Extragalactic archaeology through high-resolution integrated-light spectroscopy of globular clusters

TL;DR

This white paper argues for a new, large-scale, high-resolution spectroscopic facility (approximately $R \sim 20{,}000$) to obtain integrated-light spectra of a significant fraction of nearby globular clusters, enabling detailed chemical and kinematic studies. The approach combines chemical tagging of GCs to reconstruct galaxy assembly histories, precise line-of-sight velocities for chemodynamical mapping, and a GC-based distance indicator with typical precision around $3{-}5\%$ out to roughly $50$ Mpc. Key contributions include linking accreted GC groups to merger events, constraining dark matter halo properties from GC kinematics, and mapping the nearby large-scale structure with GC-based distances, all aided by synergies with deep imaging surveys. The proposed facility would substantially advance our understanding of galaxy formation, halo structure, and the cosmic distance scale, with practical impact on $H_0$ constraints and the interpretation of halo assembly across the local universe.

Abstract

We propose to radically expand the use of extragalactic globular clusters as tools for extragalactic archaeology. We propose a large-scale spectroscopic facility to obtain high spectral resolution (R $\sim$ 20,000) spectroscopy for a significant fraction of all globular clusters in the nearby Universe. This will facilitate the reconstruction of galaxy assembly histories via chemical tagging, trace dark matter haloes, and measure extragalactic distances.

Figures (2)

• Figure 1: [Ba/Eu] versus [Fe/H] for the Local Group GCs (data from Larsen2022Gvozdenko2024).
• Figure 2: Relation between globular cluster velocity dispersions $\sigma$ and absolute magnitudes for Milky Way (grey) and M31 GCs (orange). GCs with unreliable $\sigma$ measurements were excluded (from Beasley2024).