right maxillary central incisor possessing both lingual and labial talons, with an x-shaped appearance when viewed occlusally.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980218788','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980218788"><span>Particle Detectors and Data Analysis for <span class="hlt">Cusp</span> Transient Features Campaign</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sharber, J. R.</p> <p>1998-01-01</p> <p>Grant NAG5-5084 was awarded to support the participation of South West Research Institute (SwRI) in building the energy per unit charge particle detectors for the <span class="hlt">Cusp</span> Transient Features Campaign and analysis of flight data from these instruments. The detectors are part of an instrumented payload (Rocket 36.152, Dr. R. Pfaff, P.I.) launched from Svalbard on December 3, 1997, into the dark <span class="hlt">cusp</span>. The particle instruments, a <span class="hlt">Cusp</span> Electron Detector (CED) and a <span class="hlt">Cusp</span> Ion Detector (CID), built on this project, provided differential energy and angular measurements along the rocket trajectory throughout the flight.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MPLA...3050210C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MPLA...3050210C"><span>Predicting <span class="hlt">cusps</span> or kinks in Nambu-Goto dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cervantes, Aldrin; García-Aspeitia, Miguel A.</p> <p>2015-11-01</p> <p>It is known that Nambu-Goto extended objects present some pathological structures, such as <span class="hlt">cusps</span> and kinks, during their evolution. In this paper, we propose a model through the generalized Raychaudhuri (Rh) equation for membranes to determine if there are <span class="hlt">cusps</span> and kinks in the worldsheet. We extend the generalized Rh equation for membranes to allow the study of the effect of higher order curvature terms in the action on the issue of <span class="hlt">cusps</span> and kinks, using it as a tool for determining when a Nambu-Goto string generates <span class="hlt">cusps</span> or kinks in its evolution. Furthermore, we present three examples where we test graphically this approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920059353&hterms=polar+analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dpolar%2Banalysis','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920059353&hterms=polar+analysis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dpolar%2Banalysis"><span>Neptune's polar <span class="hlt">cusp</span> region - Observations and magnetic field analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lepping, R. P.; Burlaga, L. F.; Lazarus, A. J.; Vasyliunas, V. M.; Szabo, A.; Steinberg, J.; Ness, N. F.; Krimigis, S. M.</p> <p>1992-01-01</p> <p>This paper confirms and extends the results of Szabo et al. (1991) (which demonstrated some similarities of the Neptune's polar <span class="hlt">cusp</span> region to the earth's <span class="hlt">cusp</span>), but uses a different approach requiring plasma and vector magnetic field quantities. In addition, various MHD properties of the <span class="hlt">cusp</span>-magnetopause boundary, which separates the <span class="hlt">cusp</span> from the magnetosheath allowing thermal anisotropy, are obtained, including the magnetopause (MP) normal, mass, and normal momentum flux, the boundary speed (and thickness), and their relationships. Results demonstrate that the MP velocity is composed of two components: a propagation speed and the other component consistent with the rotational motion of the magnetosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22342099','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22342099"><span>The relationship between <span class="hlt">stellar</span> mass, gas metallicity, and star <span class="hlt">formation</span> rate for Hα-selected galaxies at z ≈ 0.8 from the NewHα survey</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Reyes, Mithi A. de los; Ly, Chun; Lee, Janice C.; Peeples, Molly S.; Feddersen, Jesse; Salim, Samir; Momcheva, Ivelina; Dale, Daniel A.; Ouchi, Masami; Ono, Yoshiaki; Finn, Rose</p> <p>2015-02-01</p> <p>Using a sample of 299 Hα-selected galaxies at z≈0.8, we study the relationship between galaxy <span class="hlt">stellar</span> mass, gas-phase metallicity, and star <span class="hlt">formation</span> rate (SFR), and compare to previous results. We use deep optical spectra obtained with the IMACS spectrograph at the Magellan telescope to measure strong oxygen lines. We combine these spectra and metallicities with (1) rest-frame UV-to-optical imaging, which allows us to determine <span class="hlt">stellar</span> masses and dust attenuation corrections, and (2) Hα narrowband imaging, which provides a robust measurement of the instantaneous SFR. Our sample spans <span class="hlt">stellar</span> masses of ∼10{sup 9}–6 × 10{sup 11} M{sub ⊙}, SFRs of 0.4–270 M{sub ⊙} yr{sup −1}, and metal abundances of 12+log(O/H)≈8.3–9.1 (≈0.4–2.6 Z{sub ⊙}). The correlations that we find between the Hα-based SFR and <span class="hlt">stellar</span> mass (i.e., the star-forming “main sequence”) and between the <span class="hlt">stellar</span> mass and metallicity are both consistent with previous z∼1 studies of star-forming galaxies. We then study the relationship between the three properties using various plane-fitting techniques and a curve-fitting projection. In all cases, we exclude strong dependence of the M{sub ⋆}–Z relation on SFR, but are unable to distinguish between moderate and no dependence. Our results are consistent with previous mass–metallicity–SFR studies. We check whether data set limitations may obscure a strong dependence on the SFR by using mock samples drawn from the Sloan Digital Sky Survey. These experiments reveal that the adopted signal-to-noise ratio cuts may have a significant effect on the measured dependence. Further work is needed to investigate these results, and to test whether a “fundamental metallicity relation” or a “fundamental plane” describes star-forming galaxies across cosmic time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21301544','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21301544"><span>A PUBLIC CATALOG OF <span class="hlt">STELLAR</span> MASSES, STAR <span class="hlt">FORMATION</span> AND METALLICITY HISTORIES, AND DUST CONTENT FROM THE SLOAN DIGITAL SKY SURVEY USING VESPA</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tojeiro, Rita; Wilkins, Stephen; Heavens, Alan F.; Panter, Ben; Jimenez, Raul</p> <p>2009-11-01</p> <p>We applied the VESPA algorithm to the Sloan Digital Sky Survey final data release of the Main Galaxies and Luminous Red Galaxies samples. The result is a catalog of <span class="hlt">stellar</span> masses, detailed star <span class="hlt">formation</span> and metallicity histories and dust content of nearly 800,000 galaxies. We make the catalog public via a T-SQL database, which is described in detail in this paper. We present the results using a range of <span class="hlt">stellar</span> population and dust models, and will continue to update the catalog as new and improved models are made public. We also present a brief exploration of the catalog, and show that the quantities derived are robust: luminous red galaxies can be described by one to three populations, whereas a main galaxy sample galaxy needs on average two to five; red galaxies are older and less dusty; the dust values we recover are well correlated with measured Balmer decrements and star <span class="hlt">formation</span> rates are also in agreement with previous measurements. We find that whereas some derived quantities are robust to the choice of modelling, many are still not.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AAS...22915405F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AAS...22915405F"><span><span class="hlt">Stellar</span> Evolution of the Star Cluster NGC 602 and Massive Star <span class="hlt">Formation</span> in the Low-Density Wing of the SMC</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fulmer, Leah; Oskinova, Lida; Ramachandran, Varsha; Hamann, Wolf-Rainer; Gallagher, John S.</p> <p>2017-01-01</p> <p>The young star cluster NGC 602 and its surroundings in the Wing of the Small Magellanic Cloud (SMC) exhibit active star <span class="hlt">formation</span> despite the sparse supply of dense gas from which to form stars. This region is also associated with the huge ionized gas ring DEM167 in the SMC. Using archival optical photometric data from the Uppsala Schmidt Telescope and new near-UV photometric data from the Galaxy Evolution Explorer, we determine the colors and consequently the relative ages of ~1000 stars in this region. Furthermore, we incorporate spectra obtained with the ESO-VLT to more accurately determine the properties of luminous massive stars. These measurements are combined to explore the recent star <span class="hlt">formation</span> history of this region near the tip of the SMC and to study how the young <span class="hlt">stellar</span> populations relate to the ISM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/40277115','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/40277115"><span>Corners, <span class="hlt">Cusps</span>, and Pearls in Running Drops</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Podgorski, T.; Flesselles, J.-M.; Limat, L.</p> <p>2001-07-16</p> <p>Small drops sliding down a partially wetting substrate bifurcate between different shapes depending on their capillary number Ca . At low Ca , they are delimited by a rounded, smooth contact line. At intermediate values they develop a corner at the trailing edge, the angle of which evolves from flat to 60{sup o} with increasing velocity. Further up, they exhibit a <span class="hlt">cusped</span> tail that emits smaller drops (''pearls''). These bifurcations may be qualitatively and quantitatively recovered by considering the dynamic contact angle along the contact line.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT........36M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT........36M"><span>Plasma Structure and Behavior of Miniature Ring-<span class="hlt">Cusp</span> Discharges</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mao, Hann-Shin</p> <p></p> <p>Miniature ring-<span class="hlt">cusp</span> ion thrusters provide a unique blend of high efficiencies and millinewton level thrust for future spacecraft. These thrusters are attractive as a primary propulsion for small satellites that require a high delta V, and as a secondary propulsion for larger spacecraft that require precision <span class="hlt">formation</span> flying, disturbance rejection, or attitude control. To ensure desirable performance throughout the life of such missions, an advancement in the understanding of the plasma structure and behavior of miniature ring-<span class="hlt">cusp</span> discharges is required. A research model was fabricated to provide a simplified experimental test bed for the analysis of the plasma discharge chamber of a miniature ion thruster. The plasma source allowed for spatially resolved measurements with a Langmuir probe along a meridian plane. Probe measurements yielded plasma density, electron temperature, and plasma potential data. The magnetic field strength was varied along with the discharge current to determine the plasma behavior under various conditions. The structure of the plasma properties were found to be independent of the discharge power under the proper scaling. It was concluded that weaker magnetic fields can improve the overall performance for ion thruster operation. To further analyze the experimental measurements, a framework was developed based on the magnetic field. A flux aligned coordinate system was developed to decouple the perpendicular and parallel plasma motion with respect to the magnetic field. This was done using the stream function and magnetic scalar potential. Magnetic formulae provided intuition on the field profiles dependence on magnet dimensions. The flux aligned coordinate system showed that the plasma was isopycnic along constant stream function values. This was used to develop an empirical relation suitable for estimating the spatial behavior and to determine the plasma volume and loss areas. The plasma geometry estimates were applied to a control volume</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ASSP...36..373L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ASSP...36..373L"><span>Molecular Gas in the Inner 500 pc of the Milky Way: Violating Star <span class="hlt">Formation</span> Relations and on the Verge of Forming Extreme <span class="hlt">Stellar</span> Clusters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Longmore, Steven N.</p> <p></p> <p>With the HOPS, MALT90 and HiGAL Galactic plane surveys we are mapping a significant fraction of the dense, star-forming, molecular gas in the Galaxy. I present results from two projects based on this combined dataset, namely, (i) looking for variations in the star <span class="hlt">formation</span> (SF) rate across the Galaxy as a function of environment, and (ii) searching for molecular cloud progenitors of the most extreme (massive and dense) <span class="hlt">stellar</span> clusters. We find the SF rate per unit mass of dense gas in the inner 500 pc of the Galaxy is at least an order of magnitude lower than that in the disk, directly challenging the predictions of proposed universal column/volume density relations. In particular, the region 1∘ < l < 3. 5∘, | b | < 0. 5∘ contains ˜ 107 M⊙ of dense molecular gas—enough to form 1,000 Orion-like clusters—but the present-day star <span class="hlt">formation</span> rate within this gas is only equivalent to that in Orion. I present follow up studies of one molecular cloud we have studied as part of project (ii) which also lies in the inner 500 pc of the Galaxy and is clearly extreme compared to the rest of the Galactic population. With a mass of 105 Msun, a radius of only ˜ 3 pc and almost no signs of star <span class="hlt">formation</span> it appears to be the progenitor of an Arches-like <span class="hlt">stellar</span> cluster. Despite detailed observational follow-up searches, this object still appears to be unique in the Galaxy, making it extremely important for testing massive cluster <span class="hlt">formation</span> models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001ApJ...563..527G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001ApJ...563..527G"><span>Ultraluminous Infrared Mergers: Elliptical Galaxies in <span class="hlt">Formation</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Genzel, R.; Tacconi, L. J.; Rigopoulou, D.; Lutz, D.; Tecza, M.</p> <p>2001-12-01</p> <p>We report high-quality near-IR spectroscopy of 12 ultraluminous infrared galaxy mergers (ULIRGs). Our new VLT and Keck data provide ~0.5" resolution, <span class="hlt">stellar</span> and gas kinematics of these galaxies, most of which are compact systems in the last merger stages. We confirm that ULIRG mergers are ``ellipticals in <span class="hlt">formation</span>.'' Random motions dominate their <span class="hlt">stellar</span> dynamics, but significant rotation is common. Gasdynamics and <span class="hlt">stellar</span> dynamics are decoupled in most systems. ULIRGs fall on or near the fundamental plane of hot <span class="hlt">stellar</span> systems, and especially on its less evolution-sensitive, reff-σ projection. The ULIRG velocity dispersion distribution, their location in the fundamental plane, and their distribution of vrotsini/σ closely resemble those of intermediate-mass (~L*), elliptical galaxies with moderate rotation. As a group ULIRGs do not resemble giant ellipticals with large cores and little rotation. Our results are in good agreement with other recent studies indicating that disky ellipticals with compact cores or <span class="hlt">cusps</span> can form through dissipative mergers of gas-rich disk galaxies while giant ellipticals with large cores have a different <span class="hlt">formation</span> history. Based on observations at the European Southern Observatory, Chile (ESO 65.N-0266, 65.N-0289), and on observations at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, The University of California, and the National Aeronautics and Space Administration. The Keck Observatory was made possible by the general financial support by the W. M. Keck Foundation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...827....9C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...827....9C"><span>Pixel Color Magnitude Diagrams for Semi-resolved <span class="hlt">Stellar</span> Populations: The Star <span class="hlt">Formation</span> History of Regions within the Disk and Bulge of M31</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Conroy, Charlie; van Dokkum, Pieter G.</p> <p>2016-08-01</p> <p>The analysis of <span class="hlt">stellar</span> populations has, by and large, been developed for two limiting cases: spatially resolved <span class="hlt">stellar</span> populations in the color-magnitude diagram, and integrated light observations of distant systems. In between these two extremes lies the semi-resolved regime, which encompasses a rich and relatively unexplored realm of observational phenomena. Here we develop the concept of pixel color-magnitude diagrams (pCMDs) as a powerful technique for analyzing <span class="hlt">stellar</span> populations in the semi-resolved regime. pCMDs show the distribution of imaging data in the plane of pixel luminosity versus pixel color. A key feature of pCMDs is that they are sensitive to all stars, including both the evolved giants and the unevolved main sequence stars. An important variable in this regime is the mean number of stars per pixel, {N}{{pix}}. Simulated pCMDs demonstrate a strong sensitivity to the star <span class="hlt">formation</span> history (SFH) and have the potential to break degeneracies between age, metallicity and dust based on two filter data for values of {N}{{pix}} up to at least 104. We extract pCMDs from Hubble Space Telescope optical imaging of M31 and derive SFHs with seven independent age bins from 106 to 1010 year for both the crowded disk and bulge regions (where {N}{{pix}}≈ 30{--}{10}3). From analyzing a small region of the disk we find a SFH that is smooth and consistent with an exponential decay timescale of 4 Gyr. The bulge SFH is also smooth and consistent with a 2 Gyr decay timescale. pCMDs will likely play an important role in maximizing the science returns from next generation ground and space-based facilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810003461','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810003461"><span><span class="hlt">Stellar</span> chromospheres</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Linsky, J. L.</p> <p>1980-01-01</p> <p>Developments in the understanding and use of chromospheric diagnostics are discussed with emphasis on the following aspects: (1) trends emerging from semiempirical models of single stars; (2) the validity of claims that theoretical models of chromospheres are becoming realistic; (3) the correlation between the widths of Ca 2 H and K line emission cores and <span class="hlt">stellar</span> absolute luminosity extending over 15 magnitudes (Wilson-Bappu relation); and (4) the existence of systematic flow patterns in <span class="hlt">stellar</span> chromospheres.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5014065','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5014065"><span>On the evolutionary advantage of multi-<span class="hlt">cusped</span> teeth</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bush, Mark B.; Barani, Amir; Lawn, Brian R.</p> <p>2016-01-01</p> <p>A hallmark of mammalian evolution is a progressive complexity in postcanine tooth morphology. However, the driving force for this complexity remains unclear: whether to expand the versatility in diet source, or to bolster tooth structural integrity. In this study, we take a quantitative approach to this question by examining the roles of number, position and height of multiple <span class="hlt">cusps</span> in determining sustainable bite forces. Our approach is to use an extended finite-element methodology with due provision for step-by-step growth of an embedded crack to determine how fracture progresses with increasing occlusal load. We argue that multi-<span class="hlt">cusp</span> postcanine teeth are well configured to withstand high bite forces provided that multiple <span class="hlt">cusps</span> are contacted simultaneously to share the load. However, contact on a single near-wall <span class="hlt">cusp</span> diminishes the strength. Location of the load points and <span class="hlt">cusp</span> height, rather than <span class="hlt">cusp</span> number or radius, are principal governing factors. Given these findings, we conclude that while complex tooth structures can enhance durability, increases in <span class="hlt">cusp</span> number are more likely to be driven by the demands of food manipulation. Structural integrity of complex teeth is maintained when individual <span class="hlt">cusps</span> remain sufficiently distant from the side walls and do not become excessively tall relative to tooth width. PMID:27558851</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AcPPB..39.3127K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AcPPB..39.3127K"><span><span class="hlt">Cusp</span> Anomalous Dimension in Maximally Supersymmetric Yang-Mills Theory</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kotanski, J.</p> <p>2008-12-01</p> <p>The main features of the <span class="hlt">cusp</span> anomalous dimension in N=4 supersymmetric Yang-Mills theory are reviewed. Moreover, the strong coupling expansion of the <span class="hlt">cusp</span> derived in B. Basso, G.P. Korchemsky, J. Kotanski, Phys. Rev. Lett. 100, 091601 (2008) is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22322022','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22322022"><span>A talon <span class="hlt">cusp</span> mistaken for a mesiodens: case report.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gosselin, Marie-Lyne; Doyle, Tracy; MacLellan, Jennifer; Anderson, Ross D; Dyment, Heather</p> <p>2012-01-01</p> <p>We present the case of an 8-year-old boy with a talon <span class="hlt">cusp</span> associated with a permanent maxillary central incisor that was mistaken for a supernumerary tooth. The importance of early and correct diagnosis of a talon <span class="hlt">cusp</span> is stressed. Diagnosis and treatment planning strategies are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.P41A1600W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.P41A1600W"><span>Observations of Mercury's Northern <span class="hlt">Cusp</span> Region with MESSENGER's Magnetometer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Winslow, R. M.; Johnson, C. L.; Anderson, B. J.; Korth, H.; Slavin, J. A.; Purucker, M. E.; Solomon, S. C.</p> <p>2011-12-01</p> <p>We have identified Mercury's northern <span class="hlt">cusp</span> region from orbital observations with the Magnetometer on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. The <span class="hlt">cusp</span> is identified from the dayside depression in the total magnetic field after removing the field predicted by a paraboloid magnetospheric model from the data. The model includes long-wavelength fields due to the internal dipole, the magnetopause, and the magnetotail, parameterized by a dipole moment of 195 nT-RM3 (where RM is Mercury's radius), offset northward from the planetary center by 484 km and aligned with the planet's spin axis, a paraboloidal magnetopause with a subsolar standoff distance of 1.4 RM, a distance to the inner edge of the tail current sheet of 1.43 RM, a tail current sheet half-width of 0.1 RM, and tail lobe field of 100 nT. We have confirmed that the <span class="hlt">cusp</span> identification is robust with respect to changes in the parameters in the baseline magnetospheric model. An increase in the high-frequency (1-10 Hz) variability of the magnetic field is also observed on each pass at these times. A superposed epoch analysis, in which individual profiles are aligned in time on their respective <span class="hlt">cusp</span> midpoints and stacked, indicates that on average the latitudinal extent of the <span class="hlt">cusp</span> region is 11°, centered on 71.2° N. <span class="hlt">Cusp</span> observations extend in local time from 7.1 hr to 17.1 hr. The minimum southerly latitude of the <span class="hlt">cusp</span> observed to date is 56.5° N, and the maximum is 83.1° N. The general location and dimensions of the high-latitude <span class="hlt">cusp</span> region are in agreement with those indicated by observations with MESSENGER'S Fast Imaging Plasma Spectrometer. To date, no clear correlation is observed between the <span class="hlt">cusp</span> traversal time or the magnitude of the magnetic field depression and the interplanetary magnetic field (IMF) direction, solar wind density, or solar wind velocity. However, the largest-amplitude magnetic field depressions associated with the <span class="hlt">cusp</span> are observed</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009MNRAS.400.1121S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009MNRAS.400.1121S"><span>A spatially resolved map of the kinematics, star <span class="hlt">formation</span> and <span class="hlt">stellar</span> mass assembly in a star-forming galaxy at z = 4.9</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Swinbank, A. M.; Webb, T. M.; Richard, J.; Bower, R. G.; Ellis, R. S.; Illingworth, G.; Jones, T.; Kriek, M.; Smail, I.; Stark, D. P.; van Dokkum, P.</p> <p>2009-12-01</p> <p>We present a detailed study of the spatially resolved kinematics, star <span class="hlt">formation</span> and <span class="hlt">stellar</span> mass in a highly amplified galaxy at z = 4.92 behind the lensing cluster MS1358+62. We use the observed optical, near- and mid-infrared imaging from Hubble Space Telescope ACS & NICMOS and Spitzer IRAC to derive the <span class="hlt">stellar</span> mass and the Gemini/NIFS IFU to investigate the velocity structure of the galaxy from the nebular [OII]λλ3726.8,3728.9 emission. Using a detailed gravitational lens model, we account for lensing amplification factor 12.5 +/- 2.0 and find that this intrinsically L* galaxy has a <span class="hlt">stellar</span> mass of M* = 7 +/- 2 × 108Msolar, a dynamical mass of Mdyn = 3 +/- 1 × 109csc2(i)Msolar (within of 2kpc) and a star <span class="hlt">formation</span> rate of 42 +/- 8Msolaryr-1. The source-plane UV/optical morphology of this galaxy is dominated by five discrete star-forming regions. Exploiting the dynamical information we derive masses for individual star-forming regions of Mcl ~ 108-9Msolar with sizes of ~200pc. We find that, at a fixed size, the star <span class="hlt">formation</span> rate density within these HII regions is approximately two orders of magnitude greater than those observed in local spiral/starburst galaxies, but consistent with the most massive HII regions in the local Universe such as 30Doradus. Finally, we compare the spatially resolved nebular emission-line velocity with the Lyα and UV interstellar medium (ISM) lines and find that this galaxy is surrounded by a galactic scale outflow in which the Lyα appears redshifted by ~150kms-1 and the UV-ISM lines blueshifted by ~ -200kms-1 from the (systemic) nebular emission. The velocity structure of the outflow mirrors that of the nebular emission suggesting the outflow is young (<~15Myr), and has yet to burst out of the system. Taken together, these results suggest that this young galaxy is undergoing its first major epoch of mass assembly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21467211','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21467211"><span>MOIRCS DEEP SURVEY. VIII. EVOLUTION OF STAR <span class="hlt">FORMATION</span> ACTIVITY AS A FUNCTION OF <span class="hlt">STELLAR</span> MASS IN GALAXIES SINCE z {approx} 3</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kajisawa, M.; Ichikawa, T.; Yamada, T.; Akiyama, M.; Uchimoto, Y. K.; Yoshikawa, T.; Onodera, M.</p> <p>2010-11-01</p> <p>We study the evolution of star <span class="hlt">formation</span> activity of galaxies at 0.5 < z < 3.5 as a function of <span class="hlt">stellar</span> mass, using very deep NIR data taken with the Multi-Object Infrared Camera and Spectrograph on the Subaru telescope in the GOODS-North region. The NIR imaging data reach K{approx} 23-24 Vega magnitude and they allow us to construct a nearly <span class="hlt">stellar</span>-mass-limited sample down to {approx}10{sup 9.5-10} M{sub sun} even at z {approx} 3. We estimated star <span class="hlt">formation</span> rates (SFRs) of the sample with two indicators, namely, the Spitzer/MIPS 24 {mu}m flux and the rest-frame 2800 A luminosity. The SFR distribution at a fixed M{sub star} shifts to higher values with increasing redshift at 0.5 < z < 3.5. More massive galaxies show stronger evolution of SFR at z {approx}> 1. We found galaxies at 2.5 < z < 3.5 show a bimodality in their SSFR distribution, which can be divided into two populations by a constant SSFR of {approx}2 Gyr{sup -1}. Galaxies in the low-SSFR group have SSFRs of {approx}0.5-1.0 Gyr{sup -1}, while the high-SSFR population shows {approx}10 Gyr{sup -1}. The cosmic SFR density (SFRD) is dominated by galaxies with M{sub star} = 10{sup 10-11} M{sub sun} at 0.5 < z < 3.5, while the contribution of massive galaxies with M{sub star} = 10{sup 11-11.5} M{sub sun} shows a strong evolution at z>1 and becomes significant at z {approx} 3, especially in the case with the SFR based on MIPS 24 {mu}m. In galaxies with M{sub star} = 10{sup 10-11.5} M{sub sun}, those with a relatively narrow range of SSFR ({approx}<1 dex) dominates the cosmic SFRD at 0.5 < z < 3.5. The SSFR of galaxies that dominate the SFRD systematically increases with redshift. At 2.5 < z < 3.5, the high-SSFR population, which is relatively small in number, dominates the SFRD. Major star <span class="hlt">formation</span> in the universe at higher redshift seems to be associated with a more rapid growth of <span class="hlt">stellar</span> mass of galaxies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JASTP..87....1P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JASTP..87....1P"><span>Sources of plasma in the high altitude <span class="hlt">cusp</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peterson, W. K.; Trattner, K. J.