The X-ray cavity around hotspot E in Cygnus A: a bubble inflated by the outgoing jet

The powerful Fanaroff-Riley class II (FRII) radio galaxy Cygnus A (Cyg A) has a compact primary hotspot and a brighter secondary hotspot in each lobe. We report the discovery, in a 2 Msec Chandra X-ray image of Cyg A, of a "hole" surrounding the primary hotspot, with a radius of ~3 kpc, in the X-ray emission from the eastern lobe. Fitting surface brightness profiles shows that the hole must be deeper along our line of sight than its projected width. The hole appears to be inflated by the expanding jet flowing out of the primary hotspot. Brightening on its rim is interpreted as X-ray synchrotron emission from a terminal shock. X-ray emission from the primary hotspot in the west is significantly brighter than in the east and there is no evident hole. These differences are likely due to Doppler beaming. We discuss some implications for the jets and hotspots of Cyg A. The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. AST-1659473, and by the Smithsonian Institution.