1. SDSS-II SN survey: Constraining Dark Energy with intermediate- redshift probes Hubert Lampeitl University Portsmouth, ICG In collaboration with: H.J. Seo, T. Giannantonio, C. Shapiro, R.C. Nichol, B. Bassett, W.J. Percival, T. Davis, B.Dilday, J. Frieman, P. Garnavich, M. Sako, M. Smith, J. Sollerman SN survey

2. Why intermediate-redshift probes? In most cosmological analysis several different probes are combined in order To derive the most constraining parameters on cosmology Most popular: SN + BAO + CMB but GS & ISW Stretch over a very wide redshift range (in case of CMB z=1089) In case of Supernova Ia combinations from Several Instruments (Nearby, ESSENCE, SNLS, HST): eg. Davis et al. 2007, Kowalski et al. 2008, Hicken et al, 2009, Kessler et al. 2009) Cross check: Are the results consistent if we limit ourself to one redshift range? - Less prone for systematic effects, but less stringent limits Systematic and statistical uncertainties for SN are now on same level! Increasing the sample doesn’t help! Kowalski et al. 2008 Eisenstein et al. 2005 Komatsu et al., 2009

3. Why intermediate-redshift probes? In most cosmological analysis several different probes are combined in order To derive the most constraining parameters on cosmology Most popular: SN + BAO + CMB but GS & ISW Stretch over a very wide redshift range (in case of CMB z=1089) In case of Supernova Ia combinations from Several Instruments (Nearby, ESSENCE, SNLS, HST): eg. Davis et al. 2007, Kowalski et al. 2008, Hicken et al, 2009, Kessler et al. 2009) Cross check: Are the results consistent if we limit our self to one redshift range? - Less prone for systematic effects, but less stringent limits Systematic and statistical uncertainties for SN are now on same level! Increasing the statistic doesn’t help! Kowalski et al. 2008 Kessler et al, 2009

4. Possible and identified problems with Supernova -Restframe u-band (UV lightcurve ~ 10%) - evolution of SN spectra over redshift and progenitor type - SN demographics --> k-corrections - Dust in host galaxy (R V =3.1 vs. 2.2) - local peculiar velocities (Hubble bubble) - selection effects - photometric cross survey calibration. Foley et al., 2008 Nugent Hasiao

5. Goals: SDSS-II SNe Survey

6. Hubert Lampeitl, ICG, 29/5/2008 484 confirmed SN with IAU designation

7. Hubert Lampeitl, ICG Z = 0.013 Z = 0.47

8. Additional spectroscopic observation time awarded on BOSS spectrograph to follow up and get redshifts for SN candidates without confirmed redshift

9. SDSS-II SN survey: 1 st year - 103 spectroscopically confirmed SN with z=[0.045;0.42] from 2005 after stringent quality cuts - All fit with MLCS2k2 for various LC fitter choices (evaluation of LC fitter systematic, Kessler et al, 2009) -Fiducial model chosen to reflect current understanding L CDM q 0 =-0.33 z=0.34 z=0.13 Scatter ~0.14 mag

10. Case for acceleration for q 0 = constant and flat universe (C. Shapiro) Principal components: a 1 <0 only if the universe has accelerated at one point: P=96% Independent of matter content content

11. Hubert Lampeitl, ICG Baryon Acoustic Oscillations (BAO) z=1089 SDSS/2dF z = 0.2 z = 0.35 Eisenstein et al., 2005 Percival et al., 2007 D V (0.35)/D V (0.2) = 1.812 ± 0.062 BAO provides a ‘standard ruler’ 1:1 scaling wit a(t)

12. Distance Duality Phase space density of photons must be conserved in all metric theories of gravity (Etherington 1933, Ellis 1971) ! BAOSN L CDM More, Bovy, &Hogg 2009 Avgoustidis, Verde, & Jimenez 2009

13. Constraining w with ISW Giannantonio et al., astro- ph/0801.4380 private communication SDSS DR6 Main galaxy sample & LRG ISW detected on with ~3 s & growth of structure Peacock, Nature 410, 169 (2001) Linder, PhRvD 72 (2005) Kaiser Effect: 2dFGRS (Hawkins, 2003) Including bias

14. Constraining Cosmological Parameters BAO SDSS-SN ISW GS flat curved (1 sigma errors) Curvature constrained by WMAP:

15. Systematic uncertainties Main uncertainty: U-band anomaly caused by uncertainties in spectral library -0.41 (sys) in w Combining other identified systematic effects uncertainty results in +/- 0.16 (sys) in w Hard to quantify and easily underestimated!

16. Summary Supernova drawn from SDSS-II SN survey finds under the Assumption of a flat universe indication of an accelerating universe with a probability>97% No compelling evidence for a violation of distance duality found using SN & BAO. Possible indication of systematic effect in one of the probes. Combining the SDSS SN data with either ISW or GS gives Limits on w: