Parsec-scale alignments of radio-optical offsets with jets in AGNs from multifrequency geodetic VLBI, Gaia EDR3, and the MOJAVE program
Parsec-scale alignments of radio-optical offsets with jets in AGNs from multifrequency geodetic VLBI, Gaia EDR3, and the MOJAVE program
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DOI：
10.1051/0004-6361/202140652
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发表时间：
2021-05
影响因子：
6.5
通讯作者：
S. Lambert;N. Liu;E. Arias;C. Barache;J. Souchay;F. Taris;J. Liu;Z. Zhu
中科院分区：
文献类型：
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作者：
S. Lambert;N. Liu;E. Arias;C. Barache;J. Souchay;F. Taris;J. Liu;Z. Zhu
目标。我们的目标是研究不同波长的类星体发射中心的相对位置，以帮助连接国际天体参考系（ICRS）的各种实现，并揭示不同波长的系统不确定性和单个源行为。方法.我们的研究基于四个目录，代表ICRS，ICRF 3的位置在三个VLBI波段X，K和Ka，和盖亚EDR 3目录的光学波长。我们用莫哈韦团队的喷流运动学结果补充了射电源位置，使我们能够获得天空中的喷流方向。一个六参数变形模型被用来消除系统的不确定性，目前在不同的目录。结果对于四个星表以及莫哈韦团队研究喷流运动学的物体所共有的一组194个物体，我们计算了不同波长位置之间相对于喷流方向的方向。我们发现，这些对象中的大多数有他们的无线电-光学矢量沿着射流，与下游的无线电质心的光学质心，和K和Ka质心最好是上游的射流相对于X质心，这是一个简单的核心射流模型的范例是一致的。对于人口的多波长的位置对准沿着喷流，天体测量信息，因此可以用来测量喷流的方向独立的成像。此外，我们发现了几个源的光学质心与固定的无线电功能与相对较高的部分偏振相一致，表明在射流中的同步加速过程占主导地位的光发射。
Aims. We aim to study the relative positions of quasar emission centers at different wavelengths in order to help link the various realizations of the International Celestial Reference System (ICRS), and to unveil systematic uncertainties and individual source behavior at different wavelengths. Methods. We based our study on four catalogs representing the ICRS, the ICRF3 positions in the three VLBI bands X, K, and Ka, and the Gaia EDR3 catalog in optical wavelengths. We complemented radio source positions with jet kinematics results from the MOJAVE team, allowing us to obtain jet directions on the sky. A six-parameter deformation model was used to remove systematic uncertainties present in the different catalogs. Results. For a set of 194 objects common to the four catalogs and to the objects whose jet kinematics was studied by the MOJAVE team, we computed the orientation between positions at the different wavelengths and with respect to the directions of the jets. We find that the majority of these objects have their radio-to-optical vector along the jet, with the optical centroid downstream from the radio centroids, and that the K and Ka centroids are preferably upstream in the jet with respect to the X centroid, which is consistent with the paradigm of a simple core–jet model. For a population of multiwavelength positions aligned along the jet, astrometric information can therefore be used to measure the direction of the jet independently of imaging. In addition, we find several sources for which the optical centroid coincides with stationary radio features with a relatively high fraction of polarization, indicating optical emission dominated by a synchrotron process in the jet.