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The Acs Virgo Cluster Survey. Xiv. Analysis Of Color-Magnitude Relations In Globular Cluster Systems, Steffen Mieske, Andres Jordan, Patrick Cote
The Acs Virgo Cluster Survey. Xiv. Analysis Of Color-Magnitude Relations In Globular Cluster Systems, Steffen Mieske, Andres Jordan, Patrick Cote
Articles
We examine the correlation between globular cluster (GC) color and magnitude using HST/ACS imaging for a sample of 79 early-type galaxies (−21.7 < MB < −15.2 mag) with accurate surfacebrightness fluctuation distances from the ACS Virgo Cluster Survey. Using the KMM mixture modeling algorithm, we find a highly significant correlation, z ≡ d(g−z) dz = −0.037 ± 0.004, between color and magnitude for the subpopulation of blue GCs in the co-added GC color-magnitude diagram of the three brightest Virgo cluster galaxies (M49, M87 and M60). The sense of the correlation is such that brighter GCs are redder than their fainter counterparts. For the single GC systems of M87 and M60, we find similar correlations; M49 does not appear to show a significant trend. There is no correlation between (g − z) and Mz for GCs belonging to the red subpopulation. The correlation g ≡ d(g−z) dg for the blue subpopulation is much weaker than z. Using Monte Carlo simulations, we attribute this finding to the fact that the blue subpopulation in Mg extends to higher luminosities than does the red subpopulation, which biases the KMM fit results. The highly significant correlation between color and Mz, however, is a real effect: this conclusion is supported by biweight fits to the same color distributions. We identify two environmental dependencies which influence the derived color-magnitude relation: (1) the slope of the color-magnitude relation decreases in significance with decreasing galaxy luminosity, although it remains detectable over the full luminosity range of our sample; and (2) the slope is stronger for GC populations located at smaller galactocentric distances. These characteristics suggest that the observed trend is, at least partially, shaped by external agents. We examine several physical mechanisms that might give rise to the observed color-magnitude relation including: (1) presence of contaminants like super-clusters, stripped galactic nuclei, or ultra-compact dwarfs; (2) accretion of GCs from low-mass galaxies; (3) stochastic effects; (4) the capture of field stars by individual GCs; and (5) GC self-enrichment. Although none of these scenarios offers a fully satisfactory explanation of the observations, we conclude that self-enrichment and field-star capture, or a combination of these processes, offer the most promising means of explaining our observations.
Contribution Of Stellar Tidal Disruptions To The X-Ray Luminosity Function Of Active Galaxies, Miloš Milosavljević, David Merritt, Luis C. Ho
Contribution Of Stellar Tidal Disruptions To The X-Ray Luminosity Function Of Active Galaxies, Miloš Milosavljević, David Merritt, Luis C. Ho
Articles
The luminosity function of active galactic nuclei has been measured down to luminosities ∼ 1042 ergs s-1 in the soft and hard X-rays. Some fraction of this activity is associated with the accretion of the material liberated by the tidal disruption of stars by massive black holes. We estimate the contribution to the X-ray luminosity function from the tidal disruption process. While the contribution depends on a number poorly known parameters, it appears that it can account for the majority of X-ray selected AGN with soft or hard Xray luminosities . 1043 - 1044 ergs s-1. If this is correct, …
A Fundamental Relation Between Compact Stellar Nuclei, Supermassive Black Holes, And Their Host Galaxies, Laura Ferrarese, Patrick Côté, Elena Dalla Bontà, David Merritt, Et Al.
A Fundamental Relation Between Compact Stellar Nuclei, Supermassive Black Holes, And Their Host Galaxies, Laura Ferrarese, Patrick Côté, Elena Dalla Bontà, David Merritt, Et Al.
Articles
Imaging surveys with the Hubble Space Telescope (HST) have shown that 50–80% of low- and intermediate-luminosity galaxies contain a compact stellar nucleus at their center, regardless of host galaxy morphological type. We combine HST imaging for early-type galaxies from the ACS Virgo Cluster Survey with ground-based long-slit spectra from KPNO to show that the masses of compact stellar nuclei in Virgo Cluster galaxies obey a tight correlation with the masses of the host galaxies. The same correlation is obeyed by the supermassive black holes (SBHs) found in predominantly massive galaxies. The compact stellar nuclei in the Local Group galaxies M33 …
The Acs Virgo Cluster Survey. Vi. Isophotal Analysis And The Structure Of Early-Type Galaxies, Laura Ferrarese, Patrick Côté, Andrés Jordán, Eric W. Peng, John P. Blakeslee, Slawomir Piatek, Simona Mei, David Merritt, Miloš Milosavljević, John L. Tonry, Michael J. West
The Acs Virgo Cluster Survey. Vi. Isophotal Analysis And The Structure Of Early-Type Galaxies, Laura Ferrarese, Patrick Côté, Andrés Jordán, Eric W. Peng, John P. Blakeslee, Slawomir Piatek, Simona Mei, David Merritt, Miloš Milosavljević, John L. Tonry, Michael J. West
Articles
We present a detailed analysis of the morphology, isophotal parameters and surface brightness profiles for 100 early-type members of the Virgo Cluster, from dwarfs (MB = −15.1 mag) to giants (MB = −21.8 mag). Each galaxy has been imaged in two filters, closely resembling the Sloan g and z passbands, using the Advanced Camera for Surveys on board the Hubble Space Telescope. Dust and complex morphological structures are common. Dust is detected in as many as 18, preferentially bright, galaxies. The incidence rate in the 26 galaxies brighter than BT = 12.15 mag, which form a magnitude limited sample, is …
The Acs Virgo Cluster Survey. Viii. The Nuclei Of Early-Type Galaxies, Patrick Côté, Slawomir Piatek, Laura Ferrarese, Andrés Jordán, David Merritt, Eric W. Peng, Monica Haşegan, John P. Blakeslee, Simona Mei, Michael J. West, Miloš Milosavljević, John L. Tonry
The Acs Virgo Cluster Survey. Viii. The Nuclei Of Early-Type Galaxies, Patrick Côté, Slawomir Piatek, Laura Ferrarese, Andrés Jordán, David Merritt, Eric W. Peng, Monica Haşegan, John P. Blakeslee, Simona Mei, Michael J. West, Miloš Milosavljević, John L. Tonry
Articles
The ACS Virgo Cluster Survey is a Hubble Space Telescope program to obtain high-resolution imaging, in widely separated bandpasses (F475W ≈ g and F850LP ≈ z), for 100 early-type members of the Virgo Cluster, spanning a range of ≈ 460 in blue luminosity. We use this large, homogenous dataset to examine the innermost structure of these galaxies and to characterize the properties of their compact central nuclei. We present a sharp upward revision in the frequency of nucleation in early-type galaxies brighter than MB ≈ −15 (66 . fn . 82%) and show that ground-based surveys underestimated the number of …