The Earliest Phases of Star Formation (EPoS): a Herschel key project - The thermal structure of low-mass molecular cloud cores-猫眼课题宝

DOI：

10.1051/0004-6361/201220477

发表时间：

2013-01

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：

R. Launhardt;A. Stutz;A. Schmiedeke;A. Schmiedeke;T. Henning;O. Krause;Z. Balog;H. Beuther;S. Birkmann;S. Birkmann;M. Hennemann;M. Hennemann;J. Kainulainen;T. Khanzadyan;H. Linz;N. Lippok;M. Nielbock;J. Pitann;S. Ragan;C. Risacher;C. Risacher;M. Schmalzl;M. Schmalzl;Y. Shirley;B. Stecklum;J. Steinacker;J. Steinacker;J. Tackenberg

上下文分子云核的温度和密度结构是决定原恒星坍缩过程及其形成的恒星性质的最重要的物理量。然而，密度分布往往依赖于简化假设的等温线或观测约束条件差的模型温度分布。赫歇尔卫星的仪器首次为我们提供了直接测量附近分子云核心尘埃温度结构所需的光谱覆盖范围和空间分辨率。目标。为了更好地约束分子云核心在原恒星坍缩开始时的初始物理条件，特别是测量它们的温度结构，我们启动了与赫歇尔卫星一起的保证时间关键项目（GTKP）“星星形成的最早阶段”（EPoS）。本文概述了EPoS项目中的低质量源，赫歇尔和补充地基观测，我们的分析方法，以及调查的初步结果。方法.我们研究的热尘埃排放的12个先前良好的特点，孤立的，附近的球状体使用FIR和submm连续谱图在100 μ m和1.2毫米之间的8个波长。我们的样本包含两个球状体与无星的核心和嵌入式原恒星在不同的早期演化阶段。尘埃排放图被用来提取空间分辨的SED，然后独立地与修改后的黑体曲线拟合，以获得视线平均尘埃温度和柱密度图。结果我们发现，所有的球状体（平均质量7米圆点）的热结构是由外部加热来自星际辐射场和薄的扩展晕适度屏蔽为主。所有球状体都有温暖的外层（14-20 K）和较冷的致密内部（8-12 K），柱密度为几个10（22）cm（-2）。嵌入某些球状体的原恒星仅在半径约5000 Au的范围内提高致密核心的局部温度，但不会显著影响球状体的整体热平衡。样本中的六个无星核心中有五个是重力束缚的，并且近似热稳定。CB 244中的无星核心被发现是超临界的，并被推测处于崩溃的边缘。我们现在第一次可以在L-smm/L-bol vs. T-bol图中包括外部加热的无星核心，并发现T-bol <25 K似乎是区分无星核心和原恒星核心的可靠标准，包括那些只有嵌入的非常低光度物体的核心。

Context. The temperature and density structure of molecular cloud cores are the most important physical quantities that determine the course of the protostellar collapse and the properties of the stars they form. Nevertheless, density profiles often rely either on the simplifying assumption of isothermality or on observationally poorly constrained model temperature profiles. The instruments of the Herschel satellite provide us for the first time with both the spectral coverage and the spatial resolution that is needed to directly measure the dust temperature structure of nearby molecular cloud cores. Aims. With the aim of better constraining the initial physical conditions in molecular cloud cores at the onset of protostellar collapse, in particular of measuring their temperature structure, we initiated the guaranteed time key project (GTKP) "The Earliest Phases of Star Formation" (EPoS) with the Herschel satellite. This paper gives an overview of the low-mass sources in the EPoS project, the Herschel and complementary ground-based observations, our analysis method, and the initial results of the survey. Methods. We study the thermal dust emission of 12 previously well-characterized, isolated, nearby globules using FIR and submm continuum maps at up to eight wavelengths between 100 mu m and 1.2 mm. Our sample contains both globules with starless cores and embedded protostars at different early evolutionary stages. The dust emission maps are used to extract spatially resolved SEDs, which are then fit independently with modified blackbody curves to obtain line-of-sight-averaged dust temperature and column density maps. Results. We find that the thermal structure of all globules (mean mass 7 M-circle dot) is dominated by external heating from the interstellar radiation field and moderate shielding by thin extended halos. All globules have warm outer envelopes (14-20 K) and colder dense interiors (8-12 K) with column densities of a few 10(22) cm(-2). The protostars embedded in some of the globules raise the local temperature of the dense cores only within radii out to about 5000 AU, but do not significantly affect the overall thermal balance of the globules. Five out of the six starless cores in the sample are gravitationally bound and approximately thermally stabilized. The starless core in CB 244 is found to be supercritical and is speculated to be on the verge of collapse. For the first time, we can now also include externally heated starless cores in the L-smm/L-bol vs. T-bol diagram and find that T-bol <25 K seems to be a robust criterion to distinguish starless from protostellar cores, including those that only have an embedded very low-luminosity object.

The Earliest Phases of Star Formation (EPoS): a Herschel key project - The thermal structure of low-mass molecular cloud cores

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