Effects of photon trapping on the Lyman-alpha properties of star-forming
  galaxies
  Recent observations show that a large number of Lyman-alpha emitters (LAEs)
at high redshift z >= 3 have unusually high Lya equivalent widths (EW > 400
angstrom). However, the origin of these high EWs is an open question. Here, we
investigate the impacts of photon trapping on the Lya EW and other properties
by tracking the Lya radiative transfer in spherical galactic clouds. We find
that the delayed escape of the Lya photons can change the Lya properties
significantly. During the transition phase from optically thick to optically
thin where the Lya photons can escape simultaneously, the EW can be boosted to
~ 1000 angstrom, the Lya luminosity can be increased by a factor of a few, and
the line profile can be significantly broadened. The boost factor appears to
depend on the galaxy properties such as mass and star formation rate and
timescale, therefore future investigation combing 3D Lya RT calculations with
cosmological simulations of galaxy formation and evolution is needed to fully
understand the Lya properties of early star-forming galaxies.
