WorldWideScience

Sample records for brightest cluster galaxies

  1. Brightest Cluster Galaxy Identification

    Science.gov (United States)

    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.

  2. Radio luminosity function of brightest cluster galaxies

    CERN Document Server

    Yuan, Z S; Wen, Z L

    2016-01-01

    By cross-matching the currently largest optical catalog of galaxy clusters and the NVSS radio survey database, we obtain the largest complete sample of brightest cluster galaxies (BCGs) in the redshift range of 0.05galaxies located in more relaxed clusters. We derived the radio luminosity functions of BCGs from the largest complete sample of BCGs, and find that the functions depend on the optical luminosity of BCGs and the dynamical state of galaxy clusters. However, the radio luminosity function does not show significant evolution with redshift.

  3. The Radio Properties of Brightest Cluster Galaxies

    Science.gov (United States)

    Hogan, M. T.

    2014-09-01

    Energetic feedback from the Active Galactic Nucleus (AGN) of the Brightest Cluster Galaxy (BCG) is required to prevent catastrophic cooling of the intra-cluster medium (ICM) in galaxy clusters. Evidence for this is seen through the inflation of cavities in the ICM by AGN-launched, radio-emitting jets, and understanding this process is an active area of research. Radio observations play an integral role in this, as they trace the active stages of the feedback cycle. Understanding the radio properties of BCGs is therefore paramount for understanding both galaxy clusters and AGN feedback processes globally. Within this thesis, the BCGs in a large (>700) sample of X-ray selected clusters are studied. We observe these BCGs with a wide variety of facilities, building a census of their radio properties across a range of frequencies, timescales and angular resolutions. Radio spectral energy distributions (SEDs) are built for over 200 BCGs, and then decomposed into two components; a core, attributable to ongoing nuclear activity, and a non-core, attributable to historical accretion. Both components are not only more common, but also significantly more powerful in cool-core (CC) clusters than non-cool core (NCC) clusters. However, it is the presence of an active core that shows BCGs in CC clusters are constantly `on' - explaining how they regulate their environments over gigayear timescales. We observe 35 currently active BCGs at high (15-353 GHz) radio frequencies, and monitor their variability. Self-absorbed, active components are found to be common at high frequency. Little variability is seen on environment to the central engine and completing the feedback cycle.

  4. BRIGHTEST CLUSTER GALAXIES AT THE PRESENT EPOCH

    Energy Technology Data Exchange (ETDEWEB)

    Lauer, Tod R. [National Optical Astronomy Observatory, P.O. Box 26732, Tucson, AZ 85726 (United States); Postman, Marc [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Strauss, Michael A.; Graves, Genevieve J.; Chisari, Nora E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    2014-12-20

    We have obtained photometry and spectroscopy of 433 z ≤ 0.08 brightest cluster galaxies (BCGs) in a full-sky survey of Abell clusters to construct a BCG sample suitable for probing deviations from the local Hubble flow. The BCG Hubble diagram over 0 < z < 0.08 is consistent to within 2% of the Hubble relation specified by a Ω {sub m} = 0.3, Λ = 0.7 cosmology. This sample allows us to explore the structural and photometric properties of BCGs at the present epoch, their location in their hosting galaxy clusters, and the effects of the cluster environment on their structure and evolution. We revisit the L{sub m} -α relation for BCGs, which uses α, the log-slope of the BCG photometric curve of growth, to predict the metric luminosity in an aperture with 14.3 kpc radius, L{sub m} , for use as a distance indicator. Residuals in the relation are 0.27 mag rms. We measure central stellar velocity dispersions, σ, of the BCGs, finding the Faber-Jackson relation to flatten as the metric aperture grows to include an increasing fraction of the total BCG luminosity. A three-parameter ''metric plane'' relation using α and σ together gives the best prediction of L{sub m} , with 0.21 mag residuals. The distribution of projected spatial offsets, r{sub x} of BCGs from the X-ray-defined cluster center is a steep γ = –2.33 power law over 1 < r{sub x} < 10{sup 3} kpc. The median offset is ∼10 kpc, but ∼15% of the BCGs have r{sub x} > 100 kpc. The absolute cluster-dispersion normalized BCG peculiar velocity |ΔV {sub 1}|/σ {sub c} follows an exponential distribution with scale length 0.39 ± 0.03. Both L{sub m} and α increase with σ {sub c}. The α parameter is further moderated by both the spatial and velocity offset from the cluster center, with larger α correlated with the proximity of the BCG to the cluster mean velocity or potential center. At the same time, position in the cluster has little effect on L{sub m} . Likewise, residuals from

  5. BRIGHTEST CLUSTER GALAXIES AT THE PRESENT EPOCH

    International Nuclear Information System (INIS)

    We have obtained photometry and spectroscopy of 433 z ≤ 0.08 brightest cluster galaxies (BCGs) in a full-sky survey of Abell clusters to construct a BCG sample suitable for probing deviations from the local Hubble flow. The BCG Hubble diagram over 0 < z < 0.08 is consistent to within 2% of the Hubble relation specified by a Ω m = 0.3, Λ = 0.7 cosmology. This sample allows us to explore the structural and photometric properties of BCGs at the present epoch, their location in their hosting galaxy clusters, and the effects of the cluster environment on their structure and evolution. We revisit the Lm -α relation for BCGs, which uses α, the log-slope of the BCG photometric curve of growth, to predict the metric luminosity in an aperture with 14.3 kpc radius, Lm , for use as a distance indicator. Residuals in the relation are 0.27 mag rms. We measure central stellar velocity dispersions, σ, of the BCGs, finding the Faber-Jackson relation to flatten as the metric aperture grows to include an increasing fraction of the total BCG luminosity. A three-parameter ''metric plane'' relation using α and σ together gives the best prediction of Lm , with 0.21 mag residuals. The distribution of projected spatial offsets, rx of BCGs from the X-ray-defined cluster center is a steep γ = –2.33 power law over 1 < rx < 103 kpc. The median offset is ∼10 kpc, but ∼15% of the BCGs have rx > 100 kpc. The absolute cluster-dispersion normalized BCG peculiar velocity |ΔV 1|/σ c follows an exponential distribution with scale length 0.39 ± 0.03. Both Lm and α increase with σ c. The α parameter is further moderated by both the spatial and velocity offset from the cluster center, with larger α correlated with the proximity of the BCG to the cluster mean velocity or potential center. At the same time, position in the cluster has little effect on Lm . Likewise, residuals from the metric plane show no correlation with either the spatial or velocity

  6. Brightest Cluster Galaxies at the Present Epoch

    CERN Document Server

    Lauer, Tod R; Strauss, Michael A; Graves, Genevieve J; Chisari, Nora E

    2014-01-01

    We have observed 433 z100 kpc. The absolute cluster-dispersion normalized BCG peculiar velocity |Delta V_1|/sigma_c follows an exponential distribution with scale length 0.39+/-0.03. Both L_m and alpha increase with sigma_c. The alpha parameter is further moderated by both the spatial and velocity offset from the cluster center, with larger alpha correlated with the proximity of the BCG to the cluster mean velocity or potential center. At the same time, position in the cluster has little effect on L_m. The luminosity difference between the BCG and second-ranked galaxy, M2, increases as the peculiar velocity of the BCG within the cluster decreases. Further, when M2 is a close luminosity "rival" of the BCG, the galaxy that is closest to either the velocity or X-ray center of the cluster is most likely to have the larger alpha. We conclude that the inner portions of the BCGs are formed outside the cluster, but interactions in the heart of the galaxy cluster grow and extend the envelopes of the BCGs.

  7. BRIGHTEST CLUSTER GALAXIES AND CORE GAS DENSITY IN REXCESS CLUSTERS

    International Nuclear Information System (INIS)

    We investigate the relationship between brightest cluster galaxies (BCGs) and their host clusters using a sample of nearby galaxy clusters from the Representative XMM-Newton Cluster Structure Survey. The sample was imaged with the Southern Observatory for Astrophysical Research in R band to investigate the mass of the old stellar population. Using a metric radius of 12 h -1 kpc, we found that the BCG luminosity depends weakly on overall cluster mass as LBCG ∝ M 0.18±0.07cl, consistent with previous work. We found that 90% of the BCGs are located within 0.035 r500 of the peak of the X-ray emission, including all of the cool core (CC) clusters. We also found an unexpected correlation between the BCG metric luminosity and the core gas density for non-cool-core (non-CC) clusters, following a power law of ne ∝ L 2.7±0.4BCG (where ne is measured at 0.008 r500). The correlation is not easily explained by star formation (which is weak in non-CC clusters) or overall cluster mass (which is not correlated with core gas density). The trend persists even when the BCG is not located near the peak of the X-ray emission, so proximity is not necessary. We suggest that, for non-CC clusters, this correlation implies that the same process that sets the central entropy of the cluster gas also determines the central stellar density of the BCG, and that this underlying physical process is likely to be mergers.

  8. The Alignment effect of brightest cluster galaxies in the SDSS

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Rita S.J.; Annis, Jim; Strauss, Michael A.; Lupton, Robert H.; Bahcall, Neta A.; Gunn, James E.; Kepner, Jeremy V.; Postman, Marc

    2001-10-01

    One of the most vital observational clues for unraveling the origin of Brightest Cluster Galaxies (BCG) is the observed alignment of the BCGs with their host cluster and its surroundings. We have examined the BCG-cluster alignment effect, using clusters of galaxies detected from the Sloan Digital Sky Survey (SDSS). We find that the BCGs are preferentially aligned with the principal axis of their hosts, to a much higher redshift (z >~ 0.3) than probed by previous studies (z <~ 0.1). The alignment effect strongly depends on the magnitude difference of the BCG and the second and third brightest cluster members: we find a strong alignment effect for the dominant BCGs, while less dominant BCGs do not show any departure from random alignment with respect to the cluster. We therefore claim that the alignment process originates from the same process that makes the BCG grow dominant, be it direct mergers in the early stage of cluster formation, or a later process that resembles the galactic cannibalism scenario. We do not find strong evidence for (or against) redshift evolution between 0clusters). However, we have developed a framework by which we can examine many more clusters in an automated fashion for the upcoming SDSS cluster catalogs, which will provide us with better statistics for systematic investigations of the alignment with redshift, richness and morphology of both the cluster and the BCG.

  9. The Alignment Effect of Brightest Cluster Galaxies in the SDSS

    CERN Document Server

    Kim, R S J; Strauss, M A; Lupton, R H; Bahcall, Neta A; Gunn, J E; Kepner, J V; Postman, M; Kim, Rita S. J.; Annis, Jim; Strauss, Michael A.; Lupton, Robert H.; Bahcall, Neta A.; Gunn, James E.; Kepner, Jeremy V.; Postman, Marc

    2002-01-01

    One of the most vital observational clues for unraveling the origin of Brightest Cluster Galaxies (BCG) is the observed alignment of the BCGs with their host cluster and its surroundings. We have examined the BCG-cluster alignment effect, using clusters of galaxies detected from the Sloan Digital Sky Survey (SDSS). We find that the BCGs are preferentially aligned with the principal axis of their hosts, to a much higher redshift (z >~ 0.3) than probed by previous studies (z <~ 0.1). The alignment effect strongly depends on the magnitude difference of the BCG and the second and third brightest cluster members: we find a strong alignment effect for the dominant BCGs, while less dominant BCGs do not show any departure from random alignment with respect to the cluster. We therefore claim that the alignment process originates from the same process that makes the BCG grow dominant, be it direct mergers in the early stage of cluster formation, or a later process that resembles the galactic cannibalism scenario. We...

  10. Growth of brightest cluster galaxies via mergers since z = 1

    CERN Document Server

    Burke, Claire

    2013-01-01

    Hierarchical assembly within clusters of galaxies is tied directly to the evolution of the Brightest Cluster Galaxies (BCGs), which dominate the stellar light in the centres of rich clusters. In this paper we investigate the number of mergers onto BCGs in 14 X-ray selected clusters over the redshift range 0.8 < z < 1.4 using HST imaging data. We find significant differences in the numbers of companion galaxies to BCGs between the clusters in our sample indicating that BCGs in similar mass clusters can have very different merging histories. Within a 50 kpc radius around the BCGs we find an average of 6.45 \\pm 1.15 companion galaxies with mass ratios (companion:BCG) between 1:1 and 1:20. The infalling companions show a 50/50 split between major (1:1 - 1:2) and minor (1:3 - 1:20) mergers. When compared to similar work using lower redshift clusters, these results demonstrate that both major and minor merging was more common in the past. Since the dynamical timescales for merging onto the BCG are relatively ...

  11. A Brightest Cluster Galaxy with an Extremely Large Flat Core

    CERN Document Server

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

    2012-01-01

    Hubble Space Telescope images of the galaxy cluster Abell 2261, 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 ~3x bigger than those typically seen in the most luminous BCGs. The morphology of the core in A2261-BCG is also unusual, having a flat or even slightly-depressed interior surface brightness profile, rather than the typical shallow cusp. 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 ~1E+10 M_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, an...

  12. Signatures of Star Formation in Brightest Cluster Galaxies

    CERN Document Server

    Donahue, Megan

    2009-01-01

    I discuss and review recent studies of the signatures of activity in brightest cluster galaxies. Mid-IR spectra appear to show indications of star formation in a sample of 9 BCGs from de Messieres et al. (2009). Other processes like cosmic ray heating and conduction may play a role. The incidence of emission-line BCGs in X-ray selected clusters is higher than in optically-selected clusters, and higher still in systems known to be cool cores. We report early results of a UV and H-alpha survey of the BCGs in the REXCESS sample, which reveals that this sample has an interestingly low number of emission-line or UV excess systems. [Note added post facto: fainter emission-line sources discovered this summer increasses the rate to 22%.

  13. Angular Momenta, Dynamical Masses, and Mergers of Brightest Cluster Galaxies

    CERN Document Server

    Jimmy,; Brough, Sarah; Gebhardt, Karl; von der Linden, Anja; Couch, Warrick J; Sharp, Rob

    2013-01-01

    Using the VIMOS Integral Field Unit (IFU) spectrograph on the Very Large Telescope (VLT), we have spatially mapped the kinematic properties of 10 nearby Brightest Cluster Galaxies (BCGs) and 4 BCG companion galaxies located within a redshift of $z=0.1$. In the hierarchical formation model, these massive galaxies $(10^{10.5} M_{\\odot} < M_{dyn} < 10^{11.9} M_{\\odot})$ are expected to undergo more mergers than lower mass galaxies, and simulations show that dry minor mergers can remove angular momentum. We test whether BCGs have low angular momenta by using the $\\lambda_{Re}$ parameter developed by the SAURON and ATLAS\\textsuperscript{3D} teams and combine our kinematics with Sloan Digital Sky Survey (SDSS) photometry to analyze the BCGs' merger status. We find that 30% (3/10) of the BCGs and 100% of the companion galaxies (4/4) are fast rotators as defined by the ATLAS\\textsuperscript{3D} criteria. Our fastest rotating BCG has a $\\lambda_{Re}=0.35\\pm0.05$. We increase the number of BCGs analyzed from 1 in...

  14. How special are Brightest Group and Cluster Galaxies?

    CERN Document Server

    Von der Linden, A; Kauffmann, G; White, S D M; Linden, Anja von der; Best, Philip N.; Kauffmann, Guinevere; White, Simon D. M.

    2006-01-01

    We use the Sloan Digital Sky Survey to construct a sample of 625 brightest group and cluster galaxies (BCGs) together with control samples of non-BCGs matched in stellar mass, redshift, and color. We investigate how the systematic properties of BCGs depend on stellar mass and on their privileged location near the cluster center. The groups and clusters that we study are drawn from the C4 catalogue of Miller et al. (2005) but we have developed improved algorithms for identifying the BCG and for measuring the cluster velocity dispersion. Since the SDSS photometric pipeline tends to underestimate the luminosities of large galaxies in dense environments, we have developed a correction for this effect which can be readily applied to the published catalog data. We find that BCGs are larger and have higher velocity dispersions than non-BCGs of the same stellar mass, which implies that BCGs contain a larger fraction of dark matter. In contrast to non-BCGs, the dynamical mass-to-light ratio of BCGs does not vary as a ...

  15. Star formation activities in early-type brightest cluster galaxies

    CERN Document Server

    Liu, F S; Meng, X M

    2012-01-01

    We identify a total of 120 early-type Brightest Cluster Galaxies (BCGs) at 0.1cluster catalogues selected from the Sloan Digital Sky Survey (SDSS). They are selected with strong emission lines in their optical spectra, with both H{\\alpha} and [O II]{\\lambda}3727 line emission, which indicates significant ongoing star formation. They constitute about ~ 0.5% of the largest, optically-selected, low-redshift BCG sample, and the fraction is a strong function of cluster richness. Their star formation history can be well described by a recent minor and short starburst superimposed on an old stellar component, with the recent episode of star formation contributing on average only less than 1 percent of the total stellar mass. We show that the more massive star-forming BCGs in richer clusters tend to have higher star formation rate (SFR) and specific SFR (SFR per unit galaxy stellar mass). We also compare their statistical properties with a control sample selected from X-ray luminous c...

  16. Angular momenta, dynamical masses, and mergers of brightest cluster galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Jimmy; Tran, Kim-Vy [George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Brough, Sarah [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); Gebhardt, Karl [Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712 (United States); Von der Linden, Anja [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94305-4085 (United States); Couch, Warrick J. [Centre for Astrophysics and Supercomputing, Swinburne University, P.O. Box 218, Hawthorn, VIC 3122 (Australia); Sharp, Rob [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia)

    2013-12-01

    Using the VIMOS integral field unit (IFU) spectrograph on the Very Large Telescope, we have spatially mapped the kinematic properties of 10 nearby brightest cluster galaxies (BCGs) and 4 BCG companion galaxies located within a redshift of z = 0.1. In the hierarchical formation model, these massive galaxies (10{sup 10.5} M {sub ☉} < M {sub dyn} < 10{sup 11.9} M {sub ☉}) are expected to undergo more mergers than lower mass galaxies, and simulations show that dry minor mergers can remove angular momentum. We test whether BCGs have low angular momenta by using the λ {sub Re} parameter developed by the SAURON and ATLAS{sup 3D} teams and combine our kinematics with Sloan Digital Sky Survey photometry to analyze the BCGs' merger status. We find that 30% (3/10) of the BCGs and 100% of the companion galaxies (4/4) are fast rotators as defined by the ATLAS{sup 3D} criteria. Our fastest rotating BCG has a λ {sub Re} = 0.35 ± 0.05. We increase the number of BCGs analyzed from 1 in the combined SAURON and ATLAS{sup 3D} surveys to 11 BCGs total and find that above M {sub dyn} ∼ 11.5 M {sub ☉}, virtually all galaxies, regardless of environment, are slow rotators. To search for signs of recent merging, we analyze the photometry of each system and use the G – M {sub 20} selection criteria to identify mergers. We find that 40% ± 20% of our BCGs are currently undergoing or have recently undergone a merger (within 0.2 Gyr). Surprisingly, we find no correlation between galaxies with high angular momentum and morphological signatures of merging.

  17. Star Formation Activity in CLASH Brightest Cluster Galaxies

    CERN Document Server

    Fogarty, Kevin; Connor, Thomas; Donahue, Megan; Moustakas, John

    2015-01-01

    The CLASH X-ray selected sample of 20 galaxy clusters contains ten brightest cluster galaxies (BCGs) that exhibit significant ($>$5 $\\sigma$) extinction-corrected star formation rates (SFRs). Star formation activity is inferred from photometric estimates of UV and H$\\alpha$+[NII] emission in knots and filaments detected in CLASH HST observations. These measurements are supplemented with [OII], [OIII], and H$\\beta$ fluxes measured from spectra obtained with the SOAR telescope. Reddening-corrected UV-derived SFRs in these BCGs are broadly consistent with H$\\alpha$-derived SFRs. Five BCGs exhibit SFRs $>$10 M$_{\\odot}$ yr$^{-1}$ and an additional two have a SFR $>$ 100 M$_{\\odot}$ yr$^{-1}$. We confirm that photoionization from ongoing star formation powers the line emission nebulae in these BCGs, although in many BCGs there is also evidence for a LINER-like contribution. Using Chandra X-ray measurements, we infer that the star formation occurs exclusively in low-entropy cluster cores and exhibits a correlation ...

  18. High Radio Frequency Properties and Variability of Brightest Cluster Galaxies

    CERN Document Server

    Hogan, M T; Geach, J E; Grainge, K J B; Hlavacek-Larrondo, J; Hovatta, T; Karim, A; McNamara, B R; Rumsey, C; Russell, H R; Salomé, P; Aller, H D; Aller, M F; Benford, D J; Fabian, A C; Readhead, A C S; Sadler, E M; Saunders, R D E

    2015-01-01

    We consider the high radio frequency (15 GHz - 353 GHz) properties and variability of 35 Brightest Cluster Galaxies (BCGs). These are the most core-dominated sources drawn from a parent sample of more than 700 X-ray selected clusters, thus allowing us to relate our results to the general population. We find that >6.0% of our parent sample (>15.1% if only cool-core clusters are considered) contain a radio-source at 150 GHz of at least 3mJy (~1x10^23 W/Hz at our median redshift of z~0.13). Furthermore, >3.4% of the BCGs in our parent sample contain a peaked component (Gigahertz Peaked Spectrum, GPS) in their spectra that peaks above 2 GHz, increasing to >8.5% if only cool-core clusters are considered. We see little evidence for strong variability at 15 GHz on short (week-month) time-scales although we see variations greater than 20% at 150 GHz over 6-month times-frames for 4 of the 23 sources with multi-epoch observations. Much more prevalent is long-term (year-decade time-scale) variability, with average annua...

  19. Globular Cluster Systems in Brightest Cluster Galaxies. II: NGC 6166

    CERN Document Server

    Harris, William E; Whitmore, Bradley C; Gnedin, Oleg Y; Geisler, Douglas; Rothberg, Barry

    2015-01-01

    We present new deep photometry of the globular cluster system (GCS) around NGC 6166, the central supergiant galaxy in Abell 2199. HST data from the ACS and WFC3 cameras in F475W, F814W are used to determine the spatial distribution of the GCS, its metallicity distribution function (MDF), and the dependence of the MDF on galactocentric radius and on GC luminosity. The MDF is extremely broad, with the classic red and blue subpopulations heavily overlapped, but a double-Gaussian model can still formally match the MDF closely. The spatial distribution follows a Sersic-like profile detectably to a projected radius of at least $R_{gc} = 250$ kpc. To that radius, the total number of clusters in the system is N_{GC} = 39000 +- 2000, the global specific frequency is S_N = 11.2 +- 0.6, and 57\\% of the total are blue, metal-poor clusters. The GCS may fade smoothly into the Intra-Cluster Medium of A2199; we see no clear transition from the core of the galaxy to the cD halo or the ICM. The radial distribution, projected e...

  20. Star Formation Activity in CLASH Brightest Cluster Galaxies

    Science.gov (United States)

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

    2015-11-01

    The CLASH X-ray selected sample of 20 galaxy clusters contains 10 brightest cluster galaxies (BCGs) that exhibit significant (>5σ) extinction-corrected star formation rates (SFRs). Star formation activity is inferred from photometric estimates of UV and Hα+[N ii] emission in knots and filaments detected in CLASH Hubble Space Telescope ACS and WFC3 observations. UV-derived SFRs in these BCGs span two orders of magnitude, including two with a SFR ≳ 100 M⊙ yr-1. These measurements are supplemented with [O ii], [O iii], and Hβ fluxes measured from spectra obtained with the SOAR telescope. We confirm that photoionization from ongoing star formation powers the line emission nebulae in these BCGs, although in many BCGs there is also evidence of a LINER-like contribution to the line emission. Coupling these data with Chandra X-ray measurements, we infer that the star formation occurs exclusively in low-entropy cluster cores and exhibits a correlation with gas properties related to cooling. We also perform an in-depth study of the starburst history of the BCG in the cluster RXJ1532.9+3021, and create 2D maps of stellar properties on scales down to ˜350 pc. These maps reveal evidence for an ongoing burst occurring in elongated filaments, generally on ˜0.5-1.0 Gyr timescales, although some filaments are consistent with much younger (≲100 Myr) burst timescales and may be correlated with recent activity from the active galactic nucleus. The relationship between BCG SFRs and the surrounding intracluster medium gas properties provide new support for the process of feedback-regulated cooling in galaxy clusters and is consistent with recent theoretical predictions. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel

  1. Globular Clusters and Spur Clusters in NGC 4921, the Brightest Spiral Galaxy in the Coma Cluster

    CERN Document Server

    Lee, Myung Gyoon

    2016-01-01

    We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in Coma. Also we find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3x10^5 M_odot. The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions (LF) of the blue (metal-poor) GCs (0.70<(V-I)<1.05) in the halo are estimated to be V(max) =27.11+-0.09 mag and I(max)=26.21+-0.11 mag. We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max)=26.25+-0.03 mag. Adopting M_I (max) = -8.56+-0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies, 91+-4 Mpc. Combining this and the Coma radial velocity, we derive a value of the Hubble constant, ...

  2. Major Cluster Mergers and the Location of the Brightest Cluster Galaxy

    CERN Document Server

    Martel, Hugo; Barai, Paramita

    2014-01-01

    Using a large N-body cosmological simulation combined with a subgrid treatment of galaxy formation, we study the formation and evolution of the galaxy and cluster population in a comoving volume (100 Mpc)^3 in a LCDM universe. At z = 0, our computational volume contains 1788 clusters with mass M_cl > 1.1x10^12 Msun, including 18 massive clusters with M_cl > 10^14 Msun. It also contains 1 088 797 galaxies with mass M_gal > 2x10^9 Msun and luminosity L > 9.5x10^5 Lsun. For each cluster, we identified the brightest cluster galaxy (BCG). We then computed the fraction f_BNC of clusters in which the BCG is not the closest galaxy to the center of the cluster in projection, and the ratio Dv/s, where Dv is the difference in radial velocity between the BCG and the whole cluster, and s is the radial velocity dispersion of the cluster. f_BNC increases from 0.05 for low-mass clusters (M_cl ~ 10^12 Msun) to 0.5 for high-mass ones (M_cl > 10^14 Msun), with no dependence on cluster redshift. The values of Dv/s vary from 0 to...

  3. Turbulent heating in galaxy clusters brightest in X-rays.

    Science.gov (United States)

    Zhuravleva, I; Churazov, E; Schekochihin, A A; Allen, S W; Arévalo, P; Fabian, A C; Forman, W R; Sanders, J S; Simionescu, A; Sunyaev, R; Vikhlinin, A; Werner, N

    2014-11-01

    The hot (10(7) to 10(8) kelvin), X-ray-emitting intracluster medium (ICM) is the dominant baryonic constituent of clusters of galaxies. In the cores of many clusters, radiative energy losses from the ICM occur on timescales much shorter than the age of the system. Unchecked, this cooling would lead to massive accumulations of cold gas and vigorous star formation, in contradiction to observations. Various sources of energy capable of compensating for these cooling losses have been proposed, the most promising being heating by the supermassive black holes in the central galaxies, through inflation of bubbles of relativistic plasma. Regardless of the original source of energy, the question of how this energy is transferred to the ICM remains open. Here we present a plausible solution to this question based on deep X-ray data and a new data analysis method that enable us to evaluate directly the ICM heating rate from the dissipation of turbulence. We find that turbulent heating is sufficient to offset radiative cooling and indeed appears to balance it locally at each radius-it may therefore be the key element in resolving the gas cooling problem in cluster cores and, more universally, in the atmospheres of X-ray-emitting, gas-rich systems on scales from galaxy clusters to groups and elliptical galaxies. PMID:25363764

  4. Chandra Observation of Abell 1142: A Cool-core Cluster Lacking a Central Brightest Cluster Galaxy?

    Science.gov (United States)

    Su, Yuanyuan; Buote, David A.; Gastaldello, Fabio; van Weeren, Reinout

    2016-04-01

    Abell 1142 is a low-mass galaxy cluster at low redshift containing two comparable brightest cluster galaxies (BCGs) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal-rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool-core cluster. The redshift distribution of its member galaxies indicates that Abell 1142 may contain two subclusters, each of which contain one BCG. The BCGs are merging at a relative velocity of ≈1200 km s-1. This ongoing merger may have shock-heated the ICM from ≈2 keV to above 3 keV, which would explain the anomalous LX-TX scaling relation for this system. This merger may have displaced the metal-enriched “cool core” of either of the subclusters from the BCG. The southern BCG consists of three individual galaxies residing within a radius of 5 kpc in projection. These galaxies should rapidly sink into the subcluster center due to the dynamical friction of a cuspy cold dark matter halo.

  5. GLOBULAR CLUSTER SYSTEMS IN BRIGHTEST CLUSTER GALAXIES: A NEAR-UNIVERSAL LUMINOSITY FUNCTION?

    Energy Technology Data Exchange (ETDEWEB)

    Harris, William E.; O' Halloran, Heather; Cockcroft, Robert, E-mail: harris@physics.mcmaster.ca, E-mail: ohallohm@mcmaster.ca, E-mail: cockcroft@physics.mcmaster.ca [Department of Physics and Astronomy, McMaster University, Hamilton, ON (Canada); and others

    2014-12-20

    We present the first results from our Hubble Space Telescope brightest cluster galaxy (BCG) survey of seven central supergiant cluster galaxies and their globular cluster (GC) systems. We measure a total of 48,000 GCs in all seven galaxies, representing the largest single GC database. We find that a log-normal shape accurately matches the observed the luminosity function (LF) of the GCs down to the globular cluster luminosity function turnover point, which is near our photometric limit. In addition, the LF has a virtually identical shape in all seven galaxies. Our data underscore the similarity in the formation mechanism of massive star clusters in diverse galactic environments. At the highest luminosities (L ≳ 10{sup 7} L {sub ☉}), we find small numbers of ''superluminous'' objects in five of the galaxies; their luminosity and color ranges are at least partly consistent with those of ultra-compact dwarfs. Last, we find preliminary evidence that in the outer halo (R ≳ 20 kpc), the LF turnover point shows a weak dependence on projected distance, scaling as L {sub 0} ∼ R {sup –0.2}, while the LF dispersion remains nearly constant.

  6. The formation of the brightest cluster galaxies in cosmological simulations: the case for AGN feedback

    OpenAIRE

    Martizzi, Davide; Teyssier, Romain; Moore, Ben

    2011-01-01

    We use 500 pc resolution cosmological simulations of a Virgo-like galaxy cluster to study the properties of the brightest cluster galaxy (BCG) that forms at the center of the halo. We compared two simulations; one incorporating only supernovae feedback and a second that also includes prescriptions for black hole growth and the resulting AGN feedback from gas accretion. As previous work has shown, with supernovae feedback alone we are unable to reproduce any of the observed properties of massi...

  7. Globular Cluster Systems in Brightest Cluster Galaxies: A Near-Universal Luminosity Function?

    CERN Document Server

    Harris, William E; Gnedin, Oleg Y; O'Halloran, Heather; Blakeslee, John P; Whitmore, Bradley C; Cote, Patrick; Geisler, Douglas; Peng, Eric W; Bailin, Jeremy; Rothberg, Barry; Cockcroft, Robert; DeGraaff, Regina Barber

    2014-01-01

    We present the first results from our HST Brightest Cluster Galaxy (BCG) survey of seven central supergiant cluster galaxies and their globular cluster (GC) systems. We measure a total of 48000 GCs in all seven galaxies, representing the largest single GC database. We find that a log-normal shape accurately matches the observed luminosity function (LF) of the GCs down to the GCLF turnover point, which is near our photometric limit. In addition, the LF has a virtually identical shape in all seven galaxies. Our data underscore the similarity in the formation mechanism of massive star clusters in diverse galactic environments. At the highest luminosities (log L > 10^7 L_Sun) we find small numbers of "superluminous" objects in five of the galaxies; their luminosity and color ranges are at least partly consistent with those of UCDs (Ultra-Compact Dwarfs). Lastly, we find preliminary evidence that in the outer halo (R > 20 kpc), the LF turnover point shows a weak dependence on projected distance, scaling as L_0 ~ R...

  8. The evolution in the stellar mass of brightest cluster galaxies over the past 10 billion years

    Science.gov (United States)

    Bellstedt, Sabine; Lidman, Chris; Muzzin, Adam; Franx, Marijn; Guatelli, Susanna; Hill, Allison R.; Hoekstra, Henk; Kurinsky, Noah; Labbe, Ivo; Marchesini, Danilo; Marsan, Z. Cemile; Safavi-Naeini, Mitra; Sifón, Cristóbal; Stefanon, Mauro; van de Sande, Jesse; van Dokkum, Pieter; Weigel, Catherine

    2016-08-01

    Using a sample of 98 galaxy clusters recently imaged in the near-infrared with the European Southern Observatory (ESO) New Technology Telescope, WIYN telescope and William Herschel Telescope, supplemented with 33 clusters from the ESO archive, we measure how the stellar mass of the most massive galaxies in the universe, namely brightest cluster galaxies (BCGs), increases with time. Most of the BCGs in this new sample lie in the redshift range 0.2 theory using mock images, is required if a more detailed comparison between the models and the data is to be made.

  9. THE STELLAR MASS GROWTH OF BRIGHTEST CLUSTER GALAXIES IN THE IRAC SHALLOW CLUSTER SURVEY

    International Nuclear Information System (INIS)

    The details of the stellar mass assembly of brightest cluster galaxies (BCGs) remain an unresolved problem in galaxy formation. We have developed a novel approach that allows us to construct a sample of clusters that form an evolutionary sequence, and have applied it to the Spitzer IRAC Shallow Cluster Survey (ISCS) to examine the evolution of BCGs in progenitors of present-day clusters with mass of (2.5-4.5) × 1014 M☉. We follow the cluster mass growth history extracted from a high resolution cosmological simulation, and then use an empirical method that infers the cluster mass based on the ranking of cluster luminosity to select high-z clusters of appropriate mass from ISCS to be progenitors of the given set of z = 0 clusters. We find that, between z = 1.5 and 0.5, the BCGs have grown in stellar mass by a factor of 2.3, which is well-matched by the predictions from a state-of-the-art semi-analytic model. Below z = 0.5 we see hints of differences in behavior between the model and observation.

  10. Turbulent Heating in Galaxy Clusters Brightest in X-rays

    CERN Document Server

    Zhuravleva, I; Schekochihin, A A; Allen, S W; Arevalo, P; Fabian, A C; Forman, W R; Sanders, J S; Simionescu, A; Sunyaev, R; Vikhlinin, A; Werner, N

    2014-01-01

    The hot, X-ray-emitting intracluster medium (ICM) is the dominant baryonic constituent of clusters of galaxies. In the cores of many clusters, radiative energy losses from the ICM occur on timescales significantly shorter than the age of the system. Unchecked, this cooling would lead to massive accumulations of cold gas and vigorous star formation, in contradiction to observations. Various sources of energy capable of compensating these cooling losses have been proposed, the most promising being heating by the supermassive black holes in the central galaxies through inflation of bubbles of relativistic plasma. Regardless of the original source of energy, the question of how this energy is transferred to the ICM has remained open. Here we present a plausible solution to this question based on deep Chandra X-ray observatory data and a new data-analysis method that enables us to evaluate directly the ICM heating rate due to the dissipation of turbulence. We find that turbulent heating is sufficient to offset rad...

  11. Chandra Observation of Abell 1142: A Cool-Core Cluster Lacking a Central Brightest Cluster Galaxy?

    CERN Document Server

    Su, Yuanyuan; Gastaldello, Fabio; van Weeren, Reinout

    2016-01-01

    Abell~1142 is a low-mass galaxy cluster at low redshift containing two comparable Brightest Cluster Galaxies (BCG) resembling a scaled-down version of the Coma Cluster. Our Chandra analysis reveals an X-ray emission peak, roughly 100 kpc away from either BCG, which we identify as the cluster center. The emission center manifests itself as a second beta-model surface brightness component distinct from that of the cluster on larger scales. The center is also substantially cooler and more metal rich than the surrounding intracluster medium (ICM), which makes Abell 1142 appear to be a cool core cluster. The redshift distribution of its member galaxies indicates that Abell 1142 may contain two subclusters with each containing one BCG. The BCGs are merging at a relative velocity of ~1200 km/s. This ongoing merger may have shock-heated the ICM from ~ 2 keV to above 3 keV, which would explain the anomalous L_X--T_X scaling relation for this system. This merger may have displaced the metal-enriched "cool core" of eith...

  12. Miscentring in Galaxy Clusters: Dark Matter to Brightest Cluster Galaxy Offsets in 10,000 SDSS Clusters

    CERN Document Server

    Zitrin, Adi; Umetsu, Keiichi; Oguri, Masamune; Broadhurst, Tom

    2012-01-01

    We characterise the typical offset between the Dark Matter (DM) projected centre and the Brightest Cluster Galaxy (BCG) in 10,000 SDSS clusters. To place constraints on the centre of DM, we use an automated strong-lensing analysis, mass-modelling technique which is based on the well-tested assumption that light traces mass. The cluster galaxies are modelled with a steep power-law, and the DM component is obtained by smoothing the galaxy distribution fitting a low-order 2D polynomial (via spline interpolation), while probing a whole range of polynomial degrees and galaxy power laws. We find that the offsets between the BCG and the peak of the smoothed light map representing the DM, \\Delta, are distributed equally around zero with no preferred direction, and are well described by a log-normal distribution with =-1.895^{+0.003}_{-0.004}, and \\sigma=0.501\\pm0.004 (95% confidence levels), or =0.564\\pm0.005, and \\sigma=0.475\\pm0.007. Some of the offsets originate in prior misidentifications of the BCG or other brig...

  13. Major cluster mergers and the location of the brightest cluster galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Martel, Hugo; Robichaud, Fidèle [Département de physique, Génie Physique et Optique, Université Laval, Québec, QC, G1V 0A6 (Canada); Barai, Paramita, E-mail: Hugo.Martel@phy.ulaval.ca [INAF-Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34143 Trieste (Italy)

    2014-05-10

    Using a large N-body cosmological simulation combined with a subgrid treatment of galaxy formation, merging, and tidal destruction, we study the formation and evolution of the galaxy and cluster population in a comoving volume (100 Mpc){sup 3} in a ΛCDM universe. At z = 0, our computational volume contains 1788 clusters with mass M {sub cl} > 1.1 × 10{sup 12} M {sub ☉}, including 18 massive clusters with M {sub cl} > 10{sup 14} M {sub ☉}. It also contains 1, 088, 797 galaxies with mass M {sub gal} ≥ 2 × 10{sup 9} M {sub ☉} and luminosity L > 9.5 × 10{sup 5} L {sub ☉}. For each cluster, we identified the brightest cluster galaxy (BCG). We then computed two separate statistics: the fraction f {sub BNC} of clusters in which the BCG is not the closest galaxy to the center of the cluster in projection, and the ratio Δv/σ, where Δv is the difference in radial velocity between the BCG and the whole cluster and σ is the radial velocity dispersion of the cluster. We found that f {sub BNC} increases from 0.05 for low-mass clusters (M {sub cl} ∼ 10{sup 12} M {sub ☉}) to 0.5 for high-mass clusters (M {sub cl} > 10{sup 14} M {sub ☉}) with very little dependence on cluster redshift. Most of this result turns out to be a projection effect and when we consider three-dimensional distances instead of projected distances, f {sub BNC} increases only to 0.2 at high-cluster mass. The values of Δv/σ vary from 0 to 1.8, with median values in the range 0.03-0.15 when considering all clusters, and 0.12-0.31 when considering only massive clusters. These results are consistent with previous observational studies and indicate that the central galaxy paradigm, which states that the BCG should be at rest at the center of the cluster, is usually valid, but exceptions are too common to be ignored. We built merger trees for the 18 most massive clusters in the simulation. Analysis of these trees reveal that 16 of these clusters have experienced 1 or several major or semi

  14. Major cluster mergers and the location of the brightest cluster galaxy

    International Nuclear Information System (INIS)

    Using a large N-body cosmological simulation combined with a subgrid treatment of galaxy formation, merging, and tidal destruction, we study the formation and evolution of the galaxy and cluster population in a comoving volume (100 Mpc)3 in a ΛCDM universe. At z = 0, our computational volume contains 1788 clusters with mass M cl > 1.1 × 1012 M ☉, including 18 massive clusters with M cl > 1014 M ☉. It also contains 1, 088, 797 galaxies with mass M gal ≥ 2 × 109 M ☉ and luminosity L > 9.5 × 105 L ☉. For each cluster, we identified the brightest cluster galaxy (BCG). We then computed two separate statistics: the fraction f BNC of clusters in which the BCG is not the closest galaxy to the center of the cluster in projection, and the ratio Δv/σ, where Δv is the difference in radial velocity between the BCG and the whole cluster and σ is the radial velocity dispersion of the cluster. We found that f BNC increases from 0.05 for low-mass clusters (M cl ∼ 1012 M ☉) to 0.5 for high-mass clusters (M cl > 1014 M ☉) with very little dependence on cluster redshift. Most of this result turns out to be a projection effect and when we consider three-dimensional distances instead of projected distances, f BNC increases only to 0.2 at high-cluster mass. The values of Δv/σ vary from 0 to 1.8, with median values in the range 0.03-0.15 when considering all clusters, and 0.12-0.31 when considering only massive clusters. These results are consistent with previous observational studies and indicate that the central galaxy paradigm, which states that the BCG should be at rest at the center of the cluster, is usually valid, but exceptions are too common to be ignored. We built merger trees for the 18 most massive clusters in the simulation. Analysis of these trees reveal that 16 of these clusters have experienced 1 or several major or semi-major mergers in the past. These mergers leave each cluster in a non-equilibrium state, but eventually the cluster settles into

  15. FURTHER DEFINITION OF THE MASS-METALLICITY RELATION IN GLOBULAR CLUSTER SYSTEMS AROUND BRIGHTEST CLUSTER GALAXIES

    International Nuclear Information System (INIS)

    We combine the globular cluster (GC) data for 15 brightest cluster galaxies and use this material to trace the mass-metallicity relations (MMRs) in their globular cluster systems (GCSs). This work extends previous studies which correlate the properties of the MMR with those of the host galaxy. Our combined data sets show a mean trend for the metal-poor subpopulation that corresponds to a scaling of heavy-element abundance with cluster mass Z ∼ M 0.30±0.05. No trend is seen for the metal-rich subpopulation which has a scaling relation that is consistent with zero. We also find that the scaling exponent is independent of the GCS specific frequency and host galaxy luminosity, except perhaps for dwarf galaxies. We present new photometry in (g',i') obtained with Gemini/GMOS for the GC populations around the southern giant ellipticals NGC 5193 and IC 4329. Both galaxies have rich cluster populations which show up as normal, bimodal sequences in the color-magnitude diagram. We test the observed MMRs and argue that they are statistically real, and not an artifact caused by the method we used. We also argue against asymmetric contamination causing the observed MMR as our mean results are no different from other contamination-free studies. Finally, we compare our method to the standard bimodal fitting method (KMM or RMIX) and find our results are consistent. Interpretation of these results is consistent with recent models for GC formation in which the MMR is determined by GC self-enrichment during their brief formation period.

  16. The properties of Brightest Cluster Galaxies in the SDSS DR6 adaptive matched filter cluster catalogue

    CERN Document Server

    Pipino, A; Pierpaoli, E; MacKenzie, S M; Dong, F

    2010-01-01

    We study the properties of Brightest Cluster Galaxies (BCGs) drawn from a catalogue of more than 69000 clusters in the SDSS DR6 based on the adaptive matched filter technique (AMF, Szabo et al., 2010). Our sample consists of more than 14300 galaxies in the redshift range 0.1-0.3. We test the catalog by showing that it includes well-known BCGs which lie in the SDSS footprint. We characterize the BCGs in terms of r-band luminosities and optical colours as well as their trends with redshift. In particular, we define and study the fraction of blue BCGs, namely those that are likely to be missed by either colour-based cluster surveys and catalogues. Richer clusters tend to have brighter BCGs, however less dominant than in poorer systems. 4-9% of our BCGs are at least 0.3 mag bluer in the g-r colour than the red-sequence at their given redshift. Such a fraction decreases to 1-6% for clusters above a richness of 50, where 3% of the BCGs are 0.5 mag below the red-sequence. A preliminary morphological study suggests t...

  17. The Relation Between Cool Cluster Cores and Herschel-Detected Star Formation in Brightest Cluster Galaxies

    CERN Document Server

    Rawle, T D; Egami, E; Rex, M; Smith, G P; Altieri, B; Fiedler, A; Haines, C P; Pereira, M J; Pérez-González, P G; Portouw, J; Valtchanov, I; Walth, G; van der Werf, P P; Zemcov, M

    2012-01-01

    We present far-infrared (FIR) analysis of 68 Brightest Cluster Galaxies (BCGs) at 0.08 2x10^11 L_sun), only a small (<0.4 mag) reddening correction is required for SFR(Ha) to agree with SFR_FIR. The relatively low Ha extinction (dust obscuration), compared to values reported for the general star-forming population, lends further weight to an alternate (external) origin for the cold gas. Finally, we use a stacking analysis of non-cool-core clusters to show that the majority of the fuel for star formation in the FIR-bright BCGs is unlikely to originate form normal stellar mass loss.

  18. A comprehensive study of the radio properties of brightest cluster galaxies

    Science.gov (United States)

    Hogan, M. T.; Edge, A. C.; Hlavacek-Larrondo, J.; Grainge, K. J. B.; Hamer, S. L.; Mahony, E. K.; Russell, H. R.; Fabian, A. C.; McNamara, B. R.; Wilman, R. J.

    2015-10-01

    We examine the radio properties of the brightest cluster galaxies (BCGs) in a large sample of X-ray selected galaxy clusters comprising the Brightest Cluster Sample (BCS), the extended BCS and ROSAT-ESO Flux Limited X-ray cluster catalogues. We have multifrequency radio observations of the BCG using a variety of data from the Australia Telescope Compact Array, Jansky Very Large Array and Very Long Baseline Array telescopes. The radio spectral energy distributions of these objects are decomposed into a component attributed to on-going accretion by the active galactic nuclei (AGN) that we refer to as `the core', and a more diffuse, ageing component we refer to as the `non-core'. These BCGs are matched to previous studies to determine whether they exhibit emission lines (principally Hα), indicative of the presence of a strong cooling cluster core. We consider how the radio properties of the BCGs vary with cluster environmental factors. Line emitting BCGs are shown to generally host more powerful radio sources, exhibiting the presence of a strong, distinguishable core component in about 60 per cent of cases. This core component more strongly correlates with the BCG's [O III] 5007 Å line emission. For BCGs in line emitting clusters, the X-ray cavity power correlates with both the extended and core radio emission, suggestive of steady fuelling of the AGN over bubble-rise time-scales in these clusters.

  19. The evolution in the stellar mass of Brightest Cluster Galaxies over the past 10 billion years

    Science.gov (United States)

    Bellstedt, Sabine; Lidman, Chris; Muzzin, Adam; Franx, Marijn; Guatelli, Susanna; Hill, Allison R.; Hoekstra, Henk; Kurinsky, Noah; Labbe, Ivo; Marchesini, Danilo; Marsan, Z. Cemile; Safavi-Naeini, Mitra; Sifón, Cristóbal; Stefanon, Mauro; van de Sande, Jesse; van Dokkum, Pieter; Weigel, Catherine

    2016-05-01

    Using a sample of 98 galaxy clusters recently imaged in the near infra-red with the ESO NTT, WIYN and WHT telescopes, supplemented with 33 clusters from the ESO archive, we measure how the stellar mass of the most massive galaxies in the universe, namely Brightest Cluster Galaxies (BCG), increases with time. Most of the BCGs in this new sample lie in the redshift range 0.2 evidence indicates that the stellar mass growth rate of BCGs may be slowing in the past 3.5 billion years. Further work in collecting larger samples, and in better comparing observations with theory using mock images is required if a more detailed comparison between the models and the data is to be made.

  20. AGN jet power and feedback controlled by Bondi accretion in brightest cluster galaxies

    CERN Document Server

    Fujita, Yutaka; Shlosman, Isaac

    2014-01-01

    (Abridged) We propose a new method to estimate the Bondi (hot gas) accretion rates onto the supermassive black holes (SMBHs) at the centres of elliptical galaxies. It can be applied even if the Bondi radius is not well-resolved in X-ray observations. This method is based on two simple assumptions: (1) hot gas outside the Bondi radius is in nearly a hydrostatic equilibrium in a gravitational potential, and (2) the gas temperature near the galaxy centre is close to the virial temperature of the galaxy. We apply this method to 28 bright elliptical galaxies in nearby galaxy clusters (27 of them are the brightest cluster galaxies; BCGs). We find a strong correlation between the Bondi accretion rates and the power of jets associated with the SMBHs. For most galaxies, the accretion rates are large enough to account for the jet powers. Our results indicate that hot gas in the elliptical galaxies directly controls the feedback from the active galactic nuclei (AGN), which leads to a stable heating of the cluster cool c...

  1. SALT spectroscopic observations of galaxy clusters detected by ACT and a Type II quasar hosted by a brightest cluster galaxy

    CERN Document Server

    Kirk, Brian; Cress, Catherine; Crawford, Steven M; Hughes, John P; Battaglia, Nicholas; Bond, J Richard; Burke, Claire; Gralla, Megan B; Hajian, Amir; Hasselfield, Matthew; Hincks, Adam D; Infante, Leopoldo; Kosowsky, Arthur; Marriage, Tobias A; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D; Sievers, Jonathan L; Sifón, Cristóbal; Wilson, Susan; Wollack, Edward J; Zunckel, Caroline

    2014-01-01

    We present Southern African Large Telescope (SALT) follow-up observations of seven massive clusters detected by the Atacama Cosmology Telescope (ACT) on the celestial equator using the Sunyaev-Zel'dovich (SZ) effect. We conducted multi-object spectroscopic observations with the Robert Stobie Spectrograph in order to measure galaxy redshifts in each cluster field, determine the cluster line-of-sight velocity dispersions, and infer the cluster dynamical masses. We find that the clusters, which span the redshift range 0.3 < z < 0.55, range in mass from (5 -- 20) x 10$^{14}$ solar masses (M200c). Their masses, given their SZ signals, are similar to those of southern hemisphere ACT clusters previously observed using Gemini and the VLT. We note that the brightest cluster galaxy in one of the systems studied, ACT-CL J0320.4+0032 at z = 0.38, hosts a Type II quasar. To our knowledge, this is only the third such system discovered, and therefore may be a rare example of a very massive halo in which quasar-mode fe...

  2. A Comprehensive Study of the Radio Properties of Brightest Cluster Galaxies

    CERN Document Server

    Hogan, M T; Hlavacek-Larrondo, J; Grainge, K J B; Hamer, S L; Mahony, E K; Russell, H R; Fabian, A C; McNamara, B R; Wilman, R J

    2015-01-01

    We examine the radio properties of the Brightest Cluster Galaxies (BCGs) in a large sample of X-ray selected galaxy clusters comprising the Brightest Cluster Sample (BCS), the extended BCS (eBCS) and ROSAT-ESO Flux Limited X-ray (REFLEX) cluster catalogues. We have multi-frequency radio observations of the BCG using a variety of data from the Australia Telescope Compact Array (ATCA), Jansky Very Large Array (VLA) and Very Long Baseline Array (VLBA) telescopes. The radio spectral energy distributions (SEDs) of these objects are decomposed into a component attributed to on-going accretion by the active galactic nuclei (AGN) that we refer to as the 'core', and a more diffuse, ageing component we refer to as the 'non-core'. These BCGs are matched to previous studies to determine whether they exhibit emission lines (principally H-alpha), indicative of the presence of a strong cooling cluster core. We consider how the radio properties of the BCGs vary with cluster environmental factors. Line emitting BCGs are shown...

  3. Brightest Cluster Galaxies in Cosmological Simulations with Adaptive Mesh Refinement: Successes and Failures

    CERN Document Server

    Martizzi, Davide; Moore, Ben

    2014-01-01

    A large sample of cosmological hydrodynamical zoom-in simulations with Adaptive Mesh Refinement (AMR) is analysed to study the properties of simulated Brightest Cluster Galaxies (BCGs). Following the formation and evolution of BCGs requires modeling an entire galaxy cluster, because the BCG properties are largely influenced by the state of the gas in the cluster and by interactions and mergers with satellites. BCG evolution is also deeply influenced by the presence of gas heating sources such as Active Galactic Nuclei (AGNs) that prevent catastrophic cooling of large amounts of gas. We show that AGN feedback is one of the most important mechanisms in shaping the properties of BCGs at low redshift by analysing our statistical sample of simulations with and without AGN feedback. When AGN feedback is included BCG masses, sizes, star formation rates and kinematic properties are closer to those of the observed systems. Some small discrepancies are observed only for the most massive BCGs, an effect that might be du...

  4. Surface photometry of brightest cluster galaxies and intracluster stars in ΛCDM

    Science.gov (United States)

    Cooper, A. P.; Gao, L.; Guo, Q.; Frenk, C. S.; Jenkins, A.; Springel, V.; White, S. D. M.

    2015-08-01

    We simulate the phase-space distribution of stellar mass in nine massive Λ cold dark matter galaxy clusters by applying the semi-analytic particle tagging method of Cooper et al. to the Phoenix suite of high-resolution N-body simulations (M200 ≈ 7.5-33 × 1014 M⊙). The resulting surface brightness (SB) profiles of brightest cluster galaxies (BCGs) match well to observations. On average, stars formed in galaxies accreted by the BCG account for ≳90 per cent of its total mass (the remainder is formed in situ). In circular BCG-centred apertures, the superposition of multiple debris clouds (each ≳10 per cent of the total BCG mass) from different progenitors can result in an extensive outer diffuse component, qualitatively similar to a `cD envelope'. These clouds typically originate from tidal stripping at z ≲ 1 and comprise both streams and the extended envelopes of other massive galaxies in the cluster. Stars at very low SB contribute a significant fraction of the total cluster stellar mass budget: in the central 1 Mpc2 of a z ˜ 0.15 cluster imaged at SDSS-like resolution, our fiducial model predicts 80-95 per cent of stellar mass below a SB of μV ˜ 26.5 mag arcsec-2 is associated with accreted stars in the envelope of the BCG. The ratio of BCG stellar mass (including this diffuse component) to total cluster stellar mass is ˜30 per cent.

  5. Abell 262 and RXJ0341: Two Brightest Cluster Galaxies with Line Emission Blanketing a Cool Core

    Science.gov (United States)

    Edwards, Louise O. V.; Heng, Renita

    2014-08-01

    Over the last decade, integral field (IFU) analysis of the brightest cluster galaxies (BCGs) in several cool core clusters has revealed the central regions of these massive old red galaxies to be far from dead. Bright line emission alongside extended X-ray emission links nearby galaxies, is superposed upon vast dust lanes and extends out in long thin filaments from the galaxy core. Yet, to date no unifying picture has come into focus, and the activity across systems is currently seen as a grab-bag of possibile emission line mechanisms. Our primary goal is to work toward a consistent picture for why the BCGs seem are undergoing a renewed level of activity. One problem is most of the current data remains focused on mapping the very core of the BCG, but neglects surrounding galaxies. We propose to discover the full extent of line emission in a complementary pair of BCGs. In Abell 262, an extensive dust patch screens large portions of an otherwise smooth central galaxy, whereas RXJ0341 appears to be a double-core dust free BCG. We will map the full extent of the line emission in order to deduce whether the line emission is a product of local interactions, or the large-scale cluster X-ray gas. The narrow band filter set and large FOV afforded by the the Mayall MOSAIC-1 (MOSA) imager allows us to concurrently conduct an emission line survey of both clusters, locating all line emitting members and beginning a search for the effect of the environment of the different regions (outskirts vs. cluster core) out to the virial radius. We will combine our results with publically available data from 2MASS to determine the upper limits on specific star formation in the BCG and other cluster galaxies within the cluster virial radius.

  6. Missing black holes in brightest cluster galaxies as evidence for the occurrence of superkicks in nature

    CERN Document Server

    Gerosa, Davide

    2014-01-01

    We investigate the consequences of superkicks on the population of supermassive black holes (SMBHs) in the Universe residing in brightest cluster galaxies (BCGs). BCGs are the most massive galaxies in the Universe, sitting at the center of galaxy clusters. There is strong observational evidence that they grew prominently at late times (up to a factor 2-4 in mass from z=1), mainly through mergers with satellite galaxies from the cluster, and they host the most massive SMBHs ever observed, with masses up to ten billion solar masses. Those SMBHs are also expected to grow hierarchically, together with their host galaxies, experiencing a series of mergers with other SMBHs brought in by merging satellites. Because of the asymmetric gravitational wave emission, some net linear momentum is emitted during the last stages of the binary inspiral and the remnant SMBH experiences a kick in the opposite direction. Kicks may be as large as ~5000 Km/s ("superkicks"), pushing the SMBHs out in the cluster outskirts for a time ...

  7. The XMM Cluster Survey: The interplay between the brightest cluster galaxy and the intra-cluster medium via AGN feedback

    CERN Document Server

    Stott, John P; Edge, Alastair C; Collins, Chris A; Hilton, Matt; Harrison, Craig D; Romer, A Kathy; Rooney, Philip J; Kay, Scott T; Miller, Christopher J; Sahlen, Martin; Lloyd-Davies, Ed J; Mehrtens, Nicola; Hoyle, Ben; Liddle, Andrew R; Viana, Pedro T P; McCarthy, Ian G; Schaye, Joop; Booth, C M

    2012-01-01

    Using a sample of 123 X-ray clusters and groups drawn from the XMM-Cluster Survey first data release, we investigate the interplay between the brightest cluster galaxy (BCG), its black hole, and the intra-cluster/group medium (ICM). It appears that for groups and clusters with a BCG likely to host significant AGN feedback, gas cooling dominates in those with Tx > 2 keV while AGN feedback dominates below. This may be understood through the sub-unity exponent found in the scaling relation we derive between the BCG mass and cluster mass over the halo mass range 10^13 2 keV) and again co-located with an effective fuel supply of dense, cooling gas. This demonstrates that the most massive black holes appear to know more about their host cluster than they do about their host galaxy. The results lead us to propose a physically motivated, empirical definition of 'cluster' and 'group', delineated at 2 keV.

  8. The evolution in the stellar mass of Brightest Cluster Galaxies over the past 10 billion years

    CERN Document Server

    Bellstedt, Sabine; Muzzin, Adam; Franx, Marijn; Guatelli, Susanna; Hill, Allison R; Hoekstra, Henk; Kurinsky, Noah; Labbe, Ivo; Marchesini, Danilo; Marsan, Z Cemile; Safavi-Naeini, Mitra; Sifon, Cristobal; Stefanon, Mauro; van de Sande, Jesse; van Dokkum, Pieter; Weigel, Catherine

    2016-01-01

    Using a sample of 98 galaxy clusters recently imaged in the near infra-red with the ESO NTT, WIYN and WHT telescopes, supplemented with 33 clusters from the ESO archive, we measure how the stellar mass of the most massive galaxies in the universe, namely Brightest Cluster Galaxies (BCG), increases with time. Most of the BCGs in this new sample lie in the redshift range $0.2clusters, we create a subsample of 102 systems that includes only those clusters that have estimates of the cluster mass. We combine the BCGs in this subsample with BCGs from the literature, and find that the growth in stellar mass of BCGs from 10 billion years ago to the present epoch is broadly consistent with recent semi-analytic and semi-empirical models. As in other recent studies, tentative evidence indicates that the stellar mass growth rate of BCGs may be slowing in the past 3.5 billi...

  9. Close companions to Brightest Cluster Galaxies: Support for minor mergers and downsizing

    CERN Document Server

    Edwards, Louise O V

    2012-01-01

    We identify close companions of Brightest Cluster Galaxies (BCGs) for the purpose of quantifying the rate at which these galaxies grow via mergers. By exploiting deep photometric data from the CFHTLS, we probe the number of companions per BCG (Nc) with luminosity ratios down to those corresponding to potential minor mergers of 20:1. We also measure the average luminosity in companions per galaxy (Lc). We find that Nc and Lc rise steeply with luminosity ratio for both the BCGs, and a control sample of other bright, red, cluster galaxies. The trend for BCGs rises more steeply, resulting in a larger number of close companions. For companions within 50kpc of a BCG, Nc= 1.38+/-0.14 and Lc=(2.14+/-0.31)x10^(10)L_sun and for companions within 50kpc of a luminosity matched control sample of non-BCGs, Nc=0.87+/-0.08 and Lc=(1.48+/-0.20)x10^(10)L_sun. This suggests that the BCGs are likely to undergo more mergers compared to otherwise comparable luminous galaxies. Additionally, compared to a local sample of luminous re...

  10. THE ROLE OF DRY MERGERS FOR THE FORMATION AND EVOLUTION OF BRIGHTEST CLUSTER GALAXIES

    International Nuclear Information System (INIS)

    Using a resimulation technique, we perform high-resolution cosmological simulations of dry mergers in a massive (1015 M sun) galaxy cluster identified in the Millennium Run. Our initial conditions include well resolved compound galaxy models consisting of dark matter halos and stellar bulges that are used to replace the most massive cluster progenitor halos at redshift z = 3, allowing us to follow the subsequent dry merger processes that build up the cluster galaxies in a self-consistent cosmological setting. By construction, our galaxy models obey the stellar mass-size relation initially. Also, we study both galaxy models with adiabatically contracted and uncompressed halos. We demonstrate that the brightest cluster galaxy (BCG) evolves away from the Kormendy relation as defined by the smaller mass galaxies (i.e., the relation bends). This is accompanied by a significantly faster dark matter mass growth within the half-light radius of the BCG compared to the increase in the stellar mass inside the same radius. As a result of the comparatively large number of mergers the BCG experiences, its total mass-to-light ratio becomes significantly higher than in typical elliptical galaxies. We also show that the mixing processes between dark matter and stars lead to a small but numerically robust tilt in the fundamental plane and that the BCG lies on the tilted plane. Our model is consistent with the observed steepening of the logarithmic mass-to-light gradient as a function of the stellar mass. As we have not included effects from gas dynamics or star formation, these trends are exclusively due to N-body and stellar dynamical effects. Surprisingly, we find only tentative weak distortion in the Faber-Jackson relation that depends on the aperture size, unlike expected based on studies of isolated merger simulations. This may be due to differences in the distribution of galaxy orbits, which is given in our approach directly by the cosmological context while it has to be

  11. The formation of the brightest cluster galaxies in cosmological simulations: the case for active galactic nucleus feedback

    OpenAIRE

    Martizzi, Davide; Teyssier, Romain; Moore, Ben

    2012-01-01

    We use 500 pc resolution cosmological simulations of a Virgo-like galaxy cluster to study the properties of the brightest cluster galaxy (BCG) that forms at the centre of the halo. We compared two simulations; one incorporating only supernova feedback and a second that also includes prescriptions for black hole growth and the resulting active galactic nucleus (AGN) feedback from gas accretion. As previous work has shown, with supernova feedback alone we are unable to reproduce any of the obse...

  12. Major Dry-Mergers In Early-Type Brightest Cluster Galaxies

    CERN Document Server

    Liu, F S; Deng, Z G; Xia, X Y; Wen, Z L

    2009-01-01

    We search for ongoing major dry-mergers in a well selected sample of local Brightest Cluster Galaxies (BCGs) from the C4 cluster catalogue. 18 out of 515 early-type BCGs with redshift between 0.03 and 0.12 are found to be in major dry-mergers, which are selected as pairs (or triples) with $r$-band magnitude difference $\\dm<1.5$ and projected separation $\\rp<30$ kpc, and showing signatures of interaction in the form of significant asymmetry in residual images. We find that the fraction of BCGs in major dry-mergers increases with the richness of the clusters, consistent with the fact that richer clusters usually have more massive (or luminous) BCGs. We estimate that present-day early-type BCGs may have experienced on average $\\sim 0.6 (\\tmerge/0.3\\Gyr)^{-1}$ major dry-mergers and through this process increases their luminosity (mass) by $15% (\\tmerge/0.3\\Gyr)^{-1} (\\fmass/0.5)$ on average since $z=0.7$, where $\\tmerge$ is the merging timescale and $\\fmass$ is the mean mass fraction of companion galaxies a...

