Sample records for virgo stellar substructure

  1. Probing Kinematic Substructures in the Virgo Overdensity using RR Lyrae from Recent Surveys

    NASA Astrophysics Data System (ADS)

    Farmer, John; Vivas, A. Katherina

    2015-01-01

    The Virgo Overdensity is one of the most intriguing features of the galactic halo, as it covers a large portion of the sky and seems to contain several kinematic substructures. It has been suggested that the remnants of several merger events coexist in this region. RR Lyrae stars are an excellent tracer for disentangling the different components of this overdensity, since they are excellent standard candles; by using both positions and pulsation-corrected radial velocities, we can identify distinct groups in phase space. In the last year, several surveys for RR Lyraes covering the Virgo region have become publicly available. We present analysis of ~300 spectra for ~200 stars in the Virgo overdensity region. This is a significant increase in the known sample of these stars in the region, spanning a significantly larger area of the sky than previous studies. Photometry for these data are taken primarily from the La Silla and Venezuela QUEST variability surveys with spectra provided by SDSS Data Release 10. Radial velocities for type ab RR Lyrae stars are corrected using the new set of template radial velocity curves for Balmer and metallic lines given by Sesar (2012). We combine data from QUEST, the Catalina Sky Survey, LINEAR, and spectroscopic observations from Duffau (2014) to give our full sample. A preliminary analysis reveals confirmation for several known stellar streams.

  2. Signatures of Kinematic Substructure in the Galactic Stellar Halo

    NASA Astrophysics Data System (ADS)

    Lisanti, Mariangela; Spergel, David N.; Madau, Piero

    2015-07-01

    Tidal debris from infalling satellites can leave observable structure in the phase-space distribution of the Galactic halo. Such substructure can be manifest in the spatial and/or velocity distributions of the stars in the halo. This paper focuses on a class of substructure that is purely kinematic in nature, with no accompanying spatial features. To study its properties, we use a simulated stellar halo created by dynamically populating the Via Lactea II high-resolution N-body simulation with stars. A significant fraction of the stars in the inner halo of Via Lactea share a common speed and metallicity, despite the fact that they are spatially diffuse. We argue that this kinematic substructure is a generic feature of tidal debris from older mergers and may explain the detection of radial-velocity substructure in the inner halo made by the Sloan Extension for Galactic Understanding and Exploration. The GAIA satellite, which will provide the proper motions of an unprecedented number of stars, should further characterize the kinematic substructure in the inner halo. Our study of the Via Lactea simulation suggests that the stellar halo can be used to map the speed distribution of the local dark matter (DM) halo, which has important consequences for DM direct-detection experiments.

  3. Stellar Substructures Around the Hercules Dwarf Spheroidal Galaxy

    NASA Astrophysics Data System (ADS)

    Roderick, T. A.; Jerjen, H.; Mackey, A. D.; Da Costa, G. S.

    2015-05-01

    We present deep g and i band Dark Energy Camera stellar photometry of the Hercules Milky Way satellite galaxy, and its surrounding field, out to a radial distance of 5.4 times the tidal radius. We have identified nine extended stellar substructures associated with the dwarf; preferentially distributed along the major axis of the galaxy. Two significant over-densities lie outside the 95% confidence band for the likely orbital path of the galaxy and appear to be free-floating tidal debris. We estimate the luminosity of the new stellar substructures, and find that approximately the same amount of stellar flux is lying in these extended structures as inside the main body of Hercules. We also analyze the distribution of candidate blue-horizontal-branch stars and find agreement with the alignment of the substructures at a confidence level greater than 98%. Our analysis provides a quantitative demonstration that Hercules is a strongly tidally disrupted system, with noticeable stellar features at least 1.9 kpc away from the galaxy.

  4. Stellar Substructures around the Hercules Dwarf Spheroidal Galaxy

    E-print Network

    Roderick, T A; Mackey, A D; Da Costa, G S

    2015-01-01

    We present deep $g,i$-band DECam stellar photometry of the Hercules Milky Way satellite galaxy, and its surrounding field, out to a radial distance of 5.4 times the tidal radius. We have identified nine extended stellar substructures associated with the dwarf; preferentially distributed along the major axis of the galaxy. Two significant over-densities lie outside the 95\\% confidence band for the likely orbital path of the galaxy and appear to be free-floating tidal debris. We estimate the luminosity of the new stellar substructures, and find that approximately the same amount of stellar flux is lying in these extended structures as inside the main body of Hercules. We also analyse the distribution of candidate blue-horizontal-branch stars and find agreement with the alignment of the substructures at a confidence level greater than 98\\%. Our analysis provides a quantitative demonstration that Hercules is a strongly tidally disrupted system, with noticeable stellar features at least 1.9 kpc away from the galax...

  5. QUANTIFYING KINEMATIC SUBSTRUCTURE IN THE MILKY WAY'S STELLAR HALO

    SciTech Connect

    Xue Xiangxiang; Zhao Gang; Luo Ali [Key Lab of Optical Astronomy, National Astronomical Observatories, CAS, 20A Datun Road, Chaoyang District, 100012 Beijing (China); Rix, Hans-Walter; Bell, Eric F.; Koposov, Sergey E.; Kang, Xi; Liu, Chao [Max-Planck-Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Yanny, Brian [Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510-5011 (United States); Beers, Timothy C.; Lee, Young Sun [Department of Physics and Astronomy and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Bullock, James S. [Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Johnston, Kathryn V. [Astronomy Department, Columbia University, New York, NY 10027 (United States); Morrison, Heather [Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States); Rockosi, Constance [Lick Observatory/University of California, Santa Cruz, CA 95060 (United States); Weaver, Benjamin A. [Center for Cosmology and Particle Physics, New York University, New York, NY 10003 (United States)

    2011-09-01

    We present and analyze the positions, distances, and radial velocities for over 4000 blue horizontal-branch (BHB) stars in the Milky Way's halo, drawn from SDSS DR8. We search for position-velocity substructure in these data, a signature of the hierarchical assembly of the stellar halo. Using a cumulative 'close pair distribution' as a statistic in the four-dimensional space of sky position, distance, and velocity, we quantify the presence of position-velocity substructure at high statistical significance among the BHB stars: pairs of BHB stars that are close in position on the sky tend to have more similar distances and radial velocities compared to a random sampling of these overall distributions. We make analogous mock observations of 11 numerical halo formation simulations, in which the stellar halo is entirely composed of disrupted satellite debris, and find a level of substructure comparable to that seen in the actually observed BHB star sample. This result quantitatively confirms the hierarchical build-up of the stellar halo through a signature in phase (position-velocity) space. In detail, the structure present in the BHB stars is somewhat less prominent than that seen in most simulated halos, quite possibly because BHB stars represent an older sub-population. BHB stars located beyond 20 kpc from the Galactic center exhibit stronger substructure than at r{sub gc} < 20 kpc.

  6. A Photometric Metallicity Estimate of the Virgo Stellar Overdensity

    E-print Network

    An, Deokkeun; Beers, Timothy C; Pinsonneault, Marc H; Terndrup, Donald M; Delahaye, Franck; Lee, Young Sun; Masseron, Thomas; Yanny, Brian

    2009-01-01

    We determine photometric metal abundance estimates for individual main-sequence stars in the Virgo Overdensity (VOD), which covers almost 1000 deg^2 on the sky, based on a calibration of the metallicity sensitivity of stellar isochrones in the gri filter passbands using field stars with well-determined spectroscopic metal abundances. Despite the low precision of the method for individual stars, we derive [Fe/H] = -2.0 +/-0.1 (internal) +/-0.5 (systematic) for the metal abundance of the VOD from photometric measurements of 0.7 million stars in the Northern Galactic hemisphere with heliocentric distances from ~10 kpc to ~20 kpc. The metallicity of the VOD is indistinguishable, within Delta [Fe/H] < 0.2, from that of field halo stars covering the same distance range. This initial application suggests that the SDSS gri passbands can be used to probe the properties of main-sequence stars beyond ~10 kpc, complementing studies of nearby stars from more metallicity-sensitive color indices that involve the u passba...

  7. A Photometric Metallicity Estimate of the Virgo Stellar Overdensity

    NASA Astrophysics Data System (ADS)

    An, Deokkeun; Johnson, Jennifer A.; Beers, Timothy C.; Pinsonneault, Marc H.; Terndrup, Donald M.; Delahaye, Franck; Lee, Young Sun; Masseron, Thomas; Yanny, Brian

    2009-12-01

    We determine photometric metal abundance estimates for individual main-sequence stars in the Virgo Overdensity (VOD), which covers almost 1000 °^2 on the sky, based on a calibration of the metallicity sensitivity of stellar isochrones in the gri filter passbands using field stars with well-determined spectroscopic metal abundances. Despite the low precision of the method for individual stars, we derive [Fe/H] = -2.0 ± 0.1(internal) ± 0.5(systematic) for the metal abundance of the VOD from photometric measurements of 0.7 million stars in the northern Galactic hemisphere with heliocentric distances from ~10 kpc to ~20 kpc. The metallicity of the VOD is indistinguishable, within ?[Fe/H] <= 0.2, from that of field halo stars covering the same distance range. This initial application suggests that the Sloan Digital Sky Survey gri passbands can be used to probe the properties of main-sequence stars beyond ~10 kpc, complementing studies of nearby stars from more metallicity-sensitive color indices that involve the u passband.

  8. INTEGRAL-FIELD STELLAR AND IONIZED GAS KINEMATICS OF PECULIAR VIRGO CLUSTER SPIRAL GALAXIES

    SciTech Connect

    Cortés, Juan R.; Hardy, Eduardo [National Radio Astronomy Observatory Avenida Nueva Costanera 4091, Vitacura, Santiago (Chile); Kenney, Jeffrey D. P., E-mail: jcortes@alma.cl, E-mail: ehardy@nrao.cl, E-mail: jeff.kenney@yale.edu [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)

    2015-01-01

    We present the stellar and ionized gas kinematics of 13 bright peculiar Virgo cluster galaxies observed with the DensePak Integral Field Unit at the WIYN 3.5 m telescope in order to look for kinematic evidence that these galaxies have experienced gravitational interactions or gas stripping. Two-dimensional maps of the stellar velocity V, stellar velocity dispersion ?, and the ionized gas velocity (H? and/or [O III]) are presented for the galaxies in the sample. The stellar rotation curves and velocity dispersion profiles are determined for 13 galaxies, and the ionized gas rotation curves are determined for 6 galaxies. Misalignments between the optical and kinematical major axes are found in several galaxies. While in some cases this is due to a bar, in other cases it seems to be associated with gravitational interaction or ongoing ram pressure stripping. Non-circular gas motions are found in nine galaxies, with various causes including bars, nuclear outflows, or gravitational disturbances. Several galaxies have signatures of kinematically distinct stellar components, which are likely signatures of accretion or mergers. For all of our galaxies, we compute the angular momentum parameter ? {sub R}. An evaluation of the galaxies in the ? {sub R} ellipticity plane shows that all but two of the galaxies have significant support from random stellar motions, and have likely experienced gravitational interactions. This includes some galaxies with very small bulges and truncated/compact H? morphologies, indicating that such galaxies cannot be fully explained by simple ram pressure stripping, but must have had significant gravitational encounters. Most of the sample galaxies show evidence for ICM-ISM stripping as well as gravitational interactions, indicating that the evolution of a significant fraction of cluster galaxies is likely strongly impacted by both effects.

  9. Stellar and Gas Kinematics in the Tully-Fisher Deviant Virgo Cluster Galaxy NGC 4424

    NASA Astrophysics Data System (ADS)

    Cortes, J. R.; Kenney, J. D. P.

    2000-05-01

    NGC 4424 is a peculiar, gas-deficient, Virgo Cluster Sa galaxy which is probably the result of a merger. This galaxy seems to deviate from the Tully-Fisher relationship, as shown by Kenney et al (1996) and Rubin et al (1999). We present stellar and gas kinematics of NGC 4424 measured with Integral Field Spectroscopy using the Densepak fiber array on the WIYN telescope. Using a cross-correlation technique, we derive velocities and velocity dispersions of the stars thoughout the central region of the galaxy. We find that the mean line-of-sight velocities for both gas and stars are approximately a factor of 2 smaller than would be expected for the rotational motions of a galaxy of its luminosity and apparent inclination. Preliminary estimates of the stellar velocity dispersion are also lower than would be expected for the Faber-Jackson relationship. We discuss possible explanations for this behaviour, including the possibility that this disturbed galaxy is rotating in a plane different than the plane of the apparent disk, and is a tumbling object.

  10. The SPITZER IRS view of stellar populations in Virgo early type galaxies

    E-print Network

    A. Bressan; P. Panuzzo; L. Buson; M. Clemens; G. L. Granato; R. Rampazzo; L. Silva; J. R. Valdes; O. Vega; L. Danese

    2006-04-04

    We have obtained high S/N Spitzer IRS spectra of 17 Virgo early-type galaxies that lie on the colour-magnitude relation of passively evolving galaxies in the cluster. To flux calibrate these extended sources we have devised a new procedure that allows us to obtain the intrinsic spectral energy distribution and to disentangle resolved and unresolved emission within the same object. Thirteen objects of the sample (76%) show a pronounced broad silicate feature (above 10micron) which is spatially extended and likely of stellar origin, in agreement with model predictions. The other 4 objects (24%) are characterized by different levels of activity. In NGC 4486 (M87) the line emission and the broad silicate emission are evidently unresolved and, given also the typical shape of the continuum, they likely originate in the nuclear torus. NGC 4636 show emission lines superimposed to extended silicate emission (i.e. likely of stellar origin, pushing the percentage of galaxies with silicate emission to 82%). Finally NGC 4550 and NGC 4435 are characterized by PAH and line emission, arising from a central unresolved region.

  11. SPITZER IRS spectra of Virgo early type galaxies: detection of stellar silicate emission

    E-print Network

    A. Bressan; P. Panuzzo; L. Buson; M. Clemens; G. L. Granato; R. Rampazzo; L. Silva; J. R. Valdes; O. Vega; L. Danese

    2006-02-01

    We present high signal to noise ratio Spitzer Infrared Spectrograph observations of 17 Virgo early-type galaxies. The galaxies were selected from those that define the colour-magnitude relation of the cluster, with the aim of detecting the silicate emission of their dusty, mass-losing evolved stars. To flux calibrate these extended sources we have devised a new procedure that allows us to obtain the intrinsic spectral energy distribution and to disentangle resolved and unresolved emission within the same object. We have found that thirteen objects of the sample (76%) are passively evolving galaxies with a pronounced broad silicate feature which is spatially extended and likely of stellar origin, in agreement with model predictions. The other 4 objects (24%) are characterized by different levels of activity. In NGC 4486 (M 87) the line emission and the broad silicate emission are evidently unresolved and, given also the typical shape of the continuum, they likely originate in the nuclear torus. NGC 4636 shows emission lines superimposed on extended (i.e. stellar) silicate emission, thus pushing the percentage of galaxies with silicate emission to 82%. Finally, NGC 4550 and NGC 4435 are characterized by polycyclic aromatic hydrocarbon (PAH) and line emission, arising from a central unresolved region. A more detailed analysis of our sample, with updated models, will be presented in a forthcoming paper.

  12. Tidal stripping stellar substructures around four metal-poor globular clusters in the galactic bulge

    SciTech Connect

    Chun, Sang-Hyun [Yonsei University Observatory, Seoul (Korea, Republic of); Kang, Minhee; Jung, DooSeok; Sohn, Young-Jong, E-mail: shchun@galaxy.yonei.ac.kr [Department of Astronomy, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2015-01-01

    We investigate the spatial density configuration of stars around four metal-poor globular clusters (NGC 6266, NGC 6626, NGC 6642, and NGC 6723) in the Galactic bulge region using wide-field deep J, H, and K imaging data obtained with the Wide Field Camera near-infrared array on the United Kingdom Infrared Telescope. A statistical weighted filtering algorithm for the stars on the color–magnitude diagram is applied in order to sort cluster member candidates from the field star contamination. In two-dimensional isodensity contour maps of the clusters, we find that all four of the globular clusters exhibit strong evidence of tidally stripped stellar features beyond the tidal radius in the form of tidal tails or small density lobes/chunks. The orientations of the extended stellar substructures are likely to be associated with the effect of dynamic interaction with the Galaxy and the cluster's space motion. The observed radial density profiles of the four globular clusters also describe the extended substructures; they depart from theoretical King and Wilson models and have an overdensity feature with a break in the slope of the profile at the outer region of clusters. The observed results could imply that four globular clusters in the Galactic bulge region have experienced strong environmental effects such as tidal forces or bulge/disk shocks of the Galaxy during the dynamical evolution of globular clusters. These observational results provide further details which add to our understanding of the evolution of clusters in the Galactic bulge region as well as the formation of the Galaxy.

  13. Tidal Stripping Stellar Substructures Around Four Metal-Poor Globular Clusters in the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Chun, Sang-Hyun; Kang, Minhee; Jung, DooSeok; Sohn, Young-Jong

    2015-01-01

    We investigate the spatial density configuration of stars around four metal-poor globular clusters (NGC 6266, NGC 6626, NGC 6642, and NGC 6723) in the Galactic bulge region using wide-field deep J, H, and K imaging data obtained with the Wide Field Camera near-infrared array on the United Kingdom Infrared Telescope. A statistical weighted filtering algorithm for the stars on the color-magnitude diagram is applied in order to sort cluster member candidates from the field star contamination. In two-dimensional isodensity contour maps of the clusters, we find that all four of the globular clusters exhibit strong evidence of tidally stripped stellar features beyond the tidal radius in the form of tidal tails or small density lobes/chunks. The orientations of the extended stellar substructures are likely to be associated with the effect of dynamic interaction with the Galaxy and the cluster's space motion. The observed radial density profiles of the four globular clusters also describe the extended substructures; they depart from theoretical King and Wilson models and have an overdensity feature with a break in the slope of the profile at the outer region of clusters. The observed results could imply that four globular clusters in the Galactic bulge region have experienced strong environmental effects such as tidal forces or bulge/disk shocks of the Galaxy during the dynamical evolution of globular clusters. These observational results provide further details which add to our understanding of the evolution of clusters in the Galactic bulge region as well as the formation of the Galaxy.

  14. A Gemini/GMOS Study of Intermediate Luminosity Early-type Virgo Cluster Galaxies. I. Globular Cluster and Stellar Kinematics

    NASA Astrophysics Data System (ADS)

    Li, Biao; Peng, Eric W.; Zhang, Hong-xin; Blakeslee, John P.; Côté, Patrick; Ferrarese, Laura; Jordán, Andrés; Liu, Chengze; Mei, Simona; Puzia, Thomas H.; Takamiya, Marianne; Trancho, Gelys; West, Michael J.

    2015-06-01

    We present a kinematic analysis of the globular cluster (GC) systems and diffuse stellar light of four intermediate luminosity (sub-L*) early-type galaxies in the Virgo cluster based on Gemini Multi-Object Spectrographs (GMOS) data. Our galaxy sample is fainter (-23.8\\lt {{M}K}\\lt -22.7) than most previous studies, nearly doubling the number of galaxies in this magnitude range that now have GC kinematics. The data for the diffuse light extends to 4Re, and the data for the GCs reaches 8–12Re. We find that the kinematics in these outer regions are all different despite the fact that these four galaxies have similar photometric properties, and are uniformly classified as “fast rotators” from their stellar kinematics within 1Re. The GC systems exhibit a wide range of kinematic morphology. The rotation axis and amplitude can change between the inner and outer regions, including a case of counter-rotation. This difference shows the importance of wide-field kinematic studies, and shows that stellar and GC kinematics can change significantly as one moves beyond the inner regions of galaxies. Moreover, the kinematics of the GC systems can differ from that of the stars, suggesting that the formation of the two populations are also distinct.

  15. A Gemini/GMOS Study of Intermediate Luminosity Early-Type Virgo Cluster Galaxies. I. Globular Cluster and Stellar Kinematics

    E-print Network

    Li, Biao; Zhang, Hong-xin; Blakeslee, John P; Côté, Patrick; Ferrarese, Laura; Jordán, Andrés; Liu, Chengze; Mei, Simona; Puzia, Thomas H; Takamiya, Marianne; Trancho, Gelys; West, Michael J

    2015-01-01

    We present a kinematic analysis of the globular cluster systems and diffuse stellar light of four intermediate luminosity (sub-$L^{\\ast}$) early-type galaxies in the Virgo cluster based on Gemini/GMOS data. Our galaxy sample is fainter ($-23.8stellar kinematics within $1R_e$. The globular cluster systems exhibit a wide range of kinematic morphology. The rotation axis and amplitude can change between the inner and outer regions, including a case of counter-rotation. This difference shows the importance of wide-field kinematic studies, and shows that stellar and GC...

  16. The Next Generation Virgo Cluster Survey. XII. Stellar Populations and Kinematics of Compact, Low-Mass Early-Type Galaxies from Gemini GMOS-IFU Spectroscopy

    E-print Network

    Guerou, Adrien; McDermid, Richard M; Cote, Patrick; Ferrarese, Laura; Blakeslee, John P; Durrell, Patrick R; MacArthur, Lauren A; Peng, Eric W; Cuillandre, Jean-Charles; Gwyn, Stephen

    2015-01-01

    We present Gemini GMOS-IFU data of eight compact low-mass early-type galaxies (ETGs) in the Virgo cluster. We analyse their stellar kinematics, stellar population, and present two-dimensional maps of these properties covering the central 5"x 7" region. We find a large variety of kinematics: from non- to highly-rotating objects, often associated with underlying disky isophotes revealed by deep images from the Next Generation Virgo Cluster Survey. In half of our objects, we find a centrally-concentrated younger and more metal-rich stellar population. We analyze the specific stellar angular momentum through the lambdaR parameter and find six fast-rotators and two slow-rotators, one having a thin counter-rotating disk. We compare the local galaxy density and stellar populations of our objects with those of 39 more extended low-mass Virgo ETGs from the SMAKCED survey and 260 massive ($M>10^{10}$\\Msun) ETGs from the A3D sample. The compact low-mass ETGs in our sample are located in high density regions, often close...

  17. Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories

    E-print Network

    Kathryn V. Johnston; James S. Bullock; Sanjib Sharma; Andreea Font; Brant E. Robertson; Samuel N. Leitner

    2008-07-24

    This paper explores the mapping between the observable properties of a stellar 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 eleven stellar halo models constructed within the context of a standard LCDM cosmology. The results demonstrate that coordinate-space studies are sensitive to the recent (0-8 Gyears ago) merger histories of galaxies (this timescale corresponds to the last few to tens of percent of mass accretion for a Milky-Way-type galaxy). Specifically, the {\\it frequency, sky coverage} and {\\it fraction of stars} in substructures in the stellar halo as a function of surface brightness are indicators of the importance of recent merging and of the luminosity function of infalling dwarfs. The {\\it morphology} of features serves as a guide to the orbital distribution of those dwarfs. Constraints on the earlier merger history (> 8 Gyears 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 [alpha/Fe] and [Fe/H] distributions of the stellar halo - halos dominated by very early accretion have higher average [alpha/Fe], while those dominated by high luminosity satellites have higher [Fe/H]. This intuition can be applied to reconstruct much about the merger histories of nearby galaxies from current and future data sets.

  18. CLOSE STELLAR ENCOUNTERS IN YOUNG, SUBSTRUCTURED, DISSOLVING STAR CLUSTERS: STATISTICS AND EFFECTS ON PLANETARY SYSTEMS

    SciTech Connect

    Craig, Jonathan; Krumholz, Mark R., E-mail: krumholz@ucolick.org [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

    2013-06-01

    Both simulations and observations indicate that stars form in filamentary, hierarchically clustered associations, most of which disperse into their galactic field once feedback destroys their parent clouds. However, during their early evolution in these substructured environments, stars can undergo close encounters with one another that might have significant impacts on their protoplanetary disks or young planetary systems. We perform N-body simulations of the early evolution of dissolving, substructured clusters with a wide range of properties, with the aim of quantifying the expected number and orbital element distributions of encounters as a function of cluster properties. We show that the presence of substructure both boosts the encounter rate and modifies the distribution of encounter velocities compared to what would be expected for a dynamically relaxed cluster. However, the boost only lasts for a dynamical time, and as a result the overall number of encounters expected remains low enough that gravitational stripping is unlikely to be a significant effect for the vast majority of star-forming environments in the Galaxy. We briefly discuss the implications of this result for models of the origin of the solar system, and of free-floating planets. We also provide tabulated encounter rates and orbital element distributions suitable for inclusion in population synthesis models of planet formation in a clustered environment.

  19. The outer regions of the giant Virgo galaxy M87 II. Kinematic separation of stellar halo and intracluster light

    E-print Network

    Longobardi, Alessia; Gerhard, Ortwin; Hanuschik, Reinhard

    2015-01-01

    We present a spectroscopic study of 287 Planetary Nebulas (PNs) in a total area of ~0.4 deg^2 around the BCG M87 in Virgo A. With these data we can distinguish the stellar halo from the co-spatial intracluster light (ICL). PNs were identified from their narrow and symmetric redshifted lambda 5007\\4959 Angstrom [OIII] emission lines, and the absence of significant continuum. We implement a robust technique to measure the halo velocity dispersion from the projected phase-space to identify PNs associated with the M87 halo and ICL. The velocity distribution of the spectroscopically confirmed PNs is bimodal, containing a narrow component centred on the systemic velocity of the BCG and an off-centred broader component, that we identify as halo and ICL, respectively. Halo and ICPN have different spatial distributions: the halo PNs follow the galaxy's light, whereas the ICPNs are characterised by a shallower power-law profile. The composite PN number density profile shows the superposition of different PN populations...

  20. Substructure in Dwarf Galaxies

    E-print Network

    Matthew Coleman

    2004-08-10

    Recent years have seen a series of large-scale photometric surveys with the aim of detecting substructure in nearby dwarf galaxies. Some of these objects display a varying distribution of each stellar population, reflecting their star formation histories. Also, dwarf galaxies are dominated by dark matter, therefore luminous substructure may represent a perturbation in the underlying dark material. Substructure can also be the effect of tidal interaction, such as the disruption of the Sagittarius dSph by the Milky Way. Therefore, substructure in dwarf galaxies manifests the stellar, structural and kinematic evolution of these objects.

  1. Virgo cluster and field dwarf ellipticals in 3D: III. Spatially and temporally resolved stellar populations

    E-print Network

    Ry?, Agnieszka; Falcón-Barroso, Jesús; Vazdekis, Alexandre; Lisker, Thorsten; Peletier, Reynier; van de Ven, Glenn

    2015-01-01

    We present the stellar population analysis of a sample of 12 dwarf elliptical galaxies, observed with the SAURON integral field unit, using the full-spectrum fitting method. We show that star formation histories (SFHs) resolved into two populations can be recovered even within a limited wavelength range, provided that high S/N data is used. We confirm that dEs have had complex SFHs, with star formation extending to (more) recent epochs: for the majority of our galaxies star formation activity was either still strong a few ($\\lesssim$ 5) Gyr ago or they experienced a secondary burst of star formation roughly at that time. This latter possibility is in agreement with the proposed dE formation scenario where tidal harassment drives the gas remaining in their progenitors inwards and induces a star formation episode. For one of our field galaxies, ID0918, we find a correlation between its stellar population and kinematic properties, pointing to a possible merger origin of its kinematically-decoupled core. One of o...

  2. Virgo cluster and field dwarf ellipticals in 3D - I. On the variety of stellar kinematic and line-strength properties

    NASA Astrophysics Data System (ADS)

    Ry?, Agnieszka; Falcón-Barroso, Jesús; van de Ven, Glenn

    2013-02-01

    We present the first large-scale stellar kinematic and line-strength maps for dwarf elliptical galaxies (nine in the Virgo cluster and three in the field environment) obtained with the SAURON (Spectrographic Areal Unit for Research on Optical Nebulae) integral-field unit. No two galaxies in our sample are alike: we see that the level of rotation is not tied to flattening (we have, e.g., round rotators and flattened non-rotators); we observe kinematic twists in one Virgo and one field object; we discover large-scale kinematically decoupled components in two field galaxies; we see varying gradients in line-strength maps, from nearly flat to strongly peaked in the centre. The great variety of morphological, kinematic and stellar population parameters seen in our data points to a formation scenario in which properties are shaped stochastically. A combined effect of ram-pressure stripping and galaxy harassment is the most probable explanation. We show the need for a comprehensive analysis of kinematic, dynamical and stellar population properties which will enable us to place dwarf ellipticals and processes that govern their evolution in the wider context of galaxy formation.

  3. Virgo status

    Microsoft Academic Search

    F. Acernese; M. Alshourbagy; P. Amico; F. Antonucci; S. Aoudia; K. G. Arun; P. Astone; S. Avino; L. Baggio; G. Ballardin; F. Barone; L. Barsotti; M. Barsuglia; Th S. Bauer; S. Bigotta; S. Birindelli; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; S. Braccini; C. Bradaschia; A. Brillet; V. Brisson; D. Buskulic; G. Cagnoli; E. Calloni; E. Campagna; F. Carbognani; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; E. Chassande-Mottin; S. Chatterji; F. Cleva; E. Coccia; C. Corda; A. Corsi; F. Cottone; J.-P. Coulon; E. Cuoco; S. D'Antonio; A. Dari; V. Dattilo; M. Davier; R. De Rosa; M. DelPrete; L. Di Fiore; A. Di Lieto; M. Di Paolo Emilio; A. Di Virgilio; M. Evans; V. Fafone; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; S. Frasca; F. Frasconi; L. Gammaitoni; F. Garufi; E. Genin; A. Gennai; A. Giazotto; V. Granata; C. Greverie; D. Grosjean; G. Guidi; S. Hamdani; S. Hebri; H. Heitmann; P. Hello; D. Huet; P. La Penna; M. Laval; N. Leroy; N. Letendre; B. Lopez; M. Lorenzini; V. Loriette; G. Losurdo; J.-M. Mackowski; E. Majorana; N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; F. Menzinger; L. Milano; Y. Minenkov; M. Mohan; J. Moreau; N. Morgado; S. Mosca; B. Mours; I. Neri; F. Nocera; G. Pagliaroli; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; O. Rabaste; P. Rapagnani; T. Regimbau; A. Remillieux; F. Ricci; I. Ricciardi; A. Rocchi; L. Rolland; R. Romano; P. Ruggi; D. Sentenac; S. Solimeno; B. L. Swinkels; R. Terenzi; A. Toncelli; M. Tonelli; E. Tournefier; F. Travasso; G. Vajente; S. van der Putten; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert

    2008-01-01

    The Virgo collaboration has just concluded its first long science run (VSR1). In these four months the detector achieved a good duty cycle, larger than 80%, and an average horizon distance for binary neutron star system sources of about 4 Mpc. An intense commissioning activity was resumed after the run was complete to further increase the performances of the detector

  4. Status of Virgo detector

    Microsoft Academic Search

    F. Acernese; P. Amico; M. Alshourbagy; F. Antonucci; S. Aoudia; P. Astone; S. Avino; D. Babusci; G. Ballardin; F. Barone; L. Barsotti; M. Barsuglia; F. Beauville; S. Bigotta; S. Birindelli; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; S. Braccini; A. Brillet; V. Brisson; D. Buskulic; E. Calloni; E. Campagna; F. Carbognani; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; E. Chassande-Mottin; N. Christensen; C. Corda; A. Corsi; F. Cottone; A.-C. Clapson; F. Cleva; J.-P. Coulon; E. Cuoco; A. Dari; V. Dattilo; M. Davier; M. del Prete; R. De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; A. Eleuteri; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; S. Frasca; F. Frasconi; L. Gammaitoni; F. Garufi; E. Genin; A. Gennai; A. Giazotto; G. Giordano; L. Giordano; R. Gouaty; D. Grosjean; G. Guidi; S. Hebri; H. Heitmann; P. Hello; S. Karkar; S. Kreckelbergh; P. La Penna; M. Laval; N. Leroy; N. Letendre; B. Lopez; M. Lorenzini; V. Loriette; G. Losurdo; J.-M. Mackowski; E. Majorana; C. N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; M. Mazzoni; L. Milano; F. Menzinger; C. Moins; J. Moreau; N. Morgado; B. Mours; F. Nocera; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; P. Ruggi; G. Russo; S. Solimeno; A. Spallicci; M. Tarallo; M. Tonelli; A. Toncelli; E. Tournefier; F. Travasso; C. Tremola; G. Vajente; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert

    2007-01-01

    The commissioning of the Virgo gravitational wave detector has restarted after several major hardware upgrades carried out during winter 2005. Now Virgo is fully operative and its sensitivity greatly improved and continually improving. A program of short scientific data taking has already started and Virgo is moving towards a period of continuous data taking, which should start at the end

  5. STELLAR KINEMATICS AND STRUCTURAL PROPERTIES OF VIRGO CLUSTER DWARF EARLY-TYPE GALAXIES FROM THE SMAKCED PROJECT. II. THE SURVEY AND A SYSTEMATIC ANALYSIS OF KINEMATIC ANOMALIES AND ASYMMETRIES

    SciTech Connect

    Toloba, E.; Guhathakurta, P. [UCO/Lick Observatory, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Peletier, R. F. [Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen (Netherlands); Boselli, A. [Laboratoire d'Astrophysique de Marseille-LAM, Université d'Aix-Marseille and CNRS, UMR 7326, 38 rue F. Joliot-Curie, 13388 Marseille Cedex 13 (France); Lisker, T. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Falcón-Barroso, J.; Ry?, A. [Instituto de Astrofísica de Canarias, Vía Láctea s/n, La Laguna, Tenerife (Spain); Simon, J. D. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Van de Ven, G. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Paudel, S. [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Emsellem, E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748, Garching (Germany); Janz, J. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Den Brok, M. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Gorgas, J. [Departamento de Astrofísica y Física de la Atmósfera, Universidad Complutense de Madrid, E-28040, Madrid (Spain); Hensler, G. [Department of Astrophysics, University of Vienna, Türkenschanzstraße 17, 1180 Vienna (Austria); Laurikainen, E.; Salo, H. [Division of Astronomy, Department of Physics, PO Box 3000, FI-90014 University of Oulu (Finland); Niemi, S.-M., E-mail: toloba@ucolick.org [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)

    2015-01-01

    We present spatially resolved kinematics and global stellar populations and mass-to-light ratios for a sample of 39 dwarf early-type (dE) galaxies in the Virgo cluster studied as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey. This sample is representative of the early-type population in the Virgo cluster in the absolute magnitude range –19.0 < M{sub r} < –16.0 and of all morphological subclasses found in this galaxy population. For each dE, we measure the rotation curve and velocity dispersion profile and fit an analytic function to the rotation curve. We study the significance of the departure of the rotation curve from the best-fit analytic function (poorly fit) and of the difference between the approaching and receding sides of the rotation curve (asymmetry). Our sample includes two dEs with kinematically decoupled cores that have been previously reported. We find that 62 ± 8% (23 out of the 39) of the dEs have a significant anomaly in their rotation curve. Analysis of the images reveals photometric anomalies for most galaxies. However, there is no clear correlation between the significance of the photometric and kinematic anomalies. We measure age-sensitive (H{sub ?} and H{sub ?A}) and metallicity sensitive (Fe4668 and Mgb) Lick spectral indices in the LIS-5 Å system. This population of galaxies exhibits a wide range of ages and metallicities; we also find that 4 dEs show clear evidence of emission partially filling in the Balmer absorption lines. Finally, we estimate the total masses and dark matter fractions of the dEs and plot them in the mass-size, the mass-velocity dispersion, and the fundamental plane scaling relations. The dEs seem to be the bridge between massive early-type galaxies and dSphs, and have a median total mass within the R{sub e} of log M{sub e} = 9.1 ± 0.2 and a median dark matter fraction within the R{sub e} of f {sub DM} = 46 ± 18%. Any formation model for the dE galaxy class must account for this diversity of kinematic and photometric anomalies and stellar populations.

  6. Status of VIRGO

    Microsoft Academic Search

    F. Acernese; P. Amico; N. Arnaud; D. Babusci; R. Barillé; F. Barone; L. Barsotti; M. Barsuglia; F. Beauville; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; L. Bracci; S. Braccini; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; G. Calamai; E. Calloni; E. Campagna; F. Cavalier; G. Cella; E. Chassande-Mottin; F. Cleva; T. Cokelaer; G. Conforto; C. Corda; J.-P. Coulon; E. Cuoco; V. Dattilo; M. Davier; R. De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; A. Eleuteri; D. Enard; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; S. Frasca; F. Frasconi; L. Gammaitoni; A. Gennai; A. Giazotto; G. Giordano; G. Guidi; H. Heitmann; P. Hello; P. Heusse; L. Holloway; S. Kreckelberg; P. La Penna; V. Loriette; M. Loupias; G. Losurdo; J.-M. Mackowski; E. Majorana; C. N. Man; F. Marion; F. Martelli; A. Masserot; L. Massonnet; M. Mazzoni; L. Milano; J. Moreau; F. Moreau; N. Morgado; F. Mornet; B. Mours; J. Pacheco; A. Pai; C. Palomba; F. Paoletti; R. Passaquieti; D. Passuello; B. Perniola; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; J. Ramonet; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; G. Russo; S. Solimeno; R. Stanga; A. Toncelli; M. Tonelli; E. Tournefier; F. Travasso; H. Trinquet; M. Varvella; D. Verkindt; F. Vetrano; O. Veziant; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert

    2004-01-01

    In this paper, we present the status of the VIRGO interferometer, the French Italian gravitational wave detector. During the last two years the construction of the apparatus has been completed. At the same time, the commissioning of the detector central part, the VIRGO central interferometer, has been used to test all the technical solutions and in particular the most original

  7. The status of VIRGO

    Microsoft Academic Search

    F. Acernese; P. Amico; M. Al-Shourbagy; S. Aoudia; S. Avino; D. Babusci; G. Ballardin; F. Barone; L. Barsotti; M. Barsuglia; F. Beauville; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; S. Birindelli; S. Braccini; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; E. Calloni; E. Campagna; F. Cavalier; R. Cavalieri; G. Cella; E. Chassande-Mottin; C. Corda; A.-C. Clapson; F. Cleva; J.-P. Coulon; E. Cuoco; V. Dattilo; M. Davier; R. De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; A. Eleuteri; D. Enard; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; O. Francois; S. Frasca; F. Frasconi; A. Freise; L. Gammaitoni; A. Gennai; A. Giazotto; G. Giordano; L. Giordano; R. Gouaty; D. Grosjean; G. Guidi; S. Hebri; H. Heitmann; P. Hello; L. Holloway; S. Karkar; S. Kreckelbergh; P. La Penna; N. Letendre; M. Lorenzini; V. Loriette; M. Loupias; G. Losurdo; J. M. Mackowski; E. Majorana; C. N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; M. Mazzoni; L. Milano; C. Moins; J. Moreau; N. Morgado; B. Mours; A. Pai; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; B. Perniola; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; P. Ruggi; G. Russo; S. Solimeno; A. Spallicci; R. Stanga; R. Taddei; M. Tonelli; A. Toncelli; E. Tournefier; F. Travasso; G. Vajente; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert; Z. Zhang

    2006-01-01

    VIRGO interferometer commissioning started in September 2003. The complete lock of the interferometer was achieved in October 2004 via several steps. The main commissioning activity deals with improvements in the interferometer stability and sensitivity. The status of the advancement of VIRGO and the short-term plans are discussed here.

  8. The Advanced Virgo detector

    NASA Astrophysics Data System (ADS)

    Acernese, F.; Adams, T.; Agathos, M.; Agatsuma, K.; Allocca, A.; Astone, P.; Ballardin, G.; Barone, F.; Barsuglia, M.; Basti, A.; Bauer, Th S.; Bavigadda, V.; Bejger, M.; Belczynski, C.; Bersanetti, D.; Bertolini, A.; Bitossi, M.; Bizouard, M. A.; Bloemen, S.; Boer, M.; Bogaert, G.; Bondu, F.; Bonelli, L.; Bonnand, R.; Boschi, V.; Bosi, L.; Bradaschia, C.; Branchesi, M.; Briant, T.; Brillet, A.; Brisson, V.; Bulik, T.; Bulten, H. J.; Buskulic, D.; Buy, C.; Cagnoli, G.; Calloni, E.; Carbognani, F.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cesarini, E.; Chassande-Mottin, E.; Chincarini, A.; Chiummo, A.; Chua, S.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Colombini, M.; Conte, A.; Coulon, J.-P.; Cuoco, E.; D'Antonio, S.; Dattilo, V.; Davier, M.; Day, R.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Dereli, H.; De Rosa, R.; Di Fiore, L.; Di Lieto, A.; Di Virgilio, A.; Dolique, V.; Drago, M.; Ducrot, M.; Endr?czi, G.; Fafone, V.; Farinon, S.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Flaminio, R.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Gammaitoni, L.; Garufi, F.; Gatto, A.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; Ghosh, S.; Giazotto, A.; Gouaty, R.; Granata, M.; Greco, G.; Groot, P.; Guidi, G. M.; Harms, J.; Heidmann, A.; Heitmann, H.; Hello, P.; Hemming, G.; Hofman, D.; Jonker, R. J. G.; Kasprzack, M.; Kéfélian, F.; Królak, A.; Kutynia, A.; Lazzaro, C.; Lebigot, E.; Leonardi, M.; Leroy, N.; Letendre, N.; Lorenzini, M.; Loriette, V.; Losurdo, G.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mangano, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marque, J.; Martelli, F.; Martinelli, L.; Masserot, A.; Meacher, D.; Meidam, J.; Mezzani, F.; Michel, C.; Milano, L.; Minenkov, Y.; Moggi, A.; Mohan, M.; Mours, B.; Nagy, M. F.; Nardecchia, I.; Naticchioni, L.; Nelemans, G.; Neri, I.; Neri, M.; Nocera, F.; Palomba, C.; Paoletti, F.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Pichot, M.; Piergiovanni, F.; Pillant, G.; Pinard, L.; Poggiani, R.; Prijatelj, M.; Prodi, G. A.; Punturo, M.; Puppo, P.; Rabeling, D. S.; Rácz, I.; Rapagnani, P.; Razzano, M.; Re, V.; Regimbau, T.; Ricci, F.; Robinet, F.; Rocchi, A.; Rolland, L.; Romano, R.; Ruggi, P.; Sassolas, B.; Sentenac, D.; Sequino, V.; Shah, S.; Siellez, K.; Straniero, N.; Swinkels, B.; Tacca, M.; Tonelli, M.; Travasso, F.; Vajente, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Sluys, M. V.; van Heijningen, J.; Vasúth, M.; Vedovato, G.; Veitch, J.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinet, J.-Y.; Vocca, H.; Wei, L.-W.; Yvert, M.; Zadro?ny, A.; Zendri, J.-P.

    2015-05-01

    The Advanced Virgo interferometer is the upgraded version of the Virgo detector having the goal to extend by a factor 10 the observation horizon in the universe and consequently increase the detection rate by three orders of magnitude. Its installation is in progress and is expected to be completed in late 2015. In this proceeding we will present the scheme and the main challenging technical features of the detector and we will give an outline of the installation status and the foreseen time schedule which will bring Advanced Virgo to its full operation.

  9. Mon. Not. R. Astron. Soc. 405, 800820 (2010) doi:10.1111/j.1365-2966.2010.16507.x Stellar populations of Virgo cluster early-type dwarf galaxies

    E-print Network

    Kuntschner, Harald

    2010-01-01

    populations of Virgo cluster early-type dwarf galaxies with and without discs: a dichotomy in age? Sanjaya. Key words: galaxies: clusters: individual: Virgo ­ galaxies: dwarf ­ galaxies: elliptical (programme 078.B-0178). E-mail: sjy@x-astro.net 1 INTRODUCTION Dwarf elliptical (dE) galaxies

  10. Signatures of LCDM substructure in tidal debris

    E-print Network

    Jennifer M. Siegal-Gaskins; Monica Valluri

    2008-03-25

    In the past decade, surveys of the stellar component of the Galaxy have revealed a number of streams from tidally disrupted dwarf galaxies and globular clusters. Simulations of hierarchical structure formation in LCDM cosmologies predict that the dark matter halo of a galaxy like the Milky Way contains hundreds of subhalos with masses of ~10^8 solar masses and greater, and it has been suggested that the existence of coherent tidal streams is incompatible with the expected abundance of substructure. We investigate the effects of dark matter substructure on tidal streams by simulating the disruption of a self-gravitating satellite on a wide range of orbits in different host models both with and without substructure. We find that the halo shape and the specific orbital path more strongly determine the overall degree of disruption of the satellite than does the presence or absence of substructure, i.e., the changes in the large-scale properties of the tidal debris due to substructure are small compared to variations in the debris from different orbits in a smooth potential. Substructure typically leads to an increase in the degree of clumpiness of the tidal debris in sky projection, and in some cases a more compact distribution in line-of-sight velocity. Substructure also leads to differences in the location of sections of debris compared to the results of the smooth halo model, which may have important implications for the interpretation of observed tidal streams. A unique signature of the presence of substructure in the halo which may be detectable by upcoming surveys is identified. We conclude, however, that predicted levels of substructure are consistent with a detection of a coherent tidal stream from a dwarf galaxy.

  11. Stellar Kinematics in the Complicated Inner Spheroid of M31: Discovery of Substructure Along the Southeastern Minor Axis and its Relationship to the Giant Southern Stream

    E-print Network

    Gilbert, K M; Singh-Kalirai, J; Guhathakurta, P; Geha, M C; Isler, J; Majewski, S R; Ostheimer, J C; Patterson, R J; Reitzel, David B; Kirby, E; Cooper, M C; Gilbert, Karoline M.; Fardal, Mark; Kalirai, Jasonjot S.; Guhathakurta, Puragra; Geha, Marla C.; Isler, Jedidah; Majewski, Steven R.; Ostheimer, James C.; Patterson, Richard J.; Reitzel, David B.; Kirby, Evan; Cooper, Michael C.

    2007-01-01

    We present the discovery of a kinematically-cold stellar population along the SE minor axis of the Andromeda galaxy (M31) that is likely the forward continuation of M31's giant southern stream. This discovery was made in the course of an on-going spectroscopic survey of red giant branch (RGB) stars in M31 using the DEIMOS instrument on the Keck II 10-m telescope. Stellar kinematics are investigated in eight fields located 9-30 kpc from M31's center (in projection). A likelihood method based on photometric and spectroscopic diagnostics is used to isolate confirmed M31 RGB stars from foreground Milky Way dwarf stars: for the first time, this is done without using radial velocity as a selection criterion, allowing an unbiased study of M31's stellar kinematics. The radial velocity distribution of the 1013 M31 RGB stars shows evidence for the presence of two components. The broad (hot) component has a velocity dispersion of 129 km/s and presumably represents M31's virialized spheroid. A significant fraction (19%) ...

  12. Status of VIRGO

    Microsoft Academic Search

    F. Acernese; P. Amico; N. Arnaud; D. Babusci; G. Ballardin; R. Barillé; F. Barone; M. Barsuglia; F. Beauville; F. Bellachia; M. A. Bizouard; C. Boccara; D. Boget; F. Bondu; C. Bourgoin; A. Bozzi; S. Braccini; C. Bradaschia; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; J. Cachenaut; G. Calamai; E. Calloni; E. Campagna; C. Casciano; C. Cattuto; F. Cavalier; S. Cavaliere; R. Cavalieri; G. Cella; E. Chassande-Mottin; F. Chollet; F. Cleva; T. Cokelaer; G. Conforto; S. Cortese; J. P. Coulon; E. Cuoco; V. Dattilo; P. Y Davíd; M. Davier; M. De Rosa; R. De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; P. Dominici; A. Eleuteri; D. Enard; G. Evangelista; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; D. Forest; J. D. Fournier; L. Fournier; S. Frasca; F. Frasconi; L. Gammaitoni; P. Ganau; A. Gennai; G. Gennaro; L. Giacobone; A. Giazotto; G. Giordano; C. Girard; G. Gougoulat; G. M. Guidi; H. Heitmann; P. Hello; R. Hermel; P. Heusse; L. Holloway; F. Honglie; M. Iannarelli; L. Journet; S. Krecklbergh; B. Lagrange; P. La Penna; M. Leliboux; B. Lieunard; T. Lomtadze; V. Loriette; G. Losurdo; M. Loupias; J. M. Mackowski; E. Majorana; C. N. Man; F. Marchesoni; F. Marion; F. Martelli; A. Masserot; L. Massonnet; S. Mataguez; F. Menzinger; M. Mazzoni; C. Michel; L. Milano; J. L. Montorio; F. Moreau; J. Moreau; N. Morgado; F. Mornet; B. Mours; P. Mugnier; F. Nenci; J. Pacheco; A. Pai; C. Palomba; F. Paoletti; A. Paoli; L. Paoli; A. Pasqualetti; R. Passaquieti; D. Passuello; M. Perciballi; S. Peruzzi; B. Perniola; L. Pinard; R. Poggiani; P. Popolizio; E. Porter; S. Puccinelli; M. Punturo; P. Puppo; K. Qipiani; J. Ramonet; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; F. Richard; J. P. Roger; P. Ruggi; G. Russo; S. Solimeno; R. Stanga; R. Taddei; J. M. Teuler; E. Tournefier; F. Travasso; H. Trinquet; E. Turri; M. Varvella; D. Verkindt; F. Vetrano; O. Veziant; A. Viceré; S. Vilalte; J. Y Vinet; H. Vocca; M. Yvert; Z. Zhang

    2003-01-01

    We report on the status of the VIRGO detector as of the beginning of 2003. In particular, we summarize the results obtained during the commissioning of the central portion of the detector, consisting of a power-recycled Michelson interferometer, and we outline the steps which will lead during 2003 and 2004 to the commissioning and operation of the full scale, 3

  13. Status of Virgo

    Microsoft Academic Search

    F. Acernese; M. Alshourbagy; P. Amico; F. Antonucci; S. Aoudia; P. Astone; S. Avino; L. Baggio; G. Ballardin; F. Barone; L. Barsotti; M. Barsuglia; Th S. Bauer; S. Bigotta; S. Birindelli; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; S. Braccini; C. Bradaschia; A. Brillet; V. Brisson; D. Buskulic; G. Cagnoli; E. Calloni; E. Campagna; F. Carbognani; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; E. Chassande-Mottin; A.-C. Clapson; F. Cleva; E. Coccia; C. Corda; A. Corsi; F. Cottone; J.-P. Coulon; E. Cuoco; S. D'Antonio; A. Dari; V. Dattilo; M. Davier; R. De Rosa; M. DelPrete; L. Di Fiore; A. Di Lieto; M. Di Paolo Emilio; A. Di Virgilio; M. Evans; V. Fafone; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; S. Frasca; F. Frasconi; L. Gammaitoni; F. Garufi; E. Genin; A. Gennai; A. Giazotto; L. Giordano; V. Granata; C. Greverie; D. Grosjean; G. Guidi; S. Hamdani; S. Hebri; H. Heitmann; P. Hello; D. Huet; S. Kreckelbergh; P. La Penna; M. Laval; N. Leroy; N. Letendre; B. Lopez; M. Lorenzini; V. Loriette; G. Losurdo; J.-M. Mackowski; E. Majorana; C. N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; F. Menzinger; L. Milano; Y. Minenkov; C. Moins; J. Moreau; N. Morgado; S. Mosca; B. Mours; I. Neri; F. Nocera; G. Pagliaroli; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; P. Rapagnani; T. Regimbau; A. Remillieux; F. Ricci; I. Ricciardi; A. Rocchi; L. Rolland; R. Romano; P. Ruggi; G. Russo; S. Solimeno; A. Spallicci; M. Tarallo; R. Terenzi; A. Toncelli; M. Tonelli; E. Tournefier; F. Travasso; C. Tremola; G. Vajente; S. van der Putten; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert

    2008-01-01

    The Virgo detector has now finished its first science run; a science mode duty cycle of more than 80% and a 4.5 Mpc horizon distance for binary neutron star inspiral sources were achieved. Commissioning breaks were organized during the run which permitted improvement of the sensitivity and the robustness of the interferometer against environmental perturbations like bad weather and earthquakes.

  14. The Virgo status

    Microsoft Academic Search

    F. Acernese; P. Amico; M. Alshourbagy; F. Antonucci; S. Aoudia; S. Avino; D. Babusci; G. Ballardin; F. Barone; L. Barsotti; M. Barsuglia; F. Beauville; S. Bigotta; S. Birindelli; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; S. Braccini; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; E. Calloni; E. Campagna; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; E. Chassande-Mottin; C. Corda; F. Cottone; A.-C. Clapson; F. Cleva; J.-P. Coulon; E. Cuoco; A. Dari; V. Dattilo; M. Davier; R. De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; A. Eleuteri; D. Enard; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; O. Francois; S. Frasca; F. Frasconi; A. Freise; L. Gammaitoni; F. Garufi; A. Gennai; A. Giazotto; G. Giordano; L. Giordano; R. Gouaty; D. Grosjean; G. Guidi; S. Hebri; H. Heitmann; P. Hello; L. Holloway; S. Karkar; S. Kreckelbergh; P. La Penna; M. Laval; N. Leroy; N. Letendre; M. Lorenzini; V. Loriette; M. Loupias; G. Losurdo; J.-M. Mackowski; E. Majorana; C. N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; M. Mazzoni; L. Milano; C. Moins; J. Moreau; N. Morgado; B. Mours; A. Pai; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; B. Perniola; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; P. Ruggi; G. Russo; S. Solimeno; A. Spallicci; R. Stanga; R. Taddei; M. Tonelli; A. Toncelli; E. Tournefier; F. Travasso; G. Vajente; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert; Z. Zhang

    2006-01-01

    We report on the status of the Virgo detector, under commissioning. We will focus on the last year's activity. The two commissioning runs performed during 2005 allowed us to reach a sensitivity of h ~ 6 × 10-22. The data obtained during the runs were used to test a few data analysis algorithms, namely coalescing binaries and burst searches. The

  15. THE NEXT GENERATION VIRGO CLUSTER SURVEY. IV. NGC 4216: A BOMBARDED SPIRAL IN THE VIRGO CLUSTER

    SciTech Connect

    Paudel, Sanjaya; Duc, Pierre-Alain; Ferriere, Etienne [Laboratoire AIM Paris-Saclay, CNRS/INSU, Universite Paris Diderot, CEA/IRFU/SAp, F-91191 Gif-sur-Yvette Cedex (France); Cote, Patrick; Ferrarese, Laura; Gwyn, Stephen D. J.; MacArthur, Lauren A. [National Research Council of Canada, Victoria, BC V9E 2E7 (Canada); Cuillandre, Jean-Charles [Canada-France-Hawaii Telescope Corporation, Kamuela, HI 96743 (United States); Mihos, J. Christopher [Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 (United States); Vollmer, Bernd [Observatoire Astronomique, Universite de Strasbourg and CNRS UMR 7550, 11 rue de l'Universite, F-67000 Strasbourg (France); Balogh, Michael L. [Department of Physics and Astronomy, University of Waterloo, Waterloo, ON N2L 3G1 (Canada); Carlberg, Ray G. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Boissier, Samuel; Boselli, Alessandro [Aix Marseille Universite, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Durrell, Patrick R. [Department of Physics and Astronomy, Youngstown State University, One University Plaza, Youngstown, OH 44555 (United States); Emsellem, Eric; Michel-Dansac, Leo [Universite de Lyon 1, CRAL, Observatoire de Lyon, CNRS UMR 5574, 9 av. Charles Andre, F-69230 Saint-Genis Laval (France); Mei, Simona; Van Driel, Wim, E-mail: sanjaya.paudel@cea.fr [GEPI, Observatoire de Paris, CNRS, Universite Paris Diderot, 5 Place J. Janssen, F-92190 Meudon Cedex (France)

    2013-04-20

    The final stages of mass assembly of present-day massive galaxies are expected to occur through the accretion of multiple satellites. Cosmological simulations thus predict a high frequency of stellar streams resulting from this mass accretion around the massive galaxies in the Local Volume. Such tidal streams are difficult to observe, especially in dense cluster environments, where they are readily destroyed. We present an investigation into the origins of a series of interlaced narrow filamentary stellar structures, loops and plumes in the vicinity of the Virgo Cluster, edge-on spiral galaxy, NGC 4216 that were previously identified by the Blackbird telescope. Using the deeper, higher-resolution, and precisely calibrated optical CFHT/MegaCam images obtained as part of the Next Generation Virgo Cluster Survey (NGVS), we confirm the previously identified features and identify a few additional structures. The NGVS data allowed us to make a physical study of these low surface brightness features and investigate their origin. The likely progenitors of the structures were identified as either already cataloged Virgo Cluster Catalog dwarfs or newly discovered satellites caught in the act of being destroyed. They have the same g - i color index and likely contain similar stellar populations. The alignment of three dwarfs along an apparently single stream is intriguing, and we cannot totally exclude that these are second-generation dwarf galaxies being born inside the filament from the debris of an original dwarf. The observed complex structures, including in particular a stream apparently emanating from a satellite of a satellite, point to a high rate of ongoing dwarf destruction/accretion in the region of the Virgo Cluster where NGC 4216 is located. We discuss the age of the interactions and whether they occurred in a group that is just falling into the cluster and shows signs of the so-called pre-processing before it gets affected by the cluster environment, or in a group which already ventured toward the central regions of Virgo Cluster. In any case, compared to the other spiral galaxies in the Virgo Cluster, but also to those located in lower density environments, NGC 4216 seems to suffer an unusually heavy bombardment. Further studies will be needed to determine whether, given the surface brightness limit of our survey, about 29 mag arcsec{sup -2}, the number of observed streams around that galaxy is as predicted by cosmological simulations or conversely, whether the possible lack of similar structures in other galaxies poses a challenge to the merger-based model of galaxy mass assembly.

  16. Detection of a large-scale structure of intracluster globular clusters in the Virgo cluster.

    PubMed

    Lee, Myung Gyoon; Park, Hong Soo; Hwang, Ho Seong

    2010-04-16

    Globular clusters are usually found in galaxies, and they are excellent tracers of dark matter. Long ago it was suggested that intracluster globular clusters (IGCs) may exist that are bound to a galaxy cluster rather than to any single galaxy. Here we present a map showing the large-scale distribution of globular clusters over the entire Virgo cluster. It shows that IGCs are found out to 5 million light years from the Virgo center and that they are concentrated in several substructures that are much larger than galaxies. These objects might have been mostly stripped off from low-mass dwarf galaxies. PMID:20223950

  17. Intracluster Planetary Nebulae in the Virgo Cluster I. Initial Results

    E-print Network

    John Feldmeier; Robin Ciardullo; George Jacoby

    1998-03-06

    We report the initial results of a survey for intracluster planetary nebulae in the Virgo Cluster. In two 16' x 16' fields, we identify 69 and 16 intracluster planetary nebula candidates, respectively. In a third 16' x 16' field near the central elliptical galaxy M87, we detect 75 planetary nebula candidates, of which a substantial fraction are intracluster in nature. By examining the number of the planetaries detected in each field and the shape of the planetary nebula luminosity function, we show that 1) the intracluster starlight of Virgo is distributed non-uniformly, and varies between subclumps A and B, 2) the Virgo Cluster core extends ~3 Mpc in front of M87, and thus is elongated along the line-of-sight, and 3) a minimum of 22% of Virgo's stellar luminosity resides between the galaxies in our fields, and that the true number may be considerably larger. We also use our planetary nebula data to argue that the intracluster stars in Virgo are likely derived from a population that is of moderate age and metallicity.

  18. Defining Spatial Extent of Sagittarius Dwarf Tidal Stream and the Virgo Overdensity with MilkyWay@home

    NASA Astrophysics Data System (ADS)

    Weiss, Jake; Newby, Matthew; Arsenault, Matthew; Bechtel, Torrin; Desell, Travis; Newberg, Heidi Jo; Thompson, Jeffery

    2015-01-01

    We refine and present tests of the statistical photometric parallax methods used to measure substructure of the halo stars with MilkyWay@home. This newer algorithm is showing promise for separating three substructure components, including the two parts of the bifurcated Sagittarius tidal stream and the Virgo Overdensity, while also fitting a smooth background component simultaneously. We show that the Sagittarius tidal streams and the Virgo Overdensity are much wider than previously imagined. We present the new results in the context of previous measurements of the properties of these halo substructures. This research was funded by NSF grant AST 10-09670, the Rensselaer Center for Open Source Software (RCOS), and crowd funding from the MilkyWay@home volunteers.

  19. The kinematics of the Virgo cluster revisited

    Microsoft Academic Search

    B. Binggeli; C. C. Popescu; G. A. Tammann

    1993-01-01

    The paper updates the velocity data of Virgo cluster galaxies and reconsiders the kinematic structure of the Virgo cluster. New velocities are given for 144 galaxies listed in the Virgo Cluster Catalog (VCC). Improved velocities are given for another 131 VCC galaxies. The Virgo cluster is disentangled from its surrounding clouds of galaxies, and the likely members of each of

  20. The Purple Rose of Virgo

    NASA Astrophysics Data System (ADS)

    2007-03-01

    Until now NGC 5584 was just one galaxy among many others, located to the West of the Virgo Cluster. Known only as a number in galaxy surveys, its sheer beauty is now revealed in all its glory in a new VLT image. Since 1 March, this purple cosmic rose also holds the brightest stellar explosion of the year, known as SN 2007af. Located about 75 million light years away towards the constellation Virgo ('the Virgin'), NGC 5584 is a galaxy slightly smaller than the Milky Way. It belongs, however, to the same category: both are barred spirals. ESO PR Photo 16/07 ESO PR Photo 16/07 The Purple Rose of Virgo Spiral galaxies are composed of a 'bulge' and a flat disc. The bulge hosts old stars and usually a central supermassive black hole. Younger stars reside in the disc, forming the characteristic spiral structures from which the galaxies get their name. Barred spirals are crossed by a bright band of stars. In 2000, using ESO's Very Large Telescope, astronomers discovered the smallest, faintest, and most massive spirals (see ESO PR 12/00 and 25/00). In this amazing new image of NGC 5584 two dominant spiral arms are clearly visible, while the others are deformed, probably due to interactions with other galaxies. Luminous patches are spread all over the disc, indicating that stars are being formed in this gigantic rose at a frantic pace. Something even brighter, however, catches the eye in this picture. Any image taken before the end of February would not have shown the luminous spot located at the lower right of the galaxy's centre. As can be seen, the newly found object is much brighter than the centre of the galaxy itself. Its name? SN 2007af, the 32nd supernova discovered this year. Its presence signals the dramatic death of a star with a mass comparable to that of the Sun. SN 2007af, the brightest supernova of the year (so far), was discovered on 1 March by the Japanese supernova hunter Koichi Itagaki. He pointed his 60-centimetre telescope towards the Virgo constellation and discovered something that was not there before: SN 2007af. When it was discovered, its brightness (apparent visible magnitude of 15.4) was about seven times fainter than that of its host galaxy, NGC 5584. It has since brightened by the same factor of 7, reaching an apparent magnitude of 13.3 and making it observable by many amateur astronomers with smaller telescopes. Observations on 4 March with ESO's New Technology Telescope at La Silla revealed that this energetic explosion is a Type Ia supernova that was observed a few days before it reached its maximal luminosity. Matter from the doomed star is ejected with velocities above 15,000 km/s. Astronomers are observing SN2007af with ESO's VLT, with the aim of studying the geometry of the material ejected by the supernova, and thereby better understanding the explosion mechanism (see also ESO 44/06). A Type Ia supernova is thought to be the result of the explosion of a small and dense star - a white dwarf - inside a binary system. As its companion continuously spills matter onto the white dwarf, the white dwarf reaches a critical mass, leading to a fatal instability and the supernova. Type Ia supernovae are apparently quite similar to one another. This gives them a very useful role as 'standard candles' that can be used to measure cosmic distances. Their peak brightness rivals that of their parent galaxy, hence qualifying them as prime cosmic yardsticks. Astronomers have exploited this fortunate circumstance to study the expansion history of our Universe. However Type Ia supernovae are rare events: a galaxy like the Milky Way may host a Type Ia supernova on average only every 400 years. Even so, SN 2007af is not the only brilliant detonation recently recorded in NGC 5584. Furthermore, it seems that Japanese amateur astronomers have a special talent for catching supernova explosions in this purple spiral. Indeed, in 1996 Aoki Masakatsu identified SN 1996aq in NGC 5584, a difficult to classify supernova subject to a hot discussion due to its ambiguous nature.

  1. The Extended Virgo Cluster Catalog

    NASA Astrophysics Data System (ADS)

    Kim, Suk; Rey, Soo-Chang; Jerjen, Helmut; Lisker, Thorsten; Sung, Eon-Chang; Lee, Youngdae; Chung, Jiwon; Pak, Mina; Yi, Wonhyeong; Lee, Woong

    2014-12-01

    We present a new catalog of galaxies in the wider region of the Virgo cluster, based on the Sloan Digital Sky Survey (SDSS) Data Release 7. The Extended Virgo Cluster Catalog (EVCC) covers an area of 725 deg2 or 60.1 Mpc2. It is 5.2 times larger than the footprint of the classical Virgo Cluster Catalog (VCC) and reaches out to 3.5 times the virial radius of the Virgo cluster. We selected 1324 spectroscopically targeted galaxies with radial velocities less than 3000 km s-1. In addition, 265 galaxies that have been overlooked in the SDSS spectroscopic survey but have available redshifts in the NASA Extragalactic Database are also included. Our selection process secured a total of 1589 galaxies, 676 of which are not included in the VCC. The certain and possible cluster members are defined by means of redshift comparison with a cluster infall model. We employed two independent and complementary galaxy classification schemes: the traditional morphological classification based on the visual inspection of optical images and a characterization of galaxies from their spectroscopic features. SDSS u, g, r, i, and z passband photometry of all EVCC galaxies was performed using Source Extractor. We compare the EVCC galaxies with the VCC in terms of morphology, spatial distribution, and luminosity function. The EVCC defines a comprehensive galaxy sample covering a wider range in galaxy density that is significantly different from the inner region of the Virgo cluster. It will be the foundation for forthcoming galaxy evolution studies in the extended Virgo cluster region, complementing ongoing and planned Virgo cluster surveys at various wavelengths.

  2. THE EXTENDED VIRGO CLUSTER CATALOG

    SciTech Connect

    Kim, Suk; Rey, Soo-Chang; Lee, Youngdae; Chung, Jiwon; Pak, Mina; Yi, Wonhyeong; Lee, Woong [Department of Astronomy and Space Science, Chungnam National University, 99 Daehak-ro, Daejeon 305-764 (Korea, Republic of); Jerjen, Helmut [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT 2611 (Australia); Lisker, Thorsten [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg (ZAH), Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Sung, Eon-Chang [Korea Astronomy and Space Science institute, 776 Daedeokdae-ro, Daejeon 305-348 (Korea, Republic of)

    2015-01-01

    We present a new catalog of galaxies in the wider region of the Virgo cluster, based on the Sloan Digital Sky Survey (SDSS) Data Release 7. The Extended Virgo Cluster Catalog (EVCC) covers an area of 725 deg{sup 2} or 60.1 Mpc{sup 2}. It is 5.2 times larger than the footprint of the classical Virgo Cluster Catalog (VCC) and reaches out to 3.5 times the virial radius of the Virgo cluster. We selected 1324 spectroscopically targeted galaxies with radial velocities less than 3000 km s{sup –1}. In addition, 265 galaxies that have been overlooked in the SDSS spectroscopic survey but have available redshifts in the NASA Extragalactic Database are also included. Our selection process secured a total of 1589 galaxies, 676 of which are not included in the VCC. The certain and possible cluster members are defined by means of redshift comparison with a cluster infall model. We employed two independent and complementary galaxy classification schemes: the traditional morphological classification based on the visual inspection of optical images and a characterization of galaxies from their spectroscopic features. SDSS u, g, r, i, and z passband photometry of all EVCC galaxies was performed using Source Extractor. We compare the EVCC galaxies with the VCC in terms of morphology, spatial distribution, and luminosity function. The EVCC defines a comprehensive galaxy sample covering a wider range in galaxy density that is significantly different from the inner region of the Virgo cluster. It will be the foundation for forthcoming galaxy evolution studies in the extended Virgo cluster region, complementing ongoing and planned Virgo cluster surveys at various wavelengths.

  3. WARM GAS IN THE VIRGO CLUSTER. I. DISTRIBUTION OF Ly{alpha} ABSORBERS

    SciTech Connect

    Yoon, Joo Heon; Putman, Mary E.; Bryan, Greg L. [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Thom, Christopher [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21211 (United States); Chen, Hsiao-Wen, E-mail: jhyoon@astro.columbia.edu [Department of Astronomy and Astrophysics and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States)

    2012-08-01

    The first systematic study of the warm gas (T = 10{sup 4-5} K) distribution across a galaxy cluster is presented using multiple background QSOs in and around the Virgo Cluster. We detect 25 Ly{alpha} absorbers (N{sub HI} = 10{sup 13.1-15.4} cm{sup -2}) in the Virgo velocity range toward 9 of 12 QSO sightlines observed with the Cosmic Origin Spectrograph, with a cluster impact parameter range of 0.36-1.65 Mpc (0.23-1.05 R{sub vir}). Including 18 Ly{alpha} absorbers previously detected by STIS or GHRS toward 7 of 11 background QSOs in and around the Virgo Cluster, we establish a sample of 43 absorbers toward a total of 23 background probes for studying the incidence of Ly{alpha} absorbers in and around the Virgo Cluster. With these absorbers, we find (1) warm gas is predominantly in the outskirts of the cluster and avoids the X-ray-detected hot intracluster medium (ICM). Also, Ly{alpha} absorption strength increases with cluster impact parameter. (2) Ly{alpha}-absorbing warm gas traces cold H I-emitting gas in the substructures of the Virgo Cluster. (3) Including the absorbers associated with the surrounding substructures, the warm gas covering fraction (100% for N{sub HI} > 10{sup 13.1} cm{sup -2}) is in agreement with cosmological simulations. We speculate that the observed warm gas is part of large-scale gas flows feeding the cluster both in the ICM and galaxies.

  4. Multiband modelling of the Sun as a variable star from VIRGO\\/SoHO data

    Microsoft Academic Search

    A. F. Lanza; M. Rodonò; I. Pagano

    2004-01-01

    The time series of total solar irradiance (TSI) and optical spectral irradiance at 402, 500 and 862 nm (SSIs) obtained by the VIRGO experiment on board the satellite SoHO are analysed in order to model their variability in the framework of a purely stellar-like approach. The different time scales of variability are estimated by means of the pooled variance method

  5. The Virgo automatic alignment system

    Microsoft Academic Search

    F. Acernese; P. Amico; M. Al-Shourbagy; S. Aoudia; S. Avino; D. Babusci; G. Ballardin; R. Barillé; F. Barone; L. Barsotti; M. Barsuglia; F. Beauville; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; S. Braccini; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; E. Calloni; E. Campagna; F. Cavalier; R. Cavalieri; G. Cella; E. Chassande-Mottin; C. Corda; A.-C. Clapson; F. Cleva; J.-P. Coulon; E. Cuoco; V. Dattilo; M. Davier; R. De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; A. Eleuteri; D. Enard; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; S. Frasca; F. Frasconi; A. Freise; L. Gammaitoni; A. Gennai; A. Giazotto; G. Giordano; L. Giordano; R. Gouaty; D. Grosjean; G. Guidi; S. Hebri; H. Heitmann; P. Hello; L. Holloway; S. Kreckelbergh; P. La Penna; V. Loriette; M. Loupias; G. Losurdo; J.-M. Mackowski; E. Majorana; C. N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; M. Mazzoni; L. Milano; C. Moins; J. Moreau; N. Morgado; B. Mours; A. Pai; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; B. Perniola; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; P. Ruggi; G. Russo; S. Solimeno; A. Spallicci; R. Stanga; R. Taddei; D. Tombolato; M. Tonelli; A. Toncelli; E. Tournefier; F. Travasso; G. Vajente; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert; Z. Zhang

    2006-01-01

    The automatic alignment system of the Virgo interferometer differs substantially from those used in similar experiments, since it uses a variant of the Anderson technique. This implies a completely different control topology with respect to other detectors, and the main feature is a strong coupling of different degrees of freedom in the optical signals. It also provides two extra output

  6. EXPLORING THE VARIABLE SKY WITH LINEAR. II. HALO STRUCTURE AND SUBSTRUCTURE TRACED BY RR LYRAE STARS TO 30 kpc

    SciTech Connect

    Sesar, Branimir [Division of Physics, Mathematics and Astronomy, Caltech, Pasadena, CA 91125 (United States); Ivezic, Zeljko; Morgan, Dylan M.; Becker, Andrew C. [University of Washington, Department of Astronomy, P.O. Box 351580, Seattle, WA 98195-1580 (United States); Stuart, J. Scott [Lincoln Laboratory, Massachusetts Institute of Technology, 244 Wood Street, Lexington, MA 02420-9108 (United States); Sharma, Sanjib [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Palaversa, Lovro [Observatoire astronomique de l'Universite de Geneve, 51 chemin des Maillettes, CH-1290 Sauverny (Switzerland); Juric, Mario [Steward Observatory, University of Arizona, Tucson, AZ 85121 (United States); Wozniak, Przemyslaw [Los Alamos National Laboratory, 30 Bikini Atoll Rd., Los Alamos, NM 87545-0001 (United States); Oluseyi, Hakeem [Florida Institute of Technology, Melbourne, FL 32901 (United States)

    2013-08-01

    We present a sample of {approx}5000 RR Lyrae stars selected from the recalibrated LINEAR data set and detected at heliocentric distances between 5 kpc and 30 kpc over {approx}8000 deg{sup 2} of sky. The coordinates and light curve properties, such as period and Oosterhoff type, are made publicly available. We analyze in detail the light curve properties and Galactic distribution of the subset of {approx}4000 type ab RR Lyrae (RRab) stars, including a search for new halo substructures and the number density distribution as a function of Oosterhoff type. We find evidence for the Oosterhoff dichotomy among field RR Lyrae stars, with the ratio of the type II and I subsamples of about 1:4, but with a weaker separation than for globular cluster stars. The wide sky coverage and depth of this sample allow unique constraints for the number density distribution of halo RRab stars as a function of galactocentric distance: it can be described as an oblate ellipsoid with an axis ratio q = 0.63 and with either a single or a double power law with a power-law index in the range -2 to -3. Consistent with previous studies, we find that the Oosterhoff type II subsample has a steeper number density profile than the Oosterhoff type I subsample. Using the group-finding algorithm EnLink, we detected seven candidate halo groups, only one of which is statistically spurious. Three of these groups are near globular clusters (M53/NGC 5053, M3, M13), and one is near a known halo substructure (Virgo Stellar Stream); the remaining three groups do not seem to be near any known halo substructures or globular clusters and seem to have a higher ratio of Oosterhoff type II to Oosterhoff type I RRab stars than what is found in the halo. The extended morphology and the position (outside the tidal radius) of some of the groups near globular clusters are suggestive of tidal streams possibly originating from globular clusters. Spectroscopic follow-up of detected halo groups is encouraged.

  7. Gravitational Imaging of CDM Substructure

    E-print Network

    L. V. E. Koopmans

    2005-08-17

    We propose the novel method of ``gravitational imaging'' to detect and quantify luminous and dark-matter substructure in gravitational-lens galaxies. The method utilizes highly-magnified Einstein rings and arcs as sensitive probes of small perturbations in the lens potential (due to the presence of mass substructure), reconstructing the gravitational lens potential non-parametrically. Numerical simulations show that the implemented algorithm can reconstruct the smooth mass distribution of a typical lens galaxy - exhibiting reasonable signal-to-noise Einstein rings - as well as compact substructure with masses as low as M_sub~10^-3 M_lens, if present. ``Gravitational imaging'' of pure dark-matter substructure around massive galaxies can provide a new window on the standard cold-dark-matter paradigm, using very different physics than ground-based direct-detection experiments, and probe the hierarchical structure-formation model which predicts this substructure to exist in great abundance.

  8. Status of the VIRGO experiment

    Microsoft Academic Search

    B. Caron; A. Dominjon; F. Marion; L. Massonnet; R. Morand; B. Mours; M. Yvert; D. Babusci; Fang H; G. Giordano; G. Matone; L. Matone; V. Sannibale; J. M. Mackowski; M. Napolitano; L. Pinard; C. Boccara; Ph. Gleizes; V. Loriette; J. P. Roger; F. Barone; E. Calloni; L. Di Fiore; A. Grado; M. Longo; L. Milano; G. Russo; S. Solimeno; F. Bondu; A. Brillet; V. Brisson; F. Cleva; M. Davier; H. Heitmann; P. Hello; J. M. Innocent; M. Jacquemet; L. Latrach; F. Le Diberder; C. N. Man; A. Marraud; G. M. Nguyen; M. Pham-Tu; J.-Y. Vinet; G. Cagnoli; L. Gammaitoni; F. Marchesoni; M. Punturo; S. Braccini; C. Bradaschia; R. Del Fabbro; A. Di Virgilio; I. Ferrante; F. Fidecaro; R. Flaminio; A. Giassi; A. Giazotto; G. Gorini; L. E. Holloway; C. X. Hong; A. Lusiani; M. Morganti; F. Palla; D. Passuello; R. Poggiani; G. Torelli; Z. Zhou

    1995-01-01

    The VIRGO experiment was approved in September 1993. The goal of the French-Italian collaboration is to detect gravitational waves using a 3 km arm-length Michelson interferometer. The construction of this detector, which will be installed in Pisa, is under way. The experiment is planned to take data, in a large bandwidth (10 Hz–10 kHz), at the beginning of the year

  9. The VIRGO interferometer for gravitational wave detection

    Microsoft Academic Search

    V. Ferrari; E. Majorana; P. Puppo; P. Rapagnani; F. Ricci; F. Marion; L. Massonnet; C. Mehmel; R. Morand; B. Mours; V. Sannibale; M. Yvert; D. Babusci; S. Bellucci; S. Candusso; G. Giordano; G. Matone; J.-M. Mackowski; L. Pinard; F. Barone; E. Calloni; L. di Fiore; M. Flagiello; F. Garuti; A. Grado; M. Longo; M. Lops; S. Marano; L. Milano; S. Solimeno; V. Brisson; F. Cavalier; M. Davier; P. Hello; P. Heusse; P. Mann; Y. Acker; M. Barsuglia; B. Bhawal; F. Bondu; A. Brillet; H. Heitmann; J.-M. Innocent; L. Latrach; C. N. Man; M. Pham-Tu; E. Tournier; M. Taubmann; J.-Y. Vinet; C. Boccara; Ph. Gleyzes; V. Loriette; J.-P. Roger; G. Cagnoli; L. Gammaitoni; J. Kovalik; F. Marchesoni; M. Punturo; M. Beccaria; M. Bernardini; E. Bougleux; S. Braccini; C. Bradaschia; G. Cella; A. Ciampa; E. Cuoco; G. Curci; R. del Fabbro; R. de Salvo; A. di Virgilio; D. Enard; I. Ferrante; F. Fidecaro; A. Giassi; A. Giazotto; L. Holloway; P. La Penna; G. Losurdo; S. Mancini; M. Mazzoni; F. Palla; H.-B. Pan; D. Passuello; P. Pelfer; R. Poggiani; R. Stanga; A. Vicere; Z. Zhang

    1997-01-01

    The Virgo gravitational wave detector is an interferometer with 3 km long arms in construction near Pisa in Italy. The accessible sources at the design sensitivity and main noises are reviewed. Virgo has devoted a significant effort to extend sensitivity to low frequency reaching the strain level h~ = 10-21 Hz-1\\/2 at 10 Hz while at 200 Hzh~ = 3

  10. Early Evolution of Stellar Clusters

    E-print Network

    Ian A. Bonnell

    1999-08-24

    Observations have revealed that most stars are born in clusters. These systems, containing from tens to thousands of stars and typically significant mass in gas in the youngest systems, evolve due to a combination of stellar and star-gas interactions. Simulations of pure stellar systems are used to investigate possible initial configurations including ellipticity, substructure and mass segregation. Simulations of gas-rich clusters investigate the effects of accretion on the cluster dynamics and on the individual masses that result in a stellar mass spectrum. Further stellar interactions, including binary destruction and eventually cluster dissolution are also discussed.

