Highlights of Spanish Astrophysics V
Highlights of Spanish Astrophysics V
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西班牙天体物理学 V 亮点
DOI：
10.1007/978-3-642-11250-8_130
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Anglés D
中科院分区：
文献类型：
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作者：
Anglés D
星星的形成是现代天体物理学中最重要的研究领域之一。在过去的20年里，一个相当可靠的演化序列已经被建立并被广泛接受，用于分子云中低质量和中等质量恒星（M≤ 8 M Θ）的形成和演化[例如2; 3; 13; 16，以及其中的参考文献]。然而，与星星形成的最早阶段有关的几个基本问题仍然没有答案。大质量恒星的形成更加复杂，因为它们与环境的相互作用很强，它们本质上的演化时间尺度较短，特征距离较大[例如17]。在目前公认的低质量星星形成的情况下，母云中冷而致密的核心/凝聚的坍塌导致引力束缚的前星核的形成，在亚毫米波长处可以观察到，但在近红外（NIR）和中红外（MIR）波段不透明[例如1]。随后，前恒星的核心朝着形成一个中央吸积原恒星和磁盘的方向发展，嵌入在一个由尘埃和气体组成的下落包层中。根据包层、星周盘和中心致密天体之间的相对质量分布，原恒星天体被分为不同的演化阶段（0类到III类，从较低到较高的演化阶段）。观测上，这种分类也与光谱能量分布（SED）的形状有关[见，例如9; 2]。除了地面近红外调查外，以前使用IRAS、MSX和ISO卫星进行的红外研究已经提供了I-III类源的完整普查[例如5]。然而，迄今为止只有少数真正的0级原恒星被发现。更长波长的观测对于探测和描述更早的进化阶段至关重要。特别是，在这些冷物体的SED峰值附近的调查是约束其物理参数的基础。前恒星和原恒星的核心已经用几种分子示踪剂观测到，在亚毫米尘埃连续体中的观测效率更高，因为它们的大部分辐射都是在那里发出的[见13，综述]。由MAMBO、SCUBA和SIMBA等亚毫米波测辐射热计阵列进行的测量代表了获得星前天体的显著样本的唯一途径。然而，这些仪器对SED的瑞利-金斯尾部进行采样，因此它们的灵敏度和/或空间覆盖范围受到部分限制。此外，大气层的高吸收使得地面望远镜很难进行亚毫米观测。
Star formation is one of the most important areas of study in modern astrophysics. Over the past two decades, a reasonably robust evolutionary sequence has been established and widely accepted for the formation and evolution of low-and intermediate-mass stars (M≤ 8MΘ) within molecular clouds [eg 2; 3; 13; 16, and references therein]. However, several fundamental questions related to the earliest stages of star formation remain unanswered. The formation of high-mass stars is even more complicated due to their strong interaction with the environment, their intrinsically shorter evolutionary timescales and larger characteristic distances [eg 17].In the current accepted scenario of low-mass star formation, the collapse of cold, dense cores/condensations in the parent cloud leads to the formation of gravitationally-bound pre-stellar cores, observable at submillimeter wavelengths, but opaque in the near-IR (NIR) and mid-IR (MIR) bands [eg 1]. Subsequently, pre-stellar cores evolve toward the formation of a central accreting protostar and disk, embedded within an infalling envelope of dust and gas. Proto-stellar objects are classified into different evolutionary phases (Class 0 to Class III, from less to more evolved stages) according to the relative mass distribution among the envelope, the circumstellar disk, and the central compact object. Observationally, this classification is also related to the shape of the spectral energy distribution (SED)[see, eg 9; 2]. Previous IR studies using IRAS, MSX, and ISO satellites in addition to ground-based NIR surveys have provided a complete census of Class I–III sources [eg 5]. However, only a few bona-fide Class 0 protostars are known to date. Observations at longer wavelengths are essential to detect and characterize even earlier evolutionary stages. In particular, surveys near the peak of the SED of these cold objects are fundamental to constrain their physical parameters. Pre-and proto-stellar cores have been observed using several molecular tracers and have been surveyed even more efficiently in the submillimeter dust continuum where most of their radiation is emitted [see 13, for a review]. Surveys conducted by submillimeter bolometer arrays, such as MAMBO, SCUBA, and SIMBA represent the only way of deriving statistically-significant samples of pre-stellar objects. Nevertheless, such instruments sample the Rayleigh-Jeans tail of the SED and thus their sensitivity and/or spatial coverage is partially limited. In addition, high absorption in the atmosphere makes submillimeter observations very difficult from ground-based telescopes.