Search

The nucleus of the Jupiter-family comet 67P/Churyumov–Gerasimenko was discovered to be bi-lobate in shape when the European Space Agency spacecraft Rosetta first approached it in 2014 July. The bi-lobate structure of the cometary nucleus has led to much discussion regarding the possible manner of its formation and on how the composition of each lobe might compare with that of the other. During its two-year-long mission from 2014 to 2016, Rosetta remained in close proximity to 67P/Churyumov–Gerasimenko, studying its coma and nucleus in situ. Based on lobe-specific measurements of HDO and H2O performed with the ROSINA Double Focusing Mass Spectrometer (DFMS) on board Rosetta, the deuterium-to-hydrogen (D/H) ratios in water from the two lobes can be compared. No appreciable difference was observed, suggesting that both lobes formed in the same region and are homogeneous in their D/H ratios.

In 2004, the Rosetta spacecraft was sent to comet 67P/Churyumov-Gerasimenko for the first ever long-term investigation of a comet. After its arrival in 2014, the spacecraft spent more than two years in immediate proximity to the comet. During these two years, the ROSINA Double Focusing Mass Spectrometer (DFMS) onboard Rosetta discovered a coma with an unexpectedly complex chemical composition that included many oxygenated molecules. Determining the exact cometary composition is an essential first step to understanding of the organic rich chemistry in star forming regions and protoplanetary disks that are ultimately conserved in cometary ices. In this study a joint approach of laboratory calibration and space data analysis was used to perform a detailed identification and quantification of CHO-compounds in the coma of 67P/Churyumov-Gerasimenko. The goal was to derive the CHO-compound abundances relative to water for masses up to 100 u. For this study, the May 2015 post-equinox period represent the best bulk abundances of comet 67P/Churyumov-Gerasimenko. A wide variety of CHO-compounds were discovered and their bulk abundances were derived. Finally, these results are compared to abundances of CHO-bearing molecules in other comets, obtained mostly from ground-based observations and modelling., Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in ACS Earth and Space Chemistry, copyright $\copyright$ American Chemical Society after peer review. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/acsearthspacechem.9b00094

While the volatile species in comet 67P/Churyumov-Gerasimenko’s coma have been analyzed in great spatial and temporal detail, e.g., Rubin et al. (2019) or Läuter et al. (2020), little is so far known about the less volatile, heavier species. There is growing evidence, however, that less volatile species, such as salts, may play a key role in explaining some of the puzzling properties of comets, as for instance shown by Altwegg et al. (2020). These authors also have demonstrated the unique capability of ROSINA/DFMS (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/ Double Focusing Mass Spectrometer; Balsiger et al. (2007)) to detect exactly such little volatile species in-situ, namely during a dust event on 5 September 2016 (when a dust grain entered the instrument and sublimated inside).Complementary information on 67P’s dusty coma can be obtained from data collected during time periods of high dust activity. A clear advantage of such data is they also allow for a quantitative interpretation thanks to the much more stable measurement conditions. Moreover, a comparison to data collected during a time period of little dust activity (e.g., to the days around end of May 2015 as in Rubin et al. 2019) also allows to link species to dust.End of July / beginning of August 2015, the comet was approaching its perihelion and ejecting a lot of dust, as seen by the OSIRIS camera (Vincent et al. 2016). The data from this period are therefore a promising starting point for the search of heavier species (m > 100 Da). Altwegg et al. (2019), for instance, reported on the tentative identifications of the simplest polyaromatic hydrocarbon species naphthalene as well as of benzoic acid, the simplest aromatic carboxylic acid. To confirm these identifications and to achieve a more complete inventory of heavier and chemically more complex species, we are now analyzing these data sets strategically. In our contribution we will share what we have learned from pushing the exploration of 67P’s dusty coma. Altwegg et al., 2020, Nat. Astron., 4, 533-540.Altwegg et al., 2019, Annu. Rev. Astron. Astrophys., 57, 113-55.Balsiger H. et al., 2007, Space Sci. Rev., 128, 745-801.Läuter et al., 2020, MNRAS, 498, 3, 3995-4004.Rubin et al., 2019, MNRAS, 489, 594-607. Vincent et al., 2016, MNRAS, 462 (Suppl_1), 184-194.

Complex organic molecules with three carbon atoms are found in the earliest stages of star formation. In particular, propenal (C$_2$H$_3$CHO) is a species of interest due to its implication in the formation of more complex species and even biotic molecules. This study aims to search for the presence of C$_2$H$_3$CHO and other three-carbon species such as propylene (C$_3$H$_6$) in the hot corino region of the low-mass protostellar binary IRAS 16293--2422 to understand their formation pathways. We use ALMA observations in Band 6 and 7 from various surveys to search for the presence of C$_3$H$_6$ and C$_2$H$_3$CHO towards the protostar IRAS 16293--2422 B (IRAS 16293B). We report the detection of both C$_3$H$_6$ and C$_2$H$_3$CHO towards IRAS 16293B, however, no unblended lines were found towards the other component of the binary system, IRAS 16293A. We derive column density upper limits for C$_3$H$_8$, HCCCHO, n-C$_3$H$_7$OH, i-C$_3$H$_7$OH, C$_3$O, and cis-HC(O)CHO towards IRAS 16293B. We then use a three-phase chemical model to simulate the formation of these species in a typical prestellar environment followed by its hydrodynamical collapse until the birth of the central protostar. Different formation paths, such as successive hydrogenation and radical-radical additions on grain surfaces, are tested and compared to the observational results. The simulations reproduce the abundances within one order of magnitude from those observed towards IRAS 16293B, with the best agreement found for a rate of $10^{-12}$ cm$^3$ s$^{-1}$ for the gas-phase reaction C$_3$ + O $\rightarrow$ C$_2$ + CO. Successive hydrogenations of C$_3$, HC(O)CHO, and CH$_3$OCHO on grain surfaces are a major and crucial formation route of complex organics molecules, whereas both successive hydrogenation pathways and radical-radical addition reactions contribute to the formation of C$_2$H$_5$CHO., Comment: Accepted for publication in A&A. 24 pages, 17 figures

The ratios of the three stable oxygen isotopes 16O, 17O, and 18O on the Earth and, as far as we know in the Solar system, show variations on the order of a few per cent at most, with a few outliers in meteorites. However, in the interstellar medium there are some highly fractionated oxygen isotopic ratios in some specific molecules. The goal of this work is to investigate the oxygen isotopic ratios in different volatile molecules found in the coma of comet 67P/Churyumov–Gerasimenko and compare them with findings from interstellar clouds in order to assess commonalities and differences. To accomplish this goal, we analysed data from the ROSINA instrument on Rosetta during its mission around the comet. 16O/18O ratios could be determined for O2, methanol, formaldehyde, carbonyl sulfide, and sulfur monoxide/dioxide. For O2 the 16O/17O ratio is also available. Some ratios are strongly enriched in the heavy isotopes, especially for sulfur-bearing molecules and formaldehyde, whereas for methanol the ratios are compatible with the ones in the Solar system. O2 falls in-between, but its oxygen isotopic ratios clearly differ from water, which likely rules out an origin of O2 from water, be it by radiolysis, dismutation during sublimation, or the Eley–Rideal process from water ions hitting the nucleus as postulated in the literature.

