The Globular Cluster System of the Canis Major Dwarf Galaxy
The Globular Cluster System of the Canis Major Dwarf Galaxy
复制标题
大犬座矮星系的球状星团系统
DOI：
10.1086/421003
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
J. Brodie
中科院分区：
文献类型：
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作者：
D. Forbes;J. Strader;J. Brodie
在发现吸积的大犬座矮星系及其相关的球状星团 (GC) 系统的推动下，我们研究了吸积的 GC 对银河系统的贡献。大犬座 GC 以及与人马座矮星系相关的 GC，表现出一系列以银河为中心的半径、顺行和逆行运动以及水平分支形态，表明这些特性在识别吸积 GC 时用途有限。相反，我们发现这些矮星系的年龄-金属丰度关系（AMR）与中高金属丰度（[Fe/H] ≳ -1.3）的主要银河GC分布不同。具有独特 AMR 的 GC 的吸积可以解释银河系 GC 系统中明显年龄分布的大部分原因。大犬座和人马座 AMR 与其他本星系群矮星系的 AMR 类似，并且与简单的封闭盒化学富集模型一致，这进一步表明这些 GC 是在银河系之外形成的。大犬座 GC 的银河系中心距离均小于平均尺寸，进一步支持其起源于银河系之外。我们的研究结果表明，类似质量的矮星的吸积似乎并没有在银河系厚盘或核球的恒星质量形成中发挥重要作用。
Prompted by the discovery of the accreted Canis Major dwarf galaxy and its associated globular cluster (GC) system, we investigate the contribution of accreted GCs to the Galactic system. The Canis Major GCs, and those associated with the Sagittarius dwarf galaxy, exhibit a range of Galactocentric radii, prograde and retrograde motions, and horizontal-branch morphologies, indicating that such properties are of limited use in identifying accreted GCs. In contrast, we find that the age-metallicity relation (AMR) of these dwarf galaxies is distinct from that of the main Galactic GC distribution at intermediate-to-high metallicities ([Fe/H] ≳ -1.3). The accretion of GCs with a distinct AMR would explain much of the apparent age spread in the Galactic GC system. The Canis Major and Sagittarius AMRs are similar to those of other Local Group dwarf galaxies and are consistent with a simple closed-box chemical enrichment model—a further indication that these GCs formed outside of the Milky Way. The Canis Major GCs all have smaller-than-average sizes for their Galactocentric distances, lending further support to their origin outside of the Milky Way. Our findings suggest that accretion of similar mass dwarfs does not appear to have played a major role in building the stellar mass of the thick disk or bulge of the Milky Way.