Highly Collimated Molecular Hydrogen Jets Near IRAS 05487+0255: NIR Imaging and Spectroscopy

We present new narrow-band near-infrared images together with K band spectra of highly collimated bipolar jets close to the IRAS 05487+0255 source. The jets are located at ∼ 50 West of the Herbig-Haro 110 outflow. The jets are not visible at optical wavelengths, and therefore, do not fall into the ‘standard’ Herbig-Haro object classification scheme. Nevertheless, they belong to an ever growing group of molecular hydrogen jets associated with YSOs which are optically undetected. The jets are very well collimated, with a length-to-width ratio ∼ 10− 20. The spectra of the jet and counter-jet in the K-band show a limited number of H2 emission lines which makes it difficult to obtain an accurate excitation temperature. We estimate Tex = 1104±67 K and Tex = 920±156 K for the red and blue jet components respectively. The radial velocities of the jet and counter-jet, based on the shift of the (1,0) S(1) 2.121 μm line, are ∼ −275 ± 50 km s and ∼ 180± 50 km s respectively, suggesting an angle of ∼ 30 − 45 between the jet and the line of sight. The H2 emission of the entire jet extends for at least 40 or ∼ 0.1 pc at the distance of Orion. If the flow velocity is comparable to that of the radial velocities, then the dynamical age of the system is quite short (∼ 500 yrs), consistent with a young jet arising from an embedded source. Entrainment in a turbulent mixing layer may explain this morphology and spectral character. Subject headings: ISM: individual (IRAS 05487+0255)— ISM: jets and outflows— infrared: ISM: lines and bands— stars: formation