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 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 Georges what became known as the Lemaître Big Bang theory of the origin of the universe, which he called his ‘hypothesis of the primeval (1894 − 1966) atom’ or the ‘Cosmic Egg.’[9]” Vesto Slipher Edwin Hubble 1917 (1922, 1923) 1929
(NASA/STScI/G. Bacon)
Observed low-redshift Hubble diagram (ideal): ) distance (
log d
Hubble’s law, v = H0d (v = cz)
log z (redshift) Scale factor (ΩM = ρave/ρcrit) a(t) Empty (ΩM=0) Low (ΩM=0.3) Medium (ΩM=1)
Dense (ΩM > 1)
t0 (now) Time t a(t0) Redshi z=0 Note:
1 + z = a(t0)/a(t) z = redshi
Redshi z = 1 Lookback mes for the various models
at fixed redshi
>1)
M
Dense Ω ( t Age t0 (now) Observer’s version: 0 0.3 ΩM 1 >1 log distance
log z (redshift)
Determining the Hubble Diagram • Redshift: easy to measure from galaxy spectrum • Distance: “Luminosity distance” dL L
f = 2 4π dL f = flux (erg/s-cm2) L = luminosity (erg/s)
• Measure f, “know” L – NOT SO EASY ! – Need a “standard candle” Light Curve of
Typical Cepheid
M31 (Andromeda)
Edwin Hubble
A03-93; SN 1998bu animation
(Peter Challis) Spectra of Sne – Ia, II a
Also discuss (but don’t show) Ib, Ic, IIb Type Ia Supernova
White Dwarf
An explosion resulting from the thermonuclear detonation of a White Dwarf Star 1051 An explosion resulting from the thermonuclear runaway of a white dwarf near M(Chandrasekhar) 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 0.5-1 billion year old stars). So consider sub-Chandra explosions (Next Slide) – but these have problems, too. Thermonuclear runaway of some sort, in any case. Calibrating the Nearly Standard Candle • Phillips (1993), Riess Absolute light curves of + (1995), Hamuy+ SN Ia in galaxies of (1995): established L known distance vs. light-curve shape Luminous correlation with ~ 10 SNe Ia have nearby SNe Ia slower light curves! • Use it to standardize other SNe Ia • Measured colors give reddening and extinction • Accurately calibrate individual SNe! MLCS: Multi-color Light-Curve Shape (Riess et al.) σ = 0.44 ∝ log dL mag
σ = 0.15 ∝ log dL mag!
(Riess et al. 1995, 1996) SN 1994d
• Brian Schmidt (ANU) • Nick Suntzeff, Bob Schommer, Chris Smith (CTIO) S. Perlmutter, G. Aldering, S. Deustua, S. Fabbro, G. Goldhaber, D. Groom, • Mark Phillips (Carnegie) A. Kim, M. Kim, R. Knop, P. Nugent, (LBL & CfPA) N. Walton (Isaac Newton Group) • Bruno Leibundgut and Jason Spyromilio (ESO) A. Fruchter, N. Panagia (STSci) • Bob Kirshner, Peter Challis, Tom Matheson (Harvard) A. Goobar (Univ of Stockholm) • AlexFilippenko , WeidongLi, Saurabh Jha(Berkeley) R. Pain (IN2P3, Paris) • Peter Garnavich, Stephen Holland (Notre Dame) I. Hook, C. Lidman (ESO) • Chris Stubbs (UW) M. DellaValle (Univ of Padova) R. Ellis (CalTech) • John Tonry, Brian Barris (University of Hawaii) R. McMahon (IofA, Cambridge) • Adam Reiss (Space Telescope) B. Schaefer (Yale) • AlejandroClocchiatti ( CatolicaChile) P. Ruiz-Lapuente (Univ of Barcelona) • Jesper Sollerman(Stockholm) H. Newberg (Fermilab) C. Pennypacker Cerro Tololo Inter-American Observatory, Chile
(CTIO)
Searching by Subtraction W. M. Keck Observatory, Hawaii (two 10-meter telescopes) Keck LRIS, 1 hour Low-z and High-z SN Ia
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 Observer’s Ω < 0 ?! version: Μ 0 0.3 ΩM 1 >1 log distance Hubble’s law, v = H0d (v = cz)
log z (redshift)
Cosmological Const.
