Search

There is evidence that the star formation process is linked to the intricate net of filaments in molecular clouds, which may be also due to gas compression from external triggers. We studied the southern region of the Perseus NGC 1333 molecular cloud, known to be heavily shaped by similar external triggers, to shed light on the process that perturbed the filament where the Class 0 IRAS4 protostars lie. We use new IRAM-NOEMA observations of SiO and CH3OH, both known to trace violent events as shocks, toward IRAS 4A as part of the Large Program Seeds Of Life in Space (SOLIS). We detected three parallel elongated ($>$6000 au) structures, called fingers, with narrow line profiles (~1.5 $km s^{-1}$) peaked at the cloud systemic velocity, tracing gas with high density (5-20 $10^5 cm^{-3}$) and high temperature (80-160 K). They are chemically different, with the northern finger traced by both SiO and CH3OH ([CH3OH]/[SiO]~160-300), while the other two only by SiO ([CH3OH]/[SiO]$$5000 yr, would be consistent with the observations if a substantial fraction of silicon, frozen onto the grain mantles, is released by the shocks.We suggest that the shock train is due to an expanding gas bubble, coming behind NGC 1333 from the southwest and clashing against the filament, where IRAS 4A lies. Finally, we propose a solution to the two-decades long debate on the nature and origin of the widespread narrow SiO emission observed in the south part of NGC 1333, namely that it is due to unresolved trains of shocks., Comment: accepted to MNRAS, stac083

Introduction Comets are the leftovers from the formation of the Solar System. Understanding their composition allow us to investigate the physical and chemical processes occurring at the early stages of its formation. In this contribution we analyze high resolution spectra of comet C/2020 F3 (NEOWISE) obtained with the High Accuracy Radial Velocity Planet Searcher (HARPS-N) echelle spectrograph at the 3.6 m Telescopio Nazionale Galileo (TNG). C/2020 F3 was discovered on 27 March 2020 as a long-period comet, the brightest one observed in the northern hemisphere since the Hale-Bopp in 1997. Its remarkable brightness offered a unique opportunity to investigate its composition through high-resolution spectroscopy, which is otherwise challenging on these targets due to their usual faintness. Our observations already allowed the identification of 4488 cometary emission lines belonging to C2, C3, CN, CH, NH2, Na I and [OI] [1]. We here follow up the molecular identifications by characterizing the gaseous environment of C2020/F3 through the analysis of the molecules’ production rates. Dataset and Methods We analyze one HARPS-N spectra of C/2020 F3 obtained on 26 July, at a heliocentric distance of 0.72 AU, covering the wavelengths between 383-693 nm at a spectral resolving power of 115000. We reduced the spectrum by performing absolute calibration, sky subtraction and dust-continuum normalization using IRAF routines and observations of the spectrophotometric standard HR5501 and the solar analog Land 107-684. The calibrated spectra were used in combination with the identified line identification [1] to measure the fluxes of given bands of molecules CN (388.3 nm band), C2 (516.5 nm band), C3 (405.0 nm band), NH2 (577.4 nm band) and OI (630.0 nm line). For each emission line or band, the flux was measured in IRAF through a fit of multiple gaussian profiles, centered at the catalog wavelengths. Cometary production rates are then estimated using a Haser model [2] which parameters were derived from literature studies (e.g., [3]) Results We estimate production rates of Q[CN]=2.2*1026 , Q[C2]=2.28*1026 , Q[C3]=2.15*1027 and finally Q[NH2]=1.08*1027 . We estimate a H2O production rate of Q[H2O]=2.89*1029 , using the OI emission line at 630 nm, therefore assuming that all the flux of this line comes from dissociation of water. Our estimate is in agreement with independent estimates from the SOHO/SWAN instrument[4]. A detailed analysis of the production rate and their comparison with other comets will be presented at the conference. References [1] P.Cambianica, et al., 2021, A&A, 656, A160. [2] Haser, L. 1957Bull. Soc. R. Sci. Liege, 43 (1957), pp. 740-750 [3] Langland-Shula, L., Smith, G. H.,2011, Icarus, Volume 213, Issue 1, 2011, 280-322, 0019-1035 [4] M. R. Combi et al 2021 ApJL 907 L38

This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made., The goal of the Ariel space mission is to observe a large and diversified population of transiting planets around a range of host star types to collect information on their atmospheric composition. The planetary bulk and atmospheric compositions bear the marks of the way the planets formed: Ariel’s observations will therefore provide an unprecedented wealth of data to advance our understanding of planet formation in our Galaxy. A number of environmental and evolutionary factors, however, can affect the final atmospheric composition. Here we provide a concise overview of which factors and effects of the star and planet formation processes can shape the atmospheric compositions that will be observed by Ariel, and highlight how Ariel’s characteristics make this mission optimally suited to address this very complex problem. © The Author(s) 2021., D.T., S.F., S.M., E.S., and A.N. acknowledge the support of the Italian Space Agency (ASI) through the ASI-INAF contract 2018-22-HH.0. D.T., C.C., D.F., and L.P. acknowledge the support of the PRIN-INAF 2016 “The Cradle of Life - GENESIS-SKA (General Conditions in Early Planetary Systems for the rise of life with SKA”. D.T., S.F., S.M. D.F, J.M., F.O., P.W. acknowledge the support of the Italian National Institute of Astrophysics (INAF) through the INAF Main Stream project “Ariel and the astrochemical link between circumstellar discs and planets” (CUP: C54I19000700005). S.M. acknowledges support from the European Research Council via the Horizon 2020 Framework Programme ERC Synergy “ECOGAL” Project GA-855130. M.K. acknowledges funding by the University of Tartu ASTRA project 2014-2020.4.01.16-0029 KOMEET “Benefits for Estonian Society from Space Research and Application”, financed by the EU European Regional Development Fund. J.M.D.K. gratefully acknowledges funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through an Emmy Noether Research Group (grant number KR4801/1-1) and the DFG Sachbeihilfe (grant number KR4801/2-1), as well as from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme via the ERC Starting Grant MUSTANG (grant agreement number 714907). The research of O.P. is funded by the Royal Society, through Royal Society Dorothy Hodgkin Fellowship DH140243. M.P. thanks the support to NuGrid from STFC (through the University of Hull’s Consolidated Grant ST/R000840/1), and access to VIPER, the University of Hull High Performance Computing Facility. M.P. acknowledges the support from the ”Lendulet-2014” Program of the Hungarian Academy of Sciences (Hungary), from the ERC Consolidator Grant (Hungary) funding scheme (Project RADIOSTAR, G.A. n. 724560), by the National Science Foundation (NSF, USA) under grant No. PHY-1430152 (JINA Center for the Evolution of the Elements). M.P. also thanks the UK network BRIDGCE and the ChETEC COST Action (CA16117), supported by COST (European Cooperation in Science and Technology). M.I. thanks the support by JSPS KAKENHI 18H05439. C.D. acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709), and the Group project Ref. PID2019-110689RB-I00/AEI/10.13039/501100011033.

Imai et al., The chemical diversity of low-mass protostellar sources has so far been recognized, and environmental effects are invoked as its origin. In this context, observations of isolated protostellar sources without the influence of nearby objects are of particular importance. Here, we report the chemical and physical structures of the low-mass Class 0 protostellar source IRAS 16544−1604 in the Bok globule CB 68, based on 1.3 mm Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of ∼70 au that were conducted as part of the large program FAUST. Three interstellar saturated complex organic molecules (iCOMs), CH3OH, HCOOCH3, and CH3OCH3, are detected toward the protostar. The rotation temperature and the emitting region size for CH3OH are derived to be 131 ± 11 K and ∼10 au, respectively. The detection of iCOMs in close proximity to the protostar indicates that CB 68 harbors a hot corino. The kinematic structure of the C18O, CH3OH, and OCS lines is explained by an infalling–rotating envelope model, and the protostellar mass and the radius of the centrifugal barrier are estimated to be 0.08–0.30 M⊙ and, This paper makes use of the following ALMA data: ADS/JAO.ALMA#2016.1.01376.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The authors acknowledge financial support from JSPS and MAEE under the Japan–France Integrated Action Program (SAKURA: 25765VC). D.J. is supported by NRC Canada and by an NSERC Discovery Grant. E.B. and G.B. acknowledge funding from the European Research Council under the European Union's Horizon 2020 research and innovation program, for the project "The Dawn of Organic Chemistry," grant agreement No. 741002. G.B. acknowledges support from the PID2020-117710GB-I00 grant funded by MCIN/AEI/10.13039/501100011033 and from the Unit of Excellence María de Maeztu 2020–2023 award to the Institute of Cosmos Sciences (CEX2019-00918-M). I.J.-S. has received partial support from the Spanish State Research Agency (AEI) through project Nos. PID2019-105552RB-C41 and MDM-2017-0737 Unidad de Excelencia "Maria de Maeztu" - Centro de Astrobiologia (CSIC-INTA). This study is supported by grants-in-aid from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (18H05222, 18J11010, 19H05069, 19K14753, and 21K13954).

