Mapping the hot gas temperature in galaxy clusters using X-ray and Sunyaev-Zel'dovich imaging

Abstract

We propose a method to map the temperature distribution of the hot gas in galaxy clusters that uses resolved images of the thermal Sunyaev-Zel'dovich (tSZ) effect in combination with X-ray data. Application to images from the New IRAM KIDs Array (NIKA) and XMM-Newton allows us to measure and determine the spatial distribution of the gas temperature in the merging cluster MACS J0717.5+3745, at $z=0.55$. Despite the complexity of the target object, we find a good morphological agreement between the temperature maps derived from X-ray spectroscopy only -- using XMM-Newton ($T_{\mathrm{XMM}}$) and Chandra ($T_{\mathrm{CXO}}$) -- and the new gas-mass-weighted tSZ+X-ray imaging method ($T_{\mathrm{SZ}}$). We correlate the temperatures from tSZ+X-ray imaging and those from X-ray spectroscopy alone and find that $T_{\mathrm{SZ}}$ is higher than $T_{\mathrm{XMM}}$ and lower than $T_{\mathrm{CXO}}$ by $\sim 10\%$ in both cases. Our results are limited by uncertainties in the geometry of the cluster gas, contamination from kinetic SZ ($\sim 10\%$), and the absolute calibration of the tSZ map ($7\%$). Investigation using a larger sample of clusters would help minimise these effects.

Accepted in AA, 8 pages, 4 figures, 1 table

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• A wide field-of-view low-resolution spectrometer at APEX: instrument design and science forecast
• Cluster cosmology with the NIKA2 SZ Large Program
• Mapping the gas thermodynamic properties of the massive cluster merger MOO J1142$+$1527 at z = 1.2
• SZ contribution to characterize the shape of galaxy cluster haloes
• NIKA: a mm camera for Sunyaev-Zel'dovich science in clusters of galaxies