HERSCHEL OBSERVATIONS OF INTERSTELLAR CHLORONIUM
HERSCHEL OBSERVATIONS OF INTERSTELLAR CHLORONIUM
复制标题
赫歇尔对星际氯的观测
DOI：
10.1088/0004-637x/748/1/37
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
M. Wolfire
中科院分区：
文献类型：
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作者：
D. Neufeld;È. Roueff;R. Snell;D. Lis;A. Benz;S. Bruderer;J. Black;M. de Luca;M. Gerin;P. Goldsmith;H. Gupta;N. Indriolo;J. Le Bourlot;Franck Le Petit;B. Larsson;G. Melnick;K. Menten;R. Monje;Z. Nagy;T. Phillips;A. Sandqvist;P. Sonnentrucker;F. V. D. van der Tak;M. Wolfire
利用赫歇尔空间天文台的远红外外差仪器，我们已经观察到对氯离子（H2 Cl+）朝向银河系中的六个源。我们在沿着视线到明亮的亚毫米波连续谱源Sgr A（+50 km s−1云）和W31 C的前景分子云中探测到星际氯离子吸收。通过分别在485.42和484.23 GHz的静止频率下观察它们的111-000跃迁，检测到对-H352 Cl+和对-H372 Cl+同位素体。对于假定的邻帕拉比（OPR）为3，所观察到的光学深度意味着氯占气相中氯核的0.4%-12%。我们检测到星际氯离子发射从两个来源在猎户座分子云1：猎户座酒吧光解离区和猎户座南凝聚。假设氯离子的OPR为3，观测到的发射线通量意味着这两个源中氯离子的总束平均柱密度分别为1.2 × 1013 cm−2和1.2 × 1013 cm−2。我们获得了猎户座分子云中H2峰1和大质量年轻星星AFGL 2591的para-H352 Cl+线强度上限。在这项研究中推断的氯丰度通常至少比含氯星际分子化学的稳态理论模型的预测大10倍。对这种差异的几种解释进行了研究，但没有一种被证明是令人满意的，因此观察到的大量氯元素仍然令人困惑。
Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have observed para-chloronium (H2Cl+) toward six sources in the Galaxy. We detected interstellar chloronium absorption in foreground molecular clouds along the sight lines to the bright submillimeter continuum sources Sgr A (+50 km s−1 cloud) and W31C. Both the para-H352Cl+ and para-H372Cl+ isotopologues were detected, through observations of their 111–000 transitions at rest frequencies of 485.42 and 484.23 GHz, respectively. For an assumed ortho-to-para ratio (OPR) of 3, the observed optical depths imply that chloronium accounts for ∼4%–12% of chlorine nuclei in the gas phase. We detected interstellar chloronium emission from two sources in the Orion Molecular Cloud 1: the Orion Bar photodissociation region and the Orion South condensation. For an assumed OPR of 3 for chloronium, the observed emission line fluxes imply total beam-averaged column densities of ∼2 × 1013 cm−2 and ∼1.2 × 1013 cm−2, respectively, for chloronium in these two sources. We obtained upper limits on the para-H352Cl+ line strengths toward H2 Peak 1 in the Orion Molecular cloud and toward the massive young star AFGL 2591. The chloronium abundances inferred in this study are typically at least a factor ∼10 larger than the predictions of steady-state theoretical models for the chemistry of interstellar molecules containing chlorine. Several explanations for this discrepancy were investigated, but none has proven satisfactory, and thus the large observed abundances of chloronium remain puzzling.