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.

star-formation

galaxies evolution

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

King Abdulaziz University

Max Planck-institutet

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 Astronomico Nacional

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 1-10 69

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

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