THE EXTENSIVE AGE GRADIENT OF THE CARINA DWARF GALAXY
THE EXTENSIVE AGE GRADIENT OF THE CARINA DWARF GALAXY
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DOI：
10.1088/2041-8205/761/2/l31
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发表时间：
2012-11
期刊：
影响因子：
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通讯作者：
G. Battaglia;M. Irwin;E. Tolstoy;T. de Boer;M. Mateo
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文献类型：
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作者：
G. Battaglia;M. Irwin;E. Tolstoy;T. de Boer;M. Mateo
像矮球状星系（dSphs）这样的小系统的演化很可能是外部环境效应和自身相对较浅的威尔斯势阱内部过程之间的平衡。因此，评估这种环境相互作用的强度是理解dSphs重子演化及其衍生暗物质分布的重要因素。在这里，我们提出了一个广泛的CTIO/MOSAIC II光度测量的船底座dSPH的结果，达到了约两个级别以下的最古老的主序列关闭（MSTO）。这个数据集使我们能够详细追踪船底座的结构，从它的中心到非常大的距离，并作为恒星年龄的函数。我们观察到一个主要由古老的MSTO恒星组成的扩展结构的存在，距离船底座中心25 ′和60 ′之间，证实了文献中的结果，即船底座远远超出其标称潮汐半径。我们调查的大量统计数据揭示了其他以前较浅的调查中未发现的等照度线扭曲和尾部等特征。这是第一次在人马座以外的银河系"经典"矮星中发现如此明确的潮汐破裂迹象。我们还证明了存在一个负的年龄梯度在船底座直接从它的MSTO，并跟踪它到非常大的距离从星系中心。与银河系相互作用的迹象使我们不清楚在船底座遭受潮汐破坏之前，年龄梯度是否已经存在。
The evolution of small systems such as dwarf spheroidal galaxies (dSphs) is likely to have been a balance between external environmental effects and internal processes within their own relatively shallow potential wells. Assessing how strong such environmental interactions may have been is therefore an important element in understanding the baryonic evolution of dSphs and their derived dark matter distribution. Here we present results from a wide-area CTIO/MOSAIC II photometric survey of the Carina dSph, reaching down to about two magnitudes below the oldest main-sequence turnoff (MSTO). This data set enables us to trace the structure of Carina in detail out to very large distances from its center, and as a function of stellar age. We observe the presence of an extended structure made up primarily of ancient MSTO stars, at distances between 25′ and 60′ from Carina's center, confirming results in the literature that Carina extends well beyond its nominal tidal radius. The large number statistics of our survey reveals features such as isophote twists and tails that were undetected in other previous, shallower surveys. This is the first time that such unambiguous signs of tidal disruption have been found in a Milky Way “classical” dwarf other than Sagittarius. We also demonstrate the presence of a negative age gradient in Carina directly from its MSTOs, and trace it out to very large distances from the galaxy center. The signs of interaction with the Milky Way make it unclear whether the age gradient was already in place before Carina underwent tidal disruption.