SMA-SPEC: A Legacy Spectral Line Survey of Protoplanetary Disks

Planets form in disks around young stars. Disk chemistry affects the outcome of planet formation in multiple ways, including elemental composition and access to water and prebiotically interesting organics for habitable zone planets. The chemistry of outer disk regions, beyond the water snowline, where comets and most giant planets likely form, can be studied using molecular emission lines at millimeter wavelengths. Molecular lines also offer some of the best probes of disk gas mass, density, temperature, and ionization. This project will use the Submillimeter Array to conduct a series of broadband line surveys towards 40 different disks. This project will form the thesis work of a graduate student. The team will also participate as YouthAstroNet STEM mentors and will answer student questions about astronomy as well as STEM career pathways. The research team will survey 120 GHz of bandwidth between 210 and 370 GHz at high spectral resolution towards 40 disks. They have already obtained 120 tracks (nights) of SMA time to pursue a ~120 GHz spectral line survey towards 40 disks around solar mass T Tauri stars and Herbig Ae stars in clusters ranging from <1Myr to >5Myrs. The team will use the survey data to address the C/O elemental ratio, quantify D/H ratios, and obtain a comprehensive inventory of the organic reservoir in the comet-forming disk regions. A grid of astrochemical models using the disk chemistry code DALI will be run to determine abundance structures, which will be converted to column density profiles and disk-averaged column densities and column density ratios for easy comparison with the observations. This unique data set will be highly significant for interpretative frameworks of exoplanets habitability and the origins of solar system volatiles. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.