AstroSat detection of Lyman continuum emission from a z=1.42 galaxy
  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 due to the steep decline of
intergalactic medium transmission. However, a number of low-redshift analogs
emitting Lyman continuum at~900 Angstrom ~restframe are now detected at $z<
0.4$ and there are detections in the range $ 2.5< z< 3.5$ also. Here, we report
the detection of Lyman continuum emission with a high escape fraction (>20%)
from a low-mass clumpy galaxy at z=1.42, in the middle of the redshift range
where no detection has been made before and near the peak of the Cosmic
Star-formation history. The observation was made in the Hubble Extreme Deep
field by the wide-field Ultra-Violet-Imaging Telescope onboard AstroSat. This
is the first detection of Extreme Ultraviolet radiation from a distant galaxy
at a rest-frame wavelength of 600 Angstrom, and it opens up a new window to
constrain the shape of the ionization spectrum. Further observations with
AstroSat should significantly increase the sample of Lyman continuum leaking
galaxies at Cosmic Noon.
