Nitrogen-bearing Molecules Research Articles

Hunting for complex cyanides in protostellar ices with the JWST

Nitrogen-bearing complex organic molecules have been commonly detected in the gas phase but not yet in interstellar ices. This has led to the long-standing question of whether these molecules form in the gas phase or in ices. The James Webb Space Telescope (JWST) offers the sensitivity, spectral resolution, and wavelength coverage needed to detect them in ices and investigate whether their abundance ratios are similar in gas and ice. We report the first tentative detection of CH3CN, C2H5CN and the simple molecule, N2O, based on the CN-stretch band in interstellar ices toward three (HOPS 153, HOPS 370, and IRAS 20126+4104) out of the five protostellar systems observed as part of the Investigating Protostellar Accretion (IPA) GO program with JWST-NIRSpec. We also provide upper limits for the two other sources with smaller luminosities in the sample. We detect OCN− in the ices of all sources with typical CH3CN/OCN− ratios of around 1. Ice and gas column density ratios of the nitrogen-bearing species with respect to each other are better matched than those with respect to methanol, which are a factor of ~5 larger in the ices than the gas. We attribute the elevated ice column densities with respect to methanol to the difference in snowline locations of nitrogen-bearing molecules and of methanol, biasing the gas-phase observations toward fewer nitrogen-bearing molecules. Moreover, we find tentative evidence of the enhancement of OCN−, CH3CN, and C2H5CN in warmer ices; although, the formation of these molecules likely starts along with methanol in the cold prestellar phase. Future surveys combining NIRSpec and MIRI, and additional laboratory spectroscopic measurements of C2H5CN ice, are necessary for robust detection and conclusions on the formation history of complex cyanides.

The GUAPOS project – V: The chemical ingredients of a massive stellar protocluster in the making

ABSTRACT Most stars, including the Sun, are born in rich stellar clusters containing massive stars. Therefore, the study of the chemical reservoir of massive star-forming regions is crucial to understand the basic chemical ingredients available at the dawn of planetary systems. We present a detailed study of the molecular inventory of the hot molecular core G31.41+0.31 from the project GUAPOS (G31.41+0.31 Unbiased ALMA sPectral Observational Survey). We analyse 34 species for the first time plus 20 species analysed in previous GUAPOS works, including oxygen, nitrogen, sulfur, phosphorus, and chlorine species. We compare the abundances derived in G31.41+0.31 with those observed in other chemically-rich sources that represent the initial and last stages of the formation of stars and planets: the hot corino in the Solar-like protostar IRAS 16293-2422 B, and the comets 67P/Churyumov-Gerasimenko and 46P/Wirtanen. The comparative analysis reveals that the chemical feedstock of the two star-forming regions are similar. The abundances of oxygen- and nitrogen-bearing molecules exhibit a good correlation for all pair of sources, including the two comets, suggesting a chemical heritage of these species during the process of star formation, and hence an early phase formation of the molecules. However, sulfur- and phosphorus-bearing species present worse correlations, being more abundant in comets. This suggests that while sulfur- and phosphorus-bearing species are pre-dominantly trapped on the surface of icy grains in the hot close surroundings of protostars, they could be more easily released into gas phase in comets, allowing their cosmic abundances to be almost recovered.

Experimental study of the binding energy of NH3 on different types of ice and its impact on the snow line of NH3 and H2O

