Relaxation properties of lower-mass galaxy groups

Establish whether more complete samples of lower-mass galaxy groups exhibit stronger signs of dynamical relaxation than indicated by the current IllustrisTNG analysis.

Background

The paper finds that only 15–23% of the analysed systems are fully relaxed at z=0z=0, but the lowest-mass end is affected by limited simulation resolution and sample completeness. The authors therefore leave unresolved whether the observed relaxation fraction and the BHG-based indicators accurately describe less massive groups.

This question motivates targeted simulations and observations of lower-mass systems, including future group catalogues and surveys extending toward substantially smaller halo masses.

References

We speculate that when a more complete sample of the less massive end of galaxy systems is provided, these systems might also show stronger signs of relaxation.

Brightest group and cluster galaxies as indicators of relaxation  (2608.16481 - Kelder et al., 17 Aug 2026) in Section Discussion and conclusion