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Astrophysical Journal, vol.1000, no.2, 2026 (SCI-Expanded, Scopus)
We present an X-ray analysis of the merging galaxy cluster system PSZ2 G279.79+39.09 (z = 0.29) using archival XMM-Newton and Chandra observations. The surface brightness image is bimodal, elongated east–west with a projected core separation of ∼1.35 Mpc. We measure gas temperatures of 5.36 keV for the eastern subcluster (PSZ-E) and 5.44 keV for the western component (PSZ-W). Assuming isothermal intracluster gas, the hydrostatic masses are log (M500/M⊙) = 14.76 for PSZ-E and 14.54 for PSZ-W, implying a mass ratio of ∼1:1.7. PSZ-E shows X-ray concentration indices of c40/c400 = 0.124 and c100/c500 = 0.278, together with a centroid shift of w = 0.016, indicating a disturbed halo that still hosts a compact cool core; PSZ-W is comparably disturbed even in its core. Both subclusters exhibit intracluster medium asymmetries consistent with ram-pressure stripping, and PSZ-W displays an X-ray tail extending nearly to PSZ-E’s outskirts. The orientation and length of this tail support an off-axis merger geometry. Thermodynamic maps reveal a hot (∼7.3 keV), high-pressure, high-entropy bridge between the cores. From the Rankine–Hugoniot temperature jump, we infer a Mach number M = 1.48 − 0.28+ 0.30, consistent with a weak merger shock propagating at 1695 − 300+ 316 [km s−1. These results indicate a merger with a nonzero impact parameter, likely observed near core passage (≲0.5 Gyr before or after), with the prepericenter scenario slightly preferred based on the projected separation and thermodynamic structure.