August 9, 2018
Finding these elusive
intermediate-mass black holes could help astronomers better
understand what the "seeds" for the largest black holes in the early
This is because their mass places them in between,
While several tantalizing
possible IMBHs have been reported in recent years, astronomers are
still trying to determine how common they are and what their
properties teach us about the formation of the first
supermassive black holes.
The characterization of
these galaxies was enabled by the rich dataset available for the
COSMOS field at different wavelengths, including data from NASA and
shows data that have provided evidence
for the existence of
intermediate-mass black holes (IMBHs).
The X-rays are produced by gas heated to millions of degrees by the enormous gravitational and magnetic forces near the black hole.
Her team identified forty growing black holes in dwarf galaxies.
Twelve of them are located at distances more than five billion light years from Earth and the most distant is 10.9 billion light years away, the most distant growing black hole in a dwarf galaxy ever seen.
One of the dwarf galaxies
is the least massive galaxy found to host a growing black hole in
In their sample, the most
distant IMBH candidate is about 2.8 billion light years from Earth
and about 90% of the IMBH candidates they discovered are no more
than 1.3 billion light years away.
They selected 305
galaxies with properties that suggested a black hole with a mass
less than 300,000 times that of the Sun was lurking in the central
regions of each of these galaxies.
Detections with Chandra and with XMM-Newton were obtained for ten sources, showing that about half of the 305 IMBH candidates are likely to be valid IMBHs.
The masses for the ten sources detected with X-ray observations were determined to be between 40,000 and 300,000 times the mass of the (our) Sun.
IMBHs may be able to explain how the very biggest black holes, the supermassive ones, were able to form so quickly after the Big Bang.
One leading explanation is that supermassive black holes grow over time from smaller black holes "seeds" containing about a hundred times the Sun's mass. Some of these seeds should merge to form IMBHs.
Another explanation is
that they form very quickly from the collapse of a giant cloud of
gas with a mass equal to hundreds of thousands of times that of the
Chilingarian's team has a different conclusion.
Another possibility is that both mechanisms actually occur.
Both teams agree that to make firm conclusions much larger samples of black holes are needed using data from future satellites.