Decomposing the growth mechanisms of galaxies over the last 10 billion years

TL;DR

This paper emphasizes the importance of understanding galaxy growth mechanisms, especially mergers, over the last 10 billion years, and advocates for advanced spectroscopic facilities to improve observational constraints.

Contribution

It highlights the critical need for a large multi-object spectroscopic facility to better measure and understand galaxy mergers and their role in galaxy evolution.

Findings

Mergers are crucial in galaxy mass assembly but are poorly constrained observationally beyond the local universe.

Current facilities are inadequate for detailed merger studies at high redshift.

A 10m+ class spectroscopic facility is essential for advancing understanding of galaxy growth mechanisms.

Abstract

Determining how galaxies accumulate stellar mass is paramount to understanding the Universe. Two primary mechanisms drive this process: star-formation (SF) & mergers. Our understanding of star formation, and to some degree the processes that influence the baryon cycle (environment, gas supply, feedback, etc), are either relatively well constrained or will develop significantly over the coming decades via upcoming facilities (i.e. through their imprint on galaxy properties measured with deep multi-wavelength and spectroscopic data). However, the same can not be said for mergers. It is telling that we indirectly know hierarchical assembly through mergers is one of the most crucial processes that shape our Universe, but the robust observational measurement of mergers is almost non-existent outside of the local Universe - let alone how these mergers impact galaxy properties. This is not likely to significantly change in the coming decades as existing or approved facilities/surveys are inadequate in charactering mergers in the distant Universe. Motivated by this, we discuss an ambitious study to first explore mergers, and then the co-dependent astrophysical process that govern the accumulation of stellar mass over the last ~10billion years, and highlight the essential need for a 10m+ class multi-object spectroscopic facility.