A search for shock-excited optical emission from the outflows of massive young stellar objects

Abstract

We have searched for optical shock-excited emission lines in the outer parts of the bipolar outflows from massive young stellar objects where the flow terminates and the extinction is expected to be low. The Taurus Tunable Filter (TTF) at the Anglo-Australian Telescope (AAT) was used to obtain narrow-band ( 12-15 angstrom) images of the H alpha, [NII] 6583, and [SII] 6717/6731 lines around Mon R2 IRS3, S255 IRS1/3, GL 961 and GL 989. No clear examples of shocked emission were found. A bow shock feature in the GL 989 region maybe related with the molecular outflow NGC2264 D. A weak optical bow- like feature is seen in GL 961, but which of the stars in the cluster is the driving source cannot be uniquely identified. Other emission line features were found in Mon R2 and S255 that are consistent with an H.. region origin. The observed fluxes and the upper limits were compared with predictions from radiative shock models available in the literature. Any head-on collisions of a jet with speeds of the order of 500 km s(-1) should have been detected if the extinction A(v) 75 degrees), which would argue against the presence of highly collimated jets from high mass young stellar objects.