The secular growth of bars revealed by flat (peak + shoulders) density profiles
The secular growth of bars revealed by flat (peak + shoulders) density profiles
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平坦（峰肩）密度分布揭示了条形的长期生长
DOI：
10.1093/mnras/stac913
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发表时间：
2022
影响因子：
4.8
通讯作者：
Anderson S
中科院分区：
文献类型：
--
作者：
Anderson S
棒的长轴密度分布已知为指数分布或“平坦”分布。我们开发了一种自动化的非参数算法来检测平面轮廓，并将其应用于一套模拟（有和没有气体）。我们证明，平坦的配置文件是一个酒吧的长期增长的表现，在其郊区产生一个“肩”区（一个指数以上的过密）。当横杠形成时，肩部不存在，但随着横杠的生长而发展。如果横杠不长，肩膀就不会形成。肩通常伴随着盒子/花生凸起，但与它们分开发展，并且是酒吧生长的独立痕迹。它们可以在很宽的观察方向上观察到，只有它们的斜率随倾斜度显著变化。我们提出的证据表明，肩膀是由循环x1轨道。由于酒吧的增长率适度相关的增长率的肩膀力量，这些轨道可能是最近被困。因此，肩是酒吧增长的证据。然而，肩部的性质并不能确定杆的年龄，因为二次屈曲或强烈的螺旋可能会破坏肩部，而且如果杆生长得不多，肩部就不会形成。特别是，我们的研究结果表明，指数曲线不一定是一个年轻的酒吧的指示。
The major-axis density profiles of bars are known to be either exponential or ‘flat’. We develop an automated non-parametric algorithm to detect flat profiles and apply it to a suite of simulations (with and without gas). We demonstrate that flat profiles are a manifestation of a bar’s secular growth, producing a ‘shoulder’ region (an overdensity above an exponential) in its outskirts. Shoulders are not present when bars form, but develop as the bar grows. If the bar does not grow, shoulders do not form. Shoulders are often accompanied by box/peanut bulges, but develop separately from them and are independent tracers of a bar’s growth. They can be observed at a wide range of viewing orientations with only their slope varying significantly with inclination. We present evidence that shoulders are produced by looped x1orbits. Since the growth rate of the bar moderately correlates with the growth rate of the shoulder strength, these orbits are probably recently trapped. Shoulders therefore are evidence of bar growth. The properties of the shoulders do not, however, establish the age of a bar, because secondary buckling or strong spirals may destroy shoulders, and also because shoulders do not form if the bar does not grow much. In particular, our results show that an exponential profile is not necessarily an indication of a young bar.