天体物理ppt课件.ppt

2024/8/25;.1第六章第六章 河外星系河外星系研究历史研究历史星系分类星系分类 星系测量星系测量特殊星系：活动星系特殊星系：活动星系 星星 系系 团团 星系演化星系演化2024/8/25;.2LEARNING GOALS LEARNING GOALS n活动星系和正常星系主要区别是什么？活动星系和正常星系主要区别是什么？n赛弗特赛弗特星系、射电星系、类星体特征？星系、射电星系、类星体特征？ n活动星系的中心能源机制和统一模型？活动星系的中心能源机制和统一模型？n活动星系的如何形成和星系演化理论？活动星系的如何形成和星系演化理论？2024/8/25;.3定义：定义：具有明显的剧烈活动的一类星系具有明显的剧烈活动的一类星系星星暴暴星星系系：：内内部部有有巨巨大大的的恒恒星星形形成成的的爆爆发发区区它它的的特特征是红外光度明显高于光学光度征是红外光度明显高于光学光度活活动动星星系系核核：：星星系系中中心心区区域域有有一一个个极极小小而而极极亮亮的的核核；；有强的非热连续谱有强的非热连续谱 活动星系的数量约为正常星系总数的活动星系的数量约为正常星系总数的1%活动星系活动星系2024/8/25;.4活动星系和正常星系活动星系和正常星系能谱分布不同能谱分布不同中心能源机制差异中心能源机制差异 2024/8/25;.5星暴星系星暴星系 Starburst Galaxies Starburst Galaxiesn星系中有巨大的星系中有巨大的恒星恒星形成的爆发区形成的爆发区n特征是红外光度明显高于光学光度特征是红外光度明显高于光学光度n普通星系也形成恒星普通星系也形成恒星,但是形成的速但是形成的速度很慢度很慢.n星暴星系中星暴星系中,恒星的形成是非常剧烈恒星的形成是非常剧烈2024/8/25;.6星暴星系中恒星形成剧烈，星暴星系中恒星形成剧烈，将在较短时间内将在较短时间内( (less less than a billion yearsthan a billion years) )消耗掉其内部的气体消耗掉其内部的气体starbursts are starbursts are temporarytemporary2024/8/25;.7星暴星系中形成很多大质量恒星，他们演化到晚期发生超新星爆发，将产生星系风星暴星系中形成很多大质量恒星，他们演化到晚期发生超新星爆发，将产生星系风M82 is the archetypal starburst galaxy. M82 is the archetypal starburst galaxy. 2024/8/25;.8A galactic wind in a A galactic wind in a small galaxy can small galaxy can drive away most of drive away most of its gasits gas2024/8/25;.9n星暴星系主要特征：星暴星系主要特征：q如果以现在的恒星形成率如果以现在的恒星形成率(SFR)(SFR)持续的形成恒星，将在远远短于宇宙年龄持续的形成恒星，将在远远短于宇宙年龄(13.7Gyr)(13.7Gyr)的的时标内消耗掉其内部气体。

时标内消耗掉其内部气体This is sometimes referred to as a "true" This is sometimes referred to as a "true" starburst. starburst. q如果以现在的恒星形成率如果以现在的恒星形成率(SFR)(SFR)持续的形成恒星，持续的形成恒星， 其恒星形成时标也远小于其动力学其恒星形成时标也远小于其动力学时标时标 (perhaps one rotation period in a disk type galaxy). (perhaps one rotation period in a disk type galaxy). qThe current SFR, normalised by the past-averaged SFR is much greater than The current SFR, normalised by the past-averaged SFR is much greater than unityunity2024/8/25;.10星暴的触发机制星暴的触发机制n星系的相互作用星系的相互作用n两个星系的并合两个星系的并合2024/8/25;.11活动星系核活动星系核 active galactic nucleus (AGN)active galactic nucleus (AGN) nAn AGN is a compact region at the centre of a An AGN is a compact region at the centre of a galaxygalaxy which has a much higher which has a much higher than normal luminosity over some or all of the electromagnetic spectrum. than normal luminosity over some or all of the electromagnetic spectrum. nA galaxy hosting an AGN A galaxy hosting an AGN is called an active galaxy. is called an active galaxy. 2024/8/25;.12活动星系核分类活动星系核分类nRadio-loud objects a contribution from the jet(s) and the lobes they inflate Radio-loud objects a contribution from the jet(s) and the lobes they inflate dominates the luminosity of the AGNdominates the luminosity of the AGNqRadio-loud quasars Radio-loud quasars ：射电类星体：射电类星体qBL Lac objectsBL Lac objects ：蝎虎天体：蝎虎天体qRadio galaxies Radio galaxies ：射电星系：射电星系nRadio-quiet objects are simpler since jet and jet-related emission can be Radio-quiet objects are simpler since jet and jet-related emission can be neglected. neglected. qLow-ionization nuclear emission-line