W51A的谱线与连续谱研究——CO,NH3谱线与3mm连续谱

以研究星系旋臂上大质量星形成区为目的,对W51 IRS1为中心的5′×4′(约等于11pc×9pc)天区的3.4mm的连续谱和CO(J=1.0)线作观测,并对NH₃(1,1),(2,2),(3,3)和(4,4)四反演线作同时观测.氨分子的谱形分析和辐射转移统计平衡计算结果表明,在波长3.4mm连续谱的W51 IRS1,IRS2以及(e1/e2)源中心方向的NH₃反演线谱有来自HⅡ区前的氨分子的相对发射线红移的吸收特征;由东部边缘区向中心,有密度3～10倍的递增趋势,进一步显示了光学不可见的分子云核的塌缩现象.在以IRS1为中心40″为半径的圆内的各个射电、近(远)红外、UCHⅡ源所形成的外场辐射对区内分子(例如NH₃)的激发产生不可忽略的影响.CO(J=1.0)的谱形在此圆区内由东到西发生由不对称的双峰(约等于60,68km·s^-1)转化为三峰,即与致密电离氢区G49.4-0.3成协的约等于53 km·s^-1分量亦在谱线上呈现.可见40″圆区内有明显的大质量星形成的各种活动迹象.     

The interstellar methanol masers and their environments

To promote the understanding of massive star formation processes, we have studied the 6.6 GHz methanol (CH3OH) masers and their environments-- the dense cores and the outer regions of the molecular cloud. The physics of the CH3OH maser or the thermal emission formation region is studied by fitting the observational data of the 6.6 GHz 51-60 A+ and the 107 GHz 31-40 A+ CH3OH maser emission, using the radiative transfer calculations. The type II characteristics of the 6.6 GHz CH3OH maser are confirmed by the calculation results. A greater intensity of the radiation field leads to an increase in the peak intensity of the maser; however, high densities tend to turn off the maser. The calculation results show that to be a maser the 6.6 GHz CH3OH emission needs a radiation field of 150-300 K and a density not higher than 107cm-3, while the 107 GHz emission requires a radiation field of 210-300 K and a density not higher than 3×106 cm-3. The 6.6 GHz line is maser towards all six studied sources, while the 107 GHz line is maser towards Cep A only. Moreover, the former's intensity is much stronger than the latter. The radiative transfer calculations also indicate that the 6.6 GHz maser emission is so strong that the requirements of its formation (e.g. The radiation field, the density and the kinetic parameters) can only be satisfied at a certain stage of the processes of the massive star formation. Therefore it is often used as one of the most prominent tracers for the massive star formation regions. The calculation results of the simultaneous observations of (1,1) through (4,4) inversion lines of the ammonia (NH3) indicate that both the temperature and the density in the 6.6 GHz CH3OH maser formation regions are higher than that of the NH3 line formation regions. Furthermore, the common fact of |Vlsr(CO)| ＞ |Vlsr(NH3)| ＞ |Vlsr(CH3OH 6.6GHz maser)| in all six sources implies the ongoing developing trends of those gas flows driven by the masers.     

天体原子、离子和分子射电谱线研究进展

简述天体原子、离子和分子射电谱线自首次探测至今,半个世纪以来的研究进展.展示空间特有的非地球稳定的自由基、同位素、同位素分子和离子及其相关的过程.天体微波激射(MASER)因能提供恒星诞生与死亡的珍贵信息成为本文之侧重点.     

星际甲醇6.6 GHz脉泽源及其环境

通过对6.6 GHz甲醇脉泽(Maser)源及其环境——分子云核和分子云外围的研究来增进对大质量恒星的形成的理解. 以理论计算结果拟合6.6 GHz 5₁-6₀ A⁺ 和 107 GHz 3₁-4₀ A⁺两条甲醇谱线的观测数据, 研究甲醇脉泽或热线形成区的物理特征. 计算确认甲醇6.6 GHz 线的Ⅱ型脉泽特征, 其流量密度的峰值随外场的加强而递增. 密度过高会导致脉泽向热线的转化. 计算表明甲醇6.6 GHz发射线在外场为150~300 K,密度不高于10⁷ cm^-3时均为脉泽, 而甲醇107 GHz线在外场为210~300 K, 密度不高于3×10⁶ cm^-3才是脉泽, 且强度远低于甲醇6.6 GHz脉泽. 涉及的6个源, 6.6 GHz线均为脉泽; 107 GHz线除在CepA中是脉泽外, 在其他5个源中均为热线. 计算表明6.6 GHz 脉泽是如此的强, 它的生成所要求的物理条件（例如外场、密度及动力学参数等）与大质量恒星形成的一个历史阶段的物理条件相吻合, 使其被认为是与大质量恒星形成相关的最显著的现象. NH3 的 (1,1), (2,2), (3,3)和(4,4)4条反演线的同时、同仪器观测和计算提示：甲醇脉泽形成区的温度与密度均高于NH₃谱线形成区. 加上对CO(1-0)线观测得到的|V_sr(CO)| > |V_sr(NH₃)| > |V_sr(CH₃OH 6.6GHz 脉泽)| 之共同特性, 反映了由于附近剧变而被激发的CH₃OH 6.6GHz 脉泽所载气体流, 在分子云核和分子云外围继续发展的势态.