Testing CMB Anomalies in E-mode Polarization with Current and Future Data
Rui Shi, Tobias A. Marriage, John W. Appel, Charles L. Bennett, David T. Chuss, Joseph Cleary, Joseph Eimer, Sumit Dahal, Rahul Datta, Francisco Espinoza, Yunyang Li, Nathan J. Miller, Carolina Núñez, Ivan L. Padilla, Matthew A. Petroff, Deniz A. N. Valle, Edward J. Wollack, Zhilei Xu
In this paper, we explore the power of the cosmic microwave background (CMB) polarization (E-mode) data to corroborate four potential anomalies in CMB temperature data: the lack of large angular-scale correlations, the alignment of the quadrupole and octupole (Q-O), the point-parity asymmetry, and the hemispherical power asymmetry. We use CMB simulations with noise representative of three experiments — the Planck satellite, the Cosmology Large Angular Scale Surveyor (CLASS), and the LiteBIRD satellite — to test how current and future data constrain the anomalies. We find the correlation coefficients ρ between temperature and E-mode estimators to be less than 0.1, except for the point-parity asymmetry (ρ=0.17 for cosmic-variance-limited simulations), confirming that E-modes provide a check on the anomalies that is largely independent of temperature data. Compared to Planck component-separated CMB data (SMICA), the putative LiteBIRD survey would reduce errors on E-mode anomaly estimators by factors of ∼3 for hemispherical power asymmetry and point-parity asymmetry, and by ∼26 for lack of large-scale correlation. The improvement in Q-O alignment is not obvious due to large cosmic variance, but we found the ability to pin down the estimator value will be improved by a factor ≳100. Improvements with CLASS are intermediate to these.

A Projected Estimate of the Reionization Optical Depth Using the CLASS Experiment’s Sample-Variance Limited E-Mode Measurement
Watts, Duncan J.; Wang, Bingjie et al.
We analyze simulated maps of the Cosmology Large Angular Scale Surveyor (CLASS) experiment and recover a nearly cosmic variance limited estimate of the reionization optical depth τ. We use a power spectrum-based likelihood to simultaneously clean foregrounds and estimate cosmological parameters in multipole space. Using software specifically designed to constrain τ, the amplitude of scalar fluctuations A s , and the tensor-to-scalar ratio r, we demonstrate that the CLASS experiment will be able to estimate τ within a factor of two of the cosmic variance limit allowed by full-sky cosmic microwave background polarization measurements. Additionally, we discuss the role of CLASS’s τ constraint in conjunction with gravitational lensing of the CMB on obtaining a ≳4σ measurement of the sum of the neutrino masses.
arXiv:1801.01481

Recovery of Large Angular Scale CMB Polarization for Instruments Employing Variable-delay Polarization Modulators
Nathan J. Miller; David T. Chuss; Tobias A. Marriage; Edward J. Wollack et al.
Variable-delay Polarization Modulators (VPMs) are currently being implemented in experiments designed to measure the polarization of the cosmic microwave background on large angular scales because of their capability for providing rapid, front-end polarization modulation and control over systematic errors. Despite the advantages provided by the VPM, it is important to identify and mitigate any time-varying effects that leak into the synchronously modulated component of the signal. In this paper, the effect of emission from a 300 K VPM on the system performance is considered and addressed. Though instrument design can greatly reduce the influence of modulated VPM emission, some residual modulated signal is expected. VPM emission is treated in the presence of rotational misalignments and temperature variation. Simulations of time-ordered data are used to evaluate the effect of these residual errors on the power spectrum. The analysis and modeling in this paper guides experimentalists on the critical aspects of observations using VPMs as front-end modulators. By implementing the characterizations and controls as described, front-end VPM modulation can be very powerful for mitigating 1/f noise in large angular scale polarimetric surveys. None of the systematic errors studied fundamentally limit the detection and characterization of B-modes on large scales for a tensor-to-scalar ratio of r = 0.01. Indeed, r < 0.01 is achievable with commensurately improved characterizations and controls.
arXiv1509.04628 [astro-ph.CO] Submitted to ApJ (2015).

