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1

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

NASA Astrophysics Data System (ADS)

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.

Farmer, John; Vivas, A. Katherina

2015-01-01

2

STELLAR POPULATIONS AND RADIAL MIGRATIONS IN VIRGO DISK GALAXIES  

E-print Network

We present new stellar age profiles, derived from well-resolved optical and near-infrared images of 64 Virgo cluster disk galaxies, whose analysis poses a challenge for current disk galaxy formation models. Our ability to ...

Roediger, Joel C.

3

Stellar Substructures around the Hercules Dwarf Spheroidal Galaxy  

E-print Network

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...

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

2015-01-01

4

SUBSTRUCTURE IN THE STELLAR HALOS OF THE AQUARIUS SIMULATIONS  

SciTech Connect

We characterize the substructure in the simulated stellar halos of Cooper et al. which were formed by the disruption of satellite galaxies within the cosmological N-body simulations of galactic halos of the Aquarius project. These stellar halos exhibit a wealth of tidal features: broad overdensities and very narrow faint streams akin to those observed around the Milky Way. The substructures are distributed anisotropically on the sky, a characteristic that should become apparent in the next generation of photometric surveys. The normalized RMS of the density of stars on the sky appears to be systematically larger for our halos compared with the value estimated for the Milky Way from main-sequence turnoff stars in the Sloan Digital Sky Survey. We show that this is likely to be due in part to contamination by faint QSOs and redder main-sequence stars, and might suggest that {approx}10% of the Milky Way halo stars have formed in situ.

Helmi, Amina [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands); Cooper, A. P.; Cole, S.; Frenk, C. S. [Institute for Computational Cosmology, Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom); White, S. D. M. [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany); Navarro, J. F., E-mail: ahelmi@astro.rug.nl [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 5C2 (Canada)

2011-05-20

5

The global properties and substructure characteristics of Andromeda's stellar halo  

NASA Astrophysics Data System (ADS)

In the paradigm of hierarchical galaxy formation, large galaxies are built through the merging of smaller systems. Over the lifetime of a galaxy, tidal debris from multiple mergers can build a stellar halo. Tidal debris in stellar halos provides insight into hierarchical structure formation, the structure and merger history of an individual galaxy, and the properties of dwarf satellite systems. Detailed comparisons between observations of stellar halos and cosmological simulations of stellar halo formation can be used to constrain models of galaxy formation. To increase the number of stellar halos which have been studied in detail, we have undertaken a large spectroscopic survey of red giant branch stars in the Andromeda galaxy (M31) with the DEIMOS spectrograph on the Keck II 10-m telescope. I present a method for determining M31 membership using empirical probability distribution functions in multiple photometric and spectroscopic diagnostics. This method is used to identify M31 red giants to distances of 165 kpc in projection from the center of the galaxy. I discuss the kinematic, chemical, and structural properties of multiple tidal debris features in M31, including the kinematic detection of several previously noted photometric overdensities in the southern quadrant of M31's halo. I present the discovery of substructure along the southeast minor-axis and show that it is likely the forward continuation of M31's giant southern stream. The properties of substructure in M31's stellar halo are compared with simulations of stellar halo formation via the accretion of smaller stellar systems; the brightest kinematic features in our M31 survey are in general the most metal- rich, which is in qualitative agreement with the simulation results. Finally, I present the global properties of M31's stellar halo, including the surface brightness profile and metallicity distribution as a function of radius. The surface brightness profile of red giant branch stars in M31 is consistent with a power-law of index -2.0 beyond a radial distance of 30 kpc from M31's center, and the outer regions of M31's stellar halo are metal-poor, with an mean metallicity of ~ -1.3 dex beyond a radial distance of 80 kpc from M31's center.

Gilbert, Karoline M.

2008-10-01

6

STELLAR POPULATIONS AND RADIAL MIGRATIONS IN VIRGO DISK GALAXIES  

SciTech Connect

We present new stellar age profiles, derived from well-resolved optical and near-infrared images of 64 Virgo cluster disk galaxies, whose analysis poses a challenge for current disk galaxy formation models. Our ability to break the age-metallicity degeneracy and the significant size of our sample represent key improvements over complementary studies of field disk galaxies. Our results can be summarized as follows: first, and contrary to observations of disk galaxies in the field, these cluster galaxies are distributed almost equally amongst the three main types of disk galaxy luminosity profiles (I/II/III), indicating that the formation and/or survival of Type II breaks is suppressed within the cluster environment. Second, we find examples of statistically significant inversions ({sup U}-shapes{sup )} in the age profiles of all three disk galaxy types, reminiscent of predictions from high-resolution simulations of classically truncated Type II disks in the field. These features characterize the age profiles for only about a third ({<=}36%) of each disk galaxy type in our sample. An even smaller fraction of cluster disks ({approx}11% of the total sample) exhibit age profiles that decrease outward (i.e., negative age gradients). Instead, flat and/or positive age gradients prevail ({>=}50%) within our Type I, II, and III subsamples. These observations thus suggest that while stellar migrations and inside-out growth can play a significant role in the evolution of all disk galaxy types, other factors contributing to the evolution of galaxies can overwhelm the predicted signatures of these processes. We interpret our observations through a scenario whereby Virgo cluster disk galaxies formed initially like their brethren in the field but which, upon falling into the cluster, were transformed into their present state through external processes linked to the environment (e.g., ram-pressure stripping and harassment). Current disk galaxy formation models, which have largely focused on field galaxies, fail to reproduce these results, thus calling for adequate hydrodynamical simulations of dense galaxy environments if we are to understand cluster disks. The current paper highlights numerous constraints for such simulations. In the Appendix, we confirm the claim by Erwin et al. that Type II breaks are absent in Virgo cluster S0s and discuss the detection of Type III breaks in such galaxies.

Roediger, Joel C.; Courteau, Stephane [Department of Physics, Engineering Physics and Astronomy, Queen's University, Kingston, Ontario (Canada); Sanchez-Blazquez, Patricia [Deptartamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); McDonald, Michael, E-mail: jroediger@astro.queensu.ca, E-mail: courteau@astro.queensu.ca, E-mail: p.sanchezblazquez@uam.es, E-mail: mcdonald@space.mit.edu [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology Cambridge, MA (United States)

2012-10-10

7

Searching for Stellar Sub-Structure in the Galactic Bulge  

NASA Astrophysics Data System (ADS)

We have discovered a group of 7 bulge giants with radial velocities of +300 km/s in a two degree field toward the Galactic bulge at (l,b) = (-6,-8). They are separated from the highest velocity bulge members by ~100 km/s. Recently, ARGOS reported a group of 4 kinematically distinct metal-poor bulge stars in their l = -20 fields. Coincidentally, these stars have radial velocities of +300 km/s. Given the scarcity of stars with velocities of +300 km/s in the Bulge, these stellar features may be related and part of a large independent stream or moving group in the inner Galaxy. We present preliminary results of high-resolution spectroscopy of 4 BRAVA stars with 300 km/s at (l, b) = (-6°,-8°) and 2 RAVE stars with 300 km/s at (l, b) = (-12°,-15°), taken with the MIKE spectrograph on the 6.5m Magellan telescope. The detailed abundance signatures provide an understanding as to the extent of this 300 km/s stellar system and a discussion on this potential newly discovered bulge stream.

Hsyu, Tiffany; Johnson, C. I.; Kunder, A.; Rich, R. M.; de Propris, R.; Koch, A.

2014-01-01

8

Integral-field Stellar and Ionized Gas Kinematics of Peculiar Virgo Cluster Spiral Galaxies  

NASA Astrophysics Data System (ADS)

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 ? R . An evaluation of the galaxies in the ? 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.

Cortés, Juan R.; Kenney, Jeffrey D. P.; Hardy, Eduardo

2015-01-01

9

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

10

The photometric properties of a vast stellar substructure in the outskirts of M33  

E-print Network

We have surveyed $\\sim40$sq.degrees surrounding M33 with CFHT MegaCam in the g and i filters, as part of the Pan-Andromeda Archaeological Survey. Our observations are deep enough to resolve the top 4mags of the red giant branch population in this galaxy. We have previously shown that the disk of M33 is surrounded by a large, irregular, low-surface brightness substructure. Here, we quantify the stellar populations and structure of this feature using the PAndAS data. We show that the stellar populations of this feature are consistent with an old population with $\\sim-1.6$dex and an interquartile range in metallicity of $\\sim0.5$dex. We construct a surface brightness map of M33 that traces this feature to $\\mu_V\\simeq33$mags\\,arcsec$^{-2}$. At these low surface brightness levels, the structure extends to projected radii of $\\sim40$kpc from the center of M33 in both the north-west and south-east quadrants of the galaxy. Overall, the structure has an "S-shaped" appearance that broadly aligns with the orientation o...

McConnachie, Alan W; Irwin, Michael J; Dubinski, John; Widrow, Lawrence M; Dotter, Aaron; Ibata, Rodrigo; Lewis, Geraint F

2010-01-01

11

Exploring Halo Substructure with Giant Stars. XIV. The Nature of the Triangulum-Andromeda Stellar Features  

NASA Astrophysics Data System (ADS)

As large-scale stellar surveys have become available over the past decade, the ability to detect and characterize substructures in the Galaxy has increased dramatically. These surveys have revealed the Triangulum-Andromeda (TriAnd) region to be rich with substructures in the distance range 20-30 kpc, and the relation of these features to each other, if any, remains unclear. An exploration using Two Micron All Sky Survey (2MASS) photometry reveals not only the faint sequence in M giants detected by Rocha-Pinto et al. spanning the range 100° < l < 160° and -50° < b < -15°, but, in addition, a second, brighter and more densely populated sequence. These sequences are likely associated with the distinct main sequences (MSs) discovered (and labeled TriAnd1 and TriAnd2) by Martin et al. in an optical survey in the direction of M31, where TriAnd2 is the optical counterpart of the fainter red giant branch (RGB)/asymptotic giant branch sequence of Rocha-Pinto et al. Here, the age, distance, and metallicity ranges for TriAnd1 and TriAnd2 are estimated by simultaneously fitting isochrones to the 2MASS RGB tracks and the optical MS/MS turn-off features. The two populations are clearly distinct in age and distance: the brighter sequence (TriAnd1) is younger (6-10 Gyr) and closer (distance of ~15-21 kpc), whereas the fainter sequence (TriAnd2) is older (10-12 Gyr) and at an estimated distance of ~24-32 kpc. A comparison with simulations demonstrates that the differences and similarities between TriAnd1 and TriAnd2 can simultaneously be explained if they represent debris originating from the disruption of the same dwarf galaxy, but torn off during two distinct pericentric passages.

Sheffield, Allyson A.; Johnston, Kathryn V.; Majewski, Steven R.; Damke, Guillermo; Richardson, Whitney; Beaton, Rachael; Rocha-Pinto, Helio J.

2014-09-01

12

The Photometric Properties of a Vast Stellar Substructure in the Outskirts of M33  

NASA Astrophysics Data System (ADS)

We have surveyed approximately 40 deg2 surrounding M33 with Canada-France-Hawaii Telescope MegaCam/MegaPrime in the g and i filters out to a maximum projected radius from this galaxy of 50 kpc, as part of the Pan-Andromeda Archaeological Survey (PAndAS). Our observations are deep enough to resolve the top ~4 mag of the red giant branch population in this galaxy. We have previously shown that the disk of M33 is surrounded by a large, irregular, low surface brightness substructure. Here, we quantify the stellar populations and structure of this feature using the PAndAS data. We show that the stellar populations of this feature are consistent with an old population with lang[Fe/H]rang ~ -1.6 dex and an interquartile range in metallicity of ~0.5 dex. We construct a surface brightness map of M33 that traces this feature to ? V ~= 33 mag arcsec-2. At these low surface brightness levels, the structure extends to projected radii of ~40 kpc from the center of M33 in both the northwest and southeast quadrants of the galaxy. Overall, the structure has an "S-shaped" appearance that broadly aligns with the orientation of the H I disk warp. We calculate a lower limit to the integrated luminosity of the structure of -12.7 ± 0.5 mag, comparable to a bright dwarf galaxy such as Fornax or Andromeda II and slightly less than 1% of the total luminosity of M33. Further, we show that there is tentative evidence for a distortion in the distribution of young stars near the edge of the H I disk that occurs at similar azimuth to the warp in H I. The data also hint at a low-level, extended stellar component at larger radius that may be an M33 halo component. We revisit studies of M33 and its stellar populations in light of these new results and discuss possible formation scenarios for the vast stellar structure. Our favored model is that of the tidal disruption of M33 in its orbit around M31.

McConnachie, Alan W.; Ferguson, Annette M. N.; Irwin, Michael J.; Dubinski, John; Widrow, Lawrence M.; Dotter, Aaron; Ibata, Rodrigo; Lewis, Geraint F.

2010-11-01

13

THE PHOTOMETRIC PROPERTIES OF A VAST STELLAR SUBSTRUCTURE IN THE OUTSKIRTS OF M33  

SciTech Connect

We have surveyed approximately 40 deg{sup 2} surrounding M33 with Canada-France-Hawaii Telescope MegaCam/MegaPrime in the g and i filters out to a maximum projected radius from this galaxy of 50 kpc, as part of the Pan-Andromeda Archaeological Survey (PAndAS). Our observations are deep enough to resolve the top {approx}4 mag of the red giant branch population in this galaxy. We have previously shown that the disk of M33 is surrounded by a large, irregular, low surface brightness substructure. Here, we quantify the stellar populations and structure of this feature using the PAndAS data. We show that the stellar populations of this feature are consistent with an old population with ([Fe/H]) {approx} -1.6 dex and an interquartile range in metallicity of {approx}0.5 dex. We construct a surface brightness map of M33 that traces this feature to {mu}{sub V} {approx_equal} 33 mag arcsec{sup -2}. At these low surface brightness levels, the structure extends to projected radii of {approx}40 kpc from the center of M33 in both the northwest and southeast quadrants of the galaxy. Overall, the structure has an 'S-shaped' appearance that broadly aligns with the orientation of the H I disk warp. We calculate a lower limit to the integrated luminosity of the structure of -12.7 {+-} 0.5 mag, comparable to a bright dwarf galaxy such as Fornax or Andromeda II and slightly less than 1% of the total luminosity of M33. Further, we show that there is tentative evidence for a distortion in the distribution of young stars near the edge of the H I disk that occurs at similar azimuth to the warp in H I. The data also hint at a low-level, extended stellar component at larger radius that may be an M33 halo component. We revisit studies of M33 and its stellar populations in light of these new results and discuss possible formation scenarios for the vast stellar structure. Our favored model is that of the tidal disruption of M33 in its orbit around M31.

McConnachie, Alan W. [NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, British Columbia, V9E 2E7 (Canada); Ferguson, Annette M. N. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Irwin, Michael J. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Dubinski, John [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario, M5S 3H4 (Canada); Widrow, Lawrence M. [Department of Physics, Engineering Physics, and Astronomy Queen's University, Kingston, Ontario, K7L 3N6 (Canada); Dotter, Aaron [Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, British Columbia, V8P 5C2 (Canada); Ibata, Rodrigo [Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg (France); Lewis, Geraint F., E-mail: alan.mcconnachie@nrc-cnrc.gc.c [Institute of Astronomy, School of Physics, A29 University of Sydney, NSW 2006 (Australia)

2010-11-10

14

Stellar Kinematics and Structural Properties of Virgo Cluster Dwarf Early-Type Galaxies from the SMAKCED Project  

NASA Astrophysics Data System (ADS)

We analyze the stellar kinematics of 39 dwarf early-type galaxies (dEs) in the Virgo cluster. This is the largest survey conducted so far on spatially resolved kinematics of dEs. This sample is representative of the early-type population in the absolute magnitude range -19.0 < M_r < -16.0. 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). 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. Based on the specific stellar angular momentum and the ellipticity, we find 11 slow rotators and 28 fast rotators. The fast rotators in the outer parts of the Virgo cluster rotate significantly faster than fast rotators in the inner parts of the cluster. Moreover, 10 out of the 11 slow rotators are located in the inner Mpc of the cluster. The fast rotators contain subtle disky structures that are visible in high-pass filtered optical images, while the slow rotators do not exhibit these structures. In addition, two of the dEs have kinematically decoupled cores and four more have emission partially filling in the Balmer absorption lines. These properties suggest that Virgo cluster dEs may have originated from late-type star-forming galaxies that were transformed by the environment after their infall into the cluster. The correlation between the specific angular momentum and the clustercentric distance can be explained by a scenario where low luminosity star-forming galaxies fall into the cluster, their gas is rapidly removed by ram pressure stripping, although some of it can be retained in their core, their star-formation is quenched but their stellar kinematics are preserved. After a long time in the cluster and several passes through its center, the galaxies are heated up and transformed into slow rotating dEs.

Toloba, Elisa; Guhathakurta, Puragra; Peletier, Reynier; Boselli, Alessandro; Lisker, Thorsten; Emsellem, Eric; Simon, Joshua D.; van de Ven, Glenn; Smakced Collaboration

2015-01-01

15

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

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...

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

16

Substructure in Dwarf Galaxies  

E-print Network

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.

Matthew Coleman

2004-08-10

17

Stellar Kinematics and Structural Properties of Virgo Cluster Dwarf Early-type Galaxies from the SMAKCED Project. III. Angular Momentum and Constraints on Formation Scenarios  

NASA Astrophysics Data System (ADS)

We analyze the stellar kinematics of 39 dwarf early-type galaxies (dEs) in the Virgo Cluster. Based on the specific stellar angular momentum ?Re and the ellipticity, we find 11 slow rotators and 28 fast rotators. The fast rotators in the outer parts of the Virgo Cluster rotate significantly faster than fast rotators in the inner parts of the cluster. Moreover, 10 out of the 11 slow rotators are located in the inner 3° (D < 1 Mpc) of the cluster. The fast rotators contain subtle disk-like structures that are visible in high-pass filtered optical images, while the slow rotators do not exhibit these structures. In addition, two of the dEs have kinematically decoupled cores and four more have emission partially filling in the Balmer absorption lines. These properties suggest that Virgo Cluster dEs may have originated from late-type star-forming galaxies that were transformed by the environment after their infall into the cluster. The correlation between ?Re and the clustercentric distance can be explained by a scenario where low luminosity star-forming galaxies fall into the cluster, their gas is rapidly removed by ram-pressure stripping, although some of it can be retained in their core, their star formation is quenched but their stellar kinematics are preserved. After a long time in the cluster and several passes through its center, the galaxies are heated up and transformed into slow rotating dEs.

Toloba, E.; Guhathakurta, P.; Boselli, A.; Peletier, R. F.; Emsellem, E.; Lisker, T.; van de Ven, G.; Simon, J. D.; Falcón-Barroso, J.; Adams, J. J.; Benson, A. J.; Boissier, S.; den Brok, M.; Gorgas, J.; Hensler, G.; Janz, J.; Laurikainen, E.; Paudel, S.; Ry?, A.; Salo, H.

2015-02-01

18

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

E-print Network

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...

Longobardi, Alessia; Gerhard, Ortwin; Hanuschik, Reinhard

2015-01-01

19

Stellar substructures in the solar neighbourhood. III. Kinematic group 2 in the Geneva-Copenhagen survey  

NASA Astrophysics Data System (ADS)

Context. From correlations between orbital parameters, several new coherent groups of stars were recently identified in the Galactic disc and suggested to correspond to remnants of disrupted satellites. To reconstruct their origin at least three main observational parameters - kinematics, chemical composition and age - must be known. Aims: We determine detailed elemental abundances in stars belonging to the so-called Group 2 of the Geneva-Copenhagen Survey and compare the chemical composition with Galactic thin- and thick-disc stars, as well as with the Arcturus and AF06 streams (Arifyanto & Fuchs 2006, A&A, 449, 533). The aim is to search for chemical signatures that might give information about the formation 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 were 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 32 stars of Group 2 is - 0.42 ± 0.10 dex. The investigated group consists mainly of two 8- and 12-Gyr-old stellar populations. Abundances of oxygen, ?-elements, and r-process-dominated elements are higher than in Galactic thin-disc dwarfs. This elemental abundance pattern has similar characteristics as that of the Galactic thick-disc. Conclusions: The similarity in chemical composition of stars in Group 2 with that in stars of the thick-disc might suggest that their formation histories are linked. The chemical composition together with the kinematic properties and ages of stars in the stars investigated provides evidence of their common origin and possible relation to an ancient merging event. A gas-rich satellite merger scenario is proposed as the most likely origin. Groups 2 and 3 of the Geneva-Copenhagen Survey might have originated in the same merging event. Tables 4 and 5 are available in electronic form at http://www.aanda.org

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

2014-03-01

20

Stellar substructures in the solar neighbourhood . IV. Kinematic Group 1 in the Geneva-Copenhagen survey  

NASA Astrophysics Data System (ADS)

Context. A combined study of kinematics and chemical composition of stars is one of the most promising tools of research in Galaxy formation. The main goal in this field of research is to reconstruct the formation history of our Galaxy, to reveal the origin of the thick disc, and to find remnants of ancient mergers. Aims: We determine detailed elemental abundances in stars belonging to the so-called Group 1 of the Geneva-Copenhagen survey (GCS) and compare the chemical composition with the Galactic thin- and thick-disc stars, with the GCS Group 2 and Group 3 stars, as well as with several kinematic streams of similar metallicities. The aim is to search for chemical signatures that might give information about the formation history of this kinematic group of stars. Methods: High-resolution spectra were obtained with the Fibre-fed Echelle Spectrograph spectrograph at the Nordic Optical Telescope, La Palma, and were 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 37 stars of Group 1 is -0.20 ± 0.14 dex. Investigated Group 1 stars can be separated into three age subgroups. Along with the main 8- and 12-Gyr-old populations, a subgroup of stars younger than 5 Gyr can be separated as well. Abundances of oxygen, ?-elements, and r-process dominated elements are higher than in Galactic thin-disc dwarfs. This elemental abundance pattern has similar characteristics to that of the Galactic thick disc and differs slightly from those in Hercules, Arcturus, and AF06 stellar streams. Conclusions: The similar chemical composition of stars in Group 1, as well as in Group 2 and 3, with that in stars of the thick disc might suggest that their formation histories are linked. The chemical composition pattern together with the kinematic properties and ages of stars in the investigated GCS groups provide evidence of their common origin and possible relation to an ancient merging event. A gas-rich satellite merger scenario is proposed as the most likely origin. Tables 4 and 5 are available in electronic form at http://www.aanda.org

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

2015-04-01

21

The GALEX Ultraviolet Virgo Cluster Survey (GUViCS). IV. The role of the cluster environment on galaxy evolution  

NASA Astrophysics Data System (ADS)

We study the role of the environment on galaxy evolution using a sample of 868 galaxies in the Virgo cluster and in its surrounding regions that are selected from the GALEX Ultraviolet Virgo Cluster Survey (GUViCS) with the purpose of understanding the origin of the red sequence in dense environments. The sample spans a wide range in morphological types (from dwarf ellipticals to Im and BCD) and stellar masses (107 ? Mstar ? 1011.5M?). We collected multifrequency data covering the whole electromagnetic spectrum for most of the galaxies, including UV, optical, mid- and far-infrared imaging data, as well as optical and HI spectroscopic data. We first identify the different dynamical substructures that compose the Virgo cluster, and we calculate the local density of galaxies using different methods. We then study the distribution of galaxies belonging to the red sequence, the green valley, and the blue cloud within the different cluster substructures or as a function of galaxy density. Our analysis indicates that all the most massive galaxies (Mstar ? 1011M?) are slow rotators and are the dominant galaxies of the different cluster substructures, which are generally associated with a diffuse X-ray emission. They are probably the result of major merging events that occurred at early epochs, as also indicated by their very old stellar populations. Slow rotators of lower stellar mass (108.5 ? Mstar ? 1011M?) are also preferentially located within the different high-density substructures of the cluster. Their position in the velocity space indicates that they are virialised within the cluster; thus, they are Virgo members since its formation. They have been shaped by gravitational perturbations occurring within the infalling groups that later form the cluster (pre-processing). On the contrary, low-mass star-forming systems are extremely rare in the inner regions of the Virgo cluster A, where the density of the intergalactic medium is at its maximum. Our ram pressure stripping models consistently indicate that these star-forming systems can be rapidly deprived of their interstellar medium during their interaction with the intergalactic medium. The lack of gas quenches their star-formation activity transforming them into quiescent dwarf ellipticals. This mild transformation does not perturb the kinematic properties of these galaxies, which still have rotation curves typical of star-forming systems. Appendices are available in electronic form at http://www.aanda.orgFull Table A.1 is 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/570/A69

Boselli, A.; Voyer, E.; Boissier, S.; Cucciati, O.; Consolandi, G.; Cortese, L.; Fumagalli, M.; Gavazzi, G.; Heinis, S.; Roehlly, Y.; Toloba, E.

2014-10-01

22

A Near-infrared Census of the Multicomponent Stellar Structure of Early-type Dwarf Galaxies in the Virgo Cluster  

NASA Astrophysics Data System (ADS)

The fraction of star-forming to quiescent dwarf galaxies varies from almost infinity in the field to zero in the centers of rich galaxy clusters. What is causing this pronounced morphology-density relation? What do quiescent dwarf galaxies look like when studied in detail, and what conclusions can be drawn about their formation mechanism? Here we study a nearly magnitude-complete sample (-19 < Mr < -16 mag) of 121 Virgo cluster early types with deep near-infrared images from the SMAKCED project. We fit two-dimensional models with optional inner and outer components, as well as bar and lens components (in ~15% of the galaxies), to the galaxy images. While a single Sérsic function may approximate the overall galaxy structure, it does not entirely capture the light distribution of two-thirds of our galaxies, for which multicomponent models provide a better fit. This fraction of complex galaxies shows a strong dependence on luminosity, being larger for brighter objects. We analyze the global and component-specific photometric scaling relations of early-type dwarf galaxies and discuss similarities with bright early and late types. The dwarfs' global galaxy parameters show scaling relations that are similar to those of bright disk galaxies. The inner components are mostly fitted with Sérsic n values close to 1. At a given magnitude, they are systematically larger than the bulges of spirals, suggesting that they are not ordinary bulges. We argue that the multicomponent structures in early-type dwarfs are mostly a phenomenon inherent to the disks and may indeed stem from environmental processing. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under program IDs 064.N-0288 and 085.B-0919.

Janz, J.; Laurikainen, E.; Lisker, T.; Salo, H.; Peletier, R. F.; Niemi, S.-M.; Toloba, E.; Hensler, G.; Falcón-Barroso, J.; Boselli, A.; den Brok, M.; Hansson, K. S. A.; Meyer, H. T.; Ry?, A.; Paudel, S.

2014-05-01

23

Keck spectroscopy and NGVS photometry in the direction of the Virgo cluster: Globular cluster satellites of dwarf ellipticals, Milky Way halo substructure, and large-scale structure in the background  

NASA Astrophysics Data System (ADS)

The Virgo cluster, the nearest large galaxy cluster, is a rich repository of dwarf elliptical (dE) galaxies. The formation mechanism of dE galaxies remains the subject of much debate. Dwarf galaxies in general are believed to be building blocks in the hierarchical growth of galaxies as per the “cold dark matter” model of structure formation. Globular cluster (GC) satellites serve as important tracers of dark matter in the outer regions of dEs (beyond 1 half-light radius). This project presents new spectroscopic data from Keck's DEIMOS, which specifically targeted low-luminosity (-17 < Mv < -15) dEs and GC satellites, in the Virgo cluster. These data are among the deepest spectroscopic data ever taken in this region. Secondary science targets - Milky Way foreground stars and galaxies in the background - are also discussed. All targets were chosen based on photometric data from the Next Generation Virgo Survey (NGVS) and the Advanced Camera for Surveys Virgo Cluster Survey (ACSVCS). Further, these two surveys were critical to the tomographic analysis of spectroscopic targets. From this analysis we were able to: identify 117 GCs associated with any one of the 21 dE targets in the Virgo cluster, identify Milky Way foreground stars as part of the Virgo Overdensity or Sagittarius streams, quantify the velocity structure of these ongoing cannibalism events, and identify two new superclusters of galaxies in the background using redshift distribution. This research was carried out under the auspices of UCSC's Science Internship Program. We thank the National Science Foundation for funding support. ET was supported by a Fulbright fellowship.

Muller, Meredith; Toloba, E.; Guhathakurta, P.; Yagati, S.; Chen, J.; Cote, P.; Dorman, C.; Ferrarese, L.; Peng, E. W.; Next Generation Virgo Cluster Survey Collaboration

2014-01-01

24

Virgo status  

Microsoft Academic Search

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

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

25

Imaging Virgo's Diffuse Intracluster Light  

NASA Astrophysics Data System (ADS)

We use deep broad-band imaging of the Virgo Cluster using Case's Burrell Schmidt telescope to study the properties of its diffuse intracluster light (ICL). Our image -- 1.5 degrees on a side with a limiting depth of mu(V)=28.5 magnitudes per square arcsecond -- reveals an intricate web of diffuse intracluster light, including long (>100 kpc) tidal streams and a myriad of tidal tails and bridges between galaxies. The diffuse halo of M87 is traced out to nearly 200 kpc, and significant diffuse light is also detected around the M84/M86 pair. The complex substructure seen in Virgo's diffuse ICL reflects the hierarchical nature of cluster assembly, rather than being the product of smooth accretion around a central galaxy. We also present quantitative comparisons between our measurements of Virgo's ICL and those obtained from discrete tracers of starlight such as planetary nebulae and red giants. This work has been sponsored by the National Science Foundation and Research Corporation.

Mihos, C.; Harding, P.; Feldmeier, J.; Morrison, H.

2005-12-01

26

The Next Generation Virgo Cluster Survey-Infrared (NGVS-IR). I. A New Near-Ultraviolet, Optical, and Near-Infrared Globular Cluster Selection Tool  

NASA Astrophysics Data System (ADS)

The NGVS-IR project (Next Generation Virgo Cluster Survey-Infrared) is a contiguous, near-infrared imaging survey of the Virgo cluster of galaxies. It complements the optical wide-field survey of Virgo (NGVS). In its current state, NGVS-IR consists of Ks -band imaging of 4 deg2 centered on M87 and J- and Ks -band imaging of ~16 deg2 covering the region between M49 and M87. We present observations of the central 4 deg2 centered on Virgo's core region. The data were acquired with WIRCam on the Canada-France-Hawaii Telescope, and the total integration time was 41 hr distributed over 34 contiguous tiles. A survey-specific strategy was designed to account for extended galaxies while still measuring accurate sky brightness within the survey area. The average 5? limiting magnitude is Ks = 24.4 AB mag, and the 50% completeness limit is Ks = 23.75 AB mag for point-source detections, when using only images with better than 0.''7 seeing (median seeing 0.''54). Star clusters are marginally resolved in these image stacks, and Virgo galaxies with \\mu _{K_s} \\simeq 24.4 AB mag arcsec-2 are detected. Combining the Ks data with optical and ultraviolet data, we build the uiKs color-color diagram, which allows a very clean color-based selection of globular clusters in Virgo. This diagnostic plot will provide reliable globular cluster candidates for spectroscopic follow-up campaigns, needed to continue the exploration of Virgo's photometric and kinematic substructures, and will help the design of future searches for globular clusters in extragalactic systems. We show that the new uiKs diagram displays significantly clearer substructure in the distribution of stars, globular clusters, and galaxies than the gzKs diagram—the NGVS + NGVS-IR equivalent of the BzK diagram that is widely used in cosmological surveys. Equipped with this powerful new tool, future NGVS-IR investigations based on the uiKs diagram will address the mapping and analysis of extended structures and compact stellar systems in and around Virgo galaxies. Based on observations obtained with WIRCam, a joint project of Canada-France-Hawaii Telescope (CFHT), Taiwan, Korea, Canada, France, and the CFHT, which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Muñoz, Roberto P.; Puzia, Thomas H.; Lançon, Ariane; Peng, Eric W.; Côté, Patrick; Ferrarese, Laura; Blakeslee, John P.; Mei, Simona; Cuillandre, Jean-Charles; Hudelot, Patrick; Courteau, Stéphane; Duc, Pierre-Alain; Balogh, Michael L.; Boselli, Alessandro; Bournaud, Frédéric; Carlberg, Raymond G.; Chapman, Scott C.; Durrell, Patrick; Eigenthaler, Paul; Emsellem, Eric; Gavazzi, Giuseppe; Gwyn, Stephen; Huertas-Company, Marc; Ilbert, Olivier; Jordán, Andrés; Läsker, Ronald; Licitra, Rossella; Liu, Chengze; MacArthur, Lauren; McConnachie, Alan; McCracken, Henry Joy; Mellier, Yannick; Peng, Chien Y.; Raichoor, Anand; Taylor, Matthew A.; Tonry, John L.; Tully, R. Brent; Zhang, Hongxin

2014-01-01

27

Status of Virgo detector  

Microsoft Academic Search

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

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

28

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  

NASA Astrophysics Data System (ADS)

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 < Mr < -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? and H?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 Re of log Me = 9.1 ± 0.2 and a median dark matter fraction within the Re of f DM = 46 ± 18%. Any formation model for the dE galaxy class must account for this diversity of kinematic and photometric anomalies and stellar populations.

Toloba, E.; Guhathakurta, P.; Peletier, R. F.; Boselli, A.; Lisker, T.; Falcón-Barroso, J.; Simon, J. D.; van de Ven, G.; Paudel, S.; Emsellem, E.; Janz, J.; den Brok, M.; Gorgas, J.; Hensler, G.; Laurikainen, E.; Niemi, S.-M.; Ry?, A.; Salo, H.

2014-12-01

29

The status of VIRGO  

Microsoft Academic Search

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.

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

30

Status of VIRGO  

Microsoft Academic Search

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

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

31

Signatures of LCDM substructure in tidal debris  

E-print Network

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.

Jennifer M. Siegal-Gaskins; Monica Valluri

2008-03-25

32

UPDATE ON THE NATURE OF VIRGO OVERDENSITY  

SciTech Connect

We use the Eighth Data Release of Sloan Digital Sky Survey catalog with its additional sky coverage of the southern Galactic hemisphere to measure the extent and to study the nature of the Virgo Overdensity (VOD). The data show that the VOD extends over no less than 2000 deg{sup 2}, with its true extent likely closer to 3000 deg{sup 2}. We test whether the VOD can be attributed to a tilt in the stellar halo ellipsoid with respect to the plane of the Galactic disk and find that the observed symmetry of the north-south Galactic hemisphere star counts excludes this possibility. We argue that the Virgo Overdensity, in spite of its wide area and cloud-like appearance, is still best explained by a minor merger. Its appearance and position are qualitatively similar to a near perigalacticon merger event and, assuming that the VOD and the Virgo Stellar Stream (VSS) share the same progenitor, consistent with the VSS orbit determined by Casetti-Dinescu et al.

Bonaca, Ana [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Juric, Mario [Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Ivezic, Zeljko [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Daniel; Pan, Kaike; Shelden, Alaina; Simmons, Audrey; Snedden, Stephanie, E-mail: ana.bonaca@yale.edu, E-mail: mjuric@cfa.harvard.edu [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349 (United States)

2012-05-15

33

Advanced Virgo: AN Update  

NASA Astrophysics Data System (ADS)

Significant progress has been made in recent years on the development of gravitational wave detectors. Several km-scale interferometers have already operated at interesting sensitivity levels. In particular, the interferometric detector for gravitational waves Virgo completed its fourth science run in August 2011, when the upgrade toward the second-generation detector Advanced Virgo started. This major upgrade is planned to be completed by 2015. The expected final sensitivity of Advanced Virgo is about ten times better than the sensitivity reached by its predecessor. Many of the components of the detector will be changed to meet this goal, including new core optics, a more powerful laser, an improved vacuum system, the implementation of the signal-recycling technique. In this paper the description of the project and the expected schedule are presented.

Fafone, Viviana

2015-01-01

34

Status of Virgo  

Microsoft Academic Search

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.

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

35

Status of VIRGO  

Microsoft Academic Search

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

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

36

The Virgo status  

Microsoft Academic Search

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

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

37

Jet Substructure Without Trees  

SciTech Connect

We present an alternative approach to identifying and characterizing jet substructure. An angular correlation function is introduced that can be used to extract angular and mass scales within a jet without reference to a clustering algorithm. This procedure gives rise to a number of useful jet observables. As an application, we construct a top quark tagging algorithm that is competitive with existing methods. In preparation for the LHC, the past several years have seen extensive work on various aspects of collider searches. With the excellent resolution of the ATLAS and CMS detectors as a catalyst, one area that has undergone significant development is jet substructure physics. The use of jet substructure techniques, which probe the fine-grained details of how energy is distributed in jets, has two broad goals. First, measuring more than just the bulk properties of jets allows for additional probes of QCD. For example, jet substructure measurements can be compared against precision perturbative QCD calculations or used to tune Monte Carlo event generators. Second, jet substructure allows for additional handles in event discrimination. These handles could play an important role at the LHC in discriminating between signal and background events in a wide variety of particle searches. For example, Monte Carlo studies indicate that jet substructure techniques allow for efficient reconstruction of boosted heavy objects such as the W{sup {+-}} and Z{sup 0} gauge bosons, the top quark, and the Higgs boson.

Jankowiak, Martin; Larkoski, Andrew J.; /SLAC /Stanford U., ITP

2011-08-19

38

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

PubMed

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

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

2010-04-16

39

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

40

Jet Substructure Without Trees  

E-print Network

We present an alternative approach to identifying and characterizing jet substructure. An angular correlation function is introduced that can be used to extract angular and mass scales within a jet without reference to a clustering algorithm. This procedure gives rise to a number of useful jet observables. As an application, we construct a top quark tagging algorithm that is competitive with existing methods.

Martin Jankowiak; Andrew J. Larkoski

2011-06-30

41

The SEGUE K Giant Survey. III. Quantifying Galactic Halo Substructure  

E-print Network

We statistically quantify the amount of substructure in the Milky Way stellar halo using a sample of 4568 halo K giant stars at Galactocentric distances ranging over 5-125 kpc. These stars have been selected photometrically and confirmed spectroscopically as K giants from the Sloan Digital Sky Survey's SEGUE project. We use a position-velocity clustering estimator (the 4distance) and a smooth stellar halo model to quantify the amount of substructure in the halo. Overall, we find that the halo as a whole is highly structured, and confirm earlier work using BHB stars which showed that there is an increasing amount of substructure with increasing Galactocentric radius. In addition, we find that the amount of substructure in the halo increases with increasing metallicity, and that the K giant sample shows significantly stronger substructure than the BHB stars, which only sample the most metal poor stars. Using a friends-of-friends algorithm to identify groups, we find that a large fraction ($\\sim 33\\%$) of the st...

Janesh, William; Ma, Zhibo; Harding, Paul; Rockosi, Constance; Starkenburg, Else; Xue, Xiang Xiang; Rix, Hans-Walter; Beers, Timothy C; Johnson, Jennifer; Lee, Young Sun; Schneider, Donald P

2015-01-01

42

Damping synthesis from substructure tests  

NASA Technical Reports Server (NTRS)

A new method is proposed for synthesizing structural damping from substructure test data. It utilizes the off-diagonal coupling terms in the substructure modal damping matrices as well as the diagonal terms which correspond to uncoupled modal damping. The coupling terms are evaluated from complex resonant response measured at each substructure mode. Both analytical and experimental verification of the method have been made. Accuracy requirements on experimental data and data reduction have been established.

Hasselman, T. K.

1974-01-01

43

The Purple Rose of Virgo  

NASA Astrophysics Data System (ADS)

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.

