Living on the edge: disk chemistry in the outskirts of dense star forming regions

Rachel Erin Gross

While most stars, including our Sun, form in massive clusters, the conditions within clusters can vary substantially. Depending on distance from massive stars or the amount of residual “shielding” gas or dust present within the cluster, the degree of external UV irradiation, parameterized by G0, can be less than the canonical ~1000s, and closer to just 10s or 100s of times stronger than the galactic background, G0=1. We present a comparative study of how disks under moderately illuminated conditions, G0=100, compare to disks in lower mass star forming regions. We additionally explore the effect of the distribution of gas mass, and how this may provide a more or less protective environment for the molecular species. We speculate on how the gas phase compositions compare between these cases. By using common tracer molecules, like N2H+, which has shown to be highly sensitive to enhanced UV flux, models suggest a unique opportunity to better distinguish the degree of photochemical processing cluster disks undergo. We further investigate whether these tracer molecules can probe potential signatures of disk photochemistry in cluster regions compared to quiescent star forming regions.