Revisiting the Type Ia Supernova Mass Step with Roman
| Program ID | 19016 |
|---|---|
| Science Category | Stellar Physics |
| Program Type | Analysis |
| Category | Small |
| Principal Investigator | Estefania Padilla Gonzalez |
| PI Institution | Johns Hopkins University |
| Co-Investigators |
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| Abstract | Type Ia supernovae (SNe Ia) are fundamental tools for measuring cosmic distances and led to the discovery of the accelerating expansion of the Universe. Their utility relies on empirical standardization relations between peak brightness, light-curve width, and color. However, several studies have found that this standardization is incomplete: after standardization, SNe Ia in more massive galaxies appear systematically brighter than those in low-mass hosts, an effect commonly referred to as the “mass-step.” The physical origin of this correlation remains uncertain and may be linked to progenitor metallicity or other host-galaxy properties. A major limitation of current studies is the lack of near-infrared (NIR) photometry for SN Ia host galaxies, which leads to biased estimates of stellar mass and metallicity. The Roman Space Telescope will significantly improve this limitation by providing NIR photometry for an additional 513 Pantheon+ host galaxies, more than doubling the largest existing sample of SN Ia hosts with infrared-constrained stellar population properties (~300 galaxies). This expanded dataset will enable a robust test of the mass-step and its potential metallicity origin by improving host-galaxy parameter estimates and filling the current gap in low-mass galaxies. Together, this will test whether the SN Ia mass-step is fundamentally driven by progenitor metallicity rather than host stellar mass; a crucial component for understanding SN Ia explosion mechanisms to enable precision of SN Ia standardization for cosmological measurements. |