高红移类星体的21cm信号研究

Study on 21 cm Signal of High Redshift Quasars

利用高精度数值模拟的结果修正了高红移类星体(QSO)电离和加热中性气体的理论模拟,并预测了500 m口径球面射电望远镜(Five-hundred-meter Aperture Spherical Telescope,FAST)观测QSO周围21cm辐射的信号特征以及信噪比,得出如下结论:(1)红移z=8且光度与ULAS J1120+0641一致的QSO在FAST望远镜视场下的21cm频率谱有完整的HII区,但在z=10且较低QSO光度下的21cm频率谱仅有一个小的凹陷;(2)光子有限旅行时间(Finite Light Travel Time,FLTT)效应明显改变高红移QSO的21cm频率谱,使得较低频率端的过渡曲线明显比较高频率端陡;(3)使用FAST望远镜观测高红移QSO的21cm辐射的信噪比非常高,最高可达~12,因此可以很好地识别HII区和FLTT效应.

We use the results of high resolution numerical simulations to fix the theoretical model of high redshift quasars(QSO)ionizing and heating neutral gas,and predict the signal characteristics and signal/noise(S/N)ratios for Five-hundred-meter Aperture Spherical Telescope(FAST)to observe the 21cm radiation around QSO.Our conclusions are summarized as:(1)the 21cm frequency spectrum under the FAST field has full HII region for the QSO at z=8 and with luminosity similar to ULAS J1120+0641,while has only a small trough for the QSO at z=10 and with low luminosity;(2)the effect of Finite Light Travel Time(FLTT)obviously changes the 21cm frequency spectrum of high redshift QSOs,makes the transition curve at lower frequency much steeper than that at higher frequency;(3)the FAST telescope can observe the 21cm radiation of high redshift QSO with very high S/N ratio as high as~12,thus can identify the HII regions and the FLTT effect.