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Active galactic nuclei and their host galaxies

Published online by Cambridge University Press:  06 October 2005

W. H. Bian
Affiliation:
Department of Physics, Nanjing Normal University, Nanjing 210097, China email: [email protected] National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China email:[email protected] Present address: 120, Ninghai Road, Nanjing, Jiangsu Province, P. R. China.
Y. H. Zhao
Affiliation:
National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China email:[email protected]
L. P. Cheng
Affiliation:
National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China email:[email protected]
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Abstract

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In recent years there has been rapid progress in the research of Active Galactic Nuclei (AGNs), such as central super-massive black holes (SBH), accretion processes, and their host galaxies. Using data from ROSAT point sources, we found that the soft X-ray spectra of narrow-line Seyfert 1 galaxies (NLS1s) and Blazars become harder during X-ray flux increases, while the spectra of broad-line AGNs (BL AGNs) become softer. From ASCA data, we found that NLS1s and BL AGNs follow the same $\sigma^{2}-M_{MBH}$ relation, where $\sigma^{2}$ is the excess variance in the hard X-ray band. With the accretion efficiency of AGNs, we found that most of the radio-loud quasars possibly possess a Kerr SBH, while the Seyfert 1 galaxies and radio-quiet quasars possess Schwarzschild SBH. We also studied the relation between the central black holes and their host galaxies. It was found that NLS1s appear to have genuinely lower MBH/bulge mass ratios. And the width of the [O III] line is not a good tracer of host velocity dispersion. NLS1s play a special role in our understanding of the evolution of galaxies and their central SBHs.

Type
Contributed Papers
Copyright
© 2005 International Astronomical Union