CLUES Publications

Publications retrieved from NASA ADS and sorted by publication date in reverse order

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Estimating cosmic velocity fields from density fields and tidal tensors
Kitaura, F.-S., Angulo, R. E., Hoffman, Y., Gottlöber, S., 2012, Monthly Notices of the Royal Astronomical Society , 425, 4 , 2422
Published: October 2012
doi:10.1111/j.1365-2966.2012.21589.x
Abstract:
In this work we investigate the non-linear and non-local relation between cosmological density and peculiar velocity fields. Our goal is to provide an algorithm for the reconstruction of the non-linear velocity field from the fully non-linear density. We find that including the gravitational tidal field tensor using second-order Lagrangian perturbation theory based upon an estimate of the linear component of the non-linear density field significantly improves the estimate of the cosmic flow in comparison to linear theory not only in the low density, but also and more dramatically in the high-density regions. In particular we test two estimates of the linear component: the lognormal model and the iterative Lagrangian linearization. The present approach relies on a rigorous higher order Lagrangian perturbation theory analysis which incorporates a non-local relation. It does not require additional fitting from simulations being in this sense parameter free, it is independent of statistical-geometrical optimization and it is straightforward and efficient to compute. The method is demonstrated to yield an unbiased estimator of the velocity field on scales ≳5 h-1 Mpc with closely Gaussian distributed errors. Moreover, the statistics of the divergence of the peculiar velocity field is extremely well recovered showing a good agreement with the true one from N-body simulations. The typical errors of about 10 km s-1 (1σ confidence intervals) are reduced by more than 80 per cent with respect to linear theory in the scale range between 5 and 10 h-1 Mpc in high-density regions (δ > 2). We also find that iterative Lagrangian linearization is significantly superior in the low-density regime with respect to the lognormal model.
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Hoffman, Y., Metuki, O., Yepes, G., Gottlöber, S., Forero-Romero, J. E., Libeskind, N. I., Knebe, A., 2012, Monthly Notices of the Royal Astronomical Society , 425, 3 , 2049
Published: September 2012
doi:10.1111/j.1365-2966.2012.21553.x
Abstract:
A new approach for the classification of the cosmic web is presented. In extension of the previous work of Hahn et al. and Forero-Romero et al., the new algorithm is based on the analysis of the velocity shear tensor rather than the gravitational tidal tensor. The procedure consists of the construction of the shear tensor at each (grid) point in space and the evaluation of its three eigenvectors. A given point is classified to be either a void, sheet, filament or a knot according to the number of eigenvalues above a certain threshold, 0, 1, 2 or 3, respectively. The threshold is treated as a free parameter that defines the web. The algorithm has been applied to a dark matter only simulation of a box of side length 64 h-1 Mpc and N = 10243 particles within the framework of the 5-year Wilkinson and Microwave Anisotropy Probe/Λ cold dark matter (ΛCDM) model. The resulting velocity-based cosmic web resolves structures down to ≲0.1 h-1 Mpc scales, as opposed to the ≈1 h-1 Mpc scale of the tidal-based web. The underdense regions are made of extended voids bisected by planar sheets, whose density is also below the mean. The overdense regions are vastly dominated by the linear filaments and knots. The resolution achieved by the velocity-based cosmic web provides a platform for studying the formation of haloes and galaxies within the framework of the cosmic web.
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Di Cintio, A., Knebe, A., Libeskind, N. I., Hoffman, Y., Yepes, G., Gottlöber, S., 2012, Monthly Notices of the Royal Astronomical Society , 423, 2 , 1883
Published: June 2012
doi:10.1111/j.1365-2966.2012.21013.x
Abstract:
We use the recently proposed scale-free mass estimators to determine the masses of the Milky Way (MW) and Andromeda (M31) galaxy in a dark matter only Constrained Local Universe Simulation. While these mass estimators work rather well for isolated spherical host systems, we examine here their applicability to a simulated binary system with a unique satellite population similar to the observed satellites of MW and M31. We confirm that the scale-free estimators work also very well in our simulated Local Group galaxies with the right number of satellites which follow the observed radial distribution. In the isotropic case and under the assumption that the satellites are tracking the total gravitating mass, the power-law index of the radial satellite distribution N(< r) ∝r3-γ is directly related to the host’s mass profile M(< r) ∝r1-α as α=γ- 2. The use of this relation for any given γ leads to highly accurate mass estimations which is a crucial point for observer, since they do not know a priori the mass profile of the MW and M31 haloes. We discuss possible bias in the mass estimators and conclude that the scale-free mass estimators can be satisfactorily applied to the real MW and M31 system.
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Libeskind, N. I., Hoffman, Y., Knebe, A., Steinmetz, M., Gottlöber, S., Metuki, O., Yepes, G., 2012, Monthly Notices of the Royal Astronomical Society , 421, 1 , L137
Published: March 2012
doi:10.1111/j.1745-3933.2012.01222.x
Abstract:
We use a 64 h-1 Mpc dark-matter-only cosmological simulation to examine the large-scale orientation of haloes and substructures with respect to the cosmic web. A web classification scheme based on the velocity shear tensor is used to assign to each halo in the simulation a web type: knot, filament, sheet or void. Using ∼106 haloes that span ∼3 orders of magnitude in mass, the orientation of the halo's spin and the orbital angular momentum of subhaloes with respect to the eigenvectors of the shear tensor is examined. We find that the orbital angular momentum of subhaloes tends to align with the intermediate eigenvector of the velocity shear tensor for all haloes in knots, filaments and sheets. This result indicates that the kinematics of substructures located deep within the virialized regions of a halo is determined by its infall which in turn is determined by the large-scale velocity shear, a surprising result given the virialized nature of haloes. The non-random nature of subhalo accretion is thus imprinted on the angular momentum measured at z= 0. We also find that the haloes' spin axis is aligned with the third eigenvector of the velocity shear tensor in filaments and sheets: the halo spin axis points along filaments and lies in the plane of cosmic sheets.
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Cuesta, A. J., Jeltema, T. E., Zandanel, F., Profumo, S., Prada, F., Yepes, G., Klypin, A., Hoffman, Y., Gottlöber, S., Primack, J., Sánchez-Conde, M. A., Pfrommer, C., 2012, The Astrophysical Journal , 745, 2 , L35
Published: February 2012
doi:10.1088/2041-8205/745/2/L35
Abstract:
No abstract available.
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