Galaxies-AntarcticAstronomyGroup.ppt

1、Galaxies with Active Nuclei有活动核的星系,Chapter 14:,0,Active Galaxies 活动星系,Galaxies with extremely violent energy release in their nuclei (pl. of nucleus). 核区活动剧烈（释放巨大能量）, “active galactic nuclei” (= AGN)活动星系核,Up to many thousand times more luminous than the entire Milky Way; energy released within a reg

2、ion approx. the size of our solar system!在太阳系大小的范围内，释放的能量可达银河系总能量的几千倍,0,Line Spectra of Galaxies星系线光谱,Taking a spectrum of the light from a normal galaxy:正常星系的光谱,The light from the galaxy should be mostly star light, and should thus contain many absorption lines from the individual stellar spectra.多

3、是恒星光，有很多吸收线,0,Seyfert Galaxies,NGC 1566,Circinus Galaxy,Unusual spiral galaxies:不寻常的漩涡星系,Very bright cores 非常亮的核,Emission line spectra 发射线光谱,Variability: 50 % in a few months 光变,Most likely power source 最可能的能源:Accretion onto a supermassive black hole (107 108 Msun)超大质量黑洞吸积物质,NGC 7742,0,Interacting G

4、alaxies 相互作用星系,Seyfert galaxy NGC 7674,Active galaxies are often associated with interacting galaxies, possibly result of recent galaxy mergers.活动星系经常和相互作用星系有联系,Seyfert galaxy 3C219,0,Cosmic Jets and Radio Lobes喷流和射电瓣,很多活动星系有很强的射电喷流,Radio image of Cygnus A,Material in the jets moves with almost the

5、speed of light (“relativistic jets”相对论性喷流).,Hot spots:Energy in the jets is released in interaction with surrounding material喷流的能量释放到与其相互作用的周围物质里，形成热点,0,Formation of Radio Jets射电喷流的形成,Jets are powered by accretion of matter onto a supermassive black hole.喷流是由黑洞吸积物质产生的,Black Hole 黑洞,Accretion Disk吸积盘

6、,Twisted magnetic fields help to confine the material in the jet and to produce synchrotron radiation.磁场束缚物质，产生射电辐射。,0,The Jets of M87,M87 = Central, giant elliptical galaxy in the Virgo cluster of galaxies,Optical and radio observations detect a jet with velocities up to 1/2 c.喷流速度达到1/2光速。,Jet: 2.5

7、 kpc long,0,The Dust Torus in NGC4261尘埃环,Dust torus is directly visible with Hubble Space Telescope哈勃空间望远镜直接观测到的尘埃环,0,Model for Seyfert Galaxies 模型,Supermassive black hole超大质量黑洞,Accretion disk吸积盘,dense dust torus尘埃环,Gas clouds气体云,UV, X-rays高能光子,Emission lines发射线,0,Jets喷流,The Origin of Supermassive B

8、lack Holes超大质量黑洞的起源,Most galaxies seem to harbor supermassive black holes in their centers大多数星系中心有黑洞.,Fed and fueled by stars and gas from the near-central environment吸积近处恒星和气体。,0,0,黑洞吸积恒星（视频）,The Discovery of Quasars类星体的发现,0,First Quasar 3C273 (1963),The discoveryThe third Cambridge (3C) catalog (1

9、959)Radio sourcesMost are galaxiesSome star-like sources (3C48, 3C273), but not stars.,First Quasar 3C273 (1963),Solar Spectrum,First Quasar 3C273 (1963),Solar Spectrum,First Quasar 3C273 (1963),QUASAR: Quasi-stellar radio sources,First Quasar 3C273 (1963),QUASAR: Quasi-stellar radio sources,First Q

10、uasar 3C273 (1963),QUASAR: Quasi-stellar radio sources,The Discovery of Quasars类星体的发现,The Quasar 3C273（第一个类星体）,光谱线红移非常大,红移 z = /0 = 0.158,0,First Quasar 3C273 (1963),QUASAR: Quasi-stellar radio sources,Doppler Effect z v/c,Expending UniverseHubbles Law,Quasars are objects outside the Milky Way.point

