对旋涡星系M33的HII区复合体IC133中H2O脉泽VLBI斑点图的分析

用多重分离的旋转膨胀环模型，分析了旋涡星系Ｍ３３的ＨＩＩ区复合体ＩＣ１３３中的１４个Ｈ２Ｏ脉泽源斑的ＶＬＢ相对位置图，发现这１４个Ｈ２Ｏ脉泽源斑在ＨＩＩ区复合体盘上成形状，分布在二个不同的旋转膨胀盘环上，同时，也得到这１４个Ｈ２Ｏ脉泽源 运动学特性。     

在Orion—KL中的OH脉泽的外流模型：多重分离的旋转膨胀环

我们从对Ｏｒｉｏｎ－ＫＬ星云中ＯＨ１６６５ＭＨｚ脉泽的单基线干涉观测的分析中，提出一种新的外流模型，即多重分离的旋转膨胀环。这种模型与观测结果是一致的。通过对２４ｋｍ单基线观测得到的１９个ＯＨ１６６５ＭＨｚ脉泽斑点的相对位置图进行分析、统计、拟合和计算，得到这１９个ＯＨ１６６５ＭＨｚ脉泽斑点分析分布在三个旋转膨胀环上。这个旋转膨胀环的视距分别为３＂．８５，５＂．８７，６＂．０；对应的环半径分别为１     

在Orion－KL中的OH脉泽的外流模型：多重分离的旋转膨胀环

我们从对Ｏｒｉｏｎ－ＫＬ星云中ＯＨ１６６５ＭＨｚ脉泽的单基线干涉观测的分析中,提出一种新的外流模型,即多重分离的旋转膨胀环．这种模型与观测结果是一致的．通过对２４ｋｍ单基线观测得到的１９个ＯＨ１６６５ＭＨｚ脉泽斑点的相对位置图进行分析、统计、拟合和计算,得到这１９个ＯＨ１６６５ＭＨｚ脉泽斑点分别分布在三个旋转膨胀环上．这三个旋转膨胀环的视距分别为３＂．８１,５＂．８７,６＂．０;对应的环半径分别为１７４２,２７２０,２７６６ＡＵ;径向膨胀速度分别为７．０７,１６．４,２６．４ｋｍｓ－１;旋转运动的切向线速度分别为１．５５,１．２３,１．２１ｋｍｓ－１．     

河外H_2O超脉泽辐射

介绍了近年来河外Ｈ２Ｏ超脉泽的主要观测结果。Ｈ２Ｏ超脉泽通常起源于活动星系核中央的拱核盘。它们主要寄生在 Ｓｅｒｆｅｒｔ ２星系或低电离核区。至今为止，已有２０个星系探测到Ｈ２Ｏ超脉泽。脉泽辐射的各向同性光度为１０～６０００Ｌ⊙。所有超脉泽星系显示出核的活动，显然，脉泽是由核活动所产生的射电和Ｘ射线光子或激波来抽运的。Ｈ２Ｏ超脉泽倾向存在于高倾斜度的星系，这使得沿视线上的分子柱密度增高，产生足够大的放大光深。最有可能产生Ｈ２Ｏ超脉泽辐射的星系应有一个包含着射电源的侧向的分子盘以及一个适当的抽运机制。     

7个新近发现的与分子外流成协的H_2O脉泽

本文发表继探测到恒星形成区的１０个新Ｈ２Ｏ脉泽［１］后，再发现和证认的７个银河系星际Ｈ２Ｏ脉泽及其有关参量和谱线图。这些新Ｈ２Ｏ脉泽是与ＣＯ分子外流源［２－５］ＡＦＧＬ５１４２，ＨＨ－３，ＡＦＯＬ５１５７，ＮＧＣ２０２３，ＲＮＯ７３，２０１２６＋４１０４，Ｌ１２５１－Ａ成协的。它们与相应的外向流的中心ＩＲＡＳ点源间的平均位置差为｜△α｜＝２４＇＇．８，｜△δ｜＝２７＇＇。     

猎户座中SiO脉泽分布的新模型

我们研究了Ｏｒｉｏｎ－ＩＲｃ２ ＳｉＯ脉泽饱和辐射谱线轮廓，找到了很好的拟和谱线轮廓的函数。在观测结果中发现，Ｏｒｉｏｎ－ＩＲｃ２ ＳｉＯ脉泽饱和辐射谱线轮廓中存在着若干峰，为了解释这一现象，我们提出了一个新的分布模型，即多重分离的旋转膨胀盘壳模型。计算结果表明，这个新模型，不仅可以解释脉泽的非饱和辐射谱，而且可以解释脉泽的饱和辐射谱。     

