Subluminous Type Ia Supernovae at High Redshift from the Supernova
  Legacy Survey
  The rate evolution of subluminous Type Ia Supernovae is presented using data
from the Supernova Legacy Survey. This sub-sample represents the faint and
rapidly-declining light-curves of the observed supernova Ia (SN Ia) population
here defined by low stretch values (s<0.8). Up to redshift z=0.6, we find 18
photometrically-identified subluminous SNe Ia, of which six have spectroscopic
redshift (and three are spectroscopically-confirmed SNe Ia). The evolution of
the subluminous volumetric rate is constant or slightly decreasing with
redshift, in contrast to the increasing SN Ia rate found for the normal stretch
population, although a rising behaviour is not conclusively ruled out. The
subluminous sample is mainly found in early-type galaxies with little or no
star formation, so that the rate evolution is consistent with a galactic mass
dependent behavior: $r(z)=A\times M_g$, with $A=(1.1\pm0.3)\times10^{-14}$ SNe
per year and solar mass.
