Characteristics of Gamma-Ray Loud Blazars in the VLBA Imaging and Polarimetry Survey

TL;DR

This study investigates the radio and polarization properties of blazars detected by Fermi-LAT, revealing differences between gamma-ray loud and quiet blazars, especially in FSRQs, linked to Doppler boosting and jet polarization.

Contribution

It provides new insights into the radio and polarization characteristics distinguishing gamma-ray loud and quiet blazars, highlighting the role of Doppler boosting and jet polarization.

Findings

LAT-detected BL Lacs are similar to non-LAT BL Lacs.

LAT-detected FSRQs differ significantly from non-LAT FSRQs.

Strong polarization at the jet base correlates with gamma-ray loudness.

Abstract

The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey (VIPS). This large, flux-limited sample of active galactic nuclei (AGN) provides insights into the mechanism that produces strong gamma-ray emission. At lower flux levels, radio flux density does not directly correlate with gamma-ray flux. We find that the LAT-detected BL Lacs tend to be similar to the non-LAT BL Lacs, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the gamma-ray loud and quiet FSRQs can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lacs. It is possible that the gamma-ray loud FSRQs are fundamentally different from the gamma-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for gamma-ray loud AGN.