limits on brane world cosmology systematic effects in sn cosmology
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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
Gravitational leakage into X-dimensionGravitational 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.
2 8
3c
H GH
r
Fairbairn & AG, 2005
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 Gravitational leakage into X-dimension (2)(2)
22
8
3c
H GH
r
Fairbairn & AG, 2005
equiv
4
SNLS 1-year + BAO prior + flatnessSNLS 1-year + BAO prior + flatness
w=w0 + w1·z
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(Known) systematic effects
Astrophysics of supernovae
Selection effects,contamination
Line of sight effects
Measurement issues
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Dust/reddening: a real problem!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 colorof low-z SNe
Extinction:MB=RB·E(B-V) with RB~ 2 - 5
Extinction correction dominates measurement error!Exception: Elliptical galaxies (E/S0) have little star-formation & dust.
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Extinction/reddening correctionsExtinction/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
SN97ff: assumed extinction- free, E-host
Riess et al 2004 (gold sample)
Uncertainties ?
V
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””GOLD”: systematics dominated?GOLD”: systematics dominated?
Spergel et al ’06
How to make progress at the highest-z?
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galaxy type dispersion
•Spiral: Sa/Sb/Scmag•Irregular Scd/Irrmag
•Elliptical: E/S0 =0.16 mag
””Dustfree and decelerated”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
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First SN discovered in a cluster First SN discovered in a cluster in this searchin this search
Cluster RCS0221-03 at z = 1.02
Host was cataloged Cluster member.
Spectrum taken for confirmation.
ACS z bandACS I bandNicmos J band
preliminary
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Intergalactic dustIntergalactic 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
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Lensing (de)magnification in the Lensing (de)magnification in the GOODS SN survey: a study case 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
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Magnification probabilityMagnification 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
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Lensing PDFs for GOODS SN-sampleLensing 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)
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SDSS II: intermediate-z SNeSDSS 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
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• 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!
Results from 2005Results from 2005
Courtesy of Bob Nichol
PreliminaryPreliminaryNo reddening corr.No reddening corr.
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SummarySummary
• 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.