EINSTEIN OBSERVATIONS OF THE HYDRA-A CLUSTER AND THE EFFICIENCY OF GALAXY FORMATION IN GROUPS AND CLUSTERS

被引:156
作者
DAVID, LP
ARNAUD, KA
FORMAN, W
JONES, C
机构
[1] NASA/Goddard Space Flight Center, Greenbelt
[2] Harvard-Smithsonian Ctr. Astrophys., Cambridge, MA 02138
关键词
Galaxies : clustering; Galaxies : formation; Galaxies : intergalactic medium; Galaxies: X-rays;
D O I
10.1086/168812
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We have analyzed the Einstein imaging proportional counter (IPC) and monitor proportional counter (MPC) observations of the poor cluster of galaxies centered on the radio galaxy Hydra A. The X-ray properties include diffuse emission with a characteristic temperature of 4.5 keV extending to at least 1 Mpc and an X-ray luminosity of 4 × 1044 ergs s-1 between 0.5-4.5 keV (for H0 = 50 km s-1 Mpc-1). We find that the cooling time of the gas in the core is short (∼5 × 109 yr). From the surface brightness profile, we infer that the X-ray-emitting gas in the Hydra A cluster must be condensing out of the intracluster medium at a rate of ≈600 M⊙ yr-1 (neglecting possible effects of heating and thermal conduction). This is one of the largest mass deposition rates observed in a cluster of galaxies. From the observed gas and galaxy distributions, we have computed the ratio of gas to galaxy mass and find that within 0.75 Mpc, the gas mass is a factor of 4h50-3/2 times that of the galaxies. We compare the ratio of gas mass to stellar mass for a variety of systems and find that this ratio correlates with the gas temperature. We explore the implications of this correlation on the efficiency of galaxy formation.
引用
收藏
页码:32 / 40
页数:9
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