A Panoramic Mid-Infrared Survey of Two Distant Clusters
A Panoramic Mid-Infrared Survey of Two Distant Clusters
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DOI：
10.1086/506469
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发表时间：
2006-06
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影响因子：
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通讯作者：
J. Geach;I. Smail;R. Ellis;S. Moran;G. Smith;T. Treu;J. Kneib;A. Edge;T. Kodama
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文献类型：
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作者：
J. Geach;I. Smail;R. Ellis;S. Moran;G. Smith;T. Treu;J. Kneib;A. Edge;T. Kodama
在z = 0.39和z = 0.55的波段，我们对两个大质量星团Cl 0024+16和MS 0451-03周围的~9 × 9 Mpc2 （25 ‘ × 25 ’）场进行了全景Spitzer MIPS 24 μm观测，达到了~200 μJy的5 σ通量极限。我们的观察涵盖了这些星团内非常广泛的环境，从核心周围的高密度区域到周转半径。我们将中红外星表与这些场的深光学和近红外成像相互关联，研究了中红外源的光学/近红外颜色。我们发现两个星团中过量的中红外源具有预期的光学/近红外颜色，并使用光谱确认的24 μm成员测试了这种选择。更显著的过剩与Cl 0024+16有关，而MS 0451-03的中红外源相对较少。Cl 0024+16中的中红外星系群似乎与形成恒星的尘埃星系（通常比一般星团群的颜色更红，最高可达AV ~ 1-2等）有关，而不是来自早期型宿主中活跃星系核周围的尘埃环面。我们比较了Cl 0024+16中红外源的总红外（8-1000 μm）光度得出的恒星形成率与发表的Hα调查估计的恒星形成率，发现恒星形成率约为Hα的5倍，表明星团群体中存在明显的模糊活动。与之前对z ~ 0-0.5的星团进行的中红外调查相比，我们发现了高密度环境中被尘埃遮蔽的恒星形成水平在z = 0.5的强烈演化的证据，类似于星团中光学选择的恒星形成星系的比例的上升，以及类似的红移。然而，在中红外源的种群中，明显存在显著的星团间差异，这可能反映了星团内介质的差异和这些系统最近的动态演化。
We present panoramic Spitzer MIPS 24 μm observations, covering ~9 × 9 Mpc2 (25′ × 25′) fields around two massive clusters, Cl 0024+16 and MS 0451-03, at z = 0.39 and z = 0.55, respectively, reaching a 5 σ flux limit of ~200 μJy. Our observations cover a very wide range of environments within these clusters, from high-density regions around the cores out to the turnaround radius. Cross-correlating the mid-infrared catalogs with deep optical and near-infrared imaging of these fields, we investigate the optical/near-infrared colors of the mid-infrared sources. We find excesses of mid-infrared sources with the optical/near-infrared colors expected of cluster members in the two clusters and test this selection using spectroscopically confirmed 24 μm members. The much more significant excess is associated with Cl 0024+16, whereas MS 0451-03 has comparatively few mid-infrared sources. The mid-infrared galaxy population in Cl 0024+16 appears to be associated with dusty star-forming galaxies (typically redder than the general cluster population by up to AV ~ 1-2 mag) rather than emission from dusty tori around active galactic nuclei in early-type hosts. We compare the star formation rates derived from the total infrared (8-1000 μm) luminosities for the mid-infrared sources in Cl 0024+16 with those estimated from a published Hα survey, finding rates ≳5 times those found from Hα, indicating significant obscured activity in the cluster population. Compared to previous mid-infrared surveys of clusters from z ~ 0-0.5, we find evidence for strong evolution of the level of dust-obscured star formation in dense environments to z = 0.5, analogous to the rise in the fraction of optically selected star-forming galaxies seen in clusters and the field out to similar redshifts. However, there are clearly significant cluster-to-cluster variations in the populations of mid-infrared sources, probably reflecting differences in the intracluster media and recent dynamical evolution of these systems.