Young Galaxy Candidates in the Hubble Frontier Fields IV. MACS J1149.5+2223

W. Zheng, A. Zitrin, L. Infante, N. Laporte, X. X. Huang, J. Moustakas, H. C. Ford, X. W. Shu, J. X. Wang, J. M. Diego, F. E. Bauer, P. T. Iribarren, T. Broadhurst, A. Molino

Published 2017-01-30Version 1

We search for high-redshift dropout galaxies behind the Hubble Frontier Fields (HFF) galaxy cluster MACS J1149.5+2223, a powerful cosmic lens that has revealed a number of unique objects in its field. Using the deep images from the Hubble and Spitzer space telescopes, we find 11 galaxies at z>7 in the MACS J1149.5+2223 cluster field, and 11 in its parallel field. The high-redshift nature of the bright z~9.6 galaxy MACS1149-JD, previously reported by Zheng et al. (2012), is further supported by non-detection in the extremely deep optical images from the HFF campaign. With the new photometry, the best photometric redshift solution for MACS1149-JD reduces slightly to z=9.44 +/- 0.12. The young galaxy has an estimated stellar mass of (7 +/- 2)X10E8 Msun, and was formed at z=13.2 +1.9-1.6 when the Universe was ~300 Myr old. Data available for the first four HFF clusters have already enabled us to find faint galaxies to an intrinsic magnitude of M(UV) ~ -15.5, approximately a factor of ten deeper than the parallel fields.