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We briefly consider the history of maser variability, and of flaring variability specifically. We consider six proposed flare generation mechanisms, and model them computationally with codes that include saturation and 3-D structure (the last mechanism is modelled in 1-D). Fits to observational light curves have been made for some sources, and we suggest that a small number of observational parameters can diagnose the flare mechanism in many cases. The strongest flares arise from mechanisms that can increase the number density of inverted molecules in addition to by geometrical effects, and in events where unsaturated quiescent masers become saturated during the flare. [ABSTRACT FROM AUTHOR]

Binary interaction with a stellar or planetary companion has been proposed to be the driving mechanism behind large-scale asymmetries, such as spirals and disks, observed within AGB outflows. We developed the first chemical kinetics model that takes the effect of a stellar companions's UV radiation into account. The presence of a stellar companion can initiate a rich photochemistry in the inner wind. Its impact is determined by the intensity of the UV radiation and the extinction the radiation experiences. The outcome of the inner wind photochemistry depends on the balance between two-body reactions and photoreactions. If photoreactions dominate, the outflow can appear molecule-poor. If two-body reactions dominate, chemical complexity within the outflow can increase, yielding daughter species with a large inner wind abundance. A comprehensive view on the molecular content of the outflow, especially combined with abundance profiles, can point towards the presence of a stellar companion. [ABSTRACT FROM AUTHOR]

We present new results from a 3D modelling code for maser flares which provides the user with control over the physical conditions; maser cloud geometry and orientation; and fast runtime via parallelisation. The statistics of simulated observables suggest that achievable amplification may be dependent on viewpoints of the source and that a randomly placed observer is likely to detect an unremarkable blue- or red-shifted maser unless the line-of-sight direction is optimal for maser amplification. A preliminary model of masers towards π 1 Gru based on SPH simulations also shows promising consistency with ALMA observations of high- j SiO transitions from the source. [ABSTRACT FROM AUTHOR]

In the interstellar medium, inelastic collisions are so rare that they cannot maintain a local thermodynamical equilibrium (LTE). Atomic and molecular populations therefore do not follow a simple Boltzmann distribution and non-LTE spectra are the rule rather than the exception. In such conditions, accurate state-to-state collisional data are crucial for a quantitative interpretation of spectra. In recent years, considerable progress has been made in quantum calculations of inelastic cross sections for a variety of targets, types of transitions and projectiles. For a few benchmark species, detailed comparisons between theory and experiment were also carried out at the state-to-state level and in the quantum regime. In this article, we highlight such comparisons for three important molecules: CO, H2O and CH+. We also describe current computational efforts to extend these advances to ever larger targets, new transition types, and new environments (e.g. stellar envelopes or cometary atmospheres). [ABSTRACT FROM AUTHOR]

Isopropyl-cyanide (iso-PrCN) was recently observed in Sagittarius B2 with an abundance higher than its straight-chain structure isomer (n-PrCN). Here we study theoretically by means of [UMP2(full)/aug-cc-pVTZ/Amber] a hybrid ab initio/molecular mechanics methodology, the routes leading to its formation on a formaldehyde doped water ice grain model of the interstellar medium. The reaction path and the energetics are calculated, the mechanism is found to be exothermic by ∼ 30 kcal/mol and the barrier is ∼ 70 kcal/mol. We use the CVT/ZCT semiclassical method to predict the kinetics of the reaction path starting from initially adsorbed HCN and CH2CHCH3 molecules colliding from the gas phase over the temperature range [100–500K]. [ABSTRACT FROM AUTHOR]

Dust particles covered by icy mantles play a crucial role in the formation of molecules in the Interstellar Medium (ISM). These icy mantles are mainly composed of water but many other chemical species are also contained in these ices. These compounds can diffuse and meet each other to react. It is through these surface reactions that new saturated species are formed. Photodissociation reactions are also thought to play a crucial role in the formation of radical species. Complex organic molecules are formed through an intricated network of photodissociation and surface reactions. Both type of reactions release energy. Surface reactions are typically exothermic by a few eV, whereas photodissociation reactions are triggered by the absorption of a UV photon, resulting in the formation of highly excited products. The excited reaction products can apply this energy for desorption or diffusion, making products more mobile than predicted when considering only thermal hopping. The energy could further lead to annealing or deformation of the ice structure. Here we would like to quantify the relative importance of these different energy dissipation routes. For this we performed thousands of Molecular Dynamics simulations for three different species (CO2, H2O and CH4) on top of a water ice surface. We consider different types of excitation such as translational, rotational, and/or vibrational excitation. The applied substrate is an amorphous solid water surface (ASW). [ABSTRACT FROM AUTHOR]

