2016ApJ...817..120C

We present the first results and design from the redshift z ∼ 9-10 Brightest of the Reionizing Galaxies Hubble Space Telescope survey BoRG[z9-10], aimed at searching for intrinsically luminous unlensed galaxies during the first 700 Myr after the Big Bang. BoRG[z9-10] is the continuation of a multi-year pure-parallel near-IR and optical imaging campaign with the Wide Field Camera 3. The ongoing survey uses five filters, optimized for detecting the most distant objects and offering continuous wavelength coverage from λ = 0.35 µm to λ = 1.7 µm. We analyze the initial ∼130 arcmin² of area over 28 independent lines of sight (∼25% of the total planned) to search for z > 7 galaxies using a combination of Lyman-break and photometric redshift selections. From an effective comoving volume of (5-25)x10⁵ Mpc³ for magnitudes brighter than m_AB = 26.5 - 24.0 in the H₁₆₀-band respectively, we find five galaxy candidates at z ∼ 8.3-10 detected at high confidence (S/N > 8), including a source at z ∼ 8.4 with m_AB = 24.5 (S/N ∼ 22), which, if confirmed, would be the brightest galaxy identified at such early times (z > 8). In addition, BoRG[z9-10] data yield four galaxies with 7.3 ≲ z ≲ 8. These new Lyman-break galaxies with m ≲ 26.5 are ideal targets for follow-up observations from ground and space-based observatories to help investigate the complex interplay between dark matter growth, galaxy assembly, and reionization.