Extreme Type IIp Supernovae as Yardsticks for Cosmology

Evolutionary effects with redshift of core collapse supernovae and their application to cosmology have been studied based on an extensive grid of stellar models between 13 and 25 Mo, and their light curves after the explosion. With decreasing metallicity Z and increasing mass, progenitors tend to explode as compact Blue Supergiants (BSG) and produce subluminous supernovae which are about 1.5 mag. dimmer compared to 'normal' SNeII with Red Supergiant (RSG) progenitors. Progenitors with small masses tend to explode as RSGs even with low Z. The consequences are obvious for probing the chemical evolution. We identify 'extreme SNe IIp' supernovae as a rather homogeneous class which may allow their use as standard candles for distance determination accurate within 30 %. Due to their unique light curves, no spectra need to be taken for their identification, and follow-up observations can be limited to a very small dynamical range in brightness. This means that distance determination by 'extreme SNe IIp" are possible up to redshifts of about 3 using 8-meter class telescopes. SIRTIF may push the limit by another magnitude.