Unlocking the synergy between CMB spectral distortions and anisotropies

Journal of Cosmology and Astroparticle Physics, vol. 2021, pp. 050

Abstract

Abstract Measurements of the cosmic microwave background (CMB) spectral distortions (SDs) will open a new window on the very early universe, providing new information complementary to that gathered from CMB temperature and polarization anisotropies. In this paper, we study their synergy as a function of the characteristics of the considered experiments. In particular, we examine a wide range of sensitivities for possible SD measurements, spanning from FIRAS up to noise levels 1000 times better than PIXIE, and study their constraining power when combined with current or future CMB anisotropy experiments such as Planck or LiteBIRD plus CMB-S4. We consider a number of different cosmological models such as the ΛCDM, as well as its extensions with the running of the scalar spectral index, the decay or the annihilation of dark matter (DM) particles. While upcoming CMB anisotropy experiments will be able to decrease the uncertainties on inflationary parameters such as As and ns by about a factor 2 in the ΛCDM case, we find that an SD experiment 100 times more sensitive than PIXIE (comparable to the proposed Super-PIXIE satellite) could potentially further contribute to constrain these parameters. This is even more significant in the case of the running of the scalar spectral index. Furthermore, as expected, constraints on DM particles decaying at redshifts probed by SDs will improve by orders of magnitude even with an experiment 10 times worse than PIXIE as compared to CMB anisotropies or Big Bang Nucleosynthesis bounds. On the contrary, DM annihilation constraints will not significantly improve over CMB anisotropy measurements. Finally, we forecast the constraints obtainable with sensitivities achievable either from the ground or from a balloon.

Authors 7

1. Hao Fu corresponding

   University of Southampton

   Affiliation as printed

   Department of Physics and Astronomy, University of Southampton, Highfield Campus, SO17 1BJ, U.K

2. Matteo Lucca corresponding

   Université Libre de Bruxelles

   Affiliation as printed

   Service de Physique Théorique, Université Libre de Bruxelles, C.P. 225, B-1050 Brussels, Belgium

3. S. Galli corresponding

   Centre National de la Recherche Scientifique · Institut d'Astrophysique de Paris · Sorbonne Université

   Affiliation as printed

   Sorbonne Université, CNRS, UMR 7095, Institut d'Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France

4. E. S. Battistelli

   Sapienza University of Rome

   Affiliation as printed

   Physics department, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185, Rome, Italy

5. Deanna C. Hooper

   Université Libre de Bruxelles

   Affiliation as printed

   Service de Physique Théorique, Université Libre de Bruxelles, C.P. 225, B-1050 Brussels, Belgium

6. Julien Lesgourgues Aachen Institute for Theoretical Particle Physics and Cosmology

   RWTH Aachen University

   Affiliation as printed

   Institute for Theoretical Particle Physics and Cosmology (TTK), RWTH Aachen University, D-52056 Aachen, Germany

7. Nils Schöneberg Aachen Institute for Theoretical Particle Physics and Cosmology

   RWTH Aachen University

   Affiliation as printed

   Institute for Theoretical Particle Physics and Cosmology (TTK), RWTH Aachen University, D-52056 Aachen, Germany