The Cosmology Large Angular Scale Surveyor
Harrington, Kathleen; Marriage, Tobias et al.
The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array designed to characterize relic primordial gravitational waves from in ation and the optical depth to reionization through a measurement of the polarized cosmic microwave background (CMB) on the largest angular scales. The frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high atmospheric emission and span the minimum of the polarized Galactic foregrounds: synchrotron emission at lower frequencies and dust emission at higher frequencies. Low-noise transition edge sensor detectors and a rapid front-end polarization modulator provide a unique combination of high sensitivity, stability, and control of systematics. The CLASS site, at 5200 m in the Chilean Atacama desert, allows for daily mapping of up to 70% of the sky and enables the characterization of CMB polarization at the largest angular scales. Using this combination of a broad frequency range, large sky coverage, control over systematics, and high sensitivity, CLASS will observe the reionization and recombination peaks of the CMB E- and B-mode power spectra. CLASS will make a cosmic variance limited measurement of the optical depth to reionization and will measure or place upper limits on the tensor-to-scalar ratio, r, down to a level of 0.01 (95% C.L.).
Proceedings of the SPIE, Volume 9914, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, pp. 99141K (2016).

Measuring the Largest Angular Scale CMB B-mode Polarization with Galactic Foregrounds on a Cut Sky
Duncan J. Watts, David Larson, Tobias A. Marriage et al.
We consider the effectiveness of foreground cleaning in the recovery of Cosmic Microwave Background (CMB) polarization sourced by gravitational waves for tensor-to-scalar ratios in the range 0<r<0.1. Using the planned survey area, frequency bands, and sensitivity of the Cosmology Large Angular Scale Surveyor (CLASS), we simulate maps of Stokes Q and U parameters at 40, 90, 150, and 220 GHz, including realistic models of the CMB, diffuse Galactic thermal dust and synchrotron foregrounds, and Gaussian white noise. We use linear combinations (LCs) of the simulated multifrequency data to obtain maximum likelihood estimates of r, the relative scalar amplitude s, and LC coefficients. We find that for 10,000 simulations of a CLASS-like experiment using only measurements of the reionization peak (ℓ≤23), there is a 95% C.L. upper limit of r<0.017 in the case of no primordial gravitational waves. For simulations with r=0.01, we recover at 68% C.L. r=0.012+0.011−0.006. The reionization peak corresponds to a fraction of the multipole moments probed by CLASS, and simulations including 30≤ℓ≤100 further improve our upper limits to r<0.008 at 95% C.L. (r=0.01+0.004−0.004 for primordial gravitational waves with r=0.01). In addition to decreasing the current upper bound on r by an order of magnitude, these foreground-cleaned low multipole data will achieve a cosmic variance limited measurement of the E-mode polarization’s reionization peak.
Astrophysical Journal, Vol. 814, 103 (2015).

CLASS: the cosmology large angular scale surveyor
Essinger-Hileman, Thomas et al.
The Cosmology Large Angular Scale Surveyor (CLASS) is an experiment to measure the signature of a gravitationalwave background from inflation in the polarization of the cosmic microwave background (CMB). CLASS is a multi-frequency array of four telescopes operating from a high-altitude site in the Atacama Desert in Chile. CLASS will survey 70% of the sky in four frequency bands centered at 38, 93, 148, and 217 GHz, which are chosen to straddle the Galactic-foreground minimum while avoiding strong atmospheric emission lines. This broad frequency coverage ensures that CLASS can distinguish Galactic emission from the CMB. The sky fraction of the CLASS survey will allow the full shape of the primordial B-mode power spectrum to be characterized, including the signal from reionization at low ɺ. Its unique combination of large sky coverage, control of systematic errors, and high sensitivity will allow CLASS to measure or place upper limits on the tensor-to-scalar ratio at a level of r = 0:01 and make a cosmic-variance-limited measurement of the optical depth to the surface of last scattering, Ƭ .
Proceedings of the SPIE, Volume 9153, id. 91531I 23 pp. (2014).