  11. A CHANDRA STUDY OF TEMPERATURE SUBSTRUCTURES IN INTERMEDIATE-REDSHIFT GALAXY CLUSTERS

    SciTech Connect

    Gu Liyi; Xu Haiguang; Gu Junhua; Wang Yu; Wang Jingying; Qin Zhenzhen; Cui Haijuan [Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Zhang Zhongli [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Wu Xiangping [National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Beijing 100012 (China)

    2009-08-01

    By analyzing the gas temperature maps created from the Chandra archive data, we reveal the prevailing existence of temperature substructures on {approx}100 h{sup -1}{sub 70} kpc scales in the central regions of nine intermediate-redshift (z {approx} 0.1) galaxy clusters, which resemble those found in the Virgo and Coma Clusters. Each substructure contains a clump of hot plasma whose temperature is about 2-3 keV higher than the environment, corresponding to an excess thermal energy of {approx}10{sup 58}-10{sup 60} erg per clump. If there were no significant nongravitational heating sources, these substructures would have perished in 10{sup 8}-10{sup 9} yr due to thermal conduction and turbulent flows, whose velocity is found to range from about 200 to 400 km s{sup -1}, we conclude that the substructures cannot be created and sustained by inhomogeneous radiative cooling. We also eliminate the possibilities that the temperature substructures are caused by supernova explosions, or by the nonthermal X-ray emission due to the inverse-Comptonization of the cosmic microwave background photons. By calculating the rising time of active galactic nucleus (AGN)-induced buoyant bubbles, we speculate that the intermittent AGN outbursts ({>=}10{sup 60} erg per burst) may have played a crucial role in the formation of the high-temperature substructures. Our results are supported by the recent study of McNamara and Nulsen, posing a tight observational constraint on future theoretical and numerical studies.

  12. NASTRAN GPWG tables for combined substructures

    NASA Technical Reports Server (NTRS)

    Allen, Tom

    1991-01-01

    A method for computing the mass and center of gravity for basic and combined substructures stored in the NASTRAN Substructure Operating File (SOF) is described. The three step method recovers SOF data blocks for the relevant substructure, processes these data blocks using a specially developed FORTRAN routine, and generates the NASTRAN gridpoint weight generator (GPWG) table for the substructure in a PHASE2 SOF execution using a Direct Matrix Abstraction Program (DMAP) sequence. Verification data for the process is also provided.

  13. Dark Matter Substructure within Galactic Halos

    Microsoft Academic Search

    Ben Moore; Sebastiano Ghigna; Fabio Governato; George Lake; Thomas Quinn; Joachim Stadel; Paolo Tozzi

    1999-01-01

    We use numerical simulations to examine the substructure within galactic and cluster mass halos that form within a hierarchical universe. Clusters are easily reproduced with a steep mass spectrum of thousands of substructure clumps that closely matches the observations. However, the survival of dark matter substructure also occurs on galactic scales, leading to the remarkable result that galaxy halos appear

  14. The Cool Stellar Populations of Early-Type Galaxies and the Galactic Bulge

    Microsoft Academic Search

    Mark L. Houdashelt

    1996-01-01

    The cool stellar populations of early-type galaxies have been examined through an analysis of red (6800-9200A) and near-infrared (K-band) spectra of the nuclear regions of 17 E\\/S0 galaxies in the Virgo cluster, ten Coma cluster members and seven field galaxies. The Virgo galaxy sample spans about 4.5 mag. in K-band luminosity. To characterize the red stellar populations of these galaxies,

  15. Characterization of the Virgo Seismic Environment

    E-print Network

    The Virgo Collaboration; T. Accadia; F. Acernese; P. Astone; G. Ballardin; F. Barone; M. Barsuglia; A. Basti; Th. S. Bauer; M. Bebronne; M. G. Beker; A. Belletoile; M. Bitossi; M. A. Bizouard; M. Blom; F. Bondu; L. Bonelli; R. Bonnand; V. Boschi; L. Bosi; B. Bouhou; S. Braccini; C. Bradaschia; M. Branchesi; T. Briant; A. Brillet; V. Brisson; T. Bulik; H. J. Bulten; D. Buskulic; C. Buy; G. Cagnoli; E. Calloni; B. Canuel; F. Carbognani; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; O. Chaibi; E. Chassande-Mottin; A. Chincarini; A. Chiummo; F. Cleva; E. Coccia; P. -F. Cohadon; C. N. Colacino; J. Colas; A. Colla; M. Colombini; A. Conte; M. Coughlin; J. -P. Coulon; E. Cuoco; S. DAntonio; V. Dattilo; M. Davier; R. Day; R. De Rosa; G. Debreczeni; W. Del Pozzo; M. del Prete; L. Di Fiore; A. Di Lieto; M. Di Paolo Emilio; A. Di Virgilio; A. Dietz; M. Drago; G. Endroczi; V. Fafone; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; L. A. Forte; J. -D. Fournier; J. Franc; S. Frasca; F. Frasconi; M. Galimberti; L. Gammaitoni; F. Garufi; M. E. Gaspar; G. Gemme; E. Genin; A. Gennai; A. Giazotto; R. Gouaty; M. Granata; C. Greverie; G. M. Guidi; J. -F. Hayau; A. Heidmann; H. Heitmann; P. Hello; P. Jaranowski; I. Kowalska; A. Krolak; N. Leroy; N. Letendre; T. G. F. Li; N. Liguori; M. Lorenzini; V. Loriette; G. Losurdo; E. Majorana; I. Maksimovic; N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; C. Michel; L. Milano; Y. Minenkov; M. Mohan; N. Morgado; A. Morgia; S. Mosca; B. Mours; L. Naticchioni; F. Nocera; G. Pagliaroli; L. Palladino; C. Palomba; F. Paoletti; M. Parisi; A. Pasqualetti; R. Passaquieti; D. Passuello; G. Persichetti; F. Piergiovanni; M. Pietka; L. Pinard; R. Poggiani; M. Prato; G. A. Prodi; M. Punturo; P. Puppo; D. S. Rabeling; I. Racz; P. Rapagnani; V. Re; T. Regimbau; F. Ricci; F. Robinet; A. Rocchi; L. Rolland; R. Romano; D. Rosinska; P. Ruggi; B. Sassolas; D. Sentenac; L. Sperandio; R. Sturani; B. Swinkels; M. Tacca; L. Taffarello; A. Toncelli; M. Tonelli; O. Torre; E. Tournefier; F. Travasso; G. Vajente; J. F. J. van den Brand; C. Van Den Broeck; S. van der Putten; M. Vasuth; M. Vavoulidis; G. Vedovato; D. Verkindt; F. Vetrano; A. Vicere; J. -Y. Vinet; S. Vitale; H. Vocca; R. L. Ward; M. Was; M. Yvert; A. Zadrozny; J. -P. Zendri

    2011-08-08

    The Virgo gravitational wave detector is an interferometer (ITF) with 3km arms located in Pisa, Italy. From July to October 2010, Virgo performed its third science run (VSR3) in coincidence with the LIGO detectors. Despite several techniques adopted to isolate the interferometer from the environment, seismic noise remains an important issue for Virgo. Vibrations produced by the detector infrastructure (such as air conditioning units, water chillers/heaters, pumps) are found to affect Virgo's sensitivity, with the main coupling mechanisms being through beam jitter and scattered light processes. The Advanced Virgo (AdV) design seeks to reduce ITF couplings to environmental noise by having most vibration-sensitive components suspended and in-vacuum, as well as muffle and relocate loud machines. During the months of June and July 2010, a Guralp-3TD seismometer was stationed at various locations around the Virgo site hosting major infrastructure machines. Seismic data were examined using spectral and coherence analysis with seismic probes close to the detector. The primary aim of this study was to identify noisy machines which seismically affect the ITF environment and thus require mitigation attention. Analyzed machines are located at various distances from the experimental halls, ranging from 10m to 100m. An attempt is made to measure the attenuation of emitted noise at the ITF and correlate it to the distance from the source and to seismic attenuation models in soil.

  16. Fast Construction of Plant Architectural Models Based on Substructure Decomposition

    Microsoft Academic Search

    Hongping Yan; Philippe De Reffye; Chunhong Pan; Bao-gang Hu

    2003-01-01

    Plant structure, representing the physical link among different organs, includes many similar substructures. In this paper, a new method is presented to construct plant architectural models of most plant species. The plant structure is decomposed into a stem, a set of lateral substructures and a terminal substructure, which is called substructure decomposition; then based on substructure decomposition, the plant structures

  17. Distinguishing neutron stars from black holes and probing the mass gap with Advanced LIGO/Virgo observations

    NASA Astrophysics Data System (ADS)

    Littenberg, Tyson; Farr, Benjamin; Coughlin, Scott; Kalogera, Vicky

    2015-04-01

    As the LIGO and Virgo detectors reach their advanced design sensitivities gravitational wave observations will become an indispensable tool for learning about the universe. The mergers of binary systems comprised of compact stellar remnants (black holes and neutron stars) are expected to be the most abundant sources detectable by ground-based interferometric detectors.Advancing our understanding of binary astrophysics has long been recognized as a primary science objective for LIGO and Virgo.The potential for using GW observations as laboratories to study the nature of binary systems, and the underlying population of compact binaries, has been explored for several decades building the signal processing framework needed for the coming rush of data. We assess LIGO/Virgo's capabilities by taking advantage of modern data analysis methods and waveform models which include spin-precession effects to study a large ensemble of plausible GW sources. From this large-scale parameter estimation investigation we make quantitative predictions for how well LIGO and Virgo will be able to distinguish between black holes and neutron stars; we appraise the prospect of using LIGO/Virgo observations to definitively confirm, or reject, the existence of a ``mass gap'' between high-mass neutron stars and low-mass black holes; and we demonstrate the importance of including spin precession effects in our model for the gravitational wave signal.

  18. Universal Substructure Distributions in LCDM halos: Can we find a Fossil Group?

    E-print Network

    E. D'Onghia; A. V. Maccio'; G. Lake; J. Stadel; B. Moore

    2007-04-19

    We use large cosmological N-body simulations to study the subhalo population in galaxy group sized halos. In particular, we look for fossil group candidates with typical masses ~10-25% of Virgo cluster but with an order of magnitude less substructure. We examine recent claims that the earliest systems to form are deficient enough in substructure to explain the luminosity function found in fossil groups. Although our simulations show a correlation between the halo formation time and the number of subhalos, the maximum suppression of subhalos is a factor of 2-2.5, whereas a factor of 6 is required to match fossil groups and galaxies. While the number of subhalos depends weakly on the formation time, the slope of the halo substructure velocity function does not. The satellite population within Cold Dark Matter (CDM) halos is self-similar at scales between galaxies and galaxy clusters regardless of mass, whereas current observations show a break in self-similarity at a mass scale corresponding to group of galaxies.

  19. Chemical substructure analysis in toxicology

    SciTech Connect

    Beauchamp, R.O. Jr. [Center for Information on Toxicology and Environment, Raleigh, NC (United States)

    1990-12-31

    A preliminary examination of chemical-substructure analysis (CSA) demonstrates the effective use of the Chemical Abstracts compound connectivity file in conjunction with the bibliographic file for relating chemical structures to biological activity. The importance of considering the role of metabolic intermediates under a variety of conditions is illustrated, suggesting structures that should be examined that may exhibit potential activity. This CSA technique, which utilizes existing large files accessible with online personal computers, is recommended for use as another tool in examining chemicals in drugs. 2 refs., 4 figs.

  20. Mass Substructure in Abell 3128

    NASA Astrophysics Data System (ADS)

    McCleary, J.; dell’Antonio, I.; Huwe, P.

    2015-05-01

    We perform a detailed two-dimensional weak gravitational lensing analysis of the nearby (z = 0.058) galaxy cluster Abell 3128 using deep ugrz imaging from the Dark Energy Camera (DECam). We have designed a pipeline to remove instrumental artifacts from DECam images and stack multiple dithered observations without inducing a spurious ellipticity signal. We develop a new technique to characterize the spatial variation of the point-spread function that enables us to circularize the field to better than 0.5% and thereby extract the intrinsic galaxy ellipticities. By fitting photometric redshifts to sources in the observation, we are able to select a sample of background galaxies for weak-lensing analysis free from low-redshift contaminants. Photometric redshifts are also used to select a high-redshift galaxy subsample with which we successfully isolate the signal from an interloping z = 0.44 cluster. We estimate the total mass of Abell 3128 by fitting the tangential ellipticity of background galaxies with the weak-lensing shear profile of a Navarro–Frenk–White (NFW) halo and also perform NFW fits to substructures detected in the 2D mass maps of the cluster. This study yields one of the highest resolution mass maps of a low-z cluster to date and is the first step in a larger effort to characterize the redshift evolution of mass substructures in clusters.

  1. Systematic Problems With Stellar Halo Modelling

    NASA Astrophysics Data System (ADS)

    Bailin, Jeremy

    2012-05-01

    Stellar halos contain a small fraction of the stellar mass of a galaxy. The dynamic range required to model the substructure within this small component while simultaneously modeling the main galaxy is currently unobtainable, which has lead to the prevalence of stellar halo models that tag stellar content onto dark matter particles in pure dark matter simulations, making it computationally feasible (e.g. Bullock & Johnston 2005; Cooper et al. 2010). Using paired simulations with identical initial conditions, we estimate the magnitude of the systematic effects these simplifications have on the structure of the halos. We find that (1) "painting" and (2) neglecting baryonic processes each introduce factor-of-several changes to the amount of substructure predicted. We therefore urge caution when interpreting differences between models and observations that are at this level.

  2. Ongoing Gas Stripping in the Virgo Cluster Spiral NGC 4522

    E-print Network

    Jeffrey D. P. Kenney; Rebecca A. Koopmann

    1998-12-19

    The Virgo cluster galaxy NGC 4522 is one of the best spiral candidates for ICM-ISM stripping in action. Optical broadband and H-alpha images from the WIYN telescope of the highly inclined galaxy reveal a relatively undisturbed stellar disk and a peculiar distribution of H-alpha emission. Ten percent of the H-alpha emission arises from extraplanar HII regions which appear to lie within filamentary structures >3 kpc long above one side of the disk. The filaments emerge from the outer edge of a disk of bright H-alpha emission which is abruptly truncated beyond 0.35R(25). Together the truncated H-alpha disk and extraplanar H-alpha filaments are reminiscent of a bow shock morphology, which strongly suggests that the interstellar medium (ISM) of NGC 4522 is being stripped by the gas pressure of the intracluster medium (ICM). The galaxy has a line-of-sight velocity of 1300 km/sec with respect to the mean Virgo cluster velocity, and thus is expected to experience a strong interaction with the intracluster gas. The existence of HII regions apparently located above the disk plane suggests that star formation is occuring in the stripped gas, and that newly formed stars will enter the galaxy halo and/or intracluster space. The absence of HII regions in the disk beyond 0.35R(25), and the existence of HII regions in the stripped gas suggest that even molecular gas has been effectively removed from the disk of the galaxy.

  3. Fractal Substructure of a Nanopowder

    E-print Network

    Thomas Schwager; Dietrich E. Wolf; Thorsten Poeschel

    2008-02-25

    The structural evolution of a nano-powder by repeated dispersion and settling can lead to characteristic fractal substructures. This is shown by numerical simulations of a two-dimensional model agglomerate of adhesive rigid particles. The agglomerate is cut into fragments of a characteristic size l, which then are settling under gravity. Repeating this procedure converges to a loosely packed structure, the properties of which are investigated: a) The final packing density is independent of the initialization, b) the short-range correlation function is independent of the fragment size, c) the structure is fractal up to the fragmentation scale l with a fractal dimension close to 1.7, and d) the relaxation time increases linearly with l.

  4. The ACS Virgo Cluster Survey. VII. Resolving the Connection between Globular Clusters and Ultracompact Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Ha?egan, Monica; Jordán, Andrés; Côté, Patrick; Djorgovski, S. G.; McLaughlin, Dean E.; Blakeslee, John P.; Mei, Simona; West, Michael J.; Peng, Eric W.; Ferrarese, Laura; Milosavljevi?, Miloš; Tonry, John L.; Merritt, David

    2005-07-01

    We investigate the connection between globular clusters and ultracompact dwarf galaxies (UCDs) by examining the properties of 10 compact, high-luminosity (-11.8 MV -10.8) objects associated with M87 (NGC 4486, VCC 1316), the cD galaxy in the Virgo Cluster. These objects, most of which were previously classified as M87 globular clusters, were selected from a combination of ground- and space-based imaging surveys. Our observational database for these objects - which we term DGTOs, or "dwarf-globular transition objects" - includes Advanced Camera for Surveys (ACS) F475W and F850LP imaging from the ACS Virgo Cluster Survey, integrated-light spectroscopy from Keck/ESI, and archival F606W WFPC2 imaging. We also present a search for DGTOs associated with other galaxies based on ACS imaging for 100 early-type galaxies in Virgo. Our main findings can be summarized as follows: 1. Of the six DGTOs in M87 with both ground-based spectroscopy and HST imaging, we find two objects to have half-light radii, velocity dispersions, and mass-to-light ratios that are consistent with the predictions of population synthesis models for old, metal-rich, high-luminosity globular clusters. 2. Three other DGTOs are much larger, with half-light radii rh ~ 20 pc, and have V-band mass-to-light ratios in the range 6 M/LV 9. These objects, which we consider to be UCDs, resemble the nuclei of nucleated dwarf elliptical galaxies in the Virgo Cluster, having similar mass-to-light ratios, luminosities, and colors. 3. The classification of the sixth object is more uncertain, but it bears a strong resemblance to simulated "stellar superclusters," which are presumed to form through the amalgamation of multiple young massive clusters. 4. In general, the UCDs in M87 are found to follow the extrapolated scaling relations of galaxies more closely than those of globular clusters. There appears to be a transition between the two types of stellar systems at a mass of 2 × 10^6 M. We suggest that the presence of dark matter is the fundamental property distinguishing globular clusters from UCDs. 5. We identify a sample of 13 DGTO candidates from the complete ACS Virgo Cluster Survey, selecting on the basis of half-light radius, magnitude, and color. For a number of these objects, membership in Virgo can be established through radial velocities or surface brightness fluctuation measurements with our ACS images. Three of these DGTO candidates are embedded in low-surface brightness envelopes. 6. Five of the 13 DGTOs in Virgo are associated with a single galaxy: M87. This finding suggests that proximity to the Virgo center may be of critical importance for the formation of these objects, although we find M87 to be more abundant in DGTOs than would be expected on the basis of its luminosity, the size of its globular cluster system, or the local galaxy density. These results show that distinguishing bona fide UCDs from high-luminosity globular clusters requires a careful analysis of their detailed structural and dynamical properties, particularly their mass-to-light ratios. In general, the properties of the UCDs in our sample are consistent with models in which these objects form through tidal stripping of nucleated dwarf galaxies. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  5. Energy correlation functions for jet substructure

    E-print Network

    Salam, Gavin P.

    We show how generalized energy correlation functions can be used as a powerful probe of jet substructure. These correlation functions are based on the energies and pair-wise angles of particles within a jet, with (N?+?1)-point ...

  6. Precision Jet Substructure from Boosted Event Shapes

    E-print Network

    Feige, Ilya

    Jet substructure has emerged as a critical tool for LHC searches, but studies so far have relied heavily on shower Monte Carlo simulations, which formally approximate QCD at the leading-log level. We demonstrate that ...

  7. The Virgo 3 km interferometer for gravitational wave detection

    Microsoft Academic Search

    F. Acernese; M. Alshourbagy; F. Antonucci; S. Aoudia; P. Astone; S. Avino; L. Baggio; G. Ballardin; F. Barone; L. Barsotti; M. Barsuglia; Th S. Bauer; S. Bigotta; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; S. Birindelli; S. Braccini; A. Brillet; V. Brisson; D. Buskulic; G. Cagnoli; E. Calloni; E. Campagna; F. Carbognani; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; E. Chassande-Mottin; A.-C. Clapson; F. Cleva; E. Coccia; C. Corda; A. Corsi; F. Cottone; J.-P. Coulon; E. Cuoco; S D’Antonio; A. Dari; V. Dattilo; M. Davier; M. del Prete; R. DeRosa; L. Di Fiore; A. Di Lieto; A. Di Virgilio; B. Dujardin; M. Evans; V. Fafone; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; S. Frasca; F. Frasconi; L. Gammaitoni; F. Garufi; E. Genin; A. Gennai; A. Giazotto; L. Giordano; V. Granata; C. Greverie; D. Grosjean; G. Guidi; S. Hamdani; S. Hebri; H. Heitmann; P. Hello; D. Huet; S. Kreckelbergh; P. La Penna; M. Laval; N. Leroy; N. Letendre; B. Lopez; M. Lorenzini; V. Loriette; G. Losurdo; J.-M. Mackowski; E. Majorana; C. N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; F. Menzinger; L. Milano; Y. Minenkov; C. Moins; J. Moreau; N. Morgado; S. Mosca; B. Mours; I. Neri; F. Nocera; G. Pagliaroli; G. V. Pallottino; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; S. van der Putten; P. Rapagnani; T. Regimbau; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; A. Rocchi; R. Romano; P. Ruggi; G. Russo; S. Solimeno; A. Spallicci; M. Tarallo; R. Terenzi; M. Tonelli; A. Toncelli; E. Tournefier; F. Travasso; C. Tremola; G. Vajente; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert

    2008-01-01

    Virgo, designed, constructed and developed by the French-Italian VIRGO collaboration located in Cascina (Pisa, Italy) and aiming to detect gravitational waves, is a ground-based power recycled Michelson interferometer, with 3 km long suspended Fabry-Perot cavities. The first Virgo scientific data-taking started in mid-May 2007, in coincidence with the corresponding LIGO detectors. The optical scheme of the interferometer and the various

  8. The Next Generation Virgo Cluster Survey. IX. Estimating the Efficiency of Galaxy Formation on the Lowest-mass Scales

    NASA Astrophysics Data System (ADS)

    Grossauer, Jonathan; Taylor, James E.; Ferrarese, Laura; MacArthur, Lauren A.; Côté, Patrick; Roediger, Joel; Courteau, Stéphane; Cuillandre, Jean-Charles; Duc, Pierre-Alain; Durrell, Patrick R.; Gwyn, S. D. J.; Jordán, Andrés; Mei, Simona; Peng, Eric W.

    2015-07-01

    The Next Generation Virgo Cluster Survey has recently determined the luminosity function of galaxies in the core of the Virgo cluster down to unprecedented magnitude and surface brightness limits. Comparing simulations of cluster formation to the derived central stellar mass function, we attempt to estimate the stellar-to-halo-mass ratio (SHMR) for dwarf galaxies, as it would have been before they fell into the cluster. This approach ignores several details and complications, e.g., the contribution of ongoing star formation to the present-day stellar mass of cluster members, and the effects of adiabatic contraction and/or violent feedback on the subhalo and cluster potentials. The final results are startlingly simple, however; we find that the trends in the SHMR determined previously for bright galaxies appear to extend down in a scale-invariant way to the faintest objects detected in the survey. These results extend measurements of the formation efficiency of field galaxies by two decades in halo mass or five decades in stellar mass, down to some of the least massive dwarf galaxies known, with stellar masses of ? {10}5 {M}? .

  9. Modeling Substructure in the Milky Way Galaxy

    NASA Astrophysics Data System (ADS)

    Grishaw-Jones, Claire; Thorman, P.; Iyer, T.; Guhathakurta, P.; Deep Lens Survey Collaboration

    2013-01-01

    We model substructure in the Milky Way halo using data taken from the five fields of the Deep Lens Survey (DLS). We select DLS objects that are consistent with the PSF to create color-magnitude Hess diagrams for each field. We observe significant substructure in at least two out of the five fields. To enhance the visibility of the substructure, we model and subtract the population of unresolved background galaxies, and subtract a smooth model of the Milky Way halo. This halo model is constructed by remapping the observed Hess diagram of stars in DLS Field 5 (F5), which has a smooth appearance. We use colors and absolute magnitudes from the Yonsei-Yale isochrones to create a map of distance modulus for main sequence stars in color-magnitude space for each DLS field. An Einasto model of the galaxy is used to predict the model density ratio of stars in each field as a function of distance modulus. The F5 Hess diagram is then multiplied by the model density ratio maps for F1 - F4 to yield semi-empirical model Hess diagrams. Subtracting these models from the observed Hess diagrams emphasizes the substructure of a given field. We fit simple models to the residual substructure in each DLS field using a Gaussian with three free parameters: distance of enhancement, depth along the LOS, and amplitude (i.e. strength). We discuss the use of this galaxy substructure model in calculating the overall density profile of the Milky Way.

  10. Spitzer IR Colors and ISM Distributions of Virgo Cluster Spirals

    NASA Astrophysics Data System (ADS)

    Kenney, Jeffrey D.; Wong, I.; Kenney, Z.; Murphy, E.; Helou, G.; Howell, J.

    2012-01-01

    IRAC infrared images of 44 spiral and peculiar galaxies from the Spitzer Survey of the Virgo Cluster help reveal the interactions which transform galaxies in clusters. We explore how the location of galaxies in the IR 3.6-8?m color-magnitude diagram is related to the spatial distributions of ISM/star formation, as traced by PAH emission in the 8?m band. Based on their 8?m/PAH radial distributions, we divide the galaxies into 4 groups: normal, truncated, truncated/compact, and anemic. Normal galaxies have relatively normal PAH distributions. They are the "bluest" galaxies, with the largest 8/3.6?m ratios. They are relatively unaffected by the cluster environment, and have probably never passed through the cluster core. Truncated galaxies have a relatively normal 8?m/PAH surface brightness in the inner disk, but are abruptly truncated with little or no emission in the outer disk. They have intermediate ("green") colors, while those which are more severely truncated are "redder". Most truncated galaxies have undisturbed stellar disks and many show direct evidence of active ram pressure stripping. Truncated/compact galaxies have high 8?m/PAH surface brightness in the very inner disk (central 1 kpc) but are abruptly truncated close to center with little or no emission in the outer disk. They have intermediate global colors, similar to the other truncated galaxies. While they have the most extreme ISM truncation, they have vigorous circumnuclear star formation. Most of these have disturbed stellar disks, and they are probably produced by a combination of gravitational interaction plus ram pressure stripping. Anemic galaxies have a low 8?m/PAH surface brightness even in the inner disk. These are the "reddest" galaxies, with the smallest 8/3.6?m ratios. The origin of the anemics seems to a combination of starvation, gravitational interactions, and long-ago ram pressure stripping.

  11. The substructure hierarchy in dark matter haloes

    NASA Astrophysics Data System (ADS)

    Giocoli, Carlo; Tormen, Giuseppe; Sheth, Ravi K.; van den Bosch, Frank C.

    2010-05-01

    We present a new algorithm for identifying the substructure within simulated dark matter haloes. The method is an extension of that proposed by Tormen, Moscardini & Yoshida and Giocoli, Tormen & van den Bosch, which identifies a subhalo as a group of self-bound particles that prior to being accreted by the main progenitor of the host halo belonged to one and the same progenitor halo (hereafter `satellite'). However, this definition does not account for the fact that these satellite haloes themselves may also have substructure, which thus gives rise to sub-subhaloes, etc. Our new algorithm identifies substructures at all levels of this hierarchy, and we use it to determine the mass function of all substructure (counting subhaloes, sub-subhaloes, etc.). On average, haloes which are formed more recently tend to have a larger mass fraction in substructure and to be less concentrated than average haloes of the same mass. We provide quantitative fits to these correlations. Even though our algorithm is very different from that of Gao et al., we also find that the subhalo mass function per unit mass at redshift z = 0 is universal. This universality extends to any redshift only if one accounts for the fact that host haloes of a given mass are less concentrated at higher redshifts, and concentration and substructure abundance are anticorrelated. This universality allows a simple parametrization of the subhalo mass function integrated over all host halo masses, at any given time. We provide analytic fits to this function which should be useful in halo model analyses which equate galaxies with halo substructure when interpreting clustering in large sky surveys. Finally, we discuss systematic differences in the subhalo mass function that arise from different definitions of (host) halo mass.

  12. The environmental impact of the Virgo Cluster on the evolution of dwarf irregular galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Henry

    Dwarf galaxies are the greatest contributor to the total number of galaxies and most are believed to be systems consisting of matter in a near-primordial state. Containing H I gas and H II regions, dwarf irregular galaxies (dIs) can be used as test bodies to evaluate the impact of the environment on their evolution. Oxygen abundances relative to hydrogen within H II regions are a measure of how far the conversion of gas in the interstellar medium into stars has proceeded as a whole, as abundances do not vary significantly with galactocentric radius in dIs. Measurements of the [O III]?4363 emission line from H II region spectroscopy provide accurate probes of the electron temperature from which oxygen abundances are directly computed. The impact of the Virgo Cluster environment is investigated by comparing the properties of a set of Virgo dIs with those of a set of dIs in the field. To ensure accurate measures of luminosity and abundance, dIs in the field are chosen to have distance determinations from well-calibrated techniques and oxygen abundances derived from [O III]?4363 measurements. Spectroscopic data are obtained for H II regions in 11 dIs distributed in the central and outer regions of the Virgo Cluster. There is no systematic difference in oxygen abundance between field dIs and Virgo dIs at a given luminosity, showing that there is no detectable difference in their stellar populations. Oxygen abundances for field dIs are well correlated with the gas fraction in a way which shows definitively that evolution has been isolated, i.e., consistent with the “closed-box” model of chemical evolution. For the gas-poor dI UGC 7636 (VCC 1249), the oxygen abundance of a newly discovered intergalactic H II region is combined with the optical luminosity of the dI and the gas mass of the adjacent H I cloud (STET) to show that STET must have once been the interstellar medium of the dI. Tidal interactions of the dI with the elliptical NGC 4472 combined with ram-pressure stripping by the intracluster medium (ICM) best explain the observed properties of the detached cloud and the dI. A “staged” model is described to examine the chemical evolution of a gas-poor dI in the Virgo Cluster. Motivated by the observations, the model is characterized by three phases: isolated evolution, then sudden stripping which removes most of the gas, followed by a second stage of isolated evolution for the residual gas. The time since a typical stripping event is found to be approximately 1 Gyr or less. The GDIs for Virgo dIs correlate roughly with values of the projected X-ray surface brightness of the intracluster gas at the positions of the dIs. Thus, ram-pressure stripping best explains the observed gas-poor dIs in the Virgo sample. Together with the lack of significant fading, these observations suggest that dIs have recently encountered the ICM for the first time. A faded remnant of a gas-poor dI in Virgo will resemble a bright dE/dSph-like object like those presently seen in the cluster core. (Abstract shortened by UMI.)

  13. SEXTANS' COLD SUBSTRUCTURES AS A DYNAMICAL JUDGE: CORE, CUSP, OR MOND?

    SciTech Connect

    Lora, V.; Grebel, E. K.; Just, A. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany); Sánchez-Salcedo, F. J., E-mail: vlora@ari.uni-heidelberg.de [Instituto de Astronomía, Universidad Nacional Autónoma de México, AP 70-264, 04510 D.F. (Mexico)

    2013-11-01

    The cold dark matter model predicts cuspy dark matter (DM) halos. However, it has been found that in some low-mass galaxies, cored dark halos provide a better description of their internal dynamics. Here we give constraints on the dark halo profile in the Sextans dwarf spheroidal galaxy by studying the longevity of two cold kinematic substructures detected in this galaxy. We perform N-body simulations of a stellar clump in the Sextans dwarf galaxy, including a live DM halo and the main stellar component. We find that if the dark halo is cuspy, stellar clumps orbiting with semi-major axis ?400 pc are disrupted in ?5 Gyr, even if the clump is initially as compact stellar cluster with a radius of r{sub c} = 5 pc. Stellar clusters in an initial orbit with semi-major axis ?250 pc may survive to dissolution, but their orbits decay toward the center by dynamical friction. In contrast, the stellar clumps can persist for a Hubble time within a cored DM halo, even if the initial clump's radius is as extended as r{sub c} = 80 pc. We also study the evolution of the clump in the MONDian context. In this scenario, we find that even an extended stellar clump with radius r{sub c} = 80 pc survives for a Hubble time, but an unrealistic value for the stellar mass-to-light ratio of 9.2 is needed.

  14. Methods of gravitational wave detection in the VIRGO Interferometer

    Microsoft Academic Search

    F. Acernese; P. Amico; M. Alshourbagy; F. Antonucci; S. Aoudia; P. Astone; S. Avino; D. Babusci; G. Ballardin; F. Barone; L. Barsotti; M. Barsuglia; F. Beauville; S. Bigotta; S. Birindelli; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; S. Braccini; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; E. Calloni; E. Campagna; F. Carbognani; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; E. Chassande-Mottin; N. Christensen; C. Corda; A. Corsi; F. Cottone; A.-C. Clapson; F. Cleva; J.-P. Coulon; E. Cuoco; A. Dari; V. Dattilo; M. Davier; M. Del Prete; R. de Rosa; L. di Fiore; A. di Virgilio; B. Dujardin; A. Eleuteri; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; O. Francois; S. Frasca; F. Frasconi; L. Gammaitoni; F. Garufi; E. Genin; A. Gennai; A. Giazotto; G. Giordano; L. Giordano; R. Gouaty; D. Grosjean; G. Guidi; S. Hebri; H. Heitmann; P. Hello; S. Karkar; S. Kreckelbergh; P. La Penna; M. Laval; N. Leroy; N. Letendre; B. Lopez; Lorenzini; V. Loriette; G. Losurdo; J.-M. Mackowski; E. Majorana; C. N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; M. Mazzoni; L. Milano; F. Menzinger; C. Moins; J. Moreau; N. Morgado; B. Mours; F. Nocera; A. Pai; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; B. Perniola; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; P. Ruggi; G. Russo; S. Solimeno; A. Spallicci; R. Stanga; T. Marco; M. Tonelli; A. Toncelli; E. Tournefier; F. Travasso; C. Tremola; G. Vajente; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert

    2007-01-01

    The gravitational wave detector VIRGO is in the final commissioning phase and some preliminary data has already been acquired. The aim of VIRGO is to directly detect gravitational waves emitted by compact objects at the time of coalescence and by other astrophysical sources. Here we report on the present sensitivity for detecting these sources and what we will achieve in

  15. A comparison of the near-infrared spectral features of early-type galaxies in the Coma Cluster, the Virgo cluster and the field

    NASA Technical Reports Server (NTRS)

    Houdashelt, Mark L.; Frogel, Jay A.

    1993-01-01

    Earlier researchers derived the relative distance between the Coma and Virgo clusters from color-magnitude relations of the early-type galaxies in each cluster. They found that the derived distance was color-dependent and concluded that the galaxies of similar luminosity in the two clusters differ in their red stellar populations. More recently, the color-dependence of the Coma-Virgo distance modulus has been called into question. However, because these two clusters differ so dramatically in their morphologies and kinematics, it is plausible that the star formation histories of the member galaxies also differed. If the conclusions of earlier researchers are indeed correct, then some signature of the resulting stellar population differences should appear in the near-infrared and/or infrared light of the respective galaxies. We have collected near-infrared spectra of 17 Virgo and 10 Coma early-type galaxies; this sample spans about four magnitudes in luminosity in each cluster. Seven field E/S0 galaxies have been observed for comparison. Pseudo-equivalent widths have been measured for all of the field galaxies, all but one of the Virgo members, and five of the Coma galaxies. The features examined are sensitive to the temperature, metallicity, and surface gravity of the reddest stars. A preliminary analysis of these spectral features has been performed, and, with a few notable exceptions, the measured pseudo-equivalent widths agree well with previously published values.

  16. Studies of the Virgo cluster. III - A classification system and an illustrated atlas of Virgo cluster dwarf galaxies

    Microsoft Academic Search

    A. Sandage; B. Binggeli

    1984-01-01

    Photographs enlarged to a common scale are given for 138 dwarf galaxies in the region of the Virgo cluster. Most are cluster members, as judged either from their uniquely low surface brightness and\\/or morphology, or occasionally from velocity data. All known Hubble galaxy types have been found in the Virgo cluster, ranging in absolute magnitude from the brightest known giant

  17. The Dynamical Properties of Virgo Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Ouellette, Nathalie N.-Q.

    By virtue of its proximity, the Virgo Cluster is an ideal laboratory for us to test our understanding of the formation of structure in our Universe. In this spirit, we present a dynamical study of 33 gas-poor and 34 gas-rich Virgo galaxies as part of the Spectroscopic and H-band Imaging of Virgo survey. Our final spectroscopic data set was acquired at the 3.5-m telescope at the Apache Point Observatory. Halpha rotation curves for the gas-rich galaxies were modelled with a multi-parameter fit function from which various velocity measurements were inferred. Analog values were measured off of the observed rotation curves, but yielded noisier scaling relations, such as the luminosity-velocity relation (also known as the Tully-Fisher relation). Our best i -band Tully-Fisher relation has slope alpha = --7.2 +/- 0.5 and intercept Mi(2.3) = --21.5 +/- 1.1 mag, matching similar previous studies. Our study takes advantage of our own, as well as literature, data; we plan to continue expanding our compilation in order to build the largest Tully-Fisher relation for a cluster to date. Following extensive testing of the IDL routine pPXF , extended velocity dispersion profiles were extracted for our gas-poor galaxies. Considering the lack of a common standard for the measurement of a fiducial galaxy velocity dispersion in the literature, we have endeavoured to rectify this situation by determining the radius at which the measured velocity dispersion, coupled with the galaxy luminosity, yields the tightest Faber-Jackson relation. We found that radius to be 1.5 R e, which exceeds the extent of most dispersion profiles in other works. The slope of our Faber-Jackson relation is alpha = --4.3 +/- 0.2, which closely matches the virial value of 4. This analysis will soon be applied to a study of the Virgo Cluster Fundamental Plane. Rotation correction of our dispersion profiles will also permit the study of galaxies' velocity dispersion profile shapes in an attempt to refine our understanding of the overall manifold of galaxy structural parameters.

  18. Discovering the Dark Side of CDM Substructure

    NASA Astrophysics Data System (ADS)

    Koopmans, Leon

    2012-10-01

    The existence of mass substructure is an inevitable consequence of the LCDM paradigm. Depite this clear theoretical prediction, a glaring discrepancy with the number of luminous satellites around the Milky Way {MW} has been identified, i.e. the "missing satellite problem". Notwithstanding great progress to address this problem, it remains unsolved. Moreover, the MW could be a biased environment, not representative of the typical universe. Surface brightness aberrations of gravitationally lensed images provide a complementary channel to detect substructure beyond the local Universe in mostly massive early-type galaxies. Simulations suggest a substructure mass fraction of f_sub<=1% inside the inner projected 5-10 kpc or around 5-10% inside the virial radius. Although the observed {flux-ratio/brightness} anomalies/aberrations in lenses can be explained by the presence of this mass substructure, its high rate requires a larger inferred fraction of 2-3%. To resolve these open issues convincingly, we propose to observe highly magnified Einstein rings/arcs in the ultra-violet, where the source is highly structured, to maximize sensitivity to dark substructures through surface brightness aberrations {i.e. the equivalent of the well-known flux-ratio anomalies}. Our simulations, modeling and statistical analyses show that our selected sample of 10 SLACS lens systems can pinpoint dark substructures down to 3x10^8 solar masses { 10^-4 of the ETG virial mass} and, for the first time, determine their mass fraction to down to f_sub 1%, at >99% CL. We request 30 orbits with HST WFC3-F390W to accomplish this goal.

  19. Dynamic Substructuring of Damped Structures Using Singular Value Decomposition

    E-print Network

    Boyer, Edmond

    Dynamic Substructuring of Damped Structures Using Singular Value Decomposition R. Ohayon Chair of structure-structure coupling by dynamic substructuring methods using modal reduction procedures; Rook and Singh, 1995). Within the context of finite element discretization of linear structural dynamic

  20. The wave-based substructuring approach for the efficient description of interface dynamics in substructuring

    NASA Astrophysics Data System (ADS)

    Donders, S.; Pluymers, B.; Ragnarsson, P.; Hadjit, R.; Desmet, W.

    2010-04-01

    In the vehicle design process, design decisions are more and more based on virtual prototypes. Due to competitive and regulatory pressure, vehicle manufacturers are forced to improve product quality, to reduce time-to-market and to launch an increasing number of design variants on the global market. To speed up the design iteration process, substructuring and component mode synthesis (CMS) methods are commonly used, involving the analysis of substructure models and the synthesis of the substructure analysis results. Substructuring and CMS enable efficient decentralized collaboration across departments and allow to benefit from the availability of parallel computing environments. However, traditional CMS methods become prohibitively inefficient when substructures are coupled along large interfaces, i.e. with a large number of degrees of freedom (DOFs) at the interface between substructures. The reason is that the analysis of substructures involves the calculation of a number of enrichment vectors, one for each interface degree of freedom (DOF). Since large interfaces are common in vehicles (e.g. the continuous line connections to connect the body with the windshield, roof or floor), this interface bottleneck poses a clear limitation in the vehicle noise, vibration and harshness (NVH) design process. Therefore there is a need to describe the interface dynamics more efficiently. This paper presents a wave-based substructuring (WBS) approach, which allows reducing the interface representation between substructures in an assembly by expressing the interface DOFs in terms of a limited set of basis functions ("waves"). As the number of basis functions can be much lower than the number of interface DOFs, this greatly facilitates the substructure analysis procedure and results in faster design predictions. The waves are calculated once from a full nominal assembly analysis, but these nominal waves can be re-used for the assembly of modified components. The WBS approach thus enables efficient structural modification predictions of the global modes, so that efficient vibro-acoustic design modification, optimization and robust design become possible. The results show that wave-based substructuring offers a clear benefit for vehicle design modifications, by improving both the speed of component reduction processes and the efficiency and accuracy of design iteration predictions, as compared to conventional substructuring approaches.

  1. Coma Dwarf Galaxies Resemble Virgo Dwarf Ellipticals

    NASA Astrophysics Data System (ADS)

    Komiyama, Y.

    We investigate the photometric properties of dwarf galaxies in the Coma cluster using deep B and R image obtained with our mosaic CCD camera mounted on the prime focus of the 4.2-m William Herschel Telescope. We detected about 5600 and 4300 galaxies in the 0.45 square degree fields centered on the Coma center and on a control field SA57, respectively, down to R = 22mag, the limit of our star/galaxy discrimination. Mean properties of Coma dwarfs are derived by subtracting SA57 galaxies from those detected in the Coma center field. Coma dwarfs are found to show the surface brightness - luminosity relation in B band almost identical to that for Virgo dwarf ellipticals. Most of the low-surface-brightness probable Coma dwarfs show the exponential profile. These results indicate that dwarf galaxies in the rich Coma cluster resemble dwarf ellipticals found in the nearby loose Virgo and Fornax clusters and that the luminosity structure of dwarf galaxies only weakly depends on the environment of the cluster they belong to.

  2. SUBSTRUCTURE AND MECHANICAL PROPERTIES OF REFRACTORY METALS

    Microsoft Academic Search

    B. S. Lement; D. A. Thomas; S. Weissmann; W. S. Owen; P. B. Hirsch

    1961-01-01

    Quantitative resuits on the substructural characteristics of tungsten, ; molybdenum, tantalum, and columbium are being obtained through the coordinated ; programs of the five participating laboratorses. Changes in subboundary spacing ; of worked materials have been measured microscopically as a function of annealing ; temperature, and corresponding changes in particle size and lattice strain have ; been obtained by Fourier

  3. Galactic Stellar Populations in the Era of the Sloan Digital Sky Survey and Other Large Surveys

    NASA Astrophysics Data System (ADS)

    Ivezi?, Željko; Beers, Timothy C.; Juri?, Mario

    2012-09-01

    Studies of stellar populations, understood to mean collections of stars with common spatial, kinematic, chemical, and/or age distributions, have been reinvigorated during the past decade by the advent of large-area sky surveys such as the Sloan Digital Sky Survey, the Two-Micron All Sky Survey, the Radial Velocity Experiment, and others. We review recent analyses of these data that, together with theoretical and modeling advances, are revolutionizing our understanding of the nature of the Milky Way and galaxy formation and evolution in general. The formation of galaxies like the Milky Way was long thought to be a steady process leading to a smooth distribution of stars. However, the abundance of substructure in the multidimensional space of various observables, such as position, kinematics, and metallicity, is now proven beyond doubt and demonstrates the importance of mergers in the growth of galaxies. Unlike smooth models that involve simple components, the new data reviewed here clearly exhibit many irregular structures, such as the Sagittarius dwarf tidal stream and the Virgo and Pisces overdensities in the halo and the Monoceros stream closer to the Galactic plane. These recent developments have made it clear that the Milky Way is a complex and dynamic structure, one that is still being shaped by the merging of neighboring smaller galaxies. We also briefly discuss the next generation of wide-field sky surveys, such as SkyMapper, Panoramic Survey Telescope & Rapid Response System, Global Astrometric Interferometer for Astrophysics, and the Large Synoptic Survey Telescope, which will improve measurement precision manyfold and include billions of individual stars. The ultimate goal, development of a coherent and detailed story of the assembly and evolutionary history of the Milky Way and other large spirals like it, now appears well within reach.

  4. Prospects for Stochastic Background Searches Using Virgo and LSC Interferometers

    E-print Network

    Giancarlo Cella; Carlo Nicola Colacino; Elena Cuoco; Angela Di Virgilio; Tania Regimbau; Emma L Robinson; John T Whelan

    2007-07-09

    We consider the question of cross-correlation measurements using Virgo and the LSC Interferometers (LIGO Livingston, LIGO Hanford, and GEO600) to search for a stochastic gravitational-wave background. We find that inclusion of Virgo into the network will substantially improve the sensitivity to correlations above 200 Hz if all detectors are operating at their design sensitivity. This is illustrated using a simulated isotropic stochastic background signal, generated with an astrophysically-motivated spectrum, injected into 24 hours of simulated noise for the LIGO and Virgo interferometers.

  5. The Next Generation Virgo Cluster Survey. IX. Estimating the Efficiency of Galaxy Formation on the Lowest-Mass Scales

    E-print Network

    Grossauer, Jonathan; Ferrarese, Laura; MacArthur, Lauren A; Cote, Patrick; Roediger, Joel; Courteau, Stephane; Cuillandre, Jean-Charles; Duc, Pierre-Alain; Durrell, Patrick R; Gwyn, S D J; Jordan, Andres; Mei, Simona; Peng, Eric W

    2015-01-01

    The Next Generation Virgo Cluster Survey has recently determined the luminosity function of galaxies in the core of the Virgo cluster down to unprecedented magnitude and surface brightness limits. Comparing simulations of cluster formation to the derived central stellar mass function, we attempt to estimate the stellar-to-halo-mass ratio (SHMR) for dwarf galaxies, as it would have been before they fell into the cluster. This approach ignores several details and complications, e.g., the contribution of ongoing star formation to the present-day stellar mass of cluster members, and the effects of adiabatic contraction and/or violent feedback on the subhalo and cluster potentials. The final results are startlingly simple, however; we find that the trends in the SHMR determined previously for bright galaxies appear to extend down in a scale-invariant way to the faintest objects detected in the survey. These results extend measurements of the formation efficiency of field galaxies by two decades in halo mass, or fi...

  6. The gamma-ray-flux PDF from galactic halo substructure

    SciTech Connect

    Lee, Samuel K.; Ando, Shin'ichiro; Kamionkowski, Marc, E-mail: sklee@astro.caltech.edu, E-mail: ando@tapir.caltech.edu, E-mail: kamion@tapir.caltech.edu [California Institute of Technology, Mail Code 350-17, Pasadena, CA 91125 (United States)

    2009-07-01

    One of the targets of the recently launched Fermi Gamma-ray Space Telescope is a diffuse gamma-ray background from dark-matter annihilation or decay in the Galactic halo. N-body simulations and theoretical arguments suggest that the dark matter in the Galactic halo may be clumped into substructure, rather than smoothly distributed. Here we propose the gamma-ray-flux probability distribution function (PDF) as a probe of substructure in the Galactic halo. We calculate this PDF for a phenomenological model of halo substructure and determine the regions of the substructure parameter space in which the PDF may be distinguished from the PDF for a smooth distribution of dark matter. In principle, the PDF allows a statistical detection of substructure, even if individual halos cannot be detected. It may also allow detection of substructure on the smallest microhalo mass scales, ? M{sub ?}, for weakly-interacting massive particles (WIMPs). Furthermore, it may also provide a method to measure the substructure mass function. However, an analysis that assumes a typical halo substructure model and a conservative estimate of the diffuse background suggests that the substructure PDF may not be detectable in the lifespan of Fermi in the specific case that the WIMP is a neutralino. Nevertheless, for a large range of substructure, WIMP annihilation, and diffuse background models, PDF analysis may provide a clear signature of substructure.

  7. Stellar evolution.

    NASA Technical Reports Server (NTRS)

    Chiu, H.-Y. (editor); Muriel, A.

    1972-01-01

    Aspects of normal stellar evolution are discussed together with evolution near the main sequence, stellar evolution from main sequence to white dwarf or carbon ignition, the structure of massive main-sequence stars, and problems of stellar stability and stellar 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 stellar opacity. Transport mechanisms in stars are examined together with thermonuclear reactions and nucleosynthesis, the instability problem in nuclear burning shells, stellar coalescence, and intense magnetic fields in astrophysics. Individual items are announced in this issue.

  8. Advanced Virgo: a 2nd generation interferometric gravitational wave detector

    E-print Network

    F. Acernese; M. Agathos; K. Agatsuma; D. Aisa; N. Allemandou; A. Allocca; J. Amarni; P. Astone; G. Balestri; G. Ballardin; F. Barone; J. -P. Baronick; M. Barsuglia; A. Basti; F. Basti; Th. S. Bauer; V. Bavigadda; M. Bejger; M. G. Beker; C. Belczynski; D. Bersanetti; A. Bertolini; M. Bitossi; M. A. Bizouard; S. Bloemen; M. Blom; M. Boer; G. Bogaert; D. Bondi; F. Bondu; L. Bonelli; R. Bonnand; V. Boschi; L. Bosi; T. Bouedo; C. Bradaschia; M. Branchesi; T. Briant; A. Brillet; V. Brisson; T. Bulik; H. J. Bulten; D. Buskulic; C. Buy; G. Cagnoli; E. Calloni; C. Campeggi; B. Canuel; F. Carbognani; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; E. Chassande-Mottin; A. Chincarini; A. Chiummo; S. Chua; F. Cleva; E. Coccia; P. -F. Cohadon; A. Colla; M. Colombini; A. Conte; J. -P. Coulon; E. Cuoco; A. Dalmaz; S. D'Antonio; V. Dattilo; M. Davier; R. Day; G. Debreczeni; J. Degallaix; S. Deléglise; W. Del Pozzo; H. Dereli; R. De Rosa; L. Di Fiore; A. Di Lieto; A. Di Virgilio; M. Doets; V. Dolique; M. Drago; M. Ducrot; G. Endr?czi; V. Fafone; S. Farinon; I. Ferrante; F. Ferrini; F. Fidecaro; I. Fiori; R. Flaminio; J. -D. Fournier; S. Franco; S. Frasca; F. Frasconi; L. Gammaitoni; F. Garufi; M. Gaspard; A. Gatto; G. Gemme; B. Gendre; E. Genin; A. Gennai; S. Ghosh; L. Giacobone; A. Giazotto; R. Gouaty; M. Granata; G. Greco; P. Groot; G. M. Guidi; J. Harms; A. Heidmann; H. Heitmann; P. Hello; G. Hemming; E. Hennes; D. Hofman; P. Jaranowski; R. J. G. Jonker; M. Kasprzack; F. Kéfélian; I. Kowalska; M. Kraan; A. Królak; A. Kutynia; C. Lazzaro; M. Leonardi; N. Leroy; N. Letendre; T. G. F. Li; B. Lieunard; M. Lorenzini; V. Loriette; G. Losurdo; C. Magazzù; E. Majorana; I. Maksimovic; V. Malvezzi; N. Man; V. Mangano; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; L. Martellini; A. Masserot; D. Meacher; J. Meidam; F. Mezzani; C. Michel; L. Milano; Y. Minenkov; A. Moggi; M. Mohan; M. Montani; N. Morgado; B. Mours; F. Mul; M. F. Nagy; I. Nardecchia; L. Naticchioni; G. Nelemans; I. Neri; M. Neri; F. Nocera; E. Pacaud; C. Palomba; F. Paoletti; A. Paoli; A. Pasqualetti; R. Passaquieti; D. Passuello; M. Perciballi; S. Petit; M. Pichot; F. Piergiovanni; G. Pillant; A Piluso; L. Pinard; R. Poggiani; M. Prijatelj; G. A. Prodi; M. Punturo; P. Puppo; D. S. Rabeling; I. Rácz; P. Rapagnani; M. Razzano; V. Re; T. Regimbau; F. Ricci; F. Robinet; A. Rocchi; L. Rolland; R. Romano; D. Rosi?ska; P. Ruggi; E. Saracco; B. Sassolas; F. Schimmel; D. Sentenac; V. Sequino; S. Shah; K. Siellez; N. Straniero; B. Swinkels; M. Tacca; M. Tonelli; F. Travasso; M. Turconi; G. Vajente; N. van Bakel; M. van Beuzekom; J. F. J. van den Brand; C. Van Den Broeck; M. V. van der Sluys; J. van Heijningen; M. Vasúth; G. Vedovato; J. Veitch; D. Verkindt; F. Vetrano; A. Viceré; J. -Y. Vinet; G. Visser; H. Vocca; R. Ward; M. Was; L. -W. Wei; M. Yvert; A. Zadro?ny; J. -P. Zendri

    2014-10-16

    Advanced Virgo is the project to upgrade the Virgo interferometric detector of gravitational waves, with the aim of increasing the number of observable galaxies (and thus the detection rate) by three orders of magnitude. The project is now in an advanced construction phase and the assembly and integration will be completed by the end of 2015. Advanced Virgo will be part of a network with the two Advanced LIGO detectors in the US and GEO HF in Germany, with the goal of contributing to the early detections of gravitational waves and to opening a new observation window on the universe. In this paper we describe the main features of the Advanced Virgo detector and outline the status of the construction.

  9. Radial Velocities of Galactic Halo Stars in Virgo

    NASA Astrophysics Data System (ADS)

    Brink, Thomas G.; Mateo, Mario; Martínez-Delgado, David

    2010-11-01

    We present multi-slit radial velocity measurements for 111 stars in the direction of the Virgo Stellar Stream (VSS). The stars were photometrically selected to be probable main-sequence stars in the Galactic halo. When compared with the radial velocity distribution expected for the halo of the Milky Way, as well as the distribution seen in a control field, we observe a significant excess of negative velocity stars in the field, which can likely be attributed to the presence of a stellar stream. This kinematic excess peaks at a Galactic standard of rest radial velocity of -75 km s-1. A rough distance estimate suggests that this feature extends from ~15 kpc out to, and possibly beyond, the ~30 kpc limit of the study. The mean velocity of these stars is incompatible with those of the VSS itself (Vgsr ~ 130 km s-1), which we weakly detect, but it is consistent with radial velocity measurements of nearby 2MASS M-giants and SDSS+SEGUE K/M-giants and blue horizontal branch stars that constitute the leading tidal tail of the Sagittarius dwarf spheroidal galaxy. Some oblate models for the shape of the Milky Way's dark matter halo predict that the leading arm of the Sagittarius Stream should pass through this volume, and have highly negative (Vgsr <~ -200 km s-1) radial velocities, as it descends down from the northern Galactic hemisphere toward the Galactic plane. The kinematic feature observed in this study, if it is in fact Sagittarius debris, is not consistent with these predictions, and instead, like other leading stream radial velocity measurements, is consistent with a recently published triaxial halo model, or, if axisymmetry is imposed, favors a prolate shape for the Galactic halo potential. However, a rough distance estimate to the observed kinematic feature places it somewhat closer (D ~ 15-30 kpc) than the Sagittarius models predict (D ~ 35-45 kpc). This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  10. A state observer for the Virgo inverted pendulum

    NASA Astrophysics Data System (ADS)

    Accadia, T.; Acernese, F.; Astone, P.; Ballardin, G.; Barone, F.; Barsuglia, M.; Basti, A.; Bauer, Th. S.; Bebronne, M.; Beker, M. G.; Belletoile, A.; Bitossi, M.; Bizouard, M. A.; Blom, M.; Bondu, F.; Bonelli, L.; Bonnand, R.; Boschi, V.; Bosi, L.; Bouhou, B.; Braccini, S.; Bradaschia, C.; Branchesi, M.; Briant, T.; Brillet, A.; Brisson, V.; Bulik, T.; Bulten, H. J.; Buskulic, D.; Buy, C.; Cagnoli, G.; Calloni, E.; Canuel, B.; Carbognani, F.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cesarini, E.; Chaibi, O.; Chassande-Mottin, E.; Chincarini, A.; Chiummo, A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, A.; Corsi, A.; Coulon, J.-P.; Cuoco, E.; D'Antonio, S.; Dattilo, V.; Davier, M.; Day, R.; De Rosa, R.; Debreczeni, G.; Del Pozzo, W.; del Prete, M.; Di Fiore, L.; Di Lieto, A.; Emilio, M. Di Paolo; Virgilio, A. Di; Dietz, A.; Drago, M.; Endr?czi, G.; Fafone, V.; Ferrante, I.; Fidecaro, F.; Fiori, I.; Flaminio, R.; Forte, L. A.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Galimberti, M.; Gammaitoni, L.; Garufi, F.; Gáspár, M. E.; Gemme, G.; Genin, E.; Gennai, A.; Giazotto, A.; Gouaty, R.; Granata, M.; Greverie, C.; Guidi, G. M.; Hayau, J.-F.; Heidmann, A.; Heitmann, H.; Hello, P.; Jaranowski, P.; Kowalska, I.; Królak, A.; Leroy, N.; Letendre, N.; Li, T. G. F.; Liguori, N.; Lorenzini, M.; Loriette, V.; Losurdo, G.; Majorana, E.; Maksimovic, I.; Man, N.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marque, J.; Martelli, F.; Masserot, A.; Michel, C.; Milano, L.; Minenkov, Y.; Mohan, M.; Morgado, N.; Morgia, A.; Mours, B.; Naticchioni, L.; Nocera, F.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Paoletti, F.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Persichetti, G.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Poggiani, R.; Prato, M.; Prodi, G. A.; Punturo, M.; Puppo, P.; Rabeling, D. S.; Rácz, I.; Rapagnani, P.; Re, V.; Regimbau, T.; Ricci, F.; Robinet, F.; Rocchi, A.; Rolland, L.; Romano, R.; Rosi?ska, D.; Ruggi, P.; Sassolas, B.; Sentenac, D.; Sperandio, L.; Sturani, R.; Swinkels, B.; Tacca, M.; Taffarello, L.; Toncelli, A.; Tonelli, M.; Torre, O.; Tournefier, E.; Travasso, F.; Vajente, G.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; Vasuth, M.; Vavoulidis, M.; Vedovato, G.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinet, J.-Y.; Vitale, S.; Vocca, H.; Ward, R. L.; Was, M.; Yvert, M.; Zadro?ny, A.; Zendri, J.-P.

    2011-09-01

    We report an application of Kalman filtering to the inverted pendulum (IP) of the Virgo gravitational wave interferometer. Using subspace method system identification techniques, we calculated a linear mechanical model of Virgo IP from experimental transfer functions. We then developed a Kalman filter, based on the obtained state space representation, that estimates from open loop time domain data, the state variables of the system. This allows the observation (and eventually control) of every resonance mode of the IP mechanical structure independently.

  11. Substructure coupling in the frequency domain

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Frequency domain analysis was found to be a suitable method for determining the transient response of systems subjected to a wide variety of loads. However, since a large number of calculations are performed within the discrete frequency loop, the method loses it computational efficiency if the loads must be represented by a large number of discrete frequencies. It was also discovered that substructure coupling in the frequency domain work particularly well for analyzing structural system with a small number of interface and loaded degrees of freedom. It was discovered that substructure coupling in the frequency domain can lead to an efficient method of obtaining natural frequencies of undamped structures. It was also found that the damped natural frequencies of a system may be determined using frequency domain techniques.

  12. Stellar Illumination

    NSDL National Science Digital Library

    This is a lesson about discovering distant planets using an Earth-based observing technique called stellar occultation. Learners will explore how a stellar occultation occurs, how planetary atmospheres can be discovered, and how planetary diameters can be determined using actual light curves from stellar occultation events. Includes adaptations for younger students and those with visual impairments.

  13. Direct Detection of Cold Dark Matter Substructure

    Microsoft Academic Search

    N. Dalal; C. S. Kochanek

    2002-01-01

    We devise a method to measure the abundance of satellite halos in gravitational lens galaxies and apply our method to a sample of seven lens systems. After using Monte Carlo simulations to verify the method, we find that substructure comprises fsat=0.02 (median, 0.006

  14. Can Photoionization Squelching Resolve the Substructure Crisis?

    Microsoft Academic Search

    Rachel S. Somerville

    2002-01-01

    Cold Dark Matter theory predicts that the Local Group should contain many more dwarf-sized objects than the observed number of dwarf galaxies — the so-called sub-structure problem. We investigate whether the suppression of star formation in these small objects due to the presence of a photoionizing background can resolve the problem. We make use of results from recent hydrodynamic simulations

  15. Dark Matter Substructure in Lensing Galaxies

    E-print Network

    Masashi Chiba; Takeo Minezaki; Kaiki T. Inoue; Nobunari Kashikawa; Hirokazu Kataza; Hajime Sugai

    2008-04-02

    To set useful limits on the abundance of small-scale dark matter halos (subhalos) in a galaxy scale, we have carried out mid-infrared imaging and integral-field spectroscopy for a sample of quadruple lens systems showing anomalous flux ratios. These observations using Subaru have been successful for distinguishing millilensing by subhalos from microlensing by stars. Current status for our lensing analysis of dark matter substructure is reported.

  16. Gemini/GMOS Spectra of Globular Clusters in the Virgo Giant Elliptical NGC 4649

    E-print Network

    Michael Pierce; Terry Bridges; Duncan A. Forbes; Robert Proctor; Michael A. Beasley; Karl Gebhardt; Favio Raul Faifer; Juan Carlos Forte; Stephen E. Zepf; Ray Sharples; David A. Hanes

    2006-01-24

    NGC 4649 (M60) is one of a handful of giant Virgo ellipticals. We have obtained Gemini/GMOS spectra for 38 GCs associated with this galaxy. Applying the multi-index chi^2 minimisation technique of Proctor & Sansom (2002) with the single stellar population models of Thomas, Maraston & Korn (2004) we derive ages, metallicities and alpha-element abundance ratios. We find several young (2--3 Gyr old) super-solar metallicity GCs, while the majority are old (>10 Gyrs), spanning a range of metallicities from solar to [Z/H]=-2. At least two of these young GCs are at large projected radii of 17-20 kpc. The galaxy itself shows no obvious signs of a recent starburst, interaction or merger. A trend of decreasing alpha-element ratio with increasing metallicity is found.

  17. Prospects for observing dynamically formed stellar mass black hole binaries with gravitational waves

    NASA Astrophysics Data System (ADS)

    Benacquista, Matthew

    2015-04-01

    Stellar mass black hole binaries are expected to be produced through dynamical interactions within globular clusters. Dynamically formed black hole binaries are likely to have higher chirp masses than binaries formed in the field. We show that these systems are observable with space-based gravitational wave detectors at extragalactic distance as far as the the Virgo cluster.

  18. Analytic Cross Sections for Substructure Lensing

    E-print Network

    Charles R. Keeton

    2002-10-28

    The magnifications of the images in a strong gravitational lens system are sensitive to small mass clumps in the lens potential; this effect has been used to infer the amount of substructure in galaxy dark matter halos. I study the theory of substructure lensing to identify important general features, and to compute analytic cross sections that will facilitate further theoretical studies. I show that the problem of a clump anywhere along the line of sight to a lens can be mapped onto an equivalent problem of a clump in a simple convergence and shear field; clumps at arbitrary redshifts are therefore not hard to handle in calculations. For clumps modeled as singular isothermal spheres (SIS), I derive simple analytic estimates of the cross section for magnification perturbations of a given strength. The results yield two interesting conceptual points. First, lensed images with positive parity are always made brighter by SIS clumps; images with negative parity can be brightened but are much more likely to be dimmed. Second, the clumps need not lie within the lens galaxy; they can be moved in redshift by several tenths and still have a significant lensing effect. Isolated small halos are expected to be common in hierarchical structure formation models, but it is not yet known whether they are abundant enough compared with clumps inside lens galaxies to affect the interpretation of substructure lensing.

  19. Composite Octet Searches with Jet Substructure

    SciTech Connect

    Bai, Yang; /SLAC; Shelton, Jessie; /Yale U.

    2012-02-14

    Many new physics models with strongly interacting sectors predict a mass hierarchy between the lightest vector meson and the lightest pseudoscalar mesons. We examine the power of jet substructure tools to extend the 7 TeV LHC sensitivity to these new states for the case of QCD octet mesons, considering both two gluon and two b-jet decay modes for the pseudoscalar mesons. We develop both a simple dijet search using only the jet mass and a more sophisticated jet substructure analysis, both of which can discover the composite octets in a dijet-like signature. The reach depends on the mass hierarchy between the vector and pseudoscalar mesons. We find that for the pseudoscalar-to-vector meson mass ratio below approximately 0.2 the simple jet mass analysis provides the best discovery limit; for a ratio between 0.2 and the QCD-like value of 0.3, the sophisticated jet substructure analysis has the best discovery potential; for a ratio above approximately 0.3, the standard four-jet analysis is more suitable.

  20. Design sensitivity analysis of boundary element substructures

    NASA Technical Reports Server (NTRS)

    Kane, James H.; Saigal, Sunil; Gallagher, Richard H.

    1989-01-01

    The ability to reduce or condense a three-dimensional model exactly, and then iterate on this reduced size model representing the parts of the design that are allowed to change in an optimization loop is discussed. The discussion presents the results obtained from an ongoing research effort to exploit the concept of substructuring within the structural shape optimization context using a Boundary Element Analysis (BEA) formulation. The first part contains a formulation for the exact condensation of portions of the overall boundary element model designated as substructures. The use of reduced boundary element models in shape optimization requires that structural sensitivity analysis can be performed. A reduced sensitivity analysis formulation is then presented that allows for the calculation of structural response sensitivities of both the substructured (reduced) and unsubstructured parts of the model. It is shown that this approach produces significant computational economy in the design sensitivity analysis and reanalysis process by facilitating the block triangular factorization and forward reduction and backward substitution of smaller matrices. The implementatior of this formulation is discussed and timings and accuracies of representative test cases presented.

  1. A NEW CHANNEL FOR DETECTING DARK MATTER SUBSTRUCTURE IN GALAXIES: GRAVITATIONAL LENS TIME DELAYS

    SciTech Connect

    Keeton, Charles R. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Moustakas, Leonidas A. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 169-327, Pasadena, CA 91109 (United States)

    2009-07-10

    We show that dark matter substructure in galaxy-scale halos perturbs the time delays between images in strong gravitational lens systems. The variance of the effect depends on the subhalo mass function, scaling as the product of the substructure mass fraction, and a characteristic mass of subhalos (namely (m {sup 2})/(m)). Time delay perturbations therefore complement gravitational lens flux ratio anomalies and astrometric perturbations by measuring a different moment of the subhalo mass function. Unlike flux ratio anomalies, 'time delay millilensing' is unaffected by dust extinction or stellar microlensing in the lens galaxy. Furthermore, we show that time delay ratios are immune to the radial profile degeneracy that usually plagues lens modeling. We lay out a mathematical theory of time delay perturbations and find it to be tractable and attractive. We predict that in 'cusp' lenses with close triplets of images, substructure may change the arrival-time order of the images (compared with smooth models). We discuss the possibility that this effect has already been observed in RX J1131-1231.

  2. A New Channel for Detecting Dark Matter Substructure in Galaxies: Gravitational Lens Time Delays

    E-print Network

    Charles R. Keeton; Leonidas A. Moustakas

    2009-05-26

    We show that dark matter substructure in galaxy-scale halos perturbs the time delays between images in strong gravitational lens systems. The variance of the effect depends on the subhalo mass function, scaling as the product of the substructure mass fraction and a characteristic mass of subhalos (namely /). Time delay perturbations therefore complement gravitational lens flux ratio anomalies and astrometric perturbations by measuring a different moment of the subhalo mass function. Unlike flux ratio anomalies, "time delay millilensing" is unaffected by dust extinction or stellar microlensing in the lens galaxy. Furthermore, we show that time delay ratios are immune to the radial profile degeneracy that usually plagues lens modeling. We lay out a mathematical theory of time delay perturbations and find it to be tractable and attractive. We predict that in "cusp" lenses with close triplets of images, substructure may change the arrival-time order of the images (compared with smooth models). We discuss the possibility that this effect has already been observed in RX J1131-1231.

  3. Grain Growth and Sub-Structure in Protoplanetary Disks

    NASA Astrophysics Data System (ADS)

    Wilner, David J.; Chandler, C.; Andrews, S.; Calvet, N.; Carpenter, J.; Corder, S.; Deller, A.; Dullemond, C.; Greaves, J.; Henning, T.; Isella, A.; Lazio, J.; Linz, H.; Mundy, L.; Perez, L.; Ricci, L.; Sargent, A.; Storm, S.; Testi, L.

    2011-01-01

    I will describe the Disks@EVLA program to survey protoplanetary disks around pre-main-sequence stars in the nearest star forming regions (Taurus, Ophiuchus, TW Hya) to investigate the millimeter/centimeter emission from large dust particles, the last observable link in the chain from sub-micron interstellar grains to planets. At these long wavelengths, dust emission is optically thin and probes the entire disk volume, including the innermost regions that become opaque in the submillimeter. Taking advantage of the new capabilities of the EVLA, we are using a staged approach that starts with photometry of approximately 60 disk systems, currently underway, to be followed by higher resolution imaging of smaller subsets of the brighter sources, ultimately reaching scales comparable to the orbital radius of Jupiter. Key goals include (1) determining the prevalence and location of grain growth to centimeter-sized "pebbles" from spectral indices, and any dependencies on stellar properties and environment, and (2) detecting physical sub-structures such as holes and gaps indicative of disk evolution and planet formation.

  4. Extraction of Substructural Flexibility from Global Frequencies and Mode Shapes

    SciTech Connect

    Alvin, K.F.; Park, K.C.

    1999-07-16

    A computational procedure for extracting substructure-by-substructure flexibility properties from global modal parameters is presented. The present procedure consists of two key features: an element-based direct flexibility method which uniquely determines the global flexibility without resorting to case-dependent redundancy selections; and, the projection of cinematically inadmissible modes that are contained in the iterated substructural matrices. The direct flexibility method is used as the basis of an inverse problem, whose goal is to determine substructural flexibilities given the global flexibility, geometrically-determined substructural rigid-body modes, and the local-to-global assembly operators. The resulting procedure, given accurate global flexibility, extracts the exact element-by-element substructural flexibilities for determinate structures. For indeterminate structures, the accuracy depends on the iteration tolerance limits. The procedure is illustrated using both simple and complex numerical examples, and appears to be effective for structural applications such as damage localization and finite element model reconciliation.

  5. The Next Generation Virgo Cluster Survey. VIII. The Spatial Distribution of Globular Clusters in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Durrell, Patrick R.; Côté, Patrick; Peng, Eric W.; Blakeslee, John P.; Ferrarese, Laura; Mihos, J. Christopher; Puzia, Thomas H.; Lançon, Ariane; Liu, Chengze; Zhang, Hongxin; Cuillandre, Jean-Charles; McConnachie, Alan; Jordán, Andrés; Accetta, Katharine; Boissier, Samuel; Boselli, Alessandro; Courteau, Stéphane; Duc, Pierre-Alain; Emsellem, Eric; Gwyn, Stephen; Mei, Simona; Taylor, James E.

    2014-10-01

    We report on a large-scale study of the distribution of globular clusters (GCs) throughout the Virgo cluster, based on photometry from the Next Generation Virgo Cluster Survey (NGVS), a large imaging survey covering Virgo's primary subclusters (Virgo A = M87 and Virgo B = M49) out to their virial radii. Using the g^{\\prime }_{o}, (g' - i') o color-magnitude diagram of unresolved and marginally resolved sources within the NGVS, we have constructed two-dimensional maps of the (irregular) GC distribution over 100 deg2 to a depth of g^{\\prime }_{o} = 24. We present the clearest evidence to date showing the difference in concentration between red and blue GCs over the full extent of the cluster, where the red (more metal-rich) GCs are largely located around the massive early-type galaxies in Virgo, while the blue (metal-poor) GCs have a much more extended spatial distribution with significant populations still present beyond 83' (~215 kpc) along the major axes of both M49 and M87. A comparison of our GC maps to the diffuse light in the outermost regions of M49 and M87 show remarkable agreement in the shape, ellipticity, and boxiness of both luminous systems. We also find evidence for spatial enhancements of GCs surrounding M87 that may be indicative of recent interactions or an ongoing merger history. We compare the GC map to that of the locations of Virgo galaxies and the X-ray intracluster gas, and find generally good agreement between these various baryonic structures. We calculate the Virgo cluster contains a total population of N GC = 67, 300 ± 14, 400, of which 35% are located in M87 and M49 alone. For the first time, we compute a cluster-wide specific frequency S N, CL = 2.8 ± 0.7, after correcting for Virgo's diffuse light. We also find a GC-to-baryonic mass fraction epsilon b = 5.7 ± 1.1 × 10-4 and a GC-to-total cluster mass formation efficiency epsilon t = 2.9 ± 0.5 × 10-5, the latter values slightly lower than but consistent with those derived for individual galactic halos. Taken as a whole, our results show that the production of the complex structures in the unrelaxed Virgo cluster core (including the production of the diffuse intracluster light) is an ongoing and continuing process.

  6. Chemical fingerprinting and chemical analysis of galactic halo substructure

    NASA Astrophysics Data System (ADS)

    Chou, Mei-Yin

    It is now known that the halo of the Milky Way was formed from the accretion of dwarf galaxies, which have left behind long-lived, dynamical halo substructure. One can investigate these substructures through "Galactic archaeology" to learn the nature of these accreted subhalo fragments. In particular, the chemistry of halo substructure allows us to glean insights into the metallicities and star formation histories of the absorbed progenitors, and to identify distinct Galactic stellar populations with specific accreted bodies. In this thesis we present an investigation of the chemical abundance patterns of halo substructures using high-resolution spectroscopic measurements. In particular, we study the abundances of the alpha-like element titanium (Ti) and the s-process elements yttrium (Y) and lanthanum (La) for M giant candidates of (a) the Sagittarius (Sgr) dwarf spheroidal (dSph) + tidal tail system, (b) the Galactic Anticenter Stellar Structure (GASS), also known as the Monoceros Ring, and (c) the Triangulum- Andromeda (TriAnd) Star Cloud. Targets are pre-selected to be likely members of each of these systems on the basis of both three-dimensional position and radial velocity. As expected, the majority of the Sgr stars show peculiar abundance patterns compared to those of nominal Milky Way stars, but as a group the stars form a coherent picture of chemical enrichment of the Sgr dSph from [Fe/H] = -1.4 to solar abundance. The overall [Ti/Fe], [Y/Fe], [La/Fe] and [La/Y] patterns with [Fe/H] of the Sgr stream plus Sgr core do, for the most part, resemble those seen in the Large Magellanic Cloud (LMC) and other current Milky Way satellites, only shifted by Delta[Fe/H]˜+0.4 from the LMC and by ˜+1 dex from Milky Way dSph satellites; these relative shifts reflect the faster and/or more efficient chemical evolution of Sgr compared to the other satellites, and show that Sgr has had an enrichment history more like the LMC than the dSph satellites. By tracking the evolution of the abundance patterns along the Sgr stream we can follow the time variation of the chemical make-up of dSph stars donated to the Galactic halo by Sgr. This evolution demonstrates that while the bulk of the stars currently in the Sgr dSph are quite unlike those of the Galactic halo, an increasing number of stars farther along the Sgr stream have abundances like Milky Way halo stars, a trend that shows clearly how the Galactic halo could have been contributed by present day satellite galaxies even if the present chemistry of those satellites is now different from typical halo field stars. We also analyze the chemical abundances of a moving group of M giants among the Sgr leading arm stars at the North Galactic Cap, but having radial velocities unlike the infalling Sgr leading arm debris there. Through use of "chemical fingerprinting", we conclude that these mostly receding northern hemisphere M giants also are Sgr stars, likely trailing arm debris overlapping the Sgr leading arm in the north. We also apply "chemical fingerprinting" to the GASS/Monoceros Ring and TriAnd Star Cloud, to explore the origins of the two systems and the hypothesized connections between them. GASS has been debated either to originate from the Galactic accretion of a satellite creating a tidal stream, or as a part of the disk, dynamically induced through warping or resonances, etc. Our exploration shows that GASS is indeed made of stars from a dSph, and that it is distinct in chemistry from outer disk stars. And whereas the TriAnd Star Cloud has been assumed to come from the tidal disruption of the same accreted Milky Way satellite as the GASS/Monoceros Ring, our comparison of the abundance patterns in Monoceros and TriAnd M giants suggests that the TriAnd Star Cloud is likely an independent halo substructure unrelated to Monoceros.

  7. Fragmented substructure and crack formation in low-alloy steel

    SciTech Connect

    Kozlov, E.V.; Veter, V.V.; Popova, N.A.; Ignatenko, L.N.

    1995-02-01

    In the work the authors studied the substructure of 30KhGSA steel after rolling. A relation has been established between the macrofracture of the specimen and its dislocation substructure. The formation and completion of a fragmented substructure with precipitation of carbides at the junctions of fragments during rolling indicate that the lifetime is close to exhaustion. Annealing that partially or completely destroys the fragmented substructure causes microcracks to collapse and heal, eliminates the microcrack nucleation sites, eliminates trajectories of facilitated microcrack growth, which follow subboundaries, and restores the plasticity of the steel.

  8. The Early-type Dwarf-to-Giant Ratio and Substructure in the Coma Cluster

    E-print Network

    Jeff Secker; William E. Harris

    1996-05-15

    We have obtained new CCD photometry for a sample of $\\simeq 800$ early-type galaxies (dwarf and giant ellipticals) in the central 700 arcmin$^2$ of the Coma cluster, complete in color and in magnitude to $R = 22.5$ mag ($M_R \\simeq -12$ mag for $H_0 = 86$ km/sec/Mpc). The composite luminosity function for all galaxies in the cluster core (excluding NGC 4874 and NGC 4889) is modeled as the sum of a Gaussian distribution for the giant galaxies and a Schechter function for the dwarf elliptical galaxies. We determine that the early-type dwarf-to-giant ratio (EDGR) for Coma is identical to that measured for the less rich Virgo cluster; i.e., the EDGR does not increase as predicted by the EDGR-richness correlation. We postulate that the presence of substructure is an important factor in determining the cluster's EDGR; that is, the EDGR for Coma is consistent with the Coma cluster being built up from the merger of multiple less-rich galaxy clusters.

  9. Optical metrology tools for the Virgo projet

    NASA Astrophysics Data System (ADS)

    Loriette, V.

