Probing the stellar remnant population with Roman Astrometry
| Program ID | 19083 |
|---|---|
| Science Category | Stellar Populations |
| Program Type | Analysis |
| Category | Large |
| Principal Investigator | Peter McGill |
| PI Institution | Lawrence Livermore National Lab |
| Co-Investigators |
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| Abstract | Roman’s Galactic Bulge Time Domain Survey (GBTDS) will deliver densely sampled, multi-epoch astrometry for 200 million stars. With approximately 1 milliarcsecond (mas) precision per well-sampled source and about 40,000 visits per star, the five-year survey yields 400 astrometric data points at 0.1 mas precision. This provides a unique view of the variable astrometric sky and strongly complements Gaia, which cannot probe the crowded, dusty Bulge and has a much lower cadence. While Roman GBTDS photometry science cases (for example, microlensing exoplanets) are well developed, astrometric cases have received less attention. We will address this by detecting and characterizing astrometric variables from microlensing and binary orbital motion. We will (1) characterize the isolated stellar-remnant and wide-binary black hole (BH) population by quantifying GBTDS completeness and sensitivity to their astrometric signals; (2) increase BH yield and enable mass measurements by extending the Microlensing Science Operations System pipeline to identify and characterize astrometric anomalies at the end of each GBTDS season; and (3) build a sample of isolated stellar remnants and detached-binary BHs to infer the remnant mass function shape. We will also validate Roman astrometric performance and recommend processing improvements to boost BH yield and astrometric characterization in the second half of GBTDS. This effort must start soon to maximize transient-signal science return and fully exploit GBTDS as the last sub-mas, high-cadence, wide-field astrometric survey for decades. |