Welcome To My Graduate Research.
In astronomy, we are constantly searching through the universe to find unusual objects that can unlock the mysteries of creation; these objects open windows to the past. One such family of objects is Lyman Alpha Emitting galaxies (LAEs). LAEs are a unique type of galaxy because they are actively birthing lots of stars, causing them to emit a special ultraviolet glow. LAEs are so ancient that the expansion of the universe transforms this ultraviolet light into visible light, making LAEs observable by ground-based telescopes. This enables LAEs to serve as ancient beacons, illuminating galaxy populations that existed over 12 billion years ago. LAEs have been identified as progenitors of typical present-day galaxies like our own Milky Way. By understanding when LAEs first formed their stars, we discover our own galaxy’s “origin story”... unlocking one of the mysteries of creation.
Through my graduate work with LAEs, I have built up expertise in photometric analysis, spectral energy distributions, and star formation histories for young, low-mass galaxies at high-redshifts.
The One-hundred-degree² DECam
Imaging in Narrowbands (ODIN) Survey
The ODIN Collaboration is led by PI Kyoung-Soo Lee and Co-I Eric Gawiser.
The ODIN team comprises many researchers in the US, Korea, Chile, Taiwan, and Argentina.
A contingent of ODIN at the Korea Institute for Advanced Study in South Korea.
The One-hundred-square-degree DECam Imaging in Narrowbands (ODIN) Survey is a NOIRLab program designed to discover Lyman Alpha Emitting Galaxies (LAEs) using the Dark Energy Camera on the Víctor M. Blanco 4m telescope at the Cerro Tololo Inter-American Observatory in Chile. This project utilizes three custom-made narrow band filters centered at wavelengths 419 nm, 501 nm, and 673 nm to create samples of candidate LAEs at redshifts 2.4, 3.1, and 4.5, respectively. These filters allow us to view snapshots of the LAE distribution 1.4, 2.1, and 2.8 billion years after the Big Bang. With the results of this survey, we expect to create a sample of >100,000 LAEs as well as protoclusters and Lyman Alpha Blobs across 7 deep fields. Examining the distribution of LAEs at these redshifts will allow us to trace the large-scale structure of the universe during the peak epoch of cluster formation and begin to answer many intriguing quandaries in modern cosmology.
Selecting the largest-ever samples of Lyman Alpha Emitting galaxies (LAEs) from the ODIN narrowband images
Narrowband surveys reveal large, uniform samples of LAEs at specific
redshifts that probe large-scale structure and the temporal evolution of
galaxy properties. In this work, we introduce the hybrid-weighted
double-broadband continuum estimation technique, which yields
improved estimation of Lyα equivalent widths. Using this method, we
discover 6032, 5691, and 4066 LAE candidates at z = 2.4, 3.1, and 4.5
in the extended COSMOS field (∼9 deg2 ). We find that [O II] emitters are a minimal contaminant in our LAE samples, but that interloping Green Pea–like [O III] emitters are important for our redshift 4.5 sample. We introduce an innovative method for identifying [O II] and [O III] emitters via a combination of narrowband excess and galaxy colors, enabling their study as separate classes of objects. We present scaled median stacked spectral energy distributions for each galaxy sample, revealing the overall success of our selection methods. We also calculate rest-frame Lyα equivalent widths for our LAE samples and find that the EW distributions are best fit by exponential functions with scale lengths of w0 = 53 ± 1, 65 ± 1, and 59 ± 1 Å, respectively.
