Primordial Black Holes in Cosmological Simulations
Being so busy for the last couple of weeks I omitted to engage in the gratuitous self-promotion that one would expect from a blogger, so I’m remedying that today by pointing out that I’m co-author of a new paper that is now on arXiv. This has already gained a bit of traction in the media, e.g. here.
Here is the abstract, which also shows the author list:
(I’ve just noticed that it says “The Netherland”, instead of “The Netherlands”. Oops!)
For those of you not in the field, there is currently a big mystery about how galaxies we have found at high redshift with JWST managed to acquire massive black holes so early in the Universe’s evolution. Black holes can grow quickly in a dense environment by accreting mass onto an initial seed, but what are the seeds? In this paper we investigate the possibility that they were primordial black holes. These form directly from fluctuations in the early Universe, as opposed to astrophysical black holes which form from stellar collapse. We don’t know exactly what mass primordial black holes would have nor how numerous they would be, but this paper uses high-resolution numerical experiments to investigate their effects if they do exist.
Here’s a pretty picture which is a zoom into 200 pc of the full simulation. I think 10pc counts as high resolution for a cosmological simulation! The blue circle shows the most massive PBH in the simulation, the green circle shows its nearest neighbour. The colour scale represents the number-density of dark matter particles.
For more details, read the paper!
P.S. This article has been submitted to the Open Journal of Astrophysics and is currently under review. As an author I am not involved in the editorial process.
In the Dark 
June 29, 2025 at 8:38 pm
I’ve wondered for many years whether supermasive black holes could have been formed by the direct collapse of collisionless cold dark matter in the early Universe. A static, spherically-symmetric dark matter halo would undergo free-fall collapse to a black hole if the dark matter particles had no, or very little, angular momentum. Gas in the halo, being collisional, would not follow the dark matter collapse. In practice, dark matter haloes would not be isolated and not perfectly spherically symmetric, meaning dark matter particles would have some angular momentum, inhibiting their collapse into a supermassive black hole.
August 28, 2025 at 10:10 am
[…] time for a quick update about a paper that I posted about at the start of the summer, when it appeared on arXiv. At that time it had already gained a bit of […]