http://arxiv.org/abs/1405.5857
We analyze BICEP2 and Planck data using a model that includes CMB lensing, gravity waves, and polarized dust. Recently published Planck dust polarization maps have highlighted the difficulty of estimating the amount of dust polarization in low intensity regions, suggesting that the polarization fractions have considerable uncertainties and may be significantly higher than previous predictions. In this paper we do not assume anything about the dust polarization, except for the power spectrum shape, which we take to be $C_{l}^{BB,{\rm dust}} \propto l^{-2.3}$. The resulting joint BICEP2+Planck analysis favors solutions without gravity waves, and the upper limit on the tensor-to-scalar ratio is $r<0.11$, a slight improvement relative to the Planck analysis alone which gives $r<0.13$ ($95\%$ c.l.). The estimated amplitude of the dust polarization power spectrum is in rough agreement with expectations for this field based on HI column density. We address the cross-correlation analysis of BICEP2 at 150 GHz with BICEP1 at 100 GHz as a test of foreground contamination. We find that the null hypothesis of dust and lensing with $r=0$ gives $\Delta \chi^2<2$ relative to the hypothesis of no dust, so the frequency analysis does not strongly favor either model over the other. We also discuss how Planck dust polarization maps may improve our constraints. If the dust polarization is measured perfectly, the limit can reach $r<0.05$ (or the corresponding detection significance if the observed dust signal plus the expected lensing signal is below the BICEP2 observations), but this degrades quickly to almost no improvement if the dust calibration error is $20\%$ or larger or if the Planck dust maps are not processed through the BICEP2 pipeline, inducing sampling variance noise.
M. Mortonson and U. Seljak
Fri, 23 May 14
39/44
Comments: 12 pages, 4 figures
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