Radio dichotomy of Active galactic nuclei Ye Yong-Chun ( 叶叶叶 ), Wang Ding-Xiong( 叶 叶叶 ) Department of Physics, Huazhong University of Science and Technology, Wuhan, 430074, China
Feb 05, 2016
Radio dichotomy of Active galactic nuclei
Ye Yong-Chun ( 叶永春 ), Wang Ding-Xiong( 汪定雄 )
Department of Physics, Huazhong University of Science and Technology,
Wuhan, 430074, China
Content
Motivation
Description of model
Discussion
Motivation
AGNs: M87 and 3C273
Two puzzles in astronomical observation
(1) A radio dichotomy of active galactic nuclei (AGNs): The radio-loud (RL) AGNs consist only about 10% of the AGN population, while other 90% are radio-quiet (RQ)
(Kellermann et al. 1989)
(2) Jet in AGNs: RL AGNs are always associated with large-scale radio jets and lobes, while the RQ sources have very little or weak radio-emitting ejecta
A number of different models have been suggested and investigated including the influence of :
Some explanation
the black hole (BH) spin (Blandford 1990 ,Wilson &Col
bert 1995, Blandford 2000);
the BH mass (Laor 2000, Metcalf & Magliocchetti 2006);
the rate of cooling gas in the host galaxy (Best et al. 2005).
Our Explanation and discussion
(2) Discuss the relation between jet power and radio-loudness of AGNs based on CEBZMC
(1) Explain the radio dichotomy of AGNs by using the model of the coexistence of the BZ and MC processes (CEBZMC)
Description of model
Configuration of magnetic field
Three processes are involved(Wang 2003):
The Blandford-Znajek (BZ) process
The magnetic coupling (MC) process
The disc accretion (DA) processFigure 1. The poloidal magnetic field connecting a rotating BH with remote load and a disc in CEBZMC
The symbols in the above equations are defined by
32
0 20
1 sin2
2 1 sinM
BZ
k k dP P a
q
32
0 2
1 sin2
2 1 sinL
MMC
dP P a
q
2 22 2 9 46 10 4 10 6.59 10p
HP B M B M M erg s
21 ,q a ,F Hk F H D H
Power expression in CEBZMC
Discussion
Definition of radio-loudness
Radio-loudness of AGNs is expressed by the ratio , where is the total radio luminosity powered by the BZ process, and is the total bolometric luminosity of the accretion disc. The expression for radio-loudness in CEBZMC
0*
0
2 /( , )(1 ) 2 /
BZ
ms D MC
P P Pa nL E M P P
&
/P L PL
We take the relation suggested in Moderski et al.(1997), arising from the balance between the pressure of the magnetic field on the horizon and the ram pressure of the innermost parts of an accretion flow,
2 2 28 ~ ~ 4H ram D HB P c M r
2 22 201 2 1 2D HM B M q P q
0* 2
0
2 /( , )(1 )(1 ) 2 /
BZ
ms MC
P P Pa nL E q P P
Then we have
Figure 2. The contours corresponding radio-loudness with = 0.001, 0.01, 0.05, 0.1 and 0.15 in parameter space.
The parameter space consisting of the BH spin and the power-law index
*an
RQ AGNs:
RL AGNs:
/P L
/ 0.001P L
/ 0.001P L
Contours of radio-loudness
Only CASE A : corresponding to RLThree CASES B, C and D : corresponding to RQ
TABLE. 1 Dependence of radio-loudness of AGNs on the para-meters and *a n
Analysis of the contours
It is consistent with the observation——most AGNs are in RQ
3
20 20
1 sin, /2 2 1 sin
M
jet jetdP a n P P a
q
Jet power expression
Considering that the BZ mechanism is regarded as the major mechanism for powering radio jets in AGNs. The expression for jet power in CEBZMC
REFERENCES. - (CR) Cao et al. 2004 MNRAS; (XLB) Xu et al. 1999 ApJ; (WHS) Wang et al. 2004 A&A; (CPG) Celotti et al. 1997 MNRAS; (WWNR) Willem et al. 1997 MNRAS.
TABLE. 2 Jet power and radio-loudness of four 3CR radio sources
Four samples
Figure 3. The dividing line of radio-loudness with , and the contours of of 3C345, 3C273, 3C390.3 and 3C29 in solid, dashed, dotted and dash-dotted lines, respectively.
jetP/ 0.001P L
Contours of jet power
Results Inspecting Figure 2, the right upper
region in parameter space corresponds to greater radio loudness
Greater jet power corresponds to the right upper region in parameter space from Figure 3.
Positive correlation
Zhang et al.(1997) mentioned that RQ BH X-ray binaries(XRBs) is corresponding to very low spin(~0), While RL BH XRBs (with superluminal jet) have very high spin(~0.93-0.95)
Nipoti et al.(2005) discussed that a typical microquasar is in the flaring mode a few percent of the time, which is similar to the fraction of quasars that are radio loud.
Radio loudness of XRBs
Best, P.N., Kaumann, G., Heckman, T.M., et al., 2005, MNRAS, 362, 25Blandford R. D., 1990, in Active Galactic Nuclei, ed. T. J.-L. Courvoisier & M. Mayor (Saas
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Reference
Thank you!