A Census of Black Hole Evolution using High-Ionization Emission Lines
| Program ID | 19067 |
|---|---|
| Science Category | Active Galaxies & Supermassive Black Holes |
| Program Type | Analysis |
| Category | Small |
| Principal Investigator | Nikko Cleri |
| PI Institution | Pennsylvania State University |
| Co-Investigators |
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| Abstract | Emission lines that probe >54 eV are critical, yet underutilized, tracers of ionization harder than normal stellar populations. High-ionization lines can clarify the evolution of accreting black holes: a fundamental goal of the NASA Science Plan and the Roman mission. We will use WFI G150 grism spectra in the High Latitude Wide Area Survey (HLWAS) to characterize the full ionizing continuum from 13.6 to > 54 eV by targeting [Ne V] 3427 and He II 4687 among the suite of rest-frame optical lines for ∼10000 galaxies at 1.1 < z < 4.6, representing a factor of 103 increase in > 54 eV line detections over all existing spectroscopy at 𝑧 > 2. [Ne V] and He II are the strongest lines in the rest-frame optical to probe > 54 eV, yet the striking scarcity of detections (< 5 at z > 5) from existing spectroscopy makes this an enticing case for Roman’s wide area and selection-blind grism census in the HLWAS Deep Tier. Our experiment will find intermediate mass black hole candidates and constrain seeding pathways by using the first population-level analysis for ∼10000 galaxies with [Ne V] and He II around the peak of cosmic star formation rate density and black hole activity. |