LFmap: A Low Frequency Sky Map Generating Program
LFmap: A Low Frequency Sky Map Generating Program
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LFmap：低频天空图生成程序
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
E. Polisensky
中科院分区：
文献类型：
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作者：
E. Polisensky
已经开发了一个C程序来生成从几十到几百MHz的天空图。计算方法以及运行程序的说明。LWA工作范围内的天空地图对LWA的发展是有用和必要的。地图可用于与原型仪器的观测结果进行比较，并用于计算单个天线的天空噪声的日变化，以与测量结果进行比较。许多地图已出版低于100兆赫，但其中大多数不是电子格式。这些映射也是在一些选择的频率，而在LWA频带中的任何频率的映射是需要的。LFmap是一个用C语言编写的程序，提供这样的地图。在低频下，天空的亮度温度是一个幂律：Tsky /温度光谱指数在低Tsky的区域是很大的，反之亦然。这被解释为Tsky是具有陡峭频谱的各向同性分量和具有一般atter频谱的各向异性分量的叠加。宇宙微波背景辐射（CMB）是各向同性的，但有一个at谱，而且温度太低，无法解释所有的各向同性辐射。各向异性分量是由于银河磁场中宇宙线电子的同步辐射。因此，在频率方向上的亮度温度可以写为：
A C program has been developed to generate maps of the sky from tens to hundreds of MHz. The method of calculation is described as well as instructions for running the program. Maps of the sky in the operating range of the LWA are useful and necessary for LWA development. Maps can be used for comparison with observations made with prototype instruments and for calculating the diurnal variation of sky noise from single antennas to compare with measurements. Many maps have been published below 100 MHz but most of these are not in electronic format. These maps are also at a few select frequencies while maps at any frequency in the LWA band are needed. LFmap is a program written in the C language to provide such maps. At low frequencies the brightness temperature of the sky is a power law: Tsky / The temperature spectral index is known to be large in regions of low Tsky and vice versa. This is interpreted as Tsky being a superposition of an isotropic component with a steep spectrum and an anisotropic component with a generally atter spectrum. The cosmic microwave background (CMB) is isotropic but has a at spectrum and is too cool to account for all the isotropic emission. The anisotropic component is due to synchrotron radiation from cosmic ray electrons in the Galactic magnetic eld. Thus the brightness temperature at frequency in direction , can be written: