Type Ia Supernovae, Dark Energy, and the Hubble Constant

Transcription

1 Type Ia Supernovae, Dark Energy, and the Hubble Constant Lemaître Workshop: Black Holes, Gravitational Waves, Spacetime Singularities Alex Filippenko University of California, Berkeley Vatican Observatory, 9 May 2017

2 Georges Lemaître ( ) Wikipedia: He proposed the theory of the expansion of the universe, widely misattributed to Edwin Hubble. [3][4] He was the first to derive what is now known as Hubble's law and made the first estimation of what is now called the Hubble constant, which he published in 1927, two years before Hubble's article. [5][6][7][8] Lemaître also proposed what became known as the Big Bang theory of the origin of the universe, which he called his hypothesis of the primeval atom or the Cosmic Egg. [9]

3 Vesto Slipher Edwin Hubble 1917 (1922, 1923) 1929 (NASA/STScI/G. Bacon)

4 Observed low-redshift Hubble diagram (ideal): log d (distance) Hubble s law, v = H 0 d (v = cz) log z (redshift)

5 Scale factor a(t) (Ω M = ρ ave /ρ crit ) Empty (Ω M =0) Low (Ω M =0.3) Medium (Ω M =1) Dense (Ω M > 1) t 0 (now) Time t

6 a(t 0 ) Note: 1 + z = a(t 0 ) / a(t) z = redshic RedshiC z=0 RedshiC z = 1 Age Dense (Ω M >1) Lookback Gmes for the various models at fixed redshic t t 0 (now)

7 Observer s version: Ω M 1 >1 log distance log z (redshift)

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9 Determining the Hubble Diagram Redshift: easy to measure from galaxy spectrum Distance: Luminosity distance d L L f = 4π d 2 L f = flux (erg/s-cm 2 ) L = luminosity (erg/s) Measure f, know L NOT SO EASY! Need a standard candle

10 Light Curve of Typical Cepheid

11 M31 (Andromeda) Edwin Hubble

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13 A03-93; SN 1998bu animation (Peter Challis)

14 Spectra of Sne Ia, II a Also discuss (but don t show) Ib, Ic, IIb

15 Type Ia Supernova White Dwarf An explosion resulting from the thermonuclear detonation of a White Dwarf Star An explosion resulting from the thermonuclear runaway of a white dwarf near M(Chandrasekhar)

16 Type Ia Supernova 03W-220, merger of 2 WDs. But not many WD-WD pairs known, that are close enough to merge in a relatively short time (some SN Ia come from billion year old stars). So consider sub-chandra explosions (Next Slide) but these have problems, too. Thermonuclear runaway of some sort, in any case.

17 Calibrating the Nearly Standard Candle Phillips (1993), Riess + (1995), Hamuy+ (1995): established L vs. light-curve shape correlation with ~ 10 nearby SNe Ia Use it to standardize other SNe Ia Measured colors give reddening and extinction Accurately calibrate individual SNe! Absolute light curves of SN Ia in galaxies of known distance Luminous SNe Ia have slower light curves! MLCS: Multi-color Light-Curve Shape (Riess et al.)

18 log d L σ = 0.44 mag log d L σ = 0.15 mag! (Riess et al. 1995, 1996)

19 SN 1994d

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21 Brian Schmidt (ANU) Nick Suntzeff, Bob Schommer, Chris Smith (CTIO) Mark Phillips (Carnegie) Bruno Leibundgut and Jason Spyromilio (ESO) Bob Kirshner, Peter Challis, Tom Matheson (Harvard) Alex Filippenko, WeidongLi, Saurabh Jha(Berkeley) Peter Garnavich, Stephen Holland (Notre Dame) Chris Stubbs (UW) John Tonry, Brian Barris (University of Hawaii) Adam Reiss (Space Telescope) Alejandro Clocchiatti (Catolica Chile) Jesper Sollerman(Stockholm) S. Perlmutter, G. Aldering, S. Deustua, S. Fabbro, G. Goldhaber, D. Groom, A. Kim, M. Kim, R. Knop, P. Nugent, (LBL & CfPA) N. Walton (Isaac Newton Group) A. Fruchter, N. Panagia (STSci) A. Goobar (Univ of Stockholm) R. Pain (IN2P3, Paris) I. Hook, C. Lidman (ESO) M. DellaValle (Univ of Padova) R. Ellis (CalTech) R. McMahon (IofA, Cambridge) B. Schaefer (Yale) P. Ruiz-Lapuente (Univ of Barcelona) H. Newberg (Fermilab) C. Pennypacker

22 Cerro Tololo Inter-American Observatory, Chile

23 (CTIO)

