Cosmological Density Fluctuations on 100Mpc Scales and their ISW Effect

TL;DR

This paper measures the matter density fluctuations on large scales using SDSS data, compares them with ΛCDM predictions, and investigates their impact on the CMB via the ISW effect, confirming previous claims about superstructure signals.

Contribution

It provides observational measurements of the matter PDF on large scales and assesses their consistency with ΛCDM and the ISW effect, including analytic modeling of superstructure impacts.

Findings

Good agreement between measured PDF and ΛCDM predictions.

Superstructures can produce CMB temperature fluctuations of about 10 μK.

Gaussian models of superstructures are consistent with observed CMB spots.

Abstract

We measure the matter probability distribution function (PDF) via counts in cells in a volume limited subsample of the Sloan Digital Sky Survey Luminous Red Galaxy Catalog on scales from $30 h^{-1}$Mpc to $150 h^{-1}$Mpc and estimate the linear Integrated Sachs--Wolfe effect produced by supervoids and superclusters in the tail of the PDF. We characterize the PDF by the variance, $S_3$, and $S_4$, and study in simulations the systematic effects due to finite volume, survey shape and redshift distortion. We compare our measurement to the prediction of $\Lambda$CDM with linear bias and find a good agreement. We use the moments to approximate the tail of the PDF with analytic functions. A simple Gaussian model for the superstructures appears to be consistent with the claim by Granett et al. that density fluctuations on $100 h^{-1}$Mpc scales produce hot and cold spots with $\Delta T \approx 10\mu K$ on the cosmic microwave background.