The ALPINE-ALMA [C ii] survey: Investigation of 10 galaxies at z ∼4.5 with [O ii] and [C ii] line emission - ISM properties and [O ii]-SFR relation

We present 10 main-sequence ALPINE galaxies (log (M/M⊙) = 9.2-11.1 and SFR=23-190M⊙yr-1) at z ∼4.5 with optical [O ii] measurements from Keck/MOSFIRE spectroscopy and Subaru/MOIRCS narrow-band imaging. This is the largest such multiwavelength sample at these redshifts, combining various measurements in the ultraviolet, optical, and far-infrared including [C ii]158 μm line emission and dust continuum from ALMA and H α emission from Spitzer photometry. For the first time, this unique sample allows us to analyse the relation between [O ii] and total star-formation rate (SFR) and the interstellar medium (ISM) properties via [O ii]/[C ii] and [O ii]/H α luminosity ratios at z ∼4.5. The [O ii]-SFR relation at z ∼4.5 cannot be described using standard local descriptions, but is consistent with a metal-dependent relation assuming metallicities around 50 per cent solar. To explain the measured dust-corrected luminosity ratios of log (L[OII]/L[CII]) ∼ 0.98+0.21-0.22 and log (L[OII]/LHα) ∼ -0.22+...