Filaments, Bubbles, and Weak Shocks in the Gaseous Atmosphere of M87

We present the first results from a 500 ks Chandra ACIS-I observation of M87. At soft energies (0.5-1.0 keV), we detect filamentary structures associated with the eastern and southwestern X-ray and radio arms. Many filaments are spatially resolved with widths of ~300 pc. This filamentary structure is particularly striking in the eastern arm, where we suggest the filaments are outer edges of a series of plasma-filled, buoyant bubbles whose ages differ by ~6 × 106 yr. These X-ray structures may be influenced by magnetic filamentation. At hard energies (3.5-7.5 keV), we detect a nearly circular ring of outer radius 2.8' (13 kpc), which provides an unambiguous signature of a weak shock, driven by an outburst from the supermassive black hole (SMBH). The density rise in the shock is ρshock/ρ0 ≈ 1.3 (Mach number, M ≈ 1.2). The observed spectral hardening in the ring corresponds to a temperature rise Tshock/T0 ≈ 1.2, or M ≈ 1.2, in agreement with the Mach number derived independently from the gas density. Thus, for the first time, we detect gas temperature and density jumps associated with a classical shock in the atmosphere around a SMBH. We also detect two additional surface brightness edges and pressure enhancements at radii of ~0.6' and ~1'. The ~0.6' feature may be overpressurized thermal gas surrounding the relativistic plasma in the radio cocoon, the "piston," produced by the current episode of AGN activity. The overpressurized gas is surrounded by a cool gas shell. The ~1' feature may be an additional weak shock from a secondary outburst. In an earlier episode, the piston was responsible for driving the 2.8' shock.