Gamma-ray Clues to the Relativistic Jet Dichotomy

TL;DR

This study analyzes gamma-ray emissions from over 200 blazars, revealing how their gamma-ray output and emission mechanisms depend on jet power and orientation, supporting models of jet beaming and emission processes.

Contribution

It provides a comprehensive analysis of gamma-ray properties across a large blazar sample, linking emission characteristics to jet power and beaming effects, and distinguishes between SSC and EC emission models.

Findings

Gamma-ray luminosity depends on beaming across all jet powers.

Weak jets show constant inverse Compton to synchrotron ratio with beaming.

Powerful jets exhibit increased Compton dominance with orientation.

Abstract

In examining a select sample of over 200 blazars of known jet kinetic power (L_kin) and well-characterized SEDs, we found (Meyer et al., 2011) that Intermediate synchrotron-peaking (ISP) blazars may have lower gamma-ray output than high synchrotron-peaking (HSP) blazars of similar L_kin, consistent with our hypothesis that ISP blazars are less-beamed versions of HSP blazars, rather than a distinct population. Further, by using the radio core dominance as a measure of relative beaming, we find that gamma-ray luminosity depends on beaming in a consistent way for blazars ranging over all jet kinetic powers (10^42 - 10^46 ergs/s). We re-examine the gamma-ray properties of this core sample of blazars using the 1-year LAT catalog (Abdo et al., 2010). We find that for weak jets, the ratio of inverse Compton to synchrotron emission remains constant with increased beaming, consistent with an SSC model for the jet emission, while the most powerful jets show a strong increase in Compton dominance with orientation, consistent with an external Compton (EC) emission model.