The nature of stable soft X-ray emissions in several types of active galactic nuclei observed by Suzaku

Hirofumi Noda, Kazuo Makishima, Kazuhiro Nakazawa, Hideki Uchiyama, Shin'Ya Yamada, Soki Sakurai

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


To constrain the origin of the soft X-ray excess phenomenon seen in many active galactic nuclei, the intensity-correlated spectral analysis, developed by Noda et al. (2011, PASJ, 63, S925) for Markarian 509, was applied to wideband (0.5-45 keV) Suzaku data of five representative objects with a relatively weak reflection signature. They are the typical bare-nucleus type 1 Seyfert Fairall 9, the bright and typical type 1.5 Seyfert MCG-2-58-22, 3C 382, which is one of the X-ray brightest broad line radio galaxies, the typical Seyfert-like radio loud quasar 4C+74.26, and the X-ray brightest radio quiet quasar MR 2251-178. In all of them, soft X-ray intensities in energies below 3 keV were tightly correlated with that in 3-10 keV, but with significant positive offsets. These offsets, when calculated in finer energy bands, define a stable soft component in 0.5-3 keV. In each object, this component successfully explained the soft excess above a power-law fit. These components were interpreted in several alternative ways, including a thermal Comptonization component that is independent of the dominant power-law emission. This interpretation, considered physically most reasonable, is discussed from a viewpoint of Multi-Zone Comptonization, which was proposed for the black hole binary Cygnus X-1 (Makishima et al. 2008, PASJ, 60, 585).

Original languageEnglish
Article number4
JournalPublications of the Astronomical Society of Japan
Issue number1
Publication statusPublished - 2013 Feb 25
Externally publishedYes


  • Galaxies: Seyfert galaxy, Radio galaxy, Radio loud quasar, Radio quiet quasar
  • Galaxies: active
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'The nature of stable soft X-ray emissions in several types of active galactic nuclei observed by Suzaku'. Together they form a unique fingerprint.

Cite this