6 Conclusions and future plans

We have presented the results of VLBA observations of the most compact sources ( $LAS \mathrel{<\kern-1.0em\lower0.9ex\hbox{$\sim$ }}1\arcsec$) in the B3-VLBA CSS sample from Paper I.

The large majority of sources have a "double type'' structure, with sizes ranging from $\sim$200 h^-1 pc to $\sim$1 h^-1 kpc. Together with the VLA data on the large size sources and with EVN & MERLIN data, presented in Dallacasa et al. (2002, Paper III) on intermediate size sources, we have at the end a new determination of the Linear Size distribution in the range $\sim$0.2  h^-1 < LS (kpc) <20 h^-1. This is an important piece of information to test the source evolution model. We will discuss it in a separate paper.

The sources presented here have just been observed with the VLBA at higher frequencies, with the aim of detecting the radio core, therefore obtaining an unambiguous classification, and of studying the structure of the hot spots. The results will be presented in a forthcoming paper.

Acknowledgements

This work has been partially supported by the Italian MURST under grant COFIN-2001-02-8773. The VLBA is operated by the U.S. National Radio Astronomy Observatory which is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.