Constraining $\mu$ and $y$ distortions in the Cosmic Microwave Background with COBE/FIRAS Data

TL;DR

This paper introduces a new method using COBE/FIRAS data and blackbody radiation inversion to tightly constrain the spectral distortions in the CMB, specifically the $$ and y parameters.

Contribution

It applies the BRI technique to derive improved constraints on CMB spectral distortions, incorporating both $$ and y distortions simultaneously.

Findings

Derived $$ and y distortion parameters with high confidence.

Results are consistent with previous measurements but with tighter bounds.

Provides a novel analytical framework for CMB spectral distortion analysis.

Abstract

This paper presents a novel approach to constrain the $\mu$- and y- distortions in the Cosmic Microwave Background (CMB) using the COBE/FIRAS data. The analysis draws from the concept of blackbody radiation inversion (BRI), a mathematical technique typically used to determine the temperature distribution from a radiated power spectrum. We study the deviations from the ideal blackbody spectrum or the spectral distortions by incorporating first a non-zero chemical potential $\mu$ via the Bose-Einstein distribution and then the Compton parameter $y$ while keeping the monopole temperature constant. We infer the results as probability distribution functions on these distortions. Finally, we derive $\mu = (8.913 \pm 0.736) \times 10^{-5}$ and $y = (1.532 \pm 0.092) \times 10^{-5}$ at a $68\%$ confidence interval. The results are consistent with prior values and provide tighter constraints on the CMB spectral distortion and synergies of the primordial Universe.