Context. Nitrogen-bearing molecules (such as N2H+ and NH3) are excellent tracers of high-density and low-temperature regions, such as dense cloud cores. Notably, they could help advance the understanding of snow lines in protoplanetary discs and the chemical evolution of comets. However, much remains unknown about the chemistry of N-bearing molecules on grain surfaces, which could play an important role in their formation and evolution. Aims. In this work, we experimentally study the behaviour of NH3 on surfaces that mimic grain surfaces under interstellar conditions in the presence of some other major components of interstellar ices (i.e. H2O, CO2, CO). We measure the binding energy distributions of NH3 from different H2O ice substrates and also investigate how it could affect the NH3 snow line in protoplanetary discs. Methods. We performed laboratory experiments using the ultra-high vacuum (UHV) set-up VENUS (VErs des NoUvelles Syntheses). We co-deposited NH3 along with other adsorbates (H2O, 13CO, and CO2) and performed temperature programmed desorption (TPD) and temperature programmed-during exposure desorption (TP-DED) experiments. The experiments were monitored using a quadrupole mass spectrometer and a Fourier transform reflection absorption infrared spectrometer (FT-RAIRS). We obtained the binding energy distribution of NH3 on crystalline ice (CI) and compact amorphous solid water ice by analysing the TPD profiles of NH3 obtained after depositions on these substrates. Results. In the co-deposition experiments, we observed a significant delay in the desorption and a decrease of the desorption rate of NH3 when H2O is introduced into the co-deposited mixture of NH3–13CO or NH3–CO2, which is not the case in the absence of H2O. Secondly, we noticed that H2O traps roughly 5–9% of the co-deposited NH3, which is released during the phase change of water from amorphous to crystalline. Thirdly, we obtained a distribution of binding energy values of NH3 on both ice substrates instead of an individual value, as assumed in previous works. For CI, we obtained an energy distribution between 3780 K and 4080 K, and in the case of amorphous ice, the binding energy values were distributed between 3630 K and 5280 K; in both cases we used a pre-exponential factor of A = 1.94 × 1015 s−1. Conclusions. From our experiments, we conclude that the behaviour of NH3 is significantly influenced by the presence of water, owing to the formation of hydrogen bonds with water, in line with quantum calculations. This interaction, in turn, preserves NH3 on the grain surfaces longer and up to higher temperatures, making it available closer to the central protostar in protoplanetary discs than previously thought. It explains well why the NH3 freeze-out in pre-stellar cores is efficient. When present along with H2O, CO2 also appears to impact the behaviour of NH3, retaining it at temperatures similar to those of water. This may impact the overall composition of comets, particularly the desorption of molecules from their surface as they approach the Sun.

Astrochemical Diagnostics of the Isolated Massive Protostar G28.20-0.05

We study the astrochemical diagnostics of the isolated massive protostar G28.20-0.05. We analyze data from Atacama Large Millimeter/submillimeter Array 1.3 mm observations with a resolution of 0.″2 (∼1000 au). We detect emission from a wealth of species, including oxygen-bearing (e.g., H2CO, CH3OH, CH3OCH3), sulfur-bearing (SO2, H2S), and nitrogen-bearing (e.g., HNCO, NH2CHO, C2H3CN, C2H5CN) molecules. We discuss their spatial distributions, physical conditions, correlation between different species, and possible chemical origins. In the central region near the protostar, we identify three hot molecular cores (HMCs). HMC1 is part of a millimeter continuum ring-like structure, is closest in projection to the protostar, has the highest temperature of ∼300 K, and shows the most line-rich spectra. HMC2 is on the other side of the ring, has a temperature of ∼250 K, and is of intermediate chemical complexity. HMC3 is further away, ∼3000 au in projection, cooler (∼70 K), and is the least line-rich. The three HMCs have similar mass surface densities (∼10 g cm−2), number densities (n H ∼ 109 cm−3), and masses of a few solar masses. The total gas mass in the cores and in the region out to 3000 au is ∼25 M ⊙, which is comparable to that of the central protostar. Based on spatial distributions of peak line intensities as a function of excitation energy, we infer that the HMCs are externally heated by the protostar. We estimate column densities and abundances of the detected species and discuss the implications for hot core astrochemistry.

Investigating the hot molecular core, G10.47+0.03: A pit of nitrogen-bearing complex organic molecules

Context. Recent observations have shown that Nitrogen-bearing complex organic species are present in large quantities in star-forming regions. Thus, investigating the N-bearing species in a hot molecular core, such as G10.47+0.03, is crucial to understanding the molecular complexity in star-forming regions. They also allow us to investigate the chemical and physical processes that determine the many phases during the structural and chemical evolution of the source in star-forming regions. Aims. The aim of this study is to investigate the spatial distribution and the chemical evolution states of N-bearing complex organic molecules in the hot core G10.47+0.03. Methods. We used the Atacama Large Millimeter/submillimeter Array (ALMA) archival data of the hot molecular core G10.47+0.03. The extracted spectra were analyzed assuming local thermodynamic equilibrium (LTE). LTE methods are used to estimate the column density of observed species. Furthermore, robust methods such as Markov chain Monte Carlo (MCMC) and rotational diagram methods are implemented for molecules for which multiple transitions were identified to constrain the temperature and column density. Finally, we used the Nautilus gas-grain code to simulate the nitrogen chemistry in the hot molecular core. We carried out both 0D and 1D simulations of the source. We compared the simulated abundances with observational results. Results. We report various transitions of nitrogen-bearing species (NH2CN, HC3N, HC5N, C2H3CN, C2H5CN, and H2NCH2CN) together with some of their isotopologues and isomers. Besides this, we also report the identification of CH3CCH and one of its isotopologues. We present detailed chemical simulation results to investigate the possible N-bearing chemistry in the source. Conclusions. In this study, various transitions of nitrogen-bearing molecules are identified and discussed. The emissions originating from vinyl cyanide, ethyl cyanide, cyanoacetylene, and cyanamide are compact, which could be explained by our astrochemical modeling. Our 0D model shows that the chemistry of certain N-bearing molecules can be very sensitive to initial local conditions such as density or dust temperature. In our 1D model, simulated higher abundances of species such as HCN, HC3N, and HC5N toward the inner shells of the source confirm the observational findings.

