论文标题
使用适当的运动选定的光环样品确定银河系的逃逸速度
Determination of the escape velocity of the Milky Way using a proper motion selected halo sample
论文作者
论文摘要
{\ it Gaia}任务提供了有史以来最大的目录，并提供了切线速度信息。但是，将此目录用于动力学研究很困难，因为大多数恒星都缺乏视线速度测量值。最近，我们提出了$ \ sim 10^7 $光晕星，其准确的距离是根据其光度法和适当的运动选择的。使用此样本，我们将速度分布的尾部建模为幂律分布，这是\ cite {leonard1990thespeed}首先建立的常用方法。我们第一次使用对前所未有的光环恒星准确测量的切向速度来估计逃逸速度。在太阳街区，我们获得了逃逸速度的非常精确的估计，即$ 497^{+8} _ { - 8}〜{\ rm km/s} $。该估计很可能是偏见的，我们最好的猜测是10 \％。结果，真正的逃逸速度很可能接近$ 550〜 {\ rm km/s} $。逃逸速度直接限制了银河系的总质量。为了找到最佳的拟合光环质量和浓度参数，我们调整了逼真的银河系潜力的深色（球形NFW）光环，同时将圆速度保持在固定在$ v_c（r_ \ odot）= 232.8〜 {\ rm km/s s} $的太阳半径上。所得的光晕参数为$ m_ {200}^{+10 \％} = 1.11^{+0.08} _ { - 0.07} \ cdot10^{12}〜{\ rm m} _ \ rm m} _ \ odot $和浓度$和浓度$和浓度$ c^{+10 \％} $ c^{+10 \％} $} = 11.8^0.3.3.3.3.3.3.3.3.3.8^= 11.8^{0.3.3.3.3.3.3.3.3.3.3.3.3.8^= 11.8^= 11.3 = 11.3^{我们使用显式符号表示已对10 \％偏差进行了校正。基于银河系模型，内部银河系中的逃生速度斜率是预期的。奇怪的是，我们发现超出太阳半径以外的分歧，这可能是速度分布形状变化的影响，并且可能与速度团块的存在有关。
The {\it Gaia} mission has provided the largest catalogue ever of sources with tangential velocity information. However, using this catalogue for dynamical studies is difficult because most of the stars lack line-of-sight velocity measurements. Recently, we presented a selection of $\sim 10^7$ halo stars with accurate distances that have been selected based on their photometry and proper motions. Using this sample, we model the tail of the velocity distribution with a power-law distribution, a commonly used approach first established by \cite{Leonard1990THESPEED}. For the first time ever we use tangential velocities measured accurately for an unprecedented number of halo stars to estimate the escape velocity. In the solar neighbourhood, we obtain a very precise estimate of the escape velocity which is $497^{+8}_{-8}~{\rm km/s}$. This estimate is most likely biased low, our best guess is by 10\%. As a result, the true escape velocity most likely is closer to $550~{\rm km/s}$. The escape velocity directly constrains the total mass of the Milky Way. To find the best fitting halo mass and concentration parameter we adjusted the dark (spherical NFW) halo of a realistic Milky Way potential while keeping the circular velocity at the solar radius fixed at $v_c(R_\odot) = 232.8~{\rm km/s}$. The resulting halo parameters are $M_{200}^{+10\%} = 1.11^{+0.08}_{-0.07} \cdot10^{12} ~{\rm M}_\odot$ and concentration parameter $c^{+10\%} = 11.8^{+0.3}_{-0.3}$, where we use the explicit notation to indicate that these have been corrected for the 10\% bias. The slope of the escape velocity with galactocentric distance is as expected in the inner Galaxy based on Milky Way models. Curiously, we find a disagreement beyond the solar radius which is likely an effect of a change in the shape of the velocity distribution and could be related to the presence of velocity clumps.
