The Identification of a Dusty Multiarm Spiral Galaxy at z = 3.06 with JWST and ALMA

Abstract

Spiral arms serve crucial purposes in star formation and galaxy evolution. In this paper, we report the identification of “A2744-DSG-z3,” a dusty, multiarm spiral galaxy at z = 3.059 using the James Webb Space Telescope (JWST) NIRISS imaging and grism spectroscopy. A2744-DSG-z3 was discovered as a gravitationally lensed submillimeter galaxy with the Atacama Large Millimeter/submillimeter Array (ALMA). This is the most distant stellar spiral structure seen thus far, consistent with cosmological simulations that suggest z ≈ 3 as the epoch when spirals emerge. Thanks to the gravitational lensing and excellent spatial resolution of JWST, the spiral arms are resolved with a spatial resolution of ≈290 pc. Based on spectral energy distribution fitting, the spiral galaxy has a delensed star formation rate of 85 ± 30 M ⊙ yr−1, and a stellar mass of ≈1010.6 M ⊙, indicating that A2744-DSG-z3 is a main-sequence galaxy. After fitting the spiral arms, we find a stellar effective radius (R e,star) of 5.0 ± 1.5 kpc. Combining with ALMA measurements, we find that the effective radii ratio between dust and stars is ≈0.4, similar to those of massive star‐forming galaxies (SFGs) at z ∼ 2, indicating a compact dusty core in A2744-DSG-z3. Moreover, this galaxy appears to be living in a group environment: including A2744-DSG-z3, at least three galaxies at z = 3.05–3.06 are spectroscopically confirmed by JWST/NIRISS and ALMA, residing within a lensing-corrected projected scale of ≈70 kpc. This, along with the asymmetric brightness profile, further suggests that the spiral arms may be triggered by minor-merger events at z ≳ 3.

JWST and ALMA Imaging of Dust-obscured, Massive Substructures in a Typical z ∼ 3 Star-forming Disk Galaxy

“…In both the Chen et al (2022) and Wu et al (2023) samples, companion and/or group environment appears to be a common attribute. We also find that UDF2 also resides in a potentially overdense region with four massive galaxies (including UDF2) identified within a projected distance of 70 kpc, spectroscopically confirmed (F. Sun, private communication based on observations presented in Oesch et al 2023) to be at z = 2.690-2.697 (Figure 5).…”

“…There are notable parallels between the substructures identified in this work and those observed at z ∼ 1-4 using JWST. For example, spiral arms have been identified optically by Wu et al (2023) using NIRCam observations of A2744-DSG-z3, a typical SFG at z = 3.06, but the angular resolution and sensitivity of their ALMA observations are insufficient to resolve the spiral structures observed by JWST. Similarly, using NIRCam observations of seven submm-selected typical SFGs at z ∼ 2, Chen et al (2022) found spiral arms and bars and also nearby companions that suggest ongoing dynamical interactions (their IR/radio observations are ∼few arcsecond resolution, still not sufficient to associate the stellar mass and SF structures).…”

COOL-LAMPS. IV. A Sample of Bright Strongly Lensed Galaxies at 3 < z < 4

“…Space-based telescopes HST and JWST have high spatial resolution and thus enable the construction of robust lens models. Recent studies of strong lensing systems using HST and JWST (e.g., Rivera-Thorsen et al 2019;Claeyssens et al 2023;Mahler et al 2023;Wu et al 2023) were able to discern morphology and star formation at the smallest scales. Furthermore, in this redshift interval, all of the rest-frame optical nebular emission lines fall in the JWST NIRSpec bandpass.…”

JADES: Resolving the Stellar Component and Filamentary Overdense Environment of Hubble Space Telescope (HST)-dark Submillimeter Galaxy HDF850.1 at z = 5.18

“…This is much smaller than the half-light radius in rest-frame V band (0 49 ± 0 02). The smaller half-mass-radius in contrast to half-light radius is a natural consequence of higher dust attenuation in the galaxy center, which flattens out the rest-frame optical light profile (e.g., Nelson et al 2016;Mosleh et al 2017;Tacchella et al 2018;Lang et al 2019;Chen et al 2022;Cheng et al 2022Cheng et al , 2023Suess et al 2022;Wu et al 2023).…”