NEW CONSTRAINTS ON COSMIC REIONIZATION FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN
NEW CONSTRAINTS ON COSMIC REIONIZATION FROM THE 2012 HUBBLE ULTRA DEEP FIELD CAMPAIGN
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DOI：
10.1088/0004-637x/768/1/71
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发表时间：
2013-01
期刊：
影响因子：
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通讯作者：
B. Robertson;S. Furlanetto;E. Schneider;S. Charlot;R. Ellis;D. Stark;R. McLure;J. Dunlop;A. Koek
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文献类型：
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作者：
B. Robertson;S. Furlanetto;E. Schneider;S. Charlot;R. Ellis;D. Stark;R. McLure;J. Dunlop;A. Koek
理解宇宙再电离需要识别和表征氢电离光子的早期来源。2012年哈勃超深场（UDF12）活动利用哈勃太空望远镜上的宽视场相机3获得了最深的红外图像，并首次系统地探索了宇宙微波背景（CMB）数据表明再电离正在进行的时代的星系群。因此，UDF12活动提供了迄今为止关于早期恒星形成星系的丰度、光度分布和光谱特性的最佳约束。我们将新的UDF12结果与CMB观测的最新约束综合起来，推断出与红移相关的紫外（UV）亮度密度、再电离历史和与现有数据一致的电子散射光学深度演化。在对氢电离光子的逃逸分数和星系间介质聚集因子的合理假设下，我们发现，为了通过红移z ~ 6使宇宙完全再电离，在红移z ~ 7 ~ 9处形成恒星的星系群的光度可能必须低于UDF12极限，达到MUV ~−13或更弱的绝对紫外星等。此外，低水平的恒星形成延伸到红移z ~ 15-25，正如z≃7-8星系的正常紫外颜色和UDF12观测到的红移丰度平滑下降到z≃10所表明的那样，也可能需要重现从CMB观测推断的光学深度到电子散射。
Understanding cosmic reionization requires the identification and characterization of early sources of hydrogen-ionizing photons. The 2012 Hubble Ultra Deep Field (UDF12) campaign has acquired the deepest infrared images with the Wide Field Camera 3 aboard Hubble Space Telescope and, for the first time, systematically explored the galaxy population deep into the era when cosmic microwave background (CMB) data indicate reionization was underway. The UDF12 campaign thus provides the best constraints to date on the abundance, luminosity distribution, and spectral properties of early star-forming galaxies. We synthesize the new UDF12 results with the most recent constraints from CMB observations to infer redshift-dependent ultraviolet (UV) luminosity densities, reionization histories, and electron scattering optical depth evolution consistent with the available data. Under reasonable assumptions about the escape fraction of hydrogen-ionizing photons and the intergalactic medium clumping factor, we find that to fully reionize the universe by redshift z ∼ 6 the population of star-forming galaxies at redshifts z ∼ 7–9 likely must extend in luminosity below the UDF12 limits to absolute UV magnitudes of MUV ∼ −13 or fainter. Moreover, low levels of star formation extending to redshifts z ∼ 15–25, as suggested by the normal UV colors of z ≃ 7–8 galaxies and the smooth decline in abundance with redshift observed by UDF12 to z ≃ 10, are additionally likely required to reproduce the optical depth to electron scattering inferred from CMB observations.