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1

The Origin of the Virgo Stellar Substructure  

NASA Astrophysics Data System (ADS)

We present three-dimensional space velocities of stars selected to be consistent with membership in the Virgo stellar substructure. Candidates were selected from SA 103, a single 40' × 40' field from our proper-motion (PM) survey in Kapteyn's Selected Areas (SAs), based on the PMs, Sloan Digital Sky Survey (SDSS) photometry, and follow-up spectroscopy of 215 stars. The signature of the Virgo substructure is clear in the SDSS color-magnitude diagram (CMD) centered on SA 103, and 16 stars are identified that have high Galactocentric-frame radial velocities (V GSR > 50 km s-1) and lie near the CMD locus of Virgo. The implied distance to the Virgo substructure from the candidates is 14 ± 3 kpc. We derive mean kinematics from these 16 stars, finding a radial velocity V GSR = 153 ± 22 km s-1 and proper motions (??cos ?, ??) = (- 5.24, -0.91) ± (0.43, 0.46) mas yr-1. From the mean kinematics of these members, we determine that the Virgo progenitor was on an eccentric (e ~ 0.8) orbit that recently passed near the Galactic center (pericentric distance Rp ~ 6 kpc). This destructive orbit is consistent with the idea that the substructure(s) in Virgo originated in the tidal disruption of a Milky Way satellite. N-body simulations suggest that the entire cloud-like Virgo substructure (encompassing the "Virgo Overdensity" and the "Virgo Stellar Stream") is likely the tidal debris remnant from a recently disrupted massive (~109 M ?) dwarf galaxy. The model also suggests that some other known stellar overdensities in the Milky Way halo (e.g., the Pisces Overdensity and debris near NGC 2419 and SEGUE 1) are explained by the disruption of the Virgo progenitor.

Carlin, Jeffrey L.; Yam, William; Casetti-Dinescu, Dana I.; Willett, Benjamin A.; Newberg, Heidi J.; Majewski, Steven R.; Girard, Terrence M.

2012-07-01

2

The Virgo Stellar Stream: Extended sample  

NASA Astrophysics Data System (ADS)

We have completed a spectroscopic study of the “12.4 hr clump”, the second largest substructure in the Quasar Equatorial Survey Team (QUEST) catalog. First discovered as an over-density of RR Lyrae stars (Vivas et al. 2001, ApJL 554 33), the region containing the “12.4 hr clump” has generated much interest (Newberg et al. (2002), Martinez-Delgado et al. (2007), Juric et al. (2008), amongst many others). Our first spectroscopic study of this clump revealed the presence of a sharp peak in the radial velocity histogram for the candidate stars (Duffau et al. 2006). The combination of this result and metal abundance estimates for the sample was then interpreted as a signature of the presence of a stellar stream within the clump. This sub-structure was named the “Virgo Stellar Stream” (VSS), given its location in the direction of the Virgo Constellation, at approximately 20 kpc from the Sun. Several other groups have studied this region and have suggested that the over-density containing the VSS could extend to larger areas of the sky (outside QUEST's observing range). We present the complete spectroscopic follow up of the clump candidates present in QUEST and the composite of the studies we performed along the same l.o.s., including data at brighter magnitudes (Vivas et al. 2008). Our study confirmed the nature of the VSS, revealed its likely extent within the QUEST survey and defined a number of its relevant properties.

Duffau, S.; Vivas, A. K.; Zinn, R.; Méndez, R. A.; Ruiz, M. T.

2010-04-01

3

A comprehensive view of the Virgo stellar stream  

NASA Astrophysics Data System (ADS)

To explore the complex halo substructure that has been reported in the direction of the Virgo constellation, radial velocities and metallicities have been measured for 82 RR Lyrae stars (RRLS) that were identified by the QUEST survey. These stars are distributed over 90 square degrees of the sky, and lie from 4 to 23 kpc from the Sun. Using an algorithm for finding groups in phase space and modeling the smooth halo component in the region, we identified the 5 most significant RRLS groups, some of which were previously known or suspected. We have examined the SEKBO and the Catalina catalog of RRLS (with available spectroscopic measurements), as well as the bright QUEST RRLS sample, the catalog of Red Giant stars from the Spaghetti survey, and three recent catalogs of blue horizontal branch (BHB) stars, for stars that may be related to the QUEST RRLS groups. The most significant group of RRLS is the Virgo stellar stream (VSS) identified here as group A, which is composed of at least 10 RRLS and 3 BHB stars. It has a mean distance of 19.6 kpc and a mean radial velocity Vgsr = 128 km s-1, as estimated from its RRLS members. With the revised velocities reported here, there is no longer an offset in velocity between the RRLS in the VSS and the prominent peak in the velocities of main-sequence turnoff stars reported by other researchers in the same direction and at a similar distance (known as S297+63-20.5). The location in phase space of two other groups (F and H) suggests a possible connection with the VSS, which cannot be discarded at this point, although the turnoff colors of the VSS and group H, as identified from other works, suggest they might be composed of different populations. Two more groups, B and D, are found at mean distances of 19.0 and 5.7 kpc, and mean radial velocities of Vgsr = -94 and 32 km s-1. The latter is the more numerous in terms of total members, as well as the more extended in RA. A comparison with the latest model of the disruption of the Sagittarius dwarf, indicates that none of the above groups is related to it. Rather than being the result of a single accretion event, the excess of stars observed in Virgo appears to be composed of several halo substructures along the same line of sight. Figure 6 is available in electronic form at http://www.aanda.orgFull Tables 5, 6, and 9 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/566/A118

Duffau, Sonia; Vivas, A. Katherina; Zinn, Robert; Méndez, René A.; Ruiz, María T.

2014-06-01

4

Quantifying Kinematic Substructure in the Milky Way's Stellar Halo  

NASA Astrophysics Data System (ADS)

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

Xue, Xiang-Xiang; Rix, Hans-Walter; Yanny, Brian; Beers, Timothy C.; Bell, Eric F.; Zhao, Gang; Bullock, James S.; Johnston, Kathryn V.; Morrison, Heather; Rockosi, Constance; Koposov, Sergey E.; Kang, Xi; Liu, Chao; Luo, Ali; Lee, Young Sun; Weaver, Benjamin A.

2011-09-01

5

Stellar Populations and Radial Migrations in Virgo Disk Galaxies  

NASA Astrophysics Data System (ADS)

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 ("U-shapes") 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 (~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, Stéphane; Sánchez-Blázquez, Patricia; McDonald, Michael

2012-10-01

6

The stellar populations and evolution of Virgo cluster galaxies  

NASA Astrophysics Data System (ADS)

Using a combination of optical and near-infrared photometry, we have studied both the resolved and integrated stellar populations for a sample of Virgo cluster galaxies spanning the full range of galaxian parameters. The derived stellar population properties are compared against galaxy structural and environmental measures to gauge the importance of these factors in establishing galaxy star formation histories and chemical evolution. Although galaxy colours do not uniquely probe a galaxy's star formation history, meaningful results may be obtained if considered in a relative sense. We find that colour profiles reflect variations in both stellar age and metallicity within galaxies. We also uncover systematic variations in colour gradients, and thus age/metallicity gradients, along the Hubble sequence, such that age and metallicity gradients become increasingly negative toward later Hubble types. However, only weak correlations exist between galaxies' stellar populations and their structure and environment. The correlations we find suggest that the star formation histories of gas-rich galaxies are strongly influenced by gas removal within the cluster, while their chemical evolution is due to a combination of stellar mass-dependent enrichment and outflow retention. The assembly of gas-poor giant galaxies is consistent with a hierarchical scenario wherein gas-rich mergers dominate by number. Gas-poor dwarfs differ from the giants, however, appearing as the product of environmentally-driven evolution. Spiral galaxies bridge the dwarf-giant gap, whereby merging and gas-stripping signatures are imprinted in their stars. Early-type spirals seem to have fallen into the cluster sooner than the later types, thereby ceasing star formation in their disks at earlier epochs. The bulges of both types, however, appear to have grown via merging. The nature of this merging (minor versus major) remains unknown. Irregular galaxies exhibit signs of a recent gravitational encounter that has redistributed both their stars and gas, the latter of which caused recent star formation.

Roediger, Joel C.

2009-11-01

7

A PHOTOMETRIC METALLICITY ESTIMATE OF THE VIRGO STELLAR OVERDENSITY  

SciTech Connect

We determine photometric metal abundance estimates for individual main-sequence stars in the Virgo Overdensity (VOD), which covers almost 1000 deg{sup 2} on the sky, based on a calibration of the metallicity sensitivity of stellar isochrones in the gri filter passbands using field stars with well-determined spectroscopic metal abundances. Despite the low precision of the method for individual stars, we derive [Fe/H] = -2.0 +- 0.1(internal) +- 0.5(systematic) for the metal abundance of the VOD from photometric measurements of 0.7 million stars in the northern Galactic hemisphere with heliocentric distances from approx10 kpc to approx20 kpc. The metallicity of the VOD is indistinguishable, within DELTA[Fe/H] <= 0.2, from that of field halo stars covering the same distance range. This initial application suggests that the Sloan Digital Sky Survey gri passbands can be used to probe the properties of main-sequence stars beyond approx10 kpc, complementing studies of nearby stars from more metallicity-sensitive color indices that involve the u passband.

An, Deokkeun [Infrared Processing and Analysis Center, California Institute of Technology, Mail Stop 100-22, Pasadena, CA 91125 (United States); Johnson, Jennifer A.; Pinsonneault, Marc H.; Terndrup, Donald M.; Masseron, Thomas [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Beers, Timothy C.; Lee, Young Sun [Department of Physics and Astronomy and JINA (Joint Institute for Nuclear Astrophysics), Michigan State University, E. Lansing, MI 48824 (United States); Delahaye, Franck [Service d'Astrophysique, CEA/DSM/IRFU/SAp, CEA Saclay, 91191 Gif-sur-Yvette Cedex (France); Yanny, Brian, E-mail: deokkeun@ipac.caltech.ed [Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States)

2009-12-10

8

Probing Stellar Populations in the Virgo and Fornax Clusters with Infrared Surface Brightness Fluctuations  

NASA Astrophysics Data System (ADS)

Surface brightness fluctuations (SBF) are a useful tool for measuring extragalactic distances. At infrared wavelengths, SBF break the age-metallicity degeneracy and are useful for probing the properties of the most luminous stars in a galaxy, even when individual stars are not resolved. We present a detailed comparison of F110W and F160W SBF measurements made using the Hubble Space Telescope WFC3/IR camera to a variety of stellar population models, including those with solar-scaled and alpha-enhanced compositions and models incorporating convective core overshoot for younger populations. We use these model comparisons to assess the star formation histories of 16 galaxies spanning a wide range in color and luminosity in the Virgo and Fornax clusters, measured as a function of distance from the galaxy center in elliptical apertures. We discuss the implications of population variations on the fluctuation magnitudes and distance measurements.

Jensen, Joseph B.; Gibson, Zachary J; Lee, Hyun-chul; Blakeslee, John

2014-06-01

9

Stellar Age versus Mass of Early-Type Galaxies in the Virgo Cluster  

NASA Astrophysics Data System (ADS)

The flux excess of elliptical galaxies in the far-ultraviolet can be reproduced by population synthesis models when accounting for the population of old, hot, helium-burning subdwarf stars. This has been achieved by Han and coworkers through a quantitative model of binary stellar evolution. Here, we compare the resulting evolutionary population synthesis model to the GALEX far-near ultraviolet colors (FUV-NUV) of Virgo Cluster early-type galaxies that were published by Boselli and coworkers. FUV-NUV is reddest at about the dividing luminosity of dwarf and giant galaxies, and becomes increasingly blue for both brighter and fainter luminosities. This behavior can be easily explained by the binary model with a continuous sequence of longer duration and later truncation of star formation at lower galaxy masses. Thus, in contrast to previous conclusions, the GALEX data do not require a dichotomy between the stellar population properties of dwarfs and giants. Their apparently opposite behavior in FUV-NUV occurs naturally when the formation of hot subdwarfs through binary evolution is taken into account.

Lisker, Thorsten; Han, Zhanwen

2008-06-01

10

PROPER MOTIONS IN KAPTEYN SELECTED AREA 103: A PRELIMINARY ORBIT FOR THE VIRGO STELLAR STREAM  

SciTech Connect

We present absolute proper motions in Kapteyn Selected Area (SA) 103. This field is located 7 deg. west of the center of the Virgo Stellar Stream (VSS), and has a well-defined main sequence representing the stream. In SA 103, we identify one RR Lyrae star as a member of the VSS, according to its metallicity, radial velocity, and distance. VSS candidate turnoff and subgiant stars have proper motions consistent with that of the RR Lyrae star. The three-dimensional velocity data imply an orbit with a pericenter of {approx}11 kpc and an apocenter of {approx}90 kpc. Thus, the VSS comprises tidal debris found near the pericenter of a highly destructive orbit. Examining the six globular clusters at distances larger than 50 kpc from the Galactic center, and the proposed orbit of the VSS, we find one tentative association, NGC 2419. We speculate that NGC 2419 is possibly the nucleus of a disrupted system of which the VSS is a part.

Casetti-Dinescu, Dana I.; Girard, Terrence M.; Van Altena, William F. [Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Majewski, Steven R.; Carlin, Jeffrey L. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Vivas, A. Katherina [Centro de Investigaciones de Astronomia (CIDA), Apartado Postal 264, Merida 5101-A (Venezuela, Bolivarian Republic of); Wilhelm, Ronald [Department of Physics, Texas Tech University, Lubbock, TX 79409 (United States); Beers, Timothy C. [Department of Physics and Astronomy, Center for the Study of Cosmic Evolution (CSCE), and Joint Institution for Nuclear Astrophysics (JINA), Michigan State University, East Lansing, MI 48824 (United States)

2009-08-10

11

The Virgo Stellar Overdensity: Mapping the Infall of the Sagittarius Tidal Stream onto the Milky Way Disk  

NASA Astrophysics Data System (ADS)

The recently discovered Virgo stellar overdensity, which extends over ~1000 deg2 perpendicular to the Galactic disk plane (7 kpcstellar overdensity is a confirmation of theoretical model predictions in which the leading arm of the Sagittarius stream crosses the Milky Way plane in the solar neighborhood. Radial velocity measurements are needed to confirm this association and to further constrain the shape of the Milky Way dark matter halo through a new generation of theoretical models. If the identification of the Virgo overdensity and the Sagittarius leading arm is correct, we predict highly negative radial velocities for the stars of the Virgo overdensity. The detection of this new portion of the Sagittarius tidal stream would represent an excellent target for ongoing and future kinematic surveys and for dark matter direct detection experiments in the proximity of the Sun.

Martínez-Delgado, David; Peñarrubia, Jorge; Juri?, Mario; Alfaro, Emilio J.; Ivezi?, Zeljko

2007-05-01

12

Extending the Virgo Stellar Stream with SEKBO Survey RR Lyrae Stars  

NASA Astrophysics Data System (ADS)

A subset of the RR Lyrae (RRL) candidates identified from the Southern Edgeworth-Kuiper Belt Object (SEKBO) survey data have been followed up photometrically (n = 106) and spectroscopically (n = 51). Period and light curve fitting reveals a 24% ± 7% contamination of SEKBO survey data by non-RRLs. This paper focuses on the region of the Virgo Stellar Stream (VSS), particularly on its extension to the south of the declination limits of the Sloan Digital Sky Survey and of the Quasar Equatorial Survey Team RRL survey. The distribution of radial velocities in the Galactic standard of rest frame (V GSR) for the 11 RRLs observed in the VSS region has two apparent peaks. The larger peak coincides with the four RRLs having langV GSRrang = 127 ± 10 km s-1 and dispersion ? = 27 km s-1, marginally larger than that expected from the errors alone. The two type ab RRLs in this group have lang[Fe/H]rang = -1.95 ± 0.1. Both the radial velocities and metal abundances are consistent with membership in the VSS. The second velocity peak, which occurs at langV GSRrang = -175 ± 10 km s-1 may indicate the presence of stars from the Sgr leading tidal tail, which is expected to have large negative velocities in this region. We explore the spatial extent of the VSS by constructing luminosity functions from the SEKBO data and comparing them to data synthesized with the Besançon Galactic model. Analysis of the excess over the model predictions reveals the VSS as a large (~760 deg2) overdensity centered at roughly (R.A., decl.) ~ (186°, -4°), spanning a length of ~15 kpc in projection, assuming a heliocentric distance of 19 kpc. The data reveal for the first time the more southern regions of the stream and trace it to decl. ?-15° and Galactic latitudes as low as b ? 45°.

Prior, Sayuri L.; Da Costa, G. S.; Keller, Stefan C.; Murphy, Simon J.

2009-01-01

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

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

SciTech Connect

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

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

2013-06-01

15

A new study of stellar substructures in the Fornax dwarf spheroidal galaxy  

NASA Astrophysics Data System (ADS)

Using deep V,B-V wide-field photometry, we have conducted a new study of stellar over-densities in the Fornax dwarf spheroidal galaxy by determining detailed star formation histories from colour-magnitude diagram analysis. We have concentrated on the relatively young stellar component (<4 Gyr old), and compared this to the underlying Fornax field population. We have studied in more detail the previously known inner shell-like structure and shown that it has a well-defined age-metallicity relation with a peak at -1.5 Gyr, [Fe/H] = -0.6 dex. Comparison to the Fornax centre shows that the over-dense feature is consistent with the age-metallicity relation of young field stars, and likely formed from Fornax gas. This is consistent with a scenario in which the over-density was formed by the re-accretion of previously expelled gas. We have also discovered a new stellar over-density, located 0.3 degrees (0.7 kpc) from the centre, which is only 100 Myr old, with solar metallicity. This feature constitutes some of the youngest, most metal-rich stars stars observed in Fornax to date. It is unclear how the young over-density was formed, although the age and metallicity of stars suggest this feature may represent the last star formation activity of the Fornax dSph. The National Optical Astronomy Observatory is operated by AURA, Inc., under cooperative agreement with the National Science Foundation.

de Boer, T. J. L.; Tolstoy, E.; Saha, A.; Olszewski, E. W.

2013-03-01

16

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

17

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

18

Intense look at Virgo Southern Extension  

NASA Astrophysics Data System (ADS)

We collected data on radial velocities and distances of galaxies to elucidate structure and kinematics of the filament attached to the Virgo cluster from south. In the region RA = [12{. ^{ {h}}}5{-}13{. ^{ {h}}}5], Dec. = [-20°,0°] there are 171 galaxies with radial velocities VLG < 2000 km s-1, and 98 of them have distance estimates. This galaxy cloud, called as `Virgo Southern Extension', is situated just on the edge of the Virgo `zero-velocity surface'. The mean distance to Virgo SEx, 17 ± 2 Mpc, and the average radial velocity, 1172 ± 23 km s-1, are very close to the Virgo cluster ones. In supergalactic coordinates the Virgo SEx dimensions are 15 × 7 × 2 Mpc, where the major axis is directed along the line of sight, the second major axis is directed towards the Virgo core and the minor one is perpendicular to the supergalactic plane. This flattened cloud consists of a dozen virialized groups with the total K-band luminosity of 1.7 × 1012 L? and the total virial mass of 6.3 × 1013 M?, having a typical dark matter-to-stellar matter ratio of 37. The Hubble diagram for Virgo SEx galaxies exhibits a tendency of a Z-shaped wave with a velocity amplitude of ˜250 km s-1 that may be caused by a mass overdensity of ˜6 × 1013 M?, and in order of magnitude agrees with the sum of virial masses of the groups.

Karachentsev, I. D.; Nasonova, O. G.

2013-03-01

19

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

20

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

21

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

22

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

23

Multifrequency surveys of the Virgo cluster: ALFALFA, HeViCS, SMAKCED, NGVS, GUViCS  

NASA Astrophysics Data System (ADS)

The Virgo cluster, the largest nearby concentration of galaxies, is the target of several multifrequency surveys aimed at studying the effects of the environment on galaxy evolution. These blind or pointed surveys are: the Arecibo Legacy Fast ALFA Survey (ALFALFA; PI. R. Giovanelli), the Herschel Virgo Cluster Survey (HeViCS; PI J. Davies), the Stellar content, MAss and Kinematics of Cluster Early-type Dwarfs (SMAKCED, PI T. Lisker), the Next Generation Virgo Cluster Survey (NGVS; PI L. Ferrarese) and the GALEX UV Virgo Cluster Survey (GUViCS; PI A. Boselli). I briefly describe the surveys mentioning some of the most interesting results obtained so far.

Boselli, A.

2012-12-01

24

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

25

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

26

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

27

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

SciTech Connect

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

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

2013-04-20

28

Sub-structures in the inner halo of the Milky Way  

NASA Astrophysics Data System (ADS)

We present a spectroscopic study of a sample of 238 RR Lyrae stars, from the QUEST survey, located in the Galactic halo at distances between 4 and 20 kpc from the Sun. Combining their spatial position and kinematics we were able to identify sub-structures in this part of the halo. Some of those sub-structures may be associated with known halo features like the Virgo Overdensity, the Hercules-Aquila Cloud, and the Anticenter Stream.

Vivas, A. K.; Zinn, R.; Duffau, S.; Jaffé, Y.

2012-02-01

29

Stellar  

NASA Technical Reports Server (NTRS)

This eerie, dark structure, resembling an imaginary sea serpent's head, is a column of cool molecular hydrogen gas (two atoms of hydrogen in each molecule) and dust that is an incubator for new stars. The stars are embedded inside finger-like protrusions extending from the top of the nebula. Each 'fingertip' is somewhat larger than our own solar system. The pillar is slowly eroding away by the ultraviolet light from nearby hot stars, a process called 'photoevaporation.' As it does, small globules of especially dense gas buried within the cloud is uncovered. These globules have been dubbed 'EGGs' -- an acronym for 'Evaporating Gaseous Globules.' The shadows of the EGGs protect gas behind them, resulting in the finger-like structures at the top of the cloud. Forming inside at least some of the EGGs are embryonic stars -- stars that abruptly stop growing when the EGGs are uncovered and they are separated from the larger reservoir of gas from which they were drawing mass. Eventually the stars emerge, as the EGGs themselves succumb to photoevaporation. The stellar EGGS are found, appropriately enough, in the 'Eagle Nebula' (also called M16 -- the 16th object in Charles Messier's 18th century catalog of 'fuzzy' permanent objects in the sky), a nearby star-forming region 7,000 light-years away in the constellation Serpens. The picture was taken on April 1, 1995 with the Hubble Space Telescope Wide Field and Planetary Camera 2. The color image is constructed from three separate images taken in the light of emission from different types of atoms. Red shows emission from singly-ionized sulfur atoms. Green shows emission from hydrogen. Blue shows light emitted by doubly-ionized oxygen atoms.

1995-01-01

30

The Herschel Virgo Cluster Survey - XIV. Transition-type dwarf galaxies in the Virgo cluster  

NASA Astrophysics Data System (ADS)

We use dust scaling relations to investigate the hypothesis that Virgo cluster transition-type dwarfs are infalling star-forming field galaxies, which is argued based on their optical features (e.g. discs, spiral arms and bars) and kinematic properties similar to late-type galaxies. After their infall, environmental effects gradually transform them into early-type galaxies through the removal of their interstellar medium and quenching of all star formation activity. In this paper, we aim to verify whether this hypothesis holds using far-infrared diagnostics based on Herschel observations of the Virgo cluster taken as part of the Herschel Virgo Cluster Survey. We select transition-type objects in the nearest cluster, Virgo, based on spectral diagnostics indicative for their residual or ongoing star formation. We detect dust (Md ˜ 105-6 M?) in 36 per cent of the transition-type dwarfs located on the high end of the stellar mass distribution. This suggests that the dust reservoirs present in non-detections fall just below the Herschel detection limit (?1.1 × 105 M?). Dust scaling relations support the hypothesis of a transformation between infalling late-type galaxies to quiescent low-mass spheroids governed by environmental effects, with dust-to-stellar mass fractions for transition-type dwarfs in between values characteristic for late-type objects and the lower dust fractions observed in early-type galaxies. Several transition-type dwarfs demonstrate blue central cores, hinting at the radially outside-in removal of gas and quenching of star formation activity. The fact that dust is also confined to the inner regions suggests that metals are stripped in the outer regions along with the gas. In the scenario of most dust being stripped from the galaxy along with the gas, we argue that the ejected metals by transition-type dwarfs significantly contribute to the enrichment of the intracluster medium over the lifetime of the Virgo cluster. The accretion of gas through tidal interactions and re-ignition of star formation in the centres of transition-type dwarfs could provide an alternative explanation for the observed dust scaling relations and blue central cores.

De Looze, Ilse; Baes, Maarten; Boselli, Alessandro; Cortese, Luca; Fritz, Jacopo; Auld, Robbie; Bendo, George J.; Bianchi, Simone; Boquien, Médéric; Clemens, Marcel; Ciesla, Laure; Davies, Jonathan; di Serego Alighieri, Sperello; Grossi, Marco; Jones, Anthony; Madden, Suzanne C.; Pappalardo, Ciro; Pierini, Daniele; Smith, Matthew W. L.; Verstappen, Joris; Vlahakis, Catherine; Zibetti, Stefano

2013-12-01

31

Diffuse Tidal Structures in the Halos of Virgo Ellipticals  

NASA Astrophysics Data System (ADS)

We use deep V-band surface photometry of five of the brightest elliptical galaxies in the Virgo Cluster to search for diffuse tidal streams, shells, and plumes in their outer halos (r>50 kpc). We fit and subtract elliptical isophotal models from the galaxy images to reveal a variety of substructure, with surface brightnesses in the range ? V = 26-29 mag arcsec-2. M49 possesses an extended, interleaved shell system reminiscent of the radial accretion of a satellite companion, while M89's complex system of shells and plumes suggests a more complicated accretion history involving either multiple events or a major merger. M87 has a set of long streamers as might be expected from stripping of low luminosity dwarfs on radial orbits in Virgo. M86 also displays a number of small streams indicative of stripping of dwarf companions, but these comprise much less luminosity than those of M87. Only M84 lacks significant tidal features. We quantify the photometric properties of these structures, and discuss their origins in the context of each galaxy's environment and kinematics within the Virgo Cluster.

Janowiecki, Steven; Mihos, J. Christopher; Harding, Paul; Feldmeier, John J.; Rudick, Craig; Morrison, Heather

2010-06-01

32

H? Morphologies and Environmental Effects in Virgo Cluster Spiral Galaxies  

NASA Astrophysics Data System (ADS)

We describe the various H? morphologies of Virgo Cluster and isolated spiral galaxies and associate the H? morphologies with the types of environmental interactions that have altered the cluster galaxies. The spatial distributions of H? and R-band emission are used to divide the star formation morphologies of the 52 Virgo Cluster spiral galaxies into several categories: normal (37%), anemic (6%), enhanced (6%), and (spatially) truncated (52%). Truncated galaxies are further subdivided on the basis of their inner star formation rates into truncated/normal (37%), truncated/compact (6%), truncated/anemic (8%), and truncated/enhanced (2%). The fraction of anemic galaxies is relatively small (6%-13%) in both environments, suggesting that starvation is not a major factor in the reduced star formation rates of Virgo spiral galaxies. The majority of Virgo spiral galaxies have their H? disks truncated (52%), whereas truncated H? disks are rarer in isolated galaxies (12%). Most of the H?-truncated galaxies have relatively undisturbed stellar disks and normal to slightly enhanced inner disk star formation rates, suggesting that intracluster medium-interstellar medium (ICM-ISM) stripping is the main mechanism causing the reduced star formation rates of Virgo spiral galaxies. Several of the truncated galaxies are peculiar, with enhanced central star formation rates, disturbed stellar disks, and barlike distributions of luminous H II complexes inside the central 1 kpc but no star formation beyond, suggesting that recent tidal interactions or minor mergers have also influenced their morphology. Two highly inclined H?-truncated spiral galaxies have numerous extraplanar H II regions and are likely in an active phase of ICM-ISM stripping. Several spiral galaxies have one-sided H? enhancements at the outer edge of their truncated H? disks, suggesting modest local enhancements in their star formation rates due to ICM-ISM interactions. Low-velocity tidal interactions and perhaps outer cluster H I accretion seem to be the triggers for enhanced global star formation in four Virgo galaxies. These results indicate that most Virgo spiral galaxies experience ICM-ISM stripping, many experience significant tidal effects, and many experience both.

Koopmann, Rebecca A.; Kenney, Jeffrey D. P.

2004-10-01

33

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

34

Substructure Discovery in SUBDUE.  

National Technical Information Service (NTIS)

This paper describes the substructure discovery method used in the SUBDUE system. The method involves a computationally constrained best-first search guided by four heuristics: cognitive savings, compactness, connectivity and coverage. The two main proces...

L. B. Holder

1988-01-01

35

Red Giants, Planetary Nebulae, and the Properties of Virgo's Intracluster Stars  

NASA Astrophysics Data System (ADS)

Intracluster starlight can be a powerful probe of the structure and evolutionary state of galaxy clusters. Recently, this field of study has been revolutionized by the ground-based discovery of intracluster planetary nebulae {IPN} in the Virgo and Fornax Clusters, and by the detection of Virgo's intracluster red giants {IRG} by HST. These two measurements should complement each other: ground-based IPN surveys can map out the distribution and kinematics of the intracluster stars, while HST IRG measurements at specific locations in the cluster can provide details about the stellar population and normalize the IPN data. Unfortunately, the IPN and the IRG observations to date are not complementary. The distribution of intracluster stars in Virgo is clumpy, and the HST IRG field has the misfortune to be located in a region of very low stellar density. Since very few IPN are located in the field, we cannot compare their luminosity function to that of the red giants. We pro po se to use the Hubble Space Telescope to detect IRG stars in regions of the Virgo cluster where the stellar density is high and the IPN luminosity function is well defined. These observations will allow us to calibrate IPN measurements in the rest of the cluster, independently confirm the Virgo Cluster morphology, and place new constraints on the parent populations of the intracluster stars.

Ciardullo, Robin

1999-07-01

36

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

37

Pre-peak ram pressure stripping in the Virgo cluster spiral galaxy NGC 4501  

Microsoft Academic Search

VIVA Hi observations of the Virgo spiral galaxy NGC 4501 are presented. The Hi disk is sharply truncated to the southwest, well within the stellar disk. A region of low surface-density gas, which is more extended than the main Hi disk, is discovered northeast of the galaxy center. These data are compared to existing 6 cm polarized radio continuum emission,

B. Vollmer; M. Soida; A. Chung; J. H. van Gorkom; K. Otmianowska-Mazur; R. Beck; M. Urbanik; J. D. P. Kenney

2008-01-01

38

Substructure system identification and synthesis  

NASA Technical Reports Server (NTRS)

This paper explores the possibility of performing system identification at the substructure level and then synthesizing the results to obtain a mathematical model for the assembled structure. The study here shows that in order to enforce interface compatibility and equilibrium conditions to the substructure test data, it is necessary to place collocated actuator/sensor pair at every interface degree-of-freedom. Procedures for assembling substructure transfer function data, substructure state-space models, and substructure Markov parameters are presented. Testing difficulties and possible solutions are also discussed. A numerical simulation example is included to illustrate the proposed substructure synthesis methods.

Su, Tzu-Jeng; Juang, Jer-Nan

1993-01-01

39

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

40

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

41

Rigid substructure search  

PubMed Central

Motivation: Identifying the location of binding sites on proteins is of fundamental importance for a wide range of applications, including molecular docking, de novo drug design, structure identification and comparison of functional sites. Here we present Erebus, a web server that searches the entire Protein Data Bank for a given substructure defined by a set of atoms of interest, such as the binding scaffolds for small molecules. The identified substructure contains atoms having the same names, belonging to same amino acids and separated by the same distances (within a given tolerance) as the atoms of the query structure. The accuracy of a match is measured by the root-mean-square deviation or by the normal weight with a given variance. Tests show that our approach can reliably locate rigid binding scaffolds of drugs and metal ions. Availability and Implementation: We provide this service through a web server at http://erebus.dokhlab.org. Contact: dokh@unc.edu

Shirvanyants, David; Alexandrova, Anastassia N.; Dokholyan, Nikolay V.

2011-01-01

42

Dust deficiency in Virgo spirals  

Microsoft Academic Search

The results of an analysis of FIR and 21-cm data for a sample of 102 spiral galaxies in the Virgo cluster are presented. It it shown that H-I deficient galaxies have lower 60-micron and 100-micron fluxes and cooler FIR color temperatures than those with normal H-I content. No reasonable selection or systematic effect can account for these variations. These results

Rene Doyon; R. D. Joseph

1989-01-01

43

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

44

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

45

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

46

Nonstandard top substructure  

NASA Astrophysics Data System (ADS)

The top quark, being the heaviest particle of the Standard Model (SM), is a prime candidate of where physics beyond the SM (BSM) might currently hide before our eyes. There are many natural extensions of the SM that rely on top compositeness, and the top quark could follow the paradigm of revealing a substructure when it is probed at high enough momentum transfers. Observing high pT top final states naturally drives us toward boosted hadronic analyses that can be tackled efficiently with jet substructure techniques. In this paper we analyze the prospects of constraining exemplary nonstandard QCD top interactions in this kinematical regime. We correctly include QCD modifications to additional gluon emission off the boosted top quark and keep track of the modified top tagging efficiencies. We conclude that nonstandard top QCD interactions can be formidably constrained at the LHC 14 TeV. Experimental systematic uncertainties are a major obstacle of the described measurement. Unless significantly improved for the 14 TeV run, they will saturate the direct sensitivity to nonresonant BSM top physics at luminosities of around 100/fb.

Englert, Christoph; Gonçalves, Dorival; Spannowsky, Michael

2014-04-01

47

Calculating Transient Vibrations Of Coupled Substructures  

NASA Technical Reports Server (NTRS)

Finite-element, numerical-integration method for estimating transient vibrational response of structure composed of coupled substructures entails less computation. Responses of substructures to external forces and to forces of interaction between substructures computed. Equations of motion of each substructure solved independently. Applicable to any number and configuration of linearly responding substructures and to both determinate and indeterminate boundary conditions at interfaces between substructures. Also applicable to changing interface boundary conditions.

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

1991-01-01

48

The WSRT virgo filament survey  

NASA Astrophysics Data System (ADS)

In the last few years, the realization has emerged that the universal baryons are almost equally distributed by mass in three components: (1) galactic concentrations, (2) a warm-hot intergalactic medium (WHIM) and (3) a diffuse intergalactic medium. These three components are predicted by hydrodynamical simulations and are probed by QSO absorption lines. To observe the WHIM in neutral hydrogen, observations are needed which are deeper than log( NHI) = 18. The WHIM should appear as a Cosmic Web, underlying the galaxies with higher column densities. We have used the WSRT to simulate a filled aperture by observing at very high hour angles, to reach very high column density sensitivity. To achieve even higher image fidelity, an accurate model of the WSRT primary beam was developed. This will be used in the joint deconvolution of the observations. To get a good overview of the distribution and kinematics of the Cosmic Web, a deep survey of 1500 square degrees of sky was undertaken, containing the galaxy filament extending between the Local Group and the Virgo Cluster. The auto-correlation data have been reduced and has an RMS of ? NHI = 4.2 × 10 16 cm -2 over 20 km s -1. Several sources have been tentatively detected, which were previously unknown, as well as an indication for diffuse intergalactic filaments.

Popping, A.; Braun, R.

2007-02-01

49

NASTRAN multipartitioning and one-shot substructuring  

NASA Technical Reports Server (NTRS)

For intermediate size problems where all the data is accessible, the present method of substructuring in three separate phases (for static analysis) is unneccessarily cumbersome. The versatility of NASTRAN's DMAP and internal logic lends itself to finding a practical alternative to these procedures whereby self-contained special-purpose ALTER packages can be written to be run in one pass. Two examples are presented here under the titles of multipartitioning and one-shot substructuring. The flow of multipartitioning resembles that of the present three-phase substructuring. The basic effect is to partition the structure into substructures and operate on each substructure separately. This can be used to reduce the bandwidth of a given problem as well as to store information which will allow a change to be made in one of the substructures in a later run. This latter procedure is carried out in a second program titled one-shot substructuring.

