Internal Kinematics of Spiral Galaxies in Distant Clusters
星系旋转对称
星系旋转对称引言星系旋转对称是指星系中恒星、星团等天体以某种规律围绕星系中心进行旋转的现象。
这种旋转对称性在宇宙中非常普遍，不仅仅存在于银河系等大型星系中，也可以观察到在小型星团和星云中。
本文将深入探讨星系旋转对称的原因、特征以及其对宇宙的影响。
星系旋转的原因星系旋转对称的原因主要可以归结为以下几个方面：1. 初始角动量在星系形成的早期阶段，星系的原始物质云具有一定的角动量。
当原始物质云开始坍缩形成星系时，由于角动量守恒定律的作用，整个星系会继承原始物质云的角动量，从而导致整个星系开始旋转。
2. 重力作用星系中的恒星和星团之间存在着引力相互作用。
这种引力作用可以使星系中的物体受到牵引，形成旋转运动。
恒星和星团的引力作用不仅仅是在星系内部存在，还可以与周围的星系相互作用，从而进一步增强星系的旋转。
3. 旋转平衡星系的旋转并不是无限制的，它会受到一些因素的制约，最终达到一种旋转平衡状态。
这种平衡状态可以通过星系内部物体的运动速度和引力相互平衡来实现。
一旦星系达到了旋转平衡，它就会保持着一定的旋转速度，形成旋转对称的结构。
星系旋转的特征星系旋转对称的特征主要表现在以下几个方面：1. 旋转曲线星系的旋转曲线是指在星系内部测量到的恒星或气体的速度随距离的变化关系。
通常情况下，星系的旋转曲线呈现出先增加后趋于平缓的趋势。
这是因为离星系中心较远的物体受到的引力较小，所以速度较快；而靠近星系中心的物体受到的引力较大，速度较慢。
2. 旋转中心星系的旋转中心通常位于星系的中心位置。
通过观测星系内部物体的运动轨迹，可以确定出星系的旋转中心。
旋转中心通常与星系内部的质量分布有关，它是星系旋转对称性的一个重要特征。
3. 旋转速度星系的旋转速度是指星系中心的物体围绕旋转中心的速度。
通常情况下，星系的旋转速度随着距离的增加而减小。
这是因为在星系的外部区域，物体受到的引力较小，所以旋转速度较慢；而在星系的内部区域，物体受到的引力较大，旋转速度较快。
天文小课堂《遥远的星辰》(关于星系与大爆炸)
棒旋星系的旋臂源于棒的两端。
佛科留斯补充了SBd型和SBm型。 SBd：散开、旋臂碎裂成独立的星云和星团，中心 的核球非常微弱。 SBm：外观看起来是不规则的，没有核球则星系（ irregular galaxy）是外形不规则，没 有明显的核和悬臂, 没有盘状对称结构或者看不出有 旋转对称性的星系，用字母Irr表示。在全天最亮星系 中，不规则星系只占5%。 哈勃定义了两种不规则星系： Irr I：星系的外观不对称，并且缺乏中央的核心或明显 的螺旋结构；取代的是只有年轻的恒星各自集结成团。 Irr II：星系是平滑的，但是外观不对称，并且不能清楚 的分辨出恒星或是恒星的集团。
1.什么是星系 2.从大爆炸到星系的诞生及星系的 演化 3.星系分类法 4.一些河外星系的介绍
“星系”这个词在英文中的词源来自希腊语，意思是满 天繁星。星系从广义上来说指的是由无数恒星系和星 际物质组成的运行系统。参照银河系，星系是由数百 万至数千亿恒星、气体、尘埃、中心大质量黑洞和暗 物质构成的天体系统，空间尺度达数千至数十万光年， 分布于百亿光年空间中的数以百亿计的星系以及星系 际物质构成了目前可观测的宇宙。
透镜状星系(Lenticular galaxies) 透镜星系可以依据中心是否有棒状结 构分成两个子系统。S0A用来表示没 有棒状结构的透镜星系；S0B用来标 示有明显棒状的透镜星系。
活动星系，有猛烈活动现象或剧烈物理过程的星系，包 括塞弗特星系、类星体、射电星系、蝎虎座BL型天体、 星爆星系等。 现在一般不严格区分活动星系和活动星系核。 活动星系核（active galactic nucleus，缩写为AGN）是 一类中央核区活动性很强的河外星系。这些星系显得比普 通星系活跃，在从无线电波到伽玛射线的全电磁波段里都 发出很强的电磁辐射。
第四篇 银河系和河外星系2(河外星系)资料
▪ 在形态上，透镜状星系与旋涡星系的主要差别是没有 旋臂；与椭圆星系的主要差别是有星系盘。
▪ 主要由年老恒星组成，气体很少。
(5)不规则星系 ▪ 外型或结构无明显对称性的星系，符号为Irr。 ▪ 无旋臂和中心核区。 ▪ 富含星际气体、尘埃和年轻恒星。
银河系实际直径30 kpc！
沙普利—柯蒂斯 (Shaplry-Curtis) 关于“宇宙尺 度”的大辩论
▪ 辩论焦点：
(1) “旋涡星云”的距离是多大？
(2) “旋涡星云”是恒星系统还是气体 云？
宇宙是由无数类 似“旋涡星云” 的星系构成的。 “宇宙岛”
“旋涡星云”是银河系内气体 云，银河系就是整个宇宙。
仙女座大星系M31(Sb)
(3) 棒旋星系 (barred spiral galaxies)
▪ 中心有棒状结构的旋涡星 系，符号为SB。
▪ 旋臂源于棒的两端。 ▪ 按照核球的大小和旋臂的
缠卷程度，旋涡星系可以 分为SBa, SBb, SBc三个次 型。其中Sa型核球最大， 旋臂缠卷最紧。
(4) 透镜状星系
因此“仙女座大星云”必定是河外星 系!
2. 星系的哈勃分类
▪ 根据星系形态的不同，1926年哈勃首先提出星系 可以分为椭圆星系、透镜状星系、旋涡星系、棒 旋星系和不规则星系5种类型，称为哈勃分类。
椭圆星系
旋涡星系 透镜状星系
不规则星系
棒旋星系
宇宙星系的数目1010数量级！ 哈勃“音叉”图
(1) 椭圆星系 (elliptical galaxies)
1920年4月26日美国科学院在华盛顿博 物馆礼堂召开了“宇宙的尺度”的辩论 会。
天文学名词
中国天文学会天文学名词审定委员会第1-6批天文学名词的推荐译名The 1st - 6th Drafts for the Chinese-Translation of Astronomical Termsrecommanded byThe Astronomical Terminology Committee of the CASabsolute stability 绝对稳定性absorbing dust mass 致吸尘物质absorption trough 吸收槽abundance standard 丰度标准星accreting binary 吸积双星accretion column 吸积柱accretion flow 吸积流accretion mound 吸积堆accretion ring 吸积环accretion stream 吸积流acoustic mode 声模active binary 活动双星active chromosphere binary 活动色球双星active chromosphere star 活动色球星active optics 主动光学actuator 促动器Adams ring 亚当斯环adaptive optics 自适应光学additional perturbation 附加摄动AGB, asymptotic giant branch 渐近巨星支Alexis, Array of Low-Energy X-ray 〈阿列克希斯〉低能X 射线Imaging Sensors 成象飞行器AM Herculis star 武仙AM 型星amplitude spectrum 变幅谱angular elongation 距角anonymous galaxy 未名星系anonymous object 未名天体anti-jovian point 对木点annular-total eclipse 全环食aperture photometry 孔径测光APM, Automated Photographic Measuring 〈APM〉底片自动测量仪systemapoapse 远质心点apoapse distance 远质心距apogalacticon 远银心点apomartian 远火点apparent association 表观成协apparent luminosity function 视光度函数apparent superluminal motion 视超光速运动apsidal advance 拱线进动apsidal precession 拱线进动Arcturus group 大角星群area image sensor 面成象敏感器area photometry 面源测光area spectroscopy 面源分光argument of pericentre 近心点幅角ASCA, Advanced Satellite for Cosmology 〈ASCA〉宇宙学和天体物理学and Astrophysics 高新卫星asteroidal dynamics 小行星动力学asteroidal resonance 小行星共振asteroid family 小行星族asteroid-like object 类小行星天体asteroseismology 星震学astration 物质改造astroparticle physics 天文粒子物理学astrostatistics 天文统计学asymptotic branch 渐近支asymptotic branch giant 渐近支巨星atmospheric parameter 大气参数ATNT, Australia Telescope National 澳大利亚国立望远镜FacilityATT, Advanced Technology Telescope 〈ATT〉高新技术望远镜automated measuring machine 天文底片自动测量仪automatic photooelectric telescope 自动光电测光望远镜( APT )AXAF, Advanced X-ray Astrophysical 高新X射线天体物理台FacilityBaade's window 巴德窗Baade—Wesselink analysis 巴德—韦塞林克分析Baade—Wesselink mass 巴德—韦塞林克质量Baade—Wesselink method 巴德—韦塞林克方法Baade—Wesselink radius 巴德—韦塞林克半径background galaxy 背景星系Barnard's galaxy ( NGC 6822 ) 巴纳德星系barycentric dynamical time ( TDB ) 质心力学时Belinda 天卫十四Bianca 天卫八bidimensional spectrography 二维摄谱bidimensional spectroscopy 二维分光Big-Bang nucleosynthesis 大爆炸核合成binarity 成双性binary asteroid 双小行星binary flare star 耀变双星binary millisecond pulsar 毫秒脉冲双星binary protostar 原双星bioastronomy 生物天文学bipolar jet 双极喷流bipolar outflow 偶极外向流bipolar planetary nebula 双极行星状星云blazar 耀变体blazarlike activity 类耀活动blazarlike object 耀变体Black-eye galaxy ( M 64 ) 黑眼星系BL Lacertae object 蝎虎天体BL Lacertid 蝎虎天体blue compact galaxy ( BCG ) 蓝致密星系blue straggler 蓝离散星bolometric albedo 热反照率bolometric light curve 全波光变曲线bolometric temperature 热温度Bootes void 牧夫巨洞bow-shock nebula 弓形激波星云box photometry 方格测光broad-band imaging 宽波段成象broad-line radio galaxy ( BLRG ) 宽线射电星系buried channel CCD 埋沟型CCDButterfly nebula 蝴蝶星云BY Draconis star 天龙BY 型星BY Draconis variable 天龙BY 型变星CAMC, Carlsberg Automatic Meridian 卡尔斯伯格自动子午环Circlecannibalism 吞食cannibalized galaxy 被吞星系cannibalizing galaxy 吞食星系cannibalizing of galaxies 星系吞食carbon dwarf 碳矮星Cassegrain spectrograph 卡焦摄谱仪Cassini 〈卡西尼〉土星探测器Cat's Eye nebula ( NGC 6543 ) 猫眼星云CCD astronomy CCD 天文学CCD camera CCD 照相机CCD photometry CCD 测光CCD spectrograph CCD 摄谱仪CCD spectrum CCD 光谱celestial clock 天体钟celestial mechanician 天体力学家celestial thermal background 天空热背景辐射celestial thermal background radiation 天空热背景辐射central overlap technique 中心重迭法Centaurus arm 半人马臂Cepheid distance 造父距离CFHT, Canada-Franch-Hawaii Telecope 〈CFHT〉望远镜CGRO, Compton Gamma-Ray Observatory 〈康普顿〉γ射线天文台chaos 混沌chaotic dynamics 混沌动力学chaotic layer 混沌层chaotic region 混沌区chemically peculiar star 化学特殊星Christmas Tree cluster ( NGC 2264 ) 圣诞树星团chromosphere-corona transition zone 色球-日冕过渡层chromospheric activity 色球活动chromospherically active banary 色球活动双星chromospherically active star 色球活动星chromospheric line 色球谱线chromospheric matirial 色球物质chromospheric spectrum 色球光谱CID, charge injected device CID、电荷注入器件circular solution 圆轨解circumnuclear star-formation 核周产星circumscribed halo 外接日晕circumstellar dust disk 星周尘盘circumstellar material 星周物质circumsystem material 双星周物质classical Algol system 经典大陵双星classical quasar 经典类星体classical R Coronae Borealis star 经典北冕R 型星classical T Tauri star 经典金牛T 型星Clementine 〈克莱芒蒂娜〉环月测绘飞行器closure phase imaging 锁相成象cluster centre 团中心cluster galaxy 团星系COBE, Cosmic Background Explorer 宇宙背景探测器coded mask imaging 编码掩模成象coded mask telescope 编码掩模望远镜collapsing cloud 坍缩云cometary burst 彗暴cometary dynamics 彗星动力学cometary flare 彗耀cometary H Ⅱregion 彗状电离氢区cometary outburst 彗爆发cometary proplyd 彗状原行星盘comet shower 彗星雨common proper-motion binary 共自行双星common proper-motion pair 共自行星对compact binary galaxy 致密双重星系compact cluster 致密星团; 致密星系团compact flare 致密耀斑composite diagram method 复合图法composite spectrum binary 复谱双星computational astrophysics 计算天体物理computational celestial mechanics 计算天体力学contact copying 接触复制contraction age 收缩年龄convective envelope 对流包层cooling flow 冷却流co-orbital satellite 共轨卫星coplanar orbits 共面轨道Copernicus 〈哥白尼〉卫星coprocessor 协处理器Cordelia 天卫六core-dominated quasar ( CDQ ) 核占优类星体coronal abundance 冕区丰度coronal activity 星冕活动、日冕活动coronal dividing line 冕区分界线coronal gas 星冕气体、日冕气体coronal green line 星冕绿线、日冕绿线coronal helmet 冕盔coronal magnetic energy 冕区磁能coronal red line 星冕红线、日冕红线cosmic abundance 宇宙丰度cosmic string 宇宙弦cosmic void 宇宙巨洞COSMOS 〈COSMOS〉底片自动测量仪C-O white dwarf 碳氧白矮星Cowling approximation 柯林近似Cowling mechnism 柯林机制Crescent nebula ( NGC 6888 ) 蛾眉月星云Cressida 天卫九critical equipotential lobe 临界等位瓣cross-correlation method 交叉相关法cross-correlation technique 交叉相关法cross disperser prism 横向色散棱镜crustal dynamics 星壳动力学cryogenic camera 致冷照相机cushion distortion 枕形畸变cut-off error 截断误差Cyclops project 〈独眼神〉计划D abundance 氘丰度Dactyl 艾卫dark halo 暗晕data acquisition 数据采集decline phase 下降阶段deep-field observation 深天区观测density arm 密度臂density profile 密度轮廓dereddening 红化改正Desdemona 天卫十destabiliizing effect 去稳效应dew shield 露罩diagonal mirror 对角镜diagnostic diagram 诊断图differential reddening 较差红化diffuse density 漫射密度diffuse dwarf 弥漫矮星系diffuse X-ray 弥漫X 射线diffusion approximation 扩散近似digital optical sky survey 数字光学巡天digital sky survey 数字巡天disappearance 掩始cisconnection event 断尾事件dish 碟形天线disk globular cluster 盘族球状星团dispersion measure 频散量度dissector 析象管distance estimator 估距关系distribution parameter 分布参数disturbed galaxy 受扰星系disturbing galaxy 扰动星系Dobsonian mounting 多布森装置Dobsonian reflector 多布森反射望远镜Dobsonian telescope 多布森望远镜dominant galaxy 主星系double-mode cepheid 双模造父变星double-mode pulsator 双模脉动星double-mode RR Lyrae star 双模天琴RR 型星double-ring galaxy 双环星系DQ Herculis star 武仙DQ 型星dredge-up 上翻drift scanning 漂移扫描driving system 驱动系统dumbbell radio galaxy 哑铃状射电星系Du Pont Telescope 杜邦望远镜dust ring 尘环dwarf carbon star 碳矮星dwarf spheroidal 矮球状星系dwarf spheroidal galaxy 矮球状星系dwarf spiral 矮旋涡星系dwarf spiral galaxy 矮旋涡星系dynamical age 动力学年龄dynamical astronomy 动力天文dynamical evolution 动力学演化Eagle nebula ( M 16 ) 鹰状星云earty cluster 早型星系团early earth 早期地球early planet 早期行星early-stage star 演化早期星early stellar evolution 恒星早期演化early sun 早期太阳earth-approaching asteroid 近地小行星earth-approaching comet 近地彗星earth-approaching object 近地天体earth-crossing asteroid 越地小行星earth-crossing comet 越地彗星earth-crossing object 越地天体earth orientation parameter 地球定向参数earth rotation parameter 地球自转参数eccentric-disk model 偏心盘模型effect of relaxation 弛豫效应Egg nebula ( AFGL 2688 ) 蛋状星云electronographic photometry 电子照相测光elemental abundance 元素丰度elliptical 椭圆星系elliptical dwarf 椭圆矮星系emulated data 仿真数据emulation 仿真encounter-type orbit 交会型轨道enhanced network 增强网络equatorial