Astrometric comparisons of quasar catalogues
Astrometric comparisons of quasar catalogues
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DOI：
10.1051/0004-6361:20078427
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发表时间：
2008-07
影响因子：
6.5
通讯作者：
J. Souchay;S. Lambert;A. Andrei;S. Bouquillon;C. Barache;C. L. Poncin-Lafitte
中科院分区：
文献类型：
--
作者：
J. Souchay;S. Lambert;A. Andrei;S. Bouquillon;C. Barache;C. L. Poncin-Lafitte
上下文大型巡天，如斯隆数字巡天（SDSS）和2度视场（2 QZ）大大增加了在可见光波段记录的类星体的数量。与此同时，对河外射电源的甚长基线干涉测量观测的密集化，提高了实现国际天球参考系的准惯性无线电参考框架的准确性。目标。从实现精确的光学对应ICRF的角度来看，我们调查的天体测量性质的类星体记录的几个调查，无论是在无线电和光学波长。方法.类星体的交叉识别是在光学（SDSS vs. 2 QZ）和无线电波长（VLBA Calibration Survey vs. SDSS）的目录之间进行的。比较了类星体的赤道坐标，以评价星表的天体测量质量。结果我们发现SDSS和2 QZ之间有2000多个共同点。我们表明，位置的差异永远不会超过1 °，均方根为0.2 °。在红移测定的协议是良好的，具有0.05均方根的典型色散。SDSS和VLBA加州调查之间的类似比较发现，在0.23 °搜索半径内有831个互相关源。系统误差，可能是由于部分天空覆盖的SDSS，被检测到的坐标差，这产生的旋转的光学框架，相对于无线电对应，在13质量的水平。因此，SDSS和2 QZ都可以提供宝贵的信息，以准确确定ICRS在光域的较暗端。我们最后指出，找到射电大声类星体的最高概率涉及在色-色空间的红色区域进行搜索。
Context. Large surveys, such as the Sloan Digital Sky Survey (SDSS) and the 2-degree Field (2QZ) considerably increased the number of recorded quasars at optical wavelengths. At the same time, the densification of very long baseline interferometry observations of extragalactic radio sources enabled an increase in the accuracy of the the quasi-inertial radio reference frame that realizes the International Celestial Reference System (ICRS). Aims. In the perspective of the realization of an accurate optical counterpart to the ICRF, we investigate the astrometric properties of quasars recorded by several surveys, both at radio and optical wavelengths. Methods. Cross-identifications of quasars are made between catalogues, both at optical (SDSS vs. 2QZ) and radio wavelengths (VLBA Calibrator Survey vs. SDSS). Equatorial coordinates of the quasars are compared to evaluate the astrometric quality of the catalogues. Results. We find more than 2000 objects in common between SDSS and 2QZ. We show that differences in position never exceed 1 �� , with a root mean square of 0.2 �� . The agreement in redshift determinations is good with a typical dispersion of 0.05 root mean square. Similar comparisons between the SDSS and the VLBA Calibrator Survey find 831 cross-correlated sources within a 0.23 �� search radius. Systematic errors, likely due to the partial sky coverage of the SDSS, are detected in the coordinate differences, which produces to a rotation of the optical frame, with respect to the radio counterpart, at the level of 13 mas. Thus both the SDSS and the 2QZ can provide invaluable information for the accurate determination of the ICRS at the fainter end of the optical domain. We finally point out that the highest probability of finding radio loud quasars involves searching in the redder regions of the color−color space.