The VMC Survey - VI. Quasars behind the Magellanic system
The VMC Survey - VI. Quasars behind the Magellanic system
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DOI：
10.1051/0004-6361/201219696
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发表时间：
2012-07
影响因子：
6.5
通讯作者：
M. Cioni;D. Kamath;S. Rubele;J. V. Loon;P. Wood;J. Emerson;B. Gibson;M. Groenewegen;V. Ivanov;B. Miszalski;V. Ripepi
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作者：
M. Cioni;D. Kamath;S. Rubele;J. V. Loon;P. Wood;J. Emerson;B. Gibson;M. Groenewegen;V. Ivanov;B. Miszalski;V. Ripepi
上下文麦哲伦星系后面已确认的类恒星天体（QSO）的数量和空间分布是有限的。这破坏了它们作为不同类型研究的天体测量参考对象的用途。目标。我们已经搜索的标准，以确定候选的类星体使用的观测，从麦哲伦云系统（VMC），提供测光的YJK（s）波段和12个历元的K-s波段的VISTA调查。方法.（Y-J）对（J-K-s）图已经被用来区分类星体候选者与银河系恒星和麦哲伦星云的恒星。然后，K-s带中的变化的斜率被用于识别高置信度候选的样本。这些标准是根据VMC调查目前观测到的117个已知类星体的特性制定的。结果给出了麦哲伦星系后已知类星体的VMC、YJK（s）等星等和K-s光变曲线。约75%的光变曲线的斜率K_s> 10（-4）mag/day，光变曲线的形状一般不规则，没有明显的周期性。在包括黄道南极和剑鱼座30区在内的瓦片中发现的类星体候选者数量分别为22个和26个，其中20%受到年轻恒星物体、行星状星云、恒星和正常星系的污染。结论.通过将类星体候选者的数量外推到整个VMC测量区域，我们预计在LMC后面发现大约1200个类星体，SMC后面有400个，桥后面有200个，流区域后面有30个，但不是所有的都适合天体测量。此外，K-s波段光变曲线可以帮助支持对变化机制的调查。
Context. The number and spatial distribution of confirmed quasi-stellar objects (QSOs) behind the Magellanic system is limited. This undermines their use as astrometric reference objects for different types of studies. Aims. We have searched for criteria to identify candidate QSOs using observations from the VISTA survey of the Magellanic Clouds system (VMC) that provides photometry in the YJK(s) bands and 12 epochs in the K-s band. Methods. The (Y - J) versus (J - K-s) diagram has been used to distinguish QSO candidates from Milky Way stars and stars of the Magellanic Clouds. Then, the slope of variation in the K-s band has been used to identify a sample of high confidence candidates. These criteria were developed based on the properties of 117 known QSOs presently observed by the VMC survey. Results. VMC YJK(s) magnitudes and K-s light-curves of known QSOs behind the Magellanic system are presented. About 75% of them show a slope of variation in K-s > 10(-4) mag/day and the shape of the light-curve is in general irregular and without any clear periodicity. The number of QSO candidates found in tiles including the south ecliptic pole and the 30 Doradus regions is 22 and 26, respectively, with a similar to 20% contamination by young stellar objects, planetary nebulae, stars and normal galaxies. Conclusions. By extrapolating the number of QSO candidates to the entire VMC survey area we expect to find about 1200 QSOs behind the LMC, 400 behind the SMC, 200 behind the Bridge and 30 behind the Stream areas, but not all will be suitable for astrometry. Further, the K-s band light-curves can help support investigations of the mechanism responsible for the variations.