Highly Collimated Molecular Hydrogen Jets near IRAS 05487+0255: Near‐Infrared Imaging and Spectroscopy

Abstract

We present new narrowband near-infrared images together with K-bandspectra of highly collimated bipolar jets close to the IRAS 05487+0255source. The jets are located similar to 50 `' west of the Herbig-Haro110 outflow. The jets are not visible at optical wavelengths andtherefore do not fall into the `'standard'' Herbig-Haro objectclassification scheme. Nevertheless, they belong to an ever growinggroup of molecular hydrogen jets associated with young stellar objectsthat are optically undetected. The jets are very well collimated, withlength-to-width ratios of similar to 10-20. The spectra of the jet andits counterjet in the K band show a limited number of H-2 emission linesthat make it difficult to obtain an accurate excitation temperature. Weestimate T-ex = 1104+/-67 K and T-ex = 920+/-156 K for the red and bluejet components, respectively. The radial velocities of the jet andcounterjet, based on the shift of the (1,0) S(1) 2.121 mu m line, aresimilar to-275+/-50 km s(-1) and similar to 180+/-50 km s(-1),respectively, suggesting an angle of similar to 30 degrees-45 degreesbetween the jet and the line of sight. The H-2 emission di the entirejet extends for ar least 40 `', similar to 0.1 pc at the distance ofOrion. If the flow velocity is comparable to that of the radialvelocities, then the dynamical age of the system is quite short (similarto 500 yr), consistent with a young jet arising from an embedded source.Entrainment in a turbulent mixing layer may explain this morphology andspectral character.