标题： 大质量恒星形成核中的化学演化（CHEMICO）。I. 温度结构的演化 显示英文标题

标题： CHemical Evolution in MassIve star-forming COres (CHEMICO). I. Evolution of the temperature structure

摘要： 越来越多的证据表明，银河系中的大多数恒星，包括太阳，都是在包含大质量恒星的恒星形成区域中诞生的，但由于观测和理论上的挑战，我们对它们的化学演化的理解远不如对低质量恒星 counterparts 的理解清晰。我们提出了项目“大质量恒星形成核心的化学演化”（CHEMICO）。该项目旨在通过观察三个主要演化类别的代表性天体来研究大质量恒星形成核心的任何方面的化学演化：大质量无恒星核心、大质量原恒星天体和超紧凑 HII 区域。我们使用毫米波射电天文研究所的 30 米望远镜对代表三个演化阶段的三个目标进行了整个带宽的无偏谱线调查。检测到的线和物种数量随着演化而增加。在本项首次工作中，我们通过分析含碳物种 C2H、c-C3H、c-C3H2、C4H、CH3CCH、HC3N、CH3CN 和 HC5N 来推导目标的温度结构。每种物质的激发温度 Tex 随着演化而增加，尽管方式不同。碳氢化合物倾向于与最小的 Tex 值和随演化增强相关，而氰化物则与最高的 Tex 值和增强相关。在每个目标中，分子中原子的数量越多，Tex 趋势越高。温度结构从大质量无恒星核心阶段由简单碳氢化合物追踪的冷且均匀的包层，演化为原恒星阶段更分层的包层（由热核、中间 Tex 的壳层和更大的冷包层组成），最终在超紧凑 HII 阶段变为仅被冷包层包围的热核。 显示英文摘要

摘要： Increasing evidence shows that most stars in the Milky Way, including the Sun, are born in star-forming regions containing also high-mass stars, but due to both observational and theoretical challenges, our comprehension of their chemical evolution is far less clear than that of their low-mass counterparts. We present the project "CHemical Evolution of MassIve star-froming COres" (CHEMICO). The project aims at investigating any aspect of the chemical evolution of high-mass star-forming cores by observing representatives of the three main evolutionary categories: high-mass starless cores, high-mass protostellar objects, and ultra-compact HII regions. We carried out an unbiased spectral line survey of the entire bandwidth at 3, 2, and 1.2 mm with the 30m telescope of the Insitut de Radioastronomie millimetrique towards three targets that represent the three evolutionary stages. The number of lines and species detected increases with evolution. In this first work, we derive the temperature structure of the targets through the analysis of the carbon-bearing species C2H, c-C3H, c-C3H2, C4H, CH3CCH, HC3N, CH3CN, and HC5N. The excitation temperature, Tex, increases with evolution in each species, although not in the same way. Hydrocarbons tend to be associated with the smallest Tex values and enhancements with evolution, while cyanides are associated with the highest Tex values and enhancements. In each target, the higher the number of atoms in the molecule, the higher Tex tends to be. The temperature structure evolves from a cold, uniform envelope traced by simple hydrocarbons in the high-mass starless core stage, to a more stratified envelope in the protostellar stage (made by a hot core, a shell with intermediate Tex, and a larger cold envelope), to finally a hot core surrounded only by a cold envelope in the Ultracompact HII stage.