2020A&A...642L...3Z

We present an analysis of archival Chandra data of the merging galaxy cluster ClG 0217+70. The FeXXV Heα X-ray emission line is clearly visible in the 25 ks observation, allowing a precise determination of the redshift of the cluster as z=0.180±0.006. We measure kT₅₀₀=8.3±0.4keV and estimate M₅₀₀=(1.06±0.11)x10¹⁵M_☉ based on existing scaling relations. Correcting both the radio and X-ray luminosities with the revised redshift reported here, which is much larger than previously inferred based on sparse optical data, this object is no longer an X-ray underluminous outlier in the L_X-P_radio scaling relation. The new redshift also means that, in terms of physical scale, ClG 0217+70 hosts one of the largest radio halos and one of the largest radio relics known to date. Most of the relic candidates lie in projection beyond r₂₀₀. The X-ray morphological parameters suggest that the intracluster medium is still dynamically disturbed. Two X-ray surface brightness discontinuities are confirmed in the northern and southern parts of the cluster, with density jumps of 1.40±0.16 and 3.0±0.6, respectively. We also find a 700x200kpc X-ray faint channel in the western part of the cluster, which may correspond to compressed heated gas or increased non-thermal pressure due to turbulence or magnetic fields.