Preferential destruction of NH2-bearing complex interstellar molecules via gas-phase proton-transfer reactions.

Complex, nitrogen-bearing interstellar molecules, especially amines, are targets of particular interest for detection in star- and planet-forming regions, due to their possible relevance to prebiotic chemistry. However, these NH2-bearing molecules are not universally detected in sources where other, oxygen-bearing complex organic molecules (COMs) are often plentiful. Nevertheless, recent astrochemical models have often predicted large abundances for NH2-bearing complex organics, based on their putative production on dust grains. Here we investigate a range of new gas-phase proton-transfer reactions and their influence on the destruction of COMs. As in past studies, reactions between protonated COMs and ammonia (NH3) are found to be important in prolonging gas-phase COM lifetimes. However, for molecules with proton affinities (PA) greater than that of ammonia, proton-transfer reactions result in drastic reductions in abundances and lifetimes. Ammonia acts as a sink for proton transfer from low-PA COMs, while passing on protons to high-PA species; dissociative recombination with electrons then destroys the resulting ions. Species strongly affected include methylamine (CH3NH2), urea (NH2C(O)NH2) and others bearing the NH2 group. The abundances of these species show a sharp time dependence, indicating that their detectability may rest on the precise chemical age of the source. Rapid gas-phase destruction of glycine (NH2CH2COOH) in the models suggests that its future detection may be yet more challenging than previously hoped.

Simple lattice model of surface-confined metal–organic networks consisting of linear nitrogen-bearing molecules and transition metals

How do the size of nitrogen-bearing groups of the linker-molecule and the type of the coordinating metal center affect the phase behavior and thermal stability of surface-confined metal–organic layers?

Interaction of CH3CN and CH3NC with He: Potential Energy Surfaces and Low-Energy Scattering.

Several nitrogen-bearing molecules, such as methyl cyanide (or acetonitrile, CH3CN) and methyl isocyanide (CH3NC) of interest here, have been observed in various astrophysical environments. The accurate modeling of their abundance requires the calculation of rate coefficients for their collisional excitation with species such as He atoms or H2 molecules at low temperatures. In this work we compute new three-dimensional potential energy surfaces for the CH3NC-He and CH3CN-He van der Waals complexes by means of the explicitly correlated coupled cluster approach with single, double and perturbative triple excitation CCSD(T)/F12a in conjunction with the aug-cc-pVTZ basis set. We find a global minimum with De = 55.10 and 58.61 cm-1 for CH3CN-He and CH3NC-He, respectively, while the dissociation energy D0 of the complexes are 18.64 and 18.65 cm-1, respectively. Low-energy scattering calculations of pure rotational (de-)excitation of CH3CN and CH3NC by collision with He atoms are carried out with the close-coupling method, and the collisional cross sections of ortho- and para-CH3NC and CH3CN are computed for kinetic energies up to 100 cm-1. While the PESs for both complexes are qualitatively similar, that of CH3NC-He is more anisotropic, leading to different propensity rules for rotational excitation. For CH3NC-He, we find that |Δj| = 1 transitions are dominant at low kinetic energy and a propensity rule that favors odd Δj transitions is observed, whereas for CH3CN the dominant cross sections are associated with transitions with |Δj| = 2. We expect that the findings of this study will be beneficial for astrophysical investigations as well as laboratory experiments.

Sustainable Synthesis of Bright Fluorescent Nitrogen-Doped Carbon Dots from Terminalia chebula for In Vitro Imaging.

