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 0710+439 1031+567 4C31.04 0035+227 OQ 208 1843+356 2021+614 1245+676 The cast 2352+495 1943+546

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 They are really young! yrs Source z Size (pc) Velocity( h -1 c) 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 1836 Taylor et al 2000 (1995-1999)[2] 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 0.14 368 Tschager et al 2000 (1982-1998) [3] 2352+495 0.238 117 0.12 ± 0.03 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 c They are really young!

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

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

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 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

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 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