Ice inventory towards the protostar Ced 110 IRS4 observed with the James Webb Space Telescope. Results from the ERS Ice Age program

Context. Protostars contains icy ingredients necessary for the formation of potential habitable worlds, and therefore it is crucial to understand their chemical and physical environments. In particular, this work is focused on the ice features toward the binary protostellar system Ced 110 IRS4A and IRS4B, separated by 250 au, and observed with the James Webb Space Telescope (JWST) as part of the Early Release Science Ice Age collaboration. Aims. We aim at exploring the JWST data of the binary protostellar system Ced 110 IRS4A and IRS4B to primarily unveil the ice inventories toward these sources and quantify them. Finally, we compare the ice abundances with those found for the same molecular cloud. Methods. We use data from multiple JWST instruments (NIRSpec, NIRCam and MIRI) to identify and quantify ice species in the Ced 110 IRS4 system. The analysis is performed by fitting or comparing laboratory infrared spectra of ices to the observations. Spectral fits are carried out with the ENIIGMA fitting tool that searches for the best fit out of a large number of solutions. The degeneracies of the fits are also addressed, and the ice column densities are calculated. In cases where the full nature of the absorption features are not known yet, we explore different laboratory ice spectra to compare with the observations. Results. We provide a list of securely and tentatively detected ice species towards the primary and the companion sources. For Ced 110 IRS4B, we detect the major ice species H2O, CO, CO2 and NH3. All species are found in a mixture except for CO and CO2, which has both a mixed and a pure ice component. In the case of Ced 110 IRS4A, we detected the major species as in Ced 110 IRS4B and the following minor species CH4, SO2, CH3OH, OCN−, NH+4 and HCOOH. Tentative detection of N2O ice (7.75 μm), forsterite dust (11.2 μm) and CH+3 gas emission (7.18 μm) in the primary source are also presented. Compared with the two lines of sight in the Chameleon I molecular cloud, the protostar has similar ice abundances, except in the case of the ions that are higher in IRS4A. The most clear differences are the absence of the 7.2 and 7.4 μm due to HCOO− and icy complex organic molecules in IRS4A and evidence of thermal processing in both IRS4A and IRS4B as probed by the CO2 ice features. Conclusions. We conclude that the binary protostellar system Ced 110 IRS4A and IRS4B has a large inventory of icy species. The similar ice abundances in comparison to the starless regions in the same molecular cloud suggests that the chemical conditions of the protostar were set at earlier stages in the molecular cloud. It is also possible that the source inclination and complex geometry cause a low column density along the line of sight, which hides the bands at 7.2 and 7.4 μm. Finally, we highlight that a comprehensive analysis using radiative transfer modelling is needed to disentangle the spectral energy distributions of these sources.