</p> <p>2012-10-01</p> <p>Ambiguities introduced by the inconsistent definitions of the low and high altitude <span class="hlt">cusp</span> lead to the inconsistency that at low altitudes the region commonly known as the <span class="hlt">cusp</span> does not include boundary layer plasmas, but at high altitudes it does. Here we examine plasma data from two high altitude <span class="hlt">cusp</span> intervals where ∼100 keV ionospheric ions were observed. We show that the data are an average over an interval that includes plasma from both boundary layer and newly injected solar wind plasmas. We find that the ∼100 keV ionospheric ions reported in the high altitude <span class="hlt">cusp</span> are energized by well-known magnetospheric processes bringing energetic ions to the dayside boundary layers. We conclude that there is no need to postulate new processes associated with waves in diamagnetic cavities commonly found in the high altitude <span class="hlt">cusp</span> to explain the observation of ∼100 keV ionospheric ions found there.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5391969','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5391969"><span>Simultaneous HF-radar and DMSP observations of the <span class="hlt">cusp</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Baker, K.B.; Greenwald, R.A.; Ruohoniemi, J.M.; Dudeney, J.R.; Pinnock, M.; Newell, P.T.; Greenspan, M.E.; Meng, C.I.</p> <p>1990-10-01</p> <p>The Geospace Environment Modeling (GEM) Program is directed toward modeling the coupled solar wind/magnetosphere/ionosphere system. The inter-calibration of ground-based observations of the ionosphere and satellite observations has been identified as an essential step in tying together the data to produce a global picture of geospace. On October 10, 1988 the DMSP-F9 satellite passed through the southern hemisphere <span class="hlt">cusp</span> while a coherent scatter HF-radar was observing 10-m scale irregularities present in the ionosphere. The combined data indicate that these irregularities were being generated in the <span class="hlt">cusp</span>, and that the <span class="hlt">cusp</span> was a region of greater than normal electric field turbulence. The radar data indicate that the <span class="hlt">cusp</span> was co-located with the region where the ionospheric convection rotated from sunward to anti-sunward with increasing latitude. These observations provide an unambiguous case where simultaneous satellite and ground-based observations of the <span class="hlt">cusp</span> can be compared.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5519994','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5519994"><span>Multiple talon <span class="hlt">cusps</span> on maxillary central incisor: A case report</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>KV, Suresh; C, Pramod R; Yadav, Seema Roodmal; Kumar, Nilesh; C D, Mounesh Kumar; Kumar, Sreeja P</p> <p>2017-01-01</p> <p>Dental anomalies affecting the teeth are relatively common. Simultaneous occurrence of multiple dental abnormalities in a single tooth is uncommon and relatively rare. One such abnormality routinely encountered in dental clinics is the talon <span class="hlt">cusp</span>. It is also referred to as dens evaginatus, characterized by the presence of an accessory <span class="hlt">cusp</span>-like structure projecting from the cingulum of anterior teeth. It has an increased predilection for maxillary teeth and permanent dentition. Although numerous cases of talon <span class="hlt">cusp</span> have been reported in the literature, occurrence of multiple talon <span class="hlt">cusps</span> in maxillary central incisors has not been found in the literature. This case report highlights the presence of talon <span class="hlt">cusps</span> in maxillary anterior teeth with multiple impacted supernumerary teeth. PMID:28748055</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22167400','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22167400"><span>PRIMUS: CONSTRAINTS ON STAR <span class="hlt">FORMATION</span> QUENCHING AND GALAXY MERGING, AND THE EVOLUTION OF THE <span class="hlt">STELLAR</span> MASS FUNCTION FROM z = 0-1</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Moustakas, John; Coil, Alison L.; Mendez, Alexander J.; Aird, James; Blanton, Michael R.; Cool, Richard J.; Eisenstein, Daniel J.; Wong, Kenneth C.; Zhu, Guangtun; Arnouts, Stephane</p> <p>2013-04-10</p> <p>We measure the evolution of the <span class="hlt">stellar</span> mass function (SMF) from z = 0-1 using multi-wavelength imaging and spectroscopic redshifts from the PRism MUlti-object Survey (PRIMUS) and the Sloan Digital Sky Survey (SDSS). From PRIMUS we construct an i < 23 flux-limited sample of {approx}40, 000 galaxies at z = 0.2-1.0 over five fields totaling Almost-Equal-To 5.5 deg{sup 2}, and from the SDSS we select {approx}170, 000 galaxies at z = 0.01-0.2 that we analyze consistently with respect to PRIMUS to minimize systematic errors in our evolutionary measurements. We find that the SMF of all galaxies evolves relatively little since z = 1, although we do find evidence for mass assembly downsizing; we measure a Almost-Equal-To 30% increase in the number density of {approx}10{sup 10} M{sub sun} galaxies since z Almost-Equal-To 0.6, and a {approx}< 10% change in the number density of all {approx}> 10{sup 11} M{sub sun} galaxies since z Almost-Equal-To 1. Dividing the sample into star-forming and quiescent using an evolving cut in specific star <span class="hlt">formation</span> rate, we find that the number density of {approx}10{sup 10} M{sub sun} star-forming galaxies stays relatively constant since z Almost-Equal-To 0.6, whereas the space density of {approx}> 10{sup 11} M{sub sun} star-forming galaxies decreases by Almost-Equal-To 50% between z Almost-Equal-To 1 and z Almost-Equal-To 0. Meanwhile, the number density of {approx}10{sup 10} M{sub sun} quiescent galaxies increases steeply toward low redshift, by a factor of {approx}2-3 since z Almost-Equal-To 0.6, while the number of massive quiescent galaxies remains approximately constant since z Almost-Equal-To 1. These results suggest that the rate at which star-forming galaxies are quenched increases with decreasing <span class="hlt">stellar</span> mass, but that the bulk of the <span class="hlt">stellar</span> mass buildup within the quiescent population occurs around {approx}10{sup 10.8} M{sub sun}. In addition, we conclude that mergers do not appear to be a dominant channel for the <span class="hlt">stellar</span> mass</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22215377','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22215377"><span>THE SPECTRAL ENERGY DISTRIBUTIONS OF z ∼ 8 GALAXIES FROM THE IRAC ULTRA DEEP FIELDS: EMISSION LINES, <span class="hlt">STELLAR</span> MASSES, AND SPECIFIC STAR <span class="hlt">FORMATION</span> RATES AT 650 MYR</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Labbé, I.; Bouwens, R. J.; Franx, M.; Oesch, P. A.; Illingworth, G. D.; Magee, D.; González, V.; Trenti, M.; Van Dokkum, P. G.; Stiavelli, M.</p> <p>2013-11-10</p> <p>Using new ultradeep Spitzer/InfraRed Array Camera (IRAC) photometry from the IRAC Ultra Deep Field program, we investigate the <span class="hlt">stellar</span> populations of a sample of 63 Y-dropout galaxy candidates at z ∼ 8, only 650 Myr after the big bang. The sources are selected from HST/ACS+WFC3/IR data over the Hubble Ultra Deep Field (HUDF), two HUDF parallel fields, and wide area data over the CANDELS/GOODS-South. The new Spitzer/IRAC data increase the coverage in [3.6] and [4.5] to ∼120h over the HUDF reaching depths of ∼28 (AB,1σ). The improved depth and inclusion of brighter candidates result in direct ≥3σ InfraRed Array Camera (IRAC) detections of 20/63 sources, of which 11/63 are detected at ≥5σ. The average [3.6]-[4.5] colors of IRAC detected galaxies at z ∼ 8 are markedly redder than those at z ∼ 7, observed only 130 Myr later. The simplest explanation is that we witness strong rest-frame optical emission lines (in particular [O III] λλ4959, 5007 + Hβ) moving through the IRAC bandpasses with redshift. Assuming that the average rest-frame spectrum is the same at both z ∼ 7 and z ∼ 8 we estimate a rest-frame equivalent width of contributing 0.56{sup +0.16}{sub -0.11} mag to the [4.5] filter at z ∼ 8. The corresponding W{sub Hα}=430{sup +160}{sub -110} Å implies an average specific star <span class="hlt">formation</span> rate of sSFR=11{sub -5}{sup +11} Gyr{sup –1} and a <span class="hlt">stellar</span> population age of 100{sub -50}{sup +100} Myr. Correcting the spectral energy distribution for the contribution of emission lines lowers the average best-fit <span class="hlt">stellar</span> masses and mass-to-light ratios by ∼3 ×, decreasing the integrated <span class="hlt">stellar</span> mass density to ρ{sup *}(z=8,M{sub UV}<-18)=0.6{sup +0.4}{sub -0.3}×10{sup 6} M{sub sun} Mpc{sup –3}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015RAA....15.1209X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015RAA....15.1209X"><span>The evolution of <span class="hlt">stellar</span> metallicity gradients of the Milky Way disk from LSS-GAC main sequence turn-off stars: a two-phase disk <span class="hlt">formation</span> history?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiang, Mao-Sheng; Liu, Xiao-Wei; Yuan, Hai-Bo; Huang, Yang; Wang, Chun; Ren, Juan-Juan; Chen, Bing-Qiu; Sun, Ning-Chen; Zhang, Hua-Wei; Huo, Zhi-Ying; Rebassa-Mansergas, Alberto</p> <p>2015-08-01</p> <p>Accurate measurements of <span class="hlt">stellar</span> metallicity gradients in the radial and vertical directions of the disk and their temporal variations provide important constraints on the <span class="hlt">formation</span> and evolution of the Milky Way disk. We use 297 042 main sequence turn-off stars selected from the LAMOST Spectroscopic Survey of the Galactic Anti-center (LSS-GAC) to determine the radial and vertical gradients of <span class="hlt">stellar</span> metallicity, Δ[Fe/H]/ΔR and Δ[Fe/H]/Δ|Z| of the Milky Way disk in the direction of the anticenter. We determine ages of those turn-off stars by isochrone fitting and measure the temporal variations of metallicity gradients. We have carried out a detailed analysis of the selection effects resulting from the selection, observation and data reduction of LSS-GAC targets and the potential biases of a magnitude limited sample on the determinations of metallicity gradients. Our results show that the gradients, both in the radial and vertical directions, exhibit significant spatial and temporal variations. The radial gradients yielded by stars with the oldest ages (≳ 11 Gyr) are essentially zero at all heights from the disk midplane, while those given by younger stars are always negative. The vertical gradients deduced from stars with the oldest ages (≳ 11 Gyr) are negative and only show very weak variations with Galactocentric distance in the disk plane, R, while those yielded by younger stars show strong variations with R. After being essentially flat at the earliest epochs of disk <span class="hlt">formation</span>, the radial gradients steepen as age decreases, reaching a maximum (steepest) at age 7-8 Gyr, and then they flatten again. Similar temporal trends are also found for the vertical gradients. We infer that the assembly of the Milky Way disk may have experienced at least two distinct phases. The earlier phase is probably related to a slow, pressure-supported collapse of gas, when the gas settles down to the disk mainly in the vertical direction. In the later phase, there are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983NIMPR.207..139S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983NIMPR.207..139S"><span>Advanced <span class="hlt">stellarators</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schlüter, Arnulf</p> <p>1983-03-01</p> <p>Toroidal confinement of a plasma by an external magnetic field is not compatible with axisymmetry, in contrast to confinement by the pinch effect of induced electric currents as in a tokomak or by the reversed field pinch configuration. The existence of magnetic surfaces throughout the region in which grad p ≠ 0 is therefore not guaranteed in such configurations, though it is necessary for MHD-equilibrium when the lines of force possess a finite twist (or "rotational transform"). These twisted equilibria are called <span class="hlt">stellarators</span>. The other type of external confinement requires all lines of force to be closed upon themselves and p to be function of the well defined quantity Q = φ d l/ B only. The resulting "bumpy" tori are sometimes also referred to as being M + S like. By discussing specific examples it is shown that <span class="hlt">stellarator</span> configurations exist which retain as much as possible the properties of M + S like configurations, combine these with the magnetic well, and with an approximation to the isodynamic requirement of D. Palumbo. These so-called Advanced <span class="hlt">Stellarators</span> shown an improvement in predicted particle confinement and beta-limit compared to the classical <span class="hlt">stellarators</span>. They can also be viewed as forming a system of linked stabilized mirrors of small mirror ratio. These fields can be produced by modular coils. A prototype of such a configuration is being designed by the <span class="hlt">stellarator</span> division of IPP under the name of Wendelstein VII-AS. Expected physical data and technical details of W VII-AS are given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.459.2054D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.459.2054D"><span>Global dust attenuation in disc galaxies: strong variation with specific star <span class="hlt">formation</span> and <span class="hlt">stellar</span> mass, and the importance of sample selection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Devour, Brian M.; Bell, Eric F.</p> <p>2016-06-01</p> <p>We study the relative dust attenuation-inclination relation in 78 721 nearby galaxies using the axis ratio dependence of optical-near-IR colour, as measured by the Sloan Digital Sky Survey, the Two Micron All Sky Survey, and the Wide-field Infrared Survey Explorer. In order to avoid to the greatest extent possible attenuation-driven biases, we carefully select galaxies using dust attenuation-independent near- and mid-IR luminosities and colours. Relative u-band attenuation between face-on and edge-on disc galaxies along the star-forming main sequence varies from ˜0.55 mag up to ˜1.55 mag. The strength of the relative attenuation varies strongly with both specific star <span class="hlt">formation</span> rate and galaxy luminosity (or <span class="hlt">stellar</span> mass). The dependence of relative attenuation on luminosity is not monotonic, but rather peaks at M3.4 μm ≈ -21.5, corresponding to M* ≈ 3 × 1010 M⊙. This behaviour stands seemingly in contrast to some older studies; we show that older works failed to reliably probe to higher luminosities, and were insensitive to the decrease in attenuation with increasing luminosity for the brightest star-forming discs. Back-of-the-envelope scaling relations predict the strong variation of dust optical depth with specific star <span class="hlt">formation</span> rate and <span class="hlt">stellar</span> mass. More in-depth comparisons using the scaling relations to model the relative attenuation require the inclusion of star-dust geometry to reproduce the details of these variations (especially at high luminosities), highlighting the importance of these geometrical effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...815...98S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...815...98S"><span>The MOSDEF Survey: Dissecting the Star <span class="hlt">Formation</span> Rate versus <span class="hlt">Stellar</span> Mass Relation Using Hα and Hβ Emission Lines at z ≤ 2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shivaei, Irene; Reddy, Naveen A.; Shapley, Alice E.; Kriek, Mariska; Siana, Brian; Mobasher, Bahram; Coil, Alison L.; Freeman, William R.; Sanders, Ryan; Price, Sedona H.; de Groot, Laura; Azadi, Mojegan</p> <p>2015-12-01</p> <p>We present results on the star <span class="hlt">formation</span> rate (SFR) versus <span class="hlt">stellar</span> mass (M*) relation (i.e., the “main sequence”) among star-forming galaxies at 1.37 ≤ z ≤ 2.61 using the MOSFIRE Deep Evolution Field (MOSDEF) survey. Based on a sample of 261 galaxies with Hα and Hβ spectroscopy, we have estimated robust dust-corrected instantaneous SFRs over a large range in M* (˜109.5-1011.5 M⊙). We find a correlation between log(SFR(Hα)) and log(M*) with a slope of 0.65 ± 0.08 (0.58 ± 0.10) at 1.4 < z < 2.6 (2.1 < z < 2.6). We find that different assumptions for the dust correction, such as using the color excess of the <span class="hlt">stellar</span> continuum to correct the nebular lines, sample selection biases against red star-forming galaxies, and not accounting for Balmer absorption, can yield steeper slopes of the log(SFR)-log(M*) relation. Our sample is immune from these biases as it is rest-frame optically selected, Hα and Hβ are corrected for Balmer absorption, and the Hα luminosity is dust corrected using the nebular color excess computed from the Balmer decrement. The scatter of the log(SFR(Hα))-log(M*) relation, after accounting for the measurement uncertainties, is 0.31 dex at 2.1 < z < 2.6, which is 0.05 dex larger than the scatter in log(SFR(UV))-log(M*). Based on comparisons to a simulated SFR-M* relation with some intrinsic scatter, we argue that in the absence of direct measurements of galaxy-to-galaxy variations in the attenuation/extinction curves and the initial mass function, one cannot use the difference in the scatter of the SFR(Hα)- and SFR(UV)-M* relations to constrain the stochasticity of star <span class="hlt">formation</span> in high-redshift galaxies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870014927','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870014927"><span>The relation between star <span class="hlt">formation</span> and active nuclei</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rieke, G. H.</p> <p>1987-01-01</p> <p>Three questions relevant to the relation between an active nucleus and surrounding star <span class="hlt">formation</span> are discussed. The infrared <span class="hlt">stellar</span> CO absorption bands can be used to identify galaxies with large populations of young, massive stars and thus can identify strong starburst unambiguously, such as in NGC 6240, and can help identify composite active/starburst systems such as Arp 220. An active nucleus is probably not required for LINER spectral characteristics; dusty starburst galaxies, particularly if they are nearly edge-on, can produce LINER spectra through the shock heating of their interstellar media by supernovae combined with the obscuration of their nuclei in the optical. The Galactic Center would be an ideal laboratory for studying the interaction of starbursts and active nuclei, if both could be demonstrated to occur there. Failure to detect a <span class="hlt">cusp</span> in the <span class="hlt">stellar</span> distribution raises questions about the presence of an active nucleus, which should be answered by additional observations in the near future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21587409','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21587409"><span>STAR <span class="hlt">FORMATION</span> RATES AND <span class="hlt">STELLAR</span> MASSES OF H{alpha} SELECTED STAR-FORMING GALAXIES AT z = 0.84: A QUANTIFICATION OF THE DOWNSIZING</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Villar, Victor; Gallego, Jesus; Perez-Gonzalez, Pablo G.; Barro, Guillermo; Zamorano, Jaime; Noeske, Kai; Koo, David C. E-mail: j.gallego@fis.ucm.es E-mail: gbarro@fis.ucm.es E-mail: noeske@stsci.edu</p> <p>2011-10-10</p> <p>In this work we analyze the physical properties of a sample of 153 star-forming galaxies at z {approx} 0.84, selected by their H{alpha} flux with a narrowband filter. B-band luminosities of the objects are higher than those of local star-forming galaxies. Most of the galaxies are located in the blue cloud, though some objects are detected in the green valley and in the red sequence. After the extinction correction is applied, virtually all these red galaxies move to the blue sequence, unveiling their dusty nature. A check on the extinction law reveals that the typical extinction law for local starbursts is well suited for our sample but with E(B - V){sub stars} = 0.55 E(B - V){sub gas}. We compare star <span class="hlt">formation</span> rates (SFRs) measured with different tracers (H{alpha}, far-ultraviolet, and infrared), finding that they agree within a factor of three after extinction correction. We find a correlation between the ratios SFR{sub FUV}/SFR{sub H{alpha}}, SFR{sub IR}/SFR{sub H{alpha}}, and the EW(H{alpha}) (i.e., weighted age), which accounts for part of the scatter. We obtain <span class="hlt">stellar</span> mass estimations by fitting templates to multi-wavelength photometry. The typical <span class="hlt">stellar</span> mass of a galaxy within our sample is {approx}10{sup 10} M{sub sun}. The SFR is correlated with <span class="hlt">stellar</span> mass and the specific SFR decreases with it, indicating that massive galaxies are less affected by star <span class="hlt">formation</span> processes than less massive ones. This result is consistent with the downsizing scenario. To quantify this downsizing we estimated the quenching mass M{sub Q} for our sample at z {approx} 0.84, finding that it declines from M{sub Q} {approx} 10{sup 12} M{sub sun} at z {approx} 0.84 to M{sub Q} {approx} 8 x 10{sup 10} M{sub sun} at the local universe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21576721','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21576721"><span>Ly{alpha}-EMITTING GALAXIES AT z = 2.1: <span class="hlt">STELLAR</span> MASSES, DUST, AND STAR <span class="hlt">FORMATION</span> HISTORIES FROM SPECTRAL ENERGY DISTRIBUTION FITTING</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Guaita, Lucia; Padilla, Nelson; Acquaviva, Viviana; Gawiser, Eric; Bond, Nicholas A.; Kurczynski, Peter; Ciardullo, Robin; Gronwall, Caryl; Treister, Ezequiel; Lira, Paulina; Schawinski, Kevin E-mail: lguai@astro.su.se</p> <p>2011-06-01</p> <p>We study the physical properties of 216 z {approx_equal} 2.1 Ly{alpha}-emitting galaxies (LAEs) discovered in an ultra-deep narrow- MUSYC image of the ECDF-S. We fit their stacked spectral energy distribution (SED) using Charlot and Bruzual templates. We consider star <span class="hlt">formation</span> histories (SFHs) parameterized by the e-folding time parameter {tau}, allowing for exponentially decreasing ({tau} > 0), exponentially increasing ({tau} < 0), and constant star <span class="hlt">formation</span> rates (SFRs). We estimated the average flux at 5015 A of our LAE sample, finding a non-detection, which translates into negligible He II line emission at z {approx_equal} 2.1. In addition to this, the lack of high equivalent width (EW) Ly{alpha} line objects ruled out the hypothesis of a top-heavy initial mass function in LAEs. The typical LAEs of our sample are characterized by best-fit parameters and 68% confidence intervals of log(M{sub *}/M{sub sun}) = 8.6[8.4-9.1], E(B - V) = 0.22[0.00-0.31], {tau} = -0.02[(- 4)-18] Gyr, and age{sub SF} = 0.018[0.009-3] Gyr. Thus, we obtain robust measurements of low <span class="hlt">stellar</span> mass and dust content, but we cannot place meaningful constraints on the age or SFH of the LAEs. We also calculate the instantaneous SFR to be 35[0.003-170] M{sub sun} yr{sup -1}, with its average over the last 100 Myr before observation giving (SFR){sub 100} = 4[2-30] M{sub sun} yr{sup -1}. When we compare the results for the same SFH, typical LAEs at z {approx_equal} 2.1 appear dustier and show higher instantaneous SFRs than z {approx_equal} 3.1 LAEs, while the observed <span class="hlt">stellar</span> masses of the two samples seem consistent. Because the majority are low-mass galaxies, our typical LAEs appear to occupy the low-mass end of the distribution of star-forming galaxies at z {approx} 2. We perform SED fitting on several sub-samples selected based on photometric properties and find that LAE sub-samples at z {approx_equal} 2.1 exhibit heterogeneous properties. The typical IRAC-bright, UV-bright, and red LAEs</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...586A.120O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...586A.120O"><span>Mg line <span class="hlt">formation</span> in late-type <span class="hlt">stellar</span> atmospheres. II. Calculations in a grid of 1D models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Osorio, Y.; Barklem, P. S.</p> <p>2016-02-01</p> <p>Context. Mg is the α element of choice for Galactic population and chemical evolution studies because it is easily detectable in all late-type stars. Such studies require precise elemental abundances, and thus departures from local thermodynamic equilibrium (LTE) need to be accounted for. Aims: Our goal is to provide reliable departure coefficients and equivalent widths in non-LTE, and for reference in LTE, for diagnostic lines of Mg studied in late-type stars. These can be used, for example, to correct LTE spectra and abundances. Methods: Using the model atom built and tested in the preceding paper in this series, we performed non-LTE radiative transfer calculations in a grid of 3945 <span class="hlt">stellar</span> 1D atmospheric models. We used a sub-grid of 86 models to explore the propagation of errors in the recent atomic collision calculations to the radiative transfer results. Results: We obtained departure coefficients for all the levels and equivalent widths (in LTE and non-LTE) for all the radiative transitions included in the "final" model atom presented in Paper I. Here we present and describe our results and show some examples of applications of the data. The errors that result from uncertainties in the collisional data are investigated and tabulated. The results for equivalent widths and departure coefficients are made freely available. Conclusions: Giants tend to have negative abundance corrections while dwarfs have positive, though small, corrections. Error analysis results show that uncertainties related to the atomic collision data are typically on the order of 0.01 dex or less, although for few <span class="hlt">stellar</span> models in specific lines uncertainties can be as large as 0.03 dex. As these errors are less than or on the same order as typical corrections, we expect that we can use these results to extract Mg abundances from high-quality spectra more reliably than from classical LTE analysis. Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5101848','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5101848"><span>Source of the dayside <span class="hlt">cusp</span> aurora</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Frey, H. U.; Angelopoulos, V.</p> <p>2016-01-01</p> <p>Abstract Monochromatic all‐sky imagers at South Pole and other Antarctic stations of the Automatic Geophysical Observatory chain recorded the aurora in the region where the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites crossed the dayside magnetopause. In several cases the magnetic field lines threading the satellites when mapped to the atmosphere were inside the imagers' field of view. From the THEMIS magnetic field and the plasma density measurements, we were able to locate the position of the magnetopause crossings and map it to the ionosphere using the Tsyganenko‐96 field model. Field line mapping is reasonably accurate on the dayside subsolar region where the field is strong, almost dipolar even though compressed. From these coordinated observations, we were able to prove that the dayside <span class="hlt">cusp</span> aurora of high 630 nm brightness is on open field lines, and it is therefore direct precipitation from the magnetosheath. The <span class="hlt">cusp</span> aurora contained significant highly structured N2 + 427.8 nm emission. The THEMIS measurements of the magnetosheath particle energy and density taken just outside the magnetopause compared to the intensity of the structured N2 + 427.8 nm emissions showed that the precipitating magnetosheath particles had to be accelerated. The most likely electron acceleration mechanism is by dispersive Alfvén waves propagating along the field line. Wave‐accelerated suprathermal electrons were seen by FAST and DMSP. The 427.8 nm wavelength channel also shows the presence of a lower latitude hard‐electron precipitation zone originating inside the magnetosphere. PMID:27867797</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.7728M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.7728M"><span>Source of the dayside <span class="hlt">cusp</span> aurora</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mende, S. B.; Frey, H. U.; Angelopoulos, V.