title: Coexisting conical bipolar and equatorial outflows from a high-mass protostar.
abstract: The BN/KL region in the Orion molecular cloud is an archetype for the study of the formation of stars much more massive than the Sun. This region contains luminous young stars and protostars but, like most star-forming regions, is difficult to study in detail because of the obscuring effects of dust and gas. Our basic expectations are shaped to some extent by the present theoretical picture of star formation, the cornerstone of which is that protostars accrete gas from rotating equatorial disks and shed angular momentum by ejecting gas in bipolar outflows. The main source of the outflow in the BN/KL region may be an object known as radio source I, which is commonly believed to be surrounded by a rotating disk of molecular material. Here we report high-resolution observations of silicon monoxide (SiO) and water maser emission from the gas surrounding source I. We show that within 60 AU of the source (about the size of the Solar System), the region is dominated by a conical bipolar outflow, rather than the expected disk. A slower outflow, close to the equatorial plane of the protostellar system, extends to radii of 1,000 AU.
authors.affiliation: Center for Astrophysics, Cambridge, Massachusetts 02138, USA. greenhill@cfa.harvard.edu
authors.forename: L J
authors.initials: LJ
authors.lastname: Greenhill
authors.forename: C R
authors.initials: CR
authors.lastname: Gwinn
authors.forename: C
authors.initials: C
authors.lastname: Schwartz
authors.forename: J M
authors.initials: JM
authors.lastname: Moran
authors.forename: P J
authors.initials: PJ
authors.lastname: Diamond
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D005740:Gases; D010087:Oxides / Q000032:analysis*; D017655:Silicon Compounds / Q000032:analysis*; D013057:Spectrum Analysis; D014867:Water
chemical_list: D005740:Gases; D010087:Oxides; D017655:Silicon Compounds; D014867:Water; C116473:silicon monoxide