The Dark Side of the Universe - I

1. TheDarkSideoftheUniverse - I Rogério Rosenfeld Instituto de Física Teórica – UNESP ICTP – SAIFR 14/12/2013

2. Cosmologyhasbecome a data drivenscience! Manyexperiments (some in Chile) are taking a hugeamountof data that are beinganalyzed in order to find out whichmodelbestdescribestheuniverse.

3. Cosmologicalprobes • CosmicMicrowave Background (CMB) • Big bangnucleosynthesis (BBN) • Supernovae (type Ia) • Baryonacousticoscilation (BAO) • Gravitationallensing • Numbercountof clusters ofgalaxies

4. Cosmologicalprobes Eisenstein HST Rogerio Rosenfeld

5. Weknowthatwedon’tknowwhattheuniverse is madeof:

6. Some experiments CosmicMicrowave Background (CMB): Planck satellite, SouthPoleTelescope, AtacamaCosmologyTelescope ACT

8. dT/T ~ 10-5

9. Great theoretical success: determines best model for the universe

10. Largegalaxysurveys: probethelargescalestructure (LSS) oftheuniverse. Sloan Digital Sky Survey(SDSS-I, 2000-2005; SDSS-II, 2005-2008, SDSS-III, 2008-2014) & Baryon Oscillation Spectroscopic Survey (BOSS) - 1.5 million Luminous Red Galaxies (LRGs) out to z~0.7 over 10,000 square degrees.

12. Large scale structure: observations Sloan Digital Sky Survey: spectra of 930,000 galaxies The outer circle is at a distance of two billion light years.

13. Dark Energy Survey • Surveyof 5000 deg2 (~ 1/8 ofthesky) • 300 millionsofgalaxiesup to z~1.4 (+ 100,000 clusters + 4,000 SNs) • Photometricredshiftwith 5 filters • Project initiated in 2003 • Observationsfrom08/2013-02/2018 (5x105 nights)

14. Rogerio Rosenfeld DES Project Timeline NOAO Blanco Announcement of Opportunity 2003 DECam R&D 2004-8 Camera construction 2008-11 Final testing, integration 2011 Shipping components to Chile 2011 Installation on telescope begins early 2012 First light DECam on telescope September 2012 Commissioning and Science Verification: Fall 2012/Spring 2013 Survey operations begin: August 31st 2013

15. DES site: 4m Blanco telescope at the Cerro Tololo Inter- American Observatory (CTIO) in Chile

16. The DES Camera: the most powerful digital space camera on Earth. Weighs around 4 tons. Built at Fermilab. Able to see light from more than 100,000 galaxies up to 8 billion light-years away in each snapshot.

17. The DES Camera: 62 large CCDs – 570 megapixels. 1st light on September 12, 2012. Fornax cluster of galaxies

18. DES image: Barred spiral galaxy NGC 1365 in the Fornax cluster of galaxies

19. Future experiments (brazilian participation?)

20. Future experiments: LSST 8.4-meter ground-based telescope, camera with 3200 Megapixels (will be the world’s largest digital camera). First light 2020?

21. Future experiments: GMT Six off-axis 8.4 meter segments surround a central on-axis segment, forming a single optical surface with an aperture of 24.5 meters in diameter. Cerro Las Campanas, Chile. Completion in 2020.

22. Future experiments: TMT Mount Mauna Kea – Hawaii. First science in 2022.

23. Future experiments: EUCLID Euclid is an ESA medium class space mission selected for launch in 2020 in the Cosmic Vision 2015-2025 programme. To achieve the Euclid’s quest a satellite is under construction equipped with a 1.2 m telescope that feeds 2 instruments: a high quality panoramic visible imager (VIS), a near infrared 3-filter (Y, J and H) photometer and a slitless spectrograph (NISP). These instruments will explore the expansion history of the Universe and the evolution of cosmic structures by measuring the modification of shapes of galaxies induced by gravitational lensing effects of dark matter, and the 3-dimension distribution of structures from spectroscopic red­shifts of galaxies and clusters of galaxies. The satellite will be launched by a Soyuz ST-2.1B rocket and transferred to the L2 Lagrange point for a 6 years mission. Euclid will observe 15,000 deg2 of the darkest sky that is free of contamination by light emissions from our Galaxy and our Solar System

