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MOJAVE. XIX. Brightness Temperatures and Intrinsic Properties of Blazar Jets

Homan, D. C. and Cohen, M. H. and Hovatta, T. and Kellermann, K. I. and Kovalev, Y. Y. and Lister, M. L. and Popkov, A. V. and Pushkarev, A. B. and Ros, E. and Savolainen, T. (2021) MOJAVE. XIX. Brightness Temperatures and Intrinsic Properties of Blazar Jets. Astrophysical Journal, 923 (1). Art. No. 67. ISSN 0004-637X. doi:10.3847/1538-4357/ac27af.

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We present multiepoch, parsec-scale core brightness temperature observations of 447 active galactic nucleus (AGN) jets from the MOJAVE and 2 cm Survey programs at 15 GHz from 1994 to 2019. The brightness temperature of each jet over time is characterized by its median value and variability. We find that the range of median brightness temperatures for AGN jets in our sample is much larger than the variations within individual jets, consistent with Doppler boosting being the primary difference between the brightness temperatures of jets in their median state. We combine the observed median brightness temperatures with apparent jet speed measurements to find the typical intrinsic Gaussian brightness temperature of 4.1( ± 0.6) × 10¹⁰ K, suggesting that jet cores are at or below equipartition between particle and magnetic field energy in their median state. We use this value to derive estimates for the Doppler factor for every source in our sample. For the 309 jets with both apparent speed and brightness temperature data, we estimate their Lorentz factors and viewing angles to the line of sight. Within the BL Lac optical class, we find that high-synchrotron-peaked BL Lacs have smaller Doppler factors, lower Lorentz factors, and larger angles to the line of sight than intermediate and low-synchrotron-peaked BL Lacs. We confirm that AGN jets with larger Doppler factors measured in their parsec-scale radio cores are more likely to be detected in γ rays, and we find a strong correlation between γ-ray luminosity and Doppler factor for the detected sources.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Homan, D. C.0000-0002-4431-0890
Cohen, M. H.0000-0002-8033-5972
Hovatta, T.0000-0002-2024-8199
Kellermann, K. I.0000-0002-0093-4917
Kovalev, Y. Y.0000-0001-9303-3263
Lister, M. L.0000-0003-1315-3412
Popkov, A. V.0000-0002-0739-700X
Pushkarev, A. B.0000-0002-9702-2307
Ros, E.0000-0001-9503-4892
Savolainen, T.0000-0001-6214-1085
Additional Information:© 2021. The American Astronomical Society. Received 2021 August 9; revised 2021 September 8; accepted 2021 September 9; published 2021 December 10. We thank Margo Aller, Alexander Plavin, and the other members of the MOJAVE team for helpful conversations and their other contributions that made this work possible. The MOJAVE project was supported by NASA-Fermi grants 80NSSC19K1579, NNX15AU76G and NNX12A087G. D.C.H. was supported by NSF grant AST-0707693. Y.Y.K. and A.B.P. were supported by the Russian Science Foundation grant 21-12-00241. A.V.P. was supported by the Russian Foundation for Basic Research grant 19-32-90140. T.H. was supported by the Academy of Finland projects 317383, 320085, and 322535. T.S. was partly supported by the Academy of Finland projects 274477 and 315721. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work made use of the Swinburne University of Technology software correlator (Deller et al. 2011), developed as part of the Australian Major National Research Facilities Program and operated under licence. This research has made use of data from the OVRO 40 m monitoring program Richards et al. (2011), which is supported in part by NASA grants NNX08AW31G, NNX11A043G, and NNX14AQ89G and NSF grants AST-0808050 and AST-1109911. This research has made use of NASA's Astrophysics Data System. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Facilities: VLBA - Very Long Baseline Array, OVRO:40 m - , NED - , ADS. -
Group:Astronomy Department
Funding AgencyGrant Number
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Active galaxies (17); Galaxy jets (601); Radio galaxies (1343); Quasars (1319); BL Lacertae objects (158); Surveys (1671)
Record Number:CaltechAUTHORS:20211213-518528000
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Official Citation:D. C. Homan et al 2021 ApJ 923 67
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112378
Deposited By: George Porter
Deposited On:13 Dec 2021 22:43
Last Modified:13 Dec 2021 22:43

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