Institution(s): 1. Laboratoire d'Astrophysique de Marseille
WISH is a new space science mission concept whose primary goal is to study the first galaxies in the early universe. WISH will be a 1.5m telescope equipped with a 1000 arcmin2 wide-field Near-IR camera that would fly in ~2020 in order to conduct unique ultra-deep and wide-area sky surveys in the wavelength range 1-5 micron. A spectroscopic mode (Integral-Field Unit) in the same Near-IR range is also planned. The primary science goal of WISH mission is to push the high-redshift frontier beyond the epoch of reionization by utilizing its unique imaging capability and the dedicated survey strategy. Which spectral range should we select to optimize the detection of very high-redshift (i.e., z > 5) galaxies ? In the rest-frame Far-UV or in the rest-frame Far-IR? In a recent paper, Burgarella et al. (2013) showed that the Far-UV dust attenuation (AFUV) reaches the same level at z ~ 3 than at z = 0 . This suggest that the early universe would be better studied in the rest-frame Far-UV. At z > 5, this Far-UV range moves into the Near-IR (1 - 5um) which is WISH’s preferred spectral range. The baseline of WISH-Spec is a 1x1 arcmin2 Integral-Field Unit (IFU) using slicers. WISH-Spec could observe in a parallel mode which translates into spectroscopic exposure times as long as the telescope lifetime. WISH features two 100-deg2 and 1000-deg2 surveys. However, WISHSpec will allow to acquire very large samples of high-redshift and primordial galaxies by combining spectroscopic detections within total (non contiguous) 1-deg2 and 10-deg2 fields of views. Therefore, the first strong advantage of WISHSpec wrt JWST is that 10^4 - 10^5 faint emission-line galaxies in 1 deg2 and 10^3 - 10^6 bright emission-line galaxies in 10 deg2 in the redshift range 3 < z < 8 will be detected.