Characteristics of EGRET Blazars in the VLBA Imaging and Polarimetry Survey (VIPS)

TL;DR

This study analyzes the radio properties of EGRET-detected blazars in the VIPS survey, revealing correlations with gamma-ray emission and suggesting higher Doppler factors in gamma-ray loud blazars.

Contribution

It provides new insights into the radio characteristics of EGRET blazars at lower flux levels and links these properties to gamma-ray emission mechanisms.

Findings

EGRET blazars have higher brightness temperatures and core fractions.

Radio flux density does not correlate with gamma-ray flux at lower flux levels.

Gamma-ray loud blazars exhibit larger Doppler factors and higher apparent velocities.

Abstract

We examine the radio properties of EGRET-detected blazars observed as part of the VLBA Imaging and Polarimetry Survey (VIPS). VIPS has a flux limit roughly an order of magnitude below the MOJAVE survey and most other samples that have been used to study the properties of EGRET blazars. At lower flux levels, radio flux density does not directly correlate with gamma-ray flux density. We do find that the EGRET-detected blazars tend to have higher brightness temperatures, greater core fractions, and possibly larger than average jet opening angles. A weak correlation is also found with jet length and with polarization. All of the well-established trends can be explained by systematically larger Doppler factors in the gamma-ray loud blazars, consistent with the measurements of higher apparent velocities found in monitoring programs carried out at radio frequencies above 10 GHz.