巨型米波Radio Telescope相位校准源及其射电谱数据库
A Database of Phase Calibration Sources and their Radio Spectra for the Giant Metrewave Radio Telescope
摘要：
我们正在进行一个项目，以建立一个数据库的相位校准源适用于巨型米波射电望远镜（GMRT）。在这里，我们提出了在235 MHz和610 MHz的45低频校准源的第一个版本。这些校准源大致分为类星体、射电星系和未识别源。我们提供了它们的通量密度，校准源模型，（u，v）图，最终去卷积恢复的地图和清洁组件列表/文件中使用的天文图像处理系统（AIPS）和通用天文软件应用程序（CASA）。我们还为每个校准源分配了一个品质因数。这些数据产品可通过全球监测轨道观测站网站在线提供。此外，我们发现：（i）这45个低频校准源均匀分布在天空中，未来增加数据库大小的努力应该进一步填充天空，（ii）这些校准源的光谱在直，弯曲和复杂形状之间大致相等，（iii）与射电星系或未识别源相比，类星体倾向于表现出更平坦的射电光谱，（iv）类星体也是射电可变的，因此可能更频繁地显示复杂的光谱，以及（v）射电星系往往具有更陡峭的光谱，这可能是由于遥远星系的大红移导致光谱向较低频率移动。
英文摘要：
We are pursuing a project to build a database of phase calibration sources suitable for Giant Metrewave Radio Telescope (GMRT). Here we present the first release of 45 low frequency calibration sources at 235 MHz and 610 MHz. These calibration sources are broadly divided into quasars, radio galaxies and unidentified sources. We provide their flux densities, models for calibration sources, (u,v) plots, final deconvolved restored maps and clean-component lists/files for use in the Astronomical Image Processing System (AIPS) and the Common Astronomy Software Applications (CASA). We also assign a quality factor to each of the calibration sources. These data products are made available online through the GMRT observatory website. In addition we find that (i) these 45 low frequency calibration sources are uniformly distributed in the sky and future efforts to increase the size of the database should populate the sky further, (ii) spectra of these calibration sources are about equally divided between straight, curved and complex shapes, (iii) quasars tend to exhibit flatter radio spectra as compared to the radio galaxies or the unidentified sources, (iv) quasars are also known to be radio variable and hence possibly show complex spectra more frequently, and (v) radio galaxies tend to have steeper spectra, which are possibly due to the large redshifts of distant galaxies causing the shift of spectrum to lower frequencies.
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。
