The dependency of Type Ia Supernova parameters on host galaxy morphology
  for the Pantheon cosmological sample
  Type Ia Supernovae (SNe Ia) are widely used to measure distances in the
Universe. Despite the recent progress achieved in SN Ia standardisation, the
Hubble diagram still shows some remaining intrinsic dispersion. The remaining
scatter in supernova luminosity could be due to the environmental effects that
are not yet accounted for by the current standardisation methods. In this work,
we compare the local and global colour $(U-V)$, the local star formation rate,
and the host stellar mass to the host galaxy morphology. The observed trends
suggest that the host galaxy morphology is a good parameter to characterize the
SN Ia environment. Therefore, we study the influence of host galaxy morphology
on light-curve parameters of SNe Ia for the Pantheon cosmological supernova
sample. We determine the Hubble morphological type of host galaxies for a
sub-sample of 330 SNe Ia. We confirm that the SALT2 stretch parameter $x_1$
depends on the host morphology with the $p$-value $\sim10^{-14}$. The
supernovae with lower stretch value are hosted mainly by elliptical and
lenticular galaxies. No correlation for the SALT2 colour parameter $c$ is
found. We also examine Hubble diagram residuals for supernovae hosted by the
"Early-type" and "Late-type" morphological groups of galaxies. The analysis
reveals that the mean distance modulus residual in early-type galaxies is
smaller than the one in late-type galaxies, which means that early-type
galaxies contain brighter supernovae. However, we do not observe any difference
in the residual dispersion for these two morphological groups. The obtained
results are in the line with other analyses showing environmental dependence of
SN Ia light-curve parameters and luminosity. We confirm the importance of
including a host galaxy parameter into the standardisation procedure of SNe Ia
for further cosmological studies.
