1. A spectroscopic study of the 3CR sample of radio galaxies
Sara Buttiglione
(SISSA, Trieste, Italy)
In collaboration with:
Alessandro Capetti (Observatory of Torino, Italy)
Annalisa Celotti (SISSA,Trieste, Italy)
Crete, 4 June The Central Kiloparsec

2. unbiased and homogeneous
3CR Catalogue
Third (revised) Cambridge Catalogue (3CR) of radio sources (Bennett 1962) using extended emission at 178 MHz
Survey of all sources North of -05 degrees with a Fr > 9Jy:
unbiased and homogeneous
Largely used Catalogue
Huge set of multiwavelengths observations (HST, Chandra, Spitzer, VLA...)
Sparse and incomplete optical spectroscopy
Our sample:
all the 3CR sources with z < 0.3
114 RL AGNs

3. Accretion disk – jets relation
Why and how are jets formed?
Through the optical emission we can infer the properties of the accretion mechanism
Through the radio core and extended emission we study the jets properties.
Are accretion properties and jets formation related processes or are they independent?

4. Emission lines – AGNs activity
We observe optical emission lines produced by excited gas clouds
The gas is photoionised by radiation originated by the accretion processes onto the central BH
 Since the emission lines intensities are proportional to the ionising radiation, the optical spectra represent a tool for the investigation:
of accretion mechanisms into BHs
and thus jets formation environment

5. Data acquisition Observational strategy: Data reduction: Modeling:
3.58 m TNG – DOLORES – 2” slit
1 long acquisition image (240 sec)
LOW and HIGH resolution grisms
Low: LRB ( Å) – res. 20 Å
High : VHRR ( ) or VHRI ( ) - res. 4 Å
Exposure time depending on source redshift (LRB=500, 750, 1000 sec, VHR= 2x LRB)
Data reduction:
IRAF (wavelengths-flux calibration)
Modeling:
Bruzual & Charlot 03 stellar spectra library
SPECFIT (emission line fit)

6. Example of stellar removal
Extraction of a 2” x 2” region (corresponding to ~ 8 Kpc for z = 0.3)
Subtraction of galaxy emission, in order to have pure AGN emission
Single stellar population subtraction using the best fit BC03 model for a narrow range of wavelengths:
around Ha : 5900 – 6900 Å
around Hb : 4500 – 5500 Å
NOTE: H lines are in absorption in the stellar spectra
3c 452

7. Example ... .. of the 3 main steps on a single object Currently:
Low resolution
Example ...
.. of the 3 main steps on a single object
High resolution
original spectrum
Currently:
~ 111 observed
~ 80 reduced spectra
3 not yet observed
ssp removal
Lines fit

8. Diagnostic Diagrams preliminary results (42 3CR)
They are formed by pairs of observed line ratios
They reveal information on the ionising radiation
High Excitation Galaxies
Low Excitation Galaxies
Starforming Galaxies
Composite Galaxies
AGN
HEG – pure AGN (FRII)
LEG – pure AGN (FRI + FRII)
???
SDSS data (~ gal) Kewley et al 2006 : radio quiet AGNs (Seyferts, LINERs) and starbursts galaxies

9. Optical – radio correlation
L[OIII] vs total radio luminosity
Preliminary results
Not classified
LEG
HEG
??? AGNs
Two different correlations for LEGs and HEGs both extending up to the highest level of radio emission
Log L[OIII] (erg/s)
L[OIII] vs radio core luminosity
Not classified
LEG
HEG
??? AGNs
Log L(178 MHz) (W/Hz)
Log L[OIII] (erg/s)
Log L(5 GHz) (W/Hz)

10. Optical Radio comparison
L[OIII] vs radio core luminosity
The two correlations differ by ~1.5 order of magnitude
 there are 2 “different” levels of ionising continua at the same level of jet power
Both the correlations cover the entire range of radio powers (22 – 26 W/Hz)
LEG are also of high power!!!
If we consider the L[OIII] proportional to the accretion disk luminosity and the radio emission as indicator of the jet
jets can be powered by different accretion disks (ADAF-like and standard disk?)
Not classified
LEG
HEG
??? AGNs
disk
Log L[OIII]
jet
Log L(5 GHz)
No relation is found between the properties of the accretion disk and the jet formation

11. “???” AGNs Comparison with HEG optical spectra:
3c192 FRII
“???” AGNs have weaker emission lines and expecially very weak OIII
Total vs core radio power
“???” AGNs
3c at 20 cm
Optical host
No evidence for a radio core (absent or just fading, i. e. below instrument threshold)
??? = Relic radio-galaxies

12. They are dead/dying FRII
“Relic” AGNs
“Relic” AGNs because:
weak emission lines (WRT radio emission)
weak radio core and low core/extended ratio
very low [OIII]/Hb ratio (cooling NLR)
FRII morphology
They are dead/dying FRII
The ratio between the number of relic (between 3 and 7) and active FRII (~30) provides constraints on the lifetime and dutycycle of radio-galaxies
by reproducing “relic” spectra with theoretical models (e.g. CLOUDY code) we can study the evolution in shape and intensity of the ionising radiation (~ accretion rates)
crucial information for the study of galaxies evolution and their relationship with the active nucleus:
Is the AGN just a phase during the galaxy evolution or is it a different galaxy?

13. Conclusions
The diagnostic diagrams distinguish radio galaxies from starburst galaxies, and they identify different kind of radio galaxies:
HEG
LEG
Relic (3C028, 3C314.1, 3C348, + ???)
optical lines emissions and radio morphology are connected but not univocally (LEG can be FRI or FRII).
LEG and HEG follow two different optical – radio correlations. Different disks with the same jet??
We discovered a new spectroscopic class associated to the “Relic” radio galaxies. They give us information on the timescales and dutycycles of the AGN activity.

14. RQ (SDSS) vs RL (3C) AGNs
RL AGNs overlap onto RQ AGNs with extreme ratios
RL HEG / LEG centres are shifted with respect to RQ ones:
our HEG and LEG have stronger OIII wrt Seyferts and LINERs
This is probably related to a strong mismatch in line luminosity as RL are much brighter than RQ X X

15. DD - Luminosity
We are exploring the effects of adding a third axis to the DD: the total luminosity (~L(OIII))
L(OIII)

16. DD + L(OIII)
38<LogL<39
SDSS LINERs + Seyferts
In the comparison with SDSS galaxies (mostly radio-quiet AGNs) one must consider that the line luminosity of 3CR sources is much higher than SDSS.
SDSS Seyferts +
3C LEG
40<LogL<40.5
40.5<LogL<41
3C HEG
L(OIII)
42<LogL<43