Ivanfest III 22 May 2012

Astronomy Department - University of Washington

Gravitational lensing

an astrophysical tool

Georges Meylan

Laboratoire d�astrophysique Ecole Polytechnique Fédérale de Lausanne (EPFL)

in collaboration with :

Frédéric Courbin, Alexander Eigenbrod, Malte Tewes at EPFL George Djorgovski, Ashish Mahabal at Caltech, Chris Kochanek, Chris Morgan at OSU,

and many others …

After the solar eclipse of 1919 and papers in 1930�s subject of g.l. nearly abandoned for about 30 years

1960�s – 1970�s • Theoretical discussions •

• Invention of CCDs • • Discovery of quasars •

⇓ In 1979, first case of a gravitational lens

extragalactic at cosmological distance

QSO 0957+561 Walsh, Carswell, Weymann, 1979, Nature, 279, 381

The disruptive action of the lensing galaxy splits the single image of the quasar into two or more componants

QSO A

QSO B

QSO

ionmagnificat=ΩΩ

=s

i

dd

µ

QSO 0957+561 : first gravitational lens at cosmological distance

•  HST/WFPC2

•  Δ(A,B) = 6.1" •  VA = VB ≅ 17.1 •  z(source) = 1.41

•  VG = 19.1 •  z(lens) = 0.36

HST Castles

•  Δ(A,B) = 6.1" •  VA = VB ≅ 17.1 •  z(source) = 1.41

Image A

Image B

Walsh, Carswell, Weymann 1979, Nature, 279, 381

CIV 1549Å CIII] 1909Å MgII 2798Å

QSO 0957+561 : first gravitational lens at cosmological distance

All pairs of quasars observed in the Universe do not always proceed from the effect of a gravitational lens

PKS 1145-071 : first tight pair of quasars

Djorgovski, Perley, Meylan, McCarthy, 1987, ApJ, 321, L17

A

B

z = 1.345

Djorgovski et al., 1987, ApJ, 321, L17

Radio image from VLA IA/IB = 2.7 in V IA/IB > 104 in radio Δ(A,B) = 4.2� Distance ~ MW-LMC

PKS 1145-071 : first tight pair of quasars

Djorgovski & Meylan, 1987, ApJ, 321, L17

Radio image from VLA IA/IB = 2.7 in V IA/IB > 104 in radio Δ(A,B) = 4.2� Distance ~ MW-LMC

PKS 1145-071 : first tight pair of quasars

Second pair of quasars : PHL 1222 Meylan & Djorgovski 1989

A

C

B

QQ 1429-008 : Discovery of a probable triple QSO at z = 2.076

S. G. Djorgovski, F. Courbin, G. Meylan, D. Sluse, D. Thompson, A. Mahabal, E. Glikman, 2007, ApJL, 662, 1

Keck spectra of the QSO components : all at z = 2.076

Absorbers: za1 = 1.512 (A,B), za2 = 1.662 (A), za3 = 1.837 (B,C)

λobs (Å)

⊕

⊕

⊕

⊕

⊕ a1

a1

a1

a1

a1 a2

a1

a3

a3 a3 a3 a3

AAS mtg. Jan�07 Djorgovski et al. 12 1

A

B

C 4

3

8

2

9

D?

R band (VLT) MCS deconvolution 3 arcsec

Disturbed host galaxy?

Our �best� lensing model predicts a massive and luminous lens galaxy, which is not seen, even if placed in an optimal position :

physical close triplet of QSOs

What about the lensing galaxy ?

Keck-VLT deep

imaging

AAS mtg. Jan�07 Djorgovski et al. 13 1

A

B

C 4

3

8

2

9

D?

R band (VLT) MCS deconvolution 3 arcsec

Disturbed host galaxy?

Our �best� lensing model predicts a massive and luminous lens galaxy, which is not seen, even if placed in an optimal position :

physical close triplet of QSOs

What about the lensing galaxy ?

