Abstract
We present the first results and design from the redshift z~9-10 Brightest of
the Reionizing Galaxies Hubble Space Telescope survey BoRGz9-10, aimed
at searching for intrinsically luminous unlensed galaxies during the first 700
Myr after the Big Bang. BoRGz9-10 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
łambda=0.35\mum to łambda=1.7\mum. We analyze the initial ~130
arcmin$^2$ 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)
$times 10^5$ Mpc$^3$ for magnitudes brighter than $m_AB=26.5-24.0$ in the
$H_160$-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 mAB=24.5
(S/N~22), which, if confirmed, would be the brightest galaxy identified at such
early times (z>8). In addition, BoRGz9-10 data yield four galaxies with $7.3
z 8$. These new Lyman break galaxies with m$łesssim26.5$ 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.
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