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Greedy Supermassive Black Holes Dislike Dark Matter

A supermassive black hole hidden by a thick donut-shaped galactic core - artist impression (credit: NASA)
It is widely accepted that supermassive black holes (SMBHs) sit in the centre of elliptical galaxies or bulges of spiral galaxies. They suck in as much matter as possible, generating blasts of radiation. Stars, gas and everything else nearby forms a compact “halo” and then falls to a gravitationally enforced death spiral. The greedy nature and the sheer size of these black holes have led to the idea that dark matter may supply (or may have supplied) the SMBH with some mass during its evolution. But could it be that dark matter may not be significantly involved after all? This might be one cosmic phenomenon dark matter can’t be blamed for…

Black hole accretion disks are compact halos created as dust, gas and other debris are pulled toward a black hole event horizon. Accretion disks radiate electromagnetic radiation, and the frequency of which depends on the mass of the black hole. The more massive it is, the higher the energy of radiation emitted into space. In the case of a SMBH, the huge mass causes very bright emission as the matter from the accretion disk falls into the event horizon (the point at which gravity becomes so strong that even light cannot escape). As accretion disk matter falls toward the event horizon, approximately 10% of the mass is converted into energy and ejected as X-rays. This is a far more efficient energy conversion rate than the most efficient nuclear fusion reaction (approximately 0.5%). This X-ray emission can then be observed, creating a quasar, signifying a SMBH is driving the active galaxy.
A simulation of an accretion disk (credit: Michael Owen, John Blondin, North Carolina State Univ.)
Interestingly, an SMBH is not thought to be formed from single dead massive star. They are thought to have been created from a “seed” and then grown over billions of years. The source of the mass feeding the growing SMBH comes from its accretion disk, but it is uncertain what form the matter comes in and at what rate it “feeds” the black hole. There are several possibilities as to how the largest black holes were seeded, but two are the most widely accepted:

  • Intermediate black holes (with masses of several thousand Suns) are created by vast clouds which collapse to a single point. Black holes form and accretion disks grow.
  • Massive primordial stars (the first stars, formed only 200 million years after the Big Bang) of a few hundred Sun masses may have collapsed to create smaller black holes, again forming accretion disks and growing over billions of years.

The mechanisms affecting the rate of accretion disk growth are not so clear-cut. Some theories suggest that huge quantities (most of the black hole mass) comes from dark matter. However, as dark matter is “non-baryonic” (i.e. the opposite to baryonic matter – the matter we know, love and observe in our universe) it will emit very little radiation as it falls into the black hole event horizon. If this is the case, SMBHs would grow disproportionately when compared with radiation emitted from galactic centres (only baryonic particles will emit X-rays).

New research headed by Sebastien Peirani (at the Institut d’Astrophysique de Paris, France) suggests only a very small fraction of a SMBH is composed from dark matter as it evolved. Dark matter is predicted to be collisionless and will be scattered very easily by baryonic gas clouds and stars. It seems unlikely that dark matter will be able to stay inside the black hole’s accretion disk for very long before it is repelled by all the “normal” matter being pulled toward the event horizon.

By modelling a “typical” accretion disk and comparing the results with observations of quasar luminosity, the French group found that most of the matter fuelling the SMBHs is relativistic baryonic matter. At a critical distance, outside the black hole, baryonic matter from the accretion disk is accelerated to a significant fraction of the speed of light, emitting radiation. Comparing this with simulations of a collisionless disk (i.e. the characteristics of dark matter), the baryonic model fits observations the best.

Application of our results to black hole seeds hosted by halos issued from cosmological simulations indicate that dark matter contributes to no more than [approx.] 10% of the total accreted mass, confirming that the bolometric quasar luminosity is related to the baryonic accretion history of the black hole.” – Abstract from “Dark Matter Accretion into Supermassive Black Holes

Source: arXiv


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Hello! My name is Ian O'Neill and I've been writing for the Universe Today since December 2007. I am a solar physics doctor, but my space interests are wide-ranging. Since becoming a science writer I have been drawn to the more extreme astrophysics concepts (like black hole dynamics), high energy physics (getting excited about the LHC!) and general space colonization efforts. I am also heavily involved with the Mars Homestead project (run by the Mars Foundation), an international organization to advance our settlement concepts on Mars. I also run my own space physics blog: Astroengine.com, be sure to check it out!

Comments on this entry are closed.

