用跨欧洲国际LOFAR望远镜将亚角秒分辨率成像推低到30 MHz
Pushing subarcsecond resolution imaging down to 30 MHz with the trans-European International LOFAR Telescope
摘要：
在超低射频，即低于50 MHz（ULF）的情况下，关于宇宙的信息相对较少，尽管ULF光谱窗口包含了大量用于研究银河系和河外现象的独特诊断。由于所需的基线较长（>1000公里）和电离层扰动较大，在这些频率下进行亚弧秒分辨率成像极为困难。我们已经进行了一个试点项目，以调查国际LOFAR望远镜（ILT）的超低频性能和潜力，一个跨欧洲的干涉阵列，基线高达~2000公里，观测频率低至10 MHz。我们已经成功地产生了6个射电源的亚弧秒分辨率的图像，频率低至30 MHz。这是一个数量级以上的分辨率比前ILT观测在类似的频率。我们拍摄到的6个目标（3C 196、3C 225、3C 273、3C 295、3C 298和3C 380）是结构紧凑的亮射电源。通过比较我们的3C 196和3C 273的观测数据在更高的频率，我们研究了它们的空间分辨射电光谱特性。我们的成功表明，在低至30 MHz的频率下，ILT的亚弧秒成像是可能的。需要进一步分析来确定观测较暗源或发射不太致密的源的可行性。
英文摘要：
Relatively little information is available about the Universe at ultra-low radio frequencies, i.e. below 50 MHz (ULF), although the ULF spectral window contains a wealth of unique diagnostics for studying galactic and extragalactic phenomena. Sub-arcsecond resolution imaging at these frequencies is extremely difficult, due to the long baselines (>1000 km) required and large ionospheric perturbations. We have conducted a pilot project to investigate the ULF performance and potential of the International LOFAR Telescope (ILT), a trans-European interferometric array with baselines up to ~2000 km and observing frequencies down to 10 MHz. We have successfully produced images with sub-arcsecond resolution for 6 radio sources at frequencies down to 30 MHz. This is more than an order of magnitude better resolution than pre-ILT observations at similar frequencies. The six targets that we have imaged (3C 196, 3C 225, 3C 273, 3C 295, 3C 298 and 3C 380) are bright radio sources with compact structures. By comparing our data of 3C 196 and 3C 273 with observations at higher frequencies, we investigate their spatially resolved radio spectral properties. Our success shows that at frequencies down to 30 MHz, sub-arcsecond imaging with the ILT is possible. Further analysis is needed to determine the feasibility of observations of fainter sources or sources with less compact emission.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
