Fast modelling of ionization balance in the intergalactic medium: I- implications for the IGM metallicity

[2604.14676] Fast modelling of ionization balance in the intergalactic medium: I- implications for the IGM metallicity Skip to main content Search Submit Donate Log in Astrophysics > Cosmology and Nongalactic Astrophysics arXiv:2604.14676 (astro-ph) [Submitted on 16 Apr 2026 ( v1 ), last revised 28 Aug 2026 (this version, v2)] Title: Fast modelling of ionization balance in the intergalactic medium: I- implications for the IGM metallicity Authors: Bhaskar Arya , Kartick C. Sarkar , Shiv K. Sethi View PDF HTML (experimental) Abstract: Ionization balance in the intergalactic medium (IGM) is central to the interpretation of quasar absorption spectra, linking observed ionic columns to the underlying gas density, temperature, metallicity, and ionizing radiation field. Because ionization, recombination, and cooling timescales can be comparable to the timescales over which the ultraviolet background (UVB) and gas thermodynamic state evolve, ion populations may retain a strong memory of their past history. To this end, we present a fast, metals-inclusive, zero-dimensional framework for modeling the redshift evolution of the IGM. The model follows the coupled thermal and ionization evolution of a Lagrangian gas parcel in a redshift-dependent UVB, solving stiff, time-dependent rate equations for H, He, and 107 metal ions while self-consistently evolving the temperature through photoheating and standard cooling processes. We validate the framework against full three-dimensional hydrodynamical non-equilibrium calculations and find that it reproduces the thermal and ionization histories of the IGM with good accuracy over a wide redshift range, including the heating associated with $\rm He_{\,\rm II}$ reionization. As an application, we predict the cosmic $\rm C_{\,\rm IV}$ density parameter, $\Omega_{\rm CIV}$, and use it to infer the origin of metal ions in the IGM and the corresponding metallicities from observational measurements, obtaining values broadly consistent with literature constraints. The framework is well suited for rapid parameter studies of how reionization timing, UVB spectral hardness, self-shielding, and UVB inhomogeneity shape the thermal and ionization history of the IGM and the resulting metal-line observables. Comments: 17 pages, 13 figures, accepted for publication in MNRAS. Corrected an error in the calculation of PIE ion fractions and revised its discussions. The main conclusions are unchanged Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO) Cite as: arXiv:2604.14676 [astro-ph.CO] (or arXiv:2604.14676v2 [astro-ph.CO] for this version) https://doi.org/10.48550/arXiv.2604.14676 Focus to learn more arXiv-issued DOI via DataCite Journal reference: Mon Not R Astron Soc (2026) Related DOI : https://doi.org/10.1093/mnras/stag1636 Focus to learn more DOI(s) linking to related resources Submission history From: Bhaskar Arya [ view email ] [v1] Thu, 16 Apr 2026 06:32:42 UTC (1,951 KB) [v2] Fri, 28 Aug 2026 05:56:15 UTC (2,222 KB) Full-text links: Access Paper: View PDF HTML (experimental) TeX Source view license Current browse context: astro-ph.CO < prev | next > new | recent | 2026-04 Change to browse by: astro-ph References & Citations INSPIRE HEP SciX Google Scholar Semantic Scholar export BibTeX citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer ( What is the Explorer? ) Connected Papers Toggle Connected Papers ( What is Connected Papers? ) Litmaps Toggle Litmaps ( What is Litmaps? ) scite.ai Toggle scite Smart Citations ( What are Smart Citations? ) Code, Data, Media Code, Data and Media Associated with this Article alphaXiv Toggle alphaXiv ( What is alphaXiv? ) Links to Code Toggle CatalyzeX Code Finder for Papers ( What is CatalyzeX? ) DagsHub Toggle DagsHub ( What is DagsHub? ) GotitPub Toggle Gotit.pub ( What is GotitPub? ) Huggingface Toggle Hugging Face ( What is Huggingface? ) ScienceCast Toggle ScienceCast ( What is ScienceCast? ) Demos Demos Replicate Toggle Replicate ( What is Replicate? ) Spaces Toggle Hugging Face Spaces ( What is Spaces? ) Spaces Toggle TXYZ.AI ( What is TXYZ.AI? ) Related Papers Recommenders and Search Tools Link to Influence Flower Influence Flower ( What are Influence Flowers? ) Core recommender toggle CORE Recommender ( What is CORE? ) IArxiv recommender toggle IArxiv Recommender ( What is IArxiv? ) Author Venue Institution Topic About arXivLabs arXivLabs: experimental projects with community collaborators arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website. 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