CLASH: Discovery of a Bright z~6.2 Dwarf Galaxy Quadruply Lensed by MACS J0329.6-0211

TL;DR

This paper reports the discovery and analysis of a highly magnified, high-redshift dwarf galaxy at z~6.2, strongly lensed by a galaxy cluster, providing insights into early galaxy properties and lensing models.

Contribution

The study presents the first strong-lensing analysis of MACS J0329.6-0211 and characterizes one of the highest-redshift multiply-lensed dwarf galaxies known.

Findings

High-redshift galaxy at z~6.2 with observed magnitude F125W=24.00

Magnifications of 11.6, 17.6, 3.9, and 3.7 for the four images

Demagnified stellar mass of ~10^9 solar masses

Abstract

We report the discovery of a z_{phot}=6.18^{+0.05}_{-0.07} (95% confidence level) dwarf galaxy, lensed into four images by the galaxy cluster MACS J0329.6-0211 (z_{l}=0.45). The galaxy is observed as a high-redshift dropout in HST/ACS/WFC3 CLASH and Spitzer/IRAC imaging. Its redshift is securely determined due to a clear detection of the Lyman-break in the 18-band photometry, making this galaxy one of the highest-redshift multiply-lensed objects known to date with an observed magnitude of F125W=24.00\pm0.04 AB mag for its highest-magnified image. We also present the first strong-lensing analysis of this cluster uncovering 15 additional multiply-imaged candidates of five lower-redshift sources spanning the range z_{s}~2-4. The mass model independently supports the high photometric redshift and reveals magnifications of 11.6^{+8.9}_{-4.1}, 17.6^{+6.2}_{-3.9}, 3.9^{+3.0}_{-1.7}, and 3.7^{+1.3}_{-0.2}, respectively, for the four images of the high-redshift galaxy. With this we construct a source image with a physical resolution of ~200 pc when the universe was ~0.9 Gyr old, where the z~6.2 galaxy occupies a source-plane area of approximately 2.2 kpc^{2}. Modeling the observed spectral energy distribution using population synthesis models, we find a demagnified stellar mass of ~10^{9} {M}_{sun}, subsolar metallicity (Z/Z_{sun}~0.5), low dust content (A_{V}~0.1 mag), a demagnified star formation rate (SFR) of ~3.2 {M}_{sun} yr^{-1}, and a specific SFR of ~3.4 Gyr^{-1}, all consistent with the properties of local dwarf galaxies.