Angular momentum evolution in the CIELO simulations. I. Temporal evolution of gas-stellar misalignments and baryonic merger timing

[2606.07160] Angular momentum evolution in the CIELO simulations. I. Temporal evolution of gas-stellar misalignments and baryonic merger timing Skip to main content Search Submit Donate Log in Astrophysics > Astrophysics of Galaxies arXiv:2606.07160 (astro-ph) [Submitted on 5 Jun 2026 ( v1 ), last revised 27 Aug 2026 (this version, v5)] Title: Angular momentum evolution in the CIELO simulations. I. Temporal evolution of gas-stellar misalignments and baryonic merger timing Authors: Catalina Casanueva-Villarreal , Patricia B. Tissera , Nelson Padilla , Lucas Bignone , Jenny Gonzalez-Jara , Brian Tapia-Contreras , Susana Pedrosa View PDF HTML (experimental) Abstract: Gas-stellar kinematic misalignments trace how galaxies assemble and reorient their angular momentum. Although well documented locally, their continuous evolution remains largely unexplored. We aim to characterise the pathways linking aligned, misaligned, and counter-rotating phases, assessing how gas accretion channels and mergers drive reorientation. We analysed 44 central galaxies from the CIELO simulations from z=3.5 to z=0. We defined kinematic episodes using the intrinsic angle, psi, between the star-forming (SF) gas and stellar angular momentum vectors, interpreting these histories by tracking accreted gas origins and evaluating paired statistical contrasts. Nearly 80% of the simulated galaxies are aligned at z=0, yet 86% experience at least one non-aligned episode. Although 19% of non-aligned episodes last >2 Gyr, their durations do not differ significantly from aligned episodes. Abrupt changes in psi coincide with intervals where accreted gas dominates the pre-existing SF reservoir and is highly tilted relative to pre-existing stars. During transitions, the median mass ratio of accreted to pre-existing SF gas rises from 0.57 to 2.14, and the median angular offset increases from 21.2 to 64.6 deg. While relevant mergers cluster near these boundaries, they can drive either alignment or misalignment regardless of mass ratios or orbits. Instead, mergers triggering abrupt transitions typically encounter hosts that are already partially decoupled. In the simulated sample, gas-stellar misalignment is fundamentally driven by reservoir competition. Mergers act as conditional triggers, but a galaxy's ultimate kinematic fate depends strictly on how newly accreted gas couples to, replaces, or mixes with the pre-existing material as it joins the central SF reservoir. Comments: Accepted for publication in Astronomy & Astrophysics (August 2026) Subjects: Astrophysics of Galaxies (astro-ph.GA) Cite as: arXiv:2606.07160 [astro-ph.GA] (or arXiv:2606.07160v5 [astro-ph.GA] for this version) https://doi.org/10.48550/arXiv.2606.07160 Focus to learn more arXiv-issued DOI via DataCite Submission history From: Catalina Casanueva [ view email ] [v1] Fri, 5 Jun 2026 11:19:52 UTC (969 KB) [v2] Mon, 8 Jun 2026 01:24:39 UTC (969 KB) [v3] Tue, 11 Aug 2026 16:34:32 UTC (993 KB) [v4] Wed, 26 Aug 2026 16:37:57 UTC (993 KB) [v5] Thu, 27 Aug 2026 01:34:44 UTC (993 KB) Full-text links: Access Paper: View PDF HTML (experimental) TeX Source view license Current browse context: astro-ph.GA < prev | next > new | recent | 2026-06 Change to browse by: astro-ph References & Citations 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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