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Results of the ESO-SEST Key Programme on CO in the Magellanic Clouds. IX. The giant LMC HII region complex N 11
The second-brightest star formation complex in the Large MagellanicCloud, N 11, was surveyed extensively in the J = 1-0 transition of12CO. In this paper we present maps and a cataloguecontaining the parameters of 29 individual molecular clouds in thecomplex, although more may be present. The distribution of molecular gasin the N 11 complex is highly structured. In the southwestern part of N11, molecular clouds occur in a ring or shell surrounding the major OBstar association LH 9. In the northeastern part, a chain of molecularclouds delineates the rim of one of the so-called supergiant shells inthe LMC. There appears to be very little diffuse molecular gasin-between the individual well-defined clouds, especially in thesouthwestern ring. Most of the clouds have dimensions only slightlylarger than those of the survey beam, i.e. diameters of 25 pc or less. Asubset of the clouds mapped in J= 1-0 12CO transition wasalso observed in the J= 2-1 12CO transition, and in thecorresponding transitions of 13CO. Clouds mapped in J= 2-112CO with a two times higher angular resolution show further,clear substructure. The elements of this substructure, however, havedimensions once again comparable to those of the mapping beam. For a fewclouds, sufficient information was available to warrant an attempt atmodelling their physical parameters. They contain fairly warm(Tkin = 60-150 K) and moderately dense (nH_2 =3000 cm-3) gas. The northeastern chain of CO clouds, althoughlacking in diffuse intercloud emission, is characteristic of the morequiescent regions of the LMC, and appears to have been subject torelatively little photo-processing. The clouds forming part of thesouthwestern shell or ring, however, are almost devoid of diffuseintercloud emission, and also exhibit other characteristics of anextreme photon-dominated region (PDR).
| Formation of the nebular complex N11 in the Large Magellanic Cloud.
N 11, the second largest nebula of the LMC, is formed of a large bubblesurrounded by 9 bright nebulae and filaments. We have observed thisnebular complex with a scanning Fabry-Perot interferometer at Hαand [OIII] 5007 wavelengths. The kinematics of this field agrees withthe results of the stellar content and of the molecular studies, andshows that such a structure can be the consequence of a sequential starformation. The elements of this result are deduced from the energeticinput inside the ionized gas by the stellar winds of the associationsLH9 and LH10. The evaluated dynamical lifespan of small nebular entitiesassociated with the more massive stars of LH10, are found significantlyshorter than for the gas ionized by the association LH9. Thereforesequential star formation can be triggered at the shock boundaries ofthe nebula excited by an OB association in a time scale shorter thanpreviously found, and of at most a few 10^6^yrs. It thus leads to theevidence for a new class of giant bubble, designated as "ring of HIIregions" bubble with several distinctive characteristics. It isdiscussed that the bubbles of this type are formed by sequential starformation over time scales shorter than previously found for somesuperbubbles.
| Ring nebulae associated with Wolf-Rayet stars in the Large Magellanic Cloud. III - Kinematics of DEM 39, 231, 240, and 315
Echellograms with 4.6 A per mm dispersion have been obtained for fourring nebulae around Wolf-Rayet stars in the Large Magellanic Cloud(LMC): DEM 39, 231, 240, and 315. Their nature is analyzed and reportedhere. DEM 39 and DEM 315 are stellar wind blown bubbles, DEM 231 isprobably an expanding hemisphere formed by the central star notnecessarily during its W-R phase, and DEM 240 may have resulted from theinteraction of stellar wind with a sheet of moving gas. A comparison ofthe bubbles blown by W-R stars in the Galaxy and the LMC is also made.
| Rotation and Mass of the Large Magellanic Cloud.
Abstract image available at:http://adsabs.harvard.edu/abs/1960ApJ...131..265D
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