Other galaxy
Milky Way galaxy
Observer’s Λ > 0 ?! version: 0 0.3 ΩM 1 >1 log distance Hubble’s law, v = H0d (v = cz)
log z (redshift) Pre-1998 ∝ log d L data: Riess et al. (1998) – blue dots Perlmutter et al. (1999) – red dots High-z data: fainter than ∝ [Δ flat or low- (log dL)] ΩM Univ.
Pre-1998 data: Riess et al. (1998) Perlmutter et al. (1999)
A nonzero cosmological constant!? THE ACCELERATING UNIVERSE (1998)
High-z Team, Sep. 1998
SCP, June 1999
et al. (AVF, …)
(SDSS, other LSS studies, and measurements of clusters: large majority agree that ΩM = 0.3 ± 0.1) CMB sky if different geometries (2000/ 2001)
LSS Clusters, large-scale structure:
ΩM = 0.3 ± 0.1 Concor- dance: (CMB) (ΩM, ΩΛ = (0.3, 0.7)
WMAP CMB Map of the Early Universe, t = 380,000 years old Riess et al. (2004), using all published high-z SN Ia data.
SN Ia + LSS: ΩM = 0.28, ΩΛ = 0.72 Precision comparable to CMB + LSS
ΩΜ = 1 ruled out at very many σ! Probing the era of deceleration
Scale "Cosmic factor (Ω = ρ /ρ ) Antigravity" M ave crit a(t) (ΩΛ > 0) Empty(ΩM=0) 0.3 Note: Low (ΩM= ) 1+z = a(t ) a(t) Medium 0 / 1 z = redshift (ΩM= )
Dense (ΩM > 1)
t0 (now) Time t
L (Riess et al. 2007)
∝ log d (mag) 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)!
Among other things, this might remove a conflict Georges between the known ages of Lemaître stars and the expansion age of the Universe. (1894 − 1966) (Expansion removed)
Evolution of Universe: simulation (A. Kravtsov) (Expansion removed)
Simulated 3D flight through Universe (V. Springel) A5er%Planck% Average Composition of the Universe
(nonbaryonic) Dark%ma1er%% 25%%
Ordinary%ma1er% 5%% Dark%energy%% (atoms) 70%% Nobel in Physics Goes to Perlmutter, Schmidt and Riess - NYT... http://www.nytimes.com/2011/10/05/science/space/05nobel.htm...
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Solar Panels for Homes 70% Lower Bills. 50% Rebates Now! Free Home Solar Evaluations. Solar-Energy-Installers.com Johns Hopkins University; University Of California At Berkeley; Australian National University From left, Adam Riess, Saul Perlmutter and Brian Schmidt shared the Nobel Prize in physics awarded Tuesday. Cost of Solar Panels Finance with $0 Down Lease. Lower or Eliminate Electric Bills! By DENNIS OVERBYE AffordableSolarLease.com Published: October 4, 2011 2011 Nobel Prize in Physics California Solar Power Three astronomers won the Nobel Prize in Physics on Tuesday for RECOMMEND 50% Off California Solar Panel Projects. Sign Up for a Free Quote. discovering that the universe is apparently being blown apart by a TWITTER www.Findsolar.com mysterious force that cosmologists now call dark energy, a finding LINKEDIN Quantum Science Pendant that has thrown the fate of the universe and indeed the nature of EHM Quantum Pendant on Sale Now Authentic Scalar Energy COMMENTS Pendants physics into doubt. (126) allthingshealthy1.com
SIGN IN TO Solar for your home The astronomers are Saul Perlmutter, E-MAIL How much does it cost? Get an instant estimate. 52, of the Lawrence Berkeley National ShouldIGoSolar.com Multimedia PRINT Laboratory and the University of SINGLE PAGE Bay Area Solar Energy California, Berkeley; Brian P. Schmidt, Provide Your Home or Business With Thermal and Electric REPRINTS Solar Energy. 44, of the Australian National SolarCraft.com SHARE University in Canberra; and Adam G. Advertise on NYTimes.com Riess, 41, of the Space Telescope Science Institute and Johns Hopkins University in Baltimore. TicketWatch: Theater Offers by E-Mail TimesCast | Nobel Nod to Dark Energy “I’m stunned,” Dr. Riess said by e-mail, after learning of his prize by reading about it on The New York Times’s Web Sign up for ticket offers from Broadway shows and other site.
