The evolution of stellar structures in dwarf galaxies
  We present a study of the variation of spatial structure of stellar
populations within dwarf galaxies as a function of the population age. We use
deep Hubble Space Telescope/Advanced Camera for Surveys imaging of nearby dwarf
galaxies in order to resolve individual stars and create composite
colour-magnitude diagrams (CMDs) for each galaxy. Using the obtained CMDs, we
select Blue Helium Burning stars (BHeBs), which can be unambiguously age-dated
by comparing the absolute magnitude of individual stars with stellar
isochrones. Additionally, we select a very young (<10 Myr) population of OB
stars for a subset of the galaxies based on the tip of the young main-sequence.
By selecting stars in different age ranges we can then study how the spatial
distribution of these stars evolves with time. We find, in agreement with
previous studies, that stars are born within galaxies with a high degree of
substructure which is made up of a continuous distribution of clusters, groups
and associations from parsec to hundreds of parsec scales. These structures
disperse on timescales of tens to hundreds of Myr, which we quantify using the
two-point correlation function and the Q-parameter developed by Cartwright &
Whitworth (2004). On galactic scales, we can place lower limits on the time it
takes to remove the original structure (i.e., structure survives for at least
this long), tevo, which varies between ~100~Myr (NGC~2366) and ~350 Myr
(DDO~165). This is similar to what we have found previously for the SMC
(~80~Myr) and the LMC (~175 Myr). We do not find any strong correlations
between tevo and the luminosity of the host galaxy.
