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Sample records for virgo stellar substructure

  1. Kinematical Clues to the Origin of the Virgo Stellar Stream

    NASA Astrophysics Data System (ADS)

    Yam, William; Carlin, J. L.; Casetti-Dinescu, D. I.; Willett, B. A.; Newberg, H.; Majewski, S. R.; Girard, T. M.

    2012-01-01

    Milky Way stellar substructure has been detected in the Virgo constellation (the so-called Virgo Stellar Stream, or VSS; and the possibly associated Virgo Overdensity) using a variety of different stellar tracers over a large (perhaps 100-1000 square degrees) area of sky, but the nature of the overdensities has yet to be determined. Fortuitously, one of Kapteyn's Selected Areas (SAs) making up our deep proper motion survey (Casetti-Dinescu et al. 2006) intersects this structure. Our data in this field, denoted SA 103, span 40x40 arcminutes centered at (RA, Dec) = (178.8, -0.6). We supplemented our proper motions with multifiber spectroscopy. VSS members are selected via kinematics (radial velocities and proper motions), as well as position on the CMD. Theoretical isochrones were fitted to the identified members in the CMD to obtain distance. We find 14 candidates with properties consistent with membership in the VSS (based in part on comparison to previous detections), and use the mean 3-D kinematics of these members to derive an orbit for the VSS debris. We show that Virgo debris is near the pericenter of a high-eccentricity, plunging orbit similar to that found by Casetti-Dinescu et al. (2009) based on one VSS RR-Lyrae star. We explore possible progenitors for the VSS by integrating an orbit with the measured kinematics and comparing this to known Milky Way satellites and stellar substructures. At least three structures (a dwarf galaxy, globular cluster, and at least one diffuse stellar overdensity) are identified whose properties suggest that they may be related to the VSS. An n-body simulation of a Sagittarius-sized dwarf galaxy on our derived orbit produces a remnant with similar properties to the extant VSS detections, supporting the idea that the VSS is the remains of a tidally disrupted dwarf galaxy. Supported by NSF grants AST 09-37523, AST 11-15146, AST 10-09670.

  2. THE NEXT GENERATION VIRGO CLUSTER SURVEY. XIX. TOMOGRAPHY OF MILKY WAY SUBSTRUCTURES IN THE NGVS FOOTPRINT

    SciTech Connect

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

    2016-03-10

    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 deg{sup 2} 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.

  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. Spectroscopy of Bright Quest RR Lyrae Stars: Velocity Substructures Toward Virgo

    NASA Astrophysics Data System (ADS)

    Vivas, A. Katherina; Jaffé, Yara L.; Zinn, Robert; Winnick, Rebeccah; Duffau, Sonia; Mateu, Cecilia

    2008-10-01

    Using a sample of 43 bright (V < 16.1, distance <13 kpc) RR Lyrae stars (RRLS) from the QUasar Equatorial Survey with spectroscopic radial velocities and metallicities, we find that several separate halo substructures contribute to the Virgo overdensity (VOD). While there is little evidence of a halo substructure in the spatial distribution of these stars, their distribution in radial velocity reveals two moving groups. These results are reinforced when the sample is combined with a sample of blue horizontal branch stars that were identified in the Sloan Digital Sky Survey, and the combined sample provides evidence for one additional moving group. These groups correspond to peaks in the radial velocity distribution of a sample of F-type main-sequence stars that was recently observed in the same direction by the Sloan Extension for Galactic Understanding and Exploration (SEGUE), although in one case the RRLS and F star groups may not lie at the same distance. One of the new substructures has a very narrow range in metallicity, which is more consistent with it being the debris from a destroyed globular cluster than from a dwarf galaxy. A small concentration of stars have radial velocities that are similar to the Virgo Stellar Stream that was identified previously in a fainter sample of RRLS. Our results suggest that this feature extends to distances as short as ~12 kpc, compared to its previous detection at ~19 kpc. None of the new groups and only one star in the sample have velocities that are consistent with membership in the leading tidal stream from the Sagittarius dwarf spheroidal galaxy, which some authors have suggested is the origin of the VOD.

  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. A very dark stellar system lost in Virgo: kinematics and metallicity of SECCO 1 with MUSE

    NASA Astrophysics Data System (ADS)

    Beccari, G.; Bellazzini, M.; Magrini, L.; Coccato, L.; Cresci, G.; Fraternali, F.; de Zeeuw, P. T.; Husemann, B.; Ibata, R.; Battaglia, G.; Martin, N.; Testa, V.; Perina, S.; Correnti, M.

    2017-02-01

    We present the results of VLT-MUSE (Very Large Telescope-Multi Unit Spectroscopic Explorer) integral field spectroscopy of SECCO 1, a faint, star-forming stellar system recently discovered as the stellar counterpart of an ultracompact high-velocity cloud (HVC 274.68+74.0), very likely residing within a substructure of the Virgo cluster of galaxies. We have obtained the radial velocity of a total of 38 individual compact sources identified as H II regions in the main and secondary bodies of the system, and derived the metallicity for 18 of them. We provide the first direct demonstration that the two stellar bodies of SECCO 1 are physically associated and that their velocities match the H I velocities. The metallicity is quite uniform over the whole system, with a dispersion lower than the uncertainty on individual metallicity estimates. The mean abundance, <12 + log(O/H)> = 8.44, is much higher than the typical values for local dwarf galaxies of similar stellar mass. This strongly suggests that the SECCO 1 stars were born from a pre-enriched gas cloud, possibly stripped from a larger galaxy. Using archival Hubble Space Telescope (HST) images, we derive a total stellar mass of ≃1.6 × 105 M⊙ for SECCO 1, confirming that it has a very high H I-to-stellar mass ratio for a dwarf galaxy, M_{H I}/M* ∼ 100. The star formation rate, derived from the Hα flux, is a factor of more than 10 higher than in typical dwarf galaxies of similar luminosity.

  8. 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.

  9. A Photometric Metallicity Estimate of the Virgo Stellar Overdensity

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  10. The Colors and Stellar Populations of Ultra-Diffuse Galaxies in the Coma and Virgo Clusters

    NASA Astrophysics Data System (ADS)

    Babakhanyan Stone, Maria; Romanowsky, Aaron J.

    2017-01-01

    Ultra-diffuse galaxies (UDGs) were recently discovered both within and beyond galaxy clusters. UDGs have low luminosities, yet some can be as large as the Milky Way. Their evolutionary histories are unknown, with proposed explanations including “failed” giant galaxies, or dwarfs that were quenched through cluster infall. Here we study trends in color for UDGs in the Coma and Virgo clusters, with comparisons to normal galaxies. We also use stellar population models to estimate ages and metallicities of the UDGs.

  11. 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.

  12. 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.

  13. 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.

  14. Characterization of Stellar Sub-Structure in the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Kunder, Andrea; De Propris, Roberto; Rich, R. Michael; Koch, Andreas; Johnson, Christian I.

    2014-02-01

    We have discovered a group of 7 bulge giants with radial velocities of +300 km/s in a two degree field toward the Galactic bulge at (l,b)=(-6,-8). They are separated from the highest velocity bulge members by ~100 km/s. Recently, ARGOS reported a group of 4 kinematically distinct metal-poor bulge stars in their bulge fields at l=-20. Coincidentally, these stars have radial velocities of +300 km/sec. Given the scarcity of stars with velocities of +300 km/s in the bulge, these stellar features are likely related and part of a large independent stream or moving group in the inner Galaxy. We propose to search for connecting stars that link these two features and trace the extent of this newly discovered stream and understand their stellar system of origin, via their chemical composition.

  15. Searching for Stellar Sub-Structure in the Galactic Bulge

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  16. Extended stellar substructure surrounding the Boötes I dwarf spheroidal galaxy

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    We present deep stellar photometry of the Boötes I dwarf spheroidal galaxy in g- and i-band filters, taken with the Dark Energy Camera at Cerro Tololo in Chile. Our analysis reveals a large, extended region of stellar substructure surrounding the dwarf, as well as a distinct overdensity encroaching on its tidal radius. A radial profile of the Boötes I stellar distribution shows a break radius indicating the presence of extra-tidal stars. These observations strongly suggest that Boötes I is experiencing tidal disruption, although not as extreme as that exhibited by the Hercules dwarf spheroidal. Combined with revised velocity dispersion measurements from the literature, we see evidence suggesting the need to review previous theoretical models of the Boötes I dwarf spheroidal galaxy.

  17. 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.

  18. 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.

  19. 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.

  20. Where stellar halos coexist with intracluster light: a case study of the giant Virgo-central galaxy M87

    NASA Astrophysics Data System (ADS)

    Longobardi, Alessia

    2016-01-01

    What is the role that accretion events play in the evolution of galaxies in dense environments, such as galaxy clusters? Cosmological simulations allow us to study in detail the evolution of galaxies' halos in cluster environments and have shown that the formation of extended halos around central cluster galaxies and intracluster light (ICL) is closely correlated to the morphological transformation of galaxies in clusters. However, the extremely low surface brightness of these components makes it difficult to gather observational constraints. Planetary nebulas (PNs) offer a unique tool to investigate these environments owing to their strong [OIII] emission line. I will present a study of the light and stellar motion in the halo of the giant elliptical galaxy M87 and its surrounding IC component at the centre of the Virgo cluster, prime targets to shed light on the hierarchical assembly of structure in the Universe. We make use of a deep and extended PN sample (~ 300 objects) to study out to ~150 kpc in radius M87. We show that at all distance the galaxy halo overlap with theVirgo ICL. However, they are dynamically distinct components with different density profiles, and parent stellarpopulations, consistent with the halo of M87 being redder and more metal rich than the ICL. Moreover, the synergy between PN kinematical information and deep V/B-band photometry made it possible to unveal an ongoing accretion process in the outskirt of M87, that has caused a non-negligible modification of the halo properties. The ongoing assembly of this galaxy at distances R>60 kpc is also shown by the overall PN halo kinematics, reflecting the dynamical complexity of a still growing system.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. A near-infrared census of the multicomponent stellar structure of early-type dwarf galaxies in the Virgo cluster

    SciTech Connect

    Janz, J.; Laurikainen, E.; Salo, H.; Lisker, T.; Hansson, K. S. A.; Meyer, H. T.; Paudel, S.; Peletier, R. F.; Den Brok, M.; Niemi, S.-M.; Toloba, E.; Falcón-Barroso, J.; Ryś, A.

    2014-05-10

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

  9. 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.

  10. 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.

  11. The Virgo cD galaxy M87 and its environment as mapped by Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Longobardi, Alessia

    2015-08-01

    Cosmological simulations predict the evolution of galaxy halos in cluster environments. Because of their low surface brightness, 1% of the night sky or lower, it is difficult to measure their spatial distribution and line-of-sight motions of the associated stars. Planetary nebulas (PNs) are very good tracers of their parent stellar populations, and we can use them to investigate these extended halos as consequence of their relatively strong [OIII] emission line. We have used PNs to study the outer halo of M87, the BCG at the center of the Virgo cluster. From the deepest and most extended narrow band survey done with Supruime Cam on Subaru, we carry out the spectroscopic follow up with FLMES at the VLT of more than 300 emission line objects in the halo of M87 out to ~150 kpc in radius. We confirm 254 PNs associated with the M87 halo and 44 with the intracluster light in the Virgo core. We show that the galaxy halo overlaps with the Virgo intracluster light (ICL) at all distance. Halo and ICL are dynamically distinct components, have different density profiles and parent stellar populations. The latter result shows that the halo of M87 is redder and more metal rich than the ICL population. Because of the excellent spectra resolution of our data, we identify a chevron structure in the projected phase space and identify the substructure in light associated to this dynamical sub-component. This accretion event account for a third of the light of the halo at 90 kpc distance from the center. It shows that at these distances the M87 halo is significantly lumpy and still growing by accretion of satellites.

  12. Disentangling the Virgo Overdensity with RR Lyrae stars

    NASA Astrophysics Data System (ADS)

    Vivas, A. Katherina; Zinn, Robert; Farmer, John; Duffau, Sonia; Ping, Yiding

    2016-11-01

    We use a combination of spatial distribution and radial velocity to search for halo substructures in a sample of 412 RR Lyrae stars (RRLSs) that covers a region of ∼525 square degrees of the Virgo overdensity (VOD) and spans distances from the Sun from 4 to 75 kpc. With a friends-of-friends algorithm we identified six high-significance groups of RRLSs in phase space, which we associate mainly with the VOD and with the Sagittarius stream. Four other groups were also flagged as less significant overdensities. Three high-significance and three lower-significance groups have distances between ∼10 and 20 kpc, which places them in the distance range attributed by others to the VOD. The largest of these is the Virgo stellar stream at 19 kpc, which has 18 RRLSs, a factor of two increase over the number known previously. While these VOD groups are distinct according to our selection criteria, their overlap in position and distance and, in a few cases, similarity in radial velocity are suggestive that they may not all stem from separate accretion events. Even so, the VOD appears to be caused by more than one overdensity. The Sagittarius (Sgr) stream is a very obvious feature in the background of the VOD at a mean distance of 44 kpc. Two additional high-significance groups were detected at distances \\gt 40 {kpc}. Their radial velocities and locations differ from the expected path of the Sgr debris in this part of the sky, and they are likely to be remnants of other accretion events.

  13. 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

  14. Exploring Milkyway Halo Substructures with Large-Area Sky Surveys

    SciTech Connect

    Li, Ting

    2016-01-01

    Over the last two decades, our understanding of the Milky Way has been improved thanks to large data sets arising from large-area digital sky surveys. The stellar halo is now known to be inhabited by a variety of spatial and kinematic stellar substructures, including stellar streams and stellar clouds, all of which are predicted by hierarchical Lambda Cold Dark Matter models of galaxy formation. In this dissertation, we first present the analysis of spectroscopic observations of individual stars from the two candidate structures discovered using an M-giant catalog from the Two Micron All-Sky Survey. The follow-up observations show that one of the candidates is a genuine structure which might be associated with the Galactic Anticenter Stellar Structure, while the other one is a false detection due to the systematic photometric errors in the survey or dust extinction in low Galactic latitudes. We then presented the discovery of an excess of main sequence turn-off stars in the direction of the constellations of Eridanus and Phoenix from the first-year data of the Dark Energy Survey (DES) – a five-year, 5,000 deg2 optical imaging survey in the Southern Hemisphere. The Eridanus-Phoenix (EriPhe) overdensity is centered around l ~ 285° and b ~ -60° and the Poisson significance of the detection is at least 9σ. The EriPhe overdensity has a cloud-like morphology and the extent is at least ~ 4 kpc by ~ 3 kpc in projection, with a heliocentric distance of about d ~ 16 kpc. The EriPhe overdensity is morphologically similar to the previously-discovered Virgo overdensity and Hercules-Aquila cloud. These three overdensities lie along a polar plane separated by ~ 120° and may share a common origin. In addition to the scientific discoveries, we also present the work to improve the photometric calibration in DES using auxiliary calibration systems, since the photometric errors can cause false detection in first the halo substructure. We present a detailed description of the two

  15. The Virgo Cluster of Galaxies in the Making

    NASA Astrophysics Data System (ADS)

    2004-10-01

    has led to the remarkable discovery that Messier 87 has a stellar halo in approximate dynamical equilibrium out to at least 65 kpc, or more than 200,000 light-years. This is more than twice the size of our own galaxy, the Milky Way, and was not known before." The velocity dispersion observed in the second field, which is far away from bright galaxies, is larger than in the first one by a factor four. This very large dispersion, indicating stars moving in very disparate directions at different speeds, also tells us that this field most probably contains many intracluster stars whose motions are barely influenced by large galaxies. The new data suggest as a tantalizing possibility that this intracluster population of stars could be the leftover from the disruption of small galaxies as they orbit M87. The velocity distribution in the third field, as deduced from FLAMES spectra, is again different. The velocities show substructures related to the large galaxies Messier 86, Messier 84 and NGC 4388. Most likely, the large majority of all these planetary nebulae belong to a very extended halo around Messier 84. Ortwin Gerhard (University of Basel, Switzerland), member of the team, is thrilled: "Taken together these velocity measurements confirm the view that the Virgo Cluster is a highly non-uniform and unrelaxed galaxy cluster, consisting of several subunits. With the FLAMES spectrograph, we have thus been able to watch the motions in the Virgo Cluster, at a moment when its subunits are still coming together. And it is certainly a view worth seeing!" More information The results presented in this ESO Press Release are based on a research paper ("The Line-of-Sight Velocity Distributions of Intracluster Planetary Nebulae in the Virgo Cluster Core" by M. Arnaboldi et al.) that has just appeared in the research journal Astrophysical Journal Letters Vol. 614, p. 33. Notes [1]: The University of Basel Press Release on this topic is available at http

  16. 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.

  17. UPDATE ON THE NATURE OF VIRGO OVERDENSITY

    SciTech Connect

    Bonaca, Ana; Juric, Mario; Ivezic, Zeljko; Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Daniel; Pan, Kaike; Shelden, Alaina; Simmons, Audrey; Snedden, Stephanie E-mail: mjuric@cfa.harvard.edu

    2012-05-15

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

  18. Update on the Nature of Virgo Overdensity

    NASA Astrophysics Data System (ADS)

    Bonaca, Ana; Jurić, Mario; Ivezić, Željko; Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Daniel; Pan, Kaike; Shelden, Alaina; Simmons, Audrey; Snedden, Stephanie

    2012-05-01

    We use the Eighth Data Release of Sloan Digital Sky Survey catalog with its additional sky coverage of the southern Galactic hemisphere to measure the extent and to study the nature of the Virgo Overdensity (VOD). The data show that the VOD extends over no less than 2000 deg2, with its true extent likely closer to 3000 deg2. We test whether the VOD can be attributed to a tilt in the stellar halo ellipsoid with respect to the plane of the Galactic disk and find that the observed symmetry of the north-south Galactic hemisphere star counts excludes this possibility. We argue that the Virgo Overdensity, in spite of its wide area and cloud-like appearance, is still best explained by a minor merger. Its appearance and position are qualitatively similar to a near perigalacticon merger event and, assuming that the VOD and the Virgo Stellar Stream (VSS) share the same progenitor, consistent with the VSS orbit determined by Casetti-Dinescu et al.

  19. 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.

  20. 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.

  1. Radio continuum and H I emission from the spiral galaxies in the Virgo cluster area

    NASA Astrophysics Data System (ADS)

    Gavazzi, G.

    The statistical method used by Hummel (1981) to derive the radioluminosity functions of galaxies is applied to the H I data obtained on a sample of 101 spiral galaxies in the Virgo cluster. The analysis permits a quantitative demonstration of H I deficiency among the Virgo spiral galaxies without invoking the deficiency parameter. In addition, evidence is presented that Virgo spiral galaxies might show a correlation between H I content and radio continuum luminosity, which is more marked among the unperturbed sample. The results are discussed from the viewpoint of stellar and galaxy evolution and its relation with the intergalactic environment.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Discovering Substructure in Examples

    DTIC Science & Technology

    1988-05-01

    the gestalt motivation for the previouslv discussed heuristics, gestalt theory suggests many additional 16 %0 [ ’ , factors identified in human...to substructure discovery. Gestalt theory motivates several of the ideas behind the substructure discovery algorithm. In the area of machine learning...5.1. Gestalt Psychology Many of the ideas in this thesis originated from work in gestalt psychology [Kohler47]. Gestalt theory identifies several

  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. THE SEGUE K GIANT SURVEY. III. QUANTIFYING GALACTIC HALO SUBSTRUCTURE

    SciTech Connect

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

    2016-01-10

    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.

  12. The Burrell Schmidt Deep Virgo Survey: Tidal Debris, Galaxy Halos, and Diffuse Intracluster Light in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    We present the results of a deep imaging survey of the Virgo cluster of galaxies, concentrated around the cores of Virgo subclusters A and B. The goal of this survey was to detect and study very low surface brightness features present in Virgo, including discrete tidal features, the faint halos of luminous galaxies, and the diffuse intracluster light (ICL). Our observations span roughly 16 degrees2 in two filters, reaching a 3σ limiting depth of {μ }B = 29.5 and {μ }V = 28.5 mag arcsec‑2. At these depths, our limiting systematic uncertainties are astrophysical: variations in faint background sources as well as scattered light from galactic dust. We show that this dust-scattered light is well traced by deep far-infrared imaging, making it possible to separate it from true diffuse light in Virgo. We use our imaging to trace and measure the color of the diffuse tidal streams and ICL in the Virgo core near M87, in fields adjacent to the core including the M86/M84 region, and to the south of the core around M49 and subcluster B, along with the more distant W{}\\prime cloud around NGC 4365. Overall, the bulk of the projected ICL is found in the Virgo core and within the W{}\\prime cloud; we find little evidence for an extensive ICL component in the field around M49. The bulk of the ICL we detect is fairly red in color (B ‑ V = 0.7–0.9), indicative of old, evolved stellar populations. Based on the luminosity of the observed ICL features in the cluster, we estimate a total Virgo ICL fraction of 7%–15%. This value is somewhat smaller than that expected for massive, evolved clusters, suggesting that Virgo is still in the process of growing its extended ICL component. We also trace the shape of M87's extremely boxy outer halo out to ∼150 kpc, and show that the current tidal stripping rate from low luminosity galaxies is insufficient to have built M87's outer halo over a Hubble time. We identify a number of previously unknown low surface brightness structures

  13. Is there substructure around M87?

    NASA Astrophysics Data System (ADS)

    Oldham, L. J.; Evans, N. W.

    2016-10-01

    We present a general method to identify infalling substructure in discrete data sets with position and line-of-sight velocity data. We exploit the fact that galaxies falling on to a brightest cluster galaxy (BCG) in a virialized cluster, or dwarf satellites falling on to a central galaxy like the Milky Way, follow nearly radial orbits. If the orbits are exactly radial, we show how to find the probability distribution for a satellite's energy, given a tracer density for the satellite population, by solving an Abel integral equation. This is an extension of Eddington's classical formula for the isotropic distribution function. When applied to a system of galaxies, clustering in energy space can then be quantified using the Kullback-Leibler divergence, and groups of objects can be identified which, though separated in the sky, may be falling in on the same orbit. This method is tested using mock data and applied to the satellite galaxy population around M87, the BCG in Virgo, and a number of associations that are found, which may represent infalling galaxy groups.

  14. Early dynamical evolution of young substructured clusters

    NASA Astrophysics Data System (ADS)

    Dorval, Julien; Boily, Christian

    2017-03-01

    Stellar clusters form with a high level of substructure, 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. 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 and velocity inheritance. We introduce a new way to create clumpy initial conditions through a ''Hubble expansion'' which naturally produces self consistent clumps, velocity-wise. In depth analysis of the resulting clumps shows consistency with hydrodynamical simulations of young star clusters. We use these initial conditions to investigate the dynamical evolution of young subvirial clusters. We find the collapse to be soft, with hierarchical merging leading to a high level of mass segregation. The subsequent evolution is less pronounced than the equilibrium achieved from a cold collapse formation scenario.

  15. 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.

  16. 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.

  17. ALMA Observations of Starless Core Substructure in Ophiuchus

    NASA Astrophysics Data System (ADS)

    Kirk, H.; Dunham, M. M.; Di Francesco, J.; Johnstone, D.; Offner, S. S. R.; Sadavoy, S. I.; Tobin, J. J.; Arce, H. G.; Bourke, T. L.; Mairs, S.; Myers, P. C.; Pineda, J. E.; Schnee, S.; Shirley, Y. L.

    2017-04-01

    Compact substructure is expected to arise in a starless core as mass becomes concentrated in the central region likely to form a protostar. Additionally, multiple peaks may form if fragmentation occurs. We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 2 observations of 60 starless and protostellar cores in the Ophiuchus molecular cloud. We detect eight compact substructures which are > 15\\prime\\prime from the nearest Spitzer young stellar object. Only one of these has strong evidence for being truly starless after considering ancillary data, e.g., from Herschel and X-ray telescopes. An additional extended emission structure has tentative evidence for starlessness. The number of our detections is consistent with estimates from a combination of synthetic observations of numerical simulations and analytical arguments. This result suggests that a similar ALMA study in the Chamaeleon I cloud, which detected no compact substructure in starless cores, may be due to the peculiar evolutionary state of cores in that cloud.

  18. 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.

  19. The WSRT virgo filament survey

    NASA Astrophysics Data System (ADS)

    Popping, A.; Braun, R.

    2007-02-01

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

  20. Environmental Extremists in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Kenney, J.; Koopmann, R.

    We discuss some of the most interesting environmentally modified galaxies in the Virgo cluster, based on H alpha and broadband imaging, and long-slit spectroscopy of 100 Virgo cluster and isolated galaxies. In Virgo, there is evidence for mergers, high velocity collisions, tidal interactions, ICM-ICM stripping, and interactions with large HI clouds. There is a population of small-bulge spiral galaxies, variously classified as Sa/Sc, S0/Sc or Sa pec, which lack star formation in the outer disk yet have normal or elevated rates of star formation in the central few kpc. While some of these galaxies are likely stripped by ICM-ISM interactions, others have peculiarities more consistent with tidal interactions or minor mergers. The peculiar Sa galaxy NGC 4424 has banana-shaped isophotes, shell-like features, star forming complexes confined to the central 1 kpc, and is likely a minor merger. NGC4438 and NGC4435 appear to have had a high velocity (~1000 km/s-1 ) collision, and much of the original ISM driven from the disks in the collision is now cooling and falling back into NGC 4438. There appears to be an HI-rich zone ~6-10 deg away from the center of the Virgo cluster. Some of the spirals with the highest star formation rates in Virgo are in the outskirts of the cluster, and are associated with large extended, clouds of HI. The evidence indicates that a variety of environmental processes are important in the Virgo cluster, and that the morphology-environment relationship may have a number of causes.

  1. Oxygen and nitrogen abundances in Virgo and field spirals

    NASA Astrophysics Data System (ADS)

    Pilyugin, L. S.; Mollá, M.; Ferrini, F.; Vílchez, J. M.

    2002-01-01

    The oxygen and nitrogen abundances in the H II regions of the nine Virgo spirals of the sample from Skillman et al. (1996) and in nine field spiral galaxies are re-determined with the recently suggested P-method. We confirm that there is an abundance segregation in the sample of Virgo spirals in the sense that the H I deficient Virgo spirals near the core of the cluster have higher oxygen abundances in comparison to the spirals at the periphery of the Virgo cluster. At the same time both the Virgo periphery and core spirals have counterparts among field spirals. Some field spirals have H I to optical radius ratios, similar to that in H I deficient Virgo core spirals. We conclude that if there is a difference in the abundance properties of the Virgo and field spirals, this difference appears to be small and masked by the observational errors.

  2. THE FIRST GENERATION OF VIRGO CLUSTER DWARF ELLIPTICAL GALAXIES?

    SciTech Connect

    Lisker, Thorsten; Janz, Joachim; Hielscher, Oliver; Paudel, Sanjaya; Hensler, Gerhard; Kim, Suk; Rey, Soo-Chang; Weinmann, Simone; Mastropietro, Chiara; Kotulla, Ralf

    2009-11-20

    In the light of the question whether most early-type dwarf (dE) galaxies in clusters formed through infall and transformation of late-type progenitors, we search for an imprint of such an infall history in the oldest, most centrally concentrated dE subclass of the Virgo cluster: the nucleated dEs that show no signatures of disks or central residual star formation. We select dEs in a (projected) region around the central elliptical galaxies, and subdivide them by their line-of-sight velocity into fast-moving and slow-moving ones. These subsamples turn out to have significantly different shapes: while the fast dEs are relatively flat objects, the slow dEs are nearly round. Likewise, when subdividing the central dEs by their projected axial ratio into flat and round ones, their distributions of line-of-sight velocities differ significantly: the flat dEs have a broad, possibly two-peaked distribution, whereas the round dEs show a narrow single peak. We conclude that the round dEs probably are on circularized orbits, while the flat dEs are still on more eccentric or radial orbits typical for an infalling population. In this picture, the round dEs would have resided in the cluster already for a long time, or would even be a cluster-born species, explaining their nearly circular orbits. They would thus be the first generation of Virgo cluster dEs. Their shape could be caused by dynamical heating through repeated tidal interactions. Further investigations through stellar population measurements and studies of simulated galaxy clusters would be desirable to obtain definite conclusions on their origin.

  3. NASTRAN GPWG tables for combined substructures

    NASA Technical Reports Server (NTRS)

    Allen, Tom

    1991-01-01

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

  4. The Herschel Virgo Cluster Survey. X. The relationship between cold dust and molecular gas content in Virgo spirals

    NASA Astrophysics Data System (ADS)

    Corbelli, E.; Bianchi, S.; Cortese, L.; Giovanardi, C.; Magrini, L.; Pappalardo, C.; Boselli, A.; Bendo, G. J.; Davies, J.; Grossi, M.; Madden, S. C.; Smith, M. W. L.; Vlahakis, C.; Auld, R.; Baes, M.; De Looze, I.; Fritz, J.; Pohlen, M.; Verstappen, J.

    2012-06-01

    Aims: We examine whether dust mass can trace the total or molecular gas mass in late-type Virgo cluster galaxies, and how the environment affects the dust-to-gas ratio and the molecular fraction. Methods: Using the far-infrared emission, as observed by the Herschel Virgo Cluster Survey (HeViCS), and the integrated HI 21-cm and CO J = 1-0 line brightness, we infer the dust and total gas mass for a magnitude limited sample of 35 metal rich spiral galaxies. Environmental disturbances on each galaxy are considered by means of the HI deficiency parameter. Results: The CO flux correlates tightly and linearly with far-infrared fluxes observed by Herschel, especially with the emission at 160, 250 and 350 μm. Molecules in these galaxies are more closely related to cold dust rather than to dust heated by star formation or to optical/NIR brightness. We show that dust mass establishes a stronger correlation with the total gas mass than with the atomic or molecular component alone. The correlation is non-linear since lower mass galaxies have a lower dust-to-gas ratio. The dust-to-gas ratio increases as the HI deficiency increases, but in highly HI deficient galaxies it stays constant. Dust is in fact less affected than atomic gas by weak cluster interactions, which remove most of the HI gas from outer and high latitudes regions. Highly disturbed galaxies, in a dense cluster environment, can instead loose a considerable fraction of gas and dust from the inner regions of the disk keeping constant the dust-to-gas ratio. There is evidence that the molecular phase is also quenched. This quencing becomes evident by considering the molecular gas mass per unit stellar mass. Its amplitude, if confirmed by future studies, highlights that molecules are missing in Virgo HI deficient spirals, but to a somewhat lesser extent than dust. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from

  5. 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

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    We describe the Herschel Virgo Cluster Survey and the first data that cover the complete survey area (four 4 × 4 deg2 regions). We use these data to measure and compare the global far-infrared properties of 78 optically bright galaxies that are selected at 500 μm and detected in all five far-infrared bands. We show that our measurements and calibration are broadly consistent with previous data obtained by the IRAS, ISO, Spitzer and Planck. We use SPIRE and PACS photometry data to produce 100-, 160-, 250-, 350- and 500-μm cluster luminosity distributions. These luminosity distributions are not power laws, but 'peaked', with small numbers of both faint and bright galaxies. We measure a cluster 100-500 μm far-infrared luminosity density of 1.6(7.0) ± 0.2 × 109 L⊙ Mpc-3. This compares to a cluster 0.4-2.5 μm optical luminosity density of 5.0(20.0) × 109 L⊙ Mpc-3, some 3.2(2.9) times larger than the far-infrared. A 'typical' photon originates from an optical depth of 0.4 ± 0.1. Most of our sample galaxies are well fitted by a single modified blackbody (β= 2), leading to a mean dust mass of log MDust= 7.31 M⊙ and temperature of 20.0 K. We also derive both stellar and atomic hydrogen masses from which we calculate mean values for the star-to-gas (atomic) and gas (atomic)-to-dust mass ratios of 15.1 and 58.2, respectively. Using our derived dust, atomic gas and stellar masses, we estimate cluster mass densities of 8.6(27.8) × 106, 4.6(13.9) × 108 and 7.8(29.7) × 109 M⊙ Mpc-3 for dust, atomic gas and stars, respectively. These values are higher than those derived for field galaxies by factors of 39(126), 6(18) and 34(129), respectively. In the above, the luminosity/mass densities are given using the whole sample with the values in brackets using just those galaxies that lie between 17 and 23 Mpc. We provide a data table of flux densities in all the Herschel bands for all 78 bright Virgo Cluster galaxies. Herschel is an ESA space observatory with science

  7. 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.

  8. Microstructure versus substructure size effect

    NASA Astrophysics Data System (ADS)

    Ghassemali, Ehsan; Jarfors, Anders E. W.; Tan, Ming-Jen; Wah, Chua Beng

    2016-10-01

    In metal deformation, size effect is generally attributed to the interactive effect of grain size and specimen dimension. This work shows, however, that relative substructure dimensions should also be considered. Micro-compression tests on the micro-pins having different grain sizes revealed no significant size effect with respect to the mechanical behavior, even if the number of grains over the diameter of the micro-pins falls below its critical value. To justify the reason laying under this fact, a recovery annealing cycle was applied on the micro-pins to change the substructure properties without altering the mean grain size. A surprising drop in the flow stress of the recovery-annealed micro-pins implied the importance of considering subgrain size rather than grain size over the diameter of component for the size effect investigation.

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

    DOE PAGES

    Belczynski, Krzysztof; Repetto, Serena; Holz, Daniel E.; ...

    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

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

    SciTech Connect

    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 ($\\lt 150\\;{M}_{\\odot }$) 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.

  11. Extragalactic Stellar Spectroscopy

    NASA Astrophysics Data System (ADS)

    Lennon, D. J.; Smartt, S. J.; Dufton, P. L.; Herrero, A.; Kudritzki, R.-P.; Venn, K.; McCarthy, J.

    1999-09-01

    The advent of large 8-10m telescopes heralds a new age in stellar astronomy. It is now possible to carry out detailed spectroscopic observations at high resolution of the brightest stars of galaxies in the Local Group, and it is envisaged that intermediate resolution observations will be extended to stars in the nearest galaxy clusters such as Virgo and Fornax. For some years the authors have been carrying out the groundwork involved in identifying young massive supergiant stars in nearby resolved galaxies, with a view to performing follow-up detailed studies of selected samples. In this article we summarize the contribution that the William Herschel Telescope has made to this project, and further, show that even a 4.2m telescope with a blue sensitive, large format CCD at a good site with dependable sub-arcsecond seeing can make an important contribution to the detailed study of our nearest spiral neighbours M31 and M33.

  12. Substructure mining using elaborate chemical representation.

    PubMed

    Kazius, Jeroen; Nijssen, Siegfried; Kok, Joost; Bäck, Thomas; Ijzerman, Adriaan P

    2006-01-01

    Substructure mining algorithms are important drug discovery tools since they can find substructures that affect physicochemical and biological properties. Current methods, however, only consider a part of all chemical information that is present within a data set of compounds. Therefore, the overall aim of our study was to enable more exhaustive data mining by designing methods that detect all substructures of any size, shape, and level of chemical detail. A means of chemical representation was developed that uses atomic hierarchies, thus enabling substructure mining to consider general and/or highly specific features. As a proof-of-concept, the efficient, multipurpose graph mining system Gaston learned substructures of any size and shape from a mutagenicity data set that was represented in this manner. From these substructures, we extracted a set of only six nonredundant, discriminative substructures that represent relevant biochemical knowledge. Our results demonstrate the individual and synergistic importance of elaborate chemical representation and mining for nonlinear substructures. We conclude that the combination of elaborate chemical representation and Gaston provides an excellent method for 2D substructure mining as this recipe systematically explores all substructures in different levels of chemical detail.

  13. Systematic Problems With Stellar Halo Modelling

    NASA Astrophysics Data System (ADS)

    Bailin, Jeremy

    2012-05-01

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

  14. 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.

  15. Evidence for a Merger in the Peculiar Virgo Cluster SA Galaxy NGC 4424

    NASA Astrophysics Data System (ADS)

    Kenney, Jeffrey D. P.; Koopmann, Rebecca A.; Rubin, Vera C.; Young, Judith S.

    1996-01-01

    We present R-band and Hα images and Hα long-slit spectroscopy of the peculiar Virgo cluster Sa galaxy NGC 4424. The broadband R image reveals banana-shaped isophotes, shell-like features, and other complex structure generally associated with mergers and significant accretion events. The only Hα emission arises from a few bright H II complexes located within 500 pc of the nucleus and inside the bulge- dominated region. Although the main stellar body of NGC 4424 is highly elongated in projection, and the outer part of the galaxy has a disk-like exponential light profile, gas velocities are remarkably low in the central kpc, indicating strong non-circular motions or complex geometry for the inner gas. The peculiar properties are consistent with an intermediate mass ratio (0.1-0.5) merger, making NGC 4424 one of the best cases among spiral galaxies in the nearby Virgo cluster for a significant and recent merger. The degree of morphological peculiarities suggest that the merger is recent, and we propose that the galaxy will become a small- bulge S0 within ~1 Gyr. We discuss the possibility that the banana-shaped stellar distribution is the result of a merger-induced bending instability.

  16. 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.

  17. Multiple Tracers of Structure, Substructure, and Dynamics of Galaxy Halos

    NASA Astrophysics Data System (ADS)

    Romanowsky, Aaron

    2015-08-01

    I will present a suite of results on the fundamental properties of galaxy halos, using a variety of observational tracers for a range of galaxy types, from giant ellipticals to spirals to dwarfs, along with comparisons to numerical simulations. The tracers include diffuse stellar light spectroscopy up to ~4 Re, resolved stellar photometry and spectroscopy, metal-poor and metal-rich globular cluster subpopulations, and planetary nebulae. The results include extended rotation and metallicity profiles, scaling relations for total angular momentum, shape inferences for the halos, orbital anisotropy estimates, kinematically "decoupled" halos, surprisingly homogeneous total mass profiles, and both detection and chemodynamical mapping of streams, shells, and other substructures. Connections are made to simulations of idealized galaxy mergers and of full cosmological formation histories, using the observed properties to make inferences about the assembly mechanisms of individual galaxies and of different galaxy types. Detailed models of stellar streams are used to infer their progenitor properties and to probe the gravitational potentials of the host galaxies. Novel observations are presented of compact stellar systems (globular clusters, ultra-compact dwarfs, compact ellipticals, and transition objects), with implications for the merger histories of their host halos.

  18. MASS SUBSTRUCTURE IN ABELL 3128

    SciTech Connect

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

    2015-05-20

    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.

  19. 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.

  20. High chemical abundances in stripped Virgo spiral galaxies

    NASA Astrophysics Data System (ADS)

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

    1993-01-01

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

  1. 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

  2. Main-Sequence Star Populations in the Virgo Overdensity Region

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  3. 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.

  4. 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.

  5. 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.

  6. 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).

  7. 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.

  8. Properties of seismic noise at the Virgo site

    NASA Astrophysics Data System (ADS)

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

    2004-03-01

    We present the results of a study of the major low-frequency sources of seismic activity at the Virgo site. These sources are of natural and human origin: oceanic microseism (below 1 Hz), local traffic and human activity on site (below 10 Hz). Using data collected during the commissioning of the central Virgo interferometer (CITF) we have measured the seismic coupling to the interferometer, demonstrating that seismic noise contributed to the CITF dark fringe noise only below approximately 2 Hz.

  9. Substructure Main Bridge, Piers B & C Huey ...

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

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

  10. Chemical substructure search in SQL.

    PubMed

    Golovin, Adel; Henrick, Kim

    2009-01-01

    We present a novel technique for a fast chemical substructure search on a relational database by use of a standard SQL query. The symmetry of a query graph is analyzed to give additional constraints. Our method is based on breadth-first search (BFS) algorithms implementation using Relational Database Management Systems (RDBMS). In addition to the chemical search we apply our technique to the field of intermolecular interactions which involves nonplanar graphs and describe how to achieve linear time performance along with the suggestion on how to sufficiently reduce the linear coefficient. From the algorithms theory perspective these results mean that subgraph isomorphism is a polynomial time problem, hence equal problems have the same complexity. The application to subgraph isomorphism in chemical search is available at http://www.ebi.ac.uk/msd-srv/chemsearch and http://www.ebi.ac.uk/msd-srv/msdmotif/chem . The application to the network of molecule interactions is available at http://www.ebi.ac.uk/msd-srv/msdmotif .

  11. Substructure-based control of flexible structures

    NASA Astrophysics Data System (ADS)

    Babuska, Vit

    The desire to build large space structures has motivated research into the problem of flexible structure control. In general, the controllers for these structures can be designed using a centralized strategy or a decentralized strategy. In the centralized approach, the controller is based on a model of the complete structure. In the decentralized approach, the structure model is decomposed into subsystems for which controllers are designed, and then these subsystem controllers are combined to control the complete structure. The subsystems can be mathematical constructs such as groups of modes, or physical subsystems like substructures. This dissertation examines substructure-based decentralized design of controllers for flexible structures. Three different, but related, topics are discussed in this work. First, a relationship is shown to exist between the substructural controller synthesis (SCS) method of designing active controllers for flexible structures and decentralized control using overlapping information sets. It is shown that, in the case of full-state feedback, the SCS method is a specific case of decentralized control using overlapping subsystems. In the case of dynamic output feedback (e.g., LQG controllers), the SCS method departs from standard decentralized control techniques. The controllers are 'assembled' by extending the concept of substructural assembly to general linear systems. Next, a new design method is proposed which combines the concept of component mode synthesis (CMS) with control theory in a decentralized method for the design of controllers for flexible structures. This method, called the augmented physical component synthesis (APCS) method, creates augmented substructural components. These components are substructures whose boundaries are loaded with some dynamics of the adjacent substructures. This allows global control objectives such as line-of-sight error minimization to be met with a substructure-based design strategy. Finally

  12. 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.

  13. 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.

  14. Large-scale Filamentary Structures around the Virgo Cluster Revisited

    NASA Astrophysics Data System (ADS)

    Kim, Suk; Rey, Soo-Chang; Bureau, Martin; Yoon, Hyein; Chung, Aeree; Jerjen, Helmut; Lisker, Thorsten; Jeong, Hyunjin; Sung, Eon-Chang; Lee, Youngdae; Lee, Woong; Chung, Jiwon

    2016-12-01

    We revisit the filamentary structures of galaxies around the Virgo cluster, exploiting a larger data set, based on the HyperLeda database, than previous studies. In particular, this includes a large number of low-luminosity galaxies, resulting in better sampled individual structures. We confirm seven known structures in the distance range 4 h -1 Mpc < SGY < 16 h -1 Mpc, now identified as filaments, where SGY is the axis of the supergalactic coordinate system roughly along the line of sight. The Hubble diagram of the filament galaxies suggests they are infalling toward the main body of the Virgo cluster. We propose that the collinear distribution of giant elliptical galaxies along the fundamental axis of the Virgo cluster is smoothly connected to two of these filaments (Leo II A and B). Behind the Virgo cluster (16 h -1 Mpc < SGY < 27 h -1 Mpc), we also identify a new filament elongated toward the NGC 5353/4 group (“NGC 5353/4 filament”) and confirm a sheet that includes galaxies from the W and M clouds of the Virgo cluster (“W-M sheet”). In the Hubble diagram, the NGC 5353/4 filament galaxies show infall toward the NGC 5353/4 group, whereas the W-M sheet galaxies do not show hints of gravitational influence from the Virgo cluster. The filamentary structures identified can now be used to better understand the generic role of filaments in the build-up of galaxy clusters at z ≈ 0.

  15. 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.

  16. 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.

  17. Stellar Tidal Streams in External Galaxies

    NASA Astrophysics Data System (ADS)

    Carlin, Jeffrey L.; Beaton, Rachael L.; Martínez-Delgado, David; Gabany, R. Jay

    In order to place the highly substructured stellar halos of the Milky Way and M31 in a larger context of hierarchical galaxy formation, it is necessary to understand the prevalence and properties of tidal substructure around external galaxies. This chapter details the current state of our observational knowledge of streams in galaxies in and beyond the Local Group, which are studied both in resolved stellar populations and in integrated light. Modeling of individual streams in extragalactic systems is hampered by our inability to obtain resolved stellar kinematics in the streams, though many streams contain alternate luminous kinematic tracers, such as globular clusters or planetary nebulae. We compare the observed structures to the predictions of models of galactic halo formation, which provide insight into the number and properties of streams expected around Milky Way like galaxies. More specifically, we discuss the inferences that can be made about stream progenitors based only on observed morphologies. We expand our discussion to consider hierarchical accretion at lower mass scales, in particular the observational evidence that substructure exists on smaller mass scales and the effects accretion events may have on the evolution of dwarf galaxies (satellite or isolated). Lastly, we discuss potential correlations between the presence of substructure in the halo and the structural properties of the disk. While many exciting discoveries have been made of tidal substructures around external galaxies, the "global" questions of galaxy formation and evolution via hierarchical accretion await a more complete census of the low surface brightness outskirts of galaxies in and beyond the Local Group.

  18. 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

  19. 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.

  20. Chandra imaging of the Virgo cluster

    NASA Astrophysics Data System (ADS)

    Young, A. J.; Wilson, A. S.; Mundell, C. G.

    2001-12-01

    We report sub-arcsecond X-ray imaging spectroscopy of M87 and the core of the Virgo cluster. The X-ray morphology shows structure on arcsecond to tens of arcminute scales, the most prominent feature being an ``arc'' running from the east, across the nucleus and off to the southwest. Depressions in the X-ray surface brightness correspond to the inner radio lobes, and farther out there are a series of X-ray ``halos''. A ridge in the radio map, ending in an ``ear''-shaped structure, follows the arc to the east, and the radio emission appears to be wrapped around the arc to the southwest. We compute temperature, pressure and cooling time maps, and confirm that the X-ray gas in the arc is cooler than, and in approximate pressure equilibrium with, the ambient cluster gas. The metal abundances of the gas in the arc are difficult to determine accurately, but the cooler gas is tentatively over-abundant relative to the ambient cluster gas, favoring a ``buoyant bubbles'' origin for the X-ray arc. This research was supported by NASA grants NAG 81027 and NAG 81755.

  1. 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.

  2. Singular behavior of jet substructure observables

    DOE PAGES

    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

  3. Singular behavior of jet substructure observables

    SciTech Connect

    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. 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 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.

