and Cosmology

8. Cosmology III: The Cosmological Parameters
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Fig. 8.14. Left panel: B-band light curves of different SNe Ia.
One sees that the shape of the light curves and the maximum
luminosity of the SNe Ia differ substantially among
the sample. A transformation was found empirically with
a single parameter described by the width of the light
curve. By means of this transformation, the different light
curves can all be made congruent, as displayed in the right
panel
class telescopes need to be used for the spectroscopic
observations.
Both teams were very successful in detecting distant
SNe Ia. In their first large campaigns, the results of
which were published in 1998, they detected and analyzed
sources out to redshifts of z 0.8. Since then,
further SNe Ia have been found, some with redshifts
≥ 1. Substantial advances have also been made by observing
with the HST. Among other achievements, the
HST detected a SN Ia at redshift z = 1.7. Of special
relevance is that the conclusions of both teams are in extraordinary
agreement. Since they use slightly different
methods in the correction of the maximum luminosity,
this agreement serves as a significant test of the
systematic uncertainties intrinsic to this method.
parameters which best describes the dependence of observed
magnitudes m obs on redshift, as is illustrated in
Fig. 8.15.
Comparing the maximum magnitude of the measured
SNe Ia, or their distance modulus respectively,
with that which would be expected for an empty universe
(Ω m = 0 = Ω Λ ), one obtains a truly surprising
8.3.3 Results
As a first result, we mention that the width of the light
curve is larger for SNe Ia at higher redshift than it is for
local objects. This is expected because, due to redshift,
the observed width evolves by a factor (1 + z). This
dependence has been convincingly confirmed, showing
in a direct way the transformation of the intrinsic to the
observed time interval as a function of redshift.
Plotting the observed magnitudes in a Hubble diagram,
one can look for the set of cosmological
Fig. 8.15. Distance modulus of nearby and distant SNe Ia,
determined from the corrected maximum flux of the source.
Diamond symbols represent supernovae that were detected
from the ground, circles those that were found by the HST.
Particularly remarkable is the small scatter of the data points
around the curve that corresponds to a cosmological model
with Ω m = 0.29, Ω Λ = 0.71