The FMOS-COSMOS survey of star-forming galaxies at $z\sim 1.6$ 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, which contains the measurements of spectroscopic redshift and flux of rest-frame optical emission lines (H$\hat{I}\pm$, [NII], [SII], H${\hat{I}}^2$, [OIII]) for 1931 galaxies out of a total of 5484 objects observed over the 1.7 deg${}^2$ COSMOS field. We obtained $H$-band and $J$-band medium-resolution ($R\sim 3000$) spectra with FMOS mounted on the Subaru telescope, which offers an in-fiber line flux sensitivity limit of $\sim 1\times 10^{-17}\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{c}{\mathrm{m}}^{-2}$ for an on-source exposure time of five hours. The full sample contains the main population of star-forming galaxies at $z\sim 1.6$ over the stellar mass range $10^{9.5}\lesssim M_{\ast }/M_{\odot }\lesssim 10^{11.5}$, as well as other subsamples of infrared-luminous galaxies detected by Spitzer and Herschel at the same and lower ($z\sim 0.9$) 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 re-define the stellar mass--star formation rate relation based on the dust-corrected H$\hat{I}\pm$ luminosity, and find that the individual galaxies are better fit with a parametrization including a bending feature at $M_{\ast }\approx 10^{10.2}{M}_{\odot }$, and that the intrinsic scatter increases with $M_{\ast }$ from 0.19 to $0.37$ dex. We also confirm with higher confidence that the massive ($M_{\ast }\gtrsim 10^{10.5}{M}_{\odot }$) galaxies are chemically mature as much as local galaxies with the same stellar masses, and that the massive galaxies have lower [SII]/H$\hat{I}\pm$ ratios for their [OIII]/H${\hat{I}}^2$, as compared to local galaxies, which is indicative of enhancement in ionization parameter.

44 pages, submitted to ApJS. The emission-line catalog is now publicly available