Research

My work sits at the intersection of observational survey design, data analysis pipeline development, and cosmological inference. I build and analyze nearby Type Ia supernova (SN Ia) samples — the critical low-redshift anchor of the cosmic distance ladder — and develop the software and statistical tools needed to extract cosmological constraints from them.

DEBASS: Dark Energy Bedrock All-Sky Survey

The Dark Energy Bedrock All-Sky Supernova (DEBASS) program is building the largest uniformly calibrated low-redshift SN Ia dataset in the southern hemisphere, using the Dark Energy Camera (DECam) — the same instrument as the Dark Energy Survey (DES) — enabling seamless photometric cross-calibration across surveys. DEBASS has accumulated more than 500 spectroscopically confirmed SNe Ia in the redshift range \(0.01 < z < 0.08\) from 2021 to mid-2025.

My work has contributed to two papers presenting an early data release of 77 SNe Ia within the DES footprint:

• Photometric data preparation (Sherman et al. 2025): I prepared the photometric data underlying the DEBASS program paper, which introduces the survey and its scientific goals. This early release achieves a Hubble diagram residual scatter of ~0.10 mag and a host-galaxy mass step of 0.06 ± 0.04 mag before bias corrections, demonstrating the promise of a well-calibrated, high-SNR low-z program.
• Systematics, calibration, and simulations (Acevedo et al. 2026, ApJ, 996, 7): I led the companion systematics paper, covering photometric calibration, selection effects, and end-to-end survey simulations. I achieved agreement at the 10 millimagnitude level among DEBASS, DES, and Pan-STARRS1 tertiary standard stars. My simulations reproduce the observed SN light-curve property distributions and yield a bias-corrected Hubble residual scatter of 0.08 mag.

I am currently working on the full cosmological analysis combining DEBASS with the DES 5-Year SN sample (DES-SN5YR), using DEBASS as the well-characterized low-redshift anchor in place of the historical low-z samples.

WHALES: Weighing Halos with Supernovae

The Weighing Halos Accurately, Locally, and Efficiently with Supernovae (WHALES) Survey is the first survey to discover and measure Type Ia supernovae in and around galaxy superclusters. The target for the first two seasons is the Shapley Supercluster (\(0.02 < z < 0.06\)), the most massive nearby concentration of matter and a major — but poorly constrained — contributor to our Local Group’s peculiar motion. No supernovae had been analyzed in the direction of Shapley prior to this work.

I led the survey overview and initial data release paper (Acevedo et al. 2026, ApJL, 998, L26), covering the end-to-end process of building and analyzing this new dataset:

• Observations: I carry out observations with SkyMapper and coordinate follow-up spectroscopy.
• Light curve pipeline: I process and reduce the multi-epoch imaging data, construct light curves by combining SkyMapper photometry with data from the Asteroid Terrestrial-impact Last Alert System (ATLAS), and fit them to extract SN distances.

Future: Roman Space Telescope

The Nancy Grace Roman Space Telescope, launching in September 2026, will conduct the largest high-redshift SN Ia survey ever undertaken. I am involved in the Roman Supernova Project Infrastructure Team (SN PIT), contributing to the analysis pipelines and infrastructure needed to connect Roman’s high-z measurements to the local distance scale established by surveys like DEBASS and WHALES.