Globular Cluster Systems of Relic Galaxies

TL;DR

This study investigates the globular cluster systems of 15 compact early-type galaxies, revealing lower specific frequencies and compact distributions, and suggests a link between galaxy angular momentum and globular cluster color diversity.

Contribution

It provides new insights into the properties of globular clusters in relic galaxies and proposes a novel proxy for their accretion history based on color distribution width.

Findings

Lower specific frequencies than typical ETGs of similar mass.

Globular cluster systems are compact and follow known relations.

An anticorrelation between galaxy angular momentum and GC color diversity.

Abstract

We analyse the globular cluster (GC) systems of a sample of 15 massive, compact early-type galaxies (ETGs), 13 of which have already been identified as good relic galaxy candidates on the basis of their compact morphologies, old stellar populations and stellar kinematics. These relic galaxy candidates are likely the nearby counterparts of high redshift red nugget galaxies. Using F814W (~I) and F160W (~H) data from the WFC3 camara onboard the Hubble Space Telescope we determine the total number, luminosity function, specific frequency, colour and spatial distribution of the GC systems. We find lower specific frequencies (SN<2.5 with a median of SN=1) than ETGs of comparable mass. This is consistent with a scenario of rapid, early dissipative formation, with relatively low levels of accretion of low-mass, high-SN satellites. The GC half-number radii are compact, but follow the relations found in normal ETGs. We identify an anticorrelation between the specific angular momentum (lambda_R) of the host galaxy and the (I-H) colour distribution width of their GC systems. Assuming that lambda_R provides a measure of the degree of dissipation in massive ETGs, we suggest that the (I-H) colour distribution width can be used as a proxy for the degree of complexity of the accretion histories in these systems.