Parameter Correlations and Cosmological Properties of BL Lac Objects

TL;DR

This study analyzes the population and evolution of BL Lac objects, finding no strong correlation between their synchrotron peak frequency and radio luminosity, with low or negative cosmological evolution observed.

Contribution

It provides a comprehensive comparison of BL Lac subclasses and investigates the correlation between peak frequency and luminosity using complete radio flux-limited samples.

Findings

Fraction of HBLs is consistent across fluxes and luminosities.

Cosmological evolution of BL Lacs is low or negative at low fluxes.

No strong correlation between synchrotron peak frequency and radio luminosity.

Abstract

Using three complete, radio flux limited, blazar samples we compare the LogN-LogS and the preliminary radio luminosity function of the general population of BL Lacs to those of the subclass of high energy synchrotron peaked (HBL) BL Lacs. We also examine recent results on the cosmological evolution in different samples of BL Lacs and we investigate the controversial issue of the correlation between the synchrotron peak frequency and radio luminosity in BL Lacertae objects. We find that the fraction of HBL objects is approximately the same at all observed radio fluxes and luminosities implying that there cannot be any strong correlation between the position of the synchrotron peak and radio luminosity. The amount of cosmological evolution in BL Lacs is confirmed to be low and negative at low radio fluxes, although the large number of objects without redshift prevents a precise estimation. At high radio fluxes the amount of cosmological evolution is zero or slightly positive but this could be induced by a possible contamination with Flat Spectrum Radio Quasars.