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Physical conditions in the gas phases of the giant H II region LMC-N 11

hal.structure.identifierAstrophysique Interprétation Modélisation [AIM (UMR_7158 / UMR_E_9005 / UM_112)]
hal.structure.identifierUniversity of North Carolina [Charlotte] [UNC]
dc.contributor.authorLEBOUTEILLER, V.
hal.structure.identifierAstrophysique Interprétation Modélisation [AIM (UMR_7158 / UMR_E_9005 / UM_112)]
dc.contributor.authorCORMIER, D.
hal.structure.identifierAstrophysique Interprétation Modélisation [AIM (UMR_7158 / UMR_E_9005 / UM_112)]
dc.contributor.authorMADDEN, S.
dc.contributor.authorGALAMETZ, M.
dc.contributor.authorHONY, S.
hal.structure.identifierAstrophysique Interprétation Modélisation [AIM (UMR_7158 / UMR_E_9005 / UM_112)]
dc.contributor.authorGALLIANO, F.
dc.contributor.authorCHEVANCE, M.
dc.contributor.authorLEE, M.-Y.
hal.structure.identifierLaboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
dc.contributor.authorBRAINE, J.
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.authorPOLLES, F.
dc.contributor.authorREQUEÑA-TORRES, M.
dc.contributor.authorINDEBETOUW, R.
hal.structure.identifierInstitut de recherche en astrophysique et planétologie [IRAP]
dc.contributor.authorHUGHES, A.
dc.contributor.authorABEL, N.
dc.date.issued2019-12
dc.identifier.issn0004-6361
dc.description.abstractEnContext. The ambiguous origin of the [C II] 158μm line in the interstellar medium complicates its use for diagnostics concerning the star-formation rate and physical conditions in photodissociation regions.Aims. We investigate the origin of [C II] in order to measure the total molecular gas content, the fraction of CO-dark H2 gas, and how these parameters are impacted by environmental effects such as stellar feedback.Methods. We observed the giant H II region N 11 in the Large Magellanic Cloud with SOFIA/GREAT. The [C II] line is resolved in velocity and compared to H I and CO, using a Bayesian approach to decompose the line profiles. A simple model accounting for collisions in the neutral atomic and molecular gas was used in order to derive the H2 column density traced by C+.Results. The profile of [C II] most closely resembles that of CO, but the integrated [C II] line width lies between that of CO and that of H I. Using various methods, we find that [C II] mostly originates from the neutral gas. We show that [C II] mostly traces the CO-dark H2 gas but there is evidence of a weak contribution from neutral atomic gas preferentially in the faintest components (as opposed to components with low [C II]/CO or low CO column density). Most of the molecular gas is CO-dark. The CO-dark H2 gas, whose density is typically a few 100s cm−3 and thermal pressure in the range 103.5−5 K cm−3, is not always in pressure equilibrium with the neutral atomic gas. The fraction of CO-dark H2 gas decreases with increasing CO column density, with a slope that seems to depend on the impinging radiation field from nearby massive stars. Finally we extend previous measurements of the photoelectric-effect heating efficiency, which we find is constant across regions probed with Herschel, with [C II] and [O I] being the main coolants in faint and diffuse, and bright and compact regions, respectively, and with polycyclic aromatic hydrocarbon emission tracing the CO-dark H2 gas heating where [C II] and [O I] emit.Conclusions. We present an innovative spectral decomposition method that allows statistical trends to be derived for the molecular gas content using CO, [C II], and H I profiles. Our study highlights the importance of velocity-resolved photodissociation region (PDR) diagnostics and higher spatial resolution for H I observations as future steps.
dc.description.sponsorshipLe cycle du gaz autour des galaxies : origine et conditions physiques des flots de gaz froid - ANR-16-CE31-0011
dc.language.isoen
dc.publisherEDP Sciences
dc.subject.enISM: general, photon-dominated region, Magellanic Clouds, submillimeter: ISM, infrared: ISM, galaxies: star formation
dc.subject.enISM: general, photon-dominated region, Magellanic Clouds, submillimeter: ISM, infrared: ISM, galaxies: star formation
dc.title.enPhysical conditions in the gas phases of the giant H II region LMC-N 11
dc.typeArticle de revue
dc.identifier.doi10.1051/0004-6361/201936303
dc.subject.halPhysique [physics]
dc.subject.halPhysique [physics]/Astrophysique [astro-ph]
dc.identifier.arxiv1911.03280
dc.description.sponsorshipEuropeCharacterizing properties of the interstellar medium to better understand how stars form in galaxies
bordeaux.journalAstronomy and Astrophysics - A&A
bordeaux.pageA106
bordeaux.volume632
bordeaux.peerReviewedoui
hal.identifierhal-03122791
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-03122791v1
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