Constraining sterile neutrino dark matter with phase space density observations

Abstract

We apply phase-space density considerations to obtain lower bounds on the mass of sterile neutrino as dark matter candidate. The bounds are different for non-resonant production, resonant production in the presence of lepton asymmetry and production in decays of heavier particles. In the former case our bound is comparable to, but independent of the Lyman-α bound, and together with X-ray upper limit it disfavors non-resonantly produced sterile neutrino dark matter. An interesting feature of the latter case is that warm dark matter may be composed of heavy particles.One candidate for dark matter particle is sterile neutrino. In the first place, the existence of sterile neutrinos is favored by the discovery of neutrino oscillations. Furthermore, by adding sterile neutrinos to the Standard Model and fine-tuning parameters in the neutrino sector, one is able to explain all known facts in high energy physics and cosmology without introducing any other new fields except for inflaton [1,2,3].The sterile neutrino dark matter should satisfy cosmological and astrophysical constraints. These constraints depend on the way sterile neutrinos are produced in the early Universe. There are several mechanisms capable of generating sterile neutrino in right amount. These include the non-resonant production via active-sterile neutrino mixing [4], resonant production in the presence of lepton asymmetry [5,6], production in decays of heavier particles (see, e.g., Refs. [3,7] in the context of νMSM model) and production in scattering (see e.g., Ref. [8]). In this paper we consider astrophysical constraints on sterile neutrino dark matter generated by the non-resonant production mechanism. We comment on other production mechanisms towards the end of this paper.Sterile neutrino is coupled to active ones through mixing only. Thus, the mixing angle controls the decay rate of sterile neutrino into active neutrino and photons. These decays in galactic halos would produce X-ray emission lines, which are severely constrained [9] by 1

Constraints on the presence of a 3.5 keV dark matter emission line fromChandraobservations of the Galactic centre

“…The underlying particle model, called the νMSM, is described in detail in a number of papers (Asaka et al , 2007Shaposhnikov & Tkachev 2006;Shaposhnikov 2008;Gorbunov & Shaposhnikov 2007;Laine & Shaposhnikov 2008;Canetti et al 2013a), and recent reviews (Boyarsky et al 2009b;Kusenko 2009;Drewes 2013). Additionally, the sterile neutrino may have interesting effects on a range of astrophysical objects, for example as an explanation for pulsar kick velocities, facilitating core collapse supernova explosions, affecting early star formation, reionization and structure formation, or assisting inflation (Kusenko & Segrè 1997;Kusenko et al 2008;Hansen & Haiman 2004;Fryer & Kusenko 2006;Hidaka & Fuller 2006;Biermann & Kusenko 2006;Mapelli et al 2006;Shaposhnikov & Tkachev 2006;Bezrukov & Shaposhnikov 2008;Petraki & Kusenko 2008;Petraki 2008;Boyanovsky 2008;Gorbunov et al 2008). The lightest of the three sterile neutrinos provides an attractive dark matter candidate.…”

Cluster X-ray line at $$3.5~\mathrm{keV}$$ 3.5 keV from axion-like dark matter

“…Including the previous various analyses of Lyman-α forest data [15] and the phase space densities derived from the dwarf galaxies of the Milky way [16][17][18], leads to the bound on the freestreaming length ranging between 0.12 Mpc λ c fs 0.60 Mpc. The comoving free-streaming length of the axion produced from the decay of a mother particle X is computed as…”

Decaying dark matter in the Draco dwarf galaxy

“…The underlying particle model, called the νMSM, is described in detail in a number of papers Asaka et al 2007;Shaposhnikov 2007;Gorbunov & Shaposhnikov 2007;Laine & Shaposhnikov 2008;Shaposhnikov 2008), and also in the excellent review by Boyarsky et al (2009b). Additionally, the sterile neutrino may have interesting effects on a range of different astrophysical objects, including as an explanation for pulsar kick velocities, facilitating core collapse supernova explosions, affecting early star formation, reionization and structure formation, or assisting inflation (Kusenko & Segrè 1997;Fryer & Kusenko 2006;Hidaka & Fuller 2006;Hansen & Haiman 2004;Mapelli et al 2006;Bezrukov & Shaposhnikov 2008;Shaposhnikov & Tkachev 2006;Kusenko et al 2008;Petraki & Kusenko 2008;Petraki 2008;Boyanovsky 2008;Gorbunov et al 2008) (see Boyarsky et al 2009b, for an extensive list of references).…”