DOCSLIB.ORG

UC Berkeley UC Berkeley Electronic Theses and Dissertations

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
UC Berkeley UC Berkeley Electronic Theses and Dissertations UC Berkeley UC Berkeley Electronic Theses and Dissertations Title Reconstruction of Cosmological Fields in Forward Model Framework Permalink https://escholarship.org/uc/item/4g05x2zh Author Modi, Chirag Publication Date 2020 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California Reconstruction of Cosmological Fields in Forward Model Framework by Chirag Modi A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Physics in the Graduate Division of the University of California, Berkeley Committee in charge: Professor UroˇsSeljak, Chair Professor Martin White Professor Fernando P´erez Summer 2020 Reconstruction of Cosmological Fields in Forward Model Framework Copyright 2020 by Chirag Modi 1 Abstract Reconstruction of Cosmological Fields in Forward Model Framework by Chirag Modi Doctor of Philosophy in Physics University of California, Berkeley Professor UroˇsSeljak, Chair The large scale structures (LSS) of the Universe contain a vast amount of information about the birth, evolution and composition of our Universe. To mine this information over the next decade, large scale imaging surveys such as the Dark Energy Spectroscopic Survey (DESI), Large Synoptic Survey Telescope (LSST), Euclid and WFIRST will probe the Universe with unprecedented precision, and on the largest scales. This provides an opportunity to shed light on the longstanding mysteries regarding the true nature of dark matter and dark energy, as well as to resolve tensions between different probes of the past decade. However to utilize the full potential these surveys which are no longer statistically limited, it is critical to develop analytic methods that extract the maximum amount of information across all scales. In this regard, the massive data volumes, the non-linearity, and non-Gaussianity of the signal in the regimes probed by these surveys will pose outstanding challenges. The focus of this thesis is to tackle aforementioned challenges with a novel framework for the analysis of the large scale structures by reconstructing cosmological fields using forward models. These forward modeling approaches are the most promising way to jointly model different cosmological observations with requisite accuracy at all scales, while accounting for their individual systematic biases and noise. We approach reconstruction within a Bayesian formalism - by optimizing the likelihood of the observed data and maximizing the cor- responding posterior of initial conditions. This requires solving optimization problems in multi-million dimensional space and we develop novel differentiable forward models as well as adiabatic optimization algorithms to assist with this. We begin by using this approach to reconstruct the initial density field from a continuous dark matter field, as well as discrete observables like dark matter halos. We also construct a power spectrum estimator for this reconstructed Gaussian density field, which is the summary statistic for optimal analysis. With 21-cm intensity mapping, we show how this framework can instead be used for secondary analysis such as de-noising the observed data and recov- ering lost cosmological information. For this, we also introduce Hidden Valley Simulations 2 - a suite of high resolution N-Body simulations and develop models to simulate HI cluster- ing. Having demonstrated the efficacy of this approach, we finally introduce FlowPM - a GPU-accelerated, distributed, and differentiable N-Body solver in TensorFlow that naturally interfaces with the most advanced machine learning tools. This will enable the community to efficiently solve large scale cosmological inference problems and develop differentiable for- ward models for the reconstruction of cosmological fields with the next generation of LSS surveys. i To my parents, Ajay and Nisha Modi, who with unconditional love, support, constant encouragement and sacrifices raised me to be the person I am today. You have always been an inspiration to me. And to my grandfather Sanat Kumar Modi, who always believed in me. I miss you Ba. ii Contents Contents ii List of Figures iv List of Tables xvi 1 Introduction1 1.1 Large Scale Structures .............................. 4 1.2 Modeling Growth and Evolution of Dark Matter................ 