Related papers: Numerical methods for non-LTE line radiative trans…
We analyze a three-dimensional smoothed particle hydrodynamics simulation of an evolving and later collapsing pre-stellar core. Using a three-dimensional continuum radiative transfer program, we generate images at 7 micron, 15 micron, 175…
Modeling the chemistry of molecular clouds is critical to accurately simulating their evolution. To reduce computational cost, 3D simulations generally restrict their chemistry to species with strong heating and cooling effects.…
We present 1D radiative transfer modelling of the envelopes of a sample of 18 low-mass protostars and pre-stellar cores with the aim of setting up realistic physical models, for use in a chemical description of the sources. The density and…
We recently proposed that molecular cloud dense cores undergo a prolonged period of quasi-static contraction prior to true collapse. This theory could explain the observation that many starless cores exhibit, through their spectral line…
We use our Monte Carlo radiative transfer code to study non-embedded prestellar cores and cores that are embedded at the centre of a molecular cloud. Our study indicates that the temperature inside embedded cores is lower than in isolated…
Absorption line spectroscopy offers one of the best opportunities to constrain the properties of galactic outflows and the environment of the circumgalactic medium. Extracting physical information from line profiles is difficult, however,…
Observations are revealing the ubiquity of filamentary structures in molecular clouds. As cores are often embedded in filaments, it is important to understand how line profiles from such systems differ from those of isolated cores. We…
Context: The solution of the nonlocal thermodynamical equilibrium (non-LTE) radiative transfer equation usually relies on stationary iterative methods, which may falsely converge in some cases. Furthermore, these methods are often unable to…
We present the theoretical framework and numerical methods we have implemented to solve the problem of the generation and transfer of polarized radiation in spectral lines out of local thermodynamical equilibrium, while accounting for…
The rotational properties of centrally condensed, turbulent molecular cloud cores with velocity fields that are characterized by Gaussian random fields are investigated. It is shown that the observed line width-size relationship can be…
A multi-transition 3$ $mm molecular line single-pointing and mapping survey was carried out towards 29 massive star-forming cores in order to search for the signature of inward motions. Up to seven different transitions, optically thick…
We report the derivation of rate coefficients for the rotational (de-)excitation of PO$^+$ induced by collisions with H$_2$. The calculations were performed on a four-dimensional potential energy surface, obtained on top of highly accurate…
The gravitational collapse of a spherical cloud core is investigated by numerical calculations. The initial conditions of the core lie close to the critical Bonnor-Ebert sphere with a central density of \sim 10^4 cm^{-3} in one model…
Aims: A large scale survey of the Galactic center region in he 3 mm rotational transitions of SiO, HCO+ and H13CO+ (beamsize ~ 3. 6 arcmin) was conducted to provide an estimate of cloud conditions, heating mechanisms, chemistry and other…
Carbon monoxide (CO) is the most abundant molecule after molecular hydrogen and is important for the chemistry in circumstellar envelopes around evolved stars. When modelling the strength and shape of molecular lines, the size of the CO…
We present observations of 25 transitions of 17 isotopologues of 9 molecules toward B335. With a goal of constraining chemical models of collapsing clouds, we compare our observations, along with data from the literature, to models of…
Utilising previous work by the authors on the spin-coupled rotational cross-sections for electron-CN collisions, data for the associated rate coefficients is presented. Data on rotational, fine-structure and hyperfine-structure transition…
The highly convergent iterative methods developed by Trujillo Bueno and Fabiani Bendicho (1995) for radiative transfer (RT) applications are generalized to spherical symmetry with velocity fields. These RT methods are based on Jacobi,…
The results are presented of a molecular line survey to search for the spectral signature of infall towards 77 850 micron continuum sources believed to be candidate high mass protostellar objects. Up to six different transitions, HCO+ 1-0,…
We present a new radiative transfer code for axi-symmetric stellar atmospheres and compare test results against 1D and 2D models with and without velocity fields. The code uses the short characteristic method with modifications to handle…