Through the Looking Glass: Bright, Highly Magnified Galaxy Candidates at z~7 Behind Abell 1703

TL;DR

This paper reports the discovery of seven highly magnified galaxy candidates at redshift around 7 behind Abell 1703, including the brightest known at this epoch, revealing detailed properties of early galaxies through gravitational lensing.

Contribution

It presents the identification and analysis of seven bright, strongly lensed z~7 galaxy candidates, including the brightest known at this redshift, with detailed stellar population and structural properties.

Findings

Discovery of seven bright z~7 galaxy candidates with high magnification.

The brightest candidate has an intrinsic magnitude of H_160=26.4 AB and exhibits extended structure.

Stellar population analysis indicates young ages, moderate star formation rates, and low dust reddening.

Abstract

We report the discovery of seven strongly lensed Lyman break galaxy (LBG) candidates at z~7 detected in Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) imaging of Abell 1703. The brightest candidate, called A1703-zD1, has an observed (lensed) magnitude of 24.0 AB (26 sigma) in the WFC3/IR F160W band, making it 0.2 magnitudes brighter than the z_850-dropout candidate recently reported behind the Bullet Cluster and 0.7 magnitudes brighter than the previously brightest known z~7.6 galaxy, A1689-zD1. With a cluster magnification of ~9, this source has an intrinsic magnitude of H_160 = 26.4 AB, a strong z_850 - J_125 break of 1.7 magnitudes, and a photometric redshift of z~6.7. Additionally, we find six other bright LBG candidates with H_160 band magnitudes of 24.9-26.4, photometric redshifts z~6.4 - 8.8, and magnifications mu~3-40. Stellar population fits to the ACS, WFC3/IR, and \Spitzer/IRAC data for A1703-zD1 and A1703-zD4 yield stellar masses (0.7 - 3.0) x 10^{9} M_sun, stellar ages 5-180 Myr, and star-formation rates ~7.8 M_sun/yr, and low reddening with A_V <= 0.7. The source-plane reconstruction of the exceptionally bright candidate A1703-zD1 exhibits an extended structure, spanning ~4 kpc in the z~6.7 source plane, and shows three resolved star-forming knots of radius r~0.4 kpc.