Warm H2 trails in molecular clouds: a close view at turbulence dissipation

Details Warm H2 trails in molecular clouds: a close view at turbulence dissipation Warm H2 trails in molecular clouds: a close view at turbulence dissipation

Mar 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008sptz.prop50490f&link_type=abstract

Spitzer Proposal ID #50490

Computer Science

Scientific paper

Unlike stars and many plasmas in the universe, gas in molecular clouds is a highly dissipative system. It is this property that allows turbulent clouds to form stars. Little is known on the detailed processes leading to turbulent dissipation. Where, how and at what rate does molecular cloud turbulence dissipate? The current paradigm is that it occurs fast, in shocks. But turbulent dissipation in clouds is mild, intermittent in space and time, and shear-layers also contribute. A statistical analysis of the velocity field of a large CO map in the Polaris molecular cloud, has allowed us to disclose a spectacular structure of large velocity-shear, extending over more than a parsec in the environment of two low-mass dense cores. We show that 25% of the turbulent energy in the field is dissipated in the 2.5% area where the shear is the largest. We show why the bulk of the dissipated energy is expected to be radiated in the pure rotational lines of H2 and rely on former detections of high HCO+ abundances in this structure to compute the expected H2 line intensity. We propose Spitzer IRS observations of the H2 pure rotational lines in that structure to test these theoretical expectations and the role of shear-layers in contributing to the turbulent dissipation. The Spitzer-IRS is ideally suited to this experiment since high sensitivity and spatial resolution at the arcsec scale are required and the IRS wavelength range covers the dominant cooling lines of the dissipation.

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