Extinction within 10° of the Galactic centre using 2MASS
Extinction within 10° of the Galactic centre using 2MASS
复制标题
使用 2MASS 银河系中心 10° 范围内的消光
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
B. Barbuy
中科院分区：
文献类型：
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作者：
C. Dutra;B. Santiago;E. Bica;B. Barbuy
从2 MASS点源星表中提取了约6 × 10 6颗恒星的J和Ks星等，其中8 ≤ Ks ≤ 13，以建立银河系中心10°范围内的A-K消光图。通过将（KS，J-KS）色星等图的上巨分支拟合到由以前研究的球场建立的去红上巨分支平均轨迹上，确定了消光。消光值从地图边缘的AK = 0.05到银河系中心附近的AK = 3.2不等。将2 MASS灭绝图与最近从DENIS数据得出的灭绝图进行了比较。这两个地图同意非常好，直到A K = 1.0。超过此限值，比较会受到两种消光测定方法中内部误差增加的影响。2 MASS消光值也进行了比较，从尘埃排放在远红外使用DIRBE/IRAS。几个系统的影响可能会导致这种比较的偏差，包括在灭绝测定中使用的大部分2 MASS恒星背景上存在尘埃。对于3° <B θ < 5°的区域，其中银河系远侧的尘埃贡献为5%，两个消光测定结果相关良好，但尘埃排放A K值系统地高于2 MASS的值。DIRBE/IRAS尘埃排放消光的校准校正系数为76%，需要消除这种系统性影响。对于1° <λ B λ < 3°和λ B λ < 0.5°的条带也进行了类似的比较，揭示了两个消光值之间的关系越来越复杂。从校准因子、背景尘埃贡献的增加、影响尘埃发射消光的温度效应以及在非常高消光区（B θ < 0.5°）确定2 MASS消光的局限性方面解释了不一致性。在尘埃图中观察到相对于银道面的不对称性，大致是在1° <B θ < 5°时，南方的A K值比北方小60%。这种不对称性是由于前景尘埃云的存在主要是在隆起的北方地区。
We extract J and K s magnitudes from the 2MASS Point Source Catalog for approximately 6 × 10 6 stars with 8 ≤ K s ≤ 13 in order to build an A K extinction map within 10° of the Galactic centre. The extinction was determined by fitting the upper giant branch of (K s , J -K s ) colour-magnitude diagrams to a dereddened upper giant branch mean locus built from previously studied bulge fields. The extinction values vary from A K = 0.05 in the edges of the map up to A K = 3.2 close to the Galactic centre. The 2MASS extinction map was compared to that recently derived from DENIS data. Both maps agree very well up to A K = 1.0. Above this limit, the comparison is affected by increased internal errors in both extinction determination methods. The 2MASS extinction values were also compared to those obtained from dust emission in the far-infrared using DIRBE/IRAS. Several systematic effects likely to bias this comparison were addressed, including the presence of dust on the background of the bulk of 2MASS stars used in the extinction determination. For the region with 3° < ‖b‖ < 5°, where the dust contribution on the far side of the Galaxy is 5 per cent, the two extinction determinations correlate well, but the dust emission A K values are systematically higher than those from 2MASS. A calibration correction factor of 76 per cent for the DIRBE/IRAS dust emission extinction is needed to eliminate this systematic effect. Similar comparisons were also carried out for the 1° < ‖b‖ < 3° and ‖b‖ < 0.5° strips, revealing an increasing complexity in the relation between the two extinction values. Discrepancies are explained in terms of the calibration factor, increasing background dust contribution, temperature effects influencing the dust emission extinction and limitations in the 2MASS extinction determination in very high extinction regions (‖b‖ < 0.5°). An asymmetry relative to the Galactic plane is observed in the dust maps, roughly in the sense that A K values are 60 per cent smaller in the south than in the north for 1° < ‖b‖ < 5°. This asymmetry is due to the presence of foreground dust clouds mostly in the northern region of the bulge.