The faint end of the UV luminosity function at $0.4<z<0.7$ from the Hubble Frontier Fields

Abstract

By extending the Hubble Frontier Fields (HFF) observations to the F225W band using HST WFC3/UVIS, we measure the rest-frame UV luminosity function (LF) of galaxies at $0.4<z<0.7$, pushing into the low-luminosity galaxy regime. In this first paper of a series, we describe the HST Cycle-27 GO-15940 F225W observations and data reduction, and present a corresponding catalog for the Abell 2744 field, which is the most data-rich HFF cluster field. Combining deep Near-UV imaging and the high magnification from strong gravitational lensing of the foreground cluster, we identify 152 faint galaxies with $-19.5<M_{UV}<-12.1$ at $0.4<z<0.7$ through hybrid photometric-spectroscopic redshift selection from the Abell 2744 F225W catalog. Using a sample defined by a $50\%$ completeness cut and applying the maximum likelihood estimation, we derive the best-fit Schechter parameters for the UV LF at $z\sim 0.55$ down to $M_{\text{UV}}<-13.5$ mag, including a faint-end slope of $\hat{I}\pm =-1.324_{-0.074}^{+0.072}$. We incorporate a curvature parameter $\hat{I}´$ in parameter estimation to account for a possible turn-over at the faint end of the UV LF, leveraging the exceedingly low luminosities probed by our sample. Our results rule out a turn-over brighter than $M_{UV}=-15.5$ at the $3\ddot{I}ƒ$ confidence level.

16 pages, 10 figures. Accepted for publication in ApJ