The HDUV Survey: Six Lyman Continuum Emitter Candidates at z~2 Revealed
  by HST UV Imaging
  We present six galaxies at z~2 that show evidence of Lyman continuum (LyC)
emission based on the newly acquired UV imaging of the Hubble Deep UV legacy
survey (HDUV) conducted with the WFC3/UVIS camera on the Hubble Space Telescope
(HST). At the redshift of these sources, the HDUV F275W images partially probe
the ionizing continuum. By exploiting the HST multi-wavelength data available
in the HDUV/GOODS fields, models of the UV spectral energy distributions, and
detailed Monte Carlo simulations of the intergalactic medium absorption, we
estimate the absolute ionizing photon escape fractions of these galaxies to be
very high -- typically >60% (>13% for all sources at 90% likelihood). Our
findings are in broad agreement with previous studies that found only a small
fraction of galaxies to show high escape fraction. These six galaxies comprise
the largest sample yet of LyC leaking candidates at z~2 whose inferred LyC flux
has been cleanly observed at HST resolution. While three of our six candidates
show evidence of hosting an active galactic nucleus (AGN), two of these are
heavily obscured and their LyC emission appears to originate from star-forming
regions rather than the central nucleus. This suggests an AGN-aided pathway for
LyC escape from these sources. Extensive multi-wavelength data in the GOODS
fields, especially the near-IR grism spectra from the 3D-HST survey, enable us
to study the candidates in detail and tentatively test some recently proposed
indirect methods to probe LyC leakage -- namely, the [OIII]/[OII] line ratio
and the H$\beta-$UV slope diagram. High-resolution spectroscopic followup of
our candidates will help constrain such indirect methods which are our only
hope of studying $f_{esc}$ at z~5-9 in the fast-approaching era of the James
Webb Space Telescope.
