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Proposal Identification No.:

A2673

Date Received:

2011-Oct-02 12:12:29

Technical Page
Proposal Type: General Category: Sub-Category: Observation Category: Total Time Requested: Minimum Useful Time: Regular Astronomy Spectroscopy Galactic 228 Hours 1 Hour

Prop osal Title: Reveal the Transition from Atomic to Molecular ISM - A Sensitive Survey of HI Absorption in Planck Cores ABSTRACT:
The transition from diffuse, atomic gas to dense, molecular gas is a key step in the life cycle of the ISM. The result of this transition sets the intial condition for star formation. The atomic ISM have been well studied by observing the HI 21cm line. The study of molecular ISM has been carried out mostly through tracers, especially CO. The transition phase, however, is unfriendly to either probe. We have studied this transition through HI narrow self-absorption (HINSA: Li and Goldsmith 2003). The analysis of HINSA provides a rare direct measurement of HI mixed with molecular gas and constrains the time scale of molecular cloud formation. In order to get a global picture of the HI-H2 transition in the Galaxy, we propose a sensitive, high spectral resolution HINSA survey of Planck cold cores. Combined with our CO survey, a systematic understanding will be achieved for the first time.

Name Di Li

Institution California Institude of Technology

E-mail dili@caltech.edu

Phone 8182926780

Student no

Remote Observing Request

X

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

Instrument Setup
ALFA Atmospheric Observation Instruments:

Sp ecial Equipment or setup:

none 1


RFI Considerations Frequency Ranges Planned
1225 - 1525

2