Carbonaceous meteorites contain a large variety of complex organic molecules, including amino acids, nucleobases, sugar derivatives, amphiphiles, and other compounds of astrobiological interest. Photoprocessing of ices condensed on cold grains with ultraviolet (UV) photons was proposed as an efficient way to form such complex organics in astrophysical environments. This hypothesis was confirmed by laboratory experiments simulating photo-irradiation of ices containing H2O, CH3OH, CO, CO2, CH4, H2CO, NH3, HCN, etc., condensed on cold (~10–80 K) substrates. These experiments resulted in the formation of amino acids, nucleobases, sugar derivatives, amphiphilic compounds, and other organics comparable to those identified in carbonaceous meteorites. This work presents results for the formation of sugars, sugar alcohols, sugar acids, and their deoxy variants from the UV irradiation of ices containing H2O and CH3OH in relative proportions 2:1, and their comparison with meteoritic data. The formation mechanisms of these compounds and the astrobiological implications are also discussed. [ABSTRACT FROM AUTHOR]

We present the results of an experimental study on the interaction of D atoms with Mg-rich amorphous silicates. The effects of D irradiation have been analyzed by infrared spectroscopy. The results indicate that HD forms by abstraction of hydrogen atoms chemisorbed in the hydroxyl groups of silicate grains. The formation process occurs for grain and atom temperatures relevant to photodissociation regions. [ABSTRACT FROM AUTHOR]

Chemistry in the interstellar medium is generally out-of-equilibrium and as such is kinetically controlled by a set of time-dependent equations, both for gas-phase chemistry and solid-state chemistry. The competition between the different possible reactions will determine toward which complex molecules the chemical network is driven to. The formation of complex molecules on the surface of the grains or in the ice mantle covering them is set by the diffusion-reaction equation, which is depending on temperature dependent reaction rate constants and diffusion coefficients. This paper shows how these two parameters can be experimentally determined by laboratory experiments. It also shows how the ice mantle reorganization plays an important role in the trapping and reactivity, which leads to the formation of complex organic molecules. [ABSTRACT FROM AUTHOR]

Two laboratory emission spectrometers have been designed and described previously. Here, we present a follow-up study with special focus on absolute intensity calibration of the new SURFER-spectrometer (SUbmillimeter Receiver For Emission spectroscopy of Rotational transitions), operational between 300 and 400 GHz and coincident with ALMA (Atacama Large Millimeter/submillimeter Array) Band 7. Furthermore, we present a feasibility study to extend the detection frequencies up to 2 THz. First results have been obtained using the SOFIA (Stratospheric Observatory for IR Astronomy) upGREAT laboratory setup which is located at the University of Cologne. Pure rotational spectra of the complex molecule vinyl cyanide have been obtained and are used to give an estimate on the sensitivity to record ro-vibrational transitions of molecules with astrophysical importance at 2 THz. [ABSTRACT FROM AUTHOR]

Electrospray ionisation has revolutionised mass spectrometry. Coupled to high mass resolution, it provides the stoichiometric formula of a lot of molecules in a mixture. The link between the mass spectrometry data and the chemical description relies on an interpretation of the measured masses. We present here the tools and tricks developed to exploit Orbitrap mass spectra. This piece of work focuses on the numerical method to assign a molecular formula to a measured mass. The problem is restrained to the solving of the Diophantine equation where the constant coefficients are stoichiometric groups. Peculiar case of a set of convenient groups is given with the chemical constraints it brings to the problem. [ABSTRACT FROM AUTHOR]

The James Webb Space Telescope (JWST) is expected to be launched in 2021. The JWST's science instruments will provide high quality spectra acquired in the line of sight to young stellar objects whose interpretation will require a robust database of laboratory data. With this in mind, an experimental work is in progress in the Laboratory for Experimental Astrophysics in Catania to study the profile (shape, width, and peak position) of the main infrared bands of molecular species expected to be present in icy grain mantles. Our study also takes into account the modifications induced on icy samples by low-energy cosmic ray bombardment and by thermal processing. Here we present some recent results on deuterium hydrogen monoxide (HDO), N-bearing species, and carbon dioxide (CO2). [ABSTRACT FROM AUTHOR]

The outflows of asymptotic giant branch (AGB) stars are important astrochemical laboratories, rich in molecular material and host to various chemical processes, including dust formation. Since the different chemistries are relatively easily probed, AGB outflows are ideal testbeds within the wider astrochemical community. Recent observations are pushing the limits of both our current chemical models and radiative transfer routines. Current chemical models are restricted by the completeness of their chemical networks and the accuracy of the reaction rates. The molecular abundances retrieved by radiative transfer routines are strongly dependent on collisional rates, which are often not measured or calculated for molecules of interest. To further our understanding of the chemistry within the outflow, collaboration with the laboratory astrophysics community is essential. This collaboration is mutually beneficial, as it in turn provides new science questions for laboratory experiments and computations. [ABSTRACT FROM AUTHOR]

Recent experimental and theoretical works concerning gas-phase radical-neutral reactions involving Complex Organic Molecules are reviewed in the context of cold interstellar objects with a special emphasis on the OH + CH3OH reaction and its potential impact on the formation of CH3O. [ABSTRACT FROM AUTHOR]