Binding energies (BEs) are one of the most important parameters for astrochemical modeling determining, because they govern whether a species stays in the gas-phase or is frozen on the grain surfaces. It is currently known that, in the denser and colder regions of the interstellar medium, sulphur is severely depleted in the gas phase. It has been suggested that it may be locked into the grain icy mantles. However, which are the main sulphur carriers is still a matter of debate. This work aims at establishing accurate BEs of 17 sulphur-containing species on two validated water ice structural models, the proton-ordered crystalline (010) surface and an amorphous water ice surface. We adopted Density Functional Theory (DFT)-based methods (the hybrid B3LYP-D3(BJ) and the hybrid meta-GGA M06-2X functionals) to predict structures and energetics of the adsorption complexes. London's dispersion interactions are shown to be crucial for an accurate estimate of the BEs due to the presence of the high polarizable sulphur element. While on the crystalline model the adsorption is restricted to a very limited number of binding sites with single valued BEs, on the amorphous model several adsorption structures are predicted, giving a BE distribution for each species. With the exception of few cases, both experimental and other computational data are in agreement with our calculated BE values. A final discussion on how useful the computed BEs are with respect to the snow lines of the same species in protoplanetary disks is provided, Comment: 22 pages, 9 figures, Accepted for publication in The Astrophysical Journal

We present ALMA high-angular resolution ($\sim$ 50 au) observations of the Class I binary system SVS13-A. We report images of SVS13-A in numerous interstellar complex organic molecules: CH$_{\rm 3}$OH, $^{13}$CH$_{\rm 3}$OH, CH$_{\rm 3}$CHO, CH$_{\rm 3}$OCH$_{\rm 3}$, and NH$_{\rm 2}$CHO. Two hot corinos at different velocities are imaged in VLA4A (V$_{sys}$= +7.7 km s$^{-1}$) and VLA4B (V$_{sys}$= +8.5 km s$^{-1}$). From a non-LTE analysis of methanol lines we derive a gas density of 3 $\times$ 10$^8$ cm$^{-3}$, and gas temperatures of 140 K and 170 K for VLA4A and VLA4B, respectively. For the other species the column densities are derived from a LTE analysis. Formamide, which is the only N-bearing species detected in our observations, is more prominent around VLA4A, while dimethyl ether, methanol and acetaldehyde are associated with both VLA4A and VLA4B. We derive in the two hot corinos abundance ratios of $\sim$ 1 for CH$_{\rm 3}$OH, $^{13}$CH$_{\rm 3}$OH, and CH$_{\rm 3}$OCH$_{\rm 3}$, $\sim$ 2 for CH$_{\rm 3}$CHO, and $\sim$ 4 for NH$_{\rm 2}$CHO. The present dataset supports a chemical segregation between the different species inside the binary system. The emerging picture is that of an onion-like structure of the two SVS13-A hot corinos, caused by the different binding energies of the species, also supported by ad hoc quantum chemistry calculations. In addition, the comparison between molecular and dust maps suggests that the interstellar complex organic molecules emission originates from slow shocks produced by accretion streamers impacting the VLA4A and VLA4B disks and enriching the gas-phase component., Comment: 20 pages, 14 figures

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution., Comment: Ariel Definition Study Report, 147 pages. Reviewed by ESA Science Advisory Structure in November 2020. Original document available at: https://www.cosmos.esa.int/documents/1783156/3267291/Ariel_RedBook_Nov2020.pdf/

Formamide (NH2CHO) is considered an important prebiotic molecule because of its potential to form peptide bonds. It was recently detected in the atmosphere of the HH 212 protostellar disk on the Solar-System scale where planets will form. Here we have mapped it and its potential parent molecules HNCO and H2CO, along with other molecules CH3OH and CH3CHO, in the disk atmosphere, studying its formation mechanism. Interestingly, we find a stratified distribution of these molecules, with the outer emission radius increasing from ~ 24 au for NH2CHO and HNCO, to 36 au for CH3CHO, to 40 au for CH3OH, and then to 48 au for H2CO. More importantly, we find that the increasing order of the outer emission radius of NH2CHO, CH3OH, and H2CO is consistent with the decreasing order of their binding energies, supporting that they are thermally desorbed from the ice mantle on dust grains. We also find that HNCO, which has much lower binding energy than NH2CHO, has almost the same spatial distribution, kinematics, and temperature as NH2CHO, and is thus more likely a daughter species of desorbed NH2CHO. On the other hand, we find that H2CO has a more extended spatial distribution with different kinematics from NH2CHO, thus questioning whether it can be the gas-phase parent molecule of NH2CHO., Comment: 22 pages, 5 figures

Introduction: Millimeter and centimeter observations are discovering an increasing number of interstellar complex organic molecules (iCOMs) in a large variety of star-forming sites from the earliest stages of star formation to protoplanetary disks. To correctly interpret the distribution and abundances of iCOMs observed along the formation process of a Sun-like star (i.e. in pre-stellar dense cores1,2, hot corinos around protostars3,4, in the associated jets and outflows5,6, and protoplanetary disks7), we need to first comprehend their formation processes and the mechanism responsible for their release in gas-phase. In this context, it is pivotal to understand the influence of the solid phase interactions between iCOMs and grain surface in the thermal desorption process and the subsequent presence of molecular species in the gas phase. Thermal desorption can be characterized through laboratory experiments using interstellar ice analogs deposited on grains similar to interstellar ones deriving important parameters such as the desorption temperatures and energies. Up to now, temperature-programmed desorption (TPD) experiments have been carried out mainly from graphite and amorphous water ice surfaces8,9,10,11. As far as we know, TPD experiments from grain surfaces are lacking in the literature, although mineral matrices can selectively adsorb, protect, and allow the iCOMs concentration on their surface. Molecules can diffuse inside the grains and so, the presence of grains can influence the desorption and release of the iCOMs in the gas phase. Laboratory measurements: We report our new recently published laboratory results12 on TPD experiments of astrophysical relevant ice mixtures of water, acetonitrile (CH3CN), and acetaldehyde (CH3COH) from micrometric grains of silicate olivine ((Mg,Fe)2SiO4) used as interstellar dust analog on which the icy mixtures were condensed at 17 K inside the ultra-high vacuum (UHV) chamber (P~6.68 × 10-10 mbar). The ice mixtures condensed on olivine dust were heated at a constant rate, so the molecules diffused and desorbed from the dusty sample, and in situ TPD analysis was made. Results: We found that in the presence of grains, only a fraction of acetaldehyde and acetonitrile desorbs at about 100 K and 120 K respectively, while 40% of the molecules are retained by fluffy grains of the order of 100 μm up to temperatures of 200 K. In contrast with the typical assumption that all molecules are desorbed in regions with temperatures higher than 100 K, this result implies that about 40% of the molecules can survive on the grains enabling the delivery of volatiles towards regions with temperatures as high as 200 K. This may be important in protoplanetary disks where the submicrometric interstellar grains begin to agglomerate into fluffy grains of hundreds of microns. The diffusion of molecules on the silicate surface is a valuable process enabling the permanence of the ices in the inner part of the disk. This implies that O-rich and N-rich volatiles ice can survive up to ∼ 200 K, broadening the snowlines of O- and N-bearing molecules, such as CH3CN and CH3COH. The presence of dust grains in the protoplanetary disk can therefore determine the approach of the snowlines towards the star and allow the presence of water and volatile species in Earth-like planets forming region. These studies offer a necessary support to interpret observational data and may help our understanding of iCOMs formation providing an estimate of the fraction of molecules released at various temperatures. G. A. Blake, E. C. Sutton, C.R. Masson, T.G. Phillips, ApJ. 1987, 315 E. Herbst & E. F. van Dishoeck, ARA&A. 2009, 47 S. Cazaux, A. G. G. M. Tielens, C. Ceccarelli et al., ApJ. 2003, 593 C. Ceccarelli, P. Caselli, E. Herbst, A. G. G. M. Tielens & E. Caux, Protostars and Planets V. 2007, 47 R. Bachiller, & M. Pérez Gutiérrez, ApJ. 1997, 48 C. Codella, B. Lefloch, C. Ceccarelli et al., A&A. 2010, 518 J. Lee, S. Lee, G. Baek et al., Nature Astronomy. 2019, 3 M. P. Collings, M. A. Anderson, R. Chen et al., MNRAS. 2004, 354 T. Hama, N. Watanabe, A. Kouchi & M. Yokoyama, ApJL. 2011, 738 J. Shi, G. A. Grieves & T. M. Orlando, ApJ. 2015, 804 H. Chaabouni, S. Diana, T. Nguyen & F. Dulieu, A&A. 2018, 612 M. A. Corazzi, J. R. Brucato, G. Poggiali, L. Podio, D. Fedele & C. Codella, accepted on ApJ. 2021

