How exactly do SMBHs in the center of galaxies form

[CrackerMcGinger]

I've been thinking for awhile now, and I still don't understand how these types of black holes form, since they can't form by conventional means.

 

[PeterDonis]

I've been thinking for awhile now

Have you looked to see what hypotheses astronomers have come up with?

they can't form by conventional means.

What do you mean by "conventional means"?

 

[CrackerMcGinger]

What do you mean by "conventional means"?

The most accepted explanation on how stellar black holes and SMBH that do not form in galactic center's.

 

[PeterDonis]

The most accepted explanation on how stellar black holes and SMBH that do not form in galactic center's.

Which is? If you claim that SMBH in galactic centers cannot form by this means, you should be able to state briefly what this means is.

 

[CrackerMcGinger]

If you claim that SMBH in galactic centers cannot form by this means, you should be able to state briefly what this means is.

I might be a little tired... so, what do you mean by that?

 

[PeterDonis]

what do you mean by that?

You said:

they can't form by conventional means.

What did you mean by "conventional means", and why do you think SMBH's cannot form by those means? Just saying "whatever the current accepted explanation is" isn't enough, because you still have to explain why you think the "current accepted explanation" can't explain the formation of SMBH's.

 

[CrackerMcGinger]

What I meant was this; If we figure out the most logical way black holes form that would be the most regular way that they can form, but that means the SMBH's form either differently or undergo changes that stellar black holes don't undergo. But my thing is with those the exist in galactic cores. The way that all known galaxies are shaped suggests a massive orbital plane, and I also think that SMBH's in galactic cores have a less intense gravity well than that of other SMBH's and maybe even some strong stellar black holes, and that the size of the orbital plane has a lot to do with this. But I'm wondering what happens to these black holes that make them behave in such a way. Is it just that these black holes are a different type of SMBH, or is it that something changed them, making them the way they are, rather than just forming differently at the start.

 

[Chronos]

It's a bit of a chicken and egg thing. SMBH and galaxies appear to have a symibiotic relationship. The bigger question may be how did billion+ solar mass black holes form so rapidly in the high zy universe. It's almost to the point it appears they must have formed around the time the first stars appeared, which is clearly a problem for the case of the hierarchical hypothesis - where SMBH essentially form through mergers of stellar mass black holes. One of the more popular ways around the problems of SMBH forming in the high z universe is the direct collapse model - where SMBH are formed by the collapse of huge primordial gas clouds directly into black holes. This sidesteps the furious merger rates necessary under the hierarchical model. For further discussion, see; http //arxiv.org/abs/1402.5675, The brief era of direct collapse black hole formation, and; http://arxiv.org/abs/1407.4472, The Direct Collapse of a Massive Black Hole Seed Under the Influence of an Anisotropic Lyman-Werner, and http://arxiv.org/abs/1411.5683, Direct formation of supermassive black holes in metal-enriched gas at the heart of high-redshift galaxy mergers.

 

[PeterDonis]

If we figure out the most logical way black holes form that would be the most regular way that they can form, but that means the SMBH's form either differently or undergo changes that stellar black holes don't undergo.

In other words, you don't know whether or not SMBH's can or can't form by "conventional means". You're asking whether the mechanisms that form, say, stellar mass BHs are the same as the mechanisms that form SMBH's. The answer to that is, most likely not. But it would have saved time if you had asked that question directly in your OP, since that's the question you appear to be interested in.

I also think that SMBH's in galactic cores have a less intense gravity well than that of other SMBH's and maybe even some strong stellar black holes

Why do you think that? (Hint: it's not correct.)

 

[CrackerMcGinger]

Why do you think that?

Black holes usually consume most of the matter around it, if that was the case then I would assume that the galactic core would have a lot less matter, but it appears to me that is not the case. I think that the black hole is more spread out, affecting a larger area and therefore not having the same intensity as more compact ones.

 

[PeterDonis]

Black holes usually consume most of the matter around it

Why do you think that? (Do you notice a pattern here? You keep on making flat statements which are, in fact, incorrect. You might want to take a step back and think about where you are getting these incorrect ideas from.)

I think that the black hole is more spread out, affecting a larger area and therefore not having the same intensity as more compact ones.

A black hole with a larger mass will be better at accreting matter than a smaller one, because it is larger. A larger hole is certainly not "more spread out" in the sense of having weaker gravity; it will have stronger gravity, because it is more massive. (It will have weaker tidal forces at its horizon, but that's a different thing, not relevant to this discussion.)

But "larger" is still relative; in absolute terms, black holes are very small compared to other objects of the same mass. For example, the hole at the center of the Milky Way is thought to have a mass a few million times that of the Sun. That means its Schwarzschild radius is a few million kilometers--or only a few times the radius of the actual Sun. If that same hole were where the Sun is now, the planets would go around in their orbits much faster than they do now, but they could still be in stable orbits quite easily--they wouldn't just fall into the hole.

 

[Ibix]

Black holes usually consume most of the matter around it

You are trying to reason from very vague non-numeric descriptions, which is what's leading to the errors Peter points out. Think about this: a black hole with a mass of a few million suns can be surrounded by just less than a few million suns and still be said to have consumed most of the mass around it. Since you haven't specified how big the volume "around" the black hole is, and you don't know how many stars you expect to be left (only that it's less than a few million) you don't have any way to say whether there are more stars "around" the black hole at the galactic core than you expect. This is why you always need to find numbers and maths before you try to make predictions, I'm afraid.

