Furuya, Ray S. and Kitamura, Yoshimi and Shinnaga, Hiroki (2009) Spectroscopic Evidence for Gas Infall in GF 9-2. Astrophysical Journal Letters, 692 (2). L96-L99. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:FURapjl09
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We present spectroscopic evidence for the infall motion of gas in the natal cloud core harboring an extremely young low-mass protostar GF 9-2. We previously discussed that the ongoing collapse of the GF 9-2 core has agreement with the Larson-Penston-Hunter (LPH) theoretical solution for the gravitational collapse of a core. To discuss the gas infall on firmer ground, we have carried out on-the-fly mapping observations of the HCO+ (1-0) line using the Nobeyama 45 m telescope equipped with the 25 Beam Array Receiver System. Furthermore, we observed the HCN (1-0) line with the 45 m telescope, and the HCO+ (3-2) line with the Caltech Submillimeter Observatory 10.4 m telescope. The optically thick HCO+ and HCN lines show blueskewed profiles whose deepest absorptions are seen at the peak velocity of optically thin lines, i.e., the systemic velocity of the cloud, indicating the presence of gas infall toward the central protostar. We compared the observed HCO+ line profiles with model ones by solving the radiative transfer in the core under LTE assumption. We found that the core gas has a constant infall velocity of ~0.5 km s^–1 in the central region, leading to a mass accretion rate of 2.5 × 10^–5 M☉ yr^–1. Consequently, we confirm that the gas infall in the GF 9-2 core is consistent with the LPH solution.
|Additional Information:||© 2009. The American Astronomical Society. Received 2008 September 13; accepted 2009 January 6; published 2009 February 3. Print publication: Issue 2 (2009 February 20). R.S.F. gratefully acknowledges Thomas A. Bell, Thomas G. Phillips, and Ruisheng Peng for their generous help during the CSO observations. The authors sincerely thank Thomas A. Bell for a critical reading of the manuscript at the final stage of preparation. This work is partially supported by Grant-in-Aids from the Ministry of Education, Culture, Sports, Science and Technology of Japan (No. 19204020 and No. 20740113). The Nobeyama Radio Observatory is a branch of the National Astronomical Observatory of Japan, National Institutes of Natural Sciences. The Caltech Submillimeter Observatory is operated by the California Institute of Technology under the grant from the US National Science Foundation (AST 05-40882). Facilities: Nobeyama 45 m telescope, Caltech Submillimeter Observatory 10.4 m telescope|
|Subject Keywords:||ISM: clouds; ISM: evolution; ISM: individual (GF 9-2, L 1082); ISM: molecules; stars: formation; stars: pre-main sequence|
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|Deposited By:||Archive Administrator|
|Deposited On:||09 Feb 2009 20:52|
|Last Modified:||26 Dec 2012 10:48|
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