The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid in the interstellar medium

TL;DR

This study reports the first detection of deuterated formamide and isocyanic acid in the interstellar medium, providing insights into their formation pathways in star-forming regions.

Contribution

First detection of deuterated formamide and isocyanic acid isotopologues in a low-mass protostellar environment, revealing their co-location and similar deuterium fractionation.

Findings

Deuterated formamide isotopologues detected in IRAS 16293-2422.

Deuterium fractionation around 2% for formamide.

Chemical relation between NH2CHO and HNCO supported.

Abstract

Formamide (NH$_2$CHO) has previously been detected in several star-forming regions and is thought to be a precursor for different prebiotic molecules. Its formation mechanism is still debated, however. Observations of formamide, related species and their isopotologues may provide useful clues to the chemical pathways leading to their formation. The Protostellar Interferometric Line Survey (PILS) represents an unbiased high angular resolution and sensitivity spectral survey of the low-mass protostellar binary IRAS 16293-2422 with the Atacama Large Millimeter/submillimeter Array (ALMA). We detect for the first time the three singly deuterated forms of NH$_2$CHO (NH$_2$CDO, cis- and trans-NHDCHO) as well as DNCO towards the component B of this binary source. The images reveal that the different isotopologues are all present in the same region. Based on observations of the $^{13}$C isotopologues of formamide and a standard $^{12}$C/$^{13}$C ratio, the deuterium fractionation is found to be similar for the three different forms with a value of about 2%. The DNCO/HNCO ratio is also comparable to the D/H ratio of formamide ($\sim$1%). These results are in agreement with the hypothesis that NH$_2$CHO and HNCO are chemically related through grain surface formation.