The clustering and evolution of Hα emitters at z ∼ 1 from HiZELS

Sobral, David and Best, Philip N. and Geach, James E. and Smail, Ian and Cirasuolo, Michele and Garn, Timothy and Dalton, Gavin B. and Kurk, Jaron (2010) The clustering and evolution of Hα emitters at z ∼ 1 from HiZELS. Monthly Notices of the Royal Astronomical Society, 404 (3). pp. 1551-1563. ISSN 0035-8711

Abstract

The clustering properties of a well-defined sample of 734 Hα emitters at z= 0.845 ± 0.015, obtained as part of the Hi-z Emission Line Survey, are investigated. The spatial correlation function of these Hα emitters is very well described by the power-law ξ = (r/r0)-1.8, with a real-space correlation, r0, of 2.7 ± 0.3 h-1 Mpc. The correlation length r0 increases strongly with Hα luminosity (LHα), from r0 ∼ 2 h-1 Mpc for the most quiescent galaxies [star formation rates (SFRs) of ∼4 M⊙ yr-1] up to r0 > 5 h-1 Mpc for the brightest galaxies in Hα. The correlation length also increases with increasing rest-frame K-band (MK) luminosity, but the r0-LHα correlation maintains its full statistical significance at fixed MK. At z = 0.84, star-forming galaxies classified as irregulars or mergers are much more clustered than discs and non-mergers, respectively; however, once the samples are matched in LHα and MK, the differences vanish, implying that the clustering is independent of morphological type at z ∼ 1 just as in the local Universe. The typical Hα emitters found at z = 0.84 reside in dark matter haloes of ≈1012 M⊙, but those with the highest SFRs reside in more massive haloes of ≈1013 M⊙. The results are compared with those of Hα surveys at different redshifts: although the break of the Hα luminosity function L*Hα evolves by a factor of ∼30 from z= 0.24 to 2.23, if the Hα luminosities at each redshift are scaled by L*Hα(z) then the correlation lengths indicate that, independently of cosmic time, galaxies with the same (LHα)/L*Hα(z) are found in dark matter haloes of similar masses. This not only confirms that the star formation efficiency in high redshift haloes is higher than locally but also suggests a fundamental connection between the strong negative evolution of L*Hα since z = 2.23 and the quenching of star formation in galaxies residing within dark matter haloes significantly more massive than 1012 M⊙ at any given epoch.