Adi Nusser

Mass growth and density profiles of dark matter haloes in hierarchical clustering

We develop a model for the growth of dark matter haloes and use it to study their evolved density profiles. In this model, haloes are spherical and form by quiescent accretion of matter in clumps, which are called satellites. The halo mass as a function of redshift is given by the mass of the most massive progenitor, and is determined from Monte Carlo realizations of the merger-history tree. Inside the halo, satellites move under the action of the gravitational force of the halo and a dynamical friction drag force. The associated equation of motion is solved numerically. The energy lost to dynamical friction is transferred to the halo in the form of kinetic energy. As satellites sink into the halo, they continually lose matter as a result of tidal stripping. The stripped matter moves inside the halo free of dynamical friction. The evolved density profiles are steeper than those obtained by assuming that, once they have been accreted on to the parent halo, satellites remain at a fixed distance from the halo centre. We find that the final density profile depends mainly on the rate of infall of matter on to the halo. This, in turn, depends on the initial fluctuation field as well as on cosmology. For mass scales where the effective spectral index of the initial density field is less than -1, the model predicts a profile that can only be approximately matched by the one-parameter family of curves suggested by Navarro, Frenk and White. For scale-free power spectra with initial slope n, the density profile, within about 1 per cent of the virial radius, is ρ∝ r-β, with 3(3+n)/(5+n)≤β≤ 3(3+n)/(4+n).

Comparison of Velocity and Gravity Fields: The Mark III Tully-Fisher Catalog versus the IRAS 1.2 Jy Survey

We consider a measure of the peculiar velocity field derived from the Mark III compilation of 2900 spiral galaxies (Willick et al.), using an analysis method that is substantially free of bias (Nusser & Davis). We expand the velocity field in a set of orthogonal, smooth modes, reducing the data to a set of 56 coefficients fitted to a maximum redshift of 6000 km s–1, and maximum spherical harmonic of l = 3. The radial resolution of the modes degrades with redshift, from 800 km s–1 locally to 3000 km s–1 at 4000 km s–1 redshift. Equivalent mode coefficients can be computed for the gravity field derived from any whole-sky redshift catalog of galaxies, such as the IRAS 1.2 Jy survey (Fisher et al.). Given the coefficients of the expansions, one can compare the velocity and gravity fields on a galaxy-by-galaxy basis, or on a mode-by-mode basis. Detailed comparison shows the two independent fields to be remarkably aligned in general. There are, however, systematic discrepancies in the fields that lead to considerable coherence in the residuals between them. These residuals take the form of a dipole field in the Local Group (LG) frame that grows with distance; it is not consistent with a bulk flow residual. We perform a likelihood analysis in the mode-mode comparison to determine which value of β≡ Ω0.6/b for the IRAS gravity field is the best fit to the Mark III velocity field, considering the errors and covariance in both the velocity and gravity coefficients. We find that the most likely value lies in the range β = 0.4-0.6. However, in contrast with results we obtain using simulated galaxy catalogs, the x2 per degree of freedom for the fit is well in excess of unity, primarily because of the coherent dipole residuals at cz 3000 km s–1. Thus, despite the general alignment of the Mark III velocity and IRAS gravity fields, they do not agree in detail, precluding a firm determination of β from these data sets at present. The method is capable of measuring β to an accuracy of 10%, but without understanding these systematic discrepancies, we cannot infer a value of β from these data.

THE COSMOLOGICAL BULK FLOW: CONSISTENCY WITH ΛCDM AND z ≈ 0 CONSTRAINTS ON σ8 AND γ

We derive estimates for the cosmological bulk flow from the SFI++ Tully-Fisher (TF) catalog. For a sphere of radius

Local gravity versus local velocity: solutions for β and non-linear bias

40 \hmpc

The Massive-black-hole–Velocity-dispersion Relation and the Halo Baryon Fraction: A Case for Positive Active Galactic Nucleus Feedback

centered on the MW, we derive a bulk flow of

Non-uniform reionization by galaxies and its effect on the cosmic microwave background

333 \pm 38\kms

A first step towards a direct inversion of the Lyman forest in QSO spectra

towards Galactic

Decontamination of cosmological 21-cm maps

(l,b)=(276^\circ,14^\circ)

Cosmological velocity-density relation in the quasi-linear regime

within a

Self‐similar spherical collapse with non‐radial motions

3^\circ