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The NGC 1333 IRAS 4A protobinary was observed in the 1.3 cm and 6.9 mmcontinuum and the ammonia and SiO lines, with an angular resolution of about0.4 arcseconds. The continuum maps show the circumstellar structures of the twoprotostars, A1 and A2. The A1 system is brighter and more massive than the A2system. The ratio of mass, including dense gas and protostar, is about 6. Theproperties of the circumstellar disks and outflows suggest that A1 may beyounger than A2. The deflected part of the northeastern jet of A2 is bright inthe SiO line, and the distance between the brightest peak and deflection pointsuggests that the enhancement of SiO takes about 100 yr after the collisionwith a dense core. The ammonia maps show a small structure that seems to be apart of the obstructing core. The outflow properties were studied by comparinginterferometric maps of SiO, ammonia, formaldehyde, and HCN lines. Theiroverall structures agree well, suggesting that these species are excited by thesame mechanism. However, the intensity distributions show that SiO ischemically unique. SiO may be directly linked to the primary jet while theother species may be tracing the entrained ambient gas.

Radio Imaging of the NGC 1333 IRAS 4A Region: Envelope, Disks, and Outflows of a Protostellar Binary System