Blanco DECam Bulge Survey (BDBS): V. Cleaning the foreground populations from Galactic bulge colour-magnitude diagrams using Gaia EDR3
Blanco DECam Bulge Survey (BDBS): V. Cleaning the foreground populations from Galactic bulge colour-magnitude diagrams using Gaia EDR3
复制标题
Blanco DECam 核球巡天 (BDBS)：V. 使用 Gaia EDR3 从银河核球颜色星等图中清理前景人口
DOI：
10.1051/0004-6361/202243921
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发表时间：
2022
影响因子：
6.5
通讯作者：
Kunder, Andrea
中科院分区：
文献类型：
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作者：
Marchetti, Tommaso;Johnson, Christian I.;Joyce, Meridith;Rich, R.Michael;Simion, Iulia T.;Young, Michael D.;Clarkson, William;Pilachowski, Catherine A.;Michael, Scott;Kunder, Andrea
目的布兰科DECam膨胀巡天（BDBS）已经拍摄了超过200平方度的南银河系膨胀区，为2.5亿颗独特的恒星提供了光度测量。一个强大的前景盘人口的存在，沿着与复杂的变红和极端的图像拥挤，已经很难约束存在的年轻和中等年龄的恒星在bulge population.MethodsWe采用了一个准确的交叉匹配的BDBS与最新的数据发布（EDR3）从theGaiamission，匹配超过140万源BDBS测光和GaiaEDR3测光和天体测量。我们依靠GaiaEDR3天体测量，没有任何光度选择，以产生干净的BDBS凸出色星等图（CMD）。Gaiaparallaxes被用来过滤明亮的前景源，高斯混合模型拟合银河系自行可以识别恒星运动学一致的凸出成员。我们将这种方法应用于127个不同的凸起区域，每个区域为1 ° 2，|ℓ| ≤ 9.5°和−9.5° ≤B≤ −2.5°。结果天体测量清理程序去除了每个视场中的大部分蓝色恒星，特别是在银河系平面附近，蓝色恒星与红色恒星的比例为10%左右，在银河系高纬度地区增加到20%左右。我们排除了普遍存在的年龄小于2 Gyr的恒星。根据他们测量的天体测量学，绝大多数比岔道亮的蓝色恒星属于前景星群。我们介绍了观察到的红巨星分支凸块和红色团块之间的距离作为一个简单的年龄代理在外地的优势人口，我们确认了一个占主导地位的老隆起的图片。还需要进一步的工作来应用该方法来估计高纬度地区的年龄，并模拟银河系隆起的复杂形态。我们还产生横向运动学地图，恢复预期的模式相关的酒吧和X形的性质的凸起的存在。
AimsThe Blanco DECam Bulge Survey (BDBS) has imaged more than 200 square degrees of the southern Galactic bulge, providing photometry in theugrizyfilters for ∼250 million unique stars. The presence of a strong foreground disk population, along with complex reddening and extreme image crowding, has made it difficult to constrain the presence of young and intermediate age stars in the bulge population.MethodsWe employed an accurate cross-match of BDBS with the latest data release (EDR3) from theGaiamission, matching more than 140 million sources with BDBS photometry andGaiaEDR3 photometry and astrometry. We relied onGaiaEDR3 astrometry, without any photometric selection, to produce clean BDBS bulge colour-magnitude diagrams (CMDs).Gaiaparallaxes were used to filter out bright foreground sources, and a Gaussian mixture model fit to Galactic proper motions could identify stars kinematically consistent with bulge membership. We applied this method to 127 different bulge fields of 1 deg2each, with |ℓ| ≤ 9.5° and −9.5° ≤b≤ −2.5°.ResultsThe astrometric cleaning procedure removes the majority of blue stars in each field, especially near the Galactic plane, where the ratio of blue to red stars is ≲10%, increasing to values ∼20% at higher Galactic latitudes. We rule out the presence of a widespread population of stars younger than 2 Gyr. The vast majority of blue stars brighter than the turnoff belong to the foreground population, according to their measured astrometry. We introduce the distance between the observed red giant branch bump and the red clump as a simple age proxy for the dominant population in the field, and we confirm the picture of a predominantly old bulge. Further work is needed to apply the method to estimate ages to fields at higher latitudes, and to model the complex morphology of the Galactic bulge. We also produce transverse kinematic maps, recovering expected patterns related to the presence of the bar and of the X-shaped nature of the bulge.