HH 223: a parsec-scale H2 outflow in the star-forming region L723
  The dark cloud Lynds 723 (L723) is a low-mass star-forming region where one
of the few known cases of a quadrupolar CO outflow has been reported. Two
recent works have found that the radio continuum source VLA 2, towards the
centre of the CO outflow, is actually a multiple system of young stellar
objects (YSOs). Several line-emission nebulae that lie projected on the
east-west CO outflow were detected in narrow-band Halpha and [SII] images. The
spectra of the knots are characteristic of shock-excited gas (Herbig-Haro
spectra), with supersonic blueshifted velocities, which suggests an optical
outflow also powered by the VLA 2 YSO system of L723. We imaged a field of ~5'
X 5' centred on HH 223, which includes the whole region of the quadrupolar CO
outflow with nir narrow-band filters . The H2 line-emission structures appear
distributed over a region of 5.5' (0.5 pc for a distance of 300 pc) at both
sides of the VLA 2 YSO system, with an S-shape morphology, and are projected
onto the east-west CO outflow. Most of them were resolved in smaller knotty
substructures. The [FeII] emission only appears associated with HH 223. An
additional nebular emission from the continuum in Hc and Kc appears associated
with HH 223-K1, the structure closest to the VLA 2 YSO system, and could be
tracing the cavity walls. We propose that the H2 structures form part of a
large-scale near-infrared outflow, which is also associated with the VLA 2 YSO
system. The current data do not allow us to discern which of the YSOs of VLA 2
is powering this large scale optical/near-infrared outflow.
