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Sample records for luminous galaxy cluster

  1. Galaxy Clustering Around Nearby Luminous Quasars

    NASA Technical Reports Server (NTRS)

    Fisher, Karl B.; Bahcall, John N.; Kirhakos, Sofia; Schneider, Donald P.

    1996-01-01

    We examine the clustering of galaxies around a sample of 20 luminous low redshift (z approx. less than 0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope (HST). The HST resolution makes possible galaxy identification brighter than V = 24.5 and as close as 1 min or 2 min to the quasar. We find a significant enhancement of galaxies within a projected separation of approx. less than 100 1/h kpc of the quasars. If we model the QSO/galaxy correlation function as a power law with a slope given by the galaxy/galaxy correlation function, we find that the ratio of the QSO/galaxy to galaxy/galaxy correlation functions is 3.8 +/- 0.8. The galaxy counts within r less than 15 1/h kpc of the quasars are too high for the density profile to have an appreciable core radius (approx. greater than 100 1/h kpc). Our results reinforce the idea that low redshift quasars are located preferentially in groups of 10-20 galaxies rather than in rich clusters. We see no significant difference in the clustering amplitudes derived from radio-loud and radio-quiet subsamples.

  2. MODELING THE VERY SMALL SCALE CLUSTERING OF LUMINOUS RED GALAXIES

    SciTech Connect

    Watson, Douglas F.; Berlind, Andreas A.; McBride, Cameron K.; Masjedi, Morad

    2010-01-20

    We model the small-scale clustering of luminous red galaxies (LRGs) in the Sloan Digital Sky Survey. Specifically, we use the halo occupation distribution formalism to model the projected two-point correlation function of LRGs on scales well within the sizes of their host halos (0.016 h {sup -1} Mpc <= r <= 0.42 h {sup -1} Mpc). We start by varying P(N|M), the probability distribution that a dark matter halo of mass M contains N LRGs, and assuming that the radial distribution of satellite LRGs within halos traces the Navarro-Frenk-White (NFW) dark matter density profile. We find that varying P(N|M) alone is not sufficient to match the small-scale data. We next allow the concentration of satellite LRG galaxies to differ from that of dark matter and find that this is also not sufficient. Finally, we relax the assumption of an NFW profile and allow the inner slope of the density profile to vary. We find that this model provides a good fit to the data and the resulting value of the slope is -2.17 +- 0.12. The radial density profile of satellite LRGs within halos is thus not compatible with that of the underlying dark matter, but rather is closer to an isothermal distribution.

  3. The Milky Way's Most Luminous Star Clusters: Engines of Galaxy Evolution

    NASA Astrophysics Data System (ADS)

    Rahman, Mubdi; Matzner, C. D.; Moon, D.

    2012-01-01

    Massive young star clusters and OB associations (M > 104 Msun) dominate the energetic feedback from stars into the interstellar medium. They contain the most massive and luminous stars in the Galaxy, which shape their environments through winds, ionizing flux, radiation pressure, and eventually supernovae, destroying their natal molecular clouds and inflating superbubbles. Few such clusters have been identified in our Galaxy. We systematically investigate the most luminous H II regions, which we identify using the WMAP foreground maps. We find that the 13 most luminous sources produce one-third of the Galaxy's total ionizing luminosity, all with expected powering populations of M > 4×104 Msun. These populations are grouped in small numbers of clusters or associations for each WMAP source. The emission from these regions is dominated by the diffuse component at large radii ( 10-70 pc) indicating a high leaking fraction of ionizing photons. Using 8 micron maps from Spitzer GLIMPSE and published radio recombination line observations, we resolve the large (>1°) WMAP sources into 40 star forming complexes (SFCs) exhibiting shell morphology with evidence of expansion due to a central powering source. We develop a method, based on differential extinction of the galactic disk, to identify the SFC's powering cluster candidates with 2MASS. We identify 25 candidate clusters within the 40 SFCs having extinctions consistent with their distances. With near-infrared spectroscopy from the New Technology Telescope, we have confirmed the existence of the most massive of these associations, the Dragonfish Association, with M = 105 Msun. Of the 50 sampled stars, we identify 2 Luminous Blue Variable candidates, a Wolf-Rayet, and 15 O-type stars, consistent with the yield expected from the candidate contamination rate, verifying the candidate cluster identification method. This investigation produces the most complete picture of the upper-end of the Galaxy's cluster mass function to

  4. A massive, cooling-flow-induced starburst in the core of a luminous cluster of galaxies.

    PubMed

    McDonald, M; Bayliss, M; Benson, B A; Foley, R J; Ruel, J; Sullivan, P; Veilleux, S; Aird, K A; Ashby, M L N; Bautz, M; Bazin, G; Bleem, L E; Brodwin, M; Carlstrom, J E; Chang, C L; Cho, H M; Clocchiatti, A; Crawford, T M; Crites, A T; de Haan, T; Desai, S; Dobbs, M A; Dudley, J P; Egami, E; Forman, W R; Garmire, G P; George, E M; Gladders, M D; Gonzalez, A H; Halverson, N W; Harrington, N L; High, F W; Holder, G P; Holzapfel, W L; Hoover, S; Hrubes, J D; Jones, C; Joy, M; Keisler, R; Knox, L; Lee, A T; Leitch, E M; Liu, J; Lueker, M; Luong-Van, D; Mantz, A; Marrone, D P; McMahon, J J; Mehl, J; Meyer, S S; Miller, E D; Mocanu, L; Mohr, J J; Montroy, T E; Murray, S S; Natoli, T; Padin, S; Plagge, T; Pryke, C; Rawle, T D; Reichardt, C L; Rest, A; Rex, M; Ruhl, J E; Saliwanchik, B R; Saro, A; Sayre, J T; Schaffer, K K; Shaw, L; Shirokoff, E; Simcoe, R; Song, J; Spieler, H G; Stalder, B; Staniszewski, Z; Stark, A A; Story, K; Stubbs, C W; Suhada, R; van Engelen, A; Vanderlinde, K; Vieira, J D; Vikhlinin, A; Williamson, R; Zahn, O; Zenteno, A

    2012-08-16

    In the cores of some clusters of galaxies the hot intracluster plasma is dense enough that it should cool radiatively in the cluster's lifetime, leading to continuous 'cooling flows' of gas sinking towards the cluster centre, yet no such cooling flow has been observed. The low observed star-formation rates and cool gas masses for these 'cool-core' clusters suggest that much of the cooling must be offset by feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical and infrared observations of the galaxy cluster SPT-CLJ2344-4243 (ref. 11) at redshift z = 0.596. These observations reveal an exceptionally luminous (8.2 × 10(45) erg s(-1)) galaxy cluster that hosts an extremely strong cooling flow (around 3,820 solar masses a year). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (formation of around 740 solar masses a year), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool-core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star-formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form through accretion of the intracluster medium, rather than (as is currently thought) assembling entirely via mergers. PMID:22895340

  5. A massive, cooling-flow-induced starburst in the core of a luminous cluster of galaxies

    NASA Astrophysics Data System (ADS)

    McDonald, M.; Bayliss, M.; Benson, B. A.; Foley, R. J.; Ruel, J.; Sullivan, P.; Veilleux, S.; Aird, K. A.; Ashby, M. L. N.; Bautz, M.; Bazin, G.; Bleem, L. E.; Brodwin, M.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.; Clocchiatti, A.; Crawford, T. M.; Crites, A. T.; de Haan, T.; Desai, S.; Dobbs, M. A.; Dudley, J. P.; Egami, E.; Forman, W. R.; Garmire, G. P.; George, E. M.; Gladders, M. D.; Gonzalez, A. H.; Halverson, N. W.; Harrington, N. L.; High, F. W.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hrubes, J. D.; Jones, C.; Joy, M.; Keisler, R.; Knox, L.; Lee, A. T.; Leitch, E. M.; Liu, J.; Lueker, M.; Luong-van, D.; Mantz, A.; Marrone, D. P.; McMahon, J. J.; Mehl, J.; Meyer, S. S.; Miller, E. D.; Mocanu, L.; Mohr, J. J.; Montroy, T. E.; Murray, S. S.; Natoli, T.; Padin, S.; Plagge, T.; Pryke, C.; Rawle, T. D.; Reichardt, C. L.; Rest, A.; Rex, M.; Ruhl, J. E.; Saliwanchik, B. R.; Saro, A.; Sayre, J. T.; Schaffer, K. K.; Shaw, L.; Shirokoff, E.; Simcoe, R.; Song, J.; Spieler, H. G.; Stalder, B.; Staniszewski, Z.; Stark, A. A.; Story, K.; Stubbs, C. W.; Šuhada, R.; van Engelen, A.; Vanderlinde, K.; Vieira, J. D.; Vikhlinin, A.; Williamson, R.; Zahn, O.; Zenteno, A.

    2012-08-01

    In the cores of some clusters of galaxies the hot intracluster plasma is dense enough that it should cool radiatively in the cluster's lifetime, leading to continuous `cooling flows' of gas sinking towards the cluster centre, yet no such cooling flow has been observed. The low observed star-formation rates and cool gas masses for these `cool-core' clusters suggest that much of the cooling must be offset by feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical and infrared observations of the galaxy cluster SPT-CLJ2344-4243 (ref. 11) at redshift z = 0.596. These observations reveal an exceptionally luminous (8.2 × 1045 erg s-1) galaxy cluster that hosts an extremely strong cooling flow (around 3,820 solar masses a year). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (formation of around 740 solar masses a year), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool-core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star-formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form through accretion of the intracluster medium, rather than (as is currently thought) assembling entirely via mergers.

  6. A Study of Four distant, Extremely X-Ray Luminous Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Tucker, Wallace

    1999-01-01

    We identified the extended Einstein IPC X-ray source 1 E 0657-56 with a previously unknown cluster of galaxies at a redshift of z = 0.296. Optical CCD images show the presence of a gravitational arc in this cluster, and galaxy spectra yield a cluster velocity dispersion of 1213(exp +352) - 191 km/s. X-ray data obtained with the ROSAT HRI and ASCA indicate that 1E 0657-56 is a highly luminous cluster in which a merger of subclusters may be occurring. The temperature of the hot gas in 1E 0657-56 is kT = l7.4 +/- 2.5 (keV) , which makes it an unusually hot cluster, with important cosmological implications. Follow-up work with optical, radio and X-ray telescopes is in progress.

  7. The Fate of Luminous Compact Blue Galaxies: Identification of Cluster LCBGs

    NASA Astrophysics Data System (ADS)

    Crawford, S. M.; Bershady, M. A.; Glenn, A. D.; Hoessel, J. G.

    2004-12-01

    Luminous Compact Blue Galaxies (LCBGs) appear to form a link between local, low mass HII galaxies and high-z, high luminosity Lyman Break Galaxies. Accounting for the majority of the star formation at intermediate redshifts (0.3 < z < 0.9), they represent a dominant phase of galaxy evolution; yet the identity of their present-day counterparts is an open question. We have undertaken a major survey of intermediate redshift galaxy clusters in search of LCBGs in order to connect this population of small, but powerful star forming galaxies to their present-day descendants through the morphology-density relationship. In this paper, we present the identification of LCBGs in two galaxy clusters, MS0451-0305 (z=0.538) and CL1604+4304 (z=0.90), and compare the photometric characteristics of cluster LCBGs to field LCBGs and other galaxy types. The LCBGs are identified through their broad and narrow band colors measured from deep imaging with the Mini-Mosaic camera on the WIYN 3.5m telescope. We use photometric redshifts and rest-frame [OII] λ 3727 emission in the narrow band images to identify star-burst galaxies associated with each galaxy clusters. LCBGs are too small for any detailed structural analysis from ground-based data, therefore we derived photometric characteristics (size, surface brightness, concentration, ellipticity, and asymmetry) from Archive HST WFPC2 and ACS imaging of the clusters. This work was supported by HST Archive grant #9917, NSF / AST-0307417, and an award from the Wisconsin Space Grant Corporation.

  8. Sloshing Gas in the Core of the Most Luminous Galaxy Cluster RXJ1347.5-1145

    NASA Technical Reports Server (NTRS)

    Markevitch, Maxim; Giacintucci, S.; Dallacasa, D.; Venturi, T.; Brunetti, G.; Cassano, R.; Athreya, R. M.; Johnson, Ryan E.; Zuhone, John; Jones, Christine; Forman, William R.

    2011-01-01

    We present new constraints on the merger history of the most X-ray luminous cluster of galaxies, RXJ1347.5-1145, based its unique multiwavelength morphology. Our X-ray analysis confirms the core gas is undergoing "sloshing" resulting from a prior, large scale, gravitational perturbation. In combination with extensive multiwavelength observations, the sloshing gas points to the primary and secondary clusters having had at least two prior strong gravitational interactions. The evidence supports a model in which the secondary subcluster with mass M=4.8+/-2.4 x 10(exp 14) Stellar Mass has previously (> or approx.=0.6 Gyr ago) passed by the primary cluster, and has now returned for a subsequent crossing where the subcluster's gas has been completely stripped from its dark matter halo. RXJ1347 is a prime example of how core gas sloshing may be used to constrain the merger histories of galaxy clusters through multiwavelength analyses.

  9. Sloshing Gas in the Core of the Most Luminous Galaxy Cluster RXJ1347.5-1145

    NASA Technical Reports Server (NTRS)

    Johnson, Ryan E.; Zuhone, John; Jones, Christine; Forman, William R.; Markevitvh, Maxim

    2011-01-01

    We present new constraints on the merger history of the most X-ray luminous cluster of galaxies, RXJ1347.5-1145, based on its unique multiwavelength morphology. Our X-ray analysis confirms the core gas is undergoing "sloshing" resulting from a prior, large scale, gravitational perturbation. In combination with extensive multiwavelength observations, the sloshing gas points to the primary and secondary clusters having had at least two prior strong gravitational interactions. The evidence supports a model in which the secondary subcluster with mass M=4.8+/-2.4x10(exp 14) solar Mass has previously (> or approx.0.6 Gyr ago) passed by the primary cluster, and has now returned for a subsequent crossing where the subcluster's gas has been completely stripped from its dark matter halo. RXJ1347 is a prime example of how core gas sloshing may be used to constrain the merger histories of galaxy clusters through multiwavelength analyses.

  10. SLOSHING GAS IN THE CORE OF THE MOST LUMINOUS GALAXY CLUSTER RXJ1347.5-1145

    SciTech Connect

    Johnson, Ryan E.; Zuhone, John; Jones, Christine; Forman, William R.; Markevitch, Maxim E-mail: cjf@cfa.harvard.edu E-mail: jzuhone@cfa.harvard.edu

    2012-06-01

    We present new constraints on the merger history of the most X-ray luminous cluster of galaxies, RXJ1347.5-1145, based on its unique multiwavelength morphology. Our X-ray analysis confirms that the core gas is undergoing 'sloshing' resulting from a prior, large-scale, gravitational perturbation. In combination with multiwavelength observations, the sloshing gas points to the primary and secondary clusters having had at least two prior strong gravitational interactions. The evidence supports a model in which the secondary subcluster with mass M = 4.8 {+-} 2.4 Multiplication-Sign 10{sup 14} M{sub Sun} has previously ({approx}>0.6 Gyr ago) passed by the primary cluster, and has now returned for a subsequent crossing where the subcluster's gas has been completely stripped from its dark matter halo. RXJ1347 is a prime example of how core gas sloshing may be used to constrain the merger histories of galaxy clusters through multiwavelength analyses.

  11. Luminous red galaxies in clusters: central occupation, spatial distributions and miscentring

    NASA Astrophysics Data System (ADS)

    Hoshino, Hanako; Leauthaud, Alexie; Lackner, Claire; Hikage, Chiaki; Rozo, Eduardo; Rykoff, Eli; Mandelbaum, Rachel; More, Surhud; More, Anupreeta; Saito, Shun; Vulcani, Benedetta

    2015-09-01

    Luminous red galaxies (LRG) from the Sloan Digital Sky Survey are among the best understood samples of galaxies and are employed in a broad range of cosmological studies. In this paper, we study how LRGs occupy massive haloes via counts in clusters and reveal several unexpected trends. Using the red-sequence Matched-filter Probabilistic Percolation (redMaPPer) cluster catalogue, we derive the central occupation of LRGs as a function richness. We show that clusters contain a significantly lower fraction of central LRGs than predicted from the two-point correlation function. At halo masses of 1014.5 M⊙, we find Ncen = 0.73 compared to Ncen = 0.89 from correlation studies. Our central occupation function for LRGs converges to 0.95 at large halo masses. A strong anticorrelation between central luminosity and cluster mass at fixed richness is required to reconcile our results with those based on clustering studies. We derive the probability that the brightest cluster member is not the central galaxy. We find PBNC ≈ 20-30 per cent which is a factor of ˜2 lower than the value found by Skibba et al. Finally, we study the radial offsets of bright non-central LRGs from cluster centres and show that bright non-central LRGs follow a different radial distribution compared to red cluster members. This work demonstrates that even the most massive clusters do not always have an LRG at the centre, and that the brightest galaxy in a cluster is not always the central galaxy.

  12. Spectroscopy of Luminous Compact Blue Galaxies in Distant Clusters. I. Spectroscopic Data

    NASA Astrophysics Data System (ADS)

    Crawford, Steven M.; Wirth, Gregory D.; Bershady, Matthew A.; Hon, Kimo

    2011-11-01

    We used the DEIMOS spectrograph on the Keck II Telescope to obtain spectra of galaxies in the fields of five distant, rich galaxy clusters over the redshift range 0.5 < z < 0.9 in a search for luminous compact blue galaxies (LCBGs). Unlike traditional studies of galaxy clusters, we preferentially targeted blue cluster members identified via multi-band photometric pre-selection based on imaging data from the WIYN telescope. Of the 1288 sources that we targeted, we determined secure spectroscopic redshifts for 848 sources, yielding a total success rate of 66%. Our redshift measurements are in good agreement with those previously reported in the literature, except for 11 targets which we believe were previously in error. Within our sample, we confirm the presence of 53 LCBGs in the five galaxy clusters. The clusters all stand out as distinct peaks in the redshift distribution of LCBGs with the average number density of LCBGs ranging from 1.65 ± 0.25 Mpc-3 at z = 0.55 to 3.13 ± 0.65 Mpc-3 at z = 0.8. The number density of LCBGs in clusters exceeds the field density by a factor of 749 ± 116 at z = 0.55; at z = 0.8, the corresponding ratio is E = 416 ± 95. At z = 0.55, this enhancement is well above that seen for blue galaxies or the overall cluster population, indicating that LCBGs are preferentially triggered in high-density environments at intermediate redshifts. Based in part on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

  13. LUMINOUS X-RAY ACTIVE GALACTIC NUCLEI IN CLUSTERS OF GALAXIES

    SciTech Connect

    Koulouridis, E.; Plionis, M.

    2010-05-10

    We present a study of X-ray active galactic nucleus (AGN) overdensities in 16 Abell clusters, within the redshift range 0.073 < z < 0.279, in order to investigate the effect of the hot inter-cluster environment on the triggering of the AGN phenomenon. The X-ray AGN overdensities, with respect to the field expectations, were estimated for sources with L{sub x} {>=} 10{sup 42} erg s{sup -1} (at the redshift of the clusters) and within an area of 1 h {sup -1} {sub 72} Mpc radius (excluding the core). To investigate the presence or absence of a true enhancement of luminous X-ray AGNs in the cluster area, we also derived the corresponding optical galaxy overdensities, using a suitable range of r-band magnitudes. We always find the latter to be significantly higher (and only in two cases roughly equal) with respect to the corresponding X-ray overdensities. Over the whole cluster sample, the mean X-ray point-source overdensity is a factor of {approx}4 less than that corresponding to bright optical galaxies, a difference which is significant at a >0.995 level, as indicated by an appropriate student's t-test. We conclude that the triggering of luminous X-ray AGNs in rich clusters is strongly suppressed. Furthermore, searching for optical Sloan Digital Sky Survey counterparts of all the X-ray sources, associated with our clusters, we found that about half appear to be background QSOs, while others are background and foreground AGNs or stars. The true overdensity of X-ray point sources, associated with the clusters, is therefore even smaller than what our statistical approach revealed.

  14. A New Measurement of the Bulk Flow of X-Ray Luminous Clusters of Galaxies

    NASA Technical Reports Server (NTRS)

    Kashlinsky, A.; Atrio-Barandela, F.; Ebeling, H.; Edge, A.; Kocevski, D.

    2010-01-01

    We present new measurements of the large-scale bulk flows of galaxy clusters based on five-year WMAP data and a significantly expanded X-ray cluster catalog. Our method probes the flow via measurements of the kinematic Sunyaev-Zel'dovich (SZ) effect produced by the hot gas in moving clusters. It computes the dipole in the cosmic microwave background data at cluster pixels, which preserves the SZ component while integrating down other contributions. Our improved catalog of over 1000 clusters enables us to further investigate possible systematic effects and, thanks to a higher median cluster redshift, allows us to measure the bulk flow to larger scales. We present a corrected error treatment and demonstrate that the more X-ray luminous clusters, while fewer in number, have much larger optical depth, resulting in a higher dipole and thus a more accurate flow measurement. This results in the observed correlation of the dipole derived at the aperture of zero monopole with the monopole measured over the cluster central regions. This correlation is expected if the dipole is produced by the SZ effect and cannot be caused by unidentified systematics (or primary cosmic microwave background anisotropies). We measure that the flow is consistent with approximately constant velocity out to at least [similar, equals]800 Mpc. The significance of the measured signal peaks around 500 h -1 70 Mpc, most likely because the contribution from more distant clusters becomes progressively more diluted by the WMAP beam. However, at present, we cannot rule out that these more distant clusters simply contribute less to the overall motion.

  15. Studying Cosmic Evolution with the XMM-Newton Distant Cluster Project: X-ray Luminous Galaxy Clusters at z>~1 and their Galaxy Populations

    NASA Astrophysics Data System (ADS)

    Fassbender, Rene

    2008-06-01

    Investigating X-ray luminous galaxy clusters at z>~1 provides a fundamental constraint on evolutionary studies of the largest virialized structures in the Universe, the baryonic matter in form of the hot ICM, their galaxy populations, and the effects of Dark Energy. The main aim of this work is to establish the observational foundation for the XMM-Newton Distant Cluster Project (XDCP). This new serendipitous survey is focused on the most distant systems at z>1, based on the selection of extended X-ray sources, their identification as clusters via two-band imaging, and their final spectroscopic confirmation. Almost 1000 extended sources were selected as cluster candidates from the analysis of 80 deg^2 of deep XMM-Newton archival data, of which 75% could be readily identified as systems at z<~0.6. For the remaining 250 distant cluster candidates a new strategy for their confirmation and redshift estimates was adopted, based on Z- and H-band photometry and the observed Z-H red-sequence color of early-type cluster galaxies. From observations of 25% of the sample, more than 20 X-ray clusters were discovered at a photometric redshift of z>~0.9. The new Z-H method has allowed a cluster sample study over an unprecedented redshift baseline of 0.2<~z<~1.5. From a comparison of the observed color evolution of the red-sequence with model predictions, the formation epoch of early-type galaxies could be constrained as z_f=4.2+-1.1, confirming their well-established old age. The preliminary investigation of the H-band luminosity evolution of 63 BCGs provides for the first time direct observational indications that the most massive cluster galaxies have doubled their stellar mass since z~1.5. The finding that BCGs were assembled in the last 9Gyr is now in qualitative agreement with the latest simulations.

  16. CLUSTERING OF SLOAN DIGITAL SKY SURVEY III PHOTOMETRIC LUMINOUS GALAXIES: THE MEASUREMENT, SYSTEMATICS, AND COSMOLOGICAL IMPLICATIONS

    SciTech Connect

    Ho, Shirley; White, Martin; Schlegel, David J.; Seljak, Uros; Reid, Beth; Cuesta, Antonio; Padmanabhan, Nikhil; Seo, Hee-Jong; De Putter, Roland; Ross, Ashley J.; Percival, Will J.; Saito, Shun; Schlafly, Eddie; Hernandez-Monteagudo, Carlos; Sanchez, Ariel G.; Blanton, Michael; Skibba, Ramin; Schneider, Don; Mena, Olga; Viel, Matteo; and others

    2012-12-10

    The Sloan Digital Sky Survey (SDSS) surveyed 14,555 deg{sup 2}, and delivered over a trillion pixels of imaging data. We present a study of galaxy clustering using 900,000 luminous galaxies with photometric redshifts, spanning between z = 0.45 and z = 0.65, constructed from the SDSS using methods described in Ross et al. This data set spans 11,000 deg{sup 2} and probes a volume of 3 h {sup -3} Gpc{sup 3}, making it the largest volume ever used for galaxy clustering measurements. We describe in detail the construction of the survey window function and various systematics affecting our measurement. With such a large volume, high-precision cosmological constraints can be obtained given careful control and understanding of the observational systematics. We present a novel treatment of the observational systematics and its applications to the clustering signals from the data set. In this paper, we measure the angular clustering using an optimal quadratic estimator at four redshift slices with an accuracy of {approx}15%, with a bin size of {delta}{sub l} = 10 on scales of the baryon acoustic oscillations (BAOs; at l {approx} 40-400). We also apply corrections to the power spectra due to systematics and derive cosmological constraints using the full shape of the power spectra. For a flat {Lambda}CDM model, when combined with cosmic microwave background Wilkinson Microwave Anisotropy Probe 7 (WMAP7) and H{sub 0} constraints from using 600 Cepheids observed by Wide Field Camera 3 (WFC3; HST), we find {Omega}{sub {Lambda}} = 0.73 {+-} 0.019 and H{sub 0} to be 70.5 {+-} 1.6 s{sup -1} Mpc{sup -1} km. For an open {Lambda}CDM model, when combined with WMAP7 + HST, we find {Omega}{sub K} = 0.0035 {+-} 0.0054, improved over WMAP7+HST alone by 40%. For a wCDM model, when combined with WMAP7+HST+SN, we find w = -1.071 {+-} 0.078, and H{sub 0} to be 71.3 {+-} 1.7 s{sup -1} Mpc{sup -1} km, which is competitive with the latest large-scale structure constraints from large spectroscopic

  17. Clustering of Sloan Digital Sky Survey III Photometric Luminous Galaxies: The Measurement, Systematics, and Cosmological Implications

    NASA Astrophysics Data System (ADS)

    Ho, Shirley; Cuesta, Antonio; Seo, Hee-Jong; de Putter, Roland; Ross, Ashley J.; White, Martin; Padmanabhan, Nikhil; Saito, Shun; Schlegel, David J.; Schlafly, Eddie; Seljak, Uros; Hernández-Monteagudo, Carlos; Sánchez, Ariel G.; Percival, Will J.; Blanton, Michael; Skibba, Ramin; Schneider, Don; Reid, Beth; Mena, Olga; Viel, Matteo; Eisenstein, Daniel J.; Prada, Francisco; Weaver, Benjamin A.; Bahcall, Neta; Bizyaev, Dimitry; Brewinton, Howard; Brinkman, Jon; Nicolaci da Costa, Luiz; Gott, John R.; Malanushenko, Elena; Malanushenko, Viktor; Nichol, Bob; Oravetz, Daniel; Pan, Kaike; Palanque-Delabrouille, Nathalie; Ross, Nicholas P.; Simmons, Audrey; de Simoni, Fernando; Snedden, Stephanie; Yeche, Christophe

    2012-12-01

    The Sloan Digital Sky Survey (SDSS) surveyed 14,555 deg2, and delivered over a trillion pixels of imaging data. We present a study of galaxy clustering using 900,000 luminous galaxies with photometric redshifts, spanning between z = 0.45 and z = 0.65, constructed from the SDSS using methods described in Ross et al. This data set spans 11,000 deg2 and probes a volume of 3 h -3 Gpc3, making it the largest volume ever used for galaxy clustering measurements. We describe in detail the construction of the survey window function and various systematics affecting our measurement. With such a large volume, high-precision cosmological constraints can be obtained given careful control and understanding of the observational systematics. We present a novel treatment of the observational systematics and its applications to the clustering signals from the data set. In this paper, we measure the angular clustering using an optimal quadratic estimator at four redshift slices with an accuracy of ~15%, with a bin size of δ l = 10 on scales of the baryon acoustic oscillations (BAOs; at l ~ 40-400). We also apply corrections to the power spectra due to systematics and derive cosmological constraints using the full shape of the power spectra. For a flat ΛCDM model, when combined with cosmic microwave background Wilkinson Microwave Anisotropy Probe 7 (WMAP7) and H 0 constraints from using 600 Cepheids observed by Wide Field Camera 3 (WFC3; HST), we find ΩΛ = 0.73 ± 0.019 and H 0 to be 70.5 ± 1.6 s-1 Mpc-1 km. For an open ΛCDM model, when combined with WMAP7 + HST, we find Ω K = 0.0035 ± 0.0054, improved over WMAP7+HST alone by 40%. For a wCDM model, when combined with WMAP7+HST+SN, we find w = -1.071 ± 0.078, and H 0 to be 71.3 ± 1.7 s-1 Mpc-1 km, which is competitive with the latest large-scale structure constraints from large spectroscopic surveys such as the SDSS Data Release 7 (DR7) and WiggleZ. We also find that systematic-corrected power spectra give consistent

  18. THE ATACAMA COSMOLOGY TELESCOPE: DETECTION OF SUNYAEV-ZEL'DOVICH DECREMENT IN GROUPS AND CLUSTERS ASSOCIATED WITH LUMINOUS RED GALAXIES

    SciTech Connect

    Hand, Nick; Das, Sudeep; Dunkley, Joanna; Hajian, Amir; Appel, John W.; Essinger-Hileman, Thomas; Fowler, Joseph W.; Hincks, Adam D.; Battaglia, Nick; Richard Bond, J.; Devlin, Mark J.; Klein, Jeff; Duenner, Rolando; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hlozek, Renee; Hughes, John P.; Irwin, Kent D.; Kosowsky, Arthur

    2011-07-20

    We present a detection of the Sunyaev-Zel'dovich (SZ) decrement associated with the luminous red galaxy (LRG) sample of the Sloan Digital Sky Survey. The SZ data come from 148 GHz maps of the equatorial region made by the Atacama Cosmology Telescope. The LRG sample is divided by luminosity into four bins, and estimates for the central SZ temperature decrement are calculated through a stacking process. We detect and account for a bias of the SZ signal due to weak radio sources. We use numerical simulations to relate the observed decrement to Y{sub 200} and clustering properties to relate the galaxy luminosity to halo mass. We also use a relation between brightest cluster galaxy luminosity and cluster mass based on stacked gravitational lensing measurements to estimate the characteristic halo masses. The masses are found to be around 10{sup 14} M{sub sun}.

  19. XMM-Newton analysis of a newly discovered, extremely X-ray luminous galaxy cluster at high redshift

    NASA Astrophysics Data System (ADS)

    Thoelken, S.; Schrabback, T.

    2016-06-01

    Galaxy clusters, the largest virialized structures in the universe, provide an excellent method to test cosmology on large scales. The galaxy cluster mass function as a function of redshift is a key tool to determine the fundamental cosmological parameters and especially measurements at high redshifts can e.g. provide constraints on dark energy. The fgas test as a direct cosmological probe is of special importance. Therefore, relaxed galaxy clusters at high redshifts are needed but these objects are considered to be extremely rare in current structure formation models. Here we present first results from an XMM-Newton analysis of an extremely X-ray luminous, newly discovered and potentially cool core cluster at a redshift of z=0.9. We carefully account for background emission and PSF effects and model the cluster emission in three radial bins. Our preliminary results suggest that this cluster is indeed a good candidate for a cool core cluster and thus potentially of extreme value for cosmology.

  20. Constraints on cold dark matter theories from observations of massive x-ray-luminous clusters of galaxies at high redshift

    NASA Technical Reports Server (NTRS)

    Luppino, G. A.; Gioia, I. M.

    1995-01-01

    During the course of a gravitational lensing survey of distant, X-ray selected Einstein Observatory Extended Medium Sensitivity Survey (EMSS) clusters of galaxies, we have studied six X-ray-luminous (L(sub x) greater than 5 x 10(exp 44)(h(sub 50)(exp -2))ergs/sec) clusters at redshifts exceeding z = 0.5. All of these clusters are apparently massive. In addition to their high X-ray luminosity, two of the clusters at z approximately 0.6 exhibit gravitationally lensed arcs. Furthermore, the highest redshift cluster in our sample, MS 1054-0321 at z = 0.826, is both extremely X-ray luminous (L(sub 0.3-3.5keV)=9.3 x 10(exp 44)(h(sub 50)(exp -2))ergs/sec) and exceedingly rich with an optical richness comparable to an Abell Richness Class 4 cluster. In this Letter, we discuss the cosmological implications of the very existence of these clusters for hierarchical structure formation theories such as standard Omega = 1 CDM (cold dark matter), hybrid Omega = 1 C + HDM (hot dark matter), and flat, low-density Lambda + CDM models.

  1. Studies of Entropy Distributions in X-ray Luminous Clusters of Galaxies

    NASA Astrophysics Data System (ADS)

    Cavagnolo, K. W.; Donahue, M. E.; Voit, G. M.; Sun, M.; Evrard, A. E.

    2005-12-01

    We present entropy distributions for a sample of galaxy clusters from the Chandra public archive, which builds on our previous analysis of nine nearby, bright clusters. By studying the entropy distribution within clusters we quantify the effect of radiative cooling, supernovae feedback, and AGN feedback on cluster properties. This expanded sample contains both cooling flow and non-cooling flow clusters while our previous work focused only on classical cooling flow clusters. We also test the predictions of Mathiesen and Evrard (2001) by checking whether the spectral fit temperature is an unbiased estimate of the mass-weighted temperature, and how this estimate effects the calculation of the intracluster medium mass. Temperature and entropy maps for the clusters in our sample using the Voronoi Tesselation method as employed by Statler et al (in preparation) will also be presented. These maps serve as a prelude to future work in which we will investigate how well such maps may represent the "true" projected quantities of a cluster by comparing deprojected real and simulated clusters from our sample and the Virtual Cluster Exploratory, respectively. Our discussion focuses on tying together feedback mechanisms with the breaking of self-similar relations expected in cluster and galaxy formation models.

  2. The Atacama Cosmology Telescope: Detection or Sunyaev-Zel'Dovich Decrement in Groups and Clusters Associated with Luminous Red Galaxies

    NASA Technical Reports Server (NTRS)

    Hand, Nick; Appel, John William; Battaglia, Nick; Bond, J. Richard; Das, Sudeep; Devlin, Mark J.; Dunkley, Joanna; Dunner, Rolando; Essinger-Hileman, Thomas; Fowler, Joseph W.; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee; Hughes, John P.; Irwin, Kent D.; Klein, Jeff; Kosowsky, Arthur; Lin, Yen-Ting; Marriage, Tobias A.; Marsden, Danica; McLaren, Mike; Wollack, Ed

    2010-01-01

    We present a detection of the Sunyaev-Zel'dovich (SZ) decrement associated with the Luminous Red Galaxy (LRG) sample of the Sloan Digital Sky Survey. The SZ data come from 148 GHz maps of the equatorial region made by the Atacama Cosmology Telescope (ACT). The LRG sample is divided by luminosity into four bins, and estimates for the central Sunyaev-Zel'dovich temperature decrement are calculated through a stacking process. We detect and account for a bias of the SZ signal due to weak radio sources. We use numerical simulations to relate the observed decrement to Y(sub 200) and clustering properties to relate the galaxy luminosity bins to mass. We also use a relation between BCG luminosity and cluster mass based on stacked gravitational lensing measurements to estimate the characteristic halo masses. The masses are found to be in the range approx.10(exp 13) - 10(exp 14)/h Stellar Mass, a lower range than has been previously probed.

  3. Luminous clusters of Wolf-Rayet stars in the SBmIII galaxy NGC 4214

    NASA Technical Reports Server (NTRS)

    Sargent, Wallace L. W.; Filippenko, Alexei V.

    1991-01-01

    Observations are reported of strong broad emission lines attributed to WR stars in the spectra of several bright knots in the nearby Magellanic irregular galaxy NGC 4214 (classified as type SBmIII), in addition to the emission produced by the more prevalent WN stars). Data are presented on measurements of the line fluxes, the line equivalent widths, and continuum flux densities in the four observed knots, showing that the strongest WR lines generally appear in knots having the most luminous stellar continuum. The significance of this observation is discussed.

  4. Colors of Luminous Bulges in Cluster MS 1054-03 and Field Galaxies at Redshifts z~0.83

    NASA Astrophysics Data System (ADS)

    Koo, David C.; Datta, Susmita; Willmer, Christopher N. A.; Simard, Luc; Tran, Kim-Vy; Im, Myungshin

    2005-11-01

    Using Hubble Space Telescope images, we separate the bulgelike (dubbed ``pbulge'') and disklike (``pdisk'') components of 71 galaxies in the rich cluster MS 1054-03 and of 21 in the field. Our key finding is that luminous pbulges are very red, with rest-frame U-B~0.45, while predicted colors are bluer by 0.20 mag. Moreover, these very red colors appear to be independent of environment, pbulge luminosity, pdisk color, and pbulge fraction. These results challenge any model of hierarchical galaxy formation that predicts the colors of distant (z~0.8) luminous field and cluster bulges will differ. Our findings also disagree with other claims that 30% to 50% of bright bulges and elliptical galaxies at z~1 are very blue (U-B<=0). Based on observations obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration; made with the NASA/ESA Hubble Space Telescope, obtained from the data archive 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 and associated with proposals GO-7372, GTO-5090, and GTO-5109.

  5. The distribution of dark and luminous matter in the unique galaxy cluster merger Abell 2146

    NASA Astrophysics Data System (ADS)

    King, Lindsay J.; Clowe, Douglas I.; Coleman, Joseph E.; Russell, Helen R.; Santana, Rebecca; White, Jacob A.; Canning, Rebecca E. A.; Deering, Nicole J.; Fabian, Andrew C.; Lee, Brandyn E.; Li, Baojiu; McNamara, Brian R.

    2016-06-01

    Abell 2146 (z = 0.232) consists of two galaxy clusters undergoing a major merger. The system was discovered in previous work, where two large shock fronts were detected using the Chandra X-ray Observatory, consistent with a merger close to the plane of the sky, caught soon after first core passage. A weak gravitational lensing analysis of the total gravitating mass in the system, using the distorted shapes of distant galaxies seen with Advanced Camera for Surveys - Wide Field Channel on Hubble Space Telescope, is presented. The highest peak in the reconstruction of the projected mass is centred on the brightest cluster galaxy (BCG) in Abell 2146-A. The mass associated with Abell 2146-B is more extended. Bootstrapped noise mass reconstructions show the mass peak in Abell 2146-A to be consistently centred on the BCG. Previous work showed that BCG-A appears to lag behind an X-ray cool core; although the peak of the mass reconstruction is centred on the BCG, it is also consistent with the X-ray peak given the resolution of the weak lensing mass map. The best-fitting mass model with two components centred on the BCGs yields M200 = 1.1^{+0.3}_{-0.4} × 1015 and 3^{+1}_{-2} × 1014 M⊙ for Abell 2146-A and Abell 2146-B, respectively, assuming a mass concentration parameter of c = 3.5 for each cluster. From the weak lensing analysis, Abell 2146-A is the primary halo component, and the origin of the apparent discrepancy with the X-ray analysis where Abell 2146-B is the primary halo is being assessed using simulations of the merger.

  6. AGN feedback in X-ray luminous galaxy cluster: PKS 0745-191

    NASA Astrophysics Data System (ADS)

    Sonkamble, Satish Shripati; Vagshette, Nilkanth Dattatray; Patil, Madhav Khushalrao

    2015-08-01

    We present 117 ks Chandra observation of the cooling flow cluster PKS 0745-191 providing evidence of the strong interaction between the radio source associated with the center dominant galaxy PGC 021813 and the intra-cluster gas. This system is one of the strongest cool core cluster, requiring extreme mechanical feedback from its central AGN to offset cooling of the ICM. This analysis has enabled us to detect two pairs of X-ray cavities in the central ˜ 20 kpc region. In addition to the cavities, we have also evidenced relatively cooler X-ray arc and a temperature jump due to the shock front at 92'' (184 kpc) on the western side. 2D temperature maps as well as spectral analysis of X-ray photons extracted from wedge shaped reigns revealed six different cold fronts, 3 along the eastern direction, 2 on the west direction and one in the south direction of the X-ray peak. The apparent positions of cold fronts are found to match with the spiral structure apparent in the X-ray surface brightness distribution of PKS 0745-191 that is probably due to the gas sloshing. The Mach number for this shock is found to be ˜ 1.36. Systematic study of the X-ray cavities revealed a mechanical power of ˜ 2.95 X 1045 erg s-1 and is sufficient to offset the cooling due to radiative loss. We found that the radio source associated with the center dominant galaxy of this cluster is efficient enough to carve the observed cavities. The ratio of radio luminosity to mechanical cavity power is ˜ 10-3 .

  7. NEAR-INFRARED ADAPTIVE OPTICS IMAGING OF INFRARED LUMINOUS GALAXIES: THE BRIGHTEST CLUSTER MAGNITUDE-STAR FORMATION RATE RELATION

    SciTech Connect

    Randriamanakoto, Z.; Väisänen, P.; Escala, A.; Kankare, E.; Kotilainen, J.; Mattila, S.; Ryder, S.

    2013-10-01

    We have established a relation between the brightest super star cluster (SSC) magnitude in a galaxy and the host star formation rate (SFR) for the first time in the near-infrared (NIR). The data come from a statistical sample of ∼40 luminous IR galaxies (LIRGs) and starbursts utilizing K-band adaptive optics imaging. While expanding the observed relation to longer wavelengths, less affected by extinction effects, it also pushes to higher SFRs. The relation we find, M{sub K} ∼ –2.6log SFR, is similar to that derived previously in the optical and at lower SFRs. It does not, however, fit the optical relation with a single optical to NIR color conversion, suggesting systematic extinction and/or age effects. While the relation is broadly consistent with a size-of-sample explanation, we argue physical reasons for the relation are likely as well. In particular, the scatter in the relation is smaller than expected from pure random sampling strongly suggesting physical constraints. We also derive a quantifiable relation tying together cluster-internal effects and host SFR properties to possibly explain the observed brightest SSC magnitude versus SFR dependency.