For a long time it was thought that the cyano (CN) radical, observed remotely many times in various stellar and interstellar environments, is exclusively a photodissociation product of hydrogen cyanide (HCN). Bockelée-Morvan et al. (1984) first questioned this notion based on remote observations of comet IRAS-Araki-Alcock. They reported an upper limit for the HCN production rate which was smaller than the CN production rate previously derived by A’Hearn et al. (1983). Even today, this discrepancy observed for some comets is not resolved although many alternative parents have been suggested. Among the volatile candidates, cyanogen (NCCN), cyanoacetylene (HC3N) and acetonitrile (CH3CN), according to Fray et al. (2005), are the most promising ones. While cyanoacetylene and acetonitrile are known to be present in trace amounts in comets, as reported for comet Hale-Bopp by Bockelée-Morvan et al. (2000) and for comet 67P/Churyumov-Gerasimenko by Le Roy et al. (2015) and Rubin et al. (2019), the abundance of cyanogen in comets is unknown. Altwegg et al. (2019) were the first to mention its detection in the inner coma of comet 67P/Churyumov-Gerasimenko, target of ESA’s Rosetta mission. In this work, we track the signatures of cyanogen in the ROSINA/DFMS (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/ Double Focusing Mass Spectrometer; Balsiger et al. (2007)) data, collected during the Rosetta mission phase. We derive abundances relative to water for three distinct periods, indicating that cyanogen is not abundant enough to explain the CN production in comet 67P together with HCN. Our findings are consistent with the non-detection of cyanogen in the interstellar medium. A’Hearn M.F., Millis R.L., 1983, IAU Circ., 3802 Altwegg K., Balsiger H., Fuselier S.A., 2019, Annu. Rev. Astron. Astrophys., 57, 113–55 Balsiger H. et al., 2007, Space Science Reviews, 128, 745-801 Bockelée-Morvan D., Crovisier J., Baudry A., Despois D., Perault M., Irvine W.M., Schloerb F.P., Swade D., 1984, Astron. Astrophys., 141, 411-418 Bockelée-Morvan et al., 2000, Astron. Astrophys., 353, 1101–1114. Fray N., Bénilan Y., Cottin H., Gazeau M.-C., Crovisier J., 2005, Planetary and Space Science, 53, 1243-1262 Le Roy L. et al., 2015, Astron. Astrophys., 583, A1 Rubin M. et al., 2019, MNRAS, 489, 594-607

The coma of active comets contains two essential components resulting from cometary activity: gas and dust. To investigate the latter, the Rosetta spacecraft was equipped with several instruments fully dedicated to the analysis of dust in the coma of comet 67P/Churyumov-Gerasimenko (67P). We show that, although not designed to observe dust, another instrument onboard Rosetta can obtain information about dust particles from 67P: the ROSINA-COPS ram gauge (RG, [1]) shown in Figure 1. In particular, it was possible to measure the sublimation of the volatile part of dust agglomerates entering the instrument. From these measurements, we find three different families of volatiles and dimensions, calculated as a diameter of an equivalent sphere of water, of hundreds of nanometres. This value is in accordance with the smallest (refractory) dust structures found so far at 67P. 1. Introduction The main scientific goal of the RG was to measure the ram pressure in the coma of 67P to derive the velocity of the gas. At times, the mostly smooth cometary signal showed sudden increases in measured density (Figure 2). This indicates the presence of a momentary additional source of gas and this is compatible with the sublimation of the volatile component of a dust particle within the RG [2]. We therefore search in the data recorded by the RG for features similar to those in Figure 2, paying attention to exclude those attributable to spacecraft background effects such as offset measurements, slews and thruster firings [3]. COPS had two operating procedures, the so-called monitoring mode and the scientific mode; we studied the measurement datasets of both of them taking into account the strengths and weaknesses of the approaches. The scientific mode provided many measurements of a single feature and allowed monitoring of dust particles that sublimate too fast to be observed by the monitoring mode. However, the science mode has only been used scarcely. On the other hand, the monitoring mode was more frequently active, but operating at lower time-resolution (one minute). Therefore, in most cases, it is not possible to extrapolate information beyond the indication that at that moment there was an agglomerate containing volatiles within the RG. Among all the features, the ones composed of at least five consecutive measurements are investigated (5+ minutes in monitoring mode and 10+ seconds in science mode). Through their distinct decay constants, we analyzed the amount of different groups of volatiles and for the total volume of the volatile part by integrating the obtained signal with time. First, we model the tail of the feature, that is the part that follows immediately after the abrupt increase in density (cf. Figure 2). After subtracting the nominal coma signal, the measurements that make up the tail are fitted by either a single exponential decay function, thus indicating that there is only one volatile component, or by the sum of two different exponentials, thus contemplating the possibility that there are two distinct groups of volatiles. As for the volume of the volatiles, we set a differential equation that describes the variation in the number of volatile particles within the RG as the difference between the sublimating molecules from the agglomerate and the particles escaping from the instrument. Thanks to this differential equation and the previously calculated fit of the tail, we determine the number of molecules of the agglomerate and calculate the diameter of an equivalent sphere based on the assumption that there is only water ice. We opted for this simplistic choice because water is the dominating volatile component in comets [4]. 2. Results We identify the sublimation of 73 agglomerates, 25 of which allow a detailed analysis. Depending on their exponential decay constants, the latter can be divided into three separate families, meaning that there are either three groups of volatiles, or multiple arrangements of the volatiles inside the agglomerates. The volatile sublimation process lasts at most a few tens of minutes, thus explaining why COSIMA [5] detected only refractories: as already pointed out by [6], the interval between collection and analysis by COSIMA is too broad. Moreover, we calculated their size as a diameter of an equivalent sphere of water. We obtain dimensions in the order of hundreds of nanometers, in accordance with the smallest (refractory) dust structures found so far at 67P [7]. 3. Summary and conclusions The RG has proven to be a very versatile tool, since it was able to obtain indications on dust particles, an element for which it was not developed. The data obtained provide redundancy to other instruments of the Rosetta mission, but also add new pieces to the complicated puzzle of cometary activity of 67P and the suggested approach may be an additional tool to better categorize dust agglomerates. References [1] Balsiger H. et al., Space Science Reviews 128, 745-801, 2007 [2] Altwegg K. et al., MNRAS 469, S130-S141, 2017 [3] Schläppi B. et al., Journal of Geophysical Research 115, A12, 2010 [4] Le Roy L. et al., Astronomy & Astrophysics 583, A1, 2015 [5] Fray, N. et al., Nature 538, 72-74, 2016 [6] Altwegg K. et al., Nature Astronomy 4, 533-540, 2020 [7] Mannel T. et al., Astronomy & Astrophysics 630, A26, 2019

