The K-band properties of Seyfert 2 galaxies

¹ Department of Astronomy, Nanjing University, Nanjing 210093, PR China e-mail: [qsgu;yhzhao]@nju.edu.cn
² European Southern Observatory, Alonso de Cordova 3107, Santiago, Chile e-mail: jmelnick@eso.org

Received: 8 December 2005
Accepted: 15 March 2006

Abstract

Aims. It is well known that the [O iii]λ5007 emission line and hard X-ray (2-10 keV) luminosities are good indicators of AGN activities and that the near and mid-infrared emission of AGN originates from re-radiation of dusty clouds heated by the UV/optical radiation from the accretion disk. In this paper we present a study of the near-infrared K-band (2.2 μm) properties for a sample of 65 Seyfert 2 galaxies.

Methods.By using the AGN/Bulge/Disk decomposition technique, we analyzed the 2MASS K_S-band images for Seyfert 2 galaxies in order to derive the K_S-band magnitudes for the central engine, bulge, and disk components.

Results.We find that the K_S-band magnitudes of the central AGN component in Seyfert 2 galaxies are tightly correlated with the [O iii]λ5007 and the hard X-ray luminosities, which suggests that the AGN K-band emission is also an excellent indicator of the nuclear activities at least for Seyfert 2 galaxies. We also confirm the good relation between the central black hole masses and bulge's K-band magnitudes for Seyfert 2s.