  4. Optical metrology tools for the Virgo projet

    NASA Astrophysics Data System (ADS)

    Loriette, V.

    is a description of the various optical components that have to be manufactured and tested for Virgo. The next sections are dedicated to the description of various metrology instruments. In chapter 2 we focus on absorption of light in multilayer coatings. The sensitivity of interferometric detectors is degraded by this loss process, not only because it decreases the laser beam power, but also and chiefly because thermo-elastic deformations and changes of the indexes of refraction modify the beam profile. Optical coatings have now reached an absorption level lower than at m. We present a method based on the mirage effect, i.e. the deflexion of light by an index of refraction gradient induced by non homogeneous heating. This “mirage bench” has a sensitivity better than 10^{-8}. We start by a discussion of the approximations that are useful to simplify the problem, we then derive the equation that give the signal amplitude versus the absorption factor. Afterwards we describe the instrument and give a few results with home made Virgo mirrors as well as commercial samples. In the following chapter we discuss the problem of measuring reflexion factors. We focus on two particular problems, the first one is common, it is to measure high (higher than 0.9999) reflexion factors by the use of Fabry-Perot cavities. We present various possible schemes and we detail a particular one which seems to be the easiest to implement. We use a pulsed laser source and measure the average reflexion factor of the two Fabry-Perot mirrors by studying the pulse shape modification after transmission by the cavity. We estimate the sensitivity of this intrument to 10^{-6}. The second problem is a less common one and is to evaluate the relative homogeneity of reflexion factors on large components. Because inhomogeneities of this parameter will degrade the sensitivity of Virgo by coupling various modes of the laser beam with the fundamental one, homogeneity higher than 1{-}10^{-4} is required. We

  5. Probing the missing baryons around Virgo with Planck

    NASA Astrophysics Data System (ADS)

    Diego, J. M.; Planck Collaboration

    2017-03-01

    We study the largest cluster in the sky (in terms of solid angle) with Planck through the SZ effect. Virgo is well resolved by Planck, and shows an elongated structure. Good agreement between the SZ signal and the expected signal inferred from X-ray observations is found. We study the gas beyond the virial radius in Virgo and find that significant amounts of low-density plasma surround Virgo, out to twice the virial radius. The observed signal is consistent with simulations and points to a shallow pressure profile in the outskirts of the cluster that can be linked with the hottest phase of the elusive warm/hot intergalactic medium. After comparing the integrated SZ and X-ray signal, we find that a prolate model is favoured, in agreement with predictions.

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    The Herschel Virgo Cluster Survey (HeViCS) is the deepest, confusion-limited survey of the Virgo Cluster at far-infrared (FIR) wavelengths. The entire survey at full depth covers ˜55 deg2 in five bands (100-500 μm), encompassing the areas around the central dominant elliptical galaxies (M87, M86 and M49) and extends as far as the NW cloud, the W cloud and the Southern extension. The survey extends beyond this region with lower sensitivity so that the total area covered is 84 deg2. In this paper we describe the data, the data acquisition techniques and present the detection rates of the optically selected Virgo Cluster Catalogue (VCC). We detect 254 (34 per cent) of 750 VCC galaxies found within the survey boundary in at least one band and 171 galaxies are detected in all five bands. For the remainder of the galaxies we have measured strict upper limits for their FIR emission. The population of detected galaxies contains early as well as late types although the latter dominate the detection statistics. We have modelled 168 galaxies, showing no evidence of a strong synchrotron component in their FIR spectra, using a single-temperature modified blackbody spectrum with a fixed emissivity index (β = 2). A study of the χ2 distribution indicates that this model is not appropriate in all cases, and this is supported by the FIR colours which indicate a spread in β = 1-2. Statistical comparison of the dust mass and temperature distributions from 140 galaxies with χ2d.o.f. = 3 < 7.8 (95 per cent confidence level) shows that late types have typically colder, more massive dust reservoirs; the early-type dust masses have a mean of log[/M⊙] = 6.3 ± 0.3, while for late types log[/M⊙] = 7.1 ± 0.1. The late-type dust temperatures have a mean of = 19.4 ± 0.2 K, while for the early types, = 21.1 ± 0.8 K. Late-type galaxies in the cluster exhibit slightly lower dust masses than those in the field, but the cluster environment seems to have little effect on

  8. Dust Content of Virgo Star-Forming Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Grossi, M.; Hunt, L. K.; Madden, S.; Vlahakis, C.; Bomans, D. J.; Baes, M.; Bendo, G. J.; Bianchi, S.; Boselli, A.; Clemens, M.; Corbelli, E.; Cortese, L.; Dariush, A.; Davies, J. I.; De Looze, I.; di Serego Alighieri, S.; Fadda, D.; Fritz, J.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Hughes, T. M.; Jones, A. P.; Pierini, D.; Pohlen, M.; Sabatini, S.; Smith, M. W. L.; Verstappen, J.; Xilouris, E. M.; Zibetti, S.

    We investigate the dust properties of a small sample of Virgo cluster dwarf galaxies drawn from the science demonstration phase data set of the Herschel Virgo Cluster Survey (HeViCS). These galaxies have low metallicities (7.8 < 12 + log(O/H) < 8.3) and star formation rates ≲ 0.1 M⊙ yr-1. We measure the spectral energy distribution (SED) from 100 to 500 μm and derive dust temperatures and masses. The SEDs are fitted by a cool component with T ≲ 20 K, implying dust masses around 105 M⊙ and dust-to-gas ratios (D) within the range 10-3-10-2.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  11. Do allopatric male Calopteryx virgo damselflies learn species recognition?

    PubMed

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

    2012-03-01

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

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

    SciTech Connect

    Chung, Aeree; Van Gorkom, J. H.; Kenney, Jeffrey D. P.; Crowl, Hugh; Vollmer, Bernd E-mail: jvangork@astro.columbia.edu E-mail: hugh@astro.yale.edu E-mail: bvollmer@astro.u-strasbg.fr

    2009-12-15

    iso}{sub HI}), and describe the H I morphology and kinematics of individual galaxies in detail. The survey has revealed details of H I features that were never seen before. In this paper, we briefly discuss differences in typical H I morphology for galaxies in regions of different galaxy densities. We confirm that galaxies near the cluster core (d {sub 87} {approx}< 0.5 Mpc) have H I disks that are smaller compared to their stellar disks (D{sub HI}/D{sub 25} < 0.5). Most of these galaxies in the core also show gas displaced from the disk, which is either currently being stripped or falling back after a stripping event. At intermediate distances (d{sub 87} {approx} 1 Mpc) from the center, we find a remarkable number of galaxies with long one-sided H I tails pointing away from M87. In a previous letter, we argue that these galaxies are recent arrivals, falling into the Virgo core for the first time. In the outskirts, we find many gas-rich galaxies, with gas disks extending far beyond their optical disks. Interestingly, we also find some galaxies with H I disks that are smaller compared to their stellar disks at large clustercentric distances.

  13. 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.

  14. 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.

  15. Unveiling the Secret of a Virgo Dwarf Galaxy

    NASA Astrophysics Data System (ADS)

    2000-05-01

    Dwarf galaxies may not be as impressive in appearance as their larger brethren, but they are at least as interesting from a scientific point of view. And sometimes they may have hidden properties that will only be found by means of careful observations, probing the signals of their stars at the faintest level. Such as the entirely unexpected, well developed spiral structure within an otherwise seemingly normal dwarf elliptical galaxy! This is the surprise result of a new study by a team of astronomers [1], headed by Helmut Jerjen from the Australian National University (Canberra) who obtained detailed observations with the ESO Very Large Telescope (VLT) of the dwarf galaxy IC 3328 in the Virgo Cluster of Galaxies, some 50 million light-years away. Dwarf galaxies Dwarf galaxies are present in all major clusters of galaxies and dominate by numbers in the universe. They may contain a few (tens of) millions of stars, as compared to galaxies of normal size with hundreds of billions of stars. About two dozen dwarf galaxies are known in the "Local Group" of galaxies of which the Milky Way galaxy in which we live is also a member. The Large and Small Magellanic Clouds are some of the best known dwarf galaxies - they are of the irregular type - while NGC 147 and NGC 205, two companions to the great Andromeda Galaxy, are of the elliptical type. Dwarf elliptical galaxies are characterized by their smooth appearance. From various studies, it is known that they are tri-axial ellipsoids of different degrees of elongation. Some are almost spherical while others are more pancake- or cigar-shaped. Like the elliptical galaxies of normal size, dwarf ellipticals are almost pure aggregates of stars. In contrast, spiral galaxies also contain clouds of gas and dust. The visible mass of spiral galaxies is in a rotating disk. Dwarf ellipticals generally keep their form because of the random motions of their stars. VLT observations of dwarf elliptical galaxies Using the FORS1 multi

  16. The Nature of the Peculiar Virgo Cluster Galaxies NGC 4064 and NGC 4424

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

    Using extensive kinematical and morphological data on two Virgo Cluster galaxies undergoing strong nuclear star formation, we show that ram pressure stripping and gravitational interactions can act together on galaxies that have recently fallen into clusters. We present a detailed study of the peculiar H I-deficient Virgo Cluster spiral galaxies NGC 4064 and NGC 4424 using 12CO 1-0 interferometry, optical imaging, and integral field spectroscopic observations in order to learn what type of environmental interactions have affected these galaxies. Optical imaging reveals that NGC 4424 has a strongly disturbed stellar disk, with banana-shaped isophotes and shells. NGC 4064, which lies in the cluster outskirts, possesses a relatively undisturbed outer stellar disk and a central bar. In both galaxies Hα emission is confined to the central kiloparsec and originates in barlike strings of luminous star-forming complexes surrounded by fainter filaments. Complexes of young blue stars exist beyond the present location of ongoing star formation, indicating rapidly shrinking star-forming disks. Disturbed dust lanes extend out to a radius of 2-3 kpc, much farther than the Hα and CO emission detected by us but similar to the blue stellar complexes. CO observations reveal bilobal molecular gas morphologies, with Hα emission peaking inside the CO lobes, implying a time sequence in the star formation process. Gas kinematics reveals strong barlike noncircular motions in the molecular gas in both galaxies, suggesting that the material is radially infalling. In NGC 4064 the stellar kinematics reveals strong barlike noncircular motions in the central 1 kpc and stars supported by rotation with V/σ>1 beyond a radius of 15" (1.2 kpc). On the other hand, NGC 4424 has extremely modest stellar rotation velocities (Vmax~30 km s-1), and stars are supported by random motions as far out as we can measure, with V/σ=0.6 at r=18'' (1.4 kpc). The ionized gas kinematics in the core are disturbed

  17. Halo Substructure Towards the Galactic Center

    NASA Astrophysics Data System (ADS)

    Amy, Paul Martin; Martin, Charles; Newberg, Heidi Jo; Shelton, Siddartha; Carlin, Jeffrey L.; Willett, Benjamin A.

    2017-01-01

    We measure the velocity substructure of blue horizontal branch stars in Data Release 10 of the Sloan Digital Sky Survey, particularly in the regions of the Hermus Stream, the Hyllus Stream, and the Hercules-Aquila Cloud. These stars are concentrated at lower latitudes (b < 50°) in the first quadrant (0°substructure, and N-body simulations that plausibly replicate the morphologies of the observed tidal debris. From comparison with N-body simulations, we estimate the mass of the stream progenitors. This project was funded by a Rensselaer Presidential Fellowship, NSF grants AST 14-09421 and AST 16-15688, the NASA/NY Space Grant fellowship, and contributions made by The Marvin Clan, Babette Josephs, Manit Limlamai, and the 2015 Crowd Funding Campaign to Support Milky Way Research.

  18. 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.

  19. Substructure Discovery of Macro-Operators

    DTIC Science & Technology

    1988-05-01

    Specifically, the PLAND (PLAN Discovery) system discovers macro-operators ( macrops ) of action subsequences by searching for interesting substructures in...construction in two important areas. Unlike [Andreae84] and [Minton85], PLAND discovers macrops from observation and does not use examples to learn the new...structures . The another difference is that PLAND does not use a problem solver to determine what the macrops for a task should be (as is done in

  20. THE NORTHERN WRAPS OF THE SAGITTARIUS STREAM AS TRACED BY RED CLUMP STARS: DISTANCES, INTRINSIC WIDTHS, AND STELLAR DENSITIES

    SciTech Connect

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

    2010-09-20

    up to {Lambda} {approx_equal} 240{sup 0} where it is replaced by more distant structures. Possible detections of more nearby wraps and of the Virgo Stellar Stream are also discussed. These measured properties provide a coherent set of observational constraints for the next generation of theoretical models of the disruption of Sgr.

  1. Precision Jet Substructure from Boosted Event Shapes

    NASA Astrophysics Data System (ADS)

    Feige, Ilya; Schwartz, Matthew D.; Stewart, Iain W.; Thaler, Jesse

    2012-08-01

    Jet substructure has emerged as a critical tool for LHC searches, but studies so far have relied heavily on shower Monte Carlo simulations, which formally approximate QCD at the leading-log level. We demonstrate that systematic higher-order QCD computations of jet substructure can be carried out by boosting global event shapes by a large momentum Q and accounting for effects due to finite jet size, initial-state radiation (ISR), and the underlying event (UE) as 1/Q corrections. In particular, we compute the 2-subjettiness substructure distribution for boosted Z→qq¯ events at the LHC at next-to-next-to-next-to-leading-log order. The calculation is greatly simplified by recycling known results for the thrust distribution in e+e- collisions. The 2-subjettiness distribution quickly saturates, becoming Q independent for Q≳400GeV. Crucially, the effects of jet contamination from ISR/UE can be subtracted out analytically at large Q without knowing their detailed form. Amusingly, the Q=∞ and Q=0 distributions are related by a scaling by e up to next-to-leading-log order.

  2. Substructures in Simulations of Relativistic Jet Formation

    NASA Astrophysics Data System (ADS)

    Garcia, Raphael de Oliveira; Oliveira, Samuel Rocha de

    2017-04-01

    We present a set of simulations of relativistic jets from accretion disk initial setup with numerical solutions of a system of general-relativistic magnetohydrodynamics (GRMHD) partial differential equations in a fixed black hole (BH) spacetime which is able to show substructures formations inside the jet as well as lobe formation on the jet head. For this, we used a central scheme of finite volume method without dimensional split and with no Riemann solvers namely the Nessyahu-Tadmor method. Thus, we were able to obtain stable numerical solutions with spurious oscillations under control and with no excessive numerical dissipation. Therefore, we developed some setups for initial conditions capable of simulating the formation of relativistic jets from the accretion disk falling onto central black hole until its ejection, both immersed in a magnetosphere. In our simulations, we were able to observe some substructure of a jet created from an accretion initial disk, namely, jet head, knots, cocoon, and lobe. Also, we present an explanation for cocoon formation and lobe formation. Each initial scenario was determined by ratio between disk density and magnetosphere density, showing that this relation is very important for the shape of the jet and its substructures.

  3. Substructures in Simulations of Relativistic Jet Formation

    NASA Astrophysics Data System (ADS)

    Garcia, Raphael de Oliveira; Oliveira, Samuel Rocha de

    2017-02-01

    We present a set of simulations of relativistic jets from accretion disk initial setup with numerical solutions of a system of general-relativistic magnetohydrodynamics (GRMHD) partial differential equations in a fixed black hole (BH) spacetime which is able to show substructures formations inside the jet as well as lobe formation on the jet head. For this, we used a central scheme of finite volume method without dimensional split and with no Riemann solvers namely the Nessyahu-Tadmor method. Thus, we were able to obtain stable numerical solutions with spurious oscillations under control and with no excessive numerical dissipation. Therefore, we developed some setups for initial conditions capable of simulating the formation of relativistic jets from the accretion disk falling onto central black hole until its ejection, both immersed in a magnetosphere. In our simulations, we were able to observe some substructure of a jet created from an accretion initial disk, namely, jet head, knots, cocoon, and lobe. Also, we present an explanation for cocoon formation and lobe formation. Each initial scenario was determined by ratio between disk density and magnetosphere density, showing that this relation is very important for the shape of the jet and its substructures.

  4. Design sensitivity analysis of boundary element substructures

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  5. Identifying a new particle with jet substructures

    NASA Astrophysics Data System (ADS)

    Han, Chengcheng; Kim, Doojin; Kim, Minho; Kong, Kyoungchul; Lim, Sung Hak; Park, Myeonghun

    2017-01-01

    We investigate a potential of determining properties of a new heavy resonance of mass O(1) TeV which decays to collimated jets via heavy Standard Model intermediary states, exploiting jet substructure techniques. Employing the Z gauge boson as a concrete example for the intermediary state, we utilize a "merged jet" defined by a large jet size to capture the two quarks from its decay. The use of the merged jet benefits the identification of a Z-induced jet as a single, reconstructed object without any combinatorial ambiguity. We find that jet substructure procedures may enhance features in some kinematic observables formed with subjet four-momenta extracted from a merged jet. This observation motivates us to feed subjet momenta into the matrix elements associated with plausible hypotheses on the nature of the heavy resonance, which are further processed to construct a matrix element method (MEM)-based observable. For both moderately and highly boosted Z bosons, we demonstrate that the MEM in combination with jet substructure techniques can be a very powerful tool for identifying its physical properties. We also discuss effects from choosing different jet sizes for merged jets and jet-grooming parameters upon the MEM analyses.

  6. 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.

  7. 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.

  8. 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.

  9. AMUSE-Virgo. II. Down-sizing in Black Hole Accretion

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    We complete the census of nuclear X-ray activity in 100 early-type Virgo galaxies observed by the Chandra X-ray Telescope as part of the AMUSE-Virgo survey, down to a (3σ) limiting luminosity of 3.7 × 1038 erg s-1 over 0.5-7 keV. The stellar mass distribution of the targeted sample, which is mostly composed of formally "inactive" galaxies, peaks below 1010 M sun, a regime where the very existence of nuclear supermassive black holes (SMBHs) is debated. Out of 100 objects, 32 show a nuclear X-ray source, including 6 hybrid nuclei which also host a massive nuclear cluster as visible from archival Hubble Space Telescope images. After carefully accounting for contamination from nuclear low-mass X-ray binaries based on the shape and normalization of their X-ray luminosity function (XLF), we conclude that between 24% and 34% of the galaxies in our sample host an X-ray active SMBH (at the 95% confidence level). This sets a firm lower limit to the black hole (BH) occupation fraction in nearby bulges within a cluster environment. The differential logarithmic XLF of active SMBHs scales with the X-ray luminosity as L X -0.4±0.1 up to 1042 erg s-1. At face value, the active fraction—down to our luminosity limit—is found to increase with host stellar mass. However, taking into account selection effects, we find that the average Eddington-scaled X-ray luminosity scales with BH mass as M BH ^{-0.62^{+0.13}_{-0.12}}, with an intrinsic scatter of 0.46+0.08 -0.06 dex. This finding can be interpreted as observational evidence for "down-sizing" of BH accretion in local early types, that is, low-mass BHs shine relatively closer to their Eddington limit than higher mass objects. As a consequence, the fraction of active galaxies, defined as those above a fixed X-ray Eddington ratio, decreases with increasing BH mass.

  10. Advanced stellarators

    NASA Astrophysics Data System (ADS)

    Schlüter, Arnulf

    1983-03-01

    Toroidal confinement of a plasma by an external magnetic field is not compatible with axisymmetry, in contrast to confinement by the pinch effect of induced electric currents as in a tokomak or by the reversed field pinch configuration. The existence of magnetic surfaces throughout the region in which grad p ≠ 0 is therefore not guaranteed in such configurations, though it is necessary for MHD-equilibrium when the lines of force possess a finite twist (or "rotational transform"). These twisted equilibria are called stellarators. The other type of external confinement requires all lines of force to be closed upon themselves and p to be function of the well defined quantity Q = φ d l/ B only. The resulting "bumpy" tori are sometimes also referred to as being M + S like. By discussing specific examples it is shown that stellarator configurations exist which retain as much as possible the properties of M + S like configurations, combine these with the magnetic well, and with an approximation to the isodynamic requirement of D. Palumbo. These so-called Advanced Stellarators shown an improvement in predicted particle confinement and beta-limit compared to the classical stellarators. They can also be viewed as forming a system of linked stabilized mirrors of small mirror ratio. These fields can be produced by modular coils. A prototype of such a configuration is being designed by the stellarator division of IPP under the name of Wendelstein VII-AS. Expected physical data and technical details of W VII-AS are given.

  11. Diverse stellar haloes in nearby Milky Way mass disc galaxies

    NASA Astrophysics Data System (ADS)

    Harmsen, Benjamin; Monachesi, Antonela; Bell, Eric F.; de Jong, Roelof S.; Bailin, Jeremy; Radburn-Smith, David J.; Holwerda, Benne W.

    2017-04-01

    We have examined the resolved stellar populations at large galactocentric distances along the minor axis (from 10 kpc up to between 40 and 75 kpc), with limited major axis coverage, of six nearby highly inclined Milky Way (MW) mass disc galaxies using Hubble Space Telescope data from the Galaxy haloes, Outer discs, Substructure, Thick discs, and Star clusters (GHOSTS) survey. We select red giant branch stars to derive stellar halo density profiles. The projected minor axis density profiles can be approximated by power laws with projected slopes of -2 to -3.7 and a diversity of stellar halo masses of 1-6 × 109 M⊙, or 2-14 per cent of the total galaxy stellar masses. The typical intrinsic scatter around a smooth power-law fit is 0.05-0.1 dex owing to substructure. By comparing the minor and major axis profiles, we infer projected axis ratios c/a at ∼25 kpc between 0.4and0.75. The GHOSTS stellar haloes are diverse, lying between the extremes charted out by the (rather atypical) haloes of the MW and M31. We find a strong correlation between the stellar halo metallicities and the stellar halo masses. We compare our results with cosmological models, finding good agreement between our observations and accretion-only models where the stellar haloes are formed by the disruption of dwarf satellites. In particular, the strong observed correlation between stellar halo metallicity and mass is naturally reproduced. Low-resolution hydrodynamical models have unrealistically high stellar halo masses. Current high-resolution hydrodynamical models appear to predict stellar halo masses somewhat higher than observed but with reasonable metallicities, metallicity gradients, and density profiles.

  12. 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.

  13. The Herschel Virgo Cluster Survey. I. Luminosity function

    NASA Astrophysics Data System (ADS)

    Davies, J. I.; Baes, M.; Bendo, G. J.; Bianchi, S.; Bomans, D. J.; Boselli, A.; Clemens, M.; Corbelli, E.; Cortese, L.; Dariush, A.; De Looze, I.; di Serego Alighieri, S.; Fadda, D.; Fritz, J.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Grossi, M.; Hughes, T. M.; Hunt, L. K.; Jones, A. P.; Madden, S.; Pierini, D.; Pohlen, M.; Sabatini, S.; Smith, M. W. L.; Verstappen, J.; Vlahakis, C.; Xilouris, E. M.; Zibetti, S.

    2010-07-01

    We describe the Herschel Virgo Cluster Survey (HeViCS) and the first data obtained as part of the science demonstration phase (SDP). The data cover a central 4×4 sq deg region of the cluster. We use SPIRE and PACS photometry data to produce 100, 160, 250, 350 and 500 μm luminosity functions (LFs) for optically bright galaxies that are selected at 500 μm and detected in all bands. We compare these LFs with those previously derived using IRAS, BLAST and Herschel-ATLAS data. The Virgo cluster LFs do not have the large numbers of faint galaxies or examples of very luminous galaxies seen previously in surveys covering less dense environments. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  14. Searches for Continuous Gravitational Waves in LIGO and Virgo Data

    NASA Astrophysics Data System (ADS)

    Riles, Keith; LIGO Scientific Collaboration Collaboration; Virgo Collaboration Collaboration

    2017-01-01

    The LIGO Scientific Collaboration and Virgo Collaboration have carried out searches for periodic continuous gravitational waves. These analyses range from targeted searches for gravitational-wave signals from known pulsars, for which precise ephemerides from radio or X-ray observations are available, to all-sky searches for unknown neutron stars, including stars in unknown binary systems. Between these extremes lie directed searches for known stars of unknown spin frequency or for new unknown sources at specific locations. These different types of searches will be presented, including final results from the Initial LIGO and Virgo data runs and, where available, new results from searches of early Advanced LIGO data. This work is supported by the National Science Foundation grant PHY-1505932.

  15. 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

  16. 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.

  17. The ACS Virgo Cluster Survey. I. Introduction to the Survey

    NASA Astrophysics Data System (ADS)

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

    2004-07-01

    The Virgo Cluster is the dominant mass concentration in the Local Supercluster and the largest collection of elliptical and lenticular galaxies in the nearby universe. In this paper, we present an introduction to the ACS Virgo Cluster Survey: a program to image, in the F475W and F850LP bandpasses (~Sloan g and z), 100 early-type galaxies in the Virgo Cluster using the Advanced Camera for Surveys on the Hubble Space Telescope. We describe the selection of the program galaxies and their ensemble properties, the choice of filters, the field placement and orientation, the limiting magnitudes of the survey, coordinated parallel observations of 100 ``intergalactic'' fields with WFPC2, and supporting ground-based spectroscopic observations of the program galaxies. In terms of depth, spatial resolution, sample size, and homogeneity, this represents the most comprehensive imaging survey to date of early-type galaxies in a cluster environment. We briefly describe the main scientific goals of the survey, which include the measurement of luminosities, metallicities, ages, and structural parameters for the many thousands of globular clusters associated with these galaxies, a high-resolution isophotal analysis of galaxies spanning a factor of ~450 in luminosity and sharing a common environment, the measurement of accurate distances for the full sample of galaxies using the method of surface brightness fluctuations, and a determination of the three-dimensional structure of Virgo itself. ID="FN1"> 1Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  18. 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.

  19. Status of the commissioning of the Virgo interferometer

    NASA Astrophysics Data System (ADS)

    Accadia, T.; Acernese, F.; Antonucci, 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.; 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.; Di Paolo Emilio, M.; Di Virgilio, A.; Dietz, A.; Drago, M.; 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.; Huet, D.; 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.; Mosca, S.; Moscatelli, V.; Mours, B.; Nocera, F.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Paoletti, F.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Persichetti, G.; Pichot, M.; 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.; 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.

    2012-06-01

    Long baseline optical interferometry is a promising technique for the detection of gravitational waves [1], [2], [3], [4]. The French-Italian detector Virgo is a Michelson interferometer with 3 km arms, equipped with high storage time Fabry-Perot cavities. In this kind of detectors, the passage of gravitational waves would be sensed as a differential length variation of the arms. After the end of the second Virgo Science Run, lasting from July 2009 to the beginning of January 2010, some important upgrades have been carried out; in particular, the mirrors of the Fabry-Perot cavities, which act as test masses of the detector, have been replaced by new ones with an higher reflectivity, which should increase by three times the finesse of the cavities; moreover the mirrors are now suspended by silica fibers in a monolithic assembly expected to significantly lower the thermal noise. Finally, the digital signal processing electronics and the global control system have been largely improved. We will present the status of the commissioning of the Virgo interferometer.

  20. 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.

  1. 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

  2. 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

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

    PubMed

    Terkovics, N; Neild, S A; Lowenberg, M; Szalai, R; Krauskopf, B

    2016-08-01

    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.

  4. UV to radio centimetric spectral energy distributions of optically-selected late-type galaxies in the Virgo cluster

    NASA Astrophysics Data System (ADS)

    Boselli, A.; Gavazzi, G.; Sanvito, G.

    2003-04-01

    We present a multifrequency dataset for an optically-selected, volume-limited, complete sample of 118 late-type galaxies (>=S0a) in the Virgo cluster. The database includes UV, visible, near-IR, mid-IR, far-IR, radio continuum photometric data as well as spectroscopic data of Hα , CO and HI lines, homogeneously reduced, obtained from our own observations or compiled from the literature. Assuming the energy balance between the absorbed stellar light and that radiated in the IR by dust, we calibarte an empirical attenuation law suitable for correcting photometric and spectroscopic data of normal galaxies. The data, corrected for internal extinction, are used to construct the spectral energy distribution (SED) of each individual galaxy, and combined to trace the median SED of galaxies in various classes of morphological type and luminosity. Low-luminosity, dwarf galaxies have on average bluer stellar continua and higher far-IR luminosities per unit galaxy mass than giant, early-type spirals. If compared to nearby starburst galaxies such as M 82 and Arp 220, normal spirals have relatively similar observed stellar spectra but 10-100 times lower IR luminosities. The temperature of the cold dust component increases with the far-IR luminosity, from giant spirals to dwarf irregulars. The SED are used to separate the stellar emission from the dust emission in the mid-IR regime. We show that the contribution of the stellar emission at 6.75 mu m to the total emission of galaxies is generally important, from ~ 80% in Sa to ~ 20% in Sc. Tables 2-5, 7, 8, and Fig. 2 are only available in electronic form at http://www.edpsciences.org Tables 10-12 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/402/37

  5. 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.

  6. Substructure of fuzzy dark matter haloes

    NASA Astrophysics Data System (ADS)

    Du, Xiaolong; Behrens, Christoph; Niemeyer, Jens C.

    2017-02-01

    We derive the halo mass function (HMF) for fuzzy dark matter (FDM) by solving the excursion set problem explicitly with a mass-dependent barrier function, which has not been done before. We find that compared to the naive approach of the Sheth-Tormen HMF for FDM, our approach has a higher cutoff mass and the cutoff mass changes less strongly with redshifts. Using merger trees constructed with a modified version of the Lacey & Cole formalism that accounts for suppressed small-scale power and the scale-dependent growth of FDM haloes and the semi-analytic GALACTICUS code, we study the statistics of halo substructure including the effects from dynamical friction and tidal stripping. We find that if the dark matter is a mixture of cold dark matter (CDM) and FDM, there will be a suppression on the halo substructure on small scales which may be able to solve the missing satellites problem faced by the pure CDM model. The suppression becomes stronger with increasing FDM fraction or decreasing FDM mass. Thus, it may be used to constrain the FDM model.

  7. GALEX Ultraviolet Observations of the Interacting Galaxy NGC 4438 in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

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

    2005-04-01

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

  8. Post-Newtonian Dynamics in Dense Stellar Systems

    NASA Astrophysics Data System (ADS)

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

    2007-08-01

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

  9. 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

    2016-12-01

    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 data set. 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 data sets 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 colour-magnitude diagrams. 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.

  10. Dark Matter Substructure, Galaxy Assembly and Star Formation Histories

    NASA Astrophysics Data System (ADS)

    Simha, Vimal

    2011-01-01

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

  11. Population Gradients in Stellar Halos from GHOSTS

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Prospecting for Elements: Galactic Halo Planetary Nebulae Abundances and Virgo Spiral Galaxy Color Profiles

    NASA Astrophysics Data System (ADS)

    Howard, Joseph William

    Halo planetary nebulae. Using published spectral line data for nine halo planetary nebulae (HPNe), I have calculated photoionization models in an attempt to gain insight into the physical conditions and chemical abundances of these nebulae. The nine HPNE reported upon are K648, DdDm-1, NGC2242, NGC4361, PN243.8-37.1, PN006-41.9, M2-29, BB-1, and H4-1. The derived abundance ranges for the HPNe are: C 6.60-8.95, N 7.18-8.00, O 7.56-8.56, Ne 6.24-7.71, Ar 4.12-7.70, and S 4.90-7.00 (log(x) + 12). The temperature range for the central stars of these nebulae is 40,000 to 140,000K. Specifically, with a few exceptions, I find that all nine objects exhibit subsolar O/H; most show enhanced C/O and N/O, and a constant Ne/O ration. I also note the existence of comparatively larger abundance scatter in the HPNe as opposed to disk PNe, and suggest that this is consistent with the accretion model of halo formation formulated by Searle & Zinn. In addition, I test the effects on derived abundances and central star temperatures of a variety of model atmospheres as well as blackbodies for input ionizing spectra. I find that nebular line strengths are relatively insensitive to atmospheric details; thus blackbody spectra are suitable for central star continua. Near-infrared Virgo cluster spiral colors. Near-infrared (NIR) surface photometry in J (1.2μm), H (1.6μm) and K (2.2μm) have been obtained for a sample of Virgo cluster spirals; NGC4321, NGC4303, NGC4571, NGC4689, and NGC4254 which span a large range in HI deficiency. The spirals range from a normal gas content to a deficiency of a factor of 10 compared to normal galaxies. Using previous HII region abundance studies along with the NIR colors an attempt has been made to calibrate any correlation between the J-K index to the overall gas phase abundance gradients as a first step to probing the underlying stellar metallicity. Decomposition techniques have been used to produce estimates of spiral bulge/disk masses and luminosities

  17. Stellar cannibalism

    NASA Astrophysics Data System (ADS)

    Astronomers have obtained evidence that stars can literally swallow other stars, leading to the ejection of stellar material into space and the formation of extremely close pairs of stars, according to the National Science Foundation (NSF). The discovery supports theoretical predictions of the evolution of double stars.While studying the central stars of planetary nebulae—disk-shaped gas clouds that vaguely resemble planets—Albert D. Grauer of the University of Arkansas at Little Rock and Howard E. Bond of Louisiana State University at Baton Rouge found that several of these central stars are actually very close stellar pairs. Previously, it had been thought that the central star in a planetary nebula was a single star that expelled a gas cloud as it neared the end of its life. Their latest discovery, the central star of planetary nebula Abell 41, consists of a pair of stars that orbit each other in 2 hours and 43 minutes. The researchers also have found three other central star pairs that have orbital periods of between 11 and 16 hours.

  18. 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.

  19. The maraging-steel blades of the Virgo super attenuator

    NASA Astrophysics Data System (ADS)

    Braccini, S.; Casciano, C.; Cordero, F.; Corvace, F.; DeSanctis, M.; Franco, R.; Frasconi, F.; Majorana, E.; Paparo, G.; Passaquieti, R.; Rapagnani, P.; Ricci, F.; Righetti, D.; Solina, A.; Valentini, R.

    2000-05-01

    The blades are crucial components of the Virgo super attenuators. The material used for their construction is maraging steel, a low-carbon-content alloy with high ultimate tensile strength and low creep under stress. Young's modulus, the shear modulus, the Poisson ratio and the corresponding elastic energy-loss coefficients have been measured. The measurements have been performed on specimens subjected to the same thermal treatments as those of elements for the Virgo interferometer realized with maraging steel. In addition, anelastic properties of the material subjected to different thermal treatments have been measured. It has been found that, for a maraging-steel structure (one free of plastic deformation), which undergoes an excitation with flexural vibrations, the elastic energy-loss coefficient can vary over a wide range as a function of the thermal treatment of the material and it is dominated by the thermo-elastic effect. The main reason for such a great alteration is supposed to be the dependence of the thermal conductivity on the average sizes of the precipitate particles and their relative separations.

  20. Possible Influence of Aperture Heating on VIRGO Radiometry on SOHO

    NASA Astrophysics Data System (ADS)

    Frohlich, C.

    2010-12-01

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

  1. COSMIC RAY DIFFUSION FRONTS IN THE VIRGO CLUSTER

    SciTech Connect

    Mathews, William G.; Guo Fulai

    2011-07-20

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

  2. Cluster X-Ray Substructure and Radio Galaxy Correlations

    NASA Astrophysics Data System (ADS)

    Ledlow, M. J.; Burns, J. O.

    1994-12-01

    Current wisdom suggests that X-ray substructure in the intracluster medium (ICM) is fairly common in galaxy clusters. This substructure takes the form of elongations, isophotal twisting, asymmetries, and sub-clumping. Substructure is also frequently present in kinematical analysis of the galaxy velocity and spatial distributions. These features include bimodality, kurtosis or skewness, and non-Gaussian velocity distributions. Consistent with the observations, Hydro/N-Body simulations suggest that cluster-subcluster mergers may be the culprit to explain these features in the ICM gas distribution, and would indicate that many clusters, even at the present epoch, are still undergoing significant dynamical evolution. From a sample of X-ray images from the Einstein satellite and, more recently, the ROSAT mission, Burns et al. (1994) found a significant correlation between the positions of radio galaxies and subclumps within the cluster-scale X-ray emission. Burns et al. have suggested that radio galaxies reside in the residue of cluster/sub-cluster merging sites, and may therefore act as pointers to clusters with ongoing and intersting dynamical activity. We are following up these ideas with a detailed substructure analysis, and a comparison to a sample of clusters without radio galaxies. In order to determine the signficance of substructure, we have reanalyzed the X-ray images using a Bootstrap-Resampling Monte-Carlo technique. In this method, asymmetries, elongations, and other forms of substructure are evaluated using a moment-analysis similar to M{o}hr et al. (1994), with the advantage that we need not assume apriori any specific substructure-free model for the source (\\ie\\ a Beta-model). The significance of individual features is determined solely from a comparison to statistical fluctuations (including noise) of the actual data. Using this technique, we place limits on the fraction of clusters with significant substructure and test the radio galaxy/substructure

  3. Synthesised H ∞ / μ Control Design for Dynamically Substructured Systems

    NASA Astrophysics Data System (ADS)

    Yamaguchi, T.; Stoten, D. P.

    2016-09-01

    In the dynamically substructured system (DSS) testing technique, a controller that synchronises the responses of physical and numerical substructures is an essential part of the testing scheme to ensure synchronisation fidelity. This paper discusses a novel approach that generates a two-degree-of-freedom (2-DOF) output feedback controller for multi-input, multioutput (MIMO) DSS via control synthesis. This 2-DOF output feedback controller yields robust stability and robust performance of the physical/numerical substructure synchronisation and enables controller tuning in the frequency domain. Simulation and experimental results have been shown to validate the efficacy of the method.

  4. 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.

  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. 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)

  7. Pi of the Sky involvement in LSC-Virgo electromagnetic follow-up project

    NASA Astrophysics Data System (ADS)

    ZadroŻny, Adam; Sokołowski, Marcin; Mankiewicz, Lech; Żarnecki, Aleksander Filip

    2016-09-01

    Pi of the Sky took part in LSC-Virgo's Electromagnetic (EM) Follow-up project during first science run of Advanced LIGO detectors between September 2015 and January 2016. More than 60 astronomical teams have signed Memorandum-of-Understanding with LSC-Virgo for EM Follow-up project. LSC-Virgo's EM Follow-up is aimed for searching electromagnetic counterparts to gravitational wave transient candidates. Observing an event both in EM and gravitational wave band might be a important step forward to multi-messenger astronomy. The aim of this paper is to show algorithms used by Pi of the Sky for analysing data taken during the science runs.

  8. 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

  9. Dynamically Substructured System Testing for Railway Vehicle Pantographs

    NASA Astrophysics Data System (ADS)

    Stoten, D. P.; Yamaguchi, T.; Yamashita, Y.

    2016-09-01

    ]The overall objective of this paper is to establish a dynamically substructured system (DSS) testing approach for railway vehicle pantographs. In this approach a pilot study quasi-pantograph (QP) is tested within a laboratory environment, where the catenary wire, contact wire and catenary support (abbreviated as ‘catenary’ in this paper) are modelled as a numerical substructure. This is simulated in real time and in parallel with the operation of the physical substructure, i.e. the QP rig itself. The entire DSS is driven by parametric excitation within the catenary model, whilst the numerical and physical substructures are synchronised at their interface via the DSS control technique of [1]. Simulation and physical experimental investigations of the pilot QP rig, constructed within the Advanced Control and Test Laboratory at the University of Bristol, UK, demonstrate the efficacy of the method when subjected to parametric variations, unknown parameter values and parametric excitation.

  10. 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

  11. Detail view of substructure, view looking at the south abutments ...

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

    Detail view of substructure, view looking at the south abutments and the pedestrian promenade - Spring Creek Bridge, Spanning Spring Creek at Milepoint 253.98 on Oregon to California Highway (US Route 97), Chiloquin, Klamath County, OR

  12. 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

  13. 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

  14. Substructure of the outer dynein arm

    PubMed Central

    1982-01-01

    The substructure of the outer dynein arm has been analyzed in quick- frozen deep-etch replicas of Tetrahymena and Chlamydomonas axonemes. Each arm is found to be composed of five morphologically discrete components: an elliptical head; two spherical feet; a slender stalk; and an interdynein linker. The feet make contact with the A microtubule of each doublet; the stalk contacts the B microtubule; the head lies between the feet and stalk; and the linker associates each arm with its neighbor. The spatial relationships between these five components are found to be distinctly different in rigor (ATP-depleted) versus relaxed (ATP- or vanadate plus ATP-treated) axonemes, and the stalk appears to alter its affinity for the B microtubule in the relaxed state. Images of living cilia attached to Tetrahymena cells show that the relaxed configuration is adopted in vivo. We relate our observations to morphological and experimental studies reported by others and propose several models that suggest how this newly described dynein morphology may relate to dynein function. PMID:6218174

  15. Dislocation substructure in fatigued duplex stainless steel

    SciTech Connect

    Polak, J. . Lab. de Mecanique de Lille Inst. of Physical Metallurgy, Brno . Academy of Sciences); Degallaix, S. . Lab. de Mecanique de Lille); Kruml, T. . Academy of Sciences)

    1993-12-15

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

  16. Sub-structure of A Map Streamer

    NASA Astrophysics Data System (ADS)

    Liniger, M. A.; Davies, H. C.

    A study is undertaken of the sub-structure of an upper-level PV streamer that ap- proached the European Alps during the field phase of the Mesoscale Alpine Pro- gramme (MAP) in November 1999. The diagnosis is based upon a Lagrangian For- ward Projection (LFP) technique that can provide a spatial refinement of the opera- tional ECMWF analysis fields and relate the past Lagrangian history to these. The re- constructed fields capture several notable fine-scale features of the streamer's structure that include: -spiral arms of a vortex-like feature; -a richly structured western flank to the streamer comprising a deep primary fold surmounted by a significant secondary fold with an intermediate distinctive striation that extends back into the stratosphere. The features are not at variance with independent high-resolution satellite water vapour images and measurements gathered in a flight mission using an airbourne wa- ter vapour DIAL instrument, and hence lend a measure of credence to both the LFP approach and the DIAL measurements. Moreover the analysis sheds light on the evo- lution and dynamics of the streamer's vortices, the origin of the folds, and it also has implications for stratosphere-troposphere exchange and the accompanying chemical mixing.

  17. 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.

  18. A new interface element for connecting independently modeled substructures

    NASA Technical Reports Server (NTRS)

    Ransom, Jonathan B.; Mccleary, Susan L.; Aminpour, Mohammad A.

    1993-01-01

    A new interface element based on the hybrid variational formulation is presented and demonstrated. The element provides a means of connecting independently modeled substructures whose nodes along the common boundary need not be coincident. The interface element extends previous work to include connecting an arbitrary number of substructures, the use of closed and generally curved interfaces, and the use of multiple, possibly nested, interfaces. Several applications of the element are presented and aspects of the implementation are discussed.

  19. Chemical Abundances of Planetary Nebulae in the Substructures of M31

    NASA Astrophysics Data System (ADS)

    Fang, Xuan; García-Benito, Rubén; Guerrero, Martín A.; Liu, Xiaowei; Yuan, Haibo; Zhang, Yong; Zhang, Bing

    2015-12-01

    We present deep spectroscopy of planetary nebulae (PNe) that are associated with the substructures of the Andromeda Galaxy (M31). The spectra were obtained with the Optical System for Imaging and low-intermediate-Resolution Integrated Spectroscopy spectrograph on the 10.4 m Gran Telescopio Canarias. Seven targets were selected for the observations, three in the Northern Spur and four associated with the Giant Stream. The most distant target in our sample, with a rectified galactocentric distance ≥slant 100 kpc, was the first PN discovered in the outer streams of M31. The [O iii] λ4363 auroral line is well detected in the spectra of all targets, enabling electron temperature determination. Ionic abundances are derived based on the [O iii] temperatures, and elemental abundances of helium, nitrogen, oxygen, neon, sulfur, and argon are estimated. The relatively low N/O and He/H ratios, as well as abundance ratios of α-elements, indicate that our target PNe might belong to populations as old as ∼2 Gyr. Our PN sample, including the current seven and the previous three observed by Fang et al., have rather homogeneous oxygen abundances. The study of abundances and the spatial and kinematical properties of our sample leads to the tempting conclusion that their progenitors might belong to the same stellar population, which hints at a possibility that the Northern Spur and the Giant Stream have the same origin. This may be explained by the stellar orbit proposed by Merrett et al. Judging from the position and kinematics, we emphasize that M32 might be responsible for the two substructures. Deep spectroscopy of PNe in M32 will help to assess this hypothesis. Based on observations made with the Gran Telescopio Canarias, installed at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma. These observations are associated with program No. GTC55-14B.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    cluster pericentre approach and are relatively recent infalls. We also find hints of a decreasing X-ray gas density profile core radius with redshift. Conclusions: The percentage of mass included in substructures was found to be roughly constant with redshift values of 5-15%, in agreement both with the general CDM framework and with the results of numerical simulations. Galaxies in substructures show the same general behaviour as regular cluster galaxies; however, in substructures, there is a deficiency of both late type and old stellar population galaxies. Late type galaxies with recent bursts of star formation seem to be missing in the substructures close to the bottom of the host cluster potential well. However, our sample would need to be increased to allow a more robust analysis. Tables 1, 2, 4 and Appendices A-C are available in electronic form at http://www.aanda.org

  1. Surface photometry of Virgo cluster galaxies - Barred galaxies

    NASA Technical Reports Server (NTRS)

    Benedict, G. F.

    1976-01-01

    Photographic surface photometry in B and V is presented for three barred galaxies in the Virgo cluster: N4548, N4596, and N4608. Intercomparisons of luminosity and color profiles and standard photometric parameters indicate that for these galaxies: (1) the nuclear component follows the fourth-root-of-radius luminosity law for both B and V, (2) the luminosity profiles along the bar show a characteristic shoulder with a slight fall in B-V color profile at the brightest point in the bar, the strength of the effect declining from N4548 to N4608, (3) the integrated bar component is slightly bluer than the nucleus, and (4) as the disk, arm, and ring components contribute less to the total luminosity of the system, the contribution of the bar increases as does the equivalent gradient.

  2. NGC 4388 - A Seyfert 2 galaxy in the Virgo cluster

    NASA Astrophysics Data System (ADS)

    Phillips, M. M.; Malin, D. F.

    1982-06-01

    Direct photographic data and preliminary spectroscopy of the spiral galaxy NGC 4388 are presented. The galaxy appears to be a barred spiral of morphological class SB(s)b pec and is almost certainly a member of the Virgo cluster. The nucleus was studied with a photon-counting image intensifier/reticon scanner and was found to emit a high-excitation, narrow emission-line spectrum of relatively low luminosity. Image-tube spectrograms and spectroscopy using an image photon-counting system revealed optical, X-ray, and radio nuclear properties consistent with a classical Seyfert 2 galaxy. The radial velocity of the peaks of the asymmetric nuclear emission lines is 55 km/s less than the H I 21 cm systemic velocity.

  3. 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

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  7. Software engineering practices for the EGO Virgo project

    NASA Astrophysics Data System (ADS)

    Carbognani, Franco; de Wet, Jacques

    2004-09-01

    The Virgo Gravitational Waves Detector has recently entered its commissioning phase. An important element in this phase is the application of Software Engineering (SE) practices to the Control and Data Analysis Software. This article focus on the experience in applying those SE practices as a simple but effective set of standards and tools. The main areas covered are software configuration management, problem reporting, integration planning, software testing and systems performance monitoring. Key elements of Software Configuration Management (SCM) are source code control allowing checkin/checkout of sources from a software archive combined with a backup plan. The tool SCVS developed on top of CVS in order to provide an easier and more structured use mode is supporting this. Tracking bugs and modifications is a necessary complement of SCM. A central database with email and web interface to submit, query and modify Software Problem Reports (SPR) has been implemented on top of the WREQ tool. Integrating software components that were not designed with integration in mind is one of the major problems in software development. An explicit Integration Plan is therefore absolutely essential. We are currently implementing a slow upgrade cycle Common Software Releases management as structured integration plan. Software Testing must be closely integrated with development and to the most feasible extent automatic. With the use of the automated test tool tat, the developer can incrementally build a unit/regression test suite that will help measure progress, spot unintended side effects, and focus the development efforts. One of the characteristics of large and complex projects, like Virgo, is the difficulty in understanding how well the different subsystems are performing and then plan for changes. In order to support System Performance Monitoring the tool Big Brother has been adopted to make it possible to trace the reliability of the different subsystems and thus providing

  8. The BRAVE Program. I. Improved Bulge Stellar Velocity Dispersion Estimates for a Sample of Active Galaxies

    NASA Astrophysics Data System (ADS)

    Batiste, Merida; Bentz, Misty C.; Manne-Nicholas, Emily R.; Onken, Christopher A.; Bershady, Matthew A.

