Schedule Jan 17, 2009
Globular Clusters Systems of Early-Type Galaxies in the Near-Infrared
Ana Chies-Santos (Univ. Utrect)

The colour distribution of globular cluster systems in the majority of galaxies is bi/multimodal in optical colours. It is widely accepted that multiple populations differing in metallicity exist implying different mechanisms/epochs of star formation, with small age differences still being allowed due to the large current uncertainties. Combining optical and NIR colours breaks the age/metallicity degeneracy inherent in optical colours alone, making age estimates for a large sample of GCs possible at the same time.

We are currently building a homogeneous NIR/optical data set of GC systems in a large sample of elliptical and lenticular galaxies with the LIRIS instrument (Ks band) on the William Herschel Telescope in combination with archival ACS g,z data. The larger field of view (~4.2X4.2 arcmin^2) of this instrument compared to earlier studies allows the exploration of radial trends. The sample is drawn from the SAURON program which will give complementary information about the host galaxies.

I will present our sample, the reduction procedures adopted and preliminary results regarding bimodality tests and age/metallicity estimates for a subsample of the galaxies: NGC 4365, NGC 4406, NGC 4486 and NGC 4649.

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