Preparing for Roman with a Per-Supernova Sightline Dust Correction
| Program ID | 19085 |
|---|---|
| Science Category | Large Scale Structure of the Universe |
| Program Type | Analysis |
| Category | Medium |
| Principal Investigator | Jacqueline McCleary |
| PI Institution | Northeastern University |
| Co-Investigators |
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| Abstract | Extragalactic dust in the circumgalactic and intergalactic media (CGM/IGM) is increasingly recognized as a significant systematic in Type Ia supernova (SN Ia) cosmology. Recent analyses show that line-of-sight dust contributes substantially to distance-modulus scatter and can bias cosmological parameters at a level comparable to current statistical uncertainties. This effect will be amplified in Stage IV surveys such as the Roman High-Latitude Time Domain Survey (HLTDS), which will deliver unprecedented statistical precision and extend to $z > 1.5$, where cumulative dust columns are larger. We propose a pilot program to develop and test a framework for per-supernova extragalactic dust corrections using the foreground galaxy population along each sightline. In Aim 1, we will measure dust extinction profiles as a function of galaxy properties (e.g., stellar mass, star formation rate, and redshift) using an optimal multi-band estimator, and translate these relations into a model based on observables available to Roman and its ancillary datasets. In Aim 2, we will combine these relations with Roman-native simulations to predict per-supernova, per-band extinction, and evaluate the impact of these corrections on SN Ia distance estimates and cosmological inference. This work will provide the first end-to-end demonstration of a galaxy-conditioned, per-sightline dust correction in SN cosmology. By quantifying its impact on bias, scatter, and correlations with foreground structure, this project will assess whether extragalactic dust can be mitigated as a leading systematic in next-generation surveys. The resulting framework and data products will be directly applicable to Roman SN analyses and broadly useful for Stage IV cosmology. |