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首页> 外文学位 >Morphological properties of star-forming galaxies: Connecting the morphological evolution of galaxies and the decline of the star formation rate density of the Universe in the past 9 billion years.
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Morphological properties of star-forming galaxies: Connecting the morphological evolution of galaxies and the decline of the star formation rate density of the Universe in the past 9 billion years.

机译：恒星形成星系的形态学特征：将过去90亿年中星系的形态演变与宇宙恒星形成率密度的下降联系起来。

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摘要

In this dissertation, we present results connecting the morphological evolution of galaxies and the decline of the star formation rate density in the Universe since z ∼ 2. For our study, we used the high-resolution HST/ACS images of the COSMOS survey to perform non-parametric automated morphological measurements on all objects with brightness IF814W ≤ 23 mag (AB) in the 2 □° field, and combined these data with UV-photometry extracted from GALEX imaging to trace objects with moderate to high star formation rates. By first looking at the morphological properties of a sub-sample of z ∼ 0.7 galaxies, we discover that the morphological bimodality is already in place, that z ∼ 0.7 galaxies have masses, sizes and morphologies similar to that of local galaxies, but that they have star formation rates higher than local galaxies by a factor 2.5--3.5, independently of their other physical properties. We infer that the decline of the star formation rate density in the past 6 Gyrs can be mostly accounted for by a global fading of the galaxy population. We discover that morphology correlates well with UV-optical color, but that there also exists a population of red and dusty star-forming galaxies with bulge-like morphologies. We conclude that bulge growth is linked with episodes of high star formation, and interpret these objects as late-phase mergers. By studying the evolution of the luminosity function at 1500A, we confirm the fading of the characteristic FUV magnitude of galaxies since z = 2.0, and discover a flattening of the faint-end slope at z 0.7. We interpret this flattening as due to a decrease in the birth rate of galaxies. The morphological composition of our UV-sources indicates that disk galaxies dominate the FUV-luminosity function at all redshifts and all luminosities while interacting systems and galaxies with bulges contribute significantly mostly at the bright-end. Early-type disks appear to be the ones to evolve the most since z ∼ 0.7, an epoch through which their faint-end slope steepens. We interpret this as an indication that most small to intermediate-size disk galaxies formed their bulges in the last 6 Gyrs. Finally, we observe, at z > 1, a progressive increase, with redshift, of the contribution of bulge-dominated galaxies to the bright-end of the FUV-luminosity function, a likely signature of the epoch of bulge formation.
机译：在本文中，我们给出了从z〜2以来与星系的形态演化和宇宙中恒星形成速率密度的下降相关的结果。为了进行研究，我们使用了COSMOS调查的高分辨率HST / ACS图像进行了研究对2平方°场中亮度IF814W≤23 mag（AB）的所有物体进行非参数自动形态学测量，并将这些数据与从GALEX成像中提取的UV光度法相结合，以追踪具有中等至高恒星形成率的物体。通过首先查看z〜0.7星系子样本的形态学特性，我们发现形态双峰已经存在，z〜0.7星系的质量，大小和形态与局部星系相似，但是它们与其他星系无关，其恒星形成率比本地星系高2.5-3.5倍。我们推断，过去6个Gyrs中恒星形成速率密度的下降可能主要是由银河系种群的全球衰落造成的。我们发现形态与UV光学颜色具有很好的相关性，但是还存在具有凸起状形态的红色和尘土形成恒星的星系。我们得出的结论是，隆起的增长与高恒星形成的事件有关，并将这些物体解释为后期合并。通过研究1500A时光度函数的演变，我们确认了自z = 2.0以来星系特征FUV量级的衰减，并发现了z <0.7时微弱的末端斜率趋于平坦。我们认为这种变平是由于星系的出生率下降。我们的紫外线源的形态组成表明，在所有红移和所有光度下，盘状星系均主导着FUV发光度功能，而与系统和具有凸起的星系相互作用则主要在明亮端起作用。早期类型的盘似乎是自z〜0.7以来发展最快的盘，这是一个其末梢斜率变陡的时期。我们将其解释为一种指示，表明大多数中小型盘状星系在最近的6个Gyrs内形成了凸起。最后，我们观察到，在z> 1时，红移主导的星系对FUV发光度函数的亮端的贡献随红移逐渐增加，这可能是凸出形成时代的标志。

著录项

  • 作者

    Zamojski, Michel A.;

  • 作者单位

    Columbia University.;

  • 授予单位 Columbia University.;
  • 学科 Physics Astronomy and Astrophysics.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 160 p.
  • 总页数 160
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 天文学;
  • 关键词

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