z ∼ 2–9 Galaxies Magnified by the Hubble Frontier Field Clusters. II. Luminosity Functions and Constraints on a Faint-end Turnover

We present new determinations of the rest-UV luminosity functions (LFs) at z=2-9 to extremely low luminosities (>-14 mag) from a sample >2500 lensed galaxies found behind HFF clusters. For first time, we faint-end slope results samples that are fully consistent with blank-field over redshift range z=2-9, while reaching much lower than possible studies. Combining deep large allows us set tight constraints on alpha UV LFs and its evolution. find smooth flattening in -2.28+/-0.10 (z=9) -1.53+/-0.03 (z=2) cosmic time (d(alpha)/dz=-0.11+/-0.01), dark matter halo buildup. utilize these measurements evolution density rho(UV) brightward -13 mag z~9 z~2. Accounting for SFR densities faint implied by our LF results, unobscured star formation dominates z>~4, obscured dominant thereafter. Having shown can quantify accurately samples, also apparent curvature shape through parameter delta. The delta strongly rule out presence turn-over -13.1 z~3, -14.3 z~6, -15.5 all other redshifts between