Complex organic molecules (COM) are detected in many sources in the warm inner regions of envelopes surrounding deeply embedded protostars. Exactly how these COM form remains an open question. 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 (IRAS16293). We utilised observations from the ALMA Protostellar Interferometric Line Survey of IRAS16293. The species identification and the rotational temperature and column density estimation were derived by fitting the extracted spectra towards IRAS16293 A and IRAS16293 B with synthetic spectra. The majority of the work in this paper pertains to the analysis of IRAS16293 A for a comparison with the results from the other binary component, which have already been published. We detect 15 different COM, as well as 16 isotopologues towards the most luminous companion protostar IRAS16293 A. Tentative detections of an additional 11 isotopologues are reported. We also searched for and report on the first detections of CH3OCH2OH and t-C2H5OCH3 towards IRAS16293 B and the follow-up detection of CH2DCHO and CH3CDO. Twenty-four lines of CHD2OH are also identified. 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 IRAS16293 A. This spatial differentiation is not resolved in IRAS16293 B and will require observations at a higher angular resolution. In parallel, the list of identified CHD2OH lines shows the need of accurate spectroscopic data including their line strength., Accepted for publication in A&A. 31 pages, 17 figures

Although the debate regarding the origin of the cyano (CN) radical in comets has been ongoing for many decades, it has yielded no definitive answer to date. CN could previously only be studied remotely, strongly hampering efforts to constrain its origin because of very limited spatial information. Thanks to the European Space Agency's Rosetta spacecraft, which orbited comet 67P/Churyumov-Gerasimenko for two years, we can investigate, for the first time, CN around a comet at high spatial and temporal resolution. On board Rosetta's orbiter module, the high-resolution double-focusing mass spectrometer DFMS, part of the ROSINA instrument suite, analyzed the neutral volatiles (including HCN and the CN radical) in the inner coma of the comet throughout that whole two-year phase and at variable cometocentric distances. From a thorough analysis of the full-mission data, the abundance of CN radicals in the cometary coma has been derived. Data from a close flyby event in February 2015 indicate a distributed origin for the CN radical in comet 67P/Churyumov-Gerasimenko., Comment: Accepted for publication in MNRAS

Cometary comae are generally depleted in nitrogen. The main carriers for volatile nitrogen in comets are NH3 and HCN. It is known that ammonia readily combines with many acids, such as HCN, HNCO and HCOOH, encountered in the interstellar medium as well as in cometary ice to form ammonium salts (NH4+X−) at low temperatures. Ammonium salts, which can have a substantial role in prebiotic chemistry, are hard to detect in space as they are unstable in the gas phase and their infrared signature is often hidden by thermal radiation or by, for example, OH in minerals. Here we report the presence of all possible sublimation products of five different ammonium salts in the comet 67P/Churyumov–Gerasimenko measured by the ROSINA instrument onboard Rosetta. The relatively high sublimation temperatures of the salts leads to an apparent lack of volatile nitrogen in the coma. This then also explains the observed trend of higher NH3/H2O ratios with decreasing perihelion distances in comets. A dust impact event detected by the ROSINA mass spectrometer towards the end of the Rosetta mission brings evidence of the presence of ammonium salts in comets. Ammonium salts can store enough nitrogen to explain the observed nitrogen depletion in comets and may have a role in amino acid formation.

Context. Gas-phase sodium, silicon, potassium, and calcium were previously identified in mass spectra recorded in the coma of comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency’s Rosetta mission. The major release process for these atoms was identified as sputtering by the solar wind. More recently, remote observations of numerous comets over a range in heliocentric distances revealed the presence of metal atoms of iron and nickel that had been released either from the nucleus or from a distributed source with a short scale length. Sputtering, however, has been dismissed as a major release process due to the attenuation of the solar wind in the comae of some of the observed targets. Aims. We investigated the presence of refractory species in the gas phase of the coma of 67P/Churyumov-Gerasimenko. This investigation includes a period close to perihelion when the solar wind was likely absent from the near-nucleus region due to the increased cometary activity. Additionally, we extended our search to iron and nickel. Methods. We analyzed in situ data from the Rosetta/ROSINA Double Focusing Mass Spectrometer DFMS. Results. We found that gas-phase silicon was present throughout the Rosetta mission. Furthermore, the presence of sodium and iron atoms near the comet’s perihelion confirms that sputtering cannot be the sole release process for refractory elements into the gas phase. Nickel was found to be below the detection limit. The search for parent species of any of the identified gas phase refractories has not been successful. Upper limits for a suite of possible fragment species (SiH, SiC, NaH, etc.) of larger parent and daughter species have been obtained. Furthermore, Si did not exhibit the same drop in signal as do common cometary gases when the spacecraft is pointed away from the nucleus. The combined results suggest that a direct release of elemental species from small grains on the surface of the nucleus or from small grains in the surrounding coma is a more likely explanation than the previous assumption of release via the dissociation of gaseous parent molecules.

