The First Large Absorption line Survey in HI (FLASH) is a wide-area survey using ASKAP to search for the 21cm neutral hydrogen (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.

This month, the FLASH team is wrapping up their observing time with our ASKAP radio telescope and entering the next phase of poring over the huge amounts of data. To celebrate this event, a “FLASH Splash” was held last week at Marsfield and on-line, with presentations covering ASKAP, the FLASH survey, and examples of FLASH science. The image above shows a selection of FLASH HI absorption line detections. Each line has been shifted to the centre and ordered by redshift covering look-back times from 4 to 8 billion years ago.