2007-03-01

44

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

significantly younger ages than fainter dEs (Mr -17.0 mag). The magnitude overlap between these two subgroups to be no significant difference between the stellar populations of dEs with and without discs when compared at the same not exhibit the same average stellar population characteristics for different morphological subclasses

Kuntschner, Harald

45

The Next Generation Virgo Cluster Survey. IV. NGC 4216: A Bombarded Spiral in the Virgo Cluster  

NASA Astrophysics Data System (ADS)

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-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. Based on observations obtained with MegaPrime/MegaCam, a joint project of Canada-France-Hawaii Telescope (CFHT) and CEA/DAPNIA, at the CFHT which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Paudel, Sanjaya; Duc, Pierre-Alain; Côté, Patrick; Cuillandre, Jean-Charles; Ferrarese, Laura; Ferriere, Etienne; Gwyn, Stephen D. J.; Mihos, J. Christopher; Vollmer, Bernd; Balogh, Michael L.; Carlberg, Ray G.; Boissier, Samuel; Boselli, Alessandro; Durrell, Patrick R.; Emsellem, Eric; MacArthur, Lauren A.; Mei, Simona; Michel-Dansac, Leo; van Driel, Wim

2013-04-01

46

The Extended Virgo Cluster Catalog  

NASA Astrophysics Data System (ADS)

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.

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

47

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

SciTech Connect

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.

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

48

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

SciTech Connect

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.

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

49

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

Microsoft Academic Search

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

A. F. Lanza; M. Rodonò; I. Pagano

2004-01-01

50

Proposed definition of crystal substructure and substructural similarity  

NASA Astrophysics Data System (ADS)

There is a clear need for a practical and mathematically rigorous description of local structure in inorganic compounds so that structures and chemistries can be easily compared across large data sets. Here a method for decomposing crystal structures into substructures is given, and a similarity function between those substructures is defined. The similarity function is based on both geometric and chemical similarity. This construction allows for large-scale data mining of substructural properties, and the analysis of substructures and void spaces within crystal structures. The method is validated via the prediction of Li-ion intercalation sites for the oxides. Tested on databases of known Li-ion-containing oxides, the method reproduces all Li-ion sites in an oxide with a maximum of 4 incorrect guesses 80% of the time.

Yang, Lusann; Dacek, Stephen; Ceder, Gerbrand

2014-08-01

51

The Virgo automatic alignment system  

Microsoft Academic Search

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

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

52

Spiral Galaxy - ICM Interactions in the Virgo Cluster  

E-print Network

We discuss HI and optical evidence for ongoing ICM-ISM interactions in 6 HI-deficient Virgo cluster spiral galaxies. One of the clearest cases is the highly inclined Virgo galaxy NGC 4522, which has a normal stellar disk but a truncated gas disk, and lots of extraplanar gas right next to the gas truncation radius in the disk. Unusually strong HI, H-alpha and radio continuum emission are all detected from the extraplanar gas. The radio continuum polarized flux and spectral index peak on the side opposite the extraplanar gas, suggesting ongoing pressure by the ICM. Four other HI-deficient edge-on Virgo spirals show evidence of extraplanar ISM gas or exhibit asymmetries in their disk HI distributions, but contain much less extraplanar HI than NGC 4522. Comparison with recent simulations suggests this difference may be evolutionary, with large surface densities of extraplanar gas observed only in early phases of an ICM-ISM interaction. In NGC 4569, the H-alpha image shows 2 effects of ICM pressure on the galaxy ISM. An anomalous arm of HII regions, possibly extraplanar, emerges from the edge of a truncated H-alpha disk. This resembles the arms seen in simulations which are formed by the combined effects of wind pressure plus rotation. An extended nebulosity near the minor axis, also in the NW, is interpreted as a starburst outflow bubble disturbed by ICM wind pressure.

Jeffrey D. P. Kenney; Hugh Crowl; Jacqueline van Gorkom; Bernd Vollmer

2004-03-04

53

The Infrared Follow-Up of the Next Generation Virgo Survey (NGVS-IR): Survey Status and First Results  

NASA Astrophysics Data System (ADS)

The Next Generation Virgo Survey (NGVS) is a multi-wavelength imaging survey of the Virgo galaxy cluster, that was designed to provide deep, high spatial resolution and contiguous coverage of Virgo from its core to the virial radius. In this talk, I will first introduce the near-IR follow-up of the NGVS survey (NGVS-IR) and show some preliminary results. The NGVS-IR survey consists of K-band imaging of 4 square degree centered on M87 with the WIRCAM instrument at the CFHT telescope, and J and K-band imaging of 5 square degree centered on M49 with the VIRCAM instrument at the VISTA telescope. The aims of the survey are to study the age and metallicity distributions of M87 globular clusters, the K-band luminosity function of Virgo cluster galaxies, and the identification of 0.8 < z < 1.4 galaxy clusters in the Virgo area. A comparison against the 2MASS, UKIDSS and HeViCS datasets covering the same area, reveals the unique characteristics of the NGVS-IR survey and places it as the best-ever done near-IR survey of the Virgo galaxy cluster. Finally, I will discuss on-going plans for studying the low-mass end of the stellar mass function of galaxies in Virgo.

Munoz, Roberto; Puzia, T.; Lançon, A.

2013-01-01

54

X-ray survey of the Virgo cluster and comparison to field galaxies  

NASA Technical Reports Server (NTRS)

X-ray observations of about 60 galaxies in the Virgo cluster and about 80 field galaxies are reviewed. M87 and its surrounding envelopes of gas and dark matter are described, and M87's dominance of the cluster in X-rays is discussed. The X-ray emission from early-type galaxies in Virgo and the field is discussed, and it is shown that these galaxies are surrounded by hot gaseous coronae which can be used to probe the masses of these galaxies. The gas masses of these coronae can be explained as the accumulated gas lost by stellar systems during their evolution. It is shown that supernovae can play an important role in heating the gas. Finally, early and late type field galaxies are compared to those in the Virgo cluster, and the possible effects of the cluster environment on their X-ray properties is discussed.

Forman, W.; Jones, C.; Defaccio, M.

1985-01-01

55

Status of the VIRGO experiment  

Microsoft Academic Search

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

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

56

Early Evolution of Stellar Clusters  

E-print Network

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.

Ian A. Bonnell

1999-08-24

57

Dark Matter Substructure within Galactic Halos  

Microsoft Academic Search

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

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

1999-01-01

58

The VIRGO interferometer for gravitational wave detection  

Microsoft Academic Search

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

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

59

A deep view on the Virgo cluster core  

NASA Astrophysics Data System (ADS)

Studies of dwarf spheroidal (dSph) galaxies with statistically significant sample sizes are still rare beyond the Local Group, since these low surface brightness objects can only be identified with deep imaging data. In galaxy clusters, where they constitute the dominant population in terms of number, they represent the faint end slope of the galaxy luminosity function and provide important insight on the interplay between galaxy mass and environment. In this study we investigate the optical photometric properties of early-type galaxies (dwarf ellipticals (dEs) and dSphs) in the Virgo cluster core region, by analysing their location on the colour magnitude relation (CMR) and the structural scaling relations down to faint magnitudes, and by constructing the luminosity function to compare it with theoretical expectations. Our work is based on deep CFHT V- and I-band data covering several square degrees of the Virgo cluster core that were obtained in 1999 using the CFH12K instrument. We visually select potential cluster members based on morphology and angular size, excluding spiral galaxies. A photometric analysis has been carried out for 295 galaxies, using surface brightness profile shape and colour as further criteria to identify probable background contaminants. 216 galaxies are considered to be certain or probable Virgo cluster members. Our study reveals 77 galaxies not catalogued in the VCC (with 13 of them already found in previous studies) that are very likely Virgo cluster members because they follow the Virgo CMR and exhibit low Sérsic indices. Those galaxies reach MV = -8.7 mag. The CMR shows a clear change in slope from dEs to dSphs, while the scatter of the CMR in the dSph regime does not increase significantly. Our sample might, however, be somewhat biased towards redder colours. The scaling relations given by the dEs appear to be continued by the dSphs indicating a similar origin. The observed change in the CMR slope may mark the point at which gas loss prevented significant metal enrichment. The almost constant scatter around the CMR possibly indicates a short formation period, resulting in similar stellar populations. The luminosity function shows a Schechter function's faint end slope of ? = -1.50 ± 0.17, implying a lack of galaxies related to the expected number of low-mass dark matter haloes from theoretical models. Our findings could be explained by suppressed star formation in low-mass dark matter halos or by tidal disruption of dwarfs in the dense core region of the cluster. Tables 3 and 4 are available in electronic form at http://www.aanda.org

Lieder, S.; Lisker, T.; Hilker, M.; Misgeld, I.; Durrell, P.

2012-02-01

60

On Kinematic Substructure in the Sextans Dwarf Spheroidal Galaxy  

E-print Network

We present multifiber echelle radial velocity results for 551 stars in the Sextans dwarf spheroidal galaxy and identify 294 stars as probable Sextans members. The projected velocity dispersion profile of the binned data remains flat to a maximum angular radius of $30^{\\prime}$. We introduce a nonparametric technique for estimating the projected velocity dispersion surface, and use this to search for kinematic substructure. Our data do not confirm previous reports of a kinematically distinct stellar population at the Sextans center. Instead we detect a region near the Sextans core radius that is kinematically colder than the overall Sextans sample with 95% confidence.

Matthew G. Walker; Mario Mateo; Edward W. Olszewski; Jayanta Kumar Pal; Bodhisattva Sen; Michael Woodroofe

2006-03-24

61

Populating the Virgo Velocity Function with Early-Type Galaxies at Gemini  

NASA Astrophysics Data System (ADS)

We propose to sample the circular velocity function (CVF) and stellar-to-halo mass relation (SHMR) of Virgo early-type galaxies (ETGs) in the stellar mass range M* = 10^(7-10) Msol. This proposal is part of a large effort to characterize the dynamical and stellar population properties of a representative sample of Virgo ETGs for which deep near-UV/optical/near-IR imaging exists. The proposed sample will significantly augment the crucial low-mass range below M* < 10^9 Msol, where the sharp LCDM predictions for the CVF and SHMR (abundance matching) are fully unconstrained due to significant incompleteness (0-20%) of current data bases. Numerous tantalizing trends, such as bifurcations and possible bimodalities of mass relations for ETGs and LTGs, may prove transformational for galaxy structure studies and must be confirmed with a study like ours. We seek GMOS absorption spectra of 35 faint ETGs for a total of 100 hours of Canadian, US, and Chilean Gemini time. Our program exploits synergies of the Gemini and VLT observatories and will deliver a benchmark dataset of lasting legacy value, building upon our large Virgo cluster team expertise.

Ouellette, Nathalie; Courteau, Stephane; Holtzman, Jon; Puzia, Thomas; Bovill, Mia; Cappellari, Michele; Cote, Patrick; Dalcanton, Julianne; Dutton, Aaron; Eigenthaler, Paul; Emsellem, Eric; Ferrarese, Laura; McDonald, Michael; Munoz, Roberto; Roediger, Joel; Tully, Brent

2014-02-01

62

Characterization of the Virgo Seismic Environment  

E-print Network

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.

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

63

Experimental Modal Substructuring to Couple and Uncouple Substructures with Flexible Fixtures and Multi-  

E-print Network

forces ­ mass normalized mode shape matrix r ­ natural frequency ­ modal damping ratio a ­ matrix1 Experimental Modal Substructuring to Couple and Uncouple Substructures with Flexible Fixtures Technical College 3550 Anderson Street, Madison, Wisconsin 53704 Abstract Modal substructuring or Component

Allen, Matthew S.

64

The Dynamics of the Northern Part of the Virgo Cluster  

NASA Astrophysics Data System (ADS)

Several regions of the Virgo cluster have been studied with XMM-Newton providing spectacular results. One of the most interesting regions, the interaction zone between the infalling M86 galaxy group and the matter in the giant X-ray halo of M87 has so far been spared. We have interesting optical data on the stellar dynamics showing a clear edge of M87 and a transition to the cluster environment. We also find evidence for gas compression in the interaction zone in shallow ROSAT observations. Therefore we proposed in AO12 to study the X-ray emission region between M86 and M87 with 3 deep XMM-Newton pointings which were approved in category C. The observations have not been performed or scheduled yet. Therefore we repropose them for AO13 if not performed by the end of AO12.

Boehringer, Hans

2013-10-01

65

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

E-print Network

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.

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

2007-04-19

66

Chemical substructure analysis in toxicology  

SciTech Connect

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.

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

1990-12-31

67

Study of modeling of substructure damping matrices.  

NASA Technical Reports Server (NTRS)

Several methods are presented for developing proportional substructure damping matrices from modal test data. Examples demonstrate the significance of the nonuniqueness of the resulting proportional damping matrices. Several alternate modal synthesis procedures are presented for the systematic calculation of system modal damping from substructure damping information. The relative merits of these procedures are discussed, and one procedure is recommended.

Hart, G. C.; Collins, J. D.

1972-01-01

68

The structure of the Virgo cluster of galaxies  

Microsoft Academic Search

A new detailed analysis of galaxies in the Virgo area shows that the conventional Virgo cluster comprises two different clouds of galaxies: the Virgo cluster I and the Southern cloud II by our definition. The Virgo cluster I centered at 12h27m.6, +13°07arcmin (1950), has a mean radial velocity of >V0< ? +980±60 km s-1 and there is no significant velocity

K. I. Tanaka

1985-01-01

69

DATA ACQUISITION AND ONLINE PROCESSING FOR THE VIRGO EXPERIMENT  

E-print Network

DATA ACQUISITION AND ONLINE PROCESSING FOR THE VIRGO EXPERIMENT D. VERKINDT, F. BELLACHIA, R of the data acquisition currently installed on Virgo site and the planned Online Processing (h reconstruction Acquisition 1.1 Introduction A 3km long interferometric detector like Virgo needs to acquire interferometer

Paris-Sud XI, Université de

70

CADIS has seen the Virgo overdensity and parts of the Monoceros and `Orphan' streams in retrospect  

E-print Network

We reanalyze deep star counts in five CADIS fields. The data are presented as vertical density distributions of stars perpendicular to the Galactic plane. In three fields the profiles are consistent with each other, while in two fields significant overdensities of stars are found. The overdensity in one field can be associated with the Virgo overdensity which can be traced right into the disk of the Milky Way. Using this detection we estimate the mass of the Virgo overdensity and show that this is equivalent to the stellar content of a Local Group dwarf spheroidal galaxy. The overdensity in the second field is more difficult to associate with a previously known overdensity. We suggest that it is related both to the Monoceros stream and the recently discovered Orphan stream.

B. Fuchs; S. Phleps; K. Meisenheimer

2006-07-19

71

Systematic Problems With Stellar Halo Modelling  

NASA Astrophysics Data System (ADS)

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.

Bailin, Jeremy

2012-05-01

72

The Spatial Distribution of Virgo's Globular Clusters  

NASA Astrophysics Data System (ADS)

We present the results for a search for globular clusters (GCs) throughout the Virgo Cluster, using deep g'i' photometry from the Next Generation Virgo Cluster Survey (NGVS), a large imaging program using the CFHT+MegaCam from which to study the entire cluster out to the virial radius. We estimate a total population of ~65000 GCs within our Virgo survey region (covering over 104 square degrees), where the red GCs are largely located within or near the many luminous early type galaxies, while the blue GCs have spatial profiles that extend into intracluster space. In particular, the core region (containing M87) shows a highly irregular spatial distribution that includes regions of likely intracluster globular clusters (IGCs).

Durrell, Patrick R.; Cote, P.; Peng, E. W.; Blakeslee, J.; Ferrarese, L.; Mihos, C.; NGVS Team

2014-01-01

73

Observations of Stripped Edge-on Virgo Cluster Galaxies  

E-print Network

We present observations of highly inclined, HI deficient, Virgo cluster spiral galaxies. Our high-resolution VLA HI observations of edge-on galaxies allow us to distinguish extraplanar gas from disk gas. All of our galaxies have truncated H-alpha disks, with little or no disk gas beyond a truncation radius. While all the gas disks are truncated, the observations show evidence for a continuum of stripping states: symmetric, undisturbed truncated gas disks indicate galaxies that were stripped long ago, while more asymmetric disks suggest ongoing or more recent stripping. We compare these timescale estimates with results obtained from two-dimensional stellar spectroscopy of the outer disks of galaxies in our sample. One of the galaxies in our sample, NGC 4522 is a clear example of active ram-pressure stripping, with 40% of its detected HI being extraplanar. As expected, the outer disk stellar populations of this galaxy show clear signs of recent (and, in fact, ongoing) stripping. Somewhat less expected, however, is the fact that the spectrum of the outer disk of this galaxy, with very strong Balmer absorption and no observable emission, would be classified as ``k+a'' if observed at higher redshift. Our observations of NGC 4522 and other galaxies at a range of cluster radii allow us to better understand the role that clusters play in the structure and evolution of disk galaxies.

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

2005-09-05

74

Parallel triangularization of substructured finite element problems  

NASA Technical Reports Server (NTRS)

Much of the computational effort of the finite element process involves the solution of a system of linear equations. The coefficient matrix of this system, known as the global stiffness matrix, is symmetric, positive definite, and generally sparse. An important technique for reducing the time required to solve this system is substructuring or matrix partitioning. Substructuring is based on the idea of dividing a structure into pieces, each of which can then be analyzed relatively indepenently. As a result of this division, each point in the finite element discretization is either interior to a substructure or on a boundary between substructures. Contributions to the global stiffness matrix from connections between boundary points from the K(bb) matrix are reported. The triangularization of a general K(bb) matrix on a parallel machine is specifically discussed.

Leuze, M. R.

1984-01-01

75

Stellarator hybrids  

SciTech Connect

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

Furth, H.P.; Ludescher, C.

1984-08-01

76

Algebraic sub-structuring for electromagnetic applications  

SciTech Connect

Algebraic sub-structuring refers to the process of applying matrix reordering and partitioning algorithms to divide a large sparse matrix into smaller submatrices from which a subset of spectral components are extracted and combined to form approximate solutions to the original problem. In this paper, we show that algebraic sub-structuring can be effectively used to solve generalized eigenvalue problems arising from the finite element analysis of an accelerator structure.

Yang, Chao; Gao, Weiguo; Bai, Zhaojun; Li, Xiaoye; Lee, Lie-Quan; Husbands, Parry; Ng, Esmond G.

2004-09-14

77

Algebraic Sub-Structuring for Electromagnetic Applications  

SciTech Connect

Algebraic sub-structuring refers to the process of applying matrix reordering and partitioning algorithms to divide a large sparse matrix into smaller submatrices from which a subset of spectral components are extracted and combined to form approximate solutions to the original problem. In this paper, they show that algebraic sub-structuring can be effectively used to solve generalized eigenvalue problems arising from the finite element analysis of an accelerator structure.

Yang, C.; Gao, W.G.; Bai, Z.J.; Li, X.Y.S.; Lee, L.Q.; Husbands, P.; Ng, E.G.; /LBL, Berkeley /UC, Davis /SLAC

2006-06-30

78

The VIRGO experiment: status of the art  

Microsoft Academic Search

The status report of the VIRGO experiment is presented. The experiment has been approved in September 1993 and is now under construction. Its aim is the detection of gravitational waves over a broad frequency range (10 Hz - 10 kHz) using a Michelson interferometer equipped with Fabry-Perot cavities 3 km long. The experiment will be installed in Cascina near Pisa

B. Caron; A. Dominjon; F. Marion; L. Massonet; R. Morand; B. Mours; M. Yvert; D. Babusci; H. Fang; G. Giordano; G. Matone; J.-M. Mackowski; M. Napolitano; L. Pinard; C. Boccara; P. Gleizes; V. Loriette; J.-P. Roger; F. Barone; E. Calloni; L. di Fiore; A. Grado; M. Longo; G. Marra; L. Milano; G. Russo; S. Solimeno; F. Bondu; A. Brillet; V. Brisson; F. Cleva; M. Davier; H. Heitman; 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; M. Barsuglia; M. Bernardini; S. Braccini; C. Bradaschia; R. Del Fabbro; A. di Virgilio; I. Ferrante; F. Fidecaro; R. Flaminio; A. Gennai; A. Giassi; A. Giazotto; G. Gorini; L. Ju; G. Losurdo; M. Morganti; F. Palla; H. B. Pan; A. Pasqualetti; D. Passuello; R. Poggiani; G. Torelli; Z. Zhou

1995-01-01

79

A structural design decomposition method utilizing substructuring  

NASA Technical Reports Server (NTRS)

A new method of design decomposition for structural analysis and optimization is described. For this method, the structure is divided into substructures where each substructure has its structural response described by a structural-response subproblem, and its structural sizing determined from a structural-sizing subproblem. The structural responses of substructures that have rigid body modes when separated from the remainder of the structure are further decomposed into displacements that have no rigid body components, and a set of rigid body modes. The structural-response subproblems are linked together through forces determined within a structural-sizing coordination subproblem which also determines the magnitude of any rigid body displacements. Structural-sizing subproblems having constraints local to the substructures are linked together through penalty terms that are determined by a structural-sizing coordination subproblem. All the substructure structural-response subproblems are totally decoupled from each other, as are all the substructure structural-sizing subproblems, thus there is significant potential for use of parallel solution methods for these subproblems.

Scotti, Stephen J.

1994-01-01

80

The Herschel Virgo Cluster Survey. XVIII. Star-forming dwarf galaxies in a cluster environment  

NASA Astrophysics Data System (ADS)

To assess the effects of the cluster environment on the different components of the interstellar medium, we analyse the far-infrared (FIR) and submillimetre (submm) properties of a sample of star-forming dwarf galaxies detected by the Herschel Virgo Cluster Survey (HeViCS). We determine dust masses and dust temperatures by fitting a modified black body function to the spectral energy distributions (SEDs). Stellar and gas masses, star formation rates (SFRs), and metallicities are obtained from the analysis of a set of ancillary data. Dust is detected in 49 out of a total 140 optically identified dwarfs covered by the HeViCS field; considering only dwarfs brighter than mB = 18 mag, this gives a detection rate of 43%. After evaluating different emissivity indices, we find that the FIR-submm SEDs are best-fit by ? = 1.5, with a median dust temperature Td = 22.4 K. Assuming ? = 1.5, 67% of the 23 galaxies detected in all five Herschel bands show emission at 500 ?m in excess of the modified black-body model. The fraction of galaxies with a submillimetre excess decreases for lower values of ?, while a similarly high fraction (54%) is found if a ?-free SED modelling is applied. The excess is inversely correlated with SFR and stellar masses. To study the variations in the global properties of our sample that come from environmental effects, we compare the Virgo dwarfs to other Herschel surveys,such as the Key Insights into Nearby Galaxies: Far-Infrared Survey with Herschel (KINGFISH), the Dwarf Galaxy Survey (DGS), and the HeViCS Bright Galaxy Catalogue (BGC). We explore the relations between stellar mass and Hi fraction, specific star formation rate, dust fraction, gas-to-dust ratio over a wide range of stellar masses (from 107 to 1011 M?) for both dwarfs and spirals. Highly Hi-deficient Virgo dwarf galaxies are mostly characterised by quenched star formation activity and lower dust fractions giving hints for dust stripping in cluster dwarfs. However, to explain the large dust-to-gas mass ratios observed in these systems, we find that the fraction of dust removed has to be less than that of the Hi component. The cluster environment seems to mostly affect the gas component and star formation activity of the dwarfs. Since the Virgo star-forming dwarfs are likely to be crossing the cluster for the first time, a longer timescale might be necessary to strip the more centrally concentrated dust distribution. Appendices are available in electronic form at http://www.aanda.org

Grossi, M.; Hunt, L. K.; Madden, S. C.; Hughes, T. M.; Auld, R.; Baes, M.; Bendo, G. J.; Bianchi, S.; Bizzocchi, L.; Boquien, M.; Boselli, A.; Clemens, M.; Corbelli, E.; Cortese, L.; Davies, J.; De Looze, I.; di Serego Alighieri, S.; Fritz, J.; Pappalardo, C.; Pierini, D.; Rémy-Ruyer, A.; Smith, M. W. L.; Verstappen, J.; Viaene, S.; Vlahakis, C.

2015-02-01

81

The substructure hierarchy in dark matter haloes  

NASA Astrophysics Data System (ADS)

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.

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

2010-05-01

82

Evidence for substructure in lens galaxies?  

E-print Network

We discuss whether one should expect that multiply imaged QSOs can be understood with `simple' lens models which contain a handful of parameters. Whereas for many lens systems such simple mass models yield a remarkably good description of the observed properties, there are some systems which are notoriously difficult to understand quantitatively. We argue that at least in one case (B 1422+231) these difficulties are not due to a `wrong' parametrization of the lens model, but that the discrepancy between observed and model-predicted flux ratios are due to substructure in the lens. Similar to microlensing for optical fluxes, such substructure can distort also the radio flux ratios predicted by `simple' mass models, in particular for highly magnified images, without appreciably changing image positions. Substructure also does not change the time delay significantly and therefore has little effect on the determination of the Hubble constant using time delays. We quantify these statements with several simple scenarios for substructure, and propose a strategy to model lens systems in which substructure is suspected.

Shude Mao; Peter Schneider

1997-07-16

83

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

SciTech Connect

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.

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

84

Blueshifted galaxies in the virgo cluster  

NASA Astrophysics Data System (ADS)

We examine a sample of 65 galaxies in the Virgo cluster with negative radial velocities relative to the Local Group. Some features of this sample are pointed out. All of these objects are positioned compactly within a virial zone of radius 6º in the cluster, but their centroid is displaced relative to the dynamic center of the cluster, M87, by 1º.1 to the northwest. The dwarf galaxies in this sample are clumped on a scale of ˜10' (50 kpc). The observed asymmetry in the distribution of the blueshifted galaxies may be caused by infall of a group of galaxies around M86 onto the main body of the cluster. We offer another attempt to explain this phenomenon, assuming a mutual tangential velocity of ˜300 km/s-1 between the Local Group and the Virgo cluster owing to their being repelled from the local cosmological void.

Karachentsev, I. D.; Nasonova (Kashibadze), O. G.

2010-01-01

85

The monolithic suspension for the Virgo interferometer  

NASA Astrophysics Data System (ADS)

Monolithic fused silica suspensions are needed to reduce the suspension thermal noise level in future, ground-based gravitational wave interferometric detectors. We present the status of the monolithic suspension system which will be employed for the test masses of the Virgo+ detector. Two fully monolithic suspensions have been realized using a spare Virgo mirror, so the assembling pipeline was checked; moreover, a very reliable recovery procedure was developed to allow an efficient and fast (about a week) suspension repairing in case of wires' failure. The performances of a full scale prototype of the last suspension stage, suspending an aluminum dummy mass, were tested and the mechanical behavior of the suspension is currently studied in vacuum. The obtained results, crucial to finalize the design of the silica suspension elements for the advanced version of the interferometer, are reported.

Lorenzini, M.; Virgo Collaboration

2010-04-01

86

Inverse substructure method for model updating of structures  

NASA Astrophysics Data System (ADS)

Traditional model updating of large-scale structures is usually time-consuming because the global structural model needs to be repeatedly re-analyzed as a whole to match global measurements. This paper proposes a new substructural model updating method. The modal data measured on the global structure are disassembled to obtain the independent substructural dynamic flexibility matrices under force and displacement compatibility conditions. The method is extended to the case when the measurement is carried out at partial degrees-of-freedom of the structure. The extracted substructural flexibility matrices are then used as references for updating the corresponding substructural models. An orthogonal projector is employed on both the extracted substructural measurements and the substructural models to remove the rigid body modes of the free-free substructures. Compared with the traditional model updating at the global structure level, only the sub-models at the substructural level are re-analyzed in the proposed substructure-based model updating process, resulting in a rapid convergence of optimization. Moreover, only measurement on the local area corresponding to the concerned substructures is required, and those on other components can be avoided. The effectiveness and efficiency of the proposed substructuring method are verified through applications to a laboratory-tested frame structure and a large-scale 600 m tall Guangzhou New TV Tower. The present technique is referred to as the inverse substructuring model updating method as the measured global modal data are disassembled into the substructure level and then the updating is conducted on the substructures only. This differs from the substructuring model updating method previously proposed by the authors, in which the model updating is still conducted in the global level and the numerical global modal data are assembled from those of substructures. That can be referred to as the forward substructuring model updating method.

Weng, Shun; Xia, Yong; Zhou, Xiao-Qing; Xu, You-Lin; Zhu, Hong-Ping

2012-12-01

87

Globular cluster formation in the Virgo cluster  

NASA Astrophysics Data System (ADS)

Metal-poor globular clusters (MPGCs) are a unique probe of the early universe, in particular the reionization era. A popular hypothesis is that the observed truncation of MPGC formation is due to reionization. Under this hypothesis, constraining the formation epoch of MPGCs provides a complementary constraint on the epoch of reionization. Moreover, as the earliest reionizing sources first formed in galaxy clusters, systems of globular clusters in galaxy clusters are of particular interest. We provide a self-consistent dark matter only zoom cosmological simulation to perform an analysis of the Virgo cluster globular cluster system by identifying the present-day globular cluster system with early, rare dark matter peaks. By analysing both the line-of-sight velocity dispersion and the surface density profile of the present-day distribution, we are able to constrain the redshift and mass of the dark matter peaks. Although found to be degenerate, we quantify a dependence on the chosen line of sight of these quantities, whose strength varies with redshift. Coupled with star formation efficiency arguments, we find a best-fitting formation mass and redshift of ?5 × 108 M? and z ? 9. We predict ?300 intracluster MPGCs in the Virgo cluster. Our results confirm the techniques pioneered by Moore et al. when applied to the Virgo cluster and extend and justify the analytic results of Spitler et al. numerically.

Corbett Moran, C.; Teyssier, R.; Lake, G.

2014-08-01

88

Synthesis of the isoquinocycline-pyrrolopyrrole substructure.  

PubMed

The synthesis of the pyrrolopyrrole substructure of the isoquinocyclines is reported. The pentacyclic (CDEFG) substructure of isoquinocycline A and B, which contains an unusual 2,4,5,6-tetrahydropyrrolo[2,3-b]pyrrole (FG) connected via an N,O-spiro acetal to the anthraquinoid core of the isoquinocycline aglycon has been synthesized. Key steps were a nickel(0)-mediated hydrocyanation of an alkynone, the conversion of an O,O-acetal into an N,O-acetal, and an intramolecular amidine alkylation. PMID:20698487

Cordes, Jens; Harms, Klaus; Koert, Ulrich

2010-09-01

89

Heterozygote deficiency, population substructure and their implications in DNA fingerprinting  

Microsoft Academic Search

Substructured populations exhibit an overall deficiency of heterozygosity whose proportional magnitude depends on the nature of substructuring, i.e., the number of subpopulations (s), their time of divergence (t) from the ancestral population, and the rate of gene flow amongst them (m). Since apparent heterozygote deficiency could be caused by many factors other than population substructuring, one must examine the nature

Ranajit Chakraborty; Li Jin

1992-01-01

90

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)

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.

Houdashelt, Mark L.; Frogel, Jay A.

1993-01-01

91

Boosted objects and jet substructure at the LHC  

E-print Network

This report of the BOOST2012 workshop presents the results of four working groups that studied key aspects of jet substructure. We discuss the potential of the description of jet substructure in first-principle QCD calculations and study the accuracy of state-of-the-art Monte Carlo tools. Experimental limitations of the ability to resolve substructure are evaluated, with a focus on the impact of additional proton proton collisions on jet substructure performance in future LHC operating scenarios. A final section summarizes the lessons learnt during the deployment of substructure analyses in searches for new physics in the production of boosted top quarks.

BOOST2012 participants- A. Altheimer; A. Arce; L. Asquith; J. Backus Mayes; E. Bergeaas Kuutmann; J. Berger; D. Bjergaard; L. Bryngemark; A. Buckley; J. Butterworth; M. Cacciari; M. Campanelli; T. Carli; M. Chala; B. Chapleau; C. Chen; J. P. Chou; Th. Cornelissen; D. Curtin; M. Dasgupta; A. Davison; F. de Almeida Dias; A. de Cosa; A. de Roeck; C. Debenedetti; C. Doglioni; S. D. Ellis; F. Fassi; J. Ferrando; S. Fleischmann; M. Freytsis; M. L. Gonzalez Silva; S. Gonzalez de la Hoz; F. Guescini; Z. Han; A. Hook; A. Hornig; E. Izaguirre; M. Jankowiak; J. Juknevich; M. Kaci; D. Kar; G. Kasieczka; R. Kogler; A. Larkoski; P. Loch; D. Lopez Mateos; S. Marzani; L. Masetti; V. Mateu; D. W. Miller; K. Mishra; P. Nef; K. Nordstrom; E. Oliver Garcia; J. Penwell; J. Pilot; T. Plehn; S. Rappoccio; A. Rizzi; G. Rodrigo; A. Safonov; G. P. Salam; J. Salt; S. Schaetzel; M. Schioppa; A. Schmidt; J. Scholtz; A. Schwartzman; M. D. Schwartz; M. Segala; M. Son; G. Soyez; M. Spannowsky; I. Stewart; D. Strom; M. Swiatlowski; V. Sanchez Martinez; M. Takeuchi; J. Thaler; E. Thompson; N. V. Tran; C. Vermilion; M. Villaplana; M. Vos; J. Wacker; J. Walsh

2013-12-04

92

Boosted objects and jet substructure at the LHC  

E-print Network

This report of the BOOST2012 workshop presents the results of four working groups that studied key aspects of jet substructure. We discuss the potential of the description of jet substructure in first-principle QCD calculations and study the accuracy of state-of-the-art Monte Carlo tools. Experimental limitations of the ability to resolve substructure are evaluated, with a focus on the impact of additional proton proton collisions on jet substructure performance in future LHC operating scenarios. A final section summarizes the lessons learnt during the deployment of substructure analyses in searches for new physics in the production of boosted top quarks.

Altheimer, A.; Asquith, L.; Backus Mayes, J.; Bergeaas Kuutmann, E.; Berger, J.; Bjergaard, D.; Bryngemark, L.; Buckley, A.; Butterworth, J.; Cacciari, M.; Campanelli, M.; Carli, T.; Chala, M.; Chen, C.; Chou, J.P.; Cornelissen, Th.; Curtin, D.; Dasgupta, M.; Davison, A.; De Almeida Dias, F.; De Cosa, A.; De Roeck, A.; Debenedetti, C.; Doglioni, C.; Ellis, S.D.; Fassi, F.; Ferrando, J.; Fleischmann, S.; Freytsis, M.; Gonzalez Silva, M.L.; Gonzalez de la Hoz, S.; Guescini, F.; Han, Z.; Hook, A.; Hornig, A.; Izaguirre, E.; Jankowiak, M.; Juknevich, J.; Kaci, M.; Kar, D.; Kasieczka, G.; Kogler, R.; Larkoski, A.; Loch, P.; Lopez Mateos, D.; Marzani, S.; Masetti, L.; Mateu, V.; Miller, D.W.; Mishra, K.; Nef, P.; Nordstrom, K.; Oliver Garcia, E.; Penwell, J.; Pilot, J.; Plehn, T.; Rappoccio, S.; Rizzi, A.; Rodrigo, G.; Safonov, A.; Salam, G.P.; Salt, J.; Schaetzel, S.; Schioppa, M.; Schmidt, A.; Scholtz, J.; Schwartzman, A.; Schwartz, M.; Segala, M.; Son, M.; Soyez, G.; Spannowsky, M.; Stewart, I.; Strom, D.; Swiatlowski, M.; Sanchez Martinez, V.; Takeuchi, M.; Thaler, J.; Thompson, E.; Tran, N.V.; Vermilion, C.; Villaplana, M.; Vos, M.; Wacker, J.; Walsh, J.

2014-01-01

93

The Dynamical Properties of Virgo Cluster Galaxies  

NASA Astrophysics Data System (ADS)

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.

Ouellette, Nathalie N.-Q.

94

Halpha3: an Halpha imaging survey of HI selected galaxies from ALFALFA. II. The star formation properties of galaxies in the Virgo cluster and surroundings  

E-print Network

We present the analysis of Halpha3, an Halpha imaging survey of 409 galaxies selected from the HI Arecibo ALFALFA Survey in the Local Supercluster, including the Virgo cluster. We explore the relations between the stellar mass, the HI mass and the current, massive SFR of nearby galaxies in the Virgo cluster and we compare them with those of isolated galaxies in the Local Supercluster, disentangling the role of the environment in shaping the star formation properties of galaxies at the present cosmological epoch. We investigate the relationships between atomic neutral gas and newly formed stars in different environments, across many morphological types, and over a wide range of stellar masses adopting an updated calibration of the HI deficiency parameter. Studying the mean properties of late-type galaxies in the Local Supercluster, we find that galaxies in increasing local galaxy density conditions (or decreasing projected angular separation from M87) show a significant decrease in the HI content and in the me...

Gavazzi, Giuseppe; Fossati, Matteo; Galardo, Vincenzo; Grossetti, Francesco; Boselli, Alessandro; Giovanelli, Riccardo; Haynes, Martha P

2013-01-01

95

The Virgo Cluster Through The AGES  

NASA Astrophysics Data System (ADS)

I present results from the neutral hydrogen Arecibo Galaxy Environment Survey (AGES) for two regions in the Virgo Cluster, covering 15 square degrees to a sensitivity of 0.6 mJy/beam. 73 objects are detected within the cluster, with 109 detections in the background. The majority of the cluster detections are associated with galaxies previously identified in the optical Virgo Cluster Catalogue, but nearly 30% of the cluster detections are new objects below the VCC completeness limit. No definite optically dark galaxies are identified, however 4 intriguing candidates are reported. All have possible optical counterparts but these are extremely faint, and their HI velocity widths appear inconsistent for such objects when compared to the more certain associations. I discuss the likelihood that these are really dark galaxies. Cluster galaxies are found to be significantly HI deficient but it is not clear where their missing gas has gone. An automated algorithm is described to try to recover faint extended HI features, but no detections are made. I assess whether this implies the cluster environment inhibits the production and survival of such features, or whether it is due to insufficient sensitivity. A small fraction ( 10%) of the early-type galaxies identified in the VCC are detected in HI. Evidence that some of these are morphologically evolving via gas loss, while others are recent additions to the cluster as yet unaffected by their new environment, is discussed. This research was funded by the Science and Technology Facilities Council of the U.K.

Taylor, Rhys

2011-01-01

96

Substructure coupling in the frequency domain  

NASA Technical Reports Server (NTRS)

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.

1985-01-01

97

Stellar evolution.  

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

98

Direct Detection of Cold Dark Matter Substructure  

Microsoft Academic Search

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

N. Dalal; C. S. Kochanek

2002-01-01

99

Composite Octet Searches with Jet Substructure  

SciTech Connect

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.

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

2012-02-14

100

Design sensitivity analysis of boundary element substructures  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

101

THE NEXT GENERATION VIRGO CLUSTER SURVEY (NGVS). I. INTRODUCTION TO THE SURVEY  

SciTech Connect

The Next Generation Virgo Cluster Survey (NGVS) is a program that uses the 1 deg{sup 2} MegaCam instrument on the Canada-France-Hawaii Telescope to carry out a comprehensive optical imaging survey of the Virgo cluster, from its core to its virial radius-covering a total area of 104 deg{sup 2}-in the u*griz bandpasses. Thanks to a dedicated data acquisition strategy and processing pipeline, the NGVS reaches a point-source depth of g Almost-Equal-To 25.9 mag (10{sigma}) and a surface brightness limit of {mu}{sub g} {approx} 29 mag arcsec{sup -2} (2{sigma} above the mean sky level), thus superseding all previous optical studies of this benchmark galaxy cluster. In this paper, we give an overview of the technical aspects of the survey, such as areal coverage, field placement, choice of filters, limiting magnitudes, observing strategies, data processing and calibration pipelines, survey timeline, and data products. We also describe the primary scientific topics of the NGVS, which include: the galaxy luminosity and mass functions; the color-magnitude relation; galaxy scaling relations; compact stellar systems; galactic nuclei; the extragalactic distance scale; the large-scale environment of the cluster and its relationship to the Local Supercluster; diffuse light and the intracluster medium; galaxy interactions and evolutionary processes; and extragalactic star clusters. In addition, we describe a number of ancillary programs dealing with 'foreground' and 'background' science topics, including the study of high-inclination trans-Neptunian objects; the structure of the Galactic halo in the direction of the Virgo Overdensity and Sagittarius Stream; the measurement of cosmic shear, galaxy-galaxy, and cluster lensing; and the identification of distant galaxy clusters, and strong-lensing events.

