Cross-correlating WMAP5 with 1.5 million LRGs: a new test for the ISW
  effect
  We present the cross-correlation of the density map of LRGs and the
temperature fluctuation in the CMB as measured by the WMAP5 observations. The
LRG samples were extracted from imaging data of the SDSS based on two previous
spectroscopic redshift surveys, the SDSS-LRG and the 2SLAQ surveys at average
redshifts z~0.35 and z~0.55. In addition we have added a higher-redshift
photometric LRG sample based on the selection of the AAOmega LRG redshift
survey at z~0.7. The total LRG sample thus comprises 1.5 million galaxies,
sampling a redshift range of 0.2 < z < 0.9 over ~7600 square degrees of the
sky, probing a total cosmic volume of ~5.5 h^{-3} Gpc^3. We find that the new
LRG sample at z~0.7 shows very little positive evidence for the ISW effect.
Indeed, the cross-correlation is negative out to ~1 deg. The standard LCDM
model is rejected at ~2-3% significance by the new LRG data. We then performed
a new test on the robustness of the LRG ISW detections at z~0.35 and 0.55. We
made 8 rotations through 360deg of the CMB maps with respect to the LRG samples
around the galactic pole. We find that in both cases there are stronger effects
at angles other than zero. This implies that the z~0.35 and 0.55 ISW detections
may still be subject to systematic errors which combined with the known
sizeable statistical errors may leave these ISW detections looking unreliable.
We have further made the rotation test on several other samples where ISW
detections have been claimed and find that they also show peaks when rotated.
We conclude that in the samples we have tested the ISW effect may be absent and
we argue that this result may not be in contradiction with previous results.
