The Bright and Dark Sides of High-redshift Starburst Galaxies from Herschel and Subaru Observations

Author(s): A. Puglisi, Emanuele Daddi, Alvio Renzini, Christian Maier
Abstract: We present rest-frame optical spectra from the FMOS-COSMOS survey of 12 z ~ 1.6 Herschel starburst galaxies, with star formation rate (SFR) elevated by ×8, on average, above the star-forming main sequence (MS). Comparing the Hα to IR luminosity ratio and the Balmer decrement, we find that the optically thin regions of the sources contain on average only ~10% of the total SFR, whereas ~90% come from an extremely obscured component that is revealed only by far-IR observations and is optically thick even in Hα. We measure the [N II]6583/Hα 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 [S II]6732/[S II]6717 ratio from the average spectrum indicates an electron density n_e ~ 1100 cm^-3 , larger than what was estimated for MS galaxies but only at the 1.5σ level. Our results provide supporting evidence that high-z MS outliers are analogous of local ULIRGs and are consistent with a major-merger origin for the starburst event.
Organisation(s): Department of Astrophysics
External organisation(s): University of Padova, European Southern Observatory (Germany), Université Paris VII - Paris-Diderot, Osservatorio Astronomico
Journal: The Astrophysical journal Letters
Volume: 838
No. of pages: 6
ISSN: 2041-8205
DOI: https://doi.org/10.3847/2041-8213/aa66c9
Publication date: 04-2017
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/55a7ac51-4e86-4231-a5a6-eaf5f3dfe796

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