Outflows from the high-mass protostars NGC 7538 IRS1/2 observed with bispectrum speckle interferometry. Signatures of flow precession
Abstract
Context.
Aims.We investigate the near-infrared morphology of the source to clarify the relations among the various axes.
Methods.K'-band bispectrum speckle interferometry was performed at two 6-meter-class telescopes - the BTA 6 m telescope and the 6.5 m MMT. Complementary IRAC images from the Spitzer Space Telescope Archive were used to relate the structures detected with the outflow at larger scales.
Results.High-dynamic range images show fan-shaped outflow structure in which we detect 18 stars and several blobs of diffuse emission. We interpret the misalignment of various outflow axes in the context of a disk precession model, including numerical hydrodynamic simulations of the molecular emission. The precession period is ~280 years and its half-opening angle is ~40°. A possible triggering mechanism is non-coplanar tidal interaction of an (undiscovered) close companion with the circumbinary protostellar disk. Our observations resolve the nearby massive protostar
Conclusions.Indications of outflow precession have been discovered to date in a number of massive protostars, all with large precession angles (~20-45°). This might explain the difference between the outflow widths in low- and high-mass stars and add support to a common collimation mechanism.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 2006
- DOI:
- 10.1051/0004-6361:20065068
- arXiv:
- arXiv:astro-ph/0604328
- Bibcode:
- 2006A&A...455..521K
- Keywords:
-
- stars: formation;
- stars: individual: NGC 7538 IRS1;
- stars: individual: NGC 7538 IRS2;
- techniques: interferometric;
- stars: winds;
- outflows;
- hydrodynamics;
- Astrophysics
- E-Print:
- 20 pages