NOAO >   Observing Info >   Approved Programs >   2009A-0454

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Proposal Information for 2009A-0454


PI: Takeshi Oka, University of Chicago, t-oka@uchicago.edu
Address: Astronomy Department, 5735 S. Ellis Avenue, Chicago, Illinois 60637, USA

CoI: Thomas R. Geballe, Gemini Observatory
CoI: Miwa Goto, Max-Planck Institute of Astronomy
CoI: Nick Indriolo, University of Illinois, Urbana Champaign
CoI: Benjamin J. McCall, University of Illinois, Urbana Champaign

Title: The physical extent of the diffuse gas in the Central Molecular Zone from \mathrmH_3^+ and CO spectroscopy

Abstract: We propose to use the Phoenix Spectrometer to observe H_3^+ and CO toward newly identified Galactic center sources in order to further characterize the diffuse cloud environment there. Our research has already identified a previously unrecognized but very extensive region of warm (T=200-300 K) and diffuse (n<=50 - 200 cm^-3) gas in the Central Molecular Zone (CMZ) of the Galactic center, mainly by using metastable H_3^+ R(3,3)^l absorption line. Although our probing of the CMZ has been based only on spectroscopy of IR sources within 30 pc of Sgr A*, circumstantial evidence suggests that the warm and diffuse gas pervades the entire CMZ. If correct, it would completely overturn previous understanding of the CMZ environment. Using newly identified IR sources suitable for spectroscopy of H_3^+ and CO we can now extend the study of the newly found gas from the vicinity of SgrA* (~ 30 pc) to a much wider region of the CMZ (~ 170 pc), an increase of ~50 in the angular area. Our extended investigation will reveal how the warm and diffuse clouds are distributed in the CMZ. We will obtain information on temperature, density, volume filling factor, and ionization rate of the diffuse CMZ gas. The extent and the nature of the cloud will in turn provide crucial information on the astrophysics in the core.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2009A-0454

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