Levy, A.

1973-01-01

50

Searching for gravitational waves from compact binary coalescence using LIGO and Virgo data  

NASA Astrophysics Data System (ADS)

This thesis describes current efforts to search for gravitational waves from compact binary coalescences (CBCs) by the LIGO Scientific Collaboration (LSC) and the Virgo Collaboration. We briefly review the physics of gravitational-wave emission and detection, describing how gravitational waves are emitted from "inspiraling" compact stellar mass objects and how the LSC and Virgo try to detect them using interferometers. Next we review the data-analysis principles used to search for potential signals in the detectors' noise. These principles are employed by "ihope," which is the data-analysis pipeline used to search for CBCs. We describe each step in this pipeline and discuss how interferometer data is stored and examined. Next we present the results from a six-month long search which occurred in early 2007, during LIGO's fifth science run. This is followed by details of tuning studies carried out on LIGO's sixth-, and Virgo's second- and third-, science runs (S6, VSR2, and VSR3), which ran from July 2009 to October 2010. No gravitational waves were detected in these searches. A "blind injection" was performed during S6/VSR3 and detected by our pipeline, however. We detail studies into assigning a statistical significance to this injection. Next we use these studies to show that we can expect to detect gravitational waves with high significance using two detectors in the advanced detector era. Finally, we review some future developments for the CBC pipeline currently being undertaken.

Capano, Collin D.

51

Amuse-virgo: Super-massive Black Holes In Low-mass Spheroids  

NASA Astrophysics Data System (ADS)

I will present the first Chandra results from the AGN Multiwavelength Survey of Early-type galaxies in the Virgo cluster (AMUSE-Virgo). This large program targets 100 early-type Virgo galaxies with Chandra ACIS-S and Spitzer MIPS, with the aim to provide an unbiased census of super-massive black hole (SMBH) activity in the local universe. The sample covers over 4 orders of magnitude in black hole mass as estimated from the mass-velocity dispersion relation, large enough that it can be divided in SMBH mass bins to test whether the nuclear activity duty cycle is mass dependent. I will report on the Chandra observations of the first 16 targets, combined with results from archival data of other, more massive, 16 targets. Hard X-ray emission from a position coincident with the galaxy nucleus is detected in 50 per cent of the galaxies, and ascribed to low-level accretion-powered activity from a SMBH. Two of the detected nuclei are hosted in galaxies with absolute B magnitudes fainter than -18, indicating that supermassive black holes are still being harbored in such faint, low-mass objects. Most importantly, the X-ray active fraction increases with the stellar mass of the host.

Gallo, Elena; AMUSE-Virgo Team

2008-03-01

52

Main-Sequence Star Populations in the Virgo Overdensity Region  

NASA Astrophysics Data System (ADS)

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 ? 24 mag. Using theoretical isochrone fitting, we derive an age of 9.1^{+1.0}_{-1.1} Gyr, a median abundance of [Fe/H] = -0.70^{+0.15}_{-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 (?? ? 265°, B ? ? 13°) are located at a mean distance of 23.3 ± 1.6 kpc and have an age of ~8.2 Gyr, and an abundance of [Fe/H] = -0.67^{+0.16}_{-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] ?-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 & 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 ~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. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Jerjen, H.; Da Costa, G. S.; Willman, B.; Tisserand, P.; Arimoto, N.; Okamoto, S.; Mateo, M.; Saviane, I.; Walsh, S.; Geha, M.; Jordán, A.; Olszewski, E.; Walker, M.; Zoccali, M.; Kroupa, P.

2013-05-01

53

The Virgo 3 km interferometer for gravitational wave detection  

Microsoft Academic Search

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

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

2008-01-01

54

Normal/independent noise in VIRGO data  

NASA Astrophysics Data System (ADS)

The analysis of data taken during the C7 VIRGO commissioning run showed strong deviations from Gaussian noise. In this work, we explore a family of distributions, derived from the hypothesis that heavy tails are an effect of a particular kind of nonstationarity, heterocedasticity (i.e. nonuniform variance), that appear to fit VIRGO noise better than a model based on the assumption of Gaussian noise. To estimate the parameters of the noise process (including the heterogeneous variance) we derived an expectation-maximization algorithm. We show the consequences of non-Gaussianity on the fitting of autoregressive filters and on the derivation of test statistics for matched filter operation. Finally, we apply the new noise model to the fitting of an autoregressive filter for whitening of data.

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

2006-10-01

55

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

56

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.

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

2014-08-01

57

Spitzer IR Colors and ISM Distributions of Virgo Cluster Spirals  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

58

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

NASA Astrophysics Data System (ADS)

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

Lee, Henry

59

Kinematic Disturbances in Rotation Curves among 89 Virgo Galaxies  

Microsoft Academic Search

For 89 (mostly) spirals in the Virgo cluster, we have obtained optical long-slit spectra of the ionized gas. We find: (1) 50% of the Virgo galaxies we observed have regular rotation patterns; 50% exhibit kinematic disturbances ranging from mild to major. Velocity complexities are consistent with those resulting from tidal encounters or accretion. Since kinematic disturbances will to fade within

V. C. Rubin; A. H. Waterman; J. D. P. Kenney

1999-01-01

60

Detection of a radio halo in the Virgo cluster  

Microsoft Academic Search

New Effelsberg 1.4 GHz observations of the central 10° × 10° of the Virgo cluster are presented. NVSS data are used to subtract point sources from our map. During the data reduction process special care is taken (i) to disentangle emission from the North Polar Spur from emission from the Virgo cluster, (ii) to disentangle emission from the strong M

B. Vollmer; W. Reich; R. Wielebinski

2004-01-01

61

Project VIRGO: creation of a surrogate companion for the elderly  

Microsoft Academic Search

The Voice Intelligent Reciprocating Gemutlich Orator (VIRGO) was developed from perceptions of companionship held by persons 65 years of age and older. The knowledge gained from ethnographic interaction with segments of the target population was applied toward the creation of a device. VIRGO is expected to fulfill various companionship needs derived from user-centered research, expert advice and those of the

Timothy Sherwood; Farilee Mintz; Miroslava Vomela

2005-01-01

62

Some approaches to substructure coupling with damping  

NASA Technical Reports Server (NTRS)

Time-domain and frequency-domain methods for coupling substructures with general linear damping are discussed. A time-domain method is presented which employs a state variable representation of each substructure. Also presented is a method which employs frequency-domain coupling together with DFT and FFT transformations to obtain transient response solutions.

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

1986-01-01

63

Substructures in cold dark matter haloes  

NASA Astrophysics Data System (ADS)

We analyse the properties of substructures within dark matter haloes (subhaloes) using a set of high-resolution numerical simulations of the formation of structure in a ?CDM universe. Our simulation set includes 11 high-resolution simulations of massive clusters as well as a region of mean density, allowing us to study the spatial and mass distribution of substructures down to a mass resolution limit of 109h-1 Msolar. We also investigate how the properties of substructures vary as a function of the mass of the `parent' halo in which they are located. We find that the substructure mass function depends at most weakly on the mass of the parent halo and is well described by a power law. The radial number density profiles of substructures are steeper in low mass haloes than in high-mass haloes. More massive substructures tend to avoid the centres of haloes and are preferentially located in the external regions of their parent haloes. We also study the mass accretion and merging histories of substructures, which we find to be largely independent of environment. We find that a significant fraction of the substructures residing in clusters at the present day were accreted at redshifts z < 1. This implies that a significant fraction of present-day `passive' cluster galaxies were still outside the cluster progenitor and were more active at z~ 1.

De Lucia, G.; Kauffmann, G.; Springel, V.; White, S. D. M.; Lanzoni, B.; Stoehr, F.; Tormen, G.; Yoshida, N.

2004-02-01

64

Substructure Allocation in Recursive Interconnection Networks  

Microsoft Academic Search

In a multiuser message passing MIMD sys tem, substructure allocation is an important aspect of sys tem design. In this paper, we present four substructure al location algorithms for a multiuser WK-Recursive network. Two algorithms are bit-map based and two are tree based. The algorithms are compared using simulation.

Ronald Fernandes; Arkady Kanevsky

1993-01-01

65

Substructure methods for structural condition assessment  

NASA Astrophysics Data System (ADS)

It is commonly known that an accurate analysis of a large structure requires an accurate analytical model. This is also true for the inverse analysis of a structural system where measured structural responses are used as input to assess the structural conditions. However, an accurate model of the structure is always not available in practice. Two substructural identification methods are presented in this paper with the structure divided into substructures and with one substructure assessed at one time. In the first method, an accurate finite element model of the whole structure is assumed known. A state space method is applied to identify the external forces acting on the structure, and a damage identification method is then applied to identify the local damages using time domain information. Iterative model updating method based on the measured acceleration in the selected substructure is employed for the assessment. The second identification method requires only the finite element model of the substructure. The interface forces and the external forces acting on the target substructure are all taken as excitations and they are identified in state space. The substructure is then assessed similar to the first method. Since the target substructure for updating consists of a much reduced number of components and the identification problem is more efficient. The validation of the proposed methods is demonstrated by a truss structure with polluted measured accelerations with promising results.

Law, S. S.; Yong, D.

2011-07-01

66

Molecular gas in Virgo cluster spiral galaxies  

NASA Astrophysics Data System (ADS)

The CO(J = 1 yields 0) observations with 45 deg resolution at over 200 positions along the major axes of 42 Virgo cluster spiral galaxies, were obtained using the the FCRAO 14 meter telescope. Although there is a general correlation between the CO flux of a galaxy and the optical diameter, the SCO/D sub opt squared ratio is found to depend on both the morphological type and the H II content. Analyses indicate that for the Sa-Sb and highest luninosity Sc Virgo galaxies, the molecular gas contents and distributions were not strongly affected by the cluster environments. There is a population of H I-rich, lower-luminosity Sc galaxies in the outer cluster with a mean S cub CO/Dopt squared ratio of a factor of 5 less than the other Scs. Galaxies which are H I-deficient by a factor of 10 are gas-deficient by only a factor of 2 to 3, due to the survival of large quantities of molecular gas. The massive-star formation rates, as indicated by H alpha, and far-infrared emission, are also lower by factors of approximately 2 to 3 in galaxies which are H I-deficient by a factor of 10. The CO emission was detected in the center of 2 small-bulge SO-So/a Virgo galaxies which remain undetected in H I. These galaxies exhibit the expected aftereffects of a severe stripping event which occurred approximately 2 x 10 to the 9th years ago, and may be the first known example of stripped spirals in the process of turning into SO-like systems.

Kenney, Jeffrey Dickson

67

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.

68

Parallel Computational Environment for Substructure Optimization  

NASA Technical Reports Server (NTRS)

Design optimization of large structural systems can be attempted through a substructure strategy when convergence difficulties are encountered. When this strategy is used, the large structure is divided into several smaller substructures and a subproblem is defined for each substructure. The solution of the large optimization problem can be obtained iteratively through repeated solutions of the modest subproblems. Substructure strategies, in sequential as well as in parallel computational modes on a Cray YMP multiprocessor computer, have been incorporated in the optimization test bed CometBoards. CometBoards is an acronym for Comparative Evaluation Test Bed of Optimization and Analysis Routines for Design of Structures. Three issues, intensive computation, convergence of the iterative process, and analytically superior optimum, were addressed in the implementation of substructure optimization into CometBoards. Coupling between subproblems as well as local and global constraint grouping are essential for convergence of the iterative process. The substructure strategy can produce an analytically superior optimum different from what can be obtained by regular optimization. For the problems solved, substructure optimization in a parallel computational mode made effective use of all assigned processors.

Gendy, Atef S.; Patnaik, Surya N.; Hopkins, Dale A.; Berke, Laszlo

1995-01-01

69

High chemical abundances in stripped Virgo spiral galaxies  

NASA Technical Reports Server (NTRS)

Based on a comparison of the oxygen abundances in H 2 regions in field and Virgo cluster late type spiral galaxies, Shields, Skillman, & Kennicutt (1991) suggested that the highly stripped spiral galaxies in the Virgo cluster have systematically higher abundances than comparable field galaxies. In April 1991 and May 1992 we used the blue channel spectrograph on the MMT to obtain new observations of 30 H 2 regions in Virgo spiral galaxies. These spectra cover the wavelength range from (O II) lambda 3727 to (S II) lambda 6731. We now have observed at least 4 H II regions in 9 spiral galaxies in the Virgo cluster. Combining (O II) and (O III) line strengths, we calculate the H II region oxygen abundances based on the empirical calibration of Edmunds & Pagel (1984). These observations show: (1) The stripped, low luminosity Virgo spirals (N4689, N4571) truly have abundances characteristic of much more luminous field spirals; (2) Virgo spirals which show no evidence of stripping (N4651, N4713) have abundances comparable to field galaxies; and (3) Evidence for transition galaxies (e.g., N4254, N4321), with marginally stripped disks and marginal abundance enhancements. The new observations presented here confirm the validity of the oxygen over-abundances in the stripped Virgo spirals. Shields et al. (1991) discussed two different mechanisms for producing the higher abundances in the disks of stripped galaxies in Virgo. The first is the supression of infall of near-primordial material, the second is the suppression of radial inflow of metal-poor gas. Distinguishing between the two cases will require more observations of the Virgo cluster spirals and a better understanding of which parameters determine the variation of abundance with radius in field spirals (cf., Garnett & Shields 1987).

Skillman, E. D.; Kennicutt, R. C.; Shields, G. A.

1993-01-01

70

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

71

Underwater Inspection and Repair of Bridge Substructures.  

National Technical Information Service (NTIS)

This synthesis will be of special interest to bridge maintenance engineers and others concerned with the inspection and repair of bridge elements below the waterline. Problems with substructures are identified, and procedures, equipment, and techniques cu...

H. C. Lamberton A. J. Sainz R. A. Crawford W. B. Ogletree J. E. Gunn

1981-01-01

72

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

73

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

74

Unexpected dividends from level 16 automated substructuring  

NASA Technical Reports Server (NTRS)

The automated multistage substructuring capability now available in NASTRAN level 16 is shown to provide a number of unexpected tools for use in both project planning and the structural design cycle. The payoffs in terms of improved design, more reliable results, and confidence are extra benefits added to the savings in cost and schedule that can be realized. To realize these advantages, some old stereotypical assumptions of what substructuring entails are must be challenged.

Field, E. I.

1977-01-01

75

An Introduction to the Virgo Suspension System  

NASA Astrophysics Data System (ADS)

Suspending the mirrors is one of the most crucial tasks in gravitational wave interferometer technology. The performance of the suspensions must provide the required attenuation of seismic noise and reduction of thermal noise, two fundamental limits to the sensitivity of any gravitational wave detector. Moreover, the suspension system must be equipped with sensors and actuators which are used to actively control some relevant degrees of freedom, so to be able to keep the interferometer at its working point (i.e., "locked"). In the first part of this chapter, we deal with the basic principles behind the Superattenuator chains developed in Virgo to reduce the seismic noise. In the second part, we illustrate the techniques to reduce the thermal noise in the detection bandwidth, according to the theory illustrated in Chap. 8 .

Frasconi, Franco; Rapagnani, Piero

76

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

77

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

78

Free-interface methods of substructure coupling for dynamic analysis  

NASA Technical Reports Server (NTRS)

Benfield, et al. (1972) showed that among fixed-interface, free-interface, and hybrid substructure coupling methods, the fixed-interface methods as the most accurate and the free-interface methods are the least accurate. In the present note, a substructure coupling method is proposed which employs free-interface substructure modes supplemented by 'reduced flexibility.' Substructure coupling based on the improved substructure model is discussed, and a numerical comparison with Hou's free-interface method is given. To simplify representation of the method proposed, the substructure equations are developed first for constrained substructures, and then the equations representing substructures with rigid-body modes are given. Finally, the equations for coupling of substructures are derived. Example calculations are included.

Craig, R. R., Jr.; Chang, C.-J.

1976-01-01

79

Stellar Populations  

NASA Astrophysics Data System (ADS)

Stellar populations encode the star-formation history and chemical evolution of a system. This chapter reviews the development of the concept of stellar populations and the current understanding of the resolved stellar populations in the Local Group, with an emphasis on the older stars and serves to introduce the topics of several later chapters.

Wyse, Rosemary F. G.

80

Stellar Illumination  

NSDL National Science Digital Library

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

81

A modal synthesis method for dynamic substructuring  

NASA Astrophysics Data System (ADS)

A new synthesis method for dynamic analysis of structures; discretized by the finite element method; has been developed. The proposed approach is based on using the mode shapes of the free-interface component substructures. In this method, no direct coupling at the interfaces between the different substructures, is assumed. Instead, some separate areas (links) through which the free substructures are coupled to each other are established. The behavior of these link areas can be nonlinear or inelastic without affecting the proposed solution method. Furthermore, an improved technique is suggested for considering the static effect of the truncated higher modes. Numerical examples are presented to demonstrate the advantages and accuracy of the method for linear elastic dynamic systems.

Lou, M.; Ghobarah, A.; Aziz, T. S.

82

Stellar Population Variations in the Milky Way's Stellar Halo  

NASA Astrophysics Data System (ADS)

If the stellar halos of disk galaxies are built up from the disruption of dwarf galaxies, models predict highly structured variations in the stellar populations within these halos. We test this prediction by studying the ratio of blue horizontal branch stars (BHB stars; more abundant in old, metal-poor populations) to main-sequence turn-off stars (MSTO stars; a feature of all populations) in the stellar halo of the Milky Way using data from the Sloan Digital Sky Survey. We develop and apply an improved technique to select BHB stars using ugr color information alone, yielding a sample of ~9000 g < 18 candidates where ~70% of them are BHB stars. We map the BHB/MSTO ratio across ~1/4 of the sky at the distance resolution permitted by the absolute magnitude distribution of MSTO stars. We find large variations of the BHB/MSTO star ratio in the stellar halo. Previously identified, stream-like halo structures have distinctive BHB/MSTO ratios, indicating different ages/metallicities. Some halo features, e.g., the low-latitude structure, appear to be almost completely devoid of BHB stars, whereas other structures appear to be rich in BHB stars. The Sagittarius tidal stream shows an apparent variation in the BHB/MSTO ratio along its extent, which we interpret in terms of population gradients within the progenitor dwarf galaxy. Our detection of coherent stellar population variations between different stellar halo substructures provides yet more support to cosmologically motivated models for stellar halo growth.

Bell, Eric F.; Xue, Xiang Xiang; Rix, Hans-Walter; Ruhland, Christine; Hogg, David W.

2010-12-01

83

Damping models for flexible communications satellites by substructural damping synthesis  

Microsoft Academic Search

Most modern spacecraft are structurally flexible and, moreover, these spacecraft can naturally and profitably be analyzed as a collection of attached substructures (solar array panels, antennas, thermal radiators, etc.). Various models are combined for substructural energy dissipation so that an overall damping model for the spacecraft results. (Four such substructural damping models are discussed, two of which are shown to

P. C. Hughes

1985-01-01

84

An introduction to the possible substructure of quarks and leptons  

Microsoft Academic Search

After an introductory discussion of the history of substructure and of the motivations for examining the possible compositeness of quarks and leptons, experiments which could be relevant to the non-point-like nature of these fermions are reviewed. Where possible the data are used to deduce limits on the substructure energy scale. Starting with very early ideas about quark and lepton substructure,

Louis Lyons

1983-01-01

85

Fracture behaviour of zirconia FPDs substructures.  

PubMed

The purpose of this study was to evaluate the occurrence of superficial flaws after machining and to identify fracture initiation and propagation in three-unit heat-treated machined fixed partial dentures (FPDs) substructures made of hot isostatic pressed (HIPed) yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) after loaded to fracture. Four three-unit HIPed Y-TZP-based FPDs substructures were examined. To evaluate the occurrence of superficial flaws after machining, the surfaces were studied utilizing a fluorescent penetrant method. After static loading to fracture, characteristic fracture features on both mating halves of the fractured specimens were studied using a stereomicroscope and a scanning electron microscope. Grinding grooves were clearly visible on the surfaces of the machined FPDs substructures, but no other flaws could be seen with the fluorescent penetrant method. After loading to fracture, the characteristic fracture features of arrest lines, compression curl, fracture mirror, fracture origin, hackle and twist hackle were detected. These findings indicated that the decisive fracture was initiated at the gingival embrasure of the pontic in association with a grinding groove. Thus, in three-unit heat-treated machined HIPed Y-TZP FPDs substructures, with the shape studied in this study, the gingival embrasure of the pontic seems to be a weak area providing a location for tensile stresses when they are occlusally loaded. In this area, fracture initiation may be located to a grinding groove. PMID:20085616

Kou, W; Sjögren, G

2010-04-01

86

Exploiting Tractable Substructures in Intractable Networks  

Microsoft Academic Search

We develop a refined mean field approximation for inference andlearning in probabilistic neural networks. Our mean field theory,unlike most, does not assume that the units behave as independentdegrees of freedom; instead, it exploits in a principled way theexistence of large substructures that are computationally tractable.To illustrate the advantages of this framework, we show how toincorporate weak higher order interactions into

Lawrence K. Saul; Michael I. Jordan

1995-01-01

87

Uncertainty quantification in experimental frequency based substructuring  

Microsoft Academic Search

Numerical conditioning of the subsystems’ interface flexibility matrix is an important issue in experimental frequency based substructuring (FBS) methods. As this matrix needs to be inverted, it is believed that ill numerical conditioning could severely magnify even small random errors in experimentally obtained subsystems, yielding erroneous FRFs of the coupled system. In this paper a method is introduced with which

S. N. Voormeeren; D. de Klerk; D. J. Rixen

2010-01-01

88

Statistics of substructures in dark matter haloes  

NASA Astrophysics Data System (ADS)

We study the amount and distribution of dark matter substructures within dark matter haloes, using a large set of high-resolution simulations ranging from group-size to cluster-size haloes, and carried out within a cosmological model consistent with Wilkinson Microwave Anisotropy Probe (WMAP) 7-year data. In particular, we study how the measured properties of subhaloes vary as a function of the parent halo mass, the physical properties of the parent halo and redshift. The fraction of halo mass in substructures increases with increasing mass: it is of the order of 5 per cent for haloes with M200˜ 1013 M? and of the order of 10 per cent for the most massive haloes in our sample, with M200˜ 1015 M?. There is, however, a very large halo-to-halo scatter that can be explained only in part by a range of halo physical properties, e.g. concentration. At a given halo mass, less concentrated haloes contain significantly larger fractions of mass in substructures because of the reduced strength of tidal disruption. Most of the substructure mass is located at the outskirts of the parent haloes, in relatively few massive subhaloes. This mass segregation appears to become stronger at increasing redshift, and should reflect into a more significant mass segregation of the galaxy population at different cosmic epochs. When haloes are accreted on to larger structures, their mass is significantly reduced by tidal stripping. Haloes that are more massive at the time of accretion (these should host more luminous galaxies) are brought closer to the centre on shorter time-scales by dynamical friction, and therefore suffer a more significant stripping. The halo merger rate depends strongly on the environment with substructure in more massive haloes suffering more important mergers than their counterparts residing in less massive systems. This should translate into a different morphological mix for haloes of different mass.

Contini, E.; De Lucia, G.; Borgani, S.

2012-03-01

89

Molecular clouds in spiral galaxies in the Virgo cluster  

NASA Astrophysics Data System (ADS)

The present CO observations of the centers of 25 spiral galaxies in the Virgo cluster indicate that the CO luminosity in the central 5 kpc is proportional to the B luminosity in the same region. The CO luminosities in the centers of the Virgo galaxies exhibit a strong correlation with the optical luminosities in the same regions, such that the high luminosity galaxies of a given type have more CO in their centers than do the low luminosity galaxies of the same type. The CO luminosity-B luminosity proportionality confirms the relation previously found in Sc field galaxies.

Young, J. S.

90

Stellarator symmetry  

NASA Astrophysics Data System (ADS)

A simple and general definition of stellarator symmetry is presented and its relation to previous definitions discussed. It is shown that the field-line flow in systems possessing stellarator symmetry is time-reversal invariant if the the toroidal angle is regarded as “time”.

Dewar, R. L.; Hudson, S. R.

1998-01-01

91

Stellar Evolution  

NSDL National Science Digital Library

This Chandra X-Ray Observatory page links to several activities and articles on stellar evolution. It includes an interactive Flash activity featuring simulations of different-mass stars evolving and a detailed "story" of stellar evolution for the interested reader, available in PDF and HTML formats.

2010-05-28

92

fSUB: Normal Mode Analysis with Flexible Substructures  

PubMed Central

In this paper, we report a novel normal mode analysis for supramolecular complexes, named as fSUB. The method models a complex as a group of flexible substructures. The low-frequency substructure modes are first determined with substructures in isolation, and the motions of the whole complex are then calculated based on substructure modes and substructure-substructure interactions. The calculation of modes in fSUB requires modal analysis without initial energy minimization, which is essential for maintaining energetic and structural consistency between substructures and whole complex. Comparing with other coarse-grained methods, such as RTB method, fSUB delivers much more accurate modes for the complex and allows for choice of much larger substructures. The method can also accommodate any type of substructure arrangement including covalent bonds across the interface. In tests on molecular chaperonin GroEL (7350 residues) and HK97 capsid complex (118,092 residues), fSUB was shown to be much more efficient in terms of combined accuracy and demand of computing resource. Our results clearly demonstrated the vital importance of including substructure flexibility in complex modal analysis, as the deformational patterns of substructures were found to play an important role even in the lowest frequency modes of the whole complex.

Lu, Mingyang; Ming, Dengming; Ma, Jianpeng

2012-01-01

93

Substructure model updating through iterative minimization of modal dynamic residual  

NASA Astrophysics Data System (ADS)

This research studies a substructure model updating approach. Requiring modal testing data from only part of a large structure (i.e. a substructure), finite element model parameters for the substructure can be updated. Prior to updating, Craig-Bampton transform is adopted to condense the entire structural model into the substructure (currently being instrumented and to be updated) and the residual structure. Finite element model of the substructure remains at high resolution, while dynamic behavior of the residual structure is approximated using only a limited number of dominant mode shapes. To update the condensed structural model, physical parameters in the substructure and modal parameters of the residual structure are chosen as optimization variables; minimization of the modal dynamic residual is chosen as the optimization objective. An iterative linearization procedure is adopted for efficiently solving the optimization problem. The proposed substructure model updating approach is validated through numerical simulation with two plane structures

Zhu, Dapeng; Dong, Xinjun; Wang, Yang

2014-04-01

94

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

95

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

96

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

97

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

98

Do allopatric male Calopteryx virgo damselflies learn species recognition?  

PubMed Central

There is a growing amount of empirical evidence that premating reproductive isolation of two closely related species can be reinforced by natural selection arising from avoidance of maladaptive hybridization. However, as an alternative for this popular reinforcement theory, it has been suggested that learning to prefer conspecifics or to discriminate heterospecifics could cause a similar pattern of reinforced premating isolation, but this possibility is much less studied. Here, we report results of a field experiment in which we examined (i) whether allopatric Calopteryx virgo damselfly males that have not encountered heterospecific females of the congener C. splendens initially show discrimination, and (ii) whether C. virgo males learn to discriminate heterospecifics or learn to associate with conspecifics during repeated experimental presentation of females. Our experiment revealed that there was a statistically nonsignificant tendency for C. virgo males to show initial discrimination against heterospecific females but because we did not use sexually naïve individuals in our experiment, we were not able to separate the effect of innate or associative learning. More importantly, however, our study revealed that species discrimination might be further strengthened by learning, especially so that C. virgo males increase their association with conspecific females during repeated presentation trials. The role of learning to discriminate C. splendens females was less clear. We conclude that learning might play a role in species recognition also when individuals are not naïve but have already encountered potential conspecific mates.

Kuitunen, Katja; Haukilehto, Elina; Raatikainen, Kaisa J; Hakkarainen, Hanne; Miettinen, Minna; Hogmander, Harri; Kotiaho, Janne S

2012-01-01

99

The magnetic fields of large Virgo Cluster spirals  

Microsoft Academic Search

Context: Because of its proximity the Virgo Cluster is an excellent target for studying interactions of galaxies with the cluster environment. Both the high-velocity tidal interactions and effects of ram pressure stripping by the intracluster gas can be investigated. Aims: Optical and\\/or H I observations do not always show the effects of weak interactions between galaxies and their encounters with

M. Wezgowiec; M. Urbanik; B. Vollmer; R. Beck; K. T. Chyzy; M. Soida; Ch. Balkowski

2007-01-01

100

Do allopatric male Calopteryx virgo damselflies learn species recognition?  

PubMed

There is a growing amount of empirical evidence that premating reproductive isolation of two closely related species can be reinforced by natural selection arising from avoidance of maladaptive hybridization. However, as an alternative for this popular reinforcement theory, it has been suggested that learning to prefer conspecifics or to discriminate heterospecifics could cause a similar pattern of reinforced premating isolation, but this possibility is much less studied. Here, we report results of a field experiment in which we examined (i) whether allopatric Calopteryx virgo damselfly males that have not encountered heterospecific females of the congener C. splendens initially show discrimination, and (ii) whether C. virgo males learn to discriminate heterospecifics or learn to associate with conspecifics during repeated experimental presentation of females. Our experiment revealed that there was a statistically nonsignificant tendency for C. virgo males to show initial discrimination against heterospecific females but because we did not use sexually naïve individuals in our experiment, we were not able to separate the effect of innate or associative learning. More importantly, however, our study revealed that species discrimination might be further strengthened by learning, especially so that C. virgo males increase their association with conspecific females during repeated presentation trials. The role of learning to discriminate C. splendens females was less clear. We conclude that learning might play a role in species recognition also when individuals are not naïve but have already encountered potential conspecific mates. PMID:22822438

Kuitunen, Katja; Haukilehto, Elina; Raatikainen, Kaisa J; Hakkarainen, Hanne; Miettinen, Minna; Högmander, Harri; Kotiaho, Janne S

2012-03-01

101

Thermal effects and their compensation in Advanced Virgo  

Microsoft Academic Search

Thermal effects in the test masses of the gravitational waves interferometric detectors may result in a strong limitation to their operation and sensitivity. Already in initial LIGO and Virgo, these effects have been observed and required the installation of dedicated compensation systems. Based on CO2 laser projectors, the thermal compensators heat the peripheral of the input test masses to reduce

A Rocchi; E Coccia; V Fafone; V Malvezzi; Y Minenkov; L Sperandio

2012-01-01

102

Photodiodes selection for the VIRGO detector, the first step.  

National Technical Information Service (NTIS)

In the framework of the Gravitational Waves detector VIRGO, the photodetector system is under construction. The diodes that will be used must satisfy at the same time quite unusual criteria, among them a good quantum efficiency at a wavelength of 1.06 (mu...

B. Caron A. Dominjon R. Flaminio R. Hermel J. C. Lacotte

1994-01-01

103

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

104

Length Sensing and Control in the Virgo Gravitational Wave Interferometer  

Microsoft Academic Search

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

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

2006-01-01

105

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

106

Galaxy Clusters: Substructure and Mass Systematics  

NASA Astrophysics Data System (ADS)

We calibrate the X-ray measured hydrostatic equilibrium (H.E.) mass and assess the origin of the H.E. mass systematics using 2-D spectrally measured X-ray properties. We obtained that the average X-ray mass derived from H.E. using XMM-Newton data is lower compared to the weak lensing mass from Subaru data for relaxed clusters in a sample of 12 clusters at z~0.2. This is comparable to the expectation of numerical simulations because of the non-thermal pressure support due to turbulence and bulk motions. The gas mass to weak lensing mass ratio shows no dependence on the cluster morphology, which indicates that the gas mass may be a good mass proxy regardless of the cluster dynamical state. To understand the origin of the systematics of the H.E. mass, we investigated 4 nearby clusters, for which the substructure is quantified by the radial fluctuations in the spectrally measured 2-D maps by a cumulative/differential scatter profile relative to the mean profile within/at a given radius. The amplitude of and the discontinuity in the scatter complements 2-D substructure diagnostics, e.g. indicating the most disturbed radial range. There is a tantalizing link between the substructure identified using the scatter of the entropy and pressure fluctuations and the deviation of the H.E. mass relative to the expected mass based on the representative scaling relation, e.g., M-Mgas, particularly at r500-the radius within which the over-density, ?, is 500 with respect to the critical density. This indicates that at larger radii, the systematic error of the H.E. mass may well be caused by substructure.

Zhang, Yu-Ying

2010-07-01

107

Grain Growth and Sub-Structure in Protoplanetary Disks  

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

108

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

109

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

110

Stellar Populations  

NASA Astrophysics Data System (ADS)

This is a summary of my lectures during the 2011 Canary Islands Winter School in Puerto de la Cruz. I give an introduction to the field of stellar populations in galaxies, and highlight some new results. Since the title of the Winter School is Secular Evolution in Galaxies I mostly concentrate on nearby galaxies, which are best suited to study this theme. Of course, the understanding of stellar populations is intimately connected to understanding the formation and evolution of galaxies, one of the great outstanding problems of astronomy. We are currently in a situation where very large observational advances have been made in recent years. Galaxies have been detected up to a redshift of ten. A huge effort has to be made so that stellar population theory can catch up with observations. Since most galaxies are far away, information about them has to come from stellar population synthesis of integrated light. Here I will discuss how stellar evolution theory, together with observations in our Milky Way and Local Group, are used as building blocks to analyse these integrated stellar populations.

Peletier, Reynier F.

2013-10-01

111

Core-collapse supernova enrichment in the core of the Virgo cluster  

NASA Astrophysics Data System (ADS)

Using a deep (574 ks) Chandra observation of M87, the dominant galaxy of the nearby Virgo cluster, we present the best measurements to date of the radial distribution of metals in the central intracluster medium (ICM). Our measurements, made in 36 independent annuli with ˜250 000 counts each, extend out to a radius r˜ 40 kpc and show that the abundance profiles of Fe, Si, S, Ar, Ca, Ne, Mg and Ni are all centrally peaked. Interestingly, the abundance profiles of Si and S - which are measured robustly and to high precision - are even more centrally peaked than Fe, while the Si/S ratio is relatively flat. These measurements challenge the standard picture of chemical enrichment in galaxy clusters, wherein Type Ia supernovae (SN Ia) from an evolved stellar population are thought to dominate the central enrichment. The observed abundance patterns are most likely due to one or more of the following processes: continuing enrichment by winds of a stellar population pre-enriched by core-collapse supernova (SNCC) products; intermittent formation of massive stars in the central cooling core; early enrichment of the low-entropy gas. We also discuss other processes that might have contributed to the observed radial profiles, such as a stellar initial mass function that changes with radius; changes in the pre-enrichment of SNCC progenitors; and a diversity in the elemental yields of SN Ia. Although systematic uncertainties prevent us from measuring the O abundance robustly, indications are that it is about two times lower than predicted by the enrichment models.

Million, E. T.; Werner, N.; Simionescu, A.; Allen, S. W.

2011-12-01

112

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

113

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

114

4. VIEW NORTH, DETAIL OF SUBSTRUCTURE CONNECTIONS ON EAST END ...  

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

4. VIEW NORTH, DETAIL OF SUBSTRUCTURE CONNECTIONS ON EAST END OF BRIDGE - Cincinnati, Jackson & Mackinaw Railroad Bridge, Abandonned Penn Central Route, spanning Tom's Run, Farmersville, Montgomery County, OH

115

Streams in the Aquarius stellar haloes  

NASA Astrophysics Data System (ADS)

We use the very high resolution, fully cosmological simulations from the Aquarius Project, coupled to a semi-analytical model of galaxy formation, to study the phase-space distribution of halo stars in `solar neighbourhood' like volumes. We find that this distribution is very rich in substructure in the form of stellar streams for all five stellar haloes we have analysed. These streams can be easily identified in velocity space, as well as in spaces of pseudo-conserved quantities such as E versus Lz. In our best resolved local volumes, the number of identified streams ranges from ?300 to 600, in very good agreement with previous analytical predictions, even in the presence of chaotic mixing. The fraction of particles linked to (massive) stellar streams in these volumes can be as large as 84 per cent. The number of identified streams is found to decrease as a power law with galactocentric radius. We show that the strongest limitation to the quantification of substructure in our poorest resolved local volumes is particle resolution rather than strong diffusion due to chaotic mixing.

