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HiFAST: An H I data calibration and imaging pipeline for the FAST IV: The stray-radiation correction |
| Qing-Ze Chen(陈箐泽)1,3,†, Jie Wang(王杰)1,2,3, Ying-Jie Jing(景英杰)1, Li-Gang Hou(侯立刚)1, Chen Xu(徐晨)1,3, Tian-Tian Liang(梁甜甜)1,3, Xu-Yang Gao(高旭阳)1,4, Jin-Lin Han(韩金林)1,4, Zi-Ming Liu(刘孜铭)1, Bin Liu(刘彬)1, Chuan-Peng Zhang(张传鹏)1, Heng-Qian Gan(甘恒谦)1, Ming Zhu(朱明)1, Yan Zhu(朱岩)1, and Peng Jiang(姜鹏)1,4 |
1 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China;
2 Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, China;
3 School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing 100049, China;
4 CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China |
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Abstract Stray radiation is a considerable challenge for radio telescopes, requiring careful assessment of its effects. This is crucial when the strong background flux from side lobes significantly affects the total flux, especially for extended sources. In this study, we introduced the beam pattern of the L-band receiver on the Five-hundred-meter Aperture Spherical Telescope (FAST), covering various frequencies based on recent observations. We discovered that the main beam efficiency of all beams exceeds 90 % throughout the L band frequencies, with efficiency decreasing slowly as frequency increases. Subsequently, we developed a module to mitigate stray radiation effects, incorporating it into FAST's standard H\textsc{i} data reduction process, referred to as HiFAST. Our analysis shows that side lobe flux's influence, particularly for extended sources with significant surface density gradients, necessitates detailed evaluation. Corrections for the extended M33 galaxy can reach up to 20 %. Moreover, the pattern data presented here is vital for studying H\textsc{i} intensity maps at high redshift. The module, along with HiFAST and beam pattern data across 15 frequency bins, can be accessed at \href{https://hifast.readthedocs.io}{https://hifast.readthedocs.io}. The datasets of beam pattern presented in this paper are openly available at \href{https://doi.org/10.57760/sciencedb.j00113.00266}{https://doi.org/10.57760/sciencedb.j00113.00266}.
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Received: 15 December 2025
Revised: 09 February 2026
Accepted manuscript online: 27 February 2026
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PACS:
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95.75.-z
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(Observation and data reduction techniques; computer modeling and simulation)
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98.58.Ge
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(H I regions and 21-cm lines; diffuse, translucent, and high-velocity clouds)
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98.70.Dk
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(Radio sources)
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| Fund: This work was supported by the National Key Research and Development Program of China (Grant Nos. 2022YFA1602901 and 2023YFA1608204), the National SKA Programme of China (Grant No. 2022SKA0110201), the National Natural Science Foundation of China (Grant Nos. 11873051, 11988101, 12033008, 12041305, 12125302, 12173016, and 12203065), the CAS Project for Young Scientists in Basic Research (Grant No. YSBR-062), the K.C. Wong Education Foundation, and the Scientific Research Grants from the China Manned Space Project. |
Corresponding Authors:
Qing-Ze Chen,E-mail:chenqz@bao.ac.cn
E-mail: chenqz@bao.ac.cn
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Cite this article:
Qing-Ze Chen(陈箐泽), Jie Wang(王杰), Ying-Jie Jing(景英杰), Li-Gang Hou(侯立刚), Chen Xu(徐晨), Tian-Tian Liang(梁甜甜), Xu-Yang Gao(高旭阳), Jin-Lin Han(韩金林), Zi-Ming Liu(刘孜铭), Bin Liu(刘彬), Chuan-Peng Zhang(张传鹏), Heng-Qian Gan(甘恒谦), Ming Zhu(朱明), Yan Zhu(朱岩), and Peng Jiang(姜鹏) HiFAST: An H I data calibration and imaging pipeline for the FAST IV: The stray-radiation correction 2026 Chin. Phys. B 35 059501
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