rotational velocity 赤道自转速度equatorium 行星定位仪equipartition of kinetic energy 动能均分eruptive period 爆发周期Eskimo nebula ( NGC 2392 ) 爱斯基摩星云estimated accuracy 估计精度estimation theory 估计理论EUVE, Extreme Ultraviolet Explorer 〈EUVE〉极紫外探测器Exclamation Mark galaxy 惊叹号星系Exosat 〈Exosat〉欧洲X 射线天文卫星extended Kalman filter 扩充卡尔曼滤波器extragalactic jet 河外喷流extragalactic radio astronomy 河外射电天文extrasolar planet 太阳系外行星extrasolar planetary system 太阳系外行星系extraterrestrial intelligence 地外智慧生物extreme helium star 极端氦星Fabry-Perot imaging spectrograph 法布里-珀罗成象摄谱仪Fabry-Perot interferometry 法布里-珀罗干涉测量Fabry-Perot spectrograph 法布里-珀罗摄谱仪face-on galaxy 正向星系face-on spiral 正向旋涡星系facility seeing 人为视宁度fall 见落陨星fast pulsar 快转脉冲星fat zero 胖零Fermi normal coordinate system 费米标准坐标系Fermi-Walker transportation 费米-沃克移动fibre spectroscopy 光纤分光field centre 场中心field galaxy 场星系field pulsar 场脉冲星filter photography 滤光片照相观测filter wheel 滤光片转盘find 发见陨星finder chart 证认图finderscope 寻星镜first-ascent giant branch 初升巨星支first giant branch 初升巨星支flare puff 耀斑喷焰flat field 平场flat field correction 平场改正flat fielding 平场处理flat-spectrum radio quasar 平谱射电类星体flux standard 流量标准星flux-tube dynamics 磁流管动力学f-mode f 模、基本模following limb 东边缘、后随边缘foreground galaxy 前景星系foreground galaxy cluster 前景星系团formal accuracy 形式精度Foucaultgram 傅科检验图样Foucault knife-edge test 傅科刀口检验fourth cosmic velocity 第四宇宙速度frame transfer 帧转移Fresnel lens 菲涅尔透镜fuzz 展云Galactic aggregate 银河星集Galactic astronomy 银河系天文Galactic bar 银河系棒galactic bar 星系棒galactic cannibalism 星系吞食galactic content 星系成分galactic merge 星系并合galactic pericentre 近银心点Galactocentric distance 银心距galaxy cluster 星系团Galle ring 伽勒环Galilean transformation 伽利略变换Galileo 〈伽利略〉木星探测器gas-dust complex 气尘复合体Genesis rock 创世岩Gemini Telescope 大型双子望远镜Geoalert, Geophysical Alert Broadcast 地球物理警报广播giant granulation 巨米粒组织giant granule 巨米粒giant radio pulse 巨射电脉冲Ginga 〈星系〉X 射线天文卫星Giotto 〈乔托〉空间探测器glassceramic 微晶玻璃glitch activity 自转突变活动global change 全球变化global sensitivity 全局灵敏度GMC, giant molecular cloud 巨分子云g-mode g 模、重力模gold spot 金斑病GONG, Global Oscillation Network 太阳全球振荡监测网GroupGPS, global positioning system 全球定位系统Granat 〈石榴〉号天文卫星grand design spiral 宏象旋涡星系gravitational astronomy 引力天文gravitational lensing 引力透镜效应gravitational micro-lensing 微引力透镜效应great attractor 巨引源Great Dark Spot 大暗斑Great White Spot 大白斑grism 棱栅GRO, Gamma-Ray Observatory γ射线天文台guidscope 导星镜GW Virginis star 室女GW 型星habitable planet 可居住行星Hakucho 〈天鹅〉X 射线天文卫星Hale Telescope 海尔望远镜halo dwarf 晕族矮星halo globular cluster 晕族球状星团Hanle effect 汉勒效应hard X-ray source 硬X 射线源Hay spot 哈伊斑HEAO, High-Energy Astronomical 〈HEAO〉高能天文台Observatoryheavy-element star 重元素星heiligenschein 灵光Helene 土卫十二helicity 螺度heliocentric radial velocity 日心视向速度heliomagnetosphere 日球磁层helioseismology 日震学helium abundance 氦丰度helium main-sequence 氦主序helium-strong star 强氦线星helium white dwarf 氦白矮星Helix galaxy ( NGC 2685 ) 螺旋星系Herbig Ae star 赫比格Ae 型星Herbig Be star 赫比格Be 型星Herbig-Haro flow 赫比格-阿罗流Herbig-Haro shock wave 赫比格-阿罗激波hidden magnetic flux 隐磁流high-field pulsar 强磁场脉冲星highly polarized quasar ( HPQ ) 高偏振类星体high-mass X-ray binary 大质量X 射线双星high-metallicity cluster 高金属度星团;高金属度星系团high-resolution spectrograph 高分辨摄谱仪high-resolution spectroscopy 高分辨分光high - z 大红移Hinotori 〈火鸟〉太阳探测器Hipparcos, High Precision Parallax 〈依巴谷〉卫星Collecting SatelliteHipparcos and Tycho Catalogues 〈依巴谷〉和〈第谷〉星表holographic grating 全息光栅Hooker Telescope 胡克望远镜host galaxy 寄主星系hot R Coronae Borealis star 高温北冕R 型星HST, Hubble Space Telescope 哈勃空间望远镜Hubble age 哈勃年龄Hubble distance 哈勃距离Hubble parameter 哈勃参数Hubble velocity 哈勃速度hump cepheid 驼峰造父变星Hyad 毕团星hybrid-chromosphere star 混合色球星hybrid star 混合大气星hydrogen-deficient star 缺氢星hydrogenous atmosphere 氢型大气hypergiant 特超巨星Ida 艾达( 小行星243号)IEH, International Extreme Ultraviolet 〈IEH〉国际极紫外飞行器HitchhikerIERS, International Earth Rotation 国际地球自转服务Serviceimage deconvolution 图象消旋image degradation 星象劣化image dissector 析象管image distoration 星象复原image photon counting system 成象光子计数系统image sharpening 星象增锐image spread 星象扩散度imaging polarimetry 成象偏振测量imaging spectrophotometry 成象分光光度测量immersed echelle 浸渍阶梯光栅impulsive solar flare 脉冲太阳耀斑infralateral arc 外侧晕弧infrared CCD 红外CCDinfrared corona 红外冕infrared helioseismology 红外日震学infrared index 红外infrared observatory 红外天文台infrared spectroscopy 红外分光initial earth 初始地球initial mass distribution 初始质量分布initial planet 初始行星initial star 初始恒星initial sun 初始太阳inner coma 内彗发inner halo cluster 内晕族星团integrability 可积性Integral Sign galaxy ( UGC 3697 ) 积分号星系integrated diode array ( IDA ) 集成二极管阵intensified CCD 增强CCDIntercosmos 〈国际宇宙〉天文卫星interline transfer 行间转移intermediate parent body 中间母体intermediate polar 中介偏振星international atomic time 国际原子时International Celestial Reference 国际天球参考系Frame ( ICRF )intraday variation 快速变化intranetwork element 网内元intrinsic dispersion 内廪弥散度ion spot 离子斑IPCS, Image Photon Counting System 图象光子计数器IRIS, Infrared Imager / Spectrograph 红外成象器/摄谱仪IRPS, Infrared Photometer / Spectro- 红外光度计/分光计meterirregular cluster 不规则星团; 不规则星系团IRTF, NASA Infrared Telescope 〈IRTF〉美国宇航局红外Facility 望远镜IRTS, Infrared Telescope in Space 〈IRTS〉空间红外望远镜ISO, Infrared Space Observatory 〈ISO〉红外空间天文台isochrone method 等龄线法IUE, International Ultraviolet 〈IUE〉国际紫外探测器ExplorerJewel Box ( NGC 4755 ) 宝盒星团Jovian magnetosphere 木星磁层Jovian ring 木星环Jovian ringlet 木星细环Jovian seismology 木震学jovicentric orbit 木心轨道J-type star J 型星Juliet 天卫十一Jupiter-crossing asteroid 越木小行星Kalman filter 卡尔曼滤波器KAO, Kuiper Air-borne Observatory 〈柯伊伯〉机载望远镜Keck ⅠTelescope 凯克Ⅰ望远镜Keck ⅡTelescope 凯克Ⅱ望远镜Kuiper belt 柯伊伯带Kuiper-belt object 柯伊伯带天体Kuiper disk 柯伊伯盘LAMOST, Large Multi-Object Fibre 大型多天体分光望远镜Spectroscopic TelescopeLaplacian plane 拉普拉斯平面late cluster 晚型星系团LBT, Large Binocular Telescope 〈LBT〉大型双筒望远镜lead oxide vidicon 氧化铅光导摄象管Leo Triplet 狮子三重星系LEST, Large Earth-based Solar 〈LEST〉大型地基太阳望远镜Telescopelevel-Ⅰcivilization Ⅰ级文明level-Ⅱcivilization Ⅱ级文明level-Ⅲcivilization Ⅲ级文明Leverrier ring 勒威耶环Liapunov characteristic number 李雅普诺夫特征数( LCN )light crown 轻冕玻璃light echo 回光light-gathering aperture 聚光孔径light pollution 光污染light sensation 光感line image sensor 线成象敏感器line locking 线锁line-ratio method 谱线比法Liner, low ionization nuclear 低电离核区emission-line regionline spread function 线扩散函数LMT, Large Millimeter Telescope 〈LMT〉大型毫米波望远镜local galaxy 局域星系local inertial frame 局域惯性架local inertial system 局域惯性系local object 局域天体local star 局域恒星look-up table ( LUT ) 对照表low-mass X-ray binary 小质量X 射线双星low-metallicity cluster 低金属度星团;低金属度星系团low-resolution spectrograph 低分辨摄谱仪low-resolution spectroscopy 低分辨分光low - z 小红移luminosity mass 光度质量luminosity segregation 光度层化luminous blue variable 高光度蓝变星lunar atmosphere 月球大气lunar chiaroscuro 月相图Lunar Prospector 〈月球勘探者〉Ly-αforest 莱曼-α森林MACHO ( massive compact halo 晕族大质量致密天体object )Magellan 〈麦哲伦〉金星探测器Magellan Telescope 〈麦哲伦〉望远镜magnetic canopy 磁蓬magnetic cataclysmic variable 磁激变变星magnetic curve 磁变曲线magnetic obliquity 磁夹角magnetic period 磁变周期magnetic phase 磁变相位magnitude range 星等范围main asteroid belt 主小行星带main-belt asteroid 主带小行星main resonance 主共振main-sequence band 主序带Mars-crossing asteroid 越火小行星Mars Pathfinder 火星探路者mass loss rate 质量损失率mass segregation 质量层化Mayall Telescope 梅奥尔望远镜Mclntosh classification 麦金托什分类McMullan camera 麦克马伦电子照相机mean motion resonance 平均运动共振membership of cluster of galaxies 星系团成员membership of star cluster 星团成员merge 并合merger 并合星系; 并合恒星merging galaxy 并合星系merging star 并合恒星mesogranulation 中米粒组织mesogranule 中米粒metallicity 金属度metallicity gradient 金属度梯度metal-poor cluster 贫金属星团metal-rich cluster 富金属星团MGS, Mars Global Surveyor 火星环球勘测者micro-arcsec astrometry 微角秒天体测量microchannel electron multiplier 微通道电子倍增管microflare 微耀斑microgravitational lens 微引力透镜microgravitational lensing 微引力透镜效应microturbulent velocity 微湍速度millimeter-wave astronomy 毫米波天文millisecond pulsar 毫秒脉冲星minimum mass 质量下限minimum variance 最小方差mixed-polarity magnetic field 极性混合磁场MMT, Multiple-Mirror Telescope 多镜面望远镜moderate-resolution spectrograph 中分辨摄谱仪moderate-resolution spectroscopy 中分辨分光modified isochrone method 改进等龄线法molecular outflow 外向分子流molecular shock 分子激波monolithic-mirror telescope 单镜面望远镜moom 行星环卫星moon-crossing asteroid 越月小行星morphological astronomy 形态天文morphology segregation 形态层化MSSSO, Mount Stromlo and Siding 斯特朗洛山和赛丁泉天文台Spring Observatorymultichannel astrometric photometer 多通道天测光度计( MAP )multi-object spectroscopy 多天体分光multiple-arc method 复弧法multiple redshift 多重红移multiple system 多重星系multi-wavelength astronomy 多波段天文multi-wavelength astrophysics 多波段天体物理naked-eye variable star 肉眼变星naked T Tauri star 显露金牛T 型星narrow-line radio galaxy ( NLRG ) 窄线射电星系Nasmyth spectrograph 内氏焦点摄谱仪natural reference frame 自然参考架natural refenence system 自然参考系natural seeing 自然视宁度near-contact binary 接近相接双星near-earth asteroid 近地小行星near-earth asteroid belt 近地小行星带near-earth comet 近地彗星NEO, near-earth object 近地天体neon nova 氖新星Nepturian ring 海王星环neutrino astrophysics 中微子天文NNTT, National New Technology Telescope国立新技术望远镜NOAO, National Optical Astronomical 国立光学天文台Observatoriesnocturnal 夜间定时仪nodal precession 交点进动nodal regression 交点退行non-destroy readout ( NDRO ) 无破坏读出nonlinear infall mode 非线性下落模型nonlinear stability 非线性稳定性nonnucleated dwarf elliptical 无核矮椭圆星系nonnucleated dwarf galaxy 无核矮星系nonpotentiality 非势场性nonredundant masking 非过剩遮幅成象nonthermal radio halo 非热射电晕normal tail 正常彗尾North Galactic Cap 北银冠NOT, Nordic Optical Telescope 北欧光学望远镜nova rate 新星频数、新星出现率NTT, New Technology Telescope 新技术望远镜nucleated dwarf elliptical 有核矮椭圆星系nucleated dwarf galaxy 有核矮星系number density profile 数密度轮廓numbered asteroid 编号小行星oblique pulsator 斜脉动星observational cosmology 观测宇宙学observational dispersion 观测弥散度observational material 观测资料observing season 观测季occultation band 掩带O-Ne-Mg white dwarf 氧氖镁白矮星one-parameter method 单参数法on-line data handling 联机数据处理on-line filtering 联机滤波open cluster of galaxies 疏散星系团Ophelia 天卫七optical aperture-synthesis imaging 光波综合孔径成象optical arm 光学臂optical disk 光学盘optical light 可见光optical luminosity function 光学光度函数optically visible object 光学可见天体optical picture 