DOCSLIB.ORG

Hubble, Hubble's Law and the Expanding Universe

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Hubble, Hubble's Law and the Expanding Universe GENERAL ⎜ ARTICLE Hubble, Hubble’s Law and the Expanding Universe J S Bagla H ubble'snam e isassociated closelyw ith theidea of an expanding universe as he discovered the relation b etw een th e recession velocity an d th e distances of galaxies. H ubble also did a lot of pioneering w ork on the distribution of galaxies in th e u n iverse. In th is article w e take a look Jasjeet Bagla works at the Harish-Chandra Research at H ubble'slaw and discuss how itrelates w ith Institute, Allahabad. His m odels of the universe. W e also give a histori- research is mainly on calperspectiveof the discoveries that led to the cosmology and he is H ubble'slaw . interested in all areas of physics. 1 . H u b b le 's L a w Edw in P H ubbleisbestknow n for hisdiscovery ofthe relation sh ip b etw een th e d istan ce an d rad ial velocities of galaxies. A llm odels of the universe are based on thisrelationship,now know n as `Hubble'slaw '.H ubble fou n d th at th e rate at w h ich galax ies are reced ing from u s is p rop ortion al to th e d istan ce, V / r, and used ob servation s to d eterm ine th e p rop ortion ality con stant. T hisconstant isnow called the `Hubble'sconstant'in hishonour. V = H 0 r: T h is form for th e relation sh ip h as im p ortan t im p lica- tion s (see Box1). W e step back a littleand ¯llinsom e background before continuingw ith our discussion oftheH ubble'slaw . T h e early p art of th e 20th cen tu ry saw con siderab le d is- Keywords: cussion and activityfocused on understan d ing th e stru c- Keywords Cosmology, Big Bang, expan- ture of our ow n galaxy. E ventually itw as understood sion of universe. th at ou r galax y is a fairly large sy stem w ith arou n d a 216 RESONANCE ⎜ March 2009 GENERAL ⎜ ARTICLE B o x 1 . H u b b le 's L a w a n d t h e C o sm o lo g ic a l P r in c ip le The Hubble's law is written as V = H 0 r; with V as the radial component of the velocity. The reason for writing down only the radial component is that this is the only component of the motion that we can observe through the shift of spectral lines. However, it is implicit in the form of the Hubble's law that the rate of expansion is independent of direction. In other words, the expansion is isotropic around us¤ . Clearly, the Hubble's law is consistent with a vectorial relationship between velocity and distance. V = H 0 r: In this form, it is easy to see that the Hubble's law retains its form if we shift the origin: as seen from the origin, the galaxy at r 1 recedes with velocity V 1 . Ifwenowtryto rewrite the recession law in the frame of this galaxy, we get: 0 r = r ¡ r 1 ; 0 0 V = V ¡ V 1 = H 0 (r ¡ r 1 )=H 0 r : As claimed, the Hubble's law retains its form in the frame of any other galaxy as well. Thus expansion appears the same in every direction, and from every place in the universe. Unless we are observing at a special moment in the history of the universe, this also means that the universe is homogeneous and isotropic. The cosmological principle [1] elevates and encapsulates this idea, and it is noteworthy that a homogeneous and isotropic model of the universe allows us to de¯ne a cosmic time. Most models of the universe are based on this principle. ¤ Exceptions are anisotropic models [2] where galaxies recede from us at di®erent rates in di®erent directions. However observations restrict the level of deviations from isotropy and one needs to construct models carefully in order to match observational data. hundred billion stars. O ur galaxy, or the G alaxy, is nearly80;000 ligh t years across. A stron om ers u se a d if- feren t u n it, a p arsec (1 p arsec = 3:26 lightyears) and the G alaxy isaround 25 kiloparsecs across. T he G alaxy is sh ap ed like a d isk w ith stars h igh ligh ting sp iral arm s inthedisk;thereisalsoa spheroidalbulge nearthecen- 1 tre of th e G alaxy . T he disk issurrounded by a faint 1 An appam is a