Research

An incomplete summary of research topics I'm engaged in:

Star Formation

All star formation occurs in molecular clouds. Molecular clouds are turbulent and magnetized.
The evolution magnetized turbulence is too complex to solve by hand, so we resort to simulations.
To do this, I added a divergence free (CT) MHD scheme to the adaptive mesh refinement (AMR) code Enzo. Enzo is free and open source, you can get it at enzo-project.org
Current and future work centers around running simulations and making fake observations. Observations of molecular clouds are quite complex, and magnetic fields are nearly impossible to measure, so we require simulations to properly understand the measurements.
Recently we ran a bunch of star formation simulations backwards to see what the initial conditions looked like. You can see hundreds of baby stars being born in our Stellar Nursery

Simulation of self-gravitating turbulence

Supernovae

Type Ia supernovae are essential for our understanding of distances in the universe. But everyone leaves out the magnetic fields! So we did that. At the right you can see a great movie of magnetic fields suppressing nuclear burning. We also showed that late-time spectra of Type Ia Supernovae show that magnetic fields as large as 1,000,000 G (that's a million times stronger than a fridge magnet) are necessary to reproduce the light.

Several deflagration waves with magnetic field of different orientation (columns) and strength (rows). For strong enough fields, the instability is suppressed. For even stronger fields (top right corner), the field locks in structure, and the front speed increases.

Turbulence

Turbulence is the chaotic result of stirring up a fluid. It creates small-scale structure from large-scale motions. We study how turbulence behaves and how magnetic fields affect the turbulence.
One cool result we have found is the Joint Distribution of Thermal and Kinetic Energy in Isothermal Turbulence. Isothermal turbulence is useful to study as it mimics the efficient cooling and compressibility of outer space. The joint distribution of kinetic and thermal energy shows that it takes high flow to make the thermal energy large. That is, the gas needs to be fast if it's going to get dense.

Kinetic Energy vs Thermal Energy

Galaxies and Clusters

The largest objects in the universe are galaxy clusters, and they're magnetized. We study how the magnetic fields evolve during the formation of galaxy clusters. At the right one can see a mock observation of radio relics at the outskirts of a galaxy cluster. Magnetic fields are important for making the gas in a cluster behave like a fluid.

A cluster of galaxies and their magnetic field.

CMB Foregrounds

The cosmic microwave background (CMB) is an image of the violence of the big bang that we can take with microwave telescopes. In order to improve our understanding of the big bang, we must understand what the magnetized turbulence of the gas inside our own galaxy.
More soon!

Foregrounds

Code

I help develop and maintain the code Enzo (enzo-project.org). I developed the divergence-free magnetic field module for Enzo in 2010.