  13. The Link Between Morphology and Structure of Brightest Cluster Galaxies: Automatic Identification of cDs

    CERN Document Server

    Zhao, Dongyao; Conselice, Christopher J

    2015-01-01

    We study a large sample of 625 low-redshift brightest cluster galaxies (BCGs) and link their morphologies to their structural properties. We derive visual morphologies and find that ~57% of the BCGs are cD galaxies, ~13% are ellipticals, and ~21% belong to the intermediate classes mostly between E and cD. There is a continuous distribution in the properties of the BCG's envelopes, ranging from undetected (E class) to clearly detected (cD class), with intermediate classes (E/cD and cD/E) showing the increasing degrees of the envelope presence. A minority (~7%) of BCGs have disk morphologies, with spirals and S0s in similar proportions, and the rest (~2%) are mergers. After carefully fitting the galaxies light distributions by using one-component (Sersic) and two-component (Sersic+Exponential) models, we find a clear link between the BCGs morphologies and their structures and conclude that a combination of the best-fit parameters derived from the fits can be used to separate cD galaxies from non-cD BCGs. In par...

  14. A Stacked Analysis of Brightest Cluster Galaxies Observed with the Fermi Large Area Telescope

    CERN Document Server

    Dutson, K L; Edge, A C; Hinton, J A; Hogan, M T

    2012-01-01

    We present the results of a search for high-energy gamma-ray emission from a large sample of galaxy clusters sharing the properties of three existing Fermi-LAT detections (in Perseus, Virgo and Abell 3392), namely a powerful radio source within their brightest cluster galaxy (BCG). From a parent, X-ray flux-limited sample of clusters, we select 114 systems with a core-dominated BCG radio flux above 50 or 75 mJy, stacking data from the first 45 months of the Fermi mission, to determine statistical limits on the gamma-ray fluxes of the ensemble of candidate sources. For a >300 MeV selection, the distribution of detection significance across the sample is consistent with that across control samples for significances 4 sigma signals which are not associated with previously identified gamma-ray emission. Modelling of the data in these fields results in the detection of four non-2FGL Fermi sources, though none appear to be unambiguously associated with the BCG candidate. A search at energies >3 GeV hints at emissio...

  15. Ultraviolet Morphologies and Star-Formation Rates of CLASH Brightest Cluster Galaxies

    CERN Document Server

    Donahue, Megan; Fogarty, Kevin; Li, Yuan; Voit, G Mark; Postman, Marc; Koekemoer, Anton; Moustakas, John; Bradley, Larry; Ford, Holland

    2015-01-01

    Brightest cluster galaxies (BCGs) are usually quiescent, but many exhibit star formation. Here we exploit the opportunity provided by rest-frame UV imaging of galaxy clusters in the CLASH (Cluster Lensing and Supernovae with Hubble) Multi-Cycle Treasury Project to reveal the diversity of UV morphologies in BCGs and to compare them with recent simulations of the cool, star-forming gas structures produced by precipitation-driven feedback. All of the CLASH BCGs are detected in the rest-frame UV (280 nm), regardless of their star-formation activity, because evolved stellar populations produce a modest amount of UV light that traces the relatively smooth, symmetric, and centrally peaked stellar distribution seen in the near infrared. Ultraviolet morphologies among the BCGs with strong UV excesses exhibit distinctive knots, multiple elongated clumps, and extended filaments of emission that distinctly differ from the smooth profiles of the UV-quiet BCGs. These structures, which are similar to those seen in the few s...

  16. THE BRIGHTEST CLUSTER GALAXY IN A85: THE LARGEST CORE KNOWN SO FAR

    Energy Technology Data Exchange (ETDEWEB)

    López-Cruz, O.; Añorve, C.; Ibarra-Medel, H. J. [Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), Astrofísica, Luis Enrique Erro No.1, Tonantzintla, Pue., C.P. 72840 (Mexico); Birkinshaw, M.; Worrall, D. M. [HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL (United Kingdom); Barkhouse, W. A. [Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND 58202 (United States); Torres-Papaqui, J. P. [Departamento de Astronomía, Universidad de Guanajuato (DAUG), Callejón Jalisco S/N Col. Valenciana, C.P. 36240 Guanajuato, Gto. (Mexico); Motta, V., E-mail: omarlx@inaoep.mx [Instituto de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111 Varaíso (Chile)

    2014-11-10

    We have found that the brightest cluster galaxy (BCG) in A85, Holm 15A, displays the largest core known so far. Its cusp radius, r {sub γ} = 4.57 ± 0.06 kpc (4.''26 ± 0.''06), is more than 18 times larger than the mean for BCGs and ≳ 1 kpc larger than A2261-BCG, hitherto the largest-cored BCG. Holm 15A hosts the luminous amorphous radio source 0039-095B and has the optical signature of a LINER. Scaling laws indicate that this core could host a supermassive black hole (SMBH) of mass M {sub •} ∼ (10{sup 9}-10{sup 11}) M {sub ☉}. We suggest that cores this large represent a relatively short phase in the evolution of BCGs, whereas the masses of their associated SBMH might be set by initial conditions.

  17. The Brightest Cluster Galaxy in Abell 85: The Largest Core Known so far

    CERN Document Server

    Lopez-Cruz, O; Birkinshaw, M; Worrall, D M; Ibarra-Medel, H J; Torres-Papaqui, J P; Barkhouse, W A; Motta, V

    2014-01-01

    We have found that the brightest cluster galaxy in Abell~85, Holm 15A, is the largest core so far known. Its cusp radius r = 4.57 +/- 0.06 kpc (4.26 +\\- 0.06 arcsec) is more than 18 times larger than the mean for BCGs, and >1 kpc larger than A2261-BCG, the former largest core BCG (Postman et al. 2012). Holm~15A hosts the luminous amorphous radio source 0039-095B and has the optical signature of a LINER. Scaling laws suggest that this core hosts a supermassive black hole (SMBH) of mass MBH~(10^9-10^11) solar masses. We suggest that a common mechanism is responsible for the formation of cores over a wide range of scales.

  18. THE BLACK HOLE MASS IN THE BRIGHTEST CLUSTER GALAXY NGC 6086

    International Nuclear Information System (INIS)

    We present the first direct measurement of the central black hole mass, M., in NGC 6086, the Brightest Cluster Galaxy (BCG) in A2162. Our investigation demonstrates for the first time that stellar-dynamical measurements of M. in BCGs are possible beyond the nearest few galaxy clusters. We observed NGC 6086 with laser guide star adaptive optics and the integral-field spectrograph (IFS) OSIRIS at the W. M. Keck Observatory and with the seeing-limited IFS GMOS-N at Gemini Observatory North. We combined the IFS data sets with existing major-axis kinematics and used axisymmetric stellar orbit models to determine M. and the R-band stellar mass-to-light ratio, M*/LR . We find M. = 3.6+1.7-1.1 x 109 Msun and M*/LR = 4.6+0.3-0.7 Msun Lsun-1 (68% confidence) from models using the most massive dark matter halo allowed within the gravitational potential of the host cluster. Models fitting only IFS data confirm M. ∼ 3 x 109 Msun and M*/LR ∼ 4 Msun Lsun-1, with weak dependence on the assumed dark matter halo structure. When data out to 19 kpc are included, the unrealistic omission of dark matter causes the best-fit black hole mass to decrease dramatically, to 0.6 x 109 Msun, and the best-fit stellar mass-to-light ratio to increase to 6.7 Msun L -1sun,R. The latter value is at further odds with stellar population studies favoring M*/LR ∼ 2 Msun L -1sun. Biases from dark matter omission could extend to dynamical models of other galaxies with stellar cores, and revised measurements of M. could steepen the empirical scaling relationships between black holes and their host galaxies.

  19. A candidate supermassive binary black hole system in the brightest cluster galaxy of RBS 797

    CERN Document Server

    Gitti, M; Giovannini, G; Feretti, L; Liuzzo, E

    2013-01-01

    The radio source at the center of the cool core galaxy cluster RBS 797 (z=0.35) is known to exhibit a misalignment of its radio jets and lobes observed at different VLA-scale, with the innermost kpc-scale jets being almost orthogonal to the radio emission which extends for tens of kpc filling the X-ray cavities. Gitti et al. suggested that this peculiar radio morphology may indicate a recurrent activity of the central radio source, where the jet orientation is changing between the different outbursts due to the effects of supermassive binary black holes (SMBBHs). We aim at unveiling the nuclear radio properties of the brightest cluster galaxy (BCG) in RBS 797 and at investigating the presence of a SMBBH system in its center. We have performed new high-resolution observations at 5 GHz with the European VLBI Network (EVN), reaching an angular resolution of 9x5 mas^2 and a sensitivity of 36 microJy/beam. We report the EVN detection of two compact components in the BCG of RBS 797, with a projected separation of ~...

  20. A Suzaku search for dark matter emission lines in the X-ray brightest galaxy clusters

    Science.gov (United States)

    Urban, O.; Werner, N.; Allen, S. W.; Simionescu, A.; Kaastra, J. S.; Strigari, L. E.

    2015-08-01

    We present the results of a search for unidentified emission lines in deep Suzaku X-ray spectra of the central regions of the X-ray brightest galaxy clusters: Perseus, Coma, Virgo and Ophiuchus. We analyse an optimized energy range (3.2-5.3 keV) that is relatively free of instrumental features, and a plasma emission model incorporating the abundances of elements with the strongest expected emission lines at these energies (S, Ar, Ca) as free parameters. For the Perseus Cluster core, employing this model, we find evidence for an additional emission feature at an energy E=3.51^{+0.02}_{-0.01} keV with a flux of 2.87_{-0.38}^{+0.33}× 10^{-7} photons s^{-1} cm^{-2} arcmin^{-2}. At slightly larger radii, we detect an emission line at 3.59 ± 0.02 keV with a flux of 4.8_{-1.4}^{+1.7}× 10^{-8} photons s^{-1} cm^{-2} arcmin^{-2}. The properties of these features are broadly consistent with previous claims, although the radial variation of the line strength appears in tension with dark matter (DM) decay model predictions. Assuming a decaying DM origin for these features allows us to predict the energies and detected line fluxes for the other clusters. We do not detect an emission feature at the predicted energy and line flux in the Coma, Virgo and Ophiuchus clusters. The formal 99.5 per cent upper limits on the line strengths in each cluster are well below the decaying DM model predictions, disfavouring a decaying DM interpretation. The results of further analysis suggest that systematic effects associated with modelling the spectra for the Perseus Cluster, details of the assumed ionization balance and errors in the predicted spectral line emissivities may be largely responsible for the ˜3.55 keV feature.

  1. The regulation of star formation in cool-core clusters: imprints on the stellar populations of brightest cluster galaxies

    CERN Document Server

    Loubser, S I; Hoekstra, H; Mahdavi, A; Donahue, M; Bildfell, C; Voit, G M

    2015-01-01

    A fraction of brightest cluster galaxies (BCGs) shows bright emission in the UV and the blue part of the optical spectrum, which has been interpreted as evidence of recent star formation. Most of these results are based on the analysis of broadband photometric data. Here, we study the optical spectra of a sample of 19 BCGs hosted by X-ray luminous galaxy clusters at 0.15 < z < 0.3, a subset from the Canadian Cluster Comparison Project (CCCP) sample. We identify plausible star formation histories of the galaxies by fitting Simple Stellar Populations (SSPs) as well as composite populations, consisting of a young stellar component superimposed on an intermediate/old stellar component, to accurately constrain their star formation histories. We detect prominent young (~200 Myr) stellar populations in 4 of the 19 galaxies. Of the four, the BCG in Abell 1835 shows remarkable A-type stellar features indicating a relatively large population of young stars, which is extremely unusual even amongst star forming BCG...

  2. Evolution of the brightest cluster galaxies: the influence of morphology, stellar mass and environment

    CERN Document Server

    Zhao, Dongyao; Conselice, Christopher J

    2015-01-01

    Using a sample of 425 nearby Brightest Cluster Galaxies (BCGs) from von der Linden et al. (2007), we study the relationship between their internal properties (stellar masses, structural parameters and morphologies) and their environment. More massive BCGs tend to inhabit denser regions and more massive clusters than lower mass BCGs. Furthermore, cDs, which are BCGs with particularly extended envelopes, seem to prefer marginally denser regions and tend to be hosted by more massive halos than elliptical BCGs. cD and elliptical BCGs show parallel positive correlations between their stellar masses and environmental densities. However, at a fixed environmental density, cDs are, on average, ~40% more massive. Our results, together with the findings of previous studies, suggest an evolutionary link between elliptical and cD BCGs. We suggest that most present-day cDs started their life as ellipticals, which subsequently grew in stellar mass and size due to mergers. In this process, the cD envelope developed. The larg...

  3. Ongoing growth of the brightest cluster galaxies via major dry mergers in the last ~6 Gyr

    CERN Document Server

    Lei, F J; Jiang, D F

    2014-01-01

    Brightest Cluster Galaxies (BCGs) might have been assembled relatively late (z<1) via mergers. By exploiting the high-resolution HST/ACS imaging, we find four BCGs (COSMOS-P 125516, 102810, 036694 and 089357) in major dry merging in 29 X-ray clusters at $0.3 \\le z \\le 0.6$ in the Cosmological Evolutionary Survey (COSMOS). These BCGs show prominent but quiescent double nuclei with a magnitude difference of $\\delta m<1.5$ and a projected separation of $r_p<$ 10 kpc. Clear signatures of interaction such as extended plumes and/or significant asymmetries are also observed in their residual images. We infer a major merger rate of $0.55\\pm0.27$ merger per Gyr at $z\\sim0.43$ assuming the merger time-scale estimate of Kitzbichler & White (2008). This inferred rate is significantly higher than the rate in the local Universe ($0.12\\pm0.03$ at $z\\sim0.07$) presented in Liu et al. (2009). We estimate that present-day BCGs increase their luminosity (mass) by $\\sim35\\pm15$ per cent $(f_{mass}/0.5)$ via major dr...

  4. A Suzaku Search for Dark Matter Emission Lines in the X-ray Brightest Galaxy Clusters

    CERN Document Server

    Urban, O; Allen, S W; Simionescu, A; Kaastra, J S; Strigari, L E

    2014-01-01

    We present the results of a search for unidentified emission lines in deep Suzaku X-ray spectra for the central regions of the four X-ray brightest galaxy clusters: Perseus, Coma, Virgo and Ophiuchus. We employ an optimized energy range for our analysis (3.2-5.3 keV) that is relatively free of instrumental features, and a baseline plasma emission model that incorporates the abundances of elements with the strongest expected emission lines at these energies (S, Ar, Ca) as free parameters. For the Perseus Cluster core, employing this baseline model, we find evidence for an additional emission feature at an energy $3.51^{+0.02}_{-0.01}$ keV with a flux of ~$2.87\\times10^{-7}$ ph/s/cm^2/arcmin^2. At slightly larger radii, we detect an emission line at 3.59+/-0.02 keV with a flux of ~$4.8\\times10^{-8}$ ph/s/cm^2/arcmin^2. The energies and fluxes of these features are broadly consistent with previous claims, although the radial variation of the line strength appears in tension with standard dark matter (DM) model p...

  5. The XMM Cluster Survey: The build up of stellar mass in Brightest Cluster Galaxies at high redshift

    CERN Document Server

    Stott, J P; Sahlen, M; Hilton, M; Lloyd-Davies, E; Capozzi, D; Hosmer, M; Liddle, A R; Mehrtens, N; Miller, C J; Romer, A K; Stanford, S A; Viana, P T P; Davidson, M; Hoyle, B; Kay, S T; Nichol, R C

    2010-01-01

    We present deep J and Ks band photometry of 20 high redshift galaxy clusters between z=0.8-1.5, 19 of which are observed with the MOIRCS instrument on the Subaru Telescope. By using near-infrared light as a proxy for stellar mass we find the surprising result that the average stellar mass of Brightest Cluster Galaxies (BCGs) has remained constant at ~9e11MSol since z~1.5. We investigate the effect on this result of differing star formation histories generated by three well known and independent stellar population codes and find it to be robust for reasonable, physically motivated choices of age and metallicity. By performing Monte Carlo simulations we find that the result is unaffected by any correlation between BCG mass and cluster mass in either the observed or model clusters. The large stellar masses imply that the assemblage of these galaxies took place at the same time as the initial burst of star formation. This result leads us to conclude that dry merging has had little effect on the average stellar ma...

  6. Starbursting brightest cluster galaxy: a Herschel view of the massive cluster MACS J1931.8-2634

    Science.gov (United States)

    Santos, J. S.; Balestra, I.; Tozzi, P.; Altieri, B.; Valtchanov, I.; Mercurio, A.; Nonino, M.; Yu, Heng; Rosati, P.; Grillo, C.; Medezinski, E.; Biviano, A.

    2016-02-01

    We investigate the dust-obscured star formation (SF) properties of the massive, X-ray-selected galaxy cluster MACS J1931.8-2634 at z = 0.352. Using far-infrared (FIR) imaging in the range 100-500 μm obtained with the Herschel telescope, we extract 31 sources (2σ) within r ˜ 1 Mpc from the brightest cluster galaxy (BCG). Among these sources, we identify six cluster members for which we perform an analysis of their spectral energy distributions (SEDs). We measure total infrared luminosity (LIR), star formation rate (SFR) and dust temperature. The BCG, with LIR = 1.4 × 1012 L⊙ is an ultraluminous infrared galaxy and hosts a type-II active galactic nuclei (AGN). We decompose its FIR SED into AGN and starburst components and find equal contributions from AGN and starburst. We also recompute the SFR of the BCG finding SFR = 150 ± 15 M⊙ yr-1. We search for an isobaric cooling flow in the cool core using Chandra X-ray data, and find no evidence for gas colder than 1.8 keV in the inner 30 kpc, for an upper limit to the instantaneous mass-deposition rate of 58 M⊙ yr-1 at 95 per cent c.l. This value is 3× lower than the SFR in the BCG, suggesting that the on-going SF episode lasts longer than the intracluster medium cooling events.

  7. Starbursting Brightest Cluster Galaxy: a Herschel view of the massive cluster MACS J1931.8-2634

    CERN Document Server

    Santos, J S; Tozzi, P; Altieri, B; Valtchanov, I; Mercurio, A; Nonino, M; Yu, Heng; Rosati, P; Grillo, C; Medezinski, E; Biviano, A

    2015-01-01

    We investigate the dust-obscured star formation properties of the massive, X-ray selected galaxy cluster MACS J1931.8-2634 at $z$=0.352. Using far-infrared (FIR) imaging in the range 100-500$\\mu$m obtained with the \\textit{Herschel} telescope, we extract 31 sources (2$\\sigma$) within $r\\sim$1 Mpc from the brightest cluster galaxy (BCG). Among these sources we identify six cluster members for which we perform an analysis of their spectral energy distributions (SEDs). We measure total infrared luminosity (L$_{IR}$), star formation rate (SFR) and dust temperature. The BCG, with L$_{IR}$=1.4$\\times$10$^{12}$L$_\\odot$ is an Ultra Luminous Infrared Galaxy and hosts a type II AGN. We decompose its FIR SED into AGN and starburst components and find equal contributions from AGN and starburst. We also recompute the SFR of the BCG finding SFR=150$\\pm$15 M$_\\odot$yr$^{-1}$. We search for an isobaric cooling flow in the cool core using {\\sl Chandra} X-ray data, and find no evidence for gas colder than 1.8 keV in the inner...

  8. Massive molecular gas flows in the Abell 1664 brightest cluster galaxy

    CERN Document Server

    Russell, H R; Edge, A C; Nulsen, P E J; Main, R A; Vantyghem, A N; Combes, F; Fabian, A C; Murray, N; Salome, P; Wilman, R J; Baum, S A; Donahue, M; O'Dea, C P; Oonk, J B R; Tremblay, G R; Voit, G M

    2013-01-01

    We report ALMA Early Science CO(1-0) and CO(3-2) observations of the brightest cluster galaxy (BCG) in Abell 1664. The BCG contains 1.1x10^{10} solar masses of molecular gas divided roughly equally between two distinct velocity systems: one from -250 to +250 km/s centred on the BCG's systemic velocity and a high velocity system blueshifted by 570 km/s with respect to the systemic velocity. The BCG's systemic component shows a smooth velocity gradient across the BCG center with velocity proportional to radius suggestive of solid body rotation about the nucleus. However, the mass and velocity structure are highly asymmetric and there is little star formation coincident with a putative disk. It may be an inflow of gas that will settle into a disk over several 10^8 yr. The high velocity system consists of two gas clumps, each ~2 kpc across, located to the north and southeast of the nucleus. Each has a line of sight velocity spread of 250-300 km/s. The velocity of the gas in the high velocity system tends to incre...

  9. The regulation of star formation in cool-core clusters: imprints on the stellar populations of brightest cluster galaxies

    Science.gov (United States)

    Loubser, S. I.; Babul, A.; Hoekstra, H.; Mahdavi, A.; Donahue, M.; Bildfell, C.; Voit, G. M.

    2016-02-01

    A fraction of brightest cluster galaxies (BCGs) show bright emission in the ultraviolet and the blue part of the optical spectrum, which has been interpreted as evidence of recent star formation. Most of these results are based on the analysis of broad-band photometric data. Here, we study the optical spectra of a sample of 19 BCGs hosted by X-ray luminous galaxy clusters at 0.15 BCG in Abell 1835 shows remarkable A-type stellar features indicating a relatively large population of young stars, which is extremely unusual even amongst star-forming BCGs. We constrain the mass contribution of these young components to the total stellar mass to be typically between 1 and 3 per cent, but rising to 7 per cent in Abell 1835. We find that the four of the BCGs with strong evidence for recent star formation (and only these four galaxies) are found within a projected distance of 5 kpc of their host cluster's X-ray peak, and the diffuse, X-ray gas surrounding the BCGs exhibits a ratio of the radiative cooling-to-free-fall time (tc/tff) of ≤10. These are also some of the clusters with the lowest central entropy. Our results are consistent with the predictions of the precipitation-driven star formation and active galactic nucleus feedback model, in which the radiatively cooling diffuse gas is subject to local thermal instabilities once the instability parameter tc/tff falls below ˜10, leading to the condensation and precipitation of cold gas. The number of galaxies in our sample where the host cluster satisfies all the criteria for recent and ongoing star formation is small, but their stellar populations suggest a time-scale for star formation to restart of the order of ˜200 Myr.

  10. STAR FORMATION AND UV COLORS OF THE BRIGHTEST CLUSTER GALAXIES IN THE REPRESENTATIVE XMM-NEWTON CLUSTER STRUCTURE SURVEY

    International Nuclear Information System (INIS)

    We present UV broadband photometry and optical emission-line measurements for a sample of 32 brightest cluster galaxies (BCGs) in clusters of the Representative XMM-Newton Cluster Structure Survey (REXCESS) with z = 0.06-0.18. The REXCESS clusters, chosen to study scaling relations in clusters of galaxies, have X-ray measurements of high quality. The trends of star formation and BCG colors with BCG and host properties can be investigated with this sample. The UV photometry comes from the XMM-Newton Optical Monitor, supplemented by existing archival Galaxy Evolution Explorer photometry. We detected Hα and forbidden line emission in seven (22%) of these BCGs, in optical spectra obtained using the Southern Astrophysical Research Goodman spectrograph. All of these emission-line BCGs occupy clusters classified as cool cores (CCs) based on the central cooling time in the cluster core, for an emission-line incidence rate of 70% for BCGs in REXCESS CC clusters. Significant correlations between the Hα equivalent widths, excess UV production in the BCG, and the presence of dense, X-ray bright intracluster gas with a short cooling time are seen, including the fact that all of the Hα emitters inhabit systems with short central cooling times and high central intracluster medium densities. Estimates of the star formation rates based on Hα and UV excesses are consistent with each other in these seven systems, ranging from 0.1to8 solar masses per year. The incidence of emission-line BCGs in the REXCESS sample is intermediate, somewhat lower than in other X-ray-selected samples (∼35%), and somewhat higher than but statistically consistent with optically selected, slightly lower redshift BCG samples (∼10%-15%). The UV-optical colors (UVW1 - R ∼4.7 ± 0.3) of REXCESS BCGs without strong optical emission lines are consistent with those predicted from templates and observations of ellipticals dominated by old stellar populations. We see no trend in UV-optical colors with

  11. The photometric properties of brightest cluster galaxies. II - SIT and CCD surface photometry

    Science.gov (United States)

    Hoessel, J. G.

    1980-01-01

    Surface photometry of the first-ranked galaxy in 108 Abell clusters is presented. Galaxy structure, as parameterized by simple Hubble law models, is found to correlate with galaxy absolute magnitude and cluster structure. All the structure data support the dynamical friction evolution model. Twenty-eight percent of the galaxies have multiple component nuclei; the short lifetimes of such systems provide the best available evidence that ongoing evolution actually occurs. Average magnitude and structure evolution rates are derived from the data.

  12. The evolution of the brightest cluster galaxies since z~1 from the ESO Distant Cluster Survey (EDisCS)

    CERN Document Server

    Whiley, I M; De Lucia, G; Von der Linden, A; Bamford, S P; Best, P; Bremer, M N; Jablonka, P; Johnson, O; Milvang-Jensen, B; Noll, S; Poggianti, B M; Rudnick, G; Saglia, R; White, S; Zaritsky, D

    2008-01-01

    [Abridged] We present K-band data for the brightest cluster galaxies (BCGs) from the ESO Distant Cluster Survey. These data are combined with photometry from Aragon-Salamanca et al. (1998) and a low-redshift comparison sample from von der Linden et al. (2007). The K-band Hubble diagram for BCGs exhibits very low scatter (~0.35mag) since z=1. The colour and $K$-band luminosity evolution of the BCGs are in good agreement with passively-evolving stellar populations formed at z>2. We do not detect any significant change in the stellar mass of the BCG since z~1. These results do not seem to depend on the velocity dispersion of the parent cluster. There is a correlation between the 1D velocity dispersion of the clusters and the K-band luminosity of the BCGs (after correcting for passive evolution). The clusters with large velocity dispersions tend to have brighter BCGs, i.e., BCGs with larger stellar masses. This dependency, although significant, is relatively weak: the stellar mass of the BCGs changes only by ~70%...

  13. A 1010 solar mass flow of molecular gas in the A1835 brightest cluster galaxy

    International Nuclear Information System (INIS)

    We report ALMA Early Science observations of the A1835 brightest cluster galaxy (BCG) in the CO (3-2) and CO (1-0) emission lines. We detect 5 × 1010 M ☉ of molecular gas within 10 kpc of the BCG. Its ensemble velocity profile width of ∼130 km s–1 FWHM is too narrow for the molecular clouds to be supported in the galaxy by dynamic pressure. The gas may instead be supported in a rotating, turbulent disk oriented nearly face-on. Roughly 1010 M ☉ of molecular gas is projected 3-10 kpc to the northwest and to the east of the nucleus with line-of-sight velocities lying between –250 km s–1 and +480 km s–1 with respect to the systemic velocity. The high-velocity gas may be either inflowing or outflowing. However, the absence of high-velocity gas toward the nucleus that would be expected in a steady inflow, and its bipolar distribution on either side of the nucleus, are more naturally explained as outflow. Star formation and radiation from the active galactic nucleus (AGN) are both incapable of driving an outflow of this magnitude. The location of the high-velocity gas projected behind buoyantly rising X-ray cavities and favorable energetics suggest an outflow driven by the radio AGN. If so, the molecular outflow may be associated with a hot outflow on larger scales reported by Kirkpatrick and colleagues. The molecular gas flow rate of approximately 200 M ☉ yr–1 is comparable to the star formation rate of 100-180 M ☉ yr–1 in the central disk. How radio bubbles would lift dense molecular gas in their updrafts, how much gas will be lost to the BCG, and how much will return to fuel future star formation and AGN activity are poorly understood. Our results imply that radio-mechanical (radio-mode) feedback not only heats hot atmospheres surrounding elliptical galaxies and BCGs, but it is able to sweep higher density molecular gas away from their centers.

  14. THE XMM CLUSTER SURVEY: THE BUILD-UP OF STELLAR MASS IN BRIGHTEST CLUSTER GALAXIES AT HIGH REDSHIFT

    International Nuclear Information System (INIS)

    We present deep J- and Ks -band photometry of 20 high redshift galaxy clusters between z = 0.8 and1.5, 19 of which are observed with the MOIRCS instrument on the Subaru telescope. By using near-infrared light as a proxy for stellar mass we find the surprising result that the average stellar mass of Brightest Cluster Galaxies (BCGs) has remained constant at ∼9 x 1011 M sun since z ∼ 1.5. We investigate the effect on this result of differing star formation histories generated by three well-known and independent stellar population codes and find it to be robust for reasonable, physically motivated choices of age and metallicity. By performing Monte Carlo simulations we find that the result is unaffected by any correlation between BCG mass and cluster mass in either the observed or model clusters. The large stellar masses imply that the assemblage of these galaxies took place at the same time as the initial burst of star formation. This result leads us to conclude that dry merging has had little effect on the average stellar mass of BCGs over the last 9-10 Gyr in stark contrast to the predictions of semi-analytic models, based on the hierarchical merging of dark matter halos, which predict a more protracted mass build-up over a Hubble time. However, we discuss that there is potential for reconciliation between observation and theory if there is a significant growth of material in the intracluster light over the same period.

  15. Massive molecular gas flows in the a1664 brightest cluster galaxy

    International Nuclear Information System (INIS)

    We report ALMA Early Science CO(1-0) and CO(3-2) observations of the brightest cluster galaxy (BCG) in A1664. The BCG contains 1.1 × 1010 M ☉ of molecular gas divided roughly equally between two distinct velocity systems: one from –250 to +250 km s–1 centered on the BCG's systemic velocity and a high-velocity system blueshifted by 570 km s–1 with respect to the systemic velocity. The BCG's systemic component shows a smooth velocity gradient across the BCG center, suggestive of rotation about the nucleus. However, the mass and velocity structure are highly asymmetric and there is little star formation coincident with a putative disk. It may be an inflow of gas that will settle into a disk over several 108 yr. The high-velocity system consists of two gas clumps, each ∼2 kpc across, located to the north and southeast of the nucleus. Each has a line of sight velocity spread of 250-300 km s–1. The velocity of the gas in the high-velocity system increases toward the BCG center and may be a massive flow into the nucleus. However, the velocity gradient is not smooth. These structures are also coincident with low optical-ultraviolet surface brightness regions, which could indicate dust extinction associated with each clump. The structure is complex, making a clear interpretation difficult, but if the dusty, molecular gas lies predominantly in front of the BCG, the blueshifted velocities would indicate an outflow. Based on the energy requirements, such a massive outflow would most likely be driven by the active galactic nucleus. A merger origin is unlikely but cannot be ruled out.

  16. Massive molecular gas flows in the a1664 brightest cluster galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Russell, H. R.; McNamara, B. R.; Main, R. A.; Vantyghem, A. N. [Department of Physics and Astronomy, University of Waterloo, Waterloo, ON N2L 3G1 (Canada); Edge, A. C.; Wilman, R. J. [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Nulsen, P. E. J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Combes, F.; Salomé, P. [L' Observatoire de Paris, 61 Av. de L' Observatoire, F-75 014 Paris (France); Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Murray, N. [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, M5S 3H8 Ontario (Canada); Baum, S. A.; O' Dea, C. P. [School of Physics and Astronomy, Rochester Institute of Technology, Rochester, NY 14623 (United States); Donahue, M.; Voit, G. M. [Department of Physics and Astronomy, Michigan State University, 567 Wilson Road, East Lansing, MI 48824 (United States); Oonk, J. B. R. [Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo (Netherlands); Tremblay, G. R. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany)

    2014-03-20

    We report ALMA Early Science CO(1-0) and CO(3-2) observations of the brightest cluster galaxy (BCG) in A1664. The BCG contains 1.1 × 10{sup 10} M {sub ☉} of molecular gas divided roughly equally between two distinct velocity systems: one from –250 to +250 km s{sup –1} centered on the BCG's systemic velocity and a high-velocity system blueshifted by 570 km s{sup –1} with respect to the systemic velocity. The BCG's systemic component shows a smooth velocity gradient across the BCG center, suggestive of rotation about the nucleus. However, the mass and velocity structure are highly asymmetric and there is little star formation coincident with a putative disk. It may be an inflow of gas that will settle into a disk over several 10{sup 8} yr. The high-velocity system consists of two gas clumps, each ∼2 kpc across, located to the north and southeast of the nucleus. Each has a line of sight velocity spread of 250-300 km s{sup –1}. The velocity of the gas in the high-velocity system increases toward the BCG center and may be a massive flow into the nucleus. However, the velocity gradient is not smooth. These structures are also coincident with low optical-ultraviolet surface brightness regions, which could indicate dust extinction associated with each clump. The structure is complex, making a clear interpretation difficult, but if the dusty, molecular gas lies predominantly in front of the BCG, the blueshifted velocities would indicate an outflow. Based on the energy requirements, such a massive outflow would most likely be driven by the active galactic nucleus. A merger origin is unlikely but cannot be ruled out.

  17. A Multi-Wavelength Photometric Census of AGN and Star Formation Activity in the Brightest Cluster Galaxies of X-ray Selected Clusters

    Science.gov (United States)

    Green, T. S.; Edge, A. C.; Stott, J. P.; Ebeling, H.; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Metcalfe, N.; Kaiser, N.; Wainscoat, R. J.; Waters, C.

    2016-06-01

    Despite their reputation as being "red and dead", the unique environment inhabited by Brightest Cluster Galaxies (BCGs) can often lead to a self-regulated feedback cycle between radiatively cooling intracluster gas and star formation and AGN activity in the BCG. However the prevalence of "active" BCGs, and details of the feedback involved, are still uncertain. We have performed an optical, UV and Mid-IR photometric analysis of the BCGs in 981 clusters at 0.03 medium.

  18. Star-Forming Brightest Cluster Galaxies at 0.25 < z < 1.25: A Transitioning Fuel Supply

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, M.; Stalder, B.; Bayliss, M.; Allen, S. W.; Applegate, D. E.; Ashby, M. L. N.; Bautz, M.; Benson, B. A.; Bleem, L. E.; Brodwin, M.; Carlstrom, J. E.

    2016-02-01

    We present a multi-wavelength study of 90 brightest cluster galaxies (BCGs) in a sample of galaxy clusters selected via the Sunyaev Zel'dovich effect by the South Pole Telescope, utilizing data from various ground- and space-based facilities. We infer the star formation rate (SFR) for the BCG in each cluster, based on the UV and IR continuum luminosity, as well as the [O II] emission line luminosity in cases where spectroscopy is available, finding 7 systems with SFR > 100 Msun/yr. We find that the BCG SFR exceeds 10 Msun/yr in 31 of 90 (34%) cases at 0.25 < z < 1.25, compared to ~1-5% at z ~ 0 from the literature. At z > 1, this fraction increases to 92(+6)(-31)%, implying a steady decrease in the BCG SFR over the past ~9 Gyr. At low-z, we find that the specific star formation rate in BCGs is declining more slowly with time than for field or cluster galaxies, most likely due to the replenishing fuel from the cooling ICM in relaxed, cool core clusters. At z > 0.6, the correlation between cluster central entropy and BCG star formation - which is well established at z ~ 0 - is not present. Instead, we find that the most star-forming BCGs at high-z are found in the cores of dynamically unrelaxed clusters. We investigate the rest-frame near-UV morphology of a subsample of the most star-forming BCGs using data from the Hubble Space Telescope, finding complex, highly asymmetric UV morphologies on scales as large as ~50-60 kpc. The high fraction of star-forming BCGs hosted in unrelaxed, non-cool core clusters at early times suggests that the dominant mode of fueling star formation in BCGs may have recently transitioned from galaxy-galaxy interactions to ICM cooling.

  19. Star-Forming Brightest Cluster Galaxies at 0.25 < z < 1.25: A Transitioning Fuel Supply

    CERN Document Server

    McDonald, M; Bayliss, M; Allen, S W; Applegate, D E; Ashby, M L N; Bautz, M; Benson, B A; Bleem, L E; Brodwin, M; Carlstrom, J E; Chiu, I; Desai, S; Gonzalez, A H; Hlavacek-Larrondo, J; Holzapfel, W L; Marrone, D P; Miller, E D; Reichardt, C L; Saliwanchik, B R; Saro, A; Schrabback, T; Stanford, S A; Stark, A A; Vieira, J D; Zenteno, A

    2015-01-01

    We present a multi-wavelength study of 90 brightest cluster galaxies (BCGs) in a sample of galaxy clusters selected via the Sunyaev Zel'dovich effect by the South Pole Telescope, utilizing data from various ground- and space-based facilities. We infer the star formation rate (SFR) for the BCG in each cluster, based on the UV and IR continuum luminosity, as well as the [O II] emission line luminosity in cases where spectroscopy is available, finding 7 systems with SFR > 100 Msun/yr. We find that the BCG SFR exceeds 10 Msun/yr in 31 of 90 (34%) cases at 0.25 1, this fraction increases to 92(+6)(-31)%, implying a steady decrease in the BCG SFR over the past ~9 Gyr. At low-z, we find that the specific star formation rate in BCGs is declining more slowly with time than for field or cluster galaxies, most likely due to the replenishing fuel from the cooling ICM in relaxed, cool core clusters. At z > 0.6, the correlation between cluster central entropy and BCG star formation - which is well established at z ~ 0 - i...

  20. Star-forming Brightest Cluster Galaxies at 0.25 > z > 1.25: A Transitioning Fuel Supply

    Science.gov (United States)

    McDonald, M.; Stalder, B.; Bayliss, M.; Allen, S. W.; Applegate, D. E.; Ashby, M. L. N.; Bautz, M.; Benson, B. A.; Bleem, L. E.; Brodwin, M.; Carlstrom, J. E.; Chiu, I.; Desai, S.; Gonzalez, A. H.; Hlavacek-Larrondo, J.; Holzapfel, W. L.; Marrone, D. P.; Miller, E. D.; Reichardt, C. L.; Saliwanchik, B. R.; Saro, A.; Schrabback, T.; Stanford, S. A.; Stark, A. A.; Vieira, J. D.; Zenteno, A.

    2016-02-01

    We present a multiwavelength study of the 90 brightest cluster galaxies (BCGs) in a sample of galaxy clusters selected via the Sunyaev Zel’dovich effect by the South Pole Telescope, utilizing data from various ground- and space-based facilities. We infer the star-formation rate (SFR) for the BCG in each cluster—based on the UV and IR continuum luminosity, as well as the [O ii]λλ3726,3729 emission line luminosity in cases where spectroscopy is available—and find seven systems with SFR > 100 M⊙ yr-1. We find that the BCG SFR exceeds 10 M⊙ yr-1 in 31 of 90 (34%) cases at 0.25 BCG SFR over the past ˜9 Gyr. At low-z, we find that the specific SFR in BCGs is declining more slowly with time than for field or cluster galaxies, which is most likely due to the replenishing fuel from the cooling ICM in relaxed, cool core clusters. At z ≳ 0.6, the correlation between the cluster central entropy and BCG star formation—which is well established at z ˜ 0—is not present. Instead, we find that the most star-forming BCGs at high-z are found in the cores of dynamically unrelaxed clusters. We use data from the Hubble Space Telescope to investigate the rest-frame near-UV morphology of a subsample of the most star-forming BCGs, and find complex, highly asymmetric UV morphologies on scales as large as ˜50-60 kpc. The high fraction of star-forming BCGs hosted in unrelaxed, non-cool core clusters at early times suggests that the dominant mode of fueling star formation in BCGs may have recently transitioned from galaxy-galaxy interactions to ICM cooling.

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

    International Nuclear Information System (INIS)

    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, MK ∼ –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

  2. Avoiding progenitor bias: The structural and mass evolution of Brightest Group and Cluster Galaxies in Hierarchical models since z~1

    CERN Document Server

    Shankar, Francesco; Rettura, Alessandro; Bouillot, Vincent; Moreno, Jorge; Licitra, Rossella; Bernardi, Mariangela; Huertas-Company, Marc; Mei, Simona; Ascaso, Begoña; Sheth, Ravi; Delaye, Lauriane; Raichoor, Anand

    2015-01-01

    The mass and structural evolution of massive galaxies is one of the hottest topics in galaxy formation. This is because it may reveal invaluable insights into the still debated evolutionary processes governing the growth and assembly of spheroids. However, direct comparison between models and observations is usually prevented by the so-called "progenitor bias", i.e., new galaxies entering the observational selection at later epochs, thus eluding a precise study of how pre-existing galaxies actually evolve in size. To limit this effect, we here gather data on high-redshift brightest group and cluster galaxies, evolve their (mean) host halo masses down to z=0 along their main progenitors, and assign as their "descendants" local SDSS central galaxies matched in host halo mass. At face value, the comparison between high redshift and local data suggests a noticeable increase in stellar mass of a factor of >2 since z~1, and of >2.5 in mean effective radius. We then compare the inferred stellar mass and size growth ...

  3. Colour Gradients and the Colour-Magnitude Relation: Different Properties of Brightest Cluster Galaxies and E/S0 Galaxies in the Sloan Digital Sky Survey

    OpenAIRE

    Roche, Nathan; Bernardi, Mariangela; Hyde, Joseph

    2009-01-01

    We examine the colour-magnitude relation of approximately 5000 Brightest Cluster Galaxies (BCGs) in the Sloan Digital Sky Survey, and compare with non-BCG E/S0 galaxies. The colour-magnitude and colour-sigma (velocity dispersion) relations are flatter in slope (by a factor of about 2) for BCGs than for non-BCG E/S0s, and the BCGs also tend to be redder by 0.01 magnitudes in g-r. We investigate radial colour gradients in both samples, using the ratio of the de Vaucouleurs radii in the g and r ...

  4. A NOVEL APPROACH TO CONSTRAIN THE MASS RATIO OF MINOR MERGERS IN ELLIPTICAL GALAXIES: APPLICATION TO NGC 4889, THE BRIGHTEST CLUSTER GALAXY IN COMA

    International Nuclear Information System (INIS)

    Minor mergers are thought to be important for the buildup and structural evolution of massive elliptical galaxies. In this work, we report the discovery of a system of four shell features in NGC 4889, one of the brightest members of the Coma cluster, using optical images taken with the Hubble Space Telescope and the Sloan Digital Sky Survey. The shells are well aligned with the major axis of the host and are likely to have been formed by the accretion of a small satellite galaxy. We have performed a detailed two-dimensional photometric decomposition of NGC 4889 and of the many overlapping nearby galaxies in its vicinity. This comprehensive model allows us not only to firmly detect the low-surface brightness shells, but, crucially, also to accurately measure their luminosities and colors. The shells are bluer than the underlying stars at the same radius in the main galaxy. We make use of the colors of the shells and the color-magnitude relation of the Coma cluster to infer the luminosity (or mass) of the progenitor galaxy. The shells in NGC 4889 appear to have been produced by the minor merger of a moderate-luminosity (MI ≈ –18.7 mag) disk (S0 or spiral) galaxy with a luminosity (mass) ratio of ∼90:1 with respect to the primary galaxy. The novel methodology presented in this work can be exploited to decode the fossil record imprinted in the photometric substructure of other nearby early-type galaxies

  5. The importance of major mergers in the build up of stellar mass in brightest cluster galaxies at z=1

    CERN Document Server

    Lidman, C; Bauer, A E; Barrientos, L F; Cerulo, P; Couch, W J; Delaye, L; Demarco, R; Ellingson, E; Faloon, A J; Gilbank, D; Huertas-Company, M; Mei, S; Meyers, J; Muzzin, A; Noble, A; Nantais, J; Rettura, A; Rosati, P; Sanchez-Janssen, R; Strazzullo, V; Webb, T M A; Wilson, G; Yan, R; Yee, H K C

    2013-01-01

    Recent independent results from numerical simulations and observations have shown that brightest cluster galaxies (BCGs) have increased their stellar mass by a factor of almost two between z~0.9 and z~0.2. The numerical simulations further suggest that more than half this mass is accreted through major mergers. Using a sample of 18 distant galaxy clusters with over 600 spectroscopically confirmed cluster members between them, we search for observational evidence that major mergers do play a significant role. We find a major merger rate of 0.38 +/- 0.14 mergers per Gyr at z~1. While the uncertainties, which stem from the small size of our sample, are relatively large, our rate is consistent with the results that are derived from numerical simulations. If we assume that this rate continues to the present day and that half of the mass of the companion is accreted onto the BCG during these mergers, then we find that this rate can explain the growth in the stellar mass of the BCGs that is observed and predicted by...

  6. The rapid evolution of AGN feedback in brightest cluster galaxies: switching from quasar-mode to radio-mode feedback

    CERN Document Server

    Hlavacek-Larrondo, J; Edge, A C; Ebeling, H; Allen, S W; Sanders, J S; Taylor, G B

    2012-01-01

    We present an analysis of the 2-10 keV X-ray emission associated with the active galactic nuclei (AGNs) in brightest cluster galaxies (BCGs). Our sample consists of 32 BCGs that lie in highly X-ray luminous cluster of galaxies [L_X-ray(0.1-2.4 keV)>3*10^44 erg/s] in which AGN-jetted outflows are creating and sustaining clear X-ray cavities. Our sample covers the redshift range 0

  7. Evidence for Significant Growth in the Stellar Mass of Brightest Cluster Galaxies over the Past 10 Billion Years

    CERN Document Server

    Lidman, C; Muzzin, A; Wilson, G; Demarco, R; Brough, S; Rettura, A; Cox, J; DeGroot, A; Yee, H K C; Gilbank, D; Hoekstra, H; Balogh, M; Ellingson, E; Hicks, A; Nantais, J; Noble, A; Lacy, M; Surace, J; Webb, T

    2012-01-01

    Using new and published data, we construct a sample of 160 brightest cluster galaxies (BCGs) spanning the redshift interval 0.03 < z < 1.63. We use this sample, which covers 70% of the history of the universe, to measure the growth in the stellar mass of BCGs after correcting for the correlation between the stellar mass of the BCG and the mass of the cluster in which it lives. We find that the stellar mass of BCGs increase by a factor of 1.8 between z=0.9 and z=0.2. Compared to earlier works, our result is closer to the predictions of semi-analytic models. However, BCGs at z=0.9, relative to BCGs at z=0.2, are still a factor of 1.5 more massive than the predictions of these models. Star formation rates in BCGs at z~1 are generally to low to result in significant amounts of mass. Instead, it is likely that most of the mass build up occurs through mainly dry mergers in which perhaps half of the mass is lost to the intra-cluster medium of the cluster.

  8. Defying jet-gas alignment in two radio galaxies at z~2 with extended light profiles: Similarities to brightest cluster galaxies

    CERN Document Server

    Collet, C; De Breuck, C; Lehnert, M D; Best, P; Bryant, J J; Dicken, D; Johnston, H; Hunstead, R; Wylezalek, D

    2015-01-01

    We report the detection of extended warm ionized gas in two powerful high-redshift radio galaxies, NVSS J210626-314003 at z=2.10 and TXS 2353-003 at z=1.49, that does not appear to be associated with the radio jets. This is contrary to what would be expected from the alignment effect, a characteristic feature of distant, powerful radio galaxies at z> 0.6. The gas also has smaller velocity gradients and line widths than most other high-z radio galaxies with similar data. Both galaxies are part of a systematic study of 50 high-redshift radio galaxies with SINFONI, and are the only two that are characterized by the presence of high surface-brightness gas not associated with the jet axis and by the absence of such gas aligned with the jet. Both galaxies are spatially resolved with ISAAC broadband imaging covering the rest-frame R band, and have extended wings that cannot be attributed to line contamination. We argue that the gas and stellar properties of these galaxies are more akin to gas-rich brightest cluster ...

  9. A $10^{10}$ Solar Mass Flow of Molecular Gas in the Abell 1835 Brightest Cluster Galaxy

    CERN Document Server

    McNamara, B R; Nulsen, P E J; Edge, A C; Murray, N W; Main, R A; Vantyghem, A N; Combes, F; Fabian, A C; Salome, P; Kirkpatrick, C C; Baum, S A; Bregman, J N; Donahue, M; Egami, E; Hamer, S; O'Dea, C P; Oonk, J B R; Tremblay, G; Voit, G M

    2014-01-01

    We report ALMA Early Science observations of the Abell 1835 brightest cluster galaxy (BCG) in the CO (3-2) and CO (1-0) emission lines. We detect $5\\times 10^{10}~\\rm M_\\odot$ of molecular gas within 10 kpc of the BCG. Its ensemble velocity profile width of $\\sim 130 ~\\rm km~s^{-1}$ FWHM is too narrow for the molecular cloud sto be supported in the galaxy by dynamic pressure. The gas may instead be supported in a rotating, turbulent disk oriented nearly face-on. Roughly $10^{10}~\\rm M_\\odot$ of molecular gas is projected $3-10 ~\\rm kpc$ to the north-west and to the east of the nucleus with line of sight velocities lying between $-250 ~\\rm km~s^{-1}$ to $+480 ~\\rm km~s^{-1}$ with respect to the systemic velocity. The high velocity gas may be either inflowing or outflowing. However, the absence of high velocity gas toward the nucleus that would be expected in a steady inflow, and its bipolar distribution on either side of the nucleus, are more naturally explained as outflow. Star formation and radiation from th...

  10. Near-infrared adaptive optics imaging of infrared luminous galaxies: the brightest cluster magnitude - star formation rate relation

    CERN Document Server

    Randriamanakoto, Zara; Vaisanen, Petri; Kankare, Erkki; Kotilainen, Jari; Mattila, Seppo; Ryder, Stuart

    2013-01-01

    We have established a relation between the brightest super star cluster 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_K ~ - 2.6 log 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...

  11. The High-Mass End of the Black Hole Mass Function: Mass Estimates in Brightest Cluster Galaxies

    CERN Document Server

    Bonta', E Dalla; Corsini, E M; Miralda-Escude', J; Coccato, L; Sarzi, M; Pizzella, A; Beifiori, A

    2008-01-01

    We present Hubble Space Telescope imaging and spectroscopic observations of three Brightest Cluster Galaxies, Abell 1836-BCG, Abell 2052-BCG, and Abell 3565-BCG, obtained with the Wide Field and Planetary Camera 2, the Advanced Camera for Surveys and the Space Telescope Imaging Spectrograph. The data provide detailed information on the structure and mass profile of the stellar component, the dust optical depth, and the spatial distribution and kinematics of the ionized gas within the innermost region of each galaxy. Dynamical models, which account for the observed stellar mass profile and include the contribution of a central supermassive black hole (SBH), are constructed to reproduce the kinematics derived from the Halpha and [N II](lambda 6548,6583) emission lines. Secure SBH detection with M_bh=3.61(+0.41,-0.50)x10^9 M_sun and M_bh=1.34(+0.21,-0.19)x10^9 M_sun, respectively, are obtained for Abell 1836-BCG and Abell 3565-BCG, which show regular rotation curves and strong central velocity gradients. In the ...

  12. SpARCS Brightest Cluster Galaxies: Evidence for significant star formation down to z~0.7

    Science.gov (United States)

    Bonaventura, Nina

    2015-08-01

    We present the first stacked Spitzer/Herschel IR broadband SED of the largest and highest-redshift sample of optically selected Brightest Cluster Galaxies (BCGs), from 1014-Msun clusters in the Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS). While semi-analytic models of structure formation predict that star formation ceases at very early times in BCGs, leaving them to passively evolve subsequently, the updated models of Tonini et al. (2012) suggest that star formation persists in BCGs to much lower redshifts than originally predicted. To address this tension between various models and gain a better understanding of the mechanisms guiding BCG stellar mass growth since z~2, we identify their dominant source of IR energy output through a comparison of their SEDs to a variety of model templates in the literature, in multiple redshift bins between z = 0.1 and 1.9. We derive estimates of LIR,TOT , SFR and sSFR , M* , Tdust , and various measures of 'starburstiness' (Chary & Elbaz 2011) from the stacked SEDs.From the observed redshift evolution of the SED emerges a picture of a star-forming BCG down to z~0.1, vigorously producing hundreds of solar masses per year at z>~0.7, with high efficiency at z>~1 and mostly between 1 and 10 solar mass at lower redshifts, with a small subset representing extreme sources and likely marking a period of intense merging activity between z = 0.4 and 0.6. We find a significant AGN contribution to the small 24μm-bright subset of the BCG sample down to z~0.4, mostly coexisting with vigorous star formation and indicative of a relatively ineffective AGN feedback mechanism in BCGs.We conclude that the star formation and AGN activity we observe in BCGs down to lower redshifts than expected is due to their unique environment at the centers of galaxy clusters, where they are continuously subjected to galaxy merger events at mid-to-high redshift, and likely cooling flows and the associated AGN response towards lower redshifts

  13. A Non-thermal Study of the Brightest Cluster Galaxy NGC 1275 - The Gamma-Radio Connection Over Four Decades

    CERN Document Server

    Dutson, K L; Hinton, J A; Hogan, M T; Gurwell, M A; Alston, W N

    2014-01-01

    Emission from the active nucleus in the core of the brightest cluster galaxy of the Perseus cluster, NGC 1275, has varied dramatically over the past four decades. Prompted by the Fermi detection of flaring in the gamma-ray band, we present the recent increased activity of this source in the context of its past radio and gamma-ray output. The broad correspondence between the high-frequency radio data and the high-energy (HE) emission is striking. However, on short timescales this correlation breaks down and the 1.3 mm Submillimeter Array flux is apparently unaffected during Fermi-detected flaring activity. The fact that NGC 1275 is also detected at TeV energies during the periods of HE gamma-ray flaring suggests that the short-timescale variation might be primarily related to changes in the inverse Compton scattering of photons by the electron population in the jet. The longer-timescale changes suggest a 30--40 year variation in the fuelling of the black hole, that affects the power of the inner jet. NCG 1275 ...

  14. Radiative efficiency, variability and Bondi accretion onto massive black holes: from mechanical to quasar feedback in brightest cluster galaxies

    CERN Document Server

    Russell, H R; Edge, A C; Hogan, M T; Main, R A; Vantyghem, A N

    2012-01-01

    We examine unresolved nuclear X-ray sources in 57 brightest cluster galaxies to study the relationship between nuclear X-ray emission and accretion onto supermassive black holes (SMBHs). The majority of the clusters in our sample have prominent X-ray cavities embedded in the surrounding hot atmospheres, which we use to estimate mean jet power and average accretion rate onto the SMBHs over the past several hundred Myr. We find that ~50% of the sample have detectable nuclear X-ray emission. The nuclear X-ray luminosity is correlated with average accretion rate determined using X-ray cavities, which is consistent with the hypothesis that nuclear X-ray emission traces ongoing accretion. The results imply that jets in systems that have experienced recent AGN outbursts, in the last ~10^7yr, are `on' at least half of the time. Nuclear X-ray sources become more luminous with respect to the mechanical jet power as the mean accretion rate rises. We show that nuclear radiation exceeds the jet power when the mean accreti...

  15. The accretion histories of brightest cluster galaxies from their stellar population gradients

    CERN Document Server

    Oliva-Altamirano, Paola; Jimmy,; Tran, Kim-Vy; Couch, Warrick J; McDermid, Richard M; Lidman, Chris; von der Linden, Anja; Sharp, Rob

    2015-01-01

    We analyse the spatially-resolved stellar populations of 9 local ($z 10^{11.3}$M$_{\\odot}$) from the ATLAS$^{3D}$ survey (median [Z/H] $= 0.04\\pm0.07$, $\\Delta$[Z/H] $= -0.19\\pm0.1$). However, massive early-type galaxies from ATLAS$^{3D}$ have consistently old ages (median Age $=12.0\\pm3.8$Gyr). We also analyse the close massive companion galaxies of two of the BCGs. These galaxies have similar stellar populations to their respective BCGs.

  16. A Ten Billion Solar Mass Outflow of Molecular Gas Launched by Radio Bubbles in the Abell 1835 Brightest Cluster Galaxy

    CERN Document Server

    McNamara, B R; Nulsen, P E J; Edge, A C; Murray, N W; Main, R A; Vantyghem, A N; Combes, F; Fabian, A C; Salome, P; Kirkpatrick, C C; Baum, S A; Bregman, J N; Donahue, M; Egami, E; Hamer, S; O'Dea, C P; Oonk, J B R; Tremblay, G; Voit, G M

    2013-01-01

    We report ALMA Early Science observations of the Abell 1835 brightest cluster galaxy (BCG) in the CO (3-2) and CO (1-0) emission lines. We detect 5E10 solar masses of molecular gas within 10 kpc of the BCG. Its velocity width of ~130 km/s FWHM is too narrow to be supported by dynamical pressure. The gas may instead be supported in a rotating, turbulent disk oriented nearly face-on. The disk is forming stars at a rate of 100-180 solar masses per year. Roughly 1E10 solar masses of molecular gas is projected 3-10 kpc to the north-west and to the east of the nucleus with line of sight velocities lying between -250 km/s to +480 km/s with respect to the systemic velocity. Although inflow cannot be ruled out, the rising velocity gradient with radius is consistent with a broad, bipolar outflow driven by radio jets or buoyantly rising X-ray cavities. The molecular outflow may be associated with an outflow of hot gas in Abell 1835 seen on larger scales. Molecular gas is flowing out of the BCG at a rate of approximately...

  17. The High-Mass End of the Black Hole Mass Function: Mass Estimates in Brightest Cluster Galaxies

    Science.gov (United States)

    Dalla Bontà, E.; Ferrarese, L.; Corsini, E. M.; Miralda-Escudé, J.; Coccato, L.; Sarzi, M.; Pizzella, A.; Beifiori, A.

    2009-01-01

    We present Hubble Space Telescope imaging and spectroscopic observations of three Brightest Cluster Galaxies, Abell 1836-BCG, Abell 2052-BCG, and Abell 3565-BCG, obtained with the Wide Field and Planetary Camera 2, the Advanced Camera for Surveys and the Space Telescope Imaging Spectrograph. The data provide detailed information on the structure and mass profile of the stellar component, the dust optical depth, and the spatial distribution and kinematics of the ionized gas within the innermost region of each galaxy. Dynamical models, which account for the observed stellar mass profile and include the contribution of a central supermassive black hole (SBH), are constructed to reproduce the kinematics derived from the Hα and [N II]λλ6548,6583 emission lines. Secure SBH detection with M • = 3.61+0.41 -0.50 × 109 M sun and M • = 1.34+0.21 -0.19 × 109 M sun, respectively, are obtained for Abell 1836-BCG and Abell 3565-BCG, which show regular rotation curves and strong central velocity gradients. In the case of Abell 2052-BCG, the lack of an orderly rotational motion prevents a secure determination, although an upper limit of M • lsim 4.60 × 109 M sun can be placed on the mass of the central SBH. These measurements represent an important step forward in the characterization of the high-mass end of the SBH mass function. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme ID 279.B-5004(A).

  18. The Rarity of Star Formation in Brightest Cluster Galaxies as Measured by WISE

    CERN Document Server

    Fraser-McKelvie, Amelia; Pimbblet, Kevin A

    2014-01-01

    We present the mid-infrared (IR) star formation rates of 245 X-ray selected, nearby (z 1x10^44 erg/s. The Wide-Field Infrared Survey Explorer (WISE) AllWISE Data Release provides the first measurement of the 12 micron star formation indicator for all BCGs in the nearby Universe. Perseus A and Cygnus A are the only galaxies in our sample to have star formation rates of > 40 M_sol/yr, indicating that these two galaxies are highly unusual at current times. Stellar populations of 99 +/- 0.6 % of local BCGs are (approximately) passively evolving, with star formation rates of <10 M_sol/yr. We find that in general, star formation produces only modest BCG growth at the current epoch.

  19. A 10{sup 10} solar mass flow of molecular gas in the A1835 brightest cluster galaxy

    Energy Technology Data Exchange (ETDEWEB)

    McNamara, B. R.; Russell, H. R.; Main, R. A.; Vantyghem, A. N.; Kirkpatrick, C. C. [Department of Physics and Astronomy, University of Waterloo, Waterloo (Canada); Nulsen, P. E. J. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Edge, A. C. [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Murray, N. W.; Hamer, S. [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, M5S 3H8 ON (Canada); Combes, F.; Salome, P. [L' Observatoire de Paris, 61 Av. de L' Observatoire, F-75014 Paris (France); Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Baum, S. A.; O' Dea, C. P. [School of Physics and Astronomy, Rochester Institute of Technology, Rochester, NY 14623 (United States); Bregman, J. N. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Donahue, M.; Voit, G. M. [Department of Physics and Astronomy, Michigan State University, 567 Wilson Road, East Lansing, MI 48824 (United States); Egami, E. [Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Oonk, J. B. R. [Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo (Netherlands); Tremblay, G. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany)

    2014-04-10

    We report ALMA Early Science observations of the A1835 brightest cluster galaxy (BCG) in the CO (3-2) and CO (1-0) emission lines. We detect 5 × 10{sup 10} M {sub ☉} of molecular gas within 10 kpc of the BCG. Its ensemble velocity profile width of ∼130 km s{sup –1} FWHM is too narrow for the molecular clouds to be supported in the galaxy by dynamic pressure. The gas may instead be supported in a rotating, turbulent disk oriented nearly face-on. Roughly 10{sup 10} M {sub ☉} of molecular gas is projected 3-10 kpc to the northwest and to the east of the nucleus with line-of-sight velocities lying between –250 km s{sup –1} and +480 km s{sup –1} with respect to the systemic velocity. The high-velocity gas may be either inflowing or outflowing. However, the absence of high-velocity gas toward the nucleus that would be expected in a steady inflow, and its bipolar distribution on either side of the nucleus, are more naturally explained as outflow. Star formation and radiation from the active galactic nucleus (AGN) are both incapable of driving an outflow of this magnitude. The location of the high-velocity gas projected behind buoyantly rising X-ray cavities and favorable energetics suggest an outflow driven by the radio AGN. If so, the molecular outflow may be associated with a hot outflow on larger scales reported by Kirkpatrick and colleagues. The molecular gas flow rate of approximately 200 M {sub ☉} yr{sup –1} is comparable to the star formation rate of 100-180 M {sub ☉} yr{sup –1} in the central disk. How radio bubbles would lift dense molecular gas in their updrafts, how much gas will be lost to the BCG, and how much will return to fuel future star formation and AGN activity are poorly understood. Our results imply that radio-mechanical (radio-mode) feedback not only heats hot atmospheres surrounding elliptical galaxies and BCGs, but it is able to sweep higher density molecular gas away from their centers.

  20. A Multi-Wavelength Photometric Census of AGN and Star Formation Activity in the Brightest Cluster Galaxies of X-ray Selected Clusters

    CERN Document Server

    Green, T S; Stott, J P; Ebeling, H; Burgett, W S; Chambers, K C; Draper, P W; Metcalfe, N; Kaiser, N; Wainscoat, R J; Waters, C

    2016-01-01

    Despite their reputation as being "red and dead", the unique environment inhabited by Brightest Cluster Galaxies (BCGs) can often lead to a self-regulated feedback cycle between radiatively cooling intracluster gas and star formation and AGN activity in the BCG. However the prevalence of "active" BCGs, and details of the feedback involved, are still uncertain. We have performed an optical, UV and Mid-IR photometric analysis of the BCGs in 981 clusters at 0.03 < z < 0.5, selected from the ROSAT All Sky Survey. Using Pan-STARRS PS1 3pi, GALEX and WISE survey data we look for BCGs with photometric colours which deviate from that of the bulk population of passive BCGs - indicative of AGN and/or star formation activity within the BCG. We find that whilst the majority of BCGs are consistent with being passive, at least 14% of our BCGs show a significant colour offset from passivity in at least one colour index. And, where available, supplementary spectroscopy reveals the majority of these particular BCGs show...

  1. PS1-12sk is a Peculiar Supernova From a He-rich Progenitor System in a Brightest Cluster Galaxy Environment

    CERN Document Server

    Sanders, N E; Foley, R J; Chornock, R; Milisavljevic, D; Margutti, R; Drout, M R; Moe, M; Berger, E; Brown, W R; Lunnan, R; Smartt, S J; Fraser, M; Kotak, R; Magill, L; Smith, K W; Wright, D; Huang, K; Urata, Y; Mulchaey, J S; Rest, A; Sand, D J; Chomiuk, L; Friedman, A S; Kirshner, R P; Marion, G H; Tonry, J L; Burgett, W S; Chambers, K C; Hodapp, K W; Kudritzki, R P; Price, P A

    2013-01-01

    (Abridged) We report on our discovery and multi-wavelength follow-up observations of the Pan-STARRS1 supernova (SN) PS1-12sk, a transient with uncommon circumstellar properties that indicate atypical star formation in its host galaxy cluster or pose a challenge to popular progenitor system models for this class of explosion. The optical spectra of PS1-12sk are dominated by intermediate-width He I emission at z = 0.054, reminiscent of the spectra of the archetypal Type Ibn SN 2006jc. Dense Pan-STARRS1 multi-band photometry provides the best constraints to date for the rise time of a SN Ibn and a peak magnitude of M_z = -18.9 mag. SN Ibn spectroscopic properties are commonly interpreted as the signature of a massive star (17 - 100 M_solar) explosion within a He-enriched circumstellar medium. However, unlike previous Type Ibn supernovae, PS1-12sk is associated with a galaxy cluster. The elliptical brightest cluster galaxy is the most likely host galaxy. We find no evidence for star formation at the explosion sit...