</p> <p>2016-08-01</p> <p>Monochromatic all-sky imagers at South Pole and other Antarctic stations of the Automatic Geophysical Observatory chain recorded the aurora in the region where the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites crossed the dayside magnetopause. In several cases the magnetic field lines threading the satellites when mapped to the atmosphere were inside the imagers' field of view. From the THEMIS magnetic field and the plasma density measurements, we were able to locate the position of the magnetopause crossings and map it to the ionosphere using the Tsyganenko-96 field model. Field line mapping is reasonably accurate on the dayside subsolar region where the field is strong, almost dipolar even though compressed. From these coordinated observations, we were able to prove that the dayside <span class="hlt">cusp</span> aurora of high 630 nm brightness is on open field lines, and it is therefore direct precipitation from the magnetosheath. The <span class="hlt">cusp</span> aurora contained significant highly structured N2+ 427.8 nm emission. The THEMIS measurements of the magnetosheath particle energy and density taken just outside the magnetopause compared to the intensity of the structured N2+ 427.8 nm emissions showed that the precipitating magnetosheath particles had to be accelerated. The most likely electron acceleration mechanism is by dispersive Alfvén waves propagating along the field line. Wave-accelerated suprathermal electrons were seen by FAST and DMSP. The 427.8 nm wavelength channel also shows the presence of a lower latitude hard-electron precipitation zone originating inside the magnetosphere.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27867797','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27867797"><span>Source of the dayside <span class="hlt">cusp</span> aurora.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mende, S B; Frey, H U; Angelopoulos, V</p> <p>2016-08-01</p> <p>Monochromatic all-sky imagers at South Pole and other Antarctic stations of the Automatic Geophysical Observatory chain recorded the aurora in the region where the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites crossed the dayside magnetopause. In several cases the magnetic field lines threading the satellites when mapped to the atmosphere were inside the imagers' field of view. From the THEMIS magnetic field and the plasma density measurements, we were able to locate the position of the magnetopause crossings and map it to the ionosphere using the Tsyganenko-96 field model. Field line mapping is reasonably accurate on the dayside subsolar region where the field is strong, almost dipolar even though compressed. From these coordinated observations, we were able to prove that the dayside <span class="hlt">cusp</span> aurora of high 630 nm brightness is on open field lines, and it is therefore direct precipitation from the magnetosheath. The <span class="hlt">cusp</span> aurora contained significant highly structured N2(+) 427.8 nm emission. The THEMIS measurements of the magnetosheath particle energy and density taken just outside the magnetopause compared to the intensity of the structured N2(+) 427.8 nm emissions showed that the precipitating magnetosheath particles had to be accelerated. The most likely electron acceleration mechanism is by dispersive Alfvén waves propagating along the field line. Wave-accelerated suprathermal electrons were seen by FAST and DMSP. The 427.8 nm wavelength channel also shows the presence of a lower latitude hard-electron precipitation zone originating inside the magnetosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22270942','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22270942"><span>A TREND BETWEEN COLD DEBRIS DISK TEMPERATURE AND <span class="hlt">STELLAR</span> TYPE: IMPLICATIONS FOR THE <span class="hlt">FORMATION</span> AND EVOLUTION OF WIDE-ORBIT PLANETS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ballering, Nicholas P.; Rieke, George H.; Su, Kate Y. L.; Montiel, Edward</p> <p>2013-09-20</p> <p>Cold debris disks trace the limits of planet <span class="hlt">formation</span> or migration in the outer regions of planetary systems, and thus have the potential to answer many of the outstanding questions in wide-orbit planet <span class="hlt">formation</span> and evolution. We characterized the infrared excess spectral energy distributions of 174 cold debris disks around 546 main-sequence stars observed by both the Spitzer Infrared Spectrograph and the Multiband Imaging Photometer for Spitzer. We found a trend between the temperature of the inner edges of cold debris disks and the <span class="hlt">stellar</span> type of the stars they orbit. This argues against the importance of strictly temperature-dependent processes (e.g., non-water ice lines) in setting the dimensions of cold debris disks. Also, we found no evidence that delayed stirring causes the trend. The trend may result from outward planet migration that traces the extent of the primordial protoplanetary disk, or it may result from planet <span class="hlt">formation</span> that halts at an orbital radius limited by the efficiency of core accretion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvX...5b1024P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvX...5b1024P"><span>High-Energy Electron Confinement in a Magnetic <span class="hlt">Cusp</span> Configuration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Park, Jaeyoung; Krall, Nicholas A.; Sieck, Paul E.; Offermann, Dustin T.; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni</p> <p>2015-04-01</p> <p>We report experimental results validating the concept that plasma confinement is enhanced in a magnetic <span class="hlt">cusp</span> configuration when β (plasma pressure/magnetic field pressure) is of order unity. This enhancement is required for a fusion power reactor based on <span class="hlt">cusp</span> confinement to be feasible. The magnetic <span class="hlt">cusp</span> configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a <span class="hlt">cusp</span> configuration were too large for net power production. Grad and others theorized that at high β a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad's work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high β . This represents critical progress toward an understanding of the plasma dynamics in a high-β <span class="hlt">cusp</span> system. We hope that these results will stimulate a renewed interest in the <span class="hlt">cusp</span> configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-β <span class="hlt">cusp</span> configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9776E..0SM','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9776E..0SM"><span>Tin LPP plasma control in the argon <span class="hlt">cusp</span> source</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McGeoch, Malcolm W.</p> <p>2016-03-01</p> <p>The argon <span class="hlt">cusp</span> plasma has been introduced [1,2] for 500W class tin LPP exhaust control in view of its high power handling, predicted low tin back-scatter from a beam dump, and avoidance of hydrogen usage. The physics of tin ion control by a plasma is first discussed. Experimentally, <span class="hlt">cusp</span> stability and exhaust disc geometry have previously been proved at full scale [2], the equivalent of 300W-500W usable EUV. Here we verify operation of the plasma barrier that maintains a high argon density next to the collector, for its protection, and a low density in the long path toward the intermediate focus, for efficiency. A pressure differential of 2Pa has been demonstrated in initial work. Other aspects of tin LPP plasma control by the <span class="hlt">cusp</span> have now been demonstrated using tin ions from a low Hz 130mJ CO2 laser pulse onto a solid tin surface at the <span class="hlt">cusp</span> center. Plasma is rejected at the <0.5% level at the collector mirror location using the <span class="hlt">cusp</span> magnetic field alone. Plasma also is rejected using a low argon density (<1x1014cm-3). We have measured the tin ion flow pattern toward the large area annular beam dump. Scaling of the <span class="hlt">cusp</span> design to match a specified exhaust power is discussed. In view of this work, argon <span class="hlt">cusp</span> exhaust control appears to be very promising for 500W class tin LPP sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20034010','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20034010"><span>Genetic integration of molar <span class="hlt">cusp</span> size variation in baboons.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Koh, Christina; Bates, Elizabeth; Broughton, Elizabeth; Do, Nicholas T; Fletcher, Zachary; Mahaney, Michael C; Hlusko, Leslea J</p> <p>2010-06-01</p> <p>Many studies of primate diversity and evolution rely on dental morphology for insight into diet, behavior, and phylogenetic relationships. Consequently, variation in molar <span class="hlt">cusp</span> size has increasingly become a phenotype of interest. In 2007 we published a quantitative genetic analysis of mandibular molar <span class="hlt">cusp</span> size variation in baboons. Those results provided more questions than answers, as the pattern of genetic integration did not fit predictions from odontogenesis. To follow up, we expanded our study to include data from the maxillary molar <span class="hlt">cusps</span>. Here we report on these later analyses, as well as inter-arch comparisons with the mandibular data. We analyzed variation in two-dimensional maxillary molar <span class="hlt">cusp</span> size using data collected from a captive pedigreed breeding colony of baboons, Papio hamadryas, housed at the Southwest National Primate Research Center. These analyses show that variation in maxillary molar <span class="hlt">cusp</span> size is heritable and sexually dimorphic. We also estimated additive genetic correlations between <span class="hlt">cusps</span> on the same crown, homologous <span class="hlt">cusps</span> along the tooth row, and maxillary and mandibular <span class="hlt">cusps</span>. The pattern for maxillary molars yields genetic correlations of one between the paracone-metacone and protocone-hypocone. Bivariate analyses of cuspal homologues on adjacent teeth yield correlations that are high or not significantly different from one. Between dental arcades, the nonoccluding <span class="hlt">cusps</span> consistently yield high genetic correlations, especially the metaconid-paracone and metaconid-metacone. This pattern of genetic correlation does not immediately accord with the pattern of development and/or calcification, however these results do follow predictions that can be made from the evolutionary history of the tribosphenic molar. Copyright 2009 Wiley-Liss, Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2914092','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2914092"><span>Genetic integration of molar <span class="hlt">cusp</span> size variation in baboons</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Koh, Christina; Bates, Elizabeth; Broughton, Elizabeth; Do, Nicholas T.; Fletcher, Zachary; Mahaney, Michael C.; Hlusko, Leslea J.</p> <p>2010-01-01</p> <p>Many studies of primate diversity and evolution rely on dental morphology for insight into diet, behavior, and phylogenetic relationships. Consequently, variation in molar <span class="hlt">cusp</span> size has increasingly become a phenotype of interest. In 2007 we published a quantitative genetic analysis of mandibular molar <span class="hlt">cusp</span> size variation in baboons. Those results provided more questions than answers, as the pattern of genetic integration did not fit predictions from odontogenesis. To follow up, we expanded our study to include data from the maxillary molar <span class="hlt">cusps</span>. Here we report on these later analyses, as well as inter-arch comparisons with the mandibular data. We analyzed variation in two-dimensional maxillary molar <span class="hlt">cusp</span> size using data collected from a captive pedigreed breeding colony of baboons, Papio hamadryas, housed at the Southwest National Primate Research Center. These analyses show that variation in maxillary molar <span class="hlt">cusp</span> size is heritable and sexually dimorphic. We also estimated additive genetic correlations between <span class="hlt">cusps</span> on the same crown, homologous <span class="hlt">cusps</span> along the tooth row, and maxillary and mandibular <span class="hlt">cusps</span>. The pattern for maxillary molars yields genetic correlations of one between the paracone-metacone and protocone-hypocone. Bivariate analyses of cuspal homologues on adjacent teeth yield correlations that are high or not significantly different from one. Between dental arcades, the non-occluding <span class="hlt">cusps</span> consistently yield high genetic correlations, especially the metaconid-paracone and metaconid-metacone. This pattern of genetic correlation does not immediately accord with the pattern of development and/or calcification, however these results do follow predictions that can be made from the evolutionary history of the tribosphenic molar. PMID:20034010</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MNRAS.465.3143M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MNRAS.465.3143M"><span>The challenging task of determining star <span class="hlt">formation</span> rates: the case of a massive <span class="hlt">stellar</span> burst in the brightest cluster galaxy of Phoenix galaxy cluster</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mittal, Rupal; McDonald, M.; Whelan, John T.; Bruzual, Gustavo</p> <p>2017-03-01</p> <p>Star <span class="hlt">formation</span> in galaxies at the centre of cooling-flow galaxy clusters is an important phenomenon in the context of <span class="hlt">formation</span> and evolution of massive galaxies in the Universe. Yet, star <span class="hlt">formation</span> rates (SFRs) in such systems continue to be elusive. We use our Bayesian-motivated spectral energy distribution (SED)-fitting code, BAYESCOOL, to estimate the plausible SFR values in the brightest cluster galaxy of a massive, X-ray luminous galaxy cluster, Phoenix. Previous studies of Phoenix have resulted in the highest measurement of SFR for any galaxy, with the estimates reaching up to 1000 M⊙ yr-1. However, a very small number of models have been considered in those studies. BAYESCOOL allows us to probe a large parameter space. We consider two models for star <span class="hlt">formation</span> history, instantaneous bursts and continuous star <span class="hlt">formation</span>, a wide range of ages for the old and the young <span class="hlt">stellar</span> population, along with other discrete parameters, such as the initial mass function, metallicities, internal extinction and extinction law. We find that in the absence of any prior except that the maximum cooling rate <3000 M⊙ yr-1, the SFR lies in the range (2230 - 2890) M⊙ yr-1. If we impose an observational prior on the internal extinction, E(B-V) < 0.6, the best-fitting SFR lies in (454 - 494) M⊙ yr-1, and we consider this as the most probable range of SFR values for Phoenix. The SFR dependence on the extinction is a reflection of the standard age-extinction degeneracy, which can be overcome by using a prior on one of the two quantities in question.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28274067','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28274067"><span>A Rare Familial Presentation of Facial Talon <span class="hlt">Cusp</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sudhakar, Sankaran; Madhavan, Abhishek; Balasubramani, Senthil; Shreenivas, Sundar</p> <p>2017-01-01</p> <p>Talon <span class="hlt">cusp</span> is a rare developmental anomaly presenting as a wisp like structure arising from the cervical region of anterior teeth. They are predominantly seen in permanent dentition with a male predilection and are commonly seen associated with incisors and on the lingual/palatal surface. The aetiology appears to be multifactorial with a possible likelihood of genetic and environmental involvement routing to disturbances in tooth development at the morphodifferentiation stage. Over the years, few cases of talon <span class="hlt">cusp</span> among the family members have been reported which strongly supports the genetic influence. We report rare presentations of talon <span class="hlt">cusp</span> among two family members involving the facial surface of incisors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5324512','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5324512"><span>A Rare Familial Presentation of Facial Talon <span class="hlt">Cusp</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Madhavan, Abhishek; Balasubramani, Senthil; Shreenivas, Sundar</p> <p>2017-01-01</p> <p>Talon <span class="hlt">cusp</span> is a rare developmental anomaly presenting as a wisp like structure arising from the cervical region of anterior teeth. They are predominantly seen in permanent dentition with a male predilection and are commonly seen associated with incisors and on the lingual/palatal surface. The aetiology appears to be multifactorial with a possible likelihood of genetic and environmental involvement routing to disturbances in tooth development at the morphodifferentiation stage. Over the years, few cases of talon <span class="hlt">cusp</span> among the family members have been reported which strongly supports the genetic influence. We report rare presentations of talon <span class="hlt">cusp</span> among two family members involving the facial surface of incisors. PMID:28274067</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930027611&hterms=Cowley&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D40%26Ntt%3DCowley','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930027611&hterms=Cowley&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D40%26Ntt%3DCowley"><span>The statistical <span class="hlt">cusp</span> - A flux transfer event model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Smith, M. F.; Lockwood, M.; Cowley, S. W. H.</p> <p>1992-01-01</p> <p>In this paper, we predict the precipitation signatures which are associated with transient magnetopause reconnection, following recent observations of the dependence of dayside ionospheric convection on the orientation of the IMF. We then employ a simple model of the longitudinal motion of flux-transfer-event signatures to show how such events can easily reproduce the local time distribution of <span class="hlt">cusp</span> occurrence probabilities, as observed by low-altitude satellites. This is true even in the limit where the <span class="hlt">cusp</span> is a series of discrete events. Furthermore, we investigate the existence of double <span class="hlt">cusp</span> patches predicted by the simple model and show how these events may be identified in the data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22521694','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22521694"><span>MERGERS AND STAR <span class="hlt">FORMATION</span>: THE ENVIRONMENT AND <span class="hlt">STELLAR</span> MASS GROWTH OF THE PROGENITORS OF ULTRA-MASSIVE GALAXIES SINCE Z = 2</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Vulcani, Benedetta; Marchesini, Danilo; De Lucia, Gabriella; Muzzin, Adam; Stefanon, Mauro; Labbé, Ivo; Brammer, Gabriel B.; Le Fèvre, Olivier; Milvang-Jensen, Bo</p> <p>2016-01-10</p> <p>The growth of galaxies is a key problem in understanding the structure and evolution of the universe. Galaxies grow their <span class="hlt">stellar</span> mass by a combination of star <span class="hlt">formation</span> and mergers, with a relative importance that is redshift dependent. Theoretical models predict quantitatively different contributions from the two channels; measuring these from the data is a crucial constraint. Exploiting the UltraVISTA catalog and a unique sample of progenitors of local ultra-massive galaxies selected with an abundance matching approach, we quantify the role of the two mechanisms from z = 2 to 0. We also compare our results to two independent incarnations of semi-analytic models. At all redshifts, progenitors are found in a variety of environments, ranging from being isolated to having 5–10 companions with mass ratio at least 1:10 within a projected radius of 500 kpc. In models, progenitors have a systematically larger number of companions, entailing a larger mass growth for mergers than in observations, at all redshifts. Generally, in both observations and models, the inferred and the expected mass growth roughly agree, within the uncertainties. Overall, our analysis confirms the model predictions, showing how the growth history of massive galaxies is dominated by in situ star <span class="hlt">formation</span> at z ∼ 2, both star <span class="hlt">formation</span> and mergers at 1 < z < 2, and by mergers alone at z < 1. Nonetheless, detailed comparisons still point out tensions between the expected mass growth and our results, which might be due to either an incorrect progenitors-descendants selection, uncertainties on star-<span class="hlt">formation</span> rate and mass estimates, or the adopted assumptions on merger rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PhST..133a4031F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PhST..133a4031F"><span>The Galactic <span class="hlt">stellar</span> disc</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Feltzing, S.; Bensby, T.</p> <p>2008-12-01</p> <p>The study of the Milky Way <span class="hlt">stellar</span> discs in the context of galaxy <span class="hlt">formation</span> is discussed. In particular, we explore the properties of the Milky Way disc using a new sample of about 550 dwarf stars for which we have recently obtained elemental abundances and ages based on high-resolution spectroscopy. For all the stars we also have full kinematic information as well as information about their <span class="hlt">stellar</span> orbits. We confirm results from previous studies that the thin and the thick discs have distinct abundance patterns. But we also explore a larger range of orbital parameters than what has been possible in our previous studies. Several new results are presented. We find that stars that reach high above the Galactic plane and have eccentric orbits show remarkably tight abundance trends. This implies that these stars formed out of well-mixed gas that had been homogenized over large volumes. We find some evidence that suggest that the event that most likely caused the heating of this <span class="hlt">stellar</span> population happened a few billion years ago. Through a simple, kinematic exploration of stars with super-solar [Fe/H], we show that the solar neighbourhood contains metal-rich, high velocity stars that are very likely associated with the thick disc. Additionally, the HR1614 moving group and the Hercules and Arcturus <span class="hlt">stellar</span> streams are discussed and it is concluded that, probably, a large fraction of the groups and streams so far identified in the disc are the result of evolution and interactions within the <span class="hlt">stellar</span> disc rather than being dissolved <span class="hlt">stellar</span> clusters or engulfed dwarf galaxies. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. Also based on observations collected at the Nordic Optical Telescope on La Palma, Spain, and at the European Southern Observatories on La Silla and Paranal, Chile, Proposals no. 65.L-0019(B), 67.B-0108(B), 69.B-0277.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...836..123L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...836..123L"><span>CO-DARK Star <span class="hlt">Formation</span> and Black Hole Activity in 3C 368 at Z = 1.131: Coeval Growth of <span class="hlt">Stellar</span> and Supermassive Black Hole Masses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lamarche, C.; Stacey, G.; Brisbin, D.; Ferkinhoff, C.; Hailey-Dunsheath, S.; Nikola, T.; Riechers, D.; Sharon, C. E.; Spoon, H.; Vishwas, A.</p> <p>2017-02-01</p> <p>We present the detection of four far-infrared fine-structure oxygen lines, as well as strong upper limits for the CO(2–1) and [N ii] 205 μm lines, in 3C 368, a well-studied radio-loud galaxy at z = 1.131. These new oxygen lines, taken in conjunction with previously observed neon and carbon fine-structure lines, suggest a powerful active galactic nucleus (AGN), accompanied by vigorous and extended star <span class="hlt">formation</span>. A starburst dominated by O8 stars, with an age of ∼6.5 Myr, provides a good fit to the fine-structure line data. This estimated age of the starburst makes it nearly concurrent with the latest episode of AGN activity, suggesting a link between the growth of the supermassive black hole and <span class="hlt">stellar</span> population in this source. We do not detect the CO(2–1) line, down to a level twelve times lower than the expected value for star-forming galaxies. This lack of CO line emission is consistent with recent star <span class="hlt">formation</span> activity if the star-forming molecular gas has low metallicity, is highly fractionated (such that CO is photodissociated throughout much of the clouds), or is chemically very young (such that CO has not yet had time to form). It is also possible, although we argue it is unlikely, that the ensemble of fine-structure lines is emitted from the region heated by the AGN.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22051363','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22051363"><span>Spatially resolved study of primary electron transport in magnetic <span class="hlt">cusps</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hubble, Aimee A.; Foster, John E.</p> <p>2012-01-15</p> <p>Spatially resolved primary electron current density profiles were measured using a planar Langmuir probe in the region above a magnetic <span class="hlt">cusp</span> in a small ion thruster discharge chamber. The probe current maps obtained were used to study the electron collection mechanics in the <span class="hlt">cusp</span> region in the limit of zero gas flow and no plasma production, and they allowed for the visualization of primary electron transport through the <span class="hlt">cusp</span>. Attenuation coefficients and loss widths were calculated as a function of probe distance above the anode at various operating conditions. Finally, the collection mechanics between two magnetic <span class="hlt">cusps</span> were studied and compared. It was found that primary electron collection was dominated by the upstream magnet ring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000021222','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000021222"><span>Enhanced Discharge Performance in a Ring <span class="hlt">Cusp</span> Plasma Source</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Foster, John E.; Patterson, Michael J.</p> <p>2000-01-01</p> <p>There is a need for a lightweight, low power ion thruster for space science missions. Such an ion thruster is under development at NASA Glenn Research Center. In an effort to better understand the discharge performance of this thruster, a thruster discharge chamber with an anode containing electrically isolated electrodes at the <span class="hlt">cusps</span> was fabricated and tested. Characteristics of this ring <span class="hlt">cusp</span> ion discharge were measured without ion beam extraction. Discharge current was measured at collection electrodes located at the magnetic <span class="hlt">cusps</span> and at the anode body itself. Discharge performance and plasma properties were measured as a function of power, which was varied between 20 and 50 W. It was found that ion production costs decreased by as much as 20 percent when the two most downstream <span class="hlt">cusp</span> electrodes were allowed to float. Floating the electrodes did not give rise to a significant increase in discharge power even though the plasma density increased markedly. The improved performance is attributed to enhanced electron containment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/1063974','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/1063974"><span>The cracked-tooth syndrome and fractured posterior <span class="hlt">cusp</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Snyder, D E</p> <p>1976-06-01</p> <p>1. Even from such a small sample as that reported in this study, it is evident that the fractured <span class="hlt">cusp</span> and cracked-tooth syndrome are common problems. The large number of fractured <span class="hlt">cusps</span> compared to the cracked-tooth syndrome suggests that some of the cases of fractured <span class="hlt">cusp</span> could have been diagnosed earlier. 2. It is most important that dentists be aware of the cracked-tooth syndrome in order to relieve the patient's discomfort, prevent the possible eventual loss of the pulp or tooth, and avoid unnecessary and possibly damaging treatment for misdiagnosed facial pain. 3. Conservation of tooth structure in restorative procedures is most necessary in order to prevent the cracked-tooth syndrome or fractured posterior <span class="hlt">cusp</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998RScI...69..968M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998RScI...69..968M"><span>Estimate of <span class="hlt">cusp</span> loss width in multicusp negative ion source</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morishita, T.; Ogasawara, M.; Hatayama, A.</p> <p>1998-02-01</p> <p>Expression of <span class="hlt">cusp</span> loss width derived by Bosch and Merlino is applied to JAERI's Kamaboko source. The width is related to the ambipolar diffusion coefficient across the <span class="hlt">cusp</span> magnetic field. Electron-ion collision is found 1.2-7.4 times larger as compared with electron-neutral collision. Averaged <span class="hlt">cusp</span> magnetic field in the diffusion coefficient is taken as a parameter in the simulation code for Kamaboko source. When the averaged magnetic field is 48 G, simulation results agree well with JAERI's experiment in a wide range of pressure and arc power variation. The value of 48 G is reasonable from the consideration of confining the equation of ion source plasma. The obtained width is about 10 times the value evaluated by two times ion Larmor radius on the surface of <span class="hlt">cusp</span> magnet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5215553','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5215553"><span>Polar <span class="hlt">cusp</span>: optical and particle characteristics-dynamics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sandholt, P.E.; Egeland, A.; Asheim, S.; Lybekk, B.; Hardy, D.A.