MACHACEK M.E., O'SULLIVAN E., RANDALL S.W., JONES C. and FORMAN W.R.
Abstract (from CDS):
We use Chandra X-ray observations of the hot gas in and around NGC 6868 and NGC 6861 in the Telescopium galaxy group (AS0851) to probe the interaction history between these galaxies. Mean surface brightness profiles for NGC 6868 and NGC 6861 are each well described by double β-models, suggesting that they are each the dominant galaxy in a galaxy subgroup about to merge. Surface brightness and temperature maps of the brightest group galaxy NGC 6868 show a cold front edge ∼23 kpc to the north, and a cool 0.62 keV spiral-shaped tail to the south. Analysis of the temperature and density across the cold front constrains the relative motion between NGC 6868 and the ambient group gas to be at most transonic; while the spiral morphology of the tail strongly suggests that the cold front edge and tail are the result of gas sloshing due to the subgroup merger. The cooler central region of NGC 6861 is surrounded by a sheath of hot gas to the east and hot, bifurcated tails of X-ray emission to the west and northwest. We discuss supersonic infall of the NGC 6861 subgroup, sloshing from the NGC 6868 and NGC 6861 subgroup merger, and AGN heating as possible explanations for these features, and discuss possible scenarios that may contribute to the order of magnitude discrepancy between the Margorrian and black hole mass-σ predictions for its central black hole.
galaxies: clusters: general - galaxies: individual (NGC 6868, NGC 6861) - intergalactic medium - X-rays: galaxies