4 1.3 Modeling Halos and Galaxy Distribution.................... 8 1.4 Analysis...................................... 13 1.5 Other Probes of Large Scale Structures..................... 19 1.6 Outline of this Thesis............................... 21 2 Differentiable Forward Models in Cosmology 23 2.1 Particle Mesh Simulations ............................ 24 2.2 Bias Model .................................... 28 2.3 Lagrangian Bias at Field Level.......................... 34 2.4 Neural Network Model.............................. 35 3 Towards optimal extraction of cosmological information from nonlinear data 40 3.1 Introduction.................................... 40 3.2 Statistical approach and heuristic derivation.................. 43 3.3 Maximum a posteriori (MAP) initial mode estimator ............. 48 3.4 Minimum variance initial power spectrum estimator.............. 51 3.5 Application to dark matter simulations..................... 63 3.6 Conclusions.................................... 75 4 Cosmological Reconstruction From Galaxy Light: Neural Network Based Light-Matter Connection 79 4.1 Introduction.................................... 79 4.2 Neural Network Model.............................. 83 iii 4.3 Simulations .................................... 88 4.4 Model Performance................................ 88 4.5 Reconstruction .................................. 96 4.6 BAO Information................................. 110 4.7 Conclusions and Discussion ........................... 113 5 Reconstructing large-scale structure with neutral hydrogen surveys 116 5.1 Introduction.................................... 117 5.2 Setting the Stage................................. 120 5.3 Hidden Valley simulation suite.......................... 123 5.4 The HI model................................... 124 5.5 Validating Hidden Valley Simualtions...................... 132 5.6 Reconstruction of HI Field............................ 145 5.7 Results....................................... 150 5.8 Implications.................................... 161 5.9 Conclusions.................................... 169 6 FlowPM: Distributed TensorFlow Implementation of the FastPM Cos- mological N-body Solver 173 6.1 Introduction.................................... 173 6.2 The FastPM particle mesh N-body solver.................... 175 6.3 Multi-grid PM Scheme.............................. 176 6.4 Mesh-TensorFlow................................. 178 6.5 FlowPM: FastPM implementation in Mesh-Tensorflow . 180 6.6 Scaling and Numerical Accuracy......................... 184 6.7 Example application: Reconstruction of initial conditions . 190 6.8 Conclusion..................................... 198 7 Conclusions 201 Bibliography 203 iv List of Figures 1.1 Cosmic history and evolution of the Universe from Big Bang to the present day. Credits ESA ..................................... 2 1.2 Evolution of dark matter field under gravity. We show (top left) the initial Gaus- sian field at z = 9, (top right) Zeldovich evolution, (bottom left) 2LPT evolution and (bottom right) FastPM [83] particle mesh evolution with 20 time steps to z = 0. ......................................... 9 1.3 (Left) Real space matter power spectrum. with measurements from various sur- veys probing LSS of the Universe. Figure taken from [6]. (Right) Matter corre- lation function in real space. Figure taken from [60] ............... 14 1.4 Modeling matter power spectrum in real space at different redshifts. We show re- sults from N-Body simulation, along with linear theory, Eulerian and Lagrangian perturbation theories at different orders and Cosmic Emu emulator. Figure taken from [242]....................................... 14 1.5 (Left) Halo (red) and galaxy (blue) power spectrum in real space. Solid lines are perturbation theory fits and points are N-Body simulations. (Right) Halo and galaxy power spectra, monopole and quadrapole, in redshift space. FOG suppression on small scales is clearly visible in case of galaxies. Figure taken from [175]........................................ 16 1.6 Baryon acoustic oscillations in SDSS-BOSS survey, data release 12, between red- shift 0:5 < z < 0:7. Lines are best fits and markers are observed data points. (Left) BAO in the power spectrum as wiggles in the monopole, and in quadrapole. We separately show SGC and NGC data. Figure taken from [27] (Right) BAO as the peak in correlation function monopole and quadrapole. Figure taken from [199]........................................... 