特殊星系活动星系.ppt

* xkong@ * M 87 (Virgo A) The first galaxy found to have jets * xkong@ * Radio emission is produced by high-speed electrons in magnetic fields through synchrotron radiation The system may appear to us as either a lobe or a core–halo radio galaxy, depending on our location with respect to the jets and lobes. * xkong@ * HST观测到的从活动星系M87 (射电星系)中心喷出的一个长度为5000光年的喷流 The synchrotron radiation of the jet (blue) contrasts with the starlight from the host galaxy (yellow). * xkong@ * * xkong@ * 赛弗特星系 Seyfert Galaxies 极亮的核区 高电离发射线谱 由谱线宽度分Sy1和Sy2 named after Carl Seyfert, 1943年首次发现了这类星系 * xkong@ * 1943 – Carl Seyfert – survey of galaxies with star-like nuclei bright emission lines NGC 7742 is a spiral galaxy with a prominent yellow nucleus surrounded by spiral arms containing many young, hot blue stars. It is a Seyfert galaxy, and first studied by astronomer Carl Seyfert in the 1940s. * xkong@ * NGC 4151的逐次深度曝光图像 Seyfert星系图像 深度观测显示其为旋涡星系 * xkong@ * * xkong@ * Almost all Seyfert galaxies are spirals. About 1% of all bright spiral galaxies are Seyfert galaxies. The luminosities of their nuclei are about ~1043-1045 ergs-1, of the same order as all the rest of the galaxy. Seyfert星系多为旋涡星系 射电星系多为椭圆星系 * xkong@ * Sy2 ≤103 kms-1 Sy1 ~104 kms-1 Type I Seyferts 宽的光谱发射线， velocities around/high 1000 km/s. Type II Seyferts 窄的光谱发射线，have very low velocities Seyfert galaxies 分类 * xkong@ * Starburst galaxy M94 Seyfert galaxy NGC 7742 核更亮，宽发射线 * xkong@ * 蝎虎座BL型天体 BL Lac Objects BL Lac Galaxies, which are also called blazars, were misnamed. The first one discovered was given a star name (BL Lac), in particular a name associated with stars that change brightness. these are actually galaxies with very bright central regions, so bright that they look like a bright star when seen at great distances. 亮核状天体，谱线很弱或无、具有快速光变 * xkong@ * 1929年发现，蝎虎座BL型天体 其名字来自其原型蝎虎座(Lacerta) 的天体BL 特征如下： 亮度变化极大，可以在几个星期内增亮100倍 光谱一般缺乏发射线和吸收线 恒星状，非热辐射主导的椭圆星系 * xkong@ * 位于大的椭圆星系 one hundred images