Astrophys. J., 814, 39 (2015/November-3)
Excitation mechanisms for HCN (1-0) and HCO+ (1-0) in galaxies from the great observatories all-sky LIRG survey.
PRIVON G.C., HERRERO-ILLANA R., EVANS A.S., IWASAWA K., PEREZ-TORRES M.A., ARMUS L., DIAZ-SANTOS T., MURPHY E.J., STIERWALT S., AALTO S., MAZZARELLA J.M., BARCOS-MUNOZ L., BORISH H.J., INAMI H., KIM D.-C., TREISTER E., SURACE J.A., LORD S., CONWAY J., FRAYER D.T. and ALBERDI A.
Abstract (from CDS):
We present new Institut de Radioastronomie Millimétrique (IRAM) 30 m spectroscopic observations of the ∼88 GHz band, including emission from the multiplet, HCN (,, and, for a sample of 58 local luminous and ultraluminous infrared galaxies from the Great Observatories All-sky LIRG Survey (GOALS). By combining our new IRAM 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 (/), compared to composite and starburst-dominated systems (/ and 0.88, respectively). However, some composite and starburst systems have/ 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 log10() and log10(LIR), consistent with most previous findings./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 galaxy-integrated and 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
erratum vol. 835, art. 112 (2017)
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