Letter to the Editor

First Sardinia Radio Telescope detection of the Sunyaev-Zel’dovich effect at 18.6 GHz

¹ Dipartimento di Fisica e Astronomia, Università di Bologna, Via P. Gobetti 93/2, 40129 Bologna, Italy
² INAF-Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047 Selargius, (CA), Italy
³ INAF, Istituto di Radio Astronomia, Via Gobetti 101, 40129 Bologna, Italy
⁴ Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, Vicolo dell’Osservatorio 3, I-35122 Padova, Italy

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 15 January 2026
Accepted: 21 February 2026

Abstract

Galaxy clusters imprint a distinctive signature on the cosmic microwave background through the thermal Sunyaev–Zel’dovich (SZ) effect, which enables to study the intracluster plasma distribution and makes them powerful cosmological probes. We present the first Sardinia Radio Telescope (SRT) detection of the SZ effect in the galaxy cluster MACS J1752+4440 at 18.6 GHz, with a resolution of 0.9′. We detected a decrement in brightness toward the cluster centre, which we attributed to the thermal SZ effect. We modelled the signal using a spherically symmetric β model for the electron density distribution and we employed a Bayesian retrieval to estimate the core radius, central electron density, and β parameter of the cluster. We found values consistent with expectations for a galaxy cluster of the mass of MACS J1752+4440: a core radius of (160 ± 30) kpc, a central electron density of (2.5^+0.7_−0.5 · 10⁻³) cm⁻³, and β = 0.6 ± 0.1. The mean Compton-y parameter within a radius of 3.5′ is (2.6 ± 0.3)⋅10⁻⁵, higher than the value reported by Planck, which is coherent considering the different resolution of the instruments and the modelling adopted. This work demonstrates the potential of the SRT to detect the onset of the SZ decrement at low frequencies, providing higher angular resolution than current all-sky surveys and enabling an improved reconstruction of the SZ decrement profile and the plasma distribution in the intracluster medium.