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The “Union” Supernova Ia Compilation and new Cosmological Constraints

The “Union” Supernova Ia Compilation and new Cosmological Constraints. Marek Kowalski Humboldt Universität zu Berlin for the Supernova Cosmology Project Moriond 2008. The Union SNe Compilation.    M 1 0 0.72 0.28 0 1. fainter. 8 new SNe. Analysis aspects.

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The “Union” Supernova Ia Compilation and new Cosmological Constraints

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  1. The “Union” Supernova Ia Compilation and new Cosmological Constraints Marek Kowalski Humboldt Universität zu Berlin for the Supernova Cosmology Project Moriond 2008

  2. The Union SNe Compilation •  M • 1 0 0.72 0.28 0 1 fainter 8 new SNe

  3. Analysis aspects • Consistent Lightcurve Fits • SALT fitter used for all SNe using mostly • original band-passes (Guy et al 2005/2007). • Blind analysis • The analysis (i.g. cuts) were developed on a • blinded data set, all luminosities were offset • by a hidden redshift-dependent amount. • Robust analysis • Initial cosmological fit using median statistics. • 3-sigma outliers removed. • Assignment of sample dependent dispersion. Large sample of SNe allows new studies of systematic errors Stretch and color corrected luminosity:

  4. A heterogenous data sample

  5. A heterogenous data sample • Study of • mean deviation • residual slope

  6. Test for Tension high-z low-z mean deviation: OK

  7. Test for Tension high-z low-z residual slope: (OK)

  8. Evolution test: Redshift Evolution test: Population Systematic errors:Evolution of Supernovae No significant evidence for evolution!

  9. Nuisance parameters for systematic errors: sample dependent common for all z>0.2 SNe Systematic errors

  10. Comparison with previous compilations without the 8 new nearby SNe 184 SNe 192 SNe 307 SNe Union w/o New SCP SNe Riess Gold Davis 2007 Union Union Union

  11.  M M Results: Cosmological fit parameters Perlmutter et al., 1999 Combination of SNe with: BAO (Eisenstein et. al., 2005) CMB (WMAP-5 year data, 2008) For a flat Universe: … and with curvature:

  12. With systematics Equation of state: w=p/ SNe + BAO + CMB ... and allowing for curvature:

  13. w0+ wa= 0 Redshift dependent w w=w0 + (1-a) wa

  14. A floating non-SNe bin to decouple low from high-redshift constraints Redshift dependent w Assuming step-wise constant w:

  15. Summary The Union SN compilation provides a consistently analyzed data set, and with new nearby SNe, is the largest available. Investigations of systematics show no significant tension between the individual samples as well as no evidence for SN evolution. The strongest constraints to date on the dark energy density and the equation of state parameter w, however, essentially no constraints at z>1. A detailed paper has been submitted to ApJ and the data will soon be made available on the web (see http://supernova.lbl.gov)

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