ESA Science & Technology - GOODS-Herschel: an infrared main sequence for star-forming galaxies

Publication date: 14 September 2011

Authors: Elbaz, D., et al.

Journal: Astronomy & Astrophysics
Volume: 533
Page: A119
Year: 2011

Copyright: ESO

We present the deepest 100 to 500 micron far-infrared observations obtained with the Herschel Space Observatory as part of the GOODS-Herschel key program, and examine the infrared (IR) 3-500 micron spectral energy distributions (SEDs) of galaxies at 0 < z < 2.5, supplemented by a local reference sample from IRAS, ISO, Spitzer and AKARI data. We determine the projected star formation densities of local galaxies from their radio and mid-IR continuum sizes. We find that the ratio of total IR luminosity to rest-frame 8 micron luminosity, IR8 (=L^tot_IR/L₈), follows a Gaussian distribution centered on IR8=4 (sigma=1.6) and defines an IR main sequence for star-forming galaxies independent of redshift and luminosity. Outliers from this main sequence produce a tail skewed toward higher values of IR8. This minority population (<20%) is shown to consist of starbursts with compact projected star formation densities. IR8 can be used to separate galaxies with normal and extended modes of star formation from compact starbursts with high-IR8, high projected IR surface brightness (Sigma_IR>3×10¹⁰ L_Sunkpc^-2) and a high specific star formation rate (i.e., starbursts). The rest-frame, UV-2700 Angstrom size of these distant starbursts is typically half that of main sequence galaxies, supporting the correlation between star formation density and starburst activity that is measured for the local sample.
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