{"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/the-evolution-of-molecular-gas-fraction","title":"The Evolution of Molecular Gas Fraction Traced by the CO Tully-Fisher Relation","arxiv_id":"1811.03107","date":"2018-11-07","proceeding":null,"authors":["Jacob W. Isbell","Rui Xue","Hai Fu"],"abstract":"Carbon monoxide (CO) observations show a luminosity$-$line-width correlation that evolves with redshift. We present a method to use CO measurements alone to infer the molecular gas fraction ($f_{\\rm mol}$) and constrain the CO$-$H$_2$ conversion factor ($\\alpha_{\\rm CO}$). We compile from the literature spatially integrated low-$J$ CO observations of six galaxy populations, including a total of 449 galaxies between $0.01 \\leq z \\leq 3.26$. The CO data of each population provide an estimate of the $\\alpha_{\\rm CO}$-normalized mean molecular gas fraction ($f_{\\rm mol}/\\alpha_{\\rm CO}$). The redshift evolution of the luminosity$-$line-width correlation thus indicates an evolution of $f_{\\rm mol}/\\alpha_{\\rm CO}$. We use a Bayesian-based Monte-Carlo Markov Chain sampler to derive the posterior probability distribution functions of $f_{\\rm mol}/\\alpha_{\\rm CO}$ for these galaxy populations, accounting for random inclination angles and measurement errors in the likelihood function. We find that the molecular gas fraction evolves rapidly with redshift, $f_{\\rm mol} \\propto (1+z)^\\beta$ with $\\beta \\simeq 2$, for both normal star-forming and starburst galaxies. Furthermore, the evolution trend agrees well with that inferred from the Kennicutt-Schmidt relation and the star-forming main sequence. Finally, at $z < 0.1$ normal star-forming galaxies require a $\\sim5\\times$ larger $\\alpha_{\\rm CO}$ than starburst galaxies to match their molecular gas fractions, but at $z > 1$ both star-forming types exhibit sub-Galactic $\\alpha_{\\rm CO}$ values and normal star-forming galaxies appear more gas-rich than starbursts. Future applications of this method include calibrating Tully-Fisher relations without inclination correction and inferring the evolution of the atomic gas fraction with HI observations.","url_abs":"https://arxiv.org/abs/1811.03107v3","url_pdf":"https://arxiv.org/pdf/1811.03107v3.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":"the-evolution-of-molecular-gas-fraction","repo_url":"https://github.com/fuhaiastro/py4astro","is_official":1,"mentioned_in_paper":1,"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}