YOUNG GALAXY CANDIDATES in the HUBBLE FRONTIER FIELDS. II. MACS J0416-2403

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, . 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 Mo, star formation rates (SFRs) of Mo yr-1, and SFR-weighted ages of . 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). © 2015. The American Astronomical Society. All rights reserved.