  2. HUBBLE SPACE TELESCOPE FAR-ULTRAVIOLET OBSERVATIONS OF BRIGHTEST CLUSTER GALAXIES: THE ROLE OF STAR FORMATION IN COOLING FLOWS AND BCG EVOLUTION

    International Nuclear Information System (INIS)

    Quillen et al. and O'Dea et al. carried out a Spitzer study of a sample of 62 brightest cluster galaxies (BCGs) from the ROSAT brightest cluster sample, which were chosen based on their elevated Hα flux. We present Hubble Space Telescope Advanced Camera for Surveys far-ultraviolet (FUV) images of the Lyα and continuum emission of the luminous emission-line nebulae in seven BCGs found to have an infrared (IR) excess. We confirm that the BCGs are actively forming stars which suggests that the IR excess seen in these BCGs is indeed associated with star formation. Our observations are consistent with a scenario in which gas that cools from the intracluster medium fuels the star formation. The FUV continuum emission extends over a region ∼7-28 kpc (largest linear size) and even larger in Lyα. The young stellar population required by the FUV observations would produce a significant fraction of the ionizing photons required to power the emission-line nebulae. Star formation rates estimated from the FUV continuum range from ∼3 to ∼14 times lower than those estimated from the IR, however, both the Balmer decrements in the central few arcseconds and detection of CO in most of these galaxies imply that there are regions of high extinction that could have absorbed much of the FUV continuum. Analysis of archival Very Large Array observations reveals compact radio sources in all seven BCGs and kpc scale jets in A-1835 and RXJ 2129+00. The four galaxies with archival deep Chandra observations exhibit asymmetric X-ray emission, the peaks of which are offset from the center of the BCG by ∼10 kpc on average. A low feedback state for the active galactic nucleus could allow increased condensation of the hot gas into the center of the galaxy and the feeding of star formation.

  3. The Non-Parametric Model for Linking Galaxy Luminosity with Halo/Subhalo Mass: Are First Brightest Galaxies Special?

    CERN Document Server

    Vale, A

    2007-01-01

    We revisit the longstanding question of whether first brightest cluster galaxies are statistically drawn from the same distribution as other cluster galaxies or are "special", using the new non-parametric, empirically based model presented in Vale&Ostriker (2006) for associating galaxy luminosity with halo/subhalo masses. We introduce scatter in galaxy luminosity at fixed halo mass into this model, building a conditional luminosity function (CLF) by considering two possible models: a simple lognormal and a model based on the distribution of concentration in haloes of a given mass. We show that this model naturally allows an identification of halo/subhalo systems with groups and clusters of galaxies, giving rise to a clear central/satellite galaxy distinction. We then use these results to build up the dependence of brightest cluster galaxy (BCG) magnitudes on cluster luminosity, focusing on two statistical indicators, the dispersion in BCG magnitude and the magnitude difference between first and second bri...

  4. OPTICAL LINE EMISSION IN BRIGHTEST CLUSTER GALAXIES AT 0 < z < 0.6: EVIDENCE FOR A LACK OF STRONG COOL CORES 3.5 Gyr AGO?

    International Nuclear Information System (INIS)

    In recent years the number of known galaxy clusters beyond z ∼> 0.2 has increased drastically with the release of multiple catalogs containing >30,000 optically detected galaxy clusters over the range 0 0.3, hinting at an earlier epoch of strong cooling. We compare the evolution of emission-line nebulae to the X-ray-derived cool core (CC) fraction from the literature over the same redshift range and find overall agreement, with the exception that an upturn in the strong CC fraction is not observed at z > 0.3. The overall agreement between the evolution of CCs and optical line emission at low redshift suggests that emission-line surveys of galaxy clusters may provide an efficient method of indirectly probing the evolution of CCs and thus provide insights into the balance of heating and cooling processes at early cosmic times.

  5. The Brightest Young Star Clusters in NGC 5253

    CERN Document Server

    Calzetti, D; Adamo, A; Gallagher, J S; Andrews, J E; Smith, L J; Clayton, G C; Lee, J C; Sabbi, E; Ubeda, L; Kim, H; Ryon, J E; Thilker, D; Bright, S N; Zackrisson, E; Kennicutt, R C; de Mink, S E; Whitmore, B C; Aloisi, A; Chandar, R; Cignoni, M; Cook, D; Dale, D A; Elmegreen, B G; Elmegreen, D M; Evans, A S; Fumagalli, M; Gouliermis, D A; Grasha, K; Grebel, E K; Krumholz, M R; Walterbos, R; Wofford, A; Brown, T M; Christian, C; Dobbs, C; Herrero, A; Kahre, L; Messa, M; Nair, P; Nota, A; Oestlin, G; Pellerin, A; Sacchi, E; Schaerer, D; Tosi, M

    2015-01-01

    The nearby dwarf starburst galaxy NGC5253 hosts a number of young, massive star clusters, the two youngest of which are centrally concentrated and surrounded by thermal radio emission (the `radio nebula'). To investigate the role of these clusters in the starburst energetics, we combine new and archival Hubble Space Telescope images of NGC5253 with wavelength coverage from 1500 Ang to 1.9 micron in 13 filters. These include H-alpha, P-beta, and P-alpha, and the imaging from the Hubble Treasury Program LEGUS (Legacy Extragalactic UV Survey). The extraordinarily well-sampled spectral energy distributions enable modeling with unprecedented accuracy the ages, masses, and extinctions of the 9 optically brightest clusters (M_V < -8.8) and the two young radio nebula clusters. The clusters have ages ~1-15 Myr and masses ~1x10^4 - 2.5x10^5 M_sun. The clusters' spatial location and ages indicate that star formation has become more concentrated towards the radio nebula over the last ~15 Myr. The most massive cluster ...

  6. Luminosity function of the brightest galaxies in the IRAS survey

    International Nuclear Information System (INIS)

    Results from a study of the far infrared properties of the brightest galaxies in the IRAS survey are described. There is a correlation between the infrared luminosity and the infrared to optical luminosity ratio and between the infrared luminosity and the far infrared color temperature in these galaxies. The infrared bright galaxies represent a significant component of extragalactic objects in the local universe, being comparable in space density to the Seyferts, optically identified starburst galaxies, and more numerous than quasars at the same bolometric luminosity. The far infrared luminosity in the local universe is approximately 25% of the starlight output in the same volume

  7. PS1-12sk is a Peculiar Supernova From a He-rich Progenitor System in a Brightest Cluster Galaxy Environment

    OpenAIRE

    Sanders, N. E.; Soderberg, A. M.; Foley, R. J.; Chornock, R.; D. Milisavljevic(SAO-Harvard CfA); Margutti, R.; Drout, M. R.; Moe, M.; Berger, E.; Brown, W R; Lunnan, R.; Smartt, S. J.; Fraser, M; Kotak, R.; Magill, L.

    2013-01-01

    We report on our discovery and observations of the Pan-STARRS1 supernova (SN) PS1-12sk, a transient with properties that indicate atypical star formation in its host galaxy cluster or pose a challenge to popular progenitor system models for this class of explosion. The optical spectra of PS1-12sk classify it as a Type Ibn SN (c.f. SN 2006jc), dominated by intermediate-width (3x10^3 km/s) and time variable He I emission. Our multi-wavelength monitoring establishes the rise time dt = 9-23 days ...

  8. Galaxy candidates at z ~ 10 in archival data from the Brightest of Reionizing Galaxies (BoRG[z8]) survey

    CERN Document Server

    Bernard, S R; Trenti, M; Oesch, P A; Wu, J F; Bradley, L D; Schmidt, K B; Bouwens, R J; Calvi, V; Mason, C A; Stiavelli, M; Treu, T

    2016-01-01

    The Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) enabled the search for the first galaxies observed at z ~ 8 - 11 (500 - 700 Myr after the Big Bang). To continue quantifying the number density of the most luminous galaxies (M_AB ~ -22.0) at the earliest epoch observable with HST, we search for z ~ 10 galaxies (F125W-dropouts) in archival data from the Brightest of Reionizing Galaxies (BoRG[z8]) survey, originally designed for detection of z ~ 8 galaxies (F098M-dropouts). By focusing on the deepest 293 arcmin^2 of the data along 62 independent lines of sight, we identify six z ~ 10 candidates satisfying the color selection criteria, detected at S/N > 8 in F160W with M_AB = -22.8 to -21.1 if at z = 10. Three of the six sources, including the two brightest, are in a single WFC3 pointing (~ 4 arcmin^2), suggestive of significant clustering, which is expected from bright galaxies at z ~ 10. However, the two brightest galaxies are too extended to be likely at z ~ 10, and one additional source is u...

  9. Galaxy Candidates at z ~ 10 in Archival Data from the Brightest of Reionizing Galaxies (BORG[z8]) Survey

    Science.gov (United States)

    Bernard, S. R.; Carrasco, D.; Trenti, M.; Oesch, P. A.; Wu, J. F.; Bradley, L. D.; Schmidt, K. B.; Bouwens, R. J.; Calvi, V.; Mason, C. A.; Stiavelli, M.; Treu, T.

    2016-08-01

    The Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) enabled the search for the first galaxies observed at z ˜ 8–11 (500–700 Myr after the Big Bang). To continue quantifying the number density of the most luminous galaxies (M AB ˜ ‑22.0) at the earliest epoch observable with HST, we search for z ˜ 10 galaxies (F125W-dropouts) in archival data from the Brightest of Reionizing Galaxies (BoRG[z8]) survey, originally designed for detection of z ˜ 8 galaxies (F098M-dropouts). By focusing on the deepest 293 arcmin2 of the data along 62 independent lines of sight, we identify six z ˜ 10 candidates satisfying the color selection criteria, detected at S/N > 8 in F160W with M AB = ‑22.8 to ‑21.1 if at z = 10. Three of the six sources, including the two brightest, are in a single WFC3 pointing (˜4 arcmin2), suggestive of significant clustering, which is expected from bright galaxies at z ˜ 10. However, the two brightest galaxies are too extended to be likely at z ˜ 10, and one additional source is unresolved and possibly a brown dwarf. The remaining three candidates have m AB ˜ 26, and given the area and completeness of our search, our best estimate is a number density of sources that is marginally higher but consistent at 2σ with searches in legacy fields. Our study highlights that z ˜ 10 searches can yield a small number of candidates, making tailored follow-ups of HST pure-parallel observations viable and effective.

  10. Super-Eight: The brightest z~8 Galaxies

    Science.gov (United States)

    Holwerda, Benne; Bouwens, R.; Bradley, L.; Calvi, V.; Illingworth, G.; Labbe, I.; Magee, D.; Oesch, P.; Roberts-Borsani, G.; Smit, R.

    2016-08-01

    What are the properties of the most massive z~8 galaxies ('Super-Eights') and how luminous can these galaxies become at that epoch? Answering these questions is challenging due to the rarity of luminous z~8 galaxies and the large field-to-field variations in their volume densities. Indeed, the full wide-area CANDELS program only shows 3 z~8 galaxy candidates brighter than 25.5 mag and all of these candidates conspicuously lie in the same CANDELS field (EGS). One of our strongest new probes for particularly luminous z~8 galaxies are the WFC3 Pure-Parallel (PP) programs. Particularly intriguing are 8 bright z~8 candidates in these observations. These candidates have similar luminosities as the 3 brightest z~8 candidates from CANDELS (all spectroscopically confirmed). However, the uncertain contamination levels at extreme bright end of z~8 selection mean that follow-up observations are critical. We propose highly-efficient pointed HST and Spitzer/IRAC observations to determine if these candidates are indeed at z~8. We estimate that anywhere from 50 to 100% of the targeted sources will be confirmed to be at z~8 based on our results from CANDELS. The estimate is very uncertain due to very large cosmic variance in the CANDELS result and contamination from rare low-redshift sources. When combined with CANDELS, our observations would provide us the strongest current constraints on the volume density of bright, massive galaxies in the early Universe (serving as a guide to models of their build-up) and also provide valuable targets for future spectroscopy (e.g. with JWST), useful for probing the ionization state of the IGM.

  11. Distances to Galaxies from the Brightest Stars in the Universe

    CERN Document Server

    Kudritzki, R -P

    2011-01-01

    Blue Supergiants (BSGs) are the brightest stars in the universe at visual light with absolute magnitudes up to Mv=-10 mag. They are ideal stellar objects for the determination of extragalactic distances, in particular, because the perennial uncertainties troubling most of the other stellar distance indicators, interstellar extinction and metallicity, do not affect them. The quantitative spectral analysis of low resolution spectra of individual BSGs provides accurate stellar parameters and chemical composition, which are then used to determine accurate reddening and extinction from photometry for each individual object. Accurate distances can be determined from stellar gravities and effective temperatures using the "Flux Weighted Gravity - Luminosity Relationship (FGLR)". Most recent results of the quantitative spectral analysis of BSGs in galaxies within and beyond the Local Group based on medium and low resolution spectra obtained with the ESO VLT and the Keck telescopes on Mauna Kea are presented and distan...

  12. VLA HI imaging of the brightest spiral galaxies in Coma

    CERN Document Server

    Bravo-Alfaro, H; Van Gorkom, J H; Balkowski, C

    1999-01-01

    We have obtained 21cm images of 19 spiral galaxies in the Coma cluster, using the VLA in its C and D configurations. The sample selection was based on morphology, brightness, and optical diameters of galaxies within one Abell radius (1.2 degrees). The HI detected, yet deficient galaxies show a strong correlation in their HI properties with projected distance from the cluster center. The most strongly HI deficient (HI Def > 0.4) galaxies are located inside a radius of 30 arcmin (aprox 0.6 Mpc) from the center of Coma, roughly the extent of the central X-ray emission. These central galaxies show clear asymmetries in their HI distribution and/or shifts between the optical and 21cm positions. Seven so called blue disk galaxies in Coma were observed in HI and six were detected. We did a more sensitive search for HI from 11 of the 15 known post starburst galaxies in Coma. None were detected with typical HI mass limits between 3 and 7x10^7 solar masses. Our results present and enhance a picture already familiar for ...

  13. Lopsidedness of cluster galaxies in modified gravity

    International Nuclear Information System (INIS)

    We point out an interesting theoretical prediction for elliptical galaxies residing inside galaxy clusters in the framework of modified Newtonian dynamics (MOND), that could be used to test this paradigm. Apart from the central brightest cluster galaxy, other galaxies close enough to the centre experience a strong gravitational influence from the other galaxies of the cluster. This influence manifests itself only as tides in standard Newtonian gravity, meaning that the systematic acceleration of the centre of mass of the galaxy has no consequence. However, in the context of MOND, a consequence of the breaking of the strong equivalence principle is that the systematic acceleration changes the own self-gravity of the galaxy. We show here that, in this framework, initially axisymmetric elliptical galaxies become lopsided along the external field's direction, and that the centroid of the galaxy, defined by the outer density contours, is shifted by a few hundreds parsecs with respect to the densest point

  14. Comparing galaxy populations in compact and loose groups of galaxies II: brightest group galaxies

    CERN Document Server

    Martínez, Héctor J; Muriel, Hernán

    2013-01-01

    The properties of the brightest galaxies (BCGs) are studied in both compact and loose groups of galaxies in order to better understand the physical mechanisms influencing galaxy evolution in different environments. Samples of BCGs are selected in the compact groups identified by McConnachie et al. (2009), and in loose groups taken from Zandivarez & Mart\\'inez (2011). The following physical properties of the BCGs in compact groups and in subsamples of loose groups are compared, defined by their mass and total luminosity. The fraction of BCGs classified as red and/or early-type as a function of galaxy luminosity are studied. The fraction of the group's total luminosity contained in the BCG and the difference in luminosity between the BCG and the second-ranked galaxy, are also analysed. Some properties of BCGs in compact and loose groups are comparable. However, BCGs in compact groups are systematically more concentrated and have larger surface brightness than their counterparts in both, high- and low-mass l...

  15. Poor cluster of galaxies containing four absolutely bright Markaryan galaxies

    International Nuclear Information System (INIS)

    The Zwicky cluster Zw 1122.3 + 6317, which contains four Markaryan galaxies, is discussed. Radial velocities are determined for three galaxies in the region of the sky occupied by this cluster. It is shown that the cluster is very open and consists mainly of spirals, that some compact ellipticals are possible cluster members, and that the Markarian galaxies are among the brightest cluster members. Spatial and kinematic characteristics of the cluster are estimated, including a mean recession velocity of 3557 km/s, a radial-velocity dispersion of 219 km/s, a virial mass of 92 trillion solar masses, a crossing time of 2.9 billion years, a luminosity of 1.1 trillion suns, and an M/L ratio of 84 (in solar units). The possibility is noted that this cluster might actually be two groups of galaxies, with mean recession velocities of approximately 3350 and 3750 km/s, projected onto each other

  16. Clumpy and Extended Starbursts in the Brightest Unlensed Submillimeter Galaxies

    CERN Document Server

    Iono, Daisuke; Aretxaga, Itziar; Hatsukade, Bunyo; Hughes, David; Ikarashi, Soh; Izumi, Takuma; Kawabe, Ryohei; Kohno, Kotaro; Lee, Minju; Matsuda, Yuichi; Nakanishi, Kouichiro; Saito, Toshiki; Tamura, Yoichi; Ueda, Junko; Umehata, Hideki; Wilson, Grant; Michiyama, Tomonari; Ando, Misaki

    2016-01-01

    The central structure in three of the brightest unlensed z=3-4 submillimeter galaxies are investigated through 0.015" - 0.05" (120 -- 360~pc) 860 micron continuum images obtained using the Atacama Large Millimeter/submillimeter Array (ALMA). The distribution in the central kpc in AzTEC1 and AzTEC8 are extremely complex, and they are composed of multiple ~200 pc clumps. AzTEC4 consists of two sources that are separated by ~1.5 kpc, indicating a mid-stage merger. The peak star formation rate densities in the central clumps are ~300 - 3000 Msun/yr/kpc^2, suggesting regions with extreme star formation near the Eddington Limit. By comparing the flux obtained by ALMA and Submillimeter Array (SMA), we find that 68-90% of the emission is extended (> 1 kpc) in AzTEC 4 and 8. For AzTEC1, we identify at least 11 additional compact (~200 pc) clumps in the extended 3 - 4 kpc region. Overall, the data presented here suggest that the luminosity surface densities observed at 1 kpc regions, some of which could also be clumpy...

  17. A GMBCG Galaxy Cluster Catalog of 55,424 Rich Clusters from SDSS DR7

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Jiangang; /Fermilab; McKay, Timothy A.; /Michigan U.; Koester, Benjamin P.; /Chicago U.; Rykoff, Eli S.; /UC, Santa Barbara /LBL, Berkeley; Rozo, Eduardo; /Chicago U.; Annis, James; /Fermilab; Wechsler, Risa H.; /SLAC; Evrard, August; /Michigan U.; Siegel, Seth R.; /Michigan U.; Becker, Matthew; /Chicago U.; Busha, Michael; /SLAC; Gerdes, David; /Michigan U.; Johnston, David E.; /Fermilab; Sheldon, Erin; /Brookhaven

    2011-08-22

    We present a large catalog of optically selected galaxy clusters from the application of a new Gaussian Mixture Brightest Cluster Galaxy (GMBCG) algorithm to SDSS Data Release 7 data. The algorithm detects clusters by identifying the red sequence plus Brightest Cluster Galaxy (BCG) feature, which is unique for galaxy clusters and does not exist among field galaxies. Red sequence clustering in color space is detected using an Error Corrected Gaussian Mixture Model. We run GMBCG on 8240 square degrees of photometric data from SDSS DR7 to assemble the largest ever optical galaxy cluster catalog, consisting of over 55,000 rich clusters across the redshift range from 0.1 < z < 0.55. We present Monte Carlo tests of completeness and purity and perform cross-matching with X-ray clusters and with the maxBCG sample at low redshift. These tests indicate high completeness and purity across the full redshift range for clusters with 15 or more members.

  18. Evolution of Galaxy Clustering

    OpenAIRE

    Bagla, J. S.

    1997-01-01

    We show that the galaxy correlation function does not evolve in proportion with the correlation function of the underlying mass distribution. Earliest galaxies cluster very strongly and the amplitude of the galaxy correlation function decreases from this large value. This continues till the average peaks have collapsed, after which, the galaxy correlation function does not evolve very strongly.

  19. Gravitational Redshifts in Simulated Galaxy Clusters

    CERN Document Server

    Kim, Y R; Kim, Young-Rae; Croft, Rupert

    2004-01-01

    We predict the amplitude of the gravitational redshift of galaxies in galaxy clusters using an N-body simulation of a Lambda CDM universe. We examine if it might be possible to detect the gravitational effect on the total redshift observed for galaxies. For clusters of mass M ~10^15 m_sun, the difference in gravitational redshift between the brightest galaxy and the rest of the cluster members is ~10 km/s. The most efficient way to detect gravitational redshifts using information from galaxies only involves using the full gravitational redshift profile of clusters. Massive clusters, while having the largest gravitational redshift suffer from large galaxy peculiar velocities and substructure, which act as a source of noise. This and their low number density make it more reasonable to try averaging over many clusters and groups of relatively low mass. We examine publicly available data for 107 rich clusters from the ESO Nearby Abell Clusters Survey (ENACS), finding no evidence for gravitational redshifts. Test ...

  20. The luminosity function of the brightest galaxies in the IRAS survey

    Science.gov (United States)

    Soifer, B. T.; Sanders, D. B.; Madore, B. F.; Neugebauer, G.; Persson, C. J.; Persson, S. E.; Rice, W. L.

    1987-01-01

    Results from a study of the far infrared properties of the brightest galaxies in the IRAS survey are described. There is a correlation between the infrared luminosity and the infrared to optical luminosity ratio and between the infrared luminosity and the far infrared color temperature in these galaxies. The infrared bright galaxies represent a significant component of extragalactic objects in the local universe, being comparable in space density to the Seyferts, optically identified starburst galaxies, and more numerous than quasars at the same bolometric luminosity. The far infrared luminosity in the local universe is approximately 25% of the starlight output in the same volume.

  1. Distances of the Virgo, Fornax and Hydra clusters of galaxies and the local value of the Hubble ratio

    International Nuclear Information System (INIS)

    Distances of these three nearby clusters of galaxies as derived from recent observations of the brightest globular clusters in the brightest galaxies are found to be in good agreement with other distance indications and suggest a local value of the Hubble constant H = 86 +- 9 km s-1 Mpc-1. (author)

  2. Coma cluster of galaxies

    Science.gov (United States)

    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).

  3. Hot Outflows in Galaxy Clusters

    CERN Document Server

    Kirkpatrick, C C

    2015-01-01

    The gas-phase metallicity distribution has been analyzed for the hot atmospheres of 29 galaxy clusters using {\\it 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 $R_{\\rm Fe} \\propto P_{\\rm jet}^{0.45}$. The estimated outflow rates are typically tens of solar masses per year but exceed $100 ~\\rm M_\\odot ~yr^{-1}$ in the most powerful AGN. The outflow rates are 10% to 20% 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 ...

  4. Mega starbirth cluster is biggest, brightest and hottest ever seen

    Science.gov (United States)

    2003-10-01

    Artist’s impression of the Lynx Arc hi-res Size hi-res: 4519 kb Credits: European Space Agency, NASA and Robert A.E. Fosbury (European Space Agency/Space Telescope-European Coordinating Facility, Germany) Artist’s impression of the Lynx Arc This illustration shows an artist’s impression of the so-called Lynx arc, a newly identified distant super-cluster that contains a million blue-white stars twice as hot as similar stars in our Milky Way galaxy. The Lynx arc is one million times brighter than the well-known Orion Nebula, a nearby prototypical ‘starbirth’ region visible with small telescopes. The stars in the Lynx arc are more than twice as hot as the Orion Nebula’s central stars, with surface temperatures up to 80 000°C. Though there are much bigger and brighter star-forming regions than the Orion Nebula in our local Universe, none are as bright as the Lynx arc, nor do they contain such large numbers of hot stars. The stars are so hot that a very large fraction of their light is emitted in the ultraviolet that makes the gas glow with the green and red colours illustrated here. The so-called Lynx Arc is one million times brighter than the well-known Orion Nebula, a nearby prototypical 'starbirth' region visible with small telescopes. The newly identified super-cluster contains a million blue-white stars that are twice as hot as similar stars in our Milky Way galaxy. It is a rarely glimpsed example of the early days of the Universe where furious firestorms of starbirth blazed across the skies. The spectacular cluster's opulence is dimmed when seen from Earth only by the fact that it is 12 000 million light years away. The discovery of this unique and tantalising object was the result of a systematic study of distant clusters of galaxies carried out with major X-ray, optical and infrared telescopes, including the NASA/ESA Hubble Space Telescope, ROSAT and the Keck Telescopes. Bob Fosbury, of the European Space Agency's Space Telescope

  5. The XMM Cluster Survey: The Stellar Mass Assembly of Fossil Galaxies

    CERN Document Server

    Harrison, Craig D; Richards, Joseph W; Lloyd-Davies, E J; Hoyle, Ben; Romer, A Kathy; Mehrtens, Nicola; Hilton, Matt; Stott, John P; Capozzi, Diego; Collins, Chris A; Deadman, Paul-James; Liddle, Andrew R; Sahlén, Martin; Stanford, S Adam; Viana, Pedro T P

    2012-01-01

    This paper presents both the result of a search for fossil systems within the XMM Cluster Survey and the Sloan Digital Sky Survey and the results of a study of the stellar mass assembly and stellar populations of their fossil galaxies. In total, 17 groups and clusters are identified at z < 0.25 with large magnitude gaps between the first and fourth brightest galaxies. All the information necessary to classify these systems as fossils is provided. For both groups and clusters, the total and fractional luminosity of the brightest galaxy are positively correlated with the magnitude gap. The brightest galaxies in fossil systems (called fossil galaxies) have stellar populations and star-formation histories which are similar to normal brightest cluster galaxies. However, at fixed group/cluster mass, the stellar masses of the fossil galaxies are larger compared to normal brightest cluster galaxies, a fact that holds true over a wide range of group/cluster masses. Moreover, the fossil galaxies are found to contain...

  6. Measuring Gravitational Redshifts in Galaxy Clusters

    CERN Document Server

    Kaiser, Nick

    2013-01-01

    Wojtak {\\it et al} have stacked 7,800 clusters from the SDSS survey in redshift space. They find a small net blue-shift for the cluster galaxies relative to the brightest cluster galaxies, which agrees quite well with the gravitational redshift from GR. Zhao {\\it et al.} have pointed out that, in addition to the gravitational redshift, one would expect to see transverse Doppler (TD) redshifts, and that these two effects are generally of the same order. Here we show that there are other corrections that are also of the same order of magnitude. The fact that we observe galaxies on our past light cone results in a bias such that more of the galaxies observed are moving away from us in the frame of the cluster than are moving towards us. This causes the observed average redshift to be $\\langle \\delta z \\rangle = -\\langle \\Phi \\rangle + \\langle \\beta^2 \\rangle / 2 + \\langle \\beta_x^2 \\rangle$, with $\\beta_x$ is the line of sight velocity. That is if we average over galaxies with equal weight. If the galaxies in ea...

  7. Analytical Approximations to Galaxy Clustering

    OpenAIRE

    Mo, H. J.

    1997-01-01

    We discuss some recent progress in constructing analytic approximations to the galaxy clustering. We show that successful models can be constructed for the clustering of both dark matter and dark matter haloes. Our understanding of galaxy clustering and galaxy biasing can be greatly enhanced by these models.

  8. Dependence of the bright end of galaxy luminosity function on cluster dynamical state

    CERN Document Server

    Wen, Z L

    2014-01-01

    Luminosity function of cluster galaxies provides a fundamental constraint on galaxy evolution in cluster environments. By using the bright member galaxies of a large sample of rich clusters identified from Sloan Digital Sky Survey, we obtain the bright end of composite luminosity functions of cluster galaxies, and study their dependence on cluster dynamical state. After a redshift-evolution correction of absolute magnitude, the luminosity function of member galaxies can be well fitted by a Schechter function when the brightest cluster galaxies (BCGs) are excluded. The absolute magnitudes of BCGs follow a Gaussian function with a characteristic width of about 0.36 mag. We find that the luminosity function of galaxies in more relaxed clusters has a fainter characteristic absolute magnitude (M_{\\ast}), and these clusters have fewer bright non-BCG member galaxies but a brighter BCG. Our results suggest the co-evolution of galaxy population with cluster dynamical state and somewhat support the hierarchical formati...

  9. Relativistic Effect in Galaxy Clustering

    OpenAIRE

    Yoo, Jaiyul

    2014-01-01

    The general relativistic description of galaxy clustering provides a complete and unified treatment of all the effects in galaxy clustering such as the redshift-space distortion, gravitational lensing, Sachs-Wolfe effects, and their relativistic effects. In particular, the relativistic description resolves the gauge issues in the standard Newtonian description of galaxy clustering by providing the gauge-invariant expression for the observed galaxy number density. The relativistic effect in ga...

  10. Galaxy cluster's rotation

    CERN Document Server

    Manolopoulou, Maria

    2016-01-01

    We study the possible rotation of cluster galaxies, developing, testing and applying a novel algorithm which identifies rotation, if such does exits, as well as its rotational centre, its axis orientation, rotational velocity amplitude and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte-Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z<~0.1 with member galaxies selected from the SDSS DR10 spectroscopic database. We find that ~35% of our clusters are rotating when using a set of strict criteria, while loosening the criteria we find this fraction increasing to ~48%. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation that the significance and strength of their...

  11. The rotation of Galaxy Clusters

    OpenAIRE

    Tovmassian, Hrant M.

    2015-01-01

    The method for detection of the galaxy cluster rotation based on the study of distribution of member galaxies with velocities lower and higher of 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 in which does not differ significantly from the cluste...

  12. Gravitational Lensing by Nearby Clusters of Galaxies

    CERN Document Server

    Cypriano, E S; Campusano, L E; Kneib, J P; Giovanelli, R; Haynes, M P; Dale, D A; Hardy, E; Cypriano, Eduardo S.; Sodré, Laerte; Campusano, Luis E.; Kneib, Jean-Paul; Giovanelli, Riccardo; Haynes, Martha P.; Dale, Daniel A.; Hardy, Eduardo

    2001-01-01

    We present an estimation of the expected number of arcs and arclets in a sample of nearby (z<0.1) clusters of galaxies, that takes into account the magnitude limit of the objects as well as seeing effects. We show that strong lensing effects are not common, but also they are not as rare as usually stated. Indeed, for a given cluster, they present a strong dependence with the magnitude limit adopted in the analysis and the seeing of the observations. We also describe the procedures and results of a search for lensing effects in a sample of 33 clusters spanning the redshift range of 0.014 to 0.076, representative of the local cluster distribution. This search produced two arc candidates. The first one is in A3408 (z=0.042), the same arc previously discovered by Campusano & Hardy (1996), with z=0.073 and associated to the brightest cluster galaxy. The second candidate is in the cluster A3266 (z=0.059) and is near a bright elliptical outside the cluster center, requiring the presence of a very massive sub-...

  13. Magnetic Bubbles in Galaxy Clusters

    OpenAIRE

    McNamara, B. R.

    2003-01-01

    I discuss Chandra X-ray Observatory measurements of cavities in galaxy clusters and their implications for heating the intracluster gas. The emerging paradigm for cooling flows has important implications for understanding self-regulated galaxy formation.

  14. Globular Clusters around Galaxies in Groups

    CERN Document Server

    Rocha, C D; Bolte, M; Ziegler, B L; Puzia, T

    2001-01-01

    We have obtained deep photometry of NGC 1199 (in the compact group HCG 22) and NGC 6868 (in the Telescopium loose group) with the Keck II and the VLT-I telescopes. Both galaxies are the optically brightest galaxy of their groups. NGC 1199 has two companion galaxies at a median projected distance of only 33 kpc and, based in its peculiar internal structure and large X-ray halo, NGC 6868 has been proposed to be a merger remnant. Our analysis of $B$ and $R$ images uncovered a population of globular clusters around both galaxies, with total (and local) specific frequency S_N = 3.6\\pm1.8 (3.4\\pm1.5) for NGC 1199 and S_N = 1.8\\pm1.1 (0.8\\pm0.4) for NGC 6868. The radial profile of the globulars of NGC 1199 follows the light distribution of the galaxy and can be fitted by a power--law and a ``core model'' with a very steep slope (\\alpha = 2.5\\pm0.3). In the case of NGC 6868, the profile of the globulars is well fitted by a power--law and a ``core model'' profile of slope 1.4\\pm0.3 and is shallower than the galaxy lig...

  15. The Assembly of Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Impact of stochastic gas motions on galaxy cluster abundance profiles

    CERN Document Server

    Rebusco, P; Böhringer, H; Forman, W

    2005-01-01

    The impact of stochastic gas motions on the metal distribution in cluster core is evaluated. Peaked abundance profiles are a characteristic feature of clusters with cool cores and abundance peaks are likely associated with the brightest cluster galaxies (BCGs) which dwell in cluster cores. The width of the abundance peaks is however significantly broader than the BCG light distribution, suggesting that some gas motions are transporting metals originating from within the BCG. Assuming that this process can be treated as diffusive and using the brightest X-ray cluster A426 (Perseus) as an example, we estimate that a diffusion coefficient of the order of $2 10^{29} {\\rm cm^2 s^{-1}}$ is needed to explain the width of the observed abundance profiles. Much lower (higher) diffusion coefficients would result in too peaked (too shallow) profiles. Such diffusion could be produced by stochastic gas motions and our analysis provides constraints on the product of their characteristic velocity and their spatial coherence ...

  17. The Rotation of Galaxy Clusters

    Science.gov (United States)

    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.

  18. The rotation of Galaxy Clusters

    CERN Document Server

    Tovmassian, Hrant M

    2015-01-01

    The method for detection of the galaxy cluster rotation based on the study of distribution of member galaxies with velocities lower and higher of 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 in 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 have merging with other clusters and groups of galaxies, in the result of which the rotation has been prevented.

  19. Cosmology with clusters of galaxies

    CERN Document Server

    Bahcall, Neta A

    1995-01-01

    Rich clusters of galaxies, the largest virialized systems known, provide a powerful tool for the study of cosmology. Some of the fundamental questions that can be addressed with clusters of galaxies include: how did galaxies and large-scale structure form and evolve? What is the amount, composition and distribution of matter in the universe? I review some of the studies utilizing clusters of galaxies to investigare, among others: - The dark matter on clusters scale and the mean mass-density of the universe; - The large-scale structure of the universe; - The peculiar velocity field on large scales; - The mass-function of groups and clusters of galaxies; - The constraints placed on specific cosmological models using the cluster data.

  20. The brightest stars as distance indicators

    International Nuclear Information System (INIS)

    The luminosities of the brightest early-type supergiants have a well known dependence on the luminosity of the galaxy. In addition, many of the brightest blue 'stars' are actually compact HII regions, clusters, and composite images. This is a serious problem in increasingly distant galaxies. Therefore, they are not recommended as distance indicators. The brightest M supergiants have an upper bound to their bolometric luminosities due to the stability limit of the most massive evolved stars, making the red supergiants potentially powerful distance indicators. 32 refs

  1. Fossil groups in the Millennium simulation. From the brightest to the faintest galaxies during the past 8 Gyr

    CERN Document Server

    Kanagusuku, Maria Jose; Zandivarez, Ariel

    2016-01-01

    We investigate the evolution of bright and faint galaxies in fossil and non-fossil groups. We used mock galaxies constructed based on the Millennium run simulation II. We identified fossil groups at redshift zero according to two different selection criteria, and then built reliable control samples of non-fossil groups that reproduce the fossil virial mass and assembly time distributions. The faint galaxies were defined as having r-band absolute magnitudes in the range [-16,-11]. We analysed the properties of the bright and faint galaxies in fossil and non-fossil groups during the past 8 Gyr. We observed that the brightest galaxy in fossil groups is typically brighter and more massive than their counterparts in control groups. Fossil groups developed their large magnitude gap between the brightest galaxies around 3.5 Gyr ago. The brightest galaxy stellar masses of all groups show a notorious increment at that time. By analysing the behaviour of the magnitude gap between the first and the second, third, and fo...

  2. The sizes of galaxy halos in galaxy cluster Abell 1689

    OpenAIRE

    Halkola, A.; Seitz, S.; Pannella, M.

    2006-01-01

    The multiple images observed in galaxy cluster Abell 1689 provide strong constraints not only on the mass distribution of the cluster but also on the ensemble properties of the cluster galaxies. Using parametric strong lensing models for the cluster, and by assuming well motivated scaling laws between the truncation radius s and the velocity dispersion sigma of a cluster galaxy we are able to derive sizes of the dark matter halos of cluster galaxies. For the scaling law expected for galaxies ...

  3. ROSAT Discovers Unique, Distant Cluster of Galaxies

    Science.gov (United States)

    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

  4. Astrophysics of galaxy clusters

    Science.gov (United States)

    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.

  5. Simulations of the merging galaxy cluster Abell 3376

    CERN Document Server

    Machado, Rubens E G

    2013-01-01

    Observed galaxy clusters often exhibit X-ray morphologies suggestive of recent interaction with an infalling subcluster. Abell 3376 is a nearby (z=0.046) massive galaxy cluster whose bullet-shaped X-ray emission indicates that it may have undergone a recent collision. It displays a pair of Mpc-scale radio relics and its brightest cluster galaxy is located 970 h_70^-1 kpc away from the peak of X-ray emission, where the second brightest galaxy lies. We attempt to recover the dynamical history of Abell 3376. We perform a set of N-body adiabatic hydrodynamical simulations using the SPH code Gadget-2. These simulations of binary cluster collisions are aimed at exploring the parameter space of possible initial configurations. By attempting to match X-ray morphology, temperature, virial mass and X-ray luminosity, we set approximate constraints on some merger parameters. Our best models suggest a collision of clusters with mass ratio in the range 1/6-1/8, and having a subcluster with central gas density four times hi...

  6. Galaxy harassment and the evolution of clusters of galaxies

    CERN Document Server

    Moore, B; Lake, G; Dressler, A; Oemler, A E; Moore, Ben; Katz, Neal; Lake, George; Dressler, Alan; Oemler, Augustus

    1995-01-01

    Disturbed spiral galaxies with high rates of star formation pervaded clusters of galaxies just a few billion years ago, but nearby clusters exclude spirals in favor of ellipticals. ``Galaxy harassment" (frequent high speed galaxy encounters) drives the morphological transformation of galaxies in clusters, provides fuel for quasars in subluminous hosts and leaves detectable debris arcs. Simulated images of harassed galaxies are strikingly similar to the distorted spirals in clusters at z \\sim 0.4 observed by the Hubble Space Telescope.

  7. The luminosity function of cluster galaxies relations among M$_{1}$, M* and the morphological type

    CERN Document Server

    Trevese, D; Appodia, B

    1996-01-01

    A study of the luminosity function of 36 Abell clusters of galaxies has been carried out using photographic plates obtained with the Palomar 1.2 m Schmidt telescope. The relation between the magnitude M_1 of the brightest cluster member and the Schechter function parameter M* has been analyzed. A positive correlation between M* and M_1 is found. However clusters appear segregated in the M_1-M* plane according to their Rood & Sastry class in such a way that on average M_1 becomes brighter while M* becomes fainter going from late to early Rood & Sastry and also Bautz & Morgan classes. Also a partial correlation analysis involving the magnitude M_10 of the 10th brightest galaxy, shows a negative intrinsic correlation between M_1 and M*. These results agree with the cannibalism model for the formation of brightest cluster members, and provide new constraints for theories of cluster formation and evolution.

  8. Brightest Group Galaxies: Stellar Mass and Star Formation Rate (paper I)

    CERN Document Server

    Gozaliasl, Ghassem; Khosroshahi, Habib G; Mirkazemi, Mohammad; Erfanianfar, Ghazaleh; Tanaka, Masayuki

    2016-01-01

    We study the distribution and evolution of the stellar mass and the star formation rate (SFR) of the brightest group galaxies (BGGs) over $ 0.04galaxy groups selected from the COSMOS, AEGIS, and XMM-LSS fields. We compare our results with predictions from the semi-analytic models based on the Millennium simulation. In contrast to model predictions, we find that, as the universe evolves, the stellar mass distribution evolves towards a normal distribution. This distribution tends to skew to low mass BGGs at all redshifts implying the presence of a star-forming population of the BGGs with $ M_S\\sim10^{10.5} M_{\\odot} $ which results in the shape of the stellar mass distribution deviating from a normal distribution. In agreement with models and previous studies, we find that the mean stellar mass of BGGs grows with time by a factor of $\\sim2$ between $z=1.3$ to $z=0.1$, however, the significant growth occurs above $ z=0.4$. The BGGs are not entirely a dormant p...

  9. Gravitational Redshift of Galaxies in Clusters from the Sloan Digital Sky Survey and the Baryon Oscillation Spectroscopic Survey

    OpenAIRE

    Sadeh, Iftach; Feng, Low Lerh; Lahav, Ofer

    2014-01-01

    The gravitational redshift effect allows one to directly probe the gravitational potential in clusters of galaxies. Following up on Wojtak et al. [Nature (London) 477, 567 (2011)], we present a new measurement. We take advantage of new data from the tenth data release of the Sloan Digital Sky Survey and the Baryon Oscillation Spectroscopic Survey. We compare the spectroscopic redshift of the brightest cluster galaxies (BCGs) with that of galaxies at the outskirts of clusters, using a sample w...

  10. The redistribution of matter in the cores of galaxy clusters

    Science.gov (United States)

    Laporte, Chervin F. P.; White, Simon D. M.

    2015-08-01

    We present cosmological N-body resimulations of the assembly of the Brightest Cluster Galaxies (BCGs) in rich clusters. At z = 2, we populate dark matter subhaloes with self-gravitating stellar systems whose abundance and structure match observed high-redshift galaxies. By z = 0, mergers have built much larger galaxies at cluster centre. Their dark matter density profiles are shallower than in corresponding dark-matter-only simulations, but their total mass density profiles (stars + dark matter) are quite similar. Differences are found only at radii where the effects of central black holes may be significant. Dark matter density slopes shallower than γ = 1.0 occur for r/r200 BCG cores as large as rc ˜ 3 kpc. The good agreement of all these properties with recent observational studies of BCG structure suggests that dissipational processes have not played a dominant role in the assembly of the observed systems.

  11. Galaxy cluster baryon fractions revisited

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, Anthony H. [Department of Astronomy, University of Florida, Gainesville, FL 32611-2055 (United States); Sivanandam, Suresh; Zabludoff, Ann I.; Zaritsky, Dennis [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2013-11-20

    We measure the baryons contained in both the stellar and hot-gas components for 12 galaxy clusters and groups at z ∼ 0.1 with M = 1-5 × 10{sup 14} M {sub ☉}. This paper improves upon our previous work through the addition of XMM-Newton X-ray data, enabling measurements of the total mass and masses of each major baryonic component—intracluster medium, intracluster stars, and stars in galaxies—for each system. We recover a mean relation for the stellar mass versus halo mass, M{sub ⋆}∝M{sub 500}{sup −0.52±0.04}, that is 1σ shallower than in our previous result. We confirm that the partitioning of baryons between the stellar and hot-gas components is a strong function of M {sub 500}; the fractions of total mass in stars and X-ray gas within a sphere of radius r {sub 500} scale as f{sub ⋆}∝M{sub 500}{sup −0.45±0.04} and f{sub gas}∝M{sub 500}{sup 0.26±0.03}, respectively. We also confirm that the combination of the brightest cluster galaxy and intracluster stars is an increasingly important contributor to the stellar baryon budget in lower halo masses. Studies that fail to fully account for intracluster stars typically underestimate the normalization of the stellar baryon fraction versus M {sub 500} relation by ∼25%. Our derived stellar baryon fractions are also higher, and the trend with halo mass weaker, than those derived from recent halo occupation distribution and abundance matching analyses. One difference from our previous work is the weak, but statistically significant, dependence here of the total baryon fraction upon halo mass: f{sub bary}∝M{sub 500}{sup 0.16±0.04}. For M {sub 500} ≳ 2 × 10{sup 14}, the total baryon fractions within r {sub 500} are on average 18% below the universal value from the seven year Wilkinson Microwave Anisotropy Probe (WMAP) analysis, or 7% below for the cosmological parameters from the Planck analysis. In the latter case, the difference between the universal value and cluster baryon fractions is

  12. Alignment of Red-Sequence Cluster Dwarf Galaxies: From the Frontier Fields to the Local Universe

    Science.gov (United States)

    Barkhouse, Wayne Alan; Archer, Haylee; Burgad, Jaford; Foote, Gregory; Rude, Cody; Lopez-Cruz, Omar

    2015-08-01

    Galaxy clusters are the largest virialized structures in the universe. Due to their high density and mass, they are an excellent laboratory for studying the environmental effects on galaxy evolution. Numerical simulations have predicted that tidal torques acting on dwarf galaxies as they fall into the cluster environment will cause the major axis of the galaxies to align with their radial position vector (a line that extends from the cluster center to the galaxy's center). We have undertaken a study to measure the redshift evolution of the alignment of red-sequence cluster dwarf galaxies based on a sample of 57 low-redshift Abell clusters imaged at KPNO using the 0.9-meter telescope, and 64 clusters from the WINGS dataset. To supplement our low-redshift sample, we have included galaxies selected from the Hubble Space Telescope Frontier fields. Leveraging the HST data allows us to look for evolutionary changes in the alignment of red-sequence cluster dwarf galaxies over a redshift range of 0 results based on the alignment of the red-sequence dwarf galaxies with: 1) the major axis of the brightest cluster galaxy, 2) the major axis of the cluster defined by the position of cluster members, and 3) a radius vector pointing from the cluster center to individual dwarf galaxies. Our combined cluster sample is sub-divided into different radial regions and redshift bins.

  13. Planck's dusty GEMS: The brightest gravitationally lensed galaxies discovered with the Planck all-sky survey

    Science.gov (United States)

    Cañameras, R.; Nesvadba, N. P. H.; Guery, D.; McKenzie, T.; König, S.; Petitpas, G.; Dole, H.; Frye, B.; Flores-Cacho, I.; Montier, L.; Negrello, M.; Beelen, A.; Boone, F.; Dicken, D.; Lagache, G.; Le Floc'h, E.; Altieri, B.; Béthermin, M.; Chary, R.; de Zotti, G.; Giard, M.; Kneissl, R.; Krips, M.; Malhotra, S.; Martinache, C.; Omont, A.; Pointecouteau, E.; Puget, J.-L.; Scott, D.; Soucail, G.; Valtchanov, I.; Welikala, N.; Yan, L.

    2015-09-01

    We present an analysis of CO spectroscopy and infrared-to-millimetre dust photometry of 11 exceptionally bright far-infrared (FIR) and sub-mm sources discovered through a combination of the Planck all-sky survey and follow-up Herschel-SPIRE imaging - "Planck's Dusty Gravitationally Enhanced subMillimetre Sources". Each source has a secure spectroscopic redshift z = 2.2-3.6 from multiple lines obtained through a blind redshift search with EMIR at the IRAM 30-m telescope. Interferometry was obtained at IRAM and the SMA, and along with optical/near-infrared imaging obtained at the CFHT and the VLT reveal morphologies consistent with strongly gravitationally lensed sources, including several giant arcs. Additional photometry was obtained with JCMT/SCUBA-2 and IRAM/GISMO at 850 μm and 2 mm, respectively. The SEDs of our sources peak near either the 350 μm or 500 μm bands of SPIRE with peak flux densities between 0.35 and 1.14 Jy. All objects are extremely bright isolated point sources in the 18'' beam of SPIREat 250 μm, with apparent FIR luminosities of up to 3 × 1014 L⊙ (not correcting for the lensing effect). Their morphologies, sizes, CO line widths, CO luminosities, dust temperatures, and FIR luminosities provide additional empirical evidence that these are amongst the brightest strongly gravitationally lensed high-redshift galaxies on the sub-mm sky. Our programme extends the successful wide-area searches for strongly gravitationally lensed high-redshift galaxies (carried out with the South Pole Telescope and Herschel) towards even brighter sources, which are so rare that their systematic identification requires a genuine all-sky survey like Planck. Six sources are above the ≃600 mJy 90% completeness limit of the Planck catalogue of compact sources (PCCS) at 545 and 857 GHz, which implies that these must literally be amongst the brightest high-redshift FIR and sub-mm sources on the extragalactic sky. We discuss their dust masses and temperatures, and use

  14. Velocity segregation effects in galaxy clusters at 0.4<~z<~1.5

    CERN Document Server

    Barsanti, S; Biviano, A; Borgani, S; Annunziatella, M; Nonino, M

    2016-01-01

    Our study is meant to extend our knowledge of the galaxy color and luminosity segregation in velocity space (VCS and VLS, resp.), to clusters at intermediate and high redshift. Our sample is a collection of 41 clusters in the 0.4=0.8. For the first time, we detect VLS in non-local clusters and confirm that VLS only affects the very luminous galaxies, with brighter galaxies having lower velocities. The threshold magnitude of VLS is ~m3+0.5, where m3 is the magnitude of the third brightest cluster galaxy, and current data suggest that the threshold value moves to fainter magnitudes at higher redshift. We also detect (marginal) evidence of VLS for blue galaxies. We conclude that the segregation effects, when their study is extended to distant clusters, can be important tracers of the galaxy evolution and cluster assembly and discuss the poor/no evidence of VCS at high redshift.

  15. Seven poor clusters of galaxies

    Science.gov (United States)

    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.

  16. THE GALAXY CONTENT OF SDSS CLUSTERS AND GROUPS

    International Nuclear Information System (INIS)

    Imaging data from the Sloan Digital Sky Survey are used to characterize the population of galaxies in groups and clusters detected with the MaxBCG algorithm. We investigate the dependence of brightest cluster galaxy (BCG) luminosity, and the distributions of satellite galaxy luminosity and satellite color, on cluster properties over the redshift range 0.1 ≤ z ≤ 0.3. The size of the data set allows us to make measurements in many bins of cluster richness, radius and redshift. We find that, within r 200 of clusters with mass above 3 x 1013 h -1 M sun, the luminosity function (LF) of both red and blue satellites is only weakly dependent on richness. We further find that the shape of the satellite LF does not depend on cluster-centric distance for magnitudes brighter than 0.25 Mi - 5log10 h =-19. However, the mix of faint red and blue galaxies changes dramatically. The satellite red fraction is dependent on cluster-centric distance, galaxy luminosity, and cluster mass, and also increases by ∼5% between redshifts 0.28 and 0.2, independent of richness. We find that BCG luminosity is tightly correlated with cluster richness, scaling as L BCG ∼ M 0.3200, and has a Gaussian distribution at fixed richness, with σlogL ∼ 0.17 for massive clusters. The ratios of BCG luminosity to total cluster luminosity and characteristic satellite luminosity scale strongly with cluster richness: in richer systems, BCGs contribute a smaller fraction of the total light, but are brighter compared to typical satellites. This study demonstrates the power of cross-correlation techniques for measuring galaxy populations in purely photometric data.

  17. Groups and clusters of galaxies

    International Nuclear Information System (INIS)

    In this thesis, a correlative study is performed with respect to the radio and X-ray parameters of galaxy clusters and groups of galaxies (Msub(v)-Psub(1.4); Msub(v)-Lsub(x); Lsub(x)-Psub(1.4); R-Msub(v) correlations). Special attention is paid to correlations with cD and elliptical galaxies. It is concluded that in rich clusters massive cD galaxies form; massive galaxies are able to bind a large X-ray halo; strong X-ray emitters fuel their central radio sources at a high rate; the total gas content of groups is low, which implies that the contribution of groups to the total matter density in the universe is small. (Auth.)

  18. Towards a realistic population of simulated galaxy groups and clusters

    CERN Document Server

    Brun, Amandine M C Le; Schaye, Joop; Ponman, Trevor J

    2013-01-01

    We present a new suite of large-volume cosmological hydrodynamical simulations called cosmo-OWLS. They form an extension to the OverWhelmingly Large Simulations (OWLS) project, and have been designed to help improve our understanding of cluster astrophysics and non-linear structure formation, which are now the limiting systematic errors when using clusters as cosmological probes. Starting from identical initial conditions in either the Planck or WMAP7 cosmologies, we systematically vary the most important 'sub-grid' physics, including feedback from supernovae and active galactic nuclei (AGN). We compare the properties of the simulated galaxy groups and clusters to a wide range of observational data, such as X-ray luminosity and temperature, gas mass fractions, entropy and density profiles, Sunyaev-Zel'dovich flux, I-band mass-to-light ratio, dominance of the brightest cluster galaxy, and central massive black hole (BH) masses, by producing synthetic observations and mimicking observational analysis techniques...

  19. Do the stellar populations of the brightest two group galaxies depend on the magnitude gap?

    CERN Document Server

    Trevisan, M; Khosroshahi, H G

    2016-01-01

    We investigate how the stellar populations of first and second brightest group galaxies (respectively BGGs and SBGGs) vary as a function of the magnitude gap, {\\Delta}M_12, using an SDSS-based sample of 569 groups with elliptical BGGs. The sample is complete in redshift, luminosity and for {\\Delta}M_12 up to 2.5 mag, and contains 75 optical fossil groups (FGs, with {\\Delta}M_12 > 2.0 mag). We determine ages, metallicities, and star formation histories (SFHs) of BGGs and SBGGs using the STARLIGHT code with two single stellar population (SSP) models, one of which (MILES) leads to significantly more extended SFHs than the other (BC03). After removing the dependence with stellar mass, there is no correlation with magnitude gap of BGG ages, metallicities, and SFHs derived with the BC03 model. However, with the MILES model, the BGGs in FGs appear to have more extended SFHs than those in regular groups. But this signature with MILES is not seen in the colours, specific star formation rates nor in the 4000 A breaks, ...

  20. Gravitational redshift of galaxies in clusters from SDSS and BOSS

    CERN Document Server

    Sadeh, Iftach; Lahav, Ofer

    2014-01-01

    The gravitational redshift effect allows one to directly probe the gravitational potential in clusters of galaxies. As such, it provides a fundamental test of general relativity (GR), and may help to constrain alternative theories of gravity. Following up on Wojtak, Hansen & Hjorth (2011), we present a new measurement. We take advantage of new data from the tenth data release of SDSS and BOSS, covering a range of redshift between 0.05 and 0.6. After selection, our dataset includes 60k galaxies, matched to 12k clusters, with an average cluster mass of $10^{14} M_{\\odot}$. The analysis is focused on optimizing the selection method of clusters and of galaxies, taking into account possible systematic biases. We compare the light originating from the brightest cluster galaxies (BCGs), to that of galaxies at the outskirts of clusters. We find that BCGs have an average relative redshift of 11 km/s, with a standard deviation of +7 and -5 km/s. The result is consistent with the measurement of Wojtak et al. and is ...

  1. Detailed modeling of cluster galaxies in free-form lenses

    Science.gov (United States)

    Lam, Daniel

    2015-08-01

    The main goal of the Frontier Fields is to characterize the population of high redshift galaxies that are gravitationally lensed and magnified by foreground massive galaxy clusters. The magnification received by lensed images has to be accurately quantified in order to derive the correct science results. The magnification is in turn computed from lens models, which are constructed from various constraints, most commonly the positions and redshifts of multiply-lensed galaxies.The locations and magnification of multiple images that appear near cluster galaxies are very sensitive to the mass distribution of those individual galaxies. In current free-form lens models, they are at best crudely approximated by arbitrary mass halos and are usually being completely neglected. Given sufficient free parameters and iterations, such models may be highly consistent but their predictive power would be rather limited. This shortcoming is particularly pronounced in light of the recent discovery of the first multiply-lensed supernova in the Frontier Fields cluster MACSJ1149. The proximity of its images to cluster galaxies mandates detailed modeling on galaxy-scales, where free-form methods solely based on grid solutions simply fail.We present a hybrid free-form lens model of Abell 2744, which for the first time incorporates a detailed mass component modeled by GALFIT that accurately captures the stellar light distribution of the hundred brightest cluster galaxies. The model better reproduces the image positions than a previous version, which modeled cluster galaxies with simplistic NFW halos. Curiously, this improvement is found in all but system 2, which has two radial images appearing around the BCG. Despite its complex light profile is being captured by GALFIT, the persistent discrepancies suggest considering mass distributions that may be largely offset from the stellar light distribution.

  2. The Morphologies and Alignments of Gas, Mass, and the Central Galaxies of CLASH Clusters of Galaxies

    Science.gov (United States)

    Donahue, Megan; Ettori, Stefano; Rasia, Elena; Sayers, Jack; Zitrin, Adi; Meneghetti, Massimo; Voit, G. Mark; Golwala, Sunil; Czakon, Nicole; Yepes, Gustavo; Baldi, Alessandro; Koekemoer, Anton; Postman, Marc

    2016-03-01

    Morphology is often used to infer the state of relaxation of galaxy clusters. The regularity, symmetry, and degree to which a cluster is centrally concentrated inform quantitative measures of cluster morphology. The Cluster Lensing and Supernova survey with Hubble Space Telescope (CLASH) used weak and strong lensing to measure the distribution of matter within a sample of 25 clusters, 20 of which were deemed to be “relaxed” based on their X-ray morphology and alignment of the X-ray emission with the Brightest Cluster Galaxy. Toward a quantitative characterization of this important sample of clusters, we present uniformly estimated X-ray morphological statistics for all 25 CLASH clusters. We compare X-ray morphologies of CLASH clusters with those identically measured for a large sample of simulated clusters from the MUSIC-2 simulations, selected by mass. We confirm a threshold in X-ray surface brightness concentration of C ≳ 0.4 for cool-core clusters, where C is the ratio of X-ray emission inside 100 h70-1 kpc compared to inside 500 {h}70-1 kpc. We report and compare morphologies of these clusters inferred from Sunyaev-Zeldovich Effect (SZE) maps of the hot gas and in from projected mass maps based on strong and weak lensing. We find a strong agreement in alignments of the orientation of major axes for the lensing, X-ray, and SZE maps of nearly all of the CLASH clusters at radii of 500 kpc (approximately 1/2 R500 for these clusters). We also find a striking alignment of clusters shapes at the 500 kpc scale, as measured with X-ray, SZE, and lensing, with that of the near-infrared stellar light at 10 kpc scales for the 20 “relaxed” clusters. This strong alignment indicates a powerful coupling between the cluster- and galaxy-scale galaxy formation processes.

  3. Combining Galaxy-Galaxy Lensing and Galaxy Clustering

    Energy Technology Data Exchange (ETDEWEB)

    Park, Youngsoo [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Krause, Elisabeth [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Dodelson, Scott [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Jain, Bhuvnesh [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Amara, Adam [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Becker, Matt [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Bridle, Sarah [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Clampitt, Joseph [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Crocce, Martin [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Honscheid, Klaus [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Gaztanaga, Enrique [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Sanchez, Carles [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Wechsler, Risa [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    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.

  4. DISTANT CLUSTER OF GALAXIES [left

    Science.gov (United States)

    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

  5. Percolation technique for galaxy clustering

    Science.gov (United States)

    Klypin, Anatoly; Shandarin, Sergei F.

    1993-01-01

    We study percolation in mass and galaxy distributions obtained in 3D simulations of the CDM, C + HDM, and the power law (n = -1) models in the Omega = 1 universe. Percolation statistics is used here as a quantitative measure of the degree to which a mass or galaxy distribution is of a filamentary or cellular type. The very fast code used calculates the statistics of clusters along with the direct detection of percolation. We found that the two parameters mu(infinity), characterizing the size of the largest cluster, and mu-squared, characterizing the weighted mean size of all clusters excluding the largest one, are extremely useful for evaluating the percolation threshold. An advantage of using these parameters is their low sensitivity to boundary effects. We show that both the CDM and the C + HDM models are extremely filamentary both in mass and galaxy distribution. The percolation thresholds for the mass distributions are determined.

  6. A chemical evolution model for galaxy clusters

    OpenAIRE

    Portinari, L.; A. Moretti(Fermilab, Batavia, IL, USA); Chiosi, C.

    2001-01-01

    We develop a toy-model for the chemical evolution of the intracluster medium, polluted by the galactic winds from elliptical galaxies. The model follows the "galaxy formation history" of cluster galaxies, constrained by the observed luminosity function.

  7. INTRINSIC ALIGNMENT OF CLUSTER GALAXIES: THE REDSHIFT EVOLUTION

    International Nuclear Information System (INIS)

    We present measurements of two types of cluster galaxy alignments based on a volume limited and highly pure (≥90%) sample of clusters from the GMBCG catalog derived from Data Release 7 of the Sloan Digital Sky Survey (SDSS DR7). We detect a clear brightest cluster galaxy (BCG) alignment (the alignment of major axis of the BCG toward the distribution of cluster satellite galaxies). We find that the BCG alignment signal becomes stronger as the redshift and BCG absolute magnitude decrease and becomes weaker as BCG stellar mass decreases. No dependence of the BCG alignment on cluster richness is found. We can detect a statistically significant (≥3σ) satellite alignment (the alignment of the major axes of the cluster satellite galaxies toward the BCG) only when we use the isophotal fit position angles (P.A.s), and the satellite alignment depends on the apparent magnitudes rather than the absolute magnitudes of the BCGs. This suggests that the detected satellite alignment based on isophotal P.A.s from the SDSS pipeline is possibly due to the contamination from the diffuse light of nearby BCGs. We caution that this should not be simply interpreted as non-existence of the satellite alignment, but rather that we cannot detect them with our current photometric SDSS data. We perform our measurements on both SDSS r-band and i-band data, but do not observe a passband dependence of the alignments.

  8. Cosmological simulations of galaxy clusters

    CERN Document Server

    Borgani, Stefano

    2009-01-01

    We review recent progress in the description of the formation and evolution of galaxy clusters in a cosmological context by using numerical simulations. We focus our presentation on the comparison between simulated and observed X-ray properties, while we will also discuss numerical predictions on properties of the galaxy population in clusters. Many of the salient observed properties of clusters, such as X-ray scaling relations, radial profiles of entropy and density of the intracluster gas, and radial distribution of galaxies are reproduced quite well. In particular, the outer regions of cluster at radii beyond about 10 per cent of the virial radius are quite regular and exhibit scaling with mass remarkably close to that expected in the simplest case in which only the action of gravity determines the evolution of the intra-cluster gas. However, simulations generally fail at reproducing the observed cool-core structure of clusters: simulated clusters generally exhibit a significant excess of gas cooling in th...

  9. Density profiles of galaxy groups and clusters from SDSS galaxy-galaxy weak lensing

    CERN Document Server

    Mandelbaum, R; Cool, R J; Blanton, M; Hirata, C M; Brinkmann, J; Mandelbaum, Rachel; Seljak, Uros; Cool, Richard J.; Blanton, Michael; Hirata, Christopher M.; Brinkmann, Jonathan

    2006-01-01

    We present results of a measurement of the shape of the density profile of galaxy groups and clusters traced by 43 335 Luminous Red Galaxies (LRGs) with spectroscopic redshifts from the Sloan Digital Sky Survey (SDSS). The galaxies are selected such that they are the brightest within a cylindrical aperture, split into two luminosity samples, and modeled as the sum of stellar and dark matter components. We present a detailed investigation of many possible systematic effects that could contaminate our signal and develop methods to remove them, including a detected intrinsic alignment for galaxies within 100 kpc/h of LRGs which we remove using photometric redshift information. The resulting lensing signal is consistent with NFW profile dark matter halos; the SIS profile is ruled out at the 96 (conservatively) and 99.96 per cent confidence level (CL) for the fainter and brighter lens samples (respectively) when we fit using lensing data between 40 kpc/h and 2 Mpc/h with total signal-to-noise of 19 and 25 for the ...

