Radial variations in the stellar initial mass function of early-type galaxies

被引:160
作者
Martin-Navarro, Ignacio [1 ,2 ]
La Barbera, Francesco [3 ]
Vazdekis, Alexandre [1 ,2 ]
Falcon-Barroso, Jesus [1 ,2 ]
Ferreras, Ignacio [4 ]
机构
[1] Inst Astrofis Canarias, E-38200 Tenerife, Spain
[2] Univ La Laguna, Dept Astrofis, E-38205 Tenerife, Spain
[3] INAF Osservatorio Astron Capodimonte, Naples, Italy
[4] Univ Coll London, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England
关键词
galaxies: elliptical and lenticular; cD; galaxies: evolution; galaxies: formation; galaxies: fundamental parameters; INFRARED CAII TRIPLET; POPULATION SYNTHESIS MODELS; ABSORPTION-LINE SPECTRA; ELLIPTIC GALAXIES; EMPIRICAL CALIBRATION; SYSTEMATIC VARIATION; LENTICULAR GALAXIES; ABUNDANCE RATIOS; DARK-MATTER; STARS;
D O I
10.1093/mnras/stu2480
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The hypothesis of a universal initialmass 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 (similar to 300 km s(-1)), and one lower mass system, with sigma similar to 100 km s(-1). 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 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.
引用
收藏
页码:1033 / 1048
页数:16
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