1. Six years of Dark Energy: present and future prospects Ariel Goobar Physics Department, Stockholm University

2. 2 SCP:Perlmutter et al + High-Z Team:Riess et al Supernova Cosmology Project (SCP)

3. 3 Year 5 AD Redshift Sullivan et al 2003

4. 4 5 AD: concordance model (see also Tonry et al 2003, Barris et al 2004)  stat  syst   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)

5. 5 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

6. 6 Spectroscopic tests of standard candle subluminous overluminous CaII (3900) velocity subluminous Folatelli et al, Garavini et al, Lidman et al

7. 7 Statistical uncertainty: Redshift dependence AG & Perlmutter 95 95

8. 8 Turning 6! Very-high Z supernovae from ACS/HST (Riess et al 2004) >19 SNe discovered from space, up to z=1.7 Reported CL-regions due to statistical errors

9. 9 Extinction corrections z-dependence in reported A v ? Problems with K-corrections/assumed intrinsic colors in UV part of the SNIa spectrum? Changing dust properties ? Selection effects? Watch out for priors on A V ! Riess et al assume P(A v )~exp(-A v ) 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 ?

10. 10 Gray(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.

11. 11 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/~ariel

12. 12 bias in the cosmology fit due to lensing bias in the cosmology fit due 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

13. 13 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

14. 14 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 w DE ≠-1 Parametrization ”forces” Metamorphosis

15. 15 Theoretical 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

16. 16 Theoretical 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

17. 17 Theoretical 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

18. 18 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)

19. 19 Dark Energy statistical precision from CFHT Legacy Survey Dark Energy statistical precision from CFHT Legacy Survey

20. 20 Dark Energy and Dark Matter. - Long term future Supernova Project Dark Energy and Dark Matter. - 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,

21. 21 The Next Generation: SNAP/JDEM – good controll of systematics SNAP

22. 22 SNAP: probing Dark Energy models

23. 23 SNAP precision on w’ Planck data provides complementarity equal to a prior  (  M )  0.01. Frieman, Huterer, Linder, Turner 2002

24. 24 SNAP: Weak Gravitational Lensing Distortion of background images by foreground matter UnlensedLensed Credits: R.Ellis

25. SNe + Weak Lensing (cf A.Taylor) √ Comprehensive: no external priors required! Independent test of flatness to 1-2% Complementary: w 0 to 5%, w to 0.11 (with systematics) Bernstein, Huterer, Linder, & Takada

26. 26 Summary & 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???