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首页> 外文期刊>Astronomy and astrophysics >Bars and boxy/peanut bulges in thin and thick discs - I. Morphology and line-of-sight velocities of a fiducial model
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Bars and boxy/peanut bulges in thin and thick discs - I. Morphology and line-of-sight velocities of a fiducial model

机译：薄圆盘和厚圆盘中的条形和方形/花生凸起-I.基准模型的形态和视线速度

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摘要

We explore trends in the morphology and line-of-sight (los) velocity of stellar populations in the inner regions of disc galaxies using N -body simulations with a thin (kinematically cold) and a thick (kinematically hot) disc which form a bar and a boxy/peanut (b/p) bulge. The bar in the thin disc component is ~ 50% stronger than the thick disc bar and is more elongated, with an axis ratio almost half that of the thick disc bar. The thin disc b/p bulge has a pronounced X-shape, while the thick disc b/p is weaker with a rather boxy shape. This leads to the signature of the b/p bulge in the thick disc being weaker and further away from the plane than in the thin disc. Regarding the kinematics, we find that the los velocity of thick disc stars in the outer parts of the b/p bulge can be higher than that of thin disc stars, by up to 40% and 20% for side-on and Milky Way-like orientations of the bar, respectively. This is due to the different orbits followed by thin and thick disc stars in the bar-b/p region, which are affected by two factors. First, thin disc stars are trapped more efficiently in the bar-b/p instability and thus lose more angular momentum than their thick disc counterparts and second, thick disc stars have large radial excursions and therefore stars from large radii with high angular momenta can be found in the bar region. We also find that the difference between the los velocities of the thin and thick disc in the b/p bulge ( Δ v _(los) ) correlates with the initial difference between the radial velocity dispersions of the two discs ( Δ σ ). We therefore conclude that stars in the bar-b/p bulge will have considerably different morphologies and kinematics depending on the kinematic properties of the disc population they originate from.
机译：我们使用N体模拟（形成一个条形的薄（运动性冷）和运动（热运动）厚的N盘，探索盘状星系内部区域恒星种群的形态和视线速度（los）趋势。和一个方形/花生（b / p）凸起。薄圆盘组件中的棒比厚圆盘棒强约50％，并且更长，其轴比几乎是厚圆盘棒的一半。薄圆盘b / p凸起具有明显的X形，而厚圆盘b / p则较弱，呈方形。这导致厚盘中的b / p凸起的特征​​比薄盘中的弱，并且距离平面更远。关于运动学，我们发现在b / p隆起的外部，厚圆盘星的损耗速度可以比薄圆盘星的损耗速度高，对于侧向和银河系，其损耗速度分别高达40％和20％。分别类似于条的方向。这是由于在bar-b / p区域中，紧随其后的圆盘恒星的轨道不同而受到两个因素的影响。首先，较薄的圆盘星比不厚的圆盘星更容易陷入bar-b / p不稳定状态，因此损失了更多的角动量;其次，较厚的圆盘星具有较大的径向偏移，因此来自大半径且角动量大的恒星可以在酒吧区域找到。我们还发现，薄/厚圆盘在b / p凸起中的速度之间的差异（Δv _（los））与两个圆盘的径向速度色散之间的初始差异（Δσ）相关。因此，我们得出的结论是，根据其起源的圆盘种群的运动学特性，bar-b / p凸起中的恒星将具有非常不同的形态和运动学。

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