Phase-Reference VLBI Observations of the Compact Steep-Spectrum Source 3C 138
Phase-Reference VLBI Observations of the Compact Steep-Spectrum Source 3C 138
复制标题
DOI：
10.1093/pasj/58.6.1033
复制
发表时间：
2006-11
影响因子：
2.3
通讯作者：
Zhi-qiang Shen;L.-L. Shang-L.;D. Jiang;H. Cai;X. Chen
中科院分区：
文献类型：
--
作者：
Zhi-qiang Shen;L.-L. Shang-L.;D. Jiang;H. Cai;X. Chen
我们描述了一个相位参考VLBI观测，进行了在15.4 GHz的快速切换VLBA天线之间的紧凑的陡谱射电源3C 138和类星体PKS 0528 + 134，这是约4度的天空。通过比较相位参考映射和传统的混合映射，我们证明了高精度天体测量的可行性，为源分离4度。VLBI相位参考映射保留了相对相位信息，因此提供了3C 138和PKS 0528 + 134之间Δ α = -9（m）46的精确相对位置。（s）531000 +/- 0。（s）000003和Δ Δ = 3度6 '26。“90311 +/- 0。“00007（J2000.0）。这给出了J2000.0中3C 138的核（组分A）的改进位置为RA = 05（h）21（m）09。（s）885748和Dec = 16度38'22。“05261，假设校准品PKS 0528 + 134的位置正确。我们进一步通过对相位参考数据进行多次CLEAN和自校准来制作混合地图，其中相位参考地图作为第一相位自校准的输入模型。与直接由条纹拟合3C 138数据得到的有限能见度数据的混合地图相比，该地图具有相似的动态范围，但具有更高的角分辨率。因此，相位参考技术不仅是一种相位连接的手段，而且是一种增加相位相干时间的手段，从而允许自校准技术应用于弱得多的源。
We describe a phase-reference VLBI observation that was conducted at 15.4 GHz by fast-switching VLBA antennas between the compact steep-spectrum radio source 3C 138 and the quasar PKS 0528 + 134, which are about 4 degrees away on the sky. By comparing the phase-reference mapping with the conventional hybrid mapping, we demonstrate the feasibility of high-precision astrometric measurements for sources separated by 4 degrees. VLBI phase-reference mapping preserves the relative phase information, and thus provides an accurate relative position between 3C 138 and PKS 0528 + 134 of Delta alpha = -9(m)46.(s)531000 +/- 0.(s)000003 and Delta delta = 3 degrees 6'26."90311 +/- 0."00007 (J2000.0) in right ascension and declination, respectively. This gives an improved position of the nucleus (component A) of 3C 138 in J2000.0 to be RA = 05(h)21(m)09.(s)885748 and Dec = 16 degrees 38'22."05261 under the assumption that the position of calibrator PKS 0528 + 134 is correct. We further made a hybrid map by performing several iterations of CLEAN and self-calibration on the phase-referenced data with the phase-reference map as an input model for the first phase self-calibration. Compared with the hybrid map from the limited visibility data directly obtained from fringe fitting 3C 138 data, this map has a similar dynamic range, but a higher angular resolution. Therefore, the phase-reference technique is not only a means of phase connection, but also a means of increasing the phase coherence time, and thus allowing the self-calibration technique to be applied to much weaker sources.