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Sample records for virgo stellar substructure

  1. THE ORIGIN OF THE VIRGO STELLAR SUBSTRUCTURE

    SciTech Connect

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

    2012-07-10

    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' Multiplication-Sign 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{sub GSR} > 50 km s{sup -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{sub GSR} = 153 {+-} 22 km s{sup -1} and proper motions ({mu}{sub {alpha}}cos {delta}, {mu}{sub {delta}}) = (- 5.24, -0.91) {+-} (0.43, 0.46) mas yr{sup -1}. From the mean kinematics of these members, we determine that the Virgo progenitor was on an eccentric (e {approx} 0.8) orbit that recently passed near the Galactic center (pericentric distance R{sub p} {approx} 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 ({approx}10{sup 9} M{sub Sun }) 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.

  2. The Origin of the Virgo Stellar Substructure

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    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 (μαcos δ, μδ) = (- 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.

  3. The Next Generation Virgo Cluster Survey. XIX. Tomography of Milky Way Substructures in the NGVS Footprint

    NASA Astrophysics Data System (ADS)

    Lokhorst, Deborah; Starkenburg, Else; McConnachie, Alan W.; Navarro, Julio F.; Ferrarese, Laura; Côté, Patrick; Liu, Chengze; Peng, Eric W.; Gwyn, Stephen D. J.; Cuillandre, Jean-Charles; Guhathakurta, Puragra

    2016-03-01

    The Next Generation Virgo Cluster Survey (NGVS) is a deep u*giz survey targeting the Virgo Cluster of galaxies at 16.5 Mpc. This survey provides high-quality photometry over an ˜100 deg2 region straddling the constellations of Virgo and Coma Berenices. This sightline through the Milky Way is noteworthy in that it intersects two of the most prominent substructures in the Galactic halo: the Virgo overdensity (VOD) and Sagittarius stellar stream (close to its bifurcation point). In this paper, we use deep u*gi imaging from the NGVS to perform tomography of the VOD and Sagittarius stream using main-sequence turnoff (MSTO) stars as a halo tracer population. The VOD, whose centroid is known to lie at somewhat lower declinations (α ˜ 190°, δ ˜ -5°) than is covered by the NGVS, is nevertheless clearly detected in the NGVS footprint at distances between ˜8 and 25 kpc. By contrast, the Sagittarius stream is found to slice directly across the NGVS field at distances between 25 and 40 kpc, with a density maximum at ≃35 kpc. No evidence is found for new substructures beyond the Sagittarius stream, at least out to a distance of ˜90 kpc—the largest distance to which we can reliably trace the halo using MSTO stars. We find clear evidence for a distance gradient in the Sagittarius stream across the ˜30° of sky covered by the NGVS and its flanking fields. We compare our distance measurements along the stream with those predicted by leading stream models.

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

    NASA Astrophysics Data System (ADS)

    Farmer, John; Vivas, A. Katherina

    2015-01-01

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

  5. A comprehensive view of the Virgo stellar stream

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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

  6. Early dynamical evolution of substructured stellar clusters

    NASA Astrophysics Data System (ADS)

    Dorval, Julien; Boily, Christian

    2015-08-01

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

  7. Stellar Populations and Radial Migrations in Virgo Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Roediger, Joel C.; Courteau, Stéphane; Sánchez-Blázquez, Patricia; McDonald, Michael

    2012-10-01

    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

  8. STELLAR POPULATIONS AND RADIAL MIGRATIONS IN VIRGO DISK GALAXIES

    SciTech Connect

    Roediger, Joel C.; Courteau, Stephane; Sanchez-Blazquez, Patricia; McDonald, Michael E-mail: courteau@astro.queensu.ca E-mail: mcdonald@space.mit.edu

    2012-10-10

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

  9. The stellar populations and evolution of Virgo cluster galaxies

    NASA Astrophysics Data System (ADS)

    Roediger, Joel C.

    2009-11-01

    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

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

    SciTech Connect

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

    2011-09-01

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

  11. SUBSTRUCTURE IN THE STELLAR HALOS OF THE AQUARIUS SIMULATIONS

    SciTech Connect

    Helmi, Amina; Cooper, A. P.; Cole, S.; Frenk, C. S.; White, S. D. M.; Navarro, J. F.

    2011-05-20

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

  12. A PHOTOMETRIC METALLICITY ESTIMATE OF THE VIRGO STELLAR OVERDENSITY

    SciTech Connect

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

    2009-12-10

    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.

  13. Detailed chemical abundances of distant RR Lyrae stars in the Virgo Stellar Stream

    NASA Astrophysics Data System (ADS)

    Duffau, S.; Sbordone, L.; Vivas, A. K.; Hansen, C. J.; Zoccali, M.; Catelan, M.; Minniti, D.; Grebel, E. K.

    2016-05-01

    We present the first detailed chemical abundances for distant RR Lyrae stars members of the Virgo Stellar Stream (VSS), derived from X- Shooter medium-resolution spectra. Sixteen elements from carbon to barium have been measured in six VSS RR Lyrae stars, sampling all main nucleosynthetic channels. For the first time we will be able to compare in detail the chemical evolution of the VSS progenitor with those of Local Group dwarf spheroidal galaxies (LG dSph) as well as the one of the smooth halo.

  14. Planetary Nebulae and their parent stellar populations. Tracing the mass assembly of M87 and Intracluster light in the Virgo cluster core

    NASA Astrophysics Data System (ADS)

    Arnaboldi, Magda; Longobardi, Alessia; Gerhard, Ortwin

    2016-08-01

    The diffuse extended outer regions of galaxies are hard to study because they are faint, with typical surface brightness of 1% of the dark night sky. We can tackle this problem by using resolved star tracers which remain visible at large distances from the galaxy centers. This article describes the use of Planetary Nebulae as tracers and the calibration of their properties as indicators of the star formation history, mean age and metallicity of the parent stars in the Milky Way and Local Group galaxies. We then report on the results from a deep, extended, planetary nebulae survey in a 0.5 deg2 region centered on the brightest cluster galaxy NGC 4486 (M87) in the Virgo cluster core, carried out with SuprimeCam@Subaru and FLAMES-GIRAFFE@VLT. Two planetary nebulae populations are identified out to 150 kpc distance from the center of M87. One population is associated with the M87 halo and the second one with the intracluster light in the Virgo cluster core. They have different line-of-sight velocity and spatial distributions, as well as different planetary nebulae specific frequencies and luminosity functions. The intracluster planetary nebulae in the surveyed region correspond to a luminosity of four times the luminosity of the Large Magellanic Cloud. The M87 halo planetary nebulae trace an older, more metal-rich, parent stellar population. A substructure detected in the projected phase-space of the line-of-sight velocity vs. major axis distance for the M87 halo planetary nebulae provides evidence for the recent accretion event of a satellite galaxy with luminosity twice that of M33. The satellite stars were tidally stripped about 1 Gyr ago, and reached apocenter at a major axis distance of 60-90 kpc from the center of M87. The M87 halo is still growing significantly at the distances where the substructure is detected.

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

    SciTech Connect

    Cortés, Juan R.; Hardy, Eduardo; Kenney, Jeffrey D. P. E-mail: ehardy@nrao.cl

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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.

  17. Exploring the reality of density substructures in the Palomar 5 stellar stream

    NASA Astrophysics Data System (ADS)

    Thomas, Guillaume F.; Ibata, R.; Famaey, B.; Martin, N. F.; Lewis, G. F.

    2016-08-01

    We present an analysis of the presence of substructures in the stellar stream of the Palomar 5 globular cluster, as derived from Sloan Digital Sky Survey data. Using a matched filter technique, we recover the positions and sizes of overdensities reported in previous studies. To explore the reality of these structures, we also create an artificial model of the stream, in which we construct a realistic background on top of which we add a perfectly smooth stream structure, taking into account the effects of photometric completeness and interstellar extinction. We find that the smooth artificial stream then shows similarly-pronounced substructures as the real structure. Interestingly, our best-fit N-body simulation does display real projected density variations linked to stellar epicyclic motions, but these become less significant when taking into account the SDSS star-count constraints. The substructures found when applying our matched filter technique to the N-body particles converted into observable stars are thus mostly unrelated to these epicyclic motions. This analysis suggests that the majority of the previously-detected substructures along the tidal tail of Palomar 5 are artefacts of observational inhomogeneities.

  18. Exploring the reality of density substructures in the Palomar 5 stellar stream

    NASA Astrophysics Data System (ADS)

    Thomas, Guillaume F.; Ibata, R.; Famaey, B.; Martin, N. F.; Lewis, G. F.

    2016-08-01

    We present an analysis of the presence of substructures in the stellar stream of the Palomar 5 globular cluster, as derived from Sloan Digital Sky Survey data. Using a matched filter technique, we recover the positions and sizes of overdensities reported in previous studies. To explore the reality of these structures, we also create an artificial model of the stream, in which we construct a realistic background on top of which we add a perfectly smooth stream structure, taking into account the effects of photometric completeness and interstellar extinction. We find that the smooth artificial stream then shows similarly pronounced substructures as the real structure. Interestingly, our best-fitting N-body simulation does display real projected density variations linked to stellar epicyclic motions, but these become less significant when taking into account the SDSS star-count constraints. The substructures found when applying our matched filter technique to the N-body particles converted into observable stars are thus mostly unrelated to these epicyclic motions. This analysis suggests that the majority of the previously detected substructures along the tidal tail of Palomar 5 are artefacts of observational inhomogeneities.

  19. The extended stellar substructures of four metal-poor globular clusters in the Galactic bulge

    NASA Astrophysics Data System (ADS)

    Chun, Sang-Hyun; Sohn, Young-Jong

    2016-08-01

    We investigated the stellar density substructures around four metal-poor globular clusters (NGC 6266, NGC 6626, NGC 6642, and NGC 6723) in the Galactic bulge. Wide-field near-infrared (JHK s ) imaging data were obtained from WFCAM of UKIRT telescope. Field stars contamination around the globular clusters was reduced by using a statistical weighted filtering algorithm. Tidal stripping stellar substructures in the form of tidal tail (NGC 6266 and NGC 6626) or small density lobes/chunk (NGC 6642 and NGC 6723) were found around the four globular clusters in the two-dimensional density contour maps. We also find the overdensity features, which deviate from the theoretical models, in the outer region of radial density profiles. The observed results imply that the four globular clusters have experienced a strong tidal force or the bulge/disk shock effect of the Galaxy.

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

    SciTech Connect

    Casetti-Dinescu, Dana I.; Girard, Terrence M.; Van Altena, William F.; Majewski, Steven R.; Carlin, Jeffrey L.; Vivas, A. Katherina; Wilhelm, Ronald; Beers, Timothy C.

    2009-08-10

    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.

  1. The extended stellar substructures of four metal-poor globular clusters in the galactic bulge

    NASA Astrophysics Data System (ADS)

    Chun, Sang-Hyun; Sohn, Young-Jong

    2015-08-01

    We investigated stellar spatial density distribution around four metal-poor globular clusters (NGC 6266, NGC 6626, NGC 6642 and NGC 6723) in order to find extended stellar substructures. Wide-field deep J, H, and K imaging data were taken using the WFCAM near-infrared array on United Kingdom Infrared Telescope (UKIRT). The contamination of field stars around clusters was minimised by applying a statistical weighted filtering algorithm for the stars on the color-magnitude diagram. In two-dimensional isodensity contour map, we find that all four of the globular clusters shows tidal stripping stellar features in the form of tidal tails (NGC 6266 and NGC 6723) or small density lobes/chunk (NGC 6642 and NGC 6723). The stellar substructures extend toward the Galactic centre or anticancer, and the proper motion direction of the clusters. The radial density profiles of the clusters also depart from theoretical King and Wilson models and show overdensity feature with a break in a slope of profile at the outer region of clusters. The observed results indicate that four globular clusters in the Galactic bulge have experienced strong tidal force or bulge/disk shock effect of the Galaxy. These observational results provide us further constraints to understand the evolution of clusters in the Galactic bulge region as well as the formation of the Galaxy.

  2. Extending the Virgo Stellar Stream with SEKBO Survey RR Lyrae Stars

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

    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 σ = 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°.

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

    SciTech Connect

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    We analyze the stellar kinematics of 39 dwarf early-type galaxies (dEs) in the Virgo cluster. This is the largest survey conducted so far on spatially resolved kinematics of dEs. This sample is representative of the early-type population in the absolute magnitude range -19.0 < M_r < -16.0. For each dE, we measure the rotation curve and velocity dispersion profile and fit an analytic function to the rotation curve. We study the significance of the departure of the rotation curve from the best fit analytic function (poorly fit) and of the difference between the approaching and receding sides of the rotation curve (asymmetry). We find that 62+/-8% (23 out of the 39) of the dEs have a significant anomaly in their rotation curve. Analysis of the images reveals photometric anomalies for most galaxies. However, there is no clear correlation between the significance of the photometric and kinematic anomalies. Based on the specific stellar angular momentum and the ellipticity, we find 11 slow rotators and 28 fast rotators. The fast rotators in the outer parts of the Virgo cluster rotate significantly faster than fast rotators in the inner parts of the cluster. Moreover, 10 out of the 11 slow rotators are located in the inner Mpc of the cluster. The fast rotators contain subtle disky structures that are visible in high-pass filtered optical images, while the slow rotators do not exhibit these structures. In addition, two of the dEs have kinematically decoupled cores and four more have emission partially filling in the Balmer absorption lines. These properties suggest that Virgo cluster dEs may have originated from late-type star-forming galaxies that were transformed by the environment after their infall into the cluster. The correlation between the specific angular momentum and the clustercentric distance can be explained by a scenario where low luminosity star-forming galaxies fall into the cluster, their gas is rapidly removed by ram pressure stripping, although some of

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  6. Exploring halo substructure with giant stars. XIV. The nature of the Triangulum-Andromeda stellar features

    SciTech Connect

    Sheffield, Allyson A.; Johnston, Kathryn V.; Majewski, Steven R.; Damke, Guillermo; Richardson, Whitney; Beaton, Rachael; Rocha-Pinto, Helio J. E-mail: kvj@astro.columbia.edu E-mail: gjd3r@virginia.edu E-mail: rlb9n@virginia.edu

    2014-09-20

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

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

    SciTech Connect

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

    2010-11-10

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    We present Gemini Multi Object Spectrograph integral-field unit (GMOS-IFU) data of eight compact, low-mass early-type galaxies (ETGs) in the Virgo cluster. We analyze their stellar kinematics and stellar population and present two-dimensional maps of these properties covering the central 5″ × 7″ region. We find a large variety of kinematics, from nonrotating to highly rotating objects, often associated with underlying disky isophotes revealed by deep images from the Next Generation Virgo Cluster Survey. In half of our objects, we find a centrally concentrated younger and more metal-rich stellar population. We analyze the specific stellar angular momentum through the λR parameter and find six fast rotators and two slow rotators, one having a thin counterrotating disk. We compare the local galaxy density and stellar populations of our objects with those of 39 more extended low-mass Virgo ETGs from the SMAKCED survey and 260 massive (M > 1010 {{M}⊙ }) ETGs from the ATLAS3D sample. The compact low-mass ETGs in our sample are located in high-density regions, often close to a massive galaxy, and have, on average, older and more metal-rich stellar populations than less compact low-mass galaxies. We find that the stellar population parameters follow lines of constant velocity dispersion in the mass-size plane, smoothly extending the comparable trends found for massive ETGs. Our study supports a scenario where low-mass compact ETGs have experienced long-lived interactions with their environment, including ram-pressure stripping and gravitational tidal forces, that may be responsible for their compact nature.

  10. STELLAR KINEMATICS AND STRUCTURAL PROPERTIES OF VIRGO CLUSTER DWARF EARLY-TYPE GALAXIES FROM THE SMAKCED PROJECT. III. ANGULAR MOMENTUM AND CONSTRAINTS ON FORMATION SCENARIOS

    SciTech Connect

    Toloba, E.; Guhathakurta, P.; Peletier, R. F.; Emsellem, E.; Lisker, T.; Van de Ven, G.; Simon, J. D.; Adams, J. J.; Benson, A. J.; Falcón-Barroso, J.; Ryś, A.; Gorgas, J.; Hensler, G.; Janz, J.; Laurikainen, E.; Salo, H.; Paudel, S.

    2015-02-01

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

  11. The outer regions of the giant Virgo galaxy M 87 Kinematic separation of stellar halo and intracluster light

    NASA Astrophysics Data System (ADS)

    Longobardi, Alessia; Arnaboldi, Magda; Gerhard, Ortwin; Hanuschik, Reinhard

    2015-07-01

    Aims: We present a spectroscopic study of a sample of 287 planetary nebulas (PNs) around the brightest cluster galaxy (BCG) M 87 in Virgo A, of which 211 are located between 40 kpc and 150 kpc from the galaxy centre. With these data we can distinguish the stellar halo from the co-spatial intracluster light (ICL) and study both components separately. Methods: We obtained PN velocities with a high resolution FLAMES/VLT survey targeting eight fields in a total area of ~0.4 deg2. We identified PNs from their narrow and symmetric redshifted λ5007 Å [OIII] emission line, the presence of the second λ4959 Å [OIII] emission line, and the absence of significant continuum. We implement a robust technique to measure the halo velocity dispersion from the projected phase-space to identify PNs associated with the M 87 halo and ICL. Using photometric magnitudes, we construct PN luminosity functions (PNLFs), which are complete down to m5007 = 28.8. Results: The velocity distribution of the spectroscopically confirmed PNs is bimodal, containing a narrow component centred on the systemic velocity of the BCG and an off-centred broader component, which we identify as halo and ICL, respectively. We find that 243 PNs are part of the velocity distribution of the M 87 halo, while the remaining subsample of 44 PNs are intracluster PNs (ICPNs). Halo and ICPNs have different spatial distributions: the number density of halo PNs follow the galaxy's surface brightness profile, whereas the ICPNs are characterised by a shallower power-law profile, IICL ∝ Rγ with γ in the range [-0.34, -0.04 ]. No evidence is found for an asymmetry in the halo and ICPN density distributions when the NW and SE fields are studied separately. A study of the composite PN number density profile confirms the superposition of different PN populations associated with the M 87 halo and the ICL, characterised by different PN specific numbers α. We derive αhalo = 1.06 × 10-8NPN L⊙,bol-1 and αICL = 2.72 × 10

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

    NASA Astrophysics Data System (ADS)

    Ryś, Agnieszka; Koleva, Mina; Falcón-Barroso, Jesús; Vazdekis, Alexandre; Lisker, Thorsten; Peletier, Reynier; van de Ven, Glenn

    2015-09-01

    We present the stellar population analysis of a sample of 12 dwarf elliptical galaxies, observed with the SAURON integral field unit, using the full-spectrum fitting method. We show that star formation histories (SFHs) resolved into two populations can be recovered even within a limited wavelength range, provided that high signal-to-noise ratio (S/N) data are used. We confirm that dEs have had complex SFHs, with star formation extending to (more) recent epochs: for the majority of our galaxies star formation activity was either still strong a few (≲5) Gyr ago or they experienced a secondary burst of star formation roughly at that time. This latter possibility is in agreement with the proposed dE formation scenario where tidal harassment drives the gas remaining in their progenitors inwards and induces a star formation episode. For one of our field galaxies, ID 0918, we find a correlation between its stellar population and kinematic properties, pointing to a possible merger origin of its kinematically decoupled core. One of our cluster objects, VCC 1431, appears to be composed exclusively of an old population (≳10-12 Gyr). Combining this with our earlier dynamical results, we conclude that the galaxy was either ram-pressure stripped early on in its evolution in a group environment and subsequently tidally heated, or that it evolved in situ in the cluster's central parts, compact enough to avoid tidal disruption. These are only two of the examples illustrating the SFH richness of these objects confirmed with our data.

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

    NASA Astrophysics Data System (ADS)

    Ryś, Agnieszka; Falcón-Barroso, Jesús; van de Ven, Glenn

    2013-02-01

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

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

    SciTech Connect

    Craig, Jonathan; Krumholz, Mark R.

    2013-06-01

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

  15. Local stellar kinematics from large astrometric surveys: mapping the Galactic phase-space substructure

    NASA Astrophysics Data System (ADS)

    Lepine, Sebastien

    2016-05-01

    The potential of future large astrometric catalogs for mapping the velocity-space distribution of local stars in the Galaxy is illustrated with a kinematic study of K and M dwarfs in the SUPERBLINK catalog of 2.5 million stars with large proper motions (mu>40 mas/yr). Low mass K and M dwarfs, found in abundance thanks to the faint magnitude limit of the catalog (V<20) provide the densest possible sampling of the [(X,Y,Z),(U,V,W)] phase-space, making them well-suited to map out substructure (so-called "streams") in the velocity-space distributions, as well as variations in said distribution over >100 parsec scale distances. The SUPERBLINK proper motion catalog thus provides kinematic data for ~1.5 million M dwarfs from the Galactic disk population, located within 200 parsecs of the Sun, and for ~180,000 K and M (sub)dwarfs from the Galactic halo population, all within 500 parsecs of the Sun. While the disk dwarfs show clear signs of velocity-space substructure, the distribution of halo subdwarf does appear to be relatively smooth ("streamless") in contrast. Evidence for spatial variations at the few hundred parsec scale is also discussed. The current and unfortunately "blurry" view of the local velocity-space distribution promises to be set in much sharper focus with the upcoming availability of data from the GAIA mission.

  16. Major substructure in the M31 outer halo: distances and metallicities along the giant stellar stream

    NASA Astrophysics Data System (ADS)

    Conn, A. R.; McMonigal, B.; Bate, N. F.; Lewis, G. F.; Ibata, R. A.; Martin, N. F.; McConnachie, A. W.; Ferguson, A. M. N.; Irwin, M. J.; Elahi, P. J.; Venn, K. A.; Mackey, A. D.

    2016-05-01

    We present a renewed look at M31's giant stellar stream along with the nearby structures streams C and D, exploiting a new algorithm capable of fitting to the red giant branch (RGB) of a structure in both colour and magnitude space. Using this algorithm, we are able to generate probability distributions in distance, metallicity and RGB width for a series of subfields spanning these structures. Specifically, we confirm a distance gradient of approximately 20 kpc per degree along a 6 deg extension of the giant stellar stream, with the farthest subfields from M31 lying ˜120 kpc more distant than the innermost subfields. Further, we find a metallicity that steadily increases from -0.7^{+0.1}_{-0.1} to -0.2^{+0.2}_{-0.1} dex along the inner half of the stream before steadily dropping to a value of -1.0^{+0.2}_{-0.2} dex at the farthest reaches of our coverage. The RGB width is found to increase rapidly from 0.4^{+0.1}_{-0.1} to 1.1^{+0.2}_{-0.1} dex in the inner portion of the stream before plateauing and decreasing marginally in the outer subfields of the stream. In addition, we estimate stream C to lie at a distance between 794 and 862 kpc and stream D between 758 and 868 kpc. We estimate the median metallicity of stream C to lie in the range -0.7 to -1.6 dex and a metallicity of -1.1^{+0.3}_{-0.2} dex for stream D. RGB widths for the two structures are estimated to lie in the range 0.4-1.2 dex and 0.3-0.7 dex, respectively. In total, measurements are obtained for 19 subfields along the giant stellar stream, four along stream C, five along stream D and three general M31 spheroid fields for comparison. We thus provide a higher resolution coverage of the structures in these parameters than has previously been available in the literature.

