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arXiv 0804.2484astro-ph
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用SDSS估算高纬星系模型参数

Estimation of galactic model parameters in high latitudes with SDSS

S. Bilir, A. Cabrera-Lavers, S. Karaali, S. Ak, E. Yaz, López-Corredoira

摘要:

我们估计了斯隆数字巡天({ \em SDSS})当前可用的数据发布5(DR 5)中包含的一组36个高纬度字段的银河系模型参数,以探索它们随银河经度的可能变化。厚盘的刻度高度从$120^{\circ}<l<150^{\circ}$的$\sim$ 550 pc移动到$250^{\circ}<l<290^{\circ}$的$\sim$ 720 pc,而薄盘的刻度高度在反中心方向上高达$\sim$ 195 pc,在$|l|<30^\circ$的$\sim$低15%。最后,晕的轴比($c/a$)从银河系前两个象限的平均值$\sim$ 0.55变为$190^{\circ}<l<300^{\circ}$的$\sim$ 0.70。对于晕,模型参数对银河经度的依赖性的原因来自于这个组件的众所周知的不对称结构。而厚盘和薄盘的模型参数随银河经度的变化则源于银河长杆的引力效应。此外,象限I(象限III)中的恒星比象限IV(象限II)中的恒星多,这与这种情况一致。

英文摘要:

We estimated the Galactic model parameters for a set of 36 high-latitude fields included in the currently available Data Release 5 (DR 5) of the Sloan Digital Sky Survey ({\em SDSS}), to explore their possible variation with the Galactic longitude. The thick disc scaleheight moves from $\sim$550 pc at $120^{\circ}<l<150^{\circ}$ to $\sim$720 pc at $250^{\circ}<l<290^{\circ}$, while the thin disc scaleheight is as large as $\sim$195 pc in the anticenter direction and $\sim$15% lower at $|l|<30^\circ$. Finally, the axis ratio ($c/a$) of the halo changes from a mean value of $\sim$0.55 in the two first quadrants of the Galaxy to $\sim$0.70 at $190^{\circ}<l<300^{\circ}$. For the halo, the reason for the dependence of the model parameters on the Galactic longitude arises from the well known asymmetric structure of this component. However, the variation of the model parameters of the thin and thick discs with Galactic longitude originates from the gravitational effect of the Galactic long bar. Moreover, the excess of stars in quadrant I (quadrant III) over quadrant IV (quadrant II) is in agreement with this scenario.

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