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arXiv 0707.4599astro-ph
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棒状镓样品的近红外表面光度测量

Near-Infrared Surface Photometry of a Sample of Barred Galaxies

Dimitri Gadotti, Lia Athanassoula, Luis Carrasco, Albert Bosma, Ronaldo de Souza, Elsa Recillas

摘要:

我们已经获得了深J和KS图像的样本9棒星系,以收集一组可靠的和均匀的图像,N体模拟棒星系将进行比较。这些观测是使用新的近红外相机进行的,该相机位于墨西哥索诺拉州卡纳内亚的天文学家吉列尔莫·哈罗天文台(OAGH)的2.1米望远镜上。我们呈现了应用于观察到的图像以及去投影图像的表面测光技术的结果。这些结果包括径向轮廓的表面亮度(椭圆平均),颜色,位置角,椭圆率和b4傅立叶分量。此外,我们提出了等照度图,彩色地图,表面亮度分布沿酒吧的长轴和短轴,特征径向尺度长度和酒吧长度估计。我们将讨论如何投影效应可以影响这些测量和不确定性所引入的星系图像去投影。我们表明,解析表达式可以用来获得可靠的估计dprojected酒吧的长度,椭圆度和位置角直接从观察到的图像。这些表达式是基于假设的外部部分的酒吧垂直薄,如理论工作所示。我们的数据在解决酒吧的形成和演变的问题的有用性也进行了讨论。特别是,我们目前的结果表明,在椭圆率曲线急剧下降,预期酒吧的形成过程中,暗物质晕起着根本性的作用。此外,我们表明,这个下降的位置是一个很好的指标,在强棒星系的酒吧结束,预测的数值模型。

英文摘要:

We have obtained deep J and Ks images of a sample of nine barred galaxies in order to collect a reliable and homogeneous set of images to which N-body simulations of barred galaxies will be compared. The observations were performed using the new near-infrared camera available at the 2.1-m telescope of the Observatorio Astrofisico Guillermo Haro (OAGH) in Cananea, Sonora, Mexico. We present the results of surface photometry techniques applied to the observed images, as well as to the deprojected images. These results include radial profiles of surface brightness (elliptically averaged), colour, position angle, ellipticity and the b4 Fourier component. In addition, we present isophotal maps, colour maps, surface brightness profiles along the bar major and minor axes, characteristic radial scale-lengths and bar length estimates. We discuss how projection effects can influence these measurements and the uncertainties introduced by deprojecting galaxy images. We show that analytical expressions can be used to obtain reliable estimates of deprojected bar lengths, ellipticities and position angles directly from the observed images. These expressions are based on the assumption that the outer parts of the bar are vertically thin, as shown by theoretical work. The usefulness of our data in addressing issues on bar formation and evolution is also discussed. In particular, we present results showing a steep drop in the ellipticity profile, as expected for bar formation processes in which the dark matter halo plays a fundamental role. Furthermore, we show that the location of this drop is a good indicator of the end of the bar in strongly barred galaxies, as predicted by numerical models.

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