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arXiv 0705.3966astro-ph
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利用COBE/DIRBE和WHAM数据确定远红外宇宙背景

Determination of the Far-Infrared Cosmic Background Using COBE/DIRBE and WHAM Data

N. Odegard, R. G. Arendt, E. Dwek, L. M. Haffner, M. G. Hauser, R. J. Reynolds

摘要:

使用COBE/DIRBE数据确定远红外波长的宇宙红外背景(CIB)受限于前景行星际和银河系尘埃排放可以建模和减去的准确性。远红外CIB的先前确定(例如,Hauser等人,1998年)是基于对天空图中残余各向同性发射的检测,从中去除了行星际尘埃和中性星际介质的发射。在本文中,我们使用威斯康星州的H-α映射(WHAM)北方巡天作为电离介质的示踪剂检查的影响,这前景分量上确定的CIB。我们分解的DIRBE远红外数据为5个高银河系纬度地区的H I和H-α相关的组件和一个残余的组件。我们发现的H-α相关的组件是一致的,为零的每个区域,我们发现,除了一个H-α相关的组件在建模的前景发射派生CIB结果的影响可以忽略不计。我们的CIB检测和2 sigma上限基本上与Hauser等人推导的相同,分别由nu I_nu(nW m-2 sr-1)< 75,< 32,25 +- 8和13 +- 3给出,在60,100,140和240微米。我们的残差还没有进行详细的各向异性测试,所以我们的CIB结果不取代豪泽等人。我们得出的电离介质的100微米发射率的上限,通常约为40%的100微米发射率的中性原子介质。这个低的值可能部分地由电离介质中比中性介质中更低的灰尘-气体质量比引起,并且部分地由使用H-α强度作为远红外发射的示踪剂的缺点引起。

英文摘要:

Determination of the cosmic infrared background (CIB) at far infrared wavelengths using COBE/DIRBE data is limited by the accuracy to which foreground interplanetary and Galactic dust emission can be modeled and subtracted. Previous determinations of the far infrared CIB (e.g., Hauser et al. 1998) were based on the detection of residual isotropic emission in skymaps from which the emission from interplanetary dust and the neutral interstellar medium were removed. In this paper we use the Wisconsin H-alpha Mapper (WHAM) Northern Sky Survey as a tracer of the ionized medium to examine the effect of this foreground component on determination of the CIB. We decompose the DIRBE far infrared data for five high Galactic latitude regions into H I and H-alpha correlated components and a residual component. We find the H-alpha correlated component to be consistent with zero for each region, and we find that addition of an H-alpha correlated component in modeling the foreground emission has negligible effect on derived CIB results. Our CIB detections and 2 sigma upper limits are essentially the same as those derived by Hauser et al. and are given by nu I_nu (nW m-2 sr-1) < 75, < 32, 25 +- 8, and 13 +- 3 at 60, 100, 140, and 240 microns, respectively. Our residuals have not been subjected to a detailed anisotropy test, so our CIB results do not supersede those of Hauser et al. We derive upper limits on the 100 micron emissivity of the ionized medium that are typically about 40% of the 100 micron emissivity of the neutral atomic medium. This low value may be caused in part by a lower dust-to-gas mass ratio in the ionized medium than in the neutral medium, and in part by a shortcoming of using H-alpha intensity as a tracer of far infrared emission.

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