SAPPHIRES: Slitless Areal Pure-Parallel High-Redshift Emission Survey

One great surprise in the early years of the JWST operation was the transformative power of the NIRCam/Grism Wide Field Slitless Spectroscopy (WFSS) mode, producing ~1000 redshifts at z=5-9 in a total area of ~120 arcmin^2 with 2 hour integrations. It is particularly suited for conducting a highly complete unbiased survey of bright line-emitting galaxies. In Cycle 3, the NIRCam/WFSS mode has become available for Pure-Parallel for the first time. To capitalize on this new opportunity, we propose here a wide-field (~1 deg^2) pure-parallel NIRCam/WFSS treasury survey SAPPHIRES (Slitless Areal Pure-Parallel HIgh-Redshift Emission Survey) with a total pure-parallel time request of 600 hours. The primary goal is to conduct a highly complete spectroscopy-based census of the most luminous (M_uv < -21 mag) galaxies at z=4-9 and beyond, thereby making a robust determination of their number density and opening up the possibility for further detailed follow-up studies. The higher-than-expected number density (~10^-5 mag^-1 Mpc^-3) of luminous (M_uv~-21) galaxies at z=10-12 reported by early JWST studies has generated much excitement, but a 1-deg-scale survey is required to achieve a statistically meaningful sampling of such luminous high-redshift galaxies. The obtained data will be rich with information, containing a variety of line detections over a wide redshift range (e.g., ~12000 H-alpha emitters at z=4-7; ~1800 [OIII] emitters at z=5-9), allowing a large number of science programs. We will release all our data products together with the softwares we have developed in a timely manner, enabling the world-wide astronomical community to exploit this exciting data set.