good descrip- h alo of stars an d glob u lar clusters; each glob u lar cluster tion of the shape of disk and is a tigh t grou p of stars an d th ese m ay con tain 10 3 ¡ 106 bulge, though not in proportion. stars each . T h e S u n is arou n d 8 k p c from th e cen tre in th e d isk. RESONANCE ⎜ March 2009 217 GENERAL ⎜ ARTICLE M any other galaxies have been know n fora long tim e. Many galaxies have Howeveritwasnotveryclearwhethertheseareapart been known for a long ofour ow n galaxy or are sim ilarsystem s located very far time. Hubble provided away. H ubbleprovided the ¯rst reliabledeterm ination the first reliable of distances to these galaxies and convincingly proved determination of th at th ese are large sy stem s of stars in th eir ow n right. distances to these galaxies and N ow w e revertto our discussion oftheH ubble'slaw . In convincingly proved th e velocity {d istan ce relation , velocities are m easu red in that these are large k m / s, d ista n c e s in m illio n s o f p a rse c s (M p c ) a n d fo r th is systems of stars in reason the H ubble'sconstant isw ritten in com plicated their own right. looking units of km /s/M pc even though ithas dim en- sions of inverse time. W e can recast the H ubble'slaw an d w rite it in term s of d irect ob servab les. W e d o th is step b y step . W e ¯ rst rew rite th e recession velocity in term s of th e red sh ift of sp ectral lines th at is d eterm ined d irectly from sp ectra. V r z = = ¡1 : c cH 0 T he speed of light is denoted by the usual sym b ol c. Herez istheD oppler redshift;note that thisde¯nition o f re d sh ift is v a lid o n ly fo r jV j=c ¿ 1. D istances are often m easu red u sing referen ce stars, or oth er ob jects th at are kn ow n to h ave a given lum inosity (see Box2). In su ch a case, th e ° u x ob served from th e referen ce ob - ject is related to th e lum inosity an d th e d istan ce. T h e en ergy em itted in u n it tim e is rad iated u n iform ly in all directionsand eventuallyspreadsoutina sphericalshell ofradius r. T he energy observed perunitarea,perunit tim e can th en b e w ritten as L S = : 4¼r2 HereS isthe observed °ux and L is th e lu m in o sity . If w e ob serve a nu m b er of ligh t sou rces th en th e red sh ifts and observed °uxes are expected to have the follow ing 218 RESONANCE ⎜ March 2009 GENERAL ⎜ ARTICLE Box2.DistanceLadder Measuring distances to other galaxies is a challenging task as there is no direct method of ascertaining the distance. There are two basic methods that are combined for measuring distances to galaxies. ² Parallax: We measure the parallax of nearby stars across Earth's orbit around the Sun. The parallax angle is 100(3:08 £ 1016m=r) ¤ . Observations from the Earth can give reliable parallax measurements of up to 0:1 00. ² Standard Candle: If there is a source with known luminosity (energy output per unit time), then the observed °ux from such a source can be used to compute the distance if the radiation from the source has not been absorbed by intervening gas and dust. Luminosity L , °ux S and distance r are related as S = L=(4¼r2 ), assuming that the source radiates uniformly in all directions. There are no standard candles where the luminosity is known apriori, therefore one needs to do a calibration. In the absence of such a calibration we can only measure relative distances and not absolute distances. Calibration is done by matching with the distance to a group of stars measured using some other method, either parallax or some other standard candle. A chain of standard candles is used and calibrated against each other, with the nearest ones calibrated using the parallax method. This sequence of distance measurement methods is often referred to as the `distance ladder'. Each step in the distance ladder involves cross-calibration and introduces errors. The H ipparcosspace mission reduced errors by a signi¯cant amount by providing accurate parallax measure- ments of up to 0:00100, increasing the number of stars with known parallax distances by a signi¯cant factor [3].
