# # Program information file # PROGRAM_ID 2023A076 PROGRAM_TITLE Characterization of JWST Targets to Probe Interstellar Dust Grain Growth PROGRAM_INV1 Laurie E. U. Chu PROGRAM_INV2 Adwin Boogert PROGRAM_INV3 Roberta Paladini PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT galactic/interstellar medium PROGRAM_ABSTRACT_BEG With the James Webb Space Telescope [JWST] now taking some of its first observations, it is imperative to obtain supporting ground-based observations to maximize scientific discoveries. One such program will seek to understand interstellar dust grain growth in dense molecular cores. Initial grain size distributions at this early stage are a key component for modeling planet formation. The conditions in these cores are so cold that ice condenses on dust grain surfaces allowing for grain growth through coagulation. Theoretical models predict that this grain growth deforms silicate band profiles at 9.7 and 18 microns. Probing lines of sight through the cores using background stars with the Mid Infrared Instrument [MIRI] on JWST it will be possible for the first time to characterize these profiles in great detail. State-of-the-art modeling will resolve degeneracies in grain size, shape, and porosity while also producing extinction curves in the 5-26 micron regime for dense cores. In order to analyze the JWST data it is critical to separate the stellar photospheric absorption features and stellar continuum from the dust extinction and absorption features. We propose to use IRTF/SpeX to determine the spectral types and intervening level of extinction for five background stars [K=11.4-15 mag] that will later be probed by JWST. Data obtained in this program using the Prism or LXD_short modes will allow us to observe photospheric features such as the CO bandhead absorption lines around 2.4 microns. We will then match the observed spectra with the IRTF Spectral Database and subtract off the stellar photosphere so that the silicate features from JWST can be analyzed. We require a total of 6 hours to achieve S/N~100 at 2.5 microns including overheads. This will be essential to create a total sample of 9 stars, where the previous four come from the IRTF/SpeX Data Archive. PROGRAM_ABSTRACT_END