Keck-VLT deep

imaging

Gravitational Lensing Theory

3 directions : - to the lens - to the source - to the image 3 angles : - α β θ 3 plans : - of the source η - of the image ξ - of the observer 3 distances : - Ds Dd Dds

The lens equation The positions of the source and of the images

are related by a non linear equation providing the possibility of multiple images :

multiple image positions θ

corresponding to a unique source position β

! !

€

β = θ − α ( θ )

The gravitational lenses classified following three regimes :

•  STRONG : the source is imaged into several componants, their shapes and luminosities are strongly perturbed

•  WEAK : one single image of the source, with its shape and luminosity strongly perturbed

•  MICRO : one single image of the source, with only its luminosity strongly perturbed

The local properties of the application source plane � lens plane are described by its jacobian matrix : A ≡ ∂β /∂θ

With the convergence κ and the shear γ :

The convergence κ has a magnification action on the light rays : the image conserves the shape of the source, but with a different size.

The shear induces an anisotropy with intensity γ and orientation ϕ.

Convergence and shear

!!"

#$$%

&

−−!!"

#$$%

&−=

φφ

φφγκ

2cos2sin2sin2cos

1001

)1(A

⇒

Abell 1689 HST ACS (2003) zamas = 0.182 σa= 1848 ± 166 km s-1

Deep HST image tint = 13.2 hours

Abell 1689 HST ACS

Shear γ as a function of the convergence κ Seitz & Schneider, 1997, A&A, 318, 687

Reconstruction of the mass distribution via the gravitational distorsions

a field very active since ~ 1995 with Kaiser, Kneib, Bartelmann, and many others

Abell 1689 HST ACS (2003) zamas = 0.182 σa = 1848 ± 166 km s-1

Deep HST image tint = 13.2 hours

The distribution of arcs and arclets provides us with a very robust estimator of the total mass : best evidence for dark matter

Since 1979

the phenomenon of gravitational lenses is the subject of intense research activities,

both theoretical and observational,

which have created a new tool

for the study of the whole Universe,

from nearby planets to the most distant galaxies

•

•

• • • •

• • • •

• •

• •

•

•

•

•

critical curves caustics

HE1104-1805

H1413+117

PG1115+080

B1422+231

The local properties of the application source plane – lens plane are described by its jacobian matrix : A ≡ ∂β /∂θ The locus of a point where A cannot be locally inverted, zero jacobian : critical curves and caustics.

A Horseshoe Einstein Ring from Hubble

LRG 3-757 was discovered in 2007 in data from the Sloan Digital Sky Survey (SDSS). This image is a follow-up observation taken with the HST WFC3 (NASA/ESA)

1 April 2012 : gravitational lensing effect by a black hole of 1 mJ 1 April 2012 : Matterhorn, Zermatt, Switzerland

Usefulness of gravitational lenses

• Direct determination of the total mass of the lensing galaxy

• Direct determination of cosmological parameters : - Hubble constant H0 - density parameters Ωm and ΩΛ

• Study of mass distribution of dark matter : - in galaxies - in clusters of galaxies - in large scale structures

• Natural telescopes for the observations of very distant objects at very high redshifts

European Southern Observatory Paranal - Chili

Earth and HST Hubble Space Telescope HST NASA/ESA STS 103 19-27 Dec 1999

QSO HE 1104-1805 ESO-MPI 2.2-m IRAC J Courbin et al., 1998, ApJ, 330, 57 Δ(A,B) = 3.19" zsource = 2.32 zlens = 0.73

Observations 0.7" After deconvolution 0.3"

