1. Thomas Collett Institute of Astronomy, Cambridge
Probing Dark Energy with Double Source-plane Strong Lenses
Thomas Collett Institute of Astronomy, Cambridge
With: Matt Auger and others

2. Probing Cosmological Parameters with Strong Lenses
Thomas Collett

3. RARE Double source plane strong lensing
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Double source plane strong lensing
A gravitational lens system with two background sources, each at a different redshift.
RARE

4. Few Probes Precise measurements Systematics important
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Few Probes
Precise measurements
Systematics important
Mantz et al. 2014

5. Uncertainty in the mass model makes cosmography hard
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Uncertainty in the mass model makes cosmography hard
Hubble constant
+ can add a term for spatial curvature
Dark Energy
Equation of State
Matter Density

6. Approximately the ratio of Einstein radii
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
The observable:
Lens Strength Ratio
Approximately the ratio of Einstein radii

7. The observable: Lens Strength Ratio
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
The observable:
Lens Strength Ratio

8. No dependence on the Hubble constant!
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
The observable:
Lens Strength Ratio
No dependence on the Hubble constant!

9. The observable: Lens Strength Ratio
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
The observable:
Lens Strength Ratio

10. The observable: Lens Strength Ratio
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
The observable:
Lens Strength Ratio

11. The observable: Lens Strength Ratio
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
The observable:
Lens Strength Ratio
Makes no assumptions about the lens mass distribution or source positions

12. Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
What do we need to do? ?

13. ρ∝ r ρ∝ r MASS LIGHT -η-1 -2 Lens modelling shear Sersic
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Lens modelling
shear
-η-1 -2
ρ∝ r
ρ∝ r ~
MASS
LIGHT
Sersic
Regularized, Pixellated Sources

14. Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Lens modelling
( ) S1 M =

15. Modelling J0946 Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Modelling J0946

16. Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Modelling J0946
σ=97±7 km/s
1.402
1.392
0.2 -1 -1
0.1
1.44
1.4 -1
1.36 -1
1.394
1.4
0.1
0.2
Powerlaw slope,

17. Second Source Redshift
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Second Source Redshift

18. Constraining Cosmology.
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Constraining Cosmology.

19. Constraining Cosmology.
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Constraining Cosmology.

20. Constraining Cosmology.
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Constraining Cosmology.

21. Constraining Cosmology.
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Constraining Cosmology.

22. Constraining Cosmology.
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Constraining Cosmology.

23. Constraining Cosmology.
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Constraining Cosmology.
J WMAP prior:

24. Constraining Cosmology.
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Constraining Cosmology.
J WMAP prior
(2013, 68% CLs)

25. Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
The Future
The Future

26. Expect at least hundreds! (maybe several hundreds) Euclid
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Euclid
Expect at least
hundreds!
(maybe several
hundreds)
~105 galaxy scale strong lenses (based on COSMOS )
1 in galaxy scale lenses will be doubles (Gavazzi+ 2008)

27. Euclid Black: 6 lenses, Ωk = 0 FoM = 14.2 Red: 100 lenses, Ωk ≠ 0
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Euclid
Black: 6 lenses, Ωk = 0
FoM = 14.2
Red: 100 lenses, Ωk ≠ 0
FoM = 38
σ(Ωk) = 0.005
Collett+ in prep.
(includes Planck prior)

28. Euclid Black: 6 lenses, Ωk = 0 FoM = 14.2 Red: 100 lenses, Ωk ≠ 0
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Euclid
Black: 6 lenses, Ωk = 0
FoM = 14.2
Red: 100 lenses, Ωk ≠ 0
FoM = 38
σ(Ωk) = 0.005
Collett+ in prep.
(includes Planck prior)

29. Summary Independent systematic errors Independent of Hubble constant
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Summary
Independent systematic errors
Independent of Hubble constant
DSPLs will be competitive and complementary cosmological probes in the Euclid/LSST/SKA era

30. Source flux only in masked region
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Idealizations
Pre-subtract galaxy
Source flux only in masked region
Deterministic location of first source mass
Curvature regularized sources
Simple Mass models
No line of sight lensing

31. Finding more systems Piggy-back on deep, large area surveys
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Finding more systems
Piggy-back on deep, large area surveys
Target known lenses
Target the most massive galaxies

32. Exotic lenses with Euclid/LSST
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Exotic lenses with Euclid/LSST
~ 40 lensed type Ia Sne
~ 30 DSPLs where one is an AGN
~ Triple source plane lenses?
~ Double time-delay systems?
*These numbers have big error-bars!

