arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1406.4149astro-ph.GAastro-ph.CO
收藏

0.3<z<0.9时最大质量星系的由内向外生长

The Inside-out Growth of the Most Massive Galaxies at 0.3<z<0.9

Lei Bai, H. K. C. Yee, Renbin Yan, Eve Lee, David G. Gilbank, E. Ellingson, L. F. Barrientos, M. D. Gladders, B. C. Hsieh, I. H. Li

摘要:

我们研究了0.3<z<0.9的最亮星系团(BCGs)样本的表面亮度轮廓。BCGs是从第一次红层序列星系团巡天和一次X射线星系团巡天中选取的。利用HST ACS图像测量了BCGs的表面亮度分布,其中大部分可以很好地用折射率约6和半光半径约30 kpc的Sersic分布来模拟。虽然单一的Sersic模型很好地拟合了廓线,但我们认为,天空背景测量的系统性和模型参数之间的耦合使得模型参数的比较模糊不清。另一方面,对BCG轮廓的直接比较揭示了这些质量最大的星系由内向外的增长:随着BCG质量的增加,星系的中心质量密度缓慢增加($ρ_{1kpc} \propto M*^{0.39}$),而外部轮廓的斜率不断变浅($α\propto M*^{-2.5}$)。这种增长方式一直延续到质量较小的早型星系(ETG),而BCGs和非BCGs之间没有明显的区别。对于非常大质量的ETG和BCG,Kormendy关系的斜率开始跟踪表面亮度轮廓的斜率,并变得不敏感的微妙的轮廓演变。这些结果与干合并是BCGs和大规模ETGs质量增长的主要驱动力基本一致。我们还发现,集团的丰富性和BCGs的性质之间的强相关性:更大的集团是,更大的BCGs($M*_{bcg} \propto M_{clusters}^{0.6}$)和浅的表面亮度轮廓。在考虑到集群样本中的偏差之后,我们发现BCG的质量从z=0.5到z=0至少增长了1.5倍,与之前没有进化的发现相反。这种演变验证了LCDM模型的预期。

英文摘要:

We study the surface brightness profiles of a sample of brightest cluster galaxies (BCGs) with 0.3<z<0.9. The BCGs are selected from the first Red-sequence Cluster Survey and an X-ray cluster survey. The surface brightness profiles of the BCGs are measured using HST ACS images, and most of them can be well modeled by a Sersic profile with index ~ 6 and half-light radius ~ 30 kpc. Although the single Sersic model fits the profiles well, we argue that the systematics in the sky background measurement and the coupling between the model parameters make the comparison of the model parameters ambiguous. Direct comparison of the BCG profiles, on the other hand, has revealed an inside-out growth for these most massive galaxies: as the mass of a BCG increases, the central mass density of the galaxy increases slowly ($ρ_{1kpc} \propto M*^{0.39}$), while the slope of the outer profile grows continuously shallower ($α\propto M*^{-2.5}$). Such a fashion of growth continues down to the less massive early-type galaxies (ETGs), without apparent distinction between BCGs and non-BCGs. For the very massive ETGs and BCGs, the slope of the Kormendy relation starts to trace the slope of the surface brightness profiles and becomes insensitive to subtle profile evolution. These results are generally consistent with dry mergers being the major driver of the mass growth for BCGs and massive ETGs. We also find strong correlations between the richness of clusters and the properties of BCGs: the more massive the clusters are, the more massive the BCGs ($M*_{bcg} \propto M_{clusters}^{0.6}$) and the shallower their surface brightness profiles. After taking into account the bias in the cluster samples, we find the masses of the BCGs have grown by at least a factor of 1.5 from z=0.5 to z=0, in contrast to the previous findings of no evolution. Such an evolution validates the expectation from the LCDM model.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