Improved cosmological constraints from a joint analysis of the SDSSII and SNLS supernova samples
Abstract
Aims: We present cosmological constraints from a joint analysis of type Ia supernova (SN Ia) observations obtained by the SDSSII and SNLS collaborations. The dataset includes several lowredshift samples (z< 0.1), all three seasons from the SDSSII (0.05 <z< 0.4), and three years from SNLS (0.2 <z< 1), and it totals 740 spectroscopically confirmed type Ia supernovae with highquality light curves.
Methods: We followed the methods and assumptions of the SNLS threeyear data analysis except for the following important improvements: 1) the addition of the full SDSSII spectroscopicallyconfirmed SN Ia sample in both the training of the SALT2 lightcurve model and in the Hubble diagram analysis (374 SNe); 2) intercalibration of the SNLS and SDSS surveys and reduced systematic uncertainties in the photometric calibration, performed blindly with respect to the cosmology analysis; and 3) a thorough investigation of systematic errors associated with the SALT2 modeling of SN Ia light curves.
Results: We produce recalibrated SN Ia light curves and associated distances for the SDSSII and SNLS samples. The large SDSSII sample provides an effective, independent, lowz anchor for the Hubble diagram and reduces the systematic error from calibration systematics in the lowz SN sample. For a flat ΛCDM cosmology, we find Ω_{m} =0.295 ± 0.034 (stat+sys), a value consistent with the most recent cosmic microwave background (CMB) measurement from the Planck and WMAP experiments. Our result is 1.8σ (stat+sys) different than the previously published result of SNLS threeyear data. The change is due primarily to improvements in the SNLS photometric calibration. When combined with CMB constraints, we measure a constant darkenergy equation of state parameter w =1.018 ± 0.057 (stat+sys) for a flat universe. Adding baryon acoustic oscillation distance measurements gives similar constraints: w =1.027 ± 0.055. Our supernova measurements provide the most stringent constraints to date on the nature of dark energy.
Appendices are available in electronic form at http://www.aanda.orgFull Table F.3 and covariance matrix are only available at the CDS via anonymous ftp to http://cdsarc.ustrasbg.fr (ftp://130.79.128.5) or via http://cdsarc.ustrasbg.fr/vizbin/qcat?J/A+A/568/A22
 Publication:

Astronomy and Astrophysics
 Pub Date:
 August 2014
 DOI:
 10.1051/00046361/201423413
 arXiv:
 arXiv:1401.4064
 Bibcode:
 2014A&A...568A..22B
 Keywords:

 cosmology: observations;
 distance scale;
 dark energy;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 30 pages, 18 figures, Submitted to A&