Quantifying the age distribution of sub-populations
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany e-mail: firstname.lastname@example.org
2 Sternwarte der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: email@example.com
3 Sternwarte der Ludwigs-Maximilians-Universität, Scheinerstr. 1, 81679 München, Germany e-mail: firstname.lastname@example.org
4 Departamento de Astronomía y Astrofísica, P. Universidad Católica, Casilla 306, Santiago 22, Chile e-mail: email@example.com
5 Space Telescope Science Institute, Instrument Division, 3700 San Martin Drive, Baltimore MD 21218, USA e-mail: firstname.lastname@example.org
Corresponding author: M. Hempel, email@example.com
Accepted: 18 April 2003
In this third paper of our series on near-IR and optical photometry of globular cluster systems in early-type galaxies we concentrate on the photometric results for NGC 5846 and NGC 7192, two group ellipticals, and on a first comparison between the globular cluster systems investigated so far. In NGC 5846 the colour-colour diagram shows clear bi-modality in , which is confirmed by a KMM test. The mean colour of both peaks were estimated to be and . The situation in NGC 7192 is different, in that the colour-colour diagram gives no evidence for a distinct second population of globular clusters. Using simulated colour distributions of globular cluster systems, we make a first step in quantifying the cumulative age distribution in globular cluster systems. Also here the result for NGC 5846 leads us to the conclusion that its metal-rich globular cluster population contains two globular cluster populations which differ in age by several Gyr. The age structure for NGC 7192 shows instead strong similarity with a single-age population.
Key words: galaxies: star clusters / galaxies: individual: NGC 5846, NGC 7192
Based on observations at the Very Large Telescope of the European Southern Observatory, Chile (Program 63.N-0287).
© ESO, 2003