</p> <p>1985-01-01</p> <p>Photometric observations from two stations on Svalbard, Norway, were used to map the location and dynamics of polar-<span class="hlt">cusp</span> auroras. Coordinated observations of low-energy electron precipitation from satellite HILAT and optical observations from the ground are discussed. Cases are presented showing the dynamical behavior of <span class="hlt">cusp</span> auroras and the local magnetic field related to changes in the interplanetary magnetic field (IMF) and irregularities in the solar wind plasma. Dynamical phenomena with different time scales are studied. South and northward expansions of the midday sector of the auroral oval are discussed in relation to IMF variations and geomagnetic substorm activity. Intensifications and rapid poleward motions of discrete auroral structures in the <span class="hlt">cusp</span> region are shown to be associated with local Pi type magnetic pulsations, each event lasting a few minutes. These small scale dynamical phenomena are discussed in relation to different models of plasma penetration across the dayside magnetopause, from the magnetosheath to the polar <span class="hlt">cusp</span> region of the magnetosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RAA....16..179L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RAA....16..179L"><span><span class="hlt">Stellar</span> populations in star clusters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Cheng-Yuan; de Grijs, Richard; Deng, Li-Cai</p> <p>2016-12-01</p> <p><span class="hlt">Stellar</span> populations contain the most important information about star cluster <span class="hlt">formation</span> and evolution. Until several decades ago, star clusters were believed to be ideal laboratories for studies of simple <span class="hlt">stellar</span> populations (SSPs). However, discoveries of multiple <span class="hlt">stellar</span> populations in Galactic globular clusters have expanded our view on <span class="hlt">stellar</span> populations in star clusters. They have simultaneously generated a number of controversies, particularly as to whether young star clusters may have the same origin as old globular clusters. In addition, extensive studies have revealed that the SSP scenario does not seem to hold for some intermediate-age and young star clusters either, thus making the origin of multiple <span class="hlt">stellar</span> populations in star clusters even more complicated. <span class="hlt">Stellar</span> population anomalies in numerous star clusters are well-documented, implying that the notion of star clusters as true SSPs faces serious challenges. In this review, we focus on <span class="hlt">stellar</span> populations in massive clusters with different ages. We present the history and progress of research in this active field, as well as some of the most recent improvements, including observational results and scenarios that have been proposed to explain the observations. Although our current ability to determine the origin of multiple <span class="hlt">stellar</span> populations in star clusters is unsatisfactory, we propose a number of promising projects that may contribute to a significantly improved understanding of this subject.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/160054','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/160054"><span>Simultaneous optical and HF radar observations of the ionsopheric <span class="hlt">cusp</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rodger, A.S.; Mende, S.B.; Rosenberg, T.J.; Baker, K.B.</p> <p>1995-08-01</p> <p>Simultaneous optical all-sky imager and photometer data from South Pole station and the PACE HF radar at Halley, Antarctica from two case studies are used to show that their respective ionospheric signatures of the magnetospheric <span class="hlt">cusp</span> are collocated to better than about 1{degrees} latitude. The plasma convection reversal as identified in the PACE data is usually observed within the region showing <span class="hlt">cusp</span> precipitation, as expected from contemporary models of this region of geospace. 21 refs., 3 figs., 1 tab.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/865514','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/865514"><span>Single-ring magnetic <span class="hlt">cusp</span> low gas pressure ion source</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Bacon, Frank M.; Brainard, John P.; O'Hagan, James B.; Walko, Robert J.</p> <p>1985-01-01</p> <p>A single-ring magnetic <span class="hlt">cusp</span> low gas pressure ion source designed for use in a sealed, nonpumped neutron generator utilizes a cathode and an anode, three electrically floating electrodes (a reflector behind the cathode, a heat shield around the anode, and an aperture plate), together with a single ring-<span class="hlt">cusp</span> magnetic field, to establish and energy-filtering mechanism for producing atomic-hydrogen ions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21611670','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21611670"><span>Magnetic <span class="hlt">Cusp</span> Configuration of the SPL Plasma Generator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kronberger, Matthias; Chaudet, Elodie; Favre, Gilles; Lettry, Jacques; Kuechler, Detlef; Moyret, Pierre; Paoluzzi, Mauro; Prever-Loiri, Laurent; Schmitzer, Claus; Scrivens, Richard; Steyaert, Didier</p> <p>2011-09-26</p> <p>The Superconducting Proton Linac (SPL) is a novel linear accelerator concept currently studied at CERN. As part of this study, a new Cs-free, RF-driven external antenna H{sup -} plasma generator has been developed to withstand an average thermal load of 6 kW. The magnetic configuration of the new plasma generator includes a dodecapole <span class="hlt">cusp</span> field and a filter field separating the plasma heating and H{sup -} production regions. Ferrites surrounding the RF antenna serve in enhancing the coupling of the RF to the plasma. Due to the space requirements of the plasma chamber cooling circuit, the <span class="hlt">cusp</span> magnets are pushed outwards compared to Linac4 and the <span class="hlt">cusp</span> field strength in the plasma region is reduced by 40% when N-S magnetized magnets are used. The <span class="hlt">cusp</span> field strength and plasma confinement can be improved by replacing the N-S magnets with offset Halbach elements of which each consists of three magnetic sub-elements with different magnetization direction. A design challenge is the dissipation of RF power induced by eddy currents in the <span class="hlt">cusp</span> and filter magnets which may lead to overheating and demagnetization. In view of this, a copper magnet cage has been developed that shields the <span class="hlt">cusp</span> magnets from the radiation of the RF antenna.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5384087','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5384087"><span>Latitudinal variation of the polar <span class="hlt">cusp</span> during a geomagnetic storm</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Meng, C.</p> <p>1982-01-01</p> <p>Large amplitude latitudinal variation of the polar <span class="hlt">cusp</span> position was observed during the intense geomagnetic storm of 15--16 February 1980. The observation of the polar <span class="hlt">cusp</span>, identified as the region of intense but extremely soft electron precipitation, was made by two nearly noon-midnight orbit DMSP satellites over both northern and southern hemispheres. The latitudinal shift of the polar <span class="hlt">cusp</span> is observed to be related to the intensity variation of the ring current indicated by the hourly Dst values. The polar <span class="hlt">cusp</span> region moved from its normal location at approx.76/sup 0/ gm lat down to approx.62/sup 0/ gm lat at the peak of this storm. This movement took about 5 hours and was detected over both hemispheres. A drastic variation in the width of the <span class="hlt">cusp</span> region was also observed; it is very narrow (approx.1/sup 0/) during the equatorial shift and expands to > or approx. =5/sup 0/ during the poleward recovery. Variation of the polar <span class="hlt">cusp</span> latitude with that of the Dst index was also seen during the period before the intense storm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AnGeo..33..395P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AnGeo..33..395P"><span>Are dayside long-period pulsations related to the <span class="hlt">cusp</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pilipenko, V.; Belakhovsky, V.; Engebretson, M. J.; Kozlovsky, A.; Yeoman, T.</p> <p>2015-03-01</p> <p>We compare simultaneous observations of long-period ultra-low-frequency (ULF) wave activity from a Svalbard/IMAGE fluxgate magnetometer latitudinal profile covering the expected <span class="hlt">cusp</span> geomagnetic latitudes. Irregular Pulsations at <span class="hlt">Cusp</span> Latitudes (IPCL) and narrowband Pc5 waves are found to be a ubiquitous element of ULF activity in the dayside high-latitude region. To identify the ionospheric projections of the <span class="hlt">cusp</span>, we use the width of return signal of the Super Dual Auroral Radar Network (SuperDARN) radar covering the Svalbard archipelago, predictions of empirical <span class="hlt">cusp</span> models, augmented whenever possible by Defense Meteorological Satellite Program (DMSP) identification of magnetospheric boundary domains. The meridional spatial structure of broadband dayside Pc5-6 pulsation spectral power has been found to have a localized latitudinal peak, not under the <span class="hlt">cusp</span> proper as was previously thought, but several degrees southward from the equatorward <span class="hlt">cusp</span> boundary. The earlier claims of the dayside monochromatic Pc5 wave association with the open-closed boundary also seems doubtful. Transient currents producing broadband Pc5-6 probably originate at the low-latitude boundary layer/central plasma sheet (LLBL/CPS) interface, though such identification with available DMSP data is not very precise. The occurrence of broadband Pc5-6 pulsations in the dayside boundary layers is a challenge to modelers because so far their mechanism has not been firmly identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..12111952P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..12111952P"><span>Pulsations of the polar <span class="hlt">cusp</span> aurora at Saturn</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palmaerts, B.; Radioti, A.; Roussos, E.; Grodent, D.; Gérard, J.-C.; Krupp, N.; Mitchell, D. G.</p> <p>2016-12-01</p> <p>The magnetospheric <span class="hlt">cusp</span> is a region connecting the interplanetary environment to the ionosphere and enabling solar wind particles to reach the ionosphere. We report the detection of several isolated high-latitude auroral emissions with the Ultraviolet Imaging Spectrograph of the Cassini spacecraft. We suggest that these auroral spots, located in the dawn-to-noon sector and poleward of the main emission, are the ionospheric signatures of the magnetospheric <span class="hlt">cusp</span>, in agreement with some previous observations with the Hubble Space Telescope. The high-latitude <span class="hlt">cusp</span> auroral signature has been associated with high-latitude lobe reconnection in the presence of a southward interplanetary magnetic field. The occurrence rate of the polar <span class="hlt">cusp</span> aurora suggests that lobe reconnection is frequent at Saturn. Several auroral imaging sequences reveal a quasiperiodic brightening of the polar <span class="hlt">cusp</span> aurora with a period in the range of 60 to 70 min. Similar pulsations in the energetic electron fluxes and in the azimuthal component of the magnetic field are simultaneously observed by Cassini instruments, suggesting the presence of field-aligned currents. Pulsed dayside magnetopause reconnection is a likely common triggering process for the <span class="hlt">cusp</span> auroral brightenings at Saturn and the quasiperiodic pulsations in the high-latitude energetic electron fluxes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM53B2226P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM53B2226P"><span>Long-Period ULF Wave Activity in the <span class="hlt">Cusp</span> Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pilipenko, V.; Belakhovsky, V.; Engebretson, M. J.; Kozlovsky, A.</p> <p>2013-12-01</p> <p>We compare simultaneous observations of long-period ULF wave activity from the Svalbard/IMAGE and Greenland fluxgate magnetometer profiles covering the expected <span class="hlt">cusp</span> geomagnetic latitudes. Irregular Pulsations at <span class="hlt">Cusp</span> Latitudes (IPCL) and narrow-band Pc5 waves are found to be a ubiquitous element of ULF activity in the dayside high-latitude region. To identify the ionospheric projections of the <span class="hlt">cusp</span>, we use the width of the return signal of the SuperDARN radar covering the Svalbard archipelago, predictions of empirical <span class="hlt">cusp</span> models, and augmented whenever possible by DMSP identification of magnetospheric boundary domains. The meridional spatial structure of IPCL/Pc5 pulsation spectral power has been found to have a localized latitudinal peak, but not under the <span class="hlt">cusp</span> proper as was previously thought, but several degrees southward from the equatorward <span class="hlt">cusp</span> boundary. Possible mechanisms and their relevance to observational data are discussed. The occurrence of IPCL and Pc5 waves in the dayside boundary layers is a challenge to modelers, because so far their mechanism has not been firmly identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ApJ...777L..19L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ApJ...777L..19L"><span>The Spectral Energy Distributions of z ~ 8 Galaxies from the IRAC Ultra Deep Fields: Emission Lines, <span class="hlt">Stellar</span> Masses, and Specific Star <span class="hlt">Formation</span> Rates at 650 Myr</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Labbé, I.; Oesch, P. A.; Bouwens, R. J.; Illingworth, G. D.; Magee, D.; González, V.; Carollo, C. M.; Franx, M.; Trenti, M.; van Dokkum, P. G.; Stiavelli, M.</p> <p>2013-11-01</p> <p>Using new ultradeep Spitzer/InfraRed Array Camera (IRAC) photometry from the IRAC Ultra Deep Field program, we investigate the <span class="hlt">stellar</span> populations of a sample of 63 Y-dropout galaxy candidates at z ~ 8, only 650 Myr after the big bang. The sources are selected from HST/ACS+WFC3/IR data over the Hubble Ultra Deep Field (HUDF), two HUDF parallel fields, and wide area data over the CANDELS/GOODS-South. The new Spitzer/IRAC data increase the coverage in [3.6] and [4.5] to ~120h over the HUDF reaching depths of ~28 (AB,1σ). The improved depth and inclusion of brighter candidates result in direct >=3σ InfraRed Array Camera (IRAC) detections of 20/63 sources, of which 11/63 are detected at >=5σ. The average [3.6]-[4.5] colors of IRAC detected galaxies at z ~ 8 are markedly redder than those at z ~ 7, observed only 130 Myr later. The simplest explanation is that we witness strong rest-frame optical emission lines (in particular [O III] λλ4959, 5007 + Hβ) moving through the IRAC bandpasses with redshift. Assuming that the average rest-frame spectrum is the same at both z ~ 7 and z ~ 8 we estimate a rest-frame equivalent width of {W}_{[O\\,\\scriptsize{III}]\\ \\lambda \\lambda 4959,5007+H\\beta }=670^{+260}_{-170} Å contributing 0.56^{+0.16}_{-0.11} mag to the [4.5] filter at z ~ 8. The corresponding {W}_{H\\alpha }=430^{+160}_{-110} Å implies an average specific star <span class="hlt">formation</span> rate of sSFR=11_{-5}^{+11} Gyr-1 and a <span class="hlt">stellar</span> population age of 100_{-50}^{+100} Myr. Correcting the spectral energy distribution for the contribution of emission lines lowers the average best-fit <span class="hlt">stellar</span> masses and mass-to-light ratios by ~3 ×, decreasing the integrated <span class="hlt">stellar</span> mass density to \\rho ^*(z=8,M_{\\rm{UV}}<-18)=0.6^{+0.4}_{-0.3}\\times 10^6 \\,M_\\odot Mpc-3. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012MNRAS.421.3464P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012MNRAS.421.3464P"><span>How supernova feedback turns dark matter <span class="hlt">cusps</span> into cores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pontzen, Andrew; Governato, Fabio</p> <p>2012-04-01</p> <p>We propose and successfully test against new cosmological simulations a novel analytical description of the physical processes associated with the origin of cored dark matter density profiles. In the simulations, the potential in the central kiloparsec changes on sub-dynamical time-scales over the redshift interval 4 > z > 2, as repeated, energetic feedback generates large underdense bubbles of expanding gas from centrally concentrated bursts of star <span class="hlt">formation</span>. The model demonstrates how fluctuations in the central potential irreversibly transfer energy into collisionless particles, thus generating a dark matter core. A supply of gas undergoing collapse and rapid expansion is therefore the essential ingredient. The framework, based on a novel impulsive approximation, breaks with the reliance on adiabatic approximations which are inappropriate in the rapidly changing limit. It shows that both outflows and galactic fountains can give rise to <span class="hlt">cusp</span> flattening, even when only a few per cent of the baryons form stars. Dwarf galaxies maintain their core to the present time. The model suggests that constant density dark matter cores will be generated in systems of a wide mass range if central starbursts or active galactic nucleus phases are sufficiently frequent and energetic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008safd.book.....T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008safd.book.....T"><span><span class="hlt">Stellar</span> Astrophysical Fluid Dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, Michael J.; Christensen-Dalsgaard, Jørgen</p> <p>2008-02-01</p> <p>Preface; 1. A selective overview Jørgen Christensen-Dalsgaard and Michael J. Thompson; Part I. <span class="hlt">Stellar</span> Convection and Oscillations: 2. On the diversity of <span class="hlt">stellar</span> pulsations Wojciech A. Dziembowski; 3. Acoustic radiation and mode excitation by turbulent convection Günter Houdek; 4. Understanding roAp stars Margarida S. Cunha; 5. Waves in the magnetised solar atmosphere Colin S. Rosenthal; Part II. <span class="hlt">Stellar</span> Rotation and Magnetic Fields: 6. <span class="hlt">Stellar</span> rotation: a historical survey Leon Mestel; 7. The oscillations of rapidly rotating stars Michel Rieutord; 8. Solar tachocline dynamics: eddy viscosity, anti-friction, or something in between? Michael E. McIntyre; 9. Dynamics of the solar tachocline Pascale Garaud; 10. Dynamo processes: the interaction of turbulence and magnetic fields Michael Proctor; 11. Dynamos in planets Chris Jones; Part III. Physics and Structure of <span class="hlt">Stellar</span> Interiors: 12. Solar constraints on the equation of state Werner Däppen; 13. 3He transport and the solar neutrino problem Chris Jordinson; 14. Mixing in <span class="hlt">stellar</span> radiation zones Jean-Paul Zahn; 15. Element settling and rotation-induced mixing in slowly rotating stars Sylvie Vauclair; Part IV. Helio- and Asteroseismology: 16. Solar structure and the neutrino problem Hiromoto Shibahashi; 17. Helioseismic data analysis Jesper Schou; 18. Seismology of solar rotation Takashi Sekii; 19. Telechronohelioseismology Alexander Kosovichev; Part V. Large-Scale Numerical Experiments: 20. Bridges between helioseismology and models of convection zone dynamics Juri Toomre; 21. Numerical simulations of the solar convection zone Julian R. Elliott; 22. Modelling solar and <span class="hlt">stellar</span> magnetoconvection Nigel Weiss; 23. Nonlinear magnetoconvection in the presence of a strong oblique field Keith Julien, Edgar Knobloch and Steven M. Tobias; 24. Simulations of astrophysical fluids Marcus Brüggen; Part VI. Dynamics: 25. A magic electromagnetic field Donald Lynden-Bell; 26. Continuum equations for <span class="hlt">stellar</span> dynamics Edward A</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003safd.book.....T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003safd.book.....T"><span><span class="hlt">Stellar</span> Astrophysical Fluid Dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, Michael J.; Christensen-Dalsgaard, Jørgen</p> <p>2003-05-01</p> <p>Preface; 1. A selective overview Jørgen Christensen-Dalsgaard and Michael J. Thompson; Part I. <span class="hlt">Stellar</span> Convection and Oscillations: 2. On the diversity of <span class="hlt">stellar</span> pulsations Wojciech A. Dziembowski; 3. Acoustic radiation and mode excitation by turbulent convection Günter Houdek; 4. Understanding roAp stars Margarida S. Cunha; 5. Waves in the magnetised solar atmosphere Colin S. Rosenthal; Part II. <span class="hlt">Stellar</span> Rotation and Magnetic Fields: 6. <span class="hlt">Stellar</span> rotation: a historical survey Leon Mestel; 7. The oscillations of rapidly rotating stars Michel Rieutord; 8. Solar tachocline dynamics: eddy viscosity, anti-friction, or something in between? Michael E. McIntyre; 9. Dynamics of the solar tachocline Pascale Garaud; 10. Dynamo processes: the interaction of turbulence and magnetic fields Michael Proctor; 11. Dynamos in planets Chris Jones; Part III. Physics and Structure of <span class="hlt">Stellar</span> Interiors: 12. Solar constraints on the equation of state Werner Däppen; 13. 3He transport and the solar neutrino problem Chris Jordinson; 14. Mixing in <span class="hlt">stellar</span> radiation zones Jean-Paul Zahn; 15. Element settling and rotation-induced mixing in slowly rotating stars Sylvie Vauclair; Part IV. Helio- and Asteroseismology: 16. Solar structure and the neutrino problem Hiromoto Shibahashi; 17. Helioseismic data analysis Jesper Schou; 18. Seismology of solar rotation Takashi Sekii; 19. Telechronohelioseismology Alexander Kosovichev; Part V. Large-Scale Numerical Experiments: 20. Bridges between helioseismology and models of convection zone dynamics Juri Toomre; 21. Numerical simulations of the solar convection zone Julian R. Elliott; 22. Modelling solar and <span class="hlt">stellar</span> magnetoconvection Nigel Weiss; 23. Nonlinear magnetoconvection in the presence of a strong oblique field Keith Julien, Edgar Knobloch and Steven M. Tobias; 24. Simulations of astrophysical fluids Marcus Brüggen; Part VI. Dynamics: 25. A magic electromagnetic field Donald Lynden-Bell; 26. Continuum equations for <span class="hlt">stellar</span> dynamics Edward A</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22521766','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22521766"><span>THE MOSDEF SURVEY: DISSECTING THE STAR <span class="hlt">FORMATION</span> RATE VERSUS <span class="hlt">STELLAR</span> MASS RELATION USING Hα AND Hβ EMISSION LINES AT z ∼ 2</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shivaei, Irene; Reddy, Naveen A.; Siana, Brian; Mobasher, Bahram; Freeman, William R.; Groot, Laura de; Shapley, Alice E.; Sanders, Ryan; Kriek, Mariska; Price, Sedona H.; Coil, Alison L.; Azadi, Mojegan</p> <p>2015-12-20</p> <p>We present results on the star <span class="hlt">formation</span> rate (SFR) versus <span class="hlt">stellar</span> mass (M{sub *}) relation (i.e., the “main sequence”) among star-forming galaxies at 1.37 ≤ z ≤ 2.61 using the MOSFIRE Deep Evolution Field (MOSDEF) survey. Based on a sample of 261 galaxies with Hα and Hβ spectroscopy, we have estimated robust dust-corrected instantaneous SFRs over a large range in M{sub *} (∼10{sup 9.5}–10{sup 11.5} M{sub ⊙}). We find a correlation between log(SFR(Hα)) and log(M{sub *}) with a slope of 0.65 ± 0.08 (0.58 ± 0.10) at 1.4 < z < 2.6 (2.1 < z < 2.6). We find that different assumptions for the dust correction, such as using the color excess of the <span class="hlt">stellar</span> continuum to correct the nebular lines, sample selection biases against red star-forming galaxies, and not accounting for Balmer absorption, can yield steeper slopes of the log(SFR)–log(M{sub *}) relation. Our sample is immune from these biases as it is rest-frame optically selected, Hα and Hβ are corrected for Balmer absorption, and the Hα luminosity is dust corrected using the nebular color excess computed from the Balmer decrement. The scatter of the log(SFR(Hα))–log(M{sub *}) relation, after accounting for the measurement uncertainties, is 0.31 dex at 2.1 < z < 2.6, which is 0.05 dex larger than the scatter in log(SFR(UV))–log(M{sub *}). Based on comparisons to a simulated SFR–M{sub *} relation with some intrinsic scatter, we argue that in the absence of direct measurements of galaxy-to-galaxy variations in the attenuation/extinction curves and the initial mass function, one cannot use the difference in the scatter of the SFR(Hα)– and SFR(UV)–M{sub *} relations to constrain the stochasticity of star <span class="hlt">formation</span> in high-redshift galaxies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AAS...22934416D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AAS...22934416D"><span>Assessing the fundamental limits of multiple star <span class="hlt">formation</span>: An imaging search for the lowest mass <span class="hlt">stellar</span> companions to intermediate-mass stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duchene, Gaspard; Tzern Oon, Jner; Kantorski, Patrick; De Rosa, Robert J.; Thomas, Sandrine; Patience, Jennifer; Pueyo, Laurent; Nielsen, Eric L.; Konopacky, Quinn M.</p> <p>2017-01-01</p> <p><span class="hlt">Stellar</span> binaries are a common byproduct of star <span class="hlt">formation</span> and therefore inform us on the processes of collapse and fragmentation of prestellar cores. While multiplicity surveys generally reveal an extensive diversity of multiple systems, with broad ranges of semi-major axis, mass ratio and eccentricities, one remarkable feature that was identified in the last two decades is the so-called brown dwarf desert, i.e., the apparent paucity of (non-planetary) substellar companions to solar-type stars. This "desert" was primarily identified among spectroscopic binaries but also appears to be a significant feature of wider, visual binaries. The physical origin of this feature has not been fully accounted for but is likely established during the <span class="hlt">formation</span> of the systems. One way to shed new light on this question is to study the frequency of low-mass <span class="hlt">stellar</span> companions to intermediate-mass star (late-B type, or 3-5 Msun), as those form through a similar, albeit scaled-up, mechanism as solar-type stars. Here we present preliminary results from two adaptive-optics based surveys to search for such multiple systems. Specifically, we are using the new ShaneAO system on the Lick3m telescope (~100 stars observed to date) and the Gemini Planet Imager (45 stars observed). We are targeting stars located both in open clusters and scattered in the Galactic field to search for potential evidence of dynamic evolution. To identify candidate low-mass companions as close in to target stars, we use advanced point spread function (PSF) subtraction algorithms, specifically implementations of the LOCI and KLIP algorithms. In the case of the ShaneAO observations, which do not allow for field rotation, we use LOCI in combination with Reference Differential Imaging (ADI), using our library of science images as input for PSF subtraction. In this contribution, we will discuss the potential of ShaneAO to reveal faint, subarcsecond companions in this context and present candidate companions from both</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003SSRv..108..577F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003SSRv..108..577F"><span><span class="hlt">Stellar</span> Coronal Astronomy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Favata, Fabio; Micela, Giuseppina</p> <p>2003-10-01</p> <p>Coronal astronomy is by now a fairly mature discipline, with a quarter century having gone by since the detection of the first <span class="hlt">stellar</span> X-ray coronal source (Capella), and having benefitted from a series of major orbiting observing facilities. Serveral observational characteristics of coronal X-ray and EUV emission have been solidly established through extensive observations, and are by now common, almost text-book, knowledge. At the same time the implications of coronal astronomy for broader astrophysical questions (e.g.Galactic structure, <span class="hlt">stellar</span> <span class="hlt">formation</span>, <span class="hlt">stellar</span> structure, etc.) have become appreciated. The interpretation of <span class="hlt">stellar</span> coronal properties is however still often open to debate, and will need qualitatively new observational data to book further progress. In the present review we try to recapitulate our view on the status of the field at the beginning of a new era, in which the high sensitivity and the high spectral resolution provided by Chandra and SMM-Newton will address new questions which were not accessible before.