Ferrarese, Laura; Cote, Patrick; Gwyn, S. D. J.; MacArthur, Lauren A.; McConnachie, Alan W.; Blakeslee, John P. [Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC, V9E 2E7 (Canada); Cuillandre, Jean-Charles [Canada-France-Hawaii Telescope Corporation, Kamuela, HI 96743 (United States); Peng, Eric W. [Department of Astronomy, Peking University, Beijing 100871 (China); Duc, Pierre-Alain [AIM Paris Saclay, CNRS/INSU, CEA/Irfu, Universite Paris Diderot, Orme des Merisiers, F-91191 Gif sur Yvette cedex (France); Boselli, A. [Laboratoire d'Astrophysique de Marseille, UMR 6110 CNRS, 38 rue F. Joliot-Curie, F-13388 Marseille (France); Mei, Simona [GEPI, Observatoire de Paris, CNRS, 5 Place Jules Jannssen, F-92195 Meudon (France); Erben, Thomas [Argelander-Institut fuer Astronomie, University of Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany); Durrell, Patrick R. [Department of Physics and Astronomy, Youngstown State University, Youngstown, OH (United States); Christopher Mihos, J. [Department of Astronomy, Case Western Reserve University, Cleveland, OH (United States); Jordan, Andres; Puzia, Thomas H. [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, 7820436 Macul, Santiago (Chile); Lancon, Ariane [Observatoire Astronomique, Universite de Strasbourg and CNRS UMR 7550, 11 rue de l'Universite, F-67000 Strasbourg (France); Emsellem, Eric [Universite de Lyon 1, CRAL, Observatoire de Lyon, 9 av. Charles Andre, F-69230 Saint-Genis Laval (France); CNRS, UMR 5574, ENS de Lyon (France); Balogh, Michael L. [Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada); Van Waerbeke, Ludovic [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, B.C., V6T 1Z1 (Canada); and others

2012-05-01

102

Rotationally Supported Virgo Cluster Dwarf Elliptical Galaxies: Stripped Dwarf Irregular Galaxies?  

E-print Network

New observations of 16 dwarf elliptical galaxies in the Virgo Cluster indicate that at least seven dEs have significant velocity gradients along their optical major axis, with typical rotation amplitudes of 20-30 km/s. Of the remaining nine galaxies in this sample, 6 have velocity gradients less than 20 km/s kpc^{-1} while the other 3 observations had too low of a signal--to--noise ratio to determine an accurate velocity gradient. Typical velocity dispersions for these galaxies are ~44 +/- 5 km/s, indicating that rotation can be a significant component of the stellar dynamics of Virgo dEs. When corrected for the limited spatial extent of the spectral data, the rotation amplitudes of the rotating dEs are comparable to those of similar brightness dIs. Evidence for a relationship between the rotation amplitude and galaxy luminosity is found, and, in fact, agrees well with the Tully-Fisher relation. The similarity in the scaling relations of dIs and dEs implies that it is unlikely that dEs evolve from significantly more luminous galaxies. These observations reaffirm the possibility that some cluster dwarf elliptical galaxies may be formed when the neutral gaseous medium is stripped from dwarf irregular galaxies in the cluster environment. We hypothesize that several different mechanisms are involved in the creation of the overall population of dE galaxies, and that stripping of infalling dIs may be the dominant process in the creation of dEs in clusters like Virgo.

L. van Zee; E. D. Skillman; M. P. Haynes

2004-09-14

103

Globular Clusters as Tracers of Dark Matter in Virgo Cluster Dwarf Elliptical Galaxies  

NASA Astrophysics Data System (ADS)

Dwarf elliptical (dE) galaxies outnumber any other galaxy class in galaxy clusters, but their formation is still debated. Their angular momentum and mass distribution contains valuable information about the physical processes they have experienced since their formation. Combining the Next Generation Virgo Cluster Survey (NGVS) and the ACS Virgo Cluster Survey (ACSVCS), we have carried out a Keck/DEIMOS survey to estimate the dark matter mass and its distribution in dEs. We target globular cluster (GC) candidates as tracers of the potential well of a total of 21 dEs in the Virgo Cluster in the luminosity range -17 < Mv < -15. The sample comprises 117 GCs that are satellites of the 21 dEs and span out to ~7 half-light radii (Re). For each galaxy, we first compare the velocity distribution of the GCs against an escape velocity function for a pure stellar mass model, finding a moderate dark matter halo extending to ~7 Re. We then calculate the total mass within 1 Re with a dispersion-based estimator and the total mass to 7 Re with a projected mass estimator. We average our estimates to create a dE representative of our sample, finding mass-to-light ratios in solar units of ~4.5 for the inner regions and ~8-20 for the entire galaxy. This indicates that dEs are not dark matter dominated, neither in their inner nor in their outer regions. Our results represent the first estimate of dark matter content beyond ~2 Re for low-luminosity dEs. These mass estimates are consistent with the prevalent tidal stripping theory of dE formation, which explains the lack of a massive, extended dark matter halo. This research was carried out under UCSC’s Science Internship Program. We thank the National Science Foundation for funding support. ET was supported by a Fulbright fellowship.

Chen, Stephanie; Toloba, E.; Guhathakurta, P.; Chen, J.; Cote, P.; Ferrarese, L.; Peng, E. W.; NGVS Collaboration

2014-01-01

104

MAIN-SEQUENCE STAR POPULATIONS IN THE VIRGO OVERDENSITY REGION  

SciTech Connect

We present deep color-magnitude diagrams (CMDs) for two Subaru Suprime-Cam fields in the Virgo Stellar Stream (VSS)/Virgo Overdensity (VOD) and compare them to a field centered on the highest concentration of Sagittarius (Sgr) Tidal Stream stars in the leading arm, Branch A of the bifurcation. A prominent population of main-sequence stars is detected in all three fields and can be traced as faint as g Almost-Equal-To 24 mag. Using theoretical isochrone fitting, we derive an age of 9.1{sup +1.0}{sub -1.1} Gyr, a median abundance of [Fe/H] = -0.70{sup +0.15}{sub -0.20} dex, and a heliocentric distance of 30.9 {+-} 3.0 kpc for the main sequence of the Sgr Stream Branch A. The dominant main-sequence populations in the two VSS/VOD fields ({Lambda}{sub Sun} Almost-Equal-To 265 Degree-Sign , B{sub Sun} Almost-Equal-To 13 Degree-Sign ) are located at a mean distance of 23.3 {+-} 1.6 kpc and have an age of {approx}8.2 Gyr, and an abundance of [Fe/H] = -0.67{sup +0.16}{sub -0.12} dex, similar to the Sgr Stream stars. These statistically robust parameters, derived from the photometry of 260 main-sequence stars, are also in good agreement with the age of the main population in the Sgr dwarf galaxy (8.0 {+-} 1.5 Gyr). They also agree with the peak in the metallicity distribution of 2-3 Gyr old M giants, [Fe/H] Almost-Equal-To -0.6 dex, in the Sgr north leading arm. We then compare the results from the VSS/VOD fields with the Sgr Tidal Stream model by Law and Majewski based on a triaxial Galactic halo shape that is empirically calibrated with Sloan Digital Sky Survey Sgr A-branch and Two Micron All Sky Survey M-giant stars. We find that the most prominent feature in the CMDs, the main-sequence population at 23 kpc, is not explained by the model. Instead the model predicts in these directions a low-density filamentary structure of Sgr debris stars at {approx}9 kpc and a slightly higher concentration of Sgr stars spread over a heliocentric distance range of 42-53 kpc. At best there is only marginal evidence for the presence of these populations in our data. Our findings then suggest that while there are probably some Sgr debris stars present, the dominant stellar population in the VOD originates from a different halo structure that has an almost identical age and metallicity as some sections of the Sgr tidal stream.

Jerjen, H.; Da Costa, G. S.; Tisserand, P. [Research School of Astronomy and Astrophysics, Australian National University, Mt Stromlo Observatory, via Cotter Road, Weston, ACT 2611 (Australia); Willman, B. [Haverford College, Department of Astronomy, 370 Lancaster Avenue, Haverford, PA 19041 (United States); Arimoto, N. [National Astronomical Observatory of Japan, Subaru Telescope, 650 North A'ohoku Place, Hilo, HI 96720 (United States); Okamoto, S. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Mateo, M. [Department of Astronomy, University of Michigan, Ann Arbor, MI (United States); Saviane, I. [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Walsh, S. [Australian Astronomical Observatory, PO Box 915, North Ryde, NSW 1670 (Australia); Geha, M. [Astronomy Department, Yale University, New Haven, CT 06520 (United States); Jordan, A.; Zoccali, M. [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, 7820436 Macul, Santiago (Chile); Olszewski, E. [Steward Observatory, University of Arizona, Tucson, AZ (United States); Walker, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kroupa, P. [Argelander Institute for Astronomy, University of Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany)

2013-05-20

105

The CaterPillar project - Exploring the dark matter substructure of Milky Way Galaxies  

NASA Astrophysics Data System (ADS)

Galaxies grow hierarchically by accreting smaller objects. The abundance of dark matter substructure in simulated Milky Way like galaxies shows evidence for this assembly process. The luminous satellites of our Galaxy are believed to be the visible counterparts to some of these substructures. Existing high-resolution galactic halo simulations show that the variations in substructure distributions and other properties among Milky Way like halos today are significant (a factor of at least 2-3). This, coupled with a few number of high resolution simulated halos, makes the interpretation of many results cosmic variance limited. In order to quantify the scatter in halo properties in a statistically meaningful way, we have initiated the CaterPillar project to perform zoom-In simulations of at least 60 highly resolved galactic size halos. Here we present our overall science goals. We aim to quantify the uniqueness of the Milky Way, to study the role that dwarf galaxies play in shaping large galaxies, to determine whether there really is a missing satellite problem, and to examine the origin of the old, metal-poor stellar halo of the Galaxy.

Frebel, Anna; Zukin, Phillip; Dooley, Gregory

2012-09-01

106

Extraction of Substructural Flexibility from Global Frequencies and Mode Shapes  

SciTech Connect

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.

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

1999-07-16

107

The chemical composition of Ultracompact Dwarf Galaxies in the Virgo and Fornax Clusters  

E-print Network

We present spectroscopic observations of ultra compact dwarf (UCD) galaxies in the Fornax and Virgo Clusters made to measure and compare their stellar populations. The spectra were obtained on the Gemini-North (Virgo) and Gemini-South (Fornax) Telescopes using the respective Gemini Multi-Object Spectrographs. We estimated the ages, metallicities and abundances of the objects from mea- surements of Lick line-strength indices in the spectra; we also estimated the ages and metallicities independently using a direct spectral fitting technique. Both methods re- vealed that the UCDs are old (mean age 10.8 \\pm 0.7 Gyr) and (generally) metal-rich (mean [Fe/H] = -0.8 \\pm 0.1). The alpha-element abundances of the objects measured from the Lick indices are super-Solar. We used these measurements to test the hypothesis that UCDs are formed by the tidal disruption of present-day nucleated dwarf elliptical galaxies. The data are not consistent with this hypothesis because both the ages and abundances are significantly high...

Francis, K J; Chilingarian, Igor V; Bolt, A M; Firth, P

2012-01-01

108

Discovering Frequent Substructures from Hierarchical Semi-structured Data  

Microsoft Academic Search

Frequent substructure discovery from a collection of semi-structured objects can serve for storage, browsing, querying, indexing and classification of semi-structured documents. This paper examines the problem of discovering frequent substructures from a collection of hierarchical semi-structured objects of the same type. The use of wildcard is an important aspect of substructure discovery from semi-structured data due to the irregularity and

Gao Cong; Lan Yi; Bing Liu; Ke Wang

2002-01-01

109

Advanced Virgo: a second-generation interferometric gravitational wave detector  

NASA Astrophysics Data System (ADS)

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, alongside the two Advanced LIGO detectors in the US and GEO HF in Germany, with the goal of contributing to the early detection of gravitational waves and to opening a new window of observation on the universe. In this paper we describe the main features of the Advanced Virgo detector and outline the status of the construction.

Acernese, F.; Agathos, M.; Agatsuma, K.; Aisa, D.; Allemandou, N.; Allocca, A.; Amarni, J.; Astone, P.; Balestri, G.; Ballardin, G.; Barone, F.; Baronick, J.-P.; Barsuglia, M.; Basti, A.; Basti, F.; Bauer, Th S.; Bavigadda, V.; Bejger, M.; Beker, M. G.; Belczynski, C.; Bersanetti, D.; Bertolini, A.; Bitossi, M.; Bizouard, M. A.; Bloemen, S.; Blom, M.; Boer, M.; Bogaert, G.; Bondi, D.; Bondu, F.; Bonelli, L.; Bonnand, R.; Boschi, V.; Bosi, L.; Bouedo, T.; Bradaschia, C.; Branchesi, M.; Briant, T.; Brillet, A.; Brisson, V.; Bulik, T.; Bulten, H. J.; Buskulic, D.; Buy, C.; Cagnoli, G.; Calloni, E.; Campeggi, C.; Canuel, B.; 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.; Dalmaz, A.; D'Antonio, S.; Dattilo, V.; Davier, M.; Day, R.; Debreczeni, G.; Degallaix, J.; Deléglise, S.; Del Pozzo, W.; Dereli, H.; De Rosa, R.; Di Fiore, L.; Di Lieto, A.; Di Virgilio, A.; Doets, M.; 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.; Gaspard, M.; Gatto, A.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; Ghosh, S.; Giacobone, L.; Giazotto, A.; Gouaty, R.; Granata, M.; Greco, G.; Groot, P.; Guidi, G. M.; Harms, J.; Heidmann, A.; Heitmann, H.; Hello, P.; Hemming, G.; Hennes, E.; Hofman, D.; Jaranowski, P.; Jonker, R. J. G.; Kasprzack, M.; Kéfélian, F.; Kowalska, I.; Kraan, M.; Królak, A.; Kutynia, A.; Lazzaro, C.; Leonardi, M.; Leroy, N.; Letendre, N.; Li, T. G. F.; Lieunard, B.; Lorenzini, M.; Loriette, V.; Losurdo, G.; Magazzù, C.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mangano, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marque, J.; Martelli, F.; Martellini, L.; Masserot, A.; Meacher, D.; Meidam, J.; Mezzani, F.; Michel, C.; Milano, L.; Minenkov, Y.; Moggi, A.; Mohan, M.; Montani, M.; Morgado, N.; Mours, B.; Mul, F.; Nagy, M. F.; Nardecchia, I.; Naticchioni, L.; Nelemans, G.; Neri, I.; Neri, M.; Nocera, F.; Pacaud, E.; Palomba, C.; Paoletti, F.; Paoli, A.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Perciballi, M.; Petit, S.; Pichot, M.; Piergiovanni, F.; Pillant, G.; Piluso, A.; 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.; Rosi?ska, D.; Ruggi, P.; Saracco, E.; Sassolas, B.; Schimmel, F.; Sentenac, D.; Sequino, V.; Shah, S.; Siellez, K.; Straniero, N.; Swinkels, B.; Tacca, M.; Tonelli, M.; Travasso, F.; Turconi, M.; 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.; Visser, G.; Vocca, H.; Ward, R.; Was, M.; Wei, L.-W.; Yvert, M.; Zadro ?ny, A.; Zendri, J.-P.

2015-01-01

110

Advanced Virgo: a 2nd generation interferometric gravitational wave detector  

E-print Network

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.

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

111

Virgo Early-Type Dwarfs in ALFALFA  

E-print Network

Early-type dwarf galaxies dominate cluster populations, but their formation and evolutionary histories are poorly understood. The ALFALFA (Arecibo Legacy Fast ALFA) survey has completed observations of the Virgo Cluster in the declination range of 6 - 16 degrees. Less than 2% of the early-type dwarf population is detected, a significantly lower fraction than reported in previous papers based on more limited samples. In contrast ~30 of the irregular/BCD dwarf population is detected. The detected early-type galaxies tend to be located in the outer regions of the cluster, with a concentration in the direction of the M Cloud. Many show evidence for ongoing/recent star formation. Galaxies such as these may be undergoing morphological transition due to cluster environmental effects.

Koopmann, Rebecca A

2007-01-01

112

Virgo Early-Type Dwarfs in ALFALFA  

E-print Network

Early-type dwarf galaxies dominate cluster populations, but their formation and evolutionary histories are poorly understood. The ALFALFA (Arecibo Legacy Fast ALFA) survey has completed observations of the Virgo Cluster in the declination range of 6 - 16 degrees. Less than 2% of the early-type dwarf population is detected, a significantly lower fraction than reported in previous papers based on more limited samples. In contrast ~30 of the irregular/BCD dwarf population is detected. The detected early-type galaxies tend to be located in the outer regions of the cluster, with a concentration in the direction of the M Cloud. Many show evidence for ongoing/recent star formation. Galaxies such as these may be undergoing morphological transition due to cluster environmental effects.

Rebecca A. Koopmann

2007-07-22

113

RADIAL VELOCITIES OF GALACTIC HALO STARS IN VIRGO  

SciTech Connect

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{sup -1}. A rough distance estimate suggests that this feature extends from {approx}15 kpc out to, and possibly beyond, the {approx}30 kpc limit of the study. The mean velocity of these stars is incompatible with those of the VSS itself (V{sub gsr} {approx} 130 km s{sup -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 (V{sub gsr} {approx}< -200 km s{sup -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 {approx} 15-30 kpc) than the Sagittarius models predict (D {approx} 35-45 kpc).

Brink, Thomas G.; Mateo, Mario [Department of Astronomy, University of Michigan, 830 Dennison Building, Ann Arbor, MI 48109-1042 (United States); Martinez-Delgado, David, E-mail: tbrink@umich.ed, E-mail: mmateo@umich.ed [Max Planck Institut fuer Astronomie, Koenigstuhl 17, 69117, Heidelberg (Germany)

2010-11-15

114

Loopy Substructural Local Search for the Bayesian Optimization Algorithm  

NASA Astrophysics Data System (ADS)

This paper presents a local search method for the Bayesian optimization algorithm (BOA) based on the concepts of substructural neighborhoods and loopy belief propagation. The probabilistic model of BOA, which automatically identifies important problem substructures, is used to define the topology of the neighborhoods explored in local search. On the other hand, belief propagation in graphical models is employed to find the most suitable configuration of conflicting substructures. The results show that performing loopy substructural local search (SLS) in BOA can dramatically reduce the number of generations necessary to converge to optimal solutions and thus provides substantial speedups.

Lima, Claudio F.; Pelikan, Martin; Lobo, Fernando G.; Goldberg, David E.

115

5. DOWNSTREAM ELEVATION OF BRIDGE AND SUBSTRUCTURE (with graduated meter ...  

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

5. DOWNSTREAM ELEVATION OF BRIDGE AND SUBSTRUCTURE (with graduated meter pole); VIEW TO NORTH-NORTHEAST. - Auwaiakeakua Bridge, Spanning Auwaiakekua Gulch at Mamalahoa Highway, Waikoloa, Hawaii County, HI

116

Blue compact dwarf galaxies and new velocities in Virgo  

Microsoft Academic Search

We present new spectral observations of 303 galaxies brighter than B_J=17.6 in the central 30 deg^2 of the Virgo cluster field. The galaxies were selected from two overlapping samples designed for a search for blue compact dwarf (BCD) galaxies and for a more general study of Virgo dwarf elliptical (dE) galaxies. Many of these galaxies were designated `background' (i.e., not

M. J. Drinkwater; M. J. Currie; C. K. Young; E. Hardy; J. M. Yearsley

1996-01-01

117

Uncovering Additional Clues to Galaxy Evolution. II. The Environmental Impact of the Virgo Cluster on the Evolution of Dwarf Irregular Galaxies  

E-print Network

The impact of the cluster environment on the evolution of dwarf galaxies is investigated by comparing the properties of a sample of dwarf irregulars (dIs) in the Virgo Cluster with a control sample of nearby ("field") dIs having oxygen abundances derived from [O III]4363 measurements and measured distances from resolved stellar constituents. Spectroscopic data are obtained for H II regions in 11 Virgo dIs distributed in the central and outer regions of the cluster. To ensure that oxygen abundances are derived in a homogeneous manner, oxygen abundances for field and Virgo dIs are computed using the bright-line method and compared with abundances directly obtained from [O III]4363, where available. They are found to agree to within about 0.2 dex with no systematic offset. At a given optical luminosity, there is no systematic difference in oxygen abundance between the sample of Virgo dIs and the sample of nearby dIs. However, five of the eleven Virgo dIs exhibit much lower baryonic gas fractions than field dIs at comparable oxygen abundances. Using field dIs as a reference, a gas-deficiency index for dIs is constructed, making it possible quantitatively to identify which galaxies have lost gas. For the Virgo sample, some of the dwarfs are gas-deficient by a factor of 30. The gas-deficiency correlates roughly with the X-ray surface brightness of the intracluster gas. Ram-pressure stripping can best explain the observed gas-poor dIs in the cluster sample. Together with the lack of significant fading and reddening of the gas-poor dIs compared to gas-normal dIs, these observations suggest that the gas-poor dIs in Virgo have recently encountered the intracluster medium for the first time. Faded remnants of gas-poor dIs in Virgo will resemble bright dwarf ellipticals presently seen in the cluster core.

Henry Lee; Marshall L. McCall; Michael G. Richer

2003-03-17

118

Disk Evolution and Bar Triggering Driven by Interactions with Dark Matter Substructure  

E-print Network

We study formation and evolution of bar-disk systems in fully self-consistent cosmological simulations of galaxy formation in the LCDM WMAP3 Universe. In a representative model we find that the first generation of bars form in response to the asymmetric dark matter (DM) distribution (i.e., DM filament) and quickly decay. Subsequent bar generations form and are destroyed during the major merger epoch permeated by interactions with a DM substructure (subhalos). A long-lived bar is triggered by a tide from a subhalo and survives for ~10 Gyr. The evolution of this bar is followed during the subsequent numerous minor mergers and interactions with the substructure. Together with intrinsic factors, these interactions largely determine the stellar bar evolution. The bar strength and its pattern speed anticorrelate, except during interactions and when the secondary (nuclear) bar is present. For about 5 Gyr bar pattern speed increases substantially despite the loss of angular momentum to stars and cuspy DM halo. We analyze the evolution of stellar populations in the bar-disk and relate them to the underlying dynamics. While the bar is made mainly of an intermediate age, ~5-6 Gyr, disk stars at z=0, a secondary nuclear bar which surfaces at z~0.1 is made of younger, ~1-3 Gyr stars.

Emilio Romano-Diaz; Isaac Shlosman; Clayton Heller; Yehuda Hoffman

2008-09-16

119

Convergence of a substructuring methodwith Lagrange multipliers  

Microsoft Academic Search

Summary.  \\u000a We analyze the convergence of a substructuring iterative method\\u000a with Lagrange multipliers, proposed recently by Farhat and Roux.\\u000a The method decomposes finite element\\u000a discretization of an elliptic boundary value problem into\\u000a Neumann problems on the subdomains plus a coarse problem for the\\u000a subdomain nullspace components. For linear conforming elements and\\u000a preconditioning by the Dirichlet problems on the subdomains,\\u000a we

Jan Mandel; Radek Tezaur

1996-01-01

120

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

E-print Network

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.

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

121

Substructure in lensing clusters and simulations  

E-print Network

We present high-resolution mass reconstructions for five massive cluster-lenses spanning a redshift range from $z = 0.18$--0.57 utilising archival {\\it Hubble Space Telescope} ({\\it HST}) data and applying galaxy-galaxy lensing techniques. These detailed mass models were obtained from the observations by combining constraints from the strong and weak lensing regimes. We ascribe local weak distortions in the shear maps to perturbations induced by the presence of galaxy haloes around individual bright early-type cluster member galaxies. This technique constrains the mass enclosed within an aperture for these subhaloes. We are sensitive to a specific mass range for these subhaloes, $10^{11}$ -- $10^{12.5} \\msun$, which we associate with galaxy-scale subhaloes. Adopting a parametric model for the subhaloes, we also derive their velocity dispersion function and the aperture radius function. The mass spectrum of substructure in the inner regions of the observed clusters is directly compared with that in simulated clusters extracted from the {\\it Millennium Simulation}. The massfunction, aperture radii and velocity dispersion function are compared in detail. Overall, we find good agreement between the distribution of substructure properties retrieved using the lensing analysis and those obtained from the simulation (truncated abstract).

Priyamvada Natarajan; Gabriella De Lucia; Volker Springel

2006-12-19

122

Matter Substructure in High Redshift Clusters of Galaxies  

NASA Astrophysics Data System (ADS)

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.

Huwe, Paul M.

2012-05-01

123

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

NASA Astrophysics Data System (ADS)

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.

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

124

The Northern Wraps of the Sagittarius Stream as Traced by Red Clump Stars: Distances, Intrinsic Widths, and Stellar Densities  

NASA Astrophysics Data System (ADS)

We trace the tidal Stream of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) using Red Clump (RC) stars from the catalog of the Sloan Digital Sky Survey-Data Release 6, in the range 150° <~ R.A. <~ 220°, corresponding to the range of orbital azimuth 220° <~ ? <~ 290°. Substructures along the line of sight (los) are identified as significant peaks in the differential star count profiles (SCPs) of candidate RC stars. A proper modeling of the SCPs allows us to obtain (1) <=10% accurate, purely differential distances with respect to the main body of Sgr, (2) estimates of the FWHM along the los, and (3) estimates of the local density, for each detected substructure. In the range 255° <~ ? <~ 290° we cleanly and continuously trace various coherent structures that can be ascribed to the Stream, in particular: the well-known northern portion of the leading arm, running from d ~= 43 kpc at ? ~= 290° to d ~= 30 kpc at ? ~= 255°, and a more nearby coherent series of detections lying at a constant distance d ~= 25 kpc, that can be identified with a wrap of the trailing arm. The latter structure, predicted by several models of the disruption of Sgr dSph, was never traced before; comparison with existing models indicates that the difference in distance between these portions of the leading and trailing arms may provide a powerful tool to discriminate between theoretical models assuming different shapes of the Galactic potential. A further, more distant wrap in the same portion of the sky is detected only along a couple of los. For ? <~ 255° the detected structures are more complex and less easily interpreted. We are confident of being able to trace the continuation of the leading arm down to ? ~= 220° and d ~= 20 kpc the trailing arm is seen up to ? ~= 240° where it is replaced by more distant structures. Possible detections of more nearby wraps and of the Virgo Stellar Stream are also discussed. These measured properties provide a coherent set of observational constraints for the next generation of theoretical models of the disruption of Sgr.

Correnti, M.; Bellazzini, M.; Ibata, R. A.; Ferraro, F. R.; Varghese, A.

2010-09-01

125

Resolved Stellar Population of Distant Galaxies in the ELT Era  

NASA Astrophysics Data System (ADS)

The expected imaging capabilities of future Extremely Large Telescopes (ELTs) will offer the unique possibility to investigate the stellar populations of distant galaxies from the photometry of the stars in very crowded fields. Using simulated images and photometric analysis we explore here two representative science cases aimed at recovering the characteristics of the stellar populations in the inner regions of distant galaxies. Specifically, case (1) at the center of the disk of a giant spiral in the Centaurus Group (?B ˜ 21, distance of 4.6 Mpc) and case (2) at half of the effective radius of a giant elliptical in the Virgo Cluster (?I ˜ 19.5, distance of 18 Mpc). We generate synthetic frames by distributing model stellar populations and adopting a representative instrumental setup, i.e., a 42 m telescope operating close to the diffraction limit. The effect of crowding is discussed in detail, showing how stars are measured preferentially brighter than they really are as the confusion limit is approached. We find that (1) accurate photometry (? ˜ 0.1, completeness ?90%) can be obtained for case 2 down to I ˜ 28.5, J ˜ 27.5, allowing us to recover the stellar metallicity distribution in the inner regions of ellipticals in Virgo to within ˜0.1 dex; (2) the same photometric accuracy holds for the science case 1 down to J ˜ 28.0, K ˜ 27.0, enabling reconstruction of the star formation history up to the Hubble time via simple star counts in diagnostic boxes. For the latter case, we discuss the possibility of deriving more detailed information on the star formation history from the analysis of their horizontal-branch stars. We show that the combined features of high sensitivity and angular resolution of ELTs may open a new era for our knowledge of the stellar content of galaxies of different morphological types up to the distance of the Virgo cluster.

Greggio, L.; Falomo, R.; Zaggia, S.; Fantinel, D.; Uslenghi, M.

2012-07-01

126

A case of poor substructure diagnostics  

NASA Technical Reports Server (NTRS)

The NASTRAN Manuals in the substructuring area are all geared toward instant success, but the solution paths are fraught with many traps for human error. Thus, the probability of suffering a fatal abort is high. In such circumstances, the necessity for diagnostics that are user friendly is paramount. This paper is written in the spirit of improving the diagnostics as well as the documentation in one area where the author felt he was backed into a blind corner as a result of his having committed a data oversight. This topic is aired by referring to an analysis of a particular structure. The structure, under discussion, used a number of local coordinate systems that simplified the preparation of input data. The principle features of this problem are introduced by reference to a series of figures.

Butler, Thomas G.

1992-01-01

127

Substructure of human von Willebrand factor.  

PubMed

Using electron microscopy, we have visualized the substructure of human von Willebrand factor (vWf) purified by two different approaches. vWf multimers, which appear as flexible strands varying in length up to 2 micron, consist of dimeric units (protomers) polymerized linearly in an end-to-end fashion through disulfide bonds. Examination of small multimers (e.g., one-mers, two-mers, and three-mers) suggests that each protomer consists of two large globular end domains (22 X 6.5 nm) connected to a small central node (6.4 X 3.4 nm) by two flexible rod domains each approximately 34 nm long and approximately 2 nm in diameter. The protomer is 120 nm in length when fully extended. These same structural features are seen both in vWf molecules that were rapidly purified from fresh plasma by a new two-step procedure and in those purified from lyophilized intermediate-purity Factor VIII/vWf concentrates. The 240,000-mol wt subunit observed by gel electrophoresis upon complete reduction of vWf apparently contains both a rod domain and a globular domain and corresponds to one half of the protomer. Two subunits are disulfide-linked, probably near their carboxyl termini, to form the protomer; disulfide bonds in the amino-terminal globular ends link promoters to form vWf multimers. The vWf multimer strands have at least two morphologically distinct types of ends, which may result from proteolytic cleavage in the globular domains after formation of large linear polymers. In addition to releasing fragments that were similar in size and shape to the repeating protomeric unit, plasmic degradation of either preparation of vWf reduced the size of multimers, but had no detectable effect on the substructure of internal protomers. PMID:2932468

Fowler, W E; Fretto, L J; Hamilton, K K; Erickson, H P; McKee, P A

1985-10-01

128

Flexible substructure online hybrid test system using conventional testing devices  

NASA Astrophysics Data System (ADS)

This paper presents a substructure online hybrid test system that is extensible for geographically distributed tests. This system consists of a set of devices conventionally used for cyclic tests to load the tested substructures onto the target displacement or the target force. Due to their robustness and portability, individual sets of conventional loading devices can be transported and reconfigured to realize physical loading in geographically remote laboratories. Another appealing feature is the flexible displacement-force mixed control that is particularly suitable for specimens having large disparities in stiffness during various performance stages. To conduct a substructure online hybrid test, an extensible framework is developed, which is equipped with a generalized interface to encapsulate each substructure. Multiple tested substructures and analyzed substructures using various structural program codes can be accommodated within the single framework, simply interfaced with the boundary displacements and forces. A coordinator program is developed to keep the boundaries among all substructures compatible and equilibrated. An Internet-based data exchange scheme is also devised to transfer data among computers equipped with different software environments. A series of online hybrid tests are introduced, and the portability, flexibility, and extensibility of the online hybrid test system are demonstrated.

Wang, Tao; Nakashima, Masayoshi

2013-09-01

129

Substructure System Identification for Finite Element Model Updating  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

130

The Herschel Virgo Cluster Survey - XII. FIR properties of optically selected Virgo cluster galaxies  

NASA Astrophysics Data System (ADS)

The Herschel Virgo Cluster Survey (HeViCS) is the deepest, confusion-limited survey of the Virgo Cluster at far-infrared (FIR) wavelengths. The entire survey at full depth covers ˜55 deg2 in five bands (100-500 ?m), encompassing the areas around the central dominant elliptical galaxies (M87, M86 and M49) and extends as far as the NW cloud, the W cloud and the Southern extension. The survey extends beyond this region with lower sensitivity so that the total area covered is 84 deg2. In this paper we describe the data, the data acquisition techniques and present the detection rates of the optically selected Virgo Cluster Catalogue (VCC). We detect 254 (34 per cent) of 750 VCC galaxies found within the survey boundary in at least one band and 171 galaxies are detected in all five bands. For the remainder of the galaxies we have measured strict upper limits for their FIR emission. The population of detected galaxies contains early as well as late types although the latter dominate the detection statistics. We have modelled 168 galaxies, showing no evidence of a strong synchrotron component in their FIR spectra, using a single-temperature modified blackbody spectrum with a fixed emissivity index (? = 2). A study of the ?2 distribution indicates that this model is not appropriate in all cases, and this is supported by the FIR colours which indicate a spread in ? = 1-2. Statistical comparison of the dust mass and temperature distributions from 140 galaxies with ?2d.o.f. = 3 < 7.8 (95 per cent confidence level) shows that late types have typically colder, more massive dust reservoirs; the early-type dust masses have a mean of log[/M?] = 6.3 ± 0.3, while for late types log[/M?] = 7.1 ± 0.1. The late-type dust temperatures have a mean of = 19.4 ± 0.2 K, while for the early types, = 21.1 ± 0.8 K. Late-type galaxies in the cluster exhibit slightly lower dust masses than those in the field, but the cluster environment seems to have little effect on the bulk dust properties of early types. In future papers we will focus more on the scientific analysis of the catalogue (e.g. measuring FIR luminosity functions, dust mass functions and resolved gas and dust properties).

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

2013-01-01

131

Optical metrology tools for the Virgo projet  

NASA Astrophysics Data System (ADS)

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

Loriette, V.

132

Stellar chromospheres  

NASA Technical Reports Server (NTRS)

Developments in the understanding and use of chromospheric diagnostics are discussed with emphasis on the following aspects: (1) trends emerging from semiempirical models of single stars; (2) the validity of claims that theoretical models of chromospheres are becoming realistic; (3) the correlation between the widths of Ca 2 H and K line emission cores and stellar absolute luminosity extending over 15 magnitudes (Wilson-Bappu relation); and (4) the existence of systematic flow patterns in stellar chromospheres.

Linsky, J. L.

1980-01-01

133

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

NASA Astrophysics Data System (ADS)

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.

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

134

Solar-stellar connection: the frequency of maximum oscillation power from solar data  

NASA Astrophysics Data System (ADS)

Stellar oscillations provide powerful tools to derive stellar fundamental parameters such as the mass and radius. These global quantities are derived from scaling relations linking seismic quantities [?max and ?? to global stellar parameters. These relations use the Sun as a reference. In this work, we used VIRGO and GOLF data to study how the solar frequency at the maximum oscillation power (?max) varies with time along the solar cycle. We show that these variations imply differences of about 4% in radius and 12% in mass. We showed also that the observational method based on intensity or velocity data has also an impact, implying differences in mass of about 22% and 7% in radius.

Barban, C.; Beuret, M.; Baudin, F.; Belkacem, K.; Goupil, M. J.; Samadi, R.

2013-06-01

135

The Herschel Virgo Cluster Survey. XIII. Dust in early-type galaxies  

NASA Astrophysics Data System (ADS)

Aims: We study the dust content of a large optical input sample of 910 early-type galaxies (ETG) in the Virgo cluster, also extending to the dwarf ETG, and examine the results in relation to those on the other cold ISM components. Methods: We have searched for far-infrared emission in all galaxies in the input sample using the 250 ?m image of the Herschel Virgo Cluster Survey (HeViCS). This image covers a large fraction of the cluster with an area of ~55 square degrees. For the detected ETG we measured fluxes in five bands from 100 to 500 ?m, and estimated the dust mass and temperature with modified black-body fits. Results: Dust is detected above the completeness limit of 25.4 mJy at 250 ?m in 46 ETG, 43 of which are in the optically complete part of the input sample. In addition, dust is present at fainter levels in another six ETG. We detect dust in the four ETG with synchrotron emission, including M 87. Dust appears to be much more concentrated than stars and more luminous ETG have higher dust temperatures. Considering only the optically complete input sample and correcting for the contamination by background galaxies, dust detection rates down to the 25.4 mJy limit are 17% for ellipticals, about 40% for lenticulars (S0 + S0a), and around 3% for dwarf ETG. Dust mass does not correlate clearly with stellar mass and is often much greater than expected for a passive galaxy in a closed-box model. The dust-to-stars mass ratio anticorrelates with galaxy luminosity, and for some dwarf ETG reaches values as high as for dusty late-type galaxies. In the Virgo cluster slow rotators appear more likely to contain dust than fast ones. Comparing the dust results with those on Hi there are only eight ETG detected both in dust and in Hi in the HeViCS area; 39 have dust but only an upper limit on Hi, and eight have Hi but only an upper limit on dust. The locations of these galaxies in the cluster are different, with the dusty ETG concentrated in the densest regions, while the Hi rich ETG are at the periphery. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Table A.1 is available in electronic form at http://www.aanda.org

di Serego Alighieri, S.; Bianchi, S.; Pappalardo, C.; Zibetti, S.; Auld, R.; Baes, M.; Bendo, G.; Corbelli, E.; Davies, J. I.; Davis, T.; De Looze, I.; Fritz, J.; Gavazzi, G.; Giovanardi, C.; Grossi, M.; Hunt, L. K.; Magrini, L.; Pierini, D.; Xilouris, E. M.

2013-04-01

136

The Next Generation Virgo Cluster Survey (NGVS). I. Introduction to the Survey  

NASA Astrophysics Data System (ADS)

The Next Generation Virgo Cluster Survey (NGVS) is a program that uses the 1 deg2 MegaCam instrument on the Canada-France-Hawaii Telescope to carry out a comprehensive optical imaging survey of the Virgo cluster, from its core to its virial radius—covering a total area of 104 deg2—in the u*griz bandpasses. Thanks to a dedicated data acquisition strategy and processing pipeline, the NGVS reaches a point-source depth of g ? 25.9 mag (10?) and a surface brightness limit of ? g ~ 29 mag arcsec-2 (2? above the mean sky level), thus superseding all previous optical studies of this benchmark galaxy cluster. In this paper, we give an overview of the technical aspects of the survey, such as areal coverage, field placement, choice of filters, limiting magnitudes, observing strategies, data processing and calibration pipelines, survey timeline, and data products. We also describe the primary scientific topics of the NGVS, which include: the galaxy luminosity and mass functions; the color-magnitude relation; galaxy scaling relations; compact stellar systems; galactic nuclei; the extragalactic distance scale; the large-scale environment of the cluster and its relationship to the Local Supercluster; diffuse light and the intracluster medium; galaxy interactions and evolutionary processes; and extragalactic star clusters. In addition, we describe a number of ancillary programs dealing with "foreground" and "background" science topics, including the study of high-inclination trans-Neptunian objects; the structure of the Galactic halo in the direction of the Virgo Overdensity and Sagittarius Stream; the measurement of cosmic shear, galaxy-galaxy, and cluster lensing; and the identification of distant galaxy clusters, and strong-lensing events. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France and the University of Hawaii.

