Abstract:
One interesting result from the cryogenic mission of the Spitzer Space telescope was the discovery of a class of extragalactic sources that exhibited powerful warm molecular hydrogen lines that are likely caused by powerful shocks and turbulence.  One example is the massive group-wide warm H2 emission extending over 55 x 35 sq. kpc in the Stephan’s Quintet compact group. I will discuss a new analysis of the excitation of the Spitzer warm molecular gas in the Quintet in terms of thermal and MHD shock modeling in this filament. Using additional deep observations of UV and far-IR cooling lines, and new CO observations, we are able to build up a complete picture of the heating and cooling in this multi-phase filament, including a direct measurement of the turbulent dissipation of mechanical energy in the gas, and how it relates to the observed kinematics.  I will review other examples of shocks and turbulent heating of H2 in the local universe, and its possible impact on star formation suppression in galaxies. Finally, I will speculate on how warm molecular gas observations may allow us to map kinetic energy dissipation from turbulence and shocks in gas at high redshift, perhaps even beyond the epoch of re-ionization. Such emission may be detectable with large far-IR/sub-mm space telescopes of the future.