scientific output
papers
2024
- Astron. Comput.MAGRITTE, a modern software library for spectral line radiative transferT Ceulemans, F De Ceuster, L Decin, and 1 more authorASTRONOMY AND COMPUTING, Oct 2024
Spectral line observations are an indispensable tool to remotely probe the physical and chemical conditions throughout the universe. Modelling their behaviour is a computational challenge that requires dedicated software. In this paper, we present the first long-term stable release of Magritte, an open-source software library for line radiative transfer. First, we establish its necessity with two applications. Then, we introduce the overall design strategy and the application/programmer interface (API). Finally, we present three key improvements over previous versions: (1) an improved re-meshing algorithm to efficiently coarsen the spatial discretisation of a model; (2) a variation on Ng-acceleration, a popular acceleration-of-convergence method for non-LTE line transfer; and, (3) a semi-analytic approximation for line optical depths in the presence of large velocity gradients.
@article{ceulemans2024magrittetransfer, author = {Ceulemans, T and De Ceuster, F and Decin, L and Yates, J}, journal = {ASTRONOMY AND COMPUTING}, month = oct, number = {ARTN 100889}, publisher = {ELSEVIER}, title = {MAGRITTE, a modern software library for spectral line radiative transfer}, volume = {49}, year = {2024}, doi = {10.1016/j.ascom.2024.100889}, issn = {2213-1337}, eissn = {2213-1345}, keyword = {CONVERGENCE}, language = {English}, publicationstatus = {published}, } - Bayesian model reconstruction based on spectral line observations with pommeF De Ceuster, T Ceulemans, L Decin, and 2 more authorsJournal of Open Source Software, Dec 2024
Spectral line observations encode a wealth of information. A key challenge, therefore, lies in the interpretation of these observations in terms of models to derive the physical and chemical properties of the astronomical environments from which they arise. In this paper, we present pomme, an open-source Python package that allows users to retrieve 1D or 3D models of physical properties, such as chemical abundance, velocity, and temperature distributions of (optically thin) astrophysical media, based on spectral line observations. We discuss how prior knowledge, for instance, in the form of a steady-state hydrodynamics model, can be used to guide the retrieval process, and we demonstrate our methods on both synthetic and real observations of cool stellar winds.
@article{deceuster2024bayesianpomme, author = {De Ceuster, F and Ceulemans, T and Decin, L and Danilovich, T and Yates, J}, journal = {Journal of Open Source Software}, month = dec, number = {104}, publisher = {Open Journals}, title = {Bayesian model reconstruction based on spectral line observations with pomme}, volume = {9}, year = {2024}, doi = {10.21105/joss.07321}, issn = {2475-9066}, eissn = {2475-9066}, day = {10}, publicationstatus = {published} } - ApJSBayesian Model Reconstruction Based on Spectral Line ObservationsF De Ceuster, T Ceulemans, L Decin, and 2 more authorsAstrophysical Journal Supplement Series, Dec 2024
Spectral line observations encode a wealth of information. A key challenge, therefore, lies in the interpretation of these observations in terms of models to derive the physical and chemical properties of the astronomical environments from which they arise. In this paper, we present pomme, an open-source Python package that allows users to retrieve 1D or 3D models of physical properties, such as chemical abundance, velocity, and temperature distributions of (optically thin) astrophysical media, based on spectral line observations. We discuss how prior knowledge, for instance, in the form of a steady-state hydrodynamics model, can be used to guide the retrieval process, and we demonstrate our methods on both synthetic and real observations of cool stellar winds.
