For refcode 1998AJ....116.1009R: Retrieve 94 NED objects in this reference. Please click here for ADS abstract
NED Abstract
Copyright by American Astronomical Society.
Reproduced by permission
1998AJ....116.1009R
OBSERVATIONAL EVIDENCE FROM SUPERNOVAE FOR AN ACCELERATING UNIVERSE AND A
COSMOLOGICAL CONSTANT
ADAM G. RIESS, ALEXEI V. FILIPPENKO, PETER CHALLIS, ALEJANDRO CLOCCHIATTI,
ALAN DIERCKS, PETER M. GARNAVICH, RON L. GILLILAND, CRAIG J. HOGAN,
SAURABH JHA, ROBERT P. KIRSHNER, B. LEIBUNDGUT, M. M. PHILLIPS, DAVID
REISS, BRIAN P. SCHMIDT, ROBERT A. SCHOMMER, R. CHRIS SMITH,
J. SPYROMILIO, CHRISTOPHER STUBBS, NICHOLAS B. SUNTZEFF, AND JOHN TONRY
Received 1998 March 13; revised 1998 May 6
ABSTRACT
We present spectral and photometric observations of 10 Type Ia
supernovae (SNe Ia) in the redshift range 0.16 <= z <= 0.62. The luminosity
distances of these objects are determined by methods that employ relations
between SN Ia luminosity and light curve shape. Combined with previous data
from our Highz Supernova Search Team and recent results by Riess et al.,
this expanded set of 16 highredshift supernovae and a set of 34 nearby
supernovae are used to place constraints on the following cosmological
parameters: the Hubble constant (H_0_), the mass density ({OMEGA}_M_), the
cosmological constant (i.e., the vacuum energy density, {OMEGA}_{LAMBDA}_),
the deceleration parameter (q_0_), and the dynamical age of the universe
(t_0_). The distances of the highredshift SNe Ia are, on average, 10%15%
farther than expected in a low mass density ({OMEGA}_M_ = 0.2) universe
without a cosmological constant. Different light curve fitting methods, SN
Ia subsamples, and prior constraints unanimously favor eternally expanding
models with positive cosmological constant (i.e.,{OMEGA}_{LAMBDA}_ > 0) and
a current acceleration of the expansion (i.e., q_0_ < 0). With no prior
constraint on mass density other than {OMEGA}_M_ >= 0, the
spectroscopically confirmed SNe Ia are statistically consistent with q_0_ <
0 at the 2.8 {sigma} and 3.9 {sigma} confidence levels, and with
{OMEGA}_{LAMBDA}_ > 0 at the 3.0 {sigma} and 4.0 {sigma} confidence levels,
for two different fitting methods, respectively. Fixing a "minimal" mass
density, {OMEGA}_M_ = 0.2, results in the weakest detection,
{OMEGA}_{LAMBDA}_ > 0 at the 3.0 {sigma} confidence level from one of the
two methods. For a flat universe prior ({OMEGA}_M_ + {OMEGA}_{LAMBDA}_ =
1), the spectroscopically confirmed SNe Ia require {OMEGA}_{LAMBDA}_ > 0 at
7 {sigma} and 9 {sigma} formal statistical significance for the two
different fitting methods. A universe closed by ordinary matter (i.e.,
{OMEGA}_M_ = 1) is formally ruled out at the 7 {sigma} to 8 {sigma}
confidence level for the two different fitting methods. We estimate the
dynamical age of the universe to be 14.2 +/ 1.7 Gyr including systematic
uncertainties in the current Cepheid distance scale. We estimate the likely
effect of several sources of systematic error, including progenitor and
metallicity evolution, extinction, sample selection bias, local
perturbations in the expansion rate, gravitational lensing, and sample
contamination. Presently, none of these effects appear to reconcile the
data with {OMEGA}_{LAMBDA}_ = 0 and q_0_ >= 0.
Key words: cosmology: observationssupernovae: general
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