ar X iv : a st ro - p h / 99 04 06 8 v 1 6 A pr 1 99 9 B 2 1144 + 35 : A Giant Low Power Radio Galaxy with Superluminal Motion

We report on centimeter VLA and VLBI observations of the giant, low power radio galaxy 1144+35. These observations are sensitive to structures on scales from less than 1 parsec to greater than 1 megaparsec. Diffuse steep spectrum lobes on the megaparsec scale are consistent with an age of ∼ 10 years. On the parsec scale, a complex jet component is seen to move away from the center of activity with an apparent velocity 2.7 h 50 c. It shows a central spine – shear layer morphology. A faint parsec scale counterjet is detected and an intrinsic jet velocity of 0.95 c and angle to the line of sight of 25◦ are derived, consistent with an intrinsically symmetric ejection. The central spine in the parsec scale jet is expected to move at a higher velocity and a Lorentz factor γ ∼ 15 has been estimated near the core. The age of this inner VLBI structure is ∼ 300 years. Assuming a constant angle to the line-of-sight, the jet velocity is found to decrease from 0.95 c at 20 mas (32 pc on the plane of the sky) to 0.02 c at 15 arcsec (24 kpc on the plane of the sky). These findings lend credence to the claim that (1) even the jets of low power radio galaxies start out relativistic; and (2) these jets are decelerated to subrelativistic velocities by the time they reach kiloparsec scales. Subject headings: radio continuum: galaxies — galaxies: individual (B1144+35) — galaxies: jets — galaxies: nuclei Dipartimento di Fisica, Universita’ di Bologna,via B.Pichat 6/2, 40127 Bologna, Italy Istituto di Radioastronomia del CNR, via Gobetti 101, 40129 Bologna, Italy National Radio Astronomy Observatory, P.O. Box 0, Socorro NM 87801, USA National Radio Astronomy Observatory, 520 Edgemont Rd, Charlottesville VA 22903-2475, USA Instituto de Astrofisica de Andalucia, CSIC, Apdo 3004, 18080 Granada, Spain