Poster Presentation

Group Therapy for Halos: Advancing Halo Mass Estimation for Galaxy Groups

Author(s): Wesley Van Kempen (Swinburne) Michelle Cluver (Swinburne; co-author) Edward Taylor (Swinburne; co-author) Daren Croton (Swinburne; co-author) Tystan Lambert (University of Western Australia; co-author)

Presenter: Wesley Van kempen (Swinburne University of Technology)

Accurate halo mass measurements across the full mass spectrum from groups to clusters are essential for understanding dark matter-baryon connections and establishing reliable scaling relations. We present two complementary methods for improving halo mass estimates across this spectrum, with utility for lower-mass systems that bridge isolated galaxies and rich clusters. Both methods are calibrated using SHARK v2.0 semi-analytical model and cross-validated with independent semi-analytical models SAGE and GAEA to assess systematic uncertainties. Our first approach establishes a stellar-to-halo mass relation optimized for galaxy groups, extending established cluster scaling relations into the low-mass regime where traditional X-ray and weak lensing techniques struggle. This method achieves higher precision with significantly reduced model-to-model variation compared to current observational techniques. Our second approach treats galaxies as dynamical tracers, leveraging velocity dispersion and maximum projected separation with a calibrated scale factor that adapts to measurement reliability. This technique performs well even in low-multiplicity systems where traditional estimates become unstable. Together, these methods enable more robust analyses of the group-cluster connection in large-scale structure and facilitate improved mass calibration across the full halo mass function. By extending reliable measurements to lower-mass halos than previously accessible, our work complements ongoing and upcoming surveys (4MOST/4HS, HSC, LSST, Euclid, DESI, PFS) that will dramatically increase samples of identified galaxy groups. Our calibrated scaling relations provide valuable tools for establishing consistent mass estimates across environments from groups to clusters, an essential for understanding the assembly history of cosmic structure.