Ferrarese, Laura; Côté, Patrick; Cuillandre, Jean-Charles; Gwyn, S. D. J.; Peng, Eric W.; MacArthur, Lauren A.; Duc, Pierre-Alain; Boselli, A.; Mei, Simona; Erben, Thomas; McConnachie, Alan W.; Durrell, Patrick R.; Mihos, J. Christopher; Jordán, Andrés; Lançon, Ariane; Puzia, Thomas H.; Emsellem, Eric; Balogh, Michael L.; Blakeslee, John P.; van Waerbeke, Ludovic; Gavazzi, Raphaël; Vollmer, Bernd; Kavelaars, J. J.; Woods, David; Ball, Nicholas M.; Boissier, S.; Courteau, Stéphane; Ferriere, E.; Gavazzi, G.; Hildebrandt, Hendrik; Hudelot, P.; Huertas-Company, M.; Liu, Chengze; McLaughlin, Dean; Mellier, Y.; Milkeraitis, Martha; Schade, David; Balkowski, Chantal; Bournaud, Frédéric; Carlberg, R. G.; Chapman, S. C.; Hoekstra, Henk; Peng, Chien; Sawicki, Marcin; Simard, Luc; Taylor, James E.; Tully, R. Brent; van Driel, Wim; Wilson, Christine D.; Burdullis, Todd; Mahoney, Billy; Manset, Nadine

2012-05-01

137

The Herschel Virgo Cluster Survey. XV. Planck submillimetre sources in the Virgo Cluster  

NASA Astrophysics Data System (ADS)

We cross-correlate the Planck Catalogue of Compact Sources (PCCS) with the fully sampled 84 deg2Herschel Virgo Cluster Survey (HeViCS) fields. We search for and identify the 857 and 545 GHz PCCS sources in the HeViCS fields by studying their FIR/submm and optical counterparts. We find 84 and 48 compact Planck sources in the HeViCS fields at 857 and 545 GHz, respectively. Almost all sources correspond to individual bright Virgo Cluster galaxies. The vast majority of the Planck detected galaxies are late-type spirals, with the Sc class dominating the numbers, while early-type galaxies are virtually absent from the sample, especially at 545 GHz. We compare the HeViCS SPIRE flux densities for the detected galaxies with the four different PCCS flux density estimators and find an excellent correlation with the aperture photometry flux densities, even at the highest flux density levels. We find only seven PCCS sources in the HeViCS fields without a nearby galaxy as obvious counterpart, and conclude that all of these are dominated by Galactic cirrus features or are spurious detections. No Planck sources in the HeViCS fields seem to be associated to high-redshift proto-clusters of dusty galaxies or strongly lensed submm sources. Finally, our study is the first empirical confirmation of the simulation-based estimated completeness of the PCCS, and provides a strong support of the internal PCCS validation procedure. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Tables 1 and 2 are available in electronic form at http://www.aanda.org

Baes, M.; Herranz, D.; Bianchi, S.; Ciesla, L.; Clemens, M.; De Zotti, G.; Allaert, F.; Auld, R.; Bendo, G. J.; Boquien, M.; Boselli, A.; Clements, D. L.; Cortese, L.; Davies, J. I.; De Looze, I.; di Serego Alighieri, S.; Fritz, J.; Gentile, G.; González-Nuevo, J.; Hughes, T.; Smith, M. W. L.; Verstappen, J.; Viaene, S.; Vlahakis, C.

2014-02-01

138

10. DETAIL OF BRIDGE SUBSTRUCTURE, SHOWING ORIGINAL CONNECTION WITH IRON ...  

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

10. DETAIL OF BRIDGE SUBSTRUCTURE, SHOWING ORIGINAL CONNECTION WITH IRON PINS. VIEW LOOKING WEST FROM FACE OF EAST ABUTMENT. - Annisquam Bridge, Spanning Lobster Cove between Washington & River Streets, Gloucester, Essex County, MA

139

Copy of "Plan of the Substructure of Center Street Bridge, ...  

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

Copy of "Plan of the Substructure of Center Street Bridge, Cleveland (October 1898)." Drawing courtesy Engineering Dept., City of Cleveland - Center Street Swing Bridge, Southwest of Public Square, Cleveland, Cuyahoga County, OH

140

THE EFFECTS OF VARYING COSMOLOGICAL PARAMETERS ON HALO SUBSTRUCTURE  

E-print Network

We investigate how different cosmological parameters, such as those delivered by the WMAP and Planck missions, affect the nature and evolution of the dark matter halo substructure. We use a series of flat ? cold dark matter ...

Zukin, Phillip

141

7. LOOKING NORTHEAST AT THE CONNECTION DETAIL OF THE SUBSTRUCTURE ...  

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

7. LOOKING NORTHEAST AT THE CONNECTION DETAIL OF THE SUBSTRUCTURE OF THE TRUSS SPAN AND THE SHARED PIER OF THE REINFORCED CONCRETE SPAN. - "S" Bridge, U.S. Route 40 spanning Little Wheeling Creek, Elm Grove, Ohio County, WV

142

Dynamic Substructuring of Damped Structures Using Singular Value Decomposition  

E-print Network

Engineering, Pontificia Universidade Cat´olica do Rio de Janeiro, 22453-900 Rio de Janeiro - RJ - Brazil C substructure have been widely developed in the litter- ature: for conservative structures see for example

Boyer, Edmond

143

Globular cluster systems as tracers of environmental effects on Virgo early-type dwarfs  

NASA Astrophysics Data System (ADS)

Early-type dwarfs (dEs) are by far the most abundant galaxy population in nearby clusters. Whether these objects are primordial, or the recent end products of the different physical mechanisms that can transform galaxies once they enter these high-density environments, is still a matter of debate. Here we present a novel approach to test these scenarios by comparing the properties of the globular cluster systems (GCSs) of Virgo dEs and their potential progenitors with simple predictions from gravitational and hydrodynamical interaction models. We show that low-mass (M? ? 2 × 108 M?) dEs have GCSs consistent with the descendants of gas-stripped late-type dwarfs. On the other hand, higher mass dEs have properties - including the high mass specific frequencies of their GCSs and their concentrated spatial distribution within Virgo - incompatible with a recent, environmentally driven evolution. They mostly comprise nucleated systems, but also dEs with recent star formation and/or disc features. Bright, nucleated dEs appear to be a population that has long resided within the cluster potential well, but have surprisingly managed to retain very rich and spatially extended GCSs - possibly an indication of high total masses. Our analysis does not favour violent evolutionary mechanisms that result in significant stellar mass-losses, but more gentle processes involving gas removal by a combination of internal and external factors, and highlights the relevant role of initial conditions. Additionally, we briefly comment on the origin of luminous cluster S0 galaxies.

Sánchez-Janssen, R.; Aguerri, J. A. L.

2012-08-01

144

VizieR Online Data Catalog: Atlas of Virgo galaxies (McDonald+ 2011)  

NASA Astrophysics Data System (ADS)

This database contains surface brightness profiles in the optical g, r, i, z bands and near-IR H-band for 286 Virgo cluster galaxies. This morphologically-complete sample spans a huge range in galaxy size, luminosity, surface brightness and stellar populations. These data have been used to study the luminosity and surface brightness distribution of Virgo cluster galaxies, in McDonald et al. (2009MNRAS.394.2022M). We find compelling evidence for bimodal populations in surface brightness, with both early- and late-type galaxies having a dearth of intermediate surface brightness galaxies. Most convincing is our confirmation of the result by Tully and Verheijen that the surface brightness of galaxy disks are strongly bimodal (1997ApJ...484..145T) The near-IR H-band data have been obtained from a variety of telescopes. We downloaded archival images for 31/286 and 84/286 bright galaxies from the 2MASS and GOLDMine online databases, respectively. The remaining 171 galaxies have new observations from the UH 2.2-m (130/286), CFHT (20/286) and UKIRT (21/286) telescopes. These data were all reduced in a homogeneous way, as outlined in our data paper. The optical g, r, i, z data were all obtained from the SDSS archives. Surface brightness profiles were extracted homogeneously from the optical and near-IR data following similar procedures, as outlined in our paper (2011MNRAS.414.2055M) The parametric and non-parametric parameters from bulge-disk decompositions of 285 optical griz and near-IR H-band surface brightness (SB) profiles are given in the bdd_* files in this directory. The profiles are stored in the "profg", "profr", "profi", "profz" and "prof_h" subdirectories, one for each color. (12 data files).

McDonald, M.; Courteau, S.; Tully, R. B.; Roediger, J.

2011-04-01

145

gSpan: Graph-Based Substructure Pattern Mining  

Microsoft Academic Search

We investigate new approaches for frequent graph-based pattern mining in graph datasets and propose a novel algo- rithm called gSpan (graph-based Substructure pattern min- ing), which discovers frequent substructures without can- didate generation. gSpan builds a new lexicographic or- der among graphs, and maps each graph to a unique mini- mum DFS code as its canonical label. Based on this

Xifeng Yan; Jiawei Han

2002-01-01

146

Effect of Dark Matter Halo Substructures on Galaxy Rotation Curves  

Microsoft Academic Search

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

Nirupam Roy; Nirupam

2010-01-01

147

Substructuring and poroelastic modelling of the intervertebral disc  

Microsoft Academic Search

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.

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

2010-01-01

148

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

SciTech Connect

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.

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

149

Resolving Galaxy Cluster Substructure with Gravitational Lensing Flexion  

NASA Astrophysics Data System (ADS)

While it is well established that clusters of galaxies reside in dark matter haloes, simulations lead us to believe that there is substantial residual dark matter substructure in those halos. Weak gravitational lensing is well suited to to studying the large scale properties of these halos but less so for studying substructure. Gravitational lensing flexion, the next-higher order lensing effect after shear, is extremely well-suited to measuring substructure, both because it acts at shorter range and because fewer background objects are needed to get a significant signal. We propose to apply a gravitational lensing analysis and mass reconstruction particularly suited to detecting substructure to a sample of 20 massive galaxy clusters, complementing strong lensing and weak lensing measurements with flexion in the mass reconstructions. Because flexion is a sensitive probe of mass gradients, we will detect structure on smaller spatial scales than are accessible to shear analyses, and will do so over a larger area than is possible with strong lensing analyses alone. Our strong+weak+flexion lensing approach will make a census of substructures down to M 3x10^12 solar masses over an entire HST/ACS field of view. Using our detailed mapping of the cluster mass distributions we will measure the normalization of the subhalo mass function {which is equivalent to the substructure mass fraction} to 10% error, and place an empirical constraint on its slope as well.

Cain, Benjamin

2013-10-01

150

Measurements of Superattenuator seismic isolation by Virgo interferometer  

Microsoft Academic Search

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

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

151

Measurement of the seismic attenuation performance of the VIRGO Superattenuator  

Microsoft Academic Search

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

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

152

Completing HI observations of galaxies in the Virgo cluster  

E-print Network

High sensitivity (rms noise $\\sim 0.5$ mJy) 21-cm HI line observations were made of 33 galaxies in the Virgo cluster, using the refurbished Arecibo telescope, which resulted in the detection of 12 objects. These data, combined with the measurements available from the literature, provide the first set of HI data that is complete for all 355 late-type (Sa-Im-BCD) galaxies in the Virgo cluster with $m_p \\leq 18.0$ mag. The Virgo cluster HI mass function (HIMF) that was derived for this optically selected galaxy sample is in agreement with the HIMF derived for the Virgo cluster from the blind HIJASS HI survey and is inconsistent with the Field HIMF. This indicates that both in this rich cluster and in the general field, neutral hydrogen is primarily associated with late-type galaxies, with marginal contributions from early-type galaxies and isolated HI clouds. The inconsistency between the cluster and the field HIMF derives primarily from the difference in the optical luminosity function of late-type galaxies in the two environments, combined with the HI deficiency that is known to occur in galaxies in rich clusters.

G. Gavazzi; A. Boselli; W. van Driel; K. O'Neil

2004-09-15

153

VIRGO: Experiment for helioseismology and solar irradiance monitoring  

NASA Technical Reports Server (NTRS)

The scientific objectives of the variability of solar irradiance and gravity oscillations (VIRGO) experiment are as follows: to determine the characteristics of pressure and internal gravity oscillations by observing irradiance and radiance variations; to measure the solar total and spectral irradiance, and to quantify their variability. Helioseismological methods can be applied to these data in order to probe the solar interior. Certain convection characteristics and their interaction with magnetic fields will be studied from the results of the irradiance monitoring and from the comparison of the amplitudes and phases of the oscillations as observed from the brightness by VIRGO and from velocity by the global oscillations at low frequency (GOLF) experiment. The VIRGO experiment contains two active-cavity radiometers that monitor the solar constant, two three-channel sunphotometers that measure the spectral irradiance, and a low resolution imager with 12 pixels that measures the radiance distribution over the solar disk at 500 nm. The scientific objectives of VIRGO are presented, the instruments and the data acquisition and control system are described, and their measured performances are given.

Froehlich, Claus; Andersen, Bo N.

1995-01-01

154

Finding Nonoverlapping Substructures of a Sparse Matrix  

SciTech Connect

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.

Pinar, Ali; Vassilevska, Virginia

2005-08-11

155

A 3D view of the Hydra I galaxy cluster core - I. Kinematic substructures  

NASA Astrophysics Data System (ADS)

We used FORS2 in MXU mode to mimic a coarse `IFU' in order to measure the 3D large-scale kinematics around the central Hydra I cluster galaxy NGC 3311. Our data show that the velocity dispersion field varies as a function of radius and azimuthal angle and violates point symmetry. Also, the velocity field shows similar dependence, hence the stellar halo of NGC 3311 is a dynamically young structure. The kinematic irregularities coincide in position with a displaced diffuse halo North-East of NGC 3311 and with tidal features of a group of disrupting dwarf galaxies. This suggests that the superposition of different velocity components is responsible for the kinematic substructure in the Hydra I cluster core.

Hilker, Michael; Barbosa, Carlos Eduardo; Richtler, Tom; Coccato, Lodovico; Arnaboldi, Magda; Mendes de Oliveira, Claudia

2015-02-01

156

EVIDENCE FOR THE DISKY ORIGIN OF LUMINOUS VIRGO DWARF ELLIPTICALS FROM THE KINEMATICS OF THEIR GLOBULAR CLUSTER SYSTEMS  

SciTech Connect

We report evidence for dynamically significant rotation in the globular cluster systems of two luminous Virgo dwarf ellipticals, VCC1261 and VCC1528. Including previous results for VCC1087, the globular cluster systems of all three Virgo dwarf ellipticals studied in detail to date exhibit v {sub rot}/{sigma}{sub los}>1. Taking the rotation seen in the globular clusters as a maximal disk rotation, and accounting for the possible fading of any hypothetical progenitor galaxy, we find all three dwarf elliptical galaxies (dEs) lie on the r-band Tully-Fisher relation. We argue that these data support the hypothesis that luminous dEs are the remnants of transformed disk galaxies. We also obtained deep, longslit data for the stars in VCC1261 and VCC1528. Both these galaxies show rapid rotation in their inner regions, with spatial scales of {approx}0.5 kpc. These rotation velocities are surprisingly similar to those seen in the globular cluster systems. At larger radii, we see little rotation in the dEs themselves. Since our longslit data for Virgo dEs extend out to 1-2 effective radii (typical of deep observations), whereas the globular clusters extend out to 4-7 effective radii, we conclude that nondetections of rotation in many luminous dEs may simply be due to a lack of radial coverage in the stellar data, and that globular clusters represent singularly sensitive probes of the dynamics of dEs. Based on these data, we suggest that gas disks are significant sites of globular cluster formation in the early universe.

Beasley, Michael A.; Cenarro, A. Javier [Instituto de AstrofIsica de Canarias, VIa Lactea s/n, 38200 La Laguna, Tenerife (Spain); Strader, Jay [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Brodie, Jean P. [UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)], E-mail: beasley@iac.es, E-mail: cenarro@iac.es, E-mail: jstrader@cfa.harvard.edu, E-mail: brodie@ucolick.org

2009-06-15

157

Seeking Counterparts to Advanced LIGO/Virgo Transients with Swift  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

158

SEEKING COUNTERPARTS TO ADVANCED LIGO/Virgo TRANSIENTS WITH SWIFT  

SciTech Connect

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.

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

159

Stellar Imager  

NASA Technical Reports Server (NTRS)

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.

Carpenter, Kenneth

2007-01-01

160

Stellar Winds  

NASA Astrophysics Data System (ADS)

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.

Owocki, Stan

161

Stellar Properties  

NSDL National Science Digital Library

Authored by Nick Strobel, "Astronomy Notes" is an educational resource for introductory astronomy classes for undergraduates. This section discusses the properties of stars. such as apparent magnitude, absolute magnitude, luminosity, color, temperature, stellar velocities, compositions, and sizes. Other topics included are descriptions of parallax, redshift, blueshift, center of mass, and the HR diagram.

Strobel, Nick

162

AMUSE-Virgo. I. Supermassive Black Holes in Low-Mass Spheroids  

NASA Astrophysics Data System (ADS)

We present the first results from the AGN Multiwavelength Survey of Early-Type Galaxies in the Virgo Cluster (AMUSE-Virgo). This large program targets 100 early-type galaxies with the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory and the Multiband Imaging Photometer on board the Spitzer Space Telescope, with the aim of providing an unbiased census of low-level supermassive black hole activity in the local universe. Here we report on the Chandra observations of the first 16 targets, and combine them with results from archival data of another, typically more massive, 16 targets. Pointlike X-ray emission from a position coincident with the optical nucleus is detected in 50% of the galaxies (down to our completeness limit of ~4×1038 ergs s-1). Two of the X-ray nuclei are hosted by galaxies (VCC 1178 [N4464] and VCC 1297 [N4486B]) with absolute B magnitudes fainter than -18, where nuclear star clusters are known to become increasingly common. After carefully accounting for possible contamination from low-mass X-ray binaries, we argue that the detected nuclear X-ray sources are most likely powered by low-level accretion on to a supermassive black hole, with a <~11% chance contamination in VCC 1178, where a star cluster is barely resolvable in archival Hubble Space Telescope images. Based on black hole mass estimates from the global properties of the host galaxies, all the detected nuclei are highly sub-Eddington, with luminosities in the range -8.4stellar mass M* of the host galaxy: only between 3% and 44% of the galaxies with M*<1010 Msolar harbor an X-ray active supermassive black hole. The fraction rises to between 49% and 87% in galaxies with stellar mass above 1010 Msolar (at the 95% confidence level).

Gallo, Elena; Treu, Tommaso; Jacob, Jeremy; Woo, Jong-Hak; Marshall, Philip J.; Antonucci, Robert

2008-06-01

163

Gamma-ray probes of dark matter substructure  

SciTech Connect

The substructure content of dark matter halos is interesting because it can be affected by complex galaxy physics and dark matter particle physics. However, observing the small scale structure of dark matter is a challenge. The subhalo abundance (mass function, minimum mass) and morphology (density profile, subhalo shape, subsubstructure) contain information about complex astrophysics (halo formation processes) and new exotic fundamental physics (dark matter interactions). Indirect detection of dark matter annihilation radiation (DMAR) in gamma rays may be the most direct method for observing small scale structure. I outline the ways in which gamma rays may probe halo substructure. If substructure is bountiful, it may be responsible for the eventual discovery of DMAR, for instance in galaxy clusters or the diffuse gamma-ray background. Otherwise, the observation of DMAR in places without much substructure, such as the Galactic center, would lead to strict limits on the properties of small scale structure. Properties of the gamma-ray angular power spectrum will also provide information or constraints on Milky Way halo substructure.

Campbell, Sheldon [Department of Physics and Center for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, 191 W. Woodruff Ave., Columbus, OH 43210 (United States)

2014-06-24

164

Identification of galaxy cluster substructures with the Caustic method  

E-print Network

We investigate the power of the caustic technique to identify substructures of galaxy clusters from optical redshift data alone. The caustic technique is designed to estimate the mass profile of galaxy clusters to radii well beyond the virial radius, where dynamical equilibrium does not hold. Two by-products of this technique are the identification of the cluster members and the identification of the cluster substructures. We test the caustic technique as a substructure detector on two samples of 150 mock redshift surveys of clusters; the clusters are extracted from a large cosmological $N$-body simulation of a $\\Lambda$CDM model and have mass $M_{200} \\sim 10^{14} h^{-1} M_{\\odot}$ and $M_{200} \\sim 10^{15} h^{-1} M_{\\odot}$ in the two samples respectively. We limit our analysis to substructures identified in the simulation with mass larger than $10^{13} h^{-1} M_{\\odot}$. With mock redshift surveys with 200 galaxies within $3R_{200}$, (1) the caustic technique recovers $\\sim 30-50$% of the real substructure...

Yu, Heng; Diaferio, Antonaldo; Baldi, Marco

2015-01-01

165

Kinematic and Spatial Substructure in NGC 2264  

NASA Astrophysics Data System (ADS)

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 m 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?rész 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 (13CO) gas. The detection of Lithium absorption and/or infrared excesses in this blueshifted 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 suggest that the stellar and gas kinematics of this region are the result of a bubble driven by the wind from O7 star S Mon. Our results emphasize the complexity of the spatial and kinematic structure of NGC 2264, important for eventually building up a comprehensive picture of cluster formation. Observations reported here were obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Tobin, John J.; Hartmann, Lee; F?rész, Gabor; Hsu, Wen-Hsin; Mateo, Mario

2015-04-01

166

The Milky Way Tomography with SDSS. I. Stellar Number Density Distribution  

NASA Astrophysics Data System (ADS)

Using the photometric parallax method we estimate the distances to ~48 million stars detected by the Sloan Digital Sky Survey (SDSS) and map their three-dimensional number density distribution in the Galaxy. The currently available data sample the distance range from 100 pc to 20 kpc and cover 6500 deg2 of sky, mostly at high Galactic latitudes (|b|>25). These stellar number density maps allow an investigation of the Galactic structure with no a priori assumptions about the functional form of its components. The data show strong evidence for a Galaxy consisting of an oblate halo, a disk component, and a number of localized overdensities. The number density distribution of stars as traced by M dwarfs in the solar neighborhood (D<2 kpc) is well fit by two exponential disks (the thin and thick disk) with scale heights and lengths, bias corrected for an assumed 35% binary fraction, of H1=300 pc and L1=2600 pc, and H2=900 pc and L2=3600 pc, and local thick-to-thin disk density normalization ?thick(Rsolar)/?thin(Rsolar)=12%. We use the stars near main-sequence turnoff to measure the shape of the Galactic halo. We find a strong preference for oblate halo models, with best-fit axis ratio c/a=0.64, ?H~r-2.8 power-law profile, and the local halo-to-thin disk normalization of 0.5%. Based on a series of Monte Carlo simulations, we estimate the errors of derived model parameters not to be larger than ~20% for the disk scales and ~10% for the density normalization, with largest contributions to error coming from the uncertainty in calibration of the photometric parallax relation and poorly constrained binary fraction. While generally consistent with the above model, the measured density distribution shows a number of statistically significant localized deviations. In addition to known features, such as the Monoceros stream, we detect two overdensities in the thick disk region at cylindrical galactocentric radii and heights (R,Z)~(6.5,1.5) kpc and (R,Z)~(9.5,0.8) kpc and a remarkable density enhancement in the halo covering over 1000 deg2 of sky toward the constellation of Virgo, at distances of ~6-20 kpc. Compared to counts in a region symmetric with respect to the l=0deg line and with the same Galactic latitude, the Virgo overdensity is responsible for a factor of 2 number density excess and may be a nearby tidal stream or a low-surface brightness dwarf galaxy merging with the Milky Way. The u-g color distribution of stars associated with it implies metallicity lower than that of thick disk stars and consistent with the halo metallicity distribution. After removal of the resolved overdensities, the remaining data are consistent with a smooth density distribution; we detect no evidence of further unresolved clumpy substructure at scales ranging from ~50 pc in the disk to ~1-2 kpc in the halo.

Juri?, Mario; Ivezi?, Željko; Brooks, Alyson; Lupton, Robert H.; Schlegel, David; Finkbeiner, Douglas; Padmanabhan, Nikhil; Bond, Nicholas; Sesar, Branimir; Rockosi, Constance M.; Knapp, Gillian R.; Gunn, James E.; Sumi, Takahiro; Schneider, Donald P.; Barentine, J. C.; Brewington, Howard J.; Brinkmann, J.; Fukugita, Masataka; Harvanek, Michael; Kleinman, S. J.; Krzesinski, Jurek; Long, Dan; Neilsen, Eric H., Jr.; Nitta, Atsuko; Snedden, Stephanie A.; York, Donald G.

2008-02-01

167

EFFECT OF DARK MATTER HALO SUBSTRUCTURES ON GALAXY ROTATION CURVES  

SciTech Connect

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.

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

2010-11-01

168

Enhancing MAD F A data for substructure determination  

PubMed Central

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

Xu, Hongliang

2010-01-01

169

Shock induced deformation substructures in a copper bicrystal  

SciTech Connect

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.

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

170

Post-Newtonian Dynamics in Dense Stellar Systems  

NASA Astrophysics Data System (ADS)

Dense stellar systems (star clusters and galactic nuclei) are some of the most promising sources of gravitational waves since black holes may form and grow in them. In the talk I will describe how relativistic dynamics is included in N-body simulations of such systems, and discuss examples how we model sources in different wavelength regimes, showing results from triple and binary black holes in galactic nuclei, and giving an outlook to projected work for star clusters. Also I'll explain how these theoretical activities are embedded into collaborative programs with gravitational wave observatories, such as the VESF (Virgo-EGO science collaboration) and the German LISA cooperation.

Spurzem, Rainer; Merritt, D.; Berczik, Peter; Berentzen, Ingo; Preto, Miguel; Downing, Jonathan

2007-08-01

171

A First Comparison Between LIGO and Virgo Inspiral Search Pipelines  

E-print Network

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.

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

172

NASA EM Followup of LIGO-Virgo Candidate Events  

NASA Technical Reports Server (NTRS)

We present a strategy for a follow-up of LIGO-Virgo candidate events using offline survey data from several NASA high-energy photon instruments aboard RXTE, Swift, and Fermi. Time and sky-location information provided by the GW trigger allows for a targeted search for prompt and afterglow EM signals. In doing so, we expect to be sensitive to signals which are too weak to be publicly reported as astrophysical EM events.

Blackburn, Lindy L.

2011-01-01

173

Assessment of Degradation of VIRGO Radiometers on Board SOHO  

Microsoft Academic Search

The determination of the total solar irradiance (TSI) from the SOHO\\/VIRGO experiment is made by first correcting the time series for all a priori known influences, and then correcting the data for instrumental degradation, using the back-up instruments PMO6-VB and DIARAD-R. The long-term behaviour of PMO6-VA shows an exponential decrease in its sensitivity with a time constant of ? =

M. Anklin; C. Frohlich; W. Finsterle; D. A. Crommelynck; S. Dewitte

1998-01-01

174

OPTICAL COLORS OF INTRACLUSTER LIGHT IN THE VIRGO CLUSTER CORE  

SciTech Connect

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.

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

175

A Robust Control Design Framework for Substructure Models  

NASA Technical Reports Server (NTRS)

A framework for designing control systems directly from substructure models and uncertainties is proposed. The technique is based on combining a set of substructure robust control problems by an interface stiffness matrix which appears as a constant gain feedback. Variations of uncertainties in the interface stiffness are treated as a parametric uncertainty. It is shown that multivariable robust control can be applied to generate centralized or decentralized controllers that guarantee performance with respect to uncertainties in the interface stiffness, reduced component modes and external disturbances. The technique is particularly suited for large, complex, and weakly coupled flexible structures.

Lim, Kyong B.

1994-01-01

176

Substructures of the (252) ferrous martensite and their crystallographic significance  

SciTech Connect

Many ferrous martensites have been found to possess a macroscopically invariant habit plane close to (252){sub f} and to exhibit complex and variable substructures that cannot be not only satisfactorily explained but also fully characterized so far. The present work attempts to examine the mechanism of occurrence of the complex substructures and their correlation to other crystallographic properties, esp. to the shape strain, on the basis of a new theory. The theory describes the atomic movements in the lattice change represented with the Bain distortion in the past.

Wang Shidao [Lanzhou Railway Inst. (China). Dept. of Mechanical Engineering] [Lanzhou Railway Inst. (China). Dept. of Mechanical Engineering; [Chinese Academy of Sciences, Shenyang (China). Lab. of Atomic Imaging of Solids; Hei Zukun [Dalian Maritime Univ. (China). Research Inst. of Materials Technology] [Dalian Maritime Univ. (China). Research Inst. of Materials Technology

1999-04-23

177

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

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

178

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

179

VizieR Online Data Catalog: Halpha3. Catalog and SFR in Virgo cluster (Gavazzi+, 2012)  

NASA Astrophysics Data System (ADS)

We present H?3 (acronym for H?-??), an H? narrow-band imaging survey of ~400 galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA) in the Local Supercluster, including the Virgo cluster. By using hydrogen recombination lines as a tracer of recent star formation, we aim to investigate the relationships between atomic neutral gas and newly formed stars in different environments (cluster and field), morphological types (spirals and dwarfs), and over a wide range of stellar masses (~107.5-1011.5M?). We image in H?+[NII] all the galaxies that contain more than 107M? of neutral atomic hydrogen in the sky region 11h

Gavazzi, G.; Fumagalli, M.; Galardo, V.; Grossetti, F.; Boselli, A.; Giovanelli, R.; Haynes, M. P.; Fabello, S.

2012-05-01

180

SUBARU SPECTROSCOPY OF THE GLOBULAR CLUSTERS IN THE VIRGO GIANT ELLIPTICAL GALAXY M86  

SciTech Connect

We present the first spectroscopic study of the globular clusters (GCs) in the giant elliptical galaxy (gE) M86 in the Virgo Cluster. Using spectra obtained in the Multi-Object Spectroscopy mode of the Faint Object Camera and Spectrograph on the Subaru telescope, we measure the radial velocities for 25 GCs in M86. The mean velocity of the GCs is derived to be v-bar{sub p} = -354{sub -79}{sup +81} km s{sup -1}, which is different from the velocity of the M86 nucleus (v{sub gal} = -234 {+-} 41 km s{sup -1}). We estimate the velocity dispersion of the GCs, {sigma}{sub p} = 292{sup +32}{sub -32} km s{sup -1}, and find a hint of rotation in the M86 GC system. A comparison of the observed velocity dispersion profiles of the GCs and stars with a prediction based on the stellar mass profile strongly suggests the existence of an extended dark matter halo in M86. We also estimate the metallicities and ages for 16 and 8 GCs, respectively. The metallicities of M86 GCs are in the range of -2.0 < [Fe/H] <-0.2 with a mean value of -1.13 {+-} 0.47. These GCs show a wide age distribution from 4 to 15 Gyr.

Park, Hong Soo; Lee, Myung Gyoon [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Hwang, Ho Seong, E-mail: hspark@astro.snu.ac.kr, E-mail: mglee@astro.snu.ac.kr, E-mail: hhwang@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

2012-10-01

181

The Virgo Cluster of Galaxies in the Making  

NASA Astrophysics Data System (ADS)

VLT Observations of Planetary Nebulae Confirm the Dynamical Youth of Virgo [1] Summary An international team of astronomers [2] has succeeded in measuring with high precision the velocities of a large number of planetary nebulae [3] in the intergalactic space within the Virgo Cluster of galaxies. For this they used the highly efficient FLAMES spectrograph [4] on the ESO Very Large Telescope at the Paranal Observatory (Chile). These planetary nebulae stars free floating in the otherwise seemingly empty space between the galaxies of large clusters can be used as "probes" of the gravitational forces acting within these clusters. They trace the masses, visible as well as invisible, within these regions. This, in turn, allows astronomers to study the formation history of these large bound structures in the universe. The accurate velocity measurements of 40 of these stars confirm the view that Virgo is a highly non-uniform galaxy cluster, consisting of several subunits that have not yet had time to come to equilibrium. These new data clearly show that the Virgo Cluster of galaxies is still in its making. They also prove for the first time that one of the bright galaxies in the region scrutinized, Messier 87, has a very extended halo of stars, reaching out to at least 65 kpc. This is more than twice the size of our own galaxy, the Milky Way. PR Photo 29a/04: Velocity Measurements of Forty Intracluster Planetary Nebulae (FLAMES/VLT) PR Photo 29b/04: Intracluster Planetary Nebulae in the SUC field in the Virgo Cluster (Digital Sky Survey) A young cluster At a distance of approximately 50 million light-years, the Virgo Cluster is the nearest galaxy cluster. It is located in the zodiacal constellation Virgo (The Virgin) and contains many hundreds of galaxies, ranging from giant and massive elliptical galaxies and spirals like our own Milky Way, to dwarf galaxies, hundreds of times smaller than their big brethren. French astronomer Charles Messier entered 16 members of the Virgo cluster in his famous catalogue of nebulae. An image of the core of the cluster obtained with the Wide Field Imager camera at the ESO La Silla Observatory was published last year as PR Photo 04a/03. Clusters of galaxies are believed to have formed over a long period of time by the assembly of smaller entities, through the strong gravitational pull from dark and luminous matter. The Virgo cluster is considered to be a relatively young cluster because previous studies have revealed small "sub-clusters of galaxies" around the major galaxies Messier 87, Messier 86 and Messier 49. These sub-clusters have yet to merge to form a denser and smoother galaxy cluster. Recent observations have shown that the so-called "intracluster" space, the region between galaxies in a cluster, is permeated by a sparse "intracluster population of stars", which can be used to study in detail the structure of the cluster. Cosmic wanderers The first discoveries of intracluster stars in the Virgo cluster were made serendipitously by Italian astronomer, Magda Arnaboldi (Torino Observatory, Italy) and her colleagues, in 1996. In order to study the extended halos of galaxies in the Virgo cluster, with the ESO New Technology Telescope at La Silla, they searched for objects known as "planetary nebulae" [3]. Planetary nebulae (PNe) can be detected out to large distances from their strong emission lines. These narrow emission lines also allow for a precise measure of their radial velocities. Planetary Nebulae can thus serve to investigate the motions of stars in the halo regions of distant galaxies. In their study, the astronomers found several planetary nebulae apparently not related to any galaxies but moving in the gravity field of the whole cluster. These "wanderers" belonged to a newly discovered intracluster population of stars. Since these first observations, several hundreds of these wanderers have been discovered. They must represent the tip of the iceberg of a huge population of stars swarming among the galaxies in these enor

2004-10-01

182

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

E-print Network

PubChem Substructure Fingerprint V1.3 http://pubchem.ncbi.nlm.nih.gov Page 1 of 21 5/1/2009 7:21:06 AM The PubChem System generates a binary substructure fingerprint for chemical structures. These fingerprints are used by PubChem for similarity neighboring and similarity searching. A substructure

Levin, Judith G.

183

Dynamic substructuring for shock spectrum analysis using component mode synthesis  

NASA Technical Reports Server (NTRS)

Component mode synthesis was used to analyze different types of structures with MSC NASTRAN. The theory and technique of using Multipoint Constraint Equations (MPCs) to connect substructures to each other or to a common foundation is presented. Computation of the dynamic response of the system from shack spectrum inputs was automated using the DMAP programming language of the MSC NASTRAN finite element code.

Mcpheeters, Barton W.; Lev, Avivi; Bogert, Philip B.; Scavuzzo, Rudolph J.

1988-01-01

184

DYNAMIC SUBSTRUCTURING OF STRUCTURAL SYSTEMS WITH DISSIPATIVE PHYSICAL INTERFACE  

E-print Network

Conservatoire National des Arts et Métiers (CNAM), Structural Mechanics and Coupled Systems Laboratory, Paris and an appropriate elastostatic lifting operator related to the linking substructure. Keywords: reduced-order model interfaces (Farhat and Geradin, 1994; Ohayon et al., 1997; Park and Park, 2004). A general synthesis

Paris-Sud XI, Université de

185

Weak Lensing Studies of Mass Substructure in Clusters of Galaxies  

NASA Astrophysics Data System (ADS)

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.

Huwe, Paul M.

2012-01-01

186

Anomalous magnetic moment and limits on fermion substructure  

Microsoft Academic Search

Experimental constraints on possible lepton and quark substructure are analyzed and expressed in terms of a general formalism for describing composite particles in terms of their constituents. In particular, the measured gyromagnetic ratios may very severely restrict possible internal structure of light leptons (electrons and muons) in some models. Simple expressions for hadronic g values and electromagnetic radii are given

Stanley Brodsky; Sidney Drell

1980-01-01

187

Experimentally implementable criteria revealing substructures of genuine multipartite entanglement  

Microsoft Academic Search

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.

Marcus Huber; Hans Schimpf; Andreas Gabriel; Christoph Spengler; Dagmar Bruß; Beatrix C. Hiesmayr

2011-01-01

188

Experimentally implementable criteria revealing substructures of genuine multipartite entanglement  

E-print Network

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.

Huber, Marcus; Gabriel, Andreas; Spengler, Christoph; Bruß, Dagmar; Hiesmayr, Beatrix C

2010-01-01

189

Experimentally implementable criteria revealing substructures of genuine multipartite entanglement  

SciTech Connect

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.

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

190

A Frequency-Domain Substructure System Identification Algorithm  

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

191

The ACS Virgo Cluster Survey. XIII. SBF Distance Catalog and the Three-dimensional Structure of the Virgo Cluster  

NASA Astrophysics Data System (ADS)

The ACS Virgo Cluster Survey consists of HST ACS imaging for 100 early-type galaxies in the Virgo Cluster, observed in the F475W (~SDSS g) and F850LP (~SDSS z) filters. We derive distances for 84 of these galaxies using the method of surface brightness fluctuations (SBFs), present the SBF distance catalog, and use this database to examine the three-dimensional distribution of early-type galaxies in the Virgo Cluster. The SBF distance moduli have a mean (random) measurement error of 0.07 mag (0.5 Mpc), or roughly 3 times better than previous SBF measurements for Virgo Cluster galaxies. Five galaxies lie at a distance of d~23 Mpc and are members of the W' cloud. The remaining 79 galaxies have a narrow distribution around our adopted distance of =16.5+/-0.1 (random mean error) +/-1.1 Mpc (systematic). The rms distance scatter of this sample is ?(d)=0.6+/-0.1 Mpc, with little or no dependence on morphological type or luminosity class (i.e., 0.7+/-0.1 and 0.5+/-0.1 Mpc for the giants and dwarfs, respectively). The back-to-front depth of the cluster measured from our sample of early-type galaxies is 2.4+/-0.4 Mpc (i.e., +/-2 ? of the intrinsic distance distribution). The M87 (cluster A) and M49 (cluster B) subclusters are found to lie at distances of 16.7+/-0.2 and 16.4+/-0.2 Mpc, respectively. There may be a third subcluster associated with M86. A weak correlation between velocity and line-of-sight distance may be a faint echo of the cluster velocity distribution not having yet completely virialized. In three dimensions, Virgo's early-type galaxies appear to define a slightly triaxial distribution, with axis ratios of (1:0.7:0.5). The principal axis of the best-fit ellipsoid is inclined ~20°-40° from the line of sight, while the galaxies belonging to the W' cloud lie on an axis inclined by ~10°-15°. 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.