regionsLow-ionization nuclear emission-line regions (LINERs) (LINERs) ：低电离核发射区：低电离核发射区qSeyfert galaxiesSeyfert galaxies ：：赛弗特星系赛弗特星系qRadio-quiet Radio-quiet quasarsquasars/QSOs/QSOs：射电宁静类星体：射电宁静类星体2024/8/25;.13活动星系核特点活动星系核特点n能量极高的星系，中心是一个超大黑洞能量极高的星系，中心是一个超大黑洞n辐射绝大部分来自星系核，其他部分弱辐射绝大部分来自星系核，其他部分弱n观测特点：观测特点：q有的有快速光变，有的有快速光变， 时标为几小时至几年时标为几小时至几年q有的有明显的爆发现有的有明显的爆发现 象，如喷流（象，如喷流（JetJet））q有的光谱中有宽的发有的光谱中有宽的发 射线，如射线，如H Ha a谱线谱线2024/8/25;.14非热辐射非热辐射n正常星系：恒星黑体正常星系：恒星黑体辐射，热辐射辐射，热辐射nAGNAGN：非热辐射，：非热辐射，SEDSED峰值在峰值在FIRFIR2024/8/25;.15Bright nucleus, jets and irregular appearanceBright nucleus, jets and irregular appearance2024/8/25;.16High, rapid variabilityHigh, rapid variability光变时标光变时标: : several days to one year several days to one year →→size of the power source < size of the power source < 1 lyr1 lyr2024/8/25;.17AGNAGN光谱：强的发射线和偏振光谱：强的发射线和偏振2024/8/25;.18射电星系射电星系 Radio galaxy Radio galaxy n通常指发出强烈的射电辐射通常指发出强烈的射电辐射（比一般的星系强一百到一（比一般的星系强一百到一百万倍）的星系百万倍）的星系 n射电星系大多为椭圆星系、射电星系大多为椭圆星系、巨椭圆星系和超巨椭圆星系巨椭圆星系和超巨椭圆星系2024/8/25;.19M87M87长时间曝光长时间曝光短时间曝光短时间曝光射电观测射电观测NIRNIR观测观测2024/8/25;.20n发出强烈的射电辐射发出强烈的射电辐射( (比一般的星系强比一般的星系强10102 2～～10106 6倍倍) ) 的星系的星系, , 射电：射电：( ( ~10 ~104242-10-104545 ergsergs-1 -1 ) ) 正常正常：：(~10(~103737-10-103939 ergsergs-1-1) ) n射电连续谱一般为幂律谱，且有偏振，谱指数平均为射电连续谱一般为幂律谱，且有偏振，谱指数平均为0.750.75n具有非热性质，起源于相对论性电子在磁场中运动时产生的同步加速辐射具有非热性质，起源于相对论性电子在磁场中运动时产生的同步加速辐射n射电星系的射电形态多样，可分为致密型、核晕型、双瓣型、头尾型和包含多个子源的射电星系的射电形态多样，可分为致密型、核晕型、双瓣型、头尾型和包含多个子源的复杂形复杂形射电星系特征射电星系特征2024/8/25;.211954 1954 – Cygnus A identified with a 17.5 Cygnus A identified with a 17.5 mag galaxy mag galaxy – strong radio sources can strong radio sources can be optically faint!be optically faint!1962 - 3C 273 identified with a star-1962 - 3C 273 identified with a star-like object with peculiar spectrumlike object with peculiar spectrum1931 1931 – Karl Jansky discovers radio emission from the Galaxy Karl Jansky discovers radio emission from the Galaxy2024/8/25;.22NGC 5128 (Cen A) NGC 5128 (Cen A) radio galaxy at about 2.5 Mpc. radio galaxy at about 2.5 Mpc.HST image + VLA (6cm) imageHST image + VLA (6cm) image2024/8/25;.232024/8/25;.24M 87 (Virgo A)M 87 (Virgo A)The first The first galaxy found galaxy found to have jetsto have jets2024/8/25;.25Radio emission is produced by high-speed electrons Radio emission is produced by high-speed electrons in magnetic fields through synchrotron radiationin magnetic fields through synchrotron radiationThe system may appear to us as The system may appear to us as either a lobe or a coreeither a lobe or a core–halo halo radio galaxy, depending on our radio galaxy, depending on our location with respect to the jets location with respect to the jets and lobes.and lobes.2024/8/25;.26HSTHST观测到的从活动星系观测到的从活动星系M87 (M87 (射电星系射电星系) )中心喷出中心喷出的一个长度为的一个长度为50005000光年的光年的喷流喷流 The The synchrotron synchrotron radiationradiation of the jet of the jet (blue) contrasts with (blue) contrasts with the starlight from the the starlight from the host galaxy (yellow). host galaxy (yellow). 