Cosmology from Gravitational
Lens Time Delays
Kenneth WongEACOA Fellow
National Astronomical Observatory of Japan

East Asia Young Astronomers Meeting 2017
November 15, 2017

The Standard Model of Cosmology
Important Parameters
H0 - sets expansion rate of universe
Ωm - matter densityΩΛ - dark energy density
Ωk - curvaturew - dark energy equation of state parameterStandard model is the “flat ΛCDM”
cosmology, where Ωk = 1-Ωm-ΩΛ = 0, w = -1
Extensions to flat ΛCDM include nonzero
curvature, w ≠ -1, time-varying w, different
number of relativistic neutrino species, etc.
Planck mission measures cosmologicalparameters by observing the cosmic
microwave background (CMB)

Kenneth Wong (NAOJ)

EAYAM
11/15/2017

Independent H0 Measurements
Planck Collaboration (2016)•The Hubble Constant (H0) sets theexpansion rate of the universe•

Planck flat ΛCDM results suggest an
H0 value lower than othermeasurements•

Independent distance ladder results(Riess+2016) favor a higher H0•Tension? New physics? Need more
precise and accurate measurementof H0

Kenneth Wong (NAOJ)

Riess+2016

EAYAM11/15/2017

Strong Gravitational Lensing•

Background object (source) magnified
by foreground object (lens)•Multiple images → create lens model•

What can we learn about lens andsource?
Total mass (within Einstein radius)
Mass profile slope
Ellipticity/orientation
Intrinsic (unlensed) source flux
Can detect/resolve source features
by taking advantage of magnification
Cosmology!

Image credit: ASIAA EPO
Movie credit: Y. Hezaveh
Kenneth Wong (NAOJ)

EAYAM
11/15/2017

Gravitational Lensing Time Delays••••

If source is variable, there is a “timedelay” between the multiple images
Can determine “time-delay distance”,
inversely proportional to H0
One-step method to infer H0, independentof CMB and distance laddere.g., lensed supernovae (e.g. Kelly+2015,Goobar+2016), but very rare!

Time delay Lens potential (from mass model)

SNe “Refsdal”

1t = D t lenscTime-delay distanceD t / H0
Kenneth Wong (NAOJ)

1EAYAM
11/15/2017

Gravitational Lensing Time Delays•Lensed quasars-•variable on short timescales (~days)
can be monitored to measure time delay
bright and easy to detect

To constrain H0, need:-Measured time delay
Accurate lens model
Estimate of mass along line of sight (LOS)Time delay Lens potential (from mass model)

1t = D t lenscTime-delay distanceD t / H0
Kenneth Wong (NAOJ)

1EAYAM
11/15/2017

H0LiCOW: H0 Lenses in
COSMOGRAIL’s Wellspring•Detailed analysis of five time-delaylenses (Suyu+2017)
long term monitoring fromCOSMOGRAIL
high-resolution HST imaging for
detailed lens modelingimaging/spectroscopy tocharacterize mass along line of sight•

Will constrain H0 to < 3.5% precision•

Four additional lenses tentatively will beadded to sample (~2% precision on H0)•First two lenses previously analyzed(Suyu+2010, 2013), latest results on 3rdlens, HE 0435-1223

B1608+656

RXJ1131-1231 HE 0435-1223

WFI2033-4723

Kenneth Wong (NAOJ)

HE 1104-1805
EAYAM
11/15/2017

Latest Results from HE0435•

Extensive dataset
HST imaging in 3 bands (F555W, F814W, F160W)
13-year monitoring by COSMOGRAIL for accurate
time delays
Lens velocity dispersion from Keck/LRIS to mitigate
lens model degeneracies
Spectroscopic data on LOS galaxies to get
perturber redshifts
Multiband photometry to get photo-zs and stellar
masses of LOS galaxies•

Full analysis and results:
Sluse+2017 (LOS galaxy spectroscopy)
Rusu+2017 (LOS photo-zs/stellar masses)
KW+2017 (Lens model)
Bonvin+2017 (Time-delay measurements)

Kenneth Wong (NAOJ)

EAYAM
11/15/2017

Accurate Time Delays•••

COSMOGRAIL: long-term monitoring of time-delay lenses using
small (1-m and 2-m) telescopes (Courbin+2011)
Well-tested algorithms for time-delay measurements (Tewes+2013)
Time delays of HE0435 from 13 years of monitoring (Bonvin+2017)- Long time baselines needed to minimize effects of microlensing

Bonvin+2017

Kenneth Wong (NAOJ)

