Structure and dynamics of galaxies with a low surface-brightness disc – II. Stellar populations of bulges
Structure and dynamics of galaxies with a low surface-brightness disc – II. Stellar populations of bulges
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DOI：
10.1111/j.1365-2966.2012.20938.x
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发表时间：
2012-03
影响因子：
4.8
通讯作者：
L. Morelli;E. Corsini;A. Pizzella;E. Bontà;L. Coccato;J. M'endez-Abreu;M. M. D. D. Astronomia-M.-M.-D.-D.-Astronomia-102561505;U. Padova;I. Padova;E. Observatory;Instituto de Astrof'isica de Canarias-Instituto-de-Astrof'isica-de-Canarias-102997450
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文献类型：
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作者：
L. Morelli;E. Corsini;A. Pizzella;E. Bontà;L. Coccato;J. M'endez-Abreu;M. M. D. D. Astronomia-M.-M.-D.-D.-Astronomia-102561505;U. Padova;I. Padova;E. Observatory;Instituto de Astrof'isica de Canarias-Instituto-de-Astrof'isica-de-Canarias-102997450
本文给出了8个具有低表面亮度星盘和球的旋涡星系的Hβ、Mg和Fe线强度指数的径向分布。线强度指数和速度色散的中心值之间的相关性与已知的早型星系和高表面亮度星系的凸起是一致的。利用变元素丰度比的星族模型，计算了膨胀区星族的年龄、金属丰度和α/Fe增强。几乎所有的样品都具有年轻恒星的特征，正在进行的星星形成和太阳α/Fe增强。它们的金属丰度从高值到太阳下值不等。年龄和α/Fe增强没有明显的梯度，而金属丰度负梯度仅在少数情况下被发现。这些性质表明，一个纯粹的耗散崩溃不能解释所有的样品隆起的形成和其他现象，如合并或收购事件，需要调用。在金属丰度极低的凸起中，中心值与金属丰度梯度之间缺乏相关性，也支持了这一观点。由低表面亮度盘承载的凸起的恒星种群与高表面亮度星系有许多共同的特性。因此，它们可能具有共同的形成情景和演化历史。凸起和圆盘之间的强烈相互作用被排除在外，尽管由具有极其不同属性的圆盘承载，但低表面亮度和高表面亮度圆盘的凸起非常相似。
We present the radial profiles of the Hβ, Mg and Fe line-strength indices for a sample of eight spiral galaxies with a low-surface-brightness stellar disc and a bulge. The correlations between the central values of the line-strength indices and velocity dispersion are consistent with those known for early-type galaxies and bulges of high-surface-brightness galaxies. The age, metallicity and α/Fe enhancement of the stellar populations in the bulge-dominated region are obtained using stellar population models with variable element abundance ratios. Almost all the sample bulges are characterized by a young stellar population, ongoing star formation and a solar α/Fe enhancement. Their metallicity spans from high to subsolar values. No significant gradient in age and α/Fe enhancement is measured, whereas a negative metallicity gradient is found only in a few cases. These properties suggest that a pure dissipative collapse cannot explain the formation of all the sample bulges and that other phenomena, such as mergers or acquisition events, need to be invoked. Such a picture is also supported by the lack of a correlation between the central value and the gradient of the metallicity in bulges with very low metallicity. The stellar populations of the bulges hosted by low-surface-brightness discs share many properties with those of high-surface-brightness galaxies. Therefore, they are likely to have common formation scenarios and evolution histories. A strong interplay between bulges and discs is ruled out by the fact that, in spite of being hosted by discs with extremely different properties, the bulges of low- and high-surface-brightness discs are remarkably similar.