Kinematics of the parsec-scale radio jet in 3C 48

T. An*, X. Y. Hong, M. J. Hardcastle, D. M. Worrall, T. Venturi, T. J. Pearson, Z. -Q. Shen, W. Zhao, W. X. Feng

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

21 Citations (Scopus)

Abstract

We present results on the compact steep-spectrum quasar 3C 48 from observations with the Very Long Baseline Array (VLBA), the Multi-Element Radio Linked Interferometer Network (MERLIN) and the European Very long baseline interferometry (VLBI) Network (EVN) at multiple radio frequencies. In the 1.5-GHz VLBI images, the radio jet is characterized by a series of bright knots. The active nucleus is embedded in the southernmost VLBI component A, which is further resolved into two sub-components A1 and A2 at 4.8 and 8.3 GHz, respectively. A1 shows a flat spectrum and A2 shows a steep spectrum. The most strongly polarized VLBI components are located at component C similar to 0.25 arcsec north of the core, where the jet starts to bend to the north-east. The polarization angles at C show gradual changes across the jet width at all observed frequencies, indicative of a gradient in the emission-weighted intrinsic polarization angle across the jet and possibly a systematic gradient in the rotation measure; moreover, the percentage of polarization increases near the curvature at C, likely consistent with the presence of a local jet-interstellar-medium interaction and/or changing magnetic-field directions. The hot spot B shows a higher rotation measure, and has no detected proper motion. These facts provide some evidence for a stationary shock in the vicinity of B. Comparison of the present VLBI observations with those made 8.43 yr ago suggests a significant northward motion for A2 with an apparent transverse velocity beta(app) = 3.7 +/- 0.4c. The apparent superluminal motion suggests that the relativistic jet plasma moves at a velocity of greater than or similar to 0.96c if the jet is viewed at an inclination angle less than 20 degrees. A simple precessing jet model and a hydrodynamical isothermal jet model with helical-mode Kelvin-Helmholtz instabilities are used to fit the oscillatory jet trajectory of 3C 48 defined by the bright knots.

Original languageEnglish
Pages (from-to)87-104
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Volume402
Issue number1
DOIs
Publication statusPublished - 11 Feb 2010

Keywords

  • galaxies: active
  • galaxies: jets
  • galaxies: kinematics and dynamics
  • quasars: individual: 3C 48
  • COMPACT STEEP-SPECTRUM
  • ACTIVE GALACTIC NUCLEI
  • 3C-48 HOST GALAXY
  • POLARIMETRIC OBSERVATIONS
  • RELATIVISTIC JETS
  • KILOPARSEC-SCALE
  • FARADAY-ROTATION
  • QUASAR 3C-48
  • X-RAY
  • 5 GHZ

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