The First Galaxies
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Olbers' Paradox
Astro 101 Fall 2013 Lecture 12 Cosmology T. Howard Cosmology = study of the Universe as a whole • ? What is it like overall? • ? What is its history? How old is it? • ? What is its future? • ? How do we find these things out from what we can observe? • In 1996, researchers at the Space Telescope Science Institute used the Hubble to make a very long exposure of a patch of seemingly empty sky. Q: What did they find? A: Galaxies “as far as The eye can see …” (nearly everything in this photo is a galaxy!) 40 hour exposure What do we know already (about the Universe) ? • Galaxies in groups; clusters; superclusters • Nearby universe has “filament” and void type of structure • More distant objects are receding from us (light is redshifted) • Hubble’s Law: V = H0 x D (Hubble's Law) Structure in the Universe What is the largest kind of structure in the universe? The ~100-Mpc filaments, shells and voids? On larger scales, things look more uniform. 600 Mpc Olbers’ Paradox • Assume the universe is homogeneous, isotropic, infinte, and static • Then: Why don’t we see light everywhere? Why is the night sky (mostly) dark? Olbers’ Paradox (cont’d.) • We believe the universe is homogeneous and isotropic • So, either it isn’t infinite OR it isn’t static • “Big Bang” theory – universe started expanding a finite time ago Given what we know of structure in the universe, assume: The Cosmological Principle On the largest scales, the universe is roughly homogeneous (same at all places) and isotropic (same in all directions). Laws of physics are everywhere the same. -
Dark Energy and Dark Matter As Inertial Effects Introduction
Dark Energy and Dark Matter as Inertial Effects Serkan Zorba Department of Physics and Astronomy, Whittier College 13406 Philadelphia Street, Whittier, CA 90608 [email protected] ABSTRACT A disk-shaped universe (encompassing the observable universe) rotating globally with an angular speed equal to the Hubble constant is postulated. It is shown that dark energy and dark matter are cosmic inertial effects resulting from such a cosmic rotation, corresponding to centrifugal (dark energy), and a combination of centrifugal and the Coriolis forces (dark matter), respectively. The physics and the cosmological and galactic parameters obtained from the model closely match those attributed to dark energy and dark matter in the standard Λ-CDM model. 20 Oct 2012 Oct 20 ph] - PACS: 95.36.+x, 95.35.+d, 98.80.-k, 04.20.Cv [physics.gen Introduction The two most outstanding unsolved problems of modern cosmology today are the problems of dark energy and dark matter. Together these two problems imply that about a whopping 96% of the energy content of the universe is simply unaccounted for within the reigning paradigm of modern cosmology. arXiv:1210.3021 The dark energy problem has been around only for about two decades, while the dark matter problem has gone unsolved for about 90 years. Various ideas have been put forward, including some fantastic ones such as the presence of ghostly fields and particles. Some ideas even suggest the breakdown of the standard Newton-Einstein gravity for the relevant scales. Although some progress has been made, particularly in the area of dark matter with the nonstandard gravity theories, the problems still stand unresolved. -
Fine-Tuning, Complexity, and Life in the Multiverse*
Fine-Tuning, Complexity, and Life in the Multiverse* Mario Livio Dept. of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154, USA E-mail: [email protected] and Martin J. Rees Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA, UK E-mail: [email protected] Abstract The physical processes that determine the properties of our everyday world, and of the wider cosmos, are determined by some key numbers: the ‘constants’ of micro-physics and the parameters that describe the expanding universe in which we have emerged. We identify various steps in the emergence of stars, planets and life that are dependent on these fundamental numbers, and explore how these steps might have been changed — or completely prevented — if the numbers were different. We then outline some cosmological models where physical reality is vastly more extensive than the ‘universe’ that astronomers observe (perhaps even involving many ‘big bangs’) — which could perhaps encompass domains governed by different physics. Although the concept of a multiverse is still speculative, we argue that attempts to determine whether it exists constitute a genuinely scientific endeavor. If we indeed inhabit a multiverse, then we may have to accept that there can be no explanation other than anthropic reasoning for some features our world. _______________________ *Chapter for the book Consolidation of Fine Tuning 1 Introduction At their fundamental level, phenomena in our universe can be described by certain laws—the so-called “laws of nature” — and by the values of some three dozen parameters (e.g., [1]). Those parameters specify such physical quantities as the coupling constants of the weak and strong interactions in the Standard Model of particle physics, and the dark energy density, the baryon mass per photon, and the spatial curvature in cosmology. -
