1 Introduction

The structural properties of "classical'' Fanaroff-Riley II radio sources (Fanaroff & Riley 1974) are usually described by a few basic parameters. The first one is the arm length ratio Q, which is defined as the ratio of the hotspot distances from the core in such a way that Q > 1 (Fig. 1). Alternatively, a similar parameter $\theta$ = (Q-1)/(Q+1) can be used (e.g. Paper I). The second parameter is the bending angle D which is the complement angle of the angle between the lines connecting the lobes to the core. The third symmetry parameter widely used is the flux ratio F of the two lobes. Together with other information of the sources, such as the relative prominence of the core ($P\rm _c$/$P\rm _{tot}$) and projected linear size (l), these symmetry parameters can be used to constrain the physical conditions in the sources and to test different unification schemes (e.g. Barthel 1989) that seek to explain the differences in source properties by different viewing angles (see e.g. Best et al. 1995).

The author is currently engaged in projects that require symmetry information for a sizable number of FR II radio sources for comparison with theoretical predictions. For this purpose a large database was created by searching the literature for high resolution radio maps and flux data from which the parameters Q, D, F, $P\rm _c$/$P\rm _{tot}$ and l could be extracted. This paper presents the database. In a forthcoming paper (Nilsson et al. 1998, Paper III) the data will be studied in the context of the kinematical double radio source models of Baryshev & Teerikorpi (1995), Paper I). Another possible application of the database is a comparison of the symmetry data to the slingshot simulations of Valtonen et al. (1994).