My Research

My research interests are in the field of computational astrophysics where I use simulation and theoretical models -- along with my extensive software development skills -- to understand the first galaxies and the transition from metal-free Population III (Pop III) to Population II (Pop II) star formation. Since no one has yet observed a metal-free star, one way to deduce their characteristics is by using theory and simulation to understand the unusual elemental abundances seen in some of the oldest stellar systems studied by observers. These ``stellar fossils'' are thought to have captured the chemical imprint of Pop III supernova (SN) and neutron star mergers (NSM) providing us with clues we can use to understand this first generation of stars.


The left frame depicts the evolution of the density field for a 16 Mpc on-a-side simulation. Galaxies are forming throughout the box and are indicated by lighter colors/white.

The right frame depicts the pollution of the gas by supernova. 

Metallicity of the gas along with observable 'regular' galaxies (white circles) and observable galaxies dominated by Pop III stellar flux (red cirlces)

Same as the far left panel, but a few 10's of millions of years after reionization. Most bright Pop III stars have gone supernova, and reionization has quenched star formation in smaller halos.

Luminosity functions for our galaxies

Observational data is limited at redshift 10 and completely lacking at higher redshifts. However, using our simulation, we makes predictions for the number of detectable (by JWST) galaxies as a function of brightness out to z=12. These will be some of the faintest objects detectable (without lensing).

Supernova induced turbulent velocity and fluid-flow (vectors).

Our simulation tracks the pristine fraction of gas at subgrid scales to better model the formation of Pop III stars in the early universe.

Left: Scatter diagram of the corrected A(C) vs. [Fe/H] from Yoon et al. [2016]. The blue and red open circles represent the 147 CEMP-s/rs stars and 127 CEMP-no stars, respectively. The black diagonal line identifies a carbon-to-metal ratio: [C/Fe] = 0.7. Right: Joint PDF depicting the mass-weighted probabilities, per Mpc3, for A(C) vs. [Fe/H] for all the stars in my simulation. Red stars are a super-set of CEMP-no stars plotted at left. The PDF correlates well with bimodal pattern of CEMP-no (red) stars analyzed by Yoon et al. [2016].

-- A(C) = log (NC/NH) + 12, is the Carbon abundance where A(C)⊙ = 8.43