Transcript Document

Radio Galaxies
Part 5
 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?
“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
0108+388
4C31.04
0710+439
1031+567
0035+227
1245+676
OQ 208
The cast
1843+356
1943+546
2352+495
2021+614
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.
Expansion Velocities
Source
z
yrs
Size (pc)Velocity(h -1c)
Age
Reference
Detections
0035+227
0.096
21.8
0.12 ± 0.06
567 Polatidis et al 2002 (1998-2001)[2]
0108+388
0.669
22.7
0.18 ± 0.01
403 Owsianik et al (1982-2000) [5]
4C31.04
0.0592
70.1
0.39 ± 0.06
550 Giroletti et al 2003(1995-2000)[2]
0710+439
0.518
87.7
0.30 ± 0.02
932 Owsianik et al (1980-2000) [8]
1031+567
0.4597
109
0.19 ± 0.07
1245+676
0.1071
9.6
0.16 ± 0.01
190 Marecki et al (1989-2001)[5]
OQ208
0.0766
7
0.10 ± 0.03
224 Stanghellini (1993-2002) [5]
1843+356
0.763
22.6
0.25 ± 0.02
285 Polatidis et al (1993-2002)[3]
1943+456
0.263
107
0.26 ± 0.04
1306 Polatidis et al (1993-2002) [4]
2021+614
0.227
16.1
0.14 ± 0.02
2352+495
0.238
117
0.12 ± 0.03
1836 Taylor et al 2000 (1995-1999)[2]
368 Tschager et al 2000 (1982-1998) [3]
3003 Polatidis et al (1983-2000) [6]
Limits
1934-638
0.183
83.2
< 0.05
Tzioumis et al 1998 [5+]
1946+708
0.101
39.4
< 0.100
Taylor & Vermeulen 1997[2]
1718-649
0.00142 2
< 0.07
Tingay [3]
-1
They are really young!
c
What do we need to start a radio galaxy?
(or how do you make a black-hole active?)
o Supermassive BH seem to be common among big
early-type galaxies: but only a minority are active.
o They need fuel!
o 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
Can we define an evolutionary sequence?
AGN phase
:
Age of the radio emission:
~ 107 yrs
Age of the merger:
~ 109 yrs
delay between the two!
>109 yr
few x 108 yr
The age of the merger derived
(to first order) from the HI
long-lived
HI structures
Recurrent activity
Mpc-scale
kpc-scale
Unified Schemes
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)
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
Different types of AGNs: a summary
Optical Emission Line Properties
Radio quiet
Type2
Type 1
narrow line
broad line
Seyfert 2
Seyfert 1
?
Quasars
Broad
absorption
line QSO
BL Lac?
BL Lac?
Radio loud
low power
Narrow-line
Blazar, OVV
and many
other weird
objects
radio galaxies
high power
broad-line RG
lobe/core
dominated QSR
Decreasing angle to line of sight
Type 0
More complicated for lower-power radio galaxies
- no thick torus?
- FRI do not show
broad lines
but BL Lacs do
Different types of AGNs: a summary
Optical Emission Line Properties
Radio quiet
Type2
Type 1
narrow line
broad line
Seyfert 2
Seyfert 1
?
Quasars
Broad
absorption
line QSO
BL Lac?
BL Lac?
Radio loud
low power
Narrow-line
Blazar, OVV
and many
other weird
objects
radio galaxies
high power
broad-line RG
lobe/core
dominated QSR
Decreasing angle to line of sight
Type 0