The halo+cluster system of the Galactic globular cluster NGC1851
A. F. Marino, A. P. Milone, D. Yong, A. Dotter, G. Da Costa, M. Asplund, H. Jerjen, D. Mackey, J. Norris, S. Cassisi, L. Sbordone, P. B. Stetson, A. Weiss, A. A… 展开作者
A. F. Marino, A. P. Milone, D. Yong, A. Dotter, G. Da Costa, M. Asplund, H. Jerjen, D. Mackey, J. Norris, S. Cassisi, L. Sbordone, P. B. Stetson, A. Weiss, A. Aparicio, L. R. Bedin, K. Lind, M. Monelli, G. Piotto, R. Angeloni, R. Buonanno
备注：
21 pages, 16 figures, accepted for publication in MNRAS
NGC 1851被一个恒星组成部分所包围，其延伸范围超过潮汐半径的十倍。虽然这种恒星结构的性质尚不清楚，但有人认为它是一个稀疏的恒星晕或与恒星流有关。我们分析的性质，这个有趣的恒星组件周围的NGC 1851通过调查其径向速度和化学成分，特别是在比较中的中央集群分析均匀的方式。我们总共观察到23颗恒星的径向速度与NGC 1851一致的晕，其中15颗我们推断[Fe/H]丰度。我们的研究结果表明：（i）与NGC 1851动力学相关的恒星至少存在于~2.5潮汐半径，支持星团周围存在恒星晕;（ii）除了NGC 1851径向速度类似的恒星外，我们观测到的速度分布与银河系模型的预期一致，表明没有其他子结构（iii）s过程元素Sr和Ba的化学丰度与NGC 1851中观测到的s正常星一致;（iv）所有晕星都有金属丰度，以及其他研究元素Ca、Mg和Cr的丰度，与星团所显示的一致。NGC 1851星系团+晕系统的复杂性可能与NGC 1851最初嵌入的潮汐破裂矮星系的情况一致。
英文摘要：
NGC1851 is surrounded by a stellar component that extends more than ten times beyond the tidal radius. Although the nature of this stellar structure is not known, it has been suggested to be a sparse halo of stars or associated with a stellar stream. We analyse the nature of this intriguing stellar component surrounding NGC1851 by investigating its radial velocities and chemical composition, in particular in comparison with those of the central cluster analysed in a homogeneous manner. In total we observed 23 stars in the halo with radial velocities consistent with NGC1851, and for 15 of them we infer [Fe/H] abundances. Our results show that: (i) stars dynamically linked to NGC1851 are present at least up to ~2.5 tidal radii, supporting the presence of a halo of stars surrounding the cluster; (ii) apart from the NGC1851 radial velocity-like stars, our observed velocity distribution agrees with that expected from Galactic models, suggesting that no other sub-structure (such as a stream) at different radial velocities is present in our field; (iii) the chemical abundances for the s-process elements Sr and Ba are consistent with the s-normal stars observed in NGC1851; (iv) all halo stars have metallicities, and abundances for the other studied elements Ca, Mg and Cr, consistent with those exhibited by the cluster. The complexity of the whole NGC1851 cluster+halo system may agree with the scenario of a tidally-disrupted dwarf galaxy in which NGC1851 was originally embedded.
The Peculiar Chemical Inventory of NGC 2419 -- An Extreme Outer Halo "Globular Cluster"
NGC 2419是一个巨大的外晕星系球状星团，其恒星先前已被证明具有某种特殊的丰度模式。我们用Keck/HIRES在合理的信噪比下观测到了NGC 2419的7颗亮巨星。其中一颗巨行星非常特殊，[Mg/Fe]极低，[K/Fe]极高，但大多数其他元素的丰度正常。丰度模式与任何超新星模型的核合成产率都不匹配。其他六颗恒星的丰度比是典型的内晕星系球状星团，图中以附近球状星团M30中的巨星为代表。虽然我们的测量表明NGC 2419在某些方面是不寻常的，但它的整体性质并没有提供令人信服的证据来证明内晕和外晕球状星团之间的差异。
New Candidate Planetary Nebulae in Galactic Globular Clusters from the VVV Survey
到目前为止，在银河系中只知道四个球状星团行星状星云（GCPN）。最近在银河系核球附近发现了大约50个新的球状星团。我们提出了一个新的球状星团的3弧分之内的行星状星云的搜索，揭示了新的候选人GCPN的识别。这些可能的关联是PN SB 2与GC Minni 06，PN G354.9-02.8与GC Minni 11，PN G356.8-03.6与GC Minni 28，以及PN Pe 2-11与GC Minni 31。我们放弃了位于新球状星团FSR 1758的投影潮汐半径内的PN H 2-14，因为它们具有不同的测量径向速度。这些都是令人感兴趣的天体，需要进行后续观测（特别是径向速度），以确认成员资格，并详细测量其物理特性。如果得到证实，这将使银河GCPN的总数翻一番。
