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BICEP2 / Keck Array VI: Improved Constraints On Cosmology and Foregrounds When Adding 95 GHz Data From Keck Array

Keck Array, BICEP2 Collaborations, :, P. A. R. Ade, Z. Ahmed, R. W. Aikin, K. D. Alexander, D. Barkats, S. J. Benton, C. A. Bischoff, J. J. Bock, R. Bowens-Rubin, J. A. Brevik, I. Buder, E. Bullock, V. Buza, J. Connors, B. P. Crill, L. Duband, C. Dvorkin, J. P. Filippini, S. Fliescher, J. Grayson, M. Halpern, S. Harrison, G. C. Hilton, H. Hui, K. D. Irwin, K. S. Karkare, E. Karpel, J. P. Kaufman, B. G. Keating, S. Kefeli, S. A. Kernasovskiy, J. M. Kovac, C. L. Kuo, E. M. Leitch, M. Lueker, K. G. Megerian, C. B. Netterfield, H. T. Nguyen, R. O'Brient, R. W. Ogburn, A. Orlando, C. Pryke, S. Richter, R. Schwarz, C. D. Sheehy, Z. K. Staniszewski, B. Steinbach, R. V. Sudiwala, G. P. Teply, K. L. Thompson, J. E. Tolan, C. Tucker, A. D. Turner, A. G. Vieregg, A. C. Weber, D. V. Wiebe, J. Willmert, C. L. Wong, W. L. K. Wu, K. W. Yoon

Abstract

We present results from an analysis of all data taken by the BICEP2 & Keck Array CMB polarization experiments up to and including the 2014 observing season. This includes the first Keck Array observations at 95 GHz. The maps reach a depth of 50 nK deg in Stokes $Q$ and $U$ in the 150 GHz band and 127 nK deg in the 95 GHz band. We take auto- and cross-spectra between these maps and publicly available maps from WMAP and Planck at frequencies from 23 GHz to 353 GHz. An excess over lensed-LCDM is detected at modest significance in the 95x150 $BB$ spectrum, and is consistent with the dust contribution expected from our previous work. No significant evidence for synchrotron emission is found in spectra such as 23x95, or for correlation between the dust and synchrotron sky patterns in spectra such as 23x353. We take the likelihood of all the spectra for a multi-component model including lensed-LCDM, dust, synchrotron and a possible contribution from inflationary gravitational waves (as parametrized by the tensor-to-scalar ratio $r$), using priors on the frequency spectral behaviors of dust and synchrotron emission from previous analyses of WMAP and Planck data in other regions of the sky. This analysis yields an upper limit $r_{0.05}<0.09$ at 95% confidence, which is robust to variations explored in analysis and priors. Combining these $B$-mode results with the (more model-dependent) constraints from Planck analysis of CMB temperature plus BAO and other data, yields a combined limit $r_{0.05}<0.07$ at 95% confidence. These are the strongest constraints to date on inflationary gravitational waves.

BICEP2 / Keck Array VI: Improved Constraints On Cosmology and Foregrounds When Adding 95 GHz Data From Keck Array

Abstract

We present results from an analysis of all data taken by the BICEP2 & Keck Array CMB polarization experiments up to and including the 2014 observing season. This includes the first Keck Array observations at 95 GHz. The maps reach a depth of 50 nK deg in Stokes and in the 150 GHz band and 127 nK deg in the 95 GHz band. We take auto- and cross-spectra between these maps and publicly available maps from WMAP and Planck at frequencies from 23 GHz to 353 GHz. An excess over lensed-LCDM is detected at modest significance in the 95x150 spectrum, and is consistent with the dust contribution expected from our previous work. No significant evidence for synchrotron emission is found in spectra such as 23x95, or for correlation between the dust and synchrotron sky patterns in spectra such as 23x353. We take the likelihood of all the spectra for a multi-component model including lensed-LCDM, dust, synchrotron and a possible contribution from inflationary gravitational waves (as parametrized by the tensor-to-scalar ratio ), using priors on the frequency spectral behaviors of dust and synchrotron emission from previous analyses of WMAP and Planck data in other regions of the sky. This analysis yields an upper limit at 95% confidence, which is robust to variations explored in analysis and priors. Combining these -mode results with the (more model-dependent) constraints from Planck analysis of CMB temperature plus BAO and other data, yields a combined limit at 95% confidence. These are the strongest constraints to date on inflationary gravitational waves.

