Narrowband filter system at the SUBARU prime focus

The Subaru telescope has an excellent performance of wide yield of view at the prime focus. A big area of 30 inches times 24 inches is observable at a time with the prime focus camera(the Suprime-Cam). Making the best use of the wide view, we are constructing narrowband(NB) filter system consisting of 20 bands. This system covers the wavelengths between 4,000 angstrom and 10,000 angstrom. The band width(BW) varies from 200 angstrom to 400 angstrom depending on the center wavelength(CW). The resolving power of the system is 23(R23). Each filter has a big dimension of 205nm times 170mm and excellent uniformities on CW, BW and peak transmittance(T_peak). Employing this filter system, spectroscopy for all objects recorded in fields of view is possible at the wavelength resolution of R23. The limiting magnitude would reach 27AB in reasonable observation time even at long wavelength bands. Such deep NB imaging spectroscopic survey should provide huge catalogue on cosmological objects. Especially, photometric redshift analyses with higher spectral resolution of R23 than ordinary broadband system of R ≈ 4, will revolutionarily develop studies on formation and evolution of galaxies together with search for large scale structures at high redshift, based on enormous statistics, for example, 10⁴ or more galaxies at high redshift of z > 3. Also, a lot of objects having strong emission lines as QSO/AGNs and Lyα galaxies will be discovered, because NB filter is strong in detection of emission line. The use of NB filter system in survey observations is surely quite conservative in concept and time consuming in general. However, combining this method with the wide field of view provided in the largest class telescope, new window to the universe is going to open.