Using a sample of galaxies at z \approx 3 with detected Lyman Continuum ( LyC ) leakage in the SSA22 field , we attempt to verify a proposed indirect method for identifying cases with high LyC escape fraction f _ { \mathrm { esc } } based on measurements of the H \beta equivalent width ( EW ) and the \beta slope of the UV continuum .
To this end , we present Keck/MOSFIRE H \beta emission line flux measurements of LyC galaxies ( LCGs ) at spectroscopic redshifts z _ { \mathrm { spec } } \sim 3.3 , Lyman break galaxies ( LBGs ) at photometric redshifts z _ { \mathrm { phot } } = 2.7 – 3.7 , and Ly \alpha emitters at z _ { \mathrm { phot } } = 3.1 .
We also reconfirm the spectroscopic redshifts and measure the H \beta emission line fluxes from 2 LCGs and 6 LBGs .
For the LCG in our sample with the most extreme f _ { \mathrm { esc } } , as revealed by the direct detection of LyC photons , we find that the EW ( H \beta ) – \beta method gives a broadly consistent estimate for f _ { \mathrm { esc } } , although the error bars remain very large .
We also discuss how a combination of f _ { \mathrm { esc } } measurements based on direct and indirect methods can shed light on the LyC escape mechanism and the anisotropy of the leakage .