标题： 从强制坍缩到Mon R2中的电离氢区膨胀：利用赫歇尔望远镜研究包层密度结构和年龄 determination 显示英文标题

标题： From forced collapse to H ii region expansion in Mon R2: Envelope density structure and age determination with Herschel

摘要： HII区域周围的环境对其发展、形态和演化有深远的影响。 本文探讨了环境对MonR2分子云中H II区域的影响。 我们的目标是研究围绕H II区域的包层密度结构，并确定它们的坍缩和电离膨胀年龄。 Mon R2分子云是一个理想的靶标，因为它包含一个H II区域关联体。 利用赫歇尔数据生成的柱密度和温度图像，结合建模H II气泡及其周围包层的结构。 所得的观测约束用于通过解析计算和数值模拟来跟踪Mon R2电离区域的发展。 与H II区域相关的四个热气泡被致密、寒冷和中性气体包层包围。 径向密度剖面类似于低质量原恒星包层的剖面。 所有四个HII区域包层的内部可能处于自由下落状态，因为它们显示浅密度剖面。 至于外部部分，两个紧凑的HII区域显示出典型的等温球平衡结构的密度剖面。 相反，中心的UC HII区域显示出更陡的外部剖面，这可能被解释为物质被迫坍缩。 加热气泡的大小、照射恒星的光谱类型以及平均初始中性气体密度用于估计电离膨胀时间texp：对于致密的UC HII和紧凑的HII区域为0.1Myr，对于扩展的HII区域为0.35 Myr。 包层在浅密度剖面和更陡密度剖面之间的过渡半径用于估计第一个原恒星胚胎形成以来的时间Tinf：对于超紧凑的为1Myr，紧凑的为1.5 / 3Myr，扩展的HII区域大于6Myr。 显示英文摘要

摘要： The surroundings of HII regions can have a profound influence on their development, morphology, and evolution. This paper explores the effect of the environment on H II regions in the MonR2 molecular cloud. We aim to investigate the density structure of envelopes surrounding HII regions and to determine their collapse and ionisation expansion ages. The Mon R2 molecular cloud is an ideal target since it hosts an H II region association. Column density and temperature images derived from Herschel data were used together to model the structure of HII bubbles and their surrounding envelopes. The resulting observational constraints were used to follow the development of the Mon R2 ionised regions with analytical calculations and numerical simulations. The four hot bubbles associated with H II regions are surrounded by dense, cold, and neutral gas envelopes. The radial density profiles are reminiscent of those of low-mass protostellar envelopes. The inner parts of envelopes of all four HII regions could be free-falling because they display shallow density profiles. As for their outer parts, the two compact HII regions show a density profile, which is typical of the equilibrium structure of an isothermal sphere. In contrast, the central UCHii region shows a steeper outer profile, that could be interpreted as material being forced to collapse. The size of the heated bubbles, the spectral type of the irradiating stars, and the mean initial neutral gas density are used to estimate the ionisation expansion time, texp, 0.1Myr,for the dense UCHII and compact HII regions and 0.35 Myr for the extended HII region. The envelope transition radii between the shallow and steeper density profiles are used to estimate the time elapsed since the formation of the first proto stellar embryo, Tinf : 1Myr, for the ultra-compact, 1.5 / 3Myr for the compact, and greater than 6Myr for the extended HII regions.