Research

My research is focused the interplay between internal and external factors affecting galaxy evolution between z=1 and today, with the ultimate goal of understanding the decline in global star-formation activity in the past 10 Gyr.

Ultra-Diffuse Galaxies

A large population of extremely extended dwarf galaxies (dubbed 'Ultra-Diffuse Galaxies,' or UDGs) has been identified by recent surveys with high sensitivity limits. Understanding the formation of these unusual galaxies is compelling, both on its own right as well as within the broader context of dwarf galaxy fromation and evolution. Although these galaxies have been observed both inside and outside clusters, UDGs seem to be both more abundant and more diffuse in high-density environments. Motivated by this observed bias, I am currently investigating environmentally-motivated UDG formation mechanisms using the Bolshoi simulation.

The UVJ Diagram & the 3D-HST survey

The location of a galaxy in U-V vs. V-J color-color space has proven extremely valuable in separating red dusty galaxies from red quiescent galaxies, particularly at high redshift. The 3D-HST survey provides deep spectroscopic follow-up of a large number of star-forming and quiescent galaxies using the HST grism. These observations, in addition to providing a direct calibration of the star-formation properties of UVJ-classified galaxies, can illuminate the how emission line-based properties of high-z galaxies compare with their light-weighted stellar populations.

Satellite Quenching at high redshift

It is well known that environment plays an important role in shutting down star formation (or quenching) in dwarf galaxies. While many physical mechanisms (e.g. ram-pressure stripping, strangulation, starvation...) have been put forward to explain this process, observational evidence is only beginning to settle the question which of these effects are at play in low mass (M*~108 M) dwarfs in the local universe, and the relative importance of each effect. Observations of satellite-quenching in similar dwarfs at high-z provide an important piece of our understanding of the mechanisms at play during the decline in star-formation.

CO-H2 Conversion Factor

Molecular gas is the principal fuel in the star formation process, so understanding the molecular gas content of high-redshift galaxies goes a long way in building our understanding of this process at high-z. A crucial component of interpreting observations of molecular gas at high-z is the CO-H2 Conversion Factor (αCO) relating the observed CO luminosity to the molecular gas mass. Using data from the PHIBSS and COLD GASS programs, I have investigated the impact of metallicity and density on the galaxy-wide αCO value. My research, which found that αCO values do not significantly evolve from z=1 to z=0, demonstrates that molecular gas conditions have not significantly evolved over the past 8 billion years.