Load more

Recommended publications
  • The Reionization of Cosmic Hydrogen by the First Galaxies Abstract 1
    David Goodstein’s Cosmology Book The Reionization of Cosmic Hydrogen by the First Galaxies Abraham Loeb Department of Astronomy, Harvard University, 60 Garden St., Cambridge MA, 02138 Abstract Cosmology is by now a mature experimental science. We are privileged to live at a time when the story of genesis (how the Universe started and developed) can be critically explored by direct observations. Looking deep into the Universe through powerful telescopes, we can see images of the Universe when it was younger because of the finite time it takes light to travel to us from distant sources. Existing data sets include an image of the Universe when it was 0.4 million years old (in the form of the cosmic microwave background), as well as images of individual galaxies when the Universe was older than a billion years. But there is a serious challenge: in between these two epochs was a period when the Universe was dark, stars had not yet formed, and the cosmic microwave background no longer traced the distribution of matter. And this is precisely the most interesting period, when the primordial soup evolved into the rich zoo of objects we now see. The observers are moving ahead along several fronts. The first involves the construction of large infrared telescopes on the ground and in space, that will provide us with new photos of the first galaxies. Current plans include ground-based telescopes which are 24-42 meter in diameter, and NASA’s successor to the Hubble Space Telescope, called the James Webb Space Telescope. In addition, several observational groups around the globe are constructing radio arrays that will be capable of mapping the three-dimensional distribution of cosmic hydrogen in the infant Universe.
    [Show full text]
  • Correcting for Peculiar Velocities of Type Ia Supernovae in Clusters of Galaxies P.-F
    A&A 615, A162 (2018) Astronomy https://doi.org/10.1051/0004-6361/201832932 & © ESO 2018 Astrophysics Correcting for peculiar velocities of Type Ia supernovae in clusters of galaxies P.-F. Léget1,2, M. V. Pruzhinskaya1,3, A. Ciulli1, E. Gangler1, G. Aldering4, P. Antilogus5, C. Aragon4, S. Bailey4, C. Baltay6, K. Barbary4, S. Bongard5, K. Boone4,7, C. Buton8, M. Childress9, N. Chotard8, Y. Copin8, S. Dixon4, P. Fagrelius4,7, U. Feindt10, D. Fouchez11, P. Gris1, B. Hayden4, W. Hillebrandt12, D. A. Howell13,14, A. Kim4, M. Kowalski15,16, D. Kuesters15, S. Lombardo15, Q. Lin17, J. Nordin15, R. Pain5, E. Pecontal18, R. Pereira8, S. Perlmutter4,7, D. Rabinowitz6, M. Rigault1, K. Runge4, D. Rubin4,19, C. Saunders5, L.-P. Says1, G. Smadja8, C. Sofiatti4,7, N. Suzuki4,22, S. Taubenberger12,20, C. Tao11,17, and R. C. Thomas21 THE NEARBY SUPERNOVA FACTORY 1 Université Clermont Auvergne, CNRS/IN2P3, Laboratoire de Physique de Clermont, 63000 Clermont-Ferrand, France e-mail: [email protected] 2 Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics, Stanford University, Stanford, CA 94305, USA 3 Lomonosov Moscow State University, Sternberg Astronomical Institute, Universitetsky pr. 13, Moscow 119234, Russia 4 Physics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA 5 Laboratoire de Physique Nucléaire et des Hautes Énergies, Université Pierre et Marie Curie Paris 6, Université Paris Diderot Paris 7, CNRS-IN2P3, 4 place Jussieu, 75252 Paris Cedex 05, France 6 Department of
    [Show full text]
  • Measuring the Velocity Field from Type Ia Supernovae in an LSST-Like Sky
    Prepared for submission to JCAP Measuring the velocity field from type Ia supernovae in an LSST-like sky survey Io Odderskov,a Steen Hannestada aDepartment of Physics and Astronomy University of Aarhus, Ny Munkegade, Aarhus C, Denmark E-mail: [email protected], [email protected] Abstract. In a few years, the Large Synoptic Survey Telescope will vastly increase the number of type Ia supernovae observed in the local universe. This will allow for a precise mapping of the velocity field and, since the source of peculiar velocities is variations in the density field, cosmological parameters related to the matter distribution can subsequently be extracted from the velocity power spectrum. One way to quantify this is through the angular power spectrum of radial peculiar velocities on spheres at different redshifts. We investigate how well this observable can be measured, despite the problems caused by areas with no information. To obtain a realistic distribution of supernovae, we create mock supernova catalogs by using a semi-analytical code for galaxy formation on the merger trees extracted from N-body simulations. We measure the cosmic variance in the velocity power spectrum by repeating the procedure many times for differently located observers, and vary several aspects of the analysis, such as the observer environment, to see how this affects the measurements. Our results confirm the findings from earlier studies regarding the precision with which the angular velocity power spectrum can be determined in the near future. This level of precision has been found to imply, that the angular velocity power spectrum from type Ia supernovae is competitive in its potential to measure parameters such as σ8.
