A Herschel Survey of the [N II] 205 μm Line in Local Luminous Infrared Galaxies: The [N II] 205 μm Emission as a Star Formation Rate Indicator

March 2013 • 2013ApJ...765L..13Z

Authors • Zhao, Yinghe • Lu, Nanyao • Xu, C. Kevin • Gao, Yu • Lord, S. • Howell, J. • Isaak, K. G. • Charmandaris, V. • Diaz-Santos, T. • Appleton, P. • Evans, A. • Iwasawa, K. • Leech, J. • Mazzarella, J. • Petric, A. O. • Sanders, D. B. • Schulz, B. • Surace, J. • van der Werf, P. P.

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.

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IPAC Authors
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Phil Appleton

Senior Scientist

Joe Mazzarella

Senior Scientist