The FMOS-COSMOS Survey of Star-forming Galaxies at z ∼ 1.6. VI. Redshift and Emission-line Catalog and Basic Properties of Star-forming Galaxies

Abstract

We present a new data release from the Fiber Multi-Object Spectrograph (FMOS)-COSMOS survey that contains the measurements of the spectroscopic redshift and flux of rest-frame optical emission lines (Hα, [N II], [S II], Hβ, [O III]) for 1931 galaxies out of a total of 5484 objects observed over the 1.7 deg² COSMOS field. We obtained H- and J-band medium-resolution (R ∼ 3000) spectra with FMOS mounted on the Subaru telescope, which offers an in-fiber line flux sensitivity limit of ∼ 1× {10}^-17 {erg} {{{s}}}^-1 {cm}}^-2 for an on-source exposure time of 5 hr. The full sample contains the main population of star-forming galaxies at z ∼ 1.6 over the stellar mass range {10}^9.5≲ {M}_* /{M}_⊙ ≲ {10}^11.5, as well as other subsamples of infrared-luminous galaxies detected by Spitzer and Herschel at the same and lower (z ∼ 0.9) redshifts and X-ray-emitting galaxies detected by Chandra. This paper presents an overview of our spectral analyses, a description of the sample characteristics, and a summary of the basic properties of emission-line galaxies. We use the larger sample to redefine the stellar mass-star formation rate relation based on the dust-corrected Hα luminosity and find that the individual galaxies are better fit with a parameterization including a bending feature at M _* ≈ 10^10.2 M _⊙, and that the intrinsic scatter increases with M _* from 0.19 to 0.37 dex. We also confirm with higher confidence that the massive (M _* ≳ 10^10.5 M _⊙) galaxies are chemically mature as much as local galaxies with the same stellar masses, and that the massive galaxies have lower [S II]/Hα ratios for their [O III]/Hβ as compared to local galaxies, which is indicative of enhancement in the ionization parameter.