Hidden Giants in JWST's PEARLS: An Ultramassive z = 4.26 Submillimeter Galaxy that Is Invisible to HST
Grogin, Norman A.; Koekemoer, Anton M.; Pirzkal, Nor; Smail, Ian; Conselice, Christopher J.; Rutkowski, Michael J.; Yan, Haojing; Cheng, Cheng; Swinbank, A. M.; Fazio, Giovanni G.; Willmer, Christopher N. A.; Keel, William C.; Zitrin, Adi; Coe, Dan; Frye, Brenda; D'Silva, Jordan C. J.; Driver, Simon P.; Summers, Jake; Windhorst, Rogier A.; Nonino, Mario; Cohen, Seth H.; Ryan, Russell E., Jr.; Willner, S. P.; Jansen, Rolf A.; Marshall, Madeline A.; Robotham, Aaron; Tompkins, Scott; Kamieneski, Patrick; Arumugam, Vinodiran; Dudzevičiūtė, Ugnė; Broadhurst, Thomas J.; Diego, José M.; Yun, Min; Gurwell, Mark; Meena, Ashish
United Kingdom, Germany, United States, France, Israel, China, Australia, Canada, Italy, Spain
Abstract
We present a multiwavelength analysis using the Submillimeter Array (SMA), James Clerk Maxwell Telescope, NOEMA, JWST, the Hubble Space Telescope (HST), and the Spitzer Space Telescope of two dusty strongly star-forming galaxies, 850.1 and 850.2, seen through the massive cluster lens A 1489. These SMA-located sources both lie at z = 4.26 and have bright dust continuum emission, but 850.2 is a UV-detected Lyman-break galaxy, while 850.1 is undetected at ≲ 2 μm, even with deep JWST/NIRCam observations. We investigate their stellar, interstellar medium, and dynamical properties, including a pixel-level spectral energy distribution analysis to derive subkiloparsec-resolution stellar-mass and A V maps. We find that 850.1 is one of the most massive and highly obscured, A V ~ 5, galaxies known at z > 4 with M * ~1011.8 M ⊙ (likely forming at z > 6), and 850.2 is one of the least massive and least obscured, A V ~ 1, members of the z > 4 dusty star-forming population. The diversity of these two dust-mass-selected galaxies illustrates the incompleteness of galaxy surveys at z ≳ 3-4 based on imaging at ≲ 2 μm, the longest wavelengths feasible from HST or the ground. The resolved mass map of 850.1 shows a compact stellar-mass distribution, ${R}_{{\rm{e}}}^{\mathrm{mass}}$ ~1 kpc, but its expected evolution means that it matches both the properties of massive, quiescent galaxies at z ~ 1.5 and ultramassive early-type galaxies at z ~ 0. We suggest that 850.1 is the central galaxy of a group in which 850.2 is a satellite that will likely merge in the near future. The stellar morphology of 850.1 shows arms and a linear bar feature that we link to the active dynamical environment it resides within.