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首页> 外文期刊>Astronomy and astrophysics >Young, metal-enriched cores in early-type dwarf galaxies in the Virgo cluster based on colour gradients
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Young, metal-enriched cores in early-type dwarf galaxies in the Virgo cluster based on colour gradients

机译：基于颜色梯度的处女座星团早期类型矮星系中年轻的，富含金属的核

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Early-type dwarf galaxies are not simply featureless, old objects, but were found to be much more diverse, hosting substructures and a variety of stellar population properties. To explore the stellar content of faint early-type galaxies, and to investigate in particular those with recent central star formation, we study colours and colour gradients within one effective radius in optical ( g ? r ) and near-infrared ( i ? H ) bands for 120 Virgo cluster early-type galaxies with ? 19 mag & M _( r )& ? 16 mag. Twelve galaxies turn out to have blue cores, when defined as g ? r colour gradients larger than 0.10 mag/ R _(eff) , which represents the positive tail of the gradient distribution. For these galaxies, we find that they have the strongest age gradients, and that even outside the blue core, their mean stellar population is younger than the mean of ordinary faint early-type galaxies. The metallicity gradients of these blue-cored early-type dwarf galaxies are, however, in the range of most normal faint early-type galaxies, which we find to have non-zero gradients with higher central metallicity. The blue central regions are consistent with star formation activity within the last few 100 Myr. We discuss whether these galaxies could be explained by environmental quenching of star formation in the outer galaxy regions while the inner star formation activity continued.
机译：早期类型的矮星系不仅是无特征的旧物体，而且还发现了更多样化的东西，拥有亚结构和各种恒星种群特性。为了探索微弱的早期类型星系的恒星含量，特别是研究最近有中心恒星形成的星系，我们研究了光学和近红外（i？H）的一个有效半径内的颜色和颜色梯度。 120个处女座星团早期类型星系的谱带19 mag＆ M _（r）＜ ？ 16点当定义为g？时，十二个星系具有蓝色核心。 r大于0.10 mag / R _（eff）的颜色渐变，代表渐变分布的正尾。对于这些星系，我们发现它们具有最强的年龄梯度，并且即使在蓝心之外，它们的平均恒星种群也比普通的淡淡的早期类型星系年轻。但是，这些蓝核早型矮星系的金属性梯度在大多数正常的淡淡早型星系的范围内，我们发现它们具有较高中心金属性的非零梯度。蓝色中心区域与最近几百Myr内的恒星形成活动一致。我们讨论了这些星系是否可以通过外部星系区域中恒星形成的环境猝灭而内部恒星形成活动继续进行来解释。

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