  10. INTERACTIONS OF GALAXIES IN THE GALAXY CLUSTER ENVIRONMENT

    International Nuclear Information System (INIS)

    We study the dependence of galaxy properties on the clustercentric radius and the environment attributed to the nearest neighbor galaxy using the Sloan Digital Sky Survey galaxies associated with the Abell galaxy clusters. We find that there exists a characteristic scale where the properties of galaxies suddenly start to depend on the clustercentric radius at fixed neighbor environment. The characteristic scale is 1-3 times the cluster virial radius depending on galaxy luminosity. Existence of the characteristic scale means that the local galaxy number density is not directly responsible for the morphology-density relation in clusters because the local density varies smoothly with the clustercentric radius and has no discontinuity in general. What is really working in clusters is the morphology-clustercentric radius-neighbor environment relation, where the neighbor environment means both neighbor morphology and the local mass density attributed to the neighbor. The morphology-density relation appears working only because of the statistical correlation between the nearest neighbor distance and the local galaxy number density. We find strong evidence that the hydrodynamic interactions with nearby early-type galaxies is the main drive to quenching star formation activity of late-type galaxies in clusters. The hot cluster gas seems to play at most a minor role down to one tenth of the cluster virial radius. We also find that the viable mechanisms which can account for the clustercentric radius dependence of the structural and internal kinematics parameters are harassment and interaction of galaxies with the cluster potential. The morphology transformation of the late-type galaxies in clusters seems to have taken place through both galaxy-galaxy hydrodynamic interactions and galaxy-cluster/galaxy-galaxy gravitational interactions.

  11. Cold fronts in galaxy clusters

    CERN Document Server

    Ghizzardi, Simona; Molendi, Silvano

    2010-01-01

    Cold fronts have been observed in a large number of galaxy clusters. Understanding their nature and origin is of primary importance for the investigation of the internal dynamics of clusters. To gain insight on the nature of these features, we carry out a statistical investigation of their occurrence in a sample of galaxy clusters observed with XMM-Newton and we correlate their presence with different cluster properties. We have selected a sample of 45 clusters starting from the B55 flux limited sample by Edge et al. (1990) and performed a systematic search of cold fronts. We find that a large fraction of clusters host at least one cold front. Cold fronts are easily detected in all systems that are manifestly undergoing a merger event in the plane of the sky while the presence of such features in the remaining clusters is related to the presence of a steep entropy gradient, in agreement with theoretical expectations. Assuming that cold fronts in cool core clusters are triggered by minor merger events, we esti...

  12. The XXL survey: first results on clusters of galaxy

    Science.gov (United States)

    Pacaud, Florian

    2016-07-01

    With a total geometric area of 50deg2, XXL is the largest contiguous survey undertaken by the XMM-Newton satellite. The final survey catalogues are expected to contain ~25000 AGNs down to a flux limit of 3e-15 erg/s/cm2 and ~500 groups and clusters of galaxies up to a redshift of z~1.5. The first results of the survey focus on a sub-sample of the 100 brightest galaxy clusters and have recently been released to the public. In this contribution, I will first describe the sample and the modeling of its selection function. Then, I will discuss some of the most significant early scientific results based on the catalogue, namely the measured scaling relations, the baryon budget of XXL groups, the detection of superstructures and the cosmological implications of the sample.

  13. Faraday rotation in clusters of galaxies

    International Nuclear Information System (INIS)

    Faraday rotation in the clusters of galaxies are estimated systematically from the rotation measures of radio sources in or behind the clusters of galaxies. A cross-correlation of the Abell catalogue of rich clusters of galaxies with the catalogue of linear polarization of radio sources resulted in the identification of 10 clusters of galaxies. The average value of the rotation measures in the clusters of galaxies is about 20 rad m-2 and correspond to the well ordered magnetic field with the value of 2 x 10-7 gauss, if the electron densities is 10-4 cm-3. (author)

  14. Likelihood Functions for Galaxy Cluster Surveys

    CERN Document Server

    Holder, G

    2006-01-01

    Galaxy cluster surveys offer great promise for measuring cosmological parameters, but survey analysis methods have not been widely studied. Using methods developed decades ago for galaxy clustering studies, it is shown that nearly exact likelihood functions can be written down for galaxy cluster surveys. The sparse sampling of the density field by galaxy clusters allows simplifications that are not possible for galaxy surveys. An application to counts in cells is explicitly tested using cluster catalogs from numerical simulations and it is found that the calculated probability distributions are very accurate at masses above several times 10^{14}h^{-1} solar masses at z=0 and lower masses at higher redshift.

  15. Planck Intermediate Results. XI: The gas content of dark matter halos: the Sunyaev-Zeldovich-stellar mass relation for locally brightest galaxies

    DEFF Research Database (Denmark)

    Planck Collaboration,; Ade, P. A. R.; Aghanim, N.;

    2013-01-01

    We present the scaling relation between Sunyaev-Zeldovich (SZ) signal and stellar mass for almost 260,000 locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey (SDSS). These are predominantly the central galaxies of their dark matter halos. We calibrate the stellar-to-halo ...

  16. Cluster Physics with Merging Galaxy Clusters

    Directory of Open Access Journals (Sweden)

    Sandor M. Molnar

    2016-02-01

    Full Text Available Collisions between galaxy clusters provide a unique opportunity to study matter in a parameter space which cannot be explored in our laboratories on Earth. In the standard LCDM model, where the total density is dominated by the cosmological constant ($Lambda$ and the matter density by cold dark matter (CDM, structure formation is hierarchical, and clusters grow mostly by merging.Mergers of two massive clusters are the most energetic events in the universe after the Big Bang,hence they provide a unique laboratory to study cluster physics.The two main mass components in clusters behave differently during collisions:the dark matter is nearly collisionless, responding only to gravity, while the gas is subject to pressure forces and dissipation, and shocks and turbulenceare developed during collisions. In the present contribution we review the different methods used to derive the physical properties of merging clusters. Different physical processes leave their signatures on different wavelengths, thusour review is based on a multifrequency analysis. In principle, the best way to analyze multifrequency observations of merging clustersis to model them using N-body/HYDRO numerical simulations. We discuss the results of such detailed analyses.New high spatial and spectral resolution ground and space based telescopeswill come online in the near future. Motivated by these new opportunities,we briefly discuss methods which will be feasible in the near future in studying merging clusters.

  17. The mass function of young star clusters in spiral galaxies

    CERN Document Server

    Larsen, S S

    2008-01-01

    The initial cluster mass function (ICMF) in spiral galaxy discs is constrained and compared with data for old globular clusters and young clusters in starbursts. It is found that the observed ages and luminosities of the brightest clusters in spiral discs can be reproduced if the ICMF is a Schechter function with a cut-off mass (Mc) of a few times 10^5 Msun and disruption of optically visible clusters is dominated by relatively slow secular evolution. A direct Schechter function fit to the combined cluster MF for all spirals in the sample studied here yields Mc = (2.1+/-0.4)x10^5 Msun. The MFs in cluster-poor and cluster-rich spirals are statistically indistinguishable. An Mc=2.1x10^5 Msun Schechter function also fits the MF of young clusters in the Large Magellanic Cloud. If the same ICMF applies in the Milky Way, a bound cluster with M>10^5 Msun will form about once every 10 Myr, while an M>10^6 Msun cluster will form only once every 50 Gyr. Luminosity functions (LFs) of model cluster populations drawn from...

  18. INTEGRAL observations of Galaxy Clusters

    CERN Document Server

    Goldoni, P; Laurent, P; Cassé, M; Paul, J; Sarazin, C L

    2000-01-01

    Cluster of galaxies are the largest concentrations of visible mass in the Universe and therefore a fundamental topic of cosmology and astrophysics. Recent radio, EUV, and X-ray observations suggest that clusters contain large populations of diffuse nonthermal relativistic and/or superthermal particles. These particles may be produced by acceleration in cluster merger shocks, AGNs, and/or supernovae in cluster galaxies. Models for the nonthermal populations in clusters indicate that they should produce substantial hard X-ray and $\\gamma$ luminosities. The possible role of nonthermal particles in the dynamics of clusters is one of the greatest uncertainties in their use as cosmological probes. INTEGRAL offers, for the first time, the possibility of simultaneous medium resolution imaging (~ 12 arcmin) and high resolution spectroscopy (DeltaE/E ~ 2 keV @ 1.3 MeV) with exceptional sensitivity in the hard X-ray/soft gamma-ray band. The spatial resolution will allow discrete sources, such as AGNs, to be separated fr...

  19. THE ACS NEARBY GALAXY SURVEY TREASURY. X. QUANTIFYING THE STAR CLUSTER FORMATION EFFICIENCY OF NEARBY DWARF GALAXIES

    International Nuclear Information System (INIS)

    We study the relationship between the field star formation and cluster formation properties in a large sample of nearby dwarf galaxies. We use optical data from the Hubble Space Telescope and from ground-based telescopes to derive the ages and masses of the young (tage ∼< 100 Myr) cluster sample. Our data provide the first constraints on two proposed relationships between the star formation rate (SFR) of galaxies and the properties of their cluster systems in the low SFR regime. The data show broad agreement with these relationships, but significant galaxy-to-galaxy scatter exists. In part, this scatter can be accounted for by simulating the small number of clusters detected from stochastically sampling the cluster mass function. However, this stochasticity does not fully account for the observed scatter in our data, suggesting that there may be true variations in the fraction of stars formed in clusters in dwarf galaxies. Comparison of the cluster formation and the brightest cluster in our sample galaxies also provide constraints on cluster destruction models.

  20. Combining cluster number counts and galaxy clustering

    CERN Document Server

    Lacasa, Fabien

    2016-01-01

    We present a detailed modelling of the joint covariance matrix between cluster number counts and the galaxy angular power spectrum. To this end, we use a Halo Model framework complemented by a Halo Occupation Distribution model (HOD), and we work in full-sky. We demonstrate the importance of accounting for non-Gaussianity to produce accurate covariance predictions, as the Gaussian part of the covariance can in fact become subdominant in certain configurations. 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, and demonstrating interesting mathematical properties. 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 noticeable better constraints, in particular because the cross-covariance introduces a synergy between the probes on small scales....

  1. Strong Lensing Analysis of the Galaxy Cluster MACS J1319.9+7003 and the Discovery of a Shell Galaxy

    CERN Document Server

    Zitrin, Adi

    2016-01-01

    We present the first strong-lensing analysis of the massive galaxy cluster MACS J1319.9+7003 (z=0.33, also known as Abell 1722), as part of our ongoing effort to analyze massive clusters with archival Hubble Space Telescope imaging. We identified and spectroscopically measured with Keck/MOSFIRE two galaxies multiply-imaged by the cluster. Our lensing analysis reveals a modest lens, with an effective Einstein radius of $\\theta_{e}(z=2)=12\\pm1"$, enclosing $2.1\\pm0.3\\times10^{13}$ $M_{\\odot}$. We briefly discuss the strong-lensing properties of the cluster, using two different modeling techniques, and make the mass models publicly-available. Independently, we identified a noteworthy, young Shell Galaxy system forming around two likely interacting cluster members, 20" north of the Brightest Cluster Galaxy (BCG), with the smaller companion only 0.66" ($\\sim$3 kpc in projection) from the host galaxy's core. Shell galaxies are rare in galaxy clusters, and indeed, a simple estimate yields that they are only expected...

  2. Bar instabilities in Coma cluster galaxies

    International Nuclear Information System (INIS)

    The radial distribution of bar versus nonbar galaxies within the Coma cluster shows that a significantly larger fraction of bar galaxies are members of the cluster core. This result can be used either to estimate the time scale for the decay of bar instabilities or to argue that galaxies in the core of Coma are confined within the core

  3. The Accelerated Build-up of the Red Sequence in High Redshift Galaxy Clusters

    CERN Document Server

    Cerulo, P; Lidman, C; Demarco, R; Huertas-Company, M; Mei, S; Sánchez-Janssen, R; Barrientos, L F; Muñoz, R P

    2016-01-01

    We analyse the evolution of the red sequence in a sample of galaxy clusters at redshifts $0.8 11.5$) red sequence galaxies in the WINGS clusters, which do not include only the brightest cluster galaxies and which are not present in the HCS clusters, suggesting that they formed at epochs later than $z=0.8$. The comparison with the luminosity distribution of a sample of passive red sequence galaxies drawn from the COSMOS/UltraVISTA field in the photometric redshift range $0.8clusters is more developed at the faint end, suggesting that halo mass plays an important role in setting the time-scales for the build-up of the red sequence.

  4. Most Massive Globular Cluster in Our Galaxy

    Science.gov (United States)

    1994-05-01

    Far down in the southern sky, in the constellation of Centaurus, a diffuse spot of light can be perceived with the unaided eye. It may be unimpressive, but when seen through a telescope, it turns out to be a beautiful, dense cluster of innumerable stars [1]. Omega Centauri, as this object is called, is the brightest of its type in the sky. We refer to it as a "globular cluster", due to its symmetric form. It belongs to our Milky Way galaxy and astrophysical investigations have shown that it is located at a distance of about 16,500 light-years (1 light-year = 9,460,000,000,000 km). Nobody knows for sure how many individual stars it contains, but recent estimates run into the millions. Most of these stars are more than 10,000 million years old and it is generally agreed that Omega Centauri has a similar age. Measurements of its motion indicate that Omega Centauri plows through the Milky Way in an elongated orbit. It is not easy to understand how it has managed to keep its stars together during such an extended period. MEASURING STELLAR VELOCITIES IN OMEGA CENTAURI A group of astronomers [2] have recently carried through a major investigation of Omega Centauri. After many nights of observations at the ESO La Silla observatory, they now conclude that not only is this globular cluster the brightest, it is indeed by far the most massive known in the Milky Way. The very time-consuming observations were made during numerous observing sessions over a period of no less than 13 years (1981-1993), with the photoelectric spectrometer CORAVEL mounted on the 1.5-m Danish telescope at La Silla. The CORAVEL instrument (COrelation RAdial VELocities) was built in a joint effort between the Geneva (Switzerland) and Marseilles (France) observatories. It functions according to the cross-correlation technique, by means of which the spectrum of the observed star is compared with a "standard stellar spectrum" [3]. HOW HEAVY IS OMEGA CENTAURI? In the present study, a total of 1701

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

    International Nuclear Information System (INIS)

    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/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

  6. Galaxy Clustering & Galaxy-Galaxy Lensing: A Promising Union to Constrain Cosmological Parameters

    OpenAIRE

    Cacciato, Marcello; Bosch, Frank C. van den; More, Surhud; Li, Ran; Mo, H. J.; Yang, Xiaohu

    2008-01-01

    Galaxy clustering and galaxy-galaxy lensing probe the connection between galaxies and their dark matter haloes in complementary ways. On one hand, the halo occupation statistics inferred from the observed clustering properties of galaxies are degenerate with the adopted cosmology. Consequently, different cosmologies imply different mass-to-light ratios for dark matter haloes. On the other hand, galaxy-galaxy lensing yields direct constraints on the actual mass-to-light ratios and it can be us...

  7. Interactions of Galaxies in the Galaxy Cluster Environment

    CERN Document Server

    Park, Changbom

    2008-01-01

    We study the dependence of galaxy properties on the clustercentric radius and the environment attributed to the nearest neighbor galaxy using the SDSS galaxies associated with the Abell galaxy clusters. We find that there exists a characteristic scale where the properties of galaxies suddenly start to depend on the clustercentric radius at fixed neighbor environment. The characteristic scale is $1\\sim 3$ times the cluster virial radius depending on galaxy luminosity. Existence of the characteristic scale means that the local galaxy number density is not directly responsible for the morphology-density relation in clusters because the local density varies smoothly with the clustercentric radius and has no discontinuity in general. What is really working in clusters is the morphology-clustercentric radius-neighbor environment relation, where the neighbor environment means both neighbor morphology and the local mass density attributed to the neighbor. The morphology-density relation appears working only because o...

  8. JELLYFISH: EVIDENCE OF EXTREME RAM-PRESSURE STRIPPING IN MASSIVE GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Ram-pressure stripping by the gaseous intracluster medium has been proposed as the dominant physical mechanism driving the rapid evolution of galaxies in dense environments. Detailed studies of this process have, however, largely been limited to relatively modest examples affecting only the outermost gas layers of galaxies in nearby and/or low-mass galaxy clusters. We here present results from our search for extreme cases of gas-galaxy interactions in much more massive, X-ray selected clusters at z > 0.3. Using Hubble Space Telescope snapshots in the F606W and F814W passbands, we have discovered dramatic evidence of ram-pressure stripping in which copious amounts of gas are first shock compressed and then removed from galaxies falling into the cluster. Vigorous starbursts triggered by this process across the galaxy-gas interface and in the debris trail cause these galaxies to temporarily become some of the brightest cluster members in the F606W passband, capable of outshining even the Brightest Cluster Galaxy. Based on the spatial distribution and orientation of systems viewed nearly edge-on in our survey, we speculate that infall at large impact parameter gives rise to particularly long-lasting stripping events. Our sample of six spectacular examples identified in clusters from the Massive Cluster Survey, all featuring M F606W < –21 mag, doubles the number of such systems presently known at z > 0.2 and facilitates detailed quantitative studies of the most violent galaxy evolution in clusters

  9. Nature of multiple-nucleus cluster galaxies

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. Galaxy Evolution in Clusters Since z ~ 1

    Science.gov (United States)

    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.

  11. Constraints on Assembly Bias from Galaxy Clustering

    OpenAIRE

    Zentner, Andrew R.; Hearin, Andrew; Bosch, Frank C. van den; Lange, Johannes U.; Villarreal, Antonio

    2016-01-01

    We constrain the newly-introduced decorated Halo Occupation Distribution (HOD) model using SDSS DR7 measurements of projected galaxy clustering or r-band luminosity threshold samples. The decorated HOD is a model for the galaxy-halo connection that augments the HOD by allowing for the possibility of galaxy assembly bias: galaxy luminosity may be correlated with dark matter halo properties besides mass, Mvir. We demonstrate that it is not possible to rule out galaxy assembly bias using DR7 mea...

  12. The clustering properties of faint galaxies

    CERN Document Server

    Infante, L; Infante, L; Pritchet, C J

    1994-01-01

    The two-point angular correlation function of galaxies, \\wte, has been computed from a new survey of faint galaxies covering a 2 deg^2 area near the North Galactic Pole. This survey, which is complete to limiting magnitudes \\jmag=24 and \\fmag=23, samples angular scales as large as 1\\degpoint5. Faint galaxies are found to be more weakly clustered (by a factor of at least two) compared to galaxies observed locally. Clustering amplitudes are closer to model predictions in the red than in the blue. The weak clustering of faint galaxies cannot be explained by any plausible model of clustering evolution with redshift. However, one possible explanation of the clustering properties of intermediate redshift galaxies is that they resemble those of starburst galaxies and H II region galaxies, which are observed locally to possess weak clustering amplitudes. Our clustering amplitudes are also similar to those of nearby late-type galaxies, which are observed to be more weakly clustered than early-type galaxies A simple, s...

  13. Planck Intermediate Results. XI: The gas content of dark matter halos: the Sunyaev-Zeldovich-stellar mass relation for locally brightest galaxies

    CERN Document Server

    Ade, P A R; Arnaud, M; Ashdown, M; Atrio-Barandela, F; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Barrena, R; Bartlett, J G; Battaner, E; Benabed, K; Bernard, J -P; Bersanelli, M; Bikmaev, I; Böhringer, H; Bonaldi, A; Bond, J R; Borrill, J; Bouchet, F R; Bourdin, H; Burenin, R; Burigana, C; Butler, R C; Chamballu, A; Chary, R -R; Chiang, L -Y; Chon, G; Christensen, P R; Clements, D L; Colafrancesco, S; Colombi, S; Colombo, L P L; Comis, B; Coulais, A; Crill, B P; Cuttaia, F; Da Silva, A; Dahle, H; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Démoclès, J; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Dupac, X; Enßlin, T A; Finelli, F; Flores-Cacho, I; Frailis, M; Franceschi, E; Frommert, M; Galeotta, S; Ganga, K; Génova-Santos, R T; Giard, M; Giraud-Héraud, Y; González-Nuevo, J; Górski, K M; Gregorio, A; Gruppuso, A; Hansen, F K; Harrison, D; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huffenberger, K M; Hurier, G; Jaffe, T R; Jaffe, A H; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Khamitov, I; Kisner, T S; Kneissl, R; Knoche, J; Kunz, M; Kurki-Suonio, H; Lähteenmäki, A; Lamarre, J -M; Lasenby, A; Lawrence, C R; Jeune, M Le; Leonardi, R; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Luzzi, G; Macías-Pérez, J F; MacTavish, C J; Maffei, B; Maino, D; Mandolesi, N; Maris, M; Marleau, F; Marshall, D J; Martínez-González, E; Masi, S; Massardi, M; Matarrese, S; Mazzotta, P; Mei, S; Melchiorri, A; Melin, J -B; Mendes, L; Mennella, A; Mitra, S; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Natoli, P; Nørgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; Osborne, S; Oxborrow, C A; Pajot, F; Paoletti, D; Perotto, L; Perrotta, F; Piacentini, F; Piat, M; Pierpaoli, E; Piffaretti, R; Plaszczynski, S; Pointecouteau, E; Polenta, G; Popa, L; Poutanen, T; Pratt, G W; Prunet, S; Puget, J -L; Rachen, J P; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Ricciardi, S; Ristorcelli, I; Rocha, G; Roman, M; Rosset, C; Rossetti, M; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Savini, G; Scott, D; Spencer, L; Starck, J -L; Stolyarov, V; Sudiwala, R; Sunyaev, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Valenziano, L; Van Tent, B; Vielva, P; Villa, F; Vittorio, N; Wade, L A; Wandelt, B D; Wang, W; Welikala, N; Weller, J; White, S D M; White, M; Zacchei, A; Zonca, A

    2012-01-01

    We present the scaling relation between Sunyaev-Zeldovich (SZ) signal and stellar mass for almost 260,000 locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey (SDSS). These are predominantly the central galaxies of their dark matter halos. We calibrate the stellar-to-halo mass conversion using realistic mock catalogues based on the Millennium Simulation. Applying a multi-frequency matched filter to the Planck data for each LBG, and averaging the results in bins of stellar mass, we measure the mean SZ signal down to $M_\\ast\\sim 2\\times 10^{11} \\Msolar$, with a clear indication of signal at even lower stellar mass. We derive the scaling relation between SZ signal and halo mass by assigning halo properties from our mock catalogues to the real LBGs and simulating the Planck observation process. This relation shows no evidence for deviation from a power law over a halo mass range extending from rich clusters down to $M_{500}\\sim 2\\times 10^{13} \\Msolar$, and there is a clear indication of s...

  14. Investigations of Galaxy Clusters Using Gravitational Lensing

    Energy Technology Data Exchange (ETDEWEB)

    Wiesner, Matthew P. [Northern Illinois Univ., DeKalb, IL (United States)

    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.

  15. Internal kinematics of spiral galaxies in distant rich galaxy clusters

    CERN Document Server

    Jäger, K; Ziegler, B L; Heidt, J; Moellenhoff, C

    2004-01-01

    We present our project on galaxy evolution in the environment of distant rich clusters aiming at disentangling the importance of specific interaction and galaxy transformation processes from the hierarchical evolution of field galaxies. Spatially resolved MOS spectra were gained with VLT/FORS to analyze the internal kinematics of disk galaxies. First results are shown for the clusters MS 1008.1-1224 (z=0.30), Cl 0303+1706 (z=0.42), and Cl 0413-6559 (z=0.51). Out of 35 late type cluster members, 13 galaxies exhibit a rotation curve of the universal form rising in the inner region and passing over into a flat part. The other members have peculiar kinematics. The 13 cluster galaxies for which a maximum rotation velocity could be derived are distributed in the Tully-Fisher diagram very similar to field galaxies from the FORS Deep Field with corresponding redshifts. The same is true for seven non-cluster galaxies observed in the cluster fields. The TF-cluster spirals do not show any significant luminosity evolutio...

  16. Witnessing galaxy clusters: from maturity to childhood

    CERN Document Server

    Ascaso, Begoña

    2012-01-01

    Galaxy clusters are the largest structures in Universe. They are very important as both cosmological 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$$1.5-2) 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.

  17. Clusters and Groups of Galaxies : International Meeting

    CERN Document Server

    Giuricin, G; Mezzetti, M

    1984-01-01

    The large-scale structure of the Universe and systems Clusters, and Groups of galaxies are topics like Superclusters, They fully justify the meeting on "Clusters of great interest. and Groups of Galaxies". The topics covered included the spatial distribution and the clustering of galaxies; the properties of Superclusters, Clusters and Groups of galaxies; radio and X-ray observations; the problem of unseen matter; theories concerning hierarchical clustering, pancakes, cluster and galaxy formation and evolution. The meeting was held at the International Center for Theoretical Physics in Trieste (Italy) from September 13 to September 16, 1983. It was attended by about 150 participants from 22 nations who presented 67 invited lectures (il) and contributed papers (cp), and 45 poster papers (pp). The Scientific Organizing Committee consisted of F. Bertola, P. Biermann, A. Cavaliere, N. Dallaporta, D. Gerba1, M. Hack, J . V . Peach, D. Sciama (Chairman), G. Setti, M. Tarenghi. We are particularly indebted to D. Scia...

  18. Radio Relics in Clusters of Galaxies

    CERN Document Server

    Giovannini, G

    2004-01-01

    In this paper we review the observational results on Relic radio sources in clusters of galaxies. We discuss their observational properties, structures and radio spectra. We will show that Relics can be divided according to their size, morphology, and location in the galaxy cluster. These differences could be related to physical properties of Relic sources. The comparison with cluster conditions suggests that Relics could be related to shock waves originated by cluster mergers.

  19. Submillimeter Galaxy Number Counts and Magnification by Galaxy Clusters

    CERN Document Server

    Lima, Marcos; Devlin, Mark; Aguirre, James

    2010-01-01

    We present an analytical model which reproduces measured galaxy number counts from surveys in the wavelength range of 500 micron to 2 mm. The model involves a single high-redshift galaxy population with a Schechter luminosity function which has been gravitationally lensed by galaxy clusters in the mass range 10^13 to 10^15 Msun. This simple model reproduces both the low flux and the high flux end of the number counts reported by the BLAST, SCUBA, AzTEC and the 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 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 submillimeter galaxies detected at wavelengths larger than 500 micron lie at redshifts greater than 2.

  20. Reconstructing Galaxy Histories from Globular Clusters

    CERN Document Server

    West, M J; Marzke, R O; Jordan, A; West, Michael J.; Cote, Patrick; Marzke, Ronald O.; Jordan, Andres

    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. 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.

  1. Gas clumping in galaxy clusters

    CERN Document Server

    Eckert, D; Molendi, S; Vazza, F; Roncarelli, M; Gastaldello, F; Rossetti, M

    2013-01-01

    The reconstruction of galaxy cluster's gas density profiles is usually performed by assuming spherical symmetry and averaging the observed X-ray emission in circular annuli. In the case of a very inhomogeneous and asymmetric gas distribution, this method has been shown to return biased results in numerical simulations because of the $n^2$ dependence of the X-ray emissivity. We propose a method to recover the true density profiles in the presence of inhomogeneities, based on the derivation of the azimuthal median of the surface brightness in concentric annuli. We demonstrate the performance of this method with numerical simulations, and apply it to a sample of 31 galaxy clusters in the redshift range 0.04-0.2 observed with ROSAT/PSPC. The emissivity biases recovered by comparing the mean and the median are mild and show a slight trend of increasing bias with radius. For $R

  2. Clustering of galaxies in brane world models

    Science.gov (United States)

    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.

  3. Jellyfish: The origin and distribution of extreme ram-pressure stripping events in massive galaxy clusters

    CERN Document Server

    McPartland, Conor; Roediger, Elke; Blumenthal, Kelly

    2015-01-01

    We investigate the observational signatures and physical origin of ram-pressure stripping (RPS) in 63 massive galaxy clusters at $z=0.3-0.7$, based on images obtained with the Hubble Space Telescope. Using a training set of a dozen "jellyfish" galaxies identified earlier in the same imaging data, we define morphological criteria to select 211 additional, less obvious cases of RPS. Spectroscopic follow-up observations of 124 candidates so far confirmed 53 as cluster members. For the brightest and most favourably aligned systems we visually derive estimates of the projected direction of motion based on the orientation of apparent compression shocks and debris trails. Our findings suggest that the onset of these events occurs primarily at large distances from the cluster core ($>400$ kpc), and that the trajectories of the affected galaxies feature high impact parameters. Simple models show that such trajectories are highly improbable for galaxy infall along filaments but common for infall at high velocities, eve...

  4. Clustering of Galaxies in Brane World Models

    OpenAIRE

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

    2015-01-01

    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 a...

  5. M$_1$ - M* correlation in galaxy clusters

    CERN Document Server

    Trevese, D; Appodia, B

    1994-01-01

    Photographic F band photometry of a sample of 36 Abell clusters has been used to study the relation between the magnitude M_1 of the brightest cluster member and the Schechter function parameter M^*. Clusters appear segregated in the M_1-M^* plane according to their Rood \\& Sastry class. We prove on a statistical basis that on average, going from early to late RS classes, M_1 becomes brighter while M^* becomes fainter. The result agrees with the predictions of galactic cannibalism models, never confirmed by previous analyses.

  6. Observing dynamical friction in galaxy clusters

    CERN Document Server

    Adhikari, Susmita; Clampitt, Joseph

    2016-01-01

    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 10-20) satellites at 99% confidence.

  7. Observing dynamical friction in galaxy clusters

    Science.gov (United States)

    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 ‑20) satellites at 99% confidence.

  8. Infall patterns around rich clusters of galaxies

    Science.gov (United States)

    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.

  9. The merging cluster of galaxies Abell 3376: an optical view

    CERN Document Server

    Durret, Florence; Neto, Gastao B Lima; Adami, Christophe; Bertin, Emmanuel; Bagchi, Joydeep

    2013-01-01

    Abell 3376 is a merging cluster of galaxies at redshift z=0.046, famous mostly for its giant radio arcs, and shows an elongated and highly substructured X-ray emission, but has not been analysed in detail at optical wavelengths. We have obtained wide field images of Abell 3376 in the B band and derive the GLF applying a statistical subtraction of the background in three regions: a circle of 0.29 deg radius (1.5 Mpc) encompassing the whole cluster, and two circles centered on each of the two brightest galaxies (BCG2, northeast, coinciding with the peak of X-ray emission, and BCG1, southwest) of radii 0.15 deg (0.775 Mpc). We also compute the GLF in the zone around BCG1, which is covered by the WINGS survey in the B and V bands, by selecting cluster members in the red sequence in a (B-V) versus V diagram. Finally, we discuss the dynamical characteristics of the cluster implied by a Serna & Gerbal analysis. The GLFs are not well fit by a single Schechter function, but satisfactory fits are obtained by summin...

  10. The clustering evolution of dusty star-forming galaxies

    Science.gov (United States)

    Cowley, William I.; Lacey, Cedric G.; Baugh, Carlton M.; Cole, Shaun

    2016-05-01

    We present predictions for the clustering of galaxies selected by their emission at far infra-red (FIR) and sub-millimetre wavelengths. This includes the first predictions for the effect of clustering biases induced by the coarse angular resolution of single-dish telescopes at these wavelengths. We combine a new version of the GALFORM model of galaxy formation with a self-consistent model for calculating the absorption and re-emission of radiation by interstellar dust. Model galaxies selected at 850 μm reside in dark matter halos of mass Mhalo ˜ 1011.5 - 1012 h-1 M⊙, independent of redshift (for 0.2 ≲ z ≲ 4) or flux (for 0.25 ≲ S850μm ≲ 4 mJy). At z ˜ 2.5, the brightest galaxies (S850μm > 4 mJy) exhibit a correlation length of r0=5.5_{-0.5}^{+0.3} h-1 Mpc, consistent with observations. We show that these galaxies have descendants with stellar masses M⋆ ˜ 1011 h-1 M⊙ occupying halos spanning a broad range in mass Mhalo ˜ 1012 - 1014 h-1 M⊙. The FIR emissivity at shorter wavelengths (250, 350 and 500 μm) is also dominated by galaxies in the halo mass range Mhalo ˜ 1011.5 - 1012 h-1 M⊙, again independent of redshift (for 0.5 ≲ z ≲ 5). We compare our predictions for the angular power spectrum of cosmic infra-red background anisotropies at these wavelengths with observations, finding agreement to within a factor of ˜2 over all scales and wavelengths, an improvement over earlier versions of the model. Simulating images at 850 μm, we show that confusion effects boost the measured angular correlation function on all scales by a factor of ˜4. This has important consequences, potentially leading to inferred halo masses being overestimated by an order of magnitude.

  11. Galaxy and Mass Assembly (GAMA): Projected Galaxy Clustering

    CERN Document Server

    Farrow, D J; Norberg, Peder; Metcalfe, N; Baldry, I; Bland-Hawthorn, Joss; Brown, Michael J I; Hopkins, A M; Lacey, Cedric G; Liske, J; Loveday, Jon; Palamara, David P; Robotham, A S G; Sridhar, Srivatsan

    2015-01-01

    We measure the projected 2-point correlation function of galaxies in the 180 deg$^2$ equatorial regions of the GAMA II survey, for four different redshift slices between z = 0.0 and z=0.5. To do this we further develop the Cole (2011) method of producing suitable random catalogues for the calculation of correlation functions. We find that more r-band luminous, more massive and redder galaxies are more clustered. We also find that red galaxies have stronger clustering on scales less than ~3 $h^{-1}$ Mpc. We compare to two different versions of the GALFORM galaxy formation model, Lacey et al (in prep.) and Gonzalez-Perez et al. (2014), and find that the models reproduce the trend of stronger clustering for more massive galaxies. However, the models under predict the clustering of blue galaxies, can incorrectly predict the correlation function on small scales and under predict the clustering in our sample of galaxies with ~3$L_r$ . We suggest possible avenues to explore to improve these cluster- ing predictions....

  12. High Energy Phenomena in Clusters of Galaxies

    OpenAIRE

    P. Blasi(INAF Arcetri); Colafrancesco, S.

    1998-01-01

    Several phenomena in high energy astrophysics have been recently related to clusters of galaxies and to cosmic ray interactions occurring inside these structures. In many of these phenomena the observable effects depend on the energy density of cosmic rays confined in the Intra Cluster (IC) medium, which is a poorly known quantity. We propose here that useful indications about this quantity can be obtained from present and future observations of galaxy clusters in the radio and hard X-ray fre...

  13. Galaxy evolution in clusters since z=1

    Science.gov (United States)

    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.

  14. Galaxy Cluster Baryon Fractions Revisited

    CERN Document Server

    Gonzalez, Anthony H; Zabludoff, Ann I; Zaritsky, Dennis

    2013-01-01

    We measure the baryons contained in both the stellar and hot gas components for twelve galaxy clusters and groups at z~0.1 with M=1-5e14 Msun. This paper improves upon our previous work through the addition of XMM data, enabling measurements of the total mass and masses of each major baryonic component --- ICM, intracluster stars, and stars in galaxies --- for each system. We recover a relation for the stellar mass versus halo mass consistent with our previous result. We confirm that the partitioning of baryons between the stellar and hot gas components is a strong function of M500; the fractions of total mass in stars and X-ray gas within r500 scale as M500^-0.45 and M500^0.26, respectively. We also confirm that the combination of the BCG and intracluster stars is an increasingly important contributor to the stellar baryon budget in lower halo masses. We find a weak, but statistically significant, dependence of the total baryon fraction upon halo mass, scaling as M500^0.16. For M500>2e14, the total baryon fr...

  15. The effects of assembly bias on cosmological inference from galaxy-galaxy lensing and galaxy clusters

    CERN Document Server

    McEwen, Joseph E

    2016-01-01

    The combination of galaxy-galaxy lensing (GGL) and galaxy clustering is a promising route to measuring the amplitude of matter clustering and testing modified gravity theories of cosmic acceleration. Halo occupation distribution (HOD) modeling can extend the approach down to nonlinear scales, but galaxy assembly bias could introduce systematic errors by causing the HOD to vary with large scale environment at fixed halo mass. We investigate this problem using the mock galaxy catalogs created by Hearin & Watson (2013, HW13), which exhibit significant assembly bias because galaxy luminosity is tied to halo peak circular velocity and galaxy colour is tied to halo formation time. The preferential placement of galaxies (especially red galaxies) in older halos affects the cutoff of the mean occupation function $\\langle N_\\text{cen}(M_\\text{min}) \\rangle$ for central galaxies, with halos in overdense regions more likely to host galaxies. The effect of assembly bias on the satellite galaxy HOD is minimal. We intro...

  16. Clustering of Galaxies in Brane World Models

    CERN Document Server

    Hameeda, Mir; Ali, Ahmed Farag

    2015-01-01

    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 an 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.

  17. Galaxy Clustering Around Nearby Luminous Quasars

    Science.gov (United States)

    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.

  18. Detailed Abundance Analysis of the Brightest Star in Segue 2, the Least Massive Galaxy

    CERN Document Server

    Roederer, Ian U

    2014-01-01

    We present the first high resolution spectroscopic observations of one red giant star in the ultra-faint dwarf galaxy Segue 2, which has the lowest total mass (including dark matter) estimated for any known galaxy. These observations were made using the MIKE spectrograph on the Magellan II Telescope at Las Campanas Observatory. We perform a standard abundance analysis of this star, SDSS J021933.13+200830.2, and present abundances of 21 species of 18 elements as well as upper limits for 25 additional species. We derive [Fe/H] = -2.9, in excellent agreement with previous estimates from medium resolution spectroscopy. Our main result is that this star bears the chemical signatures commonly found in field stars of similar metallicity. The heavy elements produced by neutron-capture reactions are present, but they are deficient at levels characteristic of stars in other ultra-faint dwarf galaxies and a few luminous dwarf galaxies. The otherwise normal abundance patterns suggest that the gas from which this star for...

  19. Star Formation and Substructure in Galaxy Clusters

    CERN Document Server

    Cohen, Seth A; Wegner, Gary A; Einasto, Maret; Vennik, Jaan

    2014-01-01

    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 (SDSS). 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^0.1_r < -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 2 sigma, correlations between substructure and SF fraction. The...

  20. Cross-correlation Weak Lensing of SDSS galaxy Clusters II: Cluster Density Profiles and the Mass--Richness Relation

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, David E.; Sheldon, Erin S.; Wechsler, Risa H.; Rozo, Eduardo; Koester, Benjamin P.; Frieman, Joshua A.; McKay, Timothy A.; Evrard, August E.; Becker, Matthew; Annis, James

    2007-09-28

    We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by Sheldon et al. (2007). We present non-parametric inversions of the 2D shear profiles to the mean 3D cluster density and mass profiles in bins of both optical richness and cluster i-band luminosity. Since the mean cluster density profile is proportional to the cluster-mass correlation function, the mean profile is spherically symmetric by the assumptions of large-scale homogeneity and isotropy. We correct the inferred 3D profiles for systematic effects, including non-linear shear and the fact that cluster halos are not all precisely centered on their brightest galaxies. We also model the measured cluster shear profile as a sum of contributions from the brightest central galaxy, the cluster dark matter halo, and neighboring halos. We infer the relations between mean cluster virial mass and optical richness and luminosity over two orders of magnitude in cluster mass; the virial mass at fixed richness or luminosity is determined with a precision of {approx} 13% including both statistical and systematic errors. We also constrain the halo concentration parameter and halo bias as a function of cluster mass; both are in good agreement with predictions from N-body simulations of LCDM models. The methods employed here will be applicable to deeper, wide-area optical surveys that aim to constrain the nature of the dark energy, such as the Dark Energy Survey, the Large Synoptic Survey Telescope and space-based surveys.

  1. Statistical issues in galaxy cluster cosmology

    DEFF Research Database (Denmark)

    Mantz, Adam; Allen, Steven W.; Rapetti Serra, David Angelo

    2013-01-01

    The number and growth of massive galaxy clusters is a sensitive probe of cosmological structure formation and dark energy. Surveys at various wavelengths can detect clusters to high redshift, but the fact that cluster mass is not directly observable complicates matters, requiring us to simultaneo...... Science+Business Media New York 2013....

  2. X-ray Analysis of Filaments in Galaxy Clusters

    CERN Document Server

    Walker, S A; Fabian, A C; Sanders, J S

    2015-01-01

    We perform a detailed X-ray study of the filaments surrounding the brightest cluster galaxies in a sample of nearby galaxy clusters using deep Chandra observations, namely the Perseus, Centaurus and Virgo clusters, and Abell 1795. We compare the X-ray properties and spectra of the filaments in all of these systems, and find that their Chandra X-ray spectra are all broadly consistent with an absorbed two temperature thermal model, with temperature components at 0.75 and 1.7 keV. We find that it is also possible to model the Chandra ACIS filament spectra with a charge exchange model provided a thermal component is also present, and the abundance of oxygen is suppressed relative to the abundance of Fe. In this model, charge exchange provides the dominant contribution to the spectrum in the 0.5-1.0 keV band. However, when we study the high spectral resolution RGS spectrum of the filamentary plume seen in X-rays in Centaurus, the opposite appears to be the case. The properties of the filaments in our sample of clu...

  3. The Lifetime and Powers of FR IIs in Galaxy Clusters

    CERN Document Server

    Antognini, Joe; Martini, Paul

    2012-01-01

    We have identified and studied a sample of 151 FR IIs found in brightest cluster galaxies (BCGs) in the MaxBCG cluster catalog with data from FIRST and NVSS. We have compared the radio luminosities and projected lengths of these FR IIs to the projected length distribution of a range of mock catalogs generated by an FR II model and estimate the FR II lifetime to be 1.9 x 10^8 yr. The uncertainty in the lifetime calculation is a factor of two, due primarily to uncertainties in the ICM density and the FR II axial ratio. We furthermore measure the jet power distribution of FR IIs in BCGs and find that it is well described by a log-normal distribution with a median power of 1.1 x 10^37 W and a coefficient of variation of 2.2. These jet powers are nearly linearly related to the observed luminosities, and this relation is steeper than many other estimates, although it is dependent on the jet model. We investigate correlations between FR II and cluster properties and find that galaxy luminosity is correlated with jet...

  4. On the Merging Cluster Abell 578 and Its Central Radio Galaxy 4C +67.13

    CERN Document Server

    Hagino, K; Siemiginowska, A; Cheung, C C; Koziel-Wierzbowska, D; Szostek, A; Madejski, G; Harris, D E; Simionescu, A; Takahashi, T

    2015-01-01

    Here we analyze radio, optical, and X-ray data for a peculiar cluster Abell 578. This cluster is not fully relaxed and consists of two merging sub-systems. The brightest cluster galaxy, CGPG 0719.8+6704, is a pair of interacting ellipticals with projected separation $\\sim$10 kpc, the brighter of which hosts the radio source 4C +67.13. The Fanaroff-Riley type-II radio morphology of 4C +67.13 is unusual for central radio galaxies in local Abell clusters. Our new optical spectroscopy revealed that both nuclei of the CGPG 0719.8+6704 pair are active, albeit at low accretion rates corresponding to the Eddington ratio $\\sim10^{-4}$ (for the estimated black hole masses of $\\sim 3 \\times 10^8\\,M_\\odot$ and $\\sim 10^9 \\, M_\\odot$). The gathered X-ray ({\\it Chandra}) data allowed us to confirm and to quantify robustly the previously noted elongation of the gaseous atmosphere in the dominant sub-cluster, as well as a large spatial offset ($\\sim 60$\\,kpc projected) between the position of the brightest cluster galaxy and...

  5. The mass distribution of a moderate redshift galaxy group and brightest group galaxy from gravitational lensing and kinematics

    CERN Document Server

    McKean, J P; Koopmans, L V E; Vegetti, S; Czoske, O; Fassnacht, C D; Treu, T; More, A; Kocevski, D D

    2009-01-01

    The gravitational lens system CLASS B2108+213 has two radio-loud lensed images separated by 4.56 arcsec. The relatively large image separation implies that the lensing is caused by a group of galaxies. In this paper, new optical imaging and spectroscopic data for the lensing galaxies of B2108+213 and the surrounding field galaxies are presented. These data are used to investigate the mass and composition of the lensing structure. The redshift and stellar velocity dispersion of the main lensing galaxy (G1) are found to be z = 0.3648 +/- 0.0002 and sigma_v = 325 +/- 25 km/s, respectively. The optical spectrum of the lensed quasar shows no obvious emission or absorption features and is consistent with a BL Lac type radio source. However, the tentative detection of the G-band and Mg-b absorption lines, and a break in the spectrum of the host galaxy of the lensed quasar gives a likely source redshift of z = 0.67. Spectroscopy of the field around B2108+213 finds 51 galaxies at a similar redshift to G1, thus confirm...

  6. Structural classification of galaxies in clusters

    CERN Document Server

    Andreon, S; Andreon, Stefano; Davoust, Emmanuel

    1996-01-01

    The traditional method of morphological classification, by visual inspection of images of uniform quality and by reference to standards for each type, is critically examined. The rate of agreement among traditional morphologists on the morphological type of galaxies is estimated from published classification works, and is estimated at about 20 %, when galaxies are classified into three bins (E, S0, S+Irr). The advantages of the quantitative method of structural classification for classifying galaxies in clusters are outlined. This method is based on the isophotal analysis of galaxy images, and on the examination of quantitative structural parameters derived from this analysis, such as the profiles of luminosity, ellipticity and deviations from ellipticity of the galaxy. The structural and traditional methods are compared on a complete sample of 190 galaxies in the Coma cluster. The morphological types derived by both methods agree to within 15 or 20 %, the same rate as among traditional morphologists alone, t...

  7. High-energy emission from NGC 5506, the brightest hard X-ray Narrow Line Seyfert 1 galaxy

    CERN Document Server

    Soldi, S; Gehrels, N; De Jong, S; Lubinski, P

    2011-01-01

    We present results on the hard X-ray emission of NGC 5506, the brightest narrow line Seyfert 1 galaxy above 20 keV. All the recent observations by INTEGRAL, Swift and Suzaku have been analysed and spectral analysis during nine separated time periods has been performed. While flux variations by a factor of 2 were detected during the last 7 years, only moderate spectral variations have been observed, with the hint of a hardening of the X-ray spectrum and a decrease of the intrinsic absorption with time. Using Suzaku observations it is possible to constrain the amount of Compton reflection to R = 0.6-1.0, in agreement with previous results on the source. The signature of Comptonisation processes can also be found in the detection of a high-energy cut-off during part of the observations, at Ec = 40-100 keV. When a Comptonisation model is applied to the Suzaku data, the temperature and the optical depth of the Comptonising electron plasma are measured at kT = 60-80 keV and tau = 0.6-1.0, respectively. The properti...

  8. Constraints on Assembly Bias from Galaxy Clustering

    CERN Document Server

    Zentner, Andrew R; Bosch, Frank C van den; Lange, Johannes U; Villarreal, Antonio

    2016-01-01

    We constrain the newly-introduced decorated Halo Occupation Distribution (HOD) model using SDSS DR7 measurements of projected galaxy clustering or r-band luminosity threshold samples. The decorated HOD is a model for the galaxy-halo connection that augments the HOD by allowing for the possibility of galaxy assembly bias: galaxy luminosity may be correlated with dark matter halo properties besides mass, Mvir. We demonstrate that it is not possible to rule out galaxy assembly bias using DR7 measurements of galaxy clustering alone. Moreover, galaxy samples with Mr < -20 and Mr < -20.5 favor strong central galaxy assembly bias. These samples prefer scenarios in which high-concentration are more likely to host a central galaxy relative to low-concentration halos of the same mass. We exclude zero assembly bias with high significance for these samples. Satellite galaxy assembly bias is significant for the faintest sample, Mr < -19. We find no evidence for assembly bias in the Mr < -21 sample. Assembly bi...

  9. The ROSAT-ESO Flux-Limited X-Ray (REFLEX) Galaxy Cluster Survey III: The Power Spectrum

    OpenAIRE

    Schuecker, Peter; Boehringer, Hans; Guzzo, Luigi; Collins, Chris A.; Neumann, Doris M.; Schindler, Sabine; Voges, Wolfgang; De Grandi, Sabrina; Chincarini, Guido; Cruddace, Ray; Mueller, Volker; Reiprich, Thomas H.; Retzlaff, Joerg; Shaver, Peter

    2000-01-01

    We present a measure of the power spectrum on scales from 15 to 800 Mpc/h using the ROSAT-ESO Flux-Limited X-Ray(REFLEX) galaxy cluster catalogue. The REFLEX survey provides a sample of the 452 X-ray brightest southern clusters of galaxies with the nominal flux limit S=3.0 10^{-12}erg/s/cm2 for the ROSAT energy band (0.1-2.4)keV. Several tests are performed showing no significant incompletenesses of the REFLEX clusters with X-ray luminosities brighter than 10^{43}erg/s up to scales of about 8...

  10. Characterizing Galaxy Clusters with Gravitational Potential

    CERN Document Server

    Lau, Erwin Tin-Hay

    2010-01-01

    We propose a simple estimator for the gravitational potential of cluster-size halos using the temperature and density profiles of the intracluster gas based on the assumptions of hydrostatic equilibrium and spherical symmetry. Using high resolution cosmological simulations of galaxy clusters, we show that the scaling relation between this estimator and the gravitational potential has a small intrinsic scatter of about 10%, and it is insensitive to baryon physics outside the cluster core. The slope and the normalization of the scaling relation vary weakly with redshift, and they are relatively independent of the choice of radial range used and the dynamical states of the clusters. The results presented here provide a way for using the cluster potential function as an alternative to the cluster mass function in constraining cosmology using galaxy clusters.

  11. A Census of Baryons in Galaxy Clusters and Groups

    Science.gov (United States)

    Gonzalez, Anthony H.; Zaritsky, Dennis; Zabludoff, Ann I.

    2007-09-01

    We determine the contribution of stars in galaxies, intracluster stars, and the intracluster medium to the total baryon budget in nearby galaxy clusters and groups. We find that the baryon mass fraction (fb≡Ωb/Ωm) within r500 is constant for systems with M500 between 6×1013 and 1×1015 Msolar. Although fb is lower than the WMAP value, the shortfall is on the order of both the observational systematic uncertainties and the depletion of baryons within r500 that is predicted by simulations. The data therefore provide no compelling evidence for undetected baryonic components, particularly any that would be expected to vary in importance with cluster mass. A unique feature of the current analysis is direct inclusion of the contribution of intracluster light (ICL) in the baryon budget. With the addition of the ICL to the stellar mass in galaxies, the increase in X-ray gas mass fraction with increasing total mass is entirely accounted for by a decrease in the total stellar mass fraction, supporting the argument that the behavior of both the stellar and X-ray gas components is dominated by a decrease in star formation efficiency in more massive environments. Within just the stellar component, the fraction of the total stellar luminosity in the central, giant brightest cluster galaxy (BCG) and ICL (hereafter the BCG+ICL component) decreases as velocity dispersion (σ) increases for systems with 145 km s-1behavior arises from our sample selection, which favored systems with central, giant elliptical galaxies, remains unclear. A more robust result is the identification of low-mass groups with large BCG+ICL components, demonstrating that the creation of ``intracluster'' stars does not require a massive cluster environment. Within r500 and r200, the BCG+ICL contributes on average 40% and 33% of the total stellar light, respectively, for the clusters and groups in our sample. Because these fractions are functions of both enclosed radius and system mass, care should be

  12. Structure of the coma cluster of galaxies

    International Nuclear Information System (INIS)

    This study is based primarily upon a sample of 1722 galaxies in the Coma cluster observed by Abell. Abell's observations of the inner part of the Coma cluster (within 75 arc-min) are compared with those of several other observers, and a catalog of observations from several observers was prepared. The distribution of galaxies is tested for irregularities, finding marginal evidence that there are some clumps of galaxies in certain regions and magnitude ranges. However, it is found that axially symmetric bumps in the radial density distribution of galaxies are not significant. The projected spatial distribution of galaxies is then fitted in order to determine the core radius. The value of the core radius is found to be larger than that found by most previous authors, and it increases with increasing galaxy magnitude. This finding implies that a degree of mass segregation exists in the cluster. Finally, the spatial luminosity density at the center of the cluster is determined. The impact of the inclusion of non-members on the analysis is discussed along with different methods of determining membership in the cluster and correcting for the effects of nonmembers upon the observations

  13. Infall patterns around rich clusters of galaxies

    International Nuclear Information System (INIS)

    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. 26 refs

  14. Relics as Probes of Galaxy Cluster Mergers

    Indian Academy of Sciences (India)

    R. J. van Weeren; M. Brüggen; H. J. A. Röttgering; M. Hoeft

    2011-12-01

    Galaxy clusters grow by mergers with other clusters and galaxy groups. These mergers create shocks within the intracluster medium (ICM). It is proposed that particles can be accelerated to extreme energies within the shocks. In the presence of a magnetic field these particles should then form large regions emitting synchrotron radiation, creating the so-called radio relics. An example of a cluster with relics is CIZA J2242.8+5301. Here we present hydrodynamical simulations of idealized binary cluster collisions with the aim of constraining the merger scenario for this cluster. We conclude that by using the location, size and width of double radio relics we can set constraints on the mass ratios, impact parameters, time scales, and viewing geometries of binary cluster merger events.

  15. Quenching star formation in cluster galaxies

    CERN Document Server

    Taranu, Dan S; Balogh, Michael L; Smith, Russell J; Power, Chris; Krane, Brad

    2012-01-01

    In order to understand the processes that quench star formation within rich clusters, we construct a library of subhalo orbits drawn from lambdaCDM cosmological N-body simulations of four rich clusters. The orbits are combined with models of star formation followed by quenching in the cluster environment to predict colours and spectroscopic line indices of satellite galaxies. Simple models with only halo mass-dependent quenching and without environmental (i.e. cluster-dependent) quenching fail to reproduce the observed cluster-centric colour and absorption linestrength gradients. Models in which star formation is instantly quenched at the virial radius also fail to match the observations. Better matches to the data are achieved by more complicated bulge-disc models in which the bulge stellar populations depend only on the galaxy subhalo mass while the disc quenching depends on the cluster environment. In the most successful models quenching begins at pericentre, operating on an exponential timescale of 2 -- 3...

  16. Optical Mass Estimates of Galaxy Clusters

    CERN Document Server

    Girardi, M; Mardirossian, F; Mezzetti, M; Boschin, W

    1998-01-01

    We evaluate in a homogeneous way the optical masses of 170 nearby clusters (z< 0.15). The sample includes both data from the literature and the new ENACS data (Katgert et al. 1996, 1998). On the assumption that mass follows the galaxy distribution, we compute the masses of each cluster by applying the virial theorem to the member galaxies. We constrain the masses of very substructured clusters (about 10% of our clusters) between two limiting values. After appropriate rescaling to the X-ray radii, we compare our optical mass estimates to those derived from X-ray analyses, which we compiled from the literature (for 66 clusters). We find a good overall agreement. This agreement is expected in the framework of two common assumptions: that mass follows the galaxy distribution, and that clusters are not far from a situation of dynamical equilibrium with both gas and galaxies reflecting the same underlying mass distribution. We stress that our study strongly supports the reliability of present cluster mass estima...

  17. On the clustering of faint red galaxies

    Science.gov (United States)

    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 introduce a method to improve the 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 senario 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.

  18. Tidally Induced Bars of Galaxies in Clusters

    Science.gov (United States)

    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.

  19. Jellyfish: Observational Properties of Extreme Ram-Pressure Stripping Events in Massive Galaxy Clusters

    Science.gov (United States)

    Conor, McPartland; Ebeling, Harald; Roediger, Elke

    2015-08-01

    We investigate the physical origin and observational signatures of extreme ram-pressure stripping (RPS) in 63 massive galaxy clusters at z=0.3-0.7, based on data in the F606W passband obtained with the Advanced Camera for Surveys aboard the Hubble Space Telescope. Using a training set of a dozen ``jellyfish" galaxies identified earlier in the same imaging data, we define quantitative morphological criteria to select candidate galaxies which are similar to known cases of RPS. Considering a sample of 16 ``jellyfish" galaxies (10 of which we present for the first time), we visually derive estimates of the projected direction of motion based on dynamical features such as apparent compression shocks and debris trails. Our findings suggest that the observed events occur primarily at large distances from the cluster core and involve infall trajectories featuring high impact parameters. Simple models of cluster growth show that such trajectories are consistent with two scenarios: 1) galaxy infall along filaments; and 2) infall at high velocities (≥1000 km/s) characteristic of cluster mergers. The observed distribution of events is best described by timescales of ˜few Myr in agreement with recent numerical simulations of RPS. The broader areal coverage of the Hubble Frontier Fields should provide an even larger sample of RPS events to determine the relative contributions of infall and cluster mergers. Prompted by the discovery of several jellyfish galaxies whose brightness in the F606W passband rivals or exceeds that of the respective brightest cluster galaxy, we attempt to constrain the luminosity function of galaxies undergoing RPS. The observed significant excess at the bright end compared to the luminosity functions of blue cluster members strongly suggests enhanced star formation, thus challenging theoretical and numerical studies according to which RPS merely displaces existing star-forming regions. In-depth studies of individual objects will help test our

  20. Pegasus I and Pegasus II clusters of galaxies

    International Nuclear Information System (INIS)

    New radial velocities are presented for 35 galaxies in the fields of the Pegasus I and Pegasus II clusters. Many background galaxies with apparent photographic magnitude brighter than 15/sup m/6 are found to be superimposed upon the Pegasus I cluster. Galaxies with radial velocities near the average for the Pegasus II cluster are detected well outside the boundary of the cluster as defined in the Catalogue of Galaxies and Clusters of Galaxies by Zwicky et al. This suggests that the Pegasus II cluster is part of a large cloud of galaxies

  1. Luminosity segregation in three clusters of galaxies (A119, 2443, 2218)

    CERN Document Server

    Pracy, M B; De Propris, R; Couch, W J; Nulsen, P E J

    2005-01-01

    We use deep wide-field V-band imaging obtained with the Wide Field Camera at the prime focus of the Issac Newton Telescope to study the spatial and luminosity distribution of galaxies in three low redshift (0.04clusters: Abell 119, Abell 2443 and Abell 2218. The absolute magnitude limits probed in these clusters are M_{V} - 5logh_{0.7} = -13.3, -15.4 and -16.7mag respectively. The galaxy population, at all luminosities, along the line-of-sight to the clusters can be described by the linear combination of a King profile and a constant surface density of field galaxies. We find that, for these three clusters, the core radius is invariant with intrinsic luminosity of the cluster population to the above limits and thus there is no evidence for luminosity segregation in these clusters. The exception is the brightest galaxies in A2218 which exhibit a more compact spatial distribution. We find the total projected luminosity distribution (within 1Mpc of the cluster centre) can be well represented by a s...

  2. The luminosity function of star clusters in 20 star-forming galaxies based on Hubble legacy archive photometry

    International Nuclear Information System (INIS)

    Luminosity functions (LFs) have been determined for star cluster populations in 20 nearby (4-30 Mpc), star-forming galaxies based on Advanced Camera for Surveys source lists generated by the Hubble Legacy Archive (HLA). These cluster catalogs provide one of the largest sets of uniform, automatically generated cluster candidates available in the literature at present. Comparisons are made with other recently generated cluster catalogs demonstrating that the HLA-generated catalogs are of similar quality, but in general do not go as deep. A typical cluster LF can be approximated by a power law, dN/dL∝L α, with an average value for α of –2.37 and rms scatter = 0.18 when using the F814W ('I') band. A comparison of fitting results based on methods that use binned and unbinned data shows good agreement, although there may be a systematic tendency for the unbinned (maximum likelihood) method to give slightly more negative values of α for galaxies with steeper LFs. We find that galaxies with high rates of star formation (or equivalently, with the brightest or largest numbers of clusters) have a slight tendency to have shallower values of α. In particular, the Antennae galaxy (NGC 4038/39), a merging system with a relatively high star formation rate (SFR), has the second flattest LF in the sample. A tentative correlation may also be present between Hubble type and values of α, in the sense that later type galaxies (i.e., Sd and Sm) appear to have flatter LFs. Hence, while there do appear to be some weak correlations, the relative similarity in the values of α for a large number of star-forming galaxies suggests that, to first order, the LFs are fairly universal. We examine the bright end of the LFs and find evidence for a downturn, although it only pertains to about 1% of the clusters. Our uniform database results in a small scatter (≈0.4 to 0.5 mag) in the correlation between the magnitude of the brightest cluster (M brightest) and log of the number of

  3. The luminosity function of star clusters in 20 star-forming galaxies based on Hubble legacy archive photometry

    Energy Technology Data Exchange (ETDEWEB)

    Whitmore, Bradley C.; Bowers, Ariel S.; Lindsay, Kevin; Ansari, Asna; Evans, Jessica [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Chandar, Rupali [Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States); Larsen, Soeren, E-mail: whitmore@stsci.edu [Department of Astrophysics/IMAPP, Radboud University Nijmegen, P. O. Box 9010, 6500 GL Nijmegen (Netherlands)

    2014-04-01

    Luminosity functions (LFs) have been determined for star cluster populations in 20 nearby (4-30 Mpc), star-forming galaxies based on Advanced Camera for Surveys source lists generated by the Hubble Legacy Archive (HLA). These cluster catalogs provide one of the largest sets of uniform, automatically generated cluster candidates available in the literature at present. Comparisons are made with other recently generated cluster catalogs demonstrating that the HLA-generated catalogs are of similar quality, but in general do not go as deep. A typical cluster LF can be approximated by a power law, dN/dL∝L {sup α}, with an average value for α of –2.37 and rms scatter = 0.18 when using the F814W ('I') band. A comparison of fitting results based on methods that use binned and unbinned data shows good agreement, although there may be a systematic tendency for the unbinned (maximum likelihood) method to give slightly more negative values of α for galaxies with steeper LFs. We find that galaxies with high rates of star formation (or equivalently, with the brightest or largest numbers of clusters) have a slight tendency to have shallower values of α. In particular, the Antennae galaxy (NGC 4038/39), a merging system with a relatively high star formation rate (SFR), has the second flattest LF in the sample. A tentative correlation may also be present between Hubble type and values of α, in the sense that later type galaxies (i.e., Sd and Sm) appear to have flatter LFs. Hence, while there do appear to be some weak correlations, the relative similarity in the values of α for a large number of star-forming galaxies suggests that, to first order, the LFs are fairly universal. We examine the bright end of the LFs and find evidence for a downturn, although it only pertains to about 1% of the clusters. Our uniform database results in a small scatter (≈0.4 to 0.5 mag) in the correlation between the magnitude of the brightest cluster (M {sub brightest}) and log of

  4. Do Relaxed Clusters of Galaxies Exist?

    Science.gov (United States)

    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.

  5. A multiwavelength view of the galaxy cluster Abell 523 and its peculiar diffuse radio source

    Science.gov (United States)

    Girardi, M.; Boschin, W.; Gastaldello, F.; Giovannini, G.; Govoni, F.; Murgia, M.; Barrena, R.; Ettori, S.; Trasatti, M.; Vacca, V.

    2016-03-01

    We study the structure of the galaxy cluster Abell 523 (A523) at z = 0.104 using new spectroscopic data for 132 galaxies acquired at the Telescopio Nazionale Galileo, new photometric data from the Isaac Newton Telescope, and X-ray and radio data from the Chandra and Very Large Array archives. We estimate the velocity dispersion of the galaxy population, σ _V=949_{-60}^{+80} km s-1, and the X-ray temperature of the hot intracluster medium, kT = 5.3 ± 0.3 keV. We infer that A523 is a massive system: M200 ˜ 7-9 × 1014 M⊙. The analysis of the optical data confirms the presence of two subclusters, 0.75 Mpc apart, tracing the SSW-NNE direction and dominated by the two brightest cluster galaxies (BCG1 and BCG2). The X-ray surface brightness is strongly elongated towards the NNE direction, and its peak is clearly offset from both the brightest cluster galaxies (BCGs). We confirm the presence of a 1.3 Mpc large radio halo, elongated in the ESE-WNW direction and perpendicular to the optical/X-ray elongation. We detect a significant radio/X-ray offset and radio polarization, two features which might be the result of a magnetic field energy spread on large spatial scales. A523 is found consistent with most scaling relations followed by clusters hosting radio haloes, but quite peculiar in the Pradio-LX relation: it is underluminous in the X-rays or overluminous in radio. A523 can be described as a binary head-on merger caught after a collision along the SSW-NNE direction. However, minor optical and radio features suggest a more complex cluster structure, with A523 forming at the crossing of two filaments along the SSW-NNE and ESE-WNW directions.

