Identifying frequency decorrelated dust residuals in B-mode maps by exploiting the spectral capability of bolometric interferometry
arXiv (Cornell University)(2023)
Abstract
Astrophysical polarized foregrounds represent the most critical challenge in
Cosmic Microwave Background (CMB) B-mode experiments. Multi-frequency
observations can be used to constrain astrophysical foregrounds to isolate the
CMB contribution. However, recent observations indicate that foreground
emission may be more complex than anticipated.
We investigate how the increased spectral resolution provided by band
splitting in Bolometric Interferometry (BI) through a technique called spectral
imaging can help control the foreground contamination in the case of
unaccounted Galactic dust frequency decorrelation along the line-of-sight.
We focus on the next generation ground-based CMB experiment CMB-S4, and
compare its anticipated sensitivities, frequency and sky coverage with a
hypothetical version of the same experiment based on BI. We perform a
Monte-Carlo analysis based on parametric component separation methods (FGBuster
and Commander) and compute the likelihood on the recovered tensor-to-scalar
ratio.
The main result of this analysis is that spectral imaging allows us to detect
systematic uncertainties on r from frequency decorrelation when this effect is
not accounted for in component separation. Conversely, an imager would detect a
biased value of r and would be unable to spot the presence of a systematic
effect. We find a similar result in the reconstruction of the dust spectral
index, where we show that with BI we can measure more precisely the dust
spectral index also when frequency decorrelation is present.
The in-band frequency resolution provided by BI allows us to identify dust
LOS frequency decorrelation residuals where an imager of similar performance
would fail. This opens the prospect to exploit this potential in the context of
future CMB polarization experiments that will be challenged by complex
foregrounds in their quest for B-modes detection.
MoreTranslated text
Key words
dust residuals,spectral capability,b-mode
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