No we can't and we should not: Once again, supernova researchers have presented us with a new data reduction exercise and a new set of assumptions, not the least of which is:
Quote:
|
Originally Posted by Blondin et al
We also test for power-law dependencies of the aging rate on redshift. The best-fit exponent for these models is consistent with the expected 1/(1 + z) factor.
|
If the proper interpretation of the spectrum includes a power law reduction of the spectrum that is consistent with aging in the supernova population, what does this tell us about prior studies? In 2001, Goldhaber and Perlmutter assumed that there was
no aging bias and determined there was no Malmquist bias in crop of supernovae up to much redshifts higher that 0.62. They published curves in which
their residuals fell evenly upon both sides of their mean at all redshifts.
In their introduction, Blondin says:
Quote:
|
Originally Posted by Blondin et al
It is problematic to disentangle this intrinsic variation of light-curve width with luminosity and the effect of time dilation. To directly test the time-dilation hypothesis one needs to accurately know the distribution of light-curve widths at z = 0 and its potential evolution with redshift, whether due to a selection effect (not taken into account by Goldhaber et al. 2001) or an evolution of the mean properties of the SN Ia sample with redshift—as possibly observed by Howell et al. (2007). Moreover, one needs to probe sufficiently high redshifts (z & 0.4, as done by Leibundgut et al. 1996; Goldhaber et al. 2001) such that the observed widths of the SN Ia light curves are broader than the intrinsic width of any nearby counterpart.
Furthermore, one might argue that at high redshift we are preferentially finding the brighter events (akin to a Malmquist bias). Such a selection effect would produce a spurious relation in which there would be broader light curves at higher redshifts, without any time dilation.
|
There are several lines of evidence that suggest Malmquist bias in a major factor: We find much brighter supernova events with longer lightcurves in the local sample that in the high redshift time-dilation corrected sample. That is a red flag. There are fewer supernova being found at high redshift than a simple extrapolation from the local population would predict. Fewer observed events at high redshift is consistent with the local population,
if cosmic attenuation factors are severely underestimated. In this case, the punitive sample of high redshift events observed is consistent with the small population of overluminous events observed locally. Finally, their is the observation of a few supernova at high redshift that have the spectra of type Ia, but their light curves are much too short (after time dilation correction) to consider them 'normal' type Ia. If space is more greatly attenuated that currently believed, this small sample of understudied events may actually be more representitive of the nominal local population.
I don't think you will see a hard verdict on supernova light curves and time dilation until the scopes are both powerful enough to more clearly identify 'underluminous' supernova at great distances and compare the 'underluminous' distributions at high and low redshifts. In any case, The distant sample should include events featuring extremely long light curves (after time dilation corrections) - lightcurves that are much longer than the longest light curves found in the local space. These extremely long lightcurves have not been observed.