17 1.7 Damping and reconstruction of BAO (Top Left) Sharp BAO peak feature at the time of decoupling. (Top Right) Broadening of BAO peak due to displacement of galaxies under gravity. (Bottom Left) Estimated Zeldovich displacements to undo the non-linear evolution of the galaxies. (Bottom Right) Reconstructed density field and sharpened BAO peak. Figure taken from [179].......... 18 v 2.1 Bias parameters as function of k: We show b1, b2 and bs2 as measured from Fourier space estimator. For clarity, we only show 2 mass bins from every box and different line-styles (dashed, solid and dotted) correspond to different boxes (of size L = 690; 1380; 3000 Mpc=h respectively), from which the corresponding mass bins (specified by
Load more

Recommended publications
  • Adrien Christian René THOB
    THE RELATIONSHIP BETWEEN THE MORPHOLOGY AND KINEMATICS OF GALAXIES AND ITS DEPENDENCE ON DARK MATTER HALO STRUCTURE IN SIMULATED GALAXIES Adrien Christian René THOB A thesis submitted in partial fulfilment of the requirements of Liverpool John Moores University for the degree of Doctor of Philosophy. 26 April 2019 To my grand-parents, René Roumeaux, Christian Thob, Yvette Roumeaux (née Bajaud) and Anne-Marie Thob (née Léglise). ii Abstract Galaxies are among nature’s most majestic and diverse structures. They can play host to as few as several thousands of stars, or as many as hundreds of billions. They exhibit a broad range of shapes, sizes, colours, and they can inhabit vastly differing cosmic environments. The physics of galaxy formation is highly non-linear and in- volves a variety of physical mechanisms, precluding the development of entirely an- alytic descriptions, thus requiring that theoretical ideas concerning the origin of this diversity are tested via the confrontation of numerical models (or “simulations”) with observational measurements. The EAGLE project (which stands for Evolution and Assembly of GaLaxies and their Environments) is a state-of-the-art suite of such cos- mological hydrodynamical simulations of the Universe. EAGLE is unique in that the ill-understood efficiencies of feedback mechanisms implemented in the model were calibrated to ensure that the observed stellar masses and sizes of present-day galaxies were reproduced. We investigate the connection between the morphology and internal 9:5 kinematics of the stellar component of central galaxies with mass M? > 10 M in the EAGLE simulations. We compare several kinematic diagnostics commonly used to describe simulated galaxies, and find good consistency between them.
    [Show full text]
  • Dark Energy and Dark Matter
    Dark Energy and Dark Matter Jeevan Regmi Department of Physics, Prithvi Narayan Campus, Pokhara [email protected] Abstract: The new discoveries and evidences in the field of astrophysics have explored new area of discussion each day. It provides an inspiration for the search of new laws and symmetries in nature. One of the interesting issues of the decade is the accelerating universe. Though much is known about universe, still a lot of mysteries are present about it. The new concepts of dark energy and dark matter are being explained to answer the mysterious facts. However it unfolds the rays of hope for solving the various properties and dimensions of space. Keywords: dark energy, dark matter, accelerating universe, space-time curvature, cosmological constant, gravitational lensing. 1. INTRODUCTION observations. Precision measurements of the cosmic It was Albert Einstein first to realize that empty microwave background (CMB) have shown that the space is not 'nothing'. Space has amazing properties. total energy density of the universe is very near the Many of which are just beginning to be understood. critical density needed to make the universe flat The first property that Einstein discovered is that it is (i.e. the curvature of space-time, defined in General possible for more space to come into existence. And Relativity, goes to zero on large scales). Since energy his cosmological constant makes a prediction that is equivalent to mass (Special Relativity: E = mc2), empty space can possess its own energy. Theorists this is usually expressed in terms of a critical mass still don't have correct explanation for this but they density needed to make the universe flat.
