Reconstructing the mass accretion histories of nearby Red Nuggets with
  their globular cluster systems
  It is generally recognized that massive galaxies form through a combination
of in-situ collapse and ex-situ accretion. The in-situ component forms early,
where gas collapse and compaction leads to the formation of massive compact
systems (blue and red "nuggets") seen at $z>1$. The subsequent accretion of
satellites brings in ex-situ material, growing these nuggets in size and mass
to appear as the massive early-type galaxies (ETGs) we see locally. Due to
stochasticity in the accretion process, in a few rare cases a red nugget will
evolve to the present day having undergone little ex-situ mass accretion. The
resulting massive, compact and ancient objects have been termed "relic
galaxies". Detailed stellar population and kinematic analyses are required to
characterise these systems. However, an additional crucial aspect lies in
determining the fraction of ex-situ mass they have accreted since their
formation. Globular cluster systems can be used to constrain this fraction,
since the oldest and most metal-poor globular clusters in massive galaxies are
primarily an accreted, ex-situ population. Models for the formation of relic
galaxies and their globular cluster systems suggest that, due to their early
compaction and limited accretion of dark-matter dominated satellites, relic
galaxies should have characteristically low dark-matter mass fractions compared
to ETGs of the same stellar mass.
