2023/10/09 by J. van Marrewijk, L. Di Mascolo, A. S. Gill +18 · 1 voice
Physics and Astronomy · #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1051/0004-6361/202348213
arxiv published 2023/10/09 · arxiv updated 2024/06/19
How protoclusters evolved from sparse galaxy overdensities to mature galaxy clusters is still not well understood. In this context, detecting and characterizing the hot ICM at high redshifts (z~2) is key to understanding how the continuous accretion from and mergers along the filamentary large-scale structure impact the first phases of cluster formation. We study the dynamical state and morphology of the z=1.98 galaxy cluster XLSSC 122 with high-resolution observations (~5") of the ICM through the SZ effect. Via Bayesian forward modeling, we map the ICM on scales from the virial radius down to the core of the cluster. To constrain such a broad range of spatial scales, we employ a new technique that jointly forward-models parametric descriptions of the pressure distribution to interferometric ACA and ALMA observations and multi-band imaging data from the 6-m, single-dish Atacama Cosmology Telescope. We detect the SZ effect with 11σ in the ALMA+ACA observations and find a flattened inner pressure profile that is consistent with a non-cool core classification with a significance of >3σ. In contrast to the previous works, we find better agreement between the SZ effect signal and the X-ray emission as well as the cluster member distribution. Further, XLSSC 122 exhibits an excess of SZ flux in the south of the cluster where no X-ray emission is detected. By reconstructing the interferometric observations and modeling in the uv-plane, we obtain a tentative detection of an infalling group or filamentary-like structure that is believed to boost and heat up the ICM while the density of the gas is low. In addition, we provide an improved SZ mass of M500,c = 1.66+0.23-0.20 × 1014 \rm M_\odot. Altogether, the observations indicate that we see XLSSC 122 in a dynamic phase of cluster formation while a large reservoir of gas is already thermalized.