    2017-02-01

    We present new bulge stellar velocity dispersion measurements for 10 active galaxies with secure MBH determinations from reverberation mapping. These new velocity dispersion measurements are based on spatially resolved kinematics from integral-field (IFU) spectroscopy. In all but one case, the field of view of the IFU extends beyond the effective radius of the galaxy, and in the case of Mrk 79 it extends to almost one half the effective radius. This combination of spatial resolution and field of view allows for secure determinations of stellar velocity dispersion within the effective radius for all 10 target galaxies. Spatially resolved maps of the first (V) and second (σ⋆) moments of the line of sight velocity distribution indicate the presence of kinematic substructure in most cases. In future projects we plan to explore methods of correcting for the effects of kinematic substructure in the derived bulge stellar velocity dispersion measurements.

  9. The Next Generation Virgo Cluster Survey. XXII. Shell Feature Early-type Dwarf Galaxies in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Paudel, Sanjaya; Smith, Rory; Duc, Pierre-Alain; Côté, Patrick; Cuillandre, Jean-Charles; Ferrarese, Laura; Blakeslee, John P.; Boselli, Alessandro; Cantiello, Michele; Gwyn, S. D. J.; Guhathakurta, Puragra; Mei, Simona; Mihos, J. Christopher; Peng, Eric W.; Powalka, Mathieu; Sánchez-Janssen, Rúben; Toloba, Elisa; Zhang, Hongxin

    2017-01-01

    The Next Generation Virgo Cluster Survey is a deep (with a 2σ detection limit μg = 29 mag arcsec‑2 in the g-band) optical panchromatic survey targeting the Virgo cluster from its core to virial radius, for a total areal coverage of 104 square degrees. As such, the survey is well suited for the study of galaxies’ outskirts, haloes, and low surface brightness features that arise from dynamical interactions within the cluster environment. We report the discovery of extremely faint (μg > 25 mag arcsec‑2) shells in three Virgo cluster early-type dwarf galaxies: VCC 1361, VCC 1447, and VCC 1668. Among them, VCC 1447 has an absolute magnitude Mg = ‑11.71 mag and is the least massive galaxy with a shell system discovered to date. We present a detailed study of these low surface brightness features. We detect between three and four shells in each of our galaxies. Within the uncertainties, we find no evidence of a color difference between the galaxy main body and shell features. The observed arcs of the shells are located up to several effective radii of the galaxies. We further explore the origin of these low surface brightness features with the help of idealized numerical simulations. We find that a near equal mass merger is best able to reproduce the main properties of the shells, including their quite symmetric appearance and their alignment along the major axis of the galaxy. The simulations provide support for a formation scenario in which a recent merger, between two near-equal mass, gas-free dwarf galaxies, forms the observed shell systems. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada–France–Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

  10. Probing Stellar Dynamics With Space Photometry

    NASA Astrophysics Data System (ADS)

    García, Rafael A.; Salabert, D.; Ballot, J.; Beck, P. G.; Bigot, L.; Corsaro, E.; Creevey, O.; Egeland, R.; Jiménez, A.; Mathur, S.; Metcalfe, T.; do Nascimento, J.; Pallé, P. L.; Pérez Hernández, F.; Regulo, C.

    2016-08-01

    The surface magnetic field has substantial influence on various stellar properties that can be probed through various techniques. With the advent of new space-borne facilities such as CoRoT and Kepler, uninterrupted long high-precision photometry is available for hundred of thousand of stars. This number will substantially grow through the forthcoming TESS and PLATO missions. The unique Kepler observations -covering up to 4 years with a 30-min cadence- allows studying stellar variability with different origins such as pulsations, convection, surface rotation, or magnetism at several time scales from hours to years. We study the photospheric magnetic activity of solar-like stars by means of the variability induced in the observed signal by starspots crossing the visible disk. We constructed a solar photometric magnetic activity proxy, Sph from SPM/VIRGO/SoHO, as if the Sun was a distant star and we compare it with several solar well-known magnetic proxies. The results validate this approach. Thus, we compute the Sph proxy for a set of CoRoT and Kepler solar-like stars for which pulsations were already detected. After characterizing the rotation and the magnetic properties of 300 solar-like stars, we use their seismic properties to characterize 18 solar analogs for which we study their magnetism. This allows us to put the Sun into context of its siblings.

  11. Chemical abundances in Virgo cluster spirals - what drives the environmental dependence of galaxy metallicity?

    NASA Astrophysics Data System (ADS)

    Ellison, Sara; Skillman, Evan; Chung, Aeree

    2009-08-01

    The Virgo cluster is not only our nearest massive cluster, but its dynamical infancy also renders it an ideal laboratory for studies of cluster formation and galaxy evolution. Given the intense interest in Virgo, it is astounding that only 9 out of over 100 spirals in its firmament have chemical abundance measurements. We propose to simultaneously address this gap in our fundamental knowledge of Virgo cluster spirals and investigate how the metallicity and abundance gradients of star forming galaxies are sensitive to environment. Our sample consists of 13 Virgo cluster spiral galaxies, preferentially gas-poor early types, which complement the existing metallicity measurements. We also sample a range of clustercentric distances (0.3 -- 3 Mpc from M87), local densities and include several galaxies which exhibit evidence for interactions with the intra-cluster medium.

  12. Pi of the Sky preparations for LSC-Virgo's electromagnetic follow-up project

    NASA Astrophysics Data System (ADS)

    ZadroŻny, Adam; Sokołowski, Marcin; Majcher, Ariel; Opiela, Rafał; Obara, Łukasz

    2015-09-01

    The presentation focuses on plans of the Pi of the Sky collaboration to participate in the future LSC-Virgo's Electromagnetic (EM) Follow-up campaigns. Pi of the Sky telescope participated in the first "EM Follow-up project", called Looc-Up1-3 2009-2010 organized by LSC-Virgo collaboration. Pi of the Sky brought to the project an instrument with the biggest field of view and with a very high time resolution. Recently Pi of the Sky has signed an Memorandum of Understanding (MOU) with LSC-Virgo for EM Follow-up observations in the Advanced Detector Era (ADE). Plans of the Pi of the Sky telescope for joint observations with advanced LIGO and Virgo detectors will be also outlined.

  13. 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.

  14. RESONANT CLUMPING AND SUBSTRUCTURE IN GALACTIC DISKS

    SciTech Connect

    Molloy, Matthew; Smith, Martin C.; Shen, Juntai; Evans, N. Wyn E-mail: msmith@shao.ac.cn E-mail: nwe@ast.cam.ac.uk

    2015-05-10

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

  15. Planck intermediate results. XL. The Sunyaev-Zeldovich signal from the Virgo cluster

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Churazov, E.; Clements, D. L.; Colombo, L. P. L.; Combet, C.; Comis, B.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dolag, K.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Harrison, D. L.; Helou, G.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Marcos-Caballero, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Meinhold, P. R.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Noviello, F.; Novikov, D.; Novikov, I.; Oppermann, N.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Schaefer, B. M.; Scott, D.; Soler, J. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Weller, J.; Yvon, D.; Zacchei, A.; Zonca, A.

    2016-12-01

    The Virgo cluster is the largest Sunyaev-Zeldovich (SZ) source in the sky, both in terms of angular size and total integrated flux. Planck's wide angular scale and frequency coverage, together with its high sensitivity, enable a detailed study of this big object through the SZ effect. Virgo is well resolved by Planck, showing an elongated structure that correlates well with the morphology observed from X-rays, but extends beyond the observed X-ray signal. We find good agreement between the SZ signal (or Compton parameter, yc) observed by Planck and the expected signal inferred from X-ray observations and simple analytical models. Owing to its proximity to us, the gas beyond the virial radius in Virgo can be studied with unprecedented sensitivity by integrating the SZ signal over tens of square degrees. We study the signal in the outskirts of Virgo and compare it with analytical models and a constrained simulation of the environment of Virgo. Planck data suggest that significant amounts of low-density plasma surround Virgo, out to twice the virial radius. We find the SZ signal in the outskirts of Virgo to be consistent with a simple model that extrapolates the inferred pressure at lower radii, while assuming that the temperature stays in the keV range beyond the virial radius. The observed signal is also consistent with simulations and points to a shallow pressure profile in the outskirts of the cluster. This reservoir of gas at large radii can be linked with the hottest phase of the elusivewarm/hot intergalactic medium. Taking the lack of symmetry of Virgo into account, we find that a prolate model is favoured by the combination of SZ and X-ray data, in agreement with predictions. Finally, based on the combination of the same SZ and X-ray data, we constrain the total amount of gas in Virgo. Under the hypothesis that the abundance of baryons in Virgo is representative of the cosmic average, we also infer a distance for Virgo of approximately 18 Mpc, in good

  16. 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.

  17. KINEMATIC AND SPATIAL SUBSTRUCTURE IN NGC 2264

    SciTech Connect

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

    2015-04-15

    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 ({sup 13}CO) 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. Wide- and contact-binary formation in substructured young stellar clusters

    NASA Astrophysics Data System (ADS)

    Dorval, J.; Boily, C. M.; Moraux, E.; Roos, O.

    2017-02-01

    We explore with collisional gravitational N-body models the evolution of binary stars in initially fragmented and globally subvirial clusters of stars. Binaries are inserted in the (initially) clumpy configurations so as to match the observed distributions of the field-binary-stars' semimajor axes a and binary fraction versus primary mass. The dissolution rate of wide binaries is very high at the start of the simulations, and is much reduced once the clumps are eroded by the global infall. The transition between the two regimes is sharper as the number of stars N is increased, from N = 1.5 k up to 80 k. The fraction of dissolved binary stars increases only mildly with N, from ≈15 per cent to ≈25 per cent for the same range in N. We repeated the calculation for two initial system mean number densities of 6 per pc3 (low) and 400 per pc3 (high). We found that the longer free-fall time of the low-density runs allows for prolonged binary-binary interactions inside clumps and the formation of very tight (a ≈ 0.01 au) binaries by exchange collisions. This is an indication that the statistics of such compact binaries bear a direct link to their environment at birth. We also explore the formation of wide (a ≳ 5 × 104 au) binaries and find a low (≈0.01 per cent) fraction mildly bound to the central star cluster. The high-precision astrometric mission Gaia could identify them as outflowing shells or streams.

  4. THE NEXT GENERATION VIRGO CLUSTER SURVEY. X. PROPERTIES OF ULTRA-COMPACT DWARFS IN THE M87, M49, AND M60 REGIONS

    SciTech Connect

    Liu, Chengze; Peng, Eric W.; Zhang, Hong-Xin; Côté, Patrick; Ferrarese, Laura; Gwyn, Stephen; Blakeslee, John P.; Jordán, Andrés; Muñoz, Roberto P.; Puzia, Thomas H.; Mihos, J. Christopher; Lançon, Ariane; Cuillandre, Jean-Charles; Durrell, Patrick R. E-mail: peng@pku.edu.cn; and others

    2015-10-10

    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*iK{sub s} 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.

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

    NASA Astrophysics Data System (ADS)

    Chung, Aeree

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

  6. 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.

  7. 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.

  8. Creating mock catalogues of stellar haloes from cosmological simulations

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  9. 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.

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

    SciTech Connect

    Wang Shidao |; Hei Zukun

    1999-04-23

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

  11. Galactic substructure and energetic neutrinos from the sun and earth.

    PubMed

    Koushiappas, Savvas M; Kamionkowski, Marc

    2009-09-18

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

  12. 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.

  13. Detecting Halo Substructure in the Gaia Era

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  14. 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.

  15. Advanced stellarator power plants

    SciTech Connect

    Miller, R.L.

    1994-07-01

    The stellarator is a class of helical/toroidal magnetic fusion devices. Recent international progress in stellarator power plant conceptual design is reviewed and comparisons in the areas of physics, engineering, and economics are made with recent tokamak design studies.

  16. 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.

  17. Stellarator status, 1989

    SciTech Connect

    Lyon, J.F. ); Grieger, G.; Rau, F. ); Iiyoshi, A. ); Navarro, A.P. ); Kovrizhnykh, L.M. . Inst. Obshchey Fiziki); Pavlichenko, O.S. (AN Ukrain

    1990-07-01

    The present status of stellarator experiments and recent progress in stellarator research (both experimental and theoretical) are reported by groups in the United States, the USSR, Japan, Australia, and the European Community (the Federal Republic of Germany and Spain). Experiments under construction and studies of large, next-generation stellarators are also described. 73 refs., 11 figs., 4 tabs.

  18. 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.

  19. 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.

  20. 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.

  1. A review of substructure coupling methods for dynamic analysis

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    The state of the art is assessed in substructure coupling for dynamic analysis. A general formulation, which permits all previously described methods to be characterized by a few constituent matrices, is developed. Limited results comparing the accuracy of various methods are presented.

  2. Trans-dimensional Bayesian inference for gravitational lens substructures

    NASA Astrophysics Data System (ADS)

    Brewer, Brendon J.; Huijser, David; Lewis, Geraint F.

    2016-01-01

    We introduce a Bayesian solution to the problem of inferring the density profile of strong gravitational lenses when the lens galaxy may contain multiple dark or faint substructures. The source and lens models are based on a superposition of an unknown number of non-negative basis functions (or `blobs') whose form was chosen with speed as a primary criterion. The prior distribution for the blobs' properties is specified hierarchically, so the mass function of substructures is a natural output of the method. We use reversible jump Markov Chain Monte Carlo within Diffusive Nested Sampling to sample the posterior distribution and evaluate the marginal likelihood of the model, including the summation over the unknown number of blobs in the source and the lens. We demonstrate the method on two simulated data sets: one with a single substructure, and the other with 10. We also apply the method to the g-band image of the `Cosmic Horseshoe' system, and find evidence for more than zero substructures. However, these have large spatial extent and probably only point to misspecifications in the model (such as the shape of the smooth lens component or the point-spread function), which are difficult to guard against in full generality.

  3. Experimentally implementable criteria revealing substructures of genuine multipartite entanglement

    SciTech Connect

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

    2011-02-15

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

  4. A Frequency-Domain Substructure System Identification Algorithm

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  5. Chemical Substructure Searching: Comparing Three Commercially Available Databases.

    ERIC Educational Resources Information Center

    Wagner, A. Ben

    1986-01-01

    Compares the differences in coverage and utility of three substructure databases--Chemical Abstracts, Index Chemicus, and Chemical Information System's Nomenclature Search System. The differences between Chemical Abstracts with two different vendors--STN International and Questel--are described and a summary guide for choosing between databases is…

  6. Mid-IR emission of galaxies in the Virgo cluster. II. Integrated properties

    NASA Astrophysics Data System (ADS)

    Boselli, A.; Lequeux, J.; Sauvage, M.; Boulade, O.; Boulanger, F.; Cesarsky, D.; Dupraz, C.; Madden, S.; Viallefond, F.; Vigroux, L.

    1998-07-01

    We analyse the integrated properties of the Mid-IR emission of a complete, optically selected sample of galaxies in the Virgo cluster observed with the ISOCAM instrument on board the ISO satellite. The ISOCAM data allows us to construct the luminosity distribution at 6.75 and 15 mu m of galaxies for different morphological classes. These data are used to study the spectral energy distribution of galaxies of different type and luminosity in the wavelength range 2000 Angstroms - 100 mu m. The analysis shows that the Mid-IR emission up to 15 mu m of optically-selected, normal early-type galaxies (E, S0 and S0a) is dominated by the Rayleigh-Jeans tail of the cold stellar component. The Mid-IR emission of late-type galaxies is instead dominated by the thermal emission from dust. As in the Milky Way, the small dust grains emitting in the Mid-IR have an excess of emission if compared to big grains emitting in the Far-IR. While the Far-IR emission of galaxies increases with the intensity of the interstellar radiation field, their Mid-IR emission is non-linearly related to the UV radiation field. The spectral energy distributions of the target galaxies indicate that there is a linear relationship between the UV radiation field and the Mid-IR emission of galaxies for low or intermediate activities of star formation, while the emission from the hot dust seems to drop for strong UV fields. The Mid-IR colour of late-type galaxies is not related to their activity of star formation. The properties of the dust emission in the Mid-IR seem more related to the mass than to the morphological type of the target galaxy. Since the activity of star formation is anticorrelated to the mass of galaxies, this reflects a relationship between the emission of dust in the Mid-IR and the UV radiation field: galaxies with the lowest Mid-IR emission for a given UV field are low mass, dwarf galaxies. These observational evidences are easily explained if the carriers of the Unidentified Infrared Bands

  7. Evolutionarily conserved substrate substructures for automated annotation of enzyme superfamilies.

    PubMed

    Chiang, Ranyee A; Sali, Andrej; Babbitt, Patricia C

    2008-08-01

    The evolution of enzymes affects how well a species can adapt to new environmental conditions. During enzyme evolution, certain aspects of molecular function are conserved while other aspects can vary. Aspects of function that are more difficult to change or that need to be reused in multiple contexts are often conserved, while those that vary may indicate functions that are more easily changed or that are no longer required. In analogy to the study of conservation patterns in enzyme sequences and structures, we have examined the patterns of conservation and variation in enzyme function by analyzing graph isomorphisms among enzyme substrates of a large number of enzyme superfamilies. This systematic analysis of substrate substructures establishes the conservation patterns that typify individual superfamilies. Specifically, we determined the chemical substructures that are conserved among all known substrates of a superfamily and the substructures that are reacting in these substrates and then examined the relationship between the two. Across the 42 superfamilies that were analyzed, substantial variation was found in how much of the conserved substructure is reacting, suggesting that superfamilies may not be easily grouped into discrete and separable categories. Instead, our results suggest that many superfamilies may need to be treated individually for analyses of evolution, function prediction, and guiding enzyme engineering strategies. Annotating superfamilies with these conserved and reacting substructure patterns provides information that is orthogonal to information provided by studies of conservation in superfamily sequences and structures, thereby improving the precision with which we can predict the functions of enzymes of unknown function and direct studies in enzyme engineering. Because the method is automated, it is suitable for large-scale characterization and comparison of fundamental functional capabilities of both characterized and uncharacterized

  8. Galaxy Strategy for Ligo-Virgo Gravitational Wave Counterpart Searches

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

    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 gravity wave (GW) triggers from LIGO (Laser Interferometer Gravitational-Wave Observatory) / Virgo. If one considers the brightest galaxies that produce 50 percent 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 is small and the error boxes large, and in the later years when the error boxes will be small and the range large. This strategy has the beneficial property of reducing the number of telescope pointings by a factor 10 to 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 plus or minus 5 galaxies for 2015, about 23 plus or minus 4 for 2017, and about 11 plus or minus for 2020. This assumes a distance localization at the putative neutron star-neutron star (NS-NS) merger range mu 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 (rotation) greatly less than mu the totals would decrease. The galaxy strategy we present in this work will enable numerous sensitive optical and X-ray telescopes 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.

  9. Education and Public Outreach at EGO/Virgo: past experiences and future projects

    NASA Astrophysics Data System (ADS)

    Razzano, Massimiliano

    2015-08-01

    We are approaching the new generation Gravitational Wave (GW) detector Era and in the next months a new exiting period for GW scientists will start enforcing collaboration and interactions among different scientific communities. We aim to reach a wider audience to spread this enthusiasm in the general public about our every day activities and let them know how it will change our understanding of the Universe, once revealed the Gravitational waves. In this talk, we will report about the activities of the last years and about the EGO/Virgo outreach plans for the future. The main goal of the Virgo/EGO outreach activity is to raise awareness and curiosity about the GW research projects. In the past years we informed the general public about science we do at EGO/Virgo site, trying to attract students in doing research, letting them know about the Virgo detector and involving them in small research activities. We run a regular program of site visits, and we often organized astronomical observations and science cafe' events which attracted a large number of people. Efforts were made also to involve kids in understanding our scientific job. We started a series of regular events in which art and science were fused.We are strengthening our outreach activities with common efforts in the Virgo laboratories which are spread all over in Europe.We plan to make available a scientific path within Virgo, where the public can do little experiences of science or for example tile, for a day, the activity of our researchers.

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

    SciTech Connect

    Sandage, A.; Tammann, G.A.

    1988-05-01

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

  11. Mapping Dark Matter Halos with Stellar Kinematics

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  12. On the local stellar populations

    NASA Astrophysics Data System (ADS)

    Fuhrmann, Klaus; Chini, Rolf; Kaderhandt, Lena; Chen, Zhiwei

    2017-01-01

    We present a study of the local stellar populations from a volume-complete all-sky survey of the about 500 bright stars with distances less than 25 pc and down to main-sequence effective temperatures Teff ≥ 5300 K. The sample is dominated by a 93 per cent fraction of Population I stars, only 22 sources (5 per cent) are Population II stars, and 9 sources (2 per cent) are intermediate-disc stars. No source belongs to the halo. By following the mass of the stars instead of their light, the resulting subset of 136 long-lived stars distributes as 22 (16.2 per cent):6 (4.4 per cent):108 (79.4 per cent) for the Population II:intermediate disc:Population I, respectively. Along with the much larger scaleheight reached by Population II, this unbiased census of long-lived stars provides plain evidence for a starburst epoch in the early Milky Way, with the formation of a massive, rotationally supported, and dark Population II. The same conclusion arises from the substantial early chemical enrichment levels, exemplified here by the elements magnesium and iron, as it arises also from the local Population II white dwarfs. The kinematics, metallicity distribution functions, star formation rates, age-metallicity relations, the inventory of young stars, and the occurrence of blue straggler stars are discussed. A potentially new aspect of the survey is the possibility for substructure among the local Population II stars that may further subdivide into metal-poor and metal-rich sources.

  13. Floating substructure flexibility of large-volume 10MW offshore wind turbine platforms in dynamic calculations

    NASA Astrophysics Data System (ADS)

    Borg, Michael; Melchior Hansen, Anders; Bredmose, Henrik

    2016-09-01

    Designing floating substructures for the next generation of 10MW and larger wind turbines has introduced new challenges in capturing relevant physical effects in dynamic simulation tools. In achieving technically and economically optimal floating substructures, structural flexibility may increase to the extent that it becomes relevant to include in addition to the standard rigid body substructure modes which are typically described through linear radiation-diffraction theory. This paper describes a method for the inclusion of substructural flexibility in aero-hydro-servo-elastic dynamic simulations for large-volume substructures, including wave-structure interactions, to form the basis of deriving sectional loads and stresses within the substructure. The method is applied to a case study to illustrate the implementation and relevance. It is found that the flexible mode is significantly excited in an extreme event, indicating an increase in predicted substructure internal loads.

  14. The Search for Stellar Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Villadsen, Jacqueline; Hallinan, Gregg; Monroe, Ryan; Bourke, Stephen; Starburst Program Team

    2017-01-01

    Coronal mass ejections (CMEs) may dramatically impact habitability and atmospheric composition of planets around magnetically active stars, including young solar analogs and many M dwarfs. Theoretical predictions of such effects are limited by the lack of observations of stellar CMEs. My thesis addresses this gap through a search for the spectral and spatial radio signatures of CMEs on active M dwarfs.Solar CMEs produce radio bursts with a distinctive spectral signature, narrow-band plasma emission that drifts to lower frequency as a CME expands outward. To search for analogous events on nearby stars, I worked on system design, software, and commissioning for the Starburst project, a wideband single-baseline radio interferometry backend dedicated to stellar observations. In addition, I led a survey of nearby active M dwarfs with the Karl G. Jansky Very Large Array (JVLA), detecting 12 bright (>10 mJy) radio bursts in 58 hours. This survey’s ultra-wide bandwidth (0.23-6.0 GHz) dynamic spectroscopy, unprecedented for stellar observations, revealed diverse behavior in the time-frequency plane. Flare star UV Ceti produced complex, luminous events reminiscent of brown dwarf aurorae; AD Leo sustained long-duration, intense, narrow-band "storms"; and YZ CMi emitted a burst with substructure with rapid frequency drift, resembling solar Type III bursts, which are attributed to electrons moving at speeds of order 10% of the speed of light.To search for the spatial signature of CMEs, I led 8.5-GHz observations with the Very Long Baseline Array simultaneous to 24 hours of the JVLA survey. This program detected non-thermal continuum emission from the stars in all epochs, as well as continuum flares on AD Leo and coherent bursts on UV Ceti, enabling measurement of the spatial offset between flaring and quiescent emission.These observations demonstrate the diversity of stellar transients that can be expected in time-domain radio surveys, especially with the advent of large low

  15. The Hierarchical Distribution of Young Stellar Clusters in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Grasha, Kathryn; Calzetti, Daniela

    2017-01-01

    We investigate the spatial distributions of young stellar clusters in six nearby galaxies to trace the large scale hierarchical star-forming structures. The six galaxies are drawn from the Legacy ExtraGalactic UV Survey (LEGUS). We quantify the strength of the clustering among stellar clusters as a function of spatial scale and age to establish the survival timescale of the substructures. We separate the clusters into different classes, compact (bound) clusters and associations (unbound), and compare the clustering among them. We find that younger star clusters are more strongly clustered over small spatial scales and that the clustering disappears rapidly for ages as young as a few tens of Myr, consistent with clusters slowly losing the fractal dimension inherited at birth from their natal molecular clouds.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  17. M31AGES: Studying the intermediate-aged populations in the satellites, smooth halo, and substructure of Andromeda

    NASA Astrophysics Data System (ADS)

    Hamren, Katherine; Beaton, Rachael; Guhathakurta, Puragra; Majewski, Steven R.; M31AGES Survey Team

    2016-01-01

    Recent large-scale surveys of M31 have enabled the study of its satellites, smooth halo, and substructure in exquisite detail. In particular, the Spectroscopic Landscape of Andromeda's Stellar Halo (SPLASH) survey has obtained moderate resolution optical spectra with the DEIMOS spectrograph on the Keck II/10-m telescope, and optical photometry from various ground-based telescopes. These data have been used to map the kinematics and metallicity distributions in the dSphs and dEs, detect and characterize substructure, and study the large-scale radial surface brightness and metallicity profiles of the "smooth" halo. Notwithstanding this progress [or] In spite of these advances, there are a number of outstanding questions that cannot be answered with these data alone, including the fraction of the halo that was formed in situ vs by accretion, and the degeneracy between massive early accretion events and less massiverecent accretion events. The M31 Asymptotic Giant Extended Survey (M31AGES) aims to address these questions by using NIR photometry to identify intermediate-age AGB stars in the satellites, streams, and smoothhalo of M31. We present the details of the observations (now completed), the plan for public release of data products, and preliminary results.

  18. The structure of early-type galaxies from the ACS Virgo and Fornax cluster surveys: cores, nuclei and supermassive black holes

    NASA Astrophysics Data System (ADS)

    Ferrarese, Laura; Côté, Patrick

    2008-07-01

    The core structure of early-type galaxies is revisited in light of recent results from the ACS Virgo and Fornax Cluster Surveys. These surveys are comprised of HST/ACS g, z band images for a representative sample of 143 early-type galaxies, spanning a factor 720 in B-band luminosity. The data indicates a clear transition in the core structure going from the brightest to the faintest galaxies. In contrast to previous claims, however, this transition is found to be a continuous function of galaxy magnitude. We characterize the core structure in terms of deviations of the observed surface brightness profile measured within ~ 2% of the galaxy effective radius relative to the inner extrapolation of the Sérsic law that best fits the profiles on larger scales. Virtually all galaxies fainter than MB ~ -20 mag contain distinct stellar nuclei, and are described by surface brightness profiles that lie above the Sérsic extrapolation, while the reverse is true for brighter galaxies. The latter are also known to host supermassive black holes. A relation between SBHs and stellar nuclei is suggested by the fact that both types of “central massive objects” contain the same fraction, 0.2% of the total mass of the host galaxy.

  19. Towards an understanding of the correlations in jet substructure

    SciTech Connect

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

    2015-09-09

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

  20. Towards an understanding of the correlations in jet substructure

    DOE PAGES

    Adams, D.; Arce, A.; Asquith, L.; ...

    2015-09-09

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

  1. Fold Recognition Using Sequence Fingerprints of Protein Local Substructures

    SciTech Connect

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

    2003-06-04

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

  2. Evolving Flare Ribbon Small-Scale Substructure: A Second Candidate

    NASA Astrophysics Data System (ADS)

    Roegge, Alissa; Brannon, Sean

    2017-01-01

    We present preliminary analysis on imaging and spectroscopic observations from the Interface Region Imaging Spectrograph (IRIS) of the evolution of the flare ribbon in the SOL2014-06-22T13:08 B-class flare event, at high spatial resolution and time cadence. IRIS is a solar observation satellite containing a high frame rate ultraviolet imaging spectrometer. This work continues the work started in Brannon et al 2015 by searching for small-scale substructure within flare ribbons, which manifest themselves as coherent quasiperiodic oscillations in both position and Doppler velocities. Using IRIS observations from October 2013 to June 2016, we selected candidate observations on the basis of physical characteristics, Si IV intensity, and shift in doppler velocity. In addition to our preliminary analysis and images, we present our techniques that can be used to find further observations also containing the periodic oscillations, and other small-substructure.

  3. Fossil group origins. VII. Galaxy substructures in fossil systems

    NASA Astrophysics Data System (ADS)

    Zarattini, S.; Girardi, M.; Aguerri, J. A. L.; Boschin, W.; Barrena, R.; del Burgo, C.; Castro-Rodriguez, N.; Corsini, E. M.; D'Onghia, E.; Kundert, A.; Méndez-Abreu, J.; Sánchez-Janssen, R.

    2016-02-01

    Context. Fossil groups (FG) are expected to be the final product of galaxy merging within galaxy groups. In simulations, they are predicted to assemble their mass at high redshift. This early formation allows for the innermost M∗ galaxies to merge into a massive central galaxy. Then, they are expected to maintain their fossil status because of the few interactions with the large-scale structure. In this context, the magnitude gap between the two brightest galaxies of the system is considered a good indicator of its dynamical status. As a consequence, the systems with the largest gaps should be dynamically relaxed. Aims: In order to examine the dynamical status of these systems, we systematically analyze, for the first time, the presence of galaxy substructures in a sample of 12 spectroscopically-confirmed fossil systems with redshift z ≤ 0.25. Methods: We apply a number of tests to investigate the substructure in fossil systems in the two-dimensional space of projected positions out to R200. Moreover, for a subsample of five systems with at least 30 spectroscopically-confirmed members we also analyze the substructure in the velocity and in the three-dimensional velocity-position spaces. Additionally, we look for signs of recent mergers in the regions around the central galaxies. Results: We find that an important fraction of fossil systems show substructure. The fraction depends critically on the adopted test, since each test is more sensitive to a particular type of substructure. Conclusions: Our interpretation of the results is that fossil systems are not, in general, as relaxed as expected from simulations. Our sample of 12 spectroscopically-confirmed fossil systems need to be extended to compute an accurate fraction, but our conclusion is that this fraction is similar to the fraction of substructure detected in nonfossil clusters. This result points out that the magnitude gap alone is not a good indicator of the dynamical status of a system. However, the

  4. Substructure of the inner core of the Earth.

    PubMed Central

    Herndon, J M

    1996-01-01

    The rationale is disclosed for a substructure within the Earth's inner core, consisting of an actinide subcore at the center of the Earth, surrounded by a subshell composed of the products of nuclear fission and radioactive decay. Estimates are made as to possible densities, physical dimensions, and chemical compositions. The feasibility for self-sustaining nuclear fission within the subcore is demonstrated, and implications bearing on the structure and geodynamic activity of the inner core are discussed. PMID:11607625

  5. Strong lensing signatures of luminous structure and substructure in early-type galaxies

    NASA Astrophysics Data System (ADS)

    Gilman, Daniel; Agnello, Adriano; Treu, Tommaso; Keeton, Charles R.; Nierenberg, Anna M.

    2017-01-01

    The arrival times, positions, and fluxes of multiple images in strong lens systems can be used to infer the presence of dark subhalos in the deflector, and thus test predictions of cold dark matter models. However, gravitational lensing does not distinguish between perturbations to a smooth gravitational potential arising from baryonic and non-baryonic mass. In this work, we quantify the extent to which the stellar mass distribution of a deflector can reproduce flux ratio and astrometric anomalies typically associated with the presence of a dark matter subhalo. Using Hubble Space Telescope images of nearby galaxies, we simulate strong lens systems with real distributions of stellar mass as they would be observed at redshift zd = 0.5. We add a dark matter halo and external shear to account for the smooth dark matter field, omitting dark substructure, and use a Monte Carlo procedure to characterize the distributions of image positions, time delays, and flux ratios for a compact background source of diameter 5 pc. By convolving high-resolution images of real galaxies with a Gaussian PSF, we simulate the most detailed smooth potential one could construct given high quality data, and find scatter in flux ratios of ≈10%, which we interpret as a typical deviation from a smooth potential caused by large and small scale structure in the lensing galaxy. We demonstrate that the flux ratio anomalies arising from galaxy-scale baryonic structure can be minimized by selecting the most massive and round deflectors, and by simultaneously modeling flux ratio and astrometric data.

  6. The Next Generation Virgo Cluster Survey (NGVS). XXIV. The Red Sequence to ~106 L ⊙ and Comparisons with Galaxy Formation Models

    NASA Astrophysics Data System (ADS)

    Roediger, Joel C.; Ferrarese, Laura; Côté, Patrick; MacArthur, Lauren A.; Sánchez-Janssen, Rúben; Blakeslee, John P.; Peng, Eric W.; Liu, Chengze; Munoz, Roberto; Cuillandre, Jean-Charles; Gwyn, Stephen; Mei, Simona; Boissier, Samuel; Boselli, Alessandro; Cantiello, Michele; Courteau, Stéphane; Duc, Pierre-Alain; Lançon, Ariane; Mihos, J. Christopher; Puzia, Thomas H.; Taylor, James E.; Durrell, Patrick R.; Toloba, Elisa; Guhathakurta, Puragra; Zhang, Hongxin

    2017-02-01

    We use deep optical photometry from the Next Generation Virgo Cluster Survey (NGVS) to investigate the color–magnitude diagram for the galaxies inhabiting the core of this cluster. The sensitivity of the NGVS imaging allows us to continuously probe galaxy colors over a factor of ∼2 × 105 in luminosity, from brightest cluster galaxies to scales overlapping classical satellites of the Milky Way ({M}g\\prime ∼ ‑9 M * ∼ 106 M ⊙), within a single environment. Remarkably, we find the first evidence that the red sequence (RS) flattens in all colors at the faint-magnitude end (starting between ‑14 ≤ {M}g\\prime ≤ ‑13, around M * ∼ 4 × 107 M ⊙), with the slope decreasing to ∼60% or less of its value at brighter magnitudes. This could indicate that the stellar populations of faint dwarfs in Virgo’s core share similar characteristics (e.g., constant mean age) over ∼3 mag in luminosity, suggesting that these galaxies were quenched coevally, likely via pre-processing in smaller hosts. We also compare our results to galaxy formation models, finding that the RS in model clusters have slopes at intermediate magnitudes that are too shallow, and in the case of semianalytic models, do not reproduce the flattening seen at both extremes (bright/faint) of the Virgo RS. Deficiencies in the chemical evolution of model galaxies likely contribute to the model-data discrepancies at all masses, while overly efficient quenching may also be a factor at dwarf scales. Deep UV and near-IR photometry are required to unambiguously diagnose the cause of the faint-end flattening.

  7. Modal Substructuring of Geometrically Nonlinear Finite-Element Models

    SciTech Connect

    Kuether, Robert J.; Allen, Matthew S.; Hollkamp, Joseph J.

    2015-12-21

    The efficiency of a modal substructuring method depends on the component modes used to reduce each subcomponent model. Methods such as Craig–Bampton have been used extensively to reduce linear finite-element models with thousands or even millions of degrees of freedom down orders of magnitude while maintaining acceptable accuracy. A novel reduction method is proposed here for geometrically nonlinear finite-element models using the fixed-interface and constraint modes of the linearized system to reduce each subcomponent model. The geometric nonlinearity requires an additional cubic and quadratic polynomial function in the modal equations, and the nonlinear stiffness coefficients are determined by applying a series of static loads and using the finite-element code to compute the response. The geometrically nonlinear, reduced modal equations for each subcomponent are then coupled by satisfying compatibility and force equilibrium. This modal substructuring approach is an extension of the Craig–Bampton method and is readily applied to geometrically nonlinear models built directly within commercial finite-element packages. The efficiency of this new approach is demonstrated on two example problems: one that couples two geometrically nonlinear beams at a shared rotational degree of freedom, and another that couples an axial spring element to the axial degree of freedom of a geometrically nonlinear beam. The nonlinear normal modes of the assembled models are compared with those of a truth model to assess the accuracy of the novel modal substructuring approach.

  8. Modal Substructuring of Geometrically Nonlinear Finite-Element Models

    DOE PAGES

    Kuether, Robert J.; Allen, Matthew S.; Hollkamp, Joseph J.

    2015-12-21

    The efficiency of a modal substructuring method depends on the component modes used to reduce each subcomponent model. Methods such as Craig–Bampton have been used extensively to reduce linear finite-element models with thousands or even millions of degrees of freedom down orders of magnitude while maintaining acceptable accuracy. A novel reduction method is proposed here for geometrically nonlinear finite-element models using the fixed-interface and constraint modes of the linearized system to reduce each subcomponent model. The geometric nonlinearity requires an additional cubic and quadratic polynomial function in the modal equations, and the nonlinear stiffness coefficients are determined by applying amore » series of static loads and using the finite-element code to compute the response. The geometrically nonlinear, reduced modal equations for each subcomponent are then coupled by satisfying compatibility and force equilibrium. This modal substructuring approach is an extension of the Craig–Bampton method and is readily applied to geometrically nonlinear models built directly within commercial finite-element packages. The efficiency of this new approach is demonstrated on two example problems: one that couples two geometrically nonlinear beams at a shared rotational degree of freedom, and another that couples an axial spring element to the axial degree of freedom of a geometrically nonlinear beam. The nonlinear normal modes of the assembled models are compared with those of a truth model to assess the accuracy of the novel modal substructuring approach.« less

  9. Predicted Sizes of Pressure-supported HI Clouds in the Outskirts of the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Burkhart, Blakesley; Loeb, Abraham

    2016-06-01

    Using data from the ALFALFA AGES Arecibo HI survey of galaxies and the Virgo cluster X-ray pressure profiles from XMM-Newton, we investigate the possibility that starless dark HI clumps, also known as “dark galaxies,” are supported by external pressure in the surrounding intercluster medium. We find that the starless HI clump masses, velocity dispersions, and positions allow these clumps to be in pressure equilibrium with the X-ray gas near the virial radius of the Virgo cluster. We predict the sizes of these clumps to range from 1 to 10 kpc, in agreement with the range of sizes found for spatially resolved HI starless clumps outside of Virgo. Based on the predicted HI surface density of the Virgo sources, as well as a sample of other similar resolved ALFALFA HI dark clumps with follow-up optical/radio observations, we predict that most of the HI dark clumps are on the cusp of forming stars. These HI sources therefore mark the transition between starless HI clouds and dwarf galaxies with stars.

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

    Context. Using Herschel data from the open time key project the Herschel Virgo Cluster Survey (HeViCS), we investigated the relationship between the metallicity gradients expressed by metal abundances in the gas phase as traced by the chemical composition of HII regions, and in the solid phase, as traced by the dust-to-gas mass ratio. Aims: We derived the radial gradient of the dust-to-gas mass ratio for all galaxies observed by HeViCS whose metallicity gradients are available in the literature. They are all late type Sbc galaxies, namely NGC 4254, NGC 4303, NGC 4321, and NGC 4501. Methods: We fitted PACS and SPIRE observations with a single-temperature modified blackbody, inferred the dust mass, and calculated two dimensional maps of the dust-to-gas mass ratio, with the total mass of gas from available HI and CO maps. HI moment-1 maps were used to derive the geometric parameters of the galaxies and extract the radial profiles. We examined different dependencies on metallicity of the CO-to-H2 conversion factor (XCO), used to transform the 12CO observations into the amount of molecular hydrogen. Results: We found that in these galaxies the dust-to-gas mass ratio radial profile is extremely sensitive to choice of the XCO value, since the molecular gas is the dominant component in the inner parts. We found that for three galaxies of our sample, namely NGC 4254, NGC 4321, and NGC 4501, the slopes of the oxygen and of the dust-to-gas radial gradients agree up to ~0.6-0.7 R25 using XCO values in the range 1/3-1/2 Galactic XCO. For NGC 4303 a lower value of XCO ~ 0.1 × 1020 is necessary. Conclusions: We suggest that such low XCO values might be due to a metallicity dependence of XCO (from close to linear for NGC 4254, NGC 4321, and NGC 4501 to superlinear for NGC 4303), especially in the radial regions RG < 0.6-0.7 R25 where the molecular gas dominates. On the other hand, the outer regions, where the atomic gas component is dominant, are less affected by the choice of

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

    NASA Astrophysics Data System (ADS)

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

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

  12. Population substructure and isolation by distance in three continental regions.

    PubMed

    Eller, E

    1999-02-01

    Isolation by distance and divergence from a shared population history are two sources of population substructure. Isolation by distance erases population history as populations approach migration-drift equilibrium, while diverging populations descended from a single ancestral population will accumulate genetic differences with time. Here I investigate how much of the worldwide genetic diversity from Jorde et al.'s ([1997] Proc. Natl. Acad. Sci. USA 94:3100-3103) 60 tetranucleotide short tandem repeat (STR) data can be explained by isolation by distance. I use Slatkin's measure of population substructure, R(ST), principal components analyses, and Mantel tests to investigate the pattern of genetic diversity at both the intercontinental and intracontinental levels. Geographic distance accounts for almost 60% of world-wide interpopulation genetic relationships. Within continents, the correlations are less, although not significantly so because of wide confidence intervals. These results suggest that populations have not reached migration-drift equilibrium and that there is information in STR data to reconstruct population history. The level of population substructure worldwide is consistent with previous observations, but at the intracontinental level substructure is less. When one examines diversity against distance from the centroid, one sees excess heterozygosity in Africa, a pattern also noted by Stoneking et al. ([1998] Genome Research 7:1061-1071). A larger effective population size in Africa could explain the excess diversity. Greater gene flow in Africa is an unlikely explanation because the African R(ST) value is slightly larger than the Asian and European R(ST)s, pointing to less gene flow and greater substructure among African populations. Furthermore, there are differences in patterns between heterozygosity and allele size variance. Heterozygosity has a higher correlation with distance from the centroid than does allele size variance, and this may reflect

  13. Stability in straight stellarators

    SciTech Connect

    Kulsrud, R.M.; Yoshikawa, S.

    1981-07-01

    The stability of the straight stellarator against localized interchange modes is investigated employing the Mercier-Greene-Johnson criterion. Critical values of ..beta.. are obtained both numerically and analytically. The conclusion is that for classical helical stellarators the average limiting ..beta..'s are quite low of order three to four percent.

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

    SciTech Connect

    Kenney, Jeffrey D. P.; Geha, Marla; Jáchym, Pavel; Dague, William; Crowl, Hugh H.; Chung, Aeree; Van Gorkom, Jacqueline; Vollmer, Bernd

    2014-01-10

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

  15. Atomic data for stellar spectroscopy: recent successes and remaining needs

    NASA Astrophysics Data System (ADS)

    Sneden, Christopher; Lawler, James E.; Wood, Michael P.; Den Hartog, Elizabeth A.; Cowan, John J.

    2014-11-01

    Stellar chemical composition analyses provide vital insights into galactic nucleosynthesis. Atomic line data are critical inputs to stellar abundance computations. Recent lab studies have made significant progress in refining and extending knowledge of transition probabilities, isotopic wavelength shifts, and hyperfine substructure patterns for the absorption lines that are of most interest to stellar spectroscopists. The observable neutron-capture (n-capture) element species (Z \\gt 30) have been scrutinized in lab studies by several groups. For many species the uncertainties in experimental oscillator strengths are ≤slant 10%, which permits detailed assessment of rapid and slow n-capture nucleosynthesis contributions. In this review, extreme examples of r-process-enriched stars in the galactic halo will be shown, which suggest that the description of observable n-capture abundances in these stars is nearly complete. Unfortunately, there are serious remaining concerns about the reliability of observed abundances of lighter elements. In particular, it is not clear that line formation in real stellar atmospheres is being modeled correctly. But for many elements with Z \\lt 30 the atomic transition data are not yet settled. Highlights will be given of some recent large improvements, with suggestions for the most important needs for the near future.

  16. Preliminary results on the determination of the theoretical non-adiabatic observable phase lag (ψT) using VIRGO color photometry

    NASA Astrophysics Data System (ADS)

    Simoniello, R.; Garrido, R.; Jiménez, A.

    2008-06-01

    The helioseismic instruments aboard the SOHO satellite make it possible to measure solar oscillations as variations of the irradiance (VIRGO) or as variations of the photospheric velocity (GOLF). Theoretically, phase differences between different photometric bands are expected to be around 0 degrees over the p-mode frequency range. By using VIRGO (red) and VIRGO (blue) data, we find a mean phase shift of 8.05±1.81°, whereas by using VIRGO (green) and VIRGO (blue) data, we got a mean value of -1.04±0.19°. Hence, when the analysis includes the VIRGO infrared range, the Sun's atmosphere does not follow an exact adiabatic behavior. In this study, we use the phase shifts obtained by VIRGO (green) and VIRGO (blue) to determine the non-adiabatic parameter phase lag (ψT) as a function of frequency. To this aim, we applied the non radial linearized formula put in the complex form by Garrido: we found a mean value of ψT = 179.95°. The lowest value being ψT = 179.90°, the departure from theoretical predictions is less then a tenth of a degree over the entire p mode frequency range. We can state that the solar atmosphere has a behavior close to the adiabatic case, when the phase shifts and amplitude ratios are computed using VIRGO (green) and VIRGO (blue) data. Nevertheless this small deviation is significant.

  17. HST Imaging of Dust Structures and Stars in the Ram Pressure Stripped Virgo Spirals NGC 4402 and NGC 4522: Stripped from the Outside In with Dense Cloud Decoupling

    NASA Astrophysics Data System (ADS)

    Abramson, A.; Kenney, J.; Crowl, H.; Tal, T.

