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Dense Gas Tracers and Star Formation Laws in Active Galaxies: APEX Survey of HCN J = 4 → 3, HCO^+ J = 4 → 3, and CS J=7 → 6

Zhang, Zhi-Yu and Gao, Yu and Henkel, Christian and Zhao, Yinghe and Wang, Junzhi and Menten, Karl M. and Güsten, Rolf (2014) Dense Gas Tracers and Star Formation Laws in Active Galaxies: APEX Survey of HCN J = 4 → 3, HCO^+ J = 4 → 3, and CS J=7 → 6. Astrophysical Journal Letters, 784 (2). Art. No. L31. ISSN 2041-8205. doi:10.1088/2041-8205/784/2/L31.

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We report HCN J = 4 → 3, HCO^+ J = 4 → 3, and CS J = 7 → 6 observations in 20 nearby star-forming galaxies with the Atacama Pathfinder EXperiment 12 m telescope. Combined with four HCN, three HCO^+, and four CS detections from the literature, we probe the empirical link between the luminosity of molecular gas L'_gas and that of infrared emission (L_(IR), up to the highest gas densities (~10^6 cm^(–3)) that have been probed so far. For nearby galaxies with large radii, we measure the IR luminosity within the submillimeter beam size (14"-18") to match the molecular emission. We find linear slopes for L'_(CSJ=7-6)-L_(IR) and L'_(HCNJ=4-3)-L_(IR), and a slightly super-linear slope for L'_(HCO^+J=4-3)-L_(IR). The correlation of L'_(CSJ=7-6)-L_(IR) even extends over eight orders of luminosity magnitude down to Galactic dense cores, with a fit of log(L_(IR)) =1.00(± 0.01)×log L'_(CSJ=7-6) + 4.03(± 0.04). Such linear correlations appear to hold for all densities >10^4 cm^(–3), and indicate that star formation rate is not related to the free-fall timescale for dense molecular gas.

Item Type:Article
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URLURL TypeDescription
Zhang, Zhi-Yu0000-0002-7299-2876
Gao, Yu0000-0003-0007-2197
Zhao, Yinghe0000-0002-9128-818X
Menten, Karl M.0000-0001-6459-0669
Additional Information:© 2014 American Astronomical Society. Received 2013 November 26; accepted 2014 February 4; published 2014 March 14. We are grateful to the MPIfR team and the APEX staff for their help and support during and after the observations. We also thank the anonymous referee for very useful comments and suggestions which improved the quality of the paper. Z.Z. thanks Padelis Papadopoulos, Thomas Greve, and Daizhong Liu for their constructive suggestions. This work is partially supported by NSFC grant Nos. 11173059 and 11390373, and CAS No. XDB09000000. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
Funding AgencyGrant Number
National Science Foundation of China (NSFC)11173059
National Science Foundation of China (NSFC)11390373
Jet Propulsion LaboratoryUNSPECIFIED
Subject Keywords: galaxies: evolution; galaxies: ISM; infrared: galaxies; ISM: molecules; radio lines: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20140520-101800898
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Official Citation:Dense Gas Tracers and Star Formation Laws in Active Galaxies: APEX Survey of HCN J = 4 → 3, HCO+ J = 4 → 3, and CS J = 7 → 6 Zhi-Yu Zhang (張智昱) et al. 2014 ApJ 784 L31
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45843
Deposited By: Ruth Sustaita
Deposited On:22 May 2014 17:50
Last Modified:10 Nov 2021 17:17

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