Panoramic Hα and mid‐infrared mapping of star formation in a z = 0.8 cluster
Panoramic Hα and mid‐infrared mapping of star formation in a z = 0.8 cluster
复制标题
DOI：
10.1111/j.1365-2966.2009.16226.x
复制
发表时间：
2009-12
影响因子：
4.8
通讯作者：
Y. Koyama;T. Kodama;K. Shimasaku;M. Hayashi;S. Okamura;I. Tanaka;C. Tokoku
中科院分区：
文献类型：
--
作者：
Y. Koyama;T. Kodama;K. Shimasaku;M. Hayashi;S. Okamura;I. Tanaka;C. Tokoku
利用MOIRCS/Subaru卫星上的窄带滤光片，首次对遥远的星团RXJ 1716.4+6708（z = 0.81）进行了宽视场Hα成像观测，揭示了该星团的星星形成活动，其星星形成速率（SFR）为10.1 M·yr-1，无需消光校正。结合AKARI卫星的宽视场中红外（MIR）成像调查，我们详细比较了星团中未遮蔽和遮蔽的星星形成活动。我们发现Hα发射星系和MIR星系都避开了星系团的中心区域，并且它们的空间分布非常相似。大多数Hα发射体显示蓝色，但我们发现一些Hα发射体在红色序列上。MIR星系倾向于系统性地比Hα发射体更红，这可能是由于大量的尘埃消光。有趣的是，红色Hα发射体和红色MIR星系（即尘埃红色星系）最常见于中等密度的环境中，如星系团的外围，星系团和星系丝，这些星系的光学颜色会发生变化。通过计算SFR（IR）/SFR（Hα），我们研究了隐藏的星星形成量，发现在极端情况下，对于SFR（IR）为20 M·yr-1的活跃恒星形成星系，A Hα超过103。值得注意的是，大多数具有AH α <$3的尘埃星系也位于中密度环境中。这些发现表明，尘埃星星的形成是在星团的陷落区触发的，这意味着星系过渡和尘埃星星形成之间可能存在联系。最后计算了星系团的总SFR，发现即使经过1等消光校正，仅基于Hα的星系团总SFR仍可能被低估102倍以上。我们认为，质量归一化的集群SFR迅速下降，因为z <$1以下<$（1 + z）6，虽然不确定性仍然很大。
We present the first wide-field Hα imaging survey around the distant cluster RXJ 1716.4+6708 at z = 0.81 with a narrow-band filter on MOIRCS/Subaru, which reveals the star formation activities down to a star formation rate (SFR) of ∼1 M ⊙ yr -1 without extinction correction. Combining with a wide-field mid-infrared (MIR) imaging survey with the AKARI satellite, we compare in detail the unobscured and obscured star formation activities in the cluster. We find that both Hα emitters and MIR galaxies avoid the cluster central region and their spatial distribution is quite similar. Most of the Hα emitters show blue colours, but we find some Hα emitters on the red sequence. The MIR galaxies tend to be systematically redder than the Hα emitters probably due to heavy dust extinction. Interestingly, the red Hα emitters and the red MIR galaxies (i.e. dusty red galaxies) are most commonly seen in the medium-density environment such as cluster outskirts, groups and filaments, where optical colours of galaxies change. We investigate the amount of hidden star formation by calculating a ratio, SFR(IR)/SFR(Hα), and find that A Hα exceeds ∼3 in extreme cases for actively star-forming galaxies with SFR(IR) ≳20 M ⊙ yr -1 . It is notable that most of such very dusty galaxies with A Hα ≳ 3 are also located in the medium-density environment. These findings suggest that dusty star formation is triggered in the infall region of the cluster, implying a probable link between galaxy transition and dusty star formation. We finally calculate the cluster total SFR and find that the cluster total SFR based on Hα alone can be underestimated more than a factor of ∼2 even after 1-mag extinction correction. We suggest that the mass-normalized cluster SFR rapidly declines since z ∼ 1 following ∝ (1 + z) 6 , although the uncertainty is still large.