Establishing the Post-Reionization Lya Transmission-Environment Baseline
| Program ID | 19005 |
|---|---|
| Science Category | Intergalactic Medium |
| Program Type | Analysis |
| Category | Small |
| Principal Investigator | Yongda Zhu |
| PI Institution | University of Arizona |
| Co-Investigators |
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| Abstract | Lyalpha is a key probe of cosmic reionization, but its interpretation is limited by the lack of a calibrated post-reionization baseline. We will establish that baseline at z~2.2, where the IGM is highly ionized, by combining Roman HLWAS-Deep grism spectroscopy with Subaru/HSC NB387 imaging across the COSMOS and XMM-LSS fields. Roman will provide a high-purity, uniform, spec-z confirmed [O III] emitter sample to define the galaxy density field, while the narrowband data will measure Lyalpha transmission from background sources over the same ~9.6 deg^2 footprint. These data will enable the first wide-area benchmark relating Lyalpha transmission to galaxy environment in the fully ionized universe. The key science goal is to separate Lyalpha physics that persists after reionization, such as local radiative-transfer and galaxy-environment effects, from reionization-era fluctuations driven by a patchy ionizing background and/or residual neutral hydrogen. The resulting Roman benchmark will provide a timely community reference for interpreting Lyalpha measurements during reionization. |