Browsing by Author "Brodie, JP"

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    Extragalactic globular clusters in the near infrared - I. A comparison between M87 and NGC 4478
    (2002) Kissler-Patig, M; Brodie, JP; Minniti, D
    We compare optical and near infrared colours of globular clusters in M87, the central giant elliptical in Virgo, and NGC 4478, an intermediate luminosity galaxy in Virgo, close in projection to M87. Combining V and I photometry obtained with the WFPC2 on HST and K-s photometry obtained with the NIRC on Keck 1, we find the broad range in colour and previously detected bi-modality in M87. We confirm that NGC 4478 only hosts a blue sub-population of globular clusters and now show that these clusters' V-I and V-K colours are very similar to those of the halo globular clusters in Milky Way and M31. Most likely, a metal-rich sub-population never formed around this galaxy (rather than having formed and been destroyed later), probably because its metal-rich gas was stripped during its passage through the centre of the Virgo cluster.
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    Toward an understanding of the globular cluster overabundance around the central giant elliptical galaxy NGC 1399
    (1999) Kissler-Patig, M; Grillmair, CJ; Meylan, G; Brodie, JP; Minniti, D; Goudfrooij, P
    We investigate the kinematics of a combined sample of 74 globular clusters around NGC 1399. Their high velocity dispersion, increasing with radius, indicates their association with the gravitational potential of the galaxy cluster rather than with that of NGC 1399 itself. We find no evidence for rotation in the full sample, although there is some indication of rotation in the outer regions. The data do not allow us to detect differences between the kinematics of the blue and red subpopulations of globular clusters. A comparison of the globular cluster systems of NGC 1399 and those of NGC 1404 and NGC 1380 indicates that the globular clusters in all three galaxies are likely to have formed via similar mechanisms and at similar epochs. The only property that distinguishes the NGC 1399 globular cluster system from these others is that it is 10 times more abundant. We summarize the evidence for associating these excess globular clusters with the galaxy cluster rather than with NGC 1399 itself and suggest that the overabundance can be explained by tidal stripping, at an early epoch, of neighboring galaxies and subsequent accumulation of globular clusters in the gravitational potential of the galaxy cluster.