Bright galaxies at Hubble's redshift detection frontier: Preliminary results and design from the redshift z~9-10 BoRG pure-parallel HST survey

TL;DR

This paper reports initial findings from the BoRG[z9-10] Hubble survey, detecting bright galaxy candidates at redshifts around 8.3 to 10, providing insights into early galaxy formation during the first 700 million years after the Big Bang.

Contribution

It presents the first results and survey design of the BoRG[z9-10] program targeting luminous galaxies at z~9-10, expanding the search for early universe galaxies with new observational data.

Findings

Detected five high-confidence galaxy candidates at z~8.3-10.

Identified a notably bright galaxy at z~8.4 with mAB=24.5.

Found four additional galaxies with 7.3 < z < 8.

Abstract

We present the first results and design from the redshift z~9-10 Brightest of the Reionizing Galaxies {\it 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 {\lambda}=0.35{\mu}m to {\lambda}=1.7{\mu}m. 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, BoRG[z9-10] data yield four galaxies with $7.3 \lesssim z \lesssim 8$. These new Lyman break galaxies with m$\lesssim26.5$ 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.