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008MNRAS.388...67K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008MNRAS.388...67K"><span>The UV colours of high-redshift early-type galaxies: evidence for recent star <span class="hlt">formation</span> and <span class="hlt">stellar</span> mass assembly over the last 8 billion years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kaviraj, S.; Khochfar, S.; Schawinski, K.; Yi, S. K.; Gawiser, E.; Silk, J.; Virani, S. N.; Cardamone, C. N.; van Dokkum, P. G.; Urry, C. M.</p> <p>2008-07-01</p> <p>We combine deep optical and NIR (UBVRIzJK) photometry from the Multiwavelength Survey by Yale-Chile (MUSYC) with redshifts from the COMBO-17 survey to perform a large-scale study of the rest-frame ultraviolet (UV) properties of 674 high-redshift (0.5 < z < 1) early-type galaxies, drawn from the Extended Chandra Deep Field-South (E-CDFS). Galaxy morphologies are determined through visual inspection of Hubble Space Telescope (HST) images taken from the GEMS survey. We harness the sensitivity of the UV to young (<1-Gyr old) stars to quantify the recent star <span class="hlt">formation</span> history of early-type galaxies across a range of luminosities [-23.5 < M(V) < -18]. Comparisons to simple <span class="hlt">stellar</span> populations forming at high redshift indicate that ~1.1 per cent of early-types in this sample are consistent with purely passive ageing since z = 2 - this value drops to ~0.24 per cent and ~0.15 per cent for z = 3 and 5, respectively. Parametrizing the recent star <span class="hlt">formation</span> (RSF) in terms of the mass fraction of stars less than a Gyr old, we find that the early-type population as a whole shows a typical RSF between 5 and 13 per cent in the redshift range 0.5 < z < 1. Early-types on the broad UV `red sequence' show RSF values less than 5 per cent, while the reddest early-types (which are also the most luminous) are virtually quiescent with RSF values of ~1 per cent. In contrast to their low-redshift (z < 0.1) counterparts, the high-redshift early-types in this sample show a pronounced bimodality in the rest-frame UV-optical colour, with a minor but significant peak centred on the blue cloud. Furthermore, star <span class="hlt">formation</span> in the most active early-types is a factor of 2 greater at z ~ 0.7 than in the local universe. Given that evolved sources of UV flux (e.g. horizontal branch stars) should be absent at z > 0.5, implying that the UV is dominated by young stars, we find compelling evidence that early-types of all luminosities form stars over the lifetime of the Universe, although the bulk of their</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1253692-role-disks-formation-stellar-systems-numerical-parameter-study-rapid-accretion','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1253692-role-disks-formation-stellar-systems-numerical-parameter-study-rapid-accretion"><span>On the role of disks in the <span class="hlt">formation</span> of <span class="hlt">stellar</span> systems: A numerical parameter study of rapid accretion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Kratter, Kaitlin M.; Matzner, Christopher D.; Krumholz, Mark R.; ...</p> <p>2009-12-23</p> <p>We study rapidly accreting, gravitationally unstable disks with a series of idealized global, numerical experiments using the code ORION. Our numerical parameter study focuses on protostellar disks, showing that one can predict disk behavior and the multiplicity of the accreting star system as a function of two dimensionless parameters which compare the infall rate to the disk sound speed and orbital period. Although gravitational instabilities become strong, we find that fragmentation into binary or multiple systems occurs only when material falls in several times more rapidly than the canonical isothermal limit. The disk-to-star accretion rate is proportional to the infallmore » rate and governed by gravitational torques generated by low-m spiral modes. Furthermore, we also confirm the existence of a maximum stable disk mass: disks that exceed ~50% of the total system mass are subject to fragmentation and the subsequent <span class="hlt">formation</span> of binary companions.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1253692','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1253692"><span>On the role of disks in the <span class="hlt">formation</span> of <span class="hlt">stellar</span> systems: A numerical parameter study of rapid accretion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kratter, Kaitlin M.; Matzner, Christopher D.; Krumholz, Mark R.; Klein, Richard I.</p> <p>2009-12-23</p> <p>We study rapidly accreting, gravitationally unstable disks with a series of idealized global, numerical experiments using the code ORION. Our numerical parameter study focuses on protostellar disks, showing that one can predict disk behavior and the multiplicity of the accreting star system as a function of two dimensionless parameters which compare the infall rate to the disk sound speed and orbital period. Although gravitational instabilities become strong, we find that fragmentation into binary or multiple systems occurs only when material falls in several times more rapidly than the canonical isothermal limit. The disk-to-star accretion rate is proportional to the infall rate and governed by gravitational torques generated by low-m spiral modes. Furthermore, we also confirm the existence of a maximum stable disk mass: disks that exceed ~50% of the total system mass are subject to fragmentation and the subsequent <span class="hlt">formation</span> of binary companions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22521406','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22521406"><span>DIFFICULTY IN THE <span class="hlt">FORMATION</span> OF COUNTER-ORBITING HOT JUPITERS FROM NEAR-COPLANAR HIERARCHICAL TRIPLE SYSTEMS: A SUB-<span class="hlt">STELLAR</span> PERTURBER</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Xue, Yuxin; Suto, Yasushi</p> <p>2016-03-20</p> <p>Among 100 transiting planets with a measured projected spin–orbit angle λ, several systems are suggested to be counter-orbiting. While these cases may be due to the projection effect, the mechanism that produces a counter-orbiting planet has not been established. A promising scenario for counter-orbiting planets is the extreme eccentricity evolution in near-coplanar hierarchical triple systems with eccentric inner and outer orbits. We examine this scenario in detail by performing a series of systematic numerical simulations, and consider the possibility of forming hot Jupiters (HJs), especially a counter-orbiting one under this mechanism with a distant sub-<span class="hlt">stellar</span> perturber. We incorporate quadrupole and octupole secular gravitational interaction between the two orbits, and also short-range forces (correction for general relativity, star and inner planetary tide, and rotational distortion) simultaneously. We find that most systems are tidally disrupted and that a small fraction of the surviving planets turn out to be prograde. The <span class="hlt">formation</span> of counter-orbiting HJs in this scenario is possible only in a very restricted parameter region, and thus is very unlikely in practice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...836..213A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...836..213A"><span>Magnetohydrodynamic Simulations of the <span class="hlt">Formation</span> of Molecular Clouds toward the <span class="hlt">Stellar</span> Cluster Westerlund 2: Interaction of a Jet with a Clumpy Interstellar Medium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Asahina, Yuta; Kawashima, Tomohisa; Furukawa, Naoko; Enokiya, Rei; Yamamoto, Hiroaki; Fukui, Yasuo; Matsumoto, Ryoji</p> <p>2017-02-01</p> <p>The <span class="hlt">formation</span> mechanism of CO clouds observed with the NANTEN2 and Mopra telescopes toward the <span class="hlt">stellar</span> 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 by 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...820...55X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...820...55X"><span>Difficulty in the <span class="hlt">Formation</span> of Counter-orbiting Hot Jupiters from Near-coplanar Hierarchical Triple Systems: A Sub-<span class="hlt">stellar</span> Perturber</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xue, Yuxin; Suto, Yasushi</p> <p>2016-03-01</p> <p>Among 100 transiting planets with a measured projected spin-orbit angle λ, several systems are suggested to be counter-orbiting. While these cases may be due to the projection effect, the mechanism that produces a counter-orbiting planet has not been established. A promising scenario for counter-orbiting planets is the extreme eccentricity evolution in near-coplanar hierarchical triple systems with eccentric inner and outer orbits. We examine this scenario in detail by performing a series of systematic numerical simulations, and consider the possibility of forming hot Jupiters (HJs), especially a counter-orbiting one under this mechanism with a distant sub-<span class="hlt">stellar</span> perturber. We incorporate quadrupole and octupole secular gravitational interaction between the two orbits, and also short-range forces (correction for general relativity, star and inner planetary tide, and rotational distortion) simultaneously. We find that most systems are tidally disrupted and that a small fraction of the surviving planets turn out to be prograde. The <span class="hlt">formation</span> of counter-orbiting HJs in this scenario is possible only in a very restricted parameter region, and thus is very unlikely in practice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...590A..72P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...590A..72P"><span>The initial conditions for <span class="hlt">stellar</span> protocluster <span class="hlt">formation</span>. III. The Herschel counterparts of the Spitzer Dark Cloud catalogue</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peretto, N.; Lenfestey, C.; Fuller, G. A.; Traficante, A.; Molinari, S.; Thompson, M. A.; Ward-Thompson, D.</p> <p>2016-05-01</p> <p>Context. Galactic plane surveys of pristine molecular clouds are key for establishing a Galactic-scale view of star <span class="hlt">formation</span>. For this reason, an unbiased sample of infrared dark clouds in the 10° < | l | < 65°, | b | < 1° region of the Galactic plane was built using Spitzer 8 μm extinction. However, intrinsic fluctuations in the mid-infrared background can be misinterpreted as foreground clouds. Aims: The main goal of this study is to disentangle real clouds in the Spitzer Dark Cloud (SDC) catalogue from artefacts due to fluctuations in the mid-infrared background. Methods: We constructed H2 column density maps at ~18″ resolution using the 160 μm and 250 μm data from the Herschel Galactic plane survey Hi-GAL. We also developed an automated detection scheme that confirms the existence of a SDC through its association with a peak on these Herschel column density maps. Detection simulations, along with visual inspection of a small sub-sample of SDCs, have been performed to get more insight into the limitations of our automated identification scheme. Results: Our analysis shows that 76( ± 19)% of the catalogued SDCs are real. This fraction drops to 55( ± 12)% for clouds with angular diameters larger than ~1 arcmin. The contamination of the PF09 catalogue by large spurious sources reflects the large uncertainties associated to the construction of the 8 μm background emission, a key stage in identiying SDCs. A comparison of the Herschel confirmed SDC sample with the BGPS and ATLASGAL samples shows that SDCs probe a unique range of cloud properties, reaching down to more compact and lower column density clouds than any of these two (sub-)millimetre Galactic plane surveys. Conclusions: Even though about half of the large SDCs are spurious sources, the vast majority of the catalogued SDCs do have a Herschel counterpart. The Herschel-confirmed sample of SDCs offers a unique opportunity to study the earliest stages of both low- and high-mass star <span class="hlt">formation</span> across</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25593665','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25593665"><span>Mandibular talon <span class="hlt">cusps</span>: A Systematic review and data analysis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mallineni, Sreekanth-Kumar; Panampally, George-Kurian; Chen, Yong; Tian, Tian</p> <p>2014-10-01</p> <p>The purpose of the present study was to evaluate mandibular talon <span class="hlt">cusps</span> distribution from the comprehensive literature search and proposal of new classification Material and Methods: The study was a review of articles published in the English language from January 1960 to December 2013. The PubMed/MEDLINE/Google Scholor databases were searched electronically using 'talon <span class="hlt">cusp</span>', 'dens evaginatus', 'anterior teeth', mandible, 'primary dentition' and ' permanent dentition' as search terms in various combinations. The citation lists from the included references were subsequently examined, and a hand search was also performed in an attempt to identify additional reports. The distribution, characteristics, common tooth type, associated dental anomaly and proposal of new classification have been included in final data analysis. Descriptive statistics were carried out using Chi square test (SPSS, version 17). Overall 37 citations were retrieved from the literature where one was prevalence studies and rest were case reports among those two were duplication. Total 35 articles with 43 patients were reported on mandibular talon <span class="hlt">cusps</span>. Males were predominantly affected than females (p<0.05). Eight cases (19%) were reported in archeological skulls 81% were clinical reports. Forty cases (93%) were reported in permanent dentition while 7% cases in primary dentition. Lingual mandibular talon are more common than facial type in permanent dentition facial talons (p<0.05). Seven cases (18%) were bilaterally involved. Double tooth (45%) was commonly associated with mandibular talons. Most of the cases reported from Asia and asia derived populations. Central incisor is the most common tooth type that effected by talon <span class="hlt">cusp</span> in permanent dentition and lateral incisor is in primary dentition. Lingual talons are common in mandible. Double tooth common dental anomaly associated with mandibular talon <span class="hlt">cusp</span>. Most of the case reported from Asia. Talon <span class="hlt">cusps</span> should be classified as facial</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...841..131A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...841..131A"><span>Legacy ExtraGalactic UV Survey with The Hubble Space Telescope: <span class="hlt">Stellar</span> Cluster Catalogs and First Insights Into Cluster <span class="hlt">Formation</span> and Evolution in NGC 628</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adamo, A.; Ryon, J. E.; Messa, M.; Kim, H.; Grasha, K.; Cook, D. O.; Calzetti, D.; Lee, J. C.; Whitmore, B. C.; Elmegreen, B. G.; Ubeda, L.; Smith, L. J.; Bright, S. N.; Runnholm, A.; Andrews, J. E.; Fumagalli, M.; Gouliermis, D. A.; Kahre, L.; Nair, P.; Thilker, D.; Walterbos, R.; Wofford, A.; Aloisi, A.; Ashworth, G.; Brown, T. M.; Chandar, R.; Christian, C.; Cignoni, M.; Clayton, G. C.; Dale, D. A.; de Mink, S. E.; Dobbs, C.; Elmegreen, D. M.; Evans, A. S.; Gallagher, J. S., III; Grebel, E. K.; Herrero, A.; Hunter, D. A.; Johnson, K. E.; Kennicutt, R. C.; Krumholz, M. R.; Lennon, D.; Levay, K.; Martin, C.; Nota, A.; Östlin, G.; Pellerin, A.; Prieto, J.; Regan, M. W.; Sabbi, E.; Sacchi, E.; Schaerer, D.; Schiminovich, D.; Shabani, F.; Tosi, M.; Van Dyk, S. D.; Zackrisson, E.</p> <p>2017-06-01</p> <p>We report the large effort that is producing comprehensive high-level young star cluster (YSC) catalogs for a significant fraction of galaxies observed with the Legacy ExtraGalactic UV Survey (LEGUS) Hubble treasury program. We present the methodology developed to extract cluster positions, verify their genuine nature, produce multiband photometry (from NUV to NIR), and derive their physical properties via spectral energy distribution fitting analyses. We use the nearby spiral galaxy NGC 628 as a test case for demonstrating the impact that LEGUS will have on our understanding of the <span class="hlt">formation</span> and evolution of YSCs and compact <span class="hlt">stellar</span> associations within their host galaxy. Our analysis of the cluster luminosity function from the UV to the NIR finds a steepening at the bright end and at all wavelengths suggesting a dearth of luminous clusters. The cluster mass function of NGC 628 is consistent with a power-law distribution of slopes ˜ -2 and a truncation of a few times 105 {M}⊙ . After their <span class="hlt">formation</span>, YSCs and compact associations follow different evolutionary paths. YSCs survive for a longer time frame, confirming their being potentially bound systems. Associations disappear on timescales comparable to hierarchically organized star-forming regions, suggesting that they are expanding systems. We find mass-independent cluster disruption in the inner region of NGC 628, while in the outer part of the galaxy there is little or no disruption. We observe faster disruption rates for low mass (≤104 {M}⊙ ) clusters, suggesting that a mass-dependent component is necessary to fully describe the YSC disruption process in NGC 628. Based on observations obtained with the NASA/ESA Hubble Space Telescope, 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21300437','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21300437"><span>Radial Compression of a Non-neutral Plasma in a Non-uniform Magnetic Field of a <span class="hlt">Cusp</span> Trap</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Saitoh, H.; Mohri, A.; Kanai, Y.; Enomoto, Y.; Yamazaki, Y.</p> <p>2009-03-30</p> <p>Spectroscopic comparison of antihydrogen and hydrogen atoms is one of the best candidates for the stringent tests of the CPT symmetry, and intensive studies are being carried out by using Antiproton Decelerator at CERN. The ASACUSA collaboration has constructed a superconducting <span class="hlt">cusp</span> trap for the <span class="hlt">formation</span>, trapping and extraction of antihydrogen atoms, where a quadrupole magnetic field is generated by a pair of anti-Helmholtz coils with anti-parallel currents. The <span class="hlt">cusp</span> configuration is considerably advantageous for the extraction of spin-polarized and ground-state antihydrogen beams that are ideal for the spectroscopic measurements of hyperfine structures of the ground state of antihydrogen. For the effective generation of antihydrogen atoms, it is essential to form high density and stable plasmas of antiproton and positrons. In this study, we applied a rotating electric field to an electron plasma in the inhomogeneous <span class="hlt">cusp</span> magnetic field, and demonstrated the effective radial compression of a non-neutral plasma in a broad frequency range. The compression rate depended on the rotating frequency and had a broad peak extending on both sides of a longitudinal (1,0) mode frequency, which was the only observed characteristic frequency. The similar procedure can in principle be applied to positron and antiproton plasmas, and the results are one of necessary steps toward antihydrogen experiments in the <span class="hlt">cusp</span> trap.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3673162','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3673162"><span>How does tooth <span class="hlt">cusp</span> radius of curvature affect brittle food item processing?</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Berthaume, Michael A.; Dumont, Elizabeth R.; Godfrey, Laurie R.; Grosse, Ian R.</p> <p>2013-01-01</p> <p>Tooth <span class="hlt">cusp</span> sharpness, measured by radius of curvature (RoC), has been predicted to play a significant role in brittle/hard food item fracture. Here, we set out to test three existing hypotheses about this relationship: namely, the Blunt and Strong <span class="hlt">Cusp</span> hypotheses, which predict that dull <span class="hlt">cusps</span> will be most efficient at brittle food item fracture, and the Pointed <span class="hlt">Cusp</span> hypothesis, which predicts that sharp <span class="hlt">cusps</span> will be most efficient at brittle food item fracture using a four <span class="hlt">cusp</span> bunodont molar. We also put forth and test the newly constructed Complex <span class="hlt">Cusp</span> hypothesis, which predicts that a mixture of dull and sharp <span class="hlt">cusps</span> will be most efficient at brittle food item fracture. We tested the four hypotheses using finite-element models of four <span class="hlt">cusped</span>, bunodont molars. When testing the three existing hypotheses, we assumed all <span class="hlt">cusps</span> had the same level of sharpness (RoC), and gained partial support for the Blunt <span class="hlt">Cusp</span> hypotheses. We found no support for the Pointed <span class="hlt">Cusp</span> or Strong <span class="hlt">Cusp</span> hypotheses. We used the Taguchi sampling method to test the Complex <span class="hlt">Cusps</span> hypothesis with a morphospace created by independently varying the radii of curvature of the four <span class="hlt">cusps</span> in the buccolingual and mesiodistal directions. The optimal occlusal morphology for fracturing brittle food items consists of a combination of sharp and dull <span class="hlt">cusps</span>, which creates high stress concentrations in the food item while stabilizing the food item and keeping the stress concentrations in the enamel low. This model performed better than the Blunt <span class="hlt">Cusp</span> hypothesis, suggesting a role for optimality in the evolution of <span class="hlt">cusp</span> form. PMID:23635495</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22167342','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22167342"><span><span class="hlt">STELLAR</span> TRANSITS IN ACTIVE GALACTIC NUCLEI</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Beky, Bence; Kocsis, Bence E-mail: bkocsis@cfa.harvard.edu</p> <p>2013-01-01</p> <p>Supermassive black holes (SMBHs) are typically surrounded by a dense <span class="hlt">stellar</span> population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of <span class="hlt">stellar</span> <span class="hlt">cusps</span>, we find that around 10{sup 6} solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or {approx}10% in UV bands or soft X-ray. It may be possible to identify <span class="hlt">stellar</span> transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear <span class="hlt">stellar</span> clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18315176','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18315176"><span>Study on an azimuthal line <span class="hlt">cusp</span> ion source for the KSTAR neutral beam injector.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jeong, Seung Ho; Chang, Doo-Hee; In, Sang Ryul; Lee, Kwang Won; Oh, Byung-Hoon; Yoon, Byung-Joo; Song, Woo Sob; Kim, Jinchoon; Kim, Tae Seong</p> <p>2008-02-01</p> <p>In this study it is found that the <span class="hlt">cusp</span> magnetic field configuration of an anode bucket influences the primary electron behavior. An electron orbit code (ELEORBIT code) showed that an azimuthal line <span class="hlt">cusp</span> (<span class="hlt">cusp</span> lines run azimuthally with respect to the beam extraction direction) provides a longer primary electron confinement time than an axial line <span class="hlt">cusp</span> configuration. Experimentally higher plasma densities were obtained under the same arc power when the azimuthal <span class="hlt">cusp</span> chamber was used. The newly designed azimuthal <span class="hlt">cusp</span> bucket has been investigated in an effort to increase the plasma density in its plasma generator per arc power.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-GSFC_20170927_Archive_e000245.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-GSFC_20170927_Archive_e000245.html"><span><span class="hlt">Stellar</span> shrapnel</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2016-08-15</p> <p>Several thousand years ago, a star some 160 000 light-years away from us exploded, scattering <span class="hlt">stellar</span> shrapnel across the sky. The aftermath of this energetic detonation is shown here in this striking image from the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3. The exploding star was a white dwarf located in the Large Magellanic Cloud, one of our nearest neighbouring galaxies. Around 97% of stars within the Milky Way that are between a tenth and eight times the mass of the Sun are expected to end up as white dwarfs. These stars can face a number of different fates, one of which is to explode as supernovae, some of the brightest events ever observed in the Universe. If a white dwarf is part of a binary star system, it can siphon material from a close companion. After gobbling up more than it can handle — and swelling to approximately one and a half times the size of the Sun — the star becomes unstable and ignites as a Type Ia supernova. This was the case for the supernova remnant pictured here, which is known as DEM L71. It formed when a white dwarf reached the end of its life and ripped itself apart, ejecting a superheated cloud of debris in the process. Slamming into the surrounding interstellar gas, this <span class="hlt">stellar</span> shrapnel gradually diffused into the separate fiery filaments of material seen scattered across this skyscape.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JETP..124..318M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JETP..124..318M"><span>Coulomb scatter of diamagnetic dust particles in a <span class="hlt">cusp</span> magnetic trap under microgravity conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Myasnikov, M. I.; D'yachkov, L. G.; Petrov, O. F.; Vasiliev, M. M.; Fortov, V. E.; Savin, S. F.; Serova, E. O.</p> <p>2017-02-01</p> <p>The effect of a dc electric field on strongly nonideal Coulomb systems consisting of a large number ( 104) of charged diamagnetic dust particles in a <span class="hlt">cusp</span> magnetic trap are carried out aboard the Russian segment of the International Space Station (ISS) within the Coulomb Crystal experiment. Graphite particles of 100-400 μm in size are used in the experiments. Coulomb scatter of a dust cluster and the <span class="hlt">formation</span> of threadlike chains of dust particles are observed experimentally. The processes observed are simulated by the molecular dynamics (MD) method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MNRAS.466.1709T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MNRAS.466.1709T"><span>Dust <span class="hlt">formation</span> and mass loss around intermediate-mass AGB stars with initial metallicity Zini ≤ 10-4 in the early Universe - I. Effect of surface opacity on <span class="hlt">stellar</span> evolution and the dust-driven wind</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tashibu, Shohei; Yasuda, Yuki; Kozasa, Takashi</p> <p>2017-04-01</p> <p>Dust <span class="hlt">formation</span> and the resulting mass loss around asymptotic giant branch (AGB) stars with initial metallicity in the range 0 ≤ Zini ≤ 10-4 and initial mass 2 ≤ Mini/M⊙ ≤ 5 are explored by hydrodynamical calculations of the dust-driven wind (DDW) along the AGB evolutionary tracks. We employ the MESA code to simulate the evolution of stars, assuming an empirical mass-loss rate in the post-main-sequence phase and considering three types of low-temperature opacity (scaled-solar, CO-enhanced and CNO-enhanced opacity) to elucidate the effect on <span class="hlt">stellar</span> evolution and the DDW. We find that the treatment of low-temperature opacity strongly affects dust <span class="hlt">formation</span> and the resulting DDW; in the carbon-rich AGB phase, the maximum dot{M} of Mini ≥ 3 M⊙ stars with the CO-enhanced opacity is at least one order of magnitude smaller than that with the CNO-enhanced opacity. A wide range of <span class="hlt">stellar</span> parameters being covered, the necessary condition for driving efficient DDW with dot{M} ≥ 10^{-6} M⊙ yr-1 is expressed as effective temperature Teff ≲ 3850 K and log (δCL/κRM) ≳ 10.43log Teff - 32.33, with the carbon excess δC defined as εC - εO, the Rosseland mean opacity κR in units of cm2 g-1 in the surface layer and the <span class="hlt">stellar</span> mass (luminosity) M(L) in solar units. The fitting formulae derived for gas and dust mass-loss rates in terms of input <span class="hlt">stellar</span> parameters could be useful for investigating the dust yield from AGB stars in the early Universe being consistent with <span class="hlt">stellar</span> evolution calculations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009A%26A...506..711G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009A%26A...506..711G"><span>Star <span class="hlt">formation</span> history of Canis Major R1. I. Wide-Field X-ray study of the young <span class="hlt">stellar</span> population</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gregorio-Hetem, J.; Montmerle, T.; Rodrigues, C. V.; Marciotto, E.; Preibisch, T.; Zinnecker, H.