Gómez, Facundo A.; Helmi, Amina; Cooper, Andrew P.; Frenk, Carlos S.; Navarro, Julio F.; White, Simon D. M.

2013-12-01

116

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

117

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

118

Searching for gravitational waves with the LIGO and Virgo interferometers  

NASA Astrophysics Data System (ADS)

The first generation of ground-based interferometric gravitational wave detectors, LIGO, GEO, and Virgo, have operated and taken data at their design sensitivities over the last few years. The data has been examined for the presence of gravitational wave signals. Presented here is a comprehensive review of the most significant results. The network of detectors is currently being upgraded and extended, providing a large likelihood for observations. These future prospects will also be discussed.

Bizouard, Marie-Anne; Papa, Maria Alessandra

2013-04-01

119

X-ray observations of galaxies in the Virgo cluster  

NASA Technical Reports Server (NTRS)

X-ray emission from individual galaxies (other than M87) in the Virgo cluster has been detected using observations from the Einstein X-ray Observatory. One of the galaxies, M86, exhibits extended emission which is interpreted as thermal bremsstrahlung from hot gas being stripped from the galaxy by the ram pressure of the intracluster medium. The observations are discussed in relation to models for the dynamical evolution of clusters of galaxies.

Forman, W.; Schwarz, J.; Jones, C.; Liller, W.; Fabian, A. C.

1979-01-01

120

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

121

The Dynamical Properties of Virgo Cluster Disk Galaxies  

NASA Astrophysics Data System (ADS)

By virtue of its proximity, the Virgo Cluster is an ideal laboratory for testing our understanding of structure formation in the Universe. In this spirit, we present a dynamical study of Virgo galaxies as part of the Spectroscopic and H-band Imaging of Virgo (SHIVir) survey. H? rotation curves (RC) for our gas-rich galaxies were modeled with a multi-parameter fit function from which various velocity measurements were inferred. Our study takes advantage of archival and our own new data as we aim to compile the largest Tully-Fisher relation (TFR) for a cluster to date. Extended velocity dispersion profiles (VDP) are integrated over varying aperture sizes to extract representative velocity dispersions (VDs) for gas-poor galaxies. Considering the lack of a common standard for the measurement of a fiducial galaxy VD in the literature, we rectify this situation by determining the radius at which the measured VD yields the tightest Fundamental Plane (FP). We found that radius to be at least 1 Re, which exceeds the extent of most dispersion profiles in other works.

Ouellette, N. N. Q.; Courteau, S.; Holtzman, J. A.; Dalcanton, J. J.; McDonald, M.; Zhu, Y.

2014-03-01

122

Jet substructures of boosted polarized top quarks  

NASA Astrophysics Data System (ADS)

We study jet substructures of a boosted polarized top quark, which undergoes the semileptonic decay t?b??, in the perturbative QCD framework. The jet mass distribution (energy profile) is factorized into the convolution of a hard top-quark decay kernel with the bottom-quark jet function (jet energy function). Computing the hard kernel to the leading order in QCD and inputting the latter functions from the resummation formalism, we observe that the jet mass distribution is not sensitive to the helicity of the top quark, but the energy profile is: energy is accumulated faster within a left-hand top jet than within a right-hand one, a feature related to the V-A structure of weak interaction. It is pointed out that the energy profile is a simple and useful jet observable for helicity discrimination of a boosted top quark, which helps identification of physics beyond the standard model at the Large Hadron Collider. The extension of our analysis to other jet substructures, including those associated with a hadronically decaying polarized top quark, is proposed.

Kitadono, Yoshio; Li, Hsiang-nan

2014-06-01

123

Stellar Distributions  

NASA Astrophysics Data System (ADS)

Our Galaxy is a collection of stars moving in orbits through the Galaxy's gravitational field (see GALAXY: STRUCTURE). A `stellar distribution' is a description of the distribution (in real space and in velocity space) of the stars in our Galaxy. Different kinds of stars have different distributions. A knowledge of the distribution of stars, obtained from counts of stars of many kin...

Upgren, A.; Murdin, P.

2002-07-01

124

Centrally Peaked core-collapse Supernova Products in the Virgo Cluster Core  

NASA Astrophysics Data System (ADS)

Using an ultra-deep (574 ks) Chandra observation of M87, the central galaxy in the Virgo Cluster, we present the best measurements to date of the distribution of metals in the central intracluster medium (ICM). Our measurements, made in 36 independent annuli with 250,000 counts each, extend out to a radius r 40 kpc and show that the abundance profiles of Fe, Si, S, Ar, Ca, Ne, Mg, and Ni are all centrally peaked. Interestingly, the abundance profiles of Si and S - which are measured robustly and to high precision - are even more centrally peaked than Fe, while the Si/S ratio is relatively flat. These measurements challenge the standard picture of chemical enrichment in galaxy clusters, wherein type Ia supernovae (SN Ia) from an evolved stellar population are thought to dominate the central enrichment. Rather, the integrated relative contribution of core-collapse supernovae (SNcc) to the chemical enrichment is higher in the central, low-entropy core than in the surrounding ICM. We discuss processes that might have contributed to the observed radial profiles.

Million, Evan T.; Werner, N.; Simionescu, A.; Allen, S.

2011-09-01

125

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

126

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

127

Sensitivity analysis of brake squeal tendency to substructures’ modal parameters  

Microsoft Academic Search

Sensitivity analysis methods are explored to determine the dominant modal parameters of substructures of a brake system for brake squeal suppression analysis. The related formulae of sensitivities of the positive real part of the eigenvalue of squeal mode (RES) to substructures’ modal parameters (SMP) are derived. The sensitivity analysis method can determine the dominant modal parameters influencing the squeal occurrence

Dihua Guan; Xindong Su; Fang Zhang

2006-01-01

128

Measuring Substructure with SEGUE K Giants and BHB Stars  

NASA Astrophysics Data System (ADS)

New substructure measurements in the Milky Way halo will be presented, using the large samples of SEGUE K giants and BHB stars which stretch into the outer halo. We see interesting differences in substructure between inner and outer halo and between K stars and BHB stars, and report a new distant stream likely to be associated with the early disruption of the Sgr dwarf.

Morrison, Heather

2012-01-01

129

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

130

Dark Matter Substructure, Galaxy Assembly and Star Formation Histories  

NASA Astrophysics Data System (ADS)

We use cosmological SPH simulations to study galaxy growth and the relationship between dark matter halos and the galaxies that form in them. We find that the distinction between central and satellite galaxies in our simulation is weaker than expected in simple models where only central galaxies are able to accrete mass and `receive' mergers of less massive systems. Instead, in our simulation, satellite galaxies continue to accrete gas and convert it to stars after halo mergers with a larger parent halo. Satellites in our simulation are 0.1-0.2 magnitudes bluer than in models that assume no gas accretion on to satellites after a halo merger (instantaneous `strangulation'), which is sufficient to shift galaxies across the boundary from the `red sequence' to the `blue cloud'. Subhalo abundance matching (SHAM) is a technique for assigning luminosities to simulated dark matter substructures by assuming a strictly monotonic relationship between luminosity and halo mass at the epoch of accretion. We carry out N-body and SPH simulations of a cosmological volume with identical initial conditions, finding that SHAM successfully matches the stellar masses and luminosities of SPH galaxies at a wide range of epochs, albeit with relatively small amounts of scatter. In our SPH simulations that include momentum driven winds, the results are more complex. We examine the relationship between halo assembly and star formation histories with the goal of extending SHAM to a wider domain of observables such as star formation history and colour. In order to guide efforts to fit star formation histories to observed colours or spectra, we investigate parametric fits to the star formation histories of SPH galaxies finding that some commonly used models fail to describe the star formation histories of SPH galaxies but other simple two parameter models achieve greater success.

Simha, Vimal

2011-01-01

131

A transient response method for linear coupled substructures  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

132

Stellar Dynamics  

NASA Astrophysics Data System (ADS)

Stellar dynamics describes systems of many point mass particles whose mutual gravitational interactions determine their orbits. These particles are usually taken to represent stars in small GALAXY CLUSTERS with about 102-103 members, or in larger GLOBULAR CLUSTERS with 104-106 members or in GALACTIC NUCLEI with up to about 109 members or in galaxies containing as many as 1012 stars. Under certain...

Saslaw, W.; Murdin, P.

2000-11-01

133

Exploring dark matter with Milky Way substructure.  

PubMed

The unambiguous detection of dark matter annihilation in our Galaxy would unravel one of the most outstanding puzzles in particle physics and cosmology. Recent observations have motivated models in which the annihilation rate is boosted by the Sommerfeld effect, a nonperturbative enhancement arising from a long-range attractive force. We applied the Sommerfeld correction to Via Lactea II, a high-resolution N-body simulation of a Milky Way-sized galaxy, to investigate the phase-space structure of the galactic halo. We found that the annihilation luminosity from kinematically cold substructure could be enhanced by orders of magnitude relative to previous calculations, leading to the prediction of gamma-ray fluxes from as many as several hundred dark clumps that should be detectable by the Fermi satellite. PMID:19608862

Kuhlen, Michael; Madau, Piero; Silk, Joseph

2009-08-21

134

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

135

Probabilistic Component Mode Synthesis of Nondeterministic Substructures  

NASA Technical Reports Server (NTRS)

Standard methods of structural dynamic analysis assume that the structural characteristics are deterministic. Recognizing that these characteristics are actually statistical in nature researchers have recently developed a variety of methods that use this information to determine probabilities of a desired response characteristic, such as natural frequency, without using expensive Monte Carlo simulations. One of the problems in these methods is correctly identifying the statistical properties of primitive variables such as geometry, stiffness, and mass. We present a method where the measured dynamic properties of substructures are used instead as the random variables. The residual flexibility method of component mode synthesis is combined with the probabilistic methods to determine the cumulative distribution function of the system eigenvalues. A simple cantilever beam test problem is presented that illustrates the theory.

Brown, Andrew M.; Ferri, Aldo A.

1996-01-01

136

All Sky Search for Gravitational-Wave Bursts in the Second Joint LIGO-Virgo Run.  

National Technical Information Service (NTIS)

We present results from a search for gravitational-wave bursts in the data collected by the LIGO and Virgo detectors between July 7, 2009 and October 20, 2010: data are analyzed when at least two of the three LIGO-Virgo detectors are in coincident operati...

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

2012-01-01

137

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

138

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

139

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

140

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

141

Stellar Over-Densities in the Outer Halo of the MilkyWay  

Microsoft Academic Search

This study presents a tomographic survey of a subset of the outer halo (10-40 kpc) drawn from the Sloan Digital Sky Survey Data Release 6. Halo substructure on spatial scales of >3 degrees is revealed as an excess in the local density of sub-giant stars. With an appropriate assumption of a model stellar isochrone it is possible for us to

Stefan C. Keller

2010-01-01

142

Damage identification of a target substructure with moving load excitation  

NASA Astrophysics Data System (ADS)

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

Li, J.; Law, S. S.

2012-07-01

143

The Local Cluster Substructure Survey (LoCuSS): I. Joint KPNO/Spitzer/Herschel/Subaru Study of the Star Formation & Assembly Histories of Massive Clusters  

NASA Astrophysics Data System (ADS)

LoCuSS (Local Cluster Substructure Survey) is a systematic multi-wavelength survey of 100 X-ray luminous galaxy clusters at z=0.2 to study the impact of the hierarchical assembly history of the clusters on the star formation histories of the cluster galaxies. Importantly, we are using gravitational lensing to measure cluster mass and substructure - we are therefore able to test the assumptions necessary in other studies to connect baryonic observables with cluster mass. Here we propose a comprehensive near-IR study of the stellar mass content of a sub-set of 32 LoCuSS clusters for which we have Subaru/Suprime-CAM weak lensing mass maps, panoramic Spitzer/MIPS 24(micron) images, and approved GALEX FUV/NUV and Herschel/PACS 100 and 160(micron) images. The proposed J/K-band observations will enable us to measure the stellar mass content of the clusters out to the virial radius, determine whether 24(micron) Spitzer sources are cluster members, and estimate the stellar mass of the 24(micron) cluster population. (We are also submitting a companion CTIO- 4m/ISPI proposal to observe the central 10'×10' area of 12 southern LoCuSS clusters, expanding the data set to explore K-band light as a probe of cluster mass and substructure.)

Egami, Eiichi; Smith, Graham P.; Haines, Chris P.; Takada, Masahiro; Okabe, Noboru; Umetsu, Keiichi; Ellis, Richard S.; Richard, Johan; Kneib, Jean-Paul; Carlstrom, John

2008-08-01

144

Present star formation in sprials of the Virgo cluster  

NASA Technical Reports Server (NTRS)

From a study of spiral galaxies in the Virgo Cluster (VC), it is shown that the RDDO anemics with smooth arms and no sign of present formation of (massive) stars have HI surface densities below a threshold value of 2 to 5 x 10 to the 20th power atoms/sq cm. This value is very consistent with predictions of theoretical models. It is likely that the HI disks of VC HI-deficient RDDO anemics were deeply affected by ram pressure stripping in the gaseous intracluster medium, while VC HI deficient RDDO spirals were only peripherally stripped.

Guiderdoni, B.

1987-01-01

145

Stellar Distributions in Dark Matter Halos: Looking Over the Edge  

NASA Astrophysics Data System (ADS)

We propose to obtain deep observations with IRAC bands 1 and 2 to trace the faint extended stellar component of nearby galaxies. Little is known about the full extent of the stellar distribution in normal galaxies; deep IR observations of the area around galaxies will allow us to trace the stellar distribution to unprecedented levels. Our sample will include galaxies with a range of morphology, inclination angle, luminosity, and environment in order to explore fully the diverse range of galaxy properties and to enhance the legacy value of this data set. These observations will enable a wide variety of projects, including investigation of thick disks and halo formation, identification of old and young star clusters, and identification of stars well beyond the bright stellar disk. The proposed observations will provide not only a census, but also the first quantitative measurements of the physical properties of low surface brightness features identified around nearby galaxies (e.g., stellar mass surface density, distribution, and fraction of total stellar mass). With sensitivity to substructures featuring stellar mass surface densities of only a few x 0.01 M_sun/pc2, this project will provide the first look at the stellar edge for a large sample of galaxies and will be instrumental in providing observational constraints for galaxy formation models.

van Zee, Liese; Dale, Daniel; Dale, Daniel A.; Barnes, Kate L.; Staudaher, Shawn; Calzetti, Daniela; Dalcanton, Julianne J.; Bullock, James S.; Chandar, Rupali

2011-05-01

146

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

147

Characterization of Chloride Thresholds in Florida Coastal Concrete Bridge Substructures.  

National Technical Information Service (NTIS)

Sea water induced reinforcing steel corrosion often results in high maintenance costs and can be service life limiting for concrete bridge substructure elements in marine environments. In the present research, a novel piling type specimen assembly and tes...

F. Presuel-Moreno R. Tanner W. H. Hartt

2009-01-01

148

2. Substructure of the main dock, looking south beneath the ...  

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

2. Substructure of the main dock, looking south beneath the Hay and Grain Warehouse. Original log pilings have been encased in concrete. - Curtis Wharf, Main Dock, O & Second Streets, Anacortes, Skagit County, WA

149

65. VIEW LOOKING UPSTREAM FROM FLUME SUBSTRUCTURE, SHOWING COLUMBIA IMPROVEMENT ...  

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

65. VIEW LOOKING UPSTREAM FROM FLUME SUBSTRUCTURE, SHOWING COLUMBIA IMPROVEMENT COMPANY'S NEISSON CREEK SAWMILL. Print No. 177, November 1903 - Electron Hydroelectric Project, Along Puyallup River, Electron, Pierce County, WA

150

3. VIEW OF SOUTH FACE AND CONSTRUCTION DETAIL OF SUBSTRUCTURE ...  

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

3. VIEW OF SOUTH FACE AND CONSTRUCTION DETAIL OF SUBSTRUCTURE FROM NORTH BANK. RETAINING WALL OF GAUGING STATION IS VISIBLE IN BACKGROUND UNDER BRIDGE. - Old Happy Isles Bridge, Spanning Merced River on service road, Yosemite Village, Mariposa County, CA

151

Computer-assisted prediction of pesticide substructure using mass spectra.  

PubMed

Mass spectral classifiers of 16 substructures that are present in basic structures of pesticides have been investigated to assist pesticide residues analysis as well as screening of pesticide lead compounds. Mass spectral data are first transformed into 396 features, and then Genetic Algorithm-Partial Least Squares (GA-PLS) as a feature selection method and Support Vector Machine (SVM) as a validation method are implemented together to get an optimization feature set for each substructure. At last, a statistical method which is AdaBoost algorithm combined with Classification and Regression Tree (AdaBoost-CART) is trained to predict the 16 substructures presence/absence using the optimization mass spectral feature set. It is demonstrated that the optimum feature sets can be used to predict the 16 pesticide substructures presence/absence with mostly 85-100% in recognition success rate instead of the original 396 features. PMID:17543608

Xiong, Qing; Zhang, Yuxi; Li, Menglong

2007-06-19

152

Ground Penetrating Radar for Railroad Track Substructure Evaluation.  

National Technical Information Service (NTIS)

The report presents the results of the first three phases of a multiphase project to adapt Ground Penetrating Radar (GPR) to railroads for use in developing useful indices of substructure condition and performance. Included are brief discussions of some b...

E. T. Selig G. R. Olhoeft J. P. Hyslip S. S. Smith

2005-01-01

153

Deformation substructures induced by high-rate deformation.  

National Technical Information Service (NTIS)

The influence of increasing strain on the deformation substructures in metals and alloys which deform predominately by slip is very similar to that seen following quasi-static deformation at increasingly lower temperatures or due to a decrease in stacking...

G. T. Gray

1991-01-01

154

Calculating Required Substructure Damping to Meet Prescribed System Damping Levels.  

National Technical Information Service (NTIS)

Structural synthesis is a method of calculating the transient dynamic response of an assemblage of substructures without explicitly assembling and solving a combined system model. While significant computational advantages are provided by this method, the...

W. D. Penetrante

2007-01-01

155

Substructure detail view of the castinplace concrete bents and steel, ...  

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

Substructure detail view of the cast-in-place concrete bents and steel, longitudinal "I" beams. - Marion Creek Bridge, Spanning Marion Creek at Milepoint 66.42 on North Santiam Highway (OR-22), Marion Forks, Linn County, OR

156

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

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

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

157

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

158

The ACS Virgo Cluster Survey. VIII. The Nuclei of Early-Type Galaxies  

NASA Astrophysics Data System (ADS)

The ACS Virgo Cluster Survey is a Hubble Space Telescope program to obtain high-resolution imaging in widely separated bandpasses (F475W~g and F850LP~z) for 100 early-type members of the Virgo Cluster, spanning a range of ~460 in blue luminosity. We use this large, homogenous data set to examine the innermost structure of these galaxies and to characterize the properties of their compact central nuclei. We present a sharp upward revision in the frequency of nucleation in early-type galaxies brighter than MB~-15 (66%<~fn<~82%) and show that ground-based surveys underestimated the number of nuclei due to surface brightness selection effects, limited sensitivity and poor spatial resolution. We speculate that previously reported claims that nucleated dwarfs are more concentrated toward the center of Virgo than their nonnucleated counterparts may be an artifact of these selection effects. There is no clear evidence from the properties of the nuclei, or from the overall incidence of nucleation, for a change at MB~-17.6, the traditional dividing point between dwarf and giant galaxies. There does, however, appear to be a fundamental transition at MB~-20.5, in the sense that the brighter, ``core-Sérsic'' galaxies lack resolved (stellar) nuclei. A search for nuclei that may be offset from the photocenters of their host galaxies reveals only five candidates with displacements of more than 0.5", all of which are in dwarf galaxies. In each case, however, the evidence suggests that these ``nuclei'' are, in fact, globular clusters projected close to the galaxy photocenter. Working from a sample of 51 galaxies with prominent nuclei, we find a median half-light radius of =4.2 pc, with the sizes of individual nuclei ranging from 62 pc down to <=2 pc (i.e., unresolved in our images) in about a half-dozen cases. Excluding these unresolved objects, the nuclei sizes are found to depend on nuclear luminosity according to the relation rh L0.50+/-0.03. Because the large majority of nuclei are resolved, we can rule out low-level AGNs as an explanation for the central luminosity excess in almost all cases. On average, the nuclei are ~3.5 mag brighter than a typical globular cluster. Based on their broadband colors, the nuclei appear to have old to intermediate age stellar populations. The colors of the nuclei in galaxies fainter than MB~-17.6 are tightly correlated with their luminosities, and less so with the luminosities of their host galaxies, suggesting that their chemical enrichment histories were governed by local or internal factors. Comparing the nuclei to the ``nuclear clusters'' found in late-type spiral galaxies reveals a close match in terms of size, luminosity, and overall frequency. A formation mechanism that is rather insensitive to the detailed properties of the host galaxy properties is required to explain this ubiquity and homogeneity. The mean of the frequency function for the nucleus-to-galaxy luminosity ratio in our nucleated galaxies, =-2.49+/-0.09 dex (?=0.59+/-0.10), is indistinguishable from that of the SBH-to-bulge mass ratio, =-2.61+/-0.07 dex (?=0.45+/-0.09), calculated in 23 early-type galaxies with detected supermassive black holes (SBHs). We argue that the compact stellar nuclei found in many of our program galaxies are the low-mass counterparts of the SBHs detected in the bright galaxies. If this interpretation is correct, then one should think in terms of ``central massive objects''-either SBHs or compact stellar nuclei-that accompany the formation of almost all early-type galaxies and contain a mean fraction ~0.3% of the total bulge mass. In this view, SBHs would be the dominant formation mode above MB~-20.5. 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 NAS5-26555.

Côté, Patrick; Piatek, Slawomir; Ferrarese, Laura; Jordán, Andrés; Merritt, David; Peng, Eric W.; Ha?egan, Monica; Blakeslee, John P.; Mei, Simona; West, Michael J.; Milosavljevi?, Miloš; Tonry, John L.

2006-07-01

159

Possible Influence of Aperture Heating on VIRGO Radiometry on SOHO  

NASA Astrophysics Data System (ADS)

The early increase, first observed by the PMO6V radiometer on VIRGO/SOHO, indicates that aperture heating may be a problem for solar radiometry, not only in space, but also on ground. Heating of the precision aperture in front of the receiver cavity increases the irradiance in proportion to the incoming solar radiation and the emitted radiation from the aperture is added to the irradiance measured. Similar effects are also observed in ACRIMs and the HF on NIMBUS-7 and seem to be inherent to radiometers with the precision aperture directly in front of the cavity and the view limiting one at some distance in front. With this arrangement the precision aperture is illuminated during the measurement phase only and the measured irradiance increased accordingly. In TIM on SORCE the precision aperture is in front of the radiometer and the cavity entrance area determines the view angle. This avoids the influence of aperture heating and it may explain - at least part of - the fact that TIM measures lower values than the classical radiometers. Experimentally this effect is very difficult to determine directly and the result of thermal-model calculations and air-vacuum ratios with different amount of aperture heating are used to learn more about the magnitude of this effect. An estimate of this effect for the PMO6V/VIRGO instrument is presented.

Frohlich, C.

2010-12-01

160

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

161

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

162

Double-helix stellarator.  

National Technical Information Service (NTIS)

A new stellarator configuration, the Double-Helix Stellarator (DHS), is introduced. This novel configuration features a double-helix center post as the only helical element of the stellarator coil system. The DHS configuration has many unique characterist...

P. E. Moroz

1997-01-01

163

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

164

Dislocation substructure in fatigued duplex stainless steel  

SciTech Connect

Cyclic plastic straining of crystalline materials results in the formation of specific dislocation structures. Considerable progress in mapping and understanding internal dislocation structures has been achieved by studying single crystal behavior: however, most structural materials have a polycrystalline structure and investigations of polycrystals in comparison to single crystal behavior of simple metals prove to be very useful in understanding more complex materials. There are some classes of materials, however, with complicated structure which do not have a direct equivalent in single crystalline form. Moreover, the specific dimensions and shapes of individual crystallites play an important role both in the cyclic stress-strain response of these materials and in the formation of their interior structure in cyclic straining. Austenitic-ferritic duplex stainless steel, which is a kind of a natural composite, is a material of this type. The widespread interest in the application of duplex steels is caused by approximately doubled mechanical properties and equal corrosion properties, when compared with classical austenitic stainless steels. Fatigue resistance of these steels as well as the surface damage evolution in cyclic straining have been studied; however, much less is known about the internal substructure development in cyclic straining. In this study the dislocation arrangement in ferritic and austenitic grains of the austenitic-ferritic duplex steel alloyed with nitrogen and cyclically strained with two strain amplitudes, is reported and compared to the dislocation arrangement found in single and polycrystals of austenitic and ferritic materials of a similar composition and with the surface relief produced in cyclic plastic straining.

Polak, J. (Ecole Centrale de Lille, Villeneuve d'Ascq (France). Lab. de Mecanique de Lille Inst. of Physical Metallurgy, Brno (Czechoslovakia). Academy of Sciences); Degallaix, S. (Ecole Centrale de Lille, Villeneuve d'Ascq (France). Lab. de Mecanique de Lille); Kruml, T. (Inst. of Physical Metallurgy, Brno (Czechoslovakia). Academy of Sciences)

1993-12-15

165

Acerca de la linealidad de la relación color-magnitud del cúmulo de Virgo  

NASA Astrophysics Data System (ADS)

In this work we revisite the color-magnitude relation (CMR) of the Virgo cluster by means of the realization of our own photometry and the analysis of images of 100 early-type galaxies, observed as part of the ACS Virgo Cluster Survey of the Hubble Space Telescope (HST). Our objective, within the framework of the discussion about the nonlinearity of the CMR in the Virgo cluster, is to draw a comparison between the results of the photometry performed in this work and the results obtained in previous ones. FULL TEXT IN SPANISH

González, N.; Smith Castelli, A.; Faifer, F.; Forte, J. C.

166

Investigating Chemical Substructure in the Galactic Disk  

NASA Astrophysics Data System (ADS)

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

Stringer, Christopher; Carney, B. W.

2010-01-01

167

The magnetic fields of large Virgo cluster spirals. II  

NASA Astrophysics Data System (ADS)

Context. The Virgo cluster of galaxies provides excellent conditions for studying interactions of galaxies with the cluster environment. Both the high-velocity tidal interactions and effects of ram pressure stripping by the intracluster gas can be investigated in detail. Aims: We extend our systematic search for possible anomalies in the magnetic field structures of Virgo cluster spirals in order to characterize a variety of effects and attribute them to different disturbing agents. Methods: Six angularly large Virgo cluster spiral galaxies (NGC 4192, NGC 4302, NGC 4303, NGC 4321, NGC 4388, and NGC 4535) were targets of a sensitive total power and polarization study using the 100-m radio telescope in Effelsberg at 4.85 GHz and 8.35 GHz (except for NGC 4388 observed only at 4.85 GHz, and NGC 4535 observed only at 8.35 GHz). The presented two-frequency studies allow Faraday rotation analysis. Results: Magnetic field structures distorted to various extent are found in all galaxies. Three galaxies (NGC 4302, NGC 4303, and NGC 4321) show some signs of possible tidal interactions, while NGC 4388 and NGC 4535 have very likely experienced strong ram-pressure and shearing effects, respectively, visible as distortions and asymmetries of polarized intensity distributions. As in our previous study, even strongly perturbed galaxies closely follow the radio-far-infrared correlation. In NGC 4303 and NGC 4321, we observe symmetric spiral patterns of the magnetic field and in NGC 4535 an asymmetric pattern. Conclusions: The cluster environment clearly affects the evolution of its member galaxies via various effects. Magnetic fields allow us to trace even weak interactions that are difficult to detect with other observations. Our results show that the degree of distortions of a galaxy is not a simple function of the distance to the cluster center but reflects also the history of its interactions. The angle ? between the velocity vector v and the rotation vector ? of a galaxy may be a general parameter that describes the level of distortions of galactic magnetic fields. Information about the motions of galaxies in the sky plane and their three-dimensional distribution, as well as information about the intracluster medium can also be obtained from the Faraday rotation analysis. Based on the observations with the 100-m telescope at Effelsberg operated by the Max-Planck-Institut für Radioastronomie (MPIfR) on behalf of the Max-Planck-Gesellschaft.

We?gowiec, M.; Urbanik, M.; Beck, R.; Chy?y, K. T.; Soida, M.

2012-09-01

168

The magnetic fields of large Virgo Cluster spirals  

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

169

Substructure Depletion in the Milky Way Halo by the Disk  

NASA Astrophysics Data System (ADS)

We employ numerical simulations and simple analytical estimates to argue that dark matter substructures orbiting in the inner regions of the Galaxy can be efficiently destroyed by disk shocking, a dynamical process known to affect globular star clusters. We carry out a set of fiducial high-resolution collisionless simulations in which we adiabatically grow a disk, allowing us to examine the impact of the disk on the substructure abundance. We also track the orbits of dark matter satellites in high-resolution Aquarius simulations and analytically estimate the cumulative halo and disk-shocking effect. Our calculations indicate that the presence of a disk with only 10% of the total Milky Way mass can significantly alter the mass function of substructures in the inner parts of halos. This has important implications especially for the relatively small number of satellites seen within ~30 kpc of the Milky Way center, where disk shocking is expected to reduce the substructure abundance by a factor of 2 at 109 M sun and a factor of 3 at 107 M sun. The most massive subhalos with 1010 M sun survive even in the presence of the disk. This suggests that there is no inner missing satellite problem and calls into question whether these substructures can produce transient features in disks, like multi-armed spiral patterns. Also, the depletion of dark matter substructures through shocking on the baryonic structures of the disk and central bulge may aggravate the problem to fully account for the observed flux anomalies in gravitational lens systems, and significantly reduces the dark matter annihilation signal expected from nearby substructures in the inner halo.

D'Onghia, Elena; Springel, Volker; Hernquist, Lars; Keres, Dusan

2010-02-01

170

SUBSTRUCTURE DEPLETION IN THE MILKY WAY HALO BY THE DISK  

SciTech Connect

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

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

2010-02-01

171

12CO(J = 1 - 0) On-the-Fly Mapping Survey of the Virgo Cluster Spirals. I. Data and Atlas  

NASA Astrophysics Data System (ADS)

We have performed an On-The-Fly (OTF) mapping survey of 12CO(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, Eun Jung; Rhee, Myung-Hyun; Kim, Hyoryoung; Yun, Min S.; Heyer, Mark; Young, Judith S.

2009-10-01

172

Vacuum ultraviolet imagery of the Virgo cluster region  

SciTech Connect

The results are reported of an experiment using the UV imager aboard an attitude-controlled S520 type sounding rocket. The total UV fluxes of galaxies in the Virgo Cluster as well as the flux level of the diffuse UV background around the cluster were measured. The data on NGC 4486 and NGC 4472 confirm the variation in the degree of the 'turnup' below 200 nm in the energy spectrum of the total light of elliptical galaxies. At two-color diagram of galaxies of visual/near-UV/vacuum UV indicates that colors of spiral galaxies are distributed within a strip and well-correlated with the morphological type, while elliptical galaxies are located differently from spiral galaxies. 51 refs.

Onaka, T.; Tanaka, W.; Watanabe, T.; Watanabe, J.; Yamaguchi, A. (Tokyo Univ. (Japan); National Astronomical Observatory, Mitaka (Japan))

1989-07-01

173

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

174

The ACS Virgo Cluster Survey. VIII. The Nuclei of Early-Type Galaxies  

Microsoft Academic Search

The ACS Virgo Cluster Survey is a Hubble Space Telescope program to obtain high-resolution imaging in widely separated bandpasses (F475W~g and F850LP~z) for 100 early-type members of the Virgo Cluster, spanning a range of ~460 in blue luminosity. We use this large, homogenous data set to examine the innermost structure of these galaxies and to characterize the properties of their

Patrick Côté; Slawomir Piatek; Laura Ferrarese; Andrés Jordán; David Merritt; Eric W. Peng; Monica Hasegan; John P. Blakeslee; Simona Mei; Michael J. West; Milos Milosavljevic; John L. Tonry

2006-01-01

175

Investigating the observational signatures of magnetic cloud substructure  

NASA Astrophysics Data System (ADS)

Magnetic clouds (MCs) represent a subset of interplanetary coronal mass ejections (ICMEs) that exhibit a magnetic flux rope structure. They are primarily identified by smooth, large-scale rotations of the magnetic field. However, both small- and large-scale fluctuations of the magnetic field are observed within some magnetic clouds. We analyzed the magnetic field in the frames of the flux ropes, approximated using a minimum variance analysis (MVA), and have identified a small number of MCs within which multiple reversals of the gradient of the azimuthal magnetic field are observed. We herein use the term “substructure” to refer to regions that exhibit this signature. We examine, in detail, one such MC observed on 13 April 2006 by the ACE and WIND spacecraft and show that substructure has distinct signatures in both the magnetic field and plasma observations. We identify two thin current sheets within the substructure and find that they bound the region in which the observations deviate most significantly from those typically expected in MCs. The majority of these clouds are followed by fast solar wind streams, and a comparison of the properties of this magnetic cloud with five similar events reveals that they have lower nondimensional expansion rates than nonovertaken magnetic clouds. We discuss and evaluate several possible explanations for this type of substructure, including the presence of multiple flux ropes and warping of the MC structure, but we conclude that none of these scenarios is able to fully explain all of the aspects of the substructure observations.

Steed, K.; Owen, C. J.; Démoulin, P.; Dasso, S.

2011-01-01

176

Stripped Spiral Galaxies as Promising Targets for the Determination of the Cepheid distance to the Virgo Cluster  

Microsoft Academic Search

The measurement of precise galaxy distances by Cepheid observations out to\\u000athe distance of the Virgo cluster is important for the determination of the\\u000aHubble constant ($H_0$). The Virgo cluster is thereby often used as an\\u000aimportant stepping stone. The first HST measurement of the distance of a Virgo\\u000agalaxy (M100) using Cepheid variables provided a value for $H_0=80(\\\\pm 17)$

H. Bohringer; Doris M. Neumann; Sabine Schindler; John Huchra

1997-01-01

177

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.

Xu, Hongliang

2010-01-01

178

Galactic Substructure and Energetic Neutrinos from the Sun and Earth  

NASA Astrophysics Data System (ADS)

We consider the effects of Galactic substructure on energetic neutrinos from annihilation of weakly interacting massive particles that have been captured by the Sun and Earth. Substructure gives rise to a time-varying capture rate and thus to time variation in the annihilation rate and resulting energetic-neutrino flux. However, there may be a time lag between the capture and annihilation rates. The energetic-neutrino flux may then be determined by the density of dark matter in the Solar System’s past trajectory, rather than the local density. The signature of such an effect may be sought in the ratio of the direct- to indirect-detection rates.

Koushiappas, Savvas M.; Kamionkowski, Marc

2009-09-01

179

System for detecting substructure microfractures and method therefore  

NASA Technical Reports Server (NTRS)

Bursts of signals at different frequencies are induced into substructure, adjacent to a borehole. The return signals from each burst of signals are normalized to compensate for the attenuation, experienced by more distant return signals. The peak amplitudes of return signals, above a selected level, are cut off, and an average signal is produced from the normalized amplitude-limited return signals of each burst. The averaged signals of the return signals of all the signal bursts at the different frequencies are processed to provide a combined signal, whose amplitude is related to the microfracture density of the substructure adjacent to the borehole.

Parthasarathy, S. P.; Narasimhan, K. Y. (inventors)

1979-01-01

180

A simple method of identifying symmetric substructures of proteins.  

