Differential evolution of the UV luminosity function of Lyman break galaxies from z ∼ 5 to 3*

Abstract

We report the ultraviolet luminosity function (UVLF) of Lyman break galaxies at z∼ 5 derived from a deep and wide survey using the prime focus camera of the 8.2 m Subaru telescope (Suprime‐Cam). Target fields consist of two blank regions of the sky, namely, the region including the Hubble Deep Field‐North and the J0053+1234 region, and the total effective surveyed area is 1290 arcmin2. Applications of carefully determined colour selection criteria in V−Ic and Ic−z′ yield a detection of 853 z∼ 5 candidates with z′AB < 26.5 mag. The UVLF at z∼ 5 based on this sample shows no significant change in the number density of bright (L≳L*z=3) LBGs from that at z∼ 3, while there is a significant decline in the LF's faint end with increasing look‐back time. This result means that the evolution of the number densities is differential with UV luminosity: the number density of UV luminous objects remains almost constant from z∼ 5 to 3 (the cosmic age is about 1.2 to 2.1 Gyr) while the number density of fainter objects gradually increases with cosmic time. This trend becomes apparent thanks to the small uncertainties in number densities both in the bright and faint parts of LFs at different epochs that are made possible by the deep and wide surveys we use. We discuss the origins of this differential evolution of the UVLF along the cosmic time and suggest that our observational findings are consistent with the biased galaxy evolution scenario: a galaxy population hosted by massive dark haloes starts active star formation preferentially at early cosmic time, while less massive galaxies increase their number density later. We also calculated the UV luminosity density by integrating the UVLF and at z∼ 5 found it to be 38.8+6.7−4.1 per cent of that at z∼ 3 for the luminosity range L > 0.1L*z=3. By combining our results with those from the literature, we find that the cosmic UV luminosity density marks its peak at and then slowly declines towards higher redshift.

Evidence of a fast evolution of the UV luminosity function beyond redshift 6 from a deep HAWK-I survey of the GOODS-S field

“…Some authors (Sawicki & Thompson 2006;Iwata et al 2007) have argued that the most significant evolution in the UV LF happens at the faint end, others (Yoshida et al 2006;Bouwens et al , 2007 find that the most significant evolution is at the bright end, while Beckwith et al (2006) claim that the evolution is similar at the bright and faint ends. Other authors suggest compensating evolutions in LBG number density and characteristic luminosity, resulting in a nearly constant UV luminosity density Giavalisco et al 2004).…”

The star formation rate density and dust attenuation evolution over 12 Gyr with the VVDS surveys

“…3 and 5, we note the following. Some authors do not take into account the role of cosmic variance (e.g., Schiminovich et al 2005;Wilson et al 2002;Iwata et al 2007); or consider it negligible with respect to statistical uncertainties (e.g., Paltani et al 2007); or consider it negligible because of the large volume explored (e.g., van der Burg et al 2010, 4 deg 2 ); or mitigate its effects using several fields in different lines of sights, although generally these fields are much smaller than the VVDS2h field (e.g., Steidel et al 1999;Reddy & Steidel 2009); or the cosmic variance has been included as uncertainty in the LF normalisation (e.g., Bouwens et al 2007). We choose to compute it with the most conservative method (see above) and to include it in our comprehensive uncertainty on the LD.…”

The UV galaxy luminosity function atz = 3–5 from the CFHT Legacy Survey Deep fields

“…At z ∼ 5, Iwata et al (2007) reported the UV LF from a combination of HDF and Subaru images, totalling a survey area about 1/9 of ours. Oesch et al (2007) based their study on approximately 100 LBGs from very deep ACS and NICMOS imaging.…”