24 Searching by Subtraction

25 W. M. Keck Observatory, Hawaii (two 10-meter telescopes)

26 Keck LRIS, 1 hour Low-z and High-z SN Ia

27 3 HST supernovae Fainter than expected. So faint that they are farther than they could have been, if Universe decelerating or expanding with constant speed. Therefore, Universe must have accelerated. Cosmic antigravity! Let me explain in more detail

28 Observer s version: Ω Μ < 0?! Ω M 1 >1 log distance Hubble s law, v = H 0 d (v = cz) log z (redshift)

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30 Cosmological Const. Other galaxy Milky Way galaxy

31 Observer s version: Λ > 0?! Ω M 1 >1 log distance Hubble s law, v = H 0 d (v = cz) log z (redshift)

32 log d L Pre-1998 data: Riess et al. (1998) blue dots Perlmutter et al. (1999) red dots [Δ (log d L )] High-z data: fainter than flat or low- Ω M Univ.

33 Pre-1998 data: Riess et al. (1998) Perlmutter et al. (1999) A nonzero cosmological constant!?

34 THE ACCELERATING UNIVERSE (1998) High-z Team, Sep SCP, June 1999 et al. (AVF, )

35 (SDSS, other LSS studies, and measurements of clusters: large majority agree that Ω M = 0.3 ± 0.1)

36 CMB sky if different geometries

37 (2000/ 2001) LSS Clusters, large-scale structure: Ω M = 0.3 ± 0.1 (CMB) Concordance: (Ω M, Ω Λ = (0.3, 0.7)

38 WMAP CMB Map of the Early Universe, t = 380,000 years old

39 Riess et al. (2004), using all published high-z SN Ia data. SN Ia + LSS: Ω M = 0.28, Ω Λ = 0.72 Precision comparable to CMB + LSS Ω Μ = 1 ruled out at very many σ!

40 Probing the era of deceleration

41 Scale factor a(t) Note: 1+z = a(t 0 ) / a(t) z = redshift "Cosmic Antigravity" (Ω Λ > 0) (Ω M = ρ ave /ρ crit ) Empty(Ω M =0) Low (Ω M =0.3) Medium (Ω M =1) Dense (Ω M > 1) t 0 (now) Time t

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43 (mag) log d L (Riess et al. 2007)

44 He retained the cosmological constant after Einstein & de Sitter (1932) had renounced it. Advocated a model with Λ in which the expansion initially decelerates and later accelerates (Lemaître 1934)! Georges Lemaître ( ) Among other things, this might remove a conflict between the known ages of stars and the expansion age of the Universe.

45 (Expansion removed) Evolution of Universe: simulation (A. Kravtsov)

46 Simulated 3D flight through Universe (V. Springel) (Expansion removed)

47 A5er%Planck% Average Composition of the Universe (nonbaryonic) Dark%ma1er%% 25%% Ordinary%ma1er% 5%% (atoms) Dark%energy%% 70%%

48 Studies of Universe s Expansion Win Physics Nobel Johns Hopkins University; University Of California At Berkeley; Australian National Univers From left, Adam Riess, Saul Perlmutter and Brian Schmidt shared the Nobel Prize in physics awarded Tuesday. By DENNIS OVERBYE Published: October 4, Nobel Prize in Physics

49 Dec. 8, pm: High-z Team celebratory lunch

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52 The 2015 Breakthrough Prize in Fundamental Physics

53 Since dark energy seems real SN Ia CMB (WMAP, Planck) + ISW, X-ray Clusters LSS what is it?

54 Λ, the Cosmological Constant? Not good quantitative agreement with theoretical expectations! Way too small (Ω Λ 0.7), and Why now? A bone in the throat. Steven Weinberg

55 Define w = P/(ρc 2 ) Equation-of-state parameter ρ (volume) (1+w) w = 0 for normal nonrelativistic matter w = 1/3 for photons w = 1 for Λ w 1 for quintessence, etc. (rolling scalar field, etc.; 1/3 for cosmic strings). In GR, gravitational acceleration (ρc 2 + 3P). If w < 1/3, the Universe accelerates!

56 (mag) Difference in apparent SN brightness vs. z ΩΛ = 0.70, flat universe

57 Betoule et al. (2014) SDSS-II + SNLS joint analysis log d L 0.01 Redshift z Redshift z

58 (Betoule et al. 2014) (Planck+WP: Planck CMB temperature fluctuations, WMAP CMB polarization. JLA: SNLS-SDSS joint SN Ia light-curve analysis. BAO: baryon acoustic osc.)

59 Time-dependent w? Assume w(a) = w 0 + w a (1 a), where a = 1/(1+z) is a scale factor (Linder 2003). For Λ: w 0 = 1 and w a = 0

60 (Betoule et al. 2014)

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62 The Most Recent Surprise The current rate of expansion still might be too high!

