Periodic structure in the megaparsec-scale jet of pks 0637-752

L. E H Godfrey*, J. E J Lovell, S. Burke-Spolaor, R. Ekers, G. V. Bicknell, M. Birkinshaw, D. M. Worrall, D. L. Jauncey, D. A. Schwartz, H. L. Marshall, J. Gelbord, E. S. Perlman, M. Georganopoulos

*Corresponding author for this work

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

23 Citations (Scopus)

Abstract

We present 18GHz Australia Telescope Compact Array imaging of the megaparsec-scale quasar jet PKS 0637-752 with angular resolution 058. We draw attention to a spectacular train of quasi-periodic knots along the inner 11″ of the jet, with average separation 1.1 arcsec (7.6kpc projected). We consider two classes of model to explain the periodic knots: those that involve a static pattern through which the jet plasma travels (e.g., stationary shocks) and those that involve modulation of the jet engine. Interpreting the knots as re-confinement shocks implies the jet kinetic power Q jet 10 46ergs-1, but the constant knot separation along the jet is not expected in a realistic external density profile. For models involving modulation of the jet engine, we find that the required modulation period is 2 × 103 yr < τ < 3 × 105 yr. The lower end of this range is applicable if the jet remains highly relativistic on kiloparsec scales, as implied by the IC/CMB model of jet X-ray emission. We suggest that the periodic jet structure in PKS 0637-752 may be analogous to the quasi-periodic jet modulation seen in the microquasar GRS 1915+105, believed to result from limit cycle behavior in an unstable accretion disk. If variations in the accretion rate are driven by a binary black hole, the predicted orbital radius is 0.7 pc ≲ a ≲ 30 pc, which corresponds to a maximum angular separation of 0.1-5 mas. © © 2012. The American Astronomical Society. All rights reserved.

Original languageEnglish
Article numberL27
Number of pages5
JournalAstrophysical Journal Letters
Volume758
Issue number2
DOIs
Publication statusPublished - 20 Oct 2012

Keywords

  • galaxies: active
  • galaxies: jets
  • quasars: individual (PKS0637-752)
  • ACTIVE GALACTIC NUCLEI
  • BINARY BLACK-HOLE
  • II RADIO-SOURCES
  • HUBBLE-SPACE-TELESCOPE
  • X-RAY-EMISSION
  • ACCRETION DISK
  • RELATIVISTIC JETS
  • GALAXY
  • INSTABILITY
  • CHANDRA

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