Radio structure of the blazar 1156+295 with sub-pc resolution

Abstract

1156+295 is a flat-spectrum quasar which is loud at radio and gamma-ray. Previous observations of the source revealed a radio morphology on pc to kpc scales consistent with a helical jet model. In our present research, this source was observed with the VLBA at 86, 43 and 15 GHz on four epochs from 10 May 2003 to 13 March 2005 aiming at studying the structure of the innermost jet in order to understand the relation between the helical structure and the astrophysical processes in the central engine. A core-jet structure with six jet components is identified. The apparent transverse velocities of the six jet components derived from proper motion measurements are in the range between 3.6 c and 11.6 c. The overall jet shape shows oscillatory morphology with multiple curvatures on pc scales which might be indicative of a helical pattern. Models of helical jet are discussed on the basis of both Kelvin-Helmholtz (K-H) instability and jet precession. The K-H instability model shows better agreement with the observed data. The overall radio structure on the scale from sub-pc to kpc appears to be fitted with a hydrodynamic model with the fundamental helical mode in Kelvin-Helmholtz (K-H) instability. This helical mode with an initial characteristic wavelength of 0.2 pc is excited at the base of the jet on the scale of 0.005 pc (or 1000R_s, the typical size of the broad line region for a super massive black hole of $4.3\times 10^8{M}_{\odot }$). A presessing jet model can also fit the observed jet structure on the scale between 10 pc and 300 pc. However, additional astrophysical processes may be required for the presessing jet model in order to explain the bendings on the inner jet structure (1 to 10 pc) and re-collimation of the large scale jet outflow (>300 pc).

18 pages, 10 figures, accepted by A&A

References in corpus (3)

• A Global 86GHz VLBI Survey of Compact Radio Sources
• Kinematics of the parsec-scale radio jet in 3C48
• Serendipitous VLBI detection of rapid, large-amplitude, intraday variability in QSO 1156+295

Cited by in corpus (16)

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• The connection between the parsec-scale radio jet and gamma-ray flares in the blazar 1156+295
• Kinematics of the Compact Symmetric Object OQ 208 revisited
• Parsec-scale jet properties of the quasar PG 1302$-$102
• Constraining the radio jet proper motion of the high-redshift quasar J2134-0419 at z=4.3
• Fast jet proper motion discovered in a blazar at z = 4.72
• Two-year monitoring of intra-day variability of quasar 1156+295 at 4.8 GHz
• The parsec-scale jet of the neutrino-emitting blazar TXS~0506+056
• Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron IV. The quasar 3C 345 at 18 cm: Magnetic field structure and brightness temperature
• Interferometric Monitoring of Gamma-ray Bright AGNs: Measuring the Magnetic Field Strength of 4C +29.45
• The Most Compact Bright Radio-loud AGN -- II. VLBA Observations of Ten Sources at 43 and 86~GHz
• Multi-scale Radio and X-ray Structure of the High-redshift Quasar PMN J0909+0354
• Parsec-scale evolution of the gigahertz-peaked spectrum quasar PKS 0858-279
• Broad band flux-density monitoring of radio sources with the Onsala twin telescopes