G45.07＋0.13羟基分子脉泽的VLBI观测

利用甚长基线干涉仪，在１６６５ＭＨｚ频率上，观测超致密氢ＩＩ区Ｇ４５．０７＋０．１３的左右圆偏振羟基（ＯＨ）分子脉泽辐射．利用多条纹率成图方法，获得了这个区域２０ｍａｓ相对位置精度的脉泽结构图．除两个弱子源以外，所有脉泽子源都位于彗状结构氢ＩＩ区“彗头”的前沿．脉泽团离致密氢ＩＩ区中心投影距离为０＂．４．在完全饱和辐射的假设下，估计脉泽活动区具有氢分子数密度约为４．５×１０８（Ｈ２）ｃｍ－３．在脉泽源中，发现一对Ｚｅｅｍａｎ对，从它们的ＬＳＲ速度差，导出脉泽区的磁场约为３ｍＧ，方向为远离地球方向．在致密氢ＩＩ区Ｇ４５．０７＋０．１３彗头附近的脉泽团的直径为６×１０１６ｃｍ．这与Ｇ３４．０３＋０．２的观测结果很类似．这给解释彗状结构的氢ＩＩ区的各种模型提供了一个可靠的观测约束条件．     

星际水脉泽源中高速气体的CO巡测

用射电天文联合实验室紫金山天文台青海站１３．７米望远镜，于１９９７年４月对９７个水脉泽源做了ＣＯ（Ｊ＝１－０）的巡测及部分成图观测，结果表明８１个源的谱线适于作成协星体活动分析．经初步证认有外向流候选者３３个，全部为首次给出高速范围．对其轮廓特点及与Ｈ２Ｏ脉泽辐射的关系作了简要讨论．ＣＯ高速气体和Ｈ２Ｏ脉泽的速度范围和峰值速度在多数情况下分别相符，这说明两者的激发可能相关．     

AGB后星OH 17.7-2.0附近一个新的弱OH脉泽源

使用澳大利亚Ｐａｒｋｅｓ６４ｍ射电望远镜,在五个不同的位置上观测了ＯＨ１７．７２．０附近的弱ＯＨ脉泽源．发现了一个新的弱ＯＨ脉泽源,其峰值速度为５２．５ｋｍ／ｓ．利用二维Ｇａｕｓｓｉａｎ拟合技术,得到了这个源的最佳拟合位置     

AGB后星OH17.7—2.0附近一个新的弱OH脉泽源

使用澳大利亚Ｐａｒｋｅｓ６４ｍ射电望远镜,在五个不同的位置上观测了ＯＨ１７．７－２．０附近的弱ＯＨ脉泽源,发现了一个新的弱ＯＨ脉泽源,其峰值速度为５２．５ｋｍ／ｓ。利用二维Ｇａｕｓｓｉａｎ拟合技术,得到了这个源的最佳拟合位置。     

NGC 7538—IRS1致密HⅡ区研究

本文在分析研究NGC7538-IRS1致密HⅡ区H_2CO和OH脉泽辐射VLBI观测结果的基础上,指出该HⅡ区合理的模型是:HⅡ区表面为厚的尘埃层包围,尘埃层两极已被突破,并形成双极流;HⅡ区外面有一个环形转动气体-尘埃云,存在由环向HⅡ区表面的物质下落;包括环和HⅡ区在内的整个系统视向速度为-61km/s,该系统居于视向速度为-57km/s的更大分子云中。H_2CO和OH脉泽发生在HⅡ区两极附近离HⅡ区表面小于0.2R_(HⅡ)的区域内。利用上述模型,还讨论了H_2O脉泽及其他分子吸收线和发射线的发生区域。     

A study of the ultra-compact H-II region NGC 7538-IRS

From an analysis of VLBI observations of H₂CO and OH maser emission in the direction of the ultra-conpact HII region NGC 7538-IRS 1, the following model is proposed: The HII region is surrounded by a thick dusty shell which breaks open at the two poles and there is a bipolar outflow. Around it is a rotating gas/dust ring and matter falls from the ring onto the surface of the HII region. The whole system, HII region and the ring, moves with a sight line velocity of −61.0 km/s inside a large cloud which moves with a sight line velocity of −57 km/s. The H₂CO and OH masers occur near the poles of the HII region and within 0.2 R_HII of the surface. The positions of the H₂O maser and other line sources are discussed in term of this model.     

W3(OH)致密HⅡ区磁场研究

本文以W3(OH)为实例,建立了与OH脉泽成协的HII区气体-尘埃壳层的磁场模型,由此可见,致密HII区所在分子云核心中的磁场强度,与分子云核心的分子数密度之间存在指数α=1/2的幂律关系;而在HII区气体-尘埃壳层中,磁场强度与分子数密度之间存在α=1的正比关系,根据讨论可知,与OH脉泽成协的HII区,其气体-尘埃壳层的分子数密度为10~6cm~(-3)量级,磁场强度为几个mG;一旦分子数密度达10~7cm~(-3)量级,OH脉泽便将熄灭。     

A Survey and Statistics of Interstellar OH and H_2O Masers

We present a statistical analysis of a sky survey of interstellar H2O and OH masers. These masers can be classified into three categories: isolated H2O masers, isolated OH masers, and simple OH/H2O maser associations. The total number of sources in each category is of the same order of magnitude, and as an evolutionary phase they can maintain -105 yr. An improved radiative pumping mechanism is proposed. This model avoids some of the deficiencies of previous radiative models, such as shortage of exciting photons. The statistical results obtained from the survey can be interpreted by the new mechanism together with the evolutionary model in which the gravitational force of the central stellar objects is responsible for the HII region.     

