CAUSE AND EFFECT OF FEEDBACK: MULTIPHASE GAS IN CLUSTER CORES HEATED BY AGN JETS

By M. Gaspari, M. Ruszkowski, Pawan Sharma. 2011

230 citations recorded by the source corpus.

Multiwavelength data indicate that the X-ray-emitting plasma in the cores of galaxy clusters is not cooling catastrophically. To a large extent, cooling is offset by heating due to active galactic nuclei (AGNs) via jets. The cool-core clusters, with cooler/denser plasmas, show multiphase gas and signs of some cooling in their cores. These observations suggest that the cool core is locally thermally unstable while maintaining global thermal equilibrium. Using high-resolution, three-dimensional simulations we study the formation of multiphase gas in cluster cores heated by collimated bipolar AGN jets. Our key conclusion is that spatially extended multiphase filaments form only when the instantaneous ratio of the thermal instability and free-fall timescales (tTI/tff) falls below a critical threshold of ≈10. When this happens, dense cold gas decouples from the hot intracluster medium (ICM) phase and generates inhomogeneous and spatially extended Hα filaments. These cold gas clumps and filaments “rain” down onto the central regions of the core, forming a cold rotating torus and in part feeding the supermassive black hole. Consequently, the self-regulated feedback enhances AGN heating and the core returns to a higher entropy level with tTI/tff > 10. Eventually, the core reaches quasi-stable global thermal equilibrium, and cold filaments condense out of the hot ICM whenever tTI/tff ≲ 10. This occurs despite the fact that the energy from AGN jets is supplied to the core in a highly anisotropic fashion. The effective spatial redistribution of heat is enabled in part by the turbulent motions in the wake of freely falling cold filaments. Increased AGN activity can locally reverse the cold gas flow, launching cold filamentary gas away from the cluster center. Our criterion for the condensation of spatially extended cold gas is in agreement with observations and previous idealized simulations.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2d81cd85ac7f19dbeda2ffc5e68ad3c067767986

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In Astronomy and Astrophysics

1. J. Silk
2. M. Gaspari
3. Alexander Y. Wagner
4. G. Bicknell
5. P. Temi
6. S. Oh
7. F. Brighenti
8. D. Mukherjee

In Instrumentation

1. G. Bicknell
2. Alexander Y. Wagner
3. P. Temi
4. M. Gaspari
5. Masayuki Umemura
6. F. Brighenti
7. J. Silk
8. S. Oh

Citations in the corpus

• Raining on black holes and massive galaxies: the top-down multiphase condensation model (2016, methodology): “Below tcool(r)/tff(r) 10, TI may grow non-linear (Gaspari et al. 2012b; McCourt et al. 2012; Sharma et al. 2012; for classic TI studies see Field 1965; Krolik & London 1983; Nulsen 1986; Balbus & Soker 1989; Pizzolato & Soker 2005), albeit such radial threshold appears crude in real perturbed…”
• Chaotic cold accretion on to black holes (2013, methodology): “…(elaborated in more detail in the following sections) provides a basis for the subgrid modelling based on cold feedback, which has been previously shown to be extremely efficient in selfregulating the thermodynamical evolution of galaxies, groups and clusters (Gaspari et al. 2012c; Section 9).”
• Mechanical AGN feedback: controlling the thermodynamical evolution of elliptical galaxies (2012, methodology): “Lowering Tc permits one to follow the formation of local thermal instabilities better; nevertheless, the global evolution of the cold gas and associated feedback is essentially the same on long time-scales (see Gaspari et al. 2012).”
• A Global Model for Circumgalactic and Cluster-core Precipitation (2016, background): “Shortly thereafter, Gaspari and collaborators produced sets of numerical simulations in which such a cold feedback loop was realized (Gaspari et al. 2012, 2013, 2015, but see also Sharma et al. 2012b).”
• DRIVING OUTFLOWS WITH RELATIVISTIC JETS AND THE DEPENDENCE OF ACTIVE GALACTIC NUCLEUS FEEDBACK EFFICIENCY ON INTERSTELLAR MEDIUM INHOMOGENEITY (2012, methodology): “…include the Hydra A (Wise et al. 2007), Perseus A (Fabian et al. 2006), and M87 in the Virgo Cluster (Million et al. 2010), and the phenomenon is well reproduced in cluster-scale grid-based hydrodynamic simulations by Gaspari et al. (2012), Dubois et al. (2010, 2011), and Teyssier et al. (2011).”
• The impact of star formation feedback on the circumgalactic medium (2016, unknown): “In the simulations of thermal instability triggered feedback in more massive haloes the feedback models have relatively high energy per unit mass or are purely thermal (e.g., Sharma et al. 2012a; Gaspari et al. 2012; Li et al. 2015).”
• Relativistic jet feedback – III. Feedback on gas discs (2018, background): “The role of jets from from supermassive black holes has largely been considered in the context of maintenance mode feedback (Gaspari et al. 2012b,a; Yang & Reynolds 2016).”