Comparison of multifrequency positions of extragalactic sources from ICRF3 and Gaia EDR3
Comparison of multifrequency positions of extragalactic sources from ICRF3 and Gaia EDR3
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DOI：
10.1051/0004-6361/202038179
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发表时间：
2021-05
影响因子：
6.5
通讯作者：
Niu Liu;S. Lambert;P. Charlot;Zi Zhu;Jia-cheng Liu;Nanyong Jiang;Xiaosheng Wan;Cheng-Yu Ding
中科院分区：
文献类型：
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作者：
Niu Liu;S. Lambert;P. Charlot;Zi Zhu;Jia-cheng Liu;Nanyong Jiang;Xiaosheng Wan;Cheng-Yu Ding
上下文通过比较盖亚使命得出的光学位置和甚长基线干涉测量法测量的射电位置，在毫弧秒尺度上探测活动星系核的结构。到目前为止，这些比较集中在使用S scinX波段（2/8 GHz）无线电位置，但没有利用存在于更高无线电频率的VLBI位置，即K波段（24 GHz）和X scinKa波段（8/32 GHz）。目标。我们扩展以前的工作，考虑两个额外的无线电频率（K波段和X scinKa波段）的目的是研究的源位置的频率依赖性和潜在的连接与基本活动星系核的物理性质。方法.我们比较了在四个不同波长下测量的绝对源位置，即盖亚早期数据发布3（EDR 3）的光学位置和S scinX-，K-和X scinKa波段的无线电位置，可从国际天体参考框架（ICRF 3）的第三个实现中获得，为512个常见的源。我们首先将三个ICRF 3单独目录与Gaia EDR 3框架对齐，并比较对齐前后的光-无线电偏移。然后，我们研究了观测（无线电）频率，源形态，震级，红移和源类型的光-无线电偏移的相关性。结果在不同的无线电波段中确定的光-无线电偏移之间的偏差小于0.5 mas，但有统计证据表明，对于显示扩展结构的源，与S scinX波段相比，K波段的光-无线电偏移较小。发现光-无线电偏移与结构指数在统计学上相关。大的光-无线电偏移似乎有利于微弱的源，但很好地解释了位置的不确定性，这也是这些源较大。我们没有检测到光学到无线电偏移和红移之间存在任何统计上显着的相关性。结论.射电源的结构似乎是一个主要原因的无线电-光学偏移。对于盖亚天体参考系的校准，S scinX波段框架仍然是目前的首选。
Context. Comparisons of optical positions derived from the Gaia mission and radio positions measured by very long baseline interferometry (VLBI) probe the structure of active galactic nuclei (AGN) on the milliarcsecond scale. So far, these comparisons have focused on using the S∕X-band (2/8 GHz) radio positions, but did not take advantage of the VLBI positions that exist at higher radio frequencies, namely at K-band (24 GHz) and X∕Ka-band (8/32 GHz). Aims. We extend previous works by considering two additional radio frequencies (K-band and X∕Ka-band) with the aim to study the frequency dependence of the source positions and its potential connection with the physical properties of the underlying AGN. Methods. We compared the absolute source positions measured at four different wavelengths, that is, the optical position from the Gaia Early Data Release 3 (EDR3) and the radio positions at the S∕X-, K-, and X∕Ka-band, as available from the third realization of the International Celestial Reference Frame (ICRF3), for 512 common sources. We first aligned the three ICRF3 individual catalogs to the Gaia EDR3 frame and compared the optical-to-radio offsets before and after the alignment. Then we studied the correlation of optical-to-radio offsets with the observing (radio) frequency, source morphology, magnitude, redshift, and source type. Results. The deviation among optical-to-radio offsets determined in the different radio bands is less than 0.5 mas, but there is statistical evidence that the optical-to-radio offset is smaller at K-band compared to S∕X-band for sources showing extended structures. The optical-to-radio offset was found to statistically correlate with the structure index. Large optical-to-radio offsets appear to favor faint sources, but are well explained by positional uncertainty, which is also larger for these sources. We did not detect any statistically significant correlation between the optical-to-radio offset and the redshift. Conclusions. The radio source structure appears to be a major cause for the radio-to-optical offset. For the alignment of the Gaia celestial reference frame, the S∕X-band frame remains the preferred choice at present.