Cause of Quasar Wind: The Mystery

[Jorrie]

I've scanned some literature, but could not find a description of the mechanism that causes the "thin vertical wind"* from the accretion disk of a quasar. Can someone please explain or point me to an accessible paper?

*Elvis M., 2000, Astrophysical Journal 545, 63

 

[turbo]

Perhaps the terminology is too ambiguous and the reference is to polar jets emerging axially from an accretion disk? If so, you should be able to find a LOT of references.

 

[blumfeld0]

Hello. I am not sure why there should be a wind. I guess because it is included in quasar models to fit the observed data. These winds should be driven by radiation. maybe try googling "radiation driven winds".
I don't know if this will help but good luck!

http://hea-www.harvard.edu/~elvis/elvism.html

http://arxiv.org/PS_cache/astro-ph/pdf/0106/0106076v1.pdf

http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v545n1/51275/51275.web.pdf
i think you have already seen this one

http://hea-www.harvard.edu/~elvis/leicester_sept04_nobk.pdf
this paper has some good links on the top of some of the slides. One of slides explains why they should be thin rather than "thick" winds.

 

[Jorrie]

Perhaps the terminology is too ambiguous and the reference is to polar jets emerging axially from an accretion disk? If so, you should be able to find a LOT of references.

No I'm referring to winds from the accretion disk, as per this RIT News Release:

“It has long been thought that such winds are launched from the accretion disk but, until now, this idea has been based on purely theoretical arguments,” says David Axon, professor and head of the physics department at RIT.

The RIT team’s study of PG 1700+518 shows that gas is both moving vertically away from the disk and also rotating at a speed similar to the disk’s rotation speed—direct observational confirmation that the disk is launching a wind.

 

[Jorrie]

http://hea-www.harvard.edu/~elvis/elvism.html

Thanks, this (2003) paper at least offers some explanation i.t.o. radiation pressure and (perhaps) magnetic field recombination.

I'm still hoping that there are some later theories that are more plausible, whatever that may mean...

 

[oldman]

Out or In?

I'm still hoping that there are some later theories that are more plausible, whatever that may mean...

The theories I'm aware of tell one that quasars radiate because of the heating up of matter falling inwards onto the accretion discs of black holes. Of course this is theory, rather than observed fact; as the RIT team report, one can't resolve accretion discs. I find it interesting that they attribute their light polarisation measurements to matter that is flowing outward, rather than inward.

This prompts me to ask: what observations support the widely-held conclusion that matter is flowing inward, or is this just a feature of a surmised model? Perhaps you or other folk can tell me, Jorrie.

 

[Jorrie]

This prompts me to ask: what observations support the widely-held conclusion that matter is flowing inward, or is this just a feature of a surmised model?

AFAIK, accretion disks are abundant in star systems, but I'm not sure if they can be directly observed even there. I think everyone agrees that matter is falling in there and the theory behind it is fairly well established - friction, instabilities, density, heat up the gas and dust and rob them of angular momentum and orbital energy by means of e.m. radiation that can be detected. This must cause the matter to slowly spiral into the star.

Apparently, there is a bit of a problem getting rid of all the angular momentum and the polar jets of accreting stars and black holes are one way of getting rid of some of the angular momentum. Apparently the 'thin vertical quasar winds' are another theoretical way of getting rid of angular momentum. The RIT team interprets the data as evidence for these winds. 'Vertical' apparently means that the winds start at 90 degrees to the disk plane, giving them the disk angular velocity plus a transverse component that, at certain radial distances, causes the the matter to exceed escape velocity.

 

[oldman]

...the 'thin vertical quasar winds' are another theoretical way of getting rid of angular momentum. The RIT team interprets the data as evidence for these winds. 'Vertical' apparently means that the winds start at 90 degrees to the disk plane, giving them the disk angular velocity plus a transverse component that, at certain radial distances, causes the the matter to exceed escape velocity.

Thanks, Jorrie. Yes, for stars and stellar-mass black holes, the twin processes of gravitational collapse and mass/energy removal by jets and radiation are, I believe, well supported by observation. They go together like a horse and carriage, harnessed together by the virial theorem.

The point I would like cleared up is this: it seems natural to extrapolate this process to explain how supermassive black holes at the centres of galaxies form. Here, however, the supporting evidence is much less direct. In the case of quasars astronomers are dealing with processes on a mass scale six or seven orders of magnitude larger than star formation. Quasars must have formed very long ago in the early universe and are so far away that their detailed structure (e.g accretion discs) cannot be resolved. So the extrapolation is quite a bold stretch, even if it is a natural one to make.

It's a bit disturbing to hear of evidence that in a quasar matter is flowing out rather than in. We already know that lots of radiation flows outwards ---- it would be reassuring to be told that outflowing matter is only part of the observational story, and that there is plenty of evidence for the infalling matter that drives the whole shebang. I'd like to know whether such evidence exists or not.