Diffuse Extreme-Ultraviolet Emission from the Coma Cluster:
Evidence for Rapidly Cooling Gases at Submegakelvin Temperatures
Richard Lieu,
*
Jonathan P. D. Mittaz,
Stuart Bowyer,
Jeffrey O. Breen,
Felix J. Lockman,
Edward M. Murphy,
Chorng-yuan Hwang
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 
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
2 × 106 kelvin and the other at 8 × 105 kelvin. The latter phase cools rapidly and, in steady
state, would have produced cold matter with a mass of
1014 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.
R. 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.
*
To whom correspondence should be addressed. E-mail:
lieur{at}cspar.uah.edu
