In the interstellar medium, cosmic rays (CRs) generate a field of ultraviolet (UV) photons via excitation and subsequent radiative decay of H2 molecules. This UV field is a major agent of ionization and dissociation in the inner regions of molecular clouds that are shielded from the effects of the interstellar radiation field. In particular, the dissociation of H2, by far the most abundant molecule in interstellar clouds, leads to the production of atomic hydrogen, which then takes part in the production of a multitude of molecules, in particular complex organics on the surfaces of interstellar dust grains. Precise knowledge of the rates of CR-induced dissociation processes is thus crucial for constructing reliable chemical models. For the present paper, we have derived a new value of k diss,CR(H2) = 0.831 zeta for the rate of H2 dissociation, where zeta is the CR ionization rate of H2. This prediction contrasts a previous value from the Leiden database which overestimated the rate due to an inconsistent treatment of the H2 abundances and photodissociation cross sections. By running a series of chemical models, we show that the overestimated dissociation rate has a large effect on the results of chemical simulations, with the abundance of methanol being overestimated by over 1 order of magnitude. Hence, we strongly recommend the adoption of our new estimate, k diss,CR(H2) = 0.831 zeta in all chemical models that include this process. Our newly derived value corresponds to H2 being purely in the para form (J '' = 0). However, in the interiors of molecular clouds, the H2 ortho-to-para ratio is low and using the rate for para-H2 is an adequate approximation.

Stars and planets form within cold, dark molecular clouds. In these dense regions, where starlight cannot penetrate, cosmic rays (CRs) are the dominant source of ionization—driving interstellar chemistry, setting the gas temperature and enabling coupling to magnetic fields. Together, these effects regulate the collapse of clouds and the onset of star formation. Despite this importance, the CR ionization rate, ζ, has never been measured directly. Instead, this fundamental parameter has been loosely inferred from indirect chemical tracers and uncertain assumptions, limiting our understanding of star formation physics. Here we report the direct detection of CR-excited vibrational H2 emission, using James Webb Space Telescope observations of the starless core Barnard 68 (B68). The observed emission pattern matches theoretical predictions for CR excitation precisely, confirming a decades-old theoretical proposal long considered observationally inaccessible. This result enables direct measurement of ζ, effectively turning molecular clouds into natural, light-year-sized, CR detectors. It opens a transformative observational window into the origin, propagation and role of CRs in star formation and galaxy evolution. The famous nebula Barnard 68 has been used as a giant cosmic-ray detector: cosmic-ray-excited vibrational H2 emission has been observed by JWST, giving a direct measurement of the CR ionization rate.

The development of molecular complexity during stellar and planetary formation owes much to the interaction of gas and dust. When the first astrochemical models including solid-state chemistry were developed more than 40 years ago, data from dedicated laboratory experiments were limited. Since then, many groups have developed specific experimental setups to address this issue, but astrochemical models have rarely been directly confronted with these new results. We want to demonstrate whether it is possible to use rate-equation-type astrochemical models developed in the context of the Interstellar Medium to compare them with laboratory astrophysics experiments. In this work, we use the case of the low-temperature hydrogenation of CO, which is known to lead to methanol, among other molecules. We carried out 9 experiments, varying the experimental parameters such as temperature and dose. We give quantitative results and detail the vocabulary used in the experiments. We use astrochemical codes, NAUTILUS, pyRate, and MONACO, to reproduce our experimental conditions, which requires good control of the change of vocabulary and scales, especially for fluxes and time scales. This work demonstrates that it is possible to use different astrochemical codes to compare modeling results directly with the output of experiments. There are discrepancies between models and experiments as well as between models, but a fair agreement is achieved. We discuss the possible origin of the differences, which could originate from the chemical network or the difference in the description of the physical processes.

