Prof. Kanak Saha

One of the outstanding problems of current observational cosmology is to understand the nature of sources that produced the bulk of the ionizing radiation after the Cosmic Dark Age. Direct detection of these reionization sources is practically infeasible at high redshift (z) due to the steep decline of intergalactic medium transmission. However, a number of low-z analogues emitting Lyman continuum at 900 Angstrom restframe are now detected at z < 0.4 and others in the range 2.5 < z < 3.5. In this talk, I report the detection of Lyman continuum emission with a high escape fraction (>20%) from a low-mass clumpy galaxy, called AUDFs01 at z = 1.42, in the middle of the redshift range where no detection has been made before. AUDFs01 happens to be near the peak of the cosmic star-formation history. The detection of extreme ultraviolet radiation from a distant galaxy at a restframe wavelength of 600 Angstrom opens up a new window to constrain the shape of the ionization spectrum. Further observations with AstroSat should substantially increase the sample of Lyman-continuum-leaking galaxies at cosmic noon.