A Brief History& Future Prospects of Dark Energy
Nao Suzuki (Kavli IPMU)§1: A Brief History of Dark Energy
Discovery Phase§2: SNIa Surveys : Era of Large Survey
Hyper-Suprime Cam SNIa Survey§3: Future Prospects on Dark Energy
in High Precision Era

Precision Cosmology : From Big Bang to Dark Energy
Nao Suzuki (Kavli IPMU, Univ of Tokyo)
Dark Energy
SNIa Cosmology
BBN:D/H

Hubble Diagram

HSTKeckSubaru

Lick

SNIa Spectra

SDSS Quasar

Acceleration

SDSS Quasar
Fundamental
Standard StarThe First Three Minutesby Steven Weinberg (1976)

From log scale to linear scale
Precision Cosmology on Big Bang Nucleosynthesis

Schram & Turner 1997

Kirkman et al 2003, my PhD

One Percent Determination of D/H
2017
DI HIarxiv 1710.11129

2003DI HI

The First Three Minutesby Steven Weinberg (1976)2017 : Now we know the Answer

1686±140.2527±0.003

A Brief History ofthe Discovery of Dark Energy• When we were observing at Lick orKeck Observatory, we were gettingphone calls from supernova people• “This supernova is ‘really’ important,could you please observe?”• At Coffee break of Keck Science

Meeting, I complained to supernova
experts that their analysis is inefficient• I was encouraged to apply PD position

Expansion Speed

Mysterious Expansion of the Universe
Deceleration to Acceleration
Dark Energy is not well understood…

ractional Error

Now

7Gyr Ago

12Gyr Ago
Big Bang
Not WellConstrainedEinstein’s ΛKosmologische Betrachtungen zur allgemeinen
Relativätstheorie (1917) : 100 Years!!!

• Poisson’s Equation2∇ φ = 4πκρ

• Rewriting a Poisson’s Equation with λ2∇ φ − λφ = 4πκρ• where λ denotes the universal constant. If ρ be
the uniform density of distribution of mass,
then4πκφ=−λρ0Tinsley predicted Λ universe
A Brief History of Dark Energy
Hints of Dark Energy• Zeldovich 1967 : 50 Years!!!
Vacuum Energy could be responsible for cosmologicalconstant• Tinseley (1975-1978)• Alcock Paczynski Test (1979)• Galaxy Number Counts (1985-95)• Globular Cluster Age, Galaxy Chemical Evolution(IAU meeting in Kyoto, 1997 Summer)• Concordance Model (‘90s)
11

Stirling Colgate (1925-2013)1980 Paper on SNIa

Adventure of Luis Alvarez (1911-88)
Nobel Prize 1968

Science, 167, 832 (Feb 1970)

Detected!!! Nature Nov 2017

LBNL Team on Fukushima Nuclear Power Plant
2015 March 20th
Probe the status of Nuclear Fuels inside the system

Lawrence Berkeley National Lab
Department of Energy : Building 50, 5F：• Nuclear Physics• Dinosaur Extinction• Climate Change Perlmutter• CMBAlvares• Dark Energy

SmootMullerDinosaur extinction

Dinosaur Extinction
Key Signature : Iridiumwith Walter Alvarez (Geology)

George Smoot, Postdoc of Luis Alvarez
Nobel Prize（2006）CMB fluctuation detection by COBE
Detection of CMB fluctuations
Quantum Mechanics + Cosmology

Climate Change : Global Warming
Richard Muler

20

Thesis Advisor : Richard Muler
Grad Student : Saul Perlmutter
PhD Thesis“An Astrometric Search for a Stellar
Companion to the Sun” PhD 198621

Supernova Cosmology Project
1986-199222

Discovery Phase ‘90s

• SN 1987A stimulated a search for supernovae• Inspired by Colgate’s paper, supernova
cosmology team was formed, but not focusedon SNIa yet• Phillips Relation directed to observe SNIa
• CCD + Keck (10m)+ Hubble Space Telescope

No Results for 4 years
Budget Crisis in 1992
Bob Cahn（LBNL)
Physics Division Director

Rise of Type Ia Supernova Cosmology
Phillips Relation (1993)
Brightness is Constant

Chandrasekah Mass Limit
Type Ia Supernova
always explodes at
1.4 Solar Mass

1910-1995

Supernova Cosmology Project:
SNIa +HST+Large Telescopes with CCDs
Phillips (’93), HST(’90), Keck (’92) ,VLT & Subaru (’98)

Saul Perlmutter

29

Discovery of Dark Energy (SCP 1997)
Gerson Goldhaber reported non-zero Λ
September 24th in 1997 : 20 Years ago!!!

m: Observed
Brightnessz:Redshift

N : Number ofSupernova

Omega m : Density ofMatter

Discovery of Dark Energy (SCP 1997)
m: Observed
Brightness

Gerson GoldhaberΛ is needed！
1997 Sep 24th
Einsteins Equation

z:Redshift
Hubble ConstantObserved magnitude (Brightness)
is a function of cosmological model
Note: Omega Lambda does not depend on H0

High-z Team : Fall 1997
Adam Riess, Brian Schmidt et al.

