We report millimeter-VLBI results of low-luminosity active galactic nuclei (M 84 and M 87) up to 88 GHz with source-frequency phase-referencing observations. We detected the weak VLBI core and obtained the first image of M 84 at 88 GHz. The derived brightness temperature of M 84 core was about 7.2×109 K, which could serve as a lower limit as the core down to 30 Schwarzschild radii was still un-resolved in our 88 GHz observations. We successfully determined the core-shifts of M 87 at 22-44 GHz and 44-88 GHz through source-frequency phase-referencing technique. The jet apex of M 87 could be deduced at about 46 μas upstream of the 43 GHz core from core-shift measurements. The estimated magnetic field strength of the 88 GHz core of M 87 is 4.8±2.4 G, which is at the same magnitude of 1-30 G near the event horizon probed by the Event Horizon Telescope.
@article{arxiv.2111.08930,
title = {Millimeter-VLBI observations of low-luminosity active galactic nuclei with source-frequency phase-referencing},
author = {Wu Jiang and Zhiqiang Shen and Ivan Marti-Vidal and Xuezheng Wang and Dongrong Jiang and Noriyuki Kawaguchi},
journal= {arXiv preprint arXiv:2111.08930},
year = {2021}
}