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首页> 外文期刊>The Astrophysical journal >LARGE HCO~+ AND HCN ABUNDANCES IN THE TRANSLUCENT CLOUD TOWARD PKS 0528 + 134
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LARGE HCO~+ AND HCN ABUNDANCES IN THE TRANSLUCENT CLOUD TOWARD PKS 0528 + 134

机译：半透明云中的大HCO〜+和HCN丰度向PKS 0528 + 134

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摘要

Observations of ~(12)CO J= 1-0, ~(13)CO 1-0, HCO~+ 1-0, HCN 1-0, and CS 2-1 absorption against the quasar PKS 0528 + 134 obtained with the Owens Valley Millimeter Array are presented. The line of sight to this standard phase calibrator crosses the diffuse outer edge of the dark cloud B30, located in the λ Ori ring of clouds. An excitation analysis of the absorption lines and ~(12)CO 1-0 emission yields an estimated H_2 number density of n_(H_2) = 100-500 cm~(-3), which is much lower than found for lines of sight studied previously by millimeter absorption lines. Surprisingly, HCO~+ and HCN are found to have abundances relative to ~(12)CO in this diffuse cloud which are comparable to or larger than those found in dark clouds. Significant differences in line width are found between ~(12)CO, HCN, and HCO~+ which cannot be attributed to line saturation. A possible explanation for the observed abundances and line widths involving cloud turbulence and the chemistry of CH~+ is proposed. It is concluded that HCO~+ absorption lines sample low-density regions which cannot be observed in molecular emission nor in CO millimeter absorption.
机译：观察到〜（12）CO J = 1-0，〜（13）CO 1-0，HCO〜+ 1-0，HCN 1-0和CS 2-1吸收通过类固醇获得的类星体PKS 0528 + 134的结果。介绍了欧文斯谷毫米阵列。该标准相位校准器的视线穿过位于λOri云环中的暗云B30的漫射外边缘。吸收线的激发分析和〜（12）CO 1-0发射产生的估计H_2数密度为n_（H_2）= 100-500 cm〜（-3），远低于所研究的视线所发现的以前是通过毫米吸收线。出乎意料的是，在该弥散云中，发现HCO〜+和HCN相对于〜（12）CO的丰度与黑云中的丰度相当或更大。发现〜（12）CO，HCN和HCO〜+之间的线宽存在显着差异，这不能归因于线饱和。提出了可能的解释，包括云湍流和CH〜+的化学反应所涉及的丰度和线宽。可以得出结论，HCO〜+吸收线对低密度区域进行采样，这些区域在分子发射和CO毫米波吸收中均无法观察到。

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