A database of phase calibration sources and their radio spectra for the Giant Metrewave Radio Telescope

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• 作者：Dharam V. Lal ; Shilpa S. Dubal ; Sachin S. Sherkar
• 关键词：Surveys – techniques ; Interferometric – techniques ; High angular resolution – Radio continuum ; General
• 刊名：Experimental Astronomy
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：42
• 期：3
• 页码：319-341
• 全文大小：
• 刊物类别：Physics and Astronomy
• 刊物主题：Astronomy, Observations and Techniques; Statistics for Engineering, Physics, Computer Science, Chemistry and Earth Sciences;
• 出版者：Springer Netherlands
• ISSN：1572-9508
• 卷排序：42

文摘

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.