March 2013 • 2013ApJ...765L..13Z
Abstract • We present, for the first time, a statistical study of [N II] 205 μm line emission for a large sample of local luminous infrared galaxies using Herschel Spectral and Photometric Imaging Receiver Fourier Transform Spectrometer (SPIRE FTS) data. For our sample of galaxies, we investigate the correlation between the [N II] luminosity (L [N II]) and the total infrared luminosity (L IR), as well as the dependence of L [N II]/L IR ratio on L IR, far-infrared colors (IRAS f 60/f 100), and the [O III] 88 μm to [N II] luminosity ratio. We find that L [N II] correlates almost linearly with L IR for non-active galactic nucleus galaxies (all having L IR < 1012 L ⊙) in our sample, which implies that L [N II] can serve as a star formation rate tracer which is particularly useful for high-redshift galaxies that will be observed with forthcoming submillimeter spectroscopic facilities such as the Atacama Large Millimeter/submillimeter Array. Our analysis shows that the deviation from the mean L [N II]-L IR relation correlates with tracers of the ionization parameter, which suggests that the scatter in this relation is mainly due to the variations in the hardness, and/or ionization parameter, of the ambient galactic UV field among the sources in our sample.Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.