EAYAM
11/15/2017

Lens Model•••••

Accurate lens model using 3-bandof HST imaging (KW+2017)
High-resolution needed to model
quasar host galaxy
Account for nearby perturber using
multi-plane lensing formalism
Influence of LOS perturbations
from weighted galaxy number
counts (Rusu+2017)
Velocity dispersion of lens galaxy
from Keck/LRIS spectrum to breakmodel degeneracies
KW+2017Kenneth Wong (NAOJ)

EAYAM
11/15/2017

Blind Analysis

KW+2017
Kenneth Wong (NAOJ)

EAYAM
11/15/2017

Results from HE0435

KW+2017

KW+2017
Kenneth Wong (NAOJ)~8% constraint on DΔt+5.7
H0 = 73.1 6.0 km/s/Mpc
for flat ΛCDM cosmology
EAYAM
11/15/2017

Combined Results from 3
H0LiCOW Lenses

Bonvin+2017~3.8% precision on H0 from 3 H0LiCOW lenses+2.4
H0 = 71.9 -3.0 km/s/Mpc for flat ΛCDM cosmology

Kenneth Wong (NAOJ)

EAYAM
11/15/2017

Combined Results from 3
H0LiCOW Lenses
Riess+2016Kenneth Wong (NAOJ)

EAYAM
11/15/2017

Ongoing/Future WorkWFI2033-4723••

Analysis of WFI2033 ongoing,
HE1104 to follow
Four additional lenses with timedelays and HST data- ancillary data (velocity dispersion,
LOS spec/photo) in progress- full sample of 9 lenses will
constrain H0 to ~2%

Data

Model

Kenneth Wong (NAOJ)

EAYAM
11/15/2017

Ongoing/Future Work••

Analysis of WFI2033 ongoing,
HE1104 to follow
Four additional lenses with timedelays and HST data- ancillary data (velocity dispersion,
LOS spec/photo) in progress- full sample of 9 lenses will
constrain H0 to ~2%

Kenneth Wong (NAOJ)

EAYAM
11/15/2017

Summary•••••Time-delay lenses are a one-stepprobe of H0, independent of the CMB
and the distance ladder
Blind analysis of HE0435- time delays from COSMOGRAIL- deep HST imaging- wide-field imaging & spectroscopy- velocity dispersion from Keck/LRISWith 3 time-delay lenses from+2.4
H0LiCOW: H0 = 71.9 -3.0 km/s/Mpc inflat ΛCDM
Full H0LiCOW sample: H0 to < 3.5%
precision from 5 lenses (possibly ~2%
precision from 9 lenses)
Current and future surveys will findthousands of new time-delay lenses,
providing competitive probe ofcosmology

Kenneth Wong (NAOJ)

EAYAM
11/15/2017

H0LiCOW Collaboration
PI: Sherry Suyu (MPA)
Adriano Agnello (ESO)
Matt Auger (Cambridge)
Roger Blandford (Stanford)
Simon Birrer (UCLA)
Vivien Bonvin (EPFL)
Geoff Chih-Fan Chen (UC Davis)
Tom Collett (Portsmouth)
Frederic Courbin (EPFL)

Xuheng Ding (UCLA)
Chris Fassnacht (UC Davis)
Stefan Hilbert (LMU)
Leon Koopmans (Kapteyn)
Kai Liao (UCLA)
Phil Marshall (Stanford)
Georges Meylan (EPFL)
Nick Rumbaugh (UIUC)
Edi Rusu (Subaru)

Anowar Shajib (UCLA)
Dominique Sluse (Liege)
Alessandro Sonnenfeld (IPMU)
Chiara Spiniello (INAF)
Malte Tewes (AIfA)
Olga Tihhonova (EPFL)
Tommaso Treu (UCLA)
Kenneth Wong (NAOJ)
Akin Yildirim (MPA)*bold/underlined: attending this conference
H0LiCOW Publications
Paper I - Suyu et al. 2017, MNRAS, 468, 2590
Paper II - Sluse et al. 2017, MNRAS, 470, 4838
Paper III - Rusu et al. 2017, MNRAS, 467, 4220
Paper IV - Wong et al. 2017, MNRAS, 465, 4895
Paper V - Bonvin et al. 2017, MNRAS, 465, 4914
Paper VI - Ding et al. 2017a, MNRAS, 465, 4634
Paper VII - Ding et al. 2017b, MNRAS, 472, 90
Paper VIII - Tihhonova et al. in preparation
H0LiCOW logo credit: O. Tihhonova

http://www.h0licow.org
Kenneth Wong (NAOJ)

EAYAM
11/15/2017