Multifrequency study of HH 137 and HH 138: Discovering new knots and
  molecular outflows with Gemini and APEX
  We present a multi-wavelength study of two HH objects (137 and 138) that may
be associated. We use Gemini H$_2$ (2.12 $\mu$m) and K (2.2 $\mu$m) images, as
well as APEX molecular line observations and Spitzer image archives. Several
H$_2$ knots, linked to the optical chain of knots of HH 137, are identified in
the Gemini and Spitzer 4.5 $\mu$m images. New shock excited regions related to
the optical knots delineating HH 138 are also reported. In addition, a bright
4.5 $\mu$m 0.09 pc-long arc-shaped structure, roughly located mid-way between
HH 137 and HH 138, is found to be associated with two Spitzer Class I/II
objects, which are likely to be the exciting stars. These sources are almost
coincident with a high-density molecular clump detected in $^{12}$CO(3-2),
$^{13}$CO(3-2), C$^{18}$O(3-2), HCO$^{+}$(3-2) and HCN(3-2) molecular lines
with an LTE mass of 36 M$_{\odot}$. The $^{12}$CO(3-2) emission distribution
over the observed region reveals molecular material underlying three molecular
outflows. Two of them (outflows 1 and 2) are linked to all optical knots of HH
137 and HH 138 and to the H$_2$ and 4.5 $\mu$m shock emission knots. In fact,
the outflow 2 shows an elongated $^{12}$CO blue lobe that coincides with all
the H$_2$ knots of HH 137 which end at a terminal H$_2$ bow shock. We propose a
simple scenario that connects the outflows to the dust clumps detected in the
region. A third possible outflow is located to the north-east projected towards
a secondary weak and cold dust clump.