    [Show full text]
  • Peculiar Transverse Velocities of Galaxies from Quasar Microlensing
    Peculiar Transverse Velocities of Galaxies from Quasar Microlensing. Tentative Estimate of the Peculiar Velocity Dispersion at z ∼ 0:5 E. MEDIAVILLA1;2, J. JIMENEZ-VICENTE´ 3;4, J. A. MUNOZ~ 5;6, E. BATTANER3;4 ABSTRACT We propose to use the flux variability of lensed quasar images induced by gravitational microlensing to measure the transverse peculiar velocity of lens galaxies over a wide range of redshift. Microlensing variability is caused by the motions of the observer, the lens galaxy (including the motion of the stars within the galaxy), and the source; hence, its frequency is directly related to the galaxy's transverse peculiar velocity. The idea is to count time-event rates (e.g., peak or caustic crossing rates) in the observed microlensing light curves of lensed quasars that can be compared with model predictions for different values of the transverse peculiar velocity. To compensate for the large time- scale of microlensing variability we propose to count and model the number of events in an ensemble of gravitational lenses. We develop the methodology to achieve this goal and apply it to an ensemble of 17 lensed quasar systems . In spite of the shortcomings of the available data, we have obtained tentative estimates of the peculiar velocity dispersion of lens galaxies at z ∼ 0:5, σpec(0:53± p −1 0:18) ' (638 ± 213) hmi=0:3M km s . Scaling at zero redshift we derive, p −1 σpec(0) ' (491 ± 164) hmi=0:3M km s , consistent with peculiar motions of nearby galaxies and with recent N-body nonlinear reconstructions of the Local Universe based on ΛCDM.
    [Show full text]
  • The Distance to Ngc 4993: the Host Galaxy of the Gravitational-Wave Event Gw170817
    DRAFT VERSION OCTOBER 17, 2017 Typeset using LATEX twocolumn style in AASTeX61 THE DISTANCE TO NGC 4993: THE HOST GALAXY OF THE GRAVITATIONAL-WAVE EVENT GW170817 JENS HJORTH,1 ANDREW J. LEVAN,2 NIAL R. TANVIR,3 JOE D. LYMAN,2 RADOSŁAW WOJTAK,1 SOPHIE L. SCHRØDER,1 ILYA MANDEL,4 CHRISTA GALL,1 AND SOFIE H. BRUUN1 1Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark 2Department of Physics, University of Warwick, Coventry, CV4 7AL, UK 3Department of Physics and Astronomy, University of Leicester, LE1 7RH, UK 4Birmingham Institute for Gravitational Wave Astronomy and School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT, UK (Received 2017 September 29; Revised revised 2017 October 2; Accepted 2017 October 3; published 2017 October 16) ABSTRACT The historic detection of gravitational waves from a binary neutron star merger (GW170817) and its electromagnetic counter- part led to the first accurate (sub-arcsecond) localization of a gravitational-wave event. The transient was found to be ∼1000 from the nucleus of the S0 galaxy NGC 4993. We report here the luminosity distance to this galaxy using two independent methods. (1) Based on our MUSE/VLT measurement of the heliocentric redshift (zhelio = 0:009783 ± 0:000023) we infer the systemic re- cession velocity of the NGC 4993 group of galaxies in the cosmic microwave background (CMB) frame to be vCMB = 3231 ± 53 -1 -1 km s . Using constrained cosmological simulations we estimate the line-of-sight peculiar velocity to be vpec = 307±230 km s , -1 resulting in a cosmic velocity of vcosmic = 2924 ± 236 km s (zcosmic = 0:00980 ± 0:00079) and a distance of Dz = 40:4 ± 3:4 Mpc -1 -1 assuming a local Hubble constant of H0 = 73:24 ± 1:74 km s Mpc .
