Steep Faint-end Slopes of Galaxy Mass and Luminosity Functions at z>=6 and the Implications for Reionisation

Understand

We present the results of a numerical study comparing photometric and physical properties of simulated z=6-9 galaxies to the observations taken by the WFC3 instrument aboard the Hubble Space Telescope.

• Using cosmological hydrodynamical simulations we find good agreement with observations in color-color space at all studied redshifts.
• We also find good agreement between observations and our Schechter luminosity function fit in the observable range, Muv<= -18, provided that a moderate dust extinction effect exists for massive galaxies.
• However beyond what currently can be observed, simulations predict a very large number of low-mass galaxies and evolving steep faint-end slopes from alpha_L = -2.15 at z=6 to alpha_L = -2.64 at z=9, with a dependence of |alpha_L| \propto (1+z)^0.59.