arXiv 0804.18212008-04-17astro-ph

SDSS中Wolf-Rayet Galerkin的聚类性质

Clustering Property of Wolf-Rayet Galaxies in the SDSS

Wei Zhang, Xu Kong, Fu-Zhen Cheng

备注：: 8 pages, 5figures
发表信息：: Chin.J.Astron.Astrophys.8:211,2008
DOI：: 10.1088/1009-9271/8/2/08

摘要：

利用SDSS第四版数据（DR 4）中选取的846个W-R星系的大样本，首次分析了W-R星系的成团性质。我们计算了W-R星系和从DR 4中提取的参考星系样本之间的交叉关联函数。我们比较的功能，控制样本的非W-R恒星形成的星系，在红移，光度，浓度，4000- 1000-break强度和特定的恒星形成率（SSFR）密切匹配的结果。在大于几个Mpc的尺度上，W-R星系与对照样本具有几乎相同的成团幅度，这表明W-R星系和非W-R对照星系填充了质量相似的暗物质晕。在0.1--1 $h^{-1}$ Mpc的尺度上，W-R星系比对照样本的聚集度要小，差异的大小取决于SSFR。基于观测和理论的考虑，我们推测，这种负偏差可以解释为W-R星系优先居住在其暗物质晕的中心。我们使用Yang等人的SDSS星系群星表更仔细地研究了W-R星系的分布，发现$\sim$ 82%的W-R星系是星系团的中心星系，而相应的控制星系的中心星系则为$\sim$ 74%。我们发现，W-R星系的主机，平均而言，由质量为$10^{12.3}M_\odot$的暗物质晕，相比之下，$10^{12.1}M_\odot$位于中心的W-R星系和$10^{12.7}M_\odot$卫星的。我们想指出的是，这一发现为我们的猜想提供了直接的观测支持，但由于W-R星系的数量很少和群星表的不完整性，这一发现确实非常粗略，需要在未来更大样本的情况下进行更多的工作。

英文摘要：

We have analysed, for the first time, the clustering properties of Wolf-Rayet (W-R) galaxies, using a large sample of 846 W-R galaxies selected from the Data Release 4 (DR4) of the SDSS. We compute the cross-correlation function between W-R galaxies and a reference sample of galaxies drawn from the DR4. We compare the function to the results for control samples of non-W-R star-forming galaxies that are matched closely in redshift, luminosity, concentration, 4000-Åbreak strength and specific star formation rate (SSFR). On scales larger than a few Mpc, W-R galaxies have almost the same clustering amplitude as the control samples, indicating that W-R galaxies and non-W-R control galaxies populate dark matter haloes of similar masses. On scales between 0.1--1$h^{-1}$ Mpc, W-R galaxies are less clustered than the control samples, and the size of the difference depends on the SSFR. Based on both observational and theoretical considerations, we speculate that this negative bias can be interpreted by W-R galaxies residing preferentially at the centers of their dark matter haloes. We examine the distribution of W-R galaxies more closely using the SDSS galaxy group catalogue of Yang et al., and find that $\sim$82% of our W-R galaxies are the central galaxies of groups, compared to $\sim$74% for the corresponding control galaxies. We find that W-R galaxies are hosted, on average, by dark matter haloes of masses of$10^{12.3}M_\odot$, compared to $10^{12.1}M_\odot$ for centrally-located W-R galaxies and $10^{12.7}M_\odot$ for satellite ones. We would like to point out that this finding, which provides a direct observational support to our conjecture, is really very crude due to the small number of W-R galaxies and the incompleteness of the group catalogue, and needs more work in future with larger samples.

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