Discovery of five low luminosity active galactic nuclei at the centre of
  the Perseus cluster
  According to optical stellar kinematics observations, an over-massive black
hole candidate has been reported by van den Bosch et al. (2012) in the normal
early-type galaxy NGC 1277. This galaxy is located in the central region of the
Perseus cluster. Westerbork Synthesis Radio Telescope (WSRT) observations have
shown that NGC 1277 and other early-type galaxies in the neighbourhood have
radio counterparts. These nuclear radio sources have stable flux densities on
time scale of years. In order to investigate the origin of the radio emission
from these normal galaxies, we selected five sources (NGC 1270, NGC 1272, NGC
1277, NGC 1278 and VZw 339) residing in the central 10 arcminute region of the
Perseus cluster and requested to re-correlate the data of an existing very long
baseline interferometry (VLBI) experiment at these new positions. With the
re-correlation data provided by the European VLBI Network (EVN), we imaged the
five sources with a resolution of about eight milliarcseconds and detected all
of them with a confidence level above 5{\sigma} at 1.4 GHz. They show compact
structure and brightness temperatures above $10^7$ K, which implies that the
radio emission is non-thermal. We rule out ongoing nuclear star formation and
conclude that these VLBI-detected radio sources are parsec-scale jet activity
associated with the supermassive black holes in low luminosity active galactic
nuclei (LLAGNs), although there are no clear signs of nuclear activity observed
in the optical and infrared bands. Using the fundamental plane relation in
black holes, we find no significant evidence for or against an extremely
massive black hole hiding in NGC 1277.
