JOYS+ study of solid state ${}^{12}$C/${}^{13}$C isotope ratios in protostellar envelopes: Observations of CO and CO${}_2$ ice with JWST

Abstract

The carbon isotope ratio is a powerful tool for studying the evolution of stellar systems. Recent detections of CO isotopologues in disks and exoplanet atmospheres pointed towards significant fractionation in these systems. In order to understand the evolution of this quantity, it is crucial to trace the isotope abundance from stellar nurseries to planetary systems. During the protostellar stage the multiple vibrational modes of CO${}_2$ and CO ice provide a unique opportunity to examine the carbon isotope ratio in the solid state. Now with the sensitivity of the \textit{James Webb Space Telescope}, these absorption features have become accessible at high S/N in Solar-mass systems. We quantify the ${}^{12}$CO${}_2$/${}^{13}$CO${}_2$ and the ${}^{12}$CO/${}^{13}$CO isotope ratios in 17 class 0/I low mass protostars from the ${}^{12}$CO${}_2$ combination modes (2.70 $\mu$m and 2.77 $\mu$m), the ${}^{12}$CO${}_2$ stretching mode (4.27 $\mu$m), the ${}^{13}$CO${}_2$ stretching mode (4.39 $\mu$m), the ${}^{12}$CO${}_2$ bending mode (15.2 $\mu$m), the ${}^{12}$CO stretching mode (4.67 $\mu$m) and the ${}^{13}$CO stretching mode (4.78 $\mu$m) using JWST observations. We also report a detection of the ${}^{12}$CO overtone mode at 2.35 $\mu$m. The ${}^{12}$CO${}_2$/${}^{13}$CO${}_2$ ratios are in agreement and we find mean ratios of 85 $\pm$ 23, 76 $\pm$ 12 and 97 $\pm$ 17 for the 2.70 $\mu$m, 4.27 $\mu$m and the 15.2 $\mu$m bands, respectively. The main source of uncertainty stem from the error on the band strengths. The ${}^{12}$CO/${}^{13}$CO ratios derived from the 4.67 $\mu$m bands are consistent, albeit elevated with respect to the ${}^{12}$CO${}_2$/${}^{13}$CO${}_2$ ratios and we find a mean ratio of 165 $\pm$ 52. These findings indicate that ices leave the pre-stellar stage with elevated carbon isotope ratios relative to the interstellar medium and that fractionation becomes significant during the later stages.

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Cited by in corpus (11)

• JWST Observations of Young protoStars (JOYS): overview of program and early results
• JWST Observations of Young protoStars (JOYS). Overview of gaseous molecular emission and absorption in low-mass protostars
• Locked In Ice: how Pebble Drift and Volatile Entrapment can Significantly Impact Carbon and Oxygen Ratios in Evolving Protoplanetary Discs
• HDO ice detected toward an isolated low-mass protostar with JWST
• PRODIGE - envelope to disk with NOEMA: V. Low 12C/13C ratios for CH3OH and CH3CN in hot corinos
• Extended source fringe flats for the JWST MIRI Medium Resolution Spectrometer
• Protostars at Subsolar Metallicity: First Detection of Large Solid-state Complex Organic Molecules in the Large Magellanic Cloud
• JOYS: Linking the molecular ice and gas-phase composition towards the high-mass hot core IRAS 18089-1732
• Molecule-specific diffusion and desorption of interstellar ices on carbonaceous dust
• Detection of CO${}_2$ ice in the planetary nebula NGC 6302
• Mapping Interstellar Ice Inventory toward Class 0 Protostars in Star-forming Region Orion A with JWST Data