</p> <p>2009-11-01</p> <p>Aims: The CMa R1 star-forming region contains several compact clusters as well as many young early-B stars. It is associated with a well-known bright rimmed nebula, the nature of which is unclear (fossil HII region or supernova remnant). To help elucidate the nature of the nebula, our goal was to reconstruct the star-<span class="hlt">formation</span> history of the CMa R1 region, including the previously unknown older, fainter low-mass <span class="hlt">stellar</span> population, using X-rays. Methods: We analyzed images obtained with the ROSAT satellite, covering 5 sq. deg. Complementary VRI photometry was performed with the Gemini South telescope. Colour-magnitude and colour-colour diagrams were used in conjunction with pre-main sequence evolutionary tracks to derive the masses and ages of the X-ray sources. Results: The ROSAT images show two distinct clusters. One is associated with the known optical clusters near Z CMa, to which 40 members are added. The other, which we name the “GU CMa” cluster, is new, and contains 60 members. The ROSAT sources are young stars with masses down to M_star 0.5 M_⊙, and ages up to 10 Myr. The mass functions of the two clusters are similar, but the GU CMa cluster is older than the cluster around Z CMa by at least a few Myr. Also, the GU CMa cluster is away from any molecular cloud, implying that star <span class="hlt">formation</span> must have ceased; on the contrary (as already known), star <span class="hlt">formation</span> is very active in the Z CMa region. Based in part on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JDE...252.1562R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JDE...252.1562R"><span>The modulus of unfoldings of <span class="hlt">cusps</span> in conformal geometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rousseau, C.</p> <p></p> <p>In this paper we give the complete classification of generic 1-parameter unfoldings of germs of real analytic curves with a cuspidal point under conformal equivalence. A <span class="hlt">cusp</span> is obtained by squaring an analytic curve having contact of order 1 with a line through the origin. We show that this point of view can be extended to the unfolding. This allows to reduce the classification of unfoldings of <span class="hlt">cusps</span> to the classification of unfoldings of a pair of curves having a contact of order 1 at the origin, one being obtained from the other through a reflection with respect to the origin. This unfolding can be studied in the same way as an unfolding of a curvilinear angle with zero angle, called a horn. We then classify the unfoldings of the special horns corresponding to <span class="hlt">cusps</span> by means of the associated diffeomorphisms. We interpret the results geometrically.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15242387','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15242387"><span>Talon <span class="hlt">cusp</span> associated with other dental anomalies: a case report.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dash, J K; Sahoo, P K; Das, S N</p> <p>2004-07-01</p> <p>Talon <span class="hlt">cusp</span> is an uncommon dental anomaly referring to an accessory <span class="hlt">cusp</span> projecting from the cingulum area, or cemento-enamel junction of maxillary or mandibular anterior teeth, in both the primary and permanent dentition. This paper reports a rare case of talon <span class="hlt">cusp</span> affecting the mandibular right central incisor and maxillary right lateral incisor, together with other dental abnormalities, viz. an inverted impacted migrating mandibular right second premolar; complete agenesis of the maxillary and mandibular third molars, the maxillary right second permanent molar, and the mandibular left permanent central incisor; severe crowding; deep bite; hypoplastic teeth; bilateral reverse cross-bite in the premolar region; and a retrognathic mandible. The presence of this number of dental anomalies in a single patient is rare.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994GeoRL..21.1919N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994GeoRL..21.1919N"><span>Freja observations of multiple injection events in <span class="hlt">cusp</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Norberg, O.; Yamauchi, M.; Eliasson, L.; Lundin, R.</p> <p></p> <p>The TICS (Three-dimensional Ion Composition Spectrometer) instrument on board the Freja satellite provides particle data with high spatial, temporal, spectral, and mass resolution. The Freja orbit (inclination 63°) is suitable for studies of the <span class="hlt">cusp</span> since the satellite traverses this region longitudinally when the <span class="hlt">cusp</span> is located lower than 75° geomagnetic latitude, i.e. when the interplanetary magnetic field (IMF) points southward. The satellite traverses the dayside polar region during two weeks every 100 days due to orbit precession, and nearly 50 <span class="hlt">cusp</span> traversals were recorded during the first year of operation. Both multiple injections and single injections are clearly identified and distinguished, the former being more frequently observed than the latter. Freja has also resolved overlapping injections (special cases of multiple injections), for the first time at low altitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6957205','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6957205"><span>Plasma confinement in a spindle <span class="hlt">cusp</span> magnetic field</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bosch, R.A.</p> <p>1986-01-01</p> <p>An experimental study of the confinement properties of a low (average) beta plasma in a spindle <span class="hlt">cusp</span> magnetic field is described. An argon discharge plasma and a plasma produced by contact ionization of potassium were investigated. Electron and ion densities, space potentials, and plasma flow velocities were measured in the ring and point <span class="hlt">cusps</span>. The leak width of the escaping plasma was measured over a wide range of magnetic field strengths and neutral gas pressures. The dependence of the leak width on neutral pressure and magnetic field strength is accounted for by a simple model is which plasma streams out of the <span class="hlt">cusps</span> along the magnetic field lines while diffusing across the magnetic field due to the combined effects of neutral particle collisions and Bohm diffusion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780068607&hterms=IMP&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DIMP','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780068607&hterms=IMP&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DIMP"><span>Imp 6 measurements in the distant polar <span class="hlt">cusp</span> during substorms</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fairfield, D. H.; Hones, E. W., Jr.</p> <p>1978-01-01</p> <p>High time-resolution data from the magnetic field, plasma, energetic particle, and VLF wave experiments performed aboard Imp 6 in a study of the distant dayside <span class="hlt">cusp</span> during substorms are described. The <span class="hlt">cusp</span> was studied when its location was slightly equatorward of its normal location and the geomagnetic dipole was tilted in the appropriate direction. The data support both reconnection and diffusion as methods of particle entry to the magnetosphere. The evidence (1) indicates an acceleration process to explain enhancements of 400 to 600-km/sec protons above their magnetosheath intensities, and (2) suggests convection of field lines over the polar cap as a means of explaining the lack of low-energy protons near the low-latitude boundary of the <span class="hlt">cusp</span>. Magnetic field fluctuations, a perturbation vector, ion cyclotron waves, and an abrupt change in the intensity of both whistler waves and electrostatic waves are characterized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JCAP...10..022C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JCAP...10..022C"><span><span class="hlt">Cusp</span> singularities in f(R) gravity: pros and cons</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Pisin; Yeom, Dong-han</p> <p>2015-10-01</p> <p>We investigate <span class="hlt">cusp</span> singularities in f(R) gravity, especially for Starobinsky and Hu-Sawicki dark energy models. We illustrate that, by using double-null numerical simulations, a <span class="hlt">cusp</span> singularity can be triggered by gravitational collapses. This singularity can be cured by adding a quadratic term, but this causes a Ricci scalar bump that can be observed by an observer outside the event horizon. Comparing with cosmological parameters, it seems that it would be difficult to see super-Planckian effects by astrophysical experiments. On the other hand, at once there exists a <span class="hlt">cusp</span> singularity, it can be a mechanism to realize a horizon scale curvature singularity that can be interpreted by a firewall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/4778567','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/4778567"><span><span class="hlt">STELLARATOR</span> INJECTOR</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Post, R.F.</p> <p>1962-09-01</p> <p>A method and means are described for injecting energetic neutral atoms or molecular ions into dense magnetically collimated plasma columns of <span class="hlt">stellarators</span> and the like in such a manner that the atoms or ions are able to significantly penetrate the column before being ionized by collision with the plasma constituent particles. Penetration of the plasma column by the neutral atoms or molecular ions is facilitated by superposition of two closely spaced magnetic mirrors on the plasma confinement field. The mirrors are moved apart to magnetically sweep plasma from a region between the mirrors and establish a relatively low plasma density therein. By virture of the low density, neutral atoms or molecular ions injected into the region significantly penetrate the plasma column before being ionized. Thereafter, the mirrors are diminished to permit the injected material to admix with the plasma in the remainder of the column. (AEC)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4282910','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4282910"><span>Mandibular talon <span class="hlt">cusps</span>: A Systematic review and data analysis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Panampally, George-Kurian; Chen, Yong; Tian, Tian</p> <p>2014-01-01</p> <p>Objectives: The purpose of the present study was to evaluate mandibular talon <span class="hlt">cusps</span> distribution from the comprehensive literature search and proposal of new classification Material and Methods: The study was a review of articles published in the English language from January 1960 to December 2013. The PubMed/MEDLINE/Google Scholor databases were searched electronically using ‘talon cusp’, ‘dens evaginatus’, ‘anterior teeth’, mandible, ‘primary dentition’ and ‘ permanent dentition’ as search terms in various combinations. The citation lists from the included references were subsequently examined, and a hand search was also performed in an attempt to identify additional reports. The distribution, characteristics, common tooth type, associated dental anomaly and proposal of new classification have been included in final data analysis. Descriptive statistics were carried out using Chi square test (SPSS, version 17). Results: Overall 37 citations were retrieved from the literature where one was prevalence studies and rest were case reports among those two were duplication. Total 35 articles with 43 patients were reported on mandibular talon <span class="hlt">cusps</span>. Males were predominantly affected than females (p<0.05). Eight cases (19%) were reported in archeological skulls 81% were clinical reports. Forty cases (93%) were reported in permanent dentition while 7% cases in primary dentition. Lingual mandibular talon are more common than facial type in permanent dentition facial talons (p<0.05). Seven cases (18%) were bilaterally involved. Double tooth (45%) was commonly associated with mandibular talons. Most of the cases reported from Asia and asia derived populations. Conclusions: Central incisor is the most common tooth type that effected by talon <span class="hlt">cusp</span> in permanent dentition and lateral incisor is in primary dentition. Lingual talons are common in mandible. Double tooth common dental anomaly associated with mandibular talon <span class="hlt">cusp</span>. Most of the case reported from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22348361','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22348361"><span>A UV-to-MIR monitoring of DR Tau: Exploring how water vapor in the planet <span class="hlt">formation</span> region is affected by <span class="hlt">stellar</span> accretion variability</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Banzatti, A.; Meyer, M. R.; Manara, C. F.; Testi, L.; Pontoppidan, K. M.</p> <p>2014-01-01</p> <p>Young stars are known to show variability due to non-steady mass accretion rate from their circumstellar disks. Accretion flares can produce strong energetic irradiation and heating that may affect the disk in the planet <span class="hlt">formation</span> region, close to the central star. During an extreme accretion outburst in the young star EX Lupi, the prototype of EXor variables, remarkable changes in molecular gas emission from ∼1 AU in the disk have recently been observed. Here, we focus on water vapor and explore how it is affected by variable accretion luminosity in T Tauri stars. We monitored a young highly variable solar-mass star, DR Tau, using simultaneously two high/medium-resolution spectrographs at the European Southern Observatory Very Large Telescope: VISIR at 12.4 μm to observe water lines from the disk and X-shooter covering from 0.3 to 2.5 μm to constrain the <span class="hlt">stellar</span> accretion. Three epochs spanning timescales from several days to several weeks were obtained. The accretion luminosity was estimated to change within a factor of ∼2 and no change in water emission was detected at a significant level. In comparison with EX Lupi and EXor outbursts, DR Tau suggests that the less long-lived and weaker variability phenomena typical of T Tauri stars may leave water at planet-forming radii in the disk mostly unaffected. We propose that these systems may provide evidence for two processes that act over different timescales: ultraviolet photochemistry in the disk atmosphere (faster) and heating of the deeper disk layers (slower).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...805..103V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...805..103V"><span>Color-Magnitude Diagram Constraints on the Metallicities, Ages, and Star <span class="hlt">Formation</span> History of the <span class="hlt">Stellar</span> Populations in the Carina Dwarf Spheroidal Galaxy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>VandenBerg, Don A.; Stetson, Peter B.; Brown, Thomas M.</p> <p>2015-06-01</p> <p>Victoria-Regina isochrones for -0.4{\\mkern 1mu} ≤slant [α/Fe] ≤slant +0.4 and a wide range in [Fe/H], along with complementary zero-age horizontal branch (ZAHB) loci, have been applied to the color-magnitude diagram (CMD) of Carina. The color transformations that we have used have been “calibrated” so that isochrones provide excellent fits to the [{{(B-V)}0},{{M}V}] diagrams of M3 and M92 when well supported estimates of the globular cluster (GC) reddenings and metallicities are assumed. The adopted distance moduli, for both the GCs and Carina, are based on our ZAHB models, which are able to reproduce the old horizontal branch (HB) component (as well as the luminosity of the HB clump) of the dwarf spheroidal galaxy quite well—even if it spans a range in [Fe/H] of ˜1.5 dex, provided that [α/Fe] varies with [Fe/H] in approximately the way that has been derived spectroscopically. Ages derived here agree reasonably well with those found previously for the old and intermediate-age turnoff (TO) stars, as well as for the period of negligible star <span class="hlt">formation</span> (SF) activity (˜6-10 Gyr ago). CMD simulations have been carried out for the faintest TO and subgiant stars. They indicate a clear preference for SF that lasted several Gyr instead of a short burst, with some indication that ages decrease with increasing [Fe/H]. In general, <span class="hlt">stellar</span> models that assume spectroscopic metallicities provide satisfactory fits to the observations, including the thin giant branch of Carina, though higher oxygen abundances than those implied by the adopted values of [α/Fe] would have favorable consequences.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...780...26B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...780...26B"><span>A UV-to-MIR Monitoring of DR Tau: Exploring How Water Vapor in the Planet <span class="hlt">Formation</span> Region is Affected by <span class="hlt">Stellar</span> Accretion Variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Banzatti, A.; Meyer, M. R.; Manara, C. F.; Pontoppidan, K. M.; Testi, L.</p> <p>2014-01-01</p> <p>Young stars are known to show variability due to non-steady mass accretion rate from their circumstellar disks. Accretion flares can produce strong energetic irradiation and heating that may affect the disk in the planet <span class="hlt">formation</span> region, close to the central star. During an extreme accretion outburst in the young star EX Lupi, the prototype of EXor variables, remarkable changes in molecular gas emission from ~1 AU in the disk have recently been observed. Here, we focus on water vapor and explore how it is affected by variable accretion luminosity in T Tauri stars. We monitored a young highly variable solar-mass star, DR Tau, using simultaneously two high/medium-resolution spectrographs at the European Southern Observatory Very Large Telescope: VISIR at 12.4 μm to observe water lines from the disk and X-shooter covering from 0.3 to 2.5 μm to constrain the <span class="hlt">stellar</span> accretion. Three epochs spanning timescales from several days to several weeks were obtained. The accretion luminosity was estimated to change within a factor of ~2 and no change in water emission was detected at a significant level. In comparison with EX Lupi and EXor outbursts, DR Tau suggests that the less long-lived and weaker variability phenomena typical of T Tauri stars may leave water at planet-forming radii in the disk mostly unaffected. We propose that these systems may provide evidence for two processes that act over different timescales: ultraviolet photochemistry in the disk atmosphere (faster) and heating of the deeper disk layers (slower).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21344242','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21344242"><span>Maass <span class="hlt">Cusp</span> Forms on Singly Punctured Two-Torus</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Siddig, Abubaker Ahmed Mohamed; Shah, Nurisya Mohd; Zainuddin, Hishamuddin</p> <p>2009-07-07</p> <p>Quantum mechanical systems on punctured surfaces modeled by hyperbolic spaces can play an interesting role in exploring quantum chaos and in studying behaviour of future quantum nano-devices. The case of singly-punctured two-torus, for example, has been well-studied in the literature particularly for its scattering states. However, the bound states on the punctured torus given by Maass <span class="hlt">cusp</span> forms are lesser known. In this note, we report on the algorithm of numerically computing these functions and we present ten lower-lying eigenvalues for each odd and even Maass <span class="hlt">cusp</span> forms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1004677','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1004677"><span>Early aortic valve <span class="hlt">cusp</span> rupture in relapsing polychondritis.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Marshall, D A; Jackson, R; Rae, A P; Capell, H A</p> <p>1992-01-01</p> <p>Aortic regurgitation associated with relapsing polychondritis usually occurs late in the disease as a result of aortic root dilatation. A case where aortic regurgitation occurred early and was due to <span class="hlt">cusp</span> rupture with a normal aortic root is reported. The patient required urgent aortic valve replacement within six weeks of developing a murmur despite apparent control of inflammation with immunosuppressive treatment. The possibility of <span class="hlt">cusp</span> rupture with sudden haemodynamic deterioration should be considered in patients with relapsing polychondritis who develop aortic regurgitation. Images PMID:1575597</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050167099','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050167099"><span><span class="hlt">Cusp</span> Dynamics-Particle Acceleration by Alfven Waves</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ergun, Robert E.; Parker, Scott A.</p> <p>2005-01-01</p> <p>Successful results were obtained from this research project. This investigation answered and/or made progresses on each of the four important questions that were proposed: (1) How do Alfven waves propagate on dayside open field lines? (2) How are precipitating electrons influenced by propagating Alfven waves? (3) How are various <span class="hlt">cusp</span> electron distributions generated? (4) How are Alfven waves modified by electrons? During the first year of this investigation, the input parameters, such as density and temperature altitude profiles, of the gyrofluid code on the <span class="hlt">cusp</span> field lines were constructed based on 3-point satellite observations. The initial gyrofluid result was presented at the GEM meeting by Dr. Samuel Jones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/7149129','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/7149129"><span>The nonthermal <span class="hlt">stellar</span> dynamics of the globular cluster M15</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Peterson, R.C.; Seitzer, P.; Cudworth, K.M. Space Telescope Science Institute, Baltimore, MD Yerkes Observatory, Williams Bay, WI )</p> <p>1989-12-01</p> <p>The velocity dispersion as a function of radius in the globular cluster M15 is derived from measurements of 120 individual stars between 0.1 and 4.6 arcmin of the cluster center, and from the integrated light of the central <span class="hlt">cusp</span>. The <span class="hlt">stellar</span> measurements, with an individual accuracy of 1 km/s, indicate a mean cluster velocity of -107.1 + or - 0.9 km/s and a mean velocity dispersion of 9.0 + or - 0.6 km/s. The velocity dispersion inside 12 arcmin varies with radius. Except for its greater velocity gradient, the spectrum of the integrated light of the <span class="hlt">cusp</span> is indistinguishable from that formed by superposition of the individual M15 giant spectra, demonstrating that the excess light at the center is due primarily to a normal M15 population. The findings indicate a nonthermal energy distribution with substantial heating in the central regions. 54 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013A%26A...556A..68C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013A%26A...556A..68C"><span>He II emitters in the VIMOS VLT Deep Survey: Population III star <span class="hlt">formation</span> or peculiar <span class="hlt">stellar</span> populations in galaxies at 2 < z < 4.6?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cassata, P.; Le Fèvre, O.; Charlot, S.; Contini, T.; Cucciati, O.; Garilli, B.; Zamorani, G.; Adami, C.; Bardelli, S.; Le Brun, V.; Lemaux, B.; Maccagni, D.; Pollo, A.; Pozzetti, L.; Tresse, L.; Vergani, D.; Zanichelli, A.; Zucca, E.</p> <p>2013-08-01</p> <p>Aims: The aim of this work is to identify He II emitters at 2 < z < 4.6 and to constrain the source of the hard ionizing continuum that powers the He II emission. Methods: We assembled a sample of 277 galaxies with a highly reliable spectroscopic redshift at 2 < z < 4.6 from the VIMOS-VLT Deep Survey (VVDS) Deep and Ultra-Deep data, and we identified 39 He II λ1640 emitters. We studied their spectral properties, measuring the fluxes, equivalent widths (EW), and full width at half maximum (FWHM) for most relevant lines, including He II λ1640, Lyα line, Si II λ1527, and C IV λ1549. Results: About 10% of galaxies at z ~ 3 and iAB ≤ 24.75 show He II in emission, with rest frame equivalent widths EW0 ~ 1-7 Å, equally distributed between galaxies with Lyα in emission or in absorption. We find 11 (3.9% of the global population) reliable He II emitters with unresolved He II lines (FWHM0 < 1200 km s-1), 13 (4.6% of the global population) reliable emitters with broad He II emission (FWHM0 > 1200 km s-1), 3 active galactic nuclei (AGN), and an additional 12 possible He II emitters. The properties of the individual broad emitters are in agreement with expectations from a Wolf-Rayet (W-R) model. Instead, the properties of the narrow emitters are not compatible with this model, nor with predictions of gravitational cooling radiation produced by gas accretion, unless this is severely underestimated by current models by more than two orders of magnitude. Rather, we find that the EW of the narrow He II line emitters are in agreement with expectations for a Population III (PopIII) star <span class="hlt">formation</span>, if the episode of star <span class="hlt">formation</span> is continuous, and we calculate that a PopIII star <span class="hlt">formation</span> rate (SFR) of 0.1-10 M⊙ yr-1 alone is enough to sustain the observed He II flux. Conclusions: We conclude that narrow He II emitters are powered either by the ionizing flux from a <span class="hlt">stellar</span> population rare at z ~ 0 but much more common at z ~ 3, or by PopIII star <span class="hlt">formation</span>. As proposed by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006eso..pres...37.','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006eso..pres...37."><span><span class="hlt">Stellar</span> Vampires Unmasked</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p></p> <p>2006-10-01</p> <p>Astronomers have found possible proofs of <span class="hlt">stellar</span> vampirism in the globular cluster 47 Tucanae. Using ESO's Very Large Telescope, they found that some hot, bright, and apparently young stars in the cluster present less carbon and oxygen than the majority of their sisters. This indicates that these few stars likely formed by taking their material from another star. "This is the first detection of a chemical signature clearly pointing to a specific scenario to form so-called 'Blue straggler stars' in a globular cluster", said Francesco Ferraro, from the Astronomy Department of Bologna University (Italy) and lead-author of the paper presenting the results. Blue stragglers are unexpectedly young-looking stars found in <span class="hlt">stellar</span> aggregates, such as globular clusters, which are known to be made up of old stars. These enigmatic objects are thought to be created in either direct <span class="hlt">stellar</span> collisions or through the evolution and coalescence of a binary star system in which one star 'sucks' material off the other, rejuvenating itself. As such, they provide interesting constraints on both binary <span class="hlt">stellar</span> evolution and star cluster dynamics. To date, the unambiguous signatures of either <span class="hlt">stellar</span> traffic accidents or <span class="hlt">stellar</span> vampirism have not been observed, and the <span class="hlt">formation</span> mechanisms of Blue stragglers are still a mystery. The astronomers used ESO's Very Large Telescope to measure the abundance of chemical elements at the surface of 43 Blue straggler stars in the globular cluster 47 Tucanae [1]. They discovered that six of these Blue straggler stars contain less carbon and oxygen than the majority of these peculiar objects. Such an anomaly indicates that the material at the surface of the blue stragglers comes from the deep interiors of a parent star [2]. Such deep material can reach the surface of the blue straggler only during the mass transfer process occurring between two stars in a binary system. Numerical simulations indeed show that the coalescence of stars should not</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4174717','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4174717"><span>A rare report of mandibular facial talon <span class="hlt">cusp</span> and its management</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Nuvvula, Sivakumar; Gaddam, Kumar Raja; Jayachandra, Bhumireddy; Mallineni, Sreekanth Kumar</p> <p>2014-01-01</p> <p>Talon <span class="hlt">cusp</span> is an uncommon dental anomaly showing morphologically well delineated, accessory <span class="hlt">cusp</span>-like structure projecting from cingulum to the incisal edge of anterior teeth. This anomaly is rare in the mandibular dentition and rarer on the facial aspect. A case of this infrequent entity of mandibular facial talon <span class="hlt">cusp</span> and its management is reported here. PMID:25298658</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004HEAD....8.2510G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004HEAD....8.2510G"><span>An Overview of ChaMPlane Accretion Sources in the Disk, Bulge and <span class="hlt">Cusp</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grindlay, J.; Hong, J.; Koenig, X.; Laycock, S.; Schlegel, E.; van den Berg, M.; Zhao, P.; Cohn, H.; Lugger, P.; Rogel, A.</p> <p>2004-08-01</p> <p>The Chandra Multiwavelength Plane (ChaMPlane) survey is an ongoing effort to survey the accretion source content of the Galaxy. Archived pointings (>30 ksec, b <12deg) on fields without bright point sources or diffuse emission are processed uniformly for source positions, fluxes, colors and variability. Our special interest is in the constraints a 0.5-8keV survey with ACIS can provide for the CV and quiescent X-ray binary (both LMXB and HMXB) numbers in the Galaxy, but <span class="hlt">stellar</span> coronal sources will be the largest (by far) by product. We describe the survey through Chandra cycles 4-5 and the (l,b) variation of logN-logS counts in the 2-8 keV band, for optimum accretion source sensitivity and minimized absorption effects. We constrain the distribution of hard sources identified with quantile analysis (see Hong et al) and focus here on our deep pointings in the low extinction Baades Window and Stanek Window near the galactic center (see van den Berg et al). These include sources identified with OGLE binaries including an M giant that are likely wind-fed systems containing WDs (or possibly NSs or BHs) and may constrain the hard sources in the central <span class="hlt">Cusp</span> around SgrA*. The Galactic Bulge source content is also constrained by our deep optical imaging and spectroscopy (see Zhao et al) and now especially by our deep IR photometry of the central <span class="hlt">Cusp</span> from Magellan (see Laycock et al) for which analysis is in progress. This work is supported by Chandra grants AR3-4002A, AR4-5003A and GO3-4033A and NSF grant AST-0098683.