Bibcode
DOI
Brodie, Jean P.; Strader, Jay; Denicoló, Glenda; Beasley, Michael A.; Cenarro, A. J.; Larsen, Søren S.; Kuntschner, Harald; Forbes, Duncan A.
Bibliographical reference
The Astronomical Journal, Volume 129, Issue 6, pp. 2643-2653.
Advertised on:
6
2005
Citations
55
Refereed citations
51
Description
High signal-to-noise ratio, low-resolution spectra have been obtained
for 22 globular clusters (GCs) in NGC 4365. Some of these were selected
as probable representatives of an intermediate-age (2-5 Gyr), extremely
metal-rich GC subpopulation. The presence of such a subpopulation had
been inferred from the unusual optical and near-infrared color
distributions of GCs in this otherwise typical Virgo elliptical galaxy.
However, ages derived from Lick indices are consistent with uniformly
old mean ages for all GCs in our sample. The metallicities of the
clusters show some evidence of a trimodal distribution. The most
metal-poor and metal-rich peaks are consistent with the values expected
for an elliptical galaxy of this luminosity, but there appears to be an
additional, intermediate-metallicity peak lying between them. New Hubble
Space Telescope photometry is consistent with this result. A plausible
scenario is that in earlier data these three peaks merged into a single
broad distribution. Our results suggest that it is difficult to identify
intermediate-age GC subpopulations solely with photometry, even when
both optical and near-infrared colors are used.