LINEAR POLARIZATION AND TOTAL FLUX DENSITY OF SILICON MONOXIDE MASERS AND ACTIVE EXTRAGALACTIC OBJECTS AT MILLIMETER WAVELENGTHS
In order to investigate the linear polarization properties of millimeter-wave radio sources, a polarimeter was constructed for use on the Five College Radio Astronomy Observatory 14m telescope. Linear polarization and total flux density observations of SiO masers (at 43 and 86 GHz) and active extragalactic objects (at 87 GHz) were conducted, resulting in the first multitransitional study of SiO maser polarization, and the first rapid time sampling (days to weeks) of extragalactic source polarization at millimeter wavelengths.
Measurements of sixteen active extragalactic objects were made over a seven month period; the millimeter polarization variations are qualitatively similar to those seen at centimeter wavelengths. Two rapid and closely spaced outbursts with rise timescales of about one week were seen in OJ287. For 3C345, observed variations in the polarization may indicate the propagation of radiating particles along a jet.
The 87 GHz total flux density measurements are combined with simultaneous centimeter-wave data to derive broadband spectra, which are compared to the predictions of a relativistic Maxwellian electron distribution model and a power law electron inhomogeneous jet model. A relativistic blast wave model for source variability incorporating a Maxwellian particle distribution is discussed.
Analysis of polarization in up to four masing transitions of SiO in late-type stars and the Orion source indicates that emission from the same rotational transition in different vibrational states often arises in the same volume of gas, but that masers in different rotational transitions within the same vibrational state arise in different regions. An inverse correlation is found between maser fractional polarization and stellar envelope expansion velocity.
A model is developed to explain the observed polarization and total intensity profiles of the Orion masers. The profiles can be simply accounted for by maser emission from a rotating and expanding disk, with an azimuthally dependent magnetic field orientation.