  17. The Stellar Populations of Nuclei, Globular Clusters, and Stars in dE Galaxies in Virgo and Fornax

    NASA Astrophysics Data System (ADS)

    Whitfield Miller, Bryan; Hyazinth Puzia, Thomas; Hilker, Michael; Sanchez-Janssen, Ruben; Kissler-Patig, Markus

    2015-08-01

    We present ages and metallicities for globular clusters, nuclei, and underlying stars in nucleated dwarf elliptical galaxies (dE,N) in the Virgo and Fornax Cluster based on Lick/IDS index measurements and SSP models. Gemini/GMOS spectroscopy shows that the globular clusters are mostly old and metal-poor, very similar to the globular clusters in the Milky Way halo. The nuclei and underlying stars tend to be more metal-rich than the globular clusters and have a wide range of ages. The [α/Fe] ratios for both the globular clusters and nuclei range between 0.0 and 0.3. Formation scenarios for globular clusters and nuclei will be discussed.

  18. Stellar kinematics and structural properties of virgo cluster dwarf early-type galaxies from the SMAKCED project. I. Kinematically decoupled cores and implications for infallen groups in clusters

    SciTech Connect

    Toloba, E.; Guhathakurta, P.; Boissier, S.; Boselli, A.; Den Brok, M.; Falcón-Barroso, J.; Ryś, A.; Janz, J.; Lisker, T.; Laurikainen, E.; Salo, H.; Paudel, S.

    2014-03-10

    We present evidence for kinematically decoupled cores (KDCs) in two dwarf early-type (dE) galaxies in the Virgo cluster, VCC 1183 and VCC 1453, studied as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey. These KDCs have radii of 1.''8 (0.14 kpc) and 4.''2 (0.33 kpc), respectively. Each of these KDCs is distinct from the main body of its host galaxy in two ways: (1) inverted sense of rotation and (2) younger (and possibly more metal-rich) stellar population. The observed stellar population differences are probably associated with the KDC, although we cannot rule out the possibility of intrinsic radial gradients in the host galaxy. We describe a statistical analysis method to detect, quantify the significance of, and characterize KDCs in long-slit rotation curve data. We apply this method to the two dE galaxies presented in this paper and to five other dEs for which KDCs have been reported in the literature. Among these seven dEs, there are four significant KDC detections, two marginal KDC detections, and one dE with an unusual central kinematic anomaly that may be an asymmetric KDC. The frequency of occurrence of KDCs and their properties provide important constraints on the formation history of their host galaxies. We discuss different formation scenarios for these KDCs in cluster environments and find that dwarf-dwarf wet mergers or gas accretion can explain the properties of these KDCs. Both of these mechanisms require that the progenitor had a close companion with a low relative velocity. This suggests that KDCs were formed in galaxy pairs residing in a poor group environment or in isolation whose subsequent infall into the cluster quenched star formation.

  19. Stellar Kinematics and Structural Properties of Virgo Cluster Dwarf Early-type Galaxies from the SMAKCED Project. I. Kinematically Decoupled Cores and Implications for Infallen Groups in Clusters

    NASA Astrophysics Data System (ADS)

    Toloba, E.; Guhathakurta, P.; van de Ven, G.; Boissier, S.; Boselli, A.; den Brok, M.; Falcón-Barroso, J.; Hensler, G.; Janz, J.; Laurikainen, E.; Lisker, T.; Paudel, S.; Peletier, R. F.; Ryś, A.; Salo, H.

    2014-03-01

    We present evidence for kinematically decoupled cores (KDCs) in two dwarf early-type (dE) galaxies in the Virgo cluster, VCC 1183 and VCC 1453, studied as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey. These KDCs have radii of 1.''8 (0.14 kpc) and 4.''2 (0.33 kpc), respectively. Each of these KDCs is distinct from the main body of its host galaxy in two ways: (1) inverted sense of rotation and (2) younger (and possibly more metal-rich) stellar population. The observed stellar population differences are probably associated with the KDC, although we cannot rule out the possibility of intrinsic radial gradients in the host galaxy. We describe a statistical analysis method to detect, quantify the significance of, and characterize KDCs in long-slit rotation curve data. We apply this method to the two dE galaxies presented in this paper and to five other dEs for which KDCs have been reported in the literature. Among these seven dEs, there are four significant KDC detections, two marginal KDC detections, and one dE with an unusual central kinematic anomaly that may be an asymmetric KDC. The frequency of occurrence of KDCs and their properties provide important constraints on the formation history of their host galaxies. We discuss different formation scenarios for these KDCs in cluster environments and find that dwarf-dwarf wet mergers or gas accretion can explain the properties of these KDCs. Both of these mechanisms require that the progenitor had a close companion with a low relative velocity. This suggests that KDCs were formed in galaxy pairs residing in a poor group environment or in isolation whose subsequent infall into the cluster quenched star formation.

  20. THE DOMINANCE OF METAL-RICH STREAMS IN STELLAR HALOS: A COMPARISON BETWEEN SUBSTRUCTURE IN M31 AND {lambda}CDM MODELS

    SciTech Connect

    Gilbert, Karoline M.; Font, Andreea S.; Johnston, Kathryn V.; Guhathakurta, Puragra E-mail: andreea.font@durham.ac.uk E-mail: raja@ucolick.org

    2009-08-10

    Extensive photometric and spectroscopic surveys of the Andromeda galaxy (M31) have discovered tidal debris features throughout M31's stellar halo. We present stellar kinematics and metallicities in fields with identified substructure from our on-going SPLASH survey of M31 red giant branch stars with the DEIMOS spectrograph on the Keck II 10 m telescope. Radial velocity criteria are used to isolate members of the kinematically cold substructures. The substructures are shown to be metal-rich relative to the rest of the dynamically hot stellar population in the fields in which they are found. We calculate the mean metallicity and average surface brightness of the various kinematical components in each field, and show that, on average, higher surface brightness features tend to be more metal-rich than lower surface brightness features. Simulations of stellar halo formation via accretion in a cosmological context are used to illustrate that the observed trend can be explained as a natural consequence of the observed dwarf galaxy mass-metallicity relation. A significant spread in metallicity at a given surface brightness is seen in the data; we show that this is due to time effects, namely, the variation in the time since accretion of the tidal streams' progenitor onto the host halo. We show that in this theoretical framework a relationship between the alpha-enhancement and surface brightness of tidal streams is expected, which arises from the varying times of accretion of the progenitor satellites onto the host halo. Thus, measurements of the alpha-enrichment, metallicity, and surface brightness of tidal debris can be used to reconstruct the luminosity and time of accretion onto the host halo of the progenitors of tidal streams.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  2. Intense look at Virgo Southern Extension

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  3. Surviving gas expulsion with substructure

    NASA Astrophysics Data System (ADS)

    Lee, Paweł L.; Goodwin, Simon P.

    2016-08-01

    We investigate the reaction of clumpy stellar distributions to gas expulsion. We show that regions containing highly unbound substructures/subclusters after gas expulsion can produce a significant final bound cluster. The key quantity in determining if a region is able to form a bound cluster is the global virial ratio, and so regions must be looked at as a whole rather than by an individual substructure/subclusters, when determining if they might survive as a bound cluster.

  4. Stellar Kinematics and Structural Properties of Virgo Cluster Dwarf Early-type Galaxies from the SMAKCED Project. II. The Survey and a Systematic Analysis of Kinematic Anomalies and Asymmetries

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    SciTech Connect

    Toloba, E.; Guhathakurta, P.; Boselli, A.; Lisker, T.; Falcón-Barroso, J.; Ryś, A.; Van de Ven, G.; Paudel, S.; Emsellem, E.; Janz, J.; Den Brok, M.; Gorgas, J.; Hensler, G.; Laurikainen, E.; Salo, H.; Niemi, S.-M.

    2015-01-01

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

  6. Status of VIRGO

    NASA Astrophysics Data System (ADS)

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

    2003-09-01

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

  7. Advanced Virgo: AN Update

    NASA Astrophysics Data System (ADS)

    Fafone, Viviana

    2015-01-01

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

  8. THE ONGOING ASSEMBLY OF A CENTRAL CLUSTER GALAXY: PHASE-SPACE SUBSTRUCTURES IN THE HALO OF M87

    SciTech Connect

    Romanowsky, Aaron J.; Brodie, Jean P.; Arnold, Jacob A.; Strader, Jay; Mihos, J. Christopher; Spitler, Lee R.; Forbes, Duncan A.; Foster, Caroline

    2012-03-20

    The halos of galaxies preserve unique records of their formation histories. We carry out the first combined observational and theoretical study of phase-space halo substructure in an early-type galaxy: M87, the central galaxy in the Virgo cluster. We analyze an unprecedented wide-field, high-precision photometric and spectroscopic data set for 488 globular clusters (GCs), which includes new, large-radius Subaru/Suprime-Cam and Keck/DEIMOS observations. We find signatures of two substructures in position-velocity phase space. One is a small, cold stream associated with a known stellar filament in the outer halo; the other is a large shell-like pattern in the inner halo that implies a massive, hitherto unrecognized accretion event. We perform extensive statistical tests and independent metallicity analyses to verify the presence and characterize the properties of these features, and to provide more general methodologies for future extragalactic studies of phase-space substructure. The cold outer stream is consistent with a dwarf galaxy accretion event, while for the inner shell there is tension between a low progenitor mass implied by the cold velocity dispersion, and a high mass from the large number of GCs, which might be resolved by a {approx}0.5 L* E/S0 progenitor. We also carry out proof-of-principle numerical simulations of the accretion of smaller galaxies in an M87-like gravitational potential. These produce analogous features to the observed substructures, which should have observable lifetimes of {approx}1 Gyr. The shell and stream GCs together support a scenario where the extended stellar envelope of M87 has been built up by a steady rain of material that continues until the present day. This phase-space method demonstrates unique potential for detailed tests of galaxy formation beyond the Local Group.

  9. Stellar Over-Densities in the Outer Halo of the MilkyWay

    NASA Astrophysics Data System (ADS)

    Keller, Stefan C.

    2010-03-01

    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 then derive distances to the sub-giant population. We describe three new candidate halo substructures; the 160- and 180-degree over-densities (at distances of 17 and 19 kpc respectively and radii of 1.3 and 1.5 kpc respectively) and an extended feature at 28 kpc that covers at least 162 deg2, the Virgo Equatorial Stream. In addition, we recover the Sagittarius dwarf galaxy (Sgr) leading-arm material and the Virgo Over-Density. The derived distances, together with the number of sub-giant stars associated with each substructure, enables us to derive the integrated luminosity for the features. The tenuous, low surface brightness of the features strongly suggests an origin from the tidal disruption of an accreted galaxy or galaxies. Given the dominance of the tidal debris of Sgr in this region of the sky we investigate if our observations can be accommodated by tidal disruption models for Sgr. The clear discordance between observations and model predictions for known Sgr features means it is difficult to tell unambiguously if the new substructures are related to Sgr or not. Radial velocities in the stellar over-densities will be critical in establishing their origins.

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

    SciTech Connect

    Paudel, Sanjaya; Duc, Pierre-Alain; Ferriere, Etienne; Cuillandre, Jean-Charles; Mihos, J. Christopher; Vollmer, Bernd; Balogh, Michael L.; Carlberg, Ray G.; Boissier, Samuel; Boselli, Alessandro; Durrell, Patrick R.; Emsellem, Eric; Michel-Dansac, Leo; Mei, Simona; Van Driel, Wim

    2013-04-20

    The final stages of mass assembly of present-day massive galaxies are expected to occur through the accretion of multiple satellites. Cosmological simulations thus predict a high frequency of stellar streams resulting from this mass accretion around the massive galaxies in the Local Volume. Such tidal streams are difficult to observe, especially in dense cluster environments, where they are readily destroyed. We present an investigation into the origins of a series of interlaced narrow filamentary stellar structures, loops and plumes in the vicinity of the Virgo Cluster, edge-on spiral galaxy, NGC 4216 that were previously identified by the Blackbird telescope. Using the deeper, higher-resolution, and precisely calibrated optical CFHT/MegaCam images obtained as part of the Next Generation Virgo Cluster Survey (NGVS), we confirm the previously identified features and identify a few additional structures. The NGVS data allowed us to make a physical study of these low surface brightness features and investigate their origin. The likely progenitors of the structures were identified as either already cataloged Virgo Cluster Catalog dwarfs or newly discovered satellites caught in the act of being destroyed. They have the same g - i color index and likely contain similar stellar populations. The alignment of three dwarfs along an apparently single stream is intriguing, and we cannot totally exclude that these are second-generation dwarf galaxies being born inside the filament from the debris of an original dwarf. The observed complex structures, including in particular a stream apparently emanating from a satellite of a satellite, point to a high rate of ongoing dwarf destruction/accretion in the region of the Virgo Cluster where NGC 4216 is located. We discuss the age of the interactions and whether they occurred in a group that is just falling into the cluster and shows signs of the so-called pre-processing before it gets affected by the cluster environment, or in a

  11. Advanced Virgo phase cameras

    NASA Astrophysics Data System (ADS)

    van der Schaaf, L.; Agatsuma, K.; van Beuzekom, M.; Gebyehu, M.; van den Brand, J.

    2016-05-01

    A century after the prediction of gravitational waves, detectors have reached the sensitivity needed to proof their existence. One of them, the Virgo interferometer in Pisa, is presently being upgraded to Advanced Virgo (AdV) and will come into operation in 2016. The power stored in the interferometer arms raises from 20 to 700 kW. This increase is expected to introduce higher order modes in the beam, which could reduce the circulating power in the interferometer, limiting the sensitivity of the instrument. To suppress these higher-order modes, the core optics of Advanced Virgo is equipped with a thermal compensation system. Phase cameras, monitoring the real-time status of the beam constitute a critical component of this compensation system. These cameras measure the phases and amplitudes of the laser-light fields at the frequencies selected to control the interferometer. The measurement combines heterodyne detection with a scan of the wave front over a photodetector with pin-hole aperture. Three cameras observe the phase front of these laser sidebands. Two of them monitor the in-and output of the interferometer arms and the third one is used in the control of the aberrations introduced by the power recycling cavity. In this paper the working principle of the phase cameras is explained and some characteristic parameters are described.

  12. Stellar

    NASA Technical Reports Server (NTRS)

    1995-01-01

    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.

  13. A 10 kpc stellar substructure at the edge of the Large Magellanic Cloud: perturbed outer disc or evidence for tidal stripping?

    NASA Astrophysics Data System (ADS)

    Mackey, A. D.; Koposov, S. E.; Erkal, D.; Belokurov, V.; Da Costa, G. S.; Gómez, F. A.

    2016-06-01

    We report the discovery of a substantial stellar overdensity in the periphery of the Large Magellanic Cloud (LMC), found using public imaging from the first year of the Dark Energy Survey. The structure appears to emanate from the edge of the outer LMC disc at a radius ≈13.5° due north of its centre, and stretches more than 10 kpc towards the east. It is roughly 1.5 kpc wide and has an integrated V-band luminosity of at least MV = -7.4. The stellar populations in the feature are indistinguishable from those in the outer LMC disc. We attempt to quantify the geometry of the outer disc using simple planar models, and find that only a disc with mild intrinsic ellipticity can simultaneously explain the observed stellar density on the sky and the azimuthal line-of-sight distance profile. We also see possible non-planar behaviour in the outer disc that may reflect a warp and/or flare, as well as deviations that resemble a ring-like structure between {˜ }9° and 12° from the LMC centre. Based on all these observations, we conclude that our remote, stream-like feature is likely comprised of material that has been stripped from the outskirts of the LMC disc, although we cannot rule out that it represents a transient overdensity in the disc itself. We conduct a simple N-body simulation to show that either type of structure could plausibly arise due to the tidal force of the Milky Way; however, we also recognize that a recent close interaction between the LMC and the Small Magellanic Cloud may be the source of the stripping or perturbation. Finally, we observe evidence for extremely diffuse LMC populations extending to radii of ˜18.5 kpc in the disc plane ({≈ } 20° on the sky), corroborating previous spectroscopic detections at comparable distances.

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

    PubMed

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

    2010-04-16

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

  15. Mapping the Galactic Halo. VIII. Quantifying Substructure

    NASA Astrophysics Data System (ADS)

    Starkenburg, Else; Helmi, Amina; Morrison, Heather L.; Harding, Paul; van Woerden, Hugo; Mateo, Mario; Olszewski, Edward W.; Sivarani, Thirupathi; Norris, John E.; Freeman, Kenneth C.; Shectman, Stephen A.; Dohm-Palmer, R. C.; Frey, Lucy; Oravetz, Dan

    2009-06-01

    We have measured the amount of kinematic substructure in the Galactic halo using the final data set from the Spaghetti project, a pencil-beam high-latitude sky survey. Our sample contains 101 photometrically selected and spectroscopically confirmed giants with accurate distance, radial velocity, and metallicity information. We have developed a new clustering estimator: the "4distance" measure, which when applied to our data set leads to the identification of one group and seven pairs of clumped stars. The group, with six members, can confidently be matched to tidal debris of the Sagittarius dwarf galaxy. Two pairs match the properties of known Virgo structures. Using models of the disruption of Sagittarius in Galactic potentials with different degrees of dark halo flattening, we show that this favors a spherical or prolate halo shape, as demonstrated by Newberg et al. using the Sloan Digital Sky Survey data. One additional pair can be linked to older Sagittarius debris. We find that 20% of the stars in the Spaghetti data set are in substructures. From comparison with random data sets, we derive a very conservative lower limit of 10% to the amount of substructure in the halo. However, comparison to numerical simulations shows that our results are also consistent with a halo entirely built up from disrupted satellites, provided that the dominating features are relatively broad due to early merging or relatively heavy progenitor satellites.

  16. The Purple Rose of Virgo

    NASA Astrophysics Data System (ADS)

    2007-03-01

    Until now NGC 5584 was just one galaxy among many others, located to the West of the Virgo Cluster. Known only as a number in galaxy surveys, its sheer beauty is now revealed in all its glory in a new VLT image. Since 1 March, this purple cosmic rose also holds the brightest stellar explosion of the year, known as SN 2007af. Located about 75 million light years away towards the constellation Virgo ('the Virgin'), NGC 5584 is a galaxy slightly smaller than the Milky Way. It belongs, however, to the same category: both are barred spirals. ESO PR Photo 16/07 ESO PR Photo 16/07 The Purple Rose of Virgo Spiral galaxies are composed of a 'bulge' and a flat disc. The bulge hosts old stars and usually a central supermassive black hole. Younger stars reside in the disc, forming the characteristic spiral structures from which the galaxies get their name. Barred spirals are crossed by a bright band of stars. In 2000, using ESO's Very Large Telescope, astronomers discovered the smallest, faintest, and most massive spirals (see ESO PR 12/00 and 25/00). In this amazing new image of NGC 5584 two dominant spiral arms are clearly visible, while the others are deformed, probably due to interactions with other galaxies. Luminous patches are spread all over the disc, indicating that stars are being formed in this gigantic rose at a frantic pace. Something even brighter, however, catches the eye in this picture. Any image taken before the end of February would not have shown the luminous spot located at the lower right of the galaxy's centre. As can be seen, the newly found object is much brighter than the centre of the galaxy itself. Its name? SN 2007af, the 32nd supernova discovered this year. Its presence signals the dramatic death of a star with a mass comparable to that of the Sun. SN 2007af, the brightest supernova of the year (so far), was discovered on 1 March by the Japanese supernova hunter Koichi Itagaki. He pointed his 60-centimetre telescope towards the Virgo constellation

  17. Substructural controller synthesis

    NASA Technical Reports Server (NTRS)

    Su, Tzu-Jeng; Craig, Roy R., Jr.

    1989-01-01

    A decentralized design procedure which combines substructural synthesis, model reduction, decentralized controller design, subcontroller synthesis, and controller reduction is proposed for the control design of flexible structures. The structure to be controlled is decomposed into several substructures, which are modeled by component mode synthesis methods. For each substructure, a subcontroller is designed by using the linear quadratic optimal control theory. Then, a controller synthesis scheme called Substructural Controller Synthesis (SCS) is used to assemble the subcontrollers into a system controller, which is to be used to control the whole structure.

  18. Predicting binary merger event rates for advanced LIGO/Virgo

    NASA Astrophysics Data System (ADS)

    Holz, Daniel; Belczynski, Chris; O'Shaughnessy, Richard; Bulik, Tomek; LIGO Collaboration

    2016-03-01

    We discuss estimates of the rates of mergers of binary systems composed of neutron stars and/or stellar mass black holes. We use the StarTrack population synthesis code, and make predictions for the detection rate of compact binary coalescences with the advanced LIGO/Virgo gravitational wave detectors. Because these instruments are sensitive to massive (M > 20M⊙) stellar-mass binary black holes mergers out to high redshift (z > 1), we discuss the cosmological effects which must be taken into account when calculating LIGO detection rates, including a generalization of the calculation of the ``peanut factor'' and the sensitive time-volume.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  20. The Extended Halo of Centaurus A: Uncovering Satellites, Streams, and Substructures

    NASA Astrophysics Data System (ADS)

    Crnojević, D.; Sand, D. J.; Spekkens, K.; Caldwell, N.; Guhathakurta, P.; McLeod, B.; Seth, A.; Simon, J. D.; Strader, J.; Toloba, E.

    2016-05-01

    We present the widest-field resolved stellar map to date of the closest (D∼ 3.8 Mpc) massive elliptical galaxy NGC 5128 (Centaurus A; Cen A), extending out to a projected galactocentric radius of ∼150 kpc. The data set is part of our ongoing Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) utilizing the Magellan/Megacam imager. We resolve a population of old red giant branch (RGB) stars down to ∼1.5 mag below the tip of the RGB, reaching surface brightness limits as low as {μ }V,0∼ 32 mag arcsec‑2. The resulting spatial stellar density map highlights a plethora of previously unknown streams, shells, and satellites, including the first tidally disrupting dwarf around Cen A (CenA-MM-Dw3), which underline its active accretion history. We report 13 previously unknown dwarf satellite candidates, of which 9 are confirmed to be at the distance of Cen A (the remaining 4 are not resolved into stars), with magnitudes in the range {M}V=-7.2 to ‑13.0, central surface brightness values of {μ }V,0=25.4{--}26.9 mag arcsec‑2, and half-light radii of {r}h=0.22{--}2.92 {{kpc}}. These values are in line with Local Group dwarfs but also lie at the faint/diffuse end of their distribution; interestingly, CenA-MM-Dw3 has similar properties to the recently discovered ultradiffuse galaxies in Virgo and Coma. Most of the new dwarfs are fainter than the previously known Cen A satellites. The newly discovered dwarfs and halo substructures are discussed in light of their stellar populations, and they are compared to those discovered by the PAndAS survey of M31. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  1. The Extended Halo of Centaurus A: Uncovering Satellites, Streams, and Substructures

    NASA Astrophysics Data System (ADS)

    Crnojević, D.; Sand, D. J.; Spekkens, K.; Caldwell, N.; Guhathakurta, P.; McLeod, B.; Seth, A.; Simon, J. D.; Strader, J.; Toloba, E.

