The Bottom Line

• ASCA PV phase observations of clusters show that...
  • In AGREEMENT with cooling flow theories we find low temperature emission lines in the spectra of the central regions of clusters of galaxies.

  • In AGREEMENT with previous results we find that the low temperature component must be absorbed.

  • In DISAGREEMENT with cooling flow theories we find that the lowest temperature emission lines observed are characteristic of temperatures in excess of 1 keV. We see no evidence for Fe XVII lines.

• HOWEVER, the cooling time of gas at kT = 1 keV is short and Fe XVII lines were observed by the Einstein FPCS from the Perseus cluster.

• SO, we surmise that the 0.5 - 1 keV spectra of cooling flows are a complicated mix of emission and absorption components which are not resolved by the ASCA SIS.

• (CAVEAT : This result is sensitive to the ionization balance calculations used in the plasma codes.)

• In addition we have shown that...
  • The ratio of the 4-2 to 3-2 transition strengths for Fe is overestimated in the plasma emission codes currently in general use.

  • Silicon is overabundant in the core of the Perseus Cluster with respect to other elements, in particular sulfur.