Mei, Simona; Blakeslee, John P.; Côté, Patrick; Tonry, John L.; West, Michael J.; Ferrarese, Laura; Jordán, Andrés; Peng, Eric W.; Anthony, André; Merritt, David

2007-01-01

192

Detecting Halo Substructure in the Gaia Era  

NASA Astrophysics Data System (ADS)

The observational data expected to come from the Gaia astrometric mission represent an unrivaled opportunity to search for tidal streams using all-sky full phase-space information for nearly a billion stars in our Galaxy. In this contribution we will describe the Modified Great Circle Cell Count (mGC3) method devised for the detection of stellar streams in the galactic halo. This method is based on the GC3 method originally devised by Johnston, Hernquist, & Bolte (1996), modified to include velocity information in order to enhance the contrast of stream signatures with respect to the galactic halo background. We present our results on the efficiency of mGC3, tested by embedding tidal streams from N-body simulations in a mock Gaia catalogue of the galactic background, which includes a realistic realization of the photometric and kinematic properties, errors and completeness limits. We investigate mGC3's efficiency as a function of initial satellite luminosity, star formation history and orbital parameters and find that satellites in the range 10^8-10^9 L_? can be recovered for streams as dynamically old as ~10 Gyr and up to galactocentric distances of ~40 kpc. For some combinations of dynamical ages and orbits, tidal streams with luminosities down to 4-5×10^7 L_? can be recovered.

Mateu, C.; Aguilar, L.; Bruzual, G.; Brown, A.; Valenzuela, O.; Carigi, L.; Velázquez, H.; Hernández, F.

2014-06-01

193

Stellar Opacity  

SciTech Connect

The monochromatic opacity, {kappa}{sub v}, quantifies the property of a material to remove energy of frequency v from a radiation field. A harmonic average of {kappa}{sub v}, known as the Rosseland mean, {kappa}{sub R}, is frequently used to simplify the calculation of energy transport in stars. The term ''opacity'' is commonly understood to refer to {kappa}{sub R}. Opacity plays an important role in stellar modeling because for most stars radiation is the primary mechanism for transporting energy from the nuclear burning region in the core to the surface. Depending on the mass, convection and electron thermal conduction can also be important modes of stellar energy transport. The efficiency of energy transport is related to the temperature gradient, which is directly proportional to the mean radiative opacity in radiation dominated regions. When the radiative opacity is large, convection can become the more efficient energy transport mechanism. Electron conductive opacity, the resistance of matter to thermal conduction, is inversely proportional to electron thermal conductivity. Thermal conduction becomes the dominant mode of energy transport at high density and low temperature.

Rogers, F J; Iglesias, C A

1999-11-07

194

H?3: an H? imaging survey of HI selected galaxies from ALFALFA. II. Star formation properties of galaxies in the Virgo cluster and surroundings  

NASA Astrophysics Data System (ADS)

Context. We present the analysis of H?3, an H? narrow-band imaging follow-up survey of 409 galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA) in the Local Supercluster, including the Virgo cluster, in the region 11h < RA < 16h ; 4o < Dec < 16°; 350 < cz < 2000 km s-1. Aims: Taking advantage of H?3, which provides the complete census of the recent massive star formation rate (SFR) in HI-rich galaxies in the local Universe and of ancillary optical data from SDSS we explore the relations between the stellar mass, the HI mass, and the current, massive SFR of nearby galaxies in the Virgo cluster. We compare these with those of isolated galaxies in the Local Supercluster, and we investigate the role of the environment in shaping the star formation properties of galaxies at the present cosmological epoch. Methods: By using the H? hydrogen recombination line as a tracer of recent star formation, we investigated the relationships between atomic neutral gas and newly formed stars in different environments (cluster and field), for many morphological types (spirals and dwarfs), and over a wide range of stellar masses (107.5 to 1011.5 M?). To quantify the degree of environmental perturbation, we adopted an updated calibration of the HI deficiency parameter which we used to divide the sample into three classes: unperturbed galaxies (DefHI ? 0.3), perturbed galaxies (0.3 < DefHI < 0.9), and highly perturbed galaxies (DefHI ? 0.9). Results: Studying the mean properties of late-type galaxies in the Local Supercluster, we find that galaxies in increasing dense local galaxy conditions (or decreasing projected angular separation from M 87) show a significant decrease in the HI content and in the mean specific SFR, along with a progressive reddening of their stellar populations. The gradual quenching of the star formation occurs outside-in, consistently with the predictions of the ram pressure model. Once considered as a whole, the Virgo cluster is effective in removing neutral hydrogen from galaxies, and this perturbation is strong enough to appreciably reduce the SFR of its entire galaxy population. Conclusions: An estimate of the present infall rate of 300-400 galaxies per Gyr in the Virgo cluster is obtained from the number of existing HI-rich late-type systems, assuming 200-300 Myr as the time scale for HI ablation. If the infall process has been acting at a constant rate, this would imply that the Virgo cluster has formed approximately 2 Gyr ago, consistently with the idea that Virgo is in a young state of dynamical evolution. Based on observations taken at the observatory of San Pedro Martir (Baja California, Mexico), belonging to the Mexican Observatorio Astronómico Nacional.

Gavazzi, G.; Fumagalli, M.; Fossati, M.; Galardo, V.; Grossetti, F.; Boselli, A.; Giovanelli, R.; Haynes, M. P.

2013-05-01

195

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

Microsoft Academic Search

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

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

196

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

Microsoft Academic Search

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

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

197

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

Microsoft Academic Search

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:

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

198

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

Microsoft Academic Search

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

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

2003-01-01

199

AMUSE-VIRGO. II. DOWN-SIZING IN BLACK HOLE ACCRETION  

E-print Network

We complete the census of nuclear X-ray activity in 100 early-type Virgo galaxies observed by the Chandra X-ray Telescope as part of the AMUSE-Virgo survey, down to a (3?) limiting luminosity of 3.7 × 10[superscript 38] ...

Gallo, Elena

200

Search for gravitational waves from low mass compact binary coalescence in LIGO’s sixth science run and Virgo’s science runs 2 and 3  

E-print Network

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 ...

Barsotti, Lisa

201

Stellar substructures in the solar neighbourhood IV. Kinematic Group 1 in the Geneva-Copenhagen survey  

E-print Network

We determine detailed elemental abundances in stars belonging to the so-called Group 1 of the Geneva-Copenhagen survey (GCS) and compare the chemical composition with the Galactic thin- and thick-disc stars, with the GCS Group 2 and Group 3 stars, as well as with several kinematic streams of similar metallicities. The aim is to search for chemical signatures that might give information about the formation history of this kinematic group of stars. High-resolution spectra were obtained with the Fibre-fed Echelle Spectrograph (FIES) spectrograph at the Nordic Optical Telescope, La Palma, and were analysed with a differential model atmosphere method. Comparison stars were observed and analysed with the same method. The average value of [Fe/H] for the 37 stars of Group 1 is -0.20 +- 0.14 dex. Investigated Group 1 stars can be separated into three age subgroups. Along with the main 8- and 12-Gyr-old populations, a subgroup of stars younger than 5 Gyr can be separated as well. Abundances of oxygen, alpha-elements, a...

Ženovien?, R; Nordström, B; Stonkut?, E; Barisevi?ius, G

2015-01-01

202

The Frequency Content of the VIRGO/SoHO Lightcurves: Implications for Planetary Transit Detection from Space  

E-print Network

Stellar micro-variability poses a serious threat to the capacities of space-based planet-finding missions such as Kepler or Eddington. The solar lightcurves obtained by the VIRGO PMO6 and SPM instruments on board SoHO from 1996 to 2001 have been studied in order to follow variability changes through the activity cycle. In all datasets, active regions-induced variability, below 2 microHz, is closely correlated to the BBSO Ca II K-line index. The PMO6 (total irradiance) data shows evidence for a meso-granulation component around tau = 8x10^3 s, while all narrow-band SPM datasets (red, green and blue) show super-granulation (tau = 5x10^4 s) but no meso-granulation. Both actvity and granulation related components have significantly smaller amplitudes in the red than in the blue channel. These results, coupled with available stellar data, allow us to generate simulated lightcurves with enhanced variability as a testbed for pre-processing and detection methods, and influence the case for using colour information in this kind of mission.

S. Aigrain; G. Gilmore; F. Favata; S. Carpano

2002-08-29

203

The nature and origin of substructure in the outskirts of M31 - II. Detailed star formation histories  

NASA Astrophysics Data System (ADS)

While wide-field surveys of M31 have revealed much substructure at large radii, understanding the nature and origin of this material is not straightforward from morphology alone. Using deep Hubble Space Telescope/Advanced Camera for Surveys data, we have derived further constraints in the form of quantitative star formation histories (SFHs) for 14 inner halo fields which sample diverse substructures. In agreement with our previous analysis of colour-magnitude diagram morphologies, we find the resultant behaviours can be broadly separated into two categories. The SFHs of `disc-like' fields indicate that most of their mass has formed since z ˜ 1, with one quarter of the mass formed in the last 5 Gyr. We find `stream-like' fields to be on average 1.5 Gyr older, with ? 10 per cent of their stellar mass formed within the last 5 Gyr. These fields are also characterized by an age-metallicity relation showing rapid chemical enrichment to solar metallicity by z = 1, suggestive of an early-type progenitor. We confirm a significant burst of star formation 2 Gyr ago, discovered in our previous work, in all the fields studied here. The presence of these young stars in our most remote fields suggests that they have not formed in situ but have been kicked-out from the thin disc through disc heating in the recent past.

Bernard, Edouard J.; Ferguson, Annette M. N.; Richardson, Jenny C.; Irwin, Mike J.; Barker, Michael K.; Hidalgo, Sebastian L.; Aparicio, Antonio; Chapman, Scott C.; Ibata, Rodrigo A.; Lewis, Geraint F.; McConnachie, Alan W.; Tanvir, Nial R.

2015-01-01

204

Synthesis of shuttle vehicle damping using substructure test results  

NASA Technical Reports Server (NTRS)

An empirical method is developed for predicting the modal damping of a combined parallel-stage shuttle model by means of damping measurements performed on the individual substructures. Correlations are first determined for each component in terms of damping energy as a function of peak kinetic energy and modal amplitude. The results are then used to predict component damping energies corresponding to the respective kinetic energies and amplitudes that occur for the new modes of the combined system. Modal characteristics for the system, other than damping, are obtained by a real eigenvalue solution of dynamic equations developed by Hurty's procedure of substructures. System equations, which include component modal damping, are also solved by a complex eigenvalue approach for comparison with results of the empirical method.

Kana, D. D.; Huzar, S.

1972-01-01

205

Tableau-based protein substructure search using quadratic programming  

PubMed Central

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

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

2009-01-01

206

AMUSE-VIRGO. III. MID-INFRARED PHOTOMETRY OF EARLY-TYPE GALAXIES AND LIMITS ON OBSCURED NUCLEAR EMISSION  

SciTech Connect

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 {mu}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 {approx}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.

Leipski, Christian [Max-Planck Institut fuer Astronomie (MPIA), Koenigstuhl 17, D-69117 Heidelberg (Germany); Gallo, Elena; Miller, Brendan P. [Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48109 (United States); Treu, Tommaso; Antonucci, Robert [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Woo, Jong-Hak, E-mail: leipski@mpia-hd.mpg.de [Department of Physics and Astronomy, Seoul National University, Seoul, 151-742 (Korea, Republic of)

2012-01-10

207

COSMIC RAY DIFFUSION FRONTS IN THE VIRGO CLUSTER  

SciTech Connect

The pair of large radio lobes in the Virgo cluster, each about 23 kpc in radius, have curiously sharp outer edges where the radio-synchrotron continuum flux declines abruptly. However, just adjacent to this sharp transition, the radio flux increases. This radio limb-brightening is observed over at least half of the perimeter of both lobes. We describe slowly propagating steady-state diffusion fronts that explain these counterintuitive features. Because of the natural buoyancy of radio lobes, the magnetic field is largely tangent to the lobe boundary, an alignment that polarizes the radio emission and dramatically reduces the diffusion coefficient of relativistic electrons. As cosmic ray electrons diffuse slowly into the cluster gas, the local magnetic field and gas density are reduced as gas flows back toward the radio lobe. Radio emission peaks can occur because the synchrotron emissivity increases with magnetic field and then decreases with the density of non-thermal electrons. A detailed comparison of steady diffusion fronts with quantitative radio observations may reveal information about the spatial variation of magnetic fields and the diffusion coefficient of relativistic electrons. On larger scales, some reduction of the gas density inside the Virgo lobes due to cosmic ray pressure must occur and may be measurable. Such X-ray observations could reveal important information about the presence of otherwise unobservable non-thermal components such as relativistic electrons of low energy or proton cosmic rays.

Mathews, William G.; Guo Fulai, E-mail: mathews@ucolick.org [Department of Astronomy and Astrophysics, University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)

2011-07-20

208

The CO Tully-Fisher Relation for the Virgo Cluster,  

E-print Network

A comparison between the CO and HI Tully-Fisher relation for a sample of 30 Virgo ga\\-la\\-xies shows no significant difference concerning the intrinsic scatter. The distance moduli from both relations after correcting for the sample incompleteness bias agree within the errors and also show no significant difference with previous studies of the Virgo cluster using a complete sample. The CO total linewidth and the CO flux were found to be not well correlated. However, if the distances to the individual galaxies were calculated by the CO Tully-Fisher relation, the CO luminosities calculated using these distances are correlated with the CO linewidths. This correlation does not show up when the distances were calculated by the conventional HI Tully-Fisher relation. Finally we give the structure of the cluster as derived from this small subsample using the distances to the individual galaxies. The large depth of the cluster is confirmed both by the HI and the CO Tully-Fisher relation.

F. Schoeniger; Y. Sofue

1995-01-31

209

The Arecibo Galaxy Environment Survey - V. The Virgo cluster (I)  

NASA Astrophysics Data System (ADS)

We present 21-cm observations of a 10 × 2 deg2 region in the Virgo cluster, obtained as part of the Arecibo Galaxy Environment Survey. 289 sources are detected over the full redshift range (-2000 < vhel < +20 000 km s-1) with 95 belonging to the cluster (vhel < 3000 km s-1). We combine our observations with data from the optically selected Virgo Cluster Catalogue (VCC) and the Sloan Digital Sky Survey. Most of our detections can be clearly associated with a unique optical counterpart, and 30 per cent of the cluster detections are new objects fainter than the VCC optical completeness limit. Seven detections may have no optical counterpart and we discuss the possible origins of these objects. Seven detections appear associated with early-type galaxies. We perform H I stacking on the H I-undetected galaxies listed in the VCC in this region and show that they must have significantly less gas than those actually detected in H I. Galaxies undetected in H I in the cluster appear to be really devoid of gas, in contrast to a sample of field galaxies from the Arecibo Legacy Fast ALFA (ALFALFA).

Taylor, R.; Davies, J. I.; Auld, R.; Minchin, R. F.

2012-06-01

210

Compact massive objects in Virgo galaxies: the black hole population  

NASA Astrophysics Data System (ADS)

We investigate the distribution of massive black holes (MBHs) in the Virgo cluster. Observations suggest that active galactic nuclei activity is widespread in massive galaxies (M* >~ 1010Msolar), while at lower galaxy masses star clusters are more abundant, which might imply a limited presence of central black holes in these galaxy-mass regimes. We explore if this possible threshold in MBH hosting is linked to nature, nurture or a mixture of both. The nature scenario arises naturally in hierarchical cosmologies, as MBH formation mechanisms typically are efficient in biased systems, which would later evolve into massive galaxies. Nurture, in the guise of MBH ejections following MBH mergers, provides an additional mechanism that is more effective for low mass, satellite galaxies. The combination of inefficient formation, and lower retention of MBHs, leads to the natural explanation of the distribution of compact massive objects in Virgo galaxies. If MBHs arrive to the correlation with the host mass and velocity dispersion during merger-triggered accretion episodes, sustained tidal stripping of the host galaxies creates a population of MBHs which lie above the expected scaling between the holes and their host mass, suggesting a possible environmental dependence.

Volonteri, Marta; Haardt, Francesco; Gültekin, Kayhan

2008-03-01

211

Future perspectives for jet substructure techniques in LHC Run2  

NASA Astrophysics Data System (ADS)

The increased pile-up expected in the LHC Run 2 and High Luminosity LHC creates a challenging environment for utilizing the jet-substructure techniques which were successfully demonstrated in the LHC Run 1. The ATLAS and CMS experiments are studying a range of methods to improve jet reconstruction to increase the resilience against high pile-up. Promising results are obtained in simulation but await validation on the first Run 2 data.

Mozer, Matthias

2015-03-01

212

Optimized Substructure Discovery for Semi-structured Data  

Microsoft Academic Search

In this paper, we consider the problem of discovering interesting substructures from a large collection of semi-structured\\u000a data in the framework of optimized pattern discovery. We model semi-structured data and patterns with labeled ordered trees,\\u000a and present an efficient algorithm that discovers the best labeled ordered trees that optimize a given statistical measure,\\u000a such as the information entropy and the

Kenji Abe; Shinji Kawasoe; Tatsuya Asai; Hiroki Arimura; Setsuo Arikawa

2002-01-01

213

A substructure analysis of the A3558 cluster complex  

E-print Network

The "algorithm driven by the density estimate for the identification of clusters" (DEDICA, Pisani 1993, 1996) is applied to the A3558 cluster complex in order to find substructures. This complex, located at the center of the Shapley Concentration supercluster, is a chain formed by the ACO clusters A3556, A3558 and A3562 and the two poor clusters SC 1327-312 and SC 1329-313. We find a large number of clumps, indicating that strong dynamical processes are active. In particular, it is necessary to use a fully three-dimensional sample(i.e. using the galaxy velocity as third coordinate) in order to recover also the clumps superimposed along the line of sight. Even if a great number of detected substructures were already found in a previous analysis (Bardelli et al. 1998), this method is more efficient and faster when compared with the use of a wide battery of tests and permits the direct estimate of the detection significance. Almost all subclusters previously detected by the wavelet analyses found in the literature are recognized by DEDICA. On the basis of the substructure analysis, we also briefly discuss the origin of the A3558 complex by comparing two hypotheses: 1) the structure is a cluster-cluster collision seen just after the first core-core encounter; 2) this complex is the result of a series of incoherent group-group and cluster-group mergings, focused in that region by the presence of the surrounding supercluster. We studied the fraction of blue galaxies in the detected substructures and found that the bluest groups reside between A3562 and A3558, i.e. in the expected position in the scenario of the cluster-cluster collision.

S. Bardelli; A. Pisani; M. Ramella; E. Zucca; G. Zamorani

1998-06-22

214

Halo Substructure in the Hercules-Aquila Cloud  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

215

Volume of hippocampal substructures in borderline personality disorder.  

PubMed

Borderline personality disorder (BPD) may be associated with smaller hippocampi in comparison to hippocampal size in controls. However, specific pathology in hippocampal substructures (i.e., head, body and tail) has not been sufficiently investigated. To address hippocampal structure in greater detail, we studied 39 psychiatric inpatients and outpatients with a DSM-IV diagnosis of BPD and 39 healthy controls. The hippocampus and its substructures were segmented manually on magnetic resonance imaging scans. The volumes of hippocampal substructures (and total hippocampal volume) did not differ between BPD patients and controls. Exploratory analysis suggests that patients with a lifetime history of posttraumatic stress disorder (PTSD) may have a significantly smaller hippocampus - affecting both the hippocampal head and body - in comparison to BPD patients without comorbid PTSD (difference in total hippocampal volume: -10.5%, 95%CI -2.6 to -18.5, significant). Also, patients fulfilling seven or more DSM-IV BPD criteria showed a hippocampal volume reduction, limited to the hippocampal head (difference in volume of the hippocampal head: -16.5%, 95%CI -6.1 to -26.8, significant). Disease heterogeneity in respect to, for example, symptom severity and psychiatric comorbidities may limit direct comparability between studies; the results presented here may reflect hippocampal volumes in patients who are "less" affected or they may simply be a chance finding. However, there is also the possibility that global effects of BPD on the hippocampus may have previously been overestimated. PMID:25624067

Kreisel, Stefan Henner; Labudda, Kirsten; Kurlandchikov, Oleg; Beblo, Thomas; Mertens, Markus; Thomas, Christine; Rullkötter, Nina; Wingenfeld, Katja; Mensebach, Christoph; Woermann, Friedrich G; Driessen, Martin

2015-03-30

216

Advancements in hybrid dynamic models combining experimental and finite element substructures  

NASA Astrophysics Data System (ADS)

This paper presents very practical enhancements to the transmission simulator method (TSM); also known as the Modal Constraints for Fixtures and Subsystems (MCFS). The enhancements allow this method to be implemented directly in finite element software, instead of having to extract the reduced finite element model from its software and implement the substructure coupling in another code. The transmission simulator method is useful for coupling substructures where one substructure is derived experimentally and the other is generated from a finite element model. This approach uses a flexible fixture in the experimental substructure to improve the modal basis of the substructure; thus, providing a higher quality substructure. The flexible fixture substructure needs to be removed (decoupled) from the experimental substructure to obtain the true system characteristics. A modified method for this removal and coupling of the experimental and analytical substructures is provided. An additional improvement guarantees that the experimental substructure matrices are positive definite, a requirement for many finite element codes. Guidelines for designing robust transmission simulator hardware are provided. The concepts are applied to two sample cases. The first case consists of a cylinder connected by eight bolts to a plate with a beam. The second example is an outer shell structure that is connected through a bolted flange to a complex internal payload structure.

Mayes, R. L.; Ross, M. R.

2012-08-01

217

Introduction to Stellar Astrophysics  

E-print Network

- Homework ! Lecture 2: -Structure and Evolution presentations -Stellar Atmospheres -Cool Stars Big missing chunks: -Stellar Evolution proper (esp star formation) -Mass accretion and Outflows -Radiative Transfer) An Introduction to the Theory of Stellar Evolution and Structure Dimitri Mihalas (Freeman) Stellar Atmospheres

Rowan-Robinson, Michael

218

A survey of 286 Virgo cluster galaxies at optical griz and near-IR H band: surface brightness profiles and bulge-disc decompositions  

NASA Astrophysics Data System (ADS)

We present and g-, r-, i-, z- and H-band surface brightness profiles and bulge-disc decompositions for a morphologically broad sample of 286 Virgo Cluster Catalogue (VCC) galaxies. The H-band data come from a variety of sources including our survey of 171 VCC galaxies at the University of Hawaii (UH) 2.2-m telescope, Canada-France-Hawaii Telescope (CFHT) and United Kingdom Infrared Telescope (UKIRT), and another 115 galaxies from the Two Micron All Sky Survey (2MASS) and GOLDMine archives. The optical data for all 286 VCC galaxies were extracted from the Sloan Digital Sky Survey (SDSS) images. The H-band and the SDSS griz data were analysed in a homogeneous manner using our own software, yielding a consistent set of deep, multiband surface brightness profiles for each galaxy. Average surface brightness profiles per morphological bin were created in order to characterize the variety of galaxy light profiles across the Hubble sequence. The 1D bulge-disc decomposition parameters, as well as non-parametric galaxy measures, such as effective radius, effective surface brightness and light concentration, are presented for all 286 VCC galaxies in each of the five optical/near-infrared wavebands. The profile decompositions account for bulge and disc components, spiral arms, nucleus and atmospheric blurring. The Virgo spiral galaxy bulges typically have a Sérsic index n˜ 1, while elliptical galaxies prefer n˜ 2. No galaxy spheroid requires n > 3. The light profiles for 70 per cent of the Virgo elliptical galaxies reveal the presence of both a spheroid and disc component. A more in-depth discussion of the structural parameter trends can be found in McDonald, Courteau & Tully. The data provided here should serve as a base for studies of galaxy structure and stellar populations in the cluster environment. The galaxy light profiles and bulge-disc decomposition results are available at the Centre de Données astronomiques de Strasbourg (CDS; ) and the author's own website ().

McDonald, Michael; Courteau, Stéphane; Tully, R. Brent; Roediger, Joel

2011-07-01

219

Creating mock catalogues of stellar haloes from cosmological simulations  

NASA Astrophysics Data System (ADS)

We present a new technique for creating mock catalogues of the individual stars that make up the accreted component of stellar haloes in cosmological simulations and show how the catalogues can be used to test and interpret observational data. The catalogues are constructed from a combination of methods. A semi-analytic galaxy formation model is used to calculate the star formation history in haloes in an N-body simulation and dark matter particles are tagged with this stellar mass. The tags are converted into individual stars using a stellar population synthesis model to obtain the number density and evolutionary stage of the stars, together with a phase-space sampling method that distributes the stars while ensuring that the phase-space structure of the original N-body simulation is maintained. A set of catalogues based on the ? cold dark matter Aquarius simulations of Milky Way mass haloes have been created and made publicly available on a website. Two example applications are discussed that demonstrate the power and flexibility of the mock catalogues. We show how the rich stellar substructure that survives in the stellar halo precludes a simple measurement of its density profile and demonstrate explicitly how pencil-beam surveys can return almost any value for the slope of the profile. We also show that localized variations in the abundance of particular types of stars, a signature of differences in the composition of stellar populations, allow streams to be easily identified.

Lowing, Ben; Wang, Wenting; Cooper, Andrew; Kennedy, Rachel; Helly, John; Cole, Shaun; Frenk, Carlos

2015-01-01

220

Mapping the substructure in the Galactic halo with the next generation of astrometric satellites  

E-print Network

We run numerical simulations of the disruption of satellite galaxies in a Galactic potential to build up the entire stellar halo, in order to investigate what the next generation of astrometric satellites will reveal by observing the halo of the Milky Way. We generate artificial DIVA, FAME and GAIA halo catalogues, in which we look for the signatures left by the accreted satellites. We develop a method based on the standard Friends-of-Friends algorithm applied to the space of integrals of motion. We find this simple method can recover about 50% of the different accretion events, when the observational uncertainties expected for GAIA are taken into account, even when the exact form of the Galactic potential is unknown. The recovery rate for DIVA and FAME is much smaller, but these missions, like GAIA, should be able to test the hierarchical formation paradigm on our Galaxy by measuring the amount of halo substructure in the form of nearby kinematically cold streams with for example, a two-point correlation function in velocity space.

Amina Helmi; P. Tim de Zeeuw

2000-07-12

221

Major Substructure in the M31 Outer Halo: the South-West Cloud  

E-print Network

We undertake the first detailed analysis of the stellar population and spatial properties of a diffuse substructure in the outer halo of M31. The South-West Cloud lies at a projected distance of ~100 kpc from the centre of M31, and extends for at least ~50 kpc in projection. We use Pan-Andromeda Archaeological Survey photometry of red giant branch stars to determine a distance to the South-West Cloud of 793 +/- 45 kpc. The metallicity of the cloud is found to be [Fe/H] = -1.3 +/- 0.1. This is consistent with the coincident globular clusters PAndAS-7 and PAndAS-8, which have metallicities determined using an independent technique of [Fe/H] = -1.35 +/- 0.15. We measure a brightness for the Cloud of M_V = -12.1 mag; this is ~75 per cent of the luminosity implied by the luminosity-metallicity relation. Under the assumption that the South-West Cloud is the visible remnant of an accreted dwarf satellite, this suggests that the progenitor object was amongst M31's brightest dwarf galaxies prior to disruption.

Bate, N F; McMonigal, B; Lewis, G F; Martin, N F; McConnachie, A W; Veljanoski, J; Mackey, A D; Ferguson, A M N; Ibata, R A; Irwin, M J; Fardal, M; Huxor, A P; Babul, A

2013-01-01

222

Major substructure in the M31 outer halo: the South-West Cloud  

NASA Astrophysics Data System (ADS)

We undertake the first detailed analysis of the stellar population and spatial properties of a diffuse substructure in the outer halo of M31. The South-West Cloud lies at a projected distance of ˜100 kpc from the centre of M31 and extends for at least ˜50 kpc in projection. We use Pan-Andromeda Archaeological Survey photometry of red giant branch stars to determine a distance to the South-West Cloud of 793^{+45}_{-45} kpc. The metallicity of the cloud is found to be [Fe/H] = -1.3 ± 0.1. This is consistent with the coincident globular clusters PAndAS-7 and PAndAS-8, which have metallicities determined using an independent technique of [Fe/H] = -1.35 ± 0.15. We measure a brightness for the Cloud of MV = -12.1 mag; this is ˜75 per cent of the luminosity implied by the luminosity-metallicity relation. Under the assumption that the South-West Cloud is the visible remnant of an accreted dwarf satellite, this suggests that the progenitor object was amongst M31's brightest dwarf galaxies prior to disruption.

Bate, N. F.; Conn, A. R.; McMonigal, B.; Lewis, G. F.; Martin, N. F.; McConnachie, A. W.; Veljanoski, J.; Mackey, A. D.; Ferguson, A. M. N.; Ibata, R. A.; Irwin, M. J.; Fardal, M.; Huxor, A. P.; Babul, A.

2014-02-01

223

VLA HI Observations of Gas Stripping in the Virgo Cluster Spiral NGC 4522  

E-print Network

We present VLA HI observations at ~20"=1.5 kpc resolution of the highly inclined, HI-deficient Virgo cluster spiral galaxy NGC 4522, which is one of the clearest and nearest cases of ongoing ICM-ISM stripping. HI is abundant and spatially coincident with the stellar disk in the center, but beyond R = 3 kpc the HI distribution in the disk is sharply truncated and the only HI is extraplanar, and all on the northwest side. The kinematics and the morphology of the HI appear more consistent with ongoing stripping, and less consistent with gas fall-back which may occur long after peak pressure. Much of the extraplanar gas exhibits a modest net blueshift with respect to the galaxy's disk rotational velocities, consistent with gas accelerated toward the mean cluster velocity. The SW side of the galaxy has less HI in the disk but more HI in the halo, suggesting more effective gas removal on the side of the galaxy which is rotating into the ICM wind. The galaxy is 3.3 degrees ~800 kpc from M87, somewhat outside the region of strongest cluster X-ray emission. The ram pressure may be significantly stronger than standard values, due to large bulk motions and local density enhancements of the ICM gas, which may occur in a dynamic, shock-filled ICM experiencing subcluster merging. The HI and H-alpha distributions are similar, implying that the star-forming molecular ISM has been effectively stripped from the outer disk of the galaxy along with the HI.

Jeffrey D. P. Kenney; J. H. van Gorkom; Bernd Vollmer

2004-03-03

224

Parity Dependence in Strong Lens Systems as a Probe of Dark Matter Substructure  

E-print Network

The amount of mass in small, dark matter clumps within galaxies (substructure) is an important test of cold dark matter. One approach to measuring the substructure mass fraction is to analyze the fluxes of images that have been strongly lensed by a galaxy. Flux ratios between images that are anomalous with respect to smooth (no substructure) models have previously suggested that there is a greater amount of substructure than found in dark matter simulations. One measure of anomalous flux ratios is parity dependence -- that the fluxes of different images of a source are perturbed differently. In this paper, we discuss parity dependence as a probe of dark matter substructure. We find that reproducing the observed parity dependence requires a significant alignment between concentrated dark matter clumps and images. The results may imply a larger fraction of mass in substructures than suggested by some dark matter simulations and that the observed parity dependence is unlikely to be reproduced by luminous satellites of lens galaxies.

Jacqueline Chen

2008-10-11

225

INSIGHT INTO THE FORMATION OF THE MILKY WAY THROUGH COLD HALO SUBSTRUCTURE. I. THE ECHOS OF MILKY WAY FORMATION  

SciTech Connect

We identify 10-seven for the first time-elements of cold halo substructure (ECHOS) in the volume within 17.5 kpc of the Sun in the inner halo of the Milky Way. Our result is based on the observed spatial and radial velocity distribution of metal-poor main-sequence turnoff (MPMSTO) stars in 137 Sloan Extension for Galactic Understanding and Exploration lines of sight. We point out that the observed radial velocity distribution is consistent with a smooth stellar component of the Milky Way's inner halo overall, but disagrees significantly at the radial velocities that correspond to our detections. We show that all of our detections are statistically significant and that we expect no false positives. These ECHOS represent the observable stellar debris of ancient merger events in the stellar accretion history of the Milky Way, and we use our detections and completeness estimates to infer a formal upper limit of 0.34{sup +0.02} {sub -0.02} on the fraction of the MPMSTO population in the inner halo that belong to ECHOS. Our detections and completeness calculations also suggest that there is a significant population of low fractional overdensity ECHOS in the inner halo, and we predict that 1/3 of the inner halo (by volume) harbors ECHOS with MPMSTO star number densities n approx 15 kpc{sup -3}. In addition, we estimate that there are of order 10{sup 3} ECHOS in the entire inner halo. ECHOS are likely older than known surface brightness substructure, so our detections provide us with a direct measure of the accretion history of the Milky Way in a region and time interval that has yet to be fully explored. In concert with previous studies, our result suggests that the level of merger activity has been roughly constant over the past few Gyr and that there has been no accretion of single stellar systems more massive than a few percent of a Milky Way mass in that interval.

Schlaufman, Kevin C.; Rockosi, Constance M., E-mail: kcs@ucolick.or, E-mail: crockosi@ucolick.or [Astronomy and Astrophysics Department, University of California, Santa Cruz, CA 95064 (United States)

2009-10-01

226

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)

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.

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

227

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

SciTech Connect

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.

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

228

Stellar Metamorphosis:  

NASA Technical Reports Server (NTRS)

[TOP LEFT AND RIGHT] The Hubble Space Telescope's Wide Field and Planetary Camera 2 has captured images of the birth of two planetary nebulae as they emerge from wrappings of gas and dust, like butterflies breaking out of their cocoons. These images highlight a fleeting phase in the stellar burnout process, occurring just before dying stars are transformed into planetary nebulae. The left-hand image is the Cotton Candy nebula, IRAS 17150-3224; the right-hand image, the Silkworm nebula, IRAS 17441-2411. Called proto-planetary nebulae, these dying stars have been caught in a transition phase between a red giant and a planetary nebula. This phase is only about 1,000 years long, very short in comparison to the 1 billion-year lifetime of a star. These images provide the earliest snapshots of the transition process. Studying images of proto-planetary nebulae is important to understanding the process of star death. A star begins to die when it has exhausted its thermonuclear fuel - hydrogen and helium. The star then becomes bright and cool (red giant phase) and swells to several tens of times its normal size. It begins puffing thin shells of gas off into space. These shells become the star's cocoon. In the Hubble images, the shells are the concentric rings seen around each nebula. But the images also reveal the nebulae breaking out from those shells. The butterfly-like wings of gas and dust are a common shape of planetary nebulae. Such butterfly shapes are created by the 'interacting winds' process, in which a more recent 'fast wind' - material propelled by radiation from the hot central star - punches a hole in the cocoon, allowing the nebula to emerge. (This 'interacting wind' theory was first proposed by Dr. Sun Kwok to explain the origin of planetary nebulae, and has been subsequently proven successful in explaining their shapes.) The nebulae are being illuminated by light from the invisible central star, which is then reflected toward us. We are viewing the nebulae edge-on, where the direct starlight is blocked by the dusty cocoon. Otherwise, the starlight would overwhelm the nebular light, making it very difficult to see the butterfly-shaped nebula. In a few hundred years, intense ultraviolet radiation from the central star will energize the surrounding gas, causing it to glow brightly, and a planetary nebula is born. These observations were made with the Wide Field and Planetary Camera 2 using three filters: yellow-green, blue, and near-infrared. The images were taken in 1997 by Sun Kwok and in 1996 by Matt Bobrowsky. Credits: Sun Kwok and Kate Su (University of Calgary), Bruce Hrivnak (Valparaiso University), and NASA ----------------- The Hubble Space Telescope Sees Remarkable Structure in the Heart of a Planetary Nebula [BOTTOM LEFT AND RIGHT] This Wide Field and Planetary Camera 2 image of NGC 6818 shows two distinct layers of gas (with dust): a spherical outer region and a brighter, vase-shaped interior 'bubble.' Astronomers believe that a fast wind - material propelled by radiation from the hot central star - is creating the inner elongated shape. The central star of the planetary nebula appears as a tiny blue dot. The material in the wind is traveling so fast that it smashes through older, slower-moving stellar debris, causing a 'blowout' at both ends of the bubble (lower right and upper left). This nebula looks like a twin of NGC 3918, another planetary nebula that has been observed by the Hubble telescope. The structure of NGC 3918 is remarkably similar to that of NGC 6818. It has an outer spherical envelope and an inner, brighter, elongated bubble. A fast-moving wind also appears to have created an orifice at one end (bottom right-hand corner) of the inner bubble. There are even faint wisps of material that were probably blown out of this hole. In the opposite direction (top left-hand corner), there is a protrusion that seems on the verge of breaking through to form a hole. By finding and studying such similar objects, astronomers hope to learn crucial details about the evolutionary history of planetary nebulae

2002-01-01

229

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

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

230

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

SciTech Connect

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.

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

231

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

E-print Network

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.

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

2008-02-12

232

Intraguild predation, cannibalism, and microhabitat use in Calopteryx virgo and Somatochlora metallica larvae: a laboratory experiment  

Microsoft Academic Search

Intraguild predation (IGP) and cannibalism among co-occurring lotic odonate species was studied in Central Finland. A laboratory\\u000a experiment was performed to assess the microhabitat use and cannibalism between intermediate and late instars of Calopteryx virgo larvae and predation by larger Somatochlora metallica larvae on the intermediate C. virgo instars. The experiment was run in small running-water aquaria where the larvae

Jari Ilmonen; Jukka Suhonen

2006-01-01

233

Distance to the Virgo cluster galaxy M100 from Hubble Space Telescope observations of Cepheids  

Microsoft Academic Search

Accurate distances to galaxies are critical for determining the present expansion rate of the Universe or Hubble constant (H0). An important step in resolving the current uncertainty in H0 is the measurement of the distance to the Virgo cluster of galaxies. New observations using the Hubble Space Telescope yield a distance of 17.1 +\\/- 1.8 Mpc to the Virgo cluster

Wendy L. Freedman; Barry F. Madore; Jeremy R. Mould; Robert Hill; Laura Ferrarese; Robert C. Kennicutt; Abhijit Saha; Peter B. Stetson; John A. Graham; Holland Ford; John G. Hoessel; John Huchra; Shaun M. Hughes; Garth D. Illingworth

1994-01-01

234

Kinematic Disturbances in Optical Rotation Curves among 89 Virgo Disk Galaxies  

E-print Network

For 89 galaxies, mostly spirals, in the Virgo cluster region, we have obtained optical long-slit major axis spectra of the ionized gas. We find: (1) One-half of the Virgo galaxies we observed have regular rotation patterns, while the other 50% exhibit kinematic disturbances ranging from mild to major. Velocity complexities are generally consistent with those resulting from tidal encounters or accretion events. Since kinematic disturbances are expected to fade within ~10^9 years, many Virgo galaxies have experienced several significant kinematic disturbances during their lifetimes. (2) A few Virgo galaxies have ionized gas of limited extent, with velocities exceptionally low for their luminosities. In these galaxies the gas must be not rotationally supported. (3) There is a remarkable difference in the distribution of galaxy systemic velocity for galaxies with Regular rotation curves and galaxies with Disturbed rotation curves. Galaxies with regular rotation patterns show a flat distribution with systemic velocity, while galaxies with disturbed kinematics have a Gaussian distribution very similar to that for the elliptical galaxies in Virgo. This suggests that spirals with disturbed kinematics are preferentially on radial orbits, which bring them to the cluster core, where tidal interactions are strong and/or more common. These interactions may alter the morphology of the galaxy, and may also play a role in driving the Virgo cluster toward dynamical equilibrium.

Vera C. Rubin; Andrew H. Waterman; Jeffrey D. P. Kenney

1999-04-03

235

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

236

Hierarchically Parallelized Constrained Nonlinear Solvers with Automated Substructuring  

NASA Technical Reports Server (NTRS)

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.