光学图optical spectroscopy 光波分光orbital circularization 轨道圆化orbital eccentricity 轨道偏心率orbital evolution 轨道演化orbital frequency 轨道频率orbital inclination 轨道倾角orbit plane 轨道面order region 有序区organon parallacticon 星位尺Orion association 猎户星协orrery 太阳系仪orthogonal transformation 正交变换oscillation phase 振动相位outer asteroid belt 外小行星带outer-belt asteroid 外带小行星outer halo cluster 外晕族星团outside-eclipse variation 食外变光overshoot 超射OVV quasar, optically violently OVV 类星体variable quasar、optically violent variablequasaroxygen sequence 氧序pan 摇镜头parry arc 彩晕弧partial-eclipse solution 偏食解particle astrophysics 粒子天体物理path of annularity 环食带path of totality 全食带PDS, photo-digitizing system、PDS、数字图象仪、photometric data system 测光数据仪penetrative convection 贯穿对流pentaprism test 五棱镜检验percolation 渗流periapse 近质心点periapse distance 近质心距periapsis distance 近拱距perigalactic distance 近银心距perigalacticon 近银心点perimartian 近火点period gap 周期空隙period-luminosity-colour relation 周光色关系PG 1159 star PG 1159 恒星photoflo 去渍剂photographic spectroscopy 照相分光photometric accuracy 测光精度photometric error 测光误差photometric night 测光夜photometric standard star 测光标准星photospheric abundance 光球丰度photospheric activity 光球活动photospheric line 光球谱线planetary biology 行星生物学planetary geology 行星地质学Pleiad 昴团星plerion 类蟹遗迹plerionic remnant 类蟹遗迹plerionic supernova remnant 类蟹超新星遗迹plumbicon 氧化铅光导摄象管pluton 类冥行星p-mode p 模、压力模pointimg accuracy 指向精度point spread function 点扩散函数polarimetric standard star 偏振标准星polarization standard star 偏振标准星polar-ring galaxy 极环星系Portia 天卫十二post AGB star AGB 后恒星post-core-collapse cluster 核心坍缩后星团post-coronal region 冕外区post-main-sequence star 主序后星post red-supergiant 红超巨后星post starburst galaxy 星暴后星系post T Tauri star 金牛T 后星potassium-argon dating 钾氩计年precataclysmic binary 激变前双星precataclysmic variable 激变前变星preceding limb 西边缘、前导边缘precessing-disk model 进动盘模型precession globe 岁差仪precession period 进动周期preflash 预照光pre-main-sequence spectroscopic 主序前分光双星binarypre-planetary disk 前行星盘pre-white dwarf 白矮前身星primary crater 初级陨击坑primordial binary 原始双星principle of mediocrity 折衷原则progenitor 前身星; 前身天体progenitor star 前身星projected density profile 投影密度轮廓proper-motion membership 自行成员星proper reference frame 固有参考架proper reference system 固有参考系proplyd 原行星盘proto-binary 原双星proto-cluster 原星团proto-cluster of galaxies 原星系团proto-earth 原地球proto-galactic cloud 原星系云proto-galactic object 原星系天体proto-Galaxy 原银河系proto-globular cluster 原球状星团proto-Jupiter 原木星proto-planet 原行星proto-planetary disk 原行星盘proto-planetary system 原行星系proto-shell star 原气壳星proto-sun 原太阳pseudo body-fixed system 准地固坐标系Puck 天卫十五pulsar time scale 脉冲星时标pulsation axis 脉动对称轴pulsation equation 脉动方程pulsation frequency 脉动频率pulsation phase 脉动阶段pulsation pole 脉动极pulse light curve 脉冲光变曲线pyrometry 高温测量QPO, quasi-periodic oscillation 似周期振荡quantum cosmology 量子宇宙学quantum universe 量子宇宙quasar astronomy 类星体天文quiescence 宁静态radial pulsator 径向脉动星radial-velocity orbit 分光解radial-velocity reference star 视向速度参考星radial-velocity standard star 视向速度标准星radial-velocity survey 视向速度巡天radio arm 射电臂radio counterpart 射电对应体radio loud quasar 强射电类星体radio observation 射电观测radio picture 射电图radio pollution 射电污染radio supernova 射电超新星rapid burster 快暴源rapidly oscillating Ap star 快速振荡Ap 星readout 读出readout noise 读出噪声recycled pulsar 再生脉冲星reddened galaxy 红化星系reddened object 红化天体reddened quasar 红化类星体red horizontal branch ( RHB ) 红水平分支red nebulous object ( RNO ) 红色云状体Red Rectangle nebula 红矩形星云redshift survey 红移巡天red straggler 红离散星reflex motion 反映运动regression period 退行周期regular cluster 规则星团; 规则星系团relaxation effect 弛豫效应reset 清零resonance overlap theory 共振重叠理论return-beam tube 回束摄象管richness parameter 富度参数Ring nebula ( M 57、NGC 6720 ) 环状星云ring-plane crossing 环面穿越Rosalind 天卫十三ROSA T, Roentgensatellit 〈ROSAT〉天文卫星Rosette Molecular Cloud ( RMC ) 玫瑰分子云Rossby number 罗斯贝数rotating variable 自转变星rotational evolution 自转演化rotational inclination 自转轴倾角rotational modulation 自转调制rotational period 自转周期rotational phase 自转相位rotational pole 自转极rotational velocity 自转速度rotation frequency 自转频率rotation phase 自转相位rotation rate 自转速率rubber second 负闰秒rubidium-strontium dating 铷锶计年Sagittarius dwarf 人马矮星系Sagittarius dwarf galaxy 人马矮星系Sagittarius galaxy 人马星系Saha equation 沙哈方程Sakigake 〈先驱〉空间探测器Saturn-crossing asteroid 越土小行星Saturnian ringlet 土星细环Saturnshine 土星反照scroll 卷滚Sculptor group 玉夫星系群Sculptor Supercluster 玉夫超星系团Sculptor void 玉夫巨洞secondary crater 次级陨击坑secondary resonance 次共振secular evolution 长期演化secular resonance 长期共振seeing management 视宁度控管segregation 层化selenogony 月球起源学separatrice 分界sequential estimation 序贯估计sequential processing 序贯处理serendipitous X-ray source 偶遇X 射线源serendipitous γ-ray source 偶遇γ射线源Serrurier truss 赛路里桁架shell galaxy 壳星系shepherd satellite 牧羊犬卫星shock temperature 激波温度silicon target vidicon 硅靶光导摄象管single-arc method 单弧法SIRTF, Space Infrared Telescope 空间红外望远镜Facilityslitless spectroscopy 无缝分光slit spectroscopy 有缝分光slow pulsar 慢转脉冲星SMM, Solar Maximum MIssion 太阳极大使者SMT, Submillimeter Telescope 亚毫米波望远镜SOFIA, Stratospheric Observatory for 〈索菲雅〉机载红外望远镜Infrared Astronomysoft γ-ray burst repeater 软γ暴复现源soft γrepeater ( SGR ) 软γ射线复现源SOHO, Solar and Heliospheric 〈索贺〉太阳和太阳风层探测器Observatorysolar circle 太阳圈solar oscillation 太阳振荡solar pulsation 太阳脉动solar-radiation pressure 太阳辐射压solar-terrestrial environment 日地环境solitary 孤子性soliton star 孤子星South Galactic Cap 南银冠South Galactic Pole 南银极space density profile 空间密度轮廓space geodesy 空间大地测量space geodynamics 空间地球动力学Spacelab 空间实验室spatial mass segregation 空间质量分层speckle masking 斑点掩模speckle photometry 斑点测光speckle spectroscopy 斑点分光spectral comparator 比长仪spectrophotometric distance 分光光度距离spectrophotometric standard 分光光度标准星spectroscopic period 分光周期specular density 定向密度spherical dwarf 椭球矮星系spin evolution 自旋演化spin period 自旋周期spin phase 自旋相位spiral 旋涡星系spiral arm tracer 示臂天体Spoerer minimum 斯珀勒极小spotted star 富黑子恒星SST, Spectroscopic Survey Telescope 分光巡天望远镜standard radial-velocity star 视向速度标准星standard rotational-velocity star 自转速度标准星standard velocity star 视向速度标准星starburst 星暴starburst galaxy 星暴星系starburst nucleus 星暴star complex 恒星复合体star-formation activity 产星活动star-formation burst 产星暴star-formation efficiency ( SFE ) 产星效率star-formation rate 产星率star-formation region 产星区star-forming region 产星区starpatch 星斑static property 静态特性statistical orbit-determination 统计定轨理论theorysteep-spectrum radio quasar 陡谱射电类星体stellar environment 恒星环境stellar halo 恒星晕stellar jet 恒星喷流stellar speedometer 恒星视向速度仪stellar seismology 星震学Stokes polarimetry 斯托克斯偏振测量strange attractor 奇异吸引体strange star 奇异星sub-arcsec radio astronomy 亚角秒射电天文学Subaru Telescope 昴星望远镜subcluster 次团subclustering 次成团subdwarf B star B 型亚矮星subdwarf O star O 型亚矮星subgiant branch 亚巨星支submilliarcsecond optical astrometry 亚毫角秒光波天体测量submillimeter astronomy 亚毫米波天文submillimeter observatory 亚毫米波天文台submillimeter photometry 亚毫米波测光submillimeter space astronomy 亚毫米波空间天文submillimeter telescope 亚毫米波望远镜submillisecond optical pulsar 亚毫秒光学脉冲星submillisecond pulsar 亚毫秒脉冲星submillisecond radio pulsar 亚毫秒射电脉冲星substellar object 亚恒星天体subsynchronism 亚同步subsynchronous rotation 亚同步自转Sunflower galaxy ( M 63 ) 葵花星系sungrazer comet 掠日彗星supercluster 超星团; 超星系团supergalactic streamer 超星系流状结构supergiant molecular cloud ( SGMC ) 超巨分子云superhump 长驼峰superhumper 长驼峰星supermaximum 长极大supernova rate 超新星频数、超新星出现率supernova shock 超新星激波superoutburst 长爆发superwind galaxy 超级风星系supporting system 支承系统surface activity 表面活动surface-brightness profile 面亮度轮廓surface-channel CCD 表面型CCDSU Ursae Majoris star 大熊SU 型星SWAS, Submillimeter Wave Astronomy 亚毫米波天文卫星Satallitesymbiotic binary 共生双星symbiotic Mira 共生刍藁symbiotic nova 共生新星synthetic-aperture radar 综合孔径雷达systemic velocity 质心速度TAMS, terminal-age main sequence 终龄主序Taurus molecular cloud ( TMC ) 金牛分子云TDT, terrestrial dynamical time 地球力学时television guider 电视导星器television-type detector 电视型探测器Tenma 〈天马〉X 射线天文卫星terrestrial reference system 地球参考系tetrad 四元基thermal background 热背景辐射thermal background radiation 热背景辐射thermal pulse 热脉冲thermonuclear runaway 热核暴涨thick-disk population 厚盘族thinned CCD 薄型CCDthird light 第三光源time-signal station 时号台timing age 计时年龄tomograph 三维结构图toner 调色剂torquetum 赤基黄道仪TRACE, Transition Region and Coronal 〈TRACE〉太阳过渡区和日冕Explorer 探测器tracker 跟踪器transfer efficiency 转移效率transition region line 过渡区谱线trans-Nepturnian object 海外天体Trapezium cluster 猎户四边形星团triad 三元基tri-dimensional spectroscopy 三维分光triquetum 三角仪tuning-fork diagram 音叉图。
星团的结构与动力学性质
星团的结构与动力学性质星团是银河系中的一颗颗闪耀的珍珠，它们以壮美的光芒点亮了宇宙的黑暗。
它们的结构和动力学性质是天文学家们长期关注的课题，在对它们的研究中，我们逐渐揭开了这些神秘天体的面纱。
首先，我们来了解一下星团的结构。
星团是由一群恒星组成的天体，分为两类：球状星团和散团。
球状星团是一群紧密聚集在一起的恒星，这些恒星相对较老，呈球状分布，通常位于银河系的星系核心附近。
而散团则是一群年轻恒星的集合，它们通常散布在银河系的外围区域。
然而，星团的结构并非一成不变。
在星团中，恒星之间存在着相互作用和引力相互作用。
这些相互作用不仅会改变星团内部的恒星分布，还会对恒星的运动轨迹产生影响。
从宏观上看，星团的结构会随时间而演化，恒星会逐渐靠近或远离彼此，整个星团的形态也会发生变化。
这种演化也受到星团内部的恒星数目和质量分布的影响。
不同恒星之间的相对位置和质量大小，决定了星团的整体结构。
除了结构，星团的动力学性质也是研究的重点之一。
恒星在星团内部的运动速度与其在星团中相对位置有关。
相对位置靠近中心的恒星速度越快，而靠近星团边缘的恒星则速度相对较慢。
这种差异主要是由引力和动量守恒定律所决定的。
恒星在星团内部相互作用下，会通过引力的作用而加速或减速。
同时，恒星的质量也会影响其运动速度。
质量越大的恒星会受到更大的引力作用，因此其运动速度也更快。
除了引力作用外，星团中可能还存在其他影响恒星运动的因素。
例如，星团内部可能存在着气体和尘埃的分布，它们的存在会导致恒星运动的摩擦，从而影响整个星团的动力学性质。
此外，星团中的恒星还可能被其他恒星的星风所影响。
星风是恒星产生的高速气流，当这些气流相互碰撞时，会产生巨大的动能，从而影响星团的运动。
结构与动力学性质是星团研究中相互关联的两个方面。
通过对星团的结构进行观测和分析，我们可以了解星团内部恒星的分布，从而推测出星团演化的历史。
而了解星团的动力学性质，则能够帮助我们更好地理解其中的物理过程和天文现象。
活动星系核
大幅度、短时标光变 → 致密核
• 3C 279几天内可变亮4倍
伽马射线爆发
X射线爆发
Blazars：相对论聚束效应
Blazars的极端特征被解释为其相对论喷流大 致沿观测者的视线方向，因而具有显著的相对 论聚束相应，使得观测到的 • 光子能量升高 • 光度放大 • 时标变短 相对论修正 内禀特征
AGN的类型与喷流和视线的夹角有关
喷流的视超光速运动 Superluminal Motion
活动星系核的喷流（抛 射物）似乎以超光速向 外运动（天球上横向） 如对类星体3C279的3 年时间的VLBI射电观测 表明喷流中最外围团块 的运动速度接近光速的 4倍
射电瓣
核nucleus
射电节 knot
室女星系团中心的巨椭圆星系 第一个观测到(光学)喷流的星系。喷流 光学 的长度约 2kpc，由不连续的团块构成， 在射电到X射线波段产生同步辐射
M87
射电
红外
射电
Centaurus (半人马座 ) A (NGC5128)
最近最壮观的双瓣射电源 光学像：非典型巨椭圆星系， 可能是星系并合而成，环形 尘埃带（兰巨星）
正常星系
相同视场：光学 vs X射线
Optical (HST)
X-ray (Chandra)
类星体 PKS 1127-145
1.1 高光度
银河系
X射线光度 光学光度 1 1 2 2 射电光度 1
射电星系 100-5,000 赛弗特星系 300-7×104
2X103-2×106 20[-2×106]
天文学导论
第13讲 活动星系核
There is a beast at the centers of galaxies!
