Constraining the physical structure of the inner few 100 AU scales of deeply embedded low-mass protostars
Constraining the physical structure of the inner few 100 AU scales of deeply embedded low-mass protostars
复制标题
约束深嵌的低质量原恒星内部几个 100 AU 尺度的物理结构
DOI：
10.1051/0004-6361/201527666
复制
发表时间：
2016
期刊：
影响因子：
--
通讯作者：
S. Lai
中科院分区：
文献类型：
--
作者：
M. Persson;D. Harsono;J. Tobin;E. Dishoeck;J. Jørgensen;N. Murillo;S. Lai
(节选)深埋在300AU以下的低质量原恒星(0级)的物理结构仍然受到很差的限制。确定这一点对于理解从核心到磁盘的物理和化学演化至关重要。在这项研究中，两种辐射模型--高斯盘强度分布模型和参数化幂律盘模型--被拟合到五个0类源的亚角秒分辨率干涉连续统观测中，其中一个源具有确认的开普勒盘。作为参考，对于较大尺度($1000 AU)的排放，拟合球对称的单幂定律包络，并对较小尺度上的一个源进行了进一步的研究。一个薄盘模型可以近似地模拟所研究的深埋低质量原恒星在100AU尺度内的发射和物理结构，为用ALMA分析更大的样本铺平了道路。虽然圆盘半径与先前的估计一致，但对于所研究的一些源，质量是不同的。假设一个典型的温度分布，在100K以上的圆盘中的质量分数在7%到30%之间变化。需要运动学数据来确定任何开普勒盘的存在。利用前人对p-H$2^{18}$O的观测，我们估计了相对气相水丰度，比以前以冷H$2和暖H$2为参照物时的推算结果大约高出一个数量级。球对称的单幂指数包络模型不能同时再现小尺度和大尺度的发射。
(Abridged) The physical structure of deeply-embedded low-mass protostars (Class 0) on scales of less than 300 AU is still poorly constrained. Determining this is crucial for understanding the physical and chemical evolution from cores to disks. In this study two models of the emission, a Gaussian disk intensity distribution and a parametrized power-law disk model, are fitted to sub-arcsecond resolution interferometric continuum observations of five Class 0 sources, including one source with a confirmed Keplerian disk. For reference, a spherically symmetric single power-law envelope is fitted to the larger scale ($\sim$1000 AU) emission and investigated further for one of the sources on smaller scales. A thin disk model can approximate the emission and physical structure in the inner few 100 AU scales of the studied deeply-embedded low-mass protostars and paves the way for analysis of a larger sample with ALMA. While the disk radii agree with previous estimates the masses are different for some of the sources studied. Assuming a typical temperature distribution, the fractional amount of mass in the disk above 100 K varies in between 7% to 30%. Kinematic data are needed to determine the presence of any Keplerian disk. Using previous observations of p-H$_2^{18}$O, we estimate the relative gas phase water abundances roughly an order of magnitude higher than previously inferred when both warm and cold H$_2$ was used as reference. A spherically symmetric single power-law envelope model fails to simultaneously reproduce both the small and large scale emission.