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تسجيل مستخدم جديدGlobular cluster candidates within the Fornax Cluster: intracluster globulars?
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We present the results of a search for globular clusters in the surroundings of 15 low surface brightness dwarf galaxies belonging to the Fornax Cluster, which was carried out on CCD images obtained with the C and T1 filters of the Washington photometric system. The globular cluster candidates show an extended and probably bimodal (C-T1) color distribution, which is inconsistent with the presence of a single population of metal-poor clusters detected in several dwarf galaxies. The surface number density of these candidates shows no concentration towards the respective dwarf galaxies, in whose outskirts they have been identified. On the contrary, if we split the candidates in two groups according to their projected distances to the center of the Fornax Cluster, those located closer to the center show a higher projected density than those located farther from it. These results suggest that the potential globular clusters might not be bound to the dwarf galaxies. Alternatively, these globulars could form part of the very peripheral regions of NGC 1399 (the central galaxy of the Fornax Cluster) or even belong to the intracluster medium.
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We have studied the Globular Cluster System of the merger galaxy NGC 1316 in Fornax, using CCD BVI photometry. A clear bimodality is not detected from the broadband colours. However, dividing the sample into red (presumably metal- rich) and blue (met
al-poor) subpopulations at B-I=1.75, we find that they follow strikingly different angular distributions. The red clusters show a strong correlation with the galaxy elongation, but the blue ones are circularly distributed. No systematic difference is seen in their radial profile and both are equally concentrated. We derive an astonishingly low Specific Frequency for NGC 1316 of only Sn=0.9, which confirms with a larger field a previous finding by Grillmair et al. (1999). Assuming a normal Sn of ~4 for early-type galaxies, we use stellar population synthesis models to estimate in 2 Gyr the age of this galaxy, if an intermediate-age population were to explain the low Sn we observe. This value agrees with the luminosity-weighted mean age of NGC 1316 derived by Kuntschner & Davies (1998) and Mackie & Fabbiano (1998). By fitting t5 functions to the Globular Cluster Luminosity Function (GCLF), we derived the following turnover magnitudes: B=24.69 +/- 0.15, V=23.87 +/- 0.20 and I=22.72 +/- 0.14. They confirm that NGC 1316, in spite of its outlying location, is at the same distance as the core of the Fornax cluster.
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We present a study of the old globular cluster (GC) population of the dwarf irregular galaxy NGC 1427A using multi-wavelength VLT observations in U, B, V, I, H_alpha, J, H, and Ks bands under excellent observing conditions. We applied color and size
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