Context. Propyne (CH$_3$CCH) has been detected in a variety of environments, from Galactic star-forming regions to extragalactic sources. Such molecules are excellent tracers of the physical conditions in star-forming regions. Aims. This study explores the emission of CH$_3$CCH in the low-mass protostellar binary, IRAS 16293$-$2422, examining the spatial scales traced by this molecule, as well as its formation and destruction pathways. Methods. ALMA observations from the Protostellar Interferometric Line Survey (PILS) are used to determine the abundances and excitation temperatures of CH$_3$CCH towards both protostars, exploring spatial scales from 70 to 2400 au. The three-phase chemical kinetics model MAGICKAL is also used, to explore the chemical reactions of this molecule. Results. CH$_3$CCH is detected towards both IRAS 16293A and IRAS 16293B and is found to trace the hot corino component around each source in the PILS dataset. Eighteen transitions above 3$\sigma$ are detected, enabling robust excitation temperatures and column densities to be determined in each source. In IRAS 16293A, an excitation temperature of 90 K and a column density of 7.8$\times$10$^{15}$ cm$^{-2}$ best fits the spectra. In IRAS 16293B, an excitation temperature of 100 K and 6.8$\times$10$^{15}$ cm$^{-2}$ best fits the spectra. The chemical modelling finds that in order to reproduce the observed abundances, both gas-phase and grain-surface reactions are needed. Conclusions. CH$_3$CCH is a molecule whose brightness and abundance in many different regions can be utilised to provide a benchmark of molecular variation with the physical properties of star-forming regions. It is essential when making such comparisons, that the abundances are determined with a good understanding of the spatial scale of the emitting region, to ensure that accurate abundances are derived., Comment: Accepted for publication in Astronomy & Astrophysics

Context. Unlike all previous cometary space missions, the Rosetta spacecraft accompanied its target, comet 67P/Churyumov-Gerasimenko, for more than two years on its way around the Sun. Thereby, an unexpected diversity and complexity of the chemical composition was revealed. Aims. Our first step of decrypting the exact chemical composition of the gaseous phase is the identifying and quantifying the bulk composition of the pure aromatic and aliphatic hydrocarbons. Methods. For this study, data from ROSINA–Double Focusing Mass Spectrometer (DFMS) onboard the Rosetta spacecraft and the laboratory twin model were used. A joint campaign of laboratory calibration measurements and space data analysis was performed to derive the hydrocarbon bulk composition for the post-inbound equinox period at 1.52 AU in May 2015. Furthermore, several other mission phases were investigated to determine the dependencies of season, location, and heliocentric distance on the relative abundances of hydrocarbons. Results. It is shown that the bulk composition of the gaseous phase includes a high number of aliphatic compounds such as methane, ethane, and propane, as well as the aromatic compounds benzene and toluene. Butane and pentane were successfully identified in measurements at closer distance to the comet in May 2016. Furthermore, the presence of hexane and heptane in the coma is confirmed on rare occasions during the mission. Their presence in DFMS space data appears to be linked to days or periods of high dust activity. In addition to the saturated aliphatic and aromatic compounds, a high number of remaining unsaturated species is present, which cannot be explained by fragmentation of saturated species or contribution from other organic molecules in addition to pure hydrocarbons. This indicates the existence of unsaturated aliphatic and aromatic hydrocarbon molecules in the coma of comet 67P.

Recent high-resolution in situ mass spectrometry at comet 67P/Churyumov-Gerasimenko visited by European Space Agency's Rosetta spacecraft raised the question, if sublimating ammonium salts can unequivocally be detected in the cometary coma. In laboratory experiments with the twin model of the space instrument, two prototypic ammonium salts NH

Nitrogen oxides are thought to play a significant role as a nitrogen reservoir and to potentially participate in the formation of more complex species. Until now, only NO, N$_2$O and HNO have been detected in the interstellar medium. We report the first interstellar detection of nitrous acid (HONO). Twelve lines were identified towards component B of the low-mass protostellar binary IRAS~16293--2422 with the Atacama Large Millimeter/submillimeter Array, at the position where NO and N$_2$O have previously been seen. A local thermodynamic equilibrium model was used to derive the column density ($\sim$ 9 $\times$ 10$^{14}$ cm$^{-2}$ in a 0.5'' beam) and excitation temperature ($\sim$ 100 K) of this molecule. HNO, NO$_2$, NO$^+$, and HNO$_3$ were also searched for in the data, but not detected. We simulated the HONO formation using an updated version of the chemical code Nautilus and compared the results with the observations. The chemical model is able to reproduce satisfactorily the HONO, N$_2$O, and NO$_2$ abundances, but not the NO, HNO, and NH$_2$OH abundances. This could be due to some thermal desorption mechanisms being destructive and therefore limiting the amount of HNO and NH$_2$OH present in the gas phase. Other options are UV photodestruction of these species in ices or missing reactions potentially relevant at protostellar temperatures., Accepted in A&A Letters

Comets are considered to be some of the most pristine and unprocessed solar system objects accessible to in-situ exploration. Investigating their molecular and elemental composition takes us on a journey back to the early period of our solar system and possibly even further. In this work, we deduce the bulk abundances of the major volatile species in comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency's Rosetta mission. The basis are measurements obtained with the ROSINA instrument suite on board the Rosetta orbiter during a suitable period of high outgassing near perihelion. The results are combined with both gas and dust composition measurements published in the literature. This provides an integrated inventory of the major elements present in the nucleus of 67P/Churyumov-Gerasimenko. Similar to comet 1P/Halley, which was visited by ESA's Giotto spacecraft in 1986, comet 67P/Churyumov-Gerasimenko also shows near-solar abundances of oxygen and carbon, whereas hydrogen and nitrogen are depleted compared to solar. Still, the degree of devolatilization is lower than that of inner solar system objects, including meteorites and the Earth. This supports the idea that comets are among the most pristine objects in our solar system., Comment: Accepted for publication in MNRAS

Comets contain abundant amounts of organic and inorganic species. Many of the volatile molecules in comets have also been observed in the interstellar medium and some of them even with similar relative abundances, indicating formation under similar conditions or even sharing a common chemical pathway. There is a growing amount of evidence that suggests comets inherit and preserve substantial fractions of materials inherited from previous evolutionary phases, potentially indicating that commonplace processes occurred throughout comet-forming regions. Through impacts, part of this material has also been transported to the inner planetary system, including the terrestrial planets. While comets have been ruled out as a major contributor to terrestrial ocean water, substantial delivery of volatile species to the Earth's atmosphere, and as a consequence also organic molecules to its biomass, appears more likely. Comets contain many species of pre-biotic relevance and molecules that are related to biological processes on Earth, and have hence been proposed as potential indicators for the presence of biological processes in the search of extraterrestrial life. While the delivery of cometary material to Earth may have played a crucial role in the emergence of life, the presence of such alleged biosignature molecules in the abiotical environment of comets complicates the detection of life elsewhere in the universe., Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in ACS Earth and Space Chemistry, copyright American Chemical Society after peer review

