CLUES Publications

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On the relation between the radial alignment of dark matter subhaloes and host mass in cosmological simulations
Knebe, A., Draganova, N., Power, C., Yepes, G., Hoffman, Y., Gottlöber, S., Gibson, B. K., 2008, Monthly Notices of the Royal Astronomical Society , 386, 1 , L52
Published: May 2008
doi:10.1111/j.1745-3933.2008.00459.x
Abstract:
We explore the dependence of the radial alignment of subhaloes on the mass of the host halo they orbit in. As the effect is seen on a broad range of scales including massive clusters as well as galactic systems it only appears natural to explore this phenomenon by means of cosmological simulations covering the same range in masses. We have 25 well resolved host dark matter haloes at our disposal ranging from 1015h-1Msolar down to 1012h-1Msolar each consisting of order of a couple of million particles within the virial radius. We observe that subhaloes tend to be more spherical than isolated objects. Both the distributions of sphericity and triaxiality of subhaloes are Gaussian-distributed with peak values of <s> ~ 0.80 and <T> ~ 0.56, irrespective of host mass. Interestingly, we note that the radial alignment is independent of host halo mass and the distribution of cosθ (i.e. the angle between the major-axis Ea of each subhalo and the radius vector of the subhalo in the reference frame of the host) is well fitted by a simple power law P(cosθ) ~ cos4θ with the same fitting parameters for all host haloes.
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Klypin, A., Hoffman, Y., Kravtsov, A. V., Gottlober, S., 2003, The Astrophysical Journal , 596, 1 , 19
Published: October 2003
doi:10.1086/377574
Abstract:
We present cosmological simulations that closely mimic the real uiverse within ~100 Mpc of the Local Group. The simulations, called constrained simulations, reproduce the large-scale density field with major nearby structures, including the Local Group, the Coma and Virgo Clusters, the Great Attractor, the Perseus-Pisces Supercluster, and the Local Supercluster, in approximately correct locations. The MARK III survey of peculiar velocities of the observed structures inside an 80h-1Mpc sphere is used to constrain the initial conditions. Fourier modes on scales larger than a (Gaussian) resolution of ~Rg=5h-1Mpc are dominated by the constraints, while small-scale waves are essentially random. The main aim of this paper is the structure of the Local Supercluster region (LSC; ~30h-1Mpc around the Virgo Cluster) and the Local Group environment. We find that at the current epoch most of the mass (~7.5×1014h-1Msolar) of the LSC is located in a filament roughly centered on the Virgo Cluster and extending over ~40h-1Mpc. The simulated Local Group (LG) is located in an adjacent smaller filament, which is not a part of the main body of the LSC and has a peculiar velocity of ~250 km s-1 toward the Virgo Cluster. The peculiar velocity field in the LSC region is complicated and is drastically different from the field assumed in the Virgocentric infall models. We find that the peculiar velocity flow in the vicinity of the LG in the simulation is relatively ``cold'': the peculiar line-of-sight velocity dispersion within 7h-1Mpc of the LG is <~60 km s-1, comparable to the observed velocity dispersion of nearby galaxies.
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Kravtsov, A. V., Klypin, A., Hoffman, Y., 2002, The Astrophysical Journal , 571, 2 , 563
Published: June 2002
doi:10.1086/340046
Abstract:
We present results of gasdynamics+N-body constrained cosmological simulations of the Local Supercluster region (LSC; about 30h-1Mpc around the Virgo cluster), which closely mimic the real universe within 100 Mpc, by imposing constraints from the MARK III catalog of galaxy peculiar velocities. The simulations are used to study the properties and possible observational signatures of intergalactic medium in the LSC region. We find that in agreement with previous unconstrained simulations, ~30% of the gas in this region is in the warm/hot phase at T~105-107 K and ~40% in the diffuse phase at T<105 K in low-density regions. The X-ray emission from the warm/hot gas may represent a small (~5%-10%) but important contribution to the X-ray background observed by the ROSAT All-Sky Survey at energies around 1 keV. The best prospects for detection of the warm/hot intergalactic medium of the LSC located in filaments and in the vicinity of virialized regions of groups and clusters are through absorption in resonant lines of O VII and O VIII in soft X-rays and in the O VI doublet in UV. If intergalactic gas in filaments (ρ/<ρ>~1-10) is enriched to typical metallicities of >~0.05, the column densities of O VI, O VII, and O VIII along a random line of sight near the north Galactic pole, especially near the supergalactic plane, have a significant probability to be in the range detectable by current (FUSE, XMM) and future (Constellation-X) instruments.
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