The Snapshot Hubble U-band Cluster Survey; A cluster complex in NGC 2146
  We present the Snapshot Hubble U-band Cluster Survey (SHUCS), an ongoing deep
U-band imaging survey of nearby star-forming galaxies. Thanks to the
information provided by the U band, together with archival Hubble Space
Telescope (HST) optical data, we are able to constrain reliable ages, masses,
and extinctions of the cluster populations of these galaxies. We show some
preliminary results from the study of one of the SHUCS galaxies, NGC 2146.
Using the recovered cluster ages we try to understand the propagation of the
star formation in one of the tidal streams where a ring-like cluster complex
has been found. The Ruby Ring, so named due to its appearance, shows a clear
ring-like distribution of star clusters around a central object. We find
evidence of a spatial and temporal correlation between the central cluster and
the clusters in the ring. The Ruby Ring is the product of an intense and
localised burst of star formation, similar to the extended cluster complexes
observed in M 51 and the Antennae, but more impressive because is quite
isolated. We discuss the formation of the Ruby Ring in a "collect & collapse"
framework. The predictions made by this model agree quite well with the
estimated bubble radius and expansion velocity produced by the feedback from
the central cluster, making the Ruby Ring an interesting case of triggered star
formation.
