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Episodic accretion is an important process in the evolution of young stars and their surroundings. A consequence of an episodic accretion event is a luminosity burst, which heats the protostellar environment and has a long lasting impact on the chemical evolution of the disk and envelope of young stars. We present a new model for the chemistry of episodic accretion based on the 2D radiation thermo-chemical disk code ProDiMo. We discuss the impact of an episodic accretion burst on the chemical evolution of CO and its observables. Furthermore we present a model for the outbursting source V883 Ori where we fitted available observational data to get an accurate physical structure that allows for a detailed study of the chemistry.
Experimental evidence for the formation of hydrogenated fullerene molecules is presented. Films of C60 were grown on a highly oriented pyrolytic graphite (substrate) and exposed to a beam of deuterium atoms. Thermal desorption combined with mass spectrometry was used to determine the deuterated fullerene products formed, revealing a maximum degree of deuteration corresponding to C60D36. Release of D2 from the deuterated C60 film occurs at a much higher temperature than for D-saturated graphite.
Experimental and theoretical studies have shown that Complex Organic Molecules (COMs) can be formed on icy dusty grains in molecular clouds and protoplanetary disks. The number of astronomical detections of solid COMs, however, is very limited. With the upcoming launch of the James Webb Space Telescope (JWST) this should change, but in order to identify solid state features of COMs, accurate laboratory data are needed. Here we present high resolution (0.5 cm–1) infrared ice spectra of acetone (C3H6O) and methyl formate (HCOOCH3), two molecules already identified in astronomical gas phase surveys, whose interstellar synthesis is expected to follow solid state pathways.
Reactions on carbonaceous surfaces play an important role in processes such as H2 formation in the interstellar medium. We have investigated the adsorption of C2 molecules on a highly oriented pyrolytic graphite (HOPG) surface and then exposed them to a beam of deuterium atoms in order to investigate the formation of deuterated fullerenes. Scanning tunneling microscopy (STM) was used to probe the adsorbed molecules and their deuteration. Deuteration of C2 films results in increased thermal stability of the film, relative to films of pristine C2, along with an evolution towards higher deuterated species. The STM data provide confirmatory evidence for the formation of deuterated fullerene species.
The identification of complex organic molecules, COMs, in inter- and circumstellar gas phase environments is steadily increasing. The formation of such COMs takes largely place on the icy dust grains, as has been shown in recent laboratory studies. Until now solid state features of smaller molecular species have been directly identified in these environments. The presented work on acetaldehyde (CH3CHO), ethanol (CH3CH2OH), and dimethyl ether (CH3OCH3) in different astronomically relevant ice environments and for temperatures in the range 15 to 160 Kelvin, provides the necessary tools to guide or interpret astronomical observations, specifically for upcoming James Webb Space Telescope observations.
Implementation of a novel experimental approach using a bright source of narrowband x-ray emission has enabled the production of a photoionized argon plasma of relevance to astrophysical modelling codes such as Cloudy. We present results showing that the photoionization parameter ζ = 4πF/ne generated using the VULCAN laser was ≈ 50 erg cm s−1, higher than those obtained previously with more powerful facilities. Comparison of our argon emission-line spectra in the 4.15 - 4.25 Å range at varying initial gas pressures with predictions from the Cloudy code and a simple time-dependent code are also presented. Finally we briefly discuss how this proof-of-principle experiment may be scaled to larger facilities such as ORION to produce the closest laboratory analogue to a photoionized plasma.
HD 66051 is an eclipsing and spectroscopic double-lined binary (SB2), hosting two chemically peculiar stars: a highly peculiar B star as primary and an Am star as secondary. The investigation of the new high-resolution UVES spectrum of HD 66051 allowed us to decide on the chemical peculiarity type of both components with more reliability. An analysis of TESS photometric time series data will further specify the physical parameters of the stars and the orbital parameters of the system.
The role of H2 in forming interstellar complex organics is still not clear due to the high activation energies required for “non-energetic” association reactions. In this work, we investigated the potential contribution of H2 to the hydrogenated species (HnNCO) formation on dust grains when the “energetic” processing is involved. The goal is to test whether an additional hydrogenation pathway is possible upon UV irradiation of a CO:H2 ice mixture. It is proposed that the electronically excited carbon monoxide (CO*) induced by UV-photons can react with a ground-state H2 to form HCO, ultimately enhancing the production of COMs in ice mantle.
