Mid‐infrared imaging and spectroscopy of the southern HII region RCW 38
Mid‐infrared imaging and spectroscopy of the southern HII region RCW 38
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HII 南部地区的中红外成像和光谱学 RCW 38
DOI：
10.1046/j.1365-8711.1999.02241.x
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发表时间：
1999
影响因子：
4.8
通讯作者：
T. Lehmann
中科院分区：
文献类型：
--
作者：
C. Smith;T. Bourke;C. Wright;H. Spoon;D. Aitken;G. Robinson;J. Storey;T. Fujiyoshi;P. Roche;T. Lehmann
我们目前的中红外图像和8- 13 μ m光谱的南部HII区域RCW 38。我们从我们的光谱和10和20 μ m的图像中确定尘埃色温，并从[SIV]精细结构线的图像以及[ArIII]，[SIV]和[NeII]精细结构线的光谱中推断气体激发。我们的观测结果与RCW 38 IRS 1区域相关的复杂源一致，这些源代表了壳或脊中的物质结，围绕着半径约为0.1 pc的空腔，这本身是由热的年轻源IRS 2的恒星风产生的。尘埃温度的峰值并不靠近IRS 2，而是沿着山脊的中心，并且在我们的图像范围内非常均匀。根据IRS 1观测到的谱线比的光电离模型，我们推导出恒星的有效温度和气体密度分别为43000 - 48000 K和104 cm-3。虽然星星或星星团IRS 2最终负责观测到的热辐射和离子辐射，但相对均匀的尘埃温度意味着该区域的大部分尘埃加热是由共振捕获的莱曼α光子提供的，而不是直接的恒星光子。这也意味着尘埃相对于气体的损耗至少是其正常星际值的100倍。连续谱发射和温度的小尺度空间变化可以用密度和/或气尘质量比的变化来解释。
We present mid-infrared images and an 8--13 μ m spectrum of the southern HII region RCW 38. We determine the dust colour temperature from both our spectrum and images at 10 and 20 μ m, and deduce the gas excitation from an image in the [SIV] fine-structure line, as well as spectra of the [ArIII], [SIV] and [NeII] fine-structure lines. Our observations are consistent with a complex of sources associated with the RCW 38 IRS1 region, which represent knots of material in a shell, or ridge, surrounding a cavity of about 0.1 pc in radius, which is itself created by the stellar wind of the hot young source IRS2. The dust temperature does not peak closest to IRS2, but rather along the centre of the ridge, and is remarkably uniform over the extent of our image. From photoionization models for the observed line ratios at IRS1 we deduce a stellar effective temperature and gas density of about 43 000--48 000 K and 104 cm-3 respectively. Whilst the star, or star cluster, IRS2 is ultimately responsible for the observed thermal and ionic emission, the relatively uniform dust temperature implies that the bulk of the dust heating in the region is provided by resonantly trapped Lyman α photons, rather than direct stellar photons. This then also implies that the dust is depleted with respect to the gas by a factor of at least 100 from its normal interstellar value. The small-scale spatial variations in the continuum emission and temperature can be explained by changes in the density and/or gas-to-dust mass ratio.