    [Show full text]
  • Roger A. Chevalier Curriculum Vitae Address
    Roger A. Chevalier Curriculum Vitae Address Department of Astronomy, University of Virginia, P. O. Box 400325, Charlottesville, VA 22904 (434) 924–4889 (office); (434) 924–3104 (fax); [email protected] Education Ph.D. Astronomy, Princeton University, 1973 B.S. Astronomy, California Institute of Technology, 1970 Employment W. H. Vanderbilt Professor of Astronomy, University of Virginia, Charlottesville, VA, 1990– Professor of Astronomy, University of Virginia, 1985–90 Chair, Department of Astronomy, University of Virginia, 1985–88, 1989–92 Associate Professor of Astronomy, University of Virginia, 1979–85 Associate Astronomer, Kitt Peak National Observatory, Tucson, AZ, 1976–79 Assistant Astronomer, Kitt Peak National Observatory, Tucson, AZ, 1973–76 Honors NASA Public Service Group Achievement Award to Supernova Science Team (SN 1987A), 1989 Virginia’s Outstanding Scientist Award, 1991 President’s and Visitors’ Research Prize, University of Virginia, 1992 Dannie Heineman Prize for Astrophysics, 1996 Elected to National Academy of Sciences, 1996 Meeting “A Festival of Cosmic Explosions: Celebrating the Contributions and Ac- complishments of Roger Chevalier” held August 21-23, 2009, Caltech, Pasadena, CA Committees American Astronomical Society: High Energy Astrophysics Division Executive Committee (1985–86); Councilor (1988–91); Heineman Prize Committee (2001– 03; Chair 2003) Associated Universities for Research in Astronomy: Observatories Visiting Com- mittee (1999–2002; Chair 2002) National Science Foundation: Committee on Large Optical/Infrared Telescopes (1985–86); Committee of Visitors, Division of Astronomical Sciences (1990, 1993); Advisory Committee, Division of Astronomical Sciences (1991–93) National Aeronautics and Space Administration: Science Working Group on Su- pernova 1987A (1987–88) National Academy of Sciences/National Research Council: Committee on Space Astronomy and Astrophysics (1987–88); Theory Panel of Astronomy Survey 1 Committee for the 1990’s (1989–90); Committee on Astronomy and Astrophysics (1997–2002); Watson Prize Committee; U.S.
    [Show full text]
  • Cosmology Meets Condensed Matter
    Cosmology Meets Condensed Matter Mark N. Brook Thesis submitted to the University of Nottingham for the degree of Doctor of Philosophy. July 2010 The Feynman Problem-Solving Algorithm: 1. Write down the problem 2. Think very hard 3. Write down the answer – R. P. Feynman att. to M. Gell-Mann Supervisor: Prof. Peter Coles Examiners: Prof. Ed Copeland Prof. Ray Rivers Abstract This thesis is concerned with the interface of cosmology and condensed matter. Although at either end of the scale spectrum, the two disciplines have more in common than one might think. Condensed matter theorists and high-energy field theorists study, usually independently, phenomena embedded in the structure of a quantum field theory. It would appear at first glance that these phenomena are disjoint, and this has often led to the two fields developing their own procedures and strategies, and adopting their own nomenclature. We will look at some concepts that have helped bridge the gap between the two sub- jects, enabling progress in both, before incorporating condensed matter techniques to our own cosmological model. By considering ideas from cosmological high-energy field theory, we then critically examine other models of astrophysical condensed mat- ter phenomena. In Chapter 1, we introduce the current cosmological paradigm, and present a somewhat historical overview of the interplay between cosmology and condensed matter. Many concepts are introduced here that later chapters will follow up on, and we give some examples in which condensed matter physics has had a very real effect on informing cosmology. We also reflect on the most recent incarnations of the condensed matter / cosmology interplay, and the future of these developments.
    [Show full text]
  • Cosmological N-Body Simulations with Generic Hot Dark Matter
    Prepared for submission to JCAP Cosmological N-body simulations with generic hot dark matter Jacob Brandbyge,a;b Steen Hannestada aDepartment of Physics and Astronomy, University of Aarhus, Ny Munkegade 120, DK{8000 Aarhus C, Denmark bCentre for Star and Planet Formation, Niels Bohr Institute & Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK{1350 Copenhagen, Denmark E-mail: [email protected], [email protected] Abstract. We have calculated the non-linear effects of generic fermionic and bosonic hot dark matter components in cosmological N-body simulations. For sub-eV masses, the non- linear power spectrum suppression caused by thermal free-streaming resembles the one seen for massive neutrinos, whereas for masses larger than 1eV, the non-linear relative suppression of power is smaller than in linear theory. We furthermore find that in the non-linear regime, one can map fermionic to bosonic models by performing a simple transformation. arXiv:1706.00025v1 [astro-ph.CO] 31 May 2017 Contents 1 Introduction1 2 Hot dark matter in linear theory2 2.1 Power spectrum suppression2 2.2 Phase space distribution of the hot dark matter4 2.3 Current constraints from linear theory4 3 Simulation methods6 3.1 Cosmology and initial conditions6 3.2 Different hot dark matter simulation methods7 3.3 The correlation of bulk and thermal velocities7 4 Non-linear results8 4.1 Generic hot dark matter power spectrum suppression 10 4.2 Fermions versus bosons 11 4.3 Convergence 13 5 Discussion and conclusions 13 1 Introduction Although many different types of observations constrain the dominant dark matter compo- nent of the Universe to be cold, a sub-dominant hot dark matter (HDM) component cannot be excluded.
