(SuzakuSuzaku) X-ray observations of the nearest non-cool core cluster, Antlia: dynamically young but with remarkably relaxed outskirts

Journal Article · Tue Sep 20 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/829/1/49· OSTI ID:22868655

Wong, Ka-Wah ^[1]; Irwin, Jimmy A. ^[2]; Wik, Daniel R. ^[3]; Sun, Ming ^[4]; Sarazin, Craig L. ^[5]; Fujita, Yutaka ^[6]

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1. Eureka Scientific, Inc., 2452 Delmer Street Suite 100, Oakland, CA 94602-3017 (United States)
2. Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487 (United States)
3. Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
4. Physics Department, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
5. Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States)
6. Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

We present the results of seven Suzaku mosaic observations (>200 ks in total) of the nearest non-cool core cluster, the Antlia Cluster (or Group), beyond its degree-scale virial radius in its eastern direction. The temperature is consistent with the scaled profiles of many other clusters. Its pressure follows the universal profile. The density slope in its outskirts is significantly steeper than that of the nearest cool core cluster (Virgo) with a similar temperature as Antlia, but shallower than those of the massive clusters. The entropy increases all the way out to R {sub 200}, which is consistent in value with the baseline model predicted by a gravity heating-only mechanism in the outskirts. Antlia is quite relaxed in this direction. However, the entropy inside ∼R {sub 500} is significantly higher than the baseline model, which is similar to many other nearby low mass clusters or groups. The enclosed gas-mass fraction does not exceed the cosmic value out to 1.3R{sub 200}. Thus, there is no evidence of significant gas clumping, electron-ion non-equipartition, or departure from the hydrostatic equilibrium approximation that are suggested to explain the entropy and gas fraction anomalies found in the outskirts of some massive clusters. We also present scaling relations for the gas fraction (f{sub gas,200}), entropy (K {sub 200}), and temperature (T {sub 500}) using 22 groups and clusters with published data in the literature. The enclosed baryon fraction at R {sub 200} is broadly consistent with the cosmic value. The power law slope of the K {sub 200}–T {sub 500} relation is 0.638 ± 0.205. The entropy deficit at R {sub 200} cannot be fully accounted for by the bias or deviation in the gas fraction.

• OSTI ID: 22868655
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 829; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BARYONS
DENSITY
ELECTRON-ION COLLISIONS
ENTROPY
EQUILIBRIUM
GALAXY CLUSTERS
GRAVITATION
HYDROSTATICS
INTERGALACTIC SPACE
MASS
UNIVERSE
X RADIATION
X-RAY GALAXIES