用SEKBO巡天RR探测室女座星流
Exploring the Virgo Stellar Stream with SEKBO Survey RR Lyrae Stars
摘要：
从南部边缘柯伊伯带天体（SEKBO）调查数据中确定的RR天琴座（RRL）候选者的一个子集已被跟踪光度（n=106）和光谱（n=51）。周期和光变曲线拟合揭示了非RRL对SEKBO调查数据的24 +/_ 7%的污染。本文重点介绍室女座恒星流（VSS）的区域，特别是它的扩展到南部的SDSS和QUEST RRL调查的December界限。在银河系静止标准坐标系（V_GSR）中，VSS区观测到的11个RRL的径向速度分布有两个明显的峰值。较大的峰值与具有<V_GSR>=127 +/-10 kms-1和色散σ =27 kms-1的四个RRL一致，略大于仅从误差预期的值。该组中的两个ab型RRL具有<[Fe/H]>=-1.95 +/_ 0.1。径向速度和金属丰度与VSS的成员资格一致。第二个速度峰值出现在<V_GSR>=-175 +/-10 kms-1处，可能表明Sgr潮汐尾的恒星存在，预计在该区域有很大的负速度。我们探索的VSS的程度，通过构建从SEKBO数据的光度函数，并将它们与贝桑松银河系模型合成的数据进行比较。对超出模型预测的超密度的分析表明，VSS是一个大的（~760度^2）超密度，中心大约在（RA，Dec）~（186度，-4度），在投影中跨越~15 kpc的长度，假设日心距离为19 kpc。这些数据首次揭示了该流更南部的区域，并将其追踪到12月~-15度和银河系低至b ~ 45度的纬度。
英文摘要：
A subset of the RR Lyrae (RRL) candidates identified from the Southern Edgeworth-Kuiper Belt Object (SEKBO) survey data has been followed up photometrically (n=106) and spectroscopically (n=51). Period and light curve fitting reveals a 24 +/_ 7% contamination of SEKBO survey data by non-RRLs. This paper focuses on the region of the Virgo Stellar Stream (VSS), particularly on its extension to the South of the declination limits of the SDSS and of the QUEST RRL survey. The distribution of radial velocities in the Galactic standard of rest frame (V_GSR) for the 11 RRLs observed in the VSS region has two apparent peaks. The larger peak coincides with the four RRLs having <V_GSR>=127 +/_ 10 kms-1 and dispersion sigma=27 kms-1, marginally larger than that expected from the errors alone. The two type ab RRLs in this group have <[Fe/H]>=-1.95 +/_ 0.1. Both the radial velocities and metal abundances are consistent with membership in the VSS. The second velocity peak, which occurs at <V_GSR>=-175 +/_ 10 kms-1 may indicate the presence of stars from the Sgr leading tidal tail, which is expected to have large negative velocities in this region. We explore the extent of the VSS by constructing luminosity functions from the SEKBO data and comparing them to data synthesized with the Besancon Galactic model. Analysis of the excess over the model predictions reveals the VSS as a large (~760 deg^2) overdensity centered at roughly (RA, Dec) ~ (186deg, -4deg), spanning a length of ~15 kpc in projection, assuming a heliocentric distance of 19kpc. The data reveal for the first time the more southern regions of the stream and trace it to Dec ~ -15deg and Galactic latitudes as low as b ~ 45deg.
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