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SAAS...39..187C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SAAS...39..187C"><span><span class="hlt">Stellar</span> Dynamos</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Charbonneau, Paul</p> <p></p> <p>This chapter steps finally away from the sun and towards the stars, the idea being to apply the physical insight gained so far to see how much of <span class="hlt">stellar</span> magnetism can be understood in terms of dynamo action. Dynamo action in the convective core of massive main-sequence stars is first considered and shown viable. For intermediate-mass main-sequence stars the fossil field hypothesis will carry the day, although possible dynamo alternatives are also briefly discussed. The extension of the solar dynamo models investigated in Chap. 3 (10.1007/978-3-642-32093-4_3) to other solar-type stars will first take us through an important detour in first having to understand rotational evolution in response to angular momentum loss in a magnetized wind. Dynamo action in fully convective stars comes next, and the chapter closes with an overview of the situation for pre- and post-main-sequence stars and compact objects, leading finally to the magnetic fields of galaxies and beyond.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20100002041&hterms=nic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dnic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20100002041&hterms=nic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dnic"><span>Oxygen Ion Heat Rate within Alfvenic Turbulence in the <span class="hlt">Cusp</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Coffey, Victoria N.; Singh, Nagendra; Chandler, Michael O.</p> <p>2009-01-01</p> <p>The role that the cleft/<span class="hlt">cusp</span> has in ionosphere-magnetosphere coupling makes it a dynamic and important region. It is directly exposed to the solar wind, making it possible for the entry of electromagnetic energy and precipitating electrons and ions from dayside reconnection and other dayside events. It is also a significant source of ionospheric plasma, contributing largely to the mass loading of the magnetosphere with large fluxes of outflowing ions. Crossing the <span class="hlt">cusp</span>/cleft near 5100 km, the Polar instruments observe the common correlation of downward Poynting flux, ion energization, soft electron precipitation, broadband extremely low-frequency (BB-ELF) emissions, and density depletions. The dominant power in the BB-ELF emissions is now identified to be from spatially broad, low frequency Alfv nic structures. For a <span class="hlt">cusp</span> crossing, we determine using the Electric Field Investigation (EFI), that the electric and magnetic field fluctuations are Alfv nic and the electric field gradients satisfy the inequality for stochastic acceleration. With all the Polar 1996 horizontal crossings of the <span class="hlt">cusp</span>, we determine the O+ heating rate using the Thermal Ion Dynamics Experiment (TIDE) and Plasma Wave Investigation (PWI). We then compare this heating rate to other heating rates assuming the electric field gradient criteria exceeds the limit for stochastic acceleration for the remaining crossings. The comparison suggests that a stochastic acceleration mechanism is operational and the heating is controlled by the transverse spatial scale of the Alfvenic waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4855876','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4855876"><span><span class="hlt">Cusp</span> Catastrophe Polynomial Model: Power and Sample Size Estimation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chen, Ding-Geng(Din); Chen, Xinguang(Jim); Lin, Feng; Tang, Wan; Lio, Y. L.; Guo, (Tammy) Yuanyuan</p> <p>2016-01-01</p> <p>Guastello’s polynomial regression method for solving <span class="hlt">cusp</span> catastrophe model has been widely applied to analyze nonlinear behavior outcomes. However, no statistical power analysis for this modeling approach has been reported probably due to the complex nature of the <span class="hlt">cusp</span> catastrophe model. Since statistical power analysis is essential for research design, we propose a novel method in this paper to fill in the gap. The method is simulation-based and can be used to calculate statistical power and sample size when Guastello’s polynomial regression method is used to <span class="hlt">cusp</span> catastrophe modeling analysis. With this novel approach, a power curve is produced first to depict the relationship between statistical power and samples size under different model specifications. This power curve is then used to determine sample size required for specified statistical power. We verify the method first through four scenarios generated through Monte Carlo simulations, and followed by an application of the method with real published data in modeling early sexual initiation among young adolescents. Findings of our study suggest that this simulation-based power analysis method can be used to estimate sample size and statistical power for Guastello’s polynomial regression method in <span class="hlt">cusp</span> catastrophe modeling. PMID:27158562</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28123270','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28123270"><span><span class="hlt">Cusp</span> expression of protostylid in deciduous and permanent molars.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moreno, Sandra; Reyes, María Paula; Moreno, Freddy</p> <p>2016-01-01</p> <p>The present article is a case report on the <span class="hlt">cusp</span> expression of protostylid in the deciduous inferior molars and in the first permanent inferior molar, in which the correspondence and bilateral symmetry of the mentioned expression can be evidenced, as well as the their relation with the foramen cecum of the mesiobuccal furrows of the deciduous and of the permanent inferior molars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5210103','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5210103"><span><span class="hlt">Cusp</span> expression of protostylid in deciduous and permanent molars</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Moreno, Sandra; Reyes, María Paula; Moreno, Freddy</p> <p>2016-01-01</p> <p>The present article is a case report on the <span class="hlt">cusp</span> expression of protostylid in the deciduous inferior molars and in the first permanent inferior molar, in which the correspondence and bilateral symmetry of the mentioned expression can be evidenced, as well as the their relation with the foramen cecum of the mesiobuccal furrows of the deciduous and of the permanent inferior molars. PMID:28123270</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21554464','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21554464"><span>Synthesis of Cold Antihydrogen in a <span class="hlt">Cusp</span> Trap</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Enomoto, Y.; Nagata, Y.; Kanai, Y.; Mohri, A.; Kuroda, N.; Kim, C. H.; Torii, H. A.; Fujii, K.; Ohtsuka, M.; Tanaka, K.; Matsuda, Y.; Michishio, K.; Nagashima, Y.; Higaki, H.; Corradini, M.; Leali, M.; Lodi-Rizzini, E.; Mascagna, V.; Venturelli, L.; Zurlo, N.</p> <p>2010-12-10</p> <p>We report here the first successful synthesis of cold antihydrogen atoms employing a <span class="hlt">cusp</span> trap, which consists of a superconducting anti-Helmholtz coil and a stack of multiple ring electrodes. This success opens a new path to make a stringent test of the CPT symmetry via high precision microwave spectroscopy of ground-state hyperfine transitions of antihydrogen atoms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27158562','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27158562"><span><span class="hlt">Cusp</span> Catastrophe Polynomial Model: Power and Sample Size Estimation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Ding-Geng Din; Chen, Xinguang Jim; Lin, Feng; Tang, Wan; Lio, Y L; Guo, Tammy Yuanyuan</p> <p>2014-12-01</p> <p>Guastello's polynomial regression method for solving <span class="hlt">cusp</span> catastrophe model has been widely applied to analyze nonlinear behavior outcomes. However, no statistical power analysis for this modeling approach has been reported probably due to the complex nature of the <span class="hlt">cusp</span> catastrophe model. Since statistical power analysis is essential for research design, we propose a novel method in this paper to fill in the gap. The method is simulation-based and can be used to calculate statistical power and sample size when Guastello's polynomial regression method is used to <span class="hlt">cusp</span> catastrophe modeling analysis. With this novel approach, a power curve is produced first to depict the relationship between statistical power and samples size under different model specifications. This power curve is then used to determine sample size required for specified statistical power. We verify the method first through four scenarios generated through Monte Carlo simulations, and followed by an application of the method with real published data in modeling early sexual initiation among young adolescents. Findings of our study suggest that this simulation-based power analysis method can be used to estimate sample size and statistical power for Guastello's polynomial regression method in <span class="hlt">cusp</span> catastrophe modeling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1284066','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1284066"><span>Behavioral <span class="hlt">cusps</span>: a developmental and pragmatic concept for behavior analysis.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Rosales-Ruiz, J; Baer, D M</p> <p>1997-01-01</p> <p>Most concepts of development explain certain behavior changes as products or markers of the invariable succession of emerging periods, stages, refinements, or achievements that define and order much of an individual's life. A different but comparable concept can be derived from the most basic mechanisms of behavior analysis, which are its environmental contingencies, and from its most basic strategy, which is to study behavior as its subject matter. From a behavior-analytic perspective, the most fundamental developmental questions are (a) whether these contingencies vary in any systematic way across the life span, and thus make behavior change in a correspondingly systematic way; (b) whether some of these contingencies and their changes have more far-reaching consequences than others, in terms of the importance to the organism and others, of the behavior classes they change. Certain behavior changes open the door to especially broad or especially important further behavior change, leading to the concept of the behavioral <span class="hlt">cusp</span>. A behavioral <span class="hlt">cusp</span>, then, is any behavior change that brings the organism's behavior into contact with new contingencies that have even more far-reaching consequences. Of all the environmental contingencies that change or maintain behavior, those that accomplish <span class="hlt">cusps</span> are developmental. Behavior change remains the fundamental phenomenon of development for a behavior-analytic view; a <span class="hlt">cusp</span> is a special instance of behavior change, a change crucial to what can come next. PMID:9316263</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=behavioral+AND+cusp&id=EJ696502','ERIC'); return false;" href="https://eric.ed.gov/?q=behavioral+AND+cusp&id=EJ696502"><span>Behavioral <span class="hlt">Cusps</span>, Basic Behavioral Repertoires, and Cumulative-Hierarchical Learning</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Hixson, Michael D.</p> <p>2004-01-01</p> <p>Much behavior development is cumulative and hierarchical in that subsequent learning is dependent on prior learning. The behavior or behavioral changes that produce subsequent important behavioral changes are referred to as basic behavioral repertoires or behavioral <span class="hlt">cusps</span>. This progression of learning is called "cumulative-hierarchical learning,"…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvD..96b3533S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvD..96b3533S"><span>Gravitational wave bursts from cosmic string <span class="hlt">cusps</span> and pseudocusps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stott, Matthew J.; Elghozi, Thomas; Sakellariadou, Mairi</p> <p>2017-07-01</p> <p>We study the relative contribution of <span class="hlt">cusps</span> and pseudocusps, on cosmic (super)strings, to the emitted bursts of gravitational waves. The gravitational wave emission in the vicinity of highly relativistic points on the string follows, for a high enough frequency, a logarithmic decrease. The slope has been analytically found to be -4 /3 for points reaching exactly the speed of light in the limit c =1 . We investigate the variations of this high-frequency behavior with respect to the velocity of the points considered, for strings formed through a numerical simulation, and we then compute numerically the gravitational waves emitted. We find that for string points moving with velocities as far as 10-3 from the theoretical (relativistic) limit c =1 , gravitational wave emission follows a behavior consistent with that of <span class="hlt">cusps</span>, effectively increasing the number of <span class="hlt">cusps</span> on a string. Indeed, depending on the velocity threshold chosen for such behavior, we show that the emitting part of the string worldsheet is enhanced by a factor O (1 03) with respect to the emission of <span class="hlt">cusps</span> only.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20100002041&hterms=Nic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DNic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20100002041&hterms=Nic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DNic"><span>Oxygen Ion Heat Rate within Alfvenic Turbulence in the <span class="hlt">Cusp</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Coffey, Victoria N.; Singh, Nagendra; Chandler, Michael O.</p> <p>2009-01-01</p> <p>The role that the cleft/<span class="hlt">cusp</span> has in ionosphere-magnetosphere coupling makes it a dynamic and important region. It is directly exposed to the solar wind, making it possible for the entry of electromagnetic energy and precipitating electrons and ions from dayside reconnection and other dayside events. It is also a significant source of ionospheric plasma, contributing largely to the mass loading of the magnetosphere with large fluxes of outflowing ions. Crossing the <span class="hlt">cusp</span>/cleft near 5100 km, the Polar instruments observe the common correlation of downward Poynting flux, ion energization, soft electron precipitation, broadband extremely low-frequency (BB-ELF) emissions, and density depletions. The dominant power in the BB-ELF emissions is now identified to be from spatially broad, low frequency Alfv nic structures. For a <span class="hlt">cusp</span> crossing, we determine using the Electric Field Investigation (EFI), that the electric and magnetic field fluctuations are Alfv nic and the electric field gradients satisfy the inequality for stochastic acceleration. With all the Polar 1996 horizontal crossings of the <span class="hlt">cusp</span>, we determine the O+ heating rate using the Thermal Ion Dynamics Experiment (TIDE) and Plasma Wave Investigation (PWI). We then compare this heating rate to other heating rates assuming the electric field gradient criteria exceeds the limit for stochastic acceleration for the remaining crossings. The comparison suggests that a stochastic acceleration mechanism is operational and the heating is controlled by the transverse spatial scale of the Alfvenic waves.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPlPh..81e4916R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPlPh..81e4916R"><span>A super-<span class="hlt">cusp</span> divertor configuration for tokamaks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ryutov, D. D.</p> <p>2015-10-01</p> <p>> This study demonstrates a remarkable flexibility of advanced divertor configurations created with the remote poloidal field coils. The emphasis here is on the configurations with three poloidal field nulls in the divertor area. We are seeking the structures where all three nulls lie on the same separatrix, thereby creating two zones of a very strong flux expansion, as envisaged in the concept of Takase's <span class="hlt">cusp</span> divertor. It turns out that the set of remote coils can indeed produce a <span class="hlt">cusp</span> divertor, with additional advantages of: (i) a large stand-off distance between the divertor and the coils and (ii) a thorough control that these coils exert over the fine features of the configuration. In reference to these additional favourable properties acquired by the <span class="hlt">cusp</span> divertor, the resulting configuration could be called `a super-<span class="hlt">cusp</span>'. General geometrical features of the three-null configurations produced by remote coils are described. Issues on the way to practical applications include the need for a more sophisticated control system and possible constraints related to excessively high currents in the divertor coils.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9316263','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9316263"><span>Behavioral <span class="hlt">cusps</span>: a developmental and pragmatic concept for behavior analysis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rosales-Ruiz, J; Baer, D M</p> <p>1997-01-01</p> <p>Most concepts of development explain certain behavior changes as products or markers of the invariable succession of emerging periods, stages, refinements, or achievements that define and order much of an individual's life. A different but comparable concept can be derived from the most basic mechanisms of behavior analysis, which are its environmental contingencies, and from its most basic strategy, which is to study behavior as its subject matter. From a behavior-analytic perspective, the most fundamental developmental questions are (a) whether these contingencies vary in any systematic way across the life span, and thus make behavior change in a correspondingly systematic way; (b) whether some of these contingencies and their changes have more far-reaching consequences than others, in terms of the importance to the organism and others, of the behavior classes they change. Certain behavior changes open the door to especially broad or especially important further behavior change, leading to the concept of the behavioral <span class="hlt">cusp</span>. A behavioral <span class="hlt">cusp</span>, then, is any behavior change that brings the organism's behavior into contact with new contingencies that have even more far-reaching consequences. Of all the environmental contingencies that change or maintain behavior, those that accomplish <span class="hlt">cusps</span> are developmental. Behavior change remains the fundamental phenomenon of development for a behavior-analytic view; a <span class="hlt">cusp</span> is a special instance of behavior change, a change crucial to what can come next.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUSMSM33A..03G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUSMSM33A..03G"><span>ULF Narrowband Emissions Analysis in the Terrestrial Polar <span class="hlt">Cusps</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grison, B.; Pisa, D.</p> <p>2013-05-01</p> <p>Polar <span class="hlt">cusps</span> are known to be a key region for transfer of mass and momentum between the adjacent magnetosheath and the magnetosphere. The 4 spacecraft of the Cluster ESA mission crossed the polar <span class="hlt">cusps</span> in their most distant part to the Earth in the early years of the mission (2000-2004) because of their highly eccentric orbit. The ULF wave activity in the <span class="hlt">cusp</span> region has been linked with the magnetosheath plasma penetration since HEOS observations (D'Angelo et al., 1974). Wave and particle interaction play an important role in this colisionless plasma. The observed wave activity certainly results from both distant and local generation mechanisms. From Cluster case studies we propose to focus on one aspect for each of this place of generation. Concerning the distant generation, the possibility of a wave generation at the magnetopause itself is investigated. For this purpose we compare the propagation of the emissions on each side of the magnetopasue, i.e. in the <span class="hlt">cusp</span> and in the magnetosheath. Concerning the local generation, the presence of locally generated waves above the local proton gyrofrequency that display a left hand polarization has been reported in Polar and Cluster studies (Le et al., 2001; Nykyri et al., 2003 ). The Doppler shift was not large enough to explain the observed frequency. We propose here to combine various techniques (k-filtering analysis, WHAMP simulations) to achieve a precise wave vector estimation and to explain these observations. References: D'Angelo, N., A. Bahnsen, and H. Rosenbauer (1974), Wave and particle measurements at the polar <span class="hlt">cusp</span>, J. Geophys. Res., 79( 22), 3129-3134, doi:10.1029/JA079i022p03129. Le, G., X. Blanco-Cano, C. T. Russell, X.-W. Zhou, F. Mozer, K. J. Trattner, S. A. Fuselier, and B. J. Anderson (2001), Electromagnetic ion cyclotron waves in the high-altitude <span class="hlt">cusp</span>: Polar observations, J. Geophys. Res., 106(A9), 19067-19079, doi:10.1029/2000JA900163. Nykyri, K., P. J. Cargill, E. A. Lucek, T. S. Horbury, A. Balogh</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993PhDT.......182M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993PhDT.......182M"><span>The Morphology and Electrodynamics of the Boreal Polar Winter <span class="hlt">Cusp</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McHarg, Matthew G.</p> <p></p> <p>The major result of this thesis is the magnetic signatures of the dayside <span class="hlt">cusp</span> region. These signatures were determined by comparing the magnetic observations to optical observations of different energy particle precipitation regions observed in the <span class="hlt">cusp</span>. In this thesis, the <span class="hlt">cusp</span> is defined as the location of most direct entry of magnetosheath particles into the ionosphere. Optical observations show that the observing station rotates daily beneath regions of different incident energy particles. Typically, the station passes from a region in the morning of high energy particles into a region near magnetic noon of very low energy precipitation, and then returns to a region of high energy precipitation after magnetic noon. A tentative identification of the <span class="hlt">cusp</span> is made on the basis of these observations. The optical observations also are used to determine the upward field aligned current density, which is found to be most intense in the region identified as the <span class="hlt">cusp</span>. The magnetic field measurements are found to correlate with the optical measurements. When the characteristic energy is high, the spectrogram shows large amplitude broad band signals. The Pc5 component of these oscillations is right hand polarized in the morning, and left hand polarized in the afternoon. During the time the optics detect precipitation with a minimum characteristic energy, the magnetic spectrogram shows a unique narrow band tone at 3-5 mHz. The occurrence statistics of the magnetic oscillations are compared to DMSP satellite observations of the <span class="hlt">cusp</span> and low latitude boundary layer. The pulses that make the narrow band tone are found to come in wave trains that are phase coherent. These trains of coherent pulses are found to be separated by phase jumps from adjacent wave trains. These jumps in phase occur when a new field aligned current appears on the equatorward edge of the <span class="hlt">cusp</span>. This combination of phase coherent wave trains associated with poleward propagating auroral forms which are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMSM13A1659C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMSM13A1659C"><span>Plasma Wave and Electron Density Structure Observed in the <span class="hlt">Cusp</span> with a Dual-Rocket Experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Colpitts, C. A.; Labelle, J. W.; Kletzing, C.; Bounds, S.; Cairns, I.</p> <p>2008-12-01</p> <p>The Twin Rockets to Investigate <span class="hlt">Cusp</span> Electrodynamics (TRICE) were launched on December 10, 2007, from Andoya Research Range in Andenes, Norway, into the active <span class="hlt">cusp</span>. Both payloads traveled north over Svalbard, with one payload reaching an apogee of ~1100 km, and the other reaching ~600 km. The payloads were separated by 100-400 km during the main portion of the flight. Both payloads included waveform receivers with 5 MHz bandwidth. These recorded several distinct types of auroral waves including whistler mode waves below ~1000 kHz and Langmuir-upper hybrid waves at 300-3000 kHz for several hundred km. Both payloads concurrently encountered a distinct period of Langmuir turbulence. Clearly defined wave cutoffs provide measurements of electron density and reveal significant density structure with density enhancements having amplitudes up to 100 percent and scale sizes from meters to tens of kilometers. Analysis of the inferred density profiles using windowed Fourier Transforms or Lomb-Scargle periodograms generates dynamic spectra of the density, which provide estimates of the spectral composition of the density irregularities for time intervals sufficiently short that the stationarity of the spectra can be investigated. The large-scale structures through which the two payloads propagated were measured by both the EISCAT and SuperDARN radars as well as by all-sky cameras operated at Longyearbyen and Ny-Alesund on Svalbard. Using this data when available, comparison of the density irregularity waveforms and spectra from the two flights is studied in relation to spatial and altitude variations of the turbulence. This examination of wave and density structures and the large scale <span class="hlt">formations</span> with which they are associated will add to the understanding of the large scale electrodynamics of the <span class="hlt">cusp</span> region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM13F4219E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM13F4219E"><span>Cluster Observations of Particle Injections in the Exterior <span class="hlt">Cusp</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Escoubet, C. P.; Grison, B.; Berchem, J.; Trattner, K. J.; Lavraud, B.; Pitout, F.; Soucek, J.; Richard, R. L.; Laakso, H. E.; Masson, A.; Dunlop, M. W.; Dandouras, I. S.; Reme, H.; Fazakerley, A. N.; Daly, P. W.