The nature of H-alpha star-forming galaxies at z~0.4 in and around Cl 0939+4713: the environment matters
The nature of H-alpha star-forming galaxies at z~0.4 in and around Cl 0939+4713: the environment matters
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Cl 0939 4713 及其周围 z~0.4 处 H-α 恒星形成星系的性质：环境很重要
DOI：
10.1093/mnras/stw534
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发表时间：
2016
影响因子：
4.8
通讯作者：
Fumiaki Nakata
中科院分区：
文献类型：
--
作者：
David Sobral;Andra Stroe;Yusei Koyama;Behnam Darvish;Joao Calhau;Ana Afonso;Tadayuki Kodama;Fumiaki Nakata
星系团恒星形成星系相对于Hα有过量的远红外辐射，这可能是由于强烈的活动星系核活动、尘埃和/或恒星形成历史的下降造成的。在这里，我们用威廉·赫歇尔望远镜上的AF2+和WYFFOS对Cl0939+4713(Abell851)超星系团atz=100.41中的Hα发射体进行了光谱观测。我们测量了星系团及其周围119Hβ发射体的[OII]、Hα、[OIII]、Hα和[NiI]。我们发现，无论环境如何，17%±5%的H-α发射体是活动星系核。对于恒星形成星系，我们用不同的方法分别和叠加得到了Balmer衰减量、金属度和电离参数。我们发现在所有环境下都有很强的质量-金属丰度关系，与环境没有明显的依赖关系。对于低质量星系，电离参数随着恒星质量的增加而减小。驻留在中间环境中的Hα发射器显示出最高的电离参数(以及高[OIII]/Hα和高[OIII]/[Oii]线比，通常是最高和最低密度下的两倍)，随着环境密度的增加而下降。尘埃消光(AHα)不仅与恒星质量密切相关，而且与环境密度密切相关。最密集环境中的恒星形成星系(AHα≈1.5−1.6)比居住在最低密度环境中的恒星形成星系(AHα≈0.6)要暗得多，这与它们的恒星质量预测有很大偏离。
Cluster star-forming galaxies are found to have an excess of far-infrared emission relative to Hα, when compared to those in the field, which could be caused by intense active galactic nuclei (AGN) activity, dust and/or declining star formation histories. Here we present spectroscopic observations of Hα emitters in the Cl 0939+4713 (Abell 851) super-cluster atz= 0.41, using AF2+ WYFFOS on theWilliam Herschel Telescope. We measure [Oii], Hβ, [Oiii], Hα and [Nii] for a sample of 119 Hα emitters in and around the cluster. We find that 17 ± 5 per cent of the Hα emitters are AGN, irrespective of environment. For star-forming galaxies, we obtain Balmer decrements, metallicities and ionization parameters with different methods, individually and by stacking. We find a strong mass–metallicity relation at all environments, with no significant dependence on environment. The ionization parameter declines with increasing stellar mass for low-mass galaxies. Hα emitters residing in intermediate environments show the highest ionization parameters (along with high [Oiii]/Hα and high [Oiii]/[Oii] line ratios, typically twice as large as in the highest and lowest densities), which decline with increasing environmental density. Dust extinction (AHα) correlates strongly with stellar mass, but also with environmental density. Star-forming galaxies in the densest environments are found to be significantly dustier (AHα≈ 1.5 − 1.6) than those residing in the lowest density environments (AHα≈ 0.6), deviating significantly from what would be predicted given their stellar masses.