Maser theory continues to be driven by advances in observational techniques. Here, I consider the responses to VLBI with space-Earth baselines and cross-correlation spectroscopy (a re-consideration of coherence properties), routine observation in full-Stokes polarization (a re-casting of the polarization transfer equations), and long-term variability monitoring (3-D modelling of irregular domains). [ABSTRACT FROM AUTHOR]

Spacecraft have visited Jupiter and Saturn at all phases of the solar cycle and thus we have a wealth of data with which to explore both upstream parameters and magnetospheric response. In this paper we review upstream parameters including interplanetary magnetic field strength and direction, solar wind dynamic pressure, plasma beta and Mach number. We consider the impact of changing solar wind on dayside coupling via reconnection. We also comment on how solar UV flux variability over a solar cycle influences the plasma and neutral tori in the inner magnetospheres of Jupiter and Saturn, and thus estimate the solar cycle effects on internally driven magnetospheric dynamics. Finally we place our results in the context of the now complete set of data from the Cassini mission at Saturn and the current data streaming in from Juno at Jupiter, outlining future avenues for research. [ABSTRACT FROM AUTHOR]

Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. Especially, saturated, hydrogen-rich molecules are formed through surface chemistry. Astrochemical models have developed over the decades to understand the molecular processes in the interstellar medium, taking into account grain surface chemistry. However, essential input information for gas-grain models, such as binding energies of molecules to the surface, have been derived experimentally only for a handful of species, leaving hundreds of species with highly uncertain estimates. Moreover, some fundamental processes are not well enough constrained to implement these into the models. The proceedings gives three examples how computational chemistry techniques can help answer fundamental questions regarding grain surface chemistry. [ABSTRACT FROM AUTHOR]

This paper provides a brief overview of the journey of molecules through the Cosmos, from local diffuse interstellar clouds and PDRs to distant galaxies, and from cold dark clouds to hot star-forming cores, protoplanetary disks, planetesimals and exoplanets. Recent developments in each area are sketched and the importance of connecting astronomy with chemistry and other disciplines is emphasized. Fourteen challenges for the field of Astrochemistry in the coming decades are formulated. [ABSTRACT FROM AUTHOR]

The detection of iso -propyl cyanide (i -C3H7CN) toward the Galactic Center hot-core source Sgr B2(N) (by Belloche et al. 2014) marked the first interstellar detection of an aliphatic molecule with a branched carbon-chain structure. Surprisingly, this branched form was found to have an almost equal abundance with its straight-chain homologue, normal-propyl cyanide (i : n = 0.40 ± 0.06). The detection of this first example of an interstellar molecule with a side-chain raises the question as to how prominent such structures may be in interstellar chemistry, and whether the large branched-to-straight chain ratio is maintained for even larger molecules. Here are presented recently published models that simulate the chemistry occurring in Sgr B2(N) using a chemical network that explicitly includes the straight-chain and branched forms of propyl cyanide (normal / iso) and butyl cyanide (normal / iso / sec / tert), as well as butane (n / i) and pentane (n / i / neo). Formation is assumed to occur on dust-grain surfaces, but a full complement of destruction mechanisms is included both on the grains and in the gas phase. The models suggest that branched structures become increasingly dominant as molecular sizes increase. In the case of butyl cyanide, the sec form is at least ∼2 times more abundant than the straight-chain normal form, and together the branched forms dominate normal -butyl cyanide by a factor of at least 3. The results for the larger alkanes suggest similarly large ratios of branched to straight-chain molecules. A key set of reactions in the surface/ice chemistry of interstellar nitriles is found to be the addition of the CN radical to unsaturated hydrocarbons, especially acetylene and ethene. The models also predict that the dominant, sec form of butyl cyanide reaches a peak abundance equal to that of n -propyl cyanide, albeit with a smaller emission radius. This makes s -C4H9CN a good candidate for detection. New ALMA observations to search for this molecule are ongoing. [ABSTRACT FROM AUTHOR]

The molecular composition of the stellar outflows of AGB stars is determined by the stellar elemental carbon-to-oxygen abundance ratio, together with the physical circumstances in the innermost region of the outflow. Near the stellar surface, thermal equilibrium (TE) can be assumed. This leads to a certain molecular composition with a O- or C-rich signature. However, several molecular species have been detected that are not expected to be present in the inner region under the assumption of TE chemistry. As a solution to explain the presence of these unexpected species, non-equilibrium chemistry in the inner region of the outflow has been proposed. The outflows of AGB stars are generally not spherically symmetric or homogeneous, which influences the penetration of interstellar UV photons throughout the outflow. We investigate the effect of a clumpy, non-homogeneous outflow on the composition of the inner region by introducing a simple porosity formalism in our chemical model. [ABSTRACT FROM AUTHOR]