  8. THE DENSITY PROFILES OF MASSIVE, RELAXED GALAXY CLUSTERS. II. SEPARATING LUMINOUS AND DARK MATTER IN CLUSTER CORES

    SciTech Connect

    Newman, Andrew B.; Ellis, Richard S.; Treu, Tommaso; Sand, David J.

    2013-03-01

    We present stellar and dark matter (DM) density profiles for a sample of seven massive, relaxed galaxy clusters derived from strong and weak gravitational lensing and resolved stellar kinematic observations within the centrally located brightest cluster galaxies (BCGs). In Paper I of the series, we demonstrated that the total density profile derived from these data, which span three decades in radius, is consistent with numerical DM-only simulations at radii {approx}> 5-10 kpc, despite the significant contribution of stellar material in the core. Here, we decompose the inner mass profiles of these clusters into stellar and dark components. Parameterizing the DM density profile as a power law {rho}{sub DM}{proportional_to}r {sup -{beta}} on small scales, we find a mean slope ({beta}) = 0.50 {+-} 0.10(random){sup +0.14} {sub -0.13}(systematic). Alternatively, cored Navarro-Frenk-White (NFW) profiles with (log r {sub core}/kpc) = 1.14 {+-} 0.13{sup +0.14} {sub -0.22} provide an equally good description. These density profiles are significantly shallower than canonical NFW models at radii {approx}< 30 kpc, comparable to the effective radii of the BCGs. The inner DM profile is correlated with the distribution of stars in the BCG, suggesting a connection between the inner halo and the assembly of stars in the central galaxy. The stellar mass-to-light ratio inferred from lensing and stellar dynamics is consistent with that inferred using stellar population synthesis models if a Salpeter initial mass function is adopted. We compare these results to theories describing the interaction between baryons and DM in cluster cores, including adiabatic contraction models and the possible effects of galaxy mergers and active galactic nucleus feedback, and evaluate possible signatures of alternative DM candidates.

  9. Luminous Stars in Galaxies Beyond 3 Mpc

    NASA Astrophysics Data System (ADS)

    Whitmore, B. C.; Wfc3 Science Oversight Committee

    2011-06-01

    I am mainly interested in the formation and destruction of young star clusters in nearby star forming galaxies such as the Antennae, M83, and M51. One of the first analysis steps is to throw out all those pesky stars that keep contaminating my young cluster samples. Recently, spurred on by our new Wide Field Camera 3 (WFC3) Early Release Science data of galaxies including M83, NGC 4214, M82, NGC 2841, and Cen A, we began taking a closer look at the stellar component. Questions we are addressing are: 1) what are the most luminous stars, 2) how can we use them to help study the destruction of star clusters and the population of the field, 3) what fraction of stars, at least the bright stars, are formed in the field, in associations, and in compact clusters. In this contribution we describe some of the beginning steps in this process. More specifically, we describe how we separate stars from clusters in our galaxies, and describe how candidate Luminous Blue Variables (LBVs) and "Single Star" HII (SSHII) regions have been identified.

  10. Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Miller, Christopher J. Miller

    2012-03-01

    There are many examples of clustering in astronomy. Stars in our own galaxy are often seen as being gravitationally bound into tight globular or open clusters. The Solar System's Trojan asteroids cluster at the gravitational Langrangian in front of Jupiter’s orbit. On the largest of scales, we find gravitationally bound clusters of galaxies, the Virgo cluster (in the constellation of Virgo at a distance of ˜50 million light years) being a prime nearby example. The Virgo cluster subtends an angle of nearly 8◦ on the sky and is known to contain over a thousand member galaxies. Galaxy clusters play an important role in our understanding of theUniverse. Clusters exist at peaks in the three-dimensional large-scale matter density field. Their sky (2D) locations are easy to detect in astronomical imaging data and their mean galaxy redshifts (redshift is related to the third spatial dimension: distance) are often better (spectroscopically) and cheaper (photometrically) when compared with the entire galaxy population in large sky surveys. Photometric redshift (z) [Photometric techniques use the broad band filter magnitudes of a galaxy to estimate the redshift. Spectroscopic techniques use the galaxy spectra and emission/absorption line features to measure the redshift] determinations of galaxies within clusters are accurate to better than delta_z = 0.05 [7] and when studied as a cluster population, the central galaxies form a line in color-magnitude space (called the the E/S0 ridgeline and visible in Figure 16.3) that contains galaxies with similar stellar populations [15]. The shape of this E/S0 ridgeline enables astronomers to measure the cluster redshift to within delta_z = 0.01 [23]. The most accurate cluster redshift determinations come from spectroscopy of the member galaxies, where only a fraction of the members need to be spectroscopically observed [25,42] to get an accurate redshift to the whole system. If light traces mass in the Universe, then the locations

  11. Coma cluster of galaxies

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Atlas Image mosaic, covering 34' x 34' on the sky, of the Coma cluster, aka Abell 1656. This is a particularly rich cluster of individual galaxies (over 1000 members), most prominently the two giant ellipticals, NGC 4874 (right) and NGC 4889 (left). The remaining members are mostly smaller ellipticals, but spiral galaxies are also evident in the 2MASS image. The cluster is seen toward the constellation Coma Berenices, but is actually at a distance of about 100 Mpc (330 million light years, or a redshift of 0.023) from us. At this distance, the cluster is in what is known as the 'Hubble flow,' or the overall expansion of the Universe. As such, astronomers can measure the Hubble Constant, or the universal expansion rate, based on the distance to this cluster. Large, rich clusters, such as Coma, allow astronomers to measure the 'missing mass,' i.e., the matter in the cluster that we cannot see, since it gravitationally influences the motions of the member galaxies within the cluster. The near-infrared maps the overall luminous mass content of the member galaxies, since the light at these wavelengths is dominated by the more numerous older stellar populations. Galaxies, as seen by 2MASS, look fairly smooth and homogeneous, as can be seen from the Hubble 'tuning fork' diagram of near-infrared galaxy morphology. Image mosaic by S. Van Dyk (IPAC).

  12. Discovery of a Very X-Ray Luminous Galaxy Cluster at Z=0.89 in the Wide Angle ROSAT Pointed Survey

    NASA Astrophysics Data System (ADS)

    Ebeling, H.; Jones, L. R.; Fairley, B. W.; Perlman, E.; Scharf, C.; Horner, D.

    2001-02-01

    We report the discovery of the galaxy cluster Cl J1226.9+3332 in the Wide Angle ROSAT Pointed Survey (WARPS). At z=0.888 and LX=1.1×1045 h-250 ergs s-1 (0.5-2.0 keV), Cl J1226.9+3332 is the most distant X-ray luminous cluster currently known. The mere existence of this system represents a huge problem for Ω0=1 world models. At the modest (off-axis) resolution of the ROSAT Position Sensitive Proportional Counter observation in which the system was detected, Cl J1226.9+3332 appears relaxed; an off-axis High Resolution Imager observation confirms this impression and rules out significant contamination from point sources. However, in moderately deep optical images (R and I band), the cluster exhibits signs of substructure in its apparent galaxy distribution. A first crude estimate of the velocity dispersion of the cluster galaxies based on six redshifts yields a high value of 1650 km s-1, indicative of a very massive cluster and/or the presence of substructure along the line of sight. While a more accurate assessment of the dynamical state of this system requires much better data at both optical and X-ray wavelengths, the high mass of the cluster has already been unambiguously confirmed by a very strong detection of the Sunyaev-Zeldovich effect in its direction. Using Cl J1226.9+3332 and Cl J0152.7-1357 (z=0.835), the second most distant X-ray luminous cluster currently known and also a WARPS discovery, we obtain a first estimate of the cluster X-ray luminosity function at 0.85×1044 h-250 ergs s-1 (0.5-2.0 keV). Using the best currently available data, we find the comoving space density of very distant, massive clusters to be in excellent agreement with the value measured locally (z<0.3) and conclude that negative evolution is not required at these luminosities out to z~1. Our findings are in conflict with earlier claims of highly significant (>3 σ) negative evolution already at 0.3cluster samples of the Einstein Extended Medium

  13. Luminous variables in the Quintuplet cluster

    NASA Astrophysics Data System (ADS)

    Glass, I. S.; Matsumoto, S.; Carter, B. S.; Sekiguchi, K.

    1999-03-01

    We report observations of variability amongst the stars of the `Quintuplet' cluster located about 30 pc in projection from the centre of the Galaxy. Two of the five cocoon star members, which may be protostars or peculiar Wolf-Rayet stars, are seen to vary slowly with moderate amplitude (0.4-0.5 mag). The bright star within the `Pistol' H ii region, suspected of being a luminous blue variable (LBV), has in fact been found to show variability, confirming its tentative classification. A second nearby presumed LBV also varies. One of the apparent Quintuplet members is likely to be a Mira variable along the same line of sight.

  14. New Constraints on Dark Energy from the ObservedGrowth of the Most X-ray Luminous Galaxy Clusters

    SciTech Connect

    Mantz, A.; Allen, S.W.; Ebeling, H.; Rapetti, D.

    2007-10-15

    We present constraints on the mean matter density, {Omega}{sub m}, normalization of the density fluctuation power spectrum, {sigma}{sub 8}, and dark energy equation of state parameter, w, obtained from the X-ray luminosity function of the Massive Cluster Survey (MACS) in combination with the local BCS and REFLEX galaxy cluster samples. Our analysis incorporates the mass function predictions of Jenkins et al. (2001), a mass-luminosity relation calibrated using the data of Reiprich and Bohringer (2002), and standard priors on the Hubble constant, H{sub 0}, and mean baryon density, {Omega}{sub b} h{sup 2}. We find {Omega}{sub m}=0.27 {sup +0.06} {sub -0.05} and {sigma}{sub 8}=0.77 {sup +0.07} {sub -0.06} for a spatially flat, cosmological constant model, and {Omega}{sub m}=0.28 {sup +0.08} {sub -0.06}, {sigma}{sub 8}=0.75 {+-} 0.08 and w=-0.97 {sup +0.20} {sub -0.19} for a flat, constant-w model. Our findings constitute the first precise determination of the dark energy equation of state from measurements of the growth of cosmic structure in galaxy clusters. The consistency of our result with w=-1 lends strong additional support to the cosmological constant model. The constraints are insensitive to uncertainties at the 10-20 percent level in the mass function and in the redshift evolution o the mass-luminosity relation; the constraint on dark energy is additionally robust against our choice of priors and known X-ray observational biases affecting the mass-luminosity relation. Our results compare favorably with those from recent analyses of type Ia supernovae, cosmic microwave background anisotropies, the X-ray gas mass fraction of relaxed galaxy clusters and cosmic shear. A simplified combination of the luminosity function data with supernova, cosmic microwave background and cluster gas fraction data using importance sampling yields the improved constraints {Omega}{sub m}=0.263 {+-} 0.014, {sigma}{sub 8}=0.79 {+-} 0.02 and w=-1.00 +- 0.05.

  15. Luminous and Dark Matter Profiles from Galaxies to Clusters: Bridging the Gap with Group-scale Lenses

    NASA Astrophysics Data System (ADS)

    Newman, Andrew B.; Ellis, Richard S.; Treu, Tommaso

    2015-11-01

    Observations of strong gravitational lensing, stellar kinematics, and larger-scale tracers enable accurate measures of the distribution of dark matter (DM) and baryons in massive early-type galaxies (ETGs). While such techniques have been applied to galaxy-scale and cluster-scale lenses, the paucity of intermediate-mass systems with high-quality data has precluded a uniform analysis of mass-dependent trends. With the aim of bridging this gap, we present new observations and analyses of 10 group-scale lenses at < z> =0.36, characterized by Einstein radii {θ }{{Ein}}=2\\buildrel{\\prime\\prime}\\over{.} 5-5\\buildrel{\\prime\\prime}\\over{.} 1 and a mean halo mass of {M}200={10}14.0 {M}ȯ . We measure a mean concentration c200 = 5.0 ± 0.8 consistent with unmodified cold dark matter halos. By combining our data with other lens samples, we analyze the mass structure of ETGs in 1013 {M}ȯ –1015 {M}ȯ halos using homogeneous techniques. We show that the slope of the total density profile γtot within the effective radius depends on the stellar surface density, as demonstrated previously, but also on the halo mass. We analyze these trends using halo occupation models and resolved stellar kinematics with the goal of testing the universality of the DM profile. Whereas the central galaxies of clusters require a shallow inner DM density profile, group-scale lenses are consistent with a Navarro–Frenk–White profile or one that is slightly contracted. The largest uncertainties arise from the sample size and likely radial gradients in stellar populations. We conclude that the net effect of baryons on the DM distribution may not be universal, but more likely varies with halo mass due to underlying trends in star formation efficiency and assembly history.

  16. Luminous red galaxies in hierarchical cosmologies

    NASA Astrophysics Data System (ADS)

    Almeida, C.; Baugh, C. M.; Wake, D. A.; Lacey, C. G.; Benson, A. J.; Bower, R. G.; Pimbblet, K.

    2008-06-01

    Luminous red galaxies (LRGs) are much rarer and more massive than L* galaxies. Coupled with their extreme colours, LRGs therefore provide a demanding testing ground for the physics of massive galaxy formation. We present the first self-consistent predictions for the abundance and properties of LRGs in hierarchical structure formation models. We test two published models which use quite different mechanisms to suppress the formation of massive galaxies: the Bower et al. model which invokes `active galactic nuclei (AGN) feedback' to prevent gas from cooling in massive haloes and the Baugh et al. model which relies upon a `superwind' to eject gas before it is turned into stars. Without adjusting any parameters, the Bower et al. model gives an excellent match to the observed luminosity function of LRGs in the Sloan Digital Sky Survey (with a median redshift of z = 0.24) and to their clustering; the Baugh et al. model is less successful in these respects. Both models fail to match the observed abundance of LRGs at z = 0.5 to better than a factor of ~2. In the models, LRGs are typically bulge-dominated systems with stellar masses of ~2 × 1011h-1Msolar and velocity dispersions of σ ~ 250kms-1. Around half of the stellar mass in the model LRGs is already formed by z ~ 2.2 and is assembled into one main progenitor by z ~ 1.5; on average, only 25 per cent of the mass of the main progenitor is added after z ~ 1. LRGs are predicted to be found in a wide range of halo masses, a conclusion which relies on properly taking into account the scatter in the formation histories of haloes. Remarkably, we find that the correlation function of LRGs is predicted to be a power law down to small pair separations, in excellent agreement with observational estimates. Neither the Bower et al. nor the Baugh et al. model is able to reproduce the observed radii of LRGs.

  17. Galaxy population properties of the massive X-ray luminous galaxy cluster XDCP J0044.0-2033 at z = 1.58. Red-sequence formation, massive galaxy assembly, and central star formation activity

    NASA Astrophysics Data System (ADS)

    Fassbender, R.; Nastasi, A.; Santos, J. S.; Lidman, C.; Verdugo, M.; Koyama, Y.; Rosati, P.; Pierini, D.; Padilla, N.; Romeo, A. D.; Menci, N.; Bongiorno, A.; Castellano, M.; Cerulo, P.; Fontana, A.; Galametz, A.; Grazian, A.; Lamastra, A.; Pentericci, L.; Sommariva, V.; Strazzullo, V.; Šuhada, R.; Tozzi, P.

    2014-08-01

    Context. Recent observational progress has enabled the detection of galaxy clusters and groups out to very high redshifts and for the first time allows detailed studies of galaxy population properties in these densest environments in what was formerly known as the "redshift desert" at z> 1.5. Aims: We aim to investigate various galaxy population properties of the massive X-ray luminous galaxy cluster XDCP J0044.0-2033 at z = 1.58, which constitutes the most extreme currently known matter-density peak at this redshift. Methods: We analyzed deep VLT/HAWK-I near-infrared data with an image quality of 0.5'' and limiting Vega magnitudes (50% completeness) of 24.2 in J- and 22.8 in the Ks band, complemented by similarly deep Subaru imaging in i and V, Spitzer observations at 4.5 μm, and new spectroscopic observations with VLT/FORS 2. Results: We detect a cluster-associated excess population of about 90 galaxies, most of them located within the inner 30'' (250 kpc) of the X-ray centroid, which follows a centrally peaked, compact NFW galaxy surface-density profile with a concentration of c200 ≃ 10. Based on the Spitzer 4.5 μm imaging data, we measure a total enclosed stellar mass of M∗500 ≃ (6.3 ± 1.6) × 1012 M⊙ and a resulting stellar mass fraction of f∗,500 = M∗,500/M500 = (3.3 ± 1.4)%, consistent with local values. The total J- and Ks-band galaxy luminosity functions of the core region yield characteristic magnitudes J* and Ks* consistent with expectations from simple zf = 3 burst models. However, a detailed look at the morphologies and color distributions of the spectroscopically confirmed members reveals that the most massive galaxies are undergoing a very active mass-assembly epoch through merging processes. Consequently, the bright end of the cluster red sequence is not in place, while a red-locus population is present at intermediate magnitudes [Ks*, Ks* + 1.6], which is then sharply truncated at magnitudes fainter than Ks* + 1.6. The dominant

  18. The Assembly of Galaxy Clusters

    SciTech Connect

    Berrier, Joel C.; Stewart, Kyle R.; Bullock, James S.; Purcell, Chris W.; Barton, Elizabeth J.; Wechsler, Risa H.

    2008-05-16

    We study the formation of fifty-three galaxy cluster-size dark matter halos (M = 10{sup 14.0-14.76} M{sub {circle_dot}}) formed within a pair of cosmological {Lambda}CDM N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host {approx} 0.1L{sub *} galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters experience no 'pre-processing' in the group environment prior to their accretion into the cluster. On average, {approx} 70% of cluster galaxies fall into the cluster potential directly from the field, with no luminous companions in their host halos at the time of accretion; and less than {approx} 12% are accreted as members of groups with five or more galaxies. Moreover, we find that cluster galaxies are significantly less likely to have experienced a merger in the recent past ({approx}< 6 Gyr) than a field halo of the same mass. These results suggest that local, cluster processes like ram-pressure stripping, galaxy harassment, or strangulation play the dominant role in explaining the difference between cluster and field populations at a fixed stellar mass; and that pre-evolution or past merging in the group environment is of secondary importance for setting cluster galaxy properties for most clusters. The accretion times for z = 0 cluster members are quite extended, with {approx} 20% incorporated into the cluster halo more than 7 Gyr ago and {approx} 20% within the last 2 Gyr. By comparing the observed morphological fractions in cluster and field populations, we estimate an approximate time-scale for late-type to early-type transformation within the cluster environment to be {approx} 6 Gyr.

  19. Evolution of luminous IRAS galaxies: Radio imaging

    NASA Technical Reports Server (NTRS)

    Neff, S. G.; Hutchings, J. B.

    1993-01-01

    In a recent study of IRAS galaxies' optical morphologies, we found that luminous IR sources lie in the IR color-luminosity plane in groups which separate out by optical spectroscopic type and also by degree of tidal disturbance. We found that the most luminous steep-IR-spectrum sources are generally galaxies in the initial stages of a major tidal interaction. Galaxies with active nuclei were generally found to have flatter IR spectra, to cover a range of IR luminosity, and to be in the later stages of a tidal interaction. We proposed a sequence of events by which luminous IR sources evolve: they start as interacting or merging galaxies, some develop active nuclei, and most undergo extensive star-formation in their central regions. Another way to study these objects and their individual evolution is to study their radio morphologies. Radio emission may arise at a detectable level from supernovae in star-forming regions and/or the appearance of an active nucleus can be accompanied by a nuclear radio source (which may develop extended structure). Therefore, the compact radio structure may trace the evolution of the inner regions of IRAS-luminous sources. If the radio sources are triggered by the interactions, we would expect to find the radio morphology related to the optical 'interactivity' of the systems. Here, we explore using the radio emission of IRAS galaxies as a possible tracer of galaxy evolution. We present and discuss observations of the compact radio morphology of 111 luminous IRAS-selected active galaxies covering a wide range of IR and optical properties.

  20. Orbital masses of nearby luminous galaxies

    SciTech Connect

    Karachentsev, Igor D.; Kudrya, Yuri N. E-mail: yukudrya@gmail.com

    2014-09-01

    We use observational properties of galaxies accumulated in the Updated Nearby Galaxy Catalog to derive a dark matter mass of luminous galaxies via motions of their companions. The data on orbital-to-stellar mass ratio are presented for 15 luminous galaxies situated within 11 Mpc from us: the Milky Way, M31, M81, NGC 5128, IC342, NGC 253, NGC 4736, NGC 5236, NGC 6946, M101, NGC 4258, NGC 4594, NGC 3115, NGC 3627, and NGC 3368, as well as for a composite suite around other nearby galaxies of moderate and low luminosity. The typical ratio for these galaxies is M {sub orb}/M {sub *} = 31, corresponding to the mean local density of matter Ω {sub m} = 0.09, i.e., one-third of the global cosmic density. This quantity seems to be rather an upper limit of dark matter density, since the peripheric population of the suites may suffer from the presence of fictitious unbound members. We note that the Milky Way and M31 halos have lower dimensions and lower stellar masses than those of the other 13 nearby luminous galaxies. However, the dark-to-stellar mass ratio for both the Milky Way and M31 is typical for other neighboring luminous galaxies. The distortion in the Hubble flow, observed around the Local Group and five other neighboring groups, yields their total masses within the radius of a zero velocity surface, R {sub 0}; these masses are slightly lower than the orbital and virial values. This difference may be due to the effect of dark energy producing a kind of 'mass defect' within R {sub 0}.

  1. Observations of Luminous Infrared Galaxies with Herschel

    NASA Astrophysics Data System (ADS)

    Armus, Lee

    2014-01-01

    A major result of the IRAS survey was the discovery of a large population of luminous infrared galaxies (LIRGs) which emit a significant fraction of their bolometric luminosity in the far-infrared. LIRGs cover the full range of morphologies from isolated disk galaxies, to advanced mergers, exhibiting enhanced star-formation rates and a higher fraction of Active Galactic Nuclei (AGN) compared to less luminous galaxies. A detailed study of low-redshift LIRGs is critical for our understanding of the cosmic evolution of galaxies and black holes, since LIRGs comprise the bulk of the cosmic far-infrared background and dominate the star-formation between 0.5 < z < 1. With ISO, it was possible to measure the full suite of infrared diagnostic lines in local normal and luminous infrared galaxies for the first time, but samples were small and observations challenging. With Herschel, we have been able to study large samples of low-redshift LIRGs, and even probe the physical conditions in poweful starburst galaxies out to significant redshifts. By combining the Herschel data with those from Spitzer, it is now possible to understand the heating and cooling of the dust and gas in complete samples of LIRGs for the first time. I will review recent results from a number of GTO, OTKP and GO programs in an attempt to summarize the advances we have made in understanding star formation and black hole accretion in LIRGs as a direct result of the Herschel mission.

  2. Compact radio sources in luminous infrared galaxies

    NASA Astrophysics Data System (ADS)

    Parra, Rodrigo

    2007-08-01

    Radio interferometry is an observational technique of high sensitivity and incomparably high spatial resolution. Moreover, because radio waves can freely propagate through interstellar dust and gas, it allows the study of regions of the universe completely obscured at other wavelengths. This thesis reports the observational and theoretical results of my research during the past four years which are mostly based on interferometric radio data. The COLA sample is an infrared selected sample of active star forming galaxies. We conducted 6 cm VLA and VLBI snapshot observations of the northern half of this sample. The radio emission seen at VLA scales is consistent with being powered by star formation activity because it follows the far infrared to radio correlation. We detect 22% of the sample sources in our VLBI snapshots. Based on luminosity arguments, we argue that these sub-parsec VLBI sources are powered by AGN activity. Furthermore, we find that VLBI detections are preferentially found in sources whose VLA scale structures have the highest peak brightnesses suggesting a strong correlation between compact starburst and AGN activity. This observational result is consistent with the theoretical picture of an Eddington-limited nuclear starburst acting as the last valve in the pipeline transporting the gas from kiloparsec scales onto the accretion disc of a buried AGN. Arp 220 is the archetypical ultra luminous infrared galaxy. For many years this source has been known to harbour a compact (~100 pc) cluster of unresolved 18 cm bright sources believed to be bright core collapse supernovae. Using multiwavelength VLBI observations, we obtained for the first time radio spectra for 18 of these sources. We find that over a half of them have spectra consistent with young supernovae. The rest can be better explained as older supernova remnants interacting with the high density starburst ISM. This finding allowed us to constrain the number of possible scenarios for the Arp 220

  3. Over-Luminous Elliptical Galaxies

    NASA Technical Reports Server (NTRS)

    Forman, William; Mushotzky, Richard (Technical Monitor)

    2004-01-01

    The first paper from our work has been completed and accepted for publication. Another paper presents a study of the ESO 30601 70 galaxy group, combining Chandra, XMM-Newton, and optical observations. We find that the system is a true fossil galaxy group - a group whose optical light is dominated by a single galaxy. The group X-ray emission is composed of a central, dense, cool core (10 kpc in radius) and an isothermal medium beyond the central 10 kpc. The region between 10 and 50 kpc (the cooling radius) has the same temperature as the gas from 50 to 400 kpc, although the gas cooling time between 10 and 50 kpc (2-6 Gyr) is shorter than the Hubble time. Thus, the ESO 3060170 group does not have a group-sized cooling core. We suggest that the group cooling core may have been heated by a central active galactic nucleus (AGN) outburst in the past and that the small, dense, cool core is the truncated relic of a previous cooling core. The Chandra observations also reveal a variety of X-ray features in the central region, including a finger, an edge-like feature, and a small tail, all aligned along a north-south axis, as are the galaxy light and group galaxy distribution. The proposed AGN outburst may cause gas to slosh around the center and produce these asymmetric features. The observed flat temperature profile to 1/3rvir is not consistent with the predicted temperature profile in recent numerical simulations. We compare the entropy profile of the ESO 3060170 group with those of three other groups and find a flatter relation than that predicted by simulations involving only shock heating, S approximately r approximately 0.85. This is direct evidence of the importance of non-gravitational processes in group centers. We derive the mass profiles within 1/3rvir and find that the ESO 3060170 group is the most massive fossil group known.

  4. Luminous red galaxies in the Sloan digital sky survey

    NASA Astrophysics Data System (ADS)

    Loh, Yeong-Shang

    2004-04-01

    We determine the luminosity function and evolution of 22,562 Luminous Red Galaxies (LRG) with 0.08 < z < 0.44 from the Sloan Digital Sky Survey (SDSS). The universal field galaxy luminosity function with a steep exponential bright end cut-off expected from a Schechter form is confirmed to z ˜ 0.4. We do not discern any evolution in the comoving number density of these luminous early-type galaxies, once biases due to photometric errors are taken into account. Using 2099 deg2 of SDSS imaging data, we search for bright early-type galaxies within 1 h-1 Mpc of LRG with 0.12 < z < 0.38 to study the bright end of the luminosity distribution at this scale. The brightest galaxies (nearly always an LRG) in LRG fields are too bright if other members in the same field are drawn from an exponentially decaying luminosity function. The luminosity gap between the brightest and the second brightest galaxy is large (˜0.8 mag). When the LRG fields were split into group-like and cluster- like environments, the former gives a larger gap. The gap shows little evolution with redshifts, putting stringent constraints on the scenario of the growth of Brightest Cluster (or Group) Galaxies by recent cannibalism of cluster members. We calibrate the observed color-magnitude-redshift relation for early-type galaxies. We use LRGs as spectroscopic references and measure the color of imaging galaxies that clustered around each LRG. We bin these galaxies in redshift and perform an optimal background subtraction to recover the color-magnitude relation. The observed scatter around this color-magnitude relation is also measured. We study the environments of LRG by counting the number of early-type galaxies brighter than M* within 1 h-1 Mpc of the LRG. LRGs are binned in redshift and treated as a single population to infer the evolution trend of their environments. Both the rich optical clusters and moderately X-ray bright clusters host at least one LRG. However, LRG are most common in group

  5. Exploring Cluster Physics with High-Resolution Sunyaev--Zel'dovich Effect Images and X-Ray Data: The Case of the Most X-Ray-Luminous Galaxy Cluster RX J1347-1145

    NASA Astrophysics Data System (ADS)

    Kitayama, Tetsu; Komatsu, Eiichiro; Ota, Naomi; Kuwabara, Takeshi; Suto, Yasushi; Yoshikawa, Kohji; Hattori, Makoto; Matsuo, Hiroshi

    2004-02-01

    Foreseeing the era of high spatial resolution measurements of the Sunyaev-Zel'dovich effect (SZE) in clusters of galaxies, we present a prototype analysis of this sort combined with Chandra X-ray data. It is applied specifically to RX J1347-1145 at z = 0.451, the most X-ray-luminous galaxy cluster known, for which the highest resolution SZE and X-ray images are currently available. We demonstrate that the combined analysis yields a unique probe of complex structures in the intracluster medium, offering determinations of their temperature, density, and line-of-sight extent. For a subclump in RX J1347-1145, previously discovered in our SZE map, the temperature inferred after removing the foreground and background components is well in excess of 20keV, indicating that the cluster has recently undergone a violent merger. Excluding the region around this subclump, the SZE signals in submillimeter to centimeter bands (350, 150, and 21GHz) are all consistent with those expected from Chandra X-ray observations. We further present a temperature deprojection technique based on the SZE and X-ray images, without any knowledge of spatially resolved X-ray spectroscopy. The methodology presented here will be applicable to a statistical sample of clusters available in the future SZE surveys.

  6. The Fate of Luminous Compact Blue Galaxies: An Environmental Approach

    NASA Astrophysics Data System (ADS)

    Crawford, Steven

    2003-07-01

    Luminous Compact Blue Galaxies {LCBGs} are the most rapidly evolving galaxy population between 0.4 < z < 1.0. Despite their small sizes of 2-3 kpc, LCBGs are powerful engines of star formation that dominate the global SFR over that redshift regime. They appear to be a link between local, low-mass HII galaxies and high-z, high-luminosity Lyman Break galaxies. As such, LCBGs may provide an important test of hierarchical structure-formation scenarios. Currently, a debate rages over what LCBGs are: Are we seeing proto-spheroidals or the formation of spiral bulges? We propose to identify a sample of LCBGs in 10 intermediate-z clusters areas from Archive WFPC2 images through photometric structural measurements {e.g., surface brightness, size, and concentration}. These galaxies cannot be resolved in ground-based images. We then will measure the relative number densities and photometric properties of LCBGs in clusters and the field. By combining this comparison with what we know about the morphology-density relationship today, we will gain new insight on the ultimate fate of LCBGs and the differences between galaxy evolution in field and cluster environments. The WFPC2 data, combined with our deep multi-color, ground-based imaging from the WIYN 3.5m telescope will provide the largest data set of intermediate-z LCBGs to date.

  7. Evolution of local luminous compact blue galaxies

    NASA Astrophysics Data System (ADS)

    Rabidoux, Katherine; Pisano, Daniel J.

    2015-01-01

    Luminous compact blue galaxies (LCBGs) are a type of very blue, very compact star-forming galaxy that was common at z~1 but is rare in the local universe. While it is clear from this discrepancy that LCBGs must be a rapidly-evolving class of galaxy, it is not clear what type(s) of galaxy they become. Fortunately, since they are bright and nearby, the rare examples of z~0 LCBGs are easily studied across a large range of wavelengths. We have conducted a study of z~0 analogs to the z~1 LCBGs to investigate their galaxy-wide internal properties in order to determine what is triggering their current episode of star formation, for how long the star formation can continue, and what the galaxies may become once their star formation rates decrease from current levels. We have taken resolved H I observations of nine LCBGs and unresolved radio continuum observations of 35 LCBGs and combined this data with archival broad-band data to probe their global properties. We conclude that LCBGs are rotationally-supported, star-forming disk galaxies that, while they may be forming small central bulges or bars, are highly unlikely to evolve into dwarf elliptical, dwarf spheroidal, or elliptical galaxies on their own due to their masses and rotation velocities. LCBGs will likely fade to be spiral galaxies with lower surface brightnesses once their current episodes of star formation conclude. In addition, we have modeled the SEDs of the LCBGs in our sample to determine whether LCBGs' star formation is ramping up or winding down, and for how much longer their current active phase of star formation will last. We have begun to put together a picture of the current evolutionary stage of this class of galaxies, and have better constrained their future evolutionary paths.

  8. The evolution of and starburst-agn connection in luminous and ultraluminous infrared galaxies and their link to globular cluster formation

    NASA Astrophysics Data System (ADS)

    Fiorenza, Stephanie Lynn

    The evolutionary connection between nuclear starbursts and active galactic nuclei (AGN) in luminous infrared galaxies (LIRGs; 1011 < LIR < 1012 L[special character omitted]) and ultraluminous infrared galaxies (ULIRGs; 1012 < LIR < 1013 L[special character omitted]), which result from galaxy interactions and mergers and produce the bulk of their radiation as infrared (IR) emission, is not well understood. To this effort, I first spectroscopically examine U/LIRGs (1011 < LIR < 1013 L[special character omitted]) within the IRAS 2 Jansky Redshift Survey with 0.05 < z < 0.16. Using new spectrophotometric data, I classify the primary source of IR radiation as being a nuclear starburst or a type of AGN by using the Baldwin-Phillips-Terlevich (BPT) diagrams. I show that for the U/LIRGs in my sample the properties that describe their nuclear starbursts and AGN (e.g. star formation rate (SFR), L[O III], optical D parameter, D4000, and EW(Hdelta)) are independent of one another, ensuring that no biases affect correlations between these properties and objects' locations on the BPT diagrams. I then derive evolutionary paths on the BPT diagram involving [N II]/Halpha that are based on how these properties vary between two U/LIRGs positioned at the end-points. The paths involve U/LIRGs that decrease in SFR and increase in AGN activity. Paths with U/LIRGs that evolve into high luminosity AGN likely do so due to recent, strong starbursts. Second, to study how the properties of the IR power sources in U/LIRGs vary, I use a combination of photometric data points that I carefully measure (using photometry from SDSS, 2MASS, WISE, and Spitzer) and that I retrieve from catalogues (IRAS, AKARI, and ISO) to perform UV to FIR SED-fitting with CIGALE (Code Investigating GALaxy Emission) for 34 U/LIRGs from the IRAS 2 Jy Redshift Survey with 0.01 < z < 0.16. I find evidence that the nuclear starburst forms first in U/LIRGs, and also find that U/LIRGs with relatively similar SFRs show

  9. LUMINOUS SATELLITES VERSUS DARK SUBHALOS: CLUSTERING IN THE MILKY WAY

    SciTech Connect

    Bozek, Brandon; Wyse, Rosemary F. G.; Gilmore, Gerard

    2013-08-01

    The observed population of the Milky Way satellite galaxies offers a unique testing ground for galaxy formation theory on small scales. Our novel approach was to investigate the clustering of the known Milky Way satellite galaxies and to quantify the amount of substructure within their distribution using a two-point correlation function statistic in each of three spaces: configuration space, line-of-sight velocity space, and four-dimensional (4D) phase space. These results were compared to those for three sets of subhalos in the Via Lactea II cold dark matter (CDM) simulation defined to represent the luminous dwarfs. We found no evidence at a significance level above 2{sigma} of substructure within the distribution of the Milky Way satellite galaxies in any of the three spaces. The 'luminous' subhalo sets are more strongly clustered than are the Milky Way satellites in all three spaces and over a broader range of scales in 4D phase space. Each of the 'luminous' subhalo sets are clustered as a result of substructure within their line-of-sight velocity space distributions at greater than 3{sigma} significance, whereas the Milky Way satellite galaxies are randomly distributed in line-of-sight velocity space. While our comparison is with only one CDM simulation, the inconsistencies between the Milky Way satellite galaxies and the Via Lactea II subhalo sets for all clustering methods suggest a potential new 'small-scale' tension between CDM theory and the observed Milky Way satellites. Future work will obtain a more robust comparison between the observed Milky Way satellites and CDM theory by studying additional simulations.

  10. The Most Luminous Galaxies Found by WISE

    NASA Astrophysics Data System (ADS)

    Eisenhardt, Peter; Tsai, Chao-Wei; Wu, Jingwen; Griffith, Roger; Yan, Lin; Stern, Daniel; Stanford, Adam; Blain, Andrew; Benford, Dominic; Bridge, Carrie; Petty, Sara; Assef, Roberto; Donoso, Emilio; Lake, Sean

    2012-08-01

    NASA's Wide-field Infrared Survey Explorer (WISE) has surveyed the entire sky at 3.4, 4.6, 12 and 22 (micron) (W1, W2, W3, and W4), reaching sensitivities hundreds of times deeper than IRAS. We have used WISE photometry to select an all-sky sample of objects which are extremely luminous. The objects are prominent in W4, but faint or undetected in W1 and W2 (W12drops). Followup spectroscopy shows that most of the sources have redshifts z>2. In combination with Herschel photometry, these redshifts lead to typical L_bol > 10^13 L_⊙, with ~10% exceeding 10^14 L_⊙. High resolution adaptive optics imaging shows these objects are typically unlensed. We request NOAO time to obtain redshifts and optical and near IR photometry of the complete all-sky sample of the brightest W12drops, all of which are in our Herschel program. This will fulfill the primary WISE objective of finding the most extreme luminous IR galaxies in the Universe. These superlative objects will be the most fruitful for detailed studies of the physics of star formation, AGN fueling, and feedback in the most active galaxies.

  11. THE Mg II CROSS-SECTION OF LUMINOUS RED GALAXIES

    SciTech Connect

    Bowen, David V.; Chelouche, Doron

    2011-01-20

    We describe a search for Mg II {lambda}{lambda}2796, 2803 absorption lines in Sloan Digital Sky Survey (SDSS) spectra of QSOs whose lines of sight pass within impact parameters {rho} {approx} 200 kpc of galaxies with photometric redshifts of z = 0.46-0.6 and errors {Delta}z {approx} 0.05. The galaxies selected have the same colors and luminosities as the Luminous Red Galaxy (LRG) population previously selected from the SDSS. A search for Mg II lines within a redshift interval of {+-}0.1 of a galaxy's photometric redshift shows that absorption by these galaxies is rare: the covering fraction is f({rho}) {approx_equal} 10%-15% between {rho} = 20 kpcand{rho} = 100 kpc, for Mg II lines with rest equivalent widths of W{sub r} {>=} 0.6 A, falling to zero at larger {rho}. There is no evidence that W{sub r} correlates with impact parameter or galaxy luminosity. Our results are consistent with existing scenarios in which cool Mg II-absorbing clouds may be absent near LRGs because of the environment of the galaxies: if LRGs reside in high-mass groups and clusters, either their halos are too hot to retain or accrete cool gas, or the galaxies themselves-which have passively evolving old stellar populations-do not produce the rates of star formation and outflows of gas necessary to fill their halos with Mg II-absorbing clouds. In the rarer cases where Mg II is detected, however, the origin of the absorption is less clear. Absorption may arise from the little cool gas able to reach into cluster halos from the intergalactic medium, or from the few star-forming and/or AGN-like LRGs that are known to exist.

  12. Warm Molecular Gas in Luminous Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Lu, N.; Zhao, Y.; Xu, C. K.; Gao, Y.; Armus, L.; Mazzarella, J. M.; Isaak, K. G.; Petric, A. O.; Charmandaris, V.; Díaz-Santos, T.; Evans, A. S.; Howell, J.; Appleton, P.; Inami, H.; Iwasawa, K.; Leech, J.; Lord, S.; Sanders, D. B.; Schulz, B.; Surace, J.; van der Werf, P. P.

    2014-06-01

    We present our initial results on the CO rotational spectral line energy distribution (SLED) of the J to J-1 transitions from J = 4 up to 13 from Herschel SPIRE spectroscopic observations of 65 luminous infrared galaxies (LIRGs) in the Great Observatories All-Sky LIRG Survey. The observed SLEDs change on average from one peaking at J <= 4 to a broad distribution peaking around J ~ 6 to 7 as the IRAS 60-to-100 μm color, C(60/100), increases. However, the ratios of a CO line luminosity to the total infrared luminosity, L IR, show the smallest variation for J around 6 or 7. This suggests that, for most LIRGs, ongoing star formation (SF) is also responsible for a warm gas component that emits CO lines primarily in the mid-J regime (5 <~ J <~ 10). As a result, the logarithmic ratios of the CO line luminosity summed over CO (5-4), (6-5), (7-6), (8-7) and (10-9) transitions to L IR, log R midCO, remain largely independent of C(60/100), and show a mean value of -4.13 (\\equiv log R^SF_midCO) and a sample standard deviation of only 0.10 for the SF-dominated galaxies. Including additional galaxies from the literature, we show, albeit with a small number of cases, the possibility that galaxies, which bear powerful interstellar shocks unrelated to the current SF, and galaxies, in which an energetic active galactic nucleus contributes significantly to the bolometric luminosity, have their R midCO higher and lower than R^SF_midCO, respectively. Based on Herschel observations. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  13. WARM MOLECULAR GAS IN LUMINOUS INFRARED GALAXIES

    SciTech Connect

    Lu, N.; Zhao, Y.; Xu, C. K.; Mazzarella, J. M.; Howell, J.; Appleton, P.; Lord, S.; Schulz, B.; Gao, Y.; Armus, L.; Díaz-Santos, T.; Surace, J.; Isaak, K. G.; Petric, A. O.; Charmandaris, V.; Evans, A. S.; Inami, H.; Iwasawa, K.; Leech, J.; Sanders, D. B.; and others

    2014-06-01

    We present our initial results on the CO rotational spectral line energy distribution (SLED) of the J to J–1 transitions from J = 4 up to 13 from Herschel SPIRE spectroscopic observations of 65 luminous infrared galaxies (LIRGs) in the Great Observatories All-Sky LIRG Survey. The observed SLEDs change on average from one peaking at J ≤ 4 to a broad distribution peaking around J ∼ 6 to 7 as the IRAS 60-to-100 μm color, C(60/100), increases. However, the ratios of a CO line luminosity to the total infrared luminosity, L {sub IR}, show the smallest variation for J around 6 or 7. This suggests that, for most LIRGs, ongoing star formation (SF) is also responsible for a warm gas component that emits CO lines primarily in the mid-J regime (5 ≲ J ≲ 10). As a result, the logarithmic ratios of the CO line luminosity summed over CO (5–4), (6–5), (7–6), (8–7) and (10–9) transitions to L {sub IR}, log R {sub midCO}, remain largely independent of C(60/100), and show a mean value of –4.13 (≡log R{sub midCO}{sup SF}) and a sample standard deviation of only 0.10 for the SF-dominated galaxies. Including additional galaxies from the literature, we show, albeit with a small number of cases, the possibility that galaxies, which bear powerful interstellar shocks unrelated to the current SF, and galaxies, in which an energetic active galactic nucleus contributes significantly to the bolometric luminosity, have their R {sub midCO} higher and lower than R{sub midCO}{sup SF}, respectively.

