Chemical Composition and Mixing in Giant H II Regions: NGC 3603, 30 Doradus, and N66
Chemical Composition and Mixing in Giant H II Regions: NGC 3603, 30 Doradus, and N66
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巨型 H II 区域的化学成分和混合：NGC 3603、30 Doradus 和 N66
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发表时间：
2007
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影响因子：
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通讯作者：
J. Houck
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作者：
V. Lebouteiller;J. Bernard;B. Brandl;D. Whelan;Yanling Wu;V. Charmandaris;D. Devost;J. Houck
我们研究了银河系中NGC 3603、大麦哲伦星云中剑鱼座30和小麦哲伦星云中N66的化学丰度。使用斯皮策太空望远镜上的红外光谱仪进行中红外观测，使我们能够探测每个物体内部不同物理区域的特性，中心电离团，周围的电离气体，光解区域和埋藏的恒星团。我们探测到[S III]、[S IV]、[Ar III]、[Ne II]、[Ne III]、[Fe II]和[Fe III]线，并推导出离子丰度。基于离子丰度比（Ne III/H）/（S III/H），我们发现在MIR中观察到的气体的特征是电离度比在光谱中观察到的气体低。我们计算了Ne、S、Ar和Fe的元素丰度。我们发现，α元素Ne、S和Ar的标度是一致的。我们的测定结果与从光学光谱中得到的丰度值吻合得很好。Ne/S比高于太阳值在三个巨大的H II区域，并指向一个适度的硫耗尽尘埃颗粒。我们发现，氖和硫的丰度显示一个非常小的分散（0.11德克斯在30剑鱼座的15个位置），这表明一个相对均匀的ISM，即使不能排除小规模的混合。
We investigate the chemical abundances of NGC 3603 in the Milky Way, of 30 Doradus in the Large Magellanic Cloud, and of N66 in the Small Magellanic Cloud. Mid-infrared observations with the Infrared Spectrograph on board the Spitzer Space Telescope allow us to probe the properties of distinct physical regions within each object, the central ionizing cluster, the surrounding ionized gas, photodissociation regions, and buried stellar clusters. We detect [S III], [S IV], [Ar III], [Ne II], [Ne III], [Fe II], and [Fe III] lines and derive the ionic abundances. Based on the ionic abundance ratio (Ne III/H)/(S III/H), we find that the gas observed in the MIR is characterized by a lower degree of ionization than the gas observed in the optical spectra. We compute the elemental abundances of Ne, S, Ar, and Fe. We find that the α-elements Ne, S, and Ar scale with each other. Our determinations agree well with the abundances derived from the optical. The Ne/S ratio is higher than the solar value in the three giant H II regions and points toward a moderate depletion of sulfur on dust grains. We find that the neon and sulfur abundances display a remarkably small dispersion (0.11 dex in 15 positions in 30 Doradus), suggesting a relatively homogeneous ISM, even though small-scale mixing cannot be ruled out.