    For more than thirty years the search for gravitationnal waves, predicted by Einstein's relativistic theory of gravitation, has been an intense research field in experimental as well as theoretical physics. Today, with the constant advance of technology in optics, lasers, data analysis and processing, ... a promising way of directly detecting gravitationnal waves with earth-based instruments is optical interferometry. Before the end of this century many experiments will be carried on in Australia, Europe, Japan and the United States to detect the passage of a gravitationnal wave through giant Michelson-type interferometers. The effects predicted are so small, (a gravitationnal wave changes the length of three kilometer long arms by one thousandth of a fermi) that the need for “perfect” optical components is a key to the success of these experiments. Still a few years ago it would have been impossible to make optical components that would satisfy the required specifications for such interferometric detectors. For nearly ten years constant R&D efforts in optical coating manufacturing, optical material fabrication and optical metrology, allow us today to make such components. This text is intended to describe the field of optical metrology as it is needed for the testing of optical parts having performances far beyond than everything previously made. The first chapter is an introduction to gravitationnal waves, their sources and their effects on detectors. Starting by newtonian mechanics we jump rapidly to the general theory of relativity and describe particular solutions of Einstein's equations in the case of weak gravitationnal fields, which are periodic perturbations of the space-time metric in the form of plane waves, the so-called gravitationnal waves. We present various candidate sources, terrestrial and extra-terrestrial and give a short description of the two families of detectors: resonnant bars and optical interferometers. The second part of this chapter is a description of the various optical components that have to be manufactured and tested for Virgo. The next sections are dedicated to the description of various metrology instruments. In chapter 2 we focus on absorption of light in multilayer coatings. The sensitivity of interferometric detectors is degraded by this loss process, not only because it decreases the laser beam power, but also and chiefly because thermo-elastic deformations and changes of the indexes of refraction modify the beam profile. Optical coatings have now reached an absorption level lower than at m. We present a method based on the mirage effect, i.e. the deflexion of light by an index of refraction gradient induced by non homogeneous heating. This “mirage bench” has a sensitivity better than 10^{-8}. We start by a discussion of the approximations that are useful to simplify the problem, we then derive the equation that give the signal amplitude versus the absorption factor. Afterwards we describe the instrument and give a few results with home made Virgo mirrors as well as commercial samples. In the following chapter we discuss the problem of measuring reflexion factors. We focus on two particular problems, the first one is common, it is to measure high (higher than 0.9999) reflexion factors by the use of Fabry-Perot cavities. We present various possible schemes and we detail a particular one which seems to be the easiest to implement. We use a pulsed laser source and measure the average reflexion factor of the two Fabry-Perot mirrors by studying the pulse shape modification after transmission by the cavity. We estimate the sensitivity of this intrument to 10^{-6}. The second problem is a less common one and is to evaluate the relative homogeneity of reflexion factors on large components. Because inhomogeneities of this parameter will degrade the sensitivity of Virgo by coupling various modes of the laser beam with the fundamental one, homogeneity higher than 1{-}10^{-4} is required. We propose a simple scheme and describe a bench built following this scheme. This bench, being

  10. Calculation of substructural analysis weights using a genetic algorithm.

    PubMed

    Holliday, John D; Sani, Nor; Willett, Peter

    2015-02-23

    This work describes a genetic algorithm for the calculation of substructural analysis for use in ligand-based virtual screening. The algorithm is simple in concept and effective in operation, with simulated virtual screening experiments using the MDDR and WOMBAT data sets showing it to be superior to substructural analysis weights based on a naive Bayesian classifier. PMID:25615712

  11. Lensing Optical Depths for Substructure and Isolated Dark Matter Halos

    Microsoft Academic Search

    Jacqueline Chen; Andrey V. Kravtsov; Charles R. Keeton

    2003-01-01

    Multiply imaged quasar lenses can be used to constrain the substructure mass fraction in galaxy-sized dark matter halos via anomalous flux ratios in lensed images. The flux ratios, however, can be affected both by the substructure in the lens halo and by isolated small-mass halos along the entire line of sight to the lensed source. While lensing by dark matter

  12. Substructure Discovery Using Minimum Description Length Principle and Background Knowledge

    Microsoft Academic Search

    Surnjani Djoko

    1994-01-01

    Discovering conceptually interesting and repetitive substruc- tures in a structural data improves the ability to interpret and compress the data. The substructures are evaluated by their ability to describe and compress the original data set using the domain's background knowledge and the minimum description length (MDL) of the data. Once discovered, the substructure concept is used to simplify the data

  13. Matter Substructure in High Redshift Clusters of Galaxies

    NASA Astrophysics Data System (ADS)

    Huwe, Paul M.

    2012-05-01

    We investigate substructure via weak gravitational lensing shear measurements of high redshift clusters with existing ACS imaging. We use a principal component analysis technique to characterize the PSF ellipticity pattern and a variable aperture filter to characterize the level of substructure. This work supported by the NASA Rhode Island Space Grant program.

  14. Substructuring and poroelastic modelling of the intervertebral disc.

    PubMed

    Swider, P; Pédrono, A; Ambard, D; Accadbled, F; Sales de Gauzy, J

    2010-05-01

    We proposed a substructure technique to predict the time-dependant response of biological tissue within the framework of a finite element resolution. Theoretical considerations in poroelasticity preceded the calculation of the sub-structured poroelastic matrix. The transient response was obtained using an exponential fitting method. We computed the creep response of an MRI 3D reconstructed L(5)-S(1) intervertebral disc of a scoliotic spine. The FE model was reduced from 10,000 degrees of freedom for the full 3D disc to only 40 degrees of freedom for the sub-structured model defined by 10 nodes attached to junction nodes located on both lower and upper surfaces of the disc. Comparisons of displacement fields were made between the full poroelastic FE model and the sub-structured model in three different loading conditions: compression, offset compression and torsion. Discrepancies in displacement were lower than 10% for the first time steps when time-dependant events were significant. The substructuring technique provided an exact solution in quasi-static behavior after pressure relaxation. Couplings between vertical and transversal displacements predicted by the reference FE model were well stored by the sub-structured model despite the drastic reduction of degrees of freedom. Finally, we demonstrated that substructuring was very efficient to reduce the size of numerical models while respecting the time-dependant behavior of the structure. This result highlighted the potential interest of substructure techniques in large-scale models of musculoskeletal structures. PMID:20170917

  15. Galactic Substructure and Energetic Neutrinos from the Sun and Earth

    Microsoft Academic Search

    Savvas M. Koushiappas; Marc Kamionkowski

    2009-01-01

    We consider the effects of Galactic substructure on energetic neutrinos from annihilation of weakly interacting massive particles that have been captured by the Sun and Earth. Substructure gives rise to a time-varying capture rate and thus to time variation in the annihilation rate and resulting energetic-neutrino flux. However, there may be a time lag between the capture and annihilation rates.

  16. A Transient Response Method for Linear Coupled Substructures

    NASA Technical Reports Server (NTRS)

    Admire, J. R.; Brunty, J. A.

    1989-01-01

    A method is presented for determining the transient response of a discrete coordinate model of a linear structural system composed of substructures. The method is applicable to systems consisting of any number of substructures, both determinate and indeterminate interface boundaries, and any topological arrangement of the substructures. The method is simple to implement from a computational point of view because the equations of motion of each of the substructures are solved independently, and the interface boundary compatibility conditions are enforced at each integration time step by a matrix multiplication. The method is demonstrated for a structural system consisting of two beam segments and acted upon by a time dependent force. The numerical results from the demonstration problem validates the accuracy of the method. The application of this method to structural systems with changing interface boundary conditions between substructures is discussed.

  17. Rapid and automated substructure solution by Shake-and-Bake.

    PubMed

    Xu, Hongliang; Weeks, Charles M

    2008-02-01

    Direct methods of phase determination have played an important role in determining heavy-atom substructures from difference amplitudes of native-derivative crystal pairs or crystals containing anomalously scattering atoms. The minimal principle-based Shake-and-Bake procedure is one of the most successful direct methods for heavy-atom substructure determination. The computer program SnB, which implements the Shake-and-Bake procedure and is part of the protein structure-determination package BnP, has recently been optimized for rapid and automated substructure determination. Specifically, SnB has been upgraded with (i) a newly developed statistical minimal function for higher success rates, (ii) an optimal FFT grid size for dramatic cost-effectiveness improvement, (iii) a dynamic figure of merit for automatic substructure-solution detection and (iv) a strategy of alternation of anomalous differences with isomorphous dispersive differences for virtually guaranteed substructure solution. PMID:18219117

  18. COLOR-MAGNITUDE RELATIONS OF EARLY-TYPE DWARF GALAXIES IN THE VIRGO CLUSTER: AN ULTRAVIOLET PERSPECTIVE

    SciTech Connect

    Kim, Suk; Rey, Soo-Chang [Department of Astronomy and Space Science, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Lisker, Thorsten [Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg (ZAH), Moenchhofstrasse 12-14, D-69120 Heidelberg (Germany); Sohn, Sangmo Tony, E-mail: s_kim@cnu.ac.k, E-mail: screy@cnu.ac.k [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2010-09-20

    We present ultraviolet (UV) color-magnitude relations (CMRs) of early-type dwarf galaxies in the Virgo cluster, based on Galaxy Evolution Explorer (GALEX) UV and Sloan Digital Sky Survey (SDSS) optical imaging data. We find that dwarf lenticular galaxies (dS0s), including peculiar dwarf elliptical galaxies (dEs) with disk substructures and blue centers, show a surprisingly distinct and tight locus separated from that of ordinary dEs, which is not clearly seen in previous CMRs. The dS0s in UV CMRs follow a steeper sequence than dEs and show bluer UV-optical color at a given magnitude. We also find that the UV CMRs of dEs in the outer cluster region are slightly steeper than that of their counterparts in the inner region, due to the existence of faint, blue dEs in the outer region. We explore the observed CMRs with population models of a luminosity-dependent delayed exponential star formation history. We confirm that the feature of delayed star formation of early-type dwarf galaxies in the Virgo cluster is strongly correlated with their morphology and environment. The observed CMR of dS0s is well matched by models with relatively long delayed star formation. Our results suggest that dS0s are most likely transitional objects at the stage of subsequent transformation of late-type progenitors to ordinary red dEs in the cluster environment. In any case, UV photometry provides a powerful tool to disentangle the diverse subpopulations of early-type dwarf galaxies and uncover their evolutionary histories.

  19. Late-Type Dwarf Galaxies in the Virgo Cluster: II. Star Formation Properties

    E-print Network

    Elchanan Almoznino; Noah Brosch

    1998-04-22

    We study star-formation-inducing mechanisms in galaxies through multi- wavelength measurements of a sample of dwarf galaxies in the Virgo cluster described in paper I. Our main goal is to test how star formation inducing mechanisms depend on several parameters of the galaxies, such as morphological type and hydrogen content. We derive the star formation rate and star formation histories of the galaxies, and check their dependence on other parameters. Comparison of the sample galaxies with population synthesis models shows that these objects have significantly lower metallicity than the Solar value. The colors can generally be explained as a combination of two different stellar populations: a young (3--20 Myr) population which represents the stars currently forming, and an older (0.1--1 Gyr) population of previous stellar generations. This is consistent with the explanation that star formation in this type of objects takes place in short bursts followed by long quiescent periods. No significant relation is found between the star formation properties of the sample galaxies and their hydrogen content. Apparently, when star formation occurs in bursts, other parameters influence the star formation properties more significantly than the amount of hydrogen. No correlation is found between the projected Virgocentric distance and the rate of star formation in the galaxies.

  20. Measurement of the seismic attenuation performance of the VIRGO Superattenuator

    Microsoft Academic Search

    S. Braccini; L. Barsotti; C. Bradaschia; G. Cella; A. Di Virgilio; I. Ferrante; F. Fidecaro; I. Fiori; F. Frasconi; A. Gennai; A. Giazotto; F. Paoletti; R. Passaquieti; D. Passuello; R. Poggiani; E. Campagna; G. Guidi; G. Losurdo; F. Martelli; M. Mazzoni; B. Perniola; F. Piergiovanni; R. Stanga; F. Vetrano; A. Viceré; L. Brocco; S. Frasca; E. Majorana; A. Pai; C. Palomba; P. Puppo; P. Rapagnani; F. Ricci; G. Ballardin; R. Barillé; R. Cavalieri; E. Cuoco; V. Dattilo; D. Enard; R. Flaminio; A. Freise; S. Hebri; L. Holloway; P. La Penna; M. Loupias; J. Marque; C. Moins; A. Pasqualetti; P. Ruggi; R. Taddei; Z. Zhang; F. Acernese; S. Avino; F. Barone; E. Calloni; R. De Rosa; L. Di Fiore; A. Eleuteri; L. Giordano; L. Milano; S. Pardi; K. Qipiani; I. Ricciardi; G. Russo; S. Solimeno; D. Babusci; G. Giordano; P. Amico; L. Bosi; L. Gammaitoni; F. Marchesoni; M. Punturo; F. Travasso; H. Vocca; C. Boccara; J. Moreau; V. Loriette; V. Reita; J. M. Mackowski; N. Morgado; L. Pinard; A. Remillieux; M. Barsuglia; M. A. Bizouard; V. Brisson; F. Cavalier; A. C. Clapson; M. Davier; P. Hello; S. Krecklbergh; F. Beauville; D. Buskulic; R. Gouaty; D. Grosjean; F. Marion; A. Masserot; B. Mours; E. Tournefier; D. Tombolato; D. Verkindt; M. Yvert; S. Aoudia; F. Bondu; A. Brillet; E. Chassande-Mottin; F. Cleva; J. P. Coulon; B. Dujardin; J. D. Fournier; H. Heitmann; C. N. Man; A. Spallicci; J. Y. Vinet

    2005-01-01

    The gravitational wave detector VIRGO aims at extending the detection band down to a few Hertz by isolating the mirrors of the interferometer from seismic noise. This result is achieved by hanging each mirror through an elastic suspension (Superattenuator), designed to filter mechanical vibrations in all the degrees of freedom. An experimental upper limit of the mirror residual seismic noise

  1. Length Sensing and Control in the Virgo Gravitational Wave Interferometer

    Microsoft Academic Search

    Fausto Acernese; P. Amico; M. Al-Shourbagy; S. Aoudia; S. Avinok; D. Babusci; G. Ballardin; R. Barille; Fabrizio Barone; L. Barsotti; M. A. Bizouardyy; F. Beauville; M. A. Bizouard; C. Bradaschia; F. Bondu; L. Bosi; S. Braccini; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; E. Calloni; E. Campagna; F. Cavalier; R. Cavalieri; G. Cella; E. Chassande-Mottin; C. Corda; A.-C. Clapson; F. Cleva; J.-P. Coulon; Elena Cuoco; V. Dattilo; M. Davier; Rosario De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; Antonio Eleuteri; D. Enard; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; S. Frasca; F. Frasconi; A. Freise; L. Gammaitoni; A. Gennai; A. Giazotto; G. Giordano; L. Giordano; R. Gouaty; D. Grosjean; G. Guidi; S. Hebri; H. Heitmann; P. Hello; L. Holloway; S. Kreckelbergh; Paolo La Penna; Vincent Loriette; M. Loupias; Giovanni Losurdo; J.-M. Mackowski; E. Majorana; C. N. Man; Marco Mantovani; Fabio Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; Massimo Mazzoni; Leopoldo Milano; C. Moins; J. Moreau; N. Morgado; B. Mours; A. Pai; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; B. Perniola; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; P. Ruggi; Giovanni Russo; S. Solimeno; A. Spallicci; Ruggero Stanga; R. Taddei; D. Tombolato; Mauro Tonelli; Alessandra Toncelli; E. Tournefier; F. Travasso; G. Vajente; D. Verkindt; F. Vetrano; Andrea Vicerè; J.-Y. Vinet; Helios Vocca; M. Yvert; Z. Zhang

    2006-01-01

    The gravitational wave detector Virgo is presently being commissioned. A significant part of last year was spent in setting up the cavity length control system. This work was carried out with steps of increasing complexity: locking a simple Fabry- Perot cavity, then a Michelson interferometer with Fabry-Perot cavities in both arms, and finally recycling the light beam into the interferometer.

  2. Measurements of Superattenuator seismic isolation by Virgo interferometer

    Microsoft Academic Search

    F. Acernese; F. Antonucci; S. Aoudia; K. G. Arun; P. Astone; G. Ballardin; F. Barone; M. Barsuglia; Th. S. Bauer; M. G. Beker; S. Bigotta; S. Birindelli; M. Bitossi; M. A. Bizouard; M. Blom; C. Boccara; F. Bondu; L. Bonelli; L. Bosi; S. Braccini; C. Bradaschia; A. Brillet; V. Brisson; R. Budzynski; T. Bulik; H. J. Bulten; D. Buskulic; G. Cagnoli; E. Calloni; E. Campagna; B. Canuel; F. Carbognani; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; E. Chassande-Mottin; A. Chincarini; F. Cleva; E. Coccia; C. N. Colacino; J. Colas; A. Colla; M. Colombini; C. Corda; A. Corsi; J.-P. Coulon; E. Cuoco; S. D’Antonio; A. Dari; V. Dattilo; M. Davier; R. Day; R. De Rosa; M. Del Prete; L. Di Fiore; A. Di Lieto; M. Di Paolo Emilio; A. Di Virgilio; A. Dietz; M. Drago; V. Fafone; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; J. Franc; S. Frasca; F. Frasconi; A. Freise; L. Gammaitoni; F. Garufi; G. Gemme; E. Genin; A. Gennai; A. Giazotto; M. Granata; C. Greverie; G. Guidi; H. Heitmann; P. Hello; S. Hild; D. Huet; P. Jaranowski; I. Kowalska; A. Królak; P. La Penna; N. Leroy; N. Letendre; T. G. F. Li; M. Lorenzini; V. Loriette; G. Losurdo; J.-M. Mackowski; E. Majorana; N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; F. Menzinger; C. Michel; L. Milano; Y. Minenkov; M. Mohan; J. Moreau; N. Morgado; A. Morgia; S. Mosca; V. Moscatelli; B. Mours; I. Neri; F. Nocera; G. Pagliaroli; C. Palomba; F. Paoletti; S. Pardi; M. Parisi; A. Pasqualetti; R. Passaquieti; D. Passuello; G. Persichetti; M. Pichot; F. Piergiovanni; M. Pietka; L. Pinard; R. Poggiani; M. Prato; G. A. Prodi; M. Punturo; P. Puppo; O. Rabaste; D. S. Rabeling; P. Rapagnani; V. Re; T. Regimbau; F. Ricci; F. Robinet; A. Rocchi; L. Rolland; R. Romano; D. Rosinska; P. Ruggi; F. Salemi; B. Sassolas; D. Sentenac; R. Sturani; B. Swinkels; A. Toncelli; M. Tonelli; E. Tournefier; F. Travasso; J. Trummer; G. Vajente; S. van der Putten; M. Vavoulidis; G. Vedovato; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert

    2010-01-01

    Each mirror of the interferometric gravitational wave antenna Virgo is attached to a Superattenuator, a chain of mechanical filters designed to suppress seismic vibrations, starting from a few Hz. The filter chain attenuation has been measured by exciting its suspension point with sinuisodal forces and using the interferometer as sensor. The attenuation, measured at different frequencies, is compliant with the

  3. The gravitational lens effect of the Virgo Supercluster

    Microsoft Academic Search

    Chongming Xu; Xuejun Wu; R. Fabbri

    1989-01-01

    The gravitational lens effect of the Virgo Supercluster has been modeled by an axisymmetric homogeneous ellipsoid. Numerical integration of the null geodesics was performed in order to determine the variation in the angular position and the brightness amplification ratio (K) of distant sources. It is shown that the maximum angular displacement, about 8 arcsec, occurs near the Supergalactic poles, and

  4. VLA IMAGING OF VIRGO SPIRALS IN ATOMIC GAS (VIVA). I. THE ATLAS AND THE H I PROPERTIES

    SciTech Connect

    Chung, Aeree; Van Gorkom, J. H. [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Kenney, Jeffrey D. P.; Crowl, Hugh [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States); Vollmer, Bernd [Observatoire astronomique de Strasbourg, 11 rue de l'universite, 67000 Strasbourg (France)], E-mail: achung@aoc.nrao.edu, E-mail: jvangork@astro.columbia.edu, E-mail: kenney@astro.yale.edu, E-mail: hugh@astro.yale.edu, E-mail: hugh@astro.umass.edu, E-mail: bvollmer@astro.u-strasbg.fr

    2009-12-15

    We present the results of a new VLA H I Imaging survey of Virgo galaxies, the VLA Imaging survey of Virgo galaxies in Atomic gas (VIVA). The survey includes high-resolution H I data of 53 carefully selected late type galaxies (48 spirals and five irregular systems). The goal is to study environmental effects on H I gas properties of cluster galaxies to understand which physical mechanisms affect galaxy evolution in different density regions, and to establish how far out the impact of the cluster reaches. As a dynamically young cluster, Virgo contains examples of galaxies experiencing a variety of environmental effects. Its nearness allows us to study each galaxy in great detail. We have selected Virgo galaxies with a range of star formation properties in low to high density regions (at projected distances from M87, d {sub 87} = 0.3-3.3 Mpc). Contrary to previous studies, more than half of the galaxies in the sample ({approx}60%) are fainter than 12 mag in B{sub T} . Overall, the selected galaxies represent the late type Virgo galaxies (S0/a to Sd/Irr) down to m{sub p} {approx}< 14.6 fairly well in morphological type, systemic velocity, subcluster membership, H I mass, and deficiency. The H I observations were done in C short (CS) configuration of the VLA radio telescope, with a typical spatial resolution of 15'' and a column density sensitivity of {approx}3-5 x 10{sup 19} cm{sup -2} in 3{sigma} per 10 km s{sup -1} channel. The survey was supplemented with data of comparable quality from the NRAO archive, taken in CS or C configuration. In this paper, we present H I channel maps, total intensity maps, velocity fields, velocity dispersions, global/radial profiles, position-velocity diagrams and overlays of H I/1.4 GHz continuum maps on the optical images. We also present H I properties such as total flux (S {sub HI}), H I mass (M {sub HI}), linewidths (W{sub 20} and W{sub 50}), velocity (V{sub HI}), deficiency (def{sub HI}), and size (D {sup eff}{sub HI} and D {sup iso}{sub HI}), and describe the H I morphology and kinematics of individual galaxies in detail. The survey has revealed details of H I features that were never seen before. In this paper, we briefly discuss differences in typical H I morphology for galaxies in regions of different galaxy densities. We confirm that galaxies near the cluster core (d {sub 87} {approx}< 0.5 Mpc) have H I disks that are smaller compared to their stellar disks (D{sub HI}/D{sub 25} < 0.5). Most of these galaxies in the core also show gas displaced from the disk, which is either currently being stripped or falling back after a stripping event. At intermediate distances (d{sub 87} {approx} 1 Mpc) from the center, we find a remarkable number of galaxies with long one-sided H I tails pointing away from M87. In a previous letter, we argue that these galaxies are recent arrivals, falling into the Virgo core for the first time. In the outskirts, we find many gas-rich galaxies, with gas disks extending far beyond their optical disks. Interestingly, we also find some galaxies with H I disks that are smaller compared to their stellar disks at large clustercentric distances.

  5. VLA Imaging of Virgo Spirals in Atomic Gas (VIVA). I. The Atlas and the H I Properties

    NASA Astrophysics Data System (ADS)

    Chung, Aeree; van Gorkom, J. H.; Kenney, Jeffrey D. P.; Crowl, Hugh; Vollmer, Bernd

    2009-12-01

    We present the results of a new VLA H I Imaging survey of Virgo galaxies, the VLA Imaging survey of Virgo galaxies in Atomic gas (VIVA). The survey includes high-resolution H I data of 53 carefully selected late type galaxies (48 spirals and five irregular systems). The goal is to study environmental effects on H I gas properties of cluster galaxies to understand which physical mechanisms affect galaxy evolution in different density regions, and to establish how far out the impact of the cluster reaches. As a dynamically young cluster, Virgo contains examples of galaxies experiencing a variety of environmental effects. Its nearness allows us to study each galaxy in great detail. We have selected Virgo galaxies with a range of star formation properties in low to high density regions (at projected distances from M87, d 87 = 0.3-3.3 Mpc). Contrary to previous studies, more than half of the galaxies in the sample (~60%) are fainter than 12 mag in BT . Overall, the selected galaxies represent the late type Virgo galaxies (S0/a to Sd/Irr) down to mp <~ 14.6 fairly well in morphological type, systemic velocity, subcluster membership, H I mass, and deficiency. The H I observations were done in C short (CS) configuration of the VLA radio telescope, with a typical spatial resolution of 15'' and a column density sensitivity of ?3-5 × 1019 cm-2 in 3? per 10 km s-1 channel. The survey was supplemented with data of comparable quality from the NRAO archive, taken in CS or C configuration. In this paper, we present H I channel maps, total intensity maps, velocity fields, velocity dispersions, global/radial profiles, position-velocity diagrams and overlays of H I/1.4 GHz continuum maps on the optical images. We also present H I properties such as total flux (S H I ), H I mass (M H I ), linewidths (W 20 and W 50), velocity (V H I ), deficiency (def H I ), and size (D eff H I and D iso H I ), and describe the H I morphology and kinematics of individual galaxies in detail. The survey has revealed details of H I features that were never seen before. In this paper, we briefly discuss differences in typical H I morphology for galaxies in regions of different galaxy densities. We confirm that galaxies near the cluster core (d 87 <~ 0.5 Mpc) have H I disks that are smaller compared to their stellar disks (D H I /D 25 < 0.5). Most of these galaxies in the core also show gas displaced from the disk, which is either currently being stripped or falling back after a stripping event. At intermediate distances (d 87 ~ 1 Mpc) from the center, we find a remarkable number of galaxies with long one-sided H I tails pointing away from M87. In a previous letter, we argue that these galaxies are recent arrivals, falling into the Virgo core for the first time. In the outskirts, we find many gas-rich galaxies, with gas disks extending far beyond their optical disks. Interestingly, we also find some galaxies with H I disks that are smaller compared to their stellar disks at large clustercentric distances.

  6. Kinematics and stellar populations of low-luminosity early-type galaxies in the Abell 496 cluster

    Microsoft Academic Search

    Igor Chilingarian; Veronique Cayatte; Florence Durret; Christophe Adami; Chantal Balkowski; Laurent Chemin; T. F. Laganá; Philippe Prugniel

    2008-01-01

    Context: The morphology and stellar populations of low-luminosity early-type galaxies in clusters have until now been limited to a few relatively nearby clusters such as Virgo or Fornax. Scenarii for the formation and evolution of dwarf galaxies in clusters are therefore not well constrained. Aims: We investigate here the morphology and stellar populations of low-luminosity galaxies in the relaxed richness

  7. Damage identification of a target substructure with moving load excitation

    NASA Astrophysics Data System (ADS)

    Li, J.; Law, S. S.

    2012-07-01

    This paper presents a substructural damage identification approach under moving vehicular loads based on a dynamic response reconstruction technique. The relationship between two sets of time response vectors from the substructure subject to moving loads is formulated with the transmissibility matrix based on impulse response function in the wavelet domain. Only the finite element model of the intact target substructure and the measured dynamic acceleration responses from the target substructure in the damaged state are required. The time-histories of moving loads and interface forces on the substructure are not required in the proposed algorithm. The dynamic response sensitivity-based method is adopted for the substructural damage identification with the local damage modeled as a reduction in the elemental stiffness factor. The adaptive Tikhonov regularization technique is employed to have an improved identification result when noise effect is included in the measurements. Numerical studies on a three-dimensional box-section girder bridge deck subject to a single moving force or a two-axle three-dimensional moving vehicle are conducted to investigate the performance of the proposed substructural damage identification approach. The simulated local damage can be identified with 5% noise in the measured data.

  8. SEEKING COUNTERPARTS TO ADVANCED LIGO/Virgo TRANSIENTS WITH SWIFT

    SciTech Connect

    Kanner, Jonah; Camp, Jordan [NASA Goddard Space Flight Center, Mail Code 663, Greenbelt, MD 20771 (United States); Racusin, Judith; Gehrels, Neil [NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States); White, Darren, E-mail: jonah.b.kanner@nasa.gov [Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

    2012-11-01

    Binary neutron star (NS) mergers are among the most promising astrophysical sources of gravitational wave (GW) emission for Advanced LIGO and Advanced Virgo, expected to be operational in 2015. Finding electromagnetic counterparts to these signals will be essential to placing them in an astronomical context. The Swift satellite carries a sensitive X-Ray Telescope (XRT), and can respond to target-of-opportunity requests within one to two hours, and so is uniquely poised to find the X-ray counterparts to LIGO/Virgo triggers. Assuming that NS mergers are the progenitors of short gamma-ray bursts (GRBs), some percentage of LIGO/Virgo triggers will be accompanied by X-ray band afterglows that are brighter than 10{sup -12} erg s{sup -1} cm{sup -2} in the XRT band one day after the trigger time. We find that a soft X-ray transient of this flux is bright enough to be extremely rare, and so could be confidently associated with even a moderately localized GW signal. We examine two possible search strategies with the Swift XRT to find bright transients in LIGO/Virgo error boxes. In the first strategy, XRT could search a volume of space with a {approx}100 Mpc radius by observing {approx}30 galaxies over the course of a day, with sufficient depth to observe the expected X-ray afterglow. For an extended LIGO/Virgo horizon distance, the XRT could employ 100 s exposures to cover an area of {approx}35 deg{sup 2} in about a day and remain sensitive enough to image GW-discovered GRB afterglows. These strategies demonstrate that discovery of X-ray band counterparts to GW triggers will be possible, though challenging, with current facilities.

  9. Seeking Counterparts to Advanced LIGO/Virgo Transients with Swift

    NASA Technical Reports Server (NTRS)

    Kanner, Jonah; Camp, Jordan; Racusin, Judith; Gehrels, Neil; White, Darren

    2012-01-01

    Binary neutron star (NS) mergers are among the most promising astrophysical sources of gravitational wave emission for Advanced LIGO and Advanced Virgo, expected to be operational in 2015 . Finding electromagnetic counterparts to these signals will be essential to placing them in an astronomical context. The Swift satellite carries a sensitive X-ray telescope (XRT), and can respond to target-of-opportunity requests within 1-2 hours, and so is uniquely poised to find the X-ray counterparts to LIGO / Virgo triggers. Assuming NS mergers are the progenitors of short gamma-ray bursts (GRBs), some percentage of LIGO/Virgo triggers will be accompanied by X-ray band afterglows that are brighter than 10(exp -12) ergs/s/sq cm in the XRT band one day after the trigger time. We find that a soft X-ray transient of this flux is bright enough to be extremely rare, and so could be confidently associated with even a moderately localized GW signal. We examine two possible search strategies with the Swift XRT to find bright transients in LIGO/Virgo error boxes. In the first strategy, XRT could search a volume of space with a approx.100 Mpc radius by observing approx 30 galaxies over the course of a day, with sufficient depth to observe the expected X-ray afterglow. For an extended LIGO / Virgo horizon distance, the XRT could employ very short 100 s exposures to cover an area of approx 35 square degrees in about a day, and still be sensitive enough to image GW discovered GRB afterglows. These strategies demonstrate that the high X-ray luminosity of short GRBs and the relatively low X-ray transient background combine to make high confidence discoveries of X-ray band counterparts to GW triggers possible, though challenging, with current satellite facilities.

  10. First Results from the Survey of the MAgellanic Stellar History (SMASH)

    NASA Astrophysics Data System (ADS)

    Nidever, David L.; Olsen, Knut A.; Gruendl, Robert A.; Besla, Gurtina; Saha, Abi; Olszewski, Edward; Munoz, Ricardo; Gallart, Carme; Monelli, Matteo; Walker, Alistair R.; Blum, Robert D.; Kaleida, Catherine C.; Vivas, Kathy; Majewski, Steven R.; Zaritsky, Dennis F.; van der Marel, Roeland P.; Bell, Eric F.; Conn, Blair; Stringfellow, Guy S.; Jin, Shoko; Monteagudo Nervion, Lara; Cioni, Maria-Rosa; Noel, Noelia; Martin, Nicolas; Monachesi, Antonela; de Boer, Thomas; Chu, You-Hua; Kim, Hwihyun; Martinez-Delgado, David; Johnson, Lent C.; Kunder, Andrea; Smash

    2015-01-01

    Clear observational signatures of hierarchical galaxy formation have been found around the Milky Way and other nearby massive galaxies. However, the build-up of smaller dwarf galaxies and the extent to which they harbor relics of past interactions such as stellar halos and substructure is not well-known. In an effort to observationally constrain structure formation on small scales, SMASH (Survey of the MAgellanic Stellar History), an approved NOAO community DECam survey, is imaging ~2400 square degrees (at 20% filling factor) to 24th mag in gri (uz~23) allowing us to map the expected stellar debris and extended stellar populations of the Clouds with unprecedented fidelity. SMASH will (a) search for the stellar components of the Magellanic Stream and Leading Arm, (b) detect and map the extended smooth components and substructure of the Magellanic Clouds, and (c) derive spatially resolved, precise star formation histories out to large radii. Our first year of data reveal (1) Large Magellanic Cloud (LMC) stellar populations extending out to a radius of at least 19 deg (~17 kpc) in several directions, (2) clear signatures of two dominant LMC star formation episodes at intermediate radii as revealed by multiple subgiant branches, and (3) evidence for an expansive stellar substructure in the Milky Way halo at a distance of ~30 kpc.

  11. Substructure System Identification for Finite Element Model Updating

    NASA Technical Reports Server (NTRS)

    Craig, Roy R., Jr.; Blades, Eric L.

    1997-01-01

    This report summarizes research conducted under a NASA grant on the topic 'Substructure System Identification for Finite Element Model Updating.' The research concerns ongoing development of the Substructure System Identification Algorithm (SSID Algorithm), a system identification algorithm that can be used to obtain mathematical models of substructures, like Space Shuttle payloads. In the present study, particular attention was given to the following topics: making the algorithm robust to noisy test data, extending the algorithm to accept experimental FRF data that covers a broad frequency bandwidth, and developing a test analytical model (TAM) for use in relating test data to reduced-order finite element models.

  12. Structure and substructure analysis of DAFT/FADA galaxy clusters in the [0.4-0.9] redshift range

    NASA Astrophysics Data System (ADS)

    Guennou, L.; Adami, C.; Durret, F.; Lima Neto, G. B.; Ulmer, M. P.; Clowe, D.; LeBrun, V.; Martinet, N.; Allam, S.; Annis, J.; Basa, S.; Benoist, C.; Biviano, A.; Cappi, A.; Cypriano, E. S.; Gavazzi, R.; Halliday, C.; Ilbert, O.; Jullo, E.; Just, D.; Limousin, M.; Márquez, I.; Mazure, A.; Murphy, K. J.; Plana, H.; Rostagni, F.; Russeil, D.; Schirmer, M.; Slezak, E.; Tucker, D.; Zaritsky, D.; Ziegler, B.

    2014-01-01

    Context. The DAFT/FADA survey is based on the study of ~90 rich (masses found in the literature >2 × 1014 M?) and moderately distant clusters (redshifts 0.4 < z < 0.9), all with HST imaging data available. This survey has two main objectives: to constrain dark energy (DE) using weak lensing tomography on galaxy clusters and to build a database (deep multi-band imaging allowing photometric redshift estimates, spectroscopic data, X-ray data) of rich distant clusters to study their properties. Aims: We analyse the structures of all the clusters in the DAFT/FADA survey for which XMM-Newton and/or a sufficient number of galaxy redshifts in the cluster range are available, with the aim of detecting substructures and evidence for merging events. These properties are discussed in the framework of standard cold dark matter (?CDM) cosmology. Methods: In X-rays, we analysed the XMM-Newton data available, fit a ?-model, and subtracted it to identify residuals. We used Chandra data, when available, to identify point sources. In the optical, we applied a Serna & Gerbal (SG) analysis to clusters with at least 15 spectroscopic galaxy redshifts available in the cluster range. We discuss the substructure detection efficiencies of both methods. Results: XMM-Newton data were available for 32 clusters, for which we derive the X-ray luminosity and a global X-ray temperature for 25 of them. For 23 clusters we were able to fit the X-ray emissivity with a ?-model and subtract it to detect substructures in the X-ray gas. A dynamical analysis based on the SG method was applied to the clusters having at least 15 spectroscopic galaxy redshifts in the cluster range: 18 X-ray clusters and 11 clusters with no X-ray data. The choice of a minimum number of 15 redshifts implies that only major substructures will be detected. Ten substructures were detected both in X-rays and by the SG method. Most of the substructures detected both in X-rays and with the SG method are probably at their first cluster pericentre approach and are relatively recent infalls. We also find hints of a decreasing X-ray gas density profile core radius with redshift. Conclusions: The percentage of mass included in substructures was found to be roughly constant with redshift values of 5-15%, in agreement both with the general CDM framework and with the results of numerical simulations. Galaxies in substructures show the same general behaviour as regular cluster galaxies; however, in substructures, there is a deficiency of both late type and old stellar population galaxies. Late type galaxies with recent bursts of star formation seem to be missing in the substructures close to the bottom of the host cluster potential well. However, our sample would need to be increased to allow a more robust analysis. Tables 1, 2, 4 and Appendices A-C are available in electronic form at http://www.aanda.org

  13. Substructure view of the Union Avenue Viaduct, view looking southeast ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Substructure view of the Union Avenue Viaduct, view looking southeast - Union Avenue Viaduct, Spanning between Southeast Harrison & Southeast Ivon Streets on Union Avenue (Old Highway 99 East), Portland, Multnomah County, OR

  14. 98. DETAIL VIEW OF STORM DAMAGE AND EXPOSED SUBSTRUCTURE, NORTHWEST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    98. DETAIL VIEW OF STORM DAMAGE AND EXPOSED SUBSTRUCTURE, NORTHWEST SIDE OF 4TH TEE, LOOKING WEST - Huntington Beach Municipal Pier, Pacific Coast Highway at Main Street, Huntington Beach, Orange County, CA

  15. 7. Underside of deck and substructure, showing proximity of main ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Underside of deck and substructure, showing proximity of main street bridge from between both bridge, looking east - Claremont Railway Bridge, Spanning Sugar River at Claremont Railroad Company Line, Claremont, Sullivan County, NH

  16. Lens Mapping of Dark Matter Substructure with VSOP-2

    E-print Network

    Shigenori Ohashi; Masashi Chiba; Kaiki Taro Inoue

    2008-02-13

    Hierarchical clustering models of cold dark matter (CDM) predict that about 5% - 10% of a galaxy-sized halo with mass ~ 10^12 solar masses (M_sun) resides in substructures (CDM subhalos) with masses <= 10^8 M_sun. To directly identify such substructures, we propose to observe radio continuum emission from multiply imaged QSOs using VSOP-2 with a high angular resolution.

  17. Substructuring and poroelastic modelling of the intervertebral disc

    Microsoft Academic Search

    P. Swider; A. Pédrono; D. Ambard; F. Accadbled; J. Sales de Gauzy

    2010-01-01

    We proposed a substructure technique to predict the time-dependant response of biological tissue within the framework of a finite element resolution. Theoretical considerations in poroelasticity preceded the calculation of the sub-structured poroelastic matrix. The transient response was obtained using an exponential fitting method. We computed the creep response of an MRI 3D reconstructed L5–S1 intervertebral disc of a scoliotic spine.

  18. 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.

  19. 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 dynamical driving processes and what they imply for key wind parameters like the wind flow speed and mass loss rate.

  20. Finding Nonoverlapping Substructures of a Sparse Matrix

    SciTech Connect

    Pinar, Ali; Vassilevska, Virginia

    2005-08-11

    Many applications of scientific computing rely on computations on sparse matrices. The design of efficient implementations of sparse matrix kernels is crucial for the overall efficiency of these applications. Due to the high compute-to-memory ratio and irregular memory access patterns, the performance of sparse matrix kernels is often far away from the peak performance on a modern processor. Alternative data structures have been proposed, which split the original matrix A into A{sub d} and A{sub s}, so that A{sub d} contains all dense blocks of a specified size in the matrix, and A{sub s} contains the remaining entries. This enables the use of dense matrix kernels on the entries of A{sub d} producing better memory performance. In this work, we study the problem of finding a maximum number of nonoverlapping dense blocks in a sparse matrix, which is previously not studied in the sparse matrix community. We show that the maximum nonoverlapping dense blocks problem is NP-complete by using a reduction from the maximum independent set problem on cubic planar graphs. We also propose a 2/3-approximation algorithm that runs in linear time in the number of nonzeros in the matrix. This extended abstract focuses on our results for 2x2 dense blocks. However we show that our results can be generalized to arbitrary sized dense blocks, and many other oriented substructures, which can be exploited to improve the memory performance of sparse matrix operations.

  1. Using Network Methodology to Infer Population Substructure

    PubMed Central

    Prokopenko, Dmitry; Hecker, Julian; Silverman, Edwin; Nöthen, Markus M.; Schmid, Matthias; Lange, Christoph; Loehlein Fier, Heide

    2015-01-01

    One of the main caveats of association studies is the possible affection by bias due to population stratification. Existing methods rely on model-based approaches like structure and ADMIXTURE or on principal component analysis like EIGENSTRAT. Here we provide a novel visualization technique and describe the problem of population substructure from a graph-theoretical point of view. We group the sequenced individuals into triads, which depict the relational structure, on the basis of a predefined pairwise similarity measure. We then merge the triads into a network and apply community detection algorithms in order to identify homogeneous subgroups or communities, which can further be incorporated as covariates into logistic regression. We apply our method to populations from different continents in the 1000 Genomes Project and evaluate the type 1 error based on the empirical p-values. The application to 1000 Genomes data suggests that the network approach provides a very fine resolution of the underlying ancestral population structure. Besides we show in simulations, that in the presence of discrete population structures, our developed approach maintains the type 1 error more precisely than existing approaches. PMID:26098940

  2. Extended Source Effects in Substructure Lensing

    E-print Network

    Kaiki Taro Inoue; Masashi Chiba

    2005-11-14

    We investigate the extended source size effects on gravitational lensing in which a lens consists of a smooth potential and small mass clumps (``substructure lensing''). We first consider a lens model that consists of a clump modeled as a singular isothermal sphere (SIS) and a primary lens modeled as an external background shear and convergence. For this simple model, we derive analytic formulae for (de)magnification of circularly symmetric top-hat sources with three types of parity for their lensed images, namely, positive, negative, and doubly negative parities. Provided that the source size is sufficiently larger than the Einstein radius of the SIS, we find that in the positive (doubly negative) parity case, an extended source is always magnified (demagnified) in comparison with the unperturbed macrolens system, whereas in the negative parity case, the (de)magnification effect, which depends on the sign of convergence minus unity is weaker than those in other parities. It is shown that a measurement of the distortion pattern in a multiply lensed image enables us to break the degeneracy between the lensing effects of clump mass and those of clump distance if lensing parameters of the relevant macrolens model are determined from the position and flux of multiple images. We also show that an actual density profile of a clump can be directly measured by analyzing the ``fine structure'' in a multiply lensed image within the Einstein radius of the clump.

  3. The Globular Cluster System of NGC 4472 in Virgo

    Microsoft Academic Search

    D. Geisler; M. G. Lee; E. Kim

    1995-01-01

    The globular cluster system of the giant elliptical galaxy NGC 4472 in the Virgo cluster is investigated. We have obtained deep images in the C and T_1 filters of the Washington system using the KPNO 4m PF\\/CCD. The photometry reaches to T_1 ~ R ~ 25, well beyond the turnover in the cluster luminosity function. The color-magnitude diagram and image

  4. Malmquist Bias and the Distance to the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Gonzalez, Anthony H.; Faber, S. M.

    1997-08-01

    This paper investigates the impact of Malmquist bias on the distance to the Virgo cluster determined by the H0 Key Project using M100, and consequently on the derived value of H0. Malmquist bias is a volume-induced statistical effect which causes the most probable distance to be different from the raw distance measured. Consideration of the bias in the distance to the Virgo cluster raises this distance and lowers the calculated value of H0. Monte Carlo simulations of the cluster have been run for several possible distributions of spirals within the cluster and of clusters in the local universe. Simulations consistent with known information regarding the cluster and the errors of measurement result in a bias of about 6.5%-8.5%. This corresponds to an unbiased distance of 17.2-17.4 Mpc and a value of H0 in the range 80-82 km s-1 Mpc-1. The problem of determining the bias to Virgo illustrates several key points regarding Malmquist bias. Essentially all conventional astonomical distance measurements are subject to this bias. In addition, the bias accumulates when an attempt is made to construct ``distance ladders'' from measurements which are individually biased. As will be shown in the case of Virgo, the magnitude and direction of the bias are sensitive to the spatial distribution of the parent population from which the observed object is drawn--a distribution which is often poorly known. This leads to uncertainty in the magnitude of the bias, and adds to the importance of minimizing the number of steps in ``distance ladders.'' Lick Observatory Bulletin, No. 1358.

  5. A First Comparison Between LIGO and Virgo Inspiral Search Pipelines

    E-print Network

    L. Blackburn; F. Beauville; M. -A. Bizouard; L. Bosi; P. Brady; L. Brocco; D. Brown; D. Buskulic; S. Chatterji; N. Christensen; A. -C. Clapson; S. Fairhurst; D. Grosjean; G. Guidi; P. Hello; E. Katsavounidis; M. Knight; A. Lazzarini; F. Marion; B. Mours; F. Ricci; A. Vicere'; M. Zanolin

    2005-04-12

    This article reports on a project that is the first step the LIGO Scientific Collaboration and the Virgo Collaboration have taken to prepare for the mutual search for inspiral signals. The project involved comparing the analysis pipelines of the two collaborations on data sets prepared by both sides, containing simulated noise and injected events. The ability of the pipelines to detect the injected events was checked, and a first comparison of how the parameters of the events were recovered has been completed.

  6. Population Gradients in Stellar Halos from GHOSTS

    NASA Astrophysics Data System (ADS)

    Bailin, Jeremy; Monachesi, Antonela; Bell, Eric F.; de Jong, Roelof S.; Ghosts Survey

    2015-01-01

    We report on recent results from the Galaxy Halos, Outer disks, Substructure, Thick disks, and Star clusters (GHOSTS) survey, an HST ACS+WFC3 imaging survey to study stellar populations in and around 16 nearby spiral galaxies. By using HST resolution to resolve the stellar halos into individual red giant branch (RGB) stars, we are able to detect distinct stellar populations at several points throughout the halo of the half dozen massive highly-inclined galaxies in the sample. In approximately half of these galaxies, we detect a gradient in the color of the RGB; which we interpret as a metallicity gradient. Stellar halo formation models predict a wide variety of metallicity gradients: those in which the halos are dominated by stars formed in situ predict stronger gradients than we observe, while accretion-dominated halo models predict weaker or nonexistent gradients. Our measurements therefore provide a useful discriminator between stellar halo models, and at first look appear most consistent with the accretion-based model of Cooper et al. (2010).

  7. OPTICAL COLORS OF INTRACLUSTER LIGHT IN THE VIRGO CLUSTER CORE

    SciTech Connect

    Rudick, Craig S.; Mihos, J. Christopher; Harding, Paul; Morrison, Heather L. [Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 (United States); Feldmeier, John J. [Department of Physics and Astronomy, Youngstown State University, Youngstown, OH 44555 (United States); Janowiecki, Steven, E-mail: csr10@case.ed [Department of Astronomy, Indiana University, 727 East 3rd Street, Bloomington, IN 47405 (United States)

    2010-09-01

    We continue our deep optical imaging survey of the Virgo cluster using the CWRU Burrell Schmidt telescope by presenting B-band surface photometry of the core of the Virgo cluster in order to study the cluster's intracluster light (ICL). We find ICL features down to {mu}{sub B} {approx}29 mag arcsec{sup -2}, confirming the results of Mihos et al., who saw a vast web of low surface brightness streams, arcs, plumes, and diffuse light in the Virgo cluster core using V-band imaging. By combining these two data sets, we are able to measure the optical colors of many of the cluster's low surface brightness features. While much of our imaging area is contaminated by galactic cirrus, the cluster core near the cD galaxy, M87, is unobscured. We trace the color profile of M87 out to over 2000'', and find a blueing trend with radius, continuing out to the largest radii. Moreover, we have measured the colors of several ICL features which extend beyond M87's outermost reaches and find that they have similar colors to the M87's halo itself, B - V {approx}0.8. The common colors of these features suggest that the extended outer envelopes of cD galaxies, such as M87, may be formed from similar streams, created by tidal interactions within the cluster, that have since dissolved into a smooth background in the cluster potential.

  8. Particle tagging and its implications for stellar population dynamics

    E-print Network

    Bret, Theo Le; Cooper, Andrew P; Frenk, Carlos; Zolotov, Adi; Brooks, Alyson M; Governato, Fabio; Parry, Owen H

    2015-01-01

    We establish a controlled comparison between the properties of galactic stellar halos obtained with hydrodynamical simulations and with `particle tagging'. Tagging is a fast way to obtain stellar population dynamics: instead of tracking gas and star formation, it `paints' stars directly onto a suitably defined subset of dark matter particles in a collisionless, dark-matter-only simulation.Our study shows that there are conditions under which particle tagging generates good fits to the hydrodynamical stellar density profiles of a central Milky-Way-like galaxy and its most prominent substructure. Phase-space diffusion processes are crucial to reshaping the distribution of stars in infalling spheroidal systems and hence the final stellar halo. We conclude that the success of any particular tagging scheme hinges on this diffusion being taken into account, at a minimum by making use of `live' tagging schemes, in which particles are regularly tagged throughout the evolution of a galaxy.

  9. SUBSTRUCTURE DEPLETION IN THE MILKY WAY HALO BY THE DISK

    SciTech Connect

    D'Onghia, Elena; Hernquist, Lars; Keres, Dusan [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Springel, Volker, E-mail: edonghia@cfa.harvard.ed [Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str. 1, 85740 Garching (Germany)

    2010-02-01

    We employ numerical simulations and simple analytical estimates to argue that dark matter substructures orbiting in the inner regions of the Galaxy can be efficiently destroyed by disk shocking, a dynamical process known to affect globular star clusters. We carry out a set of fiducial high-resolution collisionless simulations in which we adiabatically grow a disk, allowing us to examine the impact of the disk on the substructure abundance. We also track the orbits of dark matter satellites in high-resolution Aquarius simulations and analytically estimate the cumulative halo and disk-shocking effect. Our calculations indicate that the presence of a disk with only 10% of the total Milky Way mass can significantly alter the mass function of substructures in the inner parts of halos. This has important implications especially for the relatively small number of satellites seen within approx30 kpc of the Milky Way center, where disk shocking is expected to reduce the substructure abundance by a factor of 2 at 10{sup 9} M{sub sun} and a factor of 3 at 10{sup 7} M{sub sun}. The most massive subhalos with 10{sup 10} M{sub sun} survive even in the presence of the disk. This suggests that there is no inner missing satellite problem and calls into question whether these substructures can produce transient features in disks, like multi-armed spiral patterns. Also, the depletion of dark matter substructures through shocking on the baryonic structures of the disk and central bulge may aggravate the problem to fully account for the observed flux anomalies in gravitational lens systems, and significantly reduces the dark matter annihilation signal expected from nearby substructures in the inner halo.

  10. Hubble Space Telescope photometry of the central regions of Virgo cluster elliptical galaxies. 2: Isophote shapes

    NASA Technical Reports Server (NTRS)

    Bosch, Frank C. Van Den; Ferrarese, Laura; Jaffe, Walter; Ford, Holland C.; O'Connell, Robert W.

    1994-01-01

    The isophotal shapes of a magnitude limited sample of Virgo ellipticals are presented. These are derived from high resolution Hubble Space Telescope (HST) photometry. The absence of atmospheric seeing and accurate knowledge of the Point Spread Function (PSF) allows us to perform an accurate deconvolution. Model galaxies were constructed to test the deconvolution algorithms used, and showed that we can accurately recover isophotal shape parameters down to 0.5 sec. From the isophotal parameters we can classify the galaxies in two subsamples: disky and non-disky galaxies. In three of these disky galaxies we found evidence for a nuclear stellar disk in the inner 1.5 sec. In addition these galaxies also have an outer disk, that seems to break up inside 2 sec - 3 sec. In the two galaxies for which there is kinematic evidence from the literature of a decoupled core, we found no indication for such subsystem from the isophotal shape analysis. In 80% of these early type galaxies there are indications for dust. For eight of these galaxies the dust has not been detected before.

  11. Investigating Chemical Substructure in the Galactic Disk

    NASA Astrophysics Data System (ADS)

    Stringer, Christopher; Carney, B. W.

    2010-01-01

    We will present high resolution spectra measurements for Lanthanum, Europium and Iron in 760 disk stars. The bulk of our data are planet search spectra taken with HIRES on the Keck I telescope at R 50,000. A small subset of kinematicly selected stars were observed on the Harlan J. Smith Telescope at McDonald Observatory at R 60,000 and S/N 100 at the 3988 Å Lanthanum line and S/N 250 around 5240 Å near our Iron lines. We use the technique of chemical tagging to investigate the possibility that these kinematicly selected stars are remnants of accreted objects of extragalactic origin or, alternatively, dynamical in origin. Lanthanum and Europium are of special interest because they are produced primarily by the s and r processes, respectively. Because these elements are synthesized in different mass stars and are returned to the interstellar medium on different timescales, the ratio [Eu/La] is a tracer of the star formation rate. To apply spectroscopy to such a large set of data, we have developed an automated process that fits the observations to synthetic spectra using an unnormalized ?2 metric to determine [Fe/H], [Eu/H],[La/H], and vbroad. We estimate log(g) from parallax data, and then verify the results spectroscopically. We are using ATLAS 9 model atmospheres and synthetic spectra calculated using MOOG. Our kinematicly selected subset was originally noticed by Helmi et al (2006) where they statistically argued for kinematic substructure in the disk. The stars are interesting at first glance because they are in overdense portions of phase space, a hallmark of accreted objects according to computer models. Further, these stars have different photometric metallicities than the disk at large, and in color-magnitude plots one or more turn offs can be seen.

  12. Substructure and Dynamics of the Fornax Cluster

    NASA Astrophysics Data System (ADS)

    Drinkwater, Michael J.; Gregg, Michael D.; Colless, Matthew

    2001-02-01

    We present the first dynamical analysis of a galaxy cluster to include a large fraction of dwarf galaxies. Our sample of 108 Fornax Cluster members measured with the UK Schmidt Telescope FLAIR-II spectrograph contains 55 dwarf galaxies (15.5>bJ>18.0 or -16>MB>-13.5). H? emission shows that 36%+/-8% of the dwarfs are star forming, twice the fraction implied by morphological classifications. The total sample has a mean velocity of 1493+/-36 km s-1 and a velocity dispersion of 374+/-26 km s-1. The dwarf galaxies form a distinct population: their velocity dispersion (429+/-41 km s-1) is larger than that of the giants (308+/-30 km s-1) at the 98% confidence level. This suggests that the dwarf population is dominated by infalling objects whereas the giants are virialized. The Fornax system has two components, the main Fornax Cluster centered on NGC 1399 with cz=1478 km s-1 and ?cz=370 km s-1 and a subcluster centered 3° to the southwest including NGC 1316 with cz=1583 km s-1 and ?cz=377 km s-1. This partition is preferred over a single cluster at the 99% confidence level. The subcluster, a site of intense star formation, is bound to Fornax and probably infalling toward the cluster core for the first time. We discuss the implications of this substructure for distance estimates of the Fornax Cluster. We determine the cluster mass profile using the method of Diaferio, which does not assume a virialized sample. The mass within a projected radius of 1.4 Mpc is (7+/-2)×1013 Msolar, and the mass-to-light ratio is 300+/-100 Msolar/Lsolar. The mass is consistent with values derived from the projected mass virial estimator and X-ray measurements at smaller radii.

  13. Substructure and dynamics of the Fornax Cluster

    E-print Network

    M. J. Drinkwater; M. D. Gregg; M. Colless

    2000-12-19

    We present the first dynamical analysis of a galaxy cluster to include a large fraction of dwarf galaxies. Our sample of 108 Fornax Cluster members measured with the UK Schmidt Telescope FLAIR-II spectrograph contains 55 dwarf galaxies (15.5>bj>18.0 or -16>Mb>-13.5). Halpha emission shows that 36+/-8 per cent of the dwarfs are star-forming, twice the fraction implied by morphological classifications. The total sample has a mean velocity of 1493+/-36 km/s and a velocity dispersion of 374+/-26 km/s. The dwarf galaxies form a distinct population: their velocity dispersion (429+/-41 km/s) is larger than that of the giants (308+/-30 km/s) at the 98 per cent confidence level. This suggests that the dwarf population is dominated by infalling objects whereas the giants are virialized. The Fornax system has two components; the main Fornax Cluster centered on NGC 1399 with mean velocity 1478 km/s and velocity dispersion 370 km/s, and a subcluster centered 3 degrees to the south-west including NGC 1316 with mean velocity 1583 km/s and velocity dispersion 377 km/s. This partition is preferred over a single cluster at the 99 per cent confidence level. The subcluster, a site of intense star formation, is bound to Fornax and probably infalling towards the cluster core for the first time. We discuss the implications of this substructure for distance estimates of the Fornax Cluster.

  14. Resonant Clumping and Substructure in Galactic Disks

    NASA Astrophysics Data System (ADS)

    Molloy, Matthew; Smith, Martin C.; Shen, Juntai; Wyn Evans, N.

    2015-05-01

    We describe a method to extract resonant orbits from N-body simulations, exploiting the fact that they close in frames rotating with a constant pattern speed. Our method is applied to the N-body simulation of the Milky Way by Shen et al. This simulation hosts a massive bar, which drives strong resonances and persistent angular momentum exchange. Resonant orbits are found throughout the disk, both close to the bar and out to the very edges of the disk. Using Fourier spectrograms, we demonstrate that the bar is driving kinematic substructure even in the very outer parts of the disk. We identify two major orbit families in the outskirts of the disk, one of which makes significant contributions to the kinematic landscape, namely, the m:l = 3:?2 family, resonating with the bar. A mechanism is described that produces bimodal distributions of Galactocentric radial velocities at selected azimuths in the outer disk. It occurs as a result of the temporal coherence of particles on the 3:?2 resonant orbits, which causes them to arrive simultaneously at pericenter or apocenter. This resonant clumping, due to the in-phase motion of the particles through their epicycle, leads to both inward and outward moving groups that belong to the same orbital family and consequently produce bimodal radial velocity distributions. This is a possible explanation of the bimodal velocity distributions observed toward the Galactic anticenter by Liu et al. Another consequence is that transient overdensities appear and dissipate (in a symmetric fashion), resulting in a periodic pulsing of the disk’s surface density.

  15. Early Type Galaxies in the Mid Infrared: a new flavor to their stellar populations

    E-print Network

    A. Bressan; P. Panuzzo; O. Vega; L. Buson; M. Clemens; G. L. Granato; R. Rampazzo; L. Silva; J. R. Valdes

    2007-02-02

    The mid infrared emission of early type galaxies traces the presence of intermediate age stellar populations as well as even tiny amounts of ongoing star formation. Here we discuss high S/N Spitzer IRS spectra of a sample of Virgo early type galaxies, with particular reference to NGC 4435. We show that, by combining mid infrared spectroscopic observations with existing broad band fluxes, it is possible to obtain a very clean picture of the nuclear activity in this galaxy.

  16. GALEX UV observations of the interacting galaxy NGC 4438 in the Virgo cluster

    E-print Network

    A. Boselli; S. Boissier; L. Cortese; A. Gil de Paz; V. Buat; J. Iglesias-Paramo; B. F. Madore; T. Barlow; L. Bianchi; Y. -I. Byun; J. Donas; K. Forster; P. G. Friedman; T. M. Heckman; P. Jelinsky; Y. -W. Lee; R. Malina; D. C. Martin; B. Milliard; P. Morrissey; S. Neff; R. M. Rich; D. Schiminovich; M. Seibert; O. Siegmund; T. Small; A. S. Szalay; B. Welsh; T. K. Wyder

    2005-02-02

    We present GALEX NUV (2310 A) and FUV (1530 A) images of the interacting galaxy NGC 4438 (Arp 120) in the center of the Virgo cluster. These images show an extended (20 kpc) tidal tail at the north-west edge of the galaxy previously undetected at other wavelengths, at 15-25 kpc from its nucleus. Except in the nucleus, the UV morphology of NGC 4438 is totally different from the Halpha+[NII] one, more similar to the X-ray emission, confirming its gas cooling origin. We study the star formation history of NGC 4438 combining spectro-photometric data in the UV-visible-near-IR wavelength range with population synthesis and galaxy evolution models. The data are consistent with a recent (~ 10 Myr), instantaneous burst of star formation in the newly discovered UV north-western tail which is significantly younger than the age of the tidal interaction with NGC 4435, dated by dynamical models at ~ 100 Myr ago. Recent star formation events are also present at the edge of the northern arm and in the southern tail, while totally lacking in the other regions, which are dominated by the old stellar population perturbed during the dynamical interaction with NGC 4435. The contribution of this recent starburst to the total galaxy stellar mass is lower than 0.1%, an extremely low value for such a violent interaction. High-velocity, off-center tidal encounters such as that observed in Arp 120 are thus not sufficient to significantly increase the star formation activity of cluster galaxies.

  17. Quantifying the Significance of Substructure in Coronal Loops

    NASA Astrophysics Data System (ADS)

    McKeough, K. B. D.; Kashyap, V.; McKillop, S.

    2014-12-01

    A method to infer the presence of small-scale substructure in SDO/AIA (Atmospheric Imaging Assembly on the Solar Dynamics Observatory) images of coronal loops is developed. We can classify visible loop structure based on this propensity to show substructure which puts constraints on contemporary solutions to the coronal heating problem. The method uses the Bayesian algorithm Low-count Image Reconstruction and Analysis (LIRA) to infer the multi-scale component of the loops which describes deviations from a smooth model. The increase in contrast of features in this multi-scale component is determined using a statistic that estimates the sharpness across the image. Regions with significant substructure are determined using p-value upper bounds. We are able to locate substructure visible in Hi-C (High-Resolution Coronal Imager) data that are not salient features in the corresponding AIA image. Looking at coronal loops at different regions of the Sun (e.g., low-lying structure and loops in the upper corona) we are able to map where detectable substructure exists and thus the influence of the nanoflare heating process. We acknowledge support from AIA under contract SP02H1701R from Lockheed-Martin to SAO.

  18. Amplitude modulation of low degree p-modes - comparison of BISON and VIRGO

    Microsoft Academic Search

    Bo Andersen; Torben Leifsen; William J. Chaplin; Yvonne Elsworth

    2003-01-01

    Using both VIRGO and MDI data we have previously studied the amplitude variation of the l=0 p-modes for radial orders 12 to 32. In this study we extend the investigation backward in time to 1992 by including data from the BISON network. For the large amplitude modes there is a strong correlation between the space based radiance measurements from VIRGO

  19. DISCOVERY OF ULTRACOMPACT DWARF GALAXIES IN THE VIRGO CLUSTER J. B. Jones

    E-print Network

    Parker, Quentin A.

    DISCOVERY OF ULTRACOMPACT DWARF GALAXIES IN THE VIRGO CLUSTER J. B. Jones Astronomy Unit, School; accepted 2005 September 4 ABSTRACT We have discovered nine ultracompact dwarf galaxies (UCDs) in the Virgo of nucleated dwarf elliptical galaxies disrupted in the cluster core but can also be ex- plained as objects

  20. First locking of the Virgo central area interferometer with suspension hierarchical control

    Microsoft Academic Search

    F. Acernese; P. Amico; N. Arnaud; D. Babusci; R. Barillé; F. Barone; L. Barsotti; M. Barsuglia; F. Beauville; M. A Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; L. Bracci; S. Braccini; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; G. Calamai; E. Calloni; E. Campagna; F. Cavalier; G. Cella; E. Chassande-Mottin; F. Cleva; T. Cokelaer; G. Conforto; C. Corda; J.-P Coulon; E. Cuoco; V. Dattilo; M. Davier; R De Rosa; L Di Fiore; A Di Virgilio; B. Dujardin; A. Eleuteri; D. Enard; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D Fournier; S. Frasca; F. Frasconi; L. Gammaitoni; A. Gennai; A. Giazotto; G. Giordano; H. Heitmann; P. Hello; P. Heusse; L. Holloway; S. Kreckelberg; P La Penna; V. Loriette; M. Loupias; G. Losurdo; J.-M Mackowski; E. Majorana; C. N Man; F. Marion; F. Martelli; A. Masserot; L. Massonnet; M. Mazzoni; L. Milano; J. Moreau; F. Moreau; N. Morgado; F. Mornet; B. Mours; J. Pacheco; A. Pai; C. Palomba; F. Paoletti; R. Passaquieti; D. Passuello; B. Perniola; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; J. Ramonet; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; G. Russo; S. Solimeno; R. Stanga; A. Toncelli; M. Tonelli; E. Tournefier; F. Travasso; H. Trinquet; M. Varvella; D. Verkindt; F. Vetrano; O. Veziant; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert

    2004-01-01

    Operation of the central portion of Virgo as a simple 6 m Michelson interferometer has given the first demonstration of the possibility to control an interferometer suspended from Virgo full scale multistage seismic attenuators using information derived from the interferometer locking signal. A special role in the control is played by the first stage of these suspensions, an inverted pendulum:

  1. Lock acquisition of the central interferometer of the gravitational wave detector Virgo

    Microsoft Academic Search

    F. Acernese; P. Amico; N. Arnaud; D. Babusci; R. Barillé; F. Barone; L. Barsotti; M. Barsuglia; F. Beauville; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; L. Bracci; S. Braccini; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; G. Calamai; E. Calloni; E. Campagna; F. Cavalier; G. Cella; E. Chassande-Mottin; F. Cleva; T. Cokelaer; C. Corda; J.-P. Coulon; E. Cuoco; V. Dattilo; M. Davier; R. De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; A. Eleuteri; D. Enard; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; S. Frasca; F. Frasconi; L. Gammaitoni; A. Gennai; A. Giazotto; G. Giordano; G. Guidi; H. Heitmann; P. Hello; P. Heusse; L. Holloway; S. Kreckelbergh; P. La Penna; V. Loriette; M. Loupias; G. Losurdo; J.-M. Mackowski; E. Majorana; C. N Man; F. Martelli; A. Masserot; L. Massonnet; M. Mazzoni; L. Milano; J. Moreau; F. Moreau; N. Morgado; F. Mornet; B. Mours; J. Pacheco; A. Pai; C. Palomba; F. Paoletti; R. Passaquieti; D. Passuello; B. Perniola; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; J. Ramonet; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; G. Russo; S. Solimeno; R. Stanga; A. Toncelli; M. Tonelli; E. Tournefier; F. Travasso; H. Trinquet; M. Varvella; D. Verkindt; F. Vetrano; O. Veziant; A. Viceré; J.-Y Vinet; H. Vocca; M. Yvert

    2004-01-01

    We present the lock acquisition algorithm used for the central interferometer of the gravitational wave detector Virgo (CITF). The CITF was a preliminary step in the construction of the Virgo detector, which allowed to test the main components of the instrument. The problems related to the lock acquisition are discussed, together with the key points of the algorithm. Computer simulation

  2. A comparison of methods for gravitational wave burst searches from LIGO and Virgo

    Microsoft Academic Search

    F. Beauville; M.-A. Bizouard; L. Blackburn; L. Brocco; D. A. Brown; D. Buskulic; F. Cavalier; S. Chatterji; N. Christensen; A.-C. Clapson; S. Fairhurst; D. Grosjean; G. Guidi; P. Hello; S. Heng; M. Hewitson; E. Katsavounidis; S. Klimenko; M. Knight; A. Lazzarini; N. Leroy; F. Marion; J. Markowitz; C. Melachrinos; B. Mours; F. Ricci; A. Viceré; I. Yakushin; M. Zanolin

    2008-01-01

    The search procedure for burst gravitational waves has been studied using 24 h of simulated data in a network of three interferometers (Hanford 4 km, Livingston 4 km and Virgo 3 km are the example interferometers). Several methods to detect burst events developed in the LIGO Scientific Collaboration (LSC) and Virgo Collaboration have been studied and compared. We have performed

  3. Shock induced deformation substructures in a copper bicrystal

    SciTech Connect

    Cao, Fang [Los Alamos National Laboratory; Beyerlein, Irene J [Los Alamos National Laboratory; Cerreta, Ellen K [Los Alamos National Laboratory; Trujillo, Carl P [Los Alamos National Laboratory; Gray Ill, George T [Los Alamos National Laboratory; Sencer, Bulent H [NON LANL

    2008-01-01

    Controlled shock recovery experiments have been conducted to assess the role of shock pressure and orientation dependence on the substructure evolution of a [100]/[01{ovr 1}] copper bicrystal. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were utilized to characterize orientation variation and substructure evolution of the post-shock specimens. Well defined dislocation cell structures were displayed in both grains and the average cell size was observed to decrease with increasing shock pressure. Twinning was occasionally observed in the 5 GPa shocked [100] grain and became the dominant substructure at higher shock pressure. The stress and directional dependence of twinning in the bicrystal was analyzed with consideration of the energetically favorable dissociation of dislocations into Shockley partials and the stress-orientation effect on the partial width. Moreover, a critical 'tear apart' stress is proposed and a good agreement is obtained between the calculated value and the experimental observations.

  4. EFFECT OF DARK MATTER HALO SUBSTRUCTURES ON GALAXY ROTATION CURVES

    SciTech Connect

    Roy, Nirupam, E-mail: nroy@aoc.nrao.ed [NRAO, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801 (United States)

    2010-11-01

    In this paper, the effect of halo substructures on galaxy rotation curves is investigated using a simple model of dark matter clustering. A dark matter halo density profile is developed based only on the scale-free nature of clustering that leads to a statistically self-similar distribution of the substructures at the galactic scale. A semi-analytical method is used to derive rotation curves for such a clumpy dark matter density profile. It is found that the halo substructures significantly affect the galaxy velocity field. Based on the fractal geometry of the halo, this self-consistent model predicts a Navarro-Frenk-White-like rotation curve and a scale-free power spectrum of the rotation velocity fluctuations.

  5. Enhancing MAD F(A) data for substructure determination.

    PubMed

    Xu, Hongliang

    2010-08-01

    Heavy-atom substructure determination is a critical step in phasing an unknown macromolecular structure. Dual-space (Shake-and-Bake) recycling is a very effective procedure for locating the substructure (heavy) atoms using F(A) data estimated from multiple-wavelength anomalous diffraction. However, the estimated F(A) are susceptible to the accumulation of errors in the individual intensity measurements at several wavelengths and from inaccurate estimation of the anomalous atomic scattering corrections f' and f''. In this paper, a new statistical and computational procedure which merges multiple F(A) estimates into an averaged data set is used to further improve the quality of the estimated anomalous amplitudes. The results of 18 Se-atom substructure determinations provide convincing evidence in favor of using such a procedure to locate anomalous scatterers. PMID:20693694

  6. Enhancing MAD F A data for substructure determination

    PubMed Central

    Xu, Hongliang

    2010-01-01

    Heavy-atom substructure determination is a critical step in phasing an unknown macromolecular structure. Dual-space (Shake-and-Bake) recycling is a very effective procedure for locating the substructure (heavy) atoms using F A data estimated from multiple-wavelength anomalous diffraction. However, the estimated F A are susceptible to the accumulation of errors in the individual intensity measurements at several wavelengths and from inaccurate estimation of the anomalous atomic scattering corrections f? and f??. In this paper, a new statistical and computational procedure which merges multiple F A estimates into an averaged data set is used to further improve the quality of the estimated anomalous amplitudes. The results of 18 Se-atom substructure determinations provide convincing evidence in favor of using such a procedure to locate anomalous scatterers. PMID:20693694

  7. Iterative method for dynamic condensation combined with substructuring scheme

    NASA Astrophysics Data System (ADS)

    Choi, Dongsoo; Kim, Hyungi; Cho, Maenghyo

    2008-10-01

    An iterated improved reduced system (IIRS) procedure combined with substructuring scheme for both undamped and nonclassically damped structures is presented. Iterated IIRS method is an efficient reduction technique because the highly accurate eigenproperties from the repeatedly updated condensed matrices can be obtained without consuming expensive computational cost. However, single domain direct approach of this method to large structures requires much computational resources and even makes analysis intractable in the case only limited computer storage is available. These problems can be overcome by combining the substructuring scheme with IIRS procedure. The newly developed IIRS method combined with a substructuring scheme can provide an efficient methodology for large-scale eigenvalue problems. The validation of the present method and the evaluation of computational efficiency are demonstrated through the numerical examples.

  8. Lensing Optical Depth for Substructure and Isolated Dark Matter Halos

    E-print Network

    Jacqueline Chen; Andrey V. Kravtsov; Charles R. Keeton

    2003-04-01

    Multiply-imaged quasar lenses can be used to constrain the substructure mass fraction in galaxy-sized dark matter halos via anomalous flux ratios in lensed images. The flux ratios, however, can be affected by both the substructure in the lens halo and by isolated small-mass halos along the entire line-of-sight to the lensed source. While lensing by dark matter clumps near the lens galaxy is more efficient than elsewhere, the cumulative effect of all objects along the line-of-sight could be significant. Here we estimate the potential contribution of isolated clumps to the substructure lensing signal using a simple model motivated by cosmological simulations. We find that the contribution of isolated clumps to the total lensing optical depth ranges from a few to tens percent, depending on assumptions and the particular configuration of the lens. Therefore, although the contribution of isolated clumps to the lensing signal is not dominant, it should not be neglected in detailed analyses of substructure lensing. For the currently favored Lambda-CDM model, the total calculated optical depth for lensing is high, tau ~ 0.2-20 and could, therefore, naturally explain the high frequency of anomalous flux ratios in observed lenses. The prediction, however, is highly sensitive to the spatial distribution of substructure halos in the innermost regions of the lens halo, which is still very uncertain. Therefore, constraints on the properties of the substructure population or accurate cosmological constraints, such as the mass of the warm dark matter particle, are difficult if not impossible to derive at this point.

  9. A substructure coupling procedure applicable to general linear time-invariant dynamic systems

    NASA Technical Reports Server (NTRS)

    Howsman, T. G.; Craig, R. R., Jr.

    1984-01-01

    A substructure synthesis procedure applicable to structural systems containing general nonconservative terms is presented. In their final form, the nonself-adjoint substructure equations of motion are cast in state vector form through the use of a variational principle. A reduced-order mode for each substructure is implemented by representing the substructure as a combination of a small number of Ritz vectors. For the method presented, the substructure Ritz vectors are identified as a truncated set of substructure eigenmodes, which are typically complex, along with a set of generalized real attachment modes. The formation of the generalized attachment modes does not require any knowledge of the substructure flexible modes; hence, only the eigenmodes used explicitly as Ritz vectors need to be extracted from the substructure eigenproblem. An example problem is presented to illustrate the method.

  10. Mapping Substructures in Dark Matter Halos

    E-print Network

    Alexander Knebe; Stuart P. D. Gill; Daisuke Kawata; Brad K. Gibson

    2004-12-02

    We present a detailed study of the real and integrals-of-motion space distributions of a satellite obtained from a self-consistent high-resolution simulation of a galaxy cluster and re-simulated using various analytical halo potentials. We found that the disrupted satellite appears as a coherent structure in integrals-of-motion space in all models (``live'' and analytical potential) although the distribution is significantly smeared for the live host halo. Further the primary mechanism for this smearing is the mass growth of the host, which changes both the energy and angular momentum of the satellite debris. Hence, this must be considered when searching for (stellar) streams with future observational experiments such as RAVE and GAIA.

  11. Applications of a nuclear spectroscopic survey of Virgo spiral galaxies

    NASA Astrophysics Data System (ADS)

    Stauffer, J. R.

    A data base on the nuclear spectrophotometric survey of Virgo and field spirals is used as the basis of a critical discussion of the results presented by Kennicutt (1983) and Scoville et al. (1983). The optical spectra of the data base furnish no evidence of continuing nuclear star formation in any of the Scoville et al. galaxies, which had been detected at 10 microns; the 10-micron emission and optical emission lines are more simply attributed to some kind of nonthermal activity. A comment on the distance to NGC 4569 is furnished.

  12. IC 3475 - A stripped dwarf galaxy in the Virgo cluster

    NASA Technical Reports Server (NTRS)

    Vigroux, L.; Lachieze-Rey, M.; Thuan, T. X.; Vader, J. P.

    1986-01-01

    B and R CCD and H I observations of the Virgo dwarf galaxy IC 3475 were obtained. The galaxy is very large, having a diameter of about 10 kpc; its hydrogen content is at least 60 times smaller than that of a normal dwarf irregular galaxy; and the galaxy shows a central bar structure with knots and inclusions scattered throughout its body but with the majority in the bar region. The results support the hypothesis that IC 3475 is a dwarf irregular galaxy that has been stripped of its neutral gas.

  13. Noise monitor tools and their application to Virgo data

    NASA Astrophysics Data System (ADS)

    Accadia, T.; Acernese, F.; Agathos, M.; Astone, P.; Ballardin, G.; Barone, F.; Barsuglia, M.; Basti, A.; Bauer, Th S.; Bebronne, M.; Bejger, M.; Beker, M. G.; Bitossi, M.; Bizouard, M. A.; Blom, M.; Bondu, F.; Bonelli, L.; Bonnand, R.; Boschi, V.; Bosi, L.; Bouhou, B.; Braccini, S.; Bradaschia, C.; Branchesi, M.; Briant, Gabriel chardin T.; Brillet, A.; Brisson, V.; Bulik, T.; Bulten, H. J.; Buskulic, D.; Buy, C.; Calloni, E.; Canuel, B.; Carbognani, F.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cesarini, E.; Chaibi, O.; Chassande-Mottin, E.; Chincarini, A.; Chiummo, A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conte, A.; Coulon, J.-P.; Cuoco, E.; D'Antonio, S.; Dattilo, V.; Davier, M.; Day, R.; De Rosa, R.; Debreczeni, G.; Del Pozzo, W.; Di Fiore, L.; Di Lieto, A.; Emilio, M. Di Paolo; Di Virgilio, A.; Dietz, A.; Drago, M.; Endröczi, G.; Fafone, V.; Ferrante, I.; Fidecaro, F.; Fiori, I.; Flaminio, R.; Forte, L. A.; Fournier, J.-D.; Franc, J.; Franco, S.; Frasca, S.; Frasconi, F.; Galimberti, M.; Gammaitoni, L.; Garufi, F.; Gáspár, M. E.; Gemme, G.; Genin, E.; Gennai, A.; Giazotto, A.; Gouaty, R.; Granata, M.; Greverie, C.; Guidi, G. M.; Hayau, J.-F.; Heidmann, A.; Heitmann, H.; Hello, P.; Hemming, G.; Jaranowski, P.; Jonker, R. J. G.; Kasprzack, M.; Kowalska, I.; Królak, A.; Leroy, N.; Letendre, N.; Li, T. G. F.; Liguori, N.; Lorenzini, M.; Loriette, V.; Losurdo, G.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marque, J.; Martelli, F.; Masserot, A.; Michel, C.; Milano, L.; Minenkov, Y.; Mohan, M.; Morgado, N.; Morgia, A.; Mosca, S.; Mours, B.; Naticchioni, L.; Nocera, F.; Palladino, L.; Palomba, C.; Paoletti, F.; Paoletti, R.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Persichetti, G.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Poggiani, R.; Prato, M.; Prodi, G. A.; Punturo, M.; Puppo, P.; Rabeling, D. S.; Racz, I.; Rapagnani, P.; Re, V.; Regimbau, T.; Ricci, F.; Robinet, F.; Rocchi, A.; Rolland, L.; Romano, R.; Rosi?ska, D.; Ruggi, P.; Sassolas, B.; Sentenac, D.; Sperandio, L.; Sturani, R.; Swinkels, B.; Tacca, M.; Taffarello, L.; ter Braack, A. P. M.; Toncelli, A.; Tonelli, M.; Torre, O.; Tournefier, E.; Travasso, F.; Vajente, G.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; Vasuth, M.; Vavoulidis, M.; Vedovato, G.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinet, J.-Y.; Vitale, S.; Vocca, H.; Ward, R. L.; Was, M.; Yamamoto, K.; Yvert, M.; Zadro?ny, A.; Zendri, J.-P.

