First results using a new near-infrared 1% narrow-band filter in the GTC 10.4m telescope to detect galaxies at the dawn of the universe

We present the first results using a new SCHOTT 1% narrow band filter in the near infrared for the CIRCE camera of the 10.4m GTC telescope. The goal of the project is to detect very distant galaxies at the dawn of the Universe. These remote and extremely faint galaxies are selected by their Ly-alpha emission. For this project SCHOTT manufactured a high transmission 11 nm narrow band filter which has been used in the fully cryogenic near-infrared camera CIRCE of the Gran Telescopio Canarias Telescope. A steep interference filter Bandpass with FWHM 11nm centered at 1254nm was coated on a fused silica substrate. The filter achieved excellent maximum transmission and deep out of band blocking. This was achieved by using magnetron sputtering for the filter coating process. We report on the spectral and interferometric results of the filter and the scientific results achieved with a first set of observations.