Lyman continuum leakage from low-mass galaxies with Mstar < 1.E8 Msun
  We present observations with the Cosmic Origins Spectrograph onboard the
Hubble Space Telescope of nine low-mass star-forming galaxies at redshifts, z,
in the range 0.3179-0.4524, with stellar masses Mstar < 10^8 M and veruny high
specific star-formation rates sSFR~150-630 Gyr^{-1}, aiming to study the
dependence of leaking Lyman continuum (LyC) emission on stellar mass and some
other characteristics of the galaxy. We detect LyC emission in four out of nine
galaxies with escape fractions, fesc(LyC), in the range of 11-35 per cent, and
establish upper limits for fesc(LyC) in the remaining five galaxies. We observe
a narrow Ly-alpha emission line with two peaks in seven galaxies and likely
more complex Ly-alpha profiles in the two remaining galaxies. The velocity
separation between the peaks Vsep varies in the range from ~229 km/s to ~512
km/s. Our additional data on low-mass galaxies confirm and strengthen the tight
anti-correlation between fesc(LyC) and Vsep found for previous low-redshift
galaxy samples with higher stellar masses. Vsep remains the best indirect
indicator of LyC leakage. It is better than O32 on which fesc(LyC) depends
weakly, with a large scatter. Finally, contrary to expectations, we find no
increase of fesc(LyC) with decreasing galaxy stellar mass Mstar.
