The Spatial Distribution of $\rm CH_4$ and $\rm CO_2$ Ice around Protostars IRAS 16253-2429 and IRAS 23385+6053

TL;DR

This study maps the distribution of key ices around two protostars using JWST data, revealing different chemical spatial patterns that inform understanding of molecular formation and evolution in star-forming regions.

Contribution

First detailed JWST-based spatial analysis of multiple ices around protostars, highlighting contrasting chemical distributions and their implications for astrochemical processes.

Findings

CH4 distribution mirrors CO2 in IRAS 16253-2429, indicating common formation mechanisms.

IRAS 23385+6053 shows diverse molecular distributions, influenced by dynamic processes.

Results support classical dark-cloud chemistry and reveal complex chemical-environment interactions.

Abstract

The origin and evolution of organic molecules represent a pivotal issue in the fields of astrobiology and astrochemistry, potentially shedding light on the origins of life. The James Webb Space Telescope (JWST), with its exceptional sensitivity and spectral resolution, is well suitable to observe molecules such as methane ($\rm CH_4$). Our analysis focused on the distribution of $\rm CH_4$, $\rm CO_2$, $\rm H_2O$, $\rm{CH_3OH+NH_4^+}$ ice and silicate absorption dips at approximately 7.7, 15.0, 6.0, 6.7 and 10.0 micrometres in two protostars: IRAS 16253-2429 and IRAS 23385+6053. We extract the $\rm CH_4$, $\rm CO_2$, $\rm H_2O$, $\rm{CH_3OH+NH_4^+}$ ice equivalent width (EW) maps and silicate extinction maps of the two sources. Our results reveal that the spatial distribution of $\rm CH_4$ in the protostellar system IRAS 16253-2429 closely mirrors that of its $\rm CO_2$ ice, forming a surrounded distribution that encircles the central protostar. This alignment suggests a common formation mechanism and subsequent trapping within the protostellar envelope, which is consistent with the "Classical" dark-cloud chemistry with ion-molecule reaction. In contrast, the spatial distributions of various molecules in the system IRAS 23385+6053 exhibit low similarities, which may be attributed to the dynamic influences of outflows or accretion processes. These discrepancies highlight the complex interplay between physical processes and chemical evolution in protostellar environments.