Calculating Star Formation Histories of ODIN LAEs and finding that they split into three archetypes
In this work, we test the frequent assumption that Lyα-emitting galaxies
(LAEs) are experiencing their first major burst of star formation at the time
of observation. To this end, we identify 74 LAEs from the ODIN Survey with
rest-UV-through-NIR photometry from UVCANDELS. For each LAE, we
perform nonparametric star formation history (SFH) reconstruction using
the Dense Basis Gaussian-process-based method of spectral energy distribution fitting. We find that a strong majority (67%) of our LAE SFHs align with the frequently assumed archetype of a first major star formation burst, with at most modest star formation rates (SFRs) in the past. However, the rest of our LAE SFHs have significant amounts of star formation in the past, with 28% exhibiting earlier bursts of star formation, with the ongoing burst having the highest SFR (dominant bursts) and the final 5% having experienced their highest SFR in the past (nondominant bursts). Combining the SFHs indicating first and dominant bursts, ∼95% of LAEs are experiencing their largest burst yet: a formative burst. We also find that the fraction of total stellar mass created in the last 200 Myr is ∼1.3 times higher in LAEs than in mass-matched Lyman break galaxy (LBG) samples, and that a majority of LBGs are experiencing dominant bursts, reaffirming that LAEs differ from other star-forming galaxies. Overall, our results suggest that multiple evolutionary paths can produce galaxies with strong observed Lyα emission.
For a list of additional ODIN papers that I have been a coauthor on, please visit my CV.
The Hobby-Eberly Telescope Dark Energy Experiment
(HETDEX)
The HETDEX Collaboration is led by PI Karl Gebhardt.
The HETDEX team comprises many researchers, engineers, and technicians across the US and Germany.
A contingent of HETDEX and ODIN at the Cosmic Lyman Alpha Workshop in Kochel, Germany.
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is a untargeted spectroscopic survey designed to map out the large scale structure of LAEs of the 1.9 < z < 3.5 universe. HETDEX utilizes the Visible Integral-field Replicable Unit Spectrograph (VIRUS), a set of 78 50′′ × 50′′ integral field units (IFUs) distributed across the focal plane of the Hobby-Eberly Telescope (Hill et al. 2021), at the McDonald Observatory at The University of Texas. The primary goal of HETDEX is to understand how dark energy fuels the expansion of the universe across cosmic time. To accomplish this task, HETDEX uses LAEs as tracer of the underlying matter distribution through their dark matter halos. This goal necessitates a fundamental understanding of the galaxy-halo connection (i.e., the halo occupation distribution) for LAEs. One approach to probe this connection is to quantify the uniformity (and diversity) of LAE properties, notably their star formation stochasticity.
Using SFHs to place HETDEX LAEs on the SFR-M* plane as well as a newly-introduced Star Formation Stochasticity Diagram. We find that the three archetypes separate on these plots.
In this work, we aim to measure the star formation stochasticity of
Lyman Alpha Emitting Galaxies (LAEs) at Cosmic Noon. We identify
270 LAEs from the HETDEX Survey in the COSMOS field with
rest-UV-through-NIR photometry from CANDELS. For each LAE,
we perform non-parametric gaussian-process star formation history
(SFH) reconstruction using the Dense Basis method. Our HETDEX
LAE sample is described well by the three SFH archetypes defined for ODIN LAEs in Firestone et al. (2025) with comparable frequency: First Burst, Dominant Burst, and Nondominant Burst. The rapidly rising Star Formation Rates (SFRs) of First Burst LAEs are not adequately represented in traditional SFR100 − M∗ diagrams, where SFR100 is averaged over the most recent 100 Myr. This motivates the usage of SFR10 − M∗, where SFR10 is averaged over the most recent 10 Myr. We introduce the Star Formation Stochasticity Diagram, a diagnostic tool that probes variations in galaxies’ SFRs across cosmic time. By eliminating the confounding factor of redshift evolution, we are able to employ a gaussian mixture model to decompose our ratio of short- vs. long-term SFR into statistically motivated sub-populations. This agnostic component decomposition reveals three populations consistent with the empirical LAE SFH archetypes. We can, therefore, summarize the overall stellar mass assembly of LAEs with this ratio, even without viewing their full star formation histories.
My graduate work has been funded by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-2233066, NSF grant AST-2206222, NASA Astrophysics Data Analysis Program grant 80NSSC22K0487, and DOE grant DE-SC0010008.