| Title: |
Bias versus variance when fitting multi-species molecular lines with a non-LTE radiative transfer model ; 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 |
| Authors: |
Roueff, Antoine; Pety, Jérôme; Gerin, Maryvonne; Ségal, Léontine E.; Goicoechea, Javier R.; Liszt, Harvey S.; Gratier, Pierre; Beslic, Ivana; Einig, Lucas; Gaudel, Mathilde; Orkisz, Jan H.; Palud, Pierre; Santa-Maria, Miriam G.; de Souza Magalhaes, Victor; Zakardjian, Antoine; Bardeau, Sébastien; Bron, Emeric; Chainais, Pierre; Coudé, Simon; Demyk, Karine; Guzman, Viviana V.; Hughes, Annie; Languignon, David; Levrier, François; Lis, Dariusz C.; Le Bourlot, Jacques; Le Petit, Franck; Peretto, Nicolas; Roueff, Evelyne; Sievers, Albrecht; Thouvenin, Pierre-Antoine |
| Contributors: |
Institut des Matériaux, de Microélectronique et des Nanosciences de Provence (IM2NP); Aix Marseille Université (AMU)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS); Institut de RadioAstronomie Millimétrique (IRAM); Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS); LERMA Cergy (LERMA); Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (LERMA); École normale supérieure - Paris (ENS-PSL); Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris; Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY)-École normale supérieure - Paris (ENS-PSL); Centre National de la Recherche Scientifique (CNRS)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY); Instituto de Física Fundamental Madrid (IFF); Consejo Superior de Investigaciones Cientificas España = Spanish National Research Council Spain (CSIC); National Radio Astronomy Observatory Charlottesville (NRAO); National Radio Astronomy Observatory (NRAO); Laboratoire d'Astrophysique de Bordeaux Pessac (LAB); Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS); GIPSA - Signal Images Physique (GIPSA-SIGMAPHY); Observatoire des Sciences de l'Univers de Grenoble (Fédération OSUG)-GIPSA Pôle Sciences des Données (GIPSA-PSD); Grenoble Images Parole Signal Automatique (GIPSA-lab); Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP); Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP); Université Grenoble Alpes (UGA)-Grenoble Images Parole Signal Automatique (GIPSA-lab); Université Grenoble Alpes (UGA)-Observatoire des Sciences de l'Univers de Grenoble (OSUG); Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ); Chalmers University of Technology Gothenburg, Sweden; Centre de Recherche en Informatique, Signal et Automatique de Lille - UMR 9189 (CRIStAL); Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS); Institut de recherche en astrophysique et planétologie (IRAP); Université Toulouse III - Paul Sabatier (UT3); Communauté d'universités et établissements de Toulouse (Comue de Toulouse)-Communauté d'universités et établissements de Toulouse (Comue de Toulouse)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS); Worcester State University Worcester; Harvard-Smithsonian Center for Astrophysics (CfA); Harvard University-Smithsonian Institution; Instituto de Astrofisica Santiago; Pontificia Universidad Católica de Chile = Pontifical Catholic University of Chile Santiago (PUC); Astrophysique; Laboratoire de physique de l'ENS - ENS Paris (LPENS); Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL; Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL); Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL; Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL); California Institute of Technology (CALTECH); Cardiff University; ANR-21-CE31-0010,DAOISM,Analyse Détaillée du Milieu Inter-Stellaire(2021) |
| Source: |
ISSN: 0004-6361. |
| Publisher Information: |
CCSD; EDP Sciences |
| Publication Year: |
2024 |
| Collection: |
Université Toulouse III - Paul Sabatier: HAL-UPS |
| Subject Terms: |
radiative transfer; methods: data analysis; methods: statistical; ISM: clouds; ISM: general; line: profiles; [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] |
| Description: |
International audience ; Context. Robust radiative transfer techniques are requisite for efficiently extracting the physical and chemical information from molecular rotational lines.Aims. We study several hypotheses that enable robust estimations of the column densities and physical conditions when fitting one or two transitions per molecular species. We study the extent to which simplifying assumptions aimed at reducing the complexity of the problem introduce estimation biases and how to detect them.Methods. We focus on the CO and HCO+ isotopologues and analyze maps of a 50 square arcminutes field. We used the RADEX escape probability model to solve the statistical equilibrium equations and compute the emerging line profiles, assuming that all species coexist. Depending on the considered set of species, we also fixed the abundance ratio between some species and explored different values. We proposed a maximum likelihood estimator to infer the physical conditions and considered the effect of both the thermal noise and calibration uncertainty. We analyzed any potential biases induced by model misspecifications by comparing the results on the actual data for several sets of species and confirmed with Monte Carlo simulations. The variance of the estimations and the efficiency of the estimator were studied based on the Cramér-Rao lower bound.Results. Column densities can be estimated with 30% accuracy, while the best estimations of the volume density are found to be within a factor of two. Under the chosen model framework, the peak 12CO (1 – 0) is useful for constraining the kinetic temperature. The thermal pressure is better and more robustly estimated than the volume density and kinetic temperature separately. Analyzing CO and HCO+ isotopologues and fitting the full line profile are recommended practices with respect to detecting possible biases.Conclusions. Combining a non-local thermodynamic equilibrium model with a rigorous analysis of the accuracy allows us to obtain an efficient estimator and identify where ... |
| Document Type: |
article in journal/newspaper |
| Language: |
English |
| DOI: |
10.1051/0004-6361/202449148 |
| Availability: |
https://hal.science/hal-04619550; https://hal.science/hal-04619550v2/document; https://hal.science/hal-04619550v2/file/aa49148-24.pdf; https://doi.org/10.1051/0004-6361/202449148 |
| Rights: |
https://about.hal.science/hal-authorisation-v1/ ; info:eu-repo/semantics/OpenAccess |
| Accession Number: |
edsbas.8ECD661A |
| Database: |
BASE |