[Previous] | [Session 17] | [Next]
S. Bowyer (Space Sciences Laboratory, Univ. of California, Berkeley)
Observations with EUVE have shown that some clusters of galaxies produce intense EUV emission. Some of the more notable suggestions as to the source of this radiation include a "warm" inter-cluster medium which, if present, would constitute the major baryonic component of the universe; inverse Compton scattering of cosmic microwave background photons by cluster cosmic rays; synchrotron emission associated with relativistic jets; and cascading shocks from sub-cluster merging. The problems with many previous analyses of diffuse EUV cluster emission will be described and the proper analysis procedures justified. Some of the suggested source mechanisms are not supported by the data when it is analyzed correctly, and the remainder have serious limitations and/or appear to be ad hoc. Although initial work suggested that every cluster had an EUV excess, more recent analyses have shown that only the Virgo and Coma clusters have this excess. New data will be presented that show that the emission in both of these clusters is much more complex than previously supposed. Additional clusters have also been analyzed and the results will be presented.With one exception, none of these show any evidence of an EUV excess. The characteristics of the emission in the cluster that does show an excess are entirely different than the emission in either Coma or Virgo, thereby increasing the mystery of the EUV excess phenomena.