Padova talk

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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
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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
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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
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SNLS 1-year BAO prior flatness
ww0 w1z
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(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
• Exoticaaxion-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
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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 DMBRBE(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 corrections
Riess et al 2004 (gold sample)

• 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

?
?MB
?MV
SN97ff assumed extinction- free, E-host
Uncertainties ?
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GOLD systematics dominated?
Spergel et al 06
How to make progress at the highest-z?
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Dustfree and decelerated
Sullivan et al 2003

• 219 HST/ACS Orbits awarded (PI Perlmutter) in
  C14 for rolling search for SNe on galaxy clusters
  0.9ltzlt1.4.
• 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.

• galaxy type dispersion
• Spiral Sa/Sb/Sc s0.20 mag
• Irregular Scd/Irr s0.27 mag

• Elliptical E/S0 s0.16 mag

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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
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Intergalactic dust
AG,Bergström Mörtsell, AA, 2002

• Large dust grains (weak wavelength dependence)
  may exist in the IG-medium
• Evolution of dust density two limiting cases
• ?dust? (1z)3 Model A
• ?dust? (1z)3 for zlt0.5
• ?dust(zgt0.5) ?dust(z0.5) Model B
• SDSS QSO colors (gt16000 objects, zlt2) lt0.1 mag
  extinction for SN1a at z1 faintness of SNe
  cannot be only due to IG-dust

Model A
Concordance
Milne
ModelB ?M1
IG Dust cannot explain observed faintness of SNe
but is a serious concern for precision
cosmology. SNLS ??Mlt0.025 wlt0.05
Mörtsell AG, 2003, Östman Mörtsell, 2005

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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

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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 FJTF 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.

z1.27
z1.75
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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 ?w0.014 for BAO prior (SNOC simulation)

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SDSS II intermediate-z SNe

• NEW PROJECT Since Sep 2005
• Aiming at filling in the gap left by eg SNLS
  and ESSENCE with gt300 well measured, accurately
  calibrated, multicolor LCs
• Repeat imaging of 270 sq. deg. Sep-Nov 05-07

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Results from 2005

• 126 spectroscopically confirmed SN Ia (ltzgt0.21)
• 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
• gt 300 SNeIa in the
• DE dominated era!

?? 0.74
Preliminary No reddening corr. ?0.27
Courtesy of Bob Nichol
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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.

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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!

combo
today
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Combo MC data-set w/o systematics
Sne flat
BAO prior
Current SNLS
Current BAO
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Combo MC data-set w/o systematics
SNLS
Sne flat
BAO prior
Combo
Current SNLS
Current BAO
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Host galaxy extinction systematics
Bias if no correction added
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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 wDE?-1
• In fact, parametrization forces Metamorphosis

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Theoretical systematics
Test simulate fit 500 experiments ,
z-distribution and uncertainties as in Tonry
Barris et al
L-cosmology
wgt15
w diverges
Metamorphosis not required to explain the
fits! Transition redshift set by prior on ?M

Jönsson, AG, Amanullah, Bergström, 2004
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Theoretical systematics
Test simulate fit 500 experiments ,
z-distribution and uncertainties as in Tonry
Barris et al
L-cosmology
wgt15
w diverges
Metamorphosis not needed to explain the
fits! Transition redshift set by prior on ?M

Jönsson, AG, Amanullah, Bergström,
astro-ph/0404468
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Theoretical systematics
Test simulate fit 500 experiments ,
z-distribution and uncertainties as in Tonry
Barris et al
L-cosmology
wgt15
w diverges
Metamorphosis not needed to explain the
fits! Transition redshift set by prior on ?M

Jönsson, AG, Amanullah, Bergström,
astro-ph/0404468
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