Observational tests of wave VS. particle dark matter predictions for early galaxy formation in the hubble frontier fields

Abstract

Acting as powerful gravitational lenses, the strong lensing galaxy clusters of the deep Hubble Frontier Fields (HFF) program permit access to lower-luminosity galaxies lying at higher redshifts than hitherto possible. I analyzed the HFF to measure the volume density of Lyman-break galaxies at z > 4.75 by identifying a complete and reliable sample up to z ~10. A marked deficit of such galaxies was uncovered in the highly magnified regions of the clusters relative to their outskirts, implying that the magnification of the sky area dominates over additional faint galaxies magnified above the flux limit. This negative magnification bias is consistent with a slow rollover at the faint end of the UV luminosity function (LF), and indicates a preference for Bose-Einstein condensate dark matter with a light boson mass of m_B ~10^-22 eV over standard cold dark matter. It should be emphasized that, compared to standard direct reconstruction of the LF, the magnification bias test places more leverage on the contribution of galaxies at the faint end of the LF, which are accessible only in the strongly lensed regions. In addition, a distinctive downward transition in galaxy number density was detected at z > 8, which may be linked to the relatively late reionization reported by Planck. The results suggests that JWST will likely peer into an "abyss" with next to nothing detected in deep NIR imaging at z > 10.