Full-shape BOSS constraints on dark matter interacting with dark radiation and lifting the S8 tension

In this work we derive constraints on interacting dark matter-dark radiation models from a full-shape analysis of BOSS-DR12 galaxy clustering data, combined with Planck legacy cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements. We consider a set of models parameterized within the effective theory of structure formation (ETHOS), quantifying the lifting of the S8 tension in view of KiDS weak-lensing results. The most favorable scenarios point to a fraction f similar to 10 - 100% of interacting dark matter as well as a dark radiation temperature that is smaller by a factor xi similar to 0.1 - 0.15 compared to the CMB, leading to a reduction of the tension to the similar to 1 sigma level. The temperature dependence of the interaction rate favored by relaxing the S8 tension is realized for a weakly coupled unbroken non-Abelian SU(N) gauge interaction in the dark sector. To map our results onto this SU(N) model, we compute higher-order corrections due to Debye screening. We find a lower bound alpha d -gd2/(47r ) >= 10-8(10-9) for dark matter mass 1000(1) GeV for relaxing the S8 tension, consistent with upper bounds from galaxy ellipticities and compatible with self-interactions relevant for small-scale structure formation.

Automated summary

We analyze BOSS-DR12 galaxy clustering data along with Planck legacy cosmic microwave background and baryon acoustic oscillation measurements to derive constraints on interacting dark matter-dark radiation models. The results suggest a fraction of interacting dark matter ranging from 10% to 100% and a dark radiation temperature smaller than the CMB by a factor of 0.1 to 0.15, reducing the tension to about 1 sigma level. The favored interaction rate is realized through a weakly coupled unbroken non-Abelian SU(N) gauge interaction in the dark sector.