2024/8/25;.272024/8/25;.28赛弗特星系赛弗特星系 Seyfert GalaxiesSeyfert GalaxiesSeyfert GalaxiesSeyfert Galaxiesn极亮的核区极亮的核区n高电离发射线谱高电离发射线谱n由谱线宽度分由谱线宽度分Sy1Sy1和和Sy2Sy2nnamed after named after Carl SeyfertCarl Seyfert, , 19431943年首次发现了这类星系年首次发现了这类星系2024/8/25;.291943 1943 – Carl Seyfert Carl Seyfert – survey of galaxies with star-like nuclei & bright emission survey of galaxies with star-like nuclei & bright emission lineslinesNGC 7742NGC 7742 is a is a spiral galaxyspiral galaxy with a prominent yellow with a prominent yellow nucleus surrounded by nucleus surrounded by spiral spiral armsarms containing many young, containing many young, hot hot blueblue starsstars. It is a . It is a Seyfert galaxySeyfert galaxy, and first , and first studied by studied by astronomerastronomer Carl Carl SeyfertSeyfert in the in the 1940s1940s. . 2024/8/25;.30NGC 4151NGC 4151的逐次深度曝光图像的逐次深度曝光图像SeyfertSeyfert星系图像星系图像深度观测显示其为旋涡星系深度观测显示其为旋涡星系2024/8/25;.312024/8/25;.32nAlmost all Seyfert galaxies are spirals. About 1% of all bright spiral galaxies Almost all Seyfert galaxies are spirals. About 1% of all bright spiral galaxies are Seyfert galaxies.are Seyfert galaxies.nThe luminosities of their nuclei are about The luminosities of their nuclei are about ~10~104343-10-104545 ergsergs-1-1, of the same order , of the same order as all the rest of the galaxy.as all the rest of the galaxy.SeyfertSeyfert星系多为旋涡星系星系多为旋涡星系 射电星系多为椭圆星系射电星系多为椭圆星系2024/8/25;.33Sy2Sy2 ≤10≤103 3 kms kms-1-1Sy1Sy1 ~10~104 4 kms kms-1-1nType I Seyferts Type I Seyferts q宽的光谱发射线，宽的光谱发射线， velocities around/high velocities around/high 1000 km/s. 1000 km/s. nType II Seyferts Type II Seyferts q窄的光谱发射线，窄的光谱发射线，have have very low velocitiesvery low velocitiesSeyfert galaxiesSeyfert galaxies 分类分类2024/8/25;.34Starburst galaxy M94 Starburst galaxy M94 Seyfert galaxy NGC 7742 Seyfert galaxy NGC 7742 核更亮，宽发射线核更亮，宽发射线2024/8/25;.35蝎虎座蝎虎座BLBL型天体型天体 BL Lac Objects BL Lac ObjectsnBL Lac Galaxies, which are also called blazars, were misnamed. BL Lac Galaxies, which are also called blazars, were misnamed. nThe first one discovered was given a star name (BL Lac), in particular a name The first one discovered was given a star name (BL Lac), in particular a name associated with stars that change brightness. associated with stars that change brightness. nthese are actually galaxies with very bright central regions, so bright that these are actually galaxies with very bright central regions, so bright that they look like a bright star when seen at great distances.they look like a bright star when seen at great distances.n亮核状天体，谱线很弱或无、具有快速光变亮核状天体，谱线很弱或无、具有快速光变2024/8/25;.36n19291929年发现，年发现，蝎虎座蝎虎座BLBL型天体型天体n其名字来自其原型蝎虎座其名字来自其原型蝎虎座(Lacerta) (Lacerta) 的天体的天体BLBLn特征如下：特征如下：q亮度变化极大，可以在几个星期内亮度变化极大，可以在几个星期内增亮增亮100倍倍 q光谱一般缺乏发射线和吸收线光谱一般缺乏发射线和吸收线q恒星状，非热辐射主导的椭圆星系恒星状，非热辐射主导的椭圆星系2024/8/25;.37位于大的椭圆星系位于大的椭圆星系one hundred one hundred images of BL Lac images of BL Lac galaxiesgalaxiesNordic Optical Nordic Optical