  • Peter K March 10, 2008, 9:40 AM


    Good for you for reading the comments sections. I’m sure you have other things to do. I come to Universe Today religiously and really enjoy it. My favourite (sorry, Canadian) articles are the theoretical ones about Dark Matter and fundamental forces. I’m not a physicist but I know what sounds like good science and what sounds “out there”. Theories are just as interesting as discoveries and make the universe a fascinating place. I like to think my simple thoughts might be as close to the mark as the real brains in the field.
    Keep it up!
    Your fan,

  • Shaithis March 10, 2008, 10:58 AM

    I’m a physics student. I am currently in the middle of astrophysics. I have been reading UT for about two years now maybe. I love how the trolls come out in full force in the comments section. Although it is unusual to see an author defending his work on the comments, its not unwelcome.

    The Dark Matter debate is killing me.

    You all do know what dark matter is, right?

    Dark matter is the answer to the question “why is the milky way a spiral when the visible mass is not enough to maintain this interesting shape?”

    There’s nothing about interacting with particles, whether they annihilate themselves, etc. Thats the best part. How is anyone able to describe the behaviour of a bunch of particles that only exist on paper? ITS Not Real.

    Why dark matter? Simple. Because no one has the stones to tell Isaac Newton that his calculations were off.

    Thats it yall. Thats the whole argument. We can all go back to pretending we’re experts about things that we don’t know anything about and know that no one else does either.

    These articles are great, but come on. Hundreds of pages of writing about particles that just don’t exist, applying properties to some invisible matter that only interacts with gravity? What’s more likely? 80% of the universe is invisible and intangible and only interacts with the rest of the universe just so we can fit it all within our presumptuous crosshairs, or perhaps a human that lived 400 years ago might not have carried a one?

    Lets all just get over ourselves just a little bit.

  • cathbad March 10, 2008, 1:49 PM

    I a n,

    feel confirmed and criticised. Your fame is to play the sacrificial lamb.
    Your fans like the lurid botch.
    Now be a man and stand the fact that there are some people out that see and name the disease. No not me. read the comments.
    You do ignore what you dont want to hear. Your choice. The things are still visible.
    I can confirm you are an eloquent and serious writer for your fandom, but neither your lurid style (GREEDY holes and DISLIKE of DM,…..) nor this infusion about a computer simulation (yes a simulation) qualifies you as a scientific jounalist….and you know it.

    Hide in whatever excuse you prefer.
    Rather patronizing nor ignorance will save you from being charged a yellow press copycat.

    About the article. It says no more and no less that a computer simulation delivered an upper bound of 10% (could be far less) for a DM contribution to the luminosity of relativistic matter falling into a massive black hole. I am here not refering now to the fact that DM is a picture, a model not a empiric result,. This is just the thin ice your stories stand on.

    What you make out of the simple computer simulation paper ? A lurid story about greedy holes that dont like DM.
    Is that science, science exegesis, simple rephrasing in fandom scene language ?

    Be a man and stand the critics that tell you that this is not really a quantum leap, neither in your kind of ‘theorethical physics’ nor in scientific journalism.

    Go ahead and rejoice in your fans and accept that some dont fall from your intellectual bremsstrahlung.

    Finally Bob, great idea to ask me for an article.
    What do you expect ? the same kind of knock off like Ian likes to spread for some bucks of fee ?
    There is not much more to say about this analysis paper than what is already said before.
    Do you expect me to bloviate in anthropomorphisms and some free association on unsave ground ?

    Make Ian your jester and let him waffle on speculative parts of theories, since it enriches your creative process of generating new theories the scientific world has waited for.
    This is like pinpointing the physical meaning of the negative solution of a squareroot.
    You can do it if you like, but dont expect standing ovations for it.

    As a trailer I admit that Ian is good in inflating an ant to the size of an elephant and impressing the woodlouses with it. Thats a talent indeed.

  • fred March 10, 2008, 6:03 PM

    To Ian vs cathbad:

    Later this year CERN will be launching the Large Hadron Collider, whose energy capabilities are robust enough to probe for the Higgs boson, and perhaps reveal unseen properties of dark matter and dark energy. THERE WILL BE SURPRISES GALORE.

    Cathbad, keep your eyes and ears open, bu t remember to keep your mouth shut,

  • ALOKMOHAN March 10, 2008, 9:28 PM

    Any new revelation on dark matter and dark energy is what we look for.Please dont call my uncle SMB greedy.Gravity pushes food to it.Uncle does not hanker for it.

  • cathbad March 11, 2008, 7:14 AM

    Fred I can wait for the dark energy and the non-primordial black holes from LHC.

