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arXiv 1409.2876astro-ph.GA
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棒星系中的长期和合并形成的凸起

Secular- and merger-built bulges in barred galaxies

J. Mendez-Abreu, Victor P. Debattista, E. M. Corsini, J. A. L. Aguerri

摘要:

我们研究了10个面对棒星系样本中复合凸起的发生率和性质,以约束盘星系中心区域的形成和演化过程。我们分析了每个凸起的形态,光度和运动学特性。然后,通过使用一个案例一个案例的分析,我们确定复合凸起和分类成一个经典或pseudobulge的每个组件。此外,酒吧相关的盒状/花生(B/P)结构也被确定和表征。我们发现只有三个星系主办的单组件的凸起(两个pseudoclugges和一个经典的凸起)。我们发现证据的复合凸起来在两个主要类型的基础上,他们的形成:世俗建立和合并和世俗建立。我们称之为长期建造的复合隆起,完全由与长期过程相关的结构组成,如伪隆起、中心盘或B/P隆起。我们在样品中发现了四个这种复合凸起。另一方面,合并和世俗建造的凸起是那些具有不同形成路径的结构共存于同一星系内的凸起,即,一个经典的隆起与一个世俗的结构共存(伪隆起,中心盘,或B/P)。在样品中发现了三个这种凸起。我们注意到检测运动学结构,如西格玛下降,以确定复合凸起的重要性。在我们的样本中,发现很大一部分(80%)的星系具有sigma下降或sigma平台,揭示了它们在棒星系中的高发生率。在棒星系中复合凸起的高频率指向一个复杂的形成和演化的场景。此外,合并和世俗建筑并存的证据强化了这一观点。我们讨论了如何存在不同的凸起类型,不同的形成历史和时间尺度,可以限制目前的模型凸起的形成。

英文摘要:

(Abridged) We study the incidence, as well as the nature, of composite bulges in a sample of 10 face-on barred galaxies to constrain the formation and evolutionary processes of the central regions of disk galaxies. We analyze the morphological, photometric, and kinematic properties of each bulge. Then, by using a case-by-case analysis we identify composite bulges and classify every component into a classical or pseudobulge. In addition, bar-related boxy/peanut (B/P) structures were also identified and characterised. We find only three galaxies hosting a single-component bulge (two pseudobulges and one classical bulge). We find evidence of composite bulges coming in two main types based on their formation: secular-built and merger- and secular-built. We call secular-built to composite bulges made of entirely by structures associated with secular processes such as pseudo bulges, central disks, or B/P bulges. We find four composite bulges of this kind in our sample. On the other hand, merger- and secular-built bulges are those where structures with different formation paths coexist within the same galaxy, i.e., a classical bulge coexisting with a secular-built structure (pseudobulge, central disk, or B/P). Three bulges of this kind were found in the sample. We remark on the importance of detecting kinematic structures such as sigma-drops to identify composite bulges. A large fraction (80%) of galaxies were found to host sigma-drops or sigma-plateaus in our sample revealing their high incidence in barred galaxies. The high frequency of composite bulges in barred galaxies points towards a complex formation and evolutionary scenario. Moreover, the evidence for coexisting merger- and secular-built bulges reinforce this idea. We discuss how the presence of different bulge types, with different formation histories and timescales, can constrain current models of bulge formation.

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