Issue |
A&A
Volume 391, Number 2, August IV 2002
|
|
---|---|---|
Page(s) | 453 - 470 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20020835 | |
Published online | 02 August 2002 |
Extragalactic globular clusters in the near-infrared*,**
II. The globular clusters systems of NGC 3115 and NGC 4365
1
Sternwarte der Ludwig-Maximilians-Universität, Scheinerstr. 1, 81679 München, Germany e-mail: puzia@usm.uni-muenchen.de
2
Department of Astronomy, Yale University, PO Box 208101, New Haven, CT 06520-8101, USA
3
Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA e-mail: zepf@pa.msu.edu
4
European Southern Observatory, 85749 Garching bei München, Germany e-mail: mkissler@eso.org
5
Sternwarte der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: mhilker@astro.uni-bonn.de
6
Departamento de Astronomía y Astrofísica, P. Universidad Católica, Casilla 104, Santiago 22, Chile e-mail: dante@astro.puc.cl
7
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA e-mail: goudfroo@stsci.edu
Corresponding author: T. H. Puzia, puzia@usm.uni-muenchen.de
Received:
18
February
2002
Accepted:
15
May
2002
We combine near-infrared photometry obtained with the
VLT/ISAAC instrument and archival HST/WFPC2 optical images to
determine VIK magnitudes and colours of globular clusters in
two early-type galaxies, NGC 3115 and NGC 4365. The combination
of near-IR and optical photometry provides a way to lift the
age-metallicity degeneracy. For NGC 3115, the globular cluster
colours reveal two major sub-populations, consistent with
previous studies. By comparing the ,
colours of the
NGC 3115 globular clusters with stellar populations models, we
find that the colour difference between the two
10 Gyr old
major sub-populations is primarily due to a difference in
metallicity. We find Δ[ Fe/H
dex and the blue
(metal-poor) and red (metal-rich) globular cluster
sub-populations being coeval within 3 Gyr. In contrast to the
NGC 3115 globular clusters, the globular cluster system in
NGC 4365 exhibits a more complex age and metallicity
structure. We find a significant population of intermediate-age
very metal-rich globular clusters along with an old population
of both metal-rich and metal-poor clusters. Specifically, we
observe a large population of globular clusters with red
colours but intermediate
colours, for which all current
stellar population models give ages and metallicities in the
range ~
Gyr and ~
,
respectively. After 10 Gyr of passive evolution, the
intermediate-age globular clusters in NGC 4365 will have colours
which are consistent with the very metal-rich population of
globular clusters in giant elliptical galaxies, such as M 87. Our
results for both globular cluster systems are consistent with
previous age and metallicity studies of the diffuse galactic
light. In addition to the major globular cluster populations in
NGC 3115 and NGC 4365 we report on the detection of objects with
extremely red colours (
mag), whose nature could not
ultimately be revealed with the present data.
Key words: galaxies: formation / galaxies: star clusters / galaxies: individual: NGC 3115, NGC 4365
© ESO, 2002
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.