    2016-08-01

    We describe and constrain the origins of interstellar medium (ISM) structures likely created by ongoing intracluster medium (ICM) ram pressure stripping in two Virgo Cluster spirals, NGC 4522 and NGC 4402, using Hubble Space Telescope (HST) BVI images of dust extinction and stars, as well as supplementary H i, Hα, and radio continuum images. With a spatial resolution of ˜10 pc in the HST images, this is the highest-resolution study to date of the physical processes that occur during an ICM-ISM ram pressure stripping interaction, ram pressure stripping's effects on the multi-phase, multi-density ISM, and the formation and evolution of ram-pressure-stripped tails. In dust extinction, we view the leading side of NGC 4402 and the trailing side of NGC 4522, and so we see distinct types of features in both. In both galaxies, we identify some regions where dense clouds are decoupling or have decoupled and others where it appears that kiloparsec-sized sections of the ISM are moving coherently. NGC 4522 has experienced stronger, more recent pressure and has the “jellyfish” morphology characteristic of some ram-pressure-stripped galaxies. Its stripped tail extends up from the disk plane in continuous upturns of dust and stars curving up to ˜2 kpc above the disk plane. On the other side of the galaxy, there is a kinematically and morphologically distinct extraplanar arm of young, blue stars and ISM above a mostly stripped portion of the disk, and between it and the disk plane are decoupled dust clouds that have not been completely stripped. The leading side of NGC 4402 contains two kiloparsec-scale linear dust filaments with complex substructure that have partially decoupled from the surrounding ISM. NGC 4402 also contains long dust ridges, suggesting that large parts of the ISM are being pushed out at once. Both galaxies contain long ridges of polarized radio continuum emission indicating the presence of large-scale, ordered magnetic fields. We propose that magnetic

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  20. The Next Generation Virgo Cluster Survey. V. modeling the dynamics of M87 with the made-to-measure method

    SciTech Connect

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

    2014-09-01

    We study the dynamics of the giant elliptical galaxy M87 from the central to the outermost regions with the made-to-measure (M2M) method. We use a new catalog of 922 globular cluster line-of-sight velocities extending to a projected radius of 180 kpc (equivalent to 25 M87 effective radii), and SAURON integral field unit data within the central 2.4 kpc. There are 263 globular clusters, mainly located beyond 40 kpc, newly observed by the Next Generation Virgo Survey. For the M2M modeling, the gravitational potential is taken as a combination of a luminous matter potential with a constant stellar mass-to-light ratio and a dark matter potential modeled as a logarithmic potential. Our best-fit dynamical model returns a stellar mass-to-light ratio in the I band of M/L{sub I} = 6.0 ± 0.3 M{sub ⊙} L{sub ⊙}{sup −1} with a dark matter potential scale velocity of 591 ± 50 km s{sup –1} and scale radius of 42 ± 10 kpc. We determine the total mass of M87 within 180 kpc to be (1.5 ± 0.2) × 10{sup 13} M {sub ☉}. The mass within 40 kpc is smaller than previous estimates determined using globular cluster kinematics that did not extend beyond ∼45 kpc. With our new globular cluster velocities at much larger radii, we see that globular clusters around 40 kpc show an anomalously large velocity dispersion which affected previous results. The mass we derive is in good agreement with that inferred from ROSAT X-ray observation out to 180 kpc. Within 30 kpc our mass is also consistent with that inferred from Chandra and XMM-Newton X-ray observations, while within 120 kpc it is about 20% smaller. The model velocity dispersion anisotropy β parameter for the globular clusters in M87 is small, varying from –0.2 at the center to 0.2 at ∼40 kpc, and gradually decreasing to zero at ∼120 kpc.

  1. THE GLOBULAR CLUSTER SYSTEM OF THE VIRGO GIANT ELLIPTICAL GALAXY NGC 4636. II. KINEMATICS OF THE GLOBULAR CLUSTER SYSTEM

    SciTech Connect

    Lee, Myung Gyoon; Park, Hong Soo; Hwang, Ho Seong; Arimoto, Nobuo; Tamura, Naoyuki; Onodera, Masato E-mail: hspark@astro.snu.ac.k E-mail: masato.onodera@cea.f E-mail: naoyuki@subaru.naoj.or

    2010-02-01

    We present a kinematic analysis of the globular cluster (GC) system in the giant elliptical galaxy (gE) NGC 4636 in the Virgo cluster. Using the photometric and spectroscopic database of 238 GCs (108 blue GCs and 130 red GCs) at the galactocentric radius 0.'39 < R < 15.'43, we have investigated the kinematics of the GC system. The NGC 4636 GC system shows weak overall rotation, which is dominated by the red GCs. However, both the blue GCs and red GCs show some rotation in the inner region at R < 4.'3 (=2.9R{sub eff} = 18.5 kpc). The velocity dispersion for all the GCs is derived to be sigma{sub p} = 225{sup +12}{sub -9} km s{sup -1}. The velocity dispersion for the blue GCs (sigma{sub p} = 251{sup +18}{sub -12} km s{sup -1}) is slightly larger than that for the red GCs (sigma{sub p} = 205{sup +11}{sub -13} km s{sup -1}). The velocity dispersions for the blue GCs about the mean velocity and about the best-fit rotation curve have a significant variation depending on the galactocentric radius. Comparison of observed stellar and GC velocity dispersion profiles (VDPs) with the VDPs calculated from the stellar mass profile shows that the mass-to-light ratio should increase as the galactocentric distance increases, indicating the existence of an extended dark matter halo. From the comparison of the observed GC VDPs and the VDPs calculated for the X-ray mass profiles in the literature, we find that the orbit of the GC system is tangential, and that the orbit of the red GCs is slightly more tangential than that of the blue GCs. We compare the GC kinematics of NGC 4636 with those of other six gEs, finding that the kinematic properties of the GCs are diverse among gEs. We find several correlations between the kinematics of the GCs and the global parameters of their host galaxies. We discuss the implication of the results for the formation models of the GC system in gEs, and suggest a mixture scenario for the origin of the GCs in gEs.

  2. Double-helix stellarator

    SciTech Connect

    Moroz, P.E.

    1997-09-01

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

  3. Frontiers of stellar evolution

    NASA Technical Reports Server (NTRS)

    Lambert, David L. (Editor)

    1991-01-01

    The present conference discusses theoretical and observational views of star formation, spectroscopic constraints on the evolution of massive stars, very low mass stars and brown dwarfs, asteroseismology, globular clusters as tests of stellar evolution, observational tests of stellar evolution, and mass loss from cool evolved giant stars. Also discussed are white dwarfs and hot subdwarfs, neutron stars and black holes, supernovae from single stars, close binaries with evolved components, accretion disks in interacting binaries, supernovae in binary systems, stellar evolution and galactic chemical evolution, and interacting binaries containing compact components.

  4. Spectroscopy of Stellar Coronae

    NASA Astrophysics Data System (ADS)

    Laming, J. Martin

    I review the important spectroscopic results that have come from observations of stellar coronae, mainly by EUVE and ASCA, but also from HST. The plasma parameters that can be determined from such spectra include the electron density and temperature distributions, and relative element abundances. With high resolution spectra dynamical information can be obtained. Such parameters can then be used to put constraints on models of the heating and structure of stellar coronae. Throughout, I try to emphasise the similarities and differences between stellar coronal spectroscopy and that of the solar corona.

  5. Offshore deck to substructure mating system and method

    SciTech Connect

    Datta, B.N.; Baldwin, R.L.; Allen, J.D.

    1993-06-15

    An offshore platform, in combination, a deck for installation to be supported by a substructure is described including a plurality of upstanding column members, said deck including a corresponding plurality of depending legs, the improvement characterized by: at least one of said legs including a stabbing tip assembly for engagement with a corresponding column member, said stabbing tip assembly comprising an outer body for engagement with said column member to transfer permanent weight of said deck to said column member, a generally vertically movable locating pin disposed in said body for movement to stab into receiver means including means forming a receptacle on said column member for locating said dock with respect to said column member, and resilient means supported by said body for accommodating lateral and vertically-imposed loads acting between said column member and said leg during placement of said deck on said substructure to minimize the imposition of peak forces on said deck and said substructure; said receiver means comprising a generally cylindrical receiver shoe forming said receptacle, said shoe comprising part of a jack assembly supported on said column member and said shoe being operable to be moved to a position to permit contact of said leg with said column member to provide supporting relationship therebetween; and said jack assembly comprising a generally cylindrical body member supported on said column member and forming a chamber with said shoe for receiving particulate material to support said shoe in a first position for receiving said locating pin, said shoe being movable to a second position in response to removing said particulate material from said chamber to permit movement of said leg into engagement with said body member.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    In the present paper we outline the basic theory of assembling substructures for which the dynamics are described as Impulse Response Functions. The assembly procedure computes the time response of a system by evaluating per substructure the convolution product between the Impulse Response Functions and the applied forces, including the interface forces that are computed to satisfy the interface compatibility. We call this approach the Impulse Based Substructuring method since it transposes to the time domain the Frequency Based Substructuring approach. In the Impulse Based Substructuring technique the Impulse Response Functions of the substructures can be gathered either from experimental tests using a hammer impact or from time-integration of numerical submodels. In this paper the implementation of the method is outlined for the case when the impulse responses of the substructures are computed numerically. A simple bar example is shown in order to illustrate the concept. The Impulse Based Substructuring allows fast evaluation of impact response of a structure when the impulse response of its components is known. It can thus be used to efficiently optimize designs of consumer products by including impact behavior at the early stage of the design, but also for performing substructured simulations of complex structures such as offshore wind turbines.

  7. Unexpected relationships of substructured populations in Chinese Locusta migratoria

    PubMed Central

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

    2009-01-01

    Background Highly migratory species are usually expected to have minimal population substructure because strong gene flow has the effect of homogenizing genetic variation over geographical populations, counteracting random drift, selection and mutation. The migratory locust Locusta migratoria belongs to a monotypic genus, and is an infamous pest insect with exceptional migratory ability – with dispersal documented over a thousand kilometers. Its distributional area is greater than that of any other locust or grasshopper, occurring in practically all the temperate and tropical regions of the eastern hemisphere. Consequently, minimal population substructuring is expected. However, in marked contrast to its high dispersal ability, three geographical subspecies have been distinguished in China, with more than nine being biologically and morphologically identified in the world. Such subspecies status has been under considerable debate. Results By multilocus microsatellite genotyping analysis, we provide ample genetic evidence for strong population substructure in this highly migratory insect that conforms to geography. More importantly, our genetic data identified an unexpected cryptic subdivision and demonstrated a strong affiliation of the East China locusts to those in Northwest/Northern China. The migratory locusts in China formed three distinct groups, viz. (1) the Tibetan group, comprising locusts from Tibet and nearby West China high mountain regions; this is congruent with the previously recognized Tibetan subspecies, L. m. tibetensis; (2) the South China group, containing locusts from the Hainan islands; this corresponds to the Southeast Asia oriental tropical subspecies L. m. manilensis; (3) the North China group, including locusts from the Northwest and Northern China (the Asiatic subspecies L. m. migratoria), Central China and Eastern China regions. Therefore, the traditional concept on Locusta subspecies status established from Uvarov in 1930s needs to be

  8. Aligning graphs and finding substructures by a cavity approach

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  10. Fatigue reassessment for lifetime extension of offshore wind monopile substructures

    NASA Astrophysics Data System (ADS)

    Ziegler, Lisa; Muskulus, Michael

    2016-09-01

    Fatigue reassessment is required to decide about lifetime extension of aging offshore wind farms. This paper presents a methodology to identify important parameters to monitor during the operational phase of offshore wind turbines. An elementary effects method is applied to analyze the global sensitivity of residual fatigue lifetimes to environmental, structural and operational parameters. Therefore, renewed lifetime simulations are performed for a case study which consists of a 5 MW turbine with monopile substructure in 20 m water depth. Results show that corrosion, turbine availability, and turbulence intensity are the most influential parameters. This can vary strongly for other settings (water depth, turbine size, etc.) making case-specific assessments necessary.

  11. The construction of preconditioners for elliptic problems by substructuring, IV

    SciTech Connect

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

    1989-07-01

    We consider the problem of solving the algebraic system of equations which result from the discretization of elliptic boundary value problems defined on three-dimensional Euclidean space. We develop preconditioners for such systems based on substructuring (also known as domain decomposition). The resulting algorithms are well suited to emerging parallel computing architectures. We describe two techniques for developing these preconditioners. A theory for the analysis of the condition number for the resulting preconditioned system is given and the results of supporting numerical experiments are presented.

  12. The construction of preconditioners for elliptic problems by substructuring, IV

    SciTech Connect

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

    1987-06-01

    We consider the problem of solving the algebraic system of equations which result from the discretization of elliptic boundary value problems defined on three dimensional Euclidean space. We develop preconditioners for such systems based on substructuring (also known as domain decomposition). The resulting algorithms are well suited to emerging parallel computing architectures. We describe two techniques for developing these precondictioners. A theory for the analysis of the condition number for the resulting preconditioned system is given and the results of supporting numerical experiments are presented. 16 refs., 2 tabs.

  13. Hierarchically Parallelized Constrained Nonlinear Solvers with Automated Substructuring

    NASA Technical Reports Server (NTRS)

    Padovan, Joe; Kwang, Abel

    1994-01-01

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

  14. Convergence of a Substructuring Method with LaGrange Multipliers

    NASA Technical Reports Server (NTRS)

    Mandel, Jan; Tezaur, Radek

    1996-01-01

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

  15. Stellar atmospheric structural patterns

    NASA Technical Reports Server (NTRS)

    Thomas, R. N.

    1983-01-01

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

  16. Evolving sparse stellar populations

    NASA Astrophysics Data System (ADS)

    Bruzual, Gustavo; Gladis Magris, C.; Hernández-Pérez, Fabiola

    2017-03-01

    We examine the role that stochastic fluctuations in the IMF and in the number of interacting binaries have on the spectro-photometric properties of sparse stellar populations as a function of age and metallicity.

  17. Oscillations in stellar atmospheres

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  18. The Herschel Virgo Cluster Survey . II. Truncated dust disks in H I-deficient spirals

    NASA Astrophysics Data System (ADS)

    Cortese, L.; Davies, J. I.; Pohlen, M.; Baes, M.; Bendo, G. J.; Bianchi, S.; Boselli, A.; De Looze, I.; Fritz, J.; Verstappen, J.; Bomans, D. J.; Clemens, M.; Corbelli, E.; Dariush, A.; di Serego Alighieri, S.; Fadda, D.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Grossi, M.; Hughes, T. M.; Hunt, L. K.; Jones, A. P.; Madden, S.; Pierini, D.; Sabatini, S.; Smith, M. W. L.; Vlahakis, C.; Xilouris, E. M.; Zibetti, S.

    2010-07-01

    By combining Herschel-SPIRE observations obtained as part of the Herschel Virgo Cluster Survey with 21 cm Hi data from the literature, we investigate the role of the cluster environment on the dust content of Virgo spiral galaxies. We show for the first time that the extent of the dust disk is significantly reduced in Hi-deficient galaxies, following remarkably well the observed “truncation” of the Hi disk. The ratio of the submillimetre-to-optical diameter correlates with the Hi-deficiency, suggesting that the cluster environment is able to strip dust as well as gas. These results provide important insights not only into the evolution of cluster galaxies but also into the metal enrichment of the intra-cluster medium. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  19. Selecting Gravitational Wave Candidates for Electromagnetic Follow-up: Advanced LIGO/Virgo's Decision Making Process

    NASA Astrophysics Data System (ADS)

    Cho, Min-A.; LIGO Scientific Collaboration; Virgo Collaboration

    2016-03-01

    Some of the most violent events in the universe are bright in both their gravitational wave (GW) emission and electromagnetic (EM). This means that prospects for multi-messenger astronomy increase as more and more detectors join the search for gravitational waves. Here I present the protocol created by members of Advanced LIGO/Virgo's EM Follow-up Program which ultimately results in alerting its astronomy partners or not. I discuss the series of checks and questions performed by humans (follow-up advocates and control room personnel) and automated online software (Approval Processor). This talk will follow the fate of the gravitational wave candidate event after it first enters Advanced LIGO/Virgo's online candidate event database. We gratefully acknowledge the support of the U.S. National Science Foundation through Grant PHY-1404121.

  20. VIRGO: a large interferometer for gravitational wave detection started its first scientific run

    NASA Astrophysics Data System (ADS)

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

    2008-07-01

    The VIRGO interferometer is the largest ground based European gravitational wave detector operating at the EGO Laboratory in the Pisa, Italy; countryside. During the last commissioning period relevant progress have been done in approaching its design sensitivity all over the detection bandwidth. Thanks to the effort of the whole Collaboration a long scientific run has been done collecting data for more than 4 months in conjunction with the LIGO detectors. The results obtained from the detector point of view are: a very good stability and a duty-cycle as high as 81% in science mode. In this paper we present the status of the VIRGO interferometer giving an overview of the experimental apparatus together with its most relevant features.

  1. Quantum-chemical foundations of the topological substructural molecular design.

    PubMed

    Estrada, Ernesto

    2008-06-12

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

  2. Population genetic analysis and sub-structuring in Babesia bovis.

    PubMed

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

    2011-06-01

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

  3. VizieR Online Data Catalog: GALEX Ultraviolet Virgo Cluster Survey (GUViCS) (Boselli+, 2011)

    NASA Astrophysics Data System (ADS)

    Boselli, A.; Boissier, S.; Heinis, S.; Cortese, L.; Ilbert, O.; Hughes, T.; Cucciati, O.; Davies, J.; Ferrarese, L.; Giovanelli, R.; Haynes, M. P.; Baes, M.; Balkowski, C.; Brosch, N.; Chapman, S. C.; Charmandaris, V.; Clemens, M. S.; Dariush, A.; De Looze, I.; di Serego Alighieri, S.; Duc, P.-A.; Durrell, P. R.; Emsellem, E.; Erben, T.; Fritz, J.; Garcia-Appadoo, D. A.; Gavazzi, G.; Grossi, M.; Jordan, A.; Hess, K. M.; Huertas-Company, M.; Hunt, L. K.; Kent, B. R.; Lambas, D. G.; Lancon, A.; MacArthur, L. A.; Madden, S. C.; Magrini, L.; Mei, S.; Momjian, E.; Olowin, R. P.; Papastergis, E.; Smith, M. W. L.; Solanes, J. M.; Spector, O.; Spekkens, K.; Taylor, J. E.; Valotto, C.; van Driel, W.; Verstappen, J.; Vlahakis, C.; Vollmer, B.; Xilouris, E. M.

    2011-08-01

    The GALEX Ultraviolet Virgo Cluster Survey (GUViCS) is a complete blind survey of the Virgo cluster covering ~40 sq. deg in the far UV (FUV, λeff=1539Å, Δλ=442Å) and ~120 sq. deg in the near UV (NUV, λeff=2316Å, Δλ=1060Å). The goal of the survey is to study the ultraviolet (UV) properties of galaxies in a rich cluster environment, spanning a wide luminosity range from giants to dwarfs, and regardless of prior knowledge of their star formation activity. The UV data will be combined with those in other bands (optical: NGVS; far-infrared - submm: HeViCS; HI: ALFALFA) and with our multizone chemo-spectrophotometric models of galaxy evolution to make a complete and exhaustive study of the effects of the environment on the evolution of galaxies in high density regions. We present here the scientific objectives of the survey, describing the observing strategy and briefly discussing different data reduction techniques. Using UV data already in-hand for the central 12 sq. deg we determine the FUV and NUV luminosity functions of the Virgo cluster core for all cluster members and separately for early- and late-type galaxies and compare it to the one obtained in the field and other nearby clusters (Coma, A1367). This analysis shows that the FUV and NUV luminosity functions of the core of the Virgo clusters are flatter (alpha~-1.1) than those determined in Coma and A1367. We discuss the possible origin of this difference. (1 data file).

  4. The peculiar hydrogen cloud in the Virgo Cluster and 3C 273

    NASA Technical Reports Server (NTRS)

    Arp, H. C.; Burbidge, G.

    1990-01-01

    It is shown that the nearest bright extragalactic object to the peculiar hydrogen cloud recently discovered in the Virgo Cluster by Giovanelli and Haynes is the bright QSO 3C 273. Further, it is pointed out that the jet in 3C 273 points in almost the same direction as the major axis of the cloud. Despite the redshift difference, possible physical connections between the cloud and 3C 273 are explored.

  5. Probing the scale of new physics by Advanced LIGO/VIRGO

    NASA Astrophysics Data System (ADS)

    Dev, P. S. Bhupal; Mazumdar, A.

    2016-05-01

    We show that if the new physics beyond the standard model is associated with a first-order phase transition around 107- 108 GeV , the energy density stored in the resulting stochastic gravitational waves and the corresponding peak frequency are within the projected final sensitivity of the advanced LIGO/VIRGO detectors. We discuss some possible new physics scenarios that could arise at such energies, and in particular, the consequences for Peccei-Quinn and supersymmetry breaking scales.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Newby, Matthew T.

    The stellar halo that surrounds our Galaxy contains clues to understanding galaxy formation, cosmology, stellar evolution, and the nature of dark matter. Gravitationally disrupted dwarf galaxies form tidal streams, which roughly trace orbits through the Galactic halo. The Sagittarius (Sgr) dwarf tidal debris is the most dominant of these streams, and its properties place important constraints on the distribution of mass (including dark matter) in the Galaxy. Stars not associated with substructures form the "smooth" component of the stellar halo, the origin of which is still under investigation. Characterizing halo substructures such as the Sgr stream and the smooth halo provides valuable information on the formation history and evolution of our galaxy, and places constraints on cosmological models. This thesis is primarily concerned with characterizing the 3-dimensional stellar densities of the Sgr tidal debris system and the smooth stellar halo, using data from the Sloan Digital Sky Survey (SDSS). F turnoff stars are used to infer distances, as they are relatively bright, numerous, and distributed about a single intrinsic brightness (magnitude). The inherent spread in brightnesses of these stars is overcome through the use of the recently-developed technique of statistical photometric parallax, in which the bulk properties of a stellar population are used to create a probability distribution for a given star's distance. This was used to build a spatial density model for the smooth stellar halo and tidal streams. The free parameters in this model are then fit to SDSS data with a maximum likelihood technique, and the parameters are optimized by advanced computational methods. Several computing platforms are used in this study, including the RPI SUR Bluegene and the Milkyway home volunteer computing project. Fits to the Sgr stream in 18 SDSS data stripes were performed, and a continuous density profile is found for the major Sgr stream. The stellar halo is found to

  9. A History of H i Stripping in Virgo: A Phase-space View of VIVA Galaxies

    NASA Astrophysics Data System (ADS)

    Yoon, Hyein; Chung, Aeree; Smith, Rory; Jaffé, Yara L.

    2017-04-01

    We investigate the orbital histories of Virgo galaxies at various stages of H i gas stripping. In particular, we compare the location of galaxies with different H i morphology in phase space. This method is a great tool for tracing the gas stripping histories of galaxies as they fall into the cluster. Most galaxies at the early stage of H i stripping are found in the first infall region of Virgo, while galaxies undergoing active H i stripping mostly appear to be falling in or moving out near the cluster core for the first time. Galaxies with severely stripped, yet symmetric, H i disks are found in one of two locations. Some are deep inside the cluster, but others are found in the cluster outskirts with low orbital velocities. We suggest that the latter group of galaxies belong to a “backsplash” population. These present the clearest candidates for backsplashed galaxies observationally identified to date. We further investigate the distribution of a large sample of H i-detected galaxies toward Virgo in phase space, confirming that most galaxies are stripped of their gas as they settle into the gravitational potential of the cluster. In addition, we discuss the impact of tidal interactions between galaxies and group preprocessing on the H i properties of the cluster galaxies, and link the associated star formation evolution to the stripping sequence of cluster galaxies.

  10. LIGO-VIRGO Triggered Follow-Up with NASA High Energy Photon Survey Missions

    NASA Technical Reports Server (NTRS)

    Camp, Jordan

    2010-01-01

    We discuss the proposed use of LIGO-VIRGO S6 triggers from comparatively loud events to search for both prompt and afterglow EM counterparts with RXTE, SWIFT and FERMI. Using a 2 or 3-fold coincident trigger from the two LIGO and one VIRGO detectors to provide sky position information, we can search the data from these missions within a limited time window and a constrained portion of their respective FOVs, allowing us to look at a level below the threshold normally used to publicly indicate an event. Since we propose to use these missions in their survey mode, no re-pointing of the missions is envisioned. The search for a coincidence between the data from LIGO-VIRGO and the EM survey missions can then be analyzed off-line; if a coincident EM signal is found it would have a significant effect in establishing the validity of the GW trigger. We discuss some relevant aspects of the NASA missions and give some preliminary estimates of thresholds and coincident background rates.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  12. Optical studies of galaxies in clusters. Observations of spirals in Virgo. III.

    NASA Astrophysics Data System (ADS)

    Sperandio, M.; Chincarini, G.; Rampazzo, R.; de Souza, R.

    1995-04-01

    We present the analysis of the rotation curves of a sample of 32 spiral galaxies derived from the spectroscopic observations of a sample of 47 galaxies. For 15 galaxies we were either unable to detect emission lines or measure a reasonably good rotation curve. Of the 32 rotation curves 23 are of galaxies member of the Virgo Cluster and 9 selected from the "field". Analysis of mass and density distribution have been obtained. The mass distribution of cluster galaxies belongs to the Type III proposed by Burstein & Rubin (1985) with few exceptions (NGC 4519 Type I, NGC 2280, NGC 4189, NGC 5861, NGC 6070 Type II) and, is unrelated to the morphological type. Density distribution curves from equidensity surface spheroids model, computed for the Virgo sample, result to be primarily composed of three classes. Rotation curves, none of which shows a peculiar trend, have been parametrized using the criteria introduced by Whitmore et al. (1984). The clustercentric distance of Virgo spirals does not correlate neither with OG nor with OGML in agreement with the findings of Distefano et al. (1990) and Amram et al. (1993, 1994) for other clusters.

  13. Resolving the stellar outskirts of six Milky Way-like galaxies beyond the Local Group

    NASA Astrophysics Data System (ADS)

    Monachesi, A.; Bell, E. F.; Radburn-Smith, D. J.; Harmsen, B.; de Jong, R. S.; Bailin, J.; Holwerda, B. W.; Streich, D.

    2017-03-01

    Models of galaxy formation in a hierarchical universe predict substantial scatter in the halo-to-halo stellar properties, owing to stochasticity in galaxies' merger histories. Currently, only few detailed observations of galaxy's halos are available, mainly for the Milky Way and M31. The Galaxy Halos, Outer disks, Substructure, Thick disks and Star clusters (GHOSTS) HST survey is the largest study to date of the resolved stellar populations in the outskirts of disk galaxies and its observations offer a direct test of model predictions. Here we present the results we obtain for six highly inclined nearby Milky Way-mass spiral galaxies. We find a great diversity in the properties of their stellar halos.

  14. The structure and early evolution of massive star forming regions. Substructure in the infrared dark cloud SDC13

    NASA Astrophysics Data System (ADS)

    McGuire, C.; Fuller, G. A.; Peretto, N.; Zhang, Q.; Traficante, A.; Avison, A.; Jimenez-Serra, I.

    2016-10-01

    Context. Investigations into the substructure of massive star forming regions are essential for understanding the observed relationships between core mass distributions and mass distributions in stellar clusters, differentiating between proposed mechanisms of massive star formation. Aims: We study the substructure in the two largest fragments (i.e. cores) MM1 and MM2, in the infrared dark cloud complex SDC13. As MM1 appears to be in a later stage of evolution than MM2, comparing their substructure provides an insight in to the early evolution of massive clumps. Methods: We report the results of high resolution SMA dust continuum observations towards MM1 and MM2. Combining these data with Herschel observations, we carry out RADMC-3D radiative transfer modelling to characterise the observed substructure. Results: SMA continuum data indicates 4 sub-fragments in the SDC13 region. The nature of the second brightest sub-fragment (B) is uncertain as it does not appear as prominent at the lower MAMBO resolution or at radio wavelengths. Statistical analysis indicates that it is unlikely to be a background source, an AGB star, or the free-free emission of a HII region. It is plausible that B is a runaway object ejected from MM1. MM1, which is actively forming stars, consists of two sub-fragments A and C. This is confirmed by 70 μmHerschel data. While MM1 and MM2 appear quite similar in previous low resolution observations, at high resolution, the sub-fragment at the centre of MM2 (D) is much fainter than sub-fragment at the centre of MM1 (A). RADMC-3D models of MM1 and MM2 are able to reproduce these results, modelling MM2 with a steeper density profile and higher mass than is required for MM1. The relatively steep density profile of MM2 depends on a significant temperature decrease in its centre, justified by the lack of star formation in MM2. A final stellar population for MM1 was extrapolated, indicating a star formation efficiency typical of regions of core and cluster

  15. ALMA Observations of Lyα Blob 1: Halo Substructure Illuminated from Within

    NASA Astrophysics Data System (ADS)

    Geach, J. E.; Narayanan, D.; Matsuda, Y.; Hayes, M.; Mas-Ribas, Ll.; Dijkstra, M.; Steidel, C. C.; Chapman, S. C.; Feldmann, R.; Avison, A.; Agertz, O.; Ao, Y.; Birkinshaw, M.; Bremer, M. N.; Clements, D. L.; Dannerbauer, H.; Farrah, D.; Harrison, C. M.; Kubo, M.; Michałowski, M. J.; Scott, Douglas; Smith, D. J. B.; Spaans, M.; Simpson, J. M.; Swinbank, A. M.; Taniguchi, Y.; van der Werf, P.; Verma, A.; Yamada, T.

    2016-11-01

    We present new Atacama Large Millimeter/Submillimeter Array (ALMA) 850 μm continuum observations of the original Lyα Blob (LAB) in the SSA22 field at z = 3.1 (SSA22-LAB01). The ALMA map resolves the previously identified submillimeter source into three components with a total flux density of S 850 = 1.68 ± 0.06 mJy, corresponding to a star-formation rate of ˜150 M ⊙ yr-1. The submillimeter sources are associated with several faint (m ≈ 27 mag) rest-frame ultraviolet sources identified in Hubble Space Telescope Imaging Spectrograph (STIS) clear filter imaging (λ ≈ 5850 Å). One of these companions is spectroscopically confirmed with the Keck Multi-Object Spectrometer For Infra-Red Exploration to lie within 20 projected kpc and 250 km s-1 of one of the ALMA components. We postulate that some of these STIS sources represent a population of low-mass star-forming satellites surrounding the central submillimeter sources, potentially contributing to their growth and activity through accretion. Using a high-resolution cosmological zoom simulation of a 1013 M ⊙ halo at z = 3, including stellar, dust, and Lyα radiative transfer, we can model the ALMA+STIS observations and demonstrate that Lyα photons escaping from the central submillimeter sources are expected to resonantly scatter in neutral hydrogen, the majority of which is predicted to be associated with halo substructure. We show how this process gives rise to extended Lyα emission with similar surface brightness and morphology to observed giant LABs.

  16. PREFACE: A Stellar Journey A Stellar Journey

    NASA Astrophysics Data System (ADS)

    Asplund, M.

    2008-10-01

    The conference A Stellar Journey was held in Uppsala, Sweden, 23 27June 2008, in honour of Professor Bengt Gustafsson's 65th birthday. The choice of Uppsala as the location for this event was obvious given Bengt's long-standing association with the city stemming back to his school days. With the exception of a two-year postdoc stint in Copenhagen, five years as professor at Stockholm University and two years as director of the Sigtuna foundation, Bengt has forged his illustrious professional career at Uppsala University. The symposium venue was Museum Gustavianum, once the main building of the oldest university in Scandinavia. The title of the symposium is a paraphrasing of Bengt's popular astronomy book Kosmisk Resa (in English: Cosmic Journey) written in the early eighties. I think this aptly symbolizes his career that has been an astronomical voyage from near to far, from the distant past to the present. The original book title was modified slightly to reflect that most of his work to date has dealt with stars in one way or another. In addition it also gives credit to Bengt's important role as a guiding light for a very large number of students, colleagues and collaborators, indeed for several generations of astronomers. For me personally, the book Kosmisk Resa bears particular significance as it has shaped my life rather profoundly. Although I had already decided to become an astronomer, when I first read the book as a 14-year-old I made up my mind then and there that I would study under Bengt Gustafsson and work on stars. Indeed I have remained true to this somewhat audacious resolution. I suspect that a great number of us have similar stories how Bengt has had a major influence on our lives, whether on the professional or personal level. Perhaps Bengt's most outstanding characteristic is his enthralling enthusiasm. This is equally true whether he is pondering some scientific conundrum, supervising students or performing in front of an audience, be it an

  17. A Comparison of Reduced Order Modeling Techniques Used in Dynamic Substructuring [PowerPoint

    SciTech Connect

    Roettgen, Dan; Seeger, Benjamin; Tai, Wei Che; Baek, Seunghun; Dossogne, Tilan; Allen, Matthew S; Kuether, Robert J.; Brake, Matthew Robert; Mayes, Randall L.

    2016-01-01

    Experimental dynamic substructuring is a means whereby a mathematical model for a substructure can be obtained experimentally and then coupled to a model for the rest of the assembly to predict the response. Recently, various methods have been proposed that use a transmission simulator to overcome sensitivity to measurement errors and to exercise the interface between the substructures; including the Craig-Bampton, Dual Craig-Bampton, and Craig-Mayes methods. This work compares the advantages and disadvantages of these reduced order modeling strategies for two dynamic substructuring problems. The methods are first used on an analytical beam model to validate the methodologies. Then they are used to obtain an experimental model for structure consisting of a cylinder with several components inside connected to the outside case by foam with uncertain properties. This represents an exceedingly difficult structure to model and so experimental substructuring could be an attractive way to obtain a model of the system.

  18. A Comparison of Reduced Order Modeling Techniques Used in Dynamic Substructuring.

    SciTech Connect

    Roettgen, Dan; Seegar, Ben; Tai, Wei Che; Baek, Seunghun; Dossogne, Tilan; Allen, Matthew; Kuether, Robert J.; Brake, Matthew Robert; Mayes, Randall L.

    2015-10-01

    Experimental dynamic substructuring is a means whereby a mathematical model for a substructure can be obtained experimentally and then coupled to a model for the rest of the assembly to predict the response. Recently, various methods have been proposed that use a transmission simulator to overcome sensitivity to measurement errors and to exercise the interface between the substructures; including the Craig-Bampton, Dual Craig-Bampton, and Craig-Mayes methods. This work compares the advantages and disadvantages of these reduced order modeling strategies for two dynamic substructuring problems. The methods are first used on an analytical beam model to validate the methodologies. Then they are used to obtain an experimental model for structure consisting of a cylinder with several components inside connected to the outside case by foam with uncertain properties. This represents an exceedingly difficult structure to model and so experimental substructuring could be an attractive way to obtain a model of the system.

  19. Las Campanas Stellar Library

    NASA Astrophysics Data System (ADS)

    Chilingarian, Igor; Zolotukhin, Ivan; Beletsky, Yuri; Worthey, Guy

    2015-08-01

    Stellar libraries are fundamental tools required to understand stellar populations in star clusters and galaxies as well as properties of individual stars. Comprehensive libraries exist in the optical domain, but the near-infrared (NIR) domain stays a couple of decades behind. Here we present the Las Campanas Stellar Library project aiming at obtaining high signal-to-noise intermediate-resolution (R=8000) NIR spectra (0.83<λ<2.5μm) for a sample of 1200 stars in the Southern sky using the Folded-port InfraRed Echelette spectrograph at the 6.5-m Magellan Baade telescope. We developed a dedicated observing strategy and customized the telescope control software in order to achieve the highest possible level of data homogeniety. As of 2015, we observed about 600 stars of all spectral types and luminosity classes making our library the largest homogeneous collection of stellar spectra covering the entire NIR domain. We also re-calibrated in flux and wavelength the two existing optical stellar libraries, INDO-US and UVES-POP and followed up about 400 non-variable stars in the NIR in order to get complete optical-NIR coverage. Worth mentioning that our current sample includes about 80 AGB stars and a few dozens of bulge/LMC/SMC stars.

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

    SciTech Connect

    Schlaufman, Kevin C.; Rockosi, Constance M.; Lee, Young Sun; Beers, Timothy C.; Allende Prieto, Carlos E-mail: crockosi@ucolick.org E-mail: beers@pa.msu.edu

    2011-06-10

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

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

    SciTech Connect

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

    2010-06-20

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

  2. Candidates for Intracluster Planetary Nebulae in the Virgo Cluster Based on the Suprime-Cam Narrow-Band Imaging in [O III] and Hα

    NASA Astrophysics Data System (ADS)

    Okamura, Sadanori; Yasuda, Naoki; Arnaboldi, Magda; Freeman, Kenneth C.; Ando, Hiroyasu; Doi, Mamoru; Furusawa, Hisanori; Gerhard, Ortwin; Hamabe, Masaru; Kimura, Masahiko; Kajino, Toshitaka; Komiyama, Yutaka; Miyazaki, Satoshi; Nakata, Fumiaki; Napolitano, Nicola R.; Ouchi, Masami; Pannella, Maurilio; Sekiguchi, Maki; Shimasaku, Kazuhiro; Yagi, Masafumi

    2002-12-01

    We have identified 38 candidates of intracluster planetary nebulae (ICPNe) in a 34' × 27' field in the core of the Virgo cluster based on Suprime-Cam imaging through two narrow-band filters centered at redshifted wavelengths of the [O III] λ=5007Å and the Hα λ=6563Å lines. Broad-band images in the V and R bands are used to check for any emissions in the adjacent continuum. We describe the method briefly and present a list of the intracluster planetary nebula candidates, together with their finding charts. The ICPN candidates show a highly inhomogeneous distribution, which may suggest an association with the M 86-M 84 subcluster. The fraction of diffuse intracluster light with respect to the total light in galaxies is estimated to be about 10%, leading to an estimate of about 20% for the baryon fraction. A spectroscopic follow up and a wider survey are critical to reveal the nature of the intracluster stellar population.

  3. Origins of Stellar Halos

    NASA Astrophysics Data System (ADS)

    Johnston, Kathryn V.

    2016-08-01

    This contribution reviews ideas about the origins of stellar halos. It includes discussion of the theoretical understanding of and observational evidence for stellar populations formed ``in situ'' (meaning formed in orbits close to their current ones), ``kicked-out'' (meaning formed in the inner galaxy in orbits unlike their current ones) and ``accreted'' (meaning formed in a dark matter halo other than the one they currently occupy). At this point there is general agreement that a significant fraction of any stellar halo population is likely ``accreted''. There is modest evidence for the presence of a ``kicked-out'' population around both the Milky Way and M31. Our theoretical understanding of and the observational evidence for an ``in situ'' population are less clear.

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

    PubMed Central

    2014-01-01

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

  5. Substructure In The Scorpius-Centaurus OB Association

    NASA Astrophysics Data System (ADS)

    Pecaut, Mark J.; Mamajek, Eric E.

    2016-07-01

    OB associations are remnants of star formation on a large scale, producing everything from O- and B-type stars, down to the lowest mass brown dwarfs. OB associations represent the typical mode of star formation in the Galaxy. But is this process monolithic? We present the results of a survey for new, solar mass (0.7 - 1.3 Msun) members of Sco-Cen, the nearest OB Association to the Sun. We identify 150 new members and place the known B/A/F/G/K/M-type members on the Hertzsprung-Russell diagram. From these data, we construct an age map of Sco-Cen, occupying approximately 2,000 square degrees on the sky. These results indicate there is substantial substructure in Sco-Cen, and present the possibility that star formation on the largest scales can be considered a collection of many individual, small-scale star formation events along a giant molecular cloud.

  6. Probing Galaxy Clusters and Substructures using Gravitational Lensing

    NASA Astrophysics Data System (ADS)

    Choi, Miyoung; Nguyen, Hoang; King, Lindsay; Lee, Brandyn E.; McCarthy, Ian

    2017-01-01

    Gravitational lensing is one of the most promising methods of analyzing massive astronomical objects such as galaxy clusters. The weak gravitational lensing signal, which is called shear, is a measurement of the weak distortion of background galaxies in the linear regime of the lensing field. Shear analysis effectively estimates the main properties of galaxy clusters such as the mass and scale of the lensing system. The second order gravitational lensing signal, flexion, is dominant in the non-linear regime of the lensing field that bridges the strong and weak lensing regimes. It has also recently arisen as a robust method to detect substructures in galaxy clusters due to its sensitivity to the gradient of convergence and shear field. In this poster we propose that combining the shear and flexion analysis can give more information about the detailed structure of the lensing system.

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

    SciTech Connect

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

    1986-07-01

    We consider the problem of solving the algebraic system of equations which arise from the discretization of symmetric elliptic boundary value problems via finite element methods. A new class of preconditioners for the discrete system is developed based on substructuring (also known as domain decomposition). The resulting preconditioned algorithms are well suited to emerging parallel computing architectures. The proposed methods are applicable to problems on general domains involving differential operators with rather general coefficients. A basic theory for the analysis of the condition number of the preconditioned system (which determines the iterative convergence rate of the algorithm) is given. Techniques for applying the theory and algorithms to problems with irregular geometry are discussed and the results of extensive numerical experiments are reported.

  8. The Galactic stellar disc

    NASA Astrophysics Data System (ADS)

    Feltzing, S.; Bensby, T.

    2008-12-01

    The study of the Milky Way stellar discs in the context of galaxy formation is discussed. In particular, we explore the properties of the Milky Way disc using a new sample of about 550 dwarf stars for which we have recently obtained elemental abundances and ages based on high-resolution spectroscopy. For all the stars we also have full kinematic information as well as information about their stellar orbits. We confirm results from previous studies that the thin and the thick discs have distinct abundance patterns. But we also explore a larger range of orbital parameters than what has been possible in our previous studies. Several new results are presented. We find that stars that reach high above the Galactic plane and have eccentric orbits show remarkably tight abundance trends. This implies that these stars formed out of well-mixed gas that had been homogenized over large volumes. We find some evidence that suggest that the event that most likely caused the heating of this stellar population happened a few billion years ago. Through a simple, kinematic exploration of stars with super-solar [Fe/H], we show that the solar neighbourhood contains metal-rich, high velocity stars that are very likely associated with the thick disc. Additionally, the HR1614 moving group and the Hercules and Arcturus stellar streams are discussed and it is concluded that, probably, a large fraction of the groups and streams so far identified in the disc are the result of evolution and interactions within the stellar disc rather than being dissolved stellar clusters or engulfed dwarf galaxies. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. Also based on observations collected at the Nordic Optical Telescope on La Palma, Spain, and at the European Southern Observatories on La Silla and Paranal, Chile, Proposals no. 65.L-0019(B), 67.B-0108(B), 69.B-0277.

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

    SciTech Connect

    De Jong, Jelte T. A.; Rix, Hans-Walter; Martin, Nicolas F.; Yanny, Brian; Dolphin, Andrew E.; Beers, Timothy C.

    2010-05-01

    We map the stellar structure of the Galactic thick disk and halo by applying color-magnitude diagram (CMD) fitting to photometric data from the Sloan Extension for Galactic Understanding and Exploration (SEGUE) survey. The SEGUE imaging scans allow, for the first time, a comprehensive analysis of Milky Way structure at both high and low latitudes using uniform Sloan Digital Sky Survey photometry. Incorporating photometry of all relevant stars simultaneously, CMD fitting bypasses the need to choose single tracer populations. Using old stellar populations of differing metallicities as templates, we obtain a sparse three-dimensional map of the stellar mass distribution at |Z|>1 kpc. Fitting a smooth Milky Way model comprising exponential thin and thick disks and an axisymmetric power-law halo allows us to constrain the structural parameters of the thick disk and halo. The thick-disk scale height and length are well constrained at 0.75 {+-} 0.07 kpc and 4.1 {+-} 0.4 kpc, respectively. We find a stellar halo flattening within {approx}25 kpc of c/a = 0.88 {+-} 0.03 and a power-law index of 2.75 {+-} 0.07 (for 7 kpc {approx_lt}R{sub GC} {approx_lt} 30 kpc). The model fits yield thick-disk and stellar halo densities at the solar location of {rho}{sub thick,sun} = 10{sup -2.3{+-}0.1} M{sub sun} pc{sup -3} and {rho}{sub halo,sun} = 10{sup -4.20{+-}0.05} M{sub sun} pc{sup -3}, averaging over any substructures. Our analysis provides the first clear in situ evidence for a radial metallicity gradient in the Milky Way's stellar halo: within R {approx_lt} 15 kpc the stellar halo has a mean metallicity of [Fe/H] {approx_equal} -1.6, which shifts to [Fe/H] {approx_equal} -2.2 at larger radii, in line with the two-component halo deduced by Carollo et al. from a local kinematic analysis. Subtraction of the best-fit smooth and symmetric model from the overall density maps reveals a wealth of substructures at all latitudes, some attributable to known streams and overdensities, and some

  10. STELLAR POPULATIONS IN THE OUTER HALO OF THE MASSIVE ELLIPTICAL M49

    SciTech Connect

    Mihos, J. Christopher; Harding, Paul; Rudick, Craig S.; Feldmeier, John J. E-mail: paul.harding@case.edu E-mail: jjfeldmeier@ysu.edu

    2013-02-20

    We use deep surface photometry of the giant elliptical M49 (NGC 4472), obtained as part of our survey for diffuse light in the Virgo Cluster, to study the stellar populations in its outer halo. Our data trace M49's stellar halo out to {approx}100 kpc (7r{sub e}), where we find that the shallow color gradient seen in the inner regions becomes dramatically steeper. The outer regions of the galaxy are quite blue (B - V {approx} 0.7); if this is purely a metallicity effect, it argues for extremely metal-poor stellar populations with [Fe/H] < -1. We also find that the extended accretion shells around M49 are distinctly redder than the galaxy's surrounding halo, suggesting that we are likely witnessing the buildup of both the stellar mass and metallicity in M49's outer halo due to late time accretion. While such growth of galaxy halos is predicted by models of hierarchical accretion, this growth is thought to be driven by more massive accretion events which have correspondingly higher mean metallicity than inferred for M49's halo. Thus the extremely metal-poor nature of M49's extended halo provides some tension against current models for elliptical galaxy formation.

  11. Dynamics of 10 clusters of galaxies with substructures

    SciTech Connect

    Lakhchaura, Kiran; Singh, K. P.

    2014-06-01

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

  12. Nucleolonema as a fundamental substructure of the nucleolus.

    PubMed

    Sato, Seiichi; Yano, Hiroyuki; Makimoto, Yuji; Kaneta, Tsuyoshi; Sato, Yasushi

    2005-04-01

    The nucleolus is the most obvious structure in the eukaryotic nucleus. It is known to be a ribosome-producing apparatus where ribosomal (r) DNA is transcribed and the primary rRNA transcripts are processed to produce three of the four rRNA species. Electron microscopy has shown that the nucleolus consists of three major components, a dense fibrillar component (DFC), a granular component (GC) and a fibrillar center (FC). The DFC and FCs are integrated into a fundamental nucleolar substructure called the nucleolonema. The DFC corresponds to the matrix of the nucleolonema, and the FC is an electron microscopic counterpart of argyrophobic lacunae localized in the nucleolonema. The spherical FCs are intermittently arranged along the length of the nucleolonema in actively growing cells but are fused with each other to form tubular FCs when rDNA transcription is hampered. The RNase-gold complex does not bind to the FC but to the DFC and the GC, suggesting that rDNA transcription does not occur in the FC although both fluorescence in situ hybridization (FISH) and electron microscopic in situ hybridization reveal that the rDNA is specifically localized in the FCs. Immunogold-labeling after bromo-UTP (BrUTP) incorporation shows that rDNA transcription takes place in the boundary region between the FC and the DFC, and primary rRNA transcripts are expected to be processed outward within the DFC. Data have accumulated suggesting that the nucleolonema is a fundamental substructure of the nucleolus, and its skeleton is the tandem arrangement of the FCs, which are resting harbors or storages of rDNA. This paper proposes that the transversal structural organization of the nucleolonema is centrifugally built up by several structural and functional domains: condensed and/or loosened rDNA, rDNA transcription zone, and transcript processing and ribosome assembly zones.

