Circumgalactic Medium Properties and Galaxy Interactions
Summary
The circumgalactic medium (CGM) is the vast reservoir of diffuse gas that envelops galaxies out to their virial radii, linking the interstellar medium to the intergalactic medium. This multiphase environment comprises cool (T ≈ 10^4 K), warm (T ≈ 10^5 K) and hot (T > 10^6 K) components, enriched by metals ejected in galactic outflows and by inflowing streams of pristine intergalactic gas. Interactions between galaxies—through tidal encounters, minor mergers and group environments—reshape the CGM by triggering shock heating, mixing and turbulence, and by displacing gas clouds. Feedback from star formation and active galactic nuclei drives winds that seed the CGM with metals and momentum, while thermal instabilities and precipitation can cause hot gas to cool in situ, forming clumps that may rain back onto the galaxy. Together, these processes regulate galactic growth, star-formation rates and the cosmic baryon cycle, and they hold the key to resolving the “missing baryons” problem on galactic scales.
Research from Nature Portfolio
No recent Nature Portfolio content available.
Circumgalactic Medium Properties and Galaxy Interactions publication trend
The graph below shows the total number of articles in circumgalactic medium properties and galaxy interactions across all publications each year (not limited to Nature Index journals).
Technical terms
Circumgalactic Medium (CGM): The diffuse, multiphase gas surrounding a galaxy out to its virial radius, acting as an interface between the galaxy and the intergalactic medium.
Cold-mode accretion: Inflow of relatively cool (T ≲ 10^5 K), low-metallicity gas from the intergalactic medium directly onto a galaxy halo without shock heating to the virial temperature.
Thermal instability: A process in which hot, diffuse gas cools and condenses into denser, cooler clumps when cooling times become shorter than dynamical times.
Turbulence: Random, non-thermal gas motions spanning a cascade of spatial scales, contributing to mixing and energy dissipation in the CGM.
Covering fraction: The fraction of sightlines through a halo that intercept gas above a given column-density threshold for a specified ion or phase.
References
- The Cosmic Ultraviolet Baryon Survey: Empirical Characterization of Turbulence in the Cool Circumgalactic Medium. The Astrophysical Journal Letters (2023).
- The origin of cold gas in the circumgalactic medium. Astronomy & Astrophysics (2024).
- Zooming in on the circumgalactic medium with GIBLE: Resolving small-scale gas structure in cosmological simulations. Monthly Notices of the Royal Astronomical Society (2024).
About these summaries
This Nature Research Intelligence Topic summary is created with the cited references and a large language model. We take care to ground generated text with facts, and have systems in place to gain human feedback on the overall quality of the process in line with our AI principles. We strive to create accurate and useful summaries for people unfamiliar with the research topic and that supports this goal. These pages are a beta release and will be updated as we learn how best to help people gain value from a research topic summary.
Turn complex research questions into confident strategic decisions
When you're under pressure to set direction, justify investment, or understand your competitive position, you need more than raw data — you need trusted insights you can act on.
Benchmark your performance against global peers using robust, methodologically sound analysis.
Combine quantitative metrics with qualitative expert insight to uncover strengths, gaps and emerging opportunities.
Gain tailored, decision-ready recommendations aligned to your strategic priorities.
Talk to us to learn more about our data dashboards and bespoke strategy reports.
Grow research skills, confidence and careers with training built for every stage of the research lifecycle.
Developed with Nature Portfolio journal Editors and internationally renowned experts. Discover three ways to learn:
Self-paced, online courses in convenient bite-sized units, covering key skills across scientific writing, publishing, grant writing, data analysis, and more.
Expert trainer-led workshops with hands-on exercises and real-time feedback across core research skills, delivered via interactive group sessions.
Editor-led workshops combining core principles in writing and publishing, personalised 1:1 feedback from Nature Portfolio Editors and hands-on exercises.
Explore course catalogues and workshop agendas, enquire about the options or request institutional pricing.