EXCITATION MECHANISMS FOR HCN(1-0) AND HCO+ (1-0) IN GALAXIES FROM THE GREAT OBSERVATORIES ALL-SKY LIRG SURVEY
Journal article, 2015

We present new Institut de Radioastronomie Millimetrique (TRAM) 30 m spectroscopic observations of the similar to 88 GHz band, including emission from the CCH (N = 1 -> 0) multiplet, HCN (J = 1 -> 0), HCO (J = 1 -> 0), and HNC (J = 1 -> 0), for a sample of 58 local luminous and ultraluminous infrared galaxies from the Great Observatories All-sky LIRG Survey (GOALS). By combining our new TRAM data with literature data and Spitzer /IRS spectroscopy, we study the correspondence between these putative tracers of dense gas and the relative contribution of active galactic nuclei (AGNs) and star formation to the mid-infrared luminosity of each system. We find the HCN (1-0) emission to be enhanced in AGN-dominated systems (L'(HCN(1 0))/ L'(HCO+(1-o))) = 1.84), compared to composite and starburst-dominated systems (L'HCN(1413/(1-0)) = 1.14, and 0.88, respectively). However, some composite and starburst systems have LH/ CN (1 0) /LH/ CO (1 0) ratios comparable to those of AGNs, indicating that enhanced HCN emission is not uniquely associated with energetically dominant AGNs. After removing AGN-dominated systems from the sample, we find a linear relationship (within the uncertainties) between logio(L'(HCN(1-0))) and log(10)(LIR), consistent with most previous findings. Lc N(1 0) /LIR, typically interpreted as the dense-gas depletion time, appears to have no systematic trend with LIR for our sample of luminous and ultraluminous infrared galaxies, and has significant scatter. The galaxyintegrated L'(HCN(1-0)) and L'(HCO+(1-0)) emission do not appear to have a simple interpretation in terms of the AGN dominance or the star formation rate, and are likely determined by multiple processes, including density and radiative effects.

galaxies: active

galaxies: ISM

galaxies: starburst

Author

G. Privon

University of Virginia

University of Concepcion

California Institute of Technology (Caltech)

R. Herrero-Illana

CSIC - Instituto de Astrofísica de Andalucía (IAA)

A. S. Evans

National Radio Astronomy Observatory

University of Virginia

K. Iwasawa

University of Barcelona

Miguel Angel Perez-Torres

CSIC - Instituto de Astrofísica de Andalucía (IAA)

L. Armus

Spitzer Science Center

T. Diaz-Santos

Spitzer Science Center

Universidad Diego Portales

E. J. Murphy

California Institute of Technology (Caltech)

S. Stierwalt

University of Virginia

Susanne Aalto

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

J. Mazzarella

California Institute of Technology (Caltech)

Loreto Barcos-Munoz

University of Virginia

H. J. Borish

University of Virginia

H. Inami

National Optical Astronomy Observatory

D. C. Kim

National Radio Astronomy Observatory

E. Treister

University of Concepcion

J. A. Surace

Spitzer Science Center

S. Lord

SETI Institute

John Conway

Chalmers, Earth and Space Sciences, Onsala Space Observatory

D. Frayer

National Radio Astronomy Observatory

Antxon Alberdi

CSIC - Instituto de Astrofísica de Andalucía (IAA)

Astrophysical Journal

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

Vol. 814 1 39

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.1088/0004-637X/814/1/39

More information

Latest update

4/13/2018