We report results on multi-epoch Very Large Array (VLA) and pc-scale Very Long Baseline Array (VLBA) observations of candidate compact symmetric objects (CSOs) from the faint sample of high frequency peakers. New VLBA observations could resolve the radio structure in about 42 per cent of the observed sources, showing double components that may be either mini-lobes or core-jet structures. Almost all the sources monitored by the VLA show some variability on time scale of a decade, and only 1 source does not show any significant variation. In 17 sources the flux density changes randomly as it is expected in blazars, and in 4 sources the spectrum becomes flat in the last observing epoch, confirming that samples selected in the GHz regime are highly contaminated by beamed objects. In 16 objects, the pc-scale and variability properties are consistent with a young radio source in adiabatic expansion, with a steady decrease of the flux density in the optically-thin part of the spectrum, and a flux density increase in the optically-thick part. For these sources we estimate dynamical ages between a few tens to a few hundreds years. The corresponding expansion velocity is generally between 0.1c and 0.7c, similar to values found in CSOs with different approaches. The fast evolution that we observe in some CSO candidates suggests that not all the objects would become classical Fanaroff-Riley radio sources.

中文翻译：

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候选紧凑对称物体的可变性和秒差距级无线电结构。

我们报告了来自高频峰值的微弱样本的候选紧凑对称物体 (CSO) 的多时期甚大阵列 (VLA) 和 pc 规模甚长基线阵列 (VLBA) 观测结果。新的 VLBA 观测可以解析大约 42% 的观测源中的无线电结构，显示出可能是微瓣或核心喷射结构的双分量。几乎所有 VLA 监测的源都在十年的时间尺度上表现出一些变化，只有 1 个源没有表现出任何显着的变化。在 17 个源中，通量密度随机变化，正如在耀变体中所预期的那样，而在 4 个源中，在最后一个观测时期，光谱变得平坦，证实了在 GHz 范围内选择的样本被光束物体高度污染。在 16 个对象中，pc 尺度和可变性特性与绝热膨胀中的年轻无线电源一致，光谱的光学薄部分的通量密度稳步下降，而光学厚部分的通量密度增加。对于这些来源，我们估计动态年龄在几十到几百年之间。相应的扩张速度通常在 0.1c 和 0.7c 之间，类似于在不同方法的 CSO 中发现的值。我们在一些 CSO 候选对象中观察到的快速演变表明，并非所有对象都会成为经典的 Fanaroff-Riley 无线电源。对于这些来源，我们估计动态年龄在几十到几百年之间。相应的扩张速度通常在 0.1c 和 0.7c 之间，类似于在不同方法的 CSO 中发现的值。我们在一些 CSO 候选对象中观察到的快速演变表明，并非所有对象都会成为经典的 Fanaroff-Riley 无线电源。对于这些来源，我们估计动态年龄在几十到几百年之间。相应的扩张速度通常在 0.1c 和 0.7c 之间，类似于在采用不同方法的 CSO 中发现的值。我们在一些 CSO 候选对象中观察到的快速演变表明，并非所有对象都会成为经典的 Fanaroff-Riley 无线电源。