Reverberation mapping
Encyclopedia
Reverberation mapping is to-day a statistical method within astrophysics
preferably used in connection with velocity analysis of gaseous discs
around supermassive compact objects
. The technique is used to measure the size of the broad emission-line region and mass of the alleged central black hole
in active galactic nuclei
.
Direct Doppler
measures of water masers
surrounding the nucleus of nearby galaxies have revealed a very fast Keplerian motion
, only possible with a high concentration of matter in the center. Currently, the only known objects that can pack enough matter in such a small space are black holes, or things that will evolve into black holes within astrophysically short timescales. For active galaxies farther away, the width of broad spectral lines can be used to probe the gas orbiting near the event horizon
. The technique of reverberation mapping uses variability of these lines to measure the mass
, and perhaps the spin
of the presumed supermassive black hole that powers the active galaxy's "engine".
Only a small handful of AGN (less than 40) have been accurately mapped. One of the most luminous objects with reverberation mapping results, and one of the only named AGN, is Kate's Quasar.
Astrophysics
Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...
preferably used in connection with velocity analysis of gaseous discs
Accretion disc
An accretion disc is a structure formed by diffuse material in orbital motion around a central body. The central body is typically a star. Gravity causes material in the disc to spiral inward towards the central body. Gravitational forces compress the material causing the emission of...
around supermassive compact objects
Supermassive black hole
A supermassive black hole is the largest type of black hole in a galaxy, in the order of hundreds of thousands to billions of solar masses. Most, and possibly all galaxies, including the Milky Way, are believed to contain supermassive black holes at their centers.Supermassive black holes have...
. The technique is used to measure the size of the broad emission-line region and mass of the alleged central black hole
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...
in active galactic nuclei
Active galactic nucleus
An active galactic nucleus is a compact region at the centre of a galaxy that has a much higher than normal luminosity over at least some portion, and possibly all, of the electromagnetic spectrum. Such excess emission has been observed in the radio, infrared, optical, ultra-violet, X-ray and...
.
Direct Doppler
Doppler effect
The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...
measures of water masers
Astrophysical maser
An astrophysical maser is a naturally occurring source of stimulated spectral line emission, typically in the microwave portion of the electromagnetic spectrum...
surrounding the nucleus of nearby galaxies have revealed a very fast Keplerian motion
Kepler's laws of planetary motion
In astronomy, Kepler's laws give a description of the motion of planets around the Sun.Kepler's laws are:#The orbit of every planet is an ellipse with the Sun at one of the two foci....
, only possible with a high concentration of matter in the center. Currently, the only known objects that can pack enough matter in such a small space are black holes, or things that will evolve into black holes within astrophysically short timescales. For active galaxies farther away, the width of broad spectral lines can be used to probe the gas orbiting near the event horizon
Event horizon
In general relativity, an event horizon is a boundary in spacetime beyond which events cannot affect an outside observer. In layman's terms it is defined as "the point of no return" i.e. the point at which the gravitational pull becomes so great as to make escape impossible. The most common case...
. The technique of reverberation mapping uses variability of these lines to measure the mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
, and perhaps the spin
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...
of the presumed supermassive black hole that powers the active galaxy's "engine".
Only a small handful of AGN (less than 40) have been accurately mapped. One of the most luminous objects with reverberation mapping results, and one of the only named AGN, is Kate's Quasar.
External links
- Reverberation Mapping ppt-presentation (2005)