Effect of an Intergalactic Medium on the Average Sizes of Extragalactic Jets
Abstract
A boundary-following code has simulated jets emanating from active galactic nuclei as they propagate through a bimodal external medium that consists of an isothermal galactic halo with density falling roughly as a power law with radius and a hotter, less dense, uniform intergalactic medium (IGM). By varying the beam power, the radius of the galactic halo/IGM interface, the redshift, the steepness of the power-law falloff of pressure within the halo, and the temperature ratio of the IGM to the halo, models of a wide range of radio galaxies are considered. The maximum linear sizes of the beams are found as functions of the beam and media parameters using two different criteria, the nuclear activity time, t_N_, and the point at which the advance of the beam goes subsonic. Distributions of the input parameters have been employed to attempt to reproduce some of the observed statistics of radio source size in a theoretical model that includes an IGM with a constant local density and temperature. These input parameters include the total power of the jet and the scale height, temperature, and central density of the gas within the halo. Monte Carlo simulations each using 25,000 realizations based on over 100 runs which span parameter space are employed to find the median distance for plausible distributions of the parameters for a number of constant values of density and temperature of the IGM. The mean time-averaged size is presented for a range of values for the IGM density and temperature in the form of surface plots, which are discussed in terms of the physical parameters. Allowable values for combinations of IGM density and temperature, and the time for which a galactic nucleus can sustain a jet, are found. For example, an IGM adequate to explain the bulk of the background X-ray emission, with a density of n_IGM_ ~ 7 x 10^-7^ cm^-3^ and temperature T_IGM_ = 10-18 keV, is reasonable for randomly oriented radio sources if t_N_ is somewhat larger than 2 x 10^8^ yr. The effects in this picture if the differences between radio galaxies, quasars, and blazars are due to orientation effects are briefly discussed.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1990
- DOI:
- 10.1086/169093
- Bibcode:
- 1990ApJ...360...30R
- Keywords:
-
- Active Galactic Nuclei;
- Intergalactic Media;
- Radio Jets (Astronomy);
- Boundary Value Problems;
- Computational Astrophysics;
- Halos;
- Radio Galaxies;
- Red Shift;
- Astrophysics;
- GALAXIES: INTERGALACTIC MEDIUM;
- GALAXIES: JETS;
- GALAXIES: STRUCTURE;
- RADIO SOURCES: GALAXIES