The morphological mix of dwarf galaxies in the nearby Universe
The morphological mix of dwarf galaxies in the nearby Universe
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附近宇宙中矮星系的形态组合
DOI：
10.1093/mnras/stae510
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发表时间：
2024
影响因子：
4.8
通讯作者：
Lazar I
中科院分区：
文献类型：
--
作者：
Lazar I
我们使用了一个完整的，无偏的样本257矮（10）星系在z < 0.08，在宇宙领域，研究的形态混合的矮人口在低密度环境。视觉检查极深的光学图像和他们的unsharp-masked同行揭示了三个主要的侏儒形态类。43%和45%的矮星分别表现出传统的“早期型”（椭圆形/S 0）和“晚期型”（螺旋形）形态。然而，10%的星系属于“无特征”类，既没有早期类型的中心光集中，也没有任何螺旋结构--这类星系在银河系中是缺失的。14%，27%和19%的早期类型，晚期类型和无特征的矮星分别显示出相互作用的证据，这些证据驱动了矮星群体中大约20%的整体星星形成活动。与它们的大规模同行相比，矮早型显示出低得多的相互作用的发生率，是显着不太集中，并共享类似的休息帧的颜色作为矮晚型。这表明，矮和大规模的早期类型的形成历史是不同的，矮早期类型的形成较少的相互作用和长期的过程。在宇宙中缺乏大的集团或集群，而我们的矮星形态类别显示出相似的局部密度，这表明低密度环境中的无特征矮星是通过内部重子反馈而不是环境过程产生的。最后，虽然可以使用不对称参数来识别相互作用的矮星，但使用传统的形态参数，如“CAS”，M20和基尼系数（不像在银河系制度中）来干净地区分早期和晚期类型的矮星是具有挑战性的。
We use a complete, unbiased sample of 257 dwarf (10) galaxies atz< 0.08, in the COSMOS field, to study the morphological mix of the dwarf population in low-density environments. Visual inspection of extremely deep optical images and their unsharp-masked counterparts reveals three principal dwarf morphological classes. 43 per cent and 45 per cent of dwarfs exhibit the traditional ‘early-type’ (elliptical/S0) and ‘late-type’ (spiral) morphologies, respectively. However, 10 per cent populate a ‘featureless’ class, that lacks both the central light concentration seen in early-types and any spiral structure – this class is missing in the massive-galaxy regime. 14 per cent, 27 per cent, and 19 per cent of early-type, late-type, and featureless dwarfs respectively show evidence for interactions, which drive around 20 per cent of the overall star formation activity in the dwarf population. Compared to their massive counterparts, dwarf early-types show a much lower incidence of interactions, are significantly less concentrated and share similar rest-frame colours as dwarf late-types. This suggests that the formation histories of dwarf and massive early-types are different, with dwarf early-types being shaped less by interactions and more by secular processes. The lack of large groups or clusters in COSMOS atz< 0.08, and the fact that our dwarf morphological classes show similar local density, suggests that featureless dwarfs in low-density environments are created via internal baryonic feedback, rather than by environmental processes. Finally, while interacting dwarfs can be identified using the asymmetry parameter, it is challenging to cleanly separate early and late-type dwarfs using traditional morphological parameters, such as ‘CAS’,M20, and the Gini coefficient (unlike in the massive-galaxy regime).