PubMed

Accurate identifications of internal symmetric substructures of proteins are needed in protein evolution study and protein design. To overcome the difficulties met by previous methods, here we propose a simple quantitative one by using a similarity matrix plus Pearson's correlation analysis. The distance root-mean-square deviation (dRMSD) is used to measure the similarity of two substructures in a protein. We applied this method to the proteins of the beta-propeller, jelly roll, and beta-trefoil families and the results show that this method cannot only detect the internal repetitive structures in proteins effectively, but also can identify their locations easily. PMID:18782681

Chen, Hanlin; Huang, Yanzhao; Xiao, Yi

2009-02-01

181

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

182

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

183

VIVA: VLA imaging of Virgo galaxies in atomic gas  

NASA Astrophysics Data System (ADS)

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

Chung, Aeree

184

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

NASA Astrophysics Data System (ADS)

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

Popping, A.; Braun, R.

2011-04-01

185

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

186

State vector formulation of substructure coupling for damped systems  

NASA Technical Reports Server (NTRS)

A generalized substructure coupling procedure in state vector form is derived for a complex system with general viscous damping. This first-order differential equation formulation is used in order to permit complex substructure modes to be employed easily. The free-interface normal (complex) modes and rigid-body modes of the substructure are defined. Complex residual attachment modes which result from static approximation of neglected higher modes are derived. The motion of each substructure is represented by a selected set of component modes. Equations of interface compatibility are employed to obtain an independent set of system equations of motion. A new method which employs incomplete complex normal modes in conjunction with the complex residual attachment modes to account for the contribution of neglected higher order modes is derived. Examples are employed to indicate how a damped structure may be analyzed by including the effect of residual attachment modes. Numerical results indicate that the new component mode synthesis method provides sytem equations of motion with reduced number of degrees of feedom leading to more accurate approximations to the system frequencies and damping factors than are obtained by pure mode truncation.

Chung, Y.-T.; Craig, R. R., Jr.

1983-01-01

187

Direct Observations of the Substructure Network in Iron  

Microsoft Academic Search

The existence of substructure within high-energy grain boundaries has been proven for different materials.' -4 These subgrains are actually low-angle boundaries in which the orientation differences across the boundary are very small. Since this orientation difference is so slight, the procedures to show the presence of sub- structure are involved and often difficult. This Letter describes a new technique and

W. L. Mitchell; C. Hays; R. E. Swift

188

GROUND PENETRATING RADAR EVALUATION OF RAILWAY TRACK SUBSTRUCTURE CONDITIONS  

Microsoft Academic Search

ABSTRACT Ground penetrating radar has shown ,the ability to map railroad track substructure condition on a continuous top-of- rail nondestructive basis. In this study, 1 GHz radar data were acquired between ,concrete and ,wood ,ties as well ,as from the ballast shoulders beyond the ends of the ties, and with,multiple ,antenna ,orientations ,and ,polarizations. Automatic processing of the data was

G. R. Olhoeft; E. T. Selig

189

A substructure approach for the midfrequency vibration of stochastic systems  

Microsoft Academic Search

A novel substructure coupling technique based on the proper orthogonal decomposition method is presented for the midfrequency range vibration of linear dynamical systems with parameter uncertainty. For a given frequency band, the methodology permits the derivation of an adaptive basis for each subsystem and the construction of a reduced-order model of the global structure. The formulation is directed toward the

Abhijit Sarkar; Roger Ghanem

2003-01-01

190

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

191

Substructure in the Cold Front Cluster Abell 3667  

NASA Astrophysics Data System (ADS)

We present evidence for the existence of significant substructure in the cold front cluster Abell 3667 based on multiobject spectroscopy taken with the 3.9 m Anglo-Australian Telescope. This paper is the second in a series analyzing the relationship between cold fronts observed in Chandra X-ray images and merger activity observed at optical wavelengths. We have obtained 910 galaxy redshifts in the field of Abell 3667 out to 3.5 Mpc, of which 550 are confirmed cluster members, more than doubling the number of spectroscopically confirmed members previously available and probing some 3 mag down the luminosity function. From this sample, we derive a cluster redshift of z = 0.0553 ± 0.0002 and velocity dispersion of 1056 ± 38 km s-1 and use a number of statistical tests to search for substructure. We find significant evidence for substructure in the spatial distribution of member galaxies and also in the localized velocity distributions and, in spite of this evidence, find the global velocity distribution does not deviate significantly from a Gaussian. Using combined spatial and velocity information, we found the cluster can be separated into two major structures, with roughly equal velocity dispersions, but offset in peculiar velocity from each other by ~500 km s-1, and a number of minor substructures. We propose two scenarios which explain the radio and X-ray observations. Our data show the cold front is directly related to cluster merger activity, and also highlights the extent of optical data required to unambiguously detect the presence of substructure.

Owers, Matt S.; Couch, Warrick J.; Nulsen, Paul E.J.

2009-03-01

192

The Arecibo Galaxy Environment Survey - VI. The Virgo cluster (II)  

NASA Astrophysics Data System (ADS)

We present 21-cm observations of a 5 × 1 deg2 region in the Virgo cluster, obtained as part of the Arecibo Galaxy Environment Survey. 13 cluster members are detected, together with 36 objects in the background. We compare and contrast the results from this area with a larger 10 × 2 deg2 region. We combine the two data sets to produce an H i mass function, which shows a higher detection rate at low masses (but finds fewer massive galaxies) than less sensitive wider area surveys, such as ALFALFA. We find that the H i-detected galaxies are distributed differently to the non-detections, both spatially and in velocity, providing further evidence that the cluster is still assembling. We use the Tully-Fisher relation to examine the possibility of morphological evolution. We find that highly deficient galaxies, as well as some early-type galaxies, have much lower velocity widths than the Tully-Fisher relation predicts, indicating gas loss via ram-pressure stripping. We also find that H i detections without optical counterparts do not fit the predictions of the baryonic Tully-Fisher relation, implying that they are not primordial objects.

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

2013-01-01

193

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

NASA Astrophysics Data System (ADS)

We have applied a relativistic Tolman-Bondi model of the Virgo cluster to a sample of 183 galaxies with measured distances within a radius of 8 degrees from M 87. We find that the sample is significantly contaminated by background galaxies which lead to too large a cluster mean distance if not excluded. The Tolman-Bondi model predictions, together with the HI deficiency of spiral galaxies, allows one to identify these background galaxies. One such galaxy is clearly identified among the 6 calibrating galaxies with Cepheid distances. As the Tolman-Bondi model predicts the expected distance ratio to the Virgo distance, this galaxy can still be used to estimate the Virgo distance, and the average value over the 6 galaxies is 15.4 +/- 0.5 Mpc. Well-known background groups of galaxies are clearly recovered, together with filaments of galaxies which link these groups to the main cluster, and are falling into it. No foreground galaxy is clearly detected in our sample. Applying the B-band Tully-Fisher method to a sample of 51 true members of the Virgo cluster according to our classification gives a cluster distance of 18.0 +/- 1.2 Mpc, larger than the mean Cepheid distance. Finally, the same model is used to estimate the Virgo cluster mass, which is M = 1.2x 1015 Msun within 8 degrees from the cluster center (2.2 Mpc radius), and amounts to 1.7 virial mass.

Fouqué, P.; Solanes, J. M.; Sanchis, T.; Balkowski, C.

2001-09-01

194

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

195

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

196

Exploring the Stellar Halo of the Milky Way with the Sloan Digital Sky Survey and PanSTARRS1  

NASA Astrophysics Data System (ADS)

The Lambda CDM paradigm predicts that the outer parts of galaxies should, in large part, consist of material tidally stripped off of smaller dwarf galaxies as they are incorporated into the potential of the larger galaxy. We present results from the exploration of the structure and stellar populations of the Milky Way stellar halo. To date, we have focused on understanding the structure of the stellar halo as probed by two key tracer stellar populations - main sequence turn-off stars (MSTO; a well-populated diagnostic of a wide range of stellar populations), and blue horizontal branch stars (BHB; a sparsely-sampled standard candle indicative of ancient metal-poor populations, but available to larger distances). We find that the stellar halo is richly substructured as traced by MSTO and BHB stars, in both 3D space and in velocity space. Furthermore, we find that the degree and type of substructure showed by both populations are different - the ratio of BHB to MSTO stars changes from place to place in the halo, with coherent values of BHB/MSTO star number in given clearly-recognizable structured (e.g., the Sagittarius stream, low-latitude stream, etc.) Where possible, we compare quantitatively with models of galaxy formation in a cosmological context. The quantitative predictions of such models do depend on the assumptions underlying the model, and we demonstrate in particular the importance of a disk potential in driving the character and structure of stellar halos in a cosmological context. We find a close quantitative correspondence between predictions of spatial and velocity substructure from the cosmologically-motivated models and the observations for both MSTO and BHB stars, giving weight to the notion that stellar halos, at least to first order, present an unparalleled opportunity to study the formation of individual galaxies in a cosmological context.

Bell, Eric F.; Slater, C. T.; Bailin, J.; Xue, X.; Ruhland, C.; Martin, N. F.; Pan-STARRS 1 Consortium

2012-01-01

197

Kinematics and simulations of the stellar stream in the halo of the Umbrella Galaxy  

NASA Astrophysics Data System (ADS)

We study the dynamics of faint stellar substructures around the Umbrella Galaxy, NGC 4651, which hosts a dramatic system of streams and shells formed through the tidal disruption of a nucleated dwarf elliptical galaxy. We elucidate the basic characteristics of the system (colours, luminosities, stellar masses) using multiband Subaru/Suprime-Cam images. The implied stellar mass ratio of the ongoing merger event is ˜1:50. We identify candidate kinematic tracers (globular clusters, planetary nebulae, H II regions) and follow up a subset with Keck/DEIMOS (DEep Imaging Multi-object Spectrograph) spectroscopy to obtain velocities. We find that 15 of the tracers are likely associated with halo substructures, including the probable stream progenitor nucleus. These objects delineate a kinematically cold feature in position-velocity phase space. We model the stream using single test particle orbits, plus a rescaled pre-existing N-body simulation. We infer a very eccentric orbit with a period of ˜0.35 Gyr and turning points at ˜2-4 and ˜40 kpc, implying a recent passage of the satellite through the disc, which may have provoked the visible disturbances in the host galaxy. This work confirms that the kinematics of low surface brightness substructures can be recovered and modelled using discrete tracers - a breakthrough that opens up a fresh avenue for unravelling the detailed physics of minor merging.

Foster, C.; Lux, H.; Romanowsky, A. J.; Martínez-Delgado, D.; Zibetti, S.; Arnold, J. A.; Brodie, J. P.; Ciardullo, R.; GaBany, R. J.; Merrifield, M. R.; Singh, N.; Strader, J.

2014-08-01

198

Sky localization of gravitational wave sources in the early years of Advanced LIGO and Virgo  

NASA Astrophysics Data System (ADS)

Advanced LIGO and Virgo, the ground-based km-scale laser interferometers for gravitational wave detection, will start collecting data in 2015-2016.Many of the most promising sources of gravitational waves, such as compact binary coalescences, are also expected to emit in the electromagnetic spectrum. The detection of the electromagnetic counterpart to a gravitational-wave source should help answering open questions, e.g. if compact binary systems are the progenitors of short gamma ray bursts. In this talk I will report on sky localization capabilities for signals emitted by binary neutron stars, focusing on the first two years of activity of Advanced LIGO and Virgo.

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

2014-06-01

199

High-Resolution Images of Virgo Galaxies with Kinematically Distinct Cores: CYCLE4 Med  

NASA Astrophysics Data System (ADS)

Ground-based spectroscopic observations by Rubin and Kenney taken at high velocity resolution and high spatial scale show that about 20 percent of the 80 galaxies observed in the Virgo Cluster have rapidly rotating, kinematically distinct cores extending only a few arcsec. These galaxies span Hubble types E through Sc. We propose to image a sample of seven of these galaxies with the WFPC2, each in two colors (F555W and F814W). One galaxy with strong line emission (NGC 4536) will also be imaged in H-alpha. In addition, we will image 2 "normal" galaxies in the Virgo Cluster to act as a control sample.

Rubin, Vera

1994-07-01

200

The Milky Way's stellar halo - lumpy or triaxial?  

NASA Astrophysics Data System (ADS)

We present minimum chi-squared fits of power law and Hernquist density profiles to F-turnoff stars in eight 2.5° wide stripes of SDSS data: five in the North Galactic Cap and three in the South Galactic cap. Portions of the stellar Galactic halo that are known to contain large streams of tidal debris or other lumpy structure, or that may include significant contamination from the thick disk, are avoided. The data strongly favor a model that is not symmetric about the Galaxy's axis of rotation. If included as a free parameter, the best fit to the center of the spheroid is surprisingly approx 3kpc from the Galactic center in the direction of the Sun's motion. The model fits favor a low value of the density of halo stars at the solar position. The alternative to a non-axisymmetric stellar distribution is that our fits are contaminated by previously unidentified lumpy substructure.

Newberg, Heidi Jo; Yanny, Brian

2006-10-01

201

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

202

Spherical Stellarators and Stellarator-Hybrids  

NASA Astrophysics Data System (ADS)

Stellarators are typically the large aspect ratio devices, A ? 7-10, and the lowest-A stellarators ever built have A ? 5. Following the increasing interest in very compact tokamak devices, called Spherical Tokamaks (ST), an interest has also emerged recently in very compact stellarator devices with A <= 3.5, as their attractiveness for fusion is being demonstrated [1-4]. These stellarators have been called, in analogy with the ST, the Spherical Stellarators (SS). The SS devices have a number of unique features and benefit from the strong bootstrap current. The SS concept shows a path to a compact, high-?, and steady-state fusion reactor, which can be relatively simple and inexpensive. We will report on the latest results obtained, discuss various types of coil configurations advantageous for the SS, and present results of the first round of configuration optimization. Applications to ST devices [5] and new results for stellarator-spheromak hybrids [6] will be presented as well. [1] P.E. Moroz, Phys. Rev. Lett. 77, 651 (1996); [2] P.E. Moroz, Phys. Plasmas 3, 3055 (1996); [3] P.E. Moroz, D.B. Batchelor et al., Fusion Tech. 30, 1347 (1996); [4] P.E. Moroz, Plasma Phys. Reports 23, 502 (1997); [5] P.E. Moroz, Nucl. Fusion 37, No. 7 (1997); [6] P.E. Moroz, Sherwood Fus. Theor. Conf., Madison, 3C31 (1997). *Supported by DOE Grant No. DE-FG02-97ER54395.

Moroz, P. E.

1997-11-01

203

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.

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

2009-01-01

204

Sensitivity analysis of brake squeal tendency to substructures’ modal parameters  

NASA Astrophysics Data System (ADS)

Sensitivity analysis methods are explored to determine the dominant modal parameters of substructures of a brake system for brake squeal suppression analysis. The related formulae of sensitivities of the positive real part of the eigenvalue of squeal mode (RES) to substructures' modal parameters (SMP) are derived. The sensitivity analysis method can determine the dominant modal parameters influencing the squeal occurrence in a regular way, and the dominant modal parameters will be set to be the target of structural modification attempted to eliminate the squeal mode. Sensitivity analysis of a typical squealing disc brake is performed. The analysis results show that a modified rotor or a modified bracket can be used to eliminate the squealing and that the latter is taken in practice and verified experimentally.

Guan, Dihua; Su, Xindong; Zhang, Fang

2006-03-01

205

Population substructure in continuous and fragmented stands of Populus trichocarpa.  

PubMed

Population substructure has important implications for both basic and applied genetic research. We used 10 microsatellite markers to characterize population substructure in two ecologically and demographically contrasting populations of the model tree Populus trichocarpa. The Marchel site was a continuous stand growing in a mesic habitat in western Oregon, whereas the Vinson site consisted of three disjunct and isolated stands in the high desert of eastern Oregon. A previous study revealed that pollen-mediated gene flow is extensive in both populations. Surprisingly, model-based clustering, principal components analysis and analyses of molecular variance provided overwhelming support for the existence of at least two intermingled sub-populations within the continuous Marchel population (F(ST)=0.026, P<0.001), which occupied an area with a radius of only about 250?m. Genets in these two sub-populations appeared to have different relative clone ages and phenologies, leading us to hypothesize that they correspond to different seedling cohorts, each established from seeds produced by relatively few mothers. As expected, substructure was stronger in the fragmented Vinson population (F(ST)=0.071, P=0.001), and this difference appeared to result from the more extensive family structure in this population. Using group-likelihood methods, we reconstructed multiple interconnected half-sib families in the Vinson population, with some genets having as many as eight putative siblings. Researchers involved in ongoing and future association studies in P. trichocarpa should account for the likely presence of subtle but practically significant substructure in populations throughout the range of this species. PMID:20531447

Slavov, G T; Leonardi, S; Adams, W T; Strauss, S H; DiFazio, S P

2010-10-01

206

Common Substructure Learning of Multiple Graphical Gaussian Models  

Microsoft Academic Search

\\u000a Learning underlying mechanisms of data generation is of great interest in the scientific and engineering fields amongst others.\\u000a Finding dependency structures among variables in the data is one possible approach for the purpose, and is an important task\\u000a in data mining. In this paper, we focus on learning dependency substructures shared by multiple datasets. In many scenarios,\\u000a the nature of

Satoshi Hara; Takashi Washio

207

Substructure of the inner core of the Earth.  

PubMed Central

The rationale is disclosed for a substructure within the Earth's inner core, consisting of an actinide subcore at the center of the Earth, surrounded by a subshell composed of the products of nuclear fission and radioactive decay. Estimates are made as to possible densities, physical dimensions, and chemical compositions. The feasibility for self-sustaining nuclear fission within the subcore is demonstrated, and implications bearing on the structure and geodynamic activity of the inner core are discussed.

Herndon, J M

1996-01-01

208

The automated multi-stage substructuring system for NASTRAN  

NASA Technical Reports Server (NTRS)

The substructuring capability developed for eventual installation in Level 16 is now operational in a test version of NASTRAN. Its features are summarized. These include the user-oriented, Case Control type control language, the automated multi-stage matrix processing, the independent direct access data storage facilities, and the static and normal modes solution capabilities. A complete problem analysis sequence is presented with card-by-card description of the user input.

Field, E. I.; Herting, D. N.; Herendeen, D. L.; Hoesly, R. L.

1975-01-01

209

LAMOST observations of substructure in bulk velocities of Milky Way disk stars  

NASA Astrophysics Data System (ADS)

We explore the kinematics of ~400,000 F-type stars in the Galactic disk and just outside the Sun's radius using data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey. LAMOST spectroscopic velocities were combined with proper motions from the PPMXL catalog, for which we have derived corrections to the zero points based in part on spectroscopically discovered galaxies and QSOs from LAMOST, to derive three-dimensional space velocities for the stellar sample. Stars near the Galactic anticenter exhibit velocity substructures in both the Galactocentric radial and vertical components. The structure is most prominent as an asymmetry across the mid-plane, but also varies azimuthally. In the region within 2 kpc outside the Sun's radius and within 2 kpc of the Galactic midplane, stars above the plane exhibit net outward radial motions with downward vertical velocities, while stars below the plane have roughly the opposite behavior. This is likely the signature of perturbations to the disk by an external agent such as a dwarf galaxy or dark matter subhalo. We briefly show additional science results from the first year of LAMOST survey spectra. This research was supported by NSF grant AST 09-37523.

Carlin, Jeffrey L.; DeLaunay, J.; Newberg, H. J.; Deng, L.; Gole, D.; Grabowski, K.; Jin, G.; Liu, C.; Liu, X.; Luo, A.; Yuan, H.; Zhang, H.; Zhao, G.; Zhao, Y.

2014-01-01

210

Dynamical invariants and diffusion of merger substructures in time-dependent gravitational potentials  

NASA Astrophysics Data System (ADS)

This paper explores a mathematical technique for deriving dynamical invariants (i.e. constants of motion) in time-dependent gravitational potentials. The method relies on the construction of a canonical transformation that removes the explicit time-dependence from the Hamiltonian of the system. By referring the phase-space locations of particles to a coordinate frame in which the potential remains `static' the dynamical effects introduced by the time evolution vanish. It follows that dynamical invariants correspond to the integrals of motion for the static potential expressed in the transformed coordinates. The main difficulty reduces to solving the differential equations that define the canonical transformation, which are typically coupled with the equations of motion. We discuss a few examples where both sets of equations can be exactly de-coupled, and cases that require approximations. The construction of dynamical invariants has far-reaching applications. These quantities allow us, for example, to describe the evolution of (statistical) microcanonical ensembles in time-dependent gravitational potentials without relying on ergodicity or probability assumptions. As an illustration, we follow the evolution of dynamical fossils in galaxies that build up mass hierarchically. We show that the growth of the host potential tends to efface tidal substructures in the integral-of-motion space through an orbital diffusion process. The inexorable cycle of deposition, and progressive dissolution, of tidal clumps naturally leads to the formation of a `smooth' stellar halo.

Peñarrubia, Jorge

2013-08-01

211

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

212

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

NASA Astrophysics Data System (ADS)

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 50per cent 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.

Helmi, Amina; de Zeeuw, P. Tim

2000-12-01

213

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

214

Double-helix stellarator  

Microsoft Academic Search

A new stellarator configuration, the Double-Helix Stellarator (DHS), is introduced. This novel configuration features a double-helix center post as the only helical element of the stellarator coil system. The DHS configuration has many unique characteristics. One of them is the extreme low plasma aspect ratio, A â 1--1.2. Other advantages include a high enclosed volume, appreciable rotational transform, and a

Moroz

1997-01-01

215

Detailed comparison of LIGO and Virgo inspiral pipelines in preparation for a joint search  

Microsoft Academic Search

Presented in this paper is a detailed and direct comparison of the detection pipelines used by LIGO and Virgo in their attempt to observe gravitational waves from binary neutron star systems. In order to test the search programs, numerous inspiral signals were added to 24 h of simulated detector data. The efficiencies of the different pipelines were tested, and found

F. Beauville; M.-A. Bizouard; L. Blackburn; L. Bosi; 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

216

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

217

The creep problem in the VIRGO suspensions: a possible solution using Maraging steel  

Microsoft Academic Search

Each optical component of the interferometric gravitational wave detector VIRGO is suspended from a cascade of mechanical filters designed to suppress the transmission of seismic vibrations. Each mechanical filter supports the weight of the filters below it by means of a set of steel cantilever blade springs. The stress from the load acting on the blades was found to induce

M. Beccaria; M. Bernardini; S. Braccini; C. Bradaschia; G. Cagnoli; C. Casciano; G. Cella; E. Cuoco; V. Dattilo; G. De Carolis; R. De Salvo; A. Di Virgilio; G. T. Feng; I. Ferrante; F. Fidecaro; F. Frasconi; A. Gaddi; L. Gammaitoni; A. Gennai; A. Giazotto; L. Holloway; J. Kovalik; P. La Penna; G. Losurdo; S. Malik; S. Mancini; F. Marchesoni; J. Nicolas; F. Palla; H. B. Pan; F. Paoletti; A. Pasqualetti; D. Passuello; R. Poggiani; P. Popolizio; M. Punturo; F. Raffaelli; V. Rubino; R. Valentini; A. Vicere; F. Waharte; Z. Zhang

1998-01-01

218

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

219

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

220

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

221

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

Microsoft Academic Search

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

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

2012-01-01

222

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

Microsoft Academic Search

We have applied a relativistic Tolman-Bondi model of the Virgo cluster to a sample of 183 galaxies with measured distances within a radius of 8 degrees from M 87. We find that the sample is significantly contaminated by background galaxies which lead to too large a cluster mean distance if not excluded. The Tolman-Bondi model predictions, together with the HI

P. Fouqué; J. M. Solanes; T. Sanchis; C. Balkowski

2001-01-01

223

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

PubMed Central

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

2013-01-01

224

Black Holes, Stellar Dynamics and Populations in the Nuclei of a Complete Sample of Elliptical Galaxies - Cont of 2607  

NASA Astrophysics Data System (ADS)

We will determine the prevalence of massive black holes in a complete sample of bright Virgo ellipticals using FOS spectra and WFPC surface photometry. We will correlate the dynamical evidence for massive black holes with indicators of nuclear activity (radio and optical emission, and star formation). Additionally, we will use our data to study the stellar dynamics and demography of the 'cores' of these elliptical galaxies. Our observations will establish the fundamental properties of the nuclear regions: photometric profiles, rotation and dispersion velocities, and spectroscopic metallicity indicies. FOC-UV images will reveal the presence of young stars and/or nonthermal emission. We will determine black hole masses by comparing the predictions of self-consistent dynamical models of the core to the observed surface photometry and kinematics. We wil model the stellar populations by comparing the observed metallicities and spectral energy distributions to synthetic spectra constructed from stellar libraries.

Jaffe, Walter

1991-07-01

225

Dark Matter Halos of Dwarf Early-Type Galaxies in the Virgo Cluster  

NASA Astrophysics Data System (ADS)

The physical mechanisms involved in the formation and evolution of dwarf early-type galaxies (dEs) are not well understood yet. It has been shown recently that kinematical studies of dEs can distinguish between different formation scenarios. In our work, Toloba et al. (2009, 2011), we have found that dEs are likely formed via the transformation of low luminosity spiral galaxies through environmental processes. This earlier work was restricted to the most luminous dwarf members of the Virgo cluster, so we have now extended such studies to less luminous dEs, and now have a sample size of 40 dEs in Virgo. The dark matter content of these galaxies, inferred from their kinematics, is another property that provides important information about dE formation processes. We have used the Fundamental Plane to learn that dEs have around 40% more dark matter than massive elliptical galaxies. This measurement is done within the half-light radius (Re), while the dark matter halos of these systems should extend beyond that. To test this idea we have used Keck/DEIMOS to obtain spectra of a sample of 300 globular cluster (GC) candidates around 21 dEs in the Virgo cluster, selected using the Next Generation Virgo Survey. These GCs are being used as tracers of the potential well of the dEs, and provide information on the kinematics and dark matter halo of these dE systems out to an unprecedented radius of up to 15 Re. In my talk, I will summarize our latest findings about the kinematical profiles and associated dark matter content of dEs in the Virgo Cluster.

Toloba, Elisa; Guhathakurta, P.

2013-07-01

226

Evaluation of automatically generated substructure identification rules from tandem mass spectra  

Microsoft Academic Search

Substructure identification rules for phenothiazine and barbiturate substructures were generated by using a new version of\\u000a the Method for Analyzing Patterns in Spectra (MAPS) software. This software uses tandem mass spectra and known substructure\\u000a content of reference compounds to provide “feature-combination“ rules. A feature-combination is a series of tandem mass spectral\\u000a features which are completely unique to compounds containing a

K. J. Hart; A. P. Wade; B. D. Nourse; C. G. Enke

1992-01-01

227

Substructure based modeling of nickel single crystals cycled at low plastic strain amplitudes  

Microsoft Academic Search

In this dissertation a meso-scale, substructure-based, composite single crystal model is fully developed from the simple uniaxial model to the 3-D finite element method (FEM) model with explicit substructures and further with substructure evolution parameters, to simulate the completely reversed, strain controlled, low plastic strain amplitude cyclic deformation of nickel single crystals. Rate-dependent viscoplasticity and Armstrong-Frederick type kinematic hardening rules

Dong Zhou

2004-01-01

228

Effect of substructure on the mechanical properties of Fe-Ni-Co-C alloys  

Microsoft Academic Search

The effect of transformation substructure (lath or twinned plates) and its subsequent modification of carbide distribution during tempering on the mechanical properties was investigated in Fe-Ni-Co alloys with and without 0.1 pct carbon. The morphology and substructure of carbon free and 0.1 pct carbon Fe-Ni-Co martensites do not have a significant effect on fracture toughness. The transformation substructure by itself

M. Raghavan; G. Thomas

1979-01-01

229

Effects of substructure on the mechanical properties of Fe-Ni-Co-C alloys  

Microsoft Academic Search

The effect of transformation substructure (lath or twinned plates) and its subsequent modification of carbide distribution\\u000a during tempering on the mechanical properties was investigated in Fe-Ni-Co alloys with and without 0.1 pct carbon. The morphology\\u000a and substructure of carbon free and 0.1 pct carbon Fe-Ni-Co martensites do not have a significant effect on fracture toughness.\\u000a The transformation substructure by itself

M. Raghavan; G. Thomas

1979-01-01

230

LIGO\\/VIRGO searches for gravitational radiation in hypernovae  

Microsoft Academic Search

A torus around a stellar mass Kerr black hole can emit about 10% of the\\u000aspin-energy of the black hole in gravitational radiation, potentially\\u000aassociated with a gamma-ray burst. Wide tori may develop buckling modes by the\\u000aPapaloizou-Pringle instability and gravitational radiation-reaction forces in\\u000athe Burke-Thorne approximation. Gravitational wave experiments may discover\\u000athese emissions in a fraction of nearby supernovae.

2002-01-01

231

Stellar structures in the outer regions of M 33  

NASA Astrophysics Data System (ADS)

Aims: We present Subaru/Suprime-Cam deep V and I imaging of seven fields in the outer regions of M 33. Our aim is to search for stellar structures corresponding to extended Hi clouds found in a recent 21-cm survey of the galaxy. Three fields probe a large Hi complex to the southeastern (SE) side of the galaxy. An additional three fields cover the northwestern (NW) side of the galaxy along the Hi warp. A final target field was chosen further north, at a projected distance of approximately 25 kpc, to study part of the large stellar plume recently discovered around M 33. Methods: We analyse the stellar population at R > 10 kpc by means of V, I colour magnitude diagrams reaching the red clump. We constrain the age and metallicity of the different stellar populations, search for density enhancements that correspond to the Hi features, and investigate the radial surface distribution of the stars. Results: We find evolved stellar populations in all fields out to 120'(~30 kpc), while a diffuse population of young stars (~200 Myr) is detected out to a galactocentric radius of 15 kpc. The mean metallicity in the southern fields remains approximately constant at [M/H] = -0.7 beyond the edge of the optical disc, from 40'out to 80'. Along the northern fields probing the outer Hi disc, we also find a metallicity of [M/H] = -0.7 between 35'and 70'from the centre, which decreases to [M/H] = -1.0 at larger angular radii out to 120'. In the northernmost field, outside the disc extent, the stellar population of the large stellar plume possibly related to a M 33-M 31 interaction is on average more metal-poor ([M/H] = -1.3) and older (?6 Gyr). Conclusions: An exponential disc with a large scale-length (~7 kpc) fits well the average distribution of stars detected in both the SE and NW regions from a galactocentric distance of 11 kpc out to 30 kpc. The stellar disc extends beyond the Hi disc. The stellar distribution at large radii is disturbed and, although there is no clear correlation between the stellar substructures and the location of the Hi clouds, this gives evidence of tidal interaction or accretion events. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.Photometry is only available in electronic form at at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A91

Grossi, M.; Hwang, N.; Corbelli, E.; Giovanardi, C.; Okamoto, S.; Arimoto, N.

2011-09-01

232

Unexpected relationships of substructured populations in Chinese Locusta migratoria  

PubMed Central

Background Highly migratory species are usually expected to have minimal population substructure because strong gene flow has the effect of homogenizing genetic variation over geographical populations, counteracting random drift, selection and mutation. The migratory locust Locusta migratoria belongs to a monotypic genus, and is an infamous pest insect with exceptional migratory ability – with dispersal documented over a thousand kilometers. Its distributional area is greater than that of any other locust or grasshopper, occurring in practically all the temperate and tropical regions of the eastern hemisphere. Consequently, minimal population substructuring is expected. However, in marked contrast to its high dispersal ability, three geographical subspecies have been distinguished in China, with more than nine being biologically and morphologically identified in the world. Such subspecies status has been under considerable debate. Results By multilocus microsatellite genotyping analysis, we provide ample genetic evidence for strong population substructure in this highly migratory insect that conforms to geography. More importantly, our genetic data identified an unexpected cryptic subdivision and demonstrated a strong affiliation of the East China locusts to those in Northwest/Northern China. The migratory locusts in China formed three distinct groups, viz. (1) the Tibetan group, comprising locusts from Tibet and nearby West China high mountain regions; this is congruent with the previously recognized Tibetan subspecies, L. m. tibetensis; (2) the South China group, containing locusts from the Hainan islands; this corresponds to the Southeast Asia oriental tropical subspecies L. m. manilensis; (3) the North China group, including locusts from the Northwest and Northern China (the Asiatic subspecies L. m. migratoria), Central China and Eastern China regions. Therefore, the traditional concept on Locusta subspecies status established from Uvarov in 1930s needs to be revised. The three groups of locusts probably have separate evolutionary histories that were most likely linked to Quaternary glaciations events, and derived from different ancestral refugial populations following postglacial expansions. Conclusion The migratory locust populations in China have differentiated into three genetically distinct groups despite high dispersal capability. While this clarified long-standing suspicions on the subspecific diversification of this species in China, it also revealed that the locusts in the vast area of East China are not the oriental subspecies but the Asiatic subspecies, an unexpected substructuring pattern. The distribution pattern of the three locust groups in China may be primarily defined by adaptive differentiation coupled to Quaternary glaciations events. Our results are of general significance both for locust research and for phylogeographical study of flora and fauna in China, illustrating the potential importance of phylogeographical history in shaping the divergence and distribution patterns of widespread species with strong dispersal ability.

Zhang, De-Xing; Yan, Lu-Na; Ji, Ya-Jie; Hewitt, Godfrey M; Huang, Zu-Shi

2009-01-01

233

Aligning graphs and finding substructures by a cavity approach  

NASA Astrophysics Data System (ADS)

We introduce a new distributed algorithm for aligning graphs or finding substructures within a given graph. It is based on the cavity method and is used to study the maximum-clique and the graph-alignment problems in random graphs. The algorithm allows to analyze large graphs and may find applications in fields such as computational biology. As a proof of concept we use our algorithm to align the similarity graphs of two interacting protein families involved in bacterial signal transduction, and to predict actually interacting protein partners between these families.

Bradde, S.; Braunstein, A.; Mahmoudi, H.; Tria, F.; Weigt, M.; Zecchina, R.

2010-02-01

234

Convergence of a Substructuring Method with LaGrange Multipliers  

NASA Technical Reports Server (NTRS)

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

Mandel, Jan; Tezaur, Radek

1996-01-01

235

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

236

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

237

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

238

Multicolor stellar photometry  

NASA Astrophysics Data System (ADS)

The monograph describes all multicolor photometric systems which were in use for stellar photometry before 1990, particularly the UBV, Strömgren and Vilnius systems. The reviews of common properties of photometric systems, energy distribution in stellar spectra, interstellar and atmospheric extinction, photometric classification methods of stars are also given. The book includes calibrations of spectral MK types in absolute magnitudes, bolometric corrections, effective temperatures, surface gravities, masses and radii. Intrinsic color indices of the UBV, Strömgren, Vilnius and infrared systems are tabulated. The volume of the book is 570 pages. A pdf file of the book is available at: http://www.itpa.lt/MulticolorStellarPhotometry/

Straižys, Vytautas

239

Double-helix stellarator  

SciTech Connect

A new stellarator configuration, the Double-Helix Stellarator (DHS), is introduced. This novel configuration features a double-helix center post as the only helical element of the stellarator coil system. The DHS configuration has many unique characteristics. One of them is the extreme low plasma aspect ratio, A {approx} 1--1.2. Other advantages include a high enclosed volume, appreciable rotational transform, and a possibility of extreme-high-{beta} MHD equilibria. Moreover, the DHS features improved transport characteristics caused by the absence of the magnetic field ripple on the outboard of the torus. Compactness, simplicity and modularity of the coil system add to the DHS advantages for fusion applications.

Moroz, P.E.