The emergence of life on Earth may have its origin in organic molecules formed in the interstellar medium. Molecules with amide and isocyanate groups resemble structures found in peptides and nucleobases and are necessary for their formation. Their formation is expected to take place in the solid state, on icy dust grains, and is studied here by far-UV irradiating a CH4:HNCO mixture at 20 K in the laboratory. Reaction products are detected by means of infrared spectroscopy and temperature programmed desorption - mass spectrometry. Various simple amides and isocyanates are formed, showing the importance of ice chemistry for their interstellar formation. Constrained by experimental conditions, a reaction network is derived, showing possible formation pathways of these species under interstellar conditions.
The pore structure of vapour deposited ASW is poorly understood, despite its importance to fundamental processes such as grain chemistry, cooling of star forming regions, and planet formation. We studied structural changes of vapour deposited D2O on intra-molecular to 30 nm length scales at temperatures ranging from 18 to 180 K and observed enhanced mobility from 100 to 150 K. An Arrhenius type model describes the loss of surface area and porosity with a common set of kinetic parameters. The low activation energy (428 K) is commensurate with van der Waals forces between nm-scale substructures in the ice. Our findings imply that water porosity will always change with time, even at low temperatures.
HD 163296 is a young star surrounded by a planet-forming disk that shows clear signatures of dust gaps and rings; likely an indication of ongoing planet formation. We use the radiation thermochemical disk code ProDiMo to investigate the impact of dust/gas gaps on the temperature, chemistry and observables. Furthermore, we model high spatial resolution gas and dust observation of HD 163296 (ALMA/DSHARP). Our first results indicate that features in the observed radial intensity profile of the 12CO line are a consequence of the dust gaps and do not require gas depletion. Those preliminary results indicate that self-consistent modelling of the gas (chemistry, heating/cooling) and dust is necessary to accurately infer the degree of gas depletion within dust gaps. Such information is crucial to understand the processes that generate the disk substructure and their relation to planet formation.
This brief overview stresses the importance of laboratory data and theory in analyzing astronomical observations and understanding the physical and chemical processes that drive the astrophysical phenomena in our Universe. This includes basic atomic and molecular data such as spectroscopy and collisional rate coefficients, but also an improved understanding of nuclear, plasma and particle physics, as well as reactions and photoprocesses in the gaseous and solid state that lead to chemical complexity and building blocks for life. Systematic laboratory collision experiments have provided detailed insight into the steps that produce pebbles, bricks and ultimately planetesimals starting from sub-μ-sized grains. Sample return missions and meteoritic studies benefit from increasingly sophisticated laboratory machines to analyze materials and provide compositional images on nanometer scales. Prioritization of future data requirements will be needed to cope with the increasing data streams from a diverse range of future astronomical facilities within a constrained laboratory astrophysics budget.
Complex organic molecules (COMs) have been detected in the gas-phase in cold and lightless molecular cores. Recent solid-state laboratory experiments have provided strong evidence that COMs can be formed on icy grains through ‘non-energetic’ processes. In this contribution, we show that propanal and 1-propanol can be formed in this way at the low temperature of 10 K. Propanal has already been detected in space. 1-propanol is an astrobiologically relevant molecule, as it is a primary alcohol, and has not been astronomically detected. Propanal is the major product formed in the C2H2 + CO + H experiment, and 1-propanol is detected in the subsequent propanal + H experiment. ALMA observations towards IRAS 16293-2422B are discussed and provide a 1-propanol:propanal upper limit of < 0.35–0.55, which are complemented by computationally-derived activation barriers in addition to the performed laboratory experiments.
Laboratory experiments are essential to support the interpretation of astronomical observations and space mission data. Here we present a new experimental setup to characterize in the Vis-MIR range in both reflection and transmission modes astrophysically-relevant frozen volatiles deposited at low temperature and exposed to ion bombardment.
