On the Fraction of Star Clusters Surviving the Embedded Phase
  In this paper we derive ages and masses for 276 clusters in the merger galaxy
NGC 3256. This was achieved by taking accurate photometry in four wavebands
from archival HST images. Photometric measurements are compared to synthetic
stellar population (SSP) models to find the most probable age, mass and
extinction. The cluster population of NGC 3256 reveals an increase in the star
formation rate over the last 100 million years and the initial cluster mass
function (ICMF) is best described by a power law relation with slope $\alpha =
1.85 \pm 0.12$. Using the observed cluster population for NGC 3256 we calculate
the implied mass of clusters younger than 10 million years old, and convert
this to a cluster formation rate over the last 10 million years. Comparison of
this value with the star formation rate (SFR) indicates the fraction of stars
found within bound clusters after the embedded phase of cluster formation,
$\Gamma$, is $22.9% \pm^{7.3}_{9.8} $ for NGC 3256. We carried out an in-depth
analysis into the errors associated with such calculations showing that errors
introduced by the SSP fitting must be taken into account and an unconstrained
metallicity adds to these uncertainties. Observational biases should also be
considered. Using published cluster population data sets we calculate $\Gamma$
for six other galaxies and examine how $\Gamma$ varies with environment. We
show that $\Gamma$ increases with the star formation rate density and can be
described as a power law type relation of the form $\Gamma(%) = (29.0\pm{6.0})
\Sigma_{SFR}^{0.24\pm0.04} (\msol yr^{-1} kpc^{-2})$.
