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I Origin of supermassive blackholes in the very early universe

  1. Jan 2, 2018 #1
    Hi, I am new here. A while back I read articles about observations of supermassive blackholes in the early age of the universe. What are the hypotheses that would explain how these blackholes grew so large and so fast so soon? Could inflation play a role here? Like how inflation would be able to inflate microscopic blackholes in the quantum foam from tiny to gargantuan size?
     
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  3. Jan 2, 2018 #2

    bapowell

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    Inflation can generate primordial black holes but it doesn’t work the way you suggest. Inflation created density perturbations across a wide range of length scales: these perturbations seeded all the large scale structure that we observe in the cosmos. The perturbations started out small but grew into larger overdensities as time wore on. It’s possible that the perturbations on sub-galactic scales were really quite large, large enough to become black holes. The sizes, distribution, and abundance of such black holes would depend on the details of the inflation model.
     
  4. Jan 2, 2018 #3

    kimbyd

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    Modeling the physics of how these black holes grow is a very challenging endeavor. There's a lot of research involved in using computer models to describe how black holes grow through the accretion of matter.

    The big challenge comes in with the concept of feedback: as black holes eat matter, they tend to heat up their surroundings rapidly. In order to fall into a black hole, matter needs to lose energy. So if there is too much heat coming from the active black hole, then the matter will heat up and stop falling inward, which starves the black hole. This process places limits on how quickly the black hole can absorb matter from its surroundings.

    My understanding, from what I remember of the state of research a few years ago, is that computer models had made significant progress, but still weren't able to provide a full explanation for the growth rates required to explain the most massive black holes.

    As for inflation, inflation does not "inflate" black holes. It is possible for some black holes to have formed during inflation, but they would have been extremely tiny, and the inflation itself would not have made them any bigger: inflation would just move the black holes further away from one another.

    The idea that black holes might have formed in the very early universe is collectively described as "primordial black holes". These black holes would likely have formed not during inflation, but shortly thereafter. The idea is that inflation creates areas with more and less density. If some fraction of the dense regions are dense enough, then they'll be able to collapse into black holes very rapidly once the expansion slows enough. The idea has long been considered plausible, but very speculative. These black holes would still be pretty small at the start, and would need to grow by eating matter (and other black holes) in order to explain the supermassive black holes. But it's certainly plausible they could play a role in explaining the rapid growth of some black holes in the early universe.

    That said, while checking my facts on this, I ran across this paper:
    https://arxiv.org/abs/1702.00947

    If this paper is correct, primordial black holes are just too small to have much of any impact on the growth of supermassive black holes.
     
  5. Jan 6, 2018 #4
    Hello Kimbyd,

    I do not understand what the linked article has to do with SMBH made from PBH. The article concludes that there are not enough pbh's to make up for dark matter. I did not see anywhere that there was no possibility PBHs or that these could not have been the seeds for SMBH's. Could you point me in the right direction?
     
  6. Jan 7, 2018 #5

    Chronos

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    Hierachical assembly of billion+ mass black holes from small, stellar mass seeds has long been known to be problematic. The prospect of direct collapse black holes [DCBH] has been gaining ground The idea of oversized seeds forming from pop III stars has been kixked around for about 30 years as discussed here http://adsabs.harvard.edu/full/1984ApJ...277..445C, Cosmological consequences of Population III stars, and further discussed here; , Supermassive Seeds for Supermassive Black Holes.. Discussion of a candidate DCBH, known as CR7, ia addressed here; http://chandra.harvard.edu/blog/node/598, Cosmic Genealogy: the Ancestors of Supermassive Black Holes. The idea that DCBH's may be of primordial origin is gaining credence as a realistic possibility.
     
  7. Jan 7, 2018 #6

    kimbyd

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    It's not so much that they can't form the seeds of SMBH's, but rather that they don't solve the problem of big SMBH's, because they still have to grow. It's possible they play a part in the solution (if they exist), but can't be there whole of it.
     
  8. Jan 8, 2018 #7

    Grinkle

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    Are supermassive black hole observations inconsistent with multiple closely located smaller black holes that might have a more explainable history?
     
  9. Jan 8, 2018 #8

    kimbyd

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    I don't think so. The problem is you need a lot of them. The largest SMBHs are billions of solar masses in size. Primordial black holes would typically be pretty spread-out, and as they don't experience very much friction would take a lot of time to get close enough to one another to merge.

    As I understand it, the current best explanation is a combination of direct collapse (where a large cloud of gas is so massive that it just collapses directly into a black hole without forming a star first), resulting in an intermediate-mass black hole which then grows to supermassive size by eating nearby gas and dust, as well as potentially merging with other large black holes from time to time. But this is still without strong supporting evidence, so it might be entirely wrong. For now, the exact details of how supermassive black holes form are rather uncertain.
     
  10. Jan 8, 2018 #9

    Chronos

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    The discovery of numerous massive quasars at high z offers additional support for the DCBH conjecture. This result has not yet been published on arxiv, so this is the best I can do for now: https://carnegiescience.edu/news/discovery-nearly-doubles-known-quasars-ancient-universe. One of these quasars, J1342+0928, tips the scales at 800 million solar masses when the universe was less than 700 million years old as discussed here: http://www.astronomy.com/news/2017/12/lighting-up-the-dark-universe . Pretty tough to write this one off as a stellar corpse merger at a time when star formation was just cranking up in the universe..
     
  11. Jan 9, 2018 #10

    timmdeeg

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    Whereby if I see it correctly this happens at the end of inflation during or shortly after the 'reheating' era. So it happens when there exists already "condensed" matter due to the decay of the inflaton field. Now my question: Supposed inflation creates an area with overdensity large enough to represent a black hole before it ends and hence before reheating with matter condensation starts, what would happen? I'm quite sure, this question isn't consistent with inflationary theories and insofar probably makes no sense. But just in principle?

    And another question: If a melt crystallizes it contains the information (the knowledge of the molecules it consists of) to at least in principle calculate the structure of the crystals resulting from the melt. Is it correct that the inflaton field doesn't provide any information regarding the kind of matter particles which are created later? What characterizes the field so that one can say that "once the expansion slows enough" matter must be the result?
     
  12. Jan 9, 2018 #11

    Chronos

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    This paper; https://arxiv.org/abs/1003.3421, Gravity-induced vacuum dominance, suggests quantum seeds can experience runaway growth - an idea further developed here; https://arxiv.org/abs/1202.3848, Primordial seeds of supermassive black holes. Inflation would account for the quantum seeds needed to enable this process..
     
  13. Jan 10, 2018 #12

    timmdeeg

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    In the abstract the authors state "In a class of well-motivated models, inflationary epoch could include two or more periods of inflation dominated by different scalar fields. The transition between such periods of inflation could enhance the spectrum of density perturbations on some specific scale, which could lead to formation of primordial black holes with a very narrow range of masses of the order of 10^5 solar masses. These primordial black holes could have provided the requisite seeds for the observed population of supermassive black holes."
    So such black holes could have existed already in the very early universe but with the caveat that additional assumptions are required.
     
  14. Jan 10, 2018 #13

    kimbyd

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    My understanding from the paper I posted previously was that the larger mass range is ruled out by observations, so that such black holes still have to be pretty small by the time the first galaxies started forming:
    https://arxiv.org/abs/1702.00947

    The "primordial black holes are seeds of SMBH's" idea could still be recovered, potentially, if it is shown that you only need a tiny number of them to explain the seeds of SMBH's.
     
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