Friedmann Equation (1.39) for a Radiation Dominated Universe Will Thus Be (From Ada ∝ Dt)
Lecture 2 The quest for the origin of the elements The quest for the origins of the elements, C. Bertulani, RISP, 2016 1 Reading2.1 - material Geometry of the Universe 2-dimensional analogy: Surface of a sphere. The surface is finite, but has no edge. For a creature living on the sphere, having no sense of the third dimension, there is no center (on the sphere). All points are equal. Any point on the surface can be defined as the center of a coordinate system. But, how can a 2-D creature investigate the geometry of the sphere? Answer: Measure curvature of its space. Flat surface (zero curvature, k = 0) Closed surface Open surface (posiDve curvature, k = 1) (negave curvature, k = -1) The quest for the origins of the elements, C. Bertulani, RISP, 2016 2 ReadingGeometry material of the Universe These are the three possible geometries of the Universe: closed, open and flat, corresponding to a density parameter Ωm = ρ/ρcrit which is greater than, less than or equal to 1. The relation to the curvature parameter is given by Eq. (1.58). The closed universe is of finite size. Traveling far enough in one direction will lead back to one's starting point. The open and flat universes are infinite and traveling in a constant direction will never lead to the same point. The quest for the origins of the elements, C. Bertulani, RISP, 2016 3 2.2 - Static Universe 2 2 The static Universe requires a = a0 = constant and thus d a/dt = da/dt = 0. From Eq. -
Galaxy Redshifts: from Dozens to Millions
GALAXY REDSHIFTS: FROM DOZENS TO MILLIONS Chris Impey University of Arizona The Expanding Universe • Evolution of the scale factor from GR; metric assumes homogeneity and isotropy (~FLRW). • Cosmological redshift fundamentally differs from a Doppler shift. • Galaxies (and other objects) are used as space-time markers. Expansion History and Contents Science is Seeing The expansion history since the big bang and the formation of large scale structure are driven by dark matter and dark energy. Observing Galaxies Galaxy Observables: • Redshift (z) • Magnitude (color, SED) • Angular size (morphology) All other quantities (size, luminosity, mass) derive from knowing a distance, which relates to redshift via a cosmological model. The observables are poor distance indicators. Other astrophysical luminosity predictors are required. (Cowie) ~90% of the volume or look-back time is probed by deep field • Number of galaxies in observable universe: ~90% of the about 100 billion galaxies in the volume • Number of stars in the are counted observable universe: about 1022 Heading for 100 Million (Baldry/Eisenstein) Multiplex Advantage Cannon (1910) Gemini/GMOS (2010) Sluggish, Spacious, Reliable. Photography CCD Imaging Speedy, Cramped, Finicky. 100 Years of Measuring Galaxy Redshifts Who When # Galaxies Size Time Mag Scheiner 1899 1 (M31) 0.3m 7.5h V = 3.4 Slipher 1914 15 0.6m ~5h V ~ 8 Slipher 1917 25 0.6m ~5h V ~ 8 Hubble/Slipher 1929 46 1.5m ~6h V ~ 10 Hum/May/San 1956 800 5m ~2h V = 11.6 Photographic 1960s 1 ~4m ~2.5h V ~ 15 Image Intensifier 1970s -
New Constraints on Cosmic Reionization
New Constraints on Cosmic Reionization Brant Robertson UCSC Exploring the Universe with JWST ESA / ESTEC, The Netherlands October 12, 2015 1 Exploring the Universe with JWST, 10/12/2015 B. Robertson, UCSC Brief History of the Observable Universe 1100 Redshift 12 8 6 1 13.8 13.5 Billions of years ago 13.4 12.9 8 Adapted from Robertson et al. Nature, 468, 49 (2010). 2 Exploring the Universe with JWST, 10/12/2015 B. Robertson, UCSC Observational Facilities Over the Next Decade 1100 Redshift 12 8 6 1 Planck Future 21cm Current 21cm LSST Thirty Meter Telescope WFIRST ALMA Hubble Chandra Fermi James Webb Space Telescope 13.8 13.5 Billions of years ago 13.4 12.9 8 Observations with JWST, WFIRST, TMT/E-ELT, LSST, ALMA, and 21- cm will drive astronomical discoveries over the next decade. Adapted from Robertson et al. Nature, 468, 49 (2010). 3 Exploring the Universe with JWST, 10/12/2015 B. Robertson, UCSC 1100 Redshift 12 8 6 1 Planck Future 21cm Current 21cm LSST Thirty Meter Telescope WFIRST ALMA Hubble Chandra Fermi James Webb Space Telescope 13.8 13.5 Billions of years ago 13.4 12.9 8 1. What can we learn about Cosmic Dawn? Was it a dramatic event in a narrow period of time or did the birth of galaxies happen gradually? 2. Can we be sure light from early galaxies caused cosmic reionization? We have some guide on when reionization occurred from studying the thermal glow of the Big Bang (microwave background), but what were the sources of ionizing photons? 3. -
