The K-band properties of Seyfert 2 galaxies

It is well known that the [O {\sc iii}]$\lambda$5007 emission line and hard X-ray(2-10keV) luminosities are good indicators of AGN activities and that the near and mid-infrared emission of AGN originates from re-radiation of dusty clouds heated by the UV/optical radiation from the accretion disk. In this paper we present a study of the near-infrared K-band (2.2$\mu$m) properties for a sample of 65 Seyfert 2 galaxies. By using the AGN/Bulge/Disk decomposition technique, we analyzed the 2MASS K$_{\rm S}$-band images for Seyfert 2 galaxies in order to derive the K$_{\rm S}$- band magnitudes for the central engine, bulge, and disk components. We find that the K$_{\rm S}$-band magnitudes of the central AGN component in Seyfert 2 galaxies are tightly correlated with the [O {\sc iii}]$\lambda$5007 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.