# # Program information file # PROGRAM_ID 2021A092 PROGRAM_TITLE The IRTF Survey of Ices toward Embedded Massive Young Stellar Objects: Carbonyl Sulfide [OCS] PROGRAM_INV1 Adwin Boogert PROGRAM_INV2 PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT galactic/interstellar medium PROGRAM_ABSTRACT_BEG The evolution of molecular abundances, from dense clouds, via prestellar cores, protostellar envelopes, and protoplanetary disks, toward primitive Solar System bodies is still poorly known. There is evidence for complex molecules in dense clouds, which may survive into comets. There is also reason to believe that the dense cloud heritage is lost, and our molecular origins are regenerated in protoplanetary disks. The complex interplay between chemistry, time scales, temperature, density, and irradiation by particles and UV photons must be disentangled using a combination of laboratory experiments, chemical and star formation models, and, of course, observations. While observational studies of ices, the main molecular reservoir, have steadily improved for dense clouds, low mass YSOs, and comets [Rosetta mission], and will continue to do so with JWST, this has not happened for massive YSOs. Massive YSOs offer unique insights into the chemical and physical evolution of ices, in particular the effects of heating and harsh radiation fields. Also, similarities of the massive YSOs and cometary ice abundances hint at the formation of the Solar System in a stellar cluster near a massive YSO. Testing these claims requires sample sizes that approach those of dense clouds and low mass YSOs. We have obtained SpeX 2-5 micron spectra of 90 massive YSOs, all of which will saturate the JWST detectors. 67% of these show H2O ice, 30% OCN- and CH3OH, and 20% OCS. This quadruples the total number of massive YSOs studied in the ices. We find a tentative correlation between OCN- and OCS ices, possibly establishing an origin in processed ices. This provides an important link with cometary ices and addresses the missing sulfur problem in dense clouds. We propose SpeX observations to improve the quality of the weak OCS ice band in 5 targets, and add 4 new targets. PROGRAM_ABSTRACT_END