The prebiotic molecular inventory of Serpens SMM1

Abstract

Aims. Methyl isocyanate (CH3NCO) and glycolonitrile (HOCH2CN) are isomers and prebiotic molecules that are involved in the formation of peptide structures and the nucleobase adenine, respectively. These two species are investigated to study the interstellar chemistry of cyanides (CN) and isocyanates (NCO) and to gain insight into the reservoir of interstellar prebiotic molecules. Methods. ALMA observations of the intermediate-mass Class 0 protostar Serpens SMM1-a and ALMA-PILS data of the low-mass Class 0 protostar IRAS 16293B are used. Spectra are analysed with the CASSIS line analysis software package in order to identify and characterise molecules. Results. CH3NCO, HOCH2CN, and various other molecules are detected towards SMM1-a. HOCH2CN is identified in the PILS data towards IRAS 16293B in a spectrum extracted at a half-beam offset position from the peak continuum. CH3NCO and HOCH2CN are equally abundant in SMM1-a at [X]/[CH3OH] of 5.3 × 10−4 and 6.2 × 10−4, respectively. A comparison between SMM1-a and IRAS 16293B shows that HOCH2CN and HNCO are more abundant in the former source, but CH3NCO abundances do not differ significantly. Data from other sources are used to show that the [CH3NCO]/[HNCO] ratio is similar in all these sources within ~10%. Conclusions. The new detections of CH3NCO and HOCH2CN are additional evidence for a large interstellar reservoir of prebiotic molecules that can contribute to the formation of biomolecules on planets. The equal abundances of these molecules in SMM1-a indicate that their formation is driven by kinetic processes instead of thermodynamic equilibrium, which would drive the chemistry to one product. HOCH2CN is found to be much more abundant in SMM1-a than in IRAS 16293B. From the observational data, it is difficult to indicate a formation pathway for HOCH2CN, but the thermal Strecker-like reaction of CN− with H2CO is a possibility. The similar [CH3NCO]/[HNCO] ratios found in the available sample of studied interstellar sources indicate that these two species are either chemically related or their formation is affected by physical conditions in the same way. Both species likely form early during star formation, presumably via ice mantle reactions taking place in the dark cloud or when ice mantles are being heated in the hot core. The relatively high abundances of HOCH2CN and HNCO in SMM1-a may be explained by a prolonged stage of relatively warm ice mantles, where thermal and energetic processing of HCN in the ice results in the efficient formation of both species.

Molecular Precursors of the RNA-World in Space: New Nitriles in the G+0.693−0.027 Molecular Cloud

“…• HOCH 2 CN: this species was first detected in the ISM towards the hot corino IRAS 16293-2422 B (Zeng et al, 2019), and more recently towards the SMM1 hot corino in Serpens (Ligterink et al, 2021). The abundance derived in G+0.693 is 4.3 × 10 −10 , very similar to that derived in the hot component of IRAS 16293-2422 B (Figure 8).…”

Importance of source structure on complex organics emission

“…Methanol (CH 3 OH) is the most common complex organic molecule detected towards both low-and high-mass protostars in the gas over the past decades (e.g. Blake et al 1987;van Dishoeck et al 1995;Gibb et al 2000;Bisschop et al 2007;Belloche et al 2013;Jørgensen et al 2016;Ilee et al 2016;Bøgelund et al 2018;Marcelino et al 2018;Martín-Doménech et al 2019;Taquet et al 2019;van Gelder et al 2020;Manigand et al 2020;Yang et al 2020;Ligterink et al 2021;Law et al 2021). Moreover, methanol has been observed to be abundant (X H ∼ 3 × 10 −6 , with some spread) in ices towards protostellar objects (Geballe et al 1988;Dartois et al 1999Dartois et al , 2002Boogert et al 2008Boogert et al , 2015Bottinelli et al 2010;Öberg et al 2011) and in some dark cores prior to star formation (Boogert et al 2011;Qasim 2020).…”

Laboratory rotational spectroscopy of acrylamide and a search for acrylamide and propionamide toward Sgr B2(N) with ALMA

“…In astronomical settings, amides and other peptide-like species are actively subjects of investigation in star-forming regions, solar-type protostars, and other environments (e.g., Halfen et al 2011;Belloche et al 2017;Mendoza et al 2014;Ligterink et al 2020Ligterink et al , 2021Gorai et al 2020;Colzi et al 2021). These studies uncover their formation in space and their role as nodes in chemical networks connecting other prebiotic molecules.…”