    [Show full text]
  • "Southern Skies and Cosmic Questions" by Ed Bertschinger
    Edmund Bertschinger Southern Skies and Cosmic Questions how big is the observable universe? what is it made of? why does space repel itself? n January 2006—the middle of summer in the i Southern hemisphere—a bus full of MIT alumni, family, and friends ascended a narrow, winding dirt road through the coastal range of Chile up to 2400 meters (8000 feet) elevation. After visiting European and American national observatory sites during the preceding days, the group figure 1 Wide-angle view of the Southern sky was eager to see the private observatory of which MIT is a part- taken from the Andes Mountains of Argentina on January 28, 2007. Visible ner: the Magellan Telescopes at Las Campanas Observatory. Only are Comet McNaught, the brightest comet in over 40 years; the splotchy Milky Way; and one traveler in the group had been there before: five years earlier, our two satellite galaxies, the Magellanic Clouds. (Photo credit and copyright: Miloslav Jane Pappalardo had attended the dedication of the newly built Druckmüller) telescopes. The author, serving as a scientific tour guide, was excited to arrive finally at the facility his colleague, MIT Magellan director Prof. Paul Schechter, had helped design and commission. After traveling a week through Northern Chile we had reached the summit of a remarkable trip. C H i L E — a th i n st r i P of L a n d between the Pacific Ocean and the crest of the Andes—is an astronomical mecca. The cold Humboldt ocean current flow- ing northward from Antarctica keeps the marine clouds low against the wall of coastal mountains.
    [Show full text]
  • Curriculum Vitae of Robert J. Scherrer
    CURRICULUM VITAE OF ROBERT J. SCHERRER Address: Department of Physics and Astronomy Vanderbilt University Nashville, TN 37235 phone: 615-343-3230/615-343-6419 email: [email protected] Education Sept. 1977 - June 1981: Princeton University, A.B. in physics, magna cum laude Sept. 1981 - Aug. 1983: Cambridge University, M.A. in physics. Sept. 1983 - Oct. 1986: University of Chicago, Ph.D. in physics (Thesis advisor: Prof. Michael S. Turner). Positions Held Oct. 1986 - Jun. 1987, Oct. 1987 - Jul. 1988: Harvard University, Postdoctoral Research Associate. Jun. 1987 - Oct. 1987, Jul. 1988 - Dec. 1988: Queen Mary College, University of London, NATO Postdoctoral Fellow. Jan. 1989 - Sept. 1993: Assistant Professor, Department of Physics, The Ohio State University. Oct. 1993 - Sept. 1998: Associate Professor, Department of Physics, The Ohio State University. Oct. 1996 - Sept. 1998: Associate Professor, Department of Astronomy, The Ohio State University. Sept. 1997 - May 1998: Visiting Scientist, Theoretical Astrophysics Group, Fermilab Oct. 1998 - Aug. 2003: Professor, Department of Physics and Department of Astronomy, The Ohio State University. Oct. 1999 - Aug. 2003: Vice-Chair for Undergraduate Studies, Department of Physics, The Ohio State University Sept. 2003 - present: Professor, Department of Physics and Astronomy, Vanderbilt University. Jan. 2004 - present: Chair, Department of Physics and Astronomy, Vanderbilt University Honors and Awards Marshall Scholarship (1981-83). McCormick Graduate Fellowship (University of Chicago 1983-86). NATO Postdoctoral Fellowship (1987-88). The Ohio State University Alumni Award for Distinguished Teaching (1999). Fellow of the American Physical Society (2001). 5th Prize, Gravity Research Foundation Essay Competition (2007). Klopsteg Memorial Award, American Association of Physics Teachers (2010). Books Quantum Mechanics: An Accessible Introduction Robert J.