33. Einstein Dartboards Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Einstein Dartboards

34. Systematics Mass between the two rings Mass of the intermediate source
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Systematics
Mass between the two rings
Mass of the
intermediate source
Mass along the line of sight

35. Perturbations by the intermediate source
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Perturbations by the intermediate source
If completely neglected:
LMC: ~1% systematic error on η
MW: ~10% systematic error on η
Effect is detectable: include in the lens model.
(Sonnenfeld+ 2012, Fixed cosmology, photometric zs2)

36. Strong constraints on the mass profile γTOT = 1.98 ± 0.02 ± 0.01 OR
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Profile of the Lens
Strong constraints on the mass profile
γTOT = 1.98 ± 0.02 ± 0.01 OR
γDM = 1.7 ± 0.2
Using dynamics and both Einstein radii
(Sonnenfeld+ 2012)

37. Lens modelling Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Lens modelling

38. Lens modelling Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Lens modelling

39. Lens modelling Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Lens modelling

40. Lens modelling Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Lens modelling

41. Lens modelling Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Lens modelling

42. Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Lens modelling
( ) S1 M =

43. Intermediate source: θE=0.16”±0.05 σv≈100 kms-1
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Intermediate source: θE=0.16”±0.05
σv≈100 kms-1
NB// Parametric source light

44. Intermediate source: θE=0.16”±0.05 σv≈100 kms-1
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Intermediate source: θE=0.16”±0.05
σv≈100 kms-1
NB// Parametric source light

45. What about the assumption of flatness?
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
Thomas Collett 45 45 45
What about the assumption of flatness?
Ωk ≠ 0
Ωk ≡ 0

46. What if we can't measure the ratio of Einstein radii to 1%?
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett
Thomas Collett
What if we can't measure the ratio of Einstein radii to 1%?
1. Compound lensing – the intermediate source has mass
2. The lens is an astrophysical object
3. Line of sight lensing may be significant

47. Cosmology with a population of systems.
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Cosmology with a population of systems.
SLACS:
1.1mm, S > 1 mJy → ~1.5 double source plane systems (1.5 in 78)
1.1mm, S > 0.3 mJy → ~3 double source plane systems (3 in 78)
But can be more efficient if you focus only on the most massive lenses.

48. Constraints with 6 systems.
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Thomas Collett
Thomas Collett
Thomas Collett
Thomas Collett
Constraints with 6 systems.
Pick the set of systems that provided the median constraints on w.
WMAP+6 systems is ~2.5 times better than WMAP+1.
WMAP+
1 system wDE = −0.99 ± 0.27
6 systems wDE = −1.01 ± 0.11
WMAP+BAO+Time Delay+
6 systems wDE = −1.04 ± 0.09

49. Planck+6 Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Probing Cosmological Parameters with Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Constraining Dark Energy with Double Source Plane Strong Lenses
Thomas Collett 49 49 49
Planck+6

50. ρ=ρ0r-γ' Probing the mass profile of galaxies
Probing Cosmological Parameters with Strong Lenses
Cosmology with Strong Lensing.
Thomas Collett 50
Probing the mass profile of galaxies
Combine Einstein Radius with stellar dynamics
Fit a power-law:
ρ=ρ0r-γ'
Lenses are approximately isothermal (γ'=2).
(Koopmans+ 2006)
(Auger+ 2010)
γ' = ± with an intrinsic scatter of 0.16 ± 0.02