paper

The Bright and Dark Sides of High-Redshift starburst galaxies from {\it Herschel} and {\it Subaru} observations

arXiv:1703.04801 · doi:10.3847/2041-8213/aa66c9

Abstract

We present rest-frame optical spectra from the FMOS-COSMOS survey of twelve \textit{Herschel} starburst galaxies, with Star Formation Rate (SFR) elevated by 8, on average, above the star-forming Main Sequence (MS). Comparing the H to IR luminosity ratio and the Balmer Decrement we find that the optically-thin regions of the sources contain on average only percent of the total SFR whereas percent comes from an extremely obscured component which is revealed only by far-IR observations and is optically-thick even in H. We measure the [NII]/H ratio, suggesting that the less obscured regions have a metal content similar to that of the MS population at the same stellar masses and redshifts. However, our objects appear to be metal-rich outliers from the metallicity-SFR anticorrelation observed at fixed stellar mass for the MS population. The [SII]/[SII] ratio from the average spectrum indicates an electron density , larger than what estimated for MS galaxies but only at the 1.5 level. Our results provide supporting evidence that high- MS outliers are the analogous of local ULIRGs, and are consistent with a major merger origin for the starburst event.

arXiv comment6 pages, 4 figures, Accepted for publication in ApJ Letters

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