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We present a 2. 5 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 4000 deg^2 luminous red galaxy (LRG) overdensity map measured by the Sloan Digital Sky Survey. These galaxies have accurate photometric redshifts (0. 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. 5 signal in the Ka, Q, V, and W WMAP bands, after combining the information from multipoles 2<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 ₌=0. 3, _=0. 7, and ₈=0. 9, is b₆=4. 051. 54 for V band, with similar results for the other bands. This should be compared to b₆=1. 820. 02 from the autocorrelation analysis. These data provide only a weak confirmation (2. 5) of dark energy but provide a significant upper limit: _=0. 80-₀. ₀₆^+0. 03 (1) -₀. ₁₉^+0. 05 (2), assuming a cosmology with ₌+_=1, ₁=0. 05, ₈=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 (₌, ₈, 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.
Padmanabhan et al. (Wed,) studied this question.