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Excitation Mechanisms for HCN (1-0) and HCO+ (1-0) in Galaxies from the Great Observatories All-sky LIRG Survey

Privon, G. C. and Herrero-Illana, R. and Evans, A. S. and Iwasawa, K. and Pérez-Torres, M. A. and Armus, L. and Díaz-Santos, T. and Murphy, E. J. and Stierwalt, S. and Aalto, S. and Mazzarella, J. M. and Barcos-Muñoz, L. and Borish, H. J. and Inami, H. and Kim, D.-C. and Treister, E. and Surace, J. A. and Lord, S. and Conway, J. and Frayer, D. T. and Alberdi, A. (2015) Excitation Mechanisms for HCN (1-0) and HCO+ (1-0) in Galaxies from the Great Observatories All-sky LIRG Survey. Astrophysical Journal, 814 (1). Art. No. 39. ISSN 0004-637X.

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We present new Institut de Radioastronomie Millimétrique (IRAM) 30 m spectroscopic observations of the ~88 GHz band, including emission from the CCH (N = 1 → 0) multiplet, HCN (J = 1 → 0), HCO^+ (J = 1 → 0), and HNC(J = 1 → 0), for a sample of 58 local luminous and ultraluminous infrared galaxies from the Great Observatories All-sky LIRG Survey (GOALS). By combining our new IRAM data with literature data and Spitzer/IRS spectroscopy, we study the correspondence between these putative tracers of dense gas and the relative contribution of active galactic nuclei (AGNs) and star formation to the mid-infrared luminosity of each system. We find the HCN (1–0) emission to be enhanced in AGN-dominated systems (〈L'_(HCN(1-0))/L'_(HCN(1-0)^+(1-0)〉 =1.84), compared to composite and starburst-dominated systems 〈L'_(HCN(1-0))/L'_(HCN(1-0)^+(1-0)〉 = 1.14, and 0.88, respectively). However, some composite and starburst systems have 〈L'_(HCN(1-0))/L'_(HCN(1-0)^+(1-0)〉 ratios comparable to those of AGNs, indicating that enhanced HCN emission is not uniquely associated with energetically dominant AGNs. After removing AGN-dominated systems from the sample, we find a linear relationship (within the uncertainties) between log10 〈L'_(HCN(1-0))/L'_(HCN(1-0)^+(1-0)〉 and log10(L_(IR)), consistent with most previous findings. L'_(HCN(1-0))/L_(IR), typically interpreted as the dense-gas depletion time, appears to have no systematic trend with LIR for our sample of luminous and ultraluminous infrared galaxies, and has significant scatter. The galaxy-integrated L'_(HCN(1-0)) and L'_(HCN^+(1-0)) emission do not appear to have a simple interpretation in terms of the AGN dominance or the star formation rate, and are likely determined by multiple processes, including density and radiative effects.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Privon, G. C.0000-0003-3474-1125
Iwasawa, K.0000-0002-4923-3281
Díaz-Santos, T.0000-0003-0699-6083
Murphy, E. J.0000-0001-7089-7325
Mazzarella, J. M.0000-0002-8204-8619
Barcos-Muñoz, L.0000-0003-0057-8892
Surace, J. A.0000-0001-7291-0087
Additional Information:© 2015 The American Astronomical Society. Received 2015 January 28; accepted 2015 September 23; published 2015 November 16. We thank the anonymous referee for their careful reading of our manuscript and for their helpful comments and suggestions, which improved the paper. G.C.P. and A.S.E. were supported by the NSF grant AST 1109475, and by NASA through grants HST-GO10592.01-A and HST-GO11196.01-A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5–26555. G.C.P. and E.T. were supported by the CONICYT Anillo project ACT1101 (EMBIGGEN). G.C.P. was also supported by a Visiting Graduate Research Fellowship at the Infrared Processing and Analysis Center/Caltech and by a FONDECYT Postdoctoral Fellowship (No. 3150361). This work was supported in part by National Science Foundation grant No. PHYS-1066293 and the hospitality of the Aspen Center for Physics. G.C.P. acknowledges the hospitality of the National Socio-environmental Synthesis Center (SESYNC), where portions of this manuscript were written. A.S.E. was also supported by the Taiwan, R.O.C. Ministry of Science and technology grant MoST 102-2119-M-001-MY3. K.I. acknowledges support by the Spanish MINECO under grant AYA2013-47447-C3–2-P and MDM-2014–0369 of ICCUB (Unidad de Excelencia "María de Maeztu"). R.H.I., M.A.P.T., and A. A. also acknowledge support from the Spanish MINECO through grant AYA2012-38491-C02-02. E.T. was also supported by the Center of Excellence in Astrophysics and Associated Technologies (PFB 06) and by the FONDECYT regular grant 1120061. 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. This research also made use of Astropy, a community-developed core Python package for Astronomy (The Astropy Collaboration et al. 2013), the cubehelix python library23 , and NASA's Astrophysics Data System. The Spitzer Space Telescope is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. G.C.P. thanks Ina Evans for a critique of the comments of an earlier version of this manuscript. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. T.D.S. acknowledges support from ALMA-CONICYT project 31130005 and FONDECYT project 1151239. Facility: IRAM:30m - Institute de Radioastronomie Millimetrique 30 meter telescope (EMIR - , WIMA - , FTS - Faulkes Telescope South).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)ACT 1101
Infrared Processing and Analysis Center (IPAC)UNSPECIFIED
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)3150361
Ministry of Science and Technology (Taipei)102-2119-M-001-MY3
Ministerio de Economía y Competitividad (MINECO)AYA2013- 47447-C3–2-P
Ministerio de Economía y Competitividad (MINECO)MDM-2014–0369
Ministerio de Economía y Competitividad (MINECO)AYA2012-38491-C02-02
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1120061
Fondo ALMA-CONICYT31130005
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1151239
Subject Keywords:galaxies: active; galaxies: ISM; galaxies: starburst
Record Number:CaltechAUTHORS:20160106-143303015
Persistent URL:
Official Citation:G. C. Privon et al 2015 ApJ 814 39
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63434
Deposited By: Ruth Sustaita
Deposited On:07 Jan 2016 00:56
Last Modified:02 Nov 2017 21:19

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