Six years of Dark Energy: present and Six years of Dark Energy: present and future prospectsfuture prospects

Ariel Goobar

Physics Department, Stockholm University

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SCPSCP:Perlmutter et al + :Perlmutter et al + High-ZHigh-Z Team:Riess Team:Riess et alet al

Supernova Cosmology Project (SCP)

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Year 5 ADYear 5 AD

Redshift

Sullivan et al 2003

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5 AD: concordance model 5 AD: concordance model (see also Tonry et al 2003, Barris et al 2004)(see also Tonry et al 2003, Barris et al 2004)

statsyst04.006.007.075.0

Independent evidence also from eg:LSS (eg Peacock et al)

ISW (eg Boughn & Crittenden)

Cluster abundances (eg Bahcall et al)

Age of Universe

X-ray clusters (Allen et al 04)

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SN1a: systematic effects SN1a: systematic effects

• Non-Type Ia contamination• Malmquist bias• K-corrections and SN colors• Extinction by host galaxy dust • Extinction by intergalactic dust• SN brightness evolution• Shape-brightness relation• Instrumental corrections• Lightcurve fitting technique/host

galaxy subtraction• Gravitational lensing• Exotica: axion-photon oscillations, etc• …

No extinction correction. Reddened SNe excluded

With extinction correction

Largest source of identified syst in Knop et al: uncertainty in the intrinsic colors of SN1a ar short

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Spectroscopic tests of standard candleSpectroscopic tests of standard candle

subluminous

overluminous

CaII (3900) velocity

subluminous

Folatelli et al, Garavini et al , Lidman et al

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Statistical uncertainty: Redshift dependence

AG & Perlmutter 95 95

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Turning 6! Very-high Z supernovae Turning 6! Very-high Z supernovae from ACS/HST from ACS/HST (Riess et al 2004)(Riess et al 2004)

•>19 SNe discovered from space, up to z=1.7

•Reported CL-regions due to statistical errors

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Extinction correctionsExtinction corrections

• z-dependence in reported Av ?

• Problems with K-corrections/assumed intrinsic colors in UV part of the SNIa spectrum?

• Changing dust properties ?

• Selection effects?

• Watch out for priors on AV! Riess et al assume P(Av)~exp(-Av)

• A careful study of extinction correction systematics for z>0.9 SNe (as done in Knop et al for z<0.9) is still missing.

SN97ff: assumed extinction- free, E-host

Riess et al 2004 (gold sample)

Uncertainties ?

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Gray(er) IG dustGray(er) IG dust

• Large dust grains (weak wavelength dependence) may populate the IG-medium (Aguirre 1999,2000)

• Evolution of dust density: two limiting cases considered:

1. dust (1+z)3 [Model A]

2. dust (1+z)3 for z<0.5 &

dust(z>0.5)= dust(z=0.5) [Model B, ”replenishing dust”]

• Hard to rule out from SN-colors

• X-ray point-sources at very high-z, (e.g. Paerels et al) do not exclude e.g Model B

• SDSS QSO colors (2740 objects, z<2) <0.2 mag extinction for SN1a at z=1; faintness of SNe unlikely due to only IG-dust

AG,Bergström & Mörtsell, A&A, 2002

Mörtsell & AG, JCAP, 2003

Concordance

Model A

ModelB; M=1

Milne

Dust is still a serious concern for precision cosmology with SNe.

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MC + cosmology fitting code specifically developed to understand science reach and systematic uncertainties in observations of high-z SNe, e.g. due to intervening dust gravitational lensing, search biases, non-SNIa contamination, etc. A.G et al (2002) Astronomy & Astrophysics, 392,757

Download: www.physto.se/~arielDownload: www.physto.se/~ariel

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bias in the cosmology fitbias in the cosmology fitdue to lensingdue to lensing

• GL →asymmetric mag. distributions

• Bias in cosmological results

• However, with proper statistical treatment bias can be kept low + fraction of compact objects in DM derived

co

Mörtsell, Gunnarson, AG, ApJ, 2001; SNAP simulations, Mörtsell, AG, Bergström. ApJ, 2001; Amanullah, Mörtsell, AG; A&A, 2003

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Is Dark Energy = Is Dark Energy = ? ?