    2016-05-01

    We present the widest-field resolved stellar map to date of the closest (D˜ 3.8 Mpc) massive elliptical galaxy NGC 5128 (Centaurus A; Cen A), extending out to a projected galactocentric radius of ˜150 kpc. The data set is part of our ongoing Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) utilizing the Magellan/Megacam imager. We resolve a population of old red giant branch (RGB) stars down to ˜1.5 mag below the tip of the RGB, reaching surface brightness limits as low as {μ }V,0˜ 32 mag arcsec‑2. The resulting spatial stellar density map highlights a plethora of previously unknown streams, shells, and satellites, including the first tidally disrupting dwarf around Cen A (CenA-MM-Dw3), which underline its active accretion history. We report 13 previously unknown dwarf satellite candidates, of which 9 are confirmed to be at the distance of Cen A (the remaining 4 are not resolved into stars), with magnitudes in the range {M}V=-7.2 to ‑13.0, central surface brightness values of {μ }V,0=25.4{--}26.9 mag arcsec‑2, and half-light radii of {r}h=0.22{--}2.92 {{kpc}}. These values are in line with Local Group dwarfs but also lie at the faint/diffuse end of their distribution; interestingly, CenA-MM-Dw3 has similar properties to the recently discovered ultradiffuse galaxies in Virgo and Coma. Most of the new dwarfs are fainter than the previously known Cen A satellites. The newly discovered dwarfs and halo substructures are discussed in light of their stellar populations, and they are compared to those discovered by the PAndAS survey of M31. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

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

    NASA Astrophysics Data System (ADS)

    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

    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

  3. The Extended Virgo Cluster Catalog

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  4. The Extended Virgo Cluster Catalog

    NASA Astrophysics Data System (ADS)

    Rey, Soo-Chang

    2015-08-01

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

  5. THE EXTENDED VIRGO CLUSTER CATALOG

    SciTech Connect

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

    2015-01-01

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

  6. Jet Substructure Without Trees

    SciTech Connect

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

    2011-08-19

    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.

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

    SciTech Connect

    Yoon, Joo Heon; Putman, Mary E.; Bryan, Greg L.; Thom, Christopher; Chen, Hsiao-Wen

    2012-08-01

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

  8. Substructure system identification and synthesis

    NASA Technical Reports Server (NTRS)

    Su, Tzu-Jeng; Juang, Jer-Nan

    1993-01-01

    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.

  9. Distant Galactic Halo Substructures Observed by the Palomar Transient Factory

    NASA Astrophysics Data System (ADS)

    Sesar, Branimir

    2013-01-01

    Characterization of Galactic halo substructures is important as their kinematic and chemical properties help constrain the properties of the Galactic dark matter halo, the formation history of the Milky Way, and the galaxy formation process in general. The best practical choice for finding distant halo substructures are pulsating RR Lyrae stars, due to their intrinsic brightness (M_V = 0.6 mag) and distinct light curves. I will present kinematic and chemical properties of two distant halo substructures that were traced using RR Lyrae stars observed by the Palomar Transient Factory. One of these substructures, located at 90 kpc from the Sun in the Cancer constellation, consists of two groups of RR Lyrae stars moving away from the Galaxy at ~80 and ~20 km/s, respectively. The second substructure is located at ~65 kpc from the Sun in the Hercules constellation. The kinematics of RR Lyrae stars tracing this substructure suggest a presence of 2 or 3 stellar streams extending in the similar direction on the sky. Due to their spatial extent, both of these substructures are clearly disrupted and would be very difficult to detect using tradiitonal techniques such as the color-magnitude diagram filtering.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    We statistically quantify the amount of substructure in the Milky Way stellar halo using a sample of 4568 halo K giant stars at Galactocentric distances ranging over 5-125 kpc. These stars have been selected photometrically and confirmed spectroscopically as K giants from the Sloan Digital Sky Survey’s Sloan Extension for Galactic Understanding and Exploration project. Using a position-velocity clustering estimator (the 4distance) and a model of a smooth stellar halo, we quantify the amount of substructure in the halo, divided by distance and metallicity. Overall, we find that the halo as a whole is highly structured. We also confirm earlier work using blue horizontal branch (BHB) stars which showed that there is an increasing amount of substructure with increasing Galactocentric radius, and additionally find that the amount of substructure in the halo increases with increasing metallicity. Comparing to resampled BHB stars, we find that K giants and BHBs have similar amounts of substructure over equivalent ranges of Galactocentric radius. Using a friends-of-friends algorithm to identify members of individual groups, we find that a large fraction (˜33%) of grouped stars are associated with Sgr, and identify stars belonging to other halo star streams: the Orphan Stream, the Cetus Polar Stream, and others, including previously unknown substructures. A large fraction of sample K giants (more than 50%) are not grouped into any substructure. We find also that the Sgr stream strongly dominates groups in the outer halo for all except the most metal-poor stars, and suggest that this is the source of the increase of substructure with Galactocentric radius and metallicity.

  11. Galaxies at the Extremes: Ultra-diffuse Galaxies in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    We report the discovery of three large ({R}29 ≳ 1‧) extremely low surface brightness (LSB; {μ }V,0≈ 27.0) galaxies identified using our deep, wide-field imaging of the Virgo Cluster from the Burrell Schmidt telescope. Complementary data from the Next Generation Virgo Cluster Survey do not resolve red giant branch stars in these objects down to i = 24, yielding a lower distance limit of 2.5 Mpc. At the Virgo distance, these objects have half-light radii 3-10 kpc and luminosities {L}{{V}} = 2-9 × 107 {L}⊙ . These galaxies are comparable in size but lower in surface brightness than the large ultradiffuse LSB galaxies recently identified in the Coma cluster, and are located well within Virgo’s virial radius; two are projected directly on the cluster core. One object appears to be a nucleated LSB in the process of being tidally stripped to form a new Virgo ultracompact dwarf galaxy. The others show no sign of tidal disruption, despite the fact that such objects should be most vulnerable to tidal destruction in the cluster environment. The relative proximity of Virgo makes these objects amenable to detailed studies of their structural properties and resolved stellar populations. They thus provide an important new window onto the connection between cluster environment and galaxy evolution at the extremes.

  12. Rigid substructure search

    PubMed Central

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

    2011-01-01

    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 PMID:21460026

  13. How did the Virgo cluster form?

    NASA Astrophysics Data System (ADS)

    Sorce, Jenny G.; Gottlöber, Stefan; Hoffman, Yehuda; Yepes, Gustavo

    2016-08-01

    While the Virgo cluster is the nearest galaxy cluster and therefore the best observed one, little is known about its formation history. In this paper, a set of cosmological simulations that resemble the Local Universe is used to shed the first light on this mystery. The initial conditions for these simulations are constrained with galaxy peculiar velocities of the second catalogue of the Cosmicflows project using algorithms developed within the Constrained Local UniversE Simulation project. Boxes of 500 h-1 Mpc on a side are set to run a series of dark matter only constrained simulations. In each simulation, a unique dark matter halo can be reliably identified as Virgo's counterpart. The properties of these Virgo haloes are in agreement at a 10-20 per cent level with the global properties of the observed Virgo cluster. Their zero-velocity masses agree at 1σ with the observational mass estimate. In all the simulations, the matter falls on to the Virgo objects along a preferential direction that corresponds to the observational filament and the slowest direction of collapse. A study of the mass accretion history of the Virgo candidates reveals the most likely formation history of the Virgo cluster, namely a quiet accretion over the last 7 Gyr.

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

    SciTech Connect

    Sesar, Branimir; Ivezic, Zeljko; Morgan, Dylan M.; Becker, Andrew C.; Stuart, J. Scott; Sharma, Sanjib; Palaversa, Lovro; Juric, Mario; Wozniak, Przemyslaw; Oluseyi, Hakeem

    2013-08-01

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

  15. Virgo

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    (the Virgin; abbrev. Vir, gen. Virginis; area 1294 sq. deg.) an equatorial zodiacal constellation which lies between Leo and Libra, and culminates at midnight in mid-April. Its origin dates back to Babylonian times and it has been associated with numerous female deities, including Ishtar (Babylonia), Isis (ancient Egypt), Demeter (ancient Greece) and Astraea (ancient Rome). Its brightest st...

  16. Transients by substructuring with DMAP

    NASA Technical Reports Server (NTRS)

    Butler, T. G.

    1978-01-01

    Automated substructuring in level 16 of NASTRAN was employed as a preface to the solution of a direct transient analysis. The DMAP ALTER statements written to adapt the substructuring for transient purposes are explained. Data recovery was accomplished with transfer functions. Proof of the success of the method is presented with an application to a missile structure.

  17. Proposed definition of crystal substructure and substructural similarity

    NASA Astrophysics Data System (ADS)

    Yang, Lusann; Dacek, Stephen; Ceder, Gerbrand

    2014-08-01

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

  18. The Quest for the astrophysical background with Advanced LIGO/Virgo

    NASA Astrophysics Data System (ADS)

    Regimbau, Tania; LIGO Virgo Collaboration Collaboration

    2016-03-01

    In addition to the cosmological background, an astrophysical background may have resulted from the superposition of a large number of unresolved sources since the beginning of stellar activity. This astrophysical contribution could be a foreground masking the cosmological background but it can also provide very interesting informations, not only about the physical properties of the respective astrophysical populations, complementing individual GW detections, but also about the evolution of these objects with redshift, the star formation history or the metallicity. In this talk, predictions of the gravitational wave background formed by all the compact binary coalescences at cosmological distances will be given, as well as a discussion of their accessibility with the network of Advanced LIGO/Virgo detectors. Finally, the expected astrophysical and cosmological constraints to be made by Advanced LIGO/Virgo will be presented.

  19. SED Fitting of Virgo Cluster Galaxies and Evidence for Enhanced Star Formation due to Accretion

    NASA Astrophysics Data System (ADS)

    Fulmer, Leah; Kenney, Jeffrey D.; Edwards, Louise O. V.

    2016-01-01

    Using UV through FIR data in matched apertures, we modeled the spectral energy distributions (SED) of 49 Virgo cluster spiral galaxies with the modeling program Magphys (daCunha+ 2008). We used the results from these models to explore the relationships between the stellar masses (M*), specific star formation rates (sSFR), and HI properties in our sample. The poster highlights one initial result from these comparisons: supportive evidence for gas accretion in the outskirts of the Virgo cluster. The galaxies with the highest sSFRs in the mass range 10^9-10^10 M_sun are all HI-rich, have extended irregular HI envelopes, and lie in the outskirts of the cluster. We propose that these galaxies are accreting gas onto their disks, a process which enhances their SFRs.

  20. The Effect of the Transformation of Spiral Galaxies in the Virgo Cluster on Broadband Color Evolution

    NASA Astrophysics Data System (ADS)

    Crowl, Hugh H.; Chung, A.; Blanton, M. R.; Kenney, J. D. P.; van Gorkom, J. H.; Schiminovich, D.

    2009-01-01

    Galaxy evolution and the effect of environment on that evolution is one of the central questions of modern extragalactic astronomy. The nearby Virgo Cluster provides us with an ideal laboratory to study galaxy-galaxy and galaxy-cluster interactions at a level of detail impossible at higher redshift. In detailed, pan-chromatic surveys of Virgo, we have seen galaxies transformed by their interaction with the intra-cluster medium, with star-forming gas stripped from spiral galaxies. Using data from the Sloan Digital Sky Survey, we present the results of a study of the global broadband optical properties of 44 Virgo Cluster spiral galaxies from the VIVA galaxy survey. These results show that spiral galaxies actively being stripped maintain blue colors while stripping is ongoing. However, a comparison between the colors of stripped spirals and their HI content suggests that more completely stripped galaxies are, indeed, redder than those that are only modestly HI deficient. This suggests that, as galaxies become more completely stripped, their global colors become redder and that in a cluster more massive than Virgo, such stripping could effectively transform galaxies from blue to red. By comparing broadband colors to the stripping timescales derived from optical spectroscopy and stellar population synthesis, we determine that the broadband color evolution is complex, with dust and the age of the stellar population both playing a role. By comparing detailed studies of a nearby cluster with statistical results from the much larger SDSS sample, we are able to gain insights into the details of how environmentally-driven galaxy evolution affects global broadband colors.

  1. Mass and Substructure in Dwarf Spheroidal Galaxies

    NASA Astrophysics Data System (ADS)

    Walker, Matthew G.

    2006-12-01

    I present results from a large spectroscopic survey of individual stars in dwarf spheroidal (dSph) galaxies, conducted using the Michigan/MIKE Fiber System (MMFS) at the Magellan Telescopes. dSph galaxies have come under intense scrutiny because they represent the lower extreme of the galaxy mass function, and thereby provide important constraints on models of structure formation. The proximity of the Milky Way's (MW's) dSph satellites allows us to study the resolved stellar populations of these systems in detail. Toward this end I have acquired MMFS spectra (5140-5180 Angstroms at resolution 20000) for more than 5000 stars in the MW dSphs Carina, Fornax, Sculptor, and Sextans. The spectra yield measurements of both radial velocity (median precision ± 1.8 km/s) and [Fe/H] metallicity (± 0.2 dex). I present radial velocity dispersion profiles for each dSph, as well as halo mass profiles derived using a variety of models and nonparametric estimation techniques. In some cases, the bulk stellar component is separable into populations following distinct distributions in position, kinematics, and chemistry, indicating a surprising level of complexity in these diminutive galaxies. Taking advantage of the fine spatial sampling of the MMFS data, I identify regions showing tentative evidence of localized chemo-dynamical substructure. This work is supported by grants from the National Science Foundation and the University of Michigan.

  2. Fatigue of fiberglass beam substructures

    SciTech Connect

    Mandell, J.F.; Combs, D.W.; Samborsky, D.D.

    1995-09-01

    Composite material beams representative of wind turbine blade substructure have been designed, fabricated, and tested under constant amplitude flexural fatigue loading. Beam stiffness, strength, and fatigue life are predicted based on detailed finite element analysis and the materials fatigue database developed using standard test coupons and special high frequency minicoupons.Beam results are in good agreement with predictions when premature adhesive and delamination failures are avoided in the load transfer areas. The results show that fiberglass substructures can be designed and fabricated to withstand maximum strain levels on the order of 8,000 microstrain for about 10{sup 6} cycles with proper structural detail design and the use of fatigue resistant laminate constructions. The study also demonstrates that the materials fatigue database and accurate analysis can be used to predict the fatigue life of composite substructures typical of blades.

  3. Exploring Milky Way Halo Substructures with Large-Area Sky Surveys

    NASA Astrophysics Data System (ADS)

    Li, Ting

    2016-01-01

    Over the last two decades, large-area photometric surveys have provided deep photometric catalogs of stars in the Milky Way. As a result, our understanding of the formation of the Galactic halo has evolved from a simple monolitic collapse model to a much more complex and dynamic structure. The stellar halo is now known to be inhabited by a variety of spatial and kinematic stellar substructures, ranging from stellar clouds and streams to dwarf galaxies, predicted by hierarchical Lambda-CDM models of galaxy formation. In my talk, I will present the latest discoveries of the halo substructures found in the Dark Energy Survey (DES). I will also discuss the spectroscopic follow-up observations of the stellar cloud candidates found in the Two Micron All Sky Survey and the dwarf galaxy candidates found in DES. These newly discovered features can provide a more complete census of our Galaxy's formation history.

  4. The Next Generation Virgo Cluster Survey (NGVS). XIII. The Luminosity and Mass Function of Galaxies in the Core of the Virgo Cluster and the Contribution from Disrupted Satellites

    NASA Astrophysics Data System (ADS)

    Ferrarese, Laura; Côté, Patrick; Sánchez-Janssen, Rúben; Roediger, Joel; McConnachie, Alan W.; Durrell, Patrick R.; MacArthur, Lauren A.; Blakeslee, John P.; Duc, Pierre-Alain; Boissier, S.; Boselli, Alessandro; Courteau, Stéphane; Cuillandre, Jean-Charles; Emsellem, Eric; Gwyn, S. D. J.; Guhathakurta, Puragra; Jordán, Andrés; Lançon, Ariane; Liu, Chengze; Mei, Simona; Mihos, J. Christopher; Navarro, Julio F.; Peng, Eric W.; Puzia, Thomas H.; Taylor, James E.; Toloba, Elisa; Zhang, Hongxin

    2016-06-01

    We present measurements of the galaxy luminosity and stellar mass function in a 3.71 deg2 (0.3 Mpc2) area in the core of the Virgo Cluster, based on {u}\\ast griz data from the Next Generation Virgo Cluster Survey (NGVS). The galaxy sample—which consists of 352 objects brighter than M g = ‑9.13 mag, the 50% completeness limit of the survey—reaches 2.2 mag deeper than the widely used Virgo Cluster Catalog and at least 1.2 mag deeper than any sample previously used to measure the luminosity function in Virgo. Using a Bayesian analysis, we find a best-fit faint-end slope of α = ‑1.33 ± 0.02 for the g-band luminosity function; consistent results are found for the stellar mass function and the luminosity function in the other four NGVS bandpasses. We discuss the implications for the faint-end slope of adding 92 ultracompact dwarfs (UCDs)—previously compiled by the NGVS in this region—to the galaxy sample, assuming that UCDs are the stripped remnants of nucleated dwarf galaxies. Under this assumption, the slope of the luminosity function (down to the UCD faint magnitude limit, M g = ‑9.6 mag) increases dramatically, up to α = ‑1.60 ± 0.06 when correcting for the expected number of disrupted non-nucleated galaxies. We also calculate the total number of UCDs and globular clusters that may have been deposited in the core of Virgo owing to the disruption of satellites, both nucleated and non-nucleated. We estimate that ˜150 objects with M g ≲ ‑9.6 mag and that are currently classified as globular clusters might, in fact, be the nuclei of disrupted galaxies. We further estimate that as many as 40% of the (mostly blue) globular clusters in the Virgo core might once have belonged to such satellites; these same disrupted satellites might have contributed ˜40% of the total luminosity in galaxies observed in the core region today. Finally, we use an updated Local Group galaxy catalog to provide a new measurement of the luminosity function of Local Group

  5. The Next Generation Virgo Cluster Survey (NGVS). XIII. The Luminosity and Mass Function of Galaxies in the Core of the Virgo Cluster and the Contribution from Disrupted Satellites

    NASA Astrophysics Data System (ADS)

    Ferrarese, Laura; Côté, Patrick; Sánchez-Janssen, Rúben; Roediger, Joel; McConnachie, Alan W.; Durrell, Patrick R.; MacArthur, Lauren A.; Blakeslee, John P.; Duc, Pierre-Alain; Boissier, S.; Boselli, Alessandro; Courteau, Stéphane; Cuillandre, Jean-Charles; Emsellem, Eric; Gwyn, S. D. J.; Guhathakurta, Puragra; Jordán, Andrés; Lançon, Ariane; Liu, Chengze; Mei, Simona; Mihos, J. Christopher; Navarro, Julio F.; Peng, Eric W.; Puzia, Thomas H.; Taylor, James E.; Toloba, Elisa; Zhang, Hongxin

    2016-06-01

    We present measurements of the galaxy luminosity and stellar mass function in a 3.71 deg2 (0.3 Mpc2) area in the core of the Virgo Cluster, based on {u}\\ast griz data from the Next Generation Virgo Cluster Survey (NGVS). The galaxy sample—which consists of 352 objects brighter than M g = ‑9.13 mag, the 50% completeness limit of the survey—reaches 2.2 mag deeper than the widely used Virgo Cluster Catalog and at least 1.2 mag deeper than any sample previously used to measure the luminosity function in Virgo. Using a Bayesian analysis, we find a best-fit faint-end slope of α = ‑1.33 ± 0.02 for the g-band luminosity function; consistent results are found for the stellar mass function and the luminosity function in the other four NGVS bandpasses. We discuss the implications for the faint-end slope of adding 92 ultracompact dwarfs (UCDs)—previously compiled by the NGVS in this region—to the galaxy sample, assuming that UCDs are the stripped remnants of nucleated dwarf galaxies. Under this assumption, the slope of the luminosity function (down to the UCD faint magnitude limit, M g = ‑9.6 mag) increases dramatically, up to α = ‑1.60 ± 0.06 when correcting for the expected number of disrupted non-nucleated galaxies. We also calculate the total number of UCDs and globular clusters that may have been deposited in the core of Virgo owing to the disruption of satellites, both nucleated and non-nucleated. We estimate that ∼150 objects with M g ≲ ‑9.6 mag and that are currently classified as globular clusters might, in fact, be the nuclei of disrupted galaxies. We further estimate that as many as 40% of the (mostly blue) globular clusters in the Virgo core might once have belonged to such satellites; these same disrupted satellites might have contributed ∼40% of the total luminosity in galaxies observed in the core region today. Finally, we use an updated Local Group galaxy catalog to provide a new measurement of the luminosity function of Local Group

  6. Stellarator hybrids

    SciTech Connect

    Furth, H.P.; Ludescher, C.

    1984-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  8. Substructure Search by Set Reduction

    ERIC Educational Resources Information Center

    Figueras, John

    1972-01-01

    The set reduction algorithm is based on set theory and Boolean algebra rather than the graph-theoretic approach. Time trials with a small file of organic chemical structures indicate that the algorithm can be economically used for substructure (or complete structure) sequential searches on a file containing 30,000-50,000 computer-coded structures.…

  9. Compact Binary Merger Rates: Comparison with LIGO/Virgo Upper Limits

    NASA Astrophysics Data System (ADS)

    Belczynski, Krzysztof; Repetto, Serena; Holz, Daniel E.; O'Shaughnessy, Richard; Bulik, Tomasz; Berti, Emanuele; Fryer, Christopher; Dominik, Michal

    2016-03-01

    We compare evolutionary predictions of double compact object merger rate densities with initial and forthcoming LIGO/Virgo upper limits. We find that: (i) Due to the cosmological reach of advanced detectors, current conversion methods of population synthesis predictions into merger rate densities are insufficient. (ii) Our optimistic models are a factor of 18 below the initial LIGO/Virgo upper limits for BH-BH systems, indicating that a modest increase in observational sensitivity (by a factor of ˜2.5) may bring the first detections or first gravitational wave constraints on binary evolution. (iii) Stellar-origin massive BH-BH mergers should dominate event rates in advanced LIGO/Virgo and can be detected out to redshift z ≃ 2 with templates including inspiral, merger, and ringdown. Normal stars (\\lt 150 {M}⊙ ) can produce such mergers with total redshifted mass up to {M}{{tot,z}}≃ 400 {M}⊙ . (iv) High black hole (BH) natal kicks can severely limit the formation of massive BH-BH systems (both in isolated binary and in dynamical dense cluster evolution), and thus would eliminate detection of these systems even at full advanced LIGO/Virgo sensitivity. We find that low and high BH natal kicks are allowed by current observational electromagnetic constraints. (v) The majority of our models yield detections of all types of mergers (NS-NS, BH-NS, BH-BH) with advanced detectors. Numerous massive BH-BH merger detections will indicate small (if any) natal kicks for massive BHs.

