Correlating the CMB with luminous red galaxies: The integrated Sachs-Wolfe effect

Nikhil Padmanabhan, Christopher M. Hirata, Uroš Seljak, David J. Schlegel, Jonathan Brinkmann, and Donald P. Schneider
Phys. Rev. D 72, 043525 – Published 24 August 2005

Abstract

We present a 2.5σ detection of the Integrated Sachs-Wolfe (ISW) effect and discuss the constraints it places on cosmological parameters. We cross correlate microwave temperature maps from the Wilkinson microwave anisotropy probe (WMAP) satellite with a 4000deg2 luminous red galaxy (LRG) overdensity map measured by the Sloan Digital Sky Survey. These galaxies have accurate photometric redshifts (Δz0.03) and an approximately volume limited redshift distribution from z0.2 to z0.6 well suited to detecting the ISW effect. Accurate photometric redshifts allow us to perform a reliable autocorrelation analysis of the LRGs, eliminating the uncertainty in the galaxy bias, and combined with the cross correlation signal, constrains cosmological parameters—in particular, the matter density. We use a minimum-variance power spectrum estimator that optimally weights the data according to expected theoretical templates. We find a 2.5σ signal in the Ka, Q, V, and W WMAP bands, after combining the information from multipoles 2l<400. This is consistent with the expected amplitude of the ISW effect but requires a lower matter density than is usually assumed: the amplitude, parametrized by the galaxy bias assuming ΩM=0.3, ΩΛ=0.7, and σ8=0.9, is bg=4.05±1.54 for V band, with similar results for the other bands. This should be compared to bg=1.82±0.02 from the autocorrelation analysis. These data provide only a weak confirmation (2.5σ) of dark energy but provide a significant upper limit: ΩΛ=0.800.06+0.03(1σ)0.19+0.05(2σ), assuming a cosmology with ΩM+ΩΛ=1, Ωb=0.05, σ8=0.9, and w=1. The weak cross correlation signal rules out low matter density/high dark energy density universes and, in combination with other data, strongly constrains models with w<1.3. We provide a simple prescription to incorporate these constraints into cosmological parameter estimation methods for (ΩM,σ8,w). We find no evidence for a systematic contamination of ISW signal, either from galactic or extragalactic sources, but we do detect some large statistical fluctuations on smaller scales that could affect analyses without the template weighting.

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  • Received 22 October 2004

DOI:https://doi.org/10.1103/PhysRevD.72.043525

©2005 American Physical Society

Authors & Affiliations

Nikhil Padmanabhan1,*, Christopher M. Hirata1, Uroš Seljak1,2, David J. Schlegel3, Jonathan Brinkmann4, and Donald P. Schneider5

  • 1Joseph Henry Laboratories, Jadwin Hall, Princeton University, Princeton, New Jersey 08544, USA
  • 2ICTP, Strada Costiera 11, 34014 Trieste, Italy
  • 3Deptartment of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, New Jersey 08544, USA
  • 4Apache Point Observatory, 2001 Apache Point Road, Sunspot, New Mexico, 88349-0059, USA
  • 5Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, Pennsylvania 16802, USA

  • *Electronic address: npadmana@princeton.edu

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Vol. 72, Iss. 4 — 15 August 2005

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