Discovery of a Low-mass Strong-lens System in SMACS J0723.3-7327

Abstract

We report the discovery of an intriguing, low-mass galaxy-scale strong-lens system in the SMACS J0723.3-7327 galaxy cluster. By modeling James Webb Space Telescope imaging and Very Large Telescope Multi-Unit Spectroscopic Explorer spectroscopic data, we find that the lens is cluster member galaxy at $z=0.397$ with an Einstein radius of $0^{\prime \prime }.424$ $\pm$ $0^{\prime \prime }.012$, stellar mass of $M_{\ast }=(3.3\pm 0.8)\times 10^{10}{M}_{\odot }$, half-light radius of $\sim 1$ kpc, and central stellar velocity dispersion of $140\pm 6$ km s${}^{-1}$. This lens galaxy is one of the few strong lens galaxies known to date that have stellar mass as low as $M_{\ast }\sim 10^{10.5}{M}_{\odot }$, offering an exceptional opportunity to peek into the population of low-mass galaxies that has largely remained unexplored in the context of strong-lensing studies. This strong lens system can also assist in assessing the systematic uncertainty in the lens modeling of cluster member galaxies.

9 pages, 4 figures, 3 tables, published on the ApJ Letters