Origin of suspected black hole in Omega Centauri

[Nereid]

[...]

Does anyone know of a web-accessible description of a simulation of the collapse of a cloud of pure dark matter? I'm beginning to wonder if the mechanism by which such a collapsing cloud could be virialised is perhaps less obvious as I thought, in which case pre-galactic black holes might indeed form from collapsing dark matter?

Are you familiar with the landmark* NFW (Navarro, Frenk, and White) paper?

http://adsabs.harvard.edu/abs/1996ApJ...462..563N":

We use N-body simulations to investigate the structure of dark halos in the standard cold dark matter cosmogony. Halos are excised from simulations of cosmologically representative regions and are resimulated individually at high resolution. We study objects with masses ranging from those of dwarf galaxy halos to those of rich galaxy clusters. The spherically averaged density profiles of all our halos can be fitted over two decades in radius by scaling a simple "universal" profile. The characteristic over- density of a halo, or equivalently its concentration, correlates strongly with halo mass in a way that reflects the mass dependence of the epoch of halo formation. Halo profiles are approximately isothermal over a large range in radii but are significantly shallower than r -2 near the center and steeper than r-2 near the virial radius. Matching the observed rotation curves of disk galaxies requires disk mass-to-light ratios to increase systematically with luminosity. Further, it suggests that the halos of bright galaxies depend only weakly on galaxy luminosity and have circular velocities significantly lower than the disk rotation speed. This may explain why luminosity and dynamics are uncorrelated in observed samples of binary galaxies and of satellite/spiral systems. For galaxy clusters, our halo models are consistent both with the presence of giant arcs and with the observed structure of the intracluster medium, and they suggest a simple explanation for the disparate estimates of cluster core radii found by previous authors. Our results also highlight two shortcomings of the CDM model. CDM halos are too concentrated to be consistent with the halo parameters inferred for dwarf irregulars, and the predicted abundance of galaxy halos is larger than the observed abundance of galaxies. The first problem may imply that the core structure of dwarf galaxies was altered by the galaxy formation process, and the second problem may imply that galaxies failed to form (or remain undetected) in many dark halos.

Is this what you're looking for? If not, then perhaps one of the >1000 papers which cite it may be?

* ADS says it's been cited almost 1800 times!

 

[oldman]

Oldman, are you looking for something like this?
http://www.ucolick.org/~diemand/earlysubs.pdf

Yes indeed. Thanks very much for this link, Arch. It reveals that the suggestions I've made are far too oversimplified. I'd suspected that the elements of the physical processes involved in dark matter collapse (like how virialisation occurs) are not easy to disentangle from the complexities of N-body simulations using established codes, like the PDKGRAV code mentioned in this paper. It confirms that I'm in way over my head, and I must refrain from trying to project simple physics onto complex situations.

I guess you choose your input cleverly and then let the computer rip and see what emerges. Must be a bit like simulating say cirrus clouds using Navier-Stokes codes. Effective, perhaps, but not very illuminating for weather forecasters.

 

[oldman]

Are you familiar with the landmark NFW (Navarro, Frenk, and White) paper?

No, I wasn't. Thanks for pointing me at this seminal paper and so helping to modernise my outlook. Coincidentally, I'm familiar with ancient stuff published by (Frank) Nabarro, (Charles) Frank and (Guy) White.

 

[Arch2008]

You’re welcome. The problem with trusting computer models is Garbage In, Garbage Out (GIGO). However, more and more often, simulation has guided research into hopeful directions that then matched observation. I did find one paper where the observation was against galaxies forming from multiple mergers. The researchers had pictures of ancient galaxies that were supposedly too uniform and could only have formed from one huge cloud that collapsed directly into a central black hole with stars.
Their survey consisted of a whopping seven galaxies of which four were “too uniform”!