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On the cosmological evolution of BL Lacs

A. Caccianiga·T. Maccacaro·A. Wolter·R. Della Ceca·I. M. Gioia
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Abstract

We study the cosmological evolution of BL Lac objects by applying the Ve/Va analysis to a new sample of 55 objects presented for the first time in this paper. This sample has been selected from the 239 sources with the brightest X-ray flux (>4X10^-13 erg s^-1 cm^-2) and relatively bright optical counterpart (B<20.5) among the ~1600 objects included in the REX survey. The uniform distribution of the Ve/Va values found in the sample suggests that BL Lac objects are not affected by a strong cosmological evolution in contrast with the behavior observed in the emission line AGNs. The Ve/Va analysis applied to the subsample of the High energy peaked BL Lacs (HBL) does not reveal a significant departure from a uniform distribution. This result suggests either that the cosmological evolution is less extreme than that previously found in other samples or that it is carried out only by a minority of objects, namely by the most extreme HBLs.

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A. Caccianiga, T. Maccacaro, A. Wolter, R. Della Ceca, I. M. Gioia. 2001-10-15. On the cosmological evolution of BL Lacs. https://doi.org/10.1086/338073

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