A Novel Way of Measuring the Gas Disk Mass of Protoplanetary Disks Using N₂H⁺ and C¹⁸O

Abstract Measuring the gas mass of protoplanetary disks, reservoir available for giant planet formation, has proven to be difficult. We currently lack a far-infrared observatory capable observing HD, and most common tracer, CO, suffers from poorly constrained CO-to-H 2 ratio. Expanding on previous work, we investigate if N H + , chemical tracer CO-poor gas, can used observationally measure ratio correct CO-based masses. Using disk structures obtained literature, set up thermochemical models three TW Hya, DM Tau GM Aur, examine how well measured C 18 O line fluxes. Furthermore, compare these masses independently archival HD observations. The (3 − 2)/C O(2 1) scales with two lines, 4.6 × 10 −3 M ⊙ ≤ 1.1 −1 1.5 −2 9.6 Aur 3.1 Tau. These agree values within their respective uncertainties. uncertainty reduced by constraining cosmic-ray ionization rate in disks. results demonstrate potential using combination