河外水脉泽的研究进展  

Progress in the Study on Extragalactic H_2O Masers

作　　者：张江水[1] 

机构地区：[1]广州大学天体物理中心

出　　处：《天文学进展》2007年第1期36-44,共9页Progress In Astronomy

基　　金：国家自然科学基金资助项目(10573005);国家973资助项目(G19990754)

摘　　要：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．Extragalactic H2O masers have been observed for nearly 30 years and to date there are about 70 sources detected, including 64 being reported （as of May 2006）. The masers are associated with either star formation or active galactic nuclei （AGNs）. It can be classified as related to star formation, nuclear accretion disks （disk-masers）, interactions of nuclear jet with ambient molecular clouds or amplification of the jet＇s seed photons by suitably located foreground clouds （jet-masers） and nuclear outflows. The statistical analysis of extragalactic H2O masers shows that almost all the detected H2O megamasers （LH2O 〉 10L⊙） are Seyfert 2 or LINERs. Most of them arise from heavily obscured （NH 〉 10^23 cm^-2） AGN, even half from Compton-thick circumstance （NH 〉 10^24 cm^-2）. And kilomasers （LH20 〈 10L⊙）, mainly associated with star formation, are always Compton-thin, i.e. their absorbing column densities are NH 〈 10^24 cm^-2. The positional deviation between maser spots and nuclear X-ray source as well as a high degree of clumpiness in the circumnuclear interstellar medium may be responsible for the weakness of the correlation between isotropic maser luminosity and X-ray absorbing column density. The masers associated with star formation have been used to pinpoint sites of massive starforming regions and to estimate the geometric distance of host galaxies by comparing radial velocity and proper motion in groups of maser spots, and to determine the dynamical model of Local Group. VLBI observation of AGN-related masers has become a very powerful tool to investigate the most inner region of AGN. In addition, the H2O masers are detectable at high redshift, potentially providing a new cosmological observable for testing the reality and properties of dark energy and eventually the cosmology model.

关 键 词：天体物理学 水脉泽 综述 活动星系核 赛弗特星系 低电离核发射线区 

分 类 号：P155.22[天文地球—天文学]