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

D. C. Homan*, M. H. Cohen, T. Hovatta, K. Kellermann, Y. Y. Kovalev, M. L. Lister, A. Popkov, A. B. Pushkarev, E. Ros, T. Savolainen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

37 Citations (Scopus)
44 Downloads (Pure)

Abstract

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 ? rays, and we find a strong correlation between ?-ray luminosity and Doppler factor for the detected sources.

Original languageEnglish
Article number67
Number of pages23
JournalThe Astrophysical Journal
Volume923
Issue number1
DOIs
Publication statusPublished - 10 Dec 2021
MoE publication typeA1 Journal article-refereed

Keywords

  • ACTIVE GALACTIC NUCLEI
  • BL-LACERTAE OBJECTS
  • DIGITAL SKY SURVEY
  • TELESCOPE OPTICAL SPECTROSCOPY
  • SPECTRUM RADIO-SOURCES
  • EMISSION-LINE PROFILES
  • ENERGY GAMMA-RAYS
  • COMPLETE SAMPLE
  • DATA RELEASE
  • LAC OBJECTS

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