  13. Stellar Astrophysical Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Thompson, Michael J.; Christensen-Dalsgaard, Jørgen

    2008-02-01

    Preface; 1. A selective overview Jørgen Christensen-Dalsgaard and Michael J. Thompson; Part I. Stellar Convection and Oscillations: 2. On the diversity of stellar pulsations Wojciech A. Dziembowski; 3. Acoustic radiation and mode excitation by turbulent convection Günter Houdek; 4. Understanding roAp stars Margarida S. Cunha; 5. Waves in the magnetised solar atmosphere Colin S. Rosenthal; Part II. Stellar Rotation and Magnetic Fields: 6. Stellar rotation: a historical survey Leon Mestel; 7. The oscillations of rapidly rotating stars Michel Rieutord; 8. Solar tachocline dynamics: eddy viscosity, anti-friction, or something in between? Michael E. McIntyre; 9. Dynamics of the solar tachocline Pascale Garaud; 10. Dynamo processes: the interaction of turbulence and magnetic fields Michael Proctor; 11. Dynamos in planets Chris Jones; Part III. Physics and Structure of Stellar Interiors: 12. Solar constraints on the equation of state Werner Däppen; 13. 3He transport and the solar neutrino problem Chris Jordinson; 14. Mixing in stellar radiation zones Jean-Paul Zahn; 15. Element settling and rotation-induced mixing in slowly rotating stars Sylvie Vauclair; Part IV. Helio- and Asteroseismology: 16. Solar structure and the neutrino problem Hiromoto Shibahashi; 17. Helioseismic data analysis Jesper Schou; 18. Seismology of solar rotation Takashi Sekii; 19. Telechronohelioseismology Alexander Kosovichev; Part V. Large-Scale Numerical Experiments: 20. Bridges between helioseismology and models of convection zone dynamics Juri Toomre; 21. Numerical simulations of the solar convection zone Julian R. Elliott; 22. Modelling solar and stellar magnetoconvection Nigel Weiss; 23. Nonlinear magnetoconvection in the presence of a strong oblique field Keith Julien, Edgar Knobloch and Steven M. Tobias; 24. Simulations of astrophysical fluids Marcus Brüggen; Part VI. Dynamics: 25. A magic electromagnetic field Donald Lynden-Bell; 26. Continuum equations for stellar dynamics Edward A

  14. Stellar Astrophysical Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Thompson, Michael J.; Christensen-Dalsgaard, Jørgen

    2003-05-01

    Preface; 1. A selective overview Jørgen Christensen-Dalsgaard and Michael J. Thompson; Part I. Stellar Convection and Oscillations: 2. On the diversity of stellar pulsations Wojciech A. Dziembowski; 3. Acoustic radiation and mode excitation by turbulent convection Günter Houdek; 4. Understanding roAp stars Margarida S. Cunha; 5. Waves in the magnetised solar atmosphere Colin S. Rosenthal; Part II. Stellar Rotation and Magnetic Fields: 6. Stellar rotation: a historical survey Leon Mestel; 7. The oscillations of rapidly rotating stars Michel Rieutord; 8. Solar tachocline dynamics: eddy viscosity, anti-friction, or something in between? Michael E. McIntyre; 9. Dynamics of the solar tachocline Pascale Garaud; 10. Dynamo processes: the interaction of turbulence and magnetic fields Michael Proctor; 11. Dynamos in planets Chris Jones; Part III. Physics and Structure of Stellar Interiors: 12. Solar constraints on the equation of state Werner Däppen; 13. 3He transport and the solar neutrino problem Chris Jordinson; 14. Mixing in stellar radiation zones Jean-Paul Zahn; 15. Element settling and rotation-induced mixing in slowly rotating stars Sylvie Vauclair; Part IV. Helio- and Asteroseismology: 16. Solar structure and the neutrino problem Hiromoto Shibahashi; 17. Helioseismic data analysis Jesper Schou; 18. Seismology of solar rotation Takashi Sekii; 19. Telechronohelioseismology Alexander Kosovichev; Part V. Large-Scale Numerical Experiments: 20. Bridges between helioseismology and models of convection zone dynamics Juri Toomre; 21. Numerical simulations of the solar convection zone Julian R. Elliott; 22. Modelling solar and stellar magnetoconvection Nigel Weiss; 23. Nonlinear magnetoconvection in the presence of a strong oblique field Keith Julien, Edgar Knobloch and Steven M. Tobias; 24. Simulations of astrophysical fluids Marcus Brüggen; Part VI. Dynamics: 25. A magic electromagnetic field Donald Lynden-Bell; 26. Continuum equations for stellar dynamics Edward A

  15. The Stellar Populations in the Outer Banks of Massive Disk Galaxies

    NASA Astrophysics Data System (ADS)

    De Jong, Roelof; GHOSTS Team

    2006-12-01

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

  16. Opacity of stellar matter

    SciTech Connect

    Rogers, F J

    1998-09-17

    New efforts to calculate opacity have produced significant improvements in the quality of stellar models. The most dramatic effect has been large opacity enhancements for stars subject to large amplitude pulsations. Significant improvement in helioseismic modeling has also been obtained. A description and comparisons of the new opacity efforts are give

  17. Introduction to Stellar Astrophysics

    NASA Astrophysics Data System (ADS)

    Böhm-Vitense, Erika

    1992-01-01

    This book is the final one in a series of three texts which together provide a modern, complete and authoritative account of our present knowledge of the stars. It discusses the internal structure and the evolution of stars, and is completely self-contained. There is an emphasis on the basic physics governing stellar structure and the basic ideas on which our understanding of stellar structure is based. The book also provides a comprehensive discussion of stellar evolution. Careful comparison is made between theory and observation, and the author has thus provided a lucid and balanced introductory text for the student. As for volumes 1 and 2, volume 3 is self-contained and can be used as an independent textbook. The author has not only taught but has also published many original papers in this subject. Her clear and readable style should make this text a first choice for undergraduate and beginning graduate students taking courses in astronomy and particularly in stellar astrophysics.

  18. A Stellar Demonstrator

    ERIC Educational Resources Information Center

    Ros, Rosa M.

    2009-01-01

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

  19. Stellar Ontogeny: From Dust...

    ERIC Educational Resources Information Center

    MOSAIC, 1978

    1978-01-01

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

  20. Progress Toward Attractive Stellarators

    SciTech Connect

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

    2011-01-05

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

  1. Nonlinear signal-based control with an error feedback action for nonlinear substructuring control

    NASA Astrophysics Data System (ADS)

    Enokida, Ryuta; Kajiwara, Koichi

    2017-01-01

    A nonlinear signal-based control (NSBC) method utilises the 'nonlinear signal' that is obtained from the outputs of a controlled system and its linear model under the same input signal. Although this method has been examined in numerical simulations of nonlinear systems, its application in physical experiments has not been studied. In this paper, we study an application of NSBC in physical experiments and incorporate an error feedback action into the method to minimise the error and enhance the feasibility in practice. Focusing on NSBC in substructure testing methods, we propose nonlinear substructuring control (NLSC), that is a more general form of linear substructuring control (LSC) developed for dynamical substructured systems. In this study, we experimentally and numerically verified the proposed NLSC via substructuring tests on a rubber bearing used in base-isolated structures. In the examinations, NLSC succeeded in gaining accurate results despite significant nonlinear hysteresis and unknown parameters in the substructures. The nonlinear signal feedback action in NLSC was found to be notably effective in minimising the error caused by nonlinearity or unknown properties in the controlled system. In addition, the error feedback action in NLSC was found to be essential for maintaining stability. A stability analysis based on the Nyquist criterion, which is used particularly for linear systems, was also found to be efficient for predicting the instability conditions of substructuring tests with NLSC and useful for the error feedback controller design.

  2. Trends of stellar entropy along stellar evolution

    NASA Astrophysics Data System (ADS)

    de Avellar, Guilherme Bronzato, Marcio; Alvares de Souza, Rodrigo; Horvath, Jorge Ernesto

    2016-02-01

    This paper is devoted to discussing the difference in the thermodynamic entropy budget per baryon in each type of stellar object found in the Universe. We track and discuss the actual decrease of the stored baryonic thermodynamic entropy from the most primitive molecular cloud up to the final fate of matter in black holes, passing through evolved states of matter as found in white dwarfs and neutron stars. We then discuss the case of actual stars with different masses throughout their evolution, clarifying the role of the virial equilibrium condition for the decrease in entropy and related issues. Finally, we discuss the role of gravity in driving the composition and the structural changes of stars with different Main Sequence masses during their evolution up to the final product. Particularly, we discuss the entropy of a black hole in this context arguing that the dramatic increase in its entropy, differently from the other cases, is due to the gravitational field itself.

  3. Small-scale Substructure in Dark Matter Haloes: Where Does Galaxy Formation Come to an End?

    NASA Astrophysics Data System (ADS)

    Taylor, J. E.; Silk, J.; Babul, A.

    2004-07-01

    Models of structure formation based on cold dark matter predict that most of the small dark matter haloes that first formed at high redshift would have merged into larger systems by the present epoch. Substructure in present-day haloes preserves the remains of these ancient systems, providing the only direct information we may ever have about the low-mass end of the power spectrum. We describe some recent attempts to model halo substructure down to very small masses, using a semi-analytic model of halo formation. We make a preliminary comparison between the model predictions, observations of substructure in lensed systems, and the properties of local satellite galaxies.

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

    NASA Technical Reports Server (NTRS)

    Sawyer, J. W.

    1981-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

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

    PubMed Central

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

    2011-01-01

    Background Among individuals with ischemic heart disease, young women with an acute myocardial infarction (AMI) represent an extreme phenotype associated with an excess mortality risk. While women younger than 55 years of age account for less than 5% of hospitalized AMI events, almost 16,000 deaths are reported annually in this group, making heart disease a leading killer of young women. Despite a higher risk of mortality compared with similarly aged men, young women have been the subject of few studies. Methods Variation in Recovery: Role of Gender on Outcomes of Young AMI Patients (VIRGO) is a large, observational study of the presentation, treatment and outcomes of young women and men with AMI. VIRGO will enroll 2,000 women, 18–55 years of age, with AMI and a comparison cohort of 1,000 men with AMI from more than 100 participating hospitals. The aims of the study are: to determine sex differences in the distribution and prognostic importance of biological, demographic, clinical, and psychosocial risk factors; determine whether there are sex differences in the quality of care received by young AMI patients; and determine how these factors contribute to sex differences in outcomes (including mortality, hospitalization and health status). Blood serum and DNA for consenting participants will be stored for future studies. Conclusions VIRGO will seek to identify novel and prognostic factors that contribute to outcomes in this young AMI population. Results from the study will be used to develop clinically useful risk-stratification models for young AMI patients, explain sex differences in outcomes and identify targets for intervention. PMID:21081748

  7. To the Edge of M87 and Beyond: Spectroscopy of Intracluster Globular Clusters and Ultracompact Dwarfs in the Virgo Cluster

    NASA Astrophysics Data System (ADS)

    Ko, Youkyung; Hwang, Ho Seong; Lee, Myung Gyoon; Park, Hong Soo; Lim, Sungsoon; Sohn, Jubee; Jang, In Sung; Hwang, Narae; Park, Byeong-Gon

    2017-02-01

    We present the results of a wide-field spectroscopic survey of globular clusters (GCs) in the Virgo cluster. We obtain spectra for 201 GCs and 55 ultracompact dwarfs (UCDs) using Hectospec on the Multiple-Mirror Telescope and derive their radial velocities. We identify 46 genuine intracluster GCs (IGCs), not associated with any Virgo galaxies, using the 3D GMM test on the spatial and radial velocity distribution. They are located at a projected distance 200 kpc ≲ R ≲ 500 kpc from the center of M87. The radial velocity distribution of these IGCs shows two peaks, one at vr = 1023 km s‑1, associated with the Virgo main body, and another at vr = 36 km s‑1, associated with the infalling structure. The velocity dispersion of the IGCs in the Virgo main body is σGC ∼ 314 km s‑1, which is smoothly connected to the velocity dispersion profile of M87 GCs but is much lower than that of dwarf galaxies in the same survey field, σdwarf ∼ 608 km s‑1. The UCDs are more centrally concentrated on massive galaxies—M87, M86, and M84. The radial velocity dispersion of the UCD system is much smaller than that of dwarf galaxies. Our results confirm the large-scale distribution of Virgo IGCs indicated by previous photometric surveys. The color distribution of the confirmed IGCs shows a bimodality similar to that of M87 GCs. This indicates that most IGCs are stripped off dwarf galaxies and some off massive galaxies in the Virgo.

  8. VizieR Online Data Catalog: AGES sources in Virgo cluster (Taylor+, 2012)

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Two areas of the Virgo cluster have been selected for study with AGES, VC1 and VC2. This paper examines the VC1 area while Paper II (2013MNRAS.428..459T) will consider VC2 and compare the results of the two areas. Observations were taken in 2008 January-June, 2009 February-June, 2010 January-June and 2011 January, using the Arecibo L-band Feed Array (ALFA) instrument on the Arecibo telescope in spectral line mode. (4 data files).

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  10. Inspection of Asian Lacquer Substructures by Terahertz Time-Domain Imaging (THz-TDI)

    NASA Astrophysics Data System (ADS)

    Dandolo, Corinna Ludovica Koch; Fukunaga, Kaori; Kohzuma, Yoshei; Kiriyama, Kyoko; Matsuda, Kazutaka; Jepsen, Peter Uhd

    2016-11-01

    Lacquering is considered one of the most representative Asian artistic techniques. While the decorative part of lacquerwares is the lacquer itself, their substructures serve as the backbone of the object itself. Very little is known about these hidden substructures. Since lacquerwares are mostly composed of organic materials, such as urushi, wood, carbon black, and fabrics which are very X-ray transparent, standard X-ray radiography has some problems in achieving clear X-ray radiographic images. Therefore, we wanted to contribute to the understanding of the lacquer manufacturing technique by inspecting the substructures of Asian lacquerwares by means of THz time-domain imaging (THz-TDI). Three different kinds of Asian lacquerwares were examined by THz-TDI, and the outcomes have been compared with those obtained by standard X-radiography. THz-TDI provides unique information on lacquerwares substructures, aiding in the comprehension of the manufacturing technology yielding to these precious artefacts.

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

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

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

  12. Inspection of Asian Lacquer Substructures by Terahertz Time-Domain Imaging (THz-TDI)

    NASA Astrophysics Data System (ADS)

    Dandolo, Corinna Ludovica Koch; Fukunaga, Kaori; Kohzuma, Yoshei; Kiriyama, Kyoko; Matsuda, Kazutaka; Jepsen, Peter Uhd

    2017-04-01

    Lacquering is considered one of the most representative Asian artistic techniques. While the decorative part of lacquerwares is the lacquer itself, their substructures serve as the backbone of the object itself. Very little is known about these hidden substructures. Since lacquerwares are mostly composed of organic materials, such as urushi, wood, carbon black, and fabrics which are very X-ray transparent, standard X-ray radiography has some problems in achieving clear X-ray radiographic images. Therefore, we wanted to contribute to the understanding of the lacquer manufacturing technique by inspecting the substructures of Asian lacquerwares by means of THz time-domain imaging (THz-TDI). Three different kinds of Asian lacquerwares were examined by THz-TDI, and the outcomes have been compared with those obtained by standard X-radiography. THz-TDI provides unique information on lacquerwares substructures, aiding in the comprehension of the manufacturing technology yielding to these precious artefacts.

  13. DOLPHOT: Stellar photometry

    NASA Astrophysics Data System (ADS)

    Dolphin, Andrew

    2016-08-01

    DOLPHOT is a stellar photometry package that was adapted from HSTphot for general use. It supports two modes; the first is a generic PSF-fitting package, which uses analytic PSF models and can be used for any camera. The second mode uses ACS PSFs and calibrations, and is effectively an ACS adaptation of HSTphot. A number of utility programs are also included with the DOLPHOT distribution, including basic image reduction routines.

  14. Neoclassical transport in stellarators

    SciTech Connect

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

    1985-09-01

    The stellarator neoclassical transport due to particles trapped in local helical wells is calculated in the low-collisionality regime using a systematic expansion. The behavior of electron transport is found to be the same over a wide range of energies, but the behavior of ion transport for low energy ions is found to be different than that for high energy ions. Furthermore, the electron fluxes do not vary with the change in the radial ambipolar electric field nearly as much as do the ion fluxes. Thus, the particle diffusion is controlled by the electrons. A nonradial ambipolar electric field is induced by ion drift. This electric field enhances the transport by about 15 to 20%. A convenient graphical method that allows one to determine the magnitude of the radial ambipolar field for machines with different parameters is presented. Numerical examples show that electron energy confinement time is comparable to the ion energy confinement time for all the different size stellarators studied. Although the neoclassical losses are large, it is shown that ignition can be achieved in a reasonably sized stellarator reactor. Finally, from the standpoint of reactor economics, the confinement scaling law shows that in order to increase n tau, it is better to increase the aspect ratio than the overall dimensions of the reactor.

  15. Gravitational focusing and substructure effects on the rate modulation in direct dark matter searches

    SciTech Connect

    Nobile, Eugenio Del; Gelmini, Graciela B.; Witte, Samuel J.

    2015-08-21

    We study how gravitational focusing (GF) of dark matter by the Sun affects the annual and biannual modulation of the expected signal in non-directional direct dark matter searches, in the presence of dark matter substructure in the local dark halo. We consider the Sagittarius stream and a possible dark disk, and show that GF suppresses some, but not all, of the distinguishing features that would characterize substructure of the dark halo were GF neglected.

  16. Gravitational focusing and substructure effects on the rate modulation in direct dark matter searches

    SciTech Connect

    Nobile, Eugenio Del; Gelmini, Graciela B.; Witte, Samuel J. E-mail: gelmini@physics.ucla.edu

    2015-08-01

    We study how gravitational focusing (GF) of dark matter by the Sun affects the annual and biannual modulation of the expected signal in non-directional direct dark matter searches, in the presence of dark matter substructure in the local dark halo. We consider the Sagittarius stream and a possible dark disk, and show that GF suppresses some, but not all, of the distinguishing features that would characterize substructure of the dark halo were GF neglected.

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

    PubMed Central

    Charoenchitt, Masnisa; Asvanund, Chanavut

    2014-01-01

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

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

    SciTech Connect

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

    2005-06-01

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

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

    SciTech Connect

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

    2001-07-26

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

  20. The Herschel Virgo Cluster Survey . VI. The far-infrared view of M 87

    NASA Astrophysics Data System (ADS)

    Baes, M.; Clemens, M.; Xilouris, E. M.; Fritz, J.; Cotton, W. D.; Davies, J. I.; Bendo, G. J.; Bianchi, S.; Cortese, L.; De Looze, I.; Pohlen, M.; Verstappen, J.; Böhringer, H.; Bomans, D. J.; Boselli, A.; Corbelli, E.; Dariush, A.; di Serego Alighieri, S.; Fadda, D.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Grossi, M.; Hughes, T. M.; Hunt, L. K.; Jones, A. P.; Madden, S.; Pierini, D.; Sabatini, S.; Smith, M. W. L.; Vlahakis, C.; Zibetti, S.

    2010-07-01

    The origin of the far-infrared emission from the nearby radio galaxy M 87 remains a matter of debate. Some studies find evidence of a far-infrared excess due to thermal dust emission, whereas others propose that the far-infrared emission can be explained by synchrotron emission without the need for an additional dust emission component. We present Herschel PACS and SPIRE observations of M 87, taken as part of the science demonstration phase observations of the Herschel Virgo Cluster Survey. We compare these data with a synchrotron model based on mid-infrared, far-infrared, submm and radio data from the literature to investigate the origin of the far-infrared emission. Both the integrated SED and the Herschel surface brightness maps are adequately explained by synchrotron emission. At odds with previous claims, we find no evidence of a diffuse dust component in M 87, which is not unexpected in the harsh X-ray environment of this radio galaxy sitting at the core of the Virgo cluster. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  1. The Herschel Virgo Cluster Survey . VII. Dust in cluster dwarf elliptical galaxies

    NASA Astrophysics Data System (ADS)

    De Looze, I.; Baes, M.; Zibetti, S.; Fritz, J.; Cortese, L.; Davies, J. I.; Verstappen, J.; Bendo, G. J.; Bianchi, S.; Clemens, M.; Bomans, D. J.; Boselli, A.; Corbelli, E.; Dariush, A.; di Serego Alighieri, S.; Fadda, D.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Grossi, M.; Hughes, T. M.; Hunt, L. K.; Jones, A. P.; Madden, S.; Pierini, D.; Pohlen, M.; Sabatini, S.; Smith, M. W. L.; Vlahakis, C.; Xilouris, E. M.

    2010-07-01

    We use the science demonstration phase data of the Herschel Virgo Cluster Survey to search for dust emission of early-type dwarf galaxies in the central regions of the Virgo cluster as an alternative way of identifying the interstellar medium. We present the first possible far-infrared detection of cluster early-type dwarf galaxies: VCC 781 and VCC 951 are detected at the 10σ level in the SPIRE 250 μm image. Both detected galaxies have dust masses of the order of 105 M_⊙ and average dust temperatures ≈20 K. The detection rate (less than 1%) is quite high compared to the 1.7% detection rate for Hi emission, considering that dwarfs in the central regions are more Hi deficient. We conclude that the removal of interstellar dust from dwarf galaxies resulting from ram pressure stripping, harassment, or tidal effects must be as efficient as the removal of interstellar gas. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  2. Planetary nebulae as tracers of galaxy stellar populations

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

    We address the general problem of the luminosity-specific planetary nebula (PN) number, better known as the `α' ratio, given by α=NPN/Lgal, and its relationship with the age and metallicity of the parent stellar population. Our analysis relies on population synthesis models that account for simple stellar populations (SSPs), and more elaborate galaxy models covering the full star formation range of the different Hubble morphological types. This theoretical framework is compared with the updated census of the PN population in Local Group (LG) galaxies and external ellipticals in the Leo group, and the Virgo and Fornax clusters. The main conclusions of our study can be summarized as follows. (i) According to the post-asymptotic giant branch (AGB) stellar core mass, PN lifetime in a SSP is constrained by three relevant regimes, driven by the nuclear (Mcore>~ 0.57Msolar), dynamical (0.57Msolar>~Mcore>~ 0.55Msolar) and transition (0.55Msolar>~Mcore>~ 0.52Msolar) time-scales. The lower limit for Mcore also sets the minimum mass for stars to reach the AGB thermal-pulsing phase and experience the PN event. (ii) Mass loss is the crucial mechanism to constrain the value of α, through the definition of the initial-to-final mass relation (IFMR). The Reimers mass-loss parametrization, calibrated on Pop II stars of Galactic globular clusters, poorly reproduces the observed value of α in late-type galaxies, while a better fit is obtained using the empirical IFMR derived from white dwarf observations in the Galaxy open clusters. (iii) The inferred PN lifetime for LG spirals and irregulars exceeds 10000yr, which suggests that Mcore<~ 0.65Msolar cores dominate, throughout. (iv) The relative PN deficiency in elliptical galaxies, and the observed trend of α with galaxy optical colours, support the presence of a prevailing fraction of low-mass cores (Mcore<~ 0.55Msolar) in the PN distribution and a reduced visibility time-scale for the nebulae as a consequence of the increased AGB

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  4. Stellar Vampires Unmasked

    NASA Astrophysics Data System (ADS)

    2006-10-01

    Astronomers have found possible proofs of stellar vampirism in the globular cluster 47 Tucanae. Using ESO's Very Large Telescope, they found that some hot, bright, and apparently young stars in the cluster present less carbon and oxygen than the majority of their sisters. This indicates that these few stars likely formed by taking their material from another star. "This is the first detection of a chemical signature clearly pointing to a specific scenario to form so-called 'Blue straggler stars' in a globular cluster", said Francesco Ferraro, from the Astronomy Department of Bologna University (Italy) and lead-author of the paper presenting the results. Blue stragglers are unexpectedly young-looking stars found in stellar aggregates, such as globular clusters, which are known to be made up of old stars. These enigmatic objects are thought to be created in either direct stellar collisions or through the evolution and coalescence of a binary star system in which one star 'sucks' material off the other, rejuvenating itself. As such, they provide interesting constraints on both binary stellar evolution and star cluster dynamics. To date, the unambiguous signatures of either stellar traffic accidents or stellar vampirism have not been observed, and the formation mechanisms of Blue stragglers are still a mystery. The astronomers used ESO's Very Large Telescope to measure the abundance of chemical elements at the surface of 43 Blue straggler stars in the globular cluster 47 Tucanae [1]. They discovered that six of these Blue straggler stars contain less carbon and oxygen than the majority of these peculiar objects. Such an anomaly indicates that the material at the surface of the blue stragglers comes from the deep interiors of a parent star [2]. Such deep material can reach the surface of the blue straggler only during the mass transfer process occurring between two stars in a binary system. Numerical simulations indeed show that the coalescence of stars should not

  5. Architecture of the Andromeda galaxy: a quantitative analysis of clustering in the inner stellar halo

    NASA Astrophysics Data System (ADS)

    Kafle, P. R.; Sharma, S.; Robotham, A. S. G.; Lewis, G. F.; Driver, S. P.

    2017-02-01

    We present a quantitative measurement of the amount of clustering present in the inner ˜30 kpc of the stellar halo of the Andromeda galaxy (M31). For this we analyse the angular positions and radial velocities of the carefully selected planetary nebulae in the M31 stellar halo. We study the cumulative distribution of pairwise distances in angular position and line-of-sight velocity space, and find that the M31 stellar halo contains substantially more stars in the form of close pairs as compared to that of a featureless smooth halo. In comparison to a smoothed/scrambled distribution, we estimate that the clustering excess in the M31 inner halo is roughly 40 per cent at maximum and on average ˜20 per cent. Importantly, comparing against the 11 stellar halo models of Bullock & Johnston, which were simulated within the context of the ΛCDM (Λ cold dark matter) cosmological paradigm, we find that the amount of substructures in the M31 stellar halo closely resembles that of a typical ΛCDM halo.

  6. The Dragonfly Nearby Galaxies Survey: A Census of the Stellar Halos of Nearby Luminous Galaxies

    NASA Astrophysics Data System (ADS)

    Merritt, Allison T.

    2017-01-01

    The Dragonfly Telephoto Array, comprised of 48 individual Canon telephoto lenses operating together as a single telescope, is an innovative approach to low surface brightness imaging and the study of galactic stellar halos in particular. Sub-nanometer coatings on each optical element reduce scattered light from nearby bright stars and compact galaxy centers - typically a key obstacle for integrated light observations - by an order of magnitude, and Dragonfly's large field of view (2x2.6 degrees for a single frame) provides a large-scale view of stellar halos free from substructure biases. Using extremely deep (>30 mag/arcsec^2) optical imaging in g and r bands from the Dragonfly Nearby Galaxies Survey (DNGS), we have characterized the stellar halos of a sample of ~20 nearby luminous galaxies. I will present measurements of the stellar halo mass fractions of these galaxies as a function of stellar mass, morphology, and environment, and discuss the scatter in halo fractions in the context of the galaxies' individual accretion histories.

  7. Multi-scale, Hierarchically Nested Young Stellar Structures in LEGUS Galaxies

    NASA Astrophysics Data System (ADS)

    Thilker, David A.; LEGUS Team

    2017-01-01

    The study of star formation in galaxies has predominantly been limited to either young stellar clusters and HII regions, or much larger kpc-scale morphological features such as spiral arms. The HST Legacy ExtraGalactic UV Survey (LEGUS) provides a rare opportunity to link these scales in a diverse sample of nearby galaxies and obtain a more comprehensive understanding of their co-evolution for comparison against model predictions. We have utilized LEGUS stellar photometry to identify young, resolved stellar populations belonging to several age bins and then defined nested hierarchical structures as traced by these subsamples of stars. Analagous hierarchical structures were also defined using LEGUS catalogs of unresolved young stellar clusters. We will present our emerging results concerning the physical properties (e.g. area, star counts, stellar mass, star formation rate, ISM characteristics), occupancy statistics (e.g. clusters per substructure versus age and scale, parent/child demographics) and relation to overall galaxy morphology/mass for these building blocks of hierarchical star-forming structure.

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

    SciTech Connect

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

    2005-04-06

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

  9. Phase-space structures and stellar populations in the star-forming region NGC 2264

    NASA Astrophysics Data System (ADS)

    González, Marta; Alfaro, Emilio J.

    2017-02-01

    In this work, we analyse the structure of a subspace of the phase space of the star-forming region NGC 2264 using the spectrum of kinematic groupings (SKG). We show that the SKG can be used to process a collection of star data to find substructure at different scales. We have found structure associated with the NGC 2264 region and also with the background area. In the NGC 2264 region, a hierarchical analysis shows substructure compatible with that found in previous specific studies of the area but with an objective, compact methodology that allows us to homogeneously compare the structure of different clusters and star-forming regions. Moreover, this structure is compatible with the different ages of the main NGC 2264 star-forming populations. The structure found in the field can be roughly associated with giant stars far in the background, dynamically decoupled from NGC 2264, which could be related either with the Outer Arm or Monoceros Ring. The results in this paper confirm the relationship between structure in the radial velocity phase-space subspace and different kinds of populations, defined by other variables not necessarily analysed with the SKG, such as age or distance, showing the importance of detecting phase-space substructure in order to trace stellar populations in the broadest sense of the word.

  10. Expectations for Joint Gravitational Wave-Electromagnetic Detections with Advanced LIGO/Virgo and the Fermi Gamma Ray Burst Monitor

    NASA Astrophysics Data System (ADS)

    Burns, E.; Connaughton, V.; Briggs, M. S.; Goldstein, A.; Hamburg, R.; Littenberg, T.

    2016-10-01

    We estimate the fraction of GBM detected short GRBs that should be detectable by Advanced LIGO/Virgo. We also look at the fraction of GW localizations that should be visible to GBM, as well as area reduction by using joint localizations.

  11. Hubble Space Telescope First Observations of the Brightest Stars in the Virgo Galaxy M100 = NGC 4321

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  12. Using modern stellar observables to constrain stellar parameters and the physics of the stellar interior

    NASA Astrophysics Data System (ADS)

    van Saders, Jennifer L.

    2014-05-01

    The current state and future evolution of a star is, in principle, specified by a only a few physical quantities: the mass, age, hydrogen, helium, and metal abundance. These same fundamental quantities are crucial for reconstructing the history of stellar systems ranging in scale from planetary systems to galaxies. However, the fundamental parameters are rarely directly observable, and we are forced to use proxies that are not always sensitive or unique functions of the stellar parameters we wish to determine. Imprecise or inaccurate determinations of the fundamental parameters often limit our ability to draw inferences about a given system. As new technologies, instruments, and observing techniques become available, the list of viable stellar observables increases, and we can explore new links between the observables and fundamental quantities in an effort to better characterize stellar systems. In the era of missions such as Kepler, time-domain observables such as the stellar rotation period and stellar oscillations are now available for an unprecedented number of stars, and future missions promise to further expand the sample. Furthermore, despite the successes of stellar evolution models, the processes and detailed structure of the deep stellar interior remains uncertain. Even in the case of well-measured, well understood stellar observables, the link to the underlying parameters contains uncertainties due to our imperfect understanding of stellar interiors. Model uncertainties arise from sources such as the treatment of turbulent convection, transport of angular momentum and mixing, and assumptions about the physical conditions of stellar matter. By carefully examining the sensitivity of stellar observables to physical processes operating within the star and model assumptions, we can design observational tests for the theory of stellar interiors. I propose a series of tools based on new or revisited stellar observables that can be used both to constrain

  13. Common substructure in otoacoustic emission spectra of land vertebrates

    NASA Astrophysics Data System (ADS)

    Manley, Geoffrey A.; Köppl, Christine; Bergevin, Christopher

    2015-12-01

    In humans, a similar spectral periodicity is found in all otoacoustic emission types and in threshold fine structure. This may reflect travelling wave phase and reflectance from "structural roughness" in the organ of Corti, or entrainment and suppressive interactions between emissions. To further understand these phenomena, we have examined spontaneous otoacoustic emission (SOAE) spectra in 9 lizard species and the barn owl and find a comparable periodicity. Importantly, the frequency spacing between SOAE peaks was independent of the physical spacing and of the frequency space constants in hearing organs. In 9 lizard species, median spectral gaps lay between 219 and 461 Hz, with no correlation to papillar length (0.3 to 2.1 mm). Similarly in much longer organs: In humans (35 mm), SOAE spectral gaps vary up to 220 Hz at 4 kHz; in the barn owl (11 mm), the median SOAE peak spacing was 395Hz. In the barn owl, a very large space constant between 5 and 10 kHz (5 mm/octave) contrasts with stable SOAE spacing between 1 and 11 kHz. Similar SOAE spectral gaps across all species suggests they represent a basic frequency grating revealing local phase-dependent interactions between active hair cells, a feature not determined by macro-structural anatomy. Emission spectral spacing is independent of cochlear length, of the frequency space constant, of the existence of travelling waves or of a tectorial membrane. Our data suggest that there are greater similarities between frequency selectivity reflected at the level of the hair cells' spontaneous mechanical output (OAEs) than there are at the level of the auditory nerve, where macro-structural anatomy links hair-cell activity differentially to the neural output. Apparently, all hair-cell arrays show a similar frequency substructure not directly replicated in neural tuning.

  14. Jet substructure using semi-inclusive jet functions in SCET

    NASA Astrophysics Data System (ADS)

    Kang, Zhong-Bo; Ringer, Felix; Vitev, Ivan

    2016-11-01

    We propose a new method to evaluate jet substructure observables in inclusive jet measurements, based upon semi-inclusive jet functions in the framework of Soft Collinear Effective Theory (SCET). As a first example, we consider the jet fragmentation function, where a hadron h is identified inside a fully reconstructed jet. We introduce a new semi-inclusive fragmenting jet function {{G}}_i^h(z={ω}_J/ω, {z}_h={ω}_h/{ω}_J,{ω}_J,R,μ ) , which depends on the jet radius R and the large light-cone momenta of the parton ` i' initiating the jet ( ω), the jet ( ω J ), and the hadron h ( ω h ). The jet fragmentation function can then be expressed as a semi-inclusive observable, in the spirit of actual experimental measurements, rather than as an exclusive one. We demonstrate the consistency of the effective field theory treatment and standard perturbative QCD calculations of this observable at next-to-leading order (NLO). The renormalization group (RG) equation for the semi-inclusive fragmenting jet function {{G}}_i^h(z,{z}_h,{ω}_J,R,μ ) are also derived and shown to follow exactly the usual timelike DGLAP evolution equations for fragmentation functions. The newly obtained RG equations can be used to perform the resummation of single logarithms of the jet radius parameter R up to next-to-leading logarithmic (NLL R ) accuracy. In combination with the fixed NLO calculation, we obtain NLO+NLL R results for the hadron distribution inside the jet. We present numerical results for pp → (jet h) X in the new framework, and find excellent agreement with existing LHC experimental data.

  15. The solar-stellar connection

    NASA Astrophysics Data System (ADS)

    Giampapa, Mark S.

    2016-07-01

    A review of some principal results achieved in the area of stellar astrophysics with its origins in solar physics - the Solar-Stellar Connection - is presented from the perspective of an observational astronomer. The historical origins of the Solar-Stellar Connection are discussed followed by a review of key results from observations of stellar cycles analogous to the solar cycle in terms of parameters relevant to dynamo theory. A review of facets of angular momentum evolution and irradiance variations, each of which is determined by emergent, dynamo-generated magnetic fields, is given. Recent considerations of the impacts of stellar magnetic activity on the ambient radiative and energetic particle environment of the habitable zone of exoplanet systems are summarized. Some anticipated directions of the Solar-Stellar Connection in the new era of astronomy as defined by the advent of transformative facilities are presented.

  16. Substructure method in high-speed monorail dynamic problems

    NASA Astrophysics Data System (ADS)

    Ivanchenko, I. I.

    2008-12-01

    combined schemes modeling a strained elastic compound moving structure and a monorail elevated track. The problems of development of methods for dynamic analysis of monorails are very topical, especially because of increasing speeds of the rolling stock motion. These structures are studied in [16-18]. In the present paper, the above problem is solved by using the method for the moving load analysis and a step procedure of integration with respect to time, which were proposed in [9, 19], respectively. Further, these components are used to enlarge the possibilities of the substructure method in problems of dynamics. In the approach proposed for moving load analysis of structures, for a substructure (having the shape of a boundary element or a superelement) we choose an object moving at a constant speed (a monorail rolling stock); in this case, we use rod boundary elements of large length, which are gathered in a system modeling these objects. In particular, sets of such elements form a model of a monorail rolling stock, namely, carriage hulls, wheeled carts, elements of the wheel spring suspension, models of continuous beams of monorail ways and piers with foundations admitting emergency subsidence and unilateral links. These specialized rigid finite elements with linear and nonlinear links, included into the set of earlier proposed finite elements [14, 19], permit studying unsteady vibrations in the "monorail train-elevated track" (MTET) system taking into account various irregularities on the beam-rail, the pier emergency subsidence, and their elastic support by the basement. In this case, a high degree of the structure spatial digitization is obtained by using rods with distributed parameters in the analysis. The displacements are approximated by linear functions and trigonometric Fourier series, which, as was already noted, permits increasing the number of degrees of freedom of the system under study simultaneously preserving the order of the resolving system of

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

    SciTech Connect

    Gilbert, Karoline M.; Guhathakurta, Puragra; Bullock, James; Tollerud, Erik J.; Geha, Marla C.; Kalirai, Jason S.; Kirby, Evan N.; Tanaka, Mikito; Chiba, Masashi

    2012-11-20

    We present the surface brightness profile of M31's stellar halo out to a projected radius of 175 kpc. The surface brightness estimates are based on confirmed samples of M31 red giant branch stars derived from Keck/DEIMOS spectroscopic observations. A set of empirical spectroscopic and photometric M31 membership diagnostics is used to identify and reject foreground and background contaminants. This enables us to trace the stellar halo of M31 to larger projected distances and fainter surface brightnesses than previous photometric studies. The surface brightness profile of M31's halo follows a power law with index -2.2 {+-} 0.2 and extends to a projected distance of at least {approx}175 kpc ({approx}2/3 of M31's virial radius), with no evidence of a downward break at large radii. The best-fit elliptical isophotes have b/a = 0.94 with the major axis of the halo aligned along the minor axis of M31's disk, consistent with a prolate halo, although the data are also consistent with M31's halo having spherical symmetry. The fact that tidal debris features are kinematically cold is used to identify substructure in the spectroscopic fields out to projected radii of 90 kpc and investigate the effect of this substructure on the surface brightness profile. The scatter in the surface brightness profile is reduced when kinematically identified tidal debris features in M31 are statistically subtracted; the remaining profile indicates that a comparatively diffuse stellar component to M31's stellar halo exists to large distances. Beyond 90 kpc, kinematically cold tidal debris features cannot be identified due to small number statistics; nevertheless, the significant field-to-field variation in surface brightness beyond 90 kpc suggests that the outermost region of M31's halo is also comprised to a significant degree of stars stripped from accreted objects.

  18. The Herschel Virgo Cluster Survey. XX. Dust and gas in the foreground Galactic cirrus

    NASA Astrophysics Data System (ADS)

    Bianchi, S.; Giovanardi, C.; Smith, M. W. L.; Fritz, J.; Davies, J. I.; Haynes, M. P.; Giovanelli, R.; Baes, M.; Bocchio, M.; Boissier, S.; Boquien, M.; Boselli, A.; Casasola, V.; Clark, C. J. R.; De Looze, I.; di Serego Alighieri, S.; Grossi, M.; Jones, A. P.; Hughes, T. M.; Hunt, L. K.; Madden, S.; Magrini, L.; Pappalardo, C.; Ysard, N.; Zibetti, S.

    2017-01-01

    We study the correlation between far-infrared/submm dust emission and atomic gas column density in order to derive the properties of the high Galactic latitude, low density, Milky Way cirrus in the foreground of the Virgo cluster of galaxies. Dust emission maps from 60 to 850 μm are obtained from observations with the Spectral and Photometric Imaging Receiver (SPIRE) and carried out within the Herschel Virgo Cluster Survey (HeViCS); these are complemented by IRAS and Planck maps. Data from the Arecibo legacy Fast ALFA Survey is used to derive atomic gas column densities for two broad velocity components: low and intermediate velocity clouds. Dust emissivities are derived for each gas component and each far-infrared/submm band. For the low velocity clouds, we measure an average emissivity ɛLVCν = (0.79 ± 0.08) × 10-20 MJy sr-1 cm2 at 250 μm. After fitting a modified blackbody to the available bands, we estimated a dust absorption cross section of τLVCν/NH i = (0.49 ± 0.13) × 10-25 cm2 H-1 at 250 μm (with dust temperature T = 20.4 ± 1.5 K and spectral index β = 1.53 ± 0.17). The results are in excellent agreement with those obtained by Planck over a much larger coverage of the high Galactic latitude cirrus (50% of the sky versus 0.2% in our work). For dust associated with intermediate velocity gas, we confirm earlier Planck results and find a higher temperature and lower emissivity and cross section. After subtracting the modeled components, we find regions at scales smaller than 20' in which the residuals deviate significantly from the average scatter, which is dominated by cosmic infrared background. These large residuals are most likely due to local variations in the cirrus dust properties or to high-latitude molecular clouds with average NH2 ≲ 1020 cm-2. We find no conclusive evidence for intracluster dust emission in Virgo. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and

  19. Advances in stellarator gyrokinetics

    NASA Astrophysics Data System (ADS)

    Helander, P.; Bird, T.; Jenko, F.; Kleiber, R.; Plunk, G. G.; Proll, J. H. E.; Riemann, J.; Xanthopoulos, P.

    2015-05-01

    Recent progress in the gyrokinetic theory of stellarator microinstabilities and turbulence simulations is summarized. The simulations have been carried out using two different gyrokinetic codes, the global particle-in-cell code EUTERPE and the continuum code GENE, which operates in the geometry of a flux tube or a flux surface but is local in the radial direction. Ion-temperature-gradient (ITG) and trapped-electron modes are studied and compared with their counterparts in axisymmetric tokamak geometry. Several interesting differences emerge. Because of the more complicated structure of the magnetic field, the fluctuations are much less evenly distributed over each flux surface in stellarators than in tokamaks. Instead of covering the entire outboard side of the torus, ITG turbulence is localized to narrow bands along the magnetic field in regions of unfavourable curvature, and the resulting transport depends on the normalized gyroradius ρ* even in radially local simulations. Trapped-electron modes can be significantly more stable than in typical tokamaks, because of the spatial separation of regions with trapped particles from those with bad magnetic curvature. Preliminary non-linear simulations in flux-tube geometry suggest differences in the turbulence levels in Wendelstein 7-X and a typical tokamak.

  20. Advanced Virgo Interferometer: a Second Generation Detector for Gravitational Waves Observation

    NASA Astrophysics Data System (ADS)

    Accadia, T.; Acernese, F.; Agathos, M.; Allocca, A.; Astone, P.; Ballardin, G.; Barone, F.; Barsuglia, M.; Basti, A.; Bauer, Th. S.; Bejger, M.; Beker, M. G.; Belczynski, C.; Bersanetti, D.; Bertolini, A.; Bitossi, M.; Bizouard, M. A.; Blom, M.; Boer, M.; Bondu, F.; Bonelli, L.; Bonnand, R.; Boschi, V.; Bosi, L.; Bradaschia, C.; Branchesi, M.; Briant, T.; Brillet, A.; Brisson, V.; Bulik, T.; Bulten, H. J.; Buskulic, D.; Buy, C.; Cagnoli, G.; Calloni, E.; Canuel, B.; Carbognani, F.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cesarini, E.; Chassande-Mottin, E.; Chincarini, A.; Chiummo, A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Colombini, M.; Conte, A.; Coulon, J.-P.; Cuoco, E.; D'Antonio, S.; Dattilo, V.; Davier, M.; Day, R.; Debreczeni, G.; Degallaix, J.; Deléglise, S.; Del Pozzo, W.; Dereli, H.; De Rosa, R.; di Fiore, L.; di Lieto, A.; di Virgilio, A.; Drago, M.; Endrőczi, G.; Fafone, V.; Farinon, S.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Flaminio, R.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Gammaitoni, L.; Garufi, F.; Gemme, G.; Genin, E.; Gennai, A.; Giazotto, A.; Gouaty, R.; Granata, M.; Groot, P.; Guidi, G. M.; Heidmann, A.; Heitmann, H.; Hello, P.; Hemming, G.; Jaranowski, P.; Jonker, R. J. G.; Kasprzack, M.; Kéfélian, F.; Kowalska, I.; Królak, A.; Kutynia, A.; Lazzaro, C.; Leonardi, M.; Leroy, N.; Letendre, N.; Li, T. G. F.; Lorenzini, M.; Loriette, V.; Losurdo, G.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mangano, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marque, J.; Martelli, F.; Martinelli, L.; Masserot, A.; Meacher, D.; Meidam, J.; Michel, C.; Milano, L.; Minenkov, Y.; Mohan, M.; Morgado, N.; Mours, B.; Nagy, M. F.; Nardecchia, I.; Naticchioni, L.; Nelemans, G.; Neri, I.; Neri, M.; Nocera, F.; Palomba, C.; Paoletti, F.; Paoletti, R.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Pichot, M.; Piergiovanni, F.; Pinard, L.; Poggiani, R.; Prijatelj, 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.; Saracco, E.; Sassolas, B.; Sentenac, D.; Sequino, V.; Shah, S.; Siellez, K.; Sperandio, L.; Straniero, N.; Sturani, R.; Swinkels, B.; Tacca, M.; Ter Braack, A. P. M.; Toncelli, A.; Tonelli, M.; Torre, O.; Travasso, F.; Vajente, G.; van den Brand, J. F. J.; van den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Heijningen, J.; Vasúth, M.; Vedovato, G.; Veitch, J.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinet, J.-Y.; Vitale, S.; Vocca, H.; Wei, L.-W.; Yvert, M.; Zadrożny, A.; Zendri, J.-P.

    2015-03-01

    In the last ten years great improvements have been done in the development and operation of ground based detectors for Gravitational Waves direct observation and study. The second generation detectors are presently under construction in Italy, United States and Japan with a common intent to create a worldwide network of instruments able to start a new era in astronomy and astrophysics, a century after the development of the General Relativity theory predicting the existence of Gravitational Waves. The design sensitivity of the advanced detectors will be approximately ten times better with respect to the previous generation corresponding to an increment of a factor one thousand in the observational volume of the Universe where black holes, neutron stars and other enigmatic sources of these weak signals are spread around. In this paper we present a general overview of the advanced detectors with particular emphasis on Advanced VIRGO, the largest European interferometer located at the European Gravitational Observatory (EGO) site in the Pisa countryside (Italy).

  1. Near-infrared surface photometry and morphology in virgo cluster spiral galaxy nuclear regions

    NASA Astrophysics Data System (ADS)

    Rauscher, Bernard J.

