Discovery of new retrograde substructures: the shards of ω Centauri?
Discovery of new retrograde substructures: the shards of ω Centauri?
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DOI：
10.1093/mnras/sty1403
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发表时间：
2018-06
影响因子：
4.8
通讯作者：
G. Myeong;N. Evans;Belokurov;J. Sanders;Sergey E. Koposov
中科院分区：
文献类型：
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作者：
G. Myeong;N. Evans;Belokurov;J. Sanders;Sergey E. Koposov
我们使用斯隆数字巡天(SDSS) -盖亚目录来搜索恒星晕中的子结构。样品包括62 133颗晕星，具有完整的相空间坐标，并延伸到日心距离约10 kpc。由于作用在势的缓慢变化下是守恒的，它们允许识别具有共同吸积历史的恒星群。我们设计了一种基于它们在作用空间中的聚类来识别晕子结构的方法，使用金属丰度作为次要检查。这是通过平滑模型和水瓶座模拟的数值构建的恒星晕来验证的。我们在SDSS - Gaia星表中发现了21个子结构，其中包括7个高显著性、高能和逆行的子结构。我们研究逆行的亚结构是否可能是非典型球状星团半人马座ω剥离的物质。通过一个简单的半人马座ω祖星系吸积模型，我们初步论证了可能有多达5个新的子结构（标记为Rg1、Rg3、Rg4、Rg6和Rg7）与这一事件有关。这为前星设定了5 × 10 8 M （cid:3）的最小质量，从而将半人马座ω带到它在动作能量空间中的当前位置。我们的建议可以通过高分辨率光谱来测试候选恒星，以寻找ω半人马座恒星所拥有的不寻常的丰度模式。
We use the Sloan Digital Sky Survey (SDSS)– Gaia catalogue to search for substructure in the stellar halo. The sample comprises 62 133 halo stars with full phase space coordinates and extends out to heliocentric distances of ∼ 10 kpc. As actions are conserved under slow changes of the potential, they permit identification of groups of stars with a common accretion history. We devise a method to identify halo substructures based on their clustering in action space, using metallicity as a secondary check. This is validated against smooth models and numerical constructed stellar haloes from the Aquarius simulations. We identify 21 substructures in the SDSS– Gaia catalogue, including seven high-significance, high-energy and retrograde ones. We investigate whether the retrograde substructures may be material stripped off the atypical globular cluster ω Centauri. Using a simple model of the accretion of the progenitor of the ω Centauri, we tentatively argue for the possible association of up to five of our new substructures (labelled Rg1, Rg3, Rg4, Rg6 and Rg7) with this event. This sets a minimum mass of 5 × 10 8 M (cid:3) for the progenitor, so as to bring ω Centauri to its current location in action–energy space. Our proposal can be tested by high-resolution spectroscopy of the candidates to look for the unusual abundance patterns possessed by ω Centauri stars.