Extragalactic HI 21-cm absorption line observations by the Five-hundred-meter Aperture Spherical radio Telescope
Extragalactic HI 21-cm absorption line observations by the Five-hundred-meter Aperture Spherical radio Telescope
复制标题
五百米口径球面射电望远镜河外HI 21厘米吸收线观测
DOI：
10.1093/mnras/stab754
复制
发表时间：
2021
影响因子：
4.8
通讯作者：
Qiao-Li Hao
中科院分区：
文献类型：
--
作者：
Bo Zhang;Ming Zhu;Zhong-Zu Wu;Qing-Zheng Yu;Peng Jiang;You-Ling Yue;Meng-Lin Huang;Qiao-Li Hao
摘要
本文利用500米口径球面射电望远镜（FAST）对河外H i 21 cm吸收线进行了初步研究。我们观察到五个连续源的H i吸收功能，首先确定在40%的数据发布的阿雷西博遗产快速阿雷西博L波段馈电阵列（ALFA）调查（ALCAFA），包括两个系统后来发现的韦斯特博克综合射电望远镜（WSRT）。我们的大部分观测都是在FAST调试阶段进行的，我们测试了不同的观测模式以及数据简化方法，以产生最佳光谱。我们的观察成功地证实了H i吸收线的存在，在所有这些系统中，包括两个源，勉强检测到的ALTAFA。用单高斯函数和双高斯函数拟合了各源的H_i分布，计算了各源的H_i柱密度。与现有文献相比，FAST获得的H i吸收谱具有更高的光谱分辨率和信噪比，从而证明了FAST在揭示H i吸收线细节结构方面的能力。我们的试点观测和测试，使我们能够制定一项战略，寻找H i吸收源使用的数据从FAST河外H i调查，这是在FAST进行的关键项目之一。我们预计，超过1500河外氢吸收系统可以检测到的调查数据，根据灵敏度水平，我们在试点观测。
ABSTRACT
We present a pilot study of extragalactic H i 21-cm absorption lines using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We observed five continuum sources with H i absorption features first identified in the 40 per cent data release of the Arecibo Legacy Fast Arecibo L-Band Feed Array (ALFA) Survey (ALFALFA), including two systems later detected by the Westerbork Synthesis Radio Telescope (WSRT). Most of our observations were carried out during the FAST commissioning phase, and we have tested different observing modes, as well as data reduction methods, to produce the best spectra. Our observations successfully confirmed the existence of H i absorption lines in all these systems, including two sources that were marginally detected by ALFALFA. We fitted the H i profiles with single or double of Gaussian functions, and calculated the H i column densities of each source. The H i absorption profiles obtained by FAST show much higher spectral resolution and higher SNR ratio than the existing data in the literature, thus demonstrating the power of FAST in revealing detailed structures of H i absorption lines. Our pilot observations and tests have enabled us to develop a strategy to search for H i absorption sources using the data from the FAST extragalactic H i survey, which is one of the key projects undertaken at FAST. We expect that over 1500 extragalactic H i absorbing systems could be detected with survey data, based on sensitivity level that we achieved in pilot observations.