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Verfasst von:Lebouteiller, Vianney [VerfasserIn]   i
 Cormier, D. [VerfasserIn]   i
 Madden, S. C. [VerfasserIn]   i
 Galametz, M. [VerfasserIn]   i
 Hony, Sacha [VerfasserIn]   i
 Galliano, F. [VerfasserIn]   i
 Chevance, Mélanie [VerfasserIn]   i
 Lee, M.-Y. [VerfasserIn]   i
 Braine, J. [VerfasserIn]   i
 Polles, F. L. [VerfasserIn]   i
 Requeña-Torres, M. A. [VerfasserIn]   i
 Indebetouw, R. [VerfasserIn]   i
 Hughes, A. [VerfasserIn]   i
 Abel, N. [VerfasserIn]   i
Titel:Physical conditions in the gas phases of the giant H II region LMC-N 11
Titelzusatz:II. Origin of [C II] and fraction of CO-dark gas
Verf.angabe:V. Lebouteiller, D. Cormier, S.C. Madden, M. Galametz, S. Hony, F. Galliano, M. Chevance, M.-Y. Lee, J. Braine, F.L. Polles, M.A. Requeña-Torres, R. Indebetouw, A. Hughes, and N. Abel
E-Jahr:2019
Jahr:10 December 2019
Umfang:30 S.
Fussnoten:Gesehen am 06.03.2020
Titel Quelle:Enthalten in: Astronomy and astrophysics
Ort Quelle:Les Ulis : EDP Sciences, 1969
Jahr Quelle:2019
Band/Heft Quelle:632(2019) Artikel-Nummer A106, 30 Seiten
ISSN Quelle:1432-0746
Abstract:Context. The ambiguous origin of the [C II] 158μ m 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 H<sub>2<sub/> gas, and how these parameters are impacted by environmental effects such as stellar feedback.<i>Methods.<i/> 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 H<sub>2<sub/> column density traced by C<sup>+<sup/>.<i>Results.<i/> 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 H<sub>2<sub/> 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 H<sub>2<sub/> gas, whose density is typically a few 100s cm<sup>−3<sup/> and thermal pressure in the range 10<sup>3.5−5<sup/> K cm<sup>−3<sup/>, is not always in pressure equilibrium with the neutral atomic gas. The fraction of CO-dark H<sub>2<sub/> 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 <i>Herschel<i/>, 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 H<sub>2<sub/> gas heating where [C II] and [O I] emit.<i>Conclusions.<i/> 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.
DOI:doi:10.1051/0004-6361/201936303
URL:Bitte beachten Sie: Dies ist ein Bibliographieeintrag. Ein Volltextzugriff für Mitglieder der Universität besteht hier nur, falls für die entsprechende Zeitschrift/den entsprechenden Sammelband ein Abonnement besteht oder es sich um einen OpenAccess-Titel handelt.

Volltext ; Verlag: https://doi.org/10.1051/0004-6361/201936303
 Volltext: https://www.aanda.org/articles/aa/abs/2019/12/aa36303-19/aa36303-19.html
 DOI: https://doi.org/10.1051/0004-6361/201936303
Datenträger:Online-Ressource
Sprache:eng
K10plus-PPN:1691810819
Verknüpfungen:→ Zeitschrift

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