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[C ii] absorption and emission in the diffuse interstellar medium across the Galactic Plane

hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
dc.contributor.authorGERIN, Maryvonne
hal.structure.identifierAMOR 2015
dc.contributor.authorRUAUD, M.
hal.structure.identifierInstituto de Ciencia de Materiales de Madrid [ICMM]
dc.contributor.authorGOICOECHEA, Javier
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
dc.contributor.authorGUSDORF, Antoine
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
dc.contributor.authorGODARD, Benjamin
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
dc.contributor.authorDE LUCA, Massimo
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
dc.contributor.authorFALGARONE, Edith
hal.structure.identifierJet Propulsion Laboratory [JPL]
dc.contributor.authorGOLDSMITH, Paul
hal.structure.identifierLaboratoire d'Etude du Rayonnement et de la Matière en Astrophysique [LERMA]
hal.structure.identifierCalifornia Institute of Technology [CALTECH]
dc.contributor.authorLIS, Darek
hal.structure.identifierMax-Planck-Institut für Radioastronomie [MPIFR]
dc.contributor.authorMENTEN, Karl
hal.structure.identifierJohns Hopkins University [JHU]
dc.contributor.authorNEUFELD, David
hal.structure.identifierCalifornia Institute of Technology [CALTECH]
dc.contributor.authorPHILLIPS, Thomas
hal.structure.identifierNational Radio Astronomy Observatory [NRAO]
dc.contributor.authorLISZT, Harvey
dc.date.created2014-10-15
dc.date.issued2015
dc.identifier.issn0004-6361
dc.description.abstractEnIonized carbon is the main gas-phase reservoir of carbon in the neutral diffuse interstellar medium and its 158 µm fine structure transition [C ii] is the most important cooling line of the diffuse interstellar medium (ISM). We combine [C ii] absorption and emission spectroscopy to gain an improved understanding of physical conditions in the different phases of the ISM.. We present high resolution [C ii] spectra obtained with the Herschel/HIFI instrument towards bright dust continuum sources regions in the Galactic plane, probing simultaneously the diffuse gas along the line of sight and the background high-mass star forming regions. These data are complemented by single pointings in the 492 and 809 GHz fine structure lines of atomic carbon and by medium spectral resolution spectral maps of the fine structure lines of atomic oxygen at 63 and 145 µm with Herschel/PACS. We show that the presence of foreground absorption may completely cancel the emission from the background source in medium spectral resolution PACS data and that high spectral resolution spectra are needed to interpret the [C ii] and [O i] emission and the [C ii]/FIR ratio. This phenomenon may explain part of the [C ii]/FIR deficit seen in external luminous infrared galaxies where the bright emission from the nuclear regions may be partially canceled by absorption from diffuse gas in the foreground. The C + and C excitation in the diffuse gas is consistent with a median pressure of ∼ 5900 K cm −3 for a mean kinetic temperature of ∼ 100 K. A few higher pressure regions are detected along the lines of sight, as emission features in both fine structure lines of atomic carbon. The knowledge of the gas density allows us to determine the filling factor of the absorbing gas along the selected lines of sight. The derived median value of the filling factor is 2.4 %, in good agreement with the properties of the Galactic Cold Neutral Medium. The mean excitation temperature is used to derive the average cooling due to C + in the Galactic plane : 9.5 × 10 −26 ergs −1 H −1 . Along the observed lines of sight, the gas phase carbon abundance does not exhibit a strong gradient as a function of Galacto-centric radius and has a weighted average of C/H = 1.5 ± 0.4 × 10 −4 .
dc.language.isoen
dc.publisherEDP Sciences
dc.subject.enG343+015
dc.subject.enISM : general
dc.subject.enISM : structure
dc.subject.enISM : individual objects : W28A
dc.subject.enW31C
dc.subject.enW33A
dc.subject.enW49N
dc.subject.enW51
dc.subject.enDR21(OH)
dc.subject.enW3-IRS5
dc.subject.enISM : lines and bands
dc.subject.enGalaxy : disk
dc.subject.enInfrared : ISM
dc.title.en[C ii] absorption and emission in the diffuse interstellar medium across the Galactic Plane
dc.typeArticle de revue
dc.identifier.doi10.1051/0004-6361/201424349
dc.subject.halPhysique [physics]/Astrophysique [astro-ph]
dc.identifier.arxiv1410.4663
bordeaux.journalAstronomy and Astrophysics - A&A
bordeaux.pageid.A30
bordeaux.volume573
bordeaux.peerReviewedoui
hal.identifierhal-01074900
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-01074900v1
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