Gas-phase methanol was recently detected in a protoplanetary disk for the first time with ALMA. The peak abundance and distribution of methanol observed in TW Hya differed from that predicted by chemical models. Here, the chemistry of methanol gas and ice is calculated using a physical model tailored for TW Hya with the aim to contrast the results with the recent detection in this source. New pathways for the formation of larger complex molecules (e.g., ethylene glycol) are included in an updated chemical model, as well as the fragmentation of methanol ice upon photodesorption. It is found that including fragmentation upon photodesorption improves the agreement between the peak abundance reached in the chemical models with that observed in TW Hya (∼10−11 with respect to H2); however, the model predicts that the peak in emission resides a factor of 2 − 3 farther out in the disk than the ALMA images. Reasons for the persistent differences in the gas-phase methanol distribution between models and the observations of TW Hya are discussed. These include the location of the ice reservoir which may coincide with the compact mm-dust disk (≲ 60 au) and sources of gas-phase methanol which have not yet been considered in models. The possibility of detecting larger molecules with ALMA is also explored. Calculations of the rotational spectra of complex molecules other than methanol using a parametric model constrained by the TW Hya observations suggest that the detection of individual emission lines of complex molecules with ALMA remains challenging. However, the signal-to-noise ratio can be enhanced via stacking of multiple transitions which have similar upper energy levels. [ABSTRACT FROM AUTHOR]

Methanol is ubiquitous in star-forming regions, and has recently been detected in a protoplanetary disk. Astrochemical models have shown that methanol photolysis contributes to complex organic chemistry in interstellar ices. While some methanol photolysis branching ratios have been measured, infrared condensed-phase measurements rely on assumptions about the chemistry, and mass spectrometric measurements cannot distinguish structural isomers. To address these challenges, we are using pure rotational spectroscopy to quantitatively probe the methanol photolysis products. We use a VUV laser to dissociate methanol in the throat of a supersonic expansion, and probe the products downstream after cooling is complete. We then use a rotational diagram analysis to determine the relative density of each product relative to methanol. We have detected the methoxy, hydroxymethyl, and formaldehyde photolysis products. We present here the experimental setup and the initial results and discuss these results in the context of interstellar chemistry. [ABSTRACT FROM AUTHOR]

The diffusion and photoprocessing of molecules within interstellar ices has been verified experimentally but often not fully included in astrochemical models. With models that consider photodissociation, binary reactions, and diffusion for molecules on the surface and in bulk ice, we explored the chemistry of interstellar and circumstellar ices in gravitationally contracting low-mass starless and prestellar cores, and a protostellar envelope. Results. Photoprocessing gradually converts mixed H2O and CO ices into CO2 and allows for a late synthesis of icy organic species. Different layers within a single icy mantle favor the synthesis different species. Deuterium-rich molecules are concentrated on the outer surface of ice. Formation of organic molecules in bulk ice lowers their average deuterium content. The abundances of major icy species can be changed by about 25-50 % because of ice photoprocessing. Inter-layer diffusion of icy species allows sequential evaporation in protostellar envelopes, which occurs over a prolonged period. [ABSTRACT FROM AUTHOR]

In dense interstellar clouds that are shielded from high-energy radiation (e.g., UV photons or cosmic rays), H-atom addition and abstraction reactions that take place on grain surfaces play principal roles in the synthesis or decomposition of complex organic molecules (COMs). These reactions are extensively investigated with laboratory experiments by bombarding astrophysical analogue ices with a beam of low-temperature H atoms. Here we demonstrate that, although 2-4 K solid para-H2 does not represent a typical environment of the surface of interstellar grains, para-H2 matrix isolation combined with IR spectroscopy is a complementary tool to sensitively detect astrochemical hydrogenation and dehydrogenation processes. [ABSTRACT FROM AUTHOR]

Ubiquitous strong mid-infrared emission bands are observed towards many objects and are attributed to interstellar Polycyclic Aromatic Hydrocarbons (PAHs). PAHs are ionized, or even dissociate, when exposed to strong interstellar radiation fields. By means of ion trap mass spectrometry, light-induced dissociation patterns of PAH cations are measured and the mid-infrared spectroscopic signatures of the parent ion and its dissociation products are characterized. These results are then combined with density functional theory (DFT) calculations to obtain insight into the dissociation characteristics of interstellar PAHs at a molecular level. [ABSTRACT FROM AUTHOR]

Interstellar carbon has been detected in both gas-phase molecules and solid particles. The goal of this study is to identify the link between these two phases of cosmic carbon. Here we report preliminary results on the low temperature formation of carbonaceous dust grains from gas-phase aromatic hydrocarbon precursors. This is done using the supersonic expansion of an argon jet seeded with aromatic molecules and exposed to an electrical discharge. We report experimental evidence of efficient carbon dust condensation from aromatic molecules including benzene and naphthalene. The molecular content of the solid grains is probed with laser desorption mass spectrometry. The mass spectra reveal a rich molecular composition including fragments of the parent molecule but also growth into larger molecular species. [ABSTRACT FROM AUTHOR]

Water ice is the dominant constituent of icy grain mantles in the interstellar medium, and as such one of the most abundant species during all stages of star and planet formation. Its formation through atom addition reactions on grain surfaces, its destruction through different desorption channels, and its influence on the chemistry and desorption efficiencies of other species in icy grain mantles have all been the objects of intense study. This contribution reviews our current understanding of these processes, and the laboratory experiments that have been instrumental in establishing the existing paradigm. [ABSTRACT FROM PUBLISHER]