TelescopeTelescope2024/8/25;.38Spectra show no emission or absorption lines - this is a fairly unusual Spectra show no emission or absorption lines - this is a fairly unusual characteristic for a galaxy, especially an Active Galaxycharacteristic for a galaxy, especially an Active GalaxyBL Lac objects BL Lac objects have spectra have spectra dominated by a dominated by a featureless non-featureless non-thermal continuum thermal continuum 2024/8/25;.39Optical spectra of some BL Lac objectsOptical spectra of some BL Lac objects 2024/8/25;.402024/8/25;.41Rapid and violent variability within days to months.Rapid and violent variability within days to months.2024/8/25;.42类星体类星体 QSOs QSOsnQuasars were originally thought to be stars with very strange spectra. Quasars were originally thought to be stars with very strange spectra. 图像图像和恒星相似，点源和恒星相似，点源2024/8/25;.43nOptically appear almost as point Optically appear almost as point sources.sources.nQuasars Quasars – quasi-stellar radio sources quasi-stellar radio sourcesnQSOs QSOs – quasi-stellar objects. quasi-stellar objects.Quasars, QSOs Quasars, QSOs 类星体类星体3C273 z=0.1583C273 z=0.158类星体的发现类星体的发现(20(20世纪世纪6060年代四大天文发现之一年代四大天文发现之一）Maarten SchmidtMaarten Schmidt2024/8/25;.44nThe first quasar 3C273 with very The first quasar 3C273 with very strong, wide, unknown emission linesstrong, wide, unknown emission linesnIn 1963 In 1963 Maarten Schmidt interpreted the Maarten Schmidt interpreted the optical emission lines of 3C273 as optical emission lines of 3C273 as hydrogen Balmer lines redshifted by 16%.hydrogen Balmer lines redshifted by 16%.HST+VLA2024/8/25;.45大部分连续辐射位于红外波大部分连续辐射位于红外波段段QuasarsQuasars：超大质量黑洞吸积：超大质量黑洞吸积周围物质，释放能量周围物质，释放能量2024/8/25;.46 An artist's impression of a growing quasarAn artist's impression of a growing quasara quasar is a compact halo of matter surrounding the central supermassive black hole of a young galaxy. 2024/8/25;.47High-z Quasars characteristicsHigh-z Quasars characteristicsnvery fast moving very fast moving – z=6.4 (v~ 0.96*c). z=6.4 (v~ 0.96*c).nvery far away - Hubble's Lawvery far away - Hubble's Lawn光谱中有宽光谱中有宽 / / 强的发射线强的发射线 n亮度极高：高红移时仍然可以观测到亮度极高：高红移时仍然可以观测到n有些源存在光变：有些源存在光变： variable energy sources variable energy sources nenergy sourceenergy source辐射区域小：辐射区域小： 光变光变 n光谱中存在大量低红移吸收线系：光谱中存在大量低红移吸收线系：Lyman alpha forestLyman alpha forest2024/8/25;.48Spectra of the currently highest Spectra of the currently highest redshifted quasar redshifted quasar The Lyman Alpha Forest is shown in The Lyman Alpha Forest is shown in the spectrum of the quasar on the the spectrum of the quasar on the bottom.bottom. 2024/8/25;.49Gas clouds between a quasar and Earth absorb some of a quasarGas clouds between a quasar and Earth absorb some of a quasar’s lights lightWe can learn about protogalactic clouds by studying the absorption lines they We can learn about protogalactic clouds by studying the absorption lines they produce in quasar spectraproduce in quasar spectra2024/8/25;.50AGNAGN的统一模型的统一模型 Unified models of AGN Unified models of AGN n活动星系的特征活动星系的特征q高光度高光度 (>10 (>101212 L LSunSun) )q非热连续辐射非热连续辐射q快速光变快速光变  辐射源大小辐射源大小 < 1 pc < 1 pcq特殊形态（亮核、喷流）特殊形态（亮核、喷流）q宽发射线宽发射线 辐射源内气体高速运动辐射源内气体高速运动qEmit energy over a wide range of wavelengthsEmit energy over a wide range of wavelengthsn活动星系核分类：活动星系核分类：qRadio gal. Radio gal. 