A Hybrid Algorithm for Wide-Field Imaging with Radio Synthesis Arrays

Abstract

There are some wide-field imaging techniques that allow imaging for wide-fields of view for non-coplanar radio interferometric arrays. However, the imaging process is complex due to the amount of computation required at high resolutions and the large number of visibilities present in observation data. The required accuracy and computational cost of such imaging represent one of the largest challenges facing the new generation of radio interferometers such as the Square Kilometre Array. In this paper, we present a new hybrid algorithm, called $\boldsymbol{w}$-facets, that is based on an existing faceting algorithm and the $\boldsymbol{w}$-projection algorithm. The idea for $\boldsymbol{w}$-facets is based on using a faceting algorithm to split a wide-field of view into small facets and handling each facet using the $\boldsymbol{w}$-projection algorithm. We compare the image quality and imaging time by using the faceting, $\boldsymbol{w}$-projection and $\boldsymbol{w}$-facets algorithms. The data show that the imaging quality obtained from the hybrid algorithm is better than that obtained from the faceting or $\boldsymbol{w}$-projection algorithms separately. In addition, the $\boldsymbol{w}$-facets algorithm gives a good robust estimate and small dynamic range on the bright source. However, one shortcoming is that the imaging time required by the $\boldsymbol{w}$-facets algorithm is longer, and this time requirement will affect widespread use of the hybrid method in practical applications.