    [Show full text]
  • The Age of the Universe, the Hubble Constant, the Accelerated Expansion and the Hubble Effect
    The age of the universe, the Hubble constant, the accelerated expansion and the Hubble effect Domingos Soares∗ Departamento de F´ısica,ICEx, UFMG | C.P. 702 30123-970, Belo Horizonte | Brazil October 25, 2018 Abstract The idea of an accelerating universe comes almost simultaneously with the determination of Hubble's constant by one of the Hubble Space Tele- scope Key Projects. The age of the universe dilemma is probably the link between these two issues. In an appendix, I claim that \Hubble's law" might yet to be investigated for its ultimate cause, and suggest the \Hubble effect” as the searched candidate. 1 The age dilemma The age of the universe is calculated by two different ways. Firstly, a lower limit is given by the age of the presumably oldest objects in the Milky Way, e.g., globular clusters. Their ages are calculated with the aid of stellar evolu- tion models which yield 14 Gyr and 10% uncertainty. These are fairly confident figures since the basics of stellar evolution are quite solid. Secondly, a cosmo- logical age based on the Standard Cosmology Model derived from the Theory of General Relativity. The three basic models of relativistic cosmology are given by the Friedmann's solutions of Einstein's field equations. The models are char- acterized by a decelerated expansion from a spatial singularity at cosmic time t = 0, and whose magnitude is quantified by the density parameter Ω◦, the present ratio of the mass density in the universe to the so-called critical mass arXiv:0908.1864v8 [physics.gen-ph] 28 Jul 2015 density.
    [Show full text]
  • The Evolution of the IR Luminosity Function and Dust-Obscured Star Formation Over the Past 13 Billion Years
    The Astrophysical Journal, 909:165 (15pp), 2021 March 10 https://doi.org/10.3847/1538-4357/abdb27 © 2021. The American Astronomical Society. All rights reserved. The Evolution of the IR Luminosity Function and Dust-obscured Star Formation over the Past 13 Billion Years J. A. Zavala1 , C. M. Casey1 , S. M. Manning1 , M. Aravena2 , M. Bethermin3 , K. I. Caputi4,5 , D. L. Clements6 , E. da Cunha7 , P. Drew1 , S. L. Finkelstein1 , S. Fujimoto5,8 , C. Hayward9 , J. Hodge10 , J. S. Kartaltepe11 , K. Knudsen12 , A. M. Koekemoer13 , A. S. Long14 , G. E. Magdis5,8,15,16 , A. W. S. Man17 , G. Popping18 , D. Sanders19 , N. Scoville20 , K. Sheth21 , J. Staguhn22,23 , S. Toft5,8 , E. Treister24 , J. D. Vieira25 , and M. S. Yun26 1 The University of Texas at Austin, 2515 Speedway Boulevard, Stop C1400, Austin, TX 78712, USA; [email protected] 2 Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile 3 Aix Marseille Univ, CNRS, LAM, Laboratoire d’Astrophysique de Marseille, Marseille, France 4 Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700AV Groningen, The Netherlands 5 Cosmic Dawn Center (DAWN), Denmark 6 Imperial College London, Blackett Laboratory, Prince Consort Road, London, SW7 2AZ, UK 7 International Centre for Radio Astronomy Research, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia 8 Niels Bohr Institute, University of Copenhagen, Lyngbyvej 2, DK-2100 Copenhagen, Denmark 9 Center for Computational Astrophysics, Flatiron
    [Show full text]
  • AY 20 Fall 2010
    AY 20 Fall 2010 Structure & Morphology of the Milky Way Reading: Carroll & Ostlie, Chapter 24.2, 24.3 Galactic Structure cont’d: distribution of each population related to orbital characteristics thin disk <102 Myrs, thick disk 2-10 Gyrs scale heights ` 100-350 pc, 1 kpc resp. Sun in thin disk ~ 30 pc above plane number density of stars in thick disk 25 kpc radius <10% that in thin disk stars in thick disk older 100 kpc radius star formation continuing in thin disk From star counts & kinematics: 10 thin disk: mass ~ 6.5x10 Mʘ 4 kpc radius 10 LB = 1.8x 10 Lʘ 8 thick disk: LB = 2x10 Lʘ (much fainter) 9 mass ~ 2-4 x 10 Mʘ H2, cool dust: 3-8 kpc from GC HI: 3 – 25 kpc mass ~ 4 x 109 M mass ~ 109 M HI ʘ H2 ʘ neutral gas also a disk component; * scale height HI increases beyond 12 radius ~25 kpc, age < 10 Gyrs kpc radius to 900 pc 2 scale height < 100 pc*, Shape of each population depends on orbital characteristics. Note also a range of metallicities age-metallicity relation not a simple correlation! Abundance of iron (Fe) - product of type 1a SN – correlates w. star age NFe ()N star Fe log H H ()NFe indicates “metallicity” Adopt [Fe/H] = 0 for Sun NH For more metal rich stars [Fe/H] +ve; metal poorer [Fe/H] -ve Not entirely 1 to 1 correlation – iron production small and may be local [O/H] from core collapse SNs may be more accurate (occur sooner than type Ia) 3 N.B.