Segue
Sloan Extension for Galactic Underpinnings and Evolution(SEGUE)Segue(v.):To proceed to what follows without pauseHeidi Newberg1,Kurt Anderson2,3,Timothy Beers4,Jon Brinkmann3,Bing Chen5,Eva Grebel6, Jim Gunn7,Hugh Harris8,Greg Hennessy9,ˇZeljko Ivezic7,Jill Knapp7,Alexei Kniazev6,Steve Levine8,Robert Lupton7,David Martinez−Delgado6,Peregrine McGehee2,10,Dave Monet8,JeffMunn8,Michael Odenkirchen6,JeffPier8,Connie Rockosi11,Regina Schulte−Ladbeck12,J.Allyn Smith10,Paula Szkody11,Alan Uomoto13,Rosie Wyse13,Brian Yanny141Rensselaer Polytechnic Institute2New Mexico State University3Apache Point Observatory4Michigan State University5ESA/Vilspa,Madrid,Spain6Max-Planck-Institut f¨u r Astronomie,Heidelberg7Princeton University8US Naval Observatory,Flagstaff9US Naval Observatory,DC10Los Alamos National Laboratory11University of Washington12University of Pittsburgh13Johns Hopkins University14Fermi National Accelerator LaboratoryI.Project SummaryA.Science GoalsWe propose an imaging and spectroscopic survey to unravel the structure,formation history, kinematics,dynamical evolution,chemical evolution,and dark matter distribution of the Milky Way.These results underpin our knowledge of the formation of the Milky Way Galaxy and of for-mation processes within the Milky Way,and will be the cornerstone of our understanding of galaxy formation processes in general.Cosmology is entering a precision era,facilitated by new work on the Cosmic Microwave Background by the Wilkinson Microwave Anisotropy Probe(WMAP)and on the distribution of galaxies by the Sloan Digital Sky Survey(SDSS)and by smaller,deeper large-telescope surveys.Galaxy formation and evolution,however,is still as data-starved as cosmology was twenty years ago.The Milky Way is the only galaxy in which we can hope to kinematically and spatially resolve the fossil record of evolution,since here the geometry is relatively unambiguous and intrinsically faint stars can be readily observed.Two key projects which focus on Galactic history and dynamics are:(1)detection of sub-structure in the Galactic halo,and(2)defining and refining our knowledge of the Milky Way’s Galactic disks.Other projects that will be necessary to realize the full potential of the key projects include understanding the relationship between SDSS photometry and the physical properties of stars,mapping the interstellar extinction in three dimensions,and studying the chemical evolution of the earliest Milky Way stars.To accomplish these goals,the existing SDSS hardware and software will be used to image (infive SDSS passbands)four thousand square degrees of the Milky Way at low Galactic latitude and to sample the stars in this new region and in the existing high-latitude SDSS survey to targetand obtain spectra of240,000stars.These spectra will allow determinations of radial velocities and chemical abundances,which will allow us to study kinematics,dynamics,and the chemical history of the Galaxy.Key Project1:Halo SubstructureSDSS data have already been used to trace the tidal stream from the Sagittarius dwarf galaxy,and to discover a second large tidal stream in the plane of the Milky Way.The structure of the Milky Way’s halo is sufficiently lumpy that it has so far defied a consistent globalfit to the smooth component of the spheroid stars.The halo may contain a(possiblyflattened)power law component,aflattened inner halo,at least two large tidal streams,a dozen dwarf galaxies and a hundred globular clusters.Some of the dwarf galaxies and globular clusters are currently being pulled apart by tidal forces.Some of the stars in the components that appear to be smooth in density may retain kinematics of the stellar associations in which they were born.Disentangling the structure of the Milky Way halo requires that individual stellar associations can be separated by population(age and metallicity),kinematics,and spatial density.The SDSS and SEGUE photometry can be used for photometric parallax(spatial density)and isochrone fitting to stellar components(into rough age and metallicity bins).Galaxy components can be separated kinematically with radial velocities.The stellar physical properties determined from spectroscopy and from imaging of open clusters serve as a check on the isochrones and further serve to illuminate the chemical composition of each component.The dynamics of stellar streams allow us tofit the Galactic potential’s shape and orientation, and constrain parameters characterizing the lumpiness of the halo dark matter.The dark matter itself could accrete with time as the stars do;knowledge of the Galactic merger history and grav-itational potential place important constraints on N-body models of galaxy formation and on the expected velocity distribution of dark matter particles.The velocity distribution of dark matter particles can affect both the energy spectrum and annual modulation of the expected signal in dark matter direct detection experiments on the Earth.Key Project2:Disk structureImaging at low Galactic latitude will allow us to study the transition from thin disk to thick disk toflattened inner halo.There is general agreement on the number and exponential form of the Milky Way stellar disks,but little agreement on the exact parameters of each.This situation is similar to the state of our knowledge of the halo several years ago,when there was general agreement that the spheroidal population of stars was well modeled by a power law,but with no agreement on theflattening parameter(measurements range from c/a=0.4−1.0).As the current generation of precise data is beginning to show,the Milky Way’s disks are not as simple as the present models suggest.The fact that the stars associated with the large tidal stream in the plane of the Milky Way were initially widely attributed to an extended thick disk of stars underlines how little we know for sure about the number and detailed form of the Milky Way’s disks.SEGUE will use spectra(physical properties and radial velocities),photometry(stellar popu-lation and spatial density),and proper motions from outside catalogs to separate and normalize the Galactic components in the solar neighborhood.Additionally,the disk components will be traced using stars as close asfive or ten degrees from the Galactic plane,using techniques similar to those forfinding halo substructure.We do not expect to be able to trace all the spiral substructure of the young thin disk,as that is best studied at longer wavelengths,but we will be able to trace the structure,kinematics,and compositions of the other disks as a function of position in the Galaxy. This latter goal will require that we understand the three dimensional structure of the Interstellar Medium(ISM),including independent measures of dust from SEGUE observations,and its effects on our stellar photometry.Formation HistoryThe identification and characterization of the Milky Way components can be utilized as an archaeological“dig”illuminating the fossil record of galaxy evolution.We will study how many mergers and of what size and time series must have occurred to make the Milky Way.We will begin to be able to pick apart the chemical and dynamical evolution of the Galaxy as a whole.We will search for rare,especially low metallicity,stars that‘freeze-in’the state of the ISM during the earliest stages of star formation in the Universe.The rare stellar objects identified in this survey will provide followup targets of high scientific interest for the world’s largest telescopes.B.Survey DataApproximately four thousand square degrees of new imaging data,at moderate to low Galac-tic latitude,and spectra of240,000Galactic stars will be acquired.The imaging footprint was designed so that no part of the sky(aboveδ=−20◦observable from the Apache Point Observa-tory)is more than10◦from either an SDSS or a SEGUE imaging stripe.In the Galactic caps, no part of the sky is more than5◦from an imaging stripe.In addition,the scans are designed to tie the photometric calibration from the SDSS north Galactic cap to the scans in the south,and to cross each other a sufficient number of times to reduce systematic uncertainties in the overall photometric calibration.The positions of the spectroscopic plates are chosen to sample the Galaxy in all directions,so that no part of the observable sky is more than about ten degrees from a spec-troscopic plate,and to target well-studied open clusters.Figure1shows the approximate layout of the SEGUE imaging stripes and spectroscopic plates on the sky.The low Galactic latitude imaging enables studies of the metal-rich Galactic thin disk,the vertical structure of the thin and the thick disks,the Galactic warp andflaring,the three dimen-sional structure of the ISM,and present star forming regions.The imaging will be taken in similar weather conditions,at the same scanning rate(which translates to the same exposure time),and with the same instruments andfilters as the SDSS.Each stripe is2.5◦wide and requires two interleaved scans with the SDSS imaging camera,on separate nights,to complete.The imag-ing includes twelve constant Galactic longitude stripes which go through the Galactic plane and typically extend thirty-five degrees on either side(dashed green lines in Figure1).These stripes are separated by about20◦of Galactic longitude,varying somewhat to pass through known open clusters,SIRTF legacyfields,and patches of low extinction near the Galactic plane.The constant Galactic longitude stripes connect and overlap SDSS imaging of the Galactic caps to facilitate the photometric calibration of both old and new data.In addition,three new SDSS stripes(72,79,and90,shown as solid green lines in Figure1) will be imaged in the South Galactic Cap.Only three stripes were imaged in the South Galactic Cap during the SDSS survey,and the additional stripes are needed to sample that part of the sky about every ten degrees.One stripe(red line in Figure1)follows the Sagittarius dwarf tidal stream across the northern sky.Two long(half-filled)strips(magenta lines in Figure1)cross the remaining SEGUE stripes,and will be used to cross-calibrate the stellar photometry to a level of at least2%(systematic+rms),and will trace low latitude structures,including the newly discovered tidal stream in the Galactic plane.The SDSS camera must scan along great circles,so all of these stripes describe great circles on the Celestial Sphere.The spectroscopic observations include1200spectra in each of200individual sky directions. The plate positions were chosen to sample the sky in all observable directions,and spectra will be selected to sample stars from one to100kpc from the Sun and from as many Galactic substructures as possible.Additional observations target regions of high interest such as open clusters,star formation regions,and known tidal streams in the halo.Each plate position is3◦in diameter.We will design two640-fiber plates in each plate position,with a total of about1200stellar targets-60-300306090120150180210240270300-90-60-300306090-90-60-30030609010230130l b s90s86s79s72s9s16s27s37s4418h22h2h 6h 6h 17.4h 2718.0h 618.6h 837.9h 498.6h 1621.1h -022.8h 25 1.3h 32 3.6h 17 5.0h -11Figure 1.Low Latitude Imaging and Spectroscopy Plan.The SFD (1998)reddening map is shown in Galactic coordinates;note the center is shifted to (l,b )=(120◦,0◦).Green,red,magenta (purple)lines indicate new SEGUE scans to be obtained.SEGUE Imaging at l =110degrees from −30◦<b <30◦has already been obtained as of Nov 2003(SDSS runs 4134,4135,4144,4152).The red line along the great circle with (node,incl)=(32◦,35◦)follows the Sagittarius dwarf tidal stream.Magenta lines indicate half-filled “strips”in portions of the sky at low Galactic latitude,and cross the constant longitude stripes for better calibration;the great circles arcs are defined by (node,incl)=(259.9◦,43.6◦),(311.0◦,66.7◦).The total SEGUE imaging area is about 4000sq.degrees,of which 200sq.degrees has already been obtained.Black lines indicate existing or planned SDSS regular imaging.Black dotted reference lines are at b =0◦and declination (DEC)=−20◦(no SEGUE imaging or spectroscopy occurs at a DEC of <−20◦from Apache Point Observatory in the Northern hemisphere).Black long dashed lines mark constant Right Ascensions (RAs)of (18,22,2,and 6)bels above the top of the figure indicate RA,DEC start and end for a vertical SEGUE imaging stripe.Open black circles indicate positions of known Sagittarius dwarf tidal stream stars.Filled black circles indicate positions of known Monoceros stream stars.Open black diamonds indicate positions of known Galactic open clusters.The blue circles indicate individual 3-degree diameter positions of Galactic structure plate pairs (bright plate:45min exposure,plus faint plate:90min exposure),168blue plate pairs.Yellow circles indicate positions of ‘special plates,’landing on a known open cluster,the Sag.dwarf stream,or the Monoceros Ring structure.29blue plate pairs.Total:197plate pairs and about 240,000stellar spectra with resolving power R ∼2000,and 3<S/N <100for objects with 20.3>g >14.5.plus calibration objects.One plate will have the SDSS standard 45minute exposure time,and the other will be exposed for twice as long,allowing us to reach stellar targets as faint as g ∼20.3.Spectroscopic targets will include halo giants,metal-poor dwarfs,G disk and halo dwarfs,white dwarfs,and a large variety of rare stars.At low latitudes,targets within star-forming regions will be selected.II.Scientific CaseOur understanding of Galaxy evolution has advanced considerably since the monolithic col-lapse model of Eggen,Lynden-Bell and Sandage(1962)was adopted as the standard.Most experts now believe that the Galaxy was built up through a series of mergers(Searle&Zinn1978),though there is no agreement on the number and size of the merger events.These current models of galaxy formation stem from cold dark matter(CDM)simulations that show the outer halos accret-ing over billions of years(Steinmetz&Navarro2002),and from the increasing number of examples of moving groups and tidal disruption discovered in the halo of our galaxy(Majewski et al.2003; Newberg et al.2002;Odenkirchen et al.2001a;Irwin&Helmi et al.1999;Ibata,Gilmore,& Irwin1995;Grillmair et