Pinpointing the jet apex of 3C 84

Abstract

Nearby radio galaxies that contain jets are extensively studied with VLBI, addressing jet launching and the physical mechanisms at play around massive black holes. 3C 84 is unique in this regard, because the combination of its proximity and large SMBH mass provides a high spatial resolution to resolve the complex structure at the jet base. For 3C 84 an angular scale of 50 $\mu$as corresponds to 200 - 250 Schwarzschild radii ($R_s$). Recent RadioAstron VLBI imaging at 22 GHz revealed an east-west elongated feature at the northern end of the VLBI jet, which challenges interpretations. Here we propose instead that the jet apex is not located within the 22 GHz VLBI core region but more upstream of the jet. We base our arguments on a 2D cross-correlation analysis of quasi-simultaneously obtained VLBI images at 15, 43, and 86 GHz, which measures the opacity shift of the VLBI core in 3C 84. With the assumption of the power law index ($k_r$) of the core shift being set to 1, we find the jet apex to be located $83\pm 7$ $\mu$as north (upstream) of the 86 GHz VLBI core. Depending on the assumptions for $k_r$ and the particle number density power law index n, we find a mixed toroidal/poloidal magnetic field configuration, consistent with a region which is offset from the central engine by about 400-1500 $R_s$. The measured core shift is then used to estimate the magnetic field strength, which amounts to B = 1.80 - 4.0 G near the 86 GHz VLBI core. We discuss some physical implications of these findings.

8 pages, 4 figures, 5 tables, accepted for publication in Astronomy & Astrophysics Letters

References in corpus (14)

• Array Programming with NumPy
• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• MOJAVE: Monitoring of Jets in AGN with VLBA Experiments. V. Multi-epoch VLBA Images
• A magnetically collimated jet from an evolved star
• Magnetohydrodynamic Simulations of Active Galactic Nucleus Disks and Jets
• Magnetic Fields in the Center of the Perseus Cluster
• Discovery of a new subparsec counterjet in NGC 1275: the inclination angle and the environment
• Jet collimation and acceleration in the giant radio galaxy NGC 315
• Observations of CO in the eastern filaments of NGC 1275
• Evidence of internal rotation and a helical magnetic field in the jet of the quasar NRAO150
• VIMAP: an Interactive Program Providing Radio Spectral Index Maps of Active Galactic Nuclei
• Pinpointing the jet apex of 3C 84
• Constraints on Circumnuclear Disk through Free-Free Absorption in the Nucleus of 3C 84 with KaVA and KVN at 43 and 86 GHz
• Observing the Time Evolution of the Multi-Component Nucleus of 3C\,84

Cited by in corpus (4)

• Pinpointing the jet apex of 3C 84
• Ordered magnetic fields around the 3C 84 central black hole
• Enabling Transformational ngEHT Science via the Inclusion of 86 GHz Capabilities
• First VLBI detection of Fornax A