KVN observations suggest multiple $\gamma$-ray emission regions in 3C 84

TL;DR

This study uses multi-wavelength VLBI observations to identify multiple gamma-ray emission regions in 3C 84, revealing complex spatial and temporal correlations between radio and gamma-ray variability.

Contribution

It provides new evidence for multiple gamma-ray emission sites in 3C 84, linking radio and gamma-ray variability to distinct regions near the SMBH and a moving feature.

Findings

Gamma-ray and 1 mm variations are correlated, with gamma rays leading and lagging radio.

Short-term variations are more correlated with the SMBH region than with C3.

A large mm-wave radio flare in C3 coincides with a gamma-ray flare since mid-2015.

Abstract

3C 84 (NGC 1275) is a well-studied mis-aligned Active Galactic Nucleus (AGN), which has been active in Gamma rays since at least 2008. We have monitored the source at four wavelengths (14 mm, 7 mm, 3 mm and 2 mm) using the Korean VLBI network (KVN) since 2013 as part of the interferometric monitoring of $\gamma$-ray bright AGN (iMOGABA) program. 3C 84 exhibits bright radio emission both near the central supermassive black hole (SMBH) feature known as C1 and from a moving feature located to the south known as C3. Other facilities have also detected these short-term variations above a slowly rising trend at shorter wavelengths, such as in Gamma ray and 1 mm total intensity light-curves. We find that the variations in the $\gamma$ rays and 1 mm total intensity light-curves are correlated, with the $\gamma$ rays leading and lagging the radio emission. Analysis of the 2 mm KVN data shows that both the Gamma rays and 1 mm total intensity short-term variations are better correlated with the SMBH region than C3, likely placing the short-term variations in C1. We interpret the emission as being due to the random alignment of spatially separated emission regions. We place the slowly rising trend in C3, consistent with previous results. Additionally, we report that since mid-2015, a large mm-wave radio flare has been occurring in C3, with a large Gamma ray flare coincident with the onset of this flare at all radio wavelengths.