al.1995;Irwin&Hatzidimitriou1995),M31(Ferguson et al.2002),and other external galaxies(Shang et al.1998,Zucker et al.2004).It is possible that the hierarchical merging process is most important in the dark matter dominated galactic halos,while disks might form from the(angular momentum conserving)collapse of the gas within the stellar spheroid.However,Λcold dark matter simulations suggest merging may significantly affect the formation of disks as well(Abadi et al.2003).Evidence of mergers is currently most apparent in the outer halo where signatures of satellite accretion persist for many gigayears(Johnston,Spergel,&Hernquist1995).Dwarf galaxies and globular clusters are among the outer halo objects which are merging at the current epoch.It is also possible that there exist some lumps of dark matter in the outer halo that have not yet merged,and which do not contain stars(e.g.,Bullock,Kravtsov,&Weinberg2001).These latter structures could be evident by their perturbation of tidal tails and warping of disk structures.Our own Milky Way is the only galaxy that we can presently study at sufficiently high spatial and kinematical resolution,and at sufficient depth,to address many of the open questions of galaxy formation and small-scale structure evolution in sub-halos.Our goal is to obtain the spectroscopic and photometric data required to unravel the structure,the formation history,the kinematic and dynamical evolution,the chemical evolution,and the distribution of the dark matter within and around the Milky Way.We propose two key projects,which contribute to our knowledge of the Galactic mass assem-bly and disk formation models.These projects are:(1)detection of substructure in the Galactic halo,and(2)defining the structures of the Galactic disks.These are really two parts of the one key project to define the major components of the Milky Way galaxy,but are listed separately since they may require different data sets and analysis methods.One may think of this proposed project as providing a large homogeneous input data set to a21st century model of the Galaxy–one which involves not only accurate multi-color photometry such as has gone into earlier models (Bahcall&Soneira1984),but large amounts of kinematic velocity and proper motion data which can be used to complete the dynamical and evolutionary picture.This technique is most similar to that used to construct the Besancon model of the Galaxy(Robin et al.2003),but with more input data.Detection of substructure in the Galactic halo requires photometry and radial velocities in as many directions as possible.The large tidal streams that have already been discovered are more than4kpc across,setting the scale over which we must sample the sky tofind all large tidal structures.Characterizing the Galactic disks requires data collection primarily at low latitudes, and within a few kpc of the Galactic plane.The goal is to separate disk components by their stellar content,and then measure the global properties.These projects will separate and describe components using radial velocities,proper motions, chemical composition,photometric parallax,and isochronefitting to photometry.In some sense, our survey is concentrated on the“big picture”of our galaxy.We will identify and constrain all of the largest components,paving the way for future inquiries which willfindfiner substructure,S52-32-20.4S341+57-22.5S297+63-20.S6+41-20S223+20-19.4S200-24-19.8S167-54-21.5(RA,DEC)[l,b](0,0)[96,-60](15,0)[128,-63](30,0)[157,-58](45,0)[177,-49](60,0)[190,-37](75,0)[199,-25](90,0)[207,-11](105,0)[214,2](120,0)[221,15](135,0)[229,28](150,0)[239,41](165,0)[254,52](180,0)[276,60](195,0)[308,63](210,0)[337,58](225,0)[357,49](240,0)[10,37](255,0)[19,25](270,0)[27,11](285,0)[34,-2](300,0)[41,-15](315,0)[49,-28](330,0)[59,-41](345,0)[74,-52]15171921g *23171921231517192123151719212305101520253035404550Figure 2.Polar histogram of color-selected turnoffstars on the celestial equator .This data was obtained with the Sloan Digital Sky Survey.The radial distance gives the apparent dereddened g ∗magnitude.The angular position gives the RA.Galactic coordinates are labeled for reference.The shading of each cell indicates the relative number of counts of stars in each (r,θ)=(g ∗,α)bin.A typical absolute magnitude for stars with these colors is M g ∗=4.2.The feature at α=60◦is an artifact from imperfect reddening correction of a large dust cloud at this position.The streak at α=229◦represents stars in the globular cluster Palomar 5.The boldface labels indicate our names for identified structures of halo stars.S341+57-22.5at g ∗∼22.5,and S167-54-21.5at g ∗∼21.5are cross sections of the Sagittarius dwarf galaxy tidal stream.more accurately determine the chemical evolution,and measure proper motions for a large fraction of the stars in the Milky Way.A calibrated catalog of images,spectra,and associated derived quantities,will be the primary product of this survey.These will be generated in nearly real time,to be used for rapid follow-up work or as input targets to space-based or large aperture telescopes.The need for this global picture of our galaxy is well illustrated by the results of Newberg et al.(2000;Figure 2).In this figure,there are seven marked concentrations of stars.Concentrations S341+57-22.5and S167-54-21.5have been identified as cross sections through the tidal stream ofthe Sagittarius dwarf spheroidal galaxy,which is currently in the process of tidal disruption.The overdensities S223+20-19.4and S200-24-19.8are thought to be pieces of another tidal disrupting stream in the plane of the Milky Way galaxy.The concentrations in this region near the Galactic plane,at15th and17th magnitude near the anticenter are not named,but also are not understood in any global picture of the Milky Way.The overdensity S297+63-20.is thought to be another tidal stream,possibly associated with the Sagittarius dwarf galaxy,though this has not been confirmed and remains controversial.The concentrations S6+41-20and S52-32-20.4are thought to be portions of the stellar spheroid,though their density distributions do notfit standard spheroidal models within the errors of our density measurements.One sees in Figure2a strong argument for a global view of the whole Milky Way,including low Galactic latitudes,since one cannot identify substructure without understanding the major Galactic components in which that substructure is embedded,and properly accounting for inter-stellar extinction.Many of the scientific analyses that we anticipate will be based on these data have counterparts in the much smaller-scale efforts of individuals or groups,which,unavoidably, dilute their impact by acquiring data in a piecemeal and non-uniform fashion.A uniform survey creates a synergy which allows more global questions to be addressed and leaves behind a legacy data set against which future data sets will be compared.A better understanding of the Milky Way’s structure and evolution is already a“cornerstone”project in ESA’s science planning,through the GAIA satellite mission,and plays an important role in the definition of the science goals for NASA’s SIM and TPF missions,which are“key elements in NASA’s Origins Program.”We demonstrate here how a deep imaging and spectroscopic optical survey will complement as well as lay the groundwork for these ambitious satellite projects. Furthermore,SEGUE willfill a unique and vital niche complementing ongoing and planned large ground based Galactic structure programs such as RAVE and K.A.O.S.A.Characterization of the Component Stellar Structures in the Milky WayThe fossil record of galaxy evolution(star formation and mass assembly)is written in the chemical,kinematic,and spatial distribution of Galactic stars.The main recognized components of the Galaxy are the thin disk,the thick disk,the bulge,and the stellar spheroid.Recently many groups of astronomers have identified examples of Galactic structure that either requires additional components or an increase in the complexity of the traditional components.Kinematic studies show the existence of moving groups and coherent streams(numerous studies),and a group of stars(Gilmore,Wyse,&Norris2002)that may be part of the merger that puffed up the thick disk.Overdensities of stars over the Galactic bar(Parker,Humphreys,&Larsen2002)have been found in photometry.Also,a new metal-weak thick disk component has been proposed(see Norris 1994,Beers et al.2002and references therein).Clearly,even the basic stellar components of the Milky Way are not yet understood in depth. The complex substructure now being identified has undoubtedly biased the previous limited studies of thick disk structure,contributing to our present imprecise knowledge of the thick disk;study of many lines of sight over much of the sky will be necessary to unravel the substructure and obtain a more complete picture.This survey would specifically target the thick disk/halo boundary and substructure.The structures would be studied in stellar density from statistical photometric parallaxes,and in kine-matics through statistics of the radial velocities/metallicities in each component.We use the term ”statistical photometric parallax”to describe the method of using photometry to determine dis-tance(photometric parallax)in cases where the number of stars is large,so that statistics can be used to estimate the underlying spatial structure of the group.We will have a unique opportunity to study the stellar Metallicity Distribution Function(MDF),especially in the region where the thick disk and spheroid populations overlap.Figure3demonstrates preliminary results from SDSS-4-3-2-101[Fe/H]100010000100000Z D i s t a n c e (k p c )Figure 3.The distance and metallicity distribution of EDR stars.The distance distribu-tion of ∼4000stars from the SDSS Early Data Release (EDR)as a function of metallicity [Fe /H].One can clearly discriminate the presence of thick-disk stars with metallicities in the range -1.0<[Fe/H]<0and locations within a few kpc of the Sun,from the halo objects at large distances that extend to much lower metallicities.EDR spectra.Flaring and Warping of the Galactic PlaneThe disks of many galaxies both flare and warp in their outer regions.Flaring is attributed to an increasing ratio of spherically distributed dark mass to disk mass with increasing distance from the center of the galaxy,and provides one of the few available methods of measuring the three-dimensional distribution of dark matter within a galaxy.The origin of Galactic warps is still something of a mystery.Tidal interactions with satellites and neighbors is an obvious cause;for example,the warp in the Galaxy is often attributed to the tidal influence of the Magellanic Clouds (e.g.,Weinberg and Nikolaev 2001;Garcia-Ruiz et al.2002)or of the Sagittarius dwarf spheroidal galaxy (Bailin 2003).However,not all warped galaxies appear to have (presently detected)neigh-bors.The warp andflare in the outer Galactic disk has been studied primarily using(radio)obser-vations of neutral hydrogen.The depth and color sensitivity of SDSS will allow the3-D structure of the northern warp in the Galaxy to be traced to distances beyond the entire known extent of the warp(20kpc,Binney1992),using photometrically identified giants,carbon stars(especially when combined with2MASS data)and red clump stars(e.g.,Margon et al.2002;Helmi et al.2003). The Structure of the Thick DiskHawley et al.(2002)show that early M dwarfs can be traced to distances of up to1kpc above the Galactic plane,well into the domain where the thick disk population dominates that of the thin disk.Since the stars of the thick disk are more metal-deficient(typically by at least0.3-0.5 dex)than the thin disk stars,their colors,especially g−r,diverge from those of the metal-rich disk stars.One can therefore,at least in a statistical sense,separate the two populations.Afirst look at the vertical structure of the thick disk from SDSS data has been carried out by Chen et al.(2001). Star counts in the thin and thick disks can be used to determine the initial mass function,and in particular the counts of lower-metallicity stars must be understood(see the recent discussion by Zheng et al.2001and Chabrier2003).The current SDSS imaging data provide star counts at high Galactic latitude only;under-standing and disentangling the vertical structure of both the thick and thin disks requires data covering the whole range of Galactic latitude at many longitudes.The Structure of the Galactic HaloSDSS data have already demonstrated the presence of very large structures in the Galactic halo(Yanny et al.2000;Ivezic et al.2000;Odenkirchen et al.2001a,b;Newberg et al.2002; Rave et al.2003;Yanny et al.2003).These structures include extra-tidal features around globular clusters and vast comoving stellar streams from accreted dwarf galaxies.These structures,and similar more tenuous analogues,may cover a significant fraction of the sky.Imaging more sky allows such structures to be traced to larger angular sizes,and allows structures which do not completelyfill a great circle on the sky to be detected.Furthermore,high-metallicity globular clusters tend to be found at lower Galactic latitudes;there may be streamers and tails of different color(metallicity)at lower latitudes.Indeed,recently Frinchaboy et al.2004showed that many low latitude open and globular star clusters are likely to be associated with a single large tidal stream in the Galactic plane.There is increasing evidence that even“globally recognized”structures,such as“the halo,”change dramatically with increasing Galactocentric distance.An inner,“flattened”halo compo-nent,for example,has been indicated by many recent studies(Lemon et al.2003,Chiba&Beers 2000).Preston,Shectman&Beers(1991)have used the mean colors of blue horizontal-branch stars to indicate a possible decrease in the ages of stars with increasing Galactocentric distance. Sirko et al.(2004)use an analysis of the spectra of high-latitude A stars to demonstrate a change in the velocity ellipsoid of the halo with distance from the Galactic center.Both of these represent key results for understanding the formation of the Milky Way,which could be readily refined and extended using our proposed survey effort.Complexity of Galactic spheroid populations in other galaxies is traced by their globular cluster systems(at least in early-type galaxies with populous cluster systems that can be studied). Typically the globular cluster systems are bimodal,with bluer(lower metallicity)clusters mak-ing up a more extended and dynamically hotter system,and redder(higher metallicity)clusters comprising a system more centrally concentrated and sometimes rotating(e.g.many papers in IAU Symposium207,ed.Geisler,Grebel&Minniti2002).Typically thefield-star populations have color and spatial distributions suggesting properties more similar to(and perhaps having。
