Nature of the Kleinmann - Low and Becklin-Neugebauer infrared sources

An analysis is made of polarimetric observations of the Becklin-Neugebauer (BN) point infrared source, which is located inside the extended Kleinman-Low (KL) object. The BN radiation becomes polarized when it passes through an ensemble of absorbing, aspherical, aligned grains concentrated at the KL periphery. If the BN object is regarded as a protostar and the KL object as an ''early'' cluster of protostars (a contracting cloud of gas and dust that emits as radiation the gravitational energy released in the collapse), then supersonic accretion will occur at the KL periphery, with the gas and dust infalling at the same velocity. Because of the influence of radiation pressure, the dust grains will be incapable of acquiring a significant relative velocity through frequent collisions with gas molecules. As a result the grains cannot be effectively aligned at the KL periphery, and the BN radiation ought to be unpolarized. An alternative interpretation presupposes an optically thick dust cloud containing hot O and B stars whose energy is reradiated by the cloud in the infrared range. Dust repelled by radiation pressure will traverse a region of low gas density n sub(H) is approximately less than 300 cm-3 (a barometric density law is assumed) and will become aligned through collisions. An ensemble of grains aligned in this manner will produce significant linear polarization in radiation directed toward the observer only in the presence of a transverse magnetic field whose strength is of the same order as the interstellar field. The polarimetric data yield an estimate M sub(KL) is approximately equal to 104Msub(Sun) for the mass of the KL nebula