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We show that Fermi repulsion can lead to cored density profiles in dwarfgalaxies for sub-keV fermionic dark matter. We treat the dark matter as aquasi-degenerate self-gravitating Fermi gas and calculate its density profileassuming hydrostatic equilibrium. We find that suitable dwarf galaxy cores oflarger than 130 pc can be achieved for fermion dark matter with mass in therange 70 eV - 400 eV. While in conventional dark matter scenarios, such sub-keVthermal dark matter would be excluded by free streaming bounds, the constraintsare ameliorated in models with dark matter at lower temperature thanconventional thermal scenarios, such as the Flooded Dark Matter model that wehave previously considered. Modifying the arguments of Tremaine and Gunn wederive a conservative lower bound on the mass of fermionic dark matter of 70 eVand a stronger lower bound from Lyman-$\alpha$ clouds of about 470 eV, leadingto slightly smaller cores than have been observed. We comment on this resultand how the tension is relaxed in dark matter scenarios with non-thermalmomentum distributions.

Cores in Dwarf Galaxies from Fermi Repulsion