Properties of star-forming galaxies in a cluster and its surrounding structure at z=1.46
Properties of star-forming galaxies in a cluster and its surrounding structure at z=1.46
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DOI：
10.1111/j.1365-2966.2011.18892.x
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发表时间：
2011-04
影响因子：
4.8
通讯作者：
M. Hayashi;T. Kodama;Y. Koyama;K. Tadaki;I. Tanaka
中科院分区：
文献类型：
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作者：
M. Hayashi;T. Kodama;Y. Koyama;K. Tadaki;I. Tanaka
我们使用Subaru/ prime- cam对XMMXCS J2215.9−1738星团内及其周围的[O ii]发射体进行了宽视场窄带成像调查，其z= 1.46。在32 × 23 arcmin2的区域，我们选择了380个[O ii]发射的星系，最小辐射值为1.4 × 10−17 erg s−1 cm−2。其中，星团中心区域有16个[O ii]发射体被Subaru/MOIRCS近红外光谱确认，表明我们的光度选择对于z= 1.46的样品[O ii]发射体是有效的。我们发现[O ii]发射体分布在星团周围的丝状大尺度结构上，这是迄今为止发现的最大的恒星形成星系结构之一，在1.3 > z > 3.0。为了研究z= 1.46时恒星形成星系的环境依赖性，我们定义了星团核心、外围、灯丝和场等几种环境。[O ii]发射星系的z′−K与K的色等图表明，在星团核心中，具有红色z′−K颜色的[O ii]发射体的比例明显高于在其他环境中。看起来，承载这些形成红色恒星的星系的环境从z= 1.46的核心区域转移到红移较低的星团外围。对红色发射体的多色分析表明，这些星系更像是被动演化的星系，它们拥有发射活动星系核（agn）的[O ii]，而不是尘埃变红的恒星形成[O ii]发射体。因此，我们认为AGN反馈可能是在高密度区域的大质量星系中淬灭恒星形成的关键过程之一。星团核心[O ii]发射体的[O iii]/Hβ和[N ii]/Hα的发射谱线比值支持AGN对发射体的适度贡献的推断。我们还发现，与低红移星团相比，在z= 1.46时，星团经历了高的恒星形成活动，其速率与现场相当，并且星团中的恒星形成活动平均随着红移z= 1.46而增加。此外，[N ii]/Hα和[O iii]/Hβ的谱线比值表明，星团在z= 1.46处存在质量-金属丰度关系，这与z ~ 2处的恒星形成星系相似。这些结果都表明，在z ~ 1.5时，星团核心的恒星形成活动与低密度环境中的恒星形成活动一样高，并且除了红色发射器外，显然还没有很强的环境依赖性。
We conduct a wide-field narrow-band imaging survey of [O ii] emitters in and around the XMMXCS J2215.9−1738 cluster at z= 1.46 with Subaru/Suprime-Cam. In a 32 × 23 arcmin2 area, we select 380 [O ii] emitting galaxies down to 1.4 × 10−17 erg s−1 cm−2. Among them, 16 [O ii] emitters in the central region of the cluster are confirmed by near-infrared spectroscopy with Subaru/MOIRCS, suggesting that our photometric selection is valid for sample [O ii] emitters at z= 1.46. We find that [O ii] emitters are distributed along filamentary large-scale structures around the cluster, which are among the largest structures of star-forming galaxies ever identified at 1.3 ≲z≲ 3.0. We define several environments such as cluster core, outskirts, filament and field in order to investigate the environment dependence of star-forming galaxies at z= 1.46. The colour–magnitude diagram of z′−K versus K for the [O ii] emitting galaxies shows that a significantly higher fraction of [O ii] emitters with red z′−K colours is seen in the cluster core than in other environments. It seems that the environment that hosts such red star-forming galaxies shifts from the core region at z= 1.46 to the outskirts of clusters at lower redshifts. A multicolour analysis of the red emitters indicates that these galaxies are more like nearly passively evolving galaxies which host [O ii] emitting active galactic nuclei (AGNs), rather than dust-reddened star-forming [O ii] emitters. We argue therefore that AGN feedback may be one of the critical processes to quench star formation in massive galaxies in high-density regions. The emission line ratios of [O iii]/Hβ and [N ii]/Hα of the [O ii] emitters in the cluster core support the inference that there is a moderate contribution of AGN to the emitters. We also find that the cluster has experienced high star formation activities at rates comparable to that in the field at z= 1.46 in contrast to lower redshift clusters, and that star formation activity in galaxy clusters on average increases with redshift up to z= 1.46. In addition, line ratios of [N ii]/Hα and [O iii]/Hβ indicate that a mass–metallicity relation exists in the cluster at z= 1.46, which is similar to that of star-forming galaxies in the field at z∼ 2. These results all suggest that at z∼ 1.5 star formation activity in the cluster core becomes as high as those in low-density environments and that there is apparently not yet a strong environmental dependence, except for the red emitters.