The future of cm and m-wave astronomy lies with the Square Kilometre Array (SKA), a telescope under development by a consortium of 17 countries. The SKA will be 50 times more sensitive than any existing radio facility. A majority of the key science for the SKA will be addressed through large-area imaging of the Universe at frequencies from 300 MHz to a few GHz. The Australian SKA Pathfinder (ASKAP) is aimed squarely in this frequency range, and achieves instantaneous wide-area imaging through the development and deployment of phase-array feed systems on parabolic reflectors. This large field-of-view makes ASKAP an unprecedented synoptic telescope poised J. Wall is the overall editor.

The future of cm and m-wave astronomy lies with the Square Kilometre Array (SKA), a telescope under development by a consortium of 17 countries that will be 50 times more sensitive than any existing radio facility. Most of the key science for the SKA will be addressed through largearea imaging of the Universe at frequencies from a few hundred MHz to a few GHz. The Australian SKA Pathfinder (ASKAP) is a technology demonstrator aimed in the mid-frequency range, and achieves instantaneous wide-area imaging through the development and deployment of phased-array feed systems on parabolic reflectors. The large field-of-view makes ASKAP an unprecedented synoptic telescope that will make substantial advances in SKA key science. ASKAP will be located at the Murchison Radio Observatory in inland Western Australia, one of the most radio-quiet locations on the Earth and one of two sites selected by the international community as a potential location for the SKA. In this paper, we outline an ambitious science program for ASKAP, examining key science such as understanding the evolution, formation and population of galaxies including our own, understanding the magnetic Universe, revealing the transient radio sky and searching for gravitational waves.

We present a study of the discrete clouds and filaments in the Magellanic Stream using a new high-resolution survey of neutral hydrogen (H i) conducted with the H75 array of the Australia Telescope Compact Array, complemented by single-dish data from the Parkes Galactic All-Sky Survey. From the individual and combined data sets, we have compiled a catalog of 251 clouds and listed their basic parameters, including a morphological description useful for identifying cloud interactions. We find an unexpectedly large number of head-tail clouds in the region. The implication for the formation mechanism and evolution is discussed. The filaments appear to originate entirely from the Small Magellanic Cloud and extend into the northern end of the Magellanic Bridge.

We present the first direct detection of cold atomic gas in the Magellanic Stream, through 21 cm line absorption toward a background radio source, J0119−6809, using the Australia Telescope Compact Array. Two absorption components were identified at heliocentric velocities 218.6 km s −1 and 227.0 km s −1 , with optical depths of τ ≈ 0.02. The corresponding H i emission region has a column density in excess of 2 × 10 20 cm −2 . The inferred spin temperature of the emitting gas is ∼ 70 K. We failed to find cool gas in observations of three other radio continuum sources. Although we have definitively detected cool gas in the Stream, its spin temperature is higher than similar components in the LMC, SMC, and Bridge, and its contribution to the total H i density is probably lower. No corresponding 12 CO(J = 1→ 0) or dust appears to be associated with the cool gas, suggesting that the cloud is not forming stars.

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