JWST Insight into a Lensed HST-dark Galaxy and Its Quiescent Companion at z = 2.58
Abstract
Using the novel James Webb Space Telescope (JWST)/NIRCam observations in the A2744 field, we present a first spatially resolved overview of a Hubble Space Telescope (HST)-dark galaxy, spectroscopically confirmed at z = 2.58 with magnification μ ≈ 1.9. While being largely invisible at ~1 μm with NIRCam, except for sparse clumpy substructures, the object is well detected and resolved in the long-wavelength bands with a spiral shape clearly visible in F277W. By combining ancillary Atacama Large Millimeter/submillimeter Array (ALMA) and Herschel data, we infer that this object is an edge-on dusty spiral with an intrinsic stellar mass log (M */M ⊙) ~ 11.3 and a dust-obscured star formation rate ~300 M ⊙ yr-1. A massive quiescent galaxy (log (M */M ⊙) ~ 10.8) with tidal features lies 2.″0 away (r ~ 9 kpc), at a consistent redshift as inferred by JWST photometry, indicating a potential major merger. The dusty spiral lies on the main sequence of star formation, and shows high dust attenuation in the optical (3 < A V < 4.5). In the far-infrared, its integrated dust spectral energy distribution is optically thick up to λ 0 ~ 500 μm, further supporting the extremely dusty nature. Spatially resolved analysis of the HST-dark galaxy reveals a largely uniform A V ~ 4 area spanning ~57 kpc2, which spatially matches to the ALMA 1 mm continuum emission. Accounting for the surface brightness dimming and the depths of current JWST surveys, unlensed analogs of the HST-dark galaxy at z > 4 would be only detectable in F356W and F444W in an UNCOVER-like survey, and become totally JWST-dark at z ~ 6. This suggests that detecting highly attenuated galaxies in the Epoch of Reionization might be a challenging task for JWST.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2023
- DOI:
- 10.3847/2041-8213/acbd9d
- arXiv:
- arXiv:2301.04158
- Bibcode:
- 2023ApJ...945L..25K
- Keywords:
-
- Active galaxies;
- Disk galaxies;
- 17;
- 391;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 15 pages, 5 figures, 1 table. Accepted to ApJL