1 / 17

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.

tara
Download Presentation

Limits on brane world cosmology Systematic effects in SN cosmology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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.

More Related