We describe the AMBITION project, a mission to return the first-ever cryogenically-stored sample of a cometary nucleus, that has been proposed for the ESA Science Programme Voyage 2050. Comets are the leftover building blocks of giant planet cores and other planetary bodies, and fingerprints of Solar System’s formation processes. We summarise some of the most important questions still open in cometary science and Solar System formation after the successful Rosetta mission. We show that many of these scientific questions require sample analysis using techniques that are only possible in laboratories on Earth. We summarize measurements, instrumentation and mission scenarios that can address these questions. We emphasize the need for returning a sample collected at depth or, still more challenging, at cryogenic temperatures while preserving the stratigraphy of the comet nucleus surface layers. We provide requirements for the next generation of landers, for cryogenic sample acquisition and storage during the return to Earth. Rendezvous missions to the main belt comets and Centaurs, expanding our knowledge by exploring new classes of comets, are also discussed. The AMBITION project is discussed in the international context of comet and asteroid space exploration.

Formamide (NH$_2$CHO) has been identified as a potential precursor of a wide variety of organic compounds essential to life, and many biochemical studies propose it likely played a crucial role in the context of the origin of life on our planet. The detection of formamide in comets, which are believed to have --at least partially-- inherited their current chemical composition during the birth of the Solar System, raises the question whether a non-negligible amount of formamide may have been exogenously delivered onto a very young Earth about four billion years ago. A crucial part of the effort to answer this question involves searching for formamide in regions where stars and planets are forming today in our Galaxy, as this can shed light on its formation, survival, and chemical re-processing along the different evolutionary phases leading to a star and planetary system like our own. The present review primarily addresses the chemistry of formamide in the interstellar medium, from the point of view of (i) astronomical observations, (ii) experiments, and (iii) theoretical calculations. While focusing on just one molecule, this review also more generally reflects the importance of joining efforts across multiple scientific disciplines in order to make progress in the highly interdisciplinary science of astrochemistry., Review, 5 figures

To understand the origin of the diversity observed in exoplanetary systems, it is crucial to characterize the early stages of their formation, represented by Solar-type protostars. Likely, the gaseous chemical content of these objects directly depends on the composition of the dust grain mantles formed before the collapse. Directly retrieving the ice mantle composition is challenging, but it can be done indirectly by observing the major components, such as NH3 and CH3OH at cm wavelengths, once they are released into the gas-phase during the warm protostellar stage. We observed several CH3OH and NH3 lines toward three Class 0 protostars in NGC1333 (IRAS 4A1, IRAS 4A2, and IRAS 4B), at high angular resolution (1"; ~300 au) with the VLA interferometer at 24-26 GHz. Using a non-LTE LVG analysis, we derived a similar NH3/CH3OH abundance ratio in the three protostars (, accepted in ApJ Letters

Millimeter and centimeter observations are discovering an increasing number of interstellar complex organic molecules (iCOMs) in a large variety of star forming sites, from the earliest stages of star formation to protoplanetary disks and in comets. In this context it is pivotal to understand how the solid phase interactions between iCOMs and grain surfaces influence the thermal desorption process and, therefore, the presence of molecular species in the gas phase. In laboratory, it is possible to simulate the thermal desorption process deriving important parameters such as the desorption temperatures and energies. We report new laboratory results on temperature-programmed desorption (TPD) from olivine dust of astrophysical relevant ice mixtures of water, acetonitrile, and acetaldehyde. We found that in the presence of grains, only a fraction of acetaldehyde and acetonitrile desorbs at about 100 K and 120 K respectively, while 40% of the molecules are retained by fluffy grains of the order of 100 {\mu}m up to temperatures of 190-210 K. In contrast with the typical assumption that all molecules are desorbed in regions with temperatures higher than 100 K, this result implies that about 40% of the molecules can survive on the grains enabling the delivery of volatiles towards regions with temperatures as high as 200 K and shifting inwards the position of the snowlines in protoplanetary disks. These studies offer a necessary support to interpret observational data and may help our understanding of iCOMs formation providing an estimate of the fraction of molecules released at various temperatures., Comment: Accepted for Publication on Astrophysical Journal

Planets form in protoplanetary disks and inherit their chemical composition. It is therefore crucial to understand the disks molecular content. We aim to characterize the distribution and abundance of molecules in the disk of DG Tau. In the context of the ALMA chemical survey of Disk-Outflow sources in Taurus (ALMA-DOT) we analyse ALMA observations of the disk of DG Tau in H2CO 3(1,2)-2(1,1), CS 5-4, and CN 2-1 at ~0.15", i.e. ~18 au at 121 pc. H2CO and CS originate from a disk ring at the edge of the 1.3mm dust continuum, with CS probing an outer disk region with respect to H2CO (peaking at ~70 and ~60 au, respectively). CN originates from an outermost disk/envelope region peaking at ~80 au. H2CO is dominated by disk emission, while CS probes also two streams of material possibly accreting onto the disk with a peak of emission where the stream connects to the disk. The ring- and disk-height- averaged column densities are ~2.4-8.6e13 cm-2 (H2CO), ~1.7-2.5e13 cm-2 (CS), and ~1.9-4.7e13 cm-2 (CN). Unsharp masking reveals a ring of enhanced dust emission at ~40 au, i.e. just outside the CO snowline (~30 au). CS and H2CO emissions are co-spatial suggesting that they are chemically linked. The observed rings of molecular emission at the edge of the 1.3mm continuum may be due to dust opacity effects and/or continnum over-subtraction in the inner disk; as well as to increased UV penetration and/or temperature inversion at the edge of the mm-dust which would cause an enhanced gas-phase formation and desorption of these molecules. Moreover, H2CO and CS originate from outside the ring of enhanced dust emission, which also coincides with a change of the linear polarization at 0.87mm. This suggests that outside the CO snowline there could be a change of the dust properties which would reflect in the increase of the intensity (and change of polarization) of continuum, and of molecular emission., 13 pages, accepted for publication on A&A

Context. The process of mass accretion in the earliest phases of star formation is still not fully understood: does the accretion rate smoothly decline with the age of the protostar or are there short, intermittent accretion bursts? The latter option would also yield the possibility for very low-luminosity objects (VeLLOs) to be precursors of solar-type stars, even though they do not seem to have sufficiently high accretion rates to reach stellar masses during their protostellar lifetime. Nevertheless, probing such intermittent events in the deeply embedded phase is not easy. Chemical signatures in the protostellar envelope can trace a past accretion burst. Aims. We aim to explore whether or not the observed C18O and N2H+ emission pattern towards the VeLLO IRAM 04191+1522 can be understood in the framework of a scenario where the emission is chemically tracing a past accretion burst. Methods. We used high-angular-resolution Plateau de Bure Interferometer (PdBI) observations of C18O and N2H+ towards IRAM 04191+1522 that were obtained as part of the CALYPSO IRAM Large Program (Continuum And Lines in Young ProtoStellar Objects). We model these observations using a chemical code with a time-dependent physical structure coupled with a radiative transfer module, where we allow for variations in the source luminosity. Results. We find that the N2H+ line emission shows a central hole, with the N2H+ emission peaking at a radius of about 10′′ (1400 au) from the source, while the C18O emission is compact (1.3′′ FWHM, corresponding to 182 au). The morphology of these two lines cannot be reproduced with a constant luminosity model based on the present-day internal luminosity (0.08 L⊙). However, the N2H+ peaks are consistent with a constant-luminosity model of 12 L⊙. Using a model with time-dependent temperature and density profiles, we show that the observed N2H+ peak emission could indeed be caused by a past accretion burst with a luminosity 150 times higher than the present-day luminosity. Such a burst should have occurred a couple of hundred years ago. Conclusions. We suggest that an accretion burst occurred in IRAM 04191+1522 in the recent past. If such bursts are common and sufficiently long in VeLLOs, they could lead to higher accretion onto the central object than their luminosity suggests. For IRAM 04191 in particular, our results yield an estimated final mass of 0.2–0.25 M⊙ by the end of the Class 0 phase, which would make this object a low-mass star rather than a brown dwarf. More generally, our analysis demonstrates that the combination of observations of N2H+ and C18O is a more reliable diagnostic of past outburst activity than C18O or N2H+ emission alone.

