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

Abstract

We present a multiwavelength study of two Herbig-Haro (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 Atacama Pathfinder EXperiment 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 (CO)-C-12(3 - 2), (CO)-C-13(3 - 2), (CO)-O-18(3 - 2), HCO+(3 - 2), and HCN(3 - 2) molecular lines with an local thermodynamic equilibrium (LTE) mass of 36M(circle dot). The (CO)-C-12(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 (CO)-C-12 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.