Radio Galaxies part 4. Apart from the radio the thin accretion disk around the AGN produces optical, UV, X-ray radiation. The optical spectrum emitted by the gas depends upon the abundances of different elements, local ionization, density and temperature .
the thin accretion disk around the AGN produces
optical, UV, X-ray radiation
The optical spectrum emitted by the gas depends upon the abundances of different elements, local ionization, density and temperature.
In the process of recombining, line photons are emitted and this is
the origin e.g. of Balmer-line spectra.
of the ions, downward transition leads to the emission of so-called
“forbidden-line” spectrum (possible in low density conditions).
using spectra and narrow band images
models for different
(from the absence of broad forbidden lines)
Quasar luminosity:1044 — 1047 erg s-1
Luminosity integrated over lifetime:1057—1062 erg
Jet power:1043 —1047 erg s-1
Jet power integrated over lifetime:1057 — 1062 erg
Total wind power:1043 — 1046 erg s-1
Wind power integrated over lifetime:1056 — 1061 erg
+ Starburst-induced superwinds….
the presence of the nuclear activity could influence the evolution
of the galaxy (e.g. clear gas away from the nuclear regions)
Evidence for a super-massive black hole in Cygnus A
broad permitted line seen in polarized line: only the scattered component can be seen
Broad- and narrow line radio galaxies
Outflows.Clear evidence for emission line outflows in Cygnus A and some compact radio sources, but outflow driving mechanism uncertain
of the ionized gas in
coincidence with the
this suggests interaction
between radio plasma and ISM
8 kpc from the nucleus
Even if the nucleus is obscured by the torus, the extended emission line regions can tell us about the UV radiation from the nucleus.
Colors: ionized gas
In some cases the radio
galaxy seems to have a
strong effect on the
Diagnostic diagrams important to understand which mechanism is dominant
low and high power radio galaxies?
What makes the difference?
Well known dichotomy:
low vs high power radio galaxies
Differences not only in the radio
Intrinsic differences in the nuclear regions?
Accretion occurring at low rate and/or radiative efficiency?
No thick tori?
The central regions of low-power radio galaxies
No strong obscuration: optical core very often detected
The HST observations:
optical and radio cores
But so far we haven’t seen broad permitted lines
Usually the old stellar
population is the dominant - as usual in elliptical galaxies - but in
some cases a young stellar population component is observed
(typical ages between 0.5 and 2 Gyr).
old stellar pop.
young stellar pop.
Allen et al. 2002