IRTF Data Archive Program Information

# # Program information file # PROGRAM_ID 2023A080 PROGRAM_TITLE Organic Inventory of Protoplanetary Disks PROGRAM_INV1 Adwin Boogert PROGRAM_INV2 Federica Chiti PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT galactic/interstellar medium PROGRAM_ABSTRACT_BEG Ices contain much of the carbon in dense molecular clouds and protostellar envelopes. Cold grain surface chemistry favors the hydrogenation of carbon atoms and CO, and the product, CH4, H2CO and CH3OH, are frozen out on the grain mantles. Upon accretion into the protoplanetary disk, some of the ices may survive and some will sublimate in the warm disk surface or the hot inner disk [<1 AU]. The ices may well be processed by energetic radiation, while the gas will participate in a chemistry similar to hot cores surrounding massive protostars. Either way, CH4, H2CO, and CH3OH are very likely the basis of a rich organic chemistry, and the products may well be incorporated in comets and planets. In some planet formation theories, the CH4 abundance increases locally with orders of magnitude. In warm, dense planetary embryos, Fischer-Tropsch reactions facilitate the conversion of CO to CH4. In another theory, the atomic C/O ratio is strongly enhanced inside the snow line leading to a rich hydrocarbon chemistry. Little is known about the phase, location, and abundance of CH4, H2CO, CH3OH and other organics such as HCN and C2H2 in protoplanetary disks. We request 11.5 hours of iSHELL time for a search for gas phase CH4, H2CO, CH3OH, C2H2, and HCN emission and absorption in five protoplanetary disks that is more sensitive than that of previous VLT work, allowing for meaningful comparisons to ISM and cometary abundances. The observations take advantage of iSHELL's large spectral coverage, observing all these species nearly simultaenously [L2 and Lp1 settings over 2.96-3.66 micron]. Also, the atmosphere is better from Maunakea than from Paranal. PROGRAM_ABSTRACT_END