On the coherent rotation of diffuse matter in numerical simulations of clusters of galaxies

There are (at least) two unsolved problems concerning the current state of the thermal gas in clusters of galaxies. The first is to identify the source of the heating which offsets cooling in the centres of clusters with short cooling times (the ‘cooling–flow’ problem). The second to understand the mechanism which boosts the entropy in cluster and group gas. Since both of these problems involve an unknown source of heating it is tempting to identify them with the same process, particularly since active galactic nuclei heating is observed to be operating at some level in a sample of well–observed ‘cooling–flow’ clusters. Here we show, using numerical simulations of cluster formation, that much of the gas ending up in clusters cools at high redshift and so the heating is also needed at high redshift, well before the cluster forms. This indicates that the same process operating to solve the cooling–flow problem may not also resolve the cluster–entropy problem.

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3. Clusters of Galaxies

Transactions of the International Astronomical Union ◽

10.1017/s0251107x0000674x ◽

1985 ◽

Vol 19 (1) ◽

pp. 664-668

Author(s):

Jaan Einasto

Keyword(s):

Numerical Simulations ◽

Objective Evaluation ◽

Automatic Identification ◽

Clusters Of Galaxies ◽

Schmidt Telescope ◽

Absolute Magnitudes

Abell and Corwin (34.160.040) have continued the search of southern clusters on photographs taken with the U.K. Schmidt telescope at Siding Spring. A catalogue is in preparation, it continues the Abell catalogue toward southern declinations. West (32.160.019, 32.160.036, 34.160.044) has initiated a study of distant southern clusters with automatic identification of clusters and objective evaluation of their properties. Noonan (30.160.006) and Sarazin et al. (31.160.030) have listed clusters with published redshifts. Numerical simulations have demonstrated the presence of bias in observed clusters as difined by Abell (33.160.006), ranked absolute magnitudes of galaxies are distance dependent (33.160.081), some clusters may be due to projection effects (34.160.009).

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Numerical Simulations of Merging Clusters of Galaxies

The Astrophysical Journal Supplement Series ◽

10.1086/312979 ◽

1997 ◽

Vol 109 (2) ◽

pp. 307-332 ◽

Cited By ~ 135

Author(s):

Kurt Roettiger ◽

Chris Loken ◽

Jack O. Burns

Keyword(s):

Numerical Simulations ◽

Clusters Of Galaxies

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Simulations of Merging Clusters of Galaxies

Highlights of Astronomy ◽

10.1017/s1539299600014295 ◽

2002 ◽

Vol 12 ◽

pp. 531-533 ◽

Cited By ~ 1

Author(s):

Sabine Schindler

Keyword(s):

Magnetic Field ◽

Numerical Simulations ◽

Shock Structure ◽

Clusters Of Galaxies ◽

Mass Determination ◽

X Ray ◽

Dynamical State ◽

Merging Process ◽

Cluster Mergers ◽

The Magnetic Field

AbstractNumerical simulations of cluster mergers reveal many characteristics of the merging process: shock structure and strength, observational signatures of the dynamical state, effects on the mass determination, turbulence and the evolution of the X-ray luminosity and the magnetic field. In this article I review the results obtained from various simulations over the last years.

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Cluster Swapping

Symposium - International Astronomical Union ◽

10.1017/s0074180900042558 ◽

1988 ◽

Vol 126 ◽

pp. 297-309

Author(s):

Juan C. Muzzio

Keyword(s):

Gravitational Field ◽

Numerical Simulations ◽

Globular Cluster ◽

Total Mass ◽

Dynamical Evolution ◽

Clusters Of Galaxies ◽

Missing Mass ◽

Mass Problem ◽

Test Particles ◽

The Galaxy

The investigation of globular cluster swapping in clusters of galaxies has resulted in some interesting theoretical findings and, at the same time, it offers a promising field for observers. Numerical simulations of galaxy clusters where the galaxies have swarms of test particles around them showed that, in addition to tidal stripping, tidal accretion plays an important role in the dynamical evolution of clusters of galaxies; it also turns out that, even in clusters where the gravitational field is dominated by a massive background, the galaxy-galaxy attraction cannot be ignored when estimating the outcome of collisions. Cluster swapping is just an example of tidal accretion and, taking the globulars as probes of halo material, it might offer an opportunity to observe some consequences of that effect; besides, although the difficulties look formidable at present, the study of globulars lost through tidal stripping is a possibility that should not be neglected. Tidal stripping and accretion processes are very sensitive to the ratio of galactic mass to total mass, so that observations related to the cluster swapping phenomena may provide a new means to investigate the missing mass problem.

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Direct Numerical Simulations of Gas–Liquid Multiphase Flows

10.1017/cbo9780511975264 ◽

2001 ◽

Cited By ~ 151

Author(s):

Grétar Tryggvason ◽

Ruben Scardovelli ◽

Stéphane Zaleski

Keyword(s):

Numerical Simulations ◽

Multiphase Flows ◽

Direct Numerical Simulations

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Saturation mechanism and generated viscosity in gravito-turbulent accretion disks

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038023 ◽

2020 ◽

Vol 640 ◽

pp. A53

Author(s):

L. Löhnert ◽

S. Krätschmer ◽

A. G. Peeters

Keyword(s):

Growth Rate ◽

Numerical Simulations ◽

Accretion Disks ◽

Gravitational Instability ◽

Turbulent Viscosity ◽

Radial Distance ◽

Maximum Growth ◽

Wave Number ◽

Radiative Cooling ◽

Mixing Length

Here, we address the turbulent dynamics of the gravitational instability in accretion disks, retaining both radiative cooling and irradiation. Due to radiative cooling, the disk is unstable for all values of the Toomre parameter, and an accurate estimate of the maximum growth rate is derived analytically. A detailed study of the turbulent spectra shows a rapid decay with an azimuthal wave number stronger than ky−3, whereas the spectrum is more broad in the radial direction and shows a scaling in the range kx−3 to kx−2. The radial component of the radial velocity profile consists of a superposition of shocks of different heights, and is similar to that found in Burgers’ turbulence. Assuming saturation occurs through nonlinear wave steepening leading to shock formation, we developed a mixing-length model in which the typical length scale is related to the average radial distance between shocks. Furthermore, since the numerical simulations show that linear drive is necessary in order to sustain turbulence, we used the growth rate of the most unstable mode to estimate the typical timescale. The mixing-length model that was obtained agrees well with numerical simulations. The model gives an analytic expression for the turbulent viscosity as a function of the Toomre parameter and cooling time. It predicts that relevant values of α = 10−3 can be obtained in disks that have a Toomre parameter as high as Q ≈ 10.

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