    You escapists and dreamers just have no respect to real world scienctific work.

    I am sure that your kind is waiting for lurid botch freely associated from upcoming LHC results.
    Ian can feed your monkeys.

  • ScepticTim March 11, 2008, 10:17 AM

    PCY : You respond to

    “Dark matter is predicted to be collisionless and will be scattered very easily by baryonic gas clouds and stars. It seems unlikely that dark matter will be able to stay inside the black hole’s accretion disk for very long before it is repelled by all the “normal” matter being pulled toward the event horizon”
    “This statement makes no sense. If DM is collisionless both with itself and with baryonic matter, then no scattering/repulsion can occur. If only gravity is at work, then the opposite should happen.”

    First, the collisionless plasma model is, in essence: A model of a plasma in which the density is so low, or the temperature so high, that close binary (two-body) collisions have practically no significance (on certain timescales) because the time scales of interest are shorter than the collision time. Yields valid physical results for timescales much shorter than the average collision time in a real plasma.

    Collisionless dark matter ‘clouds’ can interact gravitationally with baryonic gas (largely plasma), or with itself. Collisionless simply implies that there are no, or very few, direct two body collisions. (Consider the effect of an asteroid that passes very close to the earth but does not collide. It interacts gravitationally and may be ‘scattered’ into a new orbit without a two-body collision.

  • Polygon March 11, 2008, 7:25 PM

    Wow, a scientific web page bitch fight.

    Never seen one of these before [save into Bookmarks]

    This should be, and already is, a lot of fun… :)

  • David K White March 11, 2008, 9:02 PM

    Fascinating topic and discussion. Ian, my wife teaches writing as her profession. In her educated and trained opinion, your writing is fine. Cathbad will go away faster if no one responds to him. When deciding about critcism, consider the source. The writing style of his comments effectively remove him from the realm of serious critique. The best way to deal with the peanut gallery is to ignore them.

    But to the real discussion… My only credential is a bachelors in physics. I have problems with the concept of dark matter and dark energy myself. I suspect that although the math describing gravity in the local frame of reference works quite well, there are areas where they aren’t as effective. There are many issues at the quantum scale, obviously, and possibly we should consider that we need to define a new scale, that of extreme distance.

    Another idea of interest would be the concept that areas of space/time could have higher energy densities embedded in the fabric of space/time itself. These would not be immediately apparent, because at any point in seemingly “empty” space/time the energy (expressed as vectors) sum to zero. But they could conceivably create “heavy spots” in space/time, a local curvature that isn’t created by any visible mass or energy. Alternatively, areas with unusually low embedded energy would create “light spots”.

    How this concept would interact with the data from the anisotropy map of background IR, which I understand to be the basis for the conclusion that space is “flat” in our visible universe, I don’t really know. But its an interesting area to explore.

  • cathbad March 12, 2008, 2:27 PM


    Dear david why should your educated trained and commercial wife peck an eye out of Ian.
    they are the same kind.
    They make their money with the ant to elephant size inflating.
    And why do you think your patronizing would impress me and the other sceptics when it comes to questioning the scientific and journalistic value of the botch.
    It is not important if it is written correctly from a craftsmanship point of view.
    Even a perfectly mastered DVD in a platinum box can contain crappy story and actors.

    Your bachelor seems not enough to see the epistemologic limits and the difference between science and speculation.

    Let us wait for the next ant inflation.

  • Mark March 13, 2008, 1:41 PM

    In extreme distance would not the expansion/inflation that creates new space contain gravitational eddy currents that would propergate the real God particle- time-to affect this lack of matter?

  • cathbad March 15, 2008, 7:35 AM

    Mark I 100% agree.
    This looks much more credible than the negative squarerootsolutions I read before.
    The beauty is in the precision when you formulate the ultimate theory.
    Since Ockham’s razor this has been always a good rule.
    I might add that the dualism of particle and waves also allows a God wave function and only some expectation values have a sufficient probability to burn ideas of energy vectors into bachelors brains.

  • Zardoz March 19, 2008, 10:52 AM

    Cathbad’s broken. Obviously intelligent but obsessively and compulsively argumentative. She seems unable, unwilling, or afraid to provide an objective and rational posting. The unrelenting hostility suggests fear. The way Cathbad’s sentences chain disconnected concepts unerringly toward a hostile conclusion suggests schizophrenia.

    Consider the sentence, “I might add that the dualism of particle and waves also allows a God wave function and only some expectation values have a sufficient probability to burn ideas of energy vectors into bachelors brains.”

