河外H2O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Serfert2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。     

河外H_2O超脉泽源的观测特性

研究了至今为止已发现的 2 0个河外H2 O超脉泽源的观测参数。多数河外H2 O超脉泽源的光度在几十至几百个L⊙ 之内 ,但TXFS2 2 2 6 - 184源的河外H2 O超脉泽源光度达 6 10 0L⊙ ,它属于射电星系类型 ,主要是由于其谱线轮廓较宽所造成的一种例外情况。所有 2 0个河外H2 O超脉泽源的系统速度约为几百到几千km·s- 1,16个河外H2 O超脉泽源的峰值流量密度小于 1Jy ,但有 4个河外H2 O超脉泽源的峰值流量密度大于 6Jy(6 .2～ 16Jy)。通过对这些河外H2 O超脉泽源的观测参数特征的分析和研究 ,得到这些观测参数之间的相关关系为 :河外H2 O超脉泽源的峰值流量密度的对数分别与系统速度的对数和距离的对数之间存在着反相关关系。而河外H2 O超脉泽源的光度的对数与距离平方和峰值流量密度乘积的对数之间存在着正相关关系     

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。     

河外星系OH超脉泽的观测和研究

自从首次发现河外星系OH超脉泽以来，30多年(特别是近10年)中对河外星系OH超脉泽的观测和研究取得了极大的进展。到目前为止已发现106个河外星系OH超脉泽，其中包括59个较高红移的源。对河外星系OH超脉泽的观测和研究，是探测和研究其所成协的活动星系核、星暴星系的中央源和拱核盘的有效工具。主要评述对河外星系OH超脉泽的搜索、观测和理论研究现状。     

7个新近现的与分子外流成协的H2O脉泽

本文发表继探测到恒星形成区的１０个新Ｈ２Ｏ脉泽后，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ＡＦＧＬ５１４２，ＨＨ－３，ＡＦＧＬ５１５７，ＮＧＣ２０２３，ＲＮＯ７３，２０１２６＋１＋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｜Δα｜＝２４＇＇８，｜Δδ｜＝２７＇＇。     

Extragalactic H2O Megamaser Sources： Central Black Holes, Nuclear X-ray and Maser Emissions

Extragalactic H2O megamasers are typically found within the innermost few parsecs of active galaxy nuclei (AGN) and the maser emission is considered to be excited most likely by the X-ray irradiation of the AGN.We investigate a comprehensive sample of extragalactic H2O masers in a sample of 38 maser host AGN to check potential correlations of the megamaser emission with parameters of the AGN,such as X-ray luminosity and black hole (BH) masses.We find a relation between the maser luminosities and BH masses,LH2O∝ M3.64-0.4 BH,which supports basically the theoretical prediction.The relation between the maser emission and X-ray emission is also confirmed.     

河外水脉泽的研究进展

人们对河外水脉泽的观测与研究已经30年了。目前已经在约70个河外星系中检测到水脉泽辐射（已公开发表64个）。近年来，河外水脉泽的观测及理论研究十分活跃。重点介绍了目前河外水脉泽的检测及研究进展，包括水脉泽源的分类、水脉泽对研究活动星系核的重要科学价值、水脉泽源的X射线观测研究及其各物理量之间的统计分析结果等。     

An Infrared Photometric Study of Galaxies with Extragalactic H2O Maser Sources

All galaxies with extragalactic H_2O maser sources observed so far are collected. With the 2MASS and the IRAS photometric data an infrared study is performed on those galaxies.By a comparison between the H_2O maser detected sources and non-detected sources in the infrared it is indicated that infrared properties in the IRAS 12-25μm and 60-100μm are important for producing H_2O masers in galaxies.It is also found that the H_2O maser galaxies with different nuclear activity types have rather different infrared properties mainly in the IRAS 12-60μm region.     

Velocity-Resolved Observations of Hα Emission From Comet C/1995 O1 (Hale–Bopp)

We present hydrogen Balmer-α spectra of comet C/1995 O1(Hale–Bopp) recorded on 5 nights from 1997 February 1 to April 19 by ahigh-resolution (Δ v = 5 km s^-1) Fabry–Pérot spectrometer for a4'.1 (∼2.7 × 10⁵ km) FOV centered 5' sunwardof the nucleus. The Hα line profile is an important diagnostic ofphotolytic heating in cometary atmospheres. Extraction of the spectrafrom the Fabry–Pérot ring images was complicated by obscuration of the telescope FOV due to Hale–Bopp's low elevation, but the measuredH-α line widths of 11–13 km s^-1 (FWHM) are insensitive to the spectral extraction technique. The line widths are consistent withestimates derived from a successful model of Hale–Bopp's hydrogenLyman-α coma assuming the inner coma is opaque to Hα. Wediscuss methods for improving the spectral extraction technique andderiving a precise instrument profile which will allow the detailedshape of the line profile to constrain coma models.     

Forbush Decreases Associated with Western Solar Sources and Geomagnetic Storms: A Study on Precursors

As suggested in many studies the pre-increases or pre-decreases of the cosmic ray intensity (known as precursors), which usually precede a Forbush decrease, could serve as a useful tool for studying space weather effects. The events in this study were chosen based on two criteria. Firstly, the heliolongitude of the solar flare associated with each cosmic ray intensity decrease was in the 50°?–70°W sector and, secondly, the values of the geomagnetic activity index, Kp _max, were ≥?5. Twenty five events were selected from 1967 to 2006. We have used data on solar flares, solar wind speed, geomagnetic indices (Kp and Dst), and interplanetary magnetic field in our detailed analysis. The asymptotic longitudinal cosmic ray distribution diagrams were plotted using the “Ring of Stations” method for all the events. The results reveal clear signs of precursors in 60 % of selected events.     