Deuterium fractionation is highly efficient during the early stages of star formation, particularly in starless and prestellar cores where temperatures are low (<10 K) and molecular freeze-out onto dust grains is significant. Methanol forms early in these environments following CO freeze-out via successive hydrogenation reactions on grain surfaces, while the production of deuterated methanol requires elevated gas-phase D/H ratios generated through dissociative recombination of deuterated H-3(+). Consequently, large abundances of deuterated methanol are observed towards young stellar objects where prestellar ices have recently sublimated. Here, we present laboratory broadband infrared spectra of methanol and its isotopologues in astrophysical ice analogues, complemented by anharmonic vibrational calculations used to guide band assignments. Experiments were performed at the CASICE laboratory using a Bruker Vertex 70v spectrometer coupled to a closed-cycle helium cryostat, with isotopologue ices deposited at 10 K under high-vacuum conditions. Infrared transmission spectra were recorded over 6000 to 30 cm(-1) (1.67 to 333 & micro;m) and compared with spectra of pure isotopologue ices. Distinctive mid-infrared band patterns are identified for each deuterated species. In particular, CH2DOH exhibits a characteristic doublet at 1293 cm(-1) and 1326 cm(-1) (7.73 & micro;m and 7.54 & micro;m), while CHD2OH shows a similar doublet at 1301 cm(-1) and 1329 cm(-1) (7.69 & micro;m and 7.52 & micro;m), both remaining largely invariant across all studied ice mixtures. These robust spectral signatures provide reliable tracers for identifying deuterated methanol in JWST observations and for constraining astrochemical gas-grain models of deuterium enrichment prior to star and planet formation.

We present an overview of the final data release (DR2) from the Green Bank Ammonia Survey (GAS). GAS is a large program at the Green Bank Telescope to map all Gould Belt star-forming regions with AV greater than or similar to 7 mag visible from the Northern Hemisphere in emission from NH3 and other key molecular tracers. This final release includes the data for all the regions observed: Heiles Cloud 2 and B18 in Taurus; Barnard 1, Barnard 1-E, IC 348, NGC 1333, L1448, L1451, and Per7/34 in Perseus; L1688 and L1689 in Ophiuchus; Orion A (North and South) and Orion B in Orion; Cepheus; B59 in Pipe; Corona Australis East and West; IC 5146; and Serpens Aquila and MWC297 in Serpens. Similar to what was presented in GAS DR1, we find that the NH3 emission and dust continuum emission from Herschel correspond closely. We find that the NH3 emission is generally extended beyond the typical 0.1 pc length scales of dense cores, and we find that the transition between coherent core and turbulent cloud is a common result. This shows that the regions of coherence are common throughout different star-forming regions, with a substantial fraction of the high column density regions displaying subsonic nonthermal velocity dispersions. We produce maps of the gas kinematics, temperature, and NH3 column densities through forward modeling of the hyperfine structure of the NH3 (1,1) and (2,2) lines. We show that the NH3 velocity dispersion, sigma v, and gas kinetic temperature, TK, vary systematically between the regions included in this release, with an increase in both the mean value and spread of sigma v and TK with increasing star formation activity. The data presented in this paper are publicly available via doi:10.11570/24.0091.

The mass flows and energy cycles within the inner regions of galaxies exert a powerful influence on the evolution of the galaxy population. The centre of the Milky Way is the only galactic nucleus for which it is possible to resolve the physical mechanisms that drive these cycles, namely star formation and feedback, while also tracing global (>100 pc) processes which determine where and when star formation and feedback occur. We present an overview of ACES, the 'Atacama Large Millimeter/submillimeter Array (ALMA) CMZ Exploration Survey', a 1.5" angular resolution, 0.2-3 km/s spectral resolution ALMA Band 3 (85-102 GHz), survey of the 'Central Molecular Zone' (CMZ) – the inner-100 pc of the Galaxy (l = 359.4 deg to 0.8 deg). ACES spectral setup is tuned to observe optimal tracers of the physical, chemical, and kinematic conditions in over 70 spectral features (e.g. HCO+, HNCO, SiO, H40alpha, complex molecules) of the gas in the CMZ, to derive the properties of all potentially star-forming Galactic Centre gas, from global scales (100 pc) to dense 0.05 pc structures that are expected to host individual star-forming cores, down to sub-sonic (<0.4 km/s) velocity resolution. In this overview paper, we provide the scientific justification for the ACES survey, explain the choice of observational setup, and describe the data legacy products. Finally, we show some of the initial ACES data which highlight the power of ACES' combination of high angular resolution, unprecedented spatial dynamic range, sensitivity, spectral resolution and spectral bandwidth as an illustration of how ACES aims to understand how global processes set the location, intensity, and timescales for star formation and feedback in the CMZ.

