The GMRT-CATz1 Survey: Atomic Hydrogen in Galaxies at z~1

For many decades, a critical lacuna in our understanding of galaxy evolution has been that we knew nothing about the neutral atomic hydrogen (HI) content of high-z galaxies. Over the last few years, we have used the upgraded GMRT to carry out the GMRT-CATz1 survey, a 510-hour survey of the HI 21 cm line in star-forming galaxies at z=0.74-1.45. The survey led to the first measurement and characterisation of the HI content in galaxies at z~1 and an explanation to the long-standing puzzle of why the star-formation activity of the Universe declined rapidly after its peak at z~1-3. In this talk, I will describe the above as well as present other key results from the GMRT-CATz1 survey, including the first measurements of HI scaling relations, the HI mass function and the gas accretion rate at these redshifts. Finally, I will briefly mention our many ongoing efforts to use the upgraded GMRT to study HI in high-z galaxies, including a project to push HI 21 cm emission studies to z~2-3.