The Circumgalactic & Intergalactic Medium

The gas that fuels and regulates galaxy growth

Most of a galaxy’s baryons lie outside its stellar disk, in the circumgalactic medium (CGM) — a multiphase reservoir that fuels star formation, absorbs the energy of galactic winds, and records the history of feedback. Understanding this gas is central to understanding galaxies themselves: the hot CGM can regulate star formation in the disk (Carr et al., 2023), and galaxies and their atmospheres coevolve as a single system (Pandya et al., 2023; Voit et al., 2024).

Because the CGM is intrinsically multiphase, much of our work zooms in on the small-scale physics that large simulations miss: the survival and growth of cool clouds embedded in hot winds (Abruzzo et al., 2022; Abruzzo et al., 2024), the structure of multiphase galactic outflows (Fielding & Bryan, 2022; Xu et al., 2026), and the turbulent radiative mixing layers that mediate between phases (Lancaster et al., 2026). Closer to home, we model the Milky Way’s own halo gas, including the all-sky disturbance raised by the infall of the Large Magellanic Cloud (Carr et al., 2025).

Beyond galaxy halos, gas pervades the cosmic web — the Lyman-α forest and the warm-hot intergalactic medium. The low-redshift forest turns out to be a surprisingly sharp probe of feedback: efficient, long-range AGN feedback leaves a measurable imprint on its statistics (Tillman et al., 2023; Tillman et al., 2023).

References

2026

  1. ApJ
    Resolving the Unresolved Galactic Winds in Multiphase Models. I. Methodology and Application
    Xinfeng Xu, Drummond Fielding, Timothy Heckman, and 12 more authors
    The Astrophysical Journal, Jun 2026
    DOI arXiv HTML
  2. arXiv
    Ceci n’est pas une Couche de Mélange: The Meaning of Resolved Turbulent Radiative Mixing
    Lachlan Lancaster, Rajsekhar Mohapatra, Drummond B. Fielding, and 1 more author
    arXiv e-prints, Jun 2026
    DOI arXiv HTML

2025

  1. ApJ
    The All-sky Impact of the LMC on the Milky Way Circumgalactic Medium
    Christopher Carr, Greg L. Bryan, Nicolás Garavito-Camargo, and 4 more authors
    The Astrophysical Journal, Apr 2025
    DOI arXiv HTML

2024

  1. ApJ
    Equilibrium States of Galactic Atmospheres. I. The Flip Side of Mass Loading
    G. Mark Voit, Viraj Pandya, Drummond B. Fielding, and 5 more authors
    The Astrophysical Journal, Dec 2024
    DOI arXiv HTML
  2. ApJ
    Taming the TuRMoiL: The Temperature Dependence of Turbulence in Cloud─Wind Interactions
    Matthew W. Abruzzo, Drummond B. Fielding, and Greg L. Bryan
    The Astrophysical Journal, May 2024
    DOI arXiv HTML

2023

  1. ApJ
    Regulation of Star Formation by a Hot Circumgalactic Medium
    Christopher Carr, Greg L. Bryan, Drummond B. Fielding, and 2 more authors
    The Astrophysical Journal, May 2023
    DOI arXiv HTML
  2. ApJ
    A Unified Model for the Coevolution of Galaxies and Their Circumgalactic Medium: The Relative Roles of Turbulence and Atomic Cooling Physics
    Viraj Pandya, Drummond B. Fielding, Greg L. Bryan, and 7 more authors
    The Astrophysical Journal, Oct 2023
    DOI arXiv HTML
  3. ApJ
    Efficient Long-range Active Galactic Nuclei (AGNs) Feedback Affects the Low-redshift Lyα Forest
    Megan Taylor Tillman, Blakesley Burkhart, Stephanie Tonnesen, and 5 more authors
    The Astrophysical Journal, Mar 2023
    DOI arXiv HTML
  4. AJ
    An Exploration of AGN and Stellar Feedback Effects in the Intergalactic Medium via the Low-redshift Lyα Forest
    Megan Taylor Tillman, Blakesley Burkhart, Stephanie Tonnesen, and 9 more authors
    The Astronomical Journal, Dec 2023
    DOI arXiv HTML

2022

  1. ApJ
    A Simple Model for Mixing and Cooling in Cloud-Wind Interactions
    Matthew W. Abruzzo, Greg L. Bryan, and Drummond B. Fielding
    The Astrophysical Journal, Feb 2022
    DOI arXiv HTML
  2. ApJ
    The Structure of Multiphase Galactic Winds
    Drummond B. Fielding and Greg L. Bryan
    The Astrophysical Journal, Jan 2022
    DOI arXiv HTML