69 research outputs found
Mitigating Cosmic Microwave Background Shadow Degradation of Tensor-to-scalar Ratio Measurements through Map-based Studies
It has been pointed out that the spurious Cosmic Microwave Background (CMB)
B-mode polarization signals caused by the absorption of the CMB monopole
component due to the Galactic interstellar matter, called the CMB shadow,
degrade the accuracy of detecting the CMB B-mode polarization signals imprinted
by primordial gravitational waves. We have made a realistic estimation using
simulated sky maps of how the CMB shadow affects forthcoming high-precision CMB
B-mode experiments for the first time. The Delta-map method, an internal
template method taking into account the first-order spatial variation of
foregrounds' spectral parameters, is applied as a foreground removal method. We
show that if the CMB shadow effects are not taken into account in the
foreground removal process, future observations would lead to the false
detection of the CMB B-mode polarization signals originating from primordial
gravitational waves. We also show that the effect of the CMB shadow can be
mitigated by our revised Delta-map method to target the CMB B-mode polarization
signals at the level of tensor-to-scalar ratio r=0.001.Comment: 9 pages, 2 figure
Constraints on axion-like polarization oscillations in the cosmic microwave background with POLARBEAR
Very light pseudoscalar fields, often referred to as axions, are compelling
dark matter candidates and can potentially be detected through their coupling
to the electromagnetic field. Recently a novel detection technique using the
cosmic microwave background (CMB) was proposed, which relies on the fact that
the axion field oscillates at a frequency equal to its mass in appropriate
units, leading to a time-dependent birefringence. For appropriate oscillation
periods this allows the axion field at the telescope to be detected via the
induced sinusoidal oscillation of the CMB linear polarization. We search for
this effect in two years of POLARBEAR data. We do not detect a signal, and
place a median upper limit of on the sinusoid amplitude
for oscillation frequencies between and
, which corresponds to axion masses between and . Under the
assumptions that 1) the axion constitutes all the dark matter and 2) the axion
field amplitude is a Rayleigh-distributed stochastic variable, this translates
to a limit on the axion-photon coupling .Comment: 17 pages, 5 figures, 2 tables. Published in Physical Review
Making maps of cosmic microwave background polarization for B-mode studies: The POLARBEAR example
Analysis of cosmic microwave background (CMB) datasets typically requires some filtering of the raw time-ordered data. For instance, in the context of ground-based observations, filtering is frequently used to minimize the impact of low frequency noise, atmospheric contributions and/or scan synchronous signals on the resulting maps. In this work we have explicitly constructed a general filtering operator, which can unambiguously remove any set of unwanted modes in the data, and then amend the map-making procedure in order to incorporate and correct for it. We show that such an approach is mathematically equivalent to the solution of a problem in which the sky signal and unwanted modes are estimated simultaneously and the latter are marginalized over. We investigated the conditions under which this amended map-making procedure can render an unbiased estimate of the sky signal in realistic circumstances. We then discuss the potential implications of these observations on the choice of map-making and power spectrum estimation approaches in the context of B-mode polarization studies. Specifically, we have studied the effects of time-domain filtering on the noise correlation structure in the map domain, as well as impact it may haveon the performance of the popular pseudo-spectrum estimators. We conclude that although maps produced by the proposed estimators arguably provide the most faithful representation of the sky possible given the data, they may not straightforwardly lead to the best constraints on the power spectra of the underlying sky signal and special care may need to be taken to ensure this is the case. By contrast, simplified map-makers which do not explicitly correct for time-domain filtering, but leave it to subsequent steps in the data analysis, may perform equally well and be easier and faster to implement. We focused on polarization-sensitive measurements targeting the B-mode component of the CMB signal and apply the proposed methods to realistic simulations based on characteristics of an actual CMB polarization experiment, POLARBEAR. Our analysis and conclusions are however more generally applicable. \ua9 ESO, 2017
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
CMB-S4---the next-generation ground-based cosmic microwave background (CMB)
experiment---is set to significantly advance the sensitivity of CMB
measurements and enhance our understanding of the origin and evolution of the
Universe, from the highest energies at the dawn of time through the growth of
structure to the present day. Among the science cases pursued with CMB-S4, the
quest for detecting primordial gravitational waves is a central driver of the
experimental design. This work details the development of a forecasting
framework that includes a power-spectrum-based semi-analytic projection tool,
targeted explicitly towards optimizing constraints on the tensor-to-scalar
ratio, , in the presence of Galactic foregrounds and gravitational lensing
of the CMB. This framework is unique in its direct use of information from the
achieved performance of current Stage 2--3 CMB experiments to robustly forecast
the science reach of upcoming CMB-polarization endeavors. The methodology
allows for rapid iteration over experimental configurations and offers a
flexible way to optimize the design of future experiments given a desired
scientific goal. To form a closed-loop process, we couple this semi-analytic
tool with map-based validation studies, which allow for the injection of
additional complexity and verification of our forecasts with several
independent analysis methods. We document multiple rounds of forecasts for
CMB-S4 using this process and the resulting establishment of the current
reference design of the primordial gravitational-wave component of the Stage-4
experiment, optimized to achieve our science goals of detecting primordial
gravitational waves for at greater than , or, in the
absence of a detection, of reaching an upper limit of at CL.Comment: 24 pages, 8 figures, 9 tables, submitted to ApJ. arXiv admin note:
text overlap with arXiv:1907.0447
CMB-S4: Forecasting Constraints on Primordial Gravitational Waves
Abstract: CMB-S4âthe next-generation ground-based cosmic microwave background (CMB) experimentâis set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic projection tool, targeted explicitly toward optimizing constraints on the tensor-to-scalar ratio, r, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2â3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments, given a desired scientific goal. To form a closed-loop process, we couple this semianalytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for r > 0.003 at greater than 5Ï, or in the absence of a detection, of reaching an upper limit of r < 0.001 at 95% CL
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