Star formation at z=1.47 from HiZELS: An H{\alpha}+[OII] double-blind study

TL;DR

This study uses a dual narrow-band survey to identify H-alpha and [OII] emitters at z=1.47, deriving star formation rates, luminosity functions, and dust extinction properties, thereby advancing understanding of galaxy evolution over the last 11 billion years.

Contribution

It presents the first wide, deep dual narrow-band survey at z=1.47, simultaneously measuring H-alpha and [OII] emitters, and calibrates dust extinction relations across cosmic time.

Findings

Star formation rate density at z=1.47 is ~0.16-0.17 M_sun/yr/Mpc^3.

H-alpha and [OII] luminosity functions show significant evolution since z~0.

Dust extinction correlates with stellar mass and SFR, with evolution over 11 Gyr.

Abstract

This paper presents the results from the first wide and deep dual narrow-band survey to select H-alpha (Ha) and [OII] line emitters at z=1.47+-0.02 (using matched narrow-band filters in the H and z' bands), exploiting synergies between the UKIRT and Subaru telescopes. The Ha survey at z=1.47 reaches a flux limit of ~7x10^-17 erg/s/cm^2 and detects ~200 Ha emitters over 0.7deg^2, while the much deeper [OII] survey reaches an effective flux of ~7x10^-18 erg/s/cm^2, detecting ~1400 z=1.47 [OII] emitters in a matched co-moving volume of ~2.5x10^5 Mpc^3. The combined survey results in the identification of 190 simultaneous Ha and [OII] emitters at z=1.47. Ha and [OII] luminosity functions are derived and both are shown to evolve significantly from z~0 in a consistent way. The star formation rate density of the Universe at z=1.47 is evaluated, with the Ha analysis yielding 0.16+-0.05 M_sun/yr/Mpc^3 and the [OII] analysis 0.17+-0.04 M_sun/yr/Mpc^3. The measurements are combined with other studies, providing a self-consistent measurement of the star formation history of the Universe over the last ~11Gyrs. By using a large comparison sample at z~0.1 (from the SDSS), [OII]/Ha line ratios are calibrated as probes of dust-extinction. Ha emitters at z~1.47 show on average 1 mag of extinction at Ha, similar to the SDSS sources at z~0. Although we find that dust extinction correlates with SFR, the relation evolves by about ~0.5 mag from z~1.5 to z~0, with z~0 relations over-predicting the dust extinction corrections at high-z by that amount. Stellar mass is found to be a much more fundamental extinction predictor, with the relation between mass and extinction being valid at both z~0 and z~1.5. Dust extinction corrections as a function of optical colours are also derived, offering simpler mechanisms for estimating extinction in moderately star-forming systems over the last ~9Gyrs [Abridged].