Estimations of Total Mass and Energy of the Observable Universe
Physics International 5 (1): 15-20, 2014 ISSN: 1948-9803 ©2014 Science Publication doi:10.3844/pisp.2014.15.20 Published Online 5 (1) 2014 (http://www.thescipub.com/pi.toc) ESTIMATIONS OF TOTAL MASS AND ENERGY OF THE OBSERVABLE UNIVERSE Dimitar Valev Department of Stara Zagora, Space Research and Technology Institute, Bulgarian Academy of Sciences, 6000 Stara Zagora, Bulgaria Received 2014-02-05; Revised 2014-03-18; Accepted 2014-03-21 ABSTRACT The recent astronomical observations indicate that the expanding universe is homogeneous, isotropic and asymptotically flat. The Euclidean geometry of the universe enables to determine the total gravitational and kinetic energy of the universe by Newtonian gravity in a flat space. By means of dimensional analysis, we have found the mass of the observable universe close to the Hoyle-Carvalho formula M∼c3/(GH ). This value is independent from the cosmological model and infers a size (radius) of the observable universe close to Hubble distance. It has been shown that almost the entire kinetic energy of the observable universe ensues from the cosmological expansion. Both, the total gravitational and kinetic energies of the observable universe have been determined in relation to an observer at an arbitrary location. The relativistic calculations for total kinetic energy have been made and the dark energy has been excluded from calculations. The total mechanical energy of the observable universe has been found close to zero, which is a remarkable result. This result supports the conjecture that the gravitational energy of the observable universe is approximately balanced with its kinetic energy of the expansion and favours a density of dark energy ΩΛ≈ 0.78. -
Dark Energy and CMB
Dark Energy and CMB Conveners: S. Dodelson and K. Honscheid Topical Conveners: K. Abazajian, J. Carlstrom, D. Huterer, B. Jain, A. Kim, D. Kirkby, A. Lee, N. Padmanabhan, J. Rhodes, D. Weinberg Abstract The American Physical Society's Division of Particles and Fields initiated a long-term planning exercise over 2012-13, with the goal of developing the community's long term aspirations. The sub-group \Dark Energy and CMB" prepared a series of papers explaining and highlighting the physics that will be studied with large galaxy surveys and cosmic microwave background experiments. This paper summarizes the findings of the other papers, all of which have been submitted jointly to the arXiv. arXiv:1309.5386v2 [astro-ph.CO] 24 Sep 2013 2 1 Cosmology and New Physics Maps of the Universe when it was 400,000 years old from observations of the cosmic microwave background and over the last ten billion years from galaxy surveys point to a compelling cosmological model. This model requires a very early epoch of accelerated expansion, inflation, during which the seeds of structure were planted via quantum mechanical fluctuations. These seeds began to grow via gravitational instability during the epoch in which dark matter dominated the energy density of the universe, transforming small perturbations laid down during inflation into nonlinear structures such as million light-year sized clusters, galaxies, stars, planets, and people. Over the past few billion years, we have entered a new phase, during which the expansion of the Universe is accelerating presumably driven by yet another substance, dark energy. Cosmologists have historically turned to fundamental physics to understand the early Universe, successfully explaining phenomena as diverse as the formation of the light elements, the process of electron-positron annihilation, and the production of cosmic neutrinos. -
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 . -
Cosmic Microwave Background
