Supermassive Black Holes Can’t Swallow Dark Matter

A modelled accretion disk around a black hole. Image credit: Michael Owen, John Blondin (North Carolina State Univ.). Source: http://apod.nasa.gov/apod/ap050312.html

Apparently, black holes and dark matter don’t play well together. Broadly speaking, black holes can be considered to be a significant portion of the “missing mass” in the universe, but dark matter is distinguished as “non-baryonic matter”. It seems that this mysterious non-baryonic matter is being used to explain a huge number of unexplained cosmic mysteries, but in the case of supermassive black holes, dark matter plays a very small role insofar as being used as black hole food…

I was pointed in the direction of an interesting paper complied by a French research group entitled “Dark Matter Accretion into Supermassive Black Holes“. In a nutshell they look into dark matter as a possible fuel to make supermassive black holes, well, supermassive. There has been much debate over to what extent dark matter may have to play in the evolution of black holes, so a complex numerical model was used and compared with observations.

This is the cool bit. It turns out that non-baryonic dark matter (a.k.a. dark matter), as opposed to baryonic matter (a.k.a. protons, neutrons, atoms, “normal” stuff), is highly collisionless. This means that dark matter, in its nature, is highly non-interacting. It can be easily scattered by stars and gas clouds, and it is very hard to imagine the stuff create a compact accretion disk around black holes.

Black hole accretion disks generate a lot of radiation, so much so that galactic cores can be observed as quasars. This radiation is produced as “normal” baryonic matter accumulated in the accretion disk falls to its death in the black hole event horizon. The matter has been accelerated to relativistic speeds and about 10% of the mass falling into the ‘hole is converted into energy (i.e. E=mc2). A massive quantity of energy is blasted into space as X-ray emissions.

By taking observations of galactic core quasars (the location of supermassive black holes) and using theoretical models to predict the rate of accretion disk “feeding” into the black hole, a rough estimate on how much dark matter is falling into the black hole can be found. For baryonic matter, the amount of X-rays generated by the quasar is proportional to the amount of matter falling into the black hole. Dark matter on the other hand (theoretically) does not generate X-rays as it falls into a black hole. So, from logical reasoning, if the predicted rate at which mass is falling into the black hole is more than the observed energy emitted, then perhaps some of the mass of the accretion disk is in fact dark matter.

Well, the details are sketchy, but it is looking unlikely that dark matter has any large part to play in the evolution of supermassive black holes. Less than 10% of the mass of the accretion disk will consist of dark matter; the other 90% can be easily accounted for in the form of baryonic matter.

Have a look at my Universe Today article for more on black holes and dark matter…

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12 responses to “Supermassive Black Holes Can’t Swallow Dark Matter

  1. Very very interesting. The notion that a supermassive black-hole cannot swallow dark-matter is one of the conclusions established in my newly advanced deductive Dominium model. This paper you site is quite exciting to me because it is in 100% agreement with the new model’s predictions in its conclusions #17, 18, & 19, which deal with the creation of supermassive black-holes and the role of MBH (dark matter): micellular opposite-type matter, e,g,. antimatter for the Milky Way, black-holes in that process. The reason why the supermassive black-holes can’t consume MBH relates to the model’s fundamental hypothesis that matter and antimatter gravitationally repel. This hypothesis also explains why, in your article you describe dark-matter as “collisionless.” If you wish to read the new model, a free download can be had at http://www.sendspace.com/pro/dl/u56srb or you can acquire the full version of “The Dominium” at the library.

    Debate over the new model is fierce–but not because of what I just mentioned. The most ominous implication of the new model is that mini black-holes are predicted to be stable. This is of supreme concern because CERN’s LHC project is expected to produce man’s first mini black-holes. You can see and join the debate on my Scientific American blog at: http://science-community.sciam.com/blog/Hasanuddins-Blog/300005039

  2. I’m wondering what you think of Sthephen Crothers’ research into the mathematical origins of Black Holes that appears to refute their very existence?

    ( Big Bang Busted! – The Black Hole, the Big Bang, and Modern Physics.)
    http://thunderbolts.info/thunderblogs/archives/guests08/022108_guest_sjcrothers.htm

    He seems to indicate that when one goes back to the original source documents (rather than later derivations and innovations, which may well be in error mathematically or otherwise), the black hole was categorically ruled out. Who’s right?

    Cheers,
    ~Michael Gmirkin

  3. Pingback: Supermassive Black Holes are Not Fussy Eaters | astroengine.com

  4. Does anybody know if the supermassive black hole and the dark matter are related? I mean does dark matter have anything to do when the galaxies were in the process of forming?
    I can’t find one single article about it, so I guess these two have nothing to do with each other. Or am I wrong?

    Best Wishes
    Shak

  5. I see the Cosmos as being divided into two Universes, that of the very big (protons up) and that of the very small (everything smaller) – what we currently call Dark Matter. One of the primary characteristics of the UVS is that it is non-interactive, i.e. its particles don’t build structures except under intense pressure.

    I won’t go into a long song and dance but one of the reasons you don’t see Dark Matter footprints at the level of the accretion disk is this lack of interaction, either with itself or the matter of the UVB.

    One correction: yes, the UVS is highly non-interactive but baryonic matter does not “Scatter” its matter, it rides on it. It is the UVS that enables the UVB to be so very interactive.

    Finally, the UVS is not homogeneous. Its smallest known particle is the neutrino and its largest known particle is the electron, with a lot of stuff in between.

  6. A note to Shak – SBMs belong to the UVB, there is no causal relationship between them and the UVS. You can’t find any articles because the nature of Dark Matter(the UVS)is a cipher to the Cosmological Community and it’s going to take them another 10 to 15 years to figure it out.

  7. Yes, but …
    Baryonic matter undergoes serial gravitational collapse, from nebulae to stars to degenerate stars (white dwarfs or neutron stars). At each stage, the collapse dissipates angular momentum, but is halted by some countervailing process: radiation pressure in star formation, electronic or nuclear degeneracy pressure in white dwarves & neutron stars, respectively. But if dark matter does not experience electromagnetism or nuclear forces, what would halt the collapse?
    If there are regions of dark matter with sufficiently small total angular momentum they must collapse–even if their total mass is small.

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