论文标题
Prestellar核心崩溃期间的密度曲线演变：崩溃始于大规模
Density profile evolution during prestellar core collapse: Collapse starts at the large scale
论文作者
论文摘要
我们研究了prestellar核心的重力主导的积聚驱动的演变。在我们的模型中，随着核心密度的增加，它仍然沉浸在恒定密度的环境中，因此它会从这种环境中吸收，增加其质量并减少其牛仔裤的长度。假设有幂律密度配置文件$ρ\ propto r^{ - p} $，我们计算了斜率$ p $的变化速率，并表明值$ p = 2 $是固定的，而且是吸引子。牛仔裤长度的径向剖面尺度为$ r^{p/2} $，这意味着，对于$ p <2 $，有一个半径，该区域在该地区小于其牛仔裤长度，因此在重力上显得稳定并且需要压力限制，而实际上，它是较大的崩溃的一部分，并且是较大的崩溃的一部分。在该区域，插入速度向中心降低，最终成为亚音速，因此出现“连贯”，而无需湍流耗散。我们提出了密集核中密度曲线的观察确定的汇编，并表明其斜率的分布在$ p \ sim 1.7 $ -1.7 $ -1.9处峰值，这支持了该概况随时间趋向的概念。最后，我们在核心中讨论了磁支持的情况，在该核心中，场尺度为$ b \ proptoρ^β$。对于$β= 2/3 $的预期值，这意味着质量与磁通量比也降低了核心的中央部分，使它们在磁性上似乎得到了磁的支持，而实际上它们可能是较大的倒塌超临界区域的一部分。我们得出的结论是，热或磁支持的局部特征不是稳定性的结论性证据，即必须在较大的尺度上建立区域的重力不稳定，并且倒塌的prestellar阶段是动态的，而不是准确的。
We study the gravitationally-dominated, accretion-driven evolution of a prestellar core. In our model, as the core's density increases, it remains immersed in a constant-density environment and so it accretes from this environment, increasing its mass and reducing its Jeans length. Assuming a power-law density profile $ρ\propto r^{-p}$, we compute the rate of change of the slope $p$, and show that the value $p=2$ is stationary, and furthermore, an attractor. The radial profile of the Jeans length scales as $r^{p/2}$, implying that, for $p<2$, there is a radius below which the region is smaller than its Jeans length, thus appearing gravitationally stable and in need of pressure confinement, while, in reality, it is part of a larger-scale collapse and is undergoing compression by the infalling material. In this region, the infall speed decreases towards the center, eventually becoming subsonic, thus appearing "coherent", without the need for turbulence dissipation. We present a compilation of observational determinations of density profiles in dense cores and show that the distribution of their slopes peaks at $p \sim 1.7$--1.9, supporting the notion that the profile steepens over time. Finally, we discuss the case of magnetic support in a core in which the field scales as $B \propto ρ^β$. For the expected value of $β= 2/3$, this implies that the mass to magnetic flux ratio also decreases towards the central parts of the cores, making them appear magnetically supported, while in reality they may be part of larger collapsing supercritical region. We conclude that local signatures of either thermal or magnetic support are not conclusive evidence of stability, that the gravitational instability of a region must be established at the large scales, and that the prestellar stage of collapse is dynamic rather than quasistatic.
