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arXiv 1502.02161astro-ph.SR
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球状星团NGC 6229和NGC 6779的化学丰度

Chemical Abundances in the Globular Clusters NGC 6229 and NGC 6779

Khamidullina D. A., Sharina M. E., Shimansky V. V., Davoust E

备注：
28 pages, 16 figures, 5 tables
发表信息：
2014AstBu..69..409K
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摘要：

用上普罗旺斯天文台1.93米望远镜的CARELEC摄谱仪获得的银河系球状星团NGC 6229和NGC 6779的长缝中等分辨率光谱，已被用来确定这些天体的年龄、氦丰度（Y）和金属丰度[Fe/H]，以及对C、N、O、Mg、Ca、Ti和Cr丰度的首次估计。我们解决了这个任务，通过比较观测光谱和综合合成光谱，计算与使用的恒星大气模型的参数预设的恒星从这些集群。通过比较观测到的“色星等”图和理论等时线，得到了模式质量估计值、$T_{\rm eff}$和log~g。根据Chabrier质量函数对合成的恒星光谱进行了总结。为了测试结果的准确性，我们估计的化学丰度，[Fe/H]，$\log~t$，和$Y$的NGC 5904和NGC 6254集群，根据文献，这被认为是最接近的类似物的两个GC我们的研究。使用Schiavon等人的库中的中等分辨率光谱，对于这两个聚类，我们获得了与所报道的误差内的所有参数的估计值的令人满意的一致性。我们得出了以下的聚类参数。NGC6229：[Fe/H]=-1.65 dex，t=12.6 Gyr，Y=0.26，[α/Fe]=0.28 dex; NGC6779：[Fe/H]=-1.9 dex，t=12.6 Gyr，Y=0.23，[α/Fe]=0.08 dex; NGC5904：[Fe/H]=-1.6 dex，t=12.6 Gyr，Y=0.30，[α/Fe]=0.35 dex; NGC6254：[Fe/H]=-1.52 dex，t=11.2 Gyr，Y=0.30 [α/Fe]=0.025 dex.值[α/Fe]表示Ca和Mg丰度的平均值。

英文摘要：

Long-slit medium-resolution spectra of the Galactic globular clusters (GCs) NGC6229 and NGC6779, obtained with the CARELEC spectrograph at the 1.93-m telescope of the Haute-Provence observatory, have been used to determine the age, helium abundance (Y), and metallicity [Fe/H] as well as the first estimate of the abundances of C, N, O, Mg, Ca, Ti, and Cr for these objects. We solved this task by comparing the observed spectra and the integrated synthetic spectra, calculated with the use of the stellar atmosphere models with the parameters preset for the stars from these clusters. The model mass estimates, $T_{\rm eff}$, and log~g were derived by comparing the observed "color-magnitude" diagrams and the theoretical isochrones. The summing-up of the synthetic blanketed stellar spectra was conducted according to the Chabrier mass function. To test the accuracy of the results, we estimated the chemical abundances, [Fe/H], $\log~t$, and $Y$ for the NGC5904 and NGC6254 clusters, which, according to the literature, are considered to be the closest analogues of the two GCs of our study. Using the medium-resolution spectra from the library of Schiavon et al., we obtained for these two clusters a satisfactory agreement with the reported estimates for all the parameters within the errors. We derived the following cluster parameters. NGC6229: [Fe/H]=-1.65 dex, t=12.6 Gyr, Y=0.26, [α/Fe]=0.28 dex; NGC6779: [Fe/H]=-1.9 dex, t=12.6 Gyr, Y=0.23, [α/Fe]=0.08 dex; NGC5904: [Fe/H]=-1.6 dex, t=12.6 Gyr, Y=0.30, [α/Fe]=0.35 dex; NGC6254: [Fe/H]=-1.52 dex, t=11.2 Gyr, Y=0.30 [α/Fe]=0.025 dex. The value [α/Fe] denotes the average of the Ca and Mg abundances.

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