@article{deceuster2024bayesianobservations, author = {De Ceuster, F and Ceulemans, T and Decin, L and Danilovich, T and Yates, J}, journal = {Astrophysical Journal Supplement Series}, month = dec, number = {2}, publisher = {IOP Publishing}, title = {Bayesian Model Reconstruction Based on Spectral Line Observations}, volume = {275}, year = {2024}, doi = {10.3847/1538-4365/ad89a2}, issn = {0067-0049}, eissn = {1538-4365}, day = {5}, publicationstatus = {published}, } - Modelling predicts a molecule-rich disc around the AGB star L2 PuppisM Sande, C Walsh, T Danilovich, and 2 more authorsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Jun 2024
@article{vandesande2024modellingpuppis, author = {Van de Sande, M and Walsh, C and Danilovich, T and De Ceuster, F and Ceulemans, T}, journal = {MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY}, month = jun, number = {1}, pages = {734--754}, publisher = {OXFORD UNIV PRESS}, title = {Modelling predicts a molecule-rich disc around the AGB star L<sub>2</sub> Puppis}, volume = {532}, year = {2024}, doi = {10.1093/mnras/stae1553}, issn = {0035-8711}, eissn = {1365-2966}, keyword = {GAS}, language = {English}, day = {29}, publicationstatus = {published} } - A&AATOMIUM: Molecular inventory of 17 oxygen-rich evolved stars observed with ALMAS Wallstrom, T Danilovich, H Muller, and 35 more authorsAstronomy & Astrophysics, Jan 2024
Context. The dusty winds of cool evolved stars are a major contributor of the newly synthesised material enriching the Galaxy and future generations of stars. However, the details of the physics and chemistry behind dust formation and wind launching have yet to be pinpointed. Recent spatially resolved observations show the importance of gaining a more comprehensive view of the circumstellar chemistry, but a comparative study of the intricate interplay between chemistry and physics is still difficult because observational details such as frequencies and angular resolutions are rarely comparable. Aims. Aiming to overcome these deficiencies, ATOMIUM is an ALMA Large Programme to study the physics and chemistry of the circumstellar envelopes of a diverse set of oxygen-rich evolved stars under homogeneous observing conditions at three angular resolutions between 0.02″−1.4″. Here we summarize the molecular inventory of these sources, and the correlations between stellar parameters and molecular content. Methods. Seventeen oxygen-rich or S-type asymptotic giant branch (AGB) and red supergiant (RSG) stars have been observed in several tunings with ALMA Band 6, targeting a range of molecules to probe the circumstellar envelope and especially the chemistry of dust formation close to the star. We systematically assigned the molecular carriers of the spectral lines and measured their spectroscopic parameters and the angular extent of the emission of each line from integrated intensity maps. Results. Across the ATOMIUM sample, we detect 291 transitions of 24 different molecules and their isotopologues. This includes several first detections in oxygen-rich AGB/RSG stars: PO v = 1, SO2 v1 = 1 and v2 = 2, and several high energy H2O transitions. We also find several first detections in S-type AGB stars: vibrationally excited HCN v2 = 2,3 and SiS v = 4,5,6, as well as first detections of the molecules SiC, AlCl, and AlF in W Aql. Overall, we find strong correlations between the following molecular pairs: CS and SiS, CS and AlF, NaCl and KCl, AlO and SO, SO2 and SO, and SO2 and H2O; meaning both molecules tend to have more detected emission lines in the same sources. The measured isotopic ratios of Si and S are found to be consistent with previous measurements, except for an anomalously high 29Si/30Si ratio of 4 ± 1 in the RSG VX Sgr. Conclusions. This paper presents the overall molecular inventory and an initial analysis of the large ATOMIUM dataset, laying the groundwork for future work deriving molecular abundances and abundance profiles using radiative transfer modeling which will provide more rigorous tests for chemical models.
@article{wallstrom2024atomiumalma, author = {Wallstrom, S and Danilovich, T and Muller, H and Gottlieb, C and Maes, S and Van de Sande, M and Decin, L and Richards, A and Baudry, A and Bolte, J and Ceulemans, T and De Ceuster, F and de Koter, A and El Mellah, I and Esseldeurs, M and Etoka, S and Gobrecht, D and Gottlieb, E and Gray, M and Herpin, F and Jeste, M and Kee, ND and Kervella, P and Khouri, T and Lagadec, E and Malfait, J and Marinho, L and McDonald, I and Menten, K and Millar, T and Montarges, M and Nuth, J and Plane, J and Sahai, R and Waters, R and Wong, KT and Yates, J and Zijlstra, A}, journal = {Astronomy \& Astrophysics}, month = jan, number = {50}, publisher = {EDP Sciences}, title = {ATOMIUM: Molecular inventory of 17 oxygen-rich evolved stars observed with ALMA}, volume = {681}, year = {2024}, doi = {10.1051/0004-6361/202347632}, issn = {0004-6361}, keyword = {1285221N#55744520}, day = {9}, publicationstatus = {published} }
2023
- A&A3D simulations of AGB stellar winds – II. Ray-tracer implementation and impact of radiation on the outflow morphologyM Esseldeurs, L Siess, F De Ceuster, and 6 more authorsAstronomy & Astrophysics, Jun 2023