    [Show full text]
  • Dark Matter and Dark Energy: Summary and Future Directions
    Dark Matter and Dark Energy: Summary and Future Directions By John Ellis TH Division, CERN, Geneva, Switzerland CERN–TH/2003-086 astro-ph/0304183 April 2003 This paper reviews the progress reported at this Royal Society Discussion Meeting and advertizes some possible future directions in our drive to understand dark matter and dark energy. Additionally, a first attempt is made to place in context the exciting new results from the WMAP satellite, which were published shortly after this Meeting. In the first part of this review, pieces of observational evidence shown here that bear on the amounts of dark matter and dark energy are reviewed. Subsequently, particle candidates for dark matter are mentioned, and detection strategies are discussed. Finally, ideas are presented for calculating the amounts of dark matter and dark energy, and possibly relating them to laboratory data. Keywords: cosmology, particle physics, dark matter, dark energy 1. The Density Budget of the Universe It is convenient to express the mean densities ρi of various quantities in the Universe in terms of their fractions relative to the critical density: Ωi ρi/ρcrit. The theory of cosmological inflation strongly suggests that the the total≡ density should be very close to the critical one: Ωtot 1, and this is supported by the available data on the cosmic microwave background' radiation (CMB) (Bond 2003). The fluctuations 5 observed in the CMB at a level 10− in amplitude exhibit a peak at a partial wave ` 200, as would be produced∼ by acoustic oscillations in a flat Universe with ∼ Ωtot 1. At lower partial waves, ` 200, the CMB fluctuations are believed to be dominated' by the Sachs-Wolfe effect due to the gravitational potential, and more acoustic oscillations are expected at larger `>200, whose relative heights depend on the baryon density Ωb.
    [Show full text]
  • THEO MURPHY INTERNATIONAL SCIENTIFIC MEETING on Testing
    THEO MURPHY INTERNATIONAL SCIENTIFIC MEETING ON Testing general relativity with cosmology Monday 28 February – Tuesday 1 March 2011 The Kavli Royal Society International Centre, Chicheley Hall, Buckinghamshire Organised by Professor Pedro Ferreira, Professor Rachel Bean and Professor Andrew Taylor - Programme and abstracts - Speaker biographies The abstracts that follow are provided by the presenters and the Royal Society takes no responsibility for their content. Testing general relativity with cosmology Monday 28 February – Tuesday 1 March 2011 The Kavli Royal Society Centre, Chicheley Hall, Buckinghamshire Organised by Professor Pedro Ferreira, Professor Rachel Bean and Professor Andrew Taylor Day 1 – Monday 28 February 2011 09.15 Welcome by Professor Sir Peter Knight FRS , Principal, The Kavli Royal Society Centre Welcome by Professor Pedro Ferreira , Organiser 09.30 Constraining the cosmic growth history with large scale structure Professor Rachel Bean, Cornell University, USA 10.00 Discussion 10.15 One gravitational potential or two? Forecasts and tests Professor Edmund Bertschinger, Massachusetts Institute of Technology, USA 10.45 Discussion 11.00 Coffee 11.30 Cosmological tests of gravity Dr Constantinos Skordis, The University of Nottingham, UK 12.00 Discussion 12.15 Testing modified gravity with next generation weak lensing experiments Dr Thomas Kitching, University of Edinburgh, UK 12.45 Discussion 13.00 Lunch 14.00 Model independent tests of cosmic gravity Professor Eric Linder, University of California at Berkeley, USA 14.30
    [Show full text]
  • Closing the Window on Warm Dark Matter
    View metadata, citation and similar papers at core.ac.uk LAPTH-852/01; astro-ph/0106108brought to you by CORE provided by CERN Document Server Closing the Window on Warm Dark Matter Steen H. Hansen1, Julien Lesgourgues2, Sergio Pastor3, Joseph Silk1 1 Department of Physics, Nuclear & Astrophysics Laboratory, University of Oxford, Keble Road, Oxford OX1 3RH, U.K. 2 Laboratoire de Physique Th´eorique LAPTH, B.P. 110, F-74941 Annecy-le-Vieux Cedex, France 3 Max-Planck-Institut f¨ur Physik (Werner-Heisenberg-Institut), F¨ohringer Ring 6, D-80805, Munich, Germany Sterile neutrinos may be one of the best Warm Dark Matter candidates we have today. Both lower and upper bounds on the mass of the sterile neutrino come from astronomical observations. We show that the proper inclusion of the neutrino momentum distribution and the solution of the kinetic equations with the correct coherence breaking terms lead to the near exclusion of the sterile neutrino as a dark matter candidate. PACS number(s): 14.60.Pq, 14.60.St, 95.35.+d I. INTRODUCTION do massless neutrinos. Therefore they do not share the entropy release from the successive particle annihilations. Astrophysics provides an increasing amount of inde- Since they were relativistic at decoupling, their distribu- pendent indications that the dark matter of the universe tion function in momentum space is subsequently that of is warm, so that the small-scale fluctuations are damped a massless fermion, but with a temperature, TW , which out by free streaming. This is most easily achieved by is given today by giving a keV mass to the DM particle, in which case the 1=3 preferred candidate is the sterile neutrino.
