Roman and the Rise of Giants: Black-Hole Growth in Forming Galaxy Clusters
| Program ID | 19007 |
|---|---|
| Science Category | Active Galaxies & Supermassive Black Holes |
| Program Type | Analysis |
| Category | Small |
| Principal Investigator | Wei Leong Tee |
| PI Institution | Pennsylvania State University |
| Co-Investigators |
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| Abstract | We propose a Roman HLWAS legacy program to identify and characterize z=2-4 massive protoclusters (M_h>10^14 M_s) and their galaxy and AGN members in the COSMOS and XMM-LSS Deep-Drilling Fields. Using Roman deep near-infrared imaging and grism data, together with Rubin LSST optical photometry and X-ray-to-radio ancillary datasets, we will deliver the first statistically robust census of rare, high-mass protoclusters and assess environmental impacts on SMBH growth during cosmic noon. We will (1) identify up to hundreds of high-confidence massive protocluster candidates using 3D overdensity mapping with full photometric redshift PDFs; (2) measure the scaling of black-hole accretion rates (BHAR) and AGN fractions with local overdensity, halo mass, stellar mass, and their redshift evolution; (3) quantify the AGN contribution in massive protoclusters to the cosmic SMBH accretion density. We will produce calibrated photometric-redshift PDFs and physical parameters using joint Roman+Rubin+ancillary datasets for SED fitting, incorporating Roman grism and spectroscopic samples for zeropoint and redshift validation. We will apply PCFNet, a point-cloud machine-learning overdensity finder, and benchmark its performance with spectroscopic data. This will enable robust protocluster identification, AGN classification, BHAR and AGN fraction measurements, and a comprehensive view of SMBH growth in dense environments. We will release a master multiwavelength catalog with photometry, redshifts, quality flags, stellar masses, and star-formation rates; a protocluster catalog with membership probabilities and halo-mass estimates; an AGN catalog with classifications and X-ray measurements; BHAR measurements with uncertainties; and all associated open-source pipelines. All data products will be publicly available on Zenodo and our group website, with software pipelines on GitHub. These resources will support future large-scale-structure studies using the full Roman and Rubin surveys. |