We estimate the wind speeds with a Bayesian inference and a Markov Chain Monte Carlo (MCMC) tool for the high resolution X-ray spectra of Vela X-1, to understand the effect of satellite lines on spectral analysis. After modelling continua and He-like triplets of the spectra with a parameterized two-component power-law model and a mullti-Gaussian model, respectively, we estimate the contamination from satellite lines, and improve the self-consistency of wind speeds derived from the He-like triplet lines of different elements. Moreover, our fitting shows that the column density of scatter component varies from phase to phase.

Debris disks are the natural by-products of the star and planet formation processes. Since the 1980’s several thousands of debris disks have been detected, and the presence of a disk is inferred by the detection of excess emission over the photospheric emission. This thermal emission arises from (micron-sized or slightly bigger) dust grains heated by the central star. However, in the vast majority of cases, these observations are not spatially resolving the radial distribution of the dust, resulting in strong degeneracies in the modeling approach (radial distance vs minimum grain size mostly). Therefore the properties of the small dust grains remained largely unconstrained until the arrival of high angular resolution instruments, especially at optical and near-infrared wavelengths. In these proceeding some of the main results are presented that have been obtained over the past few years on the properties of small dust grains in debris disks, and it is discussed how laboratory experiments contributed to put those results in context.

Recent laboratory studies have shown that PAH cations dehydrogenate to give charged molecules consisting of only carbon atoms. Our experiments using ion-trap time-of-flight mass spectrometry show that a key group of photodissociation fragments from the coronene cation $({{\rm{C}}_{24}}{\rm{H}}_{12}^ + )$ are carbon clusters of ${\rm{C}}_n^ +$ composition. Density functional theory calculations shed light onto potential dissociation pathways leading up to the main ${\rm{C}}_{11}^ +$ and ${\rm{C}}_{12}^ +$ clusters, and highlight the importance of pentagon formations in the carbon backbone of the precursor molecule in generating certain fragments.

Asymptotic Giant Branch (AGB) stars contribute a major part to the global dust budget in galaxies. Owing to their refractory nature alumina (stoichiometric formula AlO) is a promising candidate to be the first condensate emerging in the atmospheres of oxygen-rich AGB stars. Strong evidence for that is supplied by the presence of alumina in pristine meteorites and a broad spectral feature observed around ∼ 13 μm. The emergence of a specific condensate depends on the thermal stability of the solid, the gas density and its composition. The evaluation of the condensates is based on macroscopic bulk properties. The growth and size distribution of dust grains is commonly described by Classical Nucleation Theory (CNT). We question the applicability of CNT in an expanding circumstellar envelope as CNT presumes thermodynamic equilibrium and requires, in practise, seed nuclei on which material can condense. However, nano-sized molecular clusters differ significantly from bulk analogues. Quantum effects of the clusters lead to non-crystalline structures, whose characteristics (energy, geometry) differ substantially, compared to the bulk material. Hence, a kinetic quantum-chemical treatment involving various transition states describes dust nucleation most accurately. However, such a treatment is prohibitive for systems with more than 10 atoms. We discuss the viability of chemical-kinetic routes towards the formation of the monomer (Al2O3) and the dimer (Al4O6) of alumina.

Complex organic molecules (COMs) may have played a role in the formation of life in the early Earth (Herbst & van Dishoeck (2009)). Here we present the formation of NH2CHO and CH3CHO upon vacuum-ultraviolet (VUV) irradiation of CO:NH3 and CO:CH4 ice mixtures, simulating the UV processing of interstellar ices in the interior of dense clouds. We have found that the conversion from ${\rm{N}}{{\rm{H}}_{\dot 2}}$ radicals to NH2CHO is 4–15 times higer than that from ${\rm{N}}{{\rm{H}}_{\dot 3}}$ to CH3CHO, probably due to the competing formation of larger hydrocarbons in the latter case.

We present some new studies of the absolute photodissociation cross sections of astrophysically-relevant diatomic radicals.

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.

The focus of this work is on two topics: (i) formation of complex organic molecules (COMs) and (ii) isotope fractionation. Various COMs, which are C, H-containing molecules consisting of 6 atoms and more, have been detected in the central warm region of protostellar cores. Most of this review is about gas-grain chemical models, which have been constructed to evaluate the mechanisms and efficiency of the COM formation. The relevant physical and chemical processes are investigated in laboratory experiments, as reported in other articles in this volume.

The isotope fractionation of volatile elements is observed in both the interstellar medium (ISM) and Solar system material. While exothermic exchange reactions enrich molecules with heavier isotopes such as Deuterium, the isotope selective photodissociation can be coupled with ice formation to enrich the ice mantle with rare isotopes. The efficiency of this fractionation depends on the photodesorption yields, which has been studied in laboratory experiments.

Increasing observational evidence shows that a non-negligible fraction of the cosmic carbon is locked into macromolecules like Polycyclic Aromatic Hydrocarbons (PAHs). Interstellar PAHs live in extreme environments where there are processed by energetic photons (UV and X-rays) and by ions and electrons accelerated in hot shocked plasma and arising from cosmic rays. It is therefore important to quantify the capability of PAHs to survive under these extreme conditions and to determine the structural modifications induced by such energetic processing. I will present some novel results on this topic, focusing on the bombardment by ions and electrons in interstellar shocks. This work shows the importance of pairing an appropriate physical description of the interaction between target and projectiles with updated laboratory measurements of the relevant physical parameters. The results from physical modeling allowed to derive updated astronomical lifetimes for PAHs.