1997-09-01

240

Stellarator-Spheromak  

SciTech Connect

A novel concept for magnetic plasma confinement, Stellarator-Spheromak (SSP), is proposed. Numerical analysis with the classical-stellarator-type outboard stellarator windings demonstrates a number of potential advantages of SSP for controlled nuclear fusion. Among the main ones are: simple and compact magnet coil configuration, absence of material structures (e.g. magnet coils or conducting walls) in the center of the torus, high rotational transform, and a possibility of MHD equilibria with very high {beta} (pressure/magnetic pressure) of the confined plasma.

Moroz, P.E. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Nuclear Engineering and Engineering Physics

1997-03-01

241

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.

242

Galactic substructure and direct detection of dark matter  

SciTech Connect

We study the effects of substructure in the Galactic halo on direct detection of dark matter, on searches for energetic neutrinos from weakly interacting massive particles (WIMP) annihilation in the Sun and Earth, and on the enhancement in the WIMP annihilation rate in the halo. Our central result is a probability distribution function (PDF) P({rho}) for the local dark-matter density. This distribution must be taken into account when using null dark-matter searches to constrain the properties of dark-matter candidates. We take two approaches to calculating the PDF. The first is an analytic model that capitalizes on the scale-invariant nature of the structure-formation hierarchy in order to address early stages in the hierarchy (very small scales; high densities). Our second approach uses simulation-inspired results to describe the PDF that arises from lower-density larger-scale substructures which formed in more recent stages in the merger hierarchy. The distributions are skew positive, and they peak at densities lower than the mean density. The local dark-matter density may be as small as 1/10th the canonical value of {approx_equal}0.4 GeV cm{sup -3}, but it is probably no less than 0.2 GeV cm{sup -3}.

Kamionkowski, Marc; Koushiappas, Savvas M. [California Institute of Technology, Mail Code 130-33, Pasadena, CA 91125 (United States); Los Alamos National Laboratory, Mail Stop B227, Los Alamos, NM 87545 (United States)

2008-05-15

243

An Efficient Crankshaft Dynamic Analysis Using Substructuring with Ritz Vectors  

NASA Astrophysics Data System (ADS)

A structural analysis using dynamic substructuring with Ritz vectors is presented for predicting the dynamic response of an engine crankshaft, based on the finite-element method. A two-level dynamic substructuring is performed using a set of load-dependent Ritz vectors. The rotating crankshaft is properly coupled with the non-rotating, compliant engine block. The block compliance is represented by a distributed linear elastic foundation at each main bearing location. The stiffness of the elastic foundation can be different in the vertical and horizontal planes, thereby considering the anisotropy of the engine block compliance with respect to the crankshaft rotation. The analysis accounts for the kinematic non-linearity resulting from the crankangle-dependent circumferential contact location between each journal and the corresponding bore of the engine block. Crankshaft “bent” and block “misboring” effects due to manufacturing imperfections are considered in the analysis. The superior accuracy and reduced computational effort of the present method as compared with the equivalent superelement analysis in MSC/NASTRAN, are demonstrated using the free and forced vibrations of a slender cylindrical beam and free vibrations of a four-cylinder engine crankshaft. Subsequently, the accuracy of the present method in calculating the dynamic response of engine crankshafts is shown through comparisons between the analytical predictions and experimental results for the torsional vibrations of an in-line five cylinder engine and the bending vibrations of the crankshaft-flywheel assembly of a V6 engine.

MOURELATOS, Z. P.

2000-11-01

244

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

245

Fast approximation of synthesized frequency response functions with automated multi-level substructuring (AMLS)  

Microsoft Academic Search

This paper presents an industrial validation case to evaluate the efficiency of automated multi-level substructuring (AMLS). This relatively new technique allows analysis of large structures up to frequencies where conventional methods are too computationally expensive. The finite element model of an industrial-sized passenger vehicle will be subjected to the substructuring procedure of AMLS. The global response will then be presented

P. Ragnarsson; T. Van Gaal; B. Pluymers; S. Donders; D. Vandepitte; W. Desmet

2011-01-01

246

Pseudodynamic testing and nonlinear substructuring of damaging structures under earthquake loading  

Microsoft Academic Search

Pseudodynamic or PSD testing with substructuring technique is a highly relevant approach to capture the dynamic failure mechanisms of a structure. It allows one to realistically test a structure subject to an earthquake with accessible experimental equipment. We propose in this paper to apply such a PSD testing with substructuring to damaging structures, where the nonlinear behaviour is represented by

A. Souid; A. Delaplace; F. Ragueneau; R. Desmorat

2009-01-01

247

New UBV parameters for 46 E-SO galaxies in the Virgo cluster  

NASA Astrophysics Data System (ADS)

Multi-aperture UBV photometry of 46 Virgo cluster E-SO galaxies has been obtained. This material has been checked and completed with other photoelectric data in the literature, to provide a hopefully improved set of the parameters defined in the Second Reference Catalogue of Bright Galaxies, i.e. asymptotic magnitude BT, effective aperture diameter Ae, and colors within Ae. Interpolated UBV parameters at the standard aperture of 1' are also given, to provide calibration of surface photometry. Various known correlations are rediscussed with this material. It appears that the color-magnitude diagram (U-V)e - VT of E-SO galaxies in Virgo is curved. This effect is dependent of the choice of the parameters and would be lessened, but not suppressed, by defining the color and magnitude parameters in the same way as Visvanathan and Sandage (1977). After correction for the magnitude effect, SO galaxies appear marginally redder and SBO significantly redder than ellipticals.

Michard, R.

1982-08-01

248

Evaluating the gamma-ray evidence for self-annihilating dark matter from the Virgo cluster  

NASA Astrophysics Data System (ADS)

Based on three years of Fermi Large Area Telescope (LAT) gamma-ray data of the Virgo cluster, evidence for an extended emission associated with dark matter pair annihilation in the bb¯ channel has been reported by Han et al. [arXiv:1201.1003]. After an in-depth spatial and temporal analysis, we argue that the tentative evidence for a gamma-ray excess from the Virgo cluster is mainly due to the appearance of a population of previously unresolved gamma-ray point sources in the region of interest. These point sources are not part of the LAT second source catalog (2FGL), but are found to be above the standard detection significance threshold when three or more years of LAT data are included.

Macías-Ramírez, Oscar; Gordon, Chris; Brown, Anthony M.; Adams, Jenni

2012-10-01

249

Collisional removal of HI from the inner disks of Virgo cluster galaxies  

NASA Technical Reports Server (NTRS)

There is sufficient observational evidence to show that many Virgo Cluster spirals are HI deficient in their inner disks (in addition to being HI deficient globally, as previously established). It is shown here that collisions between galaxies in a cluster can lead to the removal of HI gas from these galaxies while leaving the H2 gas, undisturbed. This follows directly from the application of the Spitzer-Baade collisional gas removal mechanism to galaxies consisting of stars and a two-component interstellar medium (ISM) consisting of HI and H2, with HI having the largest filling factor. This can account for both the observed HI deficiency in the inner regions and the normal H2 content of these galaxies. The frequency of galaxy collisions in the Virgo Cluster is shown to be large enough to make collisional gas removal a viable mechanism.

Valluri, Monica; Jog, Chanda J.

1990-01-01

250

First Low-Latency LIGO+Virgo Search for Binary Inspirals and Their Electromagnetic Counterparts  

NASA Astrophysics Data System (ADS)

The detection and measurement of gravitational waves from coalescing neutron star binary systems is an important science goal for ground-based gravitational-wave detectors. In addition to emitting gravitational waves at frequencies that span the most sensitive bands of the LIGO and Virgo detectors, these sources are also amongst the most likely to produce an electromagnetic counterpart to the gravitational wave emission. A joint detection of the gravitational wave and electromagnetic signals would provide a powerful new probe for astronomy. During the period between September 19 and October 20, 2010, the first low-latency search for gravitational waves from binary inspirals in LIGO and Virgo data was conducted. The resulting triggers were sent to electromagnetic observatories for followup. We describe the generation and processing of the low-latency gravitational-wave triggers.

Price, Larry

2013-01-01

251

Molecular gas and star formation in HI-deficient Virgo cluster galaxies  

NASA Technical Reports Server (NTRS)

Mapping of the CO emission line in 42 Virgo cluster galaxies reveals that the molecular gas contents and distributions are roughly normal in severaly HI-deficient Virgo spirals. The survival of the molecular component mitigates the impact of the HI-stripping on star formation and subsequent galactic evolution. For spirals which are deficient in HI by a factor of 10, far-infrared, H alpha line, and nonthermal radio continuum luminosities are lower by no more than a factor of 2. The fact that the inner galactic disks are stripped of HI, while CO is normal, suggests that the lifetime of the molecular phase is approximately one billion years in the inner regions of luminous spirals.

Kenney, Jeffrey D.; Young, Judith S.

1987-01-01

252

A search for extended halos of hot gas in the Perseus, Virgo, and Coma Clusters  

NASA Technical Reports Server (NTRS)

Observations of the Perseus cluster by the HEAO 1 satellite have revealed a faint X-ray halo extending at least 2.5 deg from the center and contributing between 5% and 20% to the total luminosity. This may be of nonthermal origin, but it also may be explained in terms of hot gas bound by the gravitational field of the cluster. Statistical uncertainties made it impossible to detect any such halo in the Coma cluster. Observations of the Virgo cluster confirmed the detection by the Ariel 5 satellite of a broad region of faint X-ray emission (core radius 60 arcmin). If the very extended X-ray emission from Virgo is due to hot intracluster gas, the density of this gas is lower than expected from a consideration of gas and galaxy densities in the Perseus cluster.

Ulmer, M. P.; Cruddace, R. G.; Wood, K.; Meekins, J.; Yentis, D.; Evans, W. D.; Smathers, H. W.; Byram, E. T.; Chubb, T. A.; Friedman, H.

1980-01-01

253

INSIGHT INTO THE FORMATION OF THE MILKY WAY THROUGH COLD HALO SUBSTRUCTURE. II. THE ELEMENTAL ABUNDANCES OF ECHOS  

SciTech Connect

We determine the average metallicities of the elements of cold halo substructure (ECHOS) that we previously identified in the inner halo of the Milky Way within 17.5 kpc of the Sun. As a population, we find that stars kinematically associated with ECHOS are chemically distinct from the background kinematically smooth inner halo stellar population along the same Sloan Extension for Galactic Understanding and Exploration (SEGUE) line of sight. ECHOS are systematically more iron-rich, but less {alpha}-enhanced than the kinematically smooth component of the inner halo. ECHOS are also chemically distinct from other Milky Way components: more iron-poor than typical thick-disk stars and both more iron-poor and {alpha}-enhanced than typical thin-disk stars. In addition, the radial velocity dispersion distribution of ECHOS extends beyond {sigma} {approx} 20 km s{sup -1}. Globular clusters are unlikely ECHOS progenitors, as ECHOS have large velocity dispersions and are found in a region of the Galaxy in which iron-rich globular clusters are very rare. Likewise, the chemical composition of stars in ECHOS does not match predictions for stars formed in the Milky Way and subsequently scattered into the inner halo. Dwarf spheroidal (dSph) galaxies are possible ECHOS progenitors, and if ECHOS are formed through the tidal disruption of one or more dSph galaxies, the typical ECHOS [Fe/H] {approx} - 1.0 and radial velocity dispersion {sigma} {approx} 20 km s{sup -1} implies a dSph with M{sub tot} {approx}> 10{sup 9} M{sub sun}. Our observations confirm the predictions of theoretical models of Milky Way halo formation that suggest that prominent substructures are likely to be metal-rich, and our result implies that the most likely metallicity for a recently accreted star currently in the inner halo is [Fe/H] {approx} - 1.0.

Schlaufman, Kevin C.; Rockosi, Constance M. [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); Allende Prieto, Carlos, E-mail: kcs@ucolick.org, E-mail: crockosi@ucolick.org, E-mail: lee@pa.msu.edu, E-mail: beers@pa.msu.edu, E-mail: callende@iac.es [Instituto de Astrofisica de Canarias, 38205 La Laguna, Tenerife (Spain)

2011-06-10

254

Large-scale magnetized outflows from the Virgo Cluster spiral NGC4569  

Microsoft Academic Search

Using the Effelsberg radio telescope at 4.85GHz and 8.35 GHz we discovered large symmetric lobes of polarized radio emission around the strongly HI deficient Virgo cluster spiral galaxy NGC4569. These lobes extend up to 24 kpc from the galactic disk. Our observations were complemented by 1.4 GHz continuum emission from existing HI observations. This is the first time that such

K. T. Chyzy; M. Soida; D. J. Bomans; Ch. Balkowski; R. Beck; M. Urbanik

2005-01-01

255

Spitzer\\/IRAC Low Surface Brightness Observations of the Virgo Cluster  

Microsoft Academic Search

We present 3.6 and 4.5 mum Spitzer Infrared Array Camera (IRAC) imaging over 0.77 deg2 at the Virgo cluster core for the purpose of understanding the formation mechanisms of the low surface brightness intracluster light (ICL) features. Instrumental and astrophysical backgrounds that are hundreds of times higher than the signal were carefully characterized and removed. We examine ICL plumes as

J. E. Krick; C. Bridge; V. Desai; J. C. Mihos; E. Murphy; C. Rudick; J. Surace; J. Neill

2011-01-01

256

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

257

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

Microsoft Academic Search

We have applied a relativistic Tolman-Bondi model of the Virgo cluster to a\\u000asample of 183 galaxies with measured distances within a radius of 8 degrees\\u000afrom M87. We find that the sample is significantly contaminated by background\\u000agalaxies which lead to too large a cluster mean distance if not excluded. The\\u000aTolman-Bondi model predictions, together with the HI deficiency

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

2001-01-01

258

The Heavy-Element Enrichment of Lyalpha Clouds in the Virgo Supercluster  

Microsoft Academic Search

Using high signal-to-noise ratio echelle spectra of 3C 273 obtained with the Space Telescope Imaging Spectrograph (resolution of 7 km s-1 FWHM), we constrain the metallicities of two Lyalpha clouds in the vicinity of the Virgo Cluster. We detect C II, Si II, and Si III absorption lines in the Lyalpha absorber at zabs=0.00530. Previous observations with the Far Ultraviolet

T. M. Tripp; E. B. Jenkins; G. M. Williger; S. R. Heap; C. W. Bowers; A. C. Danks; R. Davé; R. F. Green; T. R. Gull; C. L. Joseph; M. E. Kaiser; D. Lindler; R. J. Weymann; B. E. Woodgate

2002-01-01

259

The Heavy Element Enrichment of LyClouds in the Virgo Supercluster1  

Microsoft Academic Search

Using high signal-to-noise echelle spectra of 3C 273 obtained with the Space Tele- scope Imaging Spectrograph (resolution = 7 km s?1 FWHM), we constrain the metal- licities of two Ly? clouds in the vicinity of the Virgo cluster. We detect C II, Si II, and Si III absorption lines in the Ly? absorber at zabs = 0.00530. Previous observations with

T. M. Tripp; E. B. Jenkins; G. M. Williger; S. R. Heap; C. W. Bowers; A. C. Danks

260

DISSECTING GALAXY FORMATION. II. COMPARING SUBSTRUCTURE IN PURE DARK MATTER AND BARYONIC MODELS  

SciTech Connect

We compare the substructure evolution in pure dark matter (DM) halos with those in the presence of baryons, hereafter PDM and BDM models, respectively. The prime halos have been analyzed in the previous work. Models have been evolved from identical initial conditions which have been constructed by means of the constrained realization method. The BDM model includes star formation and feedback from stellar evolution onto the gas. A comprehensive catalog of subhalo populations has been compiled and individual and statistical properties of subhalos analyzed, including their orbital differences. We find that subhalo population mass functions in PDM and BDM are consistent with a single power law, M {sup {alpha}}{sub sbh}, for each of the models in the mass range of {approx}2 x 10{sup 8} M{sub sun}-2 x 10{sup 11} M{sub sun}. However, we detect a nonnegligible shift between these functions, the time-averaged {alpha} {approx} -0.86 for the PDM and -0.98 for the BDM models. Overall, {alpha} appears to be a nearly constant in time, with variations of {+-}15%. Second, we find that the radial mass distribution of subhalo populations can be approximated by a power law, R{sup {gamma}{sub sbh}} with a steepening that occurs at the radius of a maximal circular velocity, R{sub vmax}, in the prime halos. Here we find that {gamma}{sub sbh} {approx} -1.5 for the PDM and -1 for the BDM models, when averaged over time inside R{sub vmax}. The slope is steeper outside this region and approaches -3. We detect little spatial bias (less than 10%) between the subhalo populations and the DM distribution of the main halos. Also, the subhalo population exhibits much less triaxiality in the presence of baryons, in tandem with the shape of the prime halo. Finally, we find that, counter-intuitively, the BDM population is depleted at a faster rate than the PDM one within the central 30 kpc of the prime halo. The reason for this is that although the baryons provide a substantial glue to the subhalos, the main halo exhibits the same trend. This assures a more efficient tidal disruption of the BDM subhalo population. However, this effect can be reversed for a more efficient feedback from stellar evolution and the central supermassive black holes, which will expel baryons from the center and decrease the central concentration of the prime halo. We compare our results with via Lactea and Aquarius simulations and other published results.

Romano-Diaz, Emilio; Shlosman, Isaac [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055 (United States); Heller, Clayton [Department of Physics, Georgia Southern University, Statesboro, GA 30460 (United States); Hoffman, Yehuda [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel)

2010-06-20

261

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

262

X-RAY TRANSIENTS IN THE ADVANCED LIGO/VIRGO HORIZON  

SciTech Connect

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

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

2013-09-01

263

Stellar population synthesis  

NASA Astrophysics Data System (ADS)

In this paper we review the study of stellar population synthesis. So far there exist three methods in the study of the integrated light of stellar population-trail-and error, automated, and evolutionary population synthesis (EPS). We have discussed advantages and disadvantages for these methods. Among the three methods the EPS is the most direct approach to model galaxies. In this scheme, the model builder starts with knowledge of stellar evolution and attempts to build a model galaxy with physical input parameters such as star formation rate (SFR) and the initial mass function (IMF) slope. Therefore we have discussed emphatically the EPS method. First we have described and given the often used grids of several key ingredients in the EPS studies: (1) the library of evolutionary tracks used to calculate isochrones in the color-magnitude diagram (CMD), (2) the libraries of spectra adopted, which include empirical and theoretical stellar spectral libraries, star cluster library, active galactic nuclear (AGN) library and galaxy library, to derive the integrated spectral energy distributions (ISED) or magnitudes and colors in the suitable passbands, (3) the IMF used to evaluate the relative proportions of stars in the various evolutionary phases, and (4) the assumption for the underlying star formation rate (SFR) and chemical enrichment. Then we have listed several population synthesis criterions, i.e. broadband color indices, the integrated spectral energy distribution (ISED) and narrow band color indices, given the basic method of calculating broadband colors and flux-distribution for a simple stellar population (SSP). At last we have discussed simply the existed limitations, which are caused by some uncertainties in its two principal building blocks: stellar evolution models and spectral libraries in the studies of the EPS. Stellar evolution models are often subject to limitations in the following areas: the atomic data (radiative opacities, heavy element mixture, helium content, reaction rates), the convection theory (mixing length, overshooting, semiconvection), the mixing in radiative regions (rotational mixing, thermal diffusion, gravitational settling), and the mass loss. As for stellar spectral libraries, most of them, including the empirical and the theoretical, are available only in some effective temperature ranges, surface gravity and/or metallicity. Thus in most EPS studies several stellar spectral libraries are often incorporated to convert stellar evolutionary parameters into colors. There also exist some mismatches in temperature to color conversion between synthetic/empirical estimates and the shape of the flux curve, especially that of type K and M stars.

Zhang, Feng-Hui; Li, Li-Fang; Han, Zhan-Wen

264

A Galactic-Scale Origin for Stellar Clustering  

NASA Astrophysics Data System (ADS)

We recently presented a model for the cluster formation efficiency (CFE), i.e. the fraction of star formation occurring in bound stellar clusters. It utilizes the idea that the formation of stars and stellar clusters occurs across a continuous spectrum of ISM densities. Bound stellar clusters naturally arise from the high-density end of this density spectrum. Due to short free-fall times, these high-density regions can achieve high star formation efficiencies (SFEs) and can be unaffected by gas expulsion. Lower-density regions remain gas-rich and substructured, and are unbound upon gas expulsion. The model enables the CFE to be calculated using galactic-scale observables. I present a brief summary of the model physics, assumptions and caveats, and show that it agrees well with observations. Fortran and IDL routines for calculating the CFE are publicly available at http://www.mpa-garching.mpg.de/cfe .

Kruijssen, J. M. Diederik

265

Resolving the Chemical Substructure of Orion-KL  

NASA Astrophysics Data System (ADS)

Context. The Kleinmann-Low nebula in Orion (Orion-KL) is the closest example of a high-mass star forming environment. Studying the resolved chemical structure of this complex region can provide important insight for relating the chemistry of high mass star forming regions with their evolutionary state. We present a line survey of Orion-KL obtained from the combined Submillimeter Array (SMA) and IRAM 30 m single-dish data. Covering 4 GHz bandwidth in total, this survey contains at least 160 emission lines from 27 chemical species. Aims. The goal of this work is to resolve the molecular line emission from individual substructure in Orion-KL at high spectral and spatial resolution, inferring the chemical properties of the associated gas. Methods. The spectra from different substructures are extracted and the intensity-integrated distribution maps for different molecules are imaged. We then calculate column densities, and abundances for each molecule in each identified substructure, assuming local thermal equilibrium (LTE), and that the lines are both optically thin and have uniform widths for all species. Results. By complementing interferometric data of the Orion-KL region with single-dish data to recover the short spacing information, we are able to study spatial abundance variations in this region for the first time. On one hand, at the spatial resolution of 4 arcsec, several substructures appear on the continuum map. The strongest emission from nitrogen-bearing molecules comes from the main hot core, which has chemistry typical of an active region, while sulfur-bearing and carbon monoxides have extended emission covering the cooler southern ridge and outflow regions. In contrast, the distribution of saturated complex organics is more complicated. Most of them peak at either the hot core (e.g., CH3OH) or the compact ridge (e.g., HCOOCH3), while others peak at intermediate positions between the hot core and the compact ridge (e.g., CH3CH2OH). But nevertheless, no clear distinction can classify them in different groups yet. In addition, the chemistry within the outflow lobes does not appear to differ significantly from low-mass chemically active outflows, but the low-velocity outflow exhibits stronger emission from H2 and tracers like 34SO2, SO2, O13CS, 13CS than the high-velocity one, indicating stronger shocks. On the other hand, the high sensitivity of the dataset allows us to identify and spatially locate such weak complex molecules in Orion-KL as CH3COCH3, CH3OCH3, CH3CH2OH and, tentatively detected long carbon chain molecules like C6H & HC7N. These new features in hot core chemistry and outflow chemistry, indicated by the quantitative differences in molecular abundances from our data, will be important for interpreting molecular spectra from other high mass star forming regions.

Feng, Siyi; Beuther, Henrik; Semenov, Dmitry; Henning, Thomas; Palau, Aina

2013-07-01

266

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

267

An Impulse Based Substructuring approach for impact analysis and load case simulations  

NASA Astrophysics Data System (ADS)

In the present paper we outline the basic theory of assembling substructures for which the dynamics are described as Impulse Response Functions. The assembly procedure computes the time response of a system by evaluating per substructure the convolution product between the Impulse Response Functions and the applied forces, including the interface forces that are computed to satisfy the interface compatibility. We call this approach the Impulse Based Substructuring method since it transposes to the time domain the Frequency Based Substructuring approach. In the Impulse Based Substructuring technique the Impulse Response Functions of the substructures can be gathered either from experimental tests using a hammer impact or from time-integration of numerical submodels. In this paper the implementation of the method is outlined for the case when the impulse responses of the substructures are computed numerically. A simple bar example is shown in order to illustrate the concept. The Impulse Based Substructuring allows fast evaluation of impact response of a structure when the impulse response of its components is known. It can thus be used to efficiently optimize designs of consumer products by including impact behavior at the early stage of the design, but also for performing substructured simulations of complex structures such as offshore wind turbines. >It allows the evaluation of structures that would otherwise be too large and/or complex to be simulated or measured as a whole. Experimentally obtained substructures (measurements) can be combined with numerical substructures (FE models), in order to compute the dynamic behavior of the total structure. It allows sharing and combining of substructures from different project groups. In a design process one can easily replace one of the component models, without having to do the full analysis all over again. As the substructure dynamics are already pre-computed in terms of Frequency Response Functions or reduced models, one only needs to solve the compactly formulated, global system to obtain the new responses. The main subclasses of dynamic substructuring methods are the Frequency Based Substructuring (FBS) approaches and the Component Mode Synthesis (CMS) methods. The former of these two originated in the 1980s from the desire to assemble measured substructures using the obtained Frequency Response Functions (FRFs). For a historical overview of substructuring methods, the reader is referred to [1]. When the substructures are described by FRFs obtained experimentally, tremendous care must be taken to ensure a high degree of accuracy, for instance it must satisfy reciprocity, passivity and artifacts like additional mass effects or location/orientation errors in the sensors must be very small. In practice such errors often introduce in the assembled FRFs spurious peaks [2] and non-physical properties [3] that render the obtained assembled model useless. Obtaining high quality measured FRFs is delicate since, unless slow and costly step sines are used, the dynamic properties in the frequency domain are obtained through several processing steps (anti-aliasing filters, windowing, Fourier transforms) which will unavoidably alter the information contained in the measurements.

Rixen, Daniel J.; van der Valk, Paul L. C.

2013-12-01

268

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.

2013-01-01

269

Black Holes, Stellar Dynamics and Populations in the Nuclei of a Complete Sample of Elliptical Galaxies - Cont of 2607 - Part II  

NASA Astrophysics Data System (ADS)

We will determine the prevalence of massive black holes in a complete sample of bright Virgo ellipticals using FOS spectra and WFPC surface photometry. We will correlate the dynamical evidence for massive black holes with indicators of nuclear activity (radio and optical emission, and star formation). Additionally, we will use our data to study the stellar dynamics and demography of the 'cores' of these elliptical galaxies. Our observations will establish the fundamental properties of the nuclear regions: photometric profiles, rotation and dispersion velocities, and spectroscopic metallicity indicies. FOC-UV images will reveal the presence of young stars and/or nonthermal emission. We will determine black hole masses by comparing the predictions of self-consistent dynamical models of the core to the observed surface photometry and kinematics. We wil model the stellar populations by comparing the observed metallicities and spectral energy distributions to synthetic spectra constructed from stellar libraries.

Jaffe, Walter

1991-07-01

270

The Stellar Populations in the Outer Banks of Massive Disk Galaxies  

NASA Astrophysics Data System (ADS)

In recent years we have started to appreciate that the outer banks of galaxies contain valuable information about the formation process of galaxies. In hierarchical galaxy formation the stellar halos and thick disks of galaxies are formed by accretion of minor satellites, predominantly in the earlier assembly phases. The size, metallicity, and amount of substructure in current day halos are therefore directly related to issues like the small scale properties of the primordial power spectrum of density fluctuations and the suppression of star formation in small dark matter halos after reionization. We will show initial results from our ongoing HST/ACS GHOSTS (Galaxy Halos, Outer disks, Star clusters, Thick disks, and Substructure) survey of the resolved stellar populations of 14 nearby, massive disk galaxies. We will show that the smaller galaxies have no significant halo. We will present the stellar populations of a very low surface brightness stream around M83, the first such a stream resolved into stars beyond those of the Milky Way and M31. Finally, we will show that the old RGB stars of the thick disk in an edge-on galaxy truncate at the same radius as the young thin disk stars, providing insights into the formation of both disk truncations and thick disks.

De Jong, Roelof; GHOSTS Team

2006-12-01

271

Spherical Stellarator Configuration  

SciTech Connect

A novel ultralow aspect ratio stellarator system that can be called a spherical stellarator (SS), in analogy with the spherical tokamak concept, is considered. The coil configuration of a simplest SS differs from that of a spherical tokamak by inclination of the external parts of the toroidal field coils. This system possesses many attractive properties including compact design and coil simplicity, good access to the plasma, closed vacuum flux surfaces with large enclosed volume, significant external rotational transform, strong magnetic well, and simple divertor configuration. {copyright} {ital 1996 The American Physical Society.}

Moroz, P.E. [University of Wisconsin, Madison, Wisconsin 53706 (United States)] [University of Wisconsin, Madison, Wisconsin 53706 (United States); [Lodestar Research Corporation, Boulder, Colorado 80301 (United States)

1996-07-01

272

Evaluation of the increment of the sampling in optical testing using substructured Ronchi gratings  

NASA Astrophysics Data System (ADS)

In this paper, we use Ronchi substructured gratings to evaluate the increment of the accuracy in optical testing using a liquid crystal display. For this, we perform a comparison between the aberration function and the wavefront obtained with classical Ronchi gratings against the ones obtained using substructured Ronchi gratings. This analysis is performed for different gratings positions, both outside and inside of focus. We show the results obtained in the laboratory for a concave spherical mirror of 57.27 mm diameter and a radius of curvature of 397.55 mm. We conclude that by using substructured Ronchi gratings we can test a larger area of ronchigram.

Aguirre-Aguirre, D.; Granados-Agustín, F. S.; Campos-García, M.; Cornejo-Rodriguez, A.

2011-01-01

273

PREFACE: A Stellar Journey A Stellar Journey  

NASA Astrophysics Data System (ADS)

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

Asplund, M.

2008-10-01

274

Stellar Coronal Astronomy  

NASA Astrophysics Data System (ADS)

Coronal astronomy is by now a fairly mature discipline, with a quarter century having gone by since the detection of the first stellar X-ray coronal source (Capella), and having benefitted from a series of major orbiting observing facilities. Serveral observational characteristics of coronal X-ray and EUV emission have been solidly established through extensive observations, and are by now common, almost text-book, knowledge. At the same time the implications of coronal astronomy for broader astrophysical questions (e.g.Galactic structure, stellar formation, stellar structure, etc.) have become appreciated. The interpretation of stellar coronal properties is however still often open to debate, and will need qualitatively new observational data to book further progress. In the present review we try to recapitulate our view on the status of the field at the beginning of a new era, in which the high sensitivity and the high spectral resolution provided by Chandra and SMM-Newton will address new questions which were not accessible before.

Favata, Fabio; Micela, Giuseppina

2003-10-01

275

Libraries of Stellar Spectra  

NSDL National Science Digital Library

This is a guide to online and abstract libraries of stellar spectra. This reference list also includes information about the spectra of Late-M, L, and T Dwarf stars, Morgan-Keenan spectral classification, the solar spectrum, spectrophotometric atlases, and automated and neural network classification.

2005-04-25

276

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

277

Stellarator Helical Vacuum Vessel.  

National Technical Information Service (NTIS)

A design study of a stainless steel, heavy wall, helically shaped vacuum torus has been made for use in a proposed Stellarator configuration. The study concerns itself with the shape of the vacuum vessel and the division of the vessel into components that...

E. J. Yavornik

1983-01-01

278

Disentangling the dark matter halo from the stellar halo  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

279

COLUMN DETAIL WITH SUBSTRUCTURE/STEEL BEAM/CONCRETE BEAM AT FIRST AVENUE ONRAMP. ...  

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

COLUMN DETAIL WITH SUBSTRUCTURE/STEEL BEAM/CONCRETE BEAM AT FIRST AVENUE ON-RAMP. TRIANGLE BUILDING AT RIGHT SIDE OF PHOTOGRAPH. - Alaskan Way Viaduct and Battery Street Tunnel, Seattle, King County, WA

280

Connection between deformation-induced dislocation substructures and martensite formation in stainless steel  

Microsoft Academic Search

We report a quantitative connection between the strain amplitude dependencies of the organisation of dislocation cell substructures with the formation of deformation-induced martensite during cyclic plasticity of austenitic stainless steel at ambient temperature.

Arpan Das; S. Sivaprasad; P. C. Chakraborti; S. Tarafder

2011-01-01

281

Load and Resistance Factor Design (LRFD) for Highway Bridge Substructures: Reference Manual and Participant Workbook.  

National Technical Information Service (NTIS)

Highway substructures (i.e., foundations and abutments) have traditionally been designed using Allowable Stress Design (ASD) methods whereas superstructure components have been designed used Load Factor Design (LFD) methods. This application of ASD for su...

2001-01-01

282

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

283

Basic Parameter Estimation of Binary Neutron Star Systems by the Advanced LIGO/Virgo Network  

NASA Astrophysics Data System (ADS)

Within the next five years, it is expected that the Advanced LIGO/Virgo network will have reached a sensitivity sufficient to enable the routine detection of gravitational waves. Beyond the initial detection, the scientific promise of these instruments relies on the effectiveness of our physical parameter estimation capabilities. A major part of this effort has been toward the detection and characterization of gravitational waves from compact binary coalescence, e.g., the coalescence of binary neutron stars. While several previous studies have investigated the accuracy of parameter estimation with advanced detectors, the majority have relied on approximation techniques such as the Fisher Matrix which are insensitive to the non-Gaussian nature of the gravitational wave posterior distribution function. Here we report average statistical uncertainties that will be achievable for strong detection candidates (S/N = 20) over a comprehensive sample of source parameters. We use the Markov Chain Monte Carlo based parameter estimation software developed by the LIGO/Virgo Collaboration with the goal of updating the previously quoted Fisher Matrix bounds. We find the recovery of the individual masses to be fractionally within 9% (15%) at the 68% (95%) credible intervals for equal-mass systems, and within 1.9% (3.7%) for unequal-mass systems. We also find that the Advanced LIGO/Virgo network will constrain the locations of binary neutron star mergers to a median uncertainty of 5.1 deg2 (13.5 deg2) on the sky. This region is improved to 2.3 deg2 (6 deg2) with the addition of the proposed LIGO India detector to the network. We also report the average uncertainties on the luminosity distances and orbital inclinations of strong detections that can be achieved by different network configurations.

Rodriguez, Carl L.; Farr, Benjamin; Raymond, Vivien; Farr, Will M.; Littenberg, Tyson B.; Fazi, Diego; Kalogera, Vicky

2014-04-01

284

Variation in Recovery: Role of Gender on Outcomes of Young AMI Patients (VIRGO) Study Design  

PubMed Central

Background Among individuals with ischemic heart disease, young women with an acute myocardial infarction (AMI) represent an extreme phenotype associated with an excess mortality risk. While women younger than 55 years of age account for less than 5% of hospitalized AMI events, almost 16,000 deaths are reported annually in this group, making heart disease a leading killer of young women. Despite a higher risk of mortality compared with similarly aged men, young women have been the subject of few studies. Methods Variation in Recovery: Role of Gender on Outcomes of Young AMI Patients (VIRGO) is a large, observational study of the presentation, treatment and outcomes of young women and men with AMI. VIRGO will enroll 2,000 women, 18–55 years of age, with AMI and a comparison cohort of 1,000 men with AMI from more than 100 participating hospitals. The aims of the study are: to determine sex differences in the distribution and prognostic importance of biological, demographic, clinical, and psychosocial risk factors; determine whether there are sex differences in the quality of care received by young AMI patients; and determine how these factors contribute to sex differences in outcomes (including mortality, hospitalization and health status). Blood serum and DNA for consenting participants will be stored for future studies. Conclusions VIRGO will seek to identify novel and prognostic factors that contribute to outcomes in this young AMI population. Results from the study will be used to develop clinically useful risk-stratification models for young AMI patients, explain sex differences in outcomes and identify targets for intervention.

Lichtman, Judith H.; Lorenze, Nancy P.; D'Onofrio, Gail; Spertus, John A.; Lindau, Stacy T.; Morgan, Thomas M.; Herrin, Jeph; Bueno, Hector; Mattera, Jennifer A.; Ridker, Paul M.; Krumholz, Harlan M.

