Nazé, Yaël[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Sciences spatiales >]
Chu, You-Hua[; Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801; , chu@astro.uiuc.edu, points@astro.uiuc.edu, c-chen@astro.uiuc.edu.; Visiting astronomer, Cerro Tololo Inter-American Observatory.]
Points, Sean D[; Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801; , chu@astro.uiuc.edu, points@astro.uiuc.edu, c-chen@astro.uiuc.edu.; Visiting astronomer, Cerro Tololo Inter-American Observatory.]
Danforth, Charles W[; Visiting astronomer, Cerro Tololo Inter-American Observatory.; Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218; .]
Rosado, Margarita[; Instituto de Astronomía, Universidad Nacional Autónoma de México (IA-UNAM), Apdo. Postal 70-264, 04510 México D.F., Mexico; .]
Chen, C-H Rosie[; Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801; , chu@astro.uiuc.edu, points@astro.uiuc.edu, c-chen@astro.uiuc.edu.]
[en] ISM: H II Regions ; ISM: Bubbles ; ISM: individual (N11B ; N180B) ; ISM: Kinematics and Dynamics ; Galaxies: Magellanic Clouds
[en] Massive stars are expected to produce wind-blown bubbles in the interstellar medium; however, ring nebulae, suggesting the existence of bubbles, are rarely seen around main-sequence O stars. To search for wind-blown bubbles around main-sequence O stars, we have obtained high-resolution Hubble Space Telescope WFPC2 images and high-dispersion echelle spectra of two pristine H II regions, N11B and N180B, in the Large Magellanic Cloud. These H II regions are ionized by OB associations that still contain O3 stars, suggesting that the H II regions are young and have not hosted any supernova explosions. Our observations show that wind-blown bubbles in these H II regions can be detected kinematically, but not morphologically, because their expansion velocities are comparable to or only slightly higher than the isothermal sound velocity in the H II regions. Bubbles are detected around concentrations of massive stars, individual O stars, and even an evolved red supergiant (a fossil bubble). Comparisons between the observed bubble dynamics and model predictions show a large discrepancy (1-2 orders of magnitude) between the stellar wind luminosity derived from bubble observations and models and that derived from observations of stellar winds. The number and distribution of bubbles in N11B differ from those in N180B, which can be explained by the difference in the richness of stellar content between these two H II regions. Most of the bubbles observed in N11B and N180B show a blister structure, indicating that the stars were formed on the surfaces of dense clouds. Numerous small dust clouds, similar to Bok globules or elephant trunks, are detected in these H II regions, and at least one of them hosts on-going star formation.
[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Sciences spatiales >]
