GRBs Redshift Distribution Shape Properties as Confirmation of their Progenitors Population Non-uniformity

In the supposition of sources population uniformity the GRBs redshift distribution shape could similar ones for other objects with demonstrated or theoretically required uniform space allocation. The shape of redshift distribution for uniform sources set in our Metagalaxy defined by properties of space and cosmological parameters. Supernovae of Ia type were considered as populations with real uniform distributions on redshift because of it were used for definition of Ω and Λ or our Metagalaxy.Therefore, the GRB sources redshift distribution analysis allows us to investigate the uniformity of this population. The results of redshifts distribution investigation for GRB with defined duration from Swift/BAT registered subset (308 events) are discussed. The analysis of Swift/BAT GRBs subset duration distribution allows to conclude the difference of boundary between short and long events from value of 2 s obtained from CGRO/BATSE bursts catalogue. Durations of 1 s and 0.6 s more likely correspond to this separator point for Swift/BAT GRBs subset duration distributions without and with correction on redshift.Two long GRBs with known redshift subsets were analysed: one contains the events registered from the beginning of Swift/BAT operation up to the end of autumn, 2014 (273 bursts) and other was similar but up to the end of August, 2015 (284 events). The shapes of these distributions sufficiently differ from ones for SN Ia supernovae. Also the sufficient deficit of GRB with z∼2 was found during both subsets analysis. Moreover, this feature existence retain in the same redshift region even if the bursts with sources redshift defined using one of the methods (for example, afterglow absorption lines studying) included in the analysable subset. Such deficit was not observed in QSO redshift distribution and thereof it couldn’t explained as apparatus effects caused by some difficulties to measure z because of the lack of strong emission or absorption lines covered by optical spectrometers if object located at high z values. The occurrence of minimum in long GRBs redshift distribution allows to conclude non-uniformity of its progenitors population and existence at least two subclasses in long GRB class.The obtained results allow considering that the whole GRB subset with known redshifts usage as “standard candles” for various cosmological tests could be excluded. Before such analysis different GRB samples might be separated and then various subsets could be investigated separately just as short and long events.