AI 中文总结
该研究将RACS天体测量校正框架扩展到中高频时期，用分层交叉匹配策略去除系统位置误差，减少残余散射，提高源位置精度，校正后多数区域置信区间缩小，对多领域应用有益，使RACS成南半球分米波高精度全天体测量参考。
AI 中文摘要
准确的射电天体测量对于跨波长可靠的源交叉识别、瞬变事件的精确定位以及稳定全天参考目录的构建至关重要。本文将快速ASKAP连续体调查（RACS）的天体测量校正框架扩展到中高频时期（RACS-Mid1和RACS-High1），基于之前对低频调查的校正。使用高精度外部目录的分层交叉匹配策略，去除未校正数据中存在的大规模系统位置误差，显著减少天空中的残余散射。校正后，中值位置偏移有效消除，两个时期大部分调查区域内，RACS源位置平均残差的68%置信区间从$\gtrsim 0.4''$降至$\lesssim 0.18''$。独立验证表明，校正后的RACS源位置在大部分天空中1-$\sigma$置信水平约为$\sim 0.25''$，在银道面内性能略有下降。这些校正不仅有助于改进ASKAP快速射电暴的定位，还惠及包括瞬变识别、多波长宿主关联以及银河系和河外射电群体研究等广泛科学应用。与之前工作一起，使RACS成为南半球分米波长最高精度的弧秒分辨率全天体测量参考。
英文摘要
Accurate radio astrometry is essential for reliable cross-identification of sources across wavelengths, precision localisation of transient events, and the construction of stable all-sky reference catalogues. In this work we extend our astrometric correction framework for the Rapid ASKAP Continuum Survey (RACS) to its mid- and high-frequency epochs (RACS-Mid1 and RACS-High1), building on our previous corrections to the low-frequency surveys. Using a hierarchical crossmatching strategy with high-precision external catalogues, we remove large-scale systematic positional errors that were present in the uncorrected data and significantly reduce the residual scatter across the sky. After correction, the median positional offsets are effectively eliminated, and the 68\% confidence interval of the mean residuals of RACS source positions averaged over $~\sim1$~sq.deg. regions is reduced from $\gtrsim 0.4''$ to $\lesssim 0.18''$ over most of the survey area for both epochs. Independent validation against multiple external radio astrometric references confirms that individual corrected RACS source positions are accurate to a 1-$σ$ confidence level of $\sim 0.25''$ across the bulk of the sky, with slightly degraded performance within the Galactic plane. While motivated primarily by the need for improved localisation of ASKAP fast radio bursts, these corrections also benefit a wide range of science applications, including transient identification, multiwavelength host association, and studies of Galactic and extragalactic radio populations. Together with our previous work, this establishes RACS as the highest precision arcsecond-resolution all-sky astrometric reference in the southern hemisphere at decimetre wavelengths.
CommentsManuscript has been submitted to the Publications of the Astronomical Society of Australia (PASA). 15 pages, 12 figures, 4 tables
