3C 84: Observational Evidence for Precession and a Possible Relation to TeV Emission

Abstract

3C 84 (NGC 1275, Perseus A) is a bright radio source at the center of an ongoing merger, where HST observations show two colliding spiral galaxies. 3C 84 holds promise to improve our understanding about how of the activity of active galactic nuclei, the formation of supermassive binary black holes, feedback processes, and galaxy collisions are interrelated. 3C,84 is one of only six radio galaxies, which reveal TeV emission. The origin of this TeV emission is still a matter of debate. Our present study is based on high resolution radio interferometric observations (15 GHz) of the pc-scale jet in this complex radio galaxy. We have re-modeled and re-analyzed 42 VLBA observations of 3C 84, performed between 1999.99 and 2017.65. In order to enable a proper alignment of the VLBA observations, we developed a method of a “differential” alignment whereby we select one reference point and minimize the deviations from this reference point in the remaining epochs. As a result, we find strong indication for a precession of the 3C 84 jet—not only for its central regions, but also for the outer lobe at 10 mas distance. These findings are further supported by our kinematic precession modeling of the radio flux-density monitoring data provided by the University of Michigan Radio Observatory and the Owens Valley Radio Observatory, which yields a precession time scale of about 40 yr. This time scale is further supported by literature maps obtained about 40 yr ago (1973 and 1974.1) which reveal a similar central radio structure. We suggest that the TeV flare detected by MAGIC may correlate with the precession of 3C 84, as we disentangle a projected reversal point of the precessing motion that correlates with the flaring time. This may physically be explained by a precessing jet sweeping over a new region of so far undisturbed X-ray gas which would then lead to shock-produced TeV-emission. In addition, we perform a correlation analysis between the radio data and GeV data obtained by the Fermi Gamma-ray Space Telescope and find that the γ -ray data are lagging the radio data by 300–400 days. A possible explanation could be that the radio and the GeV data stem from different emission regions. We discuss our findings and propose that the detected jet precession can also account for the observed cavities in the X-ray emission on kpc-scales.

Radio Galaxies at TeV Energies: Preface

“…In late 2016 to beginning of 2017, NGC 1275 showed an extremely bright and fast VHE outburst that was fifty times brighter than previously reported measurements. One research article in this issue by Britzen et al [9] investigates high-resolution very-long-baseline-interferometry data of NGC 1275 and studies the correlation of the parsec-scale images of the jet with the flaring VHE emission behavior.…”

A double-period oscillation signal in millimeter emission of the radio galaxy NGC 1275

“…The core appeared to have had a rising trend in brightness at multiple wavelengths in 2003-2017 (Hodgson et al 2018;Britzen et al 2019;Gulati et al 2021; see Figure 1). This long-term trend, as well as flare-like variations of NGC 1275, were revealed by high-resolution imaging to primarily arise from the emergence and flux density changes of the C3 component (Nagai et al 2010;Hodgson et al 2018;Kino et al 2018).…”

“…Related to these intriguing results for the core of the NGC 1275 jets, hints of precession of the jets have been reported. The derived precession timescales, however, have a very wide range: from as long as ∼ 33 Myr to explain the observed multi-kpc scale radio (and X-ray) bubbles (Dunn et al 2006); to ∼ 40-100 yr from parsec- scale morphological changes and long-term flux density variations of the jets (Britzen et al 2019); ∼ 28.8 yr, from determining the projected position angle of the C1 component (Dominik et al 2021); or ∼6 yr, from a possible helical path of C3 (with respect to C1; Hiura et al 2018).…”

Pinpoint the jet apex in 3C 84

“…3C 84 is also one of the very few TEV 𝛾-ray emitting sources [6,14,15]. However, possible correlations between the 𝛾-ray and radio flaring lack high significance (see Fig.…”