    1995-04-01

    This paper presents very high spatial resolution (seeing 0.75 arcsec FWHM) K band surface photometry of 15 Virgo cluster spiral galaxy nuclear regions (radii less then 1 kpc). It presents B and I CCD images of 13 of these galaxies. The goals of the study were: (1) to begin to establish a K band baseline of normal spiral galaxy nuclear regions against which peculiar galaxies may be compared, (2) to provide better contsraints on N-body models, and (3) to complement near-infrared studies of large scale structure in spiral galaxies with very high resolution imaging of the important nuclear regions. The principle findings are (1) between 1/4 and 1/3 of these nuclear regions show K band evidence of traxiality, (2) approximately 1/2 of these galaxies have axisymmetric nuclear regions, and (3) NGC 4321 has a bar that is not detectable in the optical images.

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

    NASA Technical Reports Server (NTRS)

    1985-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Adhikari, R. X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O. D.; Ajith, P.; Allen, B.; Allocca, A.; Amador Ceron, E.; Amariutei, D.; Anderson, R. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C.; Areeda, J.; Ast, S.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Austin, L.; Aylott, B. E.; Babak, S.; Baker, P. T.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barker, D.; Barnum, S. H.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Behnke, B.; Bejger, M.; Beker, M. G.; Bell, A. S.; Bell, C.; Belopolski, I.; Bergmann, G.; Berliner, J. M.; Bersanetti, D.; Bertolini, A.; Bessis, D.; Betzwieser, J.; Beyersdorf, P. T.; Bhadbhade, T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Blom, M.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogan, C.; Bond, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bowers, J.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brannen, C. A.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brückner, F.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calderón Bustillo, J.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K. C.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Castiglia, A.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chu, Q.; Chua, S. S. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Colombini, M.; Constancio, M.; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M. W.; Coulon, J.-P.; Countryman, S.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dahl, K.; Canton, T. Dal; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; Debreczeni, G.; Degallaix, J.; Del Pozzo, W.; Deleeuw, E.; Deléglise, S.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; DeRosa, R.; DeSalvo, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; Díaz, M.; Dietz, A.; Dmitry, K.; Donovan, F.; Dooley, K. L.; Doravari, S.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edwards, M.; Effler, A.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Endrőczi, G.; Essick, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W.; Favata, M.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R.; Flaminio, R.; Foley, E.; Foley, S.; Forsi, E.; Fotopoulos, N.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P.; Fyffe, M.; Gair, J.; Gammaitoni, L.; Garcia, J.; Garufi, F.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; Gergely, L.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gordon, N.; Gorodetsky, M. L.; Gossan, S.; Goßler, S.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Griffo, C.; Groot, P.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hall, B.; Hall, E.; Hammer, D.; Hammond, G.; Hanke, M.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Heefner, J.; Heidmann, A.; Heintze, M.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Horrom, T.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hu, Y.; Hua, Z.; Huang, V.; Huerta, E. A.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh, M.; Huynh-Dinh, T.; Iafrate, J.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Iyer, B. R.; Izumi, K.; Jacobson, M.; James, E.; Jang, H.; Jang, Y. J.; Jaranowski, P.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kasprzack, M.; Kasturi, R.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kaufman, K.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kéfélian, F.; Keitel, D.; Kelley, D. B.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, B. K.; Kim, C.; Kim, K.; Kim, N.; Kim, W.; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J.; Koehlenbeck, S.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kremin, A.; Kringel, V.; Królak, A.; Kucharczyk, C.; Kudla, S.; Kuehn, G.; Kumar, A.; Kumar, P.; Kumar, R.; Kurdyumov, R.; Kwee, P.; Landry, M.; Lantz, B.; Larson, S.; Lasky, P. D.; Lawrie, C.; Lazzarini, A.; Le Roux, A.; Leaci, P.; Lebigot, E. O.; Lee, C.-H.; Lee, H. K.; Lee, H. M.; Lee, J.; Lee, J.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levine, B.; Lewis, J. B.; Lhuillier, V.; Li, T. G. F.; Lin, A. C.; Littenberg, T. B.; Litvine, V.; Liu, F.; Liu, H.; Liu, Y.; Liu, Z.; Lloyd, D.; Lockerbie, N. A.; Lockett, V.; Lodhia, D.; Loew, K.; Logue, J.; Lombardi, A. L.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J.; Luan, J.; Lubinski, M. J.; Lück, H.; Lundgren, A. P.; Macarthur, J.; Macdonald, E.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magana-Sandoval, F.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Manca, G. M.; Mandel, I.; Mandic, V.; Mangano, 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.; Martinelli, L.; Martynov, D.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; May, G.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; Meacher, D.; Meadors, G. D.; Mehmet, M.; Meidam, J.; Meier, T.; Melatos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Mikhailov, E. E.; Milano, L.; Miller, J.; Minenkov, Y.; Mingarelli, C. M. F.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mohan, M.; Mohapatra, S. R. P.; Mokler, F.; Moraru, D.; Moreno, G.; Morgado, N.; Mori, T.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nagy, M. F.; Nanda Kumar, D.; Nardecchia, I.; Nash, T.; Naticchioni, L.; Nayak, R.; Necula, V.; Nelemans, G.; Neri, I.; Neri, M.; Newton, G.; Nguyen, T.; Nishida, E.; Nishizawa, A.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E.; Nuttall, L. K.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oppermann, P.; O'Reilly, B.; Ortega Larcher, W.; O'Shaughnessy, R.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Ou, J.; Overmier, H.; Owen, B. J.; Padilla, C.; Pai, A.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Paoletti, R.; Papa, M. A.; Paris, H.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Pedraza, M.; Peiris, P.; Penn, S.; Perreca, A.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pierro, V.; Pinard, L.; Pindor, B.; Pinto, I. M.; Pitkin, M.; Poeld, J.; Poggiani, R.; Poole, V.; Poux, C.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Quintero, E.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Raja, S.; Rajalakshmi, G.; Rakhmanov, M.; Ramet, C.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Robertson, N. A.; Robinet, F.; Rocchi, A.; Roddy, S.; Rodriguez, C.; Rodruck, M.; Roever, C.; Rolland, L.; Rollins, J. G.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Salemi, F.; Sammut, L.; Sandberg, V.; Sanders, J.; Sannibale, V.; Santiago-Prieto, I.; Saracco, E.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schreiber, E.; Schuette, D.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sergeev, A.; Shaddock, D.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siellez, K.; 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.; Soden, K.; Son, E. J.; Sorazu, B.; Souradeep, T.; Sperandio, L.; Staley, A.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stevens, D.; Stochino, A.; Stone, R.; Strain, K. A.; Straniero, N.; Strigin, S.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szeifert, G.; Tacca, M.; Talukder, D.; Tang, L.; Tanner, D. B.; Tarabrin, S. P.; Taylor, R.; ter Braack, A. P. M.; Thirugnanasambandam, M. P.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C. V.; Torrie, C. I.; Travasso, F.; Traylor, G.; Tse, M.; Ugolini, D.; Unnikrishnan, C. S.; Vahlbruch, H.; Vajente, G.; Vallisneri, M.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van der Sluys, M. V.; van Heijningen, J.; van Veggel, A. A.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Verma, S.; Vetrano, F.; Viceré, A.; Vincent-Finley, R.; Vinet, J.-Y.; Vitale, S.; Vlcek, B.; Vo, T.; Vocca, H.; Vorvick, C.; Vousden, W. D.; Vrinceanu, D.; Vyachanin, S. P.; Wade, A.; Wade, L.; Wade, M.; Waldman, S. J.; Walker, M.; Wallace, L.; Wan, Y.; Wang, J.; Wang, M.; Wang, X.; Wanner, A.; Ward, R. L.; Was, M.; Weaver, B.; Wei, L.-W.; 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.; Wibowo, S.; Wiesner, K.; Wilkinson, C.; Williams, L.; Williams, R.; Williams, T.; Willis, J. L.; Willke, B.; Wimmer, M.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yancey, C. C.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yum, H.; Yvert, M.; ZadroŻny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, F.; Zhang, L.; Zhao, C.; Zhu, H.; Zhu, X. J.; Zotov, N.; Zucker, M. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

    2014-04-01

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

  4. Investigating the Cores of Early-Type Galaxies Using the ACS Virgo and Fornax Cluster Surveys

    NASA Astrophysics Data System (ADS)

    Glass, Lisa; Ferrarese, L.; Côté, P.; Jordán, A.; Peng, E.; Blakeslee, J.; Chen, C.; Infante, L.; Mei, S.; Tonry, J.; West, M. J.

    2011-01-01

    Understanding the processes that shape and influence the centers of galaxies is crucial to understanding galaxies as a whole. In particular, data suggests nuclear star clusters are three times more common than previously thought and there is evidence to suggest that they may be the low-mass analogues to the supermassive black holes found in more luminous galaxies. My research focuses on the cores of early-type galaxies and how they relate, influence, and respond to processes occurring in the rest of the galaxy. I will present new results from the ACS Virgo and Fornax Cluster Surveys that shed light on these questions. The authors gratefully acknowledge support from NSERC though the Discovery and Postgraduate Scholarship programs, as well as from the University of Victoria through their fellowship program.

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

    PubMed

    Aasi, J; Abadie, J; Abbott, B P; Abbott, R; Abbott, T; Abernathy, M R; Accadia, T; Acernese, F; Adams, C; Adams, T; Adhikari, R X; Affeldt, C; Agathos, M; Aggarwal, N; Aguiar, O D; Ajith, P; Allen, B; Allocca, A; Amador Ceron, E; Amariutei, D; Anderson, R A; Anderson, S B; Anderson, W G; Arai, K; Araya, M C; Arceneaux, C; Areeda, J; Ast, S; Aston, S M; Astone, P; Aufmuth, P; Aulbert, C; Austin, L; Aylott, B E; Babak, S; Baker, P T; Ballardin, G; Ballmer, S W; Barayoga, J C; Barker, D; Barnum, S H; Barone, F; Barr, B; Barsotti, L; Barsuglia, M; Barton, M A; Bartos, I; Bassiri, R; Basti, A; Batch, J; Bauchrowitz, J; Bauer, Th S; Bebronne, M; Behnke, B; Bejger, M; Beker, M G; Bell, A S; Bell, C; Belopolski, I; Bergmann, G; Berliner, J M; Bersanetti, D; Bertolini, A; Bessis, D; Betzwieser, J; Beyersdorf, P T; Bhadbhade, T; Bilenko, I A; Billingsley, G; Birch, J; Bitossi, M; Bizouard, M A; Black, E; Blackburn, J K; Blackburn, L; Blair, D; Blom, M; Bock, O; Bodiya, T P; Boer, M; Bogan, C; Bond, C; Bondu, F; Bonelli, L; Bonnand, R; Bork, R; Born, M; Boschi, V; Bose, S; Bosi, L; Bowers, J; Bradaschia, C; Brady, P R; Braginsky, V B; Branchesi, M; Brannen, C A; Brau, J E; Breyer, J; Briant, T; Bridges, D O; Brillet, A; Brinkmann, M; Brisson, V; Britzger, M; Brooks, A F; Brown, D A; Brown, D D; Brückner, F; Bulik, T; Bulten, H J; Buonanno, A; Buskulic, D; Buy, C; Byer, R L; Cadonati, L; Cagnoli, G; Calderón Bustillo, J; Calloni, E; Camp, J B; Campsie, P; Cannon, K C; Canuel, B; Cao, J; Capano, C D; Carbognani, F; Carbone, L; Caride, S; Castiglia, A; Caudill, S; Cavaglià, M; Cavalier, F; Cavalieri, R; Cella, G; Cepeda, C; Cesarini, E; Chakraborty, R; Chalermsongsak, T; Chao, S; Charlton, P; Chassande-Mottin, E; Chen, X; Chen, Y; Chincarini, A; Chiummo, A; Cho, H S; Chow, J; Christensen, N; Chu, Q; Chua, S S Y; Chung, S; Ciani, G; Clara, F; Clark, D E; Clark, J A; Cleva, F; Coccia, E; Cohadon, P-F; Colla, A; Colombini, M; Constancio, M; Conte, A; Conte, R; Cook, D; Corbitt, T R; Cordier, M; Cornish, N; Corsi, A; Costa, C A; Coughlin, M W; Coulon, J-P; Countryman, S; Couvares, P; Coward, D M; Cowart, M; Coyne, D C; Craig, K; Creighton, J D E; Creighton, T D; Crowder, S G; Cumming, A; Cunningham, L; Cuoco, E; Dahl, K; Dal Canton, T; Damjanic, M; Danilishin, S L; D'Antonio, S; Danzmann, K; Dattilo, V; Daudert, B; Daveloza, H; Davier, M; Davies, G S; Daw, E J; Day, R; Dayanga, T; De Rosa, R; Debreczeni, G; Degallaix, J; Del Pozzo, W; Deleeuw, E; Deléglise, S; Denker, T; Dent, T; Dereli, H; Dergachev, V; DeRosa, R; DeSalvo, R; Dhurandhar, S; Di Fiore, L; Di Lieto, A; Di Palma, I; Di Virgilio, A; Díaz, M; Dietz, A; Dmitry, K; Donovan, F; Dooley, K L; Doravari, S; Drago, M; Drever, R W P; Driggers, J C; Du, Z; Dumas, J-C; Dwyer, S; Eberle, T; Edwards, M; Effler, A; Ehrens, P; Eichholz, J; Eikenberry, S S; Endrőczi, G; Essick, R; Etzel, T; Evans, K; Evans, M; Evans, T; Factourovich, M; Fafone, V; Fairhurst, S; Fang, Q; Farinon, S; Farr, B; Farr, W; Favata, M; Fazi, D; Fehrmann, H; Feldbaum, D; Ferrante, I; Ferrini, F; Fidecaro, F; Finn, L S; Fiori, I; Fisher, R; Flaminio, R; Foley, E; Foley, S; Forsi, E; Fotopoulos, N; Fournier, J-D; Franco, S; Frasca, S; Frasconi, F; Frede, M; Frei, M; Frei, Z; Freise, A; Frey, R; Fricke, T T; Fritschel, P; Frolov, V V; Fujimoto, M-K; Fulda, P; Fyffe, M; Gair, J; Gammaitoni, L; Garcia, J; Garufi, F; Gehrels, N; Gemme, G; Genin, E; Gennai, A; Gergely, L; Ghosh, S; Giaime, J A; Giampanis, S; Giardina, K D; Giazotto, A; Gil-Casanova, S; Gill, C; Gleason, J; Goetz, E; Goetz, R; Gondan, L; González, G; Gordon, N; Gorodetsky, M L; Gossan, S; Goßler, S; Gouaty, R; Graef, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greenhalgh, R J S; Gretarsson, A M; Griffo, C; Groot, P; Grote, H; Grover, K; Grunewald, S; Guidi, G M; Guido, C; Gushwa, K E; Gustafson, E K; Gustafson, R; Hall, B; Hall, E; Hammer, D; Hammond, G; Hanke, M; Hanks, J; Hanna, C; Hanson, J; Harms, J; Harry, G M; Harry, I W; Harstad, E D; Hartman, M T; Haughian, K; Hayama, K; Heefner, J; Heidmann, A; Heintze, M; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Heptonstall, A W; Heurs, M; Hild, S; Hoak, D; Hodge, K A; Holt, K; Holtrop, M; Hong, T; Hooper, S; Horrom, T; Hosken, D J; Hough, J; Howell, E J; Hu, Y; Hua, Z; Huang, V; Huerta, E A; Hughey, B; Husa, S; Huttner, S H; Huynh, M; Huynh-Dinh, T; Iafrate, J; Ingram, D R; Inta, R; Isogai, T; Ivanov, A; Iyer, B R; Izumi, K; Jacobson, M; James, E; Jang, H; Jang, Y J; Jaranowski, P; Jiménez-Forteza, F; Johnson, W W; Jones, D; Jones, D I; Jones, R; Jonker, R J G; Ju, L; K, Haris; Kalmus, P; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Kasprzack, M; Kasturi, R; Katsavounidis, E; Katzman, W; Kaufer, H; Kaufman, K; Kawabe, K; Kawamura, S; Kawazoe, F; Kéfélian, F; Keitel, D; Kelley, D B; Kells, W; Keppel, D G; Khalaidovski, A; Khalili, F Y; Khazanov, E A; Kim, B K; Kim, C; Kim, K; Kim, N; Kim, W; Kim, Y-M; King, E J; King, P J; Kinzel, D L; Kissel, J S; Klimenko, S; Kline, J; Koehlenbeck, S; Kokeyama, K; Kondrashov, V; Koranda, S; Korth, W Z; Kowalska, I; Kozak, D; Kremin, A; Kringel, V; Królak, A; Kucharczyk, C; Kudla, S; Kuehn, G; Kumar, A; Kumar, P; Kumar, R; Kurdyumov, R; Kwee, P; Landry, M; Lantz, B; Larson, S; Lasky, P D; Lawrie, C; Lazzarini, A; Le Roux, A; Leaci, P; Lebigot, E O; Lee, C-H; Lee, H K; Lee, H M; Lee, J; Lee, J; Leonardi, M; Leong, J R; Leroy, N; Letendre, N; Levine, B; Lewis, J B; Lhuillier, V; Li, T G F; Lin, A C; Littenberg, T B; Litvine, V; Liu, F; Liu, H; Liu, Y; Liu, Z; Lloyd, D; Lockerbie, N A; Lockett, V; Lodhia, D; Loew, K; Logue, J; Lombardi, A L; Lorenzini, M; Loriette, V; Lormand, M; Losurdo, G; Lough, J; Luan, J; Lubinski, M J; Lück, H; Lundgren, A P; Macarthur, J; Macdonald, E; Machenschalk, B; MacInnis, M; Macleod, D M; Magana-Sandoval, F; Mageswaran, M; Mailand, K; Majorana, E; Maksimovic, I; Malvezzi, V; Man, N; Manca, G M; Mandel, I; Mandic, V; Mangano, 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; Martinelli, L; Martynov, D; Marx, J N; Mason, K; Masserot, A; Massinger, T J; Matichard, F; Matone, L; Matzner, R A; Mavalvala, N; May, G; Mazumder, N; Mazzolo, G; McCarthy, R; McClelland, D E; McGuire, S C; McIntyre, G; McIver, J; Meacher, D; Meadors, G D; Mehmet, M; Meidam, J; Meier, T; Melatos, A; Mendell, G; Mercer, R A; Meshkov, S; Messenger, C; Meyer, M S; Miao, H; Michel, C; Mikhailov, E E; Milano, L; Miller, J; Minenkov, Y; Mingarelli, C M F; Mitra, S; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Moe, B; Mohan, M; Mohapatra, S R P; Mokler, F; Moraru, D; Moreno, G; Morgado, N; Mori, T; Morriss, S R; Mossavi, K; Mours, B; Mow-Lowry, C M; Mueller, C L; Mueller, G; Mukherjee, S; Mullavey, A; Munch, J; Murphy, D; Murray, P G; Mytidis, A; Nagy, M F; Nanda Kumar, D; Nardecchia, I; Nash, T; Naticchioni, L; Nayak, R; Necula, V; Nelemans, G; Neri, I; Neri, M; Newton, G; Nguyen, T; Nishida, E; Nishizawa, A; Nitz, A; Nocera, F; Nolting, D; Normandin, M E; Nuttall, L K; Ochsner, E; O'Dell, J; Oelker, E; Ogin, G H; Oh, J J; Oh, S H; Ohme, F; Oppermann, P; O'Reilly, B; Ortega Larcher, W; O'Shaughnessy, R; Osthelder, C; Ott, C D; Ottaway, D J; Ottens, R S; Ou, J; Overmier, H; Owen, B J; Padilla, C; Pai, A; Palomba, C; Pan, Y; Pankow, C; Paoletti, F; Paoletti, R; Papa, M A; Paris, H; Pasqualetti, A; Passaquieti, R; Passuello, D; Pedraza, M; Peiris, P; Penn, S; Perreca, A; Phelps, M; Pichot, M; Pickenpack, M; Piergiovanni, F; Pierro, V; Pinard, L; Pindor, B; Pinto, I M; Pitkin, M; Poeld, J; Poggiani, R; Poole, V; Poux, C; Predoi, V; Prestegard, T; Price, L R; Prijatelj, M; Principe, M; Privitera, S; Prix, R; Prodi, G A; Prokhorov, L; Puncken, O; Punturo, M; Puppo, P; Quetschke, V; Quintero, E; Quitzow-James, R; Raab, F J; Rabeling, D S; Rácz, I; Radkins, H; Raffai, P; Raja, S; Rajalakshmi, G; Rakhmanov, M; Ramet, C; Rapagnani, P; Raymond, V; Re, V; Reed, C M; Reed, T; Regimbau, T; Reid, S; Reitze, D H; Ricci, F; Riesen, R; Riles, K; Robertson, N A; Robinet, F; Rocchi, A; Roddy, S; Rodriguez, C; Rodruck, M; Roever, C; Rolland, L; Rollins, J G; Romano, R; Romanov, G; Romie, J H; Rosińska, D; Rowan, S; Rüdiger, A; Ruggi, P; Ryan, K; Salemi, F; Sammut, L; Sandberg, V; Sanders, J; Sannibale, V; Santiago-Prieto, I; Saracco, E; Sassolas, B; Sathyaprakash, B S; Saulson, P R; Savage, R; Schilling, R; Schnabel, R; Schofield, R M S; Schreiber, E; Schuette, D; Schulz, B; Schutz, B F; Schwinberg, P; Scott, J; Scott, S M; Seifert, F; Sellers, D; Sengupta, A S; Sentenac, D; Sergeev, A; Shaddock, D; Shah, S; Shahriar, M S; Shaltev, M; Shapiro, B; Shawhan, P; Shoemaker, D H; Sidery, T L; Siellez, K; 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; Soden, K; Son, E J; Sorazu, B; Souradeep, T; Sperandio, L; Staley, A; Steinert, E; Steinlechner, J; Steinlechner, S; Steplewski, S; Stevens, D; Stochino, A; Stone, R; Strain, K A; Straniero, N; Strigin, S; Stroeer, A S; Sturani, R; Stuver, A L; Summerscales, T Z; Susmithan, S; Sutton, P J; Swinkels, B; Szeifert, G; Tacca, M; Talukder, D; Tang, L; Tanner, D B; Tarabrin, S P; Taylor, R; ter Braack, A P M; Thirugnanasambandam, M P; Thomas, M; Thomas, P; Thorne, K A; Thorne, K S; Thrane, E; Tiwari, V; Tokmakov, K V; Tomlinson, C; Toncelli, A; Tonelli, M; Torre, O; Torres, C V; Torrie, C I; Travasso, F; Traylor, G; Tse, M; Ugolini, D; Unnikrishnan, C S; Vahlbruch, H; Vajente, G; Vallisneri, M; van den Brand, J F J; Van Den Broeck, C; van der Putten, S; van der Sluys, M V; van Heijningen, J; van Veggel, A A; Vass, S; Vasúth, M; Vaulin, R; Vecchio, A; Vedovato, G; Veitch, J; Veitch, P J; Venkateswara, K; Verkindt, D; Verma, S; Vetrano, F; Viceré, A; Vincent-Finley, R; Vinet, J-Y; Vitale, S; Vlcek, B; Vo, T; Vocca, H; Vorvick, C; Vousden, W D; Vrinceanu, D; Vyachanin, S P; Wade, A; Wade, L; Wade, M; Waldman, S J; Walker, M; Wallace, L; Wan, Y; Wang, J; Wang, M; Wang, X; Wanner, A; Ward, R L; Was, M; Weaver, B; Wei, L-W; 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; Wibowo, S; Wiesner, K; Wilkinson, C; Williams, L; Williams, R; Williams, T; Willis, J L; Willke, B; Wimmer, M; Winkelmann, L; Winkler, W; Wipf, C C; Wittel, H; Woan, G; Worden, J; Yablon, J; Yakushin, I; Yamamoto, H; Yancey, C C; Yang, H; Yeaton-Massey, D; Yoshida, S; Yum, H; Yvert, M; Zadrożny, A; Zanolin, M; Zendri, J-P; Zhang, F; Zhang, L; Zhao, C; Zhu, H; Zhu, X J; Zotov, N; Zucker, M E; Zweizig, J

    2014-04-04

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

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

    NASA Technical Reports Server (NTRS)

    Aasi, J.; Abadie, J.; Abbott, B.P.; Abbott, R.; Abbott, T.; Abernathy, M.R.; Accadia, T.; Adams, C.; Adams, T.; Adhikari, R.X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O.D.; Ajith, P.; Allen, B.; Allocca, A.; Ceron, E.A.; Amariutei, D.; Anderson, S.B.; Blackburn, L.; Camp, J.B.; Gehrels, N.; Graff, P.B.; Kanner, J.B.

    2014-01-01

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

  7. Updates to Advanced LIGO and Virgo's Low-Latency Electromagnetic Follow-Up Program

    NASA Astrophysics Data System (ADS)

    Cho, Min-A.; LIGO Scientific Collaboration; Virgo Collaboration

    2017-01-01

    Data from Advanced LIGO (and soon, Virgo) is promptly analyzed to enable electromagnetic follow-up observations by dozens of observing teams. In this talk I present three key changes made to this program for the second observing run, O2. These key changes cover (1) down-selecting from multiple gravitational wave triggers to the event candidate we follow-up on, provided these triggers all describe the same astrophysical event, (2) upgrading to 3-dimensional sky localization probability maps (skymaps) for compact binary coalescence events, and (3) providing additional information about event candidates that will be communicated via GCN notices/VOEvents to our observing partners. I will conclude by describing online low-latency pipelines. We gratefully acknowledge the support of the U.S. National Science Foundation through grant PHY-1404121.

  8. VizieR Online Data Catalog: Planck submillimetre sources in Virgo Cluster (Baes+, 2014)

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    We cross-correlate the Planck Catalogue of Compact Sources (PCCS) with the fully sampled 84deg2 Herschel Virgo Cluster Survey (HeViCS) fields. We search for and identify the 857 and 545GHz PCCS sources in the HeViCS fields by studying their FIR/submm and optical counterparts. We find 84 and 48 compact Planck sources in the HeViCS fields at 857 and 545GHz, respectively. Almost all sources correspond to individual bright Virgo Cluster galaxies. The vast majority of the Planck detected galaxies are late-type spirals, with the Sc class dominating the numbers, while early-type galaxies are virtually absent from the sample, especially at 545GHz. We compare the HeViCS SPIRE flux densities for the detected galaxies with the four different PCCS flux density estimators and find an excellent correlation with the aperture photometry flux densities, even at the highest flux density levels. We find only seven PCCS sources in the HeViCS fields without a nearby galaxy as obvious counterpart, and conclude that all of these are dominated by Galactic cirrus features or are spurious detections. No Planck sources in the HeViCS fields seem to be associated to high-redshift proto-clusters of dusty galaxies or strongly lensed submm sources. Finally, our study is the first empirical confirmation of the simulation-based estimated completeness of the PCCS, and provides a strong support of the internal PCCS validation procedure. (2 data files).

  9. LOCALIZATION OF SHORT DURATION GRAVITATIONAL-WAVE TRANSIENTS WITH THE EARLY ADVANCED LIGO AND VIRGO DETECTORS

    SciTech Connect

    Essick, Reed; Vitale, Salvatore; Katsavounidis, Erik; Vedovato, Gabriele; Klimenko, Sergey

    2015-02-20

    The Laser Interferometer Gravitational wave Observatory (LIGO) and Virgo advanced ground-based gravitational-wave detectors will begin collecting science data in 2015. With first detections expected to follow, it is important to quantify how well generic gravitational-wave transients can be localized on the sky. This is crucial for correctly identifying electromagnetic counterparts as well as understanding gravitational-wave physics and source populations. We present a study of sky localization capabilities for two search and parameter estimation algorithms: coherent WaveBurst, a constrained likelihood algorithm operating in close to real-time, and LALInferenceBurst, a Markov chain Monte Carlo parameter estimation algorithm developed to recover generic transient signals with latency of a few hours. Furthermore, we focus on the first few years of the advanced detector era, when we expect to only have two (2015) and later three (2016) operational detectors, all below design sensitivity. These detector configurations can produce significantly different sky localizations, which we quantify in detail. We observe a clear improvement in localization of the average detected signal when progressing from two-detector to three-detector networks, as expected. Although localization depends on the waveform morphology, approximately 50% of detected signals would be imaged after observing 100-200 deg{sup 2} in 2015 and 60-110 deg{sup 2} in 2016, although knowledge of the waveform can reduce this to as little as 22 deg{sup 2}. This is the first comprehensive study on sky localization capabilities for generic transients of the early network of advanced LIGO and Virgo detectors, including the early LIGO-only two-detector configuration.

  10. Localization of Short Duration Gravitational-wave Transients with the Early Advanced LIGO and Virgo Detectors

    NASA Astrophysics Data System (ADS)

    Essick, Reed; Vitale, Salvatore; Katsavounidis, Erik; Vedovato, Gabriele; Klimenko, Sergey

    2015-02-01

    The Laser Interferometer Gravitational wave Observatory (LIGO) and Virgo advanced ground-based gravitational-wave detectors will begin collecting science data in 2015. With first detections expected to follow, it is important to quantify how well generic gravitational-wave transients can be localized on the sky. This is crucial for correctly identifying electromagnetic counterparts as well as understanding gravitational-wave physics and source populations. We present a study of sky localization capabilities for two search and parameter estimation algorithms: coherent WaveBurst, a constrained likelihood algorithm operating in close to real-time, and LALInferenceBurst, a Markov chain Monte Carlo parameter estimation algorithm developed to recover generic transient signals with latency of a few hours. Furthermore, we focus on the first few years of the advanced detector era, when we expect to only have two (2015) and later three (2016) operational detectors, all below design sensitivity. These detector configurations can produce significantly different sky localizations, which we quantify in detail. We observe a clear improvement in localization of the average detected signal when progressing from two-detector to three-detector networks, as expected. Although localization depends on the waveform morphology, approximately 50% of detected signals would be imaged after observing 100-200 deg2 in 2015 and 60-110 deg2 in 2016, although knowledge of the waveform can reduce this to as little as 22 deg2. This is the first comprehensive study on sky localization capabilities for generic transients of the early network of advanced LIGO and Virgo detectors, including the early LIGO-only two-detector configuration.

  11. Modeling the formation of globular cluster systems in the Virgo cluster

    SciTech Connect

    Li, Hui; Gnedin, Oleg Y. E-mail: ognedin@umich.edu

    2014-11-20

    The mass distribution and chemical composition of globular cluster (GC) systems preserve fossil record of the early stages of galaxy formation. The observed distribution of GC colors within massive early-type galaxies in the ACS Virgo Cluster Survey (ACSVCS) reveals a multi-modal shape, which likely corresponds to a multi-modal metallicity distribution. We present a simple model for the formation and disruption of GCs that aims to match the ACSVCS data. This model tests the hypothesis that GCs are formed during major mergers of gas-rich galaxies and inherit the metallicity of their hosts. To trace merger events, we use halo merger trees extracted from a large cosmological N-body simulation. We select 20 halos in the mass range of 2 × 10{sup 12} to 7 × 10{sup 13} M {sub ☉} and match them to 19 Virgo galaxies with K-band luminosity between 3 × 10{sup 10} and 3 × 10{sup 11} L {sub ☉}. To set the [Fe/H] abundances, we use an empirical galaxy mass-metallicity relation. We find that a minimal merger ratio of 1:3 best matches the observed cluster metallicity distribution. A characteristic bimodal shape appears because metal-rich GCs are produced by late mergers between massive halos, while metal-poor GCs are produced by collective merger activities of less massive hosts at early times. The model outcome is robust to alternative prescriptions for cluster formation rate throughout cosmic time, but a gradual evolution of the mass-metallicity relation with redshift appears to be necessary to match the observed cluster metallicities. We also affirm the age-metallicity relation, predicted by an earlier model, in which metal-rich clusters are systematically several billion younger than their metal-poor counterparts.

  12. THE NEXT GENERATION VIRGO CLUSTER SURVEY. XV. THE PHOTOMETRIC REDSHIFT ESTIMATION FOR BACKGROUND SOURCES

    SciTech Connect

    Raichoor, A.; Mei, S.; Huertas-Company, M.; Licitra, R.; Erben, T.; Hildebrandt, H.; Ilbert, O.; Boissier, S.; Boselli, A.; Ball, N. M.; Côté, P.; Ferrarese, L.; Gwyn, S. D. J.; Kavelaars, J. J.; Chen, Y.-T.; Cuillandre, J.-C.; Duc, P. A.; Guhathakurta, P.; and others

    2014-12-20

    The Next Generation Virgo Cluster Survey (NGVS) is an optical imaging survey covering 104 deg{sup 2} centered on the Virgo cluster. Currently, the complete survey area has been observed in the u*giz bands and one third in the r band. We present the photometric redshift estimation for the NGVS background sources. After a dedicated data reduction, we perform accurate photometry, with special attention to precise color measurements through point-spread function homogenization. We then estimate the photometric redshifts with the Le Phare and BPZ codes. We add a new prior that extends to i {sub AB} = 12.5 mag. When using the u* griz bands, our photometric redshifts for 15.5 mag ≤ i ≲ 23 mag or z {sub phot} ≲ 1 galaxies have a bias |Δz| < 0.02, less than 5% outliers, a scatter σ{sub outl.rej.}, and an individual error on z {sub phot} that increases with magnitude (from 0.02 to 0.05 and from 0.03 to 0.10, respectively). When using the u*giz bands over the same magnitude and redshift range, the lack of the r band increases the uncertainties in the 0.3 ≲ z {sub phot} ≲ 0.8 range (–0.05 < Δz < –0.02, σ{sub outl.rej} ∼ 0.06, 10%-15% outliers, and z {sub phot.err.} ∼ 0.15). We also present a joint analysis of the photometric redshift accuracy as a function of redshift and magnitude. We assess the quality of our photometric redshifts by comparison to spectroscopic samples and by verifying that the angular auto- and cross-correlation function w(θ) of the entire NGVS photometric redshift sample across redshift bins is in agreement with the expectations.

  13. SPITZER/IRAC LOW SURFACE BRIGHTNESS OBSERVATIONS OF THE VIRGO CLUSTER

    SciTech Connect

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

    2011-07-10

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  15. The Next Generation Virgo Cluster Survey. XV. The Photometric Redshift Estimation for Background Sources

    NASA Astrophysics Data System (ADS)

    Raichoor, A.; Mei, S.; Erben, T.; Hildebrandt, H.; Huertas-Company, M.; Ilbert, O.; Licitra, R.; Ball, N. M.; Boissier, S.; Boselli, A.; Chen, Y.-T.; Côté, P.; Cuillandre, J.-C.; Duc, P. A.; Durrell, P. R.; Ferrarese, L.; Guhathakurta, P.; Gwyn, S. D. J.; Kavelaars, J. J.; Lançon, A.; Liu, C.; MacArthur, L. A.; Muller, M.; Muñoz, R. P.; Peng, E. W.; Puzia, T. H.; Sawicki, M.; Toloba, E.; Van Waerbeke, L.; Woods, D.; Zhang, H.

    2014-12-01

    The Next Generation Virgo Cluster Survey (NGVS) is an optical imaging survey covering 104 deg2 centered on the Virgo cluster. Currently, the complete survey area has been observed in the u*giz bands and one third in the r band. We present the photometric redshift estimation for the NGVS background sources. After a dedicated data reduction, we perform accurate photometry, with special attention to precise color measurements through point-spread function homogenization. We then estimate the photometric redshifts with the Le Phare and BPZ codes. We add a new prior that extends to i AB = 12.5 mag. When using the u* griz bands, our photometric redshifts for 15.5 mag <= i <~ 23 mag or z phot <~ 1 galaxies have a bias |Δz| < 0.02, less than 5% outliers, a scatter σoutl.rej., and an individual error on z phot that increases with magnitude (from 0.02 to 0.05 and from 0.03 to 0.10, respectively). When using the u*giz bands over the same magnitude and redshift range, the lack of the r band increases the uncertainties in the 0.3 <~ z phot <~ 0.8 range (-0.05 < Δz < -0.02, σoutl.rej ~ 0.06, 10%-15% outliers, and z phot.err. ~ 0.15). We also present a joint analysis of the photometric redshift accuracy as a function of redshift and magnitude. We assess the quality of our photometric redshifts by comparison to spectroscopic samples and by verifying that the angular auto- and cross-correlation function w(θ) of the entire NGVS photometric redshift sample across redshift bins is in agreement with the expectations.

  16. Probing the low surface brightness dwarf galaxy population of the virgo cluster

    NASA Astrophysics Data System (ADS)

    Davies, J. I.; Davies, L. J. M.; Keenan, O. C.

    2016-02-01

    We have used data from the Next Generation Virgo Survey to investigate the dwarf galaxy population of the Virgo cluster. We mask and smooth the data, and then use the object detection algorithm SEXTRACTOR to make our initial dwarf galaxy selection. All candidates are then visually inspected to remove artefacts and duplicates. We derive parameters to best select low surface brightness galaxies using central surface brightness values of 22.5 ≤ μ g0 ≤ 26.0 μg and exponential scale lengths of 3.0 ≤ h ≤ 10.0 arcsec to identify 443 cluster dwarf galaxies - 303 of which are new detections, with a surface density that decreases with radius from the cluster centre. We also apply our selection algorithm to `background', non-cluster, fields and find zero detections. In combination, this leads us to believe that we have isolated a cluster dwarf galaxy population. The range of objects we detect is limited because smaller scale sized galaxies are confused with the background, while larger galaxies are split into numerous smaller objects by the detection algorithm. Combining our data with that from other surveys, we find a faint-end slope to the luminosity function of -1.35 ± 0.03, which is not significantly different to what has previously been found, but is a little steeper than the slope for field galaxies. There is no evidence for a faint-end slope steep enough to correspond with galaxy formation models, unless those models invoke either strong feedback processes or use warm dark matter.

  17. Formulation of an experimental substructure model using a Craig-Bampton based transmission simulator

    NASA Astrophysics Data System (ADS)

    Kammer, Daniel C.; Allen, Mathew S.; Mayes, Randy L.

    2015-12-01

    Experimental-analytical substructuring is attractive when there is motivation to replace one or more system subcomponents with an experimental model. This experimentally derived substructure can then be coupled to finite element models of the rest of the structure to predict the system response. The transmission simulator method couples a fixture to the component of interest during a vibration test in order to improve the experimental model for the component. The transmission simulator is then subtracted from the tested system to produce the experimental component. The method reduces ill-conditioning by imposing a least squares fit of constraints between substructure modal coordinates to connect substructures, instead of directly connecting physical interface degrees of freedom. This paper presents an alternative means of deriving the experimental substructure model, in which a Craig-Bampton representation of the transmission simulator is created and subtracted from the experimental measurements. The corresponding modal basis of the transmission simulator is described by the fixed-interface modes, rather than free modes that were used in the original approach. These modes do a better job of representing the shape of the transmission simulator as it responds within the experimental system, leading to more accurate results using fewer modes. The new approach is demonstrated using a simple finite element model based example with a redundant interface.

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

    SciTech Connect

    Wing, Joshua D.; Blanton, Elizabeth L.

    2013-04-20

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

  19. Formulation of an experimental substructure model using a Craig-Bampton based transmission simulator

    SciTech Connect

    Kammer, Daniel C.; Allen, Matthew S.; Mayes, Randall L.

    2015-09-26

    An experimental–analytical substructuring is attractive when there is motivation to replace one or more system subcomponents with an experimental model. This experimentally derived substructure can then be coupled to finite element models of the rest of the structure to predict the system response. The transmission simulator method couples a fixture to the component of interest during a vibration test in order to improve the experimental model for the component. The transmission simulator is then subtracted from the tested system to produce the experimental component. This method reduces ill-conditioning by imposing a least squares fit of constraints between substructure modal coordinates to connect substructures, instead of directly connecting physical interface degrees of freedom. This paper presents an alternative means of deriving the experimental substructure model, in which a Craig–Bampton representation of the transmission simulator is created and subtracted from the experimental measurements. The corresponding modal basis of the transmission simulator is described by the fixed-interface modes, rather than free modes that were used in the original approach. Moreover, these modes do a better job of representing the shape of the transmission simulator as it responds within the experimental system, leading to more accurate results using fewer modes. The new approach is demonstrated using a simple finite element model based example with a redundant interface.

  20. Formulation of an experimental substructure model using a Craig-Bampton based transmission simulator

    DOE PAGES

    Kammer, Daniel C.; Allen, Matthew S.; Mayes, Randall L.

    2015-09-26

    An experimental–analytical substructuring is attractive when there is motivation to replace one or more system subcomponents with an experimental model. This experimentally derived substructure can then be coupled to finite element models of the rest of the structure to predict the system response. The transmission simulator method couples a fixture to the component of interest during a vibration test in order to improve the experimental model for the component. The transmission simulator is then subtracted from the tested system to produce the experimental component. This method reduces ill-conditioning by imposing a least squares fit of constraints between substructure modal coordinatesmore » to connect substructures, instead of directly connecting physical interface degrees of freedom. This paper presents an alternative means of deriving the experimental substructure model, in which a Craig–Bampton representation of the transmission simulator is created and subtracted from the experimental measurements. The corresponding modal basis of the transmission simulator is described by the fixed-interface modes, rather than free modes that were used in the original approach. Moreover, these modes do a better job of representing the shape of the transmission simulator as it responds within the experimental system, leading to more accurate results using fewer modes. The new approach is demonstrated using a simple finite element model based example with a redundant interface.« less

  1. An algebraic sub-structuring method for large-scale eigenvaluecalculation

    SciTech Connect

    Yang, C.; Gao, W.; Bai, Z.; Li, X.; Lee, L.; Husbands, P.; Ng, E.

    2004-05-26

    We examine sub-structuring methods for solving large-scalegeneralized eigenvalue problems from a purely algebraic point of view. Weuse the term "algebraic sub-structuring" to refer to the process ofapplying matrix reordering and partitioning algorithms to divide a largesparse matrix into smaller submatrices from which a subset of spectralcomponents are extracted and combined to provide approximate solutions tothe original problem. We are interested in the question of which spectralcomponentsone should extract from each sub-structure in order to producean approximate solution to the original problem with a desired level ofaccuracy. Error estimate for the approximation to the small esteigen pairis developed. The estimate leads to a simple heuristic for choosingspectral components (modes) from each sub-structure. The effectiveness ofsuch a heuristic is demonstrated with numerical examples. We show thatalgebraic sub-structuring can be effectively used to solve a generalizedeigenvalue problem arising from the simulation of an acceleratorstructure. One interesting characteristic of this application is that thestiffness matrix produced by a hierarchical vector finite elements schemecontains a null space of large dimension. We present an efficient schemeto deflate this null space in the algebraic sub-structuringprocess.

  2. Three-dimensional stellarator codes

    PubMed Central

    Garabedian, P. R.

    2002-01-01

    Three-dimensional computer codes have been used to develop quasisymmetric stellarators with modular coils that are promising candidates for a magnetic fusion reactor. The mathematics of plasma confinement raises serious questions about the numerical calculations. Convergence studies have been performed to assess the best configurations. Comparisons with recent data from large stellarator experiments serve to validate the theory. PMID:12140367

  3. Radioactive elements in stellar atmospheres

    SciTech Connect

    Gopka, Vira; Yushchenko, Alexander; Goriely, Stephane; Shavrina, Angelina; Kang, Young Woon

    2006-07-12

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

  4. A catalog of stellar spectrophotometry

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  5. Stellar populations in star clusters

    NASA Astrophysics Data System (ADS)

    Li, Cheng-Yuan; de Grijs, Richard; Deng, Li-Cai

    2016-12-01

    Stellar populations contain the most important information about star cluster formation and evolution. Until several decades ago, star clusters were believed to be ideal laboratories for studies of simple stellar populations (SSPs). However, discoveries of multiple stellar populations in Galactic globular clusters have expanded our view on stellar populations in star clusters. They have simultaneously generated a number of controversies, particularly as to whether young star clusters may have the same origin as old globular clusters. In addition, extensive studies have revealed that the SSP scenario does not seem to hold for some intermediate-age and young star clusters either, thus making the origin of multiple stellar populations in star clusters even more complicated. Stellar population anomalies in numerous star clusters are well-documented, implying that the notion of star clusters as true SSPs faces serious challenges. In this review, we focus on stellar populations in massive clusters with different ages. We present the history and progress of research in this active field, as well as some of the most recent improvements, including observational results and scenarios that have been proposed to explain the observations. Although our current ability to determine the origin of multiple stellar populations in star clusters is unsatisfactory, we propose a number of promising projects that may contribute to a significantly improved understanding of this subject.

  6. Chromospheric activity and stellar evolution

    NASA Technical Reports Server (NTRS)

    Kippenhahn, R.

    1973-01-01

    A study of stellar chromospheres based on the internal structure of particular stars is presented. Used are complex flow diagrams of the linkage paths between mass loss, angular momentum loss, magnetic field from the turbulent dynamo and its relations to differential rotations and the convection zone, and stellar evolution.

  7. Nucleosynthesis in stellar explosions

    SciTech Connect

    Woosley, S.E.; Axelrod, T.S.; Weaver, T.A.

    1983-01-01

    The final evolution and explosion of stars from 10 M/sub solar/ to 10/sup 6/ M/sub solar/ are reviewed with emphasis on factors affecting the expected nucleosynthesis. We order our paper in a sequence of decreasing mass. If, as many suspect, the stellar birth function was peaked towards larger masses at earlier times (see e.g., Silk 1977; but also see Palla, Salpeter, and Stahler 1983), this sequence of masses might also be regarded as a temporal sequence. At each stage of Galactic chemical evolution stars form from the ashes of preceding generations which typically had greater mass. A wide variety of Type I supernova models, most based upon accreting white dwarf stars, are also explored using the expected light curves, spectra, and nucleosynthesis as diagnostics. No clearly favored Type I model emerges that is capable of simultaneously satisfying all three constraints.

  8. Resolving stellar surface spots

    NASA Astrophysics Data System (ADS)

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

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

  9. Early stellar evolution

    NASA Technical Reports Server (NTRS)

    Stahler, Steven W.

    1994-01-01

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

  10. Alaska Athabascan stellar astronomy

    NASA Astrophysics Data System (ADS)

    Cannon, Christopher M.

    2014-01-01

    Stellar astronomy is a fundamental component of Alaska Athabascan cultures that facilitates time-reckoning, navigation, weather forecasting, and cosmology. Evidence from the linguistic record suggests that a group of stars corresponding to the Big Dipper is the only widely attested constellation across the Northern Athabascan languages. However, instruction from expert Athabascan consultants shows that the correlation of these names with the Big Dipper is only partial. In Alaska Gwich'in, Ahtna, and Upper Tanana languages the Big Dipper is identified as one part of a much larger circumpolar humanoid constellation that spans more than 133 degrees across the sky. The Big Dipper is identified as a tail, while the other remaining asterisms within the humanoid constellation are named using other body part terms. The concept of a whole-sky humanoid constellation provides a single unifying system for mapping the night sky, and the reliance on body-part metaphors renders the system highly mnemonic. By recognizing one part of the constellation the stargazer is immediately able to identify the remaining parts based on an existing mental map of the human body. The circumpolar position of a whole-sky constellation yields a highly functional system that facilitates both navigation and time-reckoning in the subarctic. Northern Athabascan astronomy is not only much richer than previously described; it also provides evidence for a completely novel and previously undocumented way of conceptualizing the sky---one that is unique to the subarctic and uniquely adapted to northern cultures. The concept of a large humanoid constellation may be widespread across the entire subarctic and have great antiquity. In addition, the use of cognate body part terms describing asterisms within humanoid constellations is similarly found in Navajo, suggesting a common ancestor from which Northern and Southern Athabascan stellar naming strategies derived.

