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Age Determination of Elliptical Galaxies using H γ Profile

使用 H γ 剖面确定椭圆星系的年龄

基本信息

批准号：
13640230
负责人：
ARIMOTO Nobuo
金额：
$ 2.56万
依托单位：
National Astronomical Observatory
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

This research aimed to reveal the formation epoch of elliptical galaxies by measuring their spectroscopic ages. We have taken spectra of 27 elliptical galaxies (13 in the field and group of galaxies and 14 in the Virgo cluster of galaxies) of extremely high quality with Subaru (NAOJ), WTT(Spain, UK) and NTT(ESO) telescopes and have measured their ages and chemical abundances by using the Hg profile method, which we have developed by ourselves. The Hg profile method is a quite efficient approach to disentangle age and metallicity effects in galaxy spectra and has been appreciated a lot since it was proposed by Vazdekis & Arimoto (1999). This study is the first one that applies the Hg profile method to a significantly large number of galaxy samples. In this study, we have made it clear how the ages and metallicities of elliptical galaxies depend on galaxy mass, luminosity, and the environment. The spatial distribution of age and metallicity within a galaxy has also been studied. Our resu … More lts show that 1)massive elliptical galaxies in cluster environment are uniformly old (<10 Gyrs), while those in the field show a scatter in ages spanning from 6 Gyrs to 10 Gyrs old. This indicates that some of filed ellipticals had experienced long lasting star formation until rather recently. 2)Dwarf elliptical galaxies show wide scatter in their ages, from 3 Gyrs to 10 Gyrs old, independent of where they locate. This suggests a rather complicated history of star formation in contrast to what has been thought previously. 3)Mg/Fe ratio of elliptical galaxies shows strong correlation with galaxy mass,; ie., moremassive galaxies tend to have smaller Mg/Fe ratio, suggesting shorter star formation period in more massive elliptical galaxies. 4) In a dwarf elliptical M32 (a companion galaxy of M31 spiral galaxy), the stellar age decreases towards galaxy centre and Mg/Fe ratio too. This is a strong evidence for a long lasting star formation at the galaxy center due to perhaps dissipative gas infall.In summary we could say that although it is true that formation of elliptical galaxies shows wide variety (in particular among dwarf ellipticals) more massive galaxies formed earlier in the dense cluster environment. Less

本研究旨在通过测量椭圆星系的光谱年龄来揭示其形成时代。我们用Subaru（NAOJ）、WTT（西班牙、英国）和NTT（ESO）望远镜拍摄了27个椭圆星系（13个在视场和星系群中，14个在室女座星系团中）的极高质量的光谱，并用我们自己开发的Hg剖面法测量了它们的年龄和化学丰度。Hg剖面法是解决星系光谱中年龄和金属丰度效应的一种有效方法，自Vazdekis & Arimoto（1999）提出以来，一直受到人们的重视。这项研究是第一个适用于汞配置文件的方法，以显着大量的星系样本。在这项研究中，我们清楚地表明了椭圆星系的年龄和金属丰度如何取决于星系质量，光度和环境。还研究了星系内年龄和金属丰度的空间分布。我们的成果 ...更多信息结果表明：（1）星系团环境中的大质量椭圆星系年龄一致（<10 Gyrs），而野外环境中的大质量椭圆星系年龄分散在6 Gyrs到10 Gyrs之间。这表明，一些椭圆星系经历了长期的星星形成，直到最近。2)矮椭圆星系的年龄分布很广，从3到10年不等，与它们所处的位置无关。这表明星星形成的历史相当复杂，与以前的想法相反。3）椭圆星系的Mg/Fe比值与星系质量有很强的相关性，即质量越大的星系Mg/Fe比值越小，说明质量越大的椭圆星系的星星形成周期越短。4)在一个矮椭圆星系M32（M31旋涡星系的伴星系）中，恒星年龄也向星系中心和Mg/Fe比方向递减。这是一个强有力的证据，说明星系中心的星星的形成可能是由于耗散的气体进入。总之，我们可以说，虽然椭圆星系的形成确实表现出广泛的多样性（特别是在矮椭圆星系中），但更大质量的星系在致密星系团环境中形成得更早。少