A fresh look at linear cosmological constraints on a decaying Dark Matter component

By V. Poulin, P. Serpico, Julien Lesgourgues. 2016

222 citations recorded by the source corpus.

We consider a cosmological model in which a fraction fdcdm of the Dark Matter (DM) is allowed to decay in an invisible relativistic component, and compute the resulting constraints on both the decay width (or inverse lifetime) Γdcdm and fdcdm from purely gravitational arguments. We report a full derivation of the Boltzmann hierarchy, correcting a mistake in previous literature, and compute the impact of the decay—as a function of the lifetime—on the CMB and matter power spectra. From CMB only, we obtain that no more than 3.8% of the DM could have decayed in the time between recombination and today (all bounds quoted at 95% CL). We also comment on the important application of this bound to the case where primordial black holes constitute DM, a scenario notoriously difficult to constrain. For lifetimes longer than the age of the Universe, the bounds can be cast as fdcdmΓdcdm < 6.3×10−3 Gyr−1. For the first time, we also checked that degeneracies with massive neutrinos are broken when information from the large scale structure is used. Even secondary effects like CMB lensing suffice to this purpose. Decaying DM models have been invoked to solve a possible tension between low redshift astronomical measurements of σ8 and Ωm and the ones inferred by Planck. We reassess this claim finding that with the most recent BAO, HST and σ8 data extracted from the CFHT survey, the tension is only slightly reduced despite the two additional free parameters. Nonetheless, the existing tension explains why the bound on fdcdmΓdcdm loosens to fdcdmΓdcdm < 15.9×10−3 Gyr−1 when including such additional data. The bound however improves to fdcdmΓdcdm < 5.9 ×10−3 Gyr−1 if only data consistent with the CMB are included. This highlights the importance of establishing whether the tension is due to real physical effects or unaccounted systematics, for settling the reach of achievable constraints on decaying DM.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7111a95062ba78f6c259f3f7a72e455182cf0040

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. K. Kohri
2. T. Terada
3. B. Carr
4. T. Nakama
5. V. Vaskonen
6. H. Veermae
7. M. Raidal
8. Keisuke Inomata

In Nuclear and High Energy Physics

1. T. Terada
2. K. Kohri
3. T. Nakama
4. H. Veermae
5. M. Raidal
6. Keisuke Inomata
7. Tongyan Lin
8. V. Vaskonen

Citations in the corpus

• Alleviating the H0 and σ8 anomalies with a decaying dark matter model (2019, unknown): “roduces a cut-off-like feature in the matter power spectrum at small scales, keeping the power in scales ˘8Mpc the same as in CDM. For decaying dark matter with a constant time-independent decay rate [27,36], the constraints are driven by the change to the late ISW effect on the large-scale CMB data”
• Dark matter models and direct detection (2019, background): “This, too, can be constrained with the matter power spectrum [4, 5].”
• Gravitational waves induced by scalar perturbations during a gradual transition from an early matter era to the radiation era (2019, methodology): “ as a dust-like uid throughout this paper. { 5 { where the subscripts \m&quot; and \r&quot; represent matter and radiation, respectively. The equations for perturbations in Fourier space are given by [36] 0 m = m + 3 0 a ; (3.3) 0 m = H m + k 2 ; (3.4) 0 r = 4 3 ( r 3 0) + a ˆ m ˆ r ( m r + ) ; (”
• Gravitational waves from primordial black hole mergers (2017, background): “8% of DM may have decayed into dark radiation [27].”