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Fundamental Plane of Black Hole Activity in Quiescent Regime
A correlation among the radio luminosity (), X-ray luminosity
(), and black hole mass () in active galactic nuclei
(AGNs) and black hole binaries is known to exist and is called the "Fundamental
Plane" of black hole activity. Yuan & Cui (2005) predicts that the radio/X-ray
correlation index, , changes from to
when decreases below a
critical value . While many works favor such a change, there are
also several works claiming the opposite. In this paper, we gather from
literature a largest quiescent AGN (defined as ) sample to date, consisting of sources. We find that these
quiescent AGNs follow a radio/X-ray relationship, in
excellent agreement with the Yuan \& Cui prediction. The reason for the
discrepancy between the present result and some previous works is that their
samples contain not only quiescent sources but also "normal" ones (i.e.,
). In this case, the quiescent sources will
mix up with those normal ones in and . The value of
will then be between and , with the exact value
being determined by the sample composition, i.e., the fraction of the quiescent
and normal sources. Based on this result, we propose that a more physical way
to study the Fundamental Plane is to replace and with
and , respectively.Comment: 11 pages, 7 figures, accepted for publication in The Astrophysical
Journa
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