The Faint End of the UV Luminosity Function at 0.4 < z < 0.7 from the Hubble Frontier Fields

March 2026 • 2026ApJ..1000...25S

Authors • Sun, Lei • Meng, Xiao-Lei • Wang, Xin • Zhan, Hu • Alavi, Anahita • Leethochawalit, Nicha • Siana, Brian • Zhou, Hang • Wang, Shengzhe • Hailanhazi, Shamuhawu

Abstract • By extending the Hubble Frontier Fields (HFF) observations to the F225W band using the Hubble Space Telescope (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 we present a corresponding catalog for the A2744 field, which is the most data-rich HFF cluster field. Combining deep near-UV imaging and the high magnification from the 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 A2744 F225W catalog. Using a sample defined by a 50% completeness cut and applying maximum likelihood estimation, we derive the best-fit Schechter parameters for the UV LF at z ∼ 0.55 down to M_UV < ─13.5 mag, including a faint-end slope of α=─1.324−0.074+0.072 . We incorporate a curvature parameter δ in the parameter estimation to account for a possible turnover at the faint end of the UV LF, leveraging the exceedingly low luminosities probed by our sample. Our results rule out a turnover brighter than M_UV = ─15.5 at the 3σ confidence level.

Links

• ELECTR https://doi.org/10.3847/1538-4357/ae4593
• PREPRINT http://arxiv.org/abs/2602.11681