Tracing the relic nature of compact galaxies through their globular cluster systems

TL;DR

This study uses simulated globular cluster systems to identify signatures of relic galaxies, revealing that GC properties can trace early formation and accretion histories of compact massive galaxies.

Contribution

It introduces a model linking GC systems with galaxy evolution, identifying GC signatures that distinguish relic galaxies from typical systems.

Findings

GC mass fraction better traces host assembly history than number fraction.

Three simulated galaxies are identified as strong relic analogs.

GC spatial profiles can indicate tidal stripping processes.

Abstract

We investigate the synthetic model of globular cluster (GC) systems of 17 compact massive galaxies (CMGs) from the Illustris TNG100 simulation to explore their connection with massive relic galaxies, systems that have undergone little structural evolution across cosmic time. The co-evolution of the GC systems and their host galaxies is based on a GC formation and evolution model that assigns clusters to stellar particles according to age and local conditions, providing positional, kinematic, and chemical information for individual GCs. By combining stellar assembly histories, effective radius evolution, and GC properties such as in-situ vs. ex-situ origin, metallicity, and spatial distribution, we identify consistent signatures of early formation and late-time accretion. We find that the GC mass fraction traces the host assembly history more robustly than the GC number fraction, as massive clusters better preserve the imprint of the early accretion history. Three CMGs from TNG100 emerge as strong massive relic analogs, exhibiting high in-situ GC fractions, narrow metallicity distributions, and compact spatial distributions. A tight correlation between the host stripped fraction and the extent of the ex-situ GC population further reveals the possibility to consider GC spatial profiles as a signature to identify tidal stripping processes. These results indicate that the combined analysis of GC populations and host stellar assembly offers a robust diagnostic for identifying massive relic galaxies and constraining their evolutionary histories.