CHEX-MATE: Relationship between X-ray and millimetre inferences of galaxy cluster temperature profiles

TL;DR

This work tackles potential mismatches between X-ray and Sunyaev–Zel'dovich inferences of galaxy cluster temperature profiles by performing a joint XMM- Newton and Planck analysis on 116 CHEX-MATE clusters. The authors model cluster density, temperature, and pressure profiles, incorporating relativistic corrections to the SZ signal and absorption from Galactic molecular hydrogen, to estimate the temperature-mismatch parameter η_T = T_X / T_{SZ,X}. They find ⟨η_T⟩ ≈ 1.01 ± 0.03 with a positively skewed distribution whose scatter correlates with cluster morphology; relativistic SZ corrections reduce residuals by ~18% and increase SZ pressure by ~8%, inducing an average η_T shift of ~-8% that depends on the cluster temperature (3–13 keV). There is little evidence for strong correlations with redshift, mass, or temperature, while morphology primarily governs the size of the dispersion. These results provide a robust cross-calibration between X-ray and SZ thermodynamics, with implications for cosmological constraints from cluster samples and a path forward using higher-resolution SZ data and simulations.

Abstract

Thermodynamic profiles from X-ray and millimetre observations of galaxy clusters are often compared under the simplifying assumptions of smooth, spherically symmetric intracluster medium. These approximations lead to expected discrepancies in the inferred profiles, which can provide insights about the cluster structure or cosmology. Motivated by this, we present a joint XMM-\textit{Newton} and \textit{Planck} analysis of 116 CHEX-MATE clusters to measure $η_T = T_X/T_{SZ,X}$, the ratio between spectroscopic X-ray temperatures and a temperature proxy derived from Sunyaev-Zel'dovich (SZ) pressures and X-ray densities. We considered relativistic corrections to the thermal SZ signal and implemented X-ray absorption by Galactic molecular hydrogen. The $η_T$ distribution has a mean of $1.01 \pm 0.03$, with average changes of $8.1\%$ and $2.7\%$ when relativistic corrections and molecular hydrogen absorption are not included, respectively. The $η_T$ distribution is positively skewed, with the scatter mostly affected by cluster morphology: relaxed clusters are closer to unity and less scattered than mixed and disturbed systems. We find little or no correlation with redshift, mass, or temperature.

Figures (13)

• Figure 1: Mass and redshift distribution of the CHEX-MATE sample (grey). Tier-1 and Tier-2 clusters are shown as red circles and blue triangles, respectively, while common clusters as green squares. Excluded clusters from the analysis are shown with red crosses.
• Figure 1: Continued.
• Figure 2: Stacked mean radial profiles in the Planck HFI channels towards 112 CHEX-MATE clusters. Black crosses with error bars show the observed mean SZ signal and its standard uncertainty. The CMB and GTD mean models are shown as solid green and red lines, respectively. The red dash-dotted line marks the dust component after the CTD correction. Solid and dashed blue lines represent the mean rSZ and cSZ models. Shaded areas cover the $16$th–$84$th percentiles intervals. The normalised mean covariance matrices of the observed radial profiles (within $5R_{500}$), at each frequency, are shown as inserts.
• Figure 3: Fractional differences in the pressure profile parameters (from left to right: $P_0$, $\alpha$, $\beta$) between the rSZ and cSZ models. Median (red dashed) and mean (black dot-dashed) are shown with vertical lines and in the legends with $16$th–$84$th percentiles from the reference values.
• Figure 4: Median fractional change in the pressure profiles between rSZ and cSZ models. The median at $0.1R_{500}$ is shown as a visual reference with the red dot-dashed line, while the blue interval encompasses the $16$th–$84$th percentile range.