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The quasar - elliptical galaxy connection
Pierluigi Monaco (Trieste)
The history of quasars gives precious information about the
formation of elliptical galaxies, and of galactic bulges in general.
In particular, the quasar activity at high redshift should leave large
remnant black holes in the bulges of nearby galaxies. We concentrate
on the mass density expected in black holes today, taking into account
the existence of a population of heavily obscured AGNs which
contributes to the cosmological background in the hard X-rays. The
mass function of the dormant black holes is found by exploiting both
the recently found black hole -- bulge correlation and the relation
between radio power from galactic cores and black hole mass. These
estimates agree with the mass function expected from the past quasar
activity. The data suggest a dichotomy between larger black holes,
hosted in ellipticals and responsible for bright quasars, and smaller
black holes, hosted in the bulges of spirals and still active as AGNs.
Finally, we briefly describe an analytical model for the joint
formation of quasars and ellipticals.
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