  10. Compact binary merger rates: Comparison with LIGO/Virgo upper limits

    DOE PAGESBeta

    Belczynski, Krzysztof; Repetto, Serena; Holz, Daniel E.; O'Shaugnessy, Richard; Bulik, Tomasz; Berti, Emanuele; Fryer, Christopher Lee; Dominik, Michal

    2016-03-03

    Here, we compare evolutionary predictions of double compact object merger rate densities with initial and forthcoming LIGO/Virgo upper limits. We find that: (i) Due to the cosmological reach of advanced detectors, current conversion methods of population synthesis predictions into merger rate densities are insufficient. (ii) Our optimistic models are a factor of 18 below the initial LIGO/Virgo upper limits for BH–BH systems, indicating that a modest increase in observational sensitivity (by a factor of ~2.5) may bring the first detections or first gravitational wave constraints on binary evolution. (iii) Stellar-origin massive BH–BH mergers should dominate event rates in advanced LIGO/Virgo and can be detected out to redshift z sime 2 with templates including inspiral, merger, and ringdown. Normal stars (more » $$\\lt 150\\;{M}_{\\odot }$$) can produce such mergers with total redshifted mass up to $${M}_{{\\rm{tot,z}}}\\simeq 400\\;{M}_{\\odot }$$. (iv) High black hole (BH) natal kicks can severely limit the formation of massive BH–BH systems (both in isolated binary and in dynamical dense cluster evolution), and thus would eliminate detection of these systems even at full advanced LIGO/Virgo sensitivity. We find that low and high BH natal kicks are allowed by current observational electromagnetic constraints. (v) The majority of our models yield detections of all types of mergers (NS–NS, BH–NS, BH–BH) with advanced detectors. Numerous massive BH–BH merger detections will indicate small (if any) natal kicks for massive BHs.« less

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    IRAC infrared images of 44 spiral and peculiar galaxies from the Spitzer Survey of the Virgo Cluster help reveal the interactions which transform galaxies in clusters. We explore how the location of galaxies in the IR 3.6-8μm color-magnitude diagram is related to the spatial distributions of ISM/star formation, as traced by PAH emission in the 8μm band. Based on their 8μm/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 8/3.6μm ratios. They are relatively unaffected by the cluster environment, and have probably never passed through the cluster core. Truncated galaxies have a relatively normal 8μm/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 8μm/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 8μm/PAH surface brightness even in the inner disk. These are the "reddest" galaxies, with the smallest 8/3.6μm ratios. The origin of the anemics seems to a combination of starvation, gravitational interactions, and long-ago ram pressure stripping.

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

    NASA Astrophysics Data System (ADS)

    Lee, Henry

    Dwarf galaxies are the greatest contributor to the total number of galaxies and most are believed to be systems consisting of matter in a near-primordial state. Containing H I gas and H II regions, dwarf irregular galaxies (dIs) can be used as test bodies to evaluate the impact of the environment on their evolution. Oxygen abundances relative to hydrogen within H II regions are a measure of how far the conversion of gas in the interstellar medium into stars has proceeded as a whole, as abundances do not vary significantly with galactocentric radius in dIs. Measurements of the [O III]λ4363 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]λ4363 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

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

    NASA Astrophysics Data System (ADS)

    Doherty, M.; Arnaboldi, M.; Das, P.; Gerhard, O.; Aguerri, J. A. L.; Ciardullo, R.; Feldmeier, J. J.; Freeman, K. C.; Jacoby, G. H.; Murante, G.

    2009-08-01

    Aims: We study the kinematics and dynamics of the extreme outer halo of M 87, the central galaxy in the Virgo cluster, and its transition to the intracluster light (ICL). Methods: We present high resolution FLAMES/VLT spectroscopy of intracluster planetary nebula (PN) candidates, targeting three new fields in the Virgo cluster core with surface brightness down to μB = 28.5. Based on the projected phase space information (sky positions and line-of-sight velocities) we separate galaxy and cluster components in the confirmed PN sample. We then use the spherical Jeans equation and the total gravitational potential as traced by the X-ray emission to derive the orbital distribution in the outer stellar halo of M 87. We determine the luminosity-specific PN number for the M 87 halo and the ICL from the photometric PN catalogs and sampled luminosities, and discuss the origin of the ICL in Virgo based on its measured PN velocities. Results: We confirm a further 12 PNs in Virgo, five of which are bound to the halo of M 87, and the remainder are true intracluster planetary nebulas (ICPNs). The M 87 PNs are confined to the extended stellar envelope of M 87, within a projected radius of ~160 kpc, while the ICPNs are scattered across the whole surveyed region between M 87 and M 86, supporting a truncation of M 87's luminous outer halo at a 2σ level. The line-of-sight velocity distribution of the M 87 PNs at projected radii of 60 kpc and 144 kpc shows (i) no evidence for rotation of the halo along the photometric major axis; and (ii) that the velocity dispersion decreases in the outer halo, down to σ_last = 78±25 km s-1 at 144 kpc. The Jeans model for the M 87 halo stars fits the observed line-of-sight velocity dispersion profile only if the stellar orbits are strongly radially anisotropic (β ≃ 0.4 at r ≃ 10 kpc increasing to 0.8 at the outer edge), and if additionally the stellar halo is truncated at ≃ 150 kpc average elliptical radius. The α-parameters for the M 87

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

    NASA Technical Reports Server (NTRS)

    Houdashelt, Mark L.; Frogel, Jay A.

    1993-01-01

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

  15. Chemical substructure analysis in toxicology

    SciTech Connect

    Beauchamp, R.O. Jr.

    1990-12-31

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

  16. The integrated radio spectrum of Virgo A

    NASA Astrophysics Data System (ADS)

    Vinyaikin, E. N.

    2016-08-01

    The flux density of the radio galaxy Virgo A has been measured at 38 and 151.5 MHz. These measurements and published flux densities at 59 other frequencies from 5.6 MHz to 857 GHz are used to obtain a fit to the frequency dependence of the logarithm of the flux density in the form of a second-order polynomial of the logarithm of the frequency, S_ν ^{Vir A} [Jy] = 1224.4(ν [MHz]/150)^{ - 0.817 + 0.007 log (ν [MHz]/150)} . This spectrum, which has a small positive curvature, agrees slightly better with the observed flux densities than a purely power-lawspectrumwith the spectral index 0.793±0.003 and S 150 [MHz] Vir A = 1187±23 Jy. The relative errors in using the power-law spectrum instead of this spectrum with its small, positive curvature lie in the range (-5.2-1.6)% for frequencies from 70 MHz to 857 GHz. The expected peak frequency of the spectrum of Virgo A is estimated.

  17. Mass Substructure in Abell 3128

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  18. Some approaches to substructure coupling with damping

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    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.

  19. Prospects for stochastic background searches using Virgo and LSC interferometers

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

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

  20. MAIN-SEQUENCE STAR POPULATIONS IN THE VIRGO OVERDENSITY REGION

    SciTech Connect

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

    2013-05-20

    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

  1. Discovery of Ultra-Compact Dwarf Galaxies in the Virgo Cluster

    SciTech Connect

    Jones, J; Drinkwater, M; Jurek, R; Phillips, S; Gregg, M; Bekki, K; Couch, W; Karick, A; Parker, Q; Smith, R M

    2006-01-05

    The authors have discovered nine ultra-compact dwarf galaxies (UCDs) in the Virgo Cluster, extending samples of these objects outside the Fornax Cluster. Using the 2dF multi-fiber spectrograph on the Anglo-Australian Telescope, the new Virgo members were found among 1500 color-selected, star-like targets with 16.0 < b{sub j} < 20.2 in a two-degree diameter field centered on M87 (NGC4486). The newly-found UCDs are comparable to the UCDs in the Fornax Cluster, with sizes {approx} 100 pc, -12.9 < M{sub B} < -10.7, and exhibiting red, absorption-line spectra, indicative of an older stellar population. The properties of these objects remain consistent with the tidal threshing model for the origin of UCDs from the surviving nuclei of nucleated dwarf ellipticals disrupted in the cluster core. The discovery that UCDs exist in Virgo shows that this galaxy type is probably a ubiquitous phenomenon in clusters of galaxies; coupled with their possible origin by tidal threshing, the UCD population is a potential indicator and probe of the formation history of a given cluster. They also describe one additional bright UCD with M{sub B} = -12.0 in the core of the Fornax Cluster. They find no further UCDs in our Fornax Cluster Spectroscopic Survey down to b{sub j} = 19.5 in two additional 2dF fields extending as far as 3{sup o} from the center of the cluster. All six Fornax bright UCDs identified with 2dF lie within 0.5{sup o} (projected distance of 170 kpc) of the central elliptical galaxy NGC1399.

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

    SciTech Connect

    Ferrarese, Laura; Cote, Patrick; Gwyn, S. D. J.; MacArthur, Lauren A.; McConnachie, Alan W.; Blakeslee, John P.; Cuillandre, Jean-Charles; Peng, Eric W.; Duc, Pierre-Alain; Mei, Simona; Erben, Thomas; Durrell, Patrick R.; Christopher Mihos, J.; Jordan, Andres; Puzia, Thomas H.; Lancon, Ariane; Emsellem, Eric; Balogh, Michael L.; Van Waerbeke, Ludovic; and others

    2012-05-01

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

  3. Search for Extended Gamma-Ray Emission from the Virgo Galaxy Cluster with FERMI-LAT

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Bloom, E. D.; Bonino, R.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caputo, R.; Caragiulo, M.; Caraveo, P. A.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiaro, G.; Ciprini, S.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Desiante, R.; Digel, S. W.; Di Venere, L.; Drell, P. S.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Gomez-Vargas, G. A.; Grenier, I. A.; Guiriec, S.; Gustafsson, M.; Hewitt, J. W.; Hill, A. B.; Horan, D.; Jeltema, T. E.; Jogler, T.; Johnson, A. S.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Maldera, S.; Malyshev, D.; Manfreda, A.; Mayer, M.; Mazziotta, M. N.; Michelson, P. F.; Mizuno, T.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nuss, E.; Ohsugi, T.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paneque, D.; Perkins, J. S.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Pivato, G.; Porter, T. A.; Rainó, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Sánchez-Conde, M.; Schulz, A.; Sgró, C.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Storm, E.; Tajima, H.; Takahashi, H.; Thayer, J. B.; Torres, D. F.; Tosti, G.; Troja, E.; Vianello, G.; Wood, K. S.; Wood, M.; Zaharijas, G.; Zimmer, S.; Fermi-LAT Collaboration

    2015-10-01

    Galaxy clusters are one of the prime sites to search for dark matter (DM) annihilation signals. Depending on the substructure of the DM halo of a galaxy cluster and the cross sections for DM annihilation channels, these signals might be detectable by the latest generation of γ-ray telescopes. Here we use three years of Fermi-Large Area Telescope data, which are the most suitable for searching for very extended emission in the vicinity of the nearby Virgo galaxy cluster. Our analysis reveals statistically significant extended emission which can be well characterized by a uniformly emitting disk profile with a radius of 3° that moreover is offset from the cluster center. We demonstrate that the significance of this extended emission strongly depends on the adopted interstellar emission model (IEM) and is most likely an artifact of our incomplete description of the IEM in this region. We also search for and find new point source candidates in the region. We then derive conservative upper limits on the velocity-averaged DM pair annihilation cross section from Virgo. We take into account the potential γ-ray flux enhancement due to DM sub-halos and its complex morphology as a merging cluster. For DM annihilating into b\\bar{b}, assuming a conservative sub-halo model setup, we find limits that are between 1 and 1.5 orders of magnitude above the expectation from the thermal cross section for mDM ≲ 100 GeV. In a more optimistic scenario, we exclude < σ v> ˜ 3× {10}-26 {{cm}}3 {{{s}}}-1 for mDM ≲ 40 GeV for the same channel. Finally, we derive upper limits on the γ-ray-flux produced by hadronic cosmic-ray interactions in the inter cluster medium. We find that the volume-averaged cosmic-ray-to-thermal pressure ratio is less than ˜6%.

  4. More evidence of substructure in the motions of nearby halo stars

    NASA Astrophysics Data System (ADS)

    Re Fiorentin, P.; Helmi, A.; Lattanzi, M. G.; Spagna, A.

    2004-07-01

    We explore the stellar halo of the Milky Way to search for fossil signatures of past mergers. We use the Beers et al. (2000) catalog of non-kinematically selected metal poor stars in the solar neighborhood to select subsets of halo stars within 1-2 kpc of the Sun. Motivated by the results of high resolution CDM simulations, we look for substructure in the kinematics of the fastest stars. When a two-point velocity correlation function is applied to these subsets, statistical evidence of substructure is found. This appears to be due to a small moving group with dynamical properties similar to the stellar "stream" previously discovered by Helmi et al. (1999).

  5. An Introduction to the Virgo Suspension System

    NASA Astrophysics Data System (ADS)

    Frasconi, Franco; Rapagnani, Piero

    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, 10.1007/978-3-319-03792-9_8.

  6. The Advanced Virgo monolithic fused silica suspension

    NASA Astrophysics Data System (ADS)

    Aisa, D.; Aisa, S.; Campeggi, C.; Colombini, M.; Conte, A.; Farnesini, L.; Majorana, E.; Mezzani, F.; Montani, M.; Naticchioni, L.; Perciballi, M.; Piergiovanni, F.; Piluso, A.; Puppo, P.; Rapagnani, P.; Travasso, F.; Vicerè, A.; Vocca, H.

    2016-07-01

    The detection of gravitational waves is one of the most challenging prospects faced by experimental physicists. Suspension thermal noise is an important noise source at operating frequencies between approximately 10 and 30 Hz, and represents a limit to the sensitivity of the ground based interferometric gravitational wave detectors. Its effects can be reduced by minimizing the losses and by optimizing the geometry of the suspension fiber as well as its attachment system. In this proceeding we will describe the mirrors double stage monolithic suspension system to be used in the Advanced Virgo (AdV) detector. We also present the results of the thermal noise study, performed with the help of a finite elements model, taking into account the precise geometry of the fibers attachment systems on the suspension elements. We shall demonstrate the suitability of this suspension for installation in AdV.

  7. Stellar evolution.

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    Aspects of normal stellar evolution are discussed together with evolution near the main sequence, stellar evolution from main sequence to white dwarf or carbon ignition, the structure of massive main-sequence stars, and problems of stellar stability and stellar pulsation. Other subjects considered include variable stars, white dwarfs, close binaries, novae, early supernova luminosity, neutron stars, the photometry of field horizontal-branch stars, and stellar opacity. Transport mechanisms in stars are examined together with thermonuclear reactions and nucleosynthesis, the instability problem in nuclear burning shells, stellar coalescence, and intense magnetic fields in astrophysics. Individual items are announced in this issue.

  8. RADIAL VELOCITIES OF GALACTIC HALO STARS IN VIRGO

    SciTech Connect

    Brink, Thomas G.; Mateo, Mario; Martinez-Delgado, David E-mail: mmateo@umich.ed

    2010-11-15

    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).

  9. Origin of Non-axisymmetric Features of dEs in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Kwak, SungWon; Kim, Woong-Tae; Rey, Soo-Chang; Kim, Suk

    2016-06-01

    A fraction of early-type dwarf galaxies in the Virgo cluster have a disk component and even possess disk features such as bar, lens, and spiral arms. Using N-body simulations, we propose formation scenarios of these non-axisymmetric features in the disky dwarf galaxies. By adopting VCC 856 as our progenitor, a bulgeless dwarf disk galaxy with embedded faint spiral arms, we construct 11 initial conditions with slight dynamical variations based on observational error range. After 10 Gyrs of evolution in isolation, our standard model slowly forms a bar at ~3 Gyr and then undergoes buckling instability that temporarily weakens the bar, although the bar strength continues to grow afterward. Nine of our isolated models are also unstable to bar formation and undergo buckling instability. This suggests that the disky dwarf galaxies are intrinsically unstable to form bars, accounting for a population of barred dwarf galaxies in the outskirts of the Virgo cluster. We also find that both the concentration of dark matter halo and the degree of random motions within stellar disk affect the vigor of buckling instability. To understand the origin of the faint grand-design spiral arms, we additionally construct 6 sets of tidal models by differing pericenter distances. We reveal that its formation mechanism is rather more complicated: the faint spiral arms consistent with the observations could develop on marginally unstable disk by relatively weak tidal force. We discuss our results in light of dynamical evolution of disky dwarf galaxies including mergers.

  10. Kinematic Properties as Probes of the Evolution of Dwarf Galaxies in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Toloba, E.; Boselli, A.; Gorgas, J.; Peletier, R. F.; Cenarro, A. J.; Gadotti, D. A.; Gil de Paz, A.; Pedraz, S.; Yildiz, U.

    2009-12-01

    We present new observational results on the kinematical, morphological, and stellar population properties of a sample of 21 dEs located both in the Virgo Cluster and in the field, which show that 52% of the dEs (1) are rotationally supported, (2) exhibit structural signs of typical rotating systems such as disks, bars, or spiral arms, (3) are younger (~3 Gyr) than non-rotating dEs, and (4) are preferentially located either in the outskirts of Virgo or in the field. This evidence is consistent with the idea that rotationally supported dwarfs are late-type spirals or irregulars that recently entered the cluster and lost their gas through a ram pressure stripping event, quenching their star formation and becoming dEs through passive evolution. We also find that all, but one, galaxies without photometric hints for hosting disks are pressure supported and are all situated in the inner regions of the cluster. This suggests a different evolution from the rotationally supported systems. Three different scenarios for these non-rotating galaxies are discussed (in situ formation, harassment, and ram pressure stripping).

  11. KINEMATIC PROPERTIES AS PROBES OF THE EVOLUTION OF DWARF GALAXIES IN THE VIRGO CLUSTER

    SciTech Connect

    Toloba, E.; Gorgas, J.; De Paz, A. Gil; Boselli, A.; Peletier, R. F.; Yildiz, U.; Cenarro, A. J.; Gadotti, D. A.; Pedraz, S.

    2009-12-10

    We present new observational results on the kinematical, morphological, and stellar population properties of a sample of 21 dEs located both in the Virgo Cluster and in the field, which show that 52% of the dEs (1) are rotationally supported, (2) exhibit structural signs of typical rotating systems such as disks, bars, or spiral arms, (3) are younger (approx3 Gyr) than non-rotating dEs, and (4) are preferentially located either in the outskirts of Virgo or in the field. This evidence is consistent with the idea that rotationally supported dwarfs are late-type spirals or irregulars that recently entered the cluster and lost their gas through a ram pressure stripping event, quenching their star formation and becoming dEs through passive evolution. We also find that all, but one, galaxies without photometric hints for hosting disks are pressure supported and are all situated in the inner regions of the cluster. This suggests a different evolution from the rotationally supported systems. Three different scenarios for these non-rotating galaxies are discussed (in situ formation, harassment, and ram pressure stripping).

  12. Parallel Computational Environment for Substructure Optimization

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  13. A state observer for the Virgo inverted pendulum

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  14. Substructure Main Bridge, River Piers A & V ...

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

    Substructure - Main Bridge, River Piers A & V - Huey P. Long Bridge, Spanning Mississippi River approximately midway between nine & twelve mile points upstream from & west of New Orleans, Jefferson, Jefferson Parish, LA

  15. Algebraic Sub-Structuring for Electromagnetic Applications

    SciTech Connect

    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

    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.

  16. Algebraic sub-structuring for electromagnetic applications

    SciTech Connect

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

    2004-09-14

    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.

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

    SciTech Connect

    Lora, V.; Grebel, E. K.; Just, A.; Sánchez-Salcedo, F. J.

    2013-11-01

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

  18. A structural design decomposition method utilizing substructuring

    NASA Technical Reports Server (NTRS)

    Scotti, Stephen J.

    1994-01-01

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

  19. The next generation Virgo cluster survey. VIII. The spatial distribution of globular clusters in the Virgo cluster

    SciTech Connect

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

    2014-10-20

    We report on a large-scale study of the distribution of globular clusters (GCs) throughout the Virgo cluster, based on photometry from the Next Generation Virgo Cluster Survey (NGVS), a large imaging survey covering Virgo's primary subclusters (Virgo A = M87 and Virgo B = M49) out to their virial radii. Using the g{sub o}{sup ′}, (g' – i') {sub o} color-magnitude diagram of unresolved and marginally resolved sources within the NGVS, we have constructed two-dimensional maps of the (irregular) GC distribution over 100 deg{sup 2} to a depth of g{sub o}{sup ′} = 24. We present the clearest evidence to date showing the difference in concentration between red and blue GCs over the full extent of the cluster, where the red (more metal-rich) GCs are largely located around the massive early-type galaxies in Virgo, while the blue (metal-poor) GCs have a much more extended spatial distribution with significant populations still present beyond 83' (∼215 kpc) along the major axes of both M49 and M87. A comparison of our GC maps to the diffuse light in the outermost regions of M49 and M87 show remarkable agreement in the shape, ellipticity, and boxiness of both luminous systems. We also find evidence for spatial enhancements of GCs surrounding M87 that may be indicative of recent interactions or an ongoing merger history. We compare the GC map to that of the locations of Virgo galaxies and the X-ray intracluster gas, and find generally good agreement between these various baryonic structures. We calculate the Virgo cluster contains a total population of N {sub GC} = 67, 300 ± 14, 400, of which 35% are located in M87 and M49 alone. For the first time, we compute a cluster-wide specific frequency S {sub N,} {sub CL} = 2.8 ± 0.7, after correcting for Virgo's diffuse light. We also find a GC-to-baryonic mass fraction ε {sub b} = 5.7 ± 1.1 × 10{sup –4} and a GC-to-total cluster mass formation efficiency ε {sub t} = 2.9 ± 0.5 × 10{sup –5}, the latter values

  20. Ram pressure stripping in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Verdugo, C.; Combes, F.; Dasyra, K.; Salomé, P.; Braine, J.

    2015-10-01

    Gas can be violently stripped from their galaxy disks in rich clusters, and be dispersed over 100 kpc-scale tails or plumes. Young stars have been observed in these tails, suggesting they are formed in situ. This will contribute to the intracluster light, in addition to tidal stripping of old stars. We want to quantify the efficiency of intracluster star formation. We present CO(1-0) and CO(2-1) observations, made with the IRAM-30 m telescope, towards the ram-pressure stripped tail northeast of NGC 4388 in Virgo. We selected HII regions found all along the tails, together with dust patches, as observing targets. We detect molecular gas in 4 positions along the tail, with masses between 7 × 105 to 2 × 106M⊙. Given the large distance from the NGC 4388 galaxy, the molecular clouds must have formed in situ, from the HI gas plume. We compute the relation between surface densities of star formation and molecular gas in these regions, and find that the star formation has very low efficiency. The corresponding depletion time of the molecular gas can be up to 500 Gyr and more. Since this value exceeds a by far Hubble time, this gas will not be converted into stars, and will stay in a gaseous phase to join the intracluster medium.

