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arXiv 1001.2476astro-ph.GA
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长持续时间伽马射线暴宿主星系的Wolf-Rayet特征和质量-金属丰度关系

The Wolf-Rayet features and mass-metallicity relation of long-duration gamma-ray burst host galaxies

X. H. Han, F. Hammer, Y. C. Liang, H. Flores, M. Rodrigues, J. L. Hou, J. Y. Wei

备注：
12 pages, 4 figures, A&A 514, A24 (2010)
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摘要：

目标。从VLT/FORS 2的存档数据中选取了8个长持续时间GRB宿主星系，收集了它们的光谱。我们调查是否沃尔夫-拉叶星（WR）可以在这些伽玛暴宿主星系检测。我们还试图估计伽玛暴宿主星系的物理性质，如金属丰度。方法.我们通过拟合WR凸点和WR发射线在蓝色和红色凸点中识别了这些光谱中的WR特征。我们还识别了WR星的子类型，并估算了每个子类型中的恒星数量，计算了WR/O星的比值。从电子温度（Te）和金属敏感强线比（R23）估算了γ射线暴宿主的（O/H）丰度，并打破了R23的简并性。我们比较了长持续时间伽玛暴宿主星系与其他星系的光度（恒星质量）-金属丰度关系（LZ，MZ）。结果我们在5个具有较高信噪比（S/N）光谱的GRB宿主星系中探测到WR星的存在。在LZ、MZ关系的比较中，发现伽玛暴寄主的金属丰度比光度和恒星质量相当的其他样品低。WR星的存在和观察到的高WR/O星比，以及低金属丰度，支持核心-恒星模型，并暗示在伽玛暴的宿主区域的第一阶段的恒星形成。

英文摘要：

Aims. We have gathered optical spectra of 8 long-duration GRB host galaxies selected from the archival data of VLT/FORS2. We investigated whether or not Wolf-Rayet (WR) stars can be detected in these GRB host galaxies. We also tried to estimate the physical properties of GRB host galaxies, such as metallicity. Methods. We identified the WR features in these spectra by fitting the WR bumps and WR emission lines in blue and red bumps. We also identified the subtypes of the WR stars, and estimated the numbers of stars in each subtype, then calculated the WR/O star ratios. The (O/H) abundances of GRB hosts were estimated from both the electron temperature (Te) and the metallicity-sensitive strong-line ratio (R23), for which we have broken the R23 degeneracy. We compared the environments of long-duration GRB host galaxies with those of other galaxies in terms of their luminosity (stellar mass)-metallicity relations (LZ, MZ). Results. We detected the presence of WR stars in 5 GRB host galaxies having spectra with relatively high signal-to-noise ratios (S/N). In the comparison of LZ, MZ relations, it shows that GRB hosts have lower metallicities than other samples with comparable luminosity and stellar mass. The presence of WR stars and the observed high WR/O star ratio, together with low metallicity, support the core-collapsar model and implie the first stage of star formation in the hosted regions of GRBs.

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