A theoretical unifying scheme for gamma-ray bright blazars

TLDR

Gamma‑ray bright blazars exhibit a phenomenology that can be explained by a sequence in source power and the intensity of the diffuse radiation field surrounding their relativistic jets. The authors derive a scheme based on correlations among physical parameters of 51 gamma‑ray loud blazars using synchrotron self‑Compton and external Compton models, linking equilibrium particle distribution peaks to source power and radiation field intensity. The scheme predicts that higher observed power shifts both synchrotron and inverse Compton peaks to lower frequencies while raising the high‑to‑low energy spectral power ratio, classifying blazars into high‑frequency BL Lacs, low‑frequency BL Lacs, highly polarized quasars, and lowly polarized quasars, and the authors find this trend holds for all 51 blazars studied.

Abstract

The phenomenology of gamma-ray bright blazars can be accounted for by a sequence in the source power and intensity of the diffuse radiation field surrounding the relativistic jet. Correspondingly, the equilibrium particle distribution peaks at different energies. This leads to a trend in the observed properties: an increase of the observed power corresponds to: 1) a decrease in the frequencies of the synchrotron and inverse Compton peaks; 2) an increase in the ratio of the powers of the high and low energy spectral components. Objects along this sequence would be observationally classified respectively as high frequency BL Lac objects, low frequency BL Lac objects, highly polarized quasars and lowly polarized quasars. The proposed scheme is based on the correlations among the physical parameters derived in the present paper by applying to 51 gamma ray loud blazars two of the most accepted scenarios for the broad band emission of blazars, namely the synchrotron self--Compton and external Compton models, and explains the observational trends presented by Fossati et al. (1998) in a companion paper, dealing with the spectral energy distributions of all blazars. This gives us confidence that our scheme applies to all blazars as a class.