Presentation #1235 in the session “Open Engagement Session C”.
Does external radiation environment of stellar nurseries affect protoplanetary disk properties and evolution? Protoplanetary disks are sites of planet formation, and the properties of disks and their dispersal could be strongly influenced by external UV radiation. Recent studies suggest that external photoevaporation dominates disk dispersal process over encounters in young clusters, e,g., in Orion nebula cluster. In a strong UV environment, such as in the Trapezium in Orion, the protoplanetary disks in an immediate vicinity of a massive O6V star are found strongly affected photoevaporating away from the ionizing source. Protoplanetary disks near the O6 star show lower mass and smaller disk sizes compared to the disks in weaker UV environments. We present our discoveries of photoevaporating protoplanetary disks (proplyds) in a 1-2 Myr old NGC 1977 in an intermediate UV environment around B1V star, and more new discoveries of proplyds in younger NGC 2024 near a B0.5V and around O8V+B1 stars. The proplyds found in NGC 2024 are younger than those in NGC 1977 (ages 0.2-0.5 Myr), which imply that even at such young age, planet formation may have already been affected by external photoevaporation. These proplyds were discovered from archival data of the Hubble Space Telescope and Spitzer, and we also use ground-based data including published ALMA results for our analysis. We compare properties of these proplyds and disks in these regions to those in strong and weak radiation environments. This study is part of our NExSS program, Earth in Solar System (EOS, PI Apai).