 

[CrackerMcGinger]

I don't know how to explain what I'm trying to say without using my own drawing's. I don't have a broad enough vocabulary to just say what I mean. So me trying to explain what I mean is a futile endeavor, because everything you say is correct, but what I say doesn't come out properly enough. I know their are many steps before the action I'm trying to explain takes place, but I don't know the math and vocabulary to just describe it in words. If I did just say it, I would sound like an insane moron. So, I'll see if I can do something about that.

 

[CrackerMcGinger]

Okay, I've tried, and it's not working, so instead of me trying to explain this, can someone else describe the causes that link every known galaxy to a SMBH and why these black holes are different from stellar ones, other than the obvious fact that they are more powerful.

 

[PeterDonis]

can someone else describe the causes that link every known galaxy to a SMBH

We don't know that every known galaxy has a SMBH at its center.

and why these black holes are different from stellar ones, other than the obvious fact that they are more powerful.

You're still assuming that SMBH's are somehow "different" from stellar ones in some respect other than having a larger mass. They aren't. So your question is based on a false assumption; that's why you're having so much trouble stating it in a way that will get an answer.

 

[PeterDonis]

I don't know how to explain what I'm trying to say without using my own drawing's.

Why don't you take a step back and give us a reference to wherever you got the original idea that lead to this line of thought?

 

[DrStupid]

can someone else describe the causes that link every known galaxy to a SMBH

Chronos already mentioned the direct collapse model.

 

[rootone]

I think the problem here is that you know how stellar mass black holes can form as a result of a very large star collapsing.
Yet supermassive black holes cannot possibly be produced that way, since the idea of a progenitor star having a mass of several millions times the mass of the Sun is absurd.
This leaves two reasonable possibilities:
1. SMBH are the result of solar mass black holes merging.
2. SMBH results from the direct collapse of a very large volume of matter, the are no intermediate stages (stars).

My personal preference is the second of these, but that isn't based on any actual data.
I guess it's also possible that BOTH of the above might be the case - a very large volume collapsing which already has stellar mass black holes within it.

 

[Chronos]

LIGO has the potential for detecting direct collapse black holes. They should produce gravitational waves of measurable strength.

 

[PeterDonis]

This leaves two reasonable possibilities:

I think there is actually a third possibility: a tightly bound system of stars like a globular cluster or a small galaxy (or a cluster at the core of a larger galaxy) contracts (as interactions between the stars gradually eject stars that are less tightly bound to the cluster and leave behind stars that are more tightly bound) to the point where stars in the center start to merge with each other and form a black hole, which then gradually swallows the rest of the cluster. This is sort of like your #2, but it still has stars as an intermediate stage.

 

[ebos]

It makes sense to me that some black holes formed from the first stars that formed when the universe was still very dense. Many of these black holes must have been huge while others were smaller. They hogged a lot of primordial gas which eventually became star clusters and smaller galaxies. Who knows, some may have been so huge that they formed large galaxies. But what matters is after that these large black holes began absorbing the smaller galaxies and the star clusters as well as their attendant black holes they got bigger and bigger. We still see that now. So some galaxies, and their black holes, got bigger and some stayed small and some stayed medium sized. Right now there is a medium sized black hole orbiting the SMBH at the Milky Way's center. There are also several young stars orbiting the center. These stars and the MSBH could be the relics of our galaxy's latest acquisition possibly a small galaxy or a star cluster that orbited the Milky Way at some time. Am I on the right track?

 

[nortonian]

Right now there is a medium sized black hole orbiting the SMBH at the Milky Way's center.

I am unable to find anything that supports your statement. Can you cite something?

 

[CrackerMcGinger]

I am unable to find anything that supports your statement. Can you cite something?

Have you checked for reports on gravitational lensing that could support his statement?

 

[snorkack]

We don't know that every known galaxy has a SMBH at its center.

We know several that most definitely do not have SMBH at center. Like neither Magellanic cloud, nor Triangulum galaxy.

LIGO has the potential for detecting direct collapse black holes. They should produce gravitational waves of measurable strength.

Centrally symmetric mass distribution cannot emit gravity waves even when changing. The asymmetry of a binary black hole merging is what produces changing quadrupole moment and allows emission of gravity waves.

 

[davenn]

Right now there is a medium sized black hole orbiting the SMBH at the Milky Way's center.

Have you checked for reports on gravitational lensing that could support his statement?

he may well be right, but I would prefer a specific scientific reference related directly to his claimDave

 

[ebos]

Sorry guys. I cannot find the article.

 

[ebos]

However, I did read an article about Sag* and the astronomer in the article inferred from his data that a medium sized black hole was orbiting Sag*. It makes sense though (Occam's razor and all). It's attendant stars are now part of the Milky Way and the BH itself gradually circled into the center of the Milky Way. This HAS to be the way these large galactic BH's get so massive. But I do wonder if ALL smaller galaxies that get absorbed by our own do lose their BH or just most of the stars get taken but the central BH keeps going on its way although in a slightly altered path. There may be a lot of these galaxy-less BH's out there. But, I digress. Just thinking out loud. Next time I will save the supporting documents.

 

[Chronos]

Centrally symmetric mass distribution cannot emit gravity waves even when changing. The asymmetry of a binary black hole merging is what produces changing quadrupole moment and allows emission of gravity waves.

You may find this of interest; http://arxiv.org/abs/1502.04125, Gravitational Waves from Direct Collapse Black Holes Formation

 

[CrackerMcGinger]

he may well be right, but I would prefer a specific scientific reference related directly to his claim

true, but if their is no definite statement wouldn't an unusual gravitational reading be the next best thing?

 

[ebos]

All I got is:
http://iopscience.iop.org/nsearch?t...k+hole&searchType=yourSearch&navsubmit=Search
and
http://iopscience.iop.org/article/10.1088/0004-637X/693/1/L35
but those weren't the ones I originally read from. However, they present the idea well.