Constraining Type Ia supernovae through their heights in edge-on galaxies

In this Letter, using classified 197 supernovae (SNe) Ia, we perform an analyses of their height distributions from the disc in edge-on spirals and investigate their light-curve (LC) decline rates \((\Delta m_{15})\). We demonstrate, for the first time, that 91T- and 91bg-like subclasses of SNe Ia are distributed differently toward the plane of their host disc. The average height from the disc and its comparison with scales of thin/thick disc components gives a possibility to roughly estimate the SNe Ia progenitor ages: 91T-like events, being at the smallest heights, originate from relatively younger progenitors with ages of about several 100 Myr, 91bg-like SNe, having the highest distribution, arise from progenitors with significantly older ages \(\sim 10\) Gyr, and normal SNe Ia, which distributed between those of the two others, are from progenitors of about one up to \(\sim 10\) Gyr. We find a correlation between LC decline rates and SN Ia heights, which is explained by the vertical age gradient of stellar population in discs and a sub-Chandrasekhar mass white dwarf explosion models, where the \(\Delta m_{15}\) parameter is a progenitor age indicator.