Discovery of a Dusty, Chemically Mature Companion to a z ∼ 4 Starburst Galaxy in JWST ERS Data
Abstract
We report the discovery of two companion sources to a strongly lensed galaxy SPT0418-47 ("ring") at redshift 4.225, targeted by the JWST Early Release Science program. We confirm that these sources are at a similar redshift to the ring based on Hα detected in the NIRSpec spectrum and [C II] λ158 μm line from the Atacama Large Millimeter/submillimeter Array (ALMA). Using multiple spectral lines detected in JWST/NIRSpec, the rest-frame optical to infrared images from NIRCam and MIRI and far-infrared dust continuum detected by ALMA, we argue that the newly discovered sources are actually lensed images of the same companion galaxy SPT0418-SE, hereafter referred to "SE," located within 5 kpc in the source plane of the ring. The star formation rate derived using [C II] and the dust continuum puts a lower limit of 17 M ☉ yr-1, while the SFRHα is estimated to be >2 times lower, thereby confirming that SE is a dust-obscured star-forming galaxy. Analysis using optical strong line diagnostics suggests that SE has near-solar elemental abundance, while the ring appears to have supersolar metallicity O/H and N/O. We attempt to reconcile the high metallicity in this system by invoking early onset of star formation with continuous high star-forming efficiency or by suggesting that optical strong line diagnostics need revision at high redshift. We suggest that SPT0418-47 resides in a massive dark-matter halo with yet-to-be-discovered neighbors. This work highlights the importance of joint analysis of JWST and ALMA data for a deep and complete picture of the early universe.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2023
- DOI:
- arXiv:
- arXiv:2210.16968
- Bibcode:
- 2023ApJ...944L..36P
- Keywords:
-
- James Webb Space Telescope;
- High-redshift galaxies;
- Companion galaxies;
- Gravitational lensing;
- Metallicity;
- 2291;
- 734;
- 290;
- 670;
- 1031;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 11 pages, 4 figures. Accepted by ApJL