A new study by researchers from the US and Chile suggest there is an upper limit on the mass of black holes. Using a variety of observational data they trace the accretion history of black holes, from which the mass and growth rate of the black holes can be determined. A study of the predicted distribution of black holes with varying masses according to the accretion history and its comparison to observed distribution, suggests the mass of black holes is upper bound.
The original ESO observing site is
on the mountain La Silla in the southern
part of the Atacama desert, 600 km
north of Santiago de Chile and at 2400 m
altitude. Here, ESO operates several
optical telescopes with mirror diameters
of up to 3.6 meters. (Credit: ESO, European
Organisation for Astronomical Research
in the Southern Hemisphere)
It is believed that at the center of every galaxy lies a dormant Super-Massive Black Hole (SMBH). Some of these may be classified as Ultra-Massive Black Holes (UMBHs), black holes with a mass exceeding that of 5 billion suns. These black holes grow primarily by accreting gas from the surrounding galaxy. This growth probably begins at very high redshifts, i.e. long ago (higher redshift means earlier in time).
The new study conducted by Priyamvada Natarajan from Yale University, who is currently a fellow at the Radcliffe Institute for Advanced Study at Harvard, and Ezequiel Treister from the European Southern Observatory in Santiago, Chile, trace the accretion histories of the black holes. Using the quasar (very bright black holes) luminosity function, models of the cosmic X-ray background radiation and observational data regarding the rates of accretion in quasars at various redshifts, they suggest that SMBHs spend most of their lives in a low accretion state, and only a fraction of their life as bright quasars.
By tracing the accretion behavior of black holes the mass of the black hole can be obtained, as well as the rate of its growth. A study of the black hole’s spatial density, i.e. how many black holes are present per unit of volume, as a function of the black hole's mass, reveals an abundance of UMBHs that is not in accordance with observations of today's universe.
The main component of this graphic
is an artist's representation of
M33 X-7, a binary system in the nearby galaxy
M33. In this system, a star about 70 times
more massive than the Sun (large blue object)
is revolving around a black hole. This black
hole is almost 16 times the sun's mass,
a record for black holes created from the
collapse of a giant star. Other black holes at
the centers of galaxies are much more
massive, but this object is the record-setter for
a so-called "stellar mass" black hole
(Credit: ration: NASA/CXC/M.Weiss; X-ray:
NASA/CXC/CfA/P.Plucinsky et al.; Optical:
NASA/STScI/SDSU/J.Orosz et al.)
Natarajan and Treister suggest there is a self-regulation mechanism preventing the mass of a black hole from exceeding a certain value. Introducing this modification into the study of black hole spatial density, yields results that comply with observed data. These results show that while UMBHs are rare but nevertheless likely to exist, there is an upper limit on their mass.
To determine the mass limit, the scientists make use of the correlation between the properties of a black hole and those of its galaxy. In particular the strong correlation between the mass of the black hole and the velocity dispersion of its galaxy (the distribution of velocities of stars in the galaxy) is relevant to this calculation. Using various models that describe the connection between a galaxy's velocity dispersion and the mass of the black hole lying at its center, they arrive at a limit in the area of 10 billion times the mass of the sun.
A likely place to find UMBHs is in bright and massive galaxies. The Sloan Digital Sky Survey (SDSS), a galaxy survey that began in 1998 and is still underway, may be able to detect these black holes and assist in furthering our understanding of galaxy formation and black hole assembly in the Universe.
TFOT reported on research confirming the leading theory regarding the behavior of galactic black holes, according to which the particles are accelerated by tightly-twisted magnetic fields close to the black hole. In another article TFOT covered a research that verified the blue color of quasar accretion disks. This was done by analyzing the emission spectra of the accretion disk surrounding the black hole.
exceed upper limit (09/17/08 - 8:06 - by Robert Burntwing)
How is this limit enforced? what happens if this limit is breached?
reply to Robert Burntwing (09/17/08 - 9:43 - by Shalhevet Bar-Asher)
This limit is enforced by a self regulating mechanism. The research
suggests 3 possible mechanisms, detailed in Section 5. The study does
not address a possible limit breaching scenario.
mass measurement unit (03/10/09 - 3:49 - by Tony Angelis)
Could you please help me with the symbol that comes right after the M
(unit) measuring the mass of a black hole? Example: 1000 M(?)
\" what happen if the limit is breached?\" (03/13/09 - 6:19 - by john)
You never heard of the galaxy police?
are black holes fractal? (04/20/09 - 15:49 - by jim)
Could the mass cutoff points be fractal size-invariance? since there
are mini's, why would it stop at 10 billion solar masses for a galaxy,
when a galaxy comprises a supercluster by hierarchial rank? Surely
superclusters contain much more massive blackholes then do galaxies.
Core Size?? (03/07/10 - 18:44 - by E Wyatt)
Has anyone considered the average core size of the matter within a
black hole? Some say atom size, some basketball, some several
kilometers. Shouldn't there be consensus on this?
physics black hole (08/03/10 - 5:01 - by saravanan)
Biack hole is unbelievable.un imaginable mass.I cannot accept this
theory which is only assumption. no proof.
it is a question (09/09/11 - 12:06 - by g amarnath sankar)
what is time in cosmology how can time slow down near huge bodies
BLACK HOLES (09/09/11 - 12:11 - by G AMARNATH SANKAR)