  1. Phase camera experiment for Advanced Virgo

    NASA Astrophysics Data System (ADS)

    Agatsuma, Kazuhiro; van Beuzekom, Martin; van der Schaaf, Laura; van den Brand, Jo

    2016-07-01

    We report on a study of the phase camera, which is a frequency selective wave-front sensor of a laser beam. This sensor is utilized for monitoring sidebands produced by phase modulations in a gravitational wave (GW) detector. Regarding the operation of the GW detectors, the laser modulation/demodulation method is used to measure mirror displacements and used for the position controls. This plays a significant role because the quality of controls affect the noise level of the GW detector. The phase camera is able to monitor each sideband separately, which has a great benefit for the manipulation of the delicate controls. Also, overcoming mirror aberrations will be an essential part of Advanced Virgo (AdV), which is a GW detector close to Pisa. Especially low-frequency sidebands can be affected greatly by aberrations in one of the interferometer cavities. The phase cameras allow tracking such changes because the state of the sidebands gives information on mirror aberrations. A prototype of the phase camera has been developed and is currently tested. The performance checks are almost completed and the installation of the optics at the AdV site has started. After the installation and commissioning, the phase camera will be combined to a thermal compensation system that consists of CO2 lasers and compensation plates. In this paper, we focus on the prototype and show some limitations from the scanner performance.

  2. STELLAR POPULATION VARIATIONS IN THE MILKY WAY's STELLAR HALO

    SciTech Connect

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

    2010-12-15

    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 {approx}9000 g < 18 candidates where {approx}70% of them are BHB stars. We map the BHB/MSTO ratio across {approx}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.

  3. Major substructure in the M31 Outer Halo: the East Cloud

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    We present the first detailed analysis of the East Cloud, a highly disrupted diffuse stellar substructure in the outer halo of M31. The core of the substructure lies at a projected distance of ˜100 kpc from the centre of M31 in the outer halo, with possible extensions reaching right into the inner halo. Using Pan-Andromeda Archaeological Survey photometry of red giant branch stars, we measure the distance, metallicity and brightness of the cloud. Using Hubble Space Telescope data, we independently measure the distance and metallicity to the two globular clusters coincident with the East Cloud core, PA-57 and PA-58, and find their distances to be consistent with the cloud. Four further globular clusters coincident with the substructure extensions are identified as potentially associated. Combining the analyses, we determine a distance to the cloud of 814^{+20}_{-9} kpc, a metallicity of [Fe/H] = -1.2 ± 0.1, and a brightness of MV = -10.7 ± 0.4 mag. Even allowing for the inclusion of the potential extensions, this accounts for less than 20 per cent of the progenitor luminosity implied by the luminosity-metallicity relation. Using the updated techniques developed for this analysis, we also refine our estimates of the distance and brightness of the South-West Cloud, a separate substructure analysed in the previous work in this series.

  4. Singular behavior of jet substructure observables

    NASA Astrophysics Data System (ADS)

    Larkoski, Andrew J.; Moult, Ian

    2016-01-01

    Jet substructure observables play a central role at the Large Hadron Collider for identifying the boosted hadronic decay products of electroweak scale resonances. The complete description of these observables requires understanding both the limit in which hard substructure is resolved, as well as the limit of a jet with a single hard core. In this paper we study in detail the perturbative structure of two prominent jet substructure observables, N -subjettiness and the energy correlation functions, as measured on background QCD jets. In particular, we focus on the distinction between the limits in which two-prong structure is resolved or unresolved. Depending on the choice of subjet axes, we demonstrate that at fixed order, N -subjettiness can manifest myriad behaviors in the unresolved region: smooth tails, end point singularities, or singularities in the physical region. The energy correlation functions, by contrast, only have nonsingular perturbative tails extending to the end point. We discuss the effect of hadronization on the various observables with Monte Carlo simulation and demonstrate that the modeling of these effects with nonperturbative shape functions is highly dependent on the N -subjettiness axes definitions. Our study illustrates those regions of phase space that must be controlled for high-precision jet substructure calculations, and emphasizes how such calculations can be facilitated by designing substructure observables with simple singular structures.

  5. Singular behavior of jet substructure observables

    DOE PAGESBeta

    Larkoski, Andrew J.; Moult, Ian

    2016-01-20

    Jet substructure observables play a central role at the Large Hadron Collider for identifying the boosted hadronic decay products of electroweak scale resonances. The complete description of these observables requires understanding both the limit in which hard substructure is resolved, as well as the limit of a jet with a single hard core. In this paper we study in detail the perturbative structure of two prominent jet substructure observables, N-subjettiness and the energy correlation functions, as measured on background QCD jets. In particular, we focus on the distinction between the limits in which two-prong structure is resolved or unresolved. Dependingmore » on the choice of subjet axes, we demonstrate that at fixed order, N-subjettiness can manifest myriad behaviors in the unresolved region: smooth tails, end-point singularities, or singularities in the physical region. The energy correlation functions, by contrast, only have non-singular perturbative tails extending to the end point. We discuss the effect of hadronization on the various observables with Monte Carlo simulation and demonstrate that the modeling of these effects with non-perturbative shape functions is highly dependent on the N-subjettiness axes definitions. Lastly, our study illustrates those regions of phase space that must be controlled for high-precision jet substructure calculations, and emphasizes how such calculations can be facilitated by designing substructure observables with simple singular structures.« less

  6. Kinematic Disturbances in Rotation Curves among 89 Virgo Galaxies

    NASA Astrophysics Data System (ADS)

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

    1999-05-01

    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 ~ 1Gyr, many Virgo galaxies have experienced several significant kinematic disturbances during their lifetimes. (2) There is no strong correlation of rotation curve complexity with Hubble type, galaxy luminosity, local galaxy density, or HI deficiency. (3) There is a remarkable difference in the distribution of galaxy systemic velocity for galaxies in the two classes. Galaxies with regular rotation patterns show a flat distribution with velocities ranging from V = -300 km/sec to V = +2500 km/sec; galaxies with disturbed kinematics have a Gaussian distribution which peaks at V = +1172+/-100 km/sec, near the cluster mean velocity. This distribution is virtually identical to the distribution of systemic velocities for elliptical galaxies in Virgo. However, disturbed spirals are less centrally concentrated than the ellipticals and those near the periphery are more likely to have the mean cluster velocity. We suggest that spirals with disturbed kinematics are preferentially on radial orbits, which bring them to the denser core, where tidal interactions are strong and/or more common. However, because they spend most of their time near apocenter, we observe them near the periphery of the cluster. Some may be falling into the core for the first time. For a non-virialized cluster like Virgo, galaxies may encounter either local (nearby galaxies) or global (cluster related) interactions. These interactions may alter the galaxy morphology, and may play a role in driving the Virgo cluster toward dynamical equilibrium.

  7. Quantification of Substructure in Nearby Abell Clusters

    NASA Astrophysics Data System (ADS)

    Kriessler, J. R.; Beers, T. C.; Odewahn, S. C.

    1995-05-01

    Theory, as well as numerical simulations, suggests that Omega_o may be observationally constrained by the amount of substructure observed in present-day clusters of galaxies. We have therefore begun a study of the 116 Abell clusters with richness class greater than or equal to 1 and distance class less than or equal to 4, the so-called ``volume-limited'' sample of Hoessel, Gunn, & Thuan 1980 (ApJ 241, 486) to determine the prevalence of substructure in the clusters' projected galaxy positions. We use positions of galaxies identified by the Minnesota Automated Plate Scanner to obtain contour plots of the available clusters using an adaptive kernel routine. Significance of substructure is evaluated using the 2-D Lee test as well as a likelihood-ratio test on fits made with mixtures of two-dimensional gaussians. We also present nonparametric density profile estimates obtained with the program MAPEL (Merritt and Tremblay 1994, AJ 108, 514).

  8. Inverse substructure method for model updating of structures

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  9. Star-forming dwarf galaxies in the Virgo cluster: the link between molecular gas, atomic gas, and dust

    NASA Astrophysics Data System (ADS)

    Grossi, M.; Corbelli, E.; Bizzocchi, L.; Giovanardi, C.; Bomans, D.; Coelho, B.; De Looze, I.; Gonçalves, T. S.; Hunt, L. K.; Leonardo, E.; Madden, S.; Menéndez-Delmestre, K.; Pappalardo, C.; Riguccini, L.

    2016-05-01

    We present 12CO(1-0) and 12CO(2-1) observations of a sample of 20 star-forming dwarfs selected from the Herschel Virgo Cluster Survey, with oxygen abundances ranging from 12 + log (O / H) ~ 8.1 to 8.8. CO emission is observed in ten galaxies and marginally detected in another one. CO fluxes correlate with the FIR 250 μm emission, and the dwarfs follow the same linear relation that holds for more massive spiral galaxies extended to a wider dynamical range. We compare different methods to estimate H2 molecular masses, namely a metallicity-dependent CO-to-H2 conversion factor and one dependent on H-band luminosity. The molecular-to-stellar mass ratio remains nearly constant at stellar masses ≲ 109 M⊙, contrary to the atomic hydrogen fraction, MHI/M∗, which increases inversely with M∗. The flattening of the MH2/M∗ ratio at low stellar masses does not seem to be related to the effects of the cluster environment because it occurs for both Hi-deficient and Hi-normal dwarfs. The molecular-to-atomic ratio is more tightly correlated with stellar surface density than metallicity, confirming that the interstellar gas pressure plays a key role in determining the balance between the two gaseous components of the interstellar medium. Virgo dwarfs follow the same linear trend between molecular gas mass and star formation rate as more massive spirals, but gas depletion timescales, τdep, are not constant and range between 100 Myr and 6 Gyr. The interaction with the Virgo cluster environment is removing the atomic gas and dust components of the dwarfs, but the molecular gas appears to be less affected at the current stage of evolution within the cluster. However, the correlation between Hi deficiency and the molecular gas depletion time suggests that the lack of gas replenishment from the outer regions of the disc is lowering the star formation activity. Based on observations carried out with the IRAM 30-m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany

  10. Virgo Cluster and field dwarf ellipticals in 3D - II. Internal dynamics points to tidal harassment?

    NASA Astrophysics Data System (ADS)

    Ryś, A.; van de Ven, G.; Falcón-Barroso, J.

    2014-03-01

    We present the dynamical analysis of a sample of 12 dwarf elliptical (dE) galaxies for which we have obtained SAURON large-scale two-dimensional spectroscopic data. We construct Jeans axisymmetric models and obtain total dynamical masses enclosed within one effective radius. We use the obtained values to show that the validity of the dynamical scaling relations of massive early-type galaxies can be extended to these low-mass systems, except that dEs seem to contain relatively larger fraction of dark matter in their inner parts. We then demonstrate that dE galaxies have lower angular momenta than the present-day analogues of their presumed late-type progenitors, and we show that dE circular velocity curves are steeper than the rotation curves of galaxies with equal and up to an order of magnitude higher luminosity. This requires a transformation mechanism that is not only able to lower the angular momentum but also one that needs to account for increased stellar concentration. Additionally, we match the dark matter fraction of our galaxies to their location in the Virgo Cluster and see that galaxies in the cluster outskirts tend to have a higher dark-to-stellar matter ratio. Transformation due to tidal harassment is able to explain all of the above, unless the dE progenitors were already compact and had lower angular momenta at higher redshifts.

  11. Galaxy Properties and Substructure in the Cluster Abell 160

    NASA Astrophysics Data System (ADS)

    Koontz, Craig; Pinkney, Jason

    2008-10-01

    We continue development of a procedure for building a large catalog of cluster galaxies and their photometric properties, as measured with CCDs. Our first case, Abell 160, is relatively nearby and we have already obtained spectroscopic redshifts for its brightest galaxies. We have mosaiced this cluster in R and V filters using a CCD imager on the 1.3-meter McGraw-Hill telescope. For each CCD frame we fit a WCS (world coordinate system), remove bright cosmic rays, and extract sources using ``SExtractor.'' We create software for merging source catalogs in such a way as to reject residual cosmic rays and other invalid sources, and to combine redundant measurements without double counting. The measured properties include magnitude, ellipticity, position angle, size, and color (V-R). We compare our data to those of the HST (Hubble Space Telescope) and SDSS (Sloan Digital Sky Survey) archives to examine the accuracy of our star/galaxy separation and our color measurements. For our substructure investigation, we draw several subsamples of galaxies based on stellarity index, color (the color-magnitude relation), magnitude and velocity. The smallest subsample of spectroscopically confirmed members produces significant substructure signals from 1D (velocity) and 3D (x,y,velocity) diagnostics - a small, offset group may be the culprit. The 2D (x,y) diagnostics applied to the larger samples produce some significant statistics, the cause does not seem to be a large-scale merger, but perhaps several small groups. This is consistent with previous X-ray data showing X-ray emitting gas clumped around small groupings of galaxies.

  12. Deep UV Imaging of Stripped Spiral Galaxies in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Crowl, Hugh

    We propose moderately deep GALEX observations (6 ksec) of eighteen gas-stripped Virgo Cluster spiral galaxies. These observations will give a complete sample of strongly stripped, highly inclined (i>70 degrees) Virgo spirals brighter than magnitude 16. Optical imaging and HI mapping show that these spirals all lack dust and gas in their outer disks, presumably due to ICM-ISM interactions. GALEX UV observations will provide critical information on how these interactions have affected recent star formation in the galaxies. The GALEX FUV and NUV data, particularly when combined with our existing multi-wavelength data set including broadband optical, H-alpha, and Spitzer IR imaging, and optical spectroscopy, will strongly constrain when a galaxy was stripped, how rapidly it was stripped, and the strength of any starburst at the time of stripping. The UV light changes dramatically over timescales of 0-500 Myr, which are the same timescales over which ICM-ISM interactions take place, making it possible to constrain the most recent effects of the cluster environment on galaxy evolution and if these effects can effectively drive the transformation of spirals into S0s. The deep imaging we propose will enable us to detect age gradients in the stellar populations of the outer disks, which will tell us how rapidly the galaxies are stripped. The cluster locations of recently stripped galaxies and the timescales over which the galaxies are stripped will allow us to constrain the relative importance of stripping that occurs during cluster core passages and stripping which occurs when galaxies encounter an ICM shock outside the core. Ten of these galaxies have already been imaged with GALEX, and we are requesting deep observations of these galaxies, in addition to time to image the remaining eight to the same depth.

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  14. Studying Stellar Halos with Future Facilities

    NASA Astrophysics Data System (ADS)

    Greggio, Laura; Falomo, Renato; Uslenghi, Michela

    2015-08-01

    Stellar halos around galaxies retain fundamental evidence of the processes which lead to their build up. Sophisticated models of galaxy formation in a cosmological context yield quantitative predictions about various observable characteristics, including the amount of substructure, the slope of radial mass profiles and three dimensional shapes, and the properties of the stellar populations in the galaxies halos. The comparison of such models with the observations leads to constraints on the general picture of galaxy formation in the hierarchical Universe, as well as on the physical processes taking place in the halos formation. With the current observing facilities, stellar halos can be effectively probed only for a limited number of nearby galaxies. In this contribution we illustrate the progress which we expect in this field with the future large aperture ground based telescopes (E-ELT and TNT), and with JWST. In particular we adress the following issues: (I) the characterization of the stellar populations in the halos innermost regions and substructures, (ii) the measurement of the halos profiles and shapes , and the halos mass content, (iii) the study of Globular Clusters inhabiting the halos of distant galaxies. In order to assess the expected capabilities of future facilities we present the results of a set of simulated images to evaluate to which level of accuracy it will be possible to probe the halos of distant galaxies.

  15. Stellar chromospheres

    NASA Technical Reports Server (NTRS)

    Linsky, J. L.

    1980-01-01

    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.

  16. A Synoptic Map of Halo Substructures from the Pan-STARRS1 3π Survey

    NASA Astrophysics Data System (ADS)

    Bernard, Edouard J.; Ferguson, Annette M. N.; Schlafly, Edward F.; Martin, Nicolas F.; Rix, Hans-Walter; Bell, Eric F.; Finkbeiner, Douglas P.; Goldman, Bertrand; Martínez-Delgado, David; Sesar, Branimir; Wyse, Rosemary F. G.; Burgett, William S.; Chambers, Kenneth C.; Draper, Peter W.; Hodapp, Klaus W.; Kaiser, Nicholas; Kudritzki, Rolf-Peter; Magnier, Eugene A.; Metcalfe, Nigel; Wainscoat, Richard J.; Waters, Christopher

    2016-08-01

    We present a panoramic map of the entire Milky Way halo north of δ ˜ -30° (˜ 30,000 deg2), constructed by applying the matched-filter technique to the Pan-STARRS1 3π Survey dataset. Using single-epoch photometry reaching to g ˜22, we are sensitive to stellar substructures with heliocentric distances between 3.5 and ˜35 kpc. We recover almost all previously-reported streams in this volume and demonstrate that several of these are significantly more extended than earlier datasets have indicated. In addition, we also report five new candidate stellar streams. One of these features appears significantly broader and more luminous than the others and is likely the remnant of a dwarf galaxy. The other four streams are consistent with a globular cluster origin, and three of these are rather short in projection (≲ 10°), suggesting that streams like Ophiuchus may not be that rare. Finally, a significant number of more marginal substructures are also revealed by our analysis; many of these features can also be discerned in matched-filter maps produced by other authors from SDSS data, and hence they are very likely to be genuine. However, the extant 3π data is currently too shallow to determine their properties or produce convincing CMDs. The global view of the Milky Way provided by Pan-STARRS1 provides further evidence for the important role of both globular cluster disruption and dwarf galaxy accretion in building the Milky Way's stellar halo.

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

    SciTech Connect

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

    2012-11-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  19. Stellar Populations

    NASA Astrophysics Data System (ADS)

    Peletier, Reynier F.

    2013-10-01

    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.

  20. Statistics of substructures in dark matter haloes

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    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.

  1. Dark Halos and Substructure from Arcs & Einstein Rings

    NASA Astrophysics Data System (ADS)

    Koopmans, Leon

    2006-07-01

    The surface brightness distribution of extended gravitationally lensed arcs and Einstein rings contains super-resolved information about the lensed object, and, more excitingly, about the smooth and clumpy mass distribution of the lens galaxies. The source and lens information can non-parametrically be separated, resulting in a direct "gravitational image" of the inner mass-distribution of cosmologically-distant galaxies {Koopmans 2005; Koopmans et al. 2006 [astro-ph/0601628]}. With this goal in mind, we propose deep HST ACS-F555W/F814W and NICMOS-F160W WFC imaging of 20 new gravitational-lens systems with spatially resolved lensed sources, of the 35 new lens systems discovered by the Sloan Lens ACS Survey {Bolton et al. 2005} so far, 15 of which are being imaged in Cycle-14. Each system has been selected from the SDSS and confirmed in two time-efficient HST-ACS snapshot programs {cycle 13&14}. High-fidelity multi-color HST images are required {not delivered by the 420s snapshots} to isolate these lensed images {properly cleaned, dithered and extinction-corrected} from the lens galaxy surface brightness distribution, and apply our "gravitational maging" technique. Our sample of 35 early-type lens galaxies to date is by far the largest, still growing, and most uniformly selected. This minimizes selection biases and small-number statistics, compared to smaller, often serendipitously discovered, samples. Moreover, using the WFC provides information on the field around the lens, higher S/N and a better understood PSF, compared with the HRC, and one retains high spatial resolution through drizzling. The sample of galaxy mass distributions - determined through this method from the arcs and Einstein ring HST images - will be studied to: {i} measure the smooth mass distribution of the lens galaxies {dark and luminous mass are separated using the HST images and the stellar M/L values derived from a joint stellar-dynamical analysis of each system}; {ii} quantify

  2. Evidence for the Disky Origin of Luminous Virgo Dwarf Ellipticals from the Kinematics of Their Globular Cluster Systems

    NASA Astrophysics Data System (ADS)

    Beasley, Michael A.; Cenarro, A. Javier; Strader, Jay; Brodie, Jean P.

    2009-06-01

    We report evidence for dynamically significant rotation in the globular cluster systems of two luminous Virgo dwarf ellipticals, VCC1261 and VCC1528. Including previous results for VCC1087, the globular cluster systems of all three Virgo dwarf ellipticals studied in detail to date exhibit v rot/σlos>1. Taking the rotation seen in the globular clusters as a maximal disk rotation, and accounting for the possible fading of any hypothetical progenitor galaxy, we find all three dwarf elliptical galaxies (dEs) lie on the r-band Tully-Fisher relation. We argue that these data support the hypothesis that luminous dEs are the remnants of transformed disk galaxies. We also obtained deep, longslit data for the stars in VCC1261 and VCC1528. Both these galaxies show rapid rotation in their inner regions, with spatial scales of ~0.5 kpc. These rotation velocities are surprisingly similar to those seen in the globular cluster systems. At larger radii, we see little rotation in the dEs themselves. Since our longslit data for Virgo dEs extend out to 1-2 effective radii (typical of deep observations), whereas the globular clusters extend out to 4-7 effective radii, we conclude that nondetections of rotation in many luminous dEs may simply be due to a lack of radial coverage in the stellar data, and that globular clusters represent singularly sensitive probes of the dynamics of dEs. Based on these data, we suggest that gas disks are significant sites of globular cluster formation in the early universe. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

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

    SciTech Connect

    Kim, Suk; Rey, Soo-Chang; Lisker, Thorsten; Sohn, Sangmo Tony E-mail: screy@cnu.ac.k

    2010-09-20

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

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

    NASA Astrophysics Data System (ADS)

    Lee, Samuel K.; Ando, Shin'ichiro; Kamionkowski, Marc

    2009-07-01

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

  5. Stellar Imager

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth

    2007-01-01

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

  6. Practical applications of substructuring in shell dynamics

    SciTech Connect

    Sane, A.D.; Bitner, J.L.

    1982-01-01

    Transient dynamic stress analysis of large shell structures is often required in many industrial designs. The asymmetry features of the structure often require a full three dimensional analysis. The difficulties experienced in performing the dynamic analysis of such large and complex structures result from economic feasibility and limitations on the available computer core memory. Substructuring techniques provide a way of overcoming these difficulties. The advantages and features associated with substructuring methods are discussed in general terms. The technique is then applied to perform a transient dynamic analysis of a typical shell structure. The discussion of the example problem focused to highlight the economy, flexibility and the data handling aspects of this method. The example problem demonstrates that this method can be applied with success to a wide range of structural dynamic problems and results in significant cost savings.

