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arXiv 0710.1946astro-ph
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低频无线电天空的深高分辨率巡天

A deep, high resolution survey of the low frequency radio sky

Emil Lenc, Mike A. Garrett, Olaf Wucknitz, James M. Anderson, Steven J. Tingay

摘要:

我们报告的第一个宽视场,甚长基线干涉测量(VLBI)调查在90厘米。测量区域由两个重叠的28度^2的场组成,中心位于类星体J 0226 +3421和引力透镜B 0218 +357上。根据韦斯特博克北方巡天(WENSS)数据的识别,这些领域共有618个源。在这些源中,有272个源的通量密度如果得不到解决,将超过VLBI观测的灵敏度极限。共检测到27个源,距离相位中心2弧度。调查结果表明,在90厘米处发现的中等微弱(S~100 mJy)源中,至少有10%含有小于~0.1至0.3角秒的致密成分,其总通量密度大于10%。在VLBI数据中检测到一个在WENSS和NRAO VLA巡天(NVSS)数据中没有看到的~90 mJy源,可能是一个偶然发现的瞬态或高度可变的源。这次调查是第一次对低频无线电天空进行系统(和无偏差)、深入、高分辨率的调查。这也是迄今为止最宽的单指向VLBI观测,超过了以前更高频率观测的总观测面积两个数量级。这些初步结果表明,新的低频望远镜,如LOFAR,应该探测到许多紧凑的射电源,并计划将这些阵列扩展到数千公里的基线。

英文摘要:

We report on the first wide-field, very long baseline interferometry (VLBI) survey at 90 cm. The survey area consists of two overlapping 28 deg^2 fields centred on the quasar J0226+3421 and the gravitational lens B0218+357. A total of 618 sources were targeted in these fields, based on identifications from Westerbork Northern Sky Survey (WENSS) data. Of these sources, 272 had flux densities that, if unresolved, would fall above the sensitivity limit of the VLBI observations. A total of 27 sources were detected as far as 2 arcdegrees from the phase centre. The results of the survey suggest that at least 10% of moderately faint (S~100 mJy) sources found at 90 cm contain compact components smaller than ~0.1 to 0.3 arcsec and stronger than 10% of their total flux densities. A ~90 mJy source was detected in the VLBI data that was not seen in the WENSS and NRAO VLA Sky Survey (NVSS) data and may be a transient or highly variable source that has been serendipitously detected. This survey is the first systematic (and non-biased), deep, high-resolution survey of the low-frequency radio sky. It is also the widest field of view VLBI survey with a single pointing to date, exceeding the total survey area of previous higher frequency surveys by two orders of magnitude. These initial results suggest that new low frequency telescopes, such as LOFAR, should detect many compact radio sources and that plans to extend these arrays to baselines of several thousand kilometres are warranted.

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。

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