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

G. C. Privon ; R. Herrero-Illana ; A. S. Evans ; K. Iwasawa ; M. A. Perez-Torres ; L. Armus ; T. Diaz-Santos ; E. J. Murphy ; S. Stierwalt ; Susanne Aalto (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; J. M. Mazzarella ; L. Barcos-Munoz ; H. J. Borish ; H. Inami ; D. C. Kim ; E. Treister ; J. A. Surace ; S. Lord ; John Conway (Institutionen för rymd- och geovetenskap, Onsala rymdobservatorium) ; D. T. Frayer ; A. Alberdi
Astrophysical Journal (0004-637X). Vol. 814 (2015), 1,
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: galaxies: active, galaxies: ISM, galaxies: starburst



Denna post skapades 2016-01-14. Senast ändrad 2016-01-26.
CPL Pubid: 230676

 

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