Structural stability of cooling flows

Omma, Henrik; Binney, James

doi:10.1111/j.1365-2966.2004.07809.x

Cited by 70 publications

(50 citation statements)

References 29 publications

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“…Theoretical (e.g. Tucker & David 1997; Omma & Binney 2004) and observational (e.g. Giovannini et al 1998; Giovannini, Taylor & Arbizzani 1999; Venturi, Dallacasa & Stefanachi 2004) evidence suggests that radio jets are intermittent and thus, continuing with our analogy, it makes sense to consider a stochastic forcing term.…”

Section: Radio Cocoon As An Oscillatormentioning

confidence: 59%

Sound waves in the intracluster medium

Shabala¹,

Alexander²

2009

Monthly Notices of the Royal Astronomical Society

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We present an analysis of the behaviour of a perturbed radio cocoon. Comparisons with observations of sound waves detected in the Perseus and Virgo clusters suggest the separations of observed ripples correspond to the natural oscillation frequency of the cocoon. An energy injection rate consistent with active galactic nucleus power is required to offset the strong acoustic damping of cocoon oscillations, suggesting the sources are in equilibrium with the intracluster medium (ICM), and the oscillations are effectively undamped. Viscous dissipation of sound waves provides ICM heating that can quench cooling flows on time‐scales greatly exceeding the oscillation time‐scale. Thermal conductivity is likely to be heavily suppressed.

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Section: Radio Cocoon As An Oscillatormentioning

confidence: 59%

Sound waves in the intracluster medium

Shabala¹,

Alexander²

2009

Monthly Notices of the Royal Astronomical Society

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“…It seems, however that the dynamics of these systems is qualitatively different from the dynamics of the Milky Way's corona because the central galaxies of rich clusters do not have massive stellar discs. The extent to which gas in rich clusters is cooling (as opposed to radiating) is controversial, but it is now widely accepted that radiative losses by the inner corona are largely offset by mechanical feedback from the central black hole (Binney & Tabor 1995; Omma & Binney 2004; Nipoti & Binney 2005; Best et al 2007). It is important to understand the origin of this qualitative difference in the dynamics of the coronae of star‐forming galaxies of the ‘blue cloud’ and ‘green valley’ in colour–luminosity space (Blanton et al 2003) and that of the coronae of massive galaxies within the ‘red sequence’.…”

Section: Introductionmentioning

confidence: 99%

The mode of gas accretion on to star-forming galaxies

Marinacci¹,

Binney²,

Fraternali³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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It is argued that galaxies like ours sustain their star formation by transferring gas from an extensive corona to the star‐forming disc. The transfer is effected by the galactic fountain – cool clouds that are shot up from the plane to kiloparsec heights above the plane. The Kelvin–Helmholtz instability strips gas from these clouds. If the pressure and the metallicity of the corona are high enough, the stripped gas causes a similar mass of coronal gas to condense in the cloud's wake. Hydrodynamical simulations of cloud–corona interaction are presented. These confirm the existence of a critical ablation rate above which the corona is condensed and imply that for the likely parameters of the Galactic corona this rate lies near the actual ablation rate of clouds. In external galaxies, trails of H i behind individual clouds will not be detectable, although the integrated emission from all such trails should be significant. Parts of the trails of the clouds that make up the Galaxy's fountain should be observable and may account for features in targeted 21‐cm observations of individual high‐velocity clouds and surveys of Galactic H i emission. Taken in conjunction with the known decline in the availability of cold infall with increasing cosmic time and halo mass, the proposed mechanism offers a promising explanation of the division of galaxies between the blue cloud to the red sequence in the colour–luminosity plane.

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“…For a given radiative output, the jet power depends on the composition of the outflowing matter, with leptonic (e AE ) jets demanding less overall power and mass and being easier to accelerate to relativistic bulk flow velocities than hadronic (e-p) ones. Uncertainty in the matter content results in uncertainty in the jet power, which bears on our understanding of the jet dynamics and the radio lobe energetics and their interaction and influence on the host galaxy and possibly the embedding cluster core (e.g., Omma & Binney 2004;McNamara et al 2005). The composition is also related to the fundamental problem of jet formation: the plasma in jets powered by an accretion disk ( Blandford & Payne 1982;Königl 1989) would be expected to be baryon loaded, while jets powered by the rotational energy of a black hole are more likely to result in e AE jets ( Blandford & Znajek 1977).…”

Section: Introductionmentioning

confidence: 99%

Bulk Comptonization of the Cosmic Microwave Background by Extragalactic Jets as a Probe of Their Matter Content

Georganopoulos

Kazanas

Perlman

2005

ApJ

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We propose a method for estimating the composition, i.e., the relative amounts of leptons and protons, of extragalactic jets that exhibit X-ray-bright knots in their kiloparsec-scale jets. The method relies on measuring, or setting upper limits on, the component of the cosmic microwave background (CMB) radiation that is bulk Comptonized ( BC ) by cold electrons in the relativistically flowing jet. These measurements, along with modeling of the broadband knot emission that constrains the bulk Lorentz factor À of the jets, can yield estimates of the jet power carried by protons and leptons. We provide an explicit calculation of the spectrum of the BC CMB component and apply these results to PKS 0637À752 and 3C 273, two superluminal quasars with Chandra-detected large-scale jets. What makes these sources particularly suited for such a procedure is the absence of significant nonthermal jet emission in the ''bridge,'' the region between the core and the first bright jet knot, which guarantees that most of the electrons there are cold, leaving the BC-scattered CMB radiation as the only significant source of photons in this region. At k ¼ 3:6-8.0 m, the most likely band to observe the BC-scattered CMB emission, the Spitzer angular resolution ($1 00 -3 00 ) is considerably smaller than the bridges of these jets ($10 00 ), making it possible to both measure and resolve this emission.

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Structural stability of cooling flows

Cited by 70 publications

References 29 publications

Sound waves in the intracluster medium

Sound waves in the intracluster medium

The mode of gas accretion on to star-forming galaxies

Bulk Comptonization of the Cosmic Microwave Background by Extragalactic Jets as a Probe of Their Matter Content

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