New light on the formation and evolution of M 31 and its globular cluster system
New light on the formation and evolution of M 31 and its globular cluster system
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DOI：
10.1051/0004-6361:20041813
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发表时间：
2005-01
影响因子：
6.5
通讯作者：
T. Puzia;K. Perrett;T. Bridges
中科院分区：
文献类型：
--
作者：
T. Puzia;K. Perrett;T. Bridges
我们给出了M31中70个球状星团的光谱年龄、金属丰度和（α/Fe）比值，这些数据是由Lick线指数测量得到的。一种新的年龄金属丰度和α/Fe诊断网格的插值技术被用来解释指数强度的变化，作为对丰度比变化的响应，特别是对于所有的Balmer线Lick指数。除了古老的（>10 Gyr）球状星团外，它们的金属丰度范围很广，从大约-2。除了太阳值外，我们还发现了一个年龄在150 - 80亿年之间，平均金属丰度（Z/H）为<$-0.6的中间年龄球状星团种群的证据。我们还证实了最近由比斯利等人（2004，AJ，128，1623）发现的年轻的M 31球状星团的存在，它们的年龄为9 Gyr，具有双峰金属丰度分布，并且是超太阳的（α/Fe）。盘状球状星团的年龄范围更广，平均来说更富金属，平均（α/Fe）比也稍小。M31球状星团的结构参数与光谱年龄、金属丰度和（α/Fe）比值的互相关表明，半光/潮汐半径与金属丰度之间存在相关性，这很可能是由于半光/潮汐半径与银河系距离之间的相关性。我们比较了我们的结果M31球状星团的球状星团在银河系中，大麦哲伦云，M81，和其他螺旋星系的玉夫座集团与相同的技术得到的。最后，我们比较了两个本星系群螺旋星系M31和银河系的球状星团系统，以及它们的积分球光。
We present spectroscopic ages, metallicities, and (α/Fe) ratios for 70 globular clusters in M 31 that were derived from Lick line-index measurements. A new interpolation technique of age-metallicity and α/Fe-diagnostic grids is used to account for changes in index strength as a response to abundance-ratio variations, in particular for all of the Balmer-line Lick indices. In addition to a population of old (>10 Gyr) globular clusters with a wide range of metallicities, from about −2. 0d ex to solar values, we find evidence for a population of intermediate-age globular clusters with ages between ∼ 5a nd 8G yr and a mean metallicity (Z/H) ≈− 0.6. We also confirm the presence of young M 31 globular clusters that were recently identified by Beasley et al. (2004, AJ, 128, 1623), which have ages 9 Gyr), has a bimodal metallicity distribution, and super-solar (α/Fe). Disk globular clusters have a wider range of ages, are on average more metal-rich, and have a slightly smaller mean (α/Fe) ratio. A cross-correlation of structural parameters for M 31 globular clusters with spectroscopically derived ages, metallicities, and (α/Fe) ratios shows a correlation between half-light/tidal radius and metallicity, which is most likely due to the correlation of half-light/tidal radius and galactocentric distance. We compare our results for M 31 globular clusters with those obtained with the same technique for globular clusters in the Milky Way, Large Magellanic Cloud, M 81, and other spiral galaxies in the Sculptor group. Finally, we compare the globular cluster systems of the two Local Group spirals, M 31 and Milky Way, with their integrated bulge light.