Context. Complex organic molecules are detected in many sources in the warm inner regions of envelopes surrounding deeply embedded protostars. Exactly how these species form remains an open question.Aims. This study aims to constrain the formation of complex organic molecules through comparisons of their abundances towards the Class 0 protostellar binary IRAS 16293-2422. Methods. We utilised observations from the Atacama Large Millimetre/submillimetre Array (ALMA) Protostellar Interferometric Line Survey (PILS) of IRAS 16293-2422. The species identification and the rotational temperature and column density estimation were derived by fitting the extracted spectra towards IRAS 16293-2422 A and IRAS 16293-2422 B with synthetic spectra. The majority of the work in this paper pertains to the analysis of IRAS 16293-2422 A for a comparison with the results from the other binary component, which have already been published. Results. We detect 15 different complex species, as well as 16 isotopologues towards the most luminous companion protostar IRAS 16293-2422 A. Tentative detections of an additional 11 isotopologues are reported. We also searched for and report on the first detections of methoxymethanol (CH 3 OCH 2 OH) and trans-ethyl methyl ether (t-C 2 H 5 OCH 3 ) towards IRAS 16293-2422 B and the follow-up detection of deuterated isotopologues of acetaldehyde (CH 2 DCHO and CH 3 CDO). Twenty-four lines of doubly-deuterated methanol (CHD 2 OH) are also identified. Conclusions. The comparison between the two protostars of the binary system shows significant differences in abundance for some of the species, which are partially correlated to their spatial distribution. The spatial distribution is consistent with the sublimation temperature of the species; those with higher expected sublimation temperatures are located in the most compact region of the hot corino towards IRAS 16293-2422 A. This spatial differentiation is not resolved in IRAS 16293-2422 B and will require observations at a higher angular resolution. In parallel, the list of identified CHD 2 OH lines shows the need of accurate spectroscopic data including their line strength. Article number, page 2 of 31 S. Manigand et al.: Inventory of complex organic molecules towards IRAS 16293-2422 A Notes. (a) e 0 , o 1 and e 1 corresponds to the three first torsional states. The notation of the quantum numbers is directly taken from Mukhopadhyay (2016). (b) This corresponds to the number indicated in the top-right corner of each panel in Figures D.1 and D.2. (c) W is the integrated intensity of the unblended lines, summed over the range [ν 0 − ∆ν FWHM , ν 0 + ∆ν FWHM ], given ∆ν FWHM = ν 0 FWHM c , with FWHM equal to 2.2 and 0.8 km s −1 for IRAS 16293A and B, respectively.

Studies of deuterated isotopologues of complex organic molecules can provide important constraints on their origin in regions of star formation. In particular, the abundances of deuterated species are very sensitive to the physical conditions in the environment where they form. Due to the low temperatures in regions of star formation, these isotopologues are enhanced to significant levels, making detections of multiply-deuterated species possible. However, for complex organic species, only the multiply-deuterated variants of methanol and methyl cyanide have been reported so far. The aim of this paper is to initiate the characterisation of multiply-deuterated variants of complex organic species with the first detection of doubly-deuterated methyl formate, CHD 2 OCHO. We use ALMA observations from the Protostellar Interferometric Line Survey (PILS) of the protostellar binary IRAS 16293-2422, in the spectral range of 329.1 GHz to 362.9 GHz. Spectra towards each of the two protostars are extracted and analysed using a LTE model in order to derive the abundances of methyl formate and its deuterated variants. We report the first detection of doubly-deuterated methyl formate CHD 2 OCHO in the ISM. The D/H ratio of CHD 2 OCHO is found to be 2-3 times higher than the D/H ratio of CH 2 DOCHO for both sources, similar to the results for formaldehyde from the same dataset. The observations are compared to a gas-grain chemical network coupled to a dynamical physical model, tracing the evolution of a molecular cloud until the end of the Class 0 protostellar stage. The overall D/H ratio enhancements found in the observations are of the same order of magnitude as the predictions from the model for the early stages of Class 0 protostars. However, the higher D/H ratio of CHD 2 OCHO compared to the D/H ratio of CH 2 DOCHO is still not predicted by the model. This suggests that a mechanism is enhancing the D/H ratio of singly-and doubly-deuterated methyl formate that is not in the model, e.g. mechanisms for H-D substitutions. This new detection provides an important constraint on the formation routes of methyl formate and outlines a path forward in terms of using these ratios to determine the formation of organic molecules through observations of differently deuterated isotopologues towards embedded protostars.

We report new interferometric images of cyclopropenylidene, c-C 3 H 2 , towards the young protocluster OMC-2 FIR 4. The observations were performed at 82 and 85 GHz with the NOrthern Extended Millimeter Array (NOEMA) as part of the project Seeds Of Life In Space (SOLIS). In addition, IRAM-30m data observations were used to investigate the physical structure of OMC-2 FIR 4. We find that the c-C 3 H 2 gas emits from the same region where previous SOLIS observations showed bright HC 5 N emission. From a non-LTE analysis of the IRAM-30m data, the c-C 3 H 2 gas has an average temperature of ∼40 K, a H 2 density of ∼3×10 5 cm −3 , and a c-C 3 H 2 abundance relative to H 2 of (7±1)×10 −12 . In addition, the NOEMA observations provide no sign of significant c-C 3 H 2 excitation temperature gradients across the region (about 3-4 beams), with T ex in the range 8±3 up to 16±7 K. We thus infer that our observations are inconsistent with a physical interaction of the OMC-2 FIR 4 envelope with the outflow arising from OMC-2 FIR 3, as claimed by previous studies. The comparison of the measured c-C 3 H 2 abundance with the predictions from an astrochemical PDR model indicates that OMC-2 FIR 4 is irradiated by a FUV field ∼1000 times larger than the interstellar one, and by a flux of ionising particles ∼4000 times larger than the canonical value of 1 × 10 −17 s −1 from the Galaxy cosmic rays, which is consistent with our previous HC 5 N observations. This provides an important and independent confirmation of other studies that one or more sources inside the OMC-2 FIR 4 region emit energetic (≥ 10 MeV) particles.Corresponding author: C. Favre cfavre@arcetri.astro.it * Based on observations carried out under project number L15AA with the IRAM NOEMA Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).