、、Sy1/2Sy1/2、、QSOsQSOs、、BL LacBL Lac2024/8/25;.51n中心大质量黑洞，体积小中心大质量黑洞，体积小n黑洞外围存在吸积盘黑洞外围存在吸积盘n吸积盘周围存在气体云吸积盘周围存在气体云n吸积盘可以产生垂直与盘吸积盘可以产生垂直与盘的喷流的喷流n气体云外围有一个宽的冷气体云外围有一个宽的冷尘埃环尘埃环(torus)(torus)2024/8/25;.52活动星系核的统一模型活动星系核的统一模型 n不同类型的不同类型的AGNAGN只是由于观测视角的不同：只是由于观测视角的不同：'orientation-based unified models'orientation-based unified models‘n射电宁静射电宁静 (radio-quiet) AGN (radio-quiet) AGN统一模型：射电弱统一模型：射电弱qSyISyI型星系是直接观察到的光度较低的型星系是直接观察到的光度较低的AGNAGN本身本身qSy2Sy2型星系是视线方向上受到了冷尘埃环的阻挡型星系是视线方向上受到了冷尘埃环的阻挡q如果如果AGN AGN 光度较高，直接观测到的就是类星体光度较高，直接观测到的就是类星体n射电噪射电噪 (radio-loud) AGN (radio-loud) AGN统一模型：统一模型： 射电强射电强q射电星系被遮蔽环挡住了视线射电星系被遮蔽环挡住了视线q类星体没有被遮蔽环挡住视线类星体没有被遮蔽环挡住视线q如果视线方向与喷流夹角小，观察到蝎虎如果视线方向与喷流夹角小，观察到蝎虎BLBL型天体型天体2024/8/25;.532024/8/25;.542024/8/25;.55What is the power source for AGN?What is the power source for AGN?2024/8/25;.56黑洞黑洞-吸积盘模型：能源机制吸积盘模型：能源机制n星系的活动性源于星系的核心区域超大质量星系的活动性源于星系的核心区域超大质量(106- -1010 M⊙⊙)的黑洞，黑洞的物质吸积提的黑洞，黑洞的物质吸积提供了活动星系的能源供了活动星系的能源n活动星系核的活动星系核的“中央引擎中央引擎”是一个超大质量是一个超大质量黑洞黑洞n在引力的作用下，黑洞周围的气体朝黑洞下落在引力的作用下，黑洞周围的气体朝黑洞下落n具有具有角动量角动量的物质，在黑洞周围形成了的物质，在黑洞周围形成了吸积盘吸积盘n吸积盘中有耗散作用，气体被加热到很高温度吸积盘中有耗散作用，气体被加热到很高温度n同时物质下落到黑洞中央，释放出巨大引力能同时物质下落到黑洞中央，释放出巨大引力能n能量以能量以电磁波电磁波形式辐射出来，主要是非热辐射形式辐射出来，主要是非热辐射n当黑洞的吸积率很高时，就表现为活动星系核当黑洞的吸积率很高时，就表现为活动星系核n随着黑洞周围的物质逐渐耗尽，核心光度减小，随着黑洞周围的物质逐渐耗尽，核心光度减小，AGN演化为正常的星系。

演化为正常的星系2024/8/25;.57Jets are thought to come from twisting of magnetic field in the inner part of Jets are thought to come from twisting of magnetic field in the inner part of accretion diskaccretion disk吸积盘两端沿法吸积盘两端沿法线方向形成高速线方向形成高速喷流，这一过程喷流，这一过程中，中，磁场磁场扮演了扮演了很重要的角色很重要的角色2024/8/25;.58RX J1242-11黑洞吸积的物质来自由于星系核黑洞吸积的物质来自由于星系核心附近的恒星碰撞和星系间碰撞心附近的恒星碰撞和星系间碰撞而剥离出的气体而剥离出的气体a powerful X-ray outburst2024/8/25;.592024/8/25;.60活动星系的演化活动星系的演化n星系形成时，先为星系形成时，先为AGNsAGNsq宇宙早期宇宙早期QSOsQSOs多，正常星系少多，正常星系少q类星体在宇宙早期分布比较普遍类星体在宇宙早期分布比较普遍q黑洞产能可为各类星系提供能源黑洞产能可为各类星系提供能源n形成过程形成过程qQSOs QSOs  Seyfert/Radio Seyfert/Radio  Normal gal. Normal gal.qGalaxies began to form about 10 billion years agoGalaxies began to form about 10 billion years ago 2024/8/25;.612024/8/25;.62SELF-TEST: TRUE OR FALSE? SELF-TEST: TRUE OR FALSE? nActive galaxies emit most radiation at optical wavelengthsActive galaxies emit most radiation at optical wavelengthsnThe spectrum of an active galaxy is not well described by a blackbody curve. The spectrum of an active galaxy is not well described by a blackbody curve. nQuasar luminosities are so large that astronomers have no idea what process Quasar luminosities are so large that astronomers have no idea what process can account for them. can account for them. nMany nearby normal galaxies may once have been quasars.Many nearby normal galaxies may once have been quasars.。