The standard model of low-mass star formation applied to massive stars: a multi-wavelength picture of AFGL 2591
The standard model of low-mass star formation applied to massive stars: a multi-wavelength picture of AFGL 2591
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适用于大质量恒星的低质量恒星形成标准模型：AFGL 2591的多波长图片
DOI：
10.1051/0004-6361/201219657
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发表时间：
2012
影响因子：
6.5
通讯作者：
Kenneth Wood
中科院分区：
文献类型：
--
作者：
K. Johnston;D. Shepherd;T. Robitaille;Kenneth Wood
上下文。虽然目前还不清楚从理论上讲，是什么力量和过程主导了高质量恒星的形成，从而决定了它们的形成模式，但最近的许多观测证据表明，大质量恒星的诞生方式与它们的低质量恒星相似。目标。本文旨在研究嵌入的发光星AFGL 2591-VLA 3(2.3×105经度3.33kpc)是根据低质量恒星形成的放大版本而形成的假设。方法：研究方法。为了研究AFGL 2591附近的电离气体、尘埃和分子气体的形态和运动学，我们提供了3.6 cm和7 mm的多组态甚大阵列(VLA)，以及用于毫米波天文研究的组合阵列C18O和3 mm连续谱观测。我们还将我们的结果与辅助的双子座北近红外图像进行了比较，并使用蒙特卡罗尘埃连续谱辐射传输程序模拟了AFGL 2591的近红外到亚毫米光谱能量分布(SED)和两个微米全天巡天(2MASS)图像轮廓。结果。观测到的3.6厘米图像首次揭示出，中心动力源AFGL2591-VLA3具有致密的核心和准直的喷流形态，从中心源向东延伸4000AU，在这个半径上的张开角为<；10◦。然而，在7 mm VLA 3没有表现出喷流形态，而是致密的(<；500AU)发射，其中一些(<；0.57mJy/2.9mJy)估计是来自尘埃排放。AFGL 2591-VLA 3在3.6 cm到7 mm之间的光谱指数在0.4到0.5之间，与电离风的光谱指数相似。如果将3.6厘米的辐射模拟为电离喷流，则该喷流几乎有足够的动量来驱动更大范围的流动。然而，假设激波效率为10%，喷流的动量速率不足以仅通过激波进行电离，因此很大一部分发射很可能是在光电离风中产生的。C18O的发射揭示了这些年轻恒星(S)流出的致密夹带物质。AFGL 2591-VLA 3的SED和2MASS图像的主要特征也是通过我们的模型尘埃几何图形复制的，该几何图形是一个旋转平坦的信封，有无ad isk。结论。上述结果与大质量恒星形成的图景相一致，类似于低质量原恒星的形成。然而，在它的包层内，AFGL 2591-VLA 3至少包含了另外四颗年轻恒星，构成了一个小星团。因此，AFGL 2591-VLA 3似乎能够从一个共享的气藏中获取其吸积物质，同时仍然显示出在低质量恒星形成期间预期的现象。
Context. While it is currently unclear from a theoretical standpoint which forces and processes dominate the formation of high-mass stars, and hence determine the mode in which they form, much of the recent observational evidence suggests that massive stars are born in a similar manner to their low-mass counterparts. Aims. This paper aims to investigate the hypothesis that the embedded luminous star AFGL 2591-VLA 3 (2.3 × 10 5 Lat 3.33 kpc) is forming according to a scaled-up version of a low-mass star formation scenario. Methods. We present multi-configuration Very Large Array (VLA) 3.6 cm and 7 mm, as well as Combined Array for Research in Millimeter Astronomy C 18 O and 3 mm continuum observations to investigate the morphology and kinematics of the ionized gas, dust, and molecular gas around AFGL 2591. We also compare our results to ancillary Gemini North near-IR images, and model the near-IR to sub-mm spectral energy distribution (SED) and Two Micron All Sky Survey (2MASS) image profiles of AFGL 2591 using a Monte-Carlo dust continuum radiative transfer code. Results. The observed 3.6 cm images uncover for the first time that the central powering source AFGL 2591-VLA 3 has a compact core plus collimated jet morphology, extending 4000 AU eastward from the central source with an opening angle of <10 ◦ at this radius. However, at 7 mm VLA 3 does not show a jet morphology, but instead compact (<500 AU) emission, some of which (<0.57 mJy of 2.9 mJy) is estimated to be from dust emission. The spectral index of AFGL 2591-VLA 3 between 3.6 cm and 7 mm was found to be between 0.4 and 0.5, similar to that of an ionized wind. If the 3.6 cm emission is modelled as an ionized jet, the jet has almost enough momentum to drive the larger-scale flow. However, assuming a shock efficiency of 10%, the momentum rate of the jet is not sufficient to ionize itself via only shocks, and thus a significant portion of the emission is instead likely created in a photoionized wind. The C 18 O emission uncovers dense entrained material in the outflow(s) from these young stars. The main features of the SED and 2MASS images of AFGL 2591-VLA 3 are also reproduced by our model dust geometry of a rotationally flattened envelope with and without ad isk. Conclusions. The above results are consistent with a picture of massive star formation similar to that seen for low-mass protostars. However, within its envelope, AFGL 2591-VLA 3 contains at least four other young stars, constituting a small cluster. Therefore it appears that AFGL 2591-VLA 3 may be able to source its accreting material from a shared gas reservoir while still exhibiting the phenomena expected during the formation of low-mass stars.