[142.15] A Sensitive Study of Absorption by Neutral Hydrogen and Molecular Material in Intermediate and High Velocity clouds.

AAS 205th Meeting, 9-13 January 2005
Session 142 Galactic Structure, Halo and High Velocity
Poster, Thursday, January 13, 2005, 9:20am-4:00pm, Exhibit Hall

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[142.15] A Sensitive Study of Absorption by Neutral Hydrogen and Molecular Material in Intermediate and High Velocity clouds.

C. Pantoja (University of Puerto Rico), M. Lebron, E. Muller (Arecibo Observatory)

We have conducted a sensitive study of the molecular and HI components in gas associated with selected high and intermediate velocity clouds. The Arecibo Telescope was used to measure absorption of bright continuum sources at the HI and H₂CO transitions, as well as to map the HI emission of a number of selected clouds. No molecular material was detected in any of the targets, to an rms of ~8 mK. Absorption by HVCs is uncommon and we show here two HI absorption measurements which were a product of this survey. We find that gas which can be convincingly associated with HVCs shows evidence for a warm and cool component, whereas the high velocity gas found in the periphery of the clouds is generally warm, thermally homogenous and unenriched.

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