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Title: BLACK HOLE SPIN AND THE RADIO LOUD/QUIET DICHOTOMY OF ACTIVE GALACTIC NUCLEI

Abstract

Radio loud active galactic nuclei (AGNs) are on average 1000 times brighter in the radio band compared to radio quiet AGNs. We investigate whether this radio loud/quiet dichotomy can be due to differences in the spin of the central black holes (BHs) that power the radio-emitting jets. Using general relativistic magnetohydrodynamic simulations, we construct steady state axisymmetric numerical models for a wide range of BH spins (dimensionless spin parameter 0.1 <= a <= 0.9999) and a variety of jet geometries. We assume that the total magnetic flux through the BH horizon at radius r{sub H}(a) is held constant. If the BH is surrounded by a thin accretion disk, we find that the total BH power output depends approximately quadratically on the angular frequency of the hole, P {proportional_to} OMEGA{sup 2}{sub H} {proportional_to} (a/r{sub H}){sup 2}. We conclude that, in this scenario, differences in the BH spin can produce power variations of only a few tens at most. However, if the disk is thick such that the jet subtends a narrow solid angle around the polar axis, then the power dependence becomes much steeper, P {proportional_to} OMEGA{sup 4}{sub H} or even {proportional_to}OMEGA{sup 6}{sub H}. Power variations of 1000 are then possiblemore » for realistic BH spin distributions. We derive an analytic solution that accurately reproduces the steeper scaling of jet power with OMEGA{sub H} and we provide a numerical fitting formula that reproduces all our simulation results. We discuss other physical effects that might contribute to the observed radio loud/quiet dichotomy of AGNs.« less

Authors:
;  [1]
  1. Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
Publication Date:
OSTI Identifier:
21394392
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 711; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/711/1/50; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ANALYTICAL SOLUTION; AXIAL SYMMETRY; BLACK HOLES; GALAXIES; GALAXY NUCLEI; GEOMETRY; MAGNETIC FLUX; MAGNETOHYDRODYNAMICS; QUASARS; RELATIVISTIC RANGE; SIMULATION; SPIN; STEADY-STATE CONDITIONS; ANGULAR MOMENTUM; COSMIC RADIO SOURCES; ENERGY RANGE; FLUID MECHANICS; HYDRODYNAMICS; MATHEMATICAL SOLUTIONS; MATHEMATICS; MECHANICS; PARTICLE PROPERTIES; SYMMETRY

Citation Formats

Tchekhovskoy, Alexander, Narayan, Ramesh, and McKinney, Jonathan C., E-mail: atchekho@cfa.harvard.ed, E-mail: rnarayan@cfa.harvard.ed, E-mail: jmckinne@stanford.ed. BLACK HOLE SPIN AND THE RADIO LOUD/QUIET DICHOTOMY OF ACTIVE GALACTIC NUCLEI. United States: N. p., 2010. Web. doi:10.1088/0004-637X/711/1/50.
Tchekhovskoy, Alexander, Narayan, Ramesh, & McKinney, Jonathan C., E-mail: atchekho@cfa.harvard.ed, E-mail: rnarayan@cfa.harvard.ed, E-mail: jmckinne@stanford.ed. BLACK HOLE SPIN AND THE RADIO LOUD/QUIET DICHOTOMY OF ACTIVE GALACTIC NUCLEI. United States. https://doi.org/10.1088/0004-637X/711/1/50
Tchekhovskoy, Alexander, Narayan, Ramesh, and McKinney, Jonathan C., E-mail: atchekho@cfa.harvard.ed, E-mail: rnarayan@cfa.harvard.ed, E-mail: jmckinne@stanford.ed. 2010. "BLACK HOLE SPIN AND THE RADIO LOUD/QUIET DICHOTOMY OF ACTIVE GALACTIC NUCLEI". United States. https://doi.org/10.1088/0004-637X/711/1/50.
@article{osti_21394392,
title = {BLACK HOLE SPIN AND THE RADIO LOUD/QUIET DICHOTOMY OF ACTIVE GALACTIC NUCLEI},
author = {Tchekhovskoy, Alexander and Narayan, Ramesh and McKinney, Jonathan C., E-mail: atchekho@cfa.harvard.ed, E-mail: rnarayan@cfa.harvard.ed, E-mail: jmckinne@stanford.ed},
abstractNote = {Radio loud active galactic nuclei (AGNs) are on average 1000 times brighter in the radio band compared to radio quiet AGNs. We investigate whether this radio loud/quiet dichotomy can be due to differences in the spin of the central black holes (BHs) that power the radio-emitting jets. Using general relativistic magnetohydrodynamic simulations, we construct steady state axisymmetric numerical models for a wide range of BH spins (dimensionless spin parameter 0.1 <= a <= 0.9999) and a variety of jet geometries. We assume that the total magnetic flux through the BH horizon at radius r{sub H}(a) is held constant. If the BH is surrounded by a thin accretion disk, we find that the total BH power output depends approximately quadratically on the angular frequency of the hole, P {proportional_to} OMEGA{sup 2}{sub H} {proportional_to} (a/r{sub H}){sup 2}. We conclude that, in this scenario, differences in the BH spin can produce power variations of only a few tens at most. However, if the disk is thick such that the jet subtends a narrow solid angle around the polar axis, then the power dependence becomes much steeper, P {proportional_to} OMEGA{sup 4}{sub H} or even {proportional_to}OMEGA{sup 6}{sub H}. Power variations of 1000 are then possible for realistic BH spin distributions. We derive an analytic solution that accurately reproduces the steeper scaling of jet power with OMEGA{sub H} and we provide a numerical fitting formula that reproduces all our simulation results. We discuss other physical effects that might contribute to the observed radio loud/quiet dichotomy of AGNs.},
doi = {10.1088/0004-637X/711/1/50},
url = {https://www.osti.gov/biblio/21394392}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 711,
place = {United States},
year = {Mon Mar 01 00:00:00 EST 2010},
month = {Mon Mar 01 00:00:00 EST 2010}
}