Observational Aspects of Galactic Accretion at Redshift 3.3
  We investigate the origin of extragalactic continuum emission and its
relation to the stellar population of a recently discovered peculiar z=3.344
Lyman alpha emitter. Based on an analysis of the broad-band colors and
morphology we find further support for the idea that the underlying galaxy is
being fed by a large-scale (L > 35 kpc) accretion stream. Archival HST images
show small scale (~5 kpc) tentacular filaments converging near a hot-spot of
star-formation, possibly fueled by gas falling in along the filaments. The
spectral energy distribution of the tentacles is broadly compatible with either
(1) non-ionizing rest-frame far-UV continuum emission from stars formed in an
60 million-year-old starburst; (2) nebular 2-photon-continuum radiation,
arising from collisional excitation cooling, or (3) a recombination spectrum
emitted by hydrogen fluorescing in response to ionizing radiation escaping from
the galaxy. The latter possibility simultaneously accounts for the presence of
asymmetric Lyman alpha emission from the large-scale gaseous filament and the
nebular continuum in the smaller-scale tentacles as caused by the escape of
ionizing radiation from the galaxy. Possible astrophysical explanations for the
nature of the tentacles include: a galactic wind powered by the starburst;
in-falling gas during cold accretion, or tails of interstellar medium dragged
out of the galaxy by satellite halos that have plunged through the main halo.
The possibility of detecting extragalactic 2-photon continuum emission in
space-based, broad-band images suggests a tool for studying the gaseous
environment of high redshift galaxies at much greater spatial detail than
possible with Lyman alpha or other resonance line emission.
