Carbonates and ices in the z = 0.89 galaxy-absorber towards PKS 1830-211 and within star-forming regions of the Milky Way
Carbonates and ices in the z = 0.89 galaxy-absorber towards PKS 1830-211 and within star-forming regions of the Milky Way
复制标题
朝向 PKS 1830-211 的 z = 0.89 星系吸收体以及银河系恒星形成区域内的碳酸盐和冰
DOI：
10.1093/mnras/stad1928
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发表时间：
2023
影响因子：
4.8
通讯作者：
Bowey J
中科院分区：
文献类型：
--
作者：
Bowey J
在银河系（MW）分子云和yso中经常观测到一对6.0和6.9μm的吸收特征；它们也出现在一个富含分子的螺旋星系的z= 0.886静止框架中，该星系掩盖了耀变体PKS 1830-211。我校准了χ2拟合方法，该方法将观测结果与两个或三个实验室光谱相匹配。6.0 μm组分以H2O冰为主，符合预期。根据不透明度标准选择纳入的MW源，将探测到的h2o -冰柱密度范围限制在1.6-2.4 × 1018分子cm - 2，而星系吸收体中的h2o -冰密度为（2.7±0.5）× 1018分子cm - 2。CH3OH冰和/或小的（< 0.1 μm）含钙和含镁碳酸盐在6.9μm。PKS 1830-211吸收体中41%的CH3OH:H2O分子比明显高于朝向金牛座-伊莱亚斯16的分子云（< 7.5%），与MW YSOs中的最高值（AFGL 989中的35%）相似。与在MW样品中检测到的大多数比率（0.2% - 0.4%；在AFGL 989中为~ 0%）相比，星系吸收剂中0.091%的拟合碳酸盐（-CO3）：H2O比率较低。无机碳酸盐可以解释扩散-介质-分子云转变过程中氧气消耗的增加，Jones和Ysard将其与未观察到的有机碳酸盐或C:O比为1:3的物质联系起来。
A pair of 6.0 and 6.9μm absorption features are frequently observed in Milky Way (MW) molecular-clouds and YSOs; they also occur in thez= 0.886 rest-frame of a molecule-rich spiral galaxy obscuring blazar PKS 1830–211. I calibrate χ2-fitting methods, which match observations with two or three laboratory spectra. The 6.0-μm component is dominated by H2O ice, as expected. Included MW sources were selected using opacity criteria which limit the range of explored H2O-ice column densities to 1.6–2.4 × 1018molecules cm−2, while the H2O-ice density in the galaxy absorber is (2.7 ± 0.5) × 1018molecules cm−2. CH3OH ice and / or small (< 0.1-μm-sized) Ca- and Mg-bearing carbonates contribute at 6.9μm. The 41 per cent CH3OH:H2O molecular ratio in the PKS 1830–211 absorber is significantly higher than in the molecular cloud towards Taurus-Elias 16 (<7.5 per cent) and similar to the highest value in MW YSOs (35 per cent in AFGL 989). Fitted carbonate (-CO3):H2O ratios in the galaxy absorber of 0.091 per cent are low in comparison to most of the ratios detected in the MW sample (0.2 per cent–0.4 per cent; ∼0 per cent in AFGL 989). Inorganic carbonates could explain the increased oxygen depletion at the diffuse-medium-to-molecular-cloud transition, which Jones and Ysard associated with unobserved organic carbonates or materials with a C:O ratio of 1:3.