arXiv 2102.108962021-02-22astro-ph.GAastro-ph.SR

甚低光度天体包层中的气体下落运动

Gas infalling motions in the envelopes of Very Low Luminosity Objects

Mi-Ryang Kim, Chang Won Lee, Maheswar, G, Philip C. Myers, Gwanjeong Kim

DOI：: 10.3847/1538-4357/abe4d3

摘要：

我们提出了一个单盘调查的结果，对95 VeLLO的光学厚（HCN 1-0）和薄（$\rm N_2H^+$ 1-0）线进行的目的是了解的物理过程中的信封的VeLLO的向内运动，并表征其真实性质。两条线的峰值速度之间的归一化速度差（$δV_{HCN}$）是针对在两条线中检测到的41个VeLLO导出的。这些VeLLO的$δV$分布被发现是显着偏蓝，这表明在其信封下降运动的主导地位。利用HILL 5辐射转移模式，计算了15个候选粒子的入流速度。速度范围为0.03 $\rm km~s^{-1}$至0.3 $\rm km~s^{-1}$，中值为0.16 $\rm km~s^{-1}$，与无压包线的重力自由落体速度一致。根据坠落速度计算的质量坠落率大多数为$10^{-6} M_{\odot}~yr^{-1}$的数量级，中值为$\rm 3.4 \pm 1.5 \times 10^{-6} M_{\odot}~yr^{-1}$。这些被发现也是一致的预测值与内-外崩溃模型，并显示出相当好的相关性与内部光度的VeLLOs。这再次表明，观测到的朝向VeLLO的下落运动很可能是由于其包络中的重力下落运动。我们的研究表明，大多数VeLLO是潜在的暗淡原恒星，而两个VeLLO可能是原棕矮星候选人。

英文摘要：

We present the results of a single dish survey toward 95 VeLLOs in optically thick (HCN 1-0) and thin ($\rm N_2H^+$ 1-0) lines performed for the purpose of understanding the physical processes of inward motions in the envelopes of the VeLLOs and characterizing their true nature. The normalized velocity differences ($δV_{HCN}$) between the peak velocities of the two lines were derived for 41 VeLLOs detected in both lines. The $δV$ distribution of these VeLLOs is found to be significantly skewed to the blue, indicating the dominance of infalling motions in their envelopes. The infall speeds were derived for 15 infall candidates by using the HILL5 radiative transfer model. The speeds were in the range of 0.03 $\rm km~s^{-1}$ to 0.3 $\rm km~s^{-1}$, with a median value of 0.16 $\rm km~s^{-1}$, being consistent with the gravitational free-fall speeds from pressure-free envelopes. The mass infall rates calculated from the infall speeds are mostly of the order of $10^{-6} M_{\odot}~yr^{-1}$ with a median value of $\rm 3.4 \pm 1.5 \times 10^{-6} M_{\odot}~yr^{-1}$. These are found to be also consistent with the values predicted with the inside-out collapse model and show a fairly good correlation with the internal luminosities of the VeLLOs. This again indicates that the infall motions observed toward the VeLLOs are likely to be due to the gravitational infall motions in their envelopes. Our study suggests that most of the VeLLOs are potentially faint protostars while two of the VeLLOs could possibly be proto-brown dwarf candidates.

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英文摘要：

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