0 Assigned ID: 879 ----- Attempting Submission 1 (Fri Apr 08 21:42:32 GMT 2016) ----- HST Phase I Proposal 879 (aptform.apt) successfully submitted. Receipt: # 879-1 ----- Attempting Submission 2 (Fri Apr 08 23:24:17 GMT 2016) ----- HST Phase I Proposal 879 (aptform.apt) successfully submitted. Receipt: # 879-2 ----- Attempting Submission 3 (Fri Apr 08 23:49:39 GMT 2016) ----- Gravitational lensing by massive galaxy clusters has enabled more efficient searches for high-redshift galaxies, including discoveries out to z ~ 11. Lensing has also revealed the intrinsically faintest galaxies yet known, extending luminosity function constraints several magnitudes fainter than the UDF. These faint galaxy constraints are crucial to understanding early galaxy evolution and reionization. However, current galaxy detection methods fall short of detecting the intrinsically faintest galaxies. Highly magnified galaxies are usually strongly sheared (elongated) and often blended with cluster galaxies as well. We recently showed that these two effects can lead to losses of more than half of the lensed sources in the high magnification regime, especially for the highest redshift galaxies. We have developed a promising method that can recover these lost arcs, primarily via a forward modeling approach that uses the cluster lens model to develop a spatially varying multi-epoch optimal filter to detect the faint arcs. Further testing is required to quantify our recovery rates and test the resulting photometry in surveys such as CLASH, the Frontier Fields, and RELICS. In doing so, we will realize the true power of these cosmic telescopes enabling us and others to maximize the investment of HST in these cluster surveys by finding the highest redshift sources, improving constraints on z > 8 luminosity functions, and better understanding the epoch of reionization. Additionally, this HST investment will see further returns as these lost arcs will make the ideal targets for extended follow-up with JWST and extremely large telescopes. Intergalactic Medium and Cosmology Galaxies 0 Regular false false true SUPPORTED