The study of complex organic molecules, and more specifically those of prebiotic interest, is important to understand the chemical richness of star-forming regions. The chemistry of nitrogen bearing molecules such as formamide or methyl isocyanate is poorly constrained. We study different chemical pathways to form and destroy these molecules from both the gas phase and grain surface chemistry. From comparison with observations of four different relevant astrophysical regions, we show that both the gas phase and grain surface chemistry are required to explain the observed abundances of these species. [ABSTRACT FROM AUTHOR]

Studies of gas phase ion-neutral reactions provide insight into many areas of astrochemistry, including the elusive characterization of the Diffuse Interstellar Bands (DIBs). This presentation gives an overview of our experimental studies of several classes of positive and negative ions, using the flowing afterglow-selected ion flow tube and a newly modified ion trap. Earlier studies of carbon chain anions and polycyclic aromatic hydrocarbon (PAH) cations, both of which have been suggested as carriers of the DIBs, are described. More recent work including isomeric PAHs, nitrogen-containing PAHs, negative ions of PAHs, and negative ions of 5-membered heterocyclic rings are discussed. Finally, the study of quantitative thermochemistry by coupling our results with data from Photoelectron Spectroscopy is described. [ABSTRACT FROM PUBLISHER]

About a thousand optical absorption features on the interstellar extinction curve popularly known as the Diffuse Interstellar Bands (DIBs) have been observed. The numbers are increasing every year, thanks to the improvement in telescope and spectroscopic technology. Ultra-high resolution spectroscopic observations and emission features corresponding to some of the DIBs suggest that, some if not all, of these features are due to large molecules. The strength of DIBs depend on the amount of reddening which is directly proportional to the amount of material present between the background star and the observer. Since, the strengths of the DIBs are not strongly correlated with each other, there must be several carriers. Time Dependent Density Functional Theory (TDDFT) calculations are useful in narrowing down molecular systems that may be further investigated in the laboratory.The observations of the unidentified infrared (UIR) bands point towards the widespread presence of Polycyclic Aromatic Hydrocarbon (PAH) molecules. Though, not a single PAH has been discovered in interstellar space, these are the largest molecules suspected to be present. PAHs are stable towards energetic environment prevailing under interstellar conditions rendering these molecules to be good candidates as DIB carriers. We report TDDFT calculations to predict electronic transitions of neutral, protonated-deuteronated and PAHs with five member rings with various sites of protonation and deuteronation. Compared to their neutral forms, these charged isoelectronic forms of PAHs are predicted to have active transitions in the visible region, which means they are suitable candidates as carriers for some of the DIBs and laboratory studies are warranted for these systems. [ABSTRACT FROM PUBLISHER]

Establishing the stability of cosmic fullerenes and fullerenic aggregates is extremely relevant for a variety of reasons. For instance, the emission features of C60 and C70 fall in the same spectral region as the Un-identified InfraRed (UIR) bands, which they could contribute to. To be able to contribute to the UIR emission, however, fullerenes must be able to survive long enough against the destruction mechanisms operating in the interstellar medium. In this study we focus on the effects of collisional processing, i.e., the bombardment by energetic ions and electrons. A recent experimental/theoretical study has shown that ion collisions with C60 clusters result in the dissociation of the cluster with the simultaneous formation of covalent fullerene dimers, which could play a role as DIBs carriers. We present here our first results about the collisional processing of C60 molecules and clusters by H, He and C ions in interstellar shocks. We have adapted the models that have previously been developed to successfully treat the collisional processing of PAHs in space. The nature of the interaction and the similarities between PAHs and fullerenes make this approach appropriate. In addition, our study shows that the formation of covalent dimers following ion collisions with C60 clusters is compatible with the astrophysical conditions under consideration. [ABSTRACT FROM PUBLISHER]

While the summit of the Antarctic Plateau has long been expected to harbor the best ground-based sites for terahertz (THz) frequency astronomical investigations, it is only recently that direct observations of exceptional THz atmospheric transmission and stability have been obtained. These observations, in combination with recent technological advancements in astronomical instrumentation and autonomous field platforms, make the recognition and realization of terahertz observatories on the high plateau feasible and timely. Here, we will explore the context of terahertz astronomy in the era of Herschel, and the crucial role that observatories on the Antarctic Plateau can play. We explore the important scientific questions to which observations from this unique environment may be most productively applied. We examine the importance and complementarity of Antarctic THz astronomy in the light of contemporary facilities such as ALMA, CCAT, SOFIA and (U)LDB ballooning. Finally, building from the roots of THz facilities in Antarctica to present efforts, we broadly highlight future facilities that will exploit the unique advantages of the Polar Plateau and provide a meaningful, lasting astrophysical legacy. [ABSTRACT FROM PUBLISHER]

