Pilot KaVA monitoring on the M87 jet: confirming the inner jet structure and superluminal motions at sub-pc scales

Abstract

We report the initial results of our high-cadence monitoring program on the radio jet in the active galaxy M87, obtained by the KVN and VERA Array (KaVA) at 22 GHz. This is a pilot study that preceded a larger KaVA-M87 monitoring program, which is currently ongoing. The pilot monitoring was mostly performed every two to three weeks from December 2013 to June 2014, at a recording rate of 1 Gbps, obtaining the data for a total of 10 epochs. We successfully obtained a sequence of good quality radio maps that revealed the rich structure of this jet from <~1 mas to 20 mas, corresponding to physical scales (projected) of ~0.1-2 pc (or ~140-2800 Schwarzschild radii). We detected superluminal motions at these scales, together with a trend of gradual acceleration. The first evidence for such fast motions and acceleration near the jet base were obtained from recent VLBA studies at 43 GHz, and the fact that very similar kinematics are seen at a different frequency and time with a different instrument suggests these properties are fundamental characteristics of this jet. This pilot program demonstrates that KaVA is a powerful VLBI array for studying the detailed structural evolution of the M87 jet and also other relativistic jets.

10 pages, 9 figures, accepted for publication in PASJ

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• The jet and resolved features of the central supermassive black hole of M 87 observed with EHT
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• Jet Kinematics of the Quasar 4C +21.35 from Observations with the KaVA Very Long Baseline Interferometry Array
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• Overview of the Observing System and Initial Scientific Accomplishments of the East Asian VLBI Network (EAVN)
• An International Survey of Front-End Receivers and Observing Performance of Telescopes for Radio Astronomy
• Transverse Oscillations of the M87 Jet Revealed by KaVA Observations
• Jet Collimation and Acceleration in the Flat Spectrum Radio Quasar 1928+738
• Multiwavelength study of the gravitationally lensed blazar QSO B0218+357 between 2016 and 2020
• Refining the mass estimate for the intermediate-mass black hole candidate in NGC 3319
• Matter density distribution of general relativistic highly magnetized jets driven by black holes
• Super-Resolved Image of M87 Observed with East Asian VLBI Network
• Relativistic jet acceleration region in a black hole magnetosphere
• A Jet Source of Event Horizon Telescope Correlated Flux in M87
• Analysis of Jet Dynamics and Collimation Characteristics of 0241+622 on Parsec Scales
• Wakefield Acceleration in a Jet from a Neutrino Driven Accretion Flow around a Black Hole
• Kilogauss magnetic field and jet dynamics in the quasar NRAO 530
• Transverse Oscillations and Wave Propagation in the Magnetically Dominated M87 Jet
• First Trigonometric Parallax Measurements with the KVN and VERA Array (KaVA)
• A revised view of the linear polarization in the subparsec core of M87 at 7 mm
• Probing the disk-jet coupling in M87
• PATOKA: Simulating Electromagnetic Observables of Black Hole Accretion
• Impact of non-thermal particles on the spectral and structural properties of M87