A complete view of galaxy evolution: panchromatic luminosity functions and the generation of metals

TL;DR

This paper reviews the progress and challenges in understanding galaxy evolution, emphasizing the importance of infrared observations for studying gas cooling, enrichment, and star formation across cosmic time.

Contribution

It outlines the observational requirements and tools needed for large-scale surveys and spectroscopy to advance models of galaxy formation and evolution.

Findings

Infrared observations are crucial for studying galaxy gas cooling and enrichment.

Large-area surveys out to z~5 are necessary for comprehensive galaxy evolution mapping.

Tools for deep, wide-field infrared surveys and spectroscopy are feasible and essential.

Abstract

When and how did galaxies form and their metals accumulate? Over the last decade, this has moved from an archeological question to a live investigation: there is now a broad picture of the evolution of galaxies in dark matter halos: their masses, stars, metals and supermassive blackholes. Galaxies have been found and studied in which these formation processes are taking place most vigorously, all the way back in cosmic time to when the intergalactic medium (IGM) was still largely neutral. However, the details of how and why the interstellar medium (ISM) in distant galaxies cools, is processed, recycled and enriched in metals by stars, and fuels active galactic nuclei (AGNs) remain uncertain. In particular, the cooling of gas to fuel star formation, and the chemistry and physics of the most intensely active regions is hidden from view at optical wavelengths, but can be seen and diagnosed at mid- & far-infrared (IR) wavelengths. Rest-frame IR observations are important first to identify the most luminous, interesting and important galaxies, secondly to quantify accurately their total luminosity, and finally to use spectroscopy to trace the conditions in the molecular and atomic gas out of which stars form. In order to map out these processes over the full range of environments and large-scale structures found in the universe - from the densest clusters of galaxies to the emptiest voids - we require tools for deep, large area surveys, of millions of galaxies out to z~5, and for detailed follow-up spectroscopy. The necessary tools can be realized technically. Here, we outline the requirements for gathering the crucial information to build, validate and challenge models of galaxy evolution.