Context: Stars with an initial mass below 8 Msun evolve through the asymptotic giant branch (AGB) phase, during which they develop a strong stellar wind, due to radiation pressure on newly formed dust grains. Recent observations have revealed significant morphological complexities in AGB outflows, which are most probably caused by the interaction with a companion. Aims: We aim for a more accurate description of AGB wind morphologies by accounting for both the radiation force in dust-driven winds and the impact of a companion on the AGB wind morphology. Methods: We present the implementation of a ray tracer for radiative transfer in the smoothed particle hydrodynamics (SPH) code Phantom. Our method allows for the creation of a 3D map of the optical depth around the AGB star. The effects of four different descriptions of radiative transfer, with different degrees of complexity, are compared: the free-wind approximation, the geometrical approximation, the Lucy approximation, and the attenuation approximation. Finally, we compare the Lucy and attenuation approximation to predictions with the 3D radiative transfer code Magritte. Results: The effects of the different radiative transfer treatments are analysed considering both a low and high mass-loss rate regime, and this both in the case of a single AGB star, as well as for an AGB binary system. For both low and high mass-loss rates, the velocity profile of the outflow is modified when going from the free-wind to the geometrical approximation, also resulting in a different wind morphology for AGB binary systems. In the case of a low mass-loss rate, the effect of the Lucy and attenuation approximation is negligible due to the low densities but morphological differences appear in the high mass-loss rate regime. By comparing the radiative equilibrium temperature and radiation force to the predictions from Magritte, we show that for most of the models, the Lucy approximation works best. Although, close to the companion, artificial heating occurs and it fails to simulate the shadow cast by the companion. The attenuation approximation leads to stronger absorption of the radiation field, yielding a lower equilibrium temperature and weaker radiation force, but it produces the shadow cast by the companion. From the predictions of the 3D radiative transfer code Magritte, we also conclude that a radially directed radiation force is a reasonable assumption. Conclusions: The radiation force plays a critical role in dust-driven AGB winds, impacting the velocity profile and morphological structures. For low mass-loss rates, the geometrical approximation suffices, however for high mass-loss rates, a more rigorous method is required. Among the studied approaches, the Lucy approximation provides the most accurate results, although it does not account for all effects.
@article{esseldeurs3dmorphology, author = {Esseldeurs, M and Siess, L and De Ceuster, F and Homan, W and Malfait, J and Maes, S and Konings, T and Ceulemans, T and Decin, L}, journal = {Astronomy \& Astrophysics}, month = jun, number = {A122}, publisher = {EDP Sciences}, title = {3D simulations of AGB stellar winds -- II. Ray-tracer implementation and impact of radiation on the outflow morphology}, volume = {674}, year = {2023}, doi = {10.1051/0004-6361/202346282}, issn = {0004-6361}, day = {14}, publicationstatus = {online-published} } - Radiative transfer as a Bayesian linear regression problemF De Ceuster, T Ceulemans, J Cockayne, and 2 more authorsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Feb 2023
@article{deceuster2023radiativeproblem, author = {De Ceuster, F and Ceulemans, T and Cockayne, J and Decin, L and Yates, J}, journal = {MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY}, month = feb, number = {4}, pages = {5536--5551}, publisher = {OXFORD UNIV PRESS}, title = {Radiative transfer as a Bayesian linear regression problem}, volume = {518}, year = {2023}, doi = {10.1093/mnras/stac3461}, issn = {0035-8711}, eissn = {1365-2966}, keyword = {SCHEME}, language = {English}, publicationstatus = {published} }
2022
- 3D Line Radiative Transfer & Synthetic Observations with MagritteF De Ceuster, T Ceulemans, A Srivastava, and 6 more authorsJournal of Open Source Software, Mar 2022
@article{deceuster3dmagritte, author = {De Ceuster, F and Ceulemans, T and Srivastava, A and Homan, W and Bolte, J and Yates, J and Decin, L and Boyle, P and Hetherington, J}, journal = {Journal of Open Source Software}, month = mar, number = {71}, publisher = {Open Journals}, title = {3D Line Radiative Transfer \& Synthetic Observations with Magritte}, volume = {7}, year = {2022}, doi = {10.21105/joss.03905}, issn = {2475-9066}, day = {3}, publicationstatus = {online-published} }
talks
2023
- Computational improvements to line radiative transfer in MagritteT. CeulemansAtomium 2023 spring, Mar 2023
@talk{Talks_Ceulemans2023_Atomium, title = {Computational improvements to line radiative transfer in Magritte}, author = {{Ceulemans}, T.}, month = mar, year = {2023}, conference = {Atomium 2023 spring}, }
posters
2023
- Magritte, a 3D NLTE line radiative transfer code for imaging the circumstellar environmentT. CeulemansJul 2023
author = {{Ceulemans}, T.}, month = jul, year = {2023}, conference = {EAS 2023 Krakow}, url = {https://eas2023programme.kuoni-congress.info/presentation/a-novel-numerically-stable-co-moving-method-to-speed-up-line-radiative-transfer}, }