1,364 research outputs found
Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies
We 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 halo dark matter are so weak as to imply no close 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 correlations.Comment: 136 pages, 38 postscript figures, 4 tables; requires cittable.tex,
psfig.tex, annrev4K-E.tex; accepted for publication in Volume 51 (2013) of
Annual Review of Astronomy and Astrophysics; Supplementary Information will
be submitted to arXiv separately in approximately 2013 Jun
Supermassive black holes do not correlate with dark matter halos of galaxies
Supermassive black holes have been detected in all galaxies that contain
bulge components when the galaxies observed were close enough so that the
searches were feasible. Together with the observation that bigger black holes
live in bigger bulges, this has led to the belief that black hole growth and
bulge formation regulate each other. That is, black holes and bulges
"coevolve". Therefore, reports of a similar correlation between black holes and
the dark matter halos in which visible galaxies are embedded have profound
implications. Dark matter is likely to be nonbaryonic, so these reports suggest
that unknown, exotic physics controls black hole growth. Here we show - based
in part on recent measurements of bulgeless galaxies - that there is almost no
correlation between dark matter and parameters that measure black holes unless
the galaxy also contains a bulge. We conclude that black holes do not correlate
directly with dark matter. They do not correlate with galaxy disks, either.
Therefore black holes coevolve only with bulges. This simplifies the puzzle of
their coevolution by focusing attention on purely baryonic processes in the
galaxy mergers that make bulges.Comment: 12 pages, 9 Postscript figures, 1 table; published in Nature (20
January 2011
Impact of supermassive black hole growth on star formation
Supermassive black holes are found at the centre of massive galaxies. During
the growth of these black holes they light up to become visible as active
galactic nuclei (AGN) and release extraordinary amounts of energy across the
electromagnetic spectrum. This energy is widely believed to regulate the rate
of star formation in the black holes' host galaxies via so-called "AGN
feedback". However, the details of how and when this occurs remains uncertain
from both an observational and theoretical perspective. I review some of the
observational results and discuss possible observational signatures of the
impact of super-massive black hole growth on star formation.Comment: Invited Review for Nature Astronomy - accepted for publication. 11
pages 6 figure
Mass and Mean Velocity Dispersion Relations for Supermassive Black Holes in Galactic Bulges
Growing evidence indicate supermassive black holes (SMBHs) in the mass range
of lurking in central bulges of many
galaxies. Extensive observations reveal fairly tight power laws of
versus the mean stellar velocity dispersion of the host bulge. The
dynamic evolution of a bulge and the formation of a central SMBH should be
physically linked by various observational clues. In this contribution, we
reproduce the empirical power laws based on a self-similar
general polytropic quasi-static bulge evolution and a sensible criterion of
forming a SMBH surrounding the central density singularity of a general
singular polytropic sphere (SPS) \cite{loujiang2008}. Other properties of host
bulges and central SMBHs are also examined. Based on our model, we discuss the
intrinsic scatter of the relation and a scenario for the
evolution of SMBHs in different host bulges.Comment: 8 pages, 2 figures, accepted for publication in the Proceedings of
Science for VII Microquasar Workshop: Microquasars and Beyon
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