  • Steve T March 21, 2008, 1:40 AM

    what is the current speculation of the effects of graphite wiskers on the current theoretic amount dark energy? (and is there any effect dark matter?) what does this translate into for the future state of the universe, if graphite wiskers really are offsetting the brightness of our “standard candles”. Is M~still making much progress or receiving more recognition? *as I hope it does

    i was thinking of my own self-conjectures…. is it possible that the other nearby universe we derive gravity from (and ?? the weak nuclear force, as well as the even weaker interactions which seem to cause the quantum movements of sub atomic particles) simply share and help to attract, and build upon certain aspects each other even during the early times of inflation right after the big bang to the times of our galaxy formation? let me get this straight: are matter and dark matter (whatever it is, perhaps if M~theory/ String(s) theory is correct that it really is the matter or effects of it in the nearby universe(s)) weakly interact but only via the warping of gravity and pehaps only on a minute scale even on the subatomic level or perhaps a mysterious type of neutrino (*I believe its the relic neutrino) is the culprit, however this is *unlikely due to the fact that not one has been seen (yet?).

    ~ i mean even this is easier to swallow than particle that just do not seem to exist or at least be detectable… <- fair criticisms,
    …and if graphite wiskers does kill Dark Energy, the fact of the matter is: even if graphite wiskers are obscuring our type 1A Super Novas, {and not to mention not one WIMP has been found in the lab}; this doesn’t actually “disprove” dark energy (or dark matter), …but, even you, IAN, i think can agree that this is raising some serious doubts and all Dark issues.

    ~I wonder what the standard model will look like after the calculation of the effects of the graphite wiskers are taken into account. Anyone know if Dark Energy is still around, or the new estimated amount of stuff? (including Dark matter & *esp* Dark Energy ?)

  • Aahan March 23, 2008, 5:26 PM

    I can’t wait for the LHC. But it may be dangerous to experience the beginning of the big bang all over. It may launch a black hole, It may blow up the universe. It may lead to something new. But would you risk your life for just more knowledge?

  • kevin March 30, 2008, 7:46 PM

    has the theory of propulsion in referance to gravitional properties in a black hole ever been explored or even a small scale attempt to duplicate the properties of a black hole? also if we afilliate gravity w/ magnetics and every planet and moon having some gravitational properties wouldn’t it make sence to build large electromagnetic ships just a little sci-fi and theory

  • astro man71 August 29, 2008, 9:49 AM

    I wonder who cathbad is??? Hmmm.

    It is true that Cold Dark Matter is just a theory, and it is not a perfect theory either. It describes the Universe we see pretty well, at least on the largest scales, but on the smallest scales it does not work so well. Nevertheless, this may just mean that Dark Matter is “hotter” than originally thought. Now, maybe the answer is not dark matter, but it is the best theory we have at this moment in time. And remember, just because we haven’t observed the dark matter particle, does not mean that it doesn’t exist. When I was an undergraduate student, we still had not observed the top quark, yet theory suggested that it should exist. And by the time I graduated the top quark had been observed at CERN. I’m sure there were people who didn’t believe in it then, just as there are people who do not believe in dark matter now, and just as there were people in the 19th century, who believed that humans would never be able to fly.

  • Roxes Kihunata September 30, 2008, 9:19 AM

    Dark matter is very powerfull it can atract even black holes meteors and more i think that dark matter is the main source of a black hole if dark matter mixes with crystals from the milky way a black hole is formed it is sayd that the more a black hole destroys the powerfull it gets

    a black hole started this universe when the big bang if any of you noticed there was a black hole that collapsed destroying itaself but destroying the big bang

    the big bang dint just explode it collapsed the big black hole was relly big it spreaded millions of black holes all over the universe no one knows what might be out there but if you ever pass this solar system you will all meet your DOOM

  • Joe February 2, 2009, 12:37 PM

    idk man
    its true that black holes get stronger as they eat up more and more matter. so then raises the question. what happens when the center of the galaxy eats up all the matter? i mean, in theory, we should have all these supermassive black holes just rolling around in space, because they wouldve eaten everything in the galaxy. and if thats the case then i dont wanna be there when we find one because we’ll all be dead. these black holes are so huge that they just eat up stars like skittles. imagine what it would do to earth? jupiter? our whole solar system? and Roxes kihuata you have no clue in the world do you? when a black hole collapses (if thats even possible for something with unlimited density and mass) it doesnt just break up into little tiny black holes. it would wink out of existance like most everything does when faced with that scenario.