HIGH-LYING OH ABSORPTION, [C II] DEFICITS, AND EXTREME LFIR/MH2 RATIOS IN GALAXIES
Artikel i vetenskaplig tidskrift, 2015

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 mu m.3/2 J = 9/2-7/2 line (Weq(OH65)) with lower level energy Elow 300 K, is anticorrelated with the [Cii] 158 mu m line to far-infrared luminosity ratio, and correlated with the far-infrared luminosity per unit gas mass and with the 60-to-100 mu m far-infrared color. While all sources are in the active LIR/MH2 > 50L /M mode as derived from previous CO line studies, the OH65 absorption shows a bimodal distribution with a discontinuity at LFIR/MH2 100L /M . In the most buried sources, OH65 probes material partially responsible for the silicate 9.7 mu m absorption. Combined with observations of the OH 71 mu m.1/2 J = 7/2-5/2 doublet (Elow 415 K), radiative transfer models characterized by the equivalent dust temperature, Tdust, and the continuum optical depth at 100 mu m, t100, indicate that strong [C ii] 158 mu m deficits are associated with far-IR thick (t100 0.7, NH 1024 cm-2), warm (Tdust 60 K) structures where the OH 65 mu m absorption is produced, most likely in circumnuclear disks/tori/cocoons. With their high LFIR/MH2 ratios and columns, the presence of these structures is expected to give rise to strong [C ii] deficits. Weq(OH65) probes the fraction of infrared luminosity arising from these compact/warm environments, which is 30%-50% in sources with high Weq(OH65). Sources with high Weq(OH65) have surface densities of both LIR and MH2 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.

galaxies evolution

star-formation

Författare

E. Gonzalez-Alfonso

Universidad de Alcala

J. Fischer

Naval Research Laboratory

E. Sturm

Max Planck-institutet

J. Gracia-Carpio

Max Planck-institutet

S. Veilleux

University of Maryland

M. Melendez

University of Maryland

D. Lutz

Max Planck-institutet

A. Poglitsch

Max Planck-institutet

Susanne Aalto

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

Niklas Falstad

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

H. W. W. Spoon

Cornell University

D. Farrah

Virginia Polytechnic Institute and State University

A. Blasco

Universidad de Alcala

C. Henkel

Max Planck-institutet

King Abdulaziz University

A. Contursi

Max Planck-institutet

A. Verma

University of Oxford

M. Spaans

Rijksuniversiteit Groningen

H. A. Smith

Harvard-Smithsonian Center for Astrophysics

M. L. N. Ashby

Harvard-Smithsonian Center for Astrophysics

S. Hailey-Dunsheath

CalTech

S. G. Burillo

Observatorio Astronamico Nacional (OAN-IGN)

J. Martin-Pintado

Centro de Astrobiologia (CAB)

P. van der Werf

Universiteit Leiden

R. Meijerink

Universiteit Leiden

R. Genzel

Max Planck-institutet

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 800 1 1-10 69

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1088/0004-637X/800/1/69

Mer information

Senast uppdaterat

2018-09-06