Research Overview

My research focuses on theoretical models primarily related to cosmological galaxy evolution, star formation, and the interstellar medium (ISM).   I principally develop and utilize large scale numerical simulations to simulate the interplay between small scale star formation, ISM physics, and global galaxy evolution.  Layered on top of this, I spend a good bit of time thinking about how photons traverse the dusty and molecular ISM, and how to quantitatively connect models of star formation and galaxy evolution with cutting-edge observations across the electromagnetic spectrum.

Over the last few years, I’ve focused on topics related to:

  • The formation and evolution of massive galaxies over cosmic time
  • Molecular Clouds and the Interstellar Medium
  • Star Formation
  • The Stellar IMF
  • Starburst/AGN co-evolution, and the fueling of SMBH’s
  • Galactic Winds and Outflows
  • Methods in Radiative transfer (dust and line)


Multiscale Galaxy Evolution

I work on an array of topics related to the cosmological evolution of galaxies at high-redshift, with a particular eye toward their star formation and ISM properties. Much of the work that I’ve been involved in in recent years relates to understanding the origin and evolution of active galaxies, and dusty starbursts being discovered in the early Universe.   I’ve also done a bit of work on trying to understand stellar and AGN feedback, galactic superwinds, and high-redshift quasar formation. This work has involved both constrained idealized galaxy evolution simulations, as well as cosmological hydrodynamic zoom models of galaxy formation.

Star Formation and the Interstellar Medium

I’m involved in a wide range of projects related to star formation, giant molecular clouds and the lifecycle of the interstellar medium.  These involve investigations into the structure of giant clouds in quiescent and starburst environments, origin of observed scaling relationships, and the role of feedback from massive stars in the ISM. I do this utilizing a wide range of simulation methods – these range from extremely high-resolution hydrodynamic ~parsec-scale simulations of Milky Way like galaxies and starbursts, to detailed postprocessing calculations to determine the thermodynamics of star-forming gas, to 3D dust and molecular line radiative transfer calculations to determine the observable properties of the modeled systems.

Most recently, my attention has been focused on the origin of the stellar IMF, the CO-H2 conversion factor in galaxies, the origin of the thermal structure of the ISM, and the origin of observed star formation scaling relations.

Simulation Code Development

I develop large scale radiative transfer packages for hydrodynamic simulations.  In particular, I have developed:

  • Turtlebeach – the first 3D non local thermodynamic equilibrium molecular line radiative transfer code for galaxy scales.  This C code is a Monte Carlo code that considers full statistical equilibrium, as well as a handling of subresolution ISM structure in the line transfer.   These codes are described in papers (in the publications list) from 2006-2009.  The guts of Turtlebeach are being taken apart and put back together in Powderday for public use.
  • Powderday – a publicly available dust radiative transfer package for galaxy simulations.  In collaboration with Matt Turk, Tom Robitaille and Bobby Thompson, we’re developing a package that merges galaxy simulations under a variety of frameworks with FSPS stellar population synthesis models and Hyperion dust transfer that, as an end product, will provide a mechanism for extracting a full SED (and images) from nearly any galaxy evolution simulation made with a publicly available code.See codes page for more details.