Suzaku Results on the Obscured Low-Luminosity Active Galactic Nucleus in NGC 4258
Abstract
In 2006 June, the obscured low-luminosity active galactic nucleus in the nearby Seyfert 1.9 galaxy NGC 4258 was observed with Suzaku for ∼100ks. Utilizing the XIS and the HXD, the nucleus emission was detected over a ∼2 to ∼40keV range, with an unabsorbed 2-10keV luminosity of ∼8 × 1040ergs-1; it varied by a factor of ∼2 during the observation. Its 2-40keV spectrum is reproduced by a single power law with a photon index of Γ ∼ 2.0, absorbed by an equivalent hydrogen column of ∼1.0 × 1023cm2. The spectrum within 4' of the nucleus also required a softer thin-thermal emission, as well as an intermediate hardness component, attributable to integrated point sources. A weak neutral Fe-Kα florescence line was detected at an equivalent width of ∼40eV. A cold reflection component was not required by the data, with the reflector solid angle Ω seen from the nucleus constrained as Ω/2π lesssim 0.3, assuming a general case of 60° inclination. The results suggest that the cold reflecting material around the nucleus is localized along our line of sight, rather than forming a thick torus.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- February 2009
- DOI:
- 10.1093/pasj/61.2.309
- arXiv:
- arXiv:0812.0145
- Bibcode:
- 2009PASJ...61..309Y
- Keywords:
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- galaxies: active;
- galaxies: individual (NGC 4945);
- galaxies: Seyfert;
- X-rays: galaxies;
- Astrophysics
- E-Print:
- PASJ, NGC4258, Suzaku, 12 pages, 11 figures