Radio Galaxies Part 5

Unified schemes are all AGNs really different?

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?

“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

The cast

0710+439

1245+676

2021+614

0035+227

0108+388

OQ 208

1031+567

1843+356

2352+4951943+546

4C31.04

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.

Source z Size (pc)Velocity(h-1c) Age Reference

Detections

0035+227 0.096 21.8 0.12 ± 0.06 567Polatidis et al 2002 (1998-2001)[2]

0108+388 0.669 22.7 0.18 ± 0.01 403Owsianik et al (1982-2000) [5]

4C31.04 0.0592 70.1 0.39 ± 0.06 550Giroletti et al 2003(1995-2000)[2]

0710+439 0.518 87.7 0.30 ± 0.02 932Owsianik et al (1980-2000) [8]

1031+567 0.4597 109 0.19 ± 0.07 1836Taylor et al 2000 (1995-1999)[2]

1245+676 0.1071 9.6 0.16 ± 0.01 190Marecki et al (1989-2001)[5]

OQ208 0.0766 7 0.10 ± 0.03 224Stanghellini (1993-2002) [5]

1843+356 0.763 22.6 0.25 ± 0.02 285Polatidis et al (1993-2002)[3]

1943+456 0.263 107 0.26 ± 0.04 1306Polatidis et al (1993-2002) [4]

2021+614 0.227 16.1 0.14 ± 0.02 368Tschager et al 2000 (1982-1998) [3]

2352+495 0.238 117 0.12 ± 0.03 3003Polatidis 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 c

Expansion Velocities

yrs

They are really young!

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.

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!

What do we need to start a radio galaxy?

(or how do you make a black-hole active?)

However, no clear evidence from the observations of gas fueling the BH

:

long-lived HI structures

Can we define an evolutionary sequence?

AGN phase

>109 yr few x 108 yr

The age of the merger derived (to first order) from the HI

Age of the radio emission: ~ 107 yrsAge of the merger: ~ 109 yrs

delay between the two!

Recurrent activity

Mpc-scale

kpc-scale

Unified Schemes

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)

Unified Schemes for AGNs

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

characteristics that are not orientation depended should be similar between powerful radio galaxies and quasars

core dominatedlobe dominated

broad line

narrow line

Optical Emission Line Properties

Different types of AGNs: a summary

Type2narrow line

Type 1broad line

Type 0

Radio quiet Seyfert 2 Seyfert 1

? Quasars Broad absorption line QSO

Radio loud low power

BL Lac? BL Lac?

Narrow-line radio galaxies

Blazar, OVV and many other weird objects

high power

broad-line RG

lobe/core dominated QSRDecreasing angle to line of sight

More complicated for lower-power radio galaxies

- no thick torus?- FRI do not show broad lines but BL Lacs do

Optical Emission Line Properties

Different types of AGNs: a summary

Type2narrow line

Type 1broad line

Type 0

Radio quiet Seyfert 2 Seyfert 1

? Quasars Broad absorption line QSO

Radio loud low power

BL Lac? BL Lac?

Narrow-line radio galaxies

Blazar, OVV and many other weird objects

high power

broad-line RG

lobe/core dominated QSRDecreasing angle to line of sight