High-Resolution VSOP Imaging of the Southern Blazar PKS 1921-293 at 1.6 GHz

We present a high-resolution 1.6 GHz VSOP image of the southern blazar PKS 1921-293. The image shows a typical core-jet morphology, consistent with ground-based VLBI images. However, the addition of data from the space antenna has greatly improved the angular resolution (especially along the north-south direction for this source), thus allowing us to clearly identify the core. Model fitting has revealed an inner jet component of ∼1.5 mas north of the core. This jet feature may be moving on a common curved path connecting the jet within a few parsecs to the 10-parsec-scale jet. The compact core has a brightness temperature of 2.6 x 10 12 K (in the rest frame of the quasar), an indication of relativistic beaming. We analyzed the source in terms of three models involving the inverse Compton catastrophe, an inhomogeneous relativistic jet, and the equipartition of energy between the radiating particles and the magnetic field. Our analysis of this γ-ray-quiet blazar shows no preference to any particular one of these models.