1 29. Cosmic Microwave Background 29. Cosmic Microwave Background Revised August 2019 by D. Scott (U. of British Columbia) and G.F. Smoot (HKUST; Paris U.; UC Berkeley; LBNL). 29.1 Introduction The energy content in electromagnetic radiation from beyond our Galaxy is dominated by the cosmic microwave background (CMB), discovered in 1965 [1]. The spectrum of the CMB is well described by a blackbody function with T = 2.7255 K. This spectral form is a main supporting pillar of the hot Big Bang model for the Universe. The lack of any observed deviations from a 7 blackbody spectrum constrains physical processes over cosmic history at redshifts z ∼< 10 (see earlier versions of this review). Currently the key CMB observable is the angular variation in temperature (or intensity) corre- lations, and to a growing extent polarization [2–4]. Since the first detection of these anisotropies by the Cosmic Background Explorer (COBE) satellite [5], there has been intense activity to map the sky at increasing levels of sensitivity and angular resolution by ground-based and balloon-borne measurements. These were joined in 2003 by the first results from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP)[6], which were improved upon by analyses of data added every 2 years, culminating in the 9-year results [7]. In 2013 we had the first results [8] from the third generation CMB satellite, ESA’s Planck mission [9,10], which were enhanced by results from the 2015 Planck data release [11, 12], and then the final 2018 Planck data release [13, 14]. Additionally, CMB an- isotropies have been extended to smaller angular scales by ground-based experiments, particularly the Atacama Cosmology Telescope (ACT) [15] and the South Pole Telescope (SPT) [16]. -
Appendix a the Return of a Static Universe and the End of Cosmology
Appendix A The Return of a Static Universe and the End of Cosmology Lawrence M. Krauss and Robert J. Scherrer Abstract We demonstrate that as we extrapolate the current CDM universe forward in time, all evidence of the Hubble expansion will disappear, so that observers in our “island universe” will be fundamentally incapable of determining the true nature of the universe, including the existence of the highly dominant vacuum energy, the existence of the CMB, and the primordial origin of light elements. With these pillars of the modern Big Bang gone, this epoch will mark the end of cosmology and the return of a static universe. In this sense, the coordinate system appropriate for future observers will perhaps fittingly resemble the static coordinate system in which the de Sitter universe was first presented. Shortly after Einstein’s development of general relativity, the Dutch astronomer Willem de Sitter proposed a static model of the universe containing no matter, which he thought might be a reasonable approximation to our low-density uni- verse. One can define a coordinate system in which the de Sitter metric takes a static form by defining de Sitter spacetime with a cosmological constant ƒ S W A B D 2 2 D 1 as a four-dimensional hyperboloid ƒ AB R ;R 3ƒ em- 2 D A B D bedded in a 5d Minkowski spacetime with ds AB d d ; and .AB / diag.1; 1; 1; 1; 1/;A;B D 0;:::;4: The static form of the de Sitter metric is then dr2 ds2 D .1 r2=R2/dt 2 s r2d2; s s s 2 2 s 1 rs =R L.M. -
Arxiv:0910.5224V1 [Astro-Ph.CO] 27 Oct 2009
Baryon Acoustic Oscillations Bruce A. Bassett 1,2,a & Ren´ee Hlozek1,2,3,b 1 South African Astronomical Observatory, Observatory, Cape Town, South Africa 7700 2 Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch, Cape Town, South Africa 7700 3 Department of Astrophysics, University of Oxford Keble Road, Oxford, OX1 3RH, UK a [email protected] b [email protected] Abstract Baryon Acoustic Oscillations (BAO) are frozen relics left over from the pre-decoupling universe. They are the standard rulers of choice for 21st century cosmology, provid- ing distance estimates that are, for the first time, firmly rooted in well-understood, linear physics. This review synthesises current understanding regarding all aspects of BAO cosmology, from the theoretical and statistical to the observational, and includes a map of the future landscape of BAO surveys, both spectroscopic and photometric . † 1.1 Introduction Whilst often phrased in terms of the quest to uncover the nature of dark energy, a more general rubric for cosmology in the early part of the 21st century might also be the “the distance revolution”. With new knowledge of the extra-galactic distance arXiv:0910.5224v1 [astro-ph.CO] 27 Oct 2009 ladder we are, for the first time, beginning to accurately probe the cosmic expansion history beyond the local universe. While standard candles – most notably Type Ia supernovae (SNIa) – kicked off the revolution, it is clear that Statistical Standard Rulers, and the Baryon Acoustic Oscillations (BAO) in particular, will play an increasingly important role. In this review we cover the theoretical, observational and statistical aspects of the BAO as standard rulers and examine the impact BAO will have on our understand- † This review is an extended version of a chapter in the book Dark Energy Ed.