Relativistic outflow drives γ-ray emission in 3C 345
Abstract
Aims: On the basis of the first 20 months of Fermi-LAT data and optical monitoring, the quasar 3C 345 has been identified as a γ-ray emitter. We investigate whether there is a connection between the γ-ray and optical variability of 3C 345 and the properties of its parsec-scale radio emission.
Methods: We combined the Fermi-LAT data of 3C 345, covering an energy range of 0.1-300 GeV, with 32 Very Long Baseline Array observations of the object made at 43.2 GHz in the period of January 2008-March 2010.
Results: The VLBA data reveal the morphology and kinematics of the flow on scales of up to ≈5 milliarcseconds (deprojected linear distances of 380 parsecs). The brightness temperature, Tb(r), measured along the jet first decreases with distance ∝ r-(0.95 ± 0.69) and later exhibits a break at ≈ 0.3 milliarcseconds (mas), with Tb(r) ∝ r-(4.11 ± 0.85) at larger separations. Variations in the γ-ray, optical, and parsec-scale radio emission display a similar long-term trend that persists during the entire VLBA monitoring period. The γ-ray and optical variations on shorter timescales are related to structural changes in the jet on scales of ≈ 0.3 mas ( ≈ 23 parsecs, deprojected), with the γ-ray and optical flares possibly being related to the evolution of four distinct superluminal components identified in the flow.
Conclusions: The observations indicate that both the quiescent and flaring components of the γ-ray emission are produced in a region of the jet that extends up to ~23 pc. This region may correspond to the Compton-loss dominated zone of the flow and its large extent may favor the synchrotron self-Compton mechanism for γ-ray production in the relativistic jet of the quasar 3C 345.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- January 2012
- DOI:
- 10.1051/0004-6361/201117705
- arXiv:
- arXiv:1111.2045
- Bibcode:
- 2012A&A...537A..70S
- Keywords:
-
- galaxies: jets;
- galaxies: active;
- radio continuum: galaxies;
- gamma rays: galaxies;
- Galaxy: nucleus;
- galaxies: individual: 3C 345;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 10 pages, 6 figures, 2 tables, accepted for publication in Astronomy &