  The Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) is a
next-generation survey of neutral hydrogen (HI) in the Local Universe. It uses
the widefield, high-resolution capability of the Australian Square Kilometer
Array Pathfinder (ASKAP), a radio interferometer consisting of 36 x 12-m dishes
equipped with Phased-Array Feeds (PAFs), located in an extremely radio-quiet
zone in Western Australia. WALLABY aims to survey three-quarters of the sky
(-90 degr < Dec < +30 degr) to a redshift of z < 0.26, and generate spectral
line image cubes at ~30 arcsec resolution and ~1.6 mJy/beam per 4 km/s channel
sensitivity. ASKAP's instantaneous field of view at 1.4 GHz, delivered by the
PAF's 36 beams, is about 30 sq deg. At an integrated signal-to-noise ratio of
five, WALLABY is expected to detect over half a million galaxies with a mean
redshift of z ~ 0.05 (~200 Mpc). The scientific goals of WALLABY include: (a) a
census of gas-rich galaxies in the vicinity of the Local Group; (b) a study of
the HI properties of galaxies, groups and clusters, in particular the influence
of the environment on galaxy evolution; and (c) the refinement of cosmological
parameters using the spatial and redshift distribution of low-bias gas-rich
galaxies. For context we provide an overview of previous large-scale HI
surveys. Combined with existing and new multi-wavelength sky surveys, WALLABY
will enable an exciting new generation of panchromatic studies of the Local
Universe. - First results from the WALLABY pilot survey are revealed, with
initial data products publicly available in the CSIRO ASKAP Science Data
Archive (CASDA).
