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High-lying OH Absorption, [C_(II)] Deficits, and Extreme L_(FIR)/M_(H2) Ratios in Galaxies

González-Alfonso, E and Fischer, J. and Sturm, E. and Graciá-Carpio, J. and Veilleux, S. and Meléndez, M. and Lutz, D. and Poglitsch, A. and Aalto, S. and Falstad, N. and Spoon, H. W. W. and Farrah, D. and Blasco, A. and Henkel, C. and Contursi, A. and Verma, A. and Spaans, M. and Smith, H. A. and Ashby, M. L. N. and Hailey-Dunsheath, S. and García-Burillo, S. and Martín-Pintado, J. and van der Werf, P. and Meijerink, R. and Genzel, R. (2015) High-lying OH Absorption, [C_(II)] Deficits, and Extreme L_(FIR)/M_(H2) Ratios in Galaxies. Astrophysical Journal, 800 (1). Art. No. 69. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20150316-124557171

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Abstract

Herschel/PACS observations of 29 local (ultra)luminous infrared galaxies, including both starburst and active galactic nucleus (AGN) dominated sources as diagnosed in the mid-infrared/optical, show that the equivalent width of the absorbing OH 65 μm Π_(3/2) J = 9/2-7/2 line (W_(eq)(OH65)) with lower level energy E_(low) ≈ 300 K, is anticorrelated with the [C II]158 μm line to far-infrared luminosity ratio, and correlated with the far-infrared luminosity per unit gas mass and with the 60-to-100 μm far-infrared color. While all sources are in the active L_(IR)/M_(H2) > 50L_☉/M_☉ mode as derived from previous CO line studies, the OH65 absorption shows a bimodal distribution with a discontinuity at L_(FIR)/M_(H2) ≈ 100 L_☉/M_☉. In the most buried sources, OH65 probes material partially responsible for the silicate 9.7 μm absorption. Combined with observations of the OH 71 μm Π_(1/2) J = 7/2-5/2 doublet (E_(low) ≈ 415 K), radiative transfer models characterized by the equivalent dust temperature, T_(dust), and the continuum optical depth at 100 μm, τ_(100), indicate that strong [C_(II)]158 μm deficits are associated with far-IR thick (τ_(100) ≳ 0.7, N_H ≳ 10^(24) cm^(–2)), warm (T_(dust) ≳ 60 K) structures where the OH 65 μm absorption is produced, most likely in circumnuclear disks/tori/cocoons. With their high L_(FIR)/M_(H2) ratios and columns, the presence of these structures is expected to give rise to strong [C_(II)] deficits. W_(eq)(OH65) probes the fraction of infrared luminosity arising from these compact/warm environments, which is ≳ 30%-50% in sources with high W_(eq)(OH65). Sources with high W_(eq)(OH65) have surface densities of both L_(IR) and M_(H2) higher than inferred from the half-light (CO or UV/optical) radius, tracing coherent structures that represent the most buried/active stage of (circum)nuclear starburst-AGN co-evolution.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/800/1/69DOIArticle
http://iopscience.iop.org/0004-637X/800/1/69/articlePublisherArticle
http://arxiv.org/abs/1412.4694arXivDiscussion Paper
ORCID:
AuthorORCID
Veilleux, S.0000-0002-3158-6820
Lutz, D.0000-0003-0291-9582
Spoon, H. W. W.0000-0002-8712-369X
Farrah, D.0000-0003-1748-2010
Ashby, M. L. N.0000-0002-3993-0745
Hailey-Dunsheath, S.0000-0002-8504-7988
van der Werf, P.0000-0001-5434-5942
Genzel, R.0000-0002-2767-9653
Additional Information:© 2015 American Astronomical Society. Received 2014 July 29; accepted 2014 December 14; published 2015 February 10. PACS has been developed by a consortium of institutes led by MPE (Germany) and including UVIE (Austria); KU Leuven, CSL, IMEC (Belgium); CEA, LAM (France); MPIA (Germany); INAFIFSI/OAA/OAP/OAT, LENS, SISSA (Italy); IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI/INAF (Italy), and CICYT/MCYT (Spain). E.G.-A. is a Research Associate at the Harvard-Smithsonian CfA, and thanks the Spanish Ministerio de Economía y Competitividad for support under projects AYA2010-21697-C05-0 and FIS2012-39162-C06-01. E.G.-A. and H.A.S. acknowledge partial support from NHSC/JPL RSA 1455432; H.A.S acknowledges NASA grant NNX14AJ61G. Basic research in IR astronomy at NRL is funded by the US-ONR; J.F. acknowledges support from NHSC/JPL subcontracts 139807 and 1456609. S.V. and M.M. acknowledge partial support from NHSC/JPL RSA 1427277 and 1454738. This research has made use of NASA’s Astrophysics Data System and of GILDAS (http://www.iram.fr/IRAMFR/GILDAS). Facility: Herschel (PACS)
Funders:
Funding AgencyGrant Number
Bundesministerium für Verkehr, Innovation und Technologie (BMVIT)UNSPECIFIED
ESA-PRODEX (Belgium)UNSPECIFIED
Commissariat à l’Energie Atomique (CEA)UNSPECIFIED
Deutsches Zentrum für Luft- und Raumfahrt (DLR)UNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Comisión Interministerial de Ciencia y Tecnología (CICYT)UNSPECIFIED
Ministerio de Economía y Competitividad (MINECO)AYA2010-21697-C05-0
Ministerio de Economía y Competitividad (MINECO)FIS2012-39162-C06-01
NHSC/JPL RSA1455432
NASANNX14AJ61G
Office of Naval Research (ONR)UNSPECIFIED
NHSC/JPL139807
NHSC/JPL1456609
NHSC/JPL1427277
NHSC/JPL1454738
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Ministerio de Ciencia Y Tecnologia (MCYT)UNSPECIFIED
Subject Keywords:galaxies: evolution; galaxies: ISM; infrared: galaxies; line: formation
Issue or Number:1
Record Number:CaltechAUTHORS:20150316-124557171
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150316-124557171
Official Citation:High-lying OH Absorption, [C II] Deficits, and Extreme L FIR/M H2 Ratios in Galaxies E. González-Alfonso et al. 2015 ApJ 800 69
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55790
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:16 Mar 2015 20:59
Last Modified:04 Nov 2019 04:26

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