Parkes observations for project P1321 semester 2024APRS_04

We propose to search for temporal variations in HI absorption spectra seen against background pulsars to characterise Tiny Scale Atomic Structure (TSAS) in the Milky Way interstellar medium (ISM). We will re-observe seven previously studied bright pulsars at two observing epochs in this semester, resulting in minimum and maximum experimental baselines of 0.25 and 50 years. These observations will test predictions that there is a minimum size scale set by the thermal and turbulent properties of the ISM, below which TSAS is only sporadically seen, and will potentially provide the first direct measurements of pressures in "large" TSAS features of > 1000 AU. By using a new phase-resolved spectral line mode that we have recently implemented on Parkes, we will cut data rates and processing times by factors of ~1000. Following the success of this pilot project, we plan to expand to a long-term monitoring programme. Successful demonstration of our techniques will lay the groundwork for future programmes on the SKA.

我们提出通过搜寻背景脉冲星辐射下的中性氢（HI）吸收光谱的时间变化，来表征银河系星际介质（ISM）中的小尺度原子结构（TSAS）。本观测周期内，我们将对7颗此前已被研究的明亮脉冲星开展两次重新观测，由此得到的实验基线最短为0.25年、最长可达50年。本次观测将验证一项理论预言：星际介质的热学与湍流特性设定了一个最小尺寸阈值，低于该阈值的小尺度原子结构仅会零星出现；同时本次观测还有望首次直接测量尺度大于1000天文单位（AU）的“大型”小尺度原子结构的压强。借助我们近期在帕克斯望远镜（Parkes）上搭建的新型相位分辨光谱线观测模式，我们可将数据速率与处理时长压缩约1000倍。若本次试点项目取得成功，我们计划将其拓展为长期监测项目。我们的技术若能得到成功验证，将为未来在平方公里阵列射电望远镜（SKA）上开展相关项目奠定基础。