Welcome to the ORION-B & DAOISM projects
Molecular lines and line ratios are widely used to infer the physical and chemical properties of Galactic and extragalactic star-forming regions. With modern (sub-)millimeter receivers, observations increasingly provide many molecular lines at once, making it essential to understand what information each line carries and how reliably physical conditions can be inferred from combinations of tracers.
The ORION-B project uses the Orion B Giant Molecular Cloud as a resolved laboratory for this purpose. The IRAM 30-m survey maps about five square degrees of the cloud and samples a broad range of environments, from UV-illuminated cloud edges to dense star-forming structures. The project has shown how molecular emission traces gas structure, turbulence, filaments, magnetic fields, ionization, irradiation and chemistry, and how several complementary lines can be combined to estimate otherwise difficult-to-measure physical quantities.
DAOISM extends this approach toward quantitative inference from increasingly rich data sets. It develops statistical, machine-learning and Bayesian methods for denoising molecular-line cubes, emulating expensive physical models, identifying the most informative observables, estimating physical-parameter maps and uncertainties, and interpreting observations when molecular clouds are spatially unresolved.
The above animation (credit & copyright: L. Orazi for the optical image and J. Pety, the ORION-B Collaboration & IRAM for the radio image) shows the Orion B cloud, known to house the Horsehead and Flame nebulae in optical and radio. The optical image mostly shows regions that are illuminated by the intense ultraviolet radiation from the massive young stars nearby, while the radio image reveals the hidden turbulent nature of the molecular gas where future generations of stars will be born.
Main scientific results DAOISM website at ANR
ORION-B public data products are available through the IRAM Data Management System under the ORION-B large programme.
2026
2026-06-26: Helena Mazurek's first PhD paper is accepted by A&A — Chemical diversity of dense cores in Orion B: The role of the environment (arXiv)
2026-06-16: DAOISM workshop videos are now available on YouTube — The recordings of the talks, presentation slides, book of abstracts, and concluding remarks from the DAOISM workshop Unifying Galactic and Extragalactic Views of Star Formation – Spectroscopic Studies & Data Science are available online. Watch the complete playlist on YouTube.
The presentations reporting DAOISM results can also be accessed directly:
Antoine Zakardjian — Estimating the dense gas mass of molecular clouds using spatially unresolved 3 mm line observations
Miriam Santa-Maria — Revisiting the role of the HCN(1-0) line as a tracer of the dense gas reservoir for star formation
Léontine Ségal — Toward robust estimates of the physicochemical properties of interstellar molecular clouds without ground truth
Emeric Bron — Neural network-based emulation of ISM models: the case of the Meudon PDR code
Pierre Palud — BEETROOTS, a new Bayesian framework for inverse problems
Lucas Einig — Quantifying the information content of spectral tracers for interstellar medium studies
Helena Mazurek — Dense core chemistry
Ivana Bešlić — From diffuse gas to star-forming filaments: Mapping the magnetic and ionization landscape of Orion B
2026-04-20: The DAOISM concluding workshop starts in Paris — Unifying Galactic and Extragalactic Views of Star Formation – Spectroscopic Studies & Data Science, held at the Institut d'Astrophysique de Paris from April 20 to April 24.
2026-02-02: First public announcement of the DAOISM concluding workshop — Unifying Galactic and Extragalactic Views of Star Formation – Spectroscopic Studies & Data Science.
2025
2025-11-06: Antoine Zakardjian successfully defended his PhD thesis — Inferring the internal density structure of spatially unresolved extragalactic molecular clouds
2025-10-24: Léontine Ségal successfully defended her PhD thesis — Towards a robust estimation of the physico-chemical properties of interstellar molecular clouds in the absence of reference data
2025-08-27: Antoine Zakardjian's paper is accepted by A&A — Estimating the dense gas mass of molecular clouds using spatially unresolved 3mm line observations
2025-07-14: Ivana Bešlić's paper is accepted by A&A — The first estimation of the ionization fraction in dense and translucent molecular gas across Orion B
2025-04-15: Pierre Palud's paper is accepted by A&A — BEETROOTS: Spatially regularized Bayesian inference of physical parameter maps. Application to Orion
2025-02-10: Antoine Zakardjian's first PhD paper is accepted by A&A — Understanding spatially unresolved measurements of molecular line emission.
2024
2024-10-22: Lucas Einig successfully defended his PhD thesis — Relationships between observables and astrophysical conditions: a statistical and learning approach to the Orion B giant molecular cloud. 
2024-09-24: Léontine Ségal's first paper is accepted by A&A — Toward a robust physical and chemical characterization of heterogeneous lines of sight: The case of the Horsehead nebula.
2024-09-19: Lucas Einig and Pierre Palud's paper is accepted by A&A — Quantifying the informativity of emission lines to infer physical conditions in giant molecular clouds. I. Application to model predictions.
