Age estimates for globular clusters in NGC 1399

被引:29
作者
Forbes, DA [1 ]
Beasley, MA
Brodie, JP
Kissler-Patig, M
机构
[1] Swinburne Univ, Hawthorn, Vic 3122, Australia
[2] Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA
[3] European So Observ, D-85748 Garching, Germany
基金
美国国家科学基金会;
关键词
galaxies : individual (NGC 1399); galaxies : star clusters; globular clusters : general;
D O I
10.1086/338593
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present high signal-to-noise Keck spectra for 10 globular clusters associated with the giant Fornax elliptical galaxy NGC 1399 and compare measured line indices with current stellar population models. Our data convincingly demonstrate, for the first time, that at least some of the clusters in a giant elliptical galaxy have supersolar abundance ratios, similar to the host galaxy. From H beta line strengths, the majority of clusters have ages of similar to 11 Gyr (within 2 sigma), which is similar to the luminosity-weighted stellar age of NGC 1399. Two of the clusters (which also reveal enhanced abundance ratios) show significantly higher H beta values than the others. It remains unclear whether this is due to young (2 Gyr) ages or extremely old (>15 Gyr) ages with a warm blue horizontal branch. However, a conflict with current cosmological parameters is avoided if the young age is favored. Either alternative indicates a complicated age distribution among the metal-rich clusters and sets interesting constraints on their chemical enrichment at late epochs.
引用
收藏
页码:L143 / L146
页数:4
相关论文
共 30 条
[1]   THE FORMATION OF GLOBULAR-CLUSTERS IN MERGING AND INTERACTING GALAXIES [J].
ASHMAN, KM ;
ZEPF, SE .
ASTROPHYSICAL JOURNAL, 1992, 384 (01) :50-61
[2]   Ages and metallicities of globular clusters in NGC 4472 [J].
Beasley, MA ;
Sharples, RM ;
Bridges, TJ ;
Hanes, DA ;
Zepf, SE ;
Ashman, KM ;
Geisler, D .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2000, 318 (04) :1249-1263
[3]   The constancy of [alpha/Fe] in globular clusters of differing [Fe/H] and age [J].
Carney, BW .
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 1996, 108 (728) :900-910
[4]   Distances, ages, and epoch of formation of globular clusters [J].
Carretta, E ;
Gratton, RG ;
Clementini, G ;
Pecci, FF .
ASTROPHYSICAL JOURNAL, 2000, 533 (01) :215-235
[5]   The ages and abundances of a large sample of M87 globular clusters [J].
Cohen, JG ;
Blakeslee, JP ;
Ryzhov, A .
ASTROPHYSICAL JOURNAL, 1998, 496 (02) :808-826
[6]  
FORBES D, 2001, APJ, V546, pL83
[7]   On the origin of globular clusters in elliptical and cD galaxies [J].
Forbes, DA ;
Brodie, JP ;
Grillmair, CJ .
ASTRONOMICAL JOURNAL, 1997, 113 (05) :1652-1665
[8]  
GNEDIN OY, 2001, UNPUB NATURE
[9]  
GONZALEZ JJ, 1993, THESIS U CALIFORNIA
[10]   The star cluster system of the 3-Gyr-old merger remnant NGC 1316: clues from optical and near-infrared photometry [J].
Goudfrooij, P ;
Alonso, MV ;
Maraston, C ;
Minniti, D .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2001, 328 (01) :237-256