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

Abstract

We present an identification of dust-attenuated star-forming galactic-disk substructures in a typical star-forming galaxy (SFG), UDF2, at z = 2.696. To date, substructures containing significant buildup of stellar mass and actively forming stars have yet to be found in typical (i.e., main-sequence) SFGs at z > 2. This is due to the strong dust attenuation common in massive galaxies at the epoch and the scarcity of high-resolution, high-sensitivity extinction-independent imaging. To search for disk substructures, we subtracted the central stellar-mass disk from the JWST/NIRCam rest-frame 1.2 μm image (0.″13 resolution) and subtracted, in the visibility plane, the central starburst disk from Atacama Large Millimeter/submillimeter Array (ALMA) rest-frame 240 μm observations (0.″03 resolution). The residual images revealed substructures at rest-frame 1.2 μm colocated with those found at rest-frame 240 μm, ≃2 kpc away from the galactic center. The largest substructure contains ≃20% of the total stellar mass and ≃5% of the total star formation rate of the galaxy. While UDF2 exhibits a kinematically ordered velocity field of molecular gas consistent with a secularly evolving disk, more sensitive observations are required to characterize the nature and the origin of this substructure (spiral arms, minor merger, or other types of disk instabilities). UDF2 resides in an overdense region (N ≥ 4 massive galaxies within 70 kpc projected distance at z = 2.690–2.697) and the substructures may be associated with interaction-induced instabilities. Importantly, a statistical sample of such substructures identified with JWST and ALMA could play a key role in bridging the gap between the bulge-forming starburst and the rest of the galaxy.

An ALMA Spectroscopic Survey of the Brightest Submillimeter Galaxies in the SCUBA-2-COSMOS Field (AS2COSPEC): Physical Properties of z = 2–5 Ultra- and Hyperluminous Infrared Galaxies

“…As for t depl , the best-fit slopes to the three subsets are all sublinear, which suggests that the gas depletion timescale for the SMG population is shorter compared to the one deduced based on the correlation proposed by Tacconi et al (2020). These results suggest that while on average, SMGs share a common behavior with fainter and less massive star-forming galaxies in terms of their gas fractions, SMGs are more efficient in star formation, possibly due to being preferably located in dense environments where dynamical interactions are more common (Chen et al 2022a;Rujopakarn et al 2023;Smail et al 2023).…”

JWST and ALMA Discern the Assembly of Structural and Obscured Components in a High-redshift Starburst Galaxy

“…This amalgamation of physical effects may illustrate the processes involved in triggering starbursts in the distant gasrich Universe that lead to further galaxy compaction (Tacchella et al 2016b;Kalita et al 2023). After the starburst core gradually quenches in an inside-out manner (Tacchella et al 2016a), PACS-819 may evolve into a clumpy galaxy with a stable disk and substructures, as in UDF2 (Rujopakarn et al 2023), and eventually into a massive quiescent galaxy in the nearby Universe.…”

JEMS: A Deep Medium-band Imaging Survey in the Hubble Ultra Deep Field with JWST NIRCam and NIRISS

“…Figure 4 demonstrates an F460M flux excess due to Paα emission in the SED of a mock star-forming galaxy at z ∼ 1.5 from the JADES Extragalactic Ultradeep Artificial Realization (JAGUAR) mock catalog (Williams et al 2018), whose SEDs are created using BEAGLE (Chevallard & Charlot 2016). In principle, for galaxies that exhibit strong lines that boost colors with high enough S/N, spatially resolved analyses can provide insight into how galaxies assemble their stellar mass (see Figure 3; Rujopakarn et al 2023;S. Alberts et al 2023, in preparation), building on previous studies with expensive integral field unit observations at the Very Large Telescope (e.g., Tacchella et al 2015;Förster Schreiber et al 2018) or HST grism (e.g., Nelson et al 2016;Matharu et al 2021).…”