Know Thy Star, Know Thy Chemistry: Roles of Stellar Radiation in Protoplanetary Disk Chemistry

Jamila Pegues, L Ilsedore Cleeves, Karin Oberg

Exoplanets have been discovered around a breathtaking variety of stars. To constrain the chemical origins of these exoplanets, we study the chemical composition of their birthplaces: protoplanetary disks. Over the past decade, modern interferometry has allowed us to probe volatile disk chemistry around stars across the pre-main-sequence stellar mass distribution, from cool M-stars to bright Herbig Ae stars. The different properties of these young stars cultivate differences in the radiation fields within their disks. But how much do these differences affect the disk chemistry? To help answer this question, we explore the effects of stellar radiation on protoplanetary disk chemistry from both observational and theoretical perspectives. On the observational side, we discuss recent work in conducting and analyzing samples of disk chemistry at both ends of the stellar mass distribution. By folding in a compilation of millimeter-wavelength disk chemistry studies from across the literature, we extract trends in the observed chemistry as a function of the central star. On the theoretical side, we discuss ongoing work in computing ultraviolet photochemistry for disks around young stars. Using a sample of stellar spectra and templates for a variety of spectral types, we evaluate different methodologies for calculating or approximating their wavelength-dependent photochemical rate coefficients for a database of molecular species. With this combined observational and theoretical work, we ultimately explore the role of stellar radiation in cultivating such rich disk chemistry across the pre-main-sequence stellar mass distribution.