仙王座A东侧冰和硅酸盐的全采样图
Fully Sampled Maps of Ices and Silicates in Front of Cepheus A East with Spitzer
摘要：
我们报告的第一个完整的采样地图的星际CO2冰，H2O冰和总氢核的分布，推断从9.7微米的硅酸盐功能，对恒星形成区域仙王座A东与IRS仪器机载斯皮策太空望远镜。我们发现，这些固态特征的柱密度分布都在HW 2的位置处达到峰值，并分布在HW 2的位置周围，HW 2被认为是在这个恒星形成区域中观察到的流出物之一。CO2和水冰与总氢的柱密度分布之间的相关性表明，我们映射的固态特征主要来自相同的分子团沿探测视线。因此，我们得出了相对于总氢柱密度X（CO2）_ice~1.9x10^-5和X（H2O）_ice~7.5x10^-5的平均CO2冰和水冰丰度。在误差范围内，两种冰的丰度在显示两种冰沉积的映射区域上相对恒定。相对于H2O冰的CO2冰的分数也是相对恒定的，在该映射区域的值为22%。在CO2冰剖面中可以看到明显的三峰结构。适合这些配置文件使用目前的实验室冰类似物表明存在低温极地冰混合物和高温富含甲醇的冰混合物沿探测视线。我们的研究结果进一步表明，这些冰的热处理发生在整个采样区域。
英文摘要：
We report the first fully sampled maps of the distribution of interstellar CO2 ices, H2O ices and total hydrogen nuclei, as inferred from the 9.7 micron silicate feature, toward the star-forming region Cepheus A East with the IRS instrument onboard the Spitzer Space Telescope. We find that the column density distributions for these solid state features all peak at, and are distributed around, the location of HW2, the protostar believed to power one of the outflows observed in this star-forming region. A correlation between the column density distributions of CO2 and water ice with that of total hydrogen indicates that the solid state features we mapped mostly arise from the same molecular clumps along the probed sight lines. We therefore derive average CO2 ice and water ice abundances with respect to the total hydrogen column density of X(CO2)_ice~1.9x10^-5 and X(H2O)_ice~7.5x10^-5. Within errors, the abundances for both ices are relatively constant over the mapped region exhibiting both ice absorptions. The fraction of CO2 ice with respect to H2O ice is also relatively constant at a value of 22% over that mapped region. A clear triple-peaked structure is seen in the CO2 ice profiles. Fits to those profiles using current laboratory ice analogs suggest the presence of both a low-temperature polar ice mixture and a high-temperature methanol-rich ice mixture along the probed sightlines. Our results further indicate that thermal processing of these ices occurred throughout the sampled region.
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