Volume 519, September 2010
|Number of page(s)||7|
|Published online||20 September 2010|
E/B decomposition of CMB polarization pattern of incomplete sky: a pixel space approach
Niels Bohr Institute & Discovery Center, Blegdamsvej 17, 2100 Copenhagen, Denmark e-mail: firstname.lastname@example.org
Accepted: 26 June 2010
CMB polarization pattern may be decomposed into gradient-like (E) and curl-like (B) mode, which provide invaluable information respectively. We have investigated E/B decomposition in pixel space. We find E/B mixing due to incomplete sky is localized in pixel-space, and negligible in the regions far away from the masked area. By estimating the expected local leakage power, we have diagnosed ambiguous pixels. Our criteria for ambiguous pixels (i.e. rc) is associated with the tensor-to-scalar ratio of B mode power spectrum, which the leakage power is comparable to. By setting rc to a lower value, we may reduce leakage level, but reduce sky fraction at the same time. Therefore, we have solved ∂ΔCl/∂rc = 0, and obtained the optimal rc, which minimizes the estimation uncertainty, given a foreground mask and noise level. We have applied our method to a simulated map blocked by a foreground (diffuse + point source) mask. Our simulation shows leakage power is smaller than primordial (i.e. unlensed) B mode power spectrum of tensor-to-scalar ratio r ~ 1×10-3 at wide range of multipoles (50 ≲ l ≲ 2000), while allowing us to retain sky fraction ~0.48.
Key words: methods: data analysis / cosmic background radiation
© ESO, 2010
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