论文标题
三个运动积分揭示了银河系的恒星光环的本质
The nature of the Milky Way's stellar halo revealed by the three integrals of motion
论文作者
论文摘要
我们开发了一种新的选择方法，该方法是在轴对称银河电位的三个运动积分（$ e $，$ l_z $，$ i_3 $）中定义的相位空间分布中，其中$ i_3 $是运动的第三个积分。该方法用于探索基于SDSS-SEGUE DR7和DR16-APOGEE的恒星样品的光环的一般化学动力结构，与Gaia-DR2匹配。我们发现，（a）可以通过选择超过（1）$ 0 <l_z <1500 $ \ kpckms，$（2i_3）^{1/2}> 1000 $ \ kpckms（orbital Angle $θ__{\ rm Orb} $ 15-20 $ 15-20 $ e <-11^5-11， km $^2 $ s $^{ - 2} $，（2）$ l_z <0 $ \ kpckms。这些选择标准不受近期文献中简单的高速削减所引入的运动学偏见。 （b）平均或{\ it粗粒}的光环阶段分布显示单调指数下降，随着$ e $的增加和$ i_3 $，如Michie-Bodenheimer型号； （c）发现\ citet {Carollo2007，carollo2010}中描述的内部恒星光环均包含Gaia Ecceladus Derbris（ge; \ cetealt {helmi2018}），最低$ e $ $ e $星星（可能是situ sarts and Metal-poor poor poor progralade stars the Highty the Hightife and Mether Poer the Highty vel vel velce; （d）非常金属差的外光环（[[Fe/h] $ <-2.2 $ 2.2）表现出逆行和序列旋转，比与GE Dyination Inner Halo所拥有的那些相比，对高逆行运动的不对称$ L_Z $分布和更大的$θ_{\ rm Orb} $; （e）SGR DSPH星系可能会引起对局部光环恒星的远程动力学效应。还讨论了对恒星光环的形成的影响。
We developed a new selection method of halo stars in the phase-space distribution defined by the three integrals of motion in an axisymmetric Galactic potential, ($E$, $L_z$, $I_3$), where $I_3$ is the third integral of motion. The method is used to explore the general chemo-dynamical structure of the halo based on stellar samples from SDSS-SEGUE DR7 and DR16-APOGEE, matched with Gaia-DR2. We found, (a) halo stars can be separated from disk stars by selecting over (1) $0 < L_z < 1500$ \kpckms, $(2I_3)^{1/2} > 1000$ \kpckms (orbital angle $θ_{\rm orb}$ $>$ 15-20 deg), and $E < -1.5 \times 10^5$ km$^2$ s$^{-2}$, and (2) $L_z < 0$ \kpckms. These selection criteria are free from kinematical biases introduced by the simple high-velocity cuts adopted in recent literature; (b) the averaged, or {\it coarse-grained}, halo phased-space distribution shows a monotonic exponential decrease with increasing $E$ and $I_3$ like the Michie-Bodenheimer models; (c) the inner stellar halo described in \citet{carollo2007,carollo2010} is found to comprise a combination of Gaia Enceladus debris (GE; \citealt{helmi2018}), lowest-$E$ stars (likely in-situ stars), as well as metal-poor prograde stars missed by the high velocity cuts selection; (d) the very metal poor outer halo, ([Fe/H] $< -$2.2), exhibits both retrograde and prograde rotation, with an asymmetric $L_z$ distribution towards high retrograde motions, and larger $θ_{\rm orb}$ than those possessed by the GE dominated inner halo; (e) the Sgr dSph galaxy could induce a long-range dynamical effect on local halo stars. Implication for the formation of the stellar halo are also discussed.
