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

¹ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
e-mail: leon@kurp.hut.fi
² Tuorla Observatory, Department of Physics and Astronomy, University of Turku, 20100 Turku, Finland
³ Finnish Center for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, Piikkiö, Finland

Received: 7 February 2011
Accepted: 8 June 2011

Abstract

We compare the γ-ray photon flux variability of northern blazars in the Fermi/LAT First Source Catalog with 37 GHz radio flux density curves from the Metsähovi quasar monitoring program. We find that the relationship between simultaneous millimeter (mm) flux density and γ-ray photon flux is different for different types of blazars. The flux relation between the two bands is positively correlated for quasars and does no exist for BLLacs. Furthermore, we find that the levels of γ-ray emission in high states depend on the phase of the high frequency radio flare, with the brightest γ-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 γ-ray emission is about 70 days, which places the average location of the γ-ray production at or downstream of the radio core. We discuss alternative scenarios for the production of γ-rays at distances of parsecs along the length of the jet.