• Whiting, Matthew

Abstract

The Australian Square Kilometre Array Pathfinder (ASKAP) presents a number of challenges in the area of source finding and cataloguing. The data rates and image sizes are very large, and require automated processing in a high-performance computing environment. This requires development of new tools, that are able to operate in such an environment and can reliably handle large datasets. These tools must also be able to accommodate the different types of observations ASKAP will make: continuum imaging, spectral-line imaging, transient imaging. The ASKAP project has developed a source-finder known as Selavy, built upon the Duchamp source-finder (Whiting 2012). Selavy incorporates a number of new features, which we describe here.The first allows distributed processing of large images and cubes. We describe the algorithms used to distribute the data, find an appropriate threshold and search to that threshold and form the final source catalogue.The second set of new features are those especially relevant for continuum imaging that were not included in the Duchamp package.One aspect of these is the ability to apply a variable threshold, responding to the noise properties on a local, rather than global, scale. The other aspect is the ability to fit Gaussian profiles to sources, enabling more accurate parameterisation.We also discuss the development process, in particular how the ASKAP science community has been contributing to the content of the ASKAP source-finder.

Topics

• impedance spectroscopy