The three men led two competing teams of astronomers MOST E-MAILED MOST VIEWED who were trying to use the exploding stars known as Type 1. Can Answers to Evolution Be Found in 1a supernovae as cosmic lighthouses to limn the expansion Slime? of the universe. The goal of both groups was to measure Saul Perlmutter on Dark Energy how fast the cosmos, which has been expanding since its fiery birth in the Big Bang 13.7 billion years ago, was
1 of 4 10/4/11 6:40 PM Dec. 8, pm: High-z Team celebratory lunch
The 2015 Breakthrough Prize in Fundamental Physics Since “dark energy” seems real… SN Ia CMB (WMAP, Planck)
+ ISW, X-ray Clusters
LSS
what is it? Λ, the Cosmological Constant? • Not good quantitative agreement with theo- retical expectations!
• Way too small (ΩΛ ≈ 0.7), and “Why now?”
• “A bone in the throat.” – Steven Weinberg Define w = P/(ρc2) • 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 ∝ −(ρc2 + 3P). If w < −1/3, the Universe accelerates! (mag)
Difference in apparent SN brightness vs. z ΩΛ = 0.70, flat universe Betoule et al. (2014) SDSS-II + SNLS joint analysis
L d ∝ log
0.01 Redshift z 0.1 1.0 Redshift z (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.) Time-dependent w?
Assume w(a) = w0 + wa(1−a), where a = 1/(1+z) is a scale factor (Linder 2003).
For Λ: w0 = −1 and wa = 0 (Betoule et al. 2014)
The Most Recent Surprise The current rate of expansion still might be too high! Planck satellite map of the early Universe, t = 380,000 years old Planck team, 2015, power spectrum CMB: Measure θs; know rs (rs = sound horizon length) The angular diameter distance is
defined as DA = rs/θs .
(z* = redshift of CMB = 1079) Planck Data: Predict
Current Expansion Rate (H0)
• H0 = 66.93 ± 0.62 km/s/Mpc (67.8 ± 0.9 km/s/Mpc) • Previous direct measurements:
H0 = (70−75) ± (4−7) km/s/Mpc • Possible conflict, but not clear: error bars large and uncertain
Planck team, 2015 paper
SH0ES (Riess et al. 2005, 2009a,b, 2011, 2014, 2016; see also Macri Hoffman+ 2016, Macri+ 2017)
• Goal: Measure current value of H0 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):
SN 1994d
With Cepheids and SNe Ia, we
(Riess+ 2016) Measured Current H0
• H0 = 73.24 ± 1.74 km/s/Mpc
• Planck: H0 = 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.
Measurements of H0
Possible explanations • Relaxing constraints; e.g., flatness? Evolving dark energy Planck 2015: 66.93 ± 0.62 (0.9%) • 73.24 ± 1.74 (2.4%) equation of state? (but Riess et al. 2016 data suggest w ~ -1) • >3 neutrino species? ("dark radiation")
Technique errors? New physics? (GR wrong? Weird DM?) Need independent methods to overcome systematics. 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 Strongly lensed quasars (QSOs) • QSOs are powered by accretion into SMBH • Light emitted from quasars changes in time (“flickers”)
Q2237+030
length - length The H0LiCOW QSO Sample Current Expansion Rate (H0)
• H0LiCOW: H0 = 72.8 ± 2.4 km/s/ Mpc (Bonvin et al. 2017; 3 lenses)
• H0 = 73.24 ± 1.74 km/s/Mpc (Riess et al. 2016; SNe Ia + Cepheids)
• Planck: H0 = 67.8 ± 0.9 (66.9 ± 0.6) • A new, very light, fundamental subatomic particle (neutrino?) exists?! “Dark radiation”?! ?! Stay tuned!
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 4 G. E. Addison et al. 4 G. E. Addison et al. Evidence)for)a)systema3c)error)in)the)Planck)CMB)data?)
