A Complete Census for Gravitationally Lensed Quasars with Roman
| Program ID | 19009 |
|---|---|
| Science Category | Active Galaxies & Supermassive Black Holes |
| Program Type | Analysis |
| Category | Small |
| Principal Investigator | Minghao Yue |
| PI Institution | University of Arizona, Steward Observatory |
| Co-Investigators |
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| Abstract | Gravitationally lensed quasars are high-value systems that simultaneously probe the foreground lensing galaxy and the background quasar. Previous surveys for lensed quasars have low completeness and poorly-understood selection bias; in particular, most high-redshift lensed quasars and compact lensed quasars are missed by the current sample. Here we propose a complete census for lensed quasars in Roman HLWAS, leveraging Roman's near-IR coverage and sharp PSF to recover the previously-missed populations. A complete lensed quasar census unlocks several otherwise infeasible experiments. First, the statistics of lensed quasars (number densities, magnification distribution, etc.) are essential for correcting the magnification bias of quasar luminosity functions (QLFs). Second, compact lensed quasars enable unique constraints on the mass profiles, mass-to-light ratios, and CGM enrichment for low-mass foreground galaxies. Third, high-redshift lensed quasars probe the kpc-scale variation of reionization-era IGM predicted by recent simulations. Using mock catalogs, we forecast the discovery of ~65 lensed quasars in HLWAS from the first two years of Roman observations, and ~320 from the entire HLWAS medium tier. We will use imaging and catalogs to identify systems with lens-like structure (i.e., a lensing galaxy plus several point sources with similar colors), perform lens modeling to select candidates, and use grism spectra to confirm lensed quasars via their broad lines. We will develop an AI-based inspection tool to replace traditional human inspection, fully automating the survey pipeline and ensuring reproducibility. This program will deliver: (1) an automated lensed quasar detection pipeline extensible to future Roman observations; (2) a catalog of ~65 confirmed lensed quasars from the first two-year dataset; (3) lensed quasar population statistics and magnification-corrected QLFs; and (4) a list of high-value lensed quasars for follow-up observations. |