ISOCAM Molecular Hydrogen Images of the Cepheus E Outflow

Abstract

The physical characteristics of the Cepheus E ``embedded'' outflow are analyzed using ISOCAM images in the v = 0-0 S(5) 6.91 μm and S(3) 9.66 μm molecular hydrogen lines. We find that the morphology of the Cep E outflow in the ground vibrational H_2 lines is similar to that in the near-infrared v = 1-0 2.12 μm line. At these mid-infrared wavelengths, we detect neither the second H_2 outflow that is almost perpendicular to the Cep E 2.12 μm flow nor traces of H_2 emission along the second ^12CO J = 2-1 outflow, at an angle of ~52 deg, down to a surface brightness of 12-46 muJy arcsec^-2. We do detect at 6.91 μm the likely source of the main H_2 and CO outflows, IRAS 23011+6126, and show that the source is easily seen in all IRAS bands using HIRES images. The source is not detected at 9.66 mum, but we think this agrees with the interstellar extinction curve, which has a minimum at ~7 μm but rises at ~9.7 μm as a result of the strong absorption silicate feature, enhanced in this case by a cocoon surrounding the Class 0 object. This idea is supported by our models of the spectral energy distribution (SED) of the central object. The models assume that the main source of opacity is due to bare silicates, and our best fit for the SED yields a total envelope mass of 17 M_⊙ and a dust temperature of 18 K. Based on observations with the Infrared Space Observatory, an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, the Netherlands, and the UK) with the participation of ISAS and NASA.