Padovan, Joe; Kwang, Abel

1994-01-01

237

Simulating and Synthesizing Substructures Using Neural Network and Genetic Algorithms  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

238

A 3D view of the Hydra I cluster core- II. Stellar populations  

NASA Astrophysics Data System (ADS)

Several observations of the central region of the Hydra I galaxy cluster point to a multi-epoch assembly history. Using our novel FORS2/VLT spectroscopic data set, we were able to map the luminosity-weighted age, [Fe/H] and [?/Fe] distributions for the stellar populations around the cD galaxy NGC 3311. Our results indicate that the stellar populations follow the trends of the photometric substructures, with distinct properties that may aid to constrain the evolutionary scenarios for the formation of the cluster core.

Barbosa, Carlos Eduardo; Arnaboldi, Magda; Hilker, Michael; Coccato, Lodovico; Richtler, Tom; Mendes de Oliveira, Cláudia

2015-02-01

239

History of Stellar Interferometry  

NASA Technical Reports Server (NTRS)

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.

Lawson, Peter R.

2004-01-01

240

Population genetic analysis and sub-structuring in Babesia bovis.  

PubMed

The tick-borne protozoan parasite, Babesia bovis is one of the causes of bovine babesiosis, an economically important disease of cattle in tropical and sub-tropical countries. Using the recently published genome sequence of the parasite, we developed a panel of eight mini- and micro-satellite markers and used these to investigate the role of genetic exchange in the population structure and diversity of the parasite using isolates from Zambia and Turkey. This population genetic analysis showed that genetic exchange occurs and that there are high levels of genetic diversity, with geographical sub-structuring quantified using Wright's F Index. Linkage disequilibrium was observed when isolates from both countries were treated as one population, but when isolates from Zambia were analysed separately linkage equilibrium was observed. The Turkish isolates were sub-structured, containing two genetically distinct sub-groups, both of which appeared to be in linkage equilibrium. The results of the Zambian study suggest that a sub-set of the parasite population is responsible for the westward spread of babesiosis into the previously disease-free central region of the country. The Zambian isolates had a significantly higher number of genotypes per sample than those from Turkey and age was found to be a significant predictor of the multiplicity of infection. The high levels of diversity seen in the Zambian and Turkish B. bovis populations have implications in the development of subunit vaccines against the disease and the spread of drug resistance. PMID:21316400

Simuunza, Martin; Bilgic, Huseyin; Karagenc, Tulin; Syakalima, Michelo; Shiels, Brian; Tait, Andy; Weir, William

2011-06-01

241

Pieces of the puzzle: Ancient substructure in the Galactic disk  

E-print Network

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

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

2005-11-03

242

Quantum-chemical foundations of the topological substructural molecular design.  

PubMed

The topological substructural molecular design (TOPS-MODE) approach is formulated as a tight-binding quantum-chemical method. The approach is based on certain postulates that permit to express any molecular property as a function of the spectral moments of certain types of molecular and environment-dependent energies. We use several empirical potentials to account for these intrinsic and external molecular energies. We prove that any molecular property expressed in terms of a quantitative structure-property and structure-activity relationships (QSPR/QSAR) model developed by using the TOPS-MODE method can be expressed as a bond additivity function. In addition, such a property can also be expressed as a substructural cluster expansion function. The conditions for such bond contributions being transferable are also analyzed here. Several new statistical-mechanical electronic functions are introduced as well as a bond-bond thermal Green's function or a propagator accounting for the electronic hopping between pairs of bonds. All these new concepts are applied to the development and application of a new QSAR model for describing the toxicity of polyhalogenated-dibenzo-1,4-dioxins. The QSAR model obtained displays a significant robustness and predictability. It permits an easy structural interpretation of the structure-activity relationship in terms of bond additivity functions, which display some resemblances with other theoretical parameters obtained from first principle quantum-chemical methods. PMID:18491851

Estrada, Ernesto

2008-06-12

243

PAndAS IN THE MIST: THE STELLAR AND GASEOUS MASS WITHIN THE HALOS OF M31 AND M33  

SciTech Connect

Large-scale surveys of the prominent members of the Local Group have provided compelling evidence for the hierarchical formation of massive galaxies, revealing a wealth of substructure that is thought to be the debris from ancient and ongoing accretion events. In this paper, we compare two extant surveys of the M31-M33 subgroup of galaxies: the Pan-Andromeda Archaeological Survey of the stellar structure, and a combination of observations of the H I gaseous content, detected at 21 cm. Our key finding is a marked lack of spatial correlation between these two components on all scales, with only a few potential overlaps between stars and gas. The paucity of spatial correlation significantly restricts the analysis of kinematic correlations, although there does appear to be H I kinematically associated with the Giant Stellar Stream where it passes the disk of M31. These results demonstrate that different processes must significantly influence the dynamical evolution of the stellar and H I components of substructures, such as ram pressure driving gas away from a purely gravitational path. Detailed modeling of the offset between the stellar and gaseous substructures will provide a determination of the properties of the gaseous halos of M31 and M33.

Lewis, Geraint F. [Sydney Institute for Astronomy, School of Physics A28, The University of Sydney, NSW 2006 (Australia)] [Sydney Institute for Astronomy, School of Physics A28, The University of Sydney, NSW 2006 (Australia); Braun, Robert [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia)] [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia); McConnachie, Alan W. [Dominion Astrophysical Observatory, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)] [Dominion Astrophysical Observatory, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Irwin, Michael J.; Chapman, Scott C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)] [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Ibata, Rodrigo A.; Martin, Nicolas F. [Observatoire de Strasbourg, 11, rue de l'Universite, F-67000 Strasbourg (France)] [Observatoire de Strasbourg, 11, rue de l'Universite, F-67000 Strasbourg (France); Ferguson, Annette M. N. [Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)] [Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Fardal, Mark [Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States)] [Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States); Dubinski, John [Department of Astronomy and Astrophysics, 50 St. George Street, University of Toronto, ON M5S 3H4 (Canada)] [Department of Astronomy and Astrophysics, 50 St. George Street, University of Toronto, ON M5S 3H4 (Canada); Widrow, Larry [Department of Physics, Queen's University, 99 University Avenue, Kingston, ON K7L 3N6 (Canada)] [Department of Physics, Queen's University, 99 University Avenue, Kingston, ON K7L 3N6 (Canada); Mackey, A. Dougal [Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611 (Australia)] [Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611 (Australia); Babul, Arif [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 3P6 (Canada)] [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 3P6 (Canada); Tanvir, Nial R. [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom)] [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Rich, Michael, E-mail: geraint.lewis@sydney.edu.au [Division of Astronomy, University of California, 8979 Math Sciences, Los Angeles, CA 90095-1562 (United States)] [Division of Astronomy, University of California, 8979 Math Sciences, Los Angeles, CA 90095-1562 (United States)

2013-01-20

244

PAndAS in the Mist: The Stellar and Gaseous Mass within the Halos of M31 and M33  

NASA Astrophysics Data System (ADS)

Large-scale surveys of the prominent members of the Local Group have provided compelling evidence for the hierarchical formation of massive galaxies, revealing a wealth of substructure that is thought to be the debris from ancient and ongoing accretion events. In this paper, we compare two extant surveys of the M31-M33 subgroup of galaxies: the Pan-Andromeda Archaeological Survey of the stellar structure, and a combination of observations of the H I gaseous content, detected at 21 cm. Our key finding is a marked lack of spatial correlation between these two components on all scales, with only a few potential overlaps between stars and gas. The paucity of spatial correlation significantly restricts the analysis of kinematic correlations, although there does appear to be H I kinematically associated with the Giant Stellar Stream where it passes the disk of M31. These results demonstrate that different processes must significantly influence the dynamical evolution of the stellar and H I components of substructures, such as ram pressure driving gas away from a purely gravitational path. Detailed modeling of the offset between the stellar and gaseous substructures will provide a determination of the properties of the gaseous halos of M31 and M33.

Lewis, Geraint F.; Braun, Robert; McConnachie, Alan W.; Irwin, Michael J.; Ibata, Rodrigo A.; Chapman, Scott C.; Ferguson, Annette M. N.; Martin, Nicolas F.; Fardal, Mark; Dubinski, John; Widrow, Larry; Mackey, A. Dougal; Babul, Arif; Tanvir, Nial R.; Rich, Michael

2013-01-01

245

An algebraic theory for primal and dual substructuring methods by constraints  

Microsoft Academic Search

FETI and BDD are two widely used substructuring methods for the solution of large sparse systems of linear algebraic equations arising from discretization of elliptic boundary value problems. The two most advanced variants of these methods are the FETI-DP and the BDDC methods, whose formulation does not require any information beyond the algebraic system of equations in a substructure form.

Jan Mandel; Clark R. Dohrmann; Radek Tezaur

2005-01-01

246

Identification of population substructure among Jews using STR markers and dependence on reference populations included  

Microsoft Academic Search

BACKGROUND: Detecting population substructure is a critical issue for association studies of health behaviors and other traits. Whether inherent in the population or an artifact of marker choice, determining aspects of a population's genetic history as potential sources of substructure can aid in design of future genetic studies. Jewish populations, among which association studies are often conducted, have a known

Jennifer B Listman; Deborah Hasin; Henry R Kranzler; Robert T Malison; Apiwat Mutirangura; Atapol Sughondhabirom; Efrat Aharonovich; Baruch Spivak; Joel Gelernter

2010-01-01

247

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

248

The Rising Stellar Velocity Dispersion of M87 from Integrated Starlight  

NASA Astrophysics Data System (ADS)

We have measured the line-of-sight velocity distribution from integrated stellar light at two points in the outer halo of M87 (NGC 4486), the second-rank galaxy in the Virgo Cluster. The data were taken at R = 480'' (~41.5 kpc) and R = 526'' (~45.5 kpc) along the SE major axis. The second moment for a non-parametric estimate of the full velocity distribution is 420 ± 23 km s-1 and 577 ± 35 km s-1, respectively. There is intriguing evidence in the velocity profiles for two kinematically distinct stellar components at the position of our pointing. Under this assumption, we employ a two-Gaussian decomposition and find the primary Gaussian having rest velocities equal to M87 (consistent with zero rotation) and second moments of 383 ± 32 km s-1 and 446 ± 43 km s-1, respectively. The asymmetry seen in the velocity profiles suggests that the stellar halo of M87 is not in a relaxed state and confuses a clean dynamical interpretation. That said, either measurement (full or two component model) shows a rising velocity dispersion at large radii, consistent with previous integrated light measurements, yet significantly higher than globular cluster measurements at comparable radial positions. These integrated light measurements at large radii, and the stark contrast they make to the measurements of other kinematic tracers, highlight the rich kinematic complexity of environments like the center of the Virgo Cluster and the need for caution when interpreting kinematic measurements from various dynamical tracers.

Murphy, Jeremy D.; Gebhardt, Karl; Cradit, Mason

2014-04-01

249

THE ACS VIRGO CLUSTER SURVEY. XVII. THE SPATIAL ALIGNMENT OF GLOBULAR CLUSTER SYSTEMS WITH EARLY-TYPE HOST GALAXIES  

SciTech Connect

We study the azimuthal distribution of globular clusters (GCs) in early-type galaxies and compare them to their host galaxies using data from the ACS Virgo Cluster Survey. We find that in host galaxies with visible elongation ({epsilon} > 0.2) and intermediate to high luminosities (M{sub z} < -19), the GCs are preferentially aligned along the major axis of the stellar light. The red (metal-rich) GC subpopulations show strong alignment with the major axis of the host galaxy, which supports the notion that these GCs are associated with metal-rich field stars. The metal-rich GCs in lenticular galaxies show signs of being more strongly associated with disks rather than bulges. Surprisingly, we also find that the blue (metal-poor) GCs can also show the same correlation. If the metal-poor GCs are part of the early formation of the halo and built up through mergers, then our results support a picture where halo formation and merging occur anisotropically, and that the present-day major axis is an indicator of the preferred merging axis.

Wang Qiushi; Peng, Eric W. [Department of Astronomy, Peking University, Beijing 100871 (China); Blakeslee, John P.; Cote, Patrick; Ferrarese, Laura [Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Jordan, Andres [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Mei, Simona [University of Paris 7 Denis Diderot, F-75205 Paris Cedex 13 (France); West, Michael J., E-mail: peng@pku.edu.cn [Maria Mitchell Observatory, 4 Vestal Street, Nantucket, MA 02554 (United States)

2013-06-01

250

First Hubble Space Telescope observations of the brightest stars in the Virgo galaxy M100 = NGC 4321  

NASA Technical Reports Server (NTRS)

As part of both the Early Release Observations from the Hubble Space Telescope (HST) and the Key Project on the Extragalactic Distance Scale, we have obtained multiwavelength BVR Wide Field/Planetary Camera-2 (WFPC2) images for the face-on Virgo cluster spiral galaxy M100 = NGC 4321. We report here preliminary results from those observations, in the form of a color-magnitude diagram for approximately 11,500 stars down to V approximately 27 mag and a luminosity function for the brightest blue stars which is found to have a slope of 0.7, in excellent agreement with previous results obtained for significantly nearer galaxies. With the increased resolution now available using WFPC2, the number of galaxies in which we can directly measure Population I stars and thereby quantify the recent evolution, as well as test stellar evolution theory, has dramatically increased by at least a factor of 100. Finally, we find that the stars are present in M100 at the colors and luminosities expected for the brightest Cepheid variables in galaxies.

Freedman, Wendy L.; Madore, Barry F.; Stetson, Peter B.; Hughes, Shaun M. G.; Holtzman, Jon A.; Mould, Jeremy R.; Trauger, John T.; Gallagher, John S., III; Ballester, Gilda E.; Burrows, Christopher J.

1994-01-01

251

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

SciTech Connect

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.

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

252

Formation and evolution of dwarf early-type galaxies in the Virgo cluster. II. Kinematic scaling relations  

NASA Astrophysics Data System (ADS)

We place our sample of 18 Virgo dwarf early-type galaxies (dEs) on the (V - K)e-velocity dispersion, Faber-Jackson, and fundamental plane (FP) scaling relations for massive early-type galaxies (Es). We use a generalized velocity dispersion, which includes rotation, to be able to compare the location of both rotationally and pressure supported dEs with those of early and late-type galaxies. We find that dEs seem to bend the Faber-Jackson relation of Es to lower velocity dispersions, being the link between Es and dwarf spheroidal galaxies (dSphs). Regarding the FP relation, we find that dEs are significantly offset with respect to massive hot stellar systems, and re-casting the FP into the so-called ?-space suggests that this offset is related to dEs having a total mass-to-light ratio higher than Es but still significantly lower than dSph galaxies. Given a stellar mass-to-light ratio based on the measured line indices of dEs, the FP offset allows us to infer that the dark matter fraction within the half light radii of dEs is on average ?42% (uncertainties of 17% in the K band and 20% in the V band), fully consistent with an independent estimate in an earlier paper in this series. We also find that dEs in the size-luminosity relation in the near-infrared, like in the optical, are offset from early-type galaxies, but seem to be consistent with late-type galaxies. We thus conclude that the scaling relations show that dEs are different from Es, and that they further strengthen our previous findings that dEs are closer to and likely formed from late-type galaxies.

Toloba, E.; Boselli, A.; Peletier, R. F.; Falcón-Barroso, J.; van de Ven, G.; Gorgas, J.

2012-12-01

253

The LabelHash algorithm for substructure matching  

PubMed Central

Background There is an increasing number of proteins with known structure but unknown function. Determining their function would have a significant impact on understanding diseases and designing new therapeutics. However, experimental protein function determination is expensive and very time-consuming. Computational methods can facilitate function determination by identifying proteins that have high structural and chemical similarity. Results We present LabelHash, a novel algorithm for matching substructural motifs to large collections of protein structures. The algorithm consists of two phases. In the first phase the proteins are preprocessed in a fashion that allows for instant lookup of partial matches to any motif. In the second phase, partial matches for a given motif are expanded to complete matches. The general applicability of the algorithm is demonstrated with three different case studies. First, we show that we can accurately identify members of the enolase superfamily with a single motif. Next, we demonstrate how LabelHash can complement SOIPPA, an algorithm for motif identification and pairwise substructure alignment. Finally, a large collection of Catalytic Site Atlas motifs is used to benchmark the performance of the algorithm. LabelHash runs very efficiently in parallel; matching a motif against all proteins in the 95% sequence identity filtered non-redundant Protein Data Bank typically takes no more than a few minutes. The LabelHash algorithm is available through a web server and as a suite of standalone programs at http://labelhash.kavrakilab.org. The output of the LabelHash algorithm can be further analyzed with Chimera through a plugin that we developed for this purpose. Conclusions LabelHash is an efficient, versatile algorithm for large-scale substructure matching. When LabelHash is running in parallel, motifs can typically be matched against the entire PDB on the order of minutes. The algorithm is able to identify functional homologs beyond the twilight zone of sequence identity and even beyond fold similarity. The three case studies presented in this paper illustrate the versatility of the algorithm. PMID:21070651

2010-01-01

254

Interstellar Gas in Low Mass Virgo Cluster Spiral Galaxies  

E-print Network

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.

Beverly J. Smith; Suzanne C. Madden

1997-04-14

255

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

E-print Network

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.

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

256

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

NASA Astrophysics Data System (ADS)

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.

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

257

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

NASA Technical Reports Server (NTRS)

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.

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

258

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

E-print Network

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 square degrees in 2015 to ~200 square degrees in 2016. A few distinct scenarios for the first LIGO/Virgo detections emerge from our simulations.

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

2014-10-22

259

Infall of Nearby Galaxies into the Virgo Cluster as Traced with Hubble Space Telescope  

NASA Astrophysics Data System (ADS)

We measured the tip of the red giant branch distances to nine galaxies in the direction to the Virgo cluster using the Advanced Camera for Surveys on the Hubble Space Telescope. These distances put seven galaxies (GR 34, UGC 7512, NGC 4517, IC 3583, NGC 4600, VCC 2037, and KDG 215) in front of Virgo and two galaxies (IC 3023 and KDG 177) likely inside the cluster. Distances and radial velocities of the galaxies situated between us and the Virgo core clearly exhibit the infall phenomenon toward the cluster. In the case of spherically symmetric radial infall, we estimate the radius of the "zero-velocity surface" to be (7.2 ± 0.7) Mpc, which yields a total mass of the Virgo cluster of (8.0 ± 2.3) × 1014 M ?, in good agreement with its virial mass estimates. We conclude that the Virgo outskirts do not contain significant amounts of dark matter beyond their virial radius. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO 12878.

Karachentsev, Igor. D.; Tully, R. Brent; Wu, Po-Feng; Shaya, Edward J.; Dolphin, Andrew E.

2014-02-01

260

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

PubMed Central

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

2014-01-01

261

Low temperature deformation and dislocation substructure of ruthenium aluminide polycrystals  

SciTech Connect

The flow behavior and dislocation substructure present in ruthenium aluminide polycrystals due to deformation at room temperature and 77 K have been studied. Dislocations with three different types of Burgers vectors have been identified after 1--2% deformation in compression at 77 K and room temperature: {l_angle}100{r_angle}, {l_angle}110{r_angle} and {l_angle}111{r_angle}. The {l_angle}100{r_angle} and {l_angle}110{r_angle} dislocations are present with approximately equal densities, while the {l_angle}111{r_angle} are only occasionally observed. Trace analyses show that the majority of the dislocations are mixed in character and lie on {l_angle}110{r_angle} type planes. The implications of these observations with regard to the number of independent slip systems and the intrinsic deformability of this material are discussed.

Lu, D.C.; Pollock, T.M. [Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering] [Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering

1999-02-05

262

Resonance Related Spiral Substructure in a Galactic Gaseous Disk  

E-print Network

We use high resolution 2D hydrodynamic simulations to study the formation of spiral substructure in the gaseous disk of a galaxy. The obtained gaseous response is driven by a self-consistent non-axisymmetric potential obtained from an imposed spiral mass distribution. We highlight the importance of ultraharmonic resonances in generating these features. The temporal evolution of the system is followed with the parallel ZEUS-MP code, and we follow the steepening of perturbations induced by the spiral potential until large-scale shocks emerge. These shocks exhibit bifurcations that protrude from the gaseous arms and continue to steepen until new shocks are formed. When the contribution from the spiral potential relative to the axisymmetric background is increased from our default value, spurs protrude from the main arms after several revolutions of the gaseous disk. Such spurs overlap on top of the aforementioned shocks. These results support the hypothesis that a complicated gaseous response can coexist with an...

Yáñez, Miguel A; Martos, Marco A; Hayes, John C

2007-01-01

263

Mapping Dark Matter Halos with Stellar Kinematics  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

264

Dynamics of 10 Clusters of Galaxies with Substructures  

NASA Astrophysics Data System (ADS)

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.

Lakhchaura, Kiran; Singh, K. P.

2014-06-01

265

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

Microsoft Academic Search

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

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. Budzynski; 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; I. W. Martin; R. M. Martin; J. N. Marx; K. Mason; A. Masserot; F. Matichard; L. Matone

2010-01-01

266

KCF-S: KEGG Chemical Function and Substructure for improved interpretability and prediction in chemical bioinformatics  

PubMed Central

Background In order to develop hypothesis on unknown metabolic pathways, biochemists frequently rely on literature that uses a free-text format to describe functional groups or substructures. In computational chemistry or cheminformatics, molecules are typically represented by chemical descriptors, i.e., vectors that summarize information on its various properties. However, it is difficult to interpret these chemical descriptors since they are not directly linked to the terminology of functional groups or substructures that the biochemists use. Methods In this study, we used KEGG Chemical Function (KCF) format to computationally describe biochemical substructures in seven attributes that resemble biochemists' way of dealing with substructures. Results We established KCF-S (KCF-and-Substructures) format as an additional structural information of KCF. Applying KCF-S revealed the specific appearance of substructures from various datasets of molecules that describes the characteristics of the respective datasets. Structure-based clustering of molecules using KCF-S resulted the clusters in which molecular weights and structures were less diverse than those obtained by conventional chemical fingerprints. We further applied KCF-S to find the pairs of molecules that are possibly converted to each other in enzymatic reactions, and KCF-S clearly improved predictive performance than that presented previously. Conclusions KCF-S defines biochemical substructures with keeping interpretability, suggesting the potential to apply more studies on chemical bioinformatics. KCF and KCF-S can be automatically converted from Molfile format, enabling to deal with molecules from any data sources. PMID:24564846

2013-01-01

267

Physics optimization of stellarators  

NASA Astrophysics Data System (ADS)

The theoretical and experimental development of stellarators has removed some of the specific deficiencies of this configuration, viz., the limitations in ?, the high neoclassical transport, and the low collisionless confinement of ? particles. These optimized stellarators can best be realized with a modular coil system. The W7-AS experiment [Plasma Phys. Controlled Fusion 31, 1579 (1989)] has successfully demonstrated two aspects of advanced stellarators, the improved equilibrium and the modular coil concept. Stellarator optimization will much more viably be demonstrated by W7-X [Plasma Physics and Controlled Fusion Research, Proceedings of the 12th International Conference, Nice, 1988 (IAEA, Vienna, 1989), Vol. 2, p. 369], the successor experiment presently under design. Optimized stellarators seem to offer an independent reactor option. In addition, they supplement, in a unique form, the toroidal confinement fusion program, e.g., energy transport is anomalous in stellarators too, but possibly more easily understandable in the frame of existing theoretical concepts than in tokamaks.

Grieger, G.; Lotz, W.; Merkel, P.; Nührenberg, J.; Sapper, J.; Strumberger, E.; Wobig, H.; Burhenn, R.; Erckmann, V.; Gasparino, U.; Giannone, L.; Hartfuss, H. J.; Jaenicke, R.; Kühner, G.; Ringler, H.; Weller, A.; Wagner, F.

1992-07-01

268

Deconstructing Dynamics: Improving Stellar Velocity Dispersion Measurements for Reverberation Mapped AGNs  

NASA Astrophysics Data System (ADS)

Nearly all galaxies host a central supermassive black hole, and scaling relations between black hole mass (MBH) and various host-galaxy properties are essential tools for investigating the evolution of structure across cosmic time. Since evolutionary studies are limited to active galaxies, well constrained and accurately calibrated scaling relations for AGNs are of particular interest. The tightest of these is the MBH - ?? relation, which relates MBH and bulge stellar velocity dispersion (??), and as such it is one of the most frequently used for such studies. However, its utility is currently limited by the accuracy of the calibration. The majority of active galaxies for which MBH has been determined are late-type spirals, which contain significant kinematic substructure including bars, disks, and rings, in addition to the central bulge. The presence of this substructure is known to contaminate and bias ?? determinations from long-slit spectroscopy, and thus the quality of currently available ?? measurements is perhaps the most significant hindrance to accurate calibration. We have undertaken a long-term project to significantly improve bulge stellar velocity dispersion measurements for the reverberation mapped sample of active galaxies that is currently used to calibrate the MBH - ?? relation for AGNs. Using integral field spectroscopy we will generate spatially resolved two dimensional velocity dispersion maps for these galaxies, with which we can investigate the kinematic signatures of galaxy subcomponents. We present preliminary results and show how these data can be used to identify kinematic substructure, thus allowing for better constrained ?? measurements, free from contamination by dynamically distinct subcomponents.

Batiste, Merida; Bentz, Misty C.

2015-01-01

269

Distance to the Virgo Cluster Galaxy M100 from Hubble Space Telescope Observations of Cepheids  

NASA Technical Reports Server (NTRS)

Accurate distances to galaxies are critical to determining the present expansion rate of the Universe or Hubble Constant (H(sub 0)). An important step in resolving the current uncertainty in H(sub 0) is the measurement of the distance to the Virgo cluster of galaxies. New observations using the Hubble Space Telescope yield a distance of 17.1 +/- 1.8 Mpc to the Virgo cluster galaxy M100. This distance leads to a value of H(sub 0) = 17 km/sec/Mpc. A comparable value of H(sub 0) is also derived from the Coma cluster using independent estimates of its distance ratio relative to the Virgo cluster.

Freedman, W. L.; Madore, B. F.; Mould, J. R.; Hill, R.; Ferrarese, L.; Kennicutt, R. C., Jr.; Saha, A.; Stetson, P. B.; Graham, J. A.; Ford, H.; Hoessel, J. G.; Huchra, J.; Hughes, S. M.; Illingworth, G. D.

1994-01-01

270

Overview of the optic component manufacturing and measurements for the Advanced Virgo optics  

NASA Astrophysics Data System (ADS)

Advanced Virgo is an upgrade to the Virgo detector located near Pisa, Italy designed with an ultimate goal of the detection of gravitational waves originating from cosmic sources. The upgrade will provide an order of magnitude increase in the sensitivity of the detector and allow the exploration of a volume 1,000 times larger than Virgo. The system design includes 21 `half meter' class optics for which Zygo has been selected as the primary supplier. The optic components have nanometer level low-order figure requirements along with sub-angstrom roughness requirements specified over a wide spatial frequency band. In this paper the results and methodologies used in achieving such extreme requirements that are typically associated with the semiconductor lithography industry will be presented.

Nelson, Andrew; Estrin, Aleksandr

2014-07-01

271

Spatial Structures In the Globular Cluster Distribution of the Ten Brightest Virgo Galaxies  

E-print Network

We report the discovery of significant localized structures in the projected two-dimensional (2D) spatial distributions of the Globular Cluster (GC) systems of the ten brightest galaxies in the Virgo Cluster. We use catalogs of GCs extracted from the HST ACS Virgo Cluster Survey (ACSVCS) imaging data, complemented, when available, by additional archival ACS data. These structures have projected sizes ranging from $\\sim\\!5$ arcsec to few arc-minutes ($\\sim\\!1$ to $\\sim\\!25$ kpc). Their morphologies range from localized, circular, to coherent, complex shapes resembling arcs and streams. The largest structures are preferentially aligned with the major axis of the host galaxy. A few relatively smaller structures follow the minor axis. Differences in the shape and significance of the GC structures can be noticed by investigating the spatial distribution of GCs grouped by color and luminosity. The largest coherent GC structures are located in low-density regions within the Virgo cluster. This trend is more evident ...

D'Abrusco, R; Zezas, A

2015-01-01

272

Three-dimensional deformation analysis of two-phase dislocation substructures  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

273

Effect of load eccentricity and substructure deformation on ultimate strength of shuttle orbiter thermal protection system  

NASA Technical Reports Server (NTRS)

The effect of load eccentricity and substructure deformation on the ultimate strength and stress displacement properties of the shuttle orbiter thermal protection system (TPS) was determined. The LI-900 Reusable Surface Insulation (RSI) tiles mounted on the .41 cm thick Strain Isolator Pad (SIP) were investigated. Substructure deformations reduce the ultimate strength of the SIP/tile TPS and increase the scatter in the ultimate strength data. Substructure deformations that occur unsymmetric to the tile can cause the tile to rotate when subjected to a uniform applied load. Load eccentricity reduces SIP/tile TPS ultimate strength and causes tile rotation.

Sawyer, J. W.

1981-01-01

274

Hubble constant from Pritchet and von den Bergh's nova distance to the Virgo cluster  

SciTech Connect

Two reasons are offered why the value for H(0) of 69 + or - 14 km/s/Mpc of Pritchet and van den Bergh (1987) is likely to be too high by about 20 percent even when their value of 6.8 + or - 0.4 for the M31-Virgo modulus difference is adopted. One reason concerns the free expansion velocity of the Virgo cluster core and the other concerns the apparent distance modulus of M31. Reasons for adopting a global H(0) value of 56 + or - 12 km/s/Mpc are discussed. 25 references.

Sandage, A.; Tammann, G.A.

1988-05-01

275

VizieR Online Data Catalog: Virgo early-type galaxies optical properties (Lieder+, 2012)  

NASA Astrophysics Data System (ADS)

Our work is based on deep CFHT V- and I-band data covering several square degrees of the Virgo cluster core that were obtained in 1999 using the CFH12K instrument. We visually select potential cluster members based on morphology and angular size, excluding spiral galaxies. A photometric analysis has been carried out for 295 galaxies, using surface brightness profile shape and colour as further criteria to identify probable background contaminants. 216 galaxies are considered to be certain or probable Virgo cluster members. (2 data files).

Lieder, S.; Lisker, T.; Hilker, M.; Misgeld, I.; Durrell, P.

2012-04-01

276

ROSAT PSPC observations of NGC 4636: Interaction with Virgo gas ?  

NASA Technical Reports Server (NTRS)

ROSAT Position Sensitive Proportional Counter (PSPC) observations of NGC 4636 have provided a deep image of the galaxy and its surroundings, which reveal the presence of emission well outside the optical galaxy. The source emission is measured out to r approximately 18 min, where the instrument support structure prevents us at this time from following it farther out. The nature of this emission is not fully understood, but could be evidence that the Virgo cluster gas extends as far out as this galaxy (greater than 3 Mpc from M87). Spectral analysis of the X-ray emission suggests a relatively cool (kT approximately 0.5 to 0.9 keV) interstellar medium, with temperatures increasing with radius. However, the detailed properties of the interstellar gas cannot be unambiguously determined with the present data, since the results we obtain depend strongly on the choice of the spectral model. Comparison of the spectral distributions in concentric annuli clearly indicates significant differences with radius, which can be parameterized as a general increase of the temperature. For low cosmic abundance models, kT varies from approximately 0.55 keV in the inner 1 min to approximately 0.8 keV at r approximately 6 to 8 min. Outside 8 min the average temperature is higher than in the inner region (kT approximately 0.8 to 1.2 keV) and the low-energy absorption is significantly lower. For 100% cosmic abundance and galactic line-of-sight absorption, multi-temperature fits are required, suggesting the possibility that the interstellar medi um is inhomogeneous.

Trinchieri, G.; Kim, D. -W.; Fabbiano, G.; Canizares, C. R. C.

1994-01-01

277

A Giant Outflow from the Virgo Cluster Galaxy NGC 4569  

NASA Astrophysics Data System (ADS)

The Virgo Clustere spiral galaxy NGC 4569 has been observed in X-rays and in the optical (R, B, H?). The X-ray contours show a diffuse extended halo that seems to be fed by a central bipolar outflow. Although the resulting physical properties of this X-ray halo are comparable to those derived from others in edge-on galaxies, like e. g. NGC 253, the halo is asymmetric: its western component is more extended, while the eastern counterpart is compressed and elongated along the disk toward the south. From the absorption of the softest X-radiation the inclination of the disk can be derived and agrees with results from extinction as well as rotation analyses: one is looking to below the disk from the east, so that the western X-ray halo lies behind the disk. In connection with the westwards extended X-ray halo we discovered a giant spur of diffuse H? emission. Since this stands perpendicularly to the major axis of the visible ellipsoid, it seems plausible that it sticks out also perpendicularly from the disk. Then it reaches to almost 10 kpc above the plane. In addition, information about the H? kinematics clearly shows that this filament is decoupled from the NGC 4569 disk. Most impressively the velocities prove the H? filament to be a huge outflow. We derive the physical parameters of the H? spur, discuss its possible origin and the cause for the halo asymmetry. Bomans D., Tschöke D., Hensler G., Boselli A., 2001, A&A, submitted Tschöke D., Hensler G., Bomans D., Junkes N., 2001, A&A, submitted

Hensler, G.; Bomans, D.; Tschöke, D.; Boselli, A.

278

Chameleon f(R) gravity on the Virgo cluster scale  

NASA Astrophysics Data System (ADS)

Models of modified gravity offer promising alternatives to the concordance ? cold dark matter (?CDM) cosmology to explain the late-time acceleration of the universe. A popular such model is f(R) gravity, in which the Ricci scalar in the Einstein-Hilbert action is replaced by a general function of it. We study the f(R) model of Hu & Sawicki, which recovers standard general relativity in high-density regimes, while reproducing the desired late time acceleration at cosmological scales. We run a suite of high-resolution zoom simulations using the ECOSMOG code to examine the effect of f(R) gravity on the properties of a halo that is analogous to the Virgo cluster. We show that the velocity dispersion profiles can potentially discriminate between f(R) models and ?CDM, and provide complementary analysis of lensing signal profiles to explore the possibility to further distinguish the different f(R) models. Our results confirm the techniques explored by Cabré et al. to quantify the effect of environment in the behaviour of f(R) gravity, and we extend them to study halo satellites at various redshifts. We find that the modified gravity effects in our models are most observable at low redshifts, and that effects are generally stronger for satellites far from the centre of the main halo. We show that the screening properties of halo satellites trace very well that of dark matter particles, which means that low-resolution simulations in which subhaloes are not very well resolved can in principle be used to study satellite properties. We discuss observables, particularly for halo satellites, that can potentially be used to constrain the observational viability of f(R) gravity.

Moran, C. Corbett; Teyssier, R.; Li, B.

2015-03-01

279

Unveiling the Secret of a Virgo Dwarf Galaxy  

NASA Astrophysics Data System (ADS)

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

2000-05-01

280

The sagittarius tidal stream and the shape of the galactic stellar halo  

NASA Astrophysics Data System (ADS)

The stellar halo that surrounds our Galaxy contains clues to understanding galaxy formation, cosmology, stellar evolution, and the nature of dark matter. Gravitationally disrupted dwarf galaxies form tidal streams, which roughly trace orbits through the Galactic halo. The Sagittarius (Sgr) dwarf tidal debris is the most dominant of these streams, and its properties place important constraints on the distribution of mass (including dark matter) in the Galaxy. Stars not associated with substructures form the "smooth" component of the stellar halo, the origin of which is still under investigation. Characterizing halo substructures such as the Sgr stream and the smooth halo provides valuable information on the formation history and evolution of our galaxy, and places constraints on cosmological models. This thesis is primarily concerned with characterizing the 3-dimensional stellar densities of the Sgr tidal debris system and the smooth stellar halo, using data from the Sloan Digital Sky Survey (SDSS). F turnoff stars are used to infer distances, as they are relatively bright, numerous, and distributed about a single intrinsic brightness (magnitude). The inherent spread in brightnesses of these stars is overcome through the use of the recently-developed technique of statistical photometric parallax, in which the bulk properties of a stellar population are used to create a probability distribution for a given star's distance. This was used to build a spatial density model for the smooth stellar halo and tidal streams. The free parameters in this model are then fit to SDSS data with a maximum likelihood technique, and the parameters are optimized by advanced computational methods. Several computing platforms are used in this study, including the RPI SUR Bluegene and the Milkyway home volunteer computing project. Fits to the Sgr stream in 18 SDSS data stripes were performed, and a continuous density profile is found for the major Sgr stream. The stellar halo is found to be strongly oblate (flattening parameter q=0.53). A catalog of stars consistent with this density profile is produced as a template for matching future disruption models. The results of this analysis favor a description of the Sgr debris system that includes more than one dwarf galaxy progenitor, with the major streams above and below the Galactic disk being separate substructures. Preliminary results for the minor tidal stream characterizations are presented and discussed. Additionally, a more robust characterization of halo turnoff star brightnesses is performed, and it is found that increasing color errors with distance result in a previously unaccounted for incompleteness in star counts as the SDSS magnitude limit is approached. These corrections are currently in the process of being implemented on MilkyWay home.

Newby, Matthew T.

281

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

E-print Network

In this paper, 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 ...

Lee, C.

282

STELLAR STRUCTURE AND EVOLUTION  

E-print Network

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

Mojzsis, Stephen J.

283

Statistics of magnification perturbations by substructure in the cold dark matter cosmological model  

SciTech Connect

We study the statistical properties of magnification perturbations by substructures in strong lensed systems using linear perturbation theory and an analytical substructure model including tidal truncation and a continuous substructure mass spectrum. We demonstrate that magnification perturbations are dominated by perturbers found within a tidal radius of an image, and that sizable magnification perturbations may arise from small, coherent contributions from several substructures within the lens halo. We find that the root-mean-square (rms) fluctuation of the magnification perturbation is {approx}10% to {approx}20% and both the average and rms perturbations are sensitive to the mass spectrum and density profile of the perturbers. Interestingly,we find that relative to a smooth model of the same mass, the average magnification in clumpy models is lower (higher) than that in smooth models for positive (negative) parity images. This is opposite from what is observed if one assumes that the image magnification predicted by the best-fit smooth model of a lens is a good proxy for what the observed magnification would have been if substructures were absent. While it is possible for this discrepancy to be resolved via nonlinear perturbers, we argue that a more likely explanation is that the assumption that the best-fit lens model is a good proxy for the magnification in the absence of substructure is not correct. We conclude that a better theoretical understanding of the predicted statistical properties of magnification perturbations by CDM substructure is needed in order to affirm that CDM substructures have been unambiguously detected.

Rozo, Eduardo; /Chicago U. /KICP, Chicago; Zentner, Andrew R.; /KICP, Chicago /Chicago U., Astron. Astrophys. Ctr.; Bertone, Gianfranco; /Fermilab; Chen, Jacqueline; /KICP,

2005-06-01

284

A NEW METHOD TO QUANTIFY X-RAY SUBSTRUCTURES IN CLUSTERS OF GALAXIES  

SciTech Connect

We present a new method to quantify substructures in clusters of galaxies, based on the analysis of the intensity of structures. This analysis is done in a residual image that is the result of the subtraction of a surface brightness model, obtained by fitting a two-dimensional analytical model ({beta}-model or Sersic profile) with elliptical symmetry, from the X-ray image. Our method is applied to 34 clusters observed by the Chandra Space Telescope that are in the redshift range z in [0.02, 0.2] and have a signal-to-noise ratio (S/N) greater than 100. We present the calibration of the method and the relations between the substructure level with physical quantities, such as the mass, X-ray luminosity, temperature, and cluster redshift. We use our method to separate the clusters in two sub-samples of high- and low-substructure levels. We conclude, using Monte Carlo simulations, that the method recuperates very well the true amount of substructure for small angular core radii clusters (with respect to the whole image size) and good S/N observations. We find no evidence of correlation between the substructure level and physical properties of the clusters such as gas temperature, X-ray luminosity, and redshift; however, analysis suggest a trend between the substructure level and cluster mass. The scaling relations for the two sub-samples (high- and low-substructure level clusters) are different (they present an offset, i.e., given a fixed mass or temperature, low-substructure clusters tend to be more X-ray luminous), which is an important result for cosmological tests using the mass-luminosity relation to obtain the cluster mass function, since they rely on the assumption that clusters do not present different scaling relations according to their dynamical state.