    2012-06-01

    The understanding of noise in interferometric gravitational wave detectors is fundamental in terms of both enabling prompt reactions in the mitigation of noise disturbances and in the establishment of appropriate data-cleaning strategies. Monitoring tools to perform online and offline noise analysis in areas such as transient signal detection, line identification algorithms and coherence are used to characterise the Virgo detector noise. In this paper, we describe the framework into which these tools are integrated - the Noise Monitor Application Programming Interface (NMAPI) - and provide examples of its application.

  14. View of substructure of Sixth Street Bridge overcrossing of Los ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of substructure of Sixth Street Bridge overcrossing of Los Angeles River. Looking west. Note dark hole at lower with is access ramp to river channel seen in HAER CA-176-56 - Sixth Street Bridge, Spanning 101 Freeway at Sixth Street, Los Angeles, Los Angeles County, CA

  15. Substructure of chromized steels after plastic surface deformation

    Microsoft Academic Search

    O. P. Stels'kiv; R. S. Arabskii

    1989-01-01

    1.The parameters of the fine crystal structure can be the numerical criteria of optimization of the structure of the surface layer in combined hardening treatment. (TCT + PSD).2.There is a correlation between the parameters of the substructure and the surface roughness, roughness can therefore be an indirect index of structural changes in the surface layer.3.The process of surface reeling of

  16. A Frequency-Domain Substructure System Identification Algorithm

    NASA Technical Reports Server (NTRS)

    Blades, Eric L.; Craig, Roy R., Jr.

    1996-01-01

    A new frequency-domain system identification algorithm is presented for system identification of substructures, such as payloads to be flown aboard the Space Shuttle. In the vibration test, all interface degrees of freedom where the substructure is connected to the carrier structure are either subjected to active excitation or are supported by a test stand with the reaction forces measured. The measured frequency-response data is used to obtain a linear, viscous-damped model with all interface-degree of freedom entries included. This model can then be used to validate analytical substructure models. This procedure makes it possible to obtain not only the fixed-interface modal data associated with a Craig-Bampton substructure model, but also the data associated with constraint modes. With this proposed algorithm, multiple-boundary-condition tests are not required, and test-stand dynamics is accounted for without requiring a separate modal test or finite element modeling of the test stand. Numerical simulations are used in examining the algorithm's ability to estimate valid reduced-order structural models. The algorithm's performance when frequency-response data covering narrow and broad frequency bandwidths is used as input is explored. Its performance when noise is added to the frequency-response data and the use of different least squares solution techniques are also examined. The identified reduced-order models are also compared for accuracy with other test-analysis models and a formulation for a Craig-Bampton test-analysis model is also presented.

  17. Weak Lensing Studies of Mass Substructure in Clusters of Galaxies

    NASA Astrophysics Data System (ADS)

    Huwe, Paul M.

    2012-01-01

    Cluster mass substructure is an important test of the hierarchical model of CDM. We use weak gravitational lensing shear measurements, combined with variable aperture filter methods and PSF correction, to extract information about mass subclumping in HST observations of clusters of galaxies. This work is funded by NASA Rhode Island Space Grant.

  18. Structural and Molecular Remodeling of Dendritic Spine Substructures

    E-print Network

    Sur, Mriganka

    Neuron Article Structural and Molecular Remodeling of Dendritic Spine Substructures during Long during long-term potentiation (LTP) at individual dendritic spines. Proteins translocated to the spine was rapidly remodeled while active cofilin was massively trans- ported to the spine. In the stabilization

  19. Construction of preconditioners for elliptic problems by substructuring. I

    Microsoft Academic Search

    J. H. Bramble; J. E. Pasciak; A. H. Schatz

    1986-01-01

    We consider the problem of solving the algebraic system of equations which arise from the discretization of symmetric elliptic boundary value problems via finite element methods. A new class of preconditioners for the discrete system is developed based on substructuring (also known as domain decomposition). The resulting preconditioned algorithms are well suited to emerging parallel computing architectures. The proposed methods

  20. An investigation of creep and substructure formation in 2124 Al

    Microsoft Academic Search

    Yong LI; Steven R. Nutt; Farghalli A. Mohamed

    1997-01-01

    The effect of stress on the creep behavior of powder metallurgy (PM) 2124 Al was investigated in the temperature range 618–678 K. In addition, substructure that developed during creep was examined by means of transmission electron microscopy (TEM). The creep data, which extend over seven orders of magnitude of strain rate, show that the apparent stress exponent, na, for creep

  1. Three-dimensional Mapping of CDM Substructure at Submillimeter Wavelengths

    E-print Network

    Kaiki Taro Inoue; Masashi Chiba

    2005-10-05

    The cold dark matter (CDM) structure formation model predicts that about 5-10 percent of a typical galactic halo of mass $\\sim 10^{12} \\ms$ is in substructures with masses $\\lesssim 10^8 \\ms$. To directly detect such substructures, we propose to observe dust continuum emission from a strongly lensed QSO-host galaxy using a large submillimeter interferometer array with a high angular resolution of $\\sim 0.01$arcsec such as the planned Atacama Large Submillimeter Array (ALMA). To assess their observational feasibility, we numerically simulate millilensing of an extended circular source by a CDM substructure modeled as a tidally truncated singular isothermal sphere (SIS) embedded in a typical QSO-galaxy lens system, B1422+231, modeled as a singular isothermal ellipsoid (SIE) with an external constant shear and a constant convergence. Assuming an angular resolution of 0.01arcsec, we find that the angular positions of $\\sim 10^8 \\ms$ substructures at several kpc from the center of the macrolens halo can be directly measured if the size of the dust continuum emission region and the gradient of the surface brightness at the position of the perturber are sufficiently large. From the astrometric shift on a scale of a few times $10~$mas of an image perturbed by a subhalo with respect to an unperturbed macrolensed image, we can break the degeneracy between subhalo mass and distance provided that macrolensing parameters are determined from positions and fluxes of multiple images.

  2. Dynamics of substructures in warm dark-matter cosmologies

    E-print Network

    Bastian Arnold; Alexander Knebe; Chris Power; Brad K. Gibson

    2008-11-13

    We performed cosmological simulations based upon both a cold dark matter (CDM) and a warm dark matter (WDM) model. The focus of our investigations lies with selected spatial and kinematic properties of substructure halos (subhalos) orbiting within host halos, that form in both dark-matter cosmologies. We aim at using the dynamics of the subhalos as a probe of the respective cosmology.

  3. Iterative method for dynamic condensation combined with substructuring scheme

    Microsoft Academic Search

    Dongsoo Choi; Hyungi Kim; Maenghyo Cho

    2008-01-01

    An iterated improved reduced system (IIRS) procedure combined with substructuring scheme for both undamped and nonclassically damped structures is presented. Iterated IIRS method is an efficient reduction technique because the highly accurate eigenproperties from the repeatedly updated condensed matrices can be obtained without consuming expensive computational cost. However, single domain direct approach of this method to large structures requires much

  4. Fast Algorithms of Plant Computation Based on Substructure Instances

    Microsoft Academic Search

    Hong-Ping YAN; Jean Francois Barczi; Philippe De Reffye; Bao-gang Hu; Marc Jaeger; J. Le Roux

    2002-01-01

    ABSTRACT Fast rendering and botanically faithful description of plants are a real challenge in computer graphics Usually, plant production is computed using the method internode by internode, while there exist a lot of buds in an individual tree, therefore, this approach is quite time In this paper, we present a new algorithm based on substructure instances to quickly compute plants\\

  5. AN A PRIORI BOUND FOR AUTOMATED MULTILEVEL SUBSTRUCTURING

    Microsoft Academic Search

    KOLJA ELSSELAND; HEINRICH VOSS

    2004-01-01

    The Automated Multi-Level Substructuring (AMLS) method has been developed to reduce the computational demands of frequency response analysis and has recently been proposed as an alternative to iterative projection methods like Lanczos or Jacobi-Davidson for computing a large number of eigenvalues for matrices of very large dimension. Based on Schur complements and modal approximations of submatrices on several levels AMLS

  6. Experimentally implementable criteria revealing substructures of genuine multipartite entanglement

    SciTech Connect

    Huber, Marcus; Schimpf, Hans; Gabriel, Andreas; Spengler, Christoph [Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria); Bruss, Dagmar [Heinrich-Heine-Universitaet Duesseldorf, Universitaetsstrasse 1, D-40225 Duesseldorf (Germany); Hiesmayr, Beatrix C. [Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria); Research Center for Quantum Information, Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, SK-84511 Bratislava (Slovakia)

    2011-02-15

    We present a general framework that reveals substructures of genuine multipartite entanglement. Via simple inequalities it is possible to discriminate different sets of multipartite qubit states. These inequalities are beneficial regarding experimental examinations as only local measurements are required. Furthermore, the number of observables scales favorably with system size. In exemplary cases we demonstrate the noise resistance and discuss implementations.

  7. The Arecibo Galaxy Environment Survey V : The Virgo Cluster (I)

    E-print Network

    Taylor, R; Auld, R; Minchin, R F

    2012-01-01

    We present 21 cm observations of a 10 $\\times$ 2 degree region in the Virgo cluster, obtained as part of the Arecibo Galaxy Environment Survey. 289 sources are detected over the full redshift range (-2,000 $<$ $v$$_{hel}$ $<$ + 20,000 km/s) with 95 belonging to the cluster ($v$$_{hel}$ $<$ 3,000 km/s). We combine our observations with data from the optically selected Virgo Cluster Catalogue (VCC) and the Sloan Digital Sky Survey (SDSS). Most of our detections can be clearly associated with a unique optical counterpart, and 30% of the cluster detections are new objects fainter than the VCC optical completeness limit. 7 detections may have no optical counterpart and we discuss the possible origins of these objects. 7 detections appear associated with early-type galaxies. We perform HI stacking on the HI-undetected galaxies listed in the VCC in this region and show that they must have significantly less gas than those actually detected in HI. Galaxies undetected in HI in the cluster appear to be really ...

  8. Seismic Attenuation Technology for the Advanced Virgo Gravitational Wave Detector

    NASA Astrophysics Data System (ADS)

    Beker, M. G.; Blom, M.; van den Brand, J. F. J.; Bulten, H. J.; Hennes, E.; Rabeling, D. S.

    The current interferometric gravitational wave detectors are being upgraded to what are termed 'second generation' devices. Sensitivities will be increased by an order of magnitude and these new instruments are expected to uncover the ?eld of gravitational astronomy. A main challenge in this endeavor is the mitigation of noise induced by seismic motion. Detailed studies with Virgo show that seismic noise can be reinjected into the dark fringe signal. For example, laser beam jitter and backscattered light limit the sensitivity of the interferometer. Here, we focus on seismic attenuators based on compact inverted pendulums in combination with geometric anti-prings to obtain 40 dB of attenuation above 4 Hz in six degrees of freedom. Low frequency resonances (< 0.5 Hz) are damped by using a control system based on input from LVDTs and geophones. Such systems are under development for the seismic attenuation of optical benches operated both in air and vacuum. The design and realization of the seismic attenuation system for the Virgo external injection bench, including its control scheme, will be discussed and stand-alone performance presented.

  9. Star Clusters in Virgo and Fornax Dwarf Irregular Galaxies

    E-print Network

    Anil Seth; Knut Olsen; Bryan Miller; Jennifer Lotz; Rosie Telford

    2003-11-04

    We present the results of a search for clusters in dwarf irregular galaxies in the Virgo and Fornax Cluster using HST WFPC2 snapshot data. The galaxy sample includes 28 galaxies, 11 of which are confirmed members of the Virgo and Fornax clusters. In the 11 confirmed members, we detect 237 cluster candidates and determine their V magnitudes, V-I colors and core radii. After statistical subtraction of background galaxies and foreground stars, most of the cluster candidates have V-I colors of -0.2 and 1.4, V magnitudes lying between 20 and 25th magnitude and core radii between 0 and 6 pc. Using H-alpha observations, we find that 26% of the blue cluster candidates are most likely HII regions. The rest of the cluster candidates are most likely massive (>10^4 Msol) young and old clusters. A comparison between the red cluster candidates in our sample and the Milky Way globular clusters shows that they have similar luminosity distributions, but that the red cluster candidates typically have larger core radii. Assuming that the red cluster candidates are in fact globular clusters, we derive specific frequencies (S_N) ranging from ~0-9 for the galaxies. Although the values are uncertain, seven of the galaxies appear to have specific frequencies greater than 2. These values are more typical of ellipticals and nucleated dwarf ellipticals than they are of spirals or Local Group dwarf irregulars.

  10. AMUSE-Virgo. III. Mid-infrared Photometry of Early-type Galaxies and Limits on Obscured Nuclear Emission

    NASA Astrophysics Data System (ADS)

    Leipski, Christian; Gallo, Elena; Treu, Tommaso; Woo, Jong-Hak; Miller, Brendan P.; Antonucci, Robert

    2012-01-01

    We complete our census of low-level nuclear activity in Virgo Cluster early-type galaxies by searching for obscured emission using Spitzer Space Telescope mid-infrared (MIR) imaging at 24 ?m. Of a total sample of 95 early-type galaxies, 53 objects are detected, including 16 showing kiloparsec-scale dust in optical images. One-dimensional and two-dimensional surface photometry of the 37 detections without extended dust features reveals that the MIR light is more centrally concentrated than the optical light as traced by Hubble Space Telescope F850LP-band images. No such modeling was performed for the sources with dust detected in the optical images. We explore several possible sources of the MIR excess emission, including obscured nuclear emission. We find that radial metallicity gradients in the stellar population appear to be a natural and most likely explanation for the observed behavior in a majority of the sources. Alternatively, if the concentrated MIR emission were due to nuclear activity, it would imply a MIR-to-X luminosity ratio ~5-10 for the low-luminosity active galactic nucleus (AGN) detected in X-rays by our survey. This ratio is an order of magnitude larger than that of typical low-luminosity AGNs and would imply an unusual spectral energy distribution. We conclude that the black holes found by our survey in quiescent early-type galaxies in Virgo have low bolometric Eddington ratios arising from low accretion rates and/or highly radiatively inefficient accretion.

  11. Stellar substructures in the solar neighbourhood. I. Kinematic group 3 in the Geneva-Copenhagen survey

    NASA Astrophysics Data System (ADS)

    Stonkut?, E.; Tautvaišien?, G.; Nordström, B.; Ženovien?, R.

    2012-05-01

    Context. Galactic archeology is a powerful tool for investigating the formation and evolution of the Milky Way. We use this technique to study kinematic groups of F- and G-stars in the solar neighbourhood. From correlations between orbital parameters, three new coherent groups of stars were recently identified and suggested to correspond to remnants of disrupted satellites. Aims: We determine detailed elemental abundances in stars belonging to one of these groups and compare their chemical composition with Galactic disc stars. The aim is to look for possible chemical signatures that might give information about the history of this kinematic group of stars. Methods: High-resolution spectra were obtained with the FIES spectrograph at the Nordic Optical Telescope, La Palma, and analysed with a differential model atmosphere method. Comparison stars were observed and analysed with the same method. Results: The average value of [Fe/H] for the 20 stars investigated in this study is -0.69 ± 0.05 dex. Elemental abundances of oxygen and ?-elements are overabundant in comparison with Galactic thin-disc dwarfs and thin-disc chemical evolution models. This abundance pattern has similar characteristics as the Galactic thick-disc. Conclusions: The homogeneous chemical composition together with the kinematic properties and ages of stars in the investigated Group 3 of the Geneva-Copenhagen survey provides evidence of their common origin and possible relation to an ancient merging event. The similar chemical composition of stars in the investigated group and the thick-disc stars might suggest that their formation histories are linked. Table 3 is available in electronic form at http://www.aanda.org

  12. Hubble space telescope imaging of decoupled dust clouds in the ram pressure stripped Virgo spirals NGC 4402 and NGC 4522

    SciTech Connect

    Abramson, Anne; Kenney, Jeffrey D. P., E-mail: anne.abramson@yale.edu, E-mail: jeff.kenney@yale.edu [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States)

    2014-03-01

    We present the highest-resolution study to date of the interstellar medium (ISM) in galaxies undergoing ram pressure stripping, using Hubble Space Telescope BVI imaging of NGC 4522 and NGC 4402, Virgo Cluster spirals that are well known to be experiencing intracluster medium (ICM) ram pressure. We find that throughout most of both galaxies, the main dust lane has a fairly well-defined edge, with a population of giant molecular cloud (GMC) sized (tens- to hundreds-of-pc scale), isolated, highly extincting dust clouds located up to ?1.5 kpc radially beyond it. Outside of these dense clouds, the area has little or no diffuse dust extinction, indicating that the clouds have decoupled from the lower-density ISM material that has already been stripped. Several of the dust clouds have elongated morphologies that indicate active ram pressure, including two large (kpc scale) filaments in NGC 4402 that are elongated in the projected ICM wind direction. We calculate a lower limit on the H I + H{sub 2} masses of these clouds based on their dust extinctions and find that a correction factor of ?10 gives cloud masses consistent with those measured in CO for clouds of similar diameters, probably due to the complicating factors of foreground light, cloud substructure, and resolution limitations. Assuming that the clouds' actual masses are consistent with those of GMCs of similar diameters (?10{sup 4}-10{sup 5} M {sub ?}), we estimate that only a small fraction (?1%-10%) of the original H I + H{sub 2} remains in the parts of the disks with decoupled clouds. Based on H? images, a similar fraction of star formation persists in these regions, 2%-3% of the estimated pre-stripping star formation rate. We find that the decoupled cloud lifetimes may be up to 150-200 Myr.

  13. Line-Strength Indices in Bright Spheroidals: Evidence for a Stellar Population Dichotomy between Spheroidal and Elliptical Galaxies

    Microsoft Academic Search

    Javier Gorgas; Santos Pedraz; Rafael Guzman; Nicolas Cardiel; J. Jesus Gonzalez

    1997-01-01

    We present new measurements of central line-strength indices (namely Mg2,\\u000a, and Hbeta and gradients for a sample of 6 bright spheroidal galaxies\\u000a(Sph's) in the Virgo cluster. Comparison with similar measurements for\\u000aelliptical galaxies (E's), galactic globular clusters (GGC's), and stellar\\u000apopulation models yield the following results: (1) In contrast with bright E's,\\u000abright Sph's are consistent with solar

  14. The magnetic fields of large Virgo Cluster spirals

    NASA Astrophysics Data System (ADS)

    We?gowiec, M.; Urbanik, M.; Vollmer, B.; Beck, R.; Chy?y, K. T.; Soida, M.; Balkowski, Ch.

    2007-08-01

    Context: Because of its proximity the Virgo Cluster is an excellent target for studying interactions of galaxies with the cluster environment. Both the high-velocity tidal interactions and effects of ram pressure stripping by the intracluster gas can be investigated. Aims: Optical and/or H I observations do not always show the effects of weak interactions between galaxies and their encounters with the cluster medium. For this reason we searched for possible anomalies in the magnetic field structure in Virgo Cluster spirals that could be attributed to perturbations in their gas distribution and kinematics. Methods: Five angularly large Virgo Cluster spiral galaxies (NGC 4501, NGC 4438, NGC 4535, NGC 4548, and NGC 4654) were the targets of a sensitive total power and polarization study using the 100-m radio telescope in Effelsberg at 4.85 GHz. For two objects, polarization data at higher frequencies were obtained allowing Faraday rotation analysis. Results: Distorted magnetic field structures were identified in all galaxies. Interaction-induced magnetized outflows were found in NGC 4438 (due to nuclear activity) and NGC 4654 (a combination of tidal tails and ram pressure effects). Almost all objects (except the anaemic NGC 4548), exhibit distortions in polarized radio continuum attributable to the influence of the ambient gas. For some galaxies they agree with observations of other species, but the magnetic field is sometimes (NGC 4535) the only tracer of the interaction with the cluster environment. Conclusions: The cluster environment clearly affects the evolution of the galaxies due to ram pressure and tidal effects. Magnetic fields provide a very long lasting memory of past interactions. Therefore, they are a good tracer of weak interactions that are difficult to detect by other observations. Information about motions of galaxies in the sky plane and their three-dimensional distribution can also be obtained. Based on the observations with the 100-m telescope at Effelsberg operated by the Max-Planck-Institut für Radioastronomie (MPIfR) on behalf of the Max-Planck-Gesellschaft.

  15. Microlensing and the Stellar Mass Function

    E-print Network

    Andrew Gould

    1996-04-02

    Traditional approaches to measuring the stellar mass function (MF) are fundamentally limited because objects are detected based on their luminosity, not their mass. These methods are thereby restricted to luminous and relatively nearby stellar populations. Gravitational microlensing promises to revolutionize our understanding of the MF. It is already technologically feasible to measure the MFs of the Galactic disk and Galactic bulge as functions of position, although the actual execution of this program requires aggressive ground-based observations including infrared interferometry, as well as the launching of a small satellite telescope. Rapid developments in microlensing, including the new technique of ``pixel lensing'' of unresolved stars, will allow one to probe the MF and luminosity function of nearby galaxies. Such observations of M31 are already underway, and pixel-lensing observations of M87 with the {\\it Hubble Space Telescope} would permit detection of dark intra-cluster objects in Virgo. Microlensing techniques can also be applied to investigate the star-formation history of the universe and to search for planets with masses as small as the Earth's. Based on an invited talk at the January 1996 AAS meeting in San Antonio. PASP (June 1996) in press, (c) ASP, reproduced with permission.

  16. LIGO/VIRGO searches of gravitational wave bursts in hypernovae

    NASA Astrophysics Data System (ADS)

    Van putten, Maurice

    2002-06-01

    Gamma-ray bursts from Kerr black holes are expected to be luminous in gravitational radiation powered by the spin-energy of the black hole [van Putten & Levinson, Science, 295, 1874 (2002)]. The Brown scenario of GRB-hypernovae (and their remnants in soft X-ray transients) hereby describes a contemporaneous and unbeamed explosion shell, consistent with GRB 011121 and GRB 011121 and GRB 011211. This suggests considering upcoming wide-angle supernovae surveys to guide future LIGO/VIRGO searches for bursts in gravitational waves. If all long GRBs stem from hypernovae, the expected hypernova-to-supernova ratio is about one in a few hundred in the local universe. Events for which the energy E and frequency f in these gravitational wave emissions satisfies the compactness criterion 2? ? f dE > 0.005 will provide an existence test of Kerr black holes.

  17. Gravitational wave searches with Advanced LIGO and Advanced Virgo

    E-print Network

    C. Van Den Broeck; for the LIGO Scientific Collaboration; the Virgo Collaboration

    2015-05-18

    Advanced LIGO and Advanced Virgo are expected to make the first direct detections of gravitational waves (GW) in the next several years. Possible types of GW emission include short-duration bursts, signals from the coalescence of compact binaries consisting of neutron stars or black holes, continuous radiation from fast-spinning neutron stars, and stochastic background radiation of a primordial nature or resulting from the superposition of a large number of individually unresolvable sources. We describe the different approaches that have been developed to search for these different types of signals. In this paper we focus on the GW detection methods themselves; multi-messenger searches as well as further science enabled by detections are dealt with in separate contributions to this volume.

  18. The Herschel Virgo Cluster Survey - XVI. A cluster inventory

    NASA Astrophysics Data System (ADS)

    Davies, J. I.; Bianchi, S.; Baes, M.; Bendo, G. J.; Clemens, M.; De Looze, I.; di Serego Alighieri, S.; Fritz, J.; Fuller, C.; Pappalardo, C.; Hughes, T. M.; Madden, S.; Smith, M. W. L.; Verstappen, J.; Vlahakis, C.

    2014-03-01

    Herschel far-infrared (FIR) observations are used to construct Virgo cluster galaxy luminosity functions and to show that the cluster lacks the very bright and the numerous faint sources detected in field galaxy surveys. The FIR spectral energy distributions are fitted to obtain dust masses and temperatures and the dust mass function. The cluster is overdense in dust by about a factor of 100 compared to the field. The same emissivity (?)-temperature relation applies for different galaxies as that found for different regions of M31. We use optical and H I data to show that Virgo is overdense in stars and atomic gas by about a factor of 100 and 20, respectively. Metallicity values are used to measure the mass of metals in the gas phase. The mean metallicity is ˜0.7 solar, and ˜50 per cent of the metals are in the dust. For the cluster as a whole, the mass density of stars in galaxies is eight times that of the gas and the gas mass density is 130 times that of the metals. We use our data to consider the chemical evolution of the individual galaxies, inferring that the measured variations in the effective yield are due to galaxies having different ages, being affected to varying degrees by gas loss. Four galaxy scaling relations are considered: mass-metallicity, mass-velocity, mass-star formation rate and mass-radius - we suggest that initial galaxy mass is the prime driver of a galaxy's ultimate destiny. Finally, we use X-ray observations and galaxy dynamics to assess the dark and baryonic matter content compared to the cosmological model.

  19. C II 158 ??bservations of a Sample of Late-type Galaxies from the Virgo Cluster

    NASA Technical Reports Server (NTRS)

    Leech, K.; Volk, H.; Heinrichsen, I.; Hippelein, H.; Metcalfe, L.; Pierini, D.; Popescu, C.; Tuffs, R.; Xu, C.

    1999-01-01

    We have observed 19 Virgo cluster spiral galaxies with the Long Wavelength Spectrometer (LWS) onboard ESAs Infrared Space Observatory (ISO) obtaining spectra around the [CII] 157.741 ??ine structure line.

  20. Search for Gravitational Waves from Low Mass Compact Binary Coalescence in LIGO's Sixth Science Run and Virgo's Science Runs 2 and 3

    NASA Technical Reports Server (NTRS)

    Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Affeldt, C.; Agathos, M.; Ajith, P.; Allen, B.; Allen, G. S.; Ceron, E. Amador; Amariutei, D.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Arain, M. A.; Araya, M. C.; Blackburn, L.; Camp, J. B.; Cannizzo, J.

    2012-01-01

    We report on a search for gravitational waves from coalescing compact binaries using LIGO and Virgo observations between July 7, 2009, and October 20. 2010. We searched for signals from binaries with total mass between 2 and 25 Stellar Mass; this includes binary neutron stars, binary black holes, and binaries consisting of a black hole and neutron star. The detectors were sensitive to systems up to 40 Mpc distant for binary neutron stars, and further for higher mass systems. No gravitational-wave signals were detected. We report upper limits on the rate of compact binary coalescence as a function of total mass. including the results from previous LIGO and Virgo observations. The cumulative 90% confidence rate upper limits of the binary coalescence of binary neutron star, neutron star-black hole, and binary black hole systems are 1.3 x 10(exp -4), 3.1 x 10(exp -5), and 6.4 x 10(exp -6)/cu Mpc/yr, respectively. These upper limits are up to a factor 1.4 lower than previously derived limits. We also report on results from a blind injection challenge.

  1. {sup 12}CO(J = 1 - 0) ON-THE-FLY MAPPING SURVEY OF THE VIRGO CLUSTER SPIRALS. I. DATA AND ATLAS

    SciTech Connect

    Chung, E. J. [Department of Astronomy, Yonsei University, Seoul 120-749 (Korea, Republic of); Rhee, M.-H. [Yonsei University Observatory, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, H. [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Yun, Min S.; Heyer, M.; Young, J. S. [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States)], E-mail: rigelej@yonsei.ac.kr

    2009-10-01

    We have performed an On-The-Fly (OTF) mapping survey of {sup 12}CO(J = 1-0) emission in 28 Virgo cluster spiral galaxies using the Five College Radio Astronomy Observatory (FCRAO) 14 m telescope. This survey aims to characterize the CO distribution, kinematics, and luminosity of a large sample of galaxies covering the full extents of stellar disks, rather than sampling only the inner disks or the major axis as was done by many previous single dish and interferometric CO surveys. CO emission is detected in 20 galaxies among the 28 Virgo spirals observed. An atlas consisting of global measures, radial measures, and maps is presented for each detected galaxy. A note summarizing the CO data is also presented along with relevant information from the literature. The CO properties derived from our OTF observations are presented and compared with the results from the FCRAO Extragalactic CO Survey by Young et al. which utilized position-switching observations along the major axis and a model fitting method. We find that our OTF-derived CO properties agree well with the Young et al. results in many cases, but the Young et al. measurements are larger by a factor of 1.4-2.4 for seven (out of 18) cases. We will explore further the possible causes for the discrepancy in the analysis paper currently under preparation.

  2. CAUGHT IN THE ACT: STRONG, ACTIVE RAM PRESSURE STRIPPING IN VIRGO CLUSTER SPIRAL NGC 4330

    SciTech Connect

    Abramson, Anne; Kenney, Jeffrey D. P. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States); Crowl, Hugh H.; Van Gorkom, J. H.; Schiminovich, David [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Chung, Aeree [Department of Astronomy, Yonsei University, 134 Shinchonding, Seodaemungu, Seoul 120-749 (Korea, Republic of); Vollmer, Bernd, E-mail: anne.abramson@yale.edu, E-mail: jeff.kenney@yale.edu, E-mail: hugh@astro.columbia.edu, E-mail: jvangork@astro.columbia.edu, E-mail: ds@astro.columbia.edu, E-mail: achung@yonsei.ac.kr, E-mail: bvollmer@astro.u-strasbg.fr [Observatoire astronomique de Strasbourg, 11 rue de l'universite, 67000 Strasbourg (France)

    2011-05-15

    We present a multi-wavelength study of NGC 4330, a highly inclined spiral galaxy in the Virgo Cluster which is a clear example of strong, ongoing intracluster medium-interstellar medium (ICM-ISM) ram pressure stripping. The H I has been removed from well within the undisturbed old stellar disk, to 50%-65% of R{sub 25}. Multi-wavelength data (WIYN BVR-H{alpha}, Very Large Array 21 cm H I and radio continuum, and Galaxy Evolution Explorer NUV and FUV) reveal several one-sided extraplanar features likely caused by ram pressure at an intermediate disk-wind angle. At the leading edge of the interaction, the H{alpha} and dust extinction curve sharply out of the disk in a remarkable and distinctive 'upturn' feature that may be generally useful as a diagnostic indicator of active ram pressure. On the trailing side, the ISM is stretched out in a long tail which contains 10% of the galaxy's total H I emission, 6%-9% of its NUV-FUV emission, but only 2% of the H{alpha}. The centroid of the H I tail is downwind of the UV/H{alpha} tail, suggesting that the ICM wind has shifted most of the ISM downwind over the course of the past 10-300 Myr. Along the major axis, the disk is highly asymmetric in the UV, but more symmetric in H{alpha} and H I, also implying recent changes in the distributions of gas and star formation. The UV-optical colors indicate very different star formation histories for the leading and trailing sides of the galaxy. On the leading side, a strong gradient in the UV-optical colors of the gas-stripped disk suggests that it has taken 200-400 Myr to strip the gas from a radius of >8 to 5 kpc, but on the trailing side there is no age gradient. All our data suggest a scenario in which NGC 4330 is falling into the cluster center for the first time and has experienced a significant increase in ram pressure over the last 200-400 Myr. Many of the UV-bright stars that form outside the thin disk due to ram pressure will ultimately produce stellar thick disk and halo components with characteristic morphologies and age distributions distinct from those produced by gravitational interactions.

  3. Towards an Understanding of the Correlations in Jet Substructure

    E-print Network

    D. Adams; A. Arce; L. Asquith; M. Backovic; T. Barillari; P. Berta; D. Bertolini; A. Buckley; J. Butterworth; R. C. Camacho Toro; J. Caudron; Y. -T. Chien; J. Cogan; B. Cooper; D. Curtin; C. Debenedetti; J. Dolen; M. Eklund; S. El Hedri; S. D. Ellis; T. Embry; D. Ferencek; J. Ferrando; S. Fleischmann; M. Freytsis; M. Giulini; Z. Han; D. Hare; P. Harris; A. Hinzmann; R. Hoing; A. Hornig; M. Jankowiak; K. Johns; G. Kasieczka; R. Kogler; W. Lampl; A. J. Larkoski; C. Lee; R. Leone; P. Loch; D. Lopez Mateos; H. K. Lou; M. Low; P. Maksimovic; I. Marchesini; S. Marzani; L. Masetti; R. McCarthy; S. Menke; D. W. Miller; K. Mishra; B. Nachman; P. Nef; F. T. O'Grady; A. Ovcharova; A. Picazio; C. Pollard; B. Potter-Landua; C. Potter; S. Rappoccio; J. Rojo; J. Rutherfoord; G. P. Salam; R. M. Schabinger; A. Schwartzman; M. D. Schwartz; B. Shuve; P. Sinervo; D. Soper; D. E. Sosa Corral; M. Spannowsky; E. Strauss; M. Swiatlowski; J. Thaler; C. Thomas; E. Thompson; N. V. Tran; J. Tseng; E. Usai; L. Valery; J. Veatch; M. Vos; W. Waalewijn; J. Wacker; C. Young

    2015-04-15

    Over the past decade, a large number of jet substructure observables have been proposed in the literature, and explored at the LHC experiments. Such observables attempt to utilize the internal structure of jets in order to distinguish those initiated by quarks, gluons, or by boosted heavy objects, such as top quarks and W bosons. This report, originating from and motivated by the BOOST2013 workshop, presents original particle-level studies that aim to improve our understanding of the relationships between jet substructure observables, their complementarity, and their dependence on the underlying jet properties, particularly the jet radius and jet transverse momentum. This is explored in the context of quark/gluon discrimination, boosted W boson tagging and boosted top quark tagging.

  4. Present and Future Astrometric Study of Halo Substructure

    E-print Network

    Steven R. Majewski; Allyson A. Polak; David R. Law; Helio J. Rocha-Pinto

    2005-03-31

    We focus on how astrometric surveys might be exploited for the study of Galactic halo substructure originating from the disruption of satellite systems. The Sagittarius (Sgr) dwarf spheroidal tidal stream provides a useful template to explore present and future capabilities of proper motion surveys for finding and studying substructure as well as for using individual tidal streams to probe the global properties of the Milky Way. The configuration of the Sgr stream is particularly well suited for measuring the flattening of the halo and for providing an independent means for measuring the speed of the Local Standard of Rest. For the various proposed experiments, the required proper motion accuracies are well within the capabilities of the Space Interferometry Mission (SIM PlanetQuest).

  5. Towards an Understanding of the Correlations in Jet Substructure

    E-print Network

    Adams, D; Asquith, L; Backovic, M; Barillari, T; Berta, P; Bertolini, D; Buckley, A; Butterworth, J; Toro, R C Camacho; Caudron, J; Chien, Y -T; Cogan, J; Cooper, B; Curtin, D; Debenedetti, C; Dolen, J; Eklund, M; Hedri, S El; Ellis, S D; Embry, T; Ferencek, D; Ferrando, J; Fleischmann, S; Freytsis, M; Giulini, M; Han, Z; Hare, D; Harris, P; Hinzmann, A; Hoing, R; Hornig, A; Jankowiak, M; Johns, K; Kasieczka, G; Kogler, R; Lampl, W; Larkoski, A J; Lee, C; Leone, R; Loch, P; Mateos, D Lopez; Lou, H K; Low, M; Maksimovic, P; Marchesini, I; Marzani, S; Masetti, L; McCarthy, R; Menke, S; Miller, D W; Mishra, K; Nachman, B; Nef, P; O'Grady, F T; Ovcharova, A; Picazio, A; Pollard, C; Potter-Landua, B; Potter, C; Rappoccio, S; Rojo, J; Rutherfoord, J; Salam, G P; Schabinger, J; Schwartzman, A; Schwartz, M D; Shuve, B; Sinervo, P; Soper, D; Corral, D E Sosa; Spannowsky, M; Strauss, E; Swiatlowski, M; Thaler, J; Thomas, C; Thompson, E; Tran, N V; Tseng, J; Usai, E; Valery, L; Veatch, J; Vos, M; Waalewijn, W; Wacker, J; Young, C

    2015-01-01

    Over the past decade, a large number of jet substructure observables have been proposed in the literature, and explored at the LHC experiments. Such observables attempt to utilize the internal structure of jets in order to distinguish those initiated by quarks, gluons, or by boosted heavy objects, such as top quarks and W bosons. This report, originating from and motivated by the BOOST2013 workshop, presents original particle-level studies that aim to improve our understanding of the relationships between jet substructure observables, their complementarity, and their dependence on the underlying jet properties, particularly the jet radius and jet transverse momentum. This is explored in the context of quark/gluon discrimination, boosted W boson tagging and boosted top quark tagging.

  6. Fold Recognition Using Sequence Fingerprints of Protein Local Substructures

    SciTech Connect

    Kryshtafovych, A A; Hvidsten, T; Komorowski, J; Fidelis, K

    2003-06-04

    A protein local substructure (descriptor) is a set of several short non-overlapping fragments of the polypeptide chain. Each descriptor describes local environment of a particular residue and includes only those segments that are located in the proximity of this residue. Similar descriptors from the representative set of proteins were analyzed to reveal links between the substructures and sequences of their segments. Using detected sequence-based fingerprints specific geometrical conformations are assigned to new sequences. The ability of the approach to recognize correct SCOP folds was tested on 273 sequences from the 49 most popular folds. Good predictions were obtained in 85% of cases. No performance drop was observed with decreasing sequence similarity between target sequences and sequences from the training set of proteins.

  7. Substructure in Clusters of Galaxies and the value of ${\\bf?}$

    E-print Network

    Suvendra N. Dutta

    1995-05-01

    We investigate the formation of clusters of galaxies in an expanding universe using a new code that regrids at a region of high density. In particular we investigate two models for the initial conditions, both with the standard CDM power spectrum - one has $\\Omega = 1$ and the other $\\Omega = 0.2$. Both universes have $H_0 = 100 \\kms\\mpc^{-1}$ and $\\Lambda = 0$. The level of substructure in the final cluster can be used as a discriminant of the cosmic density. We discuss various statistics which can be measured observationally from clusters of galaxies, that can be used to discriminate between the two models. We find that most of the statistics that use the clusters' member galaxies may not be the best measures of substructure. Statistics that rely more on X-ray maps and other observables depending more directly on the mass distribution could be better discriminants of $\\Omega$.

  8. Tableau-based protein substructure search using quadratic programming

    PubMed Central

    Stivala, Alex; Wirth, Anthony; Stuckey, Peter J

    2009-01-01

    Background Searching for proteins that contain similar substructures is an important task in structural biology. The exact solution of most formulations of this problem, including a recently published method based on tableaux, is too slow for practical use in scanning a large database. Results We developed an improved method for detecting substructural similarities in proteins using tableaux. Tableaux are compared efficiently by solving the quadratic program (QP) corresponding to the quadratic integer program (QIP) formulation of the extraction of maximally-similar tableaux. We compare the accuracy of the method in classifying protein folds with some existing techniques. Conclusion We find that including constraints based on the separation of secondary structure elements increases the accuracy of protein structure search using maximally-similar subtableau extraction, to a level where it has comparable or superior accuracy to existing techniques. We demonstrate that our implementation is able to search a structural database in a matter of hours on a standard PC. PMID:19450287

  9. Washington CCD Photometry of the Globular Cluster System of the Giant Elliptical Galaxy M60 in Virgo

    E-print Network

    Myung Gyoon Lee; Hong Soo Park; Eunhyeuk Kim; Ho Seong Hwang; Sang Chul Kim; Doug Geisler

    2008-02-12

    We present a photometric study of the globular clusters in the giant elliptical galaxy M60 in the Virgo cluster, based on deep, relatively wide field Washington CT_1 CCD images. The color-magnitude diagram reveals a significant population of globular clusters in M60, and a large number of young luminous clusters in NGC 4647, a small companion spiral galaxy north-west of M60. The color distribution of the globular clusters in M60 is clearly bimodal, with a blue peak at (C-T_1)=1.37, and a red peak at (C-T_1)=1.87. We derive two new transformation relations between the (C-T_1)_0 color and [Fe/H] using the data for the globular clusters in our Galaxy and M49. Using these relations we derive the metallicity distribution of the globular clusters in M60, which is also bimodal: a dominant metal-poor component with center at [Fe/H]=-1.2, and a weaker metal-rich component with center at [Fe/H]=-0.2. The radial number density profile of the globular clusters is more extended than that of the stellar halo, and the radial number density profile of the blue globular clusters is more extended than that of the red globular clusters. The number density maps of the globular clusters show that the spatial distribution of the blue globular clusters is roughly circular, while that of the red globular cluster is elongated similarly to that of the stellar halo. We estimate the total number of the globular clusters in M60 to be 3600+/-500$,and the specific frequency to be S_N=3.8+/-0.4. The mean color of the bright blue globular clusters gets redder as they get brighter in both the inner and outer region of M60. This blue tilt is seen also in the outer region of M49, the brightest Virgo galaxy. Implications of these results are discussed.

  10. Harassment Origin for Kinematic Substructures in Dwarf Elliptical Galaxies?

    E-print Network

    A. C. Gonzalez-Garcia; J. A. L. Aguerri; M. Balcells

    2005-08-29

    We have run high resolution N-body models simulating the encounter of a dwarf galaxy with a bright elliptical galaxy. The dwarf absorbs orbital angular momentum and shows counter-rotating features in the external regions of the galaxy. To explain the core-envelope kinematic decoupling observed in some dwarf galaxies in high-density environments requires nearly head-on collisions and very little dark matter bound to the dwarf. These kinematic structures appear under rather restrictive conditions. As a consequence, in a cluster like Virgo ~1% of dwarf galaxies may present counter-rotation formed by harassment.

  11. Benefits of joint LIGO -- Virgo coincidence searches for burst and inspiral signals

    E-print Network

    F. Beauville; M. -A. Bizouard; L. Blackburn; L. Bosi; P. Brady; L. Brocco; D. Brown; D. Buskulic; F. Cavalier; S. Chatterji; N. Christensen; A. -C. Clapson; S. Fairhurst; D. Grosjean; G. Guidi; P. Hello; E. Katsavounidis; M. Knight; A. Lazzarini; N. Leroy; F. Marion; B. Mours; F. Ricci; A. Vicere; M. Zanolin

    2005-09-12

    We examine the benefits of performing a joint LIGO--Virgo search for transient signals. We do this by adding burst and inspiral signals to 24 hours of simulated detector data. We find significant advantages to performing a joint coincidence analysis, above either a LIGO only or Virgo only search. These include an increased detection efficiency, at a fixed false alarm rate, to both burst and inspiral events and an ability to reconstruct the sky location of a signal.

  12. The evolution substructure I: a new identification method

    E-print Network

    Stuart P. D. Gill; Alexander Knebe; Brad K. Gibson

    2004-04-13

    We describe our new "MLAPM-halo-finder" (MHF) which is based on the adaptive grid structure of the N-body code MLAPM. We then extend the MHF code in order to track the orbital evolution of gravitationally bound objects through any given cosmological N-body simulation - our so-called "MLAPM-halo-tracker" (MHT). The mode of operation of MHT is demonstrated using a series of eight high-resolution N-body simulations of galaxy clusters. Each of these halos hosts more than one million particles within their virial radii Rvir. We use MHT as well as MHF to follow the temporal evolution of hundreds of individual satellites, and show that the radial distribution of these substructure satellites follows a "universal" radial distribution irrespective of the host halo's environment and formation history. This in fact might pose another problem for simulations of CDM structure formation as there are recent findings by Taylor et al. (2003) that the Milky Way satellites are found preferentially closer to the galactic centre and simulations underestimate the amount of central substructure, respectively. Further, this universal substructure profile is anti-biased with respect to the underlying dark matter profile. Both the halo finder MHF and the halo tracker MHT will become part of the open source MLAPM distribution.

  13. Halo Substructure in the Hercules-Aquila Cloud

    NASA Astrophysics Data System (ADS)

    Martin, Charles; Newberg, Heidi Jo; Carlin, Jeffrey L.; Willett, Benjamin A.; Yanny, Brian; Kent, Stephen M.

    2015-01-01

    We present the velocity substructure in the direction of the northern portion of the Hercules-Aquila Cloud using observations taken at Apache Point Observatory (APO), in conjunction with Data Release 10 of the Sloan Digital Sky Survey (SDSS). The Hercules Aquila Cloud is an overdensity of halo stars found at low Galactic latitudes in the direction of the Galactic center. Using Blue Horizontal Branch stars (BHBs), we identify several structures as overdensities in distance and velocity. The most prominent of these structures covers ~ 250 deg2 of the sky centered around (l,b)~(55°,45°) and ranges in distance from 16~27 kpc. This structure is found to be metal poor, [Fe/H] ~ -2.0, with a tight velocity distribution of -60 km/s < vgsr < -20 km/s. Although this halo substructure has about the same location and distance as the Hercules Aquila Cloud, the line-of-sight velocity differs by 220 km/s from the published velocity for this cloud. The other low metallicity substructures that appear to clump in distance and velocity have similarly large spatial distributions on the sky, which may point to additional ancient accretion events. This research is supported by the NSF through grants AST 09-37523 and AST 10-09670, as well as the NASA-NY Space Grant.

  14. Galaxies at the extremes: Ultra-diffuse galaxies in the Virgo Cluster

    E-print Network

    Mihos, Chris; Ferrarese, Laura; Feldmeier, John J; Côté, Patrick; Peng, Eric W; Harding, Paul; Liu, Chengze; Gwyn, Stephen; Cuillandre, Jean-Charles

    2015-01-01

    We report the discovery of three large (R29 >~ 1 arcminute) extremely low surface brightness (mu_(V,0) ~ 27.0) galaxies identified using our deep, wide-field imaging of the Virgo Cluster from the Burrell Schmidt telescope. Complementary data from the Next Generation Virgo Cluster Survey do not resolve red giant branch stars in these objects down to i=24, yielding a lower distance limit of 2.5 Mpc. At the Virgo distance, these objects have half-light radii 3-10 kpc and luminosities L_V=2-9x10^7 Lsun. These galaxies rival the most extreme LSB galaxies recently identified in the Coma cluster and are located well within Virgo's virial radius; two are projected directly on the cluster core. One object appears to be a nucleated LSB in the process of being tidally stripped to form a new Virgo ultracompact dwarf galaxy. The others show no sign of tidal disruption, despite the fact that such objects should be most vulnerable to tidal destruction in the cluster environment. The relative proximity of Virgo makes these o...

  15. Alignments of the Galaxies in and around the Virgo Cluster with the Local Velocity Shear

    NASA Astrophysics Data System (ADS)

    Lee, Jounghun; Rey, Soo Chang; Kim, Suk

    2014-08-01

    Observational evidence is presented for the alignment between the cosmic sheet and the principal axis of the velocity shear field at the position of the Virgo cluster. The galaxies in and around the Virgo cluster from the Extended Virgo Cluster Catalog that was recently constructed by Kim et al. are used to determine the direction of the local sheet. The peculiar velocity field reconstructed from the Sloan Digital Sky Survey Data Release 7 is analyzed to estimate the local velocity shear tensor at the Virgo center. Showing first that the minor principal axis of the local velocity shear tensor is almost parallel to the direction of the line of sight, we detect a clear signal of alignment between the positions of the Virgo satellites and the intermediate principal axis of the local velocity shear projected onto the plane of the sky. Furthermore, the dwarf satellites are found to appear more strongly aligned than their normal counterparts, which is interpreted as an indication of the following. (1) The normal satellites and the dwarf satellites fall in the Virgo cluster preferentially along the local filament and the local sheet, respectively. (2) The local filament is aligned with the minor principal axis of the local velocity shear while the local sheet is parallel to the plane spanned by the minor and intermediate principal axes. Our result is consistent with the recent numerical claim that the velocity shear is a good tracer of the cosmic web.

  16. The WSRT Virgo Hi filament survey. II. Cross correlation data

    NASA Astrophysics Data System (ADS)

    Popping, A.; Braun, R.

    2011-04-01

    Context. The extended environment of galaxies contains a wealth of information about the formation and life cycle of galaxies which are regulated by accretion and feedback processes. Observations of neutral hydrogen are routinely used to image the high brightness disks of galaxies and to study their kinematics. Deeper observations will give more insight into the distribution of diffuse gas in the extended halo of the galaxies and the inter-galactic medium, where numerical simulations predict a cosmic web of extended structures and gaseous filaments. Aims: To observe the extended environment of galaxies, column density sensitivities have to be achieved that probe the regime of Lyman limit systems. H i observations are typically limited to a brightness sensitivity of NHI ~ 1019 cm-2, but this must be improved upon by ~2 orders of magnitude. Methods: In this paper we present the interferometric data of the Westerbork Virgo H i Filament Survey (WVFS) - the total power product of this survey has been published in an earlier paper. By observing at extreme hour angles, a filled aperture is simulated of 300 × 25 m in size, that has the typical collecting power and sensitivity of a single dish telescope, but the well defined bandpass characteristics of an interferometer. With the very good surface brightness sensitivity of the data, we hope to make new H i detections of diffuse systems with moderate angular resolution. Results: The survey maps 135 degrees in Right Ascension between 8 and 17 h and 11 degrees in Declination between - 1 and 10 degrees, including the galaxy filament connecting the Local Group with the Virgo Cluster. Only positive declinations could be completely processed and analysed due to projection effects. A typical flux sensitivity of 6 mJy beam-1 over 16 km s-1 is achieved, that corresponds to a brightness sensitivity of NHI ~ 1018 cm-2. An unbiased search has been done with a high significance threshold as well a search with a lower significance limit but requiring an optical counterpart. In total, 199 objects have been detected, of which 17 are new H i detections. Conclusions: By observing at extreme hour angles with the WSRT, a filled aperture can be simulated in projection, with a very good brightness sensitivity, comparable to that of a single dish telescope. Despite some technical challenges, the data provide valuable constraints on faint, circum-galactic H i features. Appendix is only available at electronic form at http://www.aanda.org

  17. VIVA: VLA imaging of Virgo galaxies in atomic gas

    NASA Astrophysics Data System (ADS)

    Chung, Aeree

    In this thesis I present high resolution HI maps and kinematics of 53 carefully selected galaxies in the Virgo cluster. The goal is to study details of the cluster environmental effect on galaxy evolution, i.e. in which density regions and by which processes do galaxies feel the impact of the cluster. Studying HI content is essential to achieve this goal as it is often a useful probe of both gas-gas and tidal interactions and also a reservoir of star formation. Virgo as a dynamically young and nearby cluster, it contains many candidates for various mechanisms at work (e.g. ram-pressure or turbulent/viscous stripping, thermal evaporation, and tidal interactions) and allows us to see the details. We have sampled 48 spirals and 5 irregular/dwarf systems which show a wide range of star formation properties from anemic to starburst. The galaxies in the sample are spread throughout the cluster from near the dense cluster core to the outskirts (0.3--3.3 Mpc in projection). The result has revealed a whole spectrum of gas stripping stages from severely HI stripped galaxies to the HI as it is leaving the disk. Most HI stripped but optically undisturbed galaxies are found within 0.5 Mpc radius in projection from the cluster center. These galaxies show signatures of ongoing interactions with the hot cluster gas. Galaxies with truncated HI disks are also found at lower density regions. Some of those might have gone through the cluster core a while ago and currently be in their way out. Some however show gas stripping epochs that is inconsistent with their locations within the cluster which requires more than a simple interaction with static cluster gas; such as tidal interactions with other galaxies or locally enhanced ram-pressure due to subclusters' falling in. Beyond this region, most galaxies show normal (.08 < or = [Special characters omitted.] < 1.2) to extended ([Special characters omitted.] > or = 1.2) HI disks. Especially, 7 galaxies were found with one-sided long Hi tails in intermediate to low density regions (0.6--1.0 Mpc in projection from the cluster center). Their HI distribution and kinematics are suggestive of current/recent stripping (within < 2 × 10 8 yrs before/after the peak pressure clue to the cluster gas). We argue that these galaxies are recent arrivals, falling into the cluster for the first time. It seems that galaxies already feel the cluster impact far out from the cluster center, by losing some gas in the outer disk through interactions with the cluster gas or tidal interactions with neighbors, or combinations of both.

  18. The compressed feature matrix--a fast method for feature based substructure search.

    PubMed

    Abolmaali, S F Badreddin; Wegner, Jörg K; Zell, Andreas

    2003-08-01

    The compressed feature matrix (CFM) is a feature based molecular descriptor for the fast processing of pharmacochemical applications such as adaptive similarity search, pharmacophore development and substructure search. Depending on the particular purpose, the descriptor may be generated upon either topological or Euclidean molecular data. To assure a variable utilizability, the assignment of the structural patterns to feature types is arbitrarily determined by the user. This step is based on a graph algorithm for substructure search, which resembles the common substructure descriptors. While these merely allow a screening for the predefined patterns, the CFM permits a real substructure/subgraph search, presuming that all desired elements of the query substructure are described by the selected feature set. In this work, the CFM based substructure search is evaluated with regard to both the different outputs resulting from varying feature sets and the search speed. As a benchmark we use the programmable atom typer (PATTY) graph algorithm. When comparing the two methods, the CFM based matrix algorithm is up to several hundred times faster than PATTY and when using the CFM as a basis for substructure screening, the search speed is accelerated by three orders of magnitude. Thus, the CFM based substructure search complies with the requirements for interactive usage, even for the evaluation of several hundred thousand compounds. The concept of the CFM is implemented in the software COFEA. FIGURE CFM based substructure search using the compounds dopamine and benzene-1,2-diol PMID:12720113

  19. AMUSE-VIRGO. III: mid-infrared photometry of early-type galaxies and limits on obscured nuclear emission

    E-print Network

    Leipski, Christian; Treu, Tommaso; Woo, Jong-Hak; Miller, Brendan P; Antonucci, Robert

    2011-01-01

    We complete our census of low-level nuclear activity in Virgo Cluster early-type galaxies by searching for obscured emission using Spitzer Space Telescope mid-infrared (MIR) imaging at 24mu. Of a total sample of 95 early-type galaxies, 53 objects are detected, including 16 showing kiloparsec-scale dust in optical images. One dimensional and two dimensional surface photometry of the 37 detections without extended dust features reveals that the MIR light is more centrally concentrated than the optical light as traced by Hubble Space Telescope F850LP-band images. No such modeling was performed for the sources with dust detected in the optical images. We explore several possible sources of the MIR excess emission, including obscured nuclear emission. We find that radial metallicity gradients in the stellar population appear to be a natural and most likely explanation for the observed behavior in a majority of the sources. Alternatively, if the concentrated MIR emission were due to nuclear activity, it would imply...

  20. A Megacam Survey of Outer Halo Satellites. IV. Two Foreground Populations Possibly Associated with the Monoceros Substructure in the Direction of NGC 2419 and Koposov 2

    NASA Astrophysics Data System (ADS)

    Carballo-Bello, Julio A.; Muñoz, Ricardo R.; Carlin, Jeffrey L.; Côté, Patrick; Geha, Marla; Simon, Joshua D.; Djorgovski, S. G.

    2015-05-01

    The origin of the Galactic halo stellar structure known as the Monoceros Ring is still under debate. In this work, we study this halo substructure using deep Canada–France–Hawaii Telescope wide-field photometry obtained for the globular clusters NGC 2419 and Koposov 2, where the presence of Monoceros becomes significant because of their coincident projected position. Using Sloan Digital Sky Survey photometry and spectroscopy in the area surrounding these globulars and beyond, where the same Monoceros population is detected, we conclude that a second feature, which is not likely to be associated with Milky Way disk stars along the line of sight, is present as a foreground population. Our analysis suggests that the Monoceros Ring might be composed of an old stellar population of age t? 9 Gyr and a new component ?4 Gyr younger at the same heliocentric distance. Alternatively, this detection might be associated with a second wrap of Monoceros in that direction of the sky and might also indicate a metallicity spread in the ring. The detection of such a low-density feature in other sections of this halo substructure will shed light on its nature. Based on observations obtained at the Canada–France–Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

  1. History of Stellar Interferometry

    NASA Technical Reports Server (NTRS)

    Lawson, Peter R.

    2004-01-01

    This viewgraph presentation reviews the history of stellar interferometry from the suggestion of Fizeau that stellar interferometry was possible,to the use of the Mark I, II and III for astrometry. Photographs, and parts of original articles are presented.

  2. The Star Formation History of the Virgo early-type galaxy NGC4435: the Spitzer Mid Infrared view

    E-print Network

    P. Panuzzo; O. Vega; A. Bressan; L. Buson; M. Clemens; R. Rampazzo; L. Silva; J. R. Valdes; G. L. Granato; L. Danese

    2006-10-11

    We present a population synthesis study of NGC4435, an early-type Virgo galaxy interacting with NGC4438. We combine new spectroscopic observations obtained with the Spitzer Space Telescope IRS instrument with IRAC archival data and broad band data from the literature. The IRS spectrum shows prominent PAH features, low ionization emission lines and H_2 rotational lines arising from the dusty circumnuclear disk characterizing this galaxy. The central SED, from X-ray to radio, is well fitted by a model of an exponential burst superimposed on an old simple stellar population. From the lack of high excitation nebular lines, the [NeIII]15.5/[NeII]12.8 ratio, the temperature of molecular hydrogen, and the fit to the full X-ray to radio SED we argue that the present activity of the galaxy is driven by star formation alone. The AGN contribution to the ionizing flux is constrained to be less than 2%. The age of the burst is found to be around 190 Myr and it is fully consistent with the notion that the star formation process has been triggered by the interaction with NGC4438. The mass involved in the rejuvenation episode turns out to be less than 1.5% of the stellar galaxy mass sampled in a 5" central aperture. This is enough to render NGC4435 closely similar to a typical interacting early-type galaxy with inverted CaII[H+K] lines that will later turn into a typical cluster E+A galaxy and enforces the notion that these objects are the result of a recent rejuvenation episode rather than a genuine delayed formation.

  3. UPDATED ANALYSIS OF A 'DARK' GALAXY AND ITS BLUE COMPANION IN THE VIRGO CLOUD H I 1225 + 01

    SciTech Connect

    Matsuoka, Y.; Oyabu, S. [Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan); Ienaka, N. [Institute of Astronomy, University of Tokyo, Osawa 2-21-1, Mitaka, Tokyo 181-0015 (Japan); Wada, K. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Takino, S., E-mail: matsuoka@a.phys.nagoya-u.ac.jp [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan)

    2012-12-01

    H I 1225+01 is an intergalactic gas cloud located on the outskirts of Virgo cluster. Its main components are two large clumps of comparable H I masses (M{sub Hi}{approx}10{sup 9} M{sub Sun }) separated by about 100 kpc. One of the clumps hosts a blue low-surface-brightness galaxy J1227+0136, while the other has no identified stellar emission and is sometimes referred to as a promising candidate of a 'dark galaxy', an optically invisible massive intergalactic system. We present a deep optical image covering the whole H I 1225+01 structure for the first time, as well as a collection of archival data from ultraviolet to far-infrared (IR) spectral region of the brightest knot 'R1' in J1227+0136. We find that R1 has a young stellar population 10-100 Myr in age and mass {approx}10{sup 6} M{sub Sun }, near-IR excess brightness which may point to the presence of hot dust with color temperature {approx}600 K, and relatively faint mid- to far-IR fluxes corresponding to the dust mass of up to {approx}100 M{sub Sun }. Overall, it seems to share the general properties with low-metallicity blue compact dwarf galaxies. On the other hand, no optical counterpart to the other clump is found in our deepest-ever image. Now the limiting surface brightness reaches down to R{sub AB} > 28 mag arcsec{sup -2} for any emission extended over 10'' (comparable to R1), which is more than one hundred times fainter than the brightest part of the companion galaxy J1227+0136.

  4. GLAST And Dark Matter Substructure in the Milky Way

    SciTech Connect

    Kuhlen, Michael; /Princeton, Inst. Advanced Study; Diemand, Jurg; /UC, Santa Cruz, Astron. Astrophys.; Madau, Piero; /UC, Santa Cruz, Astron. Astrophys. /Garching, Max Planck Inst.

    2011-11-29

    We discuss the possibility of GLAST detecting gamma-rays from the annihilation of neutralino dark matter in the Galactic halo. We have used 'Via Lactea', currently the highest resolution simulation of cold dark matter substructure, to quantify the contribution of subhalos to the annihilation signal. We present a simulated allsky map of the expected gamma-ray counts from dark matter annihilation, assuming standard values of particle mass and cross section. In this case GLAST should be able to detect the Galactic center and several individual subhalos. One of the most exciting discoveries that the Gamma-ray Large Area Space Telescope (GLAST) could make, is the detection of gamma-rays from the annihilation of dark matter (DM). Such a measurement would directly address one of the major physics problems of our time: the nature of the DM particle. Whether or not GLAST will actually detect a DM annihilation signal depends on both unknown particle physics and unknown astrophysics theory. Particle physics uncertainties include the type of particle (axion, neutralino, Kaluza-Klein particle, etc.), its mass, and its interaction cross section. From the astrophysical side it appears that DM is not smoothly distributed throughout the Galaxy halo, but instead exhibits abundant clumpy substructure, in the form of thousands of so-called subhalos. The observability of DM annihilation radiation originating in Galactic DM subhalos depends on their abundance, distribution, and internal properties. Numerical simulations have been used in the past to estimate the annihilation flux from DM substructure, but since the subhalo properties, especially their central density profile, which determines their annihilation luminosity, are very sensitive to numerical resolution, it makes sense to re-examine their contribution with higher resolution simulations.

  5. Tides, Interactions, and Fine-Scale Substructures in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Conselice, Christopher J.; Gallagher, John S., III

    1999-01-01

    We present the results of a study on galaxy interactions, tides, and other processes that produce luminous fine-scale substructures in the galaxy clusters: Coma, Perseus, Abell 2199, AWM 3, and AWM 5. All unusual structures in these clusters can be categorized into seven morphologies: interacting galaxies, multiple galaxies (noninteracting), distorted galaxies, tailed galaxies, line galaxies, dwarf galaxy groups, and galaxy aggregates. The various morphologies are described, and a catalog is presented, of 248 objects in these five clusters along with color, and positional information obtained from CCD images taken with the WIYN 3.5 m telescope in broadband B and R filters. Distorted, interacting, and fine-scale substructures have a range of colors extending from blue objects with B-R~0 to redder colors at B-R~2.5. We also find that the structures with the most disturbed morphology have the bluest colors. In addition, the relative number distributions of these structures suggest that two separate classes of galaxy clusters exist: one dominated by distorted structures and the other dominated by galaxy associations. The Coma and Perseus clusters, respectively, are proposed as models for these types of clusters. These structures avoid the deep potentials of the dominant D or cD galaxies in the Coma and Perseus clusters, and tend to clump together. Possible mechanisms for the production of fine-scale substructure are reviewed and compared with observations of z~0.4 Butcher-Oemler clusters. We conclude, based on color, positional, and statistical data, that the most likely mechanism for the creation of these structures is through an interaction with the gravitational potential of the cluster, possibly coupled with effects of weak interactions with cluster ellipticals.

  6. The Herschel Virgo Cluster Survey - VIII. The Bright Galaxy Sample

    E-print Network

    Davies, J I; Cortese, L; Auld, R; Baes, M; Bendo, G J; Boselli, A; Ciesla, L; Clemens, M; Corbelli, E; De Looze, I; Alighieri, S di Serego; Fritz, J; Gavazzi, G; Pappalardo, C; Grossi, M; Hunt, L K; Madden, S; Magrini, L; Pohlen, M; Smith, M W L; Verstappen, J; Vlahakis, C

    2011-01-01

    We describe the Herschel Virgo Cluster Survey (HeViCS) and the first data that cover the complete survey area (four 4 x 4 deg2 regions). We use these data to measure and compare the global far infrared properties of 78 optically bright galaxies that are selected at 500 \\mum and detected in all five far-infrared bands. We show that our measurements and calibration are broadly consistent with previous data obtained by IRAS, ISO, Spitzer and Planck. We use SPIRE and PACS photometry data to produce 100, 160, 250, 350 and 500 \\mum cluster luminosity distributions. These luminosity distributions are not power laws, but peaked, with small numbers of both faint and bright galaxies. We measure a cluster 100-500 micron far-infrared luminosity density of 1.6(7.0) \\pm 0.2 x 10^9 Lsun/Mpc3. This compares to a cluster 0.4-2.5 \\mum optical luminosity density of 5.0(20.0) x 10^9 Lsun/Mpc3, some 3.2(2.9) times larger than the far-infrared. A typical photon originates from an optical depth of 0.4\\pm0.1. Most of our sample gala...

  7. Interstellar Gas in Low Mass Virgo Cluster Spiral Galaxies

    E-print Network

    Beverly J. Smith; Suzanne C. Madden

    1997-04-14

    We have measured the strengths of the [C II] 158 micron, [N II] 122 micron, and CO (1 - 0) lines from five low blue luminosity spiral galaxies in the Virgo Cluster, using the Infrared Space Observatory and the NRAO 12m millimeter telescope. Two of the five galaxies have high L([C II)]/L(CO) and L(FIR)/L(CO) ratios compared to higher mass spirals. These two galaxies, NGC 4294 and NGC 4299, have L([C II])/L(CO) ratios of >14,300 and 15,600, respectively, which are similar to values found in dwarf irregular galaxies. This is the first time that such enhanced L([C II])/L(CO) ratios have been found in spiral galaxies. This result may be due to low abundances of dust and heavy elements, which can cause the CO (1 - 0) measurements to underestimate the molecular gas content. Another possibility is that radiation from diffuse HI clouds may dominate the [C II] emission from these galaxies. Less than a third of the observed [C II] emission arises from HII regions.

  8. Hierarchically Parallelized Constrained Nonlinear Solvers with Automated Substructuring

    NASA Technical Reports Server (NTRS)

    Padovan, Joe; Kwang, Abel

    1994-01-01

    This paper develops a parallelizable multilevel multiple constrained nonlinear equation solver. The substructuring process is automated to yield appropriately balanced partitioning of each succeeding level. Due to the generality of the procedure,_sequential, as well as partially and fully parallel environments can be handled. This includes both single and multiprocessor assignment per individual partition. Several benchmark examples are presented. These illustrate the robustness of the procedure as well as its capability to yield significant reductions in memory utilization and calculational effort due both to updating and inversion.

  9. Convergence of a Substructuring Method with LaGrange Multipliers

    NASA Technical Reports Server (NTRS)

    Mandel, Jan; Tezaur, Radek

    1996-01-01

    We analyze the convergence of a substructuring iterative method with Lagrange multipliers, proposed recently by Farhat and Roux. The method decomposes finite element discretization of an elliptic boundary value problem into Neumann problems on the subdomains and a coarse problem for the subdomain nullspace components. For linear conforming elements and preconditioning by the Dirichlet problems on the subdomains, we prove the asymptotic bound on the condition number C(1 + log(H/h))(sup gamma), gamma = 2 or 3, where h is the characteristic element size and H is the subdomain size.

  10. Simulating and Synthesizing Substructures Using Neural Network and Genetic Algorithms

    NASA Technical Reports Server (NTRS)

    Liu, Youhua; Kapania, Rakesh K.; VanLandingham, Hugh F.

    1997-01-01

    The feasibility of simulating and synthesizing substructures by computational neural network models is illustrated by investigating a statically indeterminate beam, using both a 1-D and a 2-D plane stress modelling. The beam can be decomposed into two cantilevers with free-end loads. By training neural networks to simulate the cantilever responses to different loads, the original beam problem can be solved as a match-up between two subsystems under compatible interface conditions. The genetic algorithms are successfully used to solve the match-up problem. Simulated results are found in good agreement with the analytical or FEM solutions.

  11. Validation of metabolic pathway databases based on chemical substructure search.

    PubMed

    Félix, Liliana; Valiente, Gabriel

    2007-09-01

    Metabolic pathway databases such as KEGG contain information on thousands of biochemical reactions drawn from the biomedical literature. Ensuring consistency of such large metabolic pathways is essential to their proper use. In this paper, we present a new method to determine consistency of an important class of biochemical reactions. Our method exploits the knowledge of the atomic rearrangement pattern in biochemical reactions, to reduce the automatic atom mapping problem to a series of chemical substructure searches between the substrate and the product of a biochemical reaction. As an illustrative application, we describe the exhaustive validation of a substantial portion from the latest release of the KEGG LIGAND database. PMID:17433774

  12. The First Two Years of Electromagnetic Follow-up with Advanced LIGO and Virgo

    NASA Astrophysics Data System (ADS)

    Singer, Leo P.; Price, Larry R.; Farr, Ben; Urban, Alex L.; Pankow, Chris; Vitale, Salvatore; Veitch, John; Farr, Will M.; Hanna, Chad; Cannon, Kipp; Downes, Tom; Graff, Philip; Haster, Carl-Johan; Mandel, Ilya; Sidery, Trevor; Vecchio, Alberto

    2014-11-01

    We anticipate the first direct detections of gravitational waves (GWs) with Advanced LIGO and Virgo later this decade. Though this groundbreaking technical achievement will be its own reward, a still greater prize could be observations of compact binary mergers in both gravitational and electromagnetic channels simultaneously. During Advanced LIGO and Virgo's first two years of operation, 2015 through 2016, we expect the global GW detector array to improve in sensitivity and livetime and expand from two to three detectors. We model the detection rate and the sky localization accuracy for binary neutron star (BNS) mergers across this transition. We have analyzed a large, astrophysically motivated source population using real-time detection and sky localization codes and higher-latency parameter estimation codes that have been expressly built for operation in the Advanced LIGO/Virgo era. We show that for most BNS events, the rapid sky localization, available about a minute after a detection, is as accurate as the full parameter estimation. We demonstrate that Advanced Virgo will play an important role in sky localization, even though it is anticipated to come online with only one-third as much sensitivity as the Advanced LIGO detectors. We find that the median 90% confidence region shrinks from ~500 deg2 in 2015 to ~200 deg2 in 2016. A few distinct scenarios for the first LIGO/Virgo detections emerge from our simulations.

  13. Structure, mass and distance of the Virgo cluster from a Tolman-Bondi model

    E-print Network

    Pascal Fouque; Jose M. Solanes; Teresa Sanchis; Chantal Balkowski

    2001-06-14

    We have applied a relativistic Tolman-Bondi model of the Virgo cluster to a sample of 183 galaxies with measured distances within a radius of 8 degrees from M87. We find that the sample is significantly contaminated by background galaxies which lead to too large a cluster mean distance if not excluded. The Tolman-Bondi model predictions, together with the HI deficiency of spiral galaxies, allows one to identify these background galaxies. One such galaxy is clearly identified among the 6 calibrating galaxies with Cepheid distances. As the Tolman-Bondi model predicts the expected distance ratio to the Virgo distance, this galaxy can still be used to estimate the Virgo distance, and the average value over the 6 galaxies is 15.4 +- 0.5 Mpc. Well-known background groups of galaxies are clearly recovered, together with filaments of galaxies which link these groups to the main cluster, and are falling into it. No foreground galaxy is clearly detected in our sample. Applying the B-band Tully-Fisher method to a sample of 51 true members of the Virgo cluster according to our classification gives a cluster distance of 18.0 +- 1.2 Mpc, larger than the mean Cepheid distance. Finally, the same model is used to estimate the Virgo cluster mass, which is M = 1.2 10^{15} Msun within 8 degrees from the cluster center (2.2 Mpc radius), and amounts to 1.7 virial mass.

  14. A comparison of methods for gravitational wave burst searches from LIGO and Virgo

    E-print Network

    F. Beauville; M. -A. Bizouard; L. Blackburn; L. Bosi; L. Brocco; D. Brown; D. Buskulic; F. Cavalier; S. Chatterji; N. Christensen; A. -C. Clapson; S. Fairhurst; D. Grosjean; G. Guidi; P. Hello; S. Heng; M. Hewitson; E. Katsavounidis; S. Klimenko; M. Knight; A. Lazzarini; N. Leroy; F. Marion; J. Markowitz; C. Melachrinos; B. Mours; F. Ricci; A. Viceré; I. Yakushin; M. Zanolin

    2007-01-03

    The search procedure for burst gravitational waves has been studied using 24 hours of simulated data in a network of three interferometers (Hanford 4-km, Livingston 4-km and Virgo 3-km are the example interferometers). Several methods to detect burst events developed in the LIGO Scientific Collaboration (LSC) and Virgo collaboration have been studied and compared. We have performed coincidence analysis of the triggers obtained in the different interferometers with and without simulated signals added to the data. The benefits of having multiple interferometers of similar sensitivity are demonstrated by comparing the detection performance of the joint coincidence analysis with LSC and Virgo only burst searches. Adding Virgo to the LIGO detector network can increase by 50% the detection efficiency for this search. Another advantage of a joint LIGO-Virgo network is the ability to reconstruct the source sky position. The reconstruction accuracy depends on the timing measurement accuracy of the events in each interferometer, and is displayed in this paper with a fixed source position example.

  15. The characterization of Virgo data and its impact on gravitational-wave searches

    E-print Network

    J. Aasi; J. Abadie; B. P. Abbott; R. Abbott; T. D. Abbott; M. Abernathy; T. Accadia; F. Acernese; C. Adams; T. Adams; P. Addesso; R. Adhikari; C. Affeldt; M. Agathos; K. Agatsuma; P. Ajith; B. Allen; A. Allocca; E. Amador Ceron; D. Amariutei; S. B. Anderson; W. G. Anderson; K. Arai; M. C. Araya; S. Ast; S. M. Aston; P. Astone; D. Atkinson; P. Aufmuth; C. Aulbert; B. E. Aylott; S. Babak; P. Baker; G. Ballardin; T. Ballinger; S. Ballmer; Y. Bao; J. C. B. Barayoga; D. Barker; F. Barone; B. Barr; L. Barsotti; M. Barsuglia; M. A. Barton; I. Bartos; R. Bassiri; M. Bastarrika; A. Basti; J. Batch; J. Bauchrowitz; Th. S. Bauer; M. Bebronne; D. Beck; B. Behnke; M. Bejger; M. G. Beker; A. S. Bell; C. Bell; I. Belopolski; M. Benacquista; J. M. Berliner; A. Bertolini; J. Betzwieser; N. Beveridge; P. T. Beyersdorf; T. Bhadbade; I. A. Bilenko; G. Billingsley; J. Birch; R. Biswas; M. Bitossi; M. A. Bizouard; E. Black; J. K. Blackburn; L. Blackburn; D. Blair; B. Bland; M. Blom; O. Bock; T. P. Bodiya; C. Bogan; C. Bond; R. Bondarescu; F. Bondu; L. Bonelli; R. Bonnand; R. Bork; M. Born; V. Boschi; S. Bose; L. Bosi; B. Bouhou; S. Braccini; C. Bradaschia; P. R. Brady; V. B. Braginsky; M. Branchesi; J. E. Brau; J. Breyer; T. Briant; D. O. Bridges; A. Brillet; M. Brinkmann; V. Brisson; M. Britzger; A. F. Brooks; D. A. Brown; T. Bulik; H. J. Bulten; A. Buonanno; J. Burguet--Castell; D. Buskulic; C. Buy; R. L. Byer; L. Cadonati; G. Cagnoli; G. Cagnoli; E. Calloni; J. B. Camp; P. Campsie; K. Cannon; B. Canuel; J. Cao; C. D. Capano; F. Carbognani; L. Carbone; S. Caride; S. Caudill; M. Cavaglià; F. Cavalier; R. Cavalieri; G. Cella; C. Cepeda; E. Cesarini; T. Chalermsongsak; P. Charlton; E. Chassande-Mottin; W. Chen; X. Chen; Y. Chen; A. Chincarini; A. Chiummo; H. S. Cho; J. Chow; N. Christensen; S. S. Y. Chua; C. T. Y. Chung; S. Chung; G. Ciani; F. Clara; D. E. Clark; J. A. Clark; J. H. Clayton; F. Cleva; E. Coccia; P. -F. Cohadon; C. N. Colacino; A. Colla; M. Colombini; A. Conte; R. Conte; D. Cook; T. R. Corbitt; M. Cordier; N. Cornish; A. Corsi; C. A. Costa; M. Coughlin; J. -P. Coulon; P. Couvares; D. M. Coward; M. Cowart; D. C. Coyne; J. D. E. Creighton; T. D. Creighton; A. M. Cruise; A. Cumming; L. Cunningham; E. Cuoco; R. M. Cutler; K. Dahl; M. Damjanic; S. L. Danilishin; S. D'Antonio; K. Danzmann; V. Dattilo; B. Daudert; H. Daveloza; M. Davier; E. J. Daw; R. Day; T. Dayanga; R. De Rosa; D. DeBra; G. Debreczeni; J. Degallaix; W. Del Pozzo; T. Dent; V. Dergachev; R. DeRosa; S. Dhurandhar; L. Di Fiore; A. Di Lieto; I. Di Palma; M. Di Paolo Emilio; A. Di Virgilio; M. Díaz; A. Dietz; A. Dietz; F. Donovan; K. L. Dooley; S. Doravari; S. Dorsher; M. Drago; R. W. P. Drever; J. C. Driggers; Z. Du; J. -C. Dumas; S. Dwyer; T. Eberle; M. Edgar; M. Edwards; A. Effler; P. Ehrens; G. Endr?czi; R. Engel; T. Etzel; K. Evans; M. Evans; T. Evans; M. Factourovich; V. Fafone; S. Fairhurst; B. F. Farr; M. Favata; D. Fazi; H. Fehrmann; D. Feldbaum; I. Ferrante; F. Ferrini; F. Fidecaro; L. S. Finn; I. Fiori; R. P. Fisher; R. Flaminio; S. Foley; E. Forsi; N. Fotopoulos; J. -D. Fournier; J. Franc; S. Franco; S. Frasca; F. Frasconi; M. Frede; M. A. Frei; Z. Frei; A. Freise; R. Frey; T. T. Fricke; D. Friedrich; P. Fritschel; V. V. Frolov; M. -K. Fujimoto; P. J. Fulda; M. Fyffe; J. Gair; M. Galimberti; L. Gammaitoni; J. Garcia; F. Garufi; M. E. Gáspár; G. Gelencser; G. Gemme; E. Genin; A. Gennai; L. Á. Gergely; S. Ghosh; J. A. Giaime; S. Giampanis; K. D. Giardina; A. Giazotto; S. Gil-Casanova; C. Gill; J. Gleason; E. Goetz; G. González; M. L. Gorodetsky; S. Goßler; R. Gouaty; C. Graef; P. B. Graff; M. Granata; A. Grant; C. Gray; R. J. S. Greenhalgh; A. M. Gretarsson; C. Griffo; H. Grote; K. Grover; S. Grunewald; G. M. Guidi; C. Guido; R. Gupta; E. K. Gustafson; R. Gustafson; J. M. Hallam; D. Hammer; G. Hammond; J. Hanks; C. Hanna; J. Hanson; A. Hardt; J. Harms; G. M. Harry; I. W. Harry; E. D. Harstad; M. T. Hartman; K. Haughian; K. Hayama; J. -F. Hayau; J. Heefner; A. Heidmann; M. C. Heintze; H. Heitmann; P. Hello; M. A. Hendry; I. S. Heng; A. W. Heptonstall; V. Herrera; M. Heurs; M. Hewitson; S. Hild; D. Hoak; K. A. Hodge; K. Holt; M. Holtrop; T. Hong; S. Hooper; J. Hough; E. J. Howell; B. Hughey; S. Husa; S. H. Huttner; T. Huynh-Dinh; D. R. Ingram; R. Inta; T. Isogai; A. Ivanov; K. Izumi; M. Jacobson; E. James; Y. J. Jang; P. Jaranowski; E. Jesse; W. W. Johnson; D. I. Jones; R. Jones; R. J. G. Jonker; L. Ju; P. Kalmus; V. Kalogera; S. Kandhasamy; G. Kang; J. B. Kanner; M. Kasprzack; R. Kasturi; E. Katsavounidis; W. Katzman; H. Kaufer; K. Kaufman; K. Kawabe; S. Kawamura; F. Kawazoe; D. Keitel; D. Kelley; W. Kells; D. G. Keppel; Z. Keresztes; A. Khalaidovski; F. Y. Khalili; E. A. Khazanov; B. K. Kim; C. Kim; H. Kim; K. Kim; N. Kim; Y. M. Kim; P. J. King; D. L. Kinzel; J. S. Kissel; S. Klimenko; J. Kline; K. Kokeyama; V. Kondrashov

    2012-06-18

    Between 2007 and 2010 Virgo collected data in coincidence with the LIGO and GEO gravitational-wave (GW) detectors. These data have been searched for GWs emitted by cataclysmic phenomena in the universe, by non-axisymmetric rotating neutron stars or from a stochastic background in the frequency band of the detectors. The sensitivity of GW searches is limited by noise produced by the detector or its environment. It is therefore crucial to characterize the various noise sources in a GW detector. This paper reviews the Virgo detector noise sources, noise propagation, and conversion mechanisms which were identified in the three first Virgo observing runs. In many cases, these investigations allowed us to mitigate noise sources in the detector, or to selectively flag noise events and discard them from the data. We present examples from the joint LIGO-GEO-Virgo GW searches to show how well noise transients and narrow spectral lines have been identified and excluded from the Virgo data. We also discuss how detector characterization can improve the astrophysical reach of gravitational-wave searches.

