On comparison and combination of catalogues of radio source positions
On comparison and combination of catalogues of radio source positions
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DOI：
10.1051/0004-6361:20077450
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发表时间：
2007-03
影响因子：
6.5
通讯作者：
J. Sokolova;Z. Malkin
中科院分区：
文献类型：
--
作者：
J. Sokolova;Z. Malkin
上下文国际天文学联合会（IAU）推荐用甚长基线干涉测量（VLBI）观测得到的射电源表（RSC）作为国际天球参考架（ICRF）的实现。随着VLBI观测精度的不断提高，发展更精确的RSC构造方法是一个热门问题。目标。在本文中，我们寻找一个最佳的方法表示的RSC系统误差和调查的可能性，以改善ICRF通过结合个人RSC。方法.通过比较各个星表之间射电源位置的差异，研究了代表RSC系统差异的四种方法。8个射电源目录和最新的ICRF实现ICRF-Ext.2用于比较。在选择了最佳的差异表示方法后，我们计算了每个单独目录与ICRF之间的系统差异。这些差异随后被用于组合射电源目录的构建。结果用Legendre-Fourier函数表示RSC之间的系统差异被证明是最准确的方法。利用这种方法，我们构造了两个组合射电源表。其中第一个提供了一个随机的ICRF目前实现的改进，第二个，最后一个允许我们也占可能的系统错误的ICRF。通过对用ICRF和组合星表处理VLBI观测资料所得到的天极偏移量的比较，表明ICRF和组合星表处理结果的改进。结论.国际地球自转和参考系统服务处使用的单个无线电源目录比较的传统方法不能提供足够的准确性，应当由更适当的方法取代。一个综合的射电源目录使我们能够改善ICRF目前的实现。
Context. Radio source catalogues (RSCs) obtained from very long baseline interferometry (VLBI) observations are recommended by the International Astronomical Union (IAU) as realizations of the International Celestial Reference Frame (ICRF). As the accuracy of the VLBI observations is improving with time, development of more accurate methods of RSC construction is a topical problem. Aims. In this paper we search for an optimal method of representation of the RSC systematic errors and investigate a possibility for improving the ICRF by means of combining individual RSCs. Methods. Four methods of representing the RSC systematic differences have been examined by comparison of the differences in the radio source positions between the individual catalogues. Eight radio source catalogues and the latest ICRF realization, ICRF-Ext.2, were used for comparison. After selection of the best method of difference representation we computed the systematic differences between each individual catalogue and the ICRF. These differences were then used in the construction of the combined radio source catalogue. Results. Representation of the systematic differences between RSCs with the Legendre-Fourier functions proved to be the most accurate method. Using this method, two combined radio source catalogues have been constructed. The first of them provides a stochastic improvement of the current realization of ICRF, and the second, final one allows us to account also for possible systematic errors in the ICRF. Comparison of the celestial pole offsets obtained from the processing of VLBI observations using ICRF and the combined catalogue has shown improvement of the results. Conclusions. The conventional method of individual radio source catalogue comparisons used by the International Earth Rotation and Reference Systems Service does not provide sufficient accuracy and should be replaced by a more adequate method. A combined radio source catalogue allows us to improve the current realization of the ICRF.