Building a Cluster: Group-Group Merger NGC 6338 - poster for 20 years of Chandra meeting 2019

We present deep Chandra, XMM-Newton, GMRT and Halpha observations of the high-velocity group-group merger NGC 6338. X-ray imaging and spectral mapping show that as well as trailing tails of cool, enriched gas, the two cores are embedded in a ~250 kpc-wide region of shock heated gas with temperatures rising to ~5 keV. The merger is occurring primarily along the line of sight, with a velocity difference of ~1400 km/s between the dominant ellipticals. We estimate that the collision has produced shocks of Mach 2.3-3.1, making this one of the most violent mergers yet observed between groups. We show that both group cores host potential AGN cavities and Halpha nebulae, indicating rapid cooling. In the southern core around NGC 6338 we observe co-spatial X-ray and Halpha filaments, whose X-ray components have very low entropies (<10 keV cm^2) and short cooling times (200-300 Myr). The northern core is crossed by a bar of dense, cool X-ray gas with an Halpha cloud at one end, offset from the dominant galaxy, suggesting that ram-pressure has disrupted the connection between IGM cooling and the central AGN. Despite the disturbance caused by the merger, we find reasonable agreement between hydrostatic and Sunyaev-Zel'dovich mass estimates. Both show the combined system mass to be of order 10^14 Msol, implying that the result of this group-group merger will be a galaxy cluster

(To be presented at the 20 years of Chandra Symposium in Boston, MA, 3-6 December 2019)

Further details are presented in O'Sullivan et al. (2019) MNRAS 488, 2925