In this study, sustainable, low-cost, and environmentally friendly biomass (Terminalia chebula) was employed as a precursor for the formation of nitrogen-doped carbon dots (N-CDs). The hydrothermally assisted Terminalia chebula fruit-derived N-CDs (TC-CDs) emitted different bright fluorescent colors under various excitation wavelengths. The prepared TC-CDs showed a spherical morphology with a narrow size distribution and excellent water dispensability due to their abundant functionalities, such as oxygen- and nitrogen-bearing molecules on the surfaces of the TC-CDs. Additionally, these TC-CDs exhibited high photostability, good biocompatibility, very low toxicity, and excellent cell permeability against HCT-116 human colon carcinoma cells. The cell viability of HCT-116 human colon carcinoma cells in the presence of TC-CDs aqueous solution was calculated by MTT assay, and cell viability was higher than 95%, even at a higher concentration of 200 μg mL-1 after 24 h incubation time. Finally, the uptake of TC-CDs by HCT-116 human colon carcinoma cells displayed distinguished blue, green, and red colors during in vitro imaging when excited by three filters with different wavelengths under a laser scanning confocal microscope. Thus, TC-CDs could be used as a potential candidate for various biomedical applications. Moreover, the conversion of low-cost/waste natural biomass into products of value promotes the sustainable development of the economy and human society.

Complex Organic Molecules Detected in 12 High-mass Star-forming Regions with Atacama Large Millimeter/submillimeter Array

Recent astrochemical models and experiments have explained that complex organic molecules (COMs; molecules composed of six or more atoms) are produced on the dust grain mantles in cold and dense gas in prestellar cores. However, the detailed chemical processes and the roles of physical conditions on chemistry are still far from understood. To address these questions, we investigated 12 high-mass star-forming regions using Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations. They are associated with 44/95 GHz class I and 6.7 GHz class II CH3OH masers, indicative of undergoing active accretion. We found 28 hot cores with COM emission among 68 continuum peaks at 1.3 mm and specified 10 hot cores associated with 6.7 GHz class II CH3OH masers. Up to 19 COMs are identified including oxygen- and nitrogen-bearing molecules and their isotopologues in cores. The derived abundances show a good agreement with those from other low- and high-mass star-forming regions, implying that the COM chemistry is predominantly set by the ice chemistry in the prestellar core stage. One clear trend is that the COM detection rate steeply grows with the gas column density, which can be attributed to the efficient formation of COMs in dense cores. In addition, cores associated with a 6.7 GHz class II CH3OH maser tend to be enriched with COMs. Finally, our results suggest that the enhanced abundances of several molecules in our hot cores could be originated by the active accretion as well as different physical conditions of cores.

The Molecular Composition of Shadowed Proto-solar Disk Midplanes Beyond the Water Snowline

The disk midplane temperature is potentially affected by the dust traps/rings. The dust depletion beyond the water snowline will cast a shadow. In this study, we adopt a detailed gas-grain chemical reaction network, and investigate the radial gas and ice abundance distributions of dominant carbon-, oxygen-, and nitrogen-bearing molecules in disks with shadow structures beyond the water snowline around a proto-solar-like star. In shadowed disks, the dust grains at r ∼ 3–8 au are predicted to have more than ∼5–10 times the amount of ices of organic molecules such as H2CO, CH3OH, and NH2CHO, saturated hydrocarbon ices such as CH4 and C2H6, in addition to H2O, CO, CO2, NH3, N2, and HCN ices, compared with those in non-shadowed disks. In the shadowed regions, we find that hydrogenation (especially of CO ice) is the dominant formation mechanism of complex organic molecules. The gas-phase N/O ratios show much larger spatial variations than the gas-phase C/O ratios; thus, the N/O ratio is predicted to be a useful tracer of the shadowed region. N2H+ line emission is a potential tracer of the shadowed region. We conclude that a shadowed region allows for the recondensation of key volatiles onto dust grains, provides a region of chemical enrichment of ices that is much closer to the star than within a non-shadowed disk, and may explain to some degree the trapping of O2 ice in dust grains that formed comet 67P/Churyumov-Gerasimenko. We discuss that, if formed in a shadowed disk, Jupiter does not need to have migrated vast distances.