The cyano radical (CN) is one of the most frequently remotely observed species in space, and is also often observed in comets. Data for the inner coma of comet 67P/Churyumov-Gerasimenko collected by the high-resolution Double Focusing Mass Spectrometer (DFMS) on board the Rosetta orbiter revealed an unexpected chemical complexity, and, recently, also more CN than expected from photodissociation of its most likely parent, hydrogen cyanide (HCN). Here, we derive abundances relative to HCN of three cometary nitriles (including structural isomers) from DFMS data. Mass spectrometry of complex mixtures does not always allow isolation of structural isomers, and therefore in our analysis we assume the most stable and abundant (in similar environments) structure, that is HCN for CHN, CH3CN for C2H3N, HC3N for C3HN, and NCCN for C2N2. For cyanoacetylene (HC3N) and acetonitrile (CH3CN), the complete mission time-line was evaluated, while cyanogen (NCCN) was often below the detection limit. By carefully selecting periods where cyanogen was above the detection limit, we were able to follow the abundance ratio between NCCN and HCN from 3.16 au inbound to 3.42 au outbound. These are the first measurements of NCCN in a comet. We find that neither NCCN nor either of the other two nitriles is sufficiently abundant to be a relevant alternative parent to CN.

Hydroxylamine (NH$_{2}$OH) and methylamine (CH$_{3}$NH$_{2}$) have both been suggested as precursors to the formation of amino acids and are therefore of interest to prebiotic chemistry. Their presence in interstellar space and formation mechanisms, however, are not well established. We aim to detect both amines and their potential precursor molecules NO, N$_{2}$O and CH$_{2}$NH towards the low-mass protostellar binary IRAS 16293--2422, in order to investigate their presence and constrain their interstellar formation mechanisms around a young Sun-like protostar. ALMA observations from the unbiased, high angular resolution and sensitivity Protostellar Interferometric Line Survey (PILS) are used. Spectral transitions of the molecules under investigation are searched for with the CASSIS line analysis software. CH$_2$NH and N$_{2}$O are detected for the first time towards a low-mass source, the latter molecule through confirmation with the single-dish TIMASSS survey. NO is also detected. CH$_{3}$NH$_{2}$ and NH$_{2}$OH are not detected and stringent upper limit column densities are determined. The non-detection of CH$_{3}$NH$_{2}$ and NH$_{2}$OH limits the importance of formation routes to amino acids involving these species. The detection of CH$_{2}$NH makes amino acid formation routes starting from this molecule plausible. The low abundances of CH$_2$NH and CH$_{3}$NH$_{2}$ compared to Sgr B2 indicate that different physical conditions influence their formation in low- and high-mass sources., Accepted for publication in A&A

Context. The Class 0 protostellar binary IRAS 16293-2422 is an interesting target for (sub)millimeter observations due to, both, the rich chemistry toward the two main components of the binary and its complex morphology. Its proximity to Earth allows the study of its physical and chemical structure on solar system scales using high angular resolution observations. Such data reveal a complex morphology that cannot be accounted for in traditional, spherical 1D models of the envelope. Aims. The purpose of this paper is to study the environment of the two components of the binary through 3D radiative transfer modeling and to compare with data from the Atacama Large Millimeter/submillimeter Array. Such comparisons can be used to constrain the protoplanetary disk structures, the luminosities of the two components of the binary and the chemistry of simple species. Methods. We present 13CO, C17O and C18O J=3-2 observations from the ALMA Protostellar Interferometric Line Survey (PILS), together with a qualitative study of the dust and gas density distribution of IRAS 16293-2422. A 3D dust and gas model including disks and a dust filament between the two protostars is constructed which qualitatively reproduces the dust continuum and gas line emission. Results and conclusions. Radiative transfer modeling of source A and B, with the density solution of an infalling, rotating collapse or a protoplanetary disk model, can match the constraints for the disk-like emission around source A and B from the observed dust continuum and CO isotopologue gas emission. If a protoplanetary disk model is used around source B, it has to have an unusually high scale-height in order to reach the dust continuum peak emission value, while fulfilling the other observational constraints. Our 3D model requires source A to be much more luminous than source B; LA ~ 18 $L_\odot$ and LB ~ 3 $L_\odot$., Comment: Accepted for publication in Astronomy and Astrophysics, 20 pages, 12 figures

[abridged] The enhanced degrees of deuterium fractionation observed in envelopes around protostars demonstrate the importance of chemistry at low temperatures, relevant in pre- and protostellar cores. formaldehyde is an important species in the formation of methanol and more complex molecules. Here, we present the first study of formaldehyde deuteration on small scales around the prototypical low-mass protostar IRAS 16293-2422 using high spatial and spectral resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations. Numerous isotopologues of formaldehyde are detected, among them H$_2$C$^{17}$O, and D$_2^{13}$CO for the first time in the ISM. The large range of upper energy levels covered by the HDCO lines help constrain the excitation temperature to 106$\pm$13 K. Using the derived column densities, formaldehyde shows a deuterium fractionation of HDCO/H$_2$CO=6.5$\pm$1%, D$_2$CO/HDCO=12.8$^{+3.3}_{-4.1}$%, and D$_2$CO/H$_2$CO=0.6(4)$\pm$0.1%. The isotopic ratios derived are $^{16}$O/$^{18}$O=805, $^{18}$O/$^{17}$O=3.2 and $^{12}$C/$^{13}$C=56. The HDCO/H$_2$CO ratio is lower than found in previous studies, highlighting the uncertainties involved in interpreting single dish observations of the inner warm regions. The D$_2$CO/HDCO ratio is only slightly larger than the HDCO/H$_2$CO ratio. This is consistent with formaldehyde forming in the ice as soon as CO has frozen onto the grains, with most of the deuteration happening towards the end of the prestellar core phase. A comparison with available time-dependent chemical models indicates that the source is in the early Class 0 stage., Accepted for publication in Astronomy and Astrophysics, 14 pages, 10 figures

