Near-infrared Survey of the GOODS-North Field: Search for Luminous Galaxy Candidates at z >~ 6.5

Abstract

We present near-infrared (NIR; J and K _s) survey of the Great Observatories Origins Deep Survey-North (GOODS-N) field. The publicly available imaging data were obtained using the MOIRCS instrument on the 8.2 m Subaru and the WIRCam instrument on the 3.6 m Canada-France-Hawaii Telescope (CFHT). These observations fulfill a serious wavelength gap in the GOODS-N data, i.e., lack of deep NIR observations. We combine the Subaru/MOIRCS and CFHT/WIRCam archival data to generate deep J- and K _s-band images, covering the full GOODS-N field (~169 arcmin²) to an AB magnitude limit of ~25 mag (3σ). We applied z ₈₅₀-band dropout color selection criteria, using the NIR data generated here. We have identified two possible Lyman break galaxy (LBG) candidates at z >~ 6.5 with J <~ 24.5. The first candidate is a likely LBG at z ~= 6.5 based on a weak spectral feature tentatively identified as Lyα line in the deep Keck/DEIMOS spectrum, while the second candidate is a possible LBG at z ~= 7 based on its photometric redshift. These z ₈₅₀-dropout objects, if confirmed, are among the brightest such candidates found so far. At z >~ 6.5, their star formation rate is estimated as 100-200 M _⊙ yr^-1. If they continue to form stars at this rate, they assemble a stellar mass of ~5 × 10¹⁰ M _⊙ after about 400 million years, becoming the progenitors of massive galaxies observed at z ~= 5. We study the implication of the z ₈₅₀-band dropout candidates discovered here, in constraining the bright end of the luminosity function and understanding the nature of high-redshift galaxies.