  14. STAR FORMATION IN TWO LUMINOUS SPIRAL GALAXIES

    SciTech Connect

    Hunter, Deidre A.; Ashburn, Allison; Wright, Teresa; Elmegreen, Bruce G.; Rubin, Vera C.; Józsa, Gyula I. G.; Struve, Christian

    2013-10-01

    We examined star formation in two very luminous (M{sub V} = –22 to –23) Sc-type spiral galaxies, NGC 801 and UGC 2885, using ultra-deep Hα images. We combine these Hα images with UBV and Two-Micron All-Sky Survey JHK images and H I maps to explore the star formation characteristics of disk galaxies at high luminosity. Hα traces star formation in these galaxies to 4-6 disk scale lengths, but the lack of detection of Hα further out is likely due to the loss of Lyman continuum photons. Considering gravitational instabilities alone, we find that the gas and stars in the outer regions are marginally stable in an average sense, but considering dissipative gas and radial and azimuthal forcing, the outer regions are marginally unstable to forming spiral arms. Star formation is taking place in spiral arms, which are regions of locally higher gas densities. Furthermore, we have traced smooth exponential stellar disks over four magnitudes in V-band surface brightness and 4-6 disk scale lengths, in spite of a highly variable gravitational instability parameter. Thus, gravitational instability thresholds do not seem relevant to the stellar disk. One possibility for creating an exponential disk is that the molecular cloud densities and star formation rates have exponential profiles and this fact forces the stellar disk to build up such a profile. Another possibility is that the stellar disk is continuously adjusted to an exponential shape regardless of the star formation profile, for example, through global dynamical processes that scatter stars. However, such scattering processes are only known to operate in spiral systems, in which case they cannot explain the same dilemma of smooth exponential disks observed in dwarf irregular galaxies.

  15. Brightest Cluster Galaxy Identification

    NASA Astrophysics Data System (ADS)

    Leisman, Luke; Haarsma, D. B.; Sebald, D. A.; ACCEPT Team

    2011-01-01

    Brightest cluster galaxies (BCGs) play an important role in several fields of astronomical research. The literature includes many different methods and criteria for identifying the BCG in the cluster, such as choosing the brightest galaxy, the galaxy nearest the X-ray peak, or the galaxy with the most extended profile. Here we examine a sample of 75 clusters from the Archive of Chandra Cluster Entropy Profile Tables (ACCEPT) and the Sloan Digital Sky Survey (SDSS), measuring masked magnitudes and profiles for BCG candidates in each cluster. We first identified galaxies by hand; in 15% of clusters at least one team member selected a different galaxy than the others.We also applied 6 other identification methods to the ACCEPT sample; in 30% of clusters at least one of these methods selected a different galaxy than the other methods. We then developed an algorithm that weighs brightness, profile, and proximity to the X-ray peak and centroid. This algorithm incorporates the advantages of by-hand identification (weighing multiple properties) and automated selection (repeatable and consistent). The BCG population chosen by the algorithm is more uniform in its properties than populations selected by other methods, particularly in the relation between absolute magnitude (a proxy for galaxy mass) and average gas temperature (a proxy for cluster mass). This work supported by a Barry M. Goldwater Scholarship and a Sid Jansma Summer Research Fellowship.

  16. Galaxy dynamics in clustered environments

    NASA Astrophysics Data System (ADS)

    Pereira, Maria J. R. R.

    Galaxy orientations have been studied statistically for over 70 years now, but it is only recently that alignments have been found on scales larger than those of close interacting pairs. Large scale alignments between galaxies and their surrounding tidal fields are expected to occur during formation, but what happens when these galaxies fall into larger systems? Can their orientations tell us anything about the accretion process itself? In this dissertation I will focus on the radial alignment of satellite galaxies, in which a satellite's long axis points preferentially toward the center of its host. I present observational evidence for this type of galaxy alignment in the SDSS DR3 using a sample of X-ray selected massive clusters. Then, using results from N-body cosmological simulations, I will argue that this effect is the result of a secular tidal interaction between the galaxies and their host potential. The analysis shows that subhalos are effectively torqued by their host throughout their orbits, so that their major axes tend to be aligned with the gradient of the host potential. The significant discrepancy between the magnitude of the effect as seen in these simulations and that detected in observations motivates the work of the next chapter, where I perform numerical experiments on idealized, high resolution N-body models of elliptical galaxies. These experiments show that the more centrally concentrated luminous components of galaxies take longer to react to the external torque, and, in the particular case of mildly eccentric orbits, their orientations can figure rotate in periodic patterns that are not radially aligned on average. The mechanism is more effective on galaxies that have larger triaxialities, but the overall effect of torquing is to make galaxies rounder, since radially misaligned galaxies tend to become more spherical as they are torqued towards equilibrium. In the last chapter, I briefly discuss the impact of these results for galaxy

  17. Photometric Properties of Galaxies in Poor Clusters

    NASA Astrophysics Data System (ADS)

    Sharma, M.; Prabhu, T.

    We study several statistical properties of galaxies in four poor clusters of galaxies using optical photometry. We select these poor clusters as luminous, extended X-ray sources identified with poor galaxy systems in the EMSS catalogue of clusters of galaxies. The clusters are at moderate redshifts (0.08galaxy populations are clearly evolved, as traced by the tightness of their color--magnitude relations and accordance of the latter with those of the Virgo Cluster. The fraction of blue galaxies is similar to those of low-redshift richness 0 clusters and higher than those of richer clusters at similar redshifts. The luminosity functions (LFs) of the individual clusters are not significantly different from each other. Using these, we construct composite LFs in B, V , and R bands (to MV=-18). The faint-end of these LFs are flat, like the V-band LF of other (e.g., MKW/AWM) poor clusters, but steeper than the field LF in the R-band. In terms of the statistical properties of their member galaxies, poor clusters appear to be lower-mass extensions of their rich counterparts.

  18. Morphological classification of local luminous infrared galaxies

    NASA Astrophysics Data System (ADS)

    Psychogyios, A.; Charmandaris, V.; Diaz-Santos, T.; Armus, L.; Haan, S.; Howell, J.; Le Floc'h, E.; Petty, S. M.; Evans, A. S.

    2016-06-01

    We present analysis of the morphological classification of 89 luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey (GOALS) sample, using non-parametric coefficients and compare their morphology as a function of wavelength. We rely on images that were obtained in the optical (B- and I-band) as well as in the infrared (H-band and 5.8 μm). Our classification is based on the calculation of Gini and the second order of light (M20) non-parametric coefficients, which we explore as a function of stellar mass (M⋆), infrared luminosity (LIR), and star formation rate (SFR). We investigate the relation between M20, the specific SFR (sSFR) and the dust temperature (Tdust) in our galaxy sample. We find that M20 is a better morphological tracer than Gini, as it allows us to distinguish systems that were formed by double systems from isolated and post-merger LIRGs. The effectiveness of M20 as a morphological tracer increases with increasing wavelength, from the B to H band. In fact, the multi-wavelength analysis allows us to identify a region in the Gini-M20 parameter space where ongoing mergers reside, regardless of the band used to calculate the coefficients. In particular, when measured in the H band, a region that can be used to identify ongoing mergers, with minimal contamination from LIRGs in other stages. We also find that, while the sSFR is positively correlated with M20 when measured in the mid-infrared, i.e. star-bursting galaxies show more compact emission, it is anti-correlated with the B-band-based M20. We interpret this as the spatial decoupling between obscured and unobscured star formation, whereby the ultraviolet/optical size of an LIRG experience an intense dust-enshrouded central starburst that is larger that in the mid-infrared since the contrast between the nuclear to the extended disk emission is smaller in the mid-infrared. This has important implications for high redshift surveys of dusty sources, where sizes of galaxies

  19. The Luminous Convolution Model for Galaxy Rotation Curves

    NASA Astrophysics Data System (ADS)

    Rubin, Shanon; Mucci, Maria; Sophia Cisneros Collaboration; Kennard Chng Collaboration; Meagan Crowley Collaboration

    2016-03-01

    The LCM takes as input only the observed luminous matter profile from galaxies, and allows us to confirm these observed data by considering frame-dependent effects from the luminous mass profile of the Milky Way. The LCM is useful when looking at galaxies that have similar total enclosed mass, but varying distributions. For example, variations in luminous matter profiles from a diffuse galaxy correlate to the LCM's five different Milky Way models equally well, but LCM fits for a centrally condensed galaxy distinguish between Milky Way models. In this presentation, we show how the rotation curve data of such galaxies can be used to constrain the Milky Way luminous mass modeling, by the physical characteristics of each galaxy used to interpret the fitting. Current Investigations will be presented showing how the convolved parameters of Keplerian predictions with rotation curve observations can be extracted with respect to the crossing location of the relative curvature versus the assumption of the luminous mass profiles from photometry. Since there currently exists no direct constraint to photometric estimates of the luminous mass in these systems, the LCM gives the first constraint based on the orthogonal measurement of Doppler shifted spectra from characteristic emitters.

  20. Photometric Properties of Poor Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Sharma, M.; Prabhu, T. P.

    2002-12-01

    We study several statistical properties of galaxies in four poor clusters of galaxies using multi-color optical photometry obtained at the Vainu Bappu Telescope, India. The clusters, selected from the EMSS Catalog, are at moderate redshifts (0.08 < z < 0.25), of equivalent Abell richness R=0, and appear to be dynamically young. The early-type galaxy populations are clearly evolved, as traced by the tightness of the color-magnitude relations and the accordance of the latter with those of the Virgo cluster. The blue galaxy fractions are similar to those of R=0 clusters and higher than those of richer clusters at similar redshifts. The composite luminosity functions (LFs) in B, V, and R bands are flat at the faint end, similar to the V-band LF derived by Yamagata & Maehara for other (MKW/AWM) poor clusters but steeper than the R-band field LF derived by Lin et al. In terms of the statistical properties of their member galaxies, poor clusters appear to be lower-mass extensions of their rich counterparts. The brightest galaxies of three of these poor clusters appear to be luminous ellipticals with no incontrovertible signatures of a halo. It is likely that they were formed from multiple mergers early in the history of the clusters.

  1. Cluster galaxies die hard

    NASA Astrophysics Data System (ADS)

    Weinmann, Simone M.; Kauffmann, Guinevere; von der Linden, Anja; De Lucia, Gabriella

    2010-08-01

    We investigate how the specific star formation rates of galaxies of different masses depend on cluster-centric radius and on the central/satellite dichotomy in both field and cluster environments. Recent data from a variety of sources, including the cluster catalogue of von der Linden et al., are compared to the semi-analytic models of De Lucia & Blaizot. We find that these models predict too many passive satellite galaxies in clusters, too few passive central galaxies with low stellar masses and too many passive central galaxies with high masses. We then outline a series of modifications to the model necessary to solve these problems: (a) instead of instantaneous stripping of the external gas reservoir after a galaxy becomes a satellite, the gas supply is assumed to decrease at the same rate that the surrounding halo loses mass due to tidal stripping and (b) the active galactic nuclei (AGN) feedback efficiency is lowered to bring the fraction of massive passive centrals in better agreement with the data. We also allow for radio mode AGN feedback in satellite galaxies. (c) We assume that satellite galaxies residing in host haloes with masses below 1012h-1Msolar do not undergo any stripping. We highlight the fact that in low-mass galaxies, the external reservoir is composed primarily of gas that has been expelled from the galactic disc by supernovae-driven winds. This gas must remain available as a future reservoir for star formation, even in satellite galaxies. Finally, we present a simple recipe for the stripping of gas and dark matter in satellites that can be used in models where subhalo evolution is not followed in detail.

  2. On the clustering of faint red galaxies

    NASA Astrophysics Data System (ADS)

    Xu, Haojie; Zheng, Zheng; Guo, Hong; Zhu, Ju; Zehavi, Idit

    2016-08-01

    Faint red galaxies in the Sloan Digital Sky Survey show a puzzling clustering pattern in previous measurements. In the two-point correlation function (2PCF), they appear to be strongly clustered on small scales, indicating a tendency to reside in massive haloes as satellite galaxies. However, their weak clustering on large scales suggests that they are more likely to be found in low-mass haloes. The interpretation of the clustering pattern suffers from the large sample variance in the 2PCF measurements, given the small volume of the volume-limited sample of such faint galaxies. We present improved clustering measurements of faint galaxies by making a full use of a flux-limited sample to obtain volume-limited measurements with an increased effective volume. In the improved 2PCF measurements, the fractional uncertainties on large scales drop by more than 40 per cent, and the strong contrast between small-scale and large-scale clustering amplitudes seen in previous work is no longer prominent. From halo occupation distribution modelling of the measurements, we find that a considerable fraction of faint red galaxies to be satellites in massive haloes, a scenario supported by the strong covariance of small-scale 2PCF measurements and the relative spatial distribution of faint red galaxies and luminous galaxies. However, the satellite fraction is found to be degenerate with the slope of the distribution profile of satellites in inner haloes. We compare the modelling results with semi-analytic model predictions and discuss the implications.

  3. SUBMILLIMETER GALAXY NUMBER COUNTS AND MAGNIFICATION BY GALAXY CLUSTERS

    SciTech Connect

    Lima, Marcos; Jain, Bhuvnesh; Devlin, Mark; Aguirre, James

    2010-07-01

    We present an analytical model that reproduces measured galaxy number counts from surveys in the wavelength range of 500 {mu}m-2 mm. The model involves a single high-redshift galaxy population with a Schechter luminosity function that has been gravitationally lensed by galaxy clusters in the mass range 10{sup 13}-10{sup 15} M{sub sun}. This simple model reproduces both the low-flux and the high-flux end of the number counts reported by the BLAST, SCUBA, AzTEC, and South Pole Telescope (SPT) surveys. In particular, our model accounts for the most luminous galaxies detected by SPT as the result of high magnifications by galaxy clusters (magnification factors of 10-30). This interpretation implies that submillimeter (submm) and millimeter surveys of this population may prove to be a useful addition to ongoing cluster detection surveys. The model also implies that the bulk of submm galaxies detected at wavelengths larger than 500 {mu}m lie at redshifts greater than 2.

  4. Cosmology with galaxy clusters

    NASA Astrophysics Data System (ADS)

    Sartoris, Barbara

    2015-08-01

    Clusters of galaxies are powerful probes to constrain parameters that describe the cosmological models and to distinguish among different models. Since, the evolution of the cluster mass function and large-scale clustering contain the informations about the linear growth rate of perturbations and the expansion history of the Universe, clusters have played an important role in establishing the current cosmological paradigm. It is crucial to know how to determine the cluster mass from observational quantities when using clusters as cosmological tools. For this, numerical simulations are helpful to define and study robust cluster mass proxies that have minimal and well understood scatter across the mass and redshift ranges of interest. Additionally, the bias in cluster mass determination can be constrained via observations of the strong and weak lensing effect, X-ray emission, the Sunyaev- Zel’dovic effect, and the dynamics of galaxies.A major advantage of X-ray surveys is that the observable-mass relation is tight. Moreover, clusters can be easily identified in X-ray as continuous, extended sources. As of today, interesting cosmological constraints have been obtained from relatively small cluster samples (~102), X-ray selected by the ROSAT satellite over a wide redshift range (0clusters, the ROSAT All-Sky Survey.The next generation of X-ray telescopes will enhance the statistics of detected clusters and enlarge their redshift coverage. In particular, eROSITA will produce a catalog of >105 clusters with photometric redshifts from multi-band optical surveys (e.g. PanSTARRS, DES, and LSST). This will vastly improve upon current cosmological constraints, especially by the synergy with other cluster surveys that

  5. Quenching star formation in cluster galaxies

    NASA Astrophysics Data System (ADS)

    Taranu, Dan S.; Hudson, Michael J.; Balogh, Michael L.; Smith, Russell J.; Power, Chris; Oman, Kyle A.; Krane, Brad

    2014-05-01

    In order to understand the processes that quench star formation in cluster galaxies, we construct a library of subhalo orbits drawn from Λ cold dark matter cosmological N-body simulations of four rich clusters. We combine these orbits with models of star formation followed by environmental quenching, comparing model predictions with observed bulge and disc colours and stellar absorption line-strength indices of luminous cluster galaxies. Models in which the bulge stellar populations depend only on the galaxy subhalo mass while the disc is quenched upon infall are acceptable fits to the data. An exponential disc quenching time-scale of 3-3.5 Gyr is preferred. Quenching in lower mass groups prior to infall (`pre-processing') provides better fits, with similar quenching time-scales. Models with short (≲1 Gyr) quenching time-scales yield excessively steep cluster-centric gradients in disc colours and Balmer line indices, even if quenching is delayed for several Gyr. The data slightly prefer models where quenching occurs only for galaxies falling within ˜0.5r200. These results imply that the environments of rich clusters must impact star formation rates of infalling galaxies on relatively long time-scales, indicative of gentler quenching mechanisms such as slow `strangulation' over more rapid ram-pressure stripping.

  6. OBSERVATIONS OF DARK AND LUMINOUS MATTER: THE RADIAL DISTRIBUTION OF SATELLITE GALAXIES AROUND MASSIVE RED GALAXIES

    SciTech Connect

    Tal, Tomer; Wake, David A.; Van Dokkum, Pieter G.

    2012-05-20

    We study the projected radial distribution of satellite galaxies around more than 28,000 luminous red galaxies (LRGs) at 0.28 < z < 0.40 and trace the gravitational potential of LRG groups in the range 15 < r/kpc < 700. We show that at large radii the satellite number-density profile is well fitted by a projected Navarro-Frenk-White (NFW) profile with r{sub s} {approx} 270 kpc and that at small radii this model underestimates the number of satellite galaxies. Utilizing the previously measured stellar light distribution of LRGs from deep imaging stacks, we demonstrate that this small-scale excess is consistent with a non-negligible baryonic mass contribution to the gravitational potential of massive groups and clusters. The combined NFW+scaled stellar profile provides an excellent fit to the satellite number-density profile all the way from 15 kpc to 700 kpc. Dark matter dominates the total mass profile of LRG halos at r > 25 kpc whereas baryons account for more than 50% of the mass at smaller radii. We calculate the total dark-to-baryonic mass ratio and show that it is consistent with measurements from weak lensing for environments dominated by massive early-type galaxies. Finally, we divide the satellite galaxies in our sample into three luminosity bins and show that the satellite light profiles of all brightness levels are consistent with each other outside of roughly 25 kpc. At smaller radii we find evidence for a mild mass segregation with an increasing fraction of bright satellites close to the central LRG.

  7. Evidence for Merging or Disruption of Red Galaxies from the Evolution of Their Clustering

    SciTech Connect

    White, Martin; White, Martin; Zheng, Zheng; Brown, Michael J. I.; Dey, Arjun; Jannuzi, Buell T.

    2006-11-29

    The formation and evolution of massive red galaxies form a crucial test of theories of galaxy formation based on hierarchical assembly. In this Letter we use observations of the clustering of luminous red galaxies from the Boötes field and N-body simulations to argue that about of the most luminous satellite galaxies appear to undergo merging or disruption within massive halos between and 0.5.

  8. Are Luminous cD Halos Formed by the Disruption of Dwarf Galaxies?

    NASA Astrophysics Data System (ADS)

    López-Cruz, Omar; Yee, H. K. C.; Brown, James P.; Jones, Christine; Forman, William

    1997-02-01

    From a total sample of 45 Abell clusters observed by the Einstein X-ray observatory, we present the results on the galaxy luminosity function (LF) for a group of seven clusters that were identified by the morphology of their LFs. The LFs were derived using photometric data to a completeness limit ~5.5 mag below M*. We found that a single Schechter function with an average α ~ -1.0 gives a good fit to these individual LFs within the magnitude range. These seven clusters have common properties, which indicate they form a homogeneous class of dynamically evolved clusters that can be characterized by the presence of a dominant cD galaxy, high richness, symmetrical single-peaked X-ray emission, and high gas mass. On the other hand, steep faint-end slopes (-2.0 <= α <= -1.4) are usually detected in poorer clusters. Our result gives a direct indication that the faint-end slope of the galaxy LF is subject to environmental effects. We propose that the flatness of the faint-end slope in these clusters results from the disruption of a large fraction of dwarf galaxies during the early stages of cluster evolution. The stars and gas from the disrupted galaxies are redistributed throughout the cluster potential during violent relaxation. This heuristic scenario can explain the origin of the luminous halos of cD galaxies and a large fraction of the gas content in the intracluster medium as a by-product. The correlation between the cluster gas mass determined from the modeling of the X-ray emission and the cD halo optical luminosity is presented to support the proposed model.

  9. The Rotation of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Tovmassian, H. M.

    2015-09-01

    The method for detection of the galaxy cluster rotation based on the study of distribution of member galaxies with velocities lower and higher than the cluster mean velocity over the cluster image is proposed. The search for rotation is made for flat clusters with a/b > 1.8 and BMI type clusters which are expected to be rotating. For comparison there were studied also round clusters and clusters of NBMI type, the second by brightness galaxy, which does not differ significantly from the cluster cD galaxy. Seventeen out of studied 65 clusters are found to be rotating. It was found that the detection rate is sufficiently high for flat clusters, over 60%, and clusters of BMI type with dominant cD galaxy, ≈ 35% . The obtained results show that clusters were formed from the huge primordial gas clouds and preserved the rotation of the primordial clouds, unless they did not experience mergings with other clusters and groups of galaxies, as a result of which the rotation was prevented.

  10. On the distribution of galaxy ellipticity in clusters

    NASA Astrophysics Data System (ADS)

    D'Eugenio, F.; Houghton, R. C. W.; Davies, R. L.; Dalla Bontà, E.

    2015-07-01

    We study the distribution of projected ellipticity n(ɛ) for galaxies in a sample of 20 rich (Richness ≥ 2) nearby (z < 0.1) clusters of galaxies. We find no evidence of differences in n(ɛ), although the nearest cluster in the sample (the Coma Cluster) is the largest outlier (P(same) < 0.05). We then study n(ɛ) within the clusters, and find that ɛ increases with projected cluster-centric radius R (hereafter the ɛ-R relation). This trend is preserved at fixed magnitude, showing that this relation exists over and above the trend of more luminous galaxies to be both rounder and more common in the centres of clusters. The ɛ-R relation is particularly strong in the subsample of intrinsically flattened galaxies (ɛ > 0.4), therefore it is not a consequence of the increasing fraction of round slow rotator galaxies near cluster centers. Furthermore, the ɛ-R relation persists for just smooth flattened galaxies and for galaxies with de Vaucouleurs-like light profiles, suggesting that the variation of the spiral fraction with radius is not the underlying cause of the trend. We interpret our findings in light of the classification of early type galaxies (ETGs) as fast and slow rotators. We conclude that the observed trend of decreasing ɛ towards the centres of clusters is evidence for physical effects in clusters causing fast rotator ETGs to have a lower average intrinsic ellipticity near the centres of rich clusters.

  11. Two Galaxy Clusters: A3565 and A3560

    NASA Astrophysics Data System (ADS)

    Willmer, C. N. A.; Maia, M. A. G.; Mendes, S. O.; Alonso, M. V.; Rios, L. A.; Chaves, O. L.; de Mello, D. F.

    1999-09-01

    We report 102 new redshifts and magnitudes for a sample of galaxies to R_F~15.5 mag in a 2.17dx2.17d region centered on the galaxy IC 4296, the most luminous member of the A3565 Cluster. Up to the limiting magnitude, we find 29 cluster members and measure a velocity dispersion of sigma=228 km s^-1. The estimated total mass for this system is ~3.0x10^13 h^-1 M_solar [where h=H_0/(100 km s^-1 Mpc^-1)], and its dynamical properties are quite typical of poor clusters presenting X-ray emission. We also find that galaxies with absorption lines are more concentrated toward the center of the cluster, while systems with emission lines are mainly located in the outer parts. The small velocity dispersion of the cluster, coupled with the known presence of an interacting pair of galaxies, and the large extent of the brightest cluster galaxy, could indicate that galaxy formation through mergers may still be underway in this system. The surveyed region also contains galaxies belonging to the Shapley concentration cluster A3560. Within 30' of the cluster center, we detect 32 galaxies, for which we measure a velocity dispersion of 588 km s^-1 and a mass of ~2x10^14 h^-1 M_solar. However, because our sample is restricted to galaxies brighter than M^*, these values should be considered only as rough estimates.

  12. Cosmological constraints from the SDSS luminous red galaxies

    NASA Astrophysics Data System (ADS)

    Tegmark, Max; Eisenstein, Daniel J.; Strauss, Michael A.; Weinberg, David H.; Blanton, Michael R.; Frieman, Joshua A.; Fukugita, Masataka; Gunn, James E.; Hamilton, Andrew J. S.; Knapp, Gillian R.; Nichol, Robert C.; Ostriker, Jeremiah P.; Padmanabhan, Nikhil; Percival, Will J.; Schlegel, David J.; Schneider, Donald P.; Scoccimarro, Roman; Seljak, Uroš; Seo, Hee-Jong; Swanson, Molly; Szalay, Alexander S.; Vogeley, Michael S.; Yoo, Jaiyul; Zehavi, Idit; Abazajian, Kevork; Anderson, Scott F.; Annis, James; Bahcall, Neta A.; Bassett, Bruce; Berlind, Andreas; Brinkmann, Jon; Budavari, Tamás; Castander, Francisco; Connolly, Andrew; Csabai, Istvan; Doi, Mamoru; Finkbeiner, Douglas P.; Gillespie, Bruce; Glazebrook, Karl; Hennessy, Gregory S.; Hogg, David W.; Ivezić, Željko; Jain, Bhuvnesh; Johnston, David; Kent, Stephen; Lamb, Donald Q.; Lee, Brian C.; Lin, Huan; Loveday, Jon; Lupton, Robert H.; Munn, Jeffrey A.; Pan, Kaike; Park, Changbom; Peoples, John; Pier, Jeffrey R.; Pope, Adrian; Richmond, Michael; Rockosi, Constance; Scranton, Ryan; Sheth, Ravi K.; Stebbins, Albert; Stoughton, Christopher; Szapudi, István; Tucker, Douglas L.; vanden Berk, Daniel E.; Yanny, Brian; York, Donald G.

    2006-12-01

    We measure the large-scale real-space power spectrum P(k) using luminous red galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS) and use this measurement to sharpen constraints on cosmological parameters from the Wilkinson Microwave Anisotropy Probe (WMAP). We employ a matrix-based power spectrum estimation method using Pseudo-Karhunen-Loève eigenmodes, producing uncorrelated minimum-variance measurements in 20 k-bands of both the clustering power and its anisotropy due to redshift-space distortions, with narrow and well-behaved window functions in the range 0.01h/Mpcgalaxy samples are consistent, with the former providing higher signal-to-noise. Our results are robust to omitting angular and radial density fluctuations and are consistent between different parts of the sky. They provide a striking confirmation of the predicted large-scale ΛCDM power spectrum. Combining only SDSS LRG and WMAP data places robust constraints on many cosmological parameters that complement prior analyses of multiple data sets. The LRGs provide independent cross-checks on Ωm and the baryon fraction in good agreement with WMAP. Within the context of flat ΛCDM models, our LRG measurements complement WMAP by sharpening the constraints on the matter density, the neutrino density and the tensor amplitude by about a factor of 2, giving Ωm=0.24±0.02 (1σ), ∑mν≲0.9eV (95%) and r<0.3 (95%). Baryon oscillations are clearly detected and provide a robust measurement of the comoving distance to the median survey redshift z=0.35 independent of curvature and dark energy properties. Within the ΛCDM framework, our power spectrum measurement improves the evidence for spatial flatness, sharpening the curvature constraint Ωtot=1.05±0.05 from WMAP alone to Ωtot=1.003±0.010. Assuming Ωtot=1, the equation of state parameter is constrained to w=-0.94±0.09, indicating the potential for more ambitious future LRG measurements to provide precision

  13. Temperature distribution of dust in luminous IRAS galaxies

    NASA Technical Reports Server (NTRS)

    Carico, David P.

    1989-01-01

    Work is currently in progress to obtain temperature distributions of dust in the most infrared-luminous galaxies. The results presented are of a preliminary nature, representing a zeroth-order approximation. The objects which have been analyzed so far are all galaxies from the Infrared Astronomy Satellite (IRAS) Bright Galaxy Sample with infrared luminosities L sub IR greater than or equal to 10(exp 11) solar luminosity. They are: Arp 220, Mrk 231, Mrk 273, NGC 1614, NGC 3690, NGC 6285/6, and Zw 049.057. The analysis utilized 3.7 micron data from the Palomar 5 m Hale telescope, IRAS data at 12, 25, 60, and 100 microns, and 1 mm continuum data from the CalTech Submillimeter Observatory on Mauna Kea.

  14. Astrophysics of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Ettori, Stefano

    2016-07-01

    As the nodes of the cosmic web, clusters of galaxies trace the large-scale distribution of matter in the Universe. They are thus privileged sites in which to investigate the complex physics of structure formation. However, the complete story of how these structures grow, and how they dissipate the gravitational and non-thermal components of their energy budget over cosmic time, is still beyond our grasp. Most of the baryons gravitationally bound to the cluster's halo is in the form of a diffuse, hot, metal-enriched plasma that radiates primarily in the X-ray band. X-ray observations of the evolving cluster population provide a unique opportunity to address such fundamental open questions as: How do hot diffuse baryons accrete and dynamically evolve in dark matter potentials? How and when was the energy that we observe in the ICM generated and distributed? Where and when are heavy elements produced and how are they circulated? We will present the ongoing activities to define the strategy on how an X-ray observatory with large collecting area and an unprecedented combination of high spectral and angular resolution, such as Athena, can address these questions.

  15. A Second Luminous Blue Variable in the Quintuplet Cluster

    NASA Astrophysics Data System (ADS)

    Geballe, T. R.; Najarro, F.; Figer, D. F.

    2000-02-01

    H- and K-band moderate-resolution and 4 μm high-resolution spectra have been obtained for FMM 362, a bright star in the Quintuplet Cluster near the Galactic center. The spectral features in these bands closely match those of the Pistol Star, a luminous blue variable and one of the most luminous stars known. The new spectra and previously obtained photometry imply a very high luminosity for FMM 362, L>=106 Lsolar, and a temperature of 10,000-13,000 K. Based on its luminosity, temperature, photometric variability, and similarities to the Pistol Star, we conclude that FMM 362 is a luminous blue variable.

  16. A NEW TEST OF THE STATISTICAL NATURE OF THE BRIGHTEST CLUSTER GALAXIES

    SciTech Connect

    Lin, Yen-Ting; Ostriker, Jeremiah P.; Miller, Christopher J.

    2010-06-01

    A novel statistic is proposed to examine the hypothesis that all cluster galaxies are drawn from the same luminosity distribution (LD). In such a 'statistical model' of galaxy LD, the brightest cluster galaxies (BCGs) are simply the statistical extreme of the galaxy population. Using a large sample of nearby clusters, we show that BCGs in high luminosity clusters (e.g., L {sub tot} {approx}> 4 x 10{sup 11} h {sup -2} {sub 70} L {sub sun}) are unlikely (probability {<=}3 x 10{sup -4}) to be drawn from the LD defined by all red cluster galaxies more luminous than M{sub r} = -20. On the other hand, BCGs in less luminous clusters are consistent with being the statistical extreme. Applying our method to the second brightest galaxies, we show that they are consistent with being the statistical extreme, which implies that the BCGs are also distinct from non-BCG luminous, red, cluster galaxies. We point out some issues with the interpretation of the classical tests proposed by Tremaine and Richstone (TR) that are designed to examine the statistical nature of BCGs, investigate the robustness of both our statistical test and those of TR against difficulties in photometry of galaxies of large angular size, and discuss the implication of our findings on surveys that use the luminous red galaxies to measure the baryon acoustic oscillation features in the galaxy power spectrum.

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

    NASA Astrophysics Data System (ADS)

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

    1999-01-01

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

  18. Candidate High Redshift Clusters of Dusty Galaxies from Herschel & Planck

    NASA Astrophysics Data System (ADS)

    Clements, David L.

    2015-08-01

    The cross identification of Planck compact sources with objects in karger area Herschel surveys, such as HerMES and H-ATLAS, has led to the discovery of candidate high redshift (out to z~3) clusters of far-IR luminous star forming galaxies. These objects are not easily reproduced in the current generations of galaxy and large scale formation simulations and are thus a potentially powerful new tool for comnstraining galaxy and cluster formation models. We will review the current results on these sources and examine future prospects for progress in this novel and potentially important new field.

  19. Cosmological information in the intrinsic alignments of luminous red galaxies

    NASA Astrophysics Data System (ADS)

    Chisari, Nora Elisa; Dvorkin, Cora

    2013-12-01

    The intrinsic alignments of galaxies are usually regarded as a contaminant to weak gravitational lensing observables. The alignment of Luminous Red Galaxies, detected unambiguously in observations from the Sloan Digital Sky Survey, can be reproduced by the linear tidal alignment model of Catelan, Kamionkowski & Blandford (2001) on large scales. In this work, we explore the cosmological information encoded in the intrinsic alignments of red galaxies. We make forecasts for the ability of current and future spectroscopic surveys to constrain local primordial non-Gaussianity and Baryon Acoustic Oscillations (BAO) in the cross-correlation function of intrinsic alignments and the galaxy density field. For the Baryon Oscillation Spectroscopic Survey, we find that the BAO signal in the intrinsic alignments is marginally significant with a signal-to-noise ratio of 1.8 and 2.2 with the current LOWZ and CMASS samples of galaxies, respectively, and increasing to 2.3 and 2.7 once the survey is completed. For the Dark Energy Spectroscopic Instrument and for a spectroscopic survey following the EUCLID redshift selection function, we find signal-to-noise ratios of 12 and 15, respectively. Local type primordial non-Gaussianity, parametrized by fNL = 10, is only marginally significant in the intrinsic alignments signal with signal-to-noise ratios < 2 for the three surveys considered.

  20. Cosmological information in the intrinsic alignments of luminous red galaxies

    SciTech Connect

    Chisari, Nora Elisa; Dvorkin, Cora E-mail: cdvorkin@ias.edu

    2013-12-01

    The intrinsic alignments of galaxies are usually regarded as a contaminant to weak gravitational lensing observables. The alignment of Luminous Red Galaxies, detected unambiguously in observations from the Sloan Digital Sky Survey, can be reproduced by the linear tidal alignment model of Catelan, Kamionkowski and Blandford (2001) on large scales. In this work, we explore the cosmological information encoded in the intrinsic alignments of red galaxies. We make forecasts for the ability of current and future spectroscopic surveys to constrain local primordial non-Gaussianity and Baryon Acoustic Oscillations (BAO) in the cross-correlation function of intrinsic alignments and the galaxy density field. For the Baryon Oscillation Spectroscopic Survey, we find that the BAO signal in the intrinsic alignments is marginally significant with a signal-to-noise ratio of 1.8 and 2.2 with the current LOWZ and CMASS samples of galaxies, respectively, and increasing to 2.3 and 2.7 once the survey is completed. For the Dark Energy Spectroscopic Instrument and for a spectroscopic survey following the EUCLID redshift selection function, we find signal-to-noise ratios of 12 and 15, respectively. Local type primordial non-Gaussianity, parametrized by f{sub NL} = 10, is only marginally significant in the intrinsic alignments signal with signal-to-noise ratios < 2 for the three surveys considered.

  1. Galaxy Clustering in the Dark Energy Survey

    NASA Astrophysics Data System (ADS)

    Ross, Ashley; Dark Energy Survey Large-Scale Structure Working Group

    2016-01-01

    I will present the status of galaxy clustering results in the Dark Energy Survey (DES).DES will image the sky over 5000 deg2 in five photometric bands (grizY) to a nominal depth (iAB ~ 24), enabling the structure of the Universe to be studied to redshift 1.2 and beyond. I will present results of the clustering analyses performed to date, including those from Crocce et al. (2015), who studied the clustering of DES data over five tomographic bins, with photometric redshifts, z, in the range 0.2 < z < 1.2, and those from the `redMaGiC' sample (Rozo et al. 2015), which provides accurate (better than 2%) photometric redshifts for luminous red galaxies. I will describe how these measurements can be combined with weak lensing analyses to probe the growth of structure. Finally, I will report on how DES data can provide a 2% measurement of the angular diameter distance to z~0.9 by measuring the position of baryon acoustic oscillation feature in the clustering of DES galaxies.

  2. X-raying the Winds of Luminous Active Galaxies

    NASA Astrophysics Data System (ADS)

    Brandt, W. N.; Chartas, G.; Gallagher, S. C.; Gibson, R. R.; Miller, B. P.

    2009-12-01

    We briefly describe some recent observational results, mainly at X-ray wavelengths, on the winds of luminous active galactic nuclei (AGNs). These winds likely play a significant role in galaxy feedback. Topics covered include (1) Relations between X-ray and UV absorption in Broad Absorption Line (BAL) and mini-BAL quasars; (2) X-ray absorption in radio-loud BAL quasars; and (3) Evidence for relativistic iron K BALs in the X-ray spectra of a few bright quasars. We also mention some key outstanding problems and prospects for future advances; e.g., with the International X-ray Observatory (IXO).

  3. Observing the First Stars in Luminous, Red Galaxies

    NASA Technical Reports Server (NTRS)

    Heap, Sally; Lindler, Don

    2010-01-01

    Modern cosmological simulations predict that the first stars are to be found today in luminous, red galaxies. Although observing such stars individually against a background of younger, metal-rich stars is impossible, the first stars should make their presence known by their strong, line-free ultraviolet flux. We have found evidence for a UV-bright stellar population in Sloan spectra of LRG's at z=0.4-0.5. We present arguments for interpreting this UV-bright stellar population as the oldest stars, rather than other types of stellar populations (e.g. young stars or blue straggler stars in the dominant, metal-rich stellar population

  4. Extra-nuclear starbursts: young luminous Hinge clumps in interacting galaxies

    SciTech Connect

    Smith, Beverly J.; Giroux, Mark L.; Soria, Roberto; Struck, Curtis; Swartz, Douglas A.; Yukita, Mihoko E-mail: girouxm@etsu.edu E-mail: curt@iastate.edu

    2014-03-01

    Hinge clumps are luminous knots of star formation near the base of tidal features in some interacting galaxies. We use archival Hubble Space Telescope (HST) UV/optical/IR images and Chandra X-ray maps along with Galaxy Evolution Explorer UV, Spitzer IR, and ground-based optical/near-IR images to investigate the star forming properties in a sample of 12 hinge clumps in five interacting galaxies. The most extreme of these hinge clumps have star formation rates of 1-9 M {sub ☉} yr{sup –1}, comparable to or larger than the 'overlap' region of intense star formation between the two disks of the colliding galaxy system the Antennae. In the HST images, we have found remarkably large and luminous sources at the centers of these hinge clumps. These objects are much larger and more luminous than typical 'super star clusters' in interacting galaxies, and are sometimes embedded in a linear ridge of fainter star clusters, consistent with star formation along a narrow caustic. These central sources have FWHM diameters of ∼70 pc, compared to ∼3 pc in 'ordinary' super star clusters. Their absolute I magnitudes range from M{sub I} ∼ – 12.2 to –16.5; thus, if they are individual star clusters they would lie near the top of the 'super star cluster' luminosity function of star clusters. These sources may not be individual star clusters, but instead may be tightly packed groups of clusters that are blended together in the HST images. Comparison to population synthesis modeling indicates that the hinge clumps contain a range of stellar ages. This is consistent with expectations based on models of galaxy interactions, which suggest that star formation may be prolonged in these regions. In the Chandra images, we have found strong X-ray emission from several of these hinge clumps. In most cases, this emission is well-resolved with Chandra and has a thermal X-ray spectrum, thus it is likely due to hot gas associated with the star formation. The ratio of the extinction

  5. Luminous Red Galaxies at Z=0.4-0.5

    NASA Technical Reports Server (NTRS)

    Heap, Sally; Lindler, Don

    2009-01-01

    We report on a study of approx.20,000 luminous red galaxies (LRG's) at z=0.4-0.5 observed by the Sloan Digital Sky Survey. In order to differentiate among them, we measured restframe magnitudes, u (3000-3500 A), b (4200-4800 A), and y (5700-6300 A) from the spectra themselves. The galaxies show a significant range in restframe colors and absolute magnitudes. We binned the spectra according to the restframe u-b color and y-band absolute magnitude in order to increase the S/N. We used 3 approaches to estimate the ages and metal content of these binned spectra: via their spectral energy distributions, from spectral-line indices, and by full spectral fitting. The three methods usually produce discordant results

  6. Seven poor clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Beers, T. C.; Geller, M. J.; Huchra, J. P.; Latham, D. W.; Davis, R. J.

    1984-01-01

    The measurement of 83 new redshifts from galaxies in the region of seven of the poor clusters of galaxies identified by Morgan et al (1975) and Albert et al (1977) has been followed by an estimation of cluster masses through the application of both the virial theorem and the projected mas method. For each system, these two estimates are consistent. For the two clusters with highest X-ray luminosities, the line-of-sight velocity dispersions are about 700 km/sec, while for the five other clusters, the dispersions are of the order of less than about 370 km/sec. The D or cD galaxy in each poor cluster is at the kinematic center of each system.

  7. The KMOS Galaxy Clusters Project

    NASA Astrophysics Data System (ADS)

    Davies, Roger L.; Beifiori, A.; Bender, R.; Cappellari, M.; Chan, J.; Houghton, R.; Mendel, T.; Saglia, R.; Sharples, R.; Stott, J.; Smith, R.; Wilman, D.

