D. L. Carter

Measurements of the Cosmological Parameters

We have developed a technique to systematically discover and study high-redshift supernovae that can be used to measure the cosmological parameters. We report here results based on the initial seven of more than 28 supernovae discovered to date in the high-redshift supernova search of the Supernova Cosmology Project. We find an observational dispersion in peak magnitudes of ? -->MB=0.27; this dispersion narrows to ?MB, corr=0.19 after correcting the magnitudes using the light-curve width-luminosity relation found for nearby (z ? 0.1) Type Ia supernovae from the Cal?n/Tololo survey (Hamuy et al.). Comparing light-curve width-corrected magnitudes as a function of redshift of our distant (z = 0.35-0.46) supernovae to those of nearby Type Ia supernovae yields a global measurement of the mass density, ?M

\Omega

{r M}

and

-->=0.88 -->+ 0.69?0.60 for a ? = 0 cosmology. For a spatially flat universe (i.e., ?M + ?? = 1), we find ?M

\Lambda

{r M}

from the First 7 Supernovae at z >= 0.35

-->=0.94 -->+ 0.34?0.28 or, equivalently, a measurement of the cosmological constant, ??=0.06 -->+ 0.28?0.34 ( < 0.51 at the 95% confidence level). For the more general Friedmann-Lema?tre cosmologies with independent ?M and ??, the results are presented as a confidence region on the ?M-?? plane. This region does not correspond to a unique value of the deceleration parameter q0. We present analyses and checks for statistical and systematic errors and also show that our results do not depend on the specifics of the width-luminosity correction. The results for ??-versus-?M are inconsistent with ?-dominated, low-density, flat cosmologies that have been proposed to reconcile the ages of globular cluster stars with higher Hubble constant values.

The Type Ia Supernova Rate at z ~ 0.4

We present the first measurement of the rate of Type Ia supernovae at high redshift. The result is derived by using a large subset of data from the Supernova Cosmology Project. Three supernovae were discovered in a surveyed area of 1.7 deg2. The survey spanned a ~3 week baseline and used images with 3 σ limiting magnitudes of R ~ 23. We present our methods for estimating the numbers of galaxies and the number of solar luminosities to which the survey is sensitive, as well as the supernova detection efficiency, which is used to determine the control time, the effective time for which the survey is sensitive to a Type Ia event. We derive a rest-frame Type Ia supernova (SN) rate at z ~ 0.4 of 0.82−0.37–0.25+0.54 + 0.37 h2 SNu (1 SNu = 1 SN per century per 1010LB☉), where the first uncertainty is statistical and the second includes systematic effects. For the purposes of observers, we also determine the rate of SNe, per sky area surveyed, to be 34.4+23.9−16.2 SNe yr −1 deg −2 for SN magnitudes in the range 21.3 < R < 22.3.We present the first measurement of the rate of Type Ia supernovae at high redshift. The result is derived by using a large subset of data from the Supernova Cosmology Project. Three supernovae were discovered in a surveyed area of 1.7 deg{sup 2}. The survey spanned a {approximately}3 week baseline and used images with 3 {sigma} limiting magnitudes of {ital R}{approximately}23. We present our methods for estimating the numbers of galaxies and the number of solar luminosities to which the survey is sensitive, as well as the supernova detection efficiency, which is used to determine the control time, the effective time for which the survey is sensitive to a Type Ia event. We derive a rest-frame Type Ia supernova (SN) rate at {ital z}{approximately}0.4 of 0.82{sub {minus}0.37{minus}0.25}{sup +0.54+0.37} {ital h}{sup 2} SNu (1 SNu=1 SN per century per 10{sup 10} {ital L}{sub {ital B}{circle_dot}}), where the first uncertainty is statistical and the second includes systematic effects. For the purposes of observers, we also determine the rate of SNe, per sky area surveyed, to be 34.4{sub {minus}16.2}{sup +23.9} SNe yr{sup {minus}1} deg{sup {minus}2} for SN magnitudes in the range 21.3{lt}{ital R}{lt}22.3. {copyright} {ital 1996 The American Astronomical Society.}

A Supernova at z = 0.458 and Implications for Measuring the Cosmological Deceleration

We have begun a program to discover high-redshift supernovae (

Implications for the Hubble Constant from the First Seven Supernovae at z ? 0.35

z \approx

Implications for the Hubble Constant from the First Seven Supernovae at [CLC][ITAL]z[/ITAL][/CLC] ≥ 0.35

0.25--0.5), and study them with follow-up photometry and spectroscopy. We report here our first discovery, a supernova at

The type Ia supernova rate at {ital z}{approximately}0.4

z = 0.458