Heating, Conduction, and Minimum Temperatures in Cooling Flows

By Mateusz Ruszkowski, M. C. Begelman. 2002

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There is mounting observational evidence from Chandra for strong interaction between keV gas and active galactic nuclei (AGNs) in cooling flows. It is now widely accepted that the temperatures of cluster cores are maintained at a level of ~1 keV and that the mass deposition rates are lower than earlier ROSAT/Einstein values. Recent theoretical results suggest that thermal conduction can be very efficient even in magnetized plasmas. Motivated by these discoveries, we consider a "double heating model" that incorporates the effects of simultaneous heating by both the central AGN and thermal conduction from the hot outer layers of clusters. Using hydrodynamic simulations, we demonstrate that there exists a family of solutions that does not suffer from the cooling catastrophe. In these cases, clusters relax to a stable final state, which is characterized by minimum temperatures of order 1 keV and density and temperature profiles consistent with observations. Moreover, the accretion rates are much reduced, thereby reducing the need for the excessive mass deposition rates required by the standard cooling flow models.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/84009106a2541f484f9f7600403ef8b4f32f6322

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The many lives of active galactic nuclei: cooling flows, black holes and the luminosities and colour (2005, background): “A number of authors have suggested ways in which the radio source might replace the thermal energy lost to X-ray emission (Binney & Tabor 1995; Churazov et al. 2002; Brüggen & Kaiser 2002; Ruszkowski & Begelman 2002; Kaiser & Binney 2003; Omma et al. 2004).”
Cluster Heating by Viscous Dissipation of Sound Waves (2003, methodology): “…our results show that this heating mechanism is broadly consistent with the assumptions of the effervescent heating model (Begelman 2001; Ruszkowski & Begelman 2002), in which dissipation of waves plays an important role (Begelman 2003), and can be applied to recently reported…”
A unified model for AGN feedback in cosmological simulations of structure formation (2007, background): “There has been considerable effort from the theoretical point of view (e.g. Binney & Tabor, 1995; Churazov et al., 2001, 2002; Quilis et al., 2001; Ruszkowski & Begelman, 2002; Dalla Vecchia et al., 2004; Kawata & Gibson, 2005; Sijacki & Springel, 2006; Thacker et al., 2006; Okamoto et al., 2007)…”
Buoyancy Instabilities in Weakly Magnetized Low-Collisionality Plasmas (2007, result): “It may thus turn out that thermal conduction from large radii will prove to be less effective than previous authors have suspected (e.g., Bertschinger & Meiksin 1986; Ruszkowski & Begelman 2002; Zakamska & Narayan 2003) at heating “cooling flow” cores in clusters.”
A deep Chandra observation of the Perseus cluster: shocks and ripples (2003, background): “Begelman (2001) and Ruszkowski & Begelman (2002) assume that sound waves and small rising bubbles dissipate their energy on a pressure scalelength in their effervescent model for heating, but give no details of the mechanism.”
On the Nature of Feedback Heating in Cooling Flow Clusters (2004, methodology): “In a recent paper Höft & Brüggen (2004) use a similar heating prescription to that used by Ruszkowski & Begelman (2002) (see also Begelman 2004) to model the heating of a model taken to mimic the CF cluster A2052.”
Feedback heating by cosmic rays in clusters of galaxies (2007, background): “AGN activity is likely to be intermittent on a timescale of order the Salpeter time tS ∼ 10 7 yr, and possibly as short as ti ∼ 10 4 − 105 yr (Ruszkowski & Begelman (2002), hereafter RB02; Reynolds & Begelman (1997)), which is much shorter than the bubble rising time.”