  6. Dynamics of the Hydra I galaxy cluster

    Energy Technology Data Exchange (ETDEWEB)

    Fitchett, M.; Merritt, D.

    1988-12-01

    This paper examines the dynamics of the Hydra I cluster. This cluster has circularly symmetric galaxy and X-ray distributions, and a velocity histogram that is close to Gaussian. However, the velocity distribution of galaxies near the cluster center is very flat. Using various statistical tests, the probability that the observed velocities were drawn from a normal distribution, or from a set of spherical equilibrium models is calculated. Based on several of the tests, the data are inconsistent with the models at the approximately 2.4 sigma level. The possibility that substructure is important in this cluster is therefore considered. It is found that a model that is spherically symmetric at large radii, and clumpy at small radii, is more consistent with the kinematical data. The locations and the velocities of the brighter cluster galaxies also lend support to this hypothesis. Such a model can also explain why Hydra I does not lie along the L(x)-sigma relation for galaxy clusters. 42 references.

  7. Dynamics of the Hydra I galaxy cluster

    International Nuclear Information System (INIS)

    This paper examines the dynamics of the Hydra I cluster. This cluster has circularly symmetric galaxy and X-ray distributions, and a velocity histogram that is close to Gaussian. However, the velocity distribution of galaxies near the cluster center is very flat. Using various statistical tests, the probability that the observed velocities were drawn from a normal distribution, or from a set of spherical equilibrium models is calculated. Based on several of the tests, the data are inconsistent with the models at the approximately 2.4 sigma level. The possibility that substructure is important in this cluster is therefore considered. It is found that a model that is spherically symmetric at large radii, and clumpy at small radii, is more consistent with the kinematical data. The locations and the velocities of the brighter cluster galaxies also lend support to this hypothesis. Such a model can also explain why Hydra I does not lie along the L(x)-sigma relation for galaxy clusters. 42 references

  8. Linear clusters of galaxies - A194

    Science.gov (United States)

    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.

  9. The XXL Survey:X. K-band luminosity - weak-lensing mass relation for groups and clusters of galaxies

    OpenAIRE

    Ziparo, F.; Smith, G. P.; Mulroy, S. L.; Lieu, M.; Willis, J. P.; Hudelot, P.; McGee, S. L.; Fotopoulou, S.; Lidman, C.; Lavoie, S.; Pierre, M.; Adami, C.; Chiappetti, L.; Clerc, N.; Giles, P.

    2016-01-01

    Galaxy clusters and groups are important cosmological probes and giant cosmic laboratories for studying galaxy evolution. Much effort has been devoted to understanding how and when baryonic matter cools at the centre of potential wells. However, a clear picture of the efficiency with which baryons are converted into stars is still missing. We present the K-band luminosity–halo mass relation, LK,500−M500,WL, for a subsample of 20 of the 100 brightest clusters in the XXL Survey observed with WI...

  10. Correlation functions for extended mass galaxy clusters

    CERN Document Server

    Iqbal, Naseer; Hamid, Mubashir; Masood, Tabasum

    2012-01-01

    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 and 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.

  11. Non thermal emission in clusters of galaxies

    CERN Document Server

    Arnaud, M

    2008-01-01

    I briefly review our current knowledge of the non thermal emission from galaxy clusters and discuss future prospect with Simbol-X. Simbol-X will map the hard X-ray emission in clusters, determine its origin and disentangle the thermal and non-thermal components. Correlated with radio observations, the observation of the non-thermal X-ray emission, when confirmed, will allow to map both the magnetic field and the relativistic electron properties, key information to understand the origin and acceleration of relativistic particles in clusters and its impact on cluster evolution.

  12. Galaxy Luminosity Functions in WINGS clusters

    CERN Document Server

    Moretti, A; Poggianti, B M; Fasano, G; Varela, J; D'Onofrio, M; Vulcani, B; Cava, A; Fritz, J; Couch, W J; Moles, M; Kjærgaard, P

    2015-01-01

    Using V band photometry of the WINGS survey, we derive galaxy luminosity functions (LF) in nearby clusters. This sample is complete down to Mv=-15.15, and it is homogeneous, thus allowing the study of an unbiased sample of clusters with different characteristics. We constructed the photometric LF for 72 out of the original 76 WINGS clusters, excluding only those without a velocity dispersion estimate. For each cluster we obtained the LF for galaxies in a region of radius=0.5 x r200, and fitted them with single and double Schechter's functions. We also derive the composite LF for the entire sample, and those pertaining to different morphological classes. Finally we derive the spectroscopic cumulative LF for 2009 galaxies that are cluster members. The double Schechter fit parameters are neither correlated with the cluster velocity dispersion, nor with the X-ray luminosity. Our median values of the Schechter's fit slope are, on average, in agreement with measurements of nearby clusters, but are less steep that t...

  13. Plasma physics in clusters of galaxies

    CERN Document Server

    Eilek, J A

    2003-01-01

    Clusters of galaxies are the largest self-gravitating structures in the universe. Each cluster is filled with a large-scale plasma atmosphere, in which primordial matter is mixed with matter that has been processed inside stars. This is a wonderful plasma physics laboratory. Our diagnostics are the data we obtain from X-ray and radio telescopes. The thermal plasma is a strong X-ray source; from this we determine its density and temperature. Radio data reveal a relativistic component in the plasma, and first measurements of the intracluster magnetic field have now been made. Energization of the particles and the field must be related to the cosmological evolution of the cluster. The situation is made even richer by the few galaxies in each cluster which host radio jets. In these galaxies, electrodynamics near a massive black hole in the core of the galaxy lead to a collimated plasma beam which propagates from the nucleus out to supergalactic scales. These jets interact with the cluster plasma to form the struc...

  14. The Lifecycle of Clusters in Galaxies

    CERN Document Server

    Adamo, Angela

    2015-01-01

    We review many of the basic properties of star cluster systems, and focus in particular on how they relate to their host galaxy properties and ambient environment. The cluster mass and luminosity functions are well approximated by power-laws of the form $Ndm \\propto M^{\\alpha}dm$, with $\\alpha\\sim-2$ over most of the observable range. However, there is now clear evidence that both become steeper at high masses/luminosities, with the value of the downward turn dependent on environment. The host galaxy properties also appear to affect the cluster formation efficiency ($\\Gamma$ - i.e., the fraction of stars that form in bound clusters), with higher star-formation rate density galaxies having higher $\\Gamma$ values. Within individual galaxies, there is evidence for $\\Gamma$ to vary by a factor of 3-4, likely following the molecular gas surface density, in agreement with recent predictions. Finally, we discuss cluster disruption and its effect on the observed properties of a population, focussing on the age distri...

  15. Spectral Imaging of Galaxy Clusters with Planck

    Science.gov (United States)

    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.

  16. Luminosity function of clusters of galaxies

    CERN Document Server

    Paolillo, M; Longo, G; Puddu, E; Gal, R R; Scaramella, R; Djorgovski, S G; De Carvalho, R

    2001-01-01

    The composite galaxy luminosity function (hereafter LF) of 39 Abell clusters of galaxies is derived by computing the statistical excess of galaxy counts in the cluster direction with respect to control fields. Due to the wide field coverage of the digitised POSS-II plates, we can measure field counts around each cluster in a fully homogeneous way. Furthermore, the availability of virtually unlimited sky coverage allows us to directly compute the LF errors without having to rely on the estimated variance of the background. The wide field coverage also allows us to derive the LF of the whole cluster, including galaxies located in the cluster outskirts. The global composite LF has a slope alpha ~ -1.1+/-0.2 with minor variations from blue to red filters, and M* ~ -21.7,-22.2,-22.4 mag (H_0=50 km/s/Mpc) in g, r and i filters, respectively. These results are in quite good agreement with several previous determinations and in particular with the LF determined for the inner region of a largely overlapping set of clu...

  17. Energy Balance in Clusters of Galaxies

    Science.gov (United States)

    Motl, P. M.; Burns, J. M.

    2005-04-01

    We review different physical mechanisms that are likely to play a significant role in determining the detailed thermal state of gas in clusters of galaxies. Mergers are the dominant process impacting clusters and these collisions significantly perturb the cluster state. The continual loss of energy from the gas to radiation must also be accounted for and cooling gas can drive several positive feedback mechanisms. From simple energy arguments, AGN are likely to make a significant contribution to balance the energy lost from cluster cores. We also explore additional positive feedback mechanisms including supernovae feedback and thermal conduction. If AGN are the sole feedback mechanism, what are to be made of clusters that lack evidence for AGN activity yet have canonical cool cores? As cluster samples with high-resolution X-ray data grow larger, it is likely to be the properties of relaxed, cool-core clusters that will be the best guides to numerical simulations.

  18. Watching the Birth of a Galaxy Cluster?

    Science.gov (United States)

    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

  19. Discovery of a Strong Lensing Galaxy Embedded in a Cluster at z = 1.62

    CERN Document Server

    Wong, Kenneth C; Suyu, Sherry H; Momcheva, Ivelina G; Brammer, Gabriel B; Brodwin, Mark; Gonzalez, Anthony H; Halkola, Aleksi; Kacprzak, Glenn G; Koekemoer, Anton M; Papovich, Casey J; Rudnick, Gregory H

    2014-01-01

    We identify a strong lensing galaxy in the cluster IRC 0218 (also known as XMM-LSS J02182-05102) that is spectroscopically confirmed to be at $z=1.62$, making it the highest-redshift strong lens galaxy known. The lens is one of the two brightest cluster galaxies and lenses a background source galaxy into an arc and a counterimage. With Hubble Space Telescope grism and Keck/LRIS spectroscopy, we measure the source redshift to be $z_{\\rm S}=2.26$. Using HST imaging in ACS/F475W, ACS/F814W, WFC3/F125W, and WFC3/F160W, we model the lens mass distribution with an elliptical power-law profile and account for the effects of the cluster halo and nearby galaxies. The Einstein radius is $\\theta_{\\rm E}=0.38^{+0.02}_{-0.01}$'' ($3.2_{-0.1}^{+0.2}$ kpc) and the total enclosed mass is M$_{\\rm tot} (< \\theta_{\\rm E})=1.8^{+0.2}_{-0.1}\\times10^{11} {\\rm M}_{\\odot}$. We estimate that the cluster environment contributes $\\sim10$% of this total mass. Assuming a Chabrier IMF, the dark matter fraction within $\\theta_{{\\rm E}}...

  20. Cluster-lensing: A Python Package for Galaxy Clusters & Miscentering

    CERN Document Server

    Ford, Jes

    2016-01-01

    We describe a new open source package for calculating properties of galaxy clusters, including NFW halo profiles with and without the effects of cluster miscentering. This pure-Python package, cluster-lensing, provides well-documented and easy-to-use classes and functions for calculating cluster scaling relations, including mass-richness and mass-concentration relations from the literature, as well as the surface mass density $\\Sigma(R)$ and differential surface mass density $\\Delta\\Sigma(R)$ profiles, probed by weak lensing magnification and shear. Galaxy cluster miscentering is especially a concern for stacked weak lensing shear studies of galaxy clusters, where offsets between the assumed and the true underlying matter distribution can lead to a significant bias in the mass estimates if not accounted for. This software has been developed and released in a public GitHub repository, and is licensed under the permissive MIT license. The cluster-lensing package is archived on Zenodo (Ford 2016). Full documenta...

  1. HOMOGENEOUS UGRIZ PHOTOMETRY FOR ACS VIRGO CLUSTER SURVEY GALAXIES: A NON-PARAMETRIC ANALYSIS FROM SDSS IMAGING

    International Nuclear Information System (INIS)

    We present photometric and structural parameters for 100 ACS Virgo Cluster Survey (ACSVCS) galaxies based on homogeneous, multi-wavelength (ugriz), wide-field SDSS (DR5) imaging. These early-type galaxies, which trace out the red sequence in the Virgo Cluster, span a factor of nearly ∼103 in g-band luminosity. We describe an automated pipeline that generates background-subtracted mosaic images, masks field sources and measures mean shapes, total magnitudes, effective radii, and effective surface brightnesses using a model-independent approach. A parametric analysis of the surface brightness profiles is also carried out to obtain Sersic-based structural parameters and mean galaxy colors. We compare the galaxy parameters to those in the literature, including those from the ACSVCS, finding good agreement in most cases, although the sizes of the brightest, and most extended, galaxies are found to be most uncertain and model dependent. Our photometry provides an external measurement of the random errors on total magnitudes from the widely used Virgo Cluster Catalog, which we estimate to be σ(BT )∼ 0.13 mag for the brightest galaxies, rising to ∼ 0.3 mag for galaxies at the faint end of our sample (BT ∼ 16). The distribution of axial ratios of low-mass (dwarf) galaxies bears a strong resemblance to the one observed for the higher-mass (giant) galaxies. The global structural parameters for the full galaxy sample-profile shape, effective radius, and mean surface brightness-are found to vary smoothly and systematically as a function of luminosity, with unmistakable evidence for changes in structural homology along the red sequence. As noted in previous studies, the ugriz galaxy colors show a nonlinear but smooth variation over a ∼7 mag range in absolute magnitude, with an enhanced scatter for the faintest systems that is likely the signature of their more diverse star formation histories.

  2. Massive Star Clusters in Dwarf Galaxies

    CERN Document Server

    Larsen, Soeren S

    2015-01-01

    Dwarf galaxies can have very high globular cluster specific frequencies, and the GCs are in general significantly more metal-poor than the bulk of the field stars. In some dwarfs, such as Fornax, WLM, and IKN, the fraction of metal-poor stars that belong to GCs can be as high as 20%-25%, an order of magnitude higher than the 1%-2% typical of GCs in halos of larger galaxies. Given that chemical abundance anomalies appear to be present also in GCs in dwarf galaxies, this implies severe difficulties for self-enrichment scenarios that require GCs to have lost a large fraction of their initial masses. More generally, the number of metal-poor field stars in these galaxies is today less than what would originally have been present in the form of low-mass clusters if the initial cluster mass function was a power-law extending down to low masses. This may imply that the initial GC mass function in these dwarf galaxies was significantly more top-heavy than typically observed in present-day star forming environments.

  3. Interpreting the Clustering of Distant Red Galaxies

    CERN Document Server

    Tinker, Jeremy L; Zheng, Zheng

    2009-01-01

    We analyze the angular clustering of z~2.3 distant red galaxies (DRGs) measured by Quadri et al 2008. We find that, with robust estimates of the measurement errors and realistic halo occupation distribution modeling, the measured clustering can be well fit within standard halo occupation models, in contrast to previous results. However, in order to fit the strong break in w(theta) at theta=10 arcsec, nearly all satellite galaxies in the DRG luminosity range are required to be DRGs. Within this luminosity-threshold sample, the fraction of galaxies that are DRGs is ~44%, implying that the formation of DRGs is more efficient for satellite galaxies than for central galaxies. Despite the evolved stellar populations contained within DRGs at z=2.3, 90% of satellite galaxies in the DRG luminosity range have been accreted within 500 Myr. Thus, satellite DRGs must have known they would become satellites well before the time of their accretion. This implies that the formation of DRGs correlates with large-scale environm...

  4. Cool Core Bias in Sunyaev-Zel'dovich Galaxy Cluster Surveys

    CERN Document Server

    Lin, Henry W; Benson, Bradford; Miller, Eric

    2015-01-01

    Sunyaev-Zeldovich (SZ) surveys find massive clusters of galaxies by measuring the inverse Compton scattering of cosmic microwave background off of intra-cluster gas. The cluster selection function from such surveys is expected to be nearly independent of redshift and cluster astrophysics. In this work, we estimate the effect on the observed SZ signal of centrally-peaked gas density profiles (cool cores) and radio emission from the brightest cluster galaxy (BCG) by creating mock observations of a sample of clusters that span the observed range of classical cooling rates and radio luminosities. For each cluster, we make simulated SZ observations by the South Pole Telescope and characterize the cluster selection function, but note that our results are broadly applicable to other SZ surveys. We find that the inclusion of a cool core can cause a change in the measured SPT significance of a cluster between 0.01% - 10% at z > 0.3, increasing with cuspiness of the cool core and angular size on the sky of the cluster ...

  5. X-ray cavities in a sample of 83 SPT-selected clusters of galaxies: Tracing the evolution of AGN feedback in clusters of galaxies out to z=1.2

    CERN Document Server

    Hlavacek-Larrondo, J; Benson, B A; Forman, W R; Allen, S W; Bleem, L E; Ashby, M L N; Bocquet, S; Brodwin, M; Dietrich, J P; Jones, C; Liu, J; Saliwanchik, B R; Saro, A; Schrabback, T; Song, J; Stalder, B; Vikhlinin, A; Zenteno, A

    2014-01-01

    X-ray cavities are key tracers of mechanical (or radio mode) heating arising from the active galactic nuclei (AGN) in brightest cluster galaxies. We report on a survey for X-ray cavities in 83 massive, high-redshift (0.40.5) redshift. Despite these limitations, our results suggest that the power generated by AGN feedback in brightest cluster galaxies has remained unchanged for over half of the age of the Universe (>7 Gyrs at z=0.8). On average, the detected X-ray cavities have powers of 0.8-5*10^45 erg/s, enthalpies of 3-6*10^59 erg, and radii of 17 kpc. Integrating over 7 Gyrs, we find that the supermassive black holes in the brightest cluster galaxies may have accreted 10^8 to several 10^9M_sun of material to power these outflows. This level of accretion indicates that significant supermassive black hole growth may occur not only at early times, in the quasar era, but at late times as well. We also find that X-ray cavities at high-redshift may inject an excess heat of 0.1-1.0 keV per particle into the hot i...

  6. The dynamics and internal mass distribution of rich galaxy cluster cores

    Science.gov (United States)

    Laporte, Chervin Fabien Pierre; White, Simon

    2015-08-01

    It has often been argued that the findings of shallow dark matter density profiles in galaxy clusters may be a source of tension between observations and benign expectations in LCDM. In this talk I will present cosmological N-body resimulations of the assembly of the Brightest Cluster Galaxies (BCGs) in rich clusters within LCDM. At z=2, I populate dark matter subhalos with self-gravitating stellar systems whose abundance and structure match observed high-redshift galaxies. I then follow their evolution in the build of the final clusters. By z=0, the dark matter density profiles are shallower than in corresponding dark-matter-only simulations, but their total mass density profiles (stars + dark matter) are quite similar. Differences are found only at radii where the effects of central black holes may be significant. Dark matter density slopes shallower than gamma=1.0 occur for r/r200BCG through mergers. Based on the accretion history in the simulations I will also argue that supermassive black hole mergers could create BCG cores as large as rc~3kpc.Finally I will introduce some new re-simulations which are being currently used to study the evolution of the tidal truncation radii of cluster galaxies and making predictions on the kinematics of BCGs to large radii.

  7. Recent Dynamical Evolution of Galaxy Clusters

    CERN Document Server

    Plionis, M

    2002-01-01

    Evidence is presented for a recent evolution of the relaxation processes in clusters of galaxies, using large optical and X-ray cluster samples. The criteria of the cluster relaxation used are the cluster ellipticity, the ICM temperature and X-ray cluster luminosity. We find evidence of varying strength and significance of all three indicators evolving with redshift for z <0.15. This result supports the view that clusters have mostly stopped undergoing mergers and accreting matter, as expected in a low-Omega_matter Universe, and are now in the process of gravitational relaxation, which reduces their flattening, their ICM temperature (shock heated during the merging phase), and their X-ray luminosity. These results support similar recent claims of Melott, Chambers and Miller (2001).

  8. Interpreting the Clustering of Distant Red Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Tinker, Jeremy L.; /BCCP, Berkeley; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC; Zheng, Zheng; /Princeton, Inst. Advanced Study

    2009-08-03

    We analyze the angular clustering of z {approx} 2.3 distant red galaxies (DRGs) measured by Quadri et al. (2008). We find that, with robust estimates of the measurement errors and realistic halo occupation distribution modeling, the measured clustering can be well fit within standard halo occupation models, in contrast to previous results. However, in order to fit the strong break in w({theta}) at {theta} = 10{double_prime}, nearly all satellite galaxies in the DRG luminosity range are required to be DRGs. Within this luminosity-threshold sample, the fraction of galaxies that are DRGs is {approx} 44%, implying that the formation of DRGs is more efficient for satellite galaxies than for central galaxies. Despite the evolved stellar populations contained within DRGs at z = 2.3, 90% of satellite galaxies in the DRG luminosity range have been accreted within 500 Myr. Thus, satellite DRGs must have known they would become satellites well before the time of their accretion. This implies that the formation of DRGs correlates with large-scale environment at fixed halo mass, although the large-scale bias of DRGs can be well fit without such assumptions. Further data are required to resolve this issue. Using the observational estimate that {approx} 30% of DRGs have no ongoing star formation, we infer a timescale for star formation quenching for satellite galaxies of 450 Myr, although the uncertainty on this number is large. However, unless all non-star forming satellite DRGs were quenched before accretion, the quenching timescale is significantly shorter than z {approx} 0 estimates. Down to the completeness limit of the Quadri et al sample, we find that the halo masses of central DRGs are {approx} 50% higher than non-DRGs in the same luminosity range, but at the highest halo masses the central galaxies are DRGs only {approx} 2/3 of the time.

  9. INTERPRETING THE CLUSTERING OF DISTANT RED GALAXIES

    International Nuclear Information System (INIS)

    We analyze the angular clustering of z ∼ 2.3 distant red galaxies (DRGs) measured by Quardi et al. We find that, with robust estimates of the measurement errors and realistic halo occupation distribution modeling, the measured clustering can be well fit within standard halo occupation models, in contrast to previous results. However, in order to fit the strong break in w(θ) at θ = 10'', nearly all satellite galaxies in the DRG luminosity range are required to be DRGs. Within this luminosity-threshold sample, the fraction of galaxies that are DRGs is ∼44%, implying that the formation of DRGs is more efficient for satellite galaxies than for central galaxies. Despite the evolved stellar populations contained within DRGs at z = 2.3, 90% of satellite galaxies in the DRG luminosity range have been accreted within 500 Myr. Thus, satellite DRGs must have known they would become satellites well before the time of their accretion. This implies that the formation of DRGs correlates with large-scale environment at fixed halo mass, although the large-scale bias of DRGs can be well fit without such assumptions. Further data are required to resolve this issue. Using the observational estimate that ∼30% of DRGs have no ongoing star formation, we infer a timescale for star formation quenching for satellite galaxies of 450 Myr, although the uncertainty on this number is large. However, unless all non-star-forming satellite DRGs were quenched before accretion, the quenching timescale is significantly shorter than z ∼ 0 estimates. Down to the completeness limit of the Quadri et al. sample, we find that the halo masses of central DRGs are ∼50% higher than non-DRGs in the same luminosity range, but at the highest halo masses the central galaxies are DRGs only ∼2/3 of the time.

  10. Luminosity segregation in three clusters of galaxies (A119, A2443, A2218)

    Science.gov (United States)

    Pracy, Michael B.; Driver, Simon P.; De Propris, Roberto; Couch, Warrick J.; Nulsen, Paul E. J.

    2005-12-01

    We use deep wide-field V-band imaging obtained with the Wide Field Camera at the prime focus of the Issac Newton Telescope to study the spatial and luminosity distribution of galaxies in three low redshift (0.04 < z < 0.2) clusters: Abell 119, Abell 2443 and Abell 2218. The absolute magnitude limits probed in these clusters are MV- 5 logh0.7=-13.3, -15.4 and -16.7mag, respectively. The galaxy population, at all luminosities, along the line-of-sight to the clusters can be described by the linear combination of a King profile and a constant surface density of field galaxies. We find that, for these three clusters, the core radius is invariant with intrinsic luminosity of the cluster population to the above limits and thus there is no evidence for luminosity segregation in these clusters. The exception is the brightest galaxies in A2218 which exhibit a more compact spatial distribution. We find that the total projected luminosity distribution (within 1h-10.7Mpc of the cluster centre) can be well represented by a single Schechter function with moderately flat faint-end slopes: α=-1.22+0.07-0.06 (A119), α=-1.11+0.10-0.09 (A2443) and α=-1.14+0.08-0.07 (A2218). We perform a geometric deprojection of the cluster galaxy population and confirm that no `statistically significant' evidence of a change in the shape of the luminosity distribution with cluster-centric radius exists. Again, the exception being A2218 which exhibits a core region with a flatter faint-end slope.

  11. Barred Galaxies in the Coma Cluster

    CERN Document Server

    Marinova, Irina; Trentham, Neil; Ferguson, Henry C; Weinzirl, Tim; Balcells, Marc; Carter, David; Brok, Mark den; Erwin, Peter; Graham, Alister W; Goudfrooij, Paul; Guzman, Rafael; Hammer, Derek; Hoyos, Carlos; Peletier, Reynier F; Huxor, Avon P; Peng, Erik; Kleijn, Gijs Verdoes

    2010-01-01

    We use ACS data from the HST Treasury survey of the Coma cluster (z~0.02) to study the properties of barred galaxies in the Coma core, the densest environment in the nearby Universe. This study provides a complementary data point for studies of barred galaxies as a function of redshift and environment. From ~470 cluster members brighter than M_I = -11 mag, we select a sample of 46 disk galaxies (S0--Im) based on visual classification. The sample is dominated by S0s for which we find an optical bar fraction of 47+/-11% through ellipse fitting and visual inspection. Among the bars in the core of the Coma cluster, we do not find any very large (a_bar > 2 kpc) bars. Comparison to other studies reveals that while the optical bar fraction for S0s shows only a modest variation across low-to-intermediate density environments (field to intermediate-density clusters), it can be higher by up to a factor of ~2 in the very high-density environment of the rich Coma cluster core.

  12. VLA Discovers Giant Rings Around Galaxy Cluster

    Science.gov (United States)

    2006-11-01

    Astronomers using the National Science Foundation's Very Large Array (VLA) radio telescope have discovered giant, ring-like structures around a cluster of galaxies. The discovery provides tantalizing new information about how such galaxy clusters are assembled, about magnetic fields in the vast spaces between galaxy clusters, and possibly about the origin of cosmic rays. Radio-Optical Image of Cluster Galaxy Cluster Abell 3376 (Radio/Optical) CREDIT: Joydeep Bagchi, IUCAA, NRAO/AUI/NSF Above, a combined radio/optical image shows the galaxy cluster Abell 3376 in visible light (blue) and radio (red) images. The giant radio arcs surrounding the cluster were discovered using the Very Large Array. The visible-light image is from the Digitized Sky survey. Below, an X-ray image of Abell 3376 made using the European Space Agency's XMM-Newton telescope shows a spectacular, bullet-shaped region of X-rays coming from gas heated to 60 million degrees Kelvin. The bullet shape results from the supersonic collision of a smaller smaller galaxy subcluster with the main body of the larger cluster. Click on images for larger version. X-Ray Image of Cluster Galaxy Cluster Abell 3376 (X-Ray) CREDIT: Joydeep Bagchi, IUCAA, ESA "These giant, radio-emitting rings probably are the result of shock waves caused by violent collisions of smaller groups of galaxies within the cluster," said Joydeep Bagchi, of the Inter-University Centre for Astronomy and Astrophysics in Pune, India, who led an international research team. The scientists reported their findings in the November 3 edition of the journal Science. The newly-discovered ring segments, some 6 million light-years across, surround a galaxy cluster called Abell 3376, more than 600 million light-years from Earth. They were revealed because fast-moving electrons emitted radio waves as they spiraled around magnetic field lines in intergalactic space. "Even from this large distance, the feeble radio waves were easily picked up by the VLA

  13. Gamma rays from clusters of galaxies

    CERN Document Server

    Blasi, P; Brunetti, G; Blasi, Pasquale; Gabici, Stefano; Brunetti, Gianfranco

    2007-01-01

    Clusters of galaxies and the large scale filaments that connect neighboring clusters are expected to be sites of acceleration of charged particles and sources of non-thermal radiation from radio frequencies to gamma rays. Gamma rays are particularly interesting targets of investigation, since they may provide precious information on the nature and efficiency of the processes of acceleration and magnetic confinement of hadrons within clusters of galaxies. Here we review the status of viable scenarios that lead to the production of gamma rays from large scale structures and are compatible with the multifrequency observations that are already available. We also discuss the possibility of detection of gamma rays with space-borne telescopes such as GLAST and ground based Cherenkov telescopes, and the physical information that may be gathered from such observations.

  14. Joint Analysis of Galaxy-Galaxy Lensing and Galaxy Clustering: Methodology and Forecasts for DES

    CERN Document Server

    Park, Y; Dodelson, S; Jain, B; Amara, A; Becker, M R; Bridle, S L; Clampitt, J; Crocce, M; Fosalba, P; Gaztanaga, E; Honscheid, K; Rozo, E; Sobreira, F; Sánchez, C; Wechsler, R H; Abbott, T; Abdalla, F B; Allam, S; Benoit-Lévy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Castander, F J; da Costa, L N; DePoy, D L; Desai, S; Dietrich, J P; Gerdes, D W; Gruen, D; Gruendl, R A; Gutierrez, G; James, D J; Kent, S; Kuehn, K; Kuropatkin, N; Lima, M; Maia, M A G; Marshall, J L; Melchior, P; Miller, C J; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Soares-Santos, M; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Vikram, V; Walker, A R; Weller, J; Zuntz, J

    2015-01-01

    The joint analysis of galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth function of large scale structure. This analysis will be carried out on data from the Dark Energy Survey (DES), with its measurements of both the distribution of galaxies and the tangential shears of background galaxies induced by these foreground lenses. We develop a practical approach to modeling the assumptions and systematic effects affecting small scale lensing, which provides halo masses, and large scale galaxy clustering. Introducing parameters that characterize the halo occupation distribution (HOD), photometric redshift uncertainties, and shear measurement errors, we study how external priors on different subsets of these parameters affect our growth constraints. Degeneracies within the HOD model, as well as between the HOD and the growth function, are identified as the dominant source of complication, with other systematic effects sub-dominant. The impact of HOD parameters and their degen...

  15. Modeling the Color Magnitude Relation for Galaxy Clusters

    CERN Document Server

    Jimenez, Noelia; Castelli, Analia Smith; Bassino, Lilia P

    2011-01-01

    We investigate the origin of the colour-magnitude relation (CMR) observed in cluster galaxies by using a combination of a cosmological N-body simulation of a cluster of galaxies and a semi-analytic model of galaxy formation. The departure of galaxies in the bright end of the CMR with respect to the trend denoted by less luminous galaxies could be explained by the influence of minor mergers

  16. Tidally induced bars of galaxies in clusters

    CERN Document Server

    Lokas, Ewa L; del Pino, Andres; Sybilska, Agnieszka; Athanassoula, E; Semczuk, Marcin; Gajda, Grzegorz; Fouquet, Sylvain

    2016-01-01

    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 an NFW 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, longer and have lower pattern speeds for tighter orbits. Only for the tightest orbit the properties of the bar are controlled by the orientation of the tidal torque from the cluster at pericenters. The mechanism behind the formation of the bars is the angular momentum transfer from the galaxy stellar component to its halo. All bars undergo extended periods of buckling instability that occur earlier and lead to more pronounced boxy/peanut shapes when th...

  17. A large population of ultra-compact dwarf galaxies in the Hydra I cluster

    CERN Document Server

    Misgeld, I; Hilker, M; Richtler, T; Georgiev, I Y; Schuberth, Y

    2011-01-01

    We performed a large spectroscopic survey of compact, unresolved objects in the core of the Hydra I galaxy cluster (Abell 1060), with the aim of identifying ultra-compact dwarf galaxies (UCDs), and investigating the properties of the globular cluster (GC) system around the central cD galaxy NGC 3311. We obtained VIMOS medium resolution spectra of about 1200 candidate objects with apparent magnitudes 18.5 5 x 10^7 M_sun) and a half-light radius of 25 pc. This places it among the brightest and most massive UCDs ever discovered. Most of the GCs/UCDs are both spatially and dynamically associated to the central cD galaxy. The overall velocity dispersion of the GCs/UCDs is comparable to what is found for the cluster galaxies. However, when splitting the sample into a bright and a faint part, we observe a lower velocity dispersion for the bright UCDs/GCs than for the fainter objects. At a dividing magnitude of M_V = -10.75 mag, the dispersions differ by more than 200 km/s, and up to 300 km/s for objects within 5 ar...

  18. Young star clusters: Metallicity tracers in external galaxies

    OpenAIRE

    Anders, P.; Alvensleben, U. Fritze--v.; de Grijs, R.

    2003-01-01

    Star cluster formation is a major mode of star formation in the extreme conditions of interacting galaxies and violent starbursts. These newly-formed clusters are built from recycled gas, pre-enriched to various levels within the interacting galaxies. Hence, star clusters of different ages represent a fossil record of the chemical enrichment history of their host galaxy, as well as of the host galaxy's violent star formation history. We present a new set of evolutionary synthesis models of ou...

  19. Radio mini-halos and AGN heating in cool core clusters of galaxies

    CERN Document Server

    Gitti, Myriam

    2016-01-01

    The brightest cluster galaxy (BCG) in the majority of relaxed, cool core galaxy clusters is radio loud, showing non-thermal radio jets and lobes ejected by the central active galactic nucleus (AGN). Such relativistic plasma has been unambiguously shown to interact with the surrounding thermal intra-cluster medium (ICM) thanks to spectacular images where the lobe radio emission is observed to fill the cavities in the X-ray-emitting gas. This `radio-mode AGN feedback' phenomenon, which is thought to quench cooling flows, is widespread and is critical to understand the physics of the inner regions of galaxy clusters and the properties of the central BCG. At the same time, mechanically-powerful AGN are likely to drive turbulence in the central ICM which may contribute to gas heating and also play a role for the origin of non-thermal emission on cluster-scales. Diffuse non-thermal emission has been observed in a number of cool core clusters in the form of a radio mini-halo surrounding the radio-loud BCG on scales ...

  20. Baryon Content of Massive Galaxy Clusters (0.57 < z < 1.33)

    CERN Document Server

    Chiu, I; Mcdonald, M; Bocquet, S; Ashby, M L; Bayliss, M; Benson, B A; Bleem, L E; Brodwin, M; Desai, S; Dietrich, J P; Forman, W R; Gangkofner, C; Gonzalez, A H; Hennig, C; Liu, J; Reichardt, C L; Saro, A; Stalder, B; Stanford, S A; Song, J; Schrabback, T; Suhada, R; Strazzullo, V; Zenteno, A

    2014-01-01

    We study the stellar, Brightest Cluster Galaxy (BCG) and intracluster medium (ICM) masses of 14 South Pole Telescope (SPT) selected galaxy clusters with median redshift $z=0.9$ and median mass $M_{500}=6\\times10^{14}M_{\\odot}$. We estimate stellar masses for each cluster and BCG using six photometric bands spanning the range from the ultraviolet to the near-infrared observed with the VLT, HST and Spitzer. The ICM masses are derived from Chandra and XMM-Newton X-ray observations, and the virial masses are derived from the SPT Sunyaev-Zel'dovich Effect signature. At $z=0.9$ the BCG mass $M_{\\star}^{\\textrm{BCG}}$ constitutes $0.12\\pm0.01$% of the halo mass for a $6\\times10^{14}M_{\\odot}$ cluster, and this fraction falls as $M_{500}^{-0.58\\pm0.07}$. The cluster stellar mass function has a characteristic mass $M_{0}=10^{11.0\\pm0.1}M_{\\odot}$, and the number of galaxies per unit mass in clusters is larger than in the field by a factor $1.65\\pm0.2$. Both results are consistent with measurements on group scales and ...

  1. MASSIVE BLACK HOLES IN CENTRAL CLUSTER GALAXIES

    International Nuclear Information System (INIS)

    We explore how the co-evolution of massive black holes (MBHs) and galaxies is affected by environmental effects, addressing in particular MBHs hosted in the central cluster galaxies (we will refer to these galaxies in general as ''CCGs''). Recently, the sample of MBHs in CCGs with dynamically measured masses has increased, and it has been suggested that these MBH masses (MBH) deviate from the expected correlations with velocity dispersion (σ) and mass of the bulge (Mbulge) of the host galaxy: MBHs in CCGs appear to be ''overmassive''. This discrepancy is more pronounced when considering the MBH-σ relation than the MBH-Mbulge one. We show that this behavior stems from a combination of two natural factors: (1) CCGs experience more mergers involving spheroidal galaxies and their MBHs and (2) such mergers are preferentially gas poor. We use a combination of analytical and semi-analytical models to investigate the MBH-galaxy co-evolution in different environments and find that the combination of these two factors is in accordance with the trends observed in current data sets.

  2. ChaMP Serendipitous Galaxy Cluster Survey

    Energy Technology Data Exchange (ETDEWEB)

    Barkhouse, Wayne A.; Green, P.J.; Vikhlinin, A.; Kim, D.-W.; Perley, D.; Cameron, R.; Silverman, J.; Mossman, A.; Burenin, R.; Jannuzi, B.T.; Kim, M.; Smith, M.G.; Smith,; Tananbaum, H.; Wilkes, B.J.; /Harvard-Smithsonian Ctr. Astrophys. /UC, Berkeley, Astron. Dept. /SLAC /Garching, Max Planck Inst., MPE /Moscow, Space Res. Inst. /NOAO, Tucson

    2006-04-03

    We present a survey of serendipitous extended X-ray sources and optical cluster candidates from the Chandra Multi-wavelength Project (ChaMP). Our main goal is to make an unbiased comparison of X-ray and optical cluster detection methods. In 130 archival Chandra pointings covering 13 square degrees, we use a wavelet decomposition technique to detect 55 extended sources, of which 6 are nearby single galaxies. Our X-ray cluster catalog reaches a typical flux limit of about {approx} 10{sup -14} erg s{sup -1} cm{sup -2}, with a median cluster core radius of 21''. For 56 of the 130 X-ray fields, we use the ChaMP's deep NOAO/4m MOSAIC g', r', and i' imaging to independently detect cluster candidates using a Voronoi tessellation and percolation (VTP) method. Red-sequence filtering decreases the galaxy fore/background contamination and provides photometric redshifts to z {approx} 0.7. From the overlapping 6.1 square degree X-ray/optical imaging, we find 115 optical clusters (of which 11% are in the X-ray catalog) and 28 X-ray clusters (of which 46% are in the optical VTP catalog). The median redshift of the 13 X-ray/optical clusters is 0.41, and their median X-ray luminosity (0.5-2 keV) is L{sub X} = (2.65 {+-} 0.19) x 10{sup 43} ergs s{sup -1}. The clusters in our sample that are only detected in our optical data are poorer on average ({approx} 4{sigma}) than the X-ray/optically matched clusters, which may partially explain the difference in the detection fractions.

  3. Jellyfish: the origin and distribution of extreme ram-pressure stripping events in massive galaxy clusters

    Science.gov (United States)

    McPartland, Conor; Ebeling, Harald; Roediger, Elke; Blumenthal, Kelly

    2016-01-01

    We investigate the observational signatures and physical origin of ram-pressure stripping (RPS) in 63 massive galaxy clusters at z = 0.3-0.7, based on images obtained with the Hubble Space Telescope. Using a training set of a dozen `jellyfish' galaxies identified earlier in the same imaging data, we define morphological criteria to select 211 additional, less obvious cases of RPS. Spectroscopic follow-up observations of 124 candidates so far confirmed 53 as cluster members. For the brightest and most favourably aligned systems, we visually derive estimates of the projected direction of motion based on the orientation of apparent compression shocks and debris trails. Our findings suggest that the onset of these events occurs primarily at large distances from the cluster core (>400 kpc), and that the trajectories of the affected galaxies feature high-impact parameters. Simple models show that such trajectories are highly improbable for galaxy infall along filaments but common for infall at high velocities, even after observational biases are accounted for, provided the duration of the resulting RPS events is ≲500 Myr. We thus tentatively conclude that extreme RPS events are preferentially triggered by cluster mergers, an interpretation that is supported by the disturbed dynamical state of many of the host clusters. This hypothesis implies that extreme RPS might occur also near the cores of merging poor clusters or even merging groups of galaxies. Finally, we present nine additional `jellyfish" galaxies at z > 0.3 discovered by us, thereby doubling the number of such systems known at intermediate redshift.

  4. THE LIFETIME AND POWERS OF FR IIs IN GALAXY CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Antognini, Joe; Bird, Jonathan; Martini, Paul, E-mail: antognini@astronomy.ohio-state.edu, E-mail: bird@astronomy.ohio-state.edu, E-mail: martini@astronomy.ohio-state.edu [Department of Astronomy, Ohio State University, 140 W 18th Avenue, Columbus, OH 43210 (United States)

    2012-09-10

    We have identified and studied a sample of 151 FR IIs found in brightest cluster galaxies (BCGs) in the MaxBCG cluster catalog with data from FIRST and NVSS. We have compared the radio luminosities and projected lengths of these FR IIs to the projected length distribution of a range of mock catalogs generated by an FR II model and estimate the FR II lifetime to be 1.9 Multiplication-Sign 10{sup 8} yr. The uncertainty in the lifetime calculation is a factor of two, primarily due to uncertainties in the intracluster medium (ICM) density and the FR II axial ratio. We furthermore measure the jet power distribution of FR IIs in BCGs and find that it is well described by a log-normal distribution with a median power of 1.1 Multiplication-Sign 10{sup 37} W and a coefficient of variation of 2.2. These jet powers are nearly linearly related to the observed luminosities, and this relation is steeper than many other estimates, although it is dependent on the jet model. We investigate correlations between FR II and cluster properties and find that galaxy luminosity is correlated with jet power. This implies that jet power is also correlated with black hole mass, as the stellar luminosity of a BCG should be a good proxy for its spheroid mass and therefore the black hole mass. Jet power, however, is not correlated with cluster richness, nor is FR II lifetime strongly correlated with any cluster properties. We calculate the enthalpy of the lobes to examine the impact of the FR IIs on the ICM and find that heating due to adiabatic expansion is too small to offset radiative cooling by a factor of at least six. In contrast, the jet power is approximately an order of magnitude larger than required to counteract cooling. We conclude that if feedback from FR IIs offsets cooling of the ICM, then heating must be primarily due to another mechanism associated with FR II expansion.

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

    International Nuclear Information System (INIS)

    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 Y200 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 1014 Msun.

  6. The galaxy cluster outskirts probed by Chandra

    Science.gov (United States)

    Morandi, Andrea; Sun, Ming; Forman, William; Jones, Christine

    2015-08-01

    Exploring the virialization region of galaxy clusters has recently raised the attention of the scientific community, offering a direct view of structure formation. In this talk, I will present recent results on the physical properties of the intracluster medium in the outer volumes of a sample of 320 clusters (0.056 3 keV) in the Chandra archive, with a total integration time of ~20 Ms. We stacked the emission measure profiles of the clusters to detect a signal out to R_{100}. We then measured the average emission measure, gas density and gas fraction, which scale according to the self-similar model of cluster formation. We observe a steepening of the density profiles beyond R_{500} with slope beta ~ 0.68 at R_{500} and beta ~ 1 at R_{200} and beyond. By tracking the direction of the cosmic filaments where the clusters are embedded, we report that galaxy clusters deviate from spherical symmetry. We also did not find evolution of the gas density with redshift, confirming the self-similar evolution of the gas density. The value of the baryon fraction reaches the cosmic value at R_{200}: however, systematics due to non-thermal pressure support and clumpiness might enhance the measured gas fraction, leading to an actual deficit of the baryon budget with respect to the primordial value). This novel method, the stacking the X-ray signal of cluster outskirts, has the capacity to provide a generational leap forward in our understanding of cluster physics and formation, and the use of clusters as cosmological probes.

  7. ICM cooling, AGN feedback and BCG properties of galaxy groups-Five properties where groups differ from clusters

    OpenAIRE

    Bharadwaj, V.; Reiprich, T. H.; Schellenberger, G.; Eckmiller, H. J.; Mittal, R; Israel, H.

    2014-01-01

    Using Chandra data for a sample of 26 galaxy groups, we constrained the central cooling times (CCTs) of the ICM and classified the groups as strong cool-core (SCC), weak cool-core (WCC) and non-cool-core (NCC) based on their CCTs. The total radio luminosity of the brightest cluster galaxy (BCG) was obtained using radio catalog data and literature, which was compared to the CCT to understand the link between gas cooling and radio output. We determined K-band luminosities of the BCG with 2MASS ...

  8. Dynamical evolution of globular-cluster systems in clusters of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Muzzio, J.C.

    1987-04-01

    The dynamical processes that affect globular-cluster systems in clusters of galaxies are analyzed. Two-body and impulsive approximations are utilized to study dynamical friction, drag force, tidal stripping, tidal radii, globular-cluster swapping, tidal accretion, and galactic cannibalism. The evolution of galaxies and the collision of galaxies are simulated numerically; the steps involved in the simulation are described. The simulated data are compared with observations. Consideration is given to the number of galaxies, halo extension, location of the galaxies, distribution of the missing mass, nonequilibrium initial conditions, mass dependence, massive central galaxies, globular-cluster distribution, and lost globular clusters. 116 references.

  9. The Evolution of Galaxy Clustering in Hierarchical Models

    OpenAIRE

    Cole, Shaun; Benson, Andrew; Baugh, Carlton,; Lacey, Cedric; Frenk, Carlos

    1999-01-01

    The main ingredients of recent semi-analytic models of galaxy formation are summarised. We present predictions for the galaxy clustering properties of a well specified LCDM model whose parameters are constrained by observed local galaxy properties. We present preliminary predictions for evolution of clustering that can be probed with deep pencil beam surveys.

  10. Spectral imaging of galaxy clusters with Planck

    CERN Document Server

    Bourdin, H; Rasia, E

    2016-01-01

    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 multiscale 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 perfo...

  11. Measuring the growth of galaxy clusters

    CERN Document Server

    Diaferio, Antonaldo

    2015-01-01

    We suggest how we can use the mass profile of galaxy clusters beyond their virial radius to measure their mass accretion rate, a key prediction of structure formation models. The mass profile can be estimated by applying the caustic technique to dense redshift surveys of clusters and their outskirts, where dynamical equilibrium does not necessarily hold. An additional probe of the mass growth of clusters is their mass fraction in substructures. We show that the caustic technique, that identifies cluster substructures as a by-product, returns catalogs of substructures with mass larger than a few $10^{13}h^{-1}M_\\odot$ that are between 60% and 80% complete, depending on the density of the redshift survey.

  12. Intracluster Light in Galaxy Groups and Clusters

    Science.gov (United States)

    DeMaio, Tahlia; Gonzalez, Anthony; Zabludoff, Ann I.; Zaritsky, Dennis F.

    2016-01-01

    We present recent results from our study on the origin and assembly history of the intracluster starlight (ICL) for a sample of 29 galaxy groups and clusters with 3x1013BCG). We also find ICL luminosities of 3-9 L* in the range 10 BCG.This sample of groups and clusters is the largest with HST/WFC3 data for ICL analysis that spans two orders of magnitude in halo mass at redshifts >0.3. Because of this we can investigate how the ICL color profile changes as a function of cluster mass for the first time, as well as expand previous studies of the changing fraction of cluster luminosity that is contained in the BCG+ICL as a function of halo mass. We present our preliminary results and describe our next steps using this sample to investigate the intracluster light in massive halos.

  13. Masses of galaxy clusters from gravitational lensing

    CERN Document Server

    Hoekstra, Henk; Dahle, Haakon; Israel, Holger; Limousin, Marceau; Meneghetti, Massimo

    2013-01-01

    Despite consistent progress in numerical simulations, the observable properties of galaxy clusters are difficult to predict ab initio. It is therefore important to compare both theoretical and observational results to a direct measure of the cluster mass. This can be done by measuring the gravitational lensing effects caused by the bending of light by the cluster mass distribution. In this review we discuss how this phenomenon can be used to determine cluster masses and study the mass distribution itself. As sample sizes increase, the accuracy of the weak lensing mass estimates needs to improve accordingly. We discuss the main practical aspects of these measurements. We review a number of applications and highlight some recent results.

  14. Simulations of Buoyant Bubbles in Galaxy Clusters

    CERN Document Server

    Brüggen, M

    2003-01-01

    It is generally argued that most clusters of galaxies host cooling flows in which radiative cooling in the centre causes a slow inflow. However, recent observations by Chandra and XMM conflict with the predicted cooling flow rates. Here we report highly resolved hydrodynamic simulations which show that buoyant bubbles can offset the cooling in the inner regions of clusters and can significantly delay the deposition of cold gas. The subsonic rise of bubbles uplifts colder material from the central regions of the cluster. This colder material appears as bright rims around the bubbles. The bubbles themselves appear as depressions in the X-ray surface brightness as observed in a growing number of clusters.

  15. A Constant Clustering Amplitude for Faint Galaxies?

    OpenAIRE

    Brainerd, Tereasa G.; Smail , Ian

    1997-01-01

    The angular clustering of faint field galaxies is investigated using deep imaging (I~25) obtained with the 10-m Keck-I telescope. The autocorrelation function is consistent with w(theta) ~ theta^-0.8 and, although less steep correlation functions cannot be ruled out with high confidence, we find no compelling evidence for a systematic decrease in the power law index at the faintest magnitude limits. Results from a number of independent observational studies are combined in order to investigat...

  16. Galaxy Proto-clusters as an Interface Between Structure, Cluster, and Galaxy Formation

    Science.gov (United States)

    Chiang, Yi-Kuan

    2016-01-01

    Proto-clusters, the progenitor large-scale structures of present day galaxy clusters, are unique laboratories to study dark matter assembly, cosmic baryon cycle, galaxy growth, and environmental impact on galaxy evolution. In this dissertation talk, I will present our recent progress in this subject, both theoretical and observational. Using a set of cosmological N-body simulations and semi-analytic galaxy models, we extract the mass, size, and overdensity evolution for ˜3000 simulated clusters from z=8 to z=0. In line with the scenario of cosmic downsizing, the models predict that the fraction of cosmic star formation rate occurs in (proto-)clusters increases from <1% at z=0 to 20-30% at z=8. This result demonstrates that the seemingly sharp distinction when discussing field and cluster galaxy evolution has to be blurred at high redshift, and a significant fraction of cosmic reionization was done by cluster progenitors. Observationally, we focus on the epoch of z≈2 when the first cluster scale halos (1014 M⊙) were about to form. We perform a systematic proto-cluster search using a photometric redshift catalog in the COSMOS field, revealing a large sample of 36 candidate proto-clusters at 1.6cluster in this field at z=2.44 with Mz=0 = 1014.5±0.4 M⊙ using a sample of Lyα emitters (LAE) in the HETDEX Pilot Survey with a highly homogeneous selection function in 3D redshift space. Compared to the cosmic mean, this structure shows a LAE overdensity of 4 on a scale of few tens cMpc, a 5 times higher fraction of extended Lya blobs, a 2 times higher median stellar mass of NIR selected galaxies with photometric redshift, and a significantly enhanced intergalactic gas revealed in the Lyα absorption maps of Lee et al. (2014, 2015). With these results, I will discuss proto-clusters in the context of

  17. Linear potentials in galaxies and clusters of galaxies

    CERN Document Server

    Mannheim, P D

    1995-01-01

    In a previous paper we presented a typical set of galactic rotation curves associated with the linear gravitational potential of the conformal invariant fourth order theory of gravity which has recently been advanced by Mannheim and Kazanas as a candidate alternative to the standard second order Newton-Einstein theory. Reasonable agreement with data was obtained for four representative galaxies without the need for any non-luminous or dark matter. In this paper we present the associated formalism and compare and contrast the linear potential explanation of the general systematics of galactic rotation curves and the associated Tully-Fisher relation with that of the standard dark matter theory. Additionally, we show that the conformal gravity picture appears to have survived the recent round of microlensing observations unscathed. Finally, we make a first application of the conformal theory to the larger distance scale associated with a cluster of galaxies, with the theory being found to give a reasonable value...

  18. Prospects of detecting gamma-ray emission from galaxy clusters: cosmic rays and dark matter annihilations

    CERN Document Server

    Pinzke, Anders; Bergstrom, Lars

    2011-01-01

    We study the possibility for detecting gamma-ray emission in galaxy clusters. We consider 1) cosmic ray (CR) induced pion decay which is thought to dominate the astrophysical signal from clusters, 2) different representative benchmark models of supersymmetric dark matter (DM), and 3) leptophilic models of DM annihilation that include a Sommerfeld enhancement (SFE). To model DM annihilation, we consider hadronization of annihilating neutralinos, internal bremsstrahlung, and inverse Compton emission from the cosmic microwave background as well as from a realistic spatial and spectral distribution of dust and stellar light. We predict the Virgo and Fornax clusters to be the brightest DM sources and find a particularly low CR induced background for Fornax. For a minimum substructure mass given by the DM free-streaming scale, we find a substructure boost factor of more than 1000. Since the annihilation flux of substructures is mostly contributed by the regions around the virial radius, the resulting surface bright...

  19. The Hydra I cluster core. I. Stellar populations in the cD galaxy NGC 3311

    CERN Document Server

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

    2016-01-01

    (Abridged for arXiv) The history of the mass assembly of brightest cluster galaxies may be studied by the mapping the stellar populations at large radial distances from the galaxy centre. We provide extended and robust measurements of the stellar population parameters in NGC 3311, the cD galaxy at the centre of the Hydra I cluster and out to three effective radii. Using seven absorption-features defined in the Lick/IDS system and single stellar populations models, we obtained luminosity-weighted ages, metallicities and alpha element abundances. The trends in the Lick indices and the distribution of the stellar population parameters indicate that the stars of NGC 3311 may be divided into two radial regimes, one within and the another beyond one effective radius, $R_e = 8.4$ kpc, similar to the distinction between inner galaxy and external halo derived from the NGC 3311 velocity dispersion profile. The inner galaxy ($R\\leq R_e$) is old (age $\\sim 14$ Gyr), have negative metallicity gradients and positive alpha ...

  20. Recent galaxy mergers and residual star formation of red sequence galaxies in galaxy clusters

    CERN Document Server

    Sheen, Yun-Kyeong; Ree, Chang H; Jaffé, Yara; Demarco, Ricardo; Treister, Ezequiel

    2016-01-01

    This study explored the GALEX ultraviolet (UV) properties of optical red sequence galaxies in 4 rich Abell clusters at z \\leq 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' 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' \\leq 5), and that number was doubled (~ 72%) when using a generous criterion (NUV - r' \\leq 5.4). The trend was the same when we restricted the sample to galaxies within 0.5xR_{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 sub-structures in ...

  1. GMRT observations of the Ophiuchus galaxy cluster

    CERN Document Server

    Murgia, M; Govoni, F; Ferrari, C; Pandey-Pommier, M; Nevalainen, J; Paltani, S

    2010-01-01

    VLA observations at 1477 MHz revealed the presence of a radio mini-halo surrounding the faint central point-like radio source in the Ophiuchus cluster of galaxies. In this work we present a study of the radio emission from this cluster of galaxies at lower radio frequencies. We observed the Ophiuchus cluster at 153, 240, and 614 MHz with the GMRT. The mini-halo is clearly detected at 153 and 240 MHz while it is not detected at 610 MHz. The most prominent feature at low frequencies is a patch of diffuse steep spectrum emission located at about 5' south-east from the cluster center. By combining these images with that at 1477 MHz, we derived the spectral index of the mini-halo. Globally, the mini-halo has a low-frequency spectral index of alpha_240^153 ~1.4 +/- 0.3 and an high-frequency spectral index of alpha_1477^240 ~ 1.60 +/- 0.05. Moreover, we measure a systematic increase of the high-frequency spectral index with radius: the azimuthal radial average of alpha_1477^240 increases from about 1.3, at the clust...

  2. Heating Rate Profiles in Galaxy Clusters

    CERN Document Server

    Pope, E C D; Kaiser, C R; Fangohr, H; Pope, Edward C.D.; Pavlovski, Georgi; Kaiser, Christian R.; Fangohr, Hans

    2006-01-01

    In recent years evidence has accumulated suggesting that the gas in galaxy clusters is heated by non-gravitational processes. Here we calculate the heating rates required to maintain a physically motived mass flow rate, in a sample of seven galaxy clusters. We employ the spectroscopic mass deposition rates as an observational input along with temperature and density data for each cluster. On energetic grounds we find that thermal conduction could provide the necessary heating for A2199, Perseus, A1795 and A478. However, the suppression factor, of the clasical Spitzer value, is a different function of radius for each cluster. Based on the observations of plasma bubbles we also calculate the duty cycles for each AGN, in the absence of thermal conduction, which can provide the required energy input. With the exception of Hydra-A it appears that each of the other AGNs in our sample require duty cycles of roughly $10^{6}-10^{7}$ yrs to provide their steady-state heating requirements. If these duty cycles are unrea...

  3. Hot gas in Mach cones around Virgo Cluster spiral galaxies

    OpenAIRE

    Wezgowiec, M.; Vollmer, B.; Ehle, M.; Dettmar, R. -J.; Bomans, D. J.; Chyzy, K. T.; Urbanik, M.; Soida, M.

    2011-01-01

    The detailed comparison between observations and simulations of ram pressure stripped spiral galaxies in the Virgo cluster has led to a three dimensional view of the galaxy orbits within the hot intracluster medium. The 3D velocities and Mach numbers derived from simulations can be used to derive simple Mach cone geometries for Virgo spiral galaxies. We search for indications of hot gas within Mach cones in X-ray observations of selected Virgo Cluster spiral galaxies (NGC 4569, NGC 4388, and ...

  4. STUDYING INTERCLUSTER GALAXY FILAMENTS THROUGH STACKING gmBCG GALAXY CLUSTER PAIRS

    International Nuclear Information System (INIS)

    We present a method to study the photometric properties of galaxies in filaments by stacking the galaxy populations between pairs of galaxy clusters. Using Sloan Digital Sky Survey data, this method can detect the intercluster filament galaxy overdensity with a significance of ∼5σ out to z = 0.40. Using this approach, we study the g – r color and luminosity distribution of filament galaxies as a function of redshift. Consistent with expectation, filament galaxies are bimodal in their color distribution and contain a larger blue galaxy population than clusters. Filament galaxies are also generally fainter than cluster galaxies. More interestingly, the observed filament population seems to show redshift evolution at 0.12 < z < 0.40: the blue galaxy fraction has a trend to increase at higher redshift; such evolution is parallel to the ''Butcher-Oemler effect'' of galaxy clusters. We test the dependence of the observed filament density on the richness of the cluster pair: richer clusters are connected by higher density filaments. We also test the spatial dependence of filament galaxy overdensity: this quantity decreases when moving away from the intercluster axis between a cluster pair. This method provides an economical way to probe the photometric properties of filament galaxies and should prove useful for upcoming projects like the Dark Energy Survey

  5. Galaxy Clusters as Tele-ALP-scopes

    CERN Document Server

    CERN. Geneva

    2015-01-01

    Axion-like particles have good theoretical motivation and are characterized by conversion to photons in astrophysical magnetic fields. Galaxy clusters are the most efficient convertors of axion-like particles to photons in the universe. I discuss the physics and phenomenology of ALPs, and describe their astrophysical implications, with particular reference to the recently observed 3.5 keV X-ray line that is a candidate for a dark matter decay line. I discuss interpretations of this line in terms of dark matter decaying to an axion-like particle, that then converts to a photon in cluster magnetic fields, and describe the compatibility of this scenario with data and the different phenomenology for cool-core and non-cool-core clusters.

  6. Theory of galaxy dynamics in clusters and groups

    CERN Document Server

    Mamon, G A

    2000-01-01

    Analytical estimates of the mass and radial dependence of the rates of galaxy mergers and of tidal interactions are derived for clusters and groups of galaxies, taking into account the tides from the system potential that limit the sizes of galaxies. Only high mass galaxies undergo significant major merging before being themselves cannibalized by more massive galaxies. Strong tides from the group/cluster potential severely limit the merger/tide cross-sections in the central regions, and while tides are most efficient at the periphery, one should see merging encounters further inside rich clusters.

  7. Recovering dark-matter clustering from galaxies with Gaussianization.

    OpenAIRE

    McCullagh, N.; Neyrinck, M.; Norberg, P.; Cole, S.

    2016-01-01

    The Gaussianization transform has been proposed as a method to remove the issues of scale-dependent galaxy bias and non-linearity from galaxy clustering statistics, but these benefits have yet to be thoroughly tested for realistic galaxy samples. In this paper, we test the effectiveness of the Gaussianization transform for different galaxy types by applying it to realistic simulated blue and red galaxy samples. We show that in real space, the shapes of the Gaussianized power spectra of both r...

  8. Mapping Cluster Mass Distributions via Gravitational Lensing of Background Galaxies

    OpenAIRE

    Broadhurst, T. J.; Taylor, A. N.; Peacock, J. A.

    1994-01-01

    We present a new method for measuring the projected mass distributions of galaxy clusters. The gravitational amplification is measured by comparing the joint distribution in redshift and magnitude of galaxies behind the cluster with that of field galaxies. We show that the total amplification is directly related to the surface mass density in the weak field limit, and so it is possible to map the mass distribution of the cluster. The method is shown to be limited by discreteness noise and gal...

  9. Enhanced Abundances in Spiral Galaxies of the Pegasus I Cluster

    OpenAIRE

    Robertson, Paul; Shields, Gregory A.; Blanc, Guillermo A.

    2011-01-01

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and ve...

  10. Young star clusters: Clues to galaxy formation and evolution

    OpenAIRE

    Anders, P.; Alvensleben, U. Fritze--v.; de Grijs, R.

    2003-01-01

    Young clusters are observed to form in a variety of interacting galaxies and violent starbursts, a substantial number resembling the progenitors of the well-studied globular clusters in mass and size. By studying young clusters in merger remnants and peculiar galaxies, we can therefore learn about the violent star formation history of these galaxies. We present a new set of evolutionary synthesis models of our GALEV code specifically developed to include the gaseous emission of presently form...

  11. The XMM-Newton/SDSS galaxy cluster survey

    OpenAIRE

    Takey, Ali Said Ahmed

    2014-01-01

    Galaxy clusters are the largest known gravitationally bound objects, their study is important for both an intrinsic understanding of their systems and an investigation of the large scale structure of the universe. The multi- component nature of galaxy clusters offers multiple observable signals across the electromagnetic spectrum. At X-ray wavelengths, galaxy clusters are simply identified as X-ray luminous, spatially extended, and extragalactic sources. X-ray observations offer the most powe...

  12. The transformation of Spirals into S0 galaxies in the cluster environment

    Directory of Open Access Journals (Sweden)

    Mauro eD'onofrio

    2015-08-01

    Full Text Available We discuss the observational evidences of the morphological transformation of Spirals into S0 galaxies in the cluster environment exploiting two big databases of galaxy clusters: WINGS (0.04galaxies in clusters is almost a factor of ∼ 3 − 4 larger today than at redshift z ∼ 1; 2 the fraction of S0’s to Spirals increases on average by a factor ∼ 2 every Gyr; 3 the average rate of transformation for Spirals (not considering the infall of new galaxies from the cosmic web is: ∼ 5 Sp→S0’s per Gyr and ∼ 2 Sp→E’s per Gyr; 4 there are evidences that the interstellar gas of Spirals is stripped by an hot intergalactic medium; 5 there are also indirect hints that major/minor merging events have played a role in the transformation of Spiral galaxies. In particular, we show that: 1 the ratio between the number of S0’s and Spirals (NS0/NSp in the WINGS clusters is correlated with their X-ray luminosity LX ; 2 that the brightest and massive S0’s are always close to the cluster center; 3 that the mean Se ́rsic index of S0’s is always larger than that of Spirals (and lower than E’s for galaxy stellar masses above 10^9.5M⊙; 4 that the number of E’s in clusters cannot be constant; 5 that the largest difference between the mean mass of S0’s and E’s with respect to Spirals is observed in clusters with low velocity dispersion.Finally, by comparing the properties of the various morphological types for galaxies in clusters and in the field, we find that the most significant effect of the environment is the stripping of the outer galaxy regions, resulting in a systematic difference in effective radius and Se ́rsic index.

