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The accretion mechanism in low power radio-galaxies Ranieri D. Baldi 1, Barbara Balmaverde 2 & Alessandro Capetti 2 1: Università degli Studi di Torino.

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Presentation on theme: "The accretion mechanism in low power radio-galaxies Ranieri D. Baldi 1, Barbara Balmaverde 2 & Alessandro Capetti 2 1: Università degli Studi di Torino."— Presentation transcript:

1 The accretion mechanism in low power radio-galaxies Ranieri D. Baldi 1, Barbara Balmaverde 2 & Alessandro Capetti 2 1: Università degli Studi di Torino 2: Osservatorio Astronomico di Torino

2 Baldi Ranieri Torino, 22/05/2008 The fundamental questions: when does a galactic nucleus become active? why AGN show a huge range of nuclear luminosity? what sets the level of activity? Which quantity best correlates with the level of activity of a radio-loud AGN? Method: estimates of accretion rate using X-ray images from Chandra archive

3 P B - P J : hot gas accretion responsible of nuclear activity. Baldi Ranieri Torino, 22/05/2008

4 Heinze et al (2007): P J from empirical relation with radio core luminosity. Baldi Ranieri Torino, 22/05/2008

5 1.Capetti & Balmaverde (2005): 29 Core Galaxies 24/29 2.Chiaberge et al. (99): 33 FR I 22/33 3.Allen et al (2006): 9 radio-galaxies 9/9 CHANDRA DATA 44 objects 5 orders of magnitude in L Radio nuc Elliptical z < 0.2 Baldi Ranieri Torino, 22/05/2008

6 1.Capetti & Balmaverde (2005): 29 Core Galaxies 24/29 2.Chiaberge et al. (99): 33 FR I 22/33 3.Allen et al (2006): 9 radio-galaxies 9/9 CHANDRA DATA 44 objects 5 orders of magnitude in L Radio nuc z < 0.2 Baldi Ranieri Torino, 22/05/ objects Data quality: (6 FRI+ 8 CoreG + 9 Allen)

7 The Core Galaxies are miniature radio-galaxies (Balmaverde & Capetti 06). Baldi Ranieri Torino, 22/05/2008

8 Bondi (1952): spherical accretion onto a black hole kT from X-ray spectra and n e from X-ray surface brightness profiles at r B. M bh from literature ( stellar dynamics of empirical relation). Errore budget: logMbh = 0.5 Baldi Ranieri Torino, 22/05/2008

9 Deprojection of X-ray spectraDeprojection of surface brightness profiles

10 Weak sources: 6 objects Complex morphology: 3 objects Large P B error : 12 objects 44 – 21 = 23 objects (6 FRI+ 8 CoreG + 9 Allen) Criteria of exclusion: Baldi Ranieri Torino, 22/05/2008

11 P B – P J correlation: efficiency conversion M bh,n e,kT depedence P B – P J is a primary relation! Scatter:0.4 dex Baldi Ranieri Torino, 22/05/2008

12 CoreG: correlation L R,L O,L x FRI: high polarization of optical nuclei L X /P B ~10 -4 – Jet origin for the nuclear emission Upper limit per P accretion & ADAF,ADIOS, CDAF models: Small accretion rate and low radiative efficiency Costraints on the accretion process: Radiative efficiency: Mass flow in the jetLow X-ray luminosity

13 ADAF overpredict nuclear L X : Small mass rate accretion and low radiative efficency. ADIOS or CDAF limiti sullaccrescimento: Assuming ~5 for FR I Ma PJ da Heinz et al (2006) Using a LR = keV Bolometric correcrion (factor 8) Baldi Ranieri Torino, 22/05/2008

14 Homologic shape of Surface Brightness Profiles (SBP) S 1kpc – P J : scatter 0.67 dex Global property of hot coronae – level of AGN activity a change in power requires a global change in the host properties (a merger?) Baldi Ranieri Torino, 22/05/2008

15 P B - P J : accrection process from hot gas Bondi accretion approximation works over 4 orders of magnitude P J ! Hot coronae brightness - levels of radio-loud AGN activity Accretion process: small rate and low radiative efficiency (ADAF) S 1kpc – P J :useful tool for faint and distant objects. Baldi Ranieri Torino, 22/05/2008


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