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Diffuse Extreme-Ultraviolet Emission from the Coma Cluster: Evidence for Rapidly Cooling Gases at Submegakelvin
1R. Lieu, Department of Physics, University of Alabama, Huntsville, AL 35899, USA. J. P. D. Mittaz, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK. S. Bowyer and C.-y. Hwang, Center for Extreme Ultraviolet Astrophysics, University of California, Berkeley, CA 94720, USA. J. O. Breen and E. M. Murphy, Astronomy Department, University of Virginia, Post Office Box 3818, Charlottesville, VA 22903, USA. F. J. Lockman, National Radio Astronomy Observatory, Green Bank, WV 24944, USA.
Abstract:
The central region of the Coma cluster of galaxies was observed in the energy band from 0.065 to 0.245 kiloelectron volts by the Deep Survey telescope aboard the Extreme Ultraviolet Explorer. A diffuse emission halo of angular diameter approximately 30 arc minutes was detected. The extreme-ultraviolet (EUV) emission level exceeds that expected from the x-ray temperature gas in Coma. This halo suggests the presence of two more phases in the emitting gas, one at a temperature of approximately 2 x 10(6) kelvin and the other at approximately 8 x 10(5) kelvin. The latter phase cools rapidly and, in steady state, would have produced cold matter with a mass of approximately 10(14) solar masses within the EUV halo. Although a similar EUV enhancement was discovered in the Virgo cluster, this detection in Coma applies to a noncooling flow system.