  We investigate a novel scenario involving asymmetric keV-range dark matter
(DM) in the form of right-handed (sterile) neutrinos. Based on the Fermi-Dirac
distribution, we demonstrate that asymmetric fermionic DM forms a Fermi
degenerate gas, making it potentially colder than symmetric fermionic DM. This
setup simultaneously accounts for the Universe's baryon asymmetry through tiny
Yukawa interactions with Standard Model leptons and the Higgs field, and the
homochirality of amino acids via decay into circularly polarized photons. This
scenario can be investigated through soft X-ray searches conducted by current
and upcoming space missions. The helical X-rays is a smoking-gun signal of our
scenario. Additionally, we propose a new mechanism to suppress DM thermal
production by introducing a light modulus, which may also benefit cosmology
involving generic right-handed neutrinos with large mixing.