63 Planck satellite map of the early Universe, t = 380,000 years old

64 Planck team, 2015, power spectrum

65 CMB: Measure θ s; know r s (r s = sound horizon length) The angular diameter distance is defined as D A = r s /θ s. (z* = redshift of CMB = 1079)

66 Planck Data: Predict Current Expansion Rate (H 0 ) H 0 = ± 0.62 km/s/mpc (67.8 ± 0.9 km/s/mpc) Previous direct measurements: H 0 = (70 75) ± (4 7) km/s/mpc Possible conflict, but not clear: error bars large and uncertain

67 Planck team, 2015 paper

68 SH0ES (Riess et al. 2005, 2009a,b, 2011, 2014, 2016; see also Macri Hoffman+ 2016, Macri+ 2017) Goal: Measure current value of H 0 to ± 1%, through direct parallaxes of Galactic Cepheids, Cepheid calibration of SN Ia host galaxies, and SN Ia Hubble diagram. Latest results: Riess et al. (2016):

69 SN 1994d

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72 With Cepheids and SNe Ia, we (Riess+ 2016) Measured Current H 0 H 0 = ± 1.74 km/s/mpc Planck: H 0 = 67.8 ± 0.9 (66.93 ± 0.62), ~3σ from Cepheid/SN Ia There may be a conflict! We have smaller uncertainties than before, and we think we understand them very well.

73 Measurements of H0 Planck 2015: ± 0.62 (0.9%) ± 1.74 (2.4%) Riess et al Possible explanations Relaxing constraints; e.g., flatness? Evolving dark energy equation of state? (but data suggest w ~ -1) >3 neutrino species? ("dark radiation") Technique errors? New physics? (GR wrong? Weird DM?) Need independent methods to overcome systematics.

74 H0LiCOW: H0 Lenses in COSMOGRAIL s Wellspring Bonvil et al. (2017) and 4 other papers: use measured time delays in distinct images of gravitationally lensed QSOs

75 Strongly lensed quasars (QSOs) QSOs are powered by accretion into SMBH Light emitted from quasars changes in time ( flickers ) Q length - length

76 The H0LiCOW QSO Sample

77 Current Expansion Rate (H 0 ) H0LiCOW: H 0 = 72.8 ± 2.4 km/s/ Mpc (Bonvin et al. 2017; 3 lenses) H 0 = ± 1.74 km/s/mpc (Riess et al. 2016; SNe Ia + Cepheids) Planck: H 0 = 67.8 ± 0.9 (66.9 ± 0.6) A new, very light, fundamental subatomic particle (neutrino?) exists?! Dark radiation?!

78 ?! Stay tuned!

79 Thank You! Vatican Observatory (invitation to speak) National Science Foundation (NSF) Nat. Aeronautics & Space Adm. (NASA) US Department of Energy AutoScope Corporation TABASGO Foundation (Wayne Rosing) Sylvia and Jim Katzman Foundation Gary and Cynthia Bengier Christopher R. Redlich Fund Richard and Rhoda Goldman Fund

80 bh bh 2 Evidence)for)a)systema3c)error)in)the)Planck)CMB)data?) G. E. Addison 0.13 et al. Claimed 2.5 σ Tension Between Halves of Planck CMB ch 2 data, l>1000 vs l< (WMAP) Addison, Huang, Watts, Bennett, 0.13 Halpern, Hinshaw, Weiland 2016, ApJ, 818, 132 Planck Team, arxiv: σ 0.11 like 1.8 σ for 6 parameters, but we measure H 0! ch MC MC log(10 10 As) m log(10 10 As) H0 m ns ns Planck TT apple ` < H Ase H Ase Planck TT apple ` Planck TT apple ` < 1000 Planck TT apple ` apple 2508 igure 2. Marginalized 68.3% confidence CDM parameter constraints from fits to the ` < 1000 and ` 1000 Planck TT spectra. H e replace Figure the prior 2. on Marginalized with fixed values 68.3% of confidence 0.06, 0.07, 0.08, CDM and 0.09, parameter to more constraints clearly assess from the e ect fits tohas the on` other < 1000 parameters and ` in 10 th H 0

81 Current Status Dark energy exists, or GR wrong. Most data consistent with w 0 = 1, w a = 0: the cosmological constant! But it s possible that dark energy is growing stronger with time (or that there is a new form of relativistic particle: dark radiation ). The future looks hopeful! Larger homogeneous samples, improved techniques (e.g., Gaia parallaxes).

82 However If dark energy really is Λ, we will never know for sure. Cannot prove w 0 = and w a = Can only show w and w a And, it becomes progressively more expensive & time consuming to decrease the error bars.