Blazar host galaxies

Wright, Susan Clare (1998) Blazar host galaxies. University of Southampton, Doctoral Thesis.

Abstract

Unified schemes for radio-loud active galactic nuclei (AGN) propose that the different observed classes arise from the same basic phenomenon. The luminosity and orientation of the relativistic jet then determines the type of object seen. The luminosity division has been suggested in which low luminosity FRI radio galaxies are unified with BL Lacertae objects, and high luminosity FRII radio galaxies are unified with both non-OVV and OVV quasars. Orientation independent parameters, such as extended radio power, cluster environment and host galaxy properties, can be used to test the validity of the proposed schemes.

Optical and near-infrared data were obtained of twelve blazars, nine BL Lacertae objects (BL Lacs) and three Optically Violently Variable (OVV) quasars, in order to investigate the magnitudes and morphologies of their host galaxies. The results from the analyses conducted have been presented in the two papers Wright, McHardy & Abraham (1997a, MNRAS, accepted) and Wright et al. (1997b, MNRAS accepted). One- and two-dimensional numerical modelling routines were developed to complete the analysis of the data. Host galaxies were resolved in all three of the OVV quasars but a morphology was derived for only one object, PKS 7036+017. From modelling, the emission of the host in PKS 0736+017 was found to be best described by an elliptical morphology. For the BL Lacs, host galaxies were resolved in five of the sources. Morphological classification was not possible for the majority of the data. However tentative morphologies were determined for two sources; B2 0752+258 appears to be best described by a disc model, while S4 0954+65 appears to be an elliptical galaxy. The host galaxy of TEX 0836+182 appears elongated, which together with the blue colour derived, is probably indicative of interaction in this source. Comparison of the host galaxy properties derived for the OVV quasars and BL Lacs in the present study with those of the respective putative parent populations show them to be similar, adding weight to the unification scenario. However, the number of objects is small and larger samples are required to test unification more rigorously.

This record has no associated files available for download.

Contributors

Download statistics