  16. The Characterization of Virgo Data and Its Impact on Gravitational-Wave Searches

    NASA Technical Reports Server (NTRS)

    Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Ajith, P.; Allen, B.; Allocca, A.; Ceron, E. Amador; Amariutei, D.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Blackburn, L.; Buonanno, A.; Camp, J. B.; Capano, C.D.; Kanner, J. B.; Pan, Y.; Shawhan, P.; Yancey, C. C.

    2012-01-01

    Between 2007 and 2010 Virgo collected data in coincidence with the LIGO and GEO gravitational-wave (GW) detectors. These data have been searched for GWs emitted by cataclysmic phenomena in the universe, by non-axisymmetric rotating neutron stars or from a stochastic background in the frequency band of the detectors. The sensitivity of GW searches is limited by noise produced by the detector or its environment. It is therefore crucial to characterize the various noise sources in a GW detector. This paper reviews the Virgo detector noise sources, noise propagation, and conversion mechanisms which were identified in the three first Virgo observing runs. In many cases, these investigations allowed us to mitigate noise sources in the detector, or to selectively flag noise events and discard them from the data. We present examples from the joint LIGO-GEO-Virgo GW searches to show how well noise transients and narrow spectral lines have been identified and excluded from the Virgo data. We also discuss how detector characterization can improve the astrophysical reach of gravitational wave searches.

  17. The Study of tidal stripping substructures around four metal-poor globular clusters in the Galactic bulge

    NASA Astrophysics Data System (ADS)

    Chun, Sang-Hyun; Kang, Minhee; Sohn, Young-Jong

    2014-06-01

    We have investigated the stellar spatial density distribution around four metal-poor globular clusters (NGC 6266, NGC 6626, NGC 6642, and NGC 6723) in the Galactic bulge region, by using 45’×45’ wide-field J, H, and K images obtained with WFCAM detector on the United Kingdom Infrared Telescope. In order to minimize the field star contamination and identify the cluster’s member candidate stars, we used a statistical filtering algorithm and then weighted the stars on the color-magnitude diagram. In two-dimensional stellar density maps, we found that the spatial density distribution of stars around four globular clusters is asymmetric and show tidal stripping features. The orientation of tidal substructure seems to associate with the effect of dynamical interaction with the Galaxy and the cluster’s space motion. Indeed, the radial surface density profile accurately describes this striping structure as a break in the slope of profile. We expect that our observational results could give us further constraints to understand the evolution of clusters as well as merging scenario of the formation of the Galaxy.

  18. Pieces of the puzzle: Ancient substructure in the Galactic disk

    E-print Network

    Amina Helmi; J. F. Navarro; B. Nordstrom; J. Holmberg; M. G. Abadi; M. Steinmetz

    2005-11-03

    We search for signatures of past accretion events in the Milky Way in the recently published catalogue by Nordstrom et al.(2004), containing accurate spatial and kinematic information as well as metallicities for 13240 nearby stars. To optimize our strategy, we use numerical simulations to characterize the properties of the debris from disrupted satellites. We find that stars with a common progenitor should show distinct correlations between their orbital parameters; in particular, between the apocentre A and pericentre P, as well as their z-angular momentum (L_z). In the APL-space, such stars are expected to cluster around regions of roughly constant eccentricity. The APL space for the Nordstrom catalogue exhibits a wealth of substructure, much of which can be linked to dynamical perturbations induced by spiral arms and the Galactic bar. However, our analysis also reveals a statistically significant excess of stars on orbits of common (moderate) eccentricity, analogous to the pattern expected for merger debris. Besides being dynamically peculiar, the 274 stars in these substructures have very distinct metallicity and age distributions, providing further evidence of their extra-Galactic provenance. It is possible to identify among these stars, three coherent Groups with characteristic ages and metallicities, that, in all likelihood, correspond to the remains of disrupted satellites. [abridged

  19. Effect of substructures upon failure behavior of steel reticulated domes subjected to the severe earthquake

    Microsoft Academic Search

    Zhi-Wei Yu; Xu-Dong Zhi; Feng Fan; Chen Lu

    2011-01-01

    This paper presents the study on the influence of substructures on the failure behavior of steel reticulated domes subjected to the severe earthquake. The full-range dynamic response analysis method is applied to investigate the failure characteristics of single-layer steel reticulated domes with substructures subjected to the severe earthquake. The natural vibration properties are studied. Two typical failure modes of steel

  20. Learning Sub-structures of Document Semantic Graphs for Document Summarization

    E-print Network

    Leskovec, Jure

    Learning Sub-structures of Document Semantic Graphs for Document Summarization Jurij Leskovec Jozef of semantic graph are weighted highly by SVM in the learned model. Categories and Subject Descriptors H.3 of the document, visualized as semantic graphs, and learn the model to extract sub-structures that could be used

  1. Dislocation Substructure Gradient Formation in Aluminum by Creep under Weak Potential

    Microsoft Academic Search

    Sergey V. Konovalov; Yuri F. Ivanov; Oksana A. Stolboushkina; Victor E. Gromov

    2011-01-01

    Transmission diffraction electron microscopy of thin foils was used to study the dislocation substructure gradient of aluminum\\u000a destroyed during creep. Creep under +1 V potential resulted in the formation of a dislocation substructure gradient, which\\u000a was observed as a regular change in quantitative structural characteristics upon moving away from the sample fracture surface.

  2. Identification of long-duration noise transients in LIGO and Virgo

    NASA Astrophysics Data System (ADS)

    Coughlin, Michael W.; LIGO Scientific Collaboration; Virgo Collaboration

    2011-12-01

    The LIGO and Virgo detectors are sensitive to a variety of noise sources, such as instrumental artifacts and environmental disturbances. The Stochastic Transient Analysis Multi-detector Pipeline has been developed to search for long-duration (t ? 1 s) gravitational-wave (GW) signals. This pipeline can also be used to identify environmental noise transients. Here, we present an algorithm to determine when long-duration noise sources couple into the interferometers, as well as identify what these noise sources are. We analyze the cross-power between a GW strain channel and an environmental sensor, using pattern recognition tools to identify statistically significant structure in cross-power time-frequency maps. We identify interferometer noise from airplanes, helicopters, thunderstorms and other sources. Examples from LIGO’s sixth science run, S6, and Virgo’s third scientific run, VSR3, are presented.

  3. Unveiling the Secret of a Virgo Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    2000-05-01

    Dwarf galaxies may not be as impressive in appearance as their larger brethren, but they are at least as interesting from a scientific point of view. And sometimes they may have hidden properties that will only be found by means of careful observations, probing the signals of their stars at the faintest level. Such as the entirely unexpected, well developed spiral structure within an otherwise seemingly normal dwarf elliptical galaxy! This is the surprise result of a new study by a team of astronomers [1], headed by Helmut Jerjen from the Australian National University (Canberra) who obtained detailed observations with the ESO Very Large Telescope (VLT) of the dwarf galaxy IC 3328 in the Virgo Cluster of Galaxies, some 50 million light-years away. Dwarf galaxies Dwarf galaxies are present in all major clusters of galaxies and dominate by numbers in the universe. They may contain a few (tens of) millions of stars, as compared to galaxies of normal size with hundreds of billions of stars. About two dozen dwarf galaxies are known in the "Local Group" of galaxies of which the Milky Way galaxy in which we live is also a member. The Large and Small Magellanic Clouds are some of the best known dwarf galaxies - they are of the irregular type - while NGC 147 and NGC 205, two companions to the great Andromeda Galaxy, are of the elliptical type. Dwarf elliptical galaxies are characterized by their smooth appearance. From various studies, it is known that they are tri-axial ellipsoids of different degrees of elongation. Some are almost spherical while others are more pancake- or cigar-shaped. Like the elliptical galaxies of normal size, dwarf ellipticals are almost pure aggregates of stars. In contrast, spiral galaxies also contain clouds of gas and dust. The visible mass of spiral galaxies is in a rotating disk. Dwarf ellipticals generally keep their form because of the random motions of their stars. VLT observations of dwarf elliptical galaxies Using the FORS1 multi-mode instrument mounted at the first 8.2-m VLT Unit telescope, ANTU , the astronomers observed a series of dwarf elliptical galaxies in the Virgo Cluster of Galaxies, in the constellation of that name (The Virgin). The primary goal of the observations was to obtain carefully calibrated images of the galaxies in different colours. They can be used to study the distribution of light over the galaxy and thus its content of stars. The galaxies that are found to have smooth light distributions are of special interest, because it is then possible to measure their approximate distance by means of the so-called Surface Brightness Fluctuation method [2]. The distance to the Virgo Cluster is still not known with high accuracy, although it constitutes a most important step towards the universal distance ladder. Any additional determination of this distance would therefore be most valuable. A matter of a small difference ESO PR Photo 11/00 ESO PR Photo 11/00 [Preview - JPEG: 400 x 252 pix - 67k] [Normal - JPEG: 800 x 504 pix - 224k] Caption : The deep R-band CCD image of IC3328 (left; rendered in "negative" with dark objects and a bright background), obtained with FORS1 at VLT ANTU, illustrates the overall morphology of this galaxy that was classified as a dwarf elliptical galaxy: a quite smooth radially waning light distribution with a central nucleus. The total integration time of this composite image is 20 min with a seeing of 0.6 arcsec. After removal of the axis-symmetrical part of the light from the galaxy by a special image processing algorithm, the "residual" image reveals a remarkable 2-armed spiral structure (right). The field is 4 x 4 arcmin 2 ; North is up and east is left. The central task of the Surface Brightness Fluctuation method is to determine the pixel-to-pixel fluctuations in the light distribution of the galaxy that is due to the finite number of unresolved stars. These fluctuations are obtained by subtracting a suitably smoothed galaxy model from the CCD image. In the case of the seemingly inconspicuous dwarf galaxy IC 3382 , th

  4. A first comparison of search methods for gravitational wave bursts using LIGO and Virgo simulated data

    E-print Network

    L. Blackburn; F. Beauville; M. -A. Bizouard; L. Bosi; P. Brady; L. Brocco; D. Brown; D. Buskulic; S. Chatterji; N. Christensen; A. -C. Clapson; S. Fairhurst; D. Grosjean; G. Guidi; P. Hello; E. Katsavounidis; M. Knight; A. Lazzarini; F. Marion; B. Mours; F. Ricci; A. Vicere; M. Zanolin

    2005-04-13

    We present a comparative study of 6 search methods for gravitational wave bursts using simulated LIGO and Virgo noise data. The data's spectra were chosen to follow the design sensitivity of the two 4km LIGO interferometers and the 3km Virgo interferometer. The searches were applied on replicas of the data sets to which 8 different signals were injected. Three figures of merit were employed in this analysis: (a) Receiver Operator Characteristic curves, (b) necessary signal to noise ratios for the searches to achieve 50 percent and 90 percent efficiencies, and (c) variance and bias for the estimation of the arrival time of a gravitational wave burst.

  5. Detailed comparison of LIGO and Virgo Inspiral Pipelines in Preparation for a Joint Search

    E-print Network

    F. Beauville; M. -A. Bizouard; L. Blackburn; L. Bosi; L. Brocco; D. Brown; D. Buskulic; F. Cavalier; S. Chatterji; N. Christensen; A. -C. Clapson; S. Fairhurst; D. Grosjean; G. Guidi; P. Hello; S. Heng; M. Hewitson; E. Katsavounidis; S. Klimenko; M. Knight; A. Lazzarini; N. Leroy; F. Marion; J. Markowitz; C. Melachrinos; B. Mours; F. Ricci; A. Viceré; I. Yakushin; M. Zanolin

    2007-01-03

    Presented in this paper is a detailed and direct comparison of the LIGO and Virgo binary neutron star detection pipelines. In order to test the search programs, numerous inspiral signals were added to 24 hours of simulated detector data. The efficiencies of the different pipelines were tested, and found to be comparable. Parameter estimation routines were also tested. We demonstrate that there are definite benefits to be had if LIGO and Virgo conduct a joint coincident analysis; these advantages include increased detection efficiency and the providing of source sky location information.

  6. Mapping Dark Matter Halos with Stellar Kinematics

    NASA Astrophysics Data System (ADS)

    Murphy, Jeremy; Gebhardt, K.; Greene, J. E.; Graves, G.

    2013-07-01

    Galaxies of all sizes form and evolve in the centers of dark matter halos. As these halos constitute the large majority of the total mass of a galaxy, dark matter certainly plays a central role in the galaxy's formation and evolution. Yet despite our understanding of the importance of dark matter, observations of the extent and shape of dark matter halos have been slow in coming. The paucity of data is particularly acute in elliptical galaxies. Happily, concerted effort over the past several years by a number of groups has been shedding light on the dark matter halos around galaxies over a wide range in mass. The development of new instrumentation and large surveys, coupled with the tantalizing evidence for a direct detection of dark matter from the AMS experiment, has brought on a golden age in the study of galactic scale dark matter halos. I report on results using extended stellar kinematics from integrated light to dynamically model massive elliptical galaxies in the local universe. I use the integral field power of the Mitchell Spectrograph to explore the kinematics of stars to large radii (R > 2.5 r_e). Once the line-of-sight stellar kinematics are measured, I employ orbit-based, axisymmetric dynamical modeling to explore a range of dark matter halo parameterizations. Globular cluster kinematics at even larger radii are used to further constrain the dynamical models. The dynamical models also return information on the anisotropy of the stars which help to further illuminate the primary formation mechanisms of the galaxy. Specifically, I will show dynamical modeling results for the first and second rank galaxies in the Virgo Cluster, M49 and M87. Although similar in total luminosity and ellipticity, these two galaxies show evidence for different dark matter halo shapes, baryon to dark matter fractions, and stellar anisotropy profiles. Moreover, the stellar velocity dispersion at large radii in M87 is significantly higher than the globular clusters at the same radial extent, reinforcing the need for broad comparisons between the different methods and assumptions underlying the dynamical analysis of massive ellipticals.

  7. An Integral View on Virgo and Field Dwarf Elliptical Galaxies: Late-Type Origin and Environmental Transformations

    NASA Astrophysics Data System (ADS)

    Rys, Agnieszka; Falcon-Barroso, J.; van de Ven, G.

    2013-01-01

    Dwarf elliptical galaxies (dEs) are the most common galaxy class in dense environments. They are also a surprisingly inhomogenous class, which has made it challenging both to relate different dE subtypes to each other, as well as place the whole class in the larger context of galaxy assembly and (trans)formation processes. Here we will show the effects of environmental evolution on Virgo Cluster and field dEs, presenting the first large-scale integral-field spectroscopic (SAURON) data for this galaxy class. Our sample consists of 12 galaxies and no two of them are alike. We find that the level of rotation is not tied to flattening; we observe kinematic twists; we discover large-scale kinematically-decoupled components; we see varying gradients in line-strength maps. This great variety of morphological, kinematic, and stellar population parameters supports the claim that dEs are defunct dwarf spiral/irregular galaxies and points to a formation scenario that allows for a stochastic shaping of galaxy properties. The combined influence of ram-pressure stripping and harassment fulfils this requirement, still, their exact impact is not yet understood. We thus further investigate the properties of our sample by performing a detailed comprehensive analysis of its kinematic, dynamical, and stellar population properties. We infer the total (dark and baryonic) matter distribution by fitting the observed stellar velocity and velocity dispersion with the solutions of the Jeans equations. We obtain 2D age, metallicity, and enrichment information from line-strength analysis. We then tie these results to the galaxies' intrinsic (i.e. deprojected) locations in the cluster with the use of surface-brightness fluctuation distances. This step is essential to providing unbiased correlations with the local environment density. We show that the dark matter fraction, unlike the level of rotational support, appears to correlate with the clustrocentric distance, and that our dwarfs have kinematic properties similar to those of fast-rotating giant early-type galaxies.

  8. Vibration source description in substructuring: A theoretical depiction

    NASA Astrophysics Data System (ADS)

    Rixen, Daniel J.; Boogaard, Anthonie; van der Seijs, Maarten V.; van Schothorst, Gert; van der Poel, Tjeerd

    2015-08-01

    Analyzing the propagation of vibrational excitations from a source substructure to receiving components is an important issue in many high-tech engineering applications. Two equivalent and mutually dual methods to characterize a vibration source consist in determining either the force on its blocked interface or the vibration of its interface left free. Those source properties, together with information on the impedance (or admittance) of the system, allow predicting the coupled dynamic response of an assembly even though the detailed excitation origin in the source is not known. Despite the fact that the methods were already described more than fifty years ago, applying them in practical engineering problems remains challenging. The purpose of the present paper is to outline the blocked force and free velocity methods in a unified way, starting from the general notions of primal and dual assembly of impedances and admittances. An application example is shortly discussed.

  9. Potent Oxazolidinone Antibacterials with Heteroaromatic C-Ring Substructure

    PubMed Central

    2013-01-01

    Novel oxazolidinone analogues bearing a condensed heteroaromatic ring as the C-ring substructure were synthesized as candidate antibacterial agents. Analogues 16 and 21 bearing imidazo[1,2-a]pyridine and 18 and 23 bearing [1,2,4]triazolo[1,5-a]pyridine as the C-ring had excellent in vitro antibacterial activities against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecalis (VRE), and penicillin-resistant Streptococcus pneumoniae (PRSP). They also showed promising therapeutic effects in a mouse model of lethal infection. Preliminary safety data (inhibitory effects on cytochrome P450 isoforms and monoamine oxidases) were satisfactory. Further evaluation of 18 and 23 is ongoing. PMID:24900607

  10. Population substructure in Cache County, Utah: the Cache County study

    PubMed Central

    2014-01-01

    Background Population stratification is a key concern for genetic association analyses. In addition, extreme homogeneity of ethnic origins of a population can make it difficult to interpret how genetic associations in that population may translate into other populations. Here we have evaluated the genetic substructure of samples from the Cache County study relative to the HapMap Reference populations and data from the Alzheimer's Disease Neuroimaging Initiative (ADNI). Results Our findings show that the Cache County study is similar in ethnic diversity to the self-reported "Whites" in the ADNI sample and less homogenous than the HapMap CEU population. Conclusions We conclude that the Cache County study is genetically representative of the general European American population in the USA and is an appropriate population for conducting broadly applicable genetic studies. PMID:25078123

  11. Dynamics of 10 clusters of galaxies with substructures

    SciTech Connect

    Lakhchaura, Kiran; Singh, K. P., E-mail: kiran_astro@tifr.res.in [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005 (India)

    2014-06-01

    We present a detailed Chandra study of a sample of 10 clusters of galaxies selected based on the presence of substructures in their optical images. The X-ray surface brightness maps of most of these clusters show anisotropic morphologies, especially in the central regions. A total of 22 well resolved significantly bright X-ray peaks (corresponding with high-density regions) are seen in the central parts (within r{sub c} /2) of the clusters. Multiple peaks are seen in central parts of six clusters. We found 11 peaks to have optical counterparts (10 coinciding with the brightest cluster galaxies of the 10 clusters and 1 coinciding with the second brightest galaxy in A539). For most of the clusters, the optical substructures detected in the previous studies are found to be outside the field of view of Chandra. In the spectroscopically produced two-dimensional temperature maps, significantly lower temperatures are seen at the locations of three peaks (two in A539 and one in A376). The centers of five clusters in our sample also host regions of higher temperature compared to the ambient medium, indicating the presence of galaxy scale mergers. The X-ray luminosity, gas mass, and central cooling time estimates for all the clusters are presented. The radial X-ray surface-brightness profiles of all but one of the clusters are found to be best-fitted with a double-? model, pointing toward the presence of double-phased central gas due to cool cores. The cooling time estimates of all the clusters, however, indicate that none of them hosts a strong cool core, although the possibility of weak cool cores cannot be ruled out.

  12. Precipitation of nanostructured copper oxalate: substructure and growth mechanism.

    PubMed

    Soare, L Cristina; Bowen, Paul; Lemaitre, Jacques; Hofmann, Heinrich

    2006-09-14

    The possibility of controlling materials properties by tailoring their substructure at the nanometer scale is a current topic of great interest. To do so, a fundamental understanding of the growth mechanism is of key importance and an analytical challenge as nanostructured materials are often produced by precipitation methods at high supersaturations where formation kinetics are fast. The current study focuses on the precipitation of copper oxalate, which has been previously shown to produce self-assembled ordered nanostructured particles with the promise of being able to tailor this nanometer substructure. In the current study we investigate in detail the growth mechanism and kinetics of precipitation by using in-situ particle size measurement or by stopping the reaction at various stages and using ex-situ methods. Combining the ex-situ methods of high-resolution scanning electron microscopy, transmission electron microscopy, and X-ray powder diffraction along with the in-situ methods, we were able to follow the growth process from 2 min to 2 weeks. The results in the 2-30 min period lead to the proposal of a core-shell growth model with a poorly ordered core and a well-structured shell of nanosized crystallites (50-70 nm), adding support to the brick-by-brick model previously proposed for this phase of particle growth. Particle evolution over long periods up to 2 weeks show a ripening which produces lens-shaped particles that eliminate the "high" surface energy faces observed in the earlier stages of growth. A more complete growth mechanism for copper oxalate precipitation at moderate supersaturations is proposed similar to recent findings for other self-assembled nanostructured particles. PMID:16956260

  13. Dynamics of 10 Clusters of Galaxies with Substructures

    NASA Astrophysics Data System (ADS)

    Lakhchaura, Kiran; Singh, K. P.

    2014-06-01

    We present a detailed Chandra study of a sample of 10 clusters of galaxies selected based on the presence of substructures in their optical images. The X-ray surface brightness maps of most of these clusters show anisotropic morphologies, especially in the central regions. A total of 22 well resolved significantly bright X-ray peaks (corresponding with high-density regions) are seen in the central parts (within rc /2) of the clusters. Multiple peaks are seen in central parts of six clusters. We found 11 peaks to have optical counterparts (10 coinciding with the brightest cluster galaxies of the 10 clusters and 1 coinciding with the second brightest galaxy in A539). For most of the clusters, the optical substructures detected in the previous studies are found to be outside the field of view of Chandra. In the spectroscopically produced two-dimensional temperature maps, significantly lower temperatures are seen at the locations of three peaks (two in A539 and one in A376). The centers of five clusters in our sample also host regions of higher temperature compared to the ambient medium, indicating the presence of galaxy scale mergers. The X-ray luminosity, gas mass, and central cooling time estimates for all the clusters are presented. The radial X-ray surface-brightness profiles of all but one of the clusters are found to be best-fitted with a double-? model, pointing toward the presence of double-phased central gas due to cool cores. The cooling time estimates of all the clusters, however, indicate that none of them hosts a strong cool core, although the possibility of weak cool cores cannot be ruled out.

  14. THE EFFECTS OF HALO-TO-HALO VARIATION ON SUBSTRUCTURE LENSING

    SciTech Connect

    Chen, Jacqueline; Koushiappas, Savvas M. [Department of Physics, Brown University, 182 Hope Street, Box 1843, Providence, RI 02912 (United States); Zentner, Andrew R., E-mail: Jacqueline_Chen@brown.edu, E-mail: koushiappas@brown.edu, E-mail: zentner@pitt.edu [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States)

    2011-11-10

    We explore the halo-to-halo variation of dark matter (DM) substructure in galaxy-sized DM halos, focusing on its implications for strongly gravitational lensed systems. We find that the median value for projected substructure mass fractions within projected radii of 3% of the host halo virial radius is approximately f{sub sub} Almost-Equal-To 0.25%, but that the variance is large with a 95 percentile range of 0 {<=} f{sub sub} {<=} 1%. We quantify possible effects of substructure on quadruply imaged lens systems using the cusp relation and the simple statistic, R{sub cusp}. We estimate that the probability of obtaining the large values of the R{sub cusp} which have been observed from substructure effects is roughly {approx}10{sup -3} to {approx}10{sup -2}. We consider a variety of possible correlations between host halo properties and substructure properties in order to probe possible sample biases. In particular, low-concentration host DM halos have more large substructures and give rise to large values of R{sub cusp} more often. However, there is no known observational bias that would drive observed quadruply imaged quasars to be produced by low-concentration lens halos. Finally, we show that the substructure mass fraction is a relatively reliable predictor of the value of R{sub cusp}.

  15. The First Two Years of Electromagnetic Follow-Up with Advanced LIGO and Virgo

    NASA Astrophysics Data System (ADS)

    Farr, Benjamin F.; Singer, Leo; Price, Larry; Urban, Alex; Pankow, Chris; Vitale, Salvatore; Veitch, John; Farr, Will; Hanna, Chad; Cannon, Kipp; Downes, Tom; Graff, Philip; Haster, Carl-Johan; Mandel, Ilya; Sidery, Trevor; Vecchio, Alberto

    2014-08-01

    We anticipate the first direct detections of gravitational waves with Advanced LIGO and Virgo later this decade. Though this groundbreaking technical achievement will be its own reward, a still greater prize could be observations of compact binary mergers in both gravitational and electromagnetic channels simultaneously. During Advanced LIGO and Virgo's first two years of operation, 2015 through 2016, we expect the global gravitational-wave detector array to improve in sensitivity and livetime and expand from two to three detectors. We model the detection rate and the sky localization accuracy for binary neutron star mergers across this transition. We have analyzed a large, astrophysically motivated source population using real-time detection and sky localization codes and higher-latency parameter estimation codes that have been expressly built for operation in the Advanced LIGO/Virgo era. We show that for most binary neutron star events the rapid sky localization, available about a minute after a detection, is as accurate as the full parameter estimation. We demonstrate that Advanced Virgo will play an important role in sky localization, even though it is anticipated to come online with only 1/3 as much sensitivity as the Advanced LIGO detectors. We find that the median 90% confidence region shrinks from ~500 square degrees in 2015 to ~200 square degrees in 2016. From hundreds of simulated events unfold some likely detection scenarios.

  16. THE LOWMASS XRAY BINARY AND GLOBULAR CLUSTER CONNECTION VIRGO CLUSTER EARLYTYPE GALAXIES: OPTICAL PROPERTIES

    E-print Network

    Sarazin, Craig

    Cluster, use most accurate identification of LMXBs GCs to explore optical properties GCs with LMXBsTHE LOW­MASS X­RAY BINARY AND GLOBULAR CLUSTER CONNECTION VIRGO CLUSTER EARLY­TYPE GALAXIES: OPTICAL PROPERTIES Gregory Sivakoff, 2 Andre â??s Jorda Craig Sarazin, John Blakeslee, 4 Patrick â??, Laura

  17. Testing the detection pipelines for inspirals with Virgo commissioning run C4 data

    Microsoft Academic Search

    F. Acernese; P. Amico; M. Al-Shourbagy; S. Aoudia; S. Avino; D. Babusci; G. Ballardin; R. Barillé; F. Barone; L. Barsotti; M. Barsuglia; F. Beauville; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; S. Braccini; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; E. Calloni; E. Campagna; F. Cavalier; R. Cavalieri; G. Cella; E. Chassande-Mottin; C. Corda; A.-C. Clapson; F. Cleva; J.-P. Coulon; E. Cuoco; V. Dattilo; M. Davier; R. De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; A. Eleuteri; D. Enard; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; S. Frasca; F. Frasconi; A. Freise; L. Gammaitoni; A. Gennai; A. Giazotto; G. Giordano; L. Giordano; R. Gouaty; D. Grosjean; G. Guidi; S. Hebri; H. Heitmann; P. Hello; L. Holloway; S. Kreckelbergh; P. La Penna; V. Loriette; M. Loupias; G. Losurdo; J.-M. Mackowski; E. Majorana; C. N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; M. Mazzoni; L. Milano; C. Moins; J. Moreau; N. Morgado; B. Mours; A. Pai; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; B. Perniola; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; P. Ruggi; G. Russo; S. Solimeno; A. Spallicci; R. Stanga; R. Taddei; D. Tombolato; M. Tonelli; A. Toncelli; E. Tournefier; F. Travasso; G. Vajente; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert; Z. Zhang

    2005-01-01

    We report on an investigation of Virgo Commissioning run 4 data, dedicated to searching signals of the kind supposed to be emitted by inspiral neutron star binary systems. Given the still relatively limited sensitivity, the goal was to test some of the elements of the analysis chain, using simulated events, hardware and software injected in the data; the test allowed

  18. UBVRI Photometry of Spiral Galaxies in the Virgo and Fornax Clusters

    Microsoft Academic Search

    Anja Schroeder

    1996-01-01

    In this study multi-aperture photo electric photometry in the five passbands UBVRI for 171 and 46 galaxies in the Virgo and Fornax clusters, respectively, are presented. New radial velocities and H I profiles for 17 galaxies in Fornax have been obtained. Total magnitudes and colours are derived for around 800 individual measurements using standard growth curves in B, U-B and

  19. Low-Cost Sensor Can Diagnose Bacterial Infections Copyright 2011 by Virgo Publishing.

    E-print Network

    Suslick, Kenneth S.

    Low-Cost Sensor Can Diagnose Bacterial Infections Copyright 2011 by Virgo Publishing. http diagnose bacterial infections in only a few hours. Photo by L. Brian Stauffer Bacterial infections really sensor. Led by University of Illinois chemistry professor Ken Suslick, the team published its results

  20. VIRGO: visualization of A-to-I RNA editing sites in genomic sequences

    PubMed Central

    2013-01-01

    Background RNA Editing is a type of post-transcriptional modification that takes place in the eukaryotes. It alters the sequence of primary RNA transcripts by deleting, inserting or modifying residues. Several forms of RNA editing have been discovered including A-to-I, C-to-U, U-to-C and G-to-A. In recent years, the application of global approaches to the study of A-to-I editing, including high throughput sequencing, has led to important advances. However, in spite of enormous efforts, the real biological mechanism underlying this phenomenon remains unknown. Description In this work, we present VIRGO (http://atlas.dmi.unict.it/virgo/), a web-based tool that maps Ato-G mismatches between genomic and EST sequences as candidate A-to-I editing sites. VIRGO is built on top of a knowledge-base integrating information of genes from UCSC, EST of NCBI, SNPs, DARNED, and Next Generations Sequencing data. The tool is equipped with a user-friendly interface allowing users to analyze genomic sequences in order to identify candidate A-to-I editing sites. Conclusions VIRGO is a powerful tool allowing a systematic identification of putative A-to-I editing sites in genomic sequences. The integration of NGS data allows the computation of p-values and adjusted p-values to measure the mapped editing sites confidence. The whole knowledge base is available for download and will be continuously updated as new NGS data becomes available. PMID:23815474

  1. A local control system for the test masses of the Virgo gravitational wave detector

    Microsoft Academic Search

    F. Acernese; P. Amico; N. Arnaud; D. Babusci; R. Barillé; F. Barone; L. Barsotti; M. Barsuglia; F. Beauville; M. A Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; L. Bracci; S. Braccini; A. Brillet; V. Brisson; L. Brocco; D. Buskulic; G. Calamai; E. Calloni; E. Campagna; F. Cavalier; G. Cella; E. Chassande-Mottin; F. Cleva; T. Cokelaer; G. Conforto; C. Corda; J.-P Coulon; E. Cuoco; V. Dattilo; M. Davier; R De Rosa; L Di Fiore; A Di Virgilio; B. Dujardin; A. Eleuteri; D. Enard; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D Fournier; S. Frasca; F. Frasconi; L. Gammaitoni; A. Gennai; A. Giazotto; G. Giordano; H. Heitmann; P. Hello; P. Heusse; L. Holloway; S. Kreckelbergh; P La Penna; V. Loriette; M. Loupias; G. Losurdo; J.-M Mackowski; E. Majorana; C. N Man; F. Marion; F. Martelli; A. Masserot; L. Massonnet; M. Mazzoni; L. Milano; J. Moreau; F. Moreau; N. Morgado; F. Mornet; B. Mours; J. Pacheco; A. Pai; C. Palomba; F. Paoletti; R. Passaquieti; D. Passuello; B. Perniola; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; K. Qipiani; J. Ramonet; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; G. Russo; S. Solimeno; R. Stanga; A. Toncelli; M. Tonelli; E. Tournefier; F. Travasso; H. Trinquet; M. Varvella; D. Verkindt; F. Vetrano; O. Veziant; A. Viceré; J.-Y Vinet; H. Vocca; M. Yvert

    2004-01-01

    The mirrors of interferometric detectors of gravitational waves (GW) are suspended in order to be isolated from external disturbances. A local control system able to keep them correctly aligned and to damp the angular modes of the suspension is necessary. In this paper we present the solution adopted for Virgo based on a CCD camera sensor and on digital controls.

  2. The Real-Time Distributed Control of the Virgo Interferometric Detector of Gravitational Waves

    Microsoft Academic Search

    F. Acernese; P. Amico; M. Alshourbagy; F. Antonucci; S. Aoudia; P. Astone; S. Avino; D. Babusci; R. Barillé; G. Ballardin; F. Barone; L. Barsotti; M. Barsuglia; T. S. Bauer; F. Beauville; S. Bigotta; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; S. Birindelli; S. Braccini; A. Brillet; V. Brisson; D. Buskulic; E. Calloni; E. Campagna; F. Carbognani; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; E. Chassande-Mottin; N. Christensen; A. C. Clapson; F. Cleva; C. Corda; A. Corsi; F. Cottone; J. P. Coulon; E. Cuoco; A. Dari; V. Dattilo; M. Davier; M. del Prete; R. De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; A. Eleuteri; M. Evans; I. Ferrante; F. Fidecaro; J. D. Fournier; A. Freise; L. Gammaitoni; F. Garufi; E. Genin; A. Gennai; A. Giazotto; L. Giordano; R. Gouaty; G. Giordano; S. Hebri; H. Heitmann; P. Hello; D. Huet; S. Karkar; S. Kreckelbergh; P. La Penna; M. Laval; N. Leroy; N. Letendre; B. Lopez; V. Loriette; G. Losurdo; J. M. Mackowski; E. Majorana; C. N. Man; M. Mantovani; F. Marchesoni; F. Marion; A. Masserot; L. Milano; C. Moins; J. Moreau; N. Morgado; B. Mours; F. Nocera; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; S. van der Putten; K. Qipiani; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; P. Ruggi; G. Russo; S. Solimeno; A. Spallicci; M. Tarallo; M. Tonelli; A. Toncelli; E. Tournefier; F. Travasso; C. Tremola; G. Vajente; D. Verkindt; F. Vetrano; A. Vicere; J. Y. Vinet; H. Vocca; M. Yvert

    2008-01-01

    The VIRGO experiment for the detection of gravitational waves is a big challenge both for physics and for technology. In particular, to satisfy the stringent requirements on the alignment and position of its suspended optical components to keep the detector at its point, a very complex distributed and supervised control system has been implemented. The current constraints are about 10-10

  3. The characterization of Virgo data and its impact on gravitational-wave searches

    Microsoft Academic Search

    J Aasi; J Abadie; B P Abbott; R Abbott; T D Abbott; M Abernathy; T Accadia; F Acernese; C Adams; T Adams; P Addesso; R Adhikari; C Affeldt; M Agathos; K Agatsuma; P Ajith; B Allen; A Allocca; E Amador Ceron; D Amariutei; S B Anderson; W G Anderson; K Arai; M C Araya; S Ast; S M Aston; P Astone; D Atkinson; P Aufmuth; C Aulbert; B E Aylott; S Babak; P Baker; G Ballardin; T Ballinger; S Ballmer; Y Bao; J C B Barayoga; D Barker; F Barone; B Barr; L Barsotti; M Barsuglia; M A Barton; I Bartos; R Bassiri; M Bastarrika; A Basti; J Batch; J Bauchrowitz; Th S Bauer; M Bebronne; D Beck; B Behnke; M Bejger; M G Beker; A S Bell; C Bell; I Belopolski; M Benacquista; J M Berliner; A Bertolini; J Betzwieser; N Beveridge; P T Beyersdorf; T Bhadbade; I A Bilenko; G Billingsley; J Birch; R Biswas; M Bitossi; M A Bizouard; E Black; J K Blackburn; L Blackburn; D Blair; B Bland; M Blom; O Bock; T P Bodiya; C Bogan; C Bond; R Bondarescu; F Bondu; L Bonelli; R Bonnand; R Bork; M Born; V Boschi; S Bose; L Bosi; B Bouhou; S Braccini; C Bradaschia; P R Brady; V B Braginsky; M Branchesi; J E Brau; J Breyer; T Briant; D O Bridges; A Brillet; M Brinkmann; V Brisson; M Britzger; A F Brooks; D A Brown; T Bulik; H J Bulten; A Buonanno; D Buskulic; C Buy; R L Byer; L Cadonati; G Cagnoli; E Calloni; J B Camp; P Campsie; K Cannon; B Canuel; J Cao; C D Capano; F Carbognani; L Carbone; S Caride; S Caudill; M Cavaglià; F Cavalier; R Cavalieri; G Cella; C Cepeda; E Cesarini; T Chalermsongsak; P Charlton; E Chassande-Mottin; W Chen; X Chen; Y Chen; A Chincarini; A Chiummo; H S Cho; J Chow; N Christensen; S S Y Chua; C T Y Chung; S Chung; G Ciani; F Clara; D E Clark; J A Clark; J H Clayton; F Cleva; E Coccia; P-F Cohadon; C N Colacino; A Colla; M Colombini; A Conte; R Conte; D Cook; T R Corbitt; M Cordier; N Cornish; A Corsi; C A Costa; M Coughlin; J-P Coulon; P Couvares; D M Coward; M Cowart; D C Coyne; J D E Creighton; T D Creighton; A M Cruise; A Cumming; L Cunningham; E Cuoco; R M Cutler; K Dahl; M Damjanic; S L Danilishin; S D’Antonio; K Danzmann; V Dattilo; B Daudert; H Daveloza; M Davier; E J Daw; R Day; T Dayanga; R De Rosa; D DeBra; G Debreczeni; J Degallaix; W Del Pozzo; T Dent; V Dergachev; R DeRosa; S Dhurandhar; L Di Fiore; A Di Lieto; I Di Palma; M Di Paolo Emilio; A Di Virgilio; M Díaz; A Dietz; F Donovan; K L Dooley; S Doravari; S Dorsher; M Drago; R W P Drever; J C Driggers; Z Du; J-C Dumas; S Dwyer; T Eberle; M Edgar; M Edwards; A Effler; P Ehrens; G Endr?czi; R Engel; T Etzel; K Evans; M Evans; T Evans; M Factourovich; V Fafone; S Fairhurst; B F Farr; M Favata; D Fazi; H Fehrmann; D Feldbaum; I Ferrante; F Ferrini; F Fidecaro; L S Finn; I Fiori; R P Fisher; R Flaminio; S Foley; E Forsi; L A Forte; N Fotopoulos; J-D Fournier; J Franc; S Franco; S Frasca; F Frasconi; M Frede; M A Frei; Z Frei; A Freise; R Frey; T T Fricke; D Friedrich; P Fritschel; V V Frolov; M-K Fujimoto; P J Fulda; M Fyffe; J Gair; M Galimberti; L Gammaitoni; J Garcia; F Garufi; M E Gáspár; G Gelencser; G Gemme; E Genin; A Gennai; L Á Gergely; S Ghosh; J A Giaime; S Giampanis; K D Giardina; A Giazotto; S Gil-Casanova; C Gill; J Gleason; E Goetz; G González; M L Gorodetsky; S Goßler; R Gouaty; C Graef; P B Graff; M Granata; A Grant; C Gray; R J S Greenhalgh; A M Gretarsson; C Griffo; H Grote; K Grover; S Grunewald; G M Guidi; C Guido; R Gupta; E K Gustafson; R Gustafson; J M Hallam; D Hammer; G Hammond; J Hanks; C Hanna; J Hanson; A Hardt; J Harms; G M Harry; I W Harry; E D Harstad; M T Hartman; K Haughian; K Hayama; J-F Hayau; J Heefner; A Heidmann; M C Heintze; H Heitmann; P Hello; G Hemming; M A Hendry; I S Heng; A W Heptonstall; V Herrera; M Heurs; M Hewitson; S Hild; D Hoak; K A Hodge; K Holt; M Holtrop; T Hong; S Hooper; J Hough; E J Howell; B Hughey; S Husa; S H Huttner; T Huynh-Dinh; D R Ingram; R Inta; T Isogai; A Ivanov; K Izumi; M Jacobson; E James; Y J Jang; P Jaranowski; E Jesse; W W Johnson; D I Jones; R Jones; R J G Jonker; L Ju; P Kalmus; V Kalogera; S Kandhasamy; G Kang; J B Kanner; M Kasprzack; R Kasturi; E Katsavounidis; W Katzman; H Kaufer; K Kaufman; K Kawabe; S Kawamura; F Kawazoe; D Keitel; D Kelley; W Kells; D G Keppel; Z Keresztes; A Khalaidovski; F Y Khalili; E A Khazanov; B K Kim; C Kim; H Kim; K Kim; N Kim; Y M Kim; P J King; D L Kinzel; J S Kissel; S Klimenko; J Kline; K Kokeyama; V Kondrashov; S Koranda; W Z Korth; I Kowalska; D Kozak; V Kringel; B Krishnan; A Królak; G Kuehn; P Kumar; R Kumar; R Kurdyumov; P Kwee; P K Lam; M Landry; A Langley; B Lantz; N Lastzka; C Lawrie; A Lazzarini; A Le Roux; P Leaci; C H Lee; H K Lee; H M Lee; J R Leong; I Leonor; N Leroy; N Letendre; V Lhuillier; J Li; T G F Li; P E Lindquist; V Litvine; Y Liu; Z Liu; N A Lockerbie; D Lodhia; J Logue; M Lorenzini; V Loriette; M Lormand; G Losurdo; J Lough; M Lubinski; H Lück; A P Lundgren; J Macarthur; E Macdonald; B Machenschalk; M MacInnis; D M Macleod; M Mageswaran; K Mailand; E Majorana; I Maksimovic; V Malvezzi; N Man; I Mandel; V Mandic

    2012-01-01

    Between 2007 and 2010 Virgo collected data in coincidence with the LIGO and GEO gravitational-wave (GW) detectors. These data have been searched for GWs emitted by cataclysmic phenomena in the universe, by non-axisymmetric rotating neutron stars or from a stochastic background in the frequency band of the detectors. The sensitivity of GW searches is limited by noise produced by the

  4. VizieR Online Data Catalog: WSRT Virgo HI filament survey. II. (Popping+, 2011)

    NASA Astrophysics Data System (ADS)

    Popping, A.; Braun, R.

    2011-08-01

    In this paper we present the interferometric data of the Westerbork Virgo HI Filament Survey (WVFS) - the total power product of this survey has been published in Paper I, Popping & Braun, 2011, Cat. J/A+A/527/A90. (1 data file).

  5. Jet Substructure at the Tevatron and LHC: New results, new tools, new benchmarks

    E-print Network

    A. Altheimer; S. Arora; L. Asquith; G. Brooijmans; J. Butterworth; M. Campanelli; B. Chapleau; A. E. Cholakian; J. P. Chou; M. Dasgupta; A. Davison; J. Dolen; S. D. Ellis; R. Essig; J. J. Fan; R. Field; A. Fregoso; J. Gallicchio; Y. Gershtein; A. Gomes; A. Haas; E. Halkiadakis; V. Halyo; S. Hoeche; A. Hook; A. Hornig; P. Huang; E. Izaguirre; M. Jankowiak; G. Kribs; D. Krohn; A. J. Larkoski; A. Lath; C. Lee; S. J. Lee; P. Loch; P. Maksimovic; M. Martinez; D. W. Miller; T. Plehn; K. Prokofiev; R. Rahmat; S. Rappoccio; A. Safonov; G. P. Salam; S. Schumann; M. D. Schwartz; A. Schwartzman; M. Seymour; J. Shao; P. Sinervo; M. Son; D. E. Soper; M. Spannowsky; I. W. Stewart; M. Strassler; E. Strauss; M. Takeuchi; J. Thaler; S. Thomas; B. Tweedie; R. Vasquez Sierra; C. K. Vermilion; M. Villaplana; M. Vos; J. Wacker; D. Walker; J. R. Walsh; L. -T. Wang; S. Wilbur; W. Zhu

    2012-05-25

    In this report we review recent theoretical progress and the latest experimental results in jet substructure from the Tevatron and the LHC. We review the status of and outlook for calculation and simulation tools for studying jet substructure. Following up on the report of the Boost 2010 workshop, we present a new set of benchmark comparisons of substructure techniques, focusing on the set of variables and grooming methods that are collectively known as "top taggers". To facilitate further exploration, we have attempted to collect, harmonise, and publish software implementations of these techniques.

  6. Three-dimensional deformation analysis of two-phase dislocation substructures

    NASA Technical Reports Server (NTRS)

    Freed, Alan D.; Raj, S. V.; Walker, Kevin P.

    1992-01-01

    Three-dimensional deformation analysis of two-phase dislocation substructures was carried out, extending the Qian and Fan (1991) approach to 3D stress-strain fields by using the Budiansky and Wu (1962) criterion for strain compatibility between the 'hard' and 'soft' regions. The result is a rate-dependent viscoplastic theory, named the dislocation substructure viscoplasticity (DSV), which incorporates a self-consistent effect of dislocation substructure on material response. An algorithm developed for numerical implementation of the DSV theory is presented.

  7. STELLAR STRUCTURE AND EVOLUTION

    E-print Network

    Mojzsis, Stephen J.

    STELLAR STRUCTURE AND EVOLUTION O.R. Pols September 2009 #12;#12;Preface These lecture notes application to the theory of stellar structure and evolution, at a level appro- priate for a third and Evolution, 1990, Springer-Verlag, ISBN 3-540-50211-4 (KIPPENHAHN; K&W) Some sections of this book are still

  8. Compact Stellarator Development Plan

    E-print Network

    Development Through Proof of Principle (PoP) and Performance Extension (PE) to DEMO ­ Key Milestones and foreign PE stellarators. · Focus U.S. compact stellarator experiments on 3D physics issues. Can lead Helical Device (PE w/ S/C magnets - Japan) > 3%. Te 10 kev, Ti 5 keV. enhanced confinement. 2-minute

  9. Line-Strength Indices in Bright Spheroidals Evidence for a Stellar Population Dichotomy between Spheroidal and Elliptical Galaxies

    E-print Network

    Gorgas, J; Guzmán, R; Cardiel, N; González, J J

    1997-01-01

    We present new measurements of central line-strength indices (namely Mg2, , and Hbeta and gradients for a sample of 6 bright spheroidal galaxies (Sph's) in the Virgo cluster. Comparison with similar measurements for elliptical galaxies (E's), galactic globular clusters (GGC's), and stellar population models yield the following results: (1) In contrast with bright E's, bright Sph's are consistent with solar abundance [Mg/Fe] ratios; (2) Bright Sph's exhibit metallicities ranging from values typical for metal-rich GGC's to those for E's; (3) Although absolute mean ages are quite model dependent, we find evidence that the stellar populations of some (if not all) Sph's look significantly younger than GGC's; and (4) Mg2 gradients of bright Sph's are significantly shallower than those of E galaxies. We conclude that the dichotomy found in the structural properties of Sph and E galaxies is also observed in their stellar populations. A tentative interpretation in terms of differences in star formation histories is su...

  10. Line-Strength Indices in Bright Spheroidals: Evidence for a Stellar Population Dichotomy between Spheroidal and Elliptical Galaxies

    E-print Network

    J. Gorgas; S. Pedraz; R. Guzman; N. Cardiel; J. J. Gonzalez

    1997-03-05

    We present new measurements of central line-strength indices (namely Mg2, , and Hbeta and gradients for a sample of 6 bright spheroidal galaxies (Sph's) in the Virgo cluster. Comparison with similar measurements for elliptical galaxies (E's), galactic globular clusters (GGC's), and stellar population models yield the following results: (1) In contrast with bright E's, bright Sph's are consistent with solar abundance [Mg/Fe] ratios; (2) Bright Sph's exhibit metallicities ranging from values typical for metal-rich GGC's to those for E's; (3) Although absolute mean ages are quite model dependent, we find evidence that the stellar populations of some (if not all) Sph's look significantly younger than GGC's; and (4) Mg2 gradients of bright Sph's are significantly shallower than those of E galaxies. We conclude that the dichotomy found in the structural properties of Sph and E galaxies is also observed in their stellar populations. A tentative interpretation in terms of differences in star formation histories is suggested.

  11. Transformation of a Virgo Cluster dwarf irregular galaxy by ram pressure stripping: IC3418 and its fireballs

    SciTech Connect

    Kenney, Jeffrey D. P.; Geha, Marla; Jáchym, Pavel; Dague, William [Yale University Astronomy Department, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Crowl, Hugh H. [Bennington College, Bennington, VT (United States); Chung, Aeree [Department of Astronomy and Yonsei University Observatory, Yonsei University, 120-749 Seoul (Korea, Republic of); Van Gorkom, Jacqueline [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Vollmer, Bernd, E-mail: jeff.kenney@yale.edu [CDS, Observatoire astronomique de Strasbourg, UMR7550, 11 rue de l'université, F-67000 Strasbourg (France)

    2014-01-10

    We present optical imaging and spectroscopy and H I imaging of the Virgo Cluster galaxy IC 3418, which is likely a 'smoking gun' example of the transformation of a dwarf irregular into a dwarf elliptical galaxy by ram pressure stripping. IC 3418 has a spectacular 17 kpc length UV-bright tail comprised of knots, head-tail, and linear stellar features. The only H? emission arises from a few H II regions in the tail, the brightest of which are at the heads of head-tail UV sources whose tails point toward the galaxy ('fireballs'). Several of the elongated tail sources have H? peaks outwardly offset by ?80-150 pc from the UV peaks, suggesting that gas clumps continue to accelerate through ram pressure, leaving behind streams of newly formed stars which have decoupled from the gas. Absorption line strengths, measured from Keck DEIMOS spectra, together with UV colors, show star formation stopped 300 ± 100 Myr ago in the main body, and a strong starburst occurred prior to quenching. While neither H? nor H I emission are detected in the main body of the galaxy, we have detected 4 × 10{sup 7} M {sub ?} of H I from the tail with the Very Large Array. The velocities of tail H II regions, measured from Keck LRIS spectra, extend only a small fraction of the way to the cluster velocity, suggesting that star formation does not happen in more distant parts of the tail. Stars in the outer tail have velocities exceeding the escape speed, but some in the inner tail should fall back into the galaxy, forming halo streams.

  12. 20. Top 30/3. Plan of exposed substructure elevations. Wyoming ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. Top 30/3. Plan of exposed substructure elevations. - Wyoming Valley Flood Control System, Woodward Pumping Station, East of Toby Creek crossing by Erie-Lackawanna Railroad, Edwardsville, Luzerne County, PA

  13. Gap comparison between single crown and three-unit bridge zirconia substructures

    PubMed Central

    Charoenchitt, Masnisa; Asvanund, Chanavut

    2014-01-01

    PURPOSE To compare marginal and internal gaps of zirconia substructure of single crowns with those of three-unit fixed dental prostheses. MATERIALS AND METHODS Standardized Co-Cr alloy simulated second premolar and second molar abutments were fabricated and subsequently duplicated into type-III dental stone for working casts. After that, all zirconia substructures were made using Lava™ system. Marginal and internal gaps were measured in 2 planes (mesial-distal plane and buccal-palatal plane) at 5 locations: marginal opening (MO), chamfer area (CA), axial wall (AW), cusp tip (CT) and mid-occlusal (OA) using Replica technique. RESULTS There were significant differences between gaps at all locations. The mean ± SD of marginal gap in premolar was 43.6 ± 0.4 µm and 46.5 ± 0.5 µm for single crown and 3-unit bridge substructure respectively. For molar substructure the mean ± SD of marginal gap was 48.5 ± 0.4 µm and 52.6 ± 0.4 µm for single crown and 3-unit bridge respectively. The largest gaps were found at the occlusal area, which was 150.5 ± 0.5 µm and 154.5 ± 0.4 µm for single and 3-unit bridge premolar substructures respectively and 146.5 ± 0.4 µm and 211.5 ± 0.4 µm for single and 3-unit bridge molar substructure respectively. CONCLUSION Independent-samples t-test showed significant differences of gap in zirconia substructure between single crowns and three-unit bridge (P<.001). Therefore, the span length has the effect on the fit of zirconia substructure that is fabricated using CAD/CAM technique especially at the occlusal area. PMID:25177467

  14. Application of Resin Transfer Molding to the Manufacture of Wind Turbine Blade Substructures. Final Report

    SciTech Connect

    Hedley, C. W.; Ritter, W. J.; Ashwill, T.

    2001-07-26

    The U.S. has generally lacked the capability for an iterative process of detailed structural design, manufacturing, and testing at the full blade level to achieve specific structural performance, cost, and weight targets. This project examined the effects that different composites processing methods had on the performance of representative blade substructures. In addition, the results of the testing of these substructures was used to validate NuMAD, the design tool developed at Sandia National Laboratories.

  15. Search for gravitational wave ringdowns from perturbed intermediate mass black holes in LIGO-Virgo data from 2005–2010

    E-print Network

    Aggarwal, Nancy

    We report results from a search for gravitational waves produced by perturbed intermediate mass black holes (IMBH) in data collected by LIGO and Virgo between 2005 and 2010. The search was sensitive to astrophysical sources ...

  16. [C II] 158-micrometer Observations of a Sample of Late-type Galaxies from the Virgo Cluster

    NASA Technical Reports Server (NTRS)

    Leech, K. J.; Volk, H. J.; Heinrichsen, I.; Hippelein, H.; Metcalfe, L.; Pierini, D.; Popescu, C. C.; Tuffs, R. J.; Xu, C.

    1998-01-01

    We have observed 19 Virgo cluster spiral galaxies with the Long Wavelength Spectrometer (LWS) onboard ESAs Infrared Space Observatory (ISO) obtaining spectral around the (C II) 157.741-micrometer fine structure line.

  17. Simulation of large-scale numerical substructure in real-time dynamic hybrid testing

    NASA Astrophysics Data System (ADS)

    Zhu, Fei; Wang, Jinting; Jin, Feng; Zhou, Mengxia; Gui, Yao

    2014-12-01

    A solution scheme is proposed in this paper for an existing RTDHT system to simulate large-scale finite element (FE) numerical substructures. The analysis of the FE numerical substructure is split into response analysis and signal generation tasks, and executed in two different target computers in real-time. One target computer implements the response analysis task, wherein a large time-step is used to solve the FE substructure, and another target computer implements the signal generation task, wherein an interpolation program is used to generate control signals in a small time-step to meet the input demand of the controller. By using this strategy, the scale of the FE numerical substructure simulation may be increased significantly. The proposed scheme is initially verified by two FE numerical substructure models with 98 and 1240 degrees of freedom (DOFs). Thereafter, RTDHTs of a single frame-foundation structure are implemented where the foundation, considered as the numerical substructure, is simulated by the FE model with 1240 DOFs. Good agreements between the results of the RTDHT and those from the FE analysis in ABAQUS are obtained.

  18. Theoretical and software considerations for general dynamic analysis using multilevel substructured models

    NASA Technical Reports Server (NTRS)

    Schmidt, R. J.; Dodds, R. H., Jr.

    1985-01-01

    The dynamic analysis of complex structural systems using the finite element method and multilevel substructured models is presented. The fixed-interface method is selected for substructure reduction because of its efficiency, accuracy, and adaptability to restart and reanalysis. This method is extended to reduction of substructures which are themselves composed of reduced substructures. The implementation and performance of the method in a general purpose software system is emphasized. Solution algorithms consistent with the chosen data structures are presented. It is demonstrated that successful finite element software requires the use of software executives to supplement the algorithmic language. The complexity of the implementation of restart and reanalysis porcedures illustrates the need for executive systems to support the noncomputational aspects of the software. It is shown that significant computational efficiencies can be achieved through proper use of substructuring and reduction technbiques without sacrificing solution accuracy. The restart and reanalysis capabilities and the flexible procedures for multilevel substructured modeling gives economical yet accurate analyses of complex structural systems.

  19. The Effect Of Periodically Attached Substructures On The Excitation Of Submerged Cylindrical Shells

    NASA Astrophysics Data System (ADS)

    Choi, S.-H.; Achenbach, J. D.; Igusa, T.

    1994-10-01

    The presence of substructures in a cylindrical shell gives rise to dynamic interactions which influence the distribution of vibration along the shell. In this paper, Lagrange's equations are used to develop the equations governing the forced harmonic vibration of a submerged cylindrical shell with periodically attached internal substructures which is subjected to periodically placed loads. Modal expansions are used to describe the response of the shell and the fields in the fluid. First, a shell without substructures but subjected to periodically placed ring loads is considered. The method of this paper gives nearly the same results as a travelling wave method for an infinite shell subjected to a single ring load. Two types of substructures are examined: circular panels with hinge connections and circular ribs with rigid connections. It is shown that the substructures confine the flexural motion to a region near the location of the applied forces. The localization effect decreases when the forcing frequency is close to the substructure's natural frequencies, and becomes more pronounced when, within a periodic segment, the ribs have varying impedance.

  20. Frontiers of stellar evolution

    NASA Technical Reports Server (NTRS)

    Lambert, David L. (editor)

    1991-01-01

    The present conference discusses theoretical and observational views of star formation, spectroscopic constraints on the evolution of massive stars, very low mass stars and brown dwarfs, asteroseismology, globular clusters as tests of stellar evolution, observational tests of stellar 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, stellar evolution and galactic chemical evolution, and interacting binaries containing compact components.

  1. Nucleosynthesis in stellar flares

    E-print Network

    V. Tatischeff; J. -P. Thibaud; I. Ribas

    2008-01-11

    Nuclear interactions of ions accelerated at the surface of flaring stars can produce fresh isotopes in stellar atmospheres. Although this nucleosynthesis is not significant for the chemical evolution of the Galaxy, it can be important for a number of measurements of "anomalously" high 6-Li and 7-Li abundances. We discuss the possible role of stellar flares to explain the recent report of high 6-Li abundances in metal-poor halo stars and the well-established correlation between Li abundance and stellar activity in young open clusters. We then study the possibility of observing directly Li production during flares of nearby and active dwarfs of spectral type M.

  2. KINEMATIC DISCOVERY OF A STELLAR STREAM LOCATED IN PISCES

    SciTech Connect

    Martin, Charles; Carlin, Jeffrey L.; Newberg, Heidi Jo [Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Grillmair, Carl, E-mail: martic6@rpi.edu [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)

    2013-03-10

    We report the kinematic discovery of the Pisces Stellar Stream (PSS), at Galactic longitude l Almost-Equal-To 135 Degree-Sign and -39 Degree-Sign < b < -36 Degree-Sign . We originally identified this halo substructure from velocities of red giant branch stars in the Sloan Digital Sky Survey (SDSS) Data Release 8, and confirmed its presence in turnoff stars from SDSS photometric data. The PSS is a narrow, kinematically cold tidal stream, with {sigma}{sub v,0} Almost-Equal-To 8 km s{sup -1}. Its metallicity is [Fe/H] Almost-Equal-To -2.2, with {approx}0.3 dex dispersion. The color-magnitude signature of the stream turnoff, combined with our measured metallicity, places the PSS at a distance of 35 {+-} 3 kpc. The PSS is the same as the previously announced ''Triangulum stream'' and part of the proposed ''stream a''. We rule out an association of the PSS with other previously known Milky Way substructures in the same region of the sky.

  3. The edge of the M 87 halo and the kinematics of the diffuse light in the Virgo cluster core

    Microsoft Academic Search

    Michelle Doherty; Magda Arnaboldi; Payel Das; Ortwin Gerhard; J. A. L. Aguerri; R. Ciardullo; J. J. Feldmeier; K. C. Freeman; G. H. Jacoby; G. Murante

    2009-01-01

    Aims: We study the kinematics and dynamics of the extreme outer halo of M 87, the central galaxy in the Virgo cluster, and its transition to the intracluster light (ICL). Methods: We present high resolution FLAMES\\/VLT spectroscopy of intracluster planetary nebula (PN) candidates, targeting three new fields in the Virgo cluster core with surface brightness down to muB = 28.5.

  4. Sensitivity to Gravitational Waves from Compact Binary Coalescences Achieved during LIGO's Fifth and Virgo's First Science Run

    E-print Network

    The LIGO Scientific Collaboration; the Virgo Collaboration; J. Abadie; B. P. Abbott; R. Abbott; M Abernathy; T. Accadia; F. Acernese; C. Adams; R. Adhikari; P. Ajith; B. Allen; G. Allen; E. Amador Ceron; R. S. Amin; S. B. Anderson; W. G. Anderson; F. Antonucci; S. Aoudia; M. A. Arain; M. Araya; M. Aronsson; K. G. Arun; Y. Aso; S. Aston; P. Astone; D. E. Atkinson; P. Aufmuth; C. Aulbert; S. Babak; P. Baker; G. Ballardin; S. Ballmer; D. Barker; S. Barnum; F. Barone; B. Barr; P. Barriga; L. Barsotti; M. Barsuglia; M. A. Barton; I. Bartos; R. Bassiri; M. Bastarrika; J. Bauchrowitz; Th. S. Bauer; B. Behnke; M. G. Beker; M. Benacquista; A. Bertolini; J. Betzwieser; N. Beveridge; P. T. Beyersdorf; S. Bigotta; I. A. Bilenko; G. Billingsley; J. Birch; S. Birindelli; R. Biswas; M. Bitossi; M. A. Bizouard; E. Black; J. K. Blackburn; L. Blackburn; D. Blair; B. Bland; M. Blom; C. Boccara; O. Bock; T. P. Bodiya; R. Bondarescu; F. Bondu; L. Bonelli; R. Bork; M. Born; S. Bose; L. Bosi; M. Boyle; S. Braccini; C. Bradaschia; P. R. Brady; V. B. Braginsky; J. E. Brau; J. Breyer; D. O. Bridges; A. Brillet; M. Brinkmann; V. Brisson; M. Britzger; A. F. Brooks; D. A. Brown; R. Budzy?ski; T. Bulik; H. J. Bulten; A. Buonanno; J. Burguet--Castell; O. Burmeister; D. Buskulic; R. L. Byer; L. Cadonati; G. Cagnoli; E. Calloni; J. B. Camp; E. Campagna; P. Campsie; J. Cannizzo; K. C. Cannon; B. Canuel; J. Cao; C. Capano; F. Carbognani; S. Caride; S. Caudill; M. Cavaglià; F. Cavalier; R. Cavalieri; G. Cella; C. Cepeda; E. Cesarini; T. Chalermsongsak; E. Chalkley; P. Charlton; E. Chassande-Mottin; S. Chelkowski; Y. Chen; A. Chincarini; N. Christensen; S. S. Y. Chua; C. T. Y. Chung; D. Clark; J. Clark; J. H. Clayton; F. Cleva; E. Coccia; C. N. Colacino; J. Colas; A. Colla; M. Colombini; R. Conte; D. Cook; T. R. Corbitt; C. Corda; N. Cornish; A. Corsi; C. A. Costa; J. -P. Coulon; D. Coward; D. C. Coyne; J. D. E. Creighton; T. D. Creighton; A. M. Cruise; R. M. Culter; A. Cumming; L. Cunningham; E. Cuoco; K. Dahl; S. L. Danilishin; R. Dannenberg; S. D'Antonio; K. Danzmann; A. Dari; K. Das; V. Dattilo; B. Daudert; M. Davier; G. Davies; A. Davis; E. J. Daw; R. Day; T. Dayanga; R. De Rosa; D. DeBra; J. Degallaix; M. del Prete; V. Dergachev; R. DeRosa; R. DeSalvo; P. Devanka; S. Dhurandhar; L. Di Fiore; A. Di Lieto; I. Di Palma; M. Di Paolo Emilio; A. Di Virgilio; M. Díaz; A. Dietz; F. Donovan; K. L. Dooley; E. E. Doomes; S. Dorsher; E. S. D. Douglas; M. Drago; R. W. P. Drever; J. C. Driggers; J. Dueck; J. -C. Dumas; T. Eberle; M. Edgar; M. Edwards; A. Effler; P. Ehrens; R. Engel; T. Etzel; M. Evans; T. Evans; V. Fafone; S. Fairhurst; Y. Fan; B. F. Farr; D. Fazi; H. Fehrmann; D. Feldbaum; I. Ferrante; F. Fidecaro; L. S. Finn; I. Fiori; R. Flaminio; M. Flanigan; K. Flasch; S. Foley; C. Forrest; E. Forsi; N. Fotopoulos; J. -D. Fournier; J. Franc; S. Frasca; F. Frasconi; M. Frede; M. Frei; Z. Frei; A. Freise; R. Frey; T. T. Fricke; D. Friedrich; P. Fritschel; V. V. Frolov; P. Fulda; M. Fyffe; L. Gammaitoni; J. A. Garofoli; F. Garufi; G. Gemme; E. Genin; A. Gennai; I. Gholami; S. Ghosh; J. A. Giaime; S. Giampanis; K. D. Giardina; A. Giazotto; C. Gill; E. Goetz; L. M. Goggin; G. González; M. L. Gorodetsky; S. Goßler; R. Gouaty; C. Graef; M. Granata; A. Grant; S. Gras; C. Gray; R. J. S. Greenhalgh; A. M. Gretarsson; C. Greverie; R. Grosso; H. Grote; S. Grunewald; G. M. Guidi; E. K. Gustafson; R. Gustafson; B. Hage; P. Hall; J. M. Hallam; D. Hammer; G. Hammond; J. Hanks; C. Hanna; J. Hanson; J. Harms; G. M. Harry; I. W. Harry; E. D. Harstad; K. Haughian; K. Hayama; J. Heefner; H. Heitmann; P. Hello; I. S. Heng; A. Heptonstall; M. Hewitson; S. Hild; E. Hirose; D. Hoak; K. A. Hodge; K. Holt; D. J. Hosken; J. Hough; E. Howell; D. Hoyland; D. Huet; B. Hughey; S. Husa; S. H. Huttner; T. Huynh--Dinh; D. R. Ingram; R. Inta; T. Isogai; A. Ivanov; P. Jaranowski; W. W. Johnson; D. I. Jones; G. Jones; R. Jones; L. Ju; P. Kalmus; V. Kalogera; S. Kandhasamy; J. Kanner; E. Katsavounidis; K. Kawabe; S. Kawamura; F. Kawazoe; W. Kells; D. G. Keppel; A. Khalaidovski; F. Y. Khalili; E. A. Khazanov; C. Kim; H. Kim; P. J. King; D. L. Kinzel; J. S. Kissel; S. Klimenko; V. Kondrashov; R. Kopparapu; S. Koranda; I. Kowalska; D. Kozak; T. Krause; V. Kringel; S. Krishnamurthy; B. Krishnan; A. Królak; G. Kuehn; J. Kullman; R. Kumar; P. Kwee; M. Landry; M. Lang; B. Lantz; N. Lastzka; A. Lazzarini; P. Leaci; J. Leong; I. Leonor; N. Leroy; N. Letendre; J. Li; T. G. F. Li; H. Lin; P. E. Lindquist; N. A. Lockerbie; D. Lodhia; M. Lorenzini; V. Loriette; M. Lormand; G. Losurdo; P. Lu; J. Luan; M. Lubinski; A. Lucianetti; H. Lück; A. Lundgren; B. Machenschalk; M. MacInnis; J. M. Mackowski; M. Mageswaran; K. Mailand; E. Majorana; C. Mak; N. Man; I. Mandel; V. Mandic; M. Mantovani; F. Marchesoni; F. Marion; S. Márka; Z. Márka; E. Maros; J. Marque; F. Martelli

    2010-06-01

    We summarize the sensitivity achieved by the LIGO and Virgo gravitational wave detectors for compact binary coalescence (CBC) searches during LIGO's fifth science run and Virgo's first science run. We present noise spectral density curves for each of the four detectors that operated during these science runs which are representative of the typical performance achieved by the detectors for CBC searches. These spectra are intended for release to the public as a summary of detector performance for CBC searches during these science runs.

  5. Detecting dark matter substructure with narrow line lensing

    NASA Astrophysics Data System (ADS)

    Nierenberg, Anna

    2014-10-01

    The abundance of low mass halos is one of the key predictions of LCDM and remains at apparent odds with observations of luminous structure. Strong gravitational lensing provides a straightforward means of testing this theory as it enables the detection of dark matter subhalos at cosmological distances, without requiring the structure to contain any baryons at all. The fluxes of strongly lensed, parsec scale sources in particular, are excellent probes as they are extremely sensitive to the presence of low mass subhalos, while still being extended enough to remain unaffected by microlensing by stars which is a dominant contaminant for smaller sources. Traditionally this field has been limited to the analysis of the small number of strongly lensed, radio-loud quasars. Quasar narrow-line emission offers an alternative to radio. It is also parsec scale and microlensing free, but has the benefit of detectable in a much larger sample of systems. This proposal will combine milliarcsecond astrometry, and percent level photometry attainable with WFC3 IR grism, in order to measure spatially resolved narrow line lensing in six new systems, which cannot be studied from the ground. We have demonstrated that data of this quality can be used to detect subhalos as small as a million solar masses. This proposal will double the sample of systems which can be used to detect dark, low mass substructure using flux ratio anomalies.

  6. The GALEX Ultraviolet Virgo Cluster Survey (GUViCS). V. Ultraviolet diffuse emission and cirrus properties in the Virgo cluster direction

    NASA Astrophysics Data System (ADS)

    Boissier, S.; Boselli, A.; Voyer, E.; Bianchi, S.; Pappalardo, C.; Guhathakurta, P.; Heinis, S.; Cortese, L.; Duc, P.-A.; Cuillandre, J.-C.; Davies, J. I.; Smith, M. W. L.

    2015-07-01

    Context. The Virgo direction has been observed at many wavelengths in recent years, in particular in the ultraviolet with GALEX. The far ultraviolet (FUV) diffuse light detected by GALEX offers interesting information on the large scale distribution of Galactic dust, owing to the GALEX FUV band sensitivity and resolution. Aims: We aim to characterise the ultraviolet large scale distribution of diffuse emission in the Virgo direction. A map of this emission may become useful for various studies by identifying regions where dust affects observations by either scattering light or absorbing radiation. Methods: We constructed mosaics of the FUV and near ultraviolet (NUV) diffuse emission over a large sky region (RA 12 to 13 h, Dec 0 to 20 deg) surrounding the Virgo cluster, using all the GALEX available data in the area. We tested for the first time the utilisation of the FUV diffuse light as a Galactic extinction E(B - V) tracer. Results: The FUV diffuse light scattered on cirrus reveals details about their geometry. Despite large dispersion, the FUV diffuse light correlates roughly with other Galactic dust tracers (coming from IRAS, Herschel, Planck), offering an opportunity to use the FUV emission to locate them in future studies with a better resolution (about 5 arcsec native resolution, 20 arcsec pixels maps presented in this paper) than for several usual tracers. Estimating the Galactic dust extinction on the basis of this emission allows us to find a smaller dispersion in the NUV - i colour of background galaxies at a given E(B - V) than with other tracers. The diffuse light mosaics obtained in this work are made publicly available. The diffuse light mosaics as FITS files are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/579/A29

  7. Stellar Sea Lion Research

    NSDL National Science Digital Library

    The phenomenon is the decline in population of western Stellar Sea Lions from 1969 to 1986, shown in a series of three images. The accompanying text describes the possible factors that may be contributing to the change in population.

  8. Do gravitational lens galaxies have an excess of luminous substructure?

    E-print Network

    Nierenberg, A M; Treu, T

    2013-01-01

    Strong gravitational lensing can be used to directly measure the mass function of their satellites, thus testing one of the fundamental predictions of cold dark matter cosmological models. Given the importance of this test it is essential to ensure that galaxies acting as strong lenses have dark and luminous satellites which are representative of the overall galaxy population. We address this issue by measuring the number and spatial distribution of luminous satellites in ACS imaging around lens galaxies from the Sloan Lens Advanced Camera for Surveys (SLACS) lenses, and comparing them with the satellite population in ACS imaging of non lens galaxies selected from COSMOS, which has similar depth and resolution to the ACS images of SLACS lenses. In order to compare the samples of lens and non lens galaxies, which have intrinsically different stellar mass distributions, we measure, for the first time, the number of satellites per host as a continuous function of host stellar mass for both populations. We find t...

  9. Stellar Evolution A Statistical Model

    E-print Network

    van Dyk, David

    Stellar Evolution A Statistical Model Statistical Computation Analysis of the Hyades Cluster Embedding Computer Models for Stellar Evolution into a Coherent Statistical Analysis David A. van Dyk1 Analysis of Stellar Evolution #12;Stellar Evolution A Statistical Model Statistical Computation Analysis

  10. Stellar Evolution A Statistical Model

    E-print Network

    van Dyk, David

    Stellar Evolution A Statistical Model Statistical Computation Analysis of the Hyades Cluster Statistical Analysis of Stellar Evolution David A. van Dyk1 Steven DeGennaro2 Nathan Stein2 William H Statistical Analysis of Stellar Evolution #12;Stellar Evolution A Statistical Model Statistical Computation

  11. Stellar Astrophysical Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Thompson, Michael J.; Christensen-Dalsgaard, Jørgen

    2003-05-01

    Preface; 1. A selective overview Jørgen Christensen-Dalsgaard and Michael J. Thompson; Part I. Stellar Convection and Oscillations: 2. On the diversity of stellar 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. Stellar Rotation and Magnetic Fields: 6. Stellar 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 Stellar Interiors: 12. Solar constraints on the equation of state Werner Däppen; 13. 3He transport and the solar neutrino problem Chris Jordinson; 14. Mixing in stellar 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 stellar 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 stellar dynamics Edward A. Spiegel and Jean-Luc Thiffeault; 27. Formation of planetary systems Douglas N. C. Lin; 28. The solar-cycle global warming as inferred from sky brightness variation Wasaburo Unno and Hiromoto Shibahashi.

  12. Stellar Astrophysical Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Thompson, Michael J.; Christensen-Dalsgaard, Jørgen

    2008-02-01

    Preface; 1. A selective overview Jørgen Christensen-Dalsgaard and Michael J. Thompson; Part I. Stellar Convection and Oscillations: 2. On the diversity of stellar 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. Stellar Rotation and Magnetic Fields: 6. Stellar 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 Stellar Interiors: 12. Solar constraints on the equation of state Werner Däppen; 13. 3He transport and the solar neutrino problem Chris Jordinson; 14. Mixing in stellar 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 stellar 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 stellar dynamics Edward A. Spiegel and Jean-Luc Thiffeault; 27. Formation of planetary systems Douglas N. C. Lin; 28. The solar-cycle global warming as inferred from sky brightness variation Wasaburo Unno and Hiromoto Shibahashi.

  13. Oscillations in stellar atmospheres

    NASA Technical Reports Server (NTRS)

    Costa, A.; Ringuelet, A. E.; Fontenla, J. M.

    1989-01-01

    Atmospheric excitation and propagation of oscillations are analyzed for typical pulsating stars. The linear, plane-parallel approach for the pulsating atmosphere gives a local description of the phenomenon. From the local analysis of oscillations, the minimum frequencies are obtained for radially propagating waves. The comparison of the minimum frequencies obtained for a variety of stellar types is in good agreement with the observed periods of the oscillations. The role of the atmosphere in the globar stellar pulsations is thus emphasized.

  14. Analysis of substructural variation in families of enzymatic proteins with applications to protein function prediction

    PubMed Central

    2010-01-01

    Background Structural variations caused by a wide range of physico-chemical and biological sources directly influence the function of a protein. For enzymatic proteins, the structure and chemistry of the catalytic binding site residues can be loosely defined as a substructure of the protein. Comparative analysis of drug-receptor substructures across and within species has been used for lead evaluation. Substructure-level similarity between the binding sites of functionally similar proteins has also been used to identify instances of convergent evolution among proteins. In functionally homologous protein families, shared chemistry and geometry at catalytic sites provide a common, local point of comparison among proteins that may differ significantly at the sequence, fold, or domain topology levels. Results This paper describes two key results that can be used separately or in combination for protein function analysis. The Family-wise Analysis of SubStructural Templates (FASST) method uses all-against-all substructure comparison to determine Substructural Clusters (SCs). SCs characterize the binding site substructural variation within a protein family. In this paper we focus on examples of automatically determined SCs that can be linked to phylogenetic distance between family members, segregation by conformation, and organization by homology among convergent protein lineages. The Motif Ensemble Statistical Hypothesis (MESH) framework constructs a representative motif for each protein cluster among the SCs determined by FASST to build motif ensembles that are shown through a series of function prediction experiments to improve the function prediction power of existing motifs. Conclusions FASST contributes a critical feedback and assessment step to existing binding site substructure identification methods and can be used for the thorough investigation of structure-function relationships. The application of MESH allows for an automated, statistically rigorous procedure for incorporating structural variation data into protein function prediction pipelines. Our work provides an unbiased, automated assessment of the structural variability of identified binding site substructures among protein structure families and a technique for exploring the relation of substructural variation to protein function. As available proteomic data continues to expand, the techniques proposed will be indispensable for the large-scale analysis and interpretation of structural data. PMID:20459833

  15. Nuclear substructure reorganization during late stageerythropoiesis is selective and does not involve caspase cleavage ofmajor nuclear substructural proteins

    SciTech Connect

    Krauss, Sharon Wald; Lo, Annie J.; Short, Sarah A.; Koury, MarkJ.; Mohandas, Narla; Chasis, Joel Anne

    2005-04-06

    Enucleation, a rare feature of mammalian differentiation, occurs in three cell types: erythroblasts, lens epithelium and keratinocytes. Previous investigations suggest that caspase activation functions in lens epithelial and keratinocyte enucleation, as well as in early erythropoiesis encompassing BFU-E differentiation to proerythroblast. To determine whether caspase activation contributes to later erythropoiesis and whether nuclear substructures other than chromatin reorganize, we analyzed distributions of nuclear subcompartment proteins and assayed for caspase-induced cleavage of subcompartmental target proteins in mouse erythroblasts. We found that patterns of lamin B in the filamentous network interacting with both the nuclear envelope and DNA, nuclear matrix protein NuMA, and splicing factors Sm and SC35 persisted during nuclear condensation, consistent with effective transcription of genes expressed late in differentiation. Thus nuclear reorganization prior to enucleation is selective, allowing maintenance of critical transcriptional processes independent of extensive chromosomal reorganization. Consistent with these data, we found no evidence for caspase-induced cleavage of major nuclear subcompartment proteins during late erythropoiesis, in contrast to what has been observed in early erythropoiesis and in lens epithelial and keratinocyte differentiation. These findings imply that nuclear condensation and extrusion during terminal erythroid differentiation involve novel mechanisms that do not entail major activation of apoptotic machinery.