Andrade-Santos, Felipe; Lima Neto, Gastao B.; Lagana, Tatiana F. [Departamento de Astronomia, Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Geofisica e Ciencias Atmosfericas, Rua do Matao 1226, Cidade Universitaria, 05508-090 Sao Paulo, SP (Brazil)

2012-02-20

285

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

SciTech Connect

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.

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

2001-07-26

286

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

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

287

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

288

Resonance Related Spiral Substructure in a Galactic Gaseous Disk  

E-print Network

We use high resolution 2D hydrodynamic simulations to study the formation of spiral substructure in the gaseous disk of a galaxy. The obtained gaseous response is driven by a self-consistent non-axisymmetric potential obtained from an imposed spiral mass distribution. We highlight the importance of ultraharmonic resonances in generating these features. The temporal evolution of the system is followed with the parallel ZEUS-MP code, and we follow the steepening of perturbations induced by the spiral potential until large-scale shocks emerge. These shocks exhibit bifurcations that protrude from the gaseous arms and continue to steepen until new shocks are formed. When the contribution from the spiral potential relative to the axisymmetric background is increased from our default value, spurs protrude from the main arms after several revolutions of the gaseous disk. Such spurs overlap on top of the aforementioned shocks. These results support the hypothesis that a complicated gaseous response can coexist with an orderly spiral potential term, in the sense that the underlying background potential can be smooth yet drive a gaseous response that is far more spatially complex.

Miguel A. Yáñez; Michael L. Norman; Marco A. Martos; John C. Hayes

2007-10-25

289

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

Microsoft Academic Search

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

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

290

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

Microsoft Academic Search

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.

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

291

The surface brightness fluctuations and globular cluster populations of Virgo elliptical and lenticular galaxies  

Microsoft Academic Search

The Virgo cluster of galaxies is a complex system composed of several sub-clusters or ``clouds.'' Although the relative positions of clouds can be determined by the low precision measurement of many galaxies in each cloud, the internal structure of individual clouds requires more precise measurement. The literature provides a few such measurements, but the number of galaxies with distances known

Eric Hildaur Neilsen Jr.

1999-01-01

292

Immunocompetence and resource holding potential in the damselfly, Calopteryx virgo L  

Microsoft Academic Search

It is generally believed that resource holding potential reliably reflects male quality, but empirical evidence showing this is scarce. Here we show that the outcome of male-male competition may predict male immunocompetence in the territorial damselfly, Calopteryx virgo (Odonata: Calopterygidae). We staged contests between 27 pairs of males and found that winners of the contests showed higher immunocompetence, measured as

Jani Koskimäki; Markus J. Rantala; Jouni Taskinen; Katja Tynkkynen; Jukka Suhonen

2004-01-01

293

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

NASA Astrophysics Data System (ADS)

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.

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

294

Planetary nebulae as standard candles. V. The distance to the Virgo Cluster  

Microsoft Academic Search

The O III forbiden 5007-A line fluxes of 486 planetary nebula candidates in six early-type galaxies (NGC 4374, 4382, 4406, 4472, 4486, and 4649) in the core of the Virgo Cluster are identified and measured. Following the procedures and calibrations outlined in previous papers in this series, the observed planetary nebula luminosity functions are compared to an empirical model based

George H. Jacoby; Robin Ciardullo; Holland C. Ford

1990-01-01

295

Velocity Imager for Resolving Galaxy Origins (VIRGO): A Proposed Midex Mission  

Microsoft Academic Search

The proposed Velocity Imager for Resolving Galaxy Origins (VIRGO) is a highly capable instrument for collecting 3-D data cubes, one spectral and two spatial dimensions. The telescope will be a Hubble-class instrument having a 2.5 m aperture primary. The instrument will include an Integral Field Spectrograph (IFS) covering approx. 2\\

C. L. Joseph

2001-01-01

296

FIRST RESULTS FROM VIRGO, THE EXPERIMENT FOR HELIOSEISMOLOGY AND SOLAR IRRADIANCE MONITORING ON SOHO  

Microsoft Academic Search

First results from the VIRGO experiment (Variability of solar IRradiance and Gravity Oscillations) on the ESA\\/NASA Mission SOHO (Solar and Heliospheric Observatory) are reported. The observations started mid-January 1996 for the radiometers and sunphotometers and near the end of March for the luminosity oscillation imager. The performance of all the instruments is very good, and the time series of the

Claus Frohlich; Bo N. Andersen; Thierry Appourchaux; Gabrielle Berthomieu; Dominique A. Crommelynck; Vicente Domingo; Alain Fichot; Wolfgang Finsterle; Maria F. Gómez; Douglas Gough; Antonio Jimenez; Torben Leifsen; Marc Lombaerts; Judit M. Pap; Janine Provost; Teodoro Roca Cortés; Jose Romero; Hansjorg Roth; Takashi Sekii; Udo Telljohann; Thierry Toutain; Christoph Wehrli

1997-01-01

297

HYPERCOMPACT STELLAR SYSTEMS AROUND RECOILING SUPERMASSIVE BLACK HOLES  

SciTech Connect

A supermassive black hole ejected from the center of a galaxy by gravitational-wave recoil carries a retinue of bound stars - a 'hypercompact stellar system' (HCSS). The numbers and properties of HCSSs contain information about the merger histories of galaxies, the late evolution of binary black holes, and the distribution of gravitational-wave kicks. We relate the structural properties (size, mass, density profile) of HCSSs to the properties of their host galaxies and to the size of the kick in two regimes: collisional (M {sub BH} {approx}< 10{sup 7} M {sub sun}), i.e., short nuclear relaxation times, and collisionless (M {sub BH} {approx}> 10{sup 7} M {sub sun}), i.e., long nuclear relaxation times. HCSSs are expected to be similar in size and luminosity to globular clusters, but in extreme cases (large galaxies, kicks just above escape velocity) their stellar mass can approach that of ultracompact dwarf galaxies. However, they differ from all other classes of compact stellar system in having very high internal velocities. We show that the kick velocity is encoded in the velocity dispersion of the bound stars. Given a large enough sample of HCSSs, the distribution of gravitational-wave kicks can therefore be empirically determined. We combine a hierarchical merger algorithm with stellar population models to compute the rate of production of HCSSs over time and the probability of observing HCSSs in the local universe as a function of their apparent magnitude, color, size, and velocity dispersion, under two different assumptions about the star formation history prior to the kick. We predict that {approx}10{sup 2} HCSSs should be detectable within 2 Mpc of the center of the Virgo cluster, and that many of these should be bright enough that their kick velocities (i.e., velocity dispersions) could be measured with reasonable exposure times. We discuss other strategies for detecting HCSSs and speculate on some exotic manifestations.

Merritt, David [Center for Computational Relativity and Gravitation and Department of Physics, Rochester Institute of Technology, Rochester, NY 14623 (United States); Schnittman, Jeremy D. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Komossa, S. [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching (Germany)

2009-07-10

298

Stellar magnetic cycles  

NASA Astrophysics Data System (ADS)

The solar activity cycle is a manifestation of the hydromagnetic dynamo working inside our star. The detection of activity cycles in solar-like stars and the study of their properties allow us to put the solar dynamo in perspective, investigating how dynamo action depends on stellar parameters and stellar structure. Nevertheless, the lack of spatial resolution and the limited time extension of stellar data pose limitations to our understanding of stellar cycles and the possibility to constrain dynamo models. I briefly review some results obtained from disc-integrated proxies of stellar magnetic fields and discuss the new opportunities opened by space-borne photometry made available by MOST, CoRoT, Kepler, and GAIA, and by new ground-based spectroscopic or spectropolarimetric observations. Stellar cycles have a significant impact on the energetic output and circumstellar magnetic fields of late-type active stars which affects the interaction between stars and their planets. On the other hand, a close-in massive planet could affect the activity of its host star. Recent observations provide circumstantial evidence of such an interaction with possible consequences for stellar activity cycles.

Lanza, A. F.

2010-02-01

299

Next Generation Virgo Survey Photometry and Keck/DEIMOS Spectroscopy of Globular Cluster Satellites of Dwarf Elliptical Galaxies in the Virgo Cluster  

NASA Astrophysics Data System (ADS)

We present results from an ongoing study of globular cluster (GC) satellites of low-luminosity dwarf elliptical (dE) galaxies in the Virgo cluster. Our 21 dE targets and candidate GC satellites around them in the apparent magnitude range g ~ 20-24 were selected from the Next Generation Virgo Survey (NGVS) and followed up with medium-resolution Keck/DEIMOS spectroscopy (resolving power: R ~ 2000; wavelength coverage: 4800-9500 Angstrom). In addition, the remaining space available on the nine DEIMOS multi-slit masks were populated with "filler" targets in the form of distant Milky Way halo star candidates in a comparable apparent magnitude range. A combination of radial velocity information (measured from the Keck/DEIMOS spectra), color-color information (from four-band NGVS photometry), and sky position information was used to sort the sample into the following categories: (1) GC satellites of dEs, (2) other non-satellite GCs in the Virgo cluster (we dub them "orphan" GCs), (3) foreground Milky Way stars that are members of the Sagittarius stream, the Virgo overdensity, or the field halo population, and (4) distant background galaxies. We stack the GC satellite population across all 21 host dEs and carry out dynamical modeling of the stacked sample in order to constrain the average mass of dark matter halos that these dEs are embedded in. We study rotation in the system of GC satellites of dEs in the handful of more populated systems in our sample - i.e., those that contain 10 or more GC satellites per dE. A companion AAS poster presented at this meeting (Chu, J. et al. 2015) presents chemical composition and age constraints for these GC satellites relative to the nuclei of the host dEs based on absorption line strengths in co-added spectra. The orphan GCs are likely to be intergalactic GCs within the Virgo cluster (or, equivalently, GCs in the remote outer envelope of the cluster's central galaxy, the giant elliptical M87).This project is funded in part by the National Science Foundation. Some of this research was conducted by high-school students working under the auspices of the Science Internship Program at the University of California Santa Cruz.

Guhathakurta, Puragra; Toloba, Elisa; Peng, Eric W.; Li, Biao; Gwyn, Stephen; Ferrarese, Laura; Cote, Patrick; Chu, Jason; Sparkman, Lea; Chen, Stephanie; Yagati, Samyukta; Muller, Meredith; Next Generation Virgo Survey Collaboration

2015-01-01

300

INSIGHT INTO THE FORMATION OF THE MILKY WAY THROUGH COLD HALO SUBSTRUCTURE. III. STATISTICAL CHEMICAL TAGGING IN THE SMOOTH HALO  

SciTech Connect

We find that the relative contribution of satellite galaxies accreted at high redshift to the stellar population of the Milky Way's smooth halo increases with distance, becoming observable relative to the classical smooth halo about 15 kpc from the Galactic center. In particular, we determine line-of-sight-averaged [Fe/H] and [{alpha}/Fe] in the metal-poor main-sequence turnoff (MPMSTO) population along every Sloan Extension for Galactic Understanding and Exploration (SEGUE) spectroscopic line of sight. Restricting our sample to those lines of sight along which we do not detect elements of cold halo substructure (ECHOS), we compile the largest spectroscopic sample of stars in the smooth component of the halo ever observed in situ beyond 10 kpc. We find significant spatial autocorrelation in [Fe/H] in the MPMSTO population in the distant half of our sample beyond about 15 kpc from the Galactic center. Inside of 15 kpc however, we find no significant spatial autocorrelation in [Fe/H]. At the same time, we perform SEGUE-like observations of N-body simulations of Milky Way analog formation. While we find that halos formed entirely by accreted satellite galaxies provide a poor match to our observations of the halo within 15 kpc of the Galactic center, we do observe spatial autocorrelation in [Fe/H] in the simulations at larger distances. This observation is an example of statistical chemical tagging and indicates that spatial autocorrelation in metallicity is a generic feature of stellar halos formed from accreted satellite galaxies.

Schlaufman, Kevin C.; Rockosi, Constance M.; Rashkov, Valery; Madau, Piero [Astronomy and Astrophysics Department, University of California, Santa Cruz, CA 95064 (United States); Lee, Young Sun; Beers, Timothy C. [Department of Physics and Astronomy and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, E. Lansing, MI 48824 (United States); Prieto, Carlos Allende [Instituto de Astrofisica de Canarias, 38205 La Laguna, Tenerife (Spain); Bizyaev, Dmitry, E-mail: kcs@ucolick.org, E-mail: crockosi@ucolick.org, E-mail: valery@ucolick.org, E-mail: pmadau@ucolick.org, E-mail: lee@pa.msu.edu, E-mail: beers@pa.msu.edu, E-mail: callende@iac.es, E-mail: dmbiz@apo.nmsu.edu [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349 (United States)

2012-04-10

301

Do gravitational lens galaxies have an excess of luminous substructure?  

NASA Astrophysics Data System (ADS)

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 Cosmological Evolution Survey (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 that the number of satellites as a function of host stellar mass as well as the spatial distribution are consistent between the samples. Using these results, we predict the number of satellites we would expect to find around a subset of the Cosmic Lens All Sky Survey lenses, and find a result consistent with the number observed by Jackson et al. Thus, we conclude that within our measurement uncertainties there is no significant difference in the satellite populations of lens and non-lens galaxies.

Nierenberg, A. M.; Oldenburg, D.; Treu, T.

2013-12-01

302

MAPPING THE STELLAR STRUCTURE OF THE MILKY WAY THICK DISK AND HALO USING SEGUE PHOTOMETRY  

SciTech Connect

We map the stellar structure of the Galactic thick disk and halo by applying color-magnitude diagram (CMD) fitting to photometric data from the Sloan Extension for Galactic Understanding and Exploration (SEGUE) survey. The SEGUE imaging scans allow, for the first time, a comprehensive analysis of Milky Way structure at both high and low latitudes using uniform Sloan Digital Sky Survey photometry. Incorporating photometry of all relevant stars simultaneously, CMD fitting bypasses the need to choose single tracer populations. Using old stellar populations of differing metallicities as templates, we obtain a sparse three-dimensional map of the stellar mass distribution at |Z|>1 kpc. Fitting a smooth Milky Way model comprising exponential thin and thick disks and an axisymmetric power-law halo allows us to constrain the structural parameters of the thick disk and halo. The thick-disk scale height and length are well constrained at 0.75 {+-} 0.07 kpc and 4.1 {+-} 0.4 kpc, respectively. We find a stellar halo flattening within {approx}25 kpc of c/a = 0.88 {+-} 0.03 and a power-law index of 2.75 {+-} 0.07 (for 7 kpc {approx_lt}R{sub GC} {approx_lt} 30 kpc). The model fits yield thick-disk and stellar halo densities at the solar location of {rho}{sub thick,sun} = 10{sup -2.3{+-}0.1} M{sub sun} pc{sup -3} and {rho}{sub halo,sun} = 10{sup -4.20{+-}0.05} M{sub sun} pc{sup -3}, averaging over any substructures. Our analysis provides the first clear in situ evidence for a radial metallicity gradient in the Milky Way's stellar halo: within R {approx_lt} 15 kpc the stellar halo has a mean metallicity of [Fe/H] {approx_equal} -1.6, which shifts to [Fe/H] {approx_equal} -2.2 at larger radii, in line with the two-component halo deduced by Carollo et al. from a local kinematic analysis. Subtraction of the best-fit smooth and symmetric model from the overall density maps reveals a wealth of substructures at all latitudes, some attributable to known streams and overdensities, and some new. A simple warp cannot account for the low latitude substructure, as overdensities occur simultaneously above and below the Galactic plane.

De Jong, Jelte T. A.; Rix, Hans-Walter; Martin, Nicolas F. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Yanny, Brian [Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States); Dolphin, Andrew E. [Raytheon Company, 1151 East Hermans Road, Tucson, AZ 85756 (United States); Beers, Timothy C., E-mail: dejong@mpia.d [Department of Physics and Astronomy and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States)

2010-05-01

303

Frontiers of stellar evolution  

NASA Technical Reports Server (NTRS)

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.

Lambert, David L. (editor)

1991-01-01

304

KINEMATIC DISCOVERY OF A STELLAR STREAM LOCATED IN PISCES  

SciTech Connect

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.

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

305

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

SciTech Connect

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.

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

2005-04-06

306

The detection efficiency of on-axis short gamma-ray burst optical afterglows triggered by aLIGO/Virgo  

NASA Astrophysics Data System (ADS)

Assuming neutron star (NS) or NS/stellar-mass black hole (BH) mergers as progenitors of the short gamma-ray bursts, we derive and demonstrate a simple analysis tool for modelling the efficiency of recovering on-axis optical afterglows triggered by a candidate gravitational wave event detected by the Advanced LIGO and Virgo network. The coincident detection efficiency has been evaluated for different classes of operating telescopes using observations of gamma-ray bursts. We show how the efficiency depends on the luminosity distribution of the optical afterglows, the telescope features, and the sky localization of gravitational wave triggers. We estimate a plausible optical afterglow and gravitational wave coincidence rate of 1 yr-1 (0.1 yr-1) for NS-NS (NS-BH), and how this rate is scaled down in detection efficiency by the time it takes to image the gravitational wave sky localization and the limiting magnitude of the telescopes. For NS-NS (NS-BH), we find maximum detection efficiencies of >80 per cent when the total imaging time is less than 200 min (80 min) and the limiting magnitude fainter than 20 (21). We show that relatively small telescopes (m < 18) can achieve similar detection efficiencies to metre class facilities (m < 20) with similar fields of view, only if the less sensitive instruments can respond to the trigger and image the field within 10-15 min. The inclusion of LIGO India into the gravitational wave observatory network will significantly reduce imaging time for telescopes with limiting magnitudes ˜20 but with modest fields of view. An optimal coincidence search requires a global network of sensitive and fast response wide-field instruments that could effectively image relatively large gravitational-wave sky localizations and produce transient candidates for further photometric and spectroscopic follow-up.

Coward, D. M.; Branchesi, M.; Howell, E. J.; Lasky, P. D.; Böer, M.

2014-12-01

307

The Herschel Virgo Cluster Survey. IX. Dust-to-gas mass ratio and metallicity gradients in four Virgo spiral galaxies  

NASA Astrophysics Data System (ADS)

Context. Using Herschel data from the open time key project the Herschel Virgo Cluster Survey (HeViCS), we investigated the relationship between the metallicity gradients expressed by metal abundances in the gas phase as traced by the chemical composition of HII regions, and in the solid phase, as traced by the dust-to-gas mass ratio. Aims: We derived the radial gradient of the dust-to-gas mass ratio for all galaxies observed by HeViCS whose metallicity gradients are available in the literature. They are all late type Sbc galaxies, namely NGC 4254, NGC 4303, NGC 4321, and NGC 4501. Methods: We fitted PACS and SPIRE observations with a single-temperature modified blackbody, inferred the dust mass, and calculated two dimensional maps of the dust-to-gas mass ratio, with the total mass of gas from available HI and CO maps. HI moment-1 maps were used to derive the geometric parameters of the galaxies and extract the radial profiles. We examined different dependencies on metallicity of the CO-to-H2 conversion factor (XCO), used to transform the 12CO observations into the amount of molecular hydrogen. Results: We found that in these galaxies the dust-to-gas mass ratio radial profile is extremely sensitive to choice of the XCO value, since the molecular gas is the dominant component in the inner parts. We found that for three galaxies of our sample, namely NGC 4254, NGC 4321, and NGC 4501, the slopes of the oxygen and of the dust-to-gas radial gradients agree up to ~0.6-0.7 R25 using XCO values in the range 1/3-1/2 Galactic XCO. For NGC 4303 a lower value of XCO ~ 0.1 × 1020 is necessary. Conclusions: We suggest that such low XCO values might be due to a metallicity dependence of XCO (from close to linear for NGC 4254, NGC 4321, and NGC 4501 to superlinear for NGC 4303), especially in the radial regions RG < 0.6-0.7 R25 where the molecular gas dominates. On the other hand, the outer regions, where the atomic gas component is dominant, are less affected by the choice of XCO, and thus we cannot put constraints on its value there.

Magrini, L.; Bianchi, S.; Corbelli, E.; Cortese, L.; Hunt, L.; Smith, M.; Vlahakis, C.; Davies, J.; Bendo, G. J.; Baes, M.; Boselli, A.; Clemens, M.; Casasola, V.; De Looze, I.; Fritz, J.; Giovanardi, C.; Grossi, M.; Hughes, T.; Madden, S.; Pappalardo, C.; Pohlen, M.; di Serego Alighieri, S.; Verstappen, J.

2011-11-01

308

Stellar Populations Surface photometry  

E-print Network

Outline Stellar Populations Surface photometry Luminosity distributions Component separation Surface photometry Luminosity distributions Component separation Photometric parameters Elliptical photometry Luminosity distributions Bulge luminosity laws Luminosity distributions in disks Component

Kruit, Piet van der

309

Stellar atmospheric structural patterns  

NASA Technical Reports Server (NTRS)

The thermodynamics of stellar atmospheres is discussed. Particular attention is given to the relation between theoretical modeling and empirical evidence. The characteristics of distinctive atmospheric regions and their radical structures are discussed.

Thomas, R. N.

1983-01-01

310

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.

311

PREFACE: A Stellar Journey A Stellar Journey  

Microsoft Academic Search

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

M. Asplund

2008-01-01

312

Application of ground-penetrating radar to railway track substructure maintenance management  

NASA Astrophysics Data System (ADS)

Railway track substructure maintenance management is the process of utilizing railroad resources to maintain and upgrade the track substructure. The process begins with a measure of the track condition to evaluate the substructure performance, determine locations along the track that require maintenance, and identify appropriate solutions. Ground penetrating radar (GPR) has been proposed as a potentially valuable tool for this purpose. The objective of the research was to develop GPR testing and data interpretation techniques suitable for use by railroad personnel in this application. The principle of GPR operation is the transmission of short electromagnetic waves into the subsurface and recording the resulting signal of the reflected waves. Electromagnetic waves are influenced most significantly by the dielectric constant of the soil. The dielectric constant is most affected by moisture content making GPR a valuable tool for locating trapped water that will cause increased track deterioration rates. GPR has the potential to evaluate the thicknesses and properties of the substructure layers on a continuous, non-destructive basis to improve the process of diagnosing substructure causes of track performance deterioration. GPR railroad research at UMass started with the construction of a test track. Different track structure components were tested to determine their effects on the GPR data. Approximately 200 tests were conducted. Subsequently, about 275 miles of data were collected on several U.S. railroads including Amtrak, Conrail, New England Central, and Burlington Northern Santa Fe, and in England on AMEC Rail. The data were studied to determine how well GPR can define substructure conditions, identify track problem areas, and provide an indication of the cause of the problem. The analysis included comparison of the GPR data to track geometry, subsurface stratigraphy, and ballast condition (fouling and moisture). GPR processing techniques were developed to simplify interpretation of the data. The results showed that GPR could locate zones of increased substructure degradation at over 75% of the sites.

Sussmann, Theodore Reinhold, Jr.

313

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

Microsoft Academic Search

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

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

1998-01-01

314

The Effects of Varying Cosmological Parameters on Halo Substructure  

NASA Astrophysics Data System (ADS)

We investigate how different cosmological parameters, such as those delivered by the WMAP and Planck missions, affect the nature and evolution of the dark matter halo substructure. We use a series of flat ? cold dark matter cosmological N-body simulations of structure formation, each with a different power spectrum but with the same initial white noise field. Our fiducial simulation is based on parameters from the WMAP seventh year cosmology. We then systematically vary the spectral index, ns ; matter density, ? M ; and normalization of the power spectrum, ?8, for seven unique simulations. Across these, we study variations in the subhalo mass function, mass fraction, maximum circular velocity function, spatial distribution, concentration, formation times, accretion times, and peak mass. We eliminate dependence of subhalo properties on host halo mass and average the values over many hosts to reduce variance. While the "same" subhalos from identical initial overdensity peaks in higher ?8, ns , and ? m simulations accrete earlier and end up less massive and closer to the halo center at z = 0, the process of continuous subhalo accretion and destruction leads to a steady state distribution of these properties across all subhalos in a given host. This steady state mechanism eliminates cosmological dependence on all of the properties listed above except for subhalo concentration and V max, which remain greater for higher ?8, ns , and ? m simulations, and subhalo formation time, which remains earlier. We also find that the numerical technique for computing the scale radius and the halo finder that were used can significantly affect the concentration-mass relationship as computed for a simulation.

Dooley, Gregory A.; Griffen, Brendan F.; Zukin, Phillip; Ji, Alexander P.; Vogelsberger, Mark; Hernquist, Lars E.; Frebel, Anna

2014-05-01

315

Morphology parameters: substructure identification in X-ray galaxy clusters  

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

316

Discovering Higgs Bosons of the MSSM using Jet Substructure  

SciTech Connect

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.

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

2010-06-01

317

Stellar Evolution A Statistical Model  

E-print Network

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

van Dyk, David

318

Stellar Evolution A Statistical Model  

E-print Network

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

van Dyk, David

319

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

NASA Technical Reports Server (NTRS)

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.

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

320

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

E-print Network

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 ...

Aggarwal, Nancy

321

Search for gravitational waves from compact binary coalescence in LIGO and Virgo data from S5 and VSR1  

E-print Network

We report the results of the first search for gravitational waves from compact binary coalescence using data from the Laser Interferometer Gravitational-Wave Observatory and Virgo detectors. Five months of data were collected ...

Barsotti, Lisa

322

Galaxy Populations and Evolution in Clusters IV Deep H 1 Observations of Dwarf Elliptical Galaxies in the Virgo Cluster  

NASA Technical Reports Server (NTRS)

In this paper we present deep Arecibo H I and WIYN optical observations of Virgo Cluster dwarf elliptical galaxies. Based on this data we argue that a significant fraction of low-mass galaxies in the Virgo Cluster recently underwent evolution. Our new observations consist of H I 21 cm line observations for 22 classified dE galaxies with optical radial velocities consistent with membership in the Virgo Cluster. Cluster members VCC 390 and VCC 1713 are detected with H 1 masses M H1= 6 x 10 sup 7 and 8 x 10 sup 7 M , respectively, while MH I values in the remaining 20 dE galaxies have upper limits as low as about 5 x 1O sup 5 M. We combine our results with those for 26 other Virgo Cluster dE galaxies with H 1 observations in the literature, seven of which have H I detection claims.

Conselice, Christopher J.; ONeil, Karen; Gallagher, John S.; Wyse, Rosemary F. G.

2003-01-01

323

The Next Generation Virgo Cluster Survey. V. Modeling the Dynamics of M87 with the Made-to-measure Method  

NASA Astrophysics Data System (ADS)

We study the dynamics of the giant elliptical galaxy M87 from the central to the outermost regions with the made-to-measure (M2M) method. We use a new catalog of 922 globular cluster line-of-sight velocities extending to a projected radius of 180 kpc (equivalent to 25 M87 effective radii), and SAURON integral field unit data within the central 2.4 kpc. There are 263 globular clusters, mainly located beyond 40 kpc, newly observed by the Next Generation Virgo Survey. For the M2M modeling, the gravitational potential is taken as a combination of a luminous matter potential with a constant stellar mass-to-light ratio and a dark matter potential modeled as a logarithmic potential. Our best-fit dynamical model returns a stellar mass-to-light ratio in the I band of M/LI = 6.0 ± 0.3 M_{\\odot } \\,L_{\\odot }^{-1} with a dark matter potential scale velocity of 591 ± 50 km s-1 and scale radius of 42 ± 10 kpc. We determine the total mass of M87 within 180 kpc to be (1.5 ± 0.2) × 1013 M ?. The mass within 40 kpc is smaller than previous estimates determined using globular cluster kinematics that did not extend beyond ~45 kpc. With our new globular cluster velocities at much larger radii, we see that globular clusters around 40 kpc show an anomalously large velocity dispersion which affected previous results. The mass we derive is in good agreement with that inferred from ROSAT X-ray observation out to 180 kpc. Within 30 kpc our mass is also consistent with that inferred from Chandra and XMM-Newton X-ray observations, while within 120 kpc it is about 20% smaller. The model velocity dispersion anisotropy ? parameter for the globular clusters in M87 is small, varying from -0.2 at the center to 0.2 at ~40 kpc, and gradually decreasing to zero at ~120 kpc.

Zhu, Ling; Long, R. J.; Mao, Shude; Peng, Eric W.; Liu, Chengze; Caldwell, Nelson; Li, Biao; Blakeslee, John P.; Côté, Patrick; Cuillandre, Jean-Charles; Durrell, Patrick; Emsellem, Eric; Ferrarese, Laura; Gwyn, Stephen; Jordán, Andrés; Lançon, Ariane; Mei, Simona; Muñoz, Roberto; Puzia, Thomas

2014-09-01

324

Internal Dynamics, Structure, and Formation of Dwarf Elliptical Galaxies. I. A Keck/Hubble Space Telescope Study of Six Virgo Cluster Dwarf Galaxies  

NASA Astrophysics Data System (ADS)

Spectroscopy with the Keck II 10 m telescope and Echelle Spectrograph and Imager is presented for six Virgo Cluster dwarf elliptical (dE) galaxies in the absolute magnitude range -15.7<=MV<=-17.2. The mean line-of-sight velocity and velocity dispersion are resolved as a function of radius along the major axis of each galaxy, nearly doubling the total number of dEs with spatially resolved stellar kinematics. None of the observed objects shows evidence of strong rotation; upper limits on vrot/?, the ratio of the maximum rotational velocity to the mean velocity dispersion, are well below those expected for rotationally flattened objects. Such limits place strong constraints on dE galaxy formation models. Although these galaxies continue the trend of low rotation velocities observed in Local Group dEs, they are in contrast to recent observations of large rotation velocities in slightly brighter cluster dEs. Using surface photometry from Hubble Space Telescope Wide Field Planetary Camera 2 images and spherically symmetric dynamical models, we determine global mass-to-light ratios 3<=?V<=6. These ratios are comparable to those expected for an old to intermediate-age stellar population and are broadly consistent with the observed V-I colors of the galaxies. These dE galaxies therefore do not require a significant dark matter component inside an effective radius. We are able to rule out central black holes more massive than ~107 Msolar. For the five nucleated dEs in our sample, kinematic and photometric properties were determined for the central nucleus separately from the underlying host dE galaxy. These nuclei are as bright or brighter than the most luminous Galactic globular clusters and lie near the region of fundamental plane space occupied by globular clusters. In this space, the Virgo dE galaxies lie in the same general region as Local Group and other nearby dEs, although nonrotating dEs appear to have a slightly higher mean mass and mass-to-light ratio than rotating dEs; the dE galaxies occupy a plane parallel to, but offset from, that occupied by normal elliptical galaxies. 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.

Geha, M.; Guhathakurta, P.; van der Marel, R. P.

2002-12-01

325

Simulations of Spheroidal Systems with Substructure: Trees in Fields  

E-print Network

We present a hybrid technique of N-body simulation to deal with collisionless stellar systems having an inhomogeneous global structure. We combine a treecode and a self-consistent field code such that each of the codes model a different component of the system being investigated. The treecode is suited to treatment of dynamically cold or clumpy systems which may undergo significant evolution within a dynamically hot system. The hot system is appropriately evolved by the self-consistent field code. This combined code is particularly suited to a number of problems in galactic dynamics. Applications of the code to these problems are briefly discussed.

S. Vine; S. Sigurdsson

1997-02-09

326

Search for gravitational waves from compact binary coalescence in LIGO and Virgo data from S5 and VSR1  

Microsoft Academic Search

We report the results of the first search for gravitational waves from compact binary coalescence using data from the Laser Interferometer Gravitational-Wave Observatory and Virgo detectors. Five months of data were collected during the Laser Interferometer Gravitational-Wave Observatory's S5 and Virgo's VSR1 science runs. The search focused on signals from binary mergers with a total mass between 2 and 35M&sun;.

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; 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; T. Ballinger; 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; A. Belletoile; 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. Bonnand; R. Bork; M. Born; S. Bose; L. Bosi; B. Bouhou; 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. Budzynski; T. Bulik; H. J. Bulten; A. Buonanno; J. Burguet--Castell; O. Burmeister; D. Buskulic; C. Buy; R. L. Byer; L. Cadonati; G. Cagnoli; J. Cain; E. Calloni; J. B. Camp; E. Campagna; P. Campsie; J. Cannizzo; K. C. Cannon; B. Canuel; J. Cao; C. Capano; F. Carbognani; 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; 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; 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; G. Ely; 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; M. Galimberti; L. Gammaitoni; J. A. Garofoli; F. Garufi; G. Gemme; E. Genin; A. Gennai; S. Ghosh; J. A. Giaime; S. Giampanis; K. D. Giardina; A. Giazotto; C. Gill; E. Goetz; L. M. Goggin; G. González; 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.-F. Hayau; T. Hayler; 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; 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; M. Mageswaran; K. Mailand; E. Majorana; C. Mak; I. Maksimovic; N. Man; I. Mandel; V. Mandic; M. Mantovani; F. Marchesoni; F. Marion; S. Márka; Z. Márka; E. Maros; J. Marque; F. Martelli; I. W. Martin; R. M. Martin; J. N. Marx

2010-01-01

327

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

E-print Network

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.

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

328

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

SciTech Connect

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.

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

329

AN EXAMINATION OF THE OPTICAL SUBSTRUCTURE OF GALAXY CLUSTERS HOSTING RADIO SOURCES  

SciTech Connect

Using radio sources from the Faint Images of the Radio Sky at Twenty-cm survey, and optical counterparts in the Sloan Digital Sky Survey, we have identified a large number of galaxy clusters. The radio sources within these clusters are driven by active galactic nuclei, and our cluster samples include clusters with bent, and straight, double-lobed radio sources. We also included a single-radio-component comparison sample. We examine these galaxy clusters for evidence of optical substructure, testing the possibility that bent double-lobed radio sources are formed as a result of large-scale cluster mergers. We use a suite of substructure analysis tools to determine the location and extent of substructure visible in the optical distribution of cluster galaxies, and compare the rates of substructure in clusters with different types of radio sources. We found no preference for significant substructure in clusters hosting bent double-lobed radio sources compared to those with other types of radio sources.

Wing, Joshua D.; Blanton, Elizabeth L., E-mail: jwing@bu.edu [Astronomy Department and Institute for Astrophysical Research, Boston University, Boston, MA 02215 (United States)

2013-04-20

330

The GALEX Ultraviolet Virgo Cluster Survey (GUViCS). III. The ultraviolet source catalogs  

NASA Astrophysics Data System (ADS)

In this paper we introduce the deepest and most extensive ultraviolet extragalactic source catalogs of the Virgo Cluster area to date. Archival and targeted GALEX imaging is compiled and combined to provide the deepest possible coverage over ~120 deg2 in the NUV (?eff = 2316 Å) and ~40 deg2 in the FUV (?eff = 1539 Å) between 180°? RA ? 195° and 0° ? Dec ? 20°. We measure the integrated photometry of 1770 extended UV sources of all galaxy types and use GALEX pipeline photometry for 1 230 855 point-like sources in the foreground, within, and behind the cluster. Extended source magnitudes are reliable to mUV ~ 22, showing a ~0.01? difference from their asymptotic magnitudes. Point-like source magnitudes have a 1? standard deviation within ~0.2 mag down to muv ~ 23. The point-like source catalog is cross-matched with large optical databases and surveys including the SDSS DR9 (>1 million Virgo Cluster sources), the Next Generation Virgo Cluster Survey (NGVS; >13 million Virgo Cluster sources), and the NED (~30 000 sources in the Virgo Cluster). We find that 69% of the entire UV point-like source catalog has a unique optical counterpart, 11% of which are stars and 0.01% (129) are Virgo cluster members that are neither in the VCC nor part of the bright CGCG galaxy catalog (i.e., mpg < 14.5). These data are collected in three catalogs containing the UV extended sources, the UV point-like sources, and the most relevant optical parameters of UV-optically matched point-like sources for further studies from SDSS. The GUViCS catalogs provide a unique set of data for future work on UV and multiwavelength studies in the cluster and background environments. Full Tables H.1, I.1, J.1 and the GUViCS catalogs presented in Tables H.2, I.2, and J.2 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/569/A124

Voyer, E. N.; Boselli, A.; Boissier, S.; Heinis, S.; Cortese, L.; Ferrarese, L.; Cote, P.; Cuillandre, J.-C.; Gwyn, S. D. J.; Peng, E. W.; Zhang, H.; Liu, C.

2014-09-01

331

Substructure in the Globular Cluster System of the Milky Way  

E-print Network

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.

A. Burkert; G. Smith

1996-10-23

332

MODEST-1: Integrating Stellar Evolution and Stellar Dynamics  

E-print Network

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.

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

333

Recombination Algorithms and Jet Substructure: Pruning as a Tool for Heavy Particle Searches  

E-print Network

We discuss jet substructure in recombination algorithms for QCD jets and single jets from heavy particle decays. We demonstrate that the jet algorithm can introduce significant systematic effects into the substructure. By characterizing these systematic effects and the substructure from QCD, splash-in, and heavy particle decays, we identify a technique, pruning, to better identify heavy particle decays into single jets and distinguish them from QCD jets. Pruning removes protojets typical of soft, wide angle radiation, improves the mass resolution of jets reconstructing a heavy particle decay, and decreases the QCD background. We show that pruning provides significant improvements over unpruned jets in identifying top quarks and W bosons and separating them from a QCD background, and may be useful in a search for heavy particles.

Stephen D. Ellis; Christopher K. Vermilion; Jonathan R. Walsh

2009-12-01

334

Impact of Dark Matter Substructure on the Matter and Weak Lensing Power Spectra  

E-print Network

We explore the effect of substructure in dark matter halos on the power spectrum and bispectrum of matter fluctuations and weak lensing shear. By experimenting with substructure in a cosmological N = 512^3 simulation, we find that when a larger fraction of the host halo mass is in subhalos, the resulting power spectrum has less power at 1 power at k > 100 h Mpc^{-1}. We explain this effect using an analytic halo model including subhalos, which shows that the 1 100 h Mpc^{-1}. The corresponding effect due to substructures on the weak lensing power spectrum is up to about 11% at angular scale l power spectrum to a few percent accuracy for future surveys would therefore require large cosmological simulations that also have exquisite numerical resolution to model accurately the survivals of dark matter subhalos in the tidal fields of their hosts.

Bradley Hagan; Chung-Pei Ma; Andrey V. Kravtsov

2005-07-25

335

Reconstruction of small-scale galaxy cluster substructure with lensing flexion  

E-print Network

We present a reconstructions of galaxy-cluster-scale mass distributions from simulated gravitational lensing data sets including strong lensing, weak lensing shear, and measurements of quadratic image distortions -- flexion. The lensing data is constructed to make a direct comparison between mass reconstructions with and without flexion. We show that in the absence of flexion measurements, significant galaxy-group scale substructure can remain undetected in the reconstructed mass profiles, and that the resulting profiles underestimate the aperture mass in the substructure regions by $\\sim25-40\\%$. When flexion is included, subhaloes down to a mass of $\\sim3\\times10^{12}$ M$_\\odot$ can be detected at an angular resolution smaller than 10\\arcsec. Aperture masses from profiles reconstructed with flexion match the input distribution values to within an error of $\\sim13\\%$, including both statistical error and scatter. This demonstrates the important constraint that flexion measurements place on substructure in ga...

