Discovery of C IV Emission Filaments in M87

Abstract

Gas at intermediate temperatures between the hot X-ray-emitting coronal gas in galaxies at the centers of galaxy clusters and the much cooler optical line emitting filaments yields information on transport processes and plausible scenarios for the relationship between X-ray cool cores and other galactic phenomena such as mergers or the onset of an active galactic nucleus. Hitherto, detection of intermediate temperature gas has proven elusive. Here, we present FUV imaging of the "low excitation" emission filaments of M87 and show strong evidence for the presence of C IV 1549 Å emission which arises in gas at temperature ~10⁵ K co-located with Hα+[N II] emission from cooler ~10⁴ K gas. We infer that the hot and cool phases are in thermal communication, and show that quantitatively the emission strength is consistent with thermal conduction, which in turn may account for many of the observed characteristics of cool-core galaxy clusters.

Based on observations with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.