Discovery of a 21 Myr old stellar population in the Orion complex
Discovery of a 21 Myr old stellar population in the Orion complex
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DOI：
10.1051/0004-6361/201834710
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发表时间：
2018-11
影响因子：
6.5
通讯作者：
J. Kos;J. Bland-Hawthorn;M. Asplund;S. Buder;G. Lewis;Jane Lin;S. Martell;M. Ness;Sanjib Sharma-San
中科院分区：
文献类型：
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作者：
J. Kos;J. Bland-Hawthorn;M. Asplund;S. Buder;G. Lewis;Jane Lin;S. Martell;M. Ness;Sanjib Sharma-San
语境。猎户座复合体可以说是银河系中研究最多的恒星形成区域。虽然猎户座星云中仍在诞生恒星，但据信最古老的部分的年龄不超过 13 密尔。目标。为了研究整个猎户座复合体恒星形成的完整层次结构，我们使用新的恒星巡天对 Ori OB1a 区域进行聚类分析，并为每个已识别的恒星聚集体推导出可靠的年龄。方法。我们使用 Gaia DR2 参数辅以来自 GALAH 和 APOGEE 调查的径向速度来执行 Ori OB1a 关联的聚类。五种超密度在六维参数空间（位置、距离、自行和径向速度）中得到解决。大多数对应于先前已知的结构（ASCC 16、25 Orionis、ASCC 20、ASCC 21）。我们使用 Gaia DR2、Pan-STARRS1 和 2MASS 光度测量来将等时线拟合到已识别星团的颜色星等图上。因此，可以以约 10% 的精度测量星团的年龄。结果。虽然其中四个星团的年龄在 11 至 13 Myr 之间，但 ASCC 20 星团的年龄为 21 ± 3 Myr。这明显大于先前已知的猎户座复合体任何组成部分的年龄。在某种程度上，所有簇至少在六个相空间维度之一上重叠。结论。我们认为，必须重新考虑猎户座复合体的形成历史及其与古尔德带的关系。重建 Ori OB1a 协会历史的一个重大挑战是了解新发现的 21 Myr 老年群体对该复合体较年轻部分的影响，包括其形成。
Context. The Orion complex is arguably the most studied star-forming region in the Galaxy. While stars are still being born in the Orion nebula, the oldest part was believed to be no more than 13 Myr old. Aims. In order to study the full hierarchy of star formation across the Orion complex, we perform a clustering analysis of the Ori OB1a region using new stellar surveys and derive robust ages for each identified stellar aggregate. Methods. We use Gaia DR2 parameters supplemented with radial velocities from the GALAH and APOGEE surveys to perform clustering of the Ori OB1a association. Five overdensities are resolved in a six-dimensional parameter space (positions, distance, proper motions, and radial velocity). Most correspond to previously known structures (ASCC 16, 25 Orionis, ASCC 20, ASCC 21). We use Gaia DR2, Pan-STARRS1 and 2MASS photometry to fit isochrones to the colour-magnitude diagrams of the identified clusters. The ages of the clusters can thus be measured with ∼10% precision. Results. While four of the clusters have ages between 11 and 13 Myr, the ASCC 20 cluster stands out at an age of 21 ± 3 Myr. This is significantly greater than the age of any previously known component of the Orion complex. To some degree, all clusters overlap in at least one of the six phase-space dimensions. Conclusions. We argue that the formation history of the Orion complex, and its relation to the Gould belt, must be reconsidered. A significant challenge in reconstructing the history of the Ori OB1a association is to understand the impact of the newly discovered 21 Myr old population on the younger parts of the complex, including their formation.