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arXiv 0704.2209astro-ph
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Tully-Fisher关系中使用的旋转宽度。II。表面亮度的影响

Rotational Widths for Use in the Tully-Fisher Relation. II. The Impact of Surface Brightness

Barbara Catinella, Martha P. Haynes, Riccardo Giovanelli

摘要:

使用一个大的样本的螺旋星系,21厘米的单碟和/或长缝的光学光谱是可用的,我们做了详细的比较旋转宽度的各种估计。不同的光学宽度估计被认为是和他们的局限性进行了讨论,强调与旋转曲线特性(形状和程度)和磁盘中心表面亮度的偏差。与HI旋转速度的最佳匹配是用Polyex宽度获得的,Polyex宽度是在光学半径(包含星系总光的固定部分)处测量的,来自旋转曲线的模型拟合。与Polyex宽度相比,在2.15盘尺度长度r_d处测量的光学旋转速度偏离HI宽度的量与盘的中心表面亮度相关。这是因为星系的自转曲线在2.15 r_d处仍呈上升趋势,而在这一半径范围内的总质量所占的比例随盘面亮度的增加而减小。统计校正,所观察到的旋转曲线的径向范围参数化,提供减少到一个均匀的系统的Polyex和HI宽度测量。这产生了一个单一的强大的估计旋转速度用于磁盘缩放关系的应用程序。

英文摘要:

Using a large sample of spiral galaxies for which 21 cm single-dish and/or long-slit optical spectra are available, we make a detailed comparison between various estimates of rotational widths. Different optical width estimators are considered and their limitations discussed, with emphasis on biases associated with rotation curve properties (shape and extent) and disk central surface brightness. The best match with HI rotational velocities is obtained with Polyex widths, which are measured at the optical radius (encompassing a fixed fraction of the total light of the galaxy) from a model fit to the rotation curve. In contrast with Polyex widths, optical rotational velocities measured at 2.15 disk scale lengths r_d deviate from HI widths by an amount that correlates with the central surface brightness of the disk. This bias occurs because the rotation curves of galaxies are in general still rising at 2.15 r_d, and the fraction of total mass contained within this radius decreases with increasing disk surface brightness. Statistical corrections, parameterized by the radial extent of the observed rotation curve, are provided to reduce Polyex and HI width measurements into a homogeneous system. This yields a single robust estimate of rotational velocity to be used for applications of disk scaling relations.

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