AAS 200th meeting, Albuquerque, NM, June 2002
Session 73. Interim Stellar Materials: Gas, Dust and Clouds
Display, Thursday, June 6, 2002, 9:20am-4:00pm, SW Exhibit Hall

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[73.03] The Critical Ionization Velocity Signature Manifested in Interstellar Neutral Hydrogen Emission Profile Structure

G. L. Verschuur (Physics Department, University of Memphis)

A Gaussian decomposition of all the weak (<10 K peak) interstellar neutral hydrogen emission profiles in the Leiden-Greenbank, sidelobe-corrected, All-Sky Survey between \midb\mid =40\deg & 80\deg has been performed. The results confirm the existence of three primary families of linewidths with values of around 34, 13 and 6 km/s. These correspond to the critical ionization velocities for common atomic species, 34 km/s for helium, around 13 km/s for carbon, oxygen and nitrogen, and around 6 km/s for sodium and calcium. This discovery may be an indicator of the existence of helium in interstellar space. A general outline of the process by which the critical ionization velocity phenomenon stamps its signature onto the HI emission line profiles through the mediation of plasma waves is outlined. This work suggests that linewidths of HI emission profiles should not be interpreted as indicative of kinetic temperatures and hints at explanations for offset, parallel filaments of gas and dust as well as the odd case where spatially offset high-velocity gas features are morphologically similar to low velocity features containing dust and CO.

The author(s) of this abstract have provided an email address for comments about the abstract: gverschr@memphis.edu

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.