  11. THEORY AND SIMULATIONS OF REFRACTIVE SUBSTRUCTURE IN RESOLVED SCATTER-BROADENED IMAGES

    SciTech Connect

    Johnson, Michael D.; Gwinn, Carl R.

    2015-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Johnson, Michael D.; Gwinn, Carl R.

    2015-06-01

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

  13. Three Dimensional Defect Reconstruction Using State Space Search and Woodbury's Substructure Method

    NASA Astrophysics Data System (ADS)

    Liu, X.; Deng, Y.; Li, Y.; Udpa, L.; Udpa, S. S.

    2010-02-01

    This paper introduces a model-based approach to reconstruct the three-dimensional defect profiles using eddy-current heat exchanger tube inspection signals. The method uses a Woodbury's substructure finite element forward model to simulate the underlying physics, a state space defect representation, and a tree search algorithm to solve the inverse problem. The advantage of the substructure method is that it divides the whole solution domain into two substructures and only the region of interest (ROI) with dramatic material changes will be updated in each iterative step. Since the number of elements inside the ROI is very small compared with the number of elements in the entire mesh, the computational effort needed in both LU factorization and coefficient matrix assembly is reduced. Therefore, the execution time is reduced significantly making the inversion very efficient. The initial inversion results are presented to confirm the validity of the approach.

  14. Exploring triad-rich substructures by graph-theoretic characterizations in complex networks

    NASA Astrophysics Data System (ADS)

    Jia, Songwei; Gao, Lin; Gao, Yong; Nastos, James; Wen, Xiao; Zhang, Xindong; Wang, Haiyang

    2017-02-01

    One of the most important problems in complex networks is how to detect communities accurately. The main challenge lies in the fact that traditional definition about communities does not always capture the intrinsic features of communities. Motivated by the observation that communities in PPI networks tend to consist of an abundance of interacting triad motifs, we define a 2-club substructure with diameter 2 possessing triad-rich property to describe a community. Based on the triad-rich substructure, we design a DIVision Algorithm using our proposed edge Niche Centrality DIVANC to detect communities effectively in complex networks. We also extend DIVANC to detect overlapping communities by proposing a simple 2-hop overlapping strategy. To verify the effectiveness of triad-rich substructures, we compare DIVANC with existing algorithms on PPI networks, LFR synthetic networks and football networks. The experimental results show that DIVANC outperforms most other algorithms significantly and, in particular, can detect sparse communities.

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

    NASA Technical Reports Server (NTRS)

    Giles, G. L.

    1980-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.; Pharr, George M.

    1992-01-01

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

  17. Multimodality in galaxy clusters from SDSS DR8: substructure and velocity distribution

    NASA Astrophysics Data System (ADS)

    Einasto, M.; Vennik, J.; Nurmi, P.; Tempel, E.; Ahvensalmi, A.; Tago, E.; Liivamägi, L. J.; Saar, E.; Heinämäki, P.; Einasto, J.; Martínez, V. J.

    2012-04-01

    Context. The study of the signatures of multimodality in groups and clusters of galaxies, an environment for most of the galaxies in the Universe, gives us information about the dynamical state of clusters and about merging processes, which affect the formation and evolution of galaxies, groups and clusters, and larger structures - superclusters of galaxies and the whole cosmic web. Aims: We search for the presence of substructure, a non-Gaussian, asymmetrical velocity distribution of galaxies, and large peculiar velocities of the main galaxies in clusters with at least 50 member galaxies, drawn from the SDSS DR8. Methods: We employ a number of 3D, 2D, and 1D tests to analyse the distribution of galaxies in clusters: 3D normal mixture modelling, the Dressler-Shectman test, the Anderson-Darling and Shapiro-Wilk tests, as well as the Anscombe-Glynn and the D'Agostino tests. We find the peculiar velocities of the main galaxies, and use principal component analysis to characterise our results. Results: More than 80% of the clusters in our sample have substructure according to 3D normal mixture modelling, and the Dressler-Shectman (DS) test shows substructure in about 70% of the clusters. The median value of the peculiar velocities of the main galaxies in clusters is 206 km s-1 (41% of the rms velocity). The velocities of galaxies in more than 20% of the clusters show significant non-Gaussianity. While multidimensional normal mixture modelling is more sensitive than the DS test in resolving substructure in the sky distribution of cluster galaxies, the DS test determines better substructure expressed as tails in the velocity distribution of galaxies (possible line-of-sight mergers). Richer, larger, and more luminous clusters have larger amount of substructure and larger (compared to the rms velocity) peculiar velocities of the main galaxies. Principal component analysis of both the substructure indicators and the physical parametres of clusters shows that galaxy clusters

  18. Stellar Temporal Intensity Interferometry

    NASA Astrophysics Data System (ADS)

    Kian, Tan Peng

    Stellar intensity interferometry was developed by Hanbury-Brown & Twiss [1954, 1956b, 1957, 1958] to bypass the diffraction limit of telescope apertures, with successful measurements including the determination of 32 stellar angular diameters using the Narrabri Stellar Intensity Interferometer [Hanbury-Brown et al., 1974]. This was achieved by measuring the intensity correlations between starlight received by a pair of telescopes separated by varying baselines b which, by invoking the van Cittert-Zernicke theorem [van Cittert, 1934; Zernicke, 1938], are related to the angular intensity distributions of the stellar light sources through a Fourier transformation of the equal-time complex degree of coherence gamma(b) between the two telescopes. This intensity correlation, or the second order correlation function g(2) [Glauber, 1963], can be described in terms of two-photoevent coincidence measurements [Hanbury-Brown, 1974] for our use of photon-counting detectors. The application of intensity interferometry in astrophysics has been largely restricted to the spatial domain but not found widespread adoption due to limitations by its signal-to-noise ratio [Davis et al., 1999; Foellmi, 2009; Jensen et al., 2010; LeBohec et al., 2008, 2010], although there is a growing movement to revive its use [Barbieri et al., 2009; Capraro et al., 2009; Dravins & Lagadec, 2014; Dravins et al., 2015; Dravins & LeBohec, 2007]. In this thesis, stellar intensity interferometry in the temporal domain is investigated instead. We present a narrowband spectral filtering scheme [Tan et al., 2014] that allows direct measurements of the Lorentzian temporal correlations, or photon bunching, from the Sun, with the preliminary Solar g(2)(tau = 0) = 1.3 +/- 0.1, limited mostly by the photon detector response [Ghioni et al., 2008], compared to the theoretical value of g(2)(0) = 2. The measured temporal photon bunching signature of the Sun exceeded the previous records of g(2)(0) = 1.03 [Karmakar et al

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  20. Parametric studies of stitching effectiveness for preventing substructure disbond

    NASA Technical Reports Server (NTRS)

    Flanagan, Gerry; Furrow, Keith

    1995-01-01

    A methodology is desired that will allow a designer to select appropriate amounts of through-thickness reinforcement needed to meet design requirements. The goal is to use a relatively simple analysis to minimize the amount of testing that needs to be performed, and to make test results from simple configurations applicable to more general structures. Using this methodology one should be able to optimize the selection of stitching materials, the weight of the yarn, and the stitching density. The analysis approach is to treat substructure disbond as a crack propagation problem. In this approach, the stitches have little influence until a delamination begins to grow. Once the delamination reaches, or extends beyond a stitch, the stitch serves to reduce the strain-energy-release-rate (G) at the crack tip for a given applied load. The reduced G can then be compared to the unstitched materials toughness to predict the load required to further extend the crack. The current model treats the stitch as a simple spring which responds to displacements in the vertical (through-thickness) direction. In concept, this approach is similar to that proposed by other authors. Test results indicate that the model should be refined to include the shearing stiffness of the stitch. The strain-energy-release-rate calculations are performed using a code which uses interconnected higher-order plates to model built-up composite cross-sections. When plates are stacked vertically, the interfacial tractions between the plates can be computed. The plate differential equations are solved in closed-form. The code, called SUBLAM, was developed as part of this section in one dimension. Because of this limitation, rows of stitches are treated as a two-dimensional sheet. The spring stiffness of a row of stitches can be estimated from the stitch material, weight, and density. As a practical and conservative approach, we can assume that the stitch is bonded until a crack passes the stitch location

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

    SciTech Connect

    Adrián-Martínez, S.; Ardid, M.; Bou-Cabo, M.; André, M.; Anghinolfi, M.; Anton, G.; Anvar, S.; Astraatmadja, T.; Bogazzi, C.; Bouwhuis, M.C.; Baret, B.; Bouhou, B.; Biagi, S.; and others

    2013-06-01

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

  2. A First Search for Coincident Gravitational Waves and High Energy Neutrinos Using LIGO, Virgo and ANTARES Data from 2007

    NASA Technical Reports Server (NTRS)

    Adrian-Martinez, S.; Samarai, Al; Albert, A.; Andre, M.; Anghinolfi, M.; Anton, G.; Anvar, S.; Ardid, M; Astraatmadja, T.; Aubert, J.-J.; Baret, B.; Basa, S.; Bertin, V.; Biagi, S.; Bigongiari, C.; Bogazzi, C; Bou-Cabo, M.; Bouhou, B.; Bowhuis, M. C.; Bertin, V.; Brunner, J.; Busto, J.; Blackburn, L.; Camp, J. B.; Kanner, J. B.

    2013-01-01

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

  3. H I detection survey of a complete magnitude-limited sample of dwarf irregular galaxies in the Virgo Cluster area

    NASA Technical Reports Server (NTRS)

    Hoffman, G. Lyle; Glosson, John; Helou, George; Salpeter, E. E.; Sandage, A.

    1987-01-01

    New single-beam Arecibo H I observations of 298 late-type galaxies in the Virgo Cluster drawn mostly from the new catalog of Binggeli, Sandage, and Tammann (1985) are presented. Two hundred seventeen of these constitute a magnitude-limited 'complete sample' of such galaxies, types Sdm through Im and BCD. Sixty-one percent of this 'complete sample' was detected, greatly enhancing the store of redshifts and H I masses for such galaxies in the Virgo Cluster. For detected galaxies, heliocentric velocities, 50 percent profile widths, and single-beam fluxes are presented. For those that escaped detection, upper limits are computed to the flux appropriate to the redshift range (-600 to +3000 km/s).

  4. Stellar Snowflake Cluster

    NASA Technical Reports Server (NTRS)

    2005-01-01

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

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

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

    Star-forming clouds like this one are dynamic and evolving structures. Since the stars trace the straight line pattern of spokes of a wheel, scientists believe that these are newborn stars, or 'protostars.' At a mere 100,000 years old, these infant structures have yet to 'crawl' away from their location of birth. Over time, the natural drifting motions of each star will break this order, and the snowflake design will be no more.

    While most of the visible-light stars that give the Christmas Tree cluster its name and triangular shape do not shine brightly in Spitzer's infrared eyes, all of the stars forming from this dusty cloud are considered part of the cluster.

    Like a dusty cosmic finger pointing up to the newborn clusters, Spitzer also illuminates the optically dark and dense Cone nebula, the tip of which can be seen towards the bottom left corner of each image.

    This combined image shows the presence of organic molecules mixed with dust as wisps of green, which have been illuminated by nearby star formation. The larger yellowish dots neighboring the baby red stars in the Snowflake Cluster are massive stellar infants forming

  5. The Hibernating Stellar Magnet

    NASA Astrophysics Data System (ADS)

    2008-09-01

    First Optically Active Magnetar-Candidate Discovered Astronomers have discovered a most bizarre celestial object that emitted 40 visible-light flashes before disappearing again. It is most likely to be a missing link in the family of neutron stars, the first case of an object with an amazingly powerful magnetic field that showed some brief, strong visible-light activity. Hibernating Stellar Magnet ESO PR Photo 31/08 The Hibernating Stellar Magnet This weird object initially misled its discoverers as it showed up as a gamma-ray burst, suggesting the death of a star in the distant Universe. But soon afterwards, it exhibited some unique behaviour that indicates its origin is much closer to us. After the initial gamma-ray pulse, there was a three-day period of activity during which 40 visible-light flares were observed, followed by a brief near-infrared flaring episode 11 days later, which was recorded by ESO's Very Large Telescope. Then the source became dormant again. "We are dealing with an object that has been hibernating for decades before entering a brief period of activity", explains Alberto J. Castro-Tirado, lead author of a paper in this week's issue of Nature. The most likely candidate for this mystery object is a 'magnetar' located in our own Milky Way galaxy, about 15 000 light-years away towards the constellation of Vulpecula, the Fox. Magnetars are young neutron stars with an ultra-strong magnetic field a billion billion times stronger than that of the Earth. "A magnetar would wipe the information from all credit cards on Earth from a distance halfway to the Moon," says co-author Antonio de Ugarte Postigo. "Magnetars remain quiescent for decades. It is likely that there is a considerable population in the Milky Way, although only about a dozen have been identified." Some scientists have noted that magnetars should be evolving towards a pleasant retirement as their magnetic fields decay, but no suitable source had been identified up to now as evidence for

  6. The GALEX Ultraviolet Virgo Cluster Survey (GUViCS). I. The UV luminosity function of the central 12 sq. deg

    NASA Astrophysics Data System (ADS)

    Boselli, A.; Boissier, S.; Heinis, S.; Cortese, L.; Ilbert, O.; Hughes, T.; Cucciati, O.; Davies, J.; Ferrarese, L.; Giovanelli, R.; Haynes, M. P.; Baes, M.; Balkowski, C.; Brosch, N.; Chapman, S. C.; Charmandaris, V.; Clemens, M. S.; Dariush, A.; De Looze, I.; di Serego Alighieri, S.; Duc, P.-A.; Durrell, P. R.; Emsellem, E.; Erben, T.; Fritz, J.; Garcia-Appadoo, D. A.; Gavazzi, G.; Grossi, M.; Jordán, A.; Hess, K. M.; Huertas-Company, M.; Hunt, L. K.; Kent, B. R.; Lambas, D. G.; Lançon, A.; MacArthur, L. A.; Madden, S. C.; Magrini, L.; Mei, S.; Momjian, E.; Olowin, R. P.; Papastergis, E.; Smith, M. W. L.; Solanes, J. M.; Spector, O.; Spekkens, K.; Taylor, J. E.; Valotto, C.; van Driel, W.; Verstappen, J.; Vlahakis, C.; Vollmer, B.; Xilouris, E. M.

    2011-04-01

    The GALEX Ultraviolet Virgo Cluster Survey (GUViCS) is a complete blind survey of the Virgo cluster covering ~40 sq. deg in the far UV (FUV, λeff = 1539 Å, Δλ = 442 Å) and ~120 sq. deg in the near UV (NUV, λeff = 2316 Å, Δλ = 1060 Å). The goal of the survey is to study the ultraviolet (UV) properties of galaxies in a rich cluster environment, spanning a wide luminosity range from giants to dwarfs, and regardless of prior knowledge of their star formation activity. The UV data will be combined with those in other bands (optical: NGVS; far-infrared - submm: HeViCS; HI: ALFALFA) and with our multizone chemo-spectrophotometric models of galaxy evolution to make a complete and exhaustive study of the effects of the environment on the evolution of galaxies in high density regions. We present here the scientific objectives of the survey, describing the observing strategy and briefly discussing different data reduction techniques. Using UV data already in-hand for the central 12 sq. deg we determine the FUV and NUV luminosity functions of the Virgo cluster core for all cluster members and separately for early- and late-type galaxies and compare it to the one obtained in the field and other nearby clusters (Coma, A1367). This analysis shows that the FUV and NUV luminosity functions of the core of the Virgo clusters are flatter (α ~ -1.1) than those determined in Coma and A1367. We discuss the possible origin of this difference. Table 1 is only available in electronic form at http://www.aanda.org

  7. The spatial evolution of stellar structures in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

    We present an analysis of the spatial distribution of various stellar populations within the Large Magellanic Cloud (LMC). We combine mid-infrared selected young stellar objects, optically selected 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. For the analysis we use Fractured Minimum Spanning Trees, the statistical Q parameter and the two-point correlation function. Restricting our analysis to young massive (OB) stars, we confirm our results obtained for M33, namely that the luminosity function of the groups is well described by a power law with index -2, and that there is no characteristic length-scale of star-forming regions. We find that stars in the LMC are born with a large amount of substructure, consistent with a two-dimensional fractal distribution with dimension and evolve towards a uniform distribution on a time-scale of ~175 Myr. This is comparable to the crossing time of the galaxy, and we suggest that stellar structure, regardless of spatial scale, will be eliminated in a crossing time. This may explain the smooth distribution of stars in massive/dense young clusters in the Galaxy, while other, less massive, clusters still display large amounts of structure at similar ages. By comparing the stellar and star cluster distributions and evolving time-scales, we show that infant mortality of clusters (or `popping clusters') has a negligible influence on the galactic structure. Finally, we quantify the influence of the elongation, differential extinction and contamination of a population on the measured Q value.

  8. Stellar populations of stellar halos: Results from the Illustris simulation

    NASA Astrophysics Data System (ADS)

    Cook, B. A.; Conroy, C.; Pillepich, A.; Hernquist, L.

    2016-08-01

    The influence of both major and minor mergers is expected to significantly affect gradients of stellar ages and metallicities in the outskirts of galaxies. Measurements of observed gradients are beginning to reach large radii in galaxies, but a theoretical framework for connecting the findings to a picture of galactic build-up is still in its infancy. We analyze stellar populations of a statistically representative sample of quiescent galaxies over a wide mass range from the Illustris simulation. We measure metallicity and age profiles in the stellar halos of quiescent Illustris galaxies ranging in stellar mass from 1010 to 1012 M ⊙, accounting for observational projection and luminosity-weighting effects. We find wide variance in stellar population gradients between galaxies of similar mass, with typical gradients agreeing with observed galaxies. We show that, at fixed mass, the fraction of stars born in-situ within galaxies is correlated with the metallicity gradient in the halo, confirming that stellar halos contain unique information about the build-up and merger histories of galaxies.

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

    NASA Technical Reports Server (NTRS)

    Camp, J. B.; Camizzo, J.

    2012-01-01

    We present results from an aU-sky search for unmodeled gravitational-wave bursts in the data collected by the LIGO, GEO 600 and Virgo detectors between November 2006 and October 2007. The search is performed. by three different analysis algorithms over the frequency band 50 - 6000 Hz. Data are analyzed for times with at least two of the four LIGO-Virgo detectors in coincident operation, with a total live time of 266 days, No events produced by the search algorithms survive the selection cuts. We set a frequentist upper limit on the rate of gravitational-wave bursts impinging on our network of detectors. When combined with the previous LIGO search of the data collected between November 2005 and November 2006, the upper limit on the rate of detectable gra.vitational. wave bursts in the 64-2048 Hz band is 2,0 events per year at 90% confidence. We also present event rate versus strength exclusion plots for several types of plausible burst waveforms. The sensitivity of the combined search is expressed in terms of the root-sum-squared strain amplitude for a variety of simulated waveforms and lies in the range 6 X 10(exp -22) Hz(exp - 1/2) to 2 X 10(exp -20) Hz(exp -l/2). This is the first untriggered burst search to use data from the LIGO and Virgo detectors together, and the most sensitive untriggered burst search performed so far.

  10. ABOUT THE LINEARITY OF THE COLOR-MAGNITUDE RELATION OF EARLY-TYPE GALAXIES IN THE VIRGO CLUSTER

    SciTech Connect

    Smith Castelli, Analia V.; Faifer, Favio R.

    2013-07-20

    We revisit the color-magnitude relation of Virgo Cluster early-type galaxies in order to explore its alleged nonlinearity. To this aim, we reanalyze the relation already published from data obtained within the ACS Virgo Cluster Survey of the Hubble Space Telescope and perform our own photometry and analysis of the images of 100 early-type galaxies observed as part of this survey. In addition, we compare our results with those reported in the literature from data of the Sloan Digital Sky Survey. We have found that when the brightest galaxies and untypical systems are excluded from the sample, a linear relation arises in agreement with what is observed in other groups and clusters. The central regions of the brightest galaxies also follow this relation. In addition, we notice that Virgo contains at least four compact elliptical galaxies besides the well-known object VCC 1297 (NGC 4486B). Their locations in the ({mu}{sub eff})-luminosity diagram define a trend different from that followed by normal early-type dwarf galaxies, setting an upper limit in effective surface brightness and a lower limit in the effective radius for their luminosities. Based on the distribution of different galaxy sub-samples in the color-magnitude and ({mu}{sub eff})-luminosity diagrams, we draw some conclusions on their formation and the history of their evolution.

  11. Ultraviolet stellar astronomy

    NASA Technical Reports Server (NTRS)

    Henize, K. G.; Wray, J. D.; Kondo, Y.; Ocallaghan, F. (Principal Investigator)

    1975-01-01

    The author has identified the following significant results. During all three Skylab missions, prism-on observations were obtained in 188 starfields and prism-off observations in 31 starfields. In general, the fields are concentrated in the Milky Way where the frequency of hot stars is highest. These fields cover an area approximately 3660 degrees and include roughly 24 percent of a band 30 deg wide centered on the plane of the Milky Way. A census of stars in the prism-on fields shows that nearly 6,000 stars have measurable flux data at a wavelength of 2600A, that 1,600 have measurable data at 2000A, and that 400 show useful data at 1500A. Obvious absorption or emission features shortward of 2000A are visible in approximately 120 stars. This represents a bonanza of data useful for statistical studies of stellar classification and of interstellar reddening as well as for studies of various types of peculiar stars.

  12. Devastated Stellar Neighborhood

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This image from NASA's Spitzer Space Telescope shows the nasty effects of living near a group of massive stars: radiation and winds from the massive stars (white spot in center) are blasting planet-making material away from stars like our sun. The planetary material can be seen as comet-like tails behind three stars near the center of the picture. The tails are pointing away from the massive stellar furnaces that are blowing them outward.

    The picture is the best example yet of multiple sun-like stars being stripped of their planet-making dust by massive stars.

    The sun-like stars are about two to three million years old, an age when planets are thought to be growing out of surrounding disks of dust and gas. Astronomers say the dust being blown from the stars is from their outer disks. This means that any Earth-like planets forming around the sun-like stars would be safe, while outer planets like Uranus might be nothing more than dust in the wind.

    This image shows a portion of the W5 star-forming region, located 6,500 light-years away in the constellation Cassiopeia. It is a composite of infrared data from Spitzer's infrared array camera and multiband imaging photometer. Light with a wavelength of 3.5 microns is blue, while light from the dust of 24 microns is orange-red.

  13. Stellar duplicity and nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Izzard, Rob

    2014-09-01

    Half or more of all stars more massive than our Sun are orbited by one (or more) companion stars. Many companions are close enough that the evolution of both stars is greatly altered by the transfer of mass and angular momentum from one star to the other. Such mass transfer is highly likely during the late stages of evolution, such as on the giant branches, which are quite coincidentally also when stars undergo interesting nucleosynthesis. Direct mass transfer truncates the (A)GB prematurely compared to single stars and the ensuing stellar envelope is ejected perhaps to form a (chemically peculiar?) planetary nebula. In wider binaries, where one star has captured material from a long-dead companion, we can probe the nucleosynthesis that happened in ancient stars as well as fundamental astrophysical phenomena like wind accretion and circumbinary disc formation. I will focus on recent quantitative work on nucleosynthesis in mass-transfer systems, such as carbon-enhanced metal-poor and barium stars, and highlight some of the key open questions - and opportunities - that will dominate the next decade of duplicitous nucleosynthesis.

  14. SI: The Stellar Imager

    NASA Technical Reports Server (NTRS)

    Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita

    2006-01-01

    The ultra-sharp images of the Stellar Imager (SI) will revolutionize our view of many dynamic astrophysical processes: The 0.1 milliarcsec resolution of this deep-space telescope will transform point sources into extended sources, and simple snapshots into spellbinding evolving views. SI s science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI s prime goal is to enable long-term forecasting of solar activity and the space weather that it drives in support of the Living With a Star program in the Exploration Era by imaging a sample of magnetically active stars with enough resolution to map their evolving dynamo patterns and their internal flows. By exploring the Universe at ultra-high resolution, SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magnetohydrodynamically controlled structures and processes in the Universe.

  15. Stellar Presentations (Abstract)

    NASA Astrophysics Data System (ADS)

    Young, D.

    2015-12-01

    (Abstract only) The AAVSO is in the process of expanding its education, outreach and speakers bureau program. powerpoint presentations prepared for specific target audiences such as AAVSO members, educators, students, the general public, and Science Olympiad teams, coaches, event supervisors, and state directors will be available online for members to use. The presentations range from specific and general content relating to stellar evolution and variable stars to specific activities for a workshop environment. A presentation—even with a general topic—that works for high school students will not work for educators, Science Olympiad teams, or the general public. Each audience is unique and requires a different approach. The current environment necessitates presentations that are captivating for a younger generation that is embedded in a highly visual and sound-bite world of social media, twitter and U-Tube, and mobile devices. For educators, presentations and workshops for themselves and their students must support the Next Generation Science Standards (NGSS), the Common Core Content Standards, and the Science Technology, Engineering and Mathematics (STEM) initiative. Current best practices for developing relevant and engaging powerpoint presentations to deliver information to a variety of targeted audiences will be presented along with several examples.

  16. The Next Generation Virgo Cluster Survey. VII. The Intrinsic Shapes of Low-luminosity Galaxies in the Core of the Virgo Cluster, and a Comparison with the Local Group

    NASA Astrophysics Data System (ADS)

    Sánchez-Janssen, Rubén; Ferrarese, Laura; MacArthur, Lauren A.; Côté, Patrick; Blakeslee, John P.; Cuillandre, Jean-Charles; Duc, Pierre-Alain; Durrell, Patrick; Gwyn, Stephen; McConnacchie, Alan W.; Boselli, Alessandro; Courteau, Stéphane; Emsellem, Eric; Mei, Simona; Peng, Eric; Puzia, Thomas H.; Roediger, Joel; Simard, Luc; Boyer, Fred; Santos, Matthew

    2016-03-01

    We investigate the intrinsic shapes of low-luminosity galaxies in the central 300 kpc of the Virgo Cluster using deep imaging obtained as part of the Next Generation Virgo Cluster Survey (NGVS). We build a sample of nearly 300 red-sequence cluster members in the yet-unexplored -14 < Mg < -8 mag range, and we measure their apparent axis ratios, q, through Sérsic fits to their two-dimensional light distribution, which is well described by a constant ellipticity parameter. The resulting distribution of apparent axis ratios is then fit by families of triaxial models with normally distributed intrinsic ellipticities, E = 1 - C/A, and triaxialities, T = (A2 - B2)/(A2 - C2). We develop a Bayesian framework to explore the posterior distribution of the model parameters, which allows us to work directly on discrete data, and to account for individual, surface-brightness-dependent axis ratio uncertainties. For this population we infer a mean intrinsic ellipticity \\bar{E} = {0.43}-0.02+0.02 and a mean triaxiality \\bar{T} = {0.16}-0.06+0.07. This implies that faint Virgo galaxies are best described as a family of thick, nearly oblate spheroids with mean intrinsic axis ratios 1:0.94:0.57. The core of Virgo lacks highly elongated low-luminosity galaxies, with 95% of the population having q > 0.45. We additionally attempt a study of the intrinsic shapes of Local Group (LG) satellites of similar luminosities. For the LG population we infer a slightly larger mean intrinsic ellipticity \\bar{E} = {0.51}-0.06+0.07, and the paucity of objects with round apparent shapes translates into more triaxial mean shapes, 1:0.76:0.49. Numerical studies that follow the tidal evolution of satellites within LG-sized halos are in good agreement with the inferred shape distributions, but the mismatch for faint galaxies in Virgo highlights the need for more adequate simulations of this population in the cluster environment. We finally compare the intrinsic shapes of NGVS low-mass galaxies with

  17. Discovery of a stellar overdensity in Eridanus-Phoenix in the dark energy survey

    SciTech Connect

    Li, T. S.; Balbinot, E.; Mondrik, N.; Marshall, J. L.; Yanny, B.; Bechtol, K.; Drlica-Wagner, A.; Oscar, D.; Santiago, B.; Simon, J. D.; Vivas, A. K.; Walker, A. R.; Wang, M. Y.; Abbott, T. M. C.; Abdalla, F. B.; Benoit-Lévy, A.; Bernstein, G. M.; Bertin, E.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Costa, L. N. da; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Estrada, J.; Finley, D. A.; Flaugher, B.; Frieman, J.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; March, M.; Martini, P.; Ogando, R.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Tucker, D.; Zhang, Y.

    2016-01-27

    We report the discovery of an excess of main sequence turn-off stars in the direction of the constellations of Eridanus and Phoenix from the first year data of the Dark Energy Survey (DES). The Eridanus-Phoenix (EriPhe) overdensity is centered around l~285 deg and b~-60 deg and spans at least 30 deg in longitude and 10 deg in latitude. The Poisson significance of the detection is at least 9 sigma. The stellar population in the overdense region is similar in brightness and color to that of the nearby globular cluster NGC 1261, indicating that the heliocentric distance of EriPhe is about d~16 kpc. The extent of EriPhe in projection is therefore at least ~4 kpc by ~3 kpc. On the sky, this overdensity is located between NGC 1261 and a new stellar stream discovered by DES at a similar heliocentric distance, the so-called Phoenix Stream. Given their similar distance and proximity to each other, it is possible that these three structures may be kinematically associated. Alternatively, the EriPhe overdensity is morphologically similar to the Virgo overdensity and the Hercules-Aquila cloud, which also lie at a similar Galactocentric distance. These three overdensities lie along a polar plane separated by ~120 deg and may share a common origin. Spectroscopic follow-up observations of the stars in EriPhe are required to fully understand the nature of this overdensity.

  18. Discovery of a Stellar Overdensity in Eridanus-Phoenix in the Dark Energy Survey

    NASA Astrophysics Data System (ADS)

    Li, T. S.; Balbinot, E.; Mondrik, N.; Marshall, J. L.; Yanny, B.; Bechtol, K.; Drlica-Wagner, A.; Oscar, D.; Santiago, B.; Simon, J. D.; Vivas, A. K.; Walker, A. R.; Wang, M. Y.; Abbott, T. M. C.; Abdalla, F. B.; Benoit-Lévy, A.; Bernstein, G. M.; Bertin, E.; Brooks, D.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Estrada, J.; Finley, D. A.; Flaugher, B.; Frieman, J.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; March, M.; Martini, P.; Ogando, R.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Tucker, D.; Zhang, Y.; DES Collaboration

    2016-02-01

    We report the discovery of an excess of main-sequence turnoff stars in the direction of the constellations of Eridanus and Phoenix from the first-year data of the Dark Energy Survey (DES). The Eridanus-Phoenix (EriPhe) overdensity is centered around l˜ 285^\\circ and b˜ -60^\\circ and spans at least 30° in longitude and 10° in latitude. The Poisson significance of the detection is at least 9σ . The stellar population in the overdense region is similar in brightness and color to that of the nearby globular cluster NGC 1261, indicating that the heliocentric distance of EriPhe is about d˜ 16 {{kpc}}. The extent of EriPhe in projection is therefore at least ˜4 kpc by ˜3 kpc. On the sky, this overdensity is located between NGC 1261 and a new stellar stream discovered by DES at a similar heliocentric distance, the so-called Phoenix Stream. Given their similar distance and proximity to each other, it is possible that these three structures may be kinematically associated. Alternatively, the EriPhe overdensity is morphologically similar to the Virgo overdensity and the Hercules-Aquila cloud, which also lie at a similar Galactocentric distance. These three overdensities lie along a polar plane separated by ˜120° and may share a common origin. Spectroscopic follow-up observations of the stars in EriPhe are required to fully understand the nature of this overdensity.

  19. Discovery of a stellar overdensity in Eridanus-Phoenix in the dark energy survey

    DOE PAGES

    Li, T. S.; Balbinot, E.; Mondrik, N.; ...

    2016-01-27

    We report the discovery of an excess of main sequence turn-off stars in the direction of the constellations of Eridanus and Phoenix from the first year data of the Dark Energy Survey (DES). The Eridanus-Phoenix (EriPhe) overdensity is centered around l~285 deg and b~-60 deg and spans at least 30 deg in longitude and 10 deg in latitude. The Poisson significance of the detection is at least 9 sigma. The stellar population in the overdense region is similar in brightness and color to that of the nearby globular cluster NGC 1261, indicating that the heliocentric distance of EriPhe is aboutmore » d~16 kpc. The extent of EriPhe in projection is therefore at least ~4 kpc by ~3 kpc. On the sky, this overdensity is located between NGC 1261 and a new stellar stream discovered by DES at a similar heliocentric distance, the so-called Phoenix Stream. Given their similar distance and proximity to each other, it is possible that these three structures may be kinematically associated. Alternatively, the EriPhe overdensity is morphologically similar to the Virgo overdensity and the Hercules-Aquila cloud, which also lie at a similar Galactocentric distance. These three overdensities lie along a polar plane separated by ~120 deg and may share a common origin. Spectroscopic follow-up observations of the stars in EriPhe are required to fully understand the nature of this overdensity.« less

  20. Optimizing Stellarators for Turbulent Transport

    SciTech Connect

    H.E. Mynick, N.Pomphrey, and P. Xanthopoulos

    2010-05-27

    Up to now, the term "transport-optimized" stellarators has meant optimized to minimize neoclassical transport, while the task of also mitigating turbulent transport, usually the dominant transport channel in such designs, has not been addressed, due to the complexity of plasma turbulence in stellarators. Here, we demonstrate that stellarators can also be designed to mitigate their turbulent transport, by making use of two powerful numerical tools not available until recently, namely gyrokinetic codes valid for 3D nonlinear simulations, and stellarator optimization codes. A first proof-of-principle configuration is obtained, reducing the level of ion temperature gradient turbulent transport from the NCSX baseline design by a factor of about 2.5.

  1. Inferred properties of stellar granulation

    SciTech Connect

    Gray, D.F.; Toner, C.G.

    1985-06-01

    Apparent characteristics of stellar granulation in F and G main-sequence stars are inferred directly from observed spectral-line asymmetries and from comparisons of numerical simulations with the observations: (1) the apparent granulation velocity increases with effective temperature, (2) the dispersion of granule velocities about their mean velocity of rise increases with the apparent granulation velocity, (3) the mean velocity of rise of granules must be less than the total line broadening, (4) the apparent velocity difference between granules and dark lanes corresponds to the granulation velocity deduced from stellar line bisectors, (5) the dark lanes show velocities of fall approximately twice as large as the granule rise velocities, (6) the light contributed to the stellar flux by the granules is four to ten times more than the light from the dark lanes. Stellar rotation is predicted to produce distortions in the line bisectors which may give information on the absolute velocity displacements of the line bisectors. 37 references.

  2. A Receding Halo Sub-structure Towards Norma

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Sukanya

    2016-01-01

    We present results from follow-up spectroscopic observations of clustered Cepheid candidates identified from K-band light curves towards the Norma constellation (Chakrabarti et al. 2015), as well as others that we have found more recently. The average radial velocity of these stars is ~ 200 km/s, which is large and distinct from that of the Galaxy's stellar disk. These objects at l ~ -27 and b ~ -1 are therefore halo stars; using the period-luminosity relation of Type I Cepheids, they are at ~ 90 kpc. While the spectra do not have sufficient S/N to independently determine the metallicity and spectral type of the stars, there is a clear correspondence between the observed Brackett series lines in these observations and in known Type I Cepheids. Distances determined from the K-band period-luminosity relation (Matsunaga et al. 2013) and the 3.6 μm period-luminosity relation (Scowcroft et al. 2011) agree closely, and I-band observations have confirmed the periods of these sources. The extinction corrected J - Ks colors of these sources are comparable to known Type I Cepheids (Persson et al. 2004). The observed radial velocity of these stars agrees with predictions from dynamical models (Chakrabarti & Blitz 2009). If these stars are indeed members of the predicted dark-matter dominated dwarf galaxy that perturbed the outer HI disk of the Milky Way, this would represent the first application of Galactoseismology. These observations also challenge models of the Galactic halo. Young Cepheid variables are unexpected in models of the Galactic halo, though star formation due to infall of gas-rich dwarf galaxies may well produce a small population of yet undiscovered Cepheids in the outer halo.

  3. Stellar winds of hot stars

    NASA Astrophysics Data System (ADS)

    Stee, Ph.; Chesneau, O.

    2014-09-01

    In this paper, we summarize the basic properties of radiative stellar winds from the theoretical and observational point of views. We illustrate two examples of a radiative code applied to stellar physics: the SIMECA code successfully used to constrain the physics of the circumstellar environment of the Be star α Arae constrained by VLTI-AMBER spectrally resolved measurements and the CMFGEN code applied to the BA supergiants Deneb and Rigel constrained by CHARA-VEGA measurements.

  4. Solar and stellar coronal plasmas

    NASA Technical Reports Server (NTRS)

    Golub, L.

    1985-01-01

    Progress made in describing and interpreting coronal plasma processes and the relationship between the solar corona and its stellar counterparts is reported. Topics covered include: stellar X-ray emission, HEAO 2 X-ray survey of the Pleiades, closed coronal structures, X-ray survey of main-sequence stars with shallow convection zones, implications of the 1400 MHz flare emission, and magnetic field stochasticity.

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

    ERIC Educational Resources Information Center

    Polton, D. J.

    1972-01-01

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

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

    SciTech Connect

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

    2000-01-01

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

  7. Property Graph vs RDF Triple Store: A Comparison on Glycan Substructure Search

    PubMed Central

    Alocci, Davide; Mariethoz, Julien; Horlacher, Oliver; Bolleman, Jerven T.; Campbell, Matthew P.; Lisacek, Frederique

    2015-01-01

    Resource description framework (RDF) and Property Graph databases are emerging technologies that are used for storing graph-structured data. We compare these technologies through a molecular biology use case: glycan substructure search. Glycans are branched tree-like molecules composed of building blocks linked together by chemical bonds. The molecular structure of a glycan can be encoded into a direct acyclic graph where each node represents a building block and each edge serves as a chemical linkage between two building blocks. In this context, Graph databases are possible software solutions for storing glycan structures and Graph query languages, such as SPARQL and Cypher, can be used to perform a substructure search. Glycan substructure searching is an important feature for querying structure and experimental glycan databases and retrieving biologically meaningful data. This applies for example to identifying a region of the glycan recognised by a glycan binding protein (GBP). In this study, 19,404 glycan structures were selected from GlycomeDB (www.glycome-db.org) and modelled for being stored into a RDF triple store and a Property Graph. We then performed two different sets of searches and compared the query response times and the results from both technologies to assess performance and accuracy. The two implementations produced the same results, but interestingly we noted a difference in the query response times. Qualitative measures such as portability were also used to define further criteria for choosing the technology adapted to solving glycan substructure search and other comparable issues. PMID:26656740

  8. Property Graph vs RDF Triple Store: A Comparison on Glycan Substructure Search.

    PubMed

    Alocci, Davide; Mariethoz, Julien; Horlacher, Oliver; Bolleman, Jerven T; Campbell, Matthew P; Lisacek, Frederique

    2015-01-01

    Resource description framework (RDF) and Property Graph databases are emerging technologies that are used for storing graph-structured data. We compare these technologies through a molecular biology use case: glycan substructure search. Glycans are branched tree-like molecules composed of building blocks linked together by chemical bonds. The molecular structure of a glycan can be encoded into a direct acyclic graph where each node represents a building block and each edge serves as a chemical linkage between two building blocks. In this context, Graph databases are possible software solutions for storing glycan structures and Graph query languages, such as SPARQL and Cypher, can be used to perform a substructure search. Glycan substructure searching is an important feature for querying structure and experimental glycan databases and retrieving biologically meaningful data. This applies for example to identifying a region of the glycan recognised by a glycan binding protein (GBP). In this study, 19,404 glycan structures were selected from GlycomeDB (www.glycome-db.org) and modelled for being stored into a RDF triple store and a Property Graph. We then performed two different sets of searches and compared the query response times and the results from both technologies to assess performance and accuracy. The two implementations produced the same results, but interestingly we noted a difference in the query response times. Qualitative measures such as portability were also used to define further criteria for choosing the technology adapted to solving glycan substructure search and other comparable issues.

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

    NASA Astrophysics Data System (ADS)

    Durret, F.; DAFT/FADA Team

    2014-07-01

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

  10. Design of chemical space networks using a Tanimoto similarity variant based upon maximum common substructures.

    PubMed

    Zhang, Bijun; Vogt, Martin; Maggiora, Gerald M; Bajorath, Jürgen

    2015-10-01

    Chemical space networks (CSNs) have recently been introduced as an alternative to other coordinate-free and coordinate-based chemical space representations. In CSNs, nodes represent compounds and edges pairwise similarity relationships. In addition, nodes are annotated with compound property information such as biological activity. CSNs have been applied to view biologically relevant chemical space in comparison to random chemical space samples and found to display well-resolved topologies at low edge density levels. The way in which molecular similarity relationships are assessed is an important determinant of CSN topology. Previous CSN versions were based on numerical similarity functions or the assessment of substructure-based similarity. Herein, we report a new CSN design that is based upon combined numerical and substructure similarity evaluation. This has been facilitated by calculating numerical similarity values on the basis of maximum common substructures (MCSs) of compounds, leading to the introduction of MCS-based CSNs (MCS-CSNs). This CSN design combines advantages of continuous numerical similarity functions with a robust and chemically intuitive substructure-based assessment. Compared to earlier version of CSNs, MCS-CSNs are characterized by a further improved organization of local compound communities as exemplified by the delineation of drug-like subspaces in regions of biologically relevant chemical space.

  11. Modelling and control issues of dynamically substructured systems: adaptive forward prediction taken as an example

    PubMed Central

    Tu, Jia-Ying; Hsiao, Wei-De; Chen, Chih-Ying

    2014-01-01

    Testing techniques of dynamically substructured systems dissects an entire engineering system into parts. Components can be tested via numerical simulation or physical experiments and run synchronously. Additional actuator systems, which interface numerical and physical parts, are required within the physical substructure. A high-quality controller, which is designed to cancel unwanted dynamics introduced by the actuators, is important in order to synchronize the numerical and physical outputs and ensure successful tests. An adaptive forward prediction (AFP) algorithm based on delay compensation concepts has been proposed to deal with substructuring control issues. Although the settling performance and numerical conditions of the AFP controller are improved using new direct-compensation and singular value decomposition methods, the experimental results show that a linear dynamics-based controller still outperforms the AFP controller. Based on experimental observations, the least-squares fitting technique, effectiveness of the AFP compensation and differences between delay and ordinary differential equations are discussed herein, in order to reflect the fundamental issues of actuator modelling in relevant literature and, more specifically, to show that the actuator and numerical substructure are heterogeneous dynamic components and should not be collectively modelled as a homogeneous delay differential equation. PMID:25104902

  12. Modelling and control issues of dynamically substructured systems: adaptive forward prediction taken as an example.

    PubMed

    Tu, Jia-Ying; Hsiao, Wei-De; Chen, Chih-Ying

    2014-08-08

    Testing techniques of dynamically substructured systems dissects an entire engineering system into parts. Components can be tested via numerical simulation or physical experiments and run synchronously. Additional actuator systems, which interface numerical and physical parts, are required within the physical substructure. A high-quality controller, which is designed to cancel unwanted dynamics introduced by the actuators, is important in order to synchronize the numerical and physical outputs and ensure successful tests. An adaptive forward prediction (AFP) algorithm based on delay compensation concepts has been proposed to deal with substructuring control issues. Although the settling performance and numerical conditions of the AFP controller are improved using new direct-compensation and singular value decomposition methods, the experimental results show that a linear dynamics-based controller still outperforms the AFP controller. Based on experimental observations, the least-squares fitting technique, effectiveness of the AFP compensation and differences between delay and ordinary differential equations are discussed herein, in order to reflect the fundamental issues of actuator modelling in relevant literature and, more specifically, to show that the actuator and numerical substructure are heterogeneous dynamic components and should not be collectively modelled as a homogeneous delay differential equation.

  13. Strategic Considerations in the Design of a Screening System for Substructure Searches of Chemical Structure Files

    ERIC Educational Resources Information Center

    Adamson, George W.; And Others

    1973-01-01

    A major problem in the design of screening systems for substructure searches of chemical structure files is the development of a methodology for selection of an optimal set of structural characteristics to act as screens. Distributions of several structural characteristics of the Chemical Abstracts Service Registry System are summarized. (13…

  14. The Herschel Virgo Cluster Survey. IV. Resolved dust analysis of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Smith, M. W. L.; Vlahakis, C.; Baes, M.; Bendo, G. J.; Bianchi, S.; Bomans, D. J.; Boselli, A.; Clemens, M.; Corbelli, E.; Cortese, L.; Dariush, A.; Davies, J. I.; De Looze, I.; di Serego Alighieri, S.; Fadda, D.; Fritz, J.; Garcia-Appadoo, D. A.; Gavazzi, G.; Giovanardi, C.; Grossi, M.; Hughes, T. M.; Hunt, L. K.; Jones, A. P.; Madden, S.; Pierini, D.; Pohlen, M.; Sabatini, S.; Verstappen, J.; Xilouris, E. M.; Zibetti, S.

    2010-07-01

    We present a resolved dust analysis of three of the largest angular size spiral galaxies, NGC 4501 and NGC 4567/8, in the Herschel Virgo Cluster Survey (HeViCS) science demonstration field. Herschel has unprecedented spatial resolution at far-infrared wavelengths and with the PACS and SPIRE instruments samples both sides of the peak in the far infrared spectral energy distribution (SED). We present maps of dust temperature, dust mass, and gas-to-dust ratio, produced by fitting modified black bodies to the SED for each pixel. We find that the distribution of dust temperature in both systems is in the range ~19-22 K and peaks away from the centres of the galaxies. The distribution of dust mass in both systems is symmetrical and exhibits a single peak coincident with the galaxy centres. This Letter provides a first insight into the future analysis possible with a large sample of resolved galaxies to be observed by Herschel. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  15. Einstein Observatory solid state spectrometer observations of M87 and the Virgo cluster

    NASA Technical Reports Server (NTRS)

    Lea, S. M.; Mushotzky, R. F.; Holt, S. S.

    1982-01-01

    X-ray observations of the galaxy M87 and of a region in the Virgo cluster displaced 7 minutes from the center of M87 are presented. X-ray spectra are obtained at these two locations with the slid state spectrometer onboard the Einstein Observatory. Emission lines were observed in both locations, indicating the presence of heavy elements at abundances approximately solar (to within a factor of 2). A temperature gradient, T increases from approximately 1.4 keV at the position of M87 to T approximately 3.35 keV 7' away, was detected. There is lower temperature thermal emission at the center of M87 with T approximately 0.6 keV, consistent with models for cooling flows in this cluster. In addition to the thermal emission, a power law component in the spectrum of M87, was detected consistent with that observed by HEAO-1, indicating that this component probably originates in the galaxy itself. The presence of intracluster gas having density approximately .001 cu cm and temperature approximately 30 million K is indicated.

