Observations of the Orion Source I Disk and Outflow Interface

The Astrophysical Journal, vol. 889, pp. 155

Abstract

Abstract We imaged the continuum and molecular line emission from Orion Source I (SrcI) with up to 30 mas (12 au) resolution at 43, 99, 223, and 340 GHz in an attempt to probe the structure and chemistry of the circumstellar disk and bipolar outflow associated with this high-mass protostar. The continuum spectral index ranges from ∼2 along the midplane of the disk to ∼3 along the edges, consistent with dust that is optically thick in the midplane but becomes optically thin at the periphery. Salt (NaCl) emission is visible where the dust is optically thin; it provides a unique tracer of the velocity field within the disk. All other molecules that we have mapped—H2O, AlO, SiO, SiS, SO, and SO2—appear to originate primarily in the bipolar outflow. The base of the outflow is corotating with the disk. SiS shows a filamentary structure that is most prominent along the edges of the outflow. The molecular distributions suggest that Si and Al released from dust grains in the disk react with oxygen derived from H2O to form SiO and AlO, and with SO and SO2 to form SiS.

Authors 7

1. Melvyn C. H. Wright

   University of California, Berkeley

   Affiliation as printed

   Radio Astronomy Lab, University of California, 501 Campbell Hall, Berkeley, CA 94720-3441, USA

2. R. L. Plambeck

   University of California, Berkeley

   Affiliation as printed

   Radio Astronomy Lab, University of California, 501 Campbell Hall, Berkeley, CA 94720-3441, USA

3. Tomoya Hirota

   National Astronomical Observatory of Japan

   Affiliation as printed

   Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan

4. Adam G. Ginsburg

   National Radio Astronomy Observatory

   Affiliation as printed

   National Radio Astronomy Observatory, Charlottesville, VA 22903, USA

5. Brett A. McGuire

   National Radio Astronomy Observatory

   Affiliation as printed

   National Radio Astronomy Observatory, Charlottesville, VA 22903, USA

6. John Bally

   University of Colorado Boulder

   Affiliation as printed

   CASA, University of Colorado, 389-UCB, Boulder, CO 80309, USA

7. C. Goddi Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands