Further evidence for significant luminosity evolution in supernova
  cosmology
  Supernova (SN) cosmology is based on the assumption that the corrected
luminosity of SN Ia would not evolve with redshift. Recently, our age dating of
stellar populations in early-type host galaxies (ETGs) from high-quality
spectra has shown that this key assumption is most likely in error. It has been
argued though that the age-Hubble residual (HR) correlation from ETGs is not
confirmed from two independent age datasets measured from multi-band optical
photometry of host galaxies of all morphological types. Here we show, however,
that one of them is based on highly uncertain and inappropriate
luminosity-weighted ages derived, in many cases, under serious template
mismatch. The other dataset employs more reliable mass-weighted ages, but the
statistical analysis involved is affected by regression dilution bias, severely
underestimating both the slope and significance of the age-HR correlation.
Remarkably, when we apply regression analysis with a standard posterior
sampling method to this dataset comprising a large sample ($N=102$) of host
galaxies, very significant ($> 99.99 \%$) correlation is obtained between the
global population age and HR with the slope ($-0.047 \pm 0.011$~mag/Gyr) highly
consistent with our previous spectroscopic result from ETGs. For the local age
of the environment around the site of SN, a similarly significant ($> 99.96
\%$) correlation is obtained with a steeper slope ($-0.057 \pm 0.016$ mag/Gyr).
Therefore, the SN luminosity evolution is strongly supported by the age dating
based on multi-band optical photometry and can be a serious systematic bias in
SN cosmology.
