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arXiv 2103.00343astro-ph.GA
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CALIFA星系III中的条形图速度。解决超快棒的难题

Bar pattern speeds in CALIFA galaxies III. Solving the puzzle of ultrafast bars

Virginia Cuomo, Yun Hee Lee, Chiara Buttitta, José Alfonso Lopez Aguerri, Enrico Maria Corsini, Lorenzo Morelli

摘要:

超过10%的棒星系的直接测量的酒吧模式的速度主机超快酒吧。这些棒延伸到共转半径之外,挑战了我们对棒星系轨道结构的理解。它们中的大多数是在螺旋星系中发现的,而不是在透镜星系中。我们分析了在CALIFA调查中检测到的超快酒吧的属性,以调查它们是否是由于高估酒吧半径和/或低估的共转半径或一类新的酒吧,其轨道结构尚未被理解的人工制品。我们修正了现有的测量的杆半径的基础上椭圆拟合和傅立叶分析和的酒吧模式的速度从Tüssee-Weinberg方法。此外,我们测量的酒吧半径的分析跟踪横向径向力比的地图,我们从SDSS调查检索的星系的去投影的i波段图像获得。我们发现,几乎所有的样本星系都是具有内环或伪环的螺旋星系,它们围绕着棒星系和/或强旋臂,这妨碍了椭圆拟合和傅立叶分析对棒星系半径的测量。根据这些方法,杆端部与环或螺旋臂重叠,使得所采用的杆半径不可靠。相反,由比值映射得到的棒半径小于共转半径。这与理论预测和数值模拟结果的恒星轨道的延伸和稳定性的支持酒吧。我们的结论是,超快酒吧不再观察时,棒半径的正确测量。在有环和强旋臂的星系中推导棒半径并不简单,并且仍然缺少基于光度和运动学数据的固体测量方法。

英文摘要:

More than 10% of the barred galaxies with a direct measurement of the bar pattern speed host an ultrafast bar. These bars extend beyond the corotation radius and challenge our understanding of the orbital structure of barred galaxies. Most of them are found in spiral galaxies, rather than in lenticular ones. We analysed the properties of the ultrafast bars detected in the CALIFA Survey to investigate whether they are an artefact resulting from an overestimation of the bar radius and/or an underestimation of the corotation radius or a new class of bars, whose orbital structure has not yet been understood. We revised the available measurements of the bar radius based on ellipse fitting and Fourier analysis and of the bar pattern speed from the Tremaine-Weinberg method. In addition, we measured the bar radius from the analysis of the maps tracing the transverse-to-radial force ratio, which we obtained from the deprojected i-band images of the galaxies retrieved from the SDSS Survey. We found that nearly all the sample galaxies are spirals with an inner ring or pseudo-ring circling the bar and/or strong spiral arms, which hamper the measurement of the bar radius from the ellipse fitting and Fourier analysis. According to these methods, the bar ends overlap the ring or the spiral arms making the adopted bar radius unreliable. On the contrary, the bar radius from the ratio maps are shorter than the corotation radius. This is in agreement with the theoretical predictions and findings of numerical simulations about the extension and stability of the stellar orbits supporting the bars. We conclude that ultrafast bars are no longer observed when the correct measurement of the bar radius is adopted. Deriving the bar radius in galaxies with rings and strong spiral arms is not straightforward and a solid measurement method based on both photometric and kinematic data is still missing.

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