doughnut_esa_big.thumbnail.jpg

Greedy Supermassive Black Holes Dislike Dark Matter

Article Updated: 26 Dec , 2015

by

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


Sort by:   newest | oldest | most voted
MothyJohn
Guest
MothyJohn
March 9, 2008 6:59 AM

I thought dark matter didn’t interact with regular matter.

DaMatriX
Guest
March 9, 2008 8:24 AM

Dark matter does interact with regular matter, but only through gravity and the weak nuclear force. Dark matter just doesn’t “feel” the electromagnetic and strong nuclear forces.

alastair
Guest
March 9, 2008 10:13 AM

I’m still highly dubious about the whole “dark matter” thing. It sounds to me (as an interested layman, rather than a professional physicist) like exactly the kind of thing you’d expect to have to add if the fundamental equations are wrong somehow.

Time will tell, obviously.

PCY
Guest
PCY
March 9, 2008 12:14 PM

“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.

cathbad
Guest
cathbad
March 9, 2008 12:41 PM

Neill at his best.
Congrats.
Again only some loosely coupled astrophysics buzz words and a dash of might and woulds and voila….a pseudo scientific article for the jerks.

The key to an even more compelling BS composition is now the influence of dark energy through time.
So it will become obvious that 100 million years after the inflation period dark matter really interacted with not yet exsting elliptic galaxies and implanted the huge stars that later formed the black holes acquiring the primordial black holes. But only the dark energy could explain the would of the might be in the negative curvature of the black holes event horizon that exchanged brownies as force carriers with dark matter. Think about that Neilly.

cathbad
Guest
cathbad
March 9, 2008 2:08 PM

I a n

you write, you have to stand critics.

Dont be such a coward and hide behind ‘reporting on articles’.
You write this lurid botch or at least you repost it for a certain reason……
Write or edit a better one and you will get famous.

damien_58
Guest
damien_58
March 9, 2008 9:10 PM
My main beef with dark matter is this, there is no evidence what-so-ever to support that it exists in whatever quanity anywheresave for that it helped explain what other-wise could not be explained in some astrophysics calculation. I keep seeing people talking about ” gravitational lensing ” as evidence that dark matter exists, but gravitational lensing only means something is warping the view of a particular area of object and does not automatically mean the cause is DM, and to state that it is without evidence is clearly biased in favor of a particular speculative unproven belief. DM is treated as fact from what I have read & heard so far, and nevermind that it has not been… Read more »
anti-Cathbad
Guest
anti-Cathbad
March 9, 2008 2:55 PM

Cathbad, criticism is fine so long as it is constructive.

D2JACOURT
Guest
D2JACOURT
March 9, 2008 3:02 PM

Hey all,

I’ve been reading these theoretical physics stories for a long time and would feel better if some of them actually turned out by observation to be true. So, let’s count how many that is in the past 5 years or so: Oh yeah, now I remember, ZERO!!!

cathbad
Guest
cathbad
March 9, 2008 3:28 PM

It is constructive, but you dont want to hear it.
Learn to rely on facts and not mights and woulds.
Seperate clearly between solid phyics and accepted scientific work and pure speculation.
Leave the ground of giving feelings and anthropmorphic motives to things like black holes and dark matter and just by that avoid lurid BS and botch.

but since you are so experienced writer you know all that already.

Bob
Guest
Bob
March 9, 2008 9:17 PM
Cathbad, Since all of this dark matter and inflation theory have become so popular lately, I have read at least 20 articles in the last month regarding Strings, Branes, tachyons and extra dimensions of space, dark matter, dark energy, Black holes, Calabi-Yau manafolds, and other new concepts. The fact of the matter is, at this point, we don’t have a freakin clue about any of this stuff. It is 100% Theory with no current way of observing. People put forth their best ideas and some stick… others do not. world is not flat, not the center of the universe etc… Even E=MC2 does not look like it is the magic formula anymore. Since you felt that IAN’s article… Read more »
Johnny Blues
Guest
Johnny Blues
March 10, 2008 5:22 AM
Following along an tremendously more sober vein of thought, I am reminded of the dark matter = carbon whiskers theory. Could matter be so doggedly massive using atomic structure, that dark matter/carbon whiskers interact only so much as to get out of the way of whatever matter oriented event is transpiring, and once the event is complete the dark matter simply returns to its approximate position prior to the event? To put a finer hair on it (ah hem) You trim your beard in the sink. You run a little water in it. The hair will just float a while, or shift positions, even ride along with the water (baryonic matter), but unless other forces are brought into… Read more »
Rich L
Guest
Rich L
March 10, 2008 6:34 AM
I think Ian’s write up was slightly misleading in the way it described the process by which dark matter is predicted to be excluded from black holes. Dark matter is assumed to only interact by gravitational forces, not electromagnetic, and likely not weak or strong nuclear, although that is even less certain. I believe the key finding in this study is that what causes normal matter to spiral into a black hole is in large part the electromagnetic radiation given off when charged particles are accelerated in these very fast tight orbits. Since the dark matter does not radiate by this mechanism, it does not spiral in as rapidly and thus hangs back while the baryonic matter radiates… Read more »
Emil
Guest
Emil
March 10, 2008 1:34 AM

damien_58,
to the best of human knowledge, dark matter is at 23% now v. 63% 13.7 GY back, http://map.gsfc.nasa.gov/news/index.html. WMAP measures the density of baryonic and non-baryonic matter to an accuracy of better than 5%, http://map.gsfc.nasa.gov/universe/uni_matter.html

Emil
Guest
Emil
March 10, 2008 1:44 AM

Ian,
Some people just do not get the depressing odds of ironing out the knowledge and role that scientific ideas play in supply chain to keep the process going. Thanks for the reporting on what is going on today, so some of us can balance it with the established facts that belong to the history of science.

John Mendenhall
Member
John Mendenhall
March 10, 2008 7:40 AM
Gentlemen, a little decorum, please. First, some positioning. I don’t like dark matter. I wish there were observations to support dismissing it. There aren’t. After reading everything I could find about DM for the last couple of years, and extensive forum discussions, there isn’t any better explanation at this point. Try thinking of dark matter as some sort of non-interacting distributed mass, composed of who knows whats that are really difficult to detect. Secondly, if you don’t like the idea, offer some constructive and testable alternative that doesn’t explain dark matter at the cost of all the rest of well tested and confirmed physics, from quarks to the largest structures in the universe. I think you’ll find yourself… Read more »
Peter
Member
Peter
March 10, 2008 9:36 AM

That’s right John,

Dark Matter is, in my books, simply a digestible concept for a solution to a difficult set of questions. The idea of dark matter is of non-interacting weirdo stuff. We can all wrap our brains around that. That doesn’t mean that the solution will be the same in ten years. But why call it the “Missing Matter Solution” when Dark Matter is such an attractive name? Science tries to solve problems with the simplest solution and if we could just detect/hold/”see” this stuff, then that would solve this dilemma most satisfyingly. Rewriting years of physics doesn’t seem quite as eloquent.

wpDiscuz