UA Science

You are here

4/03/14 John Kormendy SO/NOAO Joint Colloquium Series


John Kormendy, UT Austin

Supermassive Black Holes: Coevolution (Or Not) of Black Holes and Host Galaxies

Kormendy & Ho 2013, ARA&A, 51, 511 review the observed demographics and
inferred evolution of supermassive black holes (BHs) found by dynamical
modeling of spatially resolved kinematics. Most influential was the
discovery of a tight correlation between BH mass and the velocity dispersion
of the host-galaxy bulge. It and other correlations led to the belief that
BHs and bulges coevolve by regulating each other's growth.

New results are now replacing this simple story with a richer and more plausible
picture in which BHs correlate differently with different galaxy components. BHs
are found in pure-disk galaxies, so classical (elliptical-galaxy-like) bulges
are not necessary to grow BHs. But BHs do not correlate with galaxy disks. And
any correlations with disk-grown pseudobulges or dark matter halos are so weak
as to imply no close coevolution. These results enable a substantial revision
in our picture of BH-host coevolution:

We suggest that there are four regimes of BH feedback.

1 - Local, stochastic feeding of small BHs in mainly bulgeless galaxies involves
too little energy to result in coevolution.

2 - Global feeding in major, wet galaxy mergers grows giant BHs in short,
quasar-like "AGN" events whose feedback does affect galaxies. This makes
classical bulges and coreless-rotating ellipticals.

3 - At the highest BH masses, maintenance-mode feedback into X-ray gas has the
negative effect of helping to keep baryons locked up in hot gas. This happens
in giant, core-nonrotating ellipticals. They inherit coevolution magic from
smaller progenitors.

4 - Independent of any feedback physics, the averaging that results from successive
mergers helps to engineer tight BH-host parameter correlations.

For the public
For Public

Public events include our Monday Night Lecture Series, world-reknowned Astronomy Camp and Mt Lemmon Sky Center.

For Students

A good place to start if you want to become an undergrad major or grad student, or need to find our schedule of classes.


For Scientists
For Scientists

Find telescopes and instruments, telescope time applications, staff and mountain contacts, and faculty and staff scientific interests.