HI Mapping of Abell 2029 with MeerKAT

Abell 2029 (z ≈ 0.078) is one of the most massive relaxed galaxy clusters in the local universe, and our optical spectroscopy of its members is nearly complete out to 3R₂₀₀. The cold gas is the missing piece. This project supports a MeerKAT HI (21 cm) survey proposal for the cluster, submitted in 2026 (PI: Jubee Sohn; I am a Co-I) and under review, by predicting from the existing optical and UV data how much neutral hydrogen the members hold and whether a survey can detect it.

My part: the technical justification

I built the feasibility case from the member catalog to the expected detections.

• I measured the spectroscopic completeness of the member catalog as a function of magnitude and radius, defined membership with the caustic technique, and derived the stellar mass and velocity dispersion functions, so that the predicted detections refer to a well-defined parent sample.
• I estimated HI masses and gas fractions for each galaxy from published optical and UV scaling relations, using NUV−r colour (xGASS; Catinella et al. 2018) where GALEX photometry exists and stellar mass and g−r colour (FASHI; Shulan et al. 2025) elsewhere. The stellar masses come from my own SED fits.
• I matched the members against the RACS-low and RACS-mid continuum catalogs to flag continuum-bright galaxies and AGN before trusting any line prediction.
• I compared the predicted HI mass function with the detection limit for candidate integration times; this comparison sets the time request.