Thursday, Jan 12, 2012, 9:00 AM - 2:00 PM
The Star Cluster Population of the Interacting Galaxy System Arp 261
Bradley W. Peterson
, C. Struck
, B. J. Smith
, M. Hancock
Iowa State University,
East Tennessee State University,
University of California.
We examine the effects of galaxy interactions on star formation by studying the star cluster population of the interacting galaxy system and Arp 261, using data from the Hubble Space Telescope along with ancillary data from Spitzer Space Telescope and Galaxy Evolution Explorer (GALEX) to obtain broader wavelength coverage. Combined with Starburst99 evolutionary synthesis models, we estimate the ages and masses of the clusters. The mass and luminosity distributions are found to be in good agreement with other systems from the literature.
The age distribution of the Arp 261 cluster population is more difficult to interpret because the metallicity of the galaxies is currently unknown, making the ages highly uncertain. Analysis of optical spectra, will allow us to determine the metallicity of the galaxies and improve our estimates of the cluster ages. Despite the uncertainties, it is clear that the majority of the clusters have ages ~ 20 Myr or less. We also find more evidence that large “clumps” of clusters, the smallest scale of star formation directly observable with Spitzer and GALEX, tend to have older ages than the individual clusters they contain, possibly indicating that the young clusters we detect are surrounded by their dispersed predecessors. We call this the “jewels in the crown” effect.
The cluster age distributions in the features of this system have significant implications for its dynamical history. Radio data from the NVSS already indicates that the hydrodynamical Taffy-like collision scenario suggested by the optical morphology may not be correct. Cluster ages in the northern bridge could provide support for this conclusion if the clusters are young enough to have formed in situ. The tidal interactions of a tidal flyby, in contrast, would be expected to displace older populations from the disks, so the bridge would include older clusters.
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