Weak lensing mass calibration of the ACT DR5 galaxy clusters with the DES Year 3 weak lensing data

Shin, T., Baxter, E. J., Lee, E., Battaglia, N., Alarcon, A. and Harrison, I. ORCID: https://orcid.org/0000-0002-4437-0770 2026. Weak lensing mass calibration of the ACT DR5 galaxy clusters with the DES Year 3 weak lensing data. Journal of Cosmology and Astroparticle Physics 2026 (8) , 075. 10.1088/1475-7516/2026/08/075

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Abstract

We use weak gravitational lensing measurements from Year 3 Dark Energy Survey data to calibrate the masses of 443 galaxy clusters selected via the Sunyaev-Zel'dovich effect from Atacama Cosmology Telescope Data Release 5 maps of the cosmic microwave background. We incorporate redshift and SZ measurements for individual clusters into a hierarchical model for the stacked lensing signals and perform Bayesian analyses to constrain the hydrostatic mass bias of the clusters. Our treatment of systematic uncertainties includes a prescription for measuring and accounting for the weak lensing boost factor, consideration of a miscentering effect, as well as marginalization over uncertainties in the source galaxy photometric redshift distributions and shear calibration. The resultant constraints on the normalization of the mass-observable relation have a precision of approximately 7%, with the mean WL halo mass of M500c = 5.4 × 1014M⊙. We measure the bias between the true cluster mass and the mass estimated from the SZ signal based on an X-ray–calibrated scaling relation assuming hydrostatic equilibrium, to be 1 - b = 0.74+0.06-0.05 over the full sample. When splitting the clusters into high (z = 0.43–0.70) and low (z = 0.15–0.43) redshift bins, we measure 1 - b = 0.58+0.06-0.05 and 0.81+0.08-0.06, respectively. When introducing additional freedom in redshift and mass to the hydrostatic bias model, we find that 1 - b decreases with redshift (with the power law of -1.8+0.5-0.6, 99.95% confidence), consistent with findings from other recent studies, while we do not find any significant trend in mass. We also demonstrate that our result is robust against various systematics such as a scale cut, priors on baryonic and miscentering parameters, and degree of scatter in mass-observable relation. The weak-lensing mass calibration presented in this study will be a useful tool for using the ACT clusters as probes of astrophysics, and as a step towards using their abundance as a cosmological probe.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Physics and Astronomy Schools > Physical, Chemical & Environmental Sciences
Additional Information:	For full author list see article webpage https://doi.org/10.1088/1475-7516/2026/08/075
Publisher:	IOP Publishing
Date of First Compliant Deposit:	1 September 2026
Date of Acceptance:	5 July 2026
Last Modified:	01 Sep 2026 14:30
URI:	https://orca.cardiff.ac.uk/id/eprint/189326

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