  13. Statistical Issues in Galaxy Cluster Cosmology

    Science.gov (United States)

    Mantz, Adam

    2013-01-01

    The number and growth of massive galaxy clusters are sensitive probes of cosmological structure formation. Surveys at various wavelengths can detect clusters to high redshift, but the fact that cluster mass is not directly observable complicates matters, requiring us to simultaneously constrain scaling relations of observable signals with mass. The problem can be cast as one of regression, in which the data set is truncated, the (cosmology-dependent) underlying population must be modeled, and strong, complex correlations between measurements often exist. Simulations of cosmological structure formation provide a robust prediction for the number of clusters in the Universe as a function of mass and redshift (the mass function), but they cannot reliably predict the observables used to detect clusters in sky surveys (e.g. X-ray luminosity). Consequently, observers must constrain observable-mass scaling relations using additional data, and use the scaling relation model in conjunction with the mass function to predict the number of clusters as a function of redshift and luminosity.

  14. Gas Loss in Simulated Galaxies as They Fall into Clusters

    CERN Document Server

    Cen, Renyue; Bahcall, Neta A

    2014-01-01

    We use high-resolution cosmological hydrodynamic galaxy formation simulations to gain insights on how galaxies lose their cold gas at low redshift as they migrate from the field to the high density regions of clusters of galaxies. We find that beyond three cluster virial radii, the fraction of gas-rich galaxies is constant, representing the field. Within three cluster-centric radii, the fraction of gas-rich galaxies declines steadily with decreasing radius, reaching $\\mathbf{<10%}$ near the cluster center. Our results suggest that galaxies start to feel the impact of the cluster environment on their gas content well beyond the cluster virial radius. We show that almost all gas-rich galaxies at the cluster virial radius are falling in for the first time at nearly radial orbits. Furthermore, we find that almost no galaxy moving outward at the cluster virial radius is gas-rich (with gas to baryon ratio greater than $\\mathbf{1%}$). These results suggest that galaxies that fall into clusters lose their cold gas...

  15. Dwarf galaxies in the Antlia Cluster: First results

    CERN Document Server

    Castelli, A V S; Cellone, S A; Richtler, T; Dirsch, B; Infante, L; Aruta, C; Gómez, M

    2006-01-01

    We present the first results of a project aimed to study the galaxy population of the Antlia cluster, the third nearest galaxy cluster after Virgo and Fornax. The observations for the Antlia project consist of Washington wide-field images taken with the MOSAIC camera mounted at the prime focus of the CTIO 4-m Blanco telescope. Our preliminary results correspond to the identification and classification of dwarf galaxies in the central cluster region, extending the list of Ferguson & Sandage (1990). The final aim of our project is to study the luminosity function, morphology and structural parameters of dwarf galaxies in the Antlia cluster with a more complete sample.

  16. The Evolution of [OII] Emission from Cluster Galaxies

    CERN Document Server

    Nakata, F; Balogh, M L; Wilman, D J; Nakata, Fumiaki; Bower, Richard G.; Balogh, Michael L.; Wilman, David J.

    2004-01-01

    We investigate the evolution of the star formation rate in cluster galaxies. We complement data from the CNOC1 cluster survey (0.15galaxy clusters in the 2dF galaxy redshift survey (0.05clusters, up to almost z=1. We focus our attention on galaxies in the cluster core, ie. galaxies with r<0.7h^{-1}_{70}Mpc. Averaging over clusters in redshift bins, we find that the fraction of galaxies with strong [OII] emission is < 20% in cluster cores, and the fraction evolves little with redshift. In contrast, field galaxies from the survey show a very strong increase over the same redshift range. It thus appears that the environment in the cores of rich clusters is hostile to star formation at all the redshifts studied. We compare this result with the evolution of the colours of galaxies in cluster cores, first reported by Butcher & Oemler (1984). Using the same galaxies for our analysis of the [O...

  17. An Extreme Starburst in the Core of a Rich Galaxy Cluster at z = 1.7

    Science.gov (United States)

    Webb, Tracy; Noble, Allison; DeGroot, Andrew; Wilson, Gillian; Muzzin, Adam; Bonaventura, Nina; Cooper, Mike; Delahaye, Anna; Foltz, Ryan; Lidman, Chris; Surace, Jason; Yee, H. K. C.; Chapman, Scott; Dunne, Loretta; Geach, James; Hayden, Brian; Hildebrandt, Hendrik; Huang, Jiasheng; Pope, Alexandra; Smith, Matthew W. L.; Perlmutter, Saul; Tudorica, Alex

    2015-08-01

    We have discovered an optically rich galaxy cluster at z = 1.7089 with star formation occurring in close proximity to the central galaxy. The system, SpARCS104922.6+564032.5, was detected within the Spitzer Adaptation of the red-sequence Cluster Survey, and confirmed through Keck-MOSFIRE spectroscopy. The rest-frame optical richness of Ngal (500 kpc) = 30 ± 8 implies a total halo mass, within 500 kpc, of ˜3.8 ± 1.2 × 1014 M⊙, comparable to other clusters at or above this redshift. There is a wealth of ancillary data available, including Canada-France-Hawaii Telescope optical, UKIRT-K, Spitzer-IRAC/MIPS, and Herschel-SPIRE. This work adds submillimeter imaging with the SCUBA2 camera on the James Clerk Maxwell Telescope and near-infrared imaging with the Hubble Space Telescope. The mid/far-infrared (M/FIR) data detect an Ultra-luminous Infrared Galaxy spatially coincident with the central galaxy, with LIR = 6.2 ± 0.9 × 1012 L⊙. The detection of polycyclic aromatic hydrocarbons at z = 1.7 in a Spitzer-IRS spectrum of the source implies the FIR luminosity is dominated by star formation (an Active Galactic Nucleus contribution of 20%) with a rate of ˜860 ± 130 M⊙ yr-1. The optical source corresponding to the IR emission is likely a chain of >10 individual clumps arranged as “beads on a string” over a linear scale of 66 kpc. Its morphology and proximity to the Brightest Cluster Galaxy (BCG) imply a gas-rich interaction at the center of the cluster triggered the star formation. This system indicates that wet mergers may be an important process in forming the stellar mass of BCGs at early times.

  18. Dynamics of rich clusters of galaxies. I. The Coma cluster

    International Nuclear Information System (INIS)

    The structure and dynamics of the Coma cluster are analyzed using self-consistent equilibrium dynamical models. Observational material for Coma is culled from a variety of sources. Projected surface, density, and velocity-dispersion profiles are derived extending out to a radius of 30 from the cluster center, which are essentially free from field contamination. Segregation of galaxies by luminosity and morphology are discussed and a quantitative estimate of the latter is made. The method of constructing self-consistent dynamical models is discussed. Four different forms of the distribution function are analyzed allowing for different possible dependences of f on energy and angular momentum. Properties of typical models that might resemble actual clusters are presented, and the importance of having velocity-dispersion information is empha sized. The effect of a central massive object such as a cD galaxy on the core structure is illustrated. A comparison of these models with Coma reveals that only models with a distribution function in which the ratio of tangential to radial velocity dispersions is everywhere constant give acceptable fits. In particular, it is possible to rule out models that have isotropic motions in the core and predominantly radial motions in the halo. For H0 = 50, the best-fitting models give a total projected mass inside 30 of 2.9 x 1015 M/sub sun/ , a core radius of 340--400 kpc (8.5'--10'), an upper limit to any central massive object of approx.1013 M/sub sun/ , and a mass-to-blue-light ratio of M/L = 181. From cosmological considerations the cluster ''edge'' is determined to lie at rapprox.50--60. The possible distribution of ''dark matter'' in Coma is discussed and it is argued that this distribution cannot be significantly different from that of the galaxies. The dynamics of morphological segregation are examined quantitatively, and are explained at least qualitatively

  19. Emission Line Galaxies and Active Galactic Nuclei in WINGS clusters

    CERN Document Server

    Marziani, P; Bettoni, D; Poggianti, B M; Moretti, A; Fasano, G; Fritz, J; Cava, A; Varela, J; Omizzolo, A

    2016-01-01

    We present the analysis of the emission line galaxies members of 46 low redshift (0.04 < z < 0.07) clusters observed by WINGS (WIde-field Nearby Galaxy cluster Survey, Fasano et al. 2006). Emission line galaxies were identified following criteria that are meant to minimize biases against non-star forming galaxies and classified employing diagnostic diagrams. We have examined the emission line properties and frequencies of star forming galaxies, transition objects and active galactic nuclei (AGNs: LINERs and Seyferts), unclassified galaxies with emission lines, and quiescent galaxies with no detectable line emission. A deficit of emission line galaxies in the cluster environment is indicated by both a lower frequency with respect to control samples, and by a systematically lower Balmer emission line equivalent width and luminosity (up to one order of magnitude in equivalent width with respect to control samples for transition objects) that implies a lower amount of ionised gas per unit mass and a lower s...

  20. K-mouflaging Clusters of Galaxies

    CERN Document Server

    Brax, Philippe; Valageas, Patrick

    2015-01-01

    We investigate the effects of a K-mouflage modification of gravity on the dynamics of clusters of galaxies. We extend the description of K-mouflage to situations where the scalar field responsible for the modification of gravity is coupled to a perfect fluid with pressure. We describe the coupled system at both the background cosmology and cosmological perturbations levels, focusing on cases where the pressure emanates from small-scale nonlinear physics. We derive these properties in both the Einstein and Jordan frames, as these two frames already differ by a few percents at the background level for K-mouflage scenarios, and next compute cluster properties in the Jordan frame that is better suited to these observations. Galaxy clusters are not screened by the K-mouflage mechanism and therefore feel the modification of gravity in a maximal way. This implies that the halo mass function deviates from $\\Lambda$-CDM by a factor of order one for masses $M\\gtrsim 10^{14} \\ h^{-1} M_\\odot$. We then consider the hydro...

  1. Joint Analysis of Galaxy-Galaxy Lensing and Galaxy Clustering: Methodology and Forecasts for DES

    Energy Technology Data Exchange (ETDEWEB)

    Park, Y. [Univ. of Chicago, IL (United States). et al.

    2015-07-19

    The joint analysis of galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth function of large scale structure. Our analysis will be carried out on data from the Dark Energy Survey (DES), with its measurements of both the distribution of galaxies and the tangential shears of background galaxies induced by these foreground lenses. We develop a practical approach to modeling the assumptions and systematic effects affecting small scale lensing, which provides halo masses, and large scale galaxy clustering. Introducing parameters that characterize the halo occupation distribution (HOD), photometric redshift uncertainties, and shear measurement errors, we study how external priors on different subsets of these parameters affect our growth constraints. Degeneracies within the HOD model, as well as between the HOD and the growth function, are identified as the dominant source of complication, with other systematic effects sub-dominant. The impact of HOD parameters and their degeneracies necessitate the detailed joint modeling of the galaxy sample that we employ. Finally, 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 7.9%/4.8% with its first-year data that covered over 1000 square degrees, and to 3.9%/2.3% with its full five-year data that will survey 5000 square degrees, including both statistical and systematic uncertainties.

  2. Environmental Effects on Late-Type Galaxies in Nearby Clusters

    CERN Document Server

    Boselli, A

    2006-01-01

    The transformations taking place in late-type galaxies in the environment of rich clusters of galaxies at z=0 are reviewed. From the handful of late-type galaxies that inhabit local clusters, whether they were formed in-situ and survived as such, avoiding transformation or even destruction or if they are newcomers that recently infall from outside, we can learn an important lesson on the latest stages of galaxy evolution. We start by reviewing the observational scenario, covering the broadest possible stretch of the electromagnetic spectrum, from the gas tracers, the star formation tracers, the old star tracers and the dust. Strong emphasis is given to the three nearby, well studied clusters Virgo, A1367 and Coma, representative of different evolutionary stages, from unrelaxed, spiral rich (Virgo) to relaxed, spiral poor clusters (Coma). We continue by providing a review of models of galaxy interactions relevant to clusters of galaxies. Prototypes of various mechanisms and processes are discussed and their ty...

  3. How does our choice of observable influence our estimation of the centre of a galaxy cluster? Insights from cosmological simulations

    Science.gov (United States)

    Cui, Weiguang; Power, Chris; Biffi, Veronica; Borgani, Stefano; Murante, Giuseppe; Fabjan, Dunja; Knebe, Alexander; Lewis, Geraint F.; Poole, Greg B.

    2016-03-01

    Galaxy clusters are an established and powerful test-bed for theories of both galaxy evolution and cosmology. Accurate interpretation of cluster observations often requires robust identification of the location of the centre. Using a statistical sample of clusters drawn from a suite of cosmological simulations in which we have explored a range of galaxy formation models, we investigate how the location of this centre is affected by the choice of observable - stars, hot gas, or the full mass distribution as can be probed by the gravitational potential. We explore several measures of cluster centre: the minimum of the gravitational potential, which would expect to define the centre if the cluster is in dynamical equilibrium; the peak of the density; the centre of brightest cluster galaxy (BCG); and the peak and centroid of X-ray luminosity. We find that the centre of BCG correlates more strongly with the minimum of the gravitational potential than the X-ray defined centres, while active galactic nuclei feedback acts to significantly enhance the offset between the peak X-ray luminosity and minimum gravitational potential. These results highlight the importance of centre identification when interpreting clusters observations, in particular when comparing theoretical predictions and observational data.

  4. The thousand Brightest HIPASS Galaxies : HIMass Function and Omega_HI HIMass Function and Omega_HI

    CERN Document Server

    Zwaan, M A; Koribalski, B S; Henning, P A; Kilborn, V A; Ryder, S D; Barnes, D G; Bhathal, R; Boyce, P J; De Blok, W J G; Disney, M J; Drinkwater, M J; Ekers, R D; Freeman, K C; Gibson, B K; Green, A J; Haynes, R F; Jerjen, H; Juraszek, S; Kesteven, M J; Knezek, P M; Kraan-Korteweg, R C; Mader, S; Marquarding, M; Meyer, M; Minchin, R F; Mould, J R; O'Brien, J; Oosterloo, T; Price, R M; Putman, M E; Ryan-Weber, E; Sadler, E M; Schröder, A; Stewart, I M; Stootman, F; Warren, B; Waugh, M; Webster, R L; Wright, A E

    2003-01-01

    We present a new accurate measurement of the HI mass function of galaxies from the HIPASS Bright Galaxy Catalog, a sample of 1000 galaxies with the highest HI peak flux densities in the southern hemisphere (Koribalski et al. 2003). This sample spans nearly four orders of magnitude in HI mass (from log M_HI/M_sun=6.8 to 10.6, H0=75) and is the largest sample of HI selected galaxies to date. We develop a bivariate maximum likelihood technique to measure the space density of galaxies, and show that this is a robust method, insensitive to the effects of large scale structure. The resulting HI mass function can be fitted satisfactorily with a Schechter function with faint-end slope alpha=-1.30. This slope is found to be dependent on morphological type, with later type galaxies giving steeper slopes. We extensively test various effects that potentially bias the determination of the HI mass function, including peculiar motions of galaxies, large scale structure, selection bias, and inclination effects, and quantify ...

  5. QUASAR-GALAXY CLUSTERING THROUGH PROJECTED GALAXY COUNTS AT z = 0.6-1.2

    International Nuclear Information System (INIS)

    We investigate the spatial clustering of galaxies around quasars at z = 0.6-1.2 using photometric data from Sloan Digital Sky Survey Stripe 82. The quasar and galaxy cross-correlation functions are measured through the projected galaxy number density n(rp ) on scales of 0.05 p –1 Mpc around quasars for a sample of 2300 quasars from Schneider et al. We detect strong clustering signals at all redshifts and find that the clustering amplitude increases significantly with redshift. We examine the dependence of quasar-galaxy clustering on quasar and galaxy properties and find that the clustering amplitude is significantly larger for quasars with more massive black holes or with bluer colors, while there is no dependence on quasar luminosity. We also show that quasars have a stronger correlation amplitude with blue galaxies than with red galaxies. We finally discuss the implications of our findings

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

    Energy Technology Data Exchange (ETDEWEB)

    Newman, Andrew B.; Ellis, Richard S. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Treu, Tommaso; Sand, David J., E-mail: anewman@astro.caltech.edu [Department of Physics, University of California, Santa Barbara, CA 93106 (United States)

    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.

  7. Gas loss in simulated galaxies as they fall into clusters.

    Science.gov (United States)

    Cen, Renyue; Pop, Ana Roxana; Bahcall, Neta A

    2014-06-01

    We use high-resolution cosmological hydrodynamic galaxy formation simulations to gain insights into how galaxies lose their cold gas at low redshift as they migrate from the field to the high-density regions of clusters of galaxies. We find that beyond three cluster virial radii, the fraction of gas-rich galaxies is constant, representing the field. Within three cluster-centric radii, the fraction of gas-rich galaxies declines steadily with decreasing radius, reaching galaxies start to feel the effect of the cluster environment on their gas content well beyond the cluster virial radius. We show that almost all gas-rich galaxies at the cluster virial radius are falling in for the first time at nearly radial orbits. Furthermore, we find that almost no galaxy moving outward at the cluster virial radius is gas-rich (with a gas-to-baryon ratio greater than 1%). These results suggest that galaxies that fall into clusters lose their cold gas within a single radial round-trip. PMID:24843167

  8. Detecting Galaxy Clusters in the DLS and CARS: a Bayesian Cluster Finder

    CERN Document Server

    Ascaso, Begoña; Benítez, Narciso

    2010-01-01

    The detection of galaxy clusters in present and future surveys enables measuring mass-to-light ratios, clustering properties or galaxy cluster abundances and therefore, constraining cosmological parameters. We present a new technique for detecting galaxy clusters, which is based on the Matched Filter Algorithm from a Bayesian point of view. The method is able to determine the position, redshift and richness of the cluster through the maximization of a filter depending on galaxy luminosity, density and photometric redshift combined with a galaxy cluster prior. We tested the algorithm through realistic mock galaxy catalogs, revealing that the detections are 100% complete and 80% pure for clusters up to z 25 (Abell Richness > 0). We applied the algorithm to the CFHTLS Archive Research Survey (CARS) data, recovering similar detections as previously published using the same data plus additional clusters that are very probably real. We also applied this algorithm to the Deep Lens Survey (DLS), obtaining the first ...

  9. Searching for star-forming galaxies in the Fornax and Hydra clusters

    CERN Document Server

    Vaduvescu, O; Vilchez, J M; Unda-Sanzana, E; 10.1051/0004-6361/201116651

    2011-01-01

    The formation and evolution of dwarf galaxies is relatively difficult to understand because of their faint emission in all regimes that require large aperture telescopes. We intend to study the evolution of star forming dwarf galaxies in clusters. We selected Fornax and Hydra clusters to complement our previous study of Virgo. On the basis of available literature data, we selected ten star-forming candidates in Fornax and another ten objects in Hydra. We used Gemini South with GMOS to acquire H-alpha images necessary to detect star-forming regions in the two galaxy samples. We then performed long-slit spectroscopy for the brightest six candidates, to derive their chemical properties. Finally, we employed the VLT with HAWK-I to observe all galaxies in the K' band to derive their main physical properties. We studied the morphology of our two samples, finding five objects in Fornax and six in Hydra with structures consistent with those of star-forming dwarfs, i.e., dwarf irregulars (dIs) or blue compact dwarfs (...

  10. Numerical Modeling of Gamma Radiation from Galaxy Clusters

    CERN Document Server

    Miniati, F

    2003-01-01

    We investigate the spatial and spectral properties of non-thermal emission from clusters of galaxies at The importance of such measurements in advancing our understanding of non-thermal processes in the intra-cluster medium is discussed.

  11. Detection of CO emission in Hydra 1 cluster galaxies

    International Nuclear Information System (INIS)

    A survey of bright Hydra cluster spiral galaxies for the CO(1-0) transition at 115 GHz was performed with the 15m Swedish-ESO submillimeter telescope (SEST). Five out of 15 galaxies observed have been detected in the CO(1-0) line. The largest spiral galaxy in the cluster, NGC 3312, got more CO than any spiral of the Virgo cluster. This Sa-type galaxy is optically largely distorted and disrupted on one side. It is a good candidate for ram pressure stripping while passing through the cluster's central region. A comparison with global CO properties of Virgo cluster spirals shows a relatively good agreement with the detected Hydra cluster galaxies

  12. Updating the $\\sigma$-$T$ relationship for galaxy clusters

    OpenAIRE

    Wu, Xiang-Ping; Fang, Li-Zhi; Xu, Wen

    1998-01-01

    The relationship between the X-ray determined temperature $T$ of the intracluster gas and the optical measured velocity dispersion $\\sigma$ of the cluster galaxies is often believed to be not only a straightforward but also robust test for the dynamical properties of galaxy clusters. Here, we present the $\\sigma$-$T$ relationship using the 94 clusters drawn from the largest sample of 149 clusters in literature, for which both $\\sigma$ and $T$ are observationally determined. Employment of the ...

  13. Clusters of Galaxies and the Diffuse Gamma Ray Background

    OpenAIRE

    Colafrancesco, S.; P. Blasi(INAF Arcetri)

    1998-01-01

    We discuss the diffuse emission of gamma rays and neutrinos from galaxy clusters in the viable models for structure formation in the universe. We use a self-consistent picture for cluster formation and evolution starting from a primordial density perturbation spectrum, and a realistic modelling for the distribution of the intergalactic medium which is abundantly present within galaxy clusters. We find that an evolving population of clusters can produce a fraction $\\sim 0.5 \\div 2 %$ of the di...

  14. SEARCHING FOR COOLING SIGNATURES IN STRONG LENSING GALAXY CLUSTERS: EVIDENCE AGAINST BARYONS SHAPING THE MATTER DISTRIBUTION IN CLUSTER CORES

    Energy Technology Data Exchange (ETDEWEB)

    Blanchard, Peter K. [Astronomy Department, University of California, Berkeley, B-20 Hearst Field Annex 3411, Berkeley, CA 94720-3411 (United States); Bayliss, Matthew B. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); McDonald, Michael [Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue 37-287, Cambridge, MA 02139 (United States); Dahle, Hakon [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, NO-0315 Oslo (Norway); Gladders, Michael D. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Sharon, Keren [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States); Mushotzky, Richard, E-mail: pblanchard@fas.harvard.edu [Astronomy Department, University of Maryland, College Park, MD 20742 (United States)

    2013-07-20

    The process by which the mass density profile of certain galaxy clusters becomes centrally concentrated enough to produce high strong lensing (SL) cross-sections is not well understood. It has been suggested that the baryonic condensation of the intracluster medium (ICM) due to cooling may drag dark matter to the cores and thus steepen the profile. In this work, we search for evidence of ongoing ICM cooling in the first large, well-defined sample of SL selected galaxy clusters in the range 0.1 < z < 0.6. Based on known correlations between the ICM cooling rate and both optical emission line luminosity and star formation, we measure, for a sample of 89 SL clusters, the fraction of clusters that have [O II]{lambda}{lambda}3727 emission in their brightest cluster galaxy (BCG). We find that the fraction of line-emitting BCGs is constant as a function of redshift for z > 0.2 and shows no statistically significant deviation from the total cluster population. Specific star formation rates, as traced by the strength of the 4000 A break, D{sub 4000}, are also consistent with the general cluster population. Finally, we use optical imaging of the SL clusters to measure the angular separation, R{sub arc}, between the arc and the center of mass of each lensing cluster in our sample and test for evidence of changing [O II] emission and D{sub 4000} as a function of R{sub arc}, a proxy observable for SL cross-sections. D{sub 4000} is constant with all values of R{sub arc}, and the [O II] emission fractions show no dependence on R{sub arc} for R{sub arc} > 10'' and only very marginal evidence of increased weak [O II] emission for systems with R{sub arc} < 10''. These results argue against the ability of baryonic cooling associated with cool core activity in the cores of galaxy clusters to strongly modify the underlying dark matter potential, leading to an increase in SL cross-sections.

  15. Dwarf galaxies in the Perseus Cluster: further evidence for a disc origin for dwarf ellipticals

    CERN Document Server

    Penny, Samantha J; Pimbblet, Kevin A; Floyd, David J E

    2014-01-01

    We present the results of a Keck-ESI spectroscopic study of six dwarf elliptical (dE) galaxies in the Perseus Cluster core, and confirm two dwarfs as cluster members for the first time. All six dEs follow the size-magnitude relation for dE/dSph galaxies. Central velocity dispersions are measured for three Perseus dwarfs in our sample, and all lie on the $\\sigma$-luminosity relation for early-type, pressure supported systems. We furthermore examine SA 0426-002, a unique dE in our sample with a bar-like morphology surrounded by low-surface brightness wings/lobes ($\\mu_{B} = 27$ mag arcsec$^{-2}$). Given its morphology, velocity dispersion ($\\sigma_{0} = 33.9 \\pm 6.1 $ km s$^{-1}$), velocity relative to the brightest cluster galaxy NGC 1275 (2711 km s$^{-1}$), size ($R_{e} =2.1 \\pm 0.10$ kpc), and Sersic index ($n= 1.2 \\pm 0.02$), we hypothesise the dwarf has morphologically transformed from a low mass disc to dE via harassment. The low-surface brightness lobes can be explained as a ring feature, with the bar fo...

  16. The re-distribution of matter in the cores of galaxy clusters

    CERN Document Server

    Laporte, Chervin F P

    2014-01-01

    We present cosmological N-body resimulations of the assembly of the Brightest Cluster Galaxies (BCGs) in rich clusters. At $z=2$ we populate dark matter subhalos with self-gravitating stellar systems whose abundance and structure match observed high-redshift galaxies. By $z=0$, mergers have built much larger galaxies at cluster centre. Their dark matter density profiles are shallower than in corresponding dark-matter-only simulations, but their total mass density profiles (stars + dark matter) are quite similar. Differences are found only at radii where the effects of central black holes may be significant. Dark matter density slopes shallower than $\\gamma=1.0$ occur for $r/r_{200} < 0.015$, close to the half-light radii of the BCGs. Our experiments support earlier suggestions that NFW-like profiles are an attractor for the hierarchical growth of structure in collisionless systems -- total mass density profiles asymptote to the solution found in dark-matter-only simulations over the radial range where merg...

  17. DISCOVERY OF A STRONG LENSING GALAXY EMBEDDED IN A CLUSTER AT z = 1.62

    International Nuclear Information System (INIS)

    We identify a strong lensing galaxy in the cluster IRC 0218 (also known as XMM-LSS J02182–05102) that is spectroscopically confirmed to be at z = 1.62, making it the highest-redshift strong lens galaxy known. The lens is one of the two brightest cluster galaxies and lenses a background source galaxy into an arc and a counterimage. With Hubble Space Telescope (HST) grism and Keck/LRIS spectroscopy, we measure the source redshift to be z S = 2.26. Using HST imaging in ACS/F475W, ACS/F814W, WFC3/F125W, and WFC3/F160W, we model the lens mass distribution with an elliptical power-law profile and account for the effects of the cluster halo and nearby galaxies. The Einstein radius is θE=0.38−0.01+0.02 arcsec (3.2−0.1+0.2 kpc) and the total enclosed mass is M tot(<θE)=1.8−0.1+0.2×1011 M⊙. We estimate that the cluster environment contributes ∼10% of this total mass. Assuming a Chabrier initial mass function (IMF), the dark matter fraction within θE is fDMChab=0.3−0.3+0.1, while a Salpeter IMF is marginally inconsistent with the enclosed mass (fDMSalp=−0.3−0.5+0.2). The total magnification of the source is μtot=2.1−0.3+0.4. The source has at least one bright compact region offset from the source center. Emission from Lyα and [O III] are likely to probe different regions in the source

  18. Galaxy-Cluster Interaction in NGC 7619

    CERN Document Server

    Kim, Dong-Woo; Fabbiano, Giuseppina; Trinchieri, Ginevra

    2007-01-01

    We present new observational results of NGC 7619, an elliptical galaxy with a prominent X-ray tail and a dominant member of the Pegasus group. With Chandra and XMM-Newton observations, we confirm the presence of a long X-ray tail in the SW direction; moreover, we newly identify a sharp discontinuity of the X-ray surface brightness in the opposite (NE) side of the galaxy. We interpret these features as a strong indication that NGC 7619 is moving toward the NE within its parent cluster, so that its hot ISM experiences ram pressure against the hotter ambient ICM. The density, temperature and pressure jump at the NE discontinuity suggest a Mach number ~1, corresponding to a galaxy velocity of ~500 km s-1, relative to ICM. Spectral analysis of these data shows that the Iron abundance of the hot gaseous medium is much higher (1-2 solar) near the center of NGC 7619 and in the tail extending from the core than in the surrounding regions (1/2 solar). This result offers the first clear pictorial evidence of the process...

  19. The Galaxy Population of Low-Redshift Abell Clusters

    CERN Document Server

    Barkhouse, Wayne A; Lopez-Cruz, Omar

    2009-01-01

    We present a study of the luminosity and color properties of galaxies selected from a sample of 57 low-redshift Abell clusters. We utilize the non-parametric dwarf-to-giant ratio (DGR) and the blue galaxy fraction (fb) to investigate the clustercentric radial-dependent changes in the cluster galaxy population. Composite cluster samples are combined by scaling the counting radius by r200 to minimize radius selection bias. The separation of galaxies into a red and blue population was achieved by selecting galaxies relative to the cluster color-magnitude relation. The DGR of the red and blue galaxies is found to be independent of cluster richness (Bgc), although the DGR is larger for the blue population at all measured radii. A decrease in the DGR for the red and red+blue galaxies is detected in the cluster core region, while the blue galaxy DGR is nearly independent of radius. The fb is found not to correlate with Bgc; however, a steady decline toward the inner-cluster region is observed for the giant galaxies....

  20. Star formation properties of galaxy cluster A1767

    International Nuclear Information System (INIS)

    Abell 1767 is a dynamically relaxed, cD cluster of galaxies with a redshift of 0.0703. Among 250 spectroscopically confirmed member galaxies within a projected radius of 2.5r200, 243 galaxies (∼ 97%) are spectroscopically covered by the Sloan Digital Sky Survey. Based on this homogeneous spectral sample, the stellar evolutionary synthesis code STARLIGHT is applied to investigate the stellar populations and star formation histories of galaxies in this cluster. The star formation properties of galaxies, such as mean stellar ages, metallicities, stellar masses, and star formation rates, are presented as functions of local galaxy density. A strong environmental effect is found such that massive galaxies in the high-density core region of the cluster tend to have higher metallicities, older mean stellar ages, and lower specific star formation rates (SSFRs), and their recent star formation activities have been remarkably suppressed. In addition, the correlations of the metallicity and SSFR with stellar mass are confirmed. (paper)

  1. A Universal Temperature Profile for Galaxy Clusters

    CERN Document Server

    Loken, C; Nelson, E; Burns, J; Bryan, G L; Motl, P M

    2002-01-01

    We investigate the predicted present-day temperature profiles of the hot, X-ray emitting gas in galaxy clusters for two cosmological models - a current best-guess LCDM model and standard cold dark matter (SCDM). Our numerically-simulated "catalogs" of clusters are derived from high-resolution (15/h kpc) simulations which make use of a sophisticated, Eulerian-based, Adaptive Mesh-Refinement (AMR) code that faithfully captures the shocks which are essential for correctly modelling cluster temperatures. We show that the temperature structure on Mpc-scales is highly complex and non-isothermal. However, the temperature profiles of the simulated LCDM and SCDM clusters are remarkably similar and drop-off as $T +AFw-propto (1+-r/a_x)^{-+AFw-delta}$ where $a_x +AFw-sim r_{vir}/1.5$ and $+AFw-delta +AFw-sim 1.6$. This decrease is in good agreement with the observational results of Markevitch et al.(1998) but diverges, primarily in the innermost regions, from their fit which assumes a polytropic equation of state. Our r...

  2. Cosmology with EMSS Clusters of Galaxies

    Science.gov (United States)

    Donahue, Megan; Voit, G. Mark

    1999-01-01

    We use ASCA observations of the Extended Medium Sensitivity Survey sample of clusters of galaxies to construct the first z = 0.5 - 0.8 cluster temperature function. This distant cluster temperature function, when compared to local z approximately 0 and to a similar moderate redshift (z = 0.3 - 0.4) temperature function strongly constrains the matter density of the universe. Best fits to the distributions of temperatures and redshifts of these cluster samples results in Omega(sub M) = 0.45 +/- 0.1 if Lambda = 0 and Omega = 0.27 +/- 0.1 if Lambda + Omega(sub M) = 1. The uncertainties are 1sigma statistical. We examine the systematics of our approach and find that systematics, stemming mainly from model assumptions and not measurement errors, are about the same size as the statistical uncertainty +/- 0.1. In this poster proceedings, we clarify the issue of a8 as reported in our paper Donahue & Voit (1999), since this was a matter of discussion at the meeting.

  3. The galaxy cluster outskirts via stacking

    CERN Document Server

    Morandi, Andrea; Forman, William; Jones, Christine

    2015-01-01

    We studied the physical properties of the intracluster medium in the virialization region of a sample of 320 clusters ($0.056 3$ keV) in the Chandra archive. We stacked the emission measure profiles of the clusters to detect a signal out to and beyond $R_{200}$. We then measured the average emission measure, gas density and gas fraction. We observe a steepening of the density profiles beyond $R_{500}$ with $\\beta \\sim 0.68$ at $R_{500}$ and $\\beta \\sim 1$ at $R_{200}$ and beyond. By tracking the direction of the cosmic filaments where the clusters are embedded, we report that galaxy clusters deviate from spherical symmetry, with only small differences between relaxed and disturbed systems. We also did not find evolution of the gas density with redshift, confirming the self-similar evolution of the gas density. The value of the baryon fraction reaches the cosmic value at $R_{200}$: however, systematics due to non-thermal pressure support and clumpiness might enhance the measured gas fraction, leading to an ac...

  4. The Density Profiles of Massive, Relaxed Galaxy Clusters: II. Separating Luminous and Dark Matter in Cluster Cores

    CERN Document Server

    Newman, Andrew B; Ellis, Richard S; Sand, David J

    2012-01-01

    We present stellar and dark matter (DM) density profiles for a sample of 7 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 3 decades in radius, is consistent with numerical DM-only simulations at radii \\gtrsim 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. Parametrizing the DM density profile as a power law rho_DM \\sim r^{-\\beta} on small scales, we find a mean slope = 0.50 +- 0.10 (random) +0.14-0.13 (systematic). Alternatively, cored Navarro-Frenk-White (NFW) profiles with = 1.14 +- 0.13 (rand.) +0.14-0.22 (sys.) provide an equally good description. These density profiles are significantly shallower than canonical NFW models at radi...

  5. On the distribution of galaxy ellipticity in clusters

    CERN Document Server

    D'Eugenio, Francesco; Davies, Roger L; Bontà, Elena Dalla

    2015-01-01

    We studied the distribution of projected ellipticity $\\epsilon$ for the galaxies in a sample of 20 rich ($\\mathcal{R} > 2$) nearby ($z 0.4), therefore it is not a consequence of the increasing fraction of intrinsically round Slow Rotator galaxies nearer the centre of clusters. The trend is also observed for flat, smooth galaxies and dividing the galaxies according to the shape of their light profile. This suggests that the systematic variation of the fraction of spiral galaxies with R does not explain alone the observed 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 $\\epsilon$ nearer to the centre of clusters is evidence for physical effects in clusters causing Fast Rotator ETGs to have a lower average intrinsic ellipticity near the centre of rich clusters.

  6. The Ghosts of Galaxies: Tidal Debris in Clusters

    CERN Document Server

    Gregg, M D; Gregg, Michael D.; West, Michael J.

    2003-01-01

    Gravitational interactions in rich clusters can strip material from the outer parts of galaxies or even completely disrupt entire systems, giving rise to large scale, low surface brightness ghostly features stretching across intergalactic space. The nearby Coma and Centaurus clusters both have striking examples of galaxy ghosts, in the form of 100 kpc-long plumes of intergalactic debris. By searching HST archival images, we have found numerous other examples of galaxy ghosts in rich clusters at low redshift, evidence that galaxy destruction and recycling are ubiquitous, important in cluster formation and evolution, and continue to mold clusters at the present epoch. Many ghosts appear in X-ray bright clusters, perhaps signaling a connection with energetic subcluster mergers. The fate of such material has important ramifications for cluster evolution. Our new HST WFPC2 V & I images of a portion of the Centaurus plume reveal that it contains an excess of discrete objects with -12 < M_v < -6, consisten...

  7. A Measurement of the Rate of Type Ia Supernovae in Galaxy Clusters from the SDSS-II Supernova Survey

    CERN Document Server

    Dilday, Benjamin; Becker, Andrew; Bender, Ralf; Castander, Francisco; Cinabro, David; Frieman, Joshua A; Galbany, Lluís; Garnavich, Peter; Goobar, Ariel; Hopp, Ulrich; Ihara, Yutaka; Jha, Saurabh W; Kessler, Richard; Lampeitl, Hubert; Marriner, John; Miquel, Ramon; Mollá, Mercedes; Nichol, Robert C; Nordin, Jakob; Riess, Adam G; Sako, Masao; Schneider, Donald P; Smith, Mathew; Sollerman, Jesper; Wheeler, J Craig; Östman, Linda; Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Dan; Pan, Kaike; Simmons, Audrey; Snedden, Stephanie

    2010-01-01

    ABRIDGED We present measurements of the Type Ia supernova (SN) rate in galaxy clusters based on data from the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. The cluster SN Ia rate is determined from 9 SN events in a set of 71 C4 clusters at z <0.17 and 27 SN events in 492 maxBCG clusters at 0.1 < z < 0.3$. We find values for the cluster SN Ia rate of $({0.37}^{+0.17+0.01}_{-0.12-0.01}) \\mathrm{SNu}r h^{2}$ and $({0.55}^{+0.13+0.02}_{-0.11-0.01}) \\mathrm{SNu}r h^{2}$ ($\\mathrm{SNu}x = 10^{-12} L_{x\\sun}^{-1} \\mathrm{yr}^{-1}$) in C4 and maxBCG clusters, respectively, where the quoted errors are statistical and systematic, respectively. The SN rate for early-type galaxies is found to be $({0.31}^{+0.18+0.01}_{-0.12-0.01}) \\mathrm{SNu}r h^{2}$ and $({0.49}^{+0.15+0.02}_{-0.11-0.01})$ $\\mathrm{SNu}r h^{2}$ in C4 and maxBCG clusters, respectively. The SN rate for the brightest cluster galaxies (BCG) is found to be $({2.04}^{+1.99+0.07}_{-1.11-0.04}) \\mathrm{SNu}r h^{2}$ and $({0.36}^{+0.84+0.01}_...

  8. Baryon content and dynamic state of galaxy clusters: XMM-Newton observations of A1095 and A1926

    CERN Document Server

    Ge, Chong; Tripp, Todd M; Li, Zhiyuan; Gu, Qiusheng; Ji, Li

    2016-01-01

    We have initiated a program to study the baryon content and dynamic state of galaxy clusters. Here we present results primarily from XMM-Newton observations of two optically-selected galaxy clusters, A1095 ($z \\simeq 0.210$) and A1926 ($z \\simeq 0.136$). We find that both of them are actually cluster pairs at similar redshifts. We characterize the temperatures of these individual clusters through X-ray spectral fits and then estimate their gravitational masses. We show a rich set of substructures, including large position offsets between the diffuse X-ray centroids and the brightest galaxies of the clusters, which suggests that they are dynamically young. For both A1095 and A1926, we find that the mass required for the cluster pairs to be bound is smaller than the total gravitational mass. Thus both cluster pairs appear to be ongoing major mergers. Incorporating SDSS and NVSS/FIRST data, we further examine the large-scale structure environment and radio emission of the clusters to probe their origins, which a...

  9. Far Ultraviolet Morphology of Star Forming Filaments in Cool Core Brightest Cluster Galaxies

    CERN Document Server

    Tremblay, Grant R; Baum, Stefi A; Mittal, Rupal; McDonald, Michael; Combes, Françoise; Li, Yuan; McNamara, Brian; Bremer, Malcolm N; Clarke, Tracy E; Donahue, Megan; Edge, Alastair C; Fabian, Andrew C; Hamer, Stephen L; Hogan, Michael T; Oonk, Raymond; Quillen, Alice C; Sanders, Jeremy S; Salomé, Philippe; Voit, G Mark

    2015-01-01

    We present a multiwavelength morphological analysis of star forming clouds and filaments in the central ($ 5$ \\Msol) stars reveals filamentary and clumpy morphologies, which we quantify by means of structural indices. The FUV data are compared with X-ray, Ly$\\alpha$, narrowband H$\\alpha$, broadband optical/IR, and radio maps, providing a high spatial resolution atlas of star formation locales relative to the ambient hot ($\\sim10^{7-8}$ K) and warm ionised ($\\sim 10^4$ K) gas phases, as well as the old stellar population and radio-bright AGN outflows. Nearly half of the sample possesses kpc-scale filaments that, in projection, extend toward and around radio lobes and/or X-ray cavities. These filaments may have been uplifted by the propagating jet or buoyant X-ray bubble, or may have formed {\\it in situ} by cloud collapse at the interface of a radio lobe or rapid cooling in a cavity's compressed shell. The morphological diversity of nearly the entire FUV sample is reproduced by recent hydrodynamical simulations...

  10. The Imprint of Cosmic Reionization on Galaxy Clustering

    CERN Document Server

    Wyithe, Stuart

    2007-01-01

    We consider the effect of reionization on the clustering properties of galaxy samples at intermediate redshifts (z~0.3-5.5). Current models for the reionization of intergalactic hydrogen predict that overdense regions will be reionized early, thus delaying the build up of stellar mass in the progenitors of massive lower-redshift galaxies. As a result, the stellar populations observed in intermediate redshift galaxies are somewhat younger and hence brighter in overdense regions of the Universe. Galaxy surveys would therefore be sensitive to galaxies with a somewhat lower dark matter mass in overdense regions. The corresponding increase in the observed number density of galaxies can be parameterized as a galaxy bias due to reionization. We model this process using merger trees combined with a stellar synthesis code. Our model demonstrates that reionization has a significant effect on the clustering properties of galaxy samples that are selected based on their star-formation properties. The bias correction in Ly...

  11. Challenges And Results of the Applications of Fuzzy Logic in the Classification of Rich Galaxy Clusters

    Science.gov (United States)

    Santiago Girola Schneider, Rafael

    2015-08-01

    The fuzzy logic is a branch of the artificial intelligence founded on the concept that 'everything is a matter of degree.' It intends to create mathematical approximations on the resolution of certain types of problems. In addition, it aims to produce exact results obtained from imprecise data, for which it is particularly useful for electronic and computer applications. This enables it to handle vague or unspecific information when certain parts of a system are unknown or ambiguous and, therefore, they cannot be measured in a reliable manner. Also, when the variation of a variable can produce an alteration on the others.The main focus of this paper is to prove the importance of these techniques formulated from a theoretical analysis on its application on ambiguous situations in the field of the rich clusters of galaxies. The purpose is to show its applicability in the several classification systems proposed for the rich clusters, which are based on criteria such as the level of richness of the cluster, the distribution of the brightest galaxies, whether there are signs of type-cD galaxies or not or the existence of sub-clusters.Fuzzy logic enables the researcher to work with “imprecise” information implementing fuzzy sets and combining rules to define actions. The control systems based on fuzzy logic join input variables that are defined in terms of fuzzy sets through rule groups that produce one or several output values of the system under study. From this context, the application of the fuzzy logic’s techniques approximates the solution of the mathematical models in abstractions about the rich galaxy cluster classification of physical properties in order to solve the obscurities that must be confronted by an investigation group in order to make a decision.

  12. Dissecting the Red Sequence: The Bulge and Disc Colours of Early-Type Galaxies in the Coma Cluster

    CERN Document Server

    Head, Jacob T C G; Hudson, Micheal J; Smith, Russel J

    2014-01-01

    We explore the internal structure of red sequence galaxies in the Coma cluster across a wide range of luminosities ($-17>M_g>-22$) and cluster-centric radii ($0cluster}}<1.3 r_{200}$). We present the 2D bulge-disc decomposition of galaxies in deep Canada-France-Hawaii Telescope $u,g,i$ imaging using GALFIT. Rigorous filtering is applied to identify an analysis sample of 200 galaxies which are well described by an `archetypal' S0 structure (central bulge + outer disc). We consider internal bulge and/or disc colour gradients by allowing component sizes to vary between bands. Gradients are required for $30\\%$ of analysis sample galaxies. Bulge half-light radii are found to be uncorrelated with galaxy luminosity ($R_e \\sim 1$ kpc, $n\\sim2$) for all but the brightest galaxies ($M_g<-20.5$). The S0 discs are brighter (at fixed size, or smaller at fixed luminosity) than those of star-forming spirals. A similar colour-magnitude relation is found for both bulges and discs. The global red sequence for ...

  13. Low surface brightness galaxies in the cluster A1367

    International Nuclear Information System (INIS)

    We have obtained deep CCD frames of apparently blank regions of sky in the hope of detecting very low surface brightness (LSB) objects in the cluster A1367. We discuss our data reduction, and image detection and selection techniques. If the galaxies detected are actually cluster members then they are dwarfs and the conclusions of a previous paper on the Fornax cluster are essentially confirmed. One area of variance is that the lowest surface brightness galaxies do not appear to be preferentially concentrated towards the cluster centre. This can be explained by there being a much larger density of dwarf galaxies over this bright galaxy-rich region of the universe. We find over our small area approximately four times as many LSB galaxies as would be expected from our Fornax data. We speculate on the possible origin and likely intensity of intergalactic light within clusters. (author)

  14. Universal Non-thermal Pressure Fraction Profile in Galaxy Clusters

    CERN Document Server

    Nelson, Kaylea; Nagai, Daisuke

    2014-01-01

    Cosmological constraints from X-ray and microwave observations of galaxy clusters are subjected to systematic uncertainties. Non-thermal pressure support due to internal gas motions in galaxy clusters is one of the major sources of astrophysical uncertainties. Using a mass-limited sample of galaxy clusters from a high-resolution hydrodynamical cosmological simulation, we characterize the non-thermal pressure fraction profile and study its dependence on redshift, mass, and mass accretion rate. We find that the non-thermal pressure fraction profile is universal across redshift when galaxy cluster radii are defined with respect to the mean matter density of the universe instead of the commonly used critical density. We also find that the non-thermal pressure is predominantly radial, and the gas velocity anisotropy profile exhibits strong universality when galaxy cluster radii are defined with respect to the mean matter density of the universe. However, we find that the non-thermal pressure fraction is strongly d...

  15. On the distribution of galaxy ellipticity in clusters

    Science.gov (United States)

    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 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) 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.

  16. Cosmological simulations of galaxy clusters with feedback from active galactic nuclei: profiles and scaling relations

    CERN Document Server

    Pike, Simon R; Newton, Richard D A; Thomas, Peter A; Jenkins, Adrian

    2014-01-01

    We present results from a new set of 30 cosmological simulations of galaxy clusters, including the effects of radiative cooling, star formation, supernova feedback, black hole growth and AGN feedback. We first demonstrate that our AGN model is capable of reproducing the observed cluster pressure profile at redshift, z~0, once the AGN heating temperature of the targeted particles is made to scale with the final virial temperature of the halo. This allows the ejected gas to reach larger radii in higher-mass clusters than would be possible had a fixed heating temperature been used. Such a model also successfully reduces the star formation rate in brightest cluster galaxies and broadly reproduces a number of other observational properties at low redshift, including baryon, gas and star fractions; entropy profiles outside the core; and the X-ray luminosity-mass relation. Our results are consistent with the notion that the excess entropy is generated via selective removal of the densest material through radiative c...

  17. Radio AGN in 13,240 galaxy clusters from the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    Croft, S; de Vries, W; Becker, R

    2007-05-30

    We correlate the positions of 13,240 Brightest Cluster Galaxies (BCGs) with 0.1 {le} z {le} 0.3 from the maxBCG catalog with radio sources from the FIRST survey to study the sizes and distributions of radio AGN in galaxy clusters. We find that 19.7% of our BCGs are radio-loud, and this fraction depends on the stellar mass of the BCG, and to a lesser extent on the richness of the parent cluster (in the sense of increasing radio loudness with increasing mass). The intrinsic size of the radio emission associated with the BCGs peaks at 55 kpc, with a tail extending to 200 kpc. The radio power of the extended sources places them on the divide between FR I and FR II type sources, while sources compact in the radio tend to be somewhat less radio-luminous. We also detect an excess of radio sources associated with the cluster, instead of with the BCG itself, extending out to {approx} 1.4 kpc.

  18. Central Mass Profiles of the Nearby Cool-core Galaxy Clusters Hydra A and A478

    CERN Document Server

    Okabe, N; Tamura, T; Fujita, Y; Takizawa, M; Matsushita, K; Fukazawa, Y; Futamase, T; Kawaharada, M; Miyazaki, S; Mochizuki, Y; Nakazawa, K; Ohashi, T; Ota, N; Sasaki, T; Sato, K; Tam, S I

    2015-01-01

    We perform a weak-lensing study of the nearby cool-core galaxy clusters, Hydra A ($z=0.0538$) and A478 ($z=0.0881$), of which brightest cluster galaxies (BCGs) host powerful activities of active galactic nuclei (AGNs). For each cluster, the observed tangential shear profile is well described either by a single Navarro--Frenk--White model or a two-component model including the BCG as an unresolved point mass. For A478, we determine the BCG and its host-halo masses from a joint fit to weak-lensing and stellar photometry measurements. We find that the choice of initial mass functions (IMFs) can introduce a factor of two uncertainty in the BCG mass, whereas the BCG host halo mass is well constrained by data. We perform a joint analysis of weak-lensing and stellar kinematics data available for the Hydra A cluster, which allows us to constrain the central mass profile without assuming specific IMFs.We find that the central mass profile ($r<300$ kpc) determined from the joint analysis is in excellent agreement wi...

  19. Looking Wider and Further: The Evolution of Galaxies Inside Galaxy Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yuanyuan [Univ. of Michigan, Ann Arbor, MI (United States)

    2016-01-01

    Galaxy clusters are rare objects in the universe, but on-going wide field optical surveys are identifying many thousands of them to redshift 1.0 and beyond. Using early data from the Dark Energy Survey (DES) and publicly released data from the Sloan Digital Sky Survey (SDSS), this dissertation explores the evolution of cluster galaxies in the redshift range from 0 to 1.0. As it is common for deep wide field sky surveys like DES to struggle with galaxy detection efficiency at cluster core, the first component of this dissertation describes an efficient package that helps resolving the issue. The second part focuses on the formation of cluster galaxies. The study quantifies the growth of cluster bright central galaxies (BCGs), and argues for the importance of merging and intra-cluster light production during BCG evolution. An analysis of cluster red sequence galaxy luminosity function is also performed, demonstrating that the abundance of these galaxies is mildly dependent on cluster mass and redshift. The last component of the dissertation characterizes the properties of galaxy filaments to help understanding cluster environments

  20. Hα star formation rates of z > 1 galaxy clusters in the IRAC shallow cluster survey

    International Nuclear Information System (INIS)

    We present Hubble Space Telescope near-IR spectroscopy for 18 galaxy clusters at 1.0 Cluster Survey. We use Wide Field Camera 3 grism data to spectroscopically identify Hα emitters in both the cores of galaxy clusters as well as in field galaxies. We find a large cluster-to-cluster scatter in the star formation rates within a projected radius of 500 kpc, and many of our clusters (∼60%) have significant levels of star formation within a projected radius of 200 kpc. A stacking analysis reveals that dust reddening in these star-forming galaxies is positively correlated with stellar mass and may be higher in the field than the cluster at a fixed stellar mass. This may indicate a lower amount of gas in star-forming cluster galaxies than in the field population. Also, Hα equivalent widths of star-forming galaxies in the cluster environment are still suppressed below the level of the field. This suppression is most significant for lower mass galaxies (log M * < 10.0 M ☉). We therefore conclude that environmental effects are still important at 1.0 galaxies in galaxy clusters with log M * ≲ 10.0 M ☉.

  1. Quasar-Galaxy Clustering through Projected Galaxy Counts at z=0.6-1.2

    OpenAIRE

    Zhang, Shao-hua; Wang, Ting-Gui; Wang, Hui-Yuan; Zhou, Hongyan

    2013-01-01

    We investigate the spatial clustering of galaxies around quasars at redshifts from 0.6 to 1.2 using the photometric data from Sloan Digital Sky Survey (SDSS) Stripe 82. The quasar and galaxy cross-correlation functions are measured through the projected galaxy number density n(r_p) on scales $0.05

  2. Clusters of galaxies: a fundamental pillar of cosmology

    OpenAIRE

    Castillo-Morales, A.; Schindler, S.

    2003-01-01

    Clusters of galaxies are used in a variety of ways to do cosmology. Some of them are presented here. Their X-ray emitting gas allows us to determine the baryon fraction, dark matter distribution and the matter density $\\Omega_{m}$ of the universe. Another interesting component is relativistic particles whose radio emission provide the measure of the magnetic fields ($\\approx \\mu G$) in the intra-cluster medium (ICM). The observation of distant clusters of galaxies is also important for cosmol...

  3. An IceCube Search for Dark Matter Annihilation in nearby Galaxies and Galaxy Clusters

    CERN Document Server

    Aartsen, M G; Abdou, Y; Ackermann, M; Adams, J; Aguilar, J A; Ahlers, M; Altmann, D; Auffenberg, J; Bai, X; Baker, M; Barwick, S W; Baum, V; Bay, R; Beatty, J J; Bechet, S; Tjus, J Becker; Becker, K -H; Benabderrahmane, M L; BenZvi, S; Berghaus, P; Berley, D; Bernardini, E; Bernhard, A; Bertrand, D; Besson, D Z; Binder, G; Bindig, D; Bissok, M; Blaufuss, E; Blumenthal, J; Boersma, D J; Bohaichuk, S; Bohm, C; Bose, D; Böser, S; Botner, O; Brayeur, L; Bretz, H -P; Brown, A M; Bruijn, R; Brunner, J; Carson, M; Casey, J; Casier, M; Chirkin, D; Christov, A; Christy, B; Clark, K; Clevermann, F; Coenders, S; Cohen, S; Cowen, D F; Silva, A H Cruz; Danninger, M; Daughhetee, J; Davis, J C; Day, M; De Clercq, C; De Ridder, S; Desiati, P; de Vries, K D; de With, M; DeYoung, T; D'\\iaz-Vélez, J C; Dunkman, M; Eagan, R; Eberhardt, B; Eisch, J; Ellsworth, R W; Euler, S; Evenson, P A; Fadiran, O; Fazely, A R; Fedynitch, A; Feintzeig, J; Feusels, T; Filimonov, K; Finley, C; Fischer-Wasels, T; Flis, S; Franckowiak, A; Frantzen, K; Fuchs, T; Gaisser, T K; Gallagher, J; Gerhardt, L; Gladstone, L; Glüsenkamp, T; Goldschmidt, A; Golup, G; Gonzalez, J G; Goodman, J A; Góra, D; Grandmont, D T; Grant, D; Groß, A; Ha, C; Ismail, A Haj; Hallen, P; Hallgren, A; Halzen, F; Hanson, K; Heereman, D; Heinen, D; Helbing, K; Hellauer, R; Hickford, S; Hill, G C; Hoffman, K D; Hoffmann, R; Homeier, A; Hoshina, K; Huelsnitz, W; Hulth, P O; Hultqvist, K; Hussain, S; Ishihara, A; Jacobi, E; Jacobsen, J; Jagielski, K; Japaridze, G S; Jero, K; Jlelati, O; Kaminsky, B; Kappes, A; Karg, T; Karle, A; Kelley, J L; Kiryluk, J; Kläs, J; Klein, S R; Köhne, J -H; Kohnen, G; Kolanosk, H; Köpke, L; Kopper, C; Kopper, S; Koskinen, D J; Kowalski, M; Krasberg, M; Krings, K; Kroll, G; Kunnen, J; Kurahashi, N; Kuwabara, T; Labare, M; Landsman, H; Larson, M J; Lesiak-Bzdak, M; Leuermann, M; Leute, J; Lünemann, J; Macías, O; Madsen, J; Maggi, G; Maruyama, R; Mase, K; Matis, H S; McNally, F; Meagher, K; Merck, M; Meures, T; Miarecki, S; Middell, E; Milke, N; Miller, J; Mohrmann, L; Montaruli, T; Morse, R; Nahnhauer, R; Naumann, U; Niederhausen, H; Nowicki, S C; Nygren, D R; Obertacke, A; Odrowski, S; Olivas, A; Omairat, A; O'Murchadha, A; Paul, L; Pepper, J A; Heros, C Pérez de los; Pfendner, C; Pieloth, D; Pinat, E; Posselt, J; Price, P B; Przybylski, G T; Rädel, L; Rameez, M; Rawlins, K; Redl, P; Reimann, R; Resconi, E; Rhode, W; Ribordy, M; Richman, M; Riedel, B; Rodrigues, J P; Rott, C; Ruhe, T; Ruzybayev, B; Ryckbosch, D; Saba, S M; Salameh, T; Sander, H -G; Santander, M; Sarkar, S; Schatto, K; Scheriau, F; Schmidt, T; Schmitz, M; Schoenen, S; Schöneberg, S; Schönwald, A; Schukraft, A; Schulte, L; Schulz, O; Seckel, D; Sestayo, Y; Seunarine, S; Shanidze, R; Sheremata, C; Smith, M W E; Soldin, D; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Stasik, A; Stezelberger, T; Stokstad, R G; Stößl, A; Strahler, E A; Ström, R; Sullivan, G W; Taavola, H; Taboada, I; Tamburro, A; Tepe, A; Ter-Antonyan, S; Tešić, G; Tilav, S; Toale, P A; Toscano, S; Unger, E; Usner, M; Vallecorsa, S; van Eijndhoven, N; Van Overloop, A; van Santen, J; Vehring, M; Voge1, M; Vraeghe, M; Walck, C; Waldenmaier, T; Wallraff, M; Weaver, Ch; Wellons, M; Wendt, C; Westerhoff, S; Whitehorn, N; Wiebe, K; Wiebusch, C H; Williams, D R; Wissing, H; Wolf, M; Wood, T R; Woschnagg, K; Xu, D L; Xu, X W; Yanez, J P; Yodh, G; Yoshida, S; Zarzhitsky, P; Ziemann, J; Zierke, S; Zoll, M

    2013-01-01

    We present the results of a first search for self-annihilating dark matter in nearby galaxies and galaxy clusters using a sample of high energy neutrinos acquired in 339.8 days of livetime during 2009/10 with the IceCube neutrino observatory in its 59-string configuration. The targets of interest include the Virgo and Coma galaxy clusters, the Andromeda galaxy and several dwarf galaxies. We obtain upper limits on the cross section as function of the WIMP mass between 300 GeV and 100 TeV for the annihilation into b bbar, W+W-, \\tau+\\tau-, \\mu+\\mu- and \

  4. The accretion of galaxies into groups and clusters

    CERN Document Server

    McGee, Sean L; Bower, Richard G; Font, Andreea S; McCarthy, Ian G

    2009-01-01

    We use the galaxy stellar mass and halo merger tree information from the semi-analytic model galaxy catalogue of Font et al. (2009) to examine the accretion of galaxies into a large sample of groups and clusters, covering a wide range in halo mass (10E12.9 to 10E15.3 Msun/h), and selected from each of four redshift epochs (z=0, 0.5, 1.0 and 1.5). We find that clusters at all examined redshifts have accreted a significant fraction of their final galaxy populations through galaxy groups. A 10E14.5 Msun/h mass cluster at z=0 has, on average, accreted ~ 40% of its galaxies (Mstellar > 10E9 Msun/h) from halos with masses greater than 10E13 Msun/h. Further, the galaxies which are accreted through groups are more massive, on average, than galaxies accreted through smaller halos or from the field population. We find that at a given epoch, the fraction of galaxies accreted from isolated environments is independent of the final cluster or group mass. In contrast, we find that observing a cluster of the same halo mass a...

  5. Probing Turbulence in the Coma Galaxy Cluster

    CERN Document Server

    Schücker, P; Miniati, F; Böhringer, H; Briel, U G

    2004-01-01

    Spatially-resolved gas pressure maps of the Coma galaxy cluster are obtained from a mosaic of XMM-Newton observations in the scale range between a resolution of 20 kpc and an extent of 2.8 Mpc. A Fourier analysis of the data reveals the presence of a scale-invariant pressure fluctuation spectrum in the range between 40 and 90 kpc and is found to be well described by a projected Kolmogorov/Oboukhov-type turbulence spectrum. Deprojection and integration of the spectrum yields the lower limit of $\\sim 10$ percent of the total intracluster medium pressure in turbulent form. The results also provide observational constraints on the viscosity of the gas.

  6. Probing turbulence in the Coma galaxy cluster

    Science.gov (United States)

    Schuecker, P.; Finoguenov, A.; Miniati, F.; Böhringer, H.; Briel, U. G.

    2004-11-01

    Spatially-resolved gas pressure maps of the Coma galaxy cluster are obtained from a mosaic of XMM-Newton observations in the scale range between a resolution of 20 kpc and an extent of 2.8 Mpc. A Fourier analysis of the data reveals the presence of a scale-invariant pressure fluctuation spectrum in the range between 40 and 90 kpc and is found to be well described by a projected Kolmogorov/Oboukhov-type turbulence spectrum. Deprojection and integration of the spectrum yields the lower limit of ˜ 10 percent of the total intracluster medium pressure in turbulent form. The results also provide observational constraints on the viscosity of the gas. Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).

  7. Simulating nonthermal radiation from cluster radio galaxies.

    Energy Technology Data Exchange (ETDEWEB)

    Tregillis, I. L. (Ian L.); Jones, T. W. (Thomas Walter); Ryu, Dongsu

    2004-01-01

    We present results from an extensive synthetic observation analysis of numerically-simulated radio galaxy (RG) jets. This analysis is based on the first three-dimensional simulations to treat cosmic ray acceleration and transport self-consistently within a magnetohydrodynamical calculation. We use standard observational techniques to calculate both minimum-energy and inverse-Compton field values for our simulated objects. The latter technique provides meaningful information about the field. Minimum-energy calculations retrieve reasonable field estimates in regions physically close to the minimum-energy partitioning, though the technique is highly susceptible to deviations from the underlying assumptions. We also study the reliability of published rotation measure analysis techniques. We find that gradient alignment statistics accurately reflect the physical situation, and can uncover otherwise hidden information about the source. Furthermore, correlations between rotation measure (RM) and position angle (PA) can be significant even when the RM is completely dominated by an external cluster medium.

  8. The relation between velocity dispersion and central galaxy density in clusters of galaxies

    Science.gov (United States)

    Bahcall, N. A.

    1981-01-01

    A correlation between cluster velocity dispersion and average central galaxy density is reported. The correlation covers the range from rich clusters to small groups of galaxies, or, in terms of velocity dispersion, from v sub r approximately 1500 to approximately 100 km/s. This result is useful for estimating unknown velocity dispersions in clusters with the aid of the relatively easily determined 0.5 Mpc central galaxy density parameter. When combined with the virial theorem, the above relation also suggests that the mass-to-light ratio of galaxy systems increases with the system's velocity dispersion.

  9. The local effect of Dark Energy in galaxy clusters

    CERN Document Server

    Donnari, Martina; Arca-Sedda, Manuel

    2016-01-01

    Recently, observational data and high precision mapping of the local velocity field of Local Group and Virgo cluster have revealed a linear velocity-distance relation of the outermost galaxies, properly referred to as Local Hubble Flow. By means of direct N-body method, we performed several simulations in which a galaxy cluster undergoes the action of the Dark Energy force and of the gravitational one induced by the gas. We reproduced the so-called Hubble diagrams, to highlight the outflow of the galaxies lying in the external region of the cluster. Our preliminary results suggest that the observed outflow of galaxies is likely due to the local effect of Dark Energy. Furthermore, the accuracy of the N-body method used, allows us to follow the merging process among some galaxies with the aim to reproduce the formation of a single compact object in the centre of the cluster.

  10. THE ACCRETION OF DWARF GALAXIES AND THEIR GLOBULAR CLUSTER SYSTEMS

    International Nuclear Information System (INIS)

    The question of where the low-metallicity globular clusters in early-type galaxies came from has profound implications for the formation of those galaxies. Our work supports the idea that the metal-poor globular cluster systems of giant early-type galaxies formed in dwarf galaxies that have been subsumed by the giants. To support this hypothesis, two linear relations, one involving globular cluster metallicity versus host galaxy luminosity and one involving metallicity versus velocity dispersion were studied. Tentatively, these relations show that the bright ellipticals do not obey the same trend as the dwarfs, suggesting that the low-metallicity globular clusters did not form within their parent bright ellipticals.

