AstroSat detection of Lyman continuum emission from a z = 1.42 galaxy (original) (raw)
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 1 is practically infeasible at high redshift due to the steep decline of intergalactic medium transmission 2,4. However, a number of low-redshift analogs emitting Lyman continuum at 900Å restframe are now detected at z < 0.4 [5, 6, 7, 8, 9] and there are detections in the range 2.5 < z < 3.5 [10, 11, 12, 13, 14, 15] 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 16. The observation was made in the Hubble Extreme Deep field 17 by the wide-field UltraViolet Imaging Telescope 18 on-board AstroSat 19. This is the first detection of Extreme Ultraviolet radiation from a distant galaxy at a rest-frame wavelength of 600, 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.
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