OH(1720 MHz) masers are created by the interaction of supernova remnants with molecular clouds. These masers are pumped by collisions in warm, shocked molecular gas with OH column densities in the range 1016–1017, cm−2. Excitation calculations suggest that inversion of the 6049 MHz OH line may occur at the higher column densities that have been inferred from main-line absorption studies of supernova remnants with the Green Bank Telescope. OH(6049 MHz) masers have therefore been proposed as a complementary indicator of remnant-cloud interaction.This motivated searches for 6049 MHz maser emission from supernova remnants using the Parkes 63 m and Effelsberg 100 m telescopes, and the Australia Telescope Compact Array. A total of forty-one remnants have been examined by one or more of these surveys, but without success. To check the accuracy of the OH column densities inferred from the single-dish observations we modelled OH absorption at 1667 MHz observed with the Very Large Array towards three supernova remnants, IC 443, W44 and 3C 391. The results are mixed – the OH column is revised upwards in IC443, downwards in 3C391, and is somewhat reduced in W44. We conclude that OH columns exceeding 1017 cm−2 are indeed present in some supernova remnants and so the lack of any detections is not explained by low OH column density. We discuss the possibility that non-local line overlap is responsible for suppressing the inversion of the 6049 MHz line. [ABSTRACT FROM PUBLISHER]

I have analysed the pumping scheme of 1720-MHz OH masers in great detail. [ABSTRACT FROM PUBLISHER]

Many complex organic molecules and inorganic solid-state compounds have been observed in the circumstellar shell of stars (both C-rich and O-rich) in the transition phase between Asymptotic Giant Branch (AGB) stars and Planetary Nebulae (PNe). This short (~102-104 years) phase of stellar evolution represents a wonderful laboratory for astrochemistry and provides severe constraints on any model of gas-phase and solid-state chemistry. One of the major challenges of present day astrophysics and astrochemistry is to understand the formation pathways of these complex organic molecules and inorganic solid-state compounds (e.g., polycyclic aromatic hydrocarbons, fullerenes, and graphene in the case of a C-rich chemistry and oxides and crystalline silicates in O-rich environments) in space. In this review, I present an observational review of the molecular processes in the late stages of stellar evolution with a special emphasis on the first detections of fullerenes and graphene in PNe. [ABSTRACT FROM PUBLISHER]

The Spitzer Space Telescope has three science instruments (IRAC, MIPS, and IRS) that can take images at 3.6, 4.5, 5.8, 8.0, 24, 70, and 160 μm, spectra over 5–38 μm, and spectral energy distribution over 52–100 μm. The Spitzer archive contains targeted imaging observations for more than 100 PNe. Spitzer legacy surveys, particularly the GLIMPSE survey of the Galactic plane, contain additional serendipitous imaging observations of PNe. Spitzer imaging and spectroscopic observations of PNe allow us to investigate atomic/molecular line emission and dust continuum from the nebulae as well as circumstellar dust disks around the central stars. Highlights of Spitzer observations of PNe are reviewed in this paper. [ABSTRACT FROM PUBLISHER]

Seed dormancy and germination involve the concerted operation of molecular and biochemical programmes. It has become feasible to study these processes in great detail, using the current methods for transcriptome, proteome and metabolome analysis. Yet, the large amounts of data generated by these methods are often dazzling and demand efficient tools for data visualization. We have used the freely available PageMan/MapMan package (http://MapMan.gabipd.org) to visualize transcriptome and metabolome changes in Arabidopsis thaliana seeds during dormancy and germination. Using this package we developed two seed-specific MapMan pathways, which efficiently capture the most important molecular processes in seeds. The results demonstrated the usefulness of the PageMan/MapMan package for seed research. [ABSTRACT FROM PUBLISHER]

The insoluble organic material preserved in primitive chondritic meteorites shares many similarities with the refractory organic material in interplanetary dust particles and comets, suggesting that there is a genetic link between the organic matter in objects that formed between ~3 AU and ~30 AU from the Sun. These similarities include large D and 15N enrichments in bulk and even more extreme enrichments in isotopic hotspots. The enrichments attest to formation in very cold environments, either in the outer Solar System or the protosolar molecular cloud. There are many properties of this organic material that are consistent with an interstellar origin, but a Solar System origin cannot be ruled out. Similar organic material is presumably an important component of most protoplanetary disks, and heating or sputtering of this material would be a source of PAHs in disks. The soluble organic matter was more heavily effected by processes on the chondritic parent bodies than the insoluble material. Amino acids, for instance, probably formed by reaction of ketones and aldehydes with NH3 and HCN. The accretion of the relatively volatile NH3 and HCN, presumably in ices, strengthens the chondrite-comet connection. However, unlike most comets the water in chondrites, when it was accreted, had D/H ratios that were similar to or depleted relative to Earth. [ABSTRACT FROM PUBLISHER]

By any measure, IAU Symposium 280 has been an outstanding success: more than 400 participants represented at least 30 countries with 74 presentations and more than 300 posters. Beyond these numbers, it is evident that the cross-disciplinary field of astrochemistry is flourishing with excellent prospects for growth in the future. We have enjoyed the excitement of new, unexpected results from the Herschel Space Observatory and eagerly await new opportunities and facilities that will arise in the coming months and years. [ABSTRACT FROM PUBLISHER]

