0 Assigned ID: 954 ----- Attempting Submission 1 (Fri Apr 10 22:30:09 GMT 2015) ----- HST Phase I Proposal 954 (HST_FF_AR_submitted.apt) successfully submitted. Receipt: # 954-1 ----- Attempting Submission 2 (Fri Apr 10 23:13:23 GMT 2015) ----- HST Phase I Proposal 954 (HST_FF_AR_submitted.apt) successfully submitted. Receipt: # 954-2 ----- Attempting Submission 3 (Fri Apr 10 23:17:14 GMT 2015) ----- We propose to use the exceptionally deep images of the Hubble Frontier Fields (HFF) observations of Abell 2744 and MACSJ0416.1-24.03 (z=0.31 and 0.40) to characterize the first ever compact stellar systems seen beyond a Gigaparsec in distance: globular clusters (GCs), ultra-compact dwarf galaxies (UCDs), dwarf early-type galaxy's nuclei (dEN), and compact early-type galaxies (cEs) within the clusters themselves. These two clusters are extraordinarily rich in the number and variety of galaxies they contain. Both exhibit multiple peaks in the dark matter, X-ray, and galaxy density distributions, suggesting the we are witnessing an ongoing collision of several massive clusters. Using these compact stellar systems as fossil records of the violent interactions that shaped these massive clusters and the galaxies in them, we will gain new insight of cluster formation processes and will explore the connection between star clusters and faint compact galaxies. We will model and remove the stellar light of the cluster galaxies in all seven optical and infrared bands to uncover the large hidden population of GCs and other compact stellar systems. We will use this extraordinarily deep multiwavelength dataset to analyze the spatial distribution and color-based stellar populations to explore the nature of these compact systems, the universality of their formation efficiency, probe their formation scenarios, and use them as possible tracers of the complex dynamical histories of these clusters. We will release the background subtracted images and multiwavelength photometric catalogs for all sources in both clusters. This is a key dataset optimal for a wide range of legacy science. UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 0 Regular false false false false false SUPPORTED