We present a search for the synchrotron emission from the synchrotron cosmic web by cross correlating 180MHz radio images from the Murchison Widefield Array with tracers of large scale structure (LSS). We use two versions of the radio image covering $21.76\times 21.76$ degrees with point sources brighter than 0.05 Jy subtracted, with and without filtering of Galactic emission. As tracers of the LSS we use the Two-Micron-All-Sky-Survey (2MASS) and the Widefield InfraRed Explorer (WISE) redshift catalogues to produce galaxy number density maps. The cross correlation functions all show peak amplitudes at zero degrees, decreasing with varying slopes towards zero correlation over a range of one degree. The cross correlation signals include components from point source, Galactic, and extragalactic diffuse emission. We use models of the diffuse emission from smoothing the density maps with Gaussians of sizes 1-4 Mpc to find limits on the cosmic web components. From these models we find surface brightness 99.7 per cent upper limits in the range of 0.09-2.20 mJy beam$^{-1}$ (average beam size of 2.6 arcmin), corresponding to 0.01-0.30 mJy arcmin$^{-2}$. Assuming equipartition between energy densities of cosmic rays and the magnetic field, the flux density limits translate to magnetic field strength limits of 0.03-1.98 $\mu$G, depending heavily on the spectral index. We conclude that for a 3$\sigma$ detection of 0.1 $\mu$G magnetic field strengths via cross correlations, image depths of sub-mJy to sub-$\mu$Jy are necessary. We include discussion on the treatment and effect of extragalactic point sources and Galactic emission, and next steps for building on this work.
翻译:我们通过将Murchison Widefield Array的180MHz调频目录与大比例结构(LSS)的追踪器交叉连接,从同步宇宙网中搜索同步云层释放的同步器。我们使用两个版本的无线电图像,覆盖21.76乘21.76乘21.76度,点源亮度高于0.05焦耳,同时且不过滤银河排放。作为LSS的追踪器,我们使用双米-全Sky-Suvey(2MASS)和宽野红外红外红外线仪(WISE)红外线目录,以制作星际密度地图。交叉相关函数均显示零度的高度振幅,以不同的斜度为零度,以零.76度为零度为零;交叉相关关联信号包括点源的成分、银度和银河外扩散。我们用1-4 mpc 大小的高音量地图的传播模型,为宇宙网络元排放量的极限。从这些模型中,我们发现表面亮度为99.7%的地表层温度值,以0.20.