Credit: X-ray: NASA/CXC/Washington State Univ./V. Baldassare et al.; Optical: NASA/ESA/STScI
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These new results suggest a somewhat violent path for at least some of these black holes to reach their present size — stellar destruction on a scale that has rarely if ever been seen before.
Astronomers have made detailed studies of two distinct classes of black holes. The smaller variety are "stellar-mass" black holes that typically weigh 5 to 30 times the mass of the Sun. On the other end of the spectrum are the supermassive black holes that live in the middle of most large galaxies, which weigh millions or even billions of solar masses. In recent years, there has also been evidence that an in-between class called "intermediate-mass black holes" (IMBHs) exists. The new study with Chandra could explain how such IMBHs are made through the runaway growth of stellar-mass black holes.
One key to making IMBHs may be their environment. This latest research looked at very dense clusters of stars in the centers of galaxies. With stars in such close proximity, many stars will pass within the gravitational pull of black holes in the centers of the clusters. Theoretical work by the team implies that if the density of stars in a cluster — the number packed into a given volume — is above a threshold value, a stellar-mass black hole at the center of the cluster will undergo rapid growth as it pulls in, shreds and ingests the abundant neighboring stars in close proximity.
Of the clusters in the new Chandra study, the ones with density above this threshold had about twice as many growing black holes as the ones below the density threshold. The density threshold depends also on how quickly the stars in the clusters are moving.
The process suggested by the latest Chandra study can occur at any time in the universe's history, implying that intermediate-mass black holes can form billions of years after the Big Bang, right up to the present day.
A paper describing these results was accepted and appears in The Astrophysical Journal. It is also available online. The authors of the study are Vivienne Baldassare (Washington State University), Nicolas C. Stone (Hebrew University in Jerusalem, Israel), Adi Foord (Stanford University), Elena Gallo (University of Michigan), and Jeremiah Ostriker (Princeton University).
NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
Fast Facts for NGC 1385:
Credit: X-ray: NASA/CXC/Washington State Univ./V. Baldassare et al.; Optical: NASA/ESA/STScI
Scale: Image is about 2.68 arcmin (33,400 light years) across
Category: Black Holes, Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 3h 37m 28.33s | -24° 30' 3.22"
Constellation: Fornax
Observation Dates: Dec 6, 2018
Observation Time: 1 hour 24 minutes
Obs. IDs: 21473
Instrument: ACIS
Color Code: X-ray: blue; Optical: red, green, and blue
Distance Estimate: About 43 million light years
Fast Facts for NGC 1566:
Credit: X-ray: NASA/CXC/Washington State Univ./V. Baldassare et al.; Optical: NASA/ESA/STScI
Scale: Image is about 2.77 arcmin (25,700 million light years) across
Category: Black Holes, Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 4h 20m 0.27s | Dec -54° 56' 12.02"
Constellation: Dorado
Observation Dates: Dec 3, 2018
Observation Time: 51 minutes
Obs. IDs: 21478
Instrument: ACIS
Color Code: X-ray: blue; Optical: red, green, and blue
Distance Estimate: About 32 million light years
Fast Facts for NGC 3344:
Credit: X-ray: NASA/CXC/Washington State Univ./V. Baldassare et al.; Optical: NASA/ESA/STScI
Scale: Image is about 2.58 arcmin (46,400 light years) across
Category: Black Holes, Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 10h 43m 31.08s | Dec +24° 55" 14.25'
Constellation: Leo Minor
Observation Dates: 2 observations, Jan 25, 2006 & Jan 21, 2013
Observation Time: 13 hours 40 minutes
Obs. IDs: 7087, 15387
Instrument: ACIS
Color Code: X-ray: blue; Optical: red, green, and blue
Distance Estimate: About 62 million light years
Fast Facts for NGC 6503:
Credit: X-ray: NASA/CXC/Washington State Univ./V. Baldassare et al.; Optical: NASA/ESA/STScI
Scale: Image is about 2.68 arcmin (13,700 light years) across
Category: Black Holes, Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 17h 49m 23.4s | Dec +70° 8' 51.12"
Constellation: Draco
Observation Dates: 2 observations, Mar 23, 2000 & Oct 27, 2000
Observation Time: 4 hours 14 minutes
Obs. IDs: 872, 1640
Instrument: ACIS
Color Code: X-ray: blue; Optical: red, green, and blue
Distance Estimate: About 18 million light years