</p> <p>2014-12-01</p> <p>The main process that injects solar wind plasma into the polar <span class="hlt">cusp</span> is now generally accepted to be magnetic reconnection. Depending on the IMF direction, this process takes place equatorward (for IMF southward), poleward (for IMF northward) or on the dusk or dawn sides (for IMF azimuthal) of the <span class="hlt">cusp</span>. We report a Cluster crossing on 5 January 2002 near the exterior <span class="hlt">cusp</span> on the southern dusk side. The IMF was mainly azimuthal (IMF-By around -5 nT), the solar wind speed lower than usual around 280 km/s with the density of order 5 cm-3. The four Cluster spacecraft had an elongated configuration near the magnetopause. C4 was the first spacecraft to enter the <span class="hlt">cusp</span> around 19:52:04 UT, followed by C2 at 19:52:35 UT, C1 at 19:54:24 UT and C3 at 20:13:15 UT. C4 and C1 observed two ion energy dispersions at 20:10 UT and 20:40 UT and C3 at 20:35 UT and 21:15 UT. Using the time of flight technique on the upgoing and downgoing ions, which leads to energy dispersions, we obtain distances of the ion sources between 14 and 20 RE from the spacecraft. Using Tsyganenko model, we find that these sources are located on the dusk flank, past the terminator. The first injection by C3 is seen at approximately the same time as the 2nd injection on C1 but their sources at the magnetopause were separated by more than 7 RE. This would imply that two distinct sources were active at the same time on the dusk flank of the magnetosphere. In addition, a flow reversal was observed at the magnetopause on C4 which would be an indication that reconnection is taking place near the exterior <span class="hlt">cusp</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJS..227....2S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJS..227....2S"><span>GALEX-SDSS-WISE Legacy Catalog (GSWLC): Star <span class="hlt">Formation</span> Rates, <span class="hlt">Stellar</span> Masses, and Dust Attenuations of 700,000 Low-redshift Galaxies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salim, Samir; Lee, Janice C.; Janowiecki, Steven; da Cunha, Elisabete; Dickinson, Mark; Boquien, Médéric; Burgarella, Denis; Salzer, John J.; Charlot, Stéphane</p> <p>2016-11-01</p> <p>In this paper, we present the GALEX-SDSS-WISE Legacy Catalog (GSWLC), a catalog of physical properties (<span class="hlt">stellar</span> masses, dust attenuations, and star <span class="hlt">formation</span> rates [SFRs]) for ˜700,000 galaxies with Sloan Digital Sky Survey (SDSS) redshifts below 0.3. GSWLC contains galaxies within the Galaxy Evolution Explorer footprint, regardless of a UV detection, covering 90% of SDSS. The physical properties were obtained from UV/optical spectral energy distribution (SED) fitting following Bayesian methodology of Salim et al., with improvements such as blending corrections for low-resolution UV photometry, flexible dust attenuation laws, and emission-line corrections. GSWLC also includes mid-IR SFRs derived from IR templates based on 22 μ {{m}} Wide-field Infrared Survey Explorer observations. These estimates are independent of UV/optical SED fitting, in order to separate possible systematics. The paper argues that the comparison of specific SFRs (sSFRs) is more informative and physically motivated than the comparison of SFRs. The sSFRs resulting from the UV/optical SED fitting are compared to the mid-IR sSFRs and to sSFRs from three published catalogs. For “main-sequence” galaxies with no active galactic nucleus (AGN) all sSFRs are in very good agreement (within 0.1 dex on average). In particular, the widely used aperture-corrected SFRs from the MPA/JHU catalog show no systematic offsets, in contrast to some integral field spectroscopy results. For galaxies below the main sequence (log sSFR \\lt -11), mid-IR (s)SFRs based on fixed luminosity-SFR conversion are severely biased (up to 2 dex) because the dust is primarily heated by old stars. Furthermore, mid-IR (s)SFRs are overestimated by up to 0.6 dex for galaxies with AGNs, presumably due to nonstellar dust heating. UV/optical (s)SFRs are thus preferred to IR-based (s)SFRs for quenched galaxies and those that host AGNs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017reph.conf10003F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017reph.conf10003F"><span><span class="hlt">Stellar</span> Ro</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Featherstone, Nicholas</p> <p>2017-05-01</p> <p>Our understanding of the interior dynamics that give rise to a <span class="hlt">stellar</span> dynamo draws heavily from investigations of similar dynamics in the solar context. Unfortunately, an outstanding gap persists in solar dynamo theory. Convection, an indispensable component of the dynamo, occurs in the midst of rotation, and yet we know little about how the influence of that rotation manifests across the broad range of convective scales present in the Sun. We are nevertheless well aware that the interaction of rotation and convection profoundly impacts many aspects of the dynamo, including the meridional circulation, the differential rotation, and the helicity of turbulent EMF. The rotational constraint felt by solar convection ultimately hinges on the characteristic amplitude of deep convective flow speeds, and such flows are difficult to measure helioseismically. Those measurements of deep convective power which do exist disagree by orders of magnitude, and until this disagreement is resolved, we are left with the results of models and those less ambiguous measurements derived from surface observations of solar convection. I will present numerical results from a series of nonrotating and rotating convection simulations conducted in full 3-D spherical geometry. This presentation will focus on how convective spectra differ between the rotating and non-rotating models and how that behavior changes as simulations are pushed toward more turbulent and/or more rotationally-constrained regimes. I will discuss how the surface signature of rotationally-constrained interior convection might naturally lead to observable signatures in the surface convective pattern, such as supergranulation and a dearth of giant cells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3429970','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3429970"><span>Unusual Case of a Talon <span class="hlt">Cusp</span> on a Supernumerary Tooth in Association with a Mesiodens</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Babaji, Prashant; Sanadi, Firoza; Melkundi, Mahesh</p> <p>2010-01-01</p> <p>Talon <span class="hlt">cusp</span> is an accessory <span class="hlt">cusp</span> similar to a projection, extending from the cingulum or cemento-enamel junction to the incisal edge. It occurs on labial or palatal surfaces of primary or permanent anterior teeth in both arches. This accessory <span class="hlt">cusp</span> can occur as an isolated entity or in association with other dental anomalies. Occurrence of a talon <span class="hlt">cusp</span> on supernu-merary teeth is rare and uncommon. This paper reports an unusual case of a talon <span class="hlt">cusp</span> on a supernumerary tooth in association with mesiodens. PMID:22991599</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22991599','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22991599"><span>Unusual case of a talon <span class="hlt">cusp</span> on a supernumerary tooth in association with a mesiodens.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Babaji, Prashant; Sanadi, Firoza; Melkundi, Mahesh</p> <p>2010-01-01</p> <p>Talon <span class="hlt">cusp</span> is an accessory <span class="hlt">cusp</span> similar to a projection, extending from the cingulum or cemento-enamel junction to the incisal edge. It occurs on labial or palatal surfaces of primary or permanent anterior teeth in both arches. This accessory <span class="hlt">cusp</span> can occur as an isolated entity or in association with other dental anomalies. Occurrence of a talon <span class="hlt">cusp</span> on supernu-merary teeth is rare and uncommon. This paper reports an unusual case of a talon <span class="hlt">cusp</span> on a supernumerary tooth in association with mesiodens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/773830','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/773830"><span>GRAVITATIONAL WAVES FROM <span class="hlt">STELLAR</span> COLLAPSE</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>C. L. FRYER</p> <p>2001-01-01</p> <p><span class="hlt">Stellar</span> core-collapse plays an important role in nearly all facets of astronomy: cosmology (as standard candles), <span class="hlt">formation</span> of compact objects, nucleosynthesis and energy deposition in galaxies. In addition, they release energy in powerful explosions of light over a range of energies, neutrinos, and the subject of this meeting, gravitational waves. Because of this broad range of importance, astronomers have discovered a number of constraints which can be used to help them understand the importance of <span class="hlt">stellar</span> core-collapse as gravitational wave sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950059018&hterms=plasma+simulation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dplasma%2Bsimulation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950059018&hterms=plasma+simulation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dplasma%2Bsimulation"><span>Magnetosheath-ionspheric plasma interactions in the <span class="hlt">cusp</span>/cleft. 2: Mesoscale particle simulations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Winglee, R. M.; Menietti, J. D.; Lin, C. S.</p> <p>1993-01-01</p> <p>Ionospheric plasma flowing out from the <span class="hlt">cusp</span> can be an important source of plasma to the magnetosphere. One source of free energy that can drive this outflow is the injection of magnetosheath plasma into the <span class="hlt">cusp</span>. Two-dimensional (three velocity) mesoscale particle simulations are used to investigate the particle dynamics in the <span class="hlt">cusp</span> during southward interplanetary magnetic field. This mesoscale model self-consistently incorporates (1) global influences such as the convection of plasma across the <span class="hlt">cusp</span>, the action of the mirror force, and the injection of the magnetosheath plasma, and (2) wave-particle interactions which produce the actual coupling between the magnetosheath and ionospheric plasmas. It is shown that, because the thermal speed of the electrons is higher than the bulk motion of the magnetosheath plasma, an upward current is formed on the equatorward edge of the injection region with return currents on either side. However, the poleward return currents are the stronger due to the convection and mirroring of many of the magnetosheath electrons. The electron distribution in this latter region evolves from upward directed streams to single-sided loss cones or possibly electron conics. The ion distribution also shows a variety of distinct features that are produced by spatial and/or temporal effects associated with varying convection patterns and wave-particle interactions. On the equatorward edge the distribution has a downflowing magnetosheath component and an upflowing cold ionospheric component due to continuous convection of ionospheric plasma into the region. In the center of the magnetosheath region, heating from the development of an ion-ion streaming instability causes the suppression of the cold ionospheric component and the <span class="hlt">formation</span> of downward ionospheric streams. Further poleward there is velocity filtering of ions with low pitch angles, so that the magnetosheath ions develop a ring-beam distribution and the ensuing wave instabilities generate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25733661','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25733661"><span>The acquisition of problem behavior in individuals with developmental disabilities as a behavioral <span class="hlt">cusp</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Robertson, Rachel E</p> <p>2015-07-01</p> <p>A behavioral <span class="hlt">cusp</span> has been defined as a behavior change that produces contact with new contingencies with important and far-reaching consequences. The concept of behavioral <span class="hlt">cusps</span> has most frequently been used to select target skills taught to learners and to evaluate the importance of those skills; however, the concept is equally applicable to behavior changes that bring about important and far-reaching negative consequences. Although it has been acknowledged that socially undesirable behavior change can also qualify as a behavioral <span class="hlt">cusp</span>, this area of the <span class="hlt">cusp</span> concept has been under-examined. In this article, an undesirable behavior change, the acquisition of problem behavior in individuals with developmental disabilities, is compared with criteria for behavioral <span class="hlt">cusps</span> previously identified in the literature. The advantages of viewing problem behavior as a behavioral <span class="hlt">cusp</span> are outlined, and implications for practice and research from a behavioral <span class="hlt">cusp</span> approach to problem behavior are provided.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040129618','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040129618"><span>Computational Study of Primary Electrons in the <span class="hlt">Cusp</span> Region of an Ion Engine's Discharge Chamber</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stueber, Thomas J. (Technical Monitor); Deshpande, Shirin S.; Mahalingam, Sudhakar; Menart, James A.</p> <p>2004-01-01</p> <p>In this work a computer code called PRIMA is used to study the motion of primary electrons in the magnetic <span class="hlt">cusp</span> region of the discharge chamber of an ion engine. Even though the amount of wall area covered by the <span class="hlt">cusps</span> is very small, the <span class="hlt">cusp</span> regions are important because prior computational analyses have indicated that most primary electrons leave the discharge chamber through the <span class="hlt">cusps</span>. The analysis presented here focuses on the <span class="hlt">cusp</span> region only. The affects of the shape and size of the <span class="hlt">cusp</span> region on primary electron travel are studied as well as the angle and location at which the electron enters the <span class="hlt">cusp</span> region. These affects are quantified using the confinement length and the number density distributions of the primary electrons. In addition to these results comparisons of the results from PRIMA are made to experimental results for a cylindrical discharge chamber with two magnetic rings. These comparisons indicate the validity of the computer code called PRIMA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=GL-2002-001176&hterms=Metamorphosis&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DMetamorphosis','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=GL-2002-001176&hterms=Metamorphosis&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DMetamorphosis"><span><span class="hlt">Stellar</span> Metamorphosis:</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>[TOP LEFT AND RIGHT] The Hubble Space Telescope's Wide Field and Planetary Camera 2 has captured images of the birth of two planetary nebulae as they emerge from wrappings of gas and dust, like butterflies breaking out of their cocoons. These images highlight a fleeting phase in the <span class="hlt">stellar</span> burnout process, occurring just before dying stars are transformed into planetary nebulae. The left-hand image is the Cotton Candy nebula, IRAS 17150-3224; the right-hand image, the Silkworm nebula, IRAS 17441-2411. Called proto-planetary nebulae, these dying stars have been caught in a transition phase between a red giant and a planetary nebula. This phase is only about 1,000 years long, very short in comparison to the 1 billion-year lifetime of a star. These images provide the earliest snapshots of the transition process. Studying images of proto-planetary nebulae is important to understanding the process of star death. A star begins to die when it has exhausted its thermonuclear fuel - hydrogen and helium. The star then becomes bright and cool (red giant phase) and swells to several tens of times its normal size. It begins puffing thin shells of gas off into space. These shells become the star's cocoon. In the Hubble images, the shells are the concentric rings seen around each nebula. But the images also reveal the nebulae breaking out from those shells. The butterfly-like wings of gas and dust are a common shape of planetary nebulae. Such butterfly shapes are created by the 'interacting winds' process, in which a more recent 'fast wind' - material propelled by radiation from the hot central star - punches a hole in the cocoon, allowing the nebula to emerge. (This 'interacting wind' theory was first proposed by Dr. Sun Kwok to explain the origin of planetary nebulae, and has been subsequently proven successful in explaining their shapes.) The nebulae are being illuminated by light from the invisible central star, which is then reflected toward us. We are viewing the nebulae</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=GL-2002-001176&hterms=Butterfly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DButterfly','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=GL-2002-001176&hterms=Butterfly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DButterfly"><span><span class="hlt">Stellar</span> Metamorphosis:</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>[TOP LEFT AND RIGHT] The Hubble Space Telescope's Wide Field and Planetary Camera 2 has captured images of the birth of two planetary nebulae as they emerge from wrappings of gas and dust, like butterflies breaking out of their cocoons. These images highlight a fleeting phase in the <span class="hlt">stellar</span> burnout process, occurring just before dying stars are transformed into planetary nebulae. The left-hand image is the Cotton Candy nebula, IRAS 17150-3224; the right-hand image, the Silkworm nebula, IRAS 17441-2411. Called proto-planetary nebulae, these dying stars have been caught in a transition phase between a red giant and a planetary nebula. This phase is only about 1,000 years long, very short in comparison to the 1 billion-year lifetime of a star. These images provide the earliest snapshots of the transition process. Studying images of proto-planetary nebulae is important to understanding the process of star death. A star begins to die when it has exhausted its thermonuclear fuel - hydrogen and helium. The star then becomes bright and cool (red giant phase) and swells to several tens of times its normal size. It begins puffing thin shells of gas off into space. These shells become the star's cocoon. In the Hubble images, the shells are the concentric rings seen around each nebula. But the images also reveal the nebulae breaking out from those shells. The butterfly-like wings of gas and dust are a common shape of planetary nebulae. Such butterfly shapes are created by the 'interacting winds' process, in which a more recent 'fast wind' - material propelled by radiation from the hot central star - punches a hole in the cocoon, allowing the nebula to emerge. (This 'interacting wind' theory was first proposed by Dr. Sun Kwok to explain the origin of planetary nebulae, and has been subsequently proven successful in explaining their shapes.) The nebulae are being illuminated by light from the invisible central star, which is then reflected toward us. We are viewing the nebulae</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23031031','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23031031"><span>Coulomb clusters of dust particles in a <span class="hlt">cusp</span> magnetic trap under microgravity conditions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Petrov, O F; Myasnikov, M I; D'yachkov, L G; Vasiliev, M M; Fortov, V E; Savin, S F; Kaleri, A Yu; Borisenko, A I; Morfill, G E</p> <p>2012-09-01</p> <p>We have performed experimental and theoretical investigation of the <span class="hlt">formation</span> and behavior of Coulomb clusters of charged diamagnetic particles in a <span class="hlt">cusp</span> magnetic trap under microgravity conditions aboard the International Space Station. Graphite particles of 100-400 μm in size were used in experiments due to the highest specific magnetic susceptibility. We have observed the <span class="hlt">formation</span> of clusters in the shape of an oblate ellipsoid of revolution and their oscillations after dynamical action by changing the magnetic field. Observing the excitation and damping of oscillations we have made some estimations. Molecular dynamics simulations of the observed processes have been made. Their results are in reasonable agreement with experiments. Some differences are evidently due to some unaccounted-for reasons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014hst..prop13696H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014hst..prop13696H"><span>The Anemic <span class="hlt">Stellar</span> Halo of M101</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holwerda, Benne</p> <p>2014-10-01</p> <p>Models of galaxy <span class="hlt">formation</span> in a cosmological context predict that massive disk galaxies should have richly-structured extended <span class="hlt">stellar</span> halos, containing ~10% of a galaxy's stars, originating in large part from the tidal disruption of dwarf galaxies. Observations of a number of nearby disk galaxies have generally agreed with these expectations. Recent new observations in integrated light with a novel array of low scattered-light telephoto lenses have failed to convincingly detect a <span class="hlt">stellar</span> halo in the nearby massive face-on disk galaxy M101 (van Dokkum et al. 2014). They argue that any halo has to have <0.3% of the mass of the galaxy. This halo would be the least massive of any massive disk galaxy in the local Universe (by factors of several) -- such a halo is not predicted or naturally interpreted by the models, and would present a critical challenge to the picture of ubiquitous <span class="hlt">stellar</span> halos formed from the debris of disrupting dwarf galaxies.We propose to resolve the <span class="hlt">stellar</span> populations of this uniquely anemic <span class="hlt">stellar</span> halo for 6 orbits with HST (ACS and WFC3), allowing us to reach surface brightness limits sufficient to clearly detect and characterize M101's <span class="hlt">stellar</span> halo if it carries more than 0.1% of M101's mass. With resolved <span class="hlt">stellar</span> populations, we can use the gradient of <span class="hlt">stellar</span> populations as a function of radius to separate <span class="hlt">stellar</span> halo from disk, which is impossible using integrated light observations. The resolved <span class="hlt">stellar</span> populations will reveal the halo mass to much greater accuracy, measure the halo radial profile, constrain any halo lopsidedness, estimate the halo's <span class="hlt">stellar</span> metallicity, and permit an analysis of outer disk <span class="hlt">stellar</span> populations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760021253','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760021253"><span><span class="hlt">Cusped</span> magnetic field mercury ion thruster. Ph.D. Thesis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Beattie, J. R.</p> <p>1976-01-01</p> <p>The importance of a uniform current density profile in the exhaust beam of an electrostatic ion thruster is discussed in terms of thrust level and accelerator system lifetime. A residence time approach is used to explain the nonuniform beam current density profile of the divergent magnetic field thruster. Mathematical expressions are derived which relate the thruster discharge power loss, propellant utilization, and double to single ion density ratio to the geometry and plasma properties of the discharge chamber. These relationships are applied to a cylindrical discharge chamber model of the thruster. Experimental results are presented for a wide range of the discharge chamber length. The thruster designed for this investigation was operated with a <span class="hlt">cusped</span> magnetic field as well as a divergent field geometry, and the <span class="hlt">cusped</span> field geometry is shown to be superior from the standpoint of beam profile uniformity, performance, and double ion population.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992PhDT.......147L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992PhDT.......147L"><span>The Nuclear <span class="hlt">Cusp</span> Condition in Spin-Polarized Thomas - Theory.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lung, Chien-An.</p> <p></p> <p>Thomas-Fermi theory, which was introduced in the 1920s, was developed into rigorous mathematics in the 1970s by Lieb, Simon, Benilan, Brezis, and others. Later, Goldstein and Rieder extended rigorous Thomas-Fermi theory to a spin polarized context, to include the nuclear <span class="hlt">cusp</span> condition, and to the case where a magnetic field is present. But they did not investigate incorporating the nuclear <span class="hlt">cusp</span> condition into the spin polarized context. The purpose of my thesis is to do precisely that. I proved the existence and uniqueness of the problem of minimizing the energy functional by solving a non-linear elliptic partial differential equation on { bf R}^3 which arose from the Euler -Lagrange equation. A topological argument then related the Lagrange multipliers to the numbers of spin up and spin down electrons.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22048000','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22048000"><span>ON THE CARBON-TO-OXYGEN RATIO MEASUREMENT IN NEARBY SUN-LIKE STARS: IMPLICATIONS FOR PLANET <span class="hlt">FORMATION</span> AND THE DETERMINATION OF <span class="hlt">STELLAR</span> ABUNDANCES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fortney, Jonathan J.</p> <p>2012-03-10</p> <p>Recent high-resolution spectroscopic analysis of nearby FGK stars suggests that a high C/O ratio of greater than 0.8, or even 1.0, is relatively common. Two published catalogs find C/O > 0.8 in 25%-30% of systems, and C/O > 1.0 in {approx}6%-10%. It has been suggested that in protoplanetary disks with C/O > 0.8 that the condensation pathways to refractory solids will differ from what occurred in our solar system, where C/O = 0.55. The carbon-rich disks are calculated to make carbon-dominated rocky planets, rather than oxygen-dominated ones. Here we suggest that the derived <span class="hlt">stellar</span> C/O ratios are overestimated. One constraint on the frequency of high C/O is the relative paucity of carbon dwarf stars (10{sup -3}-10{sup -5}) found in large samples of low-mass stars. We suggest reasons for this overestimation, including a high C/O ratio for the solar atmosphere model used for differential abundance analysis, the treatment of a Ni blend that affects the O abundance, and limitations of one-dimensional LTE <span class="hlt">stellar</span> atmosphere models. Furthermore, from the estimated errors on the measured <span class="hlt">stellar</span> C/O ratios, we find that the significance of the high C/O tail is weakened, with a true measured fraction of C/O > 0.8 in 10%-15% of stars, and C/O > 1.0 in 1%-5%, although these are still likely overestimates. We suggest that infrared T-dwarf spectra could show how common high C/O is in the <span class="hlt">stellar</span> neighborhood, as the chemistry and spectra of such objects would differ compared to those with solar-like abundances. While possible at C/O > 0.8, we expect that carbon-dominated rocky planets are rarer than others have suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000039220&hterms=tide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dtide','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000039220&hterms=tide&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dtide"><span>TIDE Observations of <span class="hlt">Cusp</span> and Cleft Multiple Ion Populations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Coffey, Victoria N.; Chandler, Michael O.; Moore, Thomas E.</p> <p>2000-01-01</p> <p>The southern pole pass of Polar/TIDe at 5000 km allows a study of the distributions of the <span class="hlt">cusp</span> and cleft. We discuss observations of TIDE (Thermal Ion Dynamics Experiment) as it passes the southern pole on March 29, 1999. A mixture of several cold outflowing ions (0.3-10 eV) are measured simultaneously with magnetospheric precipitation (greater than 100 eV). We will show a study of these multiple plasma distributions, their source, and their interaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70030171','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70030171"><span>Rip currents, mega-<span class="hlt">cusps</span>, and eroding dunes</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Thornton, E.B.; MacMahan, J.; Sallenger, A.H.</p> <p>2007-01-01</p> <p>Dune erosion is shown to occur at the embayment of beach mega-<span class="hlt">cusps</span> O(200 m alongshore) that are associated with rip currents. The beach is the narrowest at the embayment of the mega-<span class="hlt">cusps</span> allowing the swash of large storm waves coincident with high tides to reach the toe of the dune, to undercut the dune and to cause dune erosion. Field measurements of dune, beach, and rip current morphology are acquired along an 18 km shoreline in southern Monterey Bay, California. This section of the bay consists of a sandy shoreline backed by extensive dunes, rising to heights exceeding 40 m. There is a large increase in wave height going from small wave heights in the shadow of a headland, to the center of the bay where convergence of waves owing to refraction over the Monterey Bay submarine canyon results in larger wave heights. The large alongshore gradient in wave height results in a concomitant alongshore gradient in morphodynamic scale. The strongly refracted waves and narrow bay aperture result in near normal wave incidence, resulting in well-developed, persistent rip currents along the entire shoreline. The alongshore variations of the cuspate shoreline are found significantly correlated with the alongshore variations in rip spacing at 95% confidence. The alongshore variations of the volume of dune erosion are found significantly correlated with alongshore variations of the cuspate shoreline at 95% confidence. Therefore, it is concluded the mega-<span class="hlt">cusps</span> are associated with rip currents and that the location of dune erosion is associated with the embayment of the mega-<span class="hlt">cusp</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16321702','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16321702"><span><span class="hlt">Cusp</span> tear in bicuspid aortic valve possibly caused by phentermine.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yosefy, Chaim; Berman, Michael; Beeri, Ronen</p> <p>2006-01-13</p> <p>A 28 year old woman underwent echocardiography following an incidental finding of a diastolic murmur. She has been taking phentermine for weight reduction for 8 months. Trans-esophageal echocardiography revealed a tear of the posterior <span class="hlt">cusp</span> of the aortic valve causing severe regurgitation. Phentermine is known to cause valvular disease with prolonged use, but aortic valve rupture was not previously reported as a complication of phentermine valvulopathy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017HEAD...1610845S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017HEAD...1610845S"><span>Twin-Peak QPOs from Oscillating Torus with <span class="hlt">Cusp</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sramkova, Eva</p> <p>2017-08-01</p> <p>We propose a model of HF twin-peak quasi-periodic oscillations assuming an oscillating torus with <span class="hlt">cusp</span> that changes location of its centre around