Near-infrared observations of type 2 QSO at z = 0.9

Results of near-infrared (NIR) observations of a type 2 QSO, AX J08494+4454, at z = 0.9, which was identified in our optical follow-up observations of the ASCA Lynx deep survey, are presented. NIR J-band spectroscopic observations show presence of a narrow (FWHM = 470 km s^-1) Hα emission line and no strong broad component, which confirms that this object is type 2, as suggested in the previous optical spectroscopy (no broad Hβ emission). I_C and K-band imaging observations reveal that this object has a significantly redder color (I_C-K = 3.4 mag) than normal type 1 QSOs but has a similar color to those of nearby type 2 Seyfert galaxies and starburst galaxies. The absolute magnitude of this object in B band is much fainter than M*_B for the type 1 QSO luminosity function at z ∼ 0.9, but about 1.5 mag brighter than M*_B of the luminosity function for field galaxies at z ∼ 0.9. The red color and the faint optical magnitude may be a result of dust extinction, or we may be seeing the host galaxy with a hidden active nucleus.