Blowing Star Formation Away in AGN Hosts (BAH) -- III. Serendipitous discovery of a $z\sim2.9$ star-forming galaxy lensed by the galactic bulge of CGCG 012-070 using JWST NIRSpec

TL;DR

This paper reports the serendipitous discovery of a high-redshift star-forming galaxy lensed by a nearby galaxy using JWST NIRSpec IFU observations, providing insights into galaxy morphology and mass profiles at cosmic noon.

Contribution

It presents the first detection of a $z extasciitilde2.9$ star-forming galaxy lensed by a low-redshift galaxy with JWST, demonstrating the power of IFU observations in identifying new gravitational lenses.

Findings

Detected a $z extasciitilde2.9$ star-forming galaxy via gravitational lensing.

Modeled the lens system with an elliptical power-law mass profile.

Revealed a disturbed star-forming morphology consistent with galaxies at cosmic noon.

Abstract

We report the detection of a gravitationally lensed galaxy by the nearby spiral galaxy CGCG 012-070 ($z = 0.048$) using Integral Field Unit (IFU) observations with the Near-Infrared Spectrograph (NIRSpec) instrument on board the James Webb Space Telescope (JWST). The lensed galaxy is identified through the flux distributions of emission lines in the rest-frame optical, consistent with a source located at a redshift of $z\sim2.89$. The system is detected in [O III]$\lambda\lambda4959,5007$, H$\beta$, and H$\alpha$ emission lines, exhibiting line ratios typical of a star-forming galaxy. The emission-line flux distributions reveal three distinct components, which are modeled using an elliptical power-law (EPL) mass profile for the lens galaxy. This model provides a good characterization of the source and reveals a disturbed star-forming morphology consistent with those of galaxies at cosmic noon. This serendipitous discovery of a rare low-redshift strong lens highlights the critical role of IFU observations in expanding the lens census and advancing our understanding of galaxy mass profiles and evolution.