Ipac logo
Strongly Lensed Supernova Cosmology with the Roman HLTDS
Program ID 19038
Science Category Large Scale Structure of the Universe
Program Type Analysis
Category Medium
Principal Investigator Justin Pierel
PI Institution Space Telescope Science Institute / STScI
Co-Investigators
  • Simon Birrer (State University of New York at Stony Brook)
  • Conor Larison (Space Telescope Science Institute / STScI)
  • Aadya Agrawal (University of Illinois)
  • Rodrigo Angulo (Johns Hopkins University)
  • Wenlei Chen (Oklahoma State University)
  • David Coulter (Johns Hopkins University)
  • Tansu Daylan (Washington University in St. Louis)
  • James DerKacy (Space Telescope Science Institute / STScI)
  • Michael Engesser (Space Telescope Science Institute / STScI)
  • Ori Fox (Space Telescope Science Institute / STScI)
  • Brenda Frye (University of Arizona, Steward Observatory)
  • Massimo Griggio (Space Telescope Science Institute / STScI)
  • Xiaosheng Huang (University of San Francisco)
  • Saurabh Jha (Rutgers University)
  • Patrick Kelly (University of Minnesota)
  • Anton Koekemoer (Space Telescope Science Institute / STScI)
  • Zachary Lane (University of Canterbury)
  • Thomas Moore (Space Telescope Science Institute / STScI)
  • Leonidas Moustakas (Jet Propulsion Laboratory)
  • Gautham Narayan (University of Illinois)
  • Massimo Pascale (University of California, Los Angeles)
  • Armin Rest (Space Telescope Science Institute / STScI)
  • Melissa Shahbandeh (Space Telescope Science Institute / STScI)
  • Koji Shukawa (Johns Hopkins University)
  • Louis-Gregory Strolger (Space Telescope Science Institute / STScI)
  • Tommaso Treu (University of California, Los Angeles)
  • Estefania Padilla Gonzalez (Johns Hopkins University)
  • Matthew Siebert (Space Telescope Science Institute / STScI)
Abstract Understanding the nature of dark energy and resolving the persistent tension in the Hubble constant (H₀) are central challenges in modern cosmology. While the Nancy Grace Roman Space Telescope will deliver transformative cosmological constraints, they require the full mission and will contain significant astrophysical systematics (e.g., dust for Type Ia supernovae). Strongly lensed, multiply imaged supernovae (glSNe) provide a powerful and fully independent cosmological probe by measuring angular diameter distances through time-delay cosmography, with systematics distinct from SN Ia luminosity distances. We propose to exploit the unique capabilities of the Roman High Latitude Time-Domain Survey (HLTDS) to discover and analyze the first statistical sample of galaxy-scale glSNe. Based on survey forecasts, we expect ~22 systems within the first two years, each enabling a cosmological measurement from exquisite Roman data alone. The combination of high-cadence, multi-band near-infrared imaging and precise astrometry will yield time-delay measurements with ~1 day precision and robust mass models. Critically, the cosmological constraints from glSNe are highly complementary to those from SNe and weak lensing, offering a stringent cross-check on potential systematics and enabling a more robust determination of the dark energy equation of state. Alone, this sample will deliver a >5σ independent test of the H₀ tension, and combined with existing probes improve current dark energy constraints by a factor of ~2. Finally, this program will establish the foundation of a complete Roman HLTDS glSN sample (~70 systems), creating a legacy dataset that anchors time-delay cosmography as a premier probe of fundamental physics in the Roman era.