While quantum chemical treatment of the prebiotic, astrochemically relevant H2NCO molecule's rotational constants and fundamental vibrational frequencies produces exceptionally accurate values, the cis-HNCHO isomer is more of a challenge to standard electronic structure methods. The trans-HNCHO conformer is well-behaved like H2NCO due to the nature of the local potential energy surface, but the zero-point vibrational energy of the torsional motion is significantly greater than the barrier, implying that this isomer cannot be observed. The 2.6 kcal mol(-1) lower-energy cis-HNCHO conformer showcases a small pseudo-Jahn-Teller distortion about the HNCO torsion coordinate at planarity. This produces a challenging environment for the quartic force field (QFF) treatment of the rotational and vibrational spectroscopic data. Even so, the accuracy of the H2NCO spectroscopic constants from this explicitly correlated coupled cluster theory QFF implies that similar accuracy should be present for the mathematically well-behaved trans-HNCHO, which exists in a shallow but true minimum. The constants computed herein may allow for a more detailed search of experimental rotation spectra for cis-HNCHO, which would provide reference data necessary for potential searches for this molecule in space. Rotational constants are also provided for the four conformers of HNCOH, and the fundamental vibrational frequencies in the range of James Webb Space Telescope observation are provided for all isomers in order to allow for the possibility of multiple wavelength observation of this family of molecules, which may play a role in the molecular origins of life.

Molecules harbouring sulfur are thought to have played a key role in the biological processes of life on Earth, and thus, they are of much interest when found in space. Here we report on the astronomical detection of a six-membered sulfur-bearing cyclic hydrocarbon in the interstellar medium. Observations of the Galactic Centre molecular cloud G+0.693-0.027 reveal the presence of 2,5-cyclohexadien-1-thione, which is a structural isomer of thiophenol (c-C_6H_6S). For the astronomical identification, we first performed precise laboratory measurements of the thiophenol discharge products system. These measurements, conducted in the radio band using a chirped-pulse Fourier transform microwave spectrometer, enabled us to characterize this highly polar molecular species and provided unambiguous fingerprints needed to identify this organosulfur compound in space, which now ranks as the largest interstellar sulfur-bearing molecule. These results herald the discovery of a family of prebiotically relevant sulfur-bearing species, which potentially act as a bridge between the chemical inventory of the interstellar medium and the composition of the minor bodies of the Solar System.

Sulfur is one of the most abundant elements in the interstellar medium (ISM) and a key component for life, yet little is understood about its chemistry in the ISM. While increasingly larger molecules containing sulfur and oxygen are being observed in the ISM, the largest organic molecule containing oxygen and sulfur, monothioformic acid (HC(O)SH), was only recently detected. There is still no identification of a complex organic molecule (COM, carbon-bearing molecule with six or more atoms) containing both oxygen- and sulfur-bearing functional groups. We extended the laboratory rotational spectrum of 2-mercaptoethanol (HSCH2CH2OH), one of the simplest saturated COMs containing both oxygen and sulfur, into millimeter/submillimeter wavelengths, providing an improved spectral catalog at frequencies required for its interstellar identification. Millimeter/submillimeter transitions were measured for 2-mercaptoethanol from similar to 82 to 450 GHz. Using the resulting spectral catalog, we searched for its rotational emission toward the Galactic Center molecular cloud G+0.693-0.027, the high-mass star-forming region Sgr B2(N), the cold dark core TMC-1, the hot core in Orion, and toward the hot corino surrounding the low-mass protostar IRAS 16293-2422B. An extensive analysis of 8584 transitions of 2-mercaptoethanol with Jmax '' = 104, and Kamax '' = 64 is provided. The resulting fit includes a full set of quartic, sextic, and octic distortion constants. We report the nondetection of 2-mercaptoethanol and provide column density upper limits toward each source. While our interstellar search for 2-mercaptoethanol did not result in a detection, the upper limits on its column density provide important constraints for chemical models on the formation of oxygen- and sulfur-bearing COMs.