2024-02-19: Antoine Roueff's paper is accepted by A&A — Bias versus variance when fitting multi-species molecular lines with a non-LTE radiative transfer model: Application to the estimation of the gas temperature and volume density.
2024-01-20: Ivana Bešlić's paper is accepted by A&A — The magnetic field in the Flame nebula.
2023
2023-12-07: Pierre Palud successfully defended his PhD thesis — Sampling methods for statistical inference of non-linear inverse problems: spatial distribution of physico-chemical properties of the interstellar medium.
2023-10-01: Helena Mazurek starts her PhD thesis — From small to large scales: structure and composition of molecular gas.
2023-09-29: Miriam Santa-Maria successfully defended her PhD thesis — Characterization of the extended warm molecular gas in high-mass star-forming regions.
2023-09-05: Miriam Santa-Maria's first paper is accepted by A&A — HCN emission from translucent gas and UV-illuminated cloud edges revealed by wide-field IRAM 30 m maps of the Orion B GMC.
2023-07-31: Pierre Palud and Lucas Einig's paper is accepted by A&A — Neural network-based emulation of interstellar medium models.
2023-07-18: Lucas Einig's first paper is accepted by A&A — Deep learning denoising by dimension reduction: Application to the ORION-B line cubes.
2023-06-23: Pierre Palud's first paper is published by IEEE Transactions on Signal Processing — Efficient Sampling of Non Log-Concave Posterior Distributions With Mixture of Noises.
2022
2022-11-15: Antoine Zakardjian starts his PhD thesis — Inferring physical conditions in extragalactic GMCs through joint analysis of ORION-B and PHANGS data.
2022-11-14: Mathilde Gaudel's first paper is accepted by A&A — Gas kinematics around filamentary structures in the Orion B cloud.
2022-09-22: Léontine Ségal starts her PhD thesis — Robustness of the Estimation of Physical and Chemical Characteristics of Giant Molecular Clouds without Ground Truth.
2021
2021-10-01: Lucas Einig starts his PhD thesis — Relationships between observables and astrophysical conditions: a statistical and learning approach to the Orion B giant molecular cloud.
2020
2020-11-19: Second ORION-B press release — Artificial intelligence, a game-changer for studying stellar nurseries.
2020-10-01: Pierre Palud starts his PhD thesis — Sampling methods for statistical inference of non-linear inverse problems: spatial distribution of physico-chemical properties of the interstellar medium.
2020-08-25: Pierre Gratier's paper is accepted by A&A — Quantitative inference of the H2 column densities from 3 mm molecular emission: A case study towards Orion B.
2020-07-02: Emeric Bron's paper is accepted by A&A — Tracers of the ionization fraction in dense and translucent gas. I. Automated exploitation of massive astrochemical model grids.
2020-04-28: Antoine Roueff's paper is accepted by A&A — C18O, 13CO, and 12CO abundances and excitation temperatures in the Orion B molecular cloud: An analysis of the precision achievable when modeling spectral line within the Local Thermodynamic Equilibrium approximation.
2019
2019-02-06: Jan H. Orkisz's paper is accepted by A&A — A dynamically young, gravitationally stable network of filaments in Orion B.
2018
2018-10-22: Jan H. Orkisz successfully defended his PhD thesis — Understanding the structure of molecular clouds: multi-line wide-field imaging of Orion B.
2017
2017-10-02: Emeric Bron's paper is accepted by A&A — Clustering the Orion B giant molecular cloud based on its molecular emission.
2017-05-24: The ORION-B project is noticed in Nature — Astrophysics: Multi-molecular views of a stellar nursery.
2017-03-07: First ORION-B press release to celebrate the publications of the first three papers in the same A&A issue — Beyond the appearances: The anatomy of the Orion Jedi revealed by radio-astronomy.
2017-01-13: Pierre Gratier's paper is accepted by A&A — Dissecting the molecular structure of the Orion B cloud: Insight from Principal Component Analysis.
2017-01-02: Jan H. Orkisz's first paper is accepted by A&A — Turbulence and star formation efficiency in molecular clouds: solenoidal versus compressive motions in Orion B.
2016
2016-11-08: The first ORION-B paper (Jérôme Pety's one) is accepted by A&A — The anatomy of the Orion B Giant Molecular Cloud: A local template for studies of nearby galaxies.
2016-10-12: The ORION-B project is now on ResearchGate — ORION-B: The Anatomy of a Giant Molecular Cloud.
2016-09-27: Chloé Daudon successfully defended her internship — Statistical analysis of hyperspectral data. New keys to understand the structure, composition and the dynamics of the interstellar medium.
2016-04-01: Chloé Daudon is starting a 6 months internship with us to finish her engineering education — ENSG Géomatique
2015
2015-09-01: Jan H. Orkisz starts his PhD thesis — Understanding the structure of molecular clouds: multi-line wide-field imaging of Orion B.