TITLE:
Constraints on cosmic hemispherical power anomalies from quasars.
AUTHOR(S):
Christopher Hirata (Caltech).
DATE:
2009 Jul 03 (arXiv, posted, v1);
2009 Jul 17 (JCAP, submitted);
2009 Aug 24 (revised);
2009 Aug 27 (JCAP, accepted);
2009 Aug 27 (arXiv, posted, v2);
2009 Sep 08 (JCAP, published).
AVAILABILITY:
arXiv 0907.0703 (free);
IoP (requires subscription).
PUBLICATION INFORMATION:
JCAP, 09, 011, 2009.
ABSTRACT:
Recent analyses of the cosmic microwave background (CMB) maps from the WMAP satellite have uncovered evidence for a hemispherical power anomaly, i.e. a dipole
modulation of the CMB power spectrum at large angular scales with an amplitude of +/-14 percent. Erickcek et al have put forward an inflationary model to explain
this
anomaly. Their scenario is a variation on the curvaton scenario in which the curvaton possesses a large-scale spatial gradient that modulates the amplitude of CMB
fluctuations. We show that this scenario would also lead to a spatial gradient in the amplitude of perturbations σ8, and hence to a dipole asymmetry
in any
highly biased tracer of the underlying density field. Using the high-redshift quasars from the Sloan Digital Sky Survey, we find an upper limit on such a gradient of
|∇σ8|σ8<0.027/rlss (99% posterior probability), where rlss is the comoving distance to the
last-scattering surface. This rules out the simplest
version of the curvaton spatial gradient scenario.
ADS BIBLIOGRAPHIC CODE: 2009JCAP...09..011H
COMMENTS: N/A.