Posted: Oct 18, 2018 4:04 pm
Latest arxiv link on primordial gravitational wave measurements.
(Draft As accepted by PRL)
We present results from an analysis of all data taken by the BICEP2/Keck CMB polarization experiments up to and including the 2015 observing season. This includes the first Keck Array obser- vations at 220 GHz and additional observations at 95 & 150 GHz. The Q/U maps reach depths of 5.2, 2.9 and 26 μKcmb arcmin at 95, 150 and 220 GHz respectively over an effective area of ≈ 400 square degrees. The 220 GHz maps achieve a signal-to-noise on polarized dust emission approximately equal to that of Planck at 353GHz. We take auto- and cross-spectra between these maps and publicly available WMAP and Planck maps at frequencies from 23 to 353 GHz. We evaluate the joint likeli- hood of the spectra versus a multicomponent model of lensed-ΛCDM+r+dust+synchrotron+noise. The foreground model has seven parameters, and we impose priors on some of these using external information from Planck and WMAP derived from larger regions of sky. The model is shown to be an adequate description of the data at the current noise levels. The likelihood analysis yields the constraint r0.05 < 0.07 at 95% confidence, which tightens to r0.05 < 0.06 in conjunction with Planck temperature measurements and other data. The lensing signal is detected at 8.8σ significance. Running maximum likelihood search on simulations we obtain unbiased results and find that σ(r) = 0.020. These are the strongest constraints to date on primordial gravitational waves.
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The constraint on primordial gravitational waves parametrized by tensor to scalar ratio r is improved to r0.05 < 0.062 (95%), disfavoring the important class of inflationary models represented by a φ potential[4, 5].
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