Observational evidence for AGNs feedback at parsec scale
  In a hot accretion flow, the radiation from the innermost region of the flow
propagates outward and heats the electrons at large radii via Compton
scattering. It has been shown in previous works that if the radiation is strong
enough, $L\ga 2%L_{\rm Edd}$, the electrons at the Bondi radius ($r_B\sim 10^5
r_s$) will be heated to be above the virial temperature thus the accretion will
be stopped. The accretion will recover after the gas cools down. This results
in the oscillation of the black hole activity. In this paper we show that this
mechanism is the origin of the intermittent activity of some compact young
radio sources. Such intermittency is required to explain the population of
these sources. We calculate the timescales of the black hole oscillation and
find that the durations of active and inactive phases are $3\times 10^4
(0.1/\alpha)(M/10^8\msun) (L/2%L_{\rm Edd})^{-1/2} {\rm yr}$ and
$10^5(\alpha/0.1)(M/10^8\msun) {\rm yr}$, respectively, consistent with those
required to explain observations. Such kind of feedback occurring at parsec
scale should be common in low-luminosity AGNs and should be considered when we
consider their matter and energy output.
