From forced collapse to H ii region expansion in Mon R2: Envelope density structure and age determination with Herschel-猫眼课题宝

DOI：

10.1051/0004-6361/201526239

发表时间：

2015-10

期刊：

Astronomy and Astrophysics

影响因子：

6.5

通讯作者：

中科院分区：

物理与天体物理2区

文献类型：

作者：

P. Didelon;F. Motte;P. Tremblin;T. Hill;S. Hony;M. Hennemann;P. Hennebelle;L. Anderson;F. Galliano;N. Schneider;T. Rayner;K. Rygl;F. Louvet;A. Zavagno;V. Konyves;M. Sauvage;P. Andre';S. Bontemps;N. Peretto;M. Griffin;M. González;V. Lebouteiller;D. Arzoumanian;M. Benedettini;J. Francesco;A. Menshchikov;V. Minier;Q. N. Luong;J. Bernard;P. Palmeirim;S. Pezzuto;A. Rivera-Ingraham;D. Russeil;D. Ward-Thompson;G. White

HII区域的环境对其发育、形态和演化具有深远的影响。本文探讨了环境对MonR2分子云中H II区的影响。我们的目的是研究围绕HII区域的包膜的密度结构，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目标，因为它拥有一个H II区关联。从赫歇尔数据中得到的柱密度和温度图像一起用于模拟HII气泡及其周围包膜的结构。所得到的观测约束用解析计算和数值模拟跟踪了Mon R2电离区的发展。与H II区相关的四个热气泡被致密的、冷的和中性的气体包裹着。径向密度曲线让人想起那些低质量的原恒星包层。所有四个HII区域的包络层的内部部分可能是自由落体的，因为它们显示出较浅的密度分布。在其外部，两个致密的HII区域呈现出典型的等温球平衡结构的密度分布。相比之下，中央UCHii区域显示出一个更陡峭的外部轮廓，这可以解释为物质被迫坍缩。加热气泡的大小、辐射恒星的光谱类型和平均初始中性气体密度被用来估计电离膨胀时间，为0.1Myr，对于密集的UCHII和紧凑的HII区域，为0.35 Myr。浅密度剖面和陡密度剖面之间的包络过渡半径用于估计自第一个原始恒星胚胎形成以来所经过的时间，对于超致密区，Tinf为1Myr，致密区为1.5 / 3Myr，扩展的HII区域大于6Myr。

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.

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

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