Apparent parsec-scale jet opening angles and \gamma-ray brightness of active galactic nuclei

TL;DR

This study compares parsec-scale jet opening angles of active galactic nuclei detected by Fermi LAT with non-detected ones, revealing that gamma-ray bright AGN tend to have larger apparent opening angles, indicating smaller viewing angles.

Contribution

It provides new evidence linking gamma-ray brightness to jet opening angles and viewing angles in AGN using VLBA observations, expanding previous findings.

Findings

Gamma-ray bright AGN have larger apparent jet opening angles.

Gamma-ray bright AGN likely have smaller viewing angles.

BL Lac objects have wider intrinsic opening angles than quasars.

Abstract

We have investigated the differences in apparent opening angles between the parsec-scale jets of the active galactic nuclei (AGN) detected by the Fermi Large Area Telescope (LAT) during its first 24 months of operations and those of non-LAT-detected AGN. We used 15.4 GHz VLBA observations of 215 sources from the 2 cm VLBA MOJAVE program. The apparent opening angles were determined by analyzing transverse jet profiles from the data in the image plane by using stacked images constructed from all available MOJAVE epochs for a given source. We confirm our earlier result based on the first three months of scientific operations of the LAT. The apparent opening angles of \gamma-ray bright AGN are preferentially larger than those of \gamma-ray weak sources, suggesting smaller viewing angles to the \gamma-ray bright AGN. Intrinsic opening angles for BL Lacs are wider than those in quasars.