Observational Evidences for the Existence of 17.4 keV Decaying Degenerate Sterile Neutrinos Near the Galactic Center

Abstract

We show that the existence of a degenerate halo of sterile neutrinos with rest mass of 17.4 keV near the Galactic center (GC) can account for both the excess 8.7 keV emission observed by the Suzaku mission and the power needed (10⁴⁰ erg s^-1) to maintain the high temperature of the hot gas (8 keV) near the GC. The required decay rate and mixing angle of the sterile neutrinos are Γ >= 10^-19 s^-1 and sin²2θ ~ 10^-3, respectively. These values are consistent with a low reheating temperature, which suppresses the production of sterile neutrinos, resulting in a small sterile neutrino density parameter (Ω _s < 10^-8). They are also allowed by X-ray background data and the isotope experiment. The large mixing angle leads to the exciting possibility that a sterile-active neutrino oscillation may be visible in near future experiments.