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arXiv 0706.4347astro-ph
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穿过哈勃序列的膨胀和晕动学

Bulge and Halo Kinematics Across the Hubble Sequence

Luis C. Ho

摘要:

盘的最大旋转速度(v_m)和核球的中心恒星速度色散(sigma)之间的相关性提供了对晕和核球之间关系的见解。我们收集了792个星系的积分H I谱线宽度和中心恒星速度色散,研究了它们之间的v_m-sigma关系。与早期基于小得多的样本的研究相反,我们发现v_m-sigma关系表现出显着的内禀散射,其零点随星系形态,膨胀盘比和光浓度而系统地变化,正如从基本动力学考虑所预期的。有核但无球的晚型旋涡星系明显偏离v_m-sigma关系。虽然这些结果使任何试图用晕取代隆起作为星系中心黑洞质量的基本决定因素的尝试都受到质疑,但观测到的v_m/sigma分布(它取决于星系的密度分布和运动学结构)为星系形成模型提供了一个有用的约束。借助于近红外Tully-Fisher关系,我们确定了一组其他方面正常的明亮星系,它们具有异常低的v_m/sigma值。我们认为,在这些运动学异常的对象中的H I气体的一个显着的部分是动态unrelaxed,已获得外部通过捕获潮汐相互作用或通过冷吸积从星系际介质。

英文摘要:

The correlation between the maximum rotational velocity of the disk (v_m) and the central stellar velocity dispersion of the bulge (sigma) offers insights into the relationship between the halo and the bulge. We have assembled integrated H I line widths and central stellar velocity dispersions to study the v_m-sigma relation for 792 galaxies spanning a broad range of Hubble types. Contrary to earlier studies based on much smaller samples, we find that the v_m-sigma relation exhibits significant intrinsic scatter and that its zeropoint varies systematically with galaxy morphology, bulge-to-disk ratio, and light concentration, as expected from basic dynamical considerations. Nucleated but bulgeless late-type spiral galaxies depart significantly from the v_m-sigma relation. While these results render questionable any attempt to supplant the bulge with the halo as the fundamental determinant of the central black hole mass in galaxies, the observed distribution of v_m/sigma, which depends on both the density profile and kinematic structure of the galaxy, offers a useful constraint on galaxy formation models. With the aid of a near-infrared Tully-Fisher relation, we identify a population of otherwise normal, luminous galaxies that have exceptionally low values of v_m/sigma. We argue that a significant fraction of the H I gas in these kinematically anomalous objects is dynamically unrelaxed, having been acquired externally either through capture from tidal interactions or through cold accretion from the intergalactic medium.

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