Although appears to be the ”simplest” explanation to the data, there are fundamental theoretical problems:

1) why so small? 2) why is the vacuum density so close to matter

density now?

present SN data consistent with with w=-1, i.e cosmological constant, although rapid evolution has been suggested...

Tobias Goobar, age 6

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Rapidly changing w?Rapidly changing w?

• Alam et al (2003,2004) proposed fitting SN data with truncated Taylor expansion for DE.

• Claim: signs for rapid evolution in w: Metamorphosis

Seems like reasonable parametrization, however...•The expression of w comes from derivatives of ansatz in H(z) •Parts of parameter-space causes divergences•As z increases, limiting value of wDE≠-1•Parametrization ”forces” Metamorphosis

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Theoretical systematicsTheoretical systematics

Jönsson, AG, Amanullah, Bergström, astro-ph/0404468

Test: simulate + fit 500 experiments , z-distribution and uncertainties as in Tonry + Barris et al

cosmology

w diverges

w|>15

Metamorphosis not required to explain the fits!

”Transition redshift” set by prior on M

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Theoretical systematicsTheoretical systematics

Jönsson, AG, Amanullah, Bergström, astro-ph/0404468

Test: simulate + fit 500 experiments , z-distribution and uncertainties as in Tonry + Barris et al

cosmology

w diverges

w|>15

Metamorphosis not needed to explain the fits!

”Transition redshift” set by prior on M

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Theoretical systematicsTheoretical systematics

Jönsson, AG, Amanullah, Bergström, astro-ph/0404468

Test: simulate + fit 500 experiments , z-distribution and uncertainties as in Tonry + Barris et al

cosmology

w diverges

w|>15

Metamorphosis not needed to explain the fits!

”Transition redshift” set by prior on M

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Major ongoing/future SN programs Major ongoing/future SN programs

• Low redshift: starting in 2004

Carnegie Supernova Project ~200 SN1a with z<0.07´(UBVRIJHK)

SuperNova Factory ~300 SN1a z<0.08

• Intermediate redshift: starting 2005(?)

SLOAN ~300 0.1<z<0.4

• High-z

SNLS: 2003-2008; 700 SNe 0.3<z<0.9

ESSENCE:2002-2005; 200 SNe 0.2<z<0.7

• Very High-z (z>1) 2003-2005

PANS/GOODS + SCP: ~50 (1 < z < 2)

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Dark Energy statistical precision from CFHT Dark Energy statistical precision from CFHT Legacy SurveyLegacy Survey

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Dark Energy and Dark Matter. Dark Energy and Dark Matter. - Long term future Supernova Project - Long term future Supernova Project

SNAP/JDEM satellite: several thousend very high-z Sne/year + weak lensing survey

~2-meter mirror 0.7° FOV

imaging + spectroscopy 0.35-1.7 m,

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The Next Generation: SNAP/JDEM – good The Next Generation: SNAP/JDEM – good controll of systematicscontroll of systematics

SNAP

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SNAP: probing Dark Energy models SNAP: probing Dark Energy models

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SNAP precision on w’SNAP precision on w’

Planck data provides complementarity equal to a prior (M)0.01.

Frieman, Huterer, Linder, Turner 2002

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SNAP: Weak Gravitational SNAP: Weak Gravitational LensingLensing

Distortion of background images by foreground matter

Unlensed LensedCredits: R.Ellis

SNe + Weak Lensing SNe + Weak Lensing (cf A.Taylor)(cf A.Taylor)

√ • Comprehensive: no external priors required!

• Independent test of flatness to 1-2%

• Complementary: w0 to 5%, w to 0.11 (with systematics)

Bernstein, Huterer, Linder, & Takada

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Summary & ConclusionsSummary & Conclusions

• Quite healthy 6 year old! Evidence for DE seems robust w.r.t identified systematic effects..

• is Dark Energy=?

No convincing evidence against it!• stat ~ syst → need better quality data to

make use of large statistics to come…• New very high-z from ground and space

extremely exciting but sytematics not yet fully studied.

• Large number of ongoing projects will provide several hundreds (thousends?) of nearby and distant supernovae.

• SNAP/JDEM a very exciting mission with capability of resolving the DE mysteri...but launch in 2014???