2020MNRAS.494.4986M

Identifying non-contaminated sample of high-redshift galaxies with escaping Lyman continuum (LyC) flux is important for understanding the sources and evolution of cosmic reionization. We present CLAUDS (CFHT Large Area u-band deep survey) u-band photometry of the COSMOS field to probe LyC radiation from spectroscopically confirmed galaxies at z >= 3.5 and outside the standard Lyman-break galaxy colour-selection expectations. Complementary to the CLAUDS data, we use Subaru multifilter photometry, Hubble Space Telescope (HST) multifilter imaging, and the spectroscopic surveys D10K, VUDS, and 3D-HST. We present a sample of Lyman continuum galaxy (LCG) candidates in the redshift range 3.5 <= z <= 5.1. Here, we introduce 5 LCG candidates, where two are flagged quality 1 and three quality 2. The estimated f_ esc_^ abs^ for quality 1 candidates are in the range ∼5 - 73 per cent and ∼30 - 93 per cent. These estimates are based on our derived parameters from individual galaxies as inputs to a range of BPASS models as well as mean intergalactic medium (IGM) and maximal intergalactic and circumgalactic media (IGM+CGM) transmission. We conclude that our search for LCGs is most likely biased to lines of sight with low H I densities or free from Lyman limit systems. Our two best LCG candidates have EW (Lyα) <= 50 Å and we find no correlation or anticorrelation between EW (Lyα), f_ esc_^ abs^, and R_obs, the ratio of ionizing to non-ionizing observed flux in the measured passbands. Stacking candidates without solid LyC detections (S/N < 3) results in an estimated f_ esc_^ abs^ from galaxies not greater than 1 per cent.