We revisit sterile neutrino production enabled by nonstandard interactions (NSIs) among active neutrinos mediated by new bosons. We focus on vector mediators, including neutrinophilic, gauged $L_{\mu }-L_{\tau }$, and $B-L$ realizations, that modify in-medium dispersion and scattering, thereby altering the active-sterile conversion history. Building on a novel production framework with NSI thermal potentials and collision integrals, we compute nonthermal phase-space distributions across sterile neutrino mixing and NSI parameters and map each point to an equivalent thermal warm dark matter particle mass $m_{\mathrm{th}}$ via linear theory transfer function fitting with the cosmological structure formation Boltzmann solver. This enables a direct reinterpretation of state-of-the-art structure formation limits from Milky Way satellites, strong lensing, and the Lyman-$\alpha$ forest. These limits, in conjunction with x-ray decay searches, as well as results from a wide variety of particle physics experiments allow for a more complete examination of these models. We find that these vector-mediated models are ruled out when the full combination of current constraints, listed above, are taken into account. NSI scalar-mediated models and models with low reheating temperatures remain viable.

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• Cosmology
• Electromagnetic radiation astronomy
• Evolution of the Universe
• Extensions of fermion sector
• Neutrino interactions
• Neutrino mixing
• Particle dark matter
• Particle interactions
• Particle mixing & oscillations
• Particle production
• X ray astronomy
• Heavy neutrinos
• Neutrinos
• Sterile neutrinos