Timedependent radio fine structure of the quasar 3C 345.
Abstract
Results are reported for VLBI observations of 3C 345 at a wavelength of 3.8 cm with left circular polarization. Sixteen sets of correlated flux densities and three sets of closure phases were obtained from observations made over a threeyear period with six independent interferometers formed from up to four antennas. The mathematical models employed to represent the radio brightness distribution of the source are described, and the data are analyzed on the basis of a twocomponent model. The results show that the compact source in 3C 345 consists of two components whose separation increased by about 0.3 milliarcsec over the observational period, that the smaller and weaker component is to the east and south of the larger and stronger one, and that the apparent expansion velocity would be about 2.5c for a redshift of 0.6, a Hubble constant of 60 km/sec per Mpc, and a deceleration parameter of unity. It is concluded that these findings are difficult to reconcile with the 'Christmas tree' model for the apparent change of separation with time over any given series of observations.
 Publication:

The Astronomical Journal
 Pub Date:
 November 1976
 DOI:
 10.1086/111972
 Bibcode:
 1976AJ.....81..933W
 Keywords:

 Fine Structure;
 Quasars;
 Radio Sources (Astronomy);
 Angular Distribution;
 Brightness;
 Circular Polarization;
 Flux Density;
 Interferometry;
 Mathematical Models;
 Time Dependence;
 Astrophysics