  7. Substructure coupling in the frequency domain

    NASA Technical Reports Server (NTRS)

    1985-01-01

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

  8. Stellar Winds

    NASA Astrophysics Data System (ADS)

    Owocki, Stan

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

  9. Composite Octet Searches with Jet Substructure

    SciTech Connect

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

    2012-02-14

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

  10. Star formation and substructure in galaxy clusters

    SciTech Connect

    Cohen, Seth A.; Hickox, Ryan C.; Wegner, Gary A.; Einasto, Maret; Vennik, Jaan

    2014-03-10

    We investigate the relationship between star formation (SF) and substructure in a sample of 107 nearby galaxy clusters using data from the Sloan Digital Sky Survey. Several past studies of individual galaxy clusters have suggested that cluster mergers enhance cluster SF, while others find no such relationship. The SF fraction in multi-component clusters (0.228 ± 0.007) is higher than that in single-component clusters (0.175 ± 0.016) for galaxies with M{sub r}{sup 0.1}<−20.5. In both single- and multi-component clusters, the fraction of star-forming galaxies increases with clustercentric distance and decreases with local galaxy number density, and multi-component clusters show a higher SF fraction than single-component clusters at almost all clustercentric distances and local densities. Comparing the SF fraction in individual clusters to several statistical measures of substructure, we find weak, but in most cases significant at greater than 2σ, correlations between substructure and SF fraction. These results could indicate that cluster mergers may cause weak but significant SF enhancement in clusters, or unrelaxed clusters exhibit slightly stronger SF due to their less evolved states relative to relaxed clusters.

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

    SciTech Connect

    Keeton, Charles R.; Moustakas, Leonidas A.

    2009-07-10

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

  12. NASA EM Followup of LIGO-Virgo Candidate Events

    NASA Technical Reports Server (NTRS)

    Blackburn, Lindy L.

    2011-01-01

    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.

  13. Small-scale Conformity of the Virgo Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Hye-Ran; Lee, Joon Hyeop; Jeong, Hyunjin; Park, Byeong-Gon

    2016-06-01

    We investigate the small-scale conformity in color between bright galaxies and their faint companions in the Virgo Cluster. Cluster member galaxies are spectroscopically determined using the Extended Virgo Cluster Catalog and the Sloan Digital Sky Survey Data Release 12. We find that the luminosity-weighted mean color of faint galaxies depends on the color of adjacent bright galaxy as well as on the cluster-scale environment (gravitational potential index). From this result for the entire area of the Virgo Cluster, it is not distinguishable whether the small-scale conformity is genuine or if it is artificially produced due to cluster-scale variation of galaxy color. To disentangle this degeneracy, we divide the Virgo Cluster area into three sub-areas so that the cluster-scale environmental dependence is minimized: A1 (central), A2 (intermediate), and A3 (outermost). We find conformity in color between bright galaxies and their faint companions (color–color slope significance S ∼ 2.73σ and correlation coefficient {cc}∼ 0.50) in A2, where the cluster-scale environmental dependence is almost negligible. On the other hand, the conformity is not significant or very marginal (S ∼ 1.75σ and {cc}∼ 0.27) in A1. The conformity is not significant either in A3 (S ∼ 1.59σ and {cc}∼ 0.44), but the sample size is too small in this area. These results are consistent with a scenario in which the small-scale conformity in a cluster is a vestige of infallen groups and these groups lose conformity as they come closer to the cluster center.

  14. Small-scale Conformity of the Virgo Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Lee, Hye-Ran; Lee, Joon Hyeop; Jeong, Hyunjin; Park, Byeong-Gon

    2016-06-01

    We investigate the small-scale conformity in color between bright galaxies and their faint companions in the Virgo Cluster. Cluster member galaxies are spectroscopically determined using the Extended Virgo Cluster Catalog and the Sloan Digital Sky Survey Data Release 12. We find that the luminosity-weighted mean color of faint galaxies depends on the color of adjacent bright galaxy as well as on the cluster-scale environment (gravitational potential index). From this result for the entire area of the Virgo Cluster, it is not distinguishable whether the small-scale conformity is genuine or if it is artificially produced due to cluster-scale variation of galaxy color. To disentangle this degeneracy, we divide the Virgo Cluster area into three sub-areas so that the cluster-scale environmental dependence is minimized: A1 (central), A2 (intermediate), and A3 (outermost). We find conformity in color between bright galaxies and their faint companions (color–color slope significance S ˜ 2.73σ and correlation coefficient {cc}˜ 0.50) in A2, where the cluster-scale environmental dependence is almost negligible. On the other hand, the conformity is not significant or very marginal (S ˜ 1.75σ and {cc}˜ 0.27) in A1. The conformity is not significant either in A3 (S ˜ 1.59σ and {cc}˜ 0.44), but the sample size is too small in this area. These results are consistent with a scenario in which the small-scale conformity in a cluster is a vestige of infallen groups and these groups lose conformity as they come closer to the cluster center.

  15. The Dynamical Properties of Virgo Cluster Disk Galaxies

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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. Hα 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.

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

    SciTech Connect

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

    2010-09-01

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

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

    SciTech Connect

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

    1999-07-16

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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  19. Stellar mass and population diagnostics of cluster galaxies

    NASA Astrophysics Data System (ADS)

    Roediger, Joel C.

    2013-12-01

    We conduct a broad investigation about stellar mass and population diagnostics in order to formulate novel constraints related to the formation and evolution of galaxies from a nearby cluster environment. Our work is powered by the use of stellar population models which transform galaxy colours and/or absorption line strengths into estimates of its stellar properties. As input to such models, we assemble an extensive compilation of age and chemical abundance information for Galactic globular clusters. This compilation allows a confident expansion of these models into new regions of parameter space that promise to refine our knowledge of galactic chemical evolution. We then draw upon a state-of-the-art spectroscopic and photometric survey of the Virgo galaxy cluster in order to constrain spatial variations of the stellar ages, metallicities, and masses within its member galaxies, and their dynamical masses. We interpret these data in the context of the histories of star formation, chemical enrichment, and stellar mass assembly to formulate a broad picture of the build-up of this cluster's content over time. In it, the giant early-type galaxies formed through highly dissipational processes at early times that built up most of their stellar mass and drew significant amounts of dark matter within their optical radii. Conversely, dwarf early-types experienced environmental processes that quenched their star formation during either the early stages of cluster assembly or upon infall at later times. Somewhat perplexing is our finding that the internal dynamics of these galaxies are largely explained by their stellar masses. Lastly, Virgo spirals also suffer from their dense environment, through ram pressure stripping and/or tidal harrassment. In addition to quenching, these effects leave an imprint on their internal dynamical evolution too. Late-type spirals exhibit evidence of having ejected significant amounts of baryons from their inner regions, likely via energetic

  20. 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

  1. Damage detection using the eigenparameter decomposition of substructural flexibility matrix

    NASA Astrophysics Data System (ADS)

    Weng, Shun; Zhu, Hong-Ping; Xia, Yong; Mao, Ling

    2013-01-01

    The crack or local damage on a structure reduces the stiffness of the structure, and thus leads to the modification of the dynamic properties. Damage detection is widely performed by comparing the initial modal data of the intact structure with those of the damaged structure. For a large-scale structure, the local damage usually introduces slight change to the global modal data, which makes the local damage difficult to be detected. This paper proposes a new substructuring method for the damage detection of a structure. The global structure is divided into manageable substructures. The modal data measured on the global structure are disassembled for obtaining the independent substructural dynamic flexibility matrices, under the force and displacement compatibility constraints. Thereafter, the substructural flexibility matrix is decomposed into its eigenvalues and eigenvectors to be used as the indicators for damage detection. Since the substructuring method concerns the local area by treating it as an independent structure, the substructural eigenparameters are more sensitive to the local damage than the global eigenparameters. The proposed substructuring method is firstly verified by a laboratory-tested portal frame structure. The location of the artificial cuts can be detected successfully by comparing the change of substructural eigenparameters. The proposed method is then applied to the 600 m tall Guangzhou New TV Tower. As compared with the global eigenparameters, the substructural eigenparameters bear larger changes caused by the local damage and thus are more sensitive to the local damage.

  2. CHEMTRAN and the Interconversion of Chemical Substructure Systems

    ERIC Educational Resources Information Center

    Granito, Charles E.

    1973-01-01

    The need for the interconversion of chemical substructure systems is discussed and CHEMTRAN, a new service, designed especially for creating interconversion programs, is introduced. (7 references) (Author)

  3. Robustness analysis applied to substructure controller synthesis

    NASA Technical Reports Server (NTRS)

    Gonzalez-Oberdoerffer, Marcelo F.; Craig, Roy R., Jr.

    1993-01-01

    The stability and robustness of the controlled system obtained via the substructure control synthesis (SCS) method of Su et al. (1990) were examined using a six-bay truss model, and employing an LQG control design method to obtain controllers for two separate structures. It is found that the assembled controller provides a stability in this instance. A qualitative assessment of the stability robustness of the system with controller designed with the SCS method is provided by obtaining a controller using the complete truss model and comparing the robustness of the corresponding closed-loop systems.

  4. Substructurability: the effect of interface location on a real-time dynamic substructuring test

    PubMed Central

    Neild, S. A.; Lowenberg, M.; Szalai, R.; Krauskopf, B.

    2016-01-01

    A full-scale experimental test for large and complex structures is not always achievable. This can be due to many reasons, the most prominent one being the size limitations of the test. Real-time dynamic substructuring is a hybrid testing method where part of the system is modelled numerically and the rest of the system is kept as the physical test specimen. The numerical–physical parts are connected via actuators and sensors and the interface is controlled by advanced algorithms to ensure that the tested structure replicates the emulated system with sufficient accuracy. The main challenge in such a test is to overcome the dynamic effects of the actuator and associated controller, that inevitably introduce delay into the substructured system which, in turn, can destabilize the experiment. To date, most research concentrates on developing control strategies for stable recreation of the full system when the interface location is given a priori. Therefore, substructurability is mostly studied in terms of control. Here, we consider the interface location as a parameter and study its effect on the stability of the system in the presence of delay due to actuator dynamics and define substructurability as the system’s tolerance to delay in terms of the different interface locations. It is shown that the interface location has a major effect on the tolerable delays in an experiment and, therefore, careful selection of it is necessary. PMID:27616930

  5. Substructural QSAR approaches and topological pharmacophores.

    PubMed Central

    Franke, R; Huebel, S; Streich, W J

    1985-01-01

    For large and diverse data sets, simple QSAR methods based on linear and additive models can no longer be applied. In such cases topological methods using descriptors directly derivable from two-dimensional chemical structures provide a useful alternative. The results of such analyses can be used for lead optimization, to guide biological testing and even aid in the design of novel compounds. Various types of topological descriptors and algorithms are briefly discussed. Which of those is to be selected depends on the objective of the investigation and the properties of the data set. Two new methods, LOGANA and LOCON, are discussed in some more detail. With the help of these methods, substructural patterns ("topological pharmacophores") characteristic of compounds possessing a certain biological property can be evaluated. Both methods are designed in such a way that full use can be made of the data handling capacity of computers while maintaining an optimal impact of the experience of the researcher. They are model-free and do not require any mathematical knowledge. While LOGANA deals with semiquantitative or even qualitative biological data, LOCON can be applied to activity data on a continuous scale. The basic procedure in both cases consists in the stepwise combination of substructural descriptors by the logical operations "and," "or" and "not." With a simple example the utility of the methods is demonstrated. PMID:3905376

  6. Investigation of dwarf galaxies in the Virgo cluster

    SciTech Connect

    Bothun, G.D.; Mould, J.R.; Wirth, A.; Caldwell, N.

    1985-05-01

    We have obtained 21-cm H I observations of a sample of 32 dwarf irregular (dI) and 12 dwarf elliptical (dE) galaxies that are located in the Virgo cluster. Altogether, 18 of 32 DIs were detected in H I, but none of the dEs were detected at a sensitivity level of M/sub Htsi/ = 2--3 x 10/sup 6/ M/sub sun/. The detected dIs have M/sub Htsi/>3 x 10/sup 7/ M/sub sun/. This disparity in H I content between dIs and dEs effectively dispels the possibility that the dEs are presently in a stage of quiescence (hibernation), between bursts of star formation. In order to supplement the 21-cm data, we have acquired optical spectroscopy, CCD images, and infrared photometry for a limited subsample of these dwarfs. The most significant result provided by this additional data is that the dEs, although very H I poor, nevertheless have observed (J-K) colors which indicate somewhat high metallicity, implying some degree of enrichment due to multiple generations of star formation. In contrast, most of the dIs are quite H I rich (with some having fractional H I contents that exceed 30% by mass), yet they are apparently in a quiescent phase, judging by their low central surface brightnesses (<10% of sky) and lack of resolution into obvious regions of star formation. A small gas-poor contingent of dIs have been found but there is no apparent correlation between dI gas content and either their velocity with respect to the Virgo ICM or their position in the cluster. In general, the velocity distribution of the dIs is flat with only a weak peak that corresponds to the mean velocity of the brighter galaxies in Virgo.

  7. Halo Substructure and the Power Spectrum

    NASA Astrophysics Data System (ADS)

    Zentner, Andrew R.; Bullock, James S.

    2003-11-01

    We present a semianalytic model to investigate the merger history, destruction rate, and survival probability of substructure in hierarchically formed dark matter halos and use it to study the substructure content of halos as a function of input primordial power spectrum. For a standard cold dark matter ``concordance'' cosmology (ΛCDM n=1, σ8=0.95) we successfully reproduce the subhalo velocity function and radial distribution profile seen in N-body simulations and determine that the rate of merging and disruption peaks ~10-12 Gyr in the past for Milky Way-like halos, while surviving substructures are typically accreted within the last ~0-8 Gyr. We explore power spectra with normalizations and spectral ``tilts'' spanning the ranges σ8~=1-0.65 and n~=1-0.8, and include a ``running-index'' model with dn/dlnk=-0.03 similar to the best-fit model discussed in the first-year Wilkinson Microwave Anisotropy Probe (WMAP) report. We investigate spectra with truncated small-scale power, including a broken-scale inflation model and three warm dark matter cases with mW=0.75-3.0 keV. We find that the mass fraction in substructure is relatively insensitive to the tilt and overall normalization of the primordial power spectrum. All of the CDM-type models yield projected substructure mass fractions that are consistent with, but on the low side, of published estimates from strong lens systems: f9=0.4%-1.5% (64th percentile) for subhalos smaller than 109 Msolar within projected cylinders of radius r<10 kpc. Truncated models produce significantly smaller fractions, f9=0.02%-0.2% for mW~=1 keV, and are disfavored by lensing estimates. This suggests that lensing and similar probes can provide a robust test of the CDM paradigm and a powerful constraint on broken-scale inflation/warm particle masses, including masses larger than the ~1 keV upper limits of previous studies. We compare our predicted subhalo velocity functions with the dwarf satellite population of the Milky Way. Assuming

  8. Stellar halos and the link to galaxy formation

    NASA Astrophysics Data System (ADS)

    Helmi, Amina

    2016-08-01

    I present a brief overview of how stellar halos may be used to constrain the process of galaxy formation. In particular, streams and substructure in stellar halos trace merger events but can also be used to determine the mass distribution of the host galaxy and hence put constraints on the nature of dark matter. Much of the focus of this contribution is on the Milky Way, but I also present an attempt to understand the kinematics of the globular cluster system of M31.

  9. Substructuring and poroelastic modelling of the intervertebral disc.

    PubMed

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

    2010-05-01

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

  10. 8. Detail showing concrete abutment, showing substructure of bridge, specifically ...

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

    8. Detail showing concrete abutment, showing substructure of bridge, specifically west side of arch and substructure. - Presumpscot Falls Bridge, Spanning Presumptscot River at Allen Avenue extension, 0.75 mile west of U.S. Interstate 95, Falmouth, Cumberland County, ME

  11. Substructure synthesis method for simulating large molecular complexes

    PubMed Central

    Ming, Dengming; Kong, Yifei; Wu, Yinghao; Ma, Jianpeng

    2003-01-01

    This paper reports a computational method for describing the conformational flexibility of very large biomolecular complexes using a reduced number of degrees of freedom. It is called the substructure synthesis method, and the basic concept is to treat the motions of a given structure as a collection of those of an assemblage of substructures. The choice of substructures is arbitrary and sometimes quite natural, such as domains, subunits, or even large segments of biomolecular complexes. To start, a group of low-frequency substructure modes is determined, for instance by normal mode analysis, to represent the motions of the substructure. Next, a desired number of substructures are joined together by a set of constraints to enforce geometric compatibility at the interface of adjacent substructures, and the modes for the assembled structure can then be synthesized from the substructure modes by applying the Rayleigh–Ritz principle. Such a procedure is computationally much more desirable than solving the full eigenvalue problem for the whole assembled structure. Furthermore, to show the applicability to biomolecular complexes, the method is used to study F-actin, a large filamentous molecular complex involved in many cellular functions. The results demonstrate that the method is capable of studying the motions of very large molecular complexes that are otherwise completely beyond the reach of any conventional methods. PMID:12518058

  12. Support Substructures: Support-Induced Part-Level Structural Representation.

    PubMed

    Huang, Shi-Sheng; Fu, Hongbo; Wei, Ling-Yu; Hu, Shi-Min

    2016-08-01

    In this work we explore a support-induced structural organization of object parts. We introduce the concept of support substructures, which are special subsets of object parts with support and stability. A bottom-up approach is proposed to identify such substructures in a support relation graph. We apply the derived high-level substructures to part-based shape reshuffling between models, resulting in nontrivial functionally plausible model variations that are difficult to achieve with symmetry-induced substructures by the state-of-the-art methods. We also show how to automatically or interactively turn a single input model to new functionally plausible shapes by structure rearrangement and synthesis, enabled by support substructures. To the best of our knowledge no single existing method has been designed for all these applications. PMID:26336128

  13. Characterization of T-Even Bacteriophage Substructures

    PubMed Central

    Cummings, Donald J.; Kusy, A. R.; Chapman, V. A.; DeLong, S. S.; Stone, K. R.

    1970-01-01

    T-even bacteriophages were grown and purified in bulk quantities. The protein coats were disrupted into their component substructures by treatment with 67% dimethyl sulfoxide (DMSO). Tail fibers and tubes were purified on glycerol-CsCl-D2O gradients and examined with respect to sedimentation properties, subunit molecular weights, amino acid composition, isoelectric points, and morphology. It was found that intact tail fibers had a sedimentation coefficient of 12 to 13S and that dissociated fibers consisted of three classes of proteins having molecular weights of 150 K ± 10, 42 K ± 4, and 28 K ± 3 daltons. A model was constructed in which the 150-K subunit folded back on itself twice to give a three-stranded rope. Each 150-K subunit then represented a half-fiber and it was proposed that the role of the 42- and 28-K subunits was to hold each half-fiber together as well as serve as a possible link with other substructures. Isoelectric point studies also indicated that there were three different proteins with pI values of 3.5, 5.7, and 8.0. Amino acid analyses indicated that fibers had a composition distinct from other phage substructures. In addition, a striking difference was noted in the content of tryptophan among the phages examined. T4B had three to five times more tryptophan than did T2L, T2H, T4D, and T6. Intact tail tubes had an S20,w of 31 to 38S and dissociated tubes consisted of three proteins of molecular weights 57 K ± 5, 38 K ± 4, and 25 K ± 3 daltons. Based on degradation studies with DMSO, it was proposed that these three proteins were arranged in a helical array yielding the tube structure. Isoelectric point studies indicated that there were three major proteins in the tube whose pI values were 5.1, 5.7, and 8.5. No significant differences were observed in the amino acid content of tubes obtained from all the T-even bacteriophages. Images PMID:5497900

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

    NASA Astrophysics Data System (ADS)

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

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

  15. Exploring dark matter with Milky Way substructure.

    PubMed

    Kuhlen, Michael; Madau, Piero; Silk, Joseph

    2009-08-21

    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

  16. Star-forming Substructure within Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Di Francesco, James

    2013-03-01

    Wide-field far-infrared/submillimeter continuum maps of molecular clouds by the Herschel Space Observatory GBS and HOBYS surveys are revealing the star-forming substructures that lead to star formation in dense gas. In particular, these maps have revealed the central role in clouds of filaments, likely formed through turbulent motions. These filaments appear to be non-isothermal and fragment into cores only when their column densities exceed a stability threshold. Organizations of filament networks suggest the relative role of turbulence and gravity can be traced in different parts of a cloud, and filament intersections may lead to larger amounts of mass flow that form the precursors of high-mass stars or clusters.

  17. Probabilistic Component Mode Synthesis of Nondeterministic Substructures

    NASA Technical Reports Server (NTRS)

    Brown, Andrew M.; Ferri, Aldo A.

    1996-01-01

    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.

  18. A case of poor substructure diagnostics

    NASA Technical Reports Server (NTRS)

    Butler, Thomas G.

    1992-01-01

    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.

  19. The Properties Of The Stellar Nuclei With The Host Galaxy Morphology In The ACSVCS

    NASA Astrophysics Data System (ADS)

    Lee, Hyun-chul

    2012-01-01

    We have revisited the ACS Virgo Cluster Survey (ACSVCS), a Hubble Space Telescope program to obtain ACS/WFC g and z bands imaging for a sample of 100 early-type galaxies in the Virgo Cluster. In this study, we examine 51 nucleated early-type galaxies in the ACSVCS in order to look into the relationship between the photometric and structural properties of stellar nuclei and their host galaxies. We morphologically dissect galaxies into five classes. We note that (1) the stellar nuclei of dwarf early-type galaxies (dS0, dE, and dE,N) are generally fainter and bluer with g > 18.95 and (g-z) < 1.40 compared to some brighter and redder counterparts of the ellipticals (E) and lenticular galaxies (S0), (2) the g-band half-light radii of stellar nuclei of all dwarf early-type galaxies (dS0, dE, and dE,N) are smaller than 20 pc and their average is about 4 pc, and (3) the colors of red stellar nuclei with (g-z) > 1.40 in bright ellipticals and lenticular galaxies are bluer than their host galaxies colors. We also show that most of the unusually RED stellar nuclei with (g-z) > 1.54 in the ACSVCS are the central parts of bright ellipticals and lenticular galaxies.

  20. STELLARATOR INJECTOR

    DOEpatents

    Post, R.F.

    1962-09-01

    A method and means are described for injecting energetic neutral atoms or molecular ions into dense magnetically collimated plasma columns of stellarators and the like in such a manner that the atoms or ions are able to significantly penetrate the column before being ionized by collision with the plasma constituent particles. Penetration of the plasma column by the neutral atoms or molecular ions is facilitated by superposition of two closely spaced magnetic mirrors on the plasma confinement field. The mirrors are moved apart to magnetically sweep plasma from a region between the mirrors and establish a relatively low plasma density therein. By virture of the low density, neutral atoms or molecular ions injected into the region significantly penetrate the plasma column before being ionized. Thereafter, the mirrors are diminished to permit the injected material to admix with the plasma in the remainder of the column. (AEC)

  1. Introduction to stellar evolution

    NASA Astrophysics Data System (ADS)

    Scilla, Degl’Innocenti

    2016-04-01

    This contribution is meant as a first brief introduction to stellar physics. First I shortly describe the main physical processes active in stellar structures then I summarize the most important features during the stellar life-cycle.

