FINDING FOSSIL GROUPS: OPTICAL IDENTIFICATION AND X-RAY CONFIRMATION
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Miller-2012-FINDING FOSSIL GROUP.pdf
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2.07 MB
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Author(s)
Rykoff, Eli S.
Dupke, Renato A.
Mendes de Oliveira, Claudia
Lopes de Oliveira, Raimundo
Proctor, Robert N.
Garmire, Gordon P.
Koester, Benjamin P.
McKay, Timothy A.
Miller, Eric D
Date Issued
February 2012
Journal
The Astrophysical Journal
Publisher
IOP Publishing
Citation
Miller, Eric D., Eli S. Rykoff, Renato A. Dupke, Claudia Mendes de Oliveira, Raimundo Lopes de Oliveira, Robert N. Proctor, Gordon P. Garmire, Benjamin P. Koester, and Timothy A. McKay. “FINDING FOSSIL GROUPS: OPTICAL IDENTIFICATION AND X-RAY CONFIRMATION.” The Astrophysical Journal 747, no. 2 (February 21, 2012): 94. © 2012 The American Astronomical Society
Version
Final published version
Abstract
We report the discovery of 12 new fossil groups (FGs) of galaxies, systems dominated by a single giant elliptical galaxy and cluster-scale gravitational potential, but lacking the population of bright galaxies typically seen in galaxy clusters. These FGs, selected from the maxBCG optical cluster catalog, were detected in snapshot observations with the Chandra X-ray Observatory. We detail the highly successful selection method, with an 80% success rate in identifying 12 FGs from our target sample of 15 candidates. For 11 of the systems, we determine the X-ray luminosity, temperature, and hydrostatic mass, which do not deviate significantly from expectations for normal systems, spanning a range typical of rich groups and poor clusters of galaxies. A small number of detected FGs are morphologically irregular, possibly due to past mergers, interaction of the intra-group medium with a central active galactic nucleus (AGN), or superposition of multiple massive halos. Two-thirds of the X-ray-detected FGs exhibit X-ray emission associated with the central brightest cluster galaxy (BCG), although we are unable to distinguish between AGN and extended thermal galaxy emission using the current data. This sample representing a large increase in the number of known FGs, will be invaluable for future planned observations to determine FG temperature, gas density, metal abundance, and mass distributions, and to compare to normal (non-fossil) systems. Finally, the presence of a population of galaxy-poor systems may bias mass function determinations that measure richness from galaxy counts. When used to constrain power spectrum normalization and Ω [subscript m] , these biased mass functions may in turn bias these results.
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.1088/0004-637x/747/2/94
