Testing distance duality with CMB anisotropies

Syksy Rasanen; Jussi Valiviita; Ville Kosonen

doi:10.1088/1475-7516/2016/04/050

paper

Testing distance duality with CMB anisotropies

arXiv:1512.05346 · doi:10.1088/1475-7516/2016/04/050

Abstract

We constrain deviations of the form $T \propto (1 + z)^{1 + ε}$ from the standard redshift-temperature relation, corresponding to modifying distance duality as $D_{L} = (1 + z)^{2 (1 + ε)} D_{A}$ . We consider a consistent model, in which both the background and perturbation equations are changed. For this purpose, we introduce a species of dark radiation particles to which photon energy density is transferred, and assume $ε \geq 0$ . The Planck 2015 release high multipole temperature plus low multipole data give the limit $ε < 4.5 \times 1 0^{- 3}$ at 95% C.L. The main obstacle to improving this CMB-only result is strong degeneracy between $ε$ and the physical matter densities $ω_{b}$ and $ω_{c}$ . A constraint on deuterium abundance improves the limit to $ε < 1.8 \times 1 0^{- 3}$ . Adding the Planck high-multipole CMB polarisation and BAO data leads to a small improvement; with this maximal dataset we obtain $ε < 1.3 \times 1 0^{- 3}$ . This dataset constrains the present dark radiation energy density to at most 12% of the total photon plus dark radiation density. Finally, we discuss the degeneracy between dark radiation and the effective number of relativistic species $N_{eff}$ , and consider the impact of dark radiation perturbations and allowing $ε < 0$ on the results.

22 pages, 5 figures, 2 tables, JCAP format. v2. Added the epsilon<0 case, one plot, clarifications, and 3 references. Published version

Testing distance duality with CMB anisotropies

Abstract

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