2011-01-01

285

Substructure dependence of jet cross sections at HERA and determination of ? s  

Microsoft Academic Search

Jet substructure and differential cross sections for jets produced in the photoproduction and deep inelastic ep scattering regimes have been measured with the ZEUS detector at HERA using an integrated luminosity of 82.2?pb?1. The substructure of jets has been studied in terms of the jet shape and subjet multiplicity for jets with transverse energies ETjet>17?GeV. The data are well described

S. Bhadra; C. D. Catterall; S. Fourletov; G. Hartner; S MIGLIORANZI; M. Soares; J. Standage; J. Repond; R. Yoshida; M. C. K. Mattingly; N. Pavel; P. Antonioli; G. Bari; M. Basile; L. Bellagamba; D. Boscherini; A. Bruni; G. Bruni; G. Cara Romeo; L. Cifarelli; F. Cindolo; A. Contin; M. Corradi; S. de Pasquale; P. Giusti; G. Iacobucci; A. Margotti; A. Montanari; R. Nania; F. Palmonari; A. Pesci; L. Rinaldi; G. Sartorelli; A. Zichichi; G. Aghuzumtsyan; D. Bartsch; I. Brock; S. Goers; H. Hartmann; E. Hilger; P. Irrgang; H.-P. Jakob; O. Kind; U. Meyer; E. Paul; J. Rautenberg; R. Renner; A. Stifutkin; J. Tandler; K. C. Voss; M. Wang; D. S. Bailey; N. H. Brook; J. E. Cole; G. P. Heath; T. Namsoo; S. Robins; M. Wing; M. Capua; A. Mastroberardino; M. Schioppa; G. Susinno; J. Y. Kim; I. T. Lim; K. J. Ma; M. Y. Pac; M. Helbich; Y. Ning; Z. Ren; W. B. Schmidke; F. Sciulli; J. Chwastowski; A. Eskreys; J. Figiel; A. Galas; K. Olkiewicz; P. Stopa; L. Zawiejski; L. Adamczyk; T. Bold; I. Grabowska-Bold; D. Kisielewska; A. M. Kowal; M. Kowal; J. Lukasik; M. Przybycien; L. Suszycki; D. Szuba; J. Szuba; A. Kotanski; W. Slominski; V. Adler; U. Behrens; I. Bloch; K. Borras; V. Chiochia; D. Dannheim; G. Drews; J. Fourletova; U. Fricke; A. Geiser; P. Göttlicher; O. Gutsche; T. Haas; W. Hain; S. Hillert; C. Horn; B. Kahle; U. Kötz; H. Kowalski; G. Kramberger; H. Labes; D. Lelas; H. Lim; B. Löhr; R. Mankel; I.-A. Melzer-Pellmann; C. N. Nguyen; D. Notz; A. E. Nuncio-Quiroz; A. Polini; A. Raval; U. Schneekloth; U. Stösslein; G. Wolf; C. Youngman; W. Zeuner; S. Schlenstedt; G. Barbagli; E. Gallo; C. Genta; P. G. Pelfer; A. Bamberger; A. Benen; F. Karstens; D. Dobur; N. N. Vlasov; P. J. Bussey; A. T. Doyle; J. Ferrando; S. Hanlon; D. H. Saxon; I. O. Skillicorn; I. Gialas; T. Carli; T. Gosau; U. Holm; N. Krumnack; E. Lohrmann; M. Milite; H. Salehi; P. Schleper; T. Schörner-Sadenius; S. Stonjek; K. Wichmann; K. Wick; A. Ziegler; C. Collins-Tooth; C. Foudas; R. Gonçalo; K. R. Long; A. D. Tapper; P. Cloth; D. Filges; M. Kataoka; K. Nagano; K. Tokushuku; S. Yamada; Y. Yamazaki; A. N. Barakbaev; E. G. Boos; N. S. Pokrovskiy; B. O. Zhautykov; D. Son; J. de Favereau; K. Piotrzkowski; F. Barreiro; C. Glasman; O. González; L. Labarga; J. del Peso; E. Tassi; J. Terrón; M. Zambrana; M. Barbi; F. Corriveau; S. Gliga; J. Lainesse; S. Padhi; D. G. Stairs; R. Walsh; T. Tsurugai; A. Antonov; P. Danilov; B. A. Dolgoshein; D. Gladkov; V. Sosnovtsev; S. Suchkov; R. K. Dementiev; P. F. Ermolov; I. I. Katkov; L. A. Khein; I. A. Korzhavina; V. A. Kuzmin; B. B. Levchenko; O. Yu. Lukina; A. S. Proskuryakov; L. M. Shcheglova; S. A. Zotkin; I. Abt; C. Büttner; A. Caldwell; X. Liu; J. Sutiak; N. Coppola; G. Grigorescu; S. Grijpink; A. Keramidas; E. Koffeman; P. Kooijman; E. Maddox; A. Pellegrino; S. Schagen; H. Tiecke; M. Vázquez; L. Wiggers; E. de Wolf; N. Brümmer; B. Bylsma; L. S. Durkin; T. Y. Ling; A. M. Cooper-Sarkar; A. Cottrell; R. C. E. Devenish; B. Foster; G. Grzelak; C. Gwenlan; T. Kohno; S. Patel; P. B. Straub; R. Walczak; P. Bellan; A. Bertolin; R. Brugnera; R. Carlin; F. dal Corso; S. Dusini; A. Garfagnini; S. Limentani; A. Longhin; A. Parenti; M. Posocco; L. Stanco; M. Turcato; E. A. Heaphy; F. Metlica; B. Y. Oh; J. J. Whitmore; Y. Iga; G. D'Agostini; G. Marini; A. Nigro; C. Cormack; J. C. Hart; N. A. McCubbin; C. Heusch; I. H. Park; H. Abramowicz; A. Gabareen; S. Kananov; A. Kreisel; A. Levy; M. Kuze; T. Fusayasu; S. Kagawa; T. Tawara; T. Yamashita; R. Hamatsu; T. Hirose; M. Inuzuka; H. Kaji; S. Kitamura; K. Matsuzawa; M. Costa; M. I. Ferrero; V. Monaco; R. Sacchi; A. Solano; M. Arneodo; M. Ruspa; T. Koop; J. F. Martin; A. Mirea; J. M. Butterworth; R. Hall-Wilton; T. W. Jones; M. S. Lightwood; M. R. Sutton; C. Targett-Adams; J. Ciborowski; R. Ciesielski; P. Luzniak; R. J. Nowak; J. M. Pawlak; J. Sztuk; T. Tymieniecka; A. Ukleja; J. Ukleja; A. F. Zarnecki; M. Adamus; P. Plucinski; Y. Eisenberg; D. Hochman; U. Karshon; M. Riveline; A. Everett; L. K. Gladilin; D. Kçira; S. Lammers; L. Li; D. D. Reeder; M. Rosin; P. Ryan; A. A. Savin; W. H. Smith; S. Dhawan; S. Menary

2004-01-01

286

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, Chicago /Chicago U., Astron. Astrophys. Ctr.

2005-06-01

287

The Dusty ISM Substructure in Nearby Spiral Galaxies  

NASA Astrophysics Data System (ADS)

We propose an ACS V&I imaging snapshot survey of all nearby edge-on spiral galaxies in order to measure the small scale structures in their dust extinction down to the 10pc scale. Dust and molecular gas are thightly coupled and therefore HST high resolution reddening maps can reveal information about the cold ISM phase on a scale inaccessible from the groundby any other means. We have recently discovered a sudden change in dust lane properties using ground-based data; all galaxies with rotation speeds in access of 120km/s show dust lanes, but none of the slower rotators does. This transition may be caused by a sudden change in the state of the multiphase ISM, and HST resolution imaging is needed to fully quantify this effect. Analysis will consist of full radiative transfer modeling of dust extinction with realistic, fractal like substructure and power spectrum analysis of the structure from the global to the 10pc scale. By observing a sample of galaxies with a range in structural parameters we can quantify how the cold ISM structure changes as function of radius, rotation speed, local surface density, et cetera. This information is duly needed with SIRTF soon providing a wealth of information on dust absorption, but lacking the resolution to determine the small scale distribution of the dust.

de Jong, Roelof

2003-07-01

288

Constrained-substructure approach to optimal strain energy analysis  

NASA Astrophysics Data System (ADS)

The chief tool for design of viscoelastic-based damping treatments over the past 20 years has been the modal strain energy (MSE) approach. This approach to damping design traditionally has involved a practitioner to vary placement and stiffness of add-on elements using experience and trial and error so as to maximize the add-on element's share of system MSE in modes of interest. In this paper we develop a new technique for maximizing strain energy as a function of stiffness for add-on structural elements modeled as rank r perturbations to the original stiffness matrix. The techniques is based on a constrained substructure approach allowing us to parameterize strain energy in terms of the eigenvalues of the perturbed structure. An optimality condition is derived that relates the input-output response at the attachment location of the add-on elements to the maximum achievable strain energy. A realizability condition is also derived which indicates whether or not the optimal solution is achievable with passive structural elements. This method has applications in the design of structural treatments for controlling sound and vibration and promises an efficient means of determining the limits of performance of passive structural treatments. An advantage of our approach over existing methods is that the maximum achievable strain energy fraction in the add-on elements is directly computable with the realizability condition then indicating whether the optimal solution is achievable.

Leo, Donald J.; Austin, Eric M.; Beattie, Christopher A.

2000-04-01

289

Scalable substructuring methods for high performance structural analysis  

NASA Astrophysics Data System (ADS)

The purpose of this research is to develop a fast and efficient parallel solver for large-scale, symmetric, positive semi-definite systems of equations that arise from finite element structural applications. Emphasis is on numerical and parallel scalability, with respect to the problem and machine size. The thesis begins by motivating the need for a robust, parallel iterative solver, highlighting the potential of substructuring for achieving this goal and justifying the selection of the FETI method, which Farhat and Roux originally developed as a basis for this research work. The remainder of the thesis defines and concerns the specific extensions of the FETI method. The FETI method is a Lagrange multiplier-based domain decomposition method for the parallel, iterative solution of self-adjoint, elliptic, partial differential equations semi-discretized by the finite element method. Its original version is mathematically optimal for second-order elasticity problems. The purpose of this thesis is to develop mathematically optimal extensions to elastodynamics problems, fourth-order plate and shell problems and problems with multiple right-hand sides, because these are the most frequent problems in aerospace structural engineering. Several static and transient structural analyses of realistic aerospace systems validate these extensions and illustrate their superior performance. These realistic aerospace systems run on several parallel computers, including the Paragon X/PS and IBM SP/2 parallel processors.

Chen, Po-Shu

290

Towards solar activity maximum 24 as seen by GOLF and VIRGO/SPM instruments  

NASA Astrophysics Data System (ADS)

All p-mode parameters vary with time as a response to the changes induced by the cyclic behavior of solar magnetic activity. After the unusual long solar-activity minimum between cycles 23 and 24 -where the p-mode parameters have shown a different behavior than the surface magnetic proxies- we analyze the temporal variation of low-degree p-mode parameters measured by GOLF (in velocity) and VIRGO (in intensity) Sun-as-a-star instruments on board SoHO. We compare our results with other activity proxies.

García, R. A.; Salabert, D.; Mathur, S.; Régulo, C.; Ballot, J.; Davies, G. R.; Jiménez, A.; Simoniello, R.

2013-06-01

291

Luminosity-velocity diagrams for Virgo Cluster spirals. I - Inner rotation curves  

NASA Technical Reports Server (NTRS)

Optical rotation curves are presented for the innermost portions of nine spiral galaxies in the Virgo Cluster. The emission-line (H-alpha and forbidden N II) velocity data are to be used in combination with new CCD photometry to construct luminosity-velocity diagrams, in a continuing investigation of an apparent initial linear branch and its potential as a distance indicator. Compared to recent H I data, the present optical rotation curves generally show systematically steeper inner gradients. This effect is ascribed to the poorer resolution of the H I data and/or to holes in the gas distribution.

Woods, David; Fahlman, Gregory G.; Madore, Barry F.

1990-01-01

292

Star formation in the cooling flows of M87/Virgo and NGC 1275/Perseus  

SciTech Connect

X-ray observations indicate that M87/Virgo and NGC 1275/Perseus have cooling flows that are associated with accretion rates of 20-30 and 300-500 solar masses/year, respectively. An assessment is made as to whether star formation is necessarily occurring in these cooling flows by calculating constant mass-flux models for all reasonable parameter space. No constant-mass-flux models that are consistent with all of the relevant observations are found; hence, it is concluded that mass is dropping out of these cooling flows. 51 references.

White, R.E. III; Sarazin, C.L.

1988-12-01

293

Star formation in the cooling flows of M87/Virgo and NGC 1275/Perseus  

NASA Technical Reports Server (NTRS)

X-ray observations indicate that M87/Virgo and NGC 1275/Perseus have cooling flows that are associated with accretion rates of 20-30 and 300-500 solar masses/year, respectively. An assessment is made as to whether star formation is necessarily occurring in these cooling flows by calculating constant mass-flux models for all reasonable parameter space. No constant-mass-flux models that are consistent with all of the relevant observations are found; hence, it is concluded that mass is dropping out of these cooling flows.

White, Raymond E., III; Sarazin, Craig L.

1988-01-01

294

Measuring the Hubble constant and our Virgo-infall velocity independently  

NASA Technical Reports Server (NTRS)

A sample of spiral galaxies with B(sub T) less than 14.5 located in two local volumes, one in the direction of, but behind, the Virgo Cluster (behind-Virgo volume (BV)) and the other in the opposite direction (anti-Virgo volume (AV)), were used via a Tully-Fisher (TF) relation to derive the following two parameters: H(sub AB), the mean Hubble ratio between AV and BV, and delta v(sub parallel), the peculiar velocity of the Local Group in the direction of the Virgo Cluster (VC) with respect to a uniformly expanding reference system defined by our AV and BV sub-samples. The two sampled volumes, separated by a velocity interval of 5600 km/s, form an antipodal pair. This particular geometry not only allows us to derive the two parameters independently but also reduces the dynamical effect of the Local Supercluster on H(sub AB) without increasing the Malmquist bias. By limiting our sample to spiral galaxies having large velocity widths W(sub R), we effectively reduce the TF scatter and Malmquist bias in our sample. The TF zero point and dispersion were then determined by further correcting for the small residual Malmquist bias. An additional sample of fainter galaxies was used to test for a non-Gaussian tail to the TF disperison. We found no evidence for such a tail and formally give an upper limit of about 18% for the fractional contribution of an unseen tail. The average intrinsic TF dispersion for the dominant Gaussian component is sigma(sub TF)(sup 0) approximately 0.33 mag for W(sub R) approximately equal to or greater than 180 km/s. Our numerical results are delta v(sub parallel) approximately equals 414 +/- 82 km/s and H(sub AB) approximately equals (84.0 +/- 2.4)(1 + epsilon) km/s Mpc, where (1 + epsilon) accounts for any systematic error between the calibrators and the sample galaxies. Various dynamical models were tested to explore the effect on H(sub AB) of the uncertainties in the local velocity field. Constrained by our observed delta v(sub parallel) as well as other observational quantities, we found that the rms deviation from unity of H(sub AB)/H(sub 0) (where H(sub 0) is the Hubble constant for each model) is 5%, making H(sub AB) a good indicator for H(sub 0). Taking this variation as an additional error, our formal estimate for the Hubble constant is H(sub 0) approximately equals (84 +/- 5)(1 + epsilon) km/s Mpc.

Lu, Nanyao Y.; Salpeter, E. E.; Hoffman, G. Lyle

1994-01-01

295

Investigation of the effectiveness of using an experiment to validate experimental substructure models  

NASA Astrophysics Data System (ADS)

Experimental-to-analytical substructuring has been investigated as a way to avoid costly tests and analyses on large systems by experimentally characterizing certain subcomponents and then coupling them to an analytical model for the rest of the structure. Unfortunately, substructuring has sometimes proven difficult to implement because the substructuring calculations can be sensitive to modal truncation and experimental noise and often require the measurement of rotational motions at the interface. These issues have led to decreased confidence in substructuring calculations, causing it to remain underutilized in industry. This work proposes performing a small, inexpensive validation test to give confidence or reveal flaws in an experimentally derived model. This is only meaningful if the error in the validation test is characteristic of the error in an application of interest; this work explores this assumption. The validation test is evaluated in two scenarios which represent substructuring realities. The first scenario investigates measurement errors by applying normally distributed noise to a simple beam structure and evaluating how well the validation test compares to the application of interest. The second scenario simulates substructuring of a complicated engine-generator system with a statically indeterminate connection, where the effect of modal truncation is not easy to anticipate.

Rohe, Daniel P.; Allen, Matthew S.

2014-02-01

296

Systematic benchmark of substructure search in molecular graphs - From Ullmann to VF2  

PubMed Central

Background Searching for substructures in molecules belongs to the most elementary tasks in cheminformatics and is nowadays part of virtually every cheminformatics software. The underlying algorithms, used over several decades, are designed for the application to general graphs. Applied on molecular graphs, little effort has been spend on characterizing their performance. Therefore, it is not clear how current substructure search algorithms behave on such special graphs. One of the main reasons why such an evaluation was not performed in the past was the absence of appropriate data sets. Results In this paper, we present a systematic evaluation of Ullmann’s and the VF2 subgraph isomorphism algorithms on molecular data. The benchmark set consists of a collection of 1235 SMARTS substructure expressions and selected molecules from the ZINC database. The benchmark evaluates substructures search times for complete database scans as well as individual substructure-molecule pairs. In detail, we focus on the influence of substructure formulation and size, the impact of molecule size, and the ability of both algorithms to be used on multiple cores. Conclusions The results show a clear superiority of the VF2 algorithm in all test scenarios. In general, both algorithms solve most instances in less than one millisecond, which we consider to be acceptable. Still, in direct comparison, the VF2 is most often several folds faster than Ullmann’s algorithm. Additionally, Ullmann’s algorithm shows a surprising number of run time outliers.

2012-01-01

297

Numerical investigation of lens models with substructures using the perturbative method  

NASA Astrophysics Data System (ADS)

We present a statistical study of the effects induced by substructures on the deflection potential of dark matter haloes in the strong lensing regime. This investigation is based on the pertubative solution around the Einstein radius in which all the information on the deflection potential is specified by only a pair of 1D functions on this ring. Using direct comparison with ray-tracing solutions, we found that the iso-contours of lensed images predicted by the pertubative solution is reproduced with a mean error on their radial extension of less than 1 per cent - in units of the Einstein radius, for reasonable substructure masses. It demonstrates the efficiency of the approximation to track possible signatures of substructures. We have evaluated these two fields and studied their properties for different lens configurations modelled either through massive dark matter haloes from a cosmological N-body simulation or via toy models of Monte Carlo distribution of substructures embedded in a triaxial Hernquist potential. As expected, the angular power spectra of these two fields tend to have larger values for larger harmonic numbers when substructures are accounted for and they can be approximated by power laws, whose values are fitted as a function of the profile and the distribution of the substructures.

Peirani, S.; Alard, C.; Pichon, C.; Gavazzi, R.; Aubert, D.

2008-11-01

298

Planetary nebulae as tracers of galaxy stellar populations  

NASA Astrophysics Data System (ADS)

We address the general problem of the luminosity-specific planetary nebula (PN) number, better known as the `?' ratio, given by ?=NPN/Lgal, and its relationship with the age and metallicity of the parent stellar population. Our analysis relies on population synthesis models that account for simple stellar populations (SSPs), and more elaborate galaxy models covering the full star formation range of the different Hubble morphological types. This theoretical framework is compared with the updated census of the PN population in Local Group (LG) galaxies and external ellipticals in the Leo group, and the Virgo and Fornax clusters. The main conclusions of our study can be summarized as follows. (i) According to the post-asymptotic giant branch (AGB) stellar core mass, PN lifetime in a SSP is constrained by three relevant regimes, driven by the nuclear (Mcore>~ 0.57Msolar), dynamical (0.57Msolar>~Mcore>~ 0.55Msolar) and transition (0.55Msolar>~Mcore>~ 0.52Msolar) time-scales. The lower limit for Mcore also sets the minimum mass for stars to reach the AGB thermal-pulsing phase and experience the PN event. (ii) Mass loss is the crucial mechanism to constrain the value of ?, through the definition of the initial-to-final mass relation (IFMR). The Reimers mass-loss parametrization, calibrated on Pop II stars of Galactic globular clusters, poorly reproduces the observed value of ? in late-type galaxies, while a better fit is obtained using the empirical IFMR derived from white dwarf observations in the Galaxy open clusters. (iii) The inferred PN lifetime for LG spirals and irregulars exceeds 10000yr, which suggests that Mcore<~ 0.65Msolar cores dominate, throughout. (iv) The relative PN deficiency in elliptical galaxies, and the observed trend of ? with galaxy optical colours, support the presence of a prevailing fraction of low-mass cores (Mcore<~ 0.55Msolar) in the PN distribution and a reduced visibility time-scale for the nebulae as a consequence of the increased AGB transition time. The stellar component with Mcore<~ 0.52Msolar, which overrides the PN phase, could provide an enhanced contribution to hotter HB and post-HB evolution, as directly observed in M 32 and the bulge of M 31. This implies that the most UV-enhanced ellipticals should also display the lowest values of ?, as confirmed by the Virgo cluster early-type galaxy population. (v) Any blue-straggler population, invoked as progenitor of the Mcore>~ 0.7Msolar PNe in order to preserve the constancy of the bright luminosity-function cut-off magnitude in ellipticals, must be confined to a small fraction (a few per cent at most) of the whole galaxy PN population.

Buzzoni, Alberto; Arnaboldi, Magda; Corradi, Romano L. M.

2006-05-01

299

The initial stellar population  

NASA Technical Reports Server (NTRS)

Current theories for the origin of stellar masses and the initial mass function are surveyed, with emphasis on the formation of stars in clusters, and the possibility that several different formation mechanisms are at work in the Galaxy. Models are presented for the evolution of the 2.2-micron premain-sequence luminosity function of a young coeval star cluster, and the implications the results have for the conversion of an observed luminosity function into the underlying mass function are discussed. A description of theories which allow spectral energy distributions of young stellar objects to be used as diagnostics of their evolutionary states is given. The question of the existence of substellar objects (brown dwarfs) in nearby young clusters and regions of star formation is addressed.

Zinnecker, Hans; Mccaughrean, Mark J.; Wilking, Bruce A.

1993-01-01

300

Stellar Coronal Astronomy  

Microsoft Academic Search

Coronal astronomy is by now a fairly mature discipline, with a quarter century having gone by since the detection of the first\\u000a stellar X-ray coronal source (Capella), and having benefitted from a series of major orbiting observing facilities. Serveral\\u000a observational characteristics of coronal X-ray and EUV emission have been solidly established through extensive observations,\\u000a and are by now common, almost

Fabio Favata; Giuseppina Micela

2003-01-01

301

Helium in stellar atmospheres  

Microsoft Academic Search

Helium, which was first discovered on the sun with the help of spectral analysis, plays, together with hydrogen, a principal\\u000a role in astrophysics. We consider here two fundamental quantities: primordial helium abundance formed during Big Bang nucleosynthesis\\u000a and the current initial helium abundances in nearby stars. It is shown that stellar atmospheres are enriched in helium during\\u000a the main-sequence stage.

L. S. Lyubimkov

2010-01-01

302

Stellar Inertial Navigation Workstation  

NASA Technical Reports Server (NTRS)

Software and hardware assembled to support specific engineering activities. Stellar Inertial Navigation Workstation (SINW) is integrated computer workstation providing systems and engineering support functions for Space Shuttle guidance and navigation-system logistics, repair, and procurement activities. Consists of personal-computer hardware, packaged software, and custom software integrated together into user-friendly, menu-driven system. Designed to operate on IBM PC XT. Applied in business and industry to develop similar workstations.

Johnson, W.; Johnson, B.; Swaminathan, N.

1989-01-01

303

TYCHO: Stellar evolution code  

NASA Astrophysics Data System (ADS)

TYCHO is a general, one dimensional (spherically symmetric) stellar evolution code written in structured Fortran 77; it is designed for hydrostatic and hydrodynamic stages including mass loss, accretion, pulsations and explosions. Mixing and convection algorithms are based on 3D time-dependent simulations. It offers extensive on-line graphics using Tim Pearson's PGPLOT with X-windows and runs effectively on Linux and Mac OS X laptop and desktop computers.

Arnett, D.

2013-03-01

304

Ion transport in stellarators  

SciTech Connect

Stellarator ion transport in the low-collisionality regime with a radial electric field is calculated by a systematic expansion of the drift-Boltzmann equation. The shape of the helical well is taken into account in this calculation. It is found that the barely trapped ions with three to four times the thermal energy give the dominant contribution to the diffusion. Expressions for the ion particle and energy fluxes are derived.

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

1985-09-01

305

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

306

Stellar Imager: wavefront control  

NASA Astrophysics Data System (ADS)

Stellar Imager (SI) is a proposed NASA space-based UV imaging interferometer to resolve the stellar disks of nearby stars. SI would consist of 20 - 30 separate spacecraft flying in formation at the Earth-Sun L2 libration point. Onboard wavefront sensing and control is required to maintain alignment during science observations and after array reconfigurations. The Fizeau Interferometry Testbed (FIT), developed at the NASA/Goddard Space Flight Center, is being used to study wavefront sensing and control methodologies for Stellar Imager and other large, sparse aperture telescope systems. FIT initially consists of 7 articulated spherical mirrors in a Golay pattern, and is currently undergoing expansion to 18 elements. FIT currently uses in-focus whitelight sparse aperture PSFs and a direct solve broadband phase retrieval algorithm to sense and control its wavefront. Ultimately it will use extended scene wavelength, with a sequential diversity algorithm that modulates a subset of aperture pistons to jointly estimate the wavefront and the reconstructed image from extended scenes. The recovered wavefront is decomposed into the eigenmodes of the control matrix and actuators are moved to minimize the wavefront piston, tip and tilt in closed-loop. We discuss the testbed, wavefront control methodology and ongoing work to increase its bandwidth from 1 per 11 seconds to a few 10's of Hertz and show ongoing results.

Lyon, Richard G.; Carpenter, Kenneth G.; Petrone, Peter; Dogoda, Peter; Reed, Daniel; Mozurkewich, David

2008-08-01

307

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

PubMed Central

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

2010-01-01

308

Discovery of a cold stellar stream in the ATLAS DR1 data  

NASA Astrophysics Data System (ADS)

We report the discovery of a narrow stellar stream crossing the constellations of Sculptor and Fornax in the Southern celestial hemisphere. The portion of the stream detected in the Data Release 1 photometry of the ATLAS survey is at least 12° long, while its width is ?0.25°. The colour-magnitude diagram of this halo sub-structure is consistent with a metal-poor [Fe/H] ? -1.4 stellar population located at a heliocentric distance of 20 ± 2 kpc. There are three globular clusters that could tentatively be associated with the stream: NGC 7006, NGC 7078 (M15) and Pyxis, but NGC 7006 and 7078 seem to have proper motions incompatible with the stream orbit.

Koposov, S. E.; Irwin, M.; Belokurov, V.; Gonzalez-Solares, E.; Yoldas, A. Kupcu; Lewis, J.; Metcalfe, N.; Shanks, T.

2014-07-01

309

The ACS Virgo Cluster Survey XVI. Selection Procedure and Catalogs of Globular Cluster Candidates  

NASA Astrophysics Data System (ADS)

We present catalogs of globular cluster candidates for the 100 galaxies of the Advanced Camera for Surveys Virgo Cluster Survey, a large program to carry out imaging of early-type members of the Virgo Cluster using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. We describe the procedure used to select bona fide globular cluster candidates out of the full list of detections based on model-based clustering methods with the use of expected contamination catalogs constructed using blank field observations and which are customized for each galaxy. We also present the catalogs of expected contaminants for each of our target galaxies. For each detected source we measure its position, magnitudes in the F475W (? Sloan g) and F850LP (? Sloan z) bandpasses, and half-light radii by fitting point-spread function convolved King models to the observed light distribution. These measurements are presented for 20,375 sources, of which 12,763 are likely to be globular clusters. Finally, we detail the calculation of the aperture corrections adopted for the globular cluster photometry. 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.

Jordán, Andrés; Peng, Eric W.; Blakeslee, John P.; Côté, Patrick; Eyheramendy, Susana; Ferrarese, Laura; Mei, Simona; Tonry, John L.; West, Michael J.

2009-01-01

310

A cross-correlation method to search for gravitational wave bursts with AURIGA and Virgo  

NASA Astrophysics Data System (ADS)

We present a method to search for transient gravitational waves using a network of detectors with different spectral and directional sensitivities: the interferometer Virgo and the bar detector AURIGA. The data analysis method is based on the measurements of the correlated energy in the network by means of a weighted cross-correlation. To limit the computational load, this coherent analysis step is performed around time frequency coincident triggers selected by an excess power event trigger generator tuned at low thresholds. The final selection of gravitational wave candidates is performed by a combined cut on the correlated energy and on the significance as measured by the event trigger generator. The method has been tested on one day of data of AURIGA and Virgo during September 2005. The outcomes are compared to the results of a stand-alone time frequency coincidence search. We discuss the advantages and the limits of this approach, in view of a possible future joint search between AURIGA and one interferometric detector.

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

2008-06-01

311

Molecular gas and star formation in the centers of Virgo spirals  

NASA Technical Reports Server (NTRS)

The CO and H alpha flux distributions for a sample of Virgo spirals were mapped out in an attempt to understand the coupling between gas dynamics and star formation in spiral galaxies. A broad range of morphological types were observed (types Sab through Scd) under the hypothesis that the gas dynamics is most influential in determining the overall appearance of a spiral galaxy. Only non-barred spirals were considered so that the well-studied but complicated properties of bars and their role in inducing star formation would not be a factor. All galaxies were chosen from the Virgo cluster to eliminate uncertainties due to distance errors. Since the dynamical seat of a spiral is at its center, it was expected that the dynamics of the central region would influence global properties of the rest of the disk. This could happen through the existence or absence of an inner Lindblad resonance (according to the degree of central concentration of mass) to modulate swing amplification of spiral waves, or the persistence of an oval distortion to initiate an instability which leads to spiral structure.

Canzian, Blaise

1990-01-01

312

Near Infrared Surface Photometry and Morphology in Virgo Cluster Spiral Galaxy Nuclear Regions.  

NASA Astrophysics Data System (ADS)

This paper was published in the April 1995 Astronomical Journal as: Rauscher, B. J. 1995, "Near Infrared Surface Photometry and Morphology in Virgo Cluster Spiral Galaxy Nuclear Regions." The journal article contains color plates. The reader is strongly encouraged to read the journal article. This paper presents very high spatial resolution (seeing 0.75 arcsec FWHM) K band surface photometry of 15 Virgo cluster spiral galaxy nuclear regions (radii < 1 Kpc). It presents B and I band CCD images of 13 of these galaxies. The goals of the study were: (1) to begin to establish a K band baseline of normal spiral galaxy nuclear regions against which peculiar galaxies may be compared, (2) to provide better constraints on N-body models, and (3) to complement near infrared studies of large scale structure in spiral galaxies with very high resolution imaging of the important nuclear regions. The principal findings are: (1) between 1/4 and 1/3 of these nuclear regions show K band evidence of triaxiality, (2) approximately 1/2 of these galaxies have axisymmetric nuclear regions, and (3) NGC 4321 has a bar that is not detectable in the optical images.

Rauscher, Bernard J.

1995-01-01

313

VirGO: A Visual Browser for the ESO Science Archive Facility  

NASA Astrophysics Data System (ADS)

VirGO is the next generation Visual Browser for the ESO Science Archive Facility developed by the Virtual Observatory (VO) Systems Department. It is a plug-in for the popular open source software Stellarium adding capabilities for browsing professional astronomical data. VirGO gives astronomers the possibility to easily discover and select data from millions of observations in a new visual and intuitive way. Its main feature is to perform real-time access and graphical display of a large number of observations by showing instrumental footprints and image previews, and to allow their selection and filtering for subsequent download from the ESO SAF web interface. It also allows the loading of external FITS files or VOTables, the superimposition of Digitized Sky Survey (DSS) background images, and the visualization of the sky in a `real life' mode as seen from the main ESO sites. All data interfaces are based on Virtual Observatory standards which allow access to images and spectra from external data centers, and interaction with the ESO SAF web interface or any other VO applications supporting the PLASTIC messaging system.

Chéreau, Fabien

2012-04-01

314

An RXTE Study of M87 and the Core of the Virgo Cluster  

NASA Technical Reports Server (NTRS)

We present hard X-ray observations of the nearby radio galaxy M87 and the core of the Virgo cluster using the Rossi X-ray Timing Explorer. These are the first hard X-ray observations of M87 not affected by contamination from the nearby Seyfert 2 galaxy NGC 4388. Thermal emission from Virgo's intracluster medium is clearly detected and has a spectrum indicative of kT approx. = 2.5 keV plasma with approximately 25% cosmic abundances. No non-thermal (power-law) emission from M87 is detected in the hard X-ray band, with fluctuations in the Cosmic X-ray Background being the limiting factor. Combining with ROSAT data, we infer that the X-ray spectrum of the M87 core and jet must be steep (Gamma(sub core) greater than 1.90 and Gamma(sub jet) greater than 1.75), and we discuss the implications of this result. In particular, these results are consistent with M87 being a mis-aligned BL-Lac object.

Reynolds, Christopher S.; Heinz, Sebastian; Fabian, Andrew C.; Begelman, Mitchell C.

1998-01-01

315

An RXTE Study of M87 and the Core of the Virgo Cluster  

NASA Technical Reports Server (NTRS)

We present hard X-ray observations of the nearby radio galaxy M87 and the core of the Virgo cluster using the Rossi X-ray 7Tming Explorer. These are the first hard X-ray observations of M87 not affected by contamination from the nearby Seyfert 2 galaxy NGC 4388. Thermal emission from Virgo's intracluster medium is clearly detected and has a spectrum indicative of kT is approximately equal to 2.5 keV plasma with approximately 25% cosmic abundances. No non-thermal (power-law) emission from M87 is detected in the hard X-ray band, with fluctuations in the Cosmic X-ray Background being the limiting factor. Combining with ROSAT data, we infer that the X-ray spectrum of the M87 core and jet must be steep (Gamma (sub core) > 1.90 and Gamma (sub jet) > 1.75), and we discuss the implications of this result. In particular, these results are consistent with M87 being a mis-aligned BL-Lac object.

Reynolds, Christopher S.; Heinz, Sebastian; Fabian, Andrew C.; Begelman, Mitchell C.