    2015-04-01

    KMOS is a cryogenic infrared spectrograph fed by twentyfour deployable integral field units that patrol a 7.2 arcminute diameter field of view at the Nasmyth focus of the ESO VLT. It is well suited to the study of galaxy clusters at 1 < z < 2 where the well understood features in the restframe V-band are shifted into the KMOS spectral bands. Coupled with HST imagining, KMOS offers a window on the critical epoch for galaxy evolution, 7-10 Gyrs ago, when the key properties of cluster galaxies were established. We aim to investigate the size, mass, morphology and star formation history of galaxies in the clusters. Here we describe the instrument, discuss the status of the observations and report some preliminary results.

  8. X-Ray Emission from Ultraviolet Luminous Galaxies and Lyman Break Galaxies

    NASA Technical Reports Server (NTRS)

    Hornschemeier, Ann; Ptak, A. F.; Salim, S.; Heckman, T. P.; Overzier, R.; Mallery, R.; Rich, M.; Strickland, D.; Grimes, J.

    2009-01-01

    We present results from an XMM mini-survey of GALEX-selected Ultraviolet-Luminous Galaxies (UVLGs) that appear to include an interesting subset that are analogs to the distant (3Galaxies (LBGs). The 2-10 kev X-ray emission of LBGs appear to be broadly similar to that of galaxies in the local Universe, possibly indicating similarity in the production of accreting binaries over large evolutionary timescales in the Universe. We have detected luminous X-ray emission from one UVLG that permits basic X-ray spectroscopic analysis, and have direct X-ray constraints on a total of 6 UVLGs. We find evidence for likely large scatter in the assumed X-ray/star-formation rate relation for LBGs.

  9. A CANDIDATE FOR THE MOST LUMINOUS OB ASSOCIATION IN THE GALAXY

    SciTech Connect

    Rahman, Mubdi; Matzner, Christopher; Moon, Dae-Sik

    2011-02-20

    The Milky Way harbors giant H II regions, which may be powered by star complexes more luminous than any known Galactic OB association. Being across the disk of the Galaxy, however, these brightest associations are severely extinguished and confused. We present a search for one such association toward the most luminous H II region in the recent catalog by Murray and Rahman, which, at {approx}9.7 kpc, has a recombination rate of {approx}7 x 10{sup 51} s{sup -1}. Prior searches have identified only small-scale clustering around the rim of this shell-like region, but the primary association has not previously been identified. We apply a near-infrared color selection and find an overdensity of point sources toward its southern central part. The colors and magnitudes of these excess sources are consistent with O- and early B-type stars at extinctions 0.96 < A{sub K} < 1.2, and they are sufficiently numerous (406 {+-} 102 after subtraction of field sources) to ionize the surrounding H II region, making this a candidate for the most luminous OB association in the Galaxy. We reject an alternate theory, in which the apparent excess is caused by localized extinction, as inconsistent with source demographics.

  10. A Candidate for the Most Luminous OB Association in the Galaxy

    NASA Astrophysics Data System (ADS)

    Rahman, Mubdi; Matzner, Christopher; Moon, Dae-Sik

    2011-02-01

    The Milky Way harbors giant H II regions, which may be powered by star complexes more luminous than any known Galactic OB association. Being across the disk of the Galaxy, however, these brightest associations are severely extinguished and confused. We present a search for one such association toward the most luminous H II region in the recent catalog by Murray & Rahman, which, at ~9.7 kpc, has a recombination rate of ~7 × 1051 s-1. Prior searches have identified only small-scale clustering around the rim of this shell-like region, but the primary association has not previously been identified. We apply a near-infrared color selection and find an overdensity of point sources toward its southern central part. The colors and magnitudes of these excess sources are consistent with O- and early B-type stars at extinctions 0.96 < AK < 1.2, and they are sufficiently numerous (406 ± 102 after subtraction of field sources) to ionize the surrounding H II region, making this a candidate for the most luminous OB association in the Galaxy. We reject an alternate theory, in which the apparent excess is caused by localized extinction, as inconsistent with source demographics.

  11. Probing Globular Cluster Formation in Low Metallicity Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Johnson, Kelsey E.; Hunt, Leslie K.; Reines, Amy E.

    2008-12-01

    The ubiquitous presence of globular clusters around massive galaxies today suggests that these extreme star clusters must have been formed prolifically in the earlier universe in low-metallicity galaxies. Numerous adolescent and massive star clusters are already known to be present in a variety of galaxies in the local universe; however most of these systems have metallicities of 12 + log(O/H) > 8, and are thus not representative of the galaxies in which today's ancient globular clusters were formed. In order to better understand the formation and evolution of these massive clusters in environments with few heavy elements, we have targeted several low-metallicity dwarf galaxies with radio observations, searching for newly-formed massive star clusters still embedded in their birth material. The galaxies in this initial study are HS 0822+3542, UGC 4483, Pox 186, and SBS 0335-052, all of which have metallicities of 12 + log(O/H) < 7.75. While no thermal radio sources, indicative of natal massive star clusters, are found in three of the four galaxies, SBS 0335-052 hosts two such objects, which are incredibly luminous. The radio spectral energy distributions of these intense star-forming regions in SBS 0335-052 suggest the presence of ~12,000 equivalent O-type stars, and the implied star formation rate is nearing the maximum starburst intensity limit.

  12. Spatial and kinematic distributions of transition populations in intermediate redshift galaxy clusters

    SciTech Connect

    Crawford, Steven M.; Wirth, Gregory D.; Bershady, Matthew A. E-mail: wirth@keck.hawaii.edu

    2014-05-01

    We analyze the spatial and velocity distributions of confirmed members in five massive clusters of galaxies at intermediate redshift (0.5 < z < 0.9) to investigate the physical processes driving galaxy evolution. Based on spectral classifications derived from broad- and narrow-band photometry, we define four distinct galaxy populations representing different evolutionary stages: red sequence (RS) galaxies, blue cloud (BC) galaxies, green valley (GV) galaxies, and luminous compact blue galaxies (LCBGs). For each galaxy class, we derive the projected spatial and velocity distribution and characterize the degree of subclustering. We find that RS, BC, and GV galaxies in these clusters have similar velocity distributions, but that BC and GV galaxies tend to avoid the core of the two z ≈ 0.55 clusters. GV galaxies exhibit subclustering properties similar to RS galaxies, but their radial velocity distribution is significantly platykurtic compared to the RS galaxies. The absence of GV galaxies in the cluster cores may explain their somewhat prolonged star-formation history. The LCBGs appear to have recently fallen into the cluster based on their larger velocity dispersion, absence from the cores of the clusters, and different radial velocity distribution than the RS galaxies. Both LCBG and BC galaxies show a high degree of subclustering on the smallest scales, leading us to conclude that star formation is likely triggered by galaxy-galaxy interactions during infall into the cluster.

  13. Galaxy and cluster redshift surveys

    NASA Technical Reports Server (NTRS)

    Geller, Margaret J.; Huchra, John P.

    1988-01-01

    The present evaluation of galaxy and cluster redshift surveys gives attention to the CfA redshift survey and a deep Abell cluster redshift survey. These data support a structure in which galaxies lie on thin sheets which nearly surround vast, low-density voids. Voids such as that in Bootes are a common feature of galaxy distribution, posing a serious challenge for models. The Huchra et al. (1988) deep-cluster survey exhibits a correlation function amplitude that is a factor of about 2 smaller than that of the earlier Bahcall and Soneira (1983) sample; the difference may not be significant, however, because the cluster samples are sufficiently small to be dominated by single systems.

  14. Optical Spectroscopy of Luminous Infrared Galaxies. I. Nuclear Data

    NASA Astrophysics Data System (ADS)

    Kim, D.-C.; Sanders, D. B.; Veilleux, S.; Mazzarella, J. M.; Soifer, B. T.

    1995-05-01

    A spectroscopic survey of a large sample of luminous infrared galaxies [log (L_ir_/L_sun_)^7^ ~ 10.5-12.5; H_0_ = 75 km s^-1^ Mpc^-1^] has been carried out using the Palomar 5 m telescope,, and the University of Hawaii 2.2 m telescope. Long-slit spectra covering 375o-8000 A at a resolution of ~10 A were obtained of 200 IRAS galaxies, including 114 objects from the IRAS Bright Galaxy Survey, and 86 objects with fainter infrared fluxes selected on the basis of their "warm" far-infrared (S_60_/S_100_) colors. The methods of observation and data reduction are discussed. An atlas of the spectra extracted from the nuclear region of these objects is presented along with a large number of parameters describing the properties of the emission lines, the stellar absorption lines, and the continuum emission that were measured from the spectra. An analysis of these data is presented in a companion paper (Veilleux et al. 1995) along with a discussion of the spatial variations of these parameters in a subsample of twenty-three objects.

  15. Stormy weather in galaxy clusters

    PubMed

    Burns

    1998-04-17

    Recent x-ray, optical, and radio observations coupled with particle and gas dynamics numerical simulations reveal an unexpectedly complex environment within clusters of galaxies, driven by ongoing accretion of matter from large-scale supercluster filaments. Mergers between clusters and continuous infall of dark matter and baryons from the cluster periphery produce long-lived "stormy weather" within the gaseous cluster atmosphere-shocks, turbulence, and winds of more than 1000 kilometers per second. This weather may be responsible for shaping a rich variety of extended radio sources, which in turn act as "barometers" and "anemometers" of cluster weather. PMID:9545210

  16. Seven poor clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Beers, T. C.; Geller, M. J.; Huchra, J. P.; Latham, D. W.; Davis, R. J.

    1984-08-01

    The authors have measured 83 new redshifts for galaxies in the region of seven of the poor clusters of galaxies identified by Morgan, Kayser, and White and Albert, White, and Morgan. For three systems (MKW 1s, AWM 1, and AWM 7) complete redshift samples were obtained for galaxies brighter than mB(0) = 15.7 within 1° of the D or cD galaxy. The authors estimate masses for the clusters by applying both the virial theorem and the projected mass method. For the two clusters with the highest X-ray luminosities, the line-of-sight velocity dispersions are ≡700 km s-1, and mass-to-light ratios M/LB(0) ⪆ 400 M_sun;/L_sun;. For the five other clusters the velocity dispersions are ⪉370 km s-1, and four of the five have mass-to-light ratios ⪉250 M_sun;/L_sun;. The D or cD galaxy in each poor cluster is at the kinematic center of the system.

  17. Redshifts for galaxies in three Yerkes poor clusters

    NASA Astrophysics Data System (ADS)

    Stauffer, J.; Spinrad, H.

    1980-01-01

    Redshifts have been obtained for 11 galaxies in the Yerkes poor cluster AWM 7, five galaxies in AWM 5, and two galaxies in AWM 1. In contrast to the result for AWM 4 previously noted by Stauffer and Spinrad, both AWM 5 and AWM 7 are real clusters with apparent line-of-sight velocity dispersions of 400 km/s and 600 km/s respectively. Surface photometry of the cD galaxy in AWM 7, obtained with the Berkeley PDS from a Crossley plate of the cluster, indicates that it is quite luminous, with an absolute magnitude to r about 30 kpc of M(v) about -23.5. A rough dynamical estimate of the AWM 7 cD mass from the spectroscopic data gives M(cD) about 2.0 x 10 to the 13th solar masses.

  18. A Search for Distant Galaxy Cluster Hosting Extreme Central Galaxies

    NASA Astrophysics Data System (ADS)

    Somboonpanyakul, Taweewat

    2016-01-01

    The recent discovery of the "Phoenix cluster" which, at z = 0.6, is the most X-ray luminous clusters known and harbors a massive starburst at its center, begs the question: Why was is not discovered until recently? In fact, the object has been previously detected by several all-sky surveys at a variety of wavelengths, but it is consistently classified as a quasar (QSO) because of the extremely bright central galaxy and a (relative) lack of extended X-ray emission due to its distance. This lead us to question of how many of these Phoenix-like clusters are currently mislabelled in existing all-sky surveys.A unique property of the Phoenix cluster which helps us identify other Phoenix-like objects is that it is bright at multiple wavelength, including X-ray (intracluster medium and central AGN), near-IR (giant central elliptical galaxy), mid-IR (warm dust from starburst and AGN) and radio (radio-loud central AGN). Therefore, we can identify potential Phoenix-like clusters by cross-correlating all-sky surveys from ROSAT (X-ray), 2MASS (near-IR), WISE (mid-IR) and both SUMSS and NVSS (radio). By requiring sources to be bright in all four surveys, we can quickly find (among other sources) a sample of Phoenix-like clusters that can be followed up either by using archival images from SDSS for Northern-hemisphere objects or taking new images from the Magellan telescope for Southern-hemisphere objects. Here, we will present the preliminary result from the project.

  19. A Second Luminous Blue Variable in the Quintuplet Cluster.

    PubMed

    Geballe; Najarro; Figer

    2000-02-20

    H- and K-band moderate-resolution and 4 µm high-resolution spectra have been obtained for FMM 362, a bright star in the Quintuplet Cluster near the Galactic center. The spectral features in these bands closely match those of the Pistol Star, a luminous blue variable and one of the most luminous stars known. The new spectra and previously obtained photometry imply a very high luminosity for FMM 362, L>/=106 L middle dot in circle, and a temperature of 10,000-13,000 K. Based on its luminosity, temperature, photometric variability, and similarities to the Pistol Star, we conclude that FMM 362 is a luminous blue variable. PMID:10655174

  20. Combining Galaxy-Galaxy Lensing and Galaxy Clustering

    SciTech Connect

    Park, Youngsoo; Krause, Elisabeth; Dodelson, Scott; Jain, Bhuvnesh; Amara, Adam; Becker, Matt; Bridle, Sarah; Clampitt, Joseph; Crocce, Martin; Honscheid, Klaus; Gaztanaga, Enrique; Sanchez, Carles; Wechsler, Risa

    2015-01-01

    Combining galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth rate of large scale structure, a quantity that will shed light on the mechanism driving the acceleration of the Universe. The Dark Energy Survey (DES) is a prime candidate for such an analysis, with its measurements of both the distribution of galaxies on the sky and the tangential shears of background galaxies induced by these foreground lenses. By constructing an end-to-end analysis that combines large-scale galaxy clustering and small-scale galaxy-galaxy lensing, we also forecast the potential of a combined probes analysis on DES datasets. In particular, we develop a practical approach to a DES combined probes analysis by jointly modeling the assumptions and systematics affecting the different components of the data vector, employing a shared halo model, HOD parametrization, photometric redshift errors, and shear measurement errors. Furthermore, we study the effect of external priors on different subsets of these parameters. We conclude that DES data will provide powerful constraints on the evolution of structure growth in the universe, conservatively/ optimistically constraining the growth function to 8%/4.9% with its first-year data covering 1000 square degrees, and to 4%/2.3% with its full five-year data covering 5000 square degrees.

  1. DISTANT CLUSTER OF GALAXIES [left

    NASA Technical Reports Server (NTRS)

    2002-01-01

    One of the deepest images to date of the universe, taken with NASA's Hubble Space Telescope (HST), reveals thousands of faint galaxies at the detection limit of present day telescopes. Peering across a large volume of the observable cosmos, Hubble resolves thousands of galaxies from five to twelve billion light-years away. The light from these remote objects has taken billions of years to cross the expanding universe, making these distant galaxies fossil evidence' of events that happened when the universe was one-third its present age. A fraction of the galaxies in this image belong to a cluster located nine billion light-years away. Though the field of view (at the cluster's distance) is only two million light-years across, it contains a multitude of fragmentary objects. (By comparison, the two million light-years between our Milky Way galaxy and its nearest large companion galaxy, in the constellation Andromeda, is essentially empty space!) Very few of the cluster's members are recognizable as normal spiral galaxies (like our Milky Way), although some elongated members might be edge-on disks. Among this zoo of odd galaxies are ``tadpole-like'' objects, disturbed and apparently merging systems dubbed 'train-wrecks,' and a multitude of faint, tiny shards and fragments, dwarf galaxies or possibly an unknown population of objects. However, the cluster also contains red galaxies that resemble mature examples of today's elliptical galaxies. Their red color comes from older stars that must have formed shortly after the Big Bang. The image is the full field view of the Wide Field and Planetary Camera-2. The picture was taken in intervals between May 11 and June 15, 1994 and required an 18-hour long exposure, over 32 orbits of HST, to reveal objects down to 29th magnitude. [bottom right] A close up view of the peculiar radio galaxy 3C324 used to locate the cluster. The galaxy is nine billion light-years away as measured by its spectral redshift (z=1.2), and located in the

  2. The Most Luminous Object in the Universe: Shrouded Quasar or Proto-Galaxy

    NASA Technical Reports Server (NTRS)

    Heckman, Timothy M.

    1999-01-01

    We have used ASCA to observe the IRAS source FSC 10214+4724, which is identified with a galaxy at a redshift of 2.286. When first discovered, it was believed to be the most luminous object in the universe. Subsequent HST images have established that it is gravitationally-lensed by a foreground cluster. It is still a very powerful object, but not extraordinarily so. Observations at other wavebands have not established whether it is a dust-shrouded quasar or a young, massive galaxy in the process of formation. Since quasars are strong emitters of hard X-rays, while proto-galaxies would not be, and since the opacity of gas and dust is relatively small in the energy regime probed by ASCA (3 to 30 keV in the galaxy rest frame), we undertook these observations to search for a heavily shrouded quasar that might be invisible at lower energies. However, the observations did not detect any emission from this object. This either means that the galaxy is in fact powered by a starburst or that the putative quasar is located behind a very high column density of absorbing gas (N_H > 10(exp 25)/sq cm), so that not even hard X-rays are transmitted. A hidden quasar should be visible in reflected light in X-ray data of higher sensitivity. Observations with NASA's Chandra X-ray Observatory or ESA's XMM are required to settle the matter. No publication resulted from our null result.

  3. Brightest Cluster Galaxies & Cooling Flows

    NASA Astrophysics Data System (ADS)

    Salomé, Philippe

    2013-03-01

    In the absence of any form of feedback heating, the gas in the central regions of massive relaxed cluster should cool and initiate a cooling flow. The presence/efficiency of an additional heating and the ultimate fate of the cooling gas is the subject of an extensive debate. In the last decade, molecular and atomic gas have been found in many Brightest Cluster Galaxies. I will review these observational results and discuss their implication for galaxy formation/evolution, in the perspective of ALMA.

  4. Galaxy Cluster Smashes Distance Record

    NASA Astrophysics Data System (ADS)

    2009-10-01

    he most distant galaxy cluster yet has been discovered by combining data from NASA's Chandra X-ray Observatory and optical and infrared telescopes. The cluster is located about 10.2 billion light years away, and is observed as it was when the Universe was only about a quarter of its present age. The galaxy cluster, known as JKCS041, beats the previous record holder by about a billion light years. Galaxy clusters are the largest gravitationally bound objects in the Universe. Finding such a large structure at this very early epoch can reveal important information about how the Universe evolved at this crucial stage. JKCS041 is found at the cusp of when scientists think galaxy clusters can exist in the early Universe based on how long it should take for them to assemble. Therefore, studying its characteristics - such as composition, mass, and temperature - will reveal more about how the Universe took shape. "This object is close to the distance limit expected for a galaxy cluster," said Stefano Andreon of the National Institute for Astrophysics (INAF) in Milan, Italy. "We don't think gravity can work fast enough to make galaxy clusters much earlier." Distant galaxy clusters are often detected first with optical and infrared observations that reveal their component galaxies dominated by old, red stars. JKCS041 was originally detected in 2006 in a survey from the United Kingdom Infrared Telescope (UKIRT). The distance to the cluster was then determined from optical and infrared observations from UKIRT, the Canada-France-Hawaii telescope in Hawaii and NASA's Spitzer Space Telescope. Infrared observations are important because the optical light from the galaxies at large distances is shifted into infrared wavelengths because of the expansion of the universe. The Chandra data were the final - but crucial - piece of evidence as they showed that JKCS041 was, indeed, a genuine galaxy cluster. The extended X-ray emission seen by Chandra shows that hot gas has been detected

  5. Cosmological parameter constraints from galaxy-galaxy lensing and galaxy clustering with the SDSS DR7

    NASA Astrophysics Data System (ADS)

    Mandelbaum, Rachel; Slosar, Anže; Baldauf, Tobias; Seljak, Uroš; Hirata, Christopher M.; Nakajima, Reiko; Reyes, Reinabelle; Smith, Robert E.

    2013-06-01

    Recent studies have shown that the cross-correlation coefficient between galaxies and dark matter is very close to unity on scales outside a few virial radii of galaxy haloes, independent of the details of how galaxies populate dark matter haloes. This finding makes it possible to determine the dark matter clustering from measurements of galaxy-galaxy weak lensing and galaxy clustering. We present new cosmological parameter constraints based on large-scale measurements of spectroscopic galaxy samples from the Sloan Digital Sky Survey (SDSS) data release 7. We generalize the approach of Baldauf et al. to remove small-scale information (below 2 and 4 h-1 Mpc for lensing and clustering measurements, respectively), where the cross-correlation coefficient differs from unity. We derive constraints for three galaxy samples covering 7131 deg2, containing 69 150, 62 150 and 35 088 galaxies with mean redshifts of 0.11, 0.28 and 0.40. We clearly detect scale-dependent galaxy bias for the more luminous galaxy samples, at a level consistent with theoretical expectations. When we vary both σ8 and Ωm (and marginalize over non-linear galaxy bias) in a flat Λ cold dark matter model, the best-constrained quantity is σ8(Ωm/0.25)0.57 = 0.80 ± 0.05 (1σ, stat. + sys.), where statistical and systematic errors (photometric redshift and shear calibration) have comparable contributions, and we have fixed ns = 0.96 and h = 0.7. These strong constraints on the matter clustering suggest that this method is competitive with cosmic shear in current data, while having very complementary and in some ways less serious systematics. We therefore expect that this method will play a prominent role in future weak lensing surveys. When we combine these data with Wilkinson Microwave Anisotropy Probe 7-year (WMAP7) cosmic microwave background (CMB) data, constraints on σ8, Ωm, H0, wde and ∑mν become 30-80 per cent tighter than with CMB data alone, since our data break several parameter

  6. Combining cluster number counts and galaxy clustering

    NASA Astrophysics Data System (ADS)

    Lacasa, Fabien; Rosenfeld, Rogerio

    2016-08-01

    The abundance of clusters and the clustering of galaxies are two of the important cosmological probes for current and future large scale surveys of galaxies, such as the Dark Energy Survey. In order to combine them one has to account for the fact that they are not independent quantities, since they probe the same density field. It is important to develop a good understanding of their correlation in order to extract parameter constraints. We present a detailed modelling of the joint covariance matrix between cluster number counts and the galaxy angular power spectrum. We employ the framework of the halo model complemented by a Halo Occupation Distribution model (HOD). We demonstrate the importance of accounting for non-Gaussianity to produce accurate covariance predictions. Indeed, we show that the non-Gaussian covariance becomes dominant at small scales, low redshifts or high cluster masses. We discuss in particular the case of the super-sample covariance (SSC), including the effects of galaxy shot-noise, halo second order bias and non-local bias. We demonstrate that the SSC obeys mathematical inequalities and positivity. Using the joint covariance matrix and a Fisher matrix methodology, we examine the prospects of combining these two probes to constrain cosmological and HOD parameters. We find that the combination indeed results in noticeably better constraints, with improvements of order 20% on cosmological parameters compared to the best single probe, and even greater improvement on HOD parameters, with reduction of error bars by a factor 1.4-4.8. This happens in particular because the cross-covariance introduces a synergy between the probes on small scales. We conclude that accounting for non-Gaussian effects is required for the joint analysis of these observables in galaxy surveys.

  7. Resolved Molecular Gas Properties in Local Luminous Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Sliwa, Kazimierz; Wilson, Christine

    2015-08-01

    Luminous infrared galaxies (LIRGs) in the local universe are mergers of gas-rich galaxies. The merger event funnels the molecular gas towards the central kiloparsec, compressing the gas, and triggering an extreme starburst, making LIRGs the perfect laboratory for studying extreme modes of star formation. We use the Submillimeter Array sample and observations of Wilson et al. (2008), supplemented with new CARMA and ALMA observations, to constrain the physical conditions such as temperature, density and column density of the molecular gas in the sample of 7 LIRGs. We use the radiative transfer code RADEX (van der Tak et al. 2007) and a Bayesian likelihood code to fit the most probable physical conditions. Comparison of the molecular gas physical conditions shows that earlier merger stage LIRGs such as Arp 299 and NGC 1614 have denser (> 103cm-1) molecular gas than a later stage merger such as VV 114 and NGC 2623. We measure the CO luminosity to H2 mass conversion factor, αCO, using the radiative transfer analysis results and find that the values are a factor of 4-10 times lower than the Galactic value of 4.3 M⊙ (K km s-1 pc2)-1. We also find unusually large 12CO-to-13CO abundance ratios (> 130), more than 2 times the local Galactic value.

  8. AKARI NEAR-INFRARED SPECTROSCOPY OF LUMINOUS INFRARED GALAXIES

    SciTech Connect

    Lee, Jong Chul; Lee, Myung Gyoon; Hwang, Ho Seong

    2012-09-01

    We present the AKARI near-infrared (NIR; 2.5-5 {mu}m) spectroscopic study of 36 (ultra)luminous infrared galaxies ((U)LIRGs) at z = 0.01-0.4. We measure the NIR spectral features including the strengths of 3.3 {mu}m polycyclic aromatic hydrocarbon emission and hydrogen recombination lines (Br{alpha} and Br{beta}), optical depths at 3.1 and 3.4 {mu}m, and NIR continuum slope. These spectral features are used to identify optically elusive, buried active galactic nuclei (AGNs). We find that half of the (U)LIRGs optically classified as non-Seyferts show AGN signatures in their NIR spectra. Using a combined sample of (U)LIRGs with NIR spectra in the literature, we measure the contribution of buried AGNs to the infrared luminosity from the spectral energy distribution fitting to the IRAS photometry. The contribution of these buried AGNs to the infrared luminosity is 5%-10%, smaller than the typical AGN contribution of (U)LIRGs including Seyfert galaxies (10%-40%). We show that NIR continuum slopes correlate well with WISE [3.4]-[4.6] colors, which would be useful for identifying a large number of buried AGNs using the WISE data.

  9. VIBRATIONALLY EXCITED HCN IN THE LUMINOUS INFRARED GALAXY NGC 4418

    SciTech Connect

    Sakamoto, Kazushi; Aalto, Susanne; Evans, Aaron S.; Wiedner, Martina C.; Wilner, David J.

    2010-12-20

    Infrared pumping and its effect on the excitation of HCN molecules can be important when using rotational lines of HCN to probe dense molecular gas in galaxy nuclei. We report the first extragalactic detection of (sub)millimeter rotational lines of vibrationally excited HCN, in the dust-enshrouded nucleus of the luminous infrared galaxy NGC 4418. We estimate the excitation temperature of T{sub vib} {approx} 230 K between the vibrational ground and excited (v{sub 2} = 1) states. This excitation is most likely due to infrared radiation. At this high vibrational temperature the path through the v{sub 2} = 1 state must have a strong impact on the rotational excitation in the vibrational ground level, although it may not be dominant for all rotational levels. Our observations also revealed nearly confusion-limited lines of CO, HCN, HCO{sup +}, H{sup 13}CN, HC{sup 15}N, CS, N{sub 2}H{sup +}, and HC{sub 3}N at {lambda} {approx} 1 mm. Their relative intensities may also be affected by the infrared pumping.

  10. XMM-Newton observations of three interacting luminous infrared galaxies

    SciTech Connect

    Mudd, Dale; Mathur, Smita; Guainazzi, Matteo; Piconcelli, Enrico; Nicastro, Fabrizio; Bianchi, Stefano; Komossa, S.; Vignali, Cristian; Lanzuisi, Giorgio; Fiore, Fabrizio; Maiolino, Roberto

    2014-05-20

    We investigate the X-ray properties of three interacting luminous infrared galaxy systems. In one of these systems, IRAS 18329+5950, we resolve two separate sources. A second and third source, IRAS 19354+4559 and IRAS 20550+1656, have only a single X-ray source detected. We compare the observed emission to point-spread function (PSF) profiles and determine that they are all consistent with the PSF, albeit with large uncertainties for some of our sources. We then model the spectra to determine soft (0.5-2 keV) and hard (2-10 keV) luminosities for the resolved sources and compare these to relationships found in the literature between infrared and X-ray luminosities for starburst galaxies. We obtain luminosities (0.5-10 keV) ranging from 1.7 to 7.3 × 10{sup 41} erg s{sup –1} for our systems. These X-ray luminosities are consistent with predictions for star-formation-dominated sources and thus are most likely due to starbursts, but we cannot conclusively rule out active galactic nuclei.

  11. A red envelope around a dominant elliptical galaxy in an X-ray selected poor cluster

    NASA Technical Reports Server (NTRS)

    Maccagni, D.; Garilli, B.; Gioia, I. M.; Maccacaro, T.; Vettolani, G.

    1988-01-01

    A photometric and spectroscopic study of the optical counterpart of the X-ray source 1E 1111.9-3754 has revealed a poor cluster of galaxies dominated by a very luminous giant elliptical. Three-color surface photometry of this galaxy shows that the elliptical body is surrounded by a large envelope with colors redder than the galaxy. The formation of this system in a high velocity dispersion poor cluster is briefly discussed.

  12. Decaying neutrinos in galaxy clusters

    NASA Technical Reports Server (NTRS)

    Melott, Adrian L.; Splinter, Randall J.; Persic, Massimo; Salucci, Paolo

    1994-01-01

    Davidsen et al. (1991) have argued that the failure to detect UV photons from the dark matter (DM) in cluster A665 excludes the decaying neutrino hypothesis. Sciama et al. (1993) argued that because of high central concentration the DM in that cluster must be baryonic. We study the DM profile in clusters of galaxies simulated using the Harrison-Zel'dovich spectrum of density fluctuations, and an amplitude previously derived from numerical simulations (Melott 1984b; Anninos et al. 1991) and in agreement with microwave background fluctuations (Smoot et al. 1992). We find that with this amplitude normalization cluster neutrino DM densities are comparable to observed cluster DM values. We conclude that given this normalization, the cluster DM should be at least largely composed of neutrinos. The constraint of Davidsen et al. can be somewhat weakened by the presence of baryonic DM; but it cannot be eliminated given our assumptions.

  13. Textures and clusters. [of galaxies

    NASA Technical Reports Server (NTRS)

    Bartlett, James G.; Gooding, Andrew K.; Spergel, David N.

    1993-01-01

    We discuss the properties of galaxy clusters expected in a texture-seeded, CDM-dominated, Omega = 1 universe. Assuming that the textures are spherical, we use the spherical collapse model to compute the cluster velocity dispersion (or temperature) distribution function. For objects of mass 10 exp 11 to 10 exp 15 solar masses, we find v varies as M super gamma with gamma of about 0.25. An unbiased (b = 1) texture model predicts too many high-velocity dispersion clusters. A biased texture model appears to be compatible with cluster properties inferred from optical and X-ray observations. In the texture model, the cluster velocity distribution functio does not evolve rapidly; thus, the model predicts the existence of rich clusters at moderate redshift (about 1-2).

  14. Lensing measurements of the ellipticity of luminous red galaxies dark matter haloes

    NASA Astrophysics Data System (ADS)

    Clampitt, Joseph; Jain, Bhuvnesh

    2016-04-01

    Lensing measurements of the shapes of dark matter haloes can provide tests of gravity theories and possible dark matter interactions. We measure the quadrupole weak lensing signal from the elliptical haloes of 70 000 Sloan Digital Sky Survey luminous red galaxies. We use a new estimator that nulls the spherical halo lensing signal, isolating the shear due to anisotropy in the dark matter distribution. One of the two Cartesian components of our estimator is insensitive to the primary systematic, a spurious alignment of lens and source ellipticities, allowing us to make robust measurements of halo ellipticity. Our best-fitting value for the ellipticity of the surface mass density is 0.24 ± 0.06, which translates to an axis ratio of 0.78. We rule out the hypothesis of no ellipticity at the 4σ confidence level, and ellipticity <0.12 (axis ratio >0.89) at the 2σ level. We discuss how our measurements of halo ellipticity are revised to higher values using estimates of the misalignment of mass and light from simulations. Finally, we apply the same techniques to a smaller sample of redMaPPer galaxy clusters and obtain a 3σ measurement of cluster ellipticity. We discuss how the improved signal-to-noise ratio properties of our estimator can enable studies of halo shapes for different galaxy populations with upcoming surveys.

  15. Dwarf Elliptical Galaxies in the Coma Cluster Core

    NASA Astrophysics Data System (ADS)

    Secker, Jeff

    1995-12-01

    I have analyzed deep R- and B-band CCD images of the central ~ 700 arcmin(2) of the Coma cluster (Abell 1656, v = 7000 km/s, richness-class 2), using a statistically rigorous and automated method for the detection, photometry and classification of faint objects on digital images. The dwarf elliptical (dE) galaxies are confined to a well-defined sequence in the color range given by 0.7 <= (B-R) <= 1.9 mag; within this interval and complete to R = 22.5 mag, there are 2535 dE candidates in the cluster core, and 694 objects on the associated control field (2.57x less area). I detected a significant metallicity gradient in the radial distribution of dE galaxies, which goes as Z ~ R(-0.32) outwards from the cluster center at NGC 4874. As well, there is a strong color-luminosity correlation, in the sense that more luminous dE galaxies are redder in the mean. These observations are consistent with a model in which the intracluster gas exerted a confinement pressure (greatest near the cluster core), impeding the outflow of supernovae-driven metal-rich gas from the young dE galaxies. The spatial distribution of faint dEs is well fit by a standard King model with a core radius R_c = 18.7 arcmin ( =~ 0.44 Mpc), significantly larger than found for the brightest dEs and giant cluster galaxies, and consistent with tidal disruption of faint dEs in the dense cluster core. The composite luminosity function for Coma galaxies was modeled as the sum of a log-normal distribution for the giant galaxies and a Schechter function for the dE galaxies. Decomposing the galaxy luminosity function in this manner, I found that the early-type dwarf-to-giant ratio (EDGR) for the Coma cluster core is identical with that of the Virgo cluster. I proposed that the presence of substructure is an important factor in determining the cluster's EDGR, since during the merger of two or more richness-class 1 galaxy clusters, the total number of dwarf and giant galaxies will be conserved. Thus, this low EDGR

  16. The Host Galaxies of Nearby, Optically Luminous, AGN

    NASA Astrophysics Data System (ADS)

    Petric, Andreea

    2016-01-01

    Coevolution of galaxies and their central black holes (BH) has been the central theme of much of recent extragalactic astronomical research. Observations of the dynamics of stars and gas in the nuclear regions of nearby galaxies suggest that the majority of spheroidal galaxies in the local Universe contain massive BHs and that the masses of those central BH correlate with the velocity dispersions of the stars in the spheroid and the bulge luminosity. Cold ISM is the basic fuel for star-formation and BH growth so its study is essential to understanding how galaxies evolve.I will present high sensitivity observations taken with the Herschel Space Observatory to measure the cold dust content in a sample of 85 nearby (z <= 0.5) QSOs chosen from the optically luminous broad-line PG QSOs sample (QSO1s) and in a complementary sample of 85 narrow-line QSOs (QSO2s) chosen to match the redshift and optical luminosity distribution of the broad-line targets. The FIR data are combined with NIR and MIR measurements from the Two Micron All Sky Survey and the Wide-Field Infrared Survey Explorer to determine their IR spectral energy distributions which we use to assess and compare the aggregate dust properties of QSO1s and QSO2s. I will also present NIR spectroscopy obtained with Gemini's Near-Infrared Spectrograph of a sub-sample of QSO2s and QSO1s which I use to compare the ratio of cold to warm H2 gas that emits in the NIR in the hosts of QSO1s and QSO2s.Finally I will present a comparison of star-formation in QSO1s and QSO2s. For both QSO1s and QSO2s 3stimates of star-formation rates that are based on the total IR continuum emission correlate with those based on the 11.3 micron PAH feature. However, for the QSO1s, star-formation rates estimated from the FIR continuum are higher than those estimated from the 11.3 micron PAH emission. This result can be attributed to a variety of factors including the possible destruction of the PAHs and that, in some sources, a fraction of the

  17. Dying radio galaxies in clusters

    NASA Astrophysics Data System (ADS)

    Murgia, M.; Parma, P.; Mack, K.-H.; de Ruiter, H. R.; Fanti, R.; Govoni, F.; Tarchi, A.; Giacintucci, S.; Markevitch, M.

    2011-02-01

    Aims: We present a study of five "dying" nearby (z ≤ 0.2) radio galaxies belonging to both the WENSS minisurvey and the B2 bright catalogs WNB1734+6407, WNB1829+6911, WNB1851+5707, B2 0120+33, and B2 1610+29. Methods: These sources have been selected on the basis of their extremely steep broad-band radio spectra, which strongly indicates that either these objects belong to the rare class of dying radio galaxies or we are observing "fossil" radio plasma remaining from a previous instance of nuclear activity. We derive the relative duration of the dying phase from the fit of a synchrotron radiative model to the radio spectra of the sources. Results: The modeling of the integrated spectra and the deep spectral index images obtained with the VLA confirmed that in these sources the central engine has ceased to be active for a significant fraction of their lifetime, although their extended lobes have not yet completely faded away. We found that WNB1851+5707 is in reality composed of two distinct dying galaxies, which appear blended together as a single source in the WENSS. In the cases of WNB1829+6911 and B2 0120+33, the fossil radio lobes are seen in conjunction with a currently active core. A very faint core is also detected in a MERLIN image of WNB1851+5707a, one of the two dying sources composing WNB1851+5707. We found that all sources in our sample are located (at least in projection) at the center of an X-ray emitting cluster. Conclusions: Our results suggest that the duration of the dying phase for a radio source in a cluster can be significantly higher than that of a radio galaxy in the field, although no firm conclusions can be drawn because of the small number statistics involved. The simplest interpretation of the tendency for dying galaxies to be found in clusters is that the low-frequency radio emission from the fading radio lobes lasts longer if their expansion is somewhat reduced or even stopped. Another possibility is that the occurrence of dying

  18. Galaxy clustering on large scales.

    PubMed

    Efstathiou, G

    1993-06-01

    I describe some recent observations of large-scale structure in the galaxy distribution. The best constraints come from two-dimensional galaxy surveys and studies of angular correlation functions. Results from galaxy redshift surveys are much less precise but are consistent with the angular correlations, provided the distortions in mapping between real-space and redshift-space are relatively weak. The galaxy two-point correlation function, rich-cluster two-point correlation function, and galaxy-cluster cross-correlation function are all well described on large scales ( greater, similar 20h-1 Mpc, where the Hubble constant, H0 = 100h km.s-1.Mpc; 1 pc = 3.09 x 10(16) m) by the power spectrum of an initially scale-invariant, adiabatic, cold-dark-matter Universe with Gamma = Omegah approximately 0.2. I discuss how this fits in with the Cosmic Background Explorer (COBE) satellite detection of large-scale anisotropies in the microwave background radiation and other measures of large-scale structure in the Universe. PMID:11607400

  19. BARYONS MATTER: WHY LUMINOUS SATELLITE GALAXIES HAVE REDUCED CENTRAL MASSES

    SciTech Connect

    Zolotov, Adi; Dekel, Avishai; Brooks, Alyson M.; Willman, Beth; Governato, Fabio; Quinn, Tom; Pontzen, Andrew; Christensen, Charlotte; Wadsley, James

    2012-12-10

    Using high-resolution cosmological hydrodynamical simulations of Milky Way-massed disk galaxies, we demonstrate that supernovae feedback and tidal stripping lower the central masses of bright (-15 < M{sub V} < -8) satellite galaxies. These simulations resolve high-density regions, comparable to giant molecular clouds, where stars form. This resolution allows us to adopt a prescription for H{sub 2} formation and destruction that ties star formation to the presence of shielded, molecular gas. Before infall, supernova feedback from the clumpy, bursty star formation captured by this physically motivated model leads to reduced dark matter (DM) densities and shallower inner density profiles in the massive satellite progenitors (M{sub vir} {>=} 10{sup 9} M{sub Sun }, M{sub *} {>=} 10{sup 7} M{sub Sun }) compared with DM-only simulations. The progenitors of the lower mass satellites are unable to maintain bursty star formation histories, due to both heating at reionization and gas loss from initial star-forming events, preserving the steep inner density profile predicted by DM-only simulations. After infall, gas stripping from satellites reduces the total central masses of satellites simulated with DM+baryons relative to DM-only satellites. Additionally, enhanced tidal stripping after infall due to the baryonic disk acts to further reduce the central DM densities of the luminous satellites. Satellites that enter with cored DM halos are particularly vulnerable to the tidal effects of the disk, exacerbating the discrepancy in the central masses predicted by baryon+DM and DM-only simulations. We show that DM-only simulations, which neglect the highly non-adiabatic evolution of baryons described in this work, produce denser satellites with larger central velocities. We provide a simple correction to the central DM mass predicted for satellites by DM-only simulations. We conclude that DM-only simulations should be used with great caution when interpreting kinematic observations

  20. Decaying neutrinos in galaxy clusters

    NASA Technical Reports Server (NTRS)

    Melott, Adrian L.; Splinter, Randall J.; Persic, Massimo; Salucci, Paolo

    1993-01-01

    The DM profile in clusters of galaxies was studied and simulated using the Harrison-Zel'dovich spectrum of density fluctuations, and an amplitude previously derived from numerical simulations and in agreement with microwave background fluctuations. Neutrino DM densities, with this amplitude normalization cluster, are comparable to observed cluster DM values. It was concluded that given this normalization, the cluster DM should be al least largely composed of neutrinos. The constraint of Davidson et al., who argued that the failure to detect uv photons from the dark matter (DM) in cluster A665 excludes the decaying neutrino hypothesis, could be somewhat weakened by the presence of baryonic DM; but it cannot be eliminated given our assumptions.

  1. The Origin of the Brightest Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Dubinski, John

    1998-07-01

    Most clusters and groups of galaxies contain a giant elliptical galaxy in their centers that far outshines and outweighs normal ellipticals. The origin of these brightest cluster galaxies is intimately related to the collapse and formation of the cluster. Using an N-body simulation of a cluster of galaxies in a hierarchical cosmological model, we show that galaxy merging naturally produces a massive central galaxy with surface brightness and velocity dispersion profiles similar to those of observed BCGs. To enhance the resolution of the simulation, 100 dark halos at z = 2 are replaced with self-consistent disk + bulge + halo galaxy models following a Tully-Fisher relation using 100,000 particles for the 20 largest galaxies and 10,000 particles for the remaining ones. This technique allows us to analyze the stellar and dark-matter components independently. The central galaxy forms through the merger of several massive galaxies along a filament early in the cluster's history. Galactic cannibalism of smaller galaxies through dynamical friction over a Hubble time only accounts for a small fraction of the accreted mass. The galaxy is a flattened, triaxial object whose long axis aligns with the primordial filament and the long axis of the cluster galaxy distribution, agreeing with observed trends for galaxy cluster alignment.

