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Register a new userConstraining light sterile neutrino mass with the BICEP2/Keck Array 2014 B-mode polarization data
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Added by
Shouvik Roy Choudhury
Publication date
2018
fields
Physics
and research's language is
English
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We explore the thermal light sterile neutrino situation from cosmological perspective in the $Lambda textrm{CDM} + r_{0.05} + N_{textrm{eff}} + m^{textrm{eff}}_{textrm{s}}$ model using combinations of latest data sets available. Here, $r_{0.05}$ is the tensor-to-scalar ratio at the pivot scale of $k_*=0.05h$ Mpc$^{-1}$, $N_{textrm{eff}}$ is the effective number of relativistic species during recombination, and $m^{textrm{eff}}_{textrm{s}}$ is the effective mass of the sterile neutrino. Among Cosmic Microwave Background (CMB) datasets, we use Planck 2015 temperature and low-$l$ ($l <$ 30) polarization data and the latest data release on the B-mode polarization up to and including 2014 from the BICEP2/Keck collaboration (BK14). We also use the latest BAO data from SDSS-III BOSS DR12, MGS, and 6dFS; and a Gaussian prior (HST) on the Hubble constant ($H_0 = 73.24 pm 1.74$ km/sec/Mpc) from direct measurements. We find that inclusion of BK14 data makes the constraints on the effective mass of sterile neutrino ($m^{textrm{eff}}_{textrm{s}}$) slightly stronger by preferring higher $sigma_8$ values. The bound of $m^{textrm{eff}}_{textrm{s}} <$ 0.46 eV (95% C.L.) is found for the combination of Planck 2015, BAO and BK14 datasets, whereas the bound is $m^{textrm{eff}}_{textrm{s}} <$ 0.53 eV (95% C.L.) without the BK14 data. Our most aggressive bound of $m^{textrm{eff}}_{textrm{s}} <$ 0.28 eV (95% C.L.) is obtained with Planck 2015, HST and BK14. However, the HST prior also leads to very high $N_{textrm{eff}}$ which might be in conflict with bounds from BBN. Our analysis indicates that fully thermalized sterile neutrinos with mass $sim 1$ eV are slightly more disfavoured with the inclusion of BK14 data. It also seems to make the agreement between Planck 2015 and CFHTLenS (weak gravitational lensing data) worse due to the higher $sigma_8$ values (abstract abridged).
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We present measurements of polarization lensing using the 150 GHz maps which include all data taken by the BICEP2 & Keck Array CMB polarization experiments up to and including the 2014 observing season (BK14). Despite their modest angular resolution ($sim 0.5^circ$), the excellent sensitivity ($sim 3mu$K-arcmin) of these maps makes it possible to directly reconstruct the lensing potential using only information at larger angular scales ($ellleq 700$). From the auto-spectrum of the reconstructed potential we measure an amplitude of the spectrum to be $A^{phiphi}_{rm L}=1.15pm 0.36$ (Planck $Lambda$CDM prediction corresponds to $A^{phiphi}_{rm L}=1$), and reject the no-lensing hypothesis at 5.8$sigma$, which is the highest significance achieved to date using an EB lensing estimator. Taking the cross-spectrum of the reconstructed potential with the Planck 2015 lensing map yields $A^{phiphi}_{rm L}=1.13pm 0.20$. These direct measurements of $A^{phiphi}_{rm L}$ are consistent with the $Lambda$CDM cosmology, and with that derived from the previously reported BK14 B-mode auto-spectrum ($A^{rm BB}_{rm L}=1.20pm 0.17$). We perform a series of null tests and consistency checks to show that these results are robust against systematics and are insensitive to analysis choices. These results unambiguously demonstrate that the B-modes previously reported by BICEP / Keck at intermediate angular scales ($150lesssimelllesssim 350$) are dominated by gravitational lensing. The good agreement between the lensing amplitudes obtained from the lensing reconstruction and B-mode spectrum starts to place constraints on any alternative cosmological sources of B-modes at these angular scales.
