Research on the redshift evolution of luminosity function and selection effect of GRBs

Abstract

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) τ , with τ = 3.5 +0.4 −0.2 and τ = 0.8 +0.1 −0.08 for two kind of LGRB rate models. The corresponding local GRB rates arė R(0) = 0.86 +0.11 −0.08 yr −1 Gpc −3 andṘ(0) = 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 −7 erg/ s/ cm 2 , but has no effect on the brighter GRBs.

Metallicity effects in long gamma-ray burst populations in a ΛCDM Universe

“…Secondly, we have specially chosen to contrast our results regarding the redshift distribution of LGRBs with the 95-percent complete sample of Salvaterra et al (2012). It has been shown that bright LGRB samples, such as the one used here, are largely unaffected by redshift selection effects (Tan & Wang, 2015). This high level of redshift completeness allows us to constrain our model parameters in an unbiased way.…”

The luminosity function and formation rate of a complete sample of long gamma-ray bursts

“…This collapsar model implies that the GRB formation rate should in principle trace the cosmic star formation rate (SFR; Totani 1997;Wijers et al 1998;Lamb & Reichart 2000;Porciani & Madau 2001;Piran 2004;Zhang & Mészáros 2004;Zhang 2007). However, the Swif t observations seem to indicate that the GRB rate does not closely follow the ⋆ E-mail: gxlan@pmo.ac.cn (GXL) † E-mail: zhd@pmo.ac.cn (ZHD) ‡ E-mail: jjwei@pmo.ac.cn (JJW) § E-mail: xfwu@pmo.ac.cn (XFW) SFR but is actually enhanced by some unknown mechanisms at high-z (Daigne et al 2006;Guetta & Piran 2007; Le & Dermer 2007;Salvaterra & Chincarini 2007;Kistler et al 2008Kistler et al , 2009Li 2008;Yüksel et al 2008;Salvaterra et al 2009Salvaterra et al , 2012Campisi et al 2010;Qin et al 2010;Wanderman & Piran 2010;Cao et al 2011;Virgili et al 2011;Elliott et al 2012;Lu et al 2012;Robertson & Ellis 2012;Tan et al 2013;Wang 2013;Wei et al 2014;Tan & Wang 2015;Deng et al 2016;Wei & Wu 2017;Paul 2018). 1 Several evolution models have been proposed to explain the observed enhancement, such as 1 Using the C − statistical method proposed by Lynden-Bell (1971), Pescalli et al (2015) and Yu et al (2015) found a relative excess of the GRB formation rate with respect to the SFR at low redshifts.…”

Gamma-ray burst cosmology: Hubble diagram and star formation history

“…48 In order to explain the observed discrepancy, several possible mechanisms have been proposed, including cosmic metallicity evolution, 61,62 stellar initial mass function evolution, 63,64 and luminosity function evolution. 55,58,65,66 Of course, if we knew the mechanism responsible for the discrepancy between the GRB rate and the SFR, we could set a severe limit on the high-z SFR using the GRB data alone.…”

“…Many possible interpretations of the high-z GRB rate excess have been introduced, such as the GRB rate density evolution, 48,49 the cosmic metallicity evolution, 61,62 an evolving stellar initial mass function, 63,64 and an evolution in the break of luminosity function. 55,58,65,66 Nevertheless, it should be underlined that the exception on the LGRB rate relates strongly to the SFR models we adopted. With different star formation history models, the results on the difference between the LGRB rate and the SFR could change on some level.…”