  2. Detection of stacked filament lensing between SDSS luminous red galaxies

    NASA Astrophysics Data System (ADS)

    Clampitt, Joseph; Miyatake, Hironao; Jain, Bhuvnesh; Takada, Masahiro

    2016-04-01

    We search for the lensing signal of massive filaments between 135 000 pairs of luminous red galaxies (LRGs) from the Sloan Digital Sky Survey. We develop a new estimator that cleanly removes the much larger shear signal of the neighbouring LRG haloes, relying only on the assumption of spherical symmetry. We consider two models: a `thick'-filament model constructed from ray-tracing simulations for Λ cold dark matter model, and a `thin'-filament model which models the filament by a string of haloes along the line connecting the two LRGs. We show that the filament lensing signal is in nice agreement with the thick simulation filament, while strongly disfavouring the thin model. The magnitude of the lensing shear due to the filament is below 10-4. Employing the likelihood ratio test, we find a 4.5σ significance for the detection of the filament lensing signal, corresponding to a null hypothesis fluctuation probability of 3 × 10-6. We also carried out several null tests to verify that the residual shear signal from neighbouring LRGs and other shear systematics are minimized.

  3. Understanding Galaxy Cluster MKW10

    NASA Astrophysics Data System (ADS)

    Sanders, Tim; Henry, Swain; Coble, Kimberly A.; Rosenberg, Jessica L.; Koopmann, Rebecca A.

    2015-01-01

    As part of the Undergraduate ALFALFA Team (UAT), we are studying the galaxy cluster MKW 10 (RA = 175.454, Dec = 10.306, z ~ 0.02), a poor cluster with a compact core in which tidal interactions have occurred. This cluster has been observed in HI and Hα. We used SDSS and NED to search for optical counterparts. By comparing data at multiple wavelengths, we hope to understand the structure, environment, and star formation history of this cluster. Following the techniques of others involved in the groups project and using the program TOPCAT to manipulate the data, we explored both the spatial and velocity distributions to determine cluster membership. We have determined that this cluster consists of 11 galaxies, mostly spiral in shape. Chicago State University is new the UAT and we began our work after taking part in the winter workshop at Arecibo.This work was supported by: Undergraduate ALFALFA Team NSF Grant AST-1211005 and the Illinois Space Grant Consortium.

  4. Evidence for evolution of the luminosity function of clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Edge, A. C.; Stewart, G. C.; Fabian, A. C.; Arnaud, K. A.

    1991-01-01

    From an all sky, X-ray flux limited sample of clusters of galaxies evidence for a significant deficit in the number of high luminosity clusters is found in the redshift range z approximately 0.1 to 0.2 compared with numbers of nearby clusters. This indicates that the X-ray luminous clusters are undergoing strong evolution. The strength of the effect is consistent with hierarchical merging models. The implications of such strong evolution for clusters are discussed.

  5. Evidence for evolution of the luminosity function of clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Edge, Alastair C.; Stewart, G. C.; Fabian, A. C.; Arnaud, K. A.

    1991-01-01

    From an all sky, x-ray flux limited sample of clusters of galaxies evidence for a significant deficit in the number of high luminosity clusters is found in the redshift range z approximately 0.1 to 0.2 compared with numbers of nearby clusters. This indicates that the x-ray luminous clusters are undergoing strong evolution. The strength of the effect is consistent with hierarchical merging models. The implications of such strong evolution for clusters are discussed.

  6. Searching for Massive Star Clusters around Luminous Blue Variables

    NASA Astrophysics Data System (ADS)

    Stensland, Jared; Edwards, M. L.; Mikles, V. J.

    2011-01-01

    We present a method to search for the massive birth clusters of Luminous Blue Variables (LBVs). Using theoretical absolute magnitudes of early-type stars, we calculated expected color and magnitude limits for candidate massive stars at the distance and reddening of the Pistol Star and FMM 362 in the Quintuplet. We then applied these cuts to stars found in the 2MASS catalog surrounding the LBVs. By using a well-characterized cluster, we were able to confirm the method's effectiveness and determine the color and magnitude criteria that eliminated the highest number of false candidates while recovering the largest number of known massive cluster members. We then calculated and applied similar cuts to stars within a 1pc radius of WRA 751 to confirm its cluster, Teutsch 143a, discovered by Pasquali et al (2006) and later investigated by Froebrich et al (2008). We used our method to select 22 strong candidate massive cluster stars, 18 medium confidence candidates and 39 weak candidates, categorized based on their colors and magnitudes. These stars are prime candidates for follow-up spectroscopy to determine their spectral types and confirm cluster membership. We plan to apply a similar method to other LBVs without known birth clusters.

  7. Velocity correlations of galaxy clusters

    NASA Technical Reports Server (NTRS)

    Cen, Renyue; Bahcall, Neta A.; Gramann, Mirt

    1994-01-01

    We determine the velocity correlation function, pairwise peculiar velocity difference, and rms pairwise peculiar velocity dispersion of rich clusters of galaxies, as a function of pair separation, for three cosmological models: Omega = 1 and Omega = 0.3 cold dark matter (CDM), and Omega = 0.3 primeval baryonic isocurvature (PBI) models (all flat and Cosmic Background Explorer (COBE)-normalized). We find that close cluster pairs, with separation r is less than or equal to 10/h Mpc, exhibit strong attractive peculiar velocities in all models; the cluster pairwise velocities depend sensitively on the model. The mean pairwise attractive velocity of clusters on 5/h Mpc scale ranges from approximately 1700 km/s for Omega = 1 CDM to approximately 1000 km/s for PBI to approximately 700 km/s for Omega = 0.3 CDM. The small-scale pairwise velocities depend also on cluster mass: richer, more massive clusters exhibit stronger attractive velocities than less massive clusters. On large scales, from approximately 20 to 200/h Mpc, the cluster peculiar velocities are increasingly dominated by bulk and random motions; they are independent of cluster mass. The cluster velocity correlation function is negative on small scales for Omega = 1 and Omega = 0.3 CDM, indicating strong pairwise motion relative to bulk motion on small scales; PBI exhibits relatively larger bulk motions. The cluster velocity correlation function is positive on very large scales, from r approximately 10/h Mpc to r approximately 200/h Mpc, for all models. These positive correlations, which decrease monotonically with scale, indicate significant bulk motions of clusters up to approximately 200/h Mpc. The strong dependence of the cluster velocity functions on models, especially at small separations, makes them useful tools in constraining cosmological models when compared with observations.

  8. Radio Sources In Galaxy Clusters Using The Maxbcg Cluster Catalog, First And NVSS Surveys

    NASA Astrophysics Data System (ADS)

    Wu, Wai Ling; McKay, T. A.

    2008-05-01

    Using the maxBCG cluster catalog derived from the Sloan Digital Sky Survey, the FIRST, and the NVSS radio surveys, we studied the fraction of brightest central galaxies (BCG) in clusters that host a radio source, how much more likely is a radio source to live in a cluster environment compare to the field, and we differentiate the luminosity effect from the richness effect on the radio fraction using a sample of luminous red galaxies (LRG). We present a method to cross-correlate the optical survey and the radio surveys. We also apply the matching of radio sources to clusters to help better determine cluster centers in some pathological cases in the maxBCG cluster catalog.

  9. Host galaxies of luminous type II AGN: Winds, shocks, and comparisons to The SAMI Galaxy Survey

    NASA Astrophysics Data System (ADS)

    McElroy, Rebecca; Croom, Scott; Pracy, Michael; SAMI Galaxy Survey Team

    2016-01-01

    We present IFS observations of luminous (log(L[O III]/L⊙) > 8.7) local (z < 0.11) type II AGN, and demonstrate that winds are ubiquitous within this sample and have a direct influence on the ISM of the host galaxies. We use both non-parametric (e.g. line width and asymmetry) and multi-Gaussian fitting to decompose the complex emission profiles close to the AGN. We find line widths containing 80% flux in the range 400 - 1600 km/s with a mean of 790 ± 90 km/s, such high velocities are strongly suggestive that these AGN are driving ionized outflows. Additionally, multi-Gaussian fitting reveals that 14/17 of our targets require 3 separate kinematic components in the ionized gas in their central regions. The broadest components of these fits have FWHM = 530 - 2520 km/s, with a mean value of 920 ± 50 km/s. By simultaneously fitting both the Hβ/[O III] and Hα/[N II] complexes we construct ionization diagnostic diagrams for each component. 13/17 of our galaxies show a significant (> 95 %) correlation between the [N II]/Hα ratio and the velocity dispersion of the gas. Such a correlation is the natural consequence of a contribution to the ionization from shock excitation and we argue that this demonstrates that the outflows from these AGN are directly impacting the surrounding ISM within the galaxies. In addition, we use stellar absorption features to measure kinematics for these AGN host galaxies and those of a control sample selected from the SAMI Galaxy Survey to search for evidence of these luminous AGN being preferentially hosted by disturbed or merging systems.

  10. On the Cusp around Central Black Holes in Luminous Elliptical Galaxies.

    PubMed

    Nakano; Makino

    1999-11-10

    In this Letter, we show that a massive black hole (MBH) that falls into the center of a galaxy on the dynamical timescale leaves a weak cusp (rho~r-1&solm0;2) around it, which is in good agreement with the recent observations of luminous elliptical galaxies by the Hubble Space Telescope. Such an event is a natural outcome of the merging of two galaxies that have central MBHs. This is the only known mechanism for forming weak cusps in luminous elliptical galaxies. Therefore, the existence of the weak cusps indicates that the central black holes of luminous elliptical galaxies have fallen to the center from outside, most likely during a major merger event. PMID:10525458

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

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

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

  12. The Luminosity-Metallicity relation of distant luminous infrared galaxies

    NASA Astrophysics Data System (ADS)

    Liang, Y. C.; Hammer, F.; Flores, H.; Elbaz, D.; Marcillac, D.; Cesarsky, C. J.

    2004-09-01

    One hundred and five 15 \\mum-selected objects in three ISO (Infrared Space Observatory) deep survey fields (CFRS 3h, UDSR and UDSF) are studied on the basis of their high-quality optical spectra with resolution R>1000 from VLT/FORS2. ˜92 objects (88%) have secure redshifts, ranging from 0 to 1.16 with a median value of z_med=0.587. Considerable care is taken in estimating the extinction properties of individual galaxy, which can seriously affect diagnostic diagrams and estimates of star formation rates (SFRs) and of metal abundances. Two independent estimates of the extinction have been made, e.g. Balmer line ratio and energy balance between infrared (IR) and H\\beta luminosities. For most of the sources, we find a good agreement between the two extinction coefficients (within ±0.64 rms in AV, the extinction in V band), with median values of A_V(IR) = 2.36 and A_V(Balmer)= 1.82 for z>0.4 luminous IR galaxies (LIRGs). At z >0.4, our sample show many properties (IR luminosity, continuum color, ionization and extinction) strikingly in common with those of local (IRAS) LIRGs studied by Veilleux et al. (\\cite{Veilleux1995}). Thus, our sample can provide a good representation of LIRGs in the distant Universe. We confirm that most (>77%) ISO 15 μm-selected galaxies are dominated by star formation. Oxygen abundances in interstellar medium in the galaxies are estimated from the extinction-corrected ``strong'' emission line ratios (e.g. \\ion{[O}{ii]}/Hβ, \\ion{[O}{iii]}/Hβ and \\ion{[O}{iii]}/\\ion{[O}{ii]}). The derived 12+log(O/H) values range from 8.36 to 8.93 for the z>0.4 galaxies with a median value of 8.67. Distant LIRGs present a metal content less than half of that of the local bright disks (i.e. L*). Their properties can be reproduced with infall models although one has to limit the infall time to avoid overproduction of metals at late times. The models predict that total masses (gas + stars) of the distant LIRGs are from 1011 M⊙ to ≤1012 M⊙. A

  13. The evolution of clusters of galaxies. I - Very rich clusters

    NASA Technical Reports Server (NTRS)

    Richstone, D. O.; Malumuth, E. M.

    1983-01-01

    A multiple one-body Monte Carlo code is used to investigate the evolution of galaxies in a steady cluster potential under the influence of dynamical friction, two-body relaxation, tidal stripping, and galaxy mergers. The basic assumptions, estimated time scales, method and computer program, and effects of uncertainties in galaxy encounter physics are addressed. Numerical experiments in which the mass initially carried by galaxies and the mass function are varied are reported. It is shown that the formation of a very massive cluster galaxy depends critically on the number of galaxies, the initial division of cluster material between galaxies and a smooth intracluster medium, the mass spectrum of the galaxies, and chance. By the end of all simulations, less than half of the mass in the central regions of the cluster is bound to galaxies. It appears possible to produce any of the Bautz-Morgan classes from very similar initial conditions.

  14. Spiral galaxies in clusters. III. Gas-rich galaxies in the Pegasus I cluster of galaxies

    SciTech Connect

    Bothun, G.D.; Schommer, R.A.; Sullivan, W.T. III

    1982-05-01

    We report the results of a 21-cm and optical survey of disk galaxies in the vicinity of the Pegasus I cluster of galaxies. The color--gas content relation (log(M/sub H//L/sub B/) vs (B-V)/sup T//sub 0/ ) for this particular cluster reveals the presence of a substantial number of blue, gas-rich galaxies. With few exceptions, the disk systems in Pegasus I retain large amounts of neutral hydrogen despite their presence in a cluster. This directly shows that environmental processes have not yet removed substantial amounts of gas from these disk galaxies. We conclude that the environment has had little or no observable effect upon the evolution of disk galaxies in Pegasus I. The overall properties of the Pegasus I spirals are consistent with the suggestion that this cluster is now at an early stage in its evolution.

  15. Cluster tidal fields: Effects on disk galaxies

    NASA Technical Reports Server (NTRS)

    Valluri, Monica

    1993-01-01

    A variety of observations of galaxies in clusters indicate that the gas in these galaxies is strongly affected by the cluster environment. We present results of a study of the dynamical effects of the mean cluster tidal field on a disk galaxy as it falls into a cluster for the first time on a bound orbit with constant angular momentum (Valluri 1992). The problem is studied in the restricted 3-body framework. The cluster is modelled by a modified Hubble potential and the disk galaxy is modelled as a flattened spheroid.

  16. ROSAT Discovers Unique, Distant Cluster of Galaxies

    NASA Astrophysics Data System (ADS)

    1995-06-01

    Brightest X-ray Cluster Acts as Strong Gravitational Lens Based on exciting new data obtained with the ROSAT X-ray satellite and a ground-based telescope at the ESO La Silla Observatory, a team of European astronomers [2] has just discovered a very distant cluster of galaxies with unique properties. It emits the strongest X-ray emission of any cluster ever observed by ROSAT and is accompanied by two extraordinarily luminous arcs that represent the gravitationally deflected images of even more distant objects. The combination of these unusual characteristics makes this cluster, now known as RXJ1347.5-1145, a most interesting object for further cosmological studies. DISCOVERY AND FOLLOW-UP OBSERVATIONS This strange cluster of galaxies was discovered during the All Sky Survey with the ROSAT X-ray satellite as a moderately intense X-ray source in the constellation of Virgo. It could not be identified with any already known object and additional ground-based observations were therefore soon after performed with the Max-Planck-Society/ESO 2.2-metre telescope at the La Silla observatory in Chile. These observations took place within a large--scale redshift survey of X-ray clusters of galaxies detected by the ROSAT All Sky Survey, a so-called ``ESO Key Programme'' led by astronomers from the Max-Planck-Institut fur Extraterrestrische Physik and the Osservatorio Astronomico di Brera. The main aim of this programme is to identify cluster X-ray sources, to determine the distance to the X-ray emitting clusters and to investigate their overall properties. These observations permitted to measure the redshift of the RXJ1347.5-1145 cluster as z = 0.45, i.e. it moves away from us with a velocity (about 106,000 km/sec) equal to about one-third of the velocity of light. This is an effect of the general expansion of the universe and it allows to determine the distance as about 5,000 million light-years (assuming a Hubble constant of 75 km/sec/Mpc). In other words, we see these

  17. WISE: From the Dimmest Stars to the most Luminous Galaxies!

    NASA Astrophysics Data System (ADS)

    Craig, N.; Mendez, B. J.; Wright, E. L.

    2004-12-01

    The Wide-field Infrared Survey Explorer (WISE) Mission, led by UCLA PI Dr. Edward L. Wright is a newly selected MIDEX Mission, scheduled to launch in Summer 2008. WISE will conduct a survey of the entire sky in the infrared (3.5 - 23 microns) with far greater sensitivity than any previous program or mission. WISE will catalogue more than 100,000 asteroids, discover the coolest, dimmest, and nearest stars to the Sun, and determine which are the most luminous galaxies in the Universe. The WISE survey will consist of over a million images, from which hundreds of millions of astronomical objects will be catalogued, providing a vast storehouse of knowledge about the Solar System, the Milky Way, and the Universe. We will discuss our plans for an Education and Public Outreach (E/PO) program for WISE, including how our program will leverage resources from other IR mission E/PO programs such as Spitzer and SOFIA. We will also discuss our plans to partner with the amateur astronomer community to reach out to the K-12 education community, including underserved communities. The University of California, Berkeley's SEGway group from the Space Sciences Laboratory will lead the E/PO efforts of the WISE Mission with formal and informal education partners such as NOAO, Hands-On-Universe, the American Museum of Natural History, Space Science Institute, Space Dynamics Laboratory, the Astronomical Society of the Pacific, and Cornerstone Evaluations. The outreach program of WISE will captivate a wide range of audiences in the formal and informal science education communities with beautiful imagery and engaging science.

  18. The First Hyper-Luminous Infrared Galaxy Discovered by WISE

    NASA Technical Reports Server (NTRS)

    Eisenhardt, Peter R.; Wu, Jingwen; Tsai, Chao-Wei; Assef, Roberto; Benford, Dominic; Blain, Andrew; Bridge, Carrie; Condon, J. J.; Cushing, Michael C.; Cutri, Roc; Evans, Neal J., III; Gelino, Chris; Griffith, Roger L.; Grillmair, Carl J.; Jarrett, Tom; Lonsdale, Carol J.; Masci, Frank J.; Mason, Brian S.; Petty, Sara; Sayers, Jack; Stanford, S. Adam; Stern, Daniel; Wright, Edward L.; Yan, Lin

    2012-01-01

    We report the discovery by the Wide-field Infrared Survey Explorer of the z = 2.452 source WISEJ181417.29+341224.9, the first hyperluminous source found in the WISE survey. WISE 1814+3412 is also the prototype for an all-sky sample of approximately 1000 extremely luminous "W1W2-dropouts" (sources faint or undetected by WISE at 3.4 and 4.6 micrometers and well detected at 12 or 22 micrometers). The WISE data and a 350 micrometers detection give a minimum bolometric luminosity of 3.7 x 10(exp 13) solar luminosity, with approximately 10(exp 14) solar luminosity plausible. Followup images reveal four nearby sources: a QSO and two Lyman Break Galaxies (LBGs) at z = 2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission. Gravitational lensing is unlikely given the source locations and their different spectra and colors. The dominant LBG spectrum indicates a star formation rate approximately 300 solar mass yr(exp -1), accounting for less than or equal to 10 percent of the bolometric luminosity. Strong 22 micrometer emission relative to 350 micrometer implies that warm dust contributes significantly to the luminosity, while cooler dust normally associated with starbursts is constrained by an upper limit at 1.1 mm. Radio emission is approximately 10? above the far-infrared/radio correlation, indicating an active galactic nucleus is present. An obscured AGN combined with starburst and evolved stellar components can account for the observations. If the black hole mass follows the local MBH-bulge mass relation, the implied Eddington ratio is approximately greater than 4. WISE 1814+3412 may be a heavily obscured object where the peak AGN activity occurred prior to the peak era of star formation.

  19. Nature of multiple-nucleus cluster galaxies

    SciTech Connect

    Merritt, D.

    1984-05-01

    In models for the evolution of galaxy clusters which include dynamical friction with the dark binding matter, the distribution of galaxies becomes more concentrated to the cluster center with time. In a cluster like Coma, this evolution could increase by a factor of approximately 3 the probability of finding a galaxy very close to the cluster center, without decreasing the typical velocity of such a galaxy significantly below the cluster mean. Such an enhancement is roughly what is needed to explain the large number of first-ranked cluster galaxies which are observed to have extra ''nuclei''; it is also consistent with the high velocities typically measured for these ''nuclei.'' Unlike the cannibalism model, this model predicts that the majority of multiple-nucleus systems are transient phenomena, and not galaxies in the process of merging.

  20. Galaxy Evolution in Clusters Since z ~ 1

    NASA Astrophysics Data System (ADS)

    Aragón-Salamanca, A.

    Galaxy clusters provide some of the most extreme environments in which galaxies evolve, making them excellent laboratories to study the age old question of "nature" vs. "nurture" in galaxy evolution. Here I review some of the key observational results obtained during the last decade on the evolution of the morphology, structure, dynamics, star-formation history and stellar populations of cluster galaxies since the time when the Universe was half its present age. Many of the results presented here have been obtained within the ESO Distant Cluster Survey (EDisCS) and Space Telescope A901/02 Galaxy Evolution Survey (STAGES) collaborations.

  1. Galaxy evolution in clusters since z~1

    NASA Astrophysics Data System (ADS)

    Aragon-Salamanca, Alfonso

    2010-09-01

    Galaxy clusters provide some of the most extreme environments in which galaxies evolve, making them excellent laboratories to study the age old question of "nature" vs. "nurture" in galaxy evolution. Here I review some of the key observational results obtained during the last decade on the evolution of the morphology, structure, dynamics, star-formation history and stellar populations of cluster galaxies since the time when the universe was half its present age. Many of the results presented here have been obtained within the ESO Distant Cluster Survey (EDisCS) and Space Telescope A901/02 Galaxy Evolution Survey (STAGES) collaborations.

  2. The Discovery and Characterization of Surprisingly Luminous Galaxy Candidates at 9-10: The Power of Combining HST and Spitzer

    NASA Astrophysics Data System (ADS)

    Illingworth, Garth D.; Oesch, P.; Bouwens, R.; Labbe, I.; XDF/HUDF09 Team

    2014-01-01

    Deep observations with the WFC3/IR camera on HST have pushed the frontier for galaxies in the young universe to 9-11, just ~450 Myr from the Big Bang at the heart of the reionization epoch. However, until recently only a small number of intrinsically very faint galaxies had been identified at these redshifts from extremely deep WFC3/IR data in the XDF/HUDF and the GOODS-South field and from the CLASH cluster survey. This changed with our recent analysis of the completed CANDELS survey data over the GOODS-North/HDF-N field. We discovered four surprisingly bright Lyman-break galaxy candidates at 9-10, the brightest of which has a most probable redshift of 10.2. These sources are a factor ~10-20x more luminous than any previous candidate at redshifts 9-10. The high number of such luminous sources suggests that star-formation was highly stochastic in the very early universe resulting in large field-to-field variance. Furthermore, three of these bright candidates show significant detections in Spitzer/IRAC, substantially enhancing the probability that these galaxies are at 9-10. The IRAC data probes the rest-frame optical light and indicates that these sources already had a stellar mass of 10^9 Msol at a cosmic time of only 450-500 Myr. While the overall star formation rate density of galaxies with SFR>0.7 Msol/yr has been shown to increase rapidly in just 200 Myr from 10 to 8, the discovery of these luminous sources has very promising implications for the detection of galaxies at times significantly earlier than 450 Myr with JWST.

  3. Modelling galaxy clustering: halo occupation distribution versus subhalo matching

    NASA Astrophysics Data System (ADS)

    Guo, Hong; Zheng, Zheng; Behroozi, Peter S.; Zehavi, Idit; Chuang, Chia-Hsun; Comparat, Johan; Favole, Ginevra; Gottloeber, Stefan; Klypin, Anatoly; Prada, Francisco; Rodríguez-Torres, Sergio A.; Weinberg, David H.; Yepes, Gustavo

    2016-07-01

    We model the luminosity-dependent projected and redshift-space two-point correlation functions (2PCFs) of the Sloan Digital Sky Survey (SDSS) Data Release 7 Main galaxy sample, using the halo occupation distribution (HOD) model and the subhalo abundance matching (SHAM) model and its extension. All the models are built on the same high-resolution N-body simulations. We find that the HOD model generally provides the best performance in reproducing the clustering measurements in both projected and redshift spaces. The SHAM model with the same halo-galaxy relation for central and satellite galaxies (or distinct haloes and subhaloes), when including scatters, has a best-fitting χ2/dof around 2-3. We therefore extend the SHAM model to the subhalo clustering and abundance matching (SCAM) by allowing the central and satellite galaxies to have different galaxy-halo relations. We infer the corresponding halo/subhalo parameters by jointly fitting the galaxy 2PCFs and abundances and consider subhaloes selected based on three properties, the mass Macc at the time of accretion, the maximum circular velocity Vacc at the time of accretion, and the peak maximum circular velocity Vpeak over the history of the subhaloes. The three subhalo models work well for luminous galaxy samples (with luminosity above L*). For low-luminosity samples, the Vacc model stands out in reproducing the data, with the Vpeak model slightly worse, while the Macc model fails to fit the data. We discuss the implications of the modelling results.

  4. Modelling Galaxy Clustering: Halo Occupation Distribution versus Subhalo Matching

    NASA Astrophysics Data System (ADS)

    Guo, Hong; Zheng, Zheng; Behroozi, Peter S.; Zehavi, Idit; Chuang, Chia-Hsun; Comparat, Johan; Favole, Ginevra; Gottloeber, Stefan; Klypin, Anatoly; Prada, Francisco; Rodríguez-Torres, Sergio A.; Weinberg, David H.; Yepes, Gustavo

    2016-04-01

    We model the luminosity-dependent projected and redshift-space two-point correlation functions (2PCFs) of the Sloan Digital Sky Survey (SDSS) DR7 Main galaxy sample, using the halo occupation distribution (HOD) model and the subhalo abundance matching (SHAM) model and its extension. All the models are built on the same high-resolution N-body simulations. We find that the HOD model generally provides the best performance in reproducing the clustering measurements in both projected and redshift spaces. The SHAM model with the same halo-galaxy relation for central and satellite galaxies (or distinct haloes and subhaloes), when including scatters, has a best-fitting χ2/dof around 2-3. We therefore extend the SHAM model to the subhalo clustering and abundance matching (SCAM) by allowing the central and satellite galaxies to have different galaxy-halo relations. We infer the corresponding halo/subhalo parameters by jointly fitting the galaxy 2PCFs and abundances and consider subhaloes selected based on three properties, the mass Macc at the time of accretion, the maximum circular velocity Vacc at the time of accretion, and the peak maximum circular velocity Vpeak over the history of the subhaloes. The three subhalo models work well for luminous galaxy samples (with luminosity above L★). For low-luminosity samples, the Vacc model stands out in reproducing the data, with the Vpeak model slightly worse, while the Macc model fails to fit the data. We discuss the implications of the modeling results.

  5. Radio Galaxies in Galaxy Clusters: Feedback, Merger Signatures, and Signposts

    NASA Astrophysics Data System (ADS)

    Paterno-Mahler, Rachel; Blanton, Elizabeth L.; Randall, Scott W.; Andrade-Santos, Felipe; Ashby, Matthew; Brodwin, Mark; Bulbul, Esra; Clarke, Tracy E.; Golden-Marx, Emmet; Johnson, Ryan; Jones, Christine; Murray, Stephen S.; Wing, Joshua

    2015-01-01

    Extended, double-lobed radio sources are often located in rich galaxy clusters. I will present results of an optical and X-ray analysis of two nearby clusters with such radio sources - one of the clusters is relaxed (A2029) and one of the clusters is undergoing a merger (A98). Because of their association with clusters, extended radio sources can be used to locate clusters at a wide range of distances. The number of spectroscopically confirmed galaxy clusters with is very low compared to the number of well-studied low-redshift clusters. In the Clusters Occupied by Bent Radio AGN (COBRA) survey, we use bent, double-lobed radio sources as signposts to efficiently locate high-redshift clusters. Using a Spitzer Snapshot Survey of our sample of 653 bent, double-lobed radio sources (selected from the FIRST survey and with galaxy hosts too faint to be detected in the SDSS), we have the potential to identify approximately 400 new clusters and groups with redshifts. I will present results from the Spitzer observations regarding the efficiency of the method for finding new clusters. These newly identified clusters will be used to study galaxy formation and evolution, as well as the effect that feedback from active galactic nuclei (AGN) has on galaxies and their environments.

  6. Hot outflows in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, C. C.; McNamara, B. R.

    2015-10-01

    The gas-phase metallicity distribution has been analysed for the hot atmospheres of 29 galaxy clusters using Chandra X-ray Observatory observations. All host brightest cluster galaxies (BCGs) with X-ray cavity systems produced by radio AGN. We find high elemental abundances projected preferentially along the cavities of 16 clusters. The metal-rich plasma was apparently lifted out of the BCGs with the rising X-ray cavities (bubbles) to altitudes between twenty and several hundred kiloparsecs. A relationship between the maximum projected altitude of the uplifted gas (the `iron radius') and jet power is found with the form R_Fe ∝ P_jet^{0.45}. The estimated outflow rates are typically tens of solar masses per year but exceed 100 M⊙ yr- 1 in the most powerful AGN. The outflow rates are 10-20 per cent of the cooling rates, and thus alone are unable to offset a cooling inflow. Nevertheless, hot outflows effectively redistribute the cooling gas and may play a significant role at regulating star formation and AGN activity in BCGs and presumably in giant elliptical galaxies. The metallicity distribution overall can be complex, perhaps due to metal-rich gas returning in circulation flows or being blown around in the hot atmospheres. Roughly 15 per cent of the work done by the cavities is expended lifting the metal-enriched gas, implying their nuclear black holes have increased in mass by at least ˜107-109 M⊙. Finally, we show that hot outflows can account for the broad, gas-phase metallicity distribution compared to the stellar light profiles of BCGs, and we consider a possible connection between hot outflows and cold molecular gas flows discovered in recent Atacama Large Millimeter Array observations.

  7. Spatial and Kinematic Distributions of Transition Populations in Intermediate Redshift Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Crawford, Steven M.; Wirth, Gregory D.; Bershady, Matthew A.

    2014-05-01

    We analyze the spatial and velocity distributions of confirmed members in five massive clusters of galaxies at intermediate redshift (0.5 < z < 0.9) to investigate the physical processes driving galaxy evolution. Based on spectral classifications derived from broad- and narrow-band photometry, we define four distinct galaxy populations representing different evolutionary stages: red sequence (RS) galaxies, blue cloud (BC) galaxies, green valley (GV) galaxies, and luminous compact blue galaxies (LCBGs). For each galaxy class, we derive the projected spatial and velocity distribution and characterize the degree of subclustering. We find that RS, BC, and GV galaxies in these clusters have similar velocity distributions, but that BC and GV galaxies tend to avoid the core of the two z ≈ 0.55 clusters. GV galaxies exhibit subclustering properties similar to RS galaxies, but their radial velocity distribution is significantly platykurtic compared to the RS galaxies. The absence of GV galaxies in the cluster cores may explain their somewhat prolonged star-formation history. The LCBGs appear to have recently fallen into the cluster based on their larger velocity dispersion, absence from the cores of the clusters, and different radial velocity distribution than the RS galaxies. Both LCBG and BC galaxies show a high degree of subclustering on the smallest scales, leading us to conclude that star formation is likely triggered by galaxy-galaxy interactions during infall into the cluster. Based in part on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  8. Investigations of Galaxy Clusters Using Gravitational Lensing

    SciTech Connect

    Wiesner, Matthew P.

    2014-08-01

    In this dissertation, we discuss the properties of galaxy clusters that have been determined using strong and weak gravitational lensing. A galaxy cluster is a collection of galaxies that are bound together by the force of gravity, while gravitational lensing is the bending of light by gravity. Strong lensing is the formation of arcs or rings of light surrounding clusters and weak lensing is a change in the apparent shapes of many galaxies. In this work we examine the properties of several samples of galaxy clusters using gravitational lensing. In Chapter 1 we introduce astrophysical theory of galaxy clusters and gravitational lensing. In Chapter 2 we examine evidence from our data that galaxy clusters are more concentrated than cosmology would predict. In Chapter 3 we investigate whether our assumptions about the number of galaxies in our clusters was valid by examining new data. In Chapter 4 we describe a determination of a relationship between mass and number of galaxies in a cluster at higher redshift than has been found before. In Chapter 5 we describe a model of the mass distribution in one of the ten lensing systems discovered by our group at Fermilab. Finally in Chapter 6 we summarize our conclusions.

  9. DUST-OBSCURED STAR FORMATION IN INTERMEDIATE REDSHIFT GALAXY CLUSTERS

    SciTech Connect

    Finn, Rose A.; Desai, Vandana; Rudnick, Gregory; Poggianti, Bianca; Bell, Eric F.; Hinz, Joannah; Zaritsky, Dennis; Jablonka, Pascale; Milvang-Jensen, Bo; Moustakas, John; Rines, Kenneth E-mail: jmoustakas@ucsd.ed

    2010-09-01

    We present Spitzer MIPS 24 {mu}m observations of sixteen 0.4 < z < 0.8 galaxy clusters drawn from the ESO Distant Cluster Survey. This is the first large 24 {mu}m survey of clusters at intermediate redshift. The depth of our imaging corresponds to a total IR luminosity of 8 x 10{sup 10} L{sub sun}, just below the luminosity of luminous infrared galaxies (LIRGs), and 6{sup +1}{sub -1}% of M{sub V} < -19 cluster members show 24 {mu}m emission at or above this level. We compare with a large sample of coeval field galaxies and find that while the fraction of cluster LIRGs lies significantly below that of the field, the IR luminosities of the field and cluster galaxies are consistent. However, the stellar masses of the EDisCS LIRGs are systematically higher than those of the field LIRGs. A comparison with optical data reveals that {approx}80% of cluster LIRGs are blue and the remaining 20% lie on the red sequence. Of LIRGs with optical spectra, 88{sup +4} {sub -5}% show [O II] emission with EW([O II]) > 5 A, and {approx}75% exhibit optical signatures of dusty starbursts. On average, the fraction of cluster LIRGs increases with projected clustercentric radius but remains systematically lower than the field fraction over the area probed (<1.5x R {sub 200}). The amount of obscured star formation declines significantly over the 2.4 Gyr interval spanned by the EDisCS sample, and the rate of decline is the same for the cluster and field populations. Our results are consistent with an exponentially declining LIRG fraction, with the decline in the field delayed by {approx}1 Gyr relative to the clusters.

  10. Evidence of galaxy cluster motions with the kinematic Sunyaev-Zel'dovich effect.

    PubMed

    Hand, Nick; Addison, Graeme E; Aubourg, Eric; Battaglia, Nick; Battistelli, Elia S; Bizyaev, Dmitry; Bond, J Richard; Brewington, Howard; Brinkmann, Jon; Brown, Benjamin R; Das, Sudeep; Dawson, Kyle S; Devlin, Mark J; Dunkley, Joanna; Dunner, Rolando; Eisenstein, Daniel J; Fowler, Joseph W; Gralla, Megan B; Hajian, Amir; Halpern, Mark; Hilton, Matt; Hincks, Adam D; Hlozek, Renée; Hughes, John P; Infante, Leopoldo; Irwin, Kent D; Kosowsky, Arthur; Lin, Yen-Ting; Malanushenko, Elena; Malanushenko, Viktor; Marriage, Tobias A; Marsden, Danica; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D; Nolta, Michael R; Oravetz, Daniel; Page, Lyman A; Palanque-Delabrouille, Nathalie; Pan, Kaike; Reese, Erik D; Schlegel, David J; Schneider, Donald P; Sehgal, Neelima; Shelden, Alaina; Sievers, Jon; Sifón, Cristóbal; Simmons, Audrey; Snedden, Stephanie; Spergel, David N; Staggs, Suzanne T; Swetz, Daniel S; Switzer, Eric R; Trac, Hy; Weaver, Benjamin A; Wollack, Edward J; Yeche, Christophe; Zunckel, Caroline

    2012-07-27

    Using high-resolution microwave sky maps made by the Atacama Cosmology Telescope, we for the first time present strong evidence for motions of galaxy clusters and groups via microwave background temperature distortions due to the kinematic Sunyaev-Zel'dovich effect. Galaxy clusters are identified by their constituent luminous galaxies observed by the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. We measure the mean pairwise momentum of clusters, with a probability of the signal being due to random errors of 0.002, and the signal is consistent with the growth of cosmic structure in the standard model of cosmology. PMID:23006072

  11. Detection of Galaxy Cluster Motions with the Kinematic Sunyaev-Zel'dovich Effect

    NASA Technical Reports Server (NTRS)

    Hand, Nick; Addison, Graeme E.; Aubourg, Eric; Battaglia, Nick; Battistelli, Elia S.; Bizyaev, Dmitry; Bond, J. Richard; Brewington, Howard; Brinkmann, Jon; Brown, Benjamin R.; Das, Sudeep; Dawson, Kyle S.; Devlin, Mark J.; Dunkley, Joanna; Dunner, Rolando; Eisenstein, Daniel J.; Flowler, Joseph W.; Gralla, Megan B.; Hajian, Amir; Halpern, Mark; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee; Hughes, John P.; Wollack, Edward J.

    2012-01-01

    Using high-resolution microwave sky maps made by the Atacama Cosmology Telescope, we for the first time detect motions of galaxy clusters and groups via microwave background .temperature distortions due to the kinematic Sunyaev.Zel'dovich effect. Galaxy clusters are identified by their constituent luminous galaxies observed by the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. The mean pairwise momentum of clusters is measured. at a statistical. significance of 3.8 sigma, and the signal is consistent with the growth of cosmic structure in the standard model of cosmology

  12. Tracking star formation in dwarf cluster galaxies

    NASA Astrophysics Data System (ADS)

    Rude, Cody Millard

    The evolution of galaxies in dense environments can be affected by close encounters with neighboring galaxies and interactions with the intracluster medium (ICM). Dwarf galaxies may be especially susceptible to these effects due to their low mass. The goal of my dissertation research is to look for signs of star formation in cluster dwarf galaxies by measuring and comparing the r- and u-band luminosity functions of 15 low redshift Abell galaxy clusters using archival data from the Canada-France-Hawaii Telescope (CFHT). Luminosity functions, dwarf-to-giant ratios, and blue fractions are measured in four cluster-centric annuli from stacked cluster data. To account for differences in cluster optical richness, each cluster is scaled according to r200, where r200 is the radius of a sphere, centered on the cluster, whose average density is 200 times the critical density of the universe. The outer region of the cluster sample shows an increase in the faint-end slope of the u-band luminosity function relative to the r-band, indicating star formation in dwarf galaxies. The blue fraction for dwarf galaxies steadily rises with increasing cluster-centric radii. The change in the blue fraction of giant galaxies also increases, but at a lower rate. Additionally, the inner regions of clusters ranging from 0.185 < z < 0.7 from the "Cluster Lensing and Supernova survey with Hubble (CLASH)" are used to generate blue- and red-band luminosity functions, dwarf-to-giant ratios, and blue fractions. Comparisons of the inner region of the CLASH and CFHT clusters show an increase in the blue fraction of dwarf galaxies with redshift that is not present in giant galaxies.

  13. The Ubiquity of Coeval Starbursts in Massive Galaxy Cluster Progenitors

    NASA Astrophysics Data System (ADS)

    Casey, Caitlin M.

    2016-06-01

    The universe’s largest galaxy clusters likely built the majority of their massive >1011 M {}ȯ galaxies in simultaneous, short-lived bursts of activity well before virialization. This conclusion is reached based on emerging data sets for z\\gt 2 proto-clusters and the characteristics of their member galaxies, in particular, rare starbursts and ultraluminous active galactic nuclei (AGN). The most challenging observational hurdle in identifying such structures is their very large volumes, ∼104 comoving Mpc3 at z\\gt 2, subtending areas of approximately half a degree on the sky. Thus, the contrast afforded by an overabundance of very rare galaxies in comparison to the background can more easily distinguish overdense structures from the surrounding, normal density field. Five 2≲ z≲ 3 proto-clusters from the literature are discussed in detail and are found to contain up to 12 dusty starbursts or luminous AGN galaxies each, a phenomenon that is unlikely to occur by chance even in overdense environments. These are contrasted with three higher-redshift (4≲ z≲ 5.5) dusty star-forming galaxy (DSFG) groups, whose evolutionary fate is less clear. Measurements of DSFGs’ gas depletion times suggest that they are indeed short-lived on ∼100 Myr timescales, and accordingly the probability of finding a structure containing more than 8 such systems is ∼0.2%, unless their “triggering” is correlated on very large spatial scales, ∼10 Mpc across. The volume density of DSFG-rich proto-clusters is found to be comparable to all of the >1015 M {}ȯ galaxy clusters in the nearby universe, which is a factor of five larger than expected in some simulations. Some tension still exists between measurements of the volume density of DSFG-rich proto-clusters and the expectation that they are generated via short-lived episodes, as the latter suggests that only a fraction (\\lt \\tfrac{1}{2}) of all proto-clusters should be rich with DSFGs. However, improved observations of

  14. The clustering evolution of distant red galaxies in the GOODS-MUSIC sample

    NASA Astrophysics Data System (ADS)

    Grazian, A.; Fontana, A.; Moscardini, L.; Salimbeni, S.; Menci, N.; Giallongo, E.; de Santis, C.; Gallozzi, S.; Nonino, M.; Cristiani, S.; Vanzella, E.