The evolutionary past of our Solar System can be pieced together by comparing analogous low-mass protostars with remnants of our Protosolar Nebula - comets. Sulphur-bearing molecules may be unique tracers of the joint evolution of the volatile and refractory components. ALMA Band 7 data from the large unbiased Protostellar Interferometric Line Survey (PILS) are used to search for S-bearing molecules in the outer disc-like structure, 60 au from IRAS 16293-2422 B, and are compared with data on 67P/C-G stemming from the ROSINA instrument aboard Rosetta. Species such as SO$_{2}$, SO, OCS, CS, H$_{2}$CS, H$_{2}$S and CH$_{3}$SH are detected via at least one of their isotopologues towards IRAS 16293-2422 B. The search reveals a first-time detection of OC$^{33}$S towards this source and a tentative first-time detection of C$^{36}$S towards a low-mass protostar. The data show that IRAS 16293-2422 B contains much more OCS than H$_{2}$S in comparison to 67P/C-G; meanwhile, the SO/SO$_{2}$ ratio is in close agreement between the two targets. IRAS 16293-2422 B has a CH$_{3}$SH/H$_{2}$CS ratio in range of that of our Solar System (differences by a factor of 0.7-5.3). It is suggested that the levels of UV radiation during the initial collapse of the systems may have varied and have potentially been higher for IRAS 16293-2422 B due to its binary nature; thereby, converting more H$_{2}$S into OCS. It remains to be conclusively tested if this also promotes the formation of S-bearing complex organics. Elevated UV levels of IRAS 16293-2422 B and a warmer birth cloud of our Solar System may jointly explain the variations between the two low-mass systems., Comment: Accepted for publication in MNRAS; 47 pages, 43 figures, 6 tables

Searches for the prebiotically-relevant cyanamide (NH$_2$CN) towards solar-type protostars have not been reported in the literature. We here present the first detection of this species in the warm gas surrounding two solar-type protostars, using data from the Atacama Large Millimeter/Submillimeter Array Protostellar Interferometric Line Survey (PILS) of IRAS 16293-2422 B and observations from the IRAM Plateau de Bure Interferometer of NGC1333 IRAS2A. We furthermore detect the deuterated and $^{13}$C isotopologues of NH$_2$CN towards IRAS 16293-2422 B. This is the first detection of NHDCN in the interstellar medium. Based on a local thermodynamic equilibrium analysis, we find that the deuteration of cyanamide ($\sim$ 1.7%) is similar to that of formamide (NH$_2$CHO), which may suggest that these two molecules share NH$_2$ as a common precursor. The NH$_2$CN/NH$_2$CHO abundance ratio is about 0.2 for IRAS 16293-2422 B and 0.02 for IRAS2A, which is comparable to the range of values found for Sgr B2. We explored the possible formation of NH$_2$CN on grains through the NH$_2$ + CN reaction using the chemical model MAGICKAL. Grain-surface chemistry appears capable of reproducing the gas-phase abundance of NH$_2$CN with the correct choice of physical parameters., Accepted in A&A

Recent measurements carried out at comet 67P/C-G with the ${\it Rosetta}$ probe revealed that molecular oxygen, O$_2$, is the fourth most abundant molecule in comets. Models show that O$_2$ is likely of primordial nature, coming from the interstellar cloud from which our Solar System was formed. However, gaseous O$_2$ is an elusive molecule in the interstellar medium with only one detection towards quiescent molecular clouds, in the $\rho$ Oph A core. We perform a deep search for molecular oxygen, through the $2_1 - 0_1$ rotational transition at 234 GHz of its $^{16}$O$^{18}$O isotopologue, towards the warm compact gas surrounding the nearby Class 0 protostar IRAS 16293--2422 B with the ALMA interferometer. The targeted $^{16}$O$^{18}$O transition is surrounded by two brighter transitions at $\pm 1$ km s$^{-1}$ relative to the expected $^{16}$O$^{18}$O transition frequency. After subtraction of these two transitions, residual emission at a 3$\sigma$ level remains, but with a velocity offset of $0.3 - 0.5$ km s$^{-1}$ relative to the source velocity, rendering the detection "tentative". We derive the O$_2$ column density for two excitation temperatures $T_{\rm ex}$ of 125 and 300 K, as indicated by other molecules, in order to compare the O$_2$ abundance between IRAS16293 and comet 67P/C-G. Assuming that $^{16}$O$^{18}$O is not detected and using methanol CH$_3$OH as a reference species, we obtain a [O$_2$]/[CH$_3$OH] abundance ratio lower than $2-5$, depending on the assumed $T_{\rm ex}$, a three to four times lower abundance than the [O$_2$]/[CH$_3$OH] ratio of $5-15$ found in comet 67P/C-G. Such a low O$_2$ abundance could be explained by the lower temperature of the dense cloud precursor of IRAS16293 with respect to the one at the origin of our Solar System that prevented an efficient formation of O$_2$ in interstellar ices., Comment: 12 pages, 3 figures, accepted for publication in Astronomy & Astrophysics

Complex organic molecules are readily detected in the inner regions of the gaseous envelopes of forming protostars. In particular, molecules that contain nitrogen are interesting due to the role nitrogen plays in the development of life and the compact scales such molecules have been found to trace around forming protostars. The goal of this work is to determine the inventory of one family of nitrogen-bearing organic molecules, complex nitriles (molecules with a $-$CN functional group) towards two hot corino sources in the low-mass protostellar binary IRAS 16293$-$2422. This work explores the abundance differences between the two sources, the isotopic ratios, and the spatial extent derived from molecules containing the nitrile functional group. Using data from the Protostellar Interferometric Line Survey (PILS) obtained with ALMA we determine abundances and excitation temperatures for the detected nitriles. We also present a new method for determining the spatial structure of sources with high line density and large velocity gradients $-$ Velocity-corrected INtegrated emission (VINE) maps. We detect methyl cyanide (CH$_3$CN) as well as 5 of its isotopologues, including the detection of CHD$_2$CN which is the first detection in the ISM. We also detect ethyl cyanide (C$_2$H$_5$CN), vinyl cyanide (C$_2$H$_3$CN), and cyanoacetylene (HC$_3$N). We find that abundances are similar between IRAS 16293A and IRAS 16293B on small scales except for vinyl cyanide which is only detected towards the latter source. This suggests an important difference between the sources either in their evolutionary stage or warm-up timescales. We also detect a spatially double-peaked emission for the first time in molecular emission in the A source, suggesting that this source is showing structure related to a rotating toroid of material., Comment: A&A accepted 24th April 2018

