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Radio source I in the Orion KL region (our target) is the closest known massive YSO. Compact regions of high brightness, non-thermal (maser) emission pepper the bulk flows around source I. Observations of the maser emission with the Very Long Baseline Array (VLBA) and Very Large Array (VLA) facilities, enable us to map the structure and 3-D dynamics of the circumstellar gas with great precision (up to ~0.3 AU and ~1 km -1). We assembled a 22-month time-series of VLBA images which provide a movie of "a star in formation". The movie graphically shows dense molecular material at radii of 20-70 AU being driven at speeds of ~25 km -1 from the surface of an accretion disk to form a rotating funnel-like bipolar flow. This is a first for a high-mass young star.
In addition to the VLBA time-series images, the observations of different maser transitions from different SiO isotopologues with the VLA enabled constrained radiative transfer modelling, which allowed us to sample circumstellar gas with different physical conditions at radii 10-1000 AU from Source I.
Finally, we have also investigated the chemistry and physical conditions of the large-scale molecular material in the Orion BN/KL region with a spectral survey conducted at 7mm with the single-dish Green Bank Telescope (GBT).

The analysis of the entire dataset provides the most detailed picture yet of molecular material close to an embedded massive protostar and the most detailed evidence that massive star formation occurs via disk-mediated accretion. Under the assumption that Source I represents a common stage in the evolution of massive protostars, interpretation of the 3-D dynamical evolution of Source I provides unique constraints on models of massive star formation.

KALYPSO Data to Education

The movie will be the cornerstone of a CD-ROM and web-based education program, developed with the SAO Science Education Department and directed to both students and the general public, via schools, planetariums and museums. These materials will also be available for inclusion in education programs on star formation, the recycling of "star stuff", and the nature of scientific investigation.

Summary of Observations

Observation Date Telescope Resolution (milliarcseconds) Notes
SiO v=0
28 Aug 1999 VLA 50 Reduced
9 Jan 2001 VLA 200 Reduced (?)
1 Apr 2002 VLA 30 Reduced
15 Apr 2006 VLA 30 Reduced (?)
2 Feb 2008 VLA 200 Reduced
29SiO and 30SiO v=0
28 Aug 1999 VLA 50 Only 29SiO observed: reduced
1 Jan 2000 VLA 200 Reduced (30SiO undetected)
2 Feb 2008 VLA 200 Simultaneous imaging of
29SiO and 30SiO: reduced
SiO v=1 and v=2
9 July 1995 to
15 Sep 1995
VLBA 0.3 3 epochs: reduced (?)
30 Jun 2000 VLBA 0.3 19 epochs: reduced
16 epochs: reduction pending
2 epochs: failed
24 Jan 2001 VLA 50 reduced
Spectral Survey at 7mm
9 Nov 2007 GBT 16000 Published

KALYPSO Data Archive

We will make public all calibrated data, spectral-line image cubes, and moment maps (e.g., mean velocity as a function of position) for each epoch, via the web.

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Modified on October 19, 2007