A very deep Chandra observation of the Perseus cluster: shocks, ripples and conduction (2005, methodology): “As they remark, a double heating model with the AGN heating the inner regions and conduction the outer was proposed earlier by Ruszkowski & Begelman (2002).”
Evidence for powerful AGN winds at high redshift: dynamics of galactic outflows in radio galaxies during the “Quasar Era” (2008, background): “These were mainly proposed to overcome the cooling-flow problem (e.g., Binney & Tabor 1995; Ruszkowski & Begelman 2002; Kaiser & Binney 2003), but are also addressing the impact of the jets in individual radio galaxies (e.g., Mellema et al. 2002; Fragile et al. 2004; Saxton et al. 2005; Krause…”
CAUSE AND EFFECT OF FEEDBACK: MULTIPHASE GAS IN CLUSTER CORES HEATED BY AGN JETS (2011, background): “While the global energy balance may be achieved with the help of the AGN feedback and/or other mechanisms (Ruszkowski & Begelman 2002; Brighenti & Mathews 2003; Guo et al. 2008; Conroy & Ostriker 2008; Ruszkowski & Oh 2011), the issues regarding the coupling of the mechanical AGN energy to the…”
Hot Gas In and Around Elliptical Galaxies (2003, background): “Ruszkowski & Begelman (2002) describe a cluster flow model that is heated by conduction from the outside and the entire flow is instantaneously heated when gas flows into the central AGN.”
X-ray Spectroscopy of Cooling Clusters (2005, background): “Brighenti & Mathews (2003) (see also Ruszkowski & Begelman 2002) provide several 1D simulations of a cluster core in which various levels of heat are injected at various radii.”
How do galaxies get their gas (2002, background): “The leading hypothesis for explaining this conflict is that the central regions of the intracluster medium are heated by recurrent AGN activity, thermal conduction from the outer regions or both (e.g. Binney & Tabor 1995; Ciotti & Ostriker 2001; Narayan & Medvedev 2001; Ruszkowski & Begelman 2002).”
Heating Hot Atmospheres with Active Galactic Nuclei (2007, methodology): “Using this model, Ruszkowski & Begelman (2002) argued that cavity enthalpy needs to be supplemented by thermal conduction from the surrounding cluster in order to prevent cooling.”
Energy, momentum and mass outflows and feedback from thick accretion discs around rotating black holes (2013, background): “…BH angular velocity H and the BH magnetic flux BH. SMBH ‘feedback’ in galaxy clusters is believed to play an important role in keeping the cluster gas hot and preventing catastrophic star formation (Ciotti & Ostriker 2001; Brüggen & Kaiser 2002; Ruszkowski & Begelman 2002; Churazov et al. 2004).”
On the prevalence of radio‐loud active galactic nuclei in brightest cluster galaxies: implications for AGN heating of cooling flows (2006, unknown): “Such a double-heating model was first developed by Ruszkowski & Begelman (2002), and has been shown to provide good agreement with observed cluster properties (see also Brüggen 2003; Hoeft & Brüggen 2004; Fujita & Suzuki 2005; Roychowdhury, Ruszkowski & Nath 2005).”
AGN Feedback and Cooling Flows: Problems with Simple Hydrodynamic Models (2005, background): “This is modeled with the optically thin cooling law Λ = [C1(kBT ) α +C2(kBT ) β + C3]0.704 (ρ/mp) 2 ×10−22 ergs cm−3s−1, (7) which is the same law used by Ruszkowski & Begelman (2002) with the coefficients C1 = 8.6 × 10 −3, C2 = 5.8 × 10−2, C3 = 6.4 × 10 −2, α = −1.7, and β = 0.5 (Sutherland &…”
Hydrodynamical simulations of cluster formation with central AGN heating (2005, background): “…mesh codes, but which focused exclusively on highly idealized cluster models (e.g. Quilis, Bower & Balogh 2001; Churazov et al. 2001, 2002; Ruszkowski & Begelman 2002; Brüggen et al. 2002; Brüggen & Kaiser 2002; Brüggen 2003; Nulsen et al. 2003; Dalla Vecchia et al. 2004; Hoeft &…”