论文标题

紫外线上流与紫外线弱星系:其恒星种群的差异和相似之处由偏见的样本揭示

UV upturn versus UV weak galaxies: differences and similarities of their stellar populations unveiled by a de-biased sample

论文作者

Dantas, M. L. L., Coelho, P. R. T., Sánchez-Blázquez, P.

论文摘要

紫外线(UV)上流的特征是在Lyman极限和2500Å之间静止星系中紫外线的意外升入。通过使用颜色彩色图,可以将两组分成两组的紫外线亮红色序列星系:紫外线弱和上流。对于这两组,我们提出了它们出色的人口特性之间的比较,目的是建立差异及其之间的相似之处。我们利用倾向得分匹配(PSM)来减轻两个样本之间的潜在偏差,通过选择红移和恒星质量的对象。此外,我们利用了GAMA协作提供的Magphys的光谱能量分布(SED)拟合结果。分析是通过直接比较SED拟合的分布,并研究其参数之间的相关性差异,最后通过使用主成分分析(PCA)来进行分析。我们探讨了紫外线弱和上流星系之间的重要差异和相似性,例如:金属性,年龄,特定的恒星形成率,最后一系列恒星形成的时间,以提及一些。显着的差异是(G-R)颜色,金属性和自恒星形成以来的时间:紫外线上升以后是紫外线上升的,在光学上更加金属,它们的最后一系列恒星形成发生在时间早些时候。这些差异表明,与紫外线弱星系相比,紫外线上流系统具有较短的恒星形成史(即,正在更被动地进化)。因此,这些似乎具有更高的恒星种群。

The ultraviolet (UV) upturn is characterised by an unexpected up-rise of the UV flux in quiescent galaxies between the Lyman limit and 2500Å. By making use of colour-colour diagrams, one can subdivide UV bright red-sequence galaxies in two groups: UV weak and upturn. With these two groups, we propose a comparison between their stellar population properties with the goal of establishing differences and similarities between them. We make use of propensity score matching (PSM) to mitigate potential biases between the two samples, by selecting similar objects in terms of redshift and stellar mass. Also, we take advantage of spectral energy distribution (SED) fitting results from magphys made available by the GAMA collaboration. The analyses are made by comparing the distributions from the SED fitting directly, as well as investigating the differences in correlations between their parameters, and finally by using principal component analysis (PCA). We explore important differences and similarities between UV weak and upturn galaxies in terms of several parameters, such as: metallicity, age, specific star formation rate, time of last burst of star-formation, to mention a few. Notable differences are those concerning (g-r) colour, metallicity, and time since last burst of star-formation: UV upturn are redder in the optical, more metallic, and their last burst of star-formation happened earlier in time. These differences suggest that UV upturn systems have shorter star-formation histories (i.e. have been evolving more passively) when compared to UV weak galaxies. Consequently, these last seem to have a higher diversity of stellar populations.

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