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arXiv · 2609.21861

A two-component profile of baryonic feedback: hydrostatic and diffuse gas

Kaitlyn Shavelle·Jared Siegel·Leah Bigwood·Alexandra Amon·Romain Teyssier
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Abstract

Baryonic feedback processes redistribute gas within and beyond dark matter halos, however, the resulting gas distribution remains highly uncertain, limiting predictions of the matter distribution for precision cosmology. We introduce a physically motivated approach to modelling the gas distribution that decomposes it into an approximately hydrostatic inner component and a diffuse outer component. This approach takes advantage of the growing observational landscape: X-ray measurements primarily probe the dense inner halo, while the kinetic Sunyaev-Zel'dovich (kSZ) effect is sensitive to diffuse ionized gas extending to larger radii. We implement this two-component profile within the baryonification framework, though we note that it is applicable to any model of the large-scale gas distribution. We jointly fit X-ray gas-fraction measurements from the HSC-XXL and eROSITA samples with stacked kSZ effect measurements of BOSS CMASS galaxies from the Atacama Cosmology Telescope, demonstrating that the proposed profile retains sufficient flexibility. This proof-of-concept shows that a decomposition between hydrostatic and diffuse gas provides a simple, physically interpretable framework for connecting complementary observations of the gas distribution, and a foundation for future models of baryonic feedback.

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Kaitlyn Shavelle, Jared Siegel, Leah Bigwood, Alexandra Amon, Romain Teyssier. 2026-09-18. A two-component profile of baryonic feedback: hydrostatic and diffuse gas. https://arxiv.org/abs/2609.21861

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