JDISCS Cycle 1 Targets

Mid-infrared spectroscopy of protoplanetary disks provides a chemical inventory of gas within a few au, where planets are readily detected around older stars. With the JWST Disk Infrared Spectral Chemistry Survey (JDISCS), we explore demographic trends among 31 disks observed with MIRI (MRS) and with previous ALMA millimeter continuum imaging at high angular resolution (5-10 au). With these S/N ~ 200-450 spectra, we report emission from H2O, OH, CO, C2H2, HCN, CO2, [Ne II], [Ne III], and [Ar II]. Emission from H2O, OH and CO is nearly ubiquitous for low-mass stars, and detection rates of all molecules are higher than for similar disks observed with Spitzer-IRS. Slab model fits to the molecular emission lines demonstrate that emission from C2H2, HCN, and possibly CO2 is optically thin; thus since column densities and emitting radii are degenerate, observations are actually sensitive to the total molecular mass. C2H2 and HCN emission also typically originate in
a hotter region (920, 820 K, respectively) than CO2 (600 K). The HCN to cold H2O luminosity ratios are generally smaller in smooth disks, consistent with more efficient water delivery via icy pebbles in the absence of large dust substructures. The molecular emission line luminosities are also correlated with mass accretion rates and infrared spectral indices, similar to trends reported from Spitzer-IRS surveys. This work demonstrates the power of combining multi-wavelength observations to explore inner disk chemistry as a function of outer disk and stellar properties, which will continue to grow as the sample of observed Class II systems expands in the coming JWST observation cycles.