Molecules with a peptide link in protostellar shocks: a comprehensive study of L1157

Abstract

Interstellar molecules with a peptide link -NH-C(=O)-, like formamide (NH${}_2$CHO), acetamide (NH${}_2$COCH${}_3$) and isocyanic acid (HNCO) are particularly interesting for their potential role in pre-biotic chemistry. We have studied their emission in the protostellar shock regions L1157-B1 and L1157-B2, with the IRAM 30m telescope, as part of the ASAI Large Program. Analysis of the line profiles shows that the emission arises from the outflow cavities associated with B1 and B2. Molecular abundance of $\approx (0.4-1.1)\times 10^{-8}$ and $(3.3-8.8)\times 10^{-8}$ are derived for formamide and isocyanic acid, respectively, from a simple rotational diagram analysis. Conversely, NH${}_2$COCH${}_3$ was not detected down to a relative abundance of a few $\le 10^{-10}$. B1 and B2 appear to be among the richest Galactic sources of HNCO and NH${}_2$CHO molecules. A tight linear correlation between their abundances is observed, suggesting that the two species are chemically related. Comparison with astrochemical models favours molecule formation on ice grain mantles, with NH${}_2$CHO generated from hydrogenation of HNCO.

11 pages, 9 figures. Accepted for publication in MNRAS Main Journal. Accepted 2014 August 19, in original form 2014 July 8

References in corpus (7)

• Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model
• Testing grain-surface chemistry in massive hot-core regions
• The effect of uncertainties on chemical models of dark clouds
• Discovery of Fulminic Acid, HCNO, in Dark Clouds
• Tracing shocks and photodissociation in the Galactic center region
• A Flattened Protostellar Envelope in Absorption around L1157
• Structural effects of ice grain surfaces on the hydrogenation of CO at low temperatures

Cited by in corpus (17)

• The ALMA Protostellar Interferometric Line Survey (PILS): First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMA
• Shedding light on the formation of the pre-biotic molecule formamide with ASAI
• Seeds Of Life In Space (SOLIS): The organic composition diversity at 300--1000 au scale in Solar-type star forming regions
• Seeds of Life in Space (SOLIS) III. Formamide in protostellar shocks: evidence for gas-phase formation
• Formation and Atmosphere of Complex Organic Molecules of the HH 212 Protostellar Disk
• Chemical modelling of complex organic molecules with peptide-like bonds in star-forming regions
• Simultaneous Hydrogenation and UV-photolysis Experiments of NO in CO-rich Interstellar Ice Analogues; linking HNCO, OCN-, NH2CHO and NH2OH
• Interstellar formamide (NH${}_2$CHO), a key prebiotic precursor
• Formation of the prebiotic molecule NH${}_2$CHO on astronomical amorphous solid water surfaces: accurate tunneling rate calculations
• Complex organic molecules in strongly UV-irradiated gas
• Astrochemistry at work in the L1157-B1 shock: acetaldehyde formation
• Seeds of Life in Space (SOLIS). X. Interstellar Complex Organic Molecules in the NGC 1333 IRAS 4A outflows
• Chemical Segregation in Hot Cores With Disk Candidates: An investigation with ALMA
• Laboratory measurements and astronomical search for cyanomethanimine
• Revisiting the reactivity between HCO and CH${}_3$ on interstellar grain surfaces
• Seeds of Life in Space SOLIS. IX. Chemical segregation of $\mathrm{S}{\mathrm{O}}_2$ and SO toward the low-mass protostellar shocked region of L1157
• SPARKS II.: Complex organic molecules in accretion shocks around a hot core precursor