Sophie Koudmani, Ph.D.

I am a Flatiron Research Fellow in the Center for Computational Astrophysics at the Flatiron Institute interested in galaxy formation theory, in particular the interface between galaxies and their supermassive black holes. I received my Ph.D. in Astronomy from the University of Cambridge, where I pioneered the theoretical modelling of black hole feedback from active galactic nuclei (AGN) in dwarf galaxies, advised by professors Debora Sijacki and Martin Haehnelt. My current research focuses on developing novel models of black hole evolution (including black hole formation, growth, and feedback) for galaxy formation simulations, which take advantage of the superior resolution and allow for detailed multimessenger predictions in preparation for the next-generation electromagnetic and gravitational-wave observatories. I also hold a Junior Research Fellowship at St Catharine's College Cambridge. Download my CV.


AGN versus Supernova Feedback in Cosmological Zoom-In Simulations of Dwarfs

I performed a series of high-resolution cosmological zoom-in simulations with the moving-mesh code AREPO. Here I focused on simulating one low-mass system and carried out several ‘numerical experiments’, varying the supernova energetics, black hole accretion prescription, and black hole seeding parameters, to assess whether efficient feedback from active galactic nuclei (AGN) in tandem with more realistic supernova feedback could be a viable alternative to the commonly employed strong supernova feedback. Crucially, there are sufficient amounts of gas in dwarfs to power brief, Eddington-limited accretion episodes, which can have a profound impact on the evolution of the dwarf galaxy. The AGN feedback drives a hot bubble which lingers in the circumgalactic medium long after the AGN has switched off, preventing cosmic gas inflows from reaching the galaxy and thereby regulating star formation with maintenance mode type feedback.

Exploring AGN Feedback in Dwarf Galaxies with Cosmological Simulations

Using the cosmological simulation suite FABLE, I have further explored AGN-driven outflows in dwarfs. Note that, like most large-scale cosmological simulations, FABLE employs (artificially) strong supernova feedback to regulate star formation in dwarfs, stunting BH growth. This is in contrast with X-ray surveys which have identified highly-active BHs in dwarfs. I found that overmassive BHs drive hotter and faster outflows in FABLE’s dwarfs, in accordance with my previous work, and leave kinematic signatures detectable by MaNGA. These outflows lead to a reduced gas reservoir and, even with strong supernova feedback, AGN can suppress star formation in dwarfs in the early Universe.

Modelling AGN-Driven Outflows with Isolated Dwarf Galaxy Simulations

I investigated different models of AGN activity, ranging from simple energy-driven spherical winds to collimated, mass-loaded, bipolar outflows in high-resolution isolated simulations of dwarfs using the moving mesh code AREPO. I found that AGN activity has a crucial effect on the galactic outflows, significantly increasing outflow velocities and temperatures compared to simulations with only supernova feedback. However, there is not a substantial effect on star formation in the isolated set-up, indicating that AGN most likely play an indirect role in quenching. For example, the AGN-boosted outflows could hinder cosmic gas inflows and quench star formation by depleting the gas reservoir.

Selected Papers

  1. Sophie Koudmani, Debora Sijacki, Matthew C. Smith, Two can play at that game: constraining the role of supernova and AGN feedback in dwarf galaxies with cosmological zoom-in simulations, Monthly Notices of the Royal Astronomical Society, 2022 (516, 2112). arXiv ADS
  2. Sophie Koudmani, Nicholas A. Henden, Debora Sijacki, A little FABLE: exploring AGN feedback in dwarf galaxies with cosmological simulations, Monthly Notices of the Royal Astronomical Society, 2021 (503, 3568). arXiv ADS
  3. Sophie Koudmani, Debora Sijacki, Martin A. Bourne, Matthew C. Smith, Fast and energetic AGN-driven outflows in simulated dwarf galaxies, Monthly Notices of the Royal Astronomical Society, 2019 (484, 2047). arXiv ADS

Selected Talks

Over the years, I have given various talks as part of conferences and seminar series. Below I provide a list of selected recorded talks:

For a general introduction to supermassive black holes, supernova explosions and their role in shaping galaxy formation, check out my public talk on Supermassive Black Holes or Supernovae: Who Calls the Shots? at the (virtual) Cambridge Astronomy Open Evening.


I am a long-term developer and user of the moving-mesh code AREPO, with a special focus on investigating the role of AGN in galaxy formation. In the past, I have implemented a bipolar AGN wind model using the super-Lagrangian refinement technique as well as a supply-limited accretion scheme for black hole growth into the AREPO code. My current projects include developing and validating novel AGN prescriptions based on accretion disc theory and GR(-R-)MHD simulations.