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Tracers of the ionization fraction in dense and translucent gas: I. Automated exploitation of massive astrochemical model grids

hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres [LERMA]
dc.contributor.authorBRON, Emeric
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres [LERMA]
dc.contributor.authorROUEFF, Evelyne
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres [LERMA]
dc.contributor.authorGERIN, Maryvonne
hal.structure.identifierInstitut de RadioAstronomie Millimétrique [IRAM]
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres [LERMA]
dc.contributor.authorPETY, Jérôme
hal.structure.identifierFORMATION STELLAIRE 2020
dc.contributor.authorGRATIER, Pierre
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres [LERMA]
dc.contributor.authorPETIT, Franck Le
hal.structure.identifierPontificia Universidad Católica de Chile [UC]
dc.contributor.authorGUZMAN, Viviana
hal.structure.identifierOnsala Space Observatory [OSO]
dc.contributor.authorORKISZ, Jan
hal.structure.identifierInstitut de RadioAstronomie Millimétrique [IRAM]
dc.contributor.authorMAGALHAES, Victor De Souza
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres [LERMA]
dc.contributor.authorGAUDEL, Mathilde
hal.structure.identifierSignal et Communications [IRIT-SC]
dc.contributor.authorVONO, Maxime
hal.structure.identifierInstitut de RadioAstronomie Millimétrique [IRAM]
dc.contributor.authorBARDEAU, Sébastien
hal.structure.identifierCentre de Recherche en Informatique, Signal et Automatique de Lille - UMR 9189 [CRIStAL]
dc.contributor.authorCHAINAIS, Pierre
hal.structure.identifierInstituto de Física Fundamental [Madrid] [IFF]
dc.contributor.authorGOICOECHEA, Javier
hal.structure.identifierInstitut de recherche en astrophysique et planétologie [IRAP]
dc.contributor.authorHUGHES, Annie
hal.structure.identifierOnsala Space Observatory [OSO]
dc.contributor.authorKAINULAINEN, Jouni
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres [LERMA]
dc.contributor.authorLANGUIGNON, David
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres [LERMA]
dc.contributor.authorBOURLOT, Jacques Le
hal.structure.identifierAstrophysique
dc.contributor.authorLEVRIER, François
hal.structure.identifierNational Radio Astronomy Observatory [Charlottesville] [NRAO]
dc.contributor.authorLISZT, Harvey
hal.structure.identifierHarvard-Smithsonian Center for Astrophysics [CfA]
dc.contributor.authorÖBERG, Karin
hal.structure.identifierSchool of Physics and Astronomy [Cardiff]
dc.contributor.authorPERETTO, Nicolas
hal.structure.identifierInstitut FRESNEL [FRESNEL]
hal.structure.identifierPhyTI [PhyTI]
dc.contributor.authorROUEFF, Antoine
hal.structure.identifierInstitut de RadioAstronomie Millimétrique [IRAM]
dc.contributor.authorSIEVERS, Albrecht
dc.date.issued2021-01
dc.identifier.issn0004-6361
dc.description.abstractEnThe ionization fraction plays a key role in the physics and chemistry of the neutral interstellar medium, from controlling the coupling of the gas to the magnetic field to allowing fast ion-neutral reactions that drive interstellar chemistry. Most estimations of the ionization fraction have relied on deuterated species such as DCO+, whose detection is limited to dense cores representing an extremely small fraction of the volume of the giant molecular clouds they are part of. As large field-of-view hyperspectral maps become available, new tracers may be found. We search for the best observable tracers of the ionization fraction based on a grid of astrochemical models. We build grids of models that sample randomly a large space of physical conditions (unobservable quantities such as gas density, temperature, etc.) and compute the corresponding observables (line intensities, column densities) and the ionization fraction. We estimate the predictive power of each potential tracer by training a Random Forest model to predict the ionization fraction from that tracer, based on these model grids. In both translucent medium and cold dense medium conditions, several observable tracers with very good predictive power for the ionization fraction are found. Several tracers in cold dense medium conditions are found to be better and more widely applicable than the traditional DCO+/HCO+ ratio. We also provide simpler analytical fits for estimating the ionization fraction from the best tracers, and for estimating the associated uncertainties. We discuss the limitations of the present study and select a few recommended tracers in both types of conditions. The method presented here is very general and can be applied to the measurement of any other quantity of interest (cosmic ray flux, elemental abundances, etc.) from any type of model (PDR models, time-dependent chemical models, etc.). (abridged)
dc.language.isoen
dc.publisherEDP Sciences
dc.subject.enAstrochemistry
dc.subject.enISM: molecules
dc.subject.enISM: clouds
dc.subject.enISM: lines and bands
dc.subject.enMethods: statistical
dc.subject.enMethods: numerical
dc.title.enTracers of the ionization fraction in dense and translucent gas: I. Automated exploitation of massive astrochemical model grids
dc.typeArticle de revue
dc.identifier.doi10.1051/0004-6361/202038040
dc.subject.halPlanète et Univers [physics]
dc.identifier.arxiv2007.13593
bordeaux.journalAstronomy and Astrophysics - A&A
bordeaux.pageA28
bordeaux.volume645
bordeaux.peerReviewedoui
hal.identifierhal-03017390
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-03017390v1
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