Structure and Dynamics of Candidate O Star Bubbles in N44
Structure and Dynamics of Candidate O Star Bubbles in N44
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N44 中候选 O 星气泡的结构和动力学
DOI：
10.1086/344481
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
R. Smith
中科院分区：
文献类型：
--
作者：
Y. Nazé;Y. Chu;M. A. Guerrero;M. Oey;R. Gruendl;R. Smith
超级气泡和沃尔夫拉叶环星云的动力学研究表明，与风吹气泡的标准绝热模型存在差异。因此，我们研究了单个 O 星吹出的三个候选气泡的物理特性和运动学，以评估这些差异是否也存在于这些更简单的物体中。我们的候选样本是 N44 F、N44 J 和 N44 M，位于大麦哲伦星云中 H II 复合体 N44 的外围。我们已经获得了这些物体的地面和哈勃太空望远镜发射线图像和高色散阶梯光谱。根据这些星云的 Hα 光度和 [O III]/Hα 比率，我们估计 N44 F、N44 J 和 N44 M 的电离恒星的光谱类型分别为 O7 V、O9.5 V 和 O9.5 V。我们发现观测到的 N44 F 12 km s-1 的膨胀速度与标准气泡模型预测的中心电离星预期的星风光度一致。在不确定性范围内，观测到的 N44 J 和 N44 M 膨胀速度上限也与预期值相符。我们还报告在 N44 F 中发现了明确的尘埃柱，类似于鹰星云中的尘埃柱。这些致密尘埃特征的光蒸发可能在运动学上很重要，并且实际上可能控制着外壳的演化。因此，包含光蒸发过程可能会破坏观察到的气泡动力学与简单绝热模型之间的明显一致性。
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 Hα luminosities and the [O III]/Hα 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.