Abstract
We use the Advanced Camera for Surveys on the Hubble Space Telescope to study
the rich population of young massive star clusters in the main body of NGC
3256, a merging pair of galaxies with a high star formation rate (SFR) and SFR
per unit area ($\Sigma_SFR$). These clusters have luminosity and mass
functions that follow power laws, $dN/dL L^\alpha$ with $=
-2.23 0.07$, and $dN/dM M^\beta$ with $= -1.86 0.34$
for $< 10$ Myr clusters, similar to those found in more quiescent
galaxies. The age distribution can be described by $dN/d^
\gamma$, with $-0.67 0.08$ for clusters younger than about a
few hundred million years, with no obvious dependence on cluster mass. This is
consistent with a picture where $80 \%$ of the clusters are disrupted each
decade in time. We investigate the claim that galaxies with high
$\Sigma_SFR$ form clusters more efficiently than quiescent systems by
determining the fraction of stars in bound clusters ($\Gamma$) and the CMF/SFR
statistic (CMF is the cluster mass function) for NGC 3256 and comparing the
results with those for other galaxies. We find that the CMF/SFR statistic for
NGC 3256 agrees well with that found for galaxies with $\Sigma_SFR$ and
SFRs that are lower by $1-3$ orders of magnitude, but that estimates for
$\Gamma$ are only robust when the same sets of assumptions are applied.
Currently, $\Gamma$ values available in the literature have used different sets
of assumptions, making it more difficult to compare the results between
galaxies.
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