利用脉泽研究银河系的旋臂结构与运动学-科学技术处-南京大学
附件4：2017年度国家科技奖推荐公示内容一、项目名称：中文名：利用脉泽研究银河系的旋臂结构与运动学英文名：Study on the Spiral Arm Structure and Kinematics of the Milky Way with Maser Astrometry二、推荐单位意见：银河系结构和运动是当代天体物理中最具有挑战意义的研究课题之一。
项目组经过十多年的努力工作，在解决银河系大小和旋臂结构等天体物理难题方面取得突破性的进展。
项目组在国际上首先提出用甚长基线干涉仪(VLBI)测量甲醇脉泽的三角视差和自行，研究银河系旋臂结构和运动学性质这一开创性的学术观点。
并首次通过技术创新使射电天体测量精度达到10个微角秒，天体距离测量可达到3万光年，比传统的光学天文视差测量精度高了2个量级。
项目组在3个科学发现点：1.首次精确测量银河系英仙臂的距离；2.发现并精确测定银河系本地臂的形态和运动学性质；3.发现甲醇脉泽是银河系旋臂最好的示踪天体上具有原创性，使直接测量银河系旋臂结构成为现实。
项目获得了国内外同行和专家的高度评价，认为项目组的工作“开创了天文学三角视差测量银河系内遥远天体距离的新纪元”和银河系结构研究领域的“里程碑”。
项目引发了国际天文学界利用三角视差测量天体距离的热潮，大大推动了银河系结构的研究和射电天体测量学科的发展。
项目的多项科学发现都具有原创性，具有重大科学价值，并得到了国内外天文学届的公认。
推荐该项目为国家自然科学奖二等奖。
三、项目简介：银河系结构可能是天文学中持续时间最长，但至今仍未解决的重大问题之一。
有关银河系结构的文字记载，最早可追溯到古希腊大哲学家及天文学家亚里士多德(公元前384--322年)的卓著《气象学》。
2000多年来，天文学家苦苦追寻，仍未清晰地勾画出银河系的结构。
近20年来，项目组成员潜心研究，利用一种新的技术和方法直接测量银河系结构，对绘制银河系的真实面貌做出了开创性的工作。
天文学专用词汇
Galactic aggregate 银河星集Galactic astronomy 银河系天文Galactic bar 银河系棒galactic bar 星系棒galactic cannibalism 星系吞食galactic content 星系成分galactic merge 星系并合galactic pericentre 近银心点Galactocentric distance 银心距galaxy cluster 星系团Galle ring 伽勒环Galilean transformation 伽利略变换Galileo 〈伽利略〉木星探测器gas-dust complex 气尘复合体Genesis rock 创世岩Gemini Telescope 大型双子望远镜Geoalert, Geophysical Alert Broadcast 地球物理警报广播giant granulation 巨米粒组织giant granule 巨米粒giant radio pulse 巨射电脉冲Ginga 〈星系〉X 射线天文卫星Giotto 〈乔托〉空间探测器glassceramic 微晶玻璃glitch activity 自转突变活动global change 全球变化global sensitivity 全局灵敏度GMC, giant molecular cloud 巨分子云g-mode g 模、重力模gold spot 金斑病GONG, Global Oscillation Network 太阳全球振荡监测网GroupGPS, global positioning system 全球定位系统Granat 〈石榴〉号天文卫星grand design spiral 宏象旋涡星系gravitational astronomy 引力天文gravitational lensing 引力透镜效应gravitational micro-lensing 微引力透镜效应great attractor 巨引源Great Dark Spot 大暗斑Great White Spot 大白斑grism 棱栅GRO, Gamma-Ray Observatory γ射线天文台guidscope 导星镜GW Virginis star 室女GW 型星habitable planet 可居住行星Hakucho 〈天鹅〉X 射线天文卫星Hale Telescope 海尔望远镜halo dwarf 晕族矮星halo globular cluster 晕族球状星团Hanle effect 汉勒效应hard X-ray source 硬X 射线源Hay spot 哈伊斑HEAO, High-Energy Astronomical 〈HEAO〉高能天文台Observatoryheavy-element star 重元素星heiligenschein 灵光Helene 土卫十二helicity 螺度heliocentric radial velocity 日心视向速度heliomagnetosphere 日球磁层helioseismology 日震学helium abundance 氦丰度helium main-sequence 氦主序helium-strong star 强氦线星helium white dwarf 氦白矮星Helix galaxy （NGC 2685 ）螺旋星系Herbig Ae star 赫比格Ae 型星Herbig Be star 赫比格Be 型星Herbig-Haro flow 赫比格-阿罗流Herbig-Haro shock wave 赫比格-阿罗激波hidden magnetic flux 隐磁流high-field pulsar 强磁场脉冲星highly polarized quasar （HPQ ）高偏振类星体high-mass X-ray binary 大质量X 射线双星high-metallicity cluster 高金属度星团;高金属度星系团high-resolution spectrograph 高分辨摄谱仪high-resolution spectroscopy 高分辨分光high - z 大红移Hinotori 〈火鸟〉太阳探测器Hipparcos, High Precision Parallax 〈依巴谷〉卫星Collecting SatelliteHipparcos and Tycho Catalogues 〈依巴谷〉和〈第谷〉星表holographic grating 全息光栅Hooker Telescope 胡克望远镜host galaxy 寄主星系hot R Coronae Borealis star 高温北冕R 型星HST, Hubble Space Telescope 哈勃空间望远镜Hubble age 哈勃年龄Hubble distance 哈勃距离Hubble parameter 哈勃参数Hubble velocity 哈勃速度hump cepheid 驼峰造父变星Hyad 毕团星hybrid-chromosphere star 混合色球星hybrid star 混合大气星hydrogen-deficient star 缺氢星hydrogenous atmosphere 氢型大气hypergiant 特超巨星Ida 艾达（小行星243号）IEH, International Extreme Ultraviolet 〈IEH〉国际极紫外飞行器HitchhikerIERS, International Earth Rotation 国际地球自转服务Serviceimage deconvolution 图象消旋image degradation 星象劣化image dissector 析象管image distoration 星象复原image photon counting system 成象光子计数系统image sharpening 星象增锐image spread 星象扩散度imaging polarimetry 成象偏振测量imaging spectrophotometry 成象分光光度测量immersed echelle 浸渍阶梯光栅impulsive solar flare 脉冲太阳耀斑infralateral arc 外侧晕弧infrared CCD 红外CCDinfrared corona 红外冕infrared helioseismology 红外日震学infrared index 红外infrared observatory 红外天文台infrared spectroscopy 红外分光initial earth 初始地球initial mass distribution 初始质量分布initial planet 初始行星initial star 初始恒星initial sun 初始太阳inner coma 内彗发inner halo cluster 内晕族星团integrability 可积性Integral Sign galaxy （UGC 3697 ）积分号星系integrated diode array （IDA ）集成二极管阵intensified CCD 增强CCDIntercosmos 〈国际宇宙〉天文卫星interline transfer 行间转移intermediate parent body 中间母体intermediate polar 中介偏振星international atomic time 国际原子时International Celestial Reference 国际天球参考系Frame （ICRF ）intraday variation 快速变化intranetwork element 网内元intrinsic dispersion 内廪弥散度ion spot 离子斑IPCS, Image Photon Counting System 图象光子计数器IRIS, Infrared Imager / Spectrograph 红外成象器/摄谱仪IRPS, Infrared Photometer / Spectro- 红外光度计/分光计meterirregular cluster 不规则星团; 不规则星系团IRTF, NASA Infrared Telescope 〈IRTF〉美国宇航局红外Facility 望远镜IRTS, Infrared Telescope in Space 〈IRTS〉空间红外望远镜ISO, Infrared Space Observatory 〈ISO〉红外空间天文台isochrone method 等龄线法IUE, International Ultraviolet 〈IUE〉国际紫外探测器ExplorerJewel Box （NGC 4755 ）宝盒星团Jovian magnetosphere 木星磁层Jovian ring 木星环Jovian ringlet 木星细环Jovian seismology 木震学jovicentric orbit 木心轨道J-type star J 型星Juliet 天卫十一Jupiter-crossing asteroid 越木小行星Kalman filter 卡尔曼滤波器KAO, Kuiper Air-borne Observatory 〈柯伊伯〉机载望远镜Keck ⅠTelescope 凯克Ⅰ望远镜Keck ⅡTelescope 凯克Ⅱ望远镜Kuiper belt 柯伊伯带Kuiper-belt object 柯伊伯带天体Kuiper disk 柯伊伯盘LAMOST, Large Multi-Object Fibre 大型多天体分光望远镜Spectroscopic TelescopeLaplacian plane 拉普拉斯平面late cluster 晚型星系团LBT, Large Binocular Telescope 〈LBT〉大型双筒望远镜lead oxide vidicon 氧化铅光导摄象管Leo Triplet 狮子三重星系LEST, Large Earth-based Solar 〈LEST〉大型地基太阳望远镜Telescopelevel-Ⅰcivilization Ⅰ级文明level-Ⅱcivilization Ⅱ级文明level-Ⅲcivilization Ⅲ级文明Leverrier ring 勒威耶环Liapunov characteristic number 李雅普诺夫特征数（LCN ）light crown 轻冕玻璃light echo 回光light-gathering aperture 聚光孔径light pollution 光污染light sensation 光感line image sensor 线成象敏感器line locking 线锁line-ratio method 谱线比法Liner, low ionization nuclear 低电离核区emission-line regionline spread function 线扩散函数LMT, Large Millimeter Telescope 〈LMT〉大型毫米波望远镜local galaxy 局域星系local inertial frame 局域惯性架local inertial system 局域惯性系local object 局域天体local star 局域恒星look-up table （LUT ）对照表low-mass X-ray binary 小质量X 射线双星low-metallicity cluster 低金属度星团;低金属度星系团low-resolution spectrograph 低分辨摄谱仪low-resolution spectroscopy 低分辨分光low - z 小红移luminosity mass 光度质量luminosity segregation 光度层化luminous blue variable 高光度蓝变星lunar atmosphere 月球大气lunar chiaroscuro 月相图Lunar Prospector 〈月球勘探者〉Ly-α forest 莱曼-α 森林MACHO （massive compact halo 晕族大质量致密天体object ）Magellan 〈麦哲伦〉金星探测器Magellan Telescope 〈麦哲伦〉望远镜magnetic canopy 磁蓬magnetic cataclysmic variable 磁激变变星magnetic curve 磁变曲线magnetic obliquity 磁夹角magnetic period 磁变周期magnetic phase 磁变相位magnitude range 星等范围main asteroid belt 主小行星带main-belt asteroid 主带小行星main resonance 主共振main-sequence band 主序带Mars-crossing asteroid 越火小行星Mars Pathfinder 火星探路者mass loss rate 质量损失率mass segregation 质量层化Mayall Telescope 梅奥尔望远镜Mclntosh classification 麦金托什分类McMullan camera 麦克马伦电子照相机mean motion resonance 平均运动共振membership of cluster of galaxies 星系团成员membership of star cluster 星团成员merge 并合merger 并合星系; 并合恒星merging galaxy 并合星系merging star 并合恒星mesogranulation 中米粒组织mesogranule 中米粒metallicity 金属度metallicity gradient 金属度梯度metal-poor cluster 贫金属星团metal-rich cluster 富金属星团MGS, Mars Global Surveyor 火星环球勘测者micro-arcsec astrometry 微角秒天体测量microchannel electron multiplier 微通道电子倍增管microflare 微耀斑microgravitational lens 微引力透镜microgravitational lensing 微引力透镜效应microturbulent velocity 微湍速度millimeter-wave astronomy 毫米波天文millisecond pulsar 毫秒脉冲星minimum mass 质量下限minimum variance 最小方差mixed-polarity magnetic field 极性混合磁场MMT, Multiple-Mirror Telescope 多镜面望远镜moderate-resolution spectrograph 中分辨摄谱仪moderate-resolution spectroscopy 中分辨分光modified isochrone method 改进等龄线法molecular outflow 外向分子流molecular shock 分子激波monolithic-mirror telescope 单镜面望远镜moom 行星环卫星moon-crossing asteroid 越月小行星morphological astronomy 形态天文morphology segregation 形态层化MSSSO, Mount Stromlo and Siding 斯特朗洛山和赛丁泉天文台Spring Observatorymultichannel astrometric photometer 多通道天测光度计（MAP ）multi-object spectroscopy 多天体分光multiple-arc method 复弧法multiple redshift 多重红移multiple system 多重星系multi-wavelength astronomy 多波段天文multi-wavelength astrophysics 多波段天体物。
黑洞的准正模式(quasinormal modes)
Quasi-Normal Modes of Stars and Black HolesKostas D.KokkotasDepartment of Physics,Aristotle University of Thessaloniki,Thessaloniki54006,Greece.kokkotas@astro.auth.grhttp://www.astro.auth.gr/˜kokkotasandBernd G.SchmidtMax Planck Institute for Gravitational Physics,Albert Einstein Institute,D-14476Golm,Germany.bernd@aei-potsdam.mpg.dePublished16September1999/Articles/Volume2/1999-2kokkotasLiving Reviews in RelativityPublished by the Max Planck Institute for Gravitational PhysicsAlbert Einstein Institute,GermanyAbstractPerturbations of stars and black holes have been one of the main topics of relativistic astrophysics for the last few decades.They are of partic-ular importance today,because of their relevance to gravitational waveastronomy.In this review we present the theory of quasi-normal modes ofcompact objects from both the mathematical and astrophysical points ofview.The discussion includes perturbations of black holes(Schwarzschild,Reissner-Nordstr¨o m,Kerr and Kerr-Newman)and relativistic stars(non-rotating and slowly-rotating).The properties of the various families ofquasi-normal modes are described,and numerical techniques for calculat-ing quasi-normal modes reviewed.The successes,as well as the limits,of perturbation theory are presented,and its role in the emerging era ofnumerical relativity and supercomputers is discussed.c 1999Max-Planck-Gesellschaft and the authors.Further information on copyright is given at /Info/Copyright/.For permission to reproduce the article please contact livrev@aei-potsdam.mpg.de.Article AmendmentsOn author request a Living Reviews article can be amended to include errata and small additions to ensure that the most accurate and up-to-date infor-mation possible is provided.For detailed documentation of amendments, please go to the article’s online version at/Articles/Volume2/1999-2kokkotas/. Owing to the fact that a Living Reviews article can evolve over time,we recommend to cite the article as follows:Kokkotas,K.D.,and Schmidt,B.G.,“Quasi-Normal Modes of Stars and Black Holes”,Living Rev.Relativity,2,(1999),2.[Online Article]:cited on<date>, /Articles/Volume2/1999-2kokkotas/. The date in’cited on<date>’then uniquely identifies the version of the article you are referring to.3Quasi-Normal Modes of Stars and Black HolesContents1Introduction4 2Normal Modes–Quasi-Normal Modes–Resonances7 3Quasi-Normal Modes of Black Holes123.1Schwarzschild Black Holes (12)3.2Kerr Black Holes (17)3.3Stability and Completeness of Quasi-Normal Modes (20)4Quasi-Normal Modes of Relativistic Stars234.1Stellar Pulsations:The Theoretical Minimum (23)4.2Mode Analysis (26)4.2.1Families of Fluid Modes (26)4.2.2Families of Spacetime or w-Modes (30)4.3Stability (31)5Excitation and Detection of QNMs325.1Studies of Black Hole QNM Excitation (33)5.2Studies of Stellar QNM Excitation (34)5.3Detection of the QNM Ringing (37)5.4Parameter Estimation (39)6Numerical Techniques426.1Black Holes (42)6.1.1Evolving the Time Dependent Wave Equation (42)6.1.2Integration of the Time Independent Wave Equation (43)6.1.3WKB Methods (44)6.1.4The Method of Continued Fractions (44)6.2Relativistic Stars (45)7Where Are We Going?487.1Synergism Between Perturbation Theory and Numerical Relativity487.2Second Order Perturbations (48)7.3Mode Calculations (49)7.4The Detectors (49)8Acknowledgments50 9Appendix:Schr¨o dinger Equation Versus Wave Equation51Living Reviews in Relativity(1999-2)K.D.Kokkotas and B.G.Schmidt41IntroductionHelioseismology and asteroseismology are well known terms in classical astro-physics.From the beginning of the century the variability of Cepheids has been used for the accurate measurement of cosmic distances,while the variability of a number of stellar objects(RR Lyrae,Mira)has been associated with stel-lar oscillations.Observations of solar oscillations(with thousands of nonradial modes)have also revealed a wealth of information about the internal structure of the Sun[204].Practically every stellar object oscillates radially or nonradi-ally,and although there is great difficulty in observing such oscillations there are already results for various types of stars(O,B,...).All these types of pulsations of normal main sequence stars can be studied via Newtonian theory and they are of no importance for the forthcoming era of gravitational wave astronomy.The gravitational waves emitted by these stars are extremely weak and have very low frequencies(cf.for a discussion of the sun[70],and an im-portant new measurement of the sun’s quadrupole moment and its application in the measurement of the anomalous precession of Mercury’s perihelion[163]). This is not the case when we consider very compact stellar objects i.e.neutron stars and black holes.Their oscillations,produced mainly during the formation phase,can be strong enough to be detected by the gravitational wave detectors (LIGO,VIRGO,GEO600,SPHERE)which are under construction.In the framework of general relativity(GR)quasi-normal modes(QNM) arise,as perturbations(electromagnetic or gravitational)of stellar or black hole spacetimes.Due to the emission of gravitational waves there are no normal mode oscillations but instead the frequencies become“quasi-normal”(complex), with the real part representing the actual frequency of the oscillation and the imaginary part representing the damping.In this review we shall discuss the oscillations of neutron stars and black holes.The natural way to study these oscillations is by considering the linearized Einstein equations.Nevertheless,there has been recent work on nonlinear black hole perturbations[101,102,103,104,100]while,as yet nothing is known for nonlinear stellar oscillations in general relativity.The study of black hole perturbations was initiated by the pioneering work of Regge and Wheeler[173]in the late50s