Cain, Benjamin; Levinson, Rebecca

2015-01-01

336

ALFALFA HI Content and Star Formation in Virgo Cluster Early-Type Dwarfs  

E-print Network

The ALFALFA (Arecibo Legacy Fast ALFA) blind survey is providing a census of HI in galaxies of all types in a range of environments. Here we report on ALFALFA results for Virgo Cluster early-type dwarfs between declinations of 4 and 16 degrees. Less than 2% of the Virgo early-type dwarf population is detected, compared to 70-80% of the Im/BCD dwarf population. Most of the dwarfs detected in HI show evidence for ongoing or recent star formation. Early-type galaxies with HI tend to be located in the outer regions of the cluster and to be brighter. Early-type dwarfs with HI may be undergoing morphological transition due to cluster environmental effects.

Koopmann, R A; Haynes, M P; Brosch, N

2009-01-01

337

Chance Estimations for Detecting Gravitational Waves with LIGO/Virgo Associated with Gamma Ray Bursts  

E-print Network

Short Gamma Ray Bursts (SGRB) are believed to originate from the merger of two compact objects. If this scenario is correct, SGRB will be accompanied by the emission of strong gravitational waves, detectable by current or planned GW detectors, such as LIGO and Virgo. No detection of a gravitational wave has been made up to date. In this paper I will use a set of SGRB with observed redshifts to fit a model describing the cumulative number of SGRB as a function of redshift, to determine the rate of such merger events in the nearby universe. These estimations will be used to make probability statements about detecting a gravitational wave associated with a short gamma ray burst during the latest science run of LIGO/Virgo. Chance estimations for the enhanced and advanced detectors will also be made, and a comparison between the rates deduced from this work will be compared to the existing literature.

Alexander Dietz

2009-04-02

338

Identification of long-duration noise transients in LIGO and Virgo  

E-print Network

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.

LIGO Scientific Collaboration; Virgo Collaboration; Michael W. Coughlin

2011-11-13

339

US International Stellarator Collaboration  

NASA Astrophysics Data System (ADS)

The US program is using international collaboration to stay at the forefront of experimental stellarator science. The LHD is the premier operating stellarator in the world. The US recently installed an X-ray Imaging Crystal Spectrometer on LHD to aid in the measurement of Ti profiles in difficult plasma regimes - e. g., RF operations, high density, and low density (N. Pablant, this conf.). An effort is underway to develop equilibrium reconstruction for stellarators (S. Lazerson, and A. Sontag this conf.). Results from experiments on the MHD stability of high performance regimes observed on LHD will be presented. The US is also collaborates with W7-X. The collaboration theme on W7-X is divertor heat-flux management. Collaborations on hardware include trim coils, diagnostics (G. Wurden, this conf.), and PFCs (J. Harris, this conf.). Active control that involves real-time equilibrium control and temperature monitoring will be discussed.

Gates, D. A.; Bitter, M.; Canik, J.; Geiger, J.; Goto, M.; Harris, J. H.; Hill, K. W.; Lazerson, S.; Lore, J.; Monticello, D.; Narushima, Y.; Neilson, G. H.; Pablant, N.; Pomphrey, N.; Reiman, A.; Sakakibara, S.; Sontag, A.; Werner, A.; Wolf, R.; Wurden, G. A.

2011-11-01

340

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

Microsoft Academic Search

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

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

341

Early-type galaxies with neutral hydrogen in the Virgo cluster from the ALFALFA survey  

E-print Network

We extend our published work on the neutral hydrogen content of early-type galaxies in the Virgo cluster using the catalogue of detected sources from the ALFALFA survey, by showing the 21cm spectra of all the detected galaxies and discussing a deeper analysis of the ALFALFA datacubes, searching for lower S/N sources. A view of the multiphase interstellar medium of M86 is also presented, by comparing images of the cold, warm and hot phases.

Alighieri, S di Serego; Giovanardi, C; Pellegrini, S; Trinchieri, G

2008-01-01

342

Early-type galaxies with neutral hydrogen in the Virgo cluster from the ALFALFA survey  

E-print Network

We extend our published work on the neutral hydrogen content of early-type galaxies in the Virgo cluster using the catalogue of detected sources from the ALFALFA survey, by showing the 21cm spectra of all the detected galaxies and discussing a deeper analysis of the ALFALFA datacubes, searching for lower S/N sources. A view of the multiphase interstellar medium of M86 is also presented, by comparing images of the cold, warm and hot phases.

S. di Serego Alighieri; M. Grossi; C. Giovanardi; S. Pellegrini; G. Trinchieri

2008-03-03

343

A 500 kpc HI Tail of the Virgo Pair NGC4532/DDO137 Detected by ALFALFA  

E-print Network

HI observations of the Virgo Cluster pair NGC 4532/DDO 137, conducted as part of the Arecibo Legacy Fast ALFA Survey (ALFALFA), reveal an HI feature extending ~500 kpc to the southwest. The structure has a total mass of up to 7 x 10^8 solar masses, equivalent to 10% of the pair HI mass. Optical R imaging reveals no counterparts to a level of 26.5 magnitudes per square arcsec. The structure is likely the result of galaxy harassment.

Koopmann, Rebecca A

2007-01-01

344

A 500 kpc HI Tail of the Virgo Pair NGC4532/DDO137 Detected by ALFALFA  

E-print Network

HI observations of the Virgo Cluster pair NGC 4532/DDO 137, conducted as part of the Arecibo Legacy Fast ALFA Survey (ALFALFA), reveal an HI feature extending ~500 kpc to the southwest. The structure has a total mass of up to 7 x 10^8 solar masses, equivalent to 10% of the pair HI mass. Optical R imaging reveals no counterparts to a level of 26.5 magnitudes per square arcsec. The structure is likely the result of galaxy harassment.

Rebecca A. Koopmann

2007-07-22

345

Kinematic properties and dark matter fraction of Virgo dwarf early-type galaxies  

NASA Astrophysics Data System (ADS)

What happens to dwarf galaxies as they enter the cluster potential well is one of the main unknowns in studies of galaxy evolution. Several evidence suggests that late-type galaxies enter the cluster and are transformed to dwarf early-type galaxies (dEs). We study the Virgo cluster to understand which mechanisms are involved in this transformation. We find that the dEs in the outer parts of Virgo have rotation curves with shapes and amplitudes similar to late-type galaxies of the same luminosity (Fig. 1). These dEs are rotationally supported, have disky isophotes, and younger ages than those dEs in the center of Virgo, which are pressure supported, often have boxy isophotes and are older (Fig. 1). Ram pressure stripping, thus, explains the properties of the dEs located in the outskirts of Virgo. However, the dEs in the central cluster regions, which have lost their angular momentum, must have suffered a more violent transformation. A combination of ram pressure stripping and harassment is not enough to remove the rotation and the spiral/disky structures of these galaxies. We find that on the the Faber-Jackson and the Fundamental Plane relations dEs deviate from the trends of massive elliptical galaxies towards the position of dark matter dominated systems such as the dwarf spheroidal satellites of the Milky Way and M31. Both, rotationally and pressure supported dEs, however, populate the same region in these diagrams. This indicates that dEs have a non-negligible dark matter fraction within their half light radius.

Toloba, E.; Boselli, A.; Peletier, R.; Gorgas, J.

2015-03-01

346

In-Flight Performance of the Virgo Solar Irradiance Instruments on Soho  

Microsoft Academic Search

The in-flight performance of the total and spectral irradiance instruments within VIRGO (Variability of solar IRradiance and\\u000a Gravity Oscillations) on the ESA\\/NASA Mission SOHO (SOlar and Heliospheric Observatory) is in most aspects better than expected.\\u000a The behaviour during the first year of operation of the two types of radiometers and the sunphotometers together with a description\\u000a of their data evaluation

Claus Fröhlich; Dominique A. Crommelynck; Christoph Wehrli; Martin Anklin; Steven Dewitte; Alain Fichot; Wolfgang Finsterle; Antonio Jiménez; André Chevalier; Hansjörg Roth

1997-01-01

347

Helioseismic inferences of the solar cycles 23 and 24: GOLF and VIRGO observations  

NASA Astrophysics Data System (ADS)

The Sun-as-a star helioseismic spectrophotometer GOLF and photometer VIRGO instruments onboard the SoHO spacecraft are collecting high-quality, continuous data since April 1996. We analyze here these unique datasets in order to investigate the peculiar and weak on-going solar cycle 24. As this cycle 24 is reaching its maximum, we compare its rising phase with the rising phase of the previous solar cycle 23.

Salabert, D.; García, R. A.; Jiménez, A.

2014-12-01

348

A Megacam Survey of Outer Halo Satellites. IV. Two foreground populations possibly associated with the Monoceros substructure in the direction of NGC2419 and Koposov2  

E-print Network

The origin of the Galactic halo stellar structure known as the Monoceros ring is still under debate. In this work, we study that halo substructure using deep CFHT wide-field photometry obtained for the globular clusters NGC2419 and Koposov2, 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, not likely to be associated with Milky Way disk stars along the line-of-sight, is present as foreground population. Our analysis suggests that the Monoceros ring might be composed of an old stellar population of age t ~ 9Gyr and a new component ~ 4Gyr 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 also indicate a metallicity spread in the ring. The detection of such a low-d...

Carballo-Bello, Julio A; Carlin, Jeffrey L; Cote, Patrick; Geha, Marla; Simon, Joshua D; Djorgovski, S G

2015-01-01

349

The Gas Dynamics of Elliptical Galaxies in Virgo: Motion and Infall Toward M87  

NASA Astrophysics Data System (ADS)

Galaxy clusters are the most massive gravitationally bound systems in the Universe. Most of the baryonic matter in these objects is in the form of hot gas, typically 100 million K, which can be studied through X-ray observations. By measuring the redshifts of individual galaxies within a cluster, one can combine X-ray observations of the cold fronts around those galaxies to yield a full three-dimensional constraint on the cluster dynamics. Virgo, as the nearest rich cluster, provides an excellent opportunity to measure the motions of X-ray bright galaxies and their interaction with the hot intracluster medium (ICM), as has been done for NGC4472 (Kraft et al. 2011), M86 (Randall et al. 2008) and NGC4552 (Machacek et al. 2006). In this paper we describe the interaction of the hot gas in the outer regions of NGC4649 (M60) with the Virgo ICM and determine its velocity and direction of motion. Using data collected from the Chandra X-ray Observatory, we compare the gas characteristics of NGC4649 with those of other Virgo ellipticals and search for features indicative of ram-pressure stripping (tails, wings). We also compare the observed motions and infall toward M87 of these galaxies with hydrodynamic N-body simulations to better understand the cluster formation process and the large scale interactions of the galaxy gas with the cluster gas. This work was supported by Chandra grant G01-13141X and the Smithsonian Astrophysical Observatory.

Wood, Ryan A.; Jones, C.; Machacek, M. E.; Kraft, R. P.; Santos, F. A.; Paggi, A.

2014-01-01

350

Utilizing Astroinformatics to Maximize the Science Return of the Next Generation Virgo Cluster Survey  

NASA Astrophysics Data System (ADS)

The Next Generation Virgo Cluster Survey is a 104-square-degree survey of the Virgo Cluster, carried out using the MegaPrime camera of the Canada-France-Hawaii Telescope, from semesters 2009A-2012A. The survey will provide coverage of this nearby dense environment in the universe to unprecedented depth, providing profound insights into Galaxy formation and evolution, including definitive measurements of the properties of galaxies in a dense environment in the local universe, such as the luminosity function. The limiting magnitude of the survey is g AB = 25.7 (10? point source), and the 2? surface brightness limit is g AB ? 29 mag arcsec-2. The data volume of the survey (approximately 50 T of images), while large by contemporary astronomical standards, is not intractable. This renders the survey amenable to the methods of astroinformatics. The enormous dynamic range of objects, from the giant elliptical Galaxy M87 at M(B) = -21.6 to the faintest dwarf ellipticals at M(B)?-6, combined with photometry in five broad bands (u* g' r' i' z') and unprecedented depth revealing many previously unseen structures, creates new challenges in object detection and classification. We present results from ongoing work on the survey, including photometric redshifts, Virgo cluster membership, and the implementation of fast data mining algorithms on the infrastructure of the Canadian Astronomy Data Centre, as part of the Canadian Advanced Network for Astronomical Research.

Ball, Nicholas M.

351

Neutron stars versus black holes: probing the mass gap with LIGO/Virgo  

E-print Network

The inspirals and mergers of binary systems comprised of black holes (BHs) and/or neutron stars (NSs) 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 which include spin-precession effects by studying a large ensemble of plausible GW sources. We make quantitative predictions for how well LIGO and Virgo will be able to distinguish between black holes and neutron stars and appraise the prospect of using LIGO/Virgo observations to definitively confirm, or reject, the existence of a putative "mass gap" between NSs ($m\\leq3\\ M_\\odot$) and BHs ($m\\geq 5\\ M_\\odot$). We find sources with the smaller mass component satisfying $m_2 \\lesssim1.5\\ M_\\odot$ to be unambiguously identified as containing at least one NS, while systems with $m_2\\gtrsim6\\ M_\\odot$ will be confirmed binary BHs. However, binary BHs with $m_2<5\\ M_\\odot$ (i.e., in the gap) cannot be distinguishe...

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

2015-01-01

352

CLOUDS TOWARD THE VIRGO CLUSTER PERIPHERY: GAS-RICH OPTICALLY INERT GALAXIES  

SciTech Connect

Aperture synthesis observations of two H I cloud complexes located in the periphery of the Virgo galaxy cluster are presented. These low H I-mass clouds (M{sub H{sub I}}< 10{sup 9} M{sub sun}) are seen projected on the M region of the western Virgo cluster, where the galaxy population is thought to lie behind the main A cluster surrounding M87. The kinematic measurements of both unresolved Arecibo and resolved Very Large Array (VLA)-C observations are in good agreement. The H I detections cannot be identified with any optical, IR, or UV emission from available archival imaging. They are inert at these wavelengths. The H I masses of the individual VLA detections range from 7.28 {<=} log(M{sub H{sub I}}/M{sub sun}){<=} 7.85. The total dynamical mass estimates are several times their H I content, ranging from 7.00 {<=} log(M{sub dyn}/M{sub sun}){<=} 9.07, with the assumption that the clouds are self-gravitating and in dynamical equilibrium. We report the observed parameters derived from the VLA observations. One of these H I clouds appears to be the most isolated optically inert detection observed in the outer reaches of Virgo.

Kent, Brian R., E-mail: bkent@nrao.ed [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)

2010-12-20

353

Parametric studies of stitching effectiveness for preventing substructure disbond  

NASA Technical Reports Server (NTRS)

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.

Flanagan, Gerry; Furrow, Keith

1995-01-01

354

isochrones: Stellar model grid package  

NASA Astrophysics Data System (ADS)

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.

Morton, Timothy D.

2015-03-01

355

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.

356

Evolution of Stellar Magnetic Fields  

NASA Astrophysics Data System (ADS)

Stellar magnetic fields can reliably be characterized by several magnetic activity indicators, such as X-ray or radio luminosity. Physical processes leading to such emission provide important information on dynamic processes in stellar atmospheres and magnetic structuring.

Güdel, Manuel

2015-03-01

357

A Stellar Demonstrator  

ERIC Educational Resources Information Center

The main purpose of the stellar demonstrator is to help explain the movement of stars. In particular, students have difficulties understanding why, if they are living in the Northern Hemisphere, they may observe starts in the Southern Hemisphere, or why circumpolar stars are not the same in different parts of Europe. Using the demonstrator, these…

Ros, Rosa M.

2009-01-01

358

Progress Toward Attractive Stellarators  

SciTech Connect

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.

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

359

Stellar Ontogeny: From Dust...  

ERIC Educational Resources Information Center

Discusses the process of star formation. Infrared and radio astronomy, particularly microwave astronomy is used to provide information on different stages of stellar formation. The role of dust and gas which swirl through the interstellar regions of a galaxy and the collapse of a cloud in star formation are also presented. (HM)

MOSAIC, 1978

1978-01-01

360

Stellar Structure and Evolution  

Microsoft Academic Search

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

Rudolf Kippenhahn; Alfred Weigert

1990-01-01

361

A Scalable Substructuring Method By Lagrange Multipliers For Plate Bending Problems  

Microsoft Academic Search

. We present a new Lagrange multiplier based domain decomposition method forsolving iteratively systems of equations arising from the finite element discretization of plate bendingproblems. The proposed method is essentially an extension of the FETI substructuring algorithmto the biharmonic equation. The main idea is to enforce continuity of the transversal displacementfield at the subdomain crosspoints throughout the preconditioned conjugate gradient

Charbel Farhat; Jan Mandel; Radek Tezaur

1997-01-01

362

Graph Mining Framework for Finding and Visualizing Substructures Using Graph Database  

Microsoft Academic Search

In the scientific and commercial domains, graph as a data structure has become increasingly important for modeling sophisticated structures especially the interactions within them. Mining the knowledge from graph data has become a major research topic in recent data mining studies. Researchers have designed several efficient algorithms for mining various substructures (subgraphs) within the graph. Several graph visualization tools and

Swapnil Shrivastava; Supriya N. Pal

2009-01-01

363

Approximate Substructure Search in a Database of 3D Graphs \\Lambda  

E-print Network

Approximate Substructure Search in a Database of 3D Graphs \\Lambda Xiong Wang and Jason T. L. Wang, NJ 07102, USA Abstract Given a database D of three dimensional (3D) graphs and a query graph Q search operation in scientific databases. This paper extends the search operation to find those graphs D

Wang, Xiong

364

A Computer Process for Substructure Searches on Compound Structures Ciphered in the IUPAC Notation  

ERIC Educational Resources Information Center

Computer programs have been written which enable substructure searches to be carried out on a file of compounds ciphered using a modified version of the IUPAC (Dyson) notation. The search system outlined is to be linked with one which uses input from the chemical structure typewriter. (3 references) (Author)

Polton, D. J.

1972-01-01

365

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

Microsoft Academic Search

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

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

2000-01-01

366

POROUS SUBSTRUCTURE OF THE GLOMERULAR SLIT DIAPHRAGM IN THE RAT AND MOUSE  

Microsoft Academic Search

The highly ordered, isoporous substructure of the glomerular slit diaphragm was re- vealed in rat and mouse kidneys fixed by perfusion with tannic acid and glutaraldehyde . The slit diaphragm was similar in both animal species and appeared as a continuous junctional band, 300-450A wide, consistently present within all slits formed by the epithelial foot processes . The diaphragm exhibited

RICHARD RODEWALD; MORRIS J. KARNOVSKY

1974-01-01

367

Substructure and Scatter in the Mass-Temperature Relations of Simulated Clusters  

NASA Astrophysics Data System (ADS)

Galaxy clusters exhibit regular scaling relations among their bulk properties. These relations establish vital links between halo mass and cluster observables. Precision cosmology studies that depend on these links benefit from a better understanding of scatter in the mass-observable scaling relations. Here, we study the role of merger processes in introducing scatter into the M-TX relation, using a sample of 121 galaxy clusters simulated with radiative cooling and supernova feedback, along with three statistics previously proposed to measure X-ray surface brightness substructure. These are the centroid variation (w), the axial ratio (?), and the power ratios (P20 and P30). We find that in this set of simulated clusters, each substructure measure is correlated with a cluster's departures ?lnTX and ?lnM from the mean M-TX relation, both for emission-weighted temperatures TEW and for spectroscopic-like temperatures TSL, in the sense that clusters with more substructure tend to be cooler at a given halo mass. In all cases, a three-parameter fit to the M-TX relation that includes substructure information has less scatter than a two-parameter fit to the basic M-TX relation.

Ventimiglia, David A.; Voit, G. Mark; Donahue, Megan; Ameglio, S.

2008-09-01

368

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

PubMed Central

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

Johnson, Steven M.; Connelly, Stephen; Wilson, Ian A.; Kelly, Jeffery W.

2008-01-01

369

Can galactic dark matter substructure contribute to the cosmic gamma-ray anisotropy?  

NASA Astrophysics Data System (ADS)

The annihilation of dark matter (DM) particles in the Milky Way can contribute to the diffuse gamma-ray background (DGRB). Due to the presence of substructures, this emission will appear anisotropic in a predictable way. We generate full-sky maps of the gamma-ray emission in galactic substructures from results of the high-resolution Via Lactea II N-body simulation of the Milky Way DM halo. We calculate the anisotropy pattern, taking into account different radial profiles of the DM distribution in substructures, cosmic variance, and the detection threshold, and compare it to the anisotropy in the DGRB observed by the Fermi Large Area Telescope (LAT). By comparing the upper limits on the DM self-annihilation cross-section, , implied by the anisotropy to the intensity of the DGRB and detected sources in the LAT 2-yr Point Source Catalog, we find that galactic substructure cannot contribute to the anisotropies in the DGRB without strongly violating these observations. Our results challenge the perception that small-scale anisotropies in the DGRB can be used as a probe of DM annihilation in galactic subhaloes.

Lange, J. U.; Chu, M.-C.

2015-02-01

370

Substructural changes during hot deformation of an Fe-26Cr ferritic stainless steel  

SciTech Connect

Dynamic softening and substructural changes during hot deformation of a ferritic Fe-26Cr stainless steel were studied. The flow stress increased to reach a steady state in all the cases and the steady-state stress decreased with decreasing Z, the Zener-Hollomon parameter. A constant subgrain size was observed to correspond to the steady-state flow and the steady-state subgrain size increased with decreasing Z. Substructure examinations revealed that elongated, pancake-shaped subgrains formed in the early stage of deformation. Straight sub-boundaries and equiaxed subgrains developed progressively with strain, leading eventually to a stable substructure at strains greater than 0.7. During deformation at 1,100 C, dynamic recrystallization occurred by the migration and coalescence of sub-boundaries. Dynamic recovery dominated during deformation at 900 C, resulting in the formation of fine equiaxed subgrains. Based on microstructural observations, the process of substructural changes during hot deformation was described by a schematic diagram.

Gao, F.; Xu, Y.; Song, B.; Xia, K.

2000-01-01

371

Structure, Phase Composition, and Defective Substructure of Rails of the Highest Quality Grade  

NASA Astrophysics Data System (ADS)

Methods of transmission electron microscopy are used for layer-by-layer analysis of rails of the highest quality grade. Quantitative parameters of structure gradients, phase composition, and dislocation substructures formed by various mechanisms of ?-? transformation are determined. Sources of long-range stress fields are revealed. It is determined that possible places of microcrack origin in the steel are interfaces cementite particles - matrix.

Gromov, V. E.; Volkov, K. V.; Ivanov, Yu. F.; Morozov, K. V.; Konovalov, S. V.; Alsaraeva, K. V.

2014-06-01

372

Fast and accurate protein substructure searching with simulated annealing and GPUs  

Microsoft Academic Search

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

Alex D Stivala; Peter J. Stuckey; Anthony I Wirth

2010-01-01

373

Toward Optimization of the Linker Substructure Common to Transthyretin Amyloidogenesis Inhibitors Using Biochemical And Structural Studies  

SciTech Connect

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-X{sub 2} or a 3,5-X{sub 2}-4-OH phenyl substructure (X = Br or CH{sub 3}). Coconsideration of amyloid inhibition and ex vivo plasma TTR binding selectivity data reveal that direct connection of the two aryls or linkage through nonpolar E-olefin or -CH{sub 2}CH{sub 2}- 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 {angstrom}) provide insight into why such linkers afford inhibitors with greater potency and selectivity.

Johnson, S.M.; Connelly, S.; Wilson, I.A.; Kelly, J.W.

2009-05-18

374

Learning Sub-structures of Document Semantic Graphs for Document Summarization  

E-print Network

of semantic graph are weighted highly by SVM in the learned model. Categories and Subject Descriptors H.3Learning Sub-structures of Document Semantic Graphs for Document Summarization Jurij Leskovec Jozef@microsoft.com ABSTRACT In this paper we present a method for summarizing document by creating a semantic graph

Leskovec, Jure

375

Automatic Learning of Chemical Concepts: Research Octane Number and Molecular Substructures  

Microsoft Academic Search

A set of 230 hydrocarbons is analyzed with respect to the research octane number (RON) using an extended version of the ID3 machine learning method of Quinlan. The basic ID3 method produces a decision tree. The questions within the decision tree ask whether given substructures are present or absent within a molecule (for example, is the hexane carbon skeleton present

Edward S. Blurock

1995-01-01

376

GLOBAL PROPERTIES OF M31'S STELLAR HALO FROM THE SPLASH SURVEY. I. SURFACE BRIGHTNESS PROFILE  

SciTech Connect

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 {approx}175 kpc ({approx}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.

Gilbert, Karoline M. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Guhathakurta, Puragra [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Beaton, Rachael L.; Majewski, Steven R.; Ostheimer, James C.; Patterson, Richard J. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Bullock, James; Tollerud, Erik J. [Center for Cosmology, Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697 (United States); Geha, Marla C. [Astronomy Department, Yale University, New Haven, CT 06520 (United States); Kalirai, Jason S. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Kirby, Evan N. [California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States); Tanaka, Mikito; Chiba, Masashi, E-mail: kgilbert@astro.washington.edu [Astronomical Institute, Tohoku University, Aoba-ku, Sendai 980-8578 (Japan)

2012-11-20

377

The simultaneous formation of massive stars and stellar clusters  

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

378

Exploring Halo Substructure with Giant Stars: II. Mapping the Extended Structure of the Carina Dwarf Spheroidal Galaxy  

E-print Network

As part of our survey for substructure in the Milky Way halo as traced by giant stars, and to look for tidal stellar debris in the halo viable for measurement of the Galactic mass potential with SIM, we explore the distribution of stars beyond the nominal tidal radius of, but still associated with, the Carina dwarf spheroidal galaxy. We make use of a photometric technique described in Majewski et al. (1999) to identify giant star candidates at the distance and metallicity of Carina across the entire extent of the photometric survey covering some 2.2 deg^2 on and around Carina. These Carina-associated giant candidates are identified by a combination of (1) their M-DDO51 colors, and (2) by locations in the color-magnitude diagram commensurate with the Carina RGB in the core of the galaxy. The density distribution of the extratidal giant candidates is similar to that found from previous statistical star-counting approaches. However, we are now able to pinpoint actual, remotely-situated Carina stars individually. Because we can exclude foreground dwarf stars, our approach allows greater sensitivity and the ability to map the detailed two-dimensional distribution of extended Carina populations to much larger radii, with smaller aperture telescopes, than other techniques. Moreover, we identify candidate lists of widely displaced Carina-associated stars bright enough for spectroscopic studies of large-scale dynamical and metallicity properties of the system, and for astrometric study by SIM. We obtained spectroscopy for three such ``extratidal'' stars and from their radial velocities conclude that all three are associated with Carina.

S. R. Majewski; J. C. Ostheimer; R. J. Patterson; W. E. Kunkel; K. V. Johnston; D. Geisler

1999-11-10

379

Kinematic and Spatial Substructure in NGC 2264\\footnotemark  

E-print Network

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...

Tobin, John J; Furesz, Gabor; Hsu, Wen-Hsin; Mateo, Mario

2015-01-01

380

Identification of population substructure among Jews using STR markers and dependence on reference populations included  

PubMed Central

Background Detecting population substructure is a critical issue for association studies of health behaviors and other traits. Whether inherent in the population or an artifact of marker choice, determining aspects of a population's genetic history as potential sources of substructure can aid in design of future genetic studies. Jewish populations, among which association studies are often conducted, have a known history of migrations. As a necessary step in understanding population structure to conduct valid association studies of health behaviors among Israeli Jews, we investigated genetic signatures of this history and quantified substructure to facilitate future investigations of these phenotypes in this population. Results Using 32 autosomal STR markers and the program STRUCTURE, we differentiated between Ashkenazi (AJ, N = 135) and non-Ashkenazi (NAJ, N = 226) Jewish populations in the form of Northern and Southern geographic genetic components (AJ north 73%, south 23%, NAJ north 33%, south 60%). The ability to detect substructure within these closely related populations using a small STR panel was contingent on including additional samples representing major continental populations in the analyses. Conclusions Although clustering programs such as STRUCTURE are designed to assign proportions of ancestry to individuals without reference population information, when Jewish samples were analyzed in the absence of proxy parental populations, substructure within Jews was not detected. Generally, for samples with a given grandparental country of birth, STRUCTURE assignment values to Northern, Southern, African and Asian clusters agreed with mitochondrial DNA and Y-chromosomal data from previous studies as well as historical records of migration and intermarriage. PMID:20546593

2010-01-01

381

Life history and production of the burrowing mayfly Ephoron virgo (Olivier, 1791) (Ephemeroptera: Polymitarcyidae) in the lower Ebro river: a comparison after 18 years  

Microsoft Academic Search

The life history of the burrowing mayfly Ephoron virgo (Olivier, 1791) (Ephemeroptera: Polymitarcyidae) was studied during spring and summer 2005 in the lower Ebro river (Catalonia) and compared to a previous study performed in 1987 (Ibáñez, Escosa, Muñoz and Prat 1991). The results showed an advancement of Ephoron virgo life cycle and an increase of production estimates. In 2005 larval

Núria Cid; Carles Ibáñez; Narcís Prat

2008-01-01

382

Abundances of neutron-capture elements in stars of the Galactic disk substructures  

NASA Astrophysics Data System (ADS)

Aims: The aim of this work is to present and discuss the observations of the iron peak (Fe, Ni) and neutron-capture element (Y, Zr, Ba, La, Ce, Nd, Sm, and Eu) abundances for 276 FGK dwarfs, located in the Galactic disk with metallicity -1 < [Fe/H] < +0.3. Methods: Atmospheric parameters and chemical composition of the studied stars were determined from an high resolution, high signal-to-noise echelle spectra obtained with the echelle spectrograph ELODIE at the Observatoire de Haute-Provence (France). Effective temperatures were estimated by the line depth ratio method and from the H? line-wing fitting. Surface gravities (log g) were determined by parallaxes and the ionization balance of iron. Abundance determinations were carried out using the LTE approach, taking the hyperfine structure for Eu into account, and the abundance of Ba was computed under the NLTE approximation. Results: We are able to assign most of the stars in our sample to the substructures of the Galaxy thick disk, thin disk, or Hercules stream according to their kinematics. The classification of 27 stars is uncertain. For most of the stars in the sample, the abundances of neutron-capture elements have not been measured earlier. For all of them, we provide the chemical composition and discuss the contribution from different nucleosynthesis processes. Conclusions: The [Ni/Fe] ratio shows a flat value close to the solar one for the whole metallicity range, with a small scatter, pointing to a nearly solar Ni/Fe ratio for the ejecta of both core-collapse SN and SNIa. The increase in the [Ni/Fe] for metallicity higher than solar is confirmed, and it is due to the metallicity dependence of 56Ni ejecta from SNIa. Under large uncertainty in the age determination of observed stars, we verified that there is a large dispersion in the AMR in the thin disk, and no clear trend as in the thick disk. That may be one of the main reasons for the dispersion, observed for the s-process elements in the thin disk (e.g., Ba and La), whereas much narrower dispersion can be seen for r-process elements (e.g., Eu). Within the current uncertainties, we do not see a clear decreasing trend of [Ba/Fe] or [La/Fe] with metallicity in the thin disk, except maybe for super-solar metallicities. We cannot confirm an increase in the mentioned ratios with decreasing stellar age. Based on spectra collected with the ELODIE spectrograph at the 1.93-m telescope of the Observatoire de Haute Provence (France).Tables 4 and 5 are only available at the CDS via anonymous ftp to ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/552/A128

Mishenina, T. V.; Pignatari, M.; Korotin, S. A.; Soubiran, C.; Charbonnel, C.; Thielemann, F.-K.; Gorbaneva, T. I.; Basak, N. Yu.

2013-04-01

383

Kinematically-Decoupled Cores in Dwarf Ellipticals in the Virgo Cluster: Implications for Infallen Groups in Clusters  

NASA Astrophysics Data System (ADS)

A small fraction 8%) of elliptical galaxies contain kinematically-decoupled cores (KDCs), where the kinematical properties of the central region of the galaxy are distinct from those of the main body of the galaxy. KDCs are difficult to detect in dwarf elliptical (dE) galaxies because of their low central surface brightnesses. There was only one statistically robust detection of a KDC in a dE prior to our study. We present spectroscopic evidence for KDCs in two Virgo cluster dEs, VCC 1183 and VCC 1453, that were studied as part of the SMAKCED project. These KDCs have radii of 1.8$''$ (0.14 kpc) and 4.2$''$ (0.33 kpc), respectively. They are distinct from the main body of the galaxy is three ways: (1) inverted sense of rotation; (2) younger and more metal-rich stellar population; and (3) rounder isophotal shape. The frequency of occurence of KDCs and their properties provide important constraints on the formation history of their host galaxies. We discuss different formation scenarios for these KDCs and for dEs in general. The fact that dEs represent the most common galaxy class in clusters and have never been seen in isolation suggests that they are products of environmental processes that transformed their progenitors. However, it is unclear which types of galaxies are dE progenitors and which environmental processes are the most important. These KDCs provide new clues. Dwarf-dwarf wet mergers and gas accretion are argued to be the only mechanisms that can simultaneously explain all of the properties of these KDCs. Both of these mechanisms require that the progenitor had a close companion with a small relative velocity. Thus, we conclude that KDCs in cluster dEs were formed in galaxy pairs residing in poor groups or in isolation whose subsequent infall into the cluster quenched their star formation. This research was supported by a Fulbright fellowship and by a grant from the National Science Foundation.

Toloba, Elisa; Guhathakurta, P.; van de Ven, G.; Boselli, A.; Lisker, T.; Peletier, R.; SMAKCED Collaboration

2014-01-01

384

Boosted objects and jet substructure at the LHC. Report of BOOST2012, held at IFIC Valencia, 23rd-27th of July 2012  

NASA Astrophysics Data System (ADS)

This report of the BOOST2012 workshop presents the results of four working groups that studied key aspects of jet substructure. We discuss the potential of first-principle QCD calculations to yield a precise description of the substructure of jets and study the accuracy of state-of-the-art Monte Carlo tools. Limitations of the experiments' ability to resolve substructure are evaluated, with a focus on the impact of additional (pile-up) proton proton collisions on jet substructure performance in future LHC operating scenarios. A final section summarizes the lessons learnt from jet substructure analyses in searches for new physics in the production of boosted top quarks.

Altheimer, A.; Arce, A.; Asquith, L.; Backus Mayes, J.; Kuutmann, E. Bergeaas; Berger, J.; Bjergaard, D.; Bryngemark, L.; Buckley, A.; Butterworth, J.; Cacciari, M.; Campanelli, M.; Carli, T.; Chala, M.; Chapleau, B.; Chen, C.; Chou, J. P.; Cornelissen, Th.; Curtin, D.; Dasgupta, M.; Davison, A.; de Almeida Dias, F.; de Cosa, A.; de Roeck, A.; Debenedetti, C.; Doglioni, C.; Ellis, S. D.; Fassi, F.; Ferrando, J.; Fleischmann, S.; Freytsis, M.; Gonzalez Silva, M. L.; de la Hoz, S. Gonzalez; Guescini, F.; Han, Z.; Hook, A.; Hornig, A.; Izaguirre, E.; Jankowiak, M.; Juknevich, J.; Kaci, M.; Kar, D.; Kasieczka, G.; Kogler, R.; Larkoski, A.; Loch, P.; Lopez Mateos, D.; Marzani, S.; Masetti, L.; Mateu, V.; Miller, D. W.; Mishra, K.; Nef, P.; Nordstrom, K.; Oliver Garcia, E.; Penwell, J.; Pilot, J.; Plehn, T.; Rappoccio, S.; Rizzi, A.; Rodrigo, G.; Safonov, A.; Salam, G. P.; Salt, J.; Schaetzel, S.; Schioppa, M.; Schmidt, A.; Scholtz, J.; Schwartzman, A.; Schwartz, M. D.; Segala, M.; Son, M.; Soyez, G.; Spannowsky, M.; Stewart, I.; Strom, D.; Swiatlowski, M.; Sanchez Martinez, V.; Takeuchi, M.; Thaler, J.; Thompson, E. N.; Tran, N. V.; Vermilion, C.; Villaplana, M.; Vos, M.; Wacker, J.; Walsh, J.

2014-03-01

385

Neoclassical transport in stellarators  

SciTech Connect

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.

Ho, D.D.M.; Kulsrud, R.M.

1985-09-01

386

Stellar population synthesis diagnostics  

E-print Network

A quantitative method is presented to compare observed and synthetic colour-magnitude diagrams (CMDs). The method is based on a chi^2 merit function for a point (c_i,m_i) in the observed CMD, which has a corresponding point in the simulated CMD within n*sigma(c_i,m_i) of the error ellipse. The chi^2 merit function is then combined with the Poisson merit function of the points for which no corresponding point was found within the n*sigma(c_i,m_i) error ellipse boundary. Monte-Carlo simulations are presented to demonstrate the diagnostics obtained from the combined (chi^2, Poisson) merit function through variation of different parameters in the stellar population synthesis tool. The simulations indicate that the merit function can potentially be used to reveal information about the initial mass function. Information about the star formation history of single stellar aggregates, such as open or globular clusters and possibly dwarf galaxies with a dominating stellar population, might not be reliable if one is dealing with a relatively small age range.

Y. K. Ng

1998-03-30

387

Looking for the Sunyaev-Zel'dovich effect in the Virgo cluster from WMAP and ROSAT data  

NASA Astrophysics Data System (ADS)

Wilkinson Microwave Anisotropy Probe (WMAP) observations at millimetre wavelengths are sensitive to the Sunyaev-Zel'dovich (SZ) effect in galaxy clusters. Among all the objects in the sky, the Virgo cluster is expected to provide the largest integrated signal. Based on models compatible with the X-ray emission observed in the ROSAT All-Sky Survey, we predict an approximately 2? detection of the SZ effect from Virgo in the WMAP 3-yr data. Our analysis reveals a 3? signal on scales of 5°, although the frequency dependence deviates from the theoretical expectation for the SZ effect. The main sources of uncertainty are instrumental noise, and, most importantly, possible contamination from point sources and diffuse back/foregrounds. In particular, a population of unresolved extragalactic sources in Virgo would explain the observed intensity and frequency dependence. In order to resolve this question, one needs to wait for experiments like Planck to achieve the required accuracy.

Diego, J. M.; Ascasibar, Y.

2008-10-01

388

Chemical fingerprinting of stellar populations in the Milky Way halo  

NASA Astrophysics Data System (ADS)

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.

Chou, Mei-Yin

2015-03-01

389

Stellar Vampires Unmasked  

NASA Astrophysics Data System (ADS)

Astronomers have found possible proofs of stellar vampirism in the globular cluster 47 Tucanae. Using ESO's Very Large Telescope, they found that some hot, bright, and apparently young stars in the cluster present less carbon and oxygen than the majority of their sisters. This indicates that these few stars likely formed by taking their material from another star. "This is the first detection of a chemical signature clearly pointing to a specific scenario to form so-called 'Blue straggler stars' in a globular cluster", said Francesco Ferraro, from the Astronomy Department of Bologna University (Italy) and lead-author of the paper presenting the results. Blue stragglers are unexpectedly young-looking stars found in stellar aggregates, such as globular clusters, which are known to be made up of old stars. These enigmatic objects are thought to be created in either direct stellar collisions or through the evolution and coalescence of a binary star system in which one star 'sucks' material off the other, rejuvenating itself. As such, they provide interesting constraints on both binary stellar evolution and star cluster dynamics. To date, the unambiguous signatures of either stellar traffic accidents or stellar vampirism have not been observed, and