Size and Spatial Distributions of Sub-km Main-Belt Asteroids ∗
Size and Spatial Distributions of Sub-km Main-Belt Asteroids ∗
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DOI：
10.1093/pasj/55.3.701
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发表时间：
2003-06
影响因子：
2.3
通讯作者：
F. Yoshida;Tsuko Nakamura;J. Watanabe;D. Kinoshita;N. Yamamoto;T. Fuse
中科院分区：
文献类型：
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作者：
F. Yoshida;Tsuko Nakamura;J. Watanabe;D. Kinoshita;N. Yamamoto;T. Fuse
本文介绍了首次利用位于夏威夷莫纳克亚山顶的8.2米斯巴鲁望远镜上的斯巴鲁主焦点相机（Suprime-Cam）对主带小行星（亚千米级）进行系统观测的结果。我们称之为SMBAS（Sub-km Main-Belt Asteroid Survey）。2001年2月22日和25日（HST）进行了观测，并在对日和黄道附近搜索了一个约3.0度2的天空区域。我们探测到了1111个移动中的天体，亮度低至R = 26等（包括非常慢的海王星外天体）。在这次调查中，我们无法确定移动物体的确切轨道，因为它们的观测弧很短，只有2小时。相反，我们统计估计的半长轴（a）和倾角（I）的每个移动对象从其明显的天空运动矢量，然后获得的大小和空间分布的亚公里MBA。SMBAS的主要结果是：（1）在对日面和黄道附近，MBAs的天空数密度从290 deg −2下降到24.4 mag（对于MBAs）。(2)直径在0.5公里至1公里之间的千米以下MBA的累积尺寸分布斜率（1.2）比直径超过1.5公里的大型MBA的累积尺寸分布斜率（1.8）要小得多，后者是从过去的小行星勘测中获得的。这意味着低于千米的小行星数量比从大型小行星的大小分布推断出的结果要少得多。(3)外主带亚千米级MBA的亏损比内主带更为明显。(4)在主带外区（a = 2.8 -3.1AU），SMBAS小行星在I方向上的分布比已知的大行星更广。我们还讨论了SMBAS观测到的小行星的分布特征的可能原因。
This paper presents the result of the first systematic investigation of very small Main-Belt Asteroids (sub-km MBAs) using the Subaru Prime-Focus Camera (Suprime-Cam) with an 8K ×10K mosaic CCD array attached to the 8.2m Subaru Telescope atop Mauna Kea, Hawaii. We call this survey SMBAS (Sub-km Main-Belt Asteroid Survey). Observations were carried out on 2001 February 22 and 25 (HST) and a ∼ 3.0deg 2 sky area near the opposition and near the ecliptic was searched. We detected 1111 moving objects down to R ∼ 26mag (including very slow TransNeptunian Objects). In this survey, we could not determine the exact orbits of the moving objects, because of their short observational arc of only 2 hours. Instead, we statistically estimated the semi-major axis (a) and inclination (I) of each moving object from its apparent sky-motion vector, and then obtained the size and spatial distributions of sub-km MBAs. The main results of SMBAS are: (1) The sky number density of MBAs is found to be ∼ 290deg −2 down to R ∼ 24.4mag (for MBAs) near the opposition and near the ecliptic. (2) The slope of the cumulative size distribution for sub-km MBAs ranging from 0.5km to 1km in diameter is fairly shallower (∼ 1.2) than that for large MBAs of more than∼ 5km in diameter (∼ 1.8), which was obtained from past asteroid surveys. This means that the number of sub-km MBAs is much more depleted than a result extrapolated from the size distributions for large asteroids. (3) The depletion of sub-km MBAs is clearer in the outer main-belt than in the inner main-belt. (4) It seems that SMBAS asteroids distribute more widely in the I-direction in the outer zone (a =2 .8–3.1AU) of the main-belt than known large asteroids do. We also discuss the possible causes for the characteristics of the distributions of SMBAS-observed small asteroids.