Pilot KaVA monitoring on the M 87 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.

Two-temperature, Magnetically Arrested Disc simulations of the jet from the supermassive black hole in M87

“…At 22 GHz,they include the compact flux density value 0.35 Jy, reported by Junor & Biretta (1995). However, during the epochs reported by Junor & Biretta (1995), the total flux density of M87, including extended structure, was only ∼1.1 Jy, which is significantly lower than the values measured more recently with the Very Long Baseline Array (VLBA) and the KVN/VERA Array (KaVA) (Hada et al 2017). It is also lower than the values measured at 15 GHz and 43 GHz since 2000 (Lister et al 2018;Walker et al 2018).…”

First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring

“…We have also not yet considered how the physical properties of the jet are constrained by lower-frequency VLBI observations, which constrain jet kinematics (Mertens et al 2016;Britzen et al 2017;Hada et al 2017;Kim et al 2018;Walker et al 2018), the jet width profile (Asada & Nakamura 2012;Hada et al 2013;Nakamura et al 2018), the total jet power at kilo-parsec scale (Owen et al 2000;Stawarz et al 2006), the jet power (e.g., Kino et al 2014Kino et al , 2015, the core shift (Hada et al 2011), and the symmetric limb-brightening structure (Takahashi et al 2018;Kim et al 2018). The jet width profile is potentially very interesting because it depends on the magnetic flux f: the jet internal magnetic pressure 2 f µ .…”

East Asia VLBI Network observations of the TeV Gamma-Ray Burst 190114C

“…Moreover, this is the first phase-referencing observation of the EAVN. So far, the EAVN has mostly been limited to the observations of bright sources (e.g., [41][42][43]), therefore the capability of phase referencing will greatly expand its science applications.…”

“…The data reduction and calibration of the observed visibility amplitude, phase and bandpass were performed using the US National Radio Astronomy Observatory (NRAO) Astronomical Image Processing System (AIPS) [3] based on the standard EAVN data reduction procedures (e.g., [4,42,43]). A priori amplitude calibration (except for Tianma, see above discussion) was done using the system temperatures measured during the observations and the antenna gain curves supplied by the EAVN stations.…”