论文标题
RR Lyrae Star(Brava-RR)DR2的凸起径向速度测定:双峰凸起?
The Bulge Radial Velocity Assay for RR Lyrae stars (BRAVA-RR) DR2: a Bimodal Bulge?
论文作者
论文摘要
提出了2768个基本模式的径向速度RR Lyre恒星(RRLS)向南部银河隆起的速度,从-8 <l <+8和-3 <b <-6。从RRL的脉动特性得出的距离与Gaia的适当运动结合在一起,以对1389 RRL的轨道运动产生约束。大多数(约75%)的凸起RRL的轨道与这些恒星一致,从银河中心永久结合到<3.5 kpc,类似于棒。但是,与凸出巨头不同,RRL的旋转较慢和速度分散较高。较高的速度分散剂几乎完全来自穿过内部星系的光环介入者。我们提出了82颗恒星,其空间速度> 500 km/s,发现这些高速恒星中的大多数是光环闯入者。目前尚不清楚这些具有相似空间速度的恒星的子样本是否具有共同的起源。一旦清洁了晕圈跨行子的25%的样品,我们就可以清楚地辨别出内星系中两个凸起的RRL群体。一个RRL的人群与银河系不那么紧密结合(但仍局限于内部〜3.5 kpc),并且在空间和运动学上都与禁止的凸起一致。第二个人口更集中,并且不会追踪标准。一种可能的解释是,该人群是在钢筋形成之前诞生的,因为它的空间位置,运动学和脉动特性可能是从高红移的增生事件中出发的。
Radial velocities of 2768 fundamental mode RR Lyrae stars (RRLs) toward the Southern Galactic bulge are presented, spanning the southern bulge from -8 < l < +8 and -3 < b <-6. Distances derived from the pulsation properties of the RRLs are combined with Gaia proper motions to give constraints on the orbital motions of 1389 RRLs. The majority (~75%) of the bulge RRLs have orbits consistent with these stars being permanently bound to <3.5 kpc from the Galactic Center, similar to the bar. However, unlike the bulge giants, the RRLs exhibit slower rotation and a higher velocity dispersion. The higher velocity dispersion arises almost exclusively from halo interlopers passing through the inner Galaxy. We present 82 stars with space velocities > 500 km/s and find that the majority of these high-velocity stars are halo interlopers; it is unclear if a sub-sample of these stars with similar space velocities have a common origin. Once the 25% of the sample represented by halo interlopers is cleaned, we can clearly discern two populations of bulge RRLs in the inner Galaxy. One population of RRLs is not as tightly bound to the Galaxy (but is still confined to the inner ~3.5 kpc), and is both spatially and kinematically consistent with the barred bulge. The second population is more centrally concentrated and does not trace the bar. One possible interpretation is that this population was born prior to bar formation, as its spatial location, kinematics and pulsation properties suggest, possibly from an accretion event at high redshift.