Detection of a Far IR Excess with DIRBE at 60 and 100 Microns
Detection of a Far IR Excess with DIRBE at 60 and 100 Microns
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使用 DIRBE 在 60 和 100 微米处检测远红外过量
DOI：
10.1017/s0074180900225953
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
D. Schlegel
中科院分区：
文献类型：
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作者：
D. Finkbeiner;M. Davis;D. Schlegel
通过对 DIRBE 每周平均天空图的分析，我们检测到 60μm 和 100μm 通道中的大量通量超出了预期的黄道和银河发射。使用两种方法将黄道光与更远的发射分开。方法一利用在黄道观测到的南北年度变化的时间依赖性。该方法对于行星际尘埃 (IPD) 模型中的误差具有鲁棒性，但不能证明背景的各向同性。方法 II 测量太阳距角 e = 90° 时尘埃在黄道纬度范围 (|β| > 35°) 上的黄道纬度依赖性。这允许在 DIRBE 任务的每周中确定超额，以实现高冗余，但结果对 IPD 模型的依赖程度较弱。两种方法在 60μm 和 100μm 处给出一致的结果。观察到的信号与 60μm 处的 νIν = 28.1± 1.8± 7(syst) nW m−2sr−1 水平和 100μm 处的 24.6± 2.5± 8 nW m−2sr−1 水平处的各向同性背景一致。通过这些方法在 140 和 240μm 处检测到的红外过量与之前的测量结果一致，这被认为是宇宙红外背景（CIB）。 60 和 100μm 的检测是新的。 45−125μm 窗口中的积分 IR 过量为 23±8 nW m−2sr−1，将添加到先前使用 DIRBE 和 FIRAS 仪器在 125 − 2 mm 窗口中测量的 18±4 nW m−2sr−1 中。虽然这种新的过剩不一定是 CIB，但我们已经排除了太阳系和银河系中所有已知的排放源。因此，我们暂时将这个信号解释为 CIB，并从恒星形成效率和黑洞吸积效率的角度考虑这种能量产生的影响。然而，IR 超出了 CIB 的限制，这是由 IGM 对观测到的 TeV 光子的不透明度推断得出的，因此对这种解释产生了怀疑。目前对于 60 – 100μm 的过量还没有令人满意的解释。
From analysis of the DIRBE weekly averaged sky maps, we have detected substantial flux in the 60μm and 100μm channels in excess of expected zodiacal and Galactic emission. Two methods are used to separate zodiacal light from more distant emission. Method I makes use of the time-dependence of the North-South annual variation observed at the ecliptic poles. This method is robust against errors in the inter-planetary dust (IPD) model, but does not demonstrate isotropy of the background. Method II measures the ecliptic latitude dependence of the dust over a range of ecliptic latitudes (|β| > 35◦) at solar elongation e = 90◦. This allows the excess to be determined in each week of the DIRBE mission for high redundancy, but the results depend weakly on the IPD model. Both methods give consistent results at 60μm and 100μm. The observed signal is consistent with an isotropic background at the level νIν = 28.1± 1.8± 7(syst) nW m−2sr−1 at 60μm and 24.6± 2.5± 8 nW m−2sr−1 at 100μm. The IR excess detected at 140 and 240μm by these methods agrees with previous measurements, which are thought to be the cosmic infra-red background (CIB). The detections at 60 and 100μm are new. The integrated IR excess in the window 45−125μm is 23±8 nW m−2sr−1, to be added to the 18±4 nW m−2sr−1 previously measured with the DIRBE and FIRAS instruments in the window 125 − 2 mm. While this new excess is not necessarily the CIB, we have ruled out all known sources of emission in the solar system and Galaxy. We therefore tentatively interpret this signal as the CIB and consider the implications of such energy production from the viewpoint of star formation efficiency and black hole accretion efficiency. However, the IR excess exceeds limits on the CIB derived from the inferred opacity of the IGM to observed TeV photons, thus casting doubt on this interpretation. There is currently no satisfactory explanation for the 60 − 100μm excess.