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The accretion mechanism in low power radio-galaxies

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. AGN activity. The fundamental questions: when does a galactic nucleus become active?

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The accretion mechanism in low power radio-galaxies

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  1. The accretion mechanism in low power radio-galaxies Ranieri D. Baldi1, Barbara Balmaverde2 & Alessandro Capetti2 1: Università degli Studi di Torino 2: Osservatorio Astronomico di Torino

  2. AGN activity • 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 Baldi Ranieri Torino, 22/05/2008

  3. Allen et al (2006) PB - PJ: hot gas accretion responsible of nuclear activity. Baldi Ranieri Torino, 22/05/2008

  4. Jet Kinetic Power • Heinze et al (2007): PJ from empirical relation with radio core luminosity. Baldi Ranieri Torino, 22/05/2008

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

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

  7. Bondi Accretion Bondi (1952): spherical accretion onto a black hole • kT from X-ray spectra and ne from X-ray surface brightness profiles at rB. • Mbh from literature ( stellar dynamics of empirical relation). • Errore budget: DlogMbh = 0.5 Baldi Ranieri Torino, 22/05/2008

  8. Accretion rate Deprojection of X-ray spectra Deprojection of surface brightness profiles Baldi Ranieri Torino, 22/05/2008

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

  10. Results • PB – PJ correlation: efficiency conversion Scatter:0.4 dex • Mbh,ne,kT depedence PB – PJ is a primary relation! Baldi Ranieri Torino, 22/05/2008

  11. Constraints on the accretion Jet origin for the nuclear emission • CoreG: correlation LR,LO,Lx • FRI: high polarization of optical nuclei • LX/PB~10-4 – 10-5 & Upper limit per Paccretion Costraints on the accretion process: ADAF,ADIOS, CDAF models: Small accretion rate and low radiative efficiency Mass flow in the jet Low X-ray luminosity Radiative efficiency: Baldi Ranieri Torino, 22/05/2008

  12. Accretion power vs SBP • Homologic shape of Surface Brightness Profiles (SBP) • S1kpc – PJ: 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

  13. Conclusions • PB - PJ: accrection process from hot gas • Bondi accretion approximation works over 4 orders of magnitude PJ! • Hot coronae brightness - levels of radio-loud AGN activity • Accretion process: small rate and low radiative efficiency (ADAF) • S1kpc – PJ:useful tool for faint and distant objects. Baldi Ranieri Torino, 22/05/2008

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