The Nucleus-Host Galaxy Connection in Radio-Loud AGN

  • Matthew O’Dowd
  • C. Megan Urry
  • Riccardo Scarpa
  • Renato Falomo
  • Joseph E. Pesce
  • Aldo Treves


We studied a moderate-redshift (0.15 < z < 0.5) sample of H ST 1- imaged radio-loud (RL) AGN spanning a large range of nuclear power. The total sample consists of 57 objects, divided into sub-samples of 40 BL Lac objects and 17 RL quasars. Essentially all the AGN nuclei lie in luminous elliptical galaxies (Es), which follow the Kormendy relation for normal Es. The host galaxies occupy a narrow range of ~1 magnitude, compared to >5 orders of magnitude in nuclear power, and the two sub-samples have indistinguishable luminosity-redshift distributions over the redshift range 0.15 < z < 0.5. No correlation between nuclear brightness (corrected for beaming) and galaxy luminosity is seen. Assuming the host galaxy-black hole mass correlation for local galaxies, the derived Eddington ratios range from 2×10-4 for low-power AGN (BL Lac objects) to 2×10-1 for high power AGN (RL quasars). This implies a considerable difference in rate of fueling. At least for RL AGN, the host galaxy properties appear to have no close connection to the power of the jet.


Black Hole Active Galactic Nucleus Radio Galaxy Black Hole Mass Host Galaxy 
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Copyright information

© Springer Science+Business Media New York 2001

Authors and Affiliations

  • Matthew O’Dowd
    • 1
    • 2
  • C. Megan Urry
    • 2
  • Riccardo Scarpa
    • 3
  • Renato Falomo
    • 4
  • Joseph E. Pesce
    • 5
  • Aldo Treves
    • 6
  1. 1.School of PhysicsUniversity of MelbourneParkvilleAustralia
  2. 2.Space Telescope Science InstituteBaltimoreUSA
  3. 3.European Southern ObservatorySantiagoChile
  4. 4.Osservatorio Astronomico di PadovaPadovaItaly
  5. 5.Department of AstronomyPennsylvania State UniversityUniversity ParkUSA
  6. 6.Universita’ dell’InsubriaComoItaly

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