Constraining dark energy with double source plane strong lenses

Constraining dark energy with double source plane strong lenses

Constraining Dark Energy with Compound lenses
Constraining dark energy with double source
plane strong lenses
T. E. Collett
With Matt Auger, Vasily Belokurov, Alex Hall and Phil Marshall
Institute of Astronomy, Cambridge
Constraining Dark Energy with Compound lenses
Outline
1
What is double source plane strong lensing?
2
Why is it useful for cosmology?
3
What are the best systems for cosmology?
4
How will we find double source plane systems?
Constraining Dark Energy with Compound lenses
A sketch of a double source plane system:
Ds2
Dls1
Ds1
Dls2
Observer
Lens
Source 1
Source 2
Constraining Dark Energy with Compound lenses
Constraining Dark Energy with Compound lenses
The Einstein Radius:
s
θE =
GM(θE ) Dls
c 2 Dol Dos
Angular diameter distance (flat universe):
Z zj
c/H0
dz
p
Dij =
(1 + zi ) zi
ΩM (1 + z)3 + (1 − ΩM )(1 + z)3(1+w )
(1)
(2)
Our observable:
η=
θE,1
Dls1 Ds2
→ η SIS =
(Independant of H0 )
θE,2
Dls2 Ds1
(3)
Constraining Dark Energy with Compound lenses
The product of red distances, divided by the product of blue:
Ds2
Dls1
Ds1
Dls2
Observer
Lens
Source 1
Source 2
Constraining Dark Energy with Compound lenses
A sketch of a double source plane system:
Ds2
Dls1
Ds1
Dls2
Observer
Lens
Source 1
0.35
0.6
Source 2
1.5
Constraining Dark Energy with Compound lenses
A single system, with σ(η)/η = 1%
Constraining Dark Energy with Compound lenses
A single system, with σ(η)/η = 1%
Constraining Dark Energy with Compound lenses
A single system, with σ(η)/η = 1%
Constraining Dark Energy with Compound lenses
What about other redshift configurations?
Constraining Dark Energy with Compound lenses
The optimum system for cosmography:
1
High redshift background source
2
Close lens–source pair
3
Lens redshift > 0.2
Constraining Dark Energy with Compound lenses
The optimum system to search for second sources:
1
Massive lens
2
Small seperation between lens and source
3
Simple lens geometry (easier to model)
4
Low mass source (less secondary lensing)
Constraining Dark Energy with Compound lenses
Conclusions
1
Double source plane systems can be used for cosmography
2
The degeneracy is orthogonal to current cosmological probes
3
The best systems have a close lens-source pair, and a distant
background source
4
We should look for more double source plane systems!
Constraining Dark Energy with Compound lenses
Spare figures.
Constraining Dark Energy with Compound lenses
What if σ(η)/η 6= 1%?
Constraining Dark Energy with Compound lenses
6 Systems
1.0
6 Double source plane lenses
WMAP+BAO+∆t+6 Doubles
WMAP
BAO
0.8
ΩM
0.6
0.4
0.2
w
−
0.
4
−
0.
6
−
0.
8
−
1.
0
−
1.
2
−
1.
4
−
1.
6
−
1.
8
−
2.
0
0.0
Constraining Dark Energy with Compound lenses
What redshift will the second sources be?
Constraining Dark Energy with Compound lenses
Constraining Dark Energy with Compound lenses
Constraining Dark Energy with Compound lenses
Evolving Models
3
2
0
−1
−2
w0
0
0.2
0.4
0.6
ΩM
0.8
0.
0
−
0.
5
−
1.
0
−
1.
5
−
2.
0
−
2.
5
−3
−
3.
0
wa
1
Constraining Dark Energy with Compound lenses
2
wa
1
0
−1
−2
0.8
ΩM
0.6
0.4
0.2
wa
0.
6
ΩM
0.
8
0.
4
0.
2
2
0.
0
1
1
0
0.
5
−
2
1.
0
−
−
1.
5
−
−
2.
0
−
w0
0.
0
2.
5
−
0.0