A far-ultraviolet-driven photoevaporation flow observed in a protoplanetary disk.

Most low-mass stars form in stellar clusters that also contain massive stars, which are sources of far-ultraviolet (FUV) radiation. Theoretical models predict that this FUV radiation produces photodissociation regions (PDRs) on the surfaces of protoplanetary disks around low-mass stars, which affects planet formation within the disks. We report James Webb Space Telescope and Atacama Large Millimeter Array observations of a FUV-irradiated protoplanetary disk in the Orion Nebula.

Formation of the methyl cation by photochemistry in a protoplanetary disk.

Forty years ago, it was proposed that gas-phase organic chemistry in the interstellar medium can be initiated by the methyl cation CH (refs. ), but so far it has not been observed outside the Solar System. Alternative routes involving processes on grain surfaces have been invoked.

First detection of doubly deuterated methyl acetylene (CHDCCH and CHDCCD).

We report the first detection in space of the two doubly deuterated isotopologues of methyl acetylene. The species CHDCCH and CHDCCD were identified in the dense core L483 through nine and eight, respectively, rotational lines in the 72-116 GHz range using the IRAM 30m telescope. The astronomical frequencies observed here were combined with laboratory frequencies from the literature measured in the 29-47 GHz range to derive more accurate spectroscopic parameters for the two isotopologues.

Detection of deuterated methylcyanoacetylene, CHDCN, in TMC-1.

We report the first detection in space of the single deuterated isotopologue of methylcyanoacetylene, CHDCN. A total of fifteen rotational transitions, with = 8-12 and = 0 and 1, were identified for this species in TMC-1 in the 31.0-50.

Gas phase Elemental abundances in Molecular cloudS (GEMS) II. On the quest for the sulphur reservoir in molecular clouds: the HS case.

Context: Sulphur is one of the most abundant elements in the Universe. Surprisingly, sulphuretted molecules are not as abundant as expected in the interstellar medium and the identity of the main sulphur reservoir is still an open question.

Aims: Our goal is to investigate the HS chemistry in dark clouds, as this stable molecule is a potential sulphur reservoir.

ALMA observations of the young protostellar system Barnard 1b: signatures of an incipient hot corino in B1b-S.

The Barnard 1b core shows signatures of being at the earliest stages of low-mass star formation, with two extremely young and deeply embedded protostellar objects. Hence, this core is an ideal target to study the structure and chemistry of the first objects formed in the collapse of prestellar cores. We present ALMA Band 6 spectral line observations at ~0.

Abundances of sulphur molecules in the Horsehead nebula First NS detection in a photodissociation region.

Context: Sulphur is one of the most abundant elements in the Universe (S/H1.310 ) and plays a crucial role in biological systems on Earth. The understanding of its chemistry is therefore of major importance.

Oxygen fractionation in dense molecular clouds.

We have developed the first gas-grain chemical model for oxygen fractionation (also including sulphur fractionation) in dense molecular clouds, demonstrating that gas-phase chemistry generates variable oxygen fractionation levels, with a particularly strong effect for NO, SO, O, and SO. This large effect is due to the efficiency of the neutral O + NO, O + SO, and O + O exchange reactions. The modeling results were compared to new and existing observed isotopic ratios in a selection of cold cores.

A sensitive 3 mm line survey of L483: A broad view of the chemical composition of a core around a Class 0 object.

An exhaustive chemical characterization of dense cores is mandatory to our understanding of chemical composition changes from a starless to a protostellar stage. However, only a few sources have had their molecular composition characterized in detail. Here we present a 3 mm line survey of L483, a dense core around a Class 0 protostar, which was observed with the IRAM 30m telescope in the 80-116 GHz frequency range.

Gas phase Elemental abundances in Molecular cloudS (GEMS): I. The prototypical dark cloud TMC 1.

GEMS is an IRAM 30m Large Program whose aim is determining the elemental depletions and the ionization fraction in a set of prototypical star-forming regions. This paper presents the first results from the prototypical dark cloud TMC 1. Extensive millimeter observations have been carried out with the IRAM 30m telescope (3 mm and 2 mm) and the 40m Yebes telescope (1.

Astrochemical evolution along star formation: Overview of the IRAM Large Program ASAI.

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.

The chemistry of disks around T Tauri and Herbig Ae/Be stars.

Context: Infrared and (sub-)mm observations of disks around T Tauri and Herbig Ae/Be stars point to a chemical differentiation between both types of disks, with a lower detection rate of molecules in disks around hotter stars.

Aims: To investigate the underlying causes of the chemical differentiation indicated by observations we perform a comparative study of the chemistry of T Tauri and Herbig Ae/Be disks. This is one of the first studies to compare chemistry in the outer regions of these two types of disks.

Discovery of the Ubiquitous Cation NS in Space Confirmed by Laboratory Spectroscopy.

We report the detection in space of a new molecular species which has been characterized spectroscopically and fully identified from astrophysical data. The observations were carried out with the 30m IRAM telescopea. The molecule is ubiquitous as its =2→1 transition has been found in cold molecular clouds, prestellar cores, and shocks.

Discovery of the elusive radical NCO and confirmation of HNCO in space.

