arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1209.3877astro-ph.CO
收藏

尘埃恒星形成星系的微波和无线电发射:宇宙无线电背景的意义

Microwave and radio emission of dusty star-forming galaxies: Implication for the cosmic radio background

Nathalie Ysard, Guilaine Lagache

摘要:

我们使用最新的恒星形成(SF)星系和射电源的宇宙学演化模型计算河外星系的计数和宇宙背景从408 MHz到12 THz。SF星系的模型再现了斯皮策,赫歇尔和地面submm/mm实验获得的限制:数量计数,星系的红移分布,宇宙背景强度和各向异性。该模型的模板SED外推到无线电添加同步加速器,自由,和旋转尘埃排放。为了确定同步辐射强度,我们使用红外/射电通量比q70和光谱指数beta=-3。对于一个常数q70,我们的模型添加到活动星系核的贡献提供了一个很好的适合从12 THz到408 MHz的计数和CIB。自旋尘埃占SF星系产生的宇宙微波背景的20%,但当包括AGN时,占总背景的不到10%。SF星系占1.4GHz下1 e-4Jy通量计数的77.5%。然而,该模型不能解释ARCADE 2实验测量的CRB。考虑到q70随红移强烈减小的情况,这仍然不能解释ARCADE 2的结果。它也产生了高估的低通量数计数的无线电。因此,我们至少在z<3.5时排除了q70随红移的急剧变化。增加一群高红移的暗SF星系(Lir<1 e11 Lsun和4<z<6),这将重现ARCADE 2的结果,导致CIB的预测比观察到的要高得多,排除了ARCADE 2结果的解释。考虑到我们的发现和以前的研究,我们得出结论,如果ARCADE 2测量的无线电发射是天体物理学的起源,它必须起源于银河系或一种新的无线电源(没有中红外到远红外对应物)或发射机制仍有待发现。

英文摘要:

We use the most up-to-date cosmological evolution models of star-forming (SF) galaxies and radio sources to compute the extragalactic number counts and the cosmic background from 408MHz to 12THz. The model of SF galaxies reproduces the constraints obtained by Spitzer, Herschel, and ground-based submm/mm experiments: number counts, redshift distribution of galaxies, cosmic background intensity and anisotropies. The template SEDs of this model are extrapolated to the radio adding synchrotron, free-free, and spinning dust emissions. To fix the synchrotron intensity, we use the IR/radio flux ratio, q70, and a spectral index beta=-3. For a constant q70, our model added to the AGN contribution provides a good fit to the number counts from 12THz to 408MHz and to the CIB. Spinning dust accounts for up to 20% of the cosmic microwave background produced by SF galaxies, but for less than 10% of the total background when AGN are included. The SF galaxies account for 77.5% of the number counts at 1.4GHz for a flux of 1e-4Jy. However, the model does not explain the CRB measured with the ARCADE2 experiment. Considering the case when q70 decreases strongly with redshift, this still does not explain the ARCADE2 results. It also yields to an overestimate of the low-flux number counts in the radio. Thus, we rule out a steep variation of q70 with redshift at least for z<3.5. Adding a population of faint SF galaxies at high redshift (Lir<1e11Lsun and 4<z<6), which would reproduce the ARCADE2 results, leads to predictions of the CIB much higher than what is observed, ruling out this as the explanation for the ARCADE2 results. Considering our findings and previous studies, we conclude that if the radio emission measured by ARCADE2 is astrophysical in origin, it has to originate in the Galaxy or in a new kind of radio sources (with no mid- to far-IR counterparts) or emission mechanism still to be discovered.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