+1.039 +1.039 0.13 4 0.003 G. E. Addison0.13 et al. 0.003 2 2 Claimed 2.5 σ Tension Between Halves of Planck CMB 2 2 0.022 h 0.022 h h h b c MC b c +1.039 0.12 MC 0.002 data, >1000 vs <10000.12 (WMAP) 0.002 ✓ ✓ ⌦ l l ⌦ ⌦ ⌦ Addison, Huang, Watts, Bennett,0.13 Halpern, Hinshaw, Weiland 2016,0.003 ApJ, 818, 132 2 0.020 2 0.022 00..020001 Planck Team, arXiv: 1608.02487—”2.5 σ 0like.11 1.8 σ for 6 parameters”, but we measure 0H.001 ! h 0.11 h 0 b c 0.12 MC 0.002 ✓ ⌦ ⌦ ) ) 0.020 0.001
s 0.11 s 3.1 1.05 3.1 1.05 A A 70 70 0 0 s s 10 10
1.00 ) 1.00 n n s H 3.1 1.05 H
A 65 70 65 0 s
0.95 10 3.0 3.0 1.00 0.95 n H log(10 H log(10 0 60 65 60 3.0 0.95
log(10 1.95 0.4 0.4 60 1.95 ⌧ ⌧ 2 1.90 1.95 2 1.90 0.85 0.4 0.85 ⌧ e e 2 8 m s 8 m
1.90 s
1.85 0.85 1.85 ⌦ A e ⌦ A 8 m s 9
0.3 0.80 1.85 9 0.3 ⌦ 0.80 1.80 A 1.80 10 9
0.3 10 0.80 1.80 1.75 10 1.75 0.06 0.07 0.08 0.09 0.06 0.07 0.08 0.09 00..0606 0.07 0 0..0808 0 0..0909 0.06 0.07 01..0875 0.09 0.06 0.07 0.08 0.09 ⌧ ⌧ 0.06 0.07 0.08 0⌧.09 0.06 0.07 0.08 0.09 0.06 0.07 0.08 0.09 ⌧ ⌧ ⌧ ⌧ ⌧ ⌧ Planck TT 2015 2 ` < 1000 Planck TT 2015 1000Planck` TT2508Planck 2015 2 TT` < 201510002 ` < 1000Planck TT 2015Planck1000 `TT2508 2015 1000 ` 2508 Figure 2. Marginalized 68.3% confidence ⇤CDM parameter constraints from fitsFigure to the 2. `Marginalized< 1000 and 68.3%` 1000 confidencePlanck⇤CDMTT spectra. parameter Here constraints from fits to the ` < 1000 and ` 1000 Planck TT spectra. Here we replace the prior on ⌧ with fixed values of 0.06, 0.07, 0.08, and 0.09, to more clearlywe replaceFigure assess the prior the 2. e on↵Marginalizedect⌧ with⌧ has fixed on values other 68.3% of parameters confidence 0.06, 0.07, 0.08, in⇤ theseCDM and 0.09, parameter to more constraintsclearly assess from the e↵ fitsect ⌧ to has the on` other< 1000 parameters and ` in1000 these Planck TT spectra. Here 2⌧ fits. Asidewe replacefrom the the strong prior correlation on ⌧ with2 with⌧ fixedAs,whicharisesbecausetheTTspectrumamplitudescalesas values of 0.06, 0.07, 0.08, and 0.09, to more clearly assessAse the,dependenceon e↵ect ⌧ has⌧ onis other parameters in these fits. Aside from the strong correlation with As,whicharisesbecausetheTTspectrumamplitudescalesasAse ,dependenceon2 ⌧ is 2⌧ 2 fairly weak.fits. Tension Aside fromat the the> 2 stronglevel is correlation apparent in ⌦ withch andAs,whicharisesbecausetheTTspectrumamplitudescalesas derived parameters, including H0, ⌦m,and 8. Ase ,dependenceon⌧ is fairly weak. Tension at the > 2 level is apparent in ⌦ch and derived parameters, including H0, ⌦m,and 8. 2 fairly weak. Tension at the > 2 level is apparent in ⌦ch and derived parameters, including H0, ⌦m,and 8. rameters to the best-fit values inferred from the fit to the Lensing also induces specific non-Gaussian signatures rameters to the best-fit values inferred from the fit to the Lensingwhole alsoPlanck inducesmultipole specific range non-Gaussian rather than allowing signatures them in CMB maps that can be used to recover the lens- whole Planck multipole range rather than allowing them in CMB mapsrameters that can to the be best-fit used to values recover inferred the lens- from the fit to the Lensing also induces specific non-Gaussian signatures to varywhole separatelyPlanck in themultipole` < 1000 range and rather` 1000 than fits. allowinging potential them powerin CMBspectrum maps (hereafter that ‘ canspectrum’). be used to recover the lens- to vary separately in the ` < 1000 and ` 1000 fits. ing potentialThis helps power break spectrum degeneracies (hereafter between ‘ foregroundspectrum’). and Planck Collaboration XV (2015) report a measurement This helps break degeneracies between foreground and Planck⇤ CollaborationCDMto parameters vary separately XV and (2015) leads