GOODS-ALMA 2.0: Starbursts in the main sequence reveal compact star formation regulating galaxy evolution prequenching

TL;DR

This study investigates the role of compact star formation in dusty star-forming galaxies, revealing that certain massive galaxies exhibit starburst-like activity within the main sequence, influencing galaxy evolution and prequenching processes.

Contribution

It provides new insights into how compact star formation affects galaxy properties and evolution, especially in massive galaxies, using detailed ALMA observations from the GOODS-ALMA 2.0 survey.

Findings

Compact starbursts within the main sequence have the shortest depletion timescales.

These galaxies are the most massive and have the highest dust temperatures.

Star formation in these galaxies is driven by gas compression, influencing their evolutionary path.

Abstract

Compact star formation appears to be generally common in dusty star-forming galaxies (SFGs). However, its role in the framework set by the scaling relations in galaxy evolution remains to be understood. In this work we follow up on the galaxy sample from the GOODS-ALMA 2.0 survey, an ALMA blind survey at 1.1mm covering a continuous area of 72.42arcmin$^2$ using two array configurations. We derived physical properties, such as star formation rates, gas fractions, depletion timescales, and dust temperatures for the galaxy sample built from the survey. There exists a subset of galaxies that exhibit starburst-like short depletion timescales, but they are located within the scatter of the so-called main sequence of SFGs. These are dubbed starbursts in the main sequence and display the most compact star formation and they are characterized by the shortest depletion timescales, lowest gas fractions, and highest dust temperatures of the galaxy sample, compared to typical SFGs at the same stellar mass and redshift. They are also very massive, accounting for $\sim 60\%$ of the most massive galaxies in the sample ($\log (M_{\rm{*}}/M_{\odot}) > 11.0$). We find trends between the areas of the ongoing star formation regions and the derived physical properties for the sample, unveiling the role of compact star formation as a physical driver of these properties. Starbursts in the main sequence appear to be the extreme cases of these trends. We discuss possible scenarios of galaxy evolution to explain the results drawn from our galaxy sample. Our findings suggest that the star formation rate is sustained in SFGs by gas and star formation compression, keeping them within the main sequence even when their gas fractions are low and they are presumably on the way to quiescence.