Evidence of Evolution in the Dense Cores in Massive Star Forming Regions

The excitation of H2O masers usually needs very high density gas, hence it can serve as a marker of dense gas in HII region. We selected a sample of H2O maser sources from Plume et al. (four with, and four without detected CS(J = 7-6) emission), and observed them in 13CO(J=1-0) and C18O (J=1-0). C18O (J=1-0) emission was detected only in three of the sources with detected CS(J=7-6) emission. An analysis combined with some data in the literature suggests that these dense cores may be located at different evolutionary stages. Multi-line observation study may provide us clues on the evolution of massive star forming regions and the massive stars themselves.     

Simultaneous observations of the OH maser at 1665 and 1667 MHZ in ON2

Using Nancay radio telescope in Paris-Meudon Observatory the OH masers fromON2 have been observed. The observations were made at both frequencies of1665 and 1667 MHz, and both left and right circular polarizations, and onthe central position, respectively. The observational results indicate that the physical conditions in the central part are very different. Using a new model, i.e. the distinct multiple rotating and expanding disc-ring of OH maser,the peaks of spectra have been explained. The position parameters of the OHmaser spots corresponding to the peaks in the spectral profiles have beenobtained. Our fitting and computational results indicate that the differentpeaks are superposed by the maser spot radiation at different point indifferent disc-ring with different radii. Because the mentioned differencesare caused by the physical conditions of the OH maser formingregions, using the differences, we can study the physical characters of the OH maser forming regions of ON2.     

A model for the molecular accretion disk and H2O maser in the nucleus of the galaxy NGC 4258

A model is developed for the H₂O maser source observed in the circumnuclear region of the galaxy NGC 4258. The maser emission originates at distances of 0.15–0.29 pc from the center in a thin, cold accretion disk (gas-dust torus) rotating around a supermassive black hole of mass 4 × 10⁷ M _⊙. The conditions for the emergence of an inverse population of the signal 6₁₆?5₂₃ levels in ortho-H₂O working molecules are simulated numerically. The complex line profile, which includes both central and high-velocity components, is calculated. A comparison of the calculations with radiointerferometric and spectrophotometric observations allowed the physical conditions in the emitting region to be determined.     

A MERLIN survey of 4.7-GHz excited OH masers in star-forming regions

Phase-referenced observations of 13 star-forming regions in the  ²Π_1/2, J = 1/2  transition of rotationally excited OH at 4765 MHz have been carried out using MERLIN. Two of the regions were also observed at 4750 MHz and one at 4660 MHz. There were 10 maser detections at 4765 MHz and three non-detections. There were no detections at 4750 and 4660 MHz. The 4765-MHz masers have brightness temperatures of  ∼10⁷ K  at MERLIN resolution (∼50 mas). Several cases of 4765-MHz masers overlapping in position and velocity with 1720- and 1665-MHz masers are reported. There are also isolated 4765-MHz masers with peak flux densities ≥30 times that of any ground-state counterpart. Most of the 4.7-GHz maser spots are unresolved at 50-mas angular resolution, but in four of the nearest sources the maser spots are resolved, indicating a characteristic size for 4765-MHz maser regions of ∼100 au. In W3(OH) we discovered that 20 per cent of the 4765-MHz emission comes from a narrow low-brightness filament that stretches north–south for ∼1.0 arcec (∼2200 au) between two previously known 4765-MHz maser spots. The filament appears in projection against the H  ii region and has a brightness temperature of  ∼4 × 10⁵ K  . There are matching absorption features in mainline transitions of highly excited OH. The filament may trace a shock front in a rotating disc.     

A new VLBI observation of an OH maser in a post-asymptotic giant branch star using the European VLBI Network

OH 17.7 − 2.0 is a post-asymptotic giant branch star that is of great interest. The 1612-MHz OH emission from OH 17.7 − 2.0 is characterized by a double-peaked spectrum. Such a line profile has been assumed to represent maser emission from an expanding circumstellar shell. A new VLBI observation of the OH maser in OH 17.7 − 2.0 has been made using the European VLBI Network, and a relative position map of the eight OH maser spots has been obtained. Using the relative position map, it is found that the eight OH maser spots are distributed on an expanding circumstellar shell. The parameters of the expanding circumstellar shell have been obtained.