Star Formation and Chemical Enrichment across Time

A key question in galaxy formation is how do the connected processes of star formation, gas accretion, feedback from supernova, and metal enrichment transform galaxies across cosmic time? Answering this question requires extensive observations that measure the star formation rate, stellar population, and gas-phase metallicity of star-forming galaxies. I am leading or co-leading four independent emission-line studies in the Subaru Deep Field (Kashikawa et al. 2004, Ly et al. 2007), the NewHα Survey (Ly et al. 2011, Lee et al. 2012), and the DEEP2 Survey. These studies utilize diagnostic spectroscopy to characterize the physical properties and state of the ionized gas in galaxies.

I. The Subaru Deep Field

The Subaru 8.2-meter telescope has stared for over 30 nights at one particular region of the northern sky with one of the most sensitive optical imagers in the world, Suprime-Cam. This camera enables images to be taken over a large part of the sky that is comparable to the angular extent of the Moon. The large area allows us to look at hundreds of thousands of galaxies simultaneously. Why stare for so long? To identify some of the faintest galaxies in the early universe! To do so, the survey utilized a technique called "narrowband imaging" to pick up emission from hydrogen and oxygen gases that reside within galaxies.
      Using the MMT, Keck, and Subaru observatories, my collaborators and I have targeted some of these faint galaxies with optical and near-infrared spectrographs. We found a rare population of galaxies that are rapidly forming at an unexpected rate. Many of these galaxies show signs of interactions with other nearby galaxies (see below). We believe that these interactions trigger the extreme bursts of star formation that we see. With detections of a very weak line, [OIII]λ4363, we were able to determine that these galaxies do not have significant heavy elements. In fact, a few of our galaxies have the most metal pristine gas seen for galaxies outside the local Universe. I am trying to understand why these galaxies have so few metals. One interpretation is that these galaxy interactions can drive new metal pristine gas into the galaxies, making it appear "metal-poor" and fueling recent star formation. You can find more information in our paper.

Academia, Mentorship, and Educational Outreach

I have had the fortunate opportunity to teach, mentor, and participate in public outreach. While I was a graduate student at UCLA, I led discussion sections and lab classes for introductory astronomy classes to both non-science and science major students.
      Over the past decade, I have mentored five undergraduate students on astronomical research projects. Nearly all of them had no prior research experience and limited computer programming skills. Through daily in-person interactions, I helped guide my students through the entire scientific research process. I taught my students to inquire, to code, to analyze and interpret data, and how to search and review scientific literature. These skills have helped my students in their current pursuits. One of my students has completed her M.Sc. in Applied Science and later worked for the Lawrence Berkeley National Laboratory. Another is pursuing a Ph.D in Astronomy at Yale. My most recent student has her first scientific paper accepted for publication in the Astronomical Journal.
      I have participated in Project ASTRO, an NSF-funded program to enrich K-12 physical science education by giving students the opportunity to learn and interact with professional and amateur astronomers. My experiences as a mentor have prepared me to actively engage undergraduate students in leading scientific research.