1. Limits on brane world cosmology Systematic effects in SN cosmology (I) Extinction by dust in host galaxy or intergalactic medium/reddening Ongoing SCP High-z SN search (II) Gravitational lensing The SDSS-II SN-search Summary Ariel Goobar Stockholm University

2. 2 Gravitational leakage into X-dimension Use SNLS (Astier et al 2005) + Baryon oscillations (Eisenstein et al 2005) to examine 5D extenction of Friedmann eqn suggested by Dvali, Gabadadge,Porrati 2000; Deffayet, Dvali, Gabadadze 2001. Fairbairn & AG, 2005

3. 3 Consider more general modifications to Friedmann eqn (as in Dvali & Turner, 2003) Fit SNLS data + baryon oscillations AND flat universe Gravitational leakage into X-dimension (2) Fairbairn & AG, 2005  equiv

4. 4 SNLS 1-year + BAO prior + flatness w=w 0 + w 1 ·z

5. 5 SN brightness evolution Shape-brightness relation K-corrections and SN colors Non-Type Ia contamination Malmquist bias Host galaxy dust properties Intergalactic dust Gravitational lensing Exotica:axion-photon oscillations, etc Instrumental corrections Absolute calibration Lightcurve fitting technique/host galaxy subtraction … (Known) systematic effects Astrophysics of supernovae Selection effects,contamination Line of sight effects Measurement issues

6. 6 Dust/reddening: a real problem! Dust in SN host galaxy (or along line of sight) Correction assumes some reddening law, typically Galactic type dust (SCP,High-Z Team) or average fit to any kind of reddening/blueing (SNLS) Can only be estimated for individual SNe with a) accurate multi-wavelength data b) good knowledge of intrinsic ”color” of SNe Extinction probabilty in a given galaxy depends on where the SN explosion happens B-V color of low-z SNe Extinction:  M B =R B ·E(B-V) with R B ~ 2 - 5 Extinction correction dominates measurement error! Exception: Elliptical galaxies (E/S0) have little star-formation & dust.

7. 7 Extinction/reddening 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? Degeneracy in global fit? Watch out for priors on A V ! Riess et al assume P(A v )~exp(-A v ) Potential inconsistency for elliptical hosts SN97ff: assumed extinction- free, E-host Riess et al 2004 (gold sample) Uncertainties ?    V

8. 8 ”GOLD”: systematics dominated? Spergel et al ’06 How to make progress at the highest-z?

9. 9 galaxy type dispersion Spiral: Sa/Sb/Sc  mag Irregular Scd/Irr  mag Elliptical: E/S0  =0.16 mag ”Dustfree and decelerated” 219 HST/ACS Orbits awarded (PI: Perlmutter) in C14 for rolling search for SNe on galaxy clusters 0.9<z<1.4. Clusters are rich on elliptical galaxies which (at low-z) only host SNIa (no contamination) and extinction by dust should be minimal. Expect ~20 SNe in a ”sharp(er)” Hubble diagram. Sullivan et al 2003

10. 10 First SN discovered in a cluster in this search Cluster RCS0221-03 at z = 1.02 Host was cataloged Cluster member. Spectrum taken for confirmation. ACS z band ACS I band Nicmos J band preliminary

11. 11 Intergalactic dust Large dust grains (weak wavelength dependence) may exist in the IG- medium Evolution of dust density: two limiting cases: 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] SDSS QSO colors (>16000 objects, z<2) <0.1 mag extinction for SN1a at z=1; faintness of SNe cannot be only due to IG-dust AG,Bergström & Mörtsell, A&A, 2002 Mörtsell & AG, 2003, Östman & Mörtsell, 2005 Concordance Model A ModelB;  M =1 Milne IG Dust cannot explain observed faintness of SNe – but is a serious concern for precision cosmology. SNLS: |  M |<0.025; |w|<0.05

12. 12 Lensing (de)magnification in the GOODS SN survey: a study case Lensing (de)magnification in the GOODS SN survey: a study case The photometric redshift catalogue for GOODS used to study the line- of-sight properties of the SNIa in the Riess et al 2004 sample (see Gunnarsson et al ApJ 2006 and Jönsson et al ApJ 2006) Faber-Jackson & Tully Fischer relations used for M/L Galaxy halos modelled as truncated SIS or NFW Self-consistency loop: mass density in galaxies + unresolved matter=  M

13. 13 Magnification probability We find evidence for magnified and demagnified supernovae (  1) Uncertainty computed by error progation from:  Finite field size error  Redshift and position errors  Scatter in FJ&TF relations  Survey magnitude limit (incompleteness) PDF built up by randomizing the contributions above according to their individual uncertainties, Estimate of magnification in SN1997ff smaller than in Benitez et al 2002, Riess et al 2004. This is understood, both authors now agree with our result. z=1.27 z=1.75

14. 14 Lensing PDFs for GOODS SN-sample  We found NO evidence for selection effects due to lensing in the GOODS SN sample.Negligible corrections to  ’s & w.  Expected lensing bias on SNLS results is also small: |  M | ~0.01 in  M -   plane. Added uncertainty on w 0 is  w ~0.014 for BAO prior (SNOC simulation)

15. 15 SDSS II: intermediate-z SNe NEW PROJECT – Since Sep 2005 Aiming at filling in the ”gap” left by eg SNLS and ESSENCE with >300 well measured, accurately calibrated, multicolor LCs Repeat imaging of ~270 sq. deg. Sep- Nov 05-07

16. 16 126 spectroscopically confirmed SN Ia ( =0.21) 13 spectroscopically probable SN Ia 6 SN Ib/c (3 hypernovae) 10 SN II (4 type IIn) 5 AGN ~hundreds of other unconfirmed SNe with good light curves (galaxy spectroscopic redshifts measured for ~25 additional Ia candidates) TO BE REPEATED IN 06 & 07 WITH EVEN BETTER FOLLOW-UP: > 300 SNeIa in the DE dominated era! Results from 2005 Courtesy of Bob Nichol Preliminary No reddening corr.    

17. 17Summary Lots of activities to increase the statistics of low, intermediate and high-z Type Ia supernovae Emphasis on high-quality data – control of systematics Extinction/reddening corrections remain a source of concern –especially for the highest-z data, maybe not in elliptical hosts Gravitational lensing (de)magnification not a problem for high-z SNe Concordance model in excellent shape …so far,  seems un-challenged by SN-data.

18. 18 What to expect from on-going efforts? Data-sets in the making: SNLS ~ 700 SNe (+ ESSENCE) SDSS- II ~ 200 SNe low-z ~ 100 SNe very high-z ~ 100 SNe -------------------------------------------------- Total 1200 SNe Simulate a ”combo” data-set using the same z-distributions as today, just scale up numbers Neglect systematics – to begin with! today ”combo”

19. 19 ”Combo” MC data-set: w/o systematics Current SNLS Current BAO Sne + flat BAO prior

20. 20 ”Combo” MC data-set: w/o systematics Current SNLS Current BAO Sne + flat BAO prior SNLS Combo

21. 21 Host galaxy extinction systematics Bias if no correction added

22. 22 ”Theoretical ” systematics Alam, Shani,Saini & Starobinski (2003) proposed fitting SN data with truncated Taylor expanasion for dark energy Claim: signs for Metamorphosis, crossing of the phantom divide” Seems like reasonable parametrization, however... Parts of parameter-space causes divergences As z increases, limiting value of w DE ≠-1 In fact, parametrization forces Metamorphosis

23. 23 ”Theoretical” systematics Jönsson, AG, Amanullah, Bergström, 2004 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

24. 24 ”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

25. 25 ”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

26. 26