Book contents
- Frontmatter
- Contents
- Participants
- Preface
- Black holes, entropy, and information
- Gravitational waves from black-hole mergers
- Out-of-this-world physics: Black holes at future colliders
- Black holes in globular clusters
- Evolution of massive black holes
- Supermassive black holes in deep multiwavelength surveys
- Black-hole masses from reverberation mapping
- Black-hole masses from gas dynamics
- Evolution of supermassive black holes
- Black-hole masses of distant quasars
- The accretion history of supermassive black holes
- Strong field gravity and spin of black holes from broad iron lines
- Birth of massive black-hole binaries
- Dynamics around supermassive black holes
- Black-hole formation and growth: Simulations in general relativity
- Estimating the spins of stellar-mass black holes
- Stellar relaxation processes near the Galactic massive black hole
- Tidal disruptions of stars by supermassive black holes
- Where to look for radiatively inefficient accrection flows in low-luminosity AGN
- Making black holes visible: Accretion, radiation, and jets
Where to look for radiatively inefficient accrection flows in low-luminosity AGN
Published online by Cambridge University Press: 11 April 2011
- Frontmatter
- Contents
- Participants
- Preface
- Black holes, entropy, and information
- Gravitational waves from black-hole mergers
- Out-of-this-world physics: Black holes at future colliders
- Black holes in globular clusters
- Evolution of massive black holes
- Supermassive black holes in deep multiwavelength surveys
- Black-hole masses from reverberation mapping
- Black-hole masses from gas dynamics
- Evolution of supermassive black holes
- Black-hole masses of distant quasars
- The accretion history of supermassive black holes
- Strong field gravity and spin of black holes from broad iron lines
- Birth of massive black-hole binaries
- Dynamics around supermassive black holes
- Black-hole formation and growth: Simulations in general relativity
- Estimating the spins of stellar-mass black holes
- Stellar relaxation processes near the Galactic massive black hole
- Tidal disruptions of stars by supermassive black holes
- Where to look for radiatively inefficient accrection flows in low-luminosity AGN
- Making black holes visible: Accretion, radiation, and jets
Summary
We have studied the nuclear emission detected in HST data of carefully selected samples of low-luminosity AGN (LLAGN) in the local universe. We find faint unresolved nuclei in a significant fraction of the objects. FR I radio galaxies' optical nuclei show a tight linear correlation with the radio core emission, which argues for a common synchrotron origin. The nuclear emission in LLAGN is as low as 10−8 times the Eddington luminosity, indicating extremely low radiative efficiency for the accretion process and/or an extremely low accretion rate. When the Eddington ratio is plotted against the nuclear “radio-loudness” parameter, sources divide according to their physical properties. It is thus possible to disentangle nuclear jets and accretion disks of different radiative efficiencies. This new diagnostic plane allows us to find objects that are the best candidates for hosting (and showing) radiative inefficient accretion and determine in which ones we cannot see it. The (extremely limited) information available in the HST archive to derive the nuclear SEDs strongly supports our results.
Introduction
One of the most important results of the last few years has been the realization that most, if not all, galaxies harbor supermassive black holes (BH) in their centers. The presence of a supermassive BH can manifest itself as luminous quasar “activity,” powered by accretion of matter onto the BH itself. Such a quasar phase, which peaks somewhere around redshift 2, is likely to play an important role in the build-up of these BHs.
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- Black Holes , pp. 294 - 308Publisher: Cambridge University PressPrint publication year: 2011