The connection between gamma-ray emission and millimeter flares in Fermi/LAT blazars

TL;DR

This study investigates the relationship between gamma-ray and millimeter radio flares in blazars, revealing different correlations for quasars and BLLacs and suggesting gamma-ray production occurs near or downstream of the radio core.

Contribution

It provides new insights into the timing and location of gamma-ray emission in blazars by analyzing simultaneous gamma-ray and radio observations.

Findings

Positive correlation between gamma-ray and radio flux in quasars.

No correlation between the two in BLLacs.

Gamma-ray peaks typically occur about 70 days after the start of a radio flare.

Abstract

We compare the gamma-ray photon flux variability of northern blazars in the Fermi/LAT First Source Catalog with 37 GHz radio flux density curves from the Metsahovi quasar monitoring program. We find that the relationship between simultaneous millimeter (mm) flux density and gamma-ray photon flux is different for different types of blazars. The flux relation between the two bands is positively correlated for quasars and does not exist for BLLacs. Furthermore, we find that the levels of gamma-ray emission in high states depend on the phase of the high frequency radio flare, with the brightest gamma-ray events coinciding with the initial stages of a mm flare. The mean observed delay from the beginning of a mm flare to the peak of the gamma-ray emission is about 70 days, which places the average location of the gamma-ray production at or downstream of the radio core. We discuss alternative scenarios for the production of gamma-rays at distances of parsecs along the length the jet.