Resolving high-z Galaxy Cluster properties through joint X-ray and Millimeter analysis: a case study of SPT-CLJ0615-5746

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 perform radial measurements of thermodynamical quantities up to a characteristic radius of $1.2\, R_{500}$. We exploit 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. Besides 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 ($\eta_T$) between X-ray and millimetric temperature profiles. This approach reveals a substantial high value of the normalization parameter, $\eta_T=1.46^{+0.15}_{-0.22}$, 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 of the $\eta_T$ parameter. Consistent with earlier integrated X-ray and millimetric measurements, we infer a cluster mass of $M^{\text{HE}}_{500} = 10.67^{+0.62}_{-0.50}\,\, 10^{14}\,M_{\odot}$.