Infrared and Millimetric Study of the Young Outflow Cepheus E

Abstract

The Cepheus E outflow has been studied in the mid-and far-IR using the ISOCAM and Long Wave-length Spectrometer (LWS) instruments and at millimetric wavelengths using the Owens Valley Radio Observatory (OVRO). In the near-and mid-IR, its morphology is similar to that expected for a jet-driven outflow, where the leading bow shocks entrain and accelerate the surrounding molecular gas. As expected, fine-structure atomic/ionic emission lines arise from the bow shocks, at both the Mach disk and the stagnation tip, where J-shocks are dominant. The H2, H2O, and CO molecular emission could arise farther "downstream" at the bow shock wings where the shocks (v = 8-35 km s-1) are oblique and more likely to be C-type. The 13CO emission arises from entrained molecular gas, and a compact high-velocity emission is observed, together with an extended low-velocity component that almost coincides spatially with the H2 near-IR emission. The millimetric continuum emission shows two sources. We identify one of them with IRAS 23011 + 6126, postulating that it is the driver of the Cepheus E outflow; the other, also an embedded source, is likely to be driving one of the other outflows observed in the region. Finally, we suggest that the strong [C II] 158 μm emission must originate from an extended photodissociation region, very likely excited by the nearby Cepheus OB3 association.