The Eye of the Tornado - an isolated, high-mass young stellar object near the Galactic Centre

Abstract

We present infrared (Anglo-Australian Telescope, United Kingdom Infrared Telescope) and radio (Very Large Array, Swedish-ESO Submillimetre Telescope) observations of the Eye of the Tornado, a compact source apparently near the head of the Tornado Nebula. The near-infrared Brgamma and He I lines are broad (full width at half maximum of 40 and 30 km s(-1), respectively) and have a line centre at V(LSR)similar to-205 km s(-1). This corresponds to a feature at the same velocity in the (CO)-C-12 J= 1-0 line profile. The kinematic velocity derived from Galactic rotation places the Eye at the distance of the Galactic Centre (i.e. 8.5 kpc) and separated (probably foreground) from the Tornado Nebula. Four knots of emission are seen in the Brgamma line and at 6 and 20 cm. Together with the flat radio spectral index, we confirm that the Eye contains ionized gas, but that this is embedded within a dense molecular core. The spectral energy distribution can be modelled as a two-component blackbody + greybody, peaking at far-infrared wavelengths. The knots are ultracompact H II regions, and the core contains a luminous (similar to2 x 10(4) L-.), embedded, massive young stellar source. We also propose a geometrical model for the Eye to account for both its spectral energy distribution and its morphology.