Diffuse EUV Emission from Clusters of Galaxies
Abstract
Diffuse EUV emission has been detected in three clusters of galaxies: Virgo, Coma, and Abell 1795. This EUV emission is substantially more intense than expected from an extrapolation of the 10 to 30 keV X-ray emitting cluster gas observed with the Einstein and ROSAT satellites. Signatures of this "soft excess" are present in the lowest energy resolution band (the carbon band) of the ROSAT PSPC where it is typically a 20% effect. In the data taken with EUVE, however, the excess ranges from 70% to 600%. In the Virgo and Coma clusters the low energy emitting regions detected by EUVE and ROSAT are similar in size. However, the Abell cluster EUV emitting region is much larger than that seen by ROSAT, which provides new clues as to the character of this emission. The EUV emission has been interpreted as evidence for a "cool" gas with T ~0.5 to 1 x 106 K in these clusters, but this interpretation is controversial because gas at this temperature is near the peak of the cooling curve and hence is unstable. We present the EUV data and discuss some of the suggestions as to the source of this emission.
- Publication:
-
The Hot Universe
- Pub Date:
- 1998
- Bibcode:
- 1998IAUS..188..185B