Young Galaxy Candidates in the Hubble Frontier Fields. II. MACS J0416-2403
Broadhurst, Tom; Moustakas, John; Zheng, Wei; Brammer, Gabriel B.; Zitrin, Adi; Bauer, Franz E.; Molino, Alberto; Infante, Leopoldo; Ford, Holland C.; Kim, Sam; Shu, Xinwen; Diego, Jose M.; Laporte, Nicolas; Bina, David; Troncoso Iribarren, Paulina; Huang, Xingxing; García, Stefano
Chile, United States, Brazil, Spain, China, France
Abstract
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-1, and SFR-weighted ages of ≲ {300}-140+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).