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Durham University

Department of Physics

Staff profile

Publication details for Professor Ian Smail

Khostovan, A.A., Sobral, D., Mobasher, B., Best, P.N., Smail, I., Stott, J.P., Hemmati, S. & Nayyeri, H. (2015). Evolution of the H β + [O III] and [O II] luminosity functions and the [O II] star formation history of the Universe up to z ∼ 5 from HiZELS. Monthly Notices of the Royal Astronomical Society 452(4): 3948-3968.

Author(s) from Durham


We investigate the evolution of the H β + [O iii] and [O ii] luminosity functions from z ∼ 0.8 to ∼5 in four redshift slices per emission line using data from the High-z Emission Line Survey (HiZELS). This is the first time that the H β + [O iii] and [O ii] luminosity functions have been studied at these redshifts in a self-consistent analysis. This is also the largest sample of [O ii] and H β + [O iii] emitters (3475 and 3298 emitters, respectively) in this redshift range, with large comoving volumes ∼1 × 106 Mpc−3 in two independent volumes (COSMOS and UDS), greatly reducing the effects of cosmic variance. The emitters were selected by a combination of photometric redshift and colour–colour selections, as well as spectroscopic follow-up, including recent spectroscopic observations using DEIMOS and MOSFIRE on the Keck Telescopes and FMOS on Subaru. We find a strong increase in L⋆ and a decrease in ϕ⋆ for both H β + [O iii] and [O ii] emitters. We derive the [O ii] star formation history of the Universe since z ∼ 5 and find that the cosmic star formation rate density (SFRD) rises from z ∼ 5 to ∼3 and then drops towards z ∼ 0. We also find that our star formation history is able to reproduce the evolution of the stellar mass density up to z ∼ 5 based only on a single tracer of star formation. When comparing the H β + [O iii] SFRDs to the [O ii] and H α SFRD measurements in the literature, we find that there is a remarkable agreement, suggesting that the H β + [O iii] sample is dominated by star-forming galaxies at high-z rather than AGNs.