It has been a long standing problem in astrochemistry to explain how molecules can form in a highly dilute environment such as the interstellar medium. In the last decennium more and more evidence has been found that the observed mix of small and complex, stable and highly transient species in space is the cumulative result of gas phase and solid state reactions as well as gas-grain interactions. Solid state reactions on icy dust grains are specifically found to play an important role in the formation of the more complex “organic” compounds. In order to investigate the underlying physical and chemical processes detailed laboratory based experiments are needed that simulate surface reactions triggered by processes as different as thermal heating, photon (UV) irradiation and particle (atom, cosmic ray, electron) bombardment of interstellar ice analogues. Here, some of the latest research performed in the Sackler Laboratory for Astrophysics in Leiden, the Netherlands is reviewed. The focus is on hydrogenation, i.e., H-atom addition reactions and vacuum ultraviolet irradiation of interstellar ice analogues at astronomically relevant temperatures. It is shown that solid state processes are crucial in the chemical evolution of the interstellar medium, providing pathways towards molecular complexity in space. [ABSTRACT FROM PUBLISHER]

Water is observed in many astrophysical environments in both gas and solid phase. Water ice, for its specific properties, is probably the most important template that structures the gas-solid interaction. In cold environments, its synthesis is supposed to occur directly in the solid phase and then water acts as a catalytic matrix for subsequent synthesis of various molecules. When the medium begins to warm again, water sublimates and nourishes the gas phase, as occurs for example in comets or in star forming regions. Over the last four years, water formation on cold surfaces has been studied experimentally. Different precursors (O, O2, O3. . .) have been used to understand the complex mechanisms that take place. Although numerous questions remain unanswered, at present, it is clear that water is easily formed by different pathways, and that the ice formed has an amorphous structure. The recent observations of the ortho/para ratio of water with Herschel satellite have similarities with the previous o/p ratio observations of water in comets. Some experimental work have been recently reported in this domain, mostly rare gas matrix studies where nuclear spin conversion is measured even at 4.2 K. H2 molecules adsorbed on amorphous solid water ice also exhibit a nuclear spin conversion in presence of a tiny fraction of O2. Finally, I will discuss if microphysics properties of water desorption can explain the o/p ratio values observed. [ABSTRACT FROM PUBLISHER]

The first molecules detected at infrared wavelengths in the ejecta of a Type II supernova, namely SN1987A, consisted of CO and SiO. Since then, confirmation of the formation of these two species in several other supernovae a few hundred days after explosion has been obtained. However, supernova environments appear to hamper the synthesis of large, complex species due to the lack of microscopically-mixed hydrogen deep in supernova cores. Because these environments also form carbon and silicate dust, it is of importance to understand the role played by molecules in the depletion of elements and how chemical species get incorporated into dust grains. In the present paper, we review our current knowledge of the molecular component of supernova ejecta, and present new trends and results on the synthesis of molecules in these harsh, explosive events. [ABSTRACT FROM PUBLISHER]

In this paper we review recent progress in our understanding of the chemical evolution of protoplanetary disks. Current observational constraints and theoretical modeling on the chemical composition of gas and dust in these systems are presented. Strong variations of temperature, density, high-energy radiation intensities in these disks, both radially and vertically, result in a peculiar disk chemical structure, where a variety of processes are active. In hot, dilute and heavily irradiated atmosphere only the most photostable simple radicals and atoms and atomic ions exist, formed by gas-phase processes. Beneath the atmosphere a partly UV-shielded, warm molecular layer is located, where high-energy radiation drives rich ion-molecule and radical-radical chemistry, both in the gas phase and on dust surfaces. In a cold, dense, dark disk midplane many molecules are frozen out, forming thick icy mantles where surface chemistry is active and where complex polyatomic (organic) species are synthesized. Dynamical processes affect disk chemical composition by enriching it in abundances of complex species produced via slow surface processes, which will become detectable with ALMA. [ABSTRACT FROM PUBLISHER]

Recent models of hot cores have incorporated previously-uninvestigated chemical pathways that lead to the formation of complex organic molecules (COMs; i.e. species containing six or more atoms). In addition to the gas-phase ion-molecule reactions long thought to dominate the organic chemistry in these regions, these models now include photodissociation-driven grain surface reaction pathways that can also lead to COMs. Here, simple grain surface ice species photodissociate to form small radicals such as OH, CH3, CH2OH, CH3O, HCO, and NH2. These species become mobile at temperatures above 30 K during the warm-up phase of star formation. Radical-radical addition reactions on grain surfaces can then form an array of COMs that are ejected into the gas phase at higher temperatures. Photodissociation experiments on pure and mixed ices also show that these complex molecules can indeed form from simple species. The molecules predicted to form from this type of chemistry reasonably match the organic inventory observed in high mass hot cores such as Sgr B2(N) and Orion-KL. However, the relative abundances of the observed molecules differ from the predicted values, and also differ between sources. Given this disparity, it remains unclear whether grain surface chemistry governed by photodissociation is the dominant mechanism for the formation of COMs, or whether other unexplored gas-phase reaction pathways could also contribute significantly to their formation. The influence that the physical conditions of the source have on the chemical inventory also remains unclear. Here we overview the chemical pathways for COM formation in hot cores. We also present new modeling results that begin to narrow down the possible routes for production of COMs based on the observed relative abundances of methyl formate (HCOOCH3) and its C2H4O2 structural isomers. [ABSTRACT FROM PUBLISHER]

