Dark energy workshop

Copenhagen Aug. 2007

Why the SNLS ?

Questions to be addressed:-Can the intrinsic scatter in the Hubble diagram be further reduced?-Is it possible to detect a correlation between residuals and magnification?-Is it possible to say something about the dark matter distribution of the galaxies?

One of the biggest high-z supernova survey ~500+ supernovae at the end of the survey. + a huge catalogue of galaxies in the lines of sight

Most Sne are demagnified and some are significantly magnified

700 simulated type Ia Sne using SNLS Sne observations (Astier et al 2006)

First estimate (a feasibility check)

Magnification of each supernova is estimated using SNOC The SuperNova Observation Calculator Goobar et al (astro-ph/0206409)

Cosmological results

Uncertainties due to lensing ~ 1-2%and due to lensing ~ 2-3 %

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δΩM

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δw

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w = w0 + ′ w (a − a0) Lensing accounts for 7.5% of the dark energy task force figure of merit

Is it possible to detect a signal ?

Expected standard candle brightness(calculated from a cosmological model)

Magnification

Plots of residuals vs magnification

Expected linear correlation

For estimations of the magnificationerrors, a work on the GOODs fieldshas been used (Jonsson et al astro-ph/0612324)

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C =

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χ 2

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χ 2(no correlation) (linear correlation)-

2 different samples: -with lensing effects -without lensing effects

Confidence level of >99%

Likelihood ratio

ANALYSIS OF THE SNLS DATASET

Using the Faber-Jackson relation for ellipticals and the Tully-Fisher relation for spirals we can relate luminosity with mass (for a given model).

Analysis chain

Actual dataGalaxy catalogue

including magnitudes in the

g r i (u) and z -bands +

photometric redshift

Galaxy type +

B-band absolute

magnitude

Estimation of the mass of the galaxy

using galaxy models like SIS or NFWEstimation of

the eta-parameter

Using PEGASE : a UV to NIR spectral evolution model of galaxies

typeabsolute

magnitudesall sorts of

things

Using Q-LET, a multiple lens plane algorithm which calculates the magnification with respect to a homogeneous universe

Estimation of the

magnifi-cation of

each SNe

-Photometric redshift code

-Fits redshifted spectral templates

Pegase (a UV to NIR spectral evolution model of galaxies)

templates

Absolute B-band magnitudes

The Faber-Jackson or Tully-Fisher relations relates the velocity dispersion and the Luminosity of the galaxy.

Using a specific model (SIS or NFW) then relates the luminosity to the mass which is finite providing you choose a cut-off radius.

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L∝σ β

The Faber-Jackson/Tully-Fisher relations

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log10 σ = −0.091(MB − 4.74 + 0.85z)

F-J relation (ellipticals)Mitchell et al. (2005)

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log10 Vmax = −0.134(MB + 3.61+1.22z)

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σ =Vmax / 2

T-F relation (spirals)Bohm et al. (2004)

Truncation halo:

The radius inside which the mean mass density is 200 times the present critical density

The smoothness parameter

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ηAll “unobserved” matter is put into a smoothly distributed component.

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η(z) =1−ρ g (z)

ρ m (z)

Good test whether the galaxy model is OK

Ellipticals

Spirals

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1.56 ×1012 h−1M⊕

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1.05 ×1011h−1M⊕

Another formula relating mass and luminosity Hoekstra et al. (2005)

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M = 9.9 ⋅1011 LB

1010 h−2LΘ

⎛

⎝ ⎜

⎞

⎠ ⎟

1.5

h−1MΘ

Masse of elliptical galaxies

Jonsson

Hoekstra

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1.56 ×1012 h−1M⊕€

1.55 ×1012 h−1M⊕Mean massJonsson et al.

Mean mass Hoekstra et al.

Using the formula of Hoekstra et al. for spirals and ellipticals

Using the F-J/T-F relations for the second field

Magnifications