    2006-07-01

    Aims.We study the clustering properties of Distant Red Galaxies (DRGs) to test whether they are the progenitors of local massive galaxies. Methods.We use the GOODS-MUSIC sample, a catalog of ~3000 Ks-selected galaxies based on VLT and HST observation of the GOODS-South field with extended multi-wavelength coverage (from 0.3 to 8~μm) and accurate estimates of the photometric redshifts to select 179 DRGs with J-Ks≥ 1.3 in an area of 135 sq. arcmin.Results.We first show that the J-Ks≥ 1.3 criterion selects a rather heterogeneous sample of galaxies, going from the targeted high-redshift luminous evolved systems, to a significant fraction of lower redshift (1luminous dusty starbursts. These low-redshift DRGs are significantly less clustered than higher-z DRGs. With the aid of extreme and simplified theoretical models of clustering evolution, we show that it is unlikely that the two samples are drawn from the same population observed at two different stages of evolution. Conclusions.High-z DRGs likely represent the progenitors of the more massive and more luminous galaxies in the local Universe and might mark the regions that will later evolve into structures of intermediate mass, like groups or small galaxy clusters. Low-z DRGs, on the other hand, will likely evolve into slightly less massive field galaxies.

  15. STAR CLUSTERS IN PSEUDOBULGES OF SPIRAL GALAXIES

    SciTech Connect

    Di Nino, Daiana; Trenti, Michele; Stiavelli, Massimo; Carollo, C. Marcella; Scarlata, Claudia; Wyse, Rosemary F. G.

    2009-11-15

    We present a study of the properties of the star-cluster systems around pseudobulges of late-type spiral galaxies using a sample of 11 galaxies with distances from 17 Mpc to 37 Mpc. Star clusters are identified from multiband Hubble Space Telescope ACS and WFPC2 imaging data by combining detections in three bands (F435W and F814W with ACS and F606W with WFPC2). The photometric data are then compared to population synthesis models to infer the masses and ages of the star clusters. Photometric errors and completeness are estimated by means of artificial source Monte Carlo simulations. Dust extinction is estimated by considering F160W NICMOS observations of the central regions of the galaxies, augmenting our wavelength coverage. In all galaxies we identify star clusters with a wide range of ages, from young (age {approx}< 8 Myr) blue clusters, with typical mass of 10{sup 3} M {sub sun} to older (age >100-250 Myr), more massive, red clusters. Some of the latter might likely evolve into objects similar to the Milky Way's globular clusters. We compute the specific frequencies for the older clusters with respect to the galaxy and bulge luminosities. Specific frequencies relative to the galaxy light appear consistent with the globular cluster specific frequencies of early-type spirals. We compare the specific frequencies relative to the bulge light with the globular cluster specific frequencies of dwarf galaxies, which have a surface brightness profile that is similar to that of the pseudobulges in our sample. The specific frequencies we derive for our sample galaxies are higher than those of the dwarf galaxies, supporting an evolutionary scenario in which some of the dwarf galaxies might be the remnants of harassed late-type spiral galaxies that hosted a pseudobulge.

  16. 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.

  17. Clustering of galaxies in brane world models

    NASA Astrophysics Data System (ADS)

    Hameeda, Mir; Faizal, Mir; Ali, Ahmed Farag

    2016-04-01

    In this paper, we analyze the clustering of galaxies using a modified Newtonian potential. This modification of the Newtonian potential occurs due to the existence of extra dimensions in brane world models. We will analyze a system of galaxies interacting with each other through this modified Newtonian potential. The partition function for this system of galaxies will be calculated, and this partition function will be used to calculate the free energy of this system of galaxies. The entropy and the chemical potential for this system will also be calculated. We will derive explicit expression for the clustering parameter for this system. This parameter will determine the behavior of this system, and we will be able to express various thermodynamic quantities using this clustering parameter. Thus, we will be able to explicitly analyze the effect that modifying the Newtonian potential can have on the clustering of galaxies. We also analyse the effect of extra dimensions on the two-point functions between galaxies.

  18. The Clustering of Young Stellar Cluster Populations in Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Grasha, Kathryn; Calzetti, Daniela

    2016-01-01

    We present measurements of clustering among star clusters for several galaxies drawn from the Legacy ExtraGalactic UV Survey (LEGUS), in order to establish whether the clustering strength depends on properties of the cluster population. We use the two point autocorrelation function to study clustering as a function of spatial scale, age, concentration index (CI), and mass. We separate the clusters into different classes, defined by their (a)symmetry and number of peaks, comparing the trends of the autocorrelation functions between all the cluster classes. For one galaxy, NGC 628, 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 40 Myr. We present here a similar analysis for the other galaxies. We also measure the power-law slope and amplitude of the autocorrelation functions and discuss the results.

  19. ORIENTATION OF BRIGHTER GALAXIES IN NEARBY GALAXY CLUSTERS

    SciTech Connect

    Panko, E.; Juszczyk, T.; Flin, P. E-mail: sfflin@cyf-kr.edu.pl

    2009-12-15

    A sample of 6188 nearby galaxy structures, complete to r{sub F} = 18fm3 and containing at least 10 members each, was the observational basis for an investigation of the alignment of bright galaxies with the major axes for the parent clusters. The distribution of position angles for galaxies within the clusters, specifically the brightest, the second brightest, the third, and the tenth brightest galaxies was tested for isotropy. Galaxy position angles appear to be distributed isotropically, as are the distributions of underlying cluster structure position angles. The characterization of galaxy structures according to richness class also appears to be isotropic. Characterization according to BM types, which are known for 1056 clusters, is more interesting. Only in the case of clusters of BM type I is there an alignment of the brightest cluster member with the major axis of the parent cluster. The effect is observed at the 2 significance level. In other investigated cases the distributions are isotropic. The results confirm the special role of cD galaxies in the origin/evolution of large-scale structures.

  20. Spiral Galaxies in MKW/AWM Clusters

    NASA Astrophysics Data System (ADS)

    Williams, Barbara A.

    1997-03-01

    Observations have been made of the neutral hydrogen content of more than 170 galaxies within MKW 4, MKW 7, MKW 8, MKW 9, MKW 11, AWM 1, AWM 3, AWM 4, and AWM 5. This sample of nine clusters is representative of the general class of poor clusters identified by MKW and AWM in that they all contain D-- or cD--like dominant galaxies at their dynamical centers. We examine the neutral hydrogen (HI) content of the spiral members in these systems as a function of the local and global properties of the cluster, i.e., galaxy density, x-ray intra cluster gas pressure, x-ray and optical luminosities, and compare our findings with the HI properties of similar galaxies in rich clusters and loose groups of galaxies.

  1. Unveiling the hearts of luminous and ultra-luminous infrared galaxy mergers with laser guide star adaptive optics

    NASA Astrophysics Data System (ADS)

    Medling, Anne M.

    2013-03-01

    Gas-rich galaxies across cosmic time exhibit one or both of two phenomena: ongoing star formation and an active galactic nucleus indicating current black hole accretion. These two processes are important mechanisms through which galaxies evolve and grow, but their effects are difficult to disentangle. Both will use up some available gas, and both are capable of producing winds strong enough to eject remaining gas from the galaxy. One must look at high spatial resolutions in order to separate the dynamical effects of star formation going on near the nucleus of a galaxy from the black hole growth going on in the nucleus. We present high spatial resolution integral field spectroscopy of fifteen nearby luminous and ultra-luminous infrared galaxies. These systems are extremely bright in the infrared exactly because they host powerful starbursts and active nuclei, which in turn heat the surrounding dust. Our data provide resolved stellar and gaseous kinematics of the central kiloparsec of each of these systems by removing atmospheric blurring with adaptive optics, an observing technique that measures the turbulence in the Earth's atmosphere and then uses a deformable mirror to correct the resulting distortions. Our kinematic maps reveal nuclear disks of gas and stars with radii ˜ a few hundred parsecs surrounding the central black holes. Because the stellar and gas kinematics match well, we conclude that the stars are forming in situ from the gas in the disks. These disks may be the progenitors of kinematically decoupled cores seen in many isolated elliptical galaxies, and may have a significant effect on the merger rate of binary black holes. Additionally, these disks may be used to measure black hole masses which, when combined with host galaxy properties and placed on scaling relations, indicate that black holes grow as or more quickly than their host galaxies during a merger. This suggests that a sudden burst of black hole growth at in the final stages of the merger

  2. Gas deficiency in cluster galaxies - A comparison of nine clusters

    NASA Technical Reports Server (NTRS)

    Giovanelli, R.; Haynes, M. P.

    1985-01-01

    The available 21 cm line data in the literature for galaxies in nine clusters is combined with new high-sensitivity observations of 51 galaxies in five of the nine clusters in order to test for discriminating circumstances between those clusters which show H I deficiency among their spiral population and those which do not. An H I deficiency for the complete cluster sample is derived employing a comparison sample of galaxies chosen from the Catalog of Isolated Galaxies. The deficiency and its radial dependence is summarized for each cluster and a composite. A comparison of the environments in different clusters leads to the conclusion that the occurrence of H I deficiency is correlated with the presence of a hot X-ray intracluster medium, and that an ongoing interaction process is active through the cores of X-ray clusters.

  3. Infall patterns around rich clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Regos, Eniko; Geller, Margaret J.

    1989-01-01

    The pattern of infall velocities induced by a rich cluster of galaxies is considered, using an infall model based on the Friedmann solution to determine the exact implicit dependence of the peculiar velocity on the density enhancment and the mean cosmological mass density, Omega(0). An analytic model for the distribution of galaxies around a cluster core in redshift space is developed. The high-density caustics in redshift space are shown to appear as envelopes around rich clusters. Assuming that the galaxies trace the matter distribution, low Omega(0) models can explain observational data obtained for four clusters. The present results support the prediction that light traces mass in the infall region.

  4. Observing dynamical friction in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Adhikari, Susmita; Dalal, Neal; Clampitt, Joseph

    2016-07-01

    We present a novel method to detect the effects of dynamical friction in observed galaxy clusters. Following accretion into clusters, massive satellite galaxies will backsplash to systematically smaller radii than less massive satellites, an effect that may be detected by stacking the number density profiles of galaxies around clusters. We show that this effect may be understood using a simple toy model which reproduces the trends with halo properties observed in simulations. We search for this effect using SDSS redMaPPer clusters with richness 10 < λ < 20, and find that bright (Mi < ‑21.5) satellites have smaller splashback radii than fainter (Mi > ‑20) satellites at 99% confidence.

  5. Radio Galaxies in Abell Rich Clusters

    NASA Astrophysics Data System (ADS)

    Ledlow, M. J.

    1994-05-01

    We have defined a complete sample of radio galaxies chosen from Abell's northern catalog consisting of all clusters with measured redshifts < 0.09. This sample consists of nearly 300 clusters. A multiwavelength survey including optical CCD R-Band imaging, optical spectroscopy, and VLA 20 cm radio maps has been compiled. I have used this database to study the optical/radio properties of radio galaxies in the cluster environment. In particular, optical properties have been compared to a radio-quiet selected sample to look for optical signatures which may distinguish radio galaxies from normal radio-quiet ellipticals. The correlations between radio morphology and galaxy type, the optical dependence of the FR I/II break, and the univariate and bivariate luminosity functions have been examined for this sample. This study is aimed at understanding radio galaxies as a population and examining their status in the AGN heirarchy. The results of this work will be applied to models of radio source evolution. The results from the optical data analysis suggest that radio galaxies, as a class, cannot be distinguished from non-radio selected elliptical galaxies. The magnitude/size relationship, the surface-brightness profiles, the fundamental plane, and the intrinsic shape of the radio galaxies are consistent between our radio galaxy and control sample. The radio galaxies also trace the elliptical galaxy optical luminosity function in clusters very well; with many more L(*) galaxies than brightest cluster members. Combined with the results of the spectroscopy, the data are consistent with the idea that all elliptical galaxies may at some point in their lifetimes become radio sources. In conclusion, I present a new observational picture for radio galaxies and discuss the important properties which may determine the evolution of individual sources.

  6. Record-breaking ancient galaxy clusters

    NASA Astrophysics Data System (ADS)

    2003-12-01

    A tale of two record-breaking clusters hi-res Size hi-res: 768 kb Credits: for RDCS1252: NASA, ESA, J.Blakeslee (Johns Hopkins Univ.), M.Postman (Space Telescope Science Inst.) and P.Rosati, Chris Lidman & Ricardo Demarco (European Southern Observ.) for TNJ1338: NASA, ESA, G.Miley (Leiden Observ.) and R.Overzier (Leiden Obs) A tale of two record-breaking clusters Looking back in time to when the universe was in its formative youth, the Advanced Camera for Surveys (ACS) aboard the NASA/ESA Hubble Space Telescope captured these revealing images of two galaxy clusters. The image at left, which is made with an additional infrared exposure taken with the European Southern Observatory’s Very Large Telescope, shows mature galaxies in a massive cluster that existed when the cosmos was 5000 million years old. The cluster, called RDCS1252.9-2927, is as massive as ‘300 trillion’ suns and is the most massive known cluster for its epoch. The image reveals the core of the cluster and is part of a much larger mosaic of the entire cluster. Dominating the core are a pair of large, reddish elliptical galaxies [near centre of image]. Their red colour indicates an older population of stars. Most of the stars are at least 1000 million years old. The two galaxies appear to be interacting and may eventually merge to form a larger galaxy that is comparable to the brightest galaxies seen in present-day clusters. The red galaxies surrounding the central pair are also cluster members. The cluster probably contains many thousands of galaxies, but only about 50 can be seen in this image. The full mosaic (heic0313d) reveals several hundred cluster members. Many of the other galaxies in the image, including several of the blue galaxies, are foreground or background galaxies. The colour-composite image was assembled from two observations (through i and z filters) taken between May and June 2002 by the ACS Wide Field Camera, and one image with the ISAAC instrument on the VLT taken in 2002

  7. Galaxy clusters in the cosmic web

    NASA Astrophysics Data System (ADS)

    Acebrón, A.; Durret, F.; Martinet, N.; Adami, C.; Guennou, L.

    2014-12-01

    Simulations of large scale structure formation in the universe predict that matter is essentially distributed along filaments at the intersection of which lie galaxy clusters. We have analysed 9 clusters in the redshift range 0.4clusters. Based on colour-magnitude diagrams, we have selected the galaxies likely to be in the cluster redshift range and studied their spatial distribution. We detect a number of structures and filaments around several clusters, proving that colour-magnitude diagrams are a reliable method to detect filaments around galaxy clusters. Since this method excludes blue (spiral) galaxies at the cluster redshift, we also apply the LePhare software to compute photometric redshifts from BVRIZ images to select galaxy cluster members and study their spatial distribution. We then find that, if only galaxies classified as early-type by LePhare are considered, we obtain the same distribution than with a red sequence selection, while taking into account late-type galaxies just pollutes the background level and deteriorates our detections. The photometric redshift based method therefore does not provide any additional information.

  8. Rapid evolution of the most luminous galaxies during the first 900 million years.

    PubMed

    Bouwens, Rychard J; Illingworth, Garth D

    2006-09-14

    The first 900 million years (Myr) to redshift z approximately 6 (the first seven per cent of the age of the Universe) remains largely unexplored for the formation of galaxies. Large samples of galaxies have been found at z approximately 6 (refs 1-4) but detections at earlier times are uncertain and unreliable. It is not at all clear how galaxies built up from the first stars when the Universe was about 300 Myr old (z approximately 12-15) to z approximately 6, just 600 Myr later. Here we report the results of a search for galaxies at z approximately 7-8, about 700 Myr after the Big Bang, using the deepest near-infrared and optical images ever taken. Under conservative selection criteria we find only one candidate galaxy at z approximately 7-8, where ten would be expected if there were no evolution in the galaxy population between z approximately 7-8 and z approximately 6. Using less conservative criteria, there are four candidates, where 17 would be expected with no evolution. This demonstrates that very luminous galaxies are quite rare 700 Myr after the Big Bang. The simplest explanation is that the Universe is just too young to have built up many luminous galaxies at z approximately 7-8 by the hierarchical merging of small galaxies. PMID:16971943

  9. Reconstructing galaxy histories from globular clusters

    NASA Astrophysics Data System (ADS)

    West, Michael J.; Côté, Patrick; Marzke, Ronald O.; Jordán, Andrés

    2004-01-01

    Nearly a century after the true nature of galaxies as distant `island universes' was established, their origin and evolution remain great unsolved problems of modern astrophysics. One of the most promising ways to investigate galaxy formation is to study the ubiquitous globular star clusters that surround most galaxies. Globular clusters are compact groups of up to a few million stars. They generally formed early in the history of the Universe, but have survived the interactions and mergers that alter substantially their parent galaxies. Recent advances in our understanding of the globular cluster systems of the Milky Way and other galaxies point to a complex picture of galaxy genesis driven by cannibalism, collisions, bursts of star formation and other tumultuous events.

  10. Reconstructing galaxy histories from globular clusters.

    PubMed

    West, Michael J; Côté, Patrick; Marzke, Ronald O; Jordán, Andrés

    2004-01-01

    Nearly a century after the true nature of galaxies as distant 'island universes' was established, their origin and evolution remain great unsolved problems of modern astrophysics. One of the most promising ways to investigate galaxy formation is to study the ubiquitous globular star clusters that surround most galaxies. Globular clusters are compact groups of up to a few million stars. They generally formed early in the history of the Universe, but have survived the interactions and mergers that alter substantially their parent galaxies. Recent advances in our understanding of the globular cluster systems of the Milky Way and other galaxies point to a complex picture of galaxy genesis driven by cannibalism, collisions, bursts of star formation and other tumultuous events. PMID:14702077

  11. Galaxy evolution in clusters since z=1

    NASA Astrophysics Data System (ADS)

    Aragón-Salamanca, A.

    2011-11-01

    It is now 30 years since Alan Dressler published his seminal paper onthe morphology-density relation. Although there is still much to learnon the effect of the environment on galaxy evolution, extensive progress has been made since then both observationally and theoretically.Galaxy clusters provide some of the most extreme environments in which galaxies evolve, making them excellent laboratories to study the age old question of "nature'' vs. "nurture'' in galaxy evolution. Here I review some of the key observational results obtained during the last decade on the evolution of the morphology, structure, dynamics, star-formation history and stellar populations of cluster galaxies since the time when the universe was half its present age.Many of the results presented here have been obtainedwithin the ESO Distant Cluster Survey (EDisCS) and Space Telescope A901/02 Galaxy Evolution Survey (STAGES) collaborations.

  12. The cluster of galaxies Abell 2670

    NASA Astrophysics Data System (ADS)

    Shambrook, Anouk Aimee

    2001-10-01

    The rich cluster of galaxies Abell 2670 provides a laboratory in which to observe how galaxy properties change as a function of environment. Though initially considered a relaxed cluster, Abell 2670 exhibits substructure in optical, x-ray, and radio 21 cm H I line data. The cluster hosts a plethora of elliptical galaxies as well as spiral galaxies including galaxies rich in cold gas (some with more than 1010 Msolar in H I), and K+A galaxies. A group of galaxies rich in cold gas may be entering the cluster environment for the first time, making Abell 2670 a valuable case study. This thesis presents a catalog of UBV RI colors for objects located in an area 1° x 1° centered on Abell 2670, based on observations using the CTIO 0.9-m Schmidt telescope. Follow up observations using the Keck II 10-m and the CTIO 4-m telescopes will enable the classification of galaxy morphology. Using evolutionary synthesis models by Poggianti and Barbaro, a photometric redshift analysis yields a best- fit redshift and spectral energy distribution for each galaxy. The results are checked with galaxies observed by Sharples, Ellis, and Gray, which are known cluster members. Radial density profiles of cluster and field galaxies are modeled by King and uniform distributions respectively. A set of simulated galaxies, drawn from a combination of the two models, is compared to the data; for each redshift classification (based on the photometric redshift analysis), Kolmogorov-Smirnov tests characterize the probable fraction of cluster galaxies relative to the total. For the galaxies classified by the photometric redshift analysis as E, Sa, and Sc, an overdensity value is calculated, quantifying the density-morphology relation for this sample. A detailed study of this low redshift (z = 0.076) cluster may inform future studies of high redshift clusters. The optical UBV RI catalog is an important part of a multiwavelength set of data on Abell 2670 which in the future will probably lend itself well

  13. Nebular Line Emission in z 1 Spitzer Infrared-Luminous Galaxies

    NASA Astrophysics Data System (ADS)

    Krause, John; Papovich, C.; Finkelstein, S.; Willmer, C.; Egami, E.; Conselice, C.; Huang, J.; Koo, D.; Laird, E.; Le Floc'h, E.; Lotz, J.; Maia, M.; Marcillac, D.; Nandra, K.; Webb, T.; Weiner, B.

    2010-01-01

    We present near-infrared (IR) spectroscopic observations from the Multi-Object IR Camera and Spectrograph (MOIRCS) on the Subaru telescope of a sample of 21 IR-luminous galaxies in the approximate range 1 < z < 1.5. These galaxies were selected based on their Spitzer 24-micron flux densities (S(24 micron) > 0.1 mJy) and known spectroscopic redshifts from the All-Wavelength Extended Groth Strip International Survey (AEGIS). We measure rest-frame optical emission line fluxes for H-alpha and [NII], and also [OIII] and H-beta, where available. We use emission-line diagnostics to constrain the origin of the ionization in these objects: processes associated with star formation or AGN (including Seyferts and LINERs). The high-redshift galaxies in our sample have similar [NII] / H-alpha flux ratios compared to low-redshift (z 0.1) IR-luminous galaxies (Kim et al., 1995; Veilleux et al., 1995) for galaxies with implied IR luminosities of 11 < Log L(8-1000 micron) / L sol < 12. However, we find evidence that the IR-luminous galaxies in our sample with implied Log L(8-1000 micron) / L sol > 12 have lower [NII] / H-alpha ratios than low-redshift galaxies with comparable IR luminosity, implying the higher redshift IR-luminous galaxies may have a higher fraction of systems dominated by star formation. We also study the relation of our rest-frame optical emission-line diagnostics to other indicators of AGN activity, including the mid-IR colors and X-ray luminosities. In addition, we compare star-formation-rate indicators from our dust-corrected H-alpha emission line luminosities to those from the mid-to-far IR and compare these as a function of IR luminosity against the low-redshift sample.

  14. Faint Submillimeter Galaxies Behind the Frontier Field Clusters

    NASA Astrophysics Data System (ADS)

    Hsu, Li-Yen; Cowie, Lennox; Barger, Amy; Wang, Wei-Hao; Chen, Chian-Chou

    2015-08-01

    Faint submillimeter galaxies are the major contributors to the submillimeter extragalactic background light and hence the dominant star-forming population in the dusty universe. Determining how much these galaxies overlap the optically selected samples is critical to fully account for the cosmic star formation history. To explore this faint submillimeter population, we have been observing nine galaxy clusters with the SCUBA-2 camera on the James Clerk Maxwell Telescope, including five of the clusters in the HST Frontier Fields program. We have also been using the Submillimeter Array to determine the positions of our detected sources precisely. Our recent observations have discovered several high-redshift dusty galaxies with far-infrared luminosities similar to that of the Milky Way or luminous infrared galaxies but which are undetected in current deep radio, optical and near-infrared images. These remarkable results suggest that a substantial amount of star formation in even the faint submillimeter population may be hidden from rest-frame optical surveys.

  15. The Globular Cluster System of the Spiral Galaxy NGC 7814

    NASA Astrophysics Data System (ADS)

    Rhode, Katherine L.; Zepf, Stephen E.

    2003-11-01

    We present the results of a wide-field photometric study of the globular cluster (GC) system of the edge-on Sab spiral NGC 7814. This is the first spiral to be fully analyzed from our survey of the GC systems of a large sample of galaxies beyond the Local Group. NGC 7814 is of particular interest because a previous study estimated that it has 500-1000 GCs, giving it the largest specific frequency (SN) known for a spiral. Understanding this galaxy's GC system is important in terms of our understanding of the GC populations of spirals in general and has implications for the formation of massive galaxies. We observed the galaxy in BVR filters with the WIYN 3.5 m telescope and used image classification and three-color photometry to select GC candidates. We also analyzed archival Hubble Space Telescope (HST) Wide Field Planetary Camera 2 images of NGC 7814, both to help quantify the contamination level of the WIYN GC candidate list and to detect GCs in the inner part of the galaxy halo. Combining HST data with high-quality ground-based images allows us to trace the entire radial extent of this galaxy's GC system and determine the total number of GCs directly through observation. We find that rather than being an especially high-SN spiral, NGC 7814 has <~200 GCs and SN~1, making it comparable to the two most well-studied spiral galaxies, the Milky Way and M31. We explore the implications of these results for models of the formation of galaxies and their GC systems. The initial results from our survey suggest that the GC systems of typical elliptical galaxies can be accounted for by the merger of two or more spirals, but that for highly luminous elliptical galaxies, additional physical processes may be needed.

  16. Understanding the nature of luminous red galaxies (LRGs): connecting LRGs to central and satellite subhaloes

    NASA Astrophysics Data System (ADS)

    Masaki, Shogo; Hikage, Chiaki; Takada, Masahiro; Spergel, David N.; Sugiyama, Naoshi

    2013-08-01

    We develop a novel abundance matching method to construct a mock catalogue of luminous red galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS), using catalogues of haloes and subhaloes in N-body simulations for a Λ-dominated cold dark matter model. Motivated by observations suggesting that LRGs are passively evolving, massive early-type galaxies with a typical age ≳5 Gyr, we assume that simulated haloes at z = 2 (z2-halo) are progenitors for LRG-host subhaloes observed today, and we label the most tightly bound particles in each progenitor z2-halo as LRG `stars'. We then identify the subhaloes containing these stars to z = 0.3 (SDSS redshift) in descending order of the masses of z2-haloes until the comoving number density of the matched subhaloes becomes comparable to the measured number density of SDSS LRGs, bar{n}_LRG=10^{-4} h^3 Mpc^{-3}. Once the above prescription is determined, our only free parameter is the number density of haloes identified at z = 2 and this parameter is fixed to match the observed number density at z = 0.3. By tracing subsequent merging and assembly histories of each progenitor z2-halo, we can directly compute, from the mock catalogue, the distributions of central and satellite LRGs and their internal motions in each host halo at z = 0.3. While the SDSS LRGs are galaxies selected by the magnitude and colour cuts from the SDSS images and are not necessarily a stellar-mass-selected sample, our mock catalogue reproduces a host of SDSS measurements: the halo occupation distribution for central and satellite LRGs, the projected autocorrelation function of LRGs, the cross-correlation of LRGs with shapes of background galaxies (LRG-galaxy weak lensing) and the non-linear redshift-space distortion effect, the Finger-of-God effect, in the angle-averaged redshift-space power spectrum. The mock catalogue generated based on our method can be used for removing or calibrating systematic errors in the cosmological interpretation of LRG clustering

  17. A BRIGHTEST CLUSTER GALAXY WITH AN EXTREMELY LARGE FLAT CORE

    SciTech Connect

    Postman, Marc; Coe, Dan; Koekemoer, Anton; Bradley, Larry; Lauer, Tod R.; Donahue, Megan; Graves, Genevieve; Moustakas, John; Ford, Holland C.; Lemze, Doron; Medezinski, Elinor; Grillo, Claudio; Zitrin, Adi; Broadhurst, Tom; Ascaso, Begona

    2012-09-10

    Hubble Space Telescope images of the galaxy cluster A2261, obtained as part of the Cluster Lensing And Supernova survey with Hubble, show that the brightest galaxy in the cluster, A2261-BCG, has the largest core yet detected in any galaxy. The cusp radius of A2261-BCG is 3.2 kpc, twice as big as the next largest core known, and {approx}3 Multiplication-Sign bigger than those typically seen in the most luminous brightest cluster galaxies. The morphology of the core in A2261-BCG is also unusual, having a completely flat interior surface brightness profile, rather than the typical shallow cusp rising into the center. This implies that the galaxy has a core with constant or even centrally decreasing stellar density. Interpretation of the core as an end product of the 'scouring' action of a binary supermassive black hole implies a total black hole mass {approx}10{sup 10} M{sub Sun} from the extrapolation of most relationships between core structure and black hole mass. The core falls 1{sigma} above the cusp radius versus galaxy luminosity relation. Its large size in real terms, and the extremely large black hole mass required to generate it, raises the possibility that the core has been enlarged by additional processes, such as the ejection of the black holes that originally generated the core. The flat central stellar density profile is consistent with this hypothesis. The core is also displaced by 0.7 kpc from the center of the surrounding envelope, consistent with a local dynamical perturbation of the core.

  18. Witnessing galaxy clusters: from maturity to childhood

    NASA Astrophysics Data System (ADS)

    Ascaso, B.

    2013-05-01

    Galaxy clusters are the largest structures in Universe. They are very important as both cos- mological probes and astrophysical laboratories. Several methods have been developed to detect galaxy clusters with different techniques (optical, X-rays, Weak Lensing and Sunyaev- Zeldovich effect) providing cluster samples with a well-characterized purity and completeness rates up to moderate redshift (z<1.2). These samples allow us to study the systematic of different methods and to obtain reliable mass estimations. On the contrary, high redshift clusters only started to be explored very recently with the advent of deep IR and X-ray data surveys, providing the first proto-clusters (z>1.5-2) ever detected. In this talk, I introduce these techniques and review some of the cluster samples obtained including particular striking cases. I discuss their relevance in terms of cosmological and galaxy evolution constraints and finally, I briefly refer to the cluster science predictions for the next generation surveys.

  19. DARK AND LUMINOUS MATTER IN THINGS DWARF GALAXIES

    SciTech Connect

    Oh, Se-Heon; De Blok, W. J. G.; Brinks, Elias; Walter, Fabian; Kennicutt, Robert C. Jr. E-mail: edeblok@ast.uct.ac.za E-mail: walter@mpia.de

    2011-06-15

    We present mass models for the dark matter component of seven dwarf galaxies taken from 'The H I Nearby Galaxy Survey' (THINGS) and compare these with those taken from numerical {Lambda} cold dark matter ({Lambda}CDM) simulations. The THINGS high-resolution data significantly reduce observational uncertainties and thus allow us to derive accurate dark matter distributions in these systems. We here use the bulk velocity fields when deriving the rotation curves of the galaxies. Compared to other types of velocity fields, the bulk velocity field minimizes the effect of small-scale random motions more effectively and traces the underlying kinematics of a galaxy more properly. The 'Spitzer Infrared Nearby Galaxies Survey' 3.6 {mu}m and ancillary optical data are used for separating the baryons from their total matter content in the galaxies. The sample dwarf galaxies are found to be dark matter dominated over most radii. The relation between total baryonic (stars + gas) mass and maximum rotation velocity of the galaxies is roughly consistent with the baryonic Tully-Fisher relation calibrated from a larger sample of gas-dominated low-mass galaxies. We find discrepancies between the derived dark matter distributions of the galaxies and those of {Lambda}CDM simulations, even after corrections for non-circular motions have been applied. The observed solid body-like rotation curves of the galaxies rise too slowly to reflect the cusp-like dark matter distribution in cold dark matter halos. Instead, they are better described by core-like models such as pseudo-isothermal halo models dominated by a central constant-density core. The mean value of the logarithmic inner slopes of the mass density profiles is {alpha} = -0.29 {+-} 0.07. They are significantly different from the steep slope of {approx} - 1.0 inferred from previous dark-matter-only simulations, and are more consistent with shallower slopes found in recent {Lambda}CDM simulations of dwarf galaxies in which the effects

  20. The formation of cluster elliptical galaxies as revealed by extensive star formation.

    PubMed

    Stevens, J A; Ivison, R J; Dunlop, J S; Smail, Ian R; Percival, W J; Hughes, D H; Röttgering, H J A; Van Breugel, W J M; Reuland, M

    2003-09-18

    The most massive galaxies in the present-day Universe are found to lie in the centres of rich clusters. They have old, coeval stellar populations suggesting that the bulk of their stars must have formed at early epochs in spectacular starbursts, which should be luminous phenomena when observed at submillimetre wavelengths. The most popular model of galaxy formation predicts that these galaxies form in proto-clusters at high-density peaks in the early Universe. Such peaks are indicated by massive high-redshift radio galaxies. Here we report deep submillimetre mapping of seven high-redshift radio galaxies and their environments. These data confirm not only the presence of spatially extended regions of massive star-formation activity in the radio galaxies themselves, but also in companion objects previously undetected at any wavelength. The prevalence, orientation, and inferred masses of these submillimetre companion galaxies suggest that we are witnessing the synchronous formation of the most luminous elliptical galaxies found today at the centres of rich clusters of galaxies. PMID:13679908

  1. Chandra Finds Surprising Black Hole Activity In Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    2002-09-01

    Scientists at the Carnegie Observatories in Pasadena, California, have uncovered six times the expected number of active, supermassive black holes in a single viewing of a cluster of galaxies, a finding that has profound implications for theories as to how old galaxies fuel the growth of their central black holes. The finding suggests that voracious, central black holes might be as common in old, red galaxies as they are in younger, blue galaxies, a surprise to many astronomers. The team made this discovery with NASA'S Chandra X-ray Observatory. They also used Carnegie's 6.5-meter Walter Baade Telescope at the Las Campanas Observatory in Chile for follow-up optical observations. "This changes our view of galaxy clusters as the retirement homes for old and quiet black holes," said Dr. Paul Martini, lead author on a paper describing the results that appears in the September 10 issue of The Astrophysical Journal Letters. "The question now is, how do these black holes produce bright X-ray sources, similar to what we see from much younger galaxies?" Typical of the black hole phenomenon, the cores of these active galaxies are luminous in X-ray radiation. Yet, they are obscured, and thus essentially undetectable in the radio, infrared and optical wavebands. "X rays can penetrate obscuring gas and dust as easily as they penetrate the soft tissue of the human body to look for broken bones," said co-author Dr. Dan Kelson. "So, with Chandra, we can peer through the dust and we have found that even ancient galaxies with 10-billion-year-old stars can have central black holes still actively pulling in copious amounts of interstellar gas. This activity has simply been hidden from us all this time. This means these galaxies aren't over the hill after all and our theories need to be revised." Scientists say that supermassive black holes -- having the mass of millions to billions of suns squeezed into a region about the size of our Solar System -- are the engines in the cores of

  2. Hubble tracks down a galaxy cluster's dark matter

    NASA Astrophysics Data System (ADS)

    2003-07-01

    Unique mass map hi-res Size hi-res: 495 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Unique mass map This is a mass map of galaxy cluster Cl0024+1654 derived from an extensive Hubble Space Telescope campaign. The colour image is made from two images: a dark-matter map (the blue part of the image) and a 'luminous-matter' map determined from the galaxies in the cluster (the red part of the image). They were constructed by feeding Hubble and ground-based observations into advanced mathematical mass-mapping models. The map shows that dark matter is present where the galaxies clump together. The mass of the galaxies is shown in red, the mass of the dark matter in blue. The dark matter behaves like a 'glue', holding the cluster together. The dark-matter distribution in the cluster is not spherical. A secondary concentration of dark-matter mass is shown in blue to the upper right of the main concentration. Sky around galaxy cluster Cl0024+1654 hi-res Size hi-res: 3742 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Sky around galaxy cluster Cl0024+1654 This is a 2.5-degree field around galaxy cluster Cl0024+1654. The cluster galaxies are visible in the centre of the image in yellow. The image is a colour composite constructed from three Digitized Sky Survey 2 images: Blue (shown in blue), Red (shown in green), and Infrared (shown in red). HST observes shapes of more than 7000 faint background galaxies hi-res Size hi-res: 5593 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Hubble observes shapes of more than 7000 faint background galaxies Five days of observations produced the altogether 39 Hubble Wide Field and Planetary Camera 2 (WFPC2) images required to map the mass of the galaxy cluster Cl0024+1654. Each WFPC2 image has a size of about 1/150 the diameter of the full Moon. In

  3. Extragalactic Globular Clusters: Tracers of Galaxy Evolution

    NASA Astrophysics Data System (ADS)

    Bassino, Lilia P.

    2008-09-01

    The study of globular cluster systems provides clues about different topics related to galaxy evolution. In the past years we have been investigating the globular cluster systems of galaxies in the Fornax and Antlia clusters, particularly those associated to the cluster-dominant galaxies. We present here the main results related to these systems. All of them have bimodal color distributions, even those around low-luminosity galaxies, that correspond to the metal-poor (``blue'') and metal-rich (``red'') globular cluster subpopulations. The radial and azimuthal projected areal distributions of the globular clusters are also analyzed. Total globular cluster populations are estimated through the luminosity functions. We stress on the properties of the globular cluster systems that allow us to trace possible interaction processes between the galaxies, like tidal stripping of globular clusters. The observational material consists of CCD images obtained with the wide-field MOSAIC Imager of the CTIO 4-m telescope (La Serena, Chile), and the FORS1 camera at the VLT ``Antu'' 8-m telescope (Cerro Paranal, Chile).

  4. The dwarf galaxy population of nearby galaxy clusters

    NASA Astrophysics Data System (ADS)

    Lisker, Thorsten; Wittmann, Carolin; Pak, Mina; Janz, Joachim; Bialas, Daniel; Peletier, Reynier; Grebel, Eva; Falcon Barroso, Jesus; Toloba, Elisa; Smakced Collaboration, Focus Collaboration

    2015-01-01

    The Fornax, Virgo, Ursa Major and Perseus galaxy clusters all have very different characteristics, in terms of their density, mass, and large-scale environment. We can regard these clusters as laboratories for studying environmental influence on galaxy evolution, using the sensitive low-mass galaxies as probes for external mechanisms. Here we report on recent and ongoing observational studies of the said clusters with imaging and spectroscopy, as well as on the interpretation of present-day cluster galaxy populations with the aid of cosmological simulations.Multicolor imaging data allow us to identify residual star formation in otherwise red early-type dwarf galaxies, which hold clues to the strength of gas stripping processes. Major-axis spectra and 2D kinematical maps provide insight regarding the amount of rotational support and how much dynamical heating a dwarf galaxy may have experienced. To this end, dedicated N-body simulations that follow the evolution of galaxies since early epochs reveal their path through parameter space, and can be compared to observations in order to understand the time-integrated effect of environmental influence.

  5. Spectroscopic Confirmation of the Dragonfish Association: The Galaxy's Most Luminous OB Association

    NASA Astrophysics Data System (ADS)

    Rahman, Mubdi; Moon, Dae-Sik; Matzner, Christopher D.

    2011-12-01

    Young OB associations with masses greater than 104 M ⊙ have been inferred to exist in the Galaxy but have largely evaded detection. Recently, a candidate OB association has been identified within the most luminous star-forming complex in the Galaxy, the Dragonfish Nebula. We identify 18 young, massive stars with near-infrared spectroscopy from a sample of 50 members within the candidate OB association, including 15 O-type and 3 luminous blue variables or Wolf-Rayet stars. This number matches the expected yield of massive stars from the candidate association, confirming its existence and ability to power the parent star-forming complex. These results demonstrate the existence of a 105 M ⊙ OB association, more powerful than any previously known in the Galaxy, comparable in mass only to Westerlund 1. Further, the results also validate the color selection method used to identify the association, adding credence to others discovered in the same way.

  6. Radio luminosity function of brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Yuan, Z. S.; Han, J. L.; Wen, Z. L.

    2016-08-01

    By cross-matching the currently largest optical catalogue of galaxy clusters and the NVSS radio survey data base, we obtain a large complete sample of brightest cluster galaxies (BCGs) in the redshift range of 0.05 < z ≤ 0.45, which have radio emission and redshift information. We confirm that more powerful radio BCGs tend to be these optically very bright galaxies located in more relaxed clusters. We derived the radio luminosity functions of the largest sample of radio BCGs, and find that the functions depend on the optical luminosity of BCGs and the dynamic state of galaxy clusters. However, the radio luminosity function does not show significant evolution with redshift.

  7. The Formation of Galaxies and Clusters.

    ERIC Educational Resources Information Center

    Gregory, Stephen; Morrison, Nancy D.

    1985-01-01

    Summarizes recent research on the formation of galaxies and clusters, focusing on research examining how the materials in galaxies seen today separated from the universal expansion and collapsed into stable bodies. A list of six nontechnical books and articles for readers with less background is included. (JN)

  8. STUDYING LARGE- AND SMALL-SCALE ENVIRONMENTS OF ULTRAVIOLET LUMINOUS GALAXIES

    SciTech Connect

    Basu-Zych, Antara R.; Schiminovich, David; Heinis, Sebastien; Heckman, Tim; Bianchi, Luciana; Overzier, Roderik; Zamojski, Michel; Barlow, Tom A.; Conrow, Tim; Forster, Karl G.; Friedman, Peter G.; Martin, D. Christopher; Morrissey, Patrick; Ilbert, Olivier; Koekemoer, Anton M.; Donas, Jose; Milliard, Bruno; Lee, Young-Wook; Madore, Barry F.; Neff, Susan G.

    2009-07-10

    Studying the environments of 0.4 < z < 1.2 ultraviolet (UV)-selected galaxies, as examples of extreme star-forming galaxies (with star formation rates (SFRs) in the range of 3-30 M{sub sun} yr{sup -1}), we explore the relationship between high rates of star formation, host halo mass, and pair fractions. We study the large- and small-scale environments of local ultraviolet luminous galaxies (UVLGs) by measuring angular correlation functions. We cross-correlate these systems with other galaxy samples: a volume-limited sample (ALL), a blue luminous galaxy sample, and a luminous red galaxy (LRG) sample. We determine the UVLG comoving correlation length to be r{sub 0} = 4.8{sup +11.6}{sub -2.4} h {sup -1} Mpc at (z) = 1.0, which is unable to constrain the halo mass for this sample. However, we find that UVLGs form close (separation <30 kpc) pairs with the ALL sample, but do not frequently form pairs with LRGs. A rare subset of UVLGs, those with the highest FUV surface brightnesses, are believed to be local analogs of high-redshift Lyman break galaxies (LBGs) and are called Lyman break analogs (LBAs). LBGs and LBAs share similar characteristics (i.e., color, size, surface brightness, specific SFRs, metallicities, and dust content). Recent Hubble Space Telescope images of z {approx} 0.2 LBAs show disturbed morphologies, signs of mergers and interactions. UVLGs may be influenced by interactions with other galaxies and we discuss this result in terms of other high star-forming, merging systems.

  9. Distribution of dark and luminous mass in galaxies

    SciTech Connect

    Lovas, Stephen; Kielkopf, John F.

