CHANDRA X-Ray Observations of A119: Cold Fronts and a Shock in an Evolved Off-axis Merger

Abstract

We present Chandra X-ray observations of the dynamically complex galaxy cluster A119 ( z = 0.044). A119 is host to two narrow-angle-tail (NAT) radio sources (0053-015 and 0053-016), whose tails are oriented parallel to each other, despite orthogonally oriented jet axes. Imaging and spectral analysis reveal X-ray emission elongated along the NE–SW axis, along with the presence of complex structures, including surface brightness discontinuities, which suggest possible merger activity along this axis. From radial profiles of the X-ray surface brightness, temperature, pressure, and density, we identify two surface brightness edges that are found to be cold fronts, possibly associated with large-scale sloshing of intracluster medium gas. We also identify a brightness edge to the S that is found to be a shock front with Mach number M = 1.21 ± 0.11, consistent with a merger shock. In addition, previous optical studies show the alignment of optical substructures along the N–S direction. The elongated X-ray emission, orientations of the NAT tails, and alignment of the optical substructure all suggest recent or ongoing merger activity in the NE–SW direction.

Keywords

• Galaxy clusters
• Intracluster medium