Fan Zhou; Huang Yafang; Li Jinzeng; Zhou Xu; Ma Jun; Wu Hong; Zhang Tianmeng; Zhao Yongheng
Source Publicationresearchinastronomyandastrophysics
AbstractWe present spectroscopic observations for 11 confirmed globular clusters (GCs) of M31 with the OMR spectrograph on the 2.16m telescope at the Xinglong site of National Astronomical Observatories, Chinese Academy of Sciences. Nine of our sample clusters are located in the halo of M31 and the most remote one is out to a projected radius of 78.75 kpc from the galactic center. For all our sample clusters, we measured the Lick absorption-line indices and radial velocities. It is noted that most GCs in our sample are distinct from the HI rotation curve of galaxy M31, especially for B514, MCGC5, H12 and B517, suggesting that most of our sample clusters do not have a kinematic association with the star-forming young disk of the galaxy. We separately fitted the absorption line indices from the updated stellar population model of Thomas et al. with two different tracks of Cassisi and Padova, by applying the x2-minimization method. The fitting results show that all our sample clusters are older than 10 Gyr, and metal-poor (-2.38 ≤ Fe/H ≤ -0.91 dex). After merging the spectroscopic metallicity of our work with the previously published ones, we extended the cluster sample out to a projected radius of 117 kpc from the galaxy's center. We found the metallicity gradient exists for all the confirmed clusters with a slope of -0.028 ± 0.001 dex kpc-1. However, the slope turns out to be -0.018 ± 0.001 dex kpc-1 for all the halo clusters, which is much shallower. If we only consider the outer halo clusters with r_p > 25 kpc, the slope becomes -0.010 ± 0.002 dex kpc-1 and if one cluster G001 is excluded from the outer halo sample, the slope is -0.004 ± 0.002 dex kpc-1. Thus, we conclude that the metallicity gradient for M31's outer halo clusters is not significant, which agrees well with previous findings.
Document Type期刊论文
First Author AffilicationNational Astronomical Observatories, Chinese Academy of Sciences
Recommended Citation
GB/T 7714
Fan Zhou,Huang Yafang,Li Jinzeng,et al. spectroscopicstudyofglobularclustersinthehaloofm31withthexinglong216mtelescope[J]. researchinastronomyandastrophysics,2011,11(11):1298.
APA Fan Zhou.,Huang Yafang.,Li Jinzeng.,Zhou Xu.,Ma Jun.,...&Zhao Yongheng.(2011).spectroscopicstudyofglobularclustersinthehaloofm31withthexinglong216mtelescope.researchinastronomyandastrophysics,11(11),1298.
MLA Fan Zhou,et al."spectroscopicstudyofglobularclustersinthehaloofm31withthexinglong216mtelescope".researchinastronomyandastrophysics 11.11(2011):1298.
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