    [Show full text]
  • Warm Dark Matter
    Cosmology in the Nonlinear Domain: Warm Dark Matter Katarina Markoviˇc M¨unchen 2012 Cosmology in the Nonlinear Domain: Warm Dark Matter Katarina Markoviˇc Dissertation an der Fakult¨atf¨urPhysik der Ludwig{Maximilians{Universit¨at M¨unchen vorgelegt von Katarina Markoviˇc aus Ljubljana, Slowenien M¨unchen, den 17.12.2012 Erstgutachter: Prof. Dr. Jochen Weller Zweitgutachter: Prof. Dr. Andreas Burkert Tag der m¨undlichen Pr¨ufung:01.02.2013 Abstract The introduction of a so-called dark sector in cosmology resolved many inconsistencies be- tween cosmological theory and observation, but it also triggered many new questions. Dark Matter (DM) explained gravitational effects beyond what is accounted for by observed lumi- nous matter and Dark Energy (DE) accounted for the observed accelerated expansion of the universe. The most sought after discoveries in the field would give insight into the nature of these dark components. Dark Matter is considered to be the better established of the two, but the understanding of its nature may still lay far in the future. This thesis is concerned with explaining and eliminating the discrepancies between the current theoretical model, the standard model of cosmology, containing the cosmological constant (Λ) as the driver of accelerated expansion and Cold Dark Matter (CDM) as main source of gravitational effects, and available observational evidence pertaining to the dark sector. In particular, we focus on the small, galaxy-sized scales and below, where N-body simulations of cosmological structure in the ΛCDM universe predict much more structure and therefore much more power in the matter power spectrum than what is found by a range of different observations.
    [Show full text]
  • Arxiv:2010.00693V2 [Astro-Ph.GA] 31 Oct 2020 Total Mass of Dark Matter Around Galaxies
    Draft version November 3, 2020 Typeset using LATEX twocolumn style in AASTeX63 Tracing Dark Matter Halos with Satellite Kinematics and the Central Stellar Velocity Dispersion of Galaxies Gangil Seo1, Jubee Sohn2, Myung Gyooon Lee1;∗1, 2 11 Astronomy Program, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-742, Republic of Korea 22 Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138, USA ABSTRACT It has been suggested that the central stellar velocity dispersion of galaxies can trace dark matter halo mass directly. We test this hypothesis using a complete spectroscopic sample of isolated galaxies surrounded by faint satellite galaxies from the Sloan Digital Sky Survey Data Release 12. We apply a friends-of-friends algorithm with projected linking length ∆D < 100 kpc and radial velocity linking length ∆V < 1000 km s−1 to construct our sample. Our sample includes 2807 isolated galaxies with 3417 satellite galaxies at 0:01 < z < 0:14. We divide the sample into two groups based on the primary galaxy color: red and blue primary galaxies separated at (g − r)0 = 0:85. The central stellar velocity dispersions of the primary galaxies are proportional to the luminosities and stellar masses of the same galaxies. Stacking the sample based on the central velocity dispersion of the primary galaxies, we derive the velocity dispersions of their satellite galaxies, which trace the dark matter halo mass of the primary galaxies. The system velocity dispersion of the satellite galaxies shows a remarkably tight correlation with the central velocity dispersion of the primary galaxies for both red and blue samples.
    [Show full text]