IAU Symposium Abstract S186-059P


Near-infrared Photometry of Globular Clusters in three Giant Elliptical Galaxies


Paul Goudfrooij1, M. Victoria Alonso2, and Dante Minniti3
1 STScI, Baltimore, U.S.A. < goudfroo@stsci.edu >
2 Obs. Astronomico, Cordoba, AR < vicky@oac.uncor.edu >
3 LLNL, Livermore, U.S.A. < dminniti@igpp.llnl.gov >



We have obtained deep near-IR images of globular cluster systems associated with three giant elliptical galaxies which are all obvious merger candidates:\ NGC 5128 (Centaurus A), NGC 1316 (Fornax A), and NGC 1399, the central galaxy of the Fornax cluster, which features a cooling flow. The near-IR photometry is complemented with deep HST imaging, constituting a unique combination for studying globular clusters in nearby galaxies. The clusters are selected on the basis of their structural parameters (observed core diameters and ellipticities), as measured from WFPC2 Hubble Space Telescope (HST) images. Near-IR photometry obtained with IRAC2B at the ESO/MPI 2.2-m telescope is combined with the optical HST photometry to produce color-magnitude and color-color diagrams for the star clusters. A first striking result for NGC 5128 is that we found a few clusters that have colors and magnitudes similar to intermediate-age clusters containing carbon stars in the Magellanic Clouds. If these intermediate-age clusters were formed during a merger, then this episode must have occurred a few gigayears ago. Alternatively, we are looking at cluster members of one of the colliding galaxies, which would then have been a late-type disk galaxy. We will show these results on NGC 5128 and also new results on the globular cluster systems of NGC 1316 and NGC 1399 for which data are being analyzed at the time this abstract was submitted.