We present the first spatially resolved map of methanimine (CH2NH) in the prestellar core L1544 using the IRAM 30 m telescope. The 20,2-10,1 line at 127 GHz was mapped with 20 '' resolution (similar to 2800 au), revealing extended CH2NH emission across the core. The peak line intensity coincides with the well-known c-C3H2 peak, while the integrated intensity peaks between the HNCO and dust continuum peaks due to broader linewidths in the latter region. Column densities of CH2NH are similar to(0.5-1.4x)1012 cm-2, corresponding to fractional abundances of 5 x 10-11-1 x 10-10, with a trend decreasing from the southern, carbon-chain rich region to the dust and HNCO peak in the north. Comparison with complementary molecular maps and the gas-grain chemical model of Sipil & auml; et al. suggests that neutral-neutral gas-phase reactions and dissociative recombination dominate in the outer carbon-chain shell. This study demonstrates that CH2NH, a simple nitrogen- and carbon-bearing molecule previously detected with pointed observations in other cold cores, is present and spatially extended in the evolved prestellar core L1544. This indicates that prebiotic nitrogen-carbon chemistry continues efficiently up to the onset of gravitational collapse, providing key constraints for astrochemical models and the early stages of chemical complexity leading to amino acids.

Context. Understanding the optical properties of astrophysical ices is crucial for modeling dust continuum emission and radiative transfer in dense, cold interstellar environments. Molecular nitrogen, a primary carrier of N in protoplanetary disks, plays a key role in the formation of nitrogen-bearing species. However, the lack of direct measurements of the terahertz (THz) to infrared (IR) optical constants of N-2 ice introduces uncertainties in radiative transfer models, snow-line locations, and disk mass estimates. Aims. We present direct measurements and analysis of the optical properties of N-2 ice across a broad THz-IR spectral range by combining THz pulsed spectroscopy (TPS) and Fourier-transform IR (FTIR) spectroscopy. The observed optically active THz vibrational modes of N-2 ice are supported by density functional theory (DFT) calculations. The consistency of our measurements and calculations with datasets from the literature is also assessed. Methods. N-2 ice was grown at cryogenic temperatures via gas-phase deposition onto a cold silicon window. The optical properties of the ice samples were quantified using our earlier-reported method: it involves the direct reconstruction of the THz complex refractive index from the TPS data, combined with the derivation of the IR response from the FTIR data using the Kramers-Kronig relations. The N-2 ice response was parameterized using the Lorentz model of complex dielectric permittivity, which was verified with our DFT calculations and compared with the literature data. Results. The complex refractive index of N-2 ice is quantified in the frequency range v = 0.3-16 THz (the wavelength range lambda = 1 mm-18.75 mu m), and was compared with the DFT results as well as with the available literature data. The observed resonant absorption peaks at nu(L) = 1.47 and 2.13 THz; the damping constants of gamma(L) = 0.03 and 0.22 THz, respectively, are attributed to the well-known optically active phonons of the alpha-N-2 crystal. Conclusions. We provide a complete set of THz-IR optical constants for N-2 ice by combining TPS and FTIR spectroscopy. Our results have implications for future observational and modeling studies of protoplanetary disk evolution and planet formation.

Context. Recently, streamers have been observed causing shocks at the outer edge of protoplanetary disks. The study of sulfur-bearing species can help us to understand the physical and chemical changes caused by infalling streamers toward their landing positions. Aims. We study the physical properties traced by the emission of SO2 and SO toward the Class I protostar Per-emb 50, which is possibly related to the streamer infalling toward its disk. Methods. We present new NOrthern Extended Millimeter Array (NOEMA) A-array observations as part of the large program "Protostars and Disks: Global Evolution" (PRODIGE). We analyzed the morphology of SO2 and SO, and complement our interpretations with additional H2CO and CO data from the same program. We compared the SO2 and SO morphology with an infalling-rotating model. We applied Bayesian model selection to the brightest SO2 line to disentangle the different kinematic components traced by this molecule. We used local thermodynamic equilibrium (LTE) and non-LTE analyses to determine the temperature and density of the SO2 emission. Results. There are two separate peaks of SO2 emission offset toward the southwest of Per-emb 50: one brighter (peak 1) at about 180 au from the protostar, and a weaker one (peak 2) at about 400 au. Peak 2 is blueshifted with respect to an infalling-rotating envelope. We propose that this peak is caused by the shock between the inner envelope and the streamer. Peak 1 is consistent with the expected envelope motion, and could thus be caused by shocks at the disk-envelope interface, but potential streamer influence cannot be neglected. Both peaks show abundance ratios consistent with a low-velocity shock (similar to 3-4 km s(-1)) when compared with shock models. Conclusions. Streamers can affect the physical and chemical structure of both disks and envelopes, suggesting that streamers can play an important role in shaping both structures in the embedded stages of star formation.

