Nicolas Laporte and collaborators have compared the deep HST images of Frontier Fields cluster Abell 2744 to 50 hours of Spitzer IRAC imaging. One of the best candidates for a distant z~8 galaxy — detected in the HST WFC3/IR images — disappears in the IRAC 3.6 micron image and reappears in the IRAC 4.5 micron image. The best explanation for these strange colors is the appearance of very strong emission lines from oxygen and hydrogen ([OIII] and H-beta) which fall into the 4.5 micron band at a redshift of z~7.98.
The paper has been accepted for publication in the A&A Letters.
Check out the details: http://arxiv.org/abs/1401.8263v1.
JWST will be able to provide conclusive observations with both NIRSpec and NIRCam grism observations. Bring on 2018 and the launch of JWST!