A first step towards understanding planetary formation is the characterisation of the structure and evolution of protoplanetary discs. A variety of planetary systems has been discovered in recent years and it likely depends on the early history of their formation. Thus understanding the chemical composition of early solar-like protostars is crucial. To be able to study the lines in detail though, a good knowledge of the dust properties and in particular the optical depth is needed in order to interpreted the lines correctly. In this talk I want to present our results of the class I source Elias29 as part of the FAUST (fifty au study of the chemistry in the disk/envelope system of solar-like protostars) collaboration. The goal of FAUST is to quantify the chemical composition of the envelope/disk system of solar-lie class 0 and I protostars. With the high spatial resolution of 50 au in band 3 and band 6 ALMA data we can spatially resolve the envelope and the disk on this source and calculate the dust properties of the two components.

Understanding how molecular complexity varies in Sun-like star forming regions is mandatory to comprehend whether the chemical composition of the protostellar stages is inherited by protoplanetary disks and planets. In this perspective, our ambitious overall goal is to follow the chemical evolution from the earliest protostellar stages to the relics of our pristin Solar System, i.e. comets. We investigate the chemical composition of Class I protostars, with a typical age of 105 yr. Class I sources represent a bridge between Class 0 protostars (about 104 yr), where the bulk of the material that eventually form the protostar is still in the envelope, and the Class II protoplanetary disks (106 yr). The importance of the Class I stage has been recently strengthened by recent ALMA images showing that planet formation occurs already in disks with ages < 1 Myr. Unfortunately, only very few Class I sources, e.g. SVS13-A and Ser-17, have been chemically characterized through spectral survey at millimeter wavelengths. Therefore, we are still far to conclude if Class I protostars are also a bridge from a chemical point of view.In this context, and in the framework of the H2020 MSCA ITN Project AstroChemical Origins (www.aco-itn.org), we present a chemical census of 4 Class I sources: L1551-IRS5, L1489-IRS (in the Taurus star forming region) and B5-IRS1, L1455-IRS1 (in Perseus). We used IRAM 30m single-dish observations at 1.3 mm sampling spatial scales of 1500-2500 au. We detect up to 80 lines (depending on the source) due to 27 species: from simple molecules (e.g. S-bearing: OCS, H2S, CCS, H2CS, N-bearing: CN, HNCO, C-chains: c-C3H2, c-C3H, D-species: CCD, DCN, D2CO, CH2DOH, ions: N2D+, DCO+) to the so called interstellar Complex Organic Molecules (iCOMs), which can be considered as the bricks of a prebiotic chemistry (H2CO, H2CCO, CH3OH, CH3CN, CH3CHO, CH3CCH, HCOOCH3). All the sources are associated with high-velocity CO, H2CO, and SO outflows. In addition, our observations show a chemical differentiation, that can be summarized as follows: (1) we detect hot corino chemistry in one source, L1551 -IRS5, revealed by iCOMs as well as OCS, H2S, which could be the main S-bearing carriers on icy grains; (2) the envelopes of all the protostars are rich of carbon-chains molecules; (3) we find that the iCOMs of L1551 have similar abundance ratio, within one order of magnitude, as Class 0 and Class I hot corinos previously observed. We also compare the iCOMs abundance ratios as measured in the Class I source L1551-IRS5 with those measured in comets Hale-Bopp, Lemmon, Lovejoy, and 67P to understand if the cometary composition is inherited from the previous evolutionary stages. We find that the iCOMs abundance ratio (e.g. CH3CHO/HCOOCH3) at the Class 0 and Class I protostellar stages is comparable with that of comets, suggesting that cometary material could be inherited from the early stages of the star forming process leading to a Sun-like star. These results are a basis to future follow-up interferometric observations aimed to obtain a full inventory of the chemistry of Class I sources and to reconstruct the chemical route from Class 0 protostars to protoplanetary disks and planets.

Phosphorus is one of the most important elements in biochemistry together with carbon, oxygen, hydrogen and nitrogen. Therefore, P-bearing compounds with some prebiotic potential and their possible formation pathways in extraterrestrial environments are attracting a lot of interest. In recent years, phosphorus has been clearly identified in the in the coma of comet 67P/Churyumov-Gerasimenko (1), while only a bunch of P-bearing molecules (namely PO, PN, CP, C2P and HCP) have been observed in the gas phase of circumstellar envelopes around evolved stars (2-7) and only two simple species have been detected in star forming regions, that is, PO and PN (8-11). If we focus only on solar-type star forming regions, only two detections are available, that is PN and PO toward the shocked region L1157-B1 (12) and the Class I protostar B1-b (13). Phosphorus chemistry in the conditions of the interstellar medium is poorly understood and the interstellar reservoir of this element is strongly debated. Since the first experimental work on ion-molecule reactions by Anicich and coworkers (14), PO has been indicated as the main reservoir of phosphorus and HPO+ as its major precursor. PO can also be transformed to PN by gas-phase chemistry (15). Thirty years ago, a series of theoretical investigation on ion-molecule reactions has been performed by Largo et al. (16-18) in order to explain the formation of P-O, P-N, P-C bonds. In spite of those efforts, the chemistry of interstellar phosphorus and its connections to the P-compounds detected in small bodies of the Solar System remains mostly unexplored and poorly characterized. For this reason, we have undertaken a systematic investigation of possible gas-phase formation routes of simple P-molecules by means of electronic structure and kinetic calculations. This approach is made necessary by the fact that P is a difficult species to deal with in laboratory experiments. In this work we present a new theoretical analysis of the reaction P+ + H2O and P+ + NH3 at a higher level of theory than those employed by Largo et al. in 1991. More specifically, we make use of DFT calculations for geometry optimization and frequency analysis coupled to a CCSD(T) reevaluation of the energy for each identified stationary point of the reaction potential energy surface. The data coming from electronic structure calculations will be used to perform a kinetic analysis using a Rice-Ramsperger-Kassel-Marcus (RRKM) code implemented for this purpose in order to derive the rate coefficients and branching ratios. A possible formation mechanism is proposed for the formation of both PO and PN. In the figure, the potential energy surface for the reaction of P+ with a water molecule is reported. This process leads to the formation of the POH+ ion which can later transfer a proton to molecules like NH3 which have a large proton affinity. [1] Altwegg K. et al., Prebiotic chemicals—amino acid and phosphorus—in the coma of comet 67P/Churyumov-Gerasimenko, Sci. Adv., 2016, 2 : e1600285. [2] Turner, B. E. & Bally, J., Detection of Interstellar PN: The First Identified Phosphorus Compound in the Interstellar Medium, 1987, ApJL, 321, L75. [3] Ziurys L.M., Detection of Interstellar PN: The First Phosphorus-bearing Species Observed in Molecular Clouds, 1987, ApJL, 321, L81. [4] Guelin M. et al., Free CP in IRC +10216, 1990, ApJL, 230, L9-L11. [5] Agúndez M. et al., Discovery of Phosphaethyne (HCP) in Space: Phosphorus Chemistry in Circumstellar Envelopes, APJ, 662, ApJ, 2, L91-L94. [6] Tenenbaum E.D. et al., Identification of Phosphorus Monoxide (X2Πr) in VY Canis Majoris: Detection of the First PO Bond in Space, 2007, ApJ, 666, 1, L29-L32. [7] Halfen D.T. et al.,Detection of the CCP Radical (X2Πr) in IRC +10216: A New Interstellar Phosphorus-containing Species, 2008, ApJL, 667, 2, L101. [8] Rivilla V.M. et al., Phosphorus-bearing molecules in the Galactic Center, 2018, MNRAS, 475, 1, L30-L34. [9] Rivilla V.M et al., ALMA and ROSINA detections of phosphorus-bearing molecules: the interstellar thread between star-forming regions and comets, 2020, MNRAS, 492, 1, 1180-1198. [10] Rivilla V.M., The first detections of the key prebiotic molecule PO in star-forming regions, 2018, IAU Symposium, 332, 409-414. [11] Rivilla V.M., The First Detections of the Key Prebiotic Molecule PO in Star-forming Regions, 2016, ApJ, 826, 2, 161. [12] Lefloch B. et al., Phosphorus-bearing molecules in solar-type star-forming regions: first PO detection, 2016, MNRAS 462, 3937–3944. [13] Bergner J.B. et al., Detection of Phosphorus-bearing Molecules toward a Solar-type Protostar, 2019, The ApJ Lett., 884, 2, L36. [14] Thorne L.R et al., The chemistry of Phosphorus in Dense Interstellar Clouds, 1984, ApJ, 280, 139-143. [15] Millar T.J. et al., An efficient gas phase synthesis for interstellar PN, 1987, Mon. Not. R. Aster. Soc., 229, 41-44. [16] Largo A. et al., Theoretical Studies of Possible Processes for the Interstellar Production of Phosphorus Compounds. Reaction of P+ with Water, 1991, J. Phys. Chem., 95, 5443-5445. [17] Largo A. et al., Theoretical Sttudies of Possible Processes for the Interstellar Production of Phosphorus Compounds. Reaction of P+ with Methane, 1991, J. Phys. Chem., 95, 6553-6557. [18] Largo A. et al., Theoretical Sttudies of Possible Processes for the Interstellar Production of Phosphorus Compounds. Reaction of P+ with Ammonia, 1991, J. Phys. Chem., 95, 170-175.