Paper Structure

This paper contains 8 sections, 18 figures, 1 table.

Table of Contents

  1. Maps
  2. Keck Array 95 GHz Power Spectra and Internal Consistency Tests
  3. 150 GHz Spectral Stability
  4. Additional Spectra
  5. Likelihood Variation and Validation
  6. Likelihood Evolution
  7. Likelihood Variation
  8. Likelihood Validation

Figures (18)

  • Figure 1: Deep $Q$ maps at 95 & 150 GHz using all BICEP2/ Keck data through the end of the 2014 observing season---we refer to these maps as BK14. Noise levels are 127 nK$\,$deg (left) and 50 nK$\,$deg (right). Both maps show a high signal-to-noise pattern dominated by E-mode polarization; the 95 GHz maps appear smoother because of the larger beam size.
  • Figure 2: $EE$ and $BB$ auto- and cross-spectra between 95 & 150 GHz using all BICEP2/ Keck data up to and including that taken during the 2014 observing season---we refer to these spectra as BK14. (For clarity the sets of points are offset horizontally.) The solid black curves show the lensed-$\Lambda$CDM theory spectra. The error bars are the standard deviations of the lensed-$\Lambda$CDM+noise simulations and hence contain no sample variance on any additional signal component. The $\chi^2$ and $\chi$ (sum of deviations) against lensed-$\Lambda$CDM for the lowest five bandpowers are given, and can be compared to their expectation value/standard-deviation of 5/3.1 and 0/2.2 respectively The dashed lines show a lensed-$\Lambda$CDM+dust model derived from our previous BKP analysis.
  • Figure 3: Selected $BB$ cross-spectra between the BK14 maps at 95 (red) & 150 GHz (green) and the external maps of WMAP and Planck. The quantity plotted is $\ell \left( \ell + 1 \right) C_l / 2 \pi$ ($\mu$K$^2$), and the error bars are the standard deviations of the lensed-$\Lambda$CDM+noise simulations. The solid black curves show the lensed-$\Lambda$CDM theory spectrum and the $\chi^2$ and $\chi$ versus this model are shown. W$_{23}\times$BK14$_{95}$ and W$_{23}\times$BK14$_{150}$ are both mildly elevated showing weak evidence for synchrotron but P$_{30}\times$BK14$_{150}$ has stronger nominal anticorrelation. We see modest evidence for detection of dust emission in BK14$_{150}\times$P$_{217}$ and strong evidence in BK14$_{150}\times$P$_{353}$. The dashed lines show a lensed-$\Lambda$CDM+dust model derived from our previous BKP analysis.
  • Figure 4: Results of a multicomponent multi-spectral likelihood analysis of BICEP2/ Keck+external data. The red faint curves are the primary result from the previous BKP paper (the black curves from Fig. 6 of that paper). The bold black curves are the new baseline BK14 results. Differences between these analyses include adding synchrotron to the model, including additional external frequency bands from WMAP & Planck, and adding Keck Array data taken during the 2014 observing season at 95 & 150 GHz. We see that the peak position of the tensor/scalar ratio curve $r$ shifts down slightly and the upper limit tightens to $r_{0.05}<0.09$ at 95% confidence. The parameters $A_\mathrm{d}$ and $A_\mathrm{sync}$ are the amplitudes of the dust and synchrotron $B$-mode power spectra, where $\beta$ and $\alpha$ are the respective frequency and spatial spectral indices. The correlation coefficient between the dust and synchrotron patterns is $\epsilon$. In the $\beta$, $\alpha$ and $\epsilon$ panels the dashed red lines show the priors placed on these parameters (either Gaussian or uniform).
  • Figure 5: Likelihood results on $r$ for several intermediate steps between the BKP (previous) and BK14 (current) analyses. See text for details.
  • ...and 13 more figures