We present high angular resolution imaging of the quasar PSO J172.3556+18.7734 at z = 6.82 with the Very Long Baseline Array (VLBA). This source currently holds the record of being the highest redshift radio-loud quasar. These observations reveal a dominant radio source with a flux density of 398.4 61.4 μJy at 1.53 GHz, a deconvolved size of 9.9 3.5 mas (52.5 18.6 pc), and an intrinsic brightness temperature of (4.7 0.7) 10⁷ K. A weak unresolved radio extension from the main source is also detected at the ∼3.1σ level. The total flux density recovered with the VLBA at 1.53 GHz is consistent with that measured with the Very Large Array (VLA) at a similar frequency. The quasar is not detected at 4.67 GHz with the VLBA, suggesting a steep spectral index with a limit of 1.55. The quasar is also not detected with the VLBA at 7.67 GHz. The overall characteristics of the quasar suggest that it is a very young radio source similar to lower redshift gigahertz peaked spectrum radio sources, with an estimated kinematic age of ∼10³ yr. The VLA observations of this quasar revealed a second radio source in the field 23.″1 away. This radio source, which does not have an optical or IR counterpart, is not detected with the VLBA at any of the observed frequencies. Its nondetection at the lowest observed VLBA frequency suggests that it is resolved out, implying a size larger than ∼0.″17. It is thus likely situated at lower redshift than the quasar.

我们使用甚长基线阵列 (VLBA)在z = 6.82处呈现类星体 PSO J172.3556+18.7734 的高角分辨率成像。这个来源目前保持着最高红移射电响度类星体的记录。这些观测揭示了一个占主导地位的射电源，其通量密度为 398.4 61.4 μ Jy 在 1.53 GHz，去卷积尺寸为 9.9 3.5 mas (52.5 18.6 pc)，固有亮度温度为 (4.7 0.7) 10 ⁷ K。一个弱未解析在 ∼3.1 σ处也检测到来自主源的无线电扩展等级。使用 VLBA 在 1.53 GHz 恢复的总通量密度与使用超大阵列 (VLA) 在类似频率下测量的结果一致。使用 VLBA 在 4.67 GHz 处未检测到类星体，表明其光谱指数陡峭，极限为1.55。使用 7.67 GHz 的 VLBA 也未检测到类星体。类星体的整体特征表明它是一个非常年轻的射源，类似于低红移千兆赫峰值频谱射源，估计运动年龄约为 10 ³年 VLA 对这个类星体的观测揭示了 23.″1 外场中的第二个射电源。这种没有光学或红外对应物的无线电源在任何观察到的频率下都没有被 VLBA 检测到。它在观察到的最低 VLBA 频率下未检测到表明它已被解决，这意味着尺寸大于 ~0.″17。因此它很可能位于比类星体更低的红移处。