Formation Of Sub-Structure In Luminous Submillimeter galaxies (FOSSILS): Evidence of Multiple Pathways to Trigger Starbursts in Luminous Submillimeter Galaxies

TL;DR

This study uses JWST and ALMA observations to analyze three high-redshift luminous submillimeter galaxies, revealing diverse morphologies and multiple mechanisms triggering starbursts, including disk instability, minor mergers, and major mergers with gas reformation.

Contribution

It provides the first detailed spatially resolved analysis of multiple SMGs at high redshift, demonstrating diverse physical pathways to starburst activity.

Findings

Heterogeneous morphologies among the three SMGs.

Evidence of different starburst triggering mechanisms: disk instability, minor mergers, and major mergers.

High-resolution imaging reveals complex structures like spiral dust arms and concentrated cores.

Abstract

We present an analysis of rest-frame optical and far-infrared continuum emission in three luminous submillimeter galaxies (SMGs) at $3.0\lesssim z\lesssim4.5$. The SMGs are spatially resolved down to 400-500 pc ($\sim0.05$'') resolution by James Webb Space telescope (JWST) and Atacama Large Millimeter/submillimeter Array (ALMA) observations. Despite similarities in their observed far-infrared properties (flux density, infrared luminosity, and effective radius), the three SMGs exhibit heterogeneous morphologies both across wavelengths and among the sources themselves. While two of them (AzTEC-4 and AzTEC-8) show a disk-like structure in optical continuum, AzTEC-1 is dominated by highly concentrated component with the S\'{e}rsic index of $n=5.4$, where its far-infrared continuum emission is clumpy and less concentrated. AzTEC-4, which is confirmed to be at $z=4.198$, shows a two-arm spiral of dust, but not in the stellar distribution. These three SMGs exemplify that multiple physical mechanisms exist in triggering starbursts in luminous SMGs at high redshift: secular instability in gas disks (AzTEC-4) in addition to possible minor mergers (AzTEC-8), and a combination of the efficient gas supply to the central core induced by a gas-rich major merger and the reformation of cold gas disk (AzTEC-1).