The environs of the H II region Gum 31
The environs of the H II region Gum 31
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H II 区域 Gum 31 的周边
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
J.Vasquez
中科院分区：
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作者：
C. Cappa;V. Niemela;R. Amorín;J.Vasquez
目标。我们分析了位于复杂船底座区域的疏散星团NGC 3324激发的H ii 区Gum 31周围的星际物质分布，目的是研究大质量恒星对周围中性物质的作用。方法。我们使用中性氢 21 厘米线数据、0.843、2.4 和 4.9 GHz 的射电连续谱图像、12 个 CO(1–0) 观测值以及 IRAS 和 MSX 红外数据。结果。采用 H ii 区域和电离团簇的距离为 3 kpc，我们根据 4.9 GHz 的射电连续谱数据得出了电子密度为 $33pm3$ cm -3 和电离质量 ($3.3pm1.1) imes10^3$ $M_{odot}$。 H i 21厘米线图像显示H ii 区域周围有一个H i 壳。 H i 结构的半径为 $10.0, pm, 1.7$ pc，中性质量为 $1500,pm,500$ $M_{odot}$，并且正在以 11 km s -1 的速度膨胀。伴生分子气体总计为 ($1.1,pm,0.5) imes10^5$ $M_{odot}$，其体积密度约为 350 cm -3 。这个分子壳可能代表了年轻的疏散星团 NGC 3324 诞生的云的残余物，或者可能起源于与 H ii 区域相关的激波锋。环境密度与 H ii 区域的电子密度之间的差异表明 H ii 区域正在膨胀。
电离和分子材料的分布以及 MSX 波段 A 中的发射分布表明，在电离和分子气体之间的界面处已经形成了光解离区域。 NGC 3324 中早期型恒星产生的大量紫外光子通量使 H ii 区域保持电离。
投影到分子包膜上的相对大量的 IRAS、MSX 和 2MASS 点源的特征与原恒星候选者一致，表明存在活跃的恒星形成区域。 H ii 区域的扩张很可能引发了分子壳层中恒星的形成。
Aims. We analyze the distribution of the interstellar matter in the environs of the H ii region Gum 31, excited by the open cluster NGC 3324, located in the complex Carina region, with the aim of investigating the action of the massive stars on the surrounding neutral material. Methods. We use neutral hydrogen 21-cm line data, radio continuum images at 0.843, 2.4 and 4.9 GHz, 12 CO(1–0) observations, and IRAS and MSX infrared data. Results. Adopting a distance of 3 kpc for the H ii region and the ionizing cluster, we derived an electron density of $33pm3$ cm -3 and an ionized mass of ($3.3pm1.1) imes10^3$ $M_{odot}$ based on the radio continuum data at 4.9 GHz. The H i 21-cm line images revealed an H i shell surrounding the H ii region. The H i structure is $10.0, pm, 1.7$ pc in radius, has a neutral mass of $1500,pm,500$ $M_{odot}$, and is expanding at 11 km s -1 . The associated molecular gas amounts to ($1.1,pm,0.5) imes10^5$ $M_{odot}$, being its volume density of about 350 cm -3 . This molecular shell could represent the remains of the cloud where the young open cluster NGC 3324 was born or could have originated by the shock front associated with the H ii region. The difference between the ambient density and the electron density of the H ii region suggests that the H ii region is expanding.
The distributions of the ionized and molecular material, along with that of the emission in the MSX band A, suggest that a photodissociation region has developed at the interface between the ionized and molecular gas. The copious UV photon flux from the early type stars in NGC 3324 keeps the H ii region ionized.
The characteristics of a relatively large number of the IRAS, MSX, and 2MASS point sources projected onto the molecular envelope are compatible with protostellar candidates, showing the presence of active star forming regions. Very probably, the expansion of the H ii region has triggered stellar formation in the molecular shell.