May 3, 2000
Blazars, Jets, and the Black Hole - Galaxy Connection
Dr. Meg Urry, STScI
The rapid variability and high luminosity of blazars
are signatures of beamed emission from powerful relativistic
jets closely aligned with the line of sight. The jet emission
is magnified a thousand-fold or more by relativistic beaming
providing a unique opportunity to probe how jets are formed
and collimated near supermassive black holes. That such jets
are common to all radio-loud active galaxies -- the so-called
"unification" hypothesis -- is supported by statistical studies and
by direct observations of properties unaffected by relativistic
beaming, such as host galaxies and local environments. Our recent
HST studies of blazar host galaxies confirm they are luminous but
otherwise normal ellipticals, well matched to the hosts of their
"parent" radio galaxies. There is no sign that the active nucleus
strongly affects the host galaxy or vice versa, and no correlation
between jet/nuclear power and host galaxy luminosity/mass, as might
have been expected given an underlying relation between black hole
mas and bulge mass. These results are consistent with the
idea that all massive ellipticals harbor supermassive black
holes, with (low) duty cycles of activity, and perhaps point to
scenarios where the cosmic formation of black holes is closely
linked to that of the most massive galaxies.
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