JWST's PEARLS: resolved study of the stellar and dust components in starburst galaxies at cosmic noon

TL;DR

This study uses JWST/NIRCam imaging to analyze the detailed stellar and dust structures of three massive, dusty starburst galaxies at z~2.5, revealing their morphologies, star formation, and dust properties on sub-kiloparsec scales, and suggesting interactions drive their high SFRs.

Contribution

First spatially-resolved morphological analysis of DSFGs at cosmic noon using JWST, revealing complex dust and stellar distributions and interaction-driven starburst activity.

Findings

Galaxies are massive, dusty, with high SFRs of 340-2500 Msun/yr.

Morphologies are disk-like with substructures such as clumps and spiral arms.

Dust extinction up to Av=7 mag with asymmetric, extended distributions.

Abstract

Dusty star-forming galaxies (DSFGs) contribute significantly to the stellar buildup at cosmic noon. Major mergers and gas accretion are often invoked to explain DSFGs' prodigious star-formation rates (SFRs) and large stellar masses. We conducted a spatially-resolved morphological analysis of the rest-frame UV/NIR emission in three DSFGs at z~2.5. Initially discovered as CO emitters by NOEMA observations of a bright Herschel source, we observed them with the JWST/NIRCam as part of the PEARLS program. The NIRCam data reveal the galaxies' stellar populations and dust distributions on scales of 250 pc. Spatial variations in stellar mass, SFR, and dust extinction are determined in resolved maps obtained through pixel-based SED fitting. The CO emitters are massive, dusty starburst galaxies with SFRs=340-2500 Msun/yr, positioning them among the most active SFGs at 2<z<3. They belong to the ~1.5% of the entire JWST population with extremely red colors. Their morphologies are disk like, with radii of 2.0-4.4 kpc, and exhibit substructures such as clumps and spiral arms. The galaxies have dust extinctions up to Av=5-7 mag extending over several kpc with asymmetric distributions that include off-center regions resembling bent spiral arms and clumps. Their NIR dust-attenuation curve deviates from standard laws, possibly implying different dust-star geometries or dust grain properties than commonly assumed in starburst galaxies. The proximity of galaxies with consistent redshifts, strong color gradients, an overall disturbed appearance, asymmetric dust obscuration, and widespread star formation collectively favor interactions (minor mergers and flybys) as the mechanism driving the CO galaxies' exceptional SFRs. The galaxies' large masses and rich environment hint at membership in two proto-structures, as initially inferred from their association with a Planck-selected high-z source.