    2014-06-01

    A uniform scale relation between dark and baryonic matter is observed in galaxies over a broad range of physical parameter space. The ratio of dark to baryonic mass is found to increase proportionately with radial distance in observational data spanning a wide dynamic range of morphological type, rotation velocity, radius, surface density, and mass. This close relation between dark and baryonic mass poses a fine-tuning problem for galaxy formation models. Such a uniform scale relation, extending from the inner galactic region to the outermost kinematic data point, may play a role in clarifying the dark matter phenomenon.

  10. On the dust content of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Gutiérrez, C. M.; López-Corredoira, M.

    2014-11-01

    Context. Most of the contribution to dust emission in clusters of galaxies comes from late-type galaxies. However, several ejection processes of material from these galaxies could introduce dust in the intracluster media. Even a relatively low abundance of this dust could act as an efficient cooling agent and have a relevant role in the evolution of clusters. Aims: We present a study to estimate the dust content in galaxy clusters. Methods: This was done by using one the most complete existing catalogues of galaxy clusters based on Sloan Digital Sky Survey (SDSS) data and following two methods: the first one compares the colours of samples of galaxies in the background of clusters with those of galaxies in the field. Using this method, we have explored clustercentric distances up to 6 Mpc; this covers at least 2 × R200 for all the clusters in the sample. The galaxies used in this first method were selected from the SDSS-DR9, among those having reliable photometry and accurate estimation of photometric redshifts. Using the colours of background galaxies, we analyzed several regions at galactic latitudes | b | > 20° and >50°. The results are largely independent of the galactic cut applied. At | b | > 20°, the sample contains 56 985 clusters in the redshift range 0.05 galaxies. The second method computes the contribution of dust in clusters of galaxies to the far infrared sky. That is estimated indirectly by measuring the effect of clusters in the E(B - V) extinction map. Results: Using the first method, we did not find any dependence with clustercentric distance in the colours of background galaxies. As representative of the whole results, the surface integral of the excess of colour g - i in three rings centred in the clusters and with radius 0-1, 0-2, and 0-3 Mpc is -3.7 ± 3.5, + 3.2 ± 6.8, and -4.5 ± 10.1 milimag Mpc2, respectively. This allows us to constrain the mass of dust in the intracluster media

  11. Morphological Properties and AGN Content of High Redshift Luminous Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Kartaltepe, Jeyhan S.; CANDELS Collaboration

    2013-01-01

    We explore the evolution of the morphological properties of (Ultra) Luminous Infrared Galaxies ((U)LIRGs) over cosmic time using a large sample of galaxies from Herschel observations of the CANDELS fields (including GOODS, COSMOS, and UDS). In particular, we investigate whether the role of galaxy mergers has changed between 2 and now using the extensive visual classification catalogs produced by the CANDELS team. The combination of a selection from Herschel, near the peak of IR emission, and rest-frame optical morphologies from CANDELS, provides the ideal comparison to nearby (U)LIRGs. We then study the how role of galaxy mergers and the presence of AGN activity correspond to the galaxy's position in the star formation rate - stellar mass plane.

  12. A filament of dark matter between two clusters of galaxies.

    PubMed

    Dietrich, Jörg P; Werner, Norbert; Clowe, Douglas; Finoguenov, Alexis; Kitching, Tom; Miller, Lance; Simionescu, Aurora

    2012-07-12

    It is a firm prediction of the concordance cold-dark-matter cosmological model that galaxy clusters occur at the intersection of large-scale structure filaments. The thread-like structure of this 'cosmic web' has been traced by galaxy redshift surveys for decades. More recently, the warm–hot intergalactic medium (a sparse plasma with temperatures of 10(5) kelvin to 10(7) kelvin) residing in low-redshift filaments has been observed in emission and absorption. However, a reliable direct detection of the underlying dark-matter skeleton, which should contain more than half of all matter, has remained elusive, because earlier candidates for such detections were either falsified or suffered from low signal-to-noise ratios and unphysical misalignments of dark and luminous matter. Here we report the detection of a dark-matter filament connecting the two main components of the Abell 222/223 supercluster system from its weak gravitational lensing signal, both in a non-parametric mass reconstruction and in parametric model fits. This filament is coincident with an overdensity of galaxies and diffuse, soft-X-ray emission, and contributes a mass comparable to that of an additional galaxy cluster to the total mass of the supercluster. By combining this result with X-ray observations, we can place an upper limit of 0.09 on the hot gas fraction (the mass of X-ray-emitting gas divided by the total mass) in the filament. PMID:22763438

  13. Cooling Flow Spectra in Ginga Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    White, Raymond E., III

    1997-01-01

    The primary focus of this research project has been a joint analysis of Ginga LAC and Einstein SSS X-ray spectra of the hot gas in galaxy clusters with cooling flows is reported. We studied four clusters (A496, A1795, A2142 & A2199) and found their central temperatures to be cooler than in the exterior, which is expected from their having cooling flows. More interestingly, we found central metal abundance enhancements in two of the clusters, A496 and A2142. We have been assessing whether the abundance gradients (or lack thereof) in intracluster gas is correlated with galaxy morphological gradients in the host clusters. In rich, dense galaxy clusters, elliptical and SO galaxies are generally found in the cluster cores, while spiral galaxies are found in the outskirts. If the metals observed in clusters came from proto-ellipticals and proto-S0s blowing winds, then the metal distribution in intracluster gas may still reflect the distribution of their former host galaxies. In a research project which was inspired by the success of the Ginga LAC/Einstein SSS work, we analyzed X-ray spectra from the HEAO-A2 MED and the Einstein SSS to look for temperature gradients in cluster gas. The HEAO-A2 MED was also a non-imaging detector with a large field of view compared to the SSS, so we used the differing fields of view of the two instruments to extract spatial information. We found some evidence of cool gas in the outskirts of clusters, which may indicate that the nominally isothermal mass density distributions in these clusters are steepening in the outer parts of these clusters.

  14. Submillimeter Imaging of the Luminous Infrared Galaxy Pair VV114

    NASA Technical Reports Server (NTRS)

    Frayer, D.; Ivison, R. J.; Smail, I.; Yun, M. S.; Armus, L.

    1999-01-01

    We report on 450 and 850 mue observations of the interacting galaxy pair, VV114E+W (IC 1623), taken with the SCUBA camera on the James Clerk Maxwell Telescope, and near-infrared observations taken with UFTI on the UK Infrared Telescope.

  15. IUE observations of luminous blue star associations in irregular galaxies

    NASA Technical Reports Server (NTRS)

    Lamb, S. A.; Hunter, D. A.; Gallagher, J. S., III

    1987-01-01

    Two regions of recent star formation in blue irregular galaxies were observed with the IUE in the short wavelength, low dispersion mode. The spectra indicate that the massive star content is similar in these regions and is best fit by massive stars formed in a burst and now approximately 2.5 to 3.0 million years old.

  16. Adaptive Optics Imaging Survey of Luminous Infrared Galaxies

    SciTech Connect

    Laag, E A; Canalizo, G; van Breugel, W; Gates, E L; de Vries, W; Stanford, S A

    2006-03-13

    We present high resolution imaging observations of a sample of previously unidentified far-infrared galaxies at z < 0.3. The objects were selected by cross-correlating the IRAS Faint Source Catalog with the VLA FIRST catalog and the HST Guide Star Catalog to allow for adaptive optics observations. We found two new ULIGs (with L{sub FIR} {ge} 10{sup 12} L{sub {circle_dot}}) and 19 new LIGs (with L{sub FIR} {ge} 10{sup 11} L{sub {circle_dot}}). Twenty of the galaxies in the sample were imaged with either the Lick or Keck adaptive optics systems in H or K{prime}. Galaxy morphologies were determined using the two dimensional fitting program GALFIT and the residuals examined to look for interesting structure. The morphologies reveal that at least 30% are involved in tidal interactions, with 20% being clear mergers. An additional 50% show signs of possible interaction. Line ratios were used to determine powering mechanism; of the 17 objects in the sample showing clear emission lines--four are active galactic nuclei and seven are starburst galaxies. The rest exhibit a combination of both phenomena.

  17. Green Pea Galaxies and Cohorts: Luminous Compact Emission-line Galaxies in the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Izotov, Yuri I.; Guseva, Natalia G.; Thuan, Trinh X.

    2011-02-01

    We present a large sample of 803 star-forming luminous compact galaxies (LCGs) in the redshift range z = 0.02-0.63, selected from Data Release 7 of the Sloan Digital Sky Survey (SDSS). The global properties of these galaxies are similar to those of the so-called green pea star-forming galaxies in the redshift range z = 0.112-0.360 and selected from the SDSS on the basis of their green color and compact structure. In contrast to green pea galaxies, our LCGs are selected on the basis of both their spectroscopic and photometric properties, resulting in a ~10 times larger sample, with galaxies spanning a redshift range gsim2 times larger. We find that the oxygen abundances and the heavy element abundance ratios in LCGs do not differ from those of nearby low-metallicity blue compact dwarf galaxies. The median stellar mass of LCGs is ~109 M sun. However, for galaxies with high EW(Hβ), >= 100 Å, it is only ~7 × 108 M sun. The star formation rate in LCGs varies in the large range of 0.7-60 M sun yr-1, with a median value of ~4 M sun yr-1, a factor of ~3 lower than in high-redshift star-forming galaxies at z >~ 3. The specific star formation rates in LCGs are extremely high and vary in the range ~10-9-10-7 yr-1, comparable to those derived in high-redshift galaxies.

  18. A note on the dynamics of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Cooper, R. G.; Miller, R. H.

    1982-03-01

    When a dynamical simulation of galaxy clusters includes the elasticity of galactic collisions, a massive object forms as a result of galaxy mergers which may contain as much as 80% of the cluster mass. The inelasticity of galaxy encounters, as calibrated in galaxy collision experiments, is sufficiently strong to affect galaxy cluster evolution and is an essential part of the physics of galaxy clusters which must be incorporated into dynamical simulations. It is found that, although the merger framework offers a useful model for the formation of poor clusters with a cD galaxy, it does not fit the rich clusters, thereby raising questions as to how galaxy clusters survive and as to the physics which may account for the differences between clusters with and without cD galaxies. It is suggested that the age of galaxy clusters has been overestimated.

  19. X-ray emission from clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Mushotzky, R. F.

    1983-01-01

    Some X-ray spectral observations of approximately 30 clusters of galaxies from HEAO-1 are summarized. There exists strong correlations between X-ray luminosity, L(x), and temperature kT in the form L(x)alphaT to the 2.3 power. This result combined with the L(x) central galaxy density relation and the virial theorem indicates that the core dadius of the gas should be roughly independent of L(x) or KT and that more luminous clusters have a greater fraction of their virial mass in gas. The poor correlation of KT and optical velocity dispersion seems to indicate that clusters have a variety of equations of state. There is poor agreement between X-ray imaging observations and optical and X-ray spectral measures of the polytropic index. Most clusters show Fe emission lines with a strong indication that they all have roughly 1/2 solar abundance. The evidence for cooling in the cores of several clusters is discussed based on spectral observations with the Einstein solid state spectrometer.

  20. X-ray emission from clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Mushotzky, R. F.

    1984-01-01

    Some X-ray spectral observations of approximately 30 clusters of galaxies from HEAO-1 are summarized. There exists strong correlation betwen X-ray luminosity, L(x), and temperature kT in the form L(x)alphaT to the 2.3 power. This result combined with the L(x) central galaxy density relation and the virial theorem indicates that the core dadius of the gas should be roughly independent of L(x) or Kt and that more luminous clusters have a greater fraction of their virial mass in gas. The poor correlation of KT and optical velocity dispersion seems to indicate that clusters have a variety of equations of state. There is poor agreement between X-ray imaging observations and optical and X-ray spectral measures of the polytropic index. Most clusters show Fe emission lines with a strong indication that they all have roughly 1/2 solar abundance. The evidence for cooling in the cores several clusters is discussed based on spectral observations with the Einstein solid state spectrometer.

  1. SUPERDENSE MASSIVE GALAXIES IN WINGS LOCAL CLUSTERS

    SciTech Connect

    Valentinuzzi, T.; D'Onofrio, M.; Fritz, J.; Poggianti, B. M.; Bettoni, D.; Fasano, G.; Moretti, A.; Omizzolo, A.; Varela, J.; Cava, A.; Couch, W. J.; Dressler, A.; Moles, M.; Kjaergaard, P.; Vanzella, E.

    2010-03-20

    Massive quiescent galaxies at z > 1 have been found to have small physical sizes, and hence to be superdense. Several mechanisms, including minor mergers, have been proposed for increasing galaxy sizes from high- to low-z. We search for superdense massive galaxies in the WIde-field Nearby Galaxy-cluster Survey (WINGS) of X-ray selected galaxy clusters at 0.04 < z < 0.07. We discover a significant population of superdense massive galaxies with masses and sizes comparable to those observed at high redshift. They approximately represent 22% of all cluster galaxies more massive than 3 x 10{sup 10} M{sub sun}, are mostly S0 galaxies, have a median effective radius (R{sub e} ) = 1.61 +- 0.29 kpc, a median Sersic index (n) = 3.0 +- 0.6, and very old stellar populations with a median mass-weighted age of 12.1 +- 1.3 Gyr. We calculate a number density of 2.9 x 10{sup -2} Mpc{sup -3} for superdense galaxies in local clusters, and a hard lower limit of 1.3 x 10{sup -5} Mpc{sup -3} in the whole comoving volume between z = 0.04 and z = 0.07. We find a relation between mass, effective radius, and luminosity-weighted age in our cluster galaxies, which can mimic the claimed evolution of the radius with redshift, if not properly taken into account. We compare our data with spectroscopic high-z surveys and find that-when stellar masses are considered-there is consistency with the local WINGS galaxy sizes out to z {approx} 2, while a discrepancy of a factor of 3 exists with the only spectroscopic z > 2 study. In contrast, there is strong evidence for a large evolution in radius for the most massive galaxies with M{sub *} > 4 x 10{sup 11} M{sub sun} compared to similarly massive galaxies in WINGS, i.e., the brightest cluster galaxies.

  2. REVISITING SCALING RELATIONS FOR GIANT RADIO HALOS IN GALAXY CLUSTERS

    SciTech Connect

    Cassano, R.; Brunetti, G.; Venturi, T.; Kale, R.; Pratt, G. W.; Markevitch, M.

    2013-11-10

    Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the synchrotron power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift-limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. We find that the radio power at 1.4 GHz scales with the cluster X-ray (0.1-2.4 keV) luminosity computed within R{sub 500} as P{sub 1.4}∼L{sup 2.1±0.2}{sub 500}. Our bigger and more homogenous sample confirms that the X-ray luminous (L{sub 500} > 5 × 10{sup 44} erg s{sup –1}) clusters branch into two populations—radio halos lie on the correlation, while clusters without radio halos have their radio upper limits well below that correlation. This bimodality remains if we excise cool cores from the X-ray luminosities. We also find that P{sub 1.4} scales with the cluster integrated SZ signal within R{sub 500}, measured by Planck, as P{sub 1.4}∼Y{sup 2.05±0.28}{sub 500}, in line with previous findings. However, contrary to previous studies that were limited by incompleteness and small sample size, we find that 'SZ-luminous' Y{sub 500} > 6 × 10{sup –5} Mpc{sup 2} clusters show a bimodal behavior for the presence of radio halos, similar to that in the radio-X-ray diagram. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the relativistic particle

  3. Revisiting Scaling Relations for Giant Radio Halos in Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Cassano, R.; Ettori, S.; Brunetti, G.; Giacintucci, S.; Pratt, G. W.; Venturi, T.; Kale, R.; Dolag, K.; Markevitch, Maxim L.

    2013-01-01

    Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the synchrotron power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift-limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. We find that the radio power at 1.4 GHz scales with the cluster X-ray (0.1-2.4 keV) luminosity computed within R(sub 500) as P(sub 1.4) approx. L(2.1+/-0.2) - 500). Our bigger and more homogenous sample confirms that the X-ray luminous (L(sub 500) > 5 × 10(exp 44) erg/s)) clusters branch into two populations-radio halos lie on the correlation, while clusters without radio halos have their radio upper limits well below that correlation. This bimodality remains if we excise cool cores from the X-ray luminosities. We also find that P(sub 1.4) scales with the cluster integrated SZ signal within R(sub 500), measured by Planck, as P(sub 1.4) approx. Y(2.05+/-0.28) - 500), in line with previous findings. However, contrary to previous studies that were limited by incompleteness and small sample size, we find that "SZ-luminous" Y(sub 500) > 6×10(exp -5) Mpc(exp 2) clusters show a bimodal behavior for the presence of radio halos, similar to that in the radio-X-ray diagram. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the relativistic particle acceleration.

  4. Star Formation Histories in CLASH Brightest Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Fogarty, Kevin; Postman, Marc; Donahue, Megan; Moustakas, John; Connor, Thomas; Clash Science Team

    2015-01-01

    The CLASH sample of 25 lensing galaxy clusters contains 11 Brightest Cluster Galaxies (BCG) that exhibit significant unobscured (>5 Msol yr-1) star formation activity. The star formation is inferred from UV emission and from evidence for H-alpha filaments as detected in the ACS and WFC3 observations. We use photometry from the 16-band CLASH imaging along with spectra from the SOAR and SDSS telescopes to examine the star formation histories of these galaxies. Using SED fits to synthetic stellar population and nebular emission models, we constrain the burst histories of the two most UV and H-alpha luminous BCGs in our sample, RXJ1532.9+3021 and MACS1931.8-2635. The BCG in both of these clusters have reddening-corrected UV estimates of star formation rates in excess of 100 solar masses per year. We model the timescales and sizes of the starbursts that can account for the photometric and spectroscopic properties in these BCGs and create maps of their stellar properties on scales of ~350 pc. These maps reveal recent bursts occurring in elongated filaments on relatively long (~0.5-1.0 Gyr) timescales. In addition, we constrain the star formation properties of all of the remaining BCGs in the CLASH sample. These results and their implications for BCG formation and evolution will be presented.

  5. The HST/ACS Coma Cluster Survey - X. Nuclear star clusters in low-mass early-type galaxies: scaling relations

    NASA Astrophysics Data System (ADS)

    den Brok, Mark; Peletier, Reynier F.; Seth, Anil; Balcells, Marc; Dominguez, Lilian; Graham, Alister W.; Carter, David; Erwin, Peter; Ferguson, Henry C.; Goudfrooij, Paul; Guzmán, Rafael; Hoyos, Carlos; Jogee, Shardha; Lucey, John; Phillipps, Steven; Puzia, Thomas; Valentijn, Edwin; Kleijn, Gijs Verdoes; Weinzirl, Tim

    2014-12-01

    We present scaling relations between structural properties of nuclear star clusters and their host galaxies for a sample of early-type dwarf galaxies observed as part of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Coma Cluster Survey. We have analysed the light profiles of 200 early-type dwarf galaxies in the magnitude range 16.0 < mF814W < 22.6 mag, corresponding to -19.0 < MF814W < -12.4 mag. Nuclear star clusters are detected in 80 per cent of the galaxies, thus doubling the sample of HST-observed early-type dwarf galaxies with nuclear star clusters. We confirm that the nuclear star cluster detection fraction decreases strongly towards faint magnitudes. The luminosities of nuclear star clusters do not scale linearly with host galaxy luminosity. A linear fit yields L_nuc ˜ L_gal^{0.57± 0.05}. The nuclear star cluster-host galaxy luminosity scaling relation for low-mass early-type dwarf galaxies is consistent with formation by globular cluster (GC) accretion. We find that at similar luminosities, galaxies with higher Sérsic indices have slightly more luminous nuclear star clusters. Rounder galaxies have on average more luminous clusters. Some of the nuclear star clusters are resolved, despite the distance of Coma. We argue that the relation between nuclear star cluster mass and size is consistent with both formation by GC accretion and in situ formation. Our data are consistent with GC inspiralling being the dominant mechanism at low masses, although the observed trend with Sérsic index suggests that in situ star formation is an important second-order effect.

  6. Outflows in infrared-luminous galaxies: Absorption-line spectroscopy of starbursts and AGN

    NASA Astrophysics Data System (ADS)

    Rupke, David S.

    Large-scale galactic outflows, better known as superwinds, are driven by the powerful energy reservoirs in star forming and active galaxies. They play a significant role in galaxy formation, galaxy evolution, and the evolution of the intergalactic medium. We have performed a survey of over 100 infrared-luminous galaxies in order to address the exact frequency with which they occur in different galaxy types, the dependence of their properties on those of their host galaxies, and their properties in the most luminous starburst and active galaxies. Most of our sample consists of ultraluminous infrared galaxies (ULIRGs), and we use moderate- resolution spectroscopy of the Na I D interstellar absorption feature (which directly probes the neutral gas phase). We find superwinds in the majority of these galaxies at typical maximum, deprojected velocities of 500 700 km s-1. The detection rate increases with star formation rate (SFR) in starbursts, while the mass outflow rate appears constant with SFR, contrary to theoretical expectations. The resulting mass entrainment efficiencies in ULIRGs are quite low, of order a few percent of the star formation rate. There is some dependence of outflow velocity on host galaxy properties; the outflow velocities in LINERs are higher than those in H II galaxies, and the highest column density gas in each galaxy may have an upper envelope in velocity that increases with SFR. Outflows in most galaxies hosting a dominant AGN have very similar properties to those in starbursts, so discerning their power source is difficult. The velocities in Seyfert 2 outflows may be slightly higher than those in starbursts, and the fraction of neutral gas escaping Seyfert 2s is higher than that in starbursts (˜50% vs. ≲ 20%). The outflows in our Seyfert 1 galaxies have extreme velocities of up to ˜104 km s-1, and two of three Seyfert is with outflows possess broad absorption lines. Finally, we find that spectroscopy of a few galaxies at very high

  7. Massive Star Clusters in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Larsen, Soeren

    2015-08-01

    Dwarf galaxies are often characterized by very high globular cluster specific frequencies, in some cases exceeding that of the Milky Way by a factor of 100 or more. Moreover, the GCs are typically much more metal-poor than the bulk of the field stars, so that a substantial fraction (up to 20-25% or more) of all metal-poor stars in some dwarf galaxies are associated with GCs. The metal-poor components of these galaxies thus represent an extreme case of the "specific frequency problem". In this talk I will review the current status of our understanding of GC systems in dwarf galaxies. Particular emphasis will be placed on the implications of the high GC specific frequencies for the amount of mass loss the clusters could have experienced and the constraints this provides on theories for the origin of multiple populations in globular clusters.

  8. AGN feedback in galaxy clusters and groups

    NASA Astrophysics Data System (ADS)

    Hardcastle, Martin

    2016-07-01

    Mechanical feedback via Active Galactic Nuclei (AGN) jets in the centres of galaxy groups and clusters is a crucial ingredient in current models of galaxy formation and cluster evolution. Jet feedback is believed to regulate gas cooling and thus star formation in the most massive galaxies, but a robust physical understanding of this feedback mode is currently lacking. Athena will provide (1) the first kinematic measurements on relevant spatial scales of the hot gas in galaxy, group and cluster haloes as it absorbs the impact of AGN jets, and (2) vastly improved ability to map thermodynamic conditions on scales well-matched to the jets, lobes and gas disturbances produced by them. I will present new predictions of Athena's ability to measure the energetic impact of powerful jets based on our most recent set of numerical models.

  9. A search for X-ray bright distant clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Nichol, R. C.; Ulmer, M. P.; Kron, R. G.; Wirth, G. D.; Koo, D. C.

    1994-01-01

    We present the results of a search for X-ray luminous distant clusters of galaxies. We found extended X-ray emission characteristic of a cluster toward two of our candidate clusters of galaxies. They both have a luminosity in the ROSAT bandpass of approximately equals 10(exp 44) ergs/s and a redshift greater than 0.5; thus making them two of the most distant X-ray clusters ever observed. Furthermore, we show that both clusters are optically rich and have a known radio source associated with them. We compare our result with other recent searches for distant X-ray luminous clusters and present a lower limit of 1.2 x 10(exp -7)/cu Mpc for the number density of such high-redshift clusters. This limit is consistent with the expected abundance of such clusters in a standard (b = 2) cold dark matter universe. Finally, our clusters provide important high-redshift targets for further study into the origin and evolution of massive clusters of galaxies.

  10. Effects of Galaxy collisions on the structure and evolution of Galaxy clusters. I. Mass and luminosity functions and background light

    SciTech Connect

    Miller, G.E.

    1983-05-15

    The role of galaxy collisions in controlling the form of the galaxy mass and luminosity functions and in creating a diffuse background light is investigated by means of a direct computer simulation. Galaxy collisions are treated in a realistic manner, including both galaxy mergers and tidal encounters. A large number of theoretical studies of a galaxy collisions were consulted to formulate the basic input physics of collision cross sections. Despite this large number of studies, there remains considerable uncertainty in the effects of a collision on a galaxy due mainly to our lack of knowledge of the orbital distribution of matter in galaxies. To improve this situation, some methods of semiempirical calibration are suggested: for example, a survey of background light in clusters of different richness and morphological classes. If real galaxies are represented by galaxy models where the bulk of the matter is on radial, rather than circular, orbits, then tidal collisions are more damaging and there are a number of interesting effects: Repeated tidal encounters lead to galaxy mass and luminosity functions which are largely independent of model parameters and the initial galaxy mass function. It appears unlikely that the form of the average present-day luminosity function characteristic of both field and cluster galaxies is due to collisions, but certain observed deviations from the average found by Heiligman and Turner and by Dressler may be a signature of collisions, in particular a flat faint-end slope. The amount of luminous matter stripped from the galaxies in the simulations agrees with the amount of diffuse background light seen in the Coma Cluster.

  11. Spitzer Spectroscopy to Distinguish z>5 Sources of Reionization from z~2 Luminous Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Chary, Ranga-Ram; Dickinson, Mark; Lawrence, Charles; Teplitz, Harry

    2008-03-01

    Optical/near-infrared photometric redshifts of 13 red galaxies in GOODS favor z>5 redshift solutions which indicate that they are extremely massive galaxies with stellar masses exceeding 1E11 Msun. If true, these galaxies contribute the bulk of the stellar mass density at z~6 and the past star-formation in these galaxies is responsible for reionizing the intergalactic medium at z>>6. The majority of these galaxies have however found to be faint 24 micron sources which would instead suggest that they are luminous infrared galaxies (LIRGs) with L(IR)~3E11 Lsun at z~2. We propose ultradeep Spitzer/IRS LL spectroscopy which will measure the redshifts of two representative, optically invisible (i>27 mag) sources in this class and distinguish between these two widely disparate hypotheses. The detection of polycyclic aromatic hydrocarbons (PAH) in the spectra of these sources would imply that photometric redshifts of dusty infrared luminous galaxies are unreliable - a fundamental obstacle in estimating the comoving luminosity density of the Universe as a function of redshift. It would allow the shape of the dust extinction curve to be constrained and rule out the Balmer-'break' color selection as a reliable tracer of redshift. By virtue of being the deepest IRS/LL observations, it would yield the first measures of PAH line strengths in high redshift LIRGs. This will help refine the mid-infrared PAH templates that are used to estimate bolometric luminosities of galaxies detected in various mid-infrared surveys, including those which will be undertaken by WISE. The absence of PAH in the proposed spectra would imply the presence of Compton-thick AGN and/or confirm that we have identified the galaxies responsible for reionization without the need for changing the stellar initial mass function at high redshift. Spitzer offers the only opportunity to resolve this important conundrum until the James Webb Space Telescope.

  12. Hubble tracks down a galaxy cluster's dark matter

    NASA Astrophysics Data System (ADS)

    2003-07-01

    Unique mass map hi-res Size hi-res: 495 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Unique mass map This is a mass map of galaxy cluster Cl0024+1654 derived from an extensive Hubble Space Telescope campaign. The colour image is made from two images: a dark-matter map (the blue part of the image) and a 'luminous-matter' map determined from the galaxies in the cluster (the red part of the image). They were constructed by feeding Hubble and ground-based observations into advanced mathematical mass-mapping models. The map shows that dark matter is present where the galaxies clump together. The mass of the galaxies is shown in red, the mass of the dark matter in blue. The dark matter behaves like a 'glue', holding the cluster together. The dark-matter distribution in the cluster is not spherical. A secondary concentration of dark-matter mass is shown in blue to the upper right of the main concentration. Sky around galaxy cluster Cl0024+1654 hi-res Size hi-res: 3742 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Sky around galaxy cluster Cl0024+1654 This is a 2.5-degree field around galaxy cluster Cl0024+1654. The cluster galaxies are visible in the centre of the image in yellow. The image is a colour composite constructed from three Digitized Sky Survey 2 images: Blue (shown in blue), Red (shown in green), and Infrared (shown in red). HST observes shapes of more than 7000 faint background galaxies hi-res Size hi-res: 5593 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Hubble observes shapes of more than 7000 faint background galaxies Five days of observations produced the altogether 39 Hubble Wide Field and Planetary Camera 2 (WFPC2) images required to map the mass of the galaxy cluster Cl0024+1654. Each WFPC2 image has a size of about 1/150 the diameter of the full Moon. In

  13. Abundance Gradients in Clusters of Galaxies

    NASA Astrophysics Data System (ADS)

    Dupke, Renato De Alencar

    This dissertation presents the analysis of spatially resolved ASCA satellite X-ray spectra for four clusters of galaxies (Abell 496, Abell 2199, Abell 3571 and Abell 1060). The abundance distributions of Abell 496, Abell 2199 and Abell 3571 are shown to be centrally enhanced. The distribution of elemental abundance ratios, combined with calculations of supernovae rates, shows that the central abundance enhancement in these galaxy clusters is dominated by supernova, Type 1a iron, while the outer parts are dominated by supernovae Type II iron and the most likely mechanism proposed to produce this central iron is ram-pressure stripping, rather than accumulated stellar mass loss from the central dominant galaxy. At least 50% (by mass) of the iron in the central regions is from supernovae Type Ia, varying slightly from cluster to cluster. Although the analysis of Abell 1060 reveals no significant central abundance enhancement, supernovae Type Ia are shown to contribute significantly to the iron content of the central regions. However, accumulated stellar mass loss from the two central dominant galaxies in this cluster can account for all of the supernovae Type la iron in the central regions. The nickel to iron abundance ratio shows that delayed detonation explosion models for supernovae Type la are inconsistent with the observed abundance ratios in the inner regions of Abell 496, Abell 2199 and Abell 3571. A comparison of the distributions of iron mass and the luminosity of early type galaxies in four clusters, three of them having central abundance enhancements (Virgo, Abell 496 and Centaurus) and one having a flat abundance distribution (Coma), indicates that the iron mass traces the luminosity of early type galaxies in abundance gradient clusters better than in flat abundance clusters. This suggests that abundance gradients can be washed out by cluster mergers.

  14. Watching the Birth of a Galaxy Cluster?

    NASA Astrophysics Data System (ADS)

    1999-07-01

    First Visiting Astronomers to VLT ANTU Observe the Early Universe When the first 8.2-m VLT Unit Telescope (ANTU) was "handed over" to the scientists on April 1, 1999, the first "visiting astronomers" at Paranal were George Miley and Huub Rottgering from the Leiden Observatory (The Netherlands) [1]. They obtained unique pictures of a distant exploding galaxy known as 1138 - 262 . These images provide new information about how massive galaxies and clusters of galaxies may have formed in the early Universe. Formation of clusters of galaxies An intriguing question in modern astronomy is how the first galaxies and groupings or clusters of galaxies emerged from the primeval gas produced in the Big Bang. Some theories predict that giant galaxies, often found at the centres of rich galaxy clusters, are built up through a step-wise process. Clumps develop in this gas and stars condense out of those clumps to form small galaxies. Finally these small galaxies merge together to form larger units. An enigmatic class of objects important for investigating such scenarios are galaxies which emit intense radio emission from explosions that occur deep in their nuclei. The explosions are believed to be triggered when material from the merging swarm of smaller galaxies is fed into a rotating black hole located in the central regions. There is strong evidence that these distant radio galaxies are amongst the oldest and most massive galaxies in the early Universe and are often located at the heart of rich clusters of galaxies. They can therefore help pinpoint regions of the Universe in which large galaxies and clusters of galaxies are being formed. The radio galaxy 1138-262 The first visiting astronomers pointed ANTU towards a particularly important radio galaxy named 1138-262 . It is located in the southern constellation Hydra (The Water Snake). This galaxy was discovered some years ago using ESO's 3.5-m New Technology Telescope (NTT) at La Silla. Because 1138-262 is at a distance of

  15. The Spatial Distribution of Satellite Galaxies within Halos: Measuring the Very Small Scale Angular Clustering of SDSS Galaxies

    NASA Astrophysics Data System (ADS)

    Piscionere, Jennifer A.; Berlind, Andreas A.; McBride, Cameron K.; Scoccimarro, Román

    2015-06-01

    We measure the angular clustering of galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 7 in order to probe the spatial distribution of satellite galaxies within their dark matter halos. Specifically, we measure the angular correlation function on very small scales (7″–320″) in a range of luminosity threshold samples (absolute r-band magnitudes from ‑18 up to ‑21) that are constructed from the subset of SDSS that has been spectroscopically observed more than once (the so-called plate overlap region). We choose to measure angular clustering in this reduced survey footprint in order to minimize the effects of fiber collision incompleteness, which are otherwise substantial on these small scales, and we discuss the possible impact that fiber collisions have on our measurements. We model our clustering measurements using a fully numerical halo model that populates dark matter halos in N-body simulations to create realistic mock galaxy catalogs. The model has free parameters that specify both the number and spatial distribution of galaxies within their host halos. We adopt a flexible density profile for the spatial distribution of satellite galaxies that is similar to the dark matter Navarro–Frenk–White (NFW) profile, except that the inner slope is allowed to vary. We find that the angular clustering of our most luminous samples ({{M}r} < ‑20 and ‑21) suggests that luminous satellite galaxies have substantially steeper inner density profiles than NFW. Lower-luminosity samples are less constraining, however, and are consistent with satellite galaxies having shallow density profiles. Our results confirm the findings of Watson et al. while using different clustering measurements and modeling methodology.

  16. Exploring the Formation of Galaxies through Metallicities of Globular Clusters

    NASA Astrophysics Data System (ADS)

    Kim, Sooyoung; Yoon, Suk-Jin; Chung, Chul; Caldwell, Nelson; Schiavon, Ricardo P.; Kang, Yong Beom; Rey, Soo-Chang; Lee, Young-Wook; Tamura, Naoyuki; Sohn, S. Tony; Arimoto, Nobuo; Kodama, Tadayuki; Yamada, Yoshihiko

    2014-06-01

    Globular clusters (GCs) are among the oldest stellar objects in the universe. They have long served the role of providing constraints on many aspects of galaxy evolution theory. Bimodal color distribution of GC systems in many luminous early-type galaxies is an observationally established phenomenon and has been interpreted as evidence of two GC subgroups with different metallicities. In this study, we use spectroscopic data on the GC systems of two giant galaxies, M31 (the Andromeda) and M87 (NGC 4486), to investigate the GC bimodality and the underlying metallicity distributions. Recent high signal-to-ratio spectroscopic data on M31 GCs revealed a clear bimodality in absorption-line index distributions of old GCs. Given that spectroscopy provides a more robust probe into stellar population than photometry, the reported spectral line index bimodality may indicate the presence of two distinct GC populations. However, here we show that the spectroscopic dichotomy of M31 GCs is due to the nonlinear nature of metallicity-to-index conversion and therefore one does not need two separate GC subsystems. We consider this as an analogy to the recent interpretation in which metallicity-color nonlinearity is the prime cause for observed GC color bimodality. We present spectra of ~130 old globular clusters (GCs) associated with the Virgo giant elliptical galaxy M87, obtained with the Multi-Object Spectrography (MOS) mode of Faint Object Camera and Spectrograph (FOCAS) on the Subaru telescope. The fundamental properties of globular clusters such as age, metallicity and elemental abundance ratio are investigated by comparing with a set of Simple Stellar Population (SSP) models. M87 GCs with reliable metallicity measurements exhibit significant inflection along the color-metallicity relations, through which observed color bimodality is reproduced using a broad, unimodal metallicity distribution. Our findings lend further support to this new interpretation of the GC color

  17. Modelling galaxy clustering: halo occupation distribution versus subhalo matching

    PubMed Central

    Guo, Hong; Zheng, Zheng; Behroozi, Peter S.; Zehavi, Idit; Chuang, Chia-Hsun; Comparat, Johan; Favole, Ginevra; Gottloeber, Stefan; Klypin, Anatoly; Prada, Francisco; Rodríguez-Torres, Sergio A.; Weinberg, David H.; Yepes, Gustavo

    2016-01-01

    We model the luminosity-dependent projected and redshift-space two-point correlation functions (2PCFs) of the Sloan Digital Sky Survey (SDSS) Data Release 7 Main galaxy sample, using the halo occupation distribution (HOD) model and the subhalo abundance matching (SHAM) model and its extension. All the models are built on the same high-resolution N-body simulations. We find that the HOD model generally provides the best performance in reproducing the clustering measurements in both projected and redshift spaces. The SHAM model with the same halo–galaxy relation for central and satellite galaxies (or distinct haloes and subhaloes), when including scatters, has a best-fitting χ2/dof around 2–3. We therefore extend the SHAM model to the subhalo clustering and abundance matching (SCAM) by allowing the central and satellite galaxies to have different galaxy–halo relations. We infer the corresponding halo/subhalo parameters by jointly fitting the galaxy 2PCFs and abundances and consider subhaloes selected based on three properties, the mass Macc at the time of accretion, the maximum circular velocity Vacc at the time of accretion, and the peak maximum circular velocity Vpeak over the history of the subhaloes. The three subhalo models work well for luminous galaxy samples (with luminosity above L*). For low-luminosity samples, the Vacc model stands out in reproducing the data, with the Vpeak model slightly worse, while the Macc model fails to fit the data. We discuss the implications of the modelling results. PMID:27279784

  18. Star formation rates and chemical abundances of emission-line galaxies in intermediate-redshift clusters

    NASA Astrophysics Data System (ADS)

    Mouhcine, M.; Bamford, S. P.; Aragón-Salamanca, A.; Nakamura, O.; Milvang-Jensen, B.

    2006-06-01

    We examine the evolutionary status of luminous, star-forming galaxies in intermediate-redshift clusters by considering their star formation rates (SFRs) and the chemical and ionization properties of their interstellar emitting gas. Our sample consists of 17 massive, star-forming, mostly disc galaxies with MB<~-20, in clusters with redshifts in the range 0.31 <~z<~ 0.59, with a median of = 0.42. We compare these galaxies with the identically selected and analysed intermediate-redshift field sample of Mouhcine et al., and with local galaxies from the Nearby Field Galaxy Survey of Jansen et al. From our optical spectra, we measure the equivalent widths of [OII]λ3727, Hβ and [OIII]λ5007 emission lines to determine diagnostic line ratios, oxygen abundances and extinction-corrected SFRs. The star-forming galaxies in intermediate-redshift clusters display emission-line equivalent widths which are, on average, significantly smaller than measured for field galaxies at comparable redshifts. However, a contrasting fraction of our cluster galaxies have equivalent widths similar to the highest observed in the field. This tentatively suggests a bimodality in the SFRs per unit luminosity for galaxies in distant clusters. We find no evidence for further bimodalities, or differences between our cluster and field samples, when examining additional diagnostics and the oxygen abundances of our galaxies. This maybe because no such differences exist, perhaps because the cluster galaxies which still display signs of star formation have recently arrived from the field. In order to examine this topic with more certainty, and to further investigate the way in which any disparity varies as a function of cluster properties, larger spectroscopic samples are needed.

  19. Cosmological baryonic and matter densities from 600000 SDSS luminous red galaxies with photometric redshifts

    NASA Astrophysics Data System (ADS)

    Blake, Chris; Collister, Adrian; Bridle, Sarah; Lahav, Ofer

    2007-02-01

    We analyse MegaZ-LRG, a photometric-redshift catalogue of luminous red galaxies (LRGs) based on the imaging data of the Sloan Digital Sky Survey (SDSS) 4th Data Release. MegaZ-LRG, presented in a companion paper, contains >106 photometric redshifts derived with ANNZ, an artificial neural network method, constrained by a spectroscopic subsample of ~13000 galaxies obtained by the 2dF-SDSS LRG and Quasar (2SLAQ) survey. The catalogue spans the redshift range 0.4 < z < 0.7 with an rms redshift error σz ~ 0.03(1 + z), covering 5914 deg2 to map out a total cosmic volume 2.5h-3Gpc3. In this study we use the most reliable 600000 photometric redshifts to measure the large-scale structure using two methods: (1) a spherical harmonic analysis in redshift slices, and (2) a direct re-construction of the spatial clustering pattern using Fourier techniques. We present the first cosmological parameter fits to galaxy angular power spectra from a photometric-redshift survey. Combining the redshift slices with appropriate covariances, we determine best-fitting values for the matter density Ωm and baryon density Ωb of Ωmh = 0.195 +/- 0.023 and Ωb/Ωm = 0.16 +/- 0.036 (with the Hubble parameter h = 0.75 and scalar index of primordial fluctuations nscalar = 1 held fixed). These results are in agreement with and independent of the latest studies of the cosmic microwave background radiation, and their precision is comparable to analyses of contemporary spectroscopic-redshift surveys. We perform an extensive series of tests which conclude that our power spectrum measurements are robust against potential systematic photometric errors in the catalogue. We conclude that photometric-redshift surveys are competitive with spectroscopic surveys for measuring cosmological parameters in the simplest `vanilla' models. Future deep imaging surveys have great potential for further improvement, provided that systematic errors can be controlled.

