We would like to complete a spectroscopic follow-up of the last HSC-HST observed Type Ia supernova (SNIa) host galaxies. SNIa is one of the most powerful probes to constrain the nature of dark energy. In addition to HSC SSP Transient survey, our sister projects (long term AGN, Superluminous SNe survey) added new 206 SNe in 2021 survey. In total, we have 669 SNeIa candidates including 217 SNeIa at z>1 (photo-z), a factor of six improvement. We have sent the best 36 supernovae to the Hubble Space Telescope (HST) for IR follow-up so that we can perform accurate SN color measurement. Through our international collaboration (Keck, Gemini, VLT, GTC, AAT and DESI), we have collected 357 spec-z. However 227 SNeIa remain photo-z, they cannot be placed on the Hubble Diagram for cosmological analysis. This proposed observation is critical to make the best use of the precious HSC-HST SNeIa and to achieve the most precise measurement of dark energy. The remaining several host galaxies are very faint (24.0-24.5th mag in i-band) that are beyond reach of DESI/AAT. We need the power of 8-10m telescopes, Subaru/Keck time. Our high-z SNeIa data set would remain unique and competitive among other surveys for many years to come.
This document was translated from LATEX by HEVEA.