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Revealing a Head-on Major Merger in the Nearby NGC 6338 Group with Chandra and VLA Observations

2019; IOP Publishing; Volume: 870; Issue: 2 Linguagem: Inglês

10.3847/1538-4357/aaf234

1538-4357

Yu Wang, Fuyao Lui, Zhi-Qiang Shen, Jingying Wang, Dan Hu, Haiguang Xu,

Gamma-ray bursts and supernovae

By analyzing the Chandra archival data of the nearby NGC 6338 galaxy group, we identify two X-ray bright clumps (N-clump and S-clump) within the central 100 kpc, and detect an arc-like X-ray brightness discontinuity at the south boundary of the N-clump, which is defined as a cold front with a gas flow Mach number of M<0.8. Furthermore, at the north-east boundary of the S-clump (dominated by galaxy NGC 6338) another X-ray edge is detected that corresponds to a weaker cold front. Therefore, the two clumps are approaching each other approximately from opposite directions, and the group is undergoing a head-on collision that is in a stage of pre-core passage. This merger scenario is also supported by the study of the line-of-sight velocity distribution of the group member galaxies. The merger mass ratio is about 1:1.8 as estimated from the central gas temperature of the two clumps, which suggests the merger is most likely to be a major merger. We also analyze the VLA 1.4 and 4.9 GHz radio data, but we do not detect any extended radio emission that is associated with the merger.