Thermal Conduction in Clusters of Galaxies

By Ramesh Narayan, M. Medvedev. 2001

372 citations recorded by the source corpus.

We estimate the thermal conductivity of a weakly collisional magnetized plasma with chaotic magnetic field fluctuations. When the fluctuation spectrum extends over two or more decades in wavevector, we find that thermal conduction is very efficient; the conduction coefficient is only a factor of ~5 below the classical Spitzer estimate. We suggest that conduction could play a significant role in cooling flows in clusters of galaxies.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/c380e7d0e5b97dc4609df1cb82e206f49f9037a7

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Models of Galaxy Clusters with Thermal Conduction (2002, background): “…active galactic nucleus (AGN; Pedlar et al. 1990; Tabor & Binney 1993; Churazov et al. 2000, 2002; Ciotti & Ostriker 2001; Brüggen & Kaiser 2002) and (2) thermal energy from outer regions of the cluster transported to the central cooling gas by conduction (Narayan & Medvedev 2001, hereafter NM01).”
Thermal conduction and reduced cooling flows in galaxy clusters (2003, background): “Churazov (2001) estimated the suppression factor to be ∼ 0.01, whereas Narayan & Medvedev (2001) argue that it could be as high as 0.3.”
Hydrodynamical simulations of cluster formation with central AGN heating (2005, background): “Thermal conduction may in principle offset central cooling losses by inducing a heat current from outer, hotter regions of clusters (e.g. Narayan & Medvedev 2001), provided the conductivity is not strongly suppressed by tangled magnetic fields.”
Heating cooling flows with jets (2003, background): “These included strong internal absorption (Allen & Fabian 1997), magnetic locking of overdense regions (Tribble 1989; Balbus 1991), abundance anomalies (Fabian et al. 2001; Morris & Fabian 2003), and conduction of heat from large to small radii (Bertschinger & Meiksin 1986; Narayan & Medvedev 2001).”
The Cluster-Scale AGN Outburst in Hydra A (2004, background): “Many possibilities have been proposed, including thermal conduction (e.g. Narayan & Medvedev 2001), energy released by mergers (e.g. Motl et al. 2004) and heating by an active galactic nucleus (AGN; Tabor & Binney 1993; Tucker & David 1997).”
Spatially resolved X-ray spectroscopy of cooling clusters of galaxies (2003, positive): “Conductivity is less severelyd - creased if the magnetic field behaves chaotically over a wide range of scales: Narayan & Medvedev (2001) estimate that in this case conductivity is only a factor∼5 below the Spitzer rate (given the uncertainties this factor lies in the range∼2.5–10).”
Feedback heating by cosmic rays in clusters of galaxies (2007, background): “Recent theoretical and numerical work (e.g. Narayan & Medvedev 2001; Cho et al. 2003) has shown that a turbulent magnetic field may not be as efficient in suppressing thermal conduction as previously thought.”
Buoyancy Instabilities in Weakly Magnetized Low-Collisionality Plasmas (2007, background): “…between the heat flux and magnetic field described in this paper, it is unclear whether current calculations of the effective conductivity and heat flux in cluster plasmas (e.g., Narayan & Medvedev 2001; Chandran & Maron 2004) are correct, since they do not capture this dynamical coupling.”
CAUSE AND EFFECT OF FEEDBACK: MULTIPHASE GAS IN CLUSTER CORES HEATED BY AGN JETS (2011, background): “Other mechanisms may also help heat the ICM and redistribute the energy throughout the cool core: dynamical friction (El-Zant et al. 2004), thermal conduction (Narayan & Medvedev 2001; Bogdanović et al. ar X iv :1 11 0.”
Cosmic ray feedback in hydrodynamical simulations of galaxy formation (2006, background): “The theory of the respective diffusion coefficients is complicated, and uncertain for the case of turbulent magnetic field configurations (e.g. Rechester & Rosenbluth, 1978; Duffy et al., 1995; Bieber & Matthaeus, 1997; Giacalone & Jokipii, 1999; Narayan & Medvedev, 2001; Enßlin, 2003).”
Simulations of magnetic fields in isolated disc galaxies (2012, background): “In addition, the structure and strength of magnetic fields in galaxies determines the propagation of cosmic rays (e.g. Strong & Moskalenko 1998; Narayan & Medvedev 2001), which are another crucial ingredient influencing the gas dynamics of galaxies.”
Volume filling factors of the ISM phases in star forming galaxies. I. The role of the disk-halo interaction (2004, background): “It has been argued recently in the context of cooling flows in clusters of galaxies (e.g. Narayan & Medvedev 2001), that turbulence may boost the conduction rate and thus overcome the suppression by a magnetic field.”
Massive and refined - II. The statistical properties of turbulent motions in massive galaxy clusters with high spatial resolution (2010, background): “From the theoretical viewpoint, turbulence may have a deep impact on the physics of the ICM (e.g. Narayan & Medvedev 2001; Shekochihin et al 2005, 2010; Lazarian 2006; Ruszkowsky & Peng 2010) and on the properties of non-thermal components in galaxy clusters (e.g. Subramanian et al. 2006; Brunetti…”
On the prevalence of radio‐loud active galactic nuclei in brightest cluster galaxies: implications for AGN heating of cooling flows (2006, background): “However, in the presence of magnetic fields, thermal conduction will be suppressed; the amount of this suppression remains an open question, but Narayan & Medvedev (2001) argue that in the presence of turbulent magnetic fields it may be only a factor of a few.”
Heating Hot Atmospheres with Active Galactic Nuclei (2007, background): “However, under similar conditions in the solar wind, thermal conduction appears to be suppressed by only a modest factor and it has been argued that this should be true generally for turbulent plasmas (e.g., Sarazin 1988; Rosner & Tucker 1989; Narayan & Medvedev 2001).”
STIRRING UP THE POT: CAN COOLING FLOWS IN GALAXY CLUSTERS BE QUENCHED BY GAS SLOSHING? (2009, background): “Proposed candidates include magnetic field reconnection (Soker & Sarazin 1990), thermal conduction due to electron collisions (e.g., Narayan & Medvedev 2001; Fabian, Voigt, & Morris 2002; Zakamska & Narayan 2003) and turbulent conduction (e.g., Cho et al. 2003; Voigt & Fabian 2004), and heating by…”
Modified Entropy Models for the Intracluster Medium (2002, background): “Furthermore, recent theoretical work suggests that magnetic fields might not suppress conduction as effectively as previously believed (Malyshkin & Kulsrud 2001; Malyshkin 2001; Narayan & Medvedev 2001).”