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We present rest-frame ultraviolet (UV) images of six luminous quasars at $z\sim 4.8$ obtained with the Hubble Space Telescope (HST). These quasars exhibita wide range of star formation rates (SFRs) and lie in a wide range ofenvironments. We carefully model and subtract the point-like quasar emissionand investigate the morphology of the underlying host galaxies at kpc scales.The residual images allowed identification of potential companion sources,which enabled us to explore the role of galaxy merger scenarios in theco-evolution of the quasars and their hosts. We also search for the mechanismdriving extreme SFRs in three of the quasars. We find that the rate ofdetection of potential companions to the host galaxies does not follow trendsbetween high- and low-SFR sources; i.e., the HST imaging suggests that bothhigh- and low-SFR sources are found in both dense and sparse galacticenvironments. The suggested role of major mergers driving extreme SFRs cannotbe supported by the multiwavelength data in hand. Three of four companionsources, previously revealed by sub-millimeter observations, are not detectedin the HST images of three of our quasars. An adapted high-resolution imagingstrategy focused on high-SFR sources and extended to a larger quasar sample isrequired to determine the role of mergers in the processes of star formationand supermassive black hole growth at high redshift.

Searching for the Role of Mergers in Fast and Early SMBH Growth: Morphological Decomposition of Quasars and Their Hosts at $z \sim 4.8$