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

## TL;DR

This study identifies and characterizes high-redshift galaxy candidates behind the Hubble Frontier Fields, providing new insights into early galaxy formation and the universe's evolution at z>7.

## Contribution

It reports the discovery of 22 high-redshift galaxy candidates in the MACS J1149.5+2223 field and its parallel field, with detailed analysis of a notable z~9.6 galaxy, advancing understanding of early galaxies.

## Key findings

- 11 galaxies at z>7 in the cluster field
- 11 galaxies at z>7 in the parallel field
- The z~9.6 galaxy MACS1149-JD has a refined redshift of 9.44 ± 0.12

## Abstract

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., 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.