There is growing observational evidence that giant planet formation happens early, within a million years of the coalescence of the protoplanetary disk. Ionization rate is one of the most important parameters controlling both the chemical and dynamical processes in these disks. What few observational constrains on ionization currently exists suggest overall low ionization, limiting the processes able to take place. This is seemingly in conflict with chemical models which demonstrate the importance of ionization for the chemical processing of volatile carbon and observations which suggest such processing is ubiquitous and happens quickly. I will present new NOEMA observations which, when combined with chemical modeling, are indicative of enhanced ionization rates in the envelopes of three Class I protostars. I will then discuss the potential impact of this early enhancement on the chemical composition of the material available to forming planets.

The role of the pre-solar chemistry in the chemical composition of Solar System bodies is far to be understood. Did they inherit at least part of their composition from the earliest stages of star formation? During each step of the process leading to the formation of a Sun-like star and its planetary system, the molecular complexity increases from simple species up to interstellar Complex Organic Molecules (iCOMs, O-, N-, S-bearing species whit at least 6 atoms). In turn, iCOMs can be considered as bricks that can be used to assemble pre-biotic molecules. In this context, the study of the molecular complexity of Class 0 objects, where protostars are still deeply embedded in their parental core and still accreting their mass, is mandatory. As a matter of fact, protostellar radiation heats the surrounding medium creating the so-called hot-corinos, i.e. the regions of about 100 au with temperatures of at least 100 K, hot enough to (i) evaporate dust mantles, and (ii) trigger a warm gas phase-chemistry. As a consequence, the iCOMs abundances bloom, dramatically enriching the gas phase. The chemistry of the protostellar environments represents the first stage, and it needs to be compared with those of more evolved phase including relics of our pristine Solar System, such as comets.The investigation of star-forming regions has enormously benefited from the recent advent of the IRAM-NOEMA and ALMA (sub-) mm-interferometers, which allowed the observers to reach Solar System scales. It is of paramount importance to combine high-sensitivity spectral surveys to collect large numbers of lines for each iCOM (for reliable identifications and to analyse excitation conditions) as well as to image their spatial distribution to investigate their association with different ingredients of the Sun-like star formation recipe (e.g. warm envelopes and cavities opened from hot jets, accretion disks, disk winds). The overall goal is to analyse the protostellar disk, i.e. the region where a Solar System will form billions of years later. The imaging of these regions with molecules simpler than iCOMs, such as CO or CS is indeed paradoxically hampered by their high abundances and consequently high line opacities which do not allow the observers to disentangle all the emitting components at these small scales.In this respect, we will report recent results of a prototypical object such as IRAS4A, showing how complementing images obtained in the cm-spectral regime are to mimimise iCOMs emission hampering due to dust opacity. Finally, we will focus on the protostellar disk HH212, observed with a spatial resolution down to about 10 au. A large number of iCOMs, such as CH3OH, CH3CHO, HCOOCH3, CH3CH2OH, NH2CHO, have been imaged: their emission is clearly associated with the upper and lower rings in the outer part of the disk imaged using continuum emission. Indeed, the geometry of these features has led this source to be called a “space hamburger” in the popular press. We will discuss the possible explanations: (i) the disk has a vertically extended gaseous atmosphere (the “methanol buns”) and no gaseous methanol on the disk midplane (the “dusty meat”); (ii) the optically-thick disk midplane obscures iCOMs’ emission. The answer is essential to understand the gas composition in the equatorial plane, where planets will form.

Detection of hot corinos in Solar-like protostars has been so far mostly limited to Class 0 objects, hampering our understanding of their origin and evolution. Recent evidence suggests that planet formation probably starts already in Class I protostars, representing a key step in our understanding of their chemical composition at the planet formation scale. Therefore, understanding the fate of hot corinos in Class I protostars has become of paramount importance. In this context, we report the discovery of a hot corino at the heart of the prototypical Class I source L1551 IRS5, obtained via ALMA observations as part of the Large Program FAUST (Fifty AU Study of the chemistry in the disk/envelope system of Solar-like protostars). More specifically, FAUST is the first ALMA Large Program based on astrochemistry and is designed to survey the chemical composition of a sample of 13 Class 0 and I protostars at the planet-formation scale. We detected in L1551 IRS 5 several emission lines from interstellar complex organic molecules (iCOMs) such as methanol and its most abundant isotopologues, as well as methyl formate and ethanol. The line emission is bright toward the north component (N), although a hot corino in the south component, cannot be excluded. The non-LTE analysis of the methanol lines towards N provides constraints on the gas temperature (~ 100 K), density (≥ 1.5 x 108 cm-3) and emitting size (~0.15”, i.e. ~ 10 au in radius). The lines are predicted to be optically thick, the 13CH3OH line having an opacity ≥ 2. The methyl formate and ethanol column densities relative to methanol are ≤ 0.03 and ≤ 0.015, respectively, compatible with those measured in Class 0 sources. Thus, the present observations towards L1551 IRS5 agree with little chemical evolution in hot corinos from Class 0 to I.

How have planets formed in the Solar System? And what chemical composition they inherited from their natal environment? Is the chemical composition passed unaltered from the earliest stages of the formation of the Sun to its disk and then to the planets which assembled in the disk? Or does it reflects chemical processes occurring in the disk and/or during the planet formation process? And what was the role of comets in the delivery of volatiles and prebiotic compounds to early Earth? A viable way to answer these questions is to observe protoplanetary disks around young Sun-like stars and compare their chemical composition with that of the early Solar System, which is imprinted in comets. The impacting images recently obtained by millimetre arrays of antennas such as ALMA provided the first observational evidence of ongoing planet formation in 0.1-1 million years old disks, through rings and gaps in their dust and gas distribution. The chemical composition of the forming planets and small bodies clearly depends on the location and timescale for their formation and is intimately connected to the spatial distribution and abundance of the various molecular species in the disk. The chemical characterisation of disks is therefore crucial. This field, however, is still in its infancy, because of the small sizes of disks (~100 au) and to the low gas-phase abundance of molecules (abundances with respect to H2 down to 10-12), which requires an unprecedented combination of angular resolution and sensitivity. I will show the first pioneering results obtained as part of the ALMA chemical survey of protoplanetary disks in the Taurus star forming region (ALMA-DOT program). Thanks to the ALMA images at ~20 au resolution, we recovered the radial distribution and abundance of diatomic molecules (CO and CN), S-bearing molecules (CS, SO, SO2, H2CS), as well as simple organics (H2CO and CH3OH) which are key for the formation of prebiotic compounds. Enhanced H2CO emission in the cold outer disk, outside the CO snowline, suggests that organic molecules may be efficiently formed in disks on the icy mantles of dust grain. This could be the dawn of ice chemistry in the disk, producing ices rich of complex organic molecules (COMs) which could be incorporated by the bodies forming in the outer disk region, such as comets. The next step is the comparison of the molecules radial distribution and abundance in disks with the chemical composition of comets, which are the leftover building blocks of giant planet cores and other planetary bodies. The first pioneering results in this direction have been obtained thanks to the ESA’s Rosetta mission, which allowed obtaining in situ measurements of the COMs abundance on the comet 67P/Churyumov-Gerasimenko. The comparison with three protostellar solar analogs observed on Solar System scales has shown comparable COMs abundance, implying that the volatile composition of comets and planetesimals may be partially inherited from the protostellar stage. The advent of new mission, devoted to sample return such as AMBITION will allow us to do a step ahead in this direction.