Chondritic meteorites, and especially the most volatile-rich chondrites, the carbonaceous chondrites, preserve a record of the solar protoplanetary disk dust component and how it has been changed both in the disk environment itself and in its asteroidal parent body. Here we review some of the key features of carbonaceous chondrites and report some new data on their organics component. These show that the nebula reached temperature of >10000C, but only very locally, to produce chondrules. Most meteoritic material underwent thermal and/or aqueous processing, but some retain delicate nebular components such as complex organic molecules and amorphous silicates.
The ORGANIC experiment on EXPOSE-R spent 682 days outside the International Space Station, providing continuous exposure to the cosmic-, solar- and trapped-particle radiation background for fourteen samples: 11 polycyclic aromatic hydrocarbons (PAHs) and three fullerenes. The thin films of the ORGANIC experiment received, during space exposure, an irradiation dose of the order of 14 000 MJ m−2 over 2900 h of unshadowed solar illumination. Extensive analyses were performed on the returned samples and the results compared to ground control measurements. Analytical studies of the returned samples included spectral measurements from the vacuum ultraviolet to the infrared range and time-of-flight secondary ion mass spectrometry. Limited spectral changes were observed in most cases pointing to the stability of PAHs and fullerenes under space exposure conditions. Furthermore, the results of these experiments confirm the known trend in the stability of PAH species according to molecular structure: compact PAHs are more stable than non-compact PAHs, which are themselves more stable than PAHs containing heteroatoms, the last category being the most prone to degradation in the space environment. We estimate a depletion rate of the order of 85 ± 5% over the 17 equivalent weeks of continuous unshadowed solar exposure in the most extreme case tetracene (smallest, non-compact PAH sample). The insignificant spectral changes (below 10%) measured for solid films of large or compact PAHs and fullerenes indicate a high stability under the range of space exposure conditions investigated on EXPOSE-R.
PAHs are among the most commonly proposed and popular candidates for DIB carriers. We present a critical assessment of the PAH-DIB model in view of the progress and the advances that have recently been achieved through a series of complementary studies involving astronomical observations of DIBs, laboratory simulation of interstellar analogs for PAHs (neutrals and ions), space exposure experiments of PAHs, theoretical calculations of PAH spectra and the modeling of diffuse and translucent interstellar clouds. What have we learned from these complementary studies? What are the constraints that can now be derived for the PAHs as DIB carriers? What are the strengths and the weaknesses of the PAH model to account for the DIBs?
We present the first results of an exploratory VLT/X-Shooter survey of near-infrared diffuse interstellar bands (DIBs) in diffuse to translucent interstellar clouds. These observations confirm the presence of recently discoved NIR DIBs and provide more accurate rest wavelengths and line widths. Example spectra are shown for the reddened, AV ~ 10 mag, line-of-sight towards the distant binary system 4U 1907+09.
Synthetic biodegradable polymers are commonly used as scaffolds for tissue engineering despite their poor cell adhesion compared to natural polymers. One of the problems in using biodegradable scaffolds is that a higher cell colonization at the scaffold periphery and inadequate colonization at its center is generally noted. Such aspects could seriously compromise the in vivo regeneration of a damaged tissue and, in turn, the success of the implant. Plasma processes have been lately proven as promising scaffold modification techniques. The current work aims at enhancing cell colonization in the core of polymer scaffolds via plasma deposition of coatings with different chemical characteristics. The versatility and ability of plasma processes to modify only the outermost layer of a material can render them competitive with respect to wet chemistry approaches in the field of biomedical materials. In this paper some of the results obtained by plasma processing of 3D interconnected porous polymer scaffolds for Tissue Engineering will be shown. In particular, it will be shown how it is possible to enhance cell adhesion, growth and colonization in porous Polycaprolactone (PCL) scaffolds where gradient of surface compositions are induced from the external (e.g., hydrophobic, slightly cell-repulsive) to the internal (e.g., hydrophilic, cell-adhesive) side of the scaffolds. 3D scaffolds were modified with several RF (13.56 MHz) deposition and treatment plasma processes. Materials were characterized by means of XPS, and FT-IR techniques. Cell-growth experiments were run with cell-lines to check the efficiency of several treatments to enhance/accelerate cell in-growth inside scaffolds.