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VERTICAL STRUCTURE OF MAGNETIZED ACCRETION DISKS AROUND YOUNG STARS

机译:幼星周围磁化吸积盘的垂直结构

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We model the vertical structure of the magnetized accretion disks that are subject to viscous and resistive heating and irradiation by the central star. We apply our formalism to the radial structure of the magnetized accretion disks that are threaded by the poloidal magnetic field dragged during the process of star formation, which was developed by Shu and coworkers. We consider disks around low-mass protostars, T Tauri, and FU Orionis stars, as well as two levels of disk magnetization: (strongly magnetized disks) and (weakly magnetized disks). The rotation rates of strongly magnetized disks have large deviations from Keplerian rotation. In these models, resistive heating dominates the thermal structure for the FU Ori disk, and the T Tauri disk is very thin and cold because it is strongly compressed by magnetic pressure; it may be too thin compared with observations. Instead, in the weakly magnetized disks, rotation velocities are close to Keplerian, and resistive heating is always less than 7% of the viscous heating. In these models, the T Tauri disk has a larger aspect ratio, which is consistent with that inferred from observations. All the disks have spatially extended hot atmospheres where the irradiation flux is absorbed, although most of the mass (~90%–95%) is in the disk midplane. With the advent of ALMA one expects direct measurements of magnetic fields and their morphology at disk scales. It will then be possible to determine the mass-to-flux ratio of magnetized accretion disks around young stars, an essential parameter for their structure and evolution. Our models contribute to the understanding of the vertical structure and emission of these disks.
机译:我们对磁化吸积盘的垂直结构建模,该结构受中心恒星的粘性,电阻加热和辐射作用。我们将形式主义应用于磁化吸积盘的径向结构,该结构由舒和他的同事们在恒星形成过程中拖动的极向磁场所穿线。我们考虑低质量原恒星,T Tauri和FU Orionis恒星周围的磁盘,以及磁盘磁化的两个级别:(强磁化磁盘)和(弱磁化磁盘)。强磁化磁盘的旋转速率与开普勒旋转有很大的偏差。在这些模型中,电阻加热在FU Ori盘的热结构中占主导地位,而T Tauri盘非常薄且很冷,因为它在磁力的作用下被强烈压缩。与观察结果相比,它可能太薄了。取而代之的是,在弱磁化的磁盘中,旋转速度接近开普勒,并且电阻加热始终小于粘性加热的7%。在这些模型中,T Tauri盘具有更大的纵横比,这与从观测中推断出的一致。尽管大部分质量(约90%–95%)都在磁盘中平面内,但所有磁盘都在空间上扩展了热大气,吸收了辐射通量。随着ALMA的出现,人们期望可以直接在磁盘规模上测量磁场及其形态。这样就可以确定年轻恒星周围磁化吸积盘的质量通量比,这是它们结构和演化的基本参数。我们的模型有助于理解这些磁盘的垂直结构和发射。

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