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Arxiv: JOYS+: link between ice and gas of complex organic molecules. Comparing JWST and ALMA data of two low-mass protostars Published: 7/29/2024 5:53:40 PM Updated: 7/29/2024 5:53:40 PM

Paper abstract: A rich inventory of complex organic molecules (COMs) has been observed inhigh abundances in the gas phase toward Class 0 protostars. These molecules aresuggested to be formed in ices and sublimate in the warm inner envelope closeto the protostar. However, only the most abundant COM, methanol (CH3OH), hasbeen firmly detected in ices before the era of James Webb Space Telescope(JWST). Now it is possible to detect the interstellar ices of other COMs andconstrain their ice column densities quantitatively. We aim to determine thecolumn densities of several oxygen-bearing COMs (O-COMs) in both gas and icefor two low-mass protostellar sources, NGC 1333 IRAS 2A and B1-c, as casestudies in our JWST Observations of Young protoStars (JOYS+) program. Bycomparing the column density ratios w.r.t. CH3OH between both phases measuredin the same sources, we can probe into the evolution of COMs from ice to gas inthe early stages of star formation. We are able to fit the fingerprints rangeof COM ices between 6.8 and 8.8 um in the JWST/MIRI-MRS spectra of B1-c usingsimilar components as recently used for IRAS 2A. We claim detection of CH4,OCN-, HCOO-, HCOOH, CH3CHO, C2H5OH, CH3OCH3, CH3OCHO, and CH3COCH3 in B1-c, andupper limits are estimated for SO2, CH3COOH, and CH3CN. The comparison of O-COMratios w.r.t CH3OH between ice and gas shows two different cases. 1) the columndensity ratios of CH3OCHO and CH3OCH3 match well between the two phases, whichmay be attributed to a direct inheritance from ice to gas or strong chemicallinks with CH3OH. 2) the ice ratios of CH3CHO and C2H5OH w.r.t. CH3OH arehigher than the gas ratios by 1-2 orders of magnitudes. This difference can beexplained by the gas-phase reprocessing following sublimation, or differentspatial distributions of COMs in the envelope.