AMICO galaxy clusters in KiDS-1000: Splashback radius from weak lensing and the cluster--galaxy correlation function

We present the splashback radius analysis of the Adaptive Matched Identifier of Clustered Objects (AMICO) galaxy cluster sample in the fourth data release of the Kilo Degree Survey (KiDS). The sample contains 9049 rich galaxy clusters within z∈0.1,0.8, with shear measurements available for 8730 of them. We measured and modelled the stacked reduced shear, g_̊m t, and the cluster--galaxy correlation function, w_̊m cg, in bins of observed intrinsic richness, łambda^*, and redshift, z. Building on the methods employed in recent cosmological analyses, we modelled the average splashback radius, r_̊m sp, of the underlying dark matter halo distribution, accounting for the known systematic uncertainties that affect measurements and theoretical models. By modelling g_̊m t and w_̊m cg separately in the cluster-centric radial range R∈0.4,5 h^-1Mpc, we constrain r_̊m sp, the mass accretion rate, Γ, and the relation between mathcal R _ ̊m sp ≡ r_ ̊m sp /r_ 200̊m m and the peak height, ν_200̊m m, over the mass range M_ 200̊m m ∈ 0.4,20 10^ 14 h^ -1 M_⊙. The two probes provide consistent results that also agree with Λ-cold dark matter model predictions. Our mathcal R _ ̊m sp constraints are consistent with those from previous observations. For g_̊m t and w_̊m cg, we achieve a precision of 14% and 10% per cluster stack, respectively. The higher precision of w_̊m cg, enabled by its combination with weak-lensing constraints on the mass-richness relation, highlights the complementarity of lensing and clustering in measuring r_̊m sp and constraining the properties of the infalling material region.