用Herschel/PEP剖析宇宙红外背景
Dissecting the cosmic infra-red background with Herschel/PEP
摘要：
利用Herschel/PACS演化探测器（PEP）的GOODS-N、Lockman Hole和COSMOS场的观测资料，在峰值波长（100和160 μ m）处研究了宇宙红外背景（CIB）的组成。GOODS-N数据达到3 σ深度，在100 μ m处为~3.0 mJy，在160 μ m处为~5.7 mJy。在这些水平上，源密度分别为40和18束/源，从而达到160 μ m的混淆极限。微分数计数从几mJy扩展到100-200 mJy，并且近似为双幂律，其中中断位于5和10 mJy之间。可用的辅助信息使我们能够将计数分解到红移箱中。在z<=0.5时，我们分离出一类发光源（L（IR）~ 1 e11 Lsun），其SED类似于晚期螺旋星系，峰值在~130 um restframe，并且比基于前Herschel模型所预期的要冷得多。通过对整个覆盖通量范围内的计数进行积分，我们得到了100和160 μ m处的表面亮度分别为6.36 +/- 1.67和6.58 +/-1.62 [nW m^-2 sr^-1]，分别为CIB的45%和52%。当叠加24 μ m源时，两个谱带的CIB分别位于1.1 σ和0.5 σ之间，CIB分量增加到50%和75%，其中大部分CIB分量是在z<=1.0处辐射的，160 μ m源的红移比100 μ m源的红移高。
英文摘要：
The constituents of the cosmic IR background (CIB) are studied at its peak wavelengths (100 and 160 um) by exploiting Herschel/PACS observations of the GOODS-N, Lockman Hole, and COSMOS fields in the PACS Evolutionary Probe (PEP) guaranteed-time survey. The GOODS-N data reach 3 sigma depths of ~3.0 mJy at 100 um and ~5.7 mJy at 160 um. At these levels, source densities are 40 and 18 beams/source, respectively, thus hitting the confusion limit at 160 um. Differential number counts extend from a few mJy up to 100-200 mJy, and are approximated as a double power law, with the break lying between 5 and 10 mJy. The available ancillary information allows us to split number counts into redshift bins. At z<=0.5 we isolate a class of luminous sources (L(IR)~1e11 Lsun), whose SEDs resemble late-spiral galaxies, peaking at ~130 um restframe and significantly colder than what is expected on the basis of pre-Herschel models. By integrating number counts over the whole covered flux range, we obtain a surface brightness of 6.36 +/- 1.67 and 6.58 +/-1.62 [nW m^-2 sr^-1] at 100 and 160 um, resolving ~45% and ~52% of the CIB, respectively. When stacking 24 um sources, the inferred CIB lies within 1.1 sigma and 0.5 sigma from direct measurements in the two bands, and fractions increase to 50% and 75%.Most of this resolved CIB fraction was radiated at z<=1.0, with 160 um sources found at higher redshift than 100 um ones.
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