Transcript Padova talk
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 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. H 8 G H rc 3 2 Fairbairn & AG, 2005 2 Gravitational leakage into X-dimension (2) • Consider more general modifications to Friedmann eqn (as in Dvali & Turner, 2003) H 8 G H 2 rc 3 2 equiv Fit SNLS data + baryon oscillations AND flat universe Fairbairn & AG, 2005 3 SNLS 1-year + BAO prior + flatness w=w0 + w1·z 4 (Known) systematic effects • • • SN brightness evolution Shape-brightness relation K-corrections and SN colors Astrophysics of supernovae • • Non-Type Ia contamination Malmquist bias Selection effects,contamination • • • • Host galaxy dust properties Intergalactic dust Gravitational lensing Exotica:axion-photon oscillations, etc • • • Instrumental corrections Absolute calibration Lightcurve fitting technique/host galaxy subtraction • … Line of sight effects Measurement issues 5 Dust/reddening: a real problem! B-V color of low-z SNe • • • Extinction: DMB=RB·E(B-V) with RB~ 2 - 5 Extinction correction dominates measurement error! Exception: Elliptical galaxies (E/S0) have little star-formation & dust. • 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 6 Extinction/reddening corrections Riess et al 2004 (gold sample) ? • • • • • • D DM V M B • Uncertainties ? 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 SN97ff: assumed extinctionfree, E-host 7 ”GOLD”: systematics dominated? Spergel et al ’06 How to make progress at the highest-z? 8 ”Dustfree and decelerated” Sullivan et al 2003 • galaxy type •Elliptical: E/S0 dispersion s=0.16 mag •Spiral: Sa/Sb/Sc s0.20 mag •Irregular Scd/Irr s0.27 mag • • 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. 9 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 10 Intergalactic dust • Large dust grains (weak wavelength dependence) may exist in the IGmedium • 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] • AG,Bergström & Mörtsell, A&A, 2002 Model A Concordance Milne ModelB; M=1 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 IG Dust cannot explain observed faintness of SNe – but is a serious concern for precision cosmology. SNLS: |DM|<0.025; |w|<0.05 Mörtsell & AG, 2003, Östman & Mörtsell, 2005 11 Lensing (de)magnification in the GOODS SN survey: a study case • The photometric redshift catalogue for GOODS used to study the lineof-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 12 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, z=1.27 z=1.75 • 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. 13 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 sw~0.014 for BAO prior (SNOC simulation) 14 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. SepNov 05-07 15 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 BETTER FOLLOW-UP: > 300 SNeIa in the DE dominated era! 0.74 Preliminary No reddening corr. s0.27 Courtesy of Bob Nichol 16 Summary • 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. 17