B2 1144+35: A giant low-power radio galaxy with superluminal motion

We report on centimeter VLA and VLBI observations of the giant, low-power r adio galaxy B2 1144+35. These observations are sensitive to structures on s cales of from less than 1 pc to greater than 1 Mpc. Diffuse steep-spectrum lobes on the megaparsec scale are consistent with an age of similar to 10(8 ) yr. On the parsec scale, a complex jet component is seen to move away fro m the center of activity with an apparent velocity of 2.7 h(50)(-1) c. It s hows a central spine-shear layer morphology. A faint parsec-scale counterje t is detected, and an intrinsic jet velocity of 0.95c and an angle to the l ine of sight of 25 degrees are derived, consistent with an intrinsically sy mmetric ejection. The central spine in the parsec-scale jet is expected to move at a higher velocity, and a Lorentz factor of gamma similar to 15 has been estimated near the core. The age of this inner VLBI structure is simil ar to 300 yr. Assuming a constant angle to the line of sight, the jet veloc ity is found to decrease from 0.95c at 20 mas (32 pc on the plane of the sk y) to 0.02c at 15 " (24 kpc on the plane of the sky). These findings lend c redence to the claim that (1) even the jets of low-power radio galaxies sta rt out relativistic and (2) these jets are decelerated to subrelativistic v elocities by the time they reach kiloparsec scales.