相关论文: Nonstandard Central Engines in Nearby Galaxies
A significant fraction of nearby galaxies show evidence of weak nuclear activity unrelated to normal stellar processes. Recent high-resolution, multiwavelength observations indicate that the bulk of this activity derives from black hole…
A significant fraction of local galaxies show evidence of nuclear activity. I argue that the bulk of this activity, while energetically not remarkable, derives from accretion onto a central massive black hole. The statistics of nearby…
It has long been suspected that Active Galactic Nuclei are powered by accretion of matter onto massive black holes and this belief implies their presence in the nuclei of most nearby galaxies as "relics" of past activity. Just a few years…
We suggest that most nearby active galactic nuclei are fed by a series of small--scale, randomly--oriented accretion events. Outside a certain radius these events promote rapid star formation, while within it they fuel the supermassive…
This contribution reviews the properties of nuclear activity in nearby galaxies, with emphasis on their implications for the demography of nuclear black holes and the nature of accretion flows in the regime of very low accretion rates.
This article gives a brief overview of the direct and indirect evidence in support of the standard paradigm that active galactic nuclei are powered by supermassive black holes.
Masses of black holes in nearby galactic nuclei can be measured in a variety of ways, using stellar and gaseous kinematics. Reliable black hole masses are known for several dozen objects, so that demographic questions can start to be…
Active Galactic Nuclei are fueled from material (gas or stars) that are in general far away from the gravitational influence of the central black hole, the engine thought to be responsible for their activity. The required material has a lot…
The masses of the central black holes of Active Galactic Nuclei estimated by the reverberation virial technique seem to be significantly smaller than predicted from the black hole mass-bulge luminosity relation for massive black holes…
Supermassive black holes containing ~0.5% of the stellar mass of their host galaxies appear to be ubiquitous components of galactic nuclei. The gravitational force from these central singularities can influence the motion of stars far…
We discuss accretion flows on massive black holes in which different elements of the flow (clumps) have velocities that may differ substantially. We estimate the consequence of collisions between these clumps as they come close to the…
Only a small fraction of local galaxies harbor an accreting black hole, classified as an active galactic nucleus (AGN). However, many stellar systems are plausibly expected to host black holes, from globular clusters to nuclear star…
Active galaxies contain a supermassive black hole at their center, which grows by accreting matter from the surrounding galaxy. The accretion process in the central ~10 parsecs has not been directly resolved in previous observations, due to…
Supermassive black holes inhabit galactic nuclei, and their presence influences in crucial ways the evolution of the stellar distribution. The low-density cores observed in bright galaxies are probably a result of black hole infall, while…
Most large elliptical galaxies should now host a massive black hole leftover from an earlier quasar phase. Such galaxies also have an extensive hot gaseous halo. Here we consider why the nuclei of elliptical galaxies are not luminous…
Astronomers have discovered many potential black holes in X-ray binaries and galactic nuclei. These black holes are usually identified by the fact that they are too massive to be neutron stars. Until recently, however, there was no…
Astronomers have discovered many potential black holes in X-ray binaries and galactic nuclei. These black holes are usually identified by the fact that they are too massive to be neutron stars. Until recently, however, there was no…
The majority of nearby early-type galaxies contains detectable amounts of emission-line gas at their centers. The emission-line ratios and gas kinematics potentially form a valuable diagnostic of the nuclear activity and gravitational…
The main requirements for fueling an active galactic nucleus and to form massive black holes are reviewed. Low-luminosity AGN can be fueled easily from the local star clusters, near the nucleus, and the various stellar processes are…
The radio emission from supermassive black holes in nearby early-type galaxies can be used to test possible explanations for their low luminosities. We calculate the expected contribution from thermal synchrotron emission from hot accretion…