Resolving high-z galaxy cluster properties through joint X-ray and millimeter analysis: Case study of SPT-CLJ0615-5746

¹ Dipartimento di Fisica, Università di Roma ‘Tor Vergata’, Via della Ricerca Scientifica 1, 00133 Roma, Italy
² INFN, Sezione di Roma ‘Tor Vergata’, Via della Ricerca Scientifica, 1, 00133 Roma, Italy
e-mail: cmastromarino@roma2.infn.it
³ INFN-Padova, Via Marzolo 8, 35131 Padova, Italy

Received: 30 January 2024
Accepted: 15 April 2024

Abstract

We present a joint millimetric and X-ray analysis of hot gas properties in the distant galaxy cluster SPT-CLJ0615-5746 (z = 0.972). Combining Chandra observations with the South Pole Telescope (SPT) and Planck data, we performed radial measurements of thermodynamical quantities up to a characteristic radius of 1.2 R₅₀₀. We exploited the high angular resolution of Chandra and SPT to map the innermost region of the cluster and the high sensitivity to the larger angular scales of Planck to constrain the outskirts and improve the estimation of the cosmic microwave background and the galactic thermal dust emissions. In addition to maximizing the accuracy of radial temperature measurements, our joint analysis allows us to test the consistency between X-ray and millimetric derivations of thermodynamic quantities via the introduction of a normalization parameter (η_T) between X-ray and millimetric temperature profiles. This approach reveals a substantial high value of the normalization parameter, η_T = 1.45_−0.18^+0.17, suggesting that the gas halo is aspherical. Assuming hot gas hydrostatic equilibrium within complementary angular sectors that intercept the major and minor elongation of the X-ray image, we infer a halo mass profile that results from an effective compensation of azimuthal variations of gas densities by variations in the η_T parameter. Consistent with earlier integrated X-ray and millimetric measurements, we infer a cluster mass of M₅₀₀^HE = 10.67_−0.50^+0.62 10¹⁴ M_⊙.