Study Revises Galaxy Gas Mass Estimates

• 20 Dec 2025

In December 2025, scientists from the Raman Research Institute revealed that commonly used methods to measure gas mass around galaxies may significantly overestimate it, potentially altering current theories of galaxy formation and evolution.

Key Points

• Core Finding: The research suggests that a substantial portion of highly ionised oxygen detected around galaxies may originate from the intergalactic medium rather than the circumgalactic medium, as widely assumed.
• Galaxy Gas Structure: Galaxies are surrounded by extended halos of gas and dark matter reaching 10–20 times their visible size, with the inner gaseous region termed the circumgalactic medium and the outer region forming the intergalactic medium.
• Importance of CGM: The circumgalactic medium plays a crucial role in regulating gas inflow and outflow, directly influencing star formation and long-term galaxy evolution.
• Measurement Limitation: Astronomers estimate CGM mass by detecting highly ionised oxygen along the line of sight, but this technique cannot easily separate contributions from the CGM and the intergalactic medium.
• Model-Based Analysis: Using theoretical models, researchers found that a significant fraction of the ionised oxygen attributed to the CGM may actually originate from the intergalactic medium.