24. Geometry Matter/Energy/Pressure Standard CosmologicalModel Space tells matter how to move (J.A. Wheeler) Matter tells space how to curve Kolb

25. CosmologicalPrinciple Universe is homogeneousandisotropicatverylargescales Only small fluctuations in the CMB withdT/T ~ 10-5

26. Geometry: left-handsideofEinstein’sequation Cosmologicalprinciplesimplifiesthepossiblegeometriesofthespacetime – Friedmann-Robertson-Walkermetric: a(t):cosmologicalscalefactor convention: a=1today physicaldistances: d(t) = a(t) d0

27. Geometry: averageevolutionoftheuniverse - specifiedbyonefunction: scalefactor a(t) - determines measurementoflargescaledistances, velocitiesandacceleration • measuredthrough standard candles (SNIa’s) and standard rulers (positionof CMB peak, BAO peak,...) Redshift z: z=0 today.

28. Expansionoftheuniverse Hubble parameter: Expansion rate oftheuniverse Hubble constant: Hubble parametertoday (H0) Analogyoftheexpansionoftheuniversewith a balloon: Spaceitselfexpandsandgalaxiesget a free “ride”.

29. Expansionoftheuniverse Universehas a history!

30. i= matter (baryonicordark), radiation, neutrinos,cosmological constant,quintessence, ... Energyandmatter: right-handsideofEinstein’sequation Allformsofmatterandenergy in theuniverse are describedbytheenergy-momentum tensor. Homogeneityandisotropy:

31. DM and DE in theuniverse • Darkmatteranddarkenergyaffect: • Expansionhistoryoftheuniverse • (evolutionofthe “average”) • Historyofstructureformation • (evolutionofperturbations)

32. Dynamics oftheuniverse FollowfromEinstein’sequation Expansion rate Decelerationparameter

33. Criticaldensity Theuniverse is spatially flat (k=0)if: Thiscriticaldensity is time-dependent. Todayand 5 protons/m3

34. Densityparameter Differentcontributions to thedensity oftheuniverse: i= matter, radiation, darkenergy, neutrinos... Flat universe:

35. Dynamics oftheuniverse Need to determine howdensityofdifferent fluidschanges as a functionofthescale in order to close the system ofequations. Chooseanequationofstate for eachcomponent: w = 1/3 (radiation) w=0 (non-relativisticmatter) w=-1 (cosmologicalconstant) w= w(a) (general case)

36. Dynamics oftheuniverse 1stlawofthermodynamics: Therefore:

37. Vacuumenergy E. L. Wright

38. Dynamics oftheuniverse radiation ln r matter cosmologicalconstant lnaeq ln aDE 0 ln a

39. Model for thesmoothuniverse • Einstein’sequation • Differentcomponentsandtheirdensities • Equationofstate for eachcomponent • Hubble’sconstant H0(h0)

40. Ex.1: Estimatehowmanyphotonsexist in a cm3todaygiventhatthe CMB temperature is approx. 2.7 K Ex.2: Estimatethefractionofphotons to protons today, giventhatWb = 0.04 Ex.3: Estimatethefractionofenergy in photons to protonstoday. Ex.4: Estimatetheredshiftatwhichphotonsandmatterhaveequalenergydensity. Ex.5: Estimatetheredshiftatwhichphotonsdecouplefromatoms (lastscatteringsurface).

41. Ex.6: estimatethe age oftheuniverse

42. Age oftheuniverse: Hubble time:

43. Ex.7: Estimatetheredshiftatwhichtheuniverse starts tobedominatedbydarkenergy (= L ). Cosmologicalcoincidenceproblem Whynow?

45. Thecausalityproblem z=0 Light fromlastscatteringsurfacereaches us fromcausallydisconnectedregions – howcantheyhavethesametemperature? Angular sizetodayofhorizonatdecouplingis ~ 10 time z=1100 z=∞

46. Solution: inflation

48. Solution: inflation Exponentialgrowthoftheuniverse. • For instance, if a flat universe is dominatedby a vacuumenergy:

49. Solution: inflation • Solves causality (horizon) problem • ExplainswhyWTOT = 1 (flatnessproblem) • Generates small perturbationsfrom • quantum fluctuationsthatbecomeseeds for • thelargescalestructureoftheuniverse

50. http://arxiv.org/1303.3787