Why is there cold gas inside the Local Bubble?

[2608.27603] Why is there cold gas inside the Local Bubble? Skip to main content Search Submit Donate Log in Astrophysics > Astrophysics of Galaxies arXiv:2608.27603 (astro-ph) [Submitted on 27 Aug 2026] Title: Why is there cold gas inside the Local Bubble? Authors: Tim-Eric Rathjen , Jeffrey L. Linsky View PDF HTML (experimental) Abstract: The Local Bubble (LB) extends approximately 100--200~pc from the Sun and contains $10^6$~K plasma and warm photoionised gas. Yet the Local Leo Cold Cloud (LLCC) and the Local Ribbon of Cold Clouds lie only 11--24~pc away, well inside the LB, at temperatures near 20~K. How such cold material forms and survives in this hotter environment remains uncertain, and explanations based on colliding warm clouds are difficult to test observationally. We investigate whether LLCC-like gas can assemble locally in a feedback-driven environment or must be imported as pre-existing cold material, and whether it can survive for several Myr. We use magnetohydrodynamic simulations from the \textsc{SILCC} Project including self-consistent star formation, stellar winds and supernovae, ionising and far-ultraviolet radiation, non-equilibrium chemistry, and cosmic-ray transport. We identify cold diffuse gas with $T<100$~K and $0<n_\mathrm{H_2}\leq2$~cm$^{-3}$ and use Lagrangian tracers to reconstruct its assembly, cooling, survival, and dispersal. The simulations produce cold diffuse gas in warm--hot, feedback-driven surroundings, where non-thermal pressure support is crucial. Cosmic-ray pressure remains nearly continuous across cold-gas interfaces and establishes a pressure floor, while magnetic pressure partly offsets the external thermal-pressure excess. The structures persist in the cold diffuse phase for a median of 2.5~Myr, and most of their material remains cold after they lose spatial coherence. The gas can assemble locally from nearby cold and thermally unstable warm material, developing filamentary or sheet-like morphologies. Cooling to $\sim20$~K is driven not by adiabatic expansion but by non-adiabatic cooling. The LLCC therefore need not have entered the LB as an already-formed cold cloud. LLCC-like gas can instead assemble and cool non-adiabatically in situ. Comments: 14 pages, 11 figures, submitted to A&A, comments welcome Subjects: Astrophysics of Galaxies (astro-ph.GA) Cite as: arXiv:2608.27603 [astro-ph.GA] (or arXiv:2608.27603v1 [astro-ph.GA] for this version) https://doi.org/10.48550/arXiv.2608.27603 Focus to learn more arXiv-issued DOI via DataCite Submission history From: Tim-Eric Rathjen [ view email ] [v1] Thu, 27 Aug 2026 18:36:12 UTC (2,271 KB) Full-text links: Access Paper: View PDF HTML (experimental) TeX Source view license Current browse context: astro-ph.GA < prev | next > new | recent | 2026-08 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. Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them. Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs . Which authors of this paper are endorsers? | Disable MathJax ( What is MathJax? ) We gratefully acknowledge support from our major funders , member institutions , and all contributors. About · Help · Contact · Subscribe · Copyright · Privacy · Accessibility · Operational Status (opens in new tab) Major funding support from (opens in new tab) (opens in new tab) (opens in new tab)

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