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Accretion and Ejection in Nearby Low Luminosity AGNs
Sgr A* --- LLAGNs --- QSOs
Qing-wen Wu
Korea Astronomy and Space Science Institute
Collaborators:
Feng Yuan, Xin-Wu Cao, Min-Feng Gu (Shanghai Obs.)
Ya-Di Xu (SJTU)
Outline
1. Introduction
2. X-ray Spectral Evolution in AGNs/XRBs: Evidence for Different Accretion Mode?
3. Origin of X-ray Emission in FR Is: ADAF or Jet?
4. Accretion Power and Jet Power Extracted from ADAF, and Applications
5. Conclusion
1.1 Properties of LLAGNs
•
AGN: SMBHs + Accretion disk + BLR + Torus
+ NLR + Jet (for RL AGNs)
Type 0/I/II;
Radio Quiet [QSOs, Seyferts etc.]+
Radio Loud [FR I/II, FSRQs/BL Lacs etc];
LLAGNs=L-Seyfert; LINER;FR Is, BL Lacs etc.
•
Top 10 properties of LLAGNs (Ho 2003, 2008)
1. Very common (>~40% of nearby galaxies)
2. Low ionization (>~2/3)
3. Low accretion power (Lbol<~10 44 erg/s)
4. Sub-Eddington (Lbol/L Edd<~10-2)
5. Radiatively inefficient
6. No big blue bump
7. Big red bump
8. Radio loud
9. No broad Fe K_alpha line
10. Some show broad double-peaked emission lines
Ho 2008
1.2 Accretion-Ejection in AGNs and XRBs
High/soft state
Luminous
AGNs
Low/hard state
Low luminosity
AGNs
(1) Standard accretion disk (Shakura-Sunyaev1973 )
Optically thick, Geometrically thin (H/R<<1), Te=Ti~105-7 K
0.01<~mdot<~1
---Luminous AGNs (QSO, Seyfert etc.),high/soft XRBs
(2) Advection Dominated Accretion Flows (ADAF, Narayan & Yi 1994)
Optically thin, Geometrically thick (H/R~1),, Te~109 K, Ti~1011 K, advection
mdot<~0.01 ----Low luminosity AGNs, low/hard state XRBs
2. X-ray Spectral Evolution: Different Accretion mode?
AGNs
LLAGNs
XRBs
QSO
Gu & Cao 2009, MNRAS
•
•
•
Wu & Gu 2008, ApJ
Anti-correlation: consistent with ADAF, increase mdot  density increase 
optical depth increase  harder X-ray spectrum (Esin et al. 1997)
Positive-correlation: consistent with SSD + corona (Cao 2009)
Cross-point corresponding to ADAF-SSD transition?
3. Origin of nuclear X-ray from FR Is
• FR I: low power radio galaxy with large viewing angles.
•
FR I
Radio is from jet for FR Is and other LLAGNs (Wu & Cao 2005,…)
• Origin of X-ray (FR Is and other LLAGNs):
Jet dominated? (Falcke et al. 2004;
Markoff et al. 2004,…)
ADAF dominated? (Merloni et al. 2003)
Or both? (Yuan et al. 2005; Wu et al. 2007)
• So, we use the coupled ADAF-Jet model (Yuan & Cui 2005) to investigate the
problem of X-ray origin in FR Is.
• Radio and optical emission of FR Is is come from jet (Constrain jet model).
•
Then combine jet and ADAF to fit the X-ray spectra.
Fitting results
（1） 3C 346 ：i~320 ,v>0.8c
LX/LE=1.8*10-4
（5）B2 0055+30 : i~380,v~0.9c
LX/LE=2.4*10-6
（2）B2 0755+37 : i~300 ,v~0.9c （3）3C 31 : i~520 ,v~0.87c （4）3C 317 : i~500 ,v~0.9c
LX/LE=5.2*10-6
LX/LE=4.4*10-6
（6）3C 66B : i~450 ,v~0.9c （7）3C 449 : i~82.50 ,v~0.9c
LX/LE=1.6*10-6
LX/LE=3.6*10-6
（8）3C 272.1 : i~630 ,v~0.9c
LX/LE=8.0*10-7
High Eddington ratio----ADAF dominated
Intermediate Eddington ratio----ADAF and jet (similar level)
Low Eddington ratio----Jet dominated
The critical Eddington ratio is around Lx/LEdd~several*10-6
LX/LE=8.3*10-8
Physical reason:
LxADAF proportion to m2
LxJet proportion to m
·
·
Wu, Yuan & Cao 2007, ApJ
4. Accretion power and jet power from ADAF
a) BZ process: Energy and angular momentum are extracted from a rotating (B & Z 1977)
b) BP process: Extract energy from the
accretion disk itself to power the jet/outflow (B & P 1982).
Mbh=108Msun, mdot=0.01, based on global Kerr ADAF.
(1) Jet power is not sensitive to the ADAF parameters.
(2) Qjetdisk >~ 25 QjetBZ
(3) Our Qjetdisk is similar to that of full Kerr metric MHD
simulations (Hawley & Krolik 2006).
(4) All quantities are evaluated at R=Rms.
c) Accretion/Jet power
mdot_tr~0.01 for transition of ADAF/SSD
Wu & Cao 2008, ApJ
Jet power dominated for
mdot<mdot_c
Accretion power dominated
for mdot>mdot_c
Roughly consistent with that constrained
from XRBs (10-4-10-2, Fender et al. 2003;
Migliari & Fender 2006).
Jet power extracted from ADAF and FR I/II Dichotomy
FR I/ FR II Dichotomy
and also BL lacs/FS QSO
FR I
FR II
Xu, Cao & Wu 2009, ApJ
Ghisellini & Celloti 2001
FR I: low-power/edge-darkened
FR II: high-power/edge-brightened
Physical reasons?
(a) different physical conditions in their ambient medium (Gopal-Krishna et al. 2000)
(b) different accretion mode and/or jet physics (e.g., Bicknell 1995)
FS QSO
BL Lac
The dividing line of FR I/II and
BL Lac/FS QSO is roughly
corresponding to jet power
extracted from ADAF with
mdot~0.01, and BH spin j=0.9-0.99.
FR I/ FR II -----ADAF/SSD?
BL Lac/FS QSO ------ADAF/SSD?
Wu & Cao 2008, ApJ
Xu, Cao & Wu 2009, ApJ
BL Lac
FS QSO
5. Conclusion
• Anti-correlation and positive correlation of X-ray spectral evolution in
AGNs and XRBs may suggest different accretion mode: ADAF and SSD.
• X-ray emission from FR Is (and other LLAGNs) may dominated by
ADAF, jet or both, which is depend on Eddington ratios, and critical
Lx/LEdd~several*10-6
• Jet power will dominated at low accretion rate, while accretion power will
dominated at high accretion rate, the critical value
which is depend on BH spin.
• FR I/II dichotomy (BL Lac/FS QSO) may caused by the different accretion
mode, and BHs spin very fast in these radio galaxies (j=0.9-0.99).
Thanks for your attention!