and was continued by Zerilli[212]. The perturbations of relativistic stars in GR werefirst studied in the late60s by Kip Thorne and his collaborators[202,198,199,200].The initial aim of Regge and Wheeler was to study the stability of a black hole to small perturbations and they did not try to connect these perturbations to astrophysics.In con-trast,for the case of relativistic stars,Thorne’s aim was to extend the known properties of Newtonian oscillation theory to general relativity,and to estimate the frequencies and the energy radiated as gravitational waves.QNMs werefirst pointed out by Vishveshwara[207]in calculations of the scattering of gravitational waves by a Schwarzschild black hole,while Press[164] coined the term quasi-normal frequencies.QNM oscillations have been found in perturbation calculations of particles falling into Schwarzschild[73]and Kerr black holes[76,80]and in the collapse of a star to form a black hole[66,67,68]. Living Reviews in Relativity(1999-2)5Quasi-Normal Modes of Stars and Black Holes Numerical investigations of the fully nonlinear equations of general relativity have provided results which agree with the results of perturbation calculations;in particular numerical studies of the head-on collision of two black holes [30,29](cf.Figure 1)and gravitational collapse to a Kerr hole [191].Recently,Price,Pullin and collaborators [170,31,101,28]have pushed forward the agreement between full nonlinear numerical results and results from perturbation theory for the collision of two black holes.This proves the power of the perturbation approach even in highly nonlinear problems while at the same time indicating its limits.In the concluding remarks of their pioneering paper on nonradial oscillations of neutron stars Thorne and Campollataro [202]described it as “just a modest introduction to a story which promises to be long,complicated and fascinating ”.The story has undoubtedly proved to be intriguing,and many authors have contributed to our present understanding of the pulsations of both black holes and neutron stars.Thirty years after these prophetic words by Thorne and Campollataro hundreds of papers have been written in an attempt to understand the stability,the characteristic frequencies and the mechanisms of excitation of these oscillations.Their relevance to the emission of gravitational waves was always the basic underlying reason of each study.An account of all this work will be attempted in the next sections hoping that the interested reader will find this review useful both as a guide to the literature and as an inspiration for future work on the open problems of the field.020406080100Time (M ADM )-0.3-0.2-0.10.00.10.20.3(l =2) Z e r i l l i F u n c t i o n Numerical solutionQNM fit Figure 1:QNM ringing after the head-on collision of two unequal mass black holes [29].The continuous line corresponds to the full nonlinear numerical calculation while the dotted line is a fit to the fundamental and first overtone QNM.In the next section we attempt to give a mathematical definition of QNMs.Living Reviews in Relativity (1999-2)K.D.Kokkotas and B.G.Schmidt6 The third and fourth section will be devoted to the study of the black hole and stellar QNMs.In thefifth section we discuss the excitation and observation of QNMs andfinally in the sixth section we will mention the more significant numerical techniques used in the study of QNMs.Living Reviews in Relativity(1999-2)7Quasi-Normal Modes of Stars and Black Holes 2Normal Modes–Quasi-Normal Modes–Res-onancesBefore discussing quasi-normal modes it is useful to remember what normal modes are!Compact classical linear oscillating systems such asfinite strings,mem-branes,or cavitiesfilled with electromagnetic radiation have preferred time harmonic states of motion(ωis real):χn(t,x)=e iωn tχn(x),n=1,2,3...,(1) if dissipation is neglected.(We assumeχto be some complex valuedfield.) There is generally an infinite collection of such periodic solutions,and the“gen-eral solution”can be expressed as a superposition,χ(t,x)=∞n=1a n e iωn tχn(x),(2)of such normal modes.The simplest example is a string of length L which isfixed at its ends.All such systems can be described by systems of partial differential equations of the type(χmay be a vector)∂χ∂t=Aχ,(3)where A is a linear operator acting only on the spatial variables.Because of thefiniteness of the system the time evolution is only determined if some boundary conditions are prescribed.The search for solutions periodic in time leads to a boundary value problem in the spatial variables.In simple cases it is of the Sturm-Liouville type.The treatment of such boundary value problems for differential equations played an important role in the development of Hilbert space techniques.A Hilbert space is chosen such that the differential operator becomes sym-metric.Due to the boundary conditions dictated by the physical problem,A becomes a self-adjoint operator on the appropriate Hilbert space and has a pure point spectrum.The eigenfunctions and eigenvalues determine the periodic solutions(1).The definition of self-adjointness is rather subtle from a physicist’s point of view since fairly complicated“domain issues”play an essential role.(See[43] where a mathematical exposition for physicists is given.)The wave equation modeling thefinite string has solutions of various degrees of differentiability. To describe all“realistic situations”,clearly C∞functions should be sufficient. Sometimes it may,however,also be convenient to consider more general solu-tions.From the mathematical point of view the collection of all smooth functions is not a natural setting to study the wave equation because sequences of solutionsLiving Reviews in Relativity(1999-2)K.D.Kokkotas and B.G.Schmidt8 exist which converge to non-smooth solutions.To establish such powerful state-ments like(2)one has to study the equation on certain subsets of the Hilbert space of square integrable functions.For“nice”equations it usually happens that the eigenfunctions are in fact analytic.They can then be used to gen-erate,for example,all smooth solutions by a pointwise converging series(2). The key point is that we need some mathematical sophistication to obtain the “completeness property”of the eigenfunctions.This picture of“normal modes”changes when we consider“open systems”which can lose energy to infinity.The simplest case are waves on an infinite string.The general solution of this problem isχ(t,x)=A(t−x)+B(t+x)(4) with“arbitrary”functions A and B.Which solutions should we study?Since we have all solutions,this is not a serious question.In more general cases, however,in which the general solution is not known,we have to select a certain class of solutions which we consider as relevant for the physical problem.Let us consider for the following discussion,as an example,a wave equation with a potential on the real line,∂2∂t2χ+ −∂2∂x2+V(x)χ=0.(5)Cauchy dataχ(0,x),∂tχ(0,x)which have two derivatives determine a unique twice differentiable solution.No boundary condition is needed at infinity to determine the time evolution of the data!This can be established by fairly simple PDE theory[116].There exist solutions for which the support of thefields are spatially compact, or–the other extreme–solutions with infinite total energy for which thefields grow at spatial infinity in a quite arbitrary way!From the point of view of physics smooth solutions with spatially compact support should be the relevant class–who cares what happens near infinity! Again it turns out that mathematically it is more convenient to study all solu-tions offinite total energy.Then the relevant operator is again self-adjoint,but now its spectrum is purely“continuous”.There are no eigenfunctions which are square integrable.Only“improper eigenfunctions”like plane waves exist.This expresses the fact that wefind a solution of the form(1)for any realωand by forming appropriate superpositions one can construct solutions which are “almost eigenfunctions”.(In the case V(x)≡0these are wave packets formed from plane waves.)These solutions are the analogs of normal modes for infinite systems.Let us now turn to the discussion of“quasi-normal modes”which are concep-tually different to normal modes.To define quasi-normal modes let us consider the wave equation(5)for potentials with V≥0which vanish for|x|>x0.Then in this case all solutions determined by data of compact support are bounded: |χ(t,x)|<C.We can use Laplace transformation techniques to represent such Living Reviews in Relativity(1999-2)9Quasi-Normal Modes of Stars and Black Holes solutions.The Laplace transformˆχ(s,x)(s>0real)of a solutionχ(t,x)isˆχ(s,x)= ∞0e−stχ(t,x)dt,(6) and satisfies the ordinary differential equations2ˆχ−ˆχ +Vˆχ=+sχ(0,x)+∂tχ(0,x),(7) wheres2ˆχ−ˆχ +Vˆχ=0(8) is the homogeneous equation.The boundedness ofχimplies thatˆχis analytic for positive,real s,and has an analytic continuation onto the complex half plane Re(s)>0.Which solutionˆχof this inhomogeneous equation gives the unique solution in spacetime determined by the data?There is no arbitrariness;only one of the Green functions for the inhomogeneous equation is correct!All Green functions can be constructed by the following well known method. Choose any two linearly independent solutions of the homogeneous equation f−(s,x)and f+(s,x),and defineG(s,x,x )=1W(s)f−(s,x )f+(s,x)(x <x),f−(s,x)f+(s,x )(x >x),(9)where W(s)is the Wronskian of f−and f+.If we denote the inhomogeneity of(7)by j,a solution of(7)isˆχ(s,x)= ∞−∞G(s,x,x )j(s,x )dx .(10) We still have to select a unique pair of solutions f−,f+.Here the information that the solution in spacetime is bounded can be used.The definition of the Laplace transform implies thatˆχis bounded as a function of x.Because the potential V vanishes for|x|>x0,the solutions of the homogeneous equation(8) for|x|>x0aref=e±sx.(11) The following pair of solutionsf+=e−sx for x>x0,f−=e+sx for x<−x0,(12) which is linearly independent for Re(s)>0,gives the unique Green function which defines a bounded solution for j of compact support.Note that for Re(s)>0the solution f+is exponentially decaying for large x and f−is expo-nentially decaying for small x.For small x however,f+will be a linear com-bination a(s)e−sx+b(s)e sx which will in general grow exponentially.Similar behavior is found for f−.Living Reviews in Relativity(1999-2)K.D.Kokkotas and B.G.Schmidt 10Quasi-Normal mode frequencies s n can be defined as those complex numbers for whichf +(s n ,x )=c (s n )f −(s n ,x ),(13)that is the two functions become linearly dependent,the Wronskian vanishes and the Green function is singular!The corresponding solutions f +(s n ,x )are called quasi eigenfunctions.Are there such numbers s n ?From the boundedness of the solution in space-time we know that the unique Green function must exist for Re (s )>0.Hence f +,f −are linearly independent for those values of s .However,as solutions f +,f −of the homogeneous equation (8)they have a unique continuation to the complex s plane.In [35]it is shown that for positive potentials with compact support there is always a countable number of zeros of the Wronskian with Re (s )<0.What is the mathematical and physical significance of the quasi-normal fre-quencies s n and the corresponding quasi-normal functions f +?First of all we should note that because of Re (s )<0the function f +grows exponentially for small and large x !The corresponding spacetime solution e s n t f +(s n ,x )is therefore not a physically relevant solution,unlike the normal modes.If one studies the inverse Laplace transformation and expresses χas a com-plex line integral (a >0),χ(t,x )=12πi +∞−∞e (a +is )t ˆχ(a +is,x )ds,(14)one can deform the path of the complex integration and show that the late time behavior of solutions can be approximated in finite parts of the space by a finite sum of the form χ(t,x )∼N n =1a n e (αn +iβn )t f +(s n ,x ).(15)Here we assume that Re (s n +1)<Re (s n )<0,s n =αn +iβn .The approxi-mation ∼means that if we choose x 0,x 1, and t 0then there exists a constant C (t 0,x 0,x 1, )such that χ(t,x )−N n =1a n e (αn +iβn )t f +(s n ,x ) ≤Ce (−|αN +1|+ )t (16)holds for t >t 0,x 0<x <x 1, >0with C (t 0,x 0,x 1, )independent of t .The constants a n depend only on the data [35]!This implies in particular that all solutions defined by data of compact support decay exponentially in time on spatially bounded regions.The generic leading order decay is determined by the quasi-normal mode frequency with the largest real part s 1,i.e.slowest damping.On finite intervals and for late times the solution is approximated by a finite sum of quasi eigenfunctions (15).It is presently unclear whether one can strengthen (16)to a statement like (2),a pointwise expansion of the late time solution in terms of quasi-normal Living Reviews in Relativity (1999-2)11Quasi-Normal Modes of Stars and Black Holes modes.For one particular potential(P¨o schl-Teller)this has been shown by Beyer[42].Let us now consider the case where the potential is positive for all x,but decays near infinity as happens for example for the wave equation on the static Schwarzschild spacetime.Data of compact support determine again solutions which are bounded[117].Hence we can proceed as before.Thefirst new point concerns the definitions of f±.It can be shown that the homogeneous equation(8)has for each real positive s a unique solution f+(s,x)such that lim x→∞(e sx f+(s,x))=1holds and correspondingly for f−.These functions are uniquely determined,define the correct Green function and have analytic continuations onto the complex half plane Re(s)>0.It is however quite complicated to get a good representation of these func-tions.If the point at infinity is not a regular singular point,we do not even get converging series expansions for f±.