Following our first detection reported in Izotov et al .
( 2016 ) , we present the detection of Lyman continuum ( LyC ) radiation of four other compact star-forming galaxies observed with the Cosmic Origins Spectrograph ( COS ) onboard the Hubble Space Telescope ( HST ) .
These galaxies , at redshifts of z \sim 0.3 , are characterized by high emission-line flux ratios [ O iii ] \lambda 5007/ [ O ii ] \lambda 3727 \ga 5 .
The escape fractions of the LyC radiation f _ { esc } ( LyC ) in these galaxies are in the range of \sim 6 % – 13 % , the highest values found so far in low-redshift star-forming galaxies .
Narrow double-peaked Ly \alpha emission lines are detected in the spectra of all four galaxies , compatible with predictions for Lyman continuum leakers .
We find escape fractions of Ly \alpha , f _ { esc } ( Ly \alpha ) \sim 20 % – 40 % , among the highest known for Ly \alpha emitters ( LAEs ) .
Surface brightness profiles produced from the COS acquisition images reveal bright star-forming regions in the center and exponential discs in the outskirts with disc scale lengths \alpha in the range \sim 0.6 – 1.4 kpc .
Our galaxies are characterized by low metallicity , \sim 1 / 8 - 1 / 5 solar , low stellar mass \sim ( 0.2 - 4 ) \times 10 ^ { 9 } M _ { \odot } , high star formation rates SFR \sim 14 – 36 M _ { \odot } yr ^ { -1 } , and high SFR densities \Sigma \sim 2 – 35 M _ { \odot } yr ^ { -1 } kpc ^ { -2 } .
These properties are comparable to those of high-redshift star-forming galaxies .
Finally , our observations , combined with our first detection reported in Izotov et al .
( 2016 ) , reveal that a selection for compact star-forming galaxies showing high [ O iii ] \lambda 5007/ [ O ii ] \lambda 3727 ratios appears to pick up very efficiently sources with escaping Lyman continuum radiation : all five of our selected galaxies are LyC leakers .