- 3954 - BLACKHOLES - super massive? How does the Universe produce Ultra-Massive Black Holes? Black holes are the most massive objects that we know of in the Universe. Not stellar mass black holes, not supermassive black holes (SMBHs,) but ultra-massive black holes (UMBHs.)
---------------------- 3954 - BLACKHOLES - super massive?
- These ultra-masive blackholes sit in the center of galaxies. They have more than five billion solar masses. The largest black hole we know of is Phoenix A, a UMBH with up to 100 billion solar masses.
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- UMBHs are
rare and elusive, and their origins are unclear. Their origins have been traced back to the
Universe’s ‘Cosmic Noon‘ around 10 to 11 billion years ago.
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- One
possible formation channel for ultra-massive black holes is from the extreme
merger of massive galaxies that are most likely to happen in the epoch of the
‘cosmic noon.
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- UMBHs are
extremely rare. Creating them in scientific simulations requires a massive,
complex simulation. “Astrid” is a
large-scale “cosmological hydrodynamical simulator” that runs on the Frontera
supercomputer at the University of Texas, Austin.
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- Astrid’s
large-scale simulations can track things like dark matter, temperature,
metallicity, and neutral hydrogen. Simulations like Astrid are ranked by the
number of particles their simulations contain, and Astrid is at the top of that
list.
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- Galaxies
grow large through mergers, and it’s likely that SMBHs grow more massive at the
same time. But UMBHs are even more massive and much rarer. How do they form?
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- “Cosmic
Noon” is an important time period in the history of the Universe. Astronomers
think that half of all stars were born during the period. It corresponds to
redshift z=2 to z=3, or when the Universe was about 2 to 3 billion years old.
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- At that
time, large quantities of gas flowed from the intergalactic medium into
galaxies. Galaxies formed about half of their stellar mass during cosmic noon.
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- Astronomers
spotted an extreme and relatively fast merger of three massive galaxies. Each of the galaxy masses is 10 times the
mass of our own Milky Way, and a supermassive black hole sits in the center of
each galaxy. These quasar triplet
systems are the progenitor of those rare ultra-massive blackholes after those
triplets gravitationally interact and merge with each other.
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- Quasars’
name is misleading. It means a quasi-stellar object, but the name stems from a
time before astronomers knew what they were. Quasars are a subset of active
galactic nuclei but are extremely luminous. The luminosity comes from all of
the material falling into the SMBH at a galaxy’s center.
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Astrophysicists have determined a theoretical upper mass limit for black
holes at about 50 billion solar masses, and the post-merger UMBH approaches
that limit.
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Ultramassive black holes with extreme masses of <50 billion solar
masses can be formed in the rare events
that are multiple massive galaxy mergers happening around z = 2, the epoch when
both star formation and AGN reach their peak activity.
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- The future
space-based “NASA Laser Interferometer Space Antenna” (LISA) gravitational wave
observatory will give us a much better understanding the how these massive
black holes merge and/or coalescence, along with the hierarchical structure,
formation, and the galaxy mergers along the cosmic history.
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April 11, 2023
BLACKHOLES supermassive? 3954
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--- Wednesday, April 12, 2023 ---------------------------
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