We present an implementation of radiative transfer with flux-limited diffusion (FLD) for the moving-mesh code AREPO and use the method in a physical model for the formation of protostars with non-ideal radiation-magnetohydrodynamics (RMHD). We follow previous work in splitting the additional terms to the hydrodynamical equations arising from the inclusion of radiation into terms to be integrated explicitly and implicitly, as the diffusion and coupling terms would impose very restrictive time-step criteria. We validate the scheme with standard test problems for radiation diffusion, matter-gas coupling, and radiative shocks from the literature. Our implementation is compatible with local time-stepping, which often presents problems for implicit schemes, and we found very good agreement with results obtained with global time-steps. We present an example application of the new implementation to the collapse of a 1 M- (R) molecular cloud core to a second Larson core modelled with radiation non-ideal magnetohydrodynamics. A high-velocity jet with vrad > 10 km s(-1)is self-consistently launched from the second core, nested within the first core, which produces a lower-velocity magnetorotational outflow. We observe magnetic field amplification up to more than | B |(max) > 10(5) Gin the second core, which is surrounded by a small (< 0 . 5 au) disc. This application demonstrates the robustness of our scheme in multiscale and high-resolution simulations on arbitrary meshes and, as such, the model can be readily used for further simulations of protostar formation at high resolution.

Deuterium fractionation provides a key diagnostic of the physical and chemical evolution of prestellar and protostellar cores, where it is strongly linked to CO depletion in cold, dense gas. We present the first spatially resolved maps of deuterium fraction and CO depletion in the Barnard 5 region of the Perseus molecular cloud, covering both a starless core and the protostellar core hosting the Class 0/I source IRAS 03445+3242. Using IRAM 30 m observations of N2H+(1-0), N2D+(1-0), H13CO+(1-0), and DCO+(2-1), complemented by C18O(2-1) data, we derive column density, deuterium fraction, and CO depletion maps. We find that the deuterium fraction in the abovementioned nitrogen- and carbon-bearing species increases from the protostellar to the starless core, reaching RDN2H+=0.43 +/- 0.10 and RDHCO+=0.09 +/- 0.02 in the starless core, compared with 0.15 +/- 0.03 and 0.05 +/- 0.01, respectively, in the protostellar core. The CO depletion factor also rises from 4.1 +/- 0.1 to 5.0 +/- 0.1 across the same transition. While the embedded young stellar object reduces deuteration in the dense inner gas, the less dense envelope traced by HCO+ is only slightly affected at our resolution. Our analysis confirms that CO freeze-out and the presence of a protostar jointly regulate deuterium chemistry in star-forming regions.

