KVN observations reveal multiple γ-ray emission regions in 3C 84?

Abstract

3C 84 (NGC 1275) is a well-studied mis-aligned Active Galactic Nucleus (AGN), which has been active in γ 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 γ-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 γ-ray and 1 mm total intensity light-curves. We find that the variations in the γ rays and 1 mm total intensity lightcurves are correlated, with the γ rays leading and lagging the radio emission. Analysis of the 2 mm KVN data shows that both the γ rays and 1 mm total intensity shortterm 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 γ-ray flare coincident with the onset of this flare at all radio wavelengths.

Using variability and VLBI to measure cosmological distances

“…The VLBI morphology of the source is currently dominated by two main emitting regions: the region thought to be near the central SMBH, which is the northernmost bright emission region in the maps shown in Fig. 1, and a slowly moving emission feature to the south and which has been studied recently by several authors (Nagai et al 2016;Hiura et al 2018;Hodgson et al 2018). The slowly moving emission feature had a large flare occur in it, beginning in mid 2015, which is pointed out with black arrows (Hodgson et al 2018).…”

“…1, and a slowly moving emission feature to the south and which has been studied recently by several authors (Nagai et al 2016;Hiura et al 2018;Hodgson et al 2018). The slowly moving emission feature had a large flare occur in it, beginning in mid 2015, which is pointed out with black arrows (Hodgson et al 2018). It should be noted that the relevant quantity is not the relative motion of the emission region from the SMBH but its flux density and size.…”

Relativistic Jets from AGN Viewed at Highest Angular Resolution

“…In this context, some clues to the pc-scale circumnuclear environments have been found by monitoring the long-term trajectory of C3: the head of the restarted jet. While C3 was traveling straight towards the south after its ejection [103], during mid 2015, C3 showed a sudden change of direction, moving towards the east by 0.4 mas (0.14 pc in linear scale) [102] (Figure 4 right), together with enhanced radio emission in both total [102,104] and polarized fluxes [105]. This peculiar behavior is hard to be explained by the intrinsic motion of the jet, whereas it would be naturally explained if C3 is interacting with an inhomogeneous dense clumpy medium [106].…”

Radio Galaxies - The TeV Challenge

“…Hints of multiple γ-ray emitting regions have also been observed in T eV Rad. For instance, a study performed using the KVN (Korean VLBI Network) and γ-ray observations indicate the presence of multiple γ-ray emitting regions in 3C 84 [8]. Figure 6 presents a comparison of the flux variations observed at γ-ray and 230 GHz radio frequencies.…”

“…The γ-ray light curve is produced by adaptive binning analysis method following Lott et al[83] using the Fermi/LAT data from August 2008 until September 2017 . The radio 230 GHz light curve is from sub-millimeter array (SMA) AGN monitoring program (details are refereed to Hodgson et al[8]). Rapid flares superimposed on top of the long-term rising trend can be seen both at γ-ray and radio frequencies.…”