Multifrequency study of HH 137 and HH 138: Discovering new knots and molecular outflows with Gemini and APEX

Abstract

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.

17 pages, 13 figures, 4 tables. Accepted for publication in MNRAS

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