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arXiv 1104.4864astro-ph.CO
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本星系哈勃型与分光类的关系

Relationship between Hubble type and spectroscopic class in local galaxies

J. Sanchez Almeida, J. A. L. Aguerri, C. Munoz-Tunon, M. Huertas-Company

摘要:

我们比较了星系的哈勃型和光谱类与SDSS/DR 7中的光谱。众所周知,椭圆星系往往是红色的,而螺旋星系往往是蓝色的,然而,这种关系呈现出很大的散射,我们详细测量和量化。我们比较了自动光谱K-均值分类(ASK)与大多数常用的形态学分类。所有这些都提供了一致的结果。给定一个光谱类别,形态类型以2到3 T类型之间的标准差波动,并且相同的大离散度表征了固定形态类型的光谱类别的可变性。给定ASK类的哈勃类型的分布是非常偏斜的-它们呈现出长长的尾巴,红色星系的后期形态类型,蓝色光谱类的早期形态类型。分散不是由分类中的问题产生的,当考虑特定子集时,它仍然存在。相当一部分的红色星系是螺旋星系(40- 60%),但它们从来没有出现过很晚的哈勃类型(Sd或更晚)。尽管红光谱与椭圆星系无关,但大多数椭圆星系确实有红光谱:在Nair和Abraham的形态学目录中,97%的椭圆星系属于ASK 0,2或3。它只包含3%的蓝色椭圆星系。绿谷类(ASK~5)中的星系多为旋涡星系,活动星系核类(ASK ~ 6)中的哈勃型星系从E到Sd分布较广。从红移0.25到现在,星系从ASK 2变红到ASK 0,正如它们的恒星星族被动演化所预期的那样。两个ASK类(1和4)收集边缘螺旋,这是需要知道星系内在形状的研究中感兴趣的属性(例如,弱透镜校准)。

英文摘要:

We compare the Hubble type and the spectroscopic class of the galaxies with spectra in SDSS/DR7. As it is long known, elliptical galaxies tend to be red whereas spiral galaxies tend to be blue, however, this relationship presents a large scatter, which we measure and quantify in detail. We compare the Automatic Spectroscopic K-means based classification (ASK) with most of the commonly used morphological classifications. All of them provide consistent results. Given a spectral class, the morphological type wavers with a standard deviation between 2 and 3 T types, and the same large dispersion characterizes the variability of spectral classes fixed the morphological type. The distributions of Hubble types given an ASK class are very skewed -- they present long tails that go to the late morphological types for the red galaxies, and to the early morphological types for the blue spectroscopic classes. The scatter is not produced by problems in the classification, and it remains when particular subsets are considered. A considerable fraction of the red galaxies are spirals (40--60 %), but they never present very late Hubble types (Sd or later). Even though red spectra are not associated with ellipticals, most ellipticals do have red spectra: 97 % of the ellipticals in the morphological catalog by Nair & Abraham, used here for reference, belong to ASK 0, 2 or 3. It contains only a 3 % of blue ellipticals. The galaxies in the green valley class (ASK~5) are mostly spirals, and the AGN class (ASK 6) presents a large scatter of Hubble types from E to Sd. From redshift 0.25 to now the galaxies redden from ASK 2 to ASK 0, as expected from the passive evolution of their stellar populations. Two of the ASK classes (1 and 4) gather edge-on spirals, a property of interest in studies requiring knowing the intrinsic shape of a galaxy (e.g., weak lensing calibration).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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