Taking Census of Massive, Star-Forming Galaxies formed <1 Gyr After the Big Bang

TL;DR

This paper discusses the importance of studying dusty star-forming galaxies formed within the first billion years after the Big Bang to understand early galaxy formation and cosmic star-formation history.

Contribution

It highlights the need for future observations to measure the volume density of obscured galaxies beyond redshift 3 and their role in early Universe galaxy assembly.

Findings

Obscured galaxies dominate star formation near z~2.

The contribution of heavily obscured galaxies beyond z>3 is largely unknown.

Understanding these galaxies is key to resolving early Universe galaxy formation questions.

Abstract

Two decades of effort have been poured into both single-dish and interferometric millimeter-wave surveys of the sky to infer the volume density of dusty star-forming galaxies (DSFGs, with SFR>100M$_\odot$ yr$^{-1}$) over cosmic time. Though obscured galaxies dominate cosmic star-formation near its peak at $z\sim2$, the contribution of such heavily obscured galaxies to cosmic star-formation is unknown beyond $z\sim2.5$ in contrast to the well-studied population of Lyman-break galaxies (LBGs) studied through deep, space- and ground-based pencil beam surveys in the near-infrared. Unlocking the volume density of DSFGs beyond $z>3$, particularly within the first 1 Gyr after the Big Bang is critical to resolving key open questions about early Universe galaxy formation: (1) What is the integrated star-formation rate density of the Universe in the first few Gyr and how is it distributed among low-mass galaxies (e.g. Lyman-break galaxies) and high-mass galaxies (e.g. DSFGs and quasar host galaxies)? (2) How and where do the first massive galaxies assemble? (3) What can the most extreme DSFGs teach us about the mechanisms of dust production (e.g. supernovae, AGB stars, grain growth in the ISM) <1 Gyr after the Big Bang? We summarize the types of observations needed in the next decade to address these questions.