Early onset of the hot circumgalactic medium around Milky Way galaxies
Abstract
Hot coronae are key regulators in Milky Way (MW)-type galaxy formation and are thought to emerge once a galaxy's dark matter halo crosses a critical mass threshold, Mvir∼1012 M⊙, so that accretion shocks can heat infalling gas to virial temperatures, Tvir. Here we investigate the roles of stellar feedback and accretion shocks in establishing the circumgalactic medium (CGM) around MW-mass galaxies using the VINTERGATAN cosmological simulation suite. We find that stellar feedback drives the early formation of a hot CGM, with TCGM∼ Tvir. By contrast, in feedback-free simulations, accretion shocks alone do not produce a CGM with comparably high average temperatures at early epochs (z>2), independent of gas metallicity. We show that CGM virialisation (defined when halo-gas cooling time exceeds the free-fall time) begins with the emergence of a hot corona (T>105 K) that can appear as early as z≈3 at virial radius, Rvir, when feedback is included. This is much earlier than predicted by accretion-shock theory or feedback-free models (z≲1). While accretion shocks alone produce an inside-out virialisation pattern, feedback can alter this behaviour, driving a rapid transition (≲0.5 Gyr) that is either outside-in or nearly simultaneous throughout the halo. Finally, these early-forming coronae are largely stable from formation through to the present day, but can appear to evolve simply because the definition of Rvir grows with time. This 'CGM pseudo-evolution' is analogous to the pseudo-evolution of dark matter haloes and should be taken into account when interpreting the evolution of hot coronae.
Related
- Constraints on the Hot Circumgalactic Medium Around Nearby L * Galaxies from the SRG/eROSITA All Sky Survey
- ALMA2040: The High-Redshift Circumgalactic Medium. Imaging the fueling and feedback of galaxies in the early universe
- The multiphase circumgalactic medium in the epoch of reionization: CII and CIV absorbers around [OIII] emitters
- Using the Circumgalactic Medium of Dwarf Galaxies as a Calorimetric Dark Matter Detector
- ALMA visits the QSO MUSEUM: Connecting molecular gas and the cool circumgalactic medium around 37 z∼3 quasars
BibTeX
@misc{rufopastor2026early,
title = {{Early onset of the hot circumgalactic medium around Milky Way galaxies}},
author = {Víctor Rufo-Pastor and Oscar Agertz and Santi Roca-Fábrega and Martin P. Rey and Joss Bland-Hawthorn and Justin I. Read and Thor Tepper-García and Corentin Cadiou and Anatole Storck},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.08931},
eprint = {2610.08931},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.08931},
}
RIS
TY - UNPB
TI - Early onset of the hot circumgalactic medium around Milky Way galaxies
AU - Víctor Rufo-Pastor
AU - Oscar Agertz
AU - Santi Roca-Fábrega
AU - Martin P. Rey
AU - Joss Bland-Hawthorn
AU - Justin I. Read
AU - Thor Tepper-García
AU - Corentin Cadiou
AU - Anatole Storck
PY - 2026
DA - 2026/10/06
PB - arXiv
DO - 10.48550/arxiv.2610.08931
UR - https://arxiv.org/abs/2610.08931
AB - Hot coronae are key regulators in Milky Way (MW)-type galaxy formation and are thought to emerge once a galaxy's dark matter halo crosses a critical mass threshold, M_vir∼10^12 M_⊙, so that accretion shocks can heat infalling gas to virial temperatures, T_vir. Here we investigate the roles of stellar feedback and accretion shocks in establishing the circumgalactic medium (CGM) around MW-mass galaxies using the VINTERGATAN cosmological simulation suite. We find that stellar feedback drives the early formation of a hot CGM, with T_CGM∼ T_vir. By contrast, in feedback-free simulations, accretion shocks alone do not produce a CGM with comparably high average temperatures at early epochs (z>2), independent of gas metallicity. We show that CGM virialisation (defined when halo-gas cooling time exceeds the free-fall time) begins with the emergence of a hot corona (T>10^5 K) that can appear as early as z≈3 at virial radius, R_vir, when feedback is included. This is much earlier than predicted by accretion-shock theory or feedback-free models (z≲1). While accretion shocks alone produce an inside-out virialisation pattern, feedback can alter this behaviour, driving a rapid transition (≲0.5 Gyr) that is either outside-in or nearly simultaneous throughout the halo. Finally, these early-forming coronae are largely stable from formation through to the present day, but can appear to evolve simply because the definition of R_vir grows with time. This 'CGM pseudo-evolution' is analogous to the pseudo-evolution of dark matter haloes and should be taken into account when interpreting the evolution of hot coronae.
ER -