We study the effect of noise in the density field, such as would arise from a
finite number density of tracers, on reconstruction of the acoustic peak within
the context of Lagrangian perturbation theory. Reconstruction performs better
when the density field is determined from denser tracers, but the gains
saturate at n~1e-4(h/Mpc)^3. For low density tracers it is best to use a large
smoothing scale to define the shifts, but the optimum is very broad.

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# Your search: "author:White, Martin"

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## Scholarly Works (153 results)

This year marks the 100th anniversary of the birth of Yakov Zel'dovich. Amongst his many legacies is the Zel'dovich approximation for the growth of large-scale structure, which remains one of the most successful and insightful analytic models of structure formation. We use the Zel'dovich approximation to compute the two-point function of the matter and biased tracers, and compare to the results of N-body simulations and other Lagrangian perturbation theories.We show that Lagrangian perturbation theories converge well and that the Zel'dovich approximation provides a good fit to the N-body results except for the quadrupole moment of the halo correlation function. We extend the calculation of halo bias to third order and also consider non-local biasing schemes, none of which remove the discrepancy. We argue that a part of the discrepancy owes to an incorrect prediction of inter-halo velocity correlations. We use the Zel'dovich approximation to compute the ingredients of the Gaussian streaming model and show that this hybrid method provides a good fit to clustering of haloes in redshift space down to scales of tens of Mpc. © 2014 The Author Published by Oxford University Press on behalf of the Royal Astronomical Society.

Future large scale structure surveys will provide increasingly tight constraints on our cosmological model. These surveys will report results on the distance scale and growth rate of perturbations through measurements of Baryon Acoustic Oscillations and Redshift-Space Distortions. It is interesting to ask: what further analyses should become routine, so as to test as-yet-unknown models of cosmic acceleration? Models which aim to explain the accelerated expansion rate of the Universe by modifications to General Relativity often invoke screening mechanisms which can imprint a non-standard density dependence on their predictions. This suggests density-dependent clustering as a 'generic' constraint. This paper argues that a density-marked correlation function provides a density-dependent statistic which is easy to compute and report and requires minimal additional infrastructure beyond what is routinely available to such survey analyses. We give one realization of this idea and study it using low order perturbation theory. We encourage groups developing modified gravity theories to see whether such statistics provide discriminatory power for their models.

The ten's of micro-Kelvin variations in the temperature of the cosmic
microwave background (CMB) radiation across the sky encode a wealth of
information about the Universe. The full-sky, high-resolution maps of the CMB
that will be made in the next decade should determine cosmological parameters
to unprecedented precision and sharply test inflation and other theories of the
early Universe.

I review why we expect the CMB anisotropy to be polarized, what we can learn
from studying polarization and the level of the experimental challenge it
presents. A discussion of current and future polarization sensitive experiments
will focus on the expected sensitivity of PLANCK.

The Lya forest has emerged as one of the few systems capable of probing
small-scale structure at high-z with high precision. In this talk I highlight
two areas in which the Lya forest is shedding light on fundamental questions in
cosmology, one speculative and one which should be possible in the near future.

The Zeldovich approximation, first-order Lagrangian perturbation theory, provides a good description of the clustering of matter and galaxies on large scales. The acoustic feature in the large-scale correlation function of galaxies imprinted by sound waves in the early Universe has been successfully used as a 'standard ruler' to constrain the expansion history of the Universe. The standard ruler can be improved if a process known as density field reconstruction is employed. In this paper, we develop the Zeldovich formalism to compute the correlation function of biased tracers in both real and redshift space using the simplest reconstruction algorithm with a Gaussian kernel and compare to N-body simulations. The model qualitatively describes the effects of reconstruction on the simulations, though its quantitative success depends upon how redshift-space distortions are handled in the reconstruction algorithm.

The formation and evolution of massive red galaxies form a crucial test of theories of galaxy formation based on hierarchical assembly. In this Letter we use observations of the clustering of luminous red galaxies from the Boötes field and N-body simulations to argue that about of the most luminous satellite galaxies appear to undergo merging or disruption within massive halos between and 0.5.

We seek to prove the means, motive and opportunity of 'dropout' selected 2 ≤ z ≤ 5 galaxies for large-scale structure. Together with acquired low-z tracers, these samples would map practically every linear mode and facilitate a tomographic decomposition of the Cosmic Microwave Background (CMB) lensing kernel over an unprecedented volume. With this, one may infer (the time evolution of) matter density fluctuations and perform compelling tests of horizon-scale General Relativity, neutrino masses and Inflation - viz., curvature, running of the spectral index and a scale-dependent halo bias induced by (local) primordial non-Gaussianity. This is facilitated by the order-of-magnitude increase in sensitivity achieved by planned CMB, optical-to-near-infrared imaging and spectroscopy. Focusing on traditional color-color - rather than photometric redshift - selection, we estimate the expected completeness, contamination, and spectroscopic survey speed of tailored Lyman-break galaxy (LBG) samples. With these in hand, we forecast the potential of CMB lensing cross-correlation, 'clustering redshifts' and Redshift-Space Distortions (RSD) analyses. In particular, we estimate: the depth dependence of interlopers based on CFHTLS-Archive-Research Survey (CARS) data and propagate this to biases in cosmology; a simple relation for the dependence of the linear galaxy bias on redshift and depth; new inferences of non-linear halo bias at these redshifts using legacy data; detailed forecasts of LBG spectra as would be observed by the Dark Energy Spectroscopic Instrument, Prime Focus Spectrograph, and their successors. We further assess the relative competitiveness of these spectroscopic facilities based on an intuitive figure-of-merit and define modern equivalents to traditional color selection criteria for the Large Synoptic Survey Telescope, where necessary. We confirm these science cases to be compelling for achievable facilities in the next decade by defining a LBG sample of increasing Lyman-α equivalent width with redshift, which delivers both percent-level RSD constraints on the growth rate at high-z and measurements of CMB lensing cross-correlation at z=3 and 4 with a significance measured in the hundreds, given sufficient area overlap. Finally, we discuss the limitations of this initial exploration and provide avenues for future investigation.