The SLUGGS survey: inferring the formation epochs of metal-poor and metal-rich globular clusters

Understand

We present a novel, observationally-based framework for the formation epochs and sites of globular clusters (GCs) in a cosmological context.

• Measuring directly the mean ages of the metal-poor and metal-rich GC subpopulations in our own Galaxy, and in other galaxies, is observationally challenging.
• Here we apply an alternative approach utilising the property that the galaxy mass-metallicity relation is a strong function of redshift (or look-back age) but is relatively insensitive to galaxy mass for massive galaxies.
• Assuming that GCs follow galaxy mass-metallicity relations that evolve with redshift, one can estimate the mean formation epochs of the two GC subpopulations by knowing their mean metallicities and the growth in host galaxy mass with redshift.