Icy grain mantles are commonly observed through infrared spectroscopy toward dense clouds, cloud cores, protostellar envelopes and protoplanetary disks. Up to 80% of the available oxygen, carbon and nitrogen are found in such ices; the most common ice constituents – H2O, CO2 and CO – are second in abundance only to H2 in many star forming regions. In addition to being a molecular reservoir, ice chemistry is responsible for much of the chemical evolution from H2O to complex, prebiotic molecules. Combining the exisiting ISO, Spitzer, VLT and Keck ice data results in a large sample of ice sources (~80) that span all stages of star formation and a large range of protostellar luminosities (<0.1–105 L⊙). Here we summarize the different techniques that have been applied to mine this ice data set on information on typical ice compositions in different environments and what this implies about how ices form and evolve during star and planet formation. The focus is on how to maximize the use of empirical constraints from ice observations, followed by the application of information from experiments and models. This strategy is used to identify ice bands and to constrain which ices form early during cloud formation, which form later in the prestellar core and which require protostellar heat and/or UV radiation to form. The utility of statistical tests, survival analysis and ice maps is highlighted; the latter directly reveals that the prestellar ice formation takes place in two phases, associated with H2O and CO ice formation, respectively, and that most protostellar ice variation can be explained by differences in the prestellar CO ice formation stage. Finally, special attention is paid to the difficulty of observing complex ices directly and how gas observations, experiments and models help in constraining this ice chemistry stage. [ABSTRACT FROM PUBLISHER]

Stars like our Sun and planets like our Earth form in dense regions within interstellar molecular clouds, called pre-stellar cores (PSCs). PSCs provide the initial conditions in the process of star and planet formation. In the past 15 years, detailed observations of (low-mass) PSCs in nearby molecular cloud complexes have allowed us to find that they are cold (T < 10K) and quiescent (molecular line widths are close to thermal), with a chemistry profoundly affected by molecular freeze-out onto dust grains. In these conditions, deuterated molecules flourish, becoming the best tools to unveil the PSC physical and chemical structure. Despite their apparent simplicity, PSCs still offer puzzles to solve and they are far from being completely understood. For example, what is happening to the gas and dust in their nuclei (the future stellar cradles) is still a mystery that awaits for ALMA. Other important questions are: how do different environments and external conditions affect the PSC physical/chemical structure? Are PSCs in high-mass star forming regions similar to the well-known low-mass PSCs? Here I review observational and theoretical work on PSCs in nearby molecular cloud complexes and the ongoing search and study of massive PSCs embedded in infrared dark clouds (IRDCs), which host the initial conditions for stellar cluster and high-mass star formation. [ABSTRACT FROM PUBLISHER]

We simulate the chemical processes in the three evolution periods of the solar nebula, which are (i) the quasi-stationary prestellar cloud core, (ii) the gravitationally collapsing protostellar core, and (iii) the evolving gas-dust disk. Our purpose is to identify chemical parameters which reflect special aspects of the interactions between the gas and ice phase in the different periods, e.g. isotopic or molecular ratios. In this study we derive the D/H and 15N/14N ratio of selected compounds as well as the CO2/H2O ratio to measure the fraction of non-polar to polar ice in the grain mantles. The chosen ratios depend on the depletion-enrichment relation between the ice and gas phases driven by the thermal evolution in each period, especially during the collapse. Hence, we have made great efforts in order to derive realistic and compact hydrodynamic models to describe the evolutionary periods of the solar nebula. [ABSTRACT FROM PUBLISHER]

We study the formation of primordial proto-stars in a ΛCDM universe using ultra high-resolution cosmological simulations. Our approach includes all the relevant atomic and molecular physics to follow the thermal evolution of a prestellar gas cloud to “stellar” densities. We describe the numerical implementation of the physics. We also show the result of a simulation of the formation of primordial stars in a reionized gas. [ABSTRACT FROM PUBLISHER]

With ever changing solar abundances being reported the equation of state and opacities needed for stellar evolution models also change. A discussion of those changes in mean molecular opacities will be presented with a discussion on the effect on evolution models. Aside from changing the abundances of the base mixture the enrichment changes too. Traditionally mean opacity tables are produced for oxygen-rich mixtures, however stars will often become carbon-rich. A discussion of carbon-rich opacities tables will also be presented. [ABSTRACT FROM PUBLISHER]