Publication Date:
2015-10-09
Description:
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 L b (1 + z ) , with $\tau =3.5^{+0.4}_{-0.2}$ and $0.8^{+0.1}_{-0.08}$ for two kinds of LGRB rate models. The corresponding local GRB rates are $\dot{R}(0)=0.86^{+0.11}_{-0.08} \,{\rm yr}^{-1}\,{\rm Gpc}^{-3}$ and $0.54^{+0.25}_{-0.07} \,{\rm yr}^{-1}\,{\rm Gpc}^{-3}$ , 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 – 7 erg s – 1 cm – 2 , but has no effect on the brighter GRBs.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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