Detections of molecular lines, mainly from H2$ and CO, reveal molecular material in planetary nebulae. Observations of a variety of molecules suggest that the molecular composition in these objects differs from that found in interstellar clouds or in circumstellar envelopes. The success of the models, which are mostly devoted to explain molecular densities in specific planetary nebulae, is still partial, however. The present study aims at identifying the influence of stellar and nebular properties on the molecular composition of planetary nebulae by means of chemical models. A comparison of theoretical results with those derived from the observations may provide clues to the conditions that favor the presence of a particular molecule. A self-consistent photoionization numerical code was adapted to simulate cold molecular regions beyond the ionized zone. The code was used to obtain a grid of models and the resulting column densities are compared with those inferred from observations. Our models show that the inclusion of an incident flux of X-rays is required to explain the molecular composition derived for planetary nebulae. We also obtain a more accurate relation for the N(CO)/N(H2) ratio in these objects. Molecular masses obtained by previous works in the literature were then recalculated, showing that these masses can be underestimated by up to three orders of magnitude. We conclude that the problem of the missing mass in planetary nebulae can be solved by a more accurate calculation of the molecular mass.
Modeling the UV-photon irradiation of CS$_2$-bearing ices in the laboratory with the pyRate gas-grain astrochemical code. New insights into the missing sulfur problem
Max-Planck-Institut für Extraterrestrische Physik (MPE)（马克斯·普朗克地外物理研究所）；Centro de Astrobiología (CSIC-INTA)（天体生物学中心（西班牙国家科学技术研究委员会-国家航空航天技术研究所））
Thermally irreversible sulfur chemisorption on silicate grains as a major sulfur reservoir in molecular clouds
Institute of Low Temperature Science, Hokkaido University（北海道大学低温科学研究所）；Department of Chemistry, Hiroshima University（广岛大学化学系）；Departamento de Astrofísica Molecular, Instituto de Física Fundamental, CSIC（西班牙国家研究委员会基础物理研究所分子天体物理学部）；RIKEN Pioneering Research Institute（理研先锋研究机构）
The halo of M105 and its group environment as traced by planetary nebula populations: I. Wide-field photometric survey of planetary nebulae in the Leo I group
Non-detection of HC(S)SH: Estimating Upper Limits and Constraining Chemistry
Physical Research Laboratory（物理研究实验室）；Institute of Astronomy Space and Earth Science（天体与地球科学研究所）；Max-Planck-Institute for extraterrestrial Physics（马克斯·普朗克地外物理学研究所）；Rosseland Centre for Solar Physics, University of Oslo（奥斯陆大学罗斯兰太阳物理中心）；Institute of Theoretical Astrophysics, University of Oslo（奥斯陆大学理论天体物理研究所）；Centro de Astrobiología (CAB), INTA-CSIC（航空与空间技术国家研究所-西班牙高等科研理事会天文生物学中心）；Academia Sinica Institute of Astronomy and Astrophysics（中央研究院天文及天文物理研究所）
通过独立重新分析 ALMA 数据集，发现先前声称的 t-HC(S)SH 探测实为光谱混合所致，并给出了严格的柱密度上限（≤4×10^14 cm^-2）和丰度上限（≤1×10^-10），建立了未来搜寻含硫物种的严谨框架。
Sulphur-bearing molecule survey towards prestellar and starless cores in the Perseus molecular cloud
RIKEN Cluster for Pioneering Research（RIKEN 前沿研究集群）；National Radio Astronomy Observatory（国家射电天文台）；University of California, Berkeley（加州大学伯克利分校）；University of Virginia（弗吉尼亚大学）；University of Arizona（亚利桑那大学）；Centro de Astrobiología (CAB), CSIC-INTA（天体生物学中心（CAB），西班牙国家科学技术研究委员会-国家航空航天技术研究所）；Observatorio Astronómico Nacional (OAN)（国家天文观测台）
