Proper motions of OB stars in the far Carina Arm
Proper motions of OB stars in the far Carina Arm
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远船底座臂中 OB 星的自行运动
DOI：
10.1093/mnras/stab2905
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发表时间：
2021
影响因子：
4.8
通讯作者：
Drew J
中科院分区：
文献类型：
--
作者：
Drew J
在银河盘的大尺度地图上，船底座臂以一个清晰的螺旋形特征脱颖而出，它拥有突出的星团和富含大质量恒星的星团。我们研究了4199o和早期B的固有运动，最有可能在遥远的船底臂，距离太阳主要超过4kpc，在天空区域，282°< r < 294°和- 3°< B < +1°（银河系坐标）。该样本是通过扩展现有的蓝色选择目录并与gaiaedr3天体测量交叉匹配来构建的。观测到的固有运动模式被调制成锯齿状模式，其全振幅接近1 mas yr - 1，大约每2-3度经度出现一次（在中位obb星距离为5.8 kpc时，200-300 pc）。很可能存在潜在的圆周旋转的运动学扰动。数据还显示了一个移动的星群，包含bbb50颗OB恒星，位于远臂主运行后的r ~ 286°，b ~−1.4°。对相对固有运动的分析表明，逃逸O型恒星的发生率至少为10%（当全空间运动可用时，可能达到20%）。为了确定逃跑者逃离的地点，我们建立了假设线性轨迹的区域模拟，并测试了轨迹冲击参数，以确定可能的弹射热点。我们发现该方法目前对于高达4 Myr的飞行时间给出了很好的结果。它令人信服地表明，只有NGC 3603和Westerlund 2喷出了大量的OB恒星。事实上，这两个星系团分别在0.6-0.9和0.5-0.8兆当量之间经历了强烈的喷发。
In large-scale maps of the Galactic disc, the Carina Arm stands out as a clear spiral feature, hosting prominent star clusters and associations rich in massive stars. We study the proper motions of 4199 O and early B most likely in the far Carina Arm, at distances mainly in excess of 4 kpc from the Sun, within the sky region, 282° < ℓ < 294° and −3° <b< +1° (Galactic coordinates). The sample is constructed by extending an existing blue-selected catalogue, and cross-matching withGaiaEDR3 astrometry. The observed pattern of proper motions is modulated into a saw-tooth pattern, with full amplitude approaching 1 mas yr−1, recurring roughly every 2–3 degrees of longitude (200–300 pc at the median OB-star distance of 5.8 kpc). Kinematic perturbation of underlying circular rotation is most likely present. The data also reveal a moving group containing >50 OB stars at ℓ ∼ 286°,b∼ −1.4° behind the main run of the far arm. An analysis of relative proper motions is performed that yields an incidence of runaway O stars of at least 10 per cent (potentially >20 per cent when full space motions become available). To map where runaways have run away from, we set up simulations for the region that assume linear trajectories and test for trajectory impact parameter in order to identify likely ejection hot spots. We find the method currently gives good results for times of flight of up to ∼4 Myr. It shows convincingly that only NGC 3603 and Westerlund 2 have ejected OB stars in significant numbers. Indeed, both clusters have experienced intense spells of ejection between 0.6–0.9 and 0.5–0.8 Myr ago, respectively.