Unveiling the disk-jet system in the massive (proto)star IRAS20126+4104


R. Cesaroni (1), M. Felli (1), T. Jenness (2), R. Neri (3), L. Olmi (4), M. Robberto (5,6), L. Testi (1,7), C.M. Walmsley (1)

(1) Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze, Italy

(2)Joint Astronomy Centre, 660 N. A'ohoku Place, Hilo, HI 96720, USA

(3) IRAM, 300 Rue de la Piscine, Domaine Universitaire, F-38406 St. Martin d'Heres Cedex, France

(4) LMT Project and FCRAO, University of Massachusetts, 630 L.G.R.C., Amherst, MA 01003, USA

(5) Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg

(6) Osservatorio Astronomico di Torino, Str. Osservatorio 20, I-10025 Pino Torinese, Italy

(7) Division of Mathematics, Physics and Astronomy, MS105-24, California Institute of Technology, Pasadena, CA 91125, USA


We present the results of line and continuum observations towards the source IRAS 20126+4104, performed at 1.3mm and 3.5mm with the Plateau de Bure interferometer, from 350um to 2mm with the James Clerk Maxwell telescope, and at 10 and 20um with the United Kingdom infrared telescope. The results fully confirm the findings of Cesaroni et al. (1997), namely that IRAS20126+4104 is a very young stellar object embedded in a dense, hot core and lying at the centre of a rotating disk. The bipolar jet imaged by Cesaroni et al. (1997) in the 2.122um H2 line is seen also in the SiO(2-1) transition, which allows to study the velocity field in the jet. A simple model is developed to obtain the inclination angle of the jet (and hence of the disk axis), which turns out to be almost perpendicular to the line of sight. By studying the diameter of the disk in different transitions and the corresponding line widths and peak velocities, one can demonstrate that the disk is Keplerian and collapsing, and thus compute the mass of the central object and the accretion luminosity. We show that if all the mass inducing the Keplerian rotation is concentrated in a single star, then this cannot be a ZAMS star, but more likely a massive protostar which derives its luminosity from accretion.

Mantained by: Leonardo Testi