  16. The Search for Shock-excited H2 in Virgo Spirals Experiencing Ram Pressure Stripping

    NASA Astrophysics Data System (ADS)

    Wong, O. Ivy; Kenney, Jeffrey D. P.; Murphy, Eric J.; Helou, George

    2014-03-01

    We investigate the presence of shock-excited H2 in four Virgo cluster galaxies that show clear evidence of ongoing ram pressure stripping. Mid-infrared spectral mapping of the rotational H2 emission lines were performed using the Infrared Spectrograph on board the Spitzer Space Telescope. We target four regions along the leading side of galaxies where the intracluster medium appears to be pushing back the individual galaxy's interstellar medium. For comparison purposes, we also study two regions on the trailing side of these galaxies: a region within an edge-on disk and an extraplanar star-forming region. We find a factor of 2.6 excess of warm H2/PAH in our sample relative to the observed fractions in other nearby galaxies. We attribute the H2/PAH excess to contributions of shock-excited H2 which is likely to have been triggered by ongoing ram pressure interaction in our sample galaxies. Ram pressure driven shocks may also be responsible for the elevated ratios of [Fe II]/[Ne II] found in our sample.

  17. Prospects for Observing and Localizing Gravitational-Wave Transients with Advanced LIGO and Advanced Virgo

    NASA Astrophysics Data System (ADS)

    Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Amariutei, D. V.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Behnke, B.; Bejger, M.; Belczynski, C.; Bell, A. S.; Bell, C. J.; Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D.; Blair, R. M.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bojtos, P.; Bond, C.; Bondu, F.; Bonnand, R.; Bork, R.; Boschi, V.; Bose, S.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Constancio, M.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dattilo, V.; Dave, I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.; DeRosa, R.; De Rosa, R.; DeSalvo, R.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Lieto, A.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J. M.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier, J.-D.; Franco, S.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gatto, A.; Gaur, G.; Gehrels, N.; Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, A.; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.; Holz, D. E.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Islas, G.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; K, Haris; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Key, J. S.; Khalaidovski, A.; Khalili, F. Y.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, C.; Kim, J.; Kim, K.; Kim, N.; Kim, N.; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Kokeyama, K.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B. M.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Logue, J.; Lombardi, A. L.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lück, H.; Lundgren, A. P.; Luo, J.; Lynch, R.; Ma, Y.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magana-Sandoval, F.; Magee, R. M.; Mageswaran, M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer, R. A.; Merilh, E.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Pereira, R.; Perreca, A.; Phelps, M.; Piccinni, O.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poggiani, R.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S. S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prodi, G. A.; Prokhorov, L.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Ricci, F.; Riles, K.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, J. D.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sentenac, D.; Sequino, V.; Sergeev, A.; Serna, G.; Setyawati, Y.; Sevigny, A.; Shaddock, D. A.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sigg, D.; Silva, A. D.; Simakov, D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sutton, P. J.; Swinkels, B. L.; Szczepanczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Tonelli, M.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; van den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van der Sluys, M. V.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; White, D. J.; Whiting, B. F.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Wright, J. L.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, H.; Yvert, M.; Zadrożny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, F.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

    2016-12-01

    We present a possible observing scenario for the Advanced LIGO and Advanced Virgo gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We determine the expected sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron-star systems, which are considered the most promising for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and 90% credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5 deg2 to 20 deg2 will require at least three detectors of sensitivity within a factor of ˜ 2 of each other and with a broad frequency bandwidth. Should the third LIGO detector be relocated to India as expected, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

  18. Hubble Space Telescope photometry of the central regions of Virgo cluster elliptical galaxies. 3: Brightness profiles

    NASA Astrophysics Data System (ADS)

    Ferrarese, L.; van den Bosch, F. C.; Ford, H. C.; Jaffe, W.; O'Connell, R. W.

    1994-11-01

    We have used the Planetary Camera on the Hubble Space Telescope (HST) to study the morphology and surface brightness parameters of a luminosity-limited sample of fourteen elliptical galaxies in the Virgo cluster. The total apparent blue magnitudes of the galaxies range between 9.4 and 13.4. In this paper, the core brightness profiles are presented, while the overall morphology and the isophotal shapes are discussed in two companion papers (Jaffe et al. (1994); van den Bosch et al. (1994)). We show that, in spite of the spherical aberration affecting the HST primary mirror, deconvolution techniques allow recovery of the brightness profile up to 0.2 arcsec from the center of the galaxies. We find that none of the galaxies has an isothermal core. On the basis of their morphological and photometrical properties, the galaxies can be divided in two physically distinct groups, referred to as Type I and Type II. All of the Type I galaxies are classified as E1 to E3 in the Revised Shapley Ames Catalog (Sandage & Tammann 1981), while Type II galaxies are classified as E5 to E7. The characteristics of Type II galaxies are explained by the presence of disks component on both the 1 arcsec and the 10 arcsec scales, while Type I galaxies correspond to the classical disk-free ellipticals.

  19. Hubble Space Telescope photometry of the central regions of Virgo cluster elliptical galaxies. 3: Brightness profiles

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    We have used the Planetary Camera on the Hubble Space Telescope (HST) to study the morphology and surface brightness parameters of a luminosity-limited sample of fourteen elliptical galaxies in the Virgo cluster. The total apparent blue magnitudes of the galaxies range between 9.4 and 13.4. In this paper, the core brightness profiles are presented, while the overall morphology and the isophotal shapes are discussed in two companion papers (Jaffe et al. (1994); van den Bosch et al. (1994)). We show that, in spite of the spherical aberration affecting the HST primary mirror, deconvolution techniques allow recovery of the brightness profile up to 0.2 arcsec from the center of the galaxies. We find that none of the galaxies has an isothermal core. On the basis of their morphological and photometrical properties, the galaxies can be divided in two physically distinct groups, referred to as Type I and Type II. All of the Type I galaxies are classified as E1 to E3 in the Revised Shapley Ames Catalog (Sandage & Tammann 1981), while Type II galaxies are classified as E5 to E7. The characteristics of Type II galaxies are explained by the presence of disks component on both the 1 arcsec and the 10 arcsec scales, while Type I galaxies correspond to the classical disk-free ellipticals.

  20. Wing shape and its influence on the outcome of territorial contests in the damselfly Calopteryx virgo.

    PubMed

    Bots, Jessica; Breuker, Casper J; Kaunisto, Kari M; Koskimäki, Jani; Gossum, Hans Van; Suhonen, Jukka

    2012-01-01

    Male mating success is often determined by territory ownership and traits associated with successful territory defense. Empirical studies have shown that the territory owner wins the majority of fights with challenging males. Several physical and physiological traits have been found to correlate with resource holding potential. In addition, in aerial insects, wing design may also have a strong influence on resource holding potential, since it determines efficiency and precision during flight. However, this possibility has not yet been thoroughly evaluated using the modern technique of geometric morphometrics to analyze shape. Therefore, this study examined whether wing shape affects the outcome of male-male contests in the territorial damselfly, Calopteryx virgo (L.) (Odonata: Calopterygidae). Wing shape and also traditional flight-related morphological measures were compared between 27 pairs of winners and losers from experimental territorial contests. Contrary to expectations, there were no differences between winners and losers in all studied wing traits (shape, length, width, total surface, aspect ratio, and wing loading). However, highly significant differences in wing shape and size were detected between the fore- and hindwing. It is currently not known how these differences relate to flight performance, since previous biomechanical studies in damselflies assumed fore- and hindwings to have an identical planform.

  1. GCN capabilities and status, and the incorporation of LIGO/Virgo

    NASA Astrophysics Data System (ADS)

    Barthelmy, Scott

    2016-03-01

    The Gamma-ray Coordinates Network / Transient Astronomy Network (GCN/TAN) is a single-point source for all transient astronomy notification. It collects the astrophysical transients from the missions (space-based and nearly all ground-based), puts them into a standard format, and distributes them to whomever wants to receive them. This is all done autonomously (completely autonomous within GCN/TAN, and almost always autonomously within the producer end of operations). This automation means minimal time delays (<0.1 sec within GCN for VOEvent and binary socket-based distribution methods, and typically a few sec for email-based which is dependent on the internet email protocol and the number of hops, both of which are out of the control of GCN/TAN). The LIGO-VIRGO Collaboration (LVC) Notices are now implemented in the GCN/TAN system. During the proprietary phase, the recipients must have an MoU with LVC and LVC must authorize GCN to distribute LVC Notices to each given MoU follow-up observer. In addition to Notices, there are the GCN Circulars, which are prose-style reports of follow-up observations made and results obtains. During the LVC Proprietary phase there are also the GCN LVC Circulars, which also require authorization from LVC to join the LVC Circulars.

  2. Prospects for Observing and Localizing Gravitational-Wave Transients with Advanced LIGO and Advanced Virgo.

    PubMed

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Chua, S; Chung, S; Ciani, G; Clara, F; Clark, J A; Cleva, F; Coccia, E; Cohadon, P-F; Colla, A; Collette, C G; Constancio, M; Conte, A; Conti, L; Cook, D; Corbitt, T R; Cornish, N; Corsi, A; Cortese, S; Costa, C A; Coughlin, M W; Coughlin, S B; Coulon, J-P; Countryman, S T; Couvares, P; Coward, D M; Cowart, M J; Coyne, D C; Coyne, R; Craig, K; Creighton, J D E; Cripe, J; Crowder, S G; Cumming, A; Cunningham, L; Cuoco, E; Dal Canton, T; Danilishin, S L; D'Antonio, S; Danzmann, K; Darman, N S; Dattilo, V; Dave, I; Daveloza, H P; Davier, M; Davies, G S; Daw, E J; Day, R; DeBra, D; Debreczeni, G; Degallaix, J; De Laurentis, M; Deléglise, S; Del Pozzo, W; Denker, T; Dent, T; Dereli, H; Dergachev, V; DeRosa, R; De Rosa, R; DeSalvo, R; Dhurandhar, S; Díaz, M C; Di Fiore, L; Di Giovanni, M; Di Lieto, A; Di Palma, I; Di Virgilio, A; Dojcinoski, G; Dolique, V; Donovan, F; Dooley, K L; Doravari, S; Douglas, R; Downes, T P; Drago, M; Drever, R W P; Driggers, J C; Du, Z; Ducrot, M; Dwyer, S E; Edo, T B; Edwards, M C; Effler, A; Eggenstein, H-B; Ehrens, P; Eichholz, J M; Eikenberry, S S; Engels, W; Essick, R C; Etzel, T; Evans, M; Evans, T M; Everett, R; Factourovich, M; Fafone, V; Fair, H; Fairhurst, S; Fan, X; Fang, Q; Farinon, S; Farr, B; Farr, W M; Favata, M; Fays, M; Fehrmann, H; Fejer, M M; Ferrante, I; Ferreira, E C; Ferrini, F; Fidecaro, F; Fiori, I; Fisher, R P; Flaminio, R; Fletcher, M; Fournier, J-D; Franco, S; Frasca, S; Frasconi, F; Frei, Z; Freise, A; Frey, R; Fricke, T T; Fritschel, P; Frolov, V V; Fulda, P; Fyffe, M; Gabbard, H A G; Gair, J R; Gammaitoni, L; Gaonkar, S G; Garufi, F; Gatto, A; Gaur, G; Gehrels, N; Gemme, G; Gendre, B; Genin, E; Gennai, A; George, J; Gergely, L; Germain, V; Ghosh, A; Ghosh, S; Giaime, J A; Giardina, K D; Giazotto, A; Gill, K; Glaefke, A; Goetz, E; Goetz, R; Gondan, L; González, G; Castro, J M Gonzalez; Gopakumar, A; Gordon, N A; Gorodetsky, M L; Gossan, S E; Gosselin, M; Gouaty, R; Graef, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greco, G; Green, A C; Groot, P; Grote, H; Grunewald, S; Guidi, G M; Guo, X; Gupta, A; Gupta, M K; Gushwa, K E; Gustafson, E K; Gustafson, R; Hacker, J J; Hall, B R; Hall, E D; Hammond, G; Haney, M; Hanke, M M; Hanks, J; Hanna, C; Hannam, M D; Hanson, J; Hardwick, T; Harms, J; Harry, G M; Harry, I W; Hart, M J; Hartman, M T; Haster, C-J; Haughian, K; Heidmann, A; Heintze, M C; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Hennig, J; Heptonstall, A W; Heurs, M; Hild, S; Hoak, D; Hodge, K A; Hofman, D; Hollitt, S E; Holt, K; Holz, D E; Hopkins, P; Hosken, D J; Hough, J; Houston, E A; Howell, E J; Hu, Y M; Huang, S; Huerta, E A; Huet, D; Hughey, B; Husa, S; Huttner, S H; Huynh-Dinh, T; Idrisy, A; Indik, N; Ingram, D R; Inta, R; Isa, H N; Isac, J-M; Isi, M; Islas, G; Isogai, T; Iyer, B R; Izumi, K; Jacqmin, T; Jang, H; Jani, K; Jaranowski, P; Jawahar, S; Jiménez-Forteza, F; Johnson, W W; Jones, D I; Jones, R; Jonker, R J G; Ju, L; Haris, K; Kalaghatgi, C V; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Karki, S; Kasprzack, M; Katsavounidis, E; Katzman, W; Kaufer, S; Kaur, T; Kawabe, K; Kawazoe, F; Kéfélian, F; Kehl, M S; Keitel, D; Kelley, D B; Kells, W; Kennedy, R; Key, J S; Khalaidovski, A; Khalili, F Y; Khan, S; Khan, Z; Khazanov, E A; Kijbunchoo, N; Kim, C; Kim, J; Kim, K; Kim, N; Kim, Y-M; King, E J; King, P J; Kinzel, D L; Kissel, J S; Kleybolte, L; Klimenko, S; Koehlenbeck, S M; Kokeyama, K; Koley, S; Kondrashov, V; Kontos, A; Korobko, M; Korth, W Z; Kowalska, I; Kozak, D B; Kringel, V; Krishnan, B; Królak, A; Krueger, C; Kuehn, G; Kumar, P; Kuo, L; Kutynia, A; Lackey, B D; Landry, M; Lange, J; Lantz, B; Lasky, P D; Lazzarini, A; Lazzaro, C; Leaci, P; Leavey, S; Lebigot, E; Lee, C H; Lee, H K; Lee, H M; Lee, K; Lenon, A; Leonardi, M; Leong, J R; Leroy, N; Letendre, N; Levin, Y; Levine, B M; Li, T G F; Libson, A; Littenberg, T B; Lockerbie, N A; Logue, J; Lombardi, A L; Lord, J E; Lorenzini, M; Loriette, V; Lormand, M; Losurdo, G; Lough, J D; Lück, H; Lundgren, A P; Luo, J; Lynch, R; Ma, Y; MacDonald, T; Machenschalk, B; MacInnis, M; Macleod, D M; Magaña-Sandoval, F; Magee, R M; Mageswaran, M; Majorana, E; Maksimovic, I; Malvezzi, V; Man, N; Mandel, I; Mandic, V; Mangano, V; Mansell, G L; Manske, M; Mantovani, M; Marchesoni, F; Marion, F; Márka, S; Márka, Z; Markosyan, A S; Maros, E; Martelli, F; Martellini, L; Martin, I W; Martin, R M; Martynov, D V; Marx, J N; Mason, K; Masserot, A; Massinger, T J; Masso-Reid, M; Matichard, F; Matone, L; Mavalvala, N; Mazumder, N; Mazzolo, G; McCarthy, R; McClelland, D E; McCormick, S; McGuire, S C; McIntyre, G; McIver, J; McManus, D J; McWilliams, S T; Meacher, D; Meadors, G D; Meidam, J; Melatos, A; Mendell, G; Mendoza-Gandara, D; Mercer, R A; Merilh, E; Merzougui, M; Meshkov, S; Messenger, C; Messick, C; Meyers, P M; Mezzani, F; Miao, H; Michel, C; Middleton, H; Mikhailov, E E; Milano, L; Miller, J; Millhouse, M; Minenkov, Y; Ming, J; Mirshekari, S; Mishra, C; Mitra, S; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Moggi, A; Mohan, M; Mohapatra, S R P; Montani, M; Moore, B C; Moore, C J; Moraru, D; Moreno, G; Morriss, S R; Mossavi, K; Mours, B; Mow-Lowry, C M; Mueller, C L; Mueller, G; Muir, A W; Mukherjee, Arunava; Mukherjee, D; Mukherjee, S; Mullavey, A; Munch, J; Murphy, D J; Murray, P G; Mytidis, A; Nardecchia, I; Naticchioni, L; Nayak, R K; Necula, V; Nedkova, K; Nelemans, G; Neri, M; Neunzert, A; Newton, G; Nguyen, T T; Nielsen, A B; Nissanke, S; Nitz, A; Nocera, F; Nolting, D; Normandin, M E N; Nuttall, L K; Oberling, J; Ochsner, E; O'Dell, J; Oelker, E; Ogin, G H; Oh, J J; Oh, S H; Ohme, F; Oliver, M; Oppermann, P; Oram, R J; O'Reilly, B; O'Shaughnessy, R; Ott, C D; Ottaway, D J; Ottens, R S; Overmier, H; Owen, B J; Pai, A; Pai, S A; Palamos, J R; Palashov, O; Palomba, C; Pal-Singh, A; Pan, H; Pankow, C; Pannarale, F; Pant, B C; Paoletti, F; Paoli, A; Papa, M A; Paris, H R; Parker, W; Pascucci, D; Pasqualetti, A; Passaquieti, R; Passuello, D; Patrick, Z; Pearlstone, B L; Pedraza, M; Pedurand, R; Pekowsky, L; Pele, A; Penn, S; Pereira, R; Perreca, A; Phelps, M; Piccinni, O; Pichot, M; Piergiovanni, F; Pierro, V; Pillant, G; Pinard, L; Pinto, I M; Pitkin, M; Poggiani, R; Post, A; Powell, J; Prasad, J; Predoi, V; Premachandra, S S; Prestegard, T; Price, L R; Prijatelj, M; Principe, M; Privitera, S; Prodi, G A; Prokhorov, L; Punturo, M; Puppo, P; Pürrer, M; Qi, H; Qin, J; Quetschke, V; Quintero, E A; Quitzow-James, R; Raab, F J; Rabeling, D S; Radkins, H; Raffai, P; Raja, S; Rakhmanov, M; Rapagnani, P; Raymond, V; Razzano, M; Re, V; Read, J; Reed, C M; Regimbau, T; Rei, L; Reid, S; Reitze, D H; Rew, H; Ricci, F; Riles, K; Robertson, N A; Robie, R; Robinet, F; Rocchi, A; Rolland, L; Rollins, J G; Roma, V J; Romano, J D; Romano, R; Romanov, G; Romie, J H; Rosińska, D; Rowan, S; Rüdiger, A; Ruggi, P; Ryan, K; Sachdev, S; Sadecki, T; Sadeghian, L; Saleem, M; Salemi, F; Samajdar, A; Sammut, L; Sanchez, E J; Sandberg, V; Sandeen, B; Sanders, J R; Sassolas, B; Sathyaprakash, B S; Saulson, P R; Sauter, O; Savage, R L; Sawadsky, A; Schale, P; Schilling, R; Schmidt, J; Schmidt, P; Schnabel, R; Schofield, R M S; Schönbeck, A; Schreiber, E; Schuette, D; Schutz, B F; Scott, J; Scott, S M; Sellers, D; Sentenac, D; Sequino, V; Sergeev, A; Serna, G; Setyawati, Y; Sevigny, A; Shaddock, D A; Shah, S; Shahriar, M S; Shaltev, M; Shao, Z; Shapiro, B; Shawhan, P; Sheperd, A; Shoemaker, D H; Shoemaker, D M; Siellez, K; Siemens, X; Sigg, D; Silva, A D; Simakov, D; Singer, A; Singer, L P; Singh, A; Singh, R; Sintes, A M; Slagmolen, B J J; Smith, J R; Smith, N D; Smith, R J E; Son, E J; Sorazu, B; Sorrentino, F; Souradeep, T; Srivastava, A K; Staley, A; Steinke, M; Steinlechner, J; Steinlechner, S; Steinmeyer, D; Stephens, B C; Stone, R; Strain, K A; Straniero, N; Stratta, G; Strauss, N A; Strigin, S; Sturani, R; Stuver, A L; Summerscales, T Z; Sun, L; Sutton, P J; Swinkels, B L; Szczepanczyk, M J; Tacca, M; Talukder, D; Tanner, D B; Tápai, M; Tarabrin, S P; Taracchini, A; Taylor, R; Theeg, T; Thirugnanasambandam, M P; Thomas, E G; Thomas, M; Thomas, P; Thorne, K A; Thorne, K S; Thrane, E; Tiwari, S; Tiwari, V; Tokmakov, K V; Tomlinson, C; Tonelli, M; Torres, C V; Torrie, C I; Töyrä, D; Travasso, F; Traylor, G; Trifirò, D; Tringali, M C; Trozzo, L; Tse, M; Turconi, M; Tuyenbayev, D; Ugolini, D; Unnikrishnan, C S; Urban, A L; Usman, S A; Vahlbruch, H; Vajente, G; Valdes, G; van Bakel, N; van Beuzekom, M; van den Brand, J F J; van den Broeck, C; Vander-Hyde, D C; van der Schaaf, L; van der Sluys, M V; van Heijningen, J V; van Veggel, A A; Vardaro, M; Vass, S; Vasúth, M; Vaulin, R; Vecchio, A; Vedovato, G; Veitch, J; Veitch, P J; Venkateswara, K; Verkindt, D; Vetrano, F; Viceré, A; Vinciguerra, S; Vine, D J; Vinet, J-Y; Vitale, S; Vo, T; Vocca, H; Vorvick, C; Vousden, W D; Vyatchanin, S P; Wade, A R; Wade, L E; Wade, M; Walker, M; Wallace, L; Walsh, S; Wang, G; Wang, H; Wang, M; Wang, X; Wang, Y; Ward, R L; Warner, J; Was, M; Weaver, B; Wei, L-W; Weinert, M; Weinstein, A J; Weiss, R; Welborn, T; Wen, L; Weßels, P; Westphal, T; Wette, K; Whelan, J T; White, D J; Whiting, B F; Williams, R D; Williamson, A R; Willis, J L; Willke, B; Wimmer, M H; Winkler, W; Wipf, C C; Wittel, H; Woan, G; Worden, J; Wright, J L; Wu, G; Yablon, J; Yam, W; Yamamoto, H; Yancey, C C; Yap, M J; Yu, H; Yvert, M; Zadrożny, A; Zangrando, L; Zanolin, M; Zendri, J-P; Zevin, M; Zhang, F; Zhang, L; Zhang, M; Zhang, Y; Zhao, C; Zhou, M; Zhou, Z; Zhu, X J; Zucker, M E; Zuraw, S E; Zweizig, J

    2016-01-01

    We present a possible observing scenario for the Advanced LIGO and Advanced Virgo gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We determine the expected sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron-star systems, which are considered the most promising for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and 90% credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5 deg(2) to 20 deg(2) will require at least three detectors of sensitivity within a factor of ∼ 2 of each other and with a broad frequency bandwidth. Should the third LIGO detector be relocated to India as expected, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

  3. CHANG-ES. VII. Magnetic Outflows from the Virgo Cluster Galaxy NGC 4388

    NASA Astrophysics Data System (ADS)

    Damas-Segovia, A.; Beck, R.; Vollmer, B.; Wiegert, T.; Krause, M.; Irwin, J.; Weżgowiec, M.; Li, J.; Dettmar, R.-J.; English, J.; Wang, Q. D.

    2016-06-01

    We investigate the effects of ram pressure on the ordered magnetic field of a galaxy hosting a radio halo and strong nuclear outflows. New radio images in total and polarized intensity of the edge-on Virgo galaxy NGC 4388 were obtained within the CHANG-ES EVLA project. The unprecedented noise level reached allows us to detect striking new features of the ordered magnetic field. The nuclear outflow extends far into the halo to about 5 kpc from the center and is spatially correlated with the {{H}}α and X-ray emission. For the first time, the southern outflow is detected. Above and below both spiral arms we find extended blobs of polarized emission with an ordered field oriented perpendicular to the disk. The synchrotron lifetime of the cosmic-ray electrons (CREs) in these regions yields a mean outflow velocity of 270+/- 70 {km} {{{s}}}-1, in agreement with a galactic wind scenario. The observed symmetry of the polarized halo features in NGC 4388 excludes a compression of the halo gas by the ram pressure of the intracluster medium (ICM). The assumption of equilibrium between the halo pressure and the ICM ram pressure yields an estimate of the ICM density that is consistent with both the ICM density derived from X-ray observations and the recent Planck Sunyaev-Zel’dovich measurements. The detection of a faint radio halo around cluster galaxies could thus be used for an estimate of ICM ram pressure.

  4. CLASH-VLT: Insights on the Mass Substructures in the Frontier Fields Cluster MACS J0416.1-2403 through Accurate Strong Lens Modeling

    NASA Astrophysics Data System (ADS)

    Grillo, C.; Suyu, S. H.; Rosati, P.; Mercurio, A.; Balestra, I.; Munari, E.; Nonino, M.; Caminha, G. B.; Lombardi, M.; De Lucia, G.; Borgani, S.; Gobat, R.; Biviano, A.; Girardi, M.; Umetsu, K.; Coe, D.; Koekemoer, A. M.; Postman, M.; Zitrin, A.; Halkola, A.; Broadhurst, T.; Sartoris, B.; Presotto, V.; Annunziatella, M.; Maier, C.; Fritz, A.; Vanzella, E.; Frye, B.

    2015-02-01

    We present a detailed mass reconstruction and a novel study on the substructure properties in the core of the Cluster Lensing And Supernova survey with Hubble (CLASH) and Frontier Fields galaxy cluster MACS J0416.1-2403. We show and employ our extensive spectroscopic data set taken with the VIsible Multi-Object Spectrograph instrument as part of our CLASH-VLT program, to confirm spectroscopically 10 strong lensing systems and to select a sample of 175 plausible cluster members to a limiting stellar mass of log (M */M ⊙) ~= 8.6. We reproduce the measured positions of a set of 30 multiple images with a remarkable median offset of only 0.''3 by means of a comprehensive strong lensing model comprised of two cluster dark-matter halos, represented by cored elliptical pseudo-isothermal mass distributions, and the cluster member components, parameterized with dual pseudo-isothermal total mass profiles. The latter have total mass-to-light ratios increasing with the galaxy HST/WFC3 near-IR (F160W) luminosities. The measurement of the total enclosed mass within the Einstein radius is accurate to ~5%, including the systematic uncertainties estimated from six distinct mass models. We emphasize that the use of multiple-image systems with spectroscopic redshifts and knowledge of cluster membership based on extensive spectroscopic information is key to constructing robust high-resolution mass maps. We also produce magnification maps over the central area that is covered with HST observations. We investigate the galaxy contribution, both in terms of total and stellar mass, to the total mass budget of the cluster. When compared with the outcomes of cosmological N-body simulations, our results point to a lack of massive subhalos in the inner regions of simulated clusters with total masses similar to that of MACS J0416.1-2403. Our findings of the location and shape of the cluster dark-matter halo density profiles and on the cluster substructures provide intriguing tests of the

  5. CLASH-VLT: INSIGHTS ON THE MASS SUBSTRUCTURES IN THE FRONTIER FIELDS CLUSTER MACS J0416.1–2403 THROUGH ACCURATE STRONG LENS MODELING

    SciTech Connect

    Grillo, C.; Suyu, S. H.; Umetsu, K.; Rosati, P.; Caminha, G. B.; Mercurio, A.; Balestra, I.; Munari, E.; Nonino, M.; De Lucia, G.; Borgani, S.; Biviano, A.; Girardi, M.; Lombardi, M.; Gobat, R.; Zitrin, A.; Halkola, A. and others

    2015-02-10

    We present a detailed mass reconstruction and a novel study on the substructure properties in the core of the Cluster Lensing And Supernova survey with Hubble (CLASH) and Frontier Fields galaxy cluster MACS J0416.1–2403. We show and employ our extensive spectroscopic data set taken with the VIsible Multi-Object Spectrograph instrument as part of our CLASH-VLT program, to confirm spectroscopically 10 strong lensing systems and to select a sample of 175 plausible cluster members to a limiting stellar mass of log (M {sub *}/M {sub ☉}) ≅ 8.6. We reproduce the measured positions of a set of 30 multiple images with a remarkable median offset of only 0.''3 by means of a comprehensive strong lensing model comprised of two cluster dark-matter halos, represented by cored elliptical pseudo-isothermal mass distributions, and the cluster member components, parameterized with dual pseudo-isothermal total mass profiles. The latter have total mass-to-light ratios increasing with the galaxy HST/WFC3 near-IR (F160W) luminosities. The measurement of the total enclosed mass within the Einstein radius is accurate to ∼5%, including the systematic uncertainties estimated from six distinct mass models. We emphasize that the use of multiple-image systems with spectroscopic redshifts and knowledge of cluster membership based on extensive spectroscopic information is key to constructing robust high-resolution mass maps. We also produce magnification maps over the central area that is covered with HST observations. We investigate the galaxy contribution, both in terms of total and stellar mass, to the total mass budget of the cluster. When compared with the outcomes of cosmological N-body simulations, our results point to a lack of massive subhalos in the inner regions of simulated clusters with total masses similar to that of MACS J0416.1–2403. Our findings of the location and shape of the cluster dark-matter halo density profiles and on the cluster substructures provide intriguing

  6. Stellar diameters and temperatures. IV. Predicting stellar angular diameters

    SciTech Connect

    Boyajian, Tabetha S.; Van Belle, Gerard; Von Braun, Kaspar

    2014-03-01

    The number of stellar angular diameter measurements has greatly increased over the past few years due to innovations and developments in the field of long baseline optical interferometry. We use a collection of high-precision angular diameter measurements for nearby, main-sequence stars to develop empirical relations that allow the prediction of stellar angular sizes as a function of observed photometric color. These relations are presented for a combination of 48 broadband color indices. We empirically show for the first time a dependence on metallicity of these relations using Johnson (B – V) and Sloan (g – r) colors. Our relations are capable of predicting diameters with a random error of less than 5% and represent the most robust and empirical determinations of stellar angular sizes to date.

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

    SciTech Connect

    Altheimer, A.

    2014-03-21

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

  8. Compact Stellarator Path to DEMO

    NASA Astrophysics Data System (ADS)

    Lyon, J. F.

    2007-11-01

    Issues for a DEMO reactor are sustaining an ignited/high-Q plasma in steady state, avoiding disruptions and large variations in power flux to the wall, adequate confinement of thermal plasma and alpha-particles, control of a burning plasma, particle and power handling, etc. Compact stellarators have key advantages -- steady-state high-plasma-density operation without external current drive or disruptions, stability without a close conducting wall or active feedback systems, and low recirculating power -- in addition to moderate plasma aspect ratio, good confinement, and high-beta potential. The ARIES-CS study established that compact stellarators can be competitive with tokamaks as reactors. Many of the issues for a compact stellarator DEMO can be answered using results from large tokamaks, ITER D-T experiments and fusion materials, technology and component development programs, in addition to stellarators in operation, under construction or in development. However, a large next-generation stellarator will be needed to address some physics issues: size scaling and confinement at higher parameters, burning plasma issues, and operation with a strongly radiative divertor. Technology issues include simpler coils, structure, and divertor fabrication, and better cost information.

  9. THE STELLAR MASS–HALO MASS RELATION FOR LOW-MASS X-RAY GROUPS AT 0.5< z< 1 IN THE CDFS WITH CSI

    SciTech Connect

    Patel, Shannon G.; Kelson, Daniel D.; Williams, Rik J.; Mulchaey, John S.; Dressler, Alan; McCarthy, Patrick J.; Shectman, Stephen A.

    2015-01-30

    Since z∼1, the stellar mass density locked in low-mass groups and clusters has grown by a factor of ∼8. Here, we make the first statistical measurements of the stellar mass content of low-mass X-ray groups at 0.5stellar-to-halo mass scales for wide-field optical and infrared surveys. Groups are selected from combined Chandra and XMM-Newton X-ray observations in the Chandra Deep Field South. These ultra-deep observations allow us to identify bona fide low-mass groups at high redshift and enable measurements of their total halo masses. We compute aggregate stellar masses for these halos using galaxies from the Carnegie-Spitzer-IMACS (CSI) spectroscopic redshift survey. Stars comprise ∼3%–4% of the total mass of group halos with masses 10{sup 12.8}Virgo). Complementing our sample with higher mass halos at these redshifts, we find that the stellar-to-halo mass ratio decreases toward higher halo masses, consistent with other work in the local and high redshift universe. The observed scatter about the stellar–halo mass relation is σ∼0.25 dex, which is relatively small and suggests that total group stellar mass can serve as a rough proxy for halo mass. We find no evidence for any significant evolution in the stellar–halo mass relation since z≲1. Quantifying the stellar content in groups since this epoch is critical given that hierarchical assembly leads to such halos growing in number density and hosting increasing shares of quiescent galaxies.

  10. Improving corrosion resistance of post-tensioned substructures emphasizing high performance grouts

    NASA Astrophysics Data System (ADS)

    Schokker, Andrea Jeanne

    The use of post-tensioning in bridges can provide durability and structural benefits to the system while expediting the construction process. When post-tensioning is combined with precast elements, traffic interference can be greatly reduced through rapid construction. Post-tensioned concrete substructure elements such as bridge piers, hammerhead bents, and straddle bents have become more prevalent in recent years. Chloride induced corrosion of steel in concrete is one of the most costly forms of corrosion each year. Coastal substructure elements are exposed to seawater by immersion or spray, and inland bridges may also be at risk due to the application of deicing salts. Corrosion protection of the post-tensioning system is vital to the integrity of the structure because loss of post-tensioning can result in catastrophic failure. Documentation for durability design of the grout, ducts, and anchorage systems is very limited. The objective of this research is to evaluate the effectiveness of corrosion protection measures for post-tensioned concrete substructures by designing and testing specimens representative of typical substructure elements using state-of-the-art practices in aggressive chloride exposure environments. This was accomplished through exposure testing of twenty-seven large-scale beam specimens and ten large-scale column specimens. High performance grout for post-tensioning tendon injection was also developed through a series of fresh property tests, accelerated exposure tests, and a large-scale pumping test to simulate field conditions. A high performance fly ash grout was developed for applications with small vertical rises, and a high performance anti-bleed grout was developed for applications involving large vertical rises such as tall bridge piers. Long-term exposure testing of the beam and column specimens is ongoing, but preliminary findings indicate increased corrosion protection with increasing levels of post-tensioning, although traditional

  11. Methods and Results of a Search for Gravitational Waves Associated with Gamma-Ray Bursts Using the GEO 600, LIGO, and Virgo Detectors

    NASA Technical Reports Server (NTRS)

    Aasi, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Blackburn, Lindy L.; Camp, Jordan B.; Gehrels, N.; Graff, P. B.; Slutsky, J. P.

    2013-01-01

    In this paper we report on a search for short-duration gravitational wave bursts in the frequency range 64 Hz-1792 Hz associated with gamma-ray bursts (GRBs), using data from GEO600 and one of the LIGO or Virgo detectors. We introduce the method of a linear search grid to analyze GRB events with large sky localization uncertainties such as the localizations provided by the Fermi Gamma-ray Burst Monitor (GBM). Coherent searches for gravitational waves (GWs) can be computationally intensive when the GRB sky position is not well-localized, due to the corrections required for the difference in arrival time between detectors. Using a linear search grid we are able to reduce the computational cost of the analysis by a factor of O(10) for GBM events. Furthermore, we demonstrate that our analysis pipeline can improve upon the sky localization of GRBs detected by the GBM, if a high-frequency GW signal is observed in coincidence. We use the linear search grid method in a search for GWs associated with 129 GRBs observed satellite-based gamma-ray experiments between 2006 and 2011. The GRBs in our sample had not been previously analyzed for GW counterparts. A fraction of our GRB events are analyzed using data from GEO600 while the detector was using squeezed-light states to improve its sensitivity; this is the first search for GWs using data from a squeezed-light interferometric observatory. We find no evidence for GW signals, either with any individual GRB in this sample or with the population as a whole. For each GRB we place lower bounds on the distance to the progenitor, assuming a fixed GW emission energy of 10(exp -2)Stellar Mass sq c, with a median exclusion distance of 0.8 Mpc for emission at 500 Hz and 0.3 Mpc at 1 kHz. The reduced computational cost associated with a linear search grid will enable rapid searches for GWs associated with Fermi GBM events in the Advanced detector era.

  12. The Evolution of Stellar Populations

    NASA Astrophysics Data System (ADS)

    DÍaz, Angeles I.; Hardy, Eduardo

    We summarize the discussion section on `Evolution of Stellar Populations' we led on May 27, 2000 in Granada, Spain, as part of the Euroconference on The Evolution of Galaxies. I- Observational Clues. The discussion was organized around two groups of topics. In the first, Population Synthesis, the accent was partially placed on the use of tools and techniques centered around the question of the unicity of the models, their sensitivity to input and the question of the age-metallicity degeneracy. In the second group, Stellar Systems a stronger accent was placed on astrophysical questions, although we included there the need for `truth tests' that apply spectral synthesis techniques to objects for which there is detailed a priori knowledge of their stellar populations. We also provide a partial comparison between the present knowledge of these topics and that which existed at the time of the Crete Conference of 1995.

  13. Stellar Alignments - Identification and Analysis

    NASA Astrophysics Data System (ADS)

    Ruggles, Clive L. N.

    Fortuitous stellar alignments can be fitted to structural orientations with relative ease by the unwary. Nonetheless, cautious approaches taking into account a broader range of cultural evidence, as well as paying due attention to potential methodological pitfalls, have been successful in identifying credible stellar alignments—and constructing plausible assessments of their cultural significance—in a variety of circumstances. These range from single instances of alignments upon particular asterisms where the corroborating historical or ethnographic evidence is strong to repeated instances of oriented structures with only limited independent cultural information but where systematic, data-driven approaches can be productive. In the majority of cases, the identification and interpretation of putative stellar alignments relates to groups of similar monuments or complex single sites and involves a balance between systematic studies of the alignments themselves, backed up by statistical analysis where appropriate, and the consideration of a range of contextual evidence, either derived from the archaeological record alone or from other relevant sources.

  14. Stellar Explosions: Hydrodynamics and Nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Jose, Jordi

    2016-01-01

    Stars are the main factories of element production in the universe through a suite of complex and intertwined physical processes. Such stellar alchemy is driven by multiple nuclear interactions that through eons have transformed the pristine, metal-poor ashes leftover by the Big Bang into a cosmos with 100 distinct chemical species. The products of stellar nucleosynthesis frequently get mixed inside stars by convective transport or through hydrodynamic instabilities, and a fraction of them is eventually ejected into the interstellar medium, thus polluting the cosmos with gas and dust. The study of the physics of the stars and their role as nucleosynthesis factories owes much to cross-fertilization of different, somehow disconnected fields, ranging from observational astronomy, computational astrophysics, and cosmochemistry to experimental and theoretical nuclear physics. Few books have simultaneously addressed the multidisciplinary nature of this field in an engaging way suitable for students and young scientists. Providing the required multidisciplinary background in a coherent way has been the driving force for Stellar Explosions: Hydrodynamics and Nucleosynthesis. Written by a specialist in stellar astrophysics, this book presents a rigorous but accessible treatment of the physics of stellar explosions from a multidisciplinary perspective at the crossroads of computational astrophysics, observational astronomy, cosmochemistry, and nuclear physics. Basic concepts from all these different fields are applied to the study of classical and recurrent novae, type I and II supernovae, X-ray bursts and superbursts, and stellar mergers. The book shows how a multidisciplinary approach has been instrumental in our understanding of nucleosynthesis in stars, particularly during explosive events.

  15. Stellar Explosions: Hydrodynamics and Nucleosynthesis

    NASA Astrophysics Data System (ADS)

    José, Jordi

    2015-12-01

    Stars are the main factories of element production in the universe through a suite of complex and intertwined physical processes. Such stellar alchemy is driven by multiple nuclear interactions that through eons have transformed the pristine, metal-poor ashes leftover by the Big Bang into a cosmos with 100 distinct chemical species. The products of stellar nucleosynthesis frequently get mixed inside stars by convective transport or through hydrodynamic instabilities, and a fraction of them is eventually ejected into the interstellar medium, thus polluting the cosmos with gas and dust. The study of the physics of the stars and their role as nucleosynthesis factories owes much to cross-fertilization of different, somehow disconnected fields, ranging from observational astronomy, computational astrophysics, and cosmochemistry to experimental and theoretical nuclear physics. Few books have simultaneously addressed the multidisciplinary nature of this field in an engaging way suitable for students and young scientists. Providing the required multidisciplinary background in a coherent way has been the driving force for Stellar Explosions: Hydrodynamics and Nucleosynthesis. Written by a specialist in stellar astrophysics, this book presents a rigorous but accessible treatment of the physics of stellar explosions from a multidisciplinary perspective at the crossroads of computational astrophysics, observational astronomy, cosmochemistry, and nuclear physics. Basic concepts from all these different fields are applied to the study of classical and recurrent novae, type I and II supernovae, X-ray bursts and superbursts, and stellar mergers. The book shows how a multidisciplinary approach has been instrumental in our understanding of nucleosynthesis in stars, particularly during explosive events.

  16. A box full of chocolates: The rich structure of the nearby stellar halo revealed by Gaia and RAVE

    NASA Astrophysics Data System (ADS)

    Helmi, Amina; Veljanoski, Jovan; Breddels, Maarten A.; Tian, Hao; Sales, Laura V.

    2017-01-01

    Context. The hierarchical structure formation model predicts that stellar halos should form, at least partly, via mergers. If this was a predominant formation channel for the Milky Way's halo, imprints of this merger history in the form of moving groups or streams should also exist in the vicinity of the Sun. Aims: We study the kinematics of halo stars in the Solar neighbourhood using the very recent first data release from the Gaia mission, and in particular the TGAS dataset, in combination with data from the RAVE survey. Our aim is to determine the amount of substructure present in the phase-space distribution of halo stars that could be linked to merger debris. Methods: To characterise kinematic substructure, we measured the velocity correlation function in our sample of halo (low-metallicity) stars. We also studied the distribution of these stars in the space of energy and two components of the angular momentum, in what we call "integrals of motion" space. Results: The velocity correlation function reveals substructure in the form of an excess of pairs of stars with similar velocities, well above that expected for a smooth distribution. Comparison to cosmological simulations of the formation of stellar halos indicates that the levels found are consistent with the Galactic halo having been built solely via accretion. Similarly, the distribution of stars in the space of integrals of motion is highly complex. A strikingly high fraction (from 58% up to more than 73%) of the stars that are somewhat less bound than the Sun are on (highly) retrograde orbits. A simple comparison to Milky Way-mass galaxies in cosmological hydrodynamical simulations suggests that less than 1% have such prominently retrograde outer halos. We also identify several other statistically significant structures in integrals of motion space that could potentially be related to merger events.

  17. GRAVITATIONAL WAVES FROM STELLAR COLLAPSE

    SciTech Connect

    C. L. FRYER

    2001-01-01

    Stellar core-collapse plays an important role in nearly all facets of astronomy: cosmology (as standard candles), formation of compact objects, nucleosynthesis and energy deposition in galaxies. In addition, they release energy in powerful explosions of light over a range of energies, neutrinos, and the subject of this meeting, gravitational waves. Because of this broad range of importance, astronomers have discovered a number of constraints which can be used to help them understand the importance of stellar core-collapse as gravitational wave sources.

  18. Transonic canards and stellar wind

    NASA Astrophysics Data System (ADS)

    Carter, Paul; Knobloch, Edgar; Wechselberger, Martin

    2017-03-01

    Parker’s classical stellar wind solution [20] describing steady spherically symmetric outflow from the surface of a star is revisited. Viscous dissipation is retained. The resulting system of equations has slow-fast structure and is amenable to analysis using geometric singular perturbation theory. This technique leads to a reinterpretation of the sonic point as a folded saddle and the identification of shock solutions as canard trajectories in space [22]. The results shed light on the location of the shock and its sensitivity to the system parameters. The related spherically symmetric stellar accretion solution of Bondi [4] is described by the same theory.

  19. Hughes, Rosner, Weiss: Stellar MHD: Magnetohydrodynamics of stellar interiors

    NASA Astrophysics Data System (ADS)

    Hughes, David; Rosner, Robert; Weiss, Nigel

    2005-08-01

    David Hughes, Robert Rosner and Nigel Weiss describe what was achieved during a programme on stellar magnetic fields at the Isaac Newton Institute in Cambridge. Over a four-month period more than 90 participants visited the Institute for a mixture of structured workshops and informal collaboration.

  20. Deriving stellar inclination of slow rotators using stellar activity

    SciTech Connect

    Dumusque, X.

    2014-12-01

    Stellar inclination is an important parameter for many astrophysical studies. Although different techniques allow us to estimate stellar inclination for fast rotators, it becomes much more difficult when stars are rotating slower than ∼2-2.5 km s{sup –1}. By using the new activity simulation SOAP 2.0 which can reproduce the photometric and spectroscopic variations induced by stellar activity, we are able to fit observations of solar-type stars and derive their inclination. For HD 189733, we estimate the stellar inclination to be i=84{sub −20}{sup +6} deg, which implies a star-planet obliquity of ψ=4{sub −4}{sup +18} considering previous measurements of the spin-orbit angle. For α Cen B, we derive an inclination of i=45{sub −19}{sup +9}, which implies that the rotational spin of the star is not aligned with the orbital spin of the α Cen binary system. In addition, assuming that α Cen Bb is aligned with its host star, no transit would occur. The inclination of α Cen B can be measured using 40 radial-velocity measurements, which is remarkable given that the projected rotational velocity of the star is smaller than 1.15 km s{sup –1}.

  1. The Herschel Virgo Cluster Survey. XVII. SPIRE point-source catalogs and number counts

    NASA Astrophysics Data System (ADS)

    Pappalardo, Ciro; Bendo, George J.; Bianchi, Simone; Hunt, Leslie; Zibetti, Stefano; Corbelli, Edvige; di Serego Alighieri, Sperello; Grossi, Marco; Davies, Jonathan; Baes, Maarten; De Looze, Ilse; Fritz, Jacopo; Pohlen, Michael; Smith, Matthew W. L.; Verstappen, Joris; Boquien, Médéric; Boselli, Alessandro; Cortese, Luca; Hughes, Thomas; Viaene, Sebastien; Bizzocchi, Luca; Clemens, Marcel

    2015-01-01

    Aims: We present three independent catalogs of point-sources extracted from SPIRE images at 250, 350, and 500 μm, acquired with the Herschel Space Observatory as a part of the Herschel Virgo Cluster Survey (HeViCS). The catalogs have been cross-correlated to consistently extract the photometry at SPIRE wavelengths for each object. Methods: Sources have been detected using an iterative loop. The source positions are determined by estimating the likelihood to be a real source for each peak on the maps, according to the criterion defined in the sourceExtractorSussextractor task. The flux densities are estimated using the sourceExtractorTimeline, a timeline-based point source fitter that also determines the fitting procedure with the width of the Gaussian that best reproduces the source considered. Afterwards, each source is subtracted from the maps, removing a Gaussian function in every position with the full width half maximum equal to that estimated in sourceExtractorTimeline. This procedure improves the robustness of our algorithm in terms of source identification. We calculate the completeness and the flux accuracy by injecting artificial sources in the timeline and es