International audience; The knowledge about sulphur isotopic fractionation in volatile cometary species is limited as only measurements in five comets have been done and only for 34S/32S. The lack of information about the fractionation of 33S/32S makes it impossible to compare them with what is known from refractories. We present results of 34S/32S and for the first time 33S/32S isotopic ratio in H2S, OCS, and CS2 in the coma of comet 67P/Churyumov-Gerasimenko. Observations used for this study were performed with Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Double Focusing Mass Spectrometer during October 2014 and May 2016. Bulk isotopic 33S/32S and 34S/32S ratio derived from these three species yield δ33S = (-302 ± 29)‰ and δ34S = (-41 ± 17)‰ respectively. The observed isotopic fractionation is significantly different from the solar system standard (V-CDT) and all other reported values for solar system objects, except other comets. Furthermore we show that neither mass dependent nor mass-independent fractionation due to photo dissociation as it has been observed in recent laboratory studies can be the cause of the significant depletion compared to solar system standard. In addition, we conclude that there seems to be an intrinsic difference in sulphur isotopic fractionation in cometary volatiles and refractories while the difference between molecules is most likely due to different chemical pathways. The significant fractionation of sulphur isotopes together with a high D2O/HDO vs. HDO/H2O and non-solar isotopic ratio for xenon (Marty 2017) as well as for Si (Marty 2017) point towards a non-homogeneously mixed protosolar nebula.

Context. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) was designed to measure the composition of the gas in the coma of comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency's Rosetta mission. In addition to the volatiles, ROSINA measured refractories sputtered off the comet by the interaction of solar wind protons with the surface of the comet. Aims. The origin of different solar system materials is still heavily debated. Isotopic ratios can be used to distinguish between different reservoirs and investigate processes occurring during the formation of the solar system. Methods. ROSINA consisted of two mass spectrometers and a pressure sensor. In the ROSINA Double Focusing Mass Spectrometer (DFMS), the neutral gas of cometary origin was ionized and then deflected in an electric and a magnetic field that separated the ions based on their mass-to-charge ratio. The DFMS had a high mass resolution, dynamic range, and sensitivity that allowed detection of rare species and the known major volatiles. Results. We measured the relative abundance of all three stable silicon isotopes with the ROSINA instrument on board the Rosetta spacecraft. Furthermore, we measured $^{13}$C/$^{12}$C in C$_2$H$_4$, C$_2$H$_5$, and CO. The DFMS in situ measurements indicate that the average silicon isotopic composition shows depletion in the heavy isotopes $^{29}$Si and $^{30}$Si with respect to $^{28}$Si and solar abundances, while $^{13}$C to $^{12}$C is analytically indistinguishable from bulk planetary and meteorite compositions. Although the origin of the deficiency of the heavy silicon isotopes cannot be explained unambiguously, we discuss mechanisms that could have contributed to the measured depletion of the isotopes $^{29}$Si and $^{30}$Si., Accepted for publication in Astronomy & Astrophysics

The European Space Agency (ESA) spacecraft Rosetta accompanied the Jupiter-family comet (JFC) 67P / Churyumov-Gerasimenko for over two years along its trajectory through the inner solar system. Between 2014 and 2016, it performed almost continuous in-situ measurements of the comet's gaseous atmosphere in close proximity to its nucleus. In this study, the $^{16}$O/$^{18}$O ratio of H$_2$O in the coma of 67P / Churyumov-Gerasimenko, as measured by the ROSINA DFMS mass spectrometer on board Rosetta, was determined from the ratio of H${_2}^{16}$O / H${_2}^{18}$O and $^{16}$OH / $^{18}$OH. The value of 445 $\pm$ 35 represents an $\sim$ 11% enrichment of $^{18}$O compared with the terrestrial ratio of 498.7 $\pm$ 0.1. This cometary value is consistent with the comet containing primordial water, in accordance with leading self-shielding models. These models predict primordial water to be between 5% to 20% enriched in heavier oxygen isotopes compared to terrestrial water. Addendum: The $^{16}$O/$^{17}$O ratio of H$_2$O in the coma of 67P / Churyumov-Gerasimenko., 14 pages, 10 figures, 4 tables + Addendum. Accepted for publication in Astronomy and Astrophysics (A&A) Journal, Rosetta Special Issue 2019

The ESLAB 50 Symposium - spacecraft at comets from 1P/Halley to 67P/Churyumov-Gerasimenko; International audience; Several sulphur-bearing species have already been observed in different families of comets. However, the knowledge on the minor sulphur species is still limited. The comet's sulphur inventory is closely linked to the pre-solar cloud and holds important clues to the degree of reprocessing of the material in the solar nebula and during comet accretion. Sulphur in pre-solar clouds is highly depleted, which is quite puzzling as the S/O ratio in the diffuse interstellar medium is cosmic. This work focuses on the abundance of the previously known species H2S, OCS, SO, S2, SO2 and CS2 in the coma of comet 67P/Churyumov–Gerasimenko measured by Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Double Focusing Mass Spectrometer between equinox and perihelion 2015. Furthermore, we present the first detection of S3, S4, CH3SH and C2H6S in a comet, and we determine the elemental abundance of S/O in the bulk ice of (1.47 ± 0.05) × 10−2. We show that SO is present in the coma originating from the nucleus, but not CS in the case of 67P, and for the first time establish that S2 is present in a volatile and a refractory phase. The derived total elemental sulphur abundance of 67P is in agreement with solar photospheric elemental abundances and shows no sulphur depletion as reported for dense interstellar clouds. Also the presence of S2 at heliocentric distances larger than 3 au indicates that sulphur-bearing species have been processed by radiolysis in the pre-solar cloud and that at least some of the ice from this cloud has survived in comets up the present.

We performed a sensitive search for the ground-state emission lines of ortho- and para-water vapor in the DM Tau protoplanetary disk using the Herschel/HIFI instrument. No strong lines are detected down to 3sigma levels in 0.5 km/s channels of 4.2 mK for the 1_{10}--1_{01} line and 12.6 mK for the 1_{11}--0_{00} line. We report a very tentative detection, however, of the 1_{10}--1_{01} line in the Wide Band Spectrometer, with a strength of T_{mb}=2.7 mK, a width of 5.6 km/s and an integrated intensity of 16.0 mK km/s. The latter constitutes a 6sigma detection. Regardless of the reality of this tentative detection, model calculations indicate that our sensitive limits on the line strengths preclude efficient desorption of water in the UV illuminated regions of the disk. We hypothesize that more than 95-99% of the water ice is locked up in coagulated grains that have settled to the midplane., 5 pages, 3 figures. Accepted for publication in the Herschel HIFI special issue of A&A

