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

Abstract

We present the first results from a 500 ks Chandra ACIS-I observation of M87. At soft energies (0.5Y1.0 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 ; 10 6 yr. These X-ray structures may be influenced by magnetic filamentation. At hard energies (3.5Y7.5 keV), we detect a nearly circular ring of outer radius 2.8 0 (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 shock / 0 % 1:3 (Mach number, M % 1:2). The observed spectral hardening in the ring corresponds to a temperature rise T shock /T 0 % 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 0 and $1 0 . The $0.6 0 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 0 feature may be an additional weak shock from a secondary outburst. In an earlier episode, the piston was responsible for driving the 2.8 0 shock.

The nature and energetics of AGN-driven perturbations in the hot gas in the Perseus Cluster

“…Their approach yields a significantly larger fraction of energy in the shock, suggesting that shock/sound waves dominate transport of energy to the ICM. Our results instead provide support to the bubble-mediated AGN feedback model (Churazov et al 2000;McNamara et al 2000;Nulsen et al 2007;Forman et al 2007;Fabian 2012;Bîrzan et al 2012;Hlavacek-Larrondo et al 2012). Namely, most of the energy is first stored as the enthalpy of the bubbles.…”

“…Interacting with intracluster gas, these jets inflate bubbles of relativistic plasma, which expel the hot gas, producing cavities in the zhur@stanford.edu X-ray images of clusters (e.g., Boehringer et al 1993;Churazov et al 2000;McNamara et al 2000;Fabian 2012;Bîrzan et al 2012;Hlavacek-Larrondo et al 2012). The initial rapid expansion of the bubbles may drive shocks that propagate through intracluster medium (ICM) and heat the gas (e.g., Fabian et al 2003;Forman et al 2007; Randall et al 2015;Reynolds, Balbus, & Schekochihin 2015). With time, rapid expansion decelerates and the bubbles continue to grow subsonically until they start rising buoyantly in the cluster atmosphere, uplifting cool gas, exciting gravity waves, and driving turbulence (Churazov et al 2002;Omma et al 2004;.…”

“…In contrast, in a hard band (e.g., 4 − 8 keV), the emissivity is temperature-dependent (e.g., Forman et al 2007;Zhuravleva et al 2015). Therefore, each type of perturbation mentioned above will appear differently in the soft-and hard-band X-ray images.…”

The jet feedback mechanism (JFM) in stars, galaxies and clusters

“…Over the years the AGN feedback mechanism, mostly by jet-inflated bubbles, has been solidified (e.g., Dong et al 2010;O'Sullivan et al 2011;Farage et al 2012;Gaspari et al 2012a,b;Birzan et al 2011;Gitti et al 2012;Pfrommer 2013). Key to the establishment of the AGN-JFM in cooling flows are the many observations of X-ray deficient bubbles (e.g., Boehringer et al 1993;Fabian et al 2000;McNamara et al 2001;Heinz et al 2002;Forman et al 2007;Wise et al 2007;Baldi et al 2009;David et al 2009;Gastaldello et al 2009;Gitti et al 2010;Blanton et al 2011;David et al 2011;Machacek et al 2011;Randall et al 2011;Doria et al 2012;Pandge et al 2012;Hlavacek-Larrondo et al 2015). Many of these X-ray bipolar structures resemble visible bipolar structures observed in bipolar PNe (see Figs.…”

“…I here concentrate on results from the last five years. Randall et al (2011) and Randall et al (2015) argue, based on their X-ray observations and analysis of the galaxy group NGC 5813, that shocks excited by periodic jets activity heat the ICM (for early studies of shocks in the Virgo cluster see Forman et al 2005 andForman et al 2007). This heating mechanism is put into question by Soker et al (2016).…”