1998-01-01

316

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

317

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

318

Dynamical versus stellar masses of ultracompact dwarf galaxies in the Fornax cluster  

NASA Astrophysics Data System (ADS)

The origin of ultracompact dwarf (UCD) galaxies, compact extragalactic stellar systems, is still a puzzle for present galaxy formation models. We present the comprehensive analysis of high-resolution multi-object spectroscopic data for a sample of 24 Fornax cluster UCDs obtained with VLT with Fibre Large Array Multi Element Spectrograph (FLAMES). It comprises previously published data for 19 objects which we re-analysed, including 13 with available Hubble Space Telescope (HST) photometric data. Using Virtual Observatory technologies we found archival HST images for two more UCDs and then determined their structural properties. For all objects we derived internal velocity dispersions, stellar population parameters and stellar mass-to-light ratios (M/L)* by fitting individual simple stellar population (SSP) synthetic spectra convolved with a Gaussian against the observed spectra using the NBURSTS full spectral fitting technique. For 14 objects we estimated dynamical masses suggesting no dark matter (DM) in 12 of them and no more than 40 per cent DM mass fraction in the remaining two, in contrast to findings for several UCDs in the Virgo cluster. Some Fornax UCDs even have too high values of (M/L)* estimated using the Kroupa stellar initial mass function (IMF) resulting in negative formally computed DM mass fractions. The objects with too high (M/L)* ratios compared to the dynamical ones have relatively short dynamical relaxation time-scales, close to the Hubble time or below. We therefore suggest that their lower dynamical ratios (M/L)dyn are caused by low-mass star depletion due to dynamical evolution. Overall, the observed UCD characteristics suggest at least two formation channels: tidal threshing of nucleated dwarf galaxies for massive UCDs (?108 M?), and a classical scenario of red globular cluster formation for lower-mass UCDs (?107 M?). Based on the archival ESO VLT with Fibre Large Array Multi Element Spectrograph (FLAMES) (programme 078.B-0496) available through and Hubble Space Telescope archival data (programmes 8090 and 10129) available through

Chilingarian, Igor V.; Mieske, Steffen; Hilker, Michael; Infante, Leopoldo

2011-04-01

319

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 the formation mechanisms of Blue stragglers are still a mystery. The astronomers used ESO's Very Large Telescope to measure the abundance of chemical elements at the surface of 43 Blue straggler stars in the globular cluster 47 Tucanae [1]. They discovered that six of these Blue straggler stars contain less carbon and oxygen than the majority of these peculiar objects. Such an anomaly indicates that the material at the surface of the blue stragglers comes from the deep interiors of a parent star [2]. Such deep material can reach the surface of the blue straggler only during the mass transfer process occurring between two stars in a binary system. Numerical simulations indeed show that the coalescence of stars should not result in anomalous abundances. ESO PR Photo 37/06 ESO PR Photo 37/06 Abundances in Blue Straggler Stars In the core of a globular cluster, stars are packed extremely close to each other: more than 4000 stars are found in the innermost light-year-sized cube of 47 Tucanae. Thus, stellar collisions are thought to be very frequent and the collision channel for the formation of blue stragglers should be extremely efficient. The chemical signature detected by these observations demonstrates that also the binary mass-transfer scenario is fully active even in a high-density cluster like 47 Tuc. "Our discovery is therefore a fundamental step toward the solution of the long-standing mystery of blue straggler formation in globular clusters," said Ferraro. Measurements of so many faint stars are only possible since the advent of 8-m class telescopes equipped with multiplexing capability spectrographs. In this case, the astronomers used the FLAMES/Giraffe instrument that allows the simultaneous observation of up to 130 targets at a time, making it ideally suited for surveying individual stars in closely populated fields.

2006-10-01

320

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

321

All-Sky Search for Gravitational-Wave Bursts in the First Joint LIGO-GEO-Virgo Run.  

National Technical Information Service (NTIS)

We present results from an aU-sky search for unmodeled gravitational-wave bursts in the data collected by the LIGO, GEO 600 and Virgo detectors between November 2006 and October 2007. The search is performed. by three different analysis algorithms over th...

J. Camizzo J. B. Camp

2012-01-01

322

Hubble Space Telescope First 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 fromthe Hubble Space Telescope and the Key PRoject on the Extragalctic Distance Scale, we have obtained multi-wavelength BVR WFPC2 images for the face-on Virgo cluster spiral galaxy M11 = NGC 4321.

Freedman, W. L.; Madore, B. F.; Stetson, P. B.; Hughes, S. M. G.; Holtzman, J. A.; Mould, J. R.; Trauger, J. T.; Gallagher, J. S., III; Ballester, G. E.; Burrows, C. J.; Casertano, S.; Clarke, J. T; Crisp, D.; Ferrarese, L.; Ford, H.; Graham, J. A.; Griffiths, R. E.; Hester, J. J.; Hill, R.; Hoessel, J. G.; Huchra, J.; Kennicutt, R. C.; Scowen, P. A.; Sparks, B.; Stapelfeldt, K. R.

1994-01-01

323

STRUCTURE AND POPULATION OF THE ANDROMEDA STELLAR HALO FROM A SUBARU/SUPRIME-CAM SURVEY  

SciTech Connect

We present a photometric survey of the stellar halo of the nearest giant spiral galaxy, Andromeda (M31), using Suprime-Cam on the Subaru Telescope. A detailed analysis of VI color-magnitude diagrams of the resolved stellar population is used to measure properties such as line-of-sight distance, surface brightness, metallicity, and age. These are used to isolate and characterize different components of the M31 halo: (1) the giant southern stream (GSS); (2) several other substructures; and (3) the smooth halo. First, the GSS is characterized by a broad red giant branch (RGB) and a metal-rich/intermediate-age red clump (RC). The I magnitude of the well-defined tip of the RGB suggests that the distance to the observed GSS field is (m - M){sub 0} = 24.73 +- 0.11 (883 +- 45 kpc) at a projected radius of R approx 30 kpc from M31's center. The GSS shows a high metallicity peaked at [Fe/H]approx>-0.5 with a mean (median) of -0.7 (-0.6), estimated via comparison with theoretical isochrones. Combined with the luminosity of the RC, we estimate the mean age of its stellar population to be approx8 Gyr. The mass of its progenitor galaxy is likely in the range of 10{sup 7}-10{sup 9} M{sub sun}. Second, we study M31's halo substructure along the northwest/southeast minor axis out to R approx 100 kpc and the southwest major-axis region at R approx 60 kpc. We confirm two substructures in the southeast halo reported by Ibata et al. and discover two overdense substructures in the northwest halo. We investigate the properties of these four substructures as well as other structures including the western shelf and find that differences in stellar populations among these systems, thereby suggesting each has a different origin. Our statistical analysis implies that the M31 halo as a whole may contain at least 16 substructures, each with a different origin, so its outer halo has experienced at least this many accretion events involving dwarf satellites with mass 10{sup 7}-10{sup 9} M{sub sun} since a redshift of z approx 1. Third, we investigate the properties of an underlying, smooth, and extended halo component out to R>100 kpc. We find that the surface density of this smooth halo can be fitted to a Hernquist model of scale radius approx17 kpc or a power-law profile with SIGMA(R) propor to R {sup -2.17+}-{sup 0.15}. In contrast to the relative smoothness of the halo density profile, its metallicity distribution appears to be spatially non-uniform with non-monotonic variations with radius, suggesting that the halo population has not had sufficient time to dynamically homogenize the accreted populations. Further implications for the formation of the M31 halo are discussed.

Tanaka, Mikito [University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Chiba, Masashi [Astronomical Institute, Tohoku University, Aoba-ku, Sendai 980-8578 (Japan); Komiyama, Yutaka; Iye, Masanori [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Guhathakurta, Puragra [University of California Observatories/Lick Observatory, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Kalirai, Jason S., E-mail: mikito@astr.tohoku.ac.j [Space Telescope Science Institute, Baltimore, MD 21218 (United States)

2010-01-10

324

Structure and Population of the Andromeda Stellar Halo from a Subaru/Suprime-Cam Survey  

NASA Astrophysics Data System (ADS)

We present a photometric survey of the stellar halo of the nearest giant spiral galaxy, Andromeda (M31), using Suprime-Cam on the Subaru Telescope. A detailed analysis of VI color-magnitude diagrams of the resolved stellar population is used to measure properties such as line-of-sight distance, surface brightness, metallicity, and age. These are used to isolate and characterize different components of the M31 halo: (1) the giant southern stream (GSS); (2) several other substructures; and (3) the smooth halo. First, the GSS is characterized by a broad red giant branch (RGB) and a metal-rich/intermediate-age red clump (RC). The I magnitude of the well-defined tip of the RGB suggests that the distance to the observed GSS field is (m - M)0 = 24.73 ± 0.11 (883 ± 45 kpc) at a projected radius of R ~ 30 kpc from M31's center. The GSS shows a high metallicity peaked at [Fe/H]gsim-0.5 with a mean (median) of -0.7 (-0.6), estimated via comparison with theoretical isochrones. Combined with the luminosity of the RC, we estimate the mean age of its stellar population to be ~8 Gyr. The mass of its progenitor galaxy is likely in the range of 107-109 M sun. Second, we study M31's halo substructure along the northwest/southeast minor axis out to R ~ 100 kpc and the southwest major-axis region at R ~ 60 kpc. We confirm two substructures in the southeast halo reported by Ibata et al. and discover two overdense substructures in the northwest halo. We investigate the properties of these four substructures as well as other structures including the western shelf and find that differences in stellar populations among these systems, thereby suggesting each has a different origin. Our statistical analysis implies that the M31 halo as a whole may contain at least 16 substructures, each with a different origin, so its outer halo has experienced at least this many accretion events involving dwarf satellites with mass 107-109 M sun since a redshift of z ~ 1. Third, we investigate the properties of an underlying, smooth, and extended halo component out to R>100 kpc. We find that the surface density of this smooth halo can be fitted to a Hernquist model of scale radius ~17 kpc or a power-law profile with ?(R) vprop R -2.17±0.15. In contrast to the relative smoothness of the halo density profile, its metallicity distribution appears to be spatially non-uniform with non-monotonic variations with radius, suggesting that the halo population has not had sufficient time to dynamically homogenize the accreted populations. Further implications for the formation of the M31 halo are discussed. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Tanaka, Mikito; Chiba, Masashi; Komiyama, Yutaka; Guhathakurta, Puragra; Kalirai, Jason S.; Iye, Masanori

2010-01-01

325

Dark Matter Substructure Detection Using Spatially Resolved Spectroscopy of Lensed Dusty Galaxies  

NASA Astrophysics Data System (ADS)

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 ~108 M ? with high significance in most lensed DSFGs. Specifically, we find that in typical DSFG lenses, there is a ~55% probability of detecting a substructure with M > 108 M ? with more than 5? 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 ~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; Dalal, Neal; Holder, Gilbert; Kuhlen, Michael; Marrone, Daniel; Murray, Norman; Vieira, Joaquin

2013-04-01

326

Using multi-taper method to improve the accuracy of substructure identification for shear structures  

NASA Astrophysics Data System (ADS)

In the authors' previous work, an inductive substructure identification method was proposed for shear structures, which utilizes the frequency responses (Fourier transforms) of floor accelerations to formulate a series of inductive substructure identification problems, estimating the structural parameters from top to bottom iteratively. However, the simulation results show that the proposed method can only obtain relatively accurate results if measurement noise is not large. In order to improve the identification accuracy, an uncertainty analysis of the parameter identification errors is conducted for this method in this paper, revealing the important factors that influence the identification accuracy. Based on this result, a new substructure identification method is proposed herein, in which the cross power spectral densities (CPSDs) of structural responses, computed via multi-taper method, are utilized to formulate the substructure identification problems. A similar uncertainty analysis of the identification errors is carried out for the new method, illustrating why the new method could significantly improve the identification accuracy. Finally, a numerical example of 8-story shear building structure is utilized to verify the effectiveness of the new multi-taper based substructure method on enhancing the identification accuracy.

Zhang, Dongyu; Li, Hui; Bao, Yuequan

2014-03-01

327

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

328

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.

2010-01-01

329

Stellar Flux Monitor Proposal  

NASA Astrophysics Data System (ADS)

THE PURPOSE OF THIS TEST IS TO MONITOR THE THROUGHPUT AND PSF OF THE WF AND PC IN THE UV AND VISIBLE. Six exposures in six filters in both the WF and PC are taken of a UV flux standard star. The total duration is two orbits. The program should be repeated every four weeks. Along with the internal monitor program, this stellar monitor comprises the regular monitoring program for the throughput and focus of the WFPC and should start to be scheduled when the initial calibration programs cease, that is, in late Mar. or April 1991.

Westphal, J.

1990-07-01

330

Stellar evolution@EURO-VObs  

NASA Astrophysics Data System (ADS)

Stellar evolutionary models are a fundamental tool for addressing many astrophysical issues. For such a reason, it is of fundamental relevance to make them available to the whole scientific community in an easy and direct way. We briefly review the main ingredients requested for computing stellar models and show some illustrative scientific cases concerning the comparison between model predictions and suitable empirical evidence. We discuss also some problems related to the implementation of stellar models library inside the Virtual Observatory, and report about our experience with the our BaSTI stellar model repository.

Cassisi, S.; Pasian, F.; Salaris, M.; Manzato, P.; Pietrinferni, A.; Taffoni, G.; Molinaro, M.; Gasparo, F.

331

HIERARCHICAL STELLAR STRUCTURES IN THE LOCAL GROUP DWARF GALAXY NGC 6822  

SciTech Connect

We present a comprehensive study of the star cluster population and the hierarchical structure in the clustering of blue stars with ages {approx}<500 Myr in the Local Group dwarf irregular galaxy NGC 6822. Our observational material comprises the most complete optical stellar catalog of the galaxy from imaging with the Suprime-Cam at the 8.2 m Subaru Telescope. We identify 47 distinct star clusters with the application of the nearest-neighbor density method to this catalog for a detection threshold of 3{sigma} above the average stellar density. The size distribution of the detected clusters can be very well approximated by a Gaussian with a peak at {approx}68 pc. The total stellar masses of the clusters are estimated by extrapolating the cumulative observed stellar mass function of all clusters to be in the range 10{sup 3}-10{sup 4} M{sub sun}. Their number distribution is fitted very well by a power law with index {alpha} {approx} 1.5 {+-} 0.7, which is consistent with the cluster mass functions of other Local Group galaxies and the cluster initial mass function. In addition to the detected star clusters of the galaxy, the application of the nearest-neighbor density method for various density thresholds, other than 3{sigma}, enabled the identification of stellar concentrations in various lengthscales. The stellar density maps constructed with this technique provide a direct proof of hierarchically structured stellar concentrations in NGC 6822, in the sense that smaller dense stellar concentrations are located inside larger and looser ones. We illustrate this hierarchy by the so-called dendrogram, or structure tree of the detected stellar structures, which demonstrates that most of the detected structures split up into several substructures over at least three levels. We quantify the hierarchy of these structures with the use of the minimum spanning tree method. We find that structures detected at 1, 2, and 3{sigma} density thresholds are hierarchically constructed with a fractal dimension of D {approx} 1.8. Some of the larger stellar concentrations, particularly in the northern part of the central star-forming portion of the galaxy, coincide with IR-bright complexes previously identified with Spitzer and associated with high column density neutral gas, indicating structures that currently form stars. The morphological hierarchy in stellar clustering, which we observe in NGC 6822, resembles that of the turbulent interstellar matter, suggesting that turbulence on pc and kpc scales has been probably the major agent that regulated clustered star formation in NGC 6822.

Gouliermis, Dimitrios A.; Walter, Fabian [Max Planck Institute for Astronomy, Koenigstuhl 17, 69117 Heidelberg (Germany); Schmeja, Stefan; Klessen, Ralf S. [Zentrum fuer Astronomie der Universitaet Heidelberg, Institut fuer Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg (Germany); De Blok, W. J. G., E-mail: dgoulier@mpia-hd.mpg.d, E-mail: walter@mpia-hd.mpg.d, E-mail: sschmeja@ita.uni-heidelberg.d, E-mail: rklessen@ita.uni-heidelberg.d, E-mail: edeblok@ast.uct.ac.z [University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa)

2010-12-20

332

A multibeam HI survey of the Virgo cluster - two isolated HI clouds?  

NASA Astrophysics Data System (ADS)

We have carried out a fully sampled large area (4°× 8°) 21-cm HI line survey of part of the Virgo cluster using the Jodrell Bank multibeam instrument. The survey has a sensitivity some three times better than the standard HIJASS (HI Jodrell All Sky Survey) and HIPASS (HI Parkes All Sky Survey) surveys. We detect 31 galaxies, 27 of which are well-known cluster members. The four new detections have been confirmed in the HIPASS data and by follow-up Jodrell Bank pointed observations. One object lies behind M86, but the other three have no obvious optical counterparts upon inspection of the digital sky survey fields. These three objects were mapped at Arecibo with a smaller 3.6-arcmin half power beam width (HPBW) and a four times better sensitivity than the Jodrell Bank data, which allow an improved determination of the dimensions and location of two of the objects, but surprisingly failed to detect the third. The two objects are resolved by the Arecibo beam, giving them a size far larger than any optical images in the nearby field. To our mass limit of 5 × 107(?v/50 km s-1) Msolar and column density limit of 3 × 1018(?v/50 km s-1) atom cm-2, these new detections represent only about 2 per cent of the cluster atomic hydrogen mass. Our observations indicate that the HI mass function of the cluster turns down at the low-mass end, making it very different to the field galaxy HI mass function. This is quite different to the Virgo cluster optical luminosity function, which is much steeper than that in the general field. Many of the sample galaxies are relatively gas-poor compared with HI selected samples of field galaxies, confirming the `anaemic spirals' view of Virgo cluster late-type galaxies. The velocity distribution of the HI detected galaxies is also very different to that of the cluster as a whole. There are relatively more high-velocity galaxies in the HI sample, suggesting that they form part of a currently infalling population. The HI sample with optical identifications has a minimum HI column density cut-off more than an order of magnitude above that expected from the sensitivity of the survey. This observed column density is above the normally expected level for star formation to occur. The two detections with no optical counterparts have very much lower column densities than that of the rest of the sample, below the star formation threshold.

Davies, J.; Minchin, R.; Sabatini, S.; van Driel, W.; Baes, M.; Boyce, P.; de Blok, W. J. G.; Disney, M.; Evans, Rh.; Kilborn, V.; Lang, R.; Linder, S.; Roberts, S.; Smith, R.

2004-04-01

333

Starspots and Stellar Rotation: Stellar Activity with Kepler  

NASA Astrophysics Data System (ADS)

While the telescopic study of starspots dates back to Galileos observations of our own Sun, recent space-borne photometric missions (such as MOST, CoRoT, and Kepler) are opening a new window into understanding these ubiquitous manifestations of stellar activity. Because of the intimate link between stellar rotation and the generation of the magnetic field, starspots cause a modulation in the lightcurve at the rate of stellar rotation. To complicate matters, stars rotate differentially, so the stellar rotation rate is not really best characterized by a single value but rather by a range of rotation rates. Through high-precision, long-term photometric monitoring of stars of different spectral types and activity strengths, it is possible to determine stellar rotation rates and differential rotation measures. In addition, modeling these lightcurves can tell us about the properties of stellar spots, such as location, areal coverage, and lifetime. New observations provide precision photometry for a large cohort of stars, ranging from Sun-like to rather different stellar properties, at a spread of ages, making these lightcurves a powerful tool for understanding magnetic activity for stars of all activity levels. Here, I will discuss how Kepler can provide new insight into the continuum of stellar activity and our own Suns place amongst the stars.

Walkowicz, L. M.; Basri, G. S.

2011-12-01

334

Design studies for the transmission simulator method of experimental dynamic substructuring.  

SciTech Connect

In recent years, a successful method for generating experimental dynamic substructures has been developed using an instrumented fixture, the transmission simulator. The transmission simulator method solves many of the problems associated with experimental substructuring. These solutions effectively address: (1) rotation and moment estimation at connection points; (2) providing substructure Ritz vectors that adequately span the connection motion space; and (3) adequately addressing multiple and continuous attachment locations. However, the transmission simulator method may fail if the transmission simulator is poorly designed. Four areas of the design addressed here are: (1) designating response sensor locations; (2) designating force input locations; (3) physical design of the transmission simulator; and (4) modal test design. In addition to the transmission simulator design investigations, a review of the theory with an example problem is presented.

Mayes, Randall Lee; Arviso, Michael

2010-05-01

335

Non-linear substructure approach for dynamic analysis of rigid-flexible multibody systems  

NASA Astrophysics Data System (ADS)

This paper presents a substructure synthesis method (SSM) for nonlinear analysis of multibody systems. The detailed derivation of the equation of motion which takes into account the geometric nonlinear effects of large rotation undergoing small strain elastic deformation is presented. Using the substructure synthesis approach, the equation of motion is condensed through the boundary conditions at the interface between the flexible and rigid substructures. As a result, equations of motion for multi-flexible-body systems including the geometric non-linear effects of large rotation are derived. To demonstrate the applicability and accuracy of the proposed approach, an example of a two-link manipulator was chosen for this presentation. The results using the linear and nonlinear models are presented to highlight the effects of geometric nonlinearities.

Liu, A. Q.; Liew, K. M.

1994-04-01

336

Pyrolysis of lignin in the presence of tetramethylammonium hydroxide (TMAH): products stemming from beta-5 substructures.  

PubMed

Lignin model compounds, synthetic lignins, and cedar wood have been analyzed by pyrolysis-gas chromatography(-mass spectrometry) in the presence of tetramethylammonium hydroxide (TMAH) to examine the behavior of beta-5 substructures specifically under these conditions. Two model compounds contained a beta-5 linkage and a gamma-CH2OH group. The phenolic model compound produced stilbene products by way of a formaldehyde elimination of the gamma-CH2OH. The nonphenolic model compound underwent dehydration to give arylbenzofuran products. Dehydrogenation polymers of coniferyl alcohol gave a large amount of stilbene products in TMAH/pyrolysis. TMAH/pyrolysis of a Japanese cedar (Cryptomeria japonica) wood yielded a very small amount of stilbene products. The results demonstrated that synthetic lignins are rich in terminal beta-5 substructures, but cedar (a softwood) contains a paucity of the terminal beta-5 substructures. PMID:12033801

Kuroda, Ken-Ichi; Nakagawa-Izumi, Akiko; Dimmel, Donald R

2002-06-01

337

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

NASA Astrophysics Data System (ADS)

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 studying jet substructure. Following up on the report of the Boost 2010 workshop, we present a new set of benchmark comparisons of substructure techniques, focusing on the set of variables and grooming methods that are collectively known as ‘top taggers’. To facilitate further exploration, we have attempted to collect, harmonize and publish software implementations of these techniques. Report prepared by the participants of the BOOST 2011 Workshop at Princeton University, 22-26 May 2011. L Asquith (lasquith@hep.anl.gov), S Rappoccio (rappocc@fnal.gov) and C K Vermilion (verm@uw.edu), editors.

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

2012-06-01

338

Molecules in galaxies. IV - Molecular and atomic hydrogen in Virgo cluster galaxies  

NASA Technical Reports Server (NTRS)

If gas and dust are well mixed in a galaxy, the dust mass should be proportional to the sum of the masses of atomic and molecular gas. This assumption has been used to estimate the mean conversion ratio between the flux in the CO J = 1-0 line and the molecular gas mass of a galaxy using a set of observations of the 100 microns continuum flux density, the H I 21 cm line flux and the CO line flux for a sample of spiral galaxies in the Virgo cluster; these galaxies have a wide variation in the ratio of CO to H I line flux. The result, N(H2) = 6.3 + or - 3.5 x 10 to the 20th mol/sq cm/(K x km/s), is in agreement with values inferred from observations of the molecular interstellar medium in the Galaxy.

Knapp, G. R.; Helou, G.; Stark, A. A.

1987-01-01

339

Constraints on Cosmic Strings from the LIGO-Virgo Gravitational-Wave Detectors  

NASA Astrophysics Data System (ADS)

Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension G? below 10-8 in some regions of the cosmic string parameter space.

Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Adhikari, R. X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O. D.; Ajith, P.; Allen, B.; Allocca, A.; Amador Ceron, E.; Amariutei, D.; Anderson, R. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Areeda, J.; Ast, S.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Austin, L.; Aylott, B. E.; Babak, S.; Baker, P. T.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barker, D.; Barnum, S. H.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Behnke, B.; Bejger, M.; Beker, M. G.; Bell, A. S.; Bell, C.; Belopolski, I.; Bergmann, G.; Berliner, J. M.; Bersanetti, D.; Bertolini, A.; Bessis, D.; Betzwieser, J.; Beyersdorf, P. T.; Bhadbhade, T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Blom, M.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogan, C.; Bond, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bowers, J.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brannen, C. A.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brückner, F.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calderón Bustillo, J.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Castiglia, A.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chu, Q.; Chua, S. S. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Colombini, M.; Constancio, M.; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Coulon, J.-P.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Canton, T. Dal; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; Debreczeni, G.; Degallaix, J.; Del Pozzo, W.; Deleeuw, E.; Deléglise, S.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; DeRosa, R.; DeSalvo, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; Díaz, M.; Dietz, A.; Dmitry, K.; Donovan, F.; Dooley, K. L.; Doravari, S.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edwards, M.; Effler, A.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Endr?czi, G.; Essick, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W.; Favata, M.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R.; Flaminio, R.; Foley, E.; Foley, S.; Forsi, E.; Fotopoulos, N.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P.; Fyffe, M.; Gair, J.; Gammaitoni, L.; Garcia, J.; Garufi, F.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; Gergely, L.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Goßler, S.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Griffo, C.; Groot, P.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hall, B.; Hall, E.; Hammer, D.; Hammond, G.; Hanke, M.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Heefner, J.; Heidmann, A.; Heintze, M.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Horrom, T.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hu, Y.; Hua, Z.; Huang, V.; Huerta, E. A.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.

2014-04-01

340

Constraints on cosmic strings from the LIGO-Virgo gravitational-wave detectors.  

PubMed

Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension G? below 10(-8) in some regions of the cosmic string parameter space. PMID:24745400

Aasi, J; Abadie, J; Abbott, B P; Abbott, R; Abbott, T; Abernathy, M R; Accadia, T; Acernese, F; Adams, C; Adams, T; Adhikari, R X; Affeldt, C; Agathos, M; Aggarwal, N; Aguiar, O D; Ajith, P; Allen, B; Allocca, A; Amador Ceron, E; Amariutei, D; Anderson, R A; Anderson, S B; Anderson, W G; Arai, K; Araya, M C; Arceneaux, C; Areeda, J; Ast, S; Aston, S M; Astone, P; Aufmuth, P; Aulbert, C; Austin, L; Aylott, B E; Babak, S; Baker, P T; Ballardin, G; Ballmer, S W; Barayoga, J C; Barker, D; Barnum, S H; Barone, F; Barr, B; Barsotti, L; Barsuglia, M; Barton, M A; Bartos, I; Bassiri, R; Basti, A; Batch, J; Bauchrowitz, J; Bauer, Th S; Bebronne, M; Behnke, B; Bejger, M; Beker, M G; Bell, A S; Bell, C; Belopolski, I; Bergmann, G; Berliner, J M; Bersanetti, D; Bertolini, A; Bessis, D; Betzwieser, J; Beyersdorf, P T; Bhadbhade, T; Bilenko, I A; Billingsley, G; Birch, J; Bitossi, M; Bizouard, M A; Black, E; Blackburn, J K; Blackburn, L; Blair, D; Blom, M; Bock, O; Bodiya, T P; Boer, M; Bogan, C; Bond, C; Bondu, F; Bonelli, L; Bonnand, R; Bork, R; Born, M; Boschi, V; Bose, S; Bosi, L; Bowers, J; Bradaschia, C; Brady, P R; Braginsky, V B; Branchesi, M; Brannen, C A; Brau, J E; Breyer, J; Briant, T; Bridges, D O; Brillet, A; Brinkmann, M; Brisson, V; Britzger, M; Brooks, A F; Brown, D A; Brown, D D; Brückner, F; Bulik, T; Bulten, H J; Buonanno, A; Buskulic, D; Buy, C; Byer, R L; Cadonati, L; Cagnoli, G; Calderón Bustillo, J; Calloni, E; Camp, J B; Campsie, P; Cannon, K C; Canuel, B; Cao, J; Capano, C D; Carbognani, F; Carbone, L; Caride, S; Castiglia, A; Caudill, S; Cavaglià, M; Cavalier, F; Cavalieri, R; Cella, G; Cepeda, C; Cesarini, E; Chakraborty, R; Chalermsongsak, T; Chao, S; Charlton, P; Chassande-Mottin, E; Chen, X; Chen, Y; Chincarini, A; Chiummo, A; Cho, H S; Chow, J; Christensen, N; Chu, Q; Chua, S S Y; Chung, S; Ciani, G; Clara, F; Clark, D E; Clark, J A; Cleva, F; Coccia, E; Cohadon, P-F; Colla, A; Colombini, M; Constancio, M; Conte, A; Conte, R; Cook, D; Corbitt, T R; Cordier, M; Cornish, N; Corsi, A; Costa, C A; Coughlin, M W; Coulon, J-P; Countryman, S; Couvares, P; Coward, D M; Cowart, M; Coyne, D C; Craig, K; Creighton, J D E; Creighton, T D; Crowder, S G; Cumming, A; Cunningham, L; Cuoco, E; Dahl, K; Dal Canton, T; Damjanic, M; Danilishin, S L; D'Antonio, S; Danzmann, K; Dattilo, V; Daudert, B; Daveloza, H; Davier, M; Davies, G S; Daw, E J; Day, R; Dayanga, T; De Rosa, R; Debreczeni, G; Degallaix, J; Del Pozzo, W; Deleeuw, E; Deléglise, S; Denker, T; Dent, T; Dereli, H; Dergachev, V; DeRosa, R; DeSalvo, R; Dhurandhar, S; Di Fiore, L; Di Lieto, A; Di Palma, I; Di Virgilio, A; Díaz, M; Dietz, A; Dmitry, K; Donovan, F; Dooley, K L; Doravari, S; Drago, M; Drever, R W P; Driggers, J C; Du, Z; Dumas, J-C; Dwyer, S; Eberle, T; Edwards, M; Effler, A; Ehrens, P; Eichholz, J; Eikenberry, S S; Endr?czi, G; Essick, R; Etzel, T; Evans, K; Evans, M; Evans, T; Factourovich, M; Fafone, V; Fairhurst, S; Fang, Q; Farinon, S; Farr, B; Farr, W; Favata, M; Fazi, D; Fehrmann, H; Feldbaum, D; Ferrante, I; Ferrini, F; Fidecaro, F; Finn, L S; Fiori, I; Fisher, R; Flaminio, R; Foley, E; Foley, S; Forsi, E; Fotopoulos, N; Fournier, J-D; Franco, S; Frasca, S; Frasconi, F; Frede, M; Frei, M; Frei, Z; Freise, A; Frey, R; Fricke, T T; Fritschel, P; Frolov, V V; Fujimoto, M-K; Fulda, P; Fyffe, M; Gair, J; Gammaitoni, L; Garcia, J; Garufi, F; Gehrels, N; Gemme, G; Genin, E; Gennai, A; Gergely, L; Ghosh, S; Giaime, J A; Giampanis, S; Giardina, K D; Giazotto, A; Gil-Casanova, S; Gill, C; Gleason, J; Goetz, E; Goetz, R; Gondan, L; González, G; Gordon, N; Gorodetsky, M L; Gossan, S; Goßler, S; Gouaty, R; Graef, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greenhalgh, R J S; Gretarsson, A M; Griffo, C; Groot, P; Grote, H; Grover, K; Grunewald, S; Guidi, G M; Guido, C; Gushwa, K E; Gustafson, E K; Gustafson, R; Hall, B; Hall, E; Hammer, D; Hammond, G; Hanke, M; Hanks, J; Hanna, C; Hanson, J; Harms, J; Harry, G M; Harry, I W; Harstad, E D; Hartman, M T; Haughian, K; Hayama, K; Heefner, J; Heidmann, A; Heintze, M; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Heptonstall, A W; Heurs, M; Hild, S; Hoak, D; Hodge, K A; Holt, K; Holtrop, M; Hong, T; Hooper, S; Horrom, T; Hosken, D J; Hough, J; Howell, E J; Hu, Y; Hua, Z; Huang, V; Huerta, E A; Hughey, B; Husa, S; Huttner, S H; Huynh, M; Huynh-Dinh, T; Iafrate, J; Ingram, D R; Inta, R; Isogai, T; Ivanov, A; Iyer, B R; Izumi, K; Jacobson, M; James, E; Jang, H; Jang, Y J; Jaranowski, P; Jiménez-Forteza, F; Johnson, W W; Jones, D; Jones, D I; Jones, R; Jonker, R J G; Ju, L; K, Haris; Kalmus, P; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Kasprzack, M; Kasturi, R; Katsavounidis, E; Katzman, W; Kaufer, H; Kaufman, K; Kawabe, K; Kawamura, S; Kawazoe, F; Kéfélian, F; Keitel, D; Kelley, D B; Kells, W; Keppel, D G; Khalaidovski, A; Khalili, F Y; Khazanov, E A; Kim, B K; Kim, C

2014-04-01

341

Study of the Ism-Stripping Process in the Virgo Spiral NGC 4501 (M88)  

NASA Astrophysics Data System (ADS)

The stripping of the ISM of spiral galaxies falling into a galaxy cluster is one of the most interesting environmental effects in galaxy evolution. In the nearby Virgo cluster we may be able to observe this process in detail. From 21 cm data and from ROSAT HRI X-ray observations there is strong evidence that the spiral galaxy NGC 4501 is currently stripped from its interstellar gas. CHANDRA is ideally suited to study this effect by high spatial resolution imaging and spectroscopy. Different scenarios as e.g. interaction induced star formation, or the mixing of warm ISM with the hot cluster ICM predict distinct spectral signatures that can observed. In addition we will obtain information on the Sy2 nuclues and possible on SN1999cl in this galaxy.

Boehringer, Hans

2001-09-01

342

LIGO-Virgo searches for gravitational waves from coalescing binaries: A status update  

NASA Astrophysics Data System (ADS)

Coalescing compact binaries of neutron stars and/or black holes are considered as one of the most promising sources for Earth based gravitational wave detectors. The LIGO-Virgo joint collaboration's Compact Binary Coalescence (CBC) group is searching for gravitational waves emitted by these astrophysical systems by matched filtering the data against theoretically modeled template waveforms. A variety of waveform template families are employed depending on the mass range probed by the search and the stage of the inspiral phase targeted: restricted post-Newtonian for systems having total mass less than 35M?, numerical relativity inspired complete inspiral-merger-ringdown waveforms for more massive systems up to 100M? and ringdown templates for modeling perturbed black holes up to 500M?. We give a status update on CBC group's current efforts and upcoming plans in detecting signatures of astrophysical gravitational waves.

Sengupta, Anand S.; LIGO Scientific Collaboration; Virgo Collaboration

2010-05-01

343

X-rays from the radio halo of Virgo A = M87  

NASA Technical Reports Server (NTRS)

The purpose of this study is to investigate in more detail the associated X-ray and radio emission in the Virgo A halo discovered by SGF. Improved Einstein HRI data and new radio maps obtained with the Very Large Array are described and the relation between the X-ray and radio structures is carefully examined. Several possible explanations are presented for the X-ray emission. The inverse compton model is found to be viable only if the magnetic field is variable and substantially weaker than the equipartition value. The principal alternative is excess thermal X-rays due to compression of the intracluster medium by the radio lobe. In either case, the association of such prominent radio and X-ray structures is unique among known radio galaxies.

1985-01-01

344

Recent searches for gravitational-wave bursts associated with magnetar flares with LIGO, GEO, and Virgo  

NASA Astrophysics Data System (ADS)

Energetic electromagnetic flares from magnetars - highly magnetized neutron stars - are associated with sudden rearrangements of the mechanical and/or magnetic configurations of the star, which can give rise to mechanical oscillations, some of which may be strong radiators of gravitational waves. General arguments have indicated that gravitational-wave bursts associated temporally with (giant) flares from galactic magnetars may be observable with ground-based gravitational wave detectors. After discussing the expectations based on the astrophysical models, we present results from several campaigns to search for such bursts using the first generation of LIGO, GEO, and Virgo detectors over the period 2005-2009, emphasizing the most recent results. No detections have been made, and we present astrophysically informed limits. Finally, we discuss prospects for progress.

Frey, Raymond; LIGO Scientific Collaboration; Virgo Collaboration

2012-06-01

345

A catalog of stellar spectrophotometry  

NASA Technical Reports Server (NTRS)

A machine-readable catalog of stellar spectrophotometric measurements made with rotating grating scanner is introduced. Consideration is given to the processes by which the stellar data were collected and calibrated with the fluxes of Vega (Hayes and Latham, 1975). A sample page from the spectrophotometric catalog is presented.

Adelman, S. J.; Pyper, D. M.; Shore, S. N.; White, R. E.; Warren, W. H., Jr.

