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Six years of Dark Energy: present and future prospects

Six years of Dark Energy: present and future prospects. Ariel Goobar Physics Department, Stockholm University. SCP :Perlmutter et al + High-Z Team:Riess et al. Supernova Cosmology Project (SCP). Year 5 AD. Sullivan et al 2003. Redshift.

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Six years of Dark Energy: present and future prospects

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

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

  3. Year 5 AD Sullivan et al 2003 Redshift

  4. 5 AD: concordance model (see also Tonry et al 2003, Barris et al 2004) 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) LSS • ISW stat syst

  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 l

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

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

  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 tostatisticalerrors

  9. Extinction 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. Riess et al 2004 (gold sample) SN97ff: assumed extinction- free, E-host Uncertainties ?

  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: • dust (1+z)3[Model A] • 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 Model A Concordance Milne ModelB; M=1 Dust is still a serious concern for precision cosmology with SNe. Mörtsell & AG, JCAP, 2003

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

  12. bias in the cosmology fitdue to lensing 20% co • 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 Mörtsell, Gunnarson, AG, ApJ, 2001; SNAP simulations, Mörtsell, AG, Bergström. ApJ, 2001;Amanullah, Mörtsell, AG; A&A, 2003

  13. Is Dark Energy =  ? Although  appears to be the ”simplest” explanation to the data, there are fundamental theoretical problems: • why so small? • 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. 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

  15. Theoretical systematics Test: simulate + fit 500 experiments , z-distribution and uncertainties as in Tonry + Barris et al L-cosmology |w|>15 w diverges Metamorphosis not required to explain the fits! ”Transition redshift” set by prior on M Jönsson, AG, Amanullah, Bergström, astro-ph/0404468

  16. Theoretical systematics Test: simulate + fit 500 experiments , z-distribution and uncertainties as in Tonry + Barris et al L-cosmology |w|>15 w diverges Metamorphosis not needed to explain the fits! ”Transition redshift” set by prior on M Jönsson, AG, Amanullah, Bergström, astro-ph/0404468

  17. Theoretical systematics Test: simulate + fit 500 experiments , z-distribution and uncertainties as in Tonry + Barris et al L-cosmology |w|>15 w diverges Metamorphosis not needed to explain the fits! ”Transition redshift” set by prior on M Jönsson, AG, Amanullah, Bergström, astro-ph/0404468

  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. Dark Energy statistical precision from CFHT Legacy Survey

  20. 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 mm,

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

  22. SNAP: probing Dark Energy models

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

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

  25. √ SNe + Weak Lensing (cf A.Taylor) Bernstein, Huterer, Linder, & Takada • Comprehensive: no external priors required! • Independent test of flatness to 1-2% • Complementary: w0 to 5%, w to 0.11 (with systematics)

  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-zfrom 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???

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