摘要
利用VLBI档案数据研究了5个在40%阿雷西博河外HI巡天天区(α.40天区)发现的具有本征HI吸收线的星系,分析了它们在毫角秒尺度下的射电结构及亮温度TB,并计算了星系的q值(远红外流量与射电流量密度之比)以及利用WISE (wide-field infrared survey explorer)数据对星系进行了分类。研究发现5个源中的NGC 315,NGC 5363存在明显的射电喷流结构,IC 860和CGCG 049-057在pc尺度下存在致密的核,但流量小于NVSS流量的20%,以上4个源的核区的亮温度均超过106K,UGC 6081在毫角秒尺度下没有致密的射电结构,几乎完全分解。通过射电结构、亮温度以及q值得出这5个源的射电连续谱辐射可能来自射电喷流、星暴活动与射电喷流共存,及纯星暴活动等3种情况,说明HI吸收线的探测可能不依赖于中央核区连续谱辐射的类型。利用WISE数据分类显示5个源可以分为2类,3个为4.6μm亮星系,2个为12μm亮星系。没有贫尘埃星系,说明这类星系在α.40天区的数量较少或HI吸收线探测率较低。
We analyzed the radio structure and brightness temperature for five galaxies with intrinsic neutral hydrogen absorption lines detected in the 40%Arecibo Extragalactic Neutral Hydrogen Survey(α.40 region)using VLBI archival data.The source nature of these five objects were then studied in combination with the estimated q value(the ratio of FIR to radio flux density),and WISE data.In our five sources,we found that NGC 315 and NGC 5363 show clear radio jet structure,while IC 860 and CGCG 049-057 show only a compact core at pc scale,however the total VLBI flux is less than 20%of NVSS flux.The brightness temperature of the core region of these four sources are all higher than 106K.In contrast,the remaining source,UGC 6081,shows no compact radio structure and is almost completely resolved.Based on the analysis of radio structure,brightness temperature,and the q value,we found that the radio continuum emission of these five sources has diverse origin,ranging from the radio jet,both starburst and jet,to pure starburst activity.These results indicate that the detection of neutral hydrogen absorption line may not depend on the origin of radio continuum emission.The classification based on the WISE data shows that five sources can be divided into two categories,three 4.6µm bright galaxies,and two 12µm bright galaxies.Interestingly,there are no dust-poor galaxies in our sample,implying that either the number of this kind of galaxies in theα.40 region may be low,or the detection rate of HI absorption lines in these galaxies is likely low.
作者
宋文
吴忠祖
顾敏峰
朱明
米立功
彭毫
SONG Wen;WU Zhong-zu;GU Min-feng;ZHU Ming;MI Li-gong;PENG Hao(College of Physics,Guizhou University,Guiyang 550025,China;Key Laboratory for Research in Galaxies and Cosmology,Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai 200030,China;National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100012,China;School of Physics and Electronics,Qiannan Normal University for Nationalities,Duyun 558000,China)
出处
《天文学进展》
CSCD
北大核心
2021年第3期416-423,共8页
Progress In Astronomy
基金
国家自然科学基金(11763002,U1931203,11873073)。
关键词
星系
喷流
星暴
远红外
射电结构
galaxies
jet
starburst
far infrared
radio structure
