Decaying dark matter and the tension in σ8

Kari Enqvist; Seshadri Nadathur; Toyokazu Sekiguchi; Tomo Takahashi

doi:10.1088/1475-7516/2015/09/067

Decaying dark matter and the tension in σ₈

Kari Enqvist, Seshadri Nadathur, Toyokazu Sekiguchi, Tomo Takahashi

Institute of Cosmology & Gravitation

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Abstract

We consider decaying dark matter (DDM) as a resolution to the possible tension between cosmic microwave background (CMB) and weak lensing (WL) based determinations of the amplitude of matter fluctuations, σ₈. We perform N-body simulations in a model where dark matter decays into dark radiation and develop an accurate fitting formula for the non-linear matter power spectrum, which enables us to test the DDM model by the combined measurements of CMB, WL and the baryon acoustic oscillation (BAO). We employ a Markov chain Monte Carlo analysis to examine the overlap of posterior distributions of the cosmological parameters, comparing CMB alone with WL+BAO. We find an overlap that
is significantly larger in the DDM model than in the standard CDM model. This may be hinting at DDM, although current data is not constraining enough to unambiguously favour a non-zero dark matter decay rate Γ. From the combined CMB+WL data, we obtain a lower
bound Γ⁻¹ ≥ 97 Gyr at 95 % C.L, which is less tight than the constraint from CMB alone.

Original language	English
Article number	067
Number of pages	18
Journal	Journal of Cosmology and Astroparticle Physics
Volume	2015
Issue number	9
DOIs	https://doi.org/10.1088/1475-7516/2015/09/067
Publication status	Published - 29 Sept 2015

Keywords

cosmological simulations
particle physics - cosmology connection
cosmological parameters from LSS
weak gravitational lensing

Access to Document

10.1088/1475-7516/2015/09/067

1505.05511v2
This Accepted Manuscript is available for reuse under a CC BY-NC-ND licence after the 12 month embargo period provided that all the terms and conditions of the licence are adhered to.
Accepted author manuscript (Post-print), 875 KBLicence: CC BY-NC-ND

Cite this

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title = "Decaying dark matter and the tension in σ8",

abstract = "We consider decaying dark matter (DDM) as a resolution to the possible tension between cosmic microwave background (CMB) and weak lensing (WL) based determinations of the amplitude of matter fluctuations, σ8. We perform N-body simulations in a model where dark matter decays into dark radiation and develop an accurate fitting formula for the non-linear matter power spectrum, which enables us to test the DDM model by the combined measurements of CMB, WL and the baryon acoustic oscillation (BAO). We employ a Markov chain Monte Carlo analysis to examine the overlap of posterior distributions of the cosmological parameters, comparing CMB alone with WL+BAO. We find an overlap thatis significantly larger in the DDM model than in the standard CDM model. This may be hinting at DDM, although current data is not constraining enough to unambiguously favour a non-zero dark matter decay rate Γ. From the combined CMB+WL data, we obtain a lowerbound Γ−1 ≥ 97 Gyr at 95 % C.L, which is less tight than the constraint from CMB alone.",

keywords = "cosmological simulations, particle physics - cosmology connection, cosmological parameters from LSS, weak gravitational lensing",

author = "Kari Enqvist and Seshadri Nadathur and Toyokazu Sekiguchi and Tomo Takahashi",

note = "21 pages, 5 figures; accepted for publication in JCAP",

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T1 - Decaying dark matter and the tension in σ8

AU - Enqvist, Kari

AU - Nadathur, Seshadri

AU - Sekiguchi, Toyokazu

AU - Takahashi, Tomo

N1 - 21 pages, 5 figures; accepted for publication in JCAP

PY - 2015/9/29

Y1 - 2015/9/29

N2 - We consider decaying dark matter (DDM) as a resolution to the possible tension between cosmic microwave background (CMB) and weak lensing (WL) based determinations of the amplitude of matter fluctuations, σ8. We perform N-body simulations in a model where dark matter decays into dark radiation and develop an accurate fitting formula for the non-linear matter power spectrum, which enables us to test the DDM model by the combined measurements of CMB, WL and the baryon acoustic oscillation (BAO). We employ a Markov chain Monte Carlo analysis to examine the overlap of posterior distributions of the cosmological parameters, comparing CMB alone with WL+BAO. We find an overlap thatis significantly larger in the DDM model than in the standard CDM model. This may be hinting at DDM, although current data is not constraining enough to unambiguously favour a non-zero dark matter decay rate Γ. From the combined CMB+WL data, we obtain a lowerbound Γ−1 ≥ 97 Gyr at 95 % C.L, which is less tight than the constraint from CMB alone.

AB - We consider decaying dark matter (DDM) as a resolution to the possible tension between cosmic microwave background (CMB) and weak lensing (WL) based determinations of the amplitude of matter fluctuations, σ8. We perform N-body simulations in a model where dark matter decays into dark radiation and develop an accurate fitting formula for the non-linear matter power spectrum, which enables us to test the DDM model by the combined measurements of CMB, WL and the baryon acoustic oscillation (BAO). We employ a Markov chain Monte Carlo analysis to examine the overlap of posterior distributions of the cosmological parameters, comparing CMB alone with WL+BAO. We find an overlap thatis significantly larger in the DDM model than in the standard CDM model. This may be hinting at DDM, although current data is not constraining enough to unambiguously favour a non-zero dark matter decay rate Γ. From the combined CMB+WL data, we obtain a lowerbound Γ−1 ≥ 97 Gyr at 95 % C.L, which is less tight than the constraint from CMB alone.

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KW - cosmological parameters from LSS

KW - weak gravitational lensing

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