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

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

arXiv · 2602.11681

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

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

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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 $\alpha = -1.324^{+0.072}_{-0.074}$. We incorporate a curvature parameter $\delta$ 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 $3\sigma$ confidence level.

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Lei Sun, Xiao-Lei Meng, Xin Wang, Hu Zhan, Anahita Alavi, Nicha Leethochawalit, Brian Siana, Hang Zhou, Shengzhe Wang, Shamuhawu Hailanhazi. 2026-02-12. The faint end of the UV luminosity function at $0.4 < z < 0.7$ from the Hubble Frontier Fields. https://arxiv.org/abs/2602.11681

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