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arXiv 1801.03478astro-ph.EP
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原行星盘温度的经验测量

Empirical Temperature Measurement in Protoplanetary Disks

Erik Weaver, Andrea Isella, Yann Boehler

摘要:

精确测量原行星盘中的温度对于理解盘演化和行星形成的许多关键特征至关重要,从盘化学和动力学到星子形成。本文探讨的技术,可用于确定温度的观察,单,光学厚分子发射谱线。特别注意的问题,如列入光学薄发射,连续减法产生的问题,和并发症的实际观测。还努力详细说明发射给定线的区域的确切性质和形态。为了正确地研究和量化这些影响,本文考虑了一系列的磁盘模型,从简单的教学模型,非常详细的模型,包括完整的辐射转移。最后,我们将展示如何使用错误的方法可能会导致潜在的严重误解的数据,导致不正确的测量磁盘温度分布。我们发现,估计发射气体温度的最佳方法是分析线峰值发射图而不减去连续发射。连续减法,这是通常适用于线发射的观测,系统地导致低估的气体温度。我们进一步表明,一旦观测效应,如光束稀释和噪声占,来自峰值发射的线亮度温度是可靠的发射区域的物理温度的10-15%,假设光学厚发射。本文所描述的方法将在未来的工作中应用,以约束的温度,和相关的物理量,在原行星盘观测ALMA。

英文摘要:

Accurate measurement of temperature in protoplanetary disks is critical to understanding many key features of disk evolution and planet formation, from disk chemistry and dynamics, to planetesimal formation. This paper explores the techniques available to determine temperatures from observations of single, optically thick molecular emission lines. Specific attention is given to issues such as inclusion of optically thin emission, problems resulting from continuum subtraction, and complications of real observations. Effort is also made to detail the exact nature and morphology of the region emitting a given line. To properly study and quantify these effects, this paper considers a range of disk models, from simple pedagogical models, to very detailed models including full radiative transfer. Finally, we show how use of the wrong methods can lead to potentially severe misinterpretations of data, leading to incorrect measurements of disk temperature profiles. We show that the best way to estimate the temperature of emitting gas is to analyze the line peak emission map without subtracting continuum emission. Continuum subtraction, which is commonly applied to observations of line emission, systematically leads to underestimation of the gas temperature. We further show that once observational effects such as beam dilution and noise are accounted for, the line brightness temperature derived from the peak emission is reliably within 10-15% of the physical temperature of the emitting region, assuming optically thick emission. The methodology described in this paper will be applied in future works to constrain the temperature, and related physical quantities, in protoplanetary disks observed with ALMA.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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