On the faint-end of the high-$z$ galaxy luminosity function

Bin Yue, Andrea Ferrara, Yidong Xu

Published 2016-04-05Version 1

Recent measurement of the Luminosity Function (LF) of galaxies in the Epoch of Reionization (EoR, redshift $z>6$) indicates a very steep increase of the number density of low-mass galaxies populating the LF faint-end. As star formation in such systems can be easily quenched by radiative feedback effects, a turn-off is expected at some faint magnitude. Using a physically-motivated analytical model, we quantify reionization feedback effects on the LF. If reionization feedback is neglected, the power-law Schechter parameterization characterizing the faint-end of the LF remains valid up to $M_{\rm UV}\sim -9$. If (strong) feedback is included, the LF drops above $M_{\rm UV} \sim -15$, slightly below the detection limit of current surveys at $z\sim5$. However, the LF may rise again at higher $M_{\rm UV}$ as a result of the interplay between reionization topology and photo-evaporation physics. Moreover, we find that the stellar age -- magnitude relation might be used as a probe of feedback strength as well: in models with stronger reionization feedback, stars in galaxies with $-13 \lsim M_{\rm UV} \lsim -8$ are typically older. Other suggested constraints on feedback can come from galaxy number counts data, particularly those exploiting gravitational lensing magnification.