Constraining Globular Cluster Formation Through Studies of Young Massive
  Clusters: I. A lack of ongoing star formation within young clusters
  We present a survey of 130 Galactic and extragalactic young massive clusters
(YMCs, $10^4 < M/\msun < 10^8$, $10 < t/{\rm Myr} < 1000$) with integrated
spectroscopy or resolved stellar photometry (40 presented here and 90 from the
literature) and use the sample to search for evidence of ongoing star-formation
within the clusters. Such episodes of secondary (or continuous) star-formation
are predicted by models that attempt to explain the observed chemical and
photometric anomalies observed in globular clusters as being due to the
formation of a second stellar population within an existing first population.
Additionally, studies that have claimed extended star-formation histories
within LMC/SMC intermediate age clusters (1-2 Gyr), also imply that many young
massive clusters should show ongoing star-formation. Based on visual inspection
of the spectra and/or the colour-magnitude diagrams, we do not find evidence
for ongoing star-formation within any of the clusters, and use this to place
constraints on the above models. Models of continuous star-formation within
clusters, lasting for hundreds of Myr, are ruled out at high significance
(unless stellar IMF variations are invoked). Models for the (nearly
instantaneous) formation of a secondary population within an existing first
generation are not favoured, but are not formally discounted due to the finite
sampling of age/mass-space.
