Research

research

The Giant Magellan Telescope (GMT) is composed of seven 8.4m mirrors, which is the equivalent of ~ one 25m telescope, which gives it a light-gathering power over six times greater than the current largest telescope (~10m).

The Hobby-Eberly Telescope (HET) is a 9.2m (soon to be upgraded to 10m) telescope located in west Texas. In 2013, the VIRUS instrument will be permanently mounted to the HET, and the HETDEX survey will begin.

My Research Interests
My main research interest is in the area of galaxy evolution, at both moderate and high redshifts. On the high-redshift side, I am pursuing a number of research topics within the CANDELS (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey) collaboration. CANDELS is the largest Hubble Space Telescope program ever, consisting of 902 orbits over three years (in contrast, a typical Hubble proposal is usually 20 or so orbits). Students and postdocs working with me have access to this enormous dataset. I am also involved in HETDEX (the Hobby Eberly Telescope Dark Energy Experiment), where we are using the 10m Hobby Eberly Telescope at McDonald Observatory in West Texas to discover one million galaxies at z = 2-3 to study dark energy. We are finding these galaxies on the basis of their Lyman alpha emission, hence they are known as Lyman alpha emitters, or LAEs.
Using the CANDELS near-infrared data, we can now discover galaxies at redshifts (z) greater than 6, all the way out to z = 10 (less than 500 million years from the Big Bang, or more than 96% of the way back in the history of the universe. We first studied the colors of these galaxies, where we learned that even at such early times, these galaxies do not appear primordial in nature; that is, there must be yet more galaxies at even higher redshifts where the first stars have formed. We have also examined how galaxies affect reionization, which is the name we give to the time when high energy photons from stars ionized the gas in between galaxies (known as the intergalactic medium). We found that the galaxies we see can accomplish this by z = 6, or if fainter galaxies play a large role, reionization can happen at even earlier times.
These studies are just the tip of the iceberg, as my group is working on a wide variety of studies aimed at increasing our understanding of galaxies in the early universe. Among these are studying how the galaxy luminosity functions (this describes how many galaxies there are at a given intrinsic brightness) and the stellar mass functions (the same thing, only for stellar mass) evolve with time. We are also examining ways to constrain the star-formation histories of galaxies, to learn how they build up stars over time.
On the HETDEX side, I am very interested in studying the population of LAEs we discover. Galaxies bright in the Lyman alpha line were originally predicted to be primordial in nature. I studied LAEs extensively in my thesis (see my thesis research page), and among our findings was that they don’t appear to be primordial. However, in my thesis I used a sample of 14 LAEs. You can imagine how excited I am to get my hands on a sample of one million! I’ve begun work studying the metallicities of these enigmatic galaxies, and with the HETDEX dataset we’ll be able to study very exciting topics such as how Lyman alpha photons escape from galaxies, how the physical properties of LAEs evolve, and how galaxy properties depend on their host dark matter halo masses. Finally, I’m also getting involved in our dark energy measurement itself. Through the technique of Baryon Acoustic Oscillations, we will directly measure the expansion rate at z=2.4, to determine the imact of dark energy at this early time.

Links
Curriculum Vitae
Publications List
Current Research
Thesis Research
My NASA ADS Listings
Recent Travel
Some telescopes I’ve observed on
Cool astro videos

UT Austin Astronomy
UT Public Outreach
CANDELS
HETDEX
Giant Magellan Telescope

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