1989-01-01

346

The Dartmouth Stellar Evolution Database  

NASA Astrophysics Data System (ADS)

The ever-expanding depth and quality of photometric and spectroscopic observations of stellar populations increase the need for theoretical models in regions of age-composition parameter space that are largely unexplored at present. Stellar evolution models that employ the most advanced physics and cover a wide range of compositions are needed to extract the most information from current observations of both resolved and unresolved stellar populations. The Dartmouth Stellar Evolution Database is a collection of stellar evolution tracks and isochrones that spans a range of [Fe/H] from -2.5 to +0.5, [?/Fe] from -0.2 to +0.8 (for [Fe/H]<=0) or +0.2 (for [Fe/H]>0), and initial He mass fractions from Y=0.245 to 0.40. Stellar evolution tracks were computed for masses between 0.1 and 4 Msolar, allowing isochrones to be generated for ages as young as 250 Myr. For the range in masses where the core He flash occurs, separate He-burning tracks were computed starting from the zero age horizontal branch. The tracks and isochrones have been transformed to the observational plane in a variety of photometric systems including standard UBV(RI)C, Stromgren uvby, SDSS ugriz, 2MASS JHKs, and HST ACS/WFC and WFPC2. The Dartmouth Stellar Evolution Database is accessible through a Web site at http://stellar.dartmouth.edu/~models/ where all tracks, isochrones, and additional files can be downloaded.

Dotter, Aaron; Chaboyer, Brian; Jevremovi?, Darko; Kostov, Veselin; Baron, E.; Ferguson, Jason W.

2008-09-01

347

The study of stellar structure  

Microsoft Academic Search

The physical principles and processes introduced into the study of stellar structure during the past 100 years are reviewed, emphasizing those processes that dominate the simplest stars in their various evolutionary phases. Attention is given to hydrostatic equilibrium, stellar energy transport, nuclear and gravitational energy sources, quiet mass ejection, violent dynamical phases, and nucleosynthesis. Investigations of radiative and convective energy

M. Schwarzschild

1978-01-01

348

Radioactive elements in stellar atmospheres  

SciTech Connect

The identification of lines of radioactive elements (Tc, Pm and elements with 83stellar atmospheres, contamination of stellar atmosphere by recent SN explosion, and spallation reactions.

Gopka, Vira [Astronomical observatory, Odessa National University, Odessa (Ukraine); Yushchenko, Alexander [Astrophysical Research center for the Structure and Evolution of the Cosmos, Sejong University, Seoul (Korea, Republic of); Astronomical observatory, Odessa National University, Odessa (Ukraine); Goriely, Stephane [Institut d'Astronomie et d'Astrophysique, Universite Libre de Bruxelles, Brussels (Belgium); Shavrina, Angelina [Main Astronomical observatory, National Academy of Sciences of Ukraine, Kiev (Ukraine); Kang, Young Woon [Astrophysical Research center for the Structure and Evolution of the Cosmos, Sejong University, Seoul (Korea, Republic of)

2006-07-12

349

Helical post stellarator. Part 1: Vacuum configuration.  

National Technical Information Service (NTIS)

Results on a novel type of stellarator configuration, the Helical Post Stellarator (HPS), are presented. This configuration is different significantly from all previously known stellarators due to its unique geometrical characteristics and unique physical...

P. E. Moroz

1997-01-01

350

SPITZER/IRAC LOW SURFACE BRIGHTNESS OBSERVATIONS OF THE VIRGO CLUSTER  

SciTech Connect

We present 3.6 and 4.5 {mu}m Spitzer Infrared Array Camera (IRAC) imaging over 0.77 deg{sup 2} at the Virgo cluster core for the purpose of understanding the formation mechanisms of the low surface brightness intracluster light (ICL) features. Instrumental and astrophysical backgrounds that are hundreds of times higher than the signal were carefully characterized and removed. We examine ICL plumes as well as the outer halo of the giant elliptical M87. For two ICL plumes, we use optical colors to constrain their ages to be greater than 3 and 5 Gyr, respectively. Upper limits on the IRAC fluxes constrain the upper limits to the masses, and optical detections constrain the lower limits to the masses. In this first measurement of mass of ICL plumes we find masses in the range of 5.5 x 10{sup 8} - 4.5 x 10{sup 9} and 2.1 x 10{sup 8}-1.5 x 10{sup 9} M{sub sun} for the two plumes for which we have coverage. Given their expected short lifetimes, and a constant production rate for these types of streams, integrated over Virgo's lifetime, they can account for the total ICL content of the cluster, implying that we do not need to invoke ICL formation mechanisms other than gravitational mechanisms leading to bright plumes. We also examined the outer halo of the giant elliptical M87. The color profile from the inner to outer halo of M87 (160 kpc) is consistent with either a flat or optically blue gradient, where a blue gradient could be due to younger or lower metallicity stars at larger radii. The similarity of the age predicted by both the infrared and optical colors (> a few gigayears) indicates that the optical measurements are not strongly affected by dust extinction.

Krick, J. E.; Desai, V.; Murphy, E.; Surace, J. [Spitzer Science Center, MS 220-6, California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA 91125 (United States); Bridge, C.; Neill, J. [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Mihos, J. C. [Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States); Rudick, C., E-mail: jkrick@caltech.edu [ETH Zurich, Institute of Astronomy, CH8093 Zurich (Switzerland)

2011-07-10

351

Spitzer/IRAC Low Surface Brightness Observations of the Virgo Cluster  

NASA Astrophysics Data System (ADS)

We present 3.6 and 4.5 ?m Spitzer Infrared Array Camera (IRAC) imaging over 0.77 deg2 at the Virgo cluster core for the purpose of understanding the formation mechanisms of the low surface brightness intracluster light (ICL) features. Instrumental and astrophysical backgrounds that are hundreds of times higher than the signal were carefully characterized and removed. We examine ICL plumes as well as the outer halo of the giant elliptical M87. For two ICL plumes, we use optical colors to constrain their ages to be greater than 3 and 5 Gyr, respectively. Upper limits on the IRAC fluxes constrain the upper limits to the masses, and optical detections constrain the lower limits to the masses. In this first measurement of mass of ICL plumes we find masses in the range of 5.5 × 108 - 4.5 × 109 and 2.1 × 108-1.5 × 109 M sun for the two plumes for which we have coverage. Given their expected short lifetimes, and a constant production rate for these types of streams, integrated over Virgo's lifetime, they can account for the total ICL content of the cluster, implying that we do not need to invoke ICL formation mechanisms other than gravitational mechanisms leading to bright plumes. We also examined the outer halo of the giant elliptical M87. The color profile from the inner to outer halo of M87 (160 kpc) is consistent with either a flat or optically blue gradient, where a blue gradient could be due to younger or lower metallicity stars at larger radii. The similarity of the age predicted by both the infrared and optical colors (> a few gigayears) indicates that the optical measurements are not strongly affected by dust extinction.

Krick, J. E.; Bridge, C.; Desai, V.; Mihos, J. C.; Murphy, E.; Rudick, C.; Surace, J.; Neill, J.

2011-07-01

352

All Sky Search for Gravitational-Wave Bursts in the Second Joint LIGO-Virgo Run  

NASA Technical Reports Server (NTRS)

We present results from a search for gravitational-wave bursts in the data collected by the LIGO and Virgo detectors between July 7, 2009 and October 20, 2010: data are analyzed when at least two of the three LIGO-Virgo detectors are in coincident operation, with a total observation time of 207 days. The analysis searches for transients of duration approx. < 1 s over the frequency band 64-5000 Hz, without other assumptions on the signal wa.veform, polarization, direction or occurrence time. All identified events are c.onsistent with the expected accidental background. We set frequentist upper limits on the rate of gravitational-wave bursts by combining this search with the previous LIGOVirgo search on the data collected "between November 2005 and October 2007. The upper limit on the rate of strong gravita.tional-wave bursts at the Earth is 1.3 events per year at 90% confidence. We also present upper limits on source rate density per yea.r and Mpc3 for sample popula.tions of standard-candle sources. As in the previous joint run, typical sensitivities of the search in terms of the root-sum-squared strain amplitude for these waveforms lie in the range approx 5 x 10(exp -22 Hz(exp-1/2) approx 1 X 10(exp -20) Hz(exp -1/2) . The combination of the two joint runs entails the most sensitive all-sky search for generic gravitational-wave bursts and synthesizes the results achieved by the initial generation of interferometric detectors.

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

2012-01-01

353

Statistics of mass substructure from strong gravitational lensing: quantifying the mass fraction and mass function  

NASA Astrophysics Data System (ADS)

A Bayesian statistical formalism is developed to quantify the level at which the mass function (dN/dm ~ m-?) and the projected cumulative mass fraction (f) of [cold dark matter (CDM)] substructure in strong gravitational lens galaxies, with arcs or Einstein rings, can be recovered as function of the lens survey parameters and the detection threshold of the substructure mass. The method is applied to different sets of mock data to explore a range of observational limits: (i) the number of lens galaxies in the survey; (ii) the mass threshold, Mlow, for the detection of substructures and (iii) the uncertainty of the measured substructure masses. We explore two different priors on the mass function slope: a uniform prior and a Gaussian prior with ? = 1.90 +/- 0.1. With a substructure detection threshold Mlow = 3 × 108Msolar, the number of lenses available now (nl = 30), a true dark matter mass fraction in (CDM) substructure <=1.0 per cent and a prior of ? = 1.90 +/- 0.1, we find that the upper limit of f can be constrained down to a level <=1.0 per cent [95 per cent confidence level (CL)]. In the case of a uniform prior, the complete substructure mass distribution (i.e. mass fraction and slope) can only be characterized in a number of favourable cases with a large number of detected substructures. This can be achieved by an increase of the resolution and the signal-to-noise ratio of the lensed images. In the case of a Gaussian prior on ?, instead, it is always possible to set stringent constraints on both parameters. We also find that lowering the detection threshold has the largest impact on the ability to recover ?, because of the (expected) steep mass function slope. In the future, thanks to new surveys with telescopes, such as Square Kilometre Array (SKA), Large Synoptic Survey Telescope (LSST) and Joint Dark Energy Mission (JDEM) and follow-up telescopes with high-fidelity data, a significant increase in the number of known lenses (i.e. >>104) will allow us to recover the satellite population in its completeness. For example, a sample of 200 lenses, equivalent in data quality to the Sloan Lens ACS Survey and a detection threshold of 108Msolar, allows one to determine f = 0.5 +/- 0.1 per cent (68 per cent CL) and ? = 1.90 +/- 0.2 (68 per cent CL).

Vegetti, Simona; Koopmans, L. V. E.

2009-12-01

354

Substructure based modeling of nickel single crystals cycled at low plastic strain amplitudes  

NASA Astrophysics Data System (ADS)

In this dissertation a meso-scale, substructure-based, composite single crystal model is fully developed from the simple uniaxial model to the 3-D finite element method (FEM) model with explicit substructures and further with substructure evolution parameters, to simulate the completely reversed, strain controlled, low plastic strain amplitude cyclic deformation of nickel single crystals. Rate-dependent viscoplasticity and Armstrong-Frederick type kinematic hardening rules are applied to substructures on slip systems in the model to describe the kinematic hardening behavior of crystals. Three explicit substructure components are assumed in the composite single crystal model, namely "loop patches" and "channels" which are aligned in parallel in a "vein matrix," and persistent slip bands (PSBs) connected in series with the vein matrix. A magnetic domain rotation model is presented to describe the reverse magnetostriction of single crystal nickel. Kinematic hardening parameters are obtained by fitting responses to experimental data in the uniaxial model, and the validity of uniaxial assumption is verified in the 3-D FEM model with explicit substructures. With information gathered from experiments, all control parameters in the model including hardening parameters, volume fraction of loop patches and PSBs, and variation of Young's modulus etc. are correlated to cumulative plastic strain and/or plastic strain amplitude; and the whole cyclic deformation history of single crystal nickel at low plastic strain amplitudes is simulated in the uniaxial model. Then these parameters are implanted in the 3-D FEM model to simulate the formation of PSB bands. A resolved shear stress criterion is set to trigger the formation of PSBs, and stress perturbation in the specimen is obtained by several elements assigned with PSB material properties a priori. Displacement increment, plastic strain amplitude control and overall stress-strain monitor and output are carried out in the user subroutine DISP and URDFIL of ABAQUS, respectively, while constitutive formulations of the FEM model are coded and implemented in UMAT. The results of the simulations are compared to experiments. This model verified the validity of Winter's two-phase model and Taylor's uniform stress assumption, explored substructure evolution and "intrinsic" behavior in substructures and successfully simulated the process of PSB band formation and propagation.

Zhou, Dong

355

Jet substructure templates: data-driven QCD backgrounds for fat jet searches  

NASA Astrophysics Data System (ADS)

QCD is often the dominant background to new physics searches for which jet substructure provides a useful handle. Due to the challenges associated with modeling this background, data-driven approaches are necessary. This paper presents a novel method for determining QCD predictions using templates — probability distribution functions for jet substructure properties as a function of kinematic inputs. Templates can be extracted from a control region and then used to compute background distributions in the signal region. Using Monte Carlo, we illustrate the procedure with two case studies and show that the template approach effectively models the relevant QCD background. This work strongly motivates the application of these techniques to LHC data.

Cohen, Timothy; Jankowiak, Martin; Lisanti, Mariangela; Lou, Hou Keong; Wacker, Jay G.

2014-05-01

356

Effect of temperature on the formation of creep substructure in sodium chloride single crystals  

NASA Technical Reports Server (NTRS)

The effect of temperature on the substructure morphology and the cell and subgrain size was investigated experimentally in NaCl single crystals under creep in the temperature range 573-873 K. It is found that the effect of temperature on the cell and subgrain sizes is weak in comparison with the effect of stress. However, there was a qualitative change in the substructure morphology with temperature, with the cells and subgrains better defined at higher temperatures. The volume fraction of the cell boundaries decreased with increasing temperature, thereby indicating a refinement of the microstructure at higher temperatures.

Raj, Sai V.; Pharr, George M.

1992-01-01

357

Ashkenazi Jewish mtDNA haplogroup distribution varies among distinct subpopulations: lessons of population substructure in a closed group  

Microsoft Academic Search

The quest for genes associated with diseases is widely recognized as an essential task in the effort to investigate the genetic basis of complex human disorders and traits. A basic stage in association studies is the careful choice of the model population, with preference to closed groups having little population substructure. Here, we show evidence for significant geographic substructure (P=0.017)

Jeanette Feder; Ofer Ovadia; Benjamin Glaser; Dan Mishmar

2007-01-01

358

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

359

Early stellar evolution  

NASA Technical Reports Server (NTRS)

Research into the formation and early evolution of stars is currently an area of great interest and activity. The theoretical and observational foundations for this development are reviewed in this paper. By now, the basic physics governing cloud collapse is well understood, as is the structure of the resulting protostars. However, the theory predicts protostellar luminosities that are greater than those of most infrared sources. Observationally, it is thought that protostars emit powerful winds that push away remnant cloud gas, but both the origin of these winds and the nature of their interaction with ambient gas are controversial. Finally, the theory of pre-main-sequence stars has been modified to incorporate more realistic initial conditions. This improvement helps to explain the distribution of such stars in the H-R diagram. Many important issues, such as the origin of binary stars and stellar clusters, remain as challenges for future research.

Stahler, Steven W.

1994-01-01

360

The stellar opacities  

NASA Astrophysics Data System (ADS)

Opacities are fundamental ingredients of stellar physics. Helioseismology and asteroseismology have put in evidence anomalies that could be attributed to an insufficient knowledge of the photon-plasma interactions. We work on a revision of this plasma physics in the conditions where the anomalies have been found: the region of the iron opacity peak near log T= 5.2 and the inner radiative region of Sun and solar-like stars. The international OPAC consortium performs new calculations, compares them and looks for the origin of their differences. In parallel, experimental campaigns are realized, others are in preparation to validate some conclusions on the reliability of the new proposed calculations. New tables for astrophysics will be performed in the framework of the ANR OPACITY and their influence on seismic observables will be studied. We explicit here the difficulty of the computations together with some computation resources.

Turck-Chièze, S.; Gilles, D.; Gilleron, F.; Pain, J. C.

2013-11-01

361

Resolving stellar surface spots  

NASA Astrophysics Data System (ADS)

Doppler imaging of stellar surfaces is a novel technique with similarities to medical brain tomography (instead of a fixed brain and a rotating scanner, astronomers have a fixed spectrograph and a rotating brain, star of course). The number of free (internal) parameters is of the order of the number of surface grid points and only constrained by the number of input data points. This obviously ill-posed situation requires modern inversion algorithms with penalty functions of the form of maximum entropy or Tikhonov etc.. We present a brief status review of our Doppler imaging codes at AIP that span from temperature and spot-filling-factor mapping to full Stokes-based magnetic field mapping.

Strassmeier, K. G.; Carroll, T.; Rice, J. B.; Savanov, I. S.

362

Discovery of a Large Stellar Periphery of the Small Magellanic Cloud  

NASA Astrophysics Data System (ADS)

The Magellanic Clouds are a local laboratory for understanding the evolution and properties of dwarf irregular galaxies. To reveal the extended structure and interaction history of the Magellanic Clouds, we have undertaken a large-scale photometric and spectroscopic study of their stellar periphery (The MAgellanic Periphery Survey, MAPS). We present our first results for the Small Magellanic Cloud (SMC): Washington M, T2 + DDO51 photometry reveals metal-poor red giant branch stars in the SMC that extend out to large radii (11.1 kpc), are distributed nearly azimuthally symmetrically (ellipticity=0.1), and are well-fitted by an exponential profile (out to R=7.5 deg). We find a "break" population beyond 8 radial scalelengths having a very shallow radial density profile that looks to be a stellar halo. The outer stellar distribution contrasts with that of the inner stellar distribution, which is both more elliptical (ellipticity 0.3) and offset from the center of the outer population by 0.63 deg, although both populations share a similar radial exponential scale length. This offset is likely due to a perspective effect since stars on the eastern side of the SMC are on average at closer distances than stars on the western side. The discovery of these new outer stellar structures indicates that the SMC is more complex than previously thought. Our results indicate that it is likely that the SMC has a large stellar halo, which, if correct, would confirm predictions by Lambda CDM simulations that galaxies on all scales should have substructure and halos.

Nidever, David L.; Majewski, S. R.; Munoz, R. R.; Beaton, R. L.; Patterson, R. J.; Kunkel, W. E.

2011-01-01

363

Extreme Low Aspect Ratio Stellarators  

NASA Astrophysics Data System (ADS)

Recently proposed Spherical Stellarator (SS) concept [1] includes the devices with stellarator features and low aspect ratio, A <= 3.5, which is very unusual for stellarators (typical stellarators have A ? 7-10 or above). Strong bootstrap current and high-? equilibria are two distinguished elements of the SS concept leading to compact, steady-state, and efficient fusion reactor. Different coil configurations advantageous for the SS have been identified and analyzed [1-6]. In this report, we will present results on novel stellarator configurations which are unusual even for the SS approach. These are the extreme-low-aspect-ratio-stellarators (ELARS), with the aspect ratio A ? 1. We succeeded in finding ELARS configurations with extremely compact, modular, and simple design compatible with significant rotational transform (? ? 0.1 - 0.15), large plasma volume, and good particle transport characteristics. [1] P.E. Moroz, Phys. Rev. Lett. 77, 651 (1996); [2] P.E. Moroz, Phys. Plasmas 3, 3055 (1996); [3] P.E. Moroz, D.B. Batchelor et al., Fusion Tech. 30, 1347 (1996); [4] P.E. Moroz, Stellarator News 48, 2 (1996); [5] P.E. Moroz, Plasma Phys. Reports 23, 502 (1997); [6] P.E. Moroz, Nucl. Fusion 37, No. 8 (1997). *Supported by DOE Grant No. DE-FG02-97ER54395.

Moroz, Paul

1997-11-01

364

A possible excess rotation measure and large-scale magnetic field in the Virgo Supercluster of galaxies  

NASA Astrophysics Data System (ADS)

A search of the Broten et al. (1988) all-sky rotation-measure (RM) catalog for galaxies and quasars resulted in a possible discovery of a cluster-wide magnetic field in the Virgo Supercluster, with a magnetic field intensity near 1.5 microG consistent with an RM excess of -10 rad/sq m. The magnetic energy density of a 1.5 microG field is about 10 to the -13 ergs/cu cm, comparable to the energy density in the 2.7 K cosmic blackbody radiation of 5 x 10 to the -13th ergs/cu cm. The energetic implications for a 1.5 microG cluster-wide field in Virgo are also reasonable in view of the current theoretical models predicting such large-scale magnetic fields in cluster of galaxies.

Vallee, J. P.

1990-02-01

365

All-sky search for gravitational-wave bursts in the first joint LIGO-GEO-Virgo run  

Microsoft Academic Search

We present results from an all-sky search for unmodeled\\u000a\\u0009\\u0009 gravitational-wave bursts in the data collected by the\\u000a\\u0009\\u0009 {LIGO}, GEO 600 and Virgo detectors between November 2006\\u000a\\u0009\\u0009 and October 2007. The search is performed by three\\u000a\\u0009\\u0009 different analysis algorithms over the frequency band\\u000a\\u0009\\u0009 50-6000 Hz. Data are analyzed for times with at least two\\u000a\\u0009\\u0009 of the four {LIGO}-Virgo detectors in coincident

J. Abadie; B. P. Abbott; R. Abbott; T. Accadia; F. Acernese; 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; K. G. Arun; Y. Aso; S. Aston; P. Astone; P. Aufmuth; C. Aulbert; S. Babak; P. Baker; G. Ballardin; S. Ballmer; D. Barker; F. Barone; B. Barr; P. Barriga; L. Barsotti; M. Barsuglia; M. A. Barton; I. Bartos; R. Bassiri; M. Bastarrika; Th. S. Bauer; B. Behnke; M. G. Beker; A. Belletoile; M. Benacquista; J. Betzwieser; P. T. Beyersdorf; S. Bigotta; I. A. Bilenko; G. Billingsley; S. Birindelli; R. Biswas; 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; 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; A. Bullington; H. J. Bulten; A. Buonanno; O. Burmeister; D. Buskulic; C. Buy; R. L. Byer; L. Cadonati; G. Cagnoli; J. Cannizzo; E. Calloni; J. B. Camp; E. Campagna; K. C. Cannon; B. Canuel; J. Cao; C. D. Capano; F. Carbognani; L. Cardenas; S. Caudill; M. Cavaglià; F. Cavalier; R. Cavalieri; G. Cella; C. Cepeda; E. Cesarini; T. Chalermsongsak; E. Chalkley; P. Charlton; E. Chassande-Mottin; S. Chatterji; 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. C. Corbitt; N. Cornish; A. Corsi; 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; S. D’Antonio; K. Danzmann; V. Dattilo; B. Daudert; M. Davier; G. Davies; E. J. Daw; R. Day; T. Dayanga; R. De Rosa; D. Debra; J. Degallaix; M. del Prete; V. Dergachev; R. Desalvo; S. Dhurandhar; L. Di Fiore; A. Di Lieto; M. Di Paolo Emilio; A. Di Virgilio; M. Díaz; A. Dietz; F. Donovan; K. L. Dooley; E. E. Doomes; M. Drago; R. W. P. Drever; J. Driggers; J. Dueck; I. Duke; J.-C. Dumas; M. Edgar; M. Edwards; A. Effler; P. Ehrens; T. Etzel; M. Evans; T. Evans; V. Fafone; S. Fairhurst; Y. Faltas; Y. Fan; D. Fazi; H. Fehrmann; I. Ferrante; F. Fidecaro; Lee Samuel Finn; I. Fiori; R. Flaminio; K. Flasch; S. Foley; C. Forrest; 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; E. Goetz; L. M. Goggin; G. González; S. Goßler; R. Gouaty; 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; J. M. Hallam; D. Hammer; G. D. Hammond; 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; D. R. Ingram; 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; R. Khan; E. Khazanov; H. Kim; P. J. King; J. S. Kissel; S. Klimenko; K. Kokeyama; V. Kondrashov; R. Kopparapu; S. Koranda; I. Kowalska; D. Kozak; V. Kringel; B. Krishnan; A. Królak; G. Kuehn; J. Kullman; R. Kumar; P. Kwee; P. K. Lam; M. Landry; M. Lang; B. Lantz; N. Lastzka; A. Lazzarini; P. Leaci; M. Lei; N. Leindecker; I. Leonor; N. Leroy; N. Letendre; T. G. F. Li; H. Lin; P. E. Lindquist; T. B. Littenberg; N. A. Lockerbie; D. Lodhia; M. Lorenzini; V. Loriette; M. Lormand; G. Losurdo; P. Lu; 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; A. Markosyan; J. Markowitz; E. Maros; J. Marque; F. Martelli; I. W. Martin; R. M. Martin; J. N. Marx; K. Mason; A. Masserot; F. Matichard; L. Matone; R. A. Matzner; N. Mavalvala; R. McCarthy; D. E. McClelland; S. C. McGuire; G. McIntyre; D. J. A. McKechan; M. Mehmet; A. Melatos; A. C. Melissinos; G. Mendell; D. F. Menendez; R. A. Mercer; L. Merill; S. Meshkov; C. Messenger; M. S. Meyer; H. Miao; C. Michel; L. Milano; J. Miller

2010-01-01

366

A first search for coincident gravitational waves and high energy neutrinos using LIGO, Virgo and ANTARES data from 2007  

NASA Astrophysics Data System (ADS)

We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.

Adrián-Martínez, S.; Samarai, I. Al; Albert, A.; André, M.; Anghinolfi, M.; Anton, G.; Anvar, S.; Ardid, M.; Astraatmadja, T.; Aubert, J.-J.; Baret, B.; Basa, S.; Bertin, V.; Biagi, S.; Bigongiari, C.; Bogazzi, C.; Bou-Cabo, M.; Bouhou, B.; Bouwhuis, M. C.; Brunner, J.; Busto, J.; Capone, A.; Cârloganu, C.; Carr, J.; Cecchini, S.; Charif, Z.; Charvis, Ph.; Chiarusi, T.; Circella, M.; Coniglione, R.; Core, L.; Costantini, H.; Coyle, P.; Creusot, A.; Curtil, C.; De Bonis, G.; Decowski, M. P.; Dekeyser, I.; Deschamps, A.; Distefano, C.; Donzaud, C.; Dornic, D.; Dorosti, Q.; Drouhin, D.; Eberl, T.; Emanuele, U.; Enzenhöfer, A.; Ernenwein, J.-P.; Escoffier, S.; Fehn, K.; Fermani, P.; Ferri, M.; Ferry, S.; Flaminio, V.; Folger, F.; Fritsch, U.; Fuda, J.-L.; Galatà, S.; Gay, P.; Geyer, K.; Giacomelli, G.; Giordano, V.; Gómez-González, J. P.; Graf, K.; Guillard, G.; Hallewell, G.; Hamal, M.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Herold, B.; Hößl, J.; Hsu, C. C.; de Jong, M.; Kadler, M.; Kalekin, O.; Kappes, A.; Katz, U.; Kavatsyuk, O.; Kooijman, P.; Kopper, C.; Kouchner, A.; Kreykenbohm, I.; Kulikovskiy, V.; Lahmann, R.; Lambard, G.; Larosa, G.; Lattuada, D.; Lefèvre, D.; Lim, G.; Lo Presti, D.; Loehner, H.; Loucatos, S.; Louis, F.; Mangano, S.; Marcelin, M.; Margiotta, A.; Martínez-Mora, J. A.; Martini, S.; Meli, A.; Montaruli, T.; Morganti, M.; Moscoso, L.; Motz, H.; Neff, M.; Nezri, E.; Palioselitis, D.; P?v?la?, G. E.; Payet, K.; Petrovic, J.; Piattelli, P.; Popa, V.; Pradier, T.; Presani, E.; Racca, C.; Reed, C.; Riccobene, G.; Richardt, C.; Richter, R.; Rivière, C.; Robert, A.; Roensch, K.; Rostovtsev, A.; Ruiz-Rivas, J.; Rujoiu, M.; Russo, G. V.; Samtleben, D. F. E.; Sánchez-Losa, A.; Sapienza, P.; Schmid, J.; Schnabel, J.; Schöck, F.; Schuller, J.-P.; Schüssler, F.; Seitz, T.; Shanidze, R.; Simeone, F.; Spies, A.; Spurio, M.; Steijger, J. J. M.; Stolarczyk, Th.; Taiuti, M.; Tamburini, C.; Trovato, A.; Vallage, B.; Vallée, C.; Van Elewyck, V.; Vecchi, M.; Vernin, P.; Visser, E.; Wagner, S.; Wijnker, G.; Wilms, J.; de Wolf, E.; Yepes, H.; Zaborov, D.; Zornoza, J. D.; Zúñiga, J.; 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.; Amador Ceron, E.; Amariutei, D.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Ast, S.; Aston, S. M.; Astone, P.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Bao, Y.; Barayoga, J. C. B.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Beck, D.; Behnke, B.; Bejger, M.; Beker, M. G.; Bell, A. S.; Bell, C.; Belopolski, I.; Benacquista, M.; Berliner, J. M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bhadbade, T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Bock, O.; Bodiya, T. P.; Bogan, C.; Bond, C.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet–Castell, J.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chalermsongsak, T.; Charlton, P.; Chassande-Mottin, E.; Chen, W.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Clayton, J. H.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colacino, C. N.; Colla, A.; Colombini, M.; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M.; Coulon, J.-P.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Cutler, R. M.; Dahl, K.; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; Del Pozzo, W.; Dent, T.

2013-06-01

367

Substructure Evolution in Energetic-Driven Spherically Shock-Loaded Copper  

SciTech Connect

Post-shock-recovered metallurgical analysis of solid metal spheres shock loaded via spherical energetic(HE) loading provides a unique opportunity to quantify the substructure evolution in a material subjected to converging Taylor-wave (triangular-shock pulse) loading. In this paper detailed quantitative metallographic, orientation-imaging microscopy (OIM), and texture analysis is presented characterizing the gradient in substructure generated in Cu subjected to a spherical HE shock loading pulse at VNIIEF. The substructure in the recovered sphere is seen to include: 1) a spherical cavity generated in the center of the sphere due to shock-wave convergence and release, displaying ductile dimpled failure and no evidence of melting, 2) a gradient in deformation (slip and deformation twins) from the center outward to the surface, and 3) numerous shear cracks and/or spall planes. The substructure evolution is discussed relative to that previously observed in Cu shock prestrained via either 1-D triangular-shaped shockwave loading or 1-D square-topped pulse shock loading.

Sinitsyna, L. M.; Novikov, S. A. [RFNC-VNIIEF, Sarov, 607190 (Russian Federation); Gray, G. T. III; Cerreta, E.; Henrie, B.; Lopez, M.; Yablinsky, C. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2006-07-28

368

Cyclic shear tests on Aluminium 3004 and 5182 alloys: macroscopic behaviour and substructural development  

Microsoft Academic Search

Cyclic shear tests with various constant strain amplitudes have been carried out to characterize the microstructural development under cyclic straining of aluminium-3004 and aluminium-5182 alloys. Substructural instabilities that occur inside the microstructure, their morphologies and crystallographies are reported. The hypothetical influence of these inhomogeneities on the observed macroscopic behaviour is discussed.

G. F. Dirras

1997-01-01

369

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

370

Bayesian strong gravitational-lens modelling on adaptive grids: objective detection of mass substructure in Galaxies  

Microsoft Academic Search

We introduce a new adaptive and fully Bayesian grid-based method to model strong gravitational lenses with extended images. The primary goal of this method is to quantify the level of luminous and dark mass substructure in massive galaxies, through their effect on highly magnified arcs and Einstein rings. The method is adaptive on the source plane, where a Delaunay tessellation

Simona Vegetti; L. V. E. Koopmans

2009-01-01

371

Dynamics of flexible multibody systems using loaded-interface substructure synthesis approach  

Microsoft Academic Search

A simple numerical method for dynamic simulation of multibody systems consisting of rigid and flexible bodies is presented. This paper investigates the multibody systems with inertia properties of flexible components that undergo large angular rotations. The equation of motion is derived using the finite element\\/Lagrange formulation. A substructure synthesis method is employed to reduce the number of elastic coordinates of

S. P. Lim; A. Q. Liu; K. M. Liew

1994-01-01

372

Br?nsted Acid-Promoted Glycosylations of Disaccharide Glycal Substructures of the Saccharomicins  

PubMed Central

An acid-promoted glycosylation and alkynol cycloisomerization sequence provided direct access to the 2-deoxytrisaccharide corresponding to the fucose-saccharosamine-digitoxose substructure of saccharomicin B. In the course of this work, the absolute stereochemistry of the repeating fucose-saccharosamine disaccharide of saccharomicins was also confirmed.

Balthaser, Bradley R.; McDonald, Frank E.

2009-01-01

373

Electric fields in bone marrow substructures at power-line frequencies  

Microsoft Academic Search

Bone marrow is known to be responsible for leukemia. In order to study the hypothesis relating power-line frequencies electromagnetic fields and childhood leukemia from a subcellular perspective, two models of bone marrow substructures exposed to electric field are computed numerically. A set of cancellous bone data obtained from computed tomography scan is computed using both the finite element method (FEM)

Roanna S. Chiu; Maria A. Stuchly

2005-01-01

374

Substructure Evolution in Energetic-Driven Spherically Shock-Loaded Copper  

NASA Astrophysics Data System (ADS)

Post-shock-recovered metallurgical analysis of solid metal spheres shock loaded via spherical energetic(HE) loading provides a unique opportunity to quantify the substructure evolution in a material subjected to converging Taylor-wave (triangular-shock pulse) loading. In this paper detailed quantitative metallographic, orientation-imaging microscopy (OIM), and texture analysis is presented characterizing the gradient in substructure generated in Cu subjected to a spherical HE shock loading pulse at VNIIEF. The substructure in the recovered sphere is seen to include: 1) a spherical cavity generated in the center of the sphere due to shock-wave convergence and release, displaying ductile dimpled failure and no evidence of melting, 2) a gradient in deformation (slip and deformation twins) from the center outward to the surface, and 3) numerous shear cracks and/or spall planes. The substructure evolution is discussed relative to that previously observed in Cu shock prestrained via either 1-D triangular-shaped shockwave loading or 1-D square-topped pulse shock loading.

Sinitsyna, L. M.; Novikov, S. A.; Gray, G. T.; Cerreta, E.; Henrie, B.; Lopez, M.; Yablinsky, C.

2006-07-01

375

Substructure analysis techniques and automation. [to eliminate logistical data handling and generation chores  

NASA Technical Reports Server (NTRS)

A basic automated substructure analysis capability for NASTRAN is presented which eliminates most of the logistical data handling and generation chores that are currently associated with the method. Rigid formats are proposed which will accomplish this using three new modules, all of which can be added to level 16 with a relatively small effort.

Hennrich, C. W.; Konrath, E. J., Jr.

1973-01-01

376

Radiative Transfer in Stellar Atmospheres  

NASA Astrophysics Data System (ADS)

The main topic treated in these graduate course notes is the classical theory of radiative transfer for explaining stellar spectra. It needs relatively much attention to be mastered. Radiative transfer in gaseous media that are neither optically thin nor fully opaque and scatter to boot is a key part of astrophysics but not a transparent subject. These course notes represent a middle road between Mihalas' "Stellar Atmospheres" (graduate level and up) and the books by Novotny and Boehm-Vitense (undergraduate level). They are at about the level of Gray's "The observation and analysis of stellar photospheres" but emphasize NLTE radiative transfer rather than observational techniques and data interpretation.

Rutten, Robert J.

2003-05-01

377

Stellar Snowflake Cluster  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Figure 1 Stellar Snowflake Cluster Combined Image [figure removed for brevity, see original site] Figure 2 Infrared Array CameraFigure 3 Multiband Imaging Photometer

Newborn stars, hidden behind thick dust, are revealed in this image of a section of the Christmas Tree cluster from NASA's Spitzer Space Telescope, created in joint effort between Spitzer's infrared array camera and multiband imaging photometer instruments.

The newly revealed infant stars appear as pink and red specks toward the center of the combined image (fig. 1). The stars appear to have formed in regularly spaced intervals along linear structures in a configuration that resembles the spokes of a wheel or the pattern of a snowflake. Hence, astronomers have nicknamed this the 'Snowflake' cluster.

Star-forming clouds like this one are dynamic and evolving structures. Since the stars trace the straight line pattern of spokes of a wheel, scientists believe that these are newborn stars, or '