TRACING THE GAS TO THE VIRIAL RADIUS (R{sub 100}) IN A FOSSIL GROUP

Journal Article · Tue Mar 20 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/748/1/11· OSTI ID:22016197

Humphrey, Philip J; Buote, David A; Gastaldello, Fabio ^[1]; Brighenti, Fabrizio ^[2]; Mathews, William G ^[3]

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1. Department of Physics and Astronomy, University of California at Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States)
2. Dipartimento di Astronomia, Universita di Bologna, via Ranzani 1, Bologna 40127 (Italy)
3. University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)

We present a Chandra, Suzaku, and ROSAT study of the hot intragroup medium (IGrM) of the relaxed fossil group/poor cluster RX J1159+5531. This group exhibits an advantageous combination of flat surface brightness profile, high luminosity, and optimal distance, allowing the gas to be detected out to the virial radius (R{sub vir}{identical_to} R{sub 108} = 1100 kpc) in a single Suzaku pointing, while the complementary Chandra data reveal a round morphology and relaxed IGrM image down to kpc scales. We measure the IGrM entropy profile over {approx}3 orders of magnitude in radius, including three data bins beyond {approx}0.5R{sub 200} that have good azimuthal coverage (>30%). We find no evidence that the profile flattens at large scales (>R{sub 500}), and when corrected for the enclosed gas fraction, the entropy profile is very close to the predictions from self-similar structure formation simulations, as seen in massive clusters. Within R{sub vir}, we measure a baryon fraction of 0.17 {+-} 0.02, consistent with the cosmological value. These results are in sharp contrast to the gas behavior at large scales recently reported in the Virgo and Perseus clusters and indicate that substantial gas clumping cannot be ubiquitous near R{sub vir}, at least in highly evolved (fossil) groups.

• OSTI ID: 22016197
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 748; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BARYONS
BRIGHTNESS
COMPUTERIZED SIMULATION
ENTROPY
LUMINOSITY
NONLUMINOUS MATTER
X-RAY GALAXIES