大质量恒星形成核区的特性：^12CO、^13CO和C^18O的谱线观测及统计比较

利用青海站的13.7米射电望远镜对河内24个与水脉泽源成协并有红外Spitzer数据的巨分子云核进行12CO(J=1→0),13CO(J=1→0)和C18O(J=1→0)的同时成图观测,平均的成图范围为81×81.并全部探测到了C18O的谱线发射,其中11个源有较大范围(51-81)的C18O成图,这些分子云核均观测到C18O(J=1→0)谱线积分强度极大值的一半处,其余的13个源由于信噪比低或者成图范围较大等原因,没有进行如此大面积的成图观测.对样本中的11个已成图的稠密核进行了云核特性的分析并统计比较了CO与13CO,13CO与C18O及CO与C18O谱线积分强度之比(R12/13,R12/13,R12/18),结果是,C18O是光学薄的,可以探测到云核更加细致的结构.从核中心到边缘,3种谱线积分强度比是逐渐增加的.CO与13CO的谱线积分强度比R12/13的范围在2-6之间;13CO与C18O的比值R13/18范围在4-20之间波动,中心区域其值大部分集中在6-12之间,变化范围波动不是很大;CO与C18O之比R12/18在13-90更大的范围内,在更加致密的云核中心该比值集中在13-50之间.     

Surface temperatures and retention of H2O frost on Ganymede and Callisto

Surface temperatures and ice evaporation rates are calculated for Ganymede and Callisto as a function of latitude, time of day, and albedo. The model uses surface thermal properties determined by eclipse radiometry (Morrison and Cruikshank, 1973Icarus18 224–236) and albedos determined from photometrically decalibrated Voyager images. Daytime temperatures on Callisto are roughly 8°K warmer than those in Ganymede's cratered terrain and 11°K warmer than those in Ganymede's grooved terrain. Diurnal mean ice evaporation rates are high enough on both bodies that the surface material probably consists of a very low density lag deposit of primarily silicate dust overlying a denser regolith of silicates and ice. The difference in temperature between Ganymede and Callisto is not great enough to account for the lack of bright polar caps on Callisto. This lack seems instead to reflect a real deficiency in the amount of available H₂O frost relative to Ganymede. The temperature difference between Ganymede's grooved and cratered terrains also cannot account for the strong concentration of bright ray craters in grooved terrain. This concentration suggests instead that an internal geologic process has enriched the grooved terrain in ice relative to the cratered terrain.     

Observation and Study of the CO, CO, HCO and N2H Molecular Lines Towards IRAS 02232+6138

Using the 13.7 m millimeter-wave telescope at the Qinghai Station of Purple Mountain Observatory, we have made observations of ¹³CO, C¹⁸O, HCO⁺ and N₂H⁺ molecular lines towards IRAS 02232+6138. As the excitation density of the probe molecule increases from ¹³CO to HCO⁺, the size of the cloud core associated with IRAS 02232+6138 decreases from 2.40 pc to 0.54 pc, and the virial mass of the cloud core decreases from 2.2 × 10³M to 5.1 × 10²M. A bipolar molecular outflow is found towards IRAS 02232+6138. Using the power function n(r) ∝ r⁻ to fit the spatial density structure of the cloud core, we obtain the power-law index  = 2.3 − 1.2; and we find that, as the probed density increases, the power function becomes more flat. The abundance ratio of ¹³CO to C¹⁸O is 12.4 ± 6.9, comparable with the values 11.8 ± 5.9 for dark clouds and the values 9.0–15.6 for massive cores. The abundance of N₂H⁺ molecules is 3.5 ± 2.5 × 10⁻¹⁰, consistent with the value 1.0 − 5.0 × 10⁻¹⁰ for dark cloud cores and the value 1.2 − 12.8 × 10⁻¹⁰ for massive cores. The abundance of HCO⁺ molecules is 0.9 ± 0.5 × 10⁻⁹, close to the value 1.6 − 2.4 × 10⁻⁹ for massive cores. An increase of HCO⁺ abundance in the outflow region was not found. Combining with the IRAS data, the luminosity-mass ratio of the cloud core is obtained in the range 37–163(L/M). Based on the IRAS luminosity, it is estimated that a main-sequence O7.5 star is probably embedded in the IRAS 02232+6138 cloud core.     

A Radiative Pumping Scheme for OH and H<Subscript>2</Subscript>O Masers in Massive Star Forming Regions

Interstellar H₂O and OH masers associated with massive star-forming regions can be classified into three morphological types: isolated H₂O masers; isolated OH masers; and spatially overlapping OH/H₂O maser groups. In a large sample of star-forming regions the total number of maser groups of each type is approximately equal. In order to account for these statistics we propose a pumping scheme based on a broadband radiative pump which produces inverted populations of both OH and H₂O masers by a process involving predissociation and dissociation of H₂O. This scheme overcomes some drawbacks of earlier radiative pumping models, and may account for the association of OH and H₂O masers in massive star forming regions.