A Centiparsec-scale Compact Radio Core in the Nearby Galaxy M60
Journal article, 2024
M60, an elliptical galaxy located 16.5 Mpc away, has an active nucleus with a very low luminosity and an extremely low accretion rate. Its central supermassive black hole (SMBH) has a mass of M BH ∼ 4.5 × 109 M ⊙ and a Schwarzschild radius corresponding to R S ∼ 5.4 μas. To investigate the nature of its innermost radio nucleus, data from the Very Long Baseline Array (VLBA) at 4.4 and 7.6 GHz were reduced. The VLBA images reveal a compact component with total flux densities of ∼20 mJy at both frequencies, a size of ≤0.27 mas (99.7% confidence level), about 0.022 pc (50 R S) at 7.6 GHz, and a brightness temperature of ≥6 × 109 K. This suggests that the observed centiparsec-scale compact core could be attributed to a nonthermal jet base or an advection-dominated accretion flow (ADAF) with nonthermal electrons. The extremely compact structure also supports the presence of an SMBH in the center. Our results indicate that M60 is a promising target for broadband very long baseline interferometry observations at millimeter wavelengths to probe ADAF scenarios and tightly constrain the potential photon ring (about 28 μas) around its SMBH.
Author
X. F. Li
National Astronomical Data Center
Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province
Guangzhou University
Jun Yang
Chalmers, Space, Earth and Environment, Onsala Space Observatory
X. P. Cheng
Korea Astronomy and Space Science Institute
Mai Liao
Diego Portales University
Chinese Academy of Sciences
Xiaoyu Hong
ShanghaiTech University
Chinese Academy of Sciences
Liming Dou
Guangzhou University
National Astronomical Data Center
Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province
Tianle Zhao
Guangzhou University
National Astronomical Data Center
Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province
Zhongying Fan
National Astronomical Data Center
Guangzhou University
Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province
Fupeng Zhang
National Astronomical Data Center
Guangzhou University
Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province
Weirong Huang
Guangzhou University
Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province
National Astronomical Data Center
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 960 1 1Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
DOI
10.3847/1538-4357/ad0be6