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ACCRETION AND JET POWERS IN NEARBY
UNOBSCURED RADIO GALAXIES
E. Trussoni (1), S. Vattakunnel (2), A. Capetti (1)
(1) INAF
- Osservatorio Astrofisico di Torino
(2) INAF - Osservatorio Astronomico di Trieste
------------------------------------------A correlation has been found between the accretion and jet powers in a sample of
unobscured radio galaxies (FR I and nearby low luminosity objects) showing a flattening
of the optical brightness profiles in their central regions (core galaxies). The fraction
of accreting power converted into kinetic energy is almost constant over 5 decades. We
present the results of a similar analysis for a small sample of radio quiet objects showing
a cusped power law inner brightness
profile. In particular we discuss the possible
correlation between the accretion and jet powers exploiting the multifrequency data
available for these objects. The different properties of the core and power law
samples are shortly discussed.
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1 - Accretion onto SMBH plays a fundamental role in powering AGN
2 - In radio loud AGN the energetic power is mainly in relativistic jets
3 - The accreting material may originate either from a thick torus (obscured
objects) or from the InterGalactic Medium (IGM, unobscured objects)
4 - There is a connection between the structure of the parent galaxy and the
nuclear activity

We will discuss these two main points:
A - What is the relationship between the accretion power Pa and the jet
power Pj in AGN ? Can the accretion alone support the jet power ?
B - There is some relation between Pa and Pj , and the structure of the parent
galaxy ?
We consider unobscured objects with accretion from the IGM
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Early type galaxies harbouring unobscured AGN belong to two different
classes depending on their optical brightness profiles (1-5)
Core Sersic Galaxies (CSG)
The inner optical profile is flat
Radio loud
X-ray emitters
Major mergings in the past
Fig.1a
Power Law Cusped Galaxies (PCG)
The inner optical profile is cusped
Radio quiet or silent
X-ray emitters
Minor mergings in the past
Fig. 1b
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Accretion Power Pa
Bondi model(6) for a spherical and steady accretion from the IGM
Pa

nB M2BH TB-3/2
MBH : mass of the SMBH, from the MBH - s correlation
nB ,TB : density and temperature at the Bondi radius rB ,
deduced from the X-ray properties of the IGM
Jet Power Pj
a - For bright objects and/or good enough data, deduced from the
cavities inflated by the jets, detected in X-ray maps (7)
b - For weaker objects and/or poor data, deduced exploiting the
relation betwen Pj and the radio luminosity Lr (8)
PJ

Lr0.7
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In these last years has been confirmed that the accretion and jet powers are
connected. In particular the following strict correlation between Pa and Pj has
been found for a sample of 27 CSG (Fig. 2) (7,9,10), extracted from the sample
studied in (1):
Log Pa = 1.1 Log Pj – 1.9
This implies:
- Almost a linear dependence: Pa  Pj
- Pj ~ 0.02 Pa  The jet power can be
supported by accretion
from the IGM
Fig. 2
Does a similar correlation hold also for PSG ?
Does the inner structure of the parent Galaxy, and then
its evolution, affect the Pa – Pj correlation ?
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To test this point we referred to the sample of PCG analyzed in (2): out the
23 objects of that sample only for 9 galaxies Chandra X-ray data were
good enough for a reasonable estimate of Pa
In these objects the X-ray emission from the IGM is quite weak with no
evident cavities in the Chandra maps
Accordingly, instead to deduce Pj from the radio emission we have
considered the radio luminosity as direct estimate of the jet power
considering the correlation (7)
Lr  Pj
In the following page we plot Lr vs Pa (Fig. 3) for the two samples and
report the results of the statistical analysis where have considered the
properties of the CSG and PCG separately and as a merged sinlge sample
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CSG (27 objects):
Log Pa = 1.45 Log Lr + 35.5;
CSG + PCG (36 objects): Log Pa = 1.41 Log Lr + 35.4;
PCG (9 objects):
Pr = 0.51
Pr = 1.1 x 10-3
rms = 0.94
Pr < 10-4
rms = 0.93
Fig. 3
Pr : Probability of no correl.
For the CGS and CGS + PCG samples
the same correlation basically holds
but with quite a large scatter of the
data
Any correlation is found for PCG
alone
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As further test we have searched possible correlations with Pa of the
core X-ray luminosities LX (Fig. 4)
CSG :
Log Pa = 1.52 Log LX + 36.7;
CSG + PCG: Log Pa = 1.18 Log LX + 37.8;
PCG :
Pr = 0.87
For CGS and PCG the results for LX
and Lr vs Pa are very similar
Discrepancy for the merged sample:
the correlation between of LX and Pa
has a steeper slope
X-ray excess for the PCG
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Pr = 1.6 x 10-3, rms = 0.73
Pr = 0.008, rms = 0.92
Fig. 4
Summary
- The correlation Pa - Lr holds independently if we consider the CSG + PCG
sample or CSG alone, while no correlation emerges for PCG only
- The low number of PCG (9) does not allow a definitive univocal
interpretation of our results (it is worth reminding however that in (7) a
strict connection Pa - Pj was found for a sample of only 9 CSG, even
though with better data)
- A reasonable conclusion is that the conversion process of accretion
power into jet kinetic energy is likely different in PGC and CSG.
On the other hand the few PCG have probably a small statistical weight
on the correlation of the CGS when they are included in the sample
- The correlation Pa – LX holds for CSG with the same slope as for Pa Lr, confirming that in these objects the emission at high and low
frequencies are related to the relativistic jet
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- This correlation is modified for the CSG + PCG sample. This is the
consequence of the X-ray excess in PCG: we see in Figs. 3 and 4
that they have LX < 1042 erg/s (as for GSC) and at radio frequencies
Lr < 3 x 1038 erg/s
- Again no correlation is found considering only PGS, confirming that the
accretion - jet relationship is different in the two classes of galaxies
- As main implication, while in CSG the accreting power is mainly
converted into jet power, which emits at various frequencies, in PCG
a relevant fraction is directly converted in X-ray emission (e.g.
through the accretion disk)
- From the above arguments there are strong clues to argue that
the different evolution of these two classes of unobscured galaxies
play a relevant role in ruling the energetic processes between the
accretion and jets
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References
1) Balmaverde B., Capetti A.: A&A 447, 97 (2006)
2) Capetti A., Balmaverde B.: A&A 453, 27 (2006)
3) Capetti A., Balmaverde B: A&A 469, 75 (2007)
4) Pellegrini S.: ApJ 717, 640 (2010)
5) Kharb P., et al.: AJ 143, 78 (2012)
6) Bondi H.: MNRAS 112, 195 (1952)
7) Allen S. W., et al.: MNRAS 372, 21 (2006)
8) Heinz S., et al.: ApJ 658, L9 (2007)
9) Balmaverde B., et al.: A&A 486, 119 (2008)
10) Vattakunnel S., et al.: A&A 522, 89 (2010)
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