We use quantum chemical techniques to model the vibrational spectra of small aromatic molecules on a proton-ordered hexagonal crystalline water ice (XIh) model. We achieve a good agreement with experimental data by accounting for vibrational anharmonicity and correcting the potential energy landscape for known failures of density functional theory. A standard harmonic description of the vibrational spectra only leads to a broad qualitative agreement.

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.

A characterisation of the collision properties between icy interstellar grains is crucial to understand planet formation. Here, we measure collision properties on a reference elastic system to evaluate the inelasticity of ice particles collisions. We propose upgrades to correct for some experimental biases and to investigate water evaporation as possible explanation for the energy loss during collision.

We present here the results from a full polarisation study, an important VLBI capability, of a selected set of bright Active Galactic Nuclei (AGNs), along with the steps required to fully calibrate the Australian Long Baseline Array. We compare strategies for high-precision polarisation measurements using two polarisation correction methods: (1) Linear model and (2) Ellipticity-Orientation model and two data-recording techniques: recording (1) nominally circular polarisation at all stations and (2) mixed polarisation, where all but one station record circular polarisation and the other recorded linear polarisation. The latter is corrected post-correlation. We explored these possible solution to discover which will best accommodate the heterogeneous nature of the Australian Long Baseline Array without impacting on the science results. The targets, all compact and of low polarisation fraction, allow us to compare multiple independent solutions for polarisation characteristics. The results show that the agreement between the two polarisation correction models is excellent. However, the values from Mopra with nominally circular polarisation are larger than would be acceptable. However, we also demonstrate that recording mixed polarisation modes and correcting post-correlation provide a high quality polarisation product. We report on the detailed tests of these strategies and assess that the array is ready for full polarisation operation.

We present independent optical spectroscopic follow-up of WGD2038-4008/GRAL2038-4008, a background quasar strongly lensed by a foreground elliptical galaxy into four images, recently discovered independently by Agnello et al. [2018, MNRAS, 479, 4345] and Krone-Martins et al. [2018, A&A, 616, L11] thanks to the exquisite spatial resolution of Gaia. The quasar images are bright (i ∼ 19 mag), thus enabling us to reach S/N > 20 for the continuum within 30 min of exposure time with the Andalucia Faint Object Spectrograph and Camera spectrograph mounted on the 2.56-m Nordic Optical Telescope. The flexible scheduling and high sensitivity delivered by Andalucia Faint Object Spectrograph and Camera provide timely redshifts and reveal the nature of the quasar images; both are essential for lensing modelling and cosmography. Our analysis shows a strong emission feature in a data gap in Agnello et al. [2018, MNRAS, 479, 4345], which can be attributed to as an interloper emission line feature from the foreground lensing galaxy, or hinting to a higher redshift of the background quasar. We discuss these two scenarios and outline possible tests to verify these scenarios.

We measure the cosmic star formation history out to z = 1.3 using a sample of 918 radio-selected star-forming galaxies within the 2-deg2 COSMOS field. To increase our sample size, we combine 1.4-GHz flux densities from the VLA-COSMOS catalogue with flux densities measured from the VLA-COSMOS radio continuum image at the positions of I < 26.5 galaxies, enabling us to detect 1.4-GHz sources as faint as 40 μJy. We find that radio measurements of the cosmic star formation history are highly dependent on sample completeness and models used to extrapolate the faint end of the radio luminosity function. For our preferred model of the luminosity function, we find the star formation rate density increases from 0.017 M⊙ yr−1 Mpc−3 at z ∼ 0.225 to 0.092 M⊙ yr−1 Mpc−3 at z ∼ 1.1, which agrees to within 40% of recent UV, IR and 3-GHz measurements of the cosmic star formation history.

This is an introduction to Bayesian inference with a focus on hierarchical models and hyper-parameters. We write primarily for an audience of Bayesian novices, but we hope to provide useful insights for seasoned veterans as well. Examples are drawn from gravitational-wave astronomy, though we endeavour for the presentation to be understandable to a broader audience. We begin with a review of the fundamentals: likelihoods, priors, and posteriors. Next, we discuss Bayesian evidence, Bayes factors, odds ratios, and model selection. From there, we describe how posteriors are estimated using samplers such as Markov Chain Monte Carlo algorithms and nested sampling. Finally, we generalise the formalism to discuss hyper-parameters and hierarchical models. We include extensive appendices discussing the creation of credible intervals, Gaussian noise, explicit marginalisation, posterior predictive distributions, and selection effects.

We present Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Hubble Space Telescope (HST) and Very Large Array (VLA) observations of the inner kpc of the OH Megamaser galaxy IRAS 11506-3851. In this work we discuss the kinematics and excitation of the gas as well as its radio emission. The HST images reveal an isolated spiral galaxy and the combination with the GMOS-IFU flux distributions allowed us to identify a partial ring of star-forming regions surrounding the nucleus with a radius of ≍500 pc. The emission-line ratios and excitation map reveal that the region inside the ring present mixed/transition excitation between those of Starbursts and Active Galactic Nuclei (AGN), while regions along the ring are excited by Starbursts. We suggest that we are probing a buried or fading AGN that could be both exciting the gas and originating an outflow.