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Limits on brane world cosmology Systematic effects in SN cosmology

Supernovae & Dark Energy. 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. Ariel Goobar Stockholm University. The SDSS-II SN-search.

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Limits on brane world cosmology Systematic effects in SN cosmology

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  1. Supernovae & Dark Energy 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 Ariel Goobar Stockholm University The SDSS-II SN-search Summary

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

  4. SNLS 1-year + BAO prior + flatness w=w0 + w1·z

  5. (Known) systematic effects • 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 • … Astrophysics of supernovae Selection effects,contamination Line of sight effects Measurement issues

  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 averagefit to any kind of reddening/blueing (SNLS) • Can only be estimated for individualSNe 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: DMB=RB·E(B-V) withRB~ 2 - 5 Extinction correction dominates measurement error! Exception:Elliptical galaxies (E/S0) have little star-formation & dust.

  7. Extinction/reddening 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? • Degeneracy in global fit? • Watch out for priors on AV! Riess et al assume P(Av)~exp(-Av) • Potential inconsistency for elliptical hosts Riess et al 2004 (gold sample) ? MB MV SN97ff: assumed extinction- free, E-host Uncertainties ?

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

  9. ”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 • galaxy type dispersion • Spiral: Sa/Sb/Sc s=0.20 mag • Irregular Scd/Irr s=0.27 mag • Elliptical: E/S0 s=0.16 mag

  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. preliminary ACS z band ACS I band Nicmos J band

  11. Intergalactic dust • Large dust grains (weak wavelength dependence) may exist in the IG-medium • Evolution of dust density: two limiting cases: • dust (1+z)3[Model A] • 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 Model A Concordance Milne ModelB; M=1 IG Dust cannot explain observed faintness of SNe – but is a serious concern for precision cosmology. SNLS: |M|<0.025; |w|<0.05 Mörtsell & AG, 2003, Östman & Mörtsell, 2005

  12. 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. 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. 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 w0 is w~0.014 for BAO prior (SNOC simulation)

  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. Results from 2005 • 126 spectroscopically confirmed SN Ia (<z>=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 BETTERFOLLOW-UP: > 300 SNeIa in the DE dominated era!  = 0.74 Preliminary No reddening corr. =0.27 Courtesy of Bob Nichol

  17. Summary • Lots of activities to increase thestatisticsof 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.

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