M. S. Burns

Spectra and hubble space telescope light curves of six typE Ia supernovae at 0.511 < z < 1.12 and the union2 compilation

We report on work to increase the number of well-measured Type Ia supernovae (SNe Ia) at high redshifts. Light curves, including high signal-to-noise HST data, and spectra of six SNe Ia that were discovered during 2001 are presented. Additionally, for the two SNe with z>1, we present ground-based J-band photometry from Gemini and the VLT. These are among the most distant SNe Ia for which ground based near-IR observations have been obtained. We add these six SNe Ia together with other data sets that have recently become available in the literature to the Union compilation (Kowalski et al. 2008). We have made a number of refinements to the Union analysis chain, the most important ones being the refitting of all light curves with the SALT2 fitter and an improved handling of systematic errors. We call this new compilation, consisting of 557 supernovae, the Union2 compilation. The flat concordance LambdaCDM model remains an excellent fit to the Union2 data with the best fit constant equation of state parameter w=-0.997^{+0.050}_{-0.054} (stat) ^{+0.077}_{-0.082} (stat+sys\ together) for a flat universe, or w=-1.035^{+0.055}_{-0.059} (stat)^{+0.093}_{-0.097} (stat+sys together) with curvature. We also present improved constraints on w(z). While no significant change in w with redshift is detected, there is still considerable room for evolution in w. The strength of the constraints depend strongly on redshift. In particular, at z > 1, the existence and nature of dark energy are only weakly constrained by the data.We report on work to increase the number of well-measured Type Ia supernovae (SNe Ia) at high redshifts. Light curves, including high signal-to-noise HST data, and spectra of six SNe Ia that were discovered during 2001 are presented. Additionally, for the two SNe with z > 1, we present groundbased J-band photometry from Gemini and the VLT. These are among the most distant SNe Ia for which ground based near-IR observations have been obtained. We add these six SNe Ia together with other data sets that have recently become available in the literature to the Union compilation (Kowalski et al. 2008). We have made a number of refinements to the Union analysis chain, the most important ones being the refitting of all light curves with the SALT2 fitter and an improved handling of systematic errors. We call this new compilation, consisting of 557 supernovae, the Union2

New Constraints on ΩM, ΩΛ, and w from an Independent Set of 11 High-Redshift Supernovae Observed with the Hubble Space Telescope*

We report measurements of

The Hubble diagram of type Ia supernovae as a function of host galaxy morphology

\Omega_M

Quantitative comparison between Type Ia supernova spectra at low and high redshifts: A case study

,

Spectra of High-Redshift Type Ia Supernovae and a Comparison with Their Low-Redshift Counterparts*

\Omega_\Lambda

PRECISION MEASUREMENT OF THE MOST DISTANT SPECTROSCOPICALLY CONFIRMED SUPERNOVA Ia WITH THE HUBBLE SPACE TELESCOPE

, and w from eleven supernovae at z=0.36-0.86 with high-quality lightcurves measured using WFPC-2 on the HST. This is an independent set of high-redshift supernovae that confirms previous supernova evidence for an accelerating Universe. Combined with earlier Supernova Cosmology Project data, the new supernovae yield a flat-universe measurement of the mass density

Spectroscopic confirmation of high-redshift supernovae with the ESO VLT

\Omega_M=0.25^{+0.07}_{-0.06}

CONSTRAINING DUST AND COLOR VARIATIONS OF HIGH-z SNe USING NICMOS ON THE HUBBLE SPACE TELESCOPE *

(statistical)

SPECTRA AND HUBBLE SPACE TELESCOPE LIGHT CURVES OF SIX TYPE Ia SUPERNOVAE AT 0.511

\pm0.04

Spectroscopic Observations and Analysis of the Peculiar SN 1999aa

(identified systematics), or equivalently, a cosmological constant of