CaltechAUTHORS
Published February 10, 2015 | Version Submitted + Published
Journal Article Open

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

Creators

  • 1. ROR icon University of Alcalá
  • 2. ROR icon Max Planck Institute for Extraterrestrial Physics
  • 3. ROR icon University of Maryland, College Park
  • 4. ROR icon Chalmers University of Technology
  • 5. ROR icon Cornell University
  • 6. ROR icon Virginia Tech
  • 7. ROR icon Max Planck Institute for Radio Astronomy
  • 8. ROR icon University of Oxford
  • 9. ROR icon University of Groningen
  • 10. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 11. ROR icon California Institute of Technology
  • 12. ROR icon Spanish National Observatory
  • 13. ROR icon Spanish National Research Council
  • 14. ROR icon Leiden University

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.

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)

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Submitted - 1412.4694v1.pdf

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Additional details

Identifiers

Eprint ID
55790
Resolver ID
CaltechAUTHORS:20150316-124557171

Related works

Describes
http://arxiv.org/abs/1412.4694 (URL)

Funding

Bundesministerium für Verkehr, Innovation und Technologie (BMVIT)
ESA-PRODEX (Belgium)
Commissariat à l'Energie Atomique (CEA)
Deutsches Zentrum für Luft- und Raumfahrt (DLR)
Agenzia Spaziale Italiana (ASI)
Comisión Interministerial de Ciencia y Tecnología (CICYT)
Ministerio de Economía y Competitividad (MINECO)
AYA2010-21697-C05-0
Ministerio de Economía y Competitividad (MINECO)
FIS2012-39162-C06-01
NHSC/JPL RSA
1455432
NASA
NNX14AJ61G
Office of Naval Research (ONR)
NHSC/JPL
139807
NHSC/JPL
1456609
NHSC/JPL
1427277
NHSC/JPL
1454738
Istituto Nazionale di Astrofisica (INAF)
Centre National de la Recherche Scientifique (CNRS)
Ministerio de Ciencia Y Tecnologia (MCYT)

Dates

Created
2015-03-16
Created from EPrint's datestamp field
Updated
2021-11-10
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
Infrared Processing and Analysis Center (IPAC)