ISL’s Dr John Regan advances supermassive black hole research

Dr. John Regan, an astrophysicist and founding member of the Irish Supercomputer List has provided an explanation for how supermassive black holes got so massive, so early in our universe.

The existence of such massive black holes so early in our universe’s history has been a challenge to science’s understanding of black hole and stellar formation. However John and his coauthors have focussed on a scenario where two compact galaxies early in the universe’s existence are gravitationally locked together – an occurrence that would have been quite common in the early universe where the average density was much higher than it is today.

In this situation it is proposed that the primary galaxy’s stellar formation would have produced enough radiation to sterilise the secondary galaxy to the point that normal stellar evolution there would have been altered. This could allow conditions where super-massive stars quickly form and then subsequently collapse directly into black holes. In turn these black holes would have a large amount of matter to grow at a great rate, eventually consuming matter from the galactic partner as well as the surrounding inter-galactic medium.

The team used a modified version of the publicly available astrophysics code Enzo to  conduct their simulations. Enzo is a massively parallel code well suited to simulations of the high redshift Universe. Crucially in it’s adaptive mesh refinement mode it can “zoom” into regions of interest providing maximum resolution where it is most needed. It uses the MPI protocol for data communication across multiple nodes. The simulations were run on the Cosma5 supercomputer at the Institute of Computational Cosmology in Durham. The machine has around 7000 sandy bridge cores. Each simulation ran on 256 cores and typically wall-clock run times were 1 week. About 30 simulations made up the entire simulation suite.

For this work the team enhanced the radiation transport module within Enzo as well as the chemistry package used (Grackle).

John is a Marie Sklodowska-Curie fellowship holder at the Dublin City University Centre for Astrophysics and Relativity. Prior to joining DCU last year, John was at the Institute for Computational Cosmology at Durham University and before that at the University of Helsinki. John did his Ph.D. work with Prof. Martin Haehnelt at the Institute of Astronomy in Cambridge.

John’s article, “Rapid formation of massive black holes in close proximity to embryonic protogalaxies” was published on March 13 in Nature Astronomy and is available here, and was recently reported on by the Irish Times here. John’s personal website is here.

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