The deconvolution provides an essential step

The Hubble constant values from 1927 on

http://cfa-www.harvard.edu/~huchra

,

Hubble constant estimates from 1927 on

http://cfa-www.harvard.edu/~huchra

,

Georges Lemaître 1927

« Un univers homogène de masse constante et de rayon croissant, rendant compte de la vitesse radiale des nébuleuses extra-galactiques » in Georges Lemaître, 1927, Annales de la Société scientifique de Bruxelles, Série A, t. XLVII, avril 1927, pp. 29-39 H0 = 625 km s-1 Mpc-1 data from Strömberg (1925)

Hubble constant estimates from 1927 on

Significantly more resources (telescope time, HST Key program, FTE) have so far been allocated to Cepheids and SNIa,

when compared with strong gravitational lensing of quasars

,

de Vaucouleurs H0 = 100 km s-1 Mpc-1

Sandage & Tammann H0 = 50 km s-1 Mpc-1

Freedman et al. (2001) H0 = 72 ± 7 km s-1 Mpc-1 Sandage et al. (2008) H0 = 62.3 ± 4.0 km s-1 Mpc-1

Riess et al. (2009) H0 = 74.2 ± 3.6 km s-1 Mpc-1

Hubble constant estimates from 1970 on

Workshop on the Hubble Constant "The Hubble Constant: Current and Future Challenges"

Kavli Institute for Particle Astrophysics and Cosmology SLAC, Stanford University, February 6-8, 2012

Questions addressed included :

What are the main limitations in measuring H_0?  How do we overcome them?

"Which of the many approaches need to be pursued now?  

Five broad categories of methods: (1) Cepheids and TRGB

(2) (2) Secondary distance indicators including SN Ia, TF and SBF (3) Masers

(4) Gravitational lens time delays (5) CMB, BAO and SZ

Essential to get direct determination of the H0 value

with an uncertainty closer to 1 % than to 10 %

necessity to use all available methods

⇓ gravitational lensing and time delays

The Hubble constant from

gravitational lenses and time delays

Time delay between two different light paths with different lengths

* *

*

*

Intrinsic QSO light variations ⇒ time delay Δτ

obs

Time delay the travel time of a photon (Refsdal 1964, 1966)

•  The geometric term tgeom represents the time delay induced by the longer light path followed by the deflected photons.

•  The gravitational term tgrav represents the time delay due to the relativistic time dilation induced by the gravitational field of the deflector.

•  The term in front of the brackets ensures that the measured quantities correspond to the time delay as measured by the observer.

intrinsic variations ⇒ time delay Δτ ⇒ H0

€

t( θ ) =

(1+ zd )c

DdDs

Dds

12

θ − β ( )

2−ψ( θ )

&

' ( )

* + = tgeom + tgrav

Measure of the time delay in radio QSO 0957+561 Haarsma et al., 1997, ApJ, 479, 102

Visible: Δτ = 417 ± 3 days

H0 via QSO 0957+561 Model : redshifts, positions, magnitudes, mass profile

Observations : σv (lens) = 279 ± 12 km s-1

ΔτBA = 417 ± 3 days ⇓

H0 = 67 ± 8 km s-1 Mpc-1

Falco et al. 1997, ApJ, 484, 70

112

112110

1.1330

98 −−−

+− ""

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'

Δ""#

$%%&

'= Mpcsmkyr

smkH

BA

v

τσ Some gravitational lenses

need fine tuning for H0 determination

H0 via photometric monitoring for QSO RX 0911+05

•  17

Burud et al., 2003

ΔτAB = 146 days H0 = 74 ± 9 km s-1 Mpc-1

H0 via photometric monitoring for QSO RX 0911+05

•  17

ΔτAB = 146 days H0 = 74 ± 9 km s-1 Mpc-1

Burud et al., 2003

H0 via QSO RX 0911+05

QSO

Kneib, Cohen, Hjorth, 2000, ApJ, 544, L35

The presence of a cluster of galaxies at the same redshift as the lens z = 0.7689 complicates the gravitational potential

Goal : production of 30 time delays over the next few years

COSMOGRAIL COSmological MOnitoring of GRAvItational Lenses

For the photometric monitoring 1-2 m telescopes :

