Radial variations in the stellar initial mass function of early-type galaxies
Radial variations in the stellar initial mass function of early-type galaxies
复制标题
DOI：
10.1093/mnras/stu2480
复制
发表时间：
2014-04
影响因子：
4.8
通讯作者：
I. Mart'in-Navarro;F. L. Barbera;A. Vazdekis;J. Falc'on-Barroso;I. Ferreras
中科院分区：
文献类型：
--
作者：
I. Mart'in-Navarro;F. L. Barbera;A. Vazdekis;J. Falc'on-Barroso;I. Ferreras
一个普遍的初始质量函数（IMF）的假设-在附近的恒星系统的观测的动机-最近受到了挑战的发现的IMF的系统变化的中心速度色散，{\sigma}，早期型星系（ETGs），对高-{\sigma}星系的低质量恒星过剩。到目前为止，这种趋势是从综合光谱中推导出来的，目前仍然无法解释。为了测试这种趋势是否取决于星系内的局部性质，我们获得了新的，非常深的光谱数据，三个附近的ETG，两个星系与高{\sigma}（~300 km/s），和一个较低的质量系统，{\sigma} ~ 100 km/s。从IMF敏感的光谱特征的分析，我们发现，IMF依赖于银河系中心的距离显着的大规模ETG，与增强的小质量恒星的分数f主要局限于其中心区域。相比之下，低-{\sigma}星系没有显示出任何显着的径向梯度在IMF中，以及由一个较浅的分布，相对于大质量星系的最里面的区域，在所有半径。这样的结果表明，IMF应被视为一个本地（而不是全球）的财产，并提出了一个显着的差异的核心和外部区域的大规模ETG的形成过程。
The hypothesis of a universal initial mass function (IMF) -- motivated by observations in nearby stellar systems -- has been recently challenged by the discovery of a systematic variation of the IMF with the central velocity dispersion, {\sigma}, of early-type galaxies (ETGs), towards an excess of low-mass stars in high-{\sigma} galaxies. This trend has been derived so far from integrated spectra, and remains unexplained at present. To test whether such trend depends on the local properties within a galaxy, we have obtained new, extremely deep, spectroscopic data, for three nearby ETGs, two galaxies with high {\sigma} (~300 km/s), and one lower mass system, with {\sigma} ~ 100 km/s. From the analysis of IMF-sensitive spectral features, we find that the IMF depends significantly on galactocentric distance in the massive ETGs, with the enhanced fraction of low-mass stars f mostly confined to their central regions. In contrast, the low-{\sigma} galaxy does not show any significant radial gradient in the IMF, well described by a shallower distribution, relative to the innermost regions of massive galaxies, at all radii. Such a result indicates that the IMF should be regarded as a local (rather than global) property, and suggests a significant difference between the formation process of the core and the outer regions of massive ETGs.