ICRS上的位置和自行的PPMXL星表。结合使用USNO-B1 .0和2 MASS
The PPMXL catalog of positions and proper motions on the ICRS. Combining USNO-B1.0 and 2MASS
摘要：
USNO-B1.0和2 MASS是应用最广泛的全天巡天观测系统。然而，2 MASS根本没有自行，而USNO-B1.0只公布了相对自行，而不是绝对自行（即在ICRS上）。利用USNO-B1.0和2 MASS天体测量相结合的方法，在ICRS系统上进行了一次新的平均位置和自行的测定。这个星表被称为PPMXL {可以通过http：//vo.uni-hd.de/ppmxl访问该星表}，它的目标是从最亮的恒星到大约$V \approx 20$全天空。PPMXL包含约9亿个物体，其中约4.1亿个采用2 MASS测光，是目前最大的ICRS自行集合。作为ICRS的代表，我们选择了PPMX。最近发布的UCAC 3不能使用，因为我们发现其自行系统在-20 $^\circ$下降点以北存在板依赖性失真。UCAC 3作为$δ\leq -20^\circ$的中间系统。由此产生的自行的典型的个人平均误差范围从4质量/年到超过10质量/年，这取决于观测历史。2000.0历元位置的平均误差为80 ~ 120 mas，若采用2 MASS天体测量，则为150 ~ 300 mas。给出了将USNO-B1.0小行星观测值转换到ICRS系统的改正表。
英文摘要：
USNO-B1.0 and 2MASS are the most widely used full-sky surveys. However, 2MASS has no proper motions at all, and USNO-B1.0 published only relative, not absolute (i.e. on ICRS) proper motions. We performed a new determination of mean positions and proper motions on the ICRS system by combining USNO-B1.0 and 2MASS astrometry. This catalog is called PPMXL {VO-access to the catalog is possible via http://vo.uni-hd.de/ppmxl}, and it aims to be complete from the brightest stars down to about $V \approx 20$ full-sky. PPMXL contains about 900 million objects, some 410 million with 2MASS photometry, and is the largest collection of ICRS proper motions at present. As representative for the ICRS we chose PPMX. The recently released UCAC3 could not be used because we found plate-dependent distortions in its proper motion system north of -20$^\circ$ declination. UCAC3 served as an intermediate system for $δ\leq -20^\circ$. The resulting typical individual mean errors of the proper motions range from 4 mas/y to more than 10 mas/y depending on observational history. The mean errors of positions at epoch 2000.0 are 80 to 120 mas, if 2MASS astrometry could be used, 150 to 300 mas else. We also give correction tables to convert USNO-B1.0 observations of e.g. minor planets to the ICRS system.
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