Rapidly Star-forming Galaxies At High Redshifts

TL;DR

This paper discusses how Herschel observations reveal that high-redshift, rapidly star-forming galaxies differ from local starbursts, being driven by cold accretion and gas inflows rather than mergers, leading to distinct morphological and star formation characteristics.

Contribution

It introduces the cold accretion paradigm to explain the differences in galaxy morphology and star formation between high-redshift and local galaxies.

Findings

High-z galaxies have higher accretion rates than local counterparts.

High-z galaxies exhibit ordered rotation and distributed star formation.

Local starbursts are merger-driven, unlike high-z galaxies.

Abstract

Herschel has opened new windows into studying the evolution of rapidly star-forming galaxies out to high redshifts. Today's massive starbursts are characterized by star formation rates (SFRs) of 100+ Mo/yr and display a chaotic morphology and nucleated star formation indicative of a major merger. At z~2, galaxies of similar mass and SFR are characterized by ordered rotation and distributed star formation. The emerging cold accretion paradigm provides an intuitive understanding for such differences. In it, halo accretion rates govern the supply of gas into star-forming regions, modulated by strong outflows. The high accretion rates at high-z drive more rapid star formation, while also making disks thicker and clumpier; the clumps are expected to be short-lived in the presence of strong galactic outflows as observed. Hence equivalently rapid star-formers at high redshift are not analogous to local merger-driven starbursts, but rather to local disks with highly enhanced accretion rates.