•  Euler Swiss telescope, La Silla, Chile •  Mercator Belgian-Swiss telescope, La Palma, Canary Islands •  Maïdanak telescope, Uzbekistan •  Manchester Robotic telescope, La Palma, Canary Islands •  Himalayan Chandra telescope, Bangalore, India •  Hoher Liste, Bonn, Germany For high-resolution photometry and spectroscopy :

•  ESO-VLT, KECK, GEMINI 8-10 m telescopes •  Hubble Space Telescope NASA/ESA Deconvolution (images and spectra) whenever useful

Observations Till 2004, no organized long-term program for acquisition of time-delay data

To fully exploit the potential of gravitational lensing, need to reduce the uncertainties of measured time delays

⇓ COSMOGRAIL

La Palma Spain

Paranal La Silla Cerro Tololo Chili

Maidanak Ouzbekistan

Keck Gemini Hawaii

Himalayan Chandra Telescope India

EPFL

WFI J2033-4723 In collaboration with C.S. Kochanek, C. Morgan, M.E. Eyler, and E.E. Falco

Tewes et al. 2012, in prep.

A1+A2

B

C

J0158-4325 In collaboration with C.S. Kochanek, C. Morgan, L. Hainline (OSU & USNA)

Tewes et al. 2012, in prep.

A

B

a quasar with

disturbing microlensing

events

RXS J1131-1231 Lens with 4 images, zs = 0.66, zl = 0.29, ring θE = 1.8" (~305°)

Observations : 8 seasons Euler (01/04-07/11), 1pt / 5j

raw image

pixel = 0.34" seeing = 1.0"

deconvolved image pixel = 0.17" resol = 0.34"

but a very difficult case due to short time delays

a quasar with gentle microlensing events

RXS J1131-1231

HST ACS

a very difficult case due to short time delays and microlensing

Euler telescope

RXS J1131-1231

Tewes et al. 2012, in prep.

Light curves from Euler, Smarts, Mercator 3320 images from 630 epochs

A

B

C

D

RXS J1131-1231

strong microlensing events

can mimic spurious time delays when determined

over a few seasons

Tewes et al. 2012, in prep.

raw image

pixel = 0.34" seeing = 1.0"

deconvolved image pixel = 0.17" resol = 0.34"

Lens with 4 images, zs = 1.69, zl = 0.45, separation = 2.6� one clear Einstein ring connecting all four images

about 10 galaxies within 40�

HE 0435-1223

Swiss Euler telescope La Silla ESO

HE 0435-1223

Tewes et al. 2012, in prep.

A

B

C

D

Time delay from gravitational lensing

•  Time delay between the two images A and B :

lens potentiel from models

÷ H0-1

redshift from VLT-Keck

spectroscopy

astrometry from

HST images

time delay from

photometric survey

Step 1 : form of the lensing potential (Hernquist for stars + NFW for DM) Step 2a: MC integration of 3D spherical Jeans equs 2b: lens models 2c: minimize dyn & lensing χ2

Step 3 : estimate H0 (slope of mass profile from model and/or observations)

Status in 2004 : The Hubble constant from quasar time delays!

10 gravitational lenses ⇒ H0 = 61 ± 7 km s-1 Mpc-1

Direct method, known physics

HST KP : H0 = 72 ± 8 km s-1 Mpc-1

Lensing : H0 = 61 ± 7 km s-1 Mpc-1

Status in 2009 : The Hubble constant from quasar time delays!