  2. Stellar streams around the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Belokurov, Vasily; Koposov, Sergey E.

    2016-02-01

    Using blue horizontal branch (BHB) stars identified in the Dark Energy Survey (DES) Year 1 data, we report the detection of an extended and lumpy stellar debris distribution around the Magellanic Clouds. At the heliocentric distance of the Clouds, overdensities of BHBs are seen to reach at least to ˜30°, and perhaps as far as ˜50° from the Large Magellanic Cloud (LMC). In 3D, the stellar halo is traceable to between 25 and 50 kpc from the LMC. We catalogue the most significant of the stellar substructures revealed, and announce the discovery of a number of narrow streams and diffuse debris clouds. Two narrow streams appear approximately aligned with the Magellanic Clouds' proper motion. Moreover, one of these overlaps with the gaseous Magellanic Stream on the sky. Curiously, two diffuse BHB agglomerations seem coincident with several of the recently discovered DES satellites. Given the enormous size and the conspicuous lumpiness of the LMC's stellar halo, we speculate that the dwarf could easily have been more massive than previously had been assumed.

  3. Flexible substructure online hybrid test system using conventional testing devices

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Nakashima, Masayoshi

    2013-09-01

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

  4. The history of stellar metallicity in a simulated disc galaxy

    NASA Astrophysics Data System (ADS)

    Snaith, O. N.; Bailin, J.; Gibson, B. K.; Bell, E. F.; Stinson, G.; Valluri, M.; Wadsley, J.; Couchman, H.

    2016-03-01

    We explore the chemical distribution of stars in a simulated galaxy. Using simulations of the same initial conditions but with two different feedback schemes (McMaster Unbiased Galaxy Simulations - MUGS - and Making Galaxies in a Cosmological Context - MaGICC), we examine the features of the age-metallicity relation (AMR), and the three-dimensional age-[Fe/H]-[O/Fe] distribution, both for the galaxy as a whole and decomposed into disc, bulge, halo and satellites. The MUGS simulation, which uses traditional supernova feedback, is replete with chemical substructure. This substructure is absent from the MaGICC simulation, which includes early feedback from stellar winds, a modified initial mass function and more efficient feedback. The reduced amount of substructure is due to the almost complete lack of satellites in MaGICC. We identify a significant separation between the bulge and disc AMRs, where the bulge is considerably more metal-rich with a smaller spread in metallicity at any given time than the disc. Our results suggest, however, that identifying the substructure in observations will require exquisite age resolution, of the order of 0.25 Gyr. Certain satellites show exotic features in the AMR, even forming a `sawtooth' shape of increasing metallicity followed by sharp declines which correspond to pericentric passages. This fact, along with the large spread in stellar age at a given metallicity, compromises the use of metallicity as an age indicator, although alpha abundance provides a more robust clock at early times. This may also impact algorithms that are used to reconstruct star formation histories from resolved stellar populations, which frequently assume a monotonically increasing AMR.

  5. Substructure System Identification for Finite Element Model Updating

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  6. Substructuring by Lagrange multipliers for solids and plates

    SciTech Connect

    Mandel, J.; Tezaur, R.; Farhat, C.

    1996-12-31

    We present principles and theoreretical foundation of a substructuring method for large structural problems. The algorithm is preconditioned conjugate gradients on a subspace for the dual problem. The preconditioning is proved asymptotically optimal and the method is shown to be parallel scalable, i.e., the condition number is bounded independently of the number of substructures. For plate problems, a special modification is needed that retains continuity of the displacement solution at substructure crosspoints, resulting in an asymptically optimal method. The results are confirmed by numerical experiments.

  7. The magnetic fields of large Virgo cluster spirals. II

    NASA Astrophysics Data System (ADS)

    Weżgowiec, M.; Urbanik, M.; Beck, R.; Chyży, K. T.; Soida, M.

    2012-09-01

    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 Θ between the velocity vector v and the rotation vector Ω of a galaxy may

  8. Stellar Dynamos

    NASA Astrophysics Data System (ADS)

    Charbonneau, Paul

    This chapter steps finally away from the sun and towards the stars, the idea being to apply the physical insight gained so far to see how much of stellar magnetism can be understood in terms of dynamo action. Dynamo action in the convective core of massive main-sequence stars is first considered and shown viable. For intermediate-mass main-sequence stars the fossil field hypothesis will carry the day, although possible dynamo alternatives are also briefly discussed. The extension of the solar dynamo models investigated in Chap. 3 (10.1007/978-3-642-32093-4_3) to other solar-type stars will first take us through an important detour in first having to understand rotational evolution in response to angular momentum loss in a magnetized wind. Dynamo action in fully convective stars comes next, and the chapter closes with an overview of the situation for pre- and post-main-sequence stars and compact objects, leading finally to the magnetic fields of galaxies and beyond.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  10. Creep induced substructures in titanium aluminide

    NASA Astrophysics Data System (ADS)

    Cerreta, Ellen Kathleen

    Many investigations have examined the creep properties of titanium aluminides. Attempts to classify observed behaviors with existing models for high temperature deformation have been met with limited success. Several researchers have shown that an understanding of substructural evolution in the early stages of the creep curve may offer insight into the mechanisms, which control the rate of deformation. Creep deformation has been shown to include twinning, recrystallization, grain boundary sliding, ordinary and super dislocation activity, and faulting depending on the microstructure of the alloy and testing conditions. However, the environments that these alloys are likely to be exposed to are not similar to the test conditions in the literature. Furthermore the emphasis of much of the research into this group of alloys has been on the effects of microstructure particularly, the volume fraction of lamellar phase and ternary elemental additions. With all of these studies little information is available on the deformation behavior of the gamma phase. The alloys in these studies are mostly composed of the gamma phase and yet its creep behavior is not well understood. For this reason single phase binary gamma titanium aluminides were investigated in this study. To understand the effects of aluminum, interstitial oxygen content, and stress on creep, five alloys of varying Al concentrations and interstitial oxygen contents were deformed at temperatures ranging from 700--800°C and at stresses of 150, 200, and 250MPa. Full creep curves were developed under these conditions and phenomenological parameters for creep were calculated from these data. Additional tests were interrupted during primary and secondary creep at 760°C. Specimens from the interrupted tests as well as from the as-processed materials were examined optically and by TEM. Creep data and the microscopy were analyzed in concert to determine rate-controlling mechanisms for creep. Evolution of the substructure

  11. Discovery of a Nova in the Virgo Galaxy M100

    NASA Astrophysics Data System (ADS)

    Ferrarese, Laura; Livio, Mario; Freedman, Wendy; Saha, Abhijit; Stetson, Peter B.; Ford, Holland C.; Hill, Robert J.; Madore, Barry F.

    1996-09-01

    We present the V and I light curves of a nova discovered in the disk of the spiral galaxy M100, located in the Virgo Cluster. In spite of the fact that the light curve is not well sampled around maximum light and the reddening to the nova is not accurately known, by adopting the maximum magnitude versus rate of decline relation by Della Valle & Livio we derive a distance modulus to M100 of mu 0 ~31.0 +/- 0.3 mag, fully consistent with the Cepheid distance modulus of 31.04 +/- 0.17 mag found by Ferrarese et al. from the same set of HST/WFPC2 data.

  12. Two Isolated H I Clouds in the Virgo Cluster?

    NASA Astrophysics Data System (ADS)

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

    Seventy years after the start of radio astronomical observations and over 50 years after the first observations of the 21 cm H I line, a seemingly 'routine' H I survey at Jodrell Bank of an already thoroughly studied part of the local Universe -- the Virgo Cluster -- has yielded a surprising result: the detection of what appear to be two isolated H I clouds in the cluster, without optical counterparts, with H I masses of about 108 Msun (for an assumed distance of 16 Mpc) and angular sizes of about 4' to 6 arcmin, or 20--30 kpc, estimated from follow-up Arecibo H I observations. Their estimated peak H I column density of 4×1019 atoms/cm2 may be too low for star formation. H I synthesis observations and deep CCD imaging are planned of these objects.

  13. The spatial evolution of stellar structures in the LMC/SMC

    NASA Astrophysics Data System (ADS)

    Bastian, Nate; Gieles, Mark; Ercolano, Barbara; Gutermuth, Robert

    2009-03-01

    We present an analysis of the spatial distribution of various stellar populations within the Large and Small Magellanic Clouds. We use optically selected stellar samples with mean ages between ~9 and ~1000 Myr, and existing stellar cluster catalogues to investigate how stellar structures form and evolve within the LMC/SMC. We use two statistical techniques to study the evolution of structure within these galaxies, the Q-parameter and the two-point correlation function (TPCF). In both galaxies we find the stars are born with a high degree of substructure (i.e. are highly fractal) and that the stellar distribution approaches that of the “background” population on timescales similar to the crossing times of the galaxy (~ 80 Myr & ~ 150 Myr for the SMC/LMC respectively). By comparing our observations to simple models of structural evolution we find that “popping star clusters” do not significantly influence structural evolution in these galaxies. Instead we argue that general galactic dynamics are the main drivers, and that substructure will be erased in approximately the crossing time, regardless of spatial scale, from small clusters to whole galaxies. This can explain why many young Galactic clusters have high degrees of substructure, while others are smooth and centrally concentrated. We conclude with a general discussion on cluster “infant mortality”, in an attempt to clarify the time/spatial scales involved.

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

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

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

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

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

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

  16. Substructure view of the Young's Bay Bridge, view looking east, ...

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

    Substructure view of the Young's Bay Bridge, view looking east, north side of the bascule trusswork - Old Young's Bay Bridge, Spanning Young's Bay at Milepoint 6.89 on Warrenton-Astoria Highway (Highway No. 9), Astoria, Clatsop County, OR

  17. EAGLE CREEK BRIDGE, EAST ELEVATION, SUBSTRUCTURE DETAIL LOOKING 333 DEGREES ...

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

    EAGLE CREEK BRIDGE, EAST ELEVATION, SUBSTRUCTURE DETAIL LOOKING 333 DEGREES NORTH-NORTHWEST - Historic Columbia River Highway, Eagle Creek Bridge, Spanning Eagle Creek on Historic Columbia River Highway, Troutdale, Multnomah County, OR

  18. Substructure Main Bridge, Pier A Huey P. Long ...

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

    Substructure - Main Bridge, Pier A - Huey P. Long Bridge, Spanning Mississippi River approximately midway between nine & twelve mile points upstream from & west of New Orleans, Jefferson, Jefferson Parish, LA

  19. Substructure Main Bridge, River Pier IV Huey P. ...

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

    Substructure - Main Bridge, River Pier IV - Huey P. Long Bridge, Spanning Mississippi River approximately midway between nine & twelve mile points upstream from & west of New Orleans, Jefferson, Jefferson Parish, LA

  20. Substructure Main Bridge, River Piers I, II, III & ...

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

    Substructure - Main Bridge, River Piers I, II, III & IV - Huey P. Long Bridge, Spanning Mississippi River approximately midway between nine & twelve mile points upstream from & west of New Orleans, Jefferson, Jefferson Parish, LA

  1. 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

  2. 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

  3. Detail view of Fanno Creek trestle, showing trestle substructure, view ...

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

    Detail view of Fanno Creek trestle, showing trestle substructure, view looking north - Oregon Electric Railroad, Fanno Creek Trestle, Garden Home to Wilsonville Segment, Milepost 34.7, Garden Home, Washington County, OR

  4. 22. VIEW OF FIXED SPAN SUBSTRUCTURE, EAST SPAN, SHOWING CANTILEVEREDBEAM ...

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

    22. VIEW OF FIXED SPAN SUBSTRUCTURE, EAST SPAN, SHOWING CANTILEVERED-BEAM SIDEWALK SUPPORTS, LONGITUDINAL GIRDER AND TRANSVERSE ROADBED BEAMS, LOOKING SOUTHEAST - Congress Street Bascule Bridge, Spanning Fort Point Channel at Congress Street, Boston, Suffolk County, MA

  5. Substructure view illustrating the continuous concrete Tbeams, piers, sidewalk brackets ...

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

    Substructure view illustrating the continuous concrete T-beams, piers, sidewalk brackets and arched longitudinal beams - A Canal Bridge, Spanning the A Canal on Wall Street, Klamath Falls, Klamath County, OR

  6. 8. View of substructure showing the lower chord of the ...

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

    8. View of substructure showing the lower chord of the Howe truss, flared board-and-batten siding, and pier configuration - Drift Creek Bridge, Spanning Drift Creek on Drift Creek County Road, Lincoln City, Lincoln County, OR

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  8. A VERY LARGE ARRAY RADIO SURVEY OF EARLY-TYPE GALAXIES IN THE VIRGO CLUSTER

    SciTech Connect

    Capetti, Alessandro; Kharb, Preeti; Axon, David J.; Merritt, David; Baldi, Ranieri D.

    2009-12-15

    We present the results of an 8.4 GHz Very Large Array radio survey of early-type galaxies extracted from the sample selected by Cote and collaborators for the Advanced Camera for Surveys Virgo Cluster Survey. The aim of this survey is to investigate the origin of radio emission in early-type galaxies and its link with the host properties in an unexplored territory toward the lowest levels of both radio and optical luminosities. Radio images, available for all 63 galaxies with B {sub T} < 14.4, show the presence of a compact radio source in 12 objects, with fluxes spanning from 0.13 mJy to 2700 mJy. The remaining 51 galaxies, undetected at a flux limit of {approx}0.1 mJy, have radio luminosities L {approx}< 4 x 10{sup 18} W Hz{sup -1}. The fraction of radio-detected galaxies are a strong function of stellar mass, in agreement with previous results: none of the 30 galaxies with M {sub *} < 1.7 x 10{sup 10} M {sub sun} is detected, while 8 of the 11 most massive galaxies have radio cores. There appears to be no simple relation between the presence of a stellar nucleus and radio emission. In fact, we find radio sources associated with two nucleated galaxies, but the majority of nucleated objects are not a radio emitter above our detection threshold. A multiwavelength analysis of the active galactic nucleus (AGN) emission, combining radio and X-ray data, confirms the link between optical surface brightness profile and radio loudness in the sense that the bright core galaxies are associated with radio-loud AGNs, while non-core galaxies host radio-quiet AGNs. Not all radio-detected galaxies have an X-ray nuclear counterpart (and vice versa). A complete census of AGNs (and supermassive black holes, SMBHs) thus requires observations, at least, in both bands. Nonetheless, there are massive galaxies in the sample, expected to host a large SMBH (M {sub BH} {approx} 10{sup 8} M {sub sun}), whose nuclear emission eludes detection despite their proximity and the depth and the

  9. Dark matter and IMF normalization in Virgo dwarf early-type galaxies

    NASA Astrophysics Data System (ADS)

    Tortora, C.; La Barbera, F.; Napolitano, N. R.

    2016-01-01

    In this work, we analyse the dark matter (DM) fraction, fDM, and mass-to-light ratio mismatch parameter, δIMF (computed with respect to a Milky Way-like initial mass function), for a sample of 39 dwarf early-type galaxies in the Virgo cluster. Both fDM and δIMF are estimated within the central (one effective radius) galaxy regions, with a Jeans dynamical analysis that relies on galaxy velocity dispersions, structural parameters, and stellar mass-to-light ratios from the SMAKCED survey. In this first attempt to constrain, simultaneously, the initial mass function (IMF) normalization and the DM content, we explore the impact of different assumptions on the DM model profile. On average, for an Navarro, Frenk & White (NFW) profile, the δIMF is consistent with a Chabrier-like normalization ({δ _IMF}˜ 1), with {f_DM}˜ 0.35. One of the main results of this work is that for at least a few systems the δIMF are heavier than the Milky Way-like value (i.e. either top- or bottom-heavy). When introducing tangential anisotropy, larger δIMF and smaller fDM are derived. Adopting a steeper concentration-mass relation than that from simulations, we find lower δIMF ( ≲ 1) and larger fDM. A constant M/L profile with null fDM gives the heaviest δIMF (˜2). In the MONDian framework, we find consistent results to those for our reference NFW model. If confirmed, the large scatter of δIMF for dEs would provide (further) evidence for a non-universal IMF in early-type systems. On average, our reference fDM estimates are consistent with those found for low-σe (˜ 100 km s^{-1}) early-type galaxies (ETGs). Furthermore, we find fDM consistent with values from the SMAKCED survey, and find a double-value behaviour of fDM with stellar mass, which mirrors the trend of dynamical M/L and global star formation efficiency (from abundance matching estimates) with mass.

  10. Using Network Methodology to Infer Population Substructure

    PubMed Central

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

    2015-01-01

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

  11. Finding Nonoverlapping Substructures of a Sparse Matrix

    SciTech Connect

    Pinar, Ali; Vassilevska, Virginia

    2005-08-11

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  13. Data analysis methods for non-Gaussian, nonstationary and nonlinear features and their application to VIRGO

    NASA Astrophysics Data System (ADS)

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

    2003-09-01

    The commissioning of the VIRGO central interferometer occasioned the implementation and tests of various algorithms for the characterization of the non-Gaussianity, non-stationarity and non-linearity of the dark fringe data. This library of prototypes will serve as groundwork for the near commissioning of VIRGO (full scale). We make a summary of the activities on that subject including the description of the selected algorithms and some results obtained with the data of the engineering runs.

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

    SciTech Connect

    Abramson, Anne; Kenney, Jeffrey D. P. E-mail: jeff.kenney@yale.edu

    2014-03-01

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

  15. Cold Dark Matter Substructure and Galactic Disks I: Morphological Signatures of Hierarchical SatelliteAccretion

    SciTech Connect

    Kazantzidis, Stelios; Bullock, James S.; Zentner, Andrew R.; Kravtsov, Andrey V.; Moustakas, Leonidas A.

    2007-12-03

    We conduct a series of high-resolution, fully self-consistent dissipation less N-body simulations to investigate the cumulative effect of substructure mergers onto thin disk galaxies in the context of the {Lambda}CDM paradigm of structure formation. Our simulation campaign is based on a hybrid approach combining cosmological simulations and controlled numerical experiments. Substructure mass functions, orbital distributions, internal structures, and accretion times are culled directly from cosmological simulations of galaxy-sized cold dark matter (CDM) halos. We demonstrate that accretions of massive subhalos onto the central regions of host halos, where the galactic disk resides, since z {approx} 1 should be common occurrences. In contrast, extremely few satellites in present-day CDM halos are likely to have a significant impact on the disk structure. This is due to the fact that massive subhalos with small orbital pericenters that are most capable of strongly perturbing the disk become either tidally disrupted or suffer substantial mass loss prior to z = 0. One host halo merger history is subsequently used to seed controlled N-body experiments of repeated satellite impacts on an initially-thin Milky Way-type disk galaxy. These simulations track the effects of six dark matter substructures, with initial masses in the range {approx} (0.7-2) x 10{sup 10} M{sub {circle_dot}} ({approx} 20-60% of the disk mass), crossing the disk in the past {approx} 8 Gyr. We show that these accretion events produce several distinctive observational signatures in the stellar disk including: a long-lived, low-surface brightness, ring-like feature in the outskirts; a significant flare; a central bar; and faint filamentary structures that (spuriously) resemble tidal streams in configuration space. The final distribution of disk stars exhibits a complex vertical structure that is well-described by a standard 'thin-thick' disk decomposition, where the 'thick' disk component has emerged

  16. Alignments of the galaxies in and around the Virgo cluster with the local velocity shear

    SciTech Connect

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

    2014-08-10

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  18. Stellar Metamorphosis:

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [TOP LEFT AND RIGHT] The Hubble Space Telescope's Wide Field and Planetary Camera 2 has captured images of the birth of two planetary nebulae as they emerge from wrappings of gas and dust, like butterflies breaking out of their cocoons. These images highlight a fleeting phase in the stellar burnout process, occurring just before dying stars are transformed into planetary nebulae. The left-hand image is the Cotton Candy nebula, IRAS 17150-3224; the right-hand image, the Silkworm nebula, IRAS 17441-2411. Called proto-planetary nebulae, these dying stars have been caught in a transition phase between a red giant and a planetary nebula. This phase is only about 1,000 years long, very short in comparison to the 1 billion-year lifetime of a star. These images provide the earliest snapshots of the transition process. Studying images of proto-planetary nebulae is important to understanding the process of star death. A star begins to die when it has exhausted its thermonuclear fuel - hydrogen and helium. The star then becomes bright and cool (red giant phase) and swells to several tens of times its normal size. It begins puffing thin shells of gas off into space. These shells become the star's cocoon. In the Hubble images, the shells are the concentric rings seen around each nebula. But the images also reveal the nebulae breaking out from those shells. The butterfly-like wings of gas and dust are a common shape of planetary nebulae. Such butterfly shapes are created by the 'interacting winds' process, in which a more recent 'fast wind' - material propelled by radiation from the hot central star - punches a hole in the cocoon, allowing the nebula to emerge. (This 'interacting wind' theory was first proposed by Dr. Sun Kwok to explain the origin of planetary nebulae, and has been subsequently proven successful in explaining their shapes.) The nebulae are being illuminated by light from the invisible central star, which is then reflected toward us. We are viewing the nebulae

  19. Substructure and Dynamics of the Fornax Cluster

    NASA Astrophysics Data System (ADS)

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

    2001-02-01

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

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

    SciTech Connect

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

    2010-02-01

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

  1. The Next Generation Virgo Cluster Survey. X. Properties of Ultra-compact Dwarfs in the M87, M49, and M60 Regions.

    NASA Astrophysics Data System (ADS)

    Liu, Chengze; Peng, Eric W.; Côté, Patrick; Ferrarese, Laura; Jordán, Andrés; Mihos, J. Christopher; Zhang, Hong-Xin; Muñoz, Roberto P.; Puzia, Thomas H.; Lançon, Ariane; Gwyn, Stephen; Cuillandre, Jean-Charles; Blakeslee, John P.; Boselli, Alessandro; Durrell, Patrick R.; Duc, Pierre-Alain; Guhathakurta, Puragra; MacArthur, Lauren A.; Mei, Simona; Sánchez-Janssen, Rubén; Xu, Haiguang

    2015-10-01

    We use imaging from the Next Generation Virgo cluster Survey (NGVS) to present a comparative study of ultra-compact dwarf (UCD) galaxies associated with three prominent Virgo sub-clusters: those centered on the massive red-sequence galaxies M87, M49, and M60. We show how UCDs can be selected with high completeness using a combination of half-light radius and location in color-color diagrams (u*iKs or u*gz). Although the central galaxies in each of these sub-clusters have nearly identical luminosities and stellar masses, we find large differences in the sizes of their UCD populations, with M87 containing ˜3.5 and 7.8 times more UCDs than M49 and M60, respectively. The relative abundance of UCDs in the three regions scales in proportion to sub-cluster mass, as traced by X-ray gas mass, total gravitating mass, number of globular clusters (GCs), and number of nearby galaxies. We find that the UCDs are predominantly blue in color, with ˜85% of the UCDs having colors similar to blue GCs and stellar nuclei of dwarf galaxies. We present evidence that UCDs surrounding M87 and M49 may follow a morphological sequence ordered by the prominence of their outer, low surface brightness envelope, ultimately merging with the sequence of nucleated low-mass galaxies, and that envelope prominence correlates with distance from either galaxy. Our analysis provides evidence that tidal stripping of nucleated galaxies is an important process in the formation of UCDs.

