Dense gas in luminous infrared galaxies
Journal article, 2008

Aims. Molecules that trace the high-density regions of the interstellar medium have been observed in (ultra-) luminous (far-) infrared galaxies, in order to initiate multiple-molecule multiple-transition studies to evaluate the physical and chemical environment of the nuclear medium and its response to the ongoing nuclear activity. Methods. The HCN(1-0), HNC(1-0), HCO+ (1-0), CN(1-0) and CN(2-1), CO(2-1), and CS(3-2) transitions were observed in sources covering three decades of infrared luminosity including sources with known OH megamaser activity. The data for the molecules that trace the high-density regions were augmented with data available in the literature. Results. The integrated emissions of high-density tracer molecules show a strong relation to the far-infrared luminosity. Ratios of integrated line luminosities were used for a first-order diagnosis of the integrated molecular environment of the evolving nuclear starbursts. Diagnostic diagrams display significant differentiation among the sources that relate to the initial conditions and the radiative excitation environment. Initial differentiation was introduced between the FUV radiation field in photon-dominated-regions and the X-ray field in X-ray-dominated-regions. The galaxies displaying OH megamaser activity have line ratios typical of photon-dominated regions.

infrared : galaxies

radio line : galaxies


galaxies : active

galaxies : starburst

ISM : molecules


W.A. Baan

Netherlands Institute for Radio Astronomy (ASTRON)

C. Henkel

Max Planck Inst Radioaston

A.F. Loenen

Kapteyn Astronomical Institute

Netherlands Institute for Radio Astronomy (ASTRON)

A. Baudry

University of Bordeaux

Tommy Wiklind

Chalmers, Department of Radio and Space Science, Radio Astronomy and Astrophysics

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 477 3 747-U73

Subject Categories

Astronomy, Astrophysics and Cosmology



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