in report to the small` a< shifts measurement1000 in ⇤ andCDM` 1000of the fits. spectruming using potential temperature power andspectrum polarization (hereafter ‘ spectrum’). This helps break degeneracies between2 foreground and Planck Collaboration XV (2015) report a measurement ⇤CDM parameters and leads to small shifts in ⇤CDM of the parameterspectrum agreement, using temperature with the tension and in polarization⌦ch decreas- data with a combined significance of 40 .The 2 ing to 2⇤.3CDM for ⌧ parameters=0.07 0.02, and for example. leads to The small best-fit shifts inspectrum⇤CDM tightlyof constrains the spectrum the parameter⇠ using combination temperature and polarization parameter agreement, with the tension in ⌦ch decreas- data with2 a combined significance± of 40 .The 2 0.25 ing to 2.3 for ⌧ =0.07 0.02, for example. The best-fit spectrum is, tightlyparameter however, constrains worse agreement, by the 3.1 parameter and with 4.8⇠ thefor combination the tension` < 1000 in ⌦ch decreas-8⌦m . We computeddata with constraints a combined on this same significance combi- of 40 .The 2 ± 0.25and ` ing1000 to 2 fits,.3 respectively,for ⌧ =0.07 reflecting0.02, for the example. fact that Thenation best-fit from PlanckspectrumTT data tightly using constrains a ⌧ =0.07 the0.02 parameter⇠ combination is, however, worse by 3.1 and 4.8 for the ` < 1000 8⌦ . We computed constraints on this same combi- ± m the ` < 21000is, and however,` 1000 worse data by± mildly 3.1 prefer and 4.8 di↵erent for the `prior:< 1000 ⌦0.25. We computed constraints on this same combi- and ` 1000 fits, respectively, reflecting the fact that nationforeground from Planck parameters.TT data Overall using the a choice⌧ =0 of.07 foreground0.02 8 m and ` 1000 fits, respectively, reflecting± the fact ⌦ that0.25 =0.591nation0.021 from (PlanckPlanck2015 TT), data using a ⌧ =0.07 0.02 the ` < 1000 and ` 1000 data mildly prefer di↵erent prior: parameters does not significantly impact our conclusions. 8 m ± ± foreground parameters. Overall the choice of foreground the ` < 1000 and ` 1000 data mildly prefer di↵erent=0.583prior:0.019 (Planck 2015 TT ` < 1000), ⌦0.25 =03.1..591Comparing0.021 temperature (Planck 2015 and lensing), spectra ± parameters does not significantly impact our conclusions. 8 m foreground parameters. Overall the choice of foreground=0.662 0.0200.25 (Planck 2015 TT ` 1000). ± 8⌦m =0.591 0.021 (Planck 2015 ), Planck=0parameters.583 Collaboration0.019 does (Planck XIII not (2015) significantly2015 found TT that` < impact allowing1000), our a conclusions. ± ± (1) 3.1. Comparing temperature and lensing spectra non-physical± enhancement of the lensing e↵ect in the TT =0.583 0.019 (Planck 2015 TT ` < 1000), power=0 spectrum,.6623.1.0.020 parametrizedComparing (Planck temperatureby2015 the TT amplitude` and1000) param- lensing. spectraThe ` < 1000 and ` 1000 TT values± di↵er by 2.9 , Planck Collaboration XIII (2015) found that allowing a ± 2 eter AL, was e↵ective at relieving the tension between(1) consistent with the di↵erence=0 in.662⌦ch discussed0.020 (Planck above. 2015 TT ` 1000). non-physical enhancement of the lensing e↵ect in the TT the low andPlanck high Collaboration multipole Planck XIIITT (2015) constraints. found For that allowingThe ` a1000 and values are in tension± at the 2.4 (1) power spectrum, parametrized by the amplitude param- The `
• Most data consistent with w0 = −1, wa = 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). However… • If dark energy really is Λ, we will never know for sure.
• Cannot prove w0 = −1.0000000… and wa = 0.0000000…
• Can only show w0 ≠ −1.0000000… and wa ≠ 0.0000000… • And, it becomes progressively more expensive & time consuming to decrease the error bars.