HII regions; ISM : bubbles; ISM : individual (N44); ISM : kinematics and dynamics; Magellanic Clouds
Abstract :
[en] Dynamical studies of superbubbles and Wolf-Rayet ring nebulae show discrepancies from the standard adiabatic model for windblown bubbles. We therefore study the physical properties and kinematics of three candidate bubbles blown by single O stars to evaluate whether these discrepancies are also found in these simpler objects. Our sample candidates are N44 F, N44 J, and N44 M, in the outskirts of the H II complex N44 in the Large Magellanic Cloud. We have obtained ground-based and Hubble Space Telescope emission-line images and high-dispersion echelle spectra for these objects. From the Halpha luminosities and the [ O III]/ Halpha ratios of these nebulae, we estimate the spectral types of the ionizing stars to be O7 V, O9.5 V, and O9.5 V for N44 F, N44 J, and N44 M, respectively. We. find that the observed expansion velocity of 12 km s(-1) for N44 F is consistent with the stellar wind luminosity expected from the central ionizing star, as predicted by the standard bubble model. The observed upper limits for the expansion velocities of N44 J and N44 M are also compatible with the expected values, within the uncertainties. We also report the discovery in N44 F of strongly defined dust columns, similar to those seen in the Eagle Nebula. The photoevaporation of these dense dust features may be kinematically important and may actually govern the evolution of the shell. The inclusion of photoevaporation processes may thus undermine the apparent agreement between the observed bubble dynamics and the simple adiabatic models.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Nazé, Yaël ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE)
Chu, Y. H.
Guerrero, M. A.
Oey, M. S.
Gruendl, R. A.
Smith, R. C.
Language :
English
Title :
Structure and dynamics of candidate O star bubbles in N44
Publication date :
December 2002
Journal title :
Astronomical Journal
ISSN :
0004-6256
eISSN :
1538-3881
Publisher :
Univ Chicago Press, Chicago, United States - Illinois
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