A submillimeter galaxy illuminating its circumgalactic medium: Ly-alpha
  scattering in a cold, clumpy outflow
  We report the detection at 850um of the central source in SSA22-LAB1, the
archetypal Lyman-alpha Blob (LAB), a 100kpc-scale radio-quiet emission-line
nebula at z=3.1. The flux density of the source, $S_{850}=4.6\pm1.1$mJy implies
the presence of a galaxy, or group of galaxies, with a total luminosity of
$L_{\rm IR}\approx10^{12}L_\odot$. The position of an active source at the
center of a ~50kpc-radius ring of linearly polarized Ly-alpha emission detected
by Hayes et al. (2011) suggests that the central source is leaking Ly-alpha
photons preferentially in the plane of the sky, which undergo scattering in HI
clouds at large galactocentric radius. The Ly-alpha morphology around the
submillimeter detection is reminiscent of biconical outflow, and the average
Ly-alpha line profiles of the two `lobes' are dominated by a red peak, expected
for a resonant line emerging from a medium with a bulk velocity gradient that
is outflowing relative to the line center. Taken together, these observations
provide compelling evidence that the central active galaxy (or galaxies) is
responsible for a large fraction of the extended Ly-alpha emission and
morphology. Less clear is the history of the cold gas in the circumgalactic
medium being traced by Ly-alpha: is it mainly pristine material accreting into
the halo that has not yet been processed through an interstellar medium (ISM),
now being blown back as it encounters an outflow, or does it mainly comprise
gas that has been swept-up within the ISM and expelled from the galaxy?
