A rich molecular chemistry in the gas of the IC 348 star cluster of the Perseus Molecular Cloud

TL;DR

This study uses Spitzer spectroscopy to reveal a diverse and rich molecular composition in the gas of the IC 348 star-forming region, including molecules relevant to prebiotic chemistry and complex hydrocarbons.

Contribution

It provides the first detailed mid-IR molecular inventory of IC 348's gas, identifying numerous molecules and their abundances, and discusses implications for prebiotic chemistry.

Findings

Detection of common molecules like H2, OH, H2O, CO2, NH3.

Identification of complex hydrocarbons such as HCN, C2H2, C6H6.

Presence of PAHs and fullerenes C60 and C70.

Abstract

We present Spitzer 10-34 {\mu}m spectroscopic observations of the diffuse gas in the inner region of the star-forming region IC 348 of the Perseus Molecular Cloud. We find evidence for the strongest mid-IR bands of common molecules as H\textsubscript{2}, OH, H\textsubscript{2}O,CO\textsubscript{2} and NH\textsubscript{3} and of several carbonaceous molecules which may play an important role in the production of more complex hydrocarbons: HCN, C\textsubscript{2}H\textsubscript{2}, C\textsubscript{4}H\textsubscript{2}, HC\textsubscript{3}N, HC\textsubscript{5}N, C\textsubscript{2}H\textsubscript{6}, C\textsubscript{6}H\textsubscript{2}, C\textsubscript{6}H\textsubscript{6}. The excitation diagram of H\textsubscript{2} reveals the presence of warm gas (270 +- 30 K) at the observed locations. Assuming this temperature, the derived abundances of CO\textsubscript{2} and NH\textsubscript{3} relative to H\textsubscript{2} are 10\textsuperscript{-8} and 10\textsuperscript{-7}, respectively. From the water lines we obtain an abundance of order 10\textsuperscript{-6} and higher gas temperatures. The abundances derived for HCN and C\textsubscript{2}H\textsubscript{2}, key molecules in the development of prebiotic building blocks, are of order 10\textsuperscript{-7} and 10\textsuperscript{-9}, respectively. More complex molecules such as PAHs and the fullerenes C\textsubscript{60} and C\textsubscript{70} are also present. IC 348 appears to be very rich and diverse in molecular content. The JWST spectroscopic capabilities may provide details on the spatial distribution of all these molecules and extend the present search to more complex hydrocarbons.