2015MNRAS.454.1785T

We study the redshift evolution of the luminosity function (LF) and redshift selection effect of long gamma-ray bursts (LGRBs). The method is to fit the observed peak flux and redshift distributions, simultaneously. To account for the complex triggering algorithm of Swift, we use a flux triggering efficiency function. We find evidence supporting an evolving LF, where the break luminosity scales as Lb ∝ (1 + z)τ, with τ=3.5^+0.4_-0.2 and 0.8^+0.1_-0.08 for two kinds of LGRB rate models. The corresponding local GRB rates are {dot}R(0)=0.86^+0.11_-0.08  yr^-1 Gpc^-3 and 0.54^+0.25_-0.07  yr^-1 Gpc^-3, respectively. Furthermore, by comparing the redshift distribution between the observed one and our mocked one, we find that the redshift detection efficiency of the flux triggered GRBs decreases with redshift. Especially, a great number of GRBs miss their redshifts in the redshift range of 1 < z < 2.5, where `redshift desert' effect may be dominated. More interestingly, our results show that the `redshift desert' effect is mainly introduced by the dimmer GRBs, e.g. P < 10- 7ergs- 1cm- 2, but has no effect on the brighter GRBs.