VLBI and Single Dish Monitoring of 3C84 in the Period of 2009-2011

TL;DR

This study monitors the radio galaxy 3C 84 using VLBI and single dish observations from 2009 to 2011 to investigate the connection between radio jet structures and gamma-ray flares, finding flux increases but no direct correlation.

Contribution

It provides a detailed multi-year radio monitoring of 3C 84 during gamma-ray flares, highlighting the lack of direct correlation between radio structure changes and gamma-ray activity.

Findings

Radio flux increased during gamma-ray flares, mainly from component C3.

No clear correlation between radio light curves and gamma-ray flares on days to weeks timescales.

VLBI images did not show new components or morphological changes associated with gamma-ray flares.

Abstract

The radio galaxy 3C 84 is a representative of gamma-ray-bright misaligned active galactic nuclei (AGNs) and one of the best laboratories to study the radio properties of the sub-pc jet in connection with the gamma-ray emission. In order to identify possible radio counterparts of the gamma-ray emissions in 3C 84, we study the change in structure within the central 1 pc and the light curve of sub-pc-size components C1, C2, and C3. We search for any correlation between changes in the radio components and the gamma-ray flares by making use of VLBI and single dish data. Throughout the radio monitoring spanning over two GeV gamma-ray flares detected by the {\it Fermi}-LAT and the MAGIC Cherenkov Telescope in the periods of 2009 April to May and 2010 June to August, total flux density in radio band increases on average. This flux increase mostly originates in C3. Although the gamma-ray flares span on the timescale of days to weeks, no clear correlation with the radio light curve on this timescale is found. Any new prominent components and change in morphology associated with the gamma-ray flares are not found on the VLBI images.