Predictions for the abundance of high-redshift galaxies in a fuzzy dark matter universe

Abstract

During the last decades, rapid progress has been made in measurements of the rest-frame ultraviolet (UV) luminosity function (LF) for high-redshift galaxies (z ≥ 6). The faint-end of the galaxy LF at these redshifts provides powerful constraints on different dark matter (DM) models that suppress small-scale structure formation. In this work we perform full hydrodynamical cosmological simulations of galaxy formation using an alternative DM model composed of extremely light bosonic particles (m ∼ 10−22 eV), also known as fuzzy dark matter (FDM), and examine the predictions for the galaxy stellar mass function and LF at z ≥ 6 for a range of FDM masses. We find that for FDM models with bosonic mass m = 5 × 10−22 eV, the number density of galaxies with stellar mass M∗ ∼ 107M☉ is suppressed by ∼ 40 per cent at z = 9, ∼ 20 per cent at z = 5, and the UV LFs within magnitude range of −16 < MUV < −14 is suppressed by ∼ 60 per cent at z = 9, ∼ 20 per cent at z = 5 comparing to the cold dark matter counterpart simulation. Comparing our predictions with current measurements of the faint-end LFs (−18 ≤ MUV ≤ −14), we find that FDM models with m22 < 5 × 10−22 are ruled out at 3σ confidence level. We expect that future LF measurements by James Webb Space Telescope, which will extend down to MUV ∼ −13 for z ≲ 10, with a survey volume that is comparable to the Hubble Ultra Deep Field would have the capability to constrain FDM models to m ≳ 10−21 eV.