Maurice Cohen

TL;DR: In this paper, the structure and evolution of parsec-scale jet phenomena associated with bright radio-loud active galaxies in the northern sky were surveyed using a long-term program (MOJAVE: Monitoring of Jets in active galactic nuclei with VLBA Experiments).

TL;DR: In this paper, the structure and evolution of parsec-scale jet phenomena associated with bright radio-loud active galaxies in the northern sky were surveyed using a long-term program (MOJAVE: Monitoring of Jets in AGN with VLBA Experiments).

TL;DR: In this paper, the authors used the Very Long Baseline Array at 15 GHz to image the structure of 132 strong compact active galactic nuclei (AGNs) and quasars with a resolution better than 1 mas and a dynamic range typically exceeding 1000:1.

Abstract: We have used the VLBA at 15 GHz to image the structure of 132 strong compact AGN and quasars with a resolution better than one milliarcsecond and a dynamic range typically exceeding 1000 to 1. These observations were made as part of a program to investigate the sub-parsec structure of quasars and AGN and to study the changes in their structure with time. Many of the sources included in our study, particularly those located south of +35 degrees, have not been previously imaged with milliarcsecond resolution. Each of the sources has been observed at multiple epochs. In this paper we show images of each of the 132 sources which we have observed. For each source we present data at the epoch which had the best quality data. The milliarcsecond jets generally appear one-sided but two-sided structure is often found in lower luminosity radio galaxies and in high luminosity quasars with gigahertz peaked spectra. Usually the structure is unresolved along the direction perpendicular to the jet, but a few sources have broad plumes. In some low luminosity radio galaxies, the structure appears more symmetric at 2 cm than at long wavelengths. The apparent long wavelength symmetry in these sources is probably due to absorption by intervening material. A few sources contain only a single component with any secondary feature at least a thousand times weaker. We find no obvious correlation of radio morphology and the detection of gamma-ray emission by EGRET.

TL;DR: In this paper, maps of the radio structure of 3C273 show that it expanded with an apparent velocity 10 times the speed of light from mid-1977 to at least mid-1980.