  16. VirGO: A Visual Browser for the ESO Science Archive Facility

    NASA Astrophysics Data System (ADS)

    Hatziminaoglou, Evanthia; Chéreau, Fabien

    2009-03-01

    VirGO is the next generation Visual Browser for the ESO Science Archive Facility (SAF) developed in the Virtual Observatory Project Office. VirGO enables astronomers to discover and select data easily from millions of observations in a visual and intuitive way. It allows real-time access and the graphical display of a large number of observations by showing instrumental footprints and image previews, as well as their selection and filtering for subsequent download from the ESO SAF web interface. It also permits the loading of external FITS files or VOTables, as well as the superposition of Digitized Sky Survey images to be used as background. All data interfaces are based on Virtual Observatory (VO) standards that allow access to images and spectra from external data centres, and interaction with the ESO SAF web interface or any other VO applications.

  17. Amplitude modulation of low degree p-modes - comparison of BISON and VIRGO

    NASA Astrophysics Data System (ADS)

    Andersen, Bo; Leifsen, Torben; Chaplin, William J.; Elsworth, Yvonne

    2003-02-01

    Using both VIRGO and MDI data we have previously studied the amplitude variation of the l=0 p-modes for radial orders 12 to 32. In this study we extend the investigation backward in time to 1992 by including data from the BISON network. For the large amplitude modes there is a strong correlation between the space based radiance measurements from VIRGO and the ground based Doppler shift measurements from BISON. The extreme rotational modulation of l=0, n=22 is confirmed to be a phenomenon confined to the period of minimum solar activity. Also with neighbouring l=1, n=21 a clear modulation is seen at slightly lower frequency. Some persistent frequencies occur in other l=0,1 modes, but not to the same level in time and amplitude.

  18. A Spitzer study of star-forming regions in Virgo Cluster galaxies

    E-print Network

    O. Ivy Wong; Jeffrey D. P. Kenney

    2008-02-25

    We present a preliminary study of the star formation distribution within three Virgo Cluster galaxies using the 24 micron Spitzer observations from the Spitzer Survey of Virgo (SPITSOV) in combination with H-alpha observations. The purpose of our study is to explore the relationship between the star formation distribution within galaxies and the type (and phase) of interactions experienced within the cluster environment. Neither highly-obscured star formation nor strongly enhanced star-forming regions along the leading edges of galaxies experiencing ICM-ISM interactions were found. However, very unobscured star-forming regions were found in the outer parts of one galaxy (NGC 4402), while relatively obscured star-forming regions were found in the extraplanar regions of another galaxy (NGC 4522). We attribute the observed differences between NGC 4402 and NGC 4522 to the direction of motion of each galaxy through the ICM.

  19. Identification of long-duration noise transients in LIGO and Virgo

    E-print Network

    LIGO Scientific Collaboration; Virgo Collaboration; Michael W. Coughlin

    2011-11-13

    The LIGO and Virgo detectors are sensitive to a variety of noise sources, such as instrumental artifacts and environmental disturbances. The Stochastic Transient Analysis Multi-detector Pipeline (STAMP) has been developed to search for long-duration (t$\\gtrsim$1s) gravitational-wave (GW) signals. This pipeline can also be used to identify environmental noise transients. Here we present an algorithm to determine when long-duration noise sources couple into the interferometers, as well as identify what these noise sources are. We analyze the cross-power between a GW strain channel and an environmental sensor, using pattern recognition tools to identify statistically significant structure in cross-power time-frequency maps. We identify interferometer noise from airplanes, helicopters, thunderstorms and other sources. Examples from LIGO's sixth science run, S6, and Virgo's third scientific run, VSR3, are presented.

  20. A 10 micron survey of star formation in galactic nuclei Virgo spiral galaxies

    NASA Technical Reports Server (NTRS)

    Becklin, E. E.; Capps, R. W.; Scoville, N. Z.; Young, J. S.

    1983-01-01

    A survey for 10 micron emission in the nuclei of spiral galaxies in the Virgo cluster is reported. It is found that the nuclei of most luminous spiral galaxies are active 10 micron emitters, and that the luminosity function for the sample can be represented by a simple power law over the entire range sampled. The most luminous sources at 10 microns show only a weak correlation with total optical luminosity, and no correlation with morphological type or location in the cluster. It is argued that the 10 micron flux from the Virgo galaxies arises from active star formation regions. A mean far-IR luminosity of two billion solar luminosities is inferred for the galactic nuclei; the required rate of massive star formation is 0.1 solar masses/yr. The results suggest that the rate of star formation in galactic nuclei has little relationship to the size of the nuclear bulge or the gravitational potential near the center.

  1. Performance of "G-Pisa" ring laser gyro at the Virgo site

    NASA Astrophysics Data System (ADS)

    Belfi, Jacopo; Beverini, Nicolò; Bosi, Filippo; Carelli, Giorgio; Di Virgilio, Angela; Kolker, Dmitri; Maccioni, Enrico; Ortolan, Antonello; Passaquieti, Roberto; Stefani, Fabio

    2012-10-01

    The ring laser gyroscope "G-Pisa" has been taking data inside the Virgo interferometer central area with the aim of performing high sensitivity measurements of rotations in the vertical as well as in the horizontal orientation. We discuss the main characteristics of the instrument, describing its mechanical design and presenting the measured sensitivity limit. By applying a simple effective model for the laser gyroscope, we show that the stability of the sensor above 10 s of integration time is mainly limited by backscattering effects. The horizontal rotation rate signal is also compared with the signals recorded by the Virgo environmental monitoring system and by a biaxial mechanical tiltmeter rigidly fixed on top of the gyrolaser mounting frame.

  2. Gas sloshing, cold front formation, and metal redistribution: the Virgo cluster as a quantitative test case

    E-print Network

    Roediger, Elke; Simionescu, Aurora; Böhringer, Hans; Churazov, Eugene; Forman, William R

    2010-01-01

    (abbreviated) We perform hydrodynamical simulations of minor-merger induced gas sloshing and the subsequent formation of cold fronts. Using the Virgo cluster as a test case, we show for the first time that the sloshing scenario can reproduce the radii and the contrasts in X-ray brightness, pro jected temperature, and metallicity across the observed cold fronts quantitatively. We identify several new features typical for sloshing cold fronts: an alternating distribution of cool, metal enriched X-ray brightness excess regions and warm brightness deficit regions of reduced metallicity; a constant or radially decreasing temperature accompanied by a plateau in metallicity inside the cold fronts; a warm rim outside the CFs; and a large-scale brightness excess towards the responsible subcluster, which will be helpful for its identification. We can trace these new features not only in Virgo, but also in other clusters exhibiting sloshing cold fronts. By comparing synthetic and real observations, we estimate that the ...

  3. Coincidence analysis between periodic source candidates in C6 and C7 Virgo data

    Microsoft Academic Search

    F. Acernese; M. Alshourbagy; F. Antonucci; S. Aoudia; P. Astone; S. Avino; D. Babusci; G. Ballardin; F. Barone; L. Barsotti; M. Barsuglia; S Birindelli; F. Beauville; S. Bigotta; M. A. Bizouard; C. Boccara; F. Bondu; L. Bosi; C. Bradaschia; S. Braccini; F. J. van den Brand; A. Brillet; V. Brisson; D. Buskulic; E. Calloni; E Chassande-Mottin; F. Carbognani; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; N. Christensen; C. Corda; A. Corsi; F. Cottone; A.-C. Clapson; F. Cleva; J.-P. Coulon; E. Cuoco; A. Dari; V. Dattilo; M. Davier; M. del Prete; R. De Rosa; L. Di Fiore; A. Di Virgilio; B. Dujardin; A. Eleuteri; M. Evans; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J.-D. Fournier; S. Frasca; F. Frasconi; L. Gammaitoni; F. Garufi; E. Genin; A. Gennai; A. Giazotto; G. Giordano; L. Giordano; R. Gouaty; D. Grosjean; G. Guidi; S. Hamdani; S. Hebri; H. Heitmann; P. Hello; D. Huet; S. Karkar; S. Kreckelbergh; P. La Penna; M. Laval; N. Leroy; N. Letendre; B. Lopez; Lorenzini; V. Loriette; G. Losurdo; J.-M. Mackowski; E. Majorana; C. N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; M. Mazzoni; L. Milano; F. Menzinger; C. Moins; J. Moreau; N. Morgado; B. Mours; F. Nocera; C. Palomba; F. Paoletti; S. Pardi; A. Pasqualetti; R. Passaquieti; D. Passuello; F. Piergiovanni; L. Pinard; R. Poggiani; M. Punturo; P. Puppo; S. van der Putten; K. Qipiani; P. Rapagnani; V. Reita; A. Remillieux; F. Ricci; I. Ricciardi; P. Ruggi; G. Russo; S. Solimeno; A. Spallicci; M. Tarallo; M. Tonelli; A. Toncelli; E. Tournefier; F. Travasso; C. Tremola; G. Vajente; D. Verkindt; F. Vetrano; A. Viceré; J.-Y. Vinet; H. Vocca; M. Yvert

    2007-01-01

    In this paper, we describe the analysis performed in the data of C6 and C7 commissioning runs of Virgo for the search of periodic sources of gravitational waves. The analysis is all-sky, covers the frequency range between 50 Hz and 1050 Hz and neutron star spin-down rate below 1.58 × 10-8 Hz s-1. Coincidences in the source parameter space between

  4. Internal Properties of Ultra-Compact Dwarf Galaxies in the Virgo Cluster

    Microsoft Academic Search

    E. A. Evstigneeva; M. D. Gregg; M. J. Drinkwater; M. Hilker

    2006-01-01

    We present new imaging and spectroscopic observations of six ultra-compact\\u000adwarf (UCD) galaxies in the Virgo Cluster, along with re-analysed data for five\\u000aFornax Cluster UCDs. These are the most luminous UCDs: -14

  5. The ACS Virgo Cluster Survey. VII. Resolving the Connection between Globular Clusters and Ultracompact Dwarf Galaxies

    Microsoft Academic Search

    Monica Hasegan; Andrés Jordán; Patrick Côté; S. G. Djorgovski; Dean E. McLaughlin; John P. Blakeslee; Simona Mei; Michael J. West; Eric W. Peng; Laura Ferrarese; Milos Milosavljevic; John L. Tonry; David Merritt

    2005-01-01

    We investigate the connection between globular clusters and ultracompact dwarf galaxies (UCDs) by examining the properties of 10 compact, high-luminosity (-11.8 MV -10.8) objects associated with M87 (NGC 4486, VCC 1316), the cD galaxy in the Virgo Cluster. These objects, most of which were previously classified as M87 globular clusters, were selected from a combination of ground- and space-based imaging

  6. The VIRGO Project: A wide band antenna for gravitational wave detection

    Microsoft Academic Search

    C. Bradaschia; R. del Fabbro; A. di Virgilio; A. Giazotto; H. Kautzky; V. Montelatici; D. Passuello; A. Brillet; O. Cregut; P. Hello; C. N. Man; P. T. Manh; A. Marraud; D. Shoemaker; J. Y. Vinet; F. Barone; L. di Fiore; L. Milano; G. Russo; J. M. Aguirregabiria; H. Bel; J. P. Duruisseau; G. Le Denmat; Ph. Tourrenc; M. Capozzi; M. Longo; M. Lops; I. Pinto; G. Rotoli; T. Damour; S. Bonazzola; J. A. Marck; Y. Gourghoulon; L. E. Holloway; F. Fuligni; V. Iafolla; G. Natale

    1990-01-01

    The status of advancement of the VIRGO Project is presented: the first-generation results from the Pisa seismic noise super attenuator give an upper limit to the noise transfer function of 2 × 10-8 at 10 Hz. The upper limit to the absolute noise of the 400 kg test mass at 10 Hz has been measured to be 1.5 × 10-13

  7. Nanoscale Similarities in the Substructure of the Exines of FagusPollen Grains and LycopodiumSpores

    Microsoft Academic Search

    JESPER WITTBORN; K. V RAO; G EL-GHAZALY; J. R ROWLEY

    1998-01-01

    The exine substructure of an angiosperm,Fagus sylvatica(beech) pollen and a pteridophyte,Lycopodium clavatum(a club moss) spore was investigated by scanning tunnelling microscopy. These pollen and spores, despite their distinct differences in structure and morphology on a micrometre scale, have very similar substructure on a nanometre scale. The substructure appears to consist of a multi-helix, i.e. a helical chain in turn wound

  8. X-RAY TRANSIENTS IN THE ADVANCED LIGO/VIRGO HORIZON

    SciTech Connect

    Kanner, Jonah [LIGO-California Institute of Technology, Pasadena, CA 91125 (United States); Baker, John; Blackburn, Lindy; Camp, Jordan [NASA Goddard Space Flight Center, Mail Code 663, Greenbelt, MD 20771 (United States); Mooley, Kunal [California Institute of Technology, Astronomy Department, Mail Code 249-17, Pasadena, CA 91125 (United States); Mushotzky, Richard; Ptak, Andy, E-mail: jonah.kanner@ligo.org [NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States)

    2013-09-01

    Advanced LIGO and Advanced Virgo will be all-sky monitors for merging compact objects within a few hundred megaparsecs. Finding the electromagnetic counterparts to these events will require an understanding of the transient sky at low redshift (z < 0.1). We performed a systematic search for extragalactic, low redshift, transient events in the XMM-Newton Slew Survey. In a flux limited sample, we found that highly variable objects comprised 10% of the sample, and that of these, 10% were spatially coincident with cataloged optical galaxies. This led to 4 Multiplication-Sign 10{sup -4} transients per square degree above a flux threshold of 3 Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1} (0.2-2 keV) which might be confused with LIGO/Virgo counterparts. This represents the first extragalactic measurement of the soft X-ray transient rate within the Advanced LIGO/Virgo horizon. Our search revealed six objects that were spatially coincident with previously cataloged galaxies, lacked evidence for optical active galactic nuclei, displayed high luminosities {approx}10{sup 43} erg s{sup -1}, and varied in flux by more than a factor of 10 when compared with the ROSAT All-Sky Survey. At least four of these displayed properties consistent with previously observed tidal disruption events.

  9. Vertical and Horizontal Seismic Isolation Performance of the Advanced Virgo External Injection Bench Seismic Attenuation System

    NASA Astrophysics Data System (ADS)

    Blom, M. R.; Beker, M. G.; Bertolini, A.; van den Brand, J. F. J.; Bulten, H. J.; Doets, M.; Hennes, E.; Mul, F. A.; Rabeling, D. S.; Schimmel, A.

    During the combined commissioning and science run of Virgo in 2010, an extensive noise study revealed that vibrations of some of the injection/detection optics on the external injection bench (EIB) made a significant contribution to the interferometer's noise budget. Several resonances were identified between 10 and 100 Hz of the EIB support structure and between 200 and 300 Hz of the optics mounts. These resonances introduced a significant amount of beam jitter that would limit the sensitivity of Advanced Virgo. This beam jitter needed to be reduced for Advanced Virgo to reach its full potential. To eliminate this noise source we developed a seismic attenuation system to isolate the EIB from ground vibrations: EIB-SAS. It employs vertical and horizontal passive seismic filters based on negative stiffness technology to attenuate seismic noise by 40 dB above 10 Hz. The isolation capabilities of the system have been characterized up to 400 Hz with the aid of a custom designed piezoelectric actuated shaking platform. The results of the vertical and horizontal transfer function measurements are presented.

  10. X-ray Transients in the Advanced LIGO/Virgo Horizon

    NASA Technical Reports Server (NTRS)

    Kanner, Jonah; Baker, John G.; Blackburn, Lindy L.; Camp, Jordan B.; Mooley, Kunal; Mushotzky, Richard F.; Ptak, Andrew Francis

    2013-01-01

    Advanced LIGO and Advanced Virgo will be all-sky monitors for merging compact objects within a few hundred megaparsecs. Finding the electromagnetic counterparts to these events will require an understanding of the transient sky at low redshift (z < 0.1). We performed a systematic search for extragalactic, low redshift, transient events in the XMM-Newton Slew Survey. In a flux limited sample, we found that highly variable objects comprised 10% of the sample, and that of these, 10% were spatially coincident with cataloged optical galaxies. This led to 4 × 10(exp -4) transients per square degree above a flux threshold of 3×10(exp -12) erg/sq cm/s (0.2-2 keV) which might be confused with LIGO/Virgo counterparts. This represents the first extragalactic measurement of the soft X-ray transient rate within the Advanced LIGO/Virgo horizon. Our search revealed six objects that were spatially coincident with previously cataloged galaxies, lacked evidence for optical active galactic nuclei, displayed high luminosities approx. 10(exp 43) erg/s, and varied in flux by more than a factor of 10 when compared with the ROSAT All-Sky Survey. At least four of these displayed properties consistent with previously observed tidal disruption events.

  11. Discovering Higgs Bosons of the MSSM using Jet Substructure

    SciTech Connect

    Kribs, Graham D.; Martin, Adam; Roy, Tuhin S.; Spannowsky, Michael

    2010-06-01

    We present a qualitatively new approach to discover Higgs bosons of the MSSM at the LHC using jet substructure techniques applied to boosted Higgs decays. These techniques are ideally suited to the MSSM, since the lightest Higgs boson overwhelmingly decays to b{bar b} throughout the entire parameter space, while the heavier neutral Higgs bosons, if light enough to be produced in a cascade, also predominantly decay to b{bar b}. The Higgs production we consider arises from superpartner production where superpartners cascade decay into Higgs bosons. We study this mode of Higgs production for several superpartner hierarchies: m{sub {tilde q}},m{sub {tilde g}} > m{sub {tilde W}},{sub {tilde B}} > m{sub h} + {mu}; m{tilde q};m{sub {tilde q}},m{sub {tilde g}} > m{sub {tilde W}},{sub {tilde B}} > m {sub h,H,A} + {mu}; and m{sub {tilde q}},m{sub {tilde g}} > m{sub {tilde W}} > m{sub h} + {mu} with m{sub {tilde B}} {approx} {mu}. In these cascades, the Higgs bosons are boosted, with pT > 200 GeV a large fraction of the time. Since Higgs bosons appear in cascades originating from squarks and/or gluinos, the cross section for events with at least one Higgs boson can be the same order as squark/gluino production. Given 10 fb{sup -1} of 14 TeV LHC data, with m{sub {tilde q}} {approx}< 1 TeV, and one of the above superpartner mass hierarchies, our estimate of S{radical} B of the Higgs signal is sufficiently high that the b{bar b} mode can become the discovery mode of the lightest Higgs boson of the MSSM.

  12. Morphology parameters: substructure identification in X-ray galaxy clusters

    NASA Astrophysics Data System (ADS)

    Parekh, Viral; van der Heyden, Kurt; Ferrari, Chiara; Angus, Garry; Holwerda, Benne

    2015-03-01

    Context. In recent years multi-wavelength observations have shown the presence of substructures related to merging events in a large proportion of galaxy clusters. Clusters can be roughly grouped into two categories - relaxed and non-relaxed - and a proper characterisation of the dynamical state of these systems is crucial for both astrophysical and cosmological studies. Aims: In this paper we investigate the use of a number of morphological parameters (Gini, M20, concentration, asymmetry, smoothness, ellipticity, and Gini of the second-order moment, GM) introduced to automatically classify clusters as relaxed or dynamically disturbed systems. Methods: We apply our method to a sample of clusters at different redshifts extracted from the Chandra archive and investigate possible correlations between morphological parameters and other X-ray gas properties. Results: We conclude that a combination of the adopted parameters is a very useful tool for properly characterising the X-ray cluster morphology. According to our results, three parameters - Gini, M20, and concentration - are very promising for identifying cluster mergers. The Gini coefficient is a particularly powerful tool, especially at high redshift, because it is independent of the choice of the position of the cluster centre. We find that high Gini (>0.65), high concentration (>1.55), and low M20 (<-2.0) values are associated with relaxed clusters, while low Gini (<0.4), low concentration (<1.0), and high M20 (>-1.4) characterise dynamically perturbed systems. We also estimate the X-ray cluster morphological parameters in the case of radio loud clusters. Since they are in excellent agreement with previous analyses we confirm that diffuse intracluster radio sources are associated with major mergers. Appendix A is available in electronic form at http://www.aanda.org

  13. Stellar ages from asteroseismology

    E-print Network

    Yveline Lebreton; Josefina Montalban

    2008-11-18

    Asteroseismology provides powerful means to probe stellar interiors. The oscillations frequencies are closely related to stellar interior properties via the density and sound speed profiles. Since these are tightly linked with the mass and evolutionary state, we can expect to determine the age and mass of a star from the comparison of its oscillation spectrum with predictions of stellar models. Such a comparison suffers both from the problems we face when modeling a particular star (as the uncertainties on global parameters and chemical composition) and from our misunderstanding of processes at work in stellar interiors (as the transport processes that may lead to core mixing and affect the model ages). For stars where observations have provided precise and numerous oscillation frequencies together with accurate global parameters and additional information (as the radius or the mass if the star is in a binary system, the interferometric radius or the mean density if the star is an exoplanet host), we can also expect to better constrain the physical description of the stellar structure and to get a more reliable age estimation. After a survey of stellar pulsations, we present some seismic diagnostics that can be used to infer the age of a star as well as their limitations. We then illustrate the ability of asteroseismology to scrutinize stellar interiors on the basis of a few exemples. In the years to come, extended very precise asteroseismic observations are expected, in photometry or in spectroscopy, from ground-based (HARPS, CORALIE, ELODIE, UVES, UCLES, SIAMOIS, SONG) or spatial devices (MOST, CoRoT, WIRE, Kepler, PLATO). This will considerably enlarge the sample of stars eligible to asteroseismic age determination and should allow to estimate the age of individual stars with a 10-20% accuracy.

  14. MODEST-1: Integrating Stellar Evolution and Stellar Dynamics

    E-print Network

    Piet Hut; Michael M. Shara; Sverre J. Aarseth; Ralf S. Klessen; James C. Lombardi Jr.; Junichiro Makino; Steve McMillan; Onno R. Pols; Peter J. Teuben; Ronald F. Webbink

    2002-11-01

    We summarize the main results from MODEST-1, the first workshop on MOdeling DEnse STellar systems. Our goal is to go beyond traditional population synthesis models, by introducing dynamical interactions between single stars, binaries, and multiple systems. The challenge is to define and develop a software framework to enable us to combine in one simulation existing computer codes in stellar evolution, stellar dynamics, and stellar hydrodynamics. With this objective, the workshop brought together experts in these three fields, as well as other interested astrophysicists and computer scientists. We report here our main conclusions, questions and suggestions for further steps toward integrating stellar evolution and stellar (hydro)dynamics.

  15. Sub-Structure Survival in Galaxy Clusters from N-Body Experiments

    NASA Astrophysics Data System (ADS)

    Splinter, R. J.; Melott, A. L.

    1996-12-01

    We perform a series of N-body experiments to determine whether sub-structure in galaxy clusters is a long lasting effect, or simply a short lived stage in the evolution of a cluster. From simulations of 128(3) particles we extract groups of particles using a friends-of-a-friend algorithm which we take as our clusters. Using a variety of statistical methods first described by Bird (1994) we find that the final evolved state of the clusters all exhibit sub-structure, regardless of spectral index and the value of Omega_0 . We find a small difference in the abundance of sub-structure between critical density models and low density models, and conclude that based upon the low resolution models sub-structure is not a useful diagnostic of the cosmological initial conditions. To check for the existence of particle discreteness effects we apply the Nested-Grid Particle Mesh code of Splinter (1996) to a subset of the original clusters. Using this code with its higher force and mass resolution we will be able to make definitive statements regarding the existence of substructure.

  16. DARK MATTER SUBSTRUCTURE DETECTION USING SPATIALLY RESOLVED SPECTROSCOPY OF LENSED DUSTY GALAXIES

    SciTech Connect

    Hezaveh, Yashar; Holder, Gilbert [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec H3A 2T8 (Canada)] [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec H3A 2T8 (Canada); Dalal, Neal [Astronomy Department, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801 (United States)] [Astronomy Department, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801 (United States); Kuhlen, Michael [Theoretical Astrophysics Center, University of California, Berkeley, CA 94720 (United States)] [Theoretical Astrophysics Center, University of California, Berkeley, CA 94720 (United States); Marrone, Daniel [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)] [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Murray, Norman [CITA, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)] [CITA, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Vieira, Joaquin [California Institute of Technology, 1200 East California Blvd, MC 249-17, Pasadena, CA 91125 (United States)] [California Institute of Technology, 1200 East California Blvd, MC 249-17, Pasadena, CA 91125 (United States)

    2013-04-10

    We investigate how strong lensing of dusty, star-forming galaxies (DSFGs) by foreground galaxies can be used as a probe of dark matter halo substructure. We find that spatially resolved spectroscopy of lensed sources allows dramatic improvements to measurements of lens parameters. In particular, we find that modeling of the full, three-dimensional (angular position and radial velocity) data can significantly facilitate substructure detection, increasing the sensitivity of observables to lower mass subhalos. We carry out simulations of lensed dusty sources observed by early ALMA (Cycle 1) and use a Fisher matrix analysis to study the parameter degeneracies and mass detection limits of this method. We find that even with conservative assumptions, it is possible to detect galactic dark matter subhalos of {approx}10{sup 8} M{sub Sun} with high significance in most lensed DSFGs. Specifically, we find that in typical DSFG lenses, there is a {approx}55% probability of detecting a substructure with M > 10{sup 8} M{sub Sun} with more than 5{sigma} detection significance in each lens, if the abundance of substructure is consistent with previous lensing results. The full ALMA array, with its significantly enhanced sensitivity and resolution, should improve these estimates considerably. Given the sample of {approx}100 lenses provided by surveys such as the South Pole Telescope, our understanding of dark matter substructure in typical galaxy halos is poised to improve dramatically over the next few years.

  17. Metrics for diagnosing negative mass and stiffness when uncoupling experimental and analytical substructures.

    SciTech Connect

    Allen, Matthew S. (University of Wisconsin, Madison, WI); Kammer, Daniel C. (University of Wisconsin, Madison, WI); Mayes, Randall Lee

    2010-10-01

    Recently, a new substructure coupling/uncoupling approach has been introduced, called Modal Constraints for Fixture and Subsystem (MCFS) [Allen, Mayes, & Bergman, Journal of Sound and Vibration, vol. 329, 2010]. This method reduces ill-conditioning by imposing constraints on substructure modal coordinates instead of the physical interface coordinates. The experimental substructure is tested in a free-free configuration, and the interface is exercised by attaching a flexible fixture. An analytical representation of the fixture is then used to subtract its effects in order to create an experimental model for the subcomponent of interest. However, it has been observed that indefinite mass and stiffness matrices can be obtained for the experimental substructure in some situations. This paper presents two simple metrics that can be used by the analyst to determine the cause of indefinite mass or stiffness matrices after substructure uncoupling. The metrics rank the experimental and fixture modes based upon their contribution to offending negative eigenvalues. Once the troublesome modes have been identified, they can be inspected and often reveal why the mass has become negative. Two examples are presented to demonstrate the metrics and to illustrate the physical phenomena that they reveal.

  18. Stellar libraries for Gaia

    NASA Astrophysics Data System (ADS)

    Sordo, R.; Vallenari, A.; Tantalo, R.; Liu, C.; Smith, K.; Allard, F.; Blomme, R.; Bouret, J.-C.; Brott, I.; de Laverny, P.; Edvardsson, B.; Frémat, Y.; Heber, U.; Josselin, E.; Kochukhov, O.; Korn, A.; Lanzafame, A.; Martayan, C.; Martins, F.; Plez, B.; Schweitzer, A.; Thévenin, F.; Zorec, J.

    2011-12-01

    Gaia will observe up to a billion stellar sources. Automated algorithms are under development to derive the atmospheric parameters of all observed spectra, from low resolution optical spectra alone or in synergy with high resolution spectra in the near-IR Ca II triplet region. To do so, a large database of state-of-the-art stellar libraries has been produced for the Gaia community, computed using different codes optimized for specific purposes. The choice to use different spectral codes in different regions of the H-R diagram raises the problem of the coherence of the different spectra, specifically in the transition zones. We present a comparison between the libraries from the point of view of spectra simulations for training the Gaia algorithms. We also present the implementation of these libraries into a Simple Stellar Population code.

  19. Substructure in the Globular Cluster System of the Milky Way

    E-print Network

    A. Burkert; G. Smith

    1996-10-23

    The kinematical and spatial properties of the metal-rich globular clusters in the Galaxy ([Fe/H] > -0.8) indicates that these objects do not comprise a homogeneous population. Three subsystems are identified. The highest-mass clusters exhibit a very slow net rotation with a speed of v_rot = 24 km/s and v_rot/sigma = 0.3, indicative of a centrally condensed, spheroidal subsystem. Roughly half of the lower-mass clusters appear to be located in an elongated bar-like structure which passes through the Galactic Center, and has similar properties to the central stellar bar of the Milky Way. The remaining lower-mass clusters exhibit very rapid net rotation, with a rotation speed of v_rot = 164 km/s and v_rot/sigma = 6. These clusters are located in the Galactic plane, within a ring of 4 to 6 kpc radial distance from the Galactic Center. The highest-mass clusters may have formed during relatively advanced stages of the dissipative evolution of the inner Galactic halo. The lower-mass bar clusters may be associated with the formation of the Galactic stellar bar or bulge. The lower-mass ring clusters appear to be real disk objects. They may represent a stage in cluster formation that was intermediate between that of the halo globular clusters and the oldest extant open clusters.

  20. Disentangling the dark matter halo from the stellar halo

    NASA Astrophysics Data System (ADS)

    Libeskind, Noam I.; Knebe, Alexander; Hoffman, Yehuda; Gottlöber, Stefan; Yepes, Gustavo

    2011-11-01

    The outer haloes of the Milky Way (MW) and Andromeda (M31) galaxies contain as much important information on their assembly and formation history as the properties of the discs resident in their centres. Whereas the structure of dark matter (DM) haloes has been studied for a long time, new observations of faint structures hiding in the depths of the stellar halo have opened up the question of how the stellar halo is related to the DM underlying it. In this paper, we have used the Constrained Local UniversE Simulation (CLUES) project to disentangle the stellar and DM components of three galaxies that resemble the MW, M31 and M33 using both DM-only simulations and DM + gas-dynamical ones. We find that stars accreted in substructures and then stripped follow a completely different radial distribution than the stripped DM: the stellar halo is much more centrally concentrated than DM. In order to understand how the same physical process - tidal stripping - can lead to different z= 0 radial profiles, we examined the potential at accretion of each stripped particle. We found that star particles sit at systematically higher potentials than DM, making them harder to strip. We then searched for a threshold in the potential of accreted particles ?th, above which DM particles in a DM-only simulation behave as star particles in the gas-dynamical one. We found that in order to reproduce the radial distribution of star particles, one must choose DM particles whose potential at accretion is ?16?subhalo, where ?subhalo is the potential at a subhaloes edge at the time of accretion. A rule as simple as selecting particles according to their potential at accretion is able to reproduce the effect that the complicated physics of star formation has on the stellar distribution. This result is universal for the three haloes studied here and reproduces the stellar halo to an accuracy of within ˜2 per cent. Studies which make use of DM particles as a proxy for stars will undoubtedly miscalculate their proper radial distribution and structure unless particles are selected according to their potential at accretion. Furthermore, we have examined the time it takes to strip a given star or DM particle after accretion. We find that, owing to their higher binding energies, stars take longer to be stripped than DM. The stripped DM halo is thus considerably older than the stripped stellar halo.

  1. Detection Rate Estimates of Gravity-waves Emitted During Parabolic Encounters of Stellar Black Holes in Globular Clusters

    E-print Network

    Bence Kocsis; Merse E. Gaspar; Szabolcs Marka

    2006-05-08

    The rapid advance of gravitational-wave (GW) detector facilities makes it very important to estimate the event rates of possible detection candidates. We consider an additional possibility of GW bursts produced during parabolic encounters (PEs) of stellar mass compact objects. We estimate the rate of successful detections for specific detectors: the initial Laser Interferometric Gravitational-Wave Observatory (InLIGO), the French-Italian gravitational-wave antenna VIRGO, the near-future Advanced-LIGO (AdLIGO), the space-based Laser Interferometric Space Antenna (LISA), and the Next Generation LISA (NGLISA). Simple GC models are constructed to account for the compact object mass function, mass segregation, number density distribution, and velocity distribution. We calculate encounters both classically and account for general relativistic corrections by extrapolating the results for infinite mass ratios. We also include the cosmological redshift of waveforms and event rates. We find that typical PEs with masses m_1=m_2=40 Msun are detectable with matched filtering over a signal to noise ratio of 5 within a distance d_L~200Mpc for InLIGO and VIRGO, z=1 for AdLIGO, 0.4Mpc for LISA, and 1Gpc for NGLISA. We estimate single datastream total detection rates of 5.5 x 10^{-5} for InLIGO, 7.2 x 10^{-5} for VIRGO, 0.063 for AdLIGO, 2.9 x 10^{-6} for LISA, and 1.0 for NGLISA per year, for reasonably conservative assumptions. These estimates are subject to uncertainties in the GC parameters, most importantly the total number and mass-distribution of black holes (BHs) in the cluster core. In reasonably optimistic cases, we get >~1 detections for AdLIGO per year. The regular detection of GWs during PEs would provide a unique observational probe for constraining the stellar BH mass function of dense clusters. (abridged)

  2. Theory and Simulations of Refractive Substructure in Resolved Scatter-Broadened Images

    E-print Network

    Johnson, Michael D

    2015-01-01

    At radio wavelengths, scattering in the interstellar medium distorts the appearance of astronomical sources. Averaged over a scattering ensemble, the result is a blurred image of the source. However, Narayan & Goodman (1989) and Goodman & Narayan (1989) showed that for an incomplete average, scattering introduces refractive substructure in the image of a point source that is both persistent and wideband. We show that this substructure is not smoothed by an extended source and that the scattering can therefore introduce spurious compact features into images that would be resolved in the absence of scattering. In addition, we derive efficient strategies to numerically compute realistic scattered images, and we present characteristic examples from simulations. Our results show that refractive substructure is an important consideration for ongoing missions at the highest angular resolutions, and we discuss specific implications for RadioAstron and the Event Horizon Telescope.

  3. Analysis of substructural variation in families of enzymatic proteins with applications to protein function prediction

    Microsoft Academic Search

    Drew H. Bryant; Mark Moll; Brian Y. Chen; Viacheslav Y Fofanov; Lydia E. Kavraki

    2010-01-01

    Background Structural variations caused by a wide range of\\u000a\\u0009\\u0009 physicochemical and biological sources directly influence\\u000a\\u0009\\u0009 the function of a protein. For enzymatic proteins, the\\u000a\\u0009\\u0009 structure and chemistry of the catalytic binding site\\u000a\\u0009\\u0009 residues can be loosely defined as a substructure of the\\u000a\\u0009\\u0009 protein. Comparative analysis of drug-receptor\\u000a\\u0009\\u0009 substructures across and within species has been used for\\u000a\\u0009\\u0009 lead evaluation. Substructure-level similarity

  4. Recent advances in direct phasing methods for heavy-atom substructure determination.

    PubMed

    Xu, Hongliang; Hauptman, Herbert A

    2006-08-01

    Macromolecular crystal structure determination has typically been a two-step process. When diffraction data from multiple chemically isomorphous or anomalously scattering crystals are available, the positions of heavy atoms from amplitude differences arising from native-derivative crystal pairs or an anomalously scattering crystal are first located and phasing of the whole protein structure is then completed using the heavy-atom substructure as a bootstrap. Shake-and-Bake, a direct-methods-based dual-space refinement procedure, provides heavy-atom substructure solutions by finding the constrained global minimum of a probabilistically defined minimal function. This minimal function relies on probabilistic estimates of the cosines of the structure invariants. A novel statistically defined minimal function that utilizes the statistical properties of the structure invariants has recently been proposed and tested. Applications of the statistical Shake-and-Bake procedure show that statistical direct methods provide a simple, reliable and efficient method of heavy-atom substructure determination. PMID:16855306

  5. Theory and Simulations of Refractive Substructure in Resolved Scatter-broadened Images

    NASA Astrophysics Data System (ADS)

    Johnson, Michael D.; Gwinn, Carl R.

    2015-06-01

    At radio wavelengths, scattering in the interstellar medium distorts the appearance of astronomical sources. Averaged over a scattering ensemble, the result is a blurred image of the source. However, Narayan & Goodman and Goodman & Narayan showed that for an incomplete average, scattering introduces refractive substructure in the image of a point source that is both persistent and wideband. We show that this substructure is quenched but not smoothed by an extended source. As a result, when the scatter-broadening is comparable to or exceeds the unscattered source size, the scattering can introduce spurious compact features into images. In addition, we derive efficient strategies to numerically compute realistic scattered images, and we present characteristic examples from simulations. Our results show that refractive substructure is an important consideration for ongoing missions at the highest angular resolutions, and we discuss specific implications for RadioAstron and the Event Horizon Telescope.

  6. PREFACE: A Stellar Journey A Stellar Journey

    NASA Astrophysics Data System (ADS)

    Asplund, M.

    2008-10-01

    The conference A Stellar Journey was held in Uppsala, Sweden, 23 27June 2008, in honour of Professor Bengt Gustafsson's 65th birthday. The choice of Uppsala as the location for this event was obvious given Bengt's long-standing association with the city stemming back to his school days. With the exception of a two-year postdoc stint in Copenhagen, five years as professor at Stockholm University and two years as director of the Sigtuna foundation, Bengt has forged his illustrious professional career at Uppsala University. The symposium venue was Museum Gustavianum, once the main building of the oldest university in Scandinavia. The title of the symposium is a paraphrasing of Bengt's popular astronomy book Kosmisk Resa (in English: Cosmic Journey) written in the early eighties. I think this aptly symbolizes his career that has been an astronomical voyage from near to far, from the distant past to the present. The original book title was modified slightly to reflect that most of his work to date has dealt with stars in one way or another. In addition it also gives credit to Bengt's important role as a guiding light for a very large number of students, colleagues and collaborators, indeed for several generations of astronomers. For me personally, the book Kosmisk Resa bears particular significance as it has shaped my life rather profoundly. Although I had already decided to become an astronomer, when I first read the book as a 14-year-old I made up my mind then and there that I would study under Bengt Gustafsson and work on stars. Indeed I have remained true to this somewhat audacious resolution. I suspect that a great number of us have similar stories how Bengt has had a major influence on our lives, whether on the professional or personal level. Perhaps Bengt's most outstanding characteristic is his enthralling enthusiasm. This is equally true whether he is pondering some scientific conundrum, supervising students or performing in front of an audience, be it an astronomical talk, student lecture, musical concert or theatre play. Another attribute of Bengt is his boundless optimism, which not the least has helped many of his students overcome the unavoidable moments of despair (this is only true as long as one is aware of the well-known BG factor: multiply any of Bengt's estimates for the time required to complete a task by at least a factor of three). His personal traits make working with Bengt always very enjoyable as well as highly educating. Bengt's work also extends well beyond the domain of astronomy, including music, literature, theatre, religion, research ethics, science policy and science popularization. Bengt is an excellent role model for a successful scientist with a rich and rewarding life outside of academia. The symposium A Stellar Journey was divided into five sessions covering basically the main research areas Bengt has worked on: Stellar atmospheres, Solar/stellar spectroscopy, Stellar parameters, Stellar evolution and nucleosynthesis and Stellar populations. In addition, one afternoon was devoted to a session entitled Anything but astronomy (see the symposium program), which tried to showcase Bengt's diverse interests outside of astronomy with talks ranging from religion and history of science over science popularization and future studies to literature and music. My task, as chair of the Scientific Organizing Committee, to put together an exciting scientific program of invited reviews and talks was made considerably easier thanks to the excellent suggestions by the other SOC members: Ann Boesgaard, Sofia Feltzing, John Lattanzio, Andre Maeder, Bertrand Plez and Monique Spite. I believe in the end we were successful in achieving our charge, an impression corroborated by the many encouraging comments from various participants during and after the conference. I am particularly grateful to Nils Bergvall, Bengt Edvardsson and Bertrand Plez for their time-consuming efforts in arranging the extraordinary and greatly appreciated non-astronomical session on Tuesday afternoon; Sigbritt Ernald provided a rich sourc

  7. isochrones: Stellar model grid package

    NASA Astrophysics Data System (ADS)

    Morton, Timothy D.

    2015-03-01

    Isochrones, written in Python, simplifies common tasks often done with stellar model grids, such as simulating synthetic stellar populations, plotting evolution tracks or isochrones, or estimating the physical properties of a star given photometric and/or spectroscopic observations.

  8. Stellar Cycles Post Assessment Activity

    NSDL National Science Digital Library

    Stellar Cycles is a performance task - an assessment tool to determine student understanding of stellar evolution. Teacher guides and materials are available in powerpoint, PDF and HTML formats. An answer key is included.

  9. Dislocation substructure in NiAl single crystals deformed at ambient temperature

    SciTech Connect

    Shi, X.; Pollock, T.M.; Mahajan, S.; Arunachalam, V.S. [Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering

    1997-12-31

    Dislocation substructure in NiAl single crystals oriented for single slip and deformed at ambient temperature has been studied using weak-beam transmission electron microscopy. Deformation is localized in bands that consists mostly of near-edge dislocations, with an interspersion of a high density of elongated prismatic loops. Pure screw dislocations are not observed, but dislocations having zigzag configurations that are near-screw in orientation are present. A high density of jogs is observed on both near-edge and zigzag dislocation segments. The mechanisms for the development of this substructure are discussed, emphasizing the role of double cross slip and resulting glissile and sessile jogs of varying heights.

  10. Substructure procedure for including tile flexibility in stress analysis of shuttle thermal protection system

    NASA Technical Reports Server (NTRS)

    Giles, G. L.

    1980-01-01

    A substructure procedure to include the flexibility of the tile in the stress analysis of the shuttle thermal protection system (TPS) is described. In this procedure, the TPS is divided into substructures of (1) the tile which is modeled by linear finite elements and (2) the SIP which is modeled as a nonlinear continuum. This procedure was applied for loading cases of uniform pressure, uniform moment, and an aerodynamic shock on various tile thicknesses. The ratios of through-the-thickness stresses in the SIP which were calculated using a flexible tile compared to using a rigid tile were found to be less than 1.05 for the cases considered.

  11. Galactic Halo Substructure in the Sloan Digital Sky Survey: The Ancient Tidal Stream from the Sagittarius Dwarf Galaxy

    Microsoft Academic Search

    Rodrigo Ibata; Michael Irwin; Geraint F. Lewis; Andrea Stolte

    2001-01-01

    Two studies have recently reported the discovery of pronounced halo substructure in the Sloan Digital Sky Survey (SDSS) commissioning data. Here we show that this halo substructure is, almost in its entirety, due to the expected tidal stream torn off the Sagittarius dwarf galaxy during the course of its many close encounters with the Milky Way. This interpretation makes strong

  12. Stellar Structure and Evolution

    Microsoft Academic Search

    Rudolf Kippenhahn; Alfred Weigert

    1990-01-01

    This text gives a complete and comprehensive treatment of the physics of the stellar interior and the underlying fundamental processes and parameters. The models developed to explain the stability, dynamics and evolution of the stars are presented and great care is taken to detail the various stages in a star's life. The authors have written a unique text based on

  13. Progress Toward Attractive Stellarators

    SciTech Connect

    Neilson, G H; Brown, T G; Gates, D A; Lu, K P; Zarnstorff, M C; Boozer, A H; Harris, J H; Meneghini, O; Mynick, H E; Pomphrey, N; Reiman, A H

    2011-01-05

    The quasi-axisymmetric stellarator (QAS) concept offers a promising path to a more compact stellarator reactor, closer in linear dimensions to tokamak reactors than previous stellarator designs. Concept improvements are needed, however, to make it more maintainable and more compatible with high plant availability. Using the ARIES-CS design as a starting point, compact stellarator designs with improved maintenance characteristics have been developed. While the ARIES-CS features a through-the-port maintenance scheme, we have investigated configuration changes to enable a sector-maintenance approach, as envisioned for example in ARIES AT. Three approaches are reported. The first is to make tradeoffs within the QAS design space, giving greater emphasis to maintainability criteria. The second approach is to improve the optimization tools to more accurately and efficiently target the physics properties of importance. The third is to employ a hybrid coil topology, so that the plasma shaping functions of the main coils are shared more optimally, either with passive conductors made of high-temperature superconductor or with local compensation coils, allowing the main coils to become simpler. Optimization tools are being improved to test these approaches.

  14. Stellar oxygen abundances

    Microsoft Academic Search

    Jeremy R. King

    1993-01-01

    We address a variety of issues concerning stellar oxygen abundances. We first investigate the discrepancy in O abundances of halo stars as derived from the 7774 A O I triplet and other lines and propose a resolution to this discrepancy. Next, possible cosmological implications of the hotter Teff scale are discussed along with additional evidence supporting the need for a

  15. Stellar populations of early-type galaxies in different environments I. Line-strength indices

    E-print Network

    Sánchez-Blazquez, P; González, J; Gorgas, J

    2006-01-01

    Aims: This paper commences a series devoted to the study of the stellar content of early-type galaxies. The goal of the series is to set constraints on the evolutionary status of these objects. Methods: In this paper we describe the details of the galaxy sample, the observations, and the data reduction. Line-strength indices and velocity dispersions sigma are measured in 98 early-type galaxies drawn from different environments, and the relation of the indices with the velocity dispersion analysed in detail. Results: The present sample indicates that some of the index-sigma relations depend on galaxy environment. In particular, the slope of the relation between Balmer lines and sigma is steeper for galaxies in the Virgo cluster, small groups, and in the field than for galaxies in the Coma cluster. In several indices there is also a significant offset in the zero point between the relations defined by the different subsamples. The slopes of the index-sigma relation for the Virgo and low-density environment gala...

  16. Oscillations in stellar superflares

    NASA Astrophysics Data System (ADS)

    Balona, L. A.; Broomhall, A.-M.; Kosovichev, A.; Nakariakov, V. M.; Pugh, C. E.; Van Doorsselaere, T.

    2015-06-01

    Two different mechanisms may act to induce quasi-periodic pulsations (QPP) in whole-disc observations of stellar flares. One mechanism may be magnetohydromagnetic forces and other processes acting on flare loops as seen in the Sun. The other mechanism may be forced local acoustic oscillations due to the high-energy particle impulse generated by the flare (known as `sunquakes' in the Sun). We analyse short-cadence Kepler data of 257 flares in 75 stars to search for QPP in the flare decay branch or post-flare oscillations which may be attributed to either of these two mechanisms. About 18 per cent of stellar flares show a distinct bump in the flare decay branch of unknown origin. The bump does not seem to be a highly damped global oscillation because the periods of the bumps derived from wavelet analysis do not correlate with any stellar parameter. We detected damped oscillations covering several cycles (QPP), in seven flares on five stars. The periods of these oscillations also do not correlate with any stellar parameter, suggesting that these may be a due to flare loop oscillations. We searched for forced global oscillations which might result after a strong flare. To this end, we investigated the behaviour of the amplitudes of solar-like oscillations in eight stars before and after a flare. However, no clear amplitude change could be detected. We also analysed the amplitudes of the self-excited pulsations in two ? Scuti stars and one ? Doradus star before and after a flare. Again, no clear amplitude changes were found. Our conclusions are that a new process needs to be found to explain the high incidence of bumps in stellar flare light curves, that flare loop oscillations may have been detected in a few stars and that no conclusive evidence exists as yet for flare induced global acoustic oscillations (starquakes).

  17. Exploring the star formation history of elliptical galaxies: beyond simple stellar populations with a new line strength estimator

    NASA Astrophysics Data System (ADS)

    Rogers, Ben; Ferreras, Ignacio; Peletier, Reynier; Silk, Joseph

    2010-02-01

    We study the stellar populations of a sample of 14 elliptical galaxies in the Virgo cluster. Using spectra with high signal-to-noise ratio (S/N >~ 100Å-1) we propose an alternative approach to the standard side-band method to measure equivalent widths (EWs). Our boosted median continuum is shown to map the EWs more robustly than the side-band method, minimizing the effect from neighbouring absorption lines and reducing the uncertainty at a given S/N. Our newly defined line strengths are more successful at disentangling the age-metallicity degeneracy. We concentrate on Balmer lines (H?, H?, H?), the G band and the combination [MgFe] as the main age and metallicity indicators. We go beyond the standard comparison of the observations with simple stellar populations (SSPs) and consider four different models to describe the star formation histories, either with a continuous star formation rate or with a mixture of two different SSPs. These models improve the estimates of the more physically meaningful mass-weighted ages. Composite models are found to give more consistent fits among individual line strengths and agree with an independent estimate using the spectral energy distribution. A combination of age- and metallicity-sensitive spectral features allows us to constrain the average age and metallicity. For a Virgo sample of elliptical galaxies our age and metallicity estimates correlate well with stellar mass or velocity dispersion, with a significant threshold around 5 × 1010Msolar above which galaxies are uniformly old and metal rich. This threshold is reminiscent of the one found by Kauffmann et al. in the general population of Sloan Digital Sky Survey galaxies at a stellar mass 3 × 1010Msolar. In a more speculative way, our models suggest that it is formation epoch and not formation time-scale what drives the mass-age relationship of elliptical galaxies.

  18. STELLAR PRIME NUMBERS HEITOR BALDO

    E-print Network

    Boyer, Edmond

    , 1985. [3] H. A. Helfgott. Major arcs for Goldbach's Problem. arXiv:1305.2897v1, 2013. [4] Galaxies to represents the set of stellar primes to indicate Galaxies: a collection of many stars. Sometimes we'll call the set G of -Galaxy. 2. The -Stellar Primes Now we expose some conjectures about the stellar prime

  19. The simultaneous formation of massive stars and stellar clusters

    NASA Astrophysics Data System (ADS)

    Smith, Rowan J.; Longmore, Steven; Bonnell, Ian

    2009-12-01

    We show that massive stars and stellar clusters are formed simultaneously, the global evolution of the forming cluster is what allows the central stars to become massive. We predict that massive star-forming clumps, such as those observed in Motte et al., contract and grow in mass leading to the formation of massive stars. This occurs as mass is continually channelled from large radii on to the central protostars, which can become massive through accretion. Using smoothed particle hydrodynamic simulations of massive star-forming clumps in a giant molecular cloud, we show that clumps are initially diffuse and filamentary, and become more concentrated as they collapse. Simulated interferometry observations of our data provide an explanation as to why young massive star-forming regions show more substructure than older ones. The most massive stars in our model are found within the most bound cluster. Most of the mass accreted by the massive stars was originally distributed throughout the clump at low densities and was later funnelled to the star due to global infall. Even with radiative feedback no massive pre-stellar cores are formed. The original cores are of intermediate mass and gain their additional mass in the protostellar stage. We also find that cores which form low-mass stars exist within the volume from which the high-mass stars accrete, but are largely unaffected by this process.

  20. Neutron Stars versus Black Holes: Probing the Mass Gap with LIGO/Virgo

    NASA Astrophysics Data System (ADS)

    Littenberg, Tyson B.; Farr, Ben; Coughlin, Scott; Kalogera, Vicky; Holz, Daniel E.

    2015-07-01

    Inspirals and mergers of black hole (BH) and/or neutron star (NS) binaries are expected to be abundant sources for ground-based gravitational-wave (GW) detectors. We assess the capabilities of Advanced LIGO and Virgo to measure component masses using inspiral waveform models including spin-precession effects using a large ensemble of GW sources randomly oriented and distributed uniformly in volume. For 1000 sources this yields signal-to-noise ratios between 7 and 200. We make quantitative predictions for how well LIGO and Virgo will distinguish between BHs and NSs and appraise the prospect of using LIGO/Virgo (LV) observations to definitively confirm, or reject, the existence of a putative “mass gap” between NSs (m?slant 3 {M}? ) and BHs (m?slant 5 {M}? ). We find sources with the smaller mass component satisfying {m}2? 1.5 {M}? to be unambiguously identified as containing at least one NS, while systems with {m}2? 6 {M}? will be confirmed binary BHs. Binary BHs with {m}2\\lt 5 {M}? (i.e., in the gap) cannot generically be distinguished from NSBH binaries. High-mass NSs (2\\lt m\\lt 3 {M}? ) are often consistent with low-mass BHs (m\\lt 5 {M}? ), posing a challenge for determining the maximum NS mass from LV observations alone. Individual sources will seldom be measured well enough to confirm objects in the mass gap and statistical inferences drawn from the detected population will be strongly dependent on the underlying distribution. If nature happens to provide a mass distribution with the populations relatively cleanly separated in chirp mass space, as some population synthesis models suggest, then NSs and BHs will be more easily distinguishable.

  1. Parametric studies of stitching effectiveness for preventing substructure disbond

    NASA Technical Reports Server (NTRS)

    Flanagan, Gerry; Furrow, Keith

    1995-01-01

    A methodology is desired that will allow a designer to select appropriate amounts of through-thickness reinforcement needed to meet design requirements. The goal is to use a relatively simple analysis to minimize the amount of testing that needs to be performed, and to make test results from simple configurations applicable to more general structures. Using this methodology one should be able to optimize the selection of stitching materials, the weight of the yarn, and the stitching density. The analysis approach is to treat substructure disbond as a crack propagation problem. In this approach, the stitches have little influence until a delamination begins to grow. Once the delamination reaches, or extends beyond a stitch, the stitch serves to reduce the strain-energy-release-rate (G) at the crack tip for a given applied load. The reduced G can then be compared to the unstitched materials toughness to predict the load required to further extend the crack. The current model treats the stitch as a simple spring which responds to displacements in the vertical (through-thickness) direction. In concept, this approach is similar to that proposed by other authors. Test results indicate that the model should be refined to include the shearing stiffness of the stitch. The strain-energy-release-rate calculations are performed using a code which uses interconnected higher-order plates to model built-up composite cross-sections. When plates are stacked vertically, the interfacial tractions between the plates can be computed. The plate differential equations are solved in closed-form. The code, called SUBLAM, was developed as part of this section in one dimension. Because of this limitation, rows of stitches are treated as a two-dimensional sheet. The spring stiffness of a row of stitches can be estimated from the stitch material, weight, and density. As a practical and conservative approach, we can assume that the stitch is bonded until a crack passes the stitch location. After the crack passes, it is fully bonded. A series of tests were performed to exercise this methodology and incorporated an attached flange such that the sudden change in thickness initiated a delamination. The analysis was used to estimate the materials' critical G from that of the unstitched specimens. With this data, a prediction was made for the load required to delaminate the stitched specimens. Using the methodology, design charts have been created for simplified geometries. These charts give stitch force, along with G(sub 1) and G(sub 2) as as function of the stitch spring stiffness. Using the charts, it should be possible to determine the stitch spring stiffness and strength required to reduce the G to a desired level. From these parameters, the actual stitching material, weight, and density can be computed.

  2. A new estimate of the Hubble constant using the Virgo cluster distance

    NASA Astrophysics Data System (ADS)

    Visvanathan, N.

    The Hubble constant, which defines the size and age of the universe, remains substantially uncertain. Attention is presently given to an improved distance to the Virgo Cluster obtained by means of the 1.05-micron luminosity-H I width relation of spirals. In order to improve the absolute calibration of the relation, accurate distances to the nearby SMC, LMC, N6822, SEX A and N300 galaxies have also been obtained, on the basis of the near-IR P-L relation of the Cepheids. A value for the global Hubble constant of 67 + or 4 km/sec per Mpc is obtained.

  3. Late-Type Dwarf Galaxies in the Virgo Cluster: I. The Samples

    E-print Network

    Elchanan Almoznino; Noah Brosch

    1998-04-22

    We selected samples of late-type dwarf galaxies in the Virgo cluster with HI information. The galaxies were observed at the Wise-Observatory using several broad-band and H$\\alpha$ bandpasses. UV measurements were carried out with the IUE Observatory from VILSPA, and with the FAUST shuttle-borne UV telescope. We describe our observations in detail, paying particular attention to the determination of measurement errors, and present the observational results together with published data and far-infrared information from IRAS. The sample will be analyzed in subsequent papers, in order to study star formation mechanisms.

  4. Inertial control of the mirror suspensions of the VIRGO interferometer for gravitational wave detection

    E-print Network

    G. Losurdo; G. Calamai; E. Cuoco; L. Fabbroni; G. Guidi; M. Mazzoni; R. Stanga; F. Vetrano; L. Holloway; D. Passuello; G. Ballardin; S. Braccini; C. Bradaschia; R. Cavalieri; R. Cecchi; G. Cella; V. Dattilo; A. Di Virgilio; F. Fidecaro; F. Frasconi; A. Gennai; A. Giazotto; I. Ferrante; P. La Penna; F. Lelli; T. Lomtadze; A. Marin; S. Mancini; F. Paoletti; A. Pasqualetti; R. Passaquieti; R. Poggiani; R. Taddei; A. Vicere'; Z. Zhang

    2001-06-28

    In order to achieve full detection sensitivity at low frequencies, the mirrors of interferometric gravitational wave detectors must be isolated from seismic noise. The VIRGO vibration isolator, called 'superattenuator', is fully effective at frequencies above 4 Hz. Nevertheless, the residual motion of the mirror at the mechanical resonant frequencies of the system are too large for the interferometer locking system and must be damped. A multidimensional feedback system, using inertial sensors and digital processing, has been designed for this purpose. An experimental procedure for determining the feedback control of the system has been defined. In this paper a full description of the system is given and experimental results are presented.

  5. The compressed feature matrix—a fast method for feature based substructure search

    Microsoft Academic Search

    S. F. Badreddin Abolmaali; Jörg K. Wegner; Andreas Zell

    2003-01-01

    The compressed feature matrix (CFM) is a feature based molecular descriptor for the fast processing of pharmacochemical applications such as adaptive similarity search, pharmacophore development and substructure search. Depending on the particular purpose, the descriptor may be generated upon either topological or Euclidean molecular data. To assure a variable utilizability, the assignment of the structural patterns to feature types is

  6. Power-Law Rheology of Isolated Nuclei with Deformation Mapping of Nuclear Substructures

    E-print Network

    Discher, Dennis

    are an order of magnitude softer, with the lamina sustaining much of the load. In both cases, nuclearPower-Law Rheology of Isolated Nuclei with Deformation Mapping of Nuclear Substructures Kris Noel-induced changes in genome expression as well as remodeling of nuclear architecture in development and disease

  7. Density Profiles and Substructure of Dark Matter Halos: Converging Results at UltraHigh Numerical Resolution

    Microsoft Academic Search

    Sebastiano Ghigna; Ben Moore; Fabio Governato; George Lake; Tom Quinn; Joachim Stadel

    2000-01-01

    Can dissipationless N-body simulations be used to reliably determine the structural and substructure properties of dark matter halos? A large simulation of a galaxy cluster in a cold dark matter universe is used to increase the force and mass resolution of current ``high-resolution simulations'' by almost an order of magnitude to examine the convergence of the important physical quantities. The

  8. Substructures in DAFT/FADA survey clusters based on XMM and optical data

    NASA Astrophysics Data System (ADS)

    Durret, F.; DAFT/FADA Team

    2014-07-01

    The DAFT/FADA survey was initiated to perform weak lensing tomography on a sample of 90 massive clusters in the redshift range [0.4,0.9] with HST imaging available. The complementary deep multiband imaging constitutes a high quality imaging data base for these clusters. In X-rays, we have analysed the XMM-Newton and/or Chandra data available for 32 clusters, and for 23 clusters we fit the X-ray emissivity with a beta-model and subtract it to search for substructures in the X-ray gas. This study was coupled with a dynamical analysis for the 18 clusters with at least 15 spectroscopic galaxy redshifts in the cluster range, based on a Serna & Gerbal (SG) analysis. We detected ten substructures in eight clusters by both methods (X-rays and SG). The percentage of mass included in substructures is found to be roughly constant with redshift, with values of 5-15%. Most of the substructures detected both in X-rays and with the SG method are found to be relatively recent infalls, probably at their first cluster pericenter approach.

  9. An Empirical Study of Domain Knowledge and Its Benefits to Substructure Discovery

    Microsoft Academic Search

    Surnjani Djoko; Diane J. Cook; Lawrence B. Holder

    1999-01-01

    Discovering repetitive, interesting, and functional substructures in a structural database improves the ability to interpret and compress the data. However, scientists working with a database in their area of expertise often search for predetermined types of structures or for structures exhibiting characteristics specific to the domain. This paper presents a method for guiding the discovery process with domain-specific knowledge. In

  10. PubChem Substructure Fingerprint V1.3 http://pubchem.ncbi.nlm.nih.gov

    E-print Network

    Levin, Judith G.

    is a fragment of a chemical structure. A fingerprint is an ordered list of binary (1/0) bits. Each bit prefix, where this integer prefix indicates the length of the bit list. For the ASN.1 and XML formatted://www.faqs.org/rfcs/rfc3548.html Below is the description of each bit represented in the PubChem Substructure Fingerprint

  11. Towards optimization of the linker substructure common to transthyretin amyloidogenesis inhibitors using biochemical and structural studies

    PubMed Central

    Johnson, Steven M.; Connelly, Stephen; Wilson, Ian A.; Kelly, Jeffery W.

    2008-01-01

    To develop potent and highly selective transthyretin (TTR) amyloidogenesis inhibitors, it is useful to systematically optimize the three substructural elements that compose a typical TTR kinetic stabilizer: the two aryl rings and the linker joining them. Herein, we evaluated 40 bisaryl molecules based on 10 unique linker substructures to determine how these linkages influence inhibitor potency and selectivity. These linkers connect one unsubstituted aromatic ring to either a 3,5-X2 or a 3,5-X2-4-OH phenyl substructure (X=Br or CH3). Co-consideration of amyloid inhibition and ex vivo plasma TTR binding selectivity data reveal that direct connection of the two aryls, or linkage through non-polar E-olefin or –CH2CH2– substructures generates the most potent and selective TTR amyloidogenesis inhibitors exhibiting minimal undesirable binding to the thyroid hormone nuclear receptor or the COX-1 enzyme. Five high-resolution TTR•inhibitor crystal structures (1.4?1.8 Å) provide insight into why such linkers afford inhibitors with greater potency and selectivity. PMID:18811132

  12. Evaluation and seismic retrofit of highway bridge substructures with tapered columns

    Microsoft Academic Search

    M Saiidi; E Maragakis; D Sanders

    1998-01-01

    The purpose of this study has been: (1) to evaluate the highway bridges on the I-80 in the Reno–Sparks area for their damage potential during strong earthquakes; and (2) to determine effective means of retrofitting the substructure components in these bridges. The first part of the study was completed in the Fall of 1993, the results of which are presented

  13. Testing and evaluation of MHD materials and substructures. Quarterly technical progress report, October-December 1978

    Microsoft Academic Search

    D. L. Murphree; L. E. Bauman; C. J. Bell; R. D. Benton; H. W. Coleman; T. B. Malloy; J. B. Nail; R. E. Powe; W. S. Shepard; A. G. Wehr

    1979-01-01

    Mississippi State University's MHD research group has constructed a Test Stand that can simulate the environment in any of the various substructures of the coal-fired baseline MHD power plant. The Test Stand has been successfully operated under total computer control with air heating and oil combustion. A series of short-term shakedown tests has been performed and the Test Stand is

  14. Revealing dark matter substructure with anisotropies in the diffuse gamma-ray background

    E-print Network

    Jennifer M. Siegal-Gaskins

    2008-10-14

    The majority of gamma-ray emission from Galactic dark matter annihilation is likely to be detected as a contribution to the diffuse gamma-ray background. I show that dark matter substructure in the halo of the Galaxy induces characteristic anisotropies in the diffuse background that could be used to determine the small-scale dark matter distribution. I calculate the angular power spectrum of the emission from dark matter substructure for several models of the subhalo population, and show that features in the power spectrum can be used to infer the presence of substructure. The shape of the power spectrum is largely unaffected by the subhalo radial distribution and mass function, and for many scenarios I find that a measurement of the angular power spectrum by Fermi will be able to constrain the abundance of substructure. An anti-biased subhalo radial distribution is shown to produce emission that differs significantly in intensity and large-scale angular dependence from that of a subhalo distribution which traces the smooth dark matter halo, potentially impacting the detectability of the dark matter signal for a variety of targets and methods.

  15. Acta Cryst. (2003). D59, 5766 Uson et al. Anomalous scatterer substructures 57 research papers

    E-print Network

    2003-01-01

    surface. This paper explores the application of dual-space ab initio methods as implemented in the program scatterer substructures in halide and sulfur phasing Isabel UsoÂn,a * Bernhard Schmidt,b Rixa von Bu the weak anomalous signal derived only from the sulfurs inherent to the protein or in particular from

  16. Multi-Metric and Multi-Substructure Biclustering Analysis for Gene Expression Data

    E-print Network

    Mak, Man-Wai

    Multi-Metric and Multi-Substructure Biclustering Analysis for Gene Expression Data S.Y. Kung algorithms have been proposed for grouping gene expression data. Many of them have adopted matrix norms the mechanism of drug action, to examine the effects of drugs on gene expression in yeasts, and to identify

  17. Sommerfeld-enhanced annihilation in dark matter substructure: Consequences for constraints on cosmic-ray excesses

    NASA Astrophysics Data System (ADS)

    Slatyer, Tracy R.; Toro, Natalia; Weiner, Neal

    2012-10-01

    In models of dark matter (DM) with Sommerfeld-enhanced annihilation, where the annihilation rate scales as the inverse velocity, N-body simulations of DM structure formation suggest that the local annihilation signal may be dominated by small, dense, cold subhalos. This contrasts with the usual assumption of a signal originating from the smooth DM halo, with much higher velocity dispersion. Accounting for local substructure modifies the parameter space for which Sommerfeld-enhanced annihilating DM can explain the PAMELA and Fermi excesses. Limits from the inner galaxy and the cosmic microwave background are weakened, without introducing new tension with substructure-dependent limits, such as from dwarf galaxies or isotropic gamma-ray studies. With substructure, previously excluded parameter regions with mediators of mass ˜1-200MeV are now easily allowed. For O(MeV) mediators, subhalos in a specific range of host halo masses may be evaporated, further suppressing diffuse signals without affecting substructure in the Milky Way.

  18. arXiv:astroph/0004255 Galactic Halo substructure in the Sloan Digital Sky Survey

    E-print Network

    Irwin, Mike

    . Introduction In the standard hierarchical picture of galaxy formation, galaxies like the Milky Way grew of galaxy formation theories. These now make strong pre- dictions about the structure and substructure. These include, among others, the \\spaghetti" survey (Morrison et al. 2000), the APM carbon star survey (Totten

  19. Feeding quasars with stellar winds

    SciTech Connect

    Shull, J.M.

    1983-01-15

    Quasars may be fueled by stellar mass loss from OB stars and red giants: either normal winds and mass loss or X-ray induced stellar winds in luminous quasars with well developed cusps in the stellar density distribution. The X-ray induced mass loss may furnish part of the broad emission-line gas, as well as an accretion supply for a central black hole during transient bursts of quasar luminosity. The importance of a stellar density cusp may couple stellar dynamical processes with gas-radiative processes in the quasar nucleus, accounting for quasar variability. The coupling of X-ray luminosity with mass supply and stellar population may imply evolution of optical-to-X-ray luminosity ratios with redshift. Most importantly, the evolution of the stellar population away from the initial mass function may explain the scarcity of quasars at low redshift.

  20. Neoclassical transport in stellarators

    SciTech Connect

    Ho, D.D.M.; Kulsrud, R.M.

    1985-09-01

    The stellarator neoclassical transport due to particles trapped in local helical wells is calculated in the low-collisionality regime using a systematic expansion. The behavior of electron transport is found to be the same over a wide range of energies, but the behavior of ion transport for low energy ions is found to be different than that for high energy ions. Furthermore, the electron fluxes do not vary with the change in the radial ambipolar electric field nearly as much as do the ion fluxes. Thus, the particle diffusion is controlled by the electrons. A nonradial ambipolar electric field is induced by ion drift. This electric field enhances the transport by about 15 to 20%. A convenient graphical method that allows one to determine the magnitude of the radial ambipolar field for machines with different parameters is presented. Numerical examples show that electron energy confinement time is comparable to the ion energy confinement time for all the different size stellarators studied. Although the neoclassical losses are large, it is shown that ignition can be achieved in a reasonably sized stellarator reactor. Finally, from the standpoint of reactor economics, the confinement scaling law shows that in order to increase n tau, it is better to increase the aspect ratio than the overall dimensions of the reactor.

  1. Oscillations in stellar superflares

    E-print Network

    Balona, L A; Kosovichev, A; Nakariakov, V M; Pugh, C E; Van Doorsselaere, T

    2015-01-01

    Two different mechanisms may act to induce quasi-periodic pulsations (QPP) in whole-disk observations of stellar flares. One mechanism may be magneto-hydromagnetic (MHD) forces and other processes acting on flare loops as seen in the Sun. The other mechanism may be forced local acoustic oscillations due to the high-energy particle impulse generated by the flare (known as `sunquakes' in the Sun). We analyze short-cadence Kepler data of 257 flares in 75 stars to search for QPP in the flare decay branch or post-flare oscillations which may be attributed to either of these two mechanisms. About 18 percent of stellar flares show a distinct bump in the flare decay branch of unknown origin. The bump does not seem to be a highly-damped global oscillation because the periods of the bumps derived from wavelet analysis do not correlate with any stellar parameter. We detected damped oscillations covering several cycles (QPP), in seven flares on five stars. The periods of these oscillations also do not correlate with any ...

  2. Kinematic and Spatial Substructure in NGC 2264\\footnotemark

    E-print Network

    Tobin, John J; Furesz, Gabor; Hsu, Wen-Hsin; Mateo, Mario

    2015-01-01

    We present an expanded kinematic study of the young cluster NGC 2264 based upon optical radial velocities measured using multi-fiber echelle spectroscopy at the 6.5 meter MMT and Magellan telescopes. We report radial velocities for 695 stars, of which approximately 407 stars are confirmed or very likely members. Our results more than double the number of members with radial velocities from F{\\H u}r{\\'e}sz et al., resulting in a much better defined kinematic relationship between the stellar population and the associated molecular gas. In particular, we find that there is a significant subset of stars that are systematically blueshifted with respect to the molecular ($^{13}$CO) gas. The detection of Lithium absorption and/or infrared excesses in this blue-shifted population suggests that at least some of these stars are cluster members; we suggest some speculative scenarios to explain their kinematics. Our results also more clearly define the redshifted population of stars in the northern end of the cluster; we...

  3. Chemical fingerprinting of stellar populations in the Milky Way halo

    NASA Astrophysics Data System (ADS)

    Chou, Mei-Yin

    2015-03-01

    The idea of ``chemically fingerprinting`` stars to their birth systems has been discussed over the last decade. Here we present an investigation of the chemical abundance patterns of halo substructures using high-resolution spectra. In particular, we study the abundances of the ?-like element titanium (Ti) and the s-process elements yttrium (Y) and lanthanum (La) for M giant candidates of the Galactic Anticenter Stellar Structure (GASS, also known as the Monoceros Ring) and the Triangulum-Andromeda (TriAnd) Star Cloud. We apply ``chemical fingerprinting`` to the GASS/Monoceros Ring and TriAnd Star Cloud, to explore the origins of the two systems and the hypothesized connections between them. GASS has been debated either to originate from a part (e.g., warp) of the Galactic disk or tidal debris of a disrupted Milky Way (MW) satellite galaxy. Our exploration shows that GASS is indeed made of stars from a dwarf spheroidal (dSph) galaxy, although we still can not rule out the possibility that GASS was dynamically created out of a previously formed outer MW disk. And whereas the TriAnd Star Cloud has been assumed to come from the tidal disruption of the same accreted MW satellite as the GASS/Monoceros Ring, our comparison of the abundance patterns in GASS and TriAnd M giants suggests that the TriAnd Star Cloud is likely an independent halo substructure unrelated to the GASS/Monoceros Ring. Furthermore, our findings also suggest that the MW may have accreted other satellites in addition to the on-going, well-known Sagittarius (Sgr) dwarf galaxy.

  4. Using the etalon effect for in-situ balancing of the Advanced Virgo arm cavities

    E-print Network

    S. Hild; A. Freise; M. Mantovani; S. Chelkowski; J. Degallaix; R. Schilling

    2008-07-13

    Several large-scale interferometric gravitational-wave detectors use resonant arm cavities to enhance the light power in the interferometer arms. These cavities are based on different optical designs: One design uses wedged input mirrors to create additional optical pick-off ports for deriving control signals. The second design employs input mirrors without wedge and thus offers the possibility to use the etalon effect inside the input mirrors for tuning the finesse of the arm cavities. In this article we introduce a concept of maximized flexibility that combines both of these options, by featuring wedges at the input mirrors and using the etalon effect instead in the end mirrors. We present a design for the arm cavities of Advanced Virgo. We have used numerical simulations to derive requirements for the manufacturing accuracy of an end mirror etalon for Advanced Virgo. Furthermore, we give analytical approximations for the achievable tuning range of the etalon in dependence on the reflectance, the curvature and the orientation of the etalon back surface.

  5. Virgo calibration and reconstruction of the gravitational wave strain during VSR1

    E-print Network

    The Virgo collaboration; T. Accadia; F. Acernese; F. Antonucci; S. Aoudia; K. G. Arun; P. Astone; G. Ballardin; F. Barone; M. Barsuglia; Th. S. Bauer; M. G. Beker; A. Belletoile; S. Bigotta; S. Birindelli; M. Bitossi; M. A. Bizouard; M. Blom; C. Boccara; F. Bondu; L. Bonelli; R. Bonnand; L. Bosi; S. Braccini; C. Bradaschia; A. Brillet; V. Brisson; R. Budzynski; T. Bulik; H. J. Bulten; D. Buskulic; C. Buy; G. Cagnoli; E. Calloni; E. Campagna; B. Canuel; F. Carbognani; F. Cavalier; R. Cavalieri; G. Cella; E. Cesarini; E. Chassande-Mottin; A. Chincarini; F. Cleva; E. Coccia; C. N. Colacino; J. Colas; A. Colla; M. Colombini; A. Corsi; J. -P. Coulon; E. Cuoco; S. D'Antonio; A. Dari; V. Dattilo; M. Davier; R. Day; R. De Rosa; M. del Prete; L. Di Fiore; A. Di Lieto; M. Di Paolo Emilio; A. Di Virgilio; A. Dietz; M. Drago; V. Fafone; I. Ferrante; F. Fidecaro; I. Fiori; R. Flaminio; J. -D. Fournier; J. Franc; S. Frasca; F. Frasconi; A. Freise; M. Galimberti; L. Gammaitoni; F. Garufi; G. Gemme; E. Genin; A. Gennai; A. Giazotto; R. Gouaty; M. Granata; C. Greverie; G. M. Guidi; H. Heitmann; P. Hello; S. Hild; D. Huet; P. Jaranowski; I. Kowalska; A. Krolak; N. Leroy; N. Letendre; T. G. F. Li; M. Lorenzini; V. Loriette; G. Losurdo; J. M. Mackowski; E. Majorana; I. Maksimovic; N. Man; M. Mantovani; F. Marchesoni; F. Marion; J. Marque; F. Martelli; A. Masserot; C. Michel; L. Milano; Y. Minenkov; M. Mohan; J. Moreau; N. Morgado; A. Morgia; S. Mosca; V. Moscatelli; B. Mours; I. Neri; F. Nocera; G. Pagliaroli; L. Palladino; C. Palomba; F. Paoletti; S. Pardi; M. Parisi; A. Pasqualetti; R. Passaquieti; D. Passuello; G. Persichetti; M. Pichot; F. Piergiovanni; M. Pietka; L. Pinard; R. Poggiani; M. Prato; G. A. Prodi; M. Punturo; P. Puppo; O. Rabaste; D. S. Rabeling; P. Rapagnani; V. Re; T. Regimbau; F. Ricci; F. Robinet; A. Rocchi; L. Rolland; R. Romano; D. Rosinska; P. Ruggi; B. Sassolas; D. Sentenac; R. Sturani; B. Swinkels; A. Toncelli; M. Tonelli; O. Torre; E. Tournefier; F. Travasso; J. Trummer; G. Vajente; J. F. J. van den Brand; S. van der Putten; M. Vavoulidis; G. Vedovato; D. Verkindt; F. Vetrano; A. Vicere; J. -Y. Vinet; H. Vocca; M. Was; M. Yvert

    2010-02-19

    Virgo is a kilometer-length interferometer for gravitational waves detection located near Pisa. Its first science run, VSR1, occured from May to October 2007. The aims of the calibration are to measure the detector sensitivity and to reconstruct the time series of the gravitational wave strain h(t). The absolute length calibration is based on an original non-linear reconstruction of the differential arm length variations in free swinging Michelson configurations. It uses the laser wavelength as length standard. This method is used to calibrate the frequency dependent response of the Virgo mirror actuators and derive the detector in-loop response and sensitivity within ~5%. The principle of the strain reconstruction is highlighted and the h(t) systematic errors are estimated. A photon calibrator is used to check the sign of h(t). The reconstructed h(t) during VSR1 is valid from 10 Hz up to 10 kHz with systematic errors estimated to 6% in amplitude. The phase error is estimated to be 70 mrad below 1.9 kHz and 6 micro-seconds above.

  6. VirGO: A Visual Browser for the ESO Science Archive Facility

    NASA Astrophysics Data System (ADS)

    Chéreau, Fabien

    2012-04-01

    VirGO is the next generation Visual Browser for the ESO Science Archive Facility developed by the Virtual Observatory (VO) Systems Department. It is a plug-in for the popular open source software Stellarium adding capabilities for browsing professional astronomical data. VirGO gives astronomers the possibility to easily discover and select data from millions of observations in a new visual and intuitive way. Its main feature is to perform real-time access and graphical display of a large number of observations by showing instrumental footprints and image previews, and to allow their selection and filtering for subsequent download from the ESO SAF web interface. It also allows the loading of external FITS files or VOTables, the superimposition of Digitized Sky Survey (DSS) background images, and the visualization of the sky in a `real life' mode as seen from the main ESO sites. All data interfaces are based on Virtual Observatory standards which allow access to images and spectra from external data centers, and interaction with the ESO SAF web interface or any other VO applications supporting the PLASTIC messaging system.

  7. Probing the Low Surface Brightness Dwarf Galaxy Population of the Virgo Cluster

    E-print Network

    Davies, J I; Keenan, O C

    2015-01-01

    We have used public data from the Next Generation Virgo Survey (NGVS) to investigate the dwarf galaxy population of the Virgo cluster beyond what has previously been discovered. We initially mask and smooth the data, and then use the object detection algorithm Sextractor to make our initial dwarf galaxy selection. All candidates are then visually inspected to remove artefacts and duplicates. We derive Sextractor parameters to best select low surface brightness galaxies using g band central surface brightness values of 22.5 to 26.0 mag sq arc sec and exponential scale lengths of 3.0 - 10.0 arc sec to identify 443 cluster dwarf galaxies - 303 of which are new detections. These new detections have a surface density that decreases with radius from the cluster centre. We also apply our selection algorithm to 'background', non-cluster, fields and find zero detections. In combination, this leads us to believe that we have isolated a cluster dwarf galaxy population. The range of objects we are able to detect is limit...