Chemical Differentiation and Temperature Distribution on a Few au Scale around the Protostellar Source B335

Resolving physical and chemical structures in the vicinity of a protostar is of fundamental importance for elucidating their evolution to a planetary system. In this context, we have conducted 1.2 mm observations toward the low-mass protostellar source B335 at a resolution of 0.″03 with the Atacama Large Millimeter/submillimeter Array. More than 20 molecular species including HCOOH, NH2CHO, HNCO, CH3OH, CH2DOH, CHD2OH, and CH3OD are detected within a few tens au around the continuum peak. We find a systematic chemical differentiation between oxygen-bearing and nitrogen-bearing organic molecules by using the principal component analysis for the image cube data. The distributions of the nitrogen-bearing molecules are more compact than those of the oxygen-bearing ones except for HCOOH. The temperature distribution of the disk/envelope system is revealed by a multiline analysis for each of HCOOH, NH2CHO, CH3OH, and CH2DOH. The rotation temperatures of CH3OH and CH2DOH at the radius of 0.″06 along the envelope direction are derived to be 150–165 K. On the other hand, those of HCOOH and NH2CHO, which have a smaller distribution, are 75–112 K, and are significantly lower than those for CH3OH and CH2DOH. This means that the outer envelope traced by CH3OH and CH2DOH is heated by additional mechanisms rather than protostellar heating. We here propose the accretion shock as the heating mechanism. The chemical differentiation and the temperature structure on a scale of a few au provide us with key information to further understand chemical processes in protostellar sources.

Quantitative analysis of carbazoles and hydrocarbons in condensates and oils using comprehensive GC–MS/MS and comparative GC–MS analyses

Analysis of carbazoles, nitrogen-bearing molecules found in most petroleum fluids, is often limited to GC–MS or GC × GC methods, both of which require prior sample treatment to concentrate components and minimize matrix interference. Recently, workers have introduced a novel method for analysis of carbazoles, using GC–MS/MS, without these required cleanup procedures. In this study, six thermal condensate and crude oil samples are analyzed for carbazoles and other components in their whole-petroleum and fractionated forms by both Selective Ion Monitoring (SIM) and Multiple Reaction Monitoring (MRM) methods to compare the differences. Five additional samples are then analyzed by a new hybrid MRM-SIM mode in a single run measuring over 200 components. We provide a geochemical interpretation of each sample set, based primarily on the MRM-derived carbazole abundance. In addition, we present an updated method for the analysis of carbazoles using GC–MS/MS. This study explores (1) the benefits of a hybrid MRM-SIM method for the analysis of carbazoles and other molecular markers in a single run, (2) surrogate standards to accurately quantify up to 21 species of carbazole molecules, and (3) evidence for the advantage of GC–MS/MS over previous methods for evaluations of thermal condensates and heavy crude oil. Our recommended process for the analysis of carbazole species is whole petroleum analysis using the hybrid MRM-SIM method. Even if unsuccessful with whole petroleum, the analysis of concentrated fractions analyzed on the hybrid MRM-SIM method has advantages over previous methods.

ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – X. Chemical differentiation among the massive cores in G9.62+0.19

ABSTRACTInvestigating the physical and chemical structure of massive star-forming regions is critical for understanding the formation and early evolution of massive stars. We performed a detailed line survey toward six dense cores, named MM1, MM4, MM6, MM7, MM8, and MM11, in the G9.62+0.19 star-forming region resolved in Atacama Large Millimeter/submillimeter Array (ALMA) band 3 observations. Toward these cores, about 172 transitions have been identified and attributed to 16 species, including organic oxygen-, nitrogen-, and sulphur-bearing molecules and their isotopologues. Four dense cores, MM7, MM8, MM4, and MM11, are line-rich sources. Modelling of these spectral lines reveals that the rotational temperature lies in the range 72–115, 100–163, 102–204, and 84–123 K for MM7, MM8, MM4, and MM11, respectively. The molecular column densities are 1.6 × 1015–9.2 × 1017 cm−2 toward the four cores. The cores MM8 and MM4 show a chemical difference between oxygen- and nitrogen-bearing species, i.e. MM4 is rich in oxygen-bearing molecules, while nitrogen-bearing molecules, especially vibrationally excited HC3N lines, are mainly observed in MM8. The distinct initial temperatures at the accretion phase may lead to this N/O differentiation. Through analysing column densities and spatial distributions of O-bearing complex organic molecules (COMs), we found that C2H5OH and CH3OCH3 might have a common precursor, CH3OH. CH3OCHO and CH3OCH3 are likely chemically linked. In addition, the observed variation in HC3N and HC5N emission may indicate their different formation mechanisms in hot and cold regions.