  11. Evidence for steep luminosity functions in clusters of galaxies

    CERN Document Server

    De Propris, R; Harris, W E; McClure, R D; De Propris, R; Pritchet, C J; Harris, W E; McClure, R D

    1995-01-01

    Luminosity Functions have been obtained for very faint dwarf galaxies in the cores of four rich clusters of galaxies (Abell 2052, 2107, 2199 and 2666). It is found that the luminosity function of dwarf galaxies rises very steeply in these clusters, with a power-law slope of \\alpha -2.2 (down to absolute limiting magnitudes M_I = -13 and M_B = -11 for H_0 = 75 km/s/Mpc). A steepening of the luminosity function at faint magnitudes may in fact be a common feature of both cluster and field populations. Such a result may explain the observed excess counts of faint, intermediate redshift galaxies in the Universe, without resorting to more exotic phenomena. An alternate explanation is that star formation in dwarf galaxies is less affected by gas loss in the richest clusters, because of the dense, hot intracluster medium found in such environments.

  12. Spectacular tails of ionised gas in the Virgo cluster galaxy NGC 4569

    CERN Document Server

    Boselli, A; Fossati, M; Boissier, S; Bomans, D; Consolandi, G; Anselmi, G; Cortese, L; Cote, P; Durrell, P; Ferrarese, L; Fumagalli, M; Gavazzi, G; Gwyn, S; Hensler, G; Sun, M; Toloba, E

    2016-01-01

    We obtained using MegaCam at the CFHT a deep narrow band Halpha+[NII] wide field image of NGC 4569, the brightest late-type galaxy in the Virgo cluster. The image reveals the presence of long tails of diffuse ionised gas without any associated stellar component extending from the disc of the galaxy up to ~ 80 kpc (projected distance) with a typical surface brightness of a few 10^-18 erg s-1 cm-2 arcsec-2. These features provide direct evidence that NGC 4569 is undergoing a ram presure stripping event. The image also shows a prominent 8 kpc spur of ionised gas associated to the nucleus that spectroscopic data identify as an outflow. With some assumptions on the 3D distribution of the gas, we use the Halpha surface brightness of these extended low surface brightness features to derive the density and the mass of the gas stripped during the interaction of the galaxy with the ICM. The comparison with ad-hoc chemo-spectrophotometric models of galaxy evolution indicates that the mass of the Halpha emitting gas in t...

  13. Star Clusters in Intermediate-Age Galaxy Merger Remnants

    Science.gov (United States)

    Miller, Bryan W.; Trancho, G.; Schweizer, F.

    2011-01-01

    Studies of globular cluster systems play a critical role in our understanding of galaxy formation. Star clusters are useful tracers of major star-formation events in galaxies since they are compact, relatively easy to detect, and have properties well described by simple-stellar-population models. Imaging with the Hubble Space Telescope has revealed that young compact star clusters are formed copiously during galaxy mergers, strengthening theories in which giant elliptical galaxies are formed through mergers of spirals. However, the formation and evolution of globular cluster systems is still not well understood. We should be able to observe how cluster systems evolve from the very young systems with power-law luminosity functions to old systems with log-normal luminosity functions like those observed in old elliptical galaxies. Finding intermediate-age cluster systems would constrain theories of cluster formation and destruction (evaporation, shocking, dynamical friction) as well as show the significance of merger events in the histories of galaxies. We present results of combining HST optical photometry with ground-based K-band photometry from NIRI and Flamingos-I on Gemini to study the star cluster systems of five intermediate-age merger remnants. The galaxies were chosen based on blue colors and fine structure such as shells and ripples that are indicative of past interactions. We find evidence for star clusters with ages consistent with the estimated merger ages. The properties of the star clusters systems and implications for galaxy and star cluster formation will be discussed. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada

  14. Galaxy populations in galaxy clusters selected by the Sunyaev-Zeldovich Effect

    OpenAIRE

    Zenteno, Alfredo

    2014-01-01

    We present a study of the galaxy populations in massive galaxy clusters selected by their Sunyaev–Zel’dovich Effect (SZE) signatures. Selection via the SZE is approximately mass- limited where the mass limit varies only slightly with redshift, making it an ideal selection method for studying the evolution of the galaxy content of clusters. We begin by introducing the SZE, the South Pole Telescope (SPT), and the larger research project in which this Thesis is embedded. We then present the core...

  15. Cold Fronts in Clusters of Galaxies: Observations and Modeling

    Science.gov (United States)

    Markevitch, Maxim

    2012-01-01

    Mergers of galaxy clusters -- some of the most energetic events in the Universe -- produce disturbances in hot intracluster medium, such as shocks and cold fronts, that can be used as tools to study the physics of galaxy clusters. Cold fronts may constrain viscosity and the structure and strength of the cluster magnetic fields. Combined with radio data, these observations also shed light on the production of ultrarelativistic particles that are known to coexist with the cluster thermal plasma. This talk will summarize the current X-ray observations of cluster mergers, as well as some recent radio data and high resolution hydrodynamic simulations.

  16. The Galaxy Cluster RBS380 Xray and Optical Analysis

    CERN Document Server

    Gil-Merino, R

    2002-01-01

    We present X-ray and optical observations of the z=0.52 galaxy cluster RBS380. This is the most distant cluster in the ROSAT Bright Source catalog. The cluster was observed with the CHANDRA satellite in September 2000. The optical observations were carried out with the NTT-SUSI2 camara in filters V and R in August and September 2001. The preliminary conclusions are that we see a very rich optical galaxy cluster but with a relative low X-ray luminosity. We also compare our results to other clusters with similar properties.

  17. LENSING NOISE IN MILLIMETER-WAVE GALAXY CLUSTER SURVEYS

    International Nuclear Information System (INIS)

    We study the effects of gravitational lensing by galaxy clusters of the background of dusty star-forming galaxies (DSFGs) and the cosmic microwave background (CMB), and examine the implications for Sunyaev-Zel'dovich-based (SZ) galaxy cluster surveys. At the locations of galaxy clusters, gravitational lensing modifies the probability distribution of the background flux of the DSFGs as well as the CMB. We find that, in the case of a single-frequency 150 GHz survey, lensing of DSFGs leads both to a slight increase (∼10%) in detected cluster number counts (due to a ∼50% increase in the variance of the DSFG background, and hence an increased Eddington bias) and a rare (occurring in ∼2% of clusters) 'filling-in' of SZ cluster signals by bright strongly lensed background sources. Lensing of the CMB leads to a ∼55% reduction in CMB power at the location of massive galaxy clusters in a spatially matched single-frequency filter, leading to a net decrease in detected cluster number counts. We find that the increase in DSFG power and decrease in CMB power due to lensing at cluster locations largely cancel, such that the net effect on cluster number counts for current SZ surveys is subdominant to Poisson errors

  18. Tidal Torquing of Elliptical Galaxies in Cluster Environments

    CERN Document Server

    Pereira, Maria J; 10.1088/0004-637X/721/2/939

    2010-01-01

    Observational studies of galaxy isophotal shapes have shown that galaxy orientations are anisotropic: a galaxy's long axis tends to be oriented toward the center of its host. This radial alignment is seen across a wide range of scales, from galaxies in massive clusters to small Milky Way type satellite systems. Recently, this effect has also been detected in dark matter simulations of cosmological structure, but the degree of alignment of dark matter substructures in these studies is significantly stronger than seen in observations. In this paper we attempt to reconcile these two results by performing high-resolution numerical experiments on N-body multi-component models of triaxial galaxies orbiting in an external analytical potential. The large number of particles employed allows us to probe deep into the inner structure of the galaxy: we show that the discrepancy between observed galaxies and simulated dark matter halos is a natural consequence of induced radial shape twisting in the galaxy by the external...

  19. Small-Scale Conformity of the Virgo Cluster Galaxies

    CERN Document Server

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

    2016-01-01

    We investigate the small-scale conformity in color between bright galaxies and their faint companions in the Virgo cluster. Cluster member galaxies are spectroscopically determined using the Extended Virgo Cluster Catalog (EVCC) and the Sloan Digital Sky Survey Data Release 12 (SDSS DR12). We find that the luminosity-weighted mean color of faint galaxies depends on the color of adjacent bright galaxy as well as on the cluster-scale environment (gravitational potential index). From this result for the entire area of the Virgo cluster, it is not distinguishable whether the small-scale conformity is genuine or is artificially produced due to cluster-scale variation of galaxy color. To disentangle this degeneracy, we divide the Virgo cluster area into three sub-areas so that the cluster-scale environmental dependence is minimized: A1 (central), A2 (intermediate) and A3 (outermost). We find conformity in color between bright galaxies and their faint companions (color-color slope significance S ~ 2.73 sigma and cor...

  20. Probing dark energy via galaxy cluster outskirts

    CERN Document Server

    Morandi, Andrea

    2016-01-01

    We present a Bayesian approach to combine $Planck$ data and the X-ray physical properties of the intracluster medium in the virialization region of a sample of 320 galaxy clusters ($0.056 3$ keV) observed with $Chandra$. We exploited the high-level of similarity of the emission measure in the cluster outskirts as cosmology proxy. The cosmological parameters are thus constrained assuming that the emission measure profiles at different redshift are weakly self-similar, that is their shape is universal, explicitly allowing for temperature and redshift dependency of the gas fraction. This cosmological test, in combination with $Planck$+SNIa data, allows us to put a tight constraint on the dark energy models. For a constant-$w$ model, we have $w=-1.010\\pm0.030$ and $\\Omega_m=0.311\\pm0.014$, while for a time-evolving equation of state of dark energy $w(z)$ we have $\\Omega_m=0.308\\pm 0.017$, $w_0=-0.993\\pm0.046$ and $w_a=-0.123\\pm0.400$. Constraints on the cosmology are further improved by adding priors on the gas f...

  1. Hubble flow around Fornax cluster of galaxies

    CERN Document Server

    Nasonova, Olga G; Karachentsev, Igor D

    2011-01-01

    Aims. This work aims to provide a new mass estimate for the Fornax cluster and the Fornax-Eridanus complex, avoiding methods like the virial or fits of X-ray emission profile, which assume that the system is in equilibrium, probably not the case of Fornax, still in process of formation. Methods. Our mass estimate is based on the determination of the zero-velocity surface which, in the context of the spherical infall model permits an evaluation of the total mass inside such a surface. The zero-velocity surface radius R0 was estimated either by a running median procedure or by fitting the data to the velocity field expected from the spherical model, including effects of the cosmological constant. The velocity field in a region within 20 Mpc of the Fornax center was mapped using a list of 109 galaxies whose distances have an average accuracy of 0.31 mag in their distance modulus. Results. Our analysis indicates that the mass of the Fornax cluster itself inside a radius of [2.62-5.18] Mpc is [0.40-3.32] \\times 10...

  2. Richness-based masses of rich and famous galaxy clusters

    Science.gov (United States)

    Andreon, S.

    2016-03-01

    We present a catalog of galaxy cluster masses derived by exploiting the tight correlation between mass and richness, i.e., a properly computed number of bright cluster galaxies. The richness definition adopted in this work is properly calibrated, shows a small scatter with mass, and has a known evolution, which means that we can estimate accurate (0.16 dex) masses more precisely than by adopting any other richness estimates or X-ray or SZ-based proxies based on survey data. We measured a few hundred galaxy clusters at 0.05 html

  3. Richness-based masses of rich and famous galaxy clusters

    Science.gov (United States)

    Andreon, S.

    2016-03-01

    We present a catalog of galaxy cluster masses derived by exploiting the tight correlation between mass and richness, i.e., a properly computed number of bright cluster galaxies. The richness definition adopted in this work is properly calibrated, shows a small scatter with mass, and has a known evolution, which means that we can estimate accurate (0.16 dex) masses more precisely than by adopting any other richness estimates or X-ray or SZ-based proxies based on survey data. We measured a few hundred galaxy clusters at 0.05 URL http://www.brera.mi.astro.it/~andreon/famous.html

  4. Luminosity Function of the Cluster of Galaxies Abell 566

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We investigate the Luminosity Function (LF) of the cluster of galaxies Abell 566. The photometric data of 15 intermediate-bands are obtained from the Beijing- Arizona-Taiwan-Connecticut (BATC) photometric sky survey. For each of the 15 wavebands, the LF of cluster galaxies is well modelled by the Schechter function, with characteristic luminosities from -18.0 to -21.9 magnitude, from the a- to the p-band. Morphological dependence of the LF is investigated by separating the cluster members into 'red' and 'blue' subsamples. It is clear that late type galaxies have a steeper shape of LF than the early type galaxies. We also divided the sample galaxies by their local environment. It was found that galaxies in the sparser region have steeper shape of LF than galaxies in the denser region. Combining the results of morphological and environmental dependence of LFs, we show that Abell 566 is a well relaxed cluster with positive evidence of galaxy interaction and merger, and excess number of bright early type galaxies located in its denser region.

  5. Dynamical Mass Measurements of Contaminated Galaxy Clusters Using Machine Learning

    Science.gov (United States)

    Ntampaka, Michelle; Trac, Hy; Sutherland, Dougal; Fromenteau, Sebastien; Poczos, Barnabas; Schneider, Jeff

    2016-01-01

    Galaxy clusters are a rich source of information for examining fundamental astrophysical processes and cosmological parameters, however, employing clusters as cosmological probes requires accurate mass measurements derived from cluster observables. We study dynamical mass measurements of galaxy clusters contaminated by interlopers, and show that a modern machine learning (ML) algorithm can predict masses by better than a factor of two compared to a standard scaling relation approach. We create a mock catalog from Multidark's publicly-available N-body MDPL1 simulation where a simple cylindrical cut around the cluster center allows interlopers to contaminate the clusters. In the standard approach, we use a power law scaling relation to infer cluster mass from galaxy line of sight (LOS) velocity dispersion. The presence of interlopers in the catalog produces a wide, flat fractional mass error distribution, with width = 2.13. We employ the Support Distribution Machine (SDM) class of algorithms to learn from distributions of data to predict single values. Applied to distributions of galaxy observables such as LOS velocity and projected distance from the cluster center, SDM yields better than a factor-of-two improvement (width = 0.67). Remarkably, SDM applied to contaminated clusters is better able to recover masses than even a scaling relation approach applied to uncontaminated clusters. We show that the SDM method more accurately reproduces the cluster mass function, making it a valuable tool for employing cluster observations to evaluate cosmological models.

  6. Radio emission at the centre of the galaxy cluster Abell 3560: evidence for core sloshing?

    CERN Document Server

    Venturi, T; Bardelli, S; Giacintucci, S; Dallacasa, D; Cornacchia, M; Kantharia, N

    2013-01-01

    Previous radio observations of the galaxy cluster A3560 in the Shapley Concentration showed complex radio emission associated with the brightest cluster member.To understand its origin we observed it with the GMRT, the VLA and ATCA at 240 and 610 MHz, 1.28,1.4, 2.3,4.8 and 8.4 GHz, and performed a detailed morphological and spectral study of the radio emission associated with the BCG. We also observed the cluster with XMM-Newton and Chandra to derive the properties of the ICM. The radio emission of the N-E nucleus of the dumb-bell BCG shows an active radio galaxy, plus aged diffuse emission, which is not refurbished at present. Our Chandra data show that the radio active nucleus of the BCG has extended X-ray emission, which we classify as a low-luminosity corona. A residual image of the XMM-Newton brightness shows the presence of a spiral-like feature, which we interpret as the signature of gas sloshing. The presence of a subgroup is clear in the surface brightness residual map, and in the XMM-Newton temperat...

  7. Probing dark energy via galaxy cluster outskirts

    Science.gov (United States)

    Morandi, Andrea; Sun, Ming

    2016-04-01

    We present a Bayesian approach to combine Planck data and the X-ray physical properties of the intracluster medium in the virialization region of a sample of 320 galaxy clusters (0.056 emission measure in the cluster outskirts as cosmology proxy. The cosmological parameters are thus constrained assuming that the emission measure profiles at different redshift are weakly self-similar, that is their shape is universal, explicitly allowing for temperature and redshift dependence of the gas fraction. This cosmological test, in combination with Planck+SNIa data, allows us to put a tight constraint on the dark energy models. For a constant-w model, we have w = -1.010 ± 0.030 and Ωm = 0.311 ± 0.014, while for a time-evolving equation of state of dark energy w(z) we have Ωm = 0.308 ± 0.017, w0 = -0.993 ± 0.046 and wa = -0.123 ± 0.400. Constraints on the cosmology are further improved by adding priors on the gas fraction evolution from hydrodynamic simulations. Current data favour the cosmological constant with w ≡ -1, with no evidence for dynamic dark energy. We checked that our method is robust towards different sources of systematics, including background modelling, outlier measurements, selection effects, inhomogeneities of the gas distribution and cosmic filaments. We also provided for the first time constraints on which definition of cluster boundary radius is more tenable, namely based on a fixed overdensity with respect to the critical density of the Universe. This novel cosmological test has the capacity to provide a generational leap forward in our understanding of the equation of state of dark energy.

  8. The Brightest Galaxies at Cosmic Dawn: Securing the Largest Samples of z=9-11 galaxies for JWST by leveraging the HST archive with Spitzer/IRAC.

    Science.gov (United States)

    Bouwens, Rychard; Trenti, Michele; Calvi, Valentina; Bernard, Stephanie; Labbe, Ivo; Oesch, Pascal; Coe, Dan; Holwerda, Benne; Bradley, Larry; Mason, Charlotte; Schmidt, Kasper; Illingworth, Garth

    2015-10-01

    Hubble's WFC3 has been a game changer for studying early galaxy formation in the first 700 Myr after the Big Bang. Reliable samples of sources up to z~10, which can be discovered only from space, are now constraining the evolution of the galaxy luminosity function into the epoch of reionization. Despite these efforts, the size of the highest redshift galaxy samples (z >9 and especially z > 10) is still very small, particularly at high luminosities (L > L*). To deliver transformational results, much larger numbers of bright z > 9 galaxies are needed both to map out the bright end of the luminosity/mass function and for spectroscopic follow-up (with JWST and otherwise). One especially efficient way of expanding current samples is (1) to leverage the huge amounts of pure-parallel data available with HST to identify large numbers of candidate z ~ 9 - 11 galaxies and (2) to follow up each candidate with shallow Spitzer/IRAC observations to distinguish the bona- fide z ~ 9 - 11 galaxies from z ~ 2 old, dusty galaxies. For this program we are requesting shallow Spitzer/IRAC follow-up of 20 candidate z ~ 9 - 11 galaxies we have identified from 130 WFC3/IR pointings obtained from more than 4 separate HST programs with no existing IRAC coverage. Based on our previous CANDELS/GOODS searches, we expect to confirm 5 to 10 sources as L > L* galaxies at z >= 9. Our results will be used to constrain the bright end of the LF at z >= 9, to provide targets for Keck spectroscopy to constrain the ionization state of the z > 8 universe, and to furnish JWST with bright targets for spectroscopic follow-up studies.

  9. Gravitational Redshift of Galaxies in Clusters from the Sloan Digital Sky Survey and the Baryon Oscillation Spectroscopic Survey

    Science.gov (United States)

    Sadeh, Iftach; Feng, Low Lerh; Lahav, Ofer

    2015-02-01

    The gravitational redshift effect allows one to directly probe the gravitational potential in clusters of galaxies. Following up on Wojtak et al. [Nature (London) 477, 567 (2011)], we present a new measurement. We take advantage of new data from the tenth data release of the Sloan Digital Sky Survey and the Baryon Oscillation Spectroscopic Survey. We compare the spectroscopic redshift of the brightest cluster galaxies (BCGs) with that of galaxies at the outskirts of clusters, using a sample with an average cluster mass of 1014 M⊙ . We find that these galaxies have an average relative redshift of -11 km /s compared with that of BCGs, with a standard deviation of +7 and -5 km /s . Our measurement is consistent with that of Wojtak et al. [Nature (London) 477, 567 (2011)]. However, our derived standard deviation is larger, as we take into account various systematic effects, beyond the size of the data set. The result is in good agreement with the predictions from general relativity.

  10. Gravitational redshift of galaxies in clusters from the sloan digital sky survey and the Baryon Oscillation spectroscopic survey.

    Science.gov (United States)

    Sadeh, Iftach; Feng, Low Lerh; Lahav, Ofer

    2015-02-20

    The gravitational redshift effect allows one to directly probe the gravitational potential in clusters of galaxies. Following up on Wojtak et al. [Nature (London) 477, 567 (2011)], we present a new measurement. We take advantage of new data from the tenth data release of the Sloan Digital Sky Survey and the Baryon Oscillation Spectroscopic Survey. We compare the spectroscopic redshift of the brightest cluster galaxies (BCGs) with that of galaxies at the outskirts of clusters, using a sample with an average cluster mass of 1014M⊙. We find that these galaxies have an average relative redshift of -11  km/s compared with that of BCGs, with a standard deviation of +7 and -5  km/s. Our measurement is consistent with that of Wojtak et al. [Nature (London) 477, 567 (2011)]. However, our derived standard deviation is larger, as we take into account various systematic effects, beyond the size of the data set. The result is in good agreement with the predictions from general relativity. PMID:25763947

  11. The Colours of Satellite Galaxies in Groups and Clusters

    CERN Document Server

    Font, Andreea S; McCarthy, Ian G; Benson, Andrew J; Frenk, Carlos S; Helly, John C; Lacey, Cedric G; Baugh, Carlton M; Cole, Shaun

    2008-01-01

    Current models of galaxy formation predict satellite galaxies in groups and clusters that are redder than observed. We investigate the effect on the colours of satellite galaxies produced by the ram pressure stripping of their hot gaseous atmospheres as the satellites orbit within their parent halo. We incorporate a model of the stripping process based on detailed hydrodynamic simulations within the Durham semi-analytic model of galaxy formation. The simulations show that the environment in groups and clusters is less aggressive than previously assumed. The main uncertainty in the model is the treatment of gas expelled by supernovae. With reasonable assumptions for the stripping of this material, we find that satellite galaxies are able to retain a significant fraction of their hot gas for several Gigayears, thereby replenishing their reservoirs of cold, star forming gas and remaining blue for a relatively long period of time. A bimodal distribution of galaxy colours, similar to that observed in SDSS data, is...

  12. On the orbital and internal evolution of cluster galaxies

    CERN Document Server

    Iannuzzi, Francesca

    2012-01-01

    Galaxies inhabiting a cluster environment experience significant evolution in their orbital motions throughout time; this is accompanied by changes in the anisotropy parameter, measuring the relative importance of radial and tangential motions for a given class of objects. Along with orbital changes, galaxies in clusters are well known to undergo severe alteration in their hot/cold gas content and star formation properties. Understanding the link between the changes in the internal properties of galaxies and their orbital motion is of crucial importance in the study of galaxy evolution, as it could unveil the primary mechanism responsible for its environmental dependence. Do the changes in the internal properties happen in parallel with those in the orbital motion? Or are the orbital features at the time of infall what determines the fate of the member galaxies? Alternatively: are the properties of galaxies at a given time related to the coeval orbital anisotropy or are they better related to the anisotropy a...

  13. 60 micron luminosity evolution of rich clusters of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, D.M.; Rieke, G.H. (Steward Observatory, Tucson, AZ (USA))

    1990-10-01

    The average 60-micron flux has been determined for a collection of optically selected galaxy clusters at redshifts ranging from 0.30 to 0.92. The result, 26 mJy per cluster, represents the faintest flux determination known of using the IRAS data base. The flux from this set of clusters has been compared to the 60-micron flux from a sample of nearby galaxy clusters. It is found that the far-infrared luminosity evolution in cluster galaxies can be no more than a factor of 1.7 from z = 0.4 to the present epoch. This upper limit is close to the evolution predicted for simple aging of the stellar populations. Additional processes such as mergers, cannibalism, or enhanced rates of starbursts appear to occur at a low enough level that they have little influence on the far-infrared emission from clusters over this redshift range. 38 refs.

  14. Structures and components in galaxy clusters: observations and models

    CERN Document Server

    Bykov, A M; Ferrari, C; Forman, W R; Kaastra, J S; Klein, U; Markevitch, M; de Plaa, J

    2015-01-01

    Clusters of galaxies are the largest gravitationally bounded structures in the Universe dominated by dark matter. We review the observational appearance and physical models of plasma structures in clusters of galaxies. Bubbles of relativistic plasma which are inflated by supermassive black holes of AGNs, cooling and heating of the gas, large scale plasma shocks, cold fronts, non-thermal halos and relics are observed in clusters. These constituents are reflecting both the formation history and the dynamical properties of clusters of galaxies. We discuss X-ray spectroscopy as a tool to study the metal enrichment in clusters and fine spectroscopy of Fe X-ray lines as a powerful diagnostics of both the turbulent plasma motions and the energetics of the non-thermal electron populations. The knowledge of the complex dynamical and feedback processes is necessary to understand the energy and matter balance as well as to constrain the role of the non-thermal components of clusters.

  15. Cosmic Chronometers: Constraining the Equation of State of Dark Energy. II. A Spectroscopic Catalog of Red Galaxies in Galaxy Clusters

    OpenAIRE

    Stern, Daniel; Jimenez, Raul; Verde, Licia; Stanford, S. Adam; Kamionkowski, Marc

    2009-01-01

    We present a spectroscopic catalog of (mostly) red galaxies in 24 galaxy clusters in the redshift range 0.17 < z < 0.92 obtained with the LRIS instrument on the Keck I telescope. Here we describe the observations and the galaxy spectra, including the discovery of three cD galaxies with LINER emission spectra, and the spectroscopic discovery of four new galaxy-galaxy lenses in cluster environments.

  16. The HST/ACS Coma Cluster Survey IV. Intergalactic Globular Clusters and the Massive Globular Cluster System at the Core of the Coma Galaxy Cluster

    OpenAIRE

    Peng, Eric W.; Ferguson, Henry C.; Goudfrooij, Paul; Hammer, Derek; Lucey, John R.; Marzke, ; Ronald O.; Puzia, Thomas H.; Carter, David; Balcells, Marc; Bridges, Terry; Chiboucas, Kristin; del Burgo, Carlos; Graham, Alister W.; Guzman, Rafael; Hudson, Michael J.

    2011-01-01

    Intracluster stellar populations are a natural result of tidal interactions in galaxy clusters. Measuring these populations is difficult, but important for understanding the assembly of the most massive galaxies. The Coma cluster is one of the nearest truly massive galaxy clusters, and is host to a correspondingly large system of globular clusters (GCs). We use imaging from the HST/ACS Coma Cluster Survey to present the first definitive detection of a large population of intracluster GCs (IGC...

  17. Kinematic and Structural Evolution of Field and Cluster Spiral Galaxies

    OpenAIRE

    Ziegler, Bodo L.; Kutdemir, Elif; Da Rocha, Cristiano; Böhm, Asmus; Peletier, Reynier F; Verdugo, Miguel

    2009-01-01

    To understand the processes that build up galaxies we investigate the stellar structure and gas kinematics of spiral and irregular galaxies out to redshift 1. We target 92 galaxies in four cluster (z = 0.3 & 0.5) fields to study the environmental influence. Their stellar masses derived from multiband VLT/FORS photometry are distributed around but mostly below the characteristic Schechter-fit mass. From HST/ACS images we determine morphologies and structural parameters like disk length, positi...

  18. Mapping stellar content to dark matter halos using galaxy clustering and galaxy-galaxy lensing in the SDSS DR7

    CERN Document Server

    Zu, Ying

    2015-01-01

    The mapping between the distributions of the observed galaxy stellar mass and the underlying dark matter halos provides the crucial link from theories of large-scale structure formation to interpreting the complex phenomena of galaxy formation and evolution. We develop a novel statistical method, based on the Halo Occupation Distribution model (HOD), to solve for this mapping by jointly fitting the galaxy clustering and the galaxy-galaxy lensing measured from the Sloan Digital Sky Survey (SDSS). The method, called the iHOD model, extracts maximum information from the survey by including ~80% more galaxies than the traditional HOD methods, and takes into account the incompleteness of the stellar mass samples in a statistically consistent manner. The derived stellar-to-halo mass relation not only explains the clustering and lensing of SDSS galaxies over almost four decades in stellar mass, but also successfully predicts the stellar mass functions observed in SDSS. Due to its capability of modelling significantl...

  19. Clues on galaxy and cluster formation from their scaling relations

    CERN Document Server

    Lanzoni, B; Cappi, A; Tormen, G; Zamorani, G

    2003-01-01

    By means of high-resolution N-body simulations in a LambdaCDM cosmology, we verify that scaling relations similar to those observed for nearby galaxy clusters are also defined by their dark matter hosts; the slopes, however, are not the same. We then show that the scaling relations of galaxy clusters can be explained as the result of the cosmological collapse of density fluctuations at the appropriate scales, plus a systematic trend of the M/L ratio with cluster mass. The empirical fact that the exponent of the Faber-Jackson relation of elliptical galaxies is significantly different (higher) than that of clusters, force us to conclude that the galaxy scaling laws might derive from the cosmological collapse of density fluctuations at the epoch when galactic scales became non-linear, plus modifications afterward due to early-time dissipative merging.

  20. Total mass biases in X-ray galaxy clusters

    CERN Document Server

    Piffaretti, Rocco

    2008-01-01

    The exploitation of clusters of galaxies as cosmological probes relies on accurate measurements of their total gravitating mass. X-ray observations provide a powerful means of probing the total mass distribution in galaxy clusters, but might be affected by observational biases and rely on simplistic assumptions originating from our limited understanding of the intracluster medium physics. This paper is aimed at elucidating the reliability of X-ray total mass estimates in clusters of galaxies by properly disentangling various biases of both observational and physical origin. We use N-body/SPH simulation of a large sample of ~100 galaxy clusters and investigate total mass biases by comparing the mass reconstructed adopting an observational-like approach with the true mass in the simulations. X-ray surface brightness and temperature profiles extracted from the simulations are fitted with different models and adopting different radial fitting ranges in order to investigate modeling and extrapolation biases. Diffe...

  1. Coexistence of galaxies and antigalaxies in a cluster

    International Nuclear Information System (INIS)

    It is proposed that the detection of annihilation gamma-rays coming from any region of contact between watter and antimalter would only be possible if a cluster contains both galaxies and antigalaxies

  2. Galaxy clusters as probes for cosmology and dark matter

    CERN Document Server

    Battistelli, Elia S; de Bernardis, Paolo; Kirillov, Alexander A; Neto, Gastao B Lima; Masi, Silvia; Norgaard-Nielsen, Hans U; Ostermann, Peter; Roman, Matthieu; Rosati, Piero; Rossetti, Mariachiara

    2016-01-01

    In recent years, significant progress has been made in building new galaxy clusters samples, at low and high redshifts, from wide-area surveys, particularly exploiting the Sunyaev--Zel'dovich (SZ) effect. A large effort is underway to identify and characterize these new systems with optical/NIR and X-ray facilities, thus opening new avenues to constraint cosmological models using structure growth and geometrical tests. A census of galaxy clusters sets constraints on reionization mechanisms and epochs, which need to be reconciled with recent limits on the reionization optical depth from cosmic microwave background (CMB) experiments. Future advances in SZ effect measurements will include the possibility to (unambiguously) measure directly the kinematic SZ effect, to build an even larger catalogue of galaxy clusters able to study the high redshift universe, and to make (spatially-)resolved galaxy cluster maps with even spectral capability to (spectrally-)resolve the relativistic corrections of the SZ effect.

  3. The Role of Environment in Shaping Galaxy Evolution at High Redshift: Insights from the SpARCS Cluster Survey

    Science.gov (United States)

    Wilson, Gillian

    2015-08-01

    Between z = 2 and z = 1, the main progenitors of present-day massive clusters undergo rapid collapse, and cluster members transform from active star-forming to quiescent galaxies. The SpARCS survey is one of the largest surveys designed to detect clusters of galaxies at z> 1, and has discovered hundreds of Spitzer IR-selected clusters.I will present results from GCLASS, a 25-night Gemini/GMOS spectroscopic follow-up survey of ten of the most massive SpARCS clusters at z~1, and explain what we are learning about quenching and stellar mass assembly of galaxies in these, the densest of environments, relative to the field population. I will explain how predictions and observations of the stellar mass growth of Brightest Cluster Galaxies, previously controversially divergent, are now coming into agreement, and discuss the evidence for the relative importance of mergers versus in-situ star formation in driving this stellar mass growth as a function of redshift.I will also present a sample of newly-confirmed clusters at z~2 for which we have HST spectroscopy and imaging, and have been targeting with Keck/MOSFIRE. I will conclude by discussing GOGREEN and DEEPDRILL, two new large surveys approved by Gemini & Spitzer, designed to study the effects of environment at lower stellar mass and at higher redshift, respectively. Collectively, these powerful new surveys are beginning to allow us to place constraints on the location and timescale of quenching and, in concert with both hydro-simulations and semi-analytic models, identify the complex role of environment in shaping galaxy evolution over cosmic time.

  4. The Ursa Major Cluster of galaxies .1. Cluster definition and photometric data

    NARCIS (Netherlands)

    Tully, RB; Verheijen, MAW; Pierce, MJ; Wainscoat, RJ

    1996-01-01

    The Ursa Major Cluster has received remarkably little attention, although it is as near as the Virgo Cluster and contains a comparable number of H I-rich galaxies. In this paper, criteria for group membership are discussed and data are presented for 79 galaxies identified with the group. Of these, a

  5. Multiaperture photoelectric photometry of galaxies in the Hydra I cluster

    International Nuclear Information System (INIS)

    Multi-aperture photoelectric UBV photometry is presented for 16 galaxies in the field of the Hydra I (= A 1060) cluster. Excellent agreement with previous published photometry is obtained. The application of standard galaxy magnitude growth curves to the present observations is briefly discussed. (author)

  6. GALAXY CLUSTERING TOPOLOGY IN THE SLOAN DIGITAL SKY SURVEY MAIN GALAXY SAMPLE: A TEST FOR GALAXY FORMATION MODELS

    International Nuclear Information System (INIS)

    We measure the topology of the main galaxy distribution using the Seventh Data Release of the Sloan Digital Sky Survey, examining the dependence of galaxy clustering topology on galaxy properties. The observational results are used to test galaxy formation models. A volume-limited sample defined by Mr -1 Mpc smoothing scale, with 4.8% uncertainty including all systematics and cosmic variance. The clustering topology over the smoothing length interval from 6 to 10 h -1 Mpc reveals a mild scale dependence for the shift (Δν) and void abundance (AV ) parameters of the genus curve. We find substantial bias in the topology of galaxy clustering with respect to the predicted topology of the matter distribution, which varies with luminosity, morphology, color, and the smoothing scale of the density field. The distribution of relatively brighter galaxies shows a greater prevalence of isolated clusters and more percolated voids. Even though early (late)-type galaxies show topology similar to that of red (blue) galaxies, the morphology dependence of topology is not identical to the color dependence. In particular, the void abundance parameter AV depends on morphology more strongly than on color. We test five galaxy assignment schemes applied to cosmological N-body simulations of a ΛCDM universe to generate mock galaxies: the halo-galaxy one-to-one correspondence model, the halo occupation distribution model, and three implementations of semi-analytic models (SAMs). None of the models reproduces all aspects of the observed clustering topology; the deviations vary from one model to another but include statistically significant discrepancies in the abundance of isolated voids or isolated clusters and the amplitude and overall shift of the genus curve. SAM predictions of the topology color dependence are usually correct in sign but incorrect in magnitude. Our topology tests indicate that, in these models, voids should be emptier and more connected and the threshold for galaxy

  7. Radio emission in the Virgo cluster and in SO galaxies

    International Nuclear Information System (INIS)

    A survey of the radio continuum emission from the galaxies in the Virgo Cluster is presented. The sample of 274 galaxies in total contains a subsample of 188 galaxies complete down to magntiude msub(p) = 14. The observations consisted mostly of short (10 minutes) observations providing one-dimensional (East-West) strip distributions of the radio brightness at 1.4 GHz, with an East-West resolution of 23'' allowing separation of central sources from extended emission, and an r.m.s. noise level of 2 mJy. The radio emission of SO galaxies is examined. A sample of 145 SO galaxies is obtained by combining the Virgo cluster SO's with the nearby non-cluster SO's. The radio data, mainly from short observations, are used to derive the RLF. The radio emission in SO galaxies is at least three times weaker than that in ellipticals and spirals. Flat-spectrum compact nuclear sources are found in SO galaxies but they are at least 10 times weaker than in elliptical galaxies, which is attributed to the small mass of the bulges in SO's as compared to the mass of elliptical galaxies. The absence of steep-spectrum, extended central sources and of disk radio emission in SO's is attributed to their low neutral hydrogen content. (Auth.)

  8. Properties of hot gas in halos of active galaxies and clusters of galaxies

    International Nuclear Information System (INIS)

    The importance of the inverse Compton effect in the X-ray emission of cluster galaxies is discussed; the X-ray origin problem from galaxy clusters (spectra and emission mechanisms) is studied. The insufficiency of the X-ray bremsstrahlung emission model in an isothermal gas is proved. The ionized halos in narrow-line galaxies (NLG) are studied; after some general points on NLG, one NLG is described and a brief view an emission mechanism models is given; a detailed study of the galaxy IC 5063 and its nebulosity is given: the ionized gas density is calculated together with the evaporation rate for such clouds

  9. cluster-lensing: Tools for calculating properties and weak lensing profiles of galaxy clusters

    Science.gov (United States)

    Ford, Jes

    2016-05-01

    The cluster-lensing package calculates properties and weak lensing profiles of galaxy clusters. Implemented in Python, it includes cluster mass-richness and mass-concentration scaling relations, and NFW halo profiles for weak lensing shear, the differential surface mass density ΔΣ(r), and for magnification, Σ(r). Optionally the calculation will include the effects of cluster miscentering offsets.

  10. Clustering of HI galaxies in HIPASS and ALFALFA

    CERN Document Server

    Passmoor, S S; Faltenbacher, A

    2011-01-01

    We investigate the clustering of HI-selected galaxies in the ALFALFA survey and compare results with those obtained for HIPASS. Measurements of the angular correlation function and the inferred 3D-clustering are compared with results from direct spatial-correlation measurements. We are able to measure clustering on smaller angular scales and for galaxies with lower HI masses than was previously possible. We calculate the expected clustering of dark matter using the redshift distributions of HIPASS and ALFALFA and show that the ALFALFA sample is somewhat more anti-biased with respect to dark matter than the HIPASS sample.

  11. Thermal diffusion in the IGM of clusters of galaxies

    OpenAIRE

    Shtykovskiy, P.; M. Gilfanov(MPA Garching, Germany)

    2009-01-01

    We revisit the phenomenon of elements diffusion in the intergalactic medium (IGM) in clusters of galaxies. The diffusion is driven by gravity, concentration and temperature gradients. The latter cause thermal diffusion, which has been so far ignored in IGM studies. We consider the full problem based on the Burgers' equations and demonstrate that the temperature gradients present in clusters of galaxies may successfully compete with gravity, evacuating metals from cooler regions. Under the com...

  12. Galaxy Clustering Topology in the Sloan Digital Sky Survey Main Galaxy Sample: a Test for Galaxy Formation Models

    CERN Document Server

    Choi, Yun-Young; Kim, Juhan; Gott, J Richard; Weinberg, David H; Vogeley, Michael S; Kim, Sungsoo S

    2010-01-01

    We measure the topology of the main galaxy distribution using the Seventh Data Release of the Sloan Digital Sky Survey, examining the dependence of galaxy clustering topology on galaxy properties. The observational results are used to test galaxy formation models. A volume-limited sample defined by $M_r<-20.19$ enables us to measure the genus curve with amplitude of $G=378$ at $6h^{-1}$Mpc smoothing scale, with 4.8\\% uncertainty including all systematics and cosmic variance. The clustering topology over the smoothing length interval from 6 to $10 h^{-1}$Mpc reveals a mild scale-dependence for the shift ($\\Delta\

  13. Sliding not sloshing in Abell 3744: the influence of radio galaxies NGC 7018 and 7016 on cluster gas

    CERN Document Server

    Worrall, D M

    2013-01-01

    We present new X-ray (Chandra) and radio (JVLA) observations of the nearby cluster Abell 3744. It hosts two prominent radio galaxies with powers in the range critical for radio-mode feedback. The radio emission from these galaxies terminates in buoyant tendrils reaching the cluster's outer edge, and the radio-emitting plasma clearly influences the cluster's X-ray-emitting atmosphere. The cluster's average gas temperature, of kT=3.5 keV, is high for its bolometric luminosity of 3.2 \\times 10^{43} ergs s^{-1}, but the 100 kpc-scale cavity carved out by radio-emitting plasma shows evidence of less than 2 per cent of the excess enthalpy. We suggest instead that a high-velocity encounter with a galaxy group is responsible for dispersing and increasing the entropy of the gas in this non-cool-core cluster. We see no evidence for shocks, or established isobaric gas motions (sloshing), but there is much sub-structure associated with a dynamically active central region that encompasses the brightest radio emission. Gas...

  14. The Atacama Cosmology Telescope: the stellar content of galaxy clusters selected using the Sunyaev-Zel'dovich effect

    CERN Document Server

    Hilton, Matt; Sifón, Cristóbal; Baker, Andrew J; Barrientos, L Felipe; Battaglia, Nicholas; Bond, J Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark J; Gralla, Megan; Hajian, Amir; Hincks, Adam D; Hughes, John P; Infante, Leopoldo; Irwin, Kent D; Kosowsky, Arthur; Lin, Yen-Ting; Marriage, Tobias A; Marsden, Danica; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D; Nolta, Mike R; Page, Lyman A; Reese, Erik D; Sievers, Jon; Spergel, David N; Wollack, Edward J

    2013-01-01

    We present a first measurement of the stellar mass component of galaxy clusters selected via the Sunyaev-Zel'dovich (SZ) effect, using 3.6 um and 4.5 um photometry from the Spitzer Space Telescope. Our sample consists of 14 clusters detected by the Atacama Cosmology Telescope (ACT), which span the redshift range 0.27 < z < 1.07 (median z = 0.50), and have dynamical mass measurements, accurate to about 30 per cent, with median M500 = 6.9 x 10^{14} MSun. We measure the 3.6 um and 4.5 um galaxy luminosity functions, finding the characteristic magnitude (m*) and faint-end slope (alpha) to be similar to those for IR-selected cluster samples. We perform the first measurements of the scaling of SZ-observables (Y500 and y0) with both brightest cluster galaxy (BCG) stellar mass and total cluster stellar mass (M500star). We find a significant correlation between BCG stellar mass and Y500 (E(z)^{-2/3} DA^2 Y500 ~ M*^{1.2 +/- 0.6}), although we are not able to obtain a strong constraint on the slope of the relation...

  15. AGN feedback and entropy injection in galaxy cluster cores

    OpenAIRE

    Chaudhuri, Anya; Majumdar, Subhabrata; Nath, Biman B

    2012-01-01

    The non-gravitational energy feedback is of crucial importance in modeling/simulating clusters to be used as cosmological probes. AGNs are, arguably, of primary importance in injecting energy in the cluster cores. We make the first estimate of non-gravitational energy {\\it profiles} in galaxy cluster cores (and beyond) from observational data. Comparing the observed entropy profiles within $r_{500}$, from the Representative {\\it XMM-Newton} Cluster Structure Survey (REXCESS), to simulated ent...

  16. Gamma ray emission and stochastic particle acceleration in galaxy clusters

    OpenAIRE

    Brunetti, G.; P. Blasi(INAF Arcetri); Cassano, R.; Gabici, S.

    2008-01-01

    FERMI (formely GLAST) will shortly provide crucial information on relativistic particles in galaxy clusters. We discuss non-thermal emission in the context of general calculations in which relativistic particles (protons and secondary electrons due to proton-proton collisions) interact with MHD turbulence generated in the cluster volume during cluster mergers. Diffuse cluster-scale radio emission (Radio Halos) and hard X-rays are produced during massive mergers while gamma ray emission, at so...

  17. Small-scale Conformity of the Virgo Cluster Galaxies

    Science.gov (United States)

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

    2016-06-01

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

  18. Binary model for the coma cluster of galaxies

    International Nuclear Information System (INIS)

    We study the dynamics of galaxies in the Coma cluster and find that the cluster is probably dominated by a central binary of galaxies NGC 4874--NGC4889. We estimate their total mass to be about 3 x 1014 M/sub sun/ by two independent methods (assuming in Hubble constant of 100 km s-1 Mpc-1). This binary is efficient in dynamically ejecting smaller galaxies, some of of which are seen in projection against the inner 30 radius of the cluster and which, if erroneously considered as bound members, cause a serious overestimate of the mass of the entire cluster. Taking account of the ejected galaxies, we estimate the total cluster mass to be 4--9 x 1014 M/sub sun/, with a corresponding mass-to-light ratio for a typical galaxy in the range of 20--120 solar units. The origin of the secondary maximum observed in the radial surface density profile is studied. We consider it to be a remnant of a shell of galaxies which formed around the central binary. This shell expanded, then collapsed into the binary, and is now reexpanding. This is supported by the coincidence of the minimum in the cluster eccentricity and radical velocity dispersion at the same radial distance as the secondary maximum. Numerical simulations of a cluster model with a massive central binary and a spherical shell of test particles are performed, and they reproduce the observed shape, galaxy density, and radial velocity distributions in the Coma cluster fairly well. Consequences of extending the model to other clusters are discussed

  19. Measuring the Mass-to-Light Ratio of Cluster Galaxies

    Science.gov (United States)

    Natarajan, P.

    1996-12-01

    There is ample evidence from lensing for the clumping of dark matter on different scales within clusters, although the spatial extent of dark halos of cluster galaxies are yet to be constrained. The issue is of crucial importance as it addresses the key question of whether the mass to light ratio of galaxies is a function of the environment, and if it is indeed significantly different in the high density regions like cluster cores as opposed to the field. Weak shear maps of the outer regions of clusters have been successfully used to map the distribution of mass at large radii. However the typical smoothing lengths generally employed preclude the systematic study of the effects of galactic-scale substructure on the measured weak lensing signal. We present two new methods to study the effect of bright cluster galaxies on the cluster weak shear field - aperture averaging of the local shear and a maximum likelihood method to obtain limits on parameters that characterize galaxy halos. The composite lensing effect of a cluster is modeled by the superposition of mass clumps with different scales: a large-scale clump to describe the cluster and smaller scale ones for individual cluster galaxies. Working in the local frame of each perturber, the shear induced by the larger scale component can be efficiently subtracted, yielding the averaged shear field induced by the smaller-scale mass component. Cluster galaxy halos are modeled using simple scaling relations and the background high redshift population is modeled in consonance with observations from redshift surveys and lensing constraints. We demonstrate using simulations that these observed local weak-shear effects on galaxy scales within the cluster can be used to statistically constrain reliably the mean M/L of cluster members, and fiducial parameters like the halo size, velocity dispersion and hence mass of cluster galaxies. The results of the members, and fiducial parameters like the halo size and the velocity

  20. Galaxy Infall by Interacting with Its Environment: A Comprehensive Study of 340 Galaxy Clusters

    Science.gov (United States)

    Gu, Liyi; Wen, Zhonglue; Gandhi, Poshak; Inada, Naohisa; Kawaharada, Madoka; Kodama, Tadayuki; Konami, Saori; Nakazawa, Kazuhiro; Xu, Haiguang; Makishima, Kazuo

    2016-07-01

    To study systematically the evolution of the angular extents of the galaxy, intracluster medium (ICM), and dark matter components in galaxy clusters, we compiled the optical and X-ray properties of a sample of 340 clusters with redshifts gravitational mass distribution, was derived from a spatially resolved spectral analysis of the X-ray data. When normalizing the radial profile of galaxy number to that of the ICM mass, the relative curve was found to depend significantly on the cluster redshift; it drops more steeply toward the outside in lower-redshift subsamples. The same evolution is found in the galaxy-to-total mass profile, while the ICM-to-total mass profile varies in an opposite way. The behavior of the galaxy-to-ICM distribution does not depend on the cluster mass, suggesting that the detected redshift dependence is not due to mass-related effects, such as sample selection bias. Also, it cannot be ascribed to various redshift-dependent systematic errors. We interpret that the galaxies, the ICM, and the dark matter components had similar angular distributions when a cluster was formed, while the galaxies traveling in the interior of the cluster have continuously fallen toward the center relative to the other components, and the ICM has slightly expanded relative to the dark matter although it suffers strong radiative loss. This cosmological galaxy infall, accompanied by an ICM expansion, can be explained by considering that the galaxies interact strongly with the ICM while they are moving through it. The interaction is considered to create a large energy flow of 1044‑45 erg s‑1 per cluster from the member galaxies to their environment, which is expected to continue over cosmological timescales.

  1. The mass accretion rate of galaxy clusters: a measurable quantity

    CERN Document Server

    De Boni, Cristiano; Diaferio, Antonaldo; Giocoli, Carlo; Baldi, Marco

    2015-01-01

    We explore the possibility of measuring the mass accretion rate of galaxy clusters by using dense galaxy redshift surveys of their outer regions. By approximating the accretion with the infall of a spherical shell, the mass accretion rate only depends on the mass profile of the cluster in a thin shell at radii larger than $R_{200}$. This approximation is rather crude in hierarchical clustering scenarios, where both smooth accretion and aggregation of smaller dark matter haloes contribute to the mass accretion of clusters. Nevertheless, in the redshift range $z=[0,1]$, our prescription returns an average mass accretion rate within $20 \\%$ of the average rate derived with the more realistic merger trees of dark matter haloes extracted from $N$-body simulations. The mass accretion rate of galaxy clusters has been the topic of numerous detailed numerical and theoretical investigations, but so far it has remained inaccessible to measurements in the real Universe. Our result suggests that measuring the mass accreti...

  2. The peculiar velocity and temperature profile of galaxy clusters

    CERN Document Server

    Masood, Tabasum

    2013-01-01

    Dynamical parameters like average velocity dispersion and temperature profile of galaxy clusters are determined using a quasi equilibrium thermodynamic theory. The calculated velocity dispersion results from theory and simulations shows a good agreement with the velocity dispersion results of (Abdullah et al. \\cite{Abd11}). An Adaptive Mesh Refinement (AMR), Grid based hybrid code have been used to carry out the simulations. Our results indicate that the average velocity dispersion profile of $20$ Abell galaxy clusters falls in the range of $500-1000$ km/s and their temperature profile is of the order of $10^7$ to $10^8$K calculated on the basis of kinetic theory. The data in the plot shows a significant contribution of gravitating particles clustering together in the vicinity of cluster center and beyond a certain region this velocity dies out and gets dominated by the Hubble's flow due to which all the galaxy clusters in an expanding universe participate in Hubble's expansion.

  3. The peculiar velocity and temperature profile of galaxy clusters

    International Nuclear Information System (INIS)

    Dynamical parameters like average velocity dispersion and temperature profile of galaxy clusters are determined using the theory of quasi-equilibrium thermodynamics. The calculated results of velocity dispersion show a good agreement between theory and simulations with the results of velocity dispersion from Abdullah et al. An adaptive mesh refinement grid-based hybrid code has been used to carry out the simulations. Our results indicate that the average velocity dispersion profile of 20 Abell galaxy clusters falls in the range of 500 — 1000 km s−1 and their temperature profile is of the order of 107 to 108 K calculated on the basis of kinetic theory. The data in the plot show a significant contribution from gravitating particles clustering together in the vicinity of the cluster center and beyond a certain region this velocity dies out and becomes dominated by the Hubble flow due to which all the galaxy clusters in an expanding universe participate in Hubble expansion

  4. Gaussian covariance matrices for anisotropic galaxy clustering measurements

    CERN Document Server

    Grieb, Jan Niklas; Salazar-Albornoz, Salvador; Vecchia, Claudio dalla

    2015-01-01

    Measurements of the redshift-space galaxy clustering have been a prolific source of cosmological information in recent years. In the era of precision cosmology, accurate covariance estimates are an essential step for the validation of galaxy clustering models of the redshift-space two-point statistics. For cases where only a limited set of simulations is available, assessing the data covariance is not possible or only leads to a noisy estimate. Also, relying on simulated realisations of the survey data means that tests of the cosmology dependence of the covariance are expensive. With these two points in mind, this work aims at presenting a simple theoretical model for the linear covariance of anisotropic galaxy clustering observations with synthetic catalogues. Considering the Legendre moments (`multipoles') of the two-point statistics and projections into wide bins of the line-of-sight parameter (`clustering wedges'), we describe the modelling of the covariance for these anisotropic clustering measurements f...

  5. Dynamical Mass Measurements of Contaminated Galaxy Clusters Using Machine Learning

    CERN Document Server

    Ntampaka, M; Sutherland, D J; Fromenteau, S; Poczos, B; Schneider, J

    2015-01-01

    We study dynamical mass measurements of galaxy clusters contaminated by interlopers and show that a modern machine learning (ML) algorithm can predict masses by better than a factor of two compared to a standard scaling relation approach. We create two mock catalogs from Multidark's publicly-available N-body MDPL1 simulation, one with perfect galaxy cluster membership information and the other where a simple cylindrical cut around the cluster center allows interlopers to contaminate the clusters. In the standard approach, we use a power law scaling relation to infer cluster mass from galaxy line of sight (LOS) velocity dispersion. Assuming perfect membership knowledge, this unrealistic case produces a wide fractional mass error distribution, with width = 0.87. Interlopers introduce additional scatter, significantly widening the error distribution further (width = 2.13). We employ the Support Distribution Machine (SDM) class of algorithms to learn from distributions of data to predict single values. Applied to...

  6. Dynamics of clusters of galaxies with central dominant galaxies. I - Galaxy redshifts

    Science.gov (United States)

    Malumuth, Eliot M.; Kriss, Gerard A.; Van Dyke Dixon, W.; Ferguson, Henry C.; Ritchie, Christine

    1992-01-01

    Optical redshifts are presented for a sample of 638 galaxies in the fields of the clusters Abell 85, DC 0107-46, Abell 496, Abell 2052, and DC 1842-63. The velocity histograms and wedge diagrams show evidence for a foreground sheet of galaxies in Abell 85 and background sheets of galaxies in DC 0107-46 and Abell 2052. The foreground group projected against the center of Abell 85 found by Beers et al. (1991) is confirmed. No evidence of substructure was found in Abell 496, Abell 2052, and DC 1842-63. The clusters have global velocity dispersions ranging from 551 km/s for DC 1842-63 to 714 km/s for A496, and flat dispersion profiles. Mass estimates using the virial theorem and the projected mass method range from 2.3 x 10 exp 14 solar masses for DC 0107-46 to 1.1 x 10 exp 15 solar masses for A85.

  7. Can dark energy explain the observed outflow in galaxy clusters?

    CERN Document Server

    Donnari, M; Merafina, M

    2016-01-01

    Recent observations of the Virgo cluster and the Local Group suggested that some galaxies are flowing out from their parent cluster. This may be the signature that dark energy (DE) acts significantly also on small cosmological scales. By means of direct N-body simulations we performed several simulations, in which the effect of DE and gravity are taken into account, aiming to determine whether DE can produce an outflow of galaxies compatible with observations. Comparing the different simulations, our results suggest that the observed outflow of galaxies is likely due to the local effect of DE.

  8. Star Clusters in Pseudo-Bulges of Spiral Galaxies

    CERN Document Server

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

    2009-01-01

    We present a study of the properties of the star-cluster systems around pseudo-bulges of late-type spiral galaxies using a sample of 11 galaxies with distances from 17 to 37 Mpc. Star clusters are identified from multiband HST ACS and WFPC2 imaging data by combining detections in 3 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 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 an...

  9. The growth of the galaxy cluster Abell 85: mergers, shocks, stripping and seeding of clumping

    CERN Document Server

    Ichinohe, Y; Simionescu, A; Allen, S W; Canning, R E A; Ehlert, S; Mernier, F; Takahashi, T

    2014-01-01

    We present the results of deep Chandra, XMM-Newton and Suzaku observations of the nearby galaxy cluster Abell 85, which is currently undergoing at least two mergers, and in addition shows evidence for gas sloshing which extends out to r~600 kpc. One of the two infalling subclusters, to the south of the main cluster center, has a dense, X-ray bright cool core and a tail extending to the southeast. The northern edge of this tail is strikingly smooth and sharp (narrower than the Coulomb mean free path of the ambient gas) over a length of 200 kpc, while toward the southwest the boundary of the tail is blurred and bent, indicating a difference in the plasma transport properties between these two edges. The thermodynamic structure of the tail strongly supports an overall northwestward motion, with a sloshing-induced tangential ambient gas bulk flow bending the tail eastward. The brightest galaxy of this subcluster is at the leading edge of the dense core, and is trailed by the tail of stripped gas, suggesting that ...

  10. Stellar population gradients in early-type cluster galaxies

    OpenAIRE

    Rawle, T. D.; Smith, Russell J.; Lucey, J. R.

    2009-01-01

    We present a study of internal stellar population gradients in early-type cluster galaxies. Using the VLT VIMOS integral field unit, we observed 19 galaxies in the core of the Shapley Supercluster (z = 0.048). The radial trends in nine absorption lines (HdF to Fe5406) were measured to the effective radius for 14 galaxies, from which we derived the gradients in age, total metallicity and alpha-element over-abundance. We combine these with results from 11 galaxies studied in our previous VIMOS ...

  11. High-energy neutrinos from sources in clusters of galaxies

    CERN Document Server

    Fang, Ke

    2016-01-01

    High-energy cosmic rays can be accelerated in clusters of galaxies, by mega-parsec scale shocks induced by accretion of gas during the formation of large-scale structure, or by powerful sources harbored in clusters. Once accelerated, the highest energy particles leave the cluster via almost rectilinear trajectories, while lower energy ones can be confined by the cluster magnetic field up to cosmological time and interact with the intracluster gas. Using a realistic model of the baryon distribution and the turbulent magnetic field in clusters, we studied the propagation and hadronic interaction of high-energy protons in the intracluster medium. We report the cumulative cosmic ray and neutrino spectra generated by galaxy clusters including embedded sources, and demonstrate that clusters can contribute a significant fraction of the observed IceCube neutrinos above 30 TeV while remaining undetected in high-energy cosmic rays and $\\gamma$ rays for reasonable choices of parameters and source scenarios.

  12. Linear clusters of galaxies - A999 and A1016

    Science.gov (United States)

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

    1987-01-01

    Redshifts have been measured for galaxies in two of the 'linear' clusters of the sample of Adams, Strom, and Strom (1980), including 44 redshifts in A999 and 40 in A1016. From the data, it is concluded that the galaxies in A999 are probably drawn from a spherically symmetric distribution, while those in A1016 probably are not. Both A999 and A1016 have mass-to-light ratios lower than typical of other clusters. The effect of anisotropy on the determination of cluster masses from the virial theorem is examined, and it is found that if the shortest axes of these clusters are close to the line of sight, the mass-to-light ratio may be underestimated by about 50 percent. No significant evidence is found for alignments of individual cluster members with the cluster axis in the convincing linear cluster A1016. There is similarly no evidence of segregation by luminosity morphological type in A1016.

  13. The Hydra I cluster core. I. Stellar populations in the cD galaxy NGC 3311

    Science.gov (United States)

    Barbosa, C. E.; Arnaboldi, M.; Coccato, L.; Hilker, M.; Mendes de Oliveira, C.; Richtler, T.

    2016-05-01

    Context. The history of the mass assembly of brightest cluster galaxies may be studied by mapping the stellar populations at large radial distances from the galaxy centre, where the dynamical times are long and preserve the chemodynamical signatures of the accretion events. Aims: We provide extended and robust measurements of the stellar population parameters in NGC 3311, the cD galaxy at the centre of the Hydra I cluster, and out to three effective radii. We wish to characterize the processes that drove the build-up of the stellar light at all these radii. Methods: We obtained the spectra from several regions in NGC 3311 covering an area of ~3 arcmin2 in the wavelength range 4800 ≲ λ(Å) ≲ 5800, using the FORS2 spectrograph at the Very Large Telescope in the MXU mode. We measured the equivalent widths of seven absorption-features defined in the Lick/IDS system, which were modelled by single stellar populations, to provide luminosity-weighted ages, metallicities, and alpha element abundances. Results: The trends in the Lick indices and the distribution of the stellar population parameters indicate that the stars of NGC 3311 may be divided in two radial regimes, one within and the another beyond one effective radius, Re = 8.4 kpc, similar to the distinction between the inner galaxy and the external halo derived from the NGC 3311 velocity dispersion profile. The inner galaxy (R ≤ Re) is old (age ~14 Gyr), has negative metallicity gradients and positive alpha element gradients. The external halo is also very old, but has a negative age gradient. The metal and element abundances of the external halo both have a large scatter, indicating that stars from a variety of satellites with different masses have been accreted. The region in the extended halo associated with the off-centred envelope at 0°parent galaxies, either disks with truncated star formation, or the outer regions of early-type galaxies. Late mass accretion at large radii is now coming from the tidal

  14. XMM-Newton and Chandra Cross Calibration Using HIFLUGCS Galaxy Clusters

    CERN Document Server

    Schellenberger, G; Lovisari, L; Nevalainen, J; David, L

    2014-01-01

    Cosmological constraints from clusters rely on accurate gravitational mass estimates, which strongly depend on cluster gas temperature measurements. Therefore, systematic calibration differences may result in biased, instrument-dependent cosmological constraints. This is of special interest in the light of the tension between the Planck results of the primary temperature anisotropies of the CMB and Sunyaev-Zel'dovich plus X-ray cluster counts analyses. We quantify in detail the systematics and uncertainties of the cross-calibration of the effective area between five X-ray instruments, EPIC-MOS1/MOS2/PN onboard XMM-Newton and ACIS-I/S onboard Chandra, and the influence on temperature measurements. Furthermore, we assess the impact of the cross calibration uncertainties on cosmology. Using the HIFLUGCS sample, consisting of the 64 X-ray brightest galaxy clusters, we constrain the ICM temperatures through spectral fitting in the same, mostly isothermal, regions and compare them. Our work is an extension to a pre...

  15. Searching for star-forming dwarf galaxies in the Antlia cluster

    CERN Document Server

    Vaduvescu, O; Bassino, L P; Castelli, A V Smith; Calderon, J P

    2014-01-01

    The formation and evolution of dwarf galaxies in clusters need to be understood, and this requires large aperture telescopes. In this sense, we selected the Antlia cluster to continue our previous work in the Virgo, Fornax, and Hydra clusters and in the Local Volume (LV). Because of the scarce available literature data, we selected a small sample of five blue compact dwarf (BCD) candidates in Antlia for observation. Using the Gemini South and GMOS camera, we acquired the Halpha imaging needed to detect star-forming regions in this sample. With the long-slit spectroscopic data of the brightest seven knots detected in three BCD candidates, we derived their basic chemical properties. Using archival VISTA VHS survey images, we derived K_S magnitudes and surface brightness profile fits for the whole sample to assess basic physical properties. FS90-98, FS90-106, and FS90-147 are confirmed as BCDs and cluster members, based on their morphology, K_S surface photometry, oxygen abundance, and velocity redshift. FS90-15...

  16. Low surface brightness galaxies in the Fornax Cluster: automated galaxy surface photometry

    International Nuclear Information System (INIS)

    A sample is presented of low surface brightness galaxies (with extrapolated central surface brightness fainter than 22.0 Bμ) in the Fornax Cluster region which has been measured by the APM machine. Photometric parameters, namely profile shape, scale length, central brightness and total magnitude, are derived for the sample galaxies and correlations between the parameters of low surface brightness dwarf galaxies are discussed, with particular reference to the selection limits. Contrary to previous authors we find no evidence for a luminosity-surface brightness correlation in the sense of lower surface brightness galaxies having lower luminosities and scale sizes. In fact, the present data suggest that it is the galaxies with the largest scale lengths which are more likely to be of very low surface brightness. In addition, the larger scale length galaxies occur preferentially towards the centre of the Cluster. (author)

  17. Baryon content of massive galaxy clusters at 0.57 < z < 1.33

    Science.gov (United States)

    Chiu, I.; Mohr, J.; McDonald, M.; Bocquet, S.; Ashby, M. L. N.; Bayliss, M.; Benson, B. A.; Bleem, L. E.; Brodwin, M.; Desai, S.; Dietrich, J. P.; Forman, W. R.; Gangkofner, C.; Gonzalez, A. H.; Hennig, C.; Liu, J.; Reichardt, C. L.; Saro, A.; Stalder, B.; Stanford, S. A.; Song, J.; Schrabback, T.; Šuhada, R.; Strazzullo, V.; Zenteno, A.

