The role of self-interacting right-handed neutrinos in galactic structure

Abstract

Abstract. It has been shown previously that the DM in galactic halos can be explained by a self-gravitating system of massive keV fermions ('inos') in thermodynamic equilibrium, and predicted the existence of a denser quantum core of inos towards the center of galaxies. In this article we show that the inclusion of self-interactions among the inos, modeled within a relativistic mean-field-theory approach, allows the quantum core to become massive and compact enough to explain the dynamics of the S-cluster stars closest to the Milky Way's galactic center. The application of this model to other galaxies such as large elliptical harboring massive central dark objects of ∼ 10 9 M ⊙ is also investigated. We identify these interacting inos with sterile right-handed neutrinos pertaining to minimal extensions of the Standard Model, and calculate the corresponding total cross-section σ within an electroweak-like formalism to be compared with other observationally inferred cross-section estimates. The coincidence of an ino mass range of few tens of keV derived here only from the galactic structure, with the range obtained independently from other astrophysical and cosmological constraints, points towards an important role of the right-handed neutrinos in the cosmic structure.

Small-Scale Cosmology “Crisis” and Self-Interacting Right-Handed Neutrino Warm Dark Matter

“…Notice however that no attempt is made in the above discussions to analyze microscopic interactions that may lead to phenomenologically acceptable SIDM cross sections. A concrete example of SIDM [14,15] is based on a class of self-interacting models of massive right-EPJ Web of Conferences 182, 01001 (2018) https://doi.org/10.1051/epjconf/201818201001 ICNFP 2017 handed neutrinos that exist in minimal extensions of the standard model. It is important to stress that, in contrast to standard N-body simulations, the semi-analytical approach proposed in Refs.…”

“…It is important to stress that, in contrast to standard N-body simulations, the semi-analytical approach proposed in Refs. [14,15] includes in addition to gravity, other important physical ingredients, such as quantum (fermionic) physics and thermodynamics. Interestingly, such a scenario, in which the DM fermion (right-handed neutrino) has a mass of a order a few tens of keV, implies a universal and novel DM density profile (compact core -dilute halo), with important implications for the very central and halo regions of galaxies 2 .…”

“…[14] is based on minimal (non supersymmetric) extensions of the Standard Model with sterile neutrinos. In such models, the DM may be provided by the lightest N R 1 of three right-handed neutrino species that, e.g.…”

“…The Lagrangian of the right-handed neutrino sector, including gravity, reads (in units = c = 1, which we use throughout here) [14] …”

“…These issues present serious challenges to the ΛCDM paradigm that call urgently for explanations. Various proposals for a resolution of these problems have been proposed, some of which go beyond the ΛCDM paradigm, including either self interactions among the dark matter particles [13][14][15], due to novel kind of forces exclusive to the dark sector, or studying viscous properties of DM [16], which have important back reaction effects on the standard cosmological equations.…”