- Sołtan argument
The Sołtan argument is an astrophysical theory outlined in 1982 by Polish
astronomer Andrzej Sołtan. It maintains that ifquasar s were powered byaccretion onto asupermassive black hole , then such supermassive black holes must exist in our local universe as "dead" quasars.History
As early as 1969,
Donald Lynden-Bell wrote a paper arguing that "dead quasars" were found at the center of theMilky Way and nearby galaxies by arguing that given the quasar-number counts, luminosities, distances, and the efficiency of accretion into a "Schwarzschild throat" through the last stable circular orbit (note that at the time the term "black hole " had not yet been coined), roughly 1010 quasars existed in theobservable universe . This number density of "dead quasars" was attributed by Lynden-Bell to highmass-to-light ratio objects found at the center of galaxies. This is essentially the Sołtan argument, though the direct connection between black hole masses and quasar luminosity functions is missing. In the paper, Lynden-Bell also suggests some radical ideas that are now fully integrated into modern understanding of astrophysics including the model thataccretion disks are supported bymagnetic field s, thatextragalactic cosmic ray s are accelerated in them, and he estimates to within an order of magnitude the masses of several of the closestsupermassive black hole s including the ones in theMilky Way , M31, M32, M81, M82, M87, andNGC 4151 . [cite journal
author = Lynden-Bell, D.
title = "Galactic Nuclei as Collapsed Old Quasars"
journal = Nature
year = 1969
month = August
volume = 223
pages = 690-694
url = http://adsabs.harvard.edu/abs/1969Natur.223..690L]Thirteen years later, Sołtan explicitly showed that the
luminosity () of quasars was due to the accretion rate of mass onto black holes given by:where
* is the efficiency factor
* is thetime rate of mass falling into the black hole
* is thespeed of light cite journal
author = Ferrarese, L. and Ford, H.
title = "Supermassive Black Holes in Galactic Nuclei: Past, Present and Future Research"
journal =Space Science Reviews
eprint = arXiv:astro-ph/0411247
year = 2005
month = February
volume = 116,
pages = 523-624
doi = 10.1007/s11214-005-3947-6
url = http://adsabs.harvard.edu/abs/2005SSRv..116..523F]Given the number of observed quasars at various
redshift s, he was able to derive an integratedenergy density due to quasar output. Since observers on Earth areflux limit ed, there are always more quasars that exist than are observed and thus the energy density he derived is alower bound . Approximately 10-10erg s percubic meter was the value he obtained.cite journal
author = Sołtan, A.
title = "Masses of quasars",
journal =Monthly Notices of the Royal Astronomical Society
year = 1982
month = July
volume = 200
pages = 115-122
url = http://adsabs.harvard.edu/abs/1982MNRAS.200..115S]Sołtan calculated this the mass density of accreted material since the energy density of quasar light is directly related. He derived a value of approximately 1014
solar mass es per cubicGigaparsec . This mass has to be distributed discretely (since quasars are single point sources) and given an average mass of quasars of approximately ten million solar masses, it would be statistically likely for a "dead quasar" to be within a fewmegaparsec s of Earth.At this time, evidence was already accumulating that supermassive black holes were found at the center of large galaxies which happen to be distributed approximately on the order of a megaparsec apart from each other. This argument therefore made a reasonable case that supermassive black holes were at one time ultraluminous quasars.
Present constraints
As of 2008, the best constraints for the supermassive black hole mass per cubic megaparsec in the local universe derived from the Sołtan argument is between 2 - 5 x 105 solar masses. This value is consistent with observations of the mass of local supermassive black holes [D. Merritt and L. Ferrarese (2001), [http://adsabs.harvard.edu/abs/2001MNRAS.320L..30M| Black Hole Demographics from the M-sigma Relation] ] .
See also
#
Supermassive black holes
#M-sigma relation References
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