16715

Recent understanding of HST-STIS coronagraphic high contrast imaging mode can enable the study of quasar surroundings in visible light at high-contrast and high-resolution. We request 8 orbits of coronagraphic imaging mode to observe the surrounding environments for quasar 3C 273 with STIS as a first extragalactic science demonstration of this mode. Using the recently commissioned BAR5 occulter comma we can probe the host galaxy morphology and features of the quasar.s circumnuclear environment down to 0.2 arcsec comma or virgul520 pc. In our preparatory work comma on the one hand comma we have discovered new host galaxy structures at virgul1 arcsec in the re-analysis of non-coronagraphic STIS observations of 3C 273 on the other hand comma our pilot Keck-NIRC2 near-IR observation has revealed a candidate circumnuclear disk with a diameter of virgul1 kpc. Coronagraphic observations with STIS will not only help characterize this candidate structure comma provide critical constraints for determining whether the host galaxy is undergoing a merger comma but also provide an unprecedented view of the surroundings of 3C 273 in visible light. Moreover comma combined with archival re-analysis comma we can establish a virgul20 year baseline to study apparent motion for its jet. This project further demonstrates the necessity of multi-instrument coronagraphic imaging from visble to near-infrared in understanding the surrounding environments of quasars.