Opening angles and shapes of parsec-scale AGN jets

TL;DR

This study analyzes the shapes and opening angles of parsec-scale AGN jets using VLBA data, revealing that most jets are conical with some showing active collimation, and that Fermi-detected sources have wider apparent angles.

Contribution

It provides a detailed analysis of jet transverse profiles and opening angles, including the impact of gamma-ray detection on jet geometry characteristics.

Findings

Fermi-detected sources have wider apparent jet angles.

Most jets exhibit conical geometry at parsec scales.

Some jets show evidence of active collimation.

Abstract

We used 15 GHz VLBA observations of 366 sources having at least 5 epochs within a time interval 1995-2013 from the MOJAVE program and/or its predecessor, the 2 cm VLBA Survey. For each source we produced a corresponding stacked image averaging all available epochs for a better reconstruction of the cross section of the flow. We have analyzed jet profiles transverse to the local jet ridge line and derived both apparent and intrinsic opening angles of the parsec-scale outflows. The sources detected by the Fermi Large Area Telescope (LAT) during the first 24 months of operation show wider apparent jet opening angle and smaller viewing angles on a very high level of significance supporting our early findings. Analyzing transverse shapes of the outflows we found that most sources have conical jet geometry at parsec scales, though there are also sources that exhibit active jet collimation.