    2016-01-01

    We study the stellar, brightest cluster galaxy (BCG) and intracluster medium (ICM) masses of 14 South Pole Telescope (SPT) selected galaxy clusters with median redshift z = 0.9 and mass M500 = 6 × 1014 M⊙. We estimate stellar masses for each cluster and BCG using six photometric bands, the ICM mass using X-ray observations and the virial masses using the SPT Sunyaev-Zel'dovich effect signature. At z = 0.9, the BCG mass M_{star }^{BCG} constitutes 0.12 ± 0.01 per cent of the halo mass for a 6 × 1014 M⊙ cluster, and this fraction falls as M_{500}^{-0.58± 0.07}. The cluster stellar mass function has a characteristic mass M0 = 1011.0 ± 0.1 M⊙, and the number of galaxies per unit mass in clusters is larger than in the field by a factor of 1.65 ± 0.20. We combine our SPT sample with previously published samples at low redshift and correct to a common initial mass function and for systematic virial mass differences. We then explore mass and redshift trends in the stellar fraction f⋆, the ICM fraction fICM, the collapsed baryon fraction fc and the baryon fraction fb. At a pivot mass of 6 × 1014 M⊙ and redshift z = 0.9, the characteristic values are f⋆ = 1.1 ± 0.1 per cent, fICM = 9.6 ± 0.5 per cent, fc = 10.7 ± 1.1 per cent and fb = 10.7 ± 0.6 per cent. These fractions all vary with cluster mass at high significance, with higher mass clusters having lower f⋆ and fc and higher fICM and fb. When accounting for a 15 per cent systematic virial mass uncertainty, there is no statistically significant redshift trend at fixed mass. Our results support the scenario where clusters grow through accretion from subclusters (higher f⋆, lower fICM) and the field (lower f⋆, higher fICM), balancing to keep f⋆ and fICM approximately constant since z ˜ 0.9.

  18. Galaxy Clusters and Properties in the CFHTLS/VIPERS Survey

    Science.gov (United States)

    Gallego Gallego, Sofia Carolina; Murphy, David; Hyazinth Puzia, Thomas

    2015-08-01

    We present our analysis of clusters in the CFHTLS Wide fields using a red-sequence based cluster finding code. The deep five-band photometry and panoramic coverage permits detection of galaxy clusters between z=0 and z~1 over 132 square degrees. We present a cluster catalogue and optical richness estimates as mass proxies, derived cluster properties from a novel template-fitting analysis and cluster redshift measurements utilizing data from the VLT/VIPERS spectroscopic survey.We complement our analysis with studies of mock cluster catalogues generated from N-body simulation lightcones featuring semi-analytic prescriptions of galaxy formation. These provide us with an insight into the performance of the cluster-finding technique, uncertainties in the derived properties of the detected cluster populations and an important comparison of the popular “lambda” optical richness estimator to known dark matter halo properties.This study serves as the perfect precursor to LSST-depth cluster science, providing an important input into how models describe the evolution of clusters and their members as a function of redshift and mass, and the role high-density environments play in galaxy evolution over half the Hubble time.

  19. Halos of rich clusters of galaxies. I. An infall model for the Coma Cluster

    International Nuclear Information System (INIS)

    The large mass of a cluster of galaxies slows the Hubble expansion in a surrounding volume. The ratio of the matter density near the cluster to the average density at large distances grows as the cosmological density parameter, Ω, decreases. For values of Ω<0.2, the gravitational attraction of the Coma Cluster acting upon an initially homogeneous external medium is sufficient to account for a galaxy population comparable to that of the Coma Supercluster

  20. Clustering Property of Wolf-Rayet Galaxies in the SDSS

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Xu Kong; Fu-Zhen Cheng

    2008-01-01

    We have analysed, for the first time, the clustering properties of Wolf-Rayet (W-R) galaxies, using a large sample of 846 W-R galaxies selected from the Data Release 4 (DR4) of the Sloan Digital Sky Survey (SDSS). We compute the cross-correlation function between W- R galaxies and a reference sample of galaxies drawn from the DR4. We compare the function to the results for control samples of non-W-R star-forming galaxies that are matched closely in redshift, luminosity, concentration, 4000-A break strength and specific star formation rate (SSFR). On scales larger than a few Mpc, W-R galaxies have almost the same clustering amplitude as the control samples, indicating that W-R galaxies and non-W-R control galax- ies populate dark matter haloes of similar masses. On scales between 0.1-1 h-1 Mpc, W-R galaxies are less clustered than the control samples, and the size of the difference depends on the SSFR. Based on both observational and theoretical considerations, we speculate that this negative bias can be interpreted by W-R galaxies residing preferentially at the centers of their dark matter haloes. We examine the distribution of W-R galaxies more closely using the SDSS galaxy group catalogue of Yang et al., and find that ~82% of our W-R galaxies are the central galaxies of groups, compared to ~74% for the corresponding control galaxies. We find that W-R galaxies are hosted, on average, by dark matter haloes of masses of 1012,3 M☉, compared to 1012,1 M? For centrally-located W-R galaxies and 1012,7 M☉ For satellite ones. We would like to point out that this finding, which provides a direct observational support to our conjecture, is really very crude due to the small number of W-R galaxies and the incom- pleteness of the group catalogue, and needs more work in future with larger samples.

  1. The Apparent and Intrinsic Shape of the APM Galaxy Clusters

    CERN Document Server

    Basilakos, S; Manolis, P; Basilakos, Spyros; Maddox, Steve; Plionis, Manolis

    2000-01-01

    We estimate the distribution of intrinsic shapes of APM galaxy clusters fromthe distribution of their apparent shapes. We measure the projected clusterellipticities using two alternative methods. The first method is based onmoments of the discrete galaxy distribution while the second is based onmoments of the smoothed galaxy distribution. We study the performance of bothmethods using Monte Carlo cluster simulations covering the range of APM clusterdistances and including a random distribution of background galaxies. We findthat the first method suffers from severe systematic biases, whereas the secondis more reliable. After excluding clusters dominated by substructure andquantifying the systematic biases in our estimated shape parameters, we recovera corrected distribution of projected ellipticities. We use the non-parametrickernel method to estimate the smooth apparent ellipticity distribution, andnumerically invert a set of integral equations to recover the correspondingdistribution of intrinsic ellipticiti...

  2. Intermediate-age globular clusters in four galaxy merger remnants

    International Nuclear Information System (INIS)

    We present the results of combining Hubble Space Telescope optical photometry with ground-based Ks -band photometry from the Gemini imagers NIRI and FLAMINGOS-I to study the globular cluster (GC) populations in four early-type galaxies that are candidate remnants of recent mergers (NGC 1700, NGC 2865, NGC 4382, and NGC 7727). These galaxies were chosen based on their blue colors and fine structure, such as shells and ripples that are indicative of past interactions. We fit the combined VIKs GC data with simple toy models of mixed cluster populations that contain three subpopulations of different age and metallicity. The fits, done via chi-squared mapping of the parameter space, yield clear evidence for the presence of intermediate-age clusters in each galaxy. We find that the ages of ∼1-2 Gyr for these GC subpopulations are consistent with the previously estimated merger ages for the host galaxies.

  3. Disentangling the ICL with the CHEFs in the Pandora galaxy cluster

    Science.gov (United States)

    Jimenez-Teja, Yolanda; Dupke, Renato A.

    2016-01-01

    The intracluster light (ICL) is important for understanding the metal enrichment of the intracluster gas and constraining cosmological parameters independently of the other methods. However, its measurement it is not trivial due to the necessity of disentangling the light of stars locked up in galaxies from the proper ICL. Currently, there is no standard method to efficiently measure the ICL (Rudick et al. 2011, ApJ, 732, 48), and different approaches relying on the binding energy of the cluster galaxies, the density of the material, or the surface brightness distribution, have been tried. Moreover, a suitable way to disentangle the limits of the brightest cluster galaxy (BCG) and the ICL still has not been developed.The CHEFs (from Chebyshev-Fourier bases, Jiménez-Teja & Benítez 2012, ApJ, 745, 150) are a mathematical tool especially designed to model the two-dimensional light distribution of galaxies. We use the CHEFs and tools from differential geometry to infer the light contribution of the ICL to the total brightness, without imposing any artificial thresholds and avoiding the ambiguity introduced by free parameters that are usually set in these studies (Rudick et al. 2011).We use the extremely deep optical images from Abell 2744, the Pandora cluster, a multi-cluster merger, observed by the Hubble Frontier Fields project to show the efficiency of this new method. The CHEFs can accurately fit and remove all the galaxies close to the cluster center, including the BCG. The limits of the BCG are marked out by determining the points where the surface curvature changes, thus disentangling the ICL from the BCG light in a completely natural way. Once we have the residual image just containing ICL and background, we extrapolate the value of this latter from images of individual pointings close to the main Pandora field. We finally estimate the ICL to be ~24% of the total light, which is very consistent with the predictions from numerical simulations (Montes

  4. Galaxy cluster mass estimation from stacked spectroscopic analysis

    Science.gov (United States)

    Farahi, Arya; Evrard, August E.; Rozo, Eduardo; Rykoff, Eli S.; Wechsler, Risa H.

    2016-08-01

    We use simulated galaxy surveys to study: i) how galaxy membership in redMaPPer clusters maps to the underlying halo population, and ii) the accuracy of a mean dynamical cluster mass, $M_\\sigma(\\lambda)$, derived from stacked pairwise spectroscopy of clusters with richness $\\lambda$. Using $\\sim\\! 130,000$ galaxy pairs patterned after the SDSS redMaPPer cluster sample study of Rozo et al. (2015 RMIV), we show that the pairwise velocity PDF of central--satellite pairs with $m_i galaxy membership matching. We apply this approach, along with mis-centering and galaxy velocity bias corrections, to estimate the log-mean matched halo mass at $z=0.2$ of SDSS redMaPPer clusters. Employing the velocity bias constraints of Guo et al. (2015), we find $\\langle \\ln(M_{200c})|\\lambda \\rangle = \\ln(M_{30}) + \\alpha_m \\ln(\\lambda/30)$ with $M_{30} = 1.56 \\pm 0.35 \\times 10^{14} M_\\odot$ and $\\alpha_m = 1.31 \\pm 0.06_{stat} \\pm 0.13_{sys}$. Systematic uncertainty in the velocity bias of satellite galaxies overwhelmingly dominates the error budget.

  5. Spitzer Observations of Environmental Effects on Virgo Cluster Galaxies

    CERN Document Server

    Kenney, Jeffrey D P; Abramson, Anne; Howell, Justin H; Murphy, Eric J; Helou, George X

    2008-01-01

    We present the initial results from SPITSOV, the Spitzer Survey of Virgo, which includes MIPS and IRAC observations for a carefully selected sample of 44 Virgo cluster spiral and peculiar galaxies. SPITSOV is part of a multiwavelength campaign to understand the effects of the cluster environment on galaxy evolution. These Virgo galaxies are different from galaxies outside of clusters, since most of them have been significantly modified by their environment. The SPITSOV data can serve the community as the Spitzer sample of nearby cluster spiral galaxies, a complement to the SINGS data for nearby non-cluster galaxies. In this paper we describe the sample, the goals of the study, and present preliminary results in 3 areas: 1) Evidence for ram pressure-induced disturbances in radio morphologies based on changes in the FIR-radio (70um-20cm) correlation; 2) Evidence for ram-pressure stripped extraplanar gas tails from comparisons of dust/PAH (8um) emission and optical dust extinction; 3) Evidence for unobscured sta...

  6. Multicolor Photometry of the Nearby Galaxy Cluster A119

    CERN Document Server

    Tian, Jin-Tao; Zhou, Xu; Jiang, Zhao-Ji; Ma, Jun; Wu, Jiang-Hua; Wu, Zhen-Yu; Fan, Zhou; Zhang, Tian-Meng; Zou, Hu

    2012-01-01

    This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 (z = 0:0442) with the Beijing-Arizona-Taiwan-Connecticut (BATC) system of 15 intermediate bands. Within the BATC viewing field of 58'* 58', there are 368 galaxies with known spectroscopic redshifts, including 238 member galaxies (called sample I). Based on the spectral energy distributions (SEDs) of 1376 galaxies brighter than iBATC = 19:5, photometric redshift technique and the color-magnitude relation of earlytype galaxies are applied to select faint member galaxies. As a result, 117 faint galaxies were selected as new member galaxies. Combined with sample I, an enlarged sample (called sample II) of 355 member galaxies is obtained. Spatial distribution and localized velocity structure for two samples demonstrate that A119 is a dynamically complex cluster with at least three prominent substructures in the central region within 1 Mpc. A large velocity dispersion for the central clump indicates a merging along the line of ...

  7. The Galaxy Cluster Merger Catalog: An Online Repository of Mock Observations from Simulated Galaxy Cluster Mergers

    CERN Document Server

    ZuHone, J A

    2016-01-01

    We present the first release of the "Galaxy Cluster Merger Catalog". This catalog provides an extensive suite of mock observations and related data for N-body and hydrodynamical simulations of galaxy cluster mergers. These mock observations consist of projections of a number of important observable quantities in several different wavebands, for the entire evolution of each simulation as well as along different lines of sight through the three-dimensional simulation domain. The web interface to the catalog consists of easily browseable images over epoch and projection direction, as well as download links for the raw data and a JS9 interface for interactive data exploration. All of the data products are provided in the standard FITS file format, in image and table form. Data is being stored on the yt Hub (http://hub.yt), which allows for remote access and analysis using a Jupyter notebook server. Future versions of the catalog will include simulations from a number of research groups and a variety of research t...

  8. Prospects for SODART observations of nearby clusters of galaxies

    DEFF Research Database (Denmark)

    Pedersen, Kenneth; Westergaard, Niels Jørgen Stenfeldt

    Using the current best understanding of the SODART mirror system, the Bragg panel and of the LEPC/HEPC responses [1] we have studied the feasibility and prospects for SODART studies of nearby clusters of galaxies. From simulated HEPC data of the cluster Abell 2256, we demonstrate that SODART...

  9. The Influence of Cluster Mergers on Galaxy Evolution

    Science.gov (United States)

    Rawle, T. D.; Altieri, B.; Bouy, H.; Egami, E.; Pérez-González, P. G.; Richard, J.; Valtchanov, I.; Walth, G.

    2016-06-01

    The rich environment of galaxy clusters is understood to have a profound effect on the evolution of constituent galaxies. However, even clusters of a similar mass and at fixed redshift are not homogeneous, displaying a range in structural complexity. Here we concentrate on the effect of cluster merging, the most massive dynamic process in the Universe. Two spectacular cluster mergers at z~0.3 are explored: the archetypal Bullet cluster (1E0657-558; Rawle et al. 2012), and the HST Frontier Field, Pandora's cluster (Abell 2744; Rawle et al. 2014, 2016). We present detailed analysis of their total star formation, derived from multi-wavelength observations of both dusty and unobscured activity from Herschel, Spitzer, WISE and GALEX. Examination of the morphologies of individual cluster galaxies reveals striking evidence for transformation and enhanced star formation, triggered by the merger-induced shock front. This includes several galaxies identified as having "jellyfish" morphologies caused by the passing shock. We discuss the implications, and preview future work exploring a large sample of clusters covering a range of dynamic states and redshifts.

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

    Science.gov (United States)

    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.

  11. Modeling color-dependent galaxy clustering in cosmological simulations

    CERN Document Server

    Masaki, Shogo; Yoshida, Naoki

    2013-01-01

    We extend the subhalo abundance matching method to assign galaxy color to subhalos. We separate a luminosity-binned subhalo sample into two groups by a secondary subhalo property which is presumed to be correlated with galaxy color. The two subsamples then represent red and blue galaxy populations. We explore two models for the secondary propertty; subhalo assembly time and local dark matter density around each subhalo. The model predictions for the galaxy two-point correlation functions are compared with the recent results from the Sloan Digital Sky Survey. We show that the observed color dependence of galaxy clustering can be reproduced well by our method applied to cosmological N-body simulations without baryonic components. We then compare the model predictions for the color-dependent galaxy-mass cross correlation functions with the results from gravitational lensing observations. The comparison allows us to distinguish the models, and also to discuss what subhalo property should be used to assign color t...

  12. STAR CLUSTER DISRUPTION IN THE STARBURST GALAXY MESSIER 82

    International Nuclear Information System (INIS)

    Using high-resolution, multiple-passband Hubble Space Telescope images spanning the entire optical/near-infrared wavelength range, we obtained a statistically complete U-band-selected sample of 846 extended star clusters across the disk of the nearby starburst galaxy M82. Based on a careful analysis of the clusters' spectral energy distributions, we determined their galaxy-wide age and mass distributions. The M82 clusters exhibit three clear peaks in their age distribution, thus defining relatively young, log (t yr–1) ≤ 7.5, intermediate-age, log (t yr–1) in [7.5, 8.5], and old samples, log (t yr–1) ≥ 8.5. Comparison of the completeness-corrected mass distributions offers a firm handle on the galaxy's star cluster disruption history. The most massive star clusters in the young and old samples are (almost) all concentrated in the most densely populated central region, while the intermediate-age sample's most massive clusters are more spatially dispersed, which may reflect the distribution of the highest-density gas throughout the galaxy's evolutionary history, combined with the solid-body nature of the galaxy's central region

  13. Gaussian covariance matrices for anisotropic galaxy clustering measurements

    Science.gov (United States)

    Grieb, Jan Niklas; Sánchez, Ariel G.; Salazar-Albornoz, Salvador; Dalla Vecchia, Claudio

    2016-04-01

    Measurements of the redshift-space galaxy clustering have been a prolific source of cosmological information in recent years. Accurate covariance estimates are an essential step for the validation of galaxy clustering models of the redshift-space two-point statistics. Usually, only a limited set of accurate N-body simulations is available. Thus, assessing the data covariance is not possible or only leads to a noisy estimate. Further, relying on simulated realizations of the survey data means that tests of the cosmology dependence of the covariance are expensive. With these points in mind, this work presents a simple theoretical model for the linear covariance of anisotropic galaxy clustering observations with synthetic catalogues. Considering the Legendre moments (`multipoles') of the two-point statistics and projections into wide bins of the line-of-sight parameter (`clustering wedges'), we describe the modelling of the covariance for these anisotropic clustering measurements for galaxy samples with a trivial geometry in the case of a Gaussian approximation of the clustering likelihood. As main result of this paper, we give the explicit formulae for Fourier and configuration space covariance matrices. To validate our model, we create synthetic halo occupation distribution galaxy catalogues by populating the haloes of an ensemble of large-volume N-body simulations. Using linear and non-linear input power spectra, we find very good agreement between the model predictions and the measurements on the synthetic catalogues in the quasi-linear regime.

  14. Modeling the tidal connection between in and around galaxy clusters

    CERN Document Server

    Song, Hyunmi

    2011-01-01

    We analyze the halo and galaxy catalogs from the Millennium simulations at redshifts z=0, 0.5, 1 to determine the alignment profiles of cluster galaxies in terms of the matter density correlation coefficient and discuss a cosmological implication our result has for breaking parameter degeneracies. For each selected cluster, we measure the alignment between the major axes of the pseudo inertia tensors from all satellites within cluster's virial radius and from only those satellites within some smaller radius. Then we average the measured values over the similar-mass sample to determine the cluster galaxy alignment profile as a function of top-hat scale difference at each redshift. It is shown that the alignment profile of cluster galaxies is well approximated by a power-law of the nonlinear density correlation coefficient that is independent of the power spectrum normalization and bias factor. The alignment profile of cluster galaxies is found to have higher amplitude and lower power-law index when averaged ov...

  15. Dark matter searches with Cherenkov telescopes: nearby dwarf galaxies or local galaxy clusters?

    CERN Document Server

    Sanchez-Conde, Miguel A; Zandanel, F; Gomez, Mario E; Prada, F

    2011-01-01

    In the last few years, most of the attention in gamma-ray dark matter (DM) searches has been devoted to neutralino annihilations in nearby dwarf galaxies. However, massive galaxy clusters in the local Universe may constitute very good targets as well. The main aim of this work is to compare both dwarf galaxies and local galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies and galaxy clusters, and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure. Willman~1 appears as the best candidate in the sample and, given the morphology of its annihilation signal, it is also one of the objects more readily observable by IACTs. As for galaxy clusters, Virgo represents the one with the hi...

  16. The Density Profiles of Massive, Relaxed Galaxy Clusters: I. The Total Density Over 3 Decades in Radius

    CERN Document Server

    Newman, Andrew B; Ellis, Richard S; Sand, David J; Nipoti, Carlo; Richard, Johan; Jullo, Eric

    2012-01-01

    Clusters of galaxies are excellent locations to probe the distribution of baryons and dark matter over a wide range of scales. We study a sample of 7 massive, relaxed galaxy clusters with centrally-located brightest cluster galaxies (BCGs) at z=0.2-0.3. Using the observational tools of strong and weak gravitational lensing, combined with resolved stellar kinematics within the BCG, we measure the total radial density profile, comprising both dark and baryonic matter, over scales of \\sim3-3000 kpc. Lensing-derived mass profiles typically agree with independent X-ray estimates within \\sim15%, suggesting that departures from hydrostatic equilibrium are small and that the clusters in our sample (except A383) are not strongly elongated along the line of sight. The inner logarithmic slope gamma_tot of the total density profile measured over r/r200=0.003-0.03, where rho_tot \\sim r^(-gamma_tot), is found to be nearly universal, with a mean = 1.16 +- 0.05 (random) +0.05-0.07 (systematic) and an intrinsic scatter of &l...

  17. Active galactic nucleus feedback in clusters of galaxies.

    Science.gov (United States)

    Blanton, Elizabeth L; Clarke, T E; Sarazin, Craig L; Randall, Scott W; McNamara, Brian R

    2010-04-20

    Observations made during the last ten years with the Chandra X-ray Observatory have shed much light on the cooling gas in the centers of clusters of galaxies and the role of active galactic nucleus (AGN) heating. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes found in the nuclei of the dominant cluster galaxies leading to AGN outbursts which can reheat the gas, suppressing cooling and large amounts of star formation. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio lobes, and the dissipation of sound waves. PMID:20351250

  18. Super Star Clusters in the Blue Dwarf Galaxy UM 462

    OpenAIRE

    Vanzi, Leonardo

    2003-01-01

    I present optical observations of the Blue Compact Dwarf Galaxy UM 462. The images of this galaxy show several bright compact sources. A careful study of these sources has revealed their nature of young Super Star Clusters. The ages determined from the analysis of the stellar continuum and $H\\alpha$ are between few and few tens Myr. The total star formation taking place into the clusters is about 0.05 $\\mathrm{M_{\\odot}/yr}$. The clusters seem to be located at the edges of two large round-lik...

  19. A Hidden Radio Halo in the Galaxy Cluster A1682?

    Indian Academy of Sciences (India)

    T. Venturi; S. Giacintucci; D. Dallacasa

    2011-12-01

    High sensitivity observations of radio halos in galaxy clusters at frequencies ≤ 330 MHz are still relatively rare, and very little is known compared to the classical 1.4 GHz images. The few radio halos imaged down to 150–240 MHz show a considerable spread in size, morphology and spectral properties. All clusters belonging to the GMRT Radio Halo Survey with detected or candidate cluster-scale diffuse emission have been imaged at 325 MHz with the GMRT. Few of them were also observed with the GMRT at 240 MHz and 150 MHz. For A1682, imaging is particularly challenging due to the presence of strong and extended radio galaxies at the center. Our data analysis suggests that thew radio galaxies are superposed to very low surface brightness radio emission extended on the cluster scale, which we present here.

  20. Thermal diffusion in the IGM of clusters of galaxies

    CERN Document Server

    Shtykovskiy, P

    2009-01-01

    We revisit the phenomenon of elements diffusion in the intergalactic medium (IGM) in clusters of galaxies. The diffusion is driven by gravity, concentration and temperature gradients. The latter cause thermal diffusion, which has been so far ignored in IGM studies. We consider the full problem based on the Burgers' equations and demonstrate that the temperature gradients present in clusters of galaxies may successfully compete with gravity, evacuating metals from cooler regions. Under the combined action of gravity and temperature gradients, complicated metallicity profiles with several peaks and depressions may be formed. For a typical cool core cluster, the thermal diffusion may significantly reduce and even reverse the gravitational sedimentation of metals, resulting in the depression in their abundance in the core. This may have implications for diagnostics of the low temperature plasma in the centers of clusters of galaxies.

  1. Evolutionary Synthesis Modelling of Young Star Clusters in Merging Galaxies

    CERN Document Server

    Anders, P; De Grijs, R; Anders, Peter; Alvensleben, Uta Fritze - v.; Grijs, Richard de

    2003-01-01

    The observational properties of globular cluster systems (GCSs) are vital tools to investigate the violent star formation histories of their host galaxies. This violence is thought to have been triggered by galaxy interactions or mergers. The most basic properties of a GCS are its luminosity function (number of clusters per luminosity bin) and color distributions. A large number of observed GCS show bimodal color distributions, which can be translated into a bimodality in either metallicity and/or age. An additional uncertainty comes into play when one considers extinction. These effects can be disentangled either by obtaining spectroscopic data for the clusters or by imaging observations in at least four passbands. This allows us then to discriminate between various formation scenarios of GCSs, e.g. the merger scenario by Ashman & Zepf, and the multi-phase collapse model by Forbes et. al.. Young and metal-rich star cluster populations are seen to form in interacting and merging galaxies. We analyse multi...

  2. THE MASSIVE DISTANT CLUSTERS OF WISE SURVEY: THE FIRST DISTANT GALAXY CLUSTER DISCOVERED BY WISE

    International Nuclear Information System (INIS)

    We present spectroscopic confirmation of a z = 0.99 galaxy cluster discovered using data from the Wide-field Infrared Survey Explorer (WISE). This is the first z ∼ 1 cluster candidate from the Massive Distant Clusters of WISE Survey to be confirmed. It was selected as an overdensity of probable z ∼> 1 sources using a combination of WISE and Sloan Digital Sky Survey DR8 photometric catalogs. Deeper follow-up imaging data from Subaru and WIYN reveal the cluster to be a rich system of galaxies, and multi-object spectroscopic observations from Keck confirm five cluster members at z = 0.99. The detection and confirmation of this cluster represents a first step toward constructing a uniformly selected sample of distant, high-mass galaxy clusters over the full extragalactic sky using WISE data.

  3. The Spiderweb Galaxy: A Forming Massive Cluster Galaxy at z ~ 2

    Science.gov (United States)

    Miley, George K.; Overzier, Roderik A.; Zirm, Andrew W.; Ford, Holland C.; Kurk, Jaron; Pentericci, Laura; Blakeslee, John P.; Franx, Marijn; Illingworth, Garth D.; Postman, Marc; Rosati, Piero; Röttgering, Huub J. A.; Venemans, Bram P.; Helder, Eveline

    2006-10-01

    We present a deep image of the radio galaxy MRC 1138-262 taken with the Hubble Space Telescope (HST) at a redshift of z=2.2. The galaxy is known to have properties of a cD galaxy progenitor and be surrounded by a 3 Mpc-sized structure, identified with a protocluster. The morphology shown on the new deep HST ACS image is reminiscent of a spider's web. More than 10 individual clumpy features are observed, apparently star-forming satellite galaxies in the process of merging with the progenitor of a dominant cluster galaxy 11 Gyr ago. There is an extended emission component, implying that star formation was occurring over a 50×40 kpc region at a rate of more than 100 Msolar yr-1. A striking feature of the newly named ``Spiderweb galaxy'' is the presence of several faint linear galaxies within the merging structure. The dense environments and fast galaxy motions at the centers of protoclusters may stimulate the formation of these structures, which dominate the faint resolved galaxy populations in the Hubble Ultra Deep Field. The new image provides a unique testbed for simulations of forming dominant cluster galaxies.

  4. Starbursts versus Truncated Star Formation in Nearby Clusters of Galaxies

    CERN Document Server

    Rose, J A; Caldwell, N; Chaboyer, B; Rose, James A.; Gaba, Alejandro E.; Caldwell, Nelson; Chaboyer, Brian

    2001-01-01

    We present long-slit spectroscopy, B and R bandpass imaging, and 21 cm observations of a sample of early-type galaxies in nearby clusters which are known to be either in a star-forming phase or to have had star formation which recently terminated. From the long-slit spectra, obtained with the Blanco 4-m telescope, we find that emission lines in the star-forming cluster galaxies are significantly more centrally concentrated than in a sample of field galaxies. The broadband imaging reveals that two currently star-forming early-type galaxies in the Pegasus I cluster have blue nuclei, again indicating that recent star formation has been concentrated. In contrast, the two galaxies for which star formation has already ended show no central color gradient. The Pegasus I galaxy with the most evident signs of ongoing star formation (NGC7648), exhibits signatures of a tidal encounter. Neutral hydrogen observations of that galaxy with the Arecibo radiotelescope reveal the presence of ~4 x 10^8 solar masses of HI. Arecib...

  5. Age and Metallicities of Cluster Galaxies: A1185 and Coma

    CERN Document Server

    Rakos, K; Odell, A

    2006-01-01

    We present age and metallicities determinations based on narrow band continuum colors for the galaxies in the rich clusters A1185 and Coma. Using a new technique to extract luminosity-weighted age and [Fe/H] values for non-star-forming galaxies, we find that both clusters have two separate populations based on these parameters. One population is old ($\\tau >$ 11 Gyrs) with a distinct mass-metallicity relation. The second population is slightly younger ($\\tau \\approx$ 9 Gyrs) with lower metallicities and lower stellar masses. We find detectable correlations between age and galaxy mass in both populations such that older galaxies are more massive and have higher mean metallicities, confirming previous work with line indices for the same type of galaxies in other clusters (Kelson et al 2006, Thomas et al 2005). Our results imply shorter durations for higher mass galaxies, in contradiction to the predictions of classic galactic wind models. Since we also find a clear mass-metallicity relation for these galaxies, ...

  6. Featured Image: A Galaxy Plunges Into a Cluster Core

    Science.gov (United States)

    Kohler, Susanna

    2015-10-01

    The galaxy that takes up most of the frame in this stunning image (click for the full view!) is NGC 1427A. This is a dwarf irregular galaxy (unlike the fortuitously-located background spiral galaxy in the lower right corner of the image), and its currently in the process of plunging into the center of the Fornax galaxy cluster. Marcelo Mora (Pontifical Catholic University of Chile) and collaborators have analyzed observations of this galaxy made by both the Very Large Telescope in Chile and the Hubble Advanced Camera for Surveys, which produced the image shown here as a color composite in three channels. The team worked to characterize the clusters of star formation within NGC 1427A identifiable in the image as bright knots within the galaxy and determine how the interactions of this galaxy with its cluster environment affect the star formation within it. For more information and the original image, see the paper below.Citation:Marcelo D. Mora et al 2015 AJ 150 93. doi:10.1088/0004-6256/150/3/93

  7. Strong Lensing In The Inner Halo Of Galaxy Clusters

    OpenAIRE

    Saez, C.; Campusano, L. E.; Cypriano, E. S.; L. Sodré; Kneib, J.-P.

    2016-01-01

    We present an axially symmetric formula to calculate the probability of finding gravitational arcs in galaxy clusters, being induced by their massive dark matter haloes, as a function of clusters redshifts and virial masses. The formula includes the ellipticity of the clusters dark matter potential by using a pseudo-elliptical approximation. The probabilities are calculated and compared for two dark-matter halo profiles, the Navarro, Frenk and White (NFW) and the Non-Singular-Isothermal-Spher...

  8. Self-similar energetics in large clusters of galaxies

    OpenAIRE

    Miniati, Francesco; Beresnyak, Andrey

    2015-01-01

    Massive galaxy clusters are filled with a hot, turbulent and magnetized intra-cluster medium. Still forming under the action of gravitational instability, they grow in mass by accretion of supersonic flows. These flows partially dissipate into heat through a complex network of large-scale shocks [1], while residual transonic flows create giant turbulent eddies and cascades [2,3]. Turbulence heats the intra-cluster medium [4] and also amplifies magnetic energy by way of dynamo action [5-8]. Ho...

  9. Galaxy Cluster Bulk Flows and Collision Velocities in QUMOND

    CERN Document Server

    Katz, Harley; Teuben, Peter; Angus, G W

    2013-01-01

    We examine the formation of clusters of galaxies in numerical simulations of a QUMOND cosmogony with massive sterile neutrinos. Clusters formed in these exploratory simulations develop higher velocities than those found in {\\Lambda}CDM simulations. The bulk motions of clusters attain about 1000 km/s by low redshift, comparable to observations whereas {\\Lambda}CDM simulated clusters tend to fall short. Similarly, high pairwise velocities are common in cluster-cluster collisions like the Bullet cluster. There is also a propensity for the most massive clusters to be larger in QUMOND and to appear earlier than in {\\Lambda}CDM, potentially providing an explanation for 'pink elephants' like El Gordo. However, it is not obvious that the cluster mass function can be recovered.

  10. A Baryonic Effect on the Merger Timescale of Galaxy Clusters

    CERN Document Server

    Zhang, Congyao; Lu, Youjun

    2016-01-01

    Accurate estimation of the merger timescale of galaxy clusters is important to understand the cluster merger process and further the formation and evolution of the large-scale structure of the universe. In this paper, we explore a baryonic effect on the merger timescale of galaxy clusters by using hydrodynamical simulations. We find that the baryons play an important role in accelerating the merger process. The merger timescale decreases with increasing the gas fraction of galaxy clusters. For example, the merger timescale is shortened by a factor of up to 3 for merging clusters with gas fractions 0.15, compared with the timescale obtained with zero gas fractions. The baryonic effect is significant for a wide range of merger parameters and especially more significant for nearly head-on mergers and high merging velocities. The baryonic effect on the merger timescale of galaxy clusters is expected to have impacts on the structure formation in the universe, such as the cluster mass function and massive substruct...

  11. DISENTANGLING THE ROLE OF ENVIRONMENTAL PROCESSES IN GALAXY CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Fernandez, Jonathan D.; Vilchez, J. M.; Iglesias-Paramo, J., E-mail: jonatan@iaa.es [Instituto de Astrofisica de Andalucia, Glorieta de la Astronomia s/n, 18008 Granada (Spain)

    2012-05-20

    In this work, we present the results of a novel approach devoted to disentangling the role of the environmental processes affecting galaxies in clusters. This is based on the analysis of the near-UV (NUV) - r' distributions of a large sample of star-forming galaxies in clusters spanning more than four absolute magnitudes. The galaxies inhabit three distinct environmental regions: virial regions, cluster infall regions, and field environment. We have applied rigorous statistical tests to analyze both the complete NUV - r' distributions and their averages for three different bins of the r'-band galaxy luminosity down to M{sub r{sup '}}{approx}-18, throughout the three environmental regions considered. We have identified the environmental processes that significantly affect the star-forming galaxies in a given luminosity bin by using criteria based on the characteristics of these processes: their typical timescales, the regions where they operate, and the galaxy luminosity range for which their effects are more intense. We have found that the high-luminosity (M{sub r{sup '}}{<=}-20) star-forming galaxies do not show significant signs in their star formation activity of being affected by: (1) the environment in the last {approx}10{sup 8} yr, or (2) a sudden quenching in the last 1.5 Gyr. The intermediate-luminosity (-20< M{sub r{sup '}}{<=}-19) star-forming galaxies appear to be affected by starvation in the virial regions and by the harassment in the virial and infall regions. Low-luminosity (-19galaxies seem to be affected by the same environmental processes as intermediate-luminosity star-forming galaxies in a stronger way, which would be expected for their lower luminosities.

  12. Halo assembly bias and its effects on galaxy clustering

    CERN Document Server

    Croton, D J; White, S D M; Croton, Darren J.; Gao, Liang; White, Simon D. M.

    2006-01-01

    The clustering of dark halos depends not only on their mass but also on their assembly history, a dependence we term `assembly bias'. Using a galaxy formation model grafted onto the Millennium Simulation of the LCDM cosmogony, we study how assembly bias affects galaxy clustering. We compare the original simulation to `shuffled' versions where the galaxy populations are randomly swapped among halos of similar mass, thus isolating the effects of correlations between assembly history and environment at fixed mass. Such correlations are ignored in the halo occupation distribution models often used populate dark matter simulations with galaxies, but they are significant in our more realistic simulation. Assembly bias enhances 2-point correlations by 10% for galaxies with M_bJ-5logh brighter than -17, but suppresses them by a similar amount for galaxies brighter than -20. When such samples are split by colour, assembly bias is 5% stronger for red galaxies and 5% weaker for blue ones. Halo central galaxies are diffe...

  13. Star Formation and Relaxation in 379 Nearby Galaxy Clusters

    CERN Document Server

    Cohen, Seth A; Wegner, Gary A

    2015-01-01

    We investigate the relationship between star formation (SF) and level of relaxation in a sample of 379 galaxy clusters at z < 0.2. We use data from the Sloan Digital Sky Survey to measure cluster membership and level of relaxation, and to select star-forming galaxies based on mid-infrared emission detected with the Wide-Field Infrared Survey Explorer. For galaxies with absolute magnitudes M_r < -19.5, we find an inverse correlation between SF fraction and cluster relaxation: as a cluster becomes less relaxed, its SF fraction increases. Furthermore, in general, the subtracted SF fraction in all unrelaxed clusters (0.117 +/- 0.003) is higher than that in all relaxed clusters (0.097 +/- 0.005). We verify the validity of our SF calculation methods and membership criteria through analysis of previous work. Our results agree with previous findings that a weak correlation exists between cluster SF and dynamical state, possibly because unrelaxed clusters are less evolved relative to relaxed clusters.

  14. The estimation of masses of individual galaxies in clusters of galaxies.

    Science.gov (United States)

    Wolf, R. A.; Bahcall, J. N.

    1972-01-01

    Three different methods of estimating masses are discussed. The 'density method' is based on the analysis of the density distribution of galaxies around the object whose mass is to be found. The 'bound-galaxy method' gives estimates of the mass of a double, triple, or quadruple system from analysis of the orbital motion of the components. The 'virial method' utilizes the formulas derived for the second method to obtain estimates of the virial-theorem masses of whole clusters, and thus to obtain upper limits on the mass of an individual galaxy in a cluster. The analytic formulas are developed and compared with computer experiments, and some applications are given.

  15. Dark Matter Halos in Galaxies and Globular Cluster Populations

    CERN Document Server

    Hudson, Michael J; Harris, William E

    2014-01-01

    We combine a new, comprehensive database for globular cluster populations in all types of galaxies with a new calibration of galaxy halo masses based entirely on weak lensing. Correlating these two sets of data, we find that the mass ratio $\\eta \\equiv M_{GCS}/M_{h}$ (total mass in globular clusters, divided by halo mass) is essentially constant at $\\langle \\eta \\rangle \\sim 4 \\times 10^{-5}$, strongly confirming earlier suggestions in the literature. Globular clusters are the only known stellar population that formed in essentially direct proportion to host galaxy halo mass. The intrinsic scatter in $\\eta$ appears to be at most 0.2 dex; we argue that some of this scatter is due to differing degrees of tidal stripping of the globular cluster systems between central and satellite galaxies. We suggest that this correlation can be understood if most globular clusters form at very early stages in galaxy evolution, largely avoiding the feedback processes that inhibited the bulk of field-star formation in their hos...

  16. ENHANCED ABUNDANCES IN SPIRAL GALAXIES OF THE PEGASUS I CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Paul; Shields, Gregory A.; Blanc, Guillermo A., E-mail: paul@astro.as.utexas.edu, E-mail: shields@astro.as.utexas.edu, E-mail: gblancm@astro.as.utexas.edu [Department of Astronomy, University of Texas, Austin, TX 78712 (United States)

    2012-03-20

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and velocity dispersion, also display gas loss due to interstellar-medium-intracluster-medium interaction, albeit to a lesser degree. Based on the abundances of three H I deficient spirals and two H I normal spirals, we observe a heavy element abundance offset of +0.13 {+-} 0.07 dex for the H I deficient galaxies. This abundance differential is consistent with the differential observed in Virgo for galaxies with a similar H I deficiency, and we observe a correlation between log (O/H) and the H I deficiency parameter DEF for the two clusters analyzed together. Our results suggest that similar environmental mechanisms are driving the heavy element enhancement in both clusters.

  17. ENHANCED ABUNDANCES IN SPIRAL GALAXIES OF THE PEGASUS I CLUSTER

    International Nuclear Information System (INIS)

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and velocity dispersion, also display gas loss due to interstellar-medium-intracluster-medium interaction, albeit to a lesser degree. Based on the abundances of three H I deficient spirals and two H I normal spirals, we observe a heavy element abundance offset of +0.13 ± 0.07 dex for the H I deficient galaxies. This abundance differential is consistent with the differential observed in Virgo for galaxies with a similar H I deficiency, and we observe a correlation between log (O/H) and the H I deficiency parameter DEF for the two clusters analyzed together. Our results suggest that similar environmental mechanisms are driving the heavy element enhancement in both clusters.

  18. The Diffuse Light in Simulations of Galaxy Clusters

    CERN Document Server

    Murante, G; Gerhard, O E; Borgani, S; Cheng, L M; Diaferio, A; Dolag, K; Moscardini, L; Tormen, G; Tornatore, L; Pozzi, P

    2004-01-01

    We study the properties of the diffuse light in galaxy clusters forming in a large hydrodynamical cosmological simulation of the Lambda-CDM cosmology. The simulation includes a model for radiative cooling, star formation in dense cold gas, and feedback by SN-II explosions. We select clusters having mass M>10^(14) h^(-1) Msun and study the spatial distribution of their star particles. While most stellar light is concentrated in gravitationally bound galaxies orbiting in the cluster potential, we find evidence for a substantial diffuse component, which may account for the extended halos of light observed around central cD galaxies. We find that more massive simulated clusters have a larger fraction of stars in the diffuse light than the less massive ones. The intracluster light is more centrally concentrated than the galaxy light, and the stars in the diffuse component are on average older than the stars in cluster galaxies, supporting the view that the diffuse light is not a random sampling of the stellar popu...

  19. Galaxy Clustering and Galaxy Bias in a Lambda-CDM Universe

    OpenAIRE

    Weinberg, David H.; Dav'e, Romeel; Katz, Neal; Hernquist, Lars

    2002-01-01

    We investigate galaxy clustering and galaxy-mass correlations in the LCDM cosmological model using a large volume SPH simulation. For the most part, the predicted biases between galaxies and dark matter lead to good agreement with current observations, including: (1) a nearly constant comoving correlation length from z=3 to z=0 for mass-selected galaxy samples of constant comoving space density; (2) an rms bias factor b~1 at z=0; (3) a scale-dependent bias on small scales that transforms the ...

  20. Sommerfeld enhancement of invisible dark matter annihilation in galaxies and galaxy clusters

    CERN Document Server

    Chan, Man Ho

    2016-01-01

    Recent observations indicate that core-like dark matter structures exist in many galaxies, while numerical simulations reveal a singular dark matter density profile at the center. In this article, I show that if the annihilation of dark matter particles gives invisible sterile neutrinos, the Sommerfeld enhancement of the annihilation cross-section can give a sufficiently large annihilation rate to solve the core-cusp problem. The resultant core density, core radius, and their scaling relation generally agree with recent empirical fits from observations. Also, this model predicts that the resultant core-like structures in dwarf galaxies can be easily observed, but not for large normal galaxies and galaxy clusters.

  1. Sommerfeld enhancement of invisible dark matter annihilation in galaxies and galaxy clusters

    Science.gov (United States)

    Chan, Man Ho

    2016-07-01

    Recent observations indicate that core-like dark matter structures exist in many galaxies, while numerical simulations reveal a singular dark matter density profile at the center. In this article, I show that if the annihilation of dark matter particles gives invisible sterile neutrinos, the Sommerfeld enhancement of the annihilation cross-section can give a sufficiently large annihilation rate to solve the core-cusp problem. The resultant core density, core radius, and their scaling relation generally agree with recent empirical fits from observations. Also, this model predicts that the resultant core-like structures in dwarf galaxies can be easily observed, but not for large normal galaxies and galaxy clusters.

  2. Central mass profiles of the nearby cool-core galaxy clusters Hydra A and A478

    Science.gov (United States)

    Okabe, N.; Umetsu, K.; Tamura, T.; Fujita, Y.; Takizawa, M.; Matsushita, K.; Fukazawa, Y.; Futamase, T.; Kawaharada, M.; Miyazaki, S.; Mochizuki, Y.; Nakazawa, K.; Ohashi, T.; Ota, N.; Sasaki, T.; Sato, K.; Tam, S. I.

    2016-03-01

    We perform a weak-lensing study of the nearby cool-core galaxy clusters, Hydra A (z = 0.0538) and A478 (z = 0.0881), of which the brightest cluster galaxies (BCGs) host the powerful activities of active galactic nuclei (AGNs). For each cluster, the observed tangential shear profile is described well by either a single Navarro-Frenk-White model or a two-component model including the BCG as an unresolved point mass. For A478, we determine the BCG and its host-halo masses from a joint fit to weak-lensing and stellar photometry measurements. We find that the choice of initial mass functions (IMFs) can introduce a factor of 2 uncertainty in the BCG mass, whereas the BCG host-halo mass is constrained well by data. We perform a joint analysis of the weak-lensing and stellar kinematics data available for the Hydra A cluster, which allows us to constrain the central mass profile without assuming specific IMFs. We find that the central mass profile (r < 300 kpc) determined from the joint analysis is in excellent agreement with those from independent measurements, including dynamical masses estimated from the cold gas disc component, X-ray hydrostatic total mass estimates, and the central stellar mass estimated with the Salpeter IMF. The observed dark matter fraction around the BCG for Hydra A is found to be smaller than those predicted by adiabatic contraction models, suggesting the importance of other physical processes, such as AGN feedback and/or dissipationless mergers.

  3. Radio morphology and spectral analysis of cD galaxies in rich and poor galaxy clusters

    CERN Document Server

    Giacintucci, S; Murgia, M; Dallacasa, D; Athreya, R; Bardelli, S; Mazzotta, P; Saikia, J D

    2007-01-01

    We present a radio morphological study and spectral analysis for a sample of 13 cD galaxies in rich and poor clusters of galaxies.} Our study is based on new high sensitivity Giant Metrewave Radio Telescope (GMRT) observations at 1.28 GHz, 610 MHz and 235 MHz, and on archival data. From a statistical sample of cluster cD galaxies we selected those sources with little information available in the literature and promising for the detection of aged radio emission. Beyond the high sensitivity images for all 13 radio galaxies, we present also a detailed spectral analysis for 7 of them. We found a variety of morphologies and linear sizes, as typical for radio galaxies in the radio power range sampled here (low to intermediate power radio galaxies). The spectral analysis shows that 10/13 radio galaxies have steep radio spectrum, with spectral index $\\alpha \\ge 1$. In general, the radiative ages and growth velocities are consistent with previous findings that the evolution of radio galaxies at the cluster centres is ...

  4. The bright galaxy population of five medium redshift clusters. II. Quantitative Galaxy Morphology

    CERN Document Server

    Ascaso, B; Moles, M; Sánchez-Janssen, R; Bettoni, D

    2009-01-01

    Aims: Following the study already presented in our previous paper, based on the Nordic Optical Telescope (NOT) sample, which consists of five clusters of galaxies within the redshift range 0.18 $\\leq$ z $\\leq$ 0.25, imaged in the central 0.5-2 Mpc in very good seeing conditions, we have studied the quantitative morphology of their bright galaxy population Methods: We have analyzed the surface brightness profiles of the galaxy population in those clusters. Previously, we have performed simulations in order to check the reliability of the fits. We have also derived a quantitative morphological classification. Results: The structural parameters derived from these analysis have been analyzed. We have obtained that the structural parameters of E/S0 galaxies are similar to those showed by galaxies in low redshift clusters. However, the disc scales are different. In particular, the scales of the discs of galaxies at medium redshift clusters are statistically different than those located in similar galaxies in the Co...

  5. The descendents of Lyman Break Galaxies in galaxy clusters spatial distribution and orbital properties

    CERN Document Server

    Governato, F; Moore, B; Quinn, T; Stadel, J; Lake, G; Brera-Merate, O A

    2000-01-01

    We combine semi-analytical methods with a ultra-high resolution simulation of a galaxy cluster (of mass 2.3 10^14h-1Msolar, and 4 10^6 particles within its virial radius) formed in a standard CDM universe to study the spatial distribution and orbital properties of the present-day descendents of Lyman Break Galaxies (LBGs). At the present time only five (out of 12) of halos containing LBGs survive as separate entities inside the cluster virial radius. Their circular velocities are in the range 200 - 550 km/sec. Seven halos merged together to form the central object at the very center of the cluster. Using semi-analytical modeling of galaxy evolution we show that descendents of halos containing LBGs now host giant elliptical galaxies. Galaxy orbits are radial, with a pericenter to apocenter ratio of about 1:5. The orbital eccentricities of LBGs descendents are statistically indistinguishable from those of the average galaxy population inside the cluster, suggesting that the orbits of these galaxies are not sign...

  6. MC$^2$: Dynamical Analysis of the Merging Galaxy Cluster MACS J1149.5+2223

    CERN Document Server

    Golovich, Nathan; Wittman, David; Ogrean, Georgiana A; van Weeren, Reinout J; Bonafede, Annalisa

    2016-01-01

    We present an analysis of the merging cluster MACS J1149.5+2223 using archival imaging from Subaru/Suprime-Cam and multi-object spectroscopy from Keck/DEIMOS and Gemini/GMOS. We employ two and three dimensional substructure tests and determine that MACS J1149.5+2223 is composed of two separate mergers between three subclusters occurring $\\sim$1 Gyr apart. The primary merger gives rise to elongated X-ray morphology and a radio relic in the southeast. The brightest cluster galaxy is a member of the northern subcluster of the primary merger. This subcluster is very massive (16.7$^{+\\text{1.25}}_{-\\text{1.60}}\\times\\text{10}^{\\text{14}}$ M$_{\\odot}$). The southern subcluster is also very massive (10.8$^{+\\text{3.37}}_{-\\text{3.54}}\\times\\text{10}^{\\text{14}}$ M$_{\\odot}$), yet it lacks an associated X-ray surface brightness peak, and it has been unidentified previously despite the detailed study of this \\emph{Frontier Field} cluster. A secondary merger is occurring in the north along the line of sight with a thir...

  7. Kinematic evidence of satellite galaxy populations in the potential wells of first-ranked cluster galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Cowie, L.L.; Hu, E.M.

    1986-06-01

    The velocities of 38 centrally positioned galaxies (r much less than 100 kpc) were measured relative to the velocity of the first-ranked galaxy in 14 rich clusters. Analysis of the velocity distribution function of this sample and of previous data shows that the population cannot be fit by a single Gaussian. An adequate fit is obtained if 60 percent of the objects lie in a Gaussian with sigma = 250 km/s and the remainder in a population with sigma = 1400 km/s. All previous data sets are individually consistent with this conclusion. This suggests that there is a bound population of galaxies in the potential well of the central galaxy in addition to the normal population of the cluster core. This is taken as supporting evidence for the galactic cannibalism model of cD galaxy formation. 14 references.

  8. Sliding not sloshing in A3744: The influence of radio galaxies NGC 7018 and 7016 on cluster gas

    International Nuclear Information System (INIS)

    We present new X-ray (Chandra) and radio (JVLA) observations of the nearby cluster A3744. It hosts two prominent radio galaxies with powers in the range critical for radio-mode feedback. The radio emission from these galaxies terminates in buoyant tendrils reaching the cluster's outer edge, and the radio-emitting plasma clearly influences the cluster's X-ray-emitting atmosphere. The cluster's average gas temperature, of kT = 3.5 keV, is high for its bolometric luminosity of 3.2 × 1043 erg s–1, but the 100 kpc-scale cavity carved out by radio-emitting plasma shows evidence of less than 2% of the excess enthalpy. We suggest instead that a high-velocity encounter with a galaxy group is responsible for dispersing and increasing the entropy of the gas in this non-cool-core cluster. We see no evidence for shocks, or established isobaric gas motions (sloshing), but there is much sub-structure associated with a dynamically active central region that encompasses the brightest radio emission. Gas heating is evident in directions perpendicular to the inferred line of encounter between the infalling group and cluster. The radio-emitting tendrils run along boundaries between gas of different temperature, apparently lubricating the gas flows and inhibiting heat transfer. The first stages of the encounter may have helped trigger the radio galaxies into their current phase of activity, where we see X-rays from the nuclei, jets, and hotspots.

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

    Science.gov (United States)

    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

  10. Unbiased methods for removing systematics from galaxy clustering measurements

    CERN Document Server

    Elsner, Franz; Peiris, Hiranya V

    2015-01-01

    Measuring the angular clustering of galaxies as a function of redshift is a powerful method for tracting information from the three-dimensional galaxy distribution. The precision of such measurements will dramatically increase with ongoing and future wide-field galaxy surveys. However, these are also increasingly sensitive to observational and astrophysical contaminants. Here, we study the statistical properties of three methods proposed for controlling such systematics - template subtraction, basic mode projection, and extended mode projection - all of which make use of externally supplied template maps, designed to characterise and capture the spatial variations of potential systematic effects. Based on a detailed mathematical analysis, and in agreement with simulations, we find that the template subtraction method in its original formulation returns biased estimates of the galaxy angular clustering. We derive closed-form expressions that should be used to correct results for this shortcoming. Turning to th...

  11. High Frequency Cluster Radio Galaxies: Luminosity Functions and Implications for SZE Selected Cluster Samples

    CERN Document Server

    Gupta, N; Mohr, J J; Benson, B A; Bocquet, S; Carlstrom, J E; Capasso, R; Chiu, I; Crawford, T M; de Haan, T; Dietrich, J P; Gangkofner, C; Holzapfel, W L; McDonald, M; Rapetti, D; Reichardt, C L

    2016-01-01

    We study the overdensity of point sources in the direction of X-ray-selected galaxy clusters from the Meta-Catalog of X-ray detected Clusters of galaxies (MCXC; $\\langle z \\rangle = 0.14$) at South Pole Telescope (SPT) and Sydney University Molonglo Sky Survey (SUMSS) frequencies. Flux densities at 95, 150 and 220 GHz are extracted from the 2500 deg$^2$ SPT-SZ survey maps at the locations of SUMSS sources, producing a multi-frequency catalog of radio galaxies. In the direction of massive galaxy clusters, the radio galaxy flux densities at 95 and 150 GHz are biased low by the cluster Sunyaev-Zel'dovich Effect (SZE) signal, which is negative at these frequencies. We employ a cluster SZE model to remove the expected flux bias and then study these corrected source catalogs. We find that the high frequency radio galaxies are centrally concentrated within the clusters and that their luminosity functions (LFs) exhibit amplitudes that are characteristically an order of magnitude lower than the cluster LF at 843 MHz. ...

  12. The impact of galaxy harassment on the globular cluster systems of early-type cluster dwarf galaxies

    CERN Document Server

    Smith, Rory; Fellhauer, Michael; Puzia, Thomas H; Aguerri, J A L; Farias, Juan-Pablo

    2012-01-01

    The dynamics of globular cluster systems (GCSs) around galaxies are often used to assess the total enclosed mass, and even to constrain the dark matter distribution. The globular cluster system of a galaxy is typically assumed to be in dynamical equilibrium within the potential of the host galaxy. However cluster galaxies are subjected to a rapidly evolving and, at times, violently destructive tidal field. We investigate the impact of the harassment on the dynamics of GCs surrounding early type cluster dwarfs, using numerical simulations. We find that the dynamical behaviour of the GCS is strongly influenced by the fraction of bound dark matter f_{DM} remaining in the galaxy. Only when f_{DM} falls to ~15%, do stars and GCs begin to be stripped. Still the observed GC velocity dispersion can be used to measure the true enclosed mass to within a factor of 2, even when f_{DM} falls as low as ~3%. This is possible partly because unbound GCs quickly separate from the galaxy body. However even the distribution of {...

  13. THERMAL AND CHEMICAL EVOLUTIONS OF GALAXY CLUSTERS OBSERVED WITH SUZAKU

    Directory of Open Access Journals (Sweden)

    Kosuke Sato

    2013-12-01

    Full Text Available We studied the properties of the intracluster medium (ICM of galaxy clusters to outer regions observed with Suzaku. The observed temperature dropped by about ~30% from the central region to the virial radius of the clusters. The derived entropy profile agreed with the expectation from simulations within r500, while the entropy profile in r > r500 indicated a flatter slope than the simulations. This would suggest that the cluster outskirts were out of hydrostatic equilibrium. As for the metallicity, we studied the metal abundances from O to Fe up to ~0.5 times the virial radius of galaxy groups and clusters. Comparing the results with supernova nucleosynthesis models, the number ratio of type II to Ia supernovae is estimated to be ~3.5. We also calculated not only Fe, but also O and Mg mass-to-light ratios (MLRs with K-band luminosity. The MLRs in the clusters had a similar feature.

  14. Shaken and stirred: conduction and turbulence in clusters of galaxies

    CERN Document Server

    Ruszkowski, M

    2009-01-01

    (abridged) Uninhibited radiative cooling in clusters of galaxies would lead to excessive mass accretion rates contrary to observations. One of the key proposals to offset radiative energy losses is thermal conduction from outer, hotter layers of cool core clusters to their centers. However, conduction is sensitive to magnetic field topology. In cool-core clusters the heat buoyancy instability (HBI) leads to B-fields ordered preferentially in the direction perpendicular to that of gravity, which significantly reduces the level of conduction below the classical Spitzer-Braginskii value. However, the cluster cool cores are rarely in perfect hydrostatic equilibrium. Sloshing motions due to minor mergers, galaxy motions or AGN can significantly perturb the gas and affect the level of thermal conduction. We perform 3D AMR MHD simulations of the effect of turbulence on the properties of the anisotropic thermal conduction in cool core clusters. We show that very weak subsonic motions, well within observational constr...

  15. LoCuSS: Testing hydrostatic equilibrium in galaxy clusters

    Science.gov (United States)

    Smith, G. P.; Mazzotta, P.; Okabe, N.; Ziparo, F.; Mulroy, S. L.; Babul, A.; Finoguenov, A.; McCarthy, I. G.; Lieu, M.; Bahé, Y. M.; Bourdin, H.; Evrard, A. E.; Futamase, T.; Haines, C. P.; Jauzac, M.; Marrone, D. P.; Martino, R.; May, P. E.; Taylor, J. E.; Umetsu, K.

    2016-02-01

    We test the assumption of hydrostatic equilibrium in an X-ray luminosity selected sample of 50 galaxy clusters at 0.15 sub-4 per cent, and our hydrostatic measurements of the same achieve excellent agreement between XMM-Newton and Chandra. The mean ratio of X-ray to lensing mass for these 50 clusters is β_X= 0.95± 0.05, and for the 44 clusters also detected by Planck, the mean ratio of Planck mass estimate to LoCuSS lensing mass is β_P= 0.95± 0.04. Based on a careful like-for-like analysis, we find that LoCuSS, the Canadian Cluster Comparison Project, and Weighing the Giants agree on β_P ≃ 0.9-0.95 at 0.15 Planck cosmology results from the cosmic microwave background and galaxy cluster counts.

  16. Reconstructing the Merger History of the A3266 Galaxy Cluster

    CERN Document Server

    Henriksen, M; Davis, D S; Henriksen, Mark; Davis, David S.

    1999-01-01

    A temperature map of the A3266 galaxy cluster has been derived from the ASCA GIS observations. It shows an asymmetric pattern of heating indicative of an ongoing merger between a group sized sub-cluster and the main cluster. The galaxy distribution shows two peaks connected in a barlike structure running NE to SW through the central region of the main cluster, defining the merger axis. The temperature of the intergalactic medium generally decreases from SW to NE along the merger axis with a peak of 13.2 +3.4/-2.0 keV in a region which is perpendicular to the merger axis and extends through the main cluster density peak. The central bar has a velocity dispersion of ~1300 km/s, compared to density peaks in the distribution of galaxies, yet it has a velocity distribution which is consistent with a single Gaussian. This implies a merger in the plane of the sky. The optical and X-ray data taken together show that a loose group of about ~30 galaxies has penetrated the main cluster from the SW, decoupling from their...

  17. Metallicity distributions of globular cluster systems in galaxies

    OpenAIRE

    Eerik, Helina; Tenjes, Peeter

    2002-01-01

    We collected a sample of 100 galaxies for which different observers have determined colour indices of globular cluster candidates. The sample includes representatives of galaxies of various morphological types and different luminosities. Colour indices (in most cases (V-I), but also (B-I) and (C-T1)) were transformed into metallicities [Fe/H] according to a relation by Kissler-Patig (1998). These data were analysed with the KMM software in order to estimate similarity of the distribution with...

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

    OpenAIRE

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

    2012-01-01

    It is a firm prediction of the concordance Cold Dark Matter (CDM) cosmological model that galaxy clusters live 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 (WHIM) 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 c...

  19. Chandra Finds Most Distant X-ray Galaxy Cluster

    Science.gov (United States)

    2001-02-01

    The most distant X-ray cluster of galaxies yet has been found by astronomers using NASA’s Chandra X-ray Observatory. Approximately 10 billion light years from Earth, the cluster 3C294 is 40 percent farther than the next most distant X-ray galaxy cluster. The existence of such a distant galaxy cluster is important for understanding how the universe evolved. "Distant objects like 3C294 provide snapshots to how these galaxy clusters looked billions of years ago," said Andrew Fabian of the Institute of Astronomy, Cambridge, England and lead author of the paper accepted for publication in the Monthly Notices of Britain’s Royal Astronomical Society. "These latest results help us better understand what the universe was like when it was only 20 percent of its current age." Chandra’s image reveals an hourglass-shaped region of X-ray emission centered on the previously known central radio source. This X-ray emission extends outward from the central galaxy for at least 300,000 light years and shows that the known radio source is in the central galaxy of a massive cluster. Scientists have long suspected that distant radio-emitting galaxies like 3C294 are part of larger groups of galaxies known as "clusters." However, radio data provides astronomers with only a partial picture of these distant objects. Confirmation of the existence of clusters at great distances - and, hence, at early stages of the universe - requires information from other wavelengths. Optical observations can be used to pinpoint individual galaxies, but X-ray data are needed to detect the hot gas that fills the space within the cluster. "Galaxy clusters are the largest gravitationally bound structures in the universe," said Fabian. "We do not expect to find many massive objects, such as the 3C294 cluster, in early times because structure is thought to grow from small scales to large scales." The vast clouds of hot gas that envelope galaxies in clusters are thought to be heated by collapse toward the

  20. Optical emission line nebulae in galaxy cluster cores 1: the morphological, kinematic and spectral properties of the sample

    Science.gov (United States)

    Hamer, S. L.; Edge, A. C.; Swinbank, A. M.; Wilman, R. J.; Combes, F.; Salomé, P.; Fabian, A. C.; Crawford, C. S.; Russell, H. R.; Hlavacek-Larrondo, J.; McNamara, B. R.; Bremer, M. N.

    2016-08-01

    We present an Integral Field Unit survey of 73 galaxy clusters and groups with the VIsible Multi Object Spectrograph on the Very Large Telescope. We exploit the data to determine the H α gas dynamics on kpc scales to study the feedback processes occurring within the dense cluster cores. We determine the kinematic state of the ionized gas and show that the majority of systems (˜2/3) have relatively ordered velocity fields on kpc scales that are similar to the kinematics of rotating discs and are decoupled from the stellar kinematics of the brightest cluster galaxy. The majority of the H α flux (>50 per cent) is typically associated with these ordered kinematics and most systems show relatively simple morphologies suggesting they have not been disturbed by a recent merger or interaction. Approximately 20 per cent of the sample (13/73) have disturbed morphologies which can typically be attributed to active galactic nuclei activity disrupting the gas. Only one system shows any evidence of an interaction with another cluster member. A spectral analysis of the gas suggests that the ionization of the gas within cluster cores is dominated by non-stellar processes, possibly originating from the intracluster medium itself.