    [Show full text]
  • Pre-Big Bang, Space-Time Structure, Asymptotic Universe
    EPJ Web of Conferences 71, 0 0 063 (2 014 ) DOI: 10.1051/epjconf/20147100063 C Owned by the authors, published by EDP Sciences, 2014 Pre-Big Bang, space-time structure, asymptotic Universe Spinorial space-time and a new approach to Friedmann-like equations Luis Gonzalez-Mestres1,a 1Megatrend Cosmology Laboratory, Megatrend University, Belgrade and Paris Goce Delceva 8, 11070 Novi Beograd, Serbia Abstract. Planck and other recent data in Cosmology and Particle Physics can open the way to controversial analyses concerning the early Universe and its possible ultimate origin. Alternatives to standard cosmology include pre-Big Bang approaches, new space- time geometries and new ultimate constituents of matter. Basic issues related to a possible new cosmology along these lines clearly deserve further exploration. The Planck collab- oration reports an age of the Universe t close to 13.8 Gyr and a present ratio H between relative speeds and distances at cosmic scale around 67.3 km/s/Mpc. The product of these two measured quantities is then slightly below 1 (about 0.95), while it can be exactly 1 in the absence of matter and cosmological constant in patterns based on the spinorial space- time we have considered in previous papers. In this description of space-time we first suggested in 1996-97, the cosmic time t is given by the modulus of a SU(2) spinor and the Lundmark-Lemaître-Hubble (LLH) expansion law turns out to be of purely geometric origin previous to any introduction of standard matter and relativity. Such a fundamen- tal geometry, inspired by the role of half-integer spin in Particle Physics, may reflect an equilibrium between the dynamics of the ultimate constituents of matter and the deep structure of space and time.
    [Show full text]
  • The Ups and Downs of Baryon Oscillations
    The Ups and Downs of Baryon Oscillations Eric V. Linder Physics Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720 ABSTRACT Baryon acoustic oscillations, measured through the patterned distribution of galaxies or other baryon tracing objects on very large (∼> 100 Mpc) scales, offer a possible geometric probe of cosmological distances. Pluses and minuses in this approach’s leverage for understanding dark energy are discussed, as are systematic uncertainties requiring further investigation. Conclusions are that 1) BAO offer promise of a new avenue to distance measurements and further study is warranted, 2) the measurements will need to attain ∼ 1% accuracy (requiring a 10000 square degree spectroscopic survey) for their dark energy leverage to match that from supernovae, but do give complementary information at 2% accuracy. Because of the ties to the matter dominated era, BAO is not a replacement probe of dark energy, but a valuable complement. 1. Introduction This paper provides a pedagogical introduction to baryon acoustic oscillations (BAO), accessible to readers not necessarily familiar with details of large scale structure in the universe. In addition, it summarizes some of the current issues – plus and minus – with the use of BAO as a cosmological probe of the nature of dark energy. For more quantitative, arXiv:astro-ph/0507308v2 17 Jan 2006 technical discussions of these issues, see White (2005). The same year as the detection of the cosmic microwave background, the photon bath remnant from the hot, early universe, Sakharov (1965) predicted the presence of acoustic oscillations in a coupled baryonic matter distribution. In his case, baryons were coupled to cold electrons rather than hot photons; Peebles & Yu (1970) and Sunyaev & Zel’dovich (1970) pioneered the correct, hot case.
