Semi-empirical analysis of Sloan Digital Sky Survey galaxies – II. The bimodality of the galaxy population revisited
Semi-empirical analysis of Sloan Digital Sky Survey galaxies – II. The bimodality of the galaxy population revisited
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DOI：
10.1111/j.1365-2966.2006.10565.x
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发表时间：
2005-11
影响因子：
4.8
通讯作者：
A. Mateus;L. Sodré;R. C. Fernandes;G. Stasińska;W. Schoenell;Jean M. Gomes IAG-USP;Brazil Ufsc;
中科院分区：
文献类型：
--
作者：
A. Mateus;L. Sodré;R. C. Fernandes;G. Stasińska;W. Schoenell;Jean M. Gomes IAG-USP;Brazil Ufsc;
我们重新审视在本地宇宙中常见的星系人口的双峰分布。在这里，我们解决了在光谱合成产品，如平均恒星年龄和恒星质量，从应用这种强大的方法来获得的体积有限的样本中观察到的双峰性星系的属性，与星等极限截止M（r）=-20.5，包含约50 000个发光星系从斯隆数字巡天（SDSS）数据发布2（DR 2）。此外，星系根据它们的发射线特性分为三个不同的光谱类别：恒星形成星系，具有年轻的恒星种群;被动星系，由老恒星种群主导;和活动核的宿主，包括年轻和老恒星种群的混合。我们表明，极端的一些星系属性的分布，基本上星系的颜色，4000 A断裂指数和平均恒星年龄，与恒星形成星系在一边，被动星系在另一边。我们发现，星系的平均光加权恒星年龄是直接负责的双峰看到的星系人口。在这个观点中，恒星质量有一个额外的作用，因为在本地宇宙中存在的大多数恒星形成星系都是低质量星系。我们的研究结果也支持存在一个“缩小”的星系形成，现在看到的大规模星系有恒星人口形成的早期。
We revisit the bimodal distribution of the galaxy population commonly seen in the local universe. Here, we address the bimodality observed in galaxy properties in terms of spectral synthesis products, such as mean stellar ages and stellar masses, derived from the application of this powerful method to a volume-limited sample, with magnitude limit cut-off M(r ) =− 20.5, containing about 50 000 luminous galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 2 (DR2). In addition, galaxies are classified according to their emission-line properties in three distinct spectral classes: star-forming galaxies, with young stellar populations; passive galaxies, dominated by old stellar populations; and hosts of active nuclei, which comprise a mix of young and old stellar populations. We show that the extremes of the distribution of some galaxy properties, essentially galaxy colours, 4000 A break index and mean stellar ages, are associated to star-forming galaxies at one side, and passive galaxies at another. We find that the mean light-weighted stellar age of galaxies is directly responsible for the bimodality seen in the galaxy population. The stellar mass, in this view, has an additional role since most of the star-forming galaxies present in the local universe are low-mass galaxies. Our results also give support to the existence of a ‘downsizing’ in galaxy formation, where massive galaxies seen nowadays have stellar populations formed at early times.