首页> 外文期刊>The Astrophysical journal >THE OVERDENSITY IN VIRGO, SAGITTARIUS DEBRIS, AND THE ASYMMETRIC SPHEROID
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THE OVERDENSITY IN VIRGO, SAGITTARIUS DEBRIS, AND THE ASYMMETRIC SPHEROID

机译:处女座,射手座和不对称球体的过密度

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We investigate the relationship between several previously identified Galactic halo stellar structures in the direction of Virgo using imaging and spectroscopic observations of F turnoff stars and blue horizontal-branch stars from SDSS and SEGUE. We show that the Sagittarius dwarf leading tidal tail does not pass through the solar neighborhood; it misses the Sun by more than 15 kpc, passing through the Galactic plane outside the solar circle. Nor is it spatially coincident with the large stellar overdensity S297+63-20.5 in the Virgo constellation. S297+63-20.5 has a distinct turnoff color and kinematics. Faint (g_0 ~ 20.3) turnoff stars in S297+63-20.5 have line-of-sight, Galactic standard of rest velocities V_(gsr) = 130 ± 10 kms~(-1), opposite in sign to infalling Sgr tail stars. The path oftheSgr leading tidal tail is also inconsistent with the positions of some of the nearer stars with which it has been associated and whose velocities have favored models with prolate Milky Way potentials. We also show that the number densities of brighter (g_0 ~ 19.8) F turnoff stars are not symmetric about the Galactic center and that this discrepancy is not primarily due to the S297+63-20.5 moving group. Either the spheroid is asymmetric about the Galactic center or there are additional substructures that conspire to be on the same side of the Galaxy as S297+63-20.5. The S297+63-20.5 overdensity in Virgo is likely associated with two other previously identified Virgo substructures: the Virgo stellar stream (VSS) and the Virgo overdensity (VOD). However, the velocity difference between the VSS and S297+63-20.5 and the difference in distance estimates between the VOD and S297+63-20.5 must be reconciled.
机译:我们使用SDSS和SEGUE的F断层恒星和蓝色水平分支星的成像和光谱观察,研究了在处女座方向上几个先前确定的银河系晕星结构之间的关系。我们表明人马座矮人领先的潮汐尾巴没有穿过太阳附近;它以超过15 kpc的速度通过太阳圈外的银河平面错过了太阳。它与处女座的大恒星密度S297 + 63-20.5在空间上也不相符。 S297 + 63-20.5具有明显的截止颜色和运动学特性。 S297 + 63-20.5中微弱(g_0〜20.3)的关闭星具有视线,静止速度的银河标准V_(gsr)= 130±10 kms〜(-1),与降落的Sgr尾星相反。 Sgr引导潮汐尾部的路径也与它所关联的一些较近恒星的位置不一致,并且它们的速度有利于银河系潜在的模型。我们还表明,更亮的(g_0〜19.8)F熄灭恒星的数量密度关于银河系中心不对称,并且这种差异主要不是由于S297 + 63-20.5运动群引起的。椭球体相对于银河系中心不对称,或者有其他子结构与S297 + 63-20.5一起位于银河系的同一侧。处女座中的S297 + 63-20.5密度过高可能与其他两个先前确定的处女座子结构有关:处女座恒星流(VSS)和处女座过密度(VOD)。但是,必须调和VSS和S297 + 63-20.5之间的速度差以及VOD和S297 + 63-20.5之间的距离估计差。

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