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My research is in the field of galaxy formation. I use supercomputers to simulate the formation and evolution of the Cosmic Web, of Dark Matter halos embedded within it, and of galaxies that form in halo centers.

I run large cosmological simulations with the Arepo code, develop novel analysis tools for this kind of simulations, and apply those tools to a variety of topics in galaxy formation.

Illustris and IllustrisTNG

Some of the largest cosmological hydrodynamical simulations run to date, the Illustris and IllustrisTNG simulations reproduce many observed galaxy properties and allow us to study how galaxies form and evolve.

Tracer particles

Following individual mass elements in mesh-based simulations, such as ones run with the moving-mesh code Arepo, requires Lagrangian tracer particles. Our novel Monte Carlo method overcomes shortcomings of existing methods.

Growth of Dark Matter halos

All galaxies form in the centers of Dark Matter halos, and so the growth of these two types of objects are intimately related. I am interested in how Dark Matter halos grow both via mergers with each other and by smooth accretion.

Redshift~2 galaxies

Galaxies at 'cosmic noon' were very different from the ones around us today. They are characterized by irregular morphologies and high star-formation rates. I studied the origin and evolution of the strong turbulence and giant star-forming clumps they exhibit.

Galaxy size and angular momentum

Cosmological simulations allow us to study how feedback affects the angular momentum content of galaxies, how their sizes evolve over time, and relations between these quantities and galaxy assembly history.

With my students at Columbia University, Kirsten Blancato and Daniel DeFelippis, I have studied the possible origins for observed stellar initial mass function (IMF) variations, as well as angular momentum evolution of gas flows around galaxies. Before that, with Harvard students Dylan Nelson and Vicente Rodriguez-Gomez, I have focused on the mass growth of galaxies, both through accretion of gas from their surroundings and through mergers with other galaxies.

My main past and current collaborators are: Nicolas Bouche, Greg Bryan, Avishai Dekel, Reinhard Genzel, Lars Hernquist, Thorsten Naab, Dylan Nelson, Annalisa Pillepich, Vicente Rodriguez-Gomez, Debora Sijacki, Volker Springel, Amiel Sternberg, Paul Torrey, and Mark Vogelsberger.