6 Snapping Supernovae at z > 1 . 7

We examine the utility of very high redshift Type Ia supernovae for cosmology and systematic uncertainty control. Next generation space surveys such as the Supernova/Acceleration Probe (SNAP) will obtain thousands of supernovae at z > 1.7, beyond the design redshift for which the supernovae will be exquisitely characterized. We find that any z & 2 standard candles’ use for cosmological parameter estimation is quite modest and subject to pitfalls; we examine gravitational lensing, redshift calibration, and contamination effects in some detail. The very high redshift supernovae — both thermonuclear and core collapse — will provide copious interesting information on star formation, environment, and evolution. However, the new observational systematics that must be faced, as well as the limited expansion of SN-parameter space afforded, does not point to high value for 1.7 < z < 3 SNe Ia in controlling evolutionary systematics relative to what SNAP can already achieve at z < 1.7. Synergy with observations from JWST and thirty meter class telescopes afford rich opportunities for advances throughout astrophysics. Subject headings: cosmology: observations — cosmology: theory — supernovae