2016ApJ...818...89S

The newly established luminosity functions (LFs) of high-z galaxies at 4 ≲ z ≲ 10 can provide a stringent check on dark matter models that aim to explain the core properties of dwarf galaxies. The cores of dwarf spheroidal galaxies are understood to be too large to be accounted for by free streaming of warm dark matter without overly suppressing the formation of such galaxies. Here we demonstrate with cosmological simulations that wave dark matter, ψDM, appropriate for light bosons such as axions, does not suffer from this problem, given a boson mass of m_{psi= > 1.2 x 10^–22 eV (2σ). In this case, the halo mass function is suppressed below ∼ 10¹⁰ M_☉ at a level that is consistent with the high-z LFs, while simultaneously generating the kiloparsec-scale cores in dwarf galaxies arising from the solitonic ground state in ψDM. We demonstrate that the reionization history in this scenario is consistent with the Thomson optical depth recently reported by Planck, assuming a reasonable ionizing photon production rate. We predict that the LF should turn over slowly around an intrinsic ultraviolet luminosity of M_UV ≳ -16 at z ≳ 4. We also show that for galaxies magnified > 10x in the Hubble Frontier Fields, ψDM predicts an order of magnitude fewer detections than cold dark matter at z ≳ 10 down to M_UV ∼ -15, allowing us to distinguish between these very different interpretations for the observed coldness of dark matter.