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

-Fee Advanced Course 20) (Berling-Springer), 161 Blandford, R., 2000, Roy. Soc. London Philosophical Transactions A, 358, 811Cao X. W., Rawlings S., 2004, MNRAS, 349, 1419 Celotti A., Padovani P., Ghisellini G., 1997, MNRAS, 286, 415Kellerman K.I., Sramek R., Schmidt M., Shaffer D.B., Green R.,1989, AJ, 98, 1195 Laor, A., 2000, ApJ, 543, L111Metcalf, R.B., & Magliocchetti, M., 2006, MNRAS, 365, 101Moderski R., Sikora M., Lasota J.P., 1997, in “Relativistic Jets in AGNs” eds.M. Ostrowski,

M. Sikora, G. Madejski & M. Belgelman, Krakow, p.110 Nipoti C., Blundell K M, Binney J., 2005, MNRAS, 361, 633Wang D. X., Ma R. Y., Lei W. H., Yao G. Z., 2003, ApJ, 595, 109Wang J. M., Ho L. C., Staubert R., 2003, A&A, 409, 887 Willem W., Wang T. G., Norbert S., Roberto V., 1997, MNRAS, 288, 225 Wilson A. S., Colbert E. J. M., 1995, ApJ, 438, 62 Xu C., Livio M., Baum S., 1999, ApJ, 118, 1169 Zhang S N, Cui W and Chen W, 1997, ApJ, 482, L155

Reference

Thank you!