The first Caltech-Jodrell Bank VLBI survey

Citation

Xu, Wenge (1995) The first Caltech-Jodrell Bank VLBI survey. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/k8f8-gn20. https://resolver.caltech.edu/CaltechETD:etd-10262007-132906

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. This thesis presents the author's major contributions to the first Caltech-Jodrell Bank VLBI survey (CJ1). It demonstrates convincingly that the VLBI snapshot technique is a reliable and highly efficient method of making images of large samples of objects. The CJ1 sample consists of 135 objects with 1.3 Jy > [...] GHz [...] 0.7 Jy, [...](1950) [...] 35° and [...] > 10°. The combination of the CJ1 sample with the Pearson-Readhead sample provides a complete, flux density limited sample of 200 objects with [...] GHZ [...] 0.7 Jy, [...](1950) [...] 35° and [...] > 10° for which all of the objects accessible to Mark II VLBI have been mapped at both 5 GHz and 1.6 GHz. In this thesis we present the 5 GHz VLBI observations from the CJ1 survey and follow-up observations of 8 compact symmetric objects (CSO) or CSO candidates at 8.4 GHz. In addition, we present 5 GHz MERLIN observations of 20 objects and 1.4 GHz VLA observations of 92 objects in the CJ1+PR sample. The VLA maps, together with L band (1.3-1.7 GHz) maps available in the literature, provide a complete set of VLA maps for the CJ1+PR sample. Furthermore, we present new redshifts, optical counterparts and optical polarimetry measurements of the objects in the CJ1 sample. Based on morphological attributes on scales < 5 kpc and [...] 5 kpc, we identify six physically distinct classes in the CJ1+PR sample, one of which is the CSO class. Identification of CSO's may have a profound impact on our understanding of AGN. Detailed study of one archetypal CSO, 2352+495, has demonstrated that the CSO's are likely a class of short-lived powerful galaxies. We have confirmed the bimodal distribution of the misalignment angle and identified that the peak near 90° is contributed by a group of objects with high optical polarization, high fractional core flux, high radio variability and flat radio spectrum. All of these are symptoms of relativistic beaming. The mean angular sizes of the CJ1+PR objects show only slight dependence on redshift, contrary to the finding by Kellermann. However, our results show that the angular size distributions of objects with z < 0.1 and those with z > 0.1 are significantly different. This may indicate an evolutionary effect.

Thesis Files