The isocyanate radical (NCO) is the simplest molecule containing the backbone of the peptide bond, C(=O)-N. This bond has a prebiotic interest since is the one linking two amino acids to form large chains of proteins. It is also present in some organic molecules observed in space such as HNCO, NHCHO and CHNCO.

First Detection of Interstellar SH.

We present the first detection of gas phase SH in the Horsehead, a moderately UV-irradiated nebula. This confirms the presence of doubly sulfuretted species in the interstellar medium and opens a new challenge for sulfur chemistry. The observed SH abundance is ~5×10, only a factor 4-6 lower than that of the widespread HS molecule.

The ESO Diffuse Interstellar Bands Large Exploration Survey: EDIBLES I. Project description, survey sample and quality assessment.

The carriers of the diffuse interstellar bands (DIBs) are largely unidentified molecules ubiquitously present in the interstellar medium (ISM). After decades of study, two strong and possibly three weak near-infrared DIBs have recently been attributed to the [Formula: see text] fullerene based on observational and laboratory measurements. There is great promise for the identification of the over 400 other known DIBs, as this result could provide chemical hints towards other possible carriers.

The interstellar chemistry of CH and CH isomers.

We report the detection of linear and cyclic isomers of CH and CH towards various starless cores and review the corresponding chemical pathways involving neutral (CH with x=1,2) and ionic (CH with x = 1,2,3) isomers. We highlight the role of the branching ratio of electronic Dissociative Recombination (DR) reactions of CH and CH isomers showing that the statistical treatment of the relaxation of CH and CH produced in these DR reactions may explain the relative c,l-CH and c,l-CH abundances. We have also introduced in the model the third isomer of CH (HCCCH).

Evidence for disks at an early stage in class 0 protostars?

Aims: The formation epoch of protostellar disks is debated because of the competing roles of rotation, turbulence, and magnetic fields in the early stages of low-mass star formation. Magnetohydrodynamics simulations of collapsing cores predict that rotationally supported disks may form in strongly magnetized cores through ambipolar diffusion or misalignment between the rotation axis and the magnetic field orientation. Detailed studies of individual sources are needed to cross check the theoretical predictions.

Chemical segregation in the young protostars Barnard 1b-N and S Evidence of pseudo-disk rotation in Barnard 1b-S.

The extremely young Class 0 object B1b-S and the first hydrostatic core (FSHC) candidate, B1b-N, provide a unique opportunity to study the chemical changes produced in the elusive transition from the prestellar core to the protostellar phase. We present 40"×70" images of Barnard 1b in the CO 1→0, CO 1→0, NHD 1→1, and SO 3→2 lines obtained with the NOEMA interferometer. The observed chemical segregation allows us to unveil the physical structure of this young protostellar system down to scales of ∼500 au.

[Cii] emission from L1630 in the Orion B molecular cloud.

Context: L1630 in the Orion B molecular cloud, which includes the iconic Horsehead Nebula, illuminated by the star system Ori, is an example of a photodissociation region (PDR). In PDRs, stellar radiation impinges on the surface of dense material, often a molecular cloud, thereby inducing a complex network of chemical reactions and physical processes.

Aims: Observations toward L1630 allow us to study the interplay between stellar radiation and a molecular cloud under relatively benign conditions, that is, intermediate densities and an intermediate UV radiation field.

The first CO image: I. Probing the HI/H layer around the ultracompact HII region Mon R2.

The CO reactive ion is thought to be a tracer of the boundary between a HII region and the hot molecular gas. In this study, we present the spatial distribution of the CO rotational emission toward the Mon R2 star-forming region. The CO emission presents a clumpy ring-like morphology, arising from a narrow dense layer around the HII region.

Ionization fraction and the enhanced sulfur chemistry in Barnard 1.

Context: Barnard B1b has revealed as one of the most interesting globules from the chemical and dynamical point of view. It presents a rich molecular chemistry characterized by large abundances of deuterated and complex molecules. Furthermore, it hosts an extremely young Class 0 object and one candidate to First Hydrostatic Core (FHSC) proving the youth of this star forming region.

The interstellar chemistry of HCO isomers.

We present the detection of two HCO isomers, propynal and cyclopropenone, toward various starless cores and molecular clouds, together with upper limits for the third isomer propadienone. We review the processes controlling the abundances of HCO isomers in interstellar media showing that the reactions involved are gas-phase ones. We show that the abundances of these species are controlled by kinetic rather than thermodynamic effects.

Probing non polar interstellar molecules through their protonated form: Detection of protonated cyanogen (NCCNH).

Cyanogen (NCCN) is the simplest member of the series of dicyanopolyynes. It has been hypothesized that this family of molecules can be important constituents of interstellar and circumstellar media, although the lack of a permanent electric dipole moment prevents its detection through radioastronomical techniques. Here we present the first solid evidence of the presence of cyanogen in interstellar clouds through the detection of its protonated form toward the cold dark clouds TMC-1 and L483.

Chemical complexity in the horsehead photodissociation region.

The interstellar medium is known to be chemically complex. Organic molecules with up to 11 atoms have been detected in the interstellar medium, and are believed to be formed on the ices around dust grains. The ices can be released into the gas-phase either through thermal desorption, when a newly formed star heats the medium around it and completely evaporates the ices; or through non-thermal desorption mechanisms, such as photodesorption, when a single far-UV photon releases only a few molecules from the ices.