The Keck Array is a system of cosmic microwave background (CMB) polarimeters, each similar to the BICEP2 experiment. In this paper we report results from the 2012 and 2013 observing seasons, during which the Keck Array consisted of five receivers all operating in the same (150 GHz) frequency band and observing field as BICEP2. We again find an excess of B-mode power over the lensed-$Lambda$CDM expectation of $> 5 sigma$ in the range $30 < ell < 150$ and confirm that this is not due to systematics using jackknife tests and simulations based on detailed calibration measurements. In map difference and spectral difference tests these new data are shown to be consistent with BICEP2. Finally, we combine the maps from the two experiments to produce final Q and U maps which have a depth of 57 nK deg (3.4 $mu$K arcmin) over an effective area of 400 deg$^2$ for an equivalent survey weight of 250,000 $mu$K$^{-2}$. The final BB band powers have noise uncertainty a factor of 2.3 times better than the previous results, and a significance of detection of excess power of $> 6sigma$.
A linear polarization field on the sphere can be uniquely decomposed into an E-mode and a B-mode component. These two components are analytically defined in terms of spin-2 spherical harmonics. Maps that contain filtered modes on a partial sky can also be decomposed into E-mode and B-mode components. However, the lack of full sky information prevents orthogonally separating these components using spherical harmonics. In this paper, we present a technique for decomposing an incomplete map into E and B-mode components using E and B eigenmodes of the pixel covariance in the observed map. This method is found to orthogonally define E and B in the presence of both partial sky coverage and spatial filtering. This method has been applied to the BICEP2 and the Keck Array maps and results in reducing E to B leakage from LCDM E-modes to a level corresponding to a tensor-to-scalar ratio of $r<1times10^{-4}$.
We study models in which neutrino masses are generated dynamically at cosmologically late times. Our study is purely phenomenological and parameterized in terms of three effective parameters characterizing the redshift of mass generation, the width of the transition region, and the present day neutrino mass. We also study the possibility that neutrinos become strongly self-interacting at the time where the mass is generated. We find that in a number of cases, models with large present day neutrino masses are allowed by current CMB, BAO and supernova data. The increase in the allowed mass range makes it possible that a non-zero neutrino mass could be measured in direct detection experiments such as KATRIN. Intriguingly we also find that there are allowed models in which neutrinos become strongly self-interacting around the epoch of recombination.
We report the results of a joint analysis of data from BICEP2/Keck Array and Planck. BICEP2 and Keck Array have observed the same approximately 400 deg$^2$ patch of sky centered on RA 0h, Dec. $-57.5deg$. The combined maps reach a depth of 57 nK deg in Stokes $Q$ and $U$ in a band centered at 150 GHz. Planck has observed the full sky in polarization at seven frequencies from 30 to 353 GHz, but much less deeply in any given region (1.2 $mu$K deg in $Q$ and $U$ at 143 GHz). We detect 150$times$353 cross-correlation in $B$-modes at high significance. We fit the single- and cross-frequency power spectra at frequencies $geq 150$ GHz to a lensed-$Lambda$CDM model that includes dust and a possible contribution from inflationary gravitational waves (as parameterized by the tensor-to-scalar ratio $r$), using a prior on the frequency spectral behavior of polarized dust emission from previous planck analysis of other regions of the sky. We find strong evidence for dust and no statistically significant evidence for tensor modes. We probe various model variations and extensions, including adding a synchrotron component in combination with lower frequency data, and find that these make little difference to the $r$ constraint. Finally we present an alternative analysis which is similar to a map-based cleaning of the dust contribution, and show that this gives similar constraints. The final result is expressed as a likelihood curve for $r$, and yields an upper limit $r_{0.05}<0.12$ at 95% confidence. Marginalizing over dust and $r$, lensing $B$-modes are detected at $7.0,sigma$ significance.
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