Context. Pre-stellar cores mark the earliest phase of star formation. By characterizing their physical and chemical structure, we can establish the initial conditions for star and planet formation and assess how closely the chemical composition of these cores is connected to later evolutionary stages. Aims. We explore the differences between static and dynamically evolving physico-chemical models of pre-stellar cores. The results are compared with observations of the pre-stellar core L1544 to estimate how well 3D physico-chemical models can reproduce the chemistry at this evolutionary stage. Methods. A 3D magnetohydrodynamic model of a pre-stellar core embedded in a dynamic star-forming cloud was post-processed using sequentially dust radiative transfer, a gas-grain chemical model, and a nonlocal thermodynamic equilibrium line-radiative transfer model. The chemical evolution was modeled along ~20 000 tracer particle trajectories to capture the effect of a realistic dynamical evolution as the core formed. The emission morphology of CH3OH and c-C3H2 and the intensities of CH3OH, c-C3H2, CS, SO, HCN, HCO+, and N2H+ were compared with observations of L1544. We compared initial elemental abundances with and without depletion of heavier elements. Results. Our results show a distinct difference in chemical morphology between the dynamical and static models. The dynamical model reproduces the observed spatial distribution of CH3OH and c-C3H2 toward L1544, whereas the static model fails to reproduce this morphology. In contrast, when we compared modeled and observed intensities across a broad range of molecules, the static model agreed well with observations for L1544. The dynamical model systematically predicts lower abundances and modeled intensities for six of the seven species presented here. For sulfur-bearing species, the intensities agree better with observations when the initial abundances are not depleted in heavier elements. Conclusions. We reveal distinct differences between dynamical and static physico-chemical models. The static model predicts higher abundances and intensities for the majority of the molecules we studied than the dynamical model. This discrepancy may stem from the specific choices of initial conditions, which might limit the ability of the dynamical models to fully capture the physical and chemical history. The intensities predicted by the static model are comparable to those observed toward L1544.

Chemistry in diffuse molecular clouds relies primarily on rapid ion-molecule reactions. Formation of the initial ions, H+ and H 2+ , is dominated by cosmic-ray ionization of H and H2, making the cosmic-ray ionization rate (denoted zeta(X) for species X) an important parameter for chemical modeling. We have made observations targeting absorption lines of H 3+ , one of the most reliable tracers of zeta(H2), toward diffuse molecular cloud sight lines where the H2 column density has been directly measured in the ultraviolet, detecting H 3+ in 12 out of 27 sight lines. The 3D-PDR modeling method introduced by M. Obolentseva et al. was used to infer cosmic-ray ionization rates in the clouds along these sight lines, and our combined sample has a mean ionization rate of 5.3 x 10-17 s-1 with standard deviation 2.5 x 10-17 s-1. By associating H 3+ absorption with gas density peaks derived from the differential extinction maps of G. Edenhofer et al., we have constructed a sparsely sampled 3D map of the cosmic-ray ionization rate in targeted regions within about 1 kpc of the Sun. Specific regions show reasonably uniform ionization rates over length scales of tens of parsecs, with the average ionization rate in each region being different. Large differences (factor of 5) in zeta(H2) are found over length scales of about 100 pc. This supports a picture where the cosmic-ray ionization rate varies smoothly over small size scales, but is not uniform everywhere in the Galactic disk, likely being controlled by proximity to particle acceleration sites.

Cosmic rays (CRs) are important drivers for molecular chemistry in star-forming regions, and laboratory experiments have shown that CRs can stimulate the release of complex organic molecules (COMs) such as methanol. Observationally, this has primarily been tested in cold, low-mass cores, so studying how CRs affect COM formation in a high-mass star-forming environment is of great interest. We performed a high-sensitivity wide-band spectral line survey with the Onsala 20 m telescope towards the high-mass protostar Cepheus A HW2, which is known to host an ionised jet. Consistent with previous studies, two primary velocity components (-11 km s^-1 and -5 km s^-1) were identified. Column densities and relative abundances of the detected ions and COMs were estimated from rotational diagrams, single transitions and RADEX grid searches (CH_3OH: 1.6×10^-9, CH_3CN: 5.9×10^-11, t-HCOOH: 7.9×10^-11, H_2CCO: 1.7×10^-11, CH_3CHO: 1.9×10^-11, CH_3OCHO: 7.6×10^-10 at -11 km s^-1). Deuterium fractions were also estimated (in range 0.002-0.3 at -11 km s^-1), and the volume density of molecular hydrogen (2.6×10^5 cm^-3 at -11 km s^-1) was constrained from the RADEX grid searches. Electron fractions and CR ionisation rates (CRIR, 6.8×10^-17 s^-1 at -11 km s^-1, ≤9.2×10^-19 s^-1 at -5 km s^-1) were estimated through analytic chemistry using different ions as probes. The gas-grain chemical code Nautilus reproduced the observed abundances of CH_3OH, CH_3CN, HCO^+, N_2H^+ at the observed density, temperature and CRIR within the uncertainty of the model. The results indicate that the CR ionisation rate of the kinematic component associated with most of the COMs' emission in the region is locally enhanced.