A resorufin-based fluorescence probe for visualizing biogenic amines in cells and zebrafish.

Biogenic amines (BAs) are a family of nitrogen-bearing natural organic molecules with at least one primary amine, which play an important role in living organisms. Elevated concentration of BAs may cause neuron disorder, Parkinson's disease and many other diseases. Therefore, it is essential to monitor BAs in living organisms. Herein, we reported a resorufin-based fluorescence probe for sensing of various BAs. Upon nucleophilic substitution reaction with BAs, the probe released resorufin, affording to strong fluorescence emission at 592 nm with rapid response (<8 min), good selectivity and a low detection limit (LOD = 0.47 μM). The probe has low cytotoxicity and good membrane permeability, and has been successfully used to visualize BAs in living cells and zebrafish with good performance.

Complex organic molecules in low-mass protostars on Solar System scales

Context.The chemical inventory of planets is determined by the physical and chemical processes that govern the early phases of star formation. Nitrogen-bearing species are of interest as many provide crucial precursors in the formation of life-related matter.Aims.The aim is to investigate nitrogen-bearing complex organic molecules towards two deeply embedded Class 0 low-mass protostars (Perseus B1-c and Serpens S68N) at millimetre wavelengths with the Atacama Large Millimeter/submillimeter Array (ALMA). Next, the results of the detected nitrogen-bearing species are compared with those of oxygen-bearing species for the same and other sources. The similarities and differences are used as further input to investigate the underlying formation pathways.Methods.ALMA observations of B1-c and S68N in Band 6 (~1 mm) and Band 5 (~2 mm) are studied at ~0.5′′ resolution, complemented by Band 3 (~3 mm) data in a ~2.5′′ beam. The spectra are analysed for nitrogen-bearing species using the CASSIS spectral analysis tool, and the column densities and excitation temperatures are determined. A toy model is developed to investigate the effect of source structure on the molecular emission.Results.Formamide (NH2CHO), ethyl cyanide (C2H5CN), isocyanic acid (HNCO, HN13CO, DNCO), and methyl cyanide (CH3CN, CH2DCN, and CHD2CN) are identified towards the investigated sources. Their abundances relative to CH3OH and HNCO are similar for the two sources, with column densities that are typically an order of magnitude lower than those of oxygen-bearing species. The largest variations, of an order of magnitude, are seen for NH2CHO abundance ratios with respect to HNCO and CH3OH and do not correlate with the protostellar luminosity. In addition, within uncertainties, the nitrogen-bearing species have similar excitation temperatures to those of oxygen-bearing species (~100–300 K). The measured excitation temperatures are larger than the sublimation temperatures for the respective species.Conclusions.The similarity of most abundances with respect to HNCO for the investigated sources, including those of CH2DCN and CHD2CN, hints at a shared chemical history, especially the high D-to-H ratio in cold regions prior to star formation. However, some of the variations in abundances may reflect the sensitivity of the chemistry to local conditions such as temperature (e.g. NH2CHO), while others may arise from differences in the emitting areas of the molecules linked to their different binding energies in the ice. The excitation temperatures likely reflect the mass-weighted kinetic temperature of a gas that follows a power law structure. The two sources discussed in this work add to the small number of sources that have been subjected to such a detailed chemical analysis on Solar System scales. Future data from theJames WebbSpace Telescope will allow a direct comparison between the ice and gas abundances of both smaller and larger nitrogen-bearing species.

POSSIBLE ROUTES FOR THE FORMATION OF PREBIOTIC MOLECULES IN THE HORSEHEAD NEBULA

This article presents the results of a study concerning interstellar molecules which are useful for the bookkeeping of the organic content of the universe and for providing a glimpse into prebiotic conditions on Earth and in other environments in the universe. We explored production channels for astrobiological relevant nitrogen-bearing cyclic molecules (N-heterocycles), e. g. pyrrole and pyridine. The present simulations demonstrate how the exploration of a few possible routes of production of N-heterocycles resulted in significant abundances for these species. One particularly efficient class of channels for the production of N-heterocycles incorporates polycyclic aromatic hydrocarbons (PAHs) as catalysts. Thereby, an exploration of a variety of production paths should reveal more species to be target of astrophysical observations.

