TheSkySearchers

This is an awesome one from PBS Space Time. Matt goes into detail about some observed galaxies with supermassive black holes that seem too big for current black hole evolution models and how one particular galaxy, UHZ1, may have provided observable evidence that supports a thus far unsupported hypothesis, the heavy seed black hole model. According to the heavy seed model, these SMBHs wouldn't have formed from the collapse of pop III stars but rather a direct gravitational collapse of sufficiently massive enough gas clouds perturbed by general relativity instabilities into collapse.

For these DCBHs to form, some vital conditions must exist to facilitate the collapse process. The collapsing gas must be free of metal elements, hence before pop III stars. The gas needs to contract while at high temperatures, and there must be a sufficiently high enough flux of Lyman-Werner photons. These conditions are necessary to reduce the fragmentation of the gas cloud and prevent protostellar production. Once these conditions have been met, the cloud collapses to very high mass, bypassing the intermediate stage, and at these masses and densities, relativistic instabilities provide the conditions for the final collapse to a massive black hole that meets the heavy seed mass range, thus providing the appropriate seed black hole for the evolution of supermassive black holes.




I've also decided to link this in too as it goes into more detail about certain aspects than the PBS video, especially the caveats, but both work together well.



This also links into Michaels thread here viewtopic.php?t=33501

Seems to be a bit of a contradiction between "The collapsing gas must be free of metal elements, hence before pop III stars" and "direct gravitational collapse of sufficiently dense enough gas clouds" since before pop III stars there was no dense gas.

I'll go and watch the video now, I'm sure all will be revealed.

Graeme

Graeme1858 wrote: ↑Sat Feb 17, 2024 2:52 pm Seems to be a bit of a contradiction between "The collapsing gas must be free of metal elements, hence before pop III stars" and "direct gravitational collapse of sufficiently dense enough gas clouds" since before pop III stars there was no dense gas.

I'll go and watch the video now, I'm sure all will be revealed.

Graeme

Cheers Graeme, No contradiction, unless I'm misunderstanding you. Before Pop III stars there were no heavy elements, just hydrogen and helium, no metals. Pop III stars were the first stars(hypothetically as we have no evidence), then Pop II and I. Metals were created through the stellar evolutionary chain. But, there was plenty of hydrogen and helium before pop III stars, given the three conditions stipulated above, hydrogen can collapse to sufficient densities to form over dense areas, but not Pop III stars, which create relativistic instabilities and form DCBHs.

Very interesting links Arry.

I've been watching How the Universe works on the Science channel and there was recently an episode on Supermassive black holes. One physicist went so far as to say that the singularity was the result of a Supermassive black hole at the center of a previous universe which suddenly exploded leading to the expansion of a new universe (ours).

Gmetric wrote: ↑Sat Feb 17, 2024 3:06 pm Cheers Graeme, No contradiction, unless I'm misunderstanding you. Before Pop III stars there were no heavy elements, just hydrogen and helium, no metals. Pop III stars were the first stars(hypothetically as we have no evidence), then Pop II and I. Metals were created through the stellar evolutionary chain. But, there was plenty of hydrogen and helium before pop III stars, given the three conditions stipulated above, hydrogen can collapse to sufficient densities to form over dense areas, but not Pop III stars, which create relativistic instabilities and form DCBHs.

Yes, agreed. So why the use of the phrase "sufficiently dense enough gas clouds" if there was only hydrogen and helium? If hydrogen collapses to a more dense form it must be plasma, or metallic hydrogen or some other state that wasn't mentioned in the video. I best go and watch it again!

Graeme

Graeme1858 wrote: ↑Sat Feb 17, 2024 3:29 pm

Gmetric wrote: ↑Sat Feb 17, 2024 3:06 pm Cheers Graeme, No contradiction, unless I'm misunderstanding you. Before Pop III stars there were no heavy elements, just hydrogen and helium, no metals. Pop III stars were the first stars(hypothetically as we have no evidence), then Pop II and I. Metals were created through the stellar evolutionary chain. But, there was plenty of hydrogen and helium before pop III stars, given the three conditions stipulated above, hydrogen can collapse to sufficient densities to form over dense areas, but not Pop III stars, which create relativistic instabilities and form DCBHs.

Yes, agreed. So why the use of the phrase "sufficiently dense enough gas clouds" if there was only hydrogen and helium? If hydrogen collapses to a more dense form it must be plasma, or metallic hydrogen or some other state that wasn't mentioned in the video. I best go and watch it again!

Graeme

Ah okay, I see the problem...There is a correlation between density and relativistic instabilities in the case of DCBHs. Once the cloud collapses to matter densities of the order of 10^7 g/cm^3, at those densities relativistic instabilities are the driving mechanism for further collapse. But, you could just say mass, although mass and density are both important. It's a different mechanism than light seed processes as these are well documented and understood. You know, typical BHs.

PS I have edited my opening post which I think makes it better to understand. Hope that helps.

helicon wrote: ↑Sat Feb 17, 2024 3:27 pm Very interesting links Arry.

I've been watching How the Universe works on the Science channel and there was recently an episode on Supermassive black holes. One physicist went so far as to say that the singularity was the result of a Supermassive black hole at the center of a previous universe which suddenly exploded leading to the expansion of a new universe (ours).

Hi Michael, thanks. Indeed, Carlo Rovelli speculates along those lines with his white-hole hypothesis. An interesting idea, although almost impossible to prove as it would require jumping into a black hole and I haven't had enough whisky for that lol.