1. Radio Galaxies
Part 5

2. What is the life of a radio galaxy?
- do we know which one are the newly-born radiogalaxies?
- what do we need to start a radio galaxy? (or how do you make a black-hole active?)
- how many lives has a radio galaxy?
Unified schemes
are all AGNs really different?

3. “Compact Steep Spectrum” Radio Galaxies
small radio sources (<1kpc) with steep spectral index: really small (no shortened by projection effects!)
Morphologically similar to kpc-Mpc double-sided radio galaxies (i.e. they have mini-lobes and/or jets on scales 1pc – 1kpc).
The centre of activity, the “core” has an inverted radio spectrum and does not dominate the radio emission at cm wavelengths
They are considered to be
newly-born radio galaxies

4.
4C31.04
OQ 208
The cast

5. Detection of Expansion in young radio sources
The first upper limits on the rate of hotspot separation showed that their velocities were subrelativistic.
Velocities can now be measured in more than one frequencies. Cores are detectable at higher frequencies.
Long temporal coverage over 5-20 years enable the detections of ''slow” proper motions.

6. Expansion Velocities They are really young! yrs Source z Size (pc)
Velocity( h -1 c)
Age
Reference
Detections
0.096
21.8
0.12 ± 0.06
567
Polatidis et al ( )[2]
0.669
22.7
0.18 ± 0.01
403
Owsianik et al ( ) [5]
4C31.04
0.0592
70.1
0.39 ± 0.06
550
Giroletti et al 2003( )[2]
0.518
87.7
0.30 ± 0.02
932
Owsianik et al ( ) [8]
0.4597
109
0.19 ± 0.07
1836
Taylor et al ( )[2]
0.1071
9.6
0.16 ± 0.01
190
Marecki et al ( )[5]
OQ208
0.0766 7
0.10 ± 0.03
224
Stanghellini ( ) [5]
0.763
22.6
0.25
± 0.02
285
Polatidis et al ( )[3]
0.263
107
0.26
± 0.04
1306
Polatidis et al ( ) [4]
0.227
16.1
0.14
368
Tschager et al 2000 ( ) [3]
0.238
117
0.12
± 0.03
3003
Polatidis et al ( ) [6]
Limits
0.183
83.2
< 0.05
Tzioumis et al [5+]
0.101
39.4
< 0.100
Taylor & Vermeulen 1997
[2] 2
< 0.07
Tingay [3] -1 c
They are really young!

8. What do we need to start a radio galaxy?
(or how do you make a black-hole active?)
Supermassive BH seem to be common among big
early-type galaxies: but only a minority are active.
They need fuel!
Interactions/merger can bring gas to the
central regions to feed the monster!
Possibility: the AGN-phase (including the radio activity)
is only a “short” period in the life of a galaxy.
Possibly, every galaxy goes through it.
However, no clear evidence from the observations
of gas fueling the BH

9. Can we define an evolutionary sequence?
AGN phase :
Age of the radio emission:
~ 107 yrs
Age of the merger:
~ 109 yrs
>109 yr
few x 108 yr
The age of the merger derived (to first order) from the HI
delay between the two!
long-lived
HI structures

10. Recurrent activity
Mpc-scale
kpc-scale

12. Unified Schemes

13. Unified Schemes for AGNs
Diversity in the characteristics of some AGNs can be explained by
orientation effects combined with the presence (at least in some cases)
of a torus that obscures the central regions (for some orientations)
Parameters that can be used as orientation
indicators:
- Radio jet: superluminal motions, ratio between flux of main and
counter jet
Presence of broad optical lines
- Core dominance (or fractional radio core strength)
(radio core flux/extended flux)

14. Powerful radio galaxies
core dominated
lobe dominated
broad line
narrow line
characteristics that are not orientation
depended should be similar between
powerful radio galaxies and quasars

15. Different types of AGNs: a summary
Optical Emission Line Properties
Type2
narrow line
Type 1
broad line
Type 0
Radio quiet
Seyfert 2
Seyfert 1 ?
Quasars
Broad absorption line QSO
Radio loud
low power
BL Lac?
Narrow-line
radio galaxies
Blazar, OVV and many other weird objects
high power
broad-line RG
lobe/core dominated QSR
Decreasing angle to line of sight

16. More complicated for lower-power radio galaxies
- no thick torus?
- FRI do not show
broad lines
but BL Lacs do

17. Different types of AGNs: a summary
Optical Emission Line Properties
Type2
narrow line
Type 1
broad line
Type 0
Radio quiet
Seyfert 2
Seyfert 1 ?
Quasars
Broad absorption line QSO
Radio loud
low power
BL Lac?
Narrow-line
radio galaxies
Blazar, OVV and many other weird objects
high power
broad-line RG
lobe/core dominated QSR
Decreasing angle to line of sight