{"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/observational-constraints-on-key-parameters","title":"Observational constraints on key-parameters of cosmic reionisation history","arxiv_id":"1710.04152","date":"2017-10-11","proceeding":null,"authors":["Adélie Gorce","Marian Douspis","Nabila Aghanim","Mathieu Langer"],"abstract":"We discuss constraints on cosmic reionisation and their implications on a cosmic SFR density $\\rho_\\mathrm{SFR}$ model; we study the influence of key-parameters such as the clumping factor of ionised hydrogen in the intergalactic medium (IGM) $C_{H_{II}}$ and the fraction of ionising photons escaping star-forming galaxies to reionise the IGM $f_\\mathrm{esc}$. Our analysis uses SFR history data coming from luminosity functions, assuming that star-forming galaxies were sufficient to lead the reionisation process at high redshift. We add two other sets of constraints: measurements of the IGM ionised fraction and the most recent result from Planck Satellite about the integrated Thomson optical depth of the Cosmic Microwave Background (CMB) $\\tau_\\mathrm{Planck}$. We also consider various possibilities for the evolution of these two parameters with redshift, and confront them with observational data cited above. We conclude that, if the model of a constant clumping factor is chosen, the fiducial value of $3$ often used in papers is consistent with observations; even if a redshift-dependent model is considered, the resulting optical depth is strongly correlated to $C_{H_{II}}$ mean value at $z>7$, an additional argument in favour of the use of a constant clumping factor. Besides, the escape fraction is related to too many astrophysical parameters to allow us to use a complete and fully satisfactory model. A constant value with redshift seems again to be the most likely expression: considering it as a fit parameter, we get from the maximum likelihood (ML) model $f_\\mathrm{esc}=0.24\\pm0.08$; with a redshift-dependent model, we find an almost constant evolution, slightly increasing with $z$, around $f_\\mathrm{esc}=0.23$. Last, our analysis shows that a reionisation beginning as early as $z\\geq14$ and persisting until $z\\sim6$ is a likely storyline.","url_abs":"http://arxiv.org/abs/1710.04152v3","url_pdf":"http://arxiv.org/pdf/1710.04152v3.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":"observational-constraints-on-key-parameters","repo_url":"https://github.com/adeliegorce/tools4reionisation/tree/master/comprehensive_scenario","is_official":1,"mentioned_in_paper":0,"mentioned_in_github":0,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}