The First Large Absorption Survey in HI

Principal Investigators: Elaine Sadler (University of Sydney) and Elizabeth Mahony (CSIRO)
The First Large Absorption line Survey in HI (FLASH) is a wide-area survey using ASKAP to search for the 21cm HI line in absorption against background radio continuum sources. FLASH observations are carried out using the lowest ASKAP frequency band (711.5-999.5 MHz) providing information on the HI content of the Universe between redshifts z=0.42 and z=1.0, an epoch where the neutral gas content of galaxies is poorly constrained. The science goals of the FLASH survey include determining how the cool HI gas in galaxies has evolved since cosmic noon and examining the gas accretion mechanisms that drive the co-evolution of supermassive black holes and their host galaxies over cosmic history. FLASH will also detect OH 18-cm absorbers in diffuse molecular gas, megamaser OH emission, radio recombination lines, and stacked HI emission. A detailed description of the FLASH survey is outlined in the FLASH survey overview paper available here.
An overview of the FLASH observing parameters and sky coverage is given below:

• Frequency range: 711.5-999.5 MHz
• Spectral resolution: 18.5kHz
• Integration time per field: 2 hrs
• Footprint: Square6x6
• Sky coverage: All sky with dec <+15 and |b|>8.5 deg. 600 fields in total (matched to RACS-low footprints).
• Beam-forming frequency intervals: 5 MHz.