(This is particularly serious for values of s with negative real part because we expect exponential growth in x).The next new feature is that the analyticity properties of f±in the complex s plane depend on the decay of the potential.To obtain information about analytic continuation,even use of analyticity properties of the potential in x is made!Branch cuts may occur.Nevertheless in a lot of cases an infinite number of quasi-normal mode frequencies exists.The fact that the potential never vanishes may,however,destroy the expo-nential decay in time of the solutions and therefore the essential properties of the quasi-normal modes.This probably happens if the potential decays slower than exponentially.There is,however,the following way out:Suppose you want to study a solution determined by data of compact support from t=0to some largefinite time t=T.Up to this time the solution is–because of domain of dependence properties–completely independent of the potential for sufficiently large x.Hence we may see an exponential decay of the form(15)in a time range t1<t<T.This is the behavior seen in numerical calculations.The situation is similar in the case ofα-decay in quantum mechanics.A comparison of quasi-normal modes of wave equations and resonances in quantum theory can be found in the appendix,see section9.Living Reviews in Relativity(1999-2)K.D.Kokkotas and B.G.Schmidt123Quasi-Normal Modes of Black HolesOne of the most interesting aspects of gravitational wave detection will be the connection with the existence of black holes[201].Although there are presently several indirect ways of identifying black holes in the universe,gravitational waves emitted by an oscillating black hole will carry a uniquefingerprint which would lead to the direct identification of their existence.As we mentioned earlier,gravitational radiation from black hole oscillations exhibits certain characteristic frequencies which are independent of the pro-cesses giving rise to these oscillations.These“quasi-normal”frequencies are directly connected to the parameters of the black hole(mass,charge and angu-lar momentum)and for stellar mass black holes are expected to be inside the bandwidth of the constructed gravitational wave detectors.The perturbations of a Schwarzschild black hole reduce to a simple wave equation which has been studied extensively.The wave equation for the case of a Reissner-Nordstr¨o m black hole is more or less similar to the Schwarzschild case,but for Kerr one has to solve a system of coupled wave equations(one for the radial part and one for the angular part).For this reason the Kerr case has been studied less thoroughly.Finally,in the case of Kerr-Newman black holes we face the problem that the perturbations cannot be separated in their angular and radial parts and thus apart from special cases[124]the problem has not been studied at all.3.1Schwarzschild Black HolesThe study of perturbations of Schwarzschild black holes assumes a small per-turbation hµνon a static spherically symmetric background metricds2=g0µνdxµdxν=−e v(r)dt2+eλ(r)dr2+r2 dθ2+sin2θdφ2 ,(17) with the perturbed metric having the formgµν=g0µν+hµν,(18) which leads to a variation of the Einstein equations i.e.δGµν=4πδTµν.(19) By assuming a decomposition into tensor spherical harmonics for each hµνof the formχ(t,r,θ,φ)= mχ m(r,t)r Y m(θ,φ),(20)the perturbation problem is reduced to a single wave equation,for the func-tionχ m(r,t)(which is a combination of the various components of hµν).It should be pointed out that equation(20)is an expansion for scalar quantities only.From the10independent components of the hµνonly h tt,h tr,and h rr transform as scalars under rotations.The h tθ,h tφ,h rθ,and h rφtransform asLiving Reviews in Relativity(1999-2)13Quasi-Normal Modes of Stars and Black Holes components of two-vectors under rotations and can be expanded in a series of vector spherical harmonics while the components hθθ,hθφ,and hφφtransform as components of a2×2tensor and can be expanded in a series of tensor spher-ical harmonics(see[202,212,152]for details).There are two classes of vector spherical harmonics(polar and axial)which are build out of combinations of the Levi-Civita volume form and the gradient operator acting on the scalar spherical harmonics.The difference between the two families is their parity. Under the parity operatorπa spherical harmonic with index transforms as (−1) ,the polar class of perturbations transform under parity in the same way, as(−1) ,and the axial perturbations as(−1) +11.Finally,since we are dealing with spherically symmetric spacetimes the solution will be independent of m, thus this subscript can be omitted.The radial component of a perturbation outside the event horizon satisfies the following wave equation,∂2∂t χ + −∂2∂r∗+V (r)χ =0,(21)where r∗is the“tortoise”radial coordinate defined byr∗=r+2M log(r/2M−1),(22) and M is the mass of the black hole.For“axial”perturbationsV (r)= 1−2M r ( +1)r+2σMr(23)is the effective potential or(as it is known in the literature)Regge-Wheeler potential[173],which is a single potential barrier with a peak around r=3M, which is the location of the unstable photon orbit.The form(23)is true even if we consider scalar or electromagnetic testfields as perturbations.The parameter σtakes the values1for scalar perturbations,0for electromagnetic perturbations, and−3for gravitational perturbations and can be expressed asσ=1−s2,where s=0,1,2is the spin of the perturbingfield.For“polar”perturbations the effective potential was derived by Zerilli[212]and has the form V (r)= 1−2M r 2n2(n+1)r3+6n2Mr2+18nM2r+18M3r3(nr+3M)2,(24)1In the literature the polar perturbations are also called even-parity because they are characterized by their behavior under parity operations as discussed earlier,and in the same way the axial perturbations are called odd-parity.We will stick to the polar/axial terminology since there is a confusion with the definition of the parity operation,the reason is that to most people,the words“even”and“odd”imply that a mode transforms underπas(−1)2n or(−1)2n+1respectively(for n some integer).However only the polar modes with even have even parity and only axial modes with even have odd parity.If is odd,then polar modes have odd parity and axial modes have even parity.Another terminology is to call the polar perturbations spheroidal and the axial ones toroidal.This definition is coming from the study of stellar pulsations in Newtonian theory and represents the type offluid motions that each type of perturbation induces.Since we are dealing both with stars and black holes we will stick to the polar/axial terminology.Living Reviews in Relativity(1999-2)K.D.Kokkotas and B.G.Schmidt14where2n=( −1)( +2).(25) Chandrasekhar[54]has shown that one can transform the equation(21)for “axial”modes to the corresponding one for“polar”modes via a transforma-tion involving differential operations.It can also be shown that both forms are connected to the Bardeen-Press[38]perturbation equation derived via the Newman-Penrose formalism.The potential V (r∗)decays exponentially near the horizon,r∗→−∞,and as r−2∗for r∗→+∞.From the form of equation(21)it is evident that the study of black hole perturbations will follow the footsteps of the theory outlined in section2.Kay and Wald[117]have shown that solutions with data of compact sup-port are bounded.Hence we know that the time independent Green function G(s,r∗,r ∗)is analytic for Re(s)>0.The essential difficulty is now to obtain the solutions f±(cf.equation(10))of the equations2ˆχ−ˆχ +Vˆχ=0,(26) (prime denotes differentiation with respect to r∗)which satisfy for real,positives:f+∼e−sr∗for r∗→∞,f−∼e+r∗x for r∗→−∞.(27) To determine the quasi-normal modes we need the analytic continuations of these functions.As the horizon(r∗→∞)is a regular singular point of(26),a representation of f−(r∗,s)as a converging series exists.For M=12it reads:f−(r,s)=(r−1)s∞n=0a n(s)(r−1)n.(28)The series converges for all complex s and|r−1|<1[162].(The analytic extension of f−is investigated in[115].)The result is that f−has an extension to the complex s plane with poles only at negative real integers.The representation of f+is more complicated:Because infinity is a singular point no power series expansion like(28)exists.A representation coming from the iteration of the defining integral equation is given by Jensen and Candelas[115],see also[159]. It turns out that the continuation of f+has a branch cut Re(s)≤0due to the decay r−2for large r[115].The most extensive mathematical investigation of quasi-normal modes of the Schwarzschild solution is contained in the paper by Bachelot and Motet-Bachelot[35].Here the existence of an infinite number of quasi-normal modes is demonstrated.Truncating the potential(23)to make it of compact support leads to the estimate(16).The decay of solutions in time is not exponential because of the weak decay of the potential for large r.At late times,the quasi-normal oscillations are swamped by the radiative tail[166,167].This tail radiation is of interest in its Living Reviews in Relativity(1999-2)。
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arXiv:astro-ph/0303417v1 18 Mar 2003CarnegieObservatoriesAstrophysicsSeries,Vol.3:ClustersofGalaxies:ProbesofCosmologicalStructureandGalaxyEvolutioned.J.S.Mulchaey,A.Dressler,andA.Oemler(Pasadena;CarnegieObservatories:http://www.ociw.edu/ociw/symposia/series/symposium3/proceedings.html)
AbstractWepresentfirstresultsfromourprojecttoexaminetheinternalkinematicsofdiskgalaxiesin7richclusterswith0.3≤z<0.6.SpatiallyresolvedMOSspectrahavebeenobtainedwithFORSattheVLT.WeconcentratehereontheclustersMS1008.1–1224atz=0.30andCl0413–6559(F1557.19TC)atz=0.51.Outof22clustermembers,12galaxiesexhibitarotationcurveoftheuniversalformrisingintheinnerregionandpassingoverintoaflatpart.Theothermembershaveintrinsicallypeculiarkinematics.The12clustergalaxiesforwhichamaximumrotationvelocitycouldbederivedaredistributedintheTully–FisherdiagramverysimilartofieldgalaxiesfromtheFORSDeepFieldwithcorrespondingredshifts.Thesameistruefor6galaxiesobservedintheclusterfieldsthatturnedoutnottobemembers.Inparticular,theseclusterspiralsdonotshowanysignificantluminosityevolutionasmightbeexpectedfromcertainclusterspecificphenomena.Contrarytothat,theotherhalfoftheclus-tersamplewithdisturbedkinematicsalsoshowsahigherdegreeofstructuralassymetriesonaverageindicatingongoingorrecentinteractionprocesses.
1.1IntroductionGalaxiesinclustersexperiencevariousinteractions,somemechanismsofwhichcancausesubstantialdistortionsoftheinternalkinematicsofdiskgalaxiesleadingto“ro-tationcurves”thatnolongerfollowtheuniversalform(Persicetal.1996)ofspiralsinthefield.Inastudyof89galaxiesintheVirgocluster,Rubinetal.(1999),forexample,classifiedhalfoftheirsamplegalaxiesaskinematicallydisturbedrangingfrommodest(e.g.asymmetric)tosevere(e.g.truncatedcurves)peculiarities.Ontheotherhand,manyclustergalaxies,forwhichonlyvelocitywidths(incontrasttospatiallyresolvedvelocities)weremeasured,followatightTully–Fisherrelation(e.g.Giovanellietal.1997).Furthermore,itisnotyetclearwhetherthehaloofdarkmatterand,therefore,thetotalmassofagalaxycanalsobeaffectedbycertaininteractionphenomena.Innumericalsimulationsofclusterevolutionthatcanresolvesubstructureandusesemianalyticrecipestodescribethegalaxies’stellarpopulations,thedarkmatterhaloofagalaxythatfallsintotheclusterdoessurviveuntilredshiftzeroanddoesnotgetstripped(Springeletal.2001).Asignificantcontributiontoourcomprehensionoftheenvironmentaldependenceofgalaxykinematicswouldbemadebyobservationsathigherredshifts,sinceinmodelsofhierarchicallygrowingstructureclustersarestillintheprocessofformingatz≈1sothataB.Ziegleretal.higherinfallrateandmoreinteractionsareexpected(e.g.Kodama&Bower2001).Afirst(published)attemptwasmadebyMetevieretal.(2002&thisconference)with10Tully–FishergalaxiesintheclusterCL0024+1654(z=0.40)andbyMilvang–Jensenetal.(2003)with8spiralsinMS1054.4–0321(z=0.83).WhilethefirststudyseesalargerscatteroftheirsamplegalaxiesintheTFdiagramwithoutevidenceforanevolutionofthezeropoint,thesecondonefindsatrendtowardsbrighterluminosities(0.5–1Bmag)withrespecttolocalclusterspirals.Itisarguedthateithertruncationofstarformationorstarburstsmaycauseanincreasedordecreasedmass–to–lightratio,respectively.
1.2ProjectaimsandobservationsWehaveconductedacampaign(5nightswithFORS1&2attheESO–VLT)togainspectraofspiralgalaxieswithinsevendistantclustersintheredshiftrange0.3≤z<0.6.OneofourmaingoalsisthederivationofspatiallyresolvedrotationcurvesfortheanalysisoftheinternalkinematicsofthegalaxiesandtheconstructionofthedistantclusterTFR.Furthermore,weaimtodeterminethestarformationrates,structuralparametersandmorphologiestoinvestigatepossibleeffectsoftransformationmechanismslikemerging,tidalinteraction,harassment,strangulationorinteractionwiththeintra–clustermedium.Tocomplementourownground–basedimaging,HST/WFPC2imagesofthecoreregionswereretrievedfromthearchive.Here,wepresentfirstresultsbasedondataoftwooftheclusters,CL0413–65(z=0.51)andMS1008–12(z=0.30),whichwereobservedinNovember1999andMarch2000,re-spectively.WeusedtheFORS1instrumentmountedattheCassegrainfocusoftheESO–VLTwithgrism600Rprovidingaspatialscaleof0.2arcsec/pixelandadispersionof∼1.08Å/pixel.Ataslitwidthof1arcsec,thespectralresolutionwasR≈1200.Tomeetoursignal–to–noiserequirements,thetotalintegrationtimewassetto2.5hrs.Seeingconditionsrangedbetween0.7and1.3arcsecFWHM.TwoMOSsetupshavebeenobservedforeachcluster,yielding76spectraofgalaxieswithapparentmagnitudesof18.0
1.3DerivationofrotationvelocitiesRedshiftscouldbedeterminedfor62ofthegalaxies,ofwhich38havelate–typeSEDs,19areearly–type,and5peculiarorunidentified.Intotal,38objectsareclustermembers.22ofthesearespiralswithsufficientsignal–to–noiseoftheiremissionlinestoderivetheinternalkinematics.Rotationcurves(RCs)weredeterminedusingeitherthe[OII]3727,Hβor[OIII]5007emissionline(Fig.1.1givessomeexamples).Gaussianfitshavebeenappliedsteppingalongthespatialaxiswithamedianfilterwindowoftypically0.6arcsecstoenhancetheS/N.Sincetheapparentdisksizesofspiralsatintermediateredshiftsareonlyslightlylargerthantheslitwidth(1arcsec),thespectroscopycoversasubstantialfractionofthetwo–dimensionalvelocityfield.Thus,themaximumrotationvelocityvmax(theconstantrotationintheouterpartofagalaxyduetotheDarkMatterhalo)cannotbedetermined“straightforward”fromtheobservedrotation.Totacklethisproblem,wesimulatedthespectroscopyofeachgalax-ies’velocityfieldwiththerespectiveinclinationandpositionangle,alsotakingseeingandluminosityweightingintoaccount(seeZiegleretal.2001foramoredetaileddescription).ThesimulatedrotationcurveswhichbestreproducedtheobservedonesyieldedthevaluesofvmaxenteringourTFdiagram(Fig.1.2).