Complex organic molecules (COMs) have been detected in a few Class 0 protostars but their origin is not well understood. Going beyond studies of individual objects, we want to investigate the origin of COMs in young protostars on a statistical basis. We use the CALYPSO survey performed with the IRAM PdBI to search for COMs at high angular resolution in a sample of 26 solar-type protostars, including 22 Class 0 and four Class I objects. Methanol is detected in 12 sources and tentatively in one source, which represents half of the sample. Eight sources (30%) have detections of at least three COMs. We find a strong chemical differentiation in multiple systems with five systems having one component with at least three COMs detected but the other component devoid of COM emission. The internal luminosity is found to be the source parameter impacting the most the COM chemical composition of the sources, while there is no obvious correlation between the detection of COM emission and that of a disk-like structure. A canonical hot-corino origin may explain the COM emission in four sources, an accretion-shock origin in two or possibly three sources, and an outflow origin in three sources. The CALYPSO sources with COM detections can be classified into three groups on the basis of the abundances of oxygen-bearing molecules, cyanides, and CHO-bearing molecules. These chemical groups correlate neither with the COM origin scenarii, nor with the evolutionary status of the sources if we take the ratio of envelope mass to internal luminosity as an evolutionary tracer. We find strong correlations between molecules that are a priori not related chemically (for instance methanol and methyl cyanide), implying that the existence of a correlation does not imply a chemical link. [abridged], Comment: Accepted for publication in Astronomy and Astrophysics

Aim: In the past, observations of protostellar shocks have been able to set constraints on the formation route of formamide (NH2CHO), exploiting its observed spatial distribution and comparison with astrochemical model predictions. In this work, we follow the same strategy to study the case of acetaldehyde (CH3CHO). Method: To this end, we used the data obtained with the IRAM-NOEMA interferometer in the framework of the Large Program SOLIS to image the B0 and B1 shocks along the L1157 blueshifted outflow in methanol (CH3OH) and acetaldehyde line emission. Results: We imaged six CH3OH and eight CH3CHO lines which cover upper level energies up to 30 K. Both species trace the B0 molecular cavity as well as the northern B1 portion, i.e. the regions where the youngest shocks (1000 yr) occurred. The CH$_3$OH and CH$_3$CHO emission peaks towards the B1b clump, where we measured the following column densities and relative abundances: 1.3 x 10^16 cm-2 and 6.5 x 10-6 (methanol), and 7 x 10^13 cm-2 and 3.5 x 10-8 (acetaldehyde). We carried out a non-LTE LVG analysis of the observed CH3OH line: the average kinetic temperature and density of the emitting gas are Tkin = 90 K and nH2 = 4 x 10^5 cm-3, respectively. The CH3OH and CH3CHO abundance ratio towards B1b is 190, varying by less than a factor 3 throughout the whole B0-B1 structure. Conclusions: The comparison of astrochemical model predictions with the observed methanol and acetaldehyde spatial distribution does not allow to distinguish whether acetaldehyde is formed on the grain mantles or rather on the gas-phase, as its gas-phase formation, dominated by the reaction of ethyl radical (CH3CH2) with atomic oxygen, is very fast. Observations of acetaldehyde in younger shocks, e.g. 10^2 yr old, or/and of the ethyl radical, whose frequencies are not presently available, are necessary to settle the issue., A&A, in press

[abridged] Understanding how the infalling gas redistribute most of its initial angular momentum inherited from prestellar cores before reaching the stellar embryo is a key question. Disk formation has been naturally considered as a possible solution to this "angular momentum problem". However, how the initial angular momentum of protostellar cores is distributed and evolves during the main accretion phase and the beginning of disk formation has largely remained unconstrained up to now. In the framework of the IRAM CALYPSO survey, we used high dynamic range C$^{18}$O (2-1) and N$_2$H$^+$ (1-0) observations to quantify the distribution of specific angular momentum along the equatorial axis in a sample of 12 Class 0 protostellar envelopes from scales ~50 to 10000 au. The radial distributions of specific angular momentum in the CALYPSO sample suggest two distinct regimes within protostellar envelopes: the specific angular momentum decreases as $j \propto r^{1.6 \pm 0.2}$ down to ~1600 au and then tends to become relatively constant around 6 $\times$ 10$^{-4}$ km s$^{-1}$ pc down to ~50 au. The values of specific angular momentum measured in the inner Class 0 envelopes, namely that of the material directly involved in the star formation process ($$1600 au, suggesting that they may not be related to rotational motions of the envelopes. We conclude that the specific angular momentum observed at these scales could find its origin in core-forming motions (infall, turbulence) or trace an imprint of the initial conditions for the formation of protostellar cores., Comment: 62 pages, 66 figures

Aims: A unique environment to study how interstellar Complex Organic Molecules (iCOMs) can be formed is the shocked gas along low-mass protostellar outflows, as the dust mantles composition is sputtered into the gas phase. The chemical richness in these environments has been so far studied only in the L1157 blue shifted outflow. Methods: To understand if the L1157-B1 case is unique, we imaged the NGC 1333 IRAS 4A outflows using the NOEMA (NOrthern Extended Millimeter Array) interferometer as part of the IRAM SOLIS (Seeds Of Life in Space) Large Program and compared the observations with the GRAINOBLE+ gas phase astrochemical model. Results: Several iCOMs were detected in the IRAS 4A outflows: methanol (CH$_3$OH), acetaldehyde (CH$_3$CHO), formamide (NH$_2$CHO) and dimethyl ether (CH$_3$OCH$_3$), all sampling upper excitation energy up to $\sim$30 K. We found a significant chemical differentiation between the IRAS 4A1 outflow, showing a richer molecular content, and the IRAS 4A2 one. The CH$_3$OH/CH$_3$CHO abundance ratio is lower by a factor $\sim$4 in the former; furthermore the ratio in both outflows is lower by a factor $\sim$10 with respect to hot corinos values. Conclusions: After L1157-B1, IRAS 4A outflow is now the second outflow to show an evident chemical complexity. Given that CH$_3$OH is a grain surface species, GRAINOBLE+ reproduced our observations assuming acetaldehyde formation in gas phase by the reaction of ethyl radical (CH$_3$CH$_2$) with atomic oxygen. Moreover, the chemical differentiation between the two outflows suggests that the IRAS 4A1 outflow is likely younger than the IRAS 4A2 one. Further investigation is needed to constrain the age of the outflow and observations of even younger shocks are necessary and future spectroscopic studies on CH$_3$CH$_2$ are needed to be able to observe this species and provide strong constraints on the CH$_3$CHO formation., Comment: 12 pages, 7 figures, 5 tables

The formation of protoplanetary disks is not well understood. To understand how and when these disks are formed, it is crucial to characterize the kinematics of the youngest protostars at a high angular resolution. Here we study a sample of 16 Class 0 protostars to measure their rotation profile at scales from 50 to 500~au and search for Keplerian rotation. We used high-angular-resolution line observations obtained with the Plateau de Bure Interferometer as part of the CALYPSO large program. From $\mathrm{^{13}CO}$ ($J=2-1$), $\mathrm{C^{18}O}$ ($J=2-1$) and SO ($N_{j}=5_{6}-4_{5}$) moment maps, we find that seven sources show rotation about the jet axis at a few hundred au scales: SerpS-MM18, L1448-C, L1448-NB, L1527, NGC1333- IRAS2A, NGC1333-IRAS4B, and SVS13-B. We analyzed the kinematics of these sources in the $uv$ plane to derive the rotation profiles down to 50~au scales. We find evidence for Keplerian rotation in only two sources, L1527 and L1448-C. Overall, this suggests that Keplerian disks larger than 50 au are uncommon around Class 0 protostars. However, in some of the sources, the line emission could be optically thick and dominated by the envelope emission. Due to the optical thickness of these envelopes, some of the disks could have remained undetected in our observations., Accepted for publication in Astronomy & Astrophysics

