Studying a precessing jet of a massive young stellar object within a chemically rich region

Abstract

In addition to the large surveys and catalogs of massive young stellar objects and outflows, dedicated studies of particular sources, in which high-angular observations (mainly at near-IR and mm) are analyzed in depth, are needed to shed light on the processes involved in the formation of massive stars. The galactic source G079.1272+02.2782 (G79), a MYSO at about 1.4 kpc, is an ideal source to carry out this kind of studies. Near-IR integral field spectroscopic observations were carried out using NIFS at Gemini-North. The spectral and angular resolutions, allow us to perform a detailed study of the source and its southern jet, resolving structures with sizes between 200 and 300 au. As a complement, millimeter data retrieved from the JCMT and the IRAM 30m telescope databases were analyzed to study the molecular gas at a larger spatial scale. The analysis of a jet extending southwards shows cork-screw like structures at 2.2 um continuum, strongly suggesting that the jet is precessing. The jet velocity is estimated in 30-43 km/s and it is coming to us along the line of sight. We suggest that the precession may be produced by the gravitational tidal effects generated in a probable binary system, and we estimate a jet precession period of about 10^3 yr, indicating a slow-precessing jet, which is in agreement with the observed helical features. An analysis of H2 lines along the jet allows us to investigate in detail a bow-shock produced by this jet. We find that this bow-shock is indeed generated by a C-type shock and it is observed coming to us, with some inclination angle, along the line of sight. This is confirmed by the analysis of molecular outflows at a larger spatial scale. A brief analysis of several molecular species at millimeter wavelengths indicates a complex chemistry developing at the external layers of the molecular clump in which MYSO G79 is embedded.