18 time delays ⇒ H0 = 63.4 ± 8.4 km s-1 Mpc-1

HST KP : H0 = 74.2 ± 3.6 km s-1 Mpc-1

Lensing : H0 = 63.4 ± 8.4 km s-1 Mpc-1

Microlensing phenomenon

of a QSO

First cases of quasars not lensed by foreground galaxies

but playing the role of gravitational lenses

on background galaxies

The disruptive action of the lensing galaxy splits the single image of the quasar into two or more componants

QSO A

QSO B

QSO

ionmagnificat=ΩΩ

=s

i

dd

µ

Search in 22,298 SDSS spectra

•  The selection was carried out in searching, in each of the 22,298 SDSS QSO spectra, for at least four emission lines, all four at a redshift beyond the redshift of the foreground QSO.

•  The lensing nature was confirmed from Keck imaging and spectroscopy.

•  Further confirmation was acquired from HST/WFC3 imaging in the F475W and F814W filters.

Courbin etal. 2012 A&A 540 A36

The disruptive action of the lensing quasar splits the single image of the galaxy into two or more componants

galaxy A

galaxy B

QSO

ionmagnificat=ΩΩ

=s

i

dd

µ

First case of lensing quasar observed by EPFL (PR in March 2012)

LASTRO EPFL Press Release on 8 March 2012

Courbin(etal.(2012(A&A((540(A36(

EUCLID

EPFL - GM 68

L'École d'Athènes de Raphaël (1510-1511)

Musée du Vatican à Rome

EPFL - GM 69

Légende

1 : Zénon de Citium ou Zénon d'Élée ? 2 : Épicure 3 : Frédéric II de Mantoue ? 4 : Boèce ou Anaximandre ou Empédocle ? 5 : Averroès 6 : Pythagore 7 : Alcibiade ou Alexandre le Grand ? 8 : Antisthène ou Xénophon ?

9 : Hypatie ou Francesco Maria Ier della Rovere ? 10 : Eschine ou Xénophon ? 11 : Parménide ? 12 : Socrate 13 : Héraclite (sous les traits de Michel-Ange)

14 : Platon tenant le Timée (sous les traits de Léonard de Vinci) 15 : Aristote tenant l’Éthique 16 : Diogène de Sinope 17 : Plotin ?

18 : Euclide ou Archimède entouré d'étudiants (sous les traits de Bramante) ? 19 : Strabon ou Zoroastre ? 20 : Ptolémée R : Raphaël en Apelle

Selected by ESA on 4 Oct 2011 for launch in 2019

73 % Dark Energy

23 % Cold Dark Matter

4 % Atoms

unknown unknown

known

ΩCDM

ΩΛ

Ωb

1) Ωb baryonic matter (attractive) 2) ΩCDM dark matter (attractive) 3) ΩΛ dark energy (repulsive)

A very successful model, based on solid observational grounds, but … with two unknown quantities whose nature should revolutionise

both physics and our understanding of the Universe

dark matter and dark energy "Cosmic structure grew from gravitational instability of tiny pertubations that

reached macroscopic scales during an early inflation period """"""""

Dark matter shapes visible matter in a way that reflects the nature of dark energy. How galaxies are distributed in a Universe with no dark energy (left) would differ

measurably from one in which dark energy is significant (right). !

without dark energy with dark energy

"image colombi IAP "

!

Deflection of light rays, emitted by distant galaxies, while crossing the Universe induces of phenomenon called weak gravitational lensing

"image colombi IAP "

!

jhgjhgjhgjg Euclid : optical/near-infrared survey covering 15,000 deg2 + two 20 deg2 deep fields optimized for two independent primary cosmological probes

Weak Gravitational Lensing (WL) and Baryonic Acoustic Oscillations (BAOs)

shape & distance

tomography

bkhbkhbkhb

The 2 instruments VIS (R+I+Z) + NISP (Y, J, H) will provide shape & distance for about 1.5 billion galaxies WL : small systematic alignments in the random orientations of galaxies as a function of their distances

BAO : �wiggle� patterns in the clustering of galaxies : a standard ruler to assess the evolution of the Universe

Sarah Bridle Great08

The shape of a galaxy at ~ 1% accuracy

Ivan R. King

HAPPY BIRTHDAY

Thanks you !