Reconstructing Merger Timelines Using Star Cluster Age Distributions:
  the Case of MCG+08-11-002
  We present near infrared imaging and integral field spectroscopy of the
centre of the dusty luminous infrared galaxy merger MCG+08-11-002, taken using
the Near InfraRed Camera 2 (NIRC2) and the OH-Suppressing InfraRed Imaging
Spectrograph (OSIRIS) on Keck II. We achieve a spatial resolution of ~25 pc in
the K band, allowing us to resolve 41 star clusters in the NIRC2 images. We
calculate the ages of 22/25 star clusters within the OSIRIS field using the
equivalent widths of the CO 2.3$\mu$m absorption feature and the Br$\gamma$
nebular emission line. The star cluster age distribution has a clear peak at
ages < 20 Myr, indicative of current starburst activity associated with the
final coalescence of the progenitor galaxies. There is a possible second peak
at ~65 Myr which may be a product of the previous close passage of the galaxy
nuclei. We fit single and double starburst models to the star cluster age
distribution and use Monte Carlo sampling combined with two-sided K-S tests to
calculate the probability that the observed data are drawn from each of the
best fit distributions. There is a >90 per cent chance that the data are drawn
from either a single or double starburst star formation history, but stochastic
sampling prevents us from distinguishing between the two scenarios. Our
analysis of MCG+08-11-002 indicates that star cluster age distributions provide
valuable insights into the timelines of galaxy interactions and may therefore
play an important role in the future development of precise merger stage
classification systems.
