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arXiv 1202.1929astro-ph.CO
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过去7 Gyr的条形图速度演变

Bar pattern speed evolution over the last 7 Gyr

I. Perez, J. A. L. Aguerri, J. Mendez-Abreu

摘要:

棒料的翻滚模式是表征其动力学特性的主要参数。从数值模拟结果来看,它的演化与暗晕密切相关,暗晕是通过动力学摩擦和角动量交换形成的。观测测量的棒斑速度与红移可以限制星系形成和棒演化的模型。我们的目标是确定,第一次,条形图案的速度与红移的基础上形态学测量的演变。我们从SDSS和COSMOS巡天中选取了44个红移范围为0 <z< 0.8的低倾角环状星系作为样本,研究了条斑速度的演化。我们已经推导出了外环半径(R_{ring})和棒材尺寸(R_{bar})之间的形态比。这个量与用于分类慢旋光和快旋光中的棒的参数{ \cal R}= R_{CR} / R_{bar}有关,并允许我们研究红移的可能差异。我们得到了类似的分布$R$在所有的红移。我们没有发现任何系统性的影响,可能会迫使这一结果。这里得到的结果是兼容的,大部分的酒吧人口(~70%)是快速旋转和没有演变的模式速度与红移。我们认为,如果酒吧是持久的结构,这里提出的结果意味着酒吧和晕之间没有大量的角动量交换,如数值模拟预测的那样。因此,这可能意味着这些高表面亮度星系的圆盘是最大的。

英文摘要:

The tumbling pattern of a bar is the main parameter characterising its dynamics. From numerical simulations, its evolution since bar formation is tightly linked to the dark halo in which the bar is formed through dynamical friction and angular momentum exchange. Observational measurements of the bar pattern speed with redshift can restrict models of galaxy formation and bar evolution. We aim to determine, for the first time, the bar pattern speed evolution with redshift based on morphological measurements. We have selected a sample of 44 low inclination ringed galaxies from the SDSS and COSMOS surveys covering the redshift range 0 <z< 0.8 to investigate the evolution of the bar pattern speed. We have derived morphological ratios between the deprojected outer ring radius (R_{ring}) and the bar size (R_{bar}). This quantity is related to the parameter {\cal R}=R_{CR}/R_{bar} used for classifiying bars in slow and fast rotators, and allow us to investigate possible differences with redshift. We obtain a similar distribution of $R$ at all redshifts. We do not find any systematic effect that could be forcing this result. The results obtained here are compatible with both, the bulk of the bar population (~70%) being fast-rotators and no evolution of the pattern speed with redshift. We argue that if bars are long-lasting structures, the results presented here imply that there has not been a substantial angular momentum exchange between the bar and halo, as predicted by numerical simulations. In consequence, this might imply that the discs of these high surface-brightness galaxies are maximal.

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