The BoRG survey is primarily aimed at identifying the brightest, and hence rarest, galaxies during the reionization epoch, at redshift z > 7.5 by using broad-band imaging in the optical and near infrared with Hubble’s WFC3.
As of April 2015, the ongoing Cycle 22 BoRG[z9-10] observations, which started on October, 27 2014, covered 21 fields (an area of about 90 arcmin2) with WFC3 in five bands (F350LP, F105W, F125W, F140W, F160W). This set of bands is optimized for detection of galaxies at redshift z~9-10 [about 500 Myr after the BigBang], while still being effective in selecting galaxies at z~8 and at z~6-7. The total number of fields observed by the completion of the survey will reach 115 to 120, depending on scheduling constraints.
The BoRG[z8] portion of the dataset is from earlier observations (2010-2013), optimized for detection of galaxies at z~8. It consists of 78 fields that have been acquired with WFC3 in at least four bands (typically F606W, F098M, F125W, and F160W) for a total area exceeding 350 arcmin2. The analysis of the latest dataset has been published in Schmidt et al. (2014), where we discuss a total of 38 galaxy candidates at the bright-end of the z~8 luminosity function. This is the largest dataset for L>L* galaxies at z~8 and clearly shows that the bright-end of the galaxy luminosity function continues to be well described by a Schechter fit, as at lower redshift. Previous results have been reported in Trenti et al. (2011, 2012) and Bradley et al. (2012).
BoRG z~8 galaxies have been followed-up extensively at Keck with MOSFIRE, providing clear evidence of an evolution in the properties of Ly-alpha emission, which we interpret as an increase of the hydrogen neutral fraction from z~6 to z~8 (Treu et al. 2012, 2013).