42 Supernovae
SCP vs High-Z team

Zero Lambda is getting excludedSupernova Survey 2000-2010
Era of Large Survey• ESSENCE• SNLS (SuperNova Legacy Survey)• SDSS-II• Compilation of Different Surveys• Development of Better Templates (SALT2)• Rise of Systematic ErrorsHST Cluster SN Survey
HSTKeckVLT

Nao Suzuki & SCP
PI: Saul PerlmutterSubaru

SNIa Spectral Diversity

SN Factory, Palomar Transient Factory (PTF),
SuperNovaLegacySurvery (SNLS),
Suprnova Cosmology Project (SCP)

SCP
SNLS

• Hubble Diagram and Pictures
SNFPTFΛ in 2011
Combination of SNe with:BAO (Percival et. al., 2010)
CMB (WMAP-7 year data, 2011)
For a flat Universe:

LCDM:
Ωm = 0.271 ± 0.012(stat) ± 0.014(sys)with curvature:oLCDM:
Ωk = 0.002± 0.005(stat) ± 0.005(sys)
Dark Energy
ΩL = 0.729 ± 0.012(stat) ± 0.014(sys)５σ detection！99.99999%で53

Nobel Prize in 2013:Higgs Particle• Being First ： LHC• Two Independent Detections：ATLAS & CMS• Precision : 99.99997%（５σ）

Dark Energy
Discovery of Accelerating Universe
Nobel Prize in Physics 2011

2σ in 1997

5σ inSuzuki et al2011• 70% of Energy in the Universe is in

the form of mysterious Dark Energy

Era of Large Surveys: 2010-2020• Pan Starrs• Dark Energy Survey (DES)• Carnegie Supernova Project (CSP)• Subaru Hyper-Suprime Cam Survey• LSST• WFIRSTSubaru Telescope HSC Survey
Hyper-Suprime Cam :• Mauna Kea, Hawaii• Elevation 4200m• Mirror Size=8.2m• HSC Installed in 2012
• 104 CCD (4K x 2K)• 832 Mega pixels• 5 Year Project (2014-19)• 300 Dark Nights• 500 TB of Survey Data

Future is now! HSC DR1Hyper Suprime-Cam SSP Data Released

http://hsc.mtk.nao.ac.jp/ssp/data-release/

Subaru SSP HSC Supernova
Cosmology in 2016-18
2 Seasons : COSMOS & SXDSHSTKeck

VLTSubaru• Deepest and Best Data Set• Keck/VLT/Gemini/HST Followup is scheduled• Machine Learning is taking place(NTT + ISM)HSC Observation• Aiming Statistical Error of 2% in
distance at 10 billion light years
away, w/ HST=>0.5%• Most Precise Measurement ofDark Energy

Towards Science Applications
Spectroscopic Follow-up Procedures
Large Telescopes
Subaru : HSC
SNIa : Dark Energy
100,000 Candidates
ML Selection
HSC Imaging

10 SN Targets
Spectroscopy
Shock Break Out

100 SN Candidates

Active Galactic Nuclei
Black Hole ScienceHSC Transient Sciences
Common Interest: How to find Transients?
Transients : Time Variable ObjectsSupernova, Variable Star, Active Galaxy, Asteroids

Observation

Image Processing

Processed Image

Image Comparison through Machine Learning
CREST collaboration : NTT, ISM, Tsukuba Univ
Bogus vs Real = 100,000:100
Bogus

OldNewSubOld

NewSupernova

Sub

Hubble Space Telescope(HST) Time is awarded
Cycle 24-25 (2016-2018)
Infrared Part is Observed by Hubble Space Telescope(HST)
Optical Part is Observed by Subaru (HSC)

HSTHSC

HSC Supernova Survey : Nov ‘16 - Apr‘17z=1.06

Hubble Telescope

Dec 25 2016

Subaru Telescope

Nov 23 2016 - Jan 3 2017
HSC-HST SN Survey

Hubble Space Telescope reduces the scatter dramaticallyand enhances Figure of Merit
With HST, HSC SNIa Cosmology becomes very strong!

FoM can be increased

Uncertainty in Color
Scatter in Hubble Diagram

Color Error

w/ or w/o HSC+HST

Blue : HSC only
Red : HSC+HST

Nicolas Renault (LPNHE)
Redshift
3% Error x 2 (beta)/ sqrt(49 SNe) x 0.461=0.4% Stat Error

HSC: r2, i2,z vs HST WFC3 : F105(J), F140(H)Subaru/HSC (Optical)

Hubble Space Telescope (IR)

HSC: r2, i2,z vs HST WFC3 : F105(J), F140(H)Subaru/HSC (Optical)

Hubble Space Telescope (IR)

HSC: r2, i2,z vs HST WFC3 : F105(J), F140(H)Subaru/HSC (Optical)

Hubble Space Telescope (IR)

HSC: r2, i2,z vs HST WFC3 : F105(J), F140(H)17siv : z=1.234 SNIa, 8.57 G light years
Subaru/HSC (Optical)
Hubble Space Telescope (IR)10-15% Color Measurement

