Influence of ∼7 keV sterile neutrino dark matter on the process of reionization

Abstract

Abstract. Recent reports of a weak unidentified emission line at ∼3.5 keV found in spectra of several matter-dominated objects may give a clue to resolve the long-standing problem of dark matter. One of the best physically motivated particle candidate able to produce such an extra line is sterile neutrino with the mass of ∼7 keV. Previous works show that sterile neutrino dark matter with parameters consistent with the new line measurement modestly affects structure formation compared to conventional cold dark matter scenario. In this work, we concentrate for the first time on contribution of the sterile neutrino dark matter able to produce the observed line at ∼3.5 keV, to the process of reionization. By incorporating dark matter power spectra for ∼7 keV sterile neutrinos into extended semi-analytical 'bubble' model of reionization we obtain that such sterile neutrino dark matter would produce significantly sharper reionization compared to widely used cold dark matter models, impossible to 'imitate' within the cold dark matter scenario under any reasonable choice of our model parameters, and would have a clear tendency of lowering both the redshift of reionization and the electron scattering optical depth (although the difference is still below the existing model uncertainties). Further dedicated studies of reionization (such as 21 cm measurements or studies of kinetic Sunyaev-Zeldovich effect) will thus be essential for reconstruction of particle candidate responsible the ∼3.5 keV line.

Dark matter model favoured by reionization data: 7 keV sterile neutrino versus cold dark matter

“…According to Sec. 3.3 of Barkana & Loeb (2001), hydrogen cooling becomes efficient for T vir 10 4 K. In this paper, we fixed T vir = 10 4 K similarly to Barkana & Loeb (2001); Furlanetto et al (2004); Yue & Chen (2012); Rudakovskyi & Iakubovskyi (2016). Finally, we assume the ionizing efficiency and the recombination efficiency to vary within the very wide ranges ζ = 5−100 (which is in agreement with ) 1 and ξ = 0−9 (according to Iliev et al (2005)) 2 ).…”

“…For these models, one obtained Q II = 0.60 +0.19 −0.21 and 0.54 +0.21 −0.21 at redshift z = 7.1, and Q II = 0.79 +0.19 −0.17 and 0.72 +0.23 −0.20 at redshift z = 7.5. The observed difference between these two models is about 0.3σ, and the expected difference between the CDM and sterile neutrino models is even less (see Discussion in Rudakovskyi & Iakubovskyi 2016), so we constructed the average value Q II = 0.56 ± 0.23 for z = 7.1, and Q II = 0.75±0.23 for z = 7.5 (by incorporating the error bars from both models) to be the same for CDM and sterile neutrino dark matter.…”

“…To calculate the ionized volume-filling fraction Q II (z) and the CMB electron scattering optical depth τ es , we used the extension of the 'bubble model' (Furlanetto et al 2004;Yue & Chen 2012) of reionization, see Rudakovskyi & Iakubovskyi (2016) for more detailed description. We assume that the main source of ionizing photons are stars formed in galaxy-size dark matter haloes, while smaller haloes (starting from the Jeans mass) work as 'recombination sinks' of ionizing radiation due to their higher hydrogen density.…”

Fractional Dark Matter decay: cosmological imprints and observational constraints

“…We thus expect that future precise kSZ surveys will constrain the properties of DCDM tightly. Definitely, if the cold DM decays into electromagnetic particles, many other cosmological observables will provide additional information for detecting/constraining the decaying DM, such as the reionization history (e.g., [90,107,108]), and, the existence of DCDM can Figure 17: Comparison of the constraints on the parameters ω ini c , f dcdm and Γ dcdm for the short-lived DCDM model, from the SPT measurement of the kSZ signal at = 3000 and from the "Planck2015+BAO+RSD" dataset. The solid lines denote the SPT-measured 1σ upper limit of 4.2µK 2 and 2σ upper limit of 4.9µK 2 , and the dashed lines are the "Planck2015+BAO+RSD"-induced contours from Fig.…”

Self-interacting sterile neutrino dark matter: The heavy-mediator case

“…Other constraints could be drawn on the plot, including upper bounds on m s from Milky Way satellite counts or Lyman-α observations, which in the Dodelson-Widrow scenario severely limit the open window in Fig. 1 [14][15][16][17][18][19][20][21][22][23][24]. But the final spectrum-on which these constraints depend-is parameter-dependent in the selfinteracting model and generally differs from either a Dodelson-Widrow spectrum or a thermal one.…”