Infrared spectra of cooling flow galaxies

Abstract

We have taken K-band spectra covering seven cooling flow clusters. The spectra show many of the 1-0S transitions of molecular hydrogen, as well as some of the higher vibrational transitions, and some lines of ionized hydrogen. The line ratios allow us to conclude that the rotational states of the first excited vibrational state are in approximate local thermodynamic equilibrium (LTE), so that densities above 105 cm-3 are likely, but there is evidence that the higher vibrational states are not in LTE. The lack of pressure balance between the molecular gas and the ionized components emphasizes the need for dynamic models of the gas. The ratios of the ionized to molecular lines are relatively constant but lower than from starburst regions, indicating that alternative heating mechanisms are necessary.