ASKAP-FLASH: The First Large Absorption Survey in HI

The FLASH team wiki pages are at:
Access to these wiki pages is restricted to FLASH team members. For more information, please contact Elaine Sadler (ems (at)

Information about the survey:
ASKAP-FLASH (the First Large Absorption Survey in HI) is one of eight Survey Science Projects which will be carried out with the Australian SKA Pathfinder (ASKAP) radio telescope.

ASKAP ( will be an array of 36 antennas each 12m in diameter, capable of high dynamic range imaging and using wide-field-of-view phased array feeds. ASKAP is intended to be a world-class telescope in its own right as well as a pathfinder instrument for the Square Kilometre Array.

ASKAP's large spectral bandwidth (300 MHz bandwidth over the frequency range 700-1800 MHz) and wide field of view (30 square degrees) will open up a completely new parameter space for large, blind HI absorption-line surveys using background radio continuum sources. Since the detection limit for such surveys is independent of redshift, ASKAP-FLASH will allow us to learn about the neutral gas content of galaxies in the poorly-explored redshift range 0.5 < z < 1.0, where the HI emission line is too weak to be detectable in even the deepest ASKAP surveys.

The proposed FLASH survey aims to detect and measure several hundred HI absorption lines (from both intervening and associated absorbers). This will provide a unique dataset for studies of galaxy evolution as well as a new estimate of the HI mass density at intermediate redshifts. The FLASH data will also be used for HI emission-line stacking experiments in combination with large-area optical redshift surveys like WiggleZ and GAMA.

The survey PI is Elaine Sadler (University of Sydney), and the team currently includes around 25 members from Australia, Europe, Canada and the USA. If you are interested in this project, or in joining the survey team, please email (ems (at)