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Proposal Identification No.:

A2769

Date Received:

2012-Aug-30 15:06:14

Technical Page
Proposal Type: General Category: Sub-Category: Observation Category: Total Time Requested: Minimum Useful Time: Prop osal Title: ABSTRACT: Regular Astronomy Spectroscopy Galactic 80 Hours 1 hour

True HI column density of five ma jor giant molecular clouds

We showed in Lee et al. that the HI surface density of the atomic envelope associated with the Perseus molecular cloud is relatively constant. This could be explained with the equilibrium model for H2 formation whereby the observed HI saturation represents the shielding column necessary for the transition from atomic to molecular medium. However, an alternative explanation is the existence of high optical depth HI. While we have shown that this explanation does not hold in the case of Perseus, it is essential to investigate other Giant Molecular Clouds (GMCs) at different stages of chemical evolution. We are now investigating five GMCs covered by the GALFA-HI survey. To estimate the importance of the high optical depth HI we propose HI absorption observations in the direction of 80 radio continuum sources located behind these GMCs. We will derive the correction needed for the high HI column density and compare our findings with predictions from equilibrium and turbulent models.

Name Snezana Stanimirovic

Institution UW-Madison

E-mail sstanimi@astro.wisc.edu

Phone 6088901458

Student no

Remote Observing Request

Observer will travel to AO X Remote Observing In Absentia (instructions to operator)

Instrument Setup
L-wide Atmospheric Observation Instruments:

Sp ecial Equipment or setup:

none

RFI Considerations
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Frequency Ranges Planned
1420-1720 This proposal requires Iridium RFI protection at 1612 MHz between 10pm and 6am EST.

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