  8. The Arecibo Legacy Fast ALFA Survey: III. HI Source Catalog of the Northern Virgo Cluster Region

    E-print Network

    R. Giovanelli; M. P. Haynes; B. R. Kent; A. Saintonge; S. Stierwalt; A. Altaf; T. Balonek; N. Brosch; S. Brown; B. Catinella; A. Furniss; J. Goldstein; G. L. Hoffman; R. A. Koopmann; D. A. Kornreich; B. Mahmood; A. M. Martin; K. L. Masters; A. Mitschang; E. Momjian; P. H. Nair; J. L. Rosenberg; B. Walsh

    2007-02-12

    We present the first installment of HI sources extracted from the Arecibo Legacy Fast ALFA (ALFALFA) extragalactic survey, initiated in 2005. Sources have been extracted from 3-D spectral data cubes and then examined interactively to yield global HI parameters. A total of 730 HI detections are catalogued within the solid angle 11h44m HI Parkes All-Sky Survey (HIPASS) detected 40 HI signals in the same region. Optical counterparts are assigned via examination of digital optical imaging databases. ALFALFA HI detections are reported for three distinct classes of signals: (a) detections, typically with S/N > 6.5; (b) high velocity clouds in the Milky Way or its periphery; and (c) signals of lower S/N (to ~ 4.5) which coincide spatially with an optical object of known similar redshift. Although this region of the sky has been heavily surveyed by previous targeted observations based on optical flux-- or size-- limited samples, 69% of the extracted sources are newly reported HI detections. The resultant positional accuracy of HI sources is 20" (median). The median redshift of the sample is ~7000 \\kms and its distribution reflects the known local large scale structure including the Virgo cluster. Several extended HI features are found in the vicinity of the Virgo cluster. A small percentage (6%) of HI detections have no identifiable optical counterpart, more than half of which are high velocity clouds in the Milky Way vicinity; the remaining 17 objects do not appear connected to or associated with any known galaxy.

  9. VIRGO sensitivity to binary coalescences and the Population III black hole binaries

    E-print Network

    K. Kulczycki; T. Bulik; K. Belczynski; B. Rudak

    2006-02-24

    We analyze the properties of VIRGO detector with the aim of studying its ability to search for coalescing black hole binaries. We focus on the remnants of the Population III stars, which currently should be massive black holes ($\\sim 100-1000 M_\\odot$), some of them bound in binary systems. The coalescence of such binaries due to emission of gravitational waves may be currently observable. We use a binary population synthesis to model the evolution of Population III binaries. We calculate the signal to noise ratios of gravitational waves emitted by the system in each of the coalescence phase: inspiral, merger and ringdown, and provide simple formulae for the signal to noise ratio as a function of masses of the binaries. We estimate the detection rates for the VIRGO interferometer and also compare them with the estimates for the current LIGO. We show that these expected rates are similar to, or larger than the expected rates from coalescences of Population I and II compact object binaries.

  10. First joint analysis between Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data

    NASA Astrophysics Data System (ADS)

    Di Palma, Irene; ANTARES Collaboration; LIGO Scientific Collaboration; Virgo Collaboration

    2012-07-01

    Multi-messenger astronomy is entering an exciting period with the recent development of experimental techniques that have opened new windows of observation of the cosmic radiation in all its components. Cataclysmic cosmic events can be plausible sources of both Gravitational Waves (GWs) and High Energy Neutrinos (HENs). Such messengers could reveal new, hidden sources that are not observed by conventional astronomy. Requiring consistency between GW and HEN detection channels enables new searches and a detection would yield significant additional information about the common source. A neutrino telescope such as ANTARES can determine the time and direction of high energy neutrino events. A network of gravitational wave detectors such as LIGO and Virgo can also provide timing/directional information for gravitational wave bursts. By combining the information from these totally independent detectors, one can search for cosmic events that may arrive from common astrophysical sources. In this proceeding are presented the fundamentals of the first joint analysis between GW and HENs during the fifth LIGO science run and first Virgo science run and the 5 line configuration of ANTARES.

  11. Characterization of a subset of large amplitude noise events in VIRGO science run 1 (VSR1)

    NASA Astrophysics Data System (ADS)

    Del Prete, M.; Virgo Collaboration; LSC Collaboration

    2009-10-01

    We report about a characterization study of a subset of large amplitude noise events present in the main data channel of the VIRGO detector. The main motivation of this study is the identification of auxiliary channels which can be used to define veto procedures. We characterized large amplitude events both in the time and in the frequency domain. We found evidence of coincidences among these and disturbances detected by magnetometer's sensors or inside the main power supply. In some cases the disturbances were produced by events in the VIRGO environment such as lightnings, main power supply glitches and airplane traffic. We have found two auxiliary channels that can be used to veto events generated by main power supply glitches or lightnings. A procedure to clean the main channel based on them has been successfully tested. We have also identified two auxiliary channels which are useful for the identification of events generated by airplane traffic. These can be used to implement a vetoing procedure both in the time and in the frequency domain.

  12. Stellar populations of early-type galaxies in different environments II. Ages and metallicities

    E-print Network

    Sánchez-Blazquez, P; González, J J; Gorgas, J

    2006-01-01

    This is the second paper of a series devoted to study the stellar content of early-type galaxies. The goal of the series is to set constraints on the evolutionary status of these objects. We use a new set of models which include an improved stellar library (MILES) to derive simple stellar population (SSP)-equivalent parameters in a sample of 98 early-type galaxies. The sample contains galaxies in the field, poor groups, and galaxies in the Virgo and Coma clusters.We find that low-density environment galaxies span a larger range in SSP age and metallicity than their counterparts in high density environments, with a tendency for lower sigma galaxies to be younger. Early-type galaxies in low-density environments appear on average ~1.5 Gyr younger and more metal rich than their counterparts in high density environments. The sample of low-density environment galaxies shows an age metallicity relation in which younger galaxies are found to be more metal rich, but only when metallicity is measured with a Fe-sensitiv...

  13. Hierarchical Stellar Structures in the Local Group Dwarf Galaxy NGC 6822

    NASA Astrophysics Data System (ADS)

    Gouliermis, Dimitrios A.; Schmeja, Stefan; Klessen, Ralf S.; de Blok, W. J. G.; Walter, Fabian

    2010-12-01

    We present a comprehensive study of the star cluster population and the hierarchical structure in the clustering of blue stars with ages lsim500 Myr in the Local Group dwarf irregular galaxy NGC 6822. Our observational material comprises the most complete optical stellar catalog of the galaxy from imaging with the Suprime-Cam at the 8.2 m Subaru Telescope. We identify 47 distinct star clusters with the application of the nearest-neighbor density method to this catalog for a detection threshold of 3? above the average stellar density. The size distribution of the detected clusters can be very well approximated by a Gaussian with a peak at ~68 pc. The total stellar masses of the clusters are estimated by extrapolating the cumulative observed stellar mass function of all clusters to be in the range 103-104 M sun. Their number distribution is fitted very well by a power law with index ? ~ 1.5 ± 0.7, which is consistent with the cluster mass functions of other Local Group galaxies and the cluster initial mass function. In addition to the detected star clusters of the galaxy, the application of the nearest-neighbor density method for various density thresholds, other than 3?, enabled the identification of stellar concentrations in various lengthscales. The stellar density maps constructed with this technique provide a direct proof of hierarchically structured stellar concentrations in NGC 6822, in the sense that smaller dense stellar concentrations are located inside larger and looser ones. We illustrate this hierarchy by the so-called dendrogram, or structure tree of the detected stellar structures, which demonstrates that most of the detected structures split up into several substructures over at least three levels. We quantify the hierarchy of these structures with the use of the minimum spanning tree method. We find that structures detected at 1, 2, and 3? density thresholds are hierarchically constructed with a fractal dimension of D ? 1.8. Some of the larger stellar concentrations, particularly in the northern part of the central star-forming portion of the galaxy, coincide with IR-bright complexes previously identified with Spitzer and associated with high column density neutral gas, indicating structures that currently form stars. The morphological hierarchy in stellar clustering, which we observe in NGC 6822, resembles that of the turbulent interstellar matter, suggesting that turbulence on pc and kpc scales has been probably the major agent that regulated clustered star formation in NGC 6822.

  14. HIERARCHICAL STELLAR STRUCTURES IN THE LOCAL GROUP DWARF GALAXY NGC 6822

    SciTech Connect

    Gouliermis, Dimitrios A.; Walter, Fabian [Max Planck Institute for Astronomy, Koenigstuhl 17, 69117 Heidelberg (Germany); Schmeja, Stefan; Klessen, Ralf S. [Zentrum fuer Astronomie der Universitaet Heidelberg, Institut fuer Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg (Germany); De Blok, W. J. G., E-mail: dgoulier@mpia-hd.mpg.d, E-mail: walter@mpia-hd.mpg.d, E-mail: sschmeja@ita.uni-heidelberg.d, E-mail: rklessen@ita.uni-heidelberg.d, E-mail: edeblok@ast.uct.ac.z [University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa)

    2010-12-20

    We present a comprehensive study of the star cluster population and the hierarchical structure in the clustering of blue stars with ages {approx}<500 Myr in the Local Group dwarf irregular galaxy NGC 6822. Our observational material comprises the most complete optical stellar catalog of the galaxy from imaging with the Suprime-Cam at the 8.2 m Subaru Telescope. We identify 47 distinct star clusters with the application of the nearest-neighbor density method to this catalog for a detection threshold of 3{sigma} above the average stellar density. The size distribution of the detected clusters can be very well approximated by a Gaussian with a peak at {approx}68 pc. The total stellar masses of the clusters are estimated by extrapolating the cumulative observed stellar mass function of all clusters to be in the range 10{sup 3}-10{sup 4} M{sub sun}. Their number distribution is fitted very well by a power law with index {alpha} {approx} 1.5 {+-} 0.7, which is consistent with the cluster mass functions of other Local Group galaxies and the cluster initial mass function. In addition to the detected star clusters of the galaxy, the application of the nearest-neighbor density method for various density thresholds, other than 3{sigma}, enabled the identification of stellar concentrations in various lengthscales. The stellar density maps constructed with this technique provide a direct proof of hierarchically structured stellar concentrations in NGC 6822, in the sense that smaller dense stellar concentrations are located inside larger and looser ones. We illustrate this hierarchy by the so-called dendrogram, or structure tree of the detected stellar structures, which demonstrates that most of the detected structures split up into several substructures over at least three levels. We quantify the hierarchy of these structures with the use of the minimum spanning tree method. We find that structures detected at 1, 2, and 3{sigma} density thresholds are hierarchically constructed with a fractal dimension of D {approx} 1.8. Some of the larger stellar concentrations, particularly in the northern part of the central star-forming portion of the galaxy, coincide with IR-bright complexes previously identified with Spitzer and associated with high column density neutral gas, indicating structures that currently form stars. The morphological hierarchy in stellar clustering, which we observe in NGC 6822, resembles that of the turbulent interstellar matter, suggesting that turbulence on pc and kpc scales has been probably the major agent that regulated clustered star formation in NGC 6822.

  15. The James Clerk Maxwell Telescope Nearby Galaxies Legacy Survey. I. Star-Forming Molecular Gas in Virgo Cluster Spiral Galaxies

    Microsoft Academic Search

    C. D. Wilson; B. E. Warren; F. P. Israel; S. Serjeant; G. Bendo; E. Brinks; D. Clements; S. Courteau; J. Irwin; J. H. Knapen; J. Leech; H. E. Matthews; S. Mühle; A. M. J. Mortier; G. Petitpas; E. Sinukoff; K. Spekkens; B. K. Tan; R. P. J. Tilanus; A. Usero; P. van der Werf; T. Wiegert; M. Zhu

    2009-01-01

    We present large-area maps of the CO J = 3-2 emission obtained at the James Clerk Maxwell Telescope for four spiral galaxies in the Virgo Cluster. We combine these data with published CO J = 1-0, 24 mum, and Halpha images to measure the CO line ratios, molecular gas masses, and instantaneous gas depletion times. For three galaxies in our

  16. Halpha surface photometry of galaxies in the Virgo cluster III. Observations with INT and NOT 2.5 m telescopes

    Microsoft Academic Search

    A. Boselli; J. Iglesias-Páramo; J. M. Vílchez; G. Gavazzi

    2002-01-01

    We present Halpha line imaging observations of 30 galaxies obtained at the 2.5 m INT and NOT telescopes. The observed galaxies are mostly BCD Virgo cluster galaxies. Halpha +[NII] fluxes and equivalent widths, as well as images of all the detected targets are presented. With these observations, Halpha data are available for =~ 50% of the BCD galaxies listed in

  17. Narrow-band search of continuous gravitational-wave signals from Crab and Vela pulsars in Virgo VSR4 data

    E-print Network

    Aasi, J.

    In this paper we present the results of a coherent narrow-band search for continuous gravitational-wave signals from the Crab and Vela pulsars conducted on Virgo VSR4 data. In order to take into account a possible small ...

  18. Stellar Rotation and Age Determination

    NASA Astrophysics Data System (ADS)

    Santoro, L.

    2011-02-01

    In this preliminary analysis we discuss on a statistical inversion method applied to the measured stellar Vrot sin i. Our goal is to obtain the Vrot of the cluster stars which is a key parameter of stellar evolution computations. We estimate rotation impact on the age determination of cluster stars using the Maeder-Zahn's theory of stellar rotation in the Cesam2k code.

  19. Improving corrosion resistance of post-tensioned substructures emphasizing high performance grouts

    NASA Astrophysics Data System (ADS)

    Schokker, Andrea Jeanne

    The use of post-tensioning in bridges can provide durability and structural benefits to the system while expediting the construction process. When post-tensioning is combined with precast elements, traffic interference can be greatly reduced through rapid construction. Post-tensioned concrete substructure elements such as bridge piers, hammerhead bents, and straddle bents have become more prevalent in recent years. Chloride induced corrosion of steel in concrete is one of the most costly forms of corrosion each year. Coastal substructure elements are exposed to seawater by immersion or spray, and inland bridges may also be at risk due to the application of deicing salts. Corrosion protection of the post-tensioning system is vital to the integrity of the structure because loss of post-tensioning can result in catastrophic failure. Documentation for durability design of the grout, ducts, and anchorage systems is very limited. The objective of this research is to evaluate the effectiveness of corrosion protection measures for post-tensioned concrete substructures by designing and testing specimens representative of typical substructure elements using state-of-the-art practices in aggressive chloride exposure environments. This was accomplished through exposure testing of twenty-seven large-scale beam specimens and ten large-scale column specimens. High performance grout for post-tensioning tendon injection was also developed through a series of fresh property tests, accelerated exposure tests, and a large-scale pumping test to simulate field conditions. A high performance fly ash grout was developed for applications with small vertical rises, and a high performance anti-bleed grout was developed for applications involving large vertical rises such as tall bridge piers. Long-term exposure testing of the beam and column specimens is ongoing, but preliminary findings indicate increased corrosion protection with increasing levels of post-tensioning, although traditional fully prestressed sections may not give as high a benefit to cost ratio as partially prestressed sections with high percentages of prestressing steel. Specimens with low permeable concrete are showing better corrosion protection than specimens with the standard concrete for bridge substructures used by the Texas Department of Transportation. Recommendations and guidelines for durable design of post-tensioned bridge substructures were developed from the findings to date, and supplementary information will be provided after final autopsy of all specimens.

  20. Genomic Diversity at Thirteen Short Tandem Repeat Loci in a Substructured Caste Population, Golla, of Southern Andhra Pradesh, India

    E-print Network

    Reddy, B Mohan; Sun, Guangyun; Luis, Javier Rodriguez; Crawford, Michael H; Hemam, Natabar Shyam; Deka, Ranjan

    2001-04-01

    Genomic diversity based on 13 short tandem repeat (STR) loci was studied in seven population groups of a substructured Golla caste from Chittoor district in southern Andhra Pradesh, India. These groups are traditionally pastoral, culturally...

  1. Discovery of a Large Stellar Periphery of the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Nidever, David L.; Majewski, S. R.; Munoz, R. R.; Beaton, R. L.; Patterson, R. J.; Kunkel, W. E.

    2011-01-01

    The Magellanic Clouds are a local laboratory for understanding the evolution and properties of dwarf irregular galaxies. To reveal the extended structure and interaction history of the Magellanic Clouds, we have undertaken a large-scale photometric and spectroscopic study of their stellar periphery (The MAgellanic Periphery Survey, MAPS). We present our first results for the Small Magellanic Cloud (SMC): Washington M, T2 + DDO51 photometry reveals metal-poor red giant branch stars in the SMC that extend out to large radii (11.1 kpc), are distributed nearly azimuthally symmetrically (ellipticity=0.1), and are well-fitted by an exponential profile (out to R=7.5 deg). We find a "break" population beyond 8 radial scalelengths having a very shallow radial density profile that looks to be a stellar halo. The outer stellar distribution contrasts with that of the inner stellar distribution, which is both more elliptical (ellipticity 0.3) and offset from the center of the outer population by 0.63 deg, although both populations share a similar radial exponential scale length. This offset is likely due to a perspective effect since stars on the eastern side of the SMC are on average at closer distances than stars on the western side. The discovery of these new outer stellar structures indicates that the SMC is more complex than previously thought. Our results indicate that it is likely that the SMC has a large stellar halo, which, if correct, would confirm predictions by Lambda CDM simulations that galaxies on all scales should have substructure and halos.

  2. Hadronic Calorimeter Shower Size: Challenges and Opportunities for Jet Substructure in the Superboosted Regime

    E-print Network

    Bressler, Shikma; Kats, Yevgeny; Lee, Seung J; Perez, Gilad

    2015-01-01

    Hadrons have finite interaction size with dense material, a basic feature common to known forms of hadronic calorimeters (HCAL). We argue that substructure variables cannot use HCAL information to access the microscopic nature of jets narrower than the hadronic shower size, which we call superboosted massive jets. It implies that roughly 15% of their transverse energy profile remains inaccessible due to the presence of long-lived neutral hadrons. This unreachable part of the jet substructure is also subject to order-one fluctuations. We demonstrate that the effects of the fluctuations are not reduced when a global correction to jet variables is applied. The above leads to fundamental limitations in the ability to extract intrinsic information from jets in the superboosted regime. The neutral fraction of a jet is correlated with its flavor. This leads to an interesting and possibly useful difference between superboosted W/Z/h/t jets and their corresponding backgrounds. The QCD jets that form the background to ...

  3. Interference substructure of above-threshold ionization peaks in the stabilization regime

    NASA Astrophysics Data System (ADS)

    Toyota, Koudai; Tolstikhin, Oleg I.; Morishita, Toru; Watanabe, Shinichi

    2008-09-01

    The photoelectron spectra produced in the photodetachment of H- (treated in the single-active-electron approximation) by strong high-frequency laser pulses with adequately chosen laser parameters in the stabilization regime are theoretically studied for elliptic polarization over an extended parameter range. An oscillating substructure in the above-threshold ionization peaks is observed, which confirms similar findings in the one-dimensional (1D) [K. Toyota , Phys. Rev. A 76, 043418 (2007)] and 3D calculations for linear polarization [O. I. Tolstikhin, Phys. Rev. A 77, 032712 (2008)]. The mechanism is an interference between the photoelectron wave packets created in the rising and falling parts of the pulse which is specific to the stabilization regime. We thus conclude that this interference substructure is robust for any polarization and over a wide range of the laser parameters, and hence should be observable experimentally.

  4. Twisting phonons in complex crystals with quasi-one-dimensional substructures

    NASA Astrophysics Data System (ADS)

    Chen, Xi; Weathers, Annie; Carrete, Jesús; Mukhopadhyay, Saikat; Delaire, Olivier; Stewart, Derek A.; Mingo, Natalio; Girard, Steven N.; Ma, Jie; Abernathy, Douglas L.; Yan, Jiaqiang; Sheshka, Raman; Sellan, Daniel P.; Meng, Fei; Jin, Song; Zhou, Jianshi; Shi, Li

    2015-04-01

    A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such complex crystals. Here we employ inelastic neutron scatting measurements and density functional theory calculations to show that numerous low-energy optical vibrational modes exist in higher manganese silicides, an example of such crystals. These optical modes, including unusually low-frequency twisting motions of the Si ladders inside the Mn chimneys, provide a large phase space for scattering acoustic phonons. A hybrid phonon and diffuson model is proposed to explain the low and anisotropic thermal conductivity of higher manganese silicides and to evaluate nanostructuring as an approach to further suppress the thermal conductivity and enhance the thermoelectric energy conversion efficiency. This discovery offers new insights into the structure-property relationships of a broad class of materials with quasi-one-dimensional substructures for various applications.

  5. Serous cutaneous glands in anurans: Fourier transform analysis of the repeating secretory granule substructure

    NASA Astrophysics Data System (ADS)

    Nosi, D.; Delfino, G.; Quercioli, F.

    2013-03-01

    A combined transmission electron microscopy (TEM) and Fourier transform analysis has been performed on the secretory granules storing active peptides/proteins in serous cutaneous glands of n = 12 anuran species. Previous TEM investigation showed that the granules are provided with remarkable repeating substructures based on discrete subunits, arranged into a consistent framework. Furthermore, TEM findings revealed that this recurrent arrangement is acquired during a prolonged post-Golgian (or maturational) processing that affects the secretory product. Maturation leads to a variety of patterns depending on the degree of subunit clustering. This variety of recurrent patterns has been plotted into a range of frequency spectra. Through this quantitative approach, we found that the varying granule substructure can be reduced to a single mechanism of peptide/protein aggregation.

  6. A Note on Substructuring Preconditioning for Nonconforming Finite Element Approximations of Second Order Elliptic Problems

    NASA Technical Reports Server (NTRS)

    Maliassov, Serguei

    1996-01-01

    In this paper an algebraic substructuring preconditioner is considered for nonconforming finite element approximations of second order elliptic problems in 3D domains with a piecewise constant diffusion coefficient. Using a substructuring idea and a block Gauss elimination, part of the unknowns is eliminated and the Schur complement obtained is preconditioned by a spectrally equivalent very sparse matrix. In the case of quasiuniform tetrahedral mesh an appropriate algebraic multigrid solver can be used to solve the problem with this matrix. Explicit estimates of condition numbers and implementation algorithms are established for the constructed preconditioner. It is shown that the condition number of the preconditioned matrix does not depend on either the mesh step size or the jump of the coefficient. Finally, numerical experiments are presented to illustrate the theory being developed.

  7. Optimizing statistical Shake-and-Bake for Se-atom substructure determination.

    PubMed

    Xu, Hongliang; Weeks, Charles M; Hauptman, Herbert A

    2005-07-01

    A novel statistical approach to the phase problem in X-ray crystallography was introduced in a recent paper [Xu & Hauptman (2004), Acta Cryst. A60, 153-157]. In this approach, a new minimal function based on the statistical distribution of structure-invariant values serves as the foundation of an optimization procedure called statistical Shake-and-Bake. Favorable application of this procedure to Se-atom substructure determination depends on the choice of the statistical interval over which the function is defined. The effects of interval variation have been studied for 19 Se-atom substructures ranging in size from five to 70 Se atoms in the asymmetric unit and the results have shown an overall improvement in success rate relative to traditional Shake-and-Bake. Statistical Shake-and-Bake is being incorporated as the default optimization procedure in newly distributed versions of the SnB and BnP computer programs. PMID:15983421

  8. Structural and molecular remodeling of dendritic spine substructures during long-term potentiation

    PubMed Central

    Bosch, Miquel; Castro, Jorge; Saneyoshi, Takeo; Matsuno, Hitomi; Sur, Mriganka; Hayashi, Yasunori

    2014-01-01

    SUMMARY Synapses store information by long-lasting modifications of their structure and molecular composition, but the precise chronology of these changes has not been studied at single synapse resolution in real time. Here we describe the spatiotemporal reorganization of postsynaptic substructures during long-term potentiation (LTP) at individual dendritic spines. Proteins translocated to the spine in four distinct patterns through three sequential phases. In the initial phase, the actin cytoskeleton was rapidly remodeled while active cofilin was massively transported to the spine. In the stabilization phase, cofilin formed a stable complex with F-actin, was persistently retained at the spine, and consolidated spine expansion. In contrast, the postsynaptic density (PSD) was independently remodeled, as PSD scaffolding proteins did not change their amount and localization until a late protein synthesis-dependent third phase. Our findings show how and when spine substructures are remodeled during LTP and explain why synaptic plasticity rules change over time. PMID:24742465

  9. Programming substructure computations for elliptic problems on the CHiP system

    NASA Technical Reports Server (NTRS)

    Gannon, D.; Snyder, L.; Van Rosendale, J.

    1983-01-01

    A number of studies have been conducted with the aim to apply parallel computation to problems associated with solving finite element equations arising in structural mechanics and fluid dynamics. These studies have provided many important results. The present investigation is concerned with a set of experiments designed to test two ideas, including configurability and substructuring. The considered algorithms and tests are intended for implementation on the Configurable, Highly Parallel (CHiP) family of architecture described by Snyder (1982). The ChiP computer is composed of homogeneous processing elements (PEs) placed at regular intervals in a lattice of programmable switches. Two examples of the role of configurability and substructuring for simple iterative algorithms are considered, giving attention to conjugate gradient iterations, and tridiagonal systems of equations.

  10. Structural and substructural features of chemically deposited zinc oxide thin films

    NASA Astrophysics Data System (ADS)

    Opanasyuk, A. S.; Berestok, T. O.; Fochuk, P. M.; Bolotnikov, A. E.; James, R. B.

    2013-09-01

    We investigated the structural and sub-structural characteristics of ZnO films obtained by chemical bath deposition from solutions of zinc sulfate, thiourea, and ammonia. The duration of deposition ranged from 20- to 120-minutes. The concentration of thiourea was varied from 0.1- to 3-mol. We detailed the structural and sub-structural characteristics of these films using high-resolution scanning electron microscopy and x-ray diffraction. This research enables us to study features of the films' structural formation, and to determine their basic characteristics, viz., phase analysis, texture quality, lattice constants, grain size, and size of the coherent scattering domain. Regimes were identified for depositing films with optimal structural characteristics for eventual use in solar-energy applications.

  11. Fast and accurate protein substructure searching with simulated annealing and GPUs

    PubMed Central

    2010-01-01

    Background Searching a database of protein structures for matches to a query structure, or occurrences of a structural motif, is an important task in structural biology and bioinformatics. While there are many existing methods for structural similarity searching, faster and more accurate approaches are still required, and few current methods are capable of substructure (motif) searching. Results We developed an improved heuristic for tableau-based protein structure and substructure searching using simulated annealing, that is as fast or faster and comparable in accuracy, with some widely used existing methods. Furthermore, we created a parallel implementation on a modern graphics processing unit (GPU). Conclusions The GPU implementation achieves up to 34 times speedup over the CPU implementation of tableau-based structure search with simulated annealing, making it one of the fastest available methods. To the best of our knowledge, this is the first application of a GPU to the protein structural search problem. PMID:20813068

  12. Simulation of the effects of interstitial content and temperature on texture and substructure evolution of commercially pure titanium during ECAP

    NASA Astrophysics Data System (ADS)

    Guo, X.; Seefeldt, M.

    2015-04-01

    The effects of interstitial content and temperature on texture and substructure evolution of commercially pure titanium during the first pass of equal channel angular pressing were investigated. Different values of critical resolved shear stresses were proposed for different interstitial contents and processing temperatures. Simulation results show that texture was affected by both interstitial element and temperature. Also, in substructure simulation, the cell size was affected by interstitial content, while the fragment size was more dependent on temperature change.

  13. Substructure of bovine casein micelles by small-angle X-ray and neutron scattering

    Microsoft Academic Search

    C. Holt; C. G. de Kruif; R. Tuinier; P. A. Timmins

    2003-01-01

    The casein micelles of cow's milk are polydisperse, more-or-less spherical, protein particles of up to several hundred nanometer in size, containing about 7% by dry weight of calcium phosphate. Small-angle neutron scattering with contrast variation and small-angle X-ray scattering were used in critical tests of models of casein micelle substructure. An inflexion in the neutron scattering curve near Q=0.35 nm?1

  14. Improving corrosion resistance of post-tensioned substructures emphasizing high performance grouts

    Microsoft Academic Search

    Andrea Jeanne Schokker

    1999-01-01

    The use of post-tensioning in bridges can provide durability and structural benefits to the system while expediting the construction process. When post-tensioning is combined with precast elements, traffic interference can be greatly reduced through rapid construction. Post-tensioned concrete substructure elements such as bridge piers, hammerhead bents, and straddle bents have become more prevalent in recent years. Chloride induced corrosion of

  15. Learning sub-structures of document semantic graphs for document summarization

    Microsoft Academic Search

    Jure Leskovec; Marko Grobelnik; Natasa Milic-Frayling

    2004-01-01

    In this paper we present a method for summarizing document by creating a semantic graph of the original document and identifying the substructure of such a graph that can be used to extract sentences for a document summary. We start with deep syntactic analysis of the text and, for each sentence, extract logical form triples, subject-predicate-object. We then apply cross-sentence

  16. Correlation of creep elongation and substructure in aluminum-stainless steel composites

    Microsoft Academic Search

    M. R. Pinnel; A. Lawley

    1971-01-01

    The tensile creep behavior and associated substructural detail have been characterized in aluminum-stainless steel composites\\u000a at ambient temperature. Volume fractions in the range 0 to 0.33 were tested under constant load conditions (in the range 1.0\\u000a to 4.0 times macroscopic yield stress) with the load applied parallel to the direction of reinforcement. In both unreinforced\\u000a aluminum and the composites, steady-state

  17. Discovering the Higgs boson in new physics events using jet substructure

    Microsoft Academic Search

    Graham D. Kribs; Adam Martin; Tuhin S. Roy; Michael Spannowsky

    2010-01-01

    We present a novel method to discover the Higgs boson in new physics event\\u000asamples at the LHC. Our technique applies to broad classes of models where the\\u000aHiggs has a significant branching fraction to b-bbar. We exploit the recently\\u000adeveloped techniques for discovering a boosted Higgs using jet substructure.\\u000aOur requirements of new physics are quite general: there must

  18. Acoustic Radiation from a Finite-Length Shell with Non-Axisymmetric Substructures Using a Surface Variational Principle

    NASA Astrophysics Data System (ADS)

    Choi, S.-H.; Igusa, T.; Achenbach, J. D.

    1996-10-01

    A modal-based method is developed to analyze the acoustic radiation of axisymmetric submerged shells of finite length with non-axisymmetric internal substructures, subjected to time-harmonic loads. In this method, a variational principle is used to derive impedance relations between the surface pressure and the surface velocity of the shell. These impedance relations are combined with the structural equations of motions based on a Lagrange energy formulation to form a complete set of equations for the fluid-structure interaction problem. Fourier series expansions are used to represent the circumferential dependence of the surface pressure and velocity. The method is demonstrated for two different configurations of substructures: circular ribs supporting length-wise beams and a spatially and modally dense array of oscillators. Since the substructures couple the circumferential modes, a large system of equations must be inverted. A matrix decomposition technique is used to reduce the size of the system of equations of the first example. For the second example, the asymptotic limit for an infinite number of substructures is developed using an integral form for the substructure impedance. It is shown that the Monte Carlo simulations for the oscillator substructures converge to the asymptotic results. It is also shown that, below the ring frequency, oscillators can induce damping that is more effective in reducing far-field radiation than high loss factors in the shell.

  19. Predictions for Swift Follow-up Observations of Advanced LIGO/Virgo Gravitational Wave Sources

    NASA Astrophysics Data System (ADS)

    Racusin, Judith; Evans, Phil; Connaughton, Valerie

    2015-04-01

    The likely detection of gravitational waves associated with the inspiral of neutron star binaries by the upcoming advanced LIGO/Virgo observatories will be complemented by searches for electromagnetic counterparts over large areas of the sky by Swift and other observatories. As short gamma-ray bursts (GRB) are the most likely electromagnetic counterpart candidates to these sources, we can make predictions based upon the last decade of GRB observations by Swift and Fermi. Swift is uniquely capable of accurately localizing new transients rapidly over large areas of the sky in single and tiled pointings, enabling ground-based follow-up. We describe simulations of the detectability of short GRB afterglows by Swift given existing and hypothetical tiling schemes with realistic observing conditions and delays, which guide the optimal observing strategy and improvements provided by coincident detection with observatories such as Fermi-GBM.

  20. Gemini/GMOS Imaging of Globular Clusters in the Virgo Galaxy NGC 4649 (M60)

    E-print Network

    Duncan A. Forbes; Favio Raul Faifer; Juan Carlos Forte; Terry Bridges; Michael A. Beasley; Karl Gebhardt; David A. Hanes; Ray Sharples; Stephen E. Zepf

    2004-08-23

    We present Sloan g and i imaging from the GMOS instrument on the Gemini North telescope for the globular cluster (GC) system around the Virgo galaxy NGC 4649 (M60). Our three pointings, taken in good seeing conditions, cover an area of about 90 sq. arcmins. We detect 2,151 unresolved sources. Applying colour and magnitude selection criteria to this source list gives 995 candidate GCs that is greater than 90% complete to a magnitude of i = 23.6, with little contamination from background galaxies. We find fewer than half a dozen potential Ultra Compact Dwarf galaxies around NGC 4649. Foreground extinction from the nearby spiral NGC 4647 is limited to be A_V GMOS spectra of the NGC 4649 GCs.

  1. The Dwarf Irregular Galaxy UGC 7636 Exposed: Stripping at Work in the Virgo Cluster.

    PubMed

    Lee; Richer; McCall

    2000-02-10

    We present the results of optical spectroscopy of a newly discovered H ii region residing in the H i gas cloud located between the dwarf irregular galaxy UGC 7636 and the giant elliptical galaxy NGC 4472 in the Virgo Cluster. By comparing UGC 7636 with dwarf irregular galaxies in the field, we show that the H i cloud must have originated from UGC 7636 because (1) the oxygen abundance of the cloud agrees with that expected for a galaxy with the blue luminosity of UGC 7636 and (2) MHi&solm0;LB for UGC 7636 becomes consistent with the measured oxygen abundance of the cloud if the H i mass of the cloud is added back into UGC 7636. It is likely that tides from NGC 4472 first loosened the H i gas, after which ram pressure stripping removed the gas from UGC 7636. PMID:10642195

  2. Constraints on cosmic strings from the LIGO-Virgo gravitational-wave detectors

    E-print Network

    J. Aasi; J. Abadie; B. P. Abbott; R. Abbott; T. Abbott; M. R. Abernathy; T. Accadia; F. Acernese; C. Adams; T. Adams; R. X. Adhikari; C. Affeldt; M. Agathos; N. Aggarwal; O. D. Aguiar; P. Ajith; B. Allen; A. Allocca; E. Amador Ceron; D. Amariutei; R. A. Anderson; S. B. Anderson; W. G. Anderson; K. Arai; M. C. Araya; C. Arceneaux; J. Areeda; S. Ast; S. M. Aston; P. Astone; P. Aufmuth; C. Aulbert; L. Austin; B. E. Aylott; S. Babak; P. T. Baker; G. Ballardin; S. W. Ballmer; J. C. Barayoga; D. Barker; S. H. Barnum; F. Barone; B. Barr; L. Barsotti; M. Barsuglia; M. A. Barton; I. Bartos; R. Bassiri; A. Basti; J. Batch; J. Bauchrowitz; Th. S. Bauer; M. Bebronne; B. Behnke; M. Bejger; M. G. Beker; A. S. Bell; C. Bell; I. Belopolski; G. Bergmann; J. M. Berliner; D. Bersanetti; A. Bertolini; D. Bessis; J. Betzwieser; P. T. Beyersdorf; T. Bhadbhade; I. A. Bilenko; G. Billingsley; J. Birch; M. Bitossi; M. A. Bizouard; E. Black; J. K. Blackburn; L. Blackburn; D. Blair; M. Blom; O. Bock; T. P. Bodiya; M. Boer; C. Bogan; C. Bond; F. Bondu; L. Bonelli; R. Bonnand; R. Bork; M. Born; V. Boschi; S. Bose; L. Bosi; J. Bowers; C. Bradaschia; P. R. Brady; V. B. Braginsky; M. Branchesi; C. A. Brannen; J. E. Brau; J. Breyer; T. Briant; D. O. Bridges; A. Brillet; M. Brinkmann; V. Brisson; M. Britzger; A. F. Brooks; D. A. Brown; D. D. Brown; F. Brückner; T. Bulik; H. J. Bulten; A. Buonanno; D. Buskulic; C. Buy; R. L. Byer; L. Cadonati; G. Cagnoli; J. Calderón Bustillo; E. Calloni; J. B. Camp; P. Campsie; K. C. Cannon; B. Canuel; J. Cao; C. D. Capano; F. Carbognani; L. Carbone; S. Caride; A. Castiglia; S. Caudill; M. Cavagliá; F. Cavalier; R. Cavalieri; G. Cella; C. Cepeda; E. Cesarini; R. Chakraborty; T. Chalermsongsak; S. Chao; P. Charlton; E. Chassande-Mottin; X. Chen; Y. Chen; A. Chincarini; A. Chiummo; H. S. Cho; J. Chow; N. Christensen; Q. Chu; S. S. Y. Chua; S. Chung; G. Ciani; F. Clara; D. E. Clark; J. A. Clark; F. Cleva; E. Coccia; P. -F. Cohadon; A. Colla; M. Colombini; M. Constancio Jr.; A. Conte; R. Conte; D. Cook; T. R. Corbitt; M. Cordier; N. Cornish; A. Corsi; C. A. Costa; M. W. Coughlin; J. -P. Coulon; S. Countryman; P. Couvares; D. M. Coward; M. Cowart; D. C. Coyne; K. Craig; J. D. E. Creighton; T. D. Creighton; S. G. Crowder; A. Cumming; L. Cunningham; E. Cuoco; K. Dahl; T. Dal Canton; M. Damjanic; S. L. Danilishin; S. D'Antonio; K. Danzmann; V. Dattilo; B. Daudert; H. Daveloza; M. Davier; G. S. Davies; E. J. Daw; R. Day; T. Dayanga; R. De Rosa; G. Debreczeni; J. Degallaix; W. Del Pozzo; E. Deleeuw; S. Deléglise; T. Denker; T. Dent; H. Dereli; V. Dergachev; R. DeRosa; R. DeSalvo; S. Dhurandhar; L. Di Fiore; A. Di Lieto; I. Di Palma; A. Di Virgilio; M. Díaz; A. Dietz; K. Dmitry; F. Donovan; K. L. Dooley; S. Doravari; M. Drago; R. W. P. Drever; J. C. Driggers; Z. Du; J. -C. Dumas; S. Dwyer; T. Eberle; M. Edwards; A. Effler; P. Ehrens; J. Eichholz; S. S. Eikenberry; G. Endröczi; R. Essick; T. Etzel; K. Evans; M. Evans; T. Evans; M. Factourovich; V. Fafone; S. Fairhurst; Q. Fang; S. Farinon; B. Farr; W. Farr; M. Favata; D. Fazi; H. Fehrmann; D. Feldbaum; I. Ferrante; F. Ferrini; F. Fidecaro; L. S. Finn; I. Fiori; R. Fisher; R. Flaminio; E. Foley; S. Foley; E. Forsi; N. Fotopoulos; J. -D. Fournier; S. Franco; S. Frasca; F. Frasconi; M. Frede; M. Frei; Z. Frei; A. Freise; R. Frey; T. T. Fricke; P. Fritschel; V. V. Frolov; M. -K. Fujimoto; P. Fulda; M. Fyffe; J. Gair; L. Gammaitoni; J. Garcia; F. Garufi; N. Gehrels; G. Gemme; E. Genin; A. Gennai; L. Gergely; S. Ghosh; J. A. Giaime; S. Giampanis; K. D. Giardina; A. Giazotto; S. Gil-Casanova; C. Gill; J. Gleason; E. Goetz; R. Goetz; L. Gondan; G. González; N. Gordon; M. L. Gorodetsky; S. Gossan; S. Goßler; R. Gouaty; C. Graef; P. B. Graff; M. Granata; A. Grant; S. Gras; C. Gray; R. J. S. Greenhalgh; A. M. Gretarsson; C. Griffo; P. Groot; H. Grote; K. Grover; S. Grunewald; G. M. Guidi; C. Guido; K. E. Gushwa; E. K. Gustafson; R. Gustafson; B. Hall; E. Hall; D. Hammer; G. Hammond; M. Hanke; J. Hanks; C. Hanna; J. Hanson; J. Harms; G. M. Harry; I. W. Harry; E. D. Harstad; M. T. Hartman; K. Haughian; K. Hayama; J. Heefner; A. Heidmann; M. Heintze; H. Heitmann; P. Hello; G. Hemming; M. Hendry; I. S. Heng; A. W. Heptonstall; M. Heurs; S. Hild; D. Hoak; K. A. Hodge; K. Holt; M. Holtrop; T. Hong; S. Hooper; T. Horrom; D. J. Hosken; J. Hough; E. J. Howell; Y. Hu; Z. Hua; V. Huang; E. A. Huerta; B. Hughey; S. Husa; S. H. Huttner; M. Huynh; T. Huynh-Dinh; J. Iafrate; D. R. Ingram; R. Inta; T. Isogai; A. Ivanov; B. R. Iyer; K. Izumi; M. Jacobson; E. James; H. Jang; Y. J. Jang; P. Jaranowski; F. Jiménez-Forteza; W. W. Johnson; D. Jones; D. I. Jones; R. Jones; R. J. G. Jonker; L. Ju; Haris K; P. Kalmus; V. Kalogera; S. Kandhasamy; G. Kang; J. B. Kanner; M. Kasprzack; R. Kasturi; E. Katsavounidis; W. Katzman; H. Kaufer; K. Kaufman; K. Kawabe; S. Kawamura; F. Kawazoe

    2014-04-07

    Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension $G\\mu$ below $10^{-8}$ in some regions of the cosmic string parameter space.

  3. The Dartmouth Stellar Evolution Database

    Microsoft Academic Search

    Aaron Dotter; Brian Chaboyer; Darko Jevremovic; Veselin Kostov; E. Baron; Jason W. Ferguson

    2008-01-01

    The ever-expanding depth and quality of photometric and spectroscopic observations of stellar populations increase the need for theoretical models in regions of age-composition parameter space that are largely unexplored at present. Stellar evolution models that employ the most advanced physics and cover a wide range of compositions are needed to extract the most information from current observations of both resolved

  4. The Solar--Stellar Connection

    E-print Network

    S. M. White

    2004-09-07

    Stars have proven to be surprisingly prolific radio sources and the added sensitivity of the Square Kilometer Array will lead to advances in many directions. This chapter discusses prospects for studying the physics of stellar atmospheres and stellar winds across the HR diagram.

  5. Stellar rotation in open clusters

    NASA Astrophysics Data System (ADS)

    Santoro, L.

    2010-12-01

    The goal of this work is the analysis of rotation impact on the age determination of open clusters. In this preliminary study we discuss on a statistical method to know the key parameter Vrot. Then we use Vrot estimate in stellar evolution computations (Cesam2k code) with implemented Maeder-Zahn's theory of stellar rotation.

  6. Stellar nucleosynthesis and galactic abundances

    Microsoft Academic Search

    F.-K. Thielemann; D. Argast; F. Brachwitz; G. Martinez-Pinedo

    2001-01-01

    Galactic abundances are neither constant in time nor do they evolve in a simple fashion, e.g., by an enrichment of heavy elements in constant relative proportions. Instead, their evolution in space and time reflects the history of star formation and the lifetimes of the diverse contributing stellar objects. Stellar winds from intermediate and massive stars, as well as supernovae of

  7. Three-dimensional stellarator codes

    PubMed Central

    Garabedian, P. R.

    2002-01-01

    Three-dimensional computer codes have been used to develop quasisymmetric stellarators with modular coils that are promising candidates for a magnetic fusion reactor. The mathematics of plasma confinement raises serious questions about the numerical calculations. Convergence studies have been performed to assess the best configurations. Comparisons with recent data from large stellarator experiments serve to validate the theory. PMID:12140367

  8. Modeling the Role of Dislocation Substructure During Class M and Exponential Creep. Revised

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Iskovitz, Ilana Seiden; Freed, A. D.

    1995-01-01

    The different substructures that form in the power-law and exponential creep regimes for single phase crystalline materials under various conditions of stress, temperature and strain are reviewed. The microstructure is correlated both qualitatively and quantitatively with power-law and exponential creep as well as with steady state and non-steady state deformation behavior. These observations suggest that creep is influenced by a complex interaction between several elements of the microstructure, such as dislocations, cells and subgrains. The stability of the creep substructure is examined in both of these creep regimes during stress and temperature change experiments. These observations are rationalized on the basis of a phenomenological model, where normal primary creep is interpreted as a series of constant structure exponential creep rate-stress relationships. The implications of this viewpoint on the magnitude of the stress exponent and steady state behavior are discussed. A theory is developed to predict the macroscopic creep behavior of a single phase material using quantitative microstructural data. In this technique the thermally activated deformation mechanisms proposed by dislocation physics are interlinked with a previously developed multiphase, three-dimensional. dislocation substructure creep model. This procedure leads to several coupled differential equations interrelating macroscopic creep plasticity with microstructural evolution.

  9. Hunting for dark halo substructure using submilliarcsecond-scale observations of macrolensed radio jets

    NASA Astrophysics Data System (ADS)

    Zackrisson, Erik; Asadi, Saghar; Wiik, Kaj; Jönsson, Jakob; Scott, Pat; Datta, Kanan K.; Friedrich, Martina M.; Jensen, Hannes; Johansson, Joel; Rydberg, Claes-Erik; Sandberg, Andreas

    2013-05-01

    Dark halo substructure may reveal itself through secondary, small-scale gravitational lensing effects on light sources that are macrolensed by a foreground galaxy. Here, we explore the prospects of using Very Long Baseline Interferometry (VLBI) observations of multiply-imaged quasar jets to search for submilliarcsecond-scale image distortions produced by various forms of dark substructures in the 103-108 M? mass range. We present lensing simulations relevant for the angular resolutions attainable with the existing European VLBI Network, the global VLBI array and an upcoming observing mode in which the Atacama Large Millimeter Array (ALMA) is connected to the global VLBI array. While observations of this type would not be sensitive to standard cold dark matter subhaloes, they can be used to detect the more compact forms of halo substructure predicted in alternative structure formation scenarios. By mapping approximately five strongly lensed systems, it should be possible to detect or robustly rule out primordial black holes in the 103-106 M? mass range if they constitute ?1 per cent of the dark matter in these lenses. Ultracompact minihaloes are harder to detect using this technique, but 106-108 M? ultracompact minihaloes could in principle be detected if they constitute ?10 per cent of the dark matter.

  10. Peaks above the Maxwellian Sea: a new approach to finding substructures in N-body haloes

    NASA Astrophysics Data System (ADS)

    Elahi, Pascal J.; Thacker, Robert J.; Widrow, Lawrence M.

    2011-11-01

    We describe a new algorithm for finding substructures within dark matter haloes from N-body simulations. The algorithm relies upon the fact that dynamically distinct substructures in a halo will have a local velocity distribution that differs significantly from the mean, i.e. smooth background halo. We characterize the large-scale mean field using a coarsely grained cell-based approach, while a kernel-smoothing process is used to determined the local velocity distribution. Comparing the ratio of these two estimates allows us to identify particles that are strongly clustered in velocity space relative to the background and thus resident in a substructure. From this population of outliers, groups are identified using a Friends-of-Friends-like approach. False positives are rejected using Poisson noise arguments. This approach does not require a search of the full phase-space structure of a halo, a non-trivial task, and is thus computationally advantageous. We apply our algorithm to several test cases and show that it identifies not only subhaloes, bound overdensities in phase space, but can recover tidal streams with a high purity. Our method can even find streams which do not appear significantly overdense either physically or in phase space.

  11. All Sky Search for Gravitational-Wave Bursts in the Second Joint LIGO-Virgo Run

    NASA Technical Reports Server (NTRS)

    Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adhikari, R.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Ajith, P.; Allen, B.; Ceron, E. Amador; Amariutei, D.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Arain, M. A.; Araya, M. C.; Aylott, B. E.; Blackburn, L.; Camp, J. B.; Cannizzo, J.

    2012-01-01

    We present results from a search for gravitational-wave bursts in the data collected by the LIGO and Virgo detectors between July 7, 2009 and October 20, 2010: data are analyzed when at least two of the three LIGO-Virgo detectors are in coincident operation, with a total observation time of 207 days. The analysis searches for transients of duration approx. < 1 s over the frequency band 64-5000 Hz, without other assumptions on the signal wa.veform, polarization, direction or occurrence time. All identified events are c.onsistent with the expected accidental background. We set frequentist upper limits on the rate of gravitational-wave bursts by combining this search with the previous LIGOVirgo search on the data collected "between November 2005 and October 2007. The upper limit on the rate of strong gravita.tional-wave bursts at the Earth is 1.3 events per year at 90% confidence. We also present upper limits on source rate density per yea.r and Mpc3 for sample popula.tions of standard-candle sources. As in the previous joint run, typical sensitivities of the search in terms of the root-sum-squared strain amplitude for these waveforms lie in the range approx 5 x 10(exp -22 Hz(exp-1/2) approx 1 X 10(exp -20) Hz(exp -1/2) . The combination of the two joint runs entails the most sensitive all-sky search for generic gravitational-wave bursts and synthesizes the results achieved by the initial generation of interferometric detectors.

  12. Localization of Short Duration Gravitational-wave Transients with the Early Advanced LIGO and Virgo Detectors

    NASA Astrophysics Data System (ADS)

    Essick, Reed; Vitale, Salvatore; Katsavounidis, Erik; Vedovato, Gabriele; Klimenko, Sergey

    2015-02-01

    The Laser Interferometer Gravitational wave Observatory (LIGO) and Virgo advanced ground-based gravitational-wave detectors will begin collecting science data in 2015. With first detections expected to follow, it is important to quantify how well generic gravitational-wave transients can be localized on the sky. This is crucial for correctly identifying electromagnetic counterparts as well as understanding gravitational-wave physics and source populations. We present a study of sky localization capabilities for two search and parameter estimation algorithms: coherent WaveBurst, a constrained likelihood algorithm operating in close to real-time, and LALInferenceBurst, a Markov chain Monte Carlo parameter estimation algorithm developed to recover generic transient signals with latency of a few hours. Furthermore, we focus on the first few years of the advanced detector era, when we expect to only have two (2015) and later three (2016) operational detectors, all below design sensitivity. These detector configurations can produce significantly different sky localizations, which we quantify in detail. We observe a clear improvement in localization of the average detected signal when progressing from two-detector to three-detector networks, as expected. Although localization depends on the waveform morphology, approximately 50% of detected signals would be imaged after observing 100-200 deg2 in 2015 and 60-110 deg2 in 2016, although knowledge of the waveform can reduce this to as little as 22 deg2. This is the first comprehensive study on sky localization capabilities for generic transients of the early network of advanced LIGO and Virgo detectors, including the early LIGO-only two-detector configuration.

  13. The Next Generation Virgo Cluster Survey. XV. The Photometric Redshift Estimation for Background Sources

    NASA Astrophysics Data System (ADS)

    Raichoor, A.; Mei, S.; Erben, T.; Hildebrandt, H.; Huertas-Company, M.; Ilbert, O.; Licitra, R.; Ball, N. M.; Boissier, S.; Boselli, A.; Chen, Y.-T.; Côté, P.; Cuillandre, J.-C.; Duc, P. A.; Durrell, P. R.; Ferrarese, L.; Guhathakurta, P.; Gwyn, S. D. J.; Kavelaars, J. J.; Lançon, A.; Liu, C.; MacArthur, L. A.; Muller, M.; Muñoz, R. P.; Peng, E. W.; Puzia, T. H.; Sawicki, M.; Toloba, E.; Van Waerbeke, L.; Woods, D.; Zhang, H.

    2014-12-01

    The Next Generation Virgo Cluster Survey (NGVS) is an optical imaging survey covering 104 deg2 centered on the Virgo cluster. Currently, the complete survey area has been observed in the u*giz bands and one third in the r band. We present the photometric redshift estimation for the NGVS background sources. After a dedicated data reduction, we perform accurate photometry, with special attention to precise color measurements through point-spread function homogenization. We then estimate the photometric redshifts with the Le Phare and BPZ codes. We add a new prior that extends to i AB = 12.5 mag. When using the u* griz bands, our photometric redshifts for 15.5 mag <= i <~ 23 mag or z phot <~ 1 galaxies have a bias |?z| < 0.02, less than 5% outliers, a scatter ?outl.rej., and an individual error on z phot that increases with magnitude (from 0.02 to 0.05 and from 0.03 to 0.10, respectively). When using the u*giz bands over the same magnitude and redshift range, the lack of the r band increases the uncertainties in the 0.3 <~ z phot <~ 0.8 range (-0.05 < ?z < -0.02, ?outl.rej ~ 0.06, 10%-15% outliers, and z phot.err. ~ 0.15). We also present a joint analysis of the photometric redshift accuracy as a function of redshift and magnitude. We assess the quality of our photometric redshifts by comparison to spectroscopic samples and by verifying that the angular auto- and cross-correlation function w(?) of the entire NGVS photometric redshift sample across redshift bins is in agreement with the expectations.

  14. Probing the evolution of stellar Andreas Zezas

    E-print Network

    Wolfe, Patrick J.

    Probing the evolution of stellar systems Andreas Zezas Harvard-Smithsonian Center for Astrophysics Branch #12;CMDs : Simple cases #12;The tools : Stellar Tracks (| age, Mass, Z, stellar evolution) #12

  15. Search for gravitational radiation from intermediate mass black hole binaries in data from the second LIGO-Virgo joint science run

    E-print Network

    Aggarwal, Nancy

    This paper reports on an unmodeled, all-sky search for gravitational waves from merging intermediate mass black hole binaries (IMBHB). The search was performed on data from the second joint science run of the LIGO and Virgo ...

  16. Multimessenger search for sources of gravitational waves and high-energy neutrinos: Initial results for LIGO-Virgo and IceCube

    E-print Network

    Aartsen, M.?G.

    We report the results of a multimessenger search for coincident signals from the LIGO and Virgo gravitational-wave observatories and the partially completed IceCube high-energy neutrino detector, including periods of joint ...

  17. Stellar complexes in M33

    E-print Network

    G. R. Ivanov

    2004-07-02

    A method for identification of stellar complexes in M33 is applied. Several OB associations form a stellar complex with mean size of 0.3 - 1 kpc. We apply a correlation technique to compare different stellar populations in M33. Our results confirm the existence of a strong correlation between OB stars, HII regions and WR stars, which trace the regions of massive star formation. There is a good correlation between red supergiants (RSGs) and WR stars in the spiral arms of M33. This can be expected since the progenitors of WR stars are massive OB stars or RSGs with masses greater than 20 M_sun. The massive RSGs and WR stars probably originate from nearby sites of star formation. We consider this fact as a ground for identification of stellar complexes in M33. The presented method for identification of stellar complexes can be applied to other nearby galaxies.

  18. Sharpening stellar images.

    PubMed

    Buffington, A; Crawford, F S; Pollaine, S M; Orth, C D; Muller, R A

    1978-05-01

    Atmospherically induced phase perturbations have for years limited the resolution of large optical astronomical telescopes. A prototype telescope system with six movable elements has successfully corrected these phase perturbations. This use of real-time image sharpening has restored stellar images to the diffraction limit (in one dimension) for a 30-centimeter telescope. The double-star image presented indicates that the bulk of the atmospherically induced wave-front phase change occurred within 2 kilometers of the telescope. This implies that, at least for conditions similar to those of our measurement, real-time correction can be accomplished simultaneously for a region at least several arc seconds in angular size. With the present apparatus the technique should be practical for objects as dim as fifth magnitude, and with improvements the technique holds the promise of active image restoration for objects as dim as ninth magnitude. PMID:17839416

  19. The stellar opacities

    NASA Astrophysics Data System (ADS)

    Turck-Chièze, S.; Gilles, D.; Gilleron, F.; Pain, J. C.

    2013-11-01

    Opacities are fundamental ingredients of stellar physics. Helioseismology and asteroseismology have put in evidence anomalies that could be attributed to an insufficient knowledge of the photon-plasma interactions. We work on a revision of this plasma physics in the conditions where the anomalies have been found: the region of the iron opacity peak near log T= 5.2 and the inner radiative region of Sun and solar-like stars. The international OPAC consortium performs new calculations, compares them and looks for the origin of their differences. In parallel, experimental campaigns are realized, others are in preparation to validate some conclusions on the reliability of the new proposed calculations. New tables for astrophysics will be performed in the framework of the ANR OPACITY and their influence on seismic observables will be studied. We explicit here the difficulty of the computations together with some computation resources.

  20. Early stellar evolution

    NASA Technical Reports Server (NTRS)

    Stahler, Steven W.

    1994-01-01

    Research into the formation and early evolution of stars is currently an area of great interest and activity. The theoretical and observational foundations for this development are reviewed in this paper. By now, the basic physics governing cloud collapse is well understood, as is the structure of the resulting protostars. However, the theory predicts protostellar luminosities that are greater than those of most infrared sources. Observationally, it is thought that protostars emit powerful winds that push away remnant cloud gas, but both the origin of these winds and the nature of their interaction with ambient gas are controversial. Finally, the theory of pre-main-sequence stars has been modified to incorporate more realistic initial conditions. This improvement helps to explain the distribution of such stars in the H-R diagram. Many important issues, such as the origin of binary stars and stellar clusters, remain as challenges for future research.

  1. Asteroseismic stellar activity relations

    NASA Astrophysics Data System (ADS)

    Bonanno, A.; Corsaro, E.; Karoff, C.

    2014-11-01

    Context. In asteroseismology an important diagnostic of the evolutionary status of a star is the small frequency separation which is sensitive to the gradient of the mean molecular weight in the stellar interior. It is thus interesting to discuss the classical age-activity relations in terms of this quantity. Moreover, as the photospheric magnetic field tends to suppress the amplitudes of acoustic oscillations, it is important to quantify the importance of this effect by considering various activity indicators. Aims: We propose a new class of age-activity relations that connects the Mt. Wilson S index and the average scatter in the light curve with the small frequency separation and the amplitude of the p-mode oscillations. Methods: We used a Bayesian inference to compute the posterior probability of various empirical laws for a sample of 19 solar-like active stars observed by the Kepler telescope. Results: We demonstrate the presence of a clear correlation between the Mt. Wilson S index and the relative age of the stars as indicated by the small frequency separation, as well as an anti-correlation between the S index and the oscillation amplitudes. We argue that the average activity level of the stars shows a stronger correlation with the small frequency separation than with the absolute age that is often considered in the literature. Conclusions: The phenomenological laws discovered in this paper have the potential to become new important diagnostics to link stellar evolution theory with the dynamics of global magnetic fields. In particular we argue that the relation between the Mt. Wilson S index and the oscillation amplitudes is in good agreement with the findings of direct numerical simulations of magneto-convection.

  2. Alaska Athabascan stellar astronomy

    NASA Astrophysics Data System (ADS)

    Cannon, Christopher M.

    Stellar astronomy is a fundamental component of Alaska Athabascan cultures that facilitates time-reckoning, navigation, weather forecasting, and cosmology. Evidence from the linguistic record suggests that a group of stars corresponding to the Big Dipper is the only widely attested constellation across the Northern Athabascan languages. However, instruction from expert Athabascan consultants shows that the correlation of these names with the Big Dipper is only partial. In Alaska Gwich'in, Ahtna, and Upper Tanana languages the Big Dipper is identified as one part of a much larger circumpolar humanoid constellation that spans more than 133 degrees across the sky. The Big Dipper is identified as a tail, while the other remaining asterisms within the humanoid constellation are named using other body part terms. The concept of a whole-sky humanoid constellation provides a single unifying system for mapping the night sky, and the reliance on body-part metaphors renders the system highly mnemonic. By recognizing one part of the constellation the stargazer is immediately able to identify the remaining parts based on an existing mental map of the human body. The circumpolar position of a whole-sky constellation yields a highly functional system that facilitates both navigation and time-reckoning in the subarctic. Northern Athabascan astronomy is not only much richer than previously described; it also provides evidence for a completely novel and previously undocumented way of conceptualizing the sky---one that is unique to the subarctic and uniquely adapted to northern cultures. The concept of a large humanoid constellation may be widespread across the entire subarctic and have great antiquity. In addition, the use of cognate body part terms describing asterisms within humanoid constellations is similarly found in Navajo, suggesting a common ancestor from which Northern and Southern Athabascan stellar naming strategies derived.

  3. COLD DARK MATTER SUBSTRUCTURE AND GALACTIC DISKS. II. DYNAMICAL EFFECTS OF HIERARCHICAL SATELLITE ACCRETION

    SciTech Connect

    Kazantzidis, Stelios [Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States); Zentner, Andrew R. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Kravtsov, Andrey V. [Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States); Bullock, James S. [Center for Cosmology, University of California at Irvine, Irvine, CA 92697 (United States); Debattista, Victor P. [Center for Astrophysics, University of Central Lancashire, Preston PR1 2HE (United Kingdom)], E-mail: stelios@mps.ohio-state.edu, E-mail: Zentner@pitt.edu, E-mail: andrey@oddjob.uchicago.edu, E-mail: bullock@uci.edu, E-mail: vpdebattista@uclan.ac.uk

    2009-08-01

    We perform a set of fully self-consistent, dissipationless N-body simulations to elucidate the dynamical response of thin galactic disks to bombardment by cold dark matter (CDM) substructure. Our method combines (1) cosmological simulations of the formation of Milky Way (MW)-sized CDM halos to derive the properties of substructure, and (2) controlled numerical experiments of consecutive subhalo impacts onto an initially thin, fully formed MW-type disk galaxy. The present study is the first to account for the evolution of satellite populations over cosmic time in such an investigation of disk structure. In contrast to what can be inferred from statistics of the z = 0 surviving substructure, we find that accretions of massive subhalos onto the central regions of host halos, where the galactic disks reside, since z {approx} 1 should be common. One host halo accretion history is used to initialize the controlled simulations of satellite-disk encounters. The specific merger history involves six dark matter substructures, with initial masses in the range {approx}20%-60% of the disk mass and of comparable size to the disk, crossing the central regions of their host in the past {approx}8 Gyr. We show that these accretion events severely perturb the thin galactic disk and produce a wealth of distinctive dynamical signatures on its structure and kinematics. These include (1) considerable thickening and heating at all radii, with the disk thickness and velocity ellipsoid nearly doubling at the solar radius; (2) prominent flaring associated with an increase in disk thickness greater than a factor of 4 in the disk outskirts; (3) surface density excesses at large radii, beyond {approx}5 disk scale lengths, resembling those of the observed antitruncated disks; (4) long-lived, lopsidedness at levels similar to those measured in observational samples of disk galaxies; and (5) substantial tilting. The interaction with the most massive subhalo in the simulated accretion history drives the disk response while subsequent bombardment is much less efficient at disturbing the disk. We also explore a variety of disk and satellite properties that influence these responses. We conclude that substructure-disk encounters of the kind expected in the {lambda}CDM paradigm play a significant role in setting the structure of disk galaxies and driving galaxy evolution.

  4. 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; Krajnovi?, 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, ?e, 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.

  5. Stellar populations of early-type galaxies in different environments II. Ages and metallicities

    E-print Network

    P. Sanchez-Blazquez; J. Gorgas; N. Cardiel; J. J. Gonzalez

    2006-04-27

    This is the second paper of a series devoted to study the stellar content of early-type galaxies. The goal of the series is to set constraints on the evolutionary status of these objects. We use a new set of models which include an improved stellar library (MILES) to derive simple stellar population (SSP)-equivalent parameters in a sample of 98 early-type galaxies. The sample contains galaxies in the field, poor groups, and galaxies in the Virgo and Coma clusters.We find that low-density environment galaxies span a larger range in SSP age and metallicity than their counterparts in high density environments, with a tendency for lower sigma galaxies to be younger. Early-type galaxies in low-density environments appear on average ~1.5 Gyr younger and more metal rich than their counterparts in high density environments. The sample of low-density environment galaxies shows an age metallicity relation in which younger galaxies are found to be more metal rich, but only when metallicity is measured with a Fe-sensitive index. Conversely, there is no age-metallicity relation when the metallicity is measured with a Mg sensitive index. The mass-metallicity relation is only appreciable for the low-density environment galaxies when the metallicity is measured with a Mg-sensitive index and not when the metallicity is measured with other indicators. On the contrary, this relation exists for the high-density environment galaxies independently of the indicator used to measure the metallicity. This suggests a dependence of the mass-metallicity relation on the environment of the galaxies. Our data favour a scenario in which galaxies in low density environments have suffered a more extended star formation history than the galaxies in the Coma cluster, which appear to host more homogenous stellar populations.

  6. A First Search for Coincident Gravitational Waves and High Energy Neutrinos Using LIGO, Virgo and ANTARES Data from 2007

    NASA Technical Reports Server (NTRS)

    Adrian-Martinez, S.; Samarai, Al; Albert, A.; Andre, M.; Anghinolfi, M.; Anton, G.; Anvar, S.; Ardid, M; Astraatmadja, T.; Aubert, J.-J.; Baret, B.; Basa, S.; Bertin, V.; Biagi, S.; Bigongiari, C.; Bogazzi, C; Bou-Cabo, M.; Bouhou, B.; Bowhuis, M. C.; Bertin, V.; Brunner, J.; Busto, J.; Blackburn, L.; Camp, J. B.; Kanner, J. B.

    2013-01-01

    We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.

  7. H I detection survey of a complete magnitude-limited sample of dwarf irregular galaxies in the Virgo Cluster area

    NASA Technical Reports Server (NTRS)

    Hoffman, G. Lyle; Glosson, John; Helou, George; Salpeter, E. E.; Sandage, A.

    1987-01-01

    New single-beam Arecibo H I observations of 298 late-type galaxies in the Virgo Cluster drawn mostly from the new catalog of Binggeli, Sandage, and Tammann (1985) are presented. Two hundred seventeen of these constitute a magnitude-limited 'complete sample' of such galaxies, types Sdm through Im and BCD. Sixty-one percent of this 'complete sample' was detected, greatly enhancing the store of redshifts and H I masses for such galaxies in the Virgo Cluster. For detected galaxies, heliocentric velocities, 50 percent profile widths, and single-beam fluxes are presented. For those that escaped detection, upper limits are computed to the flux appropriate to the redshift range (-600 to +3000 km/s).

  8. The Hibernating Stellar Magnet

    NASA Astrophysics Data System (ADS)

    2008-09-01

    First Optically Active Magnetar-Candidate Discovered Astronomers have discovered a most bizarre celestial object that emitted 40 visible-light flashes before disappearing again. It is most likely to be a missing link in the family of neutron stars, the first case of an object with an amazingly powerful magnetic field that showed some brief, strong visible-light activity. Hibernating Stellar Magnet ESO PR Photo 31/08 The Hibernating Stellar Magnet This weird object initially misled its discoverers as it showed up as a gamma-ray burst, suggesting the death of a star in the distant Universe. But soon afterwards, it exhibited some unique behaviour that indicates its origin is much closer to us. After the initial gamma-ray pulse, there was a three-day period of activity during which 40 visible-light flares were observed, followed by a brief near-infrared flaring episode 11 days later, which was recorded by ESO's Very Large Telescope. Then the source became dormant again. "We are dealing with an object that has been hibernating for decades before entering a brief period of activity", explains Alberto J. Castro-Tirado, lead author of a paper in this week's issue of Nature. The most likely candidate for this mystery object is a 'magnetar' located in our own Milky Way galaxy, about 15 000 light-years away towards the constellation of Vulpecula, the Fox. Magnetars are young neutron stars with an ultra-strong magnetic field a billion billion times stronger than that of the Earth. "A magnetar would wipe the information from all credit cards on Earth from a distance halfway to the Moon," says co-author Antonio de Ugarte Postigo. "Magnetars remain quiescent for decades. It is likely that there is a considerable population in the Milky Way, although only about a dozen have been identified." Some scientists have noted that magnetars should be evolving towards a pleasant retirement as their magnetic fields decay, but no suitable source had been identified up to now as evidence for this evolutionary scheme. The newly discovered object, known as SWIFT J195509+261406 and showing up initially as a gamma-ray burst (GRB 070610), is the first candidate. The magnetar hypothesis for this object is reinforced by another analysis, based on another set of data, appearing in the same issue of Nature.

  9. Structural sandwich construction is used in many air and space vehicles, cargo containers, boats and ships. Connection of the sandwich construction component to a framework or substructure

    E-print Network

    Vel, Senthil

    , boats and ships. Connection of the sandwich construction component to a framework or substructure vehicles, ships, boats, cargo containers and residential construction. Sandwich construction provide

  10. Formation of giant globular cluster G1 and the origin of the M31 stellar halo

    E-print Network

    Kenji Bekki; Masashi Chiba

    2004-01-13

    We first demonstrate that globular cluster G1 could have been formed by tidal interaction between M31 and a nucleated dwarf galaxy (dE,N). Our fully self-consistent numerical simulations show that during tidal interaction between M31 and G1's progenitor dE,N with $M_{\\rm B}$ $\\sim$ -15 mag and its nucleus mass of $\\sim$ $10^7$ $M_{\\odot}$, the dark matter and the outer stellar envelope of the dE,N are nearly completely stripped whereas the nucleus can survive the tidal stripping because of its initially compact nature. The naked nucleus (i.e., G1) has orbital properties similar to those of its progenitor dE,N. The stripped stars form a metal-poor ([Fe/H] $\\sim$ -1) stellar halo around M31 and its structure and kinematics depend strongly on the initial orbit of G1's progenitor dE,N. We suggest that the observed large projected distance of G1 from M31 ($\\sim$ 40 kpc) can give some strong constraints on the central density of the dark matter halo of dE,N. We discuss these results in the context of substructures of M31's stellar halo recently revealed by Ferguson et al. (2002).

  11. Stellarator helical vacuum vessel

    SciTech Connect

    Yavornik, E.J.

    1983-01-01

    A design study of a stainless steel, heavy wall, helically shaped vacuum torus has been made for use in a proposed Stellarator configuration. The study concerns itself with the shape of the vacuum vessel and the division of the vessel into components that can be machined and welded together into a helical configuration. A complication in the design requires that a circular magnet coil be located at the minor toroidal axis and that this coil be embedded within the periphery of the vacuum vessel. The vacuum vessel has a minor toroidal axis diameter of 4 meters, a 68.6-cm shell diameter, and a 1.9-cm wall thickness. It twists about the minor toroidal axis twice in 360/sup 0/C. (An n value of 2). It is proposed that the unit be made of cylindrical segments with the ends of the cylinders cut at appropriate lengths and angles to form the helix. A mathematical derivation of the dimensions necessary to produce the required shapes of the segments has been made. Also, drawings of the vacuum vessel components have been produced on LANL's CTR CAD/CAM system. The procedure developed can be used for any value of n as dictated by physics requirements.

  12. SI: The Stellar Imager

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita

    2006-01-01

    The ultra-sharp images of the Stellar Imager (SI) will revolutionize our view of many dynamic astrophysical processes: The 0.1 milliarcsec resolution of this deep-space telescope will transform point sources into extended sources, and simple snapshots into spellbinding evolving views. SI s science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI 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 by imaging a sample of magnetically active stars with enough resolution to map their evolving dynamo patterns and their internal flows. By exploring the Universe at ultra-high resolution, SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magnetohydrodynamically controlled structures and processes in the Universe.

  13. Detection Rate Estimates of Gravity-waves Emitted During Parabolic Encounters of Stellar Black Holes in Globular Clusters

    E-print Network

    Kocsis, B; Marka, S; Gaspar, Merse E.; Kocsis, Bence; Marka, Szabolcs

    2006-01-01

    The rapid advance of gravitational-wave (GW) detector facilities makes it very important to estimate the event rates of possible detection candidates. We consider an additional possibility of GW bursts produced during parabolic encounters (PEs) of stellar mass compact objects. We estimate the rate of successful detections for specific detectors: the initial Laser Interferometric Gravitational-Wave Observatory (InLIGO), the French-Italian gravitational-wave antenna VIRGO, the near-future Advanced-LIGO (AdLIGO), the space-based Laser Interferometric Space Antenna (LISA), and the Next Generation LISA (NGLISA). Simple GC models are constructed to account for the compact object mass function, mass segregation, number density distribution, and velocity distribution. We calculate encounters both classically and account for general relativistic corrections by extrapolating the results for infinite mass ratios. We also include the cosmological redshift of waveforms and event rates. We find that typical PEs with masses...

  14. All-sky search for gravitational-wave bursts in the first joint LIGO-GEO-Virgo run

    SciTech Connect

    Abadie, J.; Abbott, B. P.; Abbott, R.; Adhikari, R.; Ajith, P.; Anderson, S. B.; Araya, M.; Aso, Y.; Ballmer, S.; Betzwieser, J.; Billingsley, G.; Black, E.; Blackburn, J. K.; Bork, R.; Brooks, A. F.; Cannon, K. C.; Cardenas, L.; Cepeda, C.; Chalermsongsak, T.; Chatterji, S. [LIGO - California Institute of Technology, Pasadena, California 91125 (United States)

    2010-05-15

    We present results from an all-sky search for unmodeled gravitational-wave bursts in the data collected by the LIGO, GEO 600 and Virgo detectors between November 2006 and October 2007. The search is performed by three different analysis algorithms over the frequency band 50-6000 Hz. Data are analyzed for times with at least two of the four LIGO-Virgo detectors in coincident operation, with a total live time of 266 days. No events produced by the search algorithms survive the selection cuts. We set a frequentist upper limit on the rate of gravitational-wave bursts impinging on our network of detectors. When combined with the previous LIGO search of the data collected between November 2005 and November 2006, the upper limit on the rate of detectable gravitational-wave bursts in the 64-2048 Hz band is 2.0 events per year at 90% confidence. We also present event rate versus strength exclusion plots for several types of plausible burst waveforms. The sensitivity of the combined search is expressed in terms of the root-sum-squared strain amplitude for a variety of simulated waveforms and lies in the range 6x10{sup -22} Hz{sup -1/2} to 2x10{sup -20} Hz{sup -1/2}. This is the first untriggered burst search to use data from the LIGO and Virgo detectors together, and the most sensitive untriggered burst search performed so far.

  15. All-Sky Search for Gravitational-Wave Bursts in the First Joint LIGO-GEO-Virgo Run

    NASA Technical Reports Server (NTRS)

    Camp, J. B.; Camizzo, J.

    2012-01-01

    We present results from an aU-sky search for unmodeled gravitational-wave bursts in the data collected by the LIGO, GEO 600 and Virgo detectors between November 2006 and October 2007. The search is performed. by three different analysis algorithms over the frequency band 50 - 6000 Hz. Data are analyzed for times with at least two of the four LIGO-Virgo detectors in coincident operation, with a total live time of 266 days, No events produced by the search algorithms survive the selection cuts. We set a frequentist upper limit on the rate of gravitational-wave bursts impinging on our network of detectors. When combined with the previous LIGO search of the data collected between November 2005 and November 2006, the upper limit on the rate of detectable gra.vitational. wave bursts in the 64-2048 Hz band is 2,0 events per year at 90% confidence. We also present event rate versus strength exclusion plots for several types of plausible burst waveforms. The sensitivity of the combined search is expressed in terms of the root-sum-squared strain amplitude for a variety of simulated waveforms and lies in the range 6 X 10(exp -22) Hz(exp - 1/2) to 2 X 10(exp -20) Hz(exp -l/2). This is the first untriggered burst search to use data from the LIGO and Virgo detectors together, and the most sensitive untriggered burst search performed so far.

  16. All-sky search for gravitational-wave bursts in the second joint LIGO-Virgo run

    E-print Network

    the LIGO Scientific Collaboration; the Virgo Collaboration; J. Abadie; B. P. Abbott; R. Abbott; T. D. Abbott; M. Abernathy; T. Accadia; F. Acernese; C. Adams; R. Adhikari; C. Affeldt; M. Agathos; K. Agatsuma; P. Ajith; B. Allen; E. Amador Ceron; D. Amariutei; S. B. Anderson; W. G. Anderson; K. Arai; M. A. Arain; M. C. Araya; S. M. Aston; P. Astone; D. Atkinson; P. Aufmuth; C. Aulbert; B. E. Aylott; S. Babak; P. Baker; G. Ballardin; S. Ballmer; J. C. B. Barayoga; D. Barker; F. Barone; B. Barr; L. Barsotti; M. Barsuglia; M. A. Barton; I. Bartos; R. Bassiri; M. Bastarrika; A. Basti; J. Batch; J. Bauchrowitz; Th. S. Bauer; M. Bebronne; D. Beck; B. Behnke; M. Bejger; M. G. Beker; A. S. Bell; A. Belletoile; I. Belopolski; M. Benacquista; J. M. Berliner; A. Bertolini; J. Betzwieser; N. Beveridge; P. T. Beyersdorf; I. A. Bilenko; G. Billingsley; J. Birch; R. Biswas; M. Bitossi; M. A. Bizouard; E. Black; J. K. Blackburn; L. Blackburn; D. Blair; B. Bland; M. Blom; O. Bock; T. P. Bodiya; C. Bogan; R. Bondarescu; F. Bondu; L. Bonelli; R. Bonnand; R. Bork; M. Born; V. Boschi; S. Bose; L. Bosi; B. Bouhou; S. Braccini; C. Bradaschia; P. R. Brady; V. B. Braginsky; M. Branchesi; J. E. Brau; J. Breyer; T. Briant; D. O. Bridges; A. Brillet; M. Brinkmann; V. Brisson; M. Britzger; A. F. Brooks; D. A. Brown; T. Bulik; H. J. Bulten; A. Buonanno; J. Burguet-Castell; D. Buskulic; C. Buy; R. L. Byer; L. Cadonati; G. Cagnoli; E. Calloni; J. B. Camp; P. Campsie; J. Cannizzo; K. Cannon; B. Canuel; J. Cao; C. D. Capano; F. Carbognani; L. Carbone; S. Caride; S. Caudill; M. Cavaglia; F. Cavalier; R. Cavalieri; G. Cella; C. Cepeda; E. Cesarini; O. Chaibi; T. Chalermsongsak; P. Charlton; E. Chassande-Mottin; S. Chelkowski; W. Chen; X. Chen; Y. Chen; A. Chincarini; A. Chiummo; H. Cho; J. Chow; N. Christensen; S. S. Y. Chua; C. T. Y. Chung; S. Chung; G. Ciani; D. E. Clark; J. Clark; J. H. Clayton; F. Cleva; E. Coccia; P. -F. Cohadon; C. N. Colacino; J. Colas; A. Colla; M. Colombini; A. Conte; R. Conte; D. Cook; T. R. Corbitt; M. Cordier; N. Cornish; A. Corsi; C. A. Costa; M. Coughlin; J. -P. Coulon; P. Couvares; D. M. Coward; M. Cowart; D. C. Coyne; J. D. E. Creighton; T. D. Creighton; A. M. Cruise; A. Cumming; L. Cunningham; E. Cuoco; R. M. Cutler; K. Dahl; S. L. Danilishin; R. Dannenberg; S. D'Antonio; K. Danzmann; V. Dattilo; B. Daudert; H. Daveloza; M. Davier; E. J. Daw; R. Day; T. Dayanga; R. De Rosa; D. DeBra; G. Debreczeni; W. Del Pozzo; M. del Prete; T. Dent; V. Dergachev; R. DeRosa; R. DeSalvo; S. Dhurandhar; L. Di Fiore; A. Di Lieto; I. Di Palma; M. Di Paolo Emilio; A. Di Virgilio; M. Diaz; A. Dietz; F. Donovan; K. L. Dooley; M. Drago; R. W. P. Drever; J. C. Driggers; Z. Du; J. -C. Dumas; T. Eberle; M. Edgar; M. Edwards; A. Effler; P. Ehrens; G. Endroczi; R. Engel; T. Etzel; K. Evans; M. Evans; T. Evans; M. Factourovich; V. Fafone; S. Fairhurst; Y. Fan; B. F. Farr; D. Fazi; H. Fehrmann; D. Feldbaum; F. Feroz; I. Ferrante; F. Fidecaro; L. S. Finn; I. Fiori; R. P. Fisher; R. Flaminio; M. Flanigan; S. Foley; E. Forsi; L. A. Forte; N. Fotopoulos; J. -D. Fournier; J. Franc; S. Frasca; F. Frasconi; M. Frede; M. Frei; Z. Frei; A. Freise; R. Frey; T. T. Fricke; D. Friedrich; P. Fritschel; V. V. Frolov; M. -K. Fujimoto; P. J. Fulda; M. Fyffe; J. Gair; M. Galimberti; L. Gammaitoni; J. Garcia; F. Garufi; M. E. Gaspar; G. Gemme; R. Geng; E. Genin; A. Gennai; L. A. Gergely; S. Ghosh; J. A. Giaime; S. Giampanis; K. D. Giardina; A. Giazotto; S. Gil; C. Gill; J. Gleason; E. Goetz; L. M. Goggin; G. Gonzalez; M. L. Gorodetsky; S. Gossler; R. Gouaty; C. Graef; P. B. Graff; M. Granata; A. Grant; S. Gras; C. Gray; N. Gray; R. J. S. Greenhalgh; A. M. Gretarsson; C. Greverie; R. Grosso; H. Grote; S. Grunewald; G. M. Guidi; R. Gupta; E. K. Gustafson; R. Gustafson; T. Ha; J. M. Hallam; D. Hammer; G. Hammond; J. Hanks; C. Hanna; J. Hanson; A. Hardt; J. Harms; G. M. Harry; I. W. Harry; E. D. Harstad; M. T. Hartman; K. Haughian; K. Hayama; J. -F. Hayau; J. Heefner; A. Heidmann; M. C. Heintze; H. Heitmann; P. Hello; M. A. Hendry; I. S. Heng; A. W. Heptonstall; V. Herrera; M. Hewitson; S. Hild; D. Hoak; K. A. Hodge; K. Holt; M. Holtrop; T. Hong; S. Hooper; D. J. Hosken; J. Hough; E. J. Howell; B. Hughey; S. Husa; S. H. Huttner; R. Inta; T. Isogai; A. Ivanov; K. Izumi; M. Jacobson; E. James; Y. J. Jang; P. Jaranowski; E. Jesse; W. W. Johnson; D. I. Jones; G. Jones; R. Jones; L. Ju; P. Kalmus; V. Kalogera; S. Kandhasamy; G. Kang; J. B. Kanner; R. Kasturi; E. Katsavounidis; W. Katzman; H. Kaufer; K. Kawabe; S. Kawamura; F. Kawazoe; D. Kelley; W. Kells; D. G. Keppel; Z. Keresztes; A. Khalaidovski; F. Y. Khalili; E. A. Khazanov; B. Kim; C. Kim; H. Kim; K. Kim; N. Kim; Y. -M. Kim; P. J. King; D. L. Kinzel; J. S. Kissel; S. Klimenko; K. Kokeyama; V. Kondrashov; S. Koranda; W. Z. Korth; I. Kowalska; D. Kozak; O. Kranz; V. Kringel; S. Krishnamurthy

    2012-04-20

    We present results from a search for gravitational-wave bursts in the data collected by the LIGO and Virgo detectors between July 7, 2009 and October 20, 2010: data are analyzed when at least two of the three LIGO-Virgo detectors are in coincident operation, with a total observation time of 207 days. The analysis searches for transients of duration < 1 s over the frequency band 64-5000 Hz, without other assumptions on the signal waveform, polarization, direction or occurrence time. All identified events are consistent with the expected accidental background. We set frequentist upper limits on the rate of gravitational-wave bursts by combining this search with the previous LIGO-Virgo search on the data collected between November 2005 and October 2007. The upper limit on the rate of strong gravitational-wave bursts at the Earth is 1.3 events per year at 90% confidence. We also present upper limits on source rate density per year and Mpc^3 for sample populations of standard-candle sources. As in the previous joint run, typical sensitivities of the search in terms of the root-sum-squared strain amplitude for these waveforms lie in the range 5 10^-22 Hz^-1/2 to 1 10^-20 Hz^-1/2. The combination of the two joint runs entails the most sensitive all-sky search for generic gravitational-wave bursts and synthesizes the results achieved by the initial generation of interferometric detectors.

