Compact Star-Forming Galaxies as Old Starbursts Becoming Quiescent

Understand

Optically-compact star-forming galaxies (SFGs) have been proposed as immediate progenitors of quiescent galaxies, although their origin and nature are debated.

• Were they formed in slow secular processes or in rapid merger-driven starbursts? Addressing this question would provide fundamental insight into how quenching occurs.
• We explore the location of the general population of galaxies with respect to fundamental star-forming and structural relations, identify compact SFGs based on their stellar core densities, and study three diagnostics of the burstiness of star formation: 1) Star formation efficiency, 2) interstellar medium (ISM), and 3) radio emission.
• The overall distribution of galaxies in the fundamental relations points towards a smooth transition towards quiescence while galaxies grow their stellar cores, although some galaxies suddenly increase their specific star-formation rate when they become compact.