Aims. Filamentary infrared dark clouds (IRDCs) are believed to represent the initial conditions for massive star and cluster formation. Methods. We investigated the IRDC G035.39-00.33 using SiO, H13CO+, CH3OH, and CS emission observed with ALMA at 3.5″ resolution (∼0.05 pc). The analysis of the SiO emission provides a record of shock activity within the cloud, offering insights into both the current level of star formation and the cloud’s formation mechanisms. Results. We identify several regions with broad SiO emission clearly associated with outflows, pinpointing the locations of ongoing star formation across the cloud. The ALMA images also reveal a series of spatially extended SiO emission spots with narrow line profiles aligned along an arc-like path that is also seen in CS and CH3OH emission. While the broad SiO emission is mainly associated with the main cloud filament, as seen in visual extinction, the narrow SiO arch is located at the edge of the cloud, far from the identified sites of star formation activity. The presence of these arc-like morphologies suggests that large-scale shocks may have compressed the gas in the surroundings of the G035.39-00.33 cloud, shaping its filamentary structure. By inspecting the large-scale radio continuum emission around G035.39-00.33, we find that this IRDC is part of a larger star-forming complex where the densest and coolest material appears at the interacting regions between a supernova remnant (SNR) and an expanding HII region. In particular, we hypothesise that this IRDC may be spatially coincident with the ionised expanding gas associated with the previously identified SNR G35.6-0.4. Conclusions. We suggest that collisions between giant molecular clouds and expanding gas flows from interacting SNRs and HII regions may be responsible for the observed arc-like structures. Such shock compressions could play an important role in the formation of IRDCs and in the potential triggering of star formation.

Exomoons around free-floating planets (FFPs) can survive their host planet's ejection. Such ejections can increase their orbital eccentricity, providing significant tidal heating in the absence of any stellar energy source. Previous studies suggested that liquid water could exist on such moons under thick CO_2-dominated atmospheres, but these models faced challenges with CO_2 condensation and atmospheric collapse, particularly in the high-pressure regimes that favoured long-term habitability. To address this, we employ a self-consistent model, including radiative transfer and equilibrium chemistry with condensation, to simulate a more stable hydrogen-dominated atmosphere for a range of initial chemical compositions, including C, O, and N. We find that such atmospheres can effectively trap heat via collision-induced absorption of H_2, maintaining surface temperatures suitable for liquid water for time-scales of up to 4.3 Gyr, depending on the surface pressure, while not prone to condensation-induced collapse. Wet-dry cycling caused by the strong tides together with the alkalinity of dissolved NH_3 could create favourable conditions for RNA polymerisation and thus support the emergence of life.

Astrochemical observations have revealed a surprisingly high level of chemical complexity, including long carbon chains, in the earliest stages of Sun-like star formation. The origin of these species and whether they undergo further growth, possibly contributing to the molecular complexity of planetary systems, remain open questions. We present recent observations performed using the 100-m Green Bank Telescope of the prestellar core L1544, and the protostellar system IRAS 16293-2422. In L1544, we detected several complex carbon-bearing species, including C2S, C3S, C3N, c-C3H, C4H and C6H, complementing previously reported emission of cyanopolyynes. In IRAS 16293-2422, we detected c-C3H and, for the first time, HC7N. Thanks to the high spectral resolution, we refine the rest frequencies of several c-C3H and C6H transitions. We perform radiative transfer analysis, highlighting a chemical difference between the two sources: IRAS 16293-2422 shows column densities 10 to 100 times lower than L1544. We perform astrochemical modeling, employing an up-to-date chemical network with revised reaction rates. Models reproduce the general trends, with cyanopolyyne and polyynyl radical abundances decreasing as molecular size increases, but underestimate the abundances of cyanopolyynes longer than HC5N by up to two orders of magnitude. Current models, which include the dominant neutral-neutral formation routes, cannot account for this discrepancy, suggesting that the chemical network is incomplete. We propose that additional ion-molecule reactions are crucial for the formation of these species. Developing a more comprehensive chemical network for long carbon chains is essential for accurately interpreting present and future observations.