A Joint Analysis of BICEP2/Keck Array and Planck Data

We report the results of a joint analysis of data from BICEP2/Keck Array and Planck. BICEP2 and Keck Array have observed the sameapproximately 400 deg2 patch of sky centered on RA 0 h, Dec.-57.5 ?? . The combined maps reach a depth of 57 nK deg in Stokes Qand U in a band centered at 150 GHz. Planck has observed the full sky inpolarization at seven frequencies from 30 to 353 GHz, but much lessdeeply in any given region (1.2 ?? K deg in Q and U at 143 GHz). Wedetect 150 ??353 cross-correlation in B modes at high significance.We fit the single- and cross-frequency power spectra at frequencies???150 GHz to a lensed-?? CDM model that includes dust and apossible contribution from inflationary gravitational waves (asparametrized by the tensor-to-scalar ratio r), using a prior on thefrequency spectral behavior of polarized dust emission from previousPlanck analysis of other regions of the sky. We find strong evidence fordust and no statistically significant evidence for tensor modes. Weprobe various model variations and extensions, including adding asynchrotron component in combination with lower frequency data, and findthat these make little difference to the r constraint. Finally, wepresent an alternative analysis which is similar to a map-based cleaningof the dust contribution, and show that this gives similar constraints.The final result is expressed as a likelihood curve for r, and yieldsan upper limit r0.05{\textless}0.12 at 95\% confidence. Marginalizingover dust and r, lensing B modes are detected at 7.0 ??significance.