Precipitation of kerolite and sepiolite associated with Mg-rich carbonates in a cave environment

In Castañar Cave (Cáceres, Spain), Mg-Si phases forming fibres and films occur associated with aragonite, magnesite, huntite and spheroidal dolomite in moonmilk, coatings and crust speleothems. A detailed study of bulk and carbonate-removed samples allowed us to identify the Mg-Si phases as kerolite (Mg3Si4O10(OH)2·nH2O) and sepiolite Mg4Si6O15(OH)2·6(H2O) of variable “crystallinity” and very pure composition. Under the scanning electron microscope, kerolite appears as gelatinous, smooth masses or films, showing some desiccation features. Sepiolite mostly occurs as isolated fibres 50 to 200 nm thick and up to 50 μm long and mats of interwoven fibres of several shapes. Analytical pyrolysis (Py-GC/MS) of the organic matter associated with these minerals in the moonmilk speleothems shows a compound assemblage lacking carbohydrates, nitrogen-bearing molecules and fatty acids, indicating no microbial activity.Kerolite and sepiolite most probably formed abiotically by direct precipitation in the cave waters, in conditions of high silica and magnesium activity and relatively high pH. These conditions were attained by local CO2 degassing taking place in extremely slow drips and capillary waters in speleothems with a large surface area, in a dynamic system where the renovation of infiltrated waters and diagenetic transformations of carbonates and silicates also contributed to significant hydrochemical variability at the microscale.

A Detailed View of the Circumstellar Environment and Disk of the Forming O-star AFGL 4176

Abstract We present a detailed analysis of the disk and circumstellar environment of the forming O-type star AFGL 4176 mm1, placing results from the Atacama Large Millimeter/submillimeter Array (ALMA) into context with multiwavelength data. With ALMA, we detect seventeen 1.2 mm continuum sources within 5″ (21,000 au) of AFGL 4176 mm1. We find that mm1 has a spectral index of 3.4 ± 0.2 across the ALMA band, with &gt;87% of its 1.2 mm continuum emission from dust. The source mm2, projected 4200 au from mm1, may be a companion or a blueshifted knot in a jet. We also explore the morphological differences between the molecular lines detected with ALMA, finding 203 lines from 25 molecules, which we categorize into several morphological types. Our results show that AFGL 4176 mm1 provides an example of a forming O-star with a large and chemically complex disk, which is mainly traced by nitrogen-bearing molecules. Lines that show strong emission on the blueshifted side of the disk are predominantly oxygen-bearing, which we suggest are tracing a disk accretion shock. The molecules C34S, H2CS, and CH3CCN trace a slow wide-angle wind or dense structures in the outflow cavity walls. With the Australia Telescope Compact Array (ATCA), we detect a compact continuum source (&lt;2000 × 760 au) at 1.2 cm, associated with mm1, of which &gt;96% is from ionized gas. The ATCA NH3(1, 1) and (2, 2) emission traces a large-scale (r ∼ 0.5 pc) rotating toroid with the disk source mm1 in the blueshifted part of this structure offset to the northwest.

Identification of Prebiotic Molecules Containing Peptide-like Bonds in a Hot Molecular Core, G10.47+0.03

Abstract After hydrogen, oxygen, and carbon, nitrogen is one of the most chemically active species in the interstellar medium. Nitrogen-bearing molecules are very important as they are actively involved in the formation of biomolecules. Therefore, it is essential to look for nitrogen-bearing species in various astrophysical sources, specifically around high-mass star-forming regions where the evolutionary history is comparatively poorly understood. In this paper, we report on the observation of three potential prebiotic molecules, namely, isocyanic acid (HNCO), formamide (NH2CHO), and methyl isocyanate (CH3NCO), which contain peptide-like bonds (–NH–C(=O)–) in a hot molecular core, G10.47 + 0.03 (hereafter, G10). Along with the identification of these three complex nitrogen-bearing species, we speculate on their spatial distribution in the source and discuss their possible formation pathways under such conditions. A rotational diagram method under local thermodynamic equilibrium has been employed to estimate the excitation temperature and the column density of the observed species. The Markov Chain Monte Carlo method was used to obtain the best-suited physical parameters of G10 as well as line properties of some species. We also determined the hydrogen column density and the optical depth for a different continuum observed in various frequency ranges. Finally, based on these observational results, we have constructed a chemical model to explain the observational findings. We found that HNCO, NH2CHO, and CH3NCO are chemically linked with each other.