  20. Star-formation histories of local luminous infrared galaxies

    NASA Astrophysics Data System (ADS)

    Pereira-Santaella, Miguel; Alonso-Herrero, Almudena; Colina, Luis; Miralles-Caballero, Daniel; Pérez-González, Pablo G.; Arribas, Santiago; Bellocchi, Enrica; Cazzoli, Sara; Díaz-Santos, Tanio; Piqueras López, Javier

    2015-05-01

    We present analysis of the integrated spectral energy distribution (SED) from the ultraviolet (UV) to the far-infrared and Hα of a sample of 29 local systems and individual galaxies with infrared (IR) luminosities between 1011L⊙ and 1011.8L⊙. We combined new narrow-band Hα + [N ii] and broad-band g, r optical imaging taken with the Nordic Optical Telescope (NOT), with archival GALEX, 2MASS, Spitzer, and Herschel data. Their SEDs(photometry and integrated Hα flux) were fitted simultaneously with a modified version of the magphys code using stellar population synthesis models for the UV-near-IR range and thermal emission models for the IR emission taking the energy balance between the absorbed and re-emitted radiation into account. From the SED fits, we derive the star-formation histories (SFH) of these galaxies. For nearly half of them, the star-formation rate appears to be approximately constant during the last few Gyr. In the other half, the current star-formation rate seems to be enhanced by a factor of 3-20 with respect to what occurred ~1 Gyr ago. Objects with constant SFH tend to be more massive than starbursts, and they are compatible with the expected properties of a main-sequence (M-S) galaxy. Likewise, the derived SFHs show that all our objects were M-S galaxies ~1 Gyr ago with stellar masses between 1010.1 and 1011.5 M⊙. We also derived the average extinction (Av = 0.6-3 mag) and the polycyclic aromatic hydrocarbon luminosity to LIR ratio (0.03-0.16) from our fits. We combined the Av with the total IR and Hα luminosities into a diagramthat can be used to identify objects with rapidly changing (increasing or decreasing) SFR during the past 100 Myr. Appendices are available in electronic form at http://www.aanda.orgFITS files for all the reduced images are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/577/A78

  1. A Cluster and a Sea of Galaxies

    NASA Astrophysics Data System (ADS)

    2010-05-01

    A new wide-field image released today by ESO displays many thousands of distant galaxies, and more particularly a large group belonging to the massive galaxy cluster known as Abell 315. As crowded as it may appear, this assembly of galaxies is only the proverbial "tip of the iceberg", as Abell 315 - like most galaxy clusters - is dominated by dark matter. The huge mass of this cluster deflects light from background galaxies, distorting their observed shapes slightly. When looking at the sky with the unaided eye, we mostly only see stars within our Milky Way galaxy and some of its closest neighbours. More distant galaxies are just too faint to be perceived by the human eye, but if we could see them, they would literally cover the sky. This new image released by ESO is both a wide-field and long-exposure one, and reveals thousands of galaxies crowding an area on the sky roughly as large as the full Moon. These galaxies span a vast range of distances from us. Some are relatively close, as it is possible to distinguish their spiral arms or elliptical halos, especially in the upper part of the image. The more distant appear just like the faintest of blobs - their light has travelled through the Universe for eight billion years or more before reaching Earth. Beginning in the centre of the image and extending below and to the left, a concentration of about a hundred yellowish galaxies identifies a massive galaxy cluster, designated with the number 315 in the catalogue compiled by the American astronomer George Abell in 1958 [1]. The cluster is located between the faint, red and blue galaxies and the Earth, about two billion light-years away from us. It lies in the constellation of Cetus (the Whale). Galaxy clusters are some of the largest structures in the Universe held together by gravity. But there is more in these structures than the many galaxies we can see. Galaxies in these giants contribute to only ten percent of the mass, with hot gas in between galaxies

  2. Evidence for Tides and Interactions in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Conselice, C. J.; Gallagher, J. S.

    1997-12-01

    We present preliminary results of a search for tidally distorted, or interacting galaxies in the galaxy clusters: Abell 2199, AWM 5, AWM 3, the Coma and Perseus clusters. This is part of a large study to determine the nature of small-scale structure in galaxy clusters of various morphologies. Our B and R band observations were made with the CCD imager on the WIYN 3.5-m telescope, and typically have an angular resolution of 1 arcsec or better. We are able to classify all of the observed structures into seven different types. These include: Galaxy Interactions, Multiple Galaxies, Tailed Galaxies, Dwarf Galaxy Groups, Galaxy Aggregates, Distorted Galaxies, and Line Galaxies. We present examples of objects in these categories and conclude that interactions that perturb individual galaxies are common in clusters of galaxies, despite the high relative random velocities between cluster members.

  3. THE CLUSTERING PROPERTIES OF THE FIRST GALAXIES

    SciTech Connect

    Stiavelli, Massimo; Trenti, Michele

    2010-06-20

    We study the clustering properties of the first galaxies formed in the universe. We find that, due to chemical enrichment of the interstellar medium by isolated Population III stars formed in mini-halos at redshift z {approx_gt} 30, the (chronologically) first galaxies are composed of metal-poor Population II stars and are highly clustered on small scales. In contrast, chemically pristine galaxies in halos with mass M {approx} 10{sup 8} M{sub sun} may form at z < 20 in relatively underdense regions of the universe. This occurs once self-enrichment by Population III in mini-halos is quenched by the buildup of an H{sub 2} photodissociating radiative background in the Lyman-Werner bands. We find that these chemically pristine galaxies are spatially uncorrelated. Thus, we expect that deep fields with the James Webb Space Telescope (JWST) may detect clusters of chemically enriched galaxies but individual chemically pristine objects. We predict that metal-free galaxies at 10 {approx}< z {approx}< 15 have surface densities of about 80 arcmin{sup -2} and per unit redshift but most of them will be too faint even for JWST. However, the predicted density makes these objects interesting targets for searches behind lensing clusters.

  4. Tidally Induced Bars of Galaxies in Clusters

    NASA Astrophysics Data System (ADS)

    Łokas, Ewa L.; Ebrová, Ivana; del Pino, Andrés; Sybilska, Agnieszka; Athanassoula, E.; Semczuk, Marcin; Gajda, Grzegorz; Fouquet, Sylvain

    2016-08-01

    Using N-body simulations, we study the formation and evolution of tidally induced bars in disky galaxies in clusters. Our progenitor is a massive, late-type galaxy similar to the Milky Way, composed of an exponential disk and a Navarro-Frenk-White dark matter halo. We place the galaxy on four different orbits in a Virgo-like cluster and evolve it for 10 Gyr. As a reference case, we also evolve the same model in isolation. Tidally induced bars form on all orbits soon after the first pericenter passage and survive until the end of the evolution. They appear earlier, are stronger and longer, and have lower pattern speeds for tighter orbits. Only for the tightest orbit are the properties of the bar controlled by the orientation of the tidal torque from the cluster at pericenter. The mechanism behind the formation of the bars is the angular momentum transfer from the galaxy stellar component to its halo. All of the bars undergo extended periods of buckling instability that occur earlier and lead to more pronounced boxy/peanut shapes when the tidal forces are stronger. Using all simulation outputs of galaxies at different evolutionary stages, we construct a toy model of the galaxy population in the cluster and measure the average bar strength and bar fraction as a function of clustercentric radius. Both are found to be mildly decreasing functions of radius. We conclude that tidal forces can trigger bar formation in cluster cores, but not in the outskirts, and thus can cause larger concentrations of barred galaxies toward the cluster center.

  5. HUBBLE SPIES GLOBULAR CLUSTER IN NEIGHBORING GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Hubble Space Telescope has captured a view of a globular cluster called G1, a large, bright ball of light in the center of the photograph consisting of at least 300,000 old stars. G1, also known as Mayall II, orbits the Andromeda galaxy (M31), the nearest major spiral galaxy to our Milky Way. Located 130,000 light-years from Andromeda's nucleus, G1 is the brightest globular cluster in the Local Group of galaxies. The Local Group consists of about 20 nearby galaxies, including the Milky Way. The crisp image is comparable to ground-based telescope views of similar clusters orbiting the Milky Way. The Andromeda cluster, however, is nearly 100 times farther away. A glimpse into the cluster's finer details allow astronomers to see its fainter helium-burning stars whose temperatures and brightnesses show that this cluster in Andromeda and the oldest Milky Way clusters have approximately the same age. These clusters probably were formed shortly after the beginning of the universe, providing astronomers with a record of the earliest era of galaxy formation. During the next two years, astronomers will use Hubble to study about 20 more globular clusters in Andromeda. The color picture was assembled from separate images taken in visible and near-infrared wavelengths taken in July of 1994. CREDIT: Michael Rich, Kenneth Mighell, and James D. Neill (Columbia University), and Wendy Freedman (Carnegie Observatories), and NASA Image files in GIF and JPEG format and captions may be accessed on Internet via anonymous ftp from oposite.stsci.edu in /pubinfo.

  6. ROSAT observations of Coma Cluster galaxies

    NASA Technical Reports Server (NTRS)

    Dow, K. L.; White, S. D. M.

    1995-01-01

    The approximately 86 ks ROSAT Position Sensitive Proportional Counter (PSPC) image of the Coma Cluster is deeper than any previous X-ray observation of a galaxy cluster. We search for X-ray emission from 35 individual galaxies in a magnitude-limited sample, all of which lie within 20 arcmins of the optical axis in at least one of the four Coma pointings. We detect seven galaxies in the 0.4-2.4 keV band at a significance level exceeding 3 sigma, and a further four at above 2 sigma. Although we can set only upper limits on the individual flux from each of the other galaxies, we are able to measure their mean flux by stacking the observations. The X-ray luminosities of the seven detections range from 6.2 x 10(exp 40) to 1.5 x 10(exp 42) ergs/s (0.4-2.4 keV for H(sub 0) = 50 km/s/Mpc). For galaxies with a blue absolute magnitude of about -21 we find a mean X-ray luminosity of 1.3 x 10(exp 40) ergs/s. The ratio of X-ray to optical luminosity is substantially smaller for such subjects than for the brightest galaxies in the cluster. The X-ray luminosities of the four brightest galaxies are ill-defined, however, because of ambiguity in distinguishing galaxy emission from cluster emission. Each object appears to be related to significant structure in the diffuse intracluster medium. We also investigate emission in the softer 0.2-0.4 keV band where detections are less significant because of the higher background, and we discuss the properties of a number of interesting individual sources. The X-ray luminosities of the Coma galaxies are similar to those of galaxies in the Virgo Cluster and in other regions with relatively low galaxy density. We conclude that large-scale environmental effects do not significantly enhance or suppress the average X-ray emission from galaxies, but that individual objects vary in luminosity substantially in a way which may depend on the detailed history of their environment.

  7. Host Galaxies of Luminous Quasars: Structural Properties and the Fundamental Plane

    NASA Astrophysics Data System (ADS)

    Wolf, Marsha J.; Sheinis, Andrew I.

    2008-10-01

    We present stellar velocity dispersion measurements in the host galaxies of ten luminous quasars (MV < -23) using the Ca H&K lines in off-nuclear spectra. We combine these data with effective radii and magnitudes from the literature to place the host galaxies on the fundamental plane (FP) where their properties are compared with other types of galaxies. We find that the radio-loud (RL) QSO hosts have similar properties to massive elliptical galaxies, while the radio-quiet (RQ) hosts are more similar to intermediate-mass galaxies. The RL hosts lie at the upper extreme of the FP due to their large velocity dispersions (langσ*rang = 321 km s-1), low surface brightness (langμ e (r)rang = 20.8 mag arcsec-2), and large effective radii (langRe rang = 11.4 kpc), and have langM *rang = 1.5 × 1012 M sun and langM/Lrang = 12.4. In contrast, properties of the RQ hosts are langσ*rang = 241 km s-1, langM *rang = 4.4 × 1011 M sun, and M/L ~ 5.3. The distinction between these galaxies occurs at σ*~ 300 km s-1, Re ~ 6 kpc, and corresponding M * ~ 5.9 ± 3.5 × 1011 M sun. Our data support previous results that Palomar-Green QSOs are related to gas-rich galaxy mergers that form intermediate-mass galaxies, while RL QSOs reside in massive early-type galaxies, most of which also show signs of recent mergers or interactions. Previous authors have drawn these conclusions by using estimates of the black hole mass and inferring host galaxy properties from that, while here we have relied purely on directly measured host galaxy properties.

  8. Galaxy Cluster Masses at Moderate Redshifts

    NASA Technical Reports Server (NTRS)

    Ellingson, E.

    1998-01-01

    The masses of galaxy clusters are dominated by dark matter, and a robust determination of their masses has the potential of indicating how much dark matter exists on large scales in the universe, and the cosmological parameter Omega. X-ray observations of galaxy clusters provide a direct measure of both the gas mass in the intra-cluster medium, and also the total gravitating mass of the cluster. We used new and archival ROSAT observations to measure these quantities for a sample of intermediate redshift clusters which have also been subject to intensive dynamical studies, in order to compare the mass estimates from different methods. A direct comparison of dynamical mass estimates yielded surprisingly good results.

  9. Do Relaxed Clusters of Galaxies Exist?

    NASA Astrophysics Data System (ADS)

    Motl, Patrick M.; Burns, Jack O.; Norman, Michael L.

    2004-05-01

    Clusters of galaxies lacking observational signatures of mergers and other complications are popular targets as cosmological probes. However, the assumptions of structural simplicity must be approximations that are valid to only a certain level. Especially in the new era of precision cosmology where efforts are underway to investigate the nature and evolution of dark energy, it is crucial to calibrate the approximations used to reduce cluster observations to cosmological measurements. We use high-resolution simulations of clusters of galaxies, evolved within their cosmological environment, to study the process of reducing X-ray and/or Sunyaev-Zeldovich data to cluster observables such as the gravitating mass and Hubble constant. This allows us to measure the impact of structure formation on these observables and quantify the approximations used in interpreting cluster observations.

  10. EXTENDED [C II] EMISSION IN LOCAL LUMINOUS INFRARED GALAXIES

    SciTech Connect

    Díaz-Santos, T.; Armus, L.; Surace, J. A.; Charmandaris, V.; Stacey, G.; Murphy, E. J.; Haan, S.; Stierwalt, S.; Evans, A. S.; Malhotra, S.; Appleton, P.; Inami, H.; Magdis, G. E.; Elbaz, D.; Van der Werf, P. P.; Meijerink, R.; and others

    2014-06-10

    We present Herschel/PACS observations of extended [C II] 157.7 μm line emission detected on ∼1-10 kpc scales in 60 local luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey. We find that most of the extra-nuclear emission show [C II]/FIR ratios ≥4 × 10{sup –3}, larger than the mean ratio seen in the nuclei, and similar to those found in the extended disks of normal star-forming galaxies and the diffuse interstellar medium of our Galaxy. The [C II] ''deficits'' found in the most luminous local LIRGs are therefore restricted to their nuclei. There is a trend for LIRGs with warmer nuclei to show larger differences between their nuclear and extra-nuclear [C II]/FIR ratios. We find an anti-correlation between [C II]/FIR and the luminosity surface density, Σ{sub IR}, for the extended emission in the spatially resolved galaxies. However, there is an offset between this trend and that found for the LIRG nuclei. We use this offset to derive a beam filling-factor for the star-forming regions within the LIRG disks of ∼6% relative to their nuclei. We confront the observed trend to photo-dissociation region models and find that the slope of the correlation is much shallower than the model predictions. Finally, we compare the correlation found between [C II]/FIR and Σ{sub IR} with measurements of high-redshift starbursting IR-luminous galaxies.

  11. Morphology of galaxies in the WINGS clusters

    NASA Astrophysics Data System (ADS)

    Fasano, G.; Vanzella, E.; Dressler, A.; Poggianti, B. M.; Moles, M.; Bettoni, D.; Valentinuzzi, T.; Moretti, A.; D'Onofrio, M.; Varela, J.; Couch, W. J.; Kjærgaard, P.; Fritz, J.; Omizzolo, A.; Cava, A.

    2012-02-01

    We present the morphological catalogue of galaxies in nearby clusters of the WIde-field Nearby Galaxy-clusters Survey (WINGS). The catalogue contains a total number of 39 923 galaxies, for which we provide the automated estimates of the morphological type, applying the purposely devised tool MORPHOT to the V-band WINGS imaging. For ˜3000 galaxies we also provide visual estimates of the morphological type. A substantial part of the paper is devoted to the description of the MORPHOT tool, whose application is limited, at least for the moment, to the WINGS imaging only. The approach of the tool to the automation of morphological classification is a non-parametric and fully empirical one. In particular, MORPHOT exploits 21 morphological diagnostics, directly and easily computable from the galaxy image, to provide two independent classifications: one based on a maximum likelihood (ML), semi-analytical technique and the other one on a neural network (NN) machine. A suitably selected sample of ˜1000 visually classified WINGS galaxies is used to calibrate the diagnostics for the ML estimator and as a training set in the NN machine. The final morphological estimator combines the two techniques and proves to be effective both when applied to an additional test sample of ˜1000 visually classified WINGS galaxies and when compared with small samples of Sloan Digital Sky Survey (SDSS) galaxies visually classified by Fukugita et al. and Nair et al. Finally, besides the galaxy morphology distribution (corrected for field contamination) in the WINGS clusters, we present the ellipticity (ɛ), colour (B-V) and Sersic index (n) distributions for different morphological types, as well as the morphological fractions as a function of the clustercentric distance (in units of R200).

  12. Linear clusters of galaxies - A194

    NASA Technical Reports Server (NTRS)

    Chapman, G. N. F.; Geller, M. J.; Huchra, J. P.

    1988-01-01

    New measurements for 160 redshifts and previous measurements for 108 other redshifts are presented for galaxies within 5 deg of A194. The galaxy distribution in A194 is shown to be inconsistent with a spherically symmetric King model. A mass-to-light ratio is derived using the virial theorem which is lower than the mean for the groups in the CfA redshift survey (Huchra and Geller, 1982; Geller, 1984). A nonparametric test for galaxy-cluster alignment and a Chi-squared test are used to search for alignment of galaxy major axes with the axis of A194. Evidence for neither luminosity segregation nor significant differences in the velocity or surface distributions of galaxies as a function of morphological type is found.

  13. IR Fine-Structure Line Signatures of Central Dust-Bounded Nebulae in Luminous Infrared Galaxies

    NASA Technical Reports Server (NTRS)

    Fischer, J.; Allen, R.; Dudley, C. C.; Satyapal, S.; Luhman, M.; Wolfire, M.; Smith, H. A.

    2004-01-01

    To date, the only far-infrared spectroscopic observations of ultraluminous infrared galaxies have been obtained with the European Space Agency s Infrared Space Observatory Long Wavelength Spectrometer. The spectra of these galaxies are characterized by molecular absorption lines and weak emission lines from photodissociation regions (PDRs), but no far-infrared (greater than 40 microns) lines from ionized regions have been detected. ESA s Herschel Space Observatory, slated for launch in 2007, will likely be able to detect these lines in samples of local and moderate redshift ultra luminous galaxies and to enable measurement of the ionization parameters, the slope of the ionizing continuum, and densities present in the ionized regions of these galaxies. The higher spatial resolution of proposed observatories discussed in this workshop will enable isolation of the central regions of local galaxies and detection of these lines in high-redshift galaxies for study of the evolution of galaxies. Here we discuss evidence for the e.ects of absorption by dust within ionized regions and present the spectroscopic signatures predicted by photoionization modeling of dust-bounded regions.

  14. Discovery of GeV emission from the direction of the luminous infrared galaxy NGC 2146

    SciTech Connect

    Tang, Qing-Wen; Wang, Xiang-Yu; Thomas Tam, Pak-Hin E-mail: phtam@phys.nthu.edu.tw

    2014-10-10

    Recent detections of high-energy gamma-ray emission from starburst galaxies M82 and NGC 253 suggest that starburst galaxies are huge reservoirs of cosmic rays and these cosmic rays convert a significant fraction of their energy into gamma-rays by colliding with the dense interstellar medium. In this paper, we report the search for high-energy gamma-ray emission from several nearby star-forming and starburst galaxies using the 68 month data obtained with the Fermi Large Area Telescope. We found a ∼5.5σ detection of gamma-ray emission above 200 MeV from a source spatially coincident with the location of the luminous infrared galaxy NGC 2146. Also taking into account the temporal and spectral properties of the gamma-ray emission, we suggest that the gamma-ray source is likely to be the counterpart of NGC 2146. The gamma-ray luminosity suggests that cosmic rays in NGC 2146 convert most of their energy into secondary pions, so NGC 2146 is a 'proton calorimeter'. It is also found that NGC 2146 obeys the quasi-linear scaling relation between gamma-ray luminosity and total infrared luminosity for star-forming galaxies, strengthening the connection between massive star formation and gamma-ray emission of star-forming galaxies. Possible TeV emission from NGC 2146 is predicted and the implications for high-energy neutrino emission from starburst galaxies are discussed.

  15. Luminous compact blue galaxies in the local Universe: A key reference for high-redshift studies

    NASA Astrophysics Data System (ADS)

    Pérez Gallego, J.; Guzmán, R.; Castander, F. J.; Garland, C. A.; Pisano, D. J.

    2005-05-01

    Luminous Compact Blue Galaxies (LCBGs) are high surface brightness starburst galaxies, bluer than a typical Sbc and brighter than ˜0.25Lstar. LCBGs have evolved more than any other galaxy class in the last ˜8 Gyr, and are a major contributor to the observed enhancement of the UV luminosity density of the Universe at z≤1. Despite the key role LCBGs may play in galaxy evolution, their statistical properties are still largely unknown. We have selected a complete sample of ˜25 LCBGs within 100 Mpc, after investigating over 106 nearby galaxies from the DR1 of the SDSS database. This sample, although small, provides an excellent reference for comparison with current and future surveys of similar galaxies at high redshift, including the population of Lyman-break galaxies. We present preliminary results of this study using 3D spectroscopic observations obtained over a very wide range in wavelength, using WIYN/DENSEPAK in the optical, FISICA in the infrared, and the VLA at cm wavelengths.

  16. THE WHIQII SURVEY: METALLICITIES AND SPECTROSCOPIC PROPERTIES OF LUMINOUS COMPACT BLUE GALAXIES

    SciTech Connect

    Tollerud, Erik J.; Barton, Elizabeth J.; Cooke, Jeff; Van Zee, Liese

    2010-01-10

    As part of the WIYN High Image Quality Indiana-Irvine (WHIQII) survey, we present 123 spectra of faint emission-line galaxies, selected to focus on intermediate redshift (0.4 approx< z approx< 0.8) galaxies with blue colors that appear physically compact on the sky. The sample includes 15 true Luminous Compact Blue Galaxies (LCBGs) and an additional 27 slightly less extreme emission-line systems. These galaxies represent a highly evolving class that may play an important role in the decline of star formation since z approx 1, but their exact nature and evolutionary pathways remain a mystery. Here, we use emission lines to determine metallicities and ionization parameters, constraining their intrinsic properties and state of star formation. Some LCBG metallicities are consistent with a 'bursting dwarf' scenario, while a substantial fraction of others are not, further confirming that LCBGs are a highly heterogeneous population but are broadly consistent with the intermediate redshift field. In agreement with previous studies, we observe overall evolution in the luminosity-metallicity relation at intermediate redshift. Our sample, and particularly the LCBGs, occupies a region in the empirical R{sub 23}-O{sub 32} plane that differs from luminous local galaxies and is more consistent with dwarf irregulars at the present epoch, suggesting that cosmic 'downsizing' is observable in even the most fundamental parameters that describe star formation. These properties for our sample are also generally consistent with lying between local galaxies and those at high redshift, as expected by this scenario. Surprisingly, our sample exhibits no detectable correlation between compactness and metallicity, strongly suggesting that at these epochs of rapid star formation, the morphology of compact star-forming galaxies is largely transient.

  17. ULTRA-LUMINOUS X-RAY SOURCES IN THE MOST METAL POOR GALAXIES

    SciTech Connect

    Prestwich, A. H.; Zezas, A.; Jackson, F.; Tsantaki, Maria; Roberts, T. P.; Foltz, R.; Linden, T.; Kalogera, V.

    2013-06-01

    Ultra-luminous X-ray sources (ULX) are X-ray binaries with L{sub x} >10{sup 39} erg s{sup -1}. The most spectacular examples of ULX occur in starburst galaxies and are now understood to be young, luminous high mass X-ray binaries. The conditions under which ULX form are poorly understood, but recent evidence suggests they may be more common in low metallicity systems. Here we investigate the hypothesis that ULX form preferentially in low metallicity galaxies by searching for ULX in a sample of extremely metal poor galaxies (XMPG) observed with the Chandra X-Ray Observatory. XMPG are defined as galaxies with log(O/H) + 12 < 7.65, or less than 5% solar. These are the most metal-deficient galaxies known, and a logical place to find ULX if they favor metal poor systems. We compare the number of ULX (corrected for background contamination) per unit of star formation (N{sub ULX}(SFR)) in the XMPG sample with N{sub ULX}(SFR) in a comparison sample of galaxies with higher metallicities taken from the Spitzer Infrared Galaxy Sample. We find that ULX occur preferentially in the metal poor sample with a formal statistical significance of 2.3{sigma}. We do not see strong evidence for a trend in the formation of ULX in the high metallicity sample: above 12+log(O/H) {approx} 8.0 the efficiency of ULX production appears to be flat. The effect we see is strongest in the lowest metallicity bin. We discuss briefly the implications of these results for the formation of black holes in low metallicity gas.

  18. Clusters of galaxies: a cosmological probe.

    PubMed

    Mushotzky, Richard

    2002-09-15

    The constraints on cosmological parameters presently obtained and those that can be obtained from X-ray cluster surveys are presented. Extremely strong bounds on the values of Omega, Lambda, sigma(8) and the power spectrum of fluctuations, as well as constraints on the equation of state of dark energy, can be determined. Recent Advanced Satellite for Cosmology and Astrophysics and XMM results on the chemical composition of clusters show that the Fe abundance is not universal, but is correlated with cluster mass and central gas density. The Si, S and Fe abundances do not resemble those seen in Milky Way Halo stars or those in the Lyman-limit galaxies. The XMM RGS abundances for gas in elliptical galaxies are subsolar and the abundance pattern is not alpha-element rich, in contradiction with all models of elliptical-galaxy gas abundances. PMID:12804244

  19. The missing mass in clusters of galaxies and elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Mushotzky, Richard F.

    1991-01-01

    We review the available data for the existence of dark matter in clusters of galaxies and elliptical galaxies. While the amount of dark matter in clusters is not well determined, both the X-ray and optical data show that more than 50 percent of the total mass must be dark. There is in general fair agreement in the binding mass estimates between the X-ray and optical techniques, but there is not detailed agreement on the form of the potential or the distribution of dark matter. The X-ray spectral and spatial observations of elliptical galaxies demonstrate that dark matter is also required in these objects and that it must be considerably more extended than the stellar distribution.

  20. A Cluster and a Sea of Galaxies

    NASA Astrophysics Data System (ADS)

    2010-05-01

    A new wide-field image released today by ESO displays many thousands of distant galaxies, and more particularly a large group belonging to the massive galaxy cluster known as Abell 315. As crowded as it may appear, this assembly of galaxies is only the proverbial "tip of the iceberg", as Abell 315 - like most galaxy clusters - is dominated by dark matter. The huge mass of this cluster deflects light from background galaxies, distorting their observed shapes slightly. When looking at the sky with the unaided eye, we mostly only see stars within our Milky Way galaxy and some of its closest neighbours. More distant galaxies are just too faint to be perceived by the human eye, but if we could see them, they would literally cover the sky. This new image released by ESO is both a wide-field and long-exposure one, and reveals thousands of galaxies crowding an area on the sky roughly as large as the full Moon. These galaxies span a vast range of distances from us. Some are relatively close, as it is possible to distinguish their spiral arms or elliptical halos, especially in the upper part of the image. The more distant appear just like the faintest of blobs - their light has travelled through the Universe for eight billion years or more before reaching Earth. Beginning in the centre of the image and extending below and to the left, a concentration of about a hundred yellowish galaxies identifies a massive galaxy cluster, designated with the number 315 in the catalogue compiled by the American astronomer George Abell in 1958 [1]. The cluster is located between the faint, red and blue galaxies and the Earth, about two billion light-years away from us. It lies in the constellation of Cetus (the Whale). Galaxy clusters are some of the largest structures in the Universe held together by gravity. But there is more in these structures than the many galaxies we can see. Galaxies in these giants contribute to only ten percent of the mass, with hot gas in between galaxies

  1. Buried Quasars in Ultra-luminous Infrared Galaxies

    NASA Technical Reports Server (NTRS)

    2004-01-01

    We were awarded l00kS of INTEGRAL spacecraft time (Priority A) to observe the ultraluminous infrared galaxy (ULIG) Mrk 2273 in order to measure the integrated flux of the 20-1003 KeV gamma-Ray emission, and to use this information to search for the presence of an highly obscured active galactic nucleus (AGN). With this observation we hope to be able to better assess the role of AGN in the complete class of ULIGs and therefore to better constrain their contribution to the hard X-ray and soft gamma-ray backgrounds. Our Priority A 100 kS observation of Mrk 273 was successfully carried out during revolution #73 using 4 separate exposures with the IBIS camera during May, 2003. Our IBIS observations of Mrk 273 were successfully executed, and the source was properly centered in the Field-of-view of the detectors. We are still in the process of interpreting the IBIS gamma-ray data.

  2. Recent Galaxy Mergers and Residual Star Formation of Red Sequence Galaxies in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Sheen, Yun-Kyeong; Yi, Sukyoung K.; Ree, Chang H.; Jaffé, Yara; Demarco, Ricardo; Treister, Ezequiel

    2016-08-01

    This study explored the Galaxy Evolution Explorer ultraviolet (UV) properties of optical red sequence galaxies in four rich Abell clusters at z≤slant 0.1. In particular, we tried to find a hint of merger-induced recent star formation (RSF) in red sequence galaxies. Using the NUV - r\\prime colors of the galaxies, RSF fractions were derived based on various criteria for post-merger galaxies and normal galaxies. Following k-correction, about 36% of the post-merger galaxies were classified as RSF galaxies with a conservative criterion (NUV - r\\prime ≤slant 5), and that number was doubled (∼72%) when using a generous criterion (NUV - r\\prime ≤slant 5.4). The trend was the same when we restricted the sample to galaxies within 0.5 × R 200. Post-merger galaxies with strong UV emission showed more violent, asymmetric features in the deep optical images. The RSF fractions did not show any trend along the clustocentric distance within R 200. We performed a Dressler–Shectman test to check whether the RSF galaxies had any correlation with the substructures in the galaxy clusters. Within R 200 of each cluster, the RSF galaxies did not appear to be preferentially related to the clusters’ substructures. Our results suggested that only 30% of RSF red sequence galaxies show morphological hints of recent galaxy mergers. This implies that internal processes (e.g., stellar mass loss or hot gas cooling) for the supply of cold gas to early-type galaxies may play a significant role in the residual star formation of early-type galaxies at a recent epoch.

  3. Recent Galaxy Mergers and Residual Star Formation of Red Sequence Galaxies in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Sheen, Yun-Kyeong; Yi, Sukyoung K.; Ree, Chang H.; Jaffé, Yara; Demarco, Ricardo; Treister, Ezequiel

    2016-08-01

    This study explored the Galaxy Evolution Explorer ultraviolet (UV) properties of optical red sequence galaxies in four rich Abell clusters at z≤slant 0.1. In particular, we tried to find a hint of merger-induced recent star formation (RSF) in red sequence galaxies. Using the NUV - r\\prime colors of the galaxies, RSF fractions were derived based on various criteria for post-merger galaxies and normal galaxies. Following k-correction, about 36% of the post-merger galaxies were classified as RSF galaxies with a conservative criterion (NUV - r\\prime ≤slant 5), and that number was doubled (˜72%) when using a generous criterion (NUV - r\\prime ≤slant 5.4). The trend was the same when we restricted the sample to galaxies within 0.5 × R 200. Post-merger galaxies with strong UV emission showed more violent, asymmetric features in the deep optical images. The RSF fractions did not show any trend along the clustocentric distance within R 200. We performed a Dressler–Shectman test to check whether the RSF galaxies had any correlation with the substructures in the galaxy clusters. Within R 200 of each cluster, the RSF galaxies did not appear to be preferentially related to the clusters’ substructures. Our results suggested that only 30% of RSF red sequence galaxies show morphological hints of recent galaxy mergers. This implies that internal processes (e.g., stellar mass loss or hot gas cooling) for the supply of cold gas to early-type galaxies may play a significant role in the residual star formation of early-type galaxies at a recent epoch.

  4. Properties of The Brightest Cluster Galaxy and Its Host Cluster

    NASA Astrophysics Data System (ADS)

    Katayama, H.; Hayashida, K.; Takahara, F.

    2001-09-01

    We investigate the relation between the brightest cluster galaxy (BCG) and its host cluster. A BCG is a bright and massive elliptical galaxy in a cluster of galaxies. The luminosity of a BCG is 10 times larger than that of normal field galaxy and the mass of a BCG is about 1013Msolar which corresponds to that of galaxy group. In order to explain the origin of BCGs, the following three models are proposed: (1) star formation from cooling flow. In this model, intracluster gas gradually condenses at the center of the cluster and forms the BCG. (2) ``Galactic cannibalism'' or the accretion of smaller galaxies. In this model, dynamical friction accounts for the formation of the BCG. These two models predict the BCG evolves with the evolution of cluster. (3) Galaxy merging in the early history of the formation of the cluster. In this model, the property of BCGs is determined no later than cluster collapse. In any model, the formation of BCGs is related to the collapse and formation of its host cluster. The relation between the BCG and its host cluster was studied by Edge (1991). Edge (1991) found that the optical luminosity of the BCG is positively correlated with the X-ray luminosity and temperature of its host cluster. Edge (1991) concludes that these correlations indicate that the BCG responds to the overall cluster properties. In order to investigate the other relation between the BCG and its host cluster, we analyzed ROSAT archival data and compared the displacement between the X-ray peak and the BCG with the Z parameter of the fundamental relation found by Fujita and Takahara (1999). It is found that the displacement is larger with decreasing Z. Furthermore, the large Z clusters tend to have a regular X-ray profile, which implies a relaxed system. The fundamental parameter Z depends mainly on the virial density ρvir, and is considered to be related to the formation epoch of the cluster, i.e., large Z clusters are old clusters and small Z clusters are young

  5. The Ultra-Luminous X-ray Source Population from the Chandra Archive of Galaxies

    NASA Technical Reports Server (NTRS)

    Swartz, Douglas A.; Ghosh, Kajal K.; Tennant, Allen F.; Wu, Kinwah

    2004-01-01

    One hundred fifty-four discrete non-nuclear Ultra-Luminous X-ray (ULX) sources, with spectroscopically-determined intrinsic X-ray luminosities greater than 1 e39 ergs/s, are identified in 82 galaxies observed with Chandra's Advanced CCD Imaging Spectrometer. Source positions, X-ray luminosities, and spectral and timing characteristics are tabulated. Statistical comparisons between these X-ray properties and those of the weaker discrete sources in the same fields (mainly neutron star and stellar-mass black hole binaries) are made. Sources above approximately le38 ergs per second display similar spatial, spectral, color, and variability distributions. In particular, there is no compelling evidence in the sample for a new and distinct class of X-ray object such as the intermediate-mass black holes. 83% of ULX candidates have spectra that can be described as absorbed power laws with index = 1.74 and column density = 2.24e21 l per square centimeter, or approximately 5 times the average Galactic column. About 20% of the ULX's have much steeper indices indicative of a soft, and likely thermal, spectrum. The locations of ULXs in their host galaxies are strongly peaked towards their galaxy centers. The deprojected radial distribution of the ULX candidates is somewhat steeper than an exponential disk, indistinguishable from that of the weaker sources. About 5--15% of ULX candidates are variable during the Chandra observations (which average 39.5 ks). Comparison of the cumulative X-ray luminosity functions of the ULXs to Chandra Deep Field results suggests approximately 25% of the sources may be background objects including 14% of the ULX candidates in the sample of spiral galaxies and 44% of those in elliptical galaxies implying the elliptical galaxy ULX population is severely compromised by background active galactic nuclei. Correlations with host galaxy properties confirm the number and total X-ray luminosity of the ULXs are associated with recent star formation

  6. Correlation functions for extended mass galaxy clusters

    NASA Astrophysics Data System (ADS)

    Iqbal, Naseer; Ahmad, Naveel; Hamid, Mubashir; Masood, Tabasum

    2012-07-01

    The phenomenon of clustering of galaxies on the basis of correlation functions in an expanding Universe is studied by using equation of state, taking gravitational interaction between galaxies of extended nature into consideration. The partial differential equation for the extended mass structures of a two-point correlation function developed earlier by Iqbal, Ahmad & Khan is studied on the basis of assigned boundary conditions. The solution for the correlation function for extended structures satisfies the basic boundary conditions, which seem to be sufficient for understanding the phenomena, and provides a new insight into the gravitational clustering problem for extended mass structures.

  7. Spectroscopy of Galaxies in Massive Clusters: Galaxy Properties and Dynamical Cluster Mass Calibration

    NASA Astrophysics Data System (ADS)

    Stubbs, Christopher W.; Ashby, M. L. N.; Anderson, K.; Bazin, G.; Benson, B. A.; Bleem, L. E.; Brodwin, M.; Carlstrom, J. E.; Clocchiatti, A.; Crawford, T. M.; de Haan, T.; Dobbs, M. A.; Dudley, J. P.; Foley, R.; Gladders, M. D.; High, F. W.; Holder, G. P.; Holzapfel, W. L.; Keisler, R.; Marrone, D. P.; Mohr, J. J.; Montroy, T.; Reichardt, C. L.; Rest, A.; Ruel, J.; Ruhl, J. E.; Saliwanchik, B.; Shaw, L.; Song, J.; Stalder, B.; Stanford, S. A.; Stark, A. A.; Story, K.; Vanderlinde, K.; Williamson, R.

    2011-08-01

    We propose to acquire GMOS spectroscopy of 85 clusters of galaxies selected via the Sunyaev-Zel'dovich (SZ) effect from the South Pole Telescope (SPT) microwave background survey. This will bring our total to 100 SPT clusters with velocity dispersions. The SPT survey is delivering a uniformly-selected high-mass cluster sample that is essentially volume-complete beyond z>0.3. We will target a subset (0.3 < z < 0.8) of the SPT cluster catalog, extracted from 2500 deg^2. This data set will establish competitive, independent constraints on cosmological parameters, including the nature of the dark energy. Achieving this goal requires a precise understanding of the relationship between the cluster's SZ signature and the cluster mass, and this mass normalization is currently the largest systematic error in SPT's cosmological constraints. One promising method of determining galaxy cluster masses is to probe the dark matter potential with galaxy velocities. Using data from a large cluster sample will average over random projection effects, and will enable the calibration of the SZ-mass scaling relation, in conjunction with X-ray and lensing data on a smaller sample. The cluster galaxy spectroscopy we obtain will also equip the community to address a wide range of questions in galaxy evolution and cluster astrophysics.

  8. Galactic cannibalism in the galaxy cluster C0337-2522 at z= 0.59

    NASA Astrophysics Data System (ADS)

    Nipoti, C.; Stiavelli, M.; Ciotti, L.; Treu, T.; Rosati, P.

    2003-09-01

    According to the galactic cannibalism model, cD galaxies are formed in the centre of galaxy clusters by merging of massive galaxies and accretion of smaller stellar systems; however, observational examples of the initial phases of this process are lacking. We have identified a strong candidate for this early stage of cD galaxy formation: a group of five elliptical galaxies in the core of the X-ray cluster C0337-2522 at redshift z=0.59. With the aid of numerical simulations, in which the galaxies are represented by N-body systems, we study their dynamical evolution up to z=0 the cluster dark matter distribution is also described as an N-body system. We explore the hypothesis that some of the five galaxies will have merged before z=0, making reasonable assumptions on the structural and dynamical characteristics of the cluster. We then compare the properties of the merger remnant with those of real ellipticals (such as its accordance with the fundamental plane, the Faber-Jackson and the MBH-σ0 relations) and, in particular, we check whether the remnant has the surface brightness profile typical of cD galaxies. We find that a multiple merging event in the considered group of galaxies will take place before z=0 and that the merger remnant preserves the fundamental plane and the Faber-Jackson relations, while its behaviour with respect to the MBH-σ0 relation is quite sensitive to the details of black hole merging. However, the end-products of our simulations are more similar to a `normal' giant elliptical than to a cD galaxy with its characteristic diffuse luminous halo, thus confirming previous indications that the formation of cD galaxies is not a necessary consequence of galaxy merging at the cluster centre.

  9. Spectral Imaging of Galaxy Clusters with Planck

    NASA Astrophysics Data System (ADS)

    Bourdin, H.; Mazzotta, P.; Rasia, E.

    2015-12-01

    The Sunyaev-Zeldovich (SZ) effect is a promising tool for detecting the presence of hot gas out to the galaxy cluster peripheries. We developed a spectral imaging algorithm dedicated to the SZ observations of nearby galaxy clusters with Planck, with the aim of revealing gas density anisotropies related to the filamentary accretion of materials, or pressure discontinuities induced by the propagation of shock fronts. To optimize an unavoidable trade-off between angular resolution and precision of the SZ flux measurements, the algorithm performs a multi-scale analysis of the SZ maps as well as of other extended components, such as the cosmic microwave background (CMB) anisotropies and the Galactic thermal dust. The demixing of the SZ signal is tackled through kernel-weighted likelihood maximizations. The CMB anisotropies are further analyzed through a wavelet analysis, while the Galactic foregrounds and SZ maps are analyzed via a curvelet analysis that best preserves their anisotropic details. The algorithm performance has been tested against mock observations of galaxy clusters obtained by simulating the Planck High Frequency Instrument and by pointing at a few characteristic positions in the sky. These tests suggest that Planck should easily allow us to detect filaments in the cluster peripheries and detect large-scale shocks in colliding galaxy clusters that feature favorable geometry.

  10. Star Clusters in Early-Type Galaxies

    NASA Astrophysics Data System (ADS)

    Vetens, Sidney David; Crocker, Alison Faye

    2016-01-01

    Star formation rates in early-type galaxies are notoriously hard to determine because of their very low specific star formation rates. For this project, we use Hubble Space Telescope photometric data in 4-5 visible and near-UV filters to measure the young stellar clusters in nine early-type galaxies. Aperture photometry colors were compared to colors from synthetic photometry produced by the Flexible Stellar Population Synthesis code (Conroy et. al, ApJ 699, 486-506 (2009)), using a chi-squared likelihood method to estimate the age, metallicity and extinction for each cluster. Masses were determined using the best-fit model, the distance to each galaxy and the measured fluxes. Young clusters were selected below a cutoff age of 100 Myr, and star formation rates for each galaxy were then calculated as the combined mass of the young clusters divided by the cutoff age. Star formation rates computed in this way are far below those computed using the 22 micron emission. While some completeness effects are biasing the cluster-estimated SFRs low, the extreme difference (two orders of magnitude) may also point to SFR overestimation due to contamination from older stars in the 22 micron SFRs.