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

    NASA Astrophysics Data System (ADS)

    Popping, A.; Braun, R.

    2011-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Stonkutė, E.; Tautvaišienė, G.; Nordström, B.; Ženovienė, R.

    2012-05-01

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

  4. The stability of stellar discs in Milky Way-sized dark matter haloes

    NASA Astrophysics Data System (ADS)

    Yurin, Denis; Springel, Volker

    2015-09-01

    We employ an improved methodology to insert live stellar discs into high-resolution dark matter simulations of Milky Way-sized haloes, allowing us to investigate the fate of thin stellar discs in the tumultuous environment of cold dark matter structures. We study a set of eight different haloes, drawn from the Aquarius simulation project, in which stellar discs are adiabatically grown with a prescribed structure, and then allowed to self-consistently evolve. The initial velocity distribution is set-up in very good equilibrium with the help of the GALIC code. We find that the residual triaxiality of the haloes leads to significant disc tumbling, qualitatively confirming earlier work. We show that the disc turning motion is unaffected by structural properties of the galaxies such as the presence or absence of a bulge or bar. In typical Milky Way-sized dark matter haloes, we expect an average turning of the discs by about 40°between z = 1 and 0, over the course of 7.6 Gyr. We also investigate the impact of the discs on substructures, and conversely, the disc heating rate caused by the dark matter halo substructures. The presence of discs reduces the central subhalo abundance by a about a factor of 2, due to an increased evaporation rate by gravitational shocks from disc passages. We find that substructures are important for heating the outer parts of stellar discs but do not appear to significantly affect their inner parts.

  5. Gamma-ray probes of dark matter substructure

    SciTech Connect

    Campbell, Sheldon

    2014-06-24

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

  6. Quantifying the Significance of Substructure in Coronal Loops

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  7. Substructure location and size effects on decentralized model updating

    NASA Astrophysics Data System (ADS)

    Dong, Xinjun; Zhu, Dapeng; Wang, Yang

    2015-04-01

    To improve the simulation accuracy of the finite-element (FE) model of an as-built structure, measurement data from the actual structure can be utilized for updating the model parameters, which is termed as FE model updating. During the past few decades, most efforts on FE model updating intend to update the entire structure model altogether, while using measurement data from sensors installed throughout the structure. When applied on large and complex structural models, the typical model updating approaches may fail due to computational challenges and convergence issues. In order to reduce the computational difficulty, this paper studies a decentralized FE model updating approach that intends to update one substructure at a time. The approach divides the entire structure into a substructure (currently being instrumented and updated) and the residual structure. The Craig-Bampton transform is adopted to condense the overall structural model. The optimization objective is formulated to minimize the modal dynamic residuals from the eigenvalue equations in structural dynamics involving natural frequencies and mode shapes. This paper investigates the effects of different substructure locations and sizes on updating performance. A space frame example, which is based on an actual pedestrian bridge on Georgia Tech campus, is used to study the substructure location and size effects. Keywords: substructure

  8. History of Stellar Interferometry

    NASA Technical Reports Server (NTRS)

    Lawson, Peter R.

    2004-01-01

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

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

    NASA Technical Reports Server (NTRS)

    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

    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.

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

    SciTech Connect

    Wang Qiushi; Peng, Eric W.; Blakeslee, John P.; Cote, Patrick; Ferrarese, Laura; Jordan, Andres; Mei, Simona; West, Michael J.

    2013-06-01

    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.

  11. Kinematic and Spatial Substructure in NGC 2264

    NASA Astrophysics Data System (ADS)

    Tobin, John J.; Hartmann, Lee; Fűrész, Gabor; Hsu, Wen-Hsin; Mateo, Mario

    2015-04-01

    We present an expanded kinematic study of the young cluster NGC 2264 based upon optical radial velocities measured using multi-fiber echelle spectroscopy at the 6.5 m MMT and Magellan telescopes. We report radial velocities for 695 stars, of which approximately 407 stars are confirmed or very likely members. Our results more than double the number of members with radial velocities from Fűrész et al., resulting in a much better defined kinematic relationship between the stellar population and the associated molecular gas. In particular, we find that there is a significant subset of stars that are systematically blueshifted with respect to the molecular (13CO) gas. The detection of Lithium absorption and/or infrared excesses in this blueshifted population suggests that at least some of these stars are cluster members; we suggest some speculative scenarios to explain their kinematics. Our results also more clearly define the redshifted population of stars in the northern end of the cluster; we suggest that the stellar and gas kinematics of this region are the result of a bubble driven by the wind from O7 star S Mon. Our results emphasize the complexity of the spatial and kinematic structure of NGC 2264, important for eventually building up a comprehensive picture of cluster formation. Observations reported here were obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  12. Comparative properties of Virgo Cluster dwarf irregulars and spirals

    NASA Technical Reports Server (NTRS)

    Hoffman, G. Lyle; Helou, George; Salpeter, E. E.

    1988-01-01

    The optical and neutral hydrogen data for all spiral and late-type dwarf irregular galaxies in the Virgo Cluster catalog are analyzed. In particular, the continuity of optical properties, hydrogen masses, and dynamical properties are examined as functions of morphology and luminosity from the largest spirals through the faintest dwarfs (omitting blue compact dwarf galaxies); the effects of environment on H I content; mass segregation; and the Tully-Fisher relations. The spiral plus dwarf sample forms a continuous but nonhomologous sequence. Indicative dynamical mass-to-light ratios are relatively constant throughout; hydrogen mass-to-light ratios show only a slight increase with decreasing luminosity. The Tully-Fisher relations extend with continuous slope from spirals through dwarfs. The dwarfs show some evidence of ram-pressure stripping by the intracluster medium, but as a group do not seem to be stripped more heavily than spirals. There is no evidence of mass segregation even for the very low mass dwarfs versus giant spirals.

  13. Warp Characteristics of Spiral Galaxies in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Bae, Hyun-Jin; Chung, A.; Kim, S. S.; Jozsa, G. I. G.; Yoon, S.

    2012-01-01

    We present the warp characteristics of 22 spiral galaxies in the Virgo cluster based on their VLA HI datacubes with unprecedented precision. The tilted-ring modeling method is used to examine kinematic properties of the HI disks including the inclination and position angle. The main results are as follows. First, 17 out of the 19 (89.5 %) successfully-modeled galaxies exhibit either weak or strong warps, indicating that the warps are very common not only galaxies in isolation but ones in dense environments. Second, the warp strength decreases with increasing dynamical mass, supporting the notion that the warps are primarily controlled by dark matter halos. Last, the warp characteristics in our sample are distinct from those of isolated galaxies, in that the warps in our sample varies a great deal in inclination, but little in position angle. This implies that in dense environments, the main driver of the disk warps is most likely the galactic tidal interaction, rather than other explanations such as the cosmic infall scenario.

  14. A Full Census of Intracluster Light in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Krick, Jessica; Desai, V.; Murphy, E.; Bridge, C.; Mihos, C.; Rudick, C.; Neill, J.; Surace, J.; Kenney, J.; van Gorkom, J.; Carlberg, R.

    2010-01-01

    We have begun a new multi-wavelength project to explore the interaction history and evolution of galaxies in clusters. As a cluster hierarchically grows, gravitational and gas dynamical effects (e.g. galaxy-galaxy interactions, harassment, ram pressure stripping, starvation) are capable of removing stars, gas, and dust from galaxies. The intracluster light (ICL) therefore holds a record of the growth history of the cluster. We intend to explore a full mass census of the intracluster light in the central degree of the Virgo cluster by looking at the stars, dust, and gas components. We have recently been awarded Spitzer Warm IRAC 3.6 and 4.5micron data to compare with the published V-band imaging of Mihos et al. 2005. In addition we have discovered the first ever detected ICL feature in the UV with GALEX. This feature is ˜50 kpc long, ˜40 kpc from the interacting galaxy pair NGC4438/4435, and is spatially coincident with a tidal plume detected in deep V -band imaging. The presence of this feature in the UV is extremely surpising because previous optical analyses indicate that IC stars are old, and should therefore be undetected in the FUV. Spectral energy distribution(SED) fitting of the GALEX and optical data of this plume reveal not only a population of young IC stars but also significant amounts of IC dust.

  15. HUNDRED THOUSAND DEGREE GAS IN THE VIRGO CLUSTER OF GALAXIES

    SciTech Connect

    Sparks, W. B.; Pringle, J. E.; Martin, R.; Cracraft, M.; Carswell, R. F.; Donahue, M.; Voit, M.; Manset, N.; Hough, J. H.

    2012-05-01

    The physical relationship between low-excitation gas filaments at {approx}10{sup 4} K, seen in optical line emission, and diffuse X-ray emitting coronal gas at {approx}10{sup 7} K in the centers of many galaxy clusters is not understood. It is unclear whether the {approx}10{sup 4} K filaments have cooled and condensed from the ambient hot ({approx}10{sup 7} K) medium or have some other origin such as the infall of cold gas in a merger, or the disturbance of an internal cool reservoir of gas by nuclear activity. Observations of gas at intermediate temperatures ({approx}10{sup 5}-10{sup 6} K) can potentially reveal whether the central massive galaxies are gaining cool gas through condensation or losing it through conductive evaporation and hence identify plausible scenarios for transport processes in galaxy cluster gas. Here we present spectroscopic detection of {approx}10{sup 5} K gas spatially associated with the H{alpha} filaments in a central cluster galaxy, M87, in the Virgo Cluster. The measured emission-line fluxes from triply ionized carbon (C IV 1549 A) and singly ionized helium (He II 1640 A) are consistent with a model in which thermal conduction determines the interaction between hot and cold phases.

  16. A Dark Hydrogen Cloud in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Minchin, Robert; Davies, Jonathan; Disney, Michael; Boyce, Peter; Garcia, Diego; Jordan, Christine; Kilborn, Virginia; Lang, Robert; Roberts, Sarah; Sabatini, Sabina; van Driel, Wim

    2005-03-01

    VIRGOHI 21 is an H I source detected in the Virgo Cluster survey of Davies et al. that has a neutral hydrogen mass of 108 Msolar and a velocity width of ΔV20=220 km s-1. From the Tully-Fisher relation, a galaxy with this velocity width would be expected to be 12 mag or brighter; however, deep CCD imaging has failed to turn up a counterpart down to a surface brightness level of 27.5 B mag arcsec-2. The H I observations show that it is extended over at least 16 kpc, which, if the system is bound, gives it a minimum dynamical mass of ~1011 Msolar and a mass-to-light ratio of Mdyn/LB>500 Msolar/Lsolar. If it is tidal debris, then the putative parents have vanished; the remaining viable explanation is that VIRGOHI 21 is a dark halo that does not contain the expected bright galaxy. This object was found because of the low column density limit of our survey, a limit much lower than that achieved by all sky H I surveys such as those carried out at Parkes and Jodrell Bank. Further such sensitive surveys might turn up a significant number of the dark matter halos predicted by galaxy formation models.

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    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 [νmax and Δν 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 (νmax) 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.

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

    SciTech Connect

    Roy, Nirupam

    2010-11-01

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

  19. Shock induced deformation substructures in a copper bicrystal

    SciTech Connect

    Cao, Fang; Beyerlein, Irene J; Cerreta, Ellen K; Trujillo, Carl P; Gray Ill, George T; Sencer, Bulent H

    2008-01-01

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

  20. Functional Group and Substructure Searching as a Tool in Metabolomics

    PubMed Central

    Kotera, Masaaki; McDonald, Andrew G.; Boyce, Sinéad; Tipton, Keith F.

    2008-01-01

    Background A direct link between the names and structures of compounds and the functional groups contained within them is important, not only because biochemists frequently rely on literature that uses a free-text format to describe functional groups, but also because metabolic models depend upon the connections between enzymes and substrates being known and appropriately stored in databases. Methodology We have developed a database named “Biochemical Substructure Search Catalogue” (BiSSCat), which contains 489 functional groups, >200,000 compounds and >1,000,000 different computationally constructed substructures, to allow identification of chemical compounds of biological interest. Conclusions This database and its associated web-based search program (http://bisscat.org/) can be used to find compounds containing selected combinations of substructures and functional groups. It can be used to determine possible additional substrates for known enzymes and for putative enzymes found in genome projects. Its applications to enzyme inhibitor design are also discussed. PMID:18253485

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  2. Infall of nearby galaxies into the Virgo cluster as traced with Hubble space telescope

    SciTech Connect

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

    2014-02-10

    We measured the tip of the red giant branch distances to nine galaxies in the direction to the Virgo cluster using the Advanced Camera for Surveys on the Hubble Space Telescope. These distances put seven galaxies (GR 34, UGC 7512, NGC 4517, IC 3583, NGC 4600, VCC 2037, and KDG 215) in front of Virgo and two galaxies (IC 3023 and KDG 177) likely inside the cluster. Distances and radial velocities of the galaxies situated between us and the Virgo core clearly exhibit the infall phenomenon toward the cluster. In the case of spherically symmetric radial infall, we estimate the radius of the 'zero-velocity surface' to be (7.2 ± 0.7) Mpc, which yields a total mass of the Virgo cluster of (8.0 ± 2.3) × 10{sup 14} M {sub ☉}, in good agreement with its virial mass estimates. We conclude that the Virgo outskirts do not contain significant amounts of dark matter beyond their virial radius.

  3. The first two years of electromagnetic follow-up with advanced LIGO and Virgo

    SciTech Connect

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

    2014-11-10

    We anticipate the first direct detections of gravitational waves (GWs) with Advanced LIGO and Virgo later this decade. Though this groundbreaking technical achievement will be its own reward, a still greater prize could be observations of compact binary mergers in both gravitational and electromagnetic channels simultaneously. During Advanced LIGO and Virgo's first two years of operation, 2015 through 2016, we expect the global GW detector array to improve in sensitivity and livetime and expand from two to three detectors. We model the detection rate and the sky localization accuracy for binary neutron star (BNS) mergers across this transition. We have analyzed a large, astrophysically motivated source population using real-time detection and sky localization codes and higher-latency parameter estimation codes that have been expressly built for operation in the Advanced LIGO/Virgo era. We show that for most BNS events, the rapid sky localization, available about a minute after a detection, is as accurate as the full parameter estimation. We demonstrate that Advanced Virgo will play an important role in sky localization, even though it is anticipated to come online with only one-third as much sensitivity as the Advanced LIGO detectors. We find that the median 90% confidence region shrinks from ∼500 deg{sup 2} in 2015 to ∼200 deg{sup 2} in 2016. A few distinct scenarios for the first LIGO/Virgo detections emerge from our simulations.

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

    NASA Astrophysics Data System (ADS)

    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.; Ballinger, T.; 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.; Bouhou, B.; 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.; Y Chua, S. S.; Y Chung, C. T.; 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.; Dergachev, V.; DeRosa, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Emilio, M. Di Paolo; Di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doravari, S.; Dorsher, S.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Endrőczi, G.; Engel, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Farr, B. F.; Favata, M.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Foley, S.; Forsi, E.; Forte, L. A.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M. A.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P. J.; Fyffe, M.; Gair, J.; Galimberti, M.; Gammaitoni, L.; Garcia, J.; Garufi, F.; Gáspár, M. E.; Gelencser, G.; Gemme, G.; Genin, E.; Gennai, A.; Gergely, L. Á.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Griffo, C.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gupta, R.; Gustafson, E. K.; Gustafson, R.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Hardt, A.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Hayau, J.-F.; Heefner, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M. A.; Heng, I. S.; Heptonstall, A. W.; Herrera, V.; Heurs, M.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Hough, J.; Howell, E. J.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Izumi, K.; Jacobson, M.; James, E.; Jang, Y. J.; Jaranowski, P.; Jesse, E.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; 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.; Keitel, D.; Kelley, D.; Kells, W.; Keppel, D. G.; Keresztes, Z.; Khalaidovski, A.; Y Khalili, F.; Khazanov, E. A.; Kim, B. K.; Kim, C.; Kim, H.; Kim, K.; Kim, N.; Kim, Y. M.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kringel, V.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, P.; Kumar, R.; Kurdyumov, R.; Kwee, P.; Lam, P. K.; Landry, M.; Langley, A.; Lantz, B.; Lastzka, N.; Lawrie, C.; Lazzarini, A.; Le Roux, A.; Leaci, P.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Leong, J. R.; Leonor, I.; Leroy, N.; Letendre, N.; Lhuillier, V.; Li, J.; Li, T. G. F.; Lindquist, P. E.; Litvine, V.; Liu, Y.; Liu, Z.; Lockerbie, N. A.; Lodhia, D.; Logue, J.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J.; Lubinski, M.; Lück, H.; Lundgren, A. P.; Macarthur, J.; Macdonald, E.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; Meadors, G. D.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Menéndez, D. F.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mingarelli, C. M. F.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mohan, M.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Morgado, N.; Morgia, A.; Mori, T.; Morriss, S. R.; Mosca, S.; Mossavi, K.; Mours, B.; Mow–Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nash, T.; Naticchioni, L.; Necula, V.; Nelson, J.; Neri, I.; Newton, G.; Nguyen, T.; Nishizawa, A.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E.; Nuttall, L.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Oldenberg, R. G.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Paoletti, R.; Papa, M. A.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Pedraza, M.; Penn, S.; Perreca, A.; Persichetti, G.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pierro, V.; Pihlaja, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Pöld, J.; Postiglione, F.; Poux, C.; Prato, M.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Ramet, C.; Rankins, B.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Roberts, M.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Rodriguez, C.; Rodruck, M.; Rolland, L.; Rollins, J. G.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Röver, C.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Salemi, F.; Sammut, L.; Sandberg, V.; Sankar, S.; Sannibale, V.; Santamaría, L.; Santiago-Prieto, I.; Santostasi, G.; Saracco, E.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R. L.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Seifert, F.; Sellers, D.; Sentenac, D.; Sergeev, A.; Shaddock, D. A.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siemens, X.; Sigg, D.; Simakov, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G. R.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Somiya, K.; Sorazu, B.; Speirits, F. C.; Sperandio, L.; Stefszky, M.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S. E.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szeifert, G.; Tacca, M.; Taffarello, L.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, R.; ter Braack, A. P. M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Tomlinson, C.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C. V.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Tse, M.; Tucker, E.; Ugolini, D.; Vahlbruch, H.; Vajente, G.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van Veggel, A. A.; Vass, S.; Vasuth, M.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A. E.; Vinet, J.-Y.; Vitale, S.; Vocca, H.; Vorvick, C.; Vyatchanin, S. P.; Wade, A.; Wade, L.; Wade, M.; Waldman, S. J.; Wallace, L.; Wan, Y.; Wang, M.; Wang, X.; Wanner, A.; Ward, R. L.; Was, M.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Wiesner, K.; Wilkinson, C.; Willems, P. A.; Williams, L.; Williams, R.; Willke, B.; Wimmer, M.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Wittel, H.; Woan, G.; Wooley, R.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yancey, C. C.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yvert, M.; Zadrożny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, F.; Zhang, L.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.

    2012-08-01

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

  5. Estimation of ADME properties with substructure pattern recognition.

    PubMed

    Shen, Jie; Cheng, Feixiong; Xu, You; Li, Weihua; Tang, Yun

    2010-06-28

    Over the past decade, absorption, distribution, metabolism, and excretion (ADME) property evaluation has become one of the most important issues in the process of drug discovery and development. Since in vivo and in vitro evaluations are costly and laborious, in silico techniques had been widely used to estimate ADME properties of chemical compounds. Traditional prediction methods usually try to build a functional relationship between a set of molecular descriptors and a given ADME property. Although traditional methods have been successfully used in many cases, the accuracy and efficiency of molecular descriptors must be concerned. Herein, we report a new classification method based on substructure pattern recognition, in which each molecule is represented as a substructure pattern fingerprint based on a predefined substructure dictionary, and then a support vector machine (SVM) algorithm is applied to build the prediction model. Therefore, a direct connection between substructures and molecular properties is built. The most important substructure patterns can be identified via the information gain analysis, which could help to interpret the models from a medicinal chemistry perspective. Afterward, this method was verified with two data sets, one for blood-brain barrier (BBB) penetration and the other for human intestinal absorption (HIA). The results demonstrated that the overall predictive accuracies of the best HIA model for the training and test sets were 98.5 and 98.8%, and the overall predictive accuracies of the best BBB model for the training and test sets were 98.8 and 98.4%, which confirmed the reliability of our method. In the additional validations, the predictive accuracies were 94 and 69.5% for the HIA and the BBB models, respectively. Moreover, some of the representative key substructure patterns which significantly correlated with the HIA and BBB penetration properties were also presented. PMID:20578727

  6. A Robust Control Design Framework for Substructure Models

    NASA Technical Reports Server (NTRS)

    Lim, Kyong B.

    1994-01-01

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

  7. System for detecting substructure microfractures and method therefore

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  10. Galaxy Strategy for LIGO-Virgo Gravitational Wave Counterpart Searches

    NASA Astrophysics Data System (ADS)

    Gehrels, Neil; Cannizzo, John K.; Kanner, Jonah; Kasliwal, Mansi M.; Nissanke, Samaya; Singer, Leo P.

    2016-04-01

    In this work we continue a line of inquiry begun in Kanner et al. which detailed a strategy for utilizing telescopes with narrow fields of view, such as the Swift X-ray Telescope (XRT), to localize gravitational wave (GW) triggers from LIGO/Virgo. If one considers the brightest galaxies that produce ˜50% of the light, then the number of galaxies inside typical GW error boxes will be several tens. We have found that this result applies both in the early years of Advanced LIGO when the range was small and the error boxes were large, and will apply in the later years when the error boxes will be small and the range will be large. This strategy has the beneficial property of reducing the number of telescope pointings by a factor of 10-100 compared with tiling the entire error box. Additional galaxy count reduction will come from a GW rapid distance estimate which will restrict the radial slice in search volume. Combining the bright galaxy strategy with a convolution based on anticipated GW localizations, we find that the searches can be restricted to about 18 ± 5 galaxies for 2015, about 23 ± 4 for 2017, and about 11 ± 2 for 2020. This assumes a distance localization at the putative neutron star-neutron star merger range μ for each target year, and these totals are integrated out to the range. Integrating out to the horizon would roughly double the totals. For localizations with r\\ll μ the totals would decrease. The galaxy strategy we present in this work will enable numerous sensitive optical and XRTs with small fields of view to participate meaningfully in searches wherein the prospects for rapidly fading afterglow place a premium on a fast response time.