Cosmology

Abstract:

We address the degree and rapidity of generation of small-scale power over the course of structure formation in cosmologies where the primordial power spectrum is strongly suppressed beyond a given wavenumber. We first summarize the situations where one expects such suppressed power spectra and point out their diversity. We then employ an exponential cut-off, which characterizes warm dark matter (WDM) models, as a template for the shape of the cut-off and focus on damping scales ranging from 10⁶ to 10⁹ h ^-1 M⊙. Using high-resolution simulations, we show that the suppressed part of the power spectrum is quickly (re)generated and catches up with both the linear and the non-linear evolution of the unsuppressed power spectrum. From z = 2 onwards, a power spectrum with a primordial cut-off at 10⁹ h^-1 MŁódź, becomes virtually indistinguishable from an evolved cold dark matter (CDM) power spectrum. An attractor such as that described in Zaldarriaga, Scoccimarro & Hui for power spectra with different spectral indices also emerges in the case of truncated power spectra. Measurements of z ∼ 0 non-linear power spectra at ∼100 h^-1 kpc cannot rule out the possibility of linear power spectra damped below ∼10⁹ h^-1 M ⊙. Therefore, WDM or scenarios with similar features should be difficult to exclude in this way. © 2005 RAS.

Abstract:

The 2dF QSO Redshift Survey (2QZ) has obtained redshifts for in excess of 23 000 QSOs selected by their u′, bJ, r colours using the 2-degree Field (2dF) facility at the Anglo-Australian Telescope (AAT). In this paper, we describe the creation of the input catalogue from UK Schmidt photographic plates. All the plate materials used are described along with the techniques developed for flat-fielding variations in the photometric response of photographic emulsions. The selection criteria used for the survey are defined and their rationale discussed. Finally, several simple astrometric and photometric tests are performed. These demonstrate that, over the majority of the parameter space covered by this survey (18.25

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