    [Show full text]
  • The High Redshift Universe: Galaxies and the Intergalactic Medium
    The High Redshift Universe: Galaxies and the Intergalactic Medium Koki Kakiichi M¨unchen2016 The High Redshift Universe: Galaxies and the Intergalactic Medium Koki Kakiichi Dissertation an der Fakult¨atf¨urPhysik der Ludwig{Maximilians{Universit¨at M¨unchen vorgelegt von Koki Kakiichi aus Komono, Mie, Japan M¨unchen, den 15 Juni 2016 Erstgutachter: Prof. Dr. Simon White Zweitgutachter: Prof. Dr. Jochen Weller Tag der m¨undlichen Pr¨ufung:Juli 2016 Contents Summary xiii 1 Extragalactic Astrophysics and Cosmology 1 1.1 Prologue . 1 1.2 Briefly Story about Reionization . 3 1.3 Foundation of Observational Cosmology . 3 1.4 Hierarchical Structure Formation . 5 1.5 Cosmological probes . 8 1.5.1 H0 measurement and the extragalactic distance scale . 8 1.5.2 Cosmic Microwave Background (CMB) . 10 1.5.3 Large-Scale Structure: galaxy surveys and Lyα forests . 11 1.6 Astrophysics of Galaxies and the IGM . 13 1.6.1 Physical processes in galaxies . 14 1.6.2 Physical processes in the IGM . 17 1.6.3 Radiation Hydrodynamics of Galaxies and the IGM . 20 1.7 Bridging theory and observations . 23 1.8 Observations of the High-Redshift Universe . 23 1.8.1 General demographics of galaxies . 23 1.8.2 Lyman-break galaxies, Lyα emitters, Lyα emitting galaxies . 26 1.8.3 Luminosity functions of LBGs and LAEs . 26 1.8.4 Lyα emission and absorption in LBGs: the physical state of high-z star forming galaxies . 27 1.8.5 Clustering properties of LBGs and LAEs: host dark matter haloes and galaxy environment . 30 1.8.6 Circum-/intergalactic gas environment of LBGs and LAEs .
    [Show full text]
  • AST4220: Cosmology I
    AST4220: Cosmology I Øystein Elgarøy 2 Contents 1 Cosmological models 1 1.1 Special relativity: space and time as a unity . 1 1.2 Curvedspacetime......................... 3 1.3 Curved spaces: the surface of a sphere . 4 1.4 The Robertson-Walker line element . 6 1.5 Redshifts and cosmological distances . 9 1.5.1 Thecosmicredshift . 9 1.5.2 Properdistance. 11 1.5.3 The luminosity distance . 13 1.5.4 The angular diameter distance . 14 1.5.5 The comoving coordinate r ............... 15 1.6 TheFriedmannequations . 15 1.6.1 Timetomemorize! . 20 1.7 Equationsofstate ........................ 21 1.7.1 Dust: non-relativistic matter . 21 1.7.2 Radiation: relativistic matter . 22 1.8 The evolution of the energy density . 22 1.9 The cosmological constant . 24 1.10 Some classic cosmological models . 26 1.10.1 Spatially flat, dust- or radiation-only models . 27 1.10.2 Spatially flat, empty universe with a cosmological con- stant............................ 29 1.10.3 Open and closed dust models with no cosmological constant.......................... 31 1.10.4 Models with more than one component . 34 1.10.5 Models with matter and radiation . 35 1.10.6 TheflatΛCDMmodel. 37 1.10.7 Models with matter, curvature and a cosmological con- stant............................ 40 1.11Horizons.............................. 42 1.11.1 Theeventhorizon . 44 1.11.2 Theparticlehorizon . 45 1.11.3 Examples ......................... 46 I II CONTENTS 1.12 The Steady State model . 48 1.13 Some observable quantities and how to calculate them . 50 1.14 Closingcomments . 52 1.15Exercises ............................. 53 2 The early, hot universe 61 2.1 Radiation temperature in the early universe .
    [Show full text]