Currently, I am a part of NMSU Prof. Chris Churchill's research group which studies absorption lines found in the spectra of bright, distant objects called quasars (see figure below). These absorption lines contain a treasure trove of information on the gas that surrounds galaxies and are otherwise extremely difficult to observe. The gas contained in the Circumgalactic Medium (CGM) of galaxies and the Intergalactic Medium (IGM) actually makes up most of the baryonic matter in the universe (over 90%!) and is crucial in understanding how galaxies form and evolve. Please check out our research page for more details!
An example of various absorption lines caused by intervening matter seen in a quasar (QSO) spectrum. Credits: Chris Churchill
I have been analyzing metal absorption lines found in the highest resolution quasar spectra available, from the Keck telescopes in Mauna Kea, Hawaii and the Very Large Telescopes in Mt. Paranal, Chile, to understand how metal-enriched gas evolves across cosmic time and influences the evolution of galaxies. We recently published a paper on how triply ionized Carbon (CIV) evolves across cosmic time. We found that CIV becomes more common in later times (as the figure below shows), possibly due to the enrichment of the universe with carbon and the evolution of the cosmic ultraviolet background radiation from galaxies and quasars. However, we also unexpectedly uncovered a simple mathematical formulation to describe the observed evolution! Here is the published paper.
The rise in the incidence of CIV across >12 billion years of cosmic time. Our data are shown in black, while the rest are from the literature. Please see the paper for details.
I am a trained observer on the 3.5m Astrophysical Research Consortium (ARC) telescope on Apache Point Observatory in Sunspot. NM. Currently, we're using the telescope to obtain spectroscopic redshifts of galaxies that are associated with observed CGM gas. These observations will be crucial in aiding our understanding of how gas cycles in and out of galaxies and how that affects galaxy evolution.
Apache Point Observatory, Sunspot, NM.
Past work
I worked with UC Irvine Prof. Asantha Cooray and his group on dusty star-forming galaxies at redshifts ~0.5 to ~2: Brief RNAAS Publication We quantfied star formation and dust attenuation in these systems and concluded that they lie above the Main Sequence of star formation, implying they are more massive than local starbursts with similar star formation rates. Furthermore, ionized gas (nebular lines) was found to be about as extincted as the stellar continuum.
I worked with Prof. Alison Crocker of Reed College on star formation at the center of spiral galaxy NGC 4736 (a.k.a. the Cat's eye galaxy). We used observed star clusters to determine that the central region of the galaxy is forming stars less efficiently (low star formation rate per amount of available cold gas) than the spiral arms - a phenomenon observed in our own galaxy. Here is a report we prepared on our results.
NGC 4736, the "Cat's eye galaxy." Image: Robert Gendler/HST
I wrote an undergraduate thesis on supermassive black holes (SMBH) , where I studied the demographics of galaxies and SMBHs in the local universe. From galaxies in the Sloan Digital Sky Survey, I determined the Velocity Dispersion Function (VDF) of galaxies and then the Black Hole Mass Function (BHMF) of their central black holes. Both distributions truncate rapidly past a certain value. Our results support the notion that mass accretion is primarily responsible for growing SMBHs to their present-day masses. Here is a talk I gave on my thesis at a Reed Physics seminar. The first paper in the series, on the local VDF from Sloan, has been submitted to the Astronomical journal (here is the ArXiV version).
The horror at the galactic center, from Graham 2016. Artist: Gabriel Pérez Díaz.
