HiZELS: a high-redshift survey of Hα emitters - I. The cosmic star formation rate and clustering at<i>z</i>= 2.23^★

Abstract

We present results from a near-infrared narrow-band survey of emission-line galaxies at z = 2.23, using the Wide Field Camera on the United Kingdom Infrared Telescope. The H2S1 narrow-band filter (lambdac = 2.121mum) we employ selects the Halpha emission-line redshifted to z = 2.23, and is thus suitable for selecting `typical' star-forming galaxies and active galactic nuclei at this epoch. The pilot study was undertaken in the well-studied Cosmological Evolution Survey field (COSMOS) and is already the largest near-infrared narrow-band survey at this depth, with a line flux limit of FHalpha ~ 10-16ergs-1cm-2 over 0.60deg2, probing ~220 × 103Mpc3 (comoving) down to a limiting star formation rate of ~30Msolaryr-1 (3sigma). In this paper, we present the results from our pilot survey and evaluate the Halpha luminosity function and estimate the clustering properties of Halpha emitters at z = 2.23 from 55 detected galaxies. The integrated luminosity function is used to estimate the volume-averaged star formation rate at z = 2.23: rhoSFR = 0.17+0.16-0.09Msolaryr-1Mpc-3 for LHalpha &gt; 1042ergs-1. For the first time, we use the Halpha star formation tracer to reliably constrain rhoSFR out to z = 2.23 demonstrating the rapid increase in rhoSFR out to this redshift as well as confirming the flattening in rhoSFR between z ~ 1 and 2. In addition to the luminosity distribution, we analyse the clustering properties of these galaxies. Using the two-point angular correlation function, omega(theta), we estimate a real-space correlation length of r0 = 4.2+0.4-0.2h-1Mpc. In comparison to models of clustering which take into account bias evolution, we estimate that these galaxies are hosted by dark matter haloes of mass Mhalo ~ 1012Msolar consistent with the progenitors of the Milky Way. Based on observations obtained with the Wide Field CAMera (WFCAM) on the United Kingdom Infrared Telescope (UKIRT). E-mail: [e-mail]