The SAMI Galaxy Survey: cubism and covariance, putting round pegs into square holes

Abstract

We present a methodology for the regularisation and combination of sparse\nsampled and irregularly gridded observations from fibre-optic multi-object\nintegral-field spectroscopy. The approach minimises interpolation and retains\nimage resolution on combining sub-pixel dithered data. We discuss the\nmethodology in the context of the Sydney-AAO Multi-object Integral-field\nspectrograph (SAMI) Galaxy Survey underway at the Anglo-Australian Telescope.\nThe SAMI instrument uses 13 fibre bundles to perform high-multiplex\nintegral-field spectroscopy across a one degree diameter field of view. The\nSAMI Galaxy Survey is targeting 3000 galaxies drawn from the full range of\ngalaxy environments. We demonstrate the subcritical sampling of the seeing and\nincomplete fill factor for the integral-field bundles results in only a 10%\ndegradation in the final image resolution recovered. We also implement a new\nmethodology for tracking covariance between elements of the resulting datacubes\nwhich retains 90% of the covariance information while incurring only a modest\nincrease in the survey data volume.\n