Abstract
The characterization of the spectral energy distribution (SED) of dust emission has become a critical issue in the quest for primordialB-modes. The dust SED is often approximated by a modified black body (MBB) emission law but the extent to which this is accurate is unclear. This paper addresses this question, expanding the dust SED at the power spectrum level. The expansion is performed by means of moments around the MBB law, related to derivatives with respect to the dust spectral index. We present the mathematical formalism and apply it to simulations andPlancktotal intensity data, from 143 to 857 GHz, because no polarized data are yet available that provide the required sensitivity to perform this analysis. With simulations, we demonstrate the ability of high-order moments to account for spatial variations in MBB parameters. Neglecting these moments leads to poor fits and a bias in the recovered dust spectral index. We identify the main moments that are required to fit thePlanckdata. The comparison with simulations helps us to disentangle the respective contributions from dust and the cosmic infrared background to the high-order moments, but the simulations give an insufficient description of the actualPlanckdata. Extending our model to cosmic microwave backgroundB-mode analyses within a simplified framework, we find that ignoring the dust SED distortions, or trying to model them with a single decorrelation parameter, could lead to biases that are larger than the targeted sensitivity for the next generation of CMBB-mode experiments.
Highlights
The precise characterization of the properties of the polarized dust emission from our Galaxy is a crucial issue in the quest for the primordial B-modes of the cosmic microwave background (CMB)
The Planck data have shown that the spectral energy distribution (SED) of the dust emission for total intensity and polarization can be fitted by a modified black body (MBB) law
We present the formalism to describe the spectral departures from the MBB associated with derivatives with respect to the dust spectral index β, which is known to vary across the sky (e.g., Planck Collaboration X 2016)
Summary
The precise characterization of the properties of the polarized dust emission from our Galaxy is a crucial issue in the quest for the primordial B-modes of the cosmic microwave background (CMB). If measured, this faint cosmological signal imprinted by the primordial gravitational wave background would be evidence of the inflation epoch and could be used to quantify its energy scale, providing a rigorous test of fundamental physics far beyond the reach of accelerators (Polnarev 1985; Kamionkowski et al 1997; Seljak & Zaldarriaga 1997). XXII 2015; Gandilo et al 2016; Ashton et al 2018; Guillet et al 2018; Shariff et al 2019; Planck Collaboration XI 2020)
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