Metal abundance and kinematical properties of the M81 globular cluster system  

作　　者：Jun Ma Zhen-Yu Wu Tian-Meng Zhang Song Wang Zhou Fan Jiang-Hua Wu Hu Zou Cui-Hua Du Xu Zhou Qi-Rong Yuan 

机构地区：[1]National Astronomical Observatories,Chinese Academy of Sciences [2]Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences [3]Graduate University of Chinese Academy of Sciences [4]Department of Astronomy,Beijing Normal University [5]College of Physical Sciences,Graduate University of Chinese Academy of Sciences [6]Department of Physics,Nanjing Normal University

出　　处：《Research in Astronomy and Astrophysics》2013年第4期399-410,共12页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 10873016, 10633020, 10803007,11003021, 11173016 and 11073032);the National Basic Research Program of China (973 Program, 2007CB815403)

摘　　要：We present metal abundance properties of 144 globular clusters associated with M81. These globulars represent the largest globular cluster sample in M81 till now. Our main results are： the distribution of metallicities is bimodal, with metallicity peaks at [Fe/H] -1.51 and -0.58, and the metal-poor globular clusters tend to be less spatially concentrated than the metal-rich ones; the metal-rich globular clusters in M81 do not demonstrate a centrally concentrated spatial distribution like the metalrich ones in M31 do; like our Galaxy and M31, the globular clusters in M81 have a small radial metallicity gradient. These results are consistent with those obtained from a small sample of M81 globular clusters. In addition, this paper shows that there is evidence that a strong rotation of the M81 globular cluster system around the minor axis exists, and that rotation is present in the metal-rich globular cluster subsample, but the metal-poor globular cluster subsample shows no evidence of rotation. The most significant difference between the rotation of the metal-rich and metal-poor globular clusters occurs at intermediate projected galactocentric radii. Our results confirm the conclusion of Schroder et al. that M81＇s metal-rich globular clusters at intermediate projected radii are associated with a thick disk of M81.We present metal abundance properties of 144 globular clusters associated with M81. These globulars represent the largest globular cluster sample in M81 till now. Our main results are： the distribution of metallicities is bimodal, with metallicity peaks at [Fe/H] -1.51 and -0.58, and the metal-poor globular clusters tend to be less spatially concentrated than the metal-rich ones; the metal-rich globular clusters in M81 do not demonstrate a centrally concentrated spatial distribution like the metalrich ones in M31 do; like our Galaxy and M31, the globular clusters in M81 have a small radial metallicity gradient. These results are consistent with those obtained from a small sample of M81 globular clusters. In addition, this paper shows that there is evidence that a strong rotation of the M81 globular cluster system around the minor axis exists, and that rotation is present in the metal-rich globular cluster subsample, but the metal-poor globular cluster subsample shows no evidence of rotation. The most significant difference between the rotation of the metal-rich and metal-poor globular clusters occurs at intermediate projected galactocentric radii. Our results confirm the conclusion of Schroder et al. that M81＇s metal-rich globular clusters at intermediate projected radii are associated with a thick disk of M81.

关 键 词：galaxies： individual （M81） -galaxies： star clusters globular clusters：general 

分 类 号：P154.1[天文地球—天文学]