Spectral distortions anisotropies

Constraints on primordial non-Gaussianity

Primordial non-Gaussianity can source μ-distortion anisotropies that are correlated with the large-scale temperature and polarization signals of the cosmic microwave background. A measurement of μT and μE correlations can therefore be used to constrain it on wavelengths of perturbations not directly probed by the standard CMB anisotropies. We have run thorough forecasts for a variety of state-of-the-art and upcoming surveys, and developed a pipeline based on needlet constrained internal linear combination which we have applied to Planck data. Doing so, we have reconstructed for the first time a temperature-free Planck μ map, and we have set the first constraints on local non-Gaussianity which use the whole multipole information and polarization data.
References:
AR, M. Liguori, N. Bartolo, and M. Shiraishi, Primordial non-Gaussianity with μ-type and y-type spectral distortions: exploiting Cosmic Microwave Background polarization and dealing with secondary sources, JCAP 09 (2017) 042, [arXiv:1707.04759]
M. Remazeilles, AR, and J. Chluba, Leverage on small-scale primordial non-Gaussianity through cross-correlations between CMB E-mode and μ-distortion anisotropies, Mon. Not. Roy. Astron. Soc. 512 (2022), no. 1 455–470, [arXiv:2110.14664]
A. Rotti, AR, and J. Chluba, Non-Gaussianity constraints with anisotropic μ distortion measurements from Planck, Mon. Not. Roy. Astron. Soc. 515 (2022), no. 4 5847–5868, [arXiv:2205.15971]

Evolution of anisotropic spectral distortions

Inhomogeneous spectral distortions of the cosmic microwave background, which arise naturally from non-homogeneous energy injections, evolve in a perturbed universe obeying a high-dimensional system of partial differential equation, which stems from the fact that the spectral evolution has to be explicitly taken into account. We show that by expanding the photon spectrum in a basis generated by the boost operator the complexity of the calculation reduces drastically, and the problem can be described by a common hierarchy of Boltzmann equations. These can be integrated using the procedure commonly adopted to calculate temperature fluctuation, which enabled us to calculate the spectral distortion angular power spectra. As a case study, we have forecasted the detectability of instantaneous energy injection and of a decaying particle scenario.
References:
J. Chluba, T. Kite, and AR, Spectro-spatial evolution of the CMB. Part I. Discretisation of the thermalisation Green’s function, JCAP 11 (2023) 026, [arXiv:2210.09327]
J. Chluba, AR, and T. Kite, Spectro-spatial evolution of the CMB. Part II. Generalised Boltzmann hierarchy, JCAP 11 (2023) 027, [arXiv:2210.15308]
T. Kite, AR, and J. Chluba, Spectro-spatial evolution of the CMB. Part III. Transfer functions, power spectra and Fisher forecasts, JCAP 11 (2023) 028, [arXiv:2212.02817]