A Revised SALT2 Surface for Fitting Type Ia Supernova Light Curves
  We present a revised SALT2 surface (`SALT2-2021') for fitting the light
curves of Type Ia supernovae (SNe Ia), which incorporates new measurements of
zero-point calibration offsets and Milky Way extinction. The most notable
change in the new surface occurs in the UV region. This new surface alters the
distance measurements of SNe~Ia, which can be used to investigate the nature of
dark energy by probing the expansion history of the Universe. Using the revised
SALT2 surface on public data from the first three years of the Dark Energy
Survey Supernova Program (combined with an external low-$z$ SNe Ia sample) and
combining with cosmic microwave background constraints, we find a change in the
dark energy equation of state parameter, $\Delta w = 0.015 \pm 0.004$. This
result highlights the continued importance of controlling and reducing
systematic uncertainties, particularly with the next generation of supernova
analyses aiming to improve constraints on dark energy properties.