11、 sourcelarge redshifthighly variablerich with broad and narrow emission lines,Quasar Red Shifts 类星体的红移,z = 0,z = 0.178,z = 0.240,z = 0.302,z = 0.389,Quasars have been detected at the highest redshifts, up to最大红移的类星体 z 6,z = /0,老公式/0 = vr/c只在低速（vr c）情况下适用,0,Seyfert Galaxies,The galactic neucleus emit

12、s the same amount of energy as the rest of the galaxy.,Spectrum of a galactic neucleus,Quasars are the neuclei of their host galaxies,Quasars 类星体,Active nuclei in galaxies with even more powerful central sources than Seyfert galaxies.比Seyfert星系（更远）更强的活动星系核,Also show very strong, broad emission lines

13、 in their spectra.光谱里有很强的发射谱线,Also show strong variability over time scales of a few months.亮度随时间变化（没有规律）,0,Active Galactic Neuclei Family,Quasar: Quasi-stellar radio sourceQSO: Quasi-stellar object (no radio emission)Seyfert galaxyLINERS: Low-ionization nuclear emission-line regionBL Lac.,Active Ga

14、lactic Neuclei (AGN)quasar=qso=AGN,AGN dominates the host galaxy in energy output.The Milky Way is not an active galaxy.,AGN Structure,Studying Quasars 类星体研究,The study of high-redshift quasars allows astronomers to investigate questions of利用高红移类星体可以研究：,1) Large scale structure of the universe 宇宙大尺度结

15、构,2) Early history of the universe 早期宇宙历史,3) Galaxy evolution 星系演化,4) Dark matter 暗物质,Observing quasars at high redshifts观测高红移的类星体 探测很远的距离（Gpc）,Look-back times of many billions of years 回视时间达几十亿年 Universe was only a few billion years old! 宇宙年龄只有现在的1%,0,AGN Structure,Major components:super massive bl

16、ack holeaccretion diskemision line clouds/winddusty torusjetsOptical-UV-X-ray continua arise from the accretion disk (T 104 105K).,Probing Dark Matter with High-z Quasars:Gravitational Lensing高红移类星体探测引力透镜,Use to probe the distribution of matter in the cluster.可以用来研究物质分布,星系团背后类星体的光线被星系团的质量（引力）改变方向, t

17、wo images of the same quasar!同一个类星体的两个象,0,0,Gravitational Lensing of Quasars类星体的引力透镜,AGN Structure,Structures are spatially unresolved.How do we know the structure ?,AGN Structure,Most Convincing Evidence:1. Black Hole Mass Measurement2. AGN Unified Model,Measure Black Hole Mass,Measure Black Hole M

18、ass I: Nearby AGNs,NGC4258,The Keperian motion of the accretion disk was detected using Very Long Baseline Interferometry (VLBI).Central mass is 4x107 solar mass.,Measure Black Hole Mass II: Distant AGNs,Same principle: Measure the velocity and distance of emission line clouds.,line,continuum,V from

19、 emission line width.,Measure Black Hole Mass II: Distant AGNs,line,continuum,r from echo mapping.,Time variability,continuum,line,Same principle: Measure the velocity and distance of emission line clouds.,Measure Black Hole Mass II: Distant AGNs,Same principle:M r V2/GMeasure the velocity and dista

20、nce of emission line clouds.,line,continuum,Time variability,AGN Unified Model,Two types of Seyfert galaxies:Seyfert 1 and Seyfert 2,AGN Unified Model,Narrow emission line regionSlow moving,Broad emission line regionFast moving,Dusty torus,Seyfert 1,Seyfert 2,AGN Unified Model,Seyfert 1,Seyfert 2,Seyfert 2, narrow line only,AGN Unified Model,Seyfert 1,Seyfert 2,Seyfert 2, narrow line only,AGN Unified Model,Seyfert 1,Seyfert 2,Seyfert 2, narrow line only,Broad lines appear,