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Radio dichotomy of Active galactic nuclei

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.

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Radio dichotomy of Active galactic nuclei

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  1. 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

  2. Content • Motivation • Description of model • Discussion

  3. Motivation

  4. AGNs: M87 and 3C273

  5. Two puzzles in astronomical observation • 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

  6. Some explanation A number of different models have been suggested and investigated including the influence of : • the black hole (BH) spin (Blandford 1990 ,Wilson &Colbert 1995, Blandford 2000); • the BH mass (Laor 2000, Metcalf & Magliocchetti 2006); • the rate of cooling gas in the host galaxy (Best et al. 2005).

  7. Our Explanation and discussion (1) Explain the radio dichotomy of AGNs by using the model of the coexistence of the BZ and MC processes (CEBZMC) (2) Discuss the relation between jet power and radio-loudness of AGNs based on CEBZMC

  8. Description of model

  9. Configuration of magnetic field Three processes are involved (Wang 2003): • The Blandford-Znajek (BZ) process • The magnetic coupling (MC) process • The disc accretion (DA) process Figure 1. The poloidal magnetic field connecting a rotating BH with remote load and a disc in CEBZMC

  10. Power expression in CEBZMC The symbols in the above equations are defined by

  11. Discussion

  12. 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

  13. 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, Then we have

  14. Contours of radio-loudness The parameter space consisting of the BH spin and the power-law index RQ AGNs: RL AGNs: Figure 2. The contours corresponding radio-loudness with = 0.001，0.01，0.05，0.1 and 0.15 in parameter space.

  15. TABLE. 1 Dependence of radio-loudness of AGNs on the para-meters and Analysis of the contours It is consistent with the observation——most AGNs are in RQ Only CASE A: corresponding to RL Three CASES B, C and D:corresponding to RQ

  16. 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

  17. Four samples TABLE. 2 Jet power and radio-loudness of four 3CRradio sources 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.

  18. Contours of jet power • Results • Inspecting Figure 2, the right upper region in parameter space corresponds to greater radio loudness Positive correlation • Greater jet power corresponds to the right upper region in parameter space from Figure 3. 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.

  19. Radio loudness of XRBs • 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.

  20. Reference Best, P.N., Kaumann, G., Heckman, T.M., et al., 2005, MNRAS, 362, 25 Blandford 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, 811 Cao X. W., Rawlings S., 2004, MNRAS, 349, 1419 Celotti A., Padovani P., Ghisellini G., 1997, MNRAS, 286, 415 Kellerman K.I., Sramek R., Schmidt M., Shaffer D.B., Green R.,1989, AJ, 98, 1195 Laor, A., 2000, ApJ, 543, L111 Metcalf, R.B., & Magliocchetti, M., 2006, MNRAS, 365, 101 Moderski 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, 633 Wang D. X., Ma R. Y., Lei W. H., Yao G. Z., 2003, ApJ, 595, 109 Wang 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

  21. Thank you!

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