{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/model-independent-constraints-on-the-hydrogen","title":"Model-independent constraints on the hydrogen-ionizing emissivity at z>6","arxiv_id":"1907.11332","date":"2019-07-25","proceeding":null,"authors":["Charlotte A. Mason","Rohan P. Naidu","Sandro Tacchella","Joel Leja"],"abstract":"Modelling reionization often requires significant assumptions about the properties of ionizing sources. Here, we infer the total output of hydrogen-ionizing photons (the ionizing emissivity, $\\dot{N}_\\textrm{ion}$) at $z=4-14$ from current reionization constraints, being maximally agnostic to the properties of ionizing sources. We use a Bayesian analysis to fit for a non-parametric form of $\\dot{N}_\\textrm{ion}$, allowing us to flexibly explore the entire prior volume. We infer a declining $\\dot{N}_\\textrm{ion}$ with redshift at $z>6$, which can be used as a benchmark for reionization models. Model-independent reionization constraints from the CMB optical depth and Ly$\\alpha$ and Ly$\\beta$ forest dark pixel fraction produce $\\dot{N}_\\textrm{ion}$ evolution ($d\\log_{10}\\dot{N}_\\textrm{ion}/dz|_{z=6\\rightarrow8} = -0.31\\pm0.35$ dex) consistent with the declining UV luminosity density of galaxies, assuming constant ionizing photon escape fraction and efficiency. Including measurements from Ly$\\alpha$ damping of galaxies and quasars produces a more rapid decline: $d\\log_{10}\\dot{N}_\\textrm{ion}/dz|_{z=6\\rightarrow8} =-0.44\\pm0.22$ dex, steeper than the declining galaxy luminosity density (if extrapolated beyond $M_\\mathrm{UV} \\lesssim -13$), and constrains the mid-point of reionization to $z = 6.93\\pm0.14$.","url_abs":"http://arxiv.org/abs/1907.11332v1","url_pdf":"http://arxiv.org/pdf/1907.11332v1.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"model-independent-constraints-on-the-hydrogen","repo_url":"https://github.com/charlottenosam/Nion_inference","is_official":1,"mentioned_in_paper":0,"mentioned_in_github":0,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"syntology_url":null,"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}