  17. Stellar populations of early-type galaxies in different environments I. Line-strength indices

    E-print Network

    P. Sanchez-Blazquez; J. Gorgas; N. Cardiel; J. Gonzalez

    2006-04-27

    Aims: This paper commences a series devoted to the study of the stellar content of early-type galaxies. The goal of the series is to set constraints on the evolutionary status of these objects. Methods: In this paper we describe the details of the galaxy sample, the observations, and the data reduction. Line-strength indices and velocity dispersions sigma are measured in 98 early-type galaxies drawn from different environments, and the relation of the indices with the velocity dispersion analysed in detail. Results: The present sample indicates that some of the index-sigma relations depend on galaxy environment. In particular, the slope of the relation between Balmer lines and sigma is steeper for galaxies in the Virgo cluster, small groups, and in the field than for galaxies in the Coma cluster. In several indices there is also a significant offset in the zero point between the relations defined by the different subsamples. The slopes of the index-sigma relation for the Virgo and low-density environment galaxies are explained by a variation of both age and metallicity with velocity dispersion, as previously noted in other studies. For the galaxies in the Coma cluster, however, the relation of the indices with sigma only requires a variation of the abundance along the sigma sequence. In agreement with other studies we find that the models that better reproduce the slopes are those in which the alpha elements vary more than the Fe-peak elements along the sigma sequence, while, at a given sigma, older galaxies show an higher alpha/Fe ratio. Conclusions: The results can be explained assuming that galaxies in the Coma cluster have experienced a truncated star formation and chemical enrichment history compared to a more continuous time-extended history for their counterparts in lower density environments.

  18. Drift waves in stellarator geometry

    SciTech Connect

    Persson, M.; Nadeem, M.; Lewandowski, J.L.V.; Gardner, H.J.

    2000-02-07

    Drift waves are investigated in a real three-dimensional stellarator geometry. A linear system, based on the cold ion fluid model and a ballooning mode formalism, is solved numerically in the geometry of the stellarator H1-NF. The spectra of stable and unstable modes, as well as localization, are discussed. The dependence of the spectrum of the unstable modes on the wavevector, plasma density variation, and the location in the plasma is presented.

  19. Quantified H I morphology - V. H I discs in the Virgo cluster

    NASA Astrophysics Data System (ADS)

    Holwerda, B. W.; Pirzkal, N.; de Blok, W. J. G.; van Driel, W.

    2011-10-01

    We explore the quantified morphology of atomic hydrogen (H I) discs in the Virgo cluster. These galaxies display a wealth of phenomena in their H I morphology, e.g., tails, truncation and warps. These morphological disturbances are related to the ram pressure stripping and tidal interaction that galaxies undergo in this dense cluster environment. To quantify the morphological transformation of the H I discs, we compute the morphological parameters of Concentration, Asymmetry, Smoothness, Gini and M20 and our own GM for 51 galaxies in 48 H I column density maps from the VLA Imaging of Virgo spirals in Atomic gas (VIVA) project. Some morphological phenomena can be identified in this space of relatively low-resolution H I data. Truncation of the H I disc can be cleanly identified via the Concentration parameter (C < 1), and Concentration can also be used to identify H I deficient discs (1 < C < 5). Tidal interaction is typically identified using combinations of these morphological parameters, applied to (optical) images of galaxies. We find that some selection criteria (Gini-M20, Asymmetry and a modified Concentration-M20) are still applicable for the coarse (˜15 arcsec full width at half - maximum) VIVA H I data. We note that Asymmetry is strongly affected by the choice for the centre of these galaxies. The phenomena of tidal tails can be reasonably well identified using the Gini-M20 criterion (60 per cent of galaxies with tails identified but with as many contaminants). Ram pressure does move H I discs into and out of most of our interaction criteria: the ram pressure sequence identified by previous authors tracks into and out of some of these criteria (Asymmetry-based and the Gini-M20 selections, but not the Concentration-M20 or the GM-based ones). Therefore, future searches for interaction using H I morphologies should take ram pressure into account as a mechanism to disturb H I discs enough to make them appear as gravitationally interacting. One mechanism would be to remove all the H I deficient (C < 5) discs from the sample, as these have undergone more than one H I removal mechanism.

  20. STELLAR POPULATION MODELS AND INDIVIDUAL ELEMENT ABUNDANCES. I. SENSITIVITY OF STELLAR EVOLUTION MODELS

    E-print Network

    Lee, Hyun-chul

    STELLAR POPULATION MODELS AND INDIVIDUAL ELEMENT ABUNDANCES. I. SENSITIVITY OF STELLAR EVOLUTION spectra but little has been done to address similar issues in the stellar evolution models that underlie most stellar population models. Stellar evolution models will primarily be influenced by changes

  1. Dark Matter Substructure and Gamma-Ray Annihilation in the Milky Way Halo

    Microsoft Academic Search

    Jürg Diemand; Michael Kuhlen; Piero Madau

    2007-01-01

    We present initial results from ``Via Lactea,'' the highest resolution simulation to date of Galactic CDM substructure. It follows the formation of a Milky Way-sized halo with Mhalo=1.8×1012 Msolar in a WMAP three-year cosmology, using 234 million particles. Over 10,000 subhalos can be identified at z=0: their cumulative mass function is well-fit by N(>Msub)=0.0064(Msub\\/Mhalo)-1 down to Msub=4×106 Msolar. The total

  2. Predicting target-ligand interactions using protein ligand-binding site and ligand substructures

    PubMed Central

    2015-01-01

    Background Cell proliferation, differentiation, Gene expression, metabolism, immunization and signal transduction require the participation of ligands and targets. It is a great challenge to identify rules governing molecular recognition between chemical topological substructures of ligands and the binding sites of the targets. Methods We suppose that the ligand-target interactions are determined by ligand substructures as well as the physical-chemical properties of the binding sites. Therefore, we propose a fragment interaction model (FIM) to describe the interactions between ligands and targets, with the purpose of facilitating the chemical interpretation of ligand-target binding. First we extract target-ligand complexes from sc-PDB database, based on which, we get the target binding sites and the ligands. Then we represent each binding site as a fragment vector based on a target fragment dictionary that is composed of 199 clusters (denoted as fragements in this work) obtained by clustering 4200 trimers according to their physical-chemical properties. And then, we represent each ligand as a substructure vector based on a dictionary containing 747 substructures. Finally, we build the FIM by generating the interaction matrix M (representing the fragment interaction network), and the FIM can later be used for predicting unknown ligand-target interactions as well as providing the binding details of the interactions. Results The five-fold cross validation results show that the proposed model can get higher AUC score (92%) than three prevalence algorithms CS-PD (80%), BLM-NII (85%) and RF (85%), demonstrating the remarkable predictive ability of FIM. We also show that the ligand binding sites (local information) overweight the sequence similarities (global information) in ligand-target binding, and introducing too much global information would be harmful to the predictive ability. Moreover, The derived fragment interaction network can provide the chemical insights on the interactions. Conclusions The target and ligand bindings are local events, and the local information dominate the binding ability. Though integrating of the global information can promote the predictive ability, the role is very limited. The fragment interaction network is helpful for understanding the mechanism of the ligand-target interaction. PMID:25707321

  3. The Search for Milky Way Halo Substructure WIMP Annihilations Using the GLAST LAT

    SciTech Connect

    Wai, Larry; /SLAC

    2007-02-05

    The GLAST LAT Collaboration is one among several experimental groups, covering a wide range of approaches, pursuing the search for the nature of dark matter. The GLAST LAT has the unique ability to find new sources of high energy gamma radiation emanating directly from WIMP annihilations in situ in the universe. Using it's wide band spectral and full sky spatial capabilities, the GLAST LAT can form ''images'' in high energy gamma-rays of dark matter substructures in the gamma-ray sky. We describe a preliminary feasibility study for indirect detection of milky way dark matter satellites using the GLAST LAT.

  4. TemplateTagger v1.0.0: A Template Matching Tool for Jet Substructure

    E-print Network

    Mihailo Backovi?; Jose Juknevich

    2013-05-31

    TemplateTagger is a C++ package for jet substructure analysis with Template Overlap Method. The code operates with arbitrary models within fixed-order perturbation theory and arbitrary kinematics. Specialized template generation classes allow the user to implement any model for a decay of a boosted heavy object. In addition to template overlap, the code provides ability to calculate other template shape and energy flow observables. We describe in detail the structure of the package, as well as provide examples of its usage.

  5. Stellar masers, circumstellar envelopes, and supernova remnants

    E-print Network

    Athol J. Kemball

    2007-05-15

    This paper reviews recent advances in the study or circumstellar masers and masers found toward supernova remnants. The review is organized by science focus area, including the astrophysics of extended stellar atmospheres, stellar mass-loss processes and outflows, late-type evolved stellar evolution, stellar maser excitation and chemistry, and the use of stellar masers as independent distance estimators. Masers toward supernova remnants are covered separately. Recent advances and open future questions in this field are explored.

  6. An updated MILES stellar library and stellar population models

    E-print Network

    Falcón-Barroso, J; Vazdekis, A; Ricciardelli, E; Cardiel, N; Cenarro, A J; Gorgas, J; Peletier, R F

    2011-01-01

    (Aims) We present a number of improvements to the MILES library and stellar population models. We correct some small errors in the radial velocities of the stars, measure the spectral resolution of the library and models more accurately, and give a better absolute flux calibration of the models. (Methods) We use cross-correlation techniques to correct the radial velocities of the offset stars and the penalised pixel-fitting method, together with different sets of stellar templates, to re-assess the spectral resolution of the MILES stellar library and models. We have also re-calibrated the zero-point flux level of the models using a new calibration scheme. (Results) The end result is an even more homogeneously calibrated stellar library than the originally released one, with a measured spectral resolution of ~2.5\\AA, almost constant with wavelength, for both the MILES stellar library and models. Furthermore, the new absolute flux calibration for the spectra excellently agrees with predictions based on independ...

  7. Coupling Semi-Analytic Models and N-Body Simulations: A New Way of Making Galaxies and Stellar Halos

    NASA Astrophysics Data System (ADS)

    McCord, Krista M.; Bailin, Jeremy; Croton, Darren; Valluri, Monica

    2015-01-01

    Stellar halos give insight to the initial conditions that existed when a host galaxy first formed and provide details on disrupted satellites by looking at the different stellar populations. An algorithm that is computationally inexpensive compared to hydrodynamic simulations is necessary in order to theoretically study the structure and formation of galactic stellar halos in sufficient detail to probe substructure. Currently being developed is CoSANG (Coupled Semi-Analytic/N-body Galaxies), a new computational method that will couple pure dark matter N-body simulations with a semi-analytic model. At each timestep, results from the N-body simulation will feed into the semi-analytic code, whose results will feed back into the N-body code making the evolution of the dark matter and baryonic matter dependent on one another. CoSANG will require much less computing power than hydrodynamical simulations, and will enable a variety of galaxy formation science, including analysis of stellar populations, halo merging, satellite accretion, supermassive black holes, and indirect and direct dark matter detection.

  8. Wing Shape and Its Influence on the Outcome of Territorial Contests in the Damselfly Calopteryx virgo

    PubMed Central

    Bots, Jessica; Breuker, Casper J.; Kaunisto, Kari M.; Koskimäki, Jani; Gossum, Hans Van; Suhonen, Jukka

    2012-01-01

    Male mating success is often determined by territory ownership and traits associated with successful territory defense. Empirical studies have shown that the territory owner wins the majority of fights with challenging males. Several physical and physiological traits have been found to correlate with resource holding potential. In addition, in aerial insects, wing design may also have a strong influence on resource holding potential, since it determines efficiency and precision during flight. However, this possibility has not yet been thoroughly evaluated using the modern technique of geometric morphometrics to analyze shape. Therefore, this study examined whether wing shape affects the outcome of male-male contests in the territorial damselfly, Calopteryx virgo (L.) (Odonata: Calopterygidae). Wing shape and also traditional flight-related morphological measures were compared between 27 pairs of winners and losers from experimental territorial contests. Contrary to expectations, there were no differences between winners and losers in all studied wing traits (shape, length, width, total surface, aspect ratio, and wing loading). However, highly significant differences in wing shape and size were detected between the fore- and hindwing. It is currently not known how these differences relate to flight performance, since previous biomechanical studies in damselflies assumed fore- and hindwings to have an identical planform. PMID:23425154

  9. The search for shock-excited H2 in Virgo spirals experiencing ram pressure stripping

    E-print Network

    Wong, O Ivy; Murphy, Eric J; Helou, George

    2014-01-01

    We investigate the presence of shock-excited H2 in four Virgo cluster galaxies that show clear evidence of ongoing ram pressure stripping. Mid-infrared (MIR) spectral mapping of the rotational H2 emission lines were performed using the Infrared Spectrograph (IRS) on board the Spitzer space telescope. We target four regions along the leading side of galaxies where the intracluster medium (ICM) appears to be pushing back the individual galaxy's interstellar medium (ISM). For comparison purposes, we also study two regions on the trailing side of these galaxies, a region within an edge-on disk and an extraplanar star-forming region. We find a factor of 2.6 excess of warm H2/PAH in our sample relative to the observed fractions in other nearby galaxies. We attribute the H2/PAH excess to contributions of shock-excited H2 which is likely to have been triggered by ongoing ram pressure interaction in our sample galaxies. Ram pressure driven shocks may also be responsible for the elevated fractions of FeII/NeII found in...

  10. UV properties of early-type galaxies in the Virgo cluster

    E-print Network

    A. Boselli; L. Cortese; J. M. Deharveng; G. Gavazzi; K. S. Yi; A. Gil de Paz; M. Seibert; S. Boissier; J. Donas; Y. -W. Lee; B. F. Madore; D. C. Martin; R. M. Rich; Y. -J. Sohn

    2005-07-25

    We study the UV properties of a volume limited sample of early-type galaxies in the Virgo cluster combining new GALEX far- (1530 A) and near-ultraviolet (2310 A) data with spectro-photometric data available at other wavelengths. The sample includes 264 ellipticals, lenticulars and dwarfs spanning a large range in luminosity (M(B)<-15). While the NUV to optical or near-IR color magnitude relations (CMR) are similar to those observed at optical wavelengths, with a monotonic reddening of the color index with increasing luminosity, the (FUV-V) and (FUV-H) CMRs show a discontinuity between massive and dwarf objects. An even more pronounced dichotomy is observed in the (FUV-NUV) CMR. For ellipticals the (FUV-NUV) color becomes bluer with increasing luminosity and with increasing reddening of the optical or near-IR color indices. For the dwarfs the opposite trend is observed. These observational evidences are consistent with the idea that the UV emission is dominated by hot, evolved stars in giant systems, while in dwarf ellipticals residual star formation activity is more common.

  11. A Virgo high-resolution H? kinematical survey - II. The Atlas

    NASA Astrophysics Data System (ADS)

    Chemin, L.; Balkowski, C.; Cayatte, V.; Carignan, C.; Amram, P.; Garrido, O.; Hernandez, O.; Marcelin, M.; Adami, C.; Boselli, A.; Boulesteix, J.

    2006-03-01

    A catalogue of ionized gas velocity fields for a sample of 30 spiral and irregular galaxies of the Virgo cluster has been obtained by using 3D optical data. The aim of this survey is to study the influence of high-density environments on the gaseous kinematics of local cluster galaxies. Observations of the H? line by means of Fabry-Perot interferometry have been performed at the Canada-France-Hawaii Telescope, European Southern Observatory 3.6-m telescope, Observatoire de Haute-Provence 1.93-m telescope and Observatoire du mont Mégantic telescope at angular and spectral samplings from 0.4 to 1.6arcsec and 7 to 16kms-1. A recently developed, automatic and adaptive spatial binning technique is used to reach a nearly constant signal-to-noise ratio (S/N) over the whole field of view, allowing us to keep a high spatial resolution in high-S/N regions and extend the detection of signal in low-S/N regions. This paper is part of a series and presents the integrated emission-line and velocity maps of the galaxies. Both H? morphologies and kinematics exhibit signs of perturbations in the form of, for example, external filaments, inner and nuclear spiral- and ring-like structures, inner kinematical twists, kinematical decoupling of a nuclear spiral, streaming motions along spiral arms and misalignment between kinematical and photometric orientation axes.

  12. The Globular Cluster System of the Virgo Dwarf Elliptical Galaxy VCC 1087

    E-print Network

    Michael A. Beasley; Jay Strader; Jean P. Brodie; A. Javier Cenarro; M Geha

    2005-10-26

    We have analysed the globular cluster (GC) system of the nucleated dwarf elliptical galaxy VCC 1087 in the Virgo cluster, based on Keck/LRIS spectroscopy and archival HST/ACS imaging. We estimate VCC 1087 hosts a total population of 77+/-19 GCs, which corresponds to a relatively high V-band specific frequency of 5.8+/-1.4. The g-z color distribution of the GCs shows a blue (metal-poor) peak with a tail of redder (metal-rich) clusters similar in color to those seen in luminous ellipticals. Spectroscopy of a subsample of 12 GCs suggests that the GC system is old and coeval (~10 Gyr), with a fairly broad metallicity distribution (-1.81. A compilation of the kinematics of the GC systems of 9 early-type galaxies shows surprising diversity in the v/sigma parameter for GC systems. In this context, the GC system of VCC 1087 exhibits the most significant rotation to velocity dispersion signature. Modeling the velocity dispersion profile of the GCs and galaxy stars suggest fairly constant mass-to-light ratios of ~3 out to 6.5 kpc. The present observations can entertain both baryonic and non-baryonic solutions, and GC velocities at larger radii would be most valuable with regard to this issue. We discuss the evolution of VCC 1087 in terms of the galaxy ``harassment'' scenario, and conclude that this galaxy may well be the remains of a faded, tidally perturbed Sc spiral [abridged].

  13. Hubble Space Telescope photometry of the central regions of Virgo cluster elliptical galaxies. 3: Brightness profiles

    NASA Technical Reports Server (NTRS)

    Ferrarese, Laura; Bosch, Frank C. Van Den; Ford, Holland C.; Jaffe, Walter; O'Connell, Robert W.

    1994-01-01

    We have used the Planetary Camera on the Hubble Space Telescope (HST) to study the morphology and surface brightness parameters of a luminosity-limited sample of fourteen elliptical galaxies in the Virgo cluster. The total apparent blue magnitudes of the galaxies range between 9.4 and 13.4. In this paper, the core brightness profiles are presented, while the overall morphology and the isophotal shapes are discussed in two companion papers (Jaffe et al. (1994); van den Bosch et al. (1994)). We show that, in spite of the spherical aberration affecting the HST primary mirror, deconvolution techniques allow recovery of the brightness profile up to 0.2 arcsec from the center of the galaxies. We find that none of the galaxies has an isothermal core. On the basis of their morphological and photometrical properties, the galaxies can be divided in two physically distinct groups, referred to as Type I and Type II. All of the Type I galaxies are classified as E1 to E3 in the Revised Shapley Ames Catalog (Sandage & Tammann 1981), while Type II galaxies are classified as E5 to E7. The characteristics of Type II galaxies are explained by the presence of disks component on both the 1 arcsec and the 10 arcsec scales, while Type I galaxies correspond to the classical disk-free ellipticals.

  14. Global Properties of M31's Stellar Halo from the SPLASH Survey. I. Surface Brightness Profile

    NASA Astrophysics Data System (ADS)

    Gilbert, Karoline M.; Guhathakurta, Puragra; Beaton, Rachael L.; Bullock, James; Geha, Marla C.; Kalirai, Jason S.; Kirby, Evan N.; Majewski, Steven R.; Ostheimer, James C.; Patterson, Richard J.; Tollerud, Erik J.; Tanaka, Mikito; Chiba, Masashi

    2012-11-01

    We present the surface brightness profile of M31's stellar halo out to a projected radius of 175 kpc. The surface brightness estimates are based on confirmed samples of M31 red giant branch stars derived from Keck/DEIMOS spectroscopic observations. A set of empirical spectroscopic and photometric M31 membership diagnostics is used to identify and reject foreground and background contaminants. This enables us to trace the stellar halo of M31 to larger projected distances and fainter surface brightnesses than previous photometric studies. The surface brightness profile of M31's halo follows a power law with index -2.2 ± 0.2 and extends to a projected distance of at least ~175 kpc (~2/3 of M31's virial radius), with no evidence of a downward break at large radii. The best-fit elliptical isophotes have b/a = 0.94 with the major axis of the halo aligned along the minor axis of M31's disk, consistent with a prolate halo, although the data are also consistent with M31's halo having spherical symmetry. The fact that tidal debris features are kinematically cold is used to identify substructure in the spectroscopic fields out to projected radii of 90 kpc and investigate the effect of this substructure on the surface brightness profile. The scatter in the surface brightness profile is reduced when kinematically identified tidal debris features in M31 are statistically subtracted; the remaining profile indicates that a comparatively diffuse stellar component to M31's stellar halo exists to large distances. Beyond 90 kpc, kinematically cold tidal debris features cannot be identified due to small number statistics; nevertheless, the significant field-to-field variation in surface brightness beyond 90 kpc suggests that the outermost region of M31's halo is also comprised to a significant degree of stars stripped from accreted objects. The data presented herein were obtained 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 Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  15. EBSD and TEM investigation of the hot deformation substructure characteristics of a type 316L austenitic stainless steel.

    PubMed

    Cizek, P; Whiteman, J A; Rainforth, W M; Beynon, J H

    2004-03-01

    The evolution of crystallographic texture and deformation substructure was studied in a type 316L austenitic stainless steel, deformed in rolling at 900 degrees C to true strain levels of about 0.3 and 0.7. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used in the investigation and a comparison of the substructural characteristics obtained by these techniques was made. At the lower strain level, the deformation substructure observed by EBSD appeared to be rather poorly developed. There was considerable evidence of a rotation of the pre-existing twin boundaries from their original orientation relationship, as well as the formation of highly distorted grain boundary regions. In TEM, at this strain level, the substructure was more clearly revealed, although it appeared rather inhomogeneously developed from grain to grain. The subgrains were frequently elongated and their boundaries often approximated to traces of [111] slip planes. The corresponding misorientations were small and largely displayed a non-cumulative character. At the larger strain, the substructure within most grains became well developed and the corresponding misorientations increased. This resulted in better detection of sub-boundaries by EBSD, although the percentage of indexing slightly decreased. TEM revealed splitting of some sub-boundaries to form fine microbands, as well as the localized formation of microshear bands. The substructural characteristics observed by EBSD, in particular at the larger strain, generally appeared to compare well with those obtained using TEM. With increased strain level, the mean subgrain size became finer, the corresponding mean misorientation angle increased and both these characteristics became less dependent on a particular grain orientation. The statistically representative data obtained will assist in the development of physically based models of microstructural evolution during thermomechanical processing of austenitic stainless steels. PMID:15009696

  16. Stellar diameters and temperatures. IV. Predicting stellar angular diameters

    SciTech Connect

    Boyajian, Tabetha S. [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Van Belle, Gerard [Lowell Observatory, Flagstaff, AZ 86001 (United States); Von Braun, Kaspar, E-mail: tabetha.boyajian@yale.edu [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)

    2014-03-01

    The number of stellar angular diameter measurements has greatly increased over the past few years due to innovations and developments in the field of long baseline optical interferometry. We use a collection of high-precision angular diameter measurements for nearby, main-sequence stars to develop empirical relations that allow the prediction of stellar angular sizes as a function of observed photometric color. These relations are presented for a combination of 48 broadband color indices. We empirically show for the first time a dependence on metallicity of these relations using Johnson (B – V) and Sloan (g – r) colors. Our relations are capable of predicting diameters with a random error of less than 5% and represent the most robust and empirical determinations of stellar angular sizes to date.

  17. Jet Substructure

    NASA Astrophysics Data System (ADS)

    Shelton, J.

    2013-08-01

    Jet physics is a rich and rapidly evolving field, with many applications to physics in and beyond the Standard Model. These notes, based on lectures delivered at the June 2012 Theoretical Advanced Study Institute, provide an introduction to jets at the Large Hadron Collider. Topics covered include sequential jet algorithms, jet shapes, jet grooming, and boosted Higgs and top tagging.

  18. The Substructure of the Solar Corona Observed in the Hi-C Telescope

    NASA Technical Reports Server (NTRS)

    Winebarger, A.; Cirtain, J.; Golub, L.; DeLuca, E.; Savage, S.; Alexander, C.; Schuler, T.

    2014-01-01

    In the summer of 2012, the High-resolution Coronal Imager (Hi-C) flew aboard a NASA sounding rocket and collected the highest spatial resolution images ever obtained of the solar corona. One of the goals of the Hi-C flight was to characterize the substructure of the solar corona. We therefore calculate how the intensity scales from a low-resolution (AIA) pixels to high-resolution (Hi-C) pixels for both the dynamic events and "background" emission (meaning, the steady emission over the 5 minutes of data acquisition time). We find there is no evidence of substructure in the background corona; the intensity scales smoothly from low-resolution to high-resolution Hi-C pixels. In transient events, however, the intensity observed with Hi-C is, on average, 2.6 times larger than observed with AIA. This increase in intensity suggests that AIA is not resolving these events. This result suggests a finely structured dynamic corona embedded in a smoothly varying background.

  19. A Consensus Tree Approach for Reconstructing Human Evolutionary History and Detecting Population Substructure

    PubMed Central

    Tsai, Ming-Chi; Blelloch, Guy; Ravi, R.; Schwartz, Russell

    2012-01-01

    The random accumulation of variations in the human genome over time implicitly encodes a history of how human populations have arisen, dispersed, and intermixed since we emerged as a species. Reconstructing that history is a challenging computational and statistical problem but has important applications both to basic research and to the discovery of genotype-phenotype correlations. We present a novel approach to inferring human evolutionary history from genetic variation data. We use the idea of consensus trees, a technique generally used to reconcile species trees from divergent gene trees, adapting it to the problem of finding robust relationships within a set of intraspecies phylogenies derived from local regions of the genome. Validation on both simulated and real data shows the method to be effective in recapitulating known true structure of the data closely matching our best current understanding of human evolutionary history. Additional comparison with results of leading methods for the problem of population substructure assignment verifies that our method provides comparable accuracy in identifying meaningful population subgroups in addition to inferring relationships among them. The consensus tree approach thus provides a promising new model for the robust inference of substructure and ancestry from large-scale genetic variation data. PMID:21282863

  20. Twisting phonons in complex crystals with quasi-one-dimensional substructures.

    PubMed

    Chen, Xi; Weathers, Annie; Carrete, Jesús; Mukhopadhyay, Saikat; Delaire, Olivier; Stewart, Derek A; Mingo, Natalio; Girard, Steven N; Ma, Jie; Abernathy, Douglas L; Yan, Jiaqiang; Sheshka, Raman; Sellan, Daniel P; Meng, Fei; Jin, Song; Zhou, Jianshi; Shi, Li

    2015-01-01

    A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such complex crystals. Here we employ inelastic neutron scatting measurements and density functional theory calculations to show that numerous low-energy optical vibrational modes exist in higher manganese silicides, an example of such crystals. These optical modes, including unusually low-frequency twisting motions of the Si ladders inside the Mn chimneys, provide a large phase space for scattering acoustic phonons. A hybrid phonon and diffuson model is proposed to explain the low and anisotropic thermal conductivity of higher manganese silicides and to evaluate nanostructuring as an approach to further suppress the thermal conductivity and enhance the thermoelectric energy conversion efficiency. This discovery offers new insights into the structure-property relationships of a broad class of materials with quasi-one-dimensional substructures for various applications. PMID:25872781

  1. Reheating effects in the matter power spectrum and implications for substructure

    SciTech Connect

    Erickcek, Adrienne L. [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 3H8 (Canada); Perimeter Institute for Theoretical Physics, 31 Caroline St. N, Waterloo, Ontario N2L 2Y5 (Canada); Sigurdson, Kris [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)

    2011-10-15

    The thermal and expansion history of the Universe before big bang nucleosynthesis is unknown. We investigate the evolution of cosmological perturbations through the transition from an early matter era to radiation domination. We treat reheating as the perturbative decay of an oscillating scalar field into relativistic plasma and cold dark matter. After reheating, we find that subhorizon perturbations in the decay-produced dark matter density are significantly enhanced, while subhorizon radiation perturbations are instead suppressed. If dark matter originates in the radiation bath after reheating, this suppression may be the primary cutoff in the matter power spectrum. Conversely, for dark matter produced nonthermally from scalar decay, enhanced perturbations can drive structure formation during the cosmic dark ages and dramatically increase the abundance of compact substructures. For low reheat temperatures, we find that as much as 50% of all dark matter is in microhalos with M > or approx. 0.1M{sub +} at z{approx_equal}100, compared to a fraction of {approx}10{sup -10} in the standard case. In this scenario, ultradense substructures may constitute a large fraction of dark matter in galaxies today.

  2. CLUMPY: Jeans analysis, $\\gamma$-ray and neutrino fluxes from dark matter (sub-)structures

    E-print Network

    Bonnivard, Vincent; Nezri, Emmanuel; Charbonnier, Aldée; Combet, Céline; Maurin, David

    2015-01-01

    We present an update of the CLUMPY code for the calculation of the astrophysical J-factors (from dark matter annihilation/decay) for any Galactic or extragalactic dark matter halo including substructures: the concentration-mass relationship may now be drawn from a distribution, boost factors can include several levels of substructures, and triaxiality is a new option for dark matter haloes. This new version takes advantage of the cfitsio and HEALPix libraries to propose FITS output maps using the HEALPix pixelisation scheme. Skymaps for $\\gamma$-ray and neutrino signals from generic annihilation/decay spectra are now direct outputs of CLUMPY. Smoothing by a user-defined instrumental Gaussian beam is also possible. In addition to these improvements, the main novelty is the implementation of a Jeans analysis module, to obtain dark matter density profiles from kinematic data in relaxed spherical systems (e.g., dwarf spheroidal galaxies). The code is also interfaced with the GreAT toolkit designed for Markov Chai...

  3. CLUMPY: Jeans analysis, $?$-ray and neutrino fluxes from dark matter (sub-)structures

    E-print Network

    Vincent Bonnivard; Moritz Hütten; Emmanuel Nezri; Aldée Charbonnier; Céline Combet; David Maurin

    2015-06-25

    We present an update of the CLUMPY code for the calculation of the astrophysical J-factors (from dark matter annihilation/decay) for any Galactic or extragalactic dark matter halo including substructures: the concentration-mass relationship may now be drawn from a distribution, boost factors can include several levels of substructures, and triaxiality is a new option for dark matter haloes. This new version takes advantage of the cfitsio and HEALPix libraries to propose FITS output maps using the HEALPix pixelisation scheme. Skymaps for $\\gamma$-ray and neutrino signals from generic annihilation/decay spectra are now direct outputs of CLUMPY. Smoothing by a user-defined instrumental Gaussian beam is also possible. In addition to these improvements, the main novelty is the implementation of a Jeans analysis module, to obtain dark matter density profiles from kinematic data in relaxed spherical systems (e.g., dwarf spheroidal galaxies). The code is also interfaced with the GreAT toolkit designed for Markov Chain Monte Carlo analyses, from which probability density functions and credible intervals can be obtained for velocity dispersions, dark matter profiles, and J- factors.

  4. CLCA: maximum common molecular substructure queries within the MetRxn database.

    PubMed

    Kumar, Akhil; Maranas, Costas D

    2014-12-22

    The challenge of automatically identifying the preserved molecular moieties in a chemical reaction is referred to as the atom mapping problem. Reaction atom maps provide the ability to locate the fate of individual atoms across an entire metabolic network. Atom maps are used to track atoms in isotope labeling experiments for metabolic flux elucidation, trace novel biosynthetic routes to a target compound, and contrast entire pathways for structural homology. However, rapid computation of the reaction atom mappings remains elusive despite significant research. We present a novel substructure search algorithm, canonical labeling for clique approximation (CLCA), with polynomial run-time complexity to quickly generate atom maps for all the reactions present in MetRxn. CLCA uses number theory (i.e., prime factorization) to generate canonical labels or unique IDs and identify a bijection between the vertices (atoms) of two distinct molecular graphs. CLCA utilizes molecular graphs generated by combining atomistic information on reactions and metabolites from 112 metabolic models and 8 metabolic databases. CLCA offers improvements in run time, accuracy, and memory utilization over existing heuristic and combinatorial maximum common substructure (MCS) search algorithms. We provide detailed examples on the various advantages as well as failure modes of CLCA over existing algorithms. PMID:25412255

  5. Revealing substructures of H4 and H5 hole traps in p-type InP using Laplace deep-level transient spectroscopy

    SciTech Connect

    Darwich, R.; Mani, A. A. [Department of Physics, Atomic Energy Commission of Syria, P.O. Box 6091, Damascus (Syrian Arab Republic)

    2010-08-15

    New substructures of H4 and H5 hole traps have been revealed using Laplace deep-level transient spectroscopy. Our measurements show that the hole traps H4 and H5 can have at least three components for each. Moreover, the activation energies are deduced and the microscopic nature of these substructures is discussed.

  6. Searching for nuclear stellar discs in simulations of star cluster mergers

    NASA Astrophysics Data System (ADS)

    Portaluri, E.; Corsini, E. M.; Morelli, L.; Hartmann, M.; Dalla Bontà, E.; Debattista, Victor P.; Pizzella, A.

    2013-07-01

    The nuclei of galaxies often host small stellar discs with scalelengths of a few tens of parsecs and luminosities up to 107 L?. To investigate the formation and properties of nuclear stellar discs (NSDs), we look for their presence in a set of N-body simulations studying the dissipationless merging of multiple star clusters in galactic nuclei. A few tens of star clusters with sizes and masses comparable to those of globular clusters observed in the Milky Way are accreted on to a pre-existing nuclear stellar component: either a massive super star cluster or a rapidly rotating, compact disc with a scalelength of a few parsecs, mimicking the variety of observed nuclear structures. Images and kinematic maps of the simulation time-steps are then built and analysed as if they were real and at the distance of the Virgo cluster. We use the Scorza-Bender method to search for the presence of disc structures via photometric decomposition. In one case, the merger remnant has all the observed photometric and kinematic properties of NSDs observed in real galaxies. This shows that current observations are consistent with most of the NSD mass being assembled from the migration and accretion of star clusters into the galactic centre. In the other simulation instead, we detect an elongated structure from the unsharp masked image, that does not develop the photometric or kinematic signature of an NSD. Thus, in the context of searches for a disc structure, the Scorza-Bender method is a robust and necessary tool.

  7. Mon. Not. R. Astron. Soc. 000, 000--000 (0000) Printed 26 March 1997 (MN L A T E X style file v1.4) The relative distances to the Virgo, Fornax, and Coma

    E-print Network

    Zaggia, Simone

    .4) The relative distances to the Virgo, Fornax, and Coma clusters of galaxies through the D n --oe, Fornax, and Coma clusters of galaxies by applying the Dn --oe and the Fundamental Plane (FP) relations results, the relative distance moduli to Fornax and Coma with respect to Virgo being \\Delta¯ FV = (0

  8. GRAVITATIONAL WAVES FROM STELLAR COLLAPSE

    SciTech Connect

    C. L. FRYER

    2001-01-01

    Stellar core-collapse plays an important role in nearly all facets of astronomy: cosmology (as standard candles), formation 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 stellar core-collapse as gravitational wave sources.

  9. Nuclear substructure reorganization during late-stage erythropoiesis is selective and does not involve caspase cleavage of major nuclear substructural proteins

    PubMed Central

    Krauss, Sharon Wald; Lo, Annie J.; Short, Sarah A.; Koury, Mark J.; Mohandas, Narla; Chasis, Joel Anne

    2005-01-01

    Enucleation, a rare feature of mammalian differentiation, occurs in 3 cell types: erythroblasts, lens epithelium, and keratinocytes. Previous investigations suggest that caspase activation functions in lens epithelial and keratinocyte enucleation, as well as in early erythropoiesis encompassing erythroid burst-forming unit (BFU-E) differentiation to proerythroblast. To determine whether caspase activation contributes to later erythropoiesis and whether nuclear substructures other than chromatin reorganize, we analyzed distributions of nuclear subcompartment proteins and assayed for caspase-induced cleavage of subcompartmental target proteins in mouse erythroblasts. We found that patterns of lamin B in the filamentous network interacting with both the nuclear envelope and DNA, nuclear matrix protein NuMA (Nuclear mitotic apparatus), and splicing factors Sm and SC35 persisted during nuclear condensation, consistent with effective transcription of genes expressed late in differentiation. Thus, nuclear reorganization prior to enucleation is selective, allowing maintenance of critical transcriptional processes independent of extensive chromosomal reorganization. Consistent with these data, we found no evidence for caspase-induced cleavage of major nuclear subcompartment proteins during late erythropoiesis, in contrast to what has been observed in early erythropoiesis and in lens epithelial and keratinocyte differentiation. These findings imply that nuclear condensation and extrusion during terminal erythroid differentiation involve novel mechanisms that do not entail major activation of apoptotic machinery. (Blood. 2005;106:2200-2205) PMID:15933051

  10. Stellar Imager (SI) Space Mission: Stellar Magnetic Activity

    NASA Technical Reports Server (NTRS)

    Carpenter, K. G.

    2006-01-01

    The Stellar Imager (SI) is a UV-Optical, Space-Based interferometer designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and stellar interiors (via asteroseismology) and of the Universe in general. SI is identified 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). The ultra-sharp images of the Stellar Imager will revolutionize our view of many dynamic astrophysical processes: The 0.1 mas resolution of this deep-space telescope will transform point sources into extended sources, and snapshots into evolving views. SI'S science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI'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. In this paper we will discuss the science goals of the SI Mission and a mission architecture that could meet those goals.

  11. A Maximum Stellar Surface Density in Dense Stellar Systems

    E-print Network

    Hopkins, Philip F; Quataert, Eliot; Thompson, Todd A

    2009-01-01

    We compile observations of the surface mass density profiles of dense stellar systems, including globular clusters in the Milky Way and nearby galaxies, massive star clusters in nearby starbursts, nuclear star clusters in dwarf spheroidals and late-type disks, ultra-compact dwarfs, and galaxy spheroids spanning the range from low-mass cusp bulges and ellipticals to massive core ellipticals. We show that in all cases the maximum stellar surface density attained in the central regions of these systems is similar, Sigma_max ~ 10^11 M_sun/kpc^2 (~20 g/cm^2), despite the fact that the systems span 7 orders of magnitude in total stellar mass M_star, 5 in effective radius R_e, and have a wide range in effective surface density M_star/R_e^2. The surface density limit is reached on a wide variety of physical scales in different systems and is thus not a limit on three-dimensional stellar density. Given the very different formation mechanisms involved in these different classes of objects, we argue that a single piece ...

  12. Optical spectroscopy and the UV luminosity function of galaxies in the Abell 1367, Coma and Virgo clusters

    E-print Network

    L. Cortese; G. Gavazzi; J. Iglesias-Paramo; A. Boselli; L. Carrasco

    2003-01-16

    Optical spectroscopy of 93 galaxies, 60 projected in the direction of Abell 1367, 21 onto the Coma cluster and 12 on Virgo, is reported. The targets were selected either because they were detected in previous H\\alpha, UV or r' surveys. The present observations bring to 100% the redshift completeness of H\\alpha selected galaxies in the Coma region and to 75% in Abell 1367. All observed galaxies except one show H\\alpha emission and belong to the clusters. This confirms previous determinations of the H\\alpha luminosity function of the two clusters that were based on the assumption that all H\\alpha detected galaxies were cluster members. Using the newly obtained data we re-determine the UV luminosity function of Coma and we compute for the first time the UV luminosity function of A1367. Their faint end slopes remain uncertain (-2.00 < \\alpha < -1.35) due to insufficient knowledge of the background counts. If 90% of the UV selected galaxies without redshift will be found in the background (as our survey indicates), the slope of UV luminosity function will be \\alpha ~ -1.35, in agreement with the UV luminosity function of the field (Sullivan et al. 2000) and with the H$\\alpha$ luminosity functions of the two clusters (Iglesias-Paramo et al. 2002). We discover a point like H\\alpha source in the Virgo cluster, associated with the giant galaxy VCC873, possibly an extragalactic HII region similar to the one recently observed in Virgo by Gerhard et al. (2002).

  13. Optical spectroscopy and the UV luminosity function of galaxies in the Abell 1367, Coma and Virgo clusters

    NASA Astrophysics Data System (ADS)

    Cortese, L.; Gavazzi, G.; Iglesias-Paramo, J.; Boselli, A.; Carrasco, L.

    2003-04-01

    Optical spectroscopy of 93 galaxies, 60 projected in the direction of Abell 1367, 21 onto the Coma cluster and 12 on Virgo, is reported. The targets were selected because they were detected in previous H? , UV or r' surveys. The present observations bring to 100% the redshift completeness of H? selected galaxies in the Coma region and to 75% in Abell 1367. All observed galaxies except one show H? emission and belong to the clusters. This confirms previous determinations of the H? luminosity function of the two clusters that were based on the assumption that all H? detected galaxies were cluster members. Using the newly obtained data we re-determine the UV luminosity function of Coma and we compute for the first time the UV luminosity function of A1367. Their faint end slopes remain uncertain (-2.00Virgo cluster, associated with the giant galaxy VCC873, possibly an extragalactic HII region similar to the one recently observed in Virgo by Gerhard et al. (\\cite{Gerhard}). Based on observations obtained with the Loiano telescope belonging to the University of Bologna (Italy), with the G. Haro telescope of the INAOE (Mexico) and with the Calar Alto observatory operated by the Centro Astronomico Hispano Aleman (Spain).

  14. Prospects for Localization of Gravitational Wave Transients by the Advanced LIGO and Advanced Virgo Observatories

    E-print Network

    LIGO Scientific Collaboration; Virgo Collaboration; J. Aasi; J. Abadie; B. P. Abbott; R. Abbott; T. D. Abbott; M. Abernathy; T. Accadia; F. Acernese; C. Adams; T. Adams; P. Addesso; R. X. Adhikari; C. Affeldt; M. Agathos; O. D. Aguiar; P. Ajith; B. Allen; A. Allocca; E. Amador Ceron; D. Amariutei; S. B. Anderson; W. G. Anderson; K. Arai; M. C. Araya; C. Arceneaux; S. Ast; S. M. Aston; P. Astone; D. Atkinson; P. Aufmuth; C. Aulbert; L. Austin; B. E. Aylott; S. Babak; P. Baker; G. Ballardin; S. Ballmer; Y. Bao; J. C. Barayoga; D. Barker; F. Barone; B. Barr; L. Barsotti; M. Barsuglia; M. A. Barton; I. Bartos; R. Bassiri; M. Bastarrika; A. Basti; J. Batch; J. Bauchrowitz; Th. S. Bauer; M. Bebronne; B. Behnke; M. Bejger; M. G. Beker; A. S. Bell; C. Bell; G. Bergmann; J. M. Berliner; A. Bertolini; J. Betzwieser; N. Beveridge; P. T. Beyersdorf; T. Bhadbade; I. A. Bilenko; G. Billingsley; J. Birch; S. Biscans; M. Bitossi; M. A. Bizouard; E. Black; J. K. Blackburn; L. Blackburn; D. Blair; B. Bland; M. Blom; O. Bock; T. P. Bodiya; C. Bogan; C. Bond; F. Bondu; L. Bonelli; R. Bonnand; R. Bork; M. Born; V. Boschi; S. Bose; L. Bosi; B. Bouhou; J. Bowers; C. Bradaschia; P. R. Brady; V. B. Braginsky; M. Branchesi; J. E. Brau; J. Breyer; T. Briant; D. O. Bridges; A. Brillet; M. Brinkmann; V. Brisson; M. Britzger; A. F. Brooks; D. A. Brown; D. D. Brown; F. Brueckner; K. Buckland; T. Bulik; H. J. Bulten; A. Buonanno; J. Burguet-Castell; D. Buskulic; C. Buy; R. L. Byer; L. Cadonati; G. Cagnoli; E. Calloni; J. B. Camp; P. Campsie; K. Cannon; B. Canuel; J. Cao; C. D. Capano; F. Carbognani; L. Carbone; S. Caride; A. D. Castiglia; S. Caudill; M. Cavaglià; F. Cavalier; R. Cavalieri; G. Cella; C. Cepeda; E. Cesarini; T. Chalermsongsak; S. Chao; P. Charlton; E. Chassande-Mottin; X. Chen; Y. Chen; A. Chincarini; A. Chiummo; H. S. Cho; J. Chow; N. Christensen; Q. Chu; S. S. Y. Chua; C. T. Y. Chung; G. Ciani; F. Clara; D. E. Clark; J. A. Clark; F. Cleva; E. Coccia; P. -F. Cohadon; C. N. Colacino; A. Colla; M. Colombini; M. Constancio Jr; A. Conte; D. Cook; T. R. Corbitt; M. Cordier; N. Cornish; A. Corsi; C. A. Costa; M. Coughlin; J. -P. Coulon; S. Countryman; P. Couvares; D. M. Coward; M. Cowart; D. C. Coyne; K. Craig; J. D. E. Creighton; T. D. Creighton; A. Cumming; L. Cunningham; E. Cuoco; K. Dahl; M. Damjanic; S. L. Danilishin; S. D'Antonio; K. Danzmann; V. Dattilo; B. Daudert; H. Daveloza; M. Davier; G. S. Davies; E. J. Daw; T. Dayanga; R. De Rosa; G. Debreczeni; J. Degallaix; W. Del Pozzo; E. Deleeuw; T. Denker; T. Dent; V. Dergachev; R. DeRosa; R. DeSalvo; S. Dhurandhar; L. Di Fiore; A. Di Lieto; I. Di Palma; A. Di Virgilio; M. Díaz; A. Dietz; F. Donovan; K. L. Dooley; S. Doravari; M. Drago; S. Drasco; R. W. P. Drever; J. C. Driggers; Z. Du; J. -C. Dumas; S. Dwyer; T. Eberle; M. Edwards; A. Effler; P. Ehrens; S. S. Eikenberry; G. Endröczi; R. Engel; R. Essick; T. Etzel; K. Evans; M. Evans; T. Evans; M. Factourovich; V. Fafone; S. Fairhurst; Q. Fang; B. F. Farr; W. Farr; M. Favata; D. Fazi; H. Fehrmann; D. Feldbaum; I. Ferrante; F. Ferrini; F. Fidecaro; L. S. Finn; I. Fiori; R. P. Fisher; R. Flaminio; S. Foley; E. Forsi; L. A. Forte; N. Fotopoulos; J. -D. Fournier; J. Franc; S. Franco; S. Frasca; F. Frasconi; M. Frede; M. A. Frei; Z. Frei; A. Freise; R. Frey; T. T. Fricke; D. Friedrich; P. Fritschel; V. V. Frolov; M. -K. Fujimoto; P. J. Fulda; M. Fyffe; J. Gair; M. Galimberti; L. Gammaitoni; J. Garcia; F. Garufi; M. E. Gáspár; N. Gehrels; G. Gelencser; G. Gemme; E. Genin; A. Gennai; L. Á. Gergely; S. Ghosh; J. A. Giaime; S. Giampanis; K. D. Giardina; A. Giazotto; S. Gil-Casanova; C. Gill; J. Gleason; E. Goetz; G. González; N. Gordon; M. L. Gorodetsky; S. Gossan; S. Goßler; R. Gouaty; C. Graef; P. B. Graff; M. Granata; A. Grant; S. Gras; C. Gray; R. J. S. Greenhalgh; A. M. Gretarsson; C. Griffo; H. Grote; K. Grover; S. Grunewald; G. M. Guidi; C. Guido; E. K. Gustafson; R. Gustafson; D. Hammer; G. Hammond; J. Hanks; C. Hanna; J. Hanson; K. Haris; J. Harms; G. M. Harry; I. W. Harry; E. D. Harstad; M. T. Hartman; K. Haughian; K. Hayama; J. Heefner; A. Heidmann; M. C. Heintze; H. Heitmann; P. Hello; G. Hemming; M. A. Hendry; I. S. Heng; A. W. Heptonstall; M. Heurs; M. Hewitson; S. Hild; D. Hoak; K. A. Hodge; K. Holt; M. Holtrop; T. Hong; S. Hooper; J. Hough; E. J. Howell; V. Huang; E. A. Huerta; B. Hughey; S. H. Huttner; M. Huynh; T. Huynh-Dinh; D. R. Ingram; R. Inta; T. Isogai; A. Ivanov; B. R. Iyer; K. Izumi; M. Jacobson; E. James; H. Jang; Y. J. Jang; P. Jaranowski; E. Jesse; W. W. Johnson; D. Jones; D. I. Jones; R. Jones; R. J. G. Jonker; L. Ju; P. Kalmus; V. Kalogera; S. Kandhasamy; G. Kang; J. B. Kanner; M. Kasprzack; R. Kasturi; E. Katsavounidis; W. Katzman; H. Kaufer; K. Kawabe; S. Kawamura; F. Kawazoe; D. Keitel; D. Kelley; W. Kells; D. G. Keppel; A. Khalaidovski; F. Y. Khalili; E. A. Khazanov

    2013-04-02

    We present a possible observing scenario for the Advanced LIGO and Advanced Virgo gravitational wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We determine the expected sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. For concreteness, we focus primarily on gravitational-wave signals from the inspiral of binary neutron star (BNS) systems, as the source considered likely to be the most common for detection and also promising for multimessenger astronomy. We find that confident detections will likely require at least 2 detectors operating with BNS sensitive ranges of at least 100 Mpc, while ranges approaching 200 Mpc should give at least ~1 BNS detection per year even under pessimistic predictions of signal rates. The ability to localize the source of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and can be as large as thousands of square degrees with only 2 sensitive detectors operating. Determining the sky position of a significant fraction of detected signals to areas of 5 sq deg to 20 sq deg will require at least 3 detectors of sensitivity within a factor of ~2 of each other and with a broad frequency bandwidth. Should one of the LIGO detectors be relocated in India as expected, many gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

  15. What (if anything) can few-body strange systems teach us about quark-gluon hadronic substructure

    SciTech Connect

    Maltman, K. (Toronto Univ., ON (Canada). Dept. of Physics Los Alamos National Lab., NM (USA))

    1990-01-01

    We discuss expectation, relevant to the proposed ({pi},K) program at PILAC, for the effects of hadronic quark-gluon substructure on the physics of few-body strangeness {minus}1 systems, in the context of QCD-inspired models used previously to describe the hadron spectrum and short distance nucleon-nucleon scattering. 50 refs., 2 tabs.

  16. Substructure analysis using NICE/SPAR and applications of force to linear and nonlinear structures. [spacecraft masts

    NASA Technical Reports Server (NTRS)

    Razzaq, Zia; Prasad, Venkatesh; Darbhamulla, Siva Prasad; Bhati, Ravinder; Lin, Cai

    1987-01-01

    Parallel computing studies are presented for a variety of structural analysis problems. Included are the substructure planar analysis of rectangular panels with and without a hole, the static analysis of space mast, using NICE/SPAR and FORCE, and substructure analysis of plane rigid-jointed frames using FORCE. The computations are carried out on the Flex/32 MultiComputer using one to eighteen processors. The NICE/SPAR runstream samples are documented for the panel problem. For the substructure analysis of plane frames, a computer program is developed to demonstrate the effectiveness of a substructuring technique when FORCE is enforced. Ongoing research activities for an elasto-plastic stability analysis problem using FORCE, and stability analysis of the focus problem using NICE/SPAR are briefly summarized. Speedup curves for the panel, the mast, and the frame problems provide a basic understanding of the effectiveness of parallel computing procedures utilized or developed, within the domain of the parameters considered. Although the speedup curves obtained exhibit various levels of computational efficiency, they clearly demonstrate the excellent promise which parallel computing holds for the structural analysis problem. Source code is given for the elasto-plastic stability problem and the FORCE program.

  17. A COSMOLOGICAL KINETIC THEORY FOR THE EVOLUTION OF COLD DARK MATTER HALOS WITH SUBSTRUCTURE: QUASI-LINEAR THEORY

    E-print Network

    Ma, Chung-Pei

    A COSMOLOGICAL KINETIC THEORY FOR THE EVOLUTION OF COLD DARK MATTER HALOS WITH SUBSTRUCTURE: QUASI 26; accepted 2004 April 9 ABSTRACT We present a kinetic theory for the evolution of the phase of fluctuations. This theory introduces a new way to model the formation and evolution of halos, which

  18. Erratum: A Minnesota Automated Plate Scanner Catalog of Galaxies behind the Virgo Cluster and toward Its Antipode

    NASA Astrophysics Data System (ADS)

    Hoffman, G. Lyle; Dickey, John M.; Lu, Nanyao Y.; Fromhold-Treu, René

    1997-05-01

    As a result of a publisher's error, Table 3 of the paper ``A Minnesota Automated Plate Scanner Catalog of Galaxies behind the Virgo Cluster and toward Its Antipode'' by G. Lyle Hoffman, John M. Dickey, Nanyao Y. Lu, & René Fromhold-Treu (ApJ, 473, 822 [1996]) did not appear in Volume 7 of the AAS CD-ROM Series. The table will appear in Volume 8 of the AAS CD-ROM Series. In the meantime, the data can be found at http://www.lafayette.edu/faculty/hoffmang.

  19. Electric fields and transport in optimized stellarators

    E-print Network

    Landreman, Matthew Joseph

    2011-01-01

    Recent stellarator experiments have been designed with one of two types of neoclassical optimization: quasisymmetry or quasi-isodynamism. Both types of stellarator have perfectly confined collisionless particle orbits as ...

  20. Stellar Nucleosynthesis Nuclear Data Mining

    Microsoft Academic Search

    Boris Pritychenko

    2011-01-01

    Stellar nucleosynthesis is an important nuclear physics phenomenon that is responsible for presently observed chemical elements and isotope abundances. It is also one of the corner stone hypotheses that provides basis for our understanding of Nature. Its theoretical predictions are often verified through the astrophysical observation and comparison of calculated isotopic abundances with the observed values. These calculations depend heavily

  1. Integrated Circuit Stellar Magnitude Simulator

    ERIC Educational Resources Information Center

    Blackburn, James A.

    1978-01-01

    Describes an electronic circuit which can be used to demonstrate the stellar magnitude scale. Six rectangular light-emitting diodes with independently adjustable duty cycles represent stars of magnitudes 1 through 6. Experimentally verifies the logarithmic response of the eye. (Author/GA)

  2. Stellar evolution: Theory and observations

    Microsoft Academic Search

    Alla G. Masevich; Aleksandr V. Tutukov

    1988-01-01

    The evolution of single and binary starts of different mass from their birth to their transformation into white dwarfs, neutron stars, and black holes is considered. The main trends in stellar evolution theory are presented, and attention is given to possible applications of this theory to the evolution of star clusters and galaxies. Particular emphasis is placed on a comparison

  3. The Evolution of Stellar Populations

    E-print Network

    Angeles Diaz; Eduardo Hardy

    2001-03-14

    We summarize the discussion section on ``Evolution of Stellar Populations'' we led on May 27, 2000 in Granada, Spain, as part of the Euroconference on The Evolution of Galaxies. I- Observational Clues. We also provide a partial comparison between the present knowledge of these topics and that which existed at the time of the Crete Conference of 1995.

  4. Stellar Hydrodynamics in Radiative Regions

    E-print Network

    Patrick A. Young; Karen A. Knierman; Jane R. Rigby; David Arnett

    2003-06-11

    We present an analysis of the response of a radiative region to waves generated by a convective region of the star; this wave treatment of the classical problem of ``overshooting'' gives extra mixing relative to the treatment traditionally used in stellar evolutionary codes. The interface between convectively stable and unstable regions is dynamic and nonspherical, so that the nonturbulent material is driven into motion, even in the absence of ``penetrative overshoot.'' These motions may be described by the theory of nonspherical stellar pulsations, and are related to motion measured by helioseismology. Multi-dimensional numerical simulations of convective flow show puzzling features which we explain by this simplified physical model. Gravity waves generated at the interface are dissipated, resulting in slow circulation and mixing seen outside the formal convection zone. The approach may be extended to deal with rotation and composition gradients. Tests of this description in the stellar evolution code TYCHO produce carbon stars on the asymptotic giant branch (AGB), an isochrone age for the Hyades and three young clusters with lithium depletion ages from brown dwarfs, and lithium and beryllium depletion consistent with observations of the Hyades and Pleiades, all without tuning parameters. The insight into the different contributions of rotational and hydrodynamic mixing processes could have important implications for realistic simulation of supernovae and other questions in stellar evolution.

  5. The Supernova - A Stellar Spectacle.

    ERIC Educational Resources Information Center

    Straka, W. C.

    This booklet is part of an American Astronomical Society curriculum project designed to provide teaching materials to teachers of secondary school chemistry, physics, and earth science. The following topics concerning supernovae are included: the outburst as observed and according to theory, the stellar remnant, the nebular remnant, and a summary…

  6. Stellar Chronometry-Collinder 135

    NASA Astrophysics Data System (ADS)

    Rosario, Marialis; Tijerina, R. S.; Cargile, P.; James, D.

    2013-01-01

    Open clusters are important laboratories for testing the consistency of stellar age-dating techniques due to their large population of coeval, equidistant, and chemically homogeneous stars. Collinder 135, a relatively understudied, nearby (˜300 pc), young (30-50 Myr) southern open cluster, provides a unique opportunity to test the accuracy of common stellar chronometers; namely, testing cluster isochrone ages due to its expected well populated pre-main-sequence and its previously observed well defined upper-main-sequence turnoff that includes the KIb supergaint ? Pup. In this study, we present preliminary results from our optical survey of the cluster. We discuss our data reduction techniques and provide color-magnitude diagrams based on our new, high-precision BVRI catalog. We will preform initial isochrone analysis to investigate the age of this open cluster using upper- and pre-main-sequence stellar models. Our isochrone-age analysis of Cr 135 will play a critical part in a larger effort to “triangulate” on ages of stars by using open clusters to test and calibrate commonly used stellar chronometers.

  7. Constructing efficient substructure-based preconditioners for BEM systems of equations

    SciTech Connect

    D'Araujo, Celio [Universidada Federal de Ouro Preto; D'Azevedo, Ed F [ORNL; Gray, Leonard J [ORNL

    2011-01-01

    In this work, a generic substructuring algorithm is employed to construct global block-diagonal preconditioners for BEM systems of equations. In this strategy, the allowable fill-in positions are those on-diagonal block matrices corresponding to each BE subregion. As these subsystems are independently assembled, the preconditioner for a particular BE model, after the LU decomposition of all subsystem matrices, is easily formed. So as to highlight the efficiency of the preconditioning proposed, the Bi-CG solver, which presents a quite erratic convergence behavior, is considered. In the particular applications of this paper, 3D representative volume elements (RVEs) of carbon-nanotube (CNT) composites are analyzed. The models contain up to several tens of thousands of degrees of freedom. The efficiency and relevance of the preconditioning technique is also discussed in the context of developing general (parallel) BE codes.

  8. Application of Frequency Domain Substructure Synthesis Technique for Plates Loaded with Complex Attachments

    SciTech Connect

    RL Campbell; SA Hambric

    2004-02-05

    Frequency domain substructure synthesis is a modeling technique that enables the prediction of a combined response of individual structures using experimentally measured or numerically predicted frequency response functions (FRFs). The traditional synthesis algorithm [1,2] operates on component impedances and thus generally requires several matrix inversions. An improved algorithm, developed by Jetmundsen et al. [3], requires a single matrix inversion with a completely arbitrary interface definition that can easily incorporate connection impedances. The main limitations of the method are the large data requirements and sensitivity to data truncation. The utility of this technique is demonstrated through a comparison of synthesized and measured admittances of an edge-stiffened plate with attached equipment. The plate mobilities are obtained from a numerical analysis because of the ability to accurately model this structure using a finite element representation. The attachments are characterized experimentally because of their complexity. The sections describe the synthesis technique and show numerical and experimental results for the plate and equipment.

  9. Identification of biological activity profiles using substructural analysis and genetic algorithms.

    PubMed

    Gillet, V J; Willett, P; Bradshaw, J

    1998-01-01

    A substructural analysis approach is used to calculate biological activity profiles, which contain weights that describe the differential occurrences of generic features (specifically, the numbers of hydrogen-bond donors and acceptors, the numbers of rotatable bonds and aromatic rings, the molecular weights, and the 2 kappa alpha descriptors) in active molecules taken from the World Drug Index and in (presumed) inactive molecules taken from the SPRESI database. Even with such simple structural descriptors, the profiles discriminate effectively between active and inactive compounds. The effectiveness of the approach is further increased by using a genetic algorithm for the calculation of the weights comprising a profile. The methods have been successfully applied to a number of different data sets. PMID:9538517

  10. Association between Y haplogroups and autosomal AIMs reveals intra-population substructure in Bolivian populations.

    PubMed

    Vullo, Carlos; Gomes, Verónica; Romanini, Carola; Oliveira, Andréa M; Rocabado, Omar; Aquino, Juliana; Amorim, António; Gusmão, Leonor

    2015-07-01

    For the correct evaluation of the weight of genetic evidence in a forensic context, databases must reflect the structure of the population, with all possible groups being represented. Countries with a recent history of admixture between strongly differentiated populations are usually highly heterogeneous and sub-structured. Bolivia is one of these countries, with a high diversity of ethnic groups and different levels of admixture (among Native Americans, Europeans and Africans) across the territory. For a better characterization of the male lineages in Bolivia, 17 Y-STR and 42 Y-SNP loci were genotyped in samples from La Paz and Chuquisaca. Only European and Native American Y-haplogroups were detected, and no sub-Saharan African chromosomes were found. Significant differences were observed between the two samples, with a higher frequency of European lineages in Chuquisaca than in La Paz. A sample belonging to haplogroup Q1a3a1a1-M19 was detected in La Paz, in a haplotype background different from those previously found in Argentina. This result supports an old M19 North-south dispersion in South America, possibly via two routes. When comparing the ancestry of each individual assessed through his Y chromosome with the one estimated using autosomal AIMs, (a) increased European ancestry in individuals with European Y chromosomes and (b) higher Native American ancestry in the carriers of Native American Y-haplogroups were observed, revealing an association between autosomal and Y-chromosomal markers. The results of this study demonstrate that a sub-structure does exist in Bolivia at both inter- and intrapopulation levels, a fact which must be taken into account in the evaluation of forensic genetic evidence. PMID:24878616

  11. In situ spatiotemporal measurements of the detailed azimuthal substructure of the substorm current wedge

    PubMed Central

    Forsyth, C; Fazakerley, A N; Rae, I J; J Watt, C E; Murphy, K; Wild, J A; Karlsson, T; Mutel, R; Owen, C J; Ergun, R; Masson, A; Berthomier, M; Donovan, E; Frey, H U; Matzka, J; Stolle, C; Zhang, Y

    2014-01-01

    The substorm current wedge (SCW) is a fundamental component of geomagnetic substorms. Models tend to describe the SCW as a simple line current flowing into the ionosphere toward dawn and out of the ionosphere toward dusk, linked by a westward electrojet. We use multispacecraft observations from perigee passes of the Cluster 1 and 4 spacecraft during a substorm on 15 January 2010, in conjunction with ground-based observations, to examine the spatial structuring and temporal variability of the SCW. At this time, the spacecraft traveled east-west azimuthally above the auroral region. We show that the SCW has significant azimuthal substructure on scales of 100?km at altitudes of 4000–7000?km. We identify 26 individual current sheets in the Cluster 4 data and 34 individual current sheets in the Cluster 1 data, with Cluster 1 passing through the SCW 120–240?s after Cluster 4 at 1300–2000?km higher altitude. Both spacecraft observed large-scale regions of net upward and downward field-aligned current, consistent with the large-scale characteristics of the SCW, although sheets of oppositely directed currents were observed within both regions. We show that the majority of these current sheets were closely aligned to a north-south direction, in contrast to the expected east-west orientation of the preonset aurora. Comparing our results with observations of the field-aligned current associated with bursty bulk flows (BBFs), we conclude that significant questions remain for the explanation of SCW structuring by BBF-driven “wedgelets.” Our results therefore represent constraints on future modeling and theoretical frameworks on the generation of the?SCW. Key Points The substorm current wedge (SCW) has significant azimuthal structure Current sheets within the SCW are north-south aligned The substructure of the SCW raises questions for the proposed wedgelet scenario

  12. DEFORMATION SUBSTRUCTURES AND THEIR TRANSITIONS IN LASER SHOCK-COMPRESSED COPPER-ALUMINUM ALLOYS

    SciTech Connect

    Meyers, M A; Schneider, M S; Jarmakani, H; Kad, B; Remington, B A; Kalantar, D H; McNaney, J; Cao, B; Wark, J

    2007-10-17

    It is shown that the short pulse durations (0.1-10 ns) in laser shock compression ensure a rapid decay of the pulse and quenching of the shocked sample in times that are orders of magnitude lower than in conventional explosively driven plate impact experiments. Thus, laser compression, by virtue of a much more rapid cooling, enables the retention of a deformation structure closer to the one existing during shock. The smaller pulse length also decreases the propensity for localization. Copper and copper aluminum (2 and 6 wt% Al) with orientations [001] and [{bar 1}34] were subjected to high intensity laser pulses with energy levels of 70 to 300 J delivered in an initial pulse duration of approximately 3 ns. The [001] and [{bar 1}34] orientations were chosen since they respectively maximize and minimize the number of slip systems with highest resolved shear stresses. Systematic differences of the defect substructure were observed as a function of pressure, stacking-fault energy and crystalline orientation. The changes in the mechanical properties for each condition were compared using micro- and nano-hardness measurements and correlated well with observations of the defect substructure. Three regimes of plastic deformation were identified and their transitions modeled: dislocation cells, stacking-faults, and twins. An existing constitutive description of the slip to twinning transition, based on the critical shear stress, was expanded to incorporate the effect of stacking-fault energy. A new physically-based criterion accounting for stacking-fault energy was developed that describes the transition from perfect loop to partial loop homogeneous nucleation, and consequently from cells to stacking-faults. These calculations predict transitions that are in qualitative agreement with the effect of SFE.

  13. Stellar population models based on new generation stellar library

    NASA Astrophysics Data System (ADS)

    Koleva, M.; Vazdekis, A.

    The spectral predictions of stellar population models are not as accurate in the ultra-violet (UV) as in the optical wavelength domain. One of the reasons is the lack of high-quality stellar libraries. The New Generation Stellar Library (NGSL), recently released, represents a significant step towards the improvement of this situation. To prepare NGSL for population synthesis, we determined the atmospheric parameters of its stars, we assessed the precision of the wavelength calibration and characterised its intrinsic resolution. We also measured the Galactic extinction for each of the NGSL stars. For our analyses we used Ulyss, a full spectrum fitting package, fitting the NGSL spectra against the MILES interpolator. As a second step we build preliminary single stellar population models using Vazdekis (2003) synthesis code. We find that the wavelength calibration is precise up to 0.1 px, after correcting a systematic effect in the optical range. The spectral resolution varies from 3 Å in the UV to 10 Å in the near-infrared (NIR), corresponding to a roughly constant reciprocal resolution R=?/?? ?1000 and an instrumental velocity dispersion ?_{ins} ? 130 kms. We derived the atmospheric parameters homogeneously. The precision for the FGK stars is 42 K, 0.24 and 0.09 dex for teff, logg and feh, respectively. The corresponding mean errors are 150 K, 0.50 and 0.48 dex for the M stars, and for the OBA stars they are 4.5 percent, 0.44 and 0.18 dex. The comparison with the literature shows that our results are not biased. Our first version of models compares well with models based on optical libraries, having the advantages to be free from artifacts due to the atmosphere. In future we will fine-tune our models by comparing to different models and observations of globular clusters.

  14. A revised catalog of CfA galaxy groups in the Virgo/Great Attractor flow field

    NASA Technical Reports Server (NTRS)

    Nolthenius, Richard

    1993-01-01

    A new identification of groups and clusters in the CfAl Catalog of Huchra, et al. (1983) is presented, using a percolation algorithm to identify density enhancements. The procedure differs from that of the original Geller and Huchra (1983; GH) catalog in several important respects; galaxy distances are calculated from the Virgo-Great Attractor flow model of Faber and Burnstein (1988), the adopted distance linkage criteria is only approx. 1/4 as large as in the Geller and Huchra catalog, the sky link relation is taken from Nolthenius and White (1987), correction for interstellar extinction is included, and 'by-hand' adjustments to group memberships are made in the complex regions of Virgo/Coma I/Ursa Major and Coma/A1367 (to allow for varying group velocity dispersions and to trim unphysical 'spider arms'). Since flow model distances are poorly determined in these same regions, available distances from the IR Tully-Fisher planetary nebula luminosity function and surface brightness resolution methods are adopted if possible.

  15. A New Dynamical Mass Measurement for the VIRGO Cluster Using the Radial Velocity Profile of the Filament Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Jounghun; Kim, Suk; Rey, Soo-Chang

    2015-07-01

    The radial velocities of the galaxies in the vicinity of a cluster show deviation from the pure Hubble flow due to their gravitational interaction with the cluster. According to a recent study by Falco et al. based on a high-resolution N-body simulation, the radial velocity profile of galaxies located at distances larger than three times the virial radius of a neighboring cluster can be well approximated by a universal formula, and could be reconstructed from direct observables provided that the galaxies are distributed along a one-dimensional filament. They suggested an algorithm designed to estimate the dynamic mass of a cluster {M}{{v}} by fitting the universal formula from the simulation to the reconstructed radial velocity profile of the filament galaxies around the cluster from observations. We apply the algorithm to two narrow, straight filaments (referred to as Filaments A and B) that were recently identified by Kim et al. in the vicinity of the Virgo cluster from the NASA-Sloan-Atlas catalog. The dynamical mass of the Virgo cluster is estimated to be {M}{{v}}=({0.84}-0.51+2.75)× {10}15 {h}-1 {M}? and {M}{{v}}=({3.24}-1.31+4.99)× {10}15 {h}-1 {M}? for the cases of Filaments A and B, respectively. We discuss the observational and theoretical systematics intrinsic to the method of Falco et al. as well as the physical implication of the final results.

  16. Deep HI observations of the surroundings of ram pressure stripped Virgo spiral galaxies - Where is the stripped gas?

    E-print Network

    B. Vollmer; W. Huchtmeier

    2006-11-06

    Deep Effelsberg 100-m HI observations of 5 HI deficient Virgo spiral galaxies are presented. No new extended HI tail is found in these galaxies. The already known HI tail north of NGC 4388 does not significantly extend further than a WSRT image has shown. Based on the absence of HI tails in a sample of 6 Virgo spiral galaxies and a balance of previous detections of extraplanar gas in the targeted galaxies we propose a global picture where the outer gas disk (beyond the optical radius R_25) is removed much earlier than expected by the classical ram pressure criterion. Based on the two-phase nature of atomic hydrogen located in a galactic disk, we argue that the warm diffuse HI in the outer galactic disk is evaporated much more rapidly than the cold dense HI. Therefore, after a ram pressure stripping event we can only observe atomic hydrogen which was cold and dense before it was removed from the galactic disk. This global picture is consistent with all available observations. We detect between 0.3% and 20% of the stripped mass assuming an initially non-deficient galaxy and between 3% and 70% of the stripped mass assuming an initially HI deficient galaxy (def=0.4). Under the latter assumption we estimate an evaporation rate by dividing the missing mass by the estimated time to peak ram pressure from dynamical simulations. We find evaporation rates between 10 and 100 M_solar/yr.

  17. Deriving stellar inclination of slow rotators using stellar activity signal

    NASA Astrophysics Data System (ADS)

    Dumusque, Xavier

    2015-01-01

    Stellar inclination is an important parameter for many astrophysical studies. In the context of exoplanets, this allows us to derive the true obliquity of a system if the projected stellar spin-planetary orbit angle can measured via the Rossiter-Mclaughlin effect. Although different techniques allow us to estimate stellar inclination for fast rotators, it becomes much more difficult when stars are rotating slower than 2-2.5 km.s-1. By using the new activity simulation SOAP 2.0 that can reproduce the photometric and spectroscopic variations induced by stellar activity, we are able to fit the activity variation of solar-type stars and derive their inclination. The case of the equator-on star HD189733 will be presented, as well as the case of Alpha Centauri B, which present an inclination of 45+9-19 degrees, implying that the earth-mass orbiting planet is not transiting if aligned with its host star. Other exemples will also demonstrate the power of the technique, that can infer a stellar inclination, even for slow rotators like Alpha Centauri B, that present a projected rotational velocity smaller than 1.15 km.s-1. In addition, the SOAP 2.0 simulation can be used to correct for the effect of activity when one major active region is dominating the RV signal. This could enhance the detection of small mass exoplanets orbiting slightly active stars.This project is funded by ETAEARTH (European Union Seventh Framework Programme (FP7/2007-2013) under Grant Agreement n. 313014), a transnational collaboration between European countries and the US (the Swiss Space Office, the Harvard Origin of Life Initiative, the Scottish Universities Physics Alliance, the University of Geneva, the Smithsonian Astrophysical Observatory, the Italian National Astrophysical Institute, the University of St. Andrews, Queens University Belfast, and the University of Edinburgh) setup to optimize the synergy between space-and ground-based data whose scientific potential for the characterization of extrasolar planets can only be fully exploited when analyzed together.

  18. The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. I. Data and Empirical Trends

    E-print Network

    van Dokkum, Pieter

    2012-01-01

    The strength of gravity-sensitive absorption lines in the integrated light of old stellar populations is one of the few direct probes of the stellar initial mass function (IMF) outside of the Milky Way. Owing to the advent of fully depleted CCDs with little or no fringing it has recently become possible to obtain accurate measurements of these features. Here we present spectra covering the wavelength ranges 0.35 - 0.55 micron and 0.72 - 1.03 micron for the bulge of M31 and 34 early-type galaxies from the SAURON sample, obtained with the Low Resolution Imaging Spectrometer on Keck. The signal-to-noise ratio is >200 per Angstrom out to 1 micron, which is sufficient to measure gravity-sensitive features for individual galaxies and to determine how they depend on other properties of the galaxies. Combining the new data with previously obtained spectra for globular clusters in M31 and the most massive elliptical galaxies in the Virgo cluster we find that the dwarf-sensitive Na I doublet and the FeH Wing-Ford band ...

  19. Stellar Nucleosynthesis Nuclear Data Mining

    E-print Network

    Pritychenko, Boris

    2011-01-01

    Stellar nucleosynthesis is an important nuclear physics phenomenon that is responsible for presently observed chemical elements and isotope abundances. It is also one of the corner stone hypotheses that provides basis for our understanding of Nature. Its theoretical predictions are often verified through the astrophysical observation and comparison of calculated isotopic abundances with the observed values. These calculations depend heavily on the availability of nuclear reaction rate, cross section and decay data. In this work, we will provide a review of theoretical and experimental nuclear reaction data for Big Bang, stellar and explosive nucleosynthesis and modern computer tools. Examples of evaluated and compiled nuclear reaction data will be given. Major databases and their input in nuclear reaction calculations will be discussed.

  20. Stellar models in Brane Worlds

    E-print Network

    Linares, Francisco X; Ureña-Lopez, L Arturo

    2015-01-01

    We consider here a full study of stellar dynamics from the brane-world point of view in the case of constant density and of a polytropic fluid. We start our study cataloguing the minimal requirements to obtain a compact object with a Schwarszchild exterior, highlighting the low and high energy limit, the boundary conditions, and the appropriate behavior of Weyl contributions inside and outside of the star. Under the previous requirements we show an extensive study of stellar behavior, starting with stars of constant density and its extended cases with the presence of nonlocal contributions. Finally, we focus our attention to more realistic stars with a polytropic equation of state, specially in the case of white dwarfs, and study their static configurations numerically. One of the main results is that the inclusion of the Weyl functions from braneworld models allow the existence of more compact configurations than within General Relativity.