X-ray analysis of the Planck-detected triplet-cluster system PLCK G334.8-38

¹ Université Paris-Saclay, CNRS, Institut d’astrophysique spatiale (IAS), 91405 Orsay, France
e-mail: alex@kolodzig.eu
² IRAP, Université de Toulouse, CNRS, CNES, UPS, Toulouse, France

Received: 25 February 2021
Accepted: 27 May 2021

Abstract

We conducted an X-ray analysis of one of the two Planck-detected triplet-cluster systems, PLCK G334.8-38.0, with a ∼100 ks deep XMM-Newton data. We find that the system has a redshift of z = 0.37 ± 0.01 but the precision of the X-ray spectroscopy for two members is too low to rule out a projected triplet system, demanding optical spectroscopy for further investigation. In projection, the system looks almost like an equilateral triangle with an edge length of ∼2.0 Mpc, but masses are very unevenly distributed (M₅₀₀ ∼ [2.5, 0.7, 0.3]×10¹⁴ M_⊙ from bright to faint). The brightest member appears to be a relaxed cool-core cluster and is more than twice as massive as both other members combined. The second brightest member appears to be a disturbed non-cool-core cluster and the third member was too faint to make any classification. None of the clusters have an overlapping R₅₀₀ region and no signs of cluster interaction were found; however, the XMM-Newton data alone are probably not sensitive enough to detect such signs, and a joint analysis of X-ray and the thermal Sunyaev-Zeldovich effect is needed for further investigation, which may also reveal the presence of the warm-hot intergalactic medium within the system. The comparison with the other Planck-detected triplet-cluster-system (PLCK G214.6+36.9) shows that they have rather different configurations, suggesting rather different merger scenarios, under the assumption that they are both not simply projected triplet systems.