[astro-ph/0703470] Anomalous SZ Contribution to 3 Year WMAP Data

Authors:  R.M. Bielby, T. Shanks
Abstract:  We first show that the new WMAP 3 year data confirm the detection by Myers et al. (2004) of an extended SZ signal centred on 606 Abell clusters. We also detect SZ decrements around APM and 2MASS groups at increased significance than previously. We then follow the approach of Lieu et al. (2006) and compare the stacked WMAP results for the decrement in 31 clusters with ROSAT X-ray profiles where Lieu et al. found on average less SZ decrement in the WMAP 1 year data than predicted. We confirm that in the 3 year data these same clusters also show less SZ decrement than the X-ray data predicts. We then analysed the WMAP results for the 38 X-ray clusters with OVRO/BIMA measured SZ decrements as presented by Bonamente et al. (2006). We again find that the average decrement is measured to be significantly less (5.5 sigma) than predicted by the Chandra X-ray data. These X-ray data cause us to re-interpret our previous result; rather than seeing too much SZ at large scales, we may actually be seeing too little SZ decrement near the cluster centre. One possible explanation is that there is contamination of the WMAP SZ signal by radio sources in the clusters but we argue that this appears implausible. We then consider the possibility that the SZ decrement has been lensed away by foreground galaxy groups. Such a model predicts that the SZ decrement should depend on cluster redshift. This effect is clearly detected in the ACO cluster sample and also by comparing the samples of Lieu et al. and Bonamente et al. But the mass power-spectrum would require a far higher amplitude than currently expected if lensing was to explain the SZ deficit in high redshift clusters.
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Richard Lieu
Posts: 11
Joined: November 27 2005
Affiliation: University of Alabama, Huntsville

[astro-ph/0703470] Anomalous SZ Contribution to 3 Year WMAP

Post by Richard Lieu » April 11 2007

Yet another paper for the perusal of LCDM cosmologists.

The cosmo coffee is turning quite bitter - I need more sugar!

I am alarmed by their Fig. 4b, which indicates that along the directions
to 38 of the richest clusters of the Universe WMAP detected absolutely
no SZ effect. (note the data shown are from the W band, which has the
cleanest CMB signals and the best point spread function). This is much worse
than what we originally found, which was to do with a slightly lower z sample.

So, one could blame it to the higher z of the 38-member sample, but hav'nt we
been hearing all that song and dance about how SZE is insensitive to z? What
happened to them?

Another really fascinating point is in their Fig. 5 upper panels, where the authors
further divided our lower z sample according as 20<b<40 and b>40 deg, with b=Galactic
latitude. The absence of SZE in WMAP is much more severe in the former sub-sample.
Isn't this corroborating what Verschuur and Rudnick et al are telling us (see my
two earlier postings), viz. that significant foreground effects still exist on small scales -
scales that affect SZE and acoustic peaks? Note that 20<b<40 is not a low
latitude zone. It is a zone that stays well outside the Galactic disk, where cosmological
inferences were made from WMAP observations.

Richard Lieu
Posts: 11
Joined: November 27 2005
Affiliation: University of Alabama, Huntsville

[astro-ph/0703470] Anomalous SZ Contribution to 3 Year WMAP

Post by Richard Lieu » October 06 2007

This paper is now MNRAS in press.

As I already said, in one of their samples of > 30 rich Abell clusters
WMAP detected altogether (after stacking) no SZ effect at all.
Other samples exhibit similar anomaly of too little SZE, though not
quite as severe as this sample.

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