TITLE:
Detectability of tensor modes in the presence of foregrounds.
AUTHOR(S):
Mihail Amarie (Princeton), Christopher M. Hirata (Princeton/IAS), Uros Seljak (Princeton/ICTP).
DATE:
2005 Aug 12 (arXiv, v1, posted); 2005 Aug 15 (Phys. Rev. D, submitted); 2005 Nov 15 (revised); 2005 Nov 17 (Phys. Rev. D, accepted);
2005 Dec 22 (Phys. Rev. D, published); 2006 Jan 14 (arXiv, v2, posted).
AVAILABILITY:
arXiv astro-ph/0508293 (free);
APS (requires subscription).
PUBLICATION INFORMATION: Phys. Rev. D 72, 123006 (2005).
ABSTRACT: In inflationary models gravitational waves are produced in the early universe and
generate B-type polarization in the cosmic microwave background (CMB). Since B polarization is only generated er from the usual cosmic
variance. A perfect decomposition of the CMB into B-modes and E-modes would require data from the entire sky, which in practice is not
possible because of the foreground contaminants. This leads to mixing of E polarization into B, which introduces cosmic variance
contamination of B polarization and reduces sensitivity to gravity wave amplitude even in absence of detector noise. We present
numerical results for the uncertainty in the tensor-to-scalar ratio using the Fisher matrix formalism for various resolutions and
considering several cuts of the sky, using the foreground model based on dust maps and assuming 90 GHz operating frequency. We find that
the usual scaling Delta(T/S)~fsky-1/2 is significantly degraded and becomes
Delta(T/S)~fsky-2 for fsky>0.7. This dependence is affected only weakly by the choice of sky cuts.
To put this into a context of what is required level of foreground cleaning, to achieve a T/S = 10-3 detection at 3s one needs to observe 15% of the sky as opposed to naive expectation of 0.3%. To prevent contamination over this
large sky area at required level one must be able to remove polarized dust emission at or better than 0.1% of unpolarized intensity,
assuming the cleanest part of the sky has been chosen. To achieve T/S = 10-4 detection at 3s one
needs to observe 70% of the sky, which is only possible if dust emission is removed everywhere over this region at 0.01% level. Reaching
T/S = 10-2 should be easier: 1% of the sky is needed over which polarized emission needs to be removed at 1% of unpolarized
intensity if the cleanest region is chosen. These results suggest that foreground contamination may make it difficult to achieve levels
below T/S = 10-3.
ADS BIBLIOGRAPHIC CODE: 2005PhRvD..72l3006A
COMMENTS: