A joint analysis of Planck and BICEP2 B modes including dust polarization uncertainty

By M. Mortonson, Uros Seljak. 2014

197 citations recorded by the source corpus.

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 start by assuming nothing about the dust polarization except for the power spectrum shape, which we take to be ClBB,dust ∝ l-2.42. 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 agrees with expectations for this field based on both HI column density and Planck polarization measurements at 353 GHz in the BICEP2 field. Including the latter constraint on the dust spectrum amplitude in our analysis improves the limit further to r < 0.09, placing strong constraints on theories of inflation (e.g., models with r>0.14 are excluded with 99.5% confidence). 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 0r= gives Δ χ2 < 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 more accurate 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 dust maps are not processed through the BICEP2 pipeline, inducing sampling variance noise.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/c1d245a301cd08aba25a235dce87f49560811d9e

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In Astronomy and Astrophysics

1. S. Allen
2. A. Mantz
3. H. Ebeling
4. David Rapetti
5. Andrey V. Kravtsov
6. A. V. D. Linden
7. D. Applegate
8. P. Kelly

In Instrumentation

1. S. Allen
2. A. Mantz
3. David Rapetti
4. H. Ebeling
5. A. V. D. Linden
6. D. Applegate
7. P. Kelly
8. David L. Burke

Citations in the corpus

• Higgs inflation with loop corrections in the Palatini formulation (2017, background): “2 by the BICEP2 telescope (the signal was since shown to be due to foregrounds [115]).”
• Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation (2014, background): “Evidence for the predicted inflationary gravitational waves may have been discovered (BICEP2, [16]), although the signal may also be due to the Galactic dust foreground [17, 18].”
• Higgs inflation from Standard Model criticality (2014, background): “It has been pointed out that the BICEP2 result may become consistent with r = 0 because the foreground effect can be sizable [102, 103].”
• Inflationary Cosmology in Modified Gravity Theories (2015, unknown): “, References [58–62].”
• Planck2015 results (2015, unknown): “XXX 2016; Mortonson & Seljak 2014; Flauger et al. 2014).”
• Causality constraints on corrections to the graviton three-point coupling (2014, background): “At this time, there are alternative explanations for this signal [77, 78], so we might have to wait till the dust settles.”
• The Quest for B Modes from Inflationary Gravitational Waves (2015, background): “The potentially extraordinary implications of this measurement attracted considerable scrutiny, and arguments were made that uncertainties in the various dust templates may have been underestimated (Mortonson & Seljak 2014; Flauger, Hill & Spergel 2014).”
• Weighing the giants – IV. Cosmology and neutrino mass (2014, background): “…∑ mν somewhat, because the remaining data prefer a smaller value of r than BICEP2 measures (e.g. Story et al. 2013; see also e.g. Flauger et al. 2014; Mortonson & Seljak 2014 and references therein). c© 2014 RAS, MNRAS 000, 1–22 tensor spectral index to zero as in the BICEP2 analysis (BICEP2…”
• Cosmic Discordance: Are Planck CMB and CFHTLenS weak lensing measurements out of tune? (2014, background): “…team (BICEP2 Collaboration 2014) have reported a ∼ 5σ detection of the B-mode CMB polarisation signal expected from primordial gravity waves, although whether its origin ? niall.maccrann@gmail.com is cosmological rather than galactic has been disputed (Mortonson & Seljak 2014; Flauger et al. 2014).”