Wednesday, April 12, 2023

3954 - BLACKHOLES - super massive?

 

-   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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