Hundred Thousand Degree Gas in the Virgo Cluster of Galaxies
  The physical relationship between low-excitation gas filaments at ~10^4 K,
seen in optical line emission, and diffuse X-ray emitting coronal gas at ~10^7
K in the centers of many galaxy clusters is not understood. It is unclear
whether the ~10^4 K filaments have cooled and condensed from the ambient hot
(~10^7 K) medium or have some other origin such as the infall of cold gas in a
merger, or the disturbance of an internal cool reservoir of gas by nuclear
activity. Observations of gas at intermediate temperatures (~10^5-10^6 K) can
potentially reveal whether the central massive galaxies are gaining cool gas
through condensation or losing it through conductive evaporation and hence
identify plausible scenarios for transport processes in galaxy cluster gas.
Here we present spectroscopic detection of ~10^5 K gas spatially associated
with the H-alpha filaments in a central cluster galaxy, M87 in the Virgo
Cluster. The measured emission-line fluxes from triply ionized carbon (CIV 1549
A) and singly ionized helium (HeII 1640 A) are consistent with a model in which
thermal conduction determines the interaction between hot and cold phases.
