Blanco DECam Bulge Survey (BDBS) IV: Metallicity distributions and bulge structure from 2.6 million red clump stars
Blanco DECam Bulge Survey (BDBS) IV: Metallicity distributions and bulge structure from 2.6 million red clump stars
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Blanco DECam 核球巡天 (BDBS) IV：260 万颗红丛星的金属丰度分布和球核结构
DOI：
10.1093/mnras/stac1840
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发表时间：
2022
影响因子：
4.8
通讯作者：
Kunder, Andrea
中科院分区：
文献类型：
--
作者：
Johnson, Christian I.;Rich, R. Michael;Simion, Iulia T.;Young, Michael D.;Clarkson, William I.;Pilachowski, Catherine A.;Michael, Scott;Marchetti, Tommaso;Soto, Mario;Kunder, Andrea
我们展示了从布兰科 DECam 核核巡天 (BDBS) 中提取的 260 万颗核核红色星团星样本的光度金属丰度测量结果。与之前的研究类似，我们发现凸起表现出很强的垂直金属丰度梯度，并且金属丰度分布函数中至少有两个峰值出现在b<-5°处。我们可以辨别出贫金属（[Fe/H] ∼ -0.3）和富金属（[Fe/H] ∼ +0.2）丰度分布，每个丰度分布都显示出随纬度的清晰系统趋势，并且可以通过核核恒星形成/富集过程的变化来最好地理解。两个族群都表现出不对称的尾部，因此我们认为，恒星与 [Fe/H] 空间中任一峰的接近程度不一定是对族群成员资格的肯定。贫金属峰在离平面较远的地方转移到较低的 [Fe/H] 值，而富金属峰则截断。靠近平面，富含金属的尾部沿着短轴看起来比离轴场更宽。我们还假设凸起有两个贫金属群体——一个属于低纬度贫金属尾部且主要富含金属的群体，另一个属于在凸起外部占主导地位的贫金属群体。我们检测 |Z| 场中的 X 形结构> 0.7 kpc，对于 [Fe/H] > −0.5 的恒星。 [Fe/H] < -0.5 的恒星可能形成球状或“粗条”分布，而 [Fe/H]−0.1 的恒星则强烈集中在平面附近。
We present photometric metallicity measurements for a sample of 2.6 million bulge red clump stars extracted from the Blanco DECam Bulge Survey (BDBS). Similar to previous studies, we find that the bulge exhibits a strong vertical metallicity gradient, and that at least two peaks in the metallicity distribution functions appear atb< −5°. We can discern a metal-poor ([Fe/H] ∼ −0.3) and metal-rich ([Fe/H] ∼ +0.2) abundance distribution that each show clear systematic trends with latitude, and may be best understood by changes in the bulge’s star formation/enrichment processes. Both groups exhibit asymmetric tails, and as a result we argue that the proximity of a star to either peak in [Fe/H] space is not necessarily an affirmation of group membership. The metal-poor peak shifts to lower [Fe/H] values at larger distances from the plane while the metal-rich tail truncates. Close to the plane, the metal-rich tail appears broader along the minor axis than in off-axis fields. We also posit that the bulge has two metal-poor populations – one that belongs to the metal-poor tail of the low latitude and predominantly metal-rich group, and another belonging to the metal-poor group that dominates in the outer bulge. We detect the X-shape structure in fields with |Z| > 0.7 kpc and for stars with [Fe/H] > −0.5. Stars with [Fe/H] < −0.5 may form a spheroidal or ‘thick bar’ distribution while those with [Fe/H]−0.1 are strongly concentrated near the plane.