The chemical composition of planets is inherited by the distribution of the various molecular species in the protoplanetary disk at thetime of their formation. As of today, only a handful of disks has been imaged in multiple spectral lines with high spatial resolution. As part of a small campaign devoted to the chemical characterization of disk-outflow sources in Taurus, we report on new ALMA Band 6 observations with 20 au resolution toward the embedded young star DG Tau B. Images of the continuum emission reveals a dust disk with rings and, putatively, a leading spiral arm. The disk, as well as the prominent outflow cavities, are detected in CO, H2CO, CS, and CN while they remain undetected in SO2, HDO, and CH3OH. From the absorption of the back-side outflow, we inferred that the disk emission is optically thick in the inner 50 au. This morphology explains why no line emission is detected from this inner region and poses some limitations toward the calculation of the dust mass and the characterization of the inner gaseous disk. The H2CO and CS emission from the inner 200 au is mostly from the disk and their morphology is very similar. The CN emission significantly differs from the other two molecules as it is observed only beyond 150 au. This ring-like morphology is consistent with previous observations and the predictions of thermochemical disk models. Finally, we constrained the disk-integrated column density of all molecules. In particular, we found that the CH3OH/H2CO ratio must be smaller than 2, making the methanol non-detection still consistent with the only such a ratio available from the literature (1.27 in TW Hya)., Comment: 13 pages, 6 figures, accepted by A&A

Large millimeter interferometers are revealing a growing number of rotating outflows, which are suggested to trace magneto-centrifugal disk winds (MHD DWs). However, their impact on disk accretion is not yet well quantified. Here we identify systematic biases in retrieving the true launch zone, magnetic lever arm, and angular momentum flux of an MHD DW from apparent rotation signatures. Synthetic position-velocity cuts are constructed from self-similar MHD DWs over a broad range of parameters, and three different methods are applied for estimating the specific angular momentum. We find that the launch radius inferred using the well-known relation from Anderson et al. (2006) can markedly differ from the true outermost launch radius $r_{out}$ of the DW. The "double-peak separation" and "flow width" methods provide only a strict lower limit to $r_{out}$. This bias is independent of angular resolution and can reach a factor ten. In contrast, the "rotation curve" method gives a good estimate of $r_{out}$ when the flow is well resolved, and an upper limit otherwise. The magnetic lever arm is always underestimated. Only comparison with synthetic predictions can take into account properly all observational effects. As an application, we present a comparison with ALMA observations of HH212 at resolutions from 250 au to 16 au, which represents the most stringent observational test of MHD DW to date. This comparison confirms our predicted biases for the double-peak separation method, and the large $r_{out}\sim40~$au and small magnetic lever arm first suggested by Tabone et al. (2017). We also derive the first accurate analytical expression for the fraction of disk angular momentum extracted by an MHD disk wind of given radial extent, magnetic lever arm, and mass flux. Application to HH212 confirms that MHD DWs are serious candidates for the steady angular momentum extraction process in young disks., Accepted for publication in A&A

Planet-forming disks are not isolated systems. Their interaction with the surrounding medium affects their mass budget and chemical content. In the context of the ALMA-DOT program, we obtained high-resolution maps of assorted lines from six disks that are still partly embedded in their natal envelope. In this work, we examine the SO and SO$_2$ emission that is detected from four sources: DG Tau, HL Tau, IRAS 04302+2247, and T Tau. The comparison with CO, HCO$^+$, and CS maps reveals that the SO and SO$_2$ emission originates at the intersection between extended streamers and the planet-forming disk. Two targets, DG Tau and HL Tau, offers clear cases of inflowing material inducing an accretion shock on the disk material. The measured rotational temperatures and radial velocities are consistent with this view. In contrast to younger Class 0 sources, these shocks are confined to the specific disk region impacted by the streamer. In HL Tau, the known accreting streamer induces a shock in the disk outskirt, and the released SO and SO$_2$ molecules spiral toward the star in a few hundreds years. These results suggest that shocks induced by late accreting material may be common in the disks of young star-forming regions with possible consequences on the chemical composition and mass content of the disk. They also highlight the importance of SO and SO$_2$ line observations to probe accretion shocks from a larger sample., 18 pages, 13 figures, accepted by A$\&$A

Dimethyl ether is one of the most abundant interstellar complex organic molecules. Yet its formation route remains elusive. In this work, we have performed electronic structure and kinetics calculations to derive the rate coefficients for two ion-molecule reactions recently proposed as a gas-phase formation route of dimethyl ether in interstellar objects, namely CH3OH + CH3OH_2^+ → (CH3)2OH+ + H2O followed by (CH3)2OH+ + NH3 → CH3OCH3 + NH_4^+. A comparison with previous experimental rate coefficients for the reaction CH3OH + CH3OH_2^+ sustains the accuracy of the present calculations and allows a more reliable extrapolation at the low temperatures of interest in interstellar objects (10-100 K). The rate coefficient for the reaction (CH3)2OH+ + NH3 is, instead, provided for the first time ever. The rate coefficients derived in this work essentially confirm the prediction by Taquet, Wirström & Charnley concerning dimethyl ether formation in hot cores/corinos. Nevertheless, this formation route cannot be efficient in cold objects (like pre-stellar cores) where dimethyl ether is also detected, because ammonia has a very low abundance in those environments.

Methanol is a key species in astrochemistry since it is the most abundant organic molecule in the ISM and is thought to be the mother molecule of many complex organic species. Estimating the deuteration of methanol around young protostars is of crucial importance because it highly depends on its formation mechanisms and the physical conditions during its moment of formation. We analyse dozens of transitions from deuterated methanol isotopologues coming from various existing observational datasets from the IRAM-PdBI and ALMA sub-mm interferometers to estimate the methanol deuteration surrounding three low-mass protostars on Solar System scales. A population diagram analysis allows us to derive a [CH$_2$DOH]/[CH$_3$OH] abundance ratio of 3-6 % and a [CH$_3$OD]/[CH$_3$OH] ratio of 0.4-1.6 % in the warm inner protostellar regions. These values are ten times lower than those derived with previous single-dish observations towards these sources but they are 10-100 times higher than the methanol deuteration measured in massive hot cores. Dust temperature maps obtained from Herschel and Planck observations show that massive hot cores are located in warmer molecular clouds than low-mass sources, with temperature differences of $\sim$10 K. Comparison with the predictions of the gas-grain astrochemical model GRAINOBLE shows that such a temperature difference is sufficient to explain the different deuteration observed in low- to high-mass sources, suggesting that the physical conditions of the molecular cloud at the origin of the protostars mostly govern the present observed deuteration of methanol. The methanol deuteration measured in this work is higher by a factor of 5 than the upper limit in methanol deuteration estimated in comet Hale-Bopp, implying that an important reprocessing of the organic material would have occurred in the solar nebula during the formation of the Solar System., 16 pages, 10 figures, accepted for publication in Astronomy & Astrophysics

The investigation of star forming regions have enormously benefited from the recent advent of the ALMA interferometer. More specifically, the unprecedented combination of high-sensitivity and high-angular resolution provided by ALMA allows one to shed light on the jet/disk systems associated with a Sun-like mass protostar. Also astrochemistry enjoyed the possibility to analyze complex spectra obtained using large bandwidths: several interstellar Complex Organic Molecules (iCOMs; C-bearing species with at least 6 atoms) have been imaged around protostars. This in turn boosted the study of the astrochemistry at work during the earliest phases of star formation paving the way to the chemical complexity in planetary systems where Life could emerge. There is mounting evidence that the observations of iCOMs can be used as unique tool to shed light, on Solar System scales (< 50 au), on the molecular content of protostellar disk. The increase of iCOMs abundances occur only under very selective physical conditions, such as those associated low-velocity shocks found where the infalling envelope is impacting the rotating accretion disk. The imaging of these regions with simpler molecules such as CO or CS is indeed paradoxically hampered by their high abundances and consequently high line opacities which do not allow the observers to disentangle all the emitting components at these small scales. In this respect, we review the state-of-the art of the ALMA analysis about the standard Sun-like star forming region in Orion named HH 212. We show (i) how all the physical components involved in the formation of a Sun-like star can be revealed only by observing different molecular tracers, and (ii) how the observation of iCOMs emission, observed to infer the chemical composition of star forming regions, can be used also as unique tracer to image protostellar disks on Solar System scales., To be published for ACS Earth and Space Chemistry

