2015ApJ...815...18I

We searched for z ≳ 7 Lyman-break galaxies in the optical-to-mid-infrared Hubble Frontier Field and associated parallel field observations of the strong-lensing cluster MACS J0416-2403. We discovered 22 candidates, of which 6 lie at z ≳ 9 and 1 lies at z ≳ 10. Based on the Hubble and Spitzer photometry, all have secure photometric redshifts and a negligible probability of being at lower redshifts according to their peak-probability ratios, ℜ. This substantial increase in the number of known high-redshift galaxies allows a solid determination of the luminosity function (LF) at z ≳ 8. The number of high-z candidates in the parallel field is considerably higher than that in the Abell 2744 parallel field. Our candidates have median stellar masses of log(M_* ∼ 8.44_–0.31^+0.55 M_☉, star formation rates (SFRs) of ∼ 1.8_–0.4^+0.5 M_☉/yr, and SFR-weighted ages of ≲ 300₁₄₀⁺⁷⁰ Myr. Finally, we are able to put strong constraints on the z = 7, 8, 9, and 10 LFs. One of the objects in the cluster field is a z ~= 10 candidate, with a magnification of µ ∼ 20±13. This object is likely the faintest z ∼ 10 object known to date, allowing a first look into the extreme faint end (L ∼ 0.04 L*) of the z ∼ 10 LF (It is named ''Tayna'' in the Aymara language).