Aims: We present preliminary results of the first Herschel spectroscopic observations of NGC7129 FIRS2, an intermediate mass star-forming region. We attempt to interpret the observations in the framework of an in-falling spherical envelope. Methods: The PACS instrument was used in line spectroscopy mode (R=1000-5000) with 15 spectral bands between 63 and 185 microns. This provided good detections of 26 spectral lines seen in emission, including lines of H2O, CO, OH, O I, and C II. Results: Most of the detected lines, particularly those of H2O and CO, are substantially stronger than predicted by the spherical envelope models, typically by several orders of magnitude. In this paper we focus on what can be learned from the detected CO emission lines. Conclusions: It is unlikely that the much stronger than expected line emission arises in the (spherical) envelope of the YSO. The region hot enough to produce such high excitation lines within such an envelope is too small to produce the amount of emission observed. Virtually all of this high excitation emission must arise in structures such as as along the walls of the outflow cavity with the emission produced by a combination of UV photon heating and/or non-dissociative shocks., Comment: A&A Special Issue on Herschel

'Water In Star-forming regions with Herschel' (WISH) is a key programme dedicated to studying the role of water and related species during the star-formation process and constraining the physical and chemical properties of young stellar objects. The Heterodyne Instrument for the Far-Infrared (HIFI) on the Herschel Space Observatory observed three deeply embedded protostars in the low-mass star-forming region NGC1333 in several H2-16O, H2-18O, and CO transitions. Line profiles are resolved for five H16O transitions in each source, revealing them to be surprisingly complex. The line profiles are decomposed into broad (>20 km/s), medium-broad (~5-10 km/s), and narrow (20 km/s), indicating that its physical origin is the same as for the broad H2-16O component. In one of the sources, IRAS4A, an inverse P Cygni profile is observed, a clear sign of infall in the envelope. From the line profiles alone, it is clear that the bulk of emission arises from shocks, both on small (, Accepted for publication in the A&A HIFI special issue

Methyl isocyanate (CH$_{3}$NCO) belongs to a select group of interstellar molecules considered to be relevant precursors in the formation of larger organic compounds, including those with peptide bonds. The molecule has only been detected in a couple of high-mass protostars and potentially on comets. A formation route on icy grains has been postulated for this molecule but experimental evidence is lacking. Here we extend the range of environments where methyl isocyanate is found, and unambiguously identify CH$_{3}$NCO through the detection of 43 unblended transitions in the ALMA Protostellar Interferometric Line Survey (PILS) of the low mass solar-type protostellar binary IRAS 16293-2422. The molecule is detected toward both components of the binary with a ratio HNCO/CH$_3$NCO $\sim$4--12. The isomers CH$_{3}$CNO and CH$_3$OCN are not identified, resulting in upper abundance ratios of CH$_{3}$NCO/CH$_{3}$CNO > 100 and CH$_{3}$NCO/CH$_3$OCN > 10. The resulting abundance ratios compare well with those found for related N-containing species toward high-mass protostars. To constrain its formation, a set of cryogenic UHV experiments is performed. VUV irradiation of CH$_{4}$:HNCO mixtures at 20 K strongly indicate that methyl isocyanate can be formed in the solid-state through CH$_{3}$ and (H)NCO recombinations. Combined with gas-grain models that include this reaction, the solid-state route is found to be a plausible scenario to explain the methyl isocyanate abundances found in IRAS 16293-2422., Accepted 2017 April 7. Received 2017 March 26; in original form 2017 January 24. 13 pages, 8 figures

In the framework of the Water in Star-forming regions with Herschel (WISH) key program, maps in water lines of several outflows from young stars are being obtained, to study the water production in shocks and its role in the outflow cooling. This paper reports the first results of this program, presenting a PACS map of the o-H2O 179 um transition obtained toward the young outflow L1157. The 179 um map is compared with those of other important shock tracers, and with previous single-pointing ISO, SWAS, and Odin water observations of the same source that allow us to constrain the water abundance and total cooling. Strong H2O peaks are localized on both shocked emission knots and the central source position. The H2O 179 um emission is spatially correlated with emission from H2 rotational lines, excited in shocks leading to a significant enhancement of the water abundance. Water emission peaks along the outflow also correlate with peaks of other shock-produced molecular species, such as SiO and NH3. A strong H2O peak is also observed at the location of the proto-star, where none of the other molecules have significant emission. The absolute 179 um intensity and its intensity ratio to the H2O 557 GHz line previously observed with Odin/SWAS indicate that the water emission originates in warm compact clumps, spatially unresolved by PACS, having a H2O abundance of the order of 10^-4. This testifies that the clumps have been heated for a time long enough to allow the conversion of almost all the available gas-phase oxygen into water. The total water cooling is ~10^-1 Lo, about 40% of the cooling due to H2 and 23% of the total energy released in shocks along the L1157 outflow., Comment: Accepted for publication in Astronomy and Astrophysics (Herschel special issue)

[Abridged] The majority of stars form in binary or higher order systems. The Class 0 protostellar system IRAS16293-2422 contains two protostars, 'A' and 'B', separated by ~600 au and embedded in a single, 10^4 au scale envelope. Their relative evolutionary stages have been debated. We aim to study the relation and interplay between the two protostars A and B at spatial scales of 60 to ~1000 au. We selected molecular gas line transitions of CO, H2CO, HCN, CS, SiO, and CCH from the ALMA-PILS spectral imaging survey (329-363 GHz) and used them as tracers of kinematics, density, and temperature in the IRAS16293-2422 system. The angular resolution of the PILS data set allows us to study these quantities at a resolution of 0.5 arcsec (60 au [..]). Line-of-sight velocity maps of both optically thick and optically thin molecular lines reveal: (i) new manifestations of previously known outflows emanating from protostar A; (ii) a kinematically quiescent bridge of dust and gas spanning between the two protostars, with an inferred density between 4 10^4 and 3 10^7 cm^-3; and (iii) a separate, straight filament seemingly connected to protostar B seen only in CCH, with a flat kinematic signature. Signs of various outflows, all emanating from source A, are evidence of high-density and warmer gas; none of them coincide spatially and kinematically with the bridge. We hypothesize that the bridge arc is a remnant of filamentary substructure in the protostellar envelope material from which protostellar sources A and B have formed. One particular morphological structure appears to be due to outflowing gas impacting the quiescent bridge material. The continuing lack of clear outflow signatures unambiguously associated to protostar B and the vertically extended shape derived for its disk-like structure lead us to conclude that source B may be in an earlier evolutionary stage than source A., Comment: Accepted for publication in A&A. 27 pages, 24 figures