ACCRETION AND JET POWERS IN NEARBY ACCRETION AND JET POWERS IN NEARBY UNOBSCURED RADIO GALAXIESUNOBSCURED RADIO GALAXIES

E. Trussoni (1), S. Vattakunnel (2), A. Capetti (1)

(1) INAF - Osservatorio Astrofisico di Torino

(2) INAF - Osservatorio Astronomico di Trieste

-------------------------------------------

- 1 -

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.

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

- 2 -

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 Fig.1a X-ray emitters Major mergings in the past

Power Law Cusped Galaxies (PCG)

The inner optical profile is cuspedRadio quiet or silent X-ray emitters Minor mergings in the past Fig. 1b

- 3 -

Accretion Power Pa

Bondi model(6) for a spherical and steady accretion from the IGM Pa nB M2

BH TB-3/2

MBH : mass of the SMBH, from the MBH - 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

- 4 -

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 Does a similar correlation hold also for PSGPSG ? ? Does the inner structure of the parent Galaxy, Does the inner structure of the parent Galaxy, and then and then its evolution, affect the its evolution, affect the PPaa – – PPjj correlation correlation ?

- 5 -

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 andreport the results of the statistical analysis where have considered the properties of the CSG and PCG separately and as a merged sinlge sample

- 6 -

CSG (27 objects): Log Pa = 1.45 Log Lr + 35.5; P = 1.1 x 10-3

rms = 0.94

CSG + PCG (36 objects): Log Pa = 1.41 Log Lr + 35.4; P < 10-4

rms = 0.93

PCG (9 objects): P = 0.51

P: Probability of no correl.

Fig. 3

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

- 7 -

As further test we have searched possible correlations with Pa of thecore X-ray luminosities LX (Fig. 4)

CSG : Log Pa = 1.52 Log LX + 36.7; P = 1.6 x 10-3, rms = 0.73

CSG + PCG: Log Pa = 1.18 Log LX + 37.8; P = 0.008, rms = 0.92

PCG : P = 0.87 Fig. 4For 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

- 8 -

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

- 9 -

- 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 - 10 -

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)

- 11 -