1-3% Color Measurement

HSC discovered 26 SNeIa (1st season)
observed by Hubble Space Telescope

Science Applications : Timing is Everything
Spectroscopic / Space Follow-up : (2016-2018)
Choose the very best ones (50 supernovae from 100,000 candidates)
10 Gps

HSC Observation
100,000 Candidates
ML Selection I
Real vs Bogus

Big Island

100 GpsOahuSeattle

1200 CoreImage
Processing

Tokyo

SI-Net 5 100 Gps
IPMU
in 10 sec

HST/JWST
ML Selection II Best 10 Targets
Typing
Photo-z
Keck : in 1 hour
Best One!
100 SN Candidates
Spectroscopic Follow-up

Type Ia Supernova Cosmology
with 46 HSC/HST SNeIa at z>1.0
we can be competitive against 2000 DES SNeDES: Dark Energy Survey (5 year Program)Figure of Merit (FoM)
Final FoM=58 (1% calibration Error), FoM=80 (0.5%)
WR : weather recovery, DES: Dark Energy Survey WFC3=HST
JLA : Current SNIa Compilation, N300: Low-z SNIa

Our Program
Our Competitor DESHyper-Suprime Cam Supernova Survey
Supernova Observations 1990-2015
SubaruHSTKeckVLT• Since its discovery in 1997,
Faintnearly 1000 supernovae areobserved for dark energy• Subaru Telescope (Hawaii)
HSC Observation

deployed the largest digital
camera named Hyper
Supreme Cam (HSC)

Bright• We aim to observe the mostdistant supernovae with
HSC and Hubble Space
Telescope

NearFarHyper-Suprime Cam Supernova Survey
Season III : 2018-19 Spectroscopic Follow-up
SubaruHSTKeckVLT• We will need spectra ofFaintsupernova host galaxies for
precise measurement of thedistances• Subaru Telescope deploys a
HSC Observation

new instrument called PFS,
it will tighten themeasurement of distances

Bright• We continue to work withlarge telescopes forspectroscopic follow-up

NearFarHSC+HST legacy Survey

Fractional Error

Distance

SNIa Cosmology in 2017-2025
1-2% error in distance• 1.0 < z < 1.4 70-100 HSC SNeIa• HSC+HST 46 SNeIa can becomecompetitive against 2000 DES SNeRedshiftToday

This Program• Keck/VLT/Gemini/HST Follow-up• Aiming to have 0.5% calibration
error => 1.0% distance error

2020• Our Data can survive in LSST era• LSST-Subaru-WFIRST model :2025-30• Calibration Workshop at Kavli

Future is Now
IPMU

SNIa Cosmology Today

Stat = 3.2%
Sys = 2.4%

1049 SNeIa : w=-1.031 +/- 0.04 (stat + sys)

Scolnic et al. 2017

Origin of Systematic Uncertainties

Betoule et al 2014

Discovery of Perfect Black Body Spectra:SDSS
found as a Quasar Target
Only 17 stars out of a million stars(Suzuki & Fukugita 2017)• DR8 : 605,772 stars => 5 stars• DR9 : 110,929 stars=> 9 stars• DR10: 81,892 stars=> 10 stars
SDSSGALEXGAIA will tell us precise radius

JWST F444W

JWST F356W

JWST F277W

JWST F200W

JWST F150W

JWST F115W

Looking at the Future with JWST
today 0.3%, but we can do 0.1%

Future Prospects
TMT (2027)
30m

JWST Space Telescope
2018

LSST

20TB/DayWFIRSTEuclid

Science Case :SNIa 5σ Events for WFIRST (GO)Gravitationally Lensed Supernova
SN Rafsdel z=1.49
Lensing Galaxy : z=0.54•

SNIa : Great Advantage ofhaving luminosity estimate
to test lens models•

WFIRST is needed toresolve lensed point sourcesand good photometry•

Lensed SNIa : PS1-10afx
is identified by Quimby etal but was not resolved

Science Case:
Holy Grail : First Star Explosion
Pair-Instability Supernova

Can we see them with HSC?
Detectability of high-z SLSN (Tanaka et al 2012)iz

HSCDR1

Can we find them with HSC/LSST?

WFIRST DEEP

HSC/LSSTWFIRST : FoV : 0.28 deg2

Tanaka et al 2012

JWST : NIRcam FoV 4.4x2.2 arc min =0.0026 deg2

What’s Next? Future is Bright!
be first, be best and be unique• BAO• SNIa• Weak Lensing• CMB B-Mode• Gravitational Wave
• GAIA Astrometry• 21cm Cosmology• The universe is big! New discovery iswaiting for you! (Shri Kulkarni)• Sky is for everyone! (Bob Williams)• Learn History and explore a new field (DavidWeinberg)

88In other words: We mortal, limited humans joining together in teams
from around the world, and in time across civilizations, become
capable – in our case, capable of just glimpsing one additional bit of
how the universe works. It is exhilarating,
But it is in the doing, in the process of working together to explore
the universe that we learn to truly appreciate each other, and to enjoyeach other's company and ... spark, as all humans should beappreciated. – And that, too, is exhilarating.

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