Ages and metallicities of Fornax dwarf elliptical galaxies

Citation
K. Rakos et al., Ages and metallicities of Fornax dwarf elliptical galaxies, ASTRONOM J, 121(4), 2001, pp. 1974-1991
Citations number
77
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMICAL JOURNAL
ISSN journal
00046256 → ACNP
Volume
121
Issue
4
Year of publication
2001
Pages
1974 - 1991
Database
ISI
SICI code
0004-6256(200104)121:4<1974:AAMOFD>2.0.ZU;2-5
Abstract
Narrowband photometry is presented on 27 dwarf ellipticals in the Fornax cl uster. Calibrated with Galactic globular cluster data and spectrophotometri c population models, the colors indicated that dwarf ellipticals have a mea n [Fe/H] of [1.00 +/- 0.28 ranging from [1.6 to -0.4. The mean age of dwarf ellipticals, also determined photometrically, is estimated at 10 +/- 1 Gyr compared with 13 Gyr for bright Fornax ellipticals. Comparison of our meta llicity color and Mg-2 indices demonstrates that the [Mg/Fe] ratio is lower in dwarf ellipticals than their more massive cousins, which is consistent with a longer duration of initial star formation to explain their younger a ges. There is a increase in dwarf metallicity with distance from the Fornax cluster center, where core galaxies are on average 0.5 dex more metal-poor than halo dwarfs. In addition, we find the halo dwarfs are younger in mean age compared with core dwarfs. One possible explanation is that the intrac luster medium ram pressure strips the gas from dwarf ellipticals, halting s tar formation (old age) and stopping enrichment (low metallicity) as they e nter the core.