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Thread: SMBH mergers

  1. #1
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    Default Re: SMBH mergers

    Very interesting. I had not heard of the final parsec problem until now. I don't get out much, obviously.

    Anyway, lot's of interesting ready on the topic.

    A couple of papers at arXiv:

    https://arxiv.org/abs/astro-ph/0212270

    https://arxiv.org/abs/1311.1167

    And an article from last year: Supermassive Black Hole Merger Could Finally Solve The 'Final Parsec Problem'
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    Default Re: SMBH mergers

    Thanks. I believe there is a thread here where we discussed it before too.

    What is interesting to me is that similar process (encounters with low mass objects that get ejected) that helped the early solar system reach its current configuration (Nice model) helps accelerate these mergers.
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    Default Re: SMBH mergers

    BTW it's amusing that the arxiv papers you linked seem to criticize this approach.
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    Default Re: SMBH mergers

    Quote Originally Posted by not_Fritz_Argelander View Post
    BTW it's amusing that the arxiv papers you linked seem to criticize this approach.
    Hahaha! I found that rather amusing as well.
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    Default Re: SMBH mergers

    I think the work in the OP is a clever approach to the multi scale problem and adequately answers critical questions.
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    Default Re: SMBH mergers

    Fascinating and raises many questions. 1) What is the significance of the z value selected for the merger? 2) What accounts for the gas dissipation before the merger and how does this promote the merger? 3) What does it mean that the gravitational potential is triaxial and non-spherical and how does this relate to the disrupted star orbits near the SMBH? 4) Is the presence of gas near the SMBHs the primary reason for the stalling of the merger?
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    Default Re: SMBH mergers

    Quote Originally Posted by stargazer55 View Post
    Fascinating and raises many questions. 1) What is the significance of the z value selected for the merger?
    Only a guess but if I were doing this study I would pick a z value congruent with probability of detectable events.

    2) What accounts for the gas dissipation before the merger and how does this promote the merger?
    The gas is viscous. Interstellar gases are very viscous since the viscosity is inversely proportional to the mean free path for particle collisions and that is long in the ISM. By providing an energy sink for the motion of more massive bodies the merger is promoted. The SMBHs stir the viscous gas, losing energy to it, and so the orbit becomes tighter.

    3) What does it mean that the gravitational potential is triaxial and non-spherical and how does this relate to the disrupted star orbits near the SMBH?
    This is a guess.

    One school of thought is that early in the process of coalescence dynamical friction via scattering stars will be the dominant form of energy loss causing the BHs to sink to the deepest part of the gravitational potential. The triaxial potential will scatter stars and make effective scattering events rarer.

    So the process runs that the BHs will tend to scatter stars and gas and so deprive themselves of material to lose energy to. However a triaxial potential can disturb the orbits of stars and feed them into the center where the BHs can dump orbital energy off on them by scattering.

    4) Is the presence of gas near the SMBHs the primary reason for the stalling of the merger?
    Rather it is the clearing of the region around the BHs of gas and stars that slows the merger. If gravitational radiation dominates orbit decay the merger is slow. Stars and gas are needed to keep the merger on pace.

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