Understanding the formation mechanisms of protoplanetary disks and multiple systems, and their pristine properties, is a key question for modern astrophysics. The properties of the youngest disks, embedded in rotating infalling protostellar envelopes, have largely remained unconstrained up to now. In the framework of the IRAM-PdBI CALYPSO survey, we have obtained sub-arcsecond observations of the dust continuum emission at 231 GHz and 94 GHz, for a sample of 16 solar-type Class 0 protostars. In an attempt to identify disk-like structures embedded at small scales in the protostellar envelopes, we model the dust continuum emission visibility profiles using both Plummer-like envelope models and envelope models including additional Gaussian disk-like components. Our analysis shows that in the CALYPSO sample, 11 of the 16 Class 0 protostars are better reproduced by models including a disk-like dust continuum component contributing to the flux at small scales, but less than 25% of these candidate protostellar disks are resolved at radii > 60 au. Including all available literature constraints on Class 0 disks at subarcsecond scales, we show that our results are representative: most (> 72% in a sample of 26 protostars) Class 0 protostellar disks are small and emerge only at radii < 60 au. Our multiplicity fraction at scales 100-5000 au is in global agreement with the multiplicity properties of Class I protostars at similar scales. We confront our observational constraints on the disk size distribution in Class 0 protostars to the typical disk properties from protostellar formation models. Because they reduce the centrifugal radius, and produce a disk size distribution peaking at radii, Accepted for publication in Astronomy \& Astrophysics. 24 pages of main text, 22 pages of additional content (under the form of three appendices) - revised version including language and typos corrections

We present a characterization of the binary protostar system that is forming within a dense core in the isolated dark cloud BHR71. The pair of protostars, IRS1 and IRS2, are both in the Class 0 phase, determined from observations that resolve the sources from 1 um out to 250 um and from 1.3 mm to 1.3cm. The resolved observations enable the luminosities of IRS1 and IRS2 to be independently measured (14.7 and 1.7L_sun, respectively), in addition to the bolometric temperatures 68~K, and 38~K, respectively. The surrounding core was mapped in NH3 (1,1) with the Parkes radio telescope, and followed with higher-resolution observations from ATCA in NH3 (1,1) and 1.3cm continuum. The protostars were then further characterized with ALMA observations in the 1.3~mm continuum along with N2D+ (J=3-2), 12CO, 13CO, and C18O (J=2-1) molecular lines. The Parkes observations find evidence for a velocity gradient across the core surrounding the two protostars, while ATCA reveals more complex velocity structure toward the protostars within the large-scale gradient. The ALMA observations then reveal that the two protostars are at the same velocity in C18O, and N2H+ exhibits a similar velocity structure as NH3. However, the C18O kinematics reveal that the rotation on scales $, Comment: 51 pages, 25 Figures, 2 Tables, Accepted to ApJ

HH 212 is one of the well-studied protostellar systems, showing the first vertically resolved disk with a warm atmosphere around the central protostar. Here we report a detection of 9 organic molecules (including newly detected ketene, formic acid, deuterated acetonitrile, methyl formate, and ethanol) in the disk atmosphere, confirming that the disk atmosphere is, for HH 212, the chemically rich component, identified before at a lower resolution as a "hot-corino". More importantly, we report the first systematic survey and abundance measurement of organic molecules in the disk atmosphere within $\sim$ 40 au of the central protostar. The relative abundances of these molecules are similar to those in the hot corinos around other protostars and in Comet Lovejoy. These molecules can be either (i) originally formed on icy grains and then desorbed into gas phase or (ii) quickly formed in the gas phase using simpler species ejected from the dust mantles. The abundances and spatial distributions of the molecules provide strong constraints on models of their formation and transport in star formation. These molecules are expected to form even more complex organic molecules needed for life and deeper observations are needed to find them., Comment: 12 pages, 4 figures

The reaction between atomic silicon and the mercapto radical has been computationally investigated by means of electronic structure and kinetics calculations to establish its possible role in the formation of interstellar SiS. According to our kinetics estimates based on the electronic structure calculations of the Si+SH potential energy surface, the reaction is very fast reaching the gas-kinetics limit. Therefore, the title reaction is an efficient formation route of interstellar SiS provided that silicon atoms and mercapto radicals are present. Implications for the observation of an anomalously high abundance of SiS in the shocked region around a Sun-like protostar (L1157-B1) are also presented.

We present an overview of the ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT), a campaign devoted to the characterization of the molecular emission from partly embedded, young stars. The project aims at better understanding the gaseous products that are delivered to planets by means of high-resolution maps of assorted lines probing disks at the time of the planet formation (less than 1 Myr). Nine different molecules are surveyed by our observations of six Class I/flat-spectrum sources. A series of accompanying articles analyze specific targets and molecules. Here we describe the sample and provide a general overview of the results, focusing on the spatial distribution, column densities, and abundance ratios of H$_2$CO, CS, and CN. The results of this work are a first step toward the characterization of the disk chemical evolution that need to be complemented by further observations of less exceptional disks and customized thermo-chemical modeling., Accepted for publication by A&A, 16 pages, 9 figures

In a previous study of the L1157 B1 shocked cavity, a comparison between NH$_3$(1$_0$-$0_0$) and H$_2$O(1$_{\rm 10}$--1$_{\rm 01}$) transitions showed a striking difference in the profiles, with H$_2$O emitting at definitely higher velocities. This behaviour was explained as a result of the high-temperature gas-phase chemistry occurring in the postshock gas in the B1 cavity of this outflow. If the differences in behaviour between ammonia and water are indeed a consequence of the high gas temperatures reached during the passage of a shock, then one should find such differences to be ubiquitous among chemically rich outflows. In order to determine whether the difference in profiles observed between NH$_3$ and H$_2$O is unique to L1157 or a common characteristic of chemically rich outflows, we have performed Herschel-HIFI observations of the NH$_3$(1$_0$-0$_0$) line at 572.5 GHz in a sample of 8 bright low-mass outflow spots already observed in the H$_2$O(1$_{\rm 10}$--1$_{\rm 01}$) line within the WISH KP. We detected the ammonia emission at high-velocities at most of the outflows positions. In all cases, the water emission reaches higher velocities than NH$_3$, proving that this behaviour is not exclusive of the L1157-B1 position. Comparisons with a gas-grain chemical and shock model confirms, for this larger sample, that the behaviour of ammonia is determined principally by the temperature of the gas., Comment: Accepted for publication in the Monthly Notices of the Royal Astronomical Society

We present polarimetric data of CW Tau and DG Tau, two well-known Class II disk/jet systems, obtained with the Atacama Large Millimeter/submillimeter Array at 870 $\mu$m and 0."2 average resolution. In CW Tau, the total and polarized emission are both smooth and symmetric, with polarization angles almost parallel to the minor axis of the projected disk. In contrast, DG Tau displays a structured polarized emission, with an elongated brighter region in the disk's near side and a belt-like feature beyond about 0."3 from the source. At the same time the total intensity is spatially smooth, with no features. The polarization pattern, almost parallel to the minor axis in the inner region, becomes azimuthal in the outer belt, possibly because of a drop in optical depth. The polarization fraction has average values of 1.2% in CW Tau and 0.4% in DG Tau. Our results are consistent with polarization from self-scattering of the dust thermal emission. Under this hypothesis, the maximum size of the grains contributing to polarization is in the range 100 - 150 $\mu$m for CW Tau and 50 - 70 $\mu$m for DG Tau. The polarization maps combined with dust opacity estimates indicate that these grains are distributed in a geometrically thin layer in CW Tau, representing a settling in the disk midplane. Meanwhile, such settling is not yet apparent for DG Tau. These results advocate polarization studies as a fundamental complement to total emission observations, in investigations of the structure and the evolution of protoplanetary disks., Comment: 8 pages, 5 figures. Accepted for publication in ApJ Letters

Evidence is mounting that the small bodies of our Solar System, such as comets and asteroids, have at least partially inherited their chemical composition from the first phases of the Solar System formation. It then appears that the molecular complexity of these small bodies is most likely related to the earliest stages of star formation. It is therefore important to characterize and to understand how the chemical evolution changes with solar-type protostellar evolution. We present here the Large Program "Astrochemical Surveys At IRAM" (ASAI). Its goal is to carry out unbiased millimeter line surveys between 80 and 272 GHz of a sample of ten template sources, which fully cover the first stages of the formation process of solar-type stars, from prestellar cores to the late protostellar phase. In this article, we present an overview of the surveys and results obtained from the analysis of the 3 mm band observations. The number of detected main isotopic species barely varies with the evolutionary stage and is found to be very similar to that of massive star-forming regions. The molecular content in O- and C- bearing species allows us to define two chemical classes of envelopes, whose composition is dominated by